Single-Phase Robust Charger with High Power Quality for Electric Vehicle Application

The widespread use of electric vehicles (EVs) necessitates the development of a robust charging infrastructure. The goal of this research paper is to create a high-quality, single-phase charger for electric cars. The purpose of this design is to provide a charger that is both fast and efficient but also protects against power quality problems including harmonics, power factor correction, and voltage variations. A single-phase–single-stage improved power quality EV charger for small and medium power applications has been designed and simulated. A single DC-DC converter is utilized for constant charging and improved power quality operation. The charger presented exhibits improved power quality as sinusoidal current is drawn from the utility grid supply with the total harmonic distortion (THD) in compliance with the IEEE 519 and IEC 61000-3-2 standards. In order to charge the battery of an electric vehicle, most two-stage converters first use a boost converter for power factor correction (PFC), and then they use a DC-DC converter that can accept any input voltage. These two-stage conversions are inefficient and use more parts than necessary. This work proposes a PFC converter based on a single-stage switching inductor Cuk converter, which has the advantages of high step-down gain, low current stress, high efficiency, and a small number of components. The suggested converter’s operational analysis and design equations are performed in continuous current mode. The proposed converter is the subject of extensive mathematical modelling, analysis, simulation, and experimentation presented in this study. With both constant voltage (CV) and constant current (CC) loads, the proposed converter’s performance is analysed with regard to power quality indices like voltage total harmonic distortion (THD), current THD, and total power factor. Additionally, in CV mode and CC mode, the suggested converter’s dynamic performance with battery charging is evaluated in relation to the extensive supply changes. The developed charger presents a reliable and efficient solution for EV charging, fostering the transition to a cleaner and more sustainable transportation system.

Introduction

There is an increasing interest in the deployment of electric vehicles (EVs) to reduce greenhouse emissions and fuel usage. Moreover, EV charging technologies that are fast, efficient, and low cost with a small form factor are needed. In addition to that, these technologies should have features to minimize harmonics and operate at a high power factor. Their impact on the grid should be minimal as they would contribute to a significant share of the grid load in the future. Another desirable feature is the ability to provide ancillary services to support smart grids [1]. A graph showing the grid load characteristics with different operational modes of EV chargers is shown in Fig. 1.

Fig. 1. Load impact of EV charger operation on grid [2].

People have higher expectations for the power’s quality as a result of the rapid industrialization and electrification of vehicles that have taken place in recent decades. Laptops, desktops, smart devices, and cell phones are all examples of basic power quality needs. The power quality could be poor causing the electronic equipment to either stop working altogether or work improperly. Power factor is a crucial component that directly affects power quality and is one of the factors that contribute to power quality. A low power factor will result in undesirable impacts, such as waveform distortion on the power grid and significant line loss, both of which may shorten the amount of time that power devices can remain operational. There is a development of power tools with specialised functions as the use of electricity becomes ubiquitous in modern society. Our frequency and voltage from the mains are both 50 hertz and 220 volts. The voltage and current we obtain from the national grid aren’t suitable for most power devices, so we have to convert them. The four types of conversion circuits are alternating current (AC), direct current (DC), alternating current (AC), and direct current alternating current. An alternating-current-to-direct-current (AC-DC) converter circuit. The majority of modern machinery operates on direct current. This type of circuit is known as a rectifier circuit. The rectifier circuit is used in numerous devices, including the UPS. High-quality electricity for power electronics can be generated by a rectifier circuit that acts as an interface with the power grid. This circuit is part of a DC-regulated power supply.

Disadvantage Due to Harmonic Current in Power Grid

In the real world, power factor degradation due to harmonic current has been around for quite some time. Because switching devices are not commonly utilized and the drawback of harmonic current is poorly understood, few people pay it much mind. Wherever there are switching devices, harmonics are present [3].

The power factor drops when harmonics are present. Problems with power electronic devices, such as harmonic current and low power factor, were more common in earlier years due to the widespread use of thermistors and rectifier diodes [4].

There are several harmonic current components in an AC input current waveform that take the form of an impulse. The electricity grid will be contaminated by these harmonic current components. Non-linear electric loads cause harmonics in an electrical grid. It will generate current at a frequency that is not its own. The following are some drawbacks to using harmonic current:

1. 1.The ‘secondary impact’ of harmonic current is that it causes harmonic voltage when it flows through loads, distorting the power grid’s voltage and leading to either overcurrent or overvoltage.
2. 2.The efficiency of both the generators and the wires carrying the electricity would suffer as a result of the added resistance in the circuit.
3. 3.It will shorten the useful life of power devices (including transformers, capacitors, and electric motors) and cause them to function erratically.
4. 4.Protection relays, automated machinery, and digital infrastructure will all malfunction or fail altogether or even don’t work.
5. 5.It will cause interference in communication systems, a deterioration in the quality of the signal being transmitted, and possibly even damage to the communication devices [5].

Therefore, we can get the conclusion that the presence of harmonic current causes a significant amount of pollution to the electrical grid and that we need to take certain steps to get rid of or limit harmonic current. There are two methods available for limiting the flow of harmonic current. The first method involves making use of a reactive power compensation device to generate a harmonic with the same frequency but the opposite phase. The second approach is to design and manufacture equipment that does not create harmonic currents [6].

The Main Content of the Research

1. 1.Acquire the knowledge necessary to master the control strategy of the power factor correction circuit.
2. 2.Acquaint yourself with the fundamentals of the boost converter power factor correction circuit, including its operating principle and basic control technique.
3. 3.Model the boost converter power factor correction circuit that is used in the level 1 charger for electric vehicles [7].

Objective of the Paper

1. 1.Designing a charger with high power efficiency reduces energy losses during charging. Selecting effective power conversion topologies and components maximises grid-to-EV battery power transmission.
2. 2.Power factor correction to ensure the charger has a high power factor. Reducing grid reactive power demand improves power quality and efficiency.
3. 3.Maintaining low THD through minimising current waveform distortion. High harmonic content can interfere with the charging system; thus, power quality standards must be met.
4. 4.Cost optimisation: Making a reliable and affordable charger. To balance cost and functionality, component selection, system integration, and production are crucial [8].

Literature Review

The automobile industry has expanded significantly as more people select to commute in electric vehicles. Electric cars are becoming increasingly popular as an alternative to other types of vehicles, such as two-wheelers, e-rickshaws, four-wheelers, and other types. For applications that require low to medium power, you will want a charger that has better power quality because traditional chargers do not comply with the power quality standards [9].

Utilising Level 1 charging outlets, which provide a slow charging rate, allows electric vehicle charging to be done conveniently during off-peak hours without placing a significant burden on the primary electrical grid. However, in recent years, Level 2 charging has become the norm, both in public and private spaces, because it is faster than Level 1 charging and uses a more universal 240 V voltage [10], [11]. Because of its high-power density and adaptability, level 2 charging is quickly becoming a mainstream technology.

Electric vehicle (EV) battery chargers can be either on-board or off-board [12]. Although off-board chargers don’t have to worry about size or weight restrictions, their widespread installation adds to the overall cost of the system. Additionally, onboard chargers can be either standalone devices or part of a larger system. The main objective of the battery management system is to charge the batteries, and it does this using many different methods and algorithms. There is a wide variety of charging algorithms, and these methods vary considerably in terms of charging time, implementation cost, complexity, and so on [13].

Popular methods for charging include the constant current/constant voltage algorithm and the multi-stage charging algorithm. Among these two algorithms, constant current-constant voltage (CC/CV) is the more popular choice due to its simplicity and low implementation cost, while the second is less popular because it requires an additional algorithm, an optimisation algorithm, to be used in conjunction with the charging algorithm.

There appears to be an imbalance in battery charge. Since the first stage is accountable for producing stable DC link voltage, low THD, and reduced harmonic injection into the Grid in accordance with, a specific type of rectifier known as a PFC rectifier can be used for these purposes [11]. The purpose of this circuit is to produce a sinusoidal current waveform in the input inductor that is in phase with the applied voltage.

There is an increase in power factor and a decrease in total harmonic distortion as a result. The boost design was papered to perform better than other PFC topologies because it eliminates input current cross-over distortions while also providing smooth control and reduced THD [14]. When PFC is used on an active rectifier, information must be taken from the voltage source to synchronize the control with the line frequency. Most of the time, this is done with either an open-loop or a closed-loop method [15].

Classification of EV Chargers

EV chargers can be further classified based on power stage, power flow, isolation, and whether they are on-board or off-board chargers. Here’s an overview of these classifications:

On-Board Chargers

These chargers are integrated into the electric vehicle itself. They are typically found in battery electric vehicles (BEVs) or plug-in hybrid electric vehicles (PHEVs), allowing charging directly from a power outlet or charging station.

Off-Board Chargers

These chargers are standalone units separate from the electric vehicle. They are commonly found in public charging stations or residential charging infrastructure. Off-board chargers supply power to the vehicle through a charging cable and connector.

Power Stage

Single-Stage Chargers

A single-stage EV charger refers to a charging system that operates at a single level of charging power, confer Fig. 2. Unlike multi-stage chargers that offer multiple levels of power output, single-stage chargers provide a consistent charging rate. Here’s an overview of single-stage EV chargers:

Fig. 2. Different approaches of EV battery chargers [16].

1. Charging Power: Single-stage chargers typically have a fixed power output, which determines the charging rate, Fig. 2. The power output can vary based on the charger’s capacity and specifications. For example, Level 1 chargers are considered single-stage chargers as they operate at a standard household electrical outlet voltage of 120 V, delivering a relatively low charging power.

2. Voltage: Single-stage chargers are commonly designed to operate at a specific voltage, such as 120 V for Level 1 chargers. This voltage determines the electrical input from the power source and subsequently influences the charging speed.

3. Charging Speed: Single-stage chargers may offer slower charging speeds compared to higher-powered chargers, Fig. 5. For instance, Level 1 chargers typically provide a slower charging rate of 2 to 5 miles of range per hour, which is suitable for overnight charging or longer-duration charging sessions.

4. Application: Single-stage chargers are commonly used in residential settings where the charging requirements are less demanding, and slower charging speeds are acceptable, Fig. 2. They are often used for overnight charging or as a backup charging option for electric vehicle owners who have access to other charging solutions.

5. Cost and Simplicity: Single-stage chargers are generally less complex and less expensive to manufacture compared to higher-powered chargers. Their simpler design contributes to their affordability and ease of use.

6. Compatibility: Single-stage chargers are compatible with a wide range of electric vehicles that can accept the specific voltage and power output provided by the charger. However, it is important to ensure compatibility between the charger and the vehicle’s charging port and connector.

Two-Stage Chargers

A two-stage electric vehicle charger refers to a charging system that operates at two different levels of charging power. These chargers provide the flexibility to charge at a higher power level for faster charging and at a lower power level for more convenient or lower-demand charging scenarios. Here’s an overview of two-stage EV chargers:

1. Charging Power Levels: Two-stage chargers offer two distinct charging power levels, typically Level 1 and Level 2 charging. Level 1 charging operates at a lower power output, commonly using a standard household electrical outlet at 120 V. Level 2 charging, on the other hand, operates at a higher power output, usually at 240 V, enabling faster charging rates.

2. Flexibility and Speed: The ability to switch between two charging power levels gives users flexibility in charging their electric vehicles. Level 1 charging is suitable for overnight or longer-duration charging sessions, offering convenience and compatibility with standard outlets. Level 2 charging provides a faster charging rate, reducing the time required to replenish the vehicle’s battery.

3. Residential and Commercial Use: Two-stage chargers are commonly used in both residential and commercial settings. They can be installed in private homes, allowing EV owners to charge their vehicles at home conveniently. Additionally, they are found in commercial charging stations, workplaces, and other public locations where faster charging options are desired.

4. Infrastructure Compatibility: Two-stage chargers are compatible with electric vehicles that support Level 1 and Level 2 charging. Most modern electric vehicles are designed to work with both power levels, making them suitable for use with two-stage chargers.

5. Cost and Installation: Two-stage chargers typically require a dedicated electrical circuit and higher-power electrical connections compared to Level 1 chargers. This may involve additional installation costs, such as hiring an electrician to set up the appropriate electrical infrastructure.

Two-stage electric vehicle chargers provide a balance between convenience and faster charging speeds. The availability of both Level 1 and Level 2 charging options allows users to adapt their charging strategy based on their needs and time constraints. Whether it’s overnight charging at a lower power level or quick top-ups using the higher power level, two-stage chargers offer versatility and efficient charging solutions for electric vehicle owners.

Integrated Chargers

Integrated EV chargers, also known as integrated charging systems or integrated chargers, are charging solutions that are built directly into electric vehicles or are seamlessly integrated with the vehicle’s onboard systems. These chargers eliminate the need for separate external charging equipment and provide a convenient and integrated charging experience. Here are some key features and benefits of integrated EV chargers:

1. On-Board Integration: Integrated chargers are designed to be an integral part of the electric vehicle itself. They are often located within the vehicle, close to the battery pack or powertrain components, and are specifically tailored to work seamlessly with the vehicle’s charging system.

2. Convenience: With integrated chargers, electric vehicle owners do not need to carry or install additional charging equipment. The charging capability is readily available within the vehicle, allowing for convenient charging options wherever compatible power sources are accessible.

3. Plug-and-Play: Integrated chargers typically provide a plug-and-play functionality, enabling users to connect their vehicles directly to standard power outlets or charging stations without the need for external adapters or converters. This simplifies the charging process and reduces the hassle associated with additional charging equipment.

4. Charging Efficiency: Integrated chargers are optimized to deliver efficient charging performance. They ensure proper voltage regulation, current control, and safety features to maximize the charging efficiency while protecting the vehicle’s battery pack.

5. Compatibility: Integrated chargers are designed to be compatible with the specific electric vehicle they are integrated into. They consider factors such as the vehicle’s voltage requirements, charging capabilities, and connector standards to ensure seamless compatibility and reliable charging.

6. Safety Features: Integrated chargers incorporate various safety features to protect against electrical faults and ensure user safety. These may include overcurrent protection, overvoltage protection, temperature monitoring, and insulation monitoring to detect and prevent potential hazards during the charging process.

Power Flow

Uni-Directional Chargers

These chargers only allow power flow from the grid to the vehicle, enabling charging of the EV’s battery, summarized in Table I.

Table I. Unidirectional vs. Bidirectional Charges

	Power flow and switches	Power level	Control	Battery effect	Benefits
Unidirectional chargers	One-way electrical energy flow, basic battery charge (G2V) diode bridge + unidirectional converter	Levels 1, 2 or 3	Simple, Active control of charging current. Basic control can be managed with time sensitive energy pricing	No discharging degradation	Provides services based on reactive power and dynamic adjustment of charge rates, even without reversal.
					Supplies or absorbs reactive power, without having to discharge a battery, by means of current phase angle control.
Bidirectional chargers	Two-way electrical energy flow and communication, charge/discharge (V2G) MOSFET (low power) GTO (High power level).	Expected only for level 2	Complex extra drive control circuits	Degradation due to frequent cycling	Ancillary services (Voltage regulation, Frequency regulation)
					Spinning reserves
					Reactive power support
					Peak shaving
					Valley filling
					Load following
					Energy balance

Bi-Directional Chargers

These chargers support two-way power flow, allowing the vehicle to not only charge but also discharge power back into the grid. This enables vehicle-to-grid (V2G) or vehicle-to-home (V2H) capabilities, where the EV can serve as a mobile energy source, summarized in Table I.

Isolation

Isolated and non-isolated EV chargers refer to two different types of chargers based on the presence or absence of galvanic isolation between the charging system and the power grid. Here’s an overview of isolated and non-isolated EV chargers.

Isolated EV Chargers

1. 1.Isolation: Isolated chargers incorporate galvanic isolation, which means there is a physical barrier between the vehicle’s electrical system and the power grid. This isolation prevents the flow of electrical current between the charging system and the grid, providing an added layer of safety and protection.
2. 2.Safety and Protection: Galvanic isolation in isolated chargers helps protect against electrical faults, ground faults, and voltage surges, reducing the risk of electric shock or damage to the charging equipment and the vehicle.
3. 3.Common Application: Isolated chargers are often used in residential, commercial, and public charging infrastructure where safety and electrical protection are critical requirements.

Non-Isolated EV Chargers

1. 1.Absence of Isolation: Non-isolated chargers do not have galvanic isolation, meaning there is a direct electrical connection between the vehicle’s electrical system and the power grid. They rely on other safety mechanisms to ensure electrical safety during the charging process.
2. 2.Cost and Simplicity: Non-isolated chargers are typically less complex and less expensive to manufacture compared to isolated chargers, as they do not require additional components for galvanic isolation.
3. 3.Common Application: Non-isolated chargers are commonly used in situations where the risk of electrical faults is relatively low, such as in certain commercial charging stations or applications where the charging system is already integrated into a larger electrical infrastructure.

The choice between isolated and non-isolated EV chargers depends on several factors, including safety requirements, the specific application, and regulatory standards. While isolated chargers provide enhanced electrical protection, non-isolated chargers can be suitable in situations where the risk of electrical faults is adequately mitigated and cost considerations are important. It’s important to consider local regulations and safety guidelines when selecting the appropriate charger for a given application.

Methods of Charging and Discharging Of EVs

As the world moves towards a more sustainable and environmentally friendly future, Electric Vehicles (EVs) are growing in popularity. The processes for charging and discharging EVs, which are crucial to their operation, are one of their most important features. For the battery’s performance and longevity as well as the driver’s convenience, efficient charging and discharging are essential.

When an electric vehicle (EV) is charged, electrical energy is transferred from an external power source to the battery, and when it is discharged, the energy is released back into the system so the vehicle can move. The numerous EV charging and discharging techniques, as well as their importance to the ecosystem supporting electric mobility, will be discussed in this chapter.

Electric vehicle (EV) charging techniques include wireless charging, DC charging, and AC charging. On the other hand, discharge methods use vehicle-to-grid (V2G), vehicle-to-building (V2B), and vehicle-to-home (V2H) technologies to use the energy stored in EV batteries to power structures or the grid.

Along with these approaches, we’ll talk about the factors that affect the charging and discharging process, including battery size and type, charging station size and type, temperature and environmental conditions, and the size and stability of the electricity grid. Designing effective and dependable charging and discharging systems requires a thorough understanding of these elements.

The primary objective of this chapter is to present a thorough overview of the various EV charging and discharging techniques, along with any problems and potential future advancements. By doing this, we seek to advance the ongoing study and development of efficient and sustainable electric mobility systems.

EV Charging Methods

Electric vehicle (EV) charging methods are grouped into three types: AC Charging, DC Charging, and wireless charging. Charging speeds, power levels, and protocols vary by charging type.

AC Charging

As summarized in Table II, AC charging is the most common charging method for EVs. It uses alternating current (AC) power to charge the vehicle’s battery. AC charging is further classified into two levels, as shown in Fig. 3:

Table II. AC Charging System Power Levels [17]

Charge method	Nominal supply voltage	Maximum current	Power level
AC Level 1	120 V AC, 1-Phase	12	1.08
	120 V AC, 1-Phase	16	1.44
AC Level 2	208 to 240 V AC, 1-Phase	16	3.3
	208 to 240 V AC, 1-Phase	32	6.6
	208 to 240 V AC, 1-Phase	<=80	<=14.4

Fig. 3. (a) Level 1 EV charger. (b) Level 2 EV charger.

1. 1.Level 1 Charging: With a charging power of 1.4 kW, Level 1 charging is the slowest charging technique. It takes approximately 8–12 hours to fully charge an EV with a 40-kWh battery using a typical residential 120-volt AC outlet. Level 1 charging is appropriate for charging overnight at home or work.
2. 2.Level 2 Charging: Level 2 charging is faster than Level 1 charging, with a charging power of up to 19.2 kW. It takes approximately 4–8 hours to fully charge an EV with a 40-kWh battery using a 240-volt AC power supply. Level 2 charging is appropriate for public charging stations, commercial and industrial establishments, as well as residential charging stations equipped with a dedicated Level 2 charging unit.

DC Charging

As summarized in Table III, DC charging is a faster charging method than AC charging. It uses direct current (DC) power to charge the vehicle’s battery.

Table III. SAE EV DC Charging Power Levels [18]

Charge method	Supplied DC voltage range (V)	Maximum current (A)	Power level (kw)
DC level 1	200–450 V	≤80 A	≤36 kW
DC level 2	200–450 V	≤200 A	≤90 kW
DC level 3	200–600 V	≤400 A	≤240 kW

DC charging is further classified into two levels:

1. 1.Level 3 Charging (DC Fast Charging): Level 3 charging, also known as DC fast charging, is the most commonly used fast charging method for EVs. It is capable of a high charging output of up to 350 kW and can charge a 40-kWh battery-powered EV from 0% to 80% in around 30 minutes. Level 3 charging is appropriate for public charging stations and highway rest zones.
2. 2.Ultra-Fast Charging (350 kW and above): The most recent and fastest charging method for EVs is ultra-fast charging. It has a charging power of 350 kW or higher and can charge a 40-kWh battery EV from 0% to 80% in less than 20 minutes. Ultra-fast charging is appropriate for high-traffic areas such as major roads and city centers.

Wireless Charging

Wireless charging, also known as inductive charging, is a technique of charging that eliminates the need for cables or connectors. It makes use of a wireless charging pad that is installed on the ground and is powered by a battery. The EV is equipped with a receiver coil, which transforms the electromagnetic field generated by the charging pad into electrical energy, which is then used to charge the battery. Wireless charging for electric vehicles is still in its early phases of development and is not commonly available [19].

Battery Charging Algorithms

Battery charging algorithms are critical in the efficient and successful management of the charging process for electric vehicles (EVs). This section goes into numerous charging algorithms that are often used in EV applications, covering their principles, benefits, and limitations [20].

Constant Current/Constant Voltage (CC/CV) Charging

The CC/CV charging algorithm is commonly employed for lithium-ion batteries, which dominate the EV industry. A constant current is initially supplied until the battery voltage reaches a predetermined limit, during this period voltage increases gradually. Following that, the charging process enters a constant voltage phase until the battery is fully charged. This algorithm controls charging and protects the battery from overcharging. The continuous current phase allows for fast charging, allowing the battery to achieve a specific charge level quickly. The constant voltage phase then allows for gradual charging of the battery, ensuring that the cells are charged evenly and reducing the risk of overvoltage. CC/CV charging is well-known for its ability to balance battery life, performance, and charging speed. It also aids in the prevention of problems such as thermal runaway, which can arise as a result of the excessive heat generated during fast charging [21].

Pulse Charging

Pulse charging is a cyclical procedure that involves charging pulses and rest periods. Pulse charging decreases total charge time and increases battery performance by supplying intermittent charging pulses. The charging pulses enable faster charge rates without producing excessive heat, diminishing the risk of overcharging and extending battery life. Rest times allow the battery to cool down, which prevents thermal stress and elevates safety. Pulse charging is especially useful for high-capacity batteries, and quick charging settings when charging time and energy efficiency are crucial. To optimise charging performance while guaranteeing battery integrity, the application of pulse charging necessitates careful consideration of pulse properties such as length, amplitude, and frequency [22].

Various pulse charging mechanisms, such as asymmetric pulse charging and dynamic pulse charging, have been developed. Asymmetric pulse charging uses pulses with varying charging and discharging periods to improve battery efficiency and capacity. Dynamic pulse charging optimises the charging process for the individual battery state by adjusting the pulse parameters based on real-time battery circumstances.

Delta Voltage (ΔV) Charging

The ΔV charging algorithm detects charging completion by detecting voltage fluctuations. The charging process is ended when a sudden voltage change is detected, indicating a near-full battery. Because of its simplicity and dependability, this method is simple and commonly used. However, ΔV charging is best suited for batteries that have well-defined voltage profiles while charging. Other battery chemistries that display less noticeable voltage swings near full charge may not be as effective. Proper calibration and accurate voltage monitoring are critical for detecting the ΔV point accurately and avoiding undercharging or overcharging. Variations in battery properties, such as capacity degradation or temperature fluctuations, can also affect the ΔV point, necessitating periodic recalibration [23].

Advanced techniques such as adaptive V charging have been developed to improve the accuracy and reliability of V charging. The voltage threshold is continually adjusted by adaptive V charging algorithms based on battery properties, boosting detection accuracy and optimising the charging process.

Trickle Charging

Trickle charging, also known as maintenance or float charging, is the technique of giving a low current to a fully charged battery. This continual but limited charging compensates for self-discharge and keeps the battery charged to its maximum capacity. Trickle charging keeps the battery ready for usage and increases its lifespan. The low charging current reduces heat generation, lowering the battery’s danger of thermal stress. Trickle charging is widely utilised for EVs that are inactive for long periods, such as parked or stored vehicles, to ensure that the battery retains enough charge without overcharging. However, caution must be exercised to avoid prolonged trickle charging, which can cause damage to the battery over time [24].

Smart charge controllers monitor battery conditions, adjust charging current as needed, and use intelligent charging algorithms to optimise the trickle charging process in advanced trickle charging systems. These strategies help to preserve battery health and lifespan while consuming the least amount of energy.

Adaptive Charging

Adaptive charging algorithms alter charging parameters dynamically based on criteria such as battery temperature, level of charge, and age. Adaptive algorithms increase battery health, efficiency, and lifespan by optimising the charging process in real-time. These algorithms necessitate complex battery management systems capable of continuously monitoring and analysing battery properties. Adaptive charging algorithms can modify the charging current and voltage levels, charging speeds, and charging profiles based on the data obtained to match the individual needs of the battery. This adaptability enables optimal charging performance and prevents problems like overcharging, undercharging, and overheating. External elements such as charging station capabilities and grid circumstances are also considered by adaptive charging algorithms in order to establish a balance between charging speed and overall system efficiency.

To make data-driven decisions, advanced adaptive charging algorithms use machine learning, artificial intelligence, and predictive models. These algorithms can optimise the charging process and give personalised charging experiences by learning from historical charging patterns, battery behaviour, and user preferences. They respond to changes in battery properties over time, compensating for capacity loss and extending battery life [25].

To begin, the CC/CV charging method assures controlled charging by giving a steady current initially until the battery voltage reaches a certain limit. This controlled current enables fast charging, allowing the battery to achieve a specific charge level quickly.

Second, the CC/CV charging method has been widely used for lithium-ion batteries, which are widely employed in the EV industry. Furthermore, the CC/CV charging method handles the essential issue of maintaining battery temperature during charging. The controlled current and voltage levels help to reduce excessive heat generation, lowering the risk of thermal runaway and ensuring the battery’s thermal stability. While various charging methods may provide benefits like as faster charging times or personalised charging profiles, the CC/CV charging technique strikes a balance between charging speed, battery health, and user ease. Its widespread acceptance, compatibility, and track record make it a dependable and efficient option for EV battery charging [26].

In conclusion, the CC/CV charging technique we chose for our EV battery is consistent with industry standards, battery chemistry needs, and the necessity for a controlled and efficient charging process. By using this charging algorithm, we can improve charging efficiency, extend battery life, and ensure the safe and dependable operation of our EV.

EV Discharging Methods

In addition to charging, understanding the different discharging methods of EVs is also important for designing efficient and reliable energy storage systems. EV discharging methods are classified into two categories: passive discharging and active discharging.

Passive Discharging

The most basic type of EV discharging is passive discharging, which occurs while the car is parked and the battery is not being charged. Natural self-discharge and parasitic loads, such as the vehicle’s electronic systems and alarm systems, cause the battery to drain over time. The rate of passive discharging is affected by several parameters, including battery chemistry, temperature, age, and state of charge.

Active Discharging

Active discharging is a deliberate and controlled method of discharging the EV battery to power external loads or systems. Active discharging is further classified into two types:

Vehicle-to-Load (V2L) Discharging

Vehicle-to-load (V2L) discharging is a technique for using an electric vehicle’s battery to power external loads or systems such as household appliances, emergency equipment, or electric tools. V2L discharging necessitates the use of a bi-directional charger capable of both charging and discharging the battery. In emergency scenarios, power outages, or off-grid applications, V2L discharge might be advantageous.

Vehicle-to-Grid (V2G) Discharging

Using the EV battery to discharge energy back into the grid during times of high demand or to maintain the grid frequency is known as “vehicle-to-grid” (V2G) discharging. A bi-directional charger and a communication infrastructure that can link the EV to the grid are necessary for V2G discharge. Both the EV owner and the grid operator may benefit from V2G discharging, which can lower peak demand, boost grid reliability, and pay the EV owner.

Factors Affecting Charging and Discharging

Several factors can affect the efficiency, reliability, and safety of EV charging and discharging. These factors can be classified into three categories: vehicle-related factors, infrastructure-related factors, and environmental factors.

Vehicle-Related Factors

Vehicle-related factors refer to the characteristics and condition of the EV and its battery, such as:

• Battery capacity: The EV’s range, charging time, and discharging time are all impacted by how much energy the battery can hold and deliver.
• Battery chemistry: The type of battery chemistry impacts the battery’s charging and discharging properties as well as its performance, durability, and safety.
• Battery temperature: The battery’s operating temperature has an impact on the battery’s performance, durability, and safety as well as the rate of charging and discharging.
• Battery state of charge (SOC): The SOC of the battery impacts the rate of charging and discharging, as well as the range and performance of the EV. It reflects how much energy is remaining in the battery.
• Charging and discharging rate: The charging and discharging rate of the battery determines the speed of charging and discharging and affects the efficiency and safety of the EV [27].

Infrastructure-Related Factors

Infrastructure-related factors refer to the components and characteristics of the charging and discharging infrastructure, such as:

• Charging and discharging power: The speed of charging and discharging, as well as the infrastructure’s compatibility and safety with the electric vehicle and its battery, are all influenced by the power rating of the charger or discharger.
• Connector type: The kind of connector used in the infrastructure for charging and discharging affects how quickly and easily an electric vehicle (EV) can be charged or discharged as well as how safe and compatible the infrastructure is with the EV and its battery.
• Communication protocol: The manner in which data is exchanged and controlled between the EV and the grid as well as the functionality of the charging and discharging processes are all impacted by the communication protocol utilised between the EV and the infrastructure.
• Grid integration: The integration of the charging and discharging infrastructure with the grid affects the reliability, stability, and sustainability of the grid, as well as the cost and revenue of the charging and discharging process [28].

Environmental Factors

Environmental factors refer to the external conditions and circumstances that can affect the charging and discharging process, such as:

• Temperature: The ambient temperature has an impact on the battery’s effectiveness, safety, and lifespan as well as the rate of charging and discharging and the range of the EV [29].
• Humidity: The amount of humidity has an impact on the infrastructure used for charging and discharging, as well as the corrosion and insulation of the parts.
• Dust and debris: The presence of dust and debris in the infrastructure used for charging and discharging can have an impact on the effectiveness and safety of the procedure as well as the component lifespan.
• Weather and climate: Both the range and efficiency of EVs as well as the accessibility, availability, and dependability of the infrastructure for charging and discharging can be impacted by weather and climatic conditions.

Charging and Discharging Protocols

Charging and discharging protocols are the communication protocols used to regulate and monitor the charging and discharging processes between the EV and the charging or discharging infrastructure. These protocols ensure the compatibility, safety, and efficiency of the charging and discharging processes, as well as the EV’s and infrastructure’s interoperability and reliability [30].

Charging Protocols

There are several charging protocols used in the EV industry, including:

• CHAdeMO: This protocol, which is widely utilised in Japanese and Korean EVs, is intended for DC fast charging. CHAdeMO provides a maximum power output of 62.5 kW and requires a unique connector as well as a communication protocol.
• Combined Charging System (CCS): A global standard for EV charging that combines AC and DC charging capabilities, CCS is a global standard for EV charging. CCS may produce up to 350 kW of electricity and requires a special connector and communication protocol.
• Tesla Supercharger: Tesla automobiles employ this technology for DC fast charging. The Supercharger can produce up to 250 kW of power and requires a particular connector and communication protocol.
• AC Level 1 and 2: These protocols are routinely used in home and public charging stations for EV AC charging. The maximum power output of AC Level 1 is 1.4 kW, while the maximum power output of AC Level 2 is 19.2 kW.

Discharging Protocols

Discharging protocols are used to govern and monitor the EV battery’s discharge, which is commonly accomplished through regenerative braking or vehicle-to-grid (V2G) systems. Among the most popular discharging protocols utilised in the EV are:

• CHAdeMO: CHAdeMO can also be utilised to charge an EV battery via V2G systems. The protocol offers bidirectional power flow and a maximum output of 60 kW.
• CCS: CCS can also be used to discharge an EV battery using V2G systems. The protocol offers bidirectional power flow and a maximum output of 350 kW.
• Open Vehicle to Grid Interface (OpenV2G): An open-source standard for V2G systems, this protocol provides for bidirectional power transfer and communication between the EV and the grid.

Challenges and Future Developments

While EVs have significant advantages over traditional internal combustion engine vehicles, some difficulties must be overcome before they can be widely used. In this section, we will address some of the major issues confronting the EV sector, as well as potential future innovations that may assist in overcoming these challenges [31].

Challenges

• Range anxiety: One of the most significant issues for EVs is range anxiety, which refers to the dread of running out of battery power before arriving at the destination. While EV battery technology has advanced greatly in recent years, most EVs’ short range continues to be a barrier to adoption.
• Charging infrastructure: The availability and accessibility of charging infrastructure continues to be an issue for the electric vehicle sector. Despite an increase in the number of charging stations in recent years, many places still lack adequate charging infrastructure to facilitate broad EV utilisation.
• Battery costs: The cost of EV batteries continues to be a substantial barrier to adoption, accounting for a considerable portion of total vehicle cost. While battery costs have been declining in recent years, further reductions are required to make EVs more accessible.
• Recycling and disposal: Recycling and disposal of EV batteries remains a difficulty because these batteries contain potentially hazardous components that must be disposed of appropriately to avoid environmental damage.

Future Developments

• Battery technology: new battery developments may be able to assist the EV sector in overcoming issues like battery costing and range anxiety. New battery chemistries being investigated by researchers include solid-state batteries, which have a higher energy density, a longer lifespan, and a faster charging time.
• Charging infrastructure: The development of quicker and more practical charging technologies, such wireless charging and ultra-fast charging, may aid in resolving these issues with charging infrastructure.
• Recycling and reuse: Developing more sustainable battery recycling and reuse techniques could help lessen the environmental effect of EV batteries while also improving their overall sustainability.
• V2G systems: Vehicle-to-grid systems, which allow EVs to sell excess energy back to the grid during peak demand periods, could help address the difficulties of charging infrastructure and battery costs.

In conclusion, while the challenges facing the EV industry are significant, many promising developments could help overcome these challenges and drive the widespread adoption of EVs in the future. Addressing these challenges will require a collaborative effort from industry, government, and consumers to ensure that EVs are a viable and sustainable transportation option for years to come.

While the EV industry has made significant strides in recent years, several challenges remain, such as range anxiety, charging infrastructure, battery costs, and recycling and disposal. However, promising developments in battery technology, charging infrastructure, and sustainability practices offer hope for the future of the EV industry.

To ensure the widespread adoption of EVs, it is essential to address these challenges and continue to invest in research and development to improve the performance, efficiency, and sustainability of EVs. Governments, industry leaders, and consumers must work together to support the growth of the EV industry and accelerate the transition to a cleaner, more sustainable transportation system.

In summary, the future of the EV industry looks bright, but it will require a collective effort to overcome the challenges and realize the full potential of these innovative vehicles.

Single Phase APFC’s Main Power Topology and Its Control Strategy

The fundamental concept behind power factor correction (PFC) is to use the power conversion capabilities of high frequency switching mode in order to get the form of the input current as near to a sinusoidal wave as possible, circuit configuration shown in Fig. 4. One of the more common strategies is to set the value that serves as the reference for the current to be one that is proportional to the voltage at the input. For this method, we will simply assume that the harmonic component of the input voltage is negligible and so has no bearing on the regulation of the harmonic current. The term “power factor corrector” refers to an independent component that is often responsible for making the necessary adjustments to the power factor of an electrical system. The power grid serves as the PFC’s input, and a DC voltage is typically output as the device’s output. The DC voltage will be the input of the DC-DC converter or the DC-AC current, and it will offer a reliable output for the next converter, which will make the DC-DC converter or the DC-AC converter an optimal design.

Fig. 4. (a) Full bridge rectifier circuit. (b) Input and output current before and after PFC operation.

Fig. 5. The voltage and current waveform.

Active Power Factor Correction (APFC)

In a linear circuit, the power factor is expressed using the cos $\mathrm{\phi }$ function, where $\mathrm{\phi }$ represents the phase difference between the sinusoidal voltage and sinusoidal current. Even though the input voltage is sinusoidal, the current that is rectified is not sinusoidal. This is because the diodes in the rectifier circuit are not linear. Therefore, the power factor calculation performed in a linear circuit cannot be used in an AC-DC converter because it is no longer valid. To express the power factor, we will utilise PF.

The definition is PF = active power/apparent power = P/V•I. In the equation above, V and I here are the rms voltage and rms current. We assume the input voltage vi (rms value is V) is sinusoidal, and input current is not sinusoidal, the rms of current is shown as follow:

(1) $$\begin{array}{r}I=\sqrt{I_1^2+I_2^2+\cdots +I_n^2+\cdots }\end{array}$$

In this equation, I₁, I₂, ..., I_n, are respectively the fundamental component, second harmonic, …, and Nth harmonic.

Because the input current has a terrible distortion and phase change, the definition of the power factor used in linear systems is not available anymore in switching power systems. We assume that current (I) lags Voltage (V) by phase θ as shown in Fig. 5.

(2) $$\begin{array}{r}P=V{I}_{1}coscos\theta \end{array}$$

(3) $$\begin{array}{r}PF=\frac{V{I}_{1}coscos\theta }{VI}=\frac{I_{1}coscos\theta }{I}\end{array}$$

And we know that: where I₁, I₂, ..., I_n are rms value of the fundamental component, second harmonic, …, and Nth harmonic. The equation above describes the relative magnitude of the fundamental current, which is called distortion factor. And cosα is called displacement factor, and the power factor equals the distortion factor times the displacement factor. When θ = 0, PF = I₁/I.

(4) $$\begin{array}{r}{I}_1/I=I_1/\sqrt{I_1^2+I_2^2+\cdots +I_n^2+\cdots }\end{array}$$

Therefore, the total harmonic distortion THD,

(5) $$\begin{array}{r}THD=I_h/I_1=\sqrt{(I_2^2+I_3^2+\cdots +I_n^2+\cdots )/I_1^2}\end{array}$$

I_h is the rms value of all the harmonic currents.

So, we can get the equation of distortion factor:

(6) $$\begin{array}{r}{I}_1/I=1/\sqrt{1+TH{D}^2}\end{array}$$

And when θ = 0,

(7) $$\begin{array}{r}PF=I_1/I=1/\sqrt{1+TH{D}^2}\end{array}$$

Principle of Active Power Factor Correction

The APFC circuit is composed of two parts: the main circuit, also known as the power circuit, and the control circuit. Both of these circuits are interconnected. It is clear by looking at Fig. 6 that the primary circuit is made up of a DC-DC converter as well as a single-phase bridge rectifier. And for reference voltage (Vo, ref), voltage error amplifier (Ve), multiplier (M), current error amplifier (CA), and pulse width modulator (PWM) are all components of a control circuit.

Fig. 6. Simple schematic of APFC under ACM control.

Now we will talk about the fundamental concept of PFC. The result of comparing the voltage at the output with the voltage at the reference point is then passed through the voltage error amplifier. The output of the voltage error amplifier and the rectified input voltage are both combined and sent to the multiplier. The output of the multiplier is what we use as the reference for the current feedback control. Following a comparison of the reference current with the current that was detected at the input, the result is fed into the current error amplifier, where it is used to control whether the switch S is on or off. As a result, if we can get the input current and the rectifier input voltage to be virtually in phase with one another while also reducing the amount of harmonic current, we will be able to raise the power factor and maintain a steady output voltage.

The Topologies of Active Power Factor Corrector

There are numerous different topologies for APFCs, but the most common ones are flyback converters, Ćuk converters, boost-buck converters, and boost-buck flyback converters. The most common type of APFC circuit is called a boost converter because it has various advantages over other types of APFC circuits. Among all APFC circuits, the Boost and Buck converters have the most fundamental topological structures. Other structures are created from these two structures. Now all that’s left to do is go over the specifications of the Boost, Buck, Boost-Buck, and Ćuk converters.

Buck Converter APFC

Buck converters are only able to buck the voltage because the inductor is activated when the switch is on Inductor L and capacitor C are connected in a series, shown in Fig. 7. The source has a discontinuous input current due to the fact that the switch S is turned off while Vac is present.as well as the inductor L and the conductor C being insulated Because of this, it reduces the effectiveness of the converter. It causes the input current to ripple at a high frequency. The source voltage is V_d while the switch is in the on position. However, the source voltage remains unchanged when the switch is off. is 0. Therefore, in the event that the input voltage is high, we are going to require a particular floating drive for the switch because the voltage at the source is float. As a consequence of this, it makes the circuit design more complicated. We are unable to use the buck converter for APFC because it can only be used to buck voltage. immediately, due to the fact that the source voltage V_d, after being rectified by, has a waveform that is half sinusoidal the reversal of the complete bridge. Therefore, the fluctuation range of V_d for a source that produces 110 VAC is from 0 to 155.56 V. When the input voltage V_d is lower than the output voltage V_d the converter is unable to function properly. It prevents a rise in the power factor from occurring.

Fig. 7. Buck converter-based APFC circuit.

Boost Converter APFC

(1) When the boost converter is the main circuit of the PFC, it is only able to increase the voltage to ensure that the PFC circuit continues to function normally. When the switch S is turned on, the inductor L gets charged, and when the switch S is turned off, L gets discharged, Fig. 8.

Fig. 8. The boost converter based APFC circuit.

(2) The AC input current and the inductor current are always the same, and this ensures that the input current is continuous. Continuous input current comes with its own set of benefits when it comes to the implementation of large-scale DC-DC conversion as well as power factor adjustment. When the input current is continuous, the ripple current is low, which means that there is less of a need for the filter circuit to do the processing.

(3) The switch is simple to manipulate since the voltage at the switch’s source is always zero. This makes the switch very easy to control.

Buck-Boost Converter APFC

(1) If we use a Buck-Boost converter as the primary PFC circuit, we are able to either buck the voltage or boost the voltage, circuit configuration shown in Fig. 9. This allows us to circumvent some of the challenges that arise when we only have access to a buck converter or a boost converter.

Fig. 9. The buck-boost converter based APFC circuit.

(2) The current that flows via the source’s input is discontinuous, just like the current that flows through the Buck converter; this is because the input is also a Buck converter. As a result, the requirements for the filter circuit became more stringent.

(3) If we are going to use a Buck-Boost converter as the primary PFC circuit, we will require two switches, one of which will be for drive control. Therefore, the circuit is more difficult to understand.

Ćuk Converter APFC

(1) The current flowing through the inductors L1 and L2 is continuous regardless of the position of the switch S, and the current flowing from the input source is always equal to the current flowing through the inductor L1, circuit configuration shown in Fig. 10. Additionally, this function is identical to that of the Boost converter.

Fig. 10. The Ćuk converter based APFC circuit.

(2) If we raise the value of the inductors L1 and L2, we will be able to reduce the ripple current significantly. Therefore, we do not require an additional EMI filter, and the devices can be made more compact.

(3) The UK converter functions similarly to a Buck-Boost converter in that it may either buck or boost the voltage.

Different Control Strategies of APFC

In real-world applications, we make use of a variety of control techniques, depending on the particular APFC topologies involved. In order to achieve PFC, regardless of the APFC architecture that we choose to use, we will need to take control of the following two variables:

• The output voltage must be a steady DC value and for which we are responsible.
• The input current needs to be made to follow the input voltage at the same frequency and the same phase, and the input port needs to be made to have pure resistance.

As a result, the Voltage-Current double-loop feedback control technique is typically the one that is utilised for APFC. It may result in the PFC circuit becoming more difficult in some circumstances. Industry makes extensive use of the Boost converter because it possesses a great number of benefits, including the fact that it is simple to manage, that it has continuous input current, and that it has a minimal ripple current. Stabilising the output voltage and realising unit input power factor are the two objectives that need to be accomplished in order for us to be successful with the APFC technique. In addition, many alternative control strategies have been proposed by many different academics in order to satisfy the various criteria that are imposed by various circumstances. Here we discuss the three most commonly used control strategies.

Peak Current Mode Control

The control scheme is shown in Fig. 11, and it has a reference peak for the control circuitry. The switches are turned on and off to follow the reference signal.

Fig. 11. Peak current mode control inductor current waveform.

Hysteresis Current Control

The hysteresis current control mode is a straightforward control mode for the Boost PFC because it does not require an additional modulation signal, Fig. 12. In addition to this, we can achieve a broad current bandwidth and a rapid dynamic response. Because of the obvious drawback of this circuit, which is that the load has a significant impact on the switch, we will need to consider the lowest possible switching frequency while we are designing the filter. Additionally, the hysteresis bandwidth has a significant impact on the switching frequency as well as the performance of the system. In addition, as the value of the source voltage becomes closer and closer to zero, the difference between the two reference signals gets less and smaller. As a result, we will always need some sort of compensation for this circuit.

Fig. 12. Hysteresis current control inductor current waveform.

After detecting the current flowing through the inductor, we compare it with the two current signals serving as references. The following describes the control strategy:

• When the switch S is turned on, the inductor L will begin to charge, and the current that is detected in the inductor will be compared with the signal that is received from the upper bound reference current loop. When the current in the inductor reaches the upper limit, the trigger logic control will turn off the switch S, and the inductor will begin discharging.

• The switch will be activated by the trigger logic control when the current through the inductor drops below the lower bound, at which point the inductor L will begin to be charged.

In this control mode, the amount of time that switch S is conducting current is always the same, while the amount of time it is off fluctuates. Therefore, the switching cycle does not remain the same. The magnitude of the ripple, which can be proportional to the instantaneous average current or remain constant, is determined by the bandwidth of the hysteresis.

Average Current Control

The variable in average current mode control is the average of the input current; as a result, it has a low THD and EMI; it is not susceptible to noise; it can function in both CCM and DCM mode; and the switching frequency is constant, which makes it suitable for high outputs, reference signal shown in Fig. 13. These advantages make average current mode control advantageous applications involving power. In addition, this control mode is the one that is utilised the most of the time in PFC.

Fig. 13. Average current mode control inductor current waveform.

Design of Power Circuit for the Charger and its Control Strategy

Mostly used electrical vehicle chargers are two stage means it comprised of a PFC circuit and a DC-DC converter for the charging of the battery, as shown in Fig. 14. The single-stage level 1 charging system seen in electric and hybrid electric vehicles served as the inspiration for the design of this system. This design makes use of a traditional PFC circuit, even though there are many different PFC topologies available on the market today.

Fig. 14. Conventional boost PFC topology.

The purpose of the power factor correction (PFC) circuit in the system is to stabilise the voltage at the DC/DC stage while also correcting the power factor. In this particular design, the load is represented by a Li-ion battery in series with resistance.

Working Principle of the Boost Converter

The different operating modes are shown in Fig. 15, from 0-DT, as we can see from the figure shown, that during this period the switch (MOSFET) conducts and the diode blocks. So, due the current flow through the inductor, the inductor got charged and stores some energy.

Fig. 15. Boost converter (a) During time period 0-DT and (b) During time DT-T.

From DT-T, the gate pulse applied to the MOSFET is removed and the MOSFET goes into blocking state and the diode starts to conducts, during this interval of time the inductor releases it energy and the load consumes it. The relevant waveforms for these modes are shown in Fig. 16.

Fig. 16. (a) Triggering pulse of switch, current and voltage waveforms of inductors in (b) CCM operation and (c) DCM operation.

By applying KVL for the two time periods as shown above, the voltage across the inductors in the two cases can be written as follows:

(8) $$\begin{array}{r}0-DT:V_L=V_{in}\end{array}$$

(9) $$\begin{array}{r}DT-T:V_L=V_{in}-V_{out}\end{array}$$

Apply volt-second balance:

(10) $$\begin{array}{r}{\int }_0^T{V}_{L}d=0\end{array}$$

(11) $$\begin{array}{r}{V}_{in}DT+(V_{in}-V_{out})(T-DT)=0\end{array}$$

(12) $$\begin{array}{r}{V}_{in}D+(V_{in}-V_{out})(1-D)=0\end{array}$$

(13) $$\begin{array}{r}{V}_{in}D+V_{in}-V_{in}D-V_{out}+V_{out}D=0\end{array}$$

(14) $$\begin{array}{r}{V}_{in}=V_{out}-V_{out}D\end{array}$$

(15) $$\begin{array}{r}{V}_{out}=\frac{V_{in}}{1-D}\end{array}$$

The Advantages and Disadvantages of Boost APFC

Advantages

1. There is no break in the input current, and both the EMI and the THD levels are quite low.

2. Because it already incorporates an input inductor, it reduces the need for an additional input filter. The input inductor has the ability to shield the primary circuit from the high frequency transient impulse that is derived from the power grid.

3. The peak of the output voltage is higher than the input voltage at its highest point.

4. The highest voltage that can be found across the transistor switch S is lower than the voltage that is produced.

5. The switch can be controlled with little effort, and there is no change in the potential of the source.

6. It is able to function correctly throughout a broad spectrum of voltage and frequency.

Disadvantages

1. The input and the output are not separated in any way by an insulating barrier.

2. Under the conditions of 25–100 kHz PWM frequency, there will be an overvoltage if there is stray inductance in the loop that is made of the switch S, the diode D, and the output capacitor C. This overvoltage will occur. Because of this, switch S should not be used. The boost APFC circuit is often utilised for power levels ranging from several hundred to several thousand watts.

Circuit Design Specifications

a. Maximum output power Po: 2 kW.

b. AC input voltage: 220 VAC.

c. Frequency: 50 Hz.

e. Switch frequency f_sw:10 kHz.

Boost Inductor Selection [26]

The amount of the high frequency ripple in the input current is determined by the inductor, which consists of a winding and a magnetic core. The winding performs the duty of energy transmission, storage, and filtering, while the core is responsible for the role of filtering. The performance, efficiency, and function of the circuit, as well as the question of whether or not the effect of the inductor can be satisfied, are all directly influenced by the design of the inductor.

The current ripple is at its highest point when the input current is at its lowest value. Calculating the inductor when the minimum input voltage is present is necessary for us to do so in order to ensure that the input current ripple will be within the acceptable range in that circumstance [32]:

(16) $$\begin{array}{r}L\frac{\mathrm{\Delta }{I}_L}{D{T}_s}=V_{in}\end{array}$$

(17) $$\begin{array}{r}L=\frac{V_{in}D{T}_S}{\mathrm{\Delta }{I}_L}=\frac{V_{in}D}{f_s\mathrm{\Delta }{I}_L}\end{array}$$

In (16) and (17), L is the inductance, ∆IL is the inductor ripple current, Ts is the switching period and D is the duty cycle.

Calculating the peak of maximum input current: b-The maximum inductor current ripple that is permitted is generally set to be 20% of the maximum peak inductor current: c-At last, we can calculate the value of the boost inductor combining (17) and (19).

(18) $$\begin{array}{r}{I}_{PK}=\frac{\sqrt{2}{P}_{in}}{V_{in(min)}}=\frac{\sqrt{2}\times 2000}{220}=12.85\left(A\right)\end{array}$$

(19) $$\begin{array}{r}\mathrm{\Delta }{I}_L=0.2I_{PK}=0.2\times 12.85=2.57\left(A\right)\end{array}$$

(20) $$\begin{array}{r}L=\frac{\sqrt{2}{V}_{in(min)}\cdot D}{f_s\cdot \mathrm{\Delta }{I}_L}=\frac{\sqrt{2}\times 220\times 0.5}{10\times {10}^3\times 2.57}=6\left(mH\right)\end{array}$$

Output Capacitor Selection

When choosing the output capacitor, a number of factors, including the DC output voltage, the output voltage ripple [28], the hold-up duration, and the second harmonic current, are taken into consideration. The second represents the total current flowing through the output capacitor. The harmonic of the line current and the root mean square value of the switching frequency ripple current are both shown here. In most cases, we go for aluminium electrolytic capacitors because they have a long life, low leakage resistance, the capacity to tolerate big ripple current, and the ability to function throughout a broad range.

(21) $$\begin{array}{rcl}{C}_o& \ge & \frac{P_o}{2\cdot \pi \cdot f_{line}\cdot \mathrm{\Delta }{V}_o\cdot V_o}\\ & =& \frac{2000W}{2\cdot \pi \cdot 50Hz\cdot 10V\cdot 400V}=1591\mu F\end{array}$$

Diodes and Switch Selection

When the switch transistor is turned on, the diode performs a reverse cut-off, the current that is flowing through the transistor becomes the inductor current, and the voltage that is being produced across the diode in this configuration is the output voltage. The diode begins conducting current in the opposite direction when the switch transistor is turned off. The output voltage is determined by the voltage that is measured across the switch transistor, and the inductor current is determined by the current that is flowing through the diode.

Therefore, when choosing a power switch transistor and diodes, the rated voltage needs to be higher than the output voltage, and the rated current needs to be higher than the maximum inductor current. Both of these requirements must be met. We consider a margin of safety of 1.2 and 1.5 for both the voltage and the current, respectively.

Control Design for the PFC Converter

The boost converter is used for Power factor correction as well as charging of the battery in CC-CV mode. Therefore, PFC circuit has the function of rectification as well as the function of voltage and current stabilisation, which means that the rectification function requires the input power factor to be 1, and the voltage and current stabilisation function demands stable output voltage and current.

The cascaded dual path control loop is used in the proposed charger. The dual path is used to charge the battery in two different modes (constant current and constant voltage). The outer loop’s responsibility is to maintain a constant output voltage and output current the inner loop’s responsibility is to shape the input current such that it has a conventional sinusoidal waveform and the same phase as the input voltage. The block diagram of the control circuit is shown in Fig. 17.

Fig. 17. The control circuit of the charger.

Components of the Controller Circuit

Sine Template Generator

It generates a unity sine template (u_s) from the input voltage waveform. This sine template is multiplied with the error from voltage and current controller to generate reference for PFC current controller.

Current Controller

Current controller operates as outer loop of PFC controller as shown in Fig. 17 The battery input current (I_dc) comparing with desire reference value of voltage (I_d*) and that produces error signal and that error signal is providing to PFC PI controller.

Voltage Controller

As can be seen in Fig. 17, the voltage controller performs its duties within the PFC controller’s outer loop. When the voltage of the battery, V_o, is compared to the desired reference value of voltage, V_o*, an error signal is generated. This error signal is then sent to the PI controller, where P accounts for the present value of error, I account for the past value of error, and Iin* is the minimal value of the error signal current reference.

Mode Selector

The mode selector is used to switch the mode of charging from CC to CV. The SOC of the battery is used to select the mode.

PFC Controller

For power factor correction a PI controller is used as current controller it is designed such a way that it can track the rectified supply voltage to make current in phase with voltage waveform.

PWM Generator

A Pulse width modulator is used to generate the gate pulse for the MOSFET

Working on the Controller

The block diagram of the system in CC and CV charging modes are shown in Figs. 18 and 19.

Fig. 18. Block diagram of circuit operating in CV mode of charging.

Fig. 19. Block diagram of circuit operation in CC mode of charging.

In this part, the working of control loop in CV mode (Fig. 18) is explained. The current multiplier or voltage multiplier-based strategy for CCM and DCM are utilised in order to accomplish the goal of achieving unity in the PF control. The voltage error V_e (k) is calculated by making a comparison between the reference voltage V_dc^* (k) and the voltage that is sensed across the dc link V_dc (k). The voltage error V_w (k) at any instant “k” is represented as follows:

(22) $$\begin{array}{r}{V}_e\left(k\right)=V_{dc}^{\ast }\left(k\right)-V_{dc}\left(k\right)\end{array}$$

The voltage error V_e (k) is input into a proportional-integral (PI) controller in order to provide a regulated output V_c (k) as a result of the controller’s calculations. where k_p and k_I are the proportional gain and integral gain of the PI controller for the voltage, respectively. The reference current i_Li^*(k) is produced by multiplying the controller output V_c (k) by the unit template of supply voltage u_s (k) in the manner described below: where u_s (k) is the unit template of supply voltage, and v_s (k) indicates the amplitude of supply voltage at any moment k. In order to create the pulse width modulation signal for the PFC converter switch (SW1), the reference current I_Li^*(k) is compared with the measured input current i_Li (k).

(23) $$\begin{array}{r}{V}_c(k)=k_P{V}_e+k_I\int V_e\end{array}$$

(24) $$\begin{array}{r}{u}_s(k)=\left|\frac{v_s(k)}{V_m}\right|\end{array}$$

(25) $$\begin{array}{r}{i}_{Li}^{\ast }\left(k\right)=u_s{V}_c\left(k\right);i_{Li}^{\ast }\left(k\right)=u_s{I}_c\left(k\right)\end{array}$$

The current error I_e (k) is calculated by making a comparison between the reference voltage I_Li^* (k) and the voltage that is sensed across the dc link I_Li (k). The Current error I_e (k) at any instant “k” is represented as follows:

(26) $$\begin{array}{r}Ie\left(k\right)=I_{Li}^{\ast }\left(k\right)-I_{Li}\left(k\right)\end{array}$$

This error is then processed through a PFC PI controller and the duty cycle d is generated and given to a pulse width generator and given to the switch.

The constant current (CC) mode or the constant voltage (CV) mode is chosen and utilised in accordance with the level of charge that is present in the battery. The charging cycle of a Li-ion battery (or a comparable battery) consists of a CC mode and a CV mode. CC stands for constant current, and CV stands for constant voltage. As can be seen in Fig. 1, the design of the control block incorporates not one but two different feedback channels, which are there to reflect the two different modes. In the CV mode, the voltage of the battery is regulated by a single feedback line. In order to properly regulate the loop, the obtained voltage is compared to the reference voltage. In CC mode, the current drawn from the battery is kept under control through a second feedback loop. One technique at a time is put into action by means of a mode selector block, and this block’s selection is determined by the level of charge in the battery.

Simulation and Results

According to the specifications given in Table IV, we use Simulink to build the circuit and run the simulation. The power circuit is the conventional boost converter that delivers power to the battery. The control circuit consists of an internal current loop to perform power factor correction and two external loops for the constant voltage charging and the constant current charging. The two loops are connected together by a multiplier. To perform charging operation a Li-ion battery is used whose specifications are given in Table V.

Table IV. Power Circuit Design Specification

S. no.	Parameters	Values
1.	Supply voltage	220 Vrms
2.	Supply frequency	50 Hz
3.	Switching frequency	10 kHz
4.	Max. rated power	2000 W
5.	Input inductor	6 mH
6.	Output capacitor	1600 µF
7.	Load resistance	5 Ω

Table V. Battery Specification

S. no.	Parameters	Values
1.	Nominal voltage	48 V
2.	Capacity	100 Ah
3.	Max. battery voltage	55.87 V
4.	Internal resistance	0.05 Ω
5.	Nominal discharging current	43.47 A

The MATLAB Simulink model of the proposed charger with its components like the Power circuit, sine template generator, Voltage and Current controller, and mode selector are highlighted and shown in Fig. 20.

Fig. 20. Simulink model of the proposed charger.

Fig. 21 shows the contrast diagram of the input AC current and the input AC voltage waveforms. The input voltage signal is scaled by 1/2 so that it is easier to compare. From the figure, we can obviously see that the input current waveform is a standard sinusoidal waveform and is nearly the same phase as the input voltage waveform. The input current peak value is around 75 A, and the current ripple peak-to-peak value is below 5 A, which satisfies the design objective.

Fig. 21. Input current and voltage waveform.

Fig. 22 shows the contrast diagram of the Inductor current and the inductor voltage waveforms. The inductor voltage signal is scaled by 1/2 so that it is easier to compare. From Figure, we can obviously see that the inductor current is nearly the same phase as the input voltage waveform.

Fig. 22. Inductor current.

Fig. 23 shows the THD spectrum of the input current at 220V rms input voltage. through the power factor calculating component that I designed in the Simulink, the power factor is shown as 99.79%, which means the PFC circuit greatly improves the power factor of the circuit. The Total harmonic distortion in the input source current is 3.79% which follows the IEEE519 and IEC 61000-3-2 standards.

Fig. 23. THD spectrum of the input current at 220 V rms input voltage.

For the control operation PI controllers are used power factor correction, constant current charging, and constant voltage charging. The reference for the constant voltage and constant current PI controllers is selected on the basis of maximum discharging voltage and maximum discharging current of the Li-ion battery. The mode CC or CV operation is chosen by a switch block where the switch operates according to the SOC of the battery. If the SOC crosses 80%, then the mode of charging changes from CC to CV.

For the tuning (finding the gains for the proportional and integral controller) of the PI controller the PI tuning app in the Simulink is used.

The output current and output voltage waveforms are displayed in Figs. 24 and 25. The average output current is about 20 A and the average output voltage is about 55 V.

Fig. 24. The output (a) Terminal voltage, and (b) Load current.

Fig. 25. The battery State of the Charge Chart.

In Fig. 25, the first graph shows the state of charge shows that the battery is charging continuously from 40%. The battery is charged in constant current mode up to 40.01% of SOC after the battery is charged in constant voltage mode, we can see that up to 40.01% of SOC, the voltage is increasing and after that the voltage of the battery becomes constant.

Conclusion

In this paper, MATLAB/Simulink has been used to illustrate an enhanced single-stage EV charger with a DC-DC Boost converter that acts as an active power factor correction. The system that is being shown has a DC-DC boost converter and offers good power quality indices. The number of system components is decreased when only one DC-DC converter is used. With a constant state operating at 220 V rms utility grid power, the given system enables EV charging. Implementing a control approach employing a PI controller for source current waveshaping considerably enhanced the source current waveform. Source current is less affected by the presence of a filter capacitor at the diode bridge rectifier’s output. The applied control method also results in a power factor at the source side that is almost exactly at unity. Additionally, there is a larger degree of significant reduction in the source current distortion and THD Additionally, within the given input range, the power quality performance complies with IEEE 519 and IEC 61000-3-2 requirements. As a result, the technology described in this study provides a reliable EV charger with enhanced power quality.