Investigation on Energy Flow Performance of a Photovoltaic/Battery-Based Isolated Charging Station for Battery-Powered Electric Vehicles

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Introduction
In numerous industrial applications, hybrid PV modules and battery storage packs have been incorporated.Tis system is applied to electric vehicles (EVs), the grid, and standalone applications.Initially, the applications of this system are examined yearly to ascertain and close the gap in this paper.
Maintaining the common DC bus voltage within a reasonable range is essential for a charging microgrid to function.Te plug-in EVs (PEVs) are regarded as a power terminal of the system since they are a variable DC load and photovoltaic-based production is a no dispatchable (variable) generation.As a slack terminal, the electric station unit (ESU) (station battery) is in charge of balancing the power surplus/defcit brought on by power terminals and ensuring stable system functioning [1].When connected to a DC bus system, many elements (loads, energy storage devices, and renewable resources) work as intended, although there are challenges with maintaining consistent operation with renewable sources [2].As a result, appropriate controllers must be developed to achieve the best performance from solar arrays, energy storage systems, electric vehicles (EVs), and loads that are connected to DC buses.Te energy management system (EMS) of an electric vehicle is activated immediately using a hybrid PV/battery multisource power supply [3].PV serves as the major power source and battery serves as the secondary energy storage device in [4].By taking into account PV as a power source, lead acid battery as a storage device, and DC load, the charging process of PEVs is investigated for a DC microgrid using I-V and average SMC techniques.For the purpose of delivering continuous charging and uninterruptible supply to the household loads, reference [5] covers the multimode operation of a photovoltaic (PV) array, a battery, the grid, and the diesel generator (DG) set-based charging station (CS).According to proven experimental data, the authors of [6] proposed EVCS for charging Carryall 6 EVs.Additionally, the EVCS or charger is installed to charge the majority of necessary hardware for the E-Scooter [7].
Te planning methodology for EVCS with better station location is included in the publication [8].A review of the location of EVCS and its impact on the network of distribution stations is provided in [9].A thorough analysis of EVCS, including the best sites, methods for sizing them, modelling, charging methodologies, transport networks, modes of transportation, data processing, sources of the various data types, and stakeholders, is given in [10].In [11], the authors present a grid-connected CS without any renewable source; only grid is used to supply energy to EVs without including V2G like our work.However, OGCS's control cannot maintain constant DC-link voltage without reactive power compensation.Te authors introduced FCEV dynamically which consists of HPS (fuel cell and ultracapacitor) to investigate the DC-link voltage [12].As conclusion, the results refect the correctness of proposed control system.Tis research [13] proposed multiobjective two-stage optimization for grid-connected EVCS which included the three main aspects, that is, economic, energy, and environmental.Te results show how the proposed method reduces the emission to 32%, and operation cost is reduced by 30%, and total energy consumption is reduced by 15%.
In [14], a comparison between conventional fuel vehicle and EV is presented including comparative items of energy consumption and CO 2 emission.Finally, the results show that the energy consumption of EV is less than conventional vehicle by 8 times and the CO 2 emissions from EVs are, at least, 10 times lower over a period of 15 years.In [15], a gridconnected electric vehicle charging station assisted by photovoltaic with battery pack is presented to manage all power sources of station for achieving the correct charging system under diferent irradiance conditions.Also, the authors considered the energy transmission cost and state of charge (SOC).In [16], the authors proposed a design model of grid-connected electric vehicle charging stations based on renewable energy sources (PV) to provide continuous charging for electric vehicles.Te research in [17] provided EMS for grid-connected electric vehicles in commercial area to manage the power among all station sources (PV, battery pack, and grid) for achieving maximum efciency and reducing operational cost.In [18], the authors proposed a novel confguration of of-grid fast EV charging station based on PV array of two design refectors to make the system more efcient.Te research in [19] presented all possible modes of operation of grid-connected EV charging station under current control bidirectional converters with vector control.In [20], the authors provided an optimized PV system for charging EVs in University of Technology Malaysia (UTM).
Te research in [21] introduced a grid-connected ultrafast EV charging high gain step-up SEPIC converter with three power switches and only two duty ratios.Also, it proposed the HSFNA-based MPPT tracker which provides fast convergence, accurate response, and minor complication.Te simulated and experimental results prove the correctness of the proposed ultra-fast charging system for EVs.Also, reference [22] presented a grid-connected PV system with new MPPT method (an adaptive TS-fuzzybased RBF neural network) for maximizing energy utilization with improved performance as compared to the conventional MPPT methods.Te authors in [23] proposed an inverter control strategy for single-stage grid-connected PV system (online CMPN-based AAFLC method) under varying operating conditions with rapid convergence velocity.Te real implementation of the proposed system is done using dSPACE real time platform, and the results show how the system performs efectively.Te work presented in [24] demonstrated the grid-tied PV system through the intelligent FPSO method for obtaining the maximum power from PV with experimental implementation using the interfaced dSPACE DS1104 with MATLAB/Simulink under variant ambient conditions.In addition to the modifed SVPWM-based ripple, the compensator generates the required gating signals to control the inverter with analysis only.Reference [25] provided ANFIS-PSO for rapid, maximum power, and zero oscillation tracking for MPP of grid-connected PV system.Te results show the efectiveness of the proposed method as compared to other methods.In [26], a grid tide of single stage of hybrid sources (PV and full cell) is presented based on Lyapunov function-based controller design to extract maximum power from hybrid renewable sources.Te results highlight the correctness of the presented method during the steady state and dynamic state compared to the conventional method.
For rapid charging EV/PHEV converters, the research in [27] reviewed bidirectional converters and provided comparisons between three comparable converters for this purpose.Finally, the authors claimed that high battery side voltage results in high converter efciency.Due to limitations, reference [28] selected low voltage battery packs for maintenance and safety reasons, compared three battery pack voltages (24 V, 48 V, and 300 V), and found that 48-60 V was the most promising option.Te research in [29] proposed semi-bridgeless AC-DC converters in the front end to accelerate charging with 400 V DC voltage in order to circumvent the limiting low power for residential use (level 1 and level 2) in North America.Te authors of [30] presented a grid-assisted PHEV/EV-based charging system (bidirectional converter).Tere are various charger kinds, and in this study [31], the authors provided an in-depth analysis of wireless EV charging systems and the various power electronics (PEs) designs.In [32], a grid-connected charging approach for EVs called the constant current constant voltage (CCCV) system is suggested with voltage-oriented regulation.With a CCCV profle, a novel resonant converter topology is proposed for charging EVs, and experimental fndings are also provided [33].Te study in [34] presents an 2 International Transactions on Electrical Energy Systems overview of battery charger basics, pulse charging, and CCCV for Li-ion batteries with realization of linear and switching circuits.Reference [35] focused on the creation of a charging system for electric vehicles (EVs), which supplies power to the battery of the EV under various charging situations using distributed energy resources (DERs), such as a PV array and a battery storage system.Although the BESS partially eliminates reliance on the grid, the authors in [36] ofered a design of the PV system for charging EVs with BESS and their converters in the Netherlands.Terefore, this study flls this gap, eliminating grid dependency, but in diferent places where peak sun hours (PSHs) (as in Egypt) are 10 hours year-round, a backup source is available on its own in case of unforeseen circumstances.Te EVCS of PV-powered-EVs is described in [37] to improve the advantages of employing renewable energy sources and decrease charging costs while lowering reliance on the grid.Te ICS to charge EVs using a diferent charging profle (CC charging profle), but small-scale power system for one EV, was also presented in the study presented in [38].However, using a large-scale power infrastructure, this work created an efective and secure CCCV charging profle.
Te power fow to the EVs under the fve operational modes is covered in this paper.Tese three power plants (the PV array, the EV's battery, and the station's battery) can interchange energy in all feasible ways.To handle the energy for that purpose, DC-DC converters are built and programmed.To utilize the sources for charging the vehicles with the greatest efciency and in the shortest amount of time, both voltage control mode and current control mode are used.Te suggested charging mechanism is validated through simulation in various operating scenarios.In Table 1, a comparison with similar studies is also noted.
Tis paper is organized as follows.Te power plants for the planned PV-battery-based charging station are described and modelled in Section 2. Te energy ratings of the PV and SS systems as well as the capacity of BEVs are used to determine the parameters of the buck-boost converter of PV, BEES, and PEVs in Section 3. In Section 4, each converter's control system, circumstances, and modes of operation are presented together with the power fow.Te simulation's performance evaluation and fndings are presented in Section 5. Section 6 introduces the paper's conclusion.

System Confguration with EV Connected to DC Bus.
As shown in Figure 1, the suggested system uses a battery as a secondary storage unit and PV as the primary power source.Another energy source is needed to make up for the photovoltaic source's infrequently available power output.A battery bank with sufcient power capacity is placed to give the system a constant power source in order to meet the fuctuating DC load needs.When the PV source produces more energy than it can store in the battery, the battery bank flls the gap.Likewise, when the PV source is unable to produce the necessary quantity of energy, the battery bank does so.
When the battery station is empty, the DC-link voltage is controlled by a cascaded buck DC converter in order to maximize the PV power.According to the described control system, a power buck-boost DC converter is used to charge and discharge the battery storage unit.Ten charging sockets, points, or outlets on the load side are intended to use buck-boost DC converters to charge EVs at various voltage levels.Electric vehicle batteries are often multiples of 72 V and 48 V. To prevent interruptions in the BESS's operation, two switches are utilized, as shown in Figure 2. One is directly linked to the DC link when the BESS is in the charging mode, and the other is connected to the middle of a cascaded buck converter when it is in the discharging mode.

Modelling of PV Array.
PV models are needed for design and simulation purposes.A particularly precise mathematical model [39] that is ideal for circuit modelling is the one depicted in Figure 3(a).Equations can be used to represent the PV mathematical model as indicated by the relations below.
where K i � 0.0017 A/C is the cell's short circuit current temperature coefcient, I sc is short circuit current of cell (A), and G is the solar radiation (W/m).Te impact of temperature variation and wind speed is neglected.

Modelling of Battery.
Lumped-parameter models are welcomed for the study of EV system integration, control, optimization, and the connectivity of EVs to of-grid charging stations.Te battery terminal and general properties and dynamics, such as voltage, current, temperature, and SOC, are of more interest in those investigations than the specifc electrochemical processes taking place inside the battery.In this work, the equivalent circuit model of the battery is used.As can be seen in Figure 3 ( In this model, no cooling system is considered (only natural air).
where SOC: current state of charge, SOC0: initial SOC, T: cell temperature, T ref : reference temperature, i b : battery cell current, and t: time.

Modelling of Buck-Boost DC-DC Converter.
Figure 3(c) depicts the buck-boost converter modelling circuit, with the inductor side representing the battery side and the other side representing the DC-link side.DC-DC converters for PV work in bucking mode, whereas those for BESS work in boosting mode during discharging and bucking mode during charging.Te latter mode is solely used for BEVs; V2G is not considered.In the parametric design stage for buck-boost converters, the input voltage range (V in− min and V in− max ), nominal output voltage (V out ), and maximum output current are required to compute the power stage.

Ratings and Parametric Design of Power Source, Energy Storage Units, and Converters
3.1.Load Estimation.For a given fve-battery pack of each BEV (72V − 240Ah) in parallel with another fve-battery pack of each BEV (48V − 150Ah), the total energy capacity of load is calculated as follows: 24.48 5 * 0.9 3 � 6.716 kW, (7) where T ch is the proposed charging time, η pv is the PV converter efciency, η dc is the DC converter efciency, and η BB is the buck-boost converter efciency.For rating of the PV module of 120 W, the number of the PV modules (N pv ) for the two battery vehicles is calculated as follows: So, there are 56 PV modules connected in parallel at rated voltage of 126 V and rated current of 0.95 A for the two BVs.Te total number of the PV modules for the CS (N pv tot) is calculated as follows:

Component Sizing of Battery Station.
Te station battery pack capacity E bs of each (72V − 480Ah) � 34.56KWh is used as auxiliary/backup source with PV to charge BEVs.Note that all batteries are lithium-ion type.Each capacity of the two BEVs for the station Ebs and number of it could be calculated as follows: where N bs is the number of battery stations for two BEVs and E1bs is the energy capacity of one station battery.So, there are two BESSs where each one is (72V − 480Ah) in parallel to each other.So, the total number of battery station (N bs−tot ) for the overall CS is calculated as follows: Te ratings of load and each source (PV and BESS) are shown in Figure 2.

Design of Cascaded Buck Converter for PV System.
At MPP, the voltage is 126 V.As a result, we must lower it to the prescribed 1% ripple in output voltage and 20% ripple in output current, or the DC-link voltage of 100 V. To get the most power, the frst buck converter is employed, and the second one controls the DC-link voltage.As shown in equations ( 13)-( 15), the duty ratio, inductance, and capacitance of each buck converter are as follows: Te buck-boost converter uses L and C o at their maximum values because it can function in both modes.To lower switching losses, improve overall performance as an efcient converter, and support continuous current operating mode with the inductance value, the switching frequency F sw in this article is 5 kHz.As demonstrated in [40], the peak efciency decreases when the switching frequency is high.Te outcomes based on these laws with standards values are depicted in Table 2 and are indicated by the arrows above.

Power Flow and Modes of Operation with Conditions and Constraints
Tis study presents a suggested power control strategy for a PV charging facility.Te system's design consists of several PV panel strings connected to individual DC/DC converters that share a common DC side.Te fow of power during each of the CS's fve operational modes is depicted in Figure 2.

Modes of Operation.
Figure 4 shows the direction of power fow during fve modes of operation of the ICS.

Mode 1: PV Charges EV Battery Only.
In this mode, the 10 EVs are charged only from the PV system and the two switches are opened, as shown in Figure 4(a).Tis mode is chosen when one of the following conditions exists:  20)- (22), is true, this mode is selected.
4.1.3.Mode 3: PV Charges BESS Only.As indicated in Figure 4(c), the RB-EMS will select this mode if one of the following requirements is met as in equations ( 23)- (25).In Figure 4(c), one switch is open while the other is closed.
SOC bs < SOC bs−max , (24) 4.1.4.Mode 4: PV Charges BESS and EVs.Tis mode, in which the PV charges the BESS and BEVs under light load, is depicted in Figure 4(d).Its actions and circumstances are described by equations ( 26)- (28).In Figure 4(d), one switch is open while the other is closed.
P bs � P pv − P veh−rated . (28) 4.1.5.Mode 5: PV and Battery Storage Charge EVs.As seen in Figure 4(e), in this mode, the power produced by the photovoltaic system is less than the electricity needed to charge the EV's battery.While the BESS meets peak load demand, the PV system keeps charging the BEV.Te criteria for this mode are summarized in equations ( 29)- (31).In Figure 4(e), one switch is open while the other is closed.International Transactions on Electrical Energy Systems 7 SOC bs > SOC bs−min , (30) Table 3 lists the constraints that should be considered to guarantee the continuity of the station.P pv is the PV power, P bv is the battery vehicle power, and P bs is the battery station power.

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Te charging control method typically consists of two independent loops, a voltage loop, and a current loop, to implement CC and CV operation.Te voltage loop is positioned as an upper loop, which the PI controller generates when the condition is terminated (voltage reaches 74 V), and the lower loop is based on the diference between the desired charging current and the actual battery current as shown in Figure 6(c), which illustrates a typical charging control scheme.For limiting the generated voltage reference and current, the PI controller works in tandem with a saturation block.Te desired battery-charging curve with satisfed condition is obtained by feeding the diference between the desired current and the actual charging current to the PI controller in the current loop.Te PI controller then uses this information to generate a PWM signal to turn the corresponding power switches on or of.
A charging technique that uses CC frst and then CV is suggested based on the CV control method.Tis approach is an enhanced variant meant to address issues with CV charging, namely, battery damage.Te battery is charged using this enhanced approach at a specifc CC, and when the battery voltage reaches a specifc voltage value, the battery is charged using a CV.When the battery can handle large currents, this upgraded approach assures quick charging with CC, and it also ensures CV charging when the voltage is high and signifcant polarization is present, leading the charging current to progressively drop.However, the CC and CV values are crucial since they both have the potential to impact the battery's safety and lifespan.

MPP Converter for PV.
In order to make the system operate efectively, the PV modules' maximum power is harvested in this process by applying the P&O algorithm to the PV voltage, current, duty ratio, beginning value, maximum ratio, and minimum ratio.As shown in Figure 6(a), an algorithm's output is a duty signal that is applied to the PV's buck converter switch.

DC-Link Voltage Regulation Converter.
By comparing the reference voltage to the real DC-link voltage and controlling the error with PI, the DC-link voltage is here regulated to 100 V.As indicated in Figure 6(b), the output of PI is applied to a limiter, which then takes the output of this action from a PWM generator and outputs it to a DC switch.

BS in Discharging Mode.
When the BS is operating in boosting mode, power from the BESS (72 V) fows to the DC (100 V).In the upper loop, the reference voltage (72 V) and the actual BS voltage are compared.Te error is then applied to the saturation block to limit the control signal that is controlled by PI.However, in the lower loop, the input of PI is error signal that is obtained from comparing the actual current with the reference current (72 A).Te control signal is then applied to limiter for the actual current to not exceed the limiting value as shown in Figure 6(d).

Characteristics Validation and Limitations of Power Plant.
Table 4 gives a list of the PV's simulation ratings and settings (datasheet with actual fgures for the PV model that was used in our project, including testing where 56 PV modules were utilized for each pair of 72 V and 48 V batteries).Tables 5-8 contain information about the battery specifcations based on simulations of the MATLAB LiFePO4 3.3v 1.1ah cell.10 International Transactions on Electrical Energy Systems Battery electric cars (BEVs) are charged using constant current/constant voltage (CCCV) and control voltage and SOC to prevent overcharging and deep discharging because battery voltage is dependent on SOC.Consider the efects of initial and end SOC as well so that the battery is always in a safe range.

Dynamic Performance of the Power Plants
5.2.1.Mode 1: "PV Charges Vehicles' Batteries".Te station battery is out of commission due to the mode state, as indicated in Figures 7(a) and 7(b), and the ten vehicle batteries begin charging from SOCs of 40% to 90% for 72 V vehicle batteries and for 48 V vehicle batteries, respectively.As depicted in Figure 8, the voltage of a 72 V car battery grows to 90% of its SOC when it is in charging mode (74 V).As seen in Figures 8 and 9, in CC mode, only the fve 72 V vehicle batteries achieve the setting value of 74 V, causing the vehicle batteries to draw the setting-limited current of 48 A. Once the control reaches the termination condition at 90% of SOC, the CV mode begins.Te voltage of the car battery restores to its nominal value in the of-charging mode since the internal resistance's voltage drop is eliminated.Te current changes back to 0 A. As seen in Figures 10 and 11, fve 48 V battery cars work similarly to fve 72 V battery vehicles in that they begin in the CC mode (30 A) and run until they reach the maximum voltage of 50.5 V, at which point they switch to the CV mode, and so on.
According to Figure 12, when the ten vehicle batteries are in charging mode, the output current of the PV is initially at its maximum value (peak period).Ten, after two batteries are fully charged at about 0.7 hours, the current slightly decreases and the PV voltage rises.At 1.2 hours, another two batteries are fully charged, and so on.In the of-charging mode, the current drops to 0 A and the PV voltage returns to the open circuit value of 164 V.As seen in Figure 13, the DC voltage increases somewhat during the of time while remaining constant at 100 V during the on period.At full charging, as depicted in Figure 14, the PV and vehicle battery's power changes are equal.Due to some of the vehicle batteries being fully charged, the power generated by the PV is reducing and charging mode is of.PV power and load power are both 0. Tis mode's efciency at peak load is roughly 88.54% after one hour.

Mode 2: "Station Battery Charges Vehicle Battery".
Te ten vehicle batteries start charging from SOCs of 40% to 90% for 72 V vehicle batteries and for 48 V vehicle batteries, respectively, as shown in Figures 15(a) and 15(b), logically validating the design.Te station batteries' SOC decreases because they are in discharging mode, as highlighted in Figure 15(c).Te PV is out of service due to the mode condition.Te charging rate for battery vehicles in CC mode is constant until they enter CV mode, as shown in Figures 16-19, where it changes.As can be seen in Figures 20  and 21, the station battery discharges in CC mode because it does not go beyond any set parameters and does not achieve the termination condition (Vs ≤ 72 V).Eventually, the voltage drops to its present SOC due to the positive discharging current and voltage drop.As depicted in Figure 22, the DC voltage increases somewhat when the charging system is turned of while remaining constant at 100 V  International Transactions on Electrical Energy Systems during charging.Figure 23 illustrates this in charging mode.Vehicle batteries and station batteries both experience power fuctuations.As the SOC of the battery rises, the power supplied by the BS decreases.BESS and BEV power is zero in of-charging mode.Tis mode's efciency at peak load is roughly 89.61% at 1 hour.

Mode 3: "PV Charges Station Battery". According to
Figure 24, the station battery begins charging at the lowest value (64%) and continues until the SOC reaches 90%.Te voltage and current of station batteries are under CCCV control, as shown in Figures 25 and 26, where the current is constant until the voltage reaches a specifc value of 74 V, at which point it enters CV mode until it is fully charged.Te CV period of the station battery pack is very short because it has a capacity that is twice that of the vehicle battery, despite the fact that they have the same voltage.As depicted in Figure 27, the PV's voltage and current are constant during the on period of charging until the batteries are fully charged one after the other.At this point, the voltage increases slightly, the current decreases in relation to the voltage, and at the of period, the voltage rises to no-load voltage (164 V).

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As depicted in Figure 28, during the charging phase, the DC voltage remains constant at 100 V, the reference voltage, and during the discharging phase, the voltage slightly exceeds its reference voltage (100 V).As seen in Figure 29, the station battery receives the power from the PV system as a result for this mode's conditions and constraints.Tis mode's efciency at peak load is roughly 86.86% at 1 hour.

Mode 4: "PV Charges Station and Vehicle Battery".
When there is little load, the PV can charge the battery pack at the station during the sun's peak hours.Te vehicle batteries charge from their lowest values to their highest values before stopping, as shown in Figures 30(a  on the internal resistance is removed and the current is zero in the of-charging mode, the voltage of the vehicle battery and the station battery lowers.As depicted in Figure 35, a signifcant current is initially needed to charge the batteries, and thus the PV operates at MPP. Next, the PV voltage is increased gradually, and the current remains constant while dropping, until the vehicle battery achieves its full capacity.A DC link is illustrated in Figure 36; voltage is at a constant value (100 V for the reference value).Te efect of a heavy load is depicted in the frst curve, which causes a drop in voltage.As can be seen in Figure 37, as soon as the station battery and vehicle battery SOCs are fully charged, the PV power starts to decline and eventually reaches zero.At one hour, this mode's efciency is around 89.52%.

Mode 5: "PV and Station Battery Charge Vehicle
Batteries".Te SOC of car batteries rises during charging from a minimum value of 40% to a maximum value of 90%, as shown in Figures 38(a   As seen in Figures 39 and 40, the voltage of the car batteries increases to 90% of their SOC, or 74 V and 50.5 V, respectively, while the charging mode is activated.Te car batteries initially draw the rated current during charging because their voltages (74 V and 48 V, respectively) do not exceed the limited voltage.Te current then steadily drops with constant voltage (CV), as illustrated in Figures 41 and  42.Just when the batteries reach their maximum SOC, the voltage of the battery recovers to its nominal value in the of-charging state because the voltage drop on the internal resistance is eliminated and the current drops to 0 A. As seen     International Transactions on Electrical Energy Systems voltage rises until the vehicle battery reaches 90% of its SOC; in the of-charging mode, the voltage returns to the open circuit voltage and the current decreases to 0 A. As seen in Figure 46, when the station batteries are working as a source to support the DC voltage, the DC voltage is constant at 100 V and more stable, and when the station batteries are not working as a source, the voltage slightly rises.As seen in Figure 47, the PV power and station battery power are added together to determine how much power is changing in the car battery.Because some of the car batteries' SOC reaches 90% before all are fully charged, the power provided by the PV and station batteries drops until it reaches zero.Tis mode's efciency at peak load is roughly 86.84% at 1 hour.

Efciency Calculation.
For each mode, the efciency can be calculated by dividing the output power (P o ) by the input power P in as highlighted in the following equation: Te calculated efciency for all modes is shown in Table 9.

Conclusion
In this research, a rule-based energy management approach for BEVs to manage the power fow in PV/BS-based CS has been developed with the proposed efective fexible cascaded converter to regulate the DC-link voltage and extract the possible maximum power from PV. First, parametric design and parameter selection are discussed in relation to the daily load needs.Te suggested system is then validated using appropriate control systems and modes of operation.Te simulation results are shown at the conclusion of this study, demonstrating that the second mode is the most efective mode and that the design was correct (station battery charges vehicle battery).Te future suggestion for this study is to improve the overall performance by using new control techniques and smooth mode selection.

Figure 1 :Figure 2 :
Figure 1: Schematic architecture for EV charging station: PV modules, standby energy storage battery, DC-DC converters, and batteries of EVs.

Figure 3 :
Figure 3: Te equivalent circuits of the charging station are as follows: (a) PV modelling circuit, (b) battery equivalent circuit, and (c) buckboost converter.
Buck-Boost Converters 4.2.1.Controls of a Plug-In Charger.Te controller of BS in discharging mode is ofered in another subsection, but this controller is exclusively for BVs and BS in charging mode, which the V2G does not consider.When the battery is fully charged, there is a decline in battery terminal voltage due to removable battery internal voltage drop, as shown in Figure 5. Te PHEV/BEV battery systems typically charge through two stages of operation: the CC mode and the CV mode.Te switching point for the charging mode is controlled by the charging termination voltage sent by the battery system controller as shown in Figures 6(c) and 6(d).As shown in Figure5(a), the charging current for a 72 V battery in the CC mode is 48 A for a 5-hour charging period, whereas in the CV mode, the charging termination voltage is 74 V. Additionally, the charging current for a 48 V battery in the CC mode is 30 A for a 5-hour charging period, while in the CV mode, the charging termination voltage is 50.5 V, as shown in Figure5(b).

Figure 6 :
Figure 6: Te four block diagrams of controllers of charging station are as follows: (a) MPP controller, (b) DC-link voltage controller, (c) block diagram of controller for charging battery, and (d) controller block diagram for discharging BS.

Figure 30 :Figure 29 :
Figure 30: SOC of batteries: (a) for station batteries and (b) for vehicle battery.

Figure 38 :Figure 40 :
Figure 38: SOCs of all batteries: (a) for 72 V battery vehicle, (b) for 48 V battery vehicle, and (c) for 72 V battery station.

Table 1 :
Comparison with related work.Studied (all details for 10 EVs at the same time and 30 EVs/day) International Transactions on Electrical Energy Systems mode.Te frst plug has a voltage level of 72 V for lithiumion battery vehicles, while the second plug has a voltage level of 48 V for similar lithium-ion battery vehicles.Tere are two distinct charging plugs/charging ports.As a result, there are two buck regulators for battery vehicles, and V2G is not considered.However, the boost mode occurs during the BESS's discharge, and the boost equations can be used to determine the design elements (L in , C in , C o ) of each converter.Te boost equations are displayed below.
) 3.4.2.Design of Converter for Battery Vehicle and Battery Station.Te converter can function as a buck or boost converter, charging or discharging, depending on the battery 6 DC buck converter is separated, and the BS only uses a buckboost converter in the discharging mode to supply the power needed to charge the EVs.Te battery station side DC/DC buck-boost converter controls the output voltage to charge the EVs.Te BESS keeps supplying power until the EVs are fully charged because that is how it is intended to charge them.In the fgure, one switch is open while the other is closed.When one of the circumstances listed below, as in equations ( ) 4.1.2.Mode 2: Battery Storage Charges EV Battery Only.Te photovoltaic system does not produce any power in this mode, as depicted in Figure 4(b), either because of insufcient radiation or unfavorable weather.Te PV's DC/

Table 4 :
Te datasheet of the PV module.

Table 9 :
22ciency calculation.pv is the power of PV as primary source, p bv is battery vehicle power as load, and p bs is the battery station power as backup source.22InternationalTransactions on Electrical Energy Systems P