# A Photovoltaic-Powered Modified Multiport Converter for an EV Charger with Bidirectional and Grid Connected Capability Assist PV2V, G2V, and V2G

^{*}

## Abstract

**:**

## 1. Introduction

- An Adaptable Z-Source Inverter was developed for the PV-grid integration-based EV charging station.
- The capacitor used in the Z-network was split into two equal capacitors to enable the multiport charging option.
- This modified ZSI was validated in five modes: PV-grid/charger, PV-grid, PV-charger, grid–charger, and charger–grid.
- The experimental setup was developed with three charging ports for obtaining 250 W at each charger end, which cumulatively produces 750 W output across both chargers with an efficiency of 93.8%.

## 2. Modeling and Sizing of the Proposed Adaptable Z-Source Inverter Components

_{1}and S

_{4}are turned on in the first cycle to generate a positive output voltage, while switches S

_{2}and S

_{3}are closed in the next cycle to generate a negative output voltage. When all four switches are turned on during a cycle change, this is referred to as the “shoot-through state” (ST). In this situation, the output is continuous. When the output is discontinuous, the mode of operation is in a non-shoot-through state (NST); at this state, all four switches are in the OFF position.

_{1}and C

_{2}, which are split into two equal-rated capacitors to divide voltage. The AZSI for the multiport charging environment is depicted in Figure 1, and its equivalent circuit diagram is shown in Figure 2. The conventional capacitors C

_{1}and C

_{2}are replaced with four capacitors: C

_{1UP}, C

_{1LOW}, C

_{2UP}, and C

_{2LOW}. The charging station is powered by a PV system and a grid. The charging station is operated with a PV source and battery. When the PV generates power more than the charging demands, the surplus power is delivered to the grid.

_{R}is used between the PV and AZSI to restrict the reverse current to the PV from the battery and grid. Four H-Bridge Converters (HBCs) are used between the AZSI to grid and battery. The converters are built with MOSFET switches, and these switches are operated with PWM pulses.

_{L}) and the capacitor voltage (V

_{C}) across the switches and current can be written as Equations (1) and (2):

_{SW}and the duty cycle D

_{O}. The voltage across the capacitors is represented by Equation (3):

_{PN}is given as Equation (4):

_{g}is the AC voltage of the AZSI, grid voltage v

_{g}is V

_{g}sin$\omega t$, M is the modulation index, V

_{PN}is the dc-link voltage, and I

_{PN}is the dc-link current. The ZSI’s RMS output voltage can be expressed as Equation (7) and voltage across the capacitor as (8):

_{PV}is the PV voltage, V

_{PN}is the dc-link voltage, I

_{PN}is the dc-link current, M is the modulation index, and V

_{B}is the battery voltage. Maximum battery voltage and minimum PV input voltage are used to analyze the duty ratio of ST operation (voltage across the capacitors), as given in Equation (9):

_{Omax}is the maximum ST duty ratio.

#### 2.1. Inductor L_{1} and L_{2} Design

_{1}and L

_{2}are built with a peak-to-peak high-frequency current ripple considered as 10% or 20%. The values of inductors L

_{1}and L

_{2}can be designed using Equation (10):

#### 2.2. Capacitor C_{1} and C_{2} Design

_{C}represents the maximum permissible voltage ripple, and V

_{C}denotes the average voltage across capacitors V

_{C}

_{1}and V

_{C}

_{2}. The symbol ω (rad/s) represents second-order harmonics. For the proposed topology, the maximum capacitor voltage rating is at least twice as high as the peak voltage of the energy storage device clamped across it.

_{LB}(50 percent due to the parallel primaries sharing current and another 50 percent due to the duty cycle). Fifty percent of V

_{C}is the average recovered secondary voltage. The DC-DC converters are connected to the battery load through the parallel branch from the Z-circuit capacitors.

## 3. Modes of Operations

#### 3.1. Different Modes

#### 3.1.1. Mode-I (PV to Grid and Charger)

#### 3.1.2. Mode-II (PV to Grid)

#### 3.1.3. Mode-III (PV to Charger)

#### 3.1.4. Mode-IV (Grid to Charger)

#### 3.1.5. Mode-V (Charger to Grid)

#### 3.2. Controller

#### 3.2.1. PV-Battery Loop

#### 3.2.2. Grid-to-Battery Loop

#### 3.2.3. Battery-to-Grid Loop

## 4. Simulation Analysis Results

^{®}2016a software. A DC source was used as the PV source, with a maximum output voltage of 144 V DC. This source was connected to the AZSI circuit, constructed using MOSFET switches. The PWM technique was used to generate switching pulses with a frequency of 25 kHz. A H-bridge converter was linked between the AZSI and the grid, and the conventional ZSI capacitors were split into two equal capacitors to create a multiport charger. A high-frequency transformer with a winding ratio of 2:1 was connected across these two capacitors. The charger was linked to these three HFTs via the battery arrangement. This simulation was modeled with the necessary calculations for capacitors, inductors, and switching frequency using Equations (1)–(15).

- PV to grid and charger: In this mode, the PV system supplies power to the battery, and the excess power is delivered to the grid. The PV system generates a rated power of 1500 W power with a voltage of 144 V and a current of 10.32 A. The PV delivers 750 W power to the three chargers and 750 W power to the grid.
- PV to grid: In this mode, the charging stations are inactive, and the PV power generation is completely delivered to the grid. To provide power to the grid, the PV continues to operate at the rated power of 144 V and 10.42 A. The grid receives 230 V, and 63 A is provided to the grid.
- PV to charger: In this mode of operation, the PV generates half of the rated power, and the grid is operated on low demand. The PV-generated power is delivered only to the chargers. The three chargers are powered by Charger 1 at 47.9 V and 4.93 A, Charger 2 at 47.8 V and 4.86 A, and Charger 3 at 48.2 V and 4.87 A.
- Grid to charger: This mode supplies the power from the grid to the charging stations. The PV does not generate power, and the charging station is in demand. So, the grid delivers the power requirement to the charging station.
- Charger to grid: In this mode, it is considered that the PV is completely inactive, and the charging station is inactive. The grid operates at a high level of demand. The AZSI regulates the power stored in the battery to the grid to support it in supplying the maximum demand.

## 5. Experimental Results

_{PV}= 144 V, I

_{PV}= 10.42 A). The AZSI delivers the required dc-link V

_{PN}and I

_{PN}to the grid. At the same instant, it supplies 48.1 V, 4.65 A power to Charger 1 and 47.8 V, 4.79 A power to Charger 2 and 47.7 V, 4.74 A power to Charger 3 via the HBCs. The corresponding waveforms are shown in Figure 11. It shows the converter’s performance used for the PV-grid integrated EV charging station efficiently delivering power to the grid and battery with minimum losses and lower THD values. The losses associated with the Mode-I operation are calculated in the following section. Similarly, other modes: PV to grid, PV-charger, grid–charger, and charger to grid are validated as follows:

- Charger 1 receives power at a voltage of 47.9 V and draws a current of 4.93 A.
- Charger 2 receives power at a voltage of 47.8 V and draws a current of 4.86 A.
- Charger 3 receives power at a voltage of 48.2 V and draws a current of 4.87 A.

## 6. Loss Calculation

#### 6.1. Loss Calculation

_{A}, S

_{B}, S

_{C}, and S

_{D}are given as where R

_{1UP}, R

_{2LOW}, R

_{2UP}, and R

_{2LOW}are the resistances S

_{A}, S

_{B}, S

_{C}, and S

_{D}when they are in the on state, which can be expressed as Equations (24)–(27):

_{A}, S

_{B}, S

_{C}, and S

_{D}are expressed as Equation (28):

_{A}, S

_{B}, S

_{C}, and S

_{D}are given as Equation (30):

_{a}

_{1}, D

_{a}

_{2}, D

_{a}

_{3}, and D

_{a}

_{4}can be estimated with Equation (31):

_{d}is the resistance of the diode.

_{overall}and the output power P

_{out}, the total efficiency of the AZSI can be estimated using Equation (36):

#### 6.2. Stress Analysis

## 7. Conclusions

^{®}and constructed in an experimental setup. The charging station has three charging ports of 750 W load and is powered with 1500 W solar PV and the grid. The performance of the AZSI is validated under different modes of operation. In the first case, the PV supplies 1500 W to the AZSI, which delivers 678 W to the three battery charging ports and 739 W to the grid with an efficiency of 93.8%. Compared with the conventional ZSI, the proposed AZSI has enhanced efficiency and provides multiport charging options. The proposed AZSI has many advantages over the ZSI in terms of better efficiency, a simple control method, simple construction, and low cost. The inferences from the proposed AZSI pave the way for additional study into optimizing the AZSI architecture, examining scalability alternatives, measuring its performance in real-world scenarios, and incorporating advanced control and communication systems for seamless operation and grid integration.

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 3.**Various modes of operation: (

**a**) Mode-I (PV to grid and charger), (

**b**) Mode-II (PV to grid), (

**c**) Mode-III (PV to charger), (

**d**) Mode-IV (grid to charger), and (

**e**) Mode-V (charger to grid).

**Figure 11.**(

**a**) Capacitor voltage, (

**b**) inductor voltage and inductor current, (

**c**) grid voltage and current, and (

**d**) charger output voltage and current.

S.No | Parameters | Value |
---|---|---|

1. | Inductor value, L_{1} | 950 μH |

2. | Inductor value, L_{2} | 950 μH |

3. | Input capacitor, C_{in} | 220 µF |

4. | Filter Inductance, L_{f} | 7.6 mH |

5. | Switching frequency (AZSI), F_{SW} | 25 kHz |

6. | Switching frequency (HBC), f_{s} | 50 kHz |

S.No | Parameters | Value |
---|---|---|

1. | PV voltage, V_{PV} | 144 V |

2. | Grid voltage V_{g} | 230 V |

3. | Output voltage, V_{CH}_{1} | 48 V |

4. | Output voltage, V_{CH}_{2} | 48 V |

5. | Inductor value, L_{1} = L_{2} | 950 mH |

6. | Input capacitor, C_{in} | 220 µF |

7. | Filter Inductance, L_{f} | 7.6 mH |

8. | Switching frequency (AZSI), F_{SW} | 25 kHz |

9. | Switching frequency (HBC), f_{s} | 50 kHz |

10. | PV power output, P_{PV} | 1.5 kW |

11. | Battery rating, P_{B} | 250 W |

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**MDPI and ACS Style**

Gopalasami, R.; Chokkalingam, B.
A Photovoltaic-Powered Modified Multiport Converter for an EV Charger with Bidirectional and Grid Connected Capability Assist PV2V, G2V, and V2G. *World Electr. Veh. J.* **2024**, *15*, 31.
https://doi.org/10.3390/wevj15010031

**AMA Style**

Gopalasami R, Chokkalingam B.
A Photovoltaic-Powered Modified Multiport Converter for an EV Charger with Bidirectional and Grid Connected Capability Assist PV2V, G2V, and V2G. *World Electric Vehicle Journal*. 2024; 15(1):31.
https://doi.org/10.3390/wevj15010031

**Chicago/Turabian Style**

Gopalasami, Ramanathan, and Bharatiraja Chokkalingam.
2024. "A Photovoltaic-Powered Modified Multiport Converter for an EV Charger with Bidirectional and Grid Connected Capability Assist PV2V, G2V, and V2G" *World Electric Vehicle Journal* 15, no. 1: 31.
https://doi.org/10.3390/wevj15010031