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PV Based EV Charging with V2G and G2V Operations

PV-Based EV Charging with V2G and G2V Operations


We will explore the intricate model developed for a solar PV-based electrical charging system, integrated with a Vehicle-to-Grid (V2G) system under the Grid-to-Wheel (GTW) concept. This model encompasses a main grid with a rating of 124 megawatts, which steps down to 400 volts, and an EV battery connected to the solar PV grid via a bi-directional DC-DC converter. The aim is to maintain a constant DC link voltage and facilitate seamless power flow between the grid, solar PV system, and EV battery.



Main Components of the Model

  1. Main Grid: Rated at 124 megawatts and 34.5 kilowatts, stepped down to 400 volts.

  2. EV Battery: Connects to the solar PV grid via a bi-directional DC-DC converter, acting as a voltage controller.

  3. Bi-Directional DC-DC Converter: Regulates the DC link voltage around 470 volts, ensuring efficient power management.

  4. Control Mechanism: Utilizes a Proportional-Integral (PI) controller and Pulse Width Modulation (PWM) to control the converter.



Modes of Operation

Mode 1: Daytime Operation (PV to Battery/Grid)

  • Scenario: During the day, with PV power available and State of Charge (SoC) of the EV battery less than 95%.

  • Function: The solar PV power is used to charge the EV battery. If the SoC exceeds 95%, excess power is fed to the grid.

Mode 2: Vehicle-to-Grid (V2G)

  • Scenario: When PV power is insufficient, and the EV battery's SoC is adequate.

  • Function: Power is supplied from the EV battery to the grid.

Mode 3: Grid-to-Vehicle (G2V)

  • Scenario: When PV power is unavailable, and the EV battery needs charging.

  • Function: Power is drawn from the grid to charge the EV battery.

Detailed Operation and Control

The model operates based on real-time conditions and power requirements, ensuring optimal energy management through various control strategies. Here's a step-by-step breakdown:

  1. Voltage Control: The DC link voltage is maintained at 470 volts by comparing it with a reference voltage, processed through a PI controller.

  2. Power Flow Management: Depending on the SoC of the EV battery and PV power availability, the system switches between different modes of operation.

  3. Current Regulation: In each mode, the current reference values are adjusted to ensure efficient charging or discharging of the EV battery.

  4. Transformation and Decoupling Control: The grid-side voltage and current are converted into DQ form using transformation techniques. Feed-forward decoupling control is applied to manage the inverter output effectively.

  5. Inverter Control: The inverter is controlled based on the generated reference voltage, ensuring that the power is correctly supplied to or drawn from the grid.

Simulation and Results

The model is tested under various conditions to ensure its robustness and efficiency:

  • Daytime Charging: With the PV generating power, the EV battery charges until the SoC reaches 95%. Excess power is then fed to the grid.

  • V2G Mode: When PV power is zero, the EV battery discharges power to the grid. The simulation shows the grid receiving power from the EV battery with corresponding changes in SoC.

  • G2V Mode: When PV power is unavailable, power is drawn from the grid to charge the EV battery. The system transitions smoothly between modes, maintaining optimal performance.

Conclusion

This comprehensive model for a solar PV-based electrical charging system, integrated with V2G under the GTW concept, showcases the potential for efficient energy management in renewable energy systems. By seamlessly switching between different modes of operation, the system ensures optimal use of available power resources, contributing to a sustainable energy future.

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