Coordination and Control Strategies of a Hybrid AC/DC Microgrid

Coordination and Control Strategies of a Hybrid AC/DC Microgrid

Overview of Hybrid AC/DC Microgrid

• System Components: The hybrid AC/DC microgrid comprises a solar photovoltaic (PV) panel, a boost converter, DC load, a battery storage system with a bidirectional converter, and an AC system connected through a voltage source converter.

• Integration: The DC bus is connected to the AC system through a main converter, allowing bidirectional power flow between DC and AC microgrids.

Implementation and Simulation

• Block Diagram: The system is modeled using MATLAB/Simulink, which includes components like a boost converter, solar PV panels, and a wind turbine with a double-fed induction generator (DFIG). The AC grid setup includes an AC load and power measurement tools.

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• Power Ratings:

  • Battery: Nominal voltage of 300V, capacity of 400Ah, and a state of charge of 71%.

  • DC Load: Power requirement of 15kW.

  • Solar PV: 15 parallel panels, each with a rating of 228W and voltage of 29.9V, with varying power outputs based on irradiance levels.

Control Strategies

• Boost Converter and Inverter Control: The boost converter uses a Perturb and Observe (P&O) algorithm, while the inverter utilizes a Direct-Quadrature (DQ) control method. This includes generating reference voltages and currents for optimal performance.

• Battery Management: Battery charging and discharging are controlled based on the solar PV output and irradiance variations. The system switches between charging and discharging modes to maintain efficient energy supply.

Power Flow and Load Management

• Wind Turbine: The DFIG turbine’s power rating is 45kW with a generator rating of 4kW. The wind speed varies, affecting the power output and grid interaction.

• Load Distribution: Both AC and DC loads are continuously supplied by the hybrid microgrid. Power measurements and load management ensure consistent energy delivery despite changes in solar irradiance and wind conditions.

Results and Observations

• System Performance: Initial power from the grid was negative, indicating energy supply from the DC grid and wind generator. Power varied with wind speed and solar irradiance changes, affecting grid power and battery state.

• Efficiency: The system adjusts to varying solar irradiance by shifting between battery charging and discharging states. This ensures the DC load receives a stable power supply.