PV-VSG Control Strategy Suitable for Insufficient Active Reserve

When the sudden change of light causes the maximum photovoltaic output power to be less than the grid demand power, or when the grid frequency drops, the photovoltaic frequency modulation power demand exceeds the reserved standby power, which will cause the DC bus voltage to become unstable. In order to improve the grid-connection friendliness of photovoltaic power generation, the paper proposes a control strategy of virtual synchronous machine for additional control of active power droop with insufficient active power reserve. Firstly, the working principle of the virtual synchronous machine is presented, and the system instability is simulated and analyzed in the two scenarios of sudden reduction of illumination and grid frequency drop without additional control of active power droop; Then, an additional control strategy of active power droop based on DC voltage difference is proposed, and the active power additional control loop adaptively outputs additional power when the light suddenly changes and the grid frequency drops, so that the grid-connected power is always within the range of photovoltaic output power; Finally, the simulation verifies the accuracy of the proposed active power droop additional control strategy.