An improved control strategy for photovoltaic storage VSG system

In the photovoltaic storage power generation system controlled by the traditional virtual synchronous generator (VSG), when the photovoltaic source power fluctuates, the energy storage device will charge and discharge frequently to suppress the fluctuating power. In order to decrease the charge and discharge frequency of the energy storage device and alleviate the dependence of the VSG system on the energy storage device, an improved control strategy for the photovoltaic storage VSG system is proposed. The relationship between frequency variation and DC voltage deviation of the system is studied. The virtual synchronous control unit based on DC voltage control frequency is designed to replace the active power frequency control unit of the traditional VSG, which achieves the maximum power grid connection and inertial support of the VSG system. The power control of the energy storage device is implemented based on the droop characteristic, which improves the flexibility of energy storage device power control. The DC voltage stability control scheme is designed to keep the voltage within a reasonable range when the system is working normally. The experimental results verify the effectiveness of the proposed improved control strategy.