Low Voltage Ride Through Control Strategy for VSG Based on Power Angle and Current Regulation

In the high proportion of new energy grid connected systems, virtual synchronous generator technology is often used to suppress frequency fluctuations and provide voltage support. However, due to the external performance of VSG as a voltage source, VSG will face the risk of overcurrent under the Voltage sag of the power grid, which will impact on system security and stability. In addition, VSG should maintain synchronous operation with the power grid during major disturbances and fault recovery periods. When the voltage sag is deep, stability of transient operation of VSG is largely limited by the duration of the fault. To solve these problems, a VSG low-voltage ride through strategy is presented in this paper, based on reactive power synchronization, transient power angle control, and virtual impedance coordination. The method can suppress the steady state and the transient components of the current in the fault, so that the equipment over current can be avoided and the reactive current can be output. At the same time, the transient power angle control that triggers reactive power synchronization during low-voltage faults ensures synchronous operation during VSG faults. Use MATLAB/Simulink to test the validity of the VSG transient control strategy.