Low-Voltage Ride-Through Control Strategy for a Virtual Synchronous Generator Based on Smooth Switching

Abstract

The grid-connected inverter with virtual synchronous generator (VSG) control technology can improve the friendliness of a distributed power supply to the power grid. However, its low-voltage ridethrough (LVRT) capability is insufficient, which results in difficulties in limiting the current and provide reactive power support. A new LVRT control strategy based on the smooth switching is proposed in this paper. In this strategy, the voltage source mode of VSG is transformed into current source mode to limit the output current and provide reactive power support through the proportional resonance current control algorithm under grid fault. Furthermore, the feedback tracking synchronization strategy of the phase angle is employed to realize the smooth switching between two modes. When the grid fault recovers, it can directly switch back to grid-connected operation mode through a delay module without an additional algorithm. The simulation results verify the correctness and feasibility of the proposed control strategy.