Research on Low Voltage Ride-through Control Strategy of VSG under Weak Grid Condition

In recent years, as the proportion of renewable energy in the grid increases, more adaptive grid-forming technologies for weak grid have been proposed, among which the Virtual Synchronous Generator (VSG) strategy is the most widely used. It provides a friendly grid-connected method for renewable energy sources, such as wind power and photovoltaic. However, traditional VSG is prone to be overcurrent and out of use during grid faults. In this paper, the static and transient characteristic of the VSG during symmetrical grid fault is analyzed based on its basic model. And then a Low-Voltage Ride-Through (LVRT) control method by improving the VSG power loop while combining the virtual impedance is proposed. Based on Matlab/Simulink, a simulation model of a microgrid with VSG grid-connected is constructed, and the effectiveness of the strategy proposed in this paper for limiting the transient and steady state overcurrent of VSG during fault, providing reactive power support, as well as maintaining the stable operation of the microgrid system is finally verified.