A Novel Low Voltage Ride Through Control Strategy Based on Virtual Synchronous Generator

As the popularity rate of distributed power sources continues to increase, the operational stability of the power grid is severely challenged. The virtual synchronous generator (VSG) technology has been extensively studied because it enables the inverter to imitate the operation mechanism of synchronous generators, which realizes the friendly connection of the distributed generation, and increases the stability of the power grid. However, the traditional VSG control strategy does not have the capability of low voltage ride through (LVRT). The current amplitude is likely to exceed the limit and it is difficult to provide controllable reactive power when the grid voltage drops. Therefore, this paper proposes an improved LVRT control strategy for VSG. The active and reactive power control loops of the VSG are improved and a modified current control loop is introduced to suppress transient current surge and provide reactive power support under symmetrical drop of grid voltage. In addition, the control strategy can realize flexible distribution of active and reactive power to meet the grid requirement during LVRT. Finally, the validity of the proposed strategy is verified by the simulation results.