Improvement of Internal Loop Controller for Unbalanced Control System based on Virtual Synchronous Generator

In the case of grid voltage imbalance, the virtual synchronous generator (VSG) can not suppress the unbalanced current output by the inverter and reduce the fluctuation components of the active and reactive power output by the inverter. Therefore, an improved control strategy of virtual synchronous machine under unbalanced network voltage is proposed, which can directly obtain active current and reactive current under different control targets without using positive and negative sequence dual current inner loop control structure, reducing the PI controller The number of makes the control is relatively simple. However, in the unbalanced situation, the active and reactive current components are alternating components, which can not be tracked without error with the traditional PI controller. Therefore, the traditional PI controller is improved. A discrete PI controller is proposed to track the alternating component. The results of MATLAB simulation verify the validity and effectiveness of the proposed control strategy.