Research on VSG Control Strategy for Energy Storage Microgrid Based on Virtual Impedance

  Introduction  In order to make the grid-connected power conversion system (PCS) for the energy storage microgrid has the same rotation and excitation characteristics as the synchronous generator, the virtual synchronous generation (VSG) control strategy is proposed in the grid-connected PCS control system for the energy storage microgrid.

  Method  In this paper, in view of the fact that the traditional VSG did not have the low voltage ride through (LVRT) capability, the virtual impedance reactive power control link of VSG was constructed to modify the voltage control input signal in real time and improve the support ability of system transient voltage drop. In order to obtain the amplitude and resistance inductance ratio of virtual impedance, LVRT operating conditions were divided into symmetrical and asymmetrical short-circuit failures of the line, and the positive and negative sequence voltage and current were studied to obtain the virtual impedance parameters.

  Result  In order to verify the performance of the proposed control strategy, simulation is performed using Matlab/Simulink, and the simulation conditions are set as follows: three-phase grounding and single-phase grounding faults occur in the external transmission line of the energy storage microgrid respectively.

  Conclusion  The simulation results show that the introduction of virtual impedance into VSG control system can improve the output voltage of the grid-connected PCS for the energy storage microgrid in case of short circuit, play the role of voltage transient support during LVRT, make the energy storage microgrid has LVRT capability, and provide guidance for practical application.