Evaluation and Improvement of Voltage Stability of the Paralleled Virtual Synchronous Generator and Current-Controlled VSC System

With the booming of renewables, power electronic converters have been increasingly connected to the power grid. However, when the power grid fails, the connection with the power grid should be quickly disconnected and switched to the island operation mode for improving the reliability of the power supply. The islanded system has more complicated issues with stable operation and power supply reliability. Aiming at the voltage stability problem of the islanded system, this paper firstly establishes a small-signal model of the islanded system in parallel with virtual synchronous generator (VSG) and current-controlled voltage source converter (CCS). The voltage stability of the system is evaluated and the stability boundary of the system is predicted, which guides further parameter optimization. Then the multi-objective particle swarm optimization algorithm is introduced to optimize the key controller parameters which have a great impact on the system voltage. Finally, the simulation results are given to verify the correctness of the theoretical analysis.