A Parameter Alternating VSG Controller of VSC-MTDC Systems for Low Frequency Oscillation Damping

The virtual synchronous generator (VSG) has been widely applied for mimicking the dynamic performance of a synchronous generator (SG) by power-electronic interfaced power sources. When the VSG is implemented in VSC-based multi-terminal direct current (VSC-MTDC) systems, the impact of VSG on both ac- and dc-grid dynamics, i.e., the low frequency oscillatory (LFO) modes and dc voltage stability should be taken into consideration. This paper investigates the participation of the VSG controller in low frequency oscillatory (LFO) modes and the impact on dc voltage stability. The influence of VSG parameters on the system dynamics is investigated by the Singular Value Decomposition (SVD) analysis and modal analysis. A parameter alternating VSG (AVSG) controller is proposed to improve the damping performance to LFO modes and mitigating the negative impact of VSG on dc voltage stability. The effectiveness of the proposed AVSG controller is validated according to the non-linear simulations on two test systems.