Virtual Synchronous Control and Small-Signal Stability Analysis of a Receiving-End Converter in VSC-MTDC Systems

Abstract

With the increasing integration of renewable energy generation and power-electronic converter devices, voltage-source-converter-based multi-terminal direct current (VSC-MTDC) grids have attracted growing attention for long-distance transmission, asynchronous grid interconnection, and coordinated power supply. In such systems, the receiving-end converter plays a key role in delivering DC-side power to the AC system or load side, and its dynamic performance directly affects the stability of the receiving-end AC system. To enhance the inertia and damping support of receiving-end converters, this paper introduces virtual synchronous generator (VSG) control for a receiving-end grid-connected converter in a VSC-MTDC grid. A unified mathematical model including the LCL filter, VSG control, reactive power-voltage control, virtual admittance, and current inner loop is established. Based on the steady-state operating point in the synchronous rotating $d q$ reference frame, a 13-state small-signal state-space model is developed. Eigenvalue analysis and parameter scanning are then conducted to investigate the effects of virtual inertia, damping coefficient, and reactive power control parameters on system stability. Finally, the proposed model is verified by comparing the step responses of the MATLAB-based small-signal model and the Simulink electromagnetic transient model. The results show that the established model can effectively describe the dynamic characteristics of the receiving-end converter, and proper VSG parameter design can improve system damping and enhance grid-connected stability in the VSC-MTDC grid.