Impedance Analysis of Virtual Synchronous Generator-Based Vector Controlled Converters for Weak AC Grid Integration

Voltage source converter (VSC) based high-voltage direct current (hVDC) system is an emerging technology in high-power applications. Previous research has shown that VSCs, with commonly used vector current control (VCC) technique, cannot transmit more than 0.4 p.u. of active power when connected to a very weak ac grid. This paper presents a virtual synchronous generator (VSG) control strategy integrated with VCC to allow stable power transfer for very weak ac grid integration. Impedance analysis is used to analyze the designed controller in various scenarios. In addition, sensitivity analysis is performed to study the effect of virtual inertia gains on system stability. Time-domain simulation results using MATLAB/Simscape Power System toolbox show the effectiveness of the developed controller in very weak ac grid integration of VSC-hVDC systems.