Control of Virtual Synchronous Generator with Improved Transient Angle Stability Under Symmetric and Asymmetric Short Circuit Fault

Implementation aspects of fault-ride-through (FRT) operation in voltage source converter with virtual synchronous generator (VSG) control are discussed in this paper. The phenomenon of voltage decline during fault periods is recognized to be intricately associated with the interplay between power angle movement and the trajectory of current saturation resulting from the application of current limiters. It is explained how the output reactive power is restricted once the current reaches its limit, thus rendering the manipulation of reactive power not unconditionally achievable. It is also revealed that preferably voltage support and robust transient angle stability can be attained by minimizing power angle movement and allowing reactive power to be naturally generated instead of explicitly specifying reactive power commands from the controller. Motivated by these findings, a novel FRT strategy is proposed to attain the desired FRT performance, which features a smooth transition between fault and normal states, non-invasiveness in the existing control loop, and independence from system parameters and fault detection. The proposed FRT strategy is applicable for both symmetric and asymmetric faults, and its effectiveness is verified on four types of short circuit fault, various grid condition, and an IEEE-14 bus system. A comparative simulation with a previous FRT strategy is conducted to highlight the advantage of the proposed method. Furthermore, the proposed strategy is also verified through the controller hardware-in-loop (CHIL) experiment.