Comparative Evaluation of Dynamic Performance of a Virtual Synchronous Machine and Synchronous Machines

Abstract

Increasing penetration of converter-interfaced renewable generation has led to significant operational challenges for power systems. Such challenges are mainly caused by the different capabilities and dynamic responses of the converters compared with synchronous machines, e.g. converters do not naturally provide inertia to the system and contribute limited fault level with very different fault characteristics. Virtual Synchronous Machines (VSMs) and Synchronous Condensers (SCs) are both considered as promising solutions to address the challenges in operating converter-dominated power systems. This paper presents comprehensive studies for evaluating and comparing the dynamic performance of VSM, SC and Synchronous Generators (SGs), under a range of grid contingency events, which include short circuit faults, frequency disturbances, voltage depression, etc. The studies aim to offer insights on the level of support VSMs can offer to the system as compared with SCs and SGs, and their advantages, potential issues and limitations that need to be considered for a wider application in the system. From the studies, it is found that the VSM can successfully ride through a voltage depression of 0.1 pu for 140 ms as part of the stability path-finder requirements of fault ride through. Furthermore, the VSM unit can have a comparable performance with SC and SG from the perspective of provision of inertial response. However, in terms of voltage step simulation, reactive power injection from the VSM is very low compared to SC and SG and the fault current characteristic of the VSM is controller depended and cannot inject high fault currents like SC and SG.