Short-Circuit Current of Grid-Connected Voltage Source Converters: Multi-Timescale Analysis Method

Grid-connected voltage-source converters (VSCs) exhibit very different short-circuit behaviors from synchronous generators (SGs). This paper analyzes the short-circuit current (SCC) of VSC, especially considering the typical vector control strategy and the transient control scheme during grid fault. The SCC characteristics are obtained in multi-timescale, including both AC current control and DC voltage control timescales. Further, a simple SCC expression is obtained similar to the sub transient and transient processes of traditional SG. In addition, the influences of different controllers' parameters and fault degree on the SCC characteristics are discussed. The analytical results are helpful to understand the stress distribution of power electronics devices and design of relay protection in power systems with high penetration of wind/solar power generations that are integrated into grid via VSCs.