A Novel Short Circuit Fault Ride Through Strategy Based on Adaptive Virtual Impedance for Voltage Source Inverter

Voltage source inverters (VSIs) are widely used in many important fields. In order to deal with short circuit faults, many fault ride through strategies have been developed. But they either have heavy distortion or need to switch the control mode, which reduces the reliability of VSI. To avoid these drawbacks, this paper proposes a novel short circuit fault ride through strategy based on adaptive virtual impedance. The strategy realizes fast current limitation by inserting virtual resistors controlled by a closed loop. Due to the use of virtual resistors, the VSI can avoid switching to a current limiting mode and always works in voltage control mode. This will bring the advantage of smooth fault ride through. Without any saturation block, it does not cause heavy distortion. In addition, the strategy needs no complicated calculation, and can be inserted to any voltage control loops easily. The performance and effectiveness of the proposed strategy are verified by experiments.