A Smooth Recovery Method for Asymmetrical Load Short-Circuit Fault of Three-Phase Three-Wire Inverters

The three-phase inverter usually needs to feed multiple loads simultaneously, which requires high reliability of power supply. When a branch in the load network experienced a short-circuit fault, the inverter should have the ability to limit the fault current and provide enough current to cooperate with the breakers to disconnect the faulty branch, and then the inverter output voltage needs to rise to the rated voltage quickly to resume normal power supply to other healthy loads. However, the output voltage recovery process after clearing the fault is prone to overvoltage phenomenon. To solve the above problem effectively, this paper analyzes the mechanism of overvoltage in the fault recovery process, then proposes a smooth recovery method by adding the parallel virtual impedance, and analyzes the design process of virtual impedance. Finally, the effectiveness of the proposed method is verified by the experimental results.