Current-Limiting Strategy for Asymmetric Short-Circuit of Three-Phase Inverter for Continuous Power Supply of Nonfaulty Loads

The short-circuit fault ride-through capability of the inverter directly affects the reliability of the independent power supply system under short-circuit faults. Many existing short-circuit current-limiting strategies of three-phase inverters only ensure that the inverter outputs the fault current to trip the faulty branch circuit breaker during the fault period. This leads to interruption of power supply in the nonfaulty loads in the system. In order to improve the reliability of power supply during system fault ride-through, a short-circuit current-limiting control strategy is proposed. Compared with the existing strategies, this strategy has the advantages of fast current-limiting response speed and simple control structure. When asymmetric faults occur, the proposed control strategy fully utilizes the power output capability of the inverter to maximize the output faulty phase current and ensure reliable power supply to nonfaulty loads. In addition, the strategy can adaptively change the phase angle between the faulty and nonfaulty phase inductor currents. This can enable the inverter to always meet the system power supply and current-limiting requirements with good robustness when critical sensitive loads are cut off from the system. The experimental results verify the correctness and the effectiveness of the proposed strategy.