A Current Limiting Method with Sequence-Separated Control Strategy for Modular Inverter System under Asymmetrical Short Circuit Faults

Modular inverter parallel systems are widely used in high-power power supply applications due to their redundancy. In this case, the power supply system generally needs to have fault ride-through ability to ensure power supply reliability. Therefore, current limiting strategies for short-circuit faults have been widely studied. This article first analyzes output characteristics of the modular inverter system under phase-to-phase asymmetric faults considering short circuit impedance. Then a current limiting strategy based on the separation of positive and negative sequence components is proposed. This strategy ensures that the current of fault phase reaches the expected limiting value while the nonfaulty phase can continue its working state. Compared to existing virtual impedance methods, the design of the control loop in this scheme is simpler, and in high current scenarios with multiple modules running, it can achieve tracking effect without static error for a given value. Finally, simulations and experiments verify the proposed strategy.