Experimental study on coordination of protection for low-voltage AC network in DC zonal distribution system

In the conventional AC low-voltage network of the shipboard power system, the overcurrent protection is implemented by the overcurrent protective devices and the time-current curves. The AC low-voltage grid gets power from the inverters in the DC zonal electrical distribution system (DC-ZEDS), which is a newstyle shipboard distribution system. The overcurrent output capability of inverters is limited, but the nearest utility protective devices need enough short-circuit current to clear the short-circuit fault immediately, therefore it is a problem to coordinate the inverters with the downstream protective devices in the shipboard AC low-voltage grid. The protection method for shipboard AC low-voltage grid in DC-ZEDS is discussed through three aspects, namely the main circuit topology of the inverter module, its control strategy, the setting and configuration of protective devices like circuit breakers and fuses. A simulation platform is built based on the PSCAD environment, in which an AC low-voltage network supplied by inverters is constructed, and related experiments are performed. Results from both simulation and experiments show that the proposed protection method is rational.