An improved output short-circuit protection for multilevel PWM rectifier

This paper describes an improved short-circuit protection method with a boost type rectifier using a multilevel AC/DC power converter. Since the output DC capacitors of the proposed scheme have ability to keep a floating state, the DC capacitors do not discharge even in case of short-circuit of a DC load. The output DC power of the proposed converter can be disconnected from the load within several hundred microseconds at the instant of short-circuit fault. Once the fault has been cleared the DC power is reapplied to the load. The rising time of the DC load voltage is as small as several hundred microseconds, and there is no overshoot of the DC voltage because the DC output capacitors hold undischarged state. Therefore, the proposed converter can be used for a power supply, which requires a rapid disconnection of the load from the power supply in the case of a short circuit, as well as a rapid connection the load to the power supply after the clearance of the short circuit condition. The converter, which employs the proposed method, has the characteristics of a simplified structure, reduced cost, weight, and volume compared with a conventional power supply, which has frequent output short-circuits. Experimental results are presented to verify the usefulness of the proposed converter