PWM CONVERTER WITH CAPACITIVE IMPEDANCE CONNECTED IN PARALLEL AT AC POWER SUPPLY SIDE

摘要

PROBLEM TO BE SOLVED: To reduce the capacities of switching elements by controlling in such a manner that the equivalent circuits of a reactance series circuit and a PWM converter become a series circuit of resistive impedance and a capacitive impedance. SOLUTION: This PWM converter constitutes a reactance series circuit with external reactors 24 to 26 having an inductance Lt and external capacitors 27 to 29 having a capacity Ct. The external reactors 24 to 26 are for preventing short-circuitting current of a DC power supply due to the switching of the switching elements 16 to 21. Then for each series circuit, the values of the inductance Lt and the capacity Ct are determined in such a manner that a capacitive impedance occurs for the power supply frequency of AC power supplies 1 to 3, and that a short-circuit current of the DC power supply based on switching is restricted. In this way, the switching loss at the PWM converter section can be reduced greatly, and the switching element can be made into smaller capacity and higher efficiency.