Patent ID: 6351397
Filing Date: 2002-02-26
Classification: H02M,H02P

Abstract:
A protection apparatus of a PWM cycloconverter of a power converter wherein phases of a three-phase AC power supply and phases of the power converter for outputting M phases (where M is an integer of two or more) are directly connected by two-way semiconductor switches each consisting of a pair of one-way semiconductor switches for allowing an electric current to flow only in one way and being able to be turned on and off separately, said protection apparatus comprising:fault detection means for detecting a fault of the above-mentioned PWM cycloconverter; operation stop means for turning off at least some of the above-mentioned one-way semiconductor switches of the above-mentioned PWM cycloconverter if the above-mentioned fault signal occurs; continuous flow means for allowing a load current of the above-mentioned PWM cycloconverter to continuously flow if at least some output phases of the above-mentioned PWM cycloconverter become open; and protection switching means for turning on and off the above-mentioned one-way semiconductor switches of the above-mentioned PWM cycloconverter based on the fault signal output from said fault detection means, thereby allowing the above-mentioned load current to continuously flow into the above-mentioned three-phase AC power supply via the above-mentioned PWM cycloconverter, characterized in that said protection switching means comprises input voltage information detection means for recognizing voltages of three terminals of input side of the above-mentioned two-way semiconductor switches as three-phase input voltages and detecting information based on which greater-than, equal-to, less than relation of the above-mentioned three-phase input voltages can be-determined as input voltage information; and regenerative switching means for turning on only the above-mentioned one-way semiconductor switch from each output phase to an input phase which becomes the maximum voltage of the above-mentioned three-phase input voltages or only the above-mentioned one-way semiconductor switch from an input phase which becomes the minimum voltage of the above-mentioned three-phase input voltages to each output phase based on the input voltage information.