ELECTRICITY CONVERSION DEVICE

摘要

Provided is an electricity conversion device in which an electricity converter allows either three-level or two-level operation by switching AC switches on or off, said AC switches formed by two valve devices that are serially connected between connection points of valve devices of each respective arm and connection points of DC power sources, and each of said two valve devices comprising a semiconductor element and a diode connected to the semiconductor element in reverse parallel. The electricity conversion device comprises: a comparison circuit (9) that treats the direct current that is inputted into the electricity converter as a determination element, compares same with a switching reference value, and outputs a determination instruction if there is a disparity therebetween; a determination circuit (11) which, when the determination instruction is received from the comparison circuit (9), determines the magnitudes of the determination element and the switching reference value and outputs a two-level operation switch instruction when the determination element is greater than or equal to the switching reference value; and a switching circuit (12) which, when the two-level switch instruction is received from the determination circuit (11), treats the AC switches as being off and switches on the arm valve devices in sequence, putting the electricity conversion apparatus in the two-level operation state.