Power conversion device

A power conversion device comprising:

• a boosting converter for boosting output voltage from a DC power supply unit;
• a smoothing capacitor for smoothing output voltage of the boosting converter;
• an inverter for converting voltage of the smoothing capacitor to AC voltage;
• and
• a control unit for controlling the boosting converter and the inverter, wherein
• the boosting converter includes
• a reactor having a first end connected to the DC power supply unit,
• a leg portion including four semiconductor elements composed of a first semiconductor element, a second semiconductor element, a first semiconductor switching element, and a second semiconductor switching element each of which controls conduction and interruption of current, the four semiconductor elements being connected in series between positive and negative terminals of the smoothing capacitor, a second end of the reactor being connected to a connection point between the second semiconductor element and the first semiconductor switching element, and
• an intermediate capacitor connected between a connection point of the first semiconductor element and the second semiconductor element, and a connection point of the first semiconductor switching element and the second semiconductor switching element, and
• the control unit,
• in a normal mode, performs ON/OFF control for the first semiconductor switching element and the second semiconductor switching element so as to cause the boosting converter to output multilevel voltages, and
• when voltage of the smoothing capacitor is equal to or greater than a reference voltage value, executes a protection mode to fix the first semiconductor switching element and the second semiconductor switching element in OFF states.