Patent ID: 8080958

Claim:
A power conversion device that receives a three-phase AC power supply as an input and controls an output voltage in accordance with a voltage command by PWM control so as to supply power to a load including a motor, the power conversion device comprising: a main circuit section including: forward and backward switches connecting each phase of the three-phase AC power supply to each output phase connected to the load, an LC filter having a reactor and a capacitor and being connected between the three-phase AC power supply and each of the forward and backward switches, and a current detector detecting an input current or a load current; and a four-step commutation device generating a plurality of steps on a basis of a polarity of the load current, the plurality of steps including: a step 1 in which a switch at a commutation source among the forward and backward switches having a polarity opposite to the polarity of the load current is turned off, a step 2 in which a switch at a commutation destination among the forward and backward switches having a polarity same as the polarity of the load current is turned on, a step 3 in which a switch at the commutation source among the forward and backward switches having a polarity same as the polarity of the load current is turned off, and a step 4 in which a switch at the commutation destination among the forward and backward switches having a polarity opposite to the polarity of the load current is turned on, wherein the four-step commutation device performs commutation in a sequence of the step 1, the step 2, the step 3, and the step 4, wherein times between each of the plurality of steps during a half PWM cycle for commutation from a high potential power supply phase to a low potential power supply phase are set to Td 1 , Td 2 , and Td 3 in sequence, wherein times between each of the plurality of steps during a half PWM cycle for commutation from the low potential power supply phase to the high potential power supply phase are set to Td 3 ′, Td 2 ′, and Td 1 ' in sequence, and wherein at least of one of Td 1 , Td 2 , Td 3 ′ and Td 2 ′ is differently set between when the load current flows from the three-phase AC power supply to the load and when the load current flows from the load to the three-phase AC power supply.