Provided is a power conversion device that requires neither a harmonic suppression filter nor a buffer reactor. The power conversion device injects or absorbs reactive power into or from a three-phase AC system. In the power conversion device, a delta connection unit (3) is constructed by connecting power supply circuit units (4) of respective phases in a delta connection, said power supply circuit units (4) being each formed by connecting a plurality of H-bridge unit converters (5) in series. The winding of an isolating transformer (2) for isolating the delta connection unit (3) from the three-phase AC system is inserted into the circuit of the delta connection unit (3).
