A power conversion apparatus comprising: - a rectification circuit for rectifying an input from an AC input power supply; - an inverter circuit (100, 200) including one or more single-phase inverters (100, 100a, 100b) each of which has a plurality of semiconductor switch devices (4, 5) and a DC voltage supply, AC sides of the one or more single-phase inverters (100, 100a, 100b) being connected in series with each other and being connected in series with an output of the rectification circuit, which inverter circuit (100, 200) superimposes the sum of outputs of the one or more single-phase inverters (100, 100a, 100b) onto the output of the rectification circuit; - a smoothing capacitor for smoothing an output of the inverter circuit (100, 200), the smoothing capacitor being connected via a rectification diode to the inverter circuit (100, 200) at a subsequent stage of the inverter circuit (100, 200); and - a short-circuiting switch (9, 9a) for bypassing the smoothing capacitor, one end of the short-circuiting switch (9, 9a) being connected to the inverter circuit (100, 200) and the other end being connected to one end of the smoothing capacitor, characterized in that: the inverter circuit (100, 200) is subjected to output control by using a current instruction (Iin*) such that a voltage (Vdc) of the smoothing capacitor follows a first target voltage (Vdc*) and an input power factor from the AC input power supply is improved, - wherein the short-circuiting switch (9, 9a) is subjected to ON/OFF control such that a voltage (Vsub) of the DC voltage supply of the inverter circuit (100, 200) follows a second target voltage (Vsub*), and - wherein each of ON periods of the short-circuiting switch (9, 9a) includes a zero cross phase of an input voltage from the AC input power supply. - a rectification circuit for rectifying an input from an AC input power supply; - an inverter circuit (100, 200) including one or more single-phase inverters (100, 100a, 100b) each of which has a plurality of semiconductor switch devices (4, 5) and a DC voltage supply, AC sides of the one or more single-phase inverters (100, 100a, 100b) being connected in series with each other and being connected in series with an output of the rectification circuit, which inverter circuit (100, 200) superimposes the sum of outputs of the one or more single-phase inverters (100, 100a, 100b) onto the output of the rectification circuit; - a smoothing capacitor for smoothing an output of the inverter circuit (100, 200), the smoothing capacitor being connected via a rectification diode to the inverter circuit (100, 200) at a subsequent stage of the inverter circuit (100, 200); and - a short-circuiting switch (9, 9a) for bypassing the smoothing capacitor, one end of the short-circuiting switch (9, 9a) being connected to the inverter circuit (100, 200) and the other end being connected to one end of the smoothing capacitor, the inverter circuit (100, 200) is subjected to output control by using a current instruction (Iin*) such that a voltage (Vdc) of the smoothing capacitor follows a first target voltage (Vdc*) and an input power factor from the AC input power supply is improved, - wherein the short-circuiting switch (9, 9a) is subjected to ON/OFF control such that a voltage (Vsub) of the DC voltage supply of the inverter circuit (100, 200) follows a second target voltage (Vsub*), and - wherein each of ON periods of the short-circuiting switch (9, 9a) includes a zero cross phase of an input voltage from the AC input power supply. - wherein the short-circuiting switch (9, 9a) is subjected to ON/OFF control such that a voltage (Vsub) of the DC voltage supply of the inverter circuit (100, 200) follows a second target voltage (Vsub*), and - wherein each of ON periods of the short-circuiting switch (9, 9a) includes a zero cross phase of an input voltage from the AC input power supply.