Power conversion apparatus with inverter circuit and series converter circuit having power factor control

摘要

An inverter circuit including a DC capacitor is connected in series to an AC power supply, and at the stage subsequent to the inverter circuit, a smoothing capacitor is connected via a converter circuit. A short-circuit period T for short-circuiting the AC terminals of the converter circuit is provided in one cycle, whereby the converter circuit is controlled, and PWM control is performed for the inverter circuit so as to improve an AC power supply power factor. When current control by the inverter circuit cannot be performed, the PWM control is switched to PWM control for the converter circuit, to perform current control.

主权项

1. A power conversion apparatus comprising:
an inverter circuit including a plurality of semiconductor switching devices and a DC capacitor and connected in series to a first terminal of an AC power supply; a converter circuit including a plurality of semiconductor switching devices provided between DC bus lines, the converter circuit having one AC terminal connected in series to the inverter circuit and the other AC terminal connected to a second terminal of the AC power supply, and being configured to output DC power between the DC bus lines; a smoothing capacitor connected between the DC bus lines, for smoothening output of the converter circuit; and a control circuit for controlling the inverter circuit and the converter circuit such that voltage of the DC capacitor of the inverter circuit follows a set voltage instruction value, voltage of the smoothing capacitor follows target voltage, and a power factor of input current which is current from the AC power supply is 1, wherein the control circuit provides a short-circuit period including a zero cross phase of the AC power supply in which the AC terminals of the converter circuit are continuously short-circuited to bypass the smoothing capacitor, and an open-circuit period in which DC output of the converter circuit is continuously outputted to the smoothing capacitor, and the control circuit thereby causes the voltage of the DC capacitor of the inverter circuit to follow the set voltage instruction value, the control circuit performs PWM control for the inverter circuit to control an input power factor to be 1 in the short-circuit period and in the open-circuit period and disables the PWM control for the inverter circuit in an other time period between the short-circuit period and the open-circuit period, and the control circuit provides a period for performing the PWM control for the converter circuit during the other time period when the PWM control for the inverter circuit is disabled in accordance with the voltage of the DC capacitor, and controls the power factor of the input current to be 1 by switching the PWM control for the inverter circuit and the PWM control for the converter circuit therebetween.