Power converter
A diode rectifier rectifies an AC voltage output from a neutral-grounding three-phase AC power supply to a DC voltage. A smoothing capacitor smoothes the DC voltage rectified by the diode rectifier. An inverter converts the DC voltage smoothed by the smoothing capacitor into a desired AC voltage. A bidirectional switch and a Y capacitor are connected in series between one end of the smoothing capacitor and the ground. A detector detects a voltage across both ends of the smoothing capacitor. A controller drives the bidirectional switch in response to an output of the detector.
1. A power converter comprising:
a rectifier circuit configured to rectify an AC voltage output from a neutral-grounding three-phase AC power supply to a DC voltage and output the DC voltage to a DC bus;
a smoothing capacitor configured to smooth the DC voltage rectified by the rectifier circuit;
a conversion circuit configured to convert the DC voltage smoothed by the smoothing capacitor into a desired AC voltage;
a bidirectional switch and at least one Y capacitor connected in series between one end of the smoothing capacitor and the ground, the bidirectional switch including a first end connected to the smoothing capacitor and a second end connected to a first end of the Y capacitor, the Y capacitor including a second end connected to the ground;
a detector positioned across the smoothing capacitor such that the detector is configured to detect a voltage across both ends of the smoothing capacitor; and
a controller configured to drive the bidirectional switch in response to an output of the detector,
the controller bringing the bidirectional switch into conduction when a peak value or an average value of an absolute value of a variation component of an output value of the detector is smaller than a threshold,
wherein the detector is connected to a comparator, and
wherein the bidirectional switch and the at least one Y capacitor are not directly connected to the comparator.
2. The power converter according to claim 1 , wherein the controller controls a resistance value of the bidirectional switch in accordance with the output value of the detector.
3. The power converter according to claim 1 , wherein the bidirectional switch comprises a bidirectional semiconductor switch.
4. The power converter according to claim 3 , wherein the bidirectional semiconductor switch includes IGBTs connected in inverse parallel.
5. The power converter according to claim 3 , wherein the bidirectional semiconductor switch includes reverse blocking IGBTs connected in inverse parallel.
6. The power converter according to claim 3 , wherein the bidirectional semiconductor switch includes a P-channel MOSFET and an N-channel MOSFET connected in inverse series.
7. The power converter according to claim 6 , wherein the P-channel MOSFET is connected to the DC bus.
8. The power converter according to claim 3 , wherein the bidirectional semiconductor switch comprises one bidirectional element.
9. The power converter according to claim 1 , further comprising a chopper circuit between the smoothing capacitor and the conversion circuit.
10. The power converter according to claim 1 , further comprising a common-mode choke coil between the three-phase AC power supply and the rectifier circuit.
11. The power converter according to claim 1 , wherein the at least one Y capacitor includes a plurality of Y capacitors, and the plurality of Y capacitors are connected in parallel.
12. The power converter according to claim 11 , wherein
the at least one Y capacitor includes a plurality of Y capacitors, and
the plurality of Y capacitors differ from each other in frequency characteristics and are connected in parallel.
13. The power converter according to claim 1 , wherein the threshold is a voltage value of an AC power supply frequency component.
14. A power converter comprising:
a rectifier circuit configured to rectify an AC voltage output from a neutral-grounding three-phase AC power supply to a DC voltage and output the DC voltage to a DC bus;
a smoothing capacitor configured to smooth the DC voltage rectified by the rectifier circuit;
a conversion circuit configured to convert the DC voltage smoothed by the smoothing capacitor into a desired AC voltage;
a bidirectional switch and at least one Y capacitor connected in series between one end of the smoothing capacitor and the ground, the bidirectional switch including a first end connected to the smoothing capacitor and a second end connected to a first end of the Y capacitor, the Y capacitor including a second end connected to the ground;
a detector positioned above the smoothing capacitor such that the detector is configured to detect a current flowing through the smoothing capacitor; and
a controller configured to drive the bidirectional switch in accordance with an output value of the detector,
wherein the controller brings the bidirectional switch into conduction when a peak value or an average value of an absolute value of a variation component of the output value of the detector is smaller than a threshold,
wherein the detector is connected to a comparator, and
wherein the bidirectional switch and the at least one Y capacitor are not directly connected to the comparator.
15. The power converter according to claim 14 , wherein the threshold is an AC power frequency component of a value of the current flowing into the smoothing capacitor.