Power conversion apparatus and power conversion method
A controller of a power conversion apparatus according to an embodiment causes a chopper and an inverter to generate an alternating-current (AC) voltage including first and second parts of an AC voltage waveform and causes the inverter to output the AC voltage. The chopper generates the first part having an absolute value higher than a voltage of a DC power supply, and the inverter generates the second part having an absolute value lower than the voltage of the DC power supply. The controller is configured to alternately turn on the first and second switching elements in a period during which the controller controls the chopper to generate the first part of the AC voltage waveform.
1. A power conversion apparatus comprising:
a chopper that includes a first switching element, an inductor, a diode, and a capacitor, and configured to store power supplied from a direct-current (DC) power supply in the capacitor sequentially through the inductor and the diode by turning on and off the first switching element;
an inverter connected to an output of the chopper;
a second switching element connected to the diode in reverse parallel; and
a controller configured to control the chopper and the inverter to generate an alternating-current (AC) voltage including first and second parts of an AC voltage waveform and to cause the inverter to output the AC voltage, the chopper generating the first part having an absolute value higher than a voltage of the DC power supply and the inverter generating the second part having an absolute value lower than the voltage of the DC power supply,
wherein the controller is configured to alternately turn on the first switching element and the second switching element in a period during which the controller controls the chopper to generate the first part of the AC voltage waveform, and
wherein the controller is configured to turn on the second switching element when causing the inverter to stop outputting the AC voltage.
2. The power conversion apparatus according to claim 1 , wherein the controller is configured to turn on the second switching element in a period during which the controller controls the inverter to generate the second part of the AC voltage waveform.
3. The power conversion apparatus according to claim 1 , wherein
the inverter includes a plurality of switching elements that are controlled by the controller to generate the second part of the AC voltage waveform, and
the controller configured to turn on the second switching element after turning off the first switching element, the second switching element, and the plurality of switching elements of the inverter to cause the inverter to stop outputting the AC voltage.
4. The power conversion apparatus according to claim 1 , wherein the controller is configured to turn on the second switching element when a voltage output from the chopper reaches a predetermined threshold after causing the inverter to stop outputting the AC voltage.
5. The power conversion apparatus according to claim 1 , further comprising:
a current detector that detects alternating current output from the inverter, wherein
the controller is configured to cause the inverter to stop outputting the AC voltage when the alternating current output from the inverter is equal to or more than a predetermined value.
6. The power conversion apparatus according to claim 1 , wherein the second switching element includes a field effect transistor (FET).
7. A power conversion apparatus comprising:
a chopper that includes a first switching element, an inductor, a diode, and a capacitor, and configured to store power supplied from a direct-current (DC) power supply in the capacitor sequentially through the inductor and the diode by turning on and off the first switching element;
an inverter connected to an output of the chopper;
a second switching element connected to the diode in reverse parallel; and
a controller configured to control the chopper and the inverter to generate an alternating-current (AC) voltage including first and second parts of an AC voltage waveform and to cause the inverter to output the AC voltage, the chopper generating the first part having an absolute value higher than a voltage of the DC power supply and the inverter generating the second part having an absolute value lower than the voltage of the DC power supply,
wherein the controller is configured to alternately turn on the first switching element and the second switching element in a period during which the controller controls the chopper to generate the first part of the AC voltage waveform,
wherein the controller is configured to turn on the second switching element in a period during which the controller controls the inverter to generate the second part of the AC voltage waveform, and
wherein the controller is configured to turn on the second switching element when causing the inverter to stop outputting the AC voltage.
8. The power conversion apparatus according to claim 7 , wherein
the inverter includes a plurality of switching elements that are controlled by the controller to generate the second part of the AC voltage waveform, and
the controller configured to turn on the second switching element after turning off the first switching element, the second switching element, and the plurality of switching elements of the inverter to cause the inverter to stop outputting the AC voltage.
9. The power conversion apparatus according to claim 7 , wherein the controller is configured to turn on the second switching element when a voltage output from the chopper reaches a predetermined threshold after causing the inverter to stop outputting the AC voltage.
10. The power conversion apparatus according to claim 7 , further comprising:
a current detector that detects alternating current output from the inverter, wherein
the controller is configured to cause the inverter to stop outputting the AC voltage when the alternating current output from the inverter is equal to or more than a predetermined value.
11. The power conversion apparatus according to claim 7 , wherein the second switching element includes a field effect transistor (FET).
12. A power conversion method comprising:
storing power supplied from a direct-current (DC) power supply in a capacitor sequentially through an inductor and a diode by turning on and off a first switching element, a chopper including the first switching element, the inductor, the diode, and the capacitor; and
controlling the chopper and an inverter to generate an alternating-current (AC) voltage including first and second parts of an AC voltage waveform and to cause the inverter to output the AC voltage, the chopper generating the first part having an absolute value higher than a voltage of the DC power supply and the inverter generating the second part having an absolute value lower than the voltage of the DC power supply, the inverter being connected to an output of the chopper,
wherein the controller alternately turns on the first switching element and a second switching element in a period during which the controller controls the chopper to generate the first part of the AC voltage waveform, the second switching element being connected to the diode in reverse parallel, and
wherein the controller turns on the second switching element when causing the inverter to stop outputting the AC voltage.
13. A power conversion method comprising:
storing power supplied from a direct-current (DC) power supply in a capacitor sequentially through an inductor and a diode by turning on and off a first switching element, a chopper including the first switching element, the inductor, the diode, and the capacitor; and
controlling the chopper and an inverter to generate an alternating-current (AC) voltage including first and second parts of an AC voltage waveform and to cause the inverter to output the AC voltage, the chopper generating the first part having an absolute value higher than a voltage of the DC power supply and the inverter generating the second part having an absolute value lower than the voltage of the DC power supply, the inverter being connected to an output of the chopper,
wherein the controller alternately turns on the first switching element and a second switching element in a period during which the controller controls the chopper to generate the first part of the AC voltage waveform, the second switching element being connected to the diode in reverse parallel,
wherein the controller turns on the second switching element in a period during which the controller controls the inverter to generate the second part of the AC voltage waveform, and
wherein the controller turns on the second switching element when causing the inverter to stop outputting the AC voltage.