FOUR POLE NEUTRAL-POINT CLAMPED THREE PHASE CONVERTER WITH LOW COMMON MODE VOLTAGE OUTPUT
First Claim
Patent Images
1. A three-level neutral point clamped converter comprising:
- a first pole;
a second pole;
a third pole;
a fourth pole,each of the first, second, and third poles having a first switch, a second switch, a third switch, and a fourth switch coupled in series between a positive DC bus and a negative DC bus,the fourth pole having a first switch and a second switch coupled in series between the positive DC bus and the negative DC bus,an AC bus being connected between the second switch and the third switch of the first, second, and third poles,a neutral line being connected through a diode between the first switch and the second switch and between the third switch and the fourth switch of the first, second, and third poles,the first and second switches defining an upper portion, the third and fourth switches defining a lower portion; and
a controller thatswitches states of the respective first, second, third, and fourth switches of the first, second, and third poles to produce zero common mode voltage, the fourth pole enabling all of the NPC switch states of the first, second, and third poles to be used for producing zero common mode voltage, andmodulates the first and second switches of the fourth pole to balance the positive DC bus and the negative DC bus.
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Abstract
A four pole, three-phase, NPC converter that produces virtually no common mode voltage. The low common mode voltage output is achieved by constraining the switch states of the NPC converter. A fourth pole and associated control balance the upper and lower DC link voltages. The converter may be an inverter or a rectifier.
78 Citations
16 Claims
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1. A three-level neutral point clamped converter comprising:
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a first pole; a second pole; a third pole; a fourth pole, each of the first, second, and third poles having a first switch, a second switch, a third switch, and a fourth switch coupled in series between a positive DC bus and a negative DC bus, the fourth pole having a first switch and a second switch coupled in series between the positive DC bus and the negative DC bus, an AC bus being connected between the second switch and the third switch of the first, second, and third poles, a neutral line being connected through a diode between the first switch and the second switch and between the third switch and the fourth switch of the first, second, and third poles, the first and second switches defining an upper portion, the third and fourth switches defining a lower portion; and a controller that switches states of the respective first, second, third, and fourth switches of the first, second, and third poles to produce zero common mode voltage, the fourth pole enabling all of the NPC switch states of the first, second, and third poles to be used for producing zero common mode voltage, and modulates the first and second switches of the fourth pole to balance the positive DC bus and the negative DC bus. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for controlling a three-level neutral point clamped converter having a first pole, a second pole, a third pole, and a fourth pole, each of the first, second, and third poles having a first switch, a second switch, a third switch, and a fourth switch coupled in series between a positive DC bus and a negative DC bus, the fourth pole having a first switch and a second switch coupled in series between the positive DC bus and the negative DC bus, an AC bus being connected between the second switch and the third switch of the first, second, and third poles, a neutral line being connected through a diode between the first switch and the second switch and between the third switch and the fourth switch of the first, second, and third poles, the first and second switches defining an upper portion, the third and fourth switches defining a lower portion, the method comprising the steps of:
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switching states of the respective first, second, third, and fourth switches of the first, second, and third poles to produce zero common mode voltage, the fourth pole enabling all of the NPC switch states of the first, second, and third poles to be used for producing zero common mode voltage; and modulating the first and second switches of the fourth pole to balance the positive DC bus and the negative DC bus. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification