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US 8,619,446 B2Granted
Cascaded H-bridge (CHB) inverter level shift PWM with rotation
AssigneeRockwell Automation Technologies, Inc.
InventorsJingbo Liu, Thomas Nondahl, Zhongyuan Cheng, Navid Zargari
Life of this patent
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Abstract
Cascade H-Bridge inverters and carrier-based level shift pulse width modulation techniques are presented for generating inverter stage switching control signals, in which carrier waveform levels are selectively shifted to control THD and to mitigate power distribution imbalances within multilevel inverter elements.
Claims20
A power conversion system, comprising:
- a multilevel inverter, comprising an integer number N inverter stages, N being greater than three, the inverter stages individually comprising an output, and a switching circuit including a plurality of switching devices coupled between a corresponding DC voltage source and the output, the switching circuit operative to provide an output voltage having an amplitude of one of at least two discrete levels at the output according to a plurality of switching control signals, the outputs of the inverter stages being coupled in series;
- and
- a controller operative to generate a set of 2N carrier waveform signals or values including first and second carrier waveform signals or values for each of the inverter stages, the carrier waveform signals or values individually defining a periodic carrier waveform with a waveform period, the waveform periods of the set of carrier waveform signals or values being substantially equal;
- the controller being operative to set each carrier waveform signal or value at a different one of a plurality of non-overlapping amplitude levels within an expected amplitude range of a reference signal or value;
- the controller being operative to provide the switching control signals to the multilevel inverter with the switching control signals provided to a given inverter stage based on comparison of the first and second carrier waveform signals or values for the given inverter stage with the reference signal or value;
- and
- the controller being operative to shift the amplitude level of at least two of the carrier waveform signals or values every integer number M waveform periods according to a repeating phase-opposite disposition or in-phase disposition level shifting pattern, M being greater than zero.
4 more elements
A method for generating switching control signals for an integer number N inverter stages of a multilevel inverter, N being greater than three, the method comprising:
- generating a set of 2N carrier waveform signals or values including first and second carrier waveform signals or values for each of the inverter stages, the carrier waveform signals or values individually defining a periodic carrier waveform with a waveform period, the waveform periods of the set of carrier waveform signals or values being substantially equal, and each carrier waveform signal or value being at a different one of a plurality of non-overlapping amplitude levels within an expected amplitude range of a reference signal or value;
- providing switching control signals to the multilevel inverter with the switching control signals provided to a given inverter stage based on comparison of the first and second carrier waveform signals or values for the given inverter stage with the reference signal or value;
- and
- shifting the amplitude level of at least two of the carrier waveform signals or values every integer number M waveform periods according to a repeating phase-opposite disposition or in-phase disposition level shifting pattern, M being greater than zero.
1 more element
A non-transitory computer readable medium with computer executable instructions for generating switching control signals for an integer number N inverter stages of a multilevel inverter, N being greater than three, the computer readable medium comprising computer executable instructions for:
- generating a set of 2N carrier waveform signals or values including first and second carrier waveform signals or values for each of the inverter stages, the carrier waveform signals or values individually defining a periodic carrier waveform with a waveform period, the waveform periods of the set of carrier waveform signals or values being substantially equal, and each carrier waveform signal or value being at a different one of a plurality of non-overlapping amplitude levels within an expected amplitude range of a reference signal or value;
- providing switching control signals to the multilevel inverter with the switching control signals provided to a given inverter stage based on comparison of the first and second carrier waveform signals or values for the given inverter stage with the reference signal or value;
- and
- shifting the amplitude level of at least two of the carrier waveform signals or values every integer number M waveform periods according to a repeating phase-opposite disposition or in-phase disposition level shifting pattern, M being greater than zero.
1 more element
Dependencies are inferred from the claim text.