Parallel NPC 3-level inverter without midpoint connection of the DC-links
AssigneeABB Schweiz AG
InventorsRobert Turner, Simon Walton, Sridhar Pulikanti, Arnoud Gerlof Van Der Wal, Ian Murray Porteous, Nicholas James Elliott
Life of this patent
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Abstract
Embodiments of the present disclosure relate to parallel 3-level inverter without midpoint connection. The parallel 3-level inverter includes a plurality of parallel converters coupled in parallel between a common DC bus and a common AC output, wherein each of the plurality of parallel converters comprises a midpoint and the midpoints of the plurality of parallel converters are disconnected from each other.
Claims9
A parallel 3-level inverter comprising:
- a plurality of parallel converters coupled in parallel between a common DC bus and a common AC output, wherein each of the plurality of parallel converters comprises a midpoint and the midpoints of the plurality of parallel converters are disconnected from each other;
- and
- one or more controllers configured to:
- determine a first average of upper DC bus half voltages of the plurality of parallel converters and a second average of lower DC bus half voltages of the plurality of parallel converters;
- determine a modulation index for each of the plurality of parallel converters based on the first average, the second average, and an AC voltage reference for each of the plurality of parallel converters, such that the upper DC bus half voltages of each of the plurality of parallel converters are equal to one another and the lower DC bus half voltages of each of the plurality of parallel converters are equal to one another;
- and
- perform a zero-sequence control based on the modulation index to cause the first average of the upper DC bus half voltages to be equal to the second average of the lower DC bus half voltages.
A method for use in a parallel 3-level inverter without DC midpoint connection, the method comprising:
- determining a first average of upper DC bus half voltages of a plurality of parallel converters of the inverter and a second average of lower DC bus half voltages of the plurality of parallel converters;
- determining a modulation index for each of the plurality of parallel converters based on the first average, the second average, and an AC voltage reference for the plurality of parallel converters, such that the upper DC bus half voltages of the plurality of parallel converters are equal to one another and the lower DC bus half voltages of the plurality of parallel converters are equal to one another;
- and
- performing a zero-sequence control based on the modulation index to cause the first average of the upper DC bus half voltages to be equal to the second average of the lower DC bus half voltages.
Dependencies are inferred from the claim text.