Modular multi-level AC-AC converter
OwnerGregory Kish, Anjana Wijesekerainventors
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Abstract
A modular multilevel AC-AC converter is provided which allows for the direct conversion of AC power between different voltage levels using half-bridge submodules. The converter has a partial power processing topology that exploits internal circulating DC currents to facilitate charge balance of submodule capacitors. This power transfer mechanism eliminates the centralized DC link required in conventional back-to-back modular multilevel converter (B2B-MMC) systems, thus enabling reductions in the semiconductor effort and submodule capacitor energy storage requirements typically required in a B2B-MMC solution. A modulation scheme is also provided for different AC voltage conversion ratios. The converter operation and controls are validated by simulation, and experimentation.
Claims20
A modular multilevel converter (MMC) for AC to AC power conversion, the converter comprising an input terminal for receiving input AC current, an output terminal for outputting output AC current, and at least one converter module comprising:
- (a) a circuit loop connected to the input terminal, and comprising at least one phase leg, wherein each of the at least one phase leg comprises:
- (i) an upper arm comprising an upper set of at least one series-connected half-bridge submodule;
- and
- (ii) a lower arm comprising a lower set of at least one series-connected half-bridge submodule,
- wherein, within each of the at least one phase leg, the upper and lower sets are connected in series with each other at a connection point, and oppositely oriented to each other to allow for DC power exchange between the upper and lower arm for charge balancing between capacitors of the at least one half-bridge submodule of the upper set and capacitors of the at least one half-bridge submodule of the lower set;
- and
- (b) a filter connected to the connection point and the output terminal, wherein the filter comprises one or more components allowing flow of the AC current from the connection point of the circuit loop to the output terminal.
A method for operating a modular multilevel converter (MMC) for AC to AC power conversion, the method comprising:
- applying input AC current at an input terminal of at least one converter module of the converter, wherein the at least one converter module comprises:
- (a) a circuit loop connected to the input terminal, and comprising at least one phase leg, wherein each of the at least one phase legs comprises:
- (i) an upper arm comprising an upper set of at least one series-connected half-bridge submodule;
- and
- (ii) a lower arm comprising a lower set of at least one series-connected half-bridge submodule,
- wherein, within each of the at least one phase leg, the upper and lower sets are connected in series with each other at a connection point and oppositely oriented to each other to allow for DC power exchange between the upper and lower arm for charge balancing between capacitors of the at least one half-bridge submodule of the upper set and capacitors of the at least one half-bridge submodule of the lower set;
- (b) a filter connected to the connection point and an output terminal of the converter, wherein the filter comprises one or more components to allow for flow of the AC current from the connection point of the circuit loop to the output terminal;
- and
- generating converted output AC current at the output terminal.
A modular multilevel converter (MMC) for AC to AC power conversion, the converter comprising an input terminal for receiving input AC current, an output terminal for outputting output AC current, and at least one converter module comprising:
- (a) a circuit loop connected to the input terminal, and comprising at least one phase leg, wherein each of the at least one phase leg comprises:
- (i) an upper arm comprising an upper set of at least one series-connected capacitor-based switching submodule;
- and
- (ii) an lower arm comprising a lower set of at least one series-connected capacitor-based switching submodule,
- wherein, within each of the at least one phase leg, the upper and lower sets are connected in series with each other at a connection point, and oppositely oriented to each other to allow for DC power exchange between the upper and lower arm for charge balancing between capacitors of the at least one capacitor-based submodule of the upper set and capacitors of the at least one capacitor-based submodule of the lower set;
- and
- (b) a filter connected to the connection point and the output terminal, wherein the filter comprises one or more components allowing flow of the AC current from the connection point of the circuit loop to the output terminal.
Dependencies are inferred from the claim text.