Voltage source converter

Patent metadata

Field	Value
Publication number	US-2016248341-A1
Application number	US-201415026949-A
Country	US
Kind code	A1
Filing date	Aug 1, 2014
Priority date	Oct 2, 2013
Publication date	Aug 25, 2016
Grant date	—

Abstract

A voltage source converter includes DC terminals, a plurality of single-phase limbs, and a controller. Each single-phase limb includes a phase element and switching elements. Each limb is connected between the DC terminals and is controllable to generate an AC voltage at the AC side of the corresponding phase element so as to draw a respective phase current from a multi-phase AC electrical network. The controller is configured to selectively generate a modified AC voltage demand for at least one limb in response to an imbalance in the phase currents and/or a change in electrical rating of at least one limb. The controller is configured to selectively control, in accordance with the or the respective modified AC voltage demand, the or each corresponding limb independently of the or each other limb to modify the voltage at the AC side of its phase element and thereby modify the corresponding phase current.

First claim

1 . A voltage source converter comprising:
first and second DC terminals for connection to a DC electrical network; a plurality of single-phase limbs, each single-phase limb including a phase element, each phase element including a plurality of switching elements configured to interconnect a DC voltage and an AC voltage, an AC side of each phase element being connectable to a respective phase of a multi-phase AC electrical network, each single-phase limb being connected between the first and second DC terminals, each single-phase limb being controllable to generate an AC voltage at the AC side of the corresponding phase element so as to draw a respective phase current from the multi-phase AC electrical network; and a controller configured to selectively generate a or a respective modified AC voltage demand for at least one single-phase limb in response to an imbalance in the plurality of phase currents and/or a change in electrical rating of at least one single-phase limb, wherein the controller is configured to selectively control, in accordance with the or the respective modified AC voltage demand, the or each corresponding single-phase limb independently of the or each other single-phase limb to modify the AC voltage at the AC side of its phase element and thereby modify the corresponding phase current.

2 . A voltage source converter according to claim 1 wherein the controller is configured to selectively control, in accordance with the or the respective modified AC voltage demand, the or each corresponding single-phase limb independently of the or each other single-phase limb to modify the AC voltage at the AC side of its phase element and thereby modify the corresponding phase current so as to balance the plurality of phase currents.

3 . A voltage source converter according to claim 1 wherein the controller is configured to selectively process an or a respective actual phase voltage or phase current of at least one phase of the multi-phase AC electrical network so as to derive a or a respective simulated multi-phase AC power source for the or each corresponding single-phase limb, the or each simulated multi-phase AC power source being defined by a plurality of balanced voltage or current phasors that consists of an actual voltage or current phasor and a plurality of virtual voltage or current phasors, the controller being further configured to selectively process the or each corresponding phase current and the or each plurality of balanced voltage or current phasors so as to generate a or a respective modified AC voltage demand for the or each corresponding single-phase limb in response to an imbalance in the plurality of phase currents and/or a change in electrical rating of at least one single-phase limb.

4 . A voltage source converter according to claim 3 wherein the controller is further configured to selectively process the or each plurality of balanced voltage phasors to derive voltage magnitude and frequency terms, the controller being configured to combine the voltage magnitude and frequency terms with real and reactive power demands so as to derive a or a respective reference current demand, the controller being configured to process the or each reference current demand and the or each corresponding phase current so as to generate a or a respective modified AC voltage demand for the or each corresponding single-phase limb in response to an imbalance in the plurality of phase currents and/or a change in electrical rating of at least one single-phase limb.

5 . A voltage source converter according to claim 4 wherein the controller includes at least one quadrature signal generator block configured to selectively process an or a respective actual phase voltage of at least one phase of the multi-phase AC electrical network so as to derive a or a respective simulated multi-phase AC power source for the or each corresponding single-phase limb, the or each simulated multi-phase AC power source being defined by a plurality of balanced voltage phasors that consists of an actual voltage phasor and a plurality of virtual voltage phasors, the or each quadrature signal generator block being further configured to selectively process the or each plurality of balanced voltage phasors to derive the voltage magnitude and frequency terms.

6 . A voltage source converter according to claim 3 wherein the controller is configured to selectively process an or a respective actual phase voltage or phase current of at least one phase of the multi-phase AC electrical network so as to derive a or a respective simulated multi-phase AC power source for the or each corresponding single-phase limb, the or each simulated multi-phase AC power source being defined by a plurality of balanced voltage or current phasors that consists of an actual voltage or current phasor and a plurality of virtual voltage or current phasors, the controller being further configured to selectively process the or each corresponding phase current so as to derive a or a respective current vector that corresponds to the or the respective simulated multi-phase AC power source, the controller being further configured to selectively process the or each current vector so as to generate a or a respective modified AC voltage demand for the or each corresponding single-phase limb in response to an imbalance in the plurality of phase currents and/or a change in electrical rating of at least one single-phase limb.

7 . A voltage source converter according to claim 6 wherein the controller includes at least one quadrature signal generator block configured to selectively process an or a respective actual phase voltage or phase current of at least one phase of the multi-phase AC electrical network so as to derive a or a respective simulated multi-phase AC power source for the or each corresponding single-phase limb, the or each simulated multi-phase AC power source being defined by a plurality of balanced voltage phasors that consists of an actual voltage or current phasor and a plurality of virtual voltage or current phasors, the or each quadrature signal generator block being further configured to selectively process the or each corresponding phase current so as to derive a or a respective current vector that corresponds to the or the respective simulated multi-phase AC power source, the controller further including at least one vector control block configured to selectively process the or each current vector so as to generate a or a respective modified AC voltage demand for the or each corresponding single-phase limb in response to an imbalance in the plurality of phase currents and/or a change in electrical rating of at least one single-phase limb.

8 . A voltage source converter according to claim 7 wherein the or each vector control block includes a proportional-integral control block or a proportional-resonant control block.

9 . A voltage source converter according to claim 6 wherein the or each current vector is in a synchronously rotating d-q reference frame or stationary α-β reference frame.

10 . A voltage source converter according to claim 5 wherein the or each quadrature signal generator block is configured to selectively process an or a respective actual phase voltage or phase current of at least one phase of the multi-phase AC electrical network to generate a respective output signal, the or each output signal being orthogonal to the corresponding actual phase voltage or phase current, so as to derive the or the respective simulated multi-phase AC power source for the or each corresponding single-phase limb.

11 . A voltage source converter according to claim 1 wherein the controller is configured to selectively process an or a respective actual phase

Assignees

• General Electric Technology Gmbh

Inventors

• Trainer David Reginald
• Jasim Omar Fadhel
• Simfukwe Dumisani

Classifications

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• H02M7/217 Primary

  using semiconductor devices only · CPC title

• H02M7/483 Primary

  Converters with outputs that each can have more than two voltages levels · CPC title

• H02M7/4835

  comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage · CPC title

• H02M1/0095

  Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck · CPC title