Static VAR compensator with multilevel converter

Patent metadata

Field	Value
Publication number	US-9130458-B2
Application number	US-201013634205-A
Country	US
Kind code	B2
Filing date	Mar 15, 2010
Priority date	Mar 15, 2010
Publication date	Sep 8, 2015
Grant date	Sep 8, 2015

Abstract

A static synchronous compensator for use in reactive power compensation, the static synchronous compensator comprising at least one primary compensator limb including first and second DC terminals, and an AC terminal for connection in use to an AC network, the or each primary compensator limb defining first and second limb portions, each limb portion—including at least one switching element connected in series with a chain-link converter—between a respective one of the first and second DC terminals and the AC terminal, the switching elements of the first and second limb portions being operable to switch the respective chain-link converters in and out of circuit between the respective DC terminal and the AC terminal and the chain-link converters being operable to generate a voltage waveform at the AC terminal; and a secondary compensator limb including at least one DC link capacitor connected between the first and second DC terminals, the secondary compensator limb being connected in parallel with the or each primary compensator limb.

First claim

The invention claimed is:

1. A static synchronous compensator for use in reactive power compensation, the static synchronous compensator comprising at least one primary compensator limb including first and second DC terminals, and an AC terminal for connection in use to an AC network, the or each primary compensator limb defining first and second limb portions, each limb portion including at least one switching element and a chain-link converter connected in series at a common point, said common point being shared only by the switching element and the chain-link converter, the switching element and the chain-link converter being mounted between a respective one of the first and second DC terminals and the AC terminal, wherein the switching elements of the first and second limb portions being operable to switch the respective chain-link converters in and out of circuit between the respective DC terminal and the AC terminal, wherein the switching elements of the first and second limb portions being operable to switch the chain-link converters into circuit at the same time and wherein the chain-link converters being operable to generate a voltage waveform at the AC terminal; and a secondary compensator limb including at least one DC link capacitor connected between the first and second DC terminals, the secondary compensator limb being connected in parallel with the or each primary compensator limb.

2. The static synchronous compensator according to claim 1 wherein the secondary compensator limb includes two DC link capacitors connected in series, a junction between the DC link capacitors being connected in use to ground.

3. The static synchronous compensator according to claim 1 wherein the secondary compensator limb includes a DC link capacitor with a center tap, the center tap being connected in use to ground.

4. The static synchronous compensator according to claim 1 wherein each chain-link converter is operable when the respective limb portion is switched out of circuit to generate a voltage to offset a voltage across the limb portion and thereby minimize the voltage across the respective switching element.

5. The static synchronous compensator according to claim 1 wherein the chain-link converter of each of the limb portions includes a chain of modules connected in series, each module including at least one pair of secondary switching elements connected in parallel with an energy storage device, the secondary switching elements being operable in use so that the chain of modules defines a stepped variable voltage source.

6. The static synchronous compensator according to claim 5 wherein the or each module of the chain-link converters includes two pairs of secondary switching elements connected in parallel with the respective energy storage device in a full-bridge arrangement to define a 4-quadrant bipolar module that can provide positive or negative voltage and can conduct current in both directions.

7. The static synchronous compensator according to claim 5 wherein the or each module of the chain-link converters includes a pair of secondary switching elements connected in parallel with the respective energy storage device in a half-bridge arrangement to define a 2-quadrant module that can provide positive or zero voltage and can conduct current in both directions.

8. The static synchronous compensator according to claim 5 wherein the or each energy storage device includes a capacitor, a fuel cell, a battery or an auxiliary AC generator with an associated rectifier.

9. The static synchronous compensator according to claim 1 wherein the or each switching element of each limb portion includes a semiconductor device.

10. The static synchronous compensator according to claim 9 wherein the or each semiconductor device includes an insulated gate bipolar transistor, a gate turn-off thyristor or an integrated gate-commutated thyristor.

11. The static synchronous compensator according to claim 1 wherein the chain-link converter of each limb portion includes at least one semiconductor device.

12. The static synchronous compensator according to claim 1 including multiple primary compensator limbs, each primary compensator limb including an AC terminal for connection in use to a respective phase of a multi-phase AC network.

13. The static synchronous compensator according to claim 1 wherein the chain-link converter of each limb portion is operable to generate a voltage to oppose the flow of current created by a fault, in use, in the secondary compensator limb or the AC network.

14. The static synchronous compensator according to claim 1 wherein, in each limb portion, a voltage rating of the chain-link converter and a voltage rating of the or each switching element are equal.

15. The static synchronous compensator according to claim 1 wherein, in each limb portion, a voltage rating of the chain-link converter and a voltage rating of the or each switching element are not equal.

16. The static synchronous compensator according to claim 1 wherein the switching elements in the first and second limb portions are operable to switch the chain-link converters into circuit at the same time to reset any drift in voltages in the chain-link converter elements.

Assignees

• Crookes William
• Trainer David Reginald
• Oates Donald Colin Murray
• Alstom Technology Ltd

Inventors

• Crookes William
• Trainer David Reginald
• Oates Donald Colin Murray

Classifications

• H02M7/49

  Combination of the output voltage waveforms of a plurality of converters · CPC title

• H02M2007/4835

  Electricity · mapped topic

• Y02E40/30

  Reactive power compensation · CPC title

• H02J3/1857 Primary

  the bridge converters being multilevel bridge converters or modular multilevel converters · CPC title

• H02M7/217 Primary

  using semiconductor devices only · CPC title