HVDC converter with neutral-point connected zero-sequence dump resistor

• US 8,854,843 B2
• Filed: 08/24/2010
• Issued: 10/07/2014
• Est. Priority Date: 08/24/2010
• Status: Expired due to Fees

• Current Assignee: Alstom Technology Ltd. (Alstom SA)
• Original Assignee: Alstom Technology Ltd. (Alstom SA)
• Inventors: Trainer, David Reginald, Okaeme, Nnamdi
• Primary Examiner(s): Dole, Timothy J
• Assistant Examiner(s): AHMED, YUSEF A
• Application Number:
  US13/818,654
• Publication Number:
  US 20140146583A1
• Time in Patent Office: 1,505 Days
• Field of Search: 363/35, 363/39, 363/44, 363 65- 68, 363125-132, 323205-208, 323/266
• US Class Current: 363/35
• CPC Class Codes: H02J 3/1857 wherein such bridge converter is a multilevel converter
• CPC Class Codes: H02J 3/36 Arrangements for transfer of electric power between ac networks via a high-tension dc link
• CPC Class Codes: H02M 1/0095 Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/4835 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 Class Codes: H02M 7/49 Combination of the output voltage waveforms of a plurality of converters
• CPC Class Codes: H02M 7/797 using semiconductor devices only
• CPC Class Codes: Y02E 40/20 Active power filtering [APF]
• CPC Class Codes: Y02E 60/60 Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

A power electronic converter (30)is for use in high voltage direct current power transmission and reactive power compensation, the power electronic converter (30) including three phase elements (32) defining a star connection (36) and a converter unit (34) including first and second DC terminals (50,52) for connection in use to a DC network (56) and three AC terminals (54), the converter unit (34) including a plurality of switching elements (70,74) controllable in use to facilitate power conversion between the AC and DC networks (44,56), the power electronic converter (30) further including a third DC terminal (78) connected between the first and second DC terminals (50,52), the third DC terminal (78) being connected to a common junction (40) of the star connection (36) to define an auxiliary connection (82), the auxiliary connection (82) including at least one dump resistor (84) connected between the common junction (40) and the third DC terminal (78), wherein the switching elements (70,74) of the converter unit (34) are controllable in use to modify a phase voltage at each AC terminal (54) to include a triplen harmonic voltage component so as to dissipate real power in the or each dump resistor (84) at a triplen harmonic frequency.

Claims

1. A power electronic converter (30) for use in high voltage direct current power transmission and reactive power compensation, the power electronic converter (30) including three phase elements (32) defining a star connection in which a first end (38) of each phase element is connected to a common junction (40), the power electronic converter (30) further including a converter unit (34) including first and second DC terminals (50, 52) for connection in use to a DC network (56) and three AC terminals (54), each AC terminal (54) being connected in series with a second end (58) of a respective phase element (32) of the star connection (36), the converter unit including a plurality of switching elements (70, 74) controllable in use to facilitate power conversion between the AC and DC networks (44, 56), the power electronic converter further including a third DC terminal (78) connected between the first and second DC terminals (50, 52), the third DC terminal (78) being connected to the common junction (40) of the star connection (36) to define an auxiliary connection (82), the auxiliary connection including at least one dump resistor (84) connected between the common junction (40) and the third DC terminal (78), wherein the switching elements (70, 74) of the converter unit (34) are controllable in use to modify a phase voltage at each AC terminal to include a triplen harmonic voltage component so as to dissipate real power in the or each dump resistor at a triplen harmonic frequency.

2. A power electronic converter (30) according to claim 1 wherein the switching elements of the converter unit are controllable in use to modify the phase voltage at each AC terminal to simultaneously include a fundamental voltage component and a triplen harmonic voltage component.

3. A power electronic converter (30) according to claim 1 wherein each triplen harmonic voltage component has the same magnitude.

4. A power electronic converter (30) according to claim 1 further including at least one DC link capacitor (16) connected in series between the third DC terminal and each of the first and second DC terminals.

5. A power electronic converter (30) according to claim 1 wherein each phase element includes a transformer winding.

6. A power electronic converter (30) according to claim 1 wherein the converter unit further includes three converter limbs (60), each converter limb including a respective one of the AC terminals, each converter limb defining first and second limb portions (62, 64) being respectively connected in series between the AC terminal and a respective one of the first and second DC terminals, each limb portion including a chain-link converter (66), each chain-link converter (66) including a plurality of modules connected in series, each module including at least one primary switching element (70) connected to at least one energy storage device, the or each primary switching element (70) of each chain-link converter being operable in use so that the plurality of modules connected in series defines a stepped variable voltage source.

7. A power electronic converter (30) according to claim 6 wherein each limb portion further includes at least one secondary switching element (74) connected in series with the respective chain-link converter, the or each secondary switching element (74) of each limb portion being controllable in use to switch the respective chain-link converter into or out of circuit.

8. A power electronic converter (30) according to claim 6 wherein each module of each chain-link converter (66) includes a set of series-connected primary switching elements connected in parallel with an energy storage device to define a 2-quadrant unipolar module that is capable of providing zero or positive voltage and can conduct current in two directions.

9. A power electronic converter (30) according to claim 6 wherein each module of each chain-link converter (66) includes two sets of primary series-connected switching elements connected in parallel with an energy storage device to define a 4-quadrant unipolar module that is capable of providing negative, zero or positive voltage and can conduct current in two directions.

10. A power electronic converter (30) according to claim 6 wherein the or each energy storage device of each module is a capacitor, fuel cell, photovoltaic cell, battery or an auxiliary AC generator with an associated rectifier.

11. A power electronic converter (30) according to claim 1 wherein each switching element includes at least one semiconductor device.

12. A power electronic converter (30) according to claim 11 wherein the or at least one semiconductor device is an insulated gate bipolar transistor, a gate turn-off thyristor, a field effect transistor, an insulated gate commutated thyristor, an injection enhanced gate transistor or an integrated gate commutated thyristor.

13. A power electronic converter (30) according to claim 11 wherein each switching element further includes an anti-parallel diode connected in parallel with the respective semiconductor device.

14. A power electronic converter (30) according to claim 1 further including three primary windings, wherein each phase element of the star connection is mutually coupled with a respective one of the primary windings, a first end of each primary winding is connected to a second end of a different primary winding such that the interconnection of the primary windings define a closed loop, and each junction between two primary windings is for connection in use to a respective phase of the three-phase AC network.