Hybrid high voltage direct current converter system and method of operating the same

Patent metadata

Field	Value
Publication number	US-9602021-B2
Application number	US-201414201062-A
Country	US
Kind code	B2
Filing date	Mar 7, 2014
Priority date	Mar 7, 2014
Publication date	Mar 21, 2017
Grant date	Mar 21, 2017

Abstract

A hybrid HVDC converter system includes a DC bus, at least one capacitor commutated converter (CCC) and at least one self-commutated converter (SCC) coupled in series through the DC bus. The CCC induces a first voltage on the DC buses, the SCC induces a second voltage on the DC bus, the first voltage and the second voltage are summed to define a total DC voltage. The method includes at least one of regulating the total DC voltage induced on the DC buses including regulating the first DC voltage through the CCC and regulating the second DC voltage through the SCC substantially simultaneously, regulating the total DC voltage induced on the DC bus including regulating the second DC voltage through the SCC, and regulating the total DC voltage induced on the DC bus including regulating the first DC voltage through the CCC.

First claim

What is claimed is:

1. A method for controlling a hybrid high voltage direct current (HVDC) converter system, the hybrid HVDC converter system including at least one direct current (DC) bus, at least one capacitor commutated converter (CCC), at least one self-commutated converter (SCC), the at least one CCC and the at least one SCC coupled in series to the at least one DC bus, the at least one CCC configured to induce a first DC voltage on the at least one DC bus, the at least one SCC configured to induce a second DC voltage on the at least one DC bus, the first DC voltage and the second DC voltage summed to define a total DC voltage induced on the at least one DC bus, said method comprising at least one of:
regulating the total DC voltage induced on the at least one DC bus comprising regulating the first DC voltage through the at least one CCC and regulating the second DC voltage through the at least one SCC substantially simultaneously;
regulating the total DC voltage induced on the at least one DC bus comprising regulating the second DC voltage through the at least one SCC; and
regulating the total DC voltage induced on the at least one DC bus comprising regulating the first DC voltage through the at least one CCC;
wherein the at least one CCC and the at least one SCC are coupled in series.

2. The method in accordance with claim 1 , wherein the hybrid HVDC converter system further includes at least one alternating current (AC) bus, said method further comprising regulating the at least one SCC to regulate at least one of an AC frequency, an AC voltage, and an AC current on the at least one AC bus.

3. The method in accordance with claim 2 , wherein the hybrid HVDC converter system further includes a control system configured to regulate the at least one SCC, the control system includes a volt-VAR control loop and a DC link control loop, wherein the at least one SCC includes an AC/DC converter stage, a DC/DC converter stage, and a DC link extending therebetween, wherein regulating the at least one SCC to regulate at least one of an AC frequency, an AC voltage, and an AC current on the at least one AC bus comprises at least one of:
using the volt-VAR control loop to regulate reactive power injection through the at least one AC bus;
using at least a portion of reactive power generated by the AC/DC converter stage to facilitate reducing a reactive power requirement of at least one AC filter to a predetermined range, thereby further reducing voltage support requirements from the at least one capacitive device to the hybrid HVDC converter system;
using measurements of current on the at least one AC bus to regulate the hybrid HVDC converter system to inject low order harmonic currents into the at least one AC bus, thereby facilitating decreasing a requirement of low order AC harmonic filters to compensate for low order harmonic currents;
using the DC link control loop to at least partially regulate a voltage induced on the DC link; and
determining a voltage transient condition on the at least one DC bus and prioritizing regulating the voltage induced on the DC link over regulating reactive power injection through the at least one AC bus.

4. The method in accordance with claim 1 , wherein the at least one CCC includes a plurality of thyristor valves, wherein regulating the first DC voltage through the at least one CCC comprises regulating a firing angle value of the plurality of thyristor valves to approximately a firing command reference value.

5. The method in accordance with claim 4 , wherein regulating the first DC voltage through the at least one CCC and regulating the second DC voltage through the at least one SCC substantially simultaneously comprises:
determining a voltage transient condition on the at least one DC bus;
determining if the second DC voltage induced by the at least one SCC is approaching a predetermined parameter; and
regulating the firing command reference value to increase a portion of control of the total DC voltage through regulating the first DC voltage induced by the at least one CCC, thereby facilitating increasing a margin of the second DC voltage to the predetermined parameter.

6. The method in accordance with claim 5 , wherein increasing a margin of the second DC voltage to the predetermined parameter comprises increasing an operational bandwidth of the at least one SCC to regulate the total DC voltage induced on the at least one DC bus.

7. The method in accordance with claim 4 , wherein the at least one CCC includes at least one series capacitive device configured to provide voltage support to the hybrid HVDC converter system, wherein regulating the firing angle value of the plurality of thyristor valves to approximately a firing command reference value comprises regulating the firing angle of the plurality of thyristor valves to reduce a reactive power requirement of the plurality of thyristor valves to a predetermined range, thereby reducing voltage support requirements from the at least one series capacitive device of the hybrid HVDC converter system and reducing voltage stresses induced on the plurality of thyristor valves.

8. The method in accordance with claim 7 , wherein the hybrid HVDC converter system further includes at least one AC filter, wherein regulating the firing angle value of the plurality of thyristor valves to approximately a firing command reference value comprises regulating the firing angle of the plurality of thyristor valves to reduce a reactive power requirement of the at least one AC filter to a predetermined range, thereby further reducing at least one of voltage support requirements and a reactive power nameplate rating from the at least one series capacitive device of the hybrid HVDC converter system.

9. The method in accordance with claim 1 , wherein the at least one SCC includes an AC/DC converter stage, a DC/DC converter stage, and a DC link extending therebetween, wherein the DC/DC converter stage includes a plurality of semiconductor switching devices configured to regulate the second DC voltage through pulse width modulation (PWM), wherein regulating the second DC voltage through the at least one SCC comprises regulating the PWM, thereby operating the DC/DC converter stage to induce the second DC voltage in at least two quadrants of a four quadrant voltage-current system.

10. The method in accordance with claim 9 , wherein the four quadrant voltage-current system is defined by a voltage axis and a current axis, wherein operating the DC/DC converter stage to induce the second DC voltage in at least two quadrants of a four quadrant voltage-current system comprises regulating the second DC voltage between a positive DC voltage polarity range and a negative DC voltage polarity range, thereby facilitating a reduction of a voltage rating of the at least one SCC.

11. The method in accordance with claim 1 , wherein the hybrid HVDC converter system further includes at least one AC bus, wherein the at least one transformer has a tap changing function, wherein regulating the total DC voltage induced on the at least one DC bus comprising regulating the first DC voltage through the at least one CCC and regulating the second DC voltage through the at least one SCC substantially simultaneously comprises:
determining if there is an electric power transient associated with at least one of a measured real-time voltage value, current value, power value on the at least one AC bus, and at least one of a measured real-time voltage value, current value, and power value on the at least one DC bus; and
regulating the second DC voltage generated by the at least one SCC, thereby indirectly regulating AC voltages, currents, and powers and DC voltages, currents, a

Assignees

• Gen Electric

Inventors

• Chaudhuri Nilanjan Ray
• Gupta Ranjan Kumar
• Larsen Einar Vaughn

Classifications

• H02M7/7575

  for high voltage direct transmission link · CPC title

• H02M5/4585 Primary

  having a rectifier with controlled elements · CPC title

• H02J3/36 Primary

  Arrangements for transfer of electric power between AC networks via high-voltage DC [HVDC] links; Arrangements for transfer of electric power between generators and networks via HVDC links · CPC title

• Y02E60/60

  Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD] · CPC title

• H02M7/5387

  in a bridge configuration · CPC title