High-voltage direct current converter including a 12-pulse diode recitifier connected in series with a voltage-source converter

Patent metadata

Field	Value
Publication number	US-9692311-B2
Application number	US-201414781582-A
Country	US
Kind code	B2
Filing date	Jun 27, 2014
Priority date	Aug 29, 2013
Publication date	Jun 27, 2017
Grant date	Jun 27, 2017

Abstract

The present invention relates to a high-voltage direct current (HVDC) converter comprising: a 12-pulse diode rectifier having two three-phase bridge diode rectifiers connected in series to rectify, to 12 pulses, alternating current (AC) power inputted from a point of connection on the sea; and a voltage-source converter connected in series to a lower end of the 12-pulse diode rectifier, wherein the voltage-source converter controls a voltage of the AC power inputted from the point of connection on the sea and a DC link voltage of the voltage-source converter.

First claim

What is claimed is:

1. A converter for high voltage direct current transmission, comprising:
a 12-pulse diode rectifier including two three-phase full bridge diode rectifiers connected in series and rectifying AC power input from an offshore point of common coupling (PCC) into 12-pulse power; and
a voltage-source converter connected in series to a lower end of the 12-pulse diode rectifier,
wherein the voltage-source converter is a multi-phase converter in which multiple phases are coupled in parallel with each other at the lower end of the 12-pulse diode rectifier, and
wherein the voltage-source converter controls voltage of AC power input from the offshore PCC and DC link voltage of the voltage-source converter.

2. The converter for high voltage direct current transmission according to claim 1 , further comprising:
a Y/Y/Δ 3-winding transformer connected to an input end of the 12-pulse diode rectifier and inputting AC power to each of the three-phase full bridge diode rectifiers of the 12-pulse diode rectifier.

3. The converter for high voltage direct current transmission according to claim 1 , wherein the voltage-source converter has a rated voltage corresponding to ⅓ of rated voltage of an HVDC system.

4. The converter for high voltage direct current transmission according to claim 1 , further comprising:
a filter inductor connected in series to an input side of each of the three-phase full bridge diode rectifiers,
wherein each of two secondary sides of the Y/Y/Δ 3-winding transformer is connected in series to the filter inductor.

5. The converter for high voltage direct current transmission according to claim 4 , further comprising:
an AC filter connected in parallel to a primary side of the Y/Y/Δ 3-winding transformer and removing higher order harmonics.

6. The converter for high voltage direct current transmission according to claim 5 , wherein the AC filter comprises a resistor, an inductor and a capacitor, and removes higher order harmonic components of grid current, including at least 23rd and 25th harmonic components.

7. The converter for high voltage direct current transmission according to claim 1 , further comprising:
a control unit for controlling the voltage-source converter,
wherein the control unit comprising:
an offshore PCC voltage controller receiving an AC voltage command value and a measured value of AC voltage at the offshore PCC as a feedback signal and outputting a Q-axis command signal to control reactive power;
a DC link voltage controller receiving a DC link voltage command value and a measured value of DC link voltage of the voltage-source converter as a feedback signal and outputting a D-axis command signal to control active power;
a d-q converter converting a two-phase signal of the Q-axis command signal and the D-axis command signal output from the offshore PCC voltage controller and the DC link voltage controller, respectively, into a three-phase signal;
a proportional-resonant controller removing 11th and 13th harmonic current components through band pass filtering, the harmonic current components being generated at the offshore PCC by the 12-pulse diode rectifier; and
a space-vector PWM generator receiving a command value obtained by adding output of the proportional-resonant controller to output of the d-q converter and controlling each of IGBT devices constituting the voltage-source converter in a space-vector PWM manner.

8. The converter for high voltage direct current transmission according to claim 7 , wherein each of the offshore PCC voltage controller and the DC link voltage controller is a proportional-integral (PI) controller.

9. The converter for high voltage direct current transmission according to claim 1 , wherein the voltage-source converter comprises at least one of a 2-level voltage-source converter, a multilevel NPC converter, and a modular multilevel converter.

10. A converter for high voltage direct current transmission, comprising:
a 12-pulse diode rectifier including two three-phase full bridge diode rectifiers connected in series and rectifying AC power input from an offshore point of common coupling (PCC) into 12-pulse power;
a voltage-source converter connected in series to a lower end of the 12-pulse diode rectifier; and
a Y/Y/Δ 3-winding transformer connected to an input end of the 12-pulse diode rectifier and inputting AC power to each of the three-phase full bridge diode rectifiers of the 12-pulse diode rectifier,
wherein the voltage-source converter controls voltage of AC power input from the offshore PCC and DC link voltage of the voltage-source converter, and
wherein the Y/Y/Δ 3-winding transformer removes 5th and 7th harmonic current components generated by each of the three-phase full bridge diode rectifiers by virtue of 30° phase difference between two secondary side phase voltages of the Y/Y/Δ three-winding transformer.

11. A converter for high voltage direct current transmission, comprising:
a 12-pulse diode rectifier including two three-phase full bridge diode rectifiers connected in series and rectifying AC power input from an offshore point of common coupling (PCC) into 12-pulse power;
a voltage-source converter connected in series to a lower end of the 12-pulse diode rectifier; and
a boost inductor connected in series to an input side of the voltage-source converter,
wherein the voltage-source converter controls voltage of AC power input from the offshore PCC and DC link voltage of the voltage-source converter, and
wherein the boost inductor filters out harmonic components generated in current due to switching of the voltage-source inverter, and a secondary side of a converter transformer is connected in series to the boost inductor.

12. The converter for high voltage direct current transmission according to claim 11 , further comprising:
an AC filter connected in parallel between the secondary side of the converter transformer and the boost inductor and removing higher order harmonics of grid current.

Assignees

• Korea Electric Power Corp

Inventors

• Kim Chan Ki
• Kim Jin Young
• Lee Dong Choon
• Nguyen Thanh Hai

Classifications

• H02M1/12

  Arrangements for reducing harmonics from AC input or output · CPC title

• H02M5/458 Primary

  using semiconductor devices only · CPC title

• Y02E60/60

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

• H02J3/36

  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

• H02M7/10 Primary

  arranged for operation in series, e.g. for multiplication of voltage · CPC title