Direct current transmission inverter side frequency control method

Patent metadata

Field	Value
Publication number	US-9768696-B2
Application number	US-201515116877-A
Country	US
Kind code	B2
Filing date	Jan 22, 2015
Priority date	Jul 4, 2014
Publication date	Sep 19, 2017
Grant date	Sep 19, 2017

Abstract

A high voltage/ultrahigh voltage direct current transmission inverter side frequency control implementing method includes: transmitting a deviation between the inverter side power grid frequency and rated frequency to the inverter side frequency controller, wherein the frequency controller regulates and outputs a modulation quantity by adopting self-adaptive parameters according to different operation conditions; when the interstation communication is normal, the modulation quantity output of the inverter side frequency controller causes the rectifier side and the inverter side to form a new power/current order through the interstation communication; when the interstation communication is abnormal, converting the inverter side to current control from voltage control and converting the rectifier side to voltage control from current control; superposing the modulation quantity output of the inverter side frequency controller to the power/current order of the inverter side, changing the size of the transmission power to realizing the inverter side frequency control.

First claim

The invention claimed is:

1. A direct current transmission inverter side frequency control implementing method, comprising:
(1) acquiring a frequency control function state, executing a step (2) in an entering state, and finishing frequency control in a quitting state;
(2) transmitting a deviation between an inverter side power grid frequency and rated frequency to an inverter side frequency controller, wherein the inverter side frequency controller regulates and outputs a modulation quantity ΔDP by adopting self-adaptive parameters according to different operation conditions;
(3) acquiring an interstation communication state, executing a step (4) when the interstation communication state is normal; and executing steps (5), (6) and (7) if the interstation communication state becomes failed from normal;
(4) causing a rectifier side and an inverter side to form a new power/current order through interstation communication by a modulation quantity ΔDP output of the inverter side frequency controller, regulating by a power/current controller at the rectifier side according to the new power/current order, thus realizing inverter side frequency control by changing a size of transmission power; and finishing frequency control after the modulation quantity ΔDP is executed;
(5) converting the inverter side to current control from voltage control and converting the rectifier side to voltage control from current control;
(6) forcedly updating a current actually measured power value as an inverter side power order and keeping for t1 ms, wherein an operator can set a power order per se according to a scheduling instruction after t1 ms; forcedly outputting zero from the inverter side frequency controller within ms t2 ms, resetting an output of a frequency integral controller as zero, and normally working after t2 ms; forcedly quitting the rectifier side frequency controller and resetting the output of the frequency integral controller as zero;
(7) superposing the modulation quantity ΔDP output of the inverter side frequency controller to a power/current order of the inverter side, regulating by the power/current controller of the inverter side according to the new power/current order, thus realizing the inverter side frequency control by changing the size of the transmission power; and finishing the frequency control after the modulation quantity ΔDP is executed.

2. The direct current transmission inverter side frequency control implementing method according to claim 1 , wherein
the value range of t1 is 0-200 ms and the value range of t2 is 0-100 ms.

3. The direct current transmission inverter side frequency control implementing method according to claim 1 , wherein
an inverter side frequency control function is temporarily automatically quitted in a power/current increasing or decreasing process of any pole of the rectifier side or inverter side, and is automatically entered after the power/current increasing or decreasing process is finished; the inverter side frequency control function is automatically quitted when direct current cannot be changed and is automatically entered until direct current can be changed.

4. The direct current transmission inverter side frequency control implementing method according to claim 1 , wherein
the modulation quantity ΔDP output of the inverter side frequency controller causes the rectifier side and the inverter side to form a new power/current order through the interstation communication means that when the power/current order is generated at the rectifier side, the modulation quantity ΔDP output of the inverter side frequency controller is transmitted to the rectifier side through interstation communication and superposition to the power/current order of the rectifier side to generate a new power/current order, and the inverter side follows the new power/current order through the interstation communication; when the power/current order is controlled to be generated by the inverter side, the modulation quantity ΔDP output of the inverter side frequency controller is directly superposed to the power/current order of the inverter side to generate a new power/current order, and the rectifier follows the new order by the interstation communication.

5. The direct current transmission inverter side frequency control implementing method according to claim 1 , wherein
the frequency controller works at a control pole, and the control pole with normal interstation communication is prior at the control pole; a non-control pole traces a frequency controller output of the control pole; direct current of the control pole cannot be changed, but direct current of the non-control pole can be changed, frequency control function of the control pole is not quitted, a modulation quantity generated by the frequency controller of the control pole is transmitted to the non-control pole by interpolar communication, and the non-control pole regulates transmission power to control frequency.

6. The direct current transmission inverter side frequency control implementing method according to claim 5 , wherein
the non-control pole tracing the frequency controller output of the control pole means that the frequency controller output of the non-control pole traces the frequency controller output of the control pole all times; the modulation quantity for power regulation of the non-control pole comes from the frequency controller output of the control pole.

7. The direct current transmission inverter side frequency control implementing method according to claim 1 , wherein
different operation conditions mean that a bi-pole power control mode has communications operated at different power levels or has no communications operated at different power levels; a mono-pole power control mode has communications operated at different power levels or has no communications operated at different power levels; and a mono-pole current control mode has communications operated at different power levels or has no communications operated at different power levels.

8. The direct current transmission inverter side frequency control implementing method according to claim 1 , wherein
the modulation power output of the frequency controller is distributed between two poles based on a proportion of operation direct voltage absolute values of the two poles and through a power limiting link.

9. The direct current transmission inverter side frequency control implementing method according to claim 1 , wherein
the inverter side frequency controller comprises a frequency proportional controller and the frequency integral controller; the frequency integral controller performs resetting with a coefficient k1 in a power/current increasing or decreasing process of any pole of the rectifier side or inverter side, the resetting process is stopped after the power/current increasing or decreasing process is finished and the value range of k1 is 0-1.

10. The direct current transmission inverter side frequency control implementing method according to claim 1 , wherein
interstation communication becomes failed from normal means that two poles both operate, and the interstation communication of the two poles becomes failed from normal; or two poles both operate, and the interstation communication of only one pole is normal, which becomes failed from normal; or only one pole operates, and the interstation communication of the pole becomes failed from normal.

Assignees

• Nr Electric Co Ltd
• Nr Electric Eng Co Ltd

Inventors

• Zhao Wenqiang
• Li Lin
• Wang Yongping

Classifications

• H02J3/00142

  Oscillations concerning frequency · CPC title

• H02M5/458

  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

• H02M3/24 Primary

  by static converters · CPC title

• H02M5/42

  by static converters · CPC title