LCC-MMC hybrid three-terminal high-voltage direct current transmission system and DC fault fast current limiting method thereof

A power transmission system, high-voltage direct current technology, applied to emergency protection circuit devices, circuit devices, electrical components, etc. for limiting overcurrent/overvoltage, which can solve the problem of damage to thyristor components, large power loss of diode groups, and long time required. and other problems, to achieve the effect of protecting the converter equipment, reducing the current peak value, and protecting the safe operation.

Active Publication Date: 2019-06-04
STATE GRID HENAN ELECTRIC POWER ELECTRIC POWER SCI RES INST +3
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0007] The problem of the prior art is: for the above scheme of Tang Geng et al., although the fault current can be blocked when a DC fault occurs in the system, the diode group will generate a large power loss when the system is running in a steady state, which is not conducive to the system Economical operation, and for the LCC converter, it takes a long time to force the phase shift. During the phase shift process, the LCC will generate a

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  • LCC-MMC hybrid three-terminal high-voltage direct current transmission system and DC fault fast current limiting method thereof
  • LCC-MMC hybrid three-terminal high-voltage direct current transmission system and DC fault fast current limiting method thereof
  • LCC-MMC hybrid three-terminal high-voltage direct current transmission system and DC fault fast current limiting method thereof

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specific Embodiment 1

[0046] An embodiment of the present invention provides an LCC-MMC hybrid three-terminal HVDC power transmission system, including a sending-end converter station and a receiving-end converter station;

[0047] The sending end converter station adopts LCC converter station;

[0048] The receiving end converter station adopts two MMC converter stations, denoted as MMC1 and MMC2; MMC1 and MMC2 adopt hybrid MMC;

[0049] In the system, the sending-end converter station LCC adopts constant DC current control to control the output power of the system under steady state; the receiving-end converter station MMC1 adopts constant power control to ensure stable receiving power; the receiving-end converter station MMC2 adopts Constant DC voltage control maintains the system DC voltage.

[0050] The system redesigns the control architecture of the existing hybrid DC transmission system, and the hardware architecture is composed of LCC and two MMCs to provide a hardware environment for fur...

specific Embodiment 2

[0066] An embodiment of the present invention provides a DC fault fast current limiting method for an LCC-MMC hybrid three-terminal HVDC power transmission system. The system is any one of the specific embodiment 1 including a voltage feedforward controller and a voltage comparison feedforward control. LCC-MMC hybrid three-terminal HVDC power transmission system;

[0067] The methods include:

[0068] LCC steps:

[0069] The outer loop of LCC current control adopts the combination configuration of constant DC current control and low-voltage limiter control; the inner loop of LCC current control is equipped with additional DC voltage feedforward control, and the DC voltage per unit value output by LCC is compared with the command value, and the compared Output via feedforward coefficient K L Correct the leading firing angle β;

[0070] When the system is in steady state operation, the output signal of the voltage feedforward controller is 0; when a DC fault occurs, the volta...

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Abstract

The invention discloses an LCC-MMC hybrid three-terminal high-voltage direct current transmission system and a DC fault fast current limiting method thereof. The LCC-MMC hybrid three-terminal high-voltage direct current transmission system comprises a transmitting end converter station LCC and receiving end converter stations, namely, two hybrid MMCs, and redesigns a control architecture of the existing hybrid direct current transmission system. The DC fault fast current limiting method provides a fault current limiting control strategy for the LCC and the MMCs, suppresses the magnitude of fault currents of the transmitting end LCC and the receiving end MMCs by adopting an additional control strategy during the system DC fault transient process, quickly suppresses the DC fault current whena DC fault occurs in the system, and protects current converter equipment. The LCC-MMC hybrid three-terminal high-voltage direct current transmission system and the DC fault fast current limiting method thereof realize the independent control of AC-DC control through AC-DC decoupling, enable each bridge arm to output a bridge arm output voltage reference value, and realize the control of AC and DC currents at the same time; and when a direct current fault occurs, the MMCs operate near a zero direct voltage through quickly switching the transmitting end LCC into an inverting state and negatively inputting full-bridge sub-modules of the receiving end hybrid MMCs, thereby realizing elimination of the DC fault current.

Description

technical field [0001] The invention relates to the technical field of power transmission and distribution in electric power systems, in particular to an LCC-MMC hybrid three-terminal high-voltage direct current transmission system and a fast current limiting method for direct current faults. Background technique [0002] Since the 21st century, with the increasingly prominent environmental problems, in order to reduce carbon emissions and reduce the proportion of coal-fired power generation, it is necessary to develop and utilize renewable energy on a large scale. my country's new energy bases are characterized by dispersal, remote distribution, and strong volatility, and are distributed inversely with the load center, leading to an increasing demand for large-capacity long-distance transmission of electric energy. The grid-connected high-voltage AC transmission system has inherent defects such as high cost and serious stability problems. Conventional high-voltage direct c...

Claims

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Application Information

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IPC IPC(8): H02J3/36H02H9/02
CPCY02E60/60
Inventor 刘超陈楷韩伟杨睿璋刘磊李琼林孙仕达马伟东向往文劲宇宋闯
Owner STATE GRID HENAN ELECTRIC POWER ELECTRIC POWER SCI RES INST
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