MMC-HVDC direct-current short-circuit fault ride-through method based on direct-current bus bipolar equipotential

A MMC-HVDC, DC bus technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., to achieve the effect of restoring power transmission and reducing the number

Active Publication Date: 2017-10-03
无锡军工智能电气股份有限公司
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Problems solved by technology

This method can only be applied to the full-bridge sub-module stru

Method used

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  • MMC-HVDC direct-current short-circuit fault ride-through method based on direct-current bus bipolar equipotential
  • MMC-HVDC direct-current short-circuit fault ride-through method based on direct-current bus bipolar equipotential
  • MMC-HVDC direct-current short-circuit fault ride-through method based on direct-current bus bipolar equipotential

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Embodiment Construction

[0043] The present invention will be further explained below in conjunction with the accompanying drawings.

[0044] A MMC-HVDC DC short-circuit fault ride-through method based on DC bus bipolar equipotential, such as figure 1 As shown, the specific implementation method has three steps: including 1. Detecting whether a DC bipolar short-circuit fault occurs, and switching the control mode of the converter to the fault ride-through mode after the fault occurs; 2. Running the fault ride-through mode 3. Judging whether to remove the fault , switch back to normal operation mode after the fault is cleared, and resume power transmission.

[0045] Among them, step 1 detects the fault current value of the DC bipolar short circuit through the current transformer, and after the fault current exceeds a preset threshold value, the control mode of the converter is switched from the normal operation mode to the fault ride-through mode.

[0046] like figure 2 As shown, the process of run...

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Abstract

The invention relates to an MMC-HVDC direct-current short-circuit fault ride-through method based on the direct-current bus bipolar equipotential, and belongs to a direct-current fault protection method of a flexible direct-current power transmission system. According to the method, the double-pole potential of the MMC direct-current side bus is controlled to be approximately equal, so that the short-circuit fault current of the direct-current side is close to zero, and the direct-current bipolar short-circuit fault ride-through can be realized under the condition that the MMC is controllable. The basic principle is that after the direct-current short-circuit current is detected, a fault operation mode is adopted, and on and off states of upper and lower three-phase bridge arms of the MMC three-phase are selected according to the polarity of the power grid voltage, the MMC circuit topology is equivalent to the chain type star topology, and the three-phase conducted upper and lower bridge arm voltage is controlled to withstand the voltage of the power grid, and the double-pole electric potential of the direct-current bus is approximately equal, the direct-current side short-circuit fault current is close to zero. An alternating-current circuit breaker is not needed, and the capacitor voltage balance of the MMC sub-module is maintained during the fault ride-through period, and after the fault is eliminated, the power transmission can be rapidly restored.

Description

technical field [0001] The invention relates to an MMC-HVDC DC short-circuit fault ride-through method based on bipolar equipotentiality of a DC bus, which belongs to a DC fault control and protection method for a flexible DC transmission system. Background technique [0002] The MMC-based flexible DC transmission technology has the advantages of being economical and flexible, can supply power to passive networks, independently control active power and reactive power, and output high-quality power. Distance from large-capacity power transmission and other fields. Although flexible DC transmission has many advantages mentioned above, in the current flexible DC transmission projects, whether it is two-level, three-level or half-bridge MMC topology, it cannot pass through the blocking converter when the DC side line fails. Quickly interrupt fault current. And because the DC fault current cannot naturally cross the zero point, it is difficult to extinguish the arc, and the com...

Claims

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Application Information

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IPC IPC(8): H02M1/32H02M7/483
CPCH02M1/32H02M7/483H02M1/325H02M7/4835
Inventor 王颖杰左慧芳杨波许贺李炎王超曾伟焦岚轶毛偃宇
Owner 无锡军工智能电气股份有限公司
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