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Direct current grid fault current complex frequency domain calculation method

A fault current, DC grid technology, applied in the field of power transmission and distribution, can solve problems such as no fault self-clearing capability, weak damping, and DC grid damage

Inactive Publication Date: 2019-08-09
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The characteristics of "low inertia and weak damping" of the DC power grid make it extremely poor in tolerance to DC faults, and the capacitor of the MMC sub-module discharges rapidly at the moment of a fault, causing serious harm to the entire DC power grid
[0004] Since the traditional half-bridge MMC converter station has no fault self-clearing capability, it is necessary to configure a DC circuit breaker to cut off the faulty line

Method used

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  • Direct current grid fault current complex frequency domain calculation method
  • Direct current grid fault current complex frequency domain calculation method
  • Direct current grid fault current complex frequency domain calculation method

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Embodiment Construction

[0011] In order to further illustrate the calculation process of the present invention, the principle of the invention will be described in detail below in conjunction with the accompanying drawings.

[0012] figure 1 It is a schematic diagram of a four-terminal DC grid. In the case of overhead line power transmission, the MMC DC grid usually adopts a symmetrical bipolar structure in which the positive and negative poles can operate independently. After a DC line failure of one pole, the other pole can still transmit half of the power. Thereby improving the reliability of DC grid power supply. The 4 MMC converter stations are connected by 4 positive and negative DC lines to form a network. Smoothing reactors and DC circuit breakers are installed at both ends of the lines, and grounding reactors are installed between the converter outlet and the neutral line. It is mainly used to suppress the rising speed of the fault current and buy a certain time for the action of line prote...

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Abstract

The invention provides a direct current grid fault current complex frequency domain calculation method. In the technical field of power transmission and distribution, a direct current grid is used asan effective means to collect new energy sources such as wind power and photovoltaic energy resources, and the calculation of fault currents is of great significance for operation such as equipment type selection, protection design and parameter optimization. The fault current complex frequency domain calculation method is suitable for monopole and bipolar faults and is not affected by the transition resistance, the alternating current feed of the alternating current side after the fault and the direct current feed of a remote sound branch are fully considered, for the alternating current feedof a converter station, a superposition theorem is used for dividing the direct current grid into a normal network and a fault additional network, and the normal network and the fault additional network are solved separately; and for the direct current feed of a normal line branch, an external node of the fault additional network is statically equivalent, and an equivalent circuit is subjected tofault current solution in a complex frequency domain.

Description

technical field [0001] The invention belongs to the technical field of power transmission and distribution, and in particular relates to a calculation method in the complex frequency domain of a DC power grid fault current. Background technique [0002] The Voltage Source Converter based HVDC (VSC-HVDC) with fully controlled devices has unique technical advantages such as four-quadrant independent control of active and reactive power, easy power flow reversal, and can be used as a black start power supply. Modular Multilevel Converter (MMC) is a new type of VSC topology. On the basis of the above advantages, it adopts the cascading method of sub-modules to avoid the need for two- and three-level VSC power devices. Issues such as trigger consistency and short-circuit failure caused by crimped series connection have become the development trend of VSC-HVDC. [0003] MMC has attracted extensive attention due to its advantages such as low switching loss, less output harmonics, ...

Claims

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Application Information

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IPC IPC(8): G01R31/08
CPCG01R31/085G01R31/088Y04S10/52
Inventor 赵成勇俞永杰吕煜许建中
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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