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Control method of MMC-HVDC (multi media card-high voltage direct current) during power grid malfunction of receiving end

A control method and technology of the receiving end power grid, applied in the direction of power transmission AC network, electrical components, circuit devices, etc., can solve the problems of MMC-HVDC operation instability, operation safety impact, voltage and current distortion, etc.

Inactive Publication Date: 2014-12-17
SOUTH CHINA UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] When an asymmetrical fault occurs in the AC power grid at the receiving end, a negative sequence component will be generated, and a large number of non-characteristic harmonics will be generated on the AC and DC sides of the MMC, and the voltage and current will be distorted, affecting power transmission and voltage quality. MMC's switching elements, diodes, capacitors and other equipment have an impact on the operation safety, and a large negative sequence current may cause system protection actions, resulting in unstable operation of MMC-HVDC

Method used

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  • Control method of MMC-HVDC (multi media card-high voltage direct current) during power grid malfunction of receiving end
  • Control method of MMC-HVDC (multi media card-high voltage direct current) during power grid malfunction of receiving end
  • Control method of MMC-HVDC (multi media card-high voltage direct current) during power grid malfunction of receiving end

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Embodiment

[0034] Such as figure 1 As shown, this example is a two-terminal flexible DC power transmission system in which wind farm 1 transmits power to the AC power grid at the receiving end. The wind farm 1 at the sending end passes through the step-up transformer T M1 Boost to the MMC rectifier station at the sending end, enter the DC cable 2 to transmit the power to the MMC inverter at the receiving end, and pass through the voltage regulating transformer T M2 The voltage regulation transmits the electric energy to the AC grid 4 at the receiving end through the PCC3 at the receiving end.

[0035] Such as figure 2 As shown, the hybrid multilevel converter based on the full-bridge and half-bridge modules of this embodiment includes three-phase units connected between the positive and negative DC buses, and each phase unit consists of an upper bridge arm and a lower bridge arm Composition, each bridge arm includes N half-bridge modules (SM 1 , SM 2 ,···,SM N ), N is a positive i...

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Abstract

The invention discloses a control method of MMC-HVDC (multi media card-high voltage direct current) during power grid malfunction of a receiving end. The control method includes following steps: 1, measuring to acquire a voltage instantaneous value and a current instantaneous value of a transformer outlet; 2, acquiring a positive sequence voltage d axis component, a positive sequence voltage q axis component, a negative sequence voltage d axis component and a negative sequence voltage q component through a 1 / 4 periodic signal delay principle, separating the positive and negative sequence components, and obtaining positive and negative sequence components of a network voltage under a synchronous rotating reference frame through coordinate transformation; and 3, dividing a voltage equation into a positive sequence equation and a negative sequence equation, and indicating the positive sequence components and the negative sequence components of various electrical capacities respectively by superscript P and N. The control method has the advantages of enabling a flexible direct current system to have unsymmetrical fault ride-through ability and the like.

Description

technical field [0001] The invention relates to power electronics and direct current transmission technology, in particular to an MMC-HVDC control method when a receiving-end power grid fails. Background technique [0002] With the development of wind power technology, the scale of wind farms is getting bigger and bigger, and wind power has the characteristics of intermittent, uncontrollable, and far away from the main power grid. Flexible DC transmission technology has the advantages of independent control of active and reactive power, stable AC bus voltage, isolation of interference, and easy construction of multi-terminal DC systems. It is very suitable for large-scale wind farms to be connected to the grid. [0003] In the field of flexible DC transmission based on voltage source converters, two-level topologies were first used, and the withstand voltage and transmission power of switching devices are limited, and output filtering devices need to be added. To solve thes...

Claims

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Application Information

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IPC IPC(8): H02J3/00H02J3/36
CPCY02E60/60
Inventor 夏成军黄浩宇梁君君李勇
Owner SOUTH CHINA UNIV OF TECH
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