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Control method and system for enhancing power sending-out capacity of MMC converter station under power grid fault

A technology of sending capacity and power grid failure, applied in the direction of converting AC power input to DC power output, output power conversion device, power transmission AC network, etc., can solve the problems affecting the power sending capacity of the converter and current waveform distortion

Active Publication Date: 2020-07-10
POWERCHINA HUADONG ENG COPORATION LTD
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  • Abstract
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AI Technical Summary

Problems solved by technology

However, for the MMC converter station, when a voltage asymmetrical drop fault such as single-phase grounding occurs in the large power grid, the fault point and the MMC are connected by a connecting transformer. When the connecting transformer adopts Y 0 / Y 0 When connected, an additional zero-sequence circuit will be generated
At this time, the output current of the MMC converter will contain a large number of zero-sequence components, which will further lead to distortion of the current waveform and seriously affect the power delivery capability of the converter.

Method used

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  • Control method and system for enhancing power sending-out capacity of MMC converter station under power grid fault
  • Control method and system for enhancing power sending-out capacity of MMC converter station under power grid fault
  • Control method and system for enhancing power sending-out capacity of MMC converter station under power grid fault

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Embodiment Construction

[0059] like figure 1 , figure 2 As shown, this embodiment is a control system for enhancing the power sending capability of MMC converter stations under asymmetric grid voltage drop faults, the system includes MMC converter station 1, and the connection group is Y 0 / Y 0 The connecting transformer 2, the voltage sensor 3 used to detect the three-phase voltage on the grid side, the current sensor I4 used to detect the three-phase current on the grid side, the current sensor II5 used to detect the three-phase current on the valve side of the connected transformer, the control of the system The links include phase-locked loop module 6, coordinate transformation and positive and negative sequence separation module 7, power calculation module 8, zero sequence current suppression module 9, DC bus voltage and reactive power controller 10, positive and negative sequence current controller 11, reference A differential mode voltage calculation module 12 , an internal circulation cont...

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Abstract

The invention discloses a control method for enhancing the power sending-out capability of an MMC converter station under a power grid voltage asymmetric drop fault. According to the method, in view of the problem that the power sending-out capability is obviously reduced due to zero-sequence and negative-sequence currents in an MMC converter station under an asymmetric fault of a power grid, thesuppression of zero-sequence current components is realized through a second-order generalized integrator, and the method can be combined with an existing positive and negative sequence decoupling control method to fully suppress the zero-sequence component and the negative-sequence component in the current when the power grid voltage drops asymmetrically, so that the power sending-out capabilityof the MMC converter station is effectively improved, the input frequency of a DC chopper is reduced, and the fault ride-through operation of the system can be realized even under the condition that the DC chopper is not required to be input when the fault is relatively light. The improved control strategy provided by the invention is very simple to implement and has relatively high practicability.

Description

technical field [0001] The invention relates to a control method and system for enhancing the power sending capability of an MMC converter station under a power grid fault, and is applicable to the technical field of power electronics. Background technique [0002] With the increasingly serious problems of global environmental pollution and energy crisis, vigorously developing renewable energy has become the consensus of all countries in the world. Flexible DC transmission technology has very good application prospects in the collection and transmission of large-scale renewable energy, and has received extensive attention. Especially for long-distance offshore wind farms, flexible DC transmission technology has become the best choice for connecting to large onshore power grids. Compared with the flexible DC transmission technology based on two-level or three-level topology, the flexible DC transmission technology based on the modular multilevel converter (MMC) topology has ...

Claims

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Application Information

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IPC IPC(8): H02J3/36H02M7/00
CPCH02J3/36H02M7/00Y02E60/60
Inventor 王霄鹤周才全陈晴杨文斌谢瑞杨林刚傅春翔李景一徐志辉高玉青
Owner POWERCHINA HUADONG ENG COPORATION LTD
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