AC side fault ride-through control method for hybrid multi-terminal DC transmission system

Abstract

The invention provides an AC side fault ride-through control method for a hybrid multi-terminal DC transmission system. The method comprises the steps: configuring the maximum DC voltage control for a rectification station LLC on the basis that the rectification station LCC employs constant direct current control, an inversion station MMC selects constant DC voltage control, and other inversion stations MMCs select constant direct current control; and configuring low-voltage current-limiting control for all inversion stations MMCs selecting the constant direct current control. The beneficial effects of the invention are that the rectification station and all inversion stations respectively carry out the corresponding operation (distributed control) for an AC side fault of any convertor station of a hybrid DC power transmission system, so as to coordinate the power distribution among stations; the DC voltage and current are controlled to be stable; and there is no DC overvoltage and low-voltage over-modulation risk. The method does not need quick inter-station communication for processing the AC fault, is simple in structure of a controller, is convenient for the setting of parameters, and is convenient for engineering application.

Description

technical field [0001] The invention relates to a hybrid DC power transmission system based on a grid commutation converter LCC and a modular multilevel voltage source converter MMC, belonging to the technical field of high-voltage power transmission. Background technique [0002] The traditional DC transmission technology based on the grid commutated converter (LCC: Line Commutated Converter) has the advantages of mature technology, low cost, and strong overload energy, but there are also problems such as commutation failure, large harmonic content, and reactive power compensation. Problem: The flexible DC transmission technology based on Modular Multi-level Voltage Source Converter (MMC: ModularMulti-level Converter) can independently adjust active and reactive power, and has superior controllability and flexibility. It is an effective way to receive power from weak and passive grids. However, flexible DC technology has high cost, large loss, and complicated control. The ...

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Problems solved by technology

For the control strategy of the above hybrid multi-terminal DC transmission system, the control system has the following technical problems: when the AC system of the 12-pulse rectifier station LCC fails, and the rectification capacity of the rectifier station LCC is less than the sum of the transmission power of all inverter stations MMC, the DC The voltage will continue to drop, and too low DC voltage will lead to overmodulation of the flexible DC system, poor control effect, and transmission of harmonics to the AC system; when the AC system of the fixed DC voltage inverter station MMC fails, and the inverter station MMC1 When the transmission power capability of the flexible DC is severely limited, the DC voltage will continue to rise, resulting in the risk of overvoltage breakdown of the module capacitor in the flexible DC

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