Topology structure and start-up method of hybrid direct current transmission system based on polarity switching

Abstract

The invention relates to a topological structure of a hybrid direct-current power transmission system starting way and a staring method, in particular to a topological structure of a hybrid direct-current power transmission system based on polarity switching and a starting method. The topological structure is specific to a dual-end large power grid hybrid direct-current transmission system; a VSC (Voltage Source Converter) is adopted on a rectifying side; an LCC converter is adopted on an inversion side; the two poles of a direct-current circuit are connected to opposite poles via circuit breakers respectively. The aim of starting the system is fulfilled by matching control of the LCC converter with polarity switching of the direct-current circuit. The topological structure has the advantages that 1, the problem of the lack of starting direct-current voltage can be solved effectively when the topological structure is applied to the starting process of a practical dual-end large power grid hybrid direct-current transmission system; 2, due to the adoption of the starting method, impacts of system voltage and current can be reduced effectively in a starting process, and the safety of power equipment is protected.

Description

technical field [0001] The invention relates to a topology structure and a startup method of a hybrid direct current transmission system starting mode, in particular to a topology structure and a startup method of a hybrid direct current transmission system based on polarity switching. Background technique [0002] In recent years, with the continuous development of high-voltage direct current transmission technology, based on the consideration of technical and economic factors, the hybrid direct current transmission system composed of LCC converter and VSC converter has a good application prospect. At present, the hybrid DC transmission system has outstanding cost-effective advantages in the fields of wind power grid connection, weak grid and passive network power supply, and power transmission to large cities and other load centers. The hybrid direct current transmission system will have a very broad application prospect. Due to the particularity of the hybrid DC power tr...

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Problems solved by technology

Due to the particularity of the hybrid DC power transmission system - including the unidirectional flow of the power flow and the inconsistency of the start-up conditions of the converter stations at both ends, when connecting the AC system, most of the current hybrid DC systems prefer to choose the VSC side as constant DC voltage control. This has greatly restricted the overall control strategy and application fields of the hybrid DC transmission system. When LCC is used as an inverter station to realize DC voltage control (or constant arc extinguishing angle control), the difficulty lies in the starting conditions of VSC and LCC. Contradictory, in order to solve this bottleneck, it is necessary to solve the start-up problem of the hybrid DC transmission system in this application scenario, and research in this area has not been reported in domestic public literature and reports

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