Multi-level current converter with direct-current fault ride-through capability and working method

Abstract

The invention discloses a mixed type multi-level current converter with direct-current fault ride-through capability and a working method. The current converter is based on a dislocation stacking theory and comprises a three-phase bridge rectifier circuit; each bridge arm of the three-phase bridge rectifier circuit comprises a dislocation stacking module, a cascading double-sub-module assembly, a half-bridge sub-module assembly and an electric reactor which are cascaded to one another; when a fault occurs, a discharging process before locking of the current converter is an oscillating discharging process under known initial conditions; and after the current converter is locked, equivalent capacitance values of the bridge arms are changed, if and only if backward voltages of cascading capacitors of the bridge arms are always greater than an alternating-current line voltage amplitude value in any loop states, a short-circuiting current is reduced to zero by the inverting blocking characteristic of diodes, and the direct-current fault is eliminated. The direct-current fault is eliminated in a self-limited manner by locking the current converter, and an extra high-voltage and direct-current circuit breaker is not required. The mixed type multi-level current converter with the direct-current fault ride-through capability is suitable for a common overhead circuit, and can be used for the fields of multi-terminal direct-current network establishment, new energy grid connection, passive network power supply and the like.

Description

technical field [0001] The invention relates to the technical field of power system transmission, in particular to a hybrid multilevel converter with DC fault ride-through capability and a working method. Background technique [0002] With the rapid development of power electronics technology, voltage source converters (Voltage Source Converters, VSCs) based on fully-controlled semiconductor devices have been increasingly used in the field of high-voltage direct current transmission. Compared with traditional DC transmission, VSC-based flexible DC transmission (VSC-HVDC) has the advantages of flexible and controllable transmission power, can compensate for reactive power shortage, can supply power to passive networks, and is easy to form multi-terminal networks. According to different converter structures, flexible direct current transmission can be divided into low-level VSC-HVDC and MMC-HVDC based on Modular Multilevel Converter (MMC). Compared with the former, the latter...

AI Technical Summary

Problems solved by technology

However, there are the following disadvantages: high-voltage and high-power DC circuit breakers are immature in engineering applications and the price is too high to be economical; cable transmission costs are high and are easily restricted by the laying environment; FBMMC or CDMMC has the ability to clear DC faults. However, the number of required semiconductor devices has doubled, which lacks economy and practicality

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