MMC-HVDC system, DC side isolation device and isolation method

Abstract

The invention discloses an MMC-HVDC system, a DC side isolation device and an isolation method. The DC side isolation device comprises first isolation switches, current transferring switches, input / output terminals and a DC breaker. One terminal of the DC breaker is connected to the ground, and the other terminal is connected to all first isolation switches; each of the first isolation switches is connected to one input / output terminal through the current transferring switch; the current transferring switch comprises a first lightening arrester and a first IGBT group or an H bridge group, wherein either the IGBT group or the H bridge group is connected to the lightening arrester in parallel; the first IGBT group consists of N first IGBTs and N second IGBT groups; the H bridge comprises N H bridge circuits which are connected in parallel; and each of the H bridge circuit comprises a first capacitor and four third IGBTs, wherein N>=kU0 / U1, E[element of]Z. The invention realizes the isolation between the MMC and the plurality of DC circuits and the MMC-HVDC system, and saves the investment cost of the power grid.

Description

technical field [0001] The invention relates to the technical field of power system control, in particular to an MMC-HVDC system, a DC side isolation device and an isolation method thereof. Background technique [0002] In order to solve the problem of grid connection and consumption of new energy, high-voltage direct current (HVDC) technology and DC grid technology based on voltage source converter (VSC) have become a hot spot in academic research. Compared with traditional AC transmission technology and HVDC transmission technology based on grid commutation converter, VSC-HVDC not only has the advantages of low line loss, large transmission capacity, and long transmission distance, but also has no synchronous operation stability of the system. Problems, can fully increase the utilization rate of renewable energy. [0003] Among many topologies, HVDC based on modular multilevel converter (MMC) has significant advantages. The direct series connection of Bipolar Transistor ...

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Problems solved by technology

[0005] In view of this, an embodiment of the present invention provides an MMC-HVDC system and its DC side isolation device and isolation method to solve the problem of introducing a DC circuit breaker on the MMC and each DC line of the MMC-HVDC system in the prior art. To isolate MMC and / or DC lines, to a certain extent increase the investment cost of the power grid, resulting in the problem that the investment cost of the power grid is too high

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