A single-pole ground fault ride-through and restoration method of symmetrical bipolar mmc DC side

Abstract

The invention provides a symmetrical bipolar MMC DC-side single-pole ground fault ride-through and recovery method. Through cooperation of a DC circuit breaker and a converter, DC fault current cut-off and power recovery are realized, and safe operation of the converter is protected. Through cooperation of active power and reactive power of the sound pole and the faulty pole, the active power deficiency of a converter station in the failure period is reduced. Rated reactive power is supplied to the grid, and therefore, the impact of a fault to an AC system is reduced. By actively controlling the common-mode components of the reference voltages of the upper and lower bridge arms of the converter, the risk brought to the safe operation of the system by excessive current surge stress of the converter due to reclosing failure is avoided. Based on the fact that a dual-pole short-circuit fault at the DC side of a symmetrical bipolar MMC can be regarded as a special case of single-pole ground faults of both positive and negative DC buses, the method of the invention can be used to handle a dual-pole short-circuit fault at the DC side of a symmetrical bipolar MMC.

Description

technical field [0001] The invention belongs to the field of DC fault protection of a flexible high-voltage direct current transmission system, and more specifically relates to a single-pole grounding fault ride-through and recovery method on the DC side of a symmetrical bipolar MMC. Background technique [0002] Due to the increasingly prominent problems of energy shortage and environmental protection, the proportion of new renewable energy such as wind power and solar energy in the total power generation is gradually increasing. In my country, wind energy, solar energy and other energy sources are mostly concentrated in remote areas, resulting in an uneven geographical distribution of energy and loads, requiring long-distance, large-capacity transmission of electric energy. When applied to long-distance, large-capacity power transmission, the cost and reactive power loss of high-voltage AC power transmission system increase rapidly with the increase of power transmission d...

AI Technical Summary

Problems solved by technology

[0009] In view of the above defects or improvement needs of the prior art, the present invention provides a ride-through method and recovery strategy for symmetrical bipolar MMC DC pole-to-ground faults, aiming to solve the problem of large active power shortage and The problem of large surge current stress when reclosing DC circuit breaker

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