Method and system for suppressing short-circuit current of modular multilevel converter

Abstract

The invention discloses a method and system for suppressing short-circuit current of a modular multilevel converter, and the method comprises the steps: enabling a control strategy to take effect when a fault that a circuit breaker needs to be cut off occurs in an AC system; calculating a first q-axis current reference value output by an outer ring controller of the MMC at a sampling moment before the control strategy takes effect; and controlling a second q-axis current reference value output by an outer ring controller of the MMC in real time to be consistent with the first q-axis current reference value within a preset time period when the control strategy takes effect, and controlling an inner ring controller of the MMC through the second q-axis current reference value to realize suppression of the short-circuit current output by the MMC. According to the method, MMC output current control which does not exceed the capacity limit of the circuit breaker can be realized, the short-circuit current output by the MMC can be greatly reduced within the strategy effective time, the reactive power supporting capability of the MMC to the alternating current system is recovered after the strategy exits, and the method can be used for MMC grid-connected operation guidance and supporting of voltage stability of the alternating current system.

Description

technical field [0001] The present invention relates to the control response technical field of the outer loop controller and the inner loop controller of a modular multilevel converter (Modular Multilevel Converter, MMC), and more specifically, relates to a method for suppressing modular multilevel commutation A method and system for short-circuit current of a device. Background technique [0002] The flexible DC transmission technology based on modular multi-level converter MMC has broad application prospects in the field of new energy transmission. After the AC system fault occurs, the flexible DC converter has the fault ride-through capability, does not block during the fault, and has the ability to provide fault current to the fault point. With the increasing application of power electronic equipment in the power system in the future, the moment of inertia of the power system will continue to decrease, and the ability of frequency regulation and voltage regulation will...

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Problems solved by technology

[0004] The present invention proposes a method and system for suppressing the short-circuit current of a modular multi-level converter to solve how to control the output short-circuit current of the MMC without exceeding the limit of the capacity of the circuit breaker after the AC system fails, and to realize the use of the MMC. problem of support

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