Direct current circuit breaker-based flexible direct-current power grid protection method and system

Abstract

The invention provides a direct current circuit breaker-based flexible direct-current power grid protection method and system. The method comprises the following steps of determining a protection action criterion of a direct-current circuit breaker based on the collected inductance voltage of the direct-current circuit breaker and the direct-current side voltage of a modularized multi-level converter; and according to the protection action criterion of the direct-current circuit breaker, determining protection action logic of the direct-current circuit breaker. According to the method, the protection action criterion of the direct-current circuit breaker is generated through the locally-measured electrical information, so that the occurrence and the position of a direct-current line or a bus fault can be judged quickly and effectively, the direct-current circuit breaker can be quickly and selectively isolated from the direct-current fault, and reliable protection of the direct-currentfault of the flexible direct-current power grid is realized.

Description

technical field [0001] The invention relates to the field of DC power grid safety and protection, in particular to a protection method and system for a flexible DC power grid based on a DC circuit breaker. Background technique [0002] Flexible DC grid technology is one of the effective methods to solve large-scale new energy collection, long-distance transmission and large-scale consumption. Among them, the modular multilevel converter (MMC) has become the preferred technical solution for building a flexible DC grid converter station due to its characteristics of bidirectional power flow, no commutation failure, and fast decoupling control of active and reactive power. Although the flexible DC grid including MMC has many advantages, it still faces many technical problems to be solved, especially the grid protection problem under DC fault. [0003] Since the impedance of the flexible DC grid is very small, and there is a freewheeling diode in the half-bridge MMC, the DC fau...

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Problems solved by technology

[0004] The wavelet analysis method in the prior art is to identify the faulty line by detecting the discharge of the capacitance of each line when the fault is detected, but this method is aimed at the analysis of the discharge characteristics of the two-level VSC DC capacitors, and the MMC capacitors are scattered in the sub-modules, which are different from their discharge characteristics. In the prior art, a fault identification method based on the rate of change of fault voltage (ROCOV) and short-term energy is designed for the single-pole ground fault of the star-shaped DC grid, but these two methods do not consider the DC ring network and the short circuit between poles However, the effectiveness of the protection method for the distance of the DC grid still depends to a large extent on the measurement accuracy of the initial rate of rise of the DC fault current (IRRC)

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