A Main Circuit Topology Structure of DC Breaking System

Abstract

The invention discloses a major loop topology structure of a direct current breaking system. The major loop topology structure comprises a main switch unit QF, a breaking unit, an isolation unit QS and a buffer unit, the breaking unit and the isolation unit QS are connected in series and then connected with the main switch unit QF in parallel, one terminal of the breaking unit is connected with acurrent inflow terminal of the main switch unit QF, one terminal of the isolation unit QS is connected with a current outflow terminal of the main switch unit QF, one terminal of the buffer unit is connected with the current inflow terminal of the main switch unit QF, the other terminal of the buffer unit is connected with a series terminal of the breaking unit and the isolation unit QS, and the breaking unit is formed by a capacitor C, a control switch FV, an inductor L and a varistor RV. According to the major loop topology structure, through reduction of the long-term through-current requirement of the isolation switch QS, an overvoltage of the capacitor C and the control switch FV in a breaking process of a circuit breaker can be substantially reduced, the overall size of the circuit breaker is reduced, the comprehensive cost is lowered, and the reliability in the breaking process is improved.

Description

technical field [0001] The invention belongs to the technical field of power system fault protection, and in particular relates to a main loop topology structure of a DC breaking system. Background technique [0002] Due to its unique advantages, the DC power system has been widely used in the fields of ships, rail transit, mines, pulse power and industrial DC power transmission and distribution. As an important control and protection equipment, DC circuit breaker has always been the difficulty and focus of DC power system research. [0003] The DC breaking process mainly needs to complete three tasks: (1) quickly create a current zero-crossing point in the DC system and cut off the rapidly rising fault current; (2) absorb the huge electromagnetic energy stored in the inductive components in the DC system; (3) limit the current Interrupting overvoltage due to electromagnetic energy conversion when reduced. [0004] For the above-mentioned basic breaking process, relevant r...

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Problems solved by technology

The varistor RV is connected in parallel to the two ends of the main switch QF. During the process of energy absorption and voltage limiting, the voltage at both ends includes the voltage of the capacitor C and the inductance L. The overvoltage on capacitor C is greater than the maximum protection voltage value of the varistor, especially when the inductance L is large (mH level in high-voltage DC circuit breakers), the overvoltage on capacitor C will increase significantly, resulting in increased capacitor volume and cost ; On the other hand, because there is a large voltage difference between the capacitor C and the varistor (reverse to the control switch FV), and the inductance L in the loop is large, for the commonly used vacuum trigger switch (with interception phenomenon) , diodes (with reverse recovery phenomenon) or thyristors (with reverse recovery phenomenon) and other control switches FV will generate high overvoltage during the current blocking process, which will affect the reliability of the breaking process.

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