AUXILIARY CIRCUIT FOR HYBRID DIRECT-CURRENT CIRCUIT, AND METHOD AND SYSTEM FOR IDENTIFYING PROPERTY OF FAULT OF MULTI-PORT FLEXIBLE DIRECT CURRENT GRID

摘要

An auxiliary circuit for a hybrid direct-current circuit, and a method and system for identifying the property of a fault of a multi-port flexible direct current grid. The auxiliary circuit is added to Nc IGBT sub-modules on a transfer branch of the hybrid direct current circuit breaker close to an overhead line side. The auxiliary circuit comprises: thyristors, a resistor R_g, and a fast mechanical switch. The thyristors are respectively connected in series between an overhead line and a negative electrode of a snubber capacitor of a first IGBT sub-module snubber circuit and between snubber capacitors of two adjacent IGBT sub-module snubber circuits. A positive electrode of a snubber capacitor of an Nc-th IGBT sub-module snubber circuit is sequentially connected in series to the resistor and the fast mechanical switch, and is then grounded wherein Nc is a set value. The auxiliary circuit of the hybrid direct current circuit breaker implements injection of a feature signal to identify transient faults and permanent faults, and can implement the fault localization of the permanent faults.