Fault steady-state analysis method for the AC system with LCC-HVDC infeed

Abstract

Fault steady-state analysis method can help to analyze the variation law of electrical quantities, clarify the fault characteristics, and provide the basis of power system design, protection scheme formulation, short-circuit current limitation and electrical equipment selection. Existing methods of fault steady-state analysis for alternating current (AC) system with line-commutated converter (LCC) high voltage direct current (HVDC) infeed are not suitable for high-severity AC system faults and existing equivalent models of LCC-HVDC system are inaccurate under asymmetrical AC system fault. Hence, a more accurate method is proposed in this paper. First, according to the relationship between the injected current of LCC-HVDC system and the fault phase voltage of commutation bus, equivalent models of the LCC-HVDC system under symmetrical fault and asymmetrical fault of AC system are established respectively. Based on the equivalent models of LCC-HVDC system and the fault sequence network of AC system, a fault steady-state analysis method for AC system with LCC-HVDC infeed is proposed. The proposed method is validated on CIGRE Benchmark HVDC model using PSCAD/EMTDC software. The results show that the proposed method is accurate and suitable for faults of different severities in AC system with LCC-HVDC infeed.