Study of Coherency-based Dynamic Equivalent Method for Power System with HVDC

In order to reduce the calculation amount of numerical simulation in transient analysis for large-scale power system, the network can be simplified by dynamic equivalence. This paper presents the coherency-based equivalent technique for power system with HVDC. Both frequency-domain method and weighting method are comprehensively used in parameter aggregation section in this paper. The adaptability of ac system equivalence to dc system is concerned, and the accuracy of dynamic equivalence of ac system is estimated using dc system disturbance. In numerical simulator PSASP, a dynamic equivalence of EPRI 8-machine 36-bus ac/dc hybrid power system can be derived, in which the specific model of HVDC system is considered. The comparisons of steady-state and dynamic response of original and equivalent system show that the dynamic equivalent model is feasible and available.