Reduction and modelling method of large-scale alternating current/direct current power systems for electromagnetic transient simulation

Abstract

This study presents a systematic method which enables large-scale alternating current (AC)/direct current (DC) power systems to be modelled in the electromagnetic transient (EMT) domain. A physical equivalence based dynamic reduction technique is first proposed to reduce the AC/DC system, which retains the backbone network and important components such as high-voltage direct current (HVDC) links, whereas the low-voltage networks connected to the backbone network are reduced to simple networks composed of physical components. The reduction technique is based on the preservation of the support strength of the generators within the low-voltage networks to the backbone network (i.e. the short-circuit current contribution level), the power flows within the backbone network and the total generating output. Then, a technique to construct the EMT model of the reduced AC/DC systems is developed based on the data in the transient stability program format. The validity of the proposed method is verified with the case of South China power grid, which includes a multiinfeed HVDC system.