Optimal transmission conversion from alternating current to high voltage direct current transmission systems for limiting short circuit currents

Abstract

The excess of short circuit currents (SCC) has threatened the security of electrical energy transmission and become one of the most critical problems in power grid operations. At present, high voltage direct current (HVDC) transmission technology is a practical and applicable option to limit short circuit currents by separating a synchronous power grid into several asynchronous power grids. During the transmission expansion planning, the short circuit currents can be effectively limited by strategically converting alternating current to high voltage direct current transmission systems, improving transmission capacity as well. Due to the high construction cost of high voltage direct current transmission systems, improper conversion would influence the economy of power system planning and the effect of short circuit currents reduction. Therefore, an approach of optimal transmission conversion (OTC) for limiting short circuit currents is proposed in this paper. To solve the problem with the strong nonlinearity of short circuit currents, a novel linearization method based on direct current power flow is developed. The case study based on a 22-bus power system and IEEE 118-bus system are performed for illustration and validation. The simulation results demonstrate that the short circuit currents are effectively reduced and the security of electrical energy transmission is guaranteed by applying the proposed approach and model. The major contribution of this paper is to provide a new method for limiting short circuit currents. Hopefully, the proposed approach can provide new insights for the planning and operations of large-scale hybrid power systems.