Bi-hierarchy capacity programming of co-phase TPSS with PV and HESS for minimum life cycle cost

Abstract

Co-phase traction power supply system (TPSS) with photovoltaic (PV) and hybrid energy storage system (HESS) is a promising way to improve the utilization of regenerative braking energy (RBE) and power quality. However, despite co-phase TPSS with PV and HESS being beneficial from the perspective of technology, how to coordinate the operation strategies of various devices to ensure system economy is a key issue in practical engineering applications. Therefore, this paper proposes a bi-hierarchy capacity programming strategy of co-phase TPSS to minimize life cycle cost. In the upper layer, the integrated lifetime evaluation model of HESS and PFC (HESS-PFC) is proposed for the lower long-term investment cost. Remarkably, the PFC reliability assessment and the HESS degradation process are analyzed. Meanwhile, the capacity of HESS-PFC is obtained, and the lifetime of HESS-PFC is extended. In the lower layer, the power flow of co-phase TPSS is optimized to minimize short-term operating cost under satisfying three-phase voltage unbalance standards. Traction load peak-shaving and valley-filling are achieved by coordinating HESS-PFC and PV. And it is formulated as a mixed integer linear programming model based on efficient linearization methods. Whale optimization algorithm with GUROBI solver embedded is employed to solve this bi-hierarchy model. Finally, case studies show that the proposed model can achieve 23.26% cost reduction and 63.82% PFC lifetime extension, while the voltage unbalance is within an allowable range of 2%.