Co-phase traction power supply system provides the insights for solving the existing power quality and electrical sectioning issues in high-speed railways, and the flexible control of co-phase traction substation (CTSS) with the integration of photovoltaic (PV) and hybrid energy storage system (HESS) attracts widespread attention. However, the strong volatilities and uncertainties of PV and traction load introduce challenges to the reliable and economic operation of CTSS. In this study, the energy management of CTSS aims at minimizing the operating cost of CTSS by coordinating PV, HESS, power flow controller (PFC) and the energy transactions with the power grid, where the three-phase voltage unbalance constraint is taken into account in particular. Furthermore, to handle the uncertainties of PV and traction load, a two-stage robust optimization model is proposed. The first stage determines the operating status of HESS and energy transaction status with grid, and the second stage aims at finding the optimal scheduling power of CTSS and the worst-case scenario with maximized operating cost of CTSS. A column-and-constraint generation algorithm is employed to solve this robust optimization model, along with efficient linearization approaches for the formulation of mixed-integer linear programming. The proposed methodology is tested with a real high-speed railway line case in China.

The optimization of train trajectory and timetable offer two effective methods of energy-efficient operations. Most traditional research optimizes them separately and thus the global optimality cannot be achieved. Previous work has mainly concentrated on minimizing the mechanical energy consumption of trains, not the electrical energy. This paper aims to develop an integrated model to optimize the integrated timetable, which includes both the timetable and the train trajectory, achieving the minimum electrical energy consumption. The AC power supply system model is first proposed to calculate the parameters of the AC power supply network. Then, a model is developed to calculate various energy consumptions using power flow calculation. Furthermore, an integrated timetable optimization model for minimum total energy consumption of AC railway system is proposed and the optimal integrated timetable is obtained by the proposed hybrid GA-PSO algorithm. Finally, 5 real-world case studies based on the Lanzhou Xinjiang high-speed railway are presented. The results show that the proposed integrated model can achieve a reduction in total energy consumption for the entire line up to 14.3% compared with the previous optimization model. The hybrid GA-PSO algorithm achieves the best results compared with the results achieved by the GA and PSO algorithms applied along.

The integration of hybrid energy storage systems (HESS) in alternating current (AC) electrified railway systems is attracting widespread interest. However, little attention has been paid to the interaction of optimal size and daily dispatch of HESS within the entire project period. Therefore, a novel bi-level model of railway traction substation energy management (RTSEM) system is developed, which includes a slave level of diurnal HESS dispatch and a master level of HESS sizing. The slave level is formulated as a mixed integer linear programming (MILP) model by coordinating HESS, traction load, regenerative braking energy and renewable energy. As for the master level model, comprehensive cost study within the project period is conducted, with batteries degradation and replacement cost taken into account. Grey wolf optimization technique with embedded CPLEX solver is utilized to solve this RTSEM problem. The proposed model is tested with a real high-speed railway line case in China. The simulation results of several cases with different system elements are presented, and the sensitivity analyses of several parameters are also performed. The obtained results reveal that it shows significant economic-saving potentials with the integration of HESS and renewable energy.

Single‐phase 25 kV AC traction power supply systems (TPSSs) are widely used in high‐speed railways, leading to an increasingly prominent problem of voltage unbalance (VU) in the power grid. To fairly regulate the system VU level, implementing VU limit pre‐assessment is an urgent need. A grid connection scheme including traction transformer selection and exchange phase connection design is a vital part of TPSS design that obviously affects the VU factor of power systems. A uniform mathematical model is established using Thevenin's theorem, which reveals the impact of multiple grid connection schemes on the VU propagation behaviour of a three‐phase grid. Afterwards, under the requirements of IEC/TR 61000‐3‐13, an improved VU limit pre‐assessment process is proposed, which correlates mapping between the grid connection scheme and VU limit. The unbalance compensation calculation is given, adopting the allocation limit; furthermore, the optimal design of the grid connection scheme with minimised compensation capacity as an object is presented. The correctness of the model and the rationality of the pre‐assessment process are verified by a case study.

A novel energy management model for connected co-phase traction power system (CCTPS) is proposed, in which hybrid energy storage systems (HESS) and photovoltaic (PV) are considered, and the power exchanges between adjacent traction substations (TSSs) can be fulfilled via power transfer controller (PTC). The energy management strategy aims at coordinating the regenerative braking energy, local renewable energy and the peak-valley difference between adjacent TSSs so as to minimize the daily operating costs of CCTPS, and the three phase voltage unbalance constraints are particularly considered, which is a remarkable contribution of this study. This optimization problem is formulated as a mixed integer quadratically constrained programming (MIQCP) model and solved by CPLEX solver. The proposed strategy is tested with a real high-speed railway line and two cases are analyzed and compared. The simulation results show that the developed energy management of CCTPS brings about significant economic benefits while the three-phase voltage unbalance is in line with national standards.

A methodology of energy management for the co-phase traction power system with hybrid energy storage system (HESS) and photovoltaic (PV) panels integrated is proposed in this study. This energy management problem is developed as a mixed-integer linear programming (MILP) model with the target of lower operating costs, and the constraints of three-phase voltage unbalance are taken into account in particular. Several linearization approaches are applied for the formulation of MILP model and the scenario-based technique is also adopted for the uncertainty of PV generation. A real case analysis is conducted to validate the feasibility of proposed approach.