Multi-objective optimization compensation strategy for integrating renewable energy into high-speed railway traction power supply systems

With the large-scale integration of renewable energy into power systems, high-speed railway traction power supply systems face increasing challenges, including three-phase current imbalance, higher negative-sequence current, and deterioration of power quality. To address the conflict between the limited capacity of the multi-port railway power conditioner (MRPC) in traditional full compensation mode and the simultaneous demand for integrating renewable energy and power quality improvement, this paper proposes an optimization compensation control strategy for integrating renewable energy. First, this study analyzed the power flow characteristics of the V/v traction power supply system with renewable energy integrated, along with the full compensation principle of MRPC. The influence of MPRC capacity constraints on the absorptive capacity of renewable energy under different locomotive operation combination conditions was determined. Building on this analysis, an optimization compensation mathematical model was developed with two objectives: current limit for integrating the renewable energy (DI) and the three-phase negative-sequence current (<italic>I</italic>_⁻). The model included key decision-making variables such as active current transfer between two-phase bridge arms, the locomotive power factor angle of the two-phase traction supply arms, and the three-phase current imbalance. The model was solved using the multi-objective genetic algorithm NSGA-II, and the effectiveness of the proposed strategy was validated through hardware-in-the-loop experiments. Results show that even under the most imbalanced condition with 50 kW of renewable energy integrated, the negative-sequence current can be reduced from 37.5 A to 14.4 A, significantly improving system stability and power quality. Compared to the traditional full compensation approach, the proposed optimization method not only facilitates greater absorption of renewable energy but also ensures safe and reliable system operation within the constraints of limited MRPC capacity. This study innovatively transformed the paradigm from "full compensation" to "optimization compensation", revealing the trade-off between renewable energy integration and power quality enhancement, while providing a feasible solution for the absorption of renewable energy and coordinated operation of electrified railway power supply systems.