Multi-objective optimization of the integrated grounding system for high-speed trains by balancing train body current and overvoltage

As a unique exit point for power supply systems of high-speed trains, the onboard grounding system plays a critical role in providing the path for returning the traction current to traction substations. The grounding system applies two grounding modes: the working grounding and the protective grounding, both of which share the power discharging channel, the steel rail. Current reflux normally appears between the working grounding point and the protective grounding point due to the wheel-rail coupling effect. The “train–rail” current reflux may result in the appearance of a “train body” (TB) current, which may cause the onboard partial temperature surging. Moreover, some operational conditions, such as raising pantographs or operating vacuum circuit breakers, may trigger TB overvoltage, which may threaten the safety of the onboard devices. In this article, a “rail–train” coupling grounding model is built to evaluate both the TB current and overvoltage based on the measured parameters. The particle swarm optimization (PSO) algorithm is adopted to optimize this model with the aim to achieve a satisfactory balance between the TB current and overvoltage. The main difficulties of this multivariable multiobjective task include that many grounding parameters are involved meanwhile restricting both TB current and overvoltage. Ultimately, optimal solutions are achieved, considering design demand.