Design and downhill speed control of an electric-hydrostatic hydraulic hybrid powertrain in battery-powered rail vehicles

The diesel-driven rail vehicles are gradually replaced by battery-powered rail vehicles (BRVs), due to its exhaust emissions and noise. However, the development of BRVs have two aspects that need improvement: low energy efficiency and poor downhill stability. To address these problems, this paper presents the design and downhill speed control of an electric-hydrostatic hydraulic hybrid (EH3) powertrain, which is mainly composed of a variable pump, a variable pump/motor, a proportional flow control valve (PFCV) and accumulators. Through a laboratory test bench, the hydraulic regenerative/non-friction braking performance of an EH3 powertrain is validated and experimentally analyzed. The hydraulic average energy recovery rate could be 50%. The method of downhill speed control is proposed, which is validated by the simulation results. During the downhill process, EH3 rail vehicle has a relatively high energy efficiency, which will bring good economic benefits in energy conversation and environmental protection. •An EH3 powertrain and the laboratory test bench is presented.•The hydraulic regenerative/non-friction braking is validated on experimental data.•The control strategy of downhill speed is purposed to improve energy efficiency.