Energy Flow Control Methods For Hybrid Electric Multiple Units

On-board energy storage system (ESS) and hybrid powertrain for rolling stock are the new and important trends of research in the recent few years. This thesis is relying on National Technical and Scientific Support Projects for the "12th Five-year Plan"—"Research and Development for key technologies and prototype of Hybrid Electric Multiple Units (HEMU)" and "Key technologies and prototypes for energy saving on rolling stock". This thesis is focusing on the research and optimization for hybrid powertrain, large-capacity energy storage, Bi-DC/DC converter and energy management strategies. A number of simulations, ground tests and vehicle tests are carried out to verify the theoretical research results.To realize the hybrid powertrain on rolling stock, this thesis summarized foreign applications and research results of the author’s team. On the basis of this summary, the capacity configuration of the HEMU was firstly studied. By applying traction calculation, the key components of hybrid powertrain was selected. A survey of lithium titanate battery’s charge and discharge characteristic was also done in this part.During the study, analysis of two core components of the hybrid power supply system, diesel-electrical generator set and bidirectional DC/DC converter, was expanded around their electric characteristic and modeling. The mechanical part (diesel engine and its speed regulation system) and electrical part (permanent magnet synchronous generator) of the diesel electric generator set was analyzed and their simulation model were established. The results of tests and simulations were matched and simulation model can therefore effectively reflect the electrical characteristic of the diesel-electric generator set.Application of large-capacity storage system is the core technology of on-board energy storage and hybrid systems. To fulfill the new demands of the next generation rolling stock, this thesis developed Bi-DC/DC converter, which is easily integrated within the traction system, and its control methods. By studying the physical significances of various links of dual-loop control, the mainstream control architecture, and splitting it, a novel control architecture is proposed, simulation and tests are carried out to verify the research results.Aiming at the special operation requirements for HEMU, this thesis paid more attention to the control and coordination of the hybrid powertrain. By traction calculation, a targeted analysis has been done to show the ideal cooperation of the hybrid powertrain during startup. A series of control and coordinate strategies is also designed on the basis of natural droop characteristic of permanent magnet generator, simulation and tests are carried out to verify the research results. To ensure the stable operation of HEMU under its complex operating conditions, the key research of this thesis is the systemic energy management strategies. Operating strategies and fault-tolerant methods under different operation conditions are designed. Systemic energy management strategies, including flow management and power management strategies, related experiments are carried out during the commissioning procedure and operation tests of the vehicle. The results of the tests shows that the energy flow control methods work well and meet the requirements.