Research On Hybrid Powertrain Based On Four Ports Electromechanical Converter

Four ports electromechanical converter (FPEMC) is a kind of multi ports electromechanical converter with two electrical ports and two mechanical ports. Compared with conventional electric machines, FPEMC has more energy conversion modes and great potentials in many applications such as hybrid electric vehicle (HEV), wind power generation system and underwater propulsion, etc. However, FPEMC is not the addition of two electric machines, many complex problems, like dynamic control, modeling and control strategy, field coupling, and cooling, arise with the increase of electrical and mechanical ports and produce great challenge to the design and control of traditional electric machines.This paper will focus on the theory and applied problems of an induction machine based FPEMC (IM-FPEMC) in HEVs. These problems include analysis of the field distribution and coupling, the discussion of a feasible field decoupling scheme, and the modeling, control strategy and experimental verification for the IM-FPEMC HEV.First of all, an equivalent flux path model and a finite element (FE) model will be built and used to study the field distribution and coupling rules of IM-FPEMC. The results show the existence of field coupling between inner and outer machines. Field coupling is related to yoke height of outer rotor, MMF magnitudes and phase difference of two machines. Field decoupling can be realized by controlling the phase difference and the MMF magnitudes of two machines. Incorporating the rules of field distribution, this paper proposed a dynamic modeling for field decoupling.The IM-FPEMC HEV, a kind of series-parallel HEV, is a complex electromechanical system, which includes internal combustion engine (ICE), battery, electric machines, and transmission. To clearly express the energy flows in this complex system and provide a reference to the system control scheme design, Energetic Macroscopic Representation (EMR) is introduced to analyze and build the model of the IM-FPEMC HEV. The energy flows are much clearer, and the control scheme is easier to achieve.According to the objectives and constrains of the IM-FPEMC HEV, 3 tuning chains are defined. Using inversion rules, 3 control chains are deduced by inversing the tuning chains. Speed and current controllers are also designed using specific inversion rules. This work will lay a solid foundation for developing control strategy and shows potentials in other complex electromechanical systems.A control strategy is required to manage the energy flows in the IM-FPEMC HEV. In this paper, a rule-based control strategy is developed and simulated in Matlab/Simulink environment. The simulation results show that IM-FPEMC not only satisfies the vehicle power demand, but also optimize the operation of ICE. A good fuel economy is achieved. In US06 driving cycle, the fuel economy is 4.33L/100km, and 4.87L/100km in 10.15 driving cycle. Compared with a convention vehicle, the fuel economy is increased by 32% and 23% respectively. The simulation results provide reference to designing IM-FPEMC and the system analysis.The characteristics experiments show that the outer machine fairly satisfies the vehicle requirements, but the inner machine needs further optimization on cooling and structure design. The results are approximately in accordance with the FE analysis and verify the conclusions on field distribution and coupling. Based on dSPACE platforms, all kinds of operation modes and dynamic control are realized which verify the feasibility of EMR modeling and developed control strategy. A digital signal processor (DSP) based hardware platform is developed for use in vehicles.In the future, more work will be done about a deeper study of decoupling control, and the optimization of control strategy.