| Owing to the satisfactory driving performance and fuel economy, the series-parallel hybrid electric vehicles(HEVs) have been widely accepted by consumers and automotive manufactures in recent years. However, the planetary gear unit used for power splitting in the series-parallel HEVs has problems such as complex mechanical structure, cogging noise and lubrication maintenance. The flux-modulated compound-structure permanent-magnet synchronous machine(CS-PMSM), composed of a brushless double rotor machine(DRM) and a conventional permanent-magnet machine, provides the energy transducing functions required by a series-parallel HEV with a much simpler and compact mechanical structure. Aiming at its specificity in operating theory, structure and application background, comprehensive work about the CS-PMSM control system have been carried out. The major research work can be summarized as follows.First, the operating theory of flux-modulated brushless CS-PMSM is investigated. The flux-modulated magnetic gear is analyzed with respect to working principle, and its speed-torque characteristic is compared with conventional planetary gear unit. According to the configurations of CS-PMSM in a HEV system, two CS-PMSM-based HEV schemes are proposed. The input and output speed-torque characteristics are analyzed and compared by respective lever models. The operating state of CS-PMSM under different load points is investigated through the perspective of four-quadrant energy transducing, providing theoretical reference for initial HEV system design.The unified mathematical model and system control strategy of flux-modulated CS-PMSM are built. The flux, voltage and mechanical motion equations are set up based on previous research work. According to the function of CS-PMSM in a HEV system, the coordinate control of the two integrated machines is proposed. The electric angle of DRM is calculated by the positions of dual rotors, solving the problem of field oriented control of DRM. System model is built by Matlab and simulation result proved the feasibility of the CS-PMSM model and control strategy.The power flow and characteristic capability of the flux-modulated CS-PMSM hybrid system are investigated through the perspective of vehicle system. According to the vehicle state, the power flows of various operating modes such as pure-electric propulsion, engine starting, power splitting, parallel propulsion and speed boosting, are analyzed. Methods for system characteristic capability are proposed using both analytical and numerical approaches. To verify the power flow and parameter design, US EPA, European NEDC and Japanese 10-15 mode driving cycles are used for system simulation.Finally, a prototype controller is developed for the CS-PMSM system and experiments are carried out. To guarantee the coordinate control of the two integrated machines, the topology using six-phase half bridges is employed for the controller power block, and the control algorithms of the dual machines are implemented by one processing core. To reduce the duty of that processing core, based on dual-core data access methods, the communication data between the CS-PMSM subsystem and the vehicle network are processed by another core, which provides efficient and reliable software and hardware platform for CS-PMSM system. A test bench is built up, and the speed and torque characteristics of the flux-modulated DRM discussed in previous sections are validated by observing the no-load electromotive force and load torques of the dual mechanical ports and magnetic field produced by DRM stator. A driving cycle containing various operating modes is designed. Experimental results show that the CS-PMSM controller can implement the coordinate control of the two machines efficiently, and the power flow in each operating mode agrees with theoretical analysis. |
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