Study On Key Techniques Of Range Extender For Extended Range Electric Vehicles

With the energy becoming less and less,the hybrid electric vehicle technology has become a present research hotspot due to its good fuel economy,it has great potential and promising perspect.In order to further improve the fuel economy and reduce emissions,the traditional weak mixing hybrid is unable to meet the requirements of sustainable development strategy,improving involvement of motor driving is the development trend of new energy vehicles.In the next few years,strong mix hybrid vehicle will be the mainstream before pure electric vehicles make a significant breakthrough.Extended range electrnc vehicle(EREV),as typical representative of heavy mixing hybrid type,has a lot of characteristics such as large battery capacity,electric and direct drive wheels,no mechanical coupling between range extended engine and the wheels,the engine operating point without limitation of torque and speed.Above characteristics bring a lot of benefits.It can improve engine fuel consumption.It can extend battery life by preventing it from high current charging and dis-charging with SOC stabilize function at range extend mode.It is much suitable for frequent start and stop urben driving cycle.According to the power demand and structural characteristics of urban application EREV,on the basis of the parameter matching between range extender and vehicle,the engine intake and engine exhaust system is improved to optimize the engine efficiency in operating zone,to increase the output power,to reduce the fuel consumption.By applying the equivalent magnetic circuit theory,the reluctance model is derived for the generator with 6-poles 36-slots.Simplified analytical method accomplish rapid calculation of variable parameters of generator as flux density of air-gap,iron core of stator and rotor,back-EMF,loss and output characteristics.Such analysis provides reference for the engineering design and optimization of the generator for the range extender application.Since engine is the main driver of the EREV in range-extended mode,the partial power following control strategy is designed to meet the requirements of the efficient operation of the engine and also dynamic adjust battery power distribution to minimnize power loss of battery charge and discharge.By establishing the equivalent fuel consumption model,and referring to average efficiency under the operating conditions,the threshold power to implement power following-control is calculated.The output power of the engine can quickly balance the demand among actual driving power and battery maintain power.Meanwhile,the operating point of the engine meets the demand of high efficiency.In order to obtain the high robust power following control method,the current of the generator is adjusted in the ap stationary coordinate system using the PWM converter to realize the power output of the extended range.The quasi-proportional resonant(PR)controller is introduced into the internal current loop to realize zero-static-error tracing of the system control target.The simulation and experiment results show that the proposed control strategy has excellent robust performance and robustness to parameters variation.The operating point of the engine will deviate from the low fuel consumption zone when the generator torque variation range become larger.Therefore,to further optimize the fuel consumption on the basis of the partial power following control on the fixed speed,the partial multi-points variable-speed power following strategy is designed.The operating points of the engine will be closer to the minimum fuel consumption curve.By that means,the engine operating point is always in the zone closely around the best fuel consumption curve.The multi-proportional resonant controller(MFPR)is introduced to realize the adjustment of the generator output torque.The fuel consumption of different control strategies under typical urban cycles are compared with the fuel consumption of the Pontryagin's minimum principle optimization algorithm.Compared to fix-speed partial power tracing control strategy,the optimized working point of the engine is closer to the optimal fuel consumption curve,with better fuel efficiency,and is closer to PMP optimization algorithm.In order to secure the advantages about driving comfort of EREV,the electromagnetic force harmonics of the 6-pole 36-slot permanent magnet synchronous motor is studied,regularity of harmonics frequency and orders are summarized.And combined with the motor modal analysis results,frequency of main effective electromagnetic force which causes vibration is obtained.Harmonics compensation by the method of PR controller is used to suppress electromagnetic noise.