Research On MTPA Control Based On Identification Of Flux Linkage Map For Interior Permanent Magnet Synchronous Machine

The traditional oil-fueled automotive usually needs to face serious exhaust emission problems in urban area,which not only introduces pollution into the air,but also results in an urban heat island effect.Meanwhile,the oil-fueled automotive is also quite dependant on the diminishing oil resources.Thus,countries around the world are developing zero-emission,fossil-fuel-free electric vehicles.Among all traction drive motor schemes,the interior permanent magnet synchronous machine(IPMSM)has been widely favorited in electric vehicles because of its high power density,high efficiency,small size and so on.The most commonly used drive control algorithm for IPMSM in low speed region is the maximum torque per ampere(MTPA)control,which can not only make full use of the machine’s reluctance torque so as to obtain the maximum ratio of output torque versus current,but also minimize the system copper loss.The conventional MTPA control based on the PMSM parameter model is of simple principle and easy for engineering realization.However,its control performance is quite dependent on the accuracy of PMSM parameter model.In view of this problem,an in-depth investigation on MTPA schemes based on offline and online parameter identification methods,respectively,has been conducted in this thesis,and its main research contents and works are as summarized as follows:(1)Offline parameter identification method: In order to obtain accurate mo tor parameters,offline parameter identification method s for PMSM have been investigated at the beginning,in which the permanent magnet(PM)flux linkage is measured from the back electromotive for ce(EMF)of no-load PMSM,and the dq-axis inductances are identified via the injection of sinusoidal current signals afterwards.These two methods are simple and of high accuracy in principle,and easy for implementation.However,both of them have neglected the changes in motor parameters due to the varying speed and temperature during the operation.Therefore,the online parameter identification methods are usually preferred for improving the accuracy of PMSM parameter model,which further improves the efficiency of PMSM control.(2)Online parameter identification based on flux linkage map: In view of the deficiency of offline parameter identification,the online parameter identification based on flux linkage map has been investigated.Conventional online parameter identification methods cannot identify all motor parameters at the same time,while other solutions such as the multi-step method or estimation separately,will lead to inaccurate identification results or accumulation errors.Therefore,the direct online identification of dq-axis flux linkages of PMSM has been adopted in this thesis.This method is based on the simple flux linkage map model,and it does not need to consider the cross-coupling interaction between various machine parameters.Finally,the experimental results are compared with the finite element analysis results to verify the effectiveness of proposed solution.(3)MTPA control strategy: In order to make full use of IPMSM reluctance torque,MTPA control strategy based on motor parameters has been investigated.Firstly,the mathematical model of MTPA control based on motor parameters is derived in detail,and the variation of motor parameters and its influence on output torque are analyzed.In order to compensate this effect,the MTPA controls with aiding from parameter identification schemes including both offline parameter identification and online parameter identification based on flux linkage map,have been investigated.Finally,it is obvious from the comparison experiments that the combination of MTPA and identified flux linkage map has a better torque output capacity than that of conventional MTPA control.Overall,a detailed theoretical analysis of MTPA control based on motor parameters has been conducted in this thesis,which reveals its key problems in practice and provided relevant solutions accordingly.Finally,the effectiveness of the proposed method is verified on a prototype IPMSM test rig.The proposed solution in this thesis can make full use of the reluctance torque of IPMSM,which is of important theoretical significance and practical values.