Research On Sensorless Control Of PMSM At Zero/Low Speed For Electric Vehicle Applications

Under the double challenges of global energy shortage and environmental deterioration,vigorously developing electric vehicles and accelerating the strategic transformation of traditional automobile industry are the only way to achieve sustainable transportation development.As the core component of electric drive system,permanent magnet synchronous motor(PMSM)is widely used in the field of electric vehiclesfor its advantages of high power factor,low inertia and low noise.In order to achieve high performance vector control of the PMSM motor drive system,it is necessary to use position sensors such as resolver or photoelectric encoder to accurately detect the rotor position information.However,due to the use of position sensors,the volume and cost of the vehicle system will be increased and the reliability of the driving system will be reduced.In order to effectively overcome the above problems,sensorless control technology has been attracted wide attention,and has rapidly become a research hotspot in the field of motor drive.Firstly,the structure characteristics and mathematical model of PMSM are introduced,and the vector control principle of PMSM is briefly summarized.Secondly,the high frequency injection method suitable for zero and low speed is developed.In view of the engineering background that the high frequency injection method can not realize the magnetic polarity discrimination because of the symmetry of the salient poles of PMSM,a new polarity discrimination method based on rotating high frequency injection is proposed.This method possesses the advantages of fast detection,high reliability,without the interrupt of high frequency injection,and less influence of current detection accuracy.Thirdly,considering that the position sensor in electric drive system is prone to malfunction because of the environmental impact,a fault-tolerant control strategy based on high frequency injection is proposed.The estimated position and speed are used to replace the position sensor under fault,and a fault-tolerant control system based on rotating high frequency injection for the position sensor failure of the interior permanent magnet synchronous motor(IPMSM)is built.Finally,based on the analysis of the disadvantages of the multiple filters in the traditional signal demodulation process,the frequency characteristics of each component of the stator current are analyzed.The second-order generalized integrator(SOGI)is proposed to replace the band-pass filter(BPF)and the high-pass filter(HPF).Also,the central frequency of SOGI can be adaptively adjusted from the estimated speed,which can greatly improve the position observation accuracy and dynamic characteristics of the fault-tolerant control system.In this paper,based on dSPACE1103 as the controller,the magnetic polarity discrimination test platform and the fault-tolerant performance test platform under the fault of position sensor are built,respectively.The polarity discrimination test platform verifies the validity and reliability of the proposed polarity discrimination by accurately detecting the initial position of the rotor.In addition,the proposed algorithm is comprehensively validated by the fault-tolerant test platform from the aspects of motor start-up,steady state,variable speed and disturbance rejection.The experimental results show that the fault-tolerant system has good dynamic and static characteristics and robustness.