Efficient And Wide Area Control Of Permanent Magnet Synchronous Motor For Vehicle

As the “heart” of electric vehicles,motor drive technology plays an important role in the “13th Five-Year” new energy vehicle innovation chain of China.The key technologies such as optimization of motor drive controller performance,multiplication of power density of vehicle speed control system,and integration of high-reliability power electronic converters for vehicles are one of the important measures to realize the “overtaking” of new energy vehicles and seize the highest point of international competition.This dissertation takes the vehicle IPMSM drive system as the research object.Under the background of high power density,high efficiency,and wide-area operation conditions,the main objectives are system-level efficiency improvement,full-speed operation performance optimization and system reliability improvement.In this dissertation,the optimal PWM method of vehicle inverters,MTPA control below base speed of IPMSM,optimal flux weakening control above base speed and commonmode voltage suppression of drive system are studied in depth.In view of the fact that the existing optimized PWM can not be adapted to the operating environment in which the priority of each objective control is changeable under the wide-range operating conditions of vehicle inverters,a hybrid PWM based on the principle of satisfactory optimization is proposed.Firstly,according to the switching loss model of inverters and the ideal torque equation of IPMSM,constrained mathematical programming models of PWM with switching loss and high-frequency electromagnetic torque ripple as optimization objectives are established.The global optimization of switching loss and high-frequency electromagnetic torque ripple is achieved by online programming of the special solution components of the volt-second balance equation.On this basis,through the analysis of the global optimal solutions of the two objectives,the essential causes of the contradiction between different optimization objectives are revealed.By introducing the principle of satisfactory optimization,the importance of control objectives can be flexibly adjusted by adjusting the limit of switching loss coefficient according to the preference information of decision makers.Satisfactory control of switching loss and electromagnetic torque objectives under wide operating conditions is realized,and the interaction ability between PWM and vehicle controller is increased to enhance the intelligence of PWM.Aiming at the problem of poor robustness of model-based MTPA algorithm,a sliding mode extremum search MTPA control method is proposed.The mechanism of model-based MTPA control accuracy affected by motor parameters and rotor flux orientation angle error is theoretically analyzed.A sliding mode extremum search strategy with stator current vector angle and d-axis current as search variables is designed.The sliding mode control theory is used to make the searching variable continue to run in the direction of the extremum.When the searching area is small,the adaptive property of the system is used to make the searching variable converge to the extremum point.Sliding mode extremum search MTPA control does not require either sinusoidal excitation signal or high-pass and low-pass filters to estimate the function gradient.Based on Lyapunov criterion,the stability of sliding mode extremum search MTPA control is analyzed,and the convergence speed and control accuracy of the proposed algorithm are deeply studied by analyzing the formation and switching process of sliding mode surface.In order to improve the dynamic performance and optimize the efficiency of the speed control system above the base speed,the optimal flux-weakening control of vehicle IPMSM is studied.Firstly,the small-signal model of the voltage-amplituderegulated flux-weakening controller is established.It is pointed out that the fluxweakening control loop is a non-minimum phase system under the motoring condition.The parameter design method is given through root locus analysis.In order to improve the dynamic performance of flux-weakening control,the optimal dynamic overmodulation strategy is studied,and the anti-windup method of current regulator under the condition of overmodulation of inverters is analyzed.Combining with the dynamic working condition of vehicle IPMSM in the flux-weakening operation,the optimal calculation method of d and q axis voltage is designed.The optimized dynamic over-modulation strategy can increase the adjustable range of dynamic voltage by controlling the running direction of back-EMF in the dynamic process of fluxweakening operation,improve the speed of current regulation,and help to ensure the smooth transition of the dynamic condition of flux-weakening.By extending the reference voltage boundary of the voltage amplitude-adjusted flux-weakening controller to the over-modulation region,the utilization ratio of DC bus voltage of the inverters is increased,and the efficiency optimization of the flux-weakening control of IPMSM is realized.In order to reduce the inherent common-mode voltage of vehicle inverters and improve the reliability and service life of the system,the common-mode voltage suppression strategy of vehicle IPMSM drive system is studied in depth.Firstly,the common-mode voltage effect of vehicle IPMSM drive system is analyzed,and the mechanism of motor shaft voltage and shaft current generated by common-mode voltage of inverter is emphatically analyzed.In view of the problem that the conventional common-mode voltage suppression PWM does not make full use of the control freedom under the new switching sequence,the optimal common-mode voltage suppression PWM of stator flux ripple and switching loss is proposed.On the basis of common-mode voltage suppression,the harmonics of output voltage and the switching losses are optimized respectively.A general strategy for suppressing common-mode voltage spikes due to the dead-time effect is studied.The amplitude of common-mode voltage is limited within one sixth of DC bus voltage by on-line optimization of special solution components and switching sequence types,and the shaft voltage,shaft current and common-mode EMI of IPMSM are reduced from the source.The validity and correctness of the above contents are analyzed by MATLAB simulation,and the experiment is carried out on the 50 kW IPMSM four quadrant towing experiment platform.