Sensorless Control Of IPMSM For ISA System Of Vehicle

With the rise of environmental problem and energy crisis, HEV (HybridElectric Vehicle) and ISA (Integrated Starter and Alternator) System have beenbrought into of the vehicle area focus because of its low energy consumption, lowpollution and high utilization rate of energy. For its small volume, light weight andhigh power density, PMSM (Permanent Magnet Synchronous Motor) is widelyused in ISA systems. The mechanical sensor in traditional motor control systemdoes not meet the requirements of volume and weight of ISA system, so it isreasonable to employ sensorless control method. The sensorless control methodsemployed in the present system goes well when the motor is running in a mediumor high speed, however, it loses efficacy when the motor is slow down or even stop.Based on the study of current control strategy of PMSM in ISA system, this textdoes some further research on the sensorless control method when the motor isrunning in low or zero speed.The ISA system mentioned in this text uses Interior Permanent MagnetSynchronous Motor, and only needs one motor and one converter. It is muchsmaller, lighter and cheaper than the system with several motors and converters.This text presents the structure of PMSM which is used in ISA system and builds amathematical model of PMSM firstly, based on which, some further research andanalysis have been done on several vector control method and finally confirm thecurrent control strategy. The system adopts stator current optimum control method,and switches homologous current vector control strategy in different speed arrange.This control strategy could use the capacity of the converter and the stator currentof the motor in a highest utilization rate; and realize the optimization usage ofenergy. It is of great significance for the improvement of the property of ISAsystem in HEV.After confirming the current control strategy in ISA system, this text comesup with a high frequency injection method (HFIM) based on the convex polarity ofmotor in order to improve the state quo of low efficient traditional sensorlesscontrol method. This method inputs voltage or current signal in certain frequencyat the end terminal of a motor. Then the convex polarity effect of the motor wouldmake the high frequency response of the output contain position information of themotor rotor. Then the position information of the rotor would be extracted after aseries of signal processing. HFIM does not rely on the detection of counterelectromotive force of the motor, so it has a good estimate when the motor isrunning in a low speed, thus solve the problem about incorrect estimate of the position of motor rotor in low speed.After sufficient theory analysis, this text simulates and compares the currentcontrol strategy in ISA system and no speed sensor control method by simulinktool in MATLAB and proves the correctness of theoretical derivation. Furthermore,this text also builds an actual system platform and confirms the correctness andfeasibility of the control method by taking an experiment in which a vehicleengine is imitated by a low voltage high-speed motor.