Sensorless Vector Control Design Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM)is a type of high performance motor that is capable of providing large amounts of torque over a vast speed range and the ideal choice for applications that require high reliability,efficiency and power-to-volume ratio.Because there are no brushes to replace,a PMSM can have a life expectancy in excess of 10,000 hours.They can be used in a wide variety of applications:Low power PMSMs can be used to power robotic joints or conveyors,medium power PMSMs can be used for electric vehicles and industrial machinery,while high power PMSMs can be used for high speed locomotive traction and ship propulsion,et cetera.Traditionally,PMSMs are controlled through the use of rotor position sensors which have limited application in harsh environment and added system complexity.Sensorless approaches have made significant progress over years with their inherent advantages and drawbacks.There are pros and cons of different sensorless approaches that need clarification before adopted in business decisions.The objectives of this research are to identify and develop the state-of-the-art sensorless PMSM control algorithms.In this paper,models of PMSM in various coordinates are presented.Based on coordinate transformation theory,motor model in rotor reference frame is derived from motor model in phase reference frame.Furthermore,motor model in estimated,rather than accurate rotor reference frame is also built.This model provides theoretical basis for flux observer,rotor initial position identification and motor start-up.Secondly,the vector control strategy of PMSM is designed.Based on PMSM model in rotor reference frame and linear control theory in continuous domain,formulas of speed and current loop parameters are given,taking into account discrete control delay.Based on the theoretical analysis results in discrete domain,Simulink simulation and experimental results on a dSPACE DS1103 based experiment platform,the rationality of the designed control parameters are verified.Finally,flux observers of PMSM are devised.In this paper,mathematical models and inherent errors of the EMF based and high-frequency injection based flux observers are derived,flux angle signal demodulation method is introduced,feedback gain design and discrete implementation are presented.Detained Comparisons of different flux observers which belong to these two kinds of methods are performed.Among them,zero-phase-lag flux observer outperforms other EMF-based methods.Square-wave injection based flux observer outperforms other high-frequency signal inj ection based methods.Finally,experiments are conducted on a dSPACE DS 1103 based platform,validating the performance of the zero-phase-lag flux observer in various steady and dynamic operating conditions.