Research On Sensorless Control Technology Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor can be used in various fields owing to its high power density,high efficiency,and small size.The use of more physical sensors makes the cost of PMSM drive system be higher.At the same time,the physical sensors can also affect the reliability of the system.Therefore,it is significant to study the sensorless control technology of low cost and high reliability in PMSM drive system.At present,the phase current reconstruction technique make the control without phase current sensor come true,but there is a problemof current reconstruction dead zone.Some existing methods can solve the problem fo reconstruction dead zone,but they will increase the harmonic and affect the performance of control.Position sensorless control technique can make PMSM drive system work normally without position sensor,there are mainly two method,the one is based on fundamental model and another is based on high-frequence signal injection.So,to do some research on the PMSM control without phase current sensor and positon sensor is helpful for the development of PMSM drive system in low cost and high reliability area.This paper proposes a new phase current reconstruction scheme without using null switching states for PMSM drive system,in which the three phase currents are reconstructed independently.The basic principles of the independent phase current reconstruction scheme and the corresponding PWM modulation are introcuced in detail.The calculation method of basic voltage vector action time under this scheme is given.Independent phase current reconstruction scheme solves the problem of reconstruction dead zone through a new voltage synthesis method.Under this method,the corresponding PWM modulation method is different from traditional seven-stage SVPWM,the number of switching in this PWM modelation reduce at one PWM cycle.The feasibility of proposed scheme has been verified by simulation and experiment and the reconstructed phase currents track the actual currents accurately in different working conditions.The research on sensorless control of PMSM is carried out based on the independent phase current reconstruction scheme.Which means the currents information used for position estimation is obtained through independent phase current reconstruction scheme.In the condition of zero or low speed,the rotor position estimation method based on high frequency voltage signal injection is introduced.Because the response of high frequency currents' negative sepuence refects the information of rotor position,the rotor position can be got by heterodyne method easily.The results of simulation and experiment show that the rotor position estimatin error is within ±0.2 rad.In the condition of middle or high speed,the rotor position estimation method based on sliding mode observer is studied.The sliding mode observer is used to obtain the emf of motor.The arctangent fuction is used to calculate the estimated position.The saturation fuction is used to instead of the sign function for solving the problem of chattering of sliding mode observer.The phase locked loop technique is used for solving the problem of hysteresis caused by low pass filter.The results of simulation and experiment show that the rotor position estimatin error is within ±0.05 rad.