Research On Sensorless Control Of Synchronous Reluctance Motor

Synchronous reluctance motor(SynRM)has many advantages,such as simple structure,low material cost,high temperature resistance,high torque density and high efficiency,and wide speed range.Similar to that of the permanent magnet synchronous motor(PMSM),the control strategy of the SynRM is easy to implement.Therefore,the SynRM has been studied in order to replace the PMSM or induction motor in some applications(such as fans,pumps,etc.).Some people even proposed that SynRM be used in electric vehicles to realize large torque starting and power generation over a wide speed range.Core saturation of the SynRM(including cross-saturation of d-axis and q-axes)is serious,therefore,traditional sensorless control method is often difficult to achieve high performance control.In this thesis,two sensorless control strategies based on model reference adaptive system(MRAS)and flux observation are proposed.Using look-up table method for the inductance parameters under different working conditions,the two sensorless algoritlinis can reduce the error of rotor position and speed estimation caused by the core saturation.The sensorless control strategies used in this thesis adopt the maximum torque per ampere(MTPA) control method.The MTPA curve is obtained with simulation,and the values of motor current id and iq under dififerent working conditions are also obtained with the look-up table to realize MTPA control.The proposed sensorless control strategy based on MRAS and considering the saturation of iron core can realize the motor starting at any initial position and stable operation over a wide speed range,and has the advantages of small error in position and speed estimation as well as easy convergence of the algoritlim.The proposed sensorless control strategy based on flux observation and considering the iron core saturation adopts the tliree-stage open-loop starting,and after starting,it has good dynamic response and anti-load interference ability,meeting the requirements of high perfonnance operation of the SynRM.Effectiveness of the proposed sensorless control methods is verified with both simulation and experiments.