Research On High-frequency Signal Injection MTPA Control Of Interior Permanent Magnet Synchronous Motor

The closed-loop speed control system composed of Interior Permanent Magnet Synchronous Motors(IPMSM)can achieve wonderful dynamic performance,high precision and a wide range of speed regulation,which have great application prospects in electric vehicles.The additional reluctance torque is generated due to unequal inductance of the IPMSM.In order to maximize the use of the magnetoresistance torque of IPMSM,the Maximum Torque per Ampere(MTPA)control method is often applied to the IPMSM system in many applications.In this paper,the steady-state performance of two MTPA control methods for IPMSM,namely high frequency signal injection method and virtual signal injection method,is studied.Firstly,the working principle of high-frequency signal injection method MTPA control is analyzed in detail.The MTPA control error angle formula of high-frequency signal injection method of input power is derived based on the MTPA control principle of input power high-frequency signal injection method especially.Furthermore,a series of simulation studies and analysis are carried out on its steady-state performance.The results show that if the high-frequency current regulator is an ideal regulator,the system can achieve precise MTPA control.If the proportional regulator is adopted,certain MTPA control error will be generated due to the phase error of high-frequency current.Moreover,even a small phase error of high-frequency current will generate significant MTPA error at low speed and heavy load,which will greatly affect the control performance.Based on the analysis of the internal mechanism of MTPA control error caused by high-frequency current phase error,two improvement measures to improve the steady-state performance of the system are proposed.Secondly,the formula of MTPA steady-state error angle caused by stator resistance and d-axis inductance deviation is derived based on the detailed analysis of the MTPA control principle of virtual signal injection method.And a series of theoretical analysis and simulation studies are carried out on its steady-state performance.The results show that the error angle caused by the stator resistance deviation increases with the decrease of the rotational speed,but it is small when the rotational speed is not very low;the d-axis inductance deviation is the main cause of the MTPA error angle.The error angle caused by the inductance deviation of the d axis is independent of the rotational speed,and it increases approximately linearly with the increase of the inductance deviation.Therefore,reducing the inductance deviation of the d axis is the key to ensure the control accuracy of the virtual signal injection method.Finally,the steady-state performance of two MTPA controls,high-frequency signal injection and virtual signal injection,are analyzed and compared when considering the effect of saturation.The steady-state performance of the high-frequency signal injection method with using an ideal high-frequency current regulator is analyzed theoretically when the inductance change rate is taken into account.And the MTPA error angle expression of the virtual signal injection method is derived when the inductance change rate is taken into account.Furthermore,the control performance of the two control methods is simulated and compared.The results show that the steady-state error of the high-frequency signal injection method is still mainly caused by the high-frequency current error generated by the high-frequency current regulator when the inductance change rate is taken into account.High-precision MTPA control can be achieved by using a high-frequency current regulator with zero steady-state error.Even if there is no deviation in the parameters used in the virtual signal injection algorithm,MTPA steady-state error still exists when the inductance change rate is taken into account.However,if the inductance change rate is not large or the load is light,it still can guarantee certain MTPA control accuracy.