Research On Pseudo-random Sinusoidal Injection Based Position Sensorless Control Strategy For Ipmsm Drives

Permanent magnet synchronous motor is widely used in various high performance drive systems due to its high efficiency and high power density.In order to solve the problem of high cost and low robustness caused by the mechanical sensor in the traditional rotor position information acquisition scheme,the sensorless control strategy has become a hot topic in the field of motor control.High frequency injection is a sensorless strategy commonly used in low speed and zero speed conditions based on the salient characteristics of the motor.However,this scheme will cause extra noise because of high frequency signal injection,which restricts the application in some situations.To solve this problem,this paper studies pseudo-random sinusoidal injection based position sensorless control strategy for ipmsm drives and proposes an improved signal processing method by analyzing the influence of the digital system delay on the traditional signal processing scheme.Finally,the control strategy is verified by simulation and experiment.Firstly,the principle of high frequency signal injection method is analyz ed.Based on the mathematical model of permanent magnet synchronous motor,the expression of high frequency current signal excited by high frequency injection signal is derived on the basis of the salient characteristics of the permanent magnet motor.The high frequency current containing position information is processed by demodulation,filtering and other signal processing methods.The motor rotor position is estimated,and the sensorless control of high frequency injection method is realized.The simulation model is established in MATLAB/Simulink,and the high frequency signal injection scheme is analyzed and verified.Secondly,aiming at the problem of noise generated by the traditional high frequency signal injection method,a sensorless control method based on pseudo-random sinusoidal signal is studied.The problem caused by the traditional fixed-frequency high frequency signal injection method is analyzed.Because of the fixed-frequency signal injection,the power spectrum density of the high frequenc y current excited by the injected signal produces a high peak at the injected signal frequency.The existence of the peak causes sharp noise.In this paper,pseudo-random sinusoidal signal injection method is used to improve the problem.On the basis of introducing the way of signal injection and the principle of signal frequency and amplitude selection in the pseudo-random sinusoidal injection method,the influence of the delay of the digital signal system is analyzed.The phase error between the demodulated signal and the injected signal may cause the system instability.Therefore,an improved signal processing scheme without demodulation signal is proposed to suppress the influence of digital delay on the system.Then,the noise reduction mechanism and effect of random high frequency sinusoidal signal injection method are analyzed by power spectral density calculation.The cause of noise in high frequency injection method is analyzed theoretically,and the purpose of noise reduction is achieved by eliminat ing the discrete spectrum.The power spectral density of the motor phase current is calculated based on the pseudo-random sinusoidal signal injection method,and the conditions of the injected signal selection to eliminate the discrete spectrum are given.Taking into account the sample and hold effect in the actual system,the power spectral density of phase current under this condition is analyzed,and the principle of noise reduction in the actual system of the pseudo-random sinusoidal signal injection method is explained theoretically.Finally,the digital control algorithm is implemented on ARM,and the experiments are carried out on a 2.2-k W position sensorless permanent magnet synchronous motor drive.The experimental results verify the feasibility of the proposed scheme,and the proposed pseudo-random sinusoidal injection based position sensorless control strategy for ipmsm drives has good performance,and the position estimation error satisfies the design requirements.