A New Scheme On Sensorless Vector Control Of Permanent Magnet Synchronous Motor Using High Frequency Square Wave Injection Method

Permanent magnet synchronous motor(PMSM)has been widely used for its high power density，high torque density and high efficiency.The vector motion control system composed of PMSM occupies an important position in the field of AC servo industry.The traditional PMSM vector control system needs the rotor position information to achieve accurate magnetic field orientation control,while the rotor position information can be obtained by the encoder or the rotating transformer.Considering the factors of cost and installation location,sensorless vector control technology has become a new hot research topic.At present,the rotor position information in sensorless vector control scheme is mostly obtained by the model-based observer scheme.The scheme is essentially based on the back EMF to estimate the rotor position.Once the speed is low or the starting condition is applied,the observer scheme is invalid due to the smaller back EMF or the zero back EMF.High frequency injection scheme is to solve these problems.It uses high frequency excitation signal and motor rotor inductance asymmetry to obtain high frequency response,and then extracts rotor position information from high-frequency response.Because this scheme is independent on the back EMF,it is especially suitable for low speed or even zero speed situations,and has received great attention from the related scientific and technological workers.On the basis of the study of the traditional sinusoidal high frequency voltage injection scheme,this paper focuses on the research of the sensorless vector control based on the high frequency square wave injection scheme,and debug the prototype on the TMS320F28335DSP experimental platform.The main contents are as follows:(1)On the basis of the analysis of the PMSM high frequency model,the high frequency sinusoidal voltage injection and sinusoidal pulse voltage injection scheme and its related problems are analyzed and discussed,and the corresponding vector control system is designed.(2)In order to solve the problem of low current bandwidth and high noise in vector control with high frequency sinusoidal voltage injection,the high frequency square wave injection scheme of switching frequency is adopted.The proposed scheme replaces the traditional filter by the new current demodulation scheme,which greatly improves the system bandwidth and improves the dynamic performance of the system.(3)In order to improve the accuracy of rotor position estimation in high frequency injection scheme,several main factors,such as cross coupling and dead time of inverters,are studied,and the corresponding measures are put forward.(4)A prototype experiment is carried out on the vector control scheme of the high frequency square wave pulsating voltage injected with the frequency of switching frequency,which validates the effectiveness of the scheme.