Design Of Sensorless Control System For PMSM Based On High Frequency Signal Injection

In the vector control system of permanent magnet synchronous motor(PMSM),an encoder is usually used to obtain the rotor speed and position.The encoder is usually installed on the motor shaft,which is not conducive to the miniaturization of the motor,but also increases the cost,reduces the system reliability.In this thesis,the sensorless control scheme of PMSM in low-speed and zero-speed states is studied.Two schemes based on high-frequency pulse voltage injection and high-frequency square-wave voltage injection are adopt to implement the sensorless control system.The two schemes are compared and analyzed.First,the sensorless control system based on high-frequency pulse voltage injection is studied in this thesis.The high frequency pulse voltage injection method is used to detect the initial position of the rotor.The parameters of the position tracking observer are analyzed and designed.The selection method of injection signal is given through theoretical calculation,and simulation experiment is carried out.At the same time,the influence of the filter on system is analyzed.The sensorless control system based on high-frequency squarewave voltage injection is also studied in this thesis.With a specific form of high-frequency injection signal,the signal extraction process is simplified and the system delay is reduced.The rotor initial position detection method based on high frequency square wave voltage injection is studied,and a sensorless control system is realized.A simulation platform with a variety of actual working conditions is developed,and a large amount of comparative analysis of the two schemes are conducted.Including the comparative study of the two systems under the same speed setting,the robustness study under the change of the motor parameters,the study of the speed change under actual working conditions,the study of the anti-load disturbance and so on.The experimental results show that both methods have good control performance at low-speed and zero-speed.They have good speed tracking and position observation performance,good robustness to motor parameter changes and good immunity performance to load changes.and they have certain robustness to the parameters change.The sensorless control system based on highfrequency square-wave voltage injection avoids the use of filters through a special signal extraction method,which increases the system bandwidth and reduces the system delay.Under the same conditions,it has higher position observation accuracy and better speed tracking performance.