Research On Rotor Position Detection Method Of PMSM Based On Pulsating Current Injection

In the permanent magnet synchronous motor control system, mechanical sensors generally are used to detect the rotor position and speed, but due to some defects of the mechanical sensor itself, sensorless has become a focus of research in the modern motor control technology field. Among a variety of methods of sensorless control techniques, the high frequency signal injection method has been of great concern with the advantages that the rotor position can be detected at low speed, even at zero speed. High frequency signal injection method can be divided into high frequency voltage signal injection and high frequency current signal injection method. In terms of high frequency injection, most of the papers are dedicated to researching for high frequency voltage signal injection method at home and abroad, and the high-frequency current signal injection method are often mentioned in many documents, but few of its in-depth study. This paper analyzes a series of depth studies that mainly focus on the high frequency pulsating current injection method.First, this paper analyzes the working principle of pulsating high frequency current injection method, which continually superimposes high frequency sinusoidal current signal onto the d-axis of the estimated rotor frame to detecting the amount of q-axis voltage, and the rotor position information is extracted by the specific signal processing. This paper uses the designed PID position tracking observer in process of the rotor position signal extraction.Secondly, the position estimation error of pulsating high frequency current injection is analyzed theoretically and in theoretical analysis, this paper derives the rotor position estimation error expression, whose mechanism is discussed. It is shown that the rotor position estimation error is caused by the interaction of the speed electromotive force and current deviation generated by the current regulator, whose size is related to the rotor rotating electric angular velocity, the closed loop bandwidth of d-axis and q-axis current control loop, and Lq/Ld value of the motor, and if ignoring current deviation generated by the current regulator or the speed electromotive force, the position estimation error is zero.Then, two measures are proposed to improve the rotor position estimation accuracy. Measure I which consists of three modified schemes is modified under the Premise of Using PI Current Regulator to compensate estimation error. The three schemes are the modified PI current regulator, the modified position tracking observer and combining the modified PI current regulator with the modified position tracking observer respectively, especially the third measure can achieve precise estimation of the rotor position and velocity. Measure Ⅱ with proportional resonant regulator and nonideal resonant regulator can eliminate the current phase deviation generated by the current regulator, so the estimation accuracy of the rotor position is improved.In order to verify the correctness of the above theoretical analysis, simulation model of rotor position estimation of permanent magnet synchronous motor based on pulsating high frequency current injection is established, which is used for a series of simulation investigation. It is shown that rotor position estimation error got through a series of theoretical derivation is correct, and after two schemes are modified, rotor position estimation accuracy of pulsating high frequency current injection method is improved, which can estimate the rotor position and speed in the whole speed range, even can also track the rotor position when the parameter mismatch.