Research On Rotor Position Estimation Method Of PMSM Based On High-Frequency Square-Wave Voltage Injection

Among the numerous sensorless control technologies, high-frequency signal injection method has been a focal point of research because it could operate rotor’s position estimation at low and even zero speed. Traditional high-frequency signal injection method’s principle is:a high-frequency sinusoidal voltage is superimposed on the fundamental excitation, and the rotor position information can be extracted from the processed high-frequency carrier current, however, the band-pass or low-pass filters are inevitable in the signal process, and the control system bandwidth would be limited by these filters and the dynamic performance would be influenced, which limits the application of high dynamic performance. As a result, some improved high-frequency signal injection methods are proposed recently. This thesis, based on the research on high-frequency pulsating square wave voltage injection method and high-frequency rotating square wave voltage injection method, analyses their problems and proposes the corresponding improvement measures.In the high-frequency pulsating square-wave voltage injection method, a switching frequency square-wave voltage is injected into the d axis of the estimated rotor reference frame, and the rotor’s position and speed could be estimated by the demodulation and related processing of q axis carrier current. The dynamic performance is improved significantly because of the increased frequency and the special signal processing method. This thesis analyses problems in the existed scheme and discusses the effect of motor parameter variations on estimation of rotor’s position and speed, and also, it proposes some kind of improvement measures. Among them, the improved load current estimation method could work well when the motor parameters are matched, however, the performance degrades with the motor parameters variations; the improvement of position and speed observer which combines with the improvement of load current estimation method could work well with slightly mismatched parameters; Besides, because of band-pass filter’s influence, the scheme with band-pass filter’s bandwidth is limited, which is still better than the traditional high-frequency pulsating sinusoidal voltage injection method, and has stronger adaptability to motor parameters variations.In the high-frequency rotating square-wave voltage injection method, a voltage impulse is injected in turn into a, b, c axis of three-phase static coordinate every1/3 period, and then, calculating the sampled voltage and current values in two-phase static coordinate to estimate the rotor’s position and speed. The thesis analyses the principle of high-frequency rotating square-wave voltage injection method, and improves the position and speed observer, and also, constructs the simulation model with simulink to research the performance. The results show that the high-frequency rotating square-wave voltage injection method achieve accurate and fast rotor position and speed estimation over the whole speed range, which is better than the traditional high-frequency rotating sinusoidal voltage injection method obviously, and is similar to the high-frequency pulsating square-wave voltage injection method.