Research On Sensorless Control Of Interior Permanent Magnet Synchronous Motor In Zero And Low Speed

The growing global energy crisis and environmental pollution are getting more and more serious,countries around the world are working hard to develop clean energy.Electric vehicles have many advantages such as it doesn't require fossil fuels and exhaust no polluted gas,under the support of government and deep research of automobile companies,electric vehicles have developed rapidly.As the core of electric vehicles,interior permanent magnet synchronous motors are widely used due to their unique advantages such as low price,high power density and wide speed range.In order to obtain high-performance vector control of the motors,it is necessary to know the rotor position of the motor.The conventional method for obtaining the position of the rotor is to install a position sensor,but this will increase the system cost and reduce the system robustness So the sensorless control method has been extensively and deeply studied.This dissertation summarizes the status quo of sensorless control technology for permanent magnet synchronous motors.Research shows that it is difficult to estimate the initial position of the motor rotor.Therefore,this dissertation focuses on the initial rotor position estimation of interior permanent magnet synchronous motor,adopts rotating high-frequency signal injection method to conduct in-depth research,and realizes the low-speed sensorless control of the permanent magnet synchronous motor.The first problem in achieving sensorless control of a interior permanent magnet synchronous motor is how to identify the initial rotor position.The accuracy of the identification and the reliability of the identification need to be considered.In this dissertation,rotating high frequency signal injection method is used to identify the initial rotor position,but its identification accuracy is affected by many factors such as digital control sampling and calculation delay,PWM output delay,and phase delay generated by the filter in the signal demodulation process.This dissertation proposes a unified compensation algorithm based on the analysis of the impact of those factors.The compensation algorithm utilizes the relationship between the positive sequence current and the negative sequence current.By extracting the phase deviation in the positive sequence current signal,the phase of the negative sequence current signal is uniformly compensated to improve the accuracy of position estimation.Due to the symmetry of the rotor,the position information obtained by rotating high-frequency signal injection method is not true.So polarity identification is needed to identify the rotor polarity to obtain the actual rotor position.In this dissertation,based on the detailed analysis of polarity identification methods widely used at present such as voltage pulse injection method and saturated current quadratic term method,based on the existing defects,a saturation inductance polarity identification algorithm based on current closed-loop control is proposed.In the polarity identification process,in order to make the motor stand still,the q axis current is controlled to 0,and by applying different d axis currents,the corresponding inductance values are calculated and compared to achieve the purpose of polarity identification.The sensorless control experimental platform was built on a 50kW interior permanent magnet synchronous motor.Zero-and low-speed sensorless vector control algorithm for magnetic synchronous motors is verified experimentally.The verification results prove the effectiveness of the position error compensation algorithm and the polarity identification algorithm.Based on the rotating high-frequency injection method,the interior permanent magnet synchronous motor position sensorless control system can effectively track the rotor position at zero and low speed.