Rotor Position Identification Of Ship Sensorless Permanent Magnet Synchronous Motor In Full Speed Range

In order to reduce the complexity of Marine electric propulsion system,reduce the cost and improve the reliability of propulsion system,the Permanent Magnet Synchronous Motor(PMSM)control technology is used to replace the encoder.In this paper,the strategies of improved square wave injection,rotor position estimation error based on the torque equation and algorithm fusion are adopted to improve the low accuracy of rotor position identification and rotor position identification in the full speed range.The main contents are as follows:Firstly,for the problem of the nonlinear error of inverter voltage and the measurement error of motor phase current reducing the accuracy of rotor position identification,an improved square wave injection method was adopted to improve the accuracy of rotor position identification by injecting multiple voltages.PWM frequency is higher,after injection voltage for many times,by subtracting the voltage equations in two adjacent PWM cycles,the nonlinear error of inverter voltage and phase current measurement error in the voltage equation can be ignored,so as to reduce the influence of nonlinear error of inverter voltage and phase current measurement error on identification of motor rotor position,improve the identification precision of rotor position;Secondly,in view of the problem that the cross-coupling effect reduces the accuracy of rotor position identification,the rotor position error was calculated based on the motor torque equation and used as compensation.There exists cross coupling effect when the permanent magnet synchronous motor is under load operation,the effect makes motor magnetic salient pole deviate from mechanical salient pole,and further affect the motor rotor position estimation accuracy,through changing the direction of the current vector,the rotor position error is calculated by the torque equation and used as compensation,so as to improve the motor rotor position identification accuracy.Finally,aiming at the problem of sensorless PMSM running in the full speed range,a method combining the zero voltage injection method suitable for medium or high speed with the improved square wave injection method suitable for zero or low speed is proposed.The square wave voltage injection method and zero voltage injection method switch algorithms by weighted average near the boundary point between zero or low speed and medium or high speed,which makes the transition process of motor speed more smooth,and realizes the sensorless rotor position identification within the full speed range.To sum up,this paper mainly focuses on improving the motor rotor position identification accuracy and the sensorless permanent magnet synchronous motor running in full speed range.The influence of inverter voltage nonlinear error and phase current measurement error on rotor position identification accuracy is reduced by using the improved square wave signal injection method.The rotor position estimation error caused by the cross-coupling effect is calculated and compensated by the torque equation of the motor.By combining the improved square wave signal injection method with the zero-voltage injection method,the rotor position identification of PMSM in full speed range is realized.