Research On Rotor Position Estimation Of Permanent Magnetic Synchronous Motor Based On High Frequency Injection Method

A permanent magnetic synchronous motor(PMSM)is used in helicopter electric tail control systems as usual for its simple structure,high torque inertia ratio and high power density.And the PMSM control is one of the most important part in electric tail control system.Accurate rotor position and speed are indispensable in PMSM control system,which is generally obtained by position sensors.However the control system will be bigger and heavier for the adding of the position sensor.To solve this problem,the position-free sensing technology of PMSM comes into being.The difficulty in position-free sensing technology of PMSM is the position sensorless control technology at zero-low speed.Pulse high-frequency voltage injection method is a commonly used method in sensorless control at zero-low speed,which extracts rotor position and velocity from the high frequency response signal.However in this method,the rotor position information extracted from the high-frequency response signal will produce deviations,due to the existence of cross-coupling and cross-saturation between the AC and DC shafts of PSMS,and the use of filters and inverters.In response to these problems,the following research is carried out:(1)Based on the principles of coordinate transformation and vector control,the mathematical models of the PMSM are established in different coordinate systems.The mathematical model of the pulsed high frequency voltage injection method under ideal conditions is established,where the rotor position estimation uses a phase-locked loop.(2)A strategy to suppress the cross-coupling effect is studied.The inductance of the motor is calculated using the frozen permeability method in ANSYS/MAXWELL.And then,the relationship between the rotor position error angle and the AC and DC axis current is analyzed.Finally,the error angle is compensated by checking the table method and the simulation verifies the correctness of the compensation mathod.(3)A strategy for suppressing the dead zone effect is studied.The error compensation expression in the two-phase coordinate system is derived by Fourier transform and the characteristics of the SVPWM control technology under the condition of considering the dead time.The rotor position error is compensated leveraging the expression and the further considering of the zero current clamping effect.Finally,the simulation verifies the correctness of the compensation formula.(4)Two compensation strategies to suppress phase offset caused by filters are studied.One of the compensation strategy is to keep the phase of the modulated signal consistent with the phase of the high frequency response signal.The other is to reduce the band-pass filter and use the phase-frequency difference for compensation.Finally,the effectiveness of the compensation method is verified through simulation.