Research On Control System Of PMSM Based On Overmodulation Drive

Permanent magnet synchronous motors have the characteristics of simple structure,low loss,high efficiency,reliable operation,etc.,and have been widely used in many fields.In order to further improve the utilization rate of the bus voltage of the motor control system and realize the sine wave and square wave hybrid drive,thereby increasing the turning speed,output torque and load capacity of the motor,this paper has carried out research on the overmodulation algorithm and the performance of the overmodulation output voltage;At the same time for the permanent magnet synchronous motor with Hall element as the position sensor,in order to reduce torque ripple and improve the accuracy of motor speed control,this article discusses,analyzes and improves the speed and position estimation method based on Hall sensor.First of all,in response to the needs of permanent magnet synchronous motors to increase the utilization rate of the busbar voltage and realize the sine wave and square wave hybrid drive,the inverter modulation area is extended to the over-modulation area.The traditional over modulation method is computationally intensive and time-consuming.On the basis of the SVPWM algorithm in the 120° coordinate system,an overmodulation algorithm based on the principle of minimum phase error is derived.The algorithm is based on logical judgment,and the calculation is simple.It can smoothly transition from the linear modulation area to the square wave mode,and the harmonic content is small.Compared with the traditional SVPWM over-modulation algorithm,it simplifies the calculation process and saves computing resources.The output voltage performance of the over-modulation algorithm is analyzed.The relationship between the output voltage amplitude and the reference voltage amplitude and the relationship between the output voltage harmonic content and the output voltage amplitude are calculated separately.Finally,the influence of the increase of the output voltage on the motor speed and output torque of the motor is analyzed.Secondly,for permanent magnet synchronous motors using Hall elements as position sensors,the principles of the traditional interpolation method for speed and position estimation methods are analyzed,and it is pointed out that when there is a deviation in the installation position of the Hall sensor,the interpolation method has shortcomings.The rotor speed and position estimation method based on the filter method is introduced,and the two-phase quadrature sine signal is obtained after coordinate transformation and filtering of the Hall sensor output signal,and the rotor position information is calculated through the phase-locked loop link.In view of the phase advance or lag problem caused by the output of PLL caused by the parameter of notch filter being fixed,this paper changes the fixed parameter of notch filter to the correlation between variable parameter and rotor angle frequency,and determines the coefficient relationship,which makes the observation result more accurate.Finally,the above strategies are analyzed through simulation,and an experimental platform of the permanent magnet synchronous motor control system for electric bicycles with Hall sensors is built to verify the control algorithm proposed in this paper.