Design Of High Frequency Servo Drive System Based On GaN Power Devices

The motor drive system is widely used in e quipment manufacturing,aerospace,automation and other fields,along with the rapid development of intelligent,high power density,high reliability development trends.As an important component of the motor drive system,the current power conversion system basically uses power devices based on Si materials,and the switching frequency is low,so it is difficult to balance the needs of high power density and high efficiency.With the continuous development of semiconductor technology,power devices based on gallium nitride(GaN)materials have excellent switching characteristics and high-frequency operating performance.If the GaN power device is applied to the motor drive field,it will be able to significantly reduce the system volume,reduce the loss,increase the power density,and reduce the audio noise during the operation of the motor drive system.Therefore,the study of the motor drive system based on wide bandgap power devices is of great significance to the improvement of motor control performance.In this paper,a servo driver based on GaN power device is developed,and the key control algorithm of the driver is studied.Firstly,the influence of parasitic parameters in the driving circuit and power circuit on the driving performance of GaN power device is analyzed.The optimization sequence and optimization method of parasitic parameters are given.The hardware circuit based on GaN power device is designed and a servo driver is manufactured.Next,an LC output filter is serially connected between the output side of the inverter and the input side of the motor to reduce the d v/dt and di/dt generated by the high speed switching of the switch and to realize the sine wave drive of the motor.At the same time,the resonance problem caused by the LC outp ut filter is studied,and the influence of the current loop delay on the stability of the syste m is analyzed.Based on this,undamping method is proposed to realize the suppression of electrical resonance,and a PI controller tuning method for the current regulator is given.The effectiveness of the undamped algorithm is verified through simulation and experiments.After comparing the EMI of the phase current at different switching frequencies with or without an LC output filter,the experimental results show that when the ratio of the switching frequency to the resonant frequency is within a suitable range,the introduction of the LC output filter will suppress the switching noise and reduce the EMI of the system and enable the sinusoidal drive of the motor.Finally,FPGA-based hardware current loop design is completed.The control algorithm of each module in the current loop is written in Verilog HDL,and the correctness of the current loop algorithm is verified by simulation and experiments.According to the bandwidth test of the current loop,the current loop bandwidth can be increased to 6k Hz or more at a switching frequency of 100 k Hz.Thus,compared with the traditional servo driver,the control performance of the high-frequency servo driver based on GaN power device has been significantly improved.