Research On FOC Phase Current Reconstruction Technology Based On MOSFET Internal Resistance Sampling

At present,permanent magnet synchronous motor servo systems are used in many industries.Servo systems with higher performance need to accurately detect the value of the phase current.The use of high-precision current sensors is not only expensive but also increases the volume of the system;high-precision sampling is used Resistance will increase the loss of the system under high frequency and high current conditions and reduce system performance.Therefore,it is of great significance to study new sampling methods.Based on the internal resistance sampling of the MOSFET,this paper uses half pulse width modulation(PWM)phase shifting method to reconstruct the phase current of the sampling blind area.In this paper,a mathematical model of a permanent magnet synchronous motor is established,combined with the field-oriented control(FOC)theory,to derive and summarize the current conversion relationship of the permanent magnet synchronous motor in the entire closed-loop control process.Aiming at some problems of the current sampling method of the phase current in the vector control of the permanent magnet synchronous motor,a sampling method using the internal resistance of the MOSFET is proposed.Reduce the complexity of the system and improve the efficiency of the system.Aiming at the blind area problem of phase current reconstruction in actual sampling,the phase current reconstruction strategy is studied.Although the vector pulse insertion method can reduce the blind area of phase current reconstruction,it will also increase the switching frequency of the MOSFET,increase the system loss,and produce distortion of the current waveform.In addition,the algorithm is more complicated and difficult to implement at higher frequencies.The traditional PWM phase shifting method can reduce the phase current reconstruction blind zone,and will not affect the synthesized vector voltage,but will cause the current ripple to increase,the PWM waveform is asymmetry,and affect the stability of the permanent magnet synchronous motor’s operating state.This article improves the traditional PWM phase-shifting method and proposes a half-PWM phase-shifting method.Experiments show that the semi-PWM phase-shifting method simplifies the algorithm structure,reduces the phase current reconstruction blind area generated by the internal resistance of the MOSFET,reduces the current ripple,and has no effect on the actual output voltage,and improves the vector of the permanent magnet synchronous motor.The dynamic and static control performance of the control system proves the feasibility of this method.