Research On Discrete-Time Current Control For Permanent Magnet Synchronous Motor

An important indicator of high-performance permanent magnet synchronous motor(PMSM)servo drives is the high dynamic response of the current.Usually,the current controller is designed in the continuous domain,and then discretely formed into a digital control algorithm.Affected by the digital control delay,it often causes the current loop to be decoupled incompletely,resulting in poor current loop dynamic response.Therefore,this paper directly designs the current controller in the discrete domain to solve the above problems.First,the mathematical model of the permanent magnet synchronous motor and the basic architecture of vector control are described,and the continuous complex vector current control scheme is described.By comparing the complex vector current control based on voltage feedforward decoupling and the two-degree-of-freedom complex vector current control,the latter can more effectively suppress voltage step disturbances.In the case of considering the digital control delay,through the system closed-loop zero pole analysis,as the delay increases,the system performance decreases.At the same time,it can be known from the simulation experiment that the current decoupling becomes worse.Secondly,in order to make the current loop decoupling more thorough and improve the current loop dynamic performance,the current controller is designed directly in the discrete domain.Based on the PMSM discrete control model,the calculation delay of a sampling period is considered,a two-degree-of-freedom discrete complex vector current controller is used,and the controller parameters are set using the discrete pole configuration method.According to the current loop simulation experiment results,the two-degree-of-freedom discrete complex vector current controller makes the current loop more robust to motor parameter changes,and the performance of the current controller is verified in the double closed-loop simulation experiment.Finally,on the experimental platform of PMSM double closed-loop speed regulation system,through decoupling performance comparison experiment,anti-interference performance comparison experiment and motor parameter error experiment,it is further verified that the two-degree-of-freedom discrete complex vector current controller can make the current loop decoupling more thorough,While effectively suppressing voltage step disturbances,it is more robust to motor parameter changes.