FPGA-based High-performance Current Controller For Permanent Magnet Synchronous Motor

AC servo system includes position loop, velocity loop and current loop. Current loopis the inner loop of the system, which will directly affect the performance of velocity loopand position loop. Therefore the design of current controller is very important for thecontrol of permanent magnet synchronous motor. High-performance current controller isdesigned in this thesis.Firstly, the mathematical model of PMSM current loop is analyzed to obtain twomajor constraints of current loop performance, i.e. current loop bandwidth and d-q currentdynamic coupling. Secondly, a research is conducted on the bandwidth expansion andcurrent dynamic decoupling.To expand the current loop bandwidth, the relationship between current loopbandwidth and time delay are analyzed. Then the time delay generated by several typicalcurrent loop timings is compared. Finally, based on the existed current loop timings, animproved current loop timing is proposed. The improved current loop timing can obtain aminimum delay and overcome the disadvantages of the existed timings.In order to decouple the d-q currents, three types of decoupling methods i.e. feedbackdecoupling, IMC decoupling and error compensation decoupling are derived andcompared. It is turned out that the error compensation decoupling has stronger robustnessand practicality. Furthermore, in order to decrease the overshoot and oscillation of currentresponse, a method of error compensation decoupling control with voltage anti-windupdesign is proposed.Finally, the current controller which takes the proposed bandwidth expansion anddynamic decoupling method is verified and implemented on FPGA. Experimental resultsshow that the bandwidth of the proposed current controller can be up to3kHz and thecurrent dynamic decoupling method is effective. The control performance of the AC servodrive has been significantly improved.