Discrete current control with improved disturbance rejection for surface‐mounted permanent magnet synchronous machine at high speed

Abstract

The virtual resistance technique has been widely adopted to improve the disturbance rejection of the complex vector decoupling approach for surface-mounted permanent magnet synchronous machines at high speed. Its gain selection, however, has only been discussed in the continuous domain. In this study, the virtual resistance technique is analysed directly in the discrete domain. Theoretical analyses demonstrate that there is a definite upper limit for the virtual resistance selection which is only dependent on the ratio between the time constant of the machine and the sampling period. A new discrete current controller is proposed to improve the command tracking and the disturbance rejection of the current loop. A trade-off is made between the rapidity and the robustness of the proposed controller in order to achieve a parameter error tolerance of 50%. Experimental results verify that the proposed controller gains better performance at high speed, i.e. a higher bandwidth of 0.135f s without overshoots and fewer oscillations, than the controllers designed in the continuous domain. Even deadbeat responses, to both the reference signals and the disturbance, can be achieved by the proposed controller at its limits.

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