Digital Sliding Mode Based Model-Free PWM Current Control of Switched Reluctance Machines

This article presents a digital sliding mode based robust model-free pulsewidth mode current control method for switched reluctance machine (SRM) drives. The model-free nature of the proposed controller allows complete elimination of the phase inductance or flux-linkage identification process. From the controller point of view, this exclusion yields excellent computational efficiency and low memory usage. In the proposed control method, the model information required to achieve a consistent closed-loop dynamic response is treated as an extended state and it is estimated online via unit time-step delayed approximation. The effect of this delay becomes significant as the operating speed increases. The estimation accuracy of the extended state is also affected by the noise in the current measurement. The effect of these factors on the control performance is compensated by using an auxiliary control action derived from a Lyapunov energy function analysis in the discrete-time domain. The resultant controller achieves accurate tracking of the reference phase current profile at fixed switching frequency modulation. It demonstrates a robust tracking performance throughout the controllable operating range of the SRM drive amid low signal-to-noise ratio.