A Review of Fixed Switching Frequency Current Control Techniques for Switched Reluctance Machines

Abstract

By the virtue of its highly nonlinear magnetic characteristics, the Switched Reluctance Machine (SRM) poses a formidable challenge for digital current regulators operating at a fixed switching frequency. Very fast tracking performance demanded by highly dynamic reference current profiles often surpass the conventional limits on closed-loop bandwidth posed by finite sampling frequency. The non-linear nature of matched disturbance to be compensated by the controller appearing in the form of induced emf grows in significance as a function of operating speed while the varying nature of inductance profile stipulates a need for gain adaptation by the control law in order to maintain consistency in closed-loop dynamic response. In the view of these unique SRM characteristics, the paper presents a detailed theoretical analysis of the widely implemented current control techniques from literature and provides illustrations in the context of their implementation in a digital controller. The analysis presented in this paper can also serve as a foundation for more advanced versions of these control techniques as well as their combinations.