Modeling Characterization Control and Design of Switched Reluctance Machines

Abstract

Switched reluctance machines (SRM) are permanent magnet free, and have a simple rotor construction with no current carrying parts. These are particularly suitable for high-temperature and high-speed applications. However, modeling and control of SRM are challenging on account of both phase inductance and back-emf being dependent on phase current as well as rotor position. This thesis addresses modelling and characterization of SRM, current control for low speed operation, single pulse control for high speed operation, and electromagnetic design of SRM. Further, this thesis is oriented towards providing a solution for a high-speed switched reluctance generation (SRG) system, which is directly coupled with a high-speed thermal turbomachinery. Hence this thesis focuses on modelling of SRG system (inclusive of machine, power converter and control), control techniques for high-speed generation, high-switching frequency SiC MOSFET based power converter, fast fault detection and protection schemes for such converters, and B-H characterization of magnetic materials at high frequencies. On account of direct coupling to the thermal turbine, the generator shaft temperature and consequent expansion are expected to be high. Hence, special rotor constructions utilizing a common material for shaft as well as rotor are considered and evaluated experimentally. Delta modulation and variable gain PI based current control are well known techniques for current control in an SRM. This thesis proposes and validates a fixed gain PI control with back-emf compensation for current control of SRM. A novel model predictive based current control is also proposed, which has better current tracking ability. Then a novel constant current injection based characterization method is proposed, which can yield the flux-linkage characteristics of the SRM without the requirement of blocking the rotor at known positions. The novel current control and characterization techniques are demonstrated and evaluated on a 4-phase, 8 stator pole, 6 rotor poles...