Chaos in Switched Reluctance Drive Systems
The switched reluctance (SR) drive is a specific kind of doubly-salient drive. The SR drive system has the advantages of robust structure, high reliability, simple control, wide range of constant power operation, and low manufacturing cost (Lawrenson, 1992). On the other hand, it suffers from the drawbacks of large noise, large torque ripple, special converter configuration, and high nonlinearities (Miller, 1993; Zhan, Chan and Chau, 1999). Thus, it is anticipated that the SR drive system is more prone to chaos due to the high nonlinearities.
In the SR drive, there are two driving periods, namely the commutation period and the pulse width modulation (PWM) period (Miller, 1993). The commutation period is the stroke angle determined by the phase commutation, in which the phase current always has an initial value of zero. Hence, for each phase winding, the drive system operates in a discontinuous conduction mode for the term of the commutation period. The PWM period is the period of the carrier signal for PWM regulation, which is also the switching period of power devices. This PWM period is usually short enough to force the phase current to be continuous within the commutation period. The phase current oscillation, and hence the torque oscillation, are governed by the distribution of those PWM pulses within the commutation period. At normal operation, the PWM pulses are uniformly distributed. Hence, the corresponding oscillation ...