A computationally intelligent maximum torque per ampere control strategy for switched reluctance machines

A computationally intelligent maximum torque
per ampere control strategy for
s
witched
reluctance machines

Furkan Akar, Fletcher Fleming, Chris S. Edrington

Center for Advanced Power Systems, Florida State University

Tallahassee, FL, USA

fleming@caps
.fsu.edu


Abstract
—
While currently occupying only a niche role in

industrial applications, the switched reluctance machines (SRM)

unique operational characteristics could prove useful for

additional engineering sectors given that inherent drawbacks are

add
ressed. Phase winding isolation of SRMs provides greater

fault tolerance when compared to the industrial standard, pulse

width modulation driven induction machines. Furthermore, they

may remain in a locked rotor position safely without concern of

faulting
and have higher speeds than many other electrical

machines, i.e. contributing to greater overall robustness. When

compared to other electrical machines, the SRM has higher

currents requirements, creates greater acoustic noise and torque

ripple, and require
s more advanced controls for effective

operation. Such drawbacks alienate the SRMs commercial and

industrial popularity, ultimately limiting its full potential from

being exploited.

Since SRM torque production is typically non
-
linear, various

techniques ha
ve been developed in order to maximize the torque

output per unit current excitation, i.e. maximum torque per

ampere (MTA). The “conventional” strategy, while simplistic,

assumes a constant excitation over a symmetric period of the

machine. This increases
copper and iron losses while not

effectively mitigating the current requirements or inherent

torque ripple. By using particle swarm optimization (PSO), a

stochastic search technique based on evolutionary algorithms,

phase

current MTA profiles may be obtained that optimize such

conditions. This work presents a novel MTA SRM control

strategy based on the PSO technique that obtains the optimum

phase current profiles of a 4
-
phase, 8/6 pole SRM such that

copper losses and torqu
e ripple are minimized while achieving

the desired torque at specific rotor positions.