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Control strategies and power converter topologies for switched reluctance motors in electric...
an open-loop current control strategy is intro- advantage of DITC is that it treats total torque
duced; however, this technique demonstrates sig- as the primary control parameter, rather than in-
nificant sensitivity to variations in the actual mo- dividual torques (as in TSF) or currents (as in
tor variables. On the other hand, the TSF con- current profiling). Table 2 presents the quantita-
trol strategy presents several advantages, includ- tive comparison between DITC and TSF.
ing simplicity, robustness, widespread acceptance,
efficiency, and the capability to deliver smooth 4. Power converters of switched
torque in low-speed regions. However, its inade- reluctance motors
quate current response hinders the effective moni-
Converter design represents a fundamental aspect
toring of torque distribution functions during the
of SRM research, as both the performance and
commutation process. Consequently, the torque
cost of the drive are significantly influenced by the
control performance in the medium and high-
characteristics of the converter. Numerous con-
speed regions decreases, attributable to its limited verters have been developed to reduce the num-
capability in tracking the reference current. These
indirect torque control strategies necessitate the ber of switches and enhance commutation times.
implementation of a current control loop, thereby Each SRM converter presents distinct advantages
rendering torque control performance contingent and disadvantages. Common disadvantages in-
upon the tracking capability of the current con- clude low efficiency, high voltage ratings, multiple
troller. switches, complex control schemes, and the need
for auxiliary windings. Consequently, converter
On the other hand, DTC, DITC, and MPTC design always involves a trade-off between perfor-
are direct torque control strategies. In these mance and cost.
strategies, torque control performance is directly This section presents an analysis of SRM
related to the control method. The selection of power converter topologies in recent research
appropriate switching angles in the DITC method studies. A distinction is made between hard-
enables smooth torque production up to the rated
switching and soft-switching converters, high-
speed while reducing copper losses through op-
lighting the notable advantages and disadvantages
timized commutation intervals. In contrast, the
of each topology. This analysis aims to support
presence of an additional flux-linkage loop in
the selection of the most suitable power converter
the DTC strategy imposes constraints on torque
topology for EV applications.
ripple-free operation and overall effectiveness.
Compared to DTC, MPTC demonstrates supe- 4.1. Requirements for switched reluctance
rior torque ripple suppression capabilities and op- motor power converters
timizes multiple objectives via a simple scalar cost
function, eliminating the necessity for varying A converter must satisfy multiple criteria to en-
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switching angles across different operating con- hance SRM performance. The basic require-
ditions. However, MPTC is hindered by high ments for supplying power to SRMs include the
computational complexity and notable negative following:
torque at high speeds. • Each SRM phase should be capable of
In this context, artificial intelligence-based operating independently from the other
control strategies are recognized as a viable solu- phases.
tion for torque ripple reduction in SRMs. These • The converter must ensure phase demag-
methods offer several advantages, including non- netization prior to its transition into the
linear and self-learning capabilities, as well as generating region when the machine func-
adaptive functionality. However, these techniques tions as a motor. Conversely, it must ex-
require significant computational time for algo- cite the phase before entering the generat-
rithm execution and introduce high algorithmic ing region when operating as a generator.
complexity.
4.2. Classification of switched reluctance
Figure 19 illustrates that, upon comparison of motor power converters
all the discussed control strategies for SRMs, the
DITC strategy demonstrates superior overall effi- Most power converters are selected based on their
ciency in minimizing torque ripple. Its implemen- intended application. For low-performance appli-
tation is simple, while offering flexibility across a cations, low-cost converters are suitable, as pre-
broad torque and speed range. The minimization cise torque control is not necessary. Conversely, a
of root mean square current, and consequently the high-performance converter with rapid phase de-
reduction of losses, can be accomplished through magnetization is required for applications requir-
adjusting the turn-on/off angles. Finally, a key ing accurate torque control and efficiency.
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