A novel approach of constructing
a robust variable-speed drive system
using an induction motor supplied from
a voltage-source-type PWM inverter is discussed.
The inverter is controlled so as to
generate the fabricated terminal voltages
based on the voltage-decoupled transvector
control theory where neither a current feedback
loop nor a current limiter circuit is required.
Although the hardware for this decoupling
method becomes simplified, it still
has some disadvantages, such as the discrepancy
between the command currents and
actual currents. Incorporated into the drive
system described herein is the optimal-speed
regulator adopting the exact model-matching
method, which fulfills the function of a compensator
for unfavorable errors. The operating
characteristics of the proposed drive
system are compared with conventional PI
control to verify the effectiveness under various
conditions by investigating the transient
responses for the step change of the speed
command, the load torque, and so forth.