OLIVEIRA, A. C.; http://lattes.cnpq.br/6699829609793478; OLIVEIRA, Alexandre Cunha.
Résumé:
The use of variable reluctance machines (\"RM) as viable system have been waited for
the development of suitable motor drive systems. These systems must be able to accomplish
operacional requirements as fast current commutation among the phases and also the
knowledge of the axis position.
In spite of V R M favorable inner characteristics as construction simplicity, concentration
of the electric windings of the stator, better torque volume relationship, low inertia and
operation capability at high speeds, the YRM presents high torque ripple due to its double
saliency structure and switching current effects among phases, that moves i t away of high
performance applications, as robotics. The difficulty of generating torque with low ripple
is outlined by the use of strategies that control the form and the instants of current application
for the phases of the machine based on the characteristic curves of inductance and
derived of inductance versus position of it. The accurate knowledge of these curves allows
implementing high performance systems. In this work, it will be analyzed some procedures
that allow to obtain these curves in a faster way. keeping the precision of the estimation
method based on the flux x current x position curves
The current loop control is one of the most important loops in a drive system based
on variable reluctance machines. Among the more commonly used controllers, stand out
the hysteresis control and PWM, usually implemented with PI or PID regulator. The first
controller is indicated for operations in high-speed while the second one is more efficient
in low and medium speeds. An alternative to the previous controllers is the predictive
controller, which is proposed in this work. It will be shown that the use of this type
of controller for regulation of the variable reluctance machine phase current is technically
viable and simple and robust to parametric variations as well.
The implementation of the control action is accomplished by the inverter switches command
that is usually for a voltage source inverter. The variable reluctance machines can
operate w i t h unidirectional currents simplifying the project of the inverter and allowing the
use of inverter w i t h just a switch for each phase, but imposing severe operation restrictions
to the machine. The use of the inverter with integrated structures, as the three phase
bridge inverter are shown as alternatives to drive variable reluctance machines. Following
this direction, i t w i l l be presented alterations in the form as these structures have been used
allowing them to reach equivalent performance to the half bridge inverter.
To conclude, the effects of the dead time compensation will be analyzed in three phase
bridge inverters. In spite of the simplicity and efficiency of the compensation strategies
based on the modification of the inverter switches command pulses, i t will be shown that
the strategies should be monitored to avoid that the command compensated times extrapolate
the up or down limits of the sample time. This situation can cause distortion in the
synthesized voltage by the inverter.