| Abstract |
The paper introduces a new concept of a sensorless induction machine (IM) drive supplied with the
impressed stator voltage. In order to reduce side effects of conventional sensorless drives relying on
impressed stator currents (i.e. thermal stress, noise and parasitic capacitive currents that stress the
insulation system,…), a new inverter topology with controlled sinusoidal output voltage is proposed.
Its power stage consists of a three-phase Voltage Source Inverter (VSI) and an output LC filter
combined into a unique controlled voltage source. This is accomplished with the applied feedbackfeedforward
voltage control loop whose main attraction is the control of filter capacitor current. In this
way, output voltage is attained indirectly through an impressed filter capacitor current. In the case of a
cosinusoidal capacitor current, the output voltage is sinusoidal and therefore no longer of a pulsed
shape, which is the main drawback of the conventional inverter. In the same manner, the frequency
and load dependance of output voltage are reduced while its dynamics compared to other known
solutions with passive LC filter is increased. In addition, it is shown that the implementation of the
speed-sensorless control with the proposed inverter has become an easy attainable feature. Firstly,
upon mathematical expressions of current and voltage fed IM, a model for calculation of the IM speed
ù and frequency of the magnetizing current vector ùmR is defined. Additionally, a Field-Oriented
Control (FOC) scheme of the microcomputer controlled IM drive is presented. The proposed concept
has been verified through experimental tests using a laboratory three-phase VSI and exhibits very
promising results. |
