ADAPTIVE COMPENSATION OF VOLTAGE-FED INVERTER NON-LINEARITIES FOR THE SENSORLESS VECTOR CONTROL AT LOW SPEED

The analysis of non-linear properties of a voltage-fed inverter, that is the base of the modern low-voltage variable-frequency electric drive, has been introduced. The negative influence of non-linearities of the inverter on the form of its output current as well as the complications of the performance of the sensorless vector control system of an induction motor have been proved, the reasons for decreasing of speed control range are analyzed. Available methods of compensation of the inverter non-linearity have been considered, an adaptive method of compensation that differs from the available methods in that there is no need to pre estimate the inverter parameters and that it has stability towards electromagnetic disturbances in the channels of inverter output currents estimation has been proposed. The investigated method based on adaptive current observer, this allow to reduce delay in the compensation system, due to the transport delay in current measurement channels The advantages of the proposed method over the available ones have been proved by means of mathematical simulation and experiments.