Sensorless Vector Control for a Load Commutated Inverter fed Active-Reactive Induction Motor Drive

Load Commutated Inverter fed drives are the most popular choice for medium voltage high power drives in the multi-megawatt range. The simplicity and ruggedness of the converter structure are the main advantages of these drives. But they are typically used only in conjunction with synchronous motors. LCI fed induction motor drives for high power MV drives are not available in the market. The main reason is the lagging power factor operation of the induction motor which does not allow natural commutation of thyristors in the LCI. However, the Active-Reactive Induction Motor (ARIM) which is a six-phase motor configuration proposed in literature, overcomes this disadvantage of the induction motor by sending active power from one set of three-phase windings and reactive power from another set. The LCI fed ARIM drive thus combines the advantages of the LCI and the induction motor to provide an excellent alternative to LCI fed synchronous motor drives in the high power segment. This paper explores the sensorless operation of the vector controlled, LCI-fed ARIM drive. A basic stator voltage model with an error correction mechanism is adapted for the sensorless implementation. The proposed method is verified experimentally using a 1.65 kV ARIM prototype.