Sensorless Vector Control of a Load-Commutated Current Source Inverter-Fed Induction Motor Using V/f Control for Starting

A new load-commutated current source inverter(LCCSI)-fed induction machine drive is presented,using three phase capacitors connected to the motor,To drive a large induction motor, which is usually high voltage machine,the step-up transformer is used because of the limitation of switching element's voltage rating. In this system, the performance of machine control is effected by the ouput transformer and output capacitors. A speed sensorless direct-vector control scheme, with either torque and flux loops or capacitive currnet compensation has been tested In simulation. V/f control for starting is also done to prevent flux's saturation of output transformer and overcome the effect of low signal level at low frequency.