Controllers for traction inverter drives

The authors present a study of two different types of controllers for a traction voltage source inverter (VSI) drive. The first is a simple scalar control scheme which ensures constant torque operation down to low motor speed. With this controller the inverter V/f characteristic is automatically varied to compensate for different levels of motor load. This type of controller is essentially designed for good steady state operation over a wide range of inverter frequency. The second controller is based on state feedback control of the induction motor and is designed specifically to achieve a good transient response requirement. The author shoes that with this type of controller it is possible to achieve near decoupled flux and torque control as is possible with DC traction drives. The transient and steady state results obtained with this controller are described in detail.