Closed Loop Controlled High Speed Induction Generators Using Adaptive Control Technique

High speed generators offer very high power density solution for electric power requirements in airborne applications. Induction generators are suitable for the high speed environment because of the ability to provide controlled voltage and power output with a reliable rotor construction. An important issue of power control for the high speed induction generator is maintenance of the steady state output voltage within the specified limits over the entire range of speed and load variations. This paper discusses the development of a closed loop control system for a 200 kW induction generator under different load conditions.

Field Oriented Control (FOC) schemes are implemented to both operate the generator in the maximum torque conditions available and to decouple the maximum torque from the field under transient and steady state operation. FOC uses Classical Proportional and Integral (PI) controllers for regulation because of their simple implementation. However, PI controllers do not perform well when controlling high order non-linear dynamic plants - such as the high speed induction generators - due to the overshoot response and the output saturation when generator is loaded. To resolve this issue, the proportional gains need adjustments with respect to the load variation as well as the overshoot response in realtime.

A gain scheduling control algorithm has been developed to select the appropriate controller gains with respect to the generator load. Further, a relationship between the generator loads and the controller gains have been established. This relationship was modeled using adaptive control technique to vary the gains automatically under any load condition.

The adaptive control technique has been successfully generalized for real time DSP implementation to regulate the DC voltage for high speed induction generators rated from 5 kW to 200 kW.