Input filter state feed-forward stabilising controller for constant power load systems

An input filter state feed-forward stabilising controller is presented to stabilise a constant power load and is validated using a brushless DC motor drive system. The strategy is to feed-forward a stabilising signal which is a function of the DC-link filter variables, capacitor voltage and the inductor current, into the current control loop of the motor drive to modify the magnitude and phase of the system input admittance around the input filter natural frequency and thereby damp the input filter. The controller design and parameter selection are described. The impact of the stabilising controller is examined on the motor controller performance and finally the effectiveness of the controller is verified by simulation and experimentally.