Stabilization procedures based on fuzzy inference algorithms for PWM drives

The problem of instability areas of the general purpose drive system with PWM inverter and an induction motor was investigated. The first task of detection of instability (or excessive angular velocity oscillations with a poor damping factor) was solved in the drive system without velocity feedback and without velocity signal. The fuzzy inference based algorithm uses for processing only one signal from power circuit-inverter supply current signal, and two other signals from the control circuit of the inverter. It activates the adequate reference frequency correcting procedure. The improvement of stability is achieved only by the influence on the reference frequency signal