Sensorless Control of Im Drives Considering 0 Hz Crossover: Control Theoretical Analysis and Synthesis

Electrical drives based on sensorless control has the advantage that neither encoder or speedsensor on the rotorshaft is needed. This book presents sensorless control adopted on the induction machine by a fairly unique kind of rotorflux estimator based on the so-called voltage model (VM). The VM estimates frequency and is developed from a vector controlled scheme of the machine model, here with one of the two channels open controlled. Then the VM and machine dynamics together defines a complete model for further control theoretical analysis and design. The analysis mainly considers instability problems and parameter variations, here especially focused on the 0 Hz crossover problem. The open controlled channel then gives an important mean for stabilizing design and parameteridentification. By nonlinear and linear analysis an optimized solution is achieved for the 0 Hz crossover problem, completed with Kalmanfiltering design for parameteridentification in the nominal speed range.