Implementation of a direct digital predictive current controller for single and three phase voltage source inverters

The three major approaches for regulating current in hard switched inverters are ramp comparison, hysteresis control and predictive current control. Of these three, predictive current control offers the potential for achieving more precise current control with minimum distortion and harmonic noise, but is generally more difficult to implement and usually must be matched to a specific load. Also, errors caused by computational delays create further problems in a real system. This paper presents algorithms for directly implementing a predictive current controller in a microprocessor for load situations where the back-EMF is both known and unknown. The algorithms fully compensate for sampling delays and discretisation errors, and are simple enough to be readily implemented in a practical system. Both simulation and experimental results are presented as confirmation of the approach presented.