A Simple Full Digital Adaptive Current Hysteresis Control with Constant Modulation Frequency for Active Power Filters

This paper describes an algorithm to implement a full digital adaptive current hysteresis control. The algorithm can be applied in all types of inverters. The proposed strategy takes care of DC link voltage fluctuations, load parameters variations, and it guaranties constant switching frequency operation keeping the ripple at the smaller possible value. The Fuzzy based algorithm has been developed in such way that no hysteresis-band calculations are needed. The constant switching frequency is important to minimize the power semiconductors losses and to maintain the optimal operation of the output ripple filter. The algorithm is full digitally implemented in DSP and it doesn´t need any additional circuits to do the job. It is easy to be programmed, fast and extendable to three-phase applications. Simulation and experimental results have shown the good performance of the algorithm in all practical situations: normal operation, fast load transient, load parameters variation and harmonics follow-up.