Simple adaptive control for a single phase shunt active filter

The authors deal with the problem of controlling of single phase active filters. Some algorithms for active filters controlling are well known today, but some of them can´t be used in case of single phase filters. For example the PQ Theory (Theory of the Instantaneous Reactive Power) is excellent for three phase solutions, but for single phase solutions it can´t be implemented. The main challenge in the single phase controlling method is to get the fundamental harmonic function in a proper magnitude and phase. The authors proposed a simple and fast method, which is based on the LMS algorithm (“Least Mean Square” algorithms are a class of adaptive filters). This method can be easily implemented also in 8-bit microcontroller units only with the need of sum and multiplication instructions. Because the same algorithm can be used also for converter control synchronization, the authors constructed a test device detecting mains phase voltage zero-crossings with an 8-bit ATmega8L processor, where the algorithm was implemented.