Novel structure for unbalance, reactive power and harmonic compensation based on VFF-RLS and SOGI-FLL in three phase four wire power system

In this paper a new unbalance, reactive power and load harmonic compensation procedure based on variable forgetting factor-recursive least squares (VFF-RLS) and new phase locked loop is proposed. For this purpose, harmonic component of load current and its positive sequence are estimated with VFF-RLS. Independency on order and amplitude of harmonics, fast dynamic and high accuracy is the bold features of designed estimators. As in the case of load increase/decrease, sag/swell and phase jump in voltage, the optimal compensation is done in less than half a cycle with low THD value. In addition to compensate an infected power network by oscillation frequency, second order general integrator-frequency locked loop (SOGI-FLL) control loop based on wavelet transform (WT) and fuzzy logic controller (FLC) has been proposed. This phase detector can track the reference phase of network in the best manner in the presence of frequency oscillation. Efficiency of the discussed method in a three-phase power system has been validated using both simulations in MATLAB and experimental results.