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A phase-locked loop (PLL) plays an integral part in synchronisation circuits and is immensely used in grid-connected systems, active filters, and uninterrupted power supplies. A number of these circuits based on synchronous reference frame and its modifications, second-order generalised integrator, enhanced PLL (EPLL) have recently been reported in literature. This article proposes an adaptive version of EPLL whose gain adjusts automatically with the variation of error. Adaptive EPLL (A-EPLL) is developed for positive sequence extraction of load current and its performance is tested for active filter operation. A PV system is also connected at the DC link of the shunt active power filter (SAPF) and the developed controller is tested under dynamic load changes. The complete control technique is tested for harmonics reduction, load balancing, and power balance between grid, load, and photovoltaic (PV) source. Detailed experimental results showing a new adaptive PLL for load compensation are illustrated here.

A new adaptive control technique is proposed for a three-phase shunt active power filter (SAPF) in this study. The proposed control algorithm is based on recursive inverse theory which is used here to extract weighted values corresponding to fundamental active and reactive power components of load currents. This adaptive control algorithm possesses advantages over other control algorithms in terms of its reduced computational complexity, fast weight convergence and robust performance in distorted environment. The SAPF is used to mitigate current related power quality problems such as harmonics, reactive power and load unbalancing in both modes of power factor correction and voltage regulation. The performance of proposed control algorithm of SAPF is demonstrated through simulation results in Matlab/Simulink environment, which are validated with test results obtained on the developed experimental prototype of SAPF in the laboratory.