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.
This study deals with the performance analysis of three digital filters viz. multiple complex coefficient filter (MCCF), moving average (MA) and Butterworth in distribution static compensator (DSTATCOM) for non-linear loads. The filters are designed to extract the fundamental component of load current and tested in the closed-loop control of DSTATCOM. The filters are used to extract fundamental signal from the non-linear distorted source/load currents and all the lower-order harmonics present in the non-linear current drawn by the load. The performance of MCCF filter is compared to conventional filters such as Butterworth and MA filter. The detailed frequency response of MCCF is analysed. The magnitude and phase response plot of the MCCF suggest that this filter has unity gain and zero phase shift at fundamental frequency. All the three filters are implemented on a DSTATCOM for three-phase, three-wire distribution system. The DSTATCOM is implemented using a threephase voltage source converter controlled using dSPACE 1104 controller. The closed-loop operation of DSTATCOM designed using MCCF is tested under steady state and dynamic system conditions. Simulation and experimental results are demonstrated with relevant waveforms under different load conditions.
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