Adaptive EPLL for improving power quality in three‐phase three‐wire grid‐connected photovoltaic system

Abstract

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 Single-Phase Globally Stable Frequency-Locked Loop Based on the Second-Order Harmonic Oscillator Model

“…The proposed SOHObased FLL is enhanced with an adaptive law (13) to reconstructω 0 , which is referred to as the fundamental frequency estimator (FFE). Notice that the estimation of theω 0 in (13) involves the use of the product between the orthogonal signals as a mechanism to detect the phase in the FFE. The estimateω 0 is then used in the SOHO-QSG.…”

“…Moreover, despite the synchronization in three-phase systems, possibly motivated by traditional power systems (see some applications in REG systems [12,13]), singlephase PLLs are becoming of central interest for investigation and development due to the current massive deployment of grid-tie inverters at residential levels, due to domestic photovoltaic (PV) installations [14]. Additionally, PLL has been extensively used for the control purposes and for stability improvement [15,16].…”

Phase-Locked Strategy of Photovoltaic Connected to Distribution Network With High Proportion Electric Arc Furnace

“…Although these PLL control strategies are feasible to some extent, there are still large errors in PLL due to the disadvantages of poor dynamic performance and a small amount of harmonics in the positive sequence voltage component. In [25], a control strategy of SOGI-PLL based on self-regulation technology is proposed. Although this technology can filter out a large number of harmonics in the system, there are still some higher harmonics, which will reduce the accuracy of the PLL.…”

Robust MMSOGI‐FLL control algorithm for power quality improvement of solar PV‐SyRG pico hydro‐BES based islanded microgrid with dynamic load

“…Therefore, various control algorithms are available in the literature, like enhanced phase locked loop (EPLL), improved least mean square (ILMS), and besides second‐order generalised integrator (SOGI) for extracting the required reference currents. Chittora et al [25] have used the conventional EPLL controls, which have a disadvantage, that their operation is reliant on the coefficient of loop gains and non‐existence of adaptive performance at variable frequency. Bhotto and Antoniou [26] have reported adaptive algorithms such as ILMS, which is widely used in the microgrid due to their easy implementation, but they have poor convergence rate and do not have the capability to remove DC offset.…”