A novel proposal for harmonic compensation in the grid-connected photovoltaic system under electric anomalies

Abstract

The accurate estimation and online calibration of the fundamental weight components (FWC) from harmonically contaminated load current is crucial to evaluate the performance of grid-integrated photovoltaic (PV) units especially when exposed to grid anomalies. Driven by this motivation, an adaptive regularized least logarithmic absolute difference (RLLAD) filter is proposed for FWC estimation during nonlinear loading. The proposed filter pertinently captures the FWC of the harmonically distorted load currents. The resulting FWC guarantees balanced and sinusoidal grid currents even under disturbances in the grid voltage and load current thereby achieving different power quality (PQ) improvement targets i.e., grid current balancing and harmonic suppression, active and reactive power management, neutral current compensation, and power factor correction. The proposed RLLAD filter ensures comparable convergence performance and minimum steady-state oscillations in the grid reference currents. Proceeding further, to counter the nonlinearity introduced by the PV array, a feed-forward compensator is judiciously equipped. From a practical standpoint, it ensures superior DC-link voltage stabilization especially under abrupt transition in solar insolation level. The performance of the RLLAD filter is comprehensively assessed through numerical simulations in MATLAB/Simulink software. Furthermore, the practical viability of devised RLLAD filter is confirmed under rigorous experimental scenarios through OPAL-RT control suite. The experimental results demonstrate practicability of the proposed adaptive RLLAD filter and thus, considered to be a promising solution as compared to existing benchmarks and state-of-the-art approaches for online FWC estimation and PQ improvement. Most importantly, in terms of nonlinear load tracking capability, the proposed RLLAD filter is shown to outperform the classical LLAD filter with a response speed of less than 400 μs.