Optimization of distribution static compensator for mitigation of power quality issues in grid-tied photovoltaic systems

Abstract

The global energy demand is rising above the all-time average, and fossil fuel reserves, which power a large chunk of the existing power generation plants, are being depleted. Hence, Renewable Energy Technologies (RET) have become the alternative to meet demand and provide sustainable power. Solar photovoltaic (PV) energy, an essential aspect of RET, which generates emission-free power, is one of the world's emerging resources. Rooftop PV technology installation is advanced in residential and commercial applications due to government subsidies, lower investment costs, and feed-in tariffs. The rapid penetration of PV systems into conventional distribution grids has created some power quality and power stability issues. Power quality (PQ) distortion is the most critical problem in distribution grids. The literature studied revealed that the several nonlinear loads and PV systems power electronic-based inverters that penetrate the grid and contribute to poor power quality issues, i.e., voltage rise, voltage dip, voltage unbalance, flicker, and harmonics. Also, the PV system maximum power point (MPP) controller's performance was investigated since the current-voltage (I-V) characteristic of PV panels is nonlinear and dependent on variables such as solar radiation and temperature. A comparative analysis conducted showed that the incremental conductance tracks the maximum power point better than the perturb and observe method for better power generation. MATLAB/Simulink system model simulations were run for several case studies to analyze the maximum power point tracking (MPPT) algorithm's performance under varied solar irradiation. The results obtained suggested a course to the implementation of the proposed incremental conductance MPPT algorithm. Selected power quality problems in a grid-tied PV system were analyzed via simulations and enhanced with the application of conventional proportional-integral (PI) controlled DSTATCOM. Also, field measurement-based experiments were conducted to determine system performance in a typical grid-tied PV system. The real-life 110 kW grid-tied PV system installed at the Durban University of Technology (DUT), Steve Biko campus, was used for the fieldwork. Taken into consideration was the impact of solar radiation dynamic variation on the field study. According to the results obtained, the 110 kW PV system's voltage quality data were within the limits of the local and internationally defined standards. The concept of DSTATCOM was implemented with an Enhanced Jaya (E-Jaya) optimization algorithm to mitigate specific power quality issues, such as voltage rise, voltage dip, voltage unbalance, and current harmonics. The precision with which the DSTATCOM reference compensation current is selected is vital to the device's performance. The synchronous reference frame theory of phase lock loop (PLL) for a three-phase system is described in this thesis. The objective was to keep the source current THD below 5% to comply with the recommended limits of the IEEE519 Standard harmonic limits. The implemented novel E-Jaya control optimization algorithm-based D-STATCOM provided continuous and adequate voltage regulation and harmonic compensation to mitigate power quality issues in the grid-tied PV distribution system. Simulation comparative analysis results of the developed control method with Artificial Bee Colony (ABC) and Jaya optimization algorithm indicated that the developed novel E-Jaya optimization algorithm enhanced the grid-tied PV system's performance by providing superior voltage regulation and source current THD compensation significantly declined to 1.01% from 31.93%.