INTELLIGENT TRANSFORMERLESS UPQC FOR HARMONIC REDUCTION AND VOLTAGE REGULATION IN SMART GRIDS

Abstract

As a consequence of the growing use of nonlinear loads, power electronic equipment and renewable energy resources, power quality is now a major concern in modern electrical distribution systems. Sensitive electrical equipment can be impaired by disturbances like voltage sag, voltage swell, harmonic distortion, reactive power demand and poor power factor, which negatively impact its performance and reliability. These problems can be overcome using conventional Unified Power Quality Conditioners (UPQCs); however, in general, these UPQCs come at the expense of high number of components, high power losses, complex control structures, and relatively large line-frequency transformers. To overcome these limitations, this project introduces an Enhanced Power Quality Management System Using a Transformerless Unified Power Quality Conditioner Based on Three-Leg and Standby Converters. The proposed system is a three-leg converter with an auxiliary standby converter and a common DClink capacitor. The transformerless design allows the system to be considerably smaller, lighter and cheaper with better efficiency. The three-leg converter is used for both voltage and current compensation during normal operation and voltage sag conditions, while the standby converter is only used during voltage swell conditions. A selective operation reduces switching losses and increases savings in energy. To achieve precise voltage regulation, harmonic reduction and reactive power compensation, advanced control methods such as Phase Locked Loop (PLL), Proportional-Integral (PI) controllers, and Pulse Width Modulation (PWM) are utilized. The proposed UPQC system is modelled and analyzed in MATLAB/Simulink in the presence of different power quality disturbances. The simulation results show that the voltage fluctuation mitigation, reduction of Total Harmonic Distortion (THD), improvement of power factor, stable DC-link voltage regulation and load voltage quality are all satisfied. The proposed system is suitable for the modern smart grid and industrial power distribution applications because it is simple, reliable and cost-effective.