DESIGN AND CONTROL OF CUSTOM POWER DEVICES FOR MITIGATION OF POWER QUALITY PROBLEMS

Abstract

The combination of various power electronic loads and linear loads in the modern distributed grid offers a dynamic and complex electrical environment. These loads may have a major impact on power quality, resulting in problems like low power factor and harmonic production that compromise the grid's stability and effectiveness. This thesis work includes both current and voltage related PQ issues such as voltage sag, voltage swell, voltage harmonics, load unbalancing, reactive power compensation and poor power factor. In this work, design and control of single and three-phase grid connected PV system has been presented. It permits power quality enhancement, load balancing, and active and reactive distribution compensation in single-phase and three-phase grid connected system. A single-phase, single-stage topology of a grid-integrated PV system is utilized to feed nonlinear loads at the point of common coupling (PCC). A simple Perturb and observe (P&O) MPPT technique is used to extract the maximum available power from PV in single stage single phase and three-phase grid connected PV system. The Parameters of grid connected PV system are estimated and hence the prototype of single-phase and three-phase grid connected PV system are designed for Shunt Active Power Filter (SAPF), Series Active Power Filter and Unified Power Quality Compensator (UPQC). The shunt and series active power filter are also named as DSTATCOM and DVR respectively in the thesis work. Ideally, a control algorithm requires a synchronizing technique, fundamental component, a DC link voltage controller and the feed-forward term. The generation of reference source current for providing switching signals to voltage source converter (VSC) requires synchronizing signals or sine template. Most of the proposed control scheme for DSTATCOM and DVR are using unit template based synchronizing signals. But the unit template method will not generate balanced and sinusoidal synchronizing signals under weak grid conditions. For that weak grid condition, a conventional Synchronous Reference Frame Theory (SRFT), Second order generalized integrator and modified PLL is utilized in the single and three-phase grid connected system. The fundamental component extraction techniques are used to estimate the fundamental component of load current and source voltage. SRFT, Instantaneous Reactive Power Theory (IRPT), Hermite Polynomial, and Bernoulli Polynomial based load compensation control schemes are used in single-phase grid connected PV system. The fundamental load component is extracted from distorted load current using a single layer neural network. The objective of the designed controller is to fulfill the load’s active power demand from the generated solar PV power and feed the excess power back to the grid when surplus. When solar PV is not integrated with the grid, the voltage source converter (VSC) acts as a distribution static compensator (DSTATCOM), improving the system's utilization factor. In order to mitigate power quality issues in electrical systems, specialised power device design and control are essential. The development and implementation of novel solutions to problems including voltage sags, swells, harmonics, transients, and other power quality issues is the main goal of this research. The research highlights the incorporation of customised power components designed for particular uses, providing improved efficiency and dependability. The results are validated as per IEEE-519 standards. Developing advanced power electronics solutions, such as shunt active power filter, series active power filter, and unified power quality compensator, is included in the design part. These devices are designed to deliver a modified response to the system's particular features under consideration, enabling focused mitigation of power quality issues. A significant aspect of this research is control techniques, which highlight the innovative and flexible management of customized power devices. The study investigates advanced control methods, including as adaptive ε NSRLMMN, and q-LMF to maximise device performance in various kinds of operating conditions. The objective is to assure efficient power quality improvement by real-time monitoring, efficient responses, and effective compensation. In conclusion, this research advances custom power devices as useful equipment for reducing issues with power quality. The integration of detailed design techniques with smart control methods presents an auspicious path towards enhancing the dependability and efficiency of electrical systems, consequently strengthening the reliable and sustainable functioning of modern power grids.