http://dspace.dtu.ac.in:8080/jspui/handle/123456789/80 2026-04-28T04:03:24Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/22689 Title: DESIGN AND ANALYSIS OF SYNCHRONIZATION TECHNIQUES FOR CONTROL OF POWER ELECTRONIC CONVERTERS Authors: DEVI, OINAM LOTIKA; Singh, Alka (SUPERVISOR) Abstract: The increasing integration of renewable energy sources into electrical power systems has necessitated advanced synchronization techniques for power electronics converters. This thesis investigates synchronization methods, with particular emphasis on Phase-Locked Loop (PLL) technologies, to address challenges in grid-integrated systems under various disturbances. The primary objective is to develop and validate enhanced synchronization algorithms that overcome limitations of conventional PLLs in applications including photovoltaic systems, doubly fed induction generator (DFIG) wind energy converters, and electric vehicles. A comprehensive methodology combining mathematical modelling, stability analysis, extensive MATLAB Simulink simulations, and experimental validation using OPAL- RT real-time simulator was employed. Multiple PLL architectures were evaluated under abnormal grid conditions including voltage sags/swells, frequency jumps, DC offsets, and harmonic distortions. The research examined single-phase and three-phase PLLs, including Synchronous Reference Frame (SRF), Second-Order Generalized Integrator (SOGI), Least Mean Square (LMS), Least Mean Fourth (LMF), Modified Synchronous Reference Frame (MSRF), and fractional-order PLLs. Key findings demonstrate that the LMF PLL outperforms SRF PLL under phase shift and frequency change disturbances, while Type III Enhanced PLL exhibits superior frequency response with polluted grid voltage and DC offset. The proposed fractional- order FO-LPFO-PI MSRF-PLL with optimized parameters shows enhanced stability during grid abnormalities. Additionally, the novel H-LMS-SOGI PLL architecture provides exceptional dynamic responses, surpassing conventional structures under all adverse grid conditions tested. Experimental validation of DFIG systems with LMF- PLL confirms satisfactory performance under variable wind speeds and grid disturbances. This research significantly contributes to grid stability and renewable energy integration by providing validated solutions for maintaining reliable power system operation with high penetration of distributed energy resources. The dual validation approach ensures practical applicability, offering a comprehensive framework for xxi designing robust power electronics-based systems capable of handling complex grid disturbances in modern power networks. 2026-02-01T00:00:00Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/22688 Title: DESIGN AND DEVELOPMENT OF SECURITY FRAMEWORK FOR SMART GRID INFRASTRUCTURE Authors: KUMAR, CHANDAN; Chittora, rakash (SUPERVISOR) Abstract: The smart grid is considered the future of electricity networks because it brings in intelligence, flexibility, and reliability to the power system. Unlike traditional power grids, smart grids use advanced information and communication technologies to enable two-way communication between utility companies and consumers. This makes it possible to integrate renewable energy sources, improve energy efficiency, and ensure better management of resources. However, as the smart grid becomes more connected and dependent on digital systems, it faces serious challenges related to cybersecurity. The openness and interconnectedness that make it efficient also make it vulnerable to different types of cyberattacks, data breaches, and unautho- rized access. If these issues are not addressed properly, they can affect the privacy of consumers, disrupt services, or even cause large-scale blackouts. This thesis presents an advanced, multi-layered framework for secure smart grid in- frastructure, integrating the strengths of deep learning, blockchain technology, and immersive collaborative platforms. Addressing the critical gaps in cybersecurity, privacy, and operational scalability, the research rethinks smart grid protection by unifying decentralized trust, intelligent anomaly detection, and efficient large-scale data management. The first major contribution is a robust secure data sharing architecture combin- ing a hybrid deep learning intrusion detection system using Variational Autoen- iv v coder (VAE) and Attention-based Bidirectional LSTM (ABiLSTM) with blockchain- backed audit trails and off-chain Inter Planetary File System (IPFS) storage. Ex- perimental validation on benchmark ToN-IoT and BoT-IoT datasets demonstrates significant performance improvements. The proposed system achieves near-perfect detection in percentage, accuracy (99.99), precision (98.99), recall (99.9), and F1 score (99.91), outperforming classical approaches (Naive Bayes, Decision Tree, Ran- dom Forest) by wide margins. Importantly, the hybrid on/off-chain design substan- tially reduces blockchain overhead, enabling real-time scalability lacking in earlier ledger-centric models. The research extends to IoT-enabled Electric Vehicles (EVs), devising a secure and privacy-preserving framework that leverages Stacked Sparse Denoising Autoencoders (SSDAE) and Attention-based LSTM for anomaly detection and data anonymiza- tion. Coupled with smart contract-driven authentication, this approach achieves highly effective multi-class threat detection and privacy protection, with detection and recall rates surpassing leading prior Long Short Term Memory (LSTM) and Artificial Neural Network (ANN) models while ensuring low-latency communication essential for mobile EV-grid integration. A novel facet of this thesis is the application of metaverse and digital twin technolo- gies, which enable unprecedented real-time, immersive collaboration and situational awareness for grid operators. Through federated and collaborative intrusion detec- tion, multi-operator security, and grid incident response now occur with reduced detection latency and enhanced visibility, an improvement over the isolated or man- ual supervision that dominated earlier solutions. In summary, this thesis offers (1) higher detection accuracy and reliability through advanced deep learning architectures; (2) integrated, scalable security and privacy vi solutions across grid and IoT-vehicle domains; (3) immersive, collaborative security and operational platforms; and (4) efficient, tamper-evident storage and auditing suitable for next-generation smart grid requirements. Collectively, these contribu- tions pave the way for intelligent, secure, and sustainable energy systems addressing technical, economic, and social imperatives in real-world smart grid deployments. 2025-06-01T00:00:00Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/22541 Title: VIRTUAL SYNCHRONOUS MACHINE CONTROL STRATEGIES IN LOW INERTIA MICRO-GRID Authors: YEGON, PHILEMON Abstract: In the recent past, energy sector has undergone significant transformations. On one hand, world demand is rising, while tradition power sources, mostly reliant on fossil fuels, are fast phased out by de-commissioning of old power plants. Furthermore, these conventional methods lack ecological sustainability. The combustion of coal releases greenhouse gases (GHGs), which pollute the environment and endanger the surrounding ecosystem. Furthermore, they emit carbon dioxide, methane gas and nitrogen dioxide which are the highest contributors of global warming. The hazardous effect of global warming includes melting of mountain ice caps, extreme weather pattern alterations, flooding, storms, and droughts. This scenario has compelled policymakers from various countries to reconsider how to address the always increasing energy demand while mitigating the adverse effects of traditional energy sources. To tackle these difficulties, renewable energy sources (RES) have assumed a more significant role. However, high penetration of RES reduces inertia in the system due to their integration with power electronics devices which lack rotational mass for kinetic energy. Reduced inertia contributes heavily on frequency instability. The modern power system easily loss synchronism over the slightest disturbance because of low inertia. Microgrid concept is taking shape as the alternative sources of energy. It can be either grid connected or islanding mode. Grid forming voltage converters enable islanding mode as they are designed to participate in regulation of voltage and frequency at the point of common coupling (PLL). Its contained energy storage system in the cluster of energy sources. The grid-connected is commonly grid following voltage converters, it only delivers power and does not participate in voltage or frequency control. Microgrid provide power to specific group of consumers. It can be hospital, school or residential areas. Microgrids comprises of diverse sources energy, such as energy storage systems, fuel cells, solar PV panels, and wind turbines. Notwithstanding the intermittent nature of RES, the microgrid frequency control vi take into account the changes from both the source and load sides, the control of microgrid frequency becomes more important for maintaining reliable operation and energy security. To simulate the isolated microgrid, a complex technique is used to address the requirements of the secondary controller and the primary frequency regulation of the diesel engine generating unit. In addition, the isolated microgrid is connected to a diesel power plant, wind turbine, solar plant and battery/ultracapacitor to conduct experiments on load fluctuations, wind speed variations and solar radiation variations and their total shutdown. In best practices, integrated microgrid with the diesel power plant allows possibility of distributing the economic load demand between the microgrid and the diesel power units. The thermal unit only provides power during periods of high demand. The baseload needs are met by other units within the integrated microgrid. The investigations are conducted in different scenarios to determine the viability of energy storage devices in isolated and integrated microgrids. The primary difficulties in microgrid voltage and frequency regulation for converter regulation. Microgrid distributed generation incorporates the use of the Virtual Synchronous machine (VSM), droop controller, optimisation technology, and RES to increase the transient and small signal responsiveness in the microgrid (MG). The purpose of the power converter is to deliver voltage and current in a way that is appropriate for consumer loads in order to process and regulate the supply of power. In order to enhance the frequency responsiveness of the microgrid during disturbances such as significant frequency deviations. Typically, the PI controller or PID controller utilizes as a secondary controller in the frequency control of the microgrid. Further research was conducted on the control architecture of combining standard secondary controllers in a cascading manner to create innovative combinations of cascaded controllers. The effectiveness of this cascaded controller is evaluated by implementing improved swam optimization algorithm, genetic algorithm and model predictive control (MPC). The novel modified PSO techniques was formulated and implemented in the system to fine tune PID controller. The purpose of modified PSO technique is to maximise the control parameters in order to regulate the disturbances occurred in the microgrid such as frequency, RoCoF as well as voltage due to inertia variation. The results were compared with conventional techniques. Hybrid energy storage system that’s battery and ultracapacitor were vii incorporated in the microgrid to supplied the needed energy during the disturbances and also during the normal working of the microgrid. Battery is known for its high energy density but low power density (slow response) while ultracapacitor has high power density and low energy density (quick response). The two energy storage devices complement each other while responding to the disturbances. The control seeks to simulate inertia and damping using ultracapacitor which replicate prime mover of synchronous generators (kinetic energy). In this thesis, energy needed for inertia and damping is determined to compensate for energy loss. MATLAB Simulink environment was used to test effectiveness of the proposed techniques consequently, the comparison was conducted with the conventional methods and the results clearly demonstrated the efficacy of the proposed strategies microgrid frequency response. Finaly, real time validation was conducted on OP4510 OPAL-RT emulator. 2024-10-01T00:00:00Z http://dspace.dtu.ac.in:8080/jspui/handle/repository/22539 Title: GRID SYNCHRONIZATION AND OPERATION OF PARALLEL INVERTERS Authors: NARULA, ADITYA Abstract: With rapid industrialization in developing nations, the power demand from the end consumer has exponentially grown. To support the conventional power generation sources (based on fossil fuels) in meeting the rising power demand, power generation based on Distributed Energy Resources (DER’s) enacting as small power sources are gaining popularity. The microgrid architecture with local energy generating sources like photovoltaic, wind, battery systems have opened the pathway for small scale smart distribution grids interfacing the sustainable and clean energy sources with the grid through a voltage / current controlled voltage source inverter. Interfacing a voltage sourced inverter with the grid additionally allows the inverter to support the power quality of grid during grid sag and swell condition. Further based on the power demand at the consumer end the number of interfacing inverters can be added or reduced allowing a scale up or scale down approach in the connected network. The response and dynamics of the microgrid are governed by three major factors – 1) The dynamics of the renewable energy source at the DC side, 2) the synchronization dynamics of the interfaced inverter, 3) Control technique of the interfacing inverter and 4) Effect of high penetration of the low inertial inverters with high switching frequency. The interfacing voltage source inverter is vulnerable to disturbance from both grid side and the renewable energy source or input side, with common intermittencies like partial shading of the photovoltaic panel, different wind speeds, low battery voltages etc. The disturbances at the grid side can be controlled through the control technique of the interfacing inverter or a synchronization algorithm with fast tracking capability. On the DC side the conventional practice is to use a non-isolated boost or buck converter based upon the series parallel combination of the installed solar panels. Conventional converters like buck converter or boost converter struggle with the operating duty requirement at time of partial shading, with the operating duty reaching the nonlinear region, thereby compromising on the operating efficiency. Also, addition of the natural output impedance network through the interfacing vii converter will help in mitigating the spike and transients in the DC link and the control signals during intermittencies at either grid side or input side. This would result in smooth running of the inverter. A VSI interfaced with the renewable energy source typically has low inertia due to lack of moving parts unlike a synchronous generator. As a result, the system remains sensitive towards grid frequency variations. With multiple injection of VSI in the system, the inertia of the system would not increase making the system vulnerable unless and until a fast control on frequency change is not incorporated or virtual inertia is embedded, even though such arrangement provides better reliability. With paralleled VSI having different situations on the connected nodes the response to the change of voltage or frequency often lead to issues of circulating current and large variations during transients due to lack of inertia or damping system. For parallel combination of inverters aligned with the stringent grid codes, synchronization algorithm plays a crucial role. Noncompliance of the code would result in outage of the inverter. The stability of synchronization algorithm dictates the capability dictates the capability of the parallel operation of the inverter especially during off grid mode of operation in master slave configuration. The synchronization algorithms like zero crossing detection (ZCD), voltage unit template-based algorithms and SRF – PLL provide the requisite tracking but suffer immensely during grid disturbances. SOGI adaptive filter based PLL with filtering capability has a superior tracking and filtering capability when compared to conventional PLL. Moreover, the capability of the SOGI filter to generate orthogonal signals eliminates the requirement of Clarke’s transformation reducing the complexity and computation of the algorithm. The work proposes impedance based continuous input current converters for photovoltaic and battery charging applications. The same have been modelled; simulated and experimentally validated under various test conditions. The impedance network allows auxiliary boost supporting the system under severe conditions like partial shading, irradiance change and battery deep discharge. Additionally, the impedance network installed at the input side of the inverter limits the flow of circulating current within the system. viii Synchronization algorithm based on Second Order Generalized Integrator (SOGI) resonating at 100Hz is proposed and experimentally validated for severe grid disturbances. The synchronization algorithm enhances the fault bearing capability of the inverter allowing it to remain synchronized with the grid with minimum transients. A resynchronization algorithm embedded in the Second Order Generalized Integrator Phase Locked Loop (SOGI – PLL) is proposed in the work working with adaptive droop filter. The resynchronization algorithm seamlessly transfers the inverter from grid forming mode to grid connected mode and vice versa while limiting the circulating current among the inverters. The resynchronization algorithm limits the transitional spikes besides administering fast dynamics with prominent signal filtering. The development of algorithm and hardware including development of various control and interface cards have been indigenously done. The simulation and hardware results are presented which show good agreement with the theoretical modeling and analysis. 2025-12-01T00:00:00Z