Design Control And Harmonic Compensation For Stand Alone And Grid Connected Voltage Source Converters Simulation And Experimental Validations

Voltage source converters (VSCs), among other power converters, play a crucial role in supplying power to both local loads and the grid at the PCC. During stand-alone operation, VSCs ensure stable power for loads by regulating the output voltage. In grid-connected mode, the regulation shifts to controlling output current, such as converter side current (CSC) or grid side current (GSC), to inject sinusoidal current into the electrical grid. The nonlinear characteristics of the loads connected to the power converters result in significantly distorted output voltages. This capability is crucial for applications such as uninterruptible power supply (UPS), emphasizing the importance of precise output voltage control. Similarly, in grid-connected mode, the CSC or the GSC is regulated to inject low THD current. The aim is to mitigate grid current harmonics arising from dead time and distorted grid voltages. Therefore, the harmonic mitigation of the grid current control is investigated in this work. This work presents the implementation of the proportional resonant plus multi-resonant (PR-MR) and practical proportional resonant plus multi-resonant (PMR-MR) harmonic controllers in the voltage and current control loops to mitigate the high-order harmonic currents.

"This dissertation proposes new control algorithms dedicated towards improving the reliability, computational burden and stability in grid-connected and stand-alone based power electronic converter systems applicable for ac microgrids. Two voltage sensorless control architectures, one for stand-alone applications and the other for grid-connected application are established in this thesis. The output voltage of a standalone single-phase inverter is controlled directly by controlling the output filter capacitor current without using a dedicated output voltage sensor. A method to estimate the output filter capacitance is also presented. For the grid connected converter, a novel closed loop estimation is presented to estimate the grid voltage. In addition to the estimation of the grid voltage, the proposed method also generates the unit vectors and frequency information similar to a conventional phase-locked loop structure. The voltage sensorless algorithm is then extended to LCL filter based grid connected converters thereby proposing a new indirect method of controlling the grid current. Furthermore, addressing the stability issues in current-controlled grid tied converters, this dissertation also analyzes the power angle synchronization control of grid-tied bidirectional converters for low voltage grids. The power flow equations for the low voltage grid are analyzed and compensators are designed to ensure the decoupled control of active and reactive power. It is demonstrated that the proposed compensators are immune to grid fluctuations and ensure stable operation controlling the desired power flow to and from the grid. Detailed plant modeling, controller design, simulation and experimental results are presented for all of the proposed schemes"--Abstract, page iv.

A comprehensive survey of advanced multilevel converter design, control, operation and grid-connected applications Advanced Multilevel Converters and Applications in Grid Integration presents a comprehensive review of the core principles of advanced multilevel converters, which require fewer components and provide higher power conversion efficiency and output power quality. The authors – noted experts in the field – explain in detail the operation principles and control strategies and present the mathematical expressions and design procedures of their components. The text examines the advantages and disadvantages compared to the classical multilevel and two level power converters. The authors also include examples of the industrial applications of the advanced multilevel converters and offer thoughtful explanations on their control strategies. Advanced Multilevel Converters and Applications in Grid Integration provides a clear understanding of the gap difference between research conducted and the current industrial needs. This important guide: Puts the focus on the new challenges and topics in related areas such as modulation methods, harmonic analysis, voltage balancing and balanced current injection Makes a strong link between the fundamental concepts of power converters and advances multilevel converter topologies and examines their control strategies, together with practical engineering considerations Provides a valid reference for further developments in the multilevel converters design issue Contains simulations files for further study Written for university students in electrical engineering, researchers in areas of multilevel converters, high-power converters and engineers and operators in power industry, Advanced Multilevel Converters and Applications in Grid Integration offers a comprehensive review of the core principles of advanced multilevel converters, with contributions from noted experts in the field.

Voltage source converter (VSC) is an inseparable interfacing fixture for utilizing distributed energy resource (DER) as an AC power supply. This dissertation investigates different control and synchronization techniques for stand-alone and grid-connected DC-AC VSCs. The most common control reference frame for VSCs is the dq reference frame (dq-RF), also known as the synchronous reference frame. The main challenge associated with the VSC control in this reference frame is the strong coupling between d and q axes. In this dissertation, a multi-loop dq-RF control system with a coupling compensation scheme is presented. Then, the droop-based power control technique, which eliminates the need for communication between parallel-connected VSCs and consequently offers a higher reliability, is investigated. A dq-RF-based approach of impedance design, for compensating the inequality of parallel VSCs connecting lines, along with the dq-RF droop control are also proposed. This approach results in an accurate power-sharing among parallel VSCs. The major challenges related to the synchronization unit of a grid-connected VSC control system in the presence of a distorted AC voltage are also briefly investigated in this dissertation. To deal with these challenges, an enhanced complex coefficient filter based PLL is designed and presented. This PLL completely removes the grid voltage imbalance and considerably attenuates the grid voltage dc offset and harmonics while maintaining a fast dynamic response and a simple structure. The VSC-interfaced DER is often required to switch between the islanded and grid-connected operation modes. The VSC integrated into the grid is current-controlled, while in the islanded operation mode is controlled as a voltage source. In the transition between these two modes, first the intended VSC operation mode should be detected, then its control system is reconfigured. To avoid the complexity of the control system and alleviate the drawbacks associated with the control mode transition, a VSC control approach, which mimics the traditional synchronous generator's universal mode of operation, is studied. A method of power-based active synchronization of the VSC-interfaced DER, with the ability of seamless transition between the islanded mode and connected to the grid, is proposed and integrated with this technique of the VSC control.

Harmonic Modeling of Voltage Source Converters using Basic Numerical Methods One of the first books to bridge the gap between frequency domain and time-domain methods of steady-state modeling of power electronic converters Harmonic Modeling of Voltage Source Converters using Basic Numerical Methods presents detailed coverage of steady-state modeling of power electronic devices (PEDs). This authoritative resource describes both large-signal and small-signal modeling of power converters and how some of the simple and commonly used numerical methods can be applied for harmonic analysis and modeling of power converter systems. The book covers a variety of power converters including DC-DC converters, diode bridge rectifiers (AC-DC), and voltage source converters (DC-AC). The authors provide in-depth guidance on modeling and simulating power converter systems. Detailed chapters contain relevant theory, practical examples, clear illustrations, sample Python and MATLAB codes, and validation enabling readers to build their own harmonic models for various PEDs and integrate them with existing power flow programs such as OpenDss. This book: Presents comprehensive large-signal and small-signal harmonic modeling of voltage source converters with various topologies Describes how to use accurate steady-state models of PEDs to predict how device harmonics will interact with the rest of the power system Explains the definitions of harmonics, power quality indices, and steady-state analysis of power systems Covers generalized steady-state modeling techniques, and accelerated methods for closed-loop converters Shows how the presented models can be combined with neural networks for power system parameter estimations Harmonic Modeling of Voltage Source Converters using Basic Numerical Methods is an indispensable reference and guide for researchers and graduate students involved in power quality and harmonic analysis, power engineers working in the field of harmonic power flow, developers of power simulation software, and academics and power industry professionals wanting to learn about harmonic modeling on power converters.

Grid Connected Converters: Modeling, Stability and Control discusses the foundations and core applications of this diverse field, from structure, modeling and dynamic equivalencing through power and microgrids dynamics and stability, before moving on to controller synthesis methodologies for a powerful range of applications. The work opens with physical constraints and engineering aspects of advanced control schemes. Robust and adaptive control strategies are evaluated using real-time simulation and experimental studies. Once foundations have been established, the work goes on to address new technical challenges such as virtual synchronous generators and synergic inertia emulation in response to low inertia challenges in modern power grids. The book also addresses advanced systematic control synthesis methodologies to enhance system stability and dynamic performance in the presence of uncertainties, practical constraints and cyberattacks. Addresses new approaches for modeling, stability analysis and control design of GCCs Proposes robust and flexible GCC control frameworks for supporting grid regulation Emphasizes the application of GCCs in inertia emulation, oscillation damping control, and dynamic shaping Addresses systematic control synthesis methodologies for system security and dynamic performance

This thesis addresses the integration of renewable energy resources into the grid-connected and isolated distribution systems using voltage- and current-source converters. Motivated by its promising potential and attractive features, a one-stage current-source converter (CSC) is selected as an effective interfacing device for the photovoltaic (PV) generators to the utility-grid. The operation of the grid-connected CSC-based PV system is investigated under different operating conditions, parameters variation, and control topologies. From the dc-side, it is found that the variation in the weather conditions, e.g., solar irradiance levels, might affect the dynamic performance of the vector-controlled grid-connected CSCs. Small-signal dc-side impedance models for the CSC and the PV generators are developed to investigate the system stability. Active compensation techniques are proposed so that the system performance is well maintained under different operating points. From the ac-side, a susceptible potential to instabilities is yielded under the very weak grid conditions. This potential significantly increases in the vector-controlled converters. The implementation of the phase-locked loop (PLL) is found to have a detrimental impact on the system stability as the grid impedance increases. Two solutions for the very weak grid integration have been proposed. Firstly, the power synchronization control (PSC) scheme is developed for CSCs in PV applications so that the PLL is no longer needed, and hence a seamless integration to the very weak grid is achieved. Secondly, supplementary compensation loops are proposed and added to the conventional PLL-based vector-controlled CSC so that the negative impacts of the PLL are completely alleviated. In both cases, small-signal state-space models are developed to investigate the system stability and provide a detailed design approach for the proposed controllers. A larger system level integration is considered in this thesis by interfacing multiple distributed generation (DG) units to the conventional distribution system. A generalized hybrid alternating-current (ac)/direct-current (dc) system that constitutes ac and dc subgrids is created to efficiently accommodate the dc-type renewable sources (such as PVs, batteries, fuel cells, etc.) to the ac-type conventional distribution system. Both subgrids are interconnected using voltage-source converters (VSCs) to facilitate a bidirectional power exchange via multiple inversion-rectification processes. To achieve an accurate and efficient operation, a supervisory power management algorithm is proposed. The algorithm operates successfully regardless of the control mode of the individual DG units. However, the integration of severe dynamic loads, such as direct online inductions motors (IMs) into the ac-side of the hybrid system reflects very lightly damped modes, which in turns induce instabilities, particularly in the isolated mode of operation. Therefore, active compensation techniques have been proposed to increase the system damping. Throughout this thesis, time domain simulations under Matlab/Simulink® environment for the systems under study are presented to validate the analytical results and show the effectiveness of the proposed techniques.

This book is a collection of research articles and critical review articles, describing the overall approach to energy management. The book emphasizes the technical issues that drive energy efficiency in context of power systems. This book contains case studies with and without solutions on modelling, simulation and optimization techniques. It covers some innovative topics such as medium voltage (MV) back-to-back (BTB) system, cost optimization of a ring frame unit in textile industry, rectenna for radio frequency (RF) energy harvesting, ecology and energy dimension in infrastructural designs, 2.4 kW three-phase inverter for aircraft application, study of automatic generation control (AGC) in a two area hydrothermal power system, energy-efficient and reliable depth-based routing protocol for underwater wireless sensor network, and power line communication using LabVIEW. This book is primarily targeted at researchers and senior graduate students, but is also highly useful for the industry professional and scientists.

This book covers advancements of power electronic converters and their control techniques for grid integration of large-scale renewable energy sources and electrical vehicles. Major emphasis is on transformer-less direct grid integration, bidirectional power transfer, compensation of grid power quality issues, DC system protection and grounding, interaction in mixed AC/DC systems, AC and DC system stability, design of high-frequency high power density systems with advanced soft magnetic materials, modeling and simulation of mixed AC/DC systems, switching strategies for enhanced efficiency, and protection and reliability for sustainable grid integration. This book is an invaluable resource for professionals active in the field of renewable energy and power conversion. Md. Rabiul Islam received his PhD from the University of Technology Sydney (UTS), Australia. He was appointed as a Lecturer at Rajshahi University of Engineering & Technology (RUET) in 2005 and promoted to full-term Professor in 2017. In early 2018, he joined the School of Electrical, Computer, and Telecommunications Engineering, University of Wollongong, Australia. He is a Senior Member of IEEE. His research interests include the fields of power electronic converters, renewable energy technologies, power quality, electrical machines, electric vehicles, and smart grids. He has authored or coauthored more than 200 publications including 50 IEEE Transactions/IEEE Journal papers. He has been serving as an editor for IEEE Transactions on Energy Conversion and IEEE Power Engineering Letters, and associate editor for IEEE Access. Md. Rakibuzzaman Shah is a Senior Lecturer with the School of Engineering, Information Technology and Physical Science at Federation University Australia. He has worked and consulted with distribution network operators and transmission system operators on individual projects and has done collaborative work on a large number of projects (EPSRC project on multi-terminal HVDC, Scottish and Southern Energy multi-infeed HVDC) - primarily on the dynamic impact of integrating new technologies and power electronics into large systems. He is an active member of the IEEE and CIGRE. He has more than 70 international publications and has spoken at the leading power system conferences around the world. His research interests include future power grids (i.e., renewable energy integration, wide-area control), asynchronous grid connection through VSC-HVDC, application of data mining in power system, distribution system energy management, and low carbon energy systems. Mohd. Hasan Ali is currently an Associate Professor with the Electrical and Computer Engineering Department at the University of Memphis, USA, where he leads the Electric Power and Energy Systems (EPES) Laboratory. His research interests include advanced power systems, smart-grid and microgrid systems, renewable energy systems, and cybersecurity issues in modern power grids. Dr. Ali has more than 190 publications, including 2 books, 4 book chapters, 2 patents, 60 top ranked journal papers, 96 peer-reviewed international conference papers, and 20 national conference papers. He serves as the editor of the IEEE Transactions on Sustainable Energy and IET-Generation, Transmission and Distribution (GTD) journal. Dr. Ali is a Senior Member of the IEEE Power and Energy Society (PES). He is also the Chair of the PES of the IEEE Memphis Section.

An invaluable academic reference for the area of high-power converters, covering all the latest developments in the field High-power multilevel converters are well known in industry and academia as one of the preferred choices for efficient power conversion. Over the past decade, several power converters have been developed and commercialized in the form of standard and customized products that power a wide range of industrial applications. Currently, the modular multilevel converter is a fast-growing technology and has received wide acceptance from both industry and academia. Providing adequate technical background for graduate- and undergraduate-level teaching, this book includes a comprehensive analysis of the conventional and advanced modular multilevel converters employed in motor drives, HVDC systems, and power quality improvement. Modular Multilevel Converters: Analysis, Control, and Applications provides an overview of high-power converters, reference frame theory, classical control methods, pulse width modulation schemes, advanced model predictive control methods, modeling of ac drives, advanced drive control schemes, modeling and control of HVDC systems, active and reactive power control, power quality problems, reactive power, harmonics and unbalance compensation, modeling and control of static synchronous compensators (STATCOM) and unified power quality compensators. Furthermore, this book: Explores technical challenges, modeling, and control of various modular multilevel converters in a wide range of applications such as transformer and transformerless motor drives, high voltage direct current transmission systems, and power quality improvement Reflects the latest developments in high-power converters in medium-voltage motor drive systems Offers design guidance with tables, charts graphs, and MATLAB simulations Modular Multilevel Converters: Analysis, Control, and Applications is a valuable reference book for academic researchers, practicing engineers, and other professionals in the field of high power converters. It also serves well as a textbook for graduate-level students.