As we are moving towards a future carbon-neutralsociety, development of residential microgrids attracts much attentionaround the world with its efficient utilization of renewableenergy. A residential microgrid is a small power system fora house, which consists of a solar photovoltaic (PV) source,a battery storage, residential loads, and an interface to thegrid. In this paper, a hybrid AC-DC microgrid is proposed,studied and simulated in Matlab/Simulink. A coordinated controlstrategy is developed so that the PV converter is controlledto maximize its power generation, the battery converter iscontrolled to stabilize the system with the battery state of chargeconstraints, and an interlinking converter is controlled to decidethe connection/disconnection and the power flow with the grid.The simulation results show the effectiveness of the proposedsolution under various operating conditions. / I det här pappret föreslås, studeras ochsimuleras ett hybrid-anpassat lokalt självförsörjande elnät iSimulink och Matlab. Solpaneler utgör den distribueradeförnyelsebara energikällan i nätet. Panelerna styrs med enMPPT-algoritm för att maximera kraftgenereringen. Batterietsladdningstillstånd används i det designade batterilagringssystemetför att garantera lång livstid och för att fatta beslut omladdning och urladdning. Kraftöverföring mellan ACoch DCnätverk sker via en dubbelriktad omvandlare. Det konstrueradehybridnätet fungerar självständigt samt vid sammankopplingtill huvudnätet. Ett koordinerat kontrollsystem implementerasför att möjliggöra kommunikationen mellan lokalnätets olikadelar. Resultaten från simuleringstestet visar att det föreslagnanätet uppfyller stabilitetskrav och god funktion under varierandedriftstillstånd. / Kandidatexjobb i elektroteknik 2021, KTH, Stockholm

<p>In this research, a Split-Shaft Wind Energy Conversion System (SS-WECS) is investigated</p> <p>to improve the performance and cost of the system and reduce the wind power</p> <p>uncertainty influences on the power grid. This system utilizes a lightweight Hydraulic Transmission</p> <p>System (HTS) instead of the traditional gearbox and uses a Doubly-Fed Induction</p> <p>Generator (DFIG) instead of a synchronous generator. This type of wind turbine provides</p> <p>several benefits, including decoupling the shaft speed controls at the turbine and the generator.</p> <p>Hence, maintaining the generator’s frequency and seeking maximum power point</p> <p>can be accomplished independently. The frequency control relies on the mechanical torque</p> <p>adjustment on the hydraulic motor that is coupled with the generator. This research provides</p> <p>modeling of an SS-WECS to show its dependence on mechanical torque and a control</p> <p>technique to realize the mechanical torque adjustments utilizing a Doubly-Fed Induction</p> <p>Generator (DFIG). To this end, a vector control technique is employed, and the generator</p> <p>electrical torque is controlled to adjust the frequency while the wind turbine dynamics</p> <p>influence the system operation. The results demonstrate that the generator’s frequency is</p> <p>maintained under any wind speed experienced at the turbine.</p> <p>Next, to reduce the size of power converters required for controlling DFIG, this research</p> <p>introduces a control technique that allows achieving MPPT in a narrow window of generator</p> <p>speed in an SS-WECS. Consequently, the size of the power converters is reduced</p> <p>significantly. The proposed configuration is investigated by analytical calculations and simulations</p> <p>to demonstrate the reduced size of the converter and dynamic performance of the</p> <p>power generation. Furthermore, a new configuration is proposed to eliminate the Grid-</p> <p>Side Converter (GSC). This configuration employs only a reduced-size Rotor-Side Converter</p> <p>(RSC) in tandem with a supercapacitor. This is accomplished by employing the hydraulic</p> <p>transmission system (HTS) as a continuously variable and shaft decoupling transmission</p> <p>unit. In this configuration, the speed of the DFIG is controlled by the RSC to regulate the</p> <p>supercapacitor voltage without GSC. The proposed system is investigated and simulated in</p> <p>MATLAB Simulink at various wind speeds to validate the results.</p> <p>Next, to reduce the wind power uncertainty, this research introduces an SS-WECS where the system’s inertia is adjusted to store the energy. Accordingly, a flywheel is mechanically</p> <p>coupled with the rotor of the DFIG. Employing the HTS in such a configuration allows the</p> <p>turbine controller to track the point of maximum power (MPPT) while the generator controller</p> <p>can adjust the generator speed. As a result, the flywheel, which is directly connected</p> <p>to the shaft of the generator, can be charged and discharged by controlling the generator</p> <p>speed. In this process, the flywheel energy can be used to modify the electric power generation</p> <p>of the generator on-demand. This improves the quality of injected power to the</p> <p>grid. Furthermore, the structure of the flywheel energy storage is simplified by removing</p> <p>its dedicated motor/generator and the power electronics driver. Two separate supervisory</p> <p>controllers are developed using fuzzy logic regulators to generate a real-time output power</p> <p>reference. Furthermore, small-signal models are developed to analyze and improve the MPPT</p> <p>controller. Extensive simulation results demonstrate the feasibility of such a system and its</p> <p>improved quality of power generation.</p> <p>Next, an integrated Hybrid Energy Storage System (HESS) is developed to support the</p> <p>new DFIG excitation system in the SS-WECS. The goal is to improve the power quality</p> <p>while significantly reducing the generator excitation power rating and component counts.</p> <p>Therefore, the rotor excitation circuit is modified to add the storage to its DC link directly.</p> <p>In this configuration, the output power fluctuation is attenuated solely by utilizing the RSC,</p> <p>making it self-sufficient from the grid connection. The storage characteristics are identified</p> <p>based on several system design parameters, including the system inertia, inverter capacity,</p> <p>and energy storage capacity. The obtained power generation characteristics suggest an energy</p> <p>storage system as a mix of fast-acting types and a high energy capacity with moderate</p> <p>acting time. Then, a feedback controller is designed to maintain the charge in the storage</p> <p>within the required limits. Additionally, an adaptive model-predictive controller is developed</p> <p>to reduce power generation fluctuations. The proposed system is investigated and simulated</p> <p>in MATLAB Simulink at various wind speeds to validate the results and demonstrate the</p> <p>system’s dynamic performance. It is shown that the system’s inertia is critical to damping</p> <p>the high-frequency oscillations of the wind power fluctuations. Then, an optimization approach</p> <p>using the Response Surface Method (RSM) is conducted to minimize the annualized</p> <p>cost of the Hybrid Energy Storage System (HESS); consisting of a flywheel, supercapacitor, and battery. The goal is to smooth out the output power fluctuations by the optimal</p> <p>size of the HESS. Thus, a 1.5 MW hydraulic wind turbine is simulated, and the HESS is</p> <p>configured and optimized. The direct connection of the flywheel allows reaching a suitable</p> <p>level of smoothness at a reasonable cost. The proposed configuration is compared with the</p> <p>conventional storage, and the results demonstrate that the proposed integrated HESS can</p> <p>decrease the annualized storage cost by 71 %.</p> <p>Finally, this research investigates the effects of the reduced-size RSC on the Low Voltage</p> <p>Ride Through (LVRT) capabilities required from all wind turbines. One of the significant</p> <p>achievements of an SS-WECS is the reduced size excitation circuit. The grid side converter is</p> <p>eliminated, and the size of the rotor side converter (RSC) can be safely reduced to a fraction</p> <p>of a full-size excitation. Therefore, this low-power-rated converter operates at low voltage</p> <p>and handles the regular operation well. However, the fault conditions may expose conditions</p> <p>on the converter and push it to its limits. Therefore, four different protection circuits are</p> <p>employed, and their effects are investigated and compared to evaluate their performance.</p> <p>These four protection circuits include the active crowbar, active crowbar along a resistorinductor</p> <p>circuit (C-RL), series dynamic resistor (SDR), and new-bridge fault current limiter</p> <p>(NBFCL). The wind turbine controllers are also adapted to reduce the impact of the fault</p> <p>on the power electronic converters. One of the effective methods is to store the excess energy</p> <p>in the generator’s rotor. Finally, the proposed LVRT strategies are simulated in MATLAB</p> <p>Simulink to validate the results and demonstrate their effectiveness and functionality.</p>

Research in sustainable energy sources has become the interest of many studies due to the increasing energy demand and the amount of wasted energy released from existing methods, along with their effect on climate change and environment sustainability. Thermo-Electric Generators (TEGs) are a potential solution that is being studied and implemented as they can convert low grade thermal energy to useful electrical energy at various operating conditions. The integration of a TEG within a heat exchanger (TEG/HX) system connected to an electrical DC micro-grid, using a Maximum Power Point Tracking (MPPT) system is the focus of this study. Using a numerical TEG/HX model from a previous study and a developed DC micro-grid model the interaction between the thermal and electrical aspects were investigated with the focus on the electrical performance of the system. The main concern of this study is to investigate the effect of the sub components of the DC micro-grid on the overall available energy. An analytic model was developed to estimate the power loss in the electrical circuit of the micro-grid, the model utilizes the equations for switching and conduction losses which have been used by several studies. Other variables such as the battery characteristics and electrical load profiles were also investigated by simulating several case studies including changing operating conditions. This study shows the effect of a TEG configuration on the power loss in an electrical system using power loss curves in comparison with the Open Circuit Voltage (OCV) of such configuration. It also covers important modes of operation for the battery, loads and MPPT for a stable and reliable operation of an isolated DC micro-grid system were TEGs are the only source of power. The result of the study presented is a system design that is able to maximize the electrical energy harvested from the TEGs to extend the operation of the dc-micro-grid first by applying a suitable TEG configuration and consequently a suitable electrical circuit. Secondly, by adapting to the changing operating conditions of the TEGs and the loads; and compensating for these changes using the battery storage system. / Thesis / Master of Applied Science (MASc)

Sufficient power supply to run GPS machinery and transmit data on a long-term basis remains to be the key challenge for wildlife tracking technology. Traditional ways of replacing battery periodically is not only time and money consuming but also dangerous to live-trapping wild animals. In this paper, an innovative wildlife tracking collar with multi-source energy harvester with advantage of high efficiency and reliability is proposed. This multi-source energy harvester entails a solar energy harvester and an innovative rotational electromagnetic energy harvester is mounted on the "wildlife tracking collar" which will extend the duration of wild life tracking by 20% time as was estimated. A feedforward and feedback control of DC-DC converter circuit is adopted to passively realize the Maximum Power Point Tracking (MPPT) logic for the solar energy harvester. A novel electromagnetic pendulum energy harvester with motion regulator is proposed which can mechanically rectify the irregular bidirectional swing motion of the pendulum into unidirectional rotational motion of the motor. No electrical rectifier is needed and voltage drops from diodes can be avoided, the EM pendulum energy harvester can provide 200~300 mW under the 0.4g base excitation of 4.5 Hz. The nonlinearity of the disengage mechanism in the pendulum energy harvester will lead to a broad bandwidth frequency response. Simulation results shows the broadband advantage of the proposed energy harvester and experiment results verified that at some frequencies over the natural frequency the efficiency is increased. / Master of Science

Renewable power systems are becoming more affordable and provide better options than fossil-fuel generation, for not only the environment, but a benefit of a reduced cost of operation. Methods to optimize charging batteries from renewable technologies is an important subject for off-grid and micro-grids, and is becoming more relevant for larger installations. Overcharging or undercharging the battery can result in failure and reduction of battery life. The Arduino hybrid MPPT controller takes the advantage of solar and wind energy sources by controlling two systems simultaneously. The ability to manage two systems with one controller is better for an overall production of energy, cost, and manageability, at a minor expense of efficiency. The hybrid MPPT uses two synchronous buck DC-DC converters to control both wind and solar. The hybrid MPPT performed at a maximum of 93.6% efficiency, while the individual controller operated at a maximum 97.1% efficiency when working on the bench test. When designing the controller to manage power production from a larger generator, the inductor size was too large due to the frequency provided by the Arduino. A larger inductor means less allowable current to flow before the inductor becomes over saturated, reducing the efficiency of the controller. Utilizing a different microcontroller like the PIC16C63A produces a much faster frequency, which will reduce the inductor size needed and allow more current before over saturation.

This thesis dealing with description and of autonomous solar systems and algorithms for control of decision-making mechanism. Optimal set of these machanism has effeect in raise of efficiency in hole autonomous system. In practical purposes propose create one by using microprocesor ATMEGA8, which measure all electrical data in system and control all decisions of implemented algorithm.

This thesis deals with energy self-sufficiency focusing on the independence of the electric grid. Basic line emanating project form a concrete proposal for autonomous energy supply system. Emphasis is placed primarily on photovoltaic systems, electric energy accumulation and selection of individual components of such a system. Another important part of the thesis is also an economic evaluation of design variations. The thesis also deals with a market research, and thereof derived benefit assessment of each technology. The accompanying chapters are then devoted to the history of autonomous life style or classification of buildings according to their energy performance.

Growing concerns about climate change have led to the world experiencing an unprecedented push towards renewable energy. Economic drivers and government policies mean that small, distributed forms of generation, like solar photovoltaics, will play a large role in our transition to a clean energy future. In this thesis, a novel DC-DC converter known as the Coupled Inductors Combined Cuk-SEPIC' (CI-CCS) converter is explored, which is particularly attractive for these photovoltaic applications. A topological modification is investigated which provides several benefits, including increased power density, efficiency, and operational advantages for solar energy conversion. The converter, which is based on the combination of the Cuk and SEPIC converters, provides a bipolar output (i.e. both positive and negative voltages). This converter also offers both step-up and step-down capabilities with a continuous input current, and uses only a single, ground-referenced switching device. A significant enhancement to this converter is proposed: magnetic coupling of the converter's three inductors. This can substantially reduce the CI-CCS converter's input current ripple - an important benefit for maximum power point tracking (MPPT) in photovoltaic applications. The effect of this coupling is examined theoretically, and optimisations are performed - both analytically and in simulations - to inform the design of a 4 kW prototype CI-CCS converter, switched at a high frequency (100 kHz) with a silicon carbide (SiC) MOSFET. Simulation and experimental results are then presented to demonstrate the CI-CCS converter's operation and highlight the benefits of coupling its inductors. An efficiency analysis is also undertaken and its sources of losses are quantified. The converter is subsequently integrated into a domestic photovoltaic system to provide a practical demonstration of its suitability for such applications. MPPT is integrated into the CI-CCS DC-DC converter, and a combined half bridge/T-type converter is developed and paired with the CI-CCS converter to form an entirely transformerless single-phase solar energy conversion system. The combination of the CI-CCS converter's bipolar DC output with the combined half bridge/T-type converter's bipolar DC input allows grounding at both the photovoltaic panels and the AC grid's neutral point. This eliminates high frequency common mode voltages from the PV array, which in turn prevents leakage currents. The entire system can be operated in grid-connected mode - where the objective is to maximise power extracted from the photovoltaic system, and is demonstrated in stand-alone mode - where the objective is to match solar generation with the load's power demands.

This thesis discusses the modeling of a micro-grid with photovoltaic (PV)-wind-fuel cell (FC) hybrid energy system and its operations. The system consists of the PV power, wind power, FC power, static var compensator (SVC) and an intelligent power controller. Wind and PV are primary power sources of the system, and an FC-electrolyzer combination is used as a backup and a long-term storage system. A simulation model for the micro-grid control of hybrid energy system has been developed using MATLAB/Simulink. A SVC was used to supply reactive power and regulate the voltage of the hybrid system. To achieve a fast and stable response for the real power control, the intelligent controller consists of a Radial Basis Function Network-Sliding Mode Control (RBFNSM) and a General Regression Neural Network (GRNN) for maximum power point tracking (MPPT). The pitch angle of wind turbine is controlled by RBFNSM, and the PV system uses GRNN, where the output signal is used to control the DC/DC boost converters to achieve the MPPT.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The increased demand for energy, the possibility of reducing the supply of conventional fuels and growing concerns about the preservation of the environment have led to several researches and development of alternative energy sources which are clean, renewable and with minor environmental impact. Among the various alternative energy sources, PV solar has been considered an excellent option as it is free, abundant, clean and distributed through all places. Solar energy incident on Earth\'s surface is estimated at about ten thousand times the total energy consumed in the world. Even with all the advantages offered by the generation of energy through the use of photovoltaic panels, the initial cost of deployment is high and the efficiency of energy conversion is currently still low. Thus, it is essential to use techniques to extract the maximum power from these panels to increase the system operation efficiency. This work aims to present studies of a complete photovoltaic solar system, connected to low voltage power grid including the solar panel, a step-up voltage converter, its corresponding Maximum Power Point Tracking (MPPT) control, the voltage inverter with its control, the phase locked loop, and by means of an inductive coupling, the connection of the whole system to the grid. For modeling and simulations of the solar photovoltaic system, it was used the Alternative Transients Program - ATP. Initially it is presented simulation results with parts that comprises the PV array, and only at the end, it is performed a case study with the complete PV system developed in this work. / O aumento da demanda de energia, a possibilidade de redução do suprimento de combustíveis convencionais e a crescente preocupação com a preservação do meio ambiente têm levado a várias pesquisas e desenvolvimento de fontes alternativas de energia que sejam limpas, renováveis e com menor impacto ambiental. Dentre as diversas fontes alternativas de energia, a solar fotovoltaica tem sido considerada uma excelente opção já que é livre, abundante, limpa e distribuída. A energia solar incidente na superfície da Terra é estimada em cerca de dez mil vezes a energia total consumida no mundo. Mesmo com todas as vantagens apresentadas pela geração de energia por meio do uso de painéis fotovoltaicos, a eficiência da conversão de energia é atualmente ainda baixa e com custo inicial de implantação elevado. Assim, é imprescindível o uso de técnicas para extração da máxima potência destes painéis para aumentar a eficiência de operação do sistema. Este trabalho visa apresentar estudos de um sistema fotovoltaico completo conectado à rede elétrica de baixa tensão, compreendendo o painel solar, um conversor elevador de tensão, seu correspondente controle de rastreamento de máxima potência, o inversor de tensão com seu controle, a malha de captura de fase e, por meio de um indutor de acoplamento, a conexão de todo este sistema à rede elétrica. Para a modelagem e simulações do sistema solar fotovoltaico foi utilizado o Alternative Transients Program - ATP. Inicialmente são apresentados resultados de simulação de partes constituintes do arranjo fotovoltaico e somente ao final, é realizado um estudo de caso com o sistema completo desenvolvido neste trabalho. / Mestre em Ciências