Dissertations / Theses on the topic 'Inverter-based generation'

The system inertia of the Nordic power system is expected decrease in the future. This is due to an expected reduction in synchronous generation from nuclear and thermal power. This will be compensated by an increase in power from inverter-based generation due to wind power’s expansion in the power system. In this thesis, a power system’s ability to handle a large under-frequency fault is studied and how this is affected by a lower system inertia. The thesis also studies how different types of frequency response from wind power plants affects the systems ability to handle the fault. The frequency of a modelled transmission system is studied through dynamic simulations in the software PSS/E. Changes are made to the system to replace nuclear power (and eventually also thermal power) with type 4 (full-sized converter) wind turbines. A large under-frequency event is induced and the frequency nadir and bus voltages are compared against system limits used by the Swedish TSO. While gradually adding wind power to the system as nuclear power is removed, different versions of the system with different amounts of wind power are compared. Two studies are carried out. In the first study, the voltage response study, nuclear power is decreased by scaling down the size of the generators. Besides reducing their power output and inertia, this also decreases their capacity for voltage support. To compensate for the reduced voltage support in the system, the wind power plants are made to provide voltage support. In the second study, the inertia study, the nuclear power in the system is instead decreased by reducing the active power output and the inertia constant of the nuclear generator. The size of the generator and reactive power output stay the same as in the original system so the nuclear power plant can continue to supply voltage support. In this way the problems caused by reduced inertia in the system are isolated. In both studies, three different frequency responses are applied to the wind power plants. The three frequency responses are aimed to as closely as possible follow the minimum requirements from the Swedish TSO for the frequency response products FCR-N, FCR-D and FFR alt A. In both studies, FCR-N provided by wind power causes a lower the system frequency during the fault compared to the original system without wind power. FCR-N can not fully compensate for the loss of inertia the replacement of synchronous generation is causing. In the voltage response study, FCR-D causes a slightly lower system frequency than the original system without wind. In the inertia study the frequency is slightly raised with wind power providing FCR-D. In both studies, FCR-D is or is very close to fully compensating for the loss of inertia. In both studies with FFR alt A, more wind power and therefor more FFR alt A in the system means a significantly improved frequency nadir. One conclusion from this project is that both FCR-D and FFR alt A from wind power are effective at counter-acting the effects reduced system inertia has on the system frequency stability in this system. For both FCR-D and FFR alt A, the frequency deviation during the fault is lower or close to equal to the frequency deviation when the original system (no wind power) is subjected to the same fault. The second conclusion is that in the studied system the reduced capacity of voltage support due to removal of nuclear power in the system is more influential than the reduced system inertia in the expansion of wind power. This indicates that there may need to be more focus from power producers, TSOs and legislators on voltage support in the future as the power system moves from large synchronous power plants to more distributed inverter-based production.<br>Det nordiska elkraftsystemets systemtröghet förväntas minska i framtiden. Detta beror på minskad synkroniserad kraftproduktion från kärnkraft och värmekraft som väntas ersättas av ökad kraftproduktion från inverterar-baserad kraftgenerering där vindkraft står för en stor del av ökningen. I detta examensarbete studeras ett kraftsystems förmåga att hantera en större störning och hur detta påverkas av minskad systemtröghet. Examensarbetet jämför också hur olika typer av frekvensreglering från vindkraft påverkar systemets förmåga att hantera störningen. Systemfrekvensen av ett modellerat transmissionssystem studeras genom dynamiska simuleringar i PSS/E. Ändringar görs till systemet för att byta ut produktion från kärnkraft (och så småningom också värmekraft) med icke-synkrona vindkraftsturbiner. En större störning induceras och systemets frekvens och nodspänningar jämförs med systemgränser som används av den svenska systemansvariga. Genom att gradvis addera vindkraft till systemet och ta bort kärnkraft, skapas olika versioner av systemet med olika andelar produktion från vindkraft som sedan jämförs. Två studier genomförs. I den första studien minskas kärnkraften i systemet genom att skala ned storleken på kärnkraftsgeneratorerna. Förutom att reducera deras aktiva och reaktiva kraftproduktion så sänker detta också deras kapacitet för spänningsreglering vilket skapar problem med låga spänningar. För att kompensera för den minskade spänningsregleringen så förses vindkraften i systemet med spänningsreglering. I den andra studien minskas mängden kärnkraft i systemet genom att minska dess aktiva kraftproduktion och tröghetskonstant. Storleken på generatorerna och deras reaktiva kraftproduktion ändras inte vilket gör att kärnkraftsgeneratorerna kan fortsätta bidra med spänningsreglering. På detta sätt isoleras problemen som minskad systemtröghet ger upphov till. I båda studier appliceras tre olika frekvensregleringstyper på vindkraftverken i systemet. De tre frekvensregleringarna är ämnade att så nära som möjligt följa de tekniska kraven från den svenska systemansvarige för frekvensregleringsprodukterna FCR-N, FCR-D och FFR alt A. FCRN från vindkraft ger i båda studier upphov till en lägre systemfrekvens under felet jämfört med det ursprungliga systemet utan vindkraft. Detta betyder att FCR-N inte fullt kompenserar för den reducerade systemtrögheten orsakad av minskad mängd kärnkraft i systemet. FCR-D ger upphov till något lägre frekvens i den första studien och något högre frekvens in den andra studien jämfört med ett system utan vindkraft. FFR alt A leder i båda studier till en betydligt förbättrad frekvens jämfört med det ursprungliga systemet utan vindkraft. En slutsats från detta arbete är att både FCR-D och FFR alt A från vindkraft är effektiva i att motarbeta effekterna som en sänkt systemtröghet har på detta systems frekvensstabilitet. I båda fall är frekvensavvikelsen under störningen lägre eller nära samma som i originalsystemet utan vindkraft när de utsätts för samma störning. Den andra slutsatsen är att i detta är system är förlusten av spänningsreglering, som kärn- och värmekraften bidrog med, mer begränsande för mängden vindkraft som kan introduceras än vad sänkningen av systemtröghet var. Detta indikerar att det kan behövas mer fokus på spänningsreglering från kraftproducenter, systemansvariga och lagstiftare i framtiden när kraftsystemet rör sig från större synkroniserade kraftverk till mer distribuerad inverterar-baserad kraftproduktion.

The work presented in this thesis focuses on developing and experimentally verifying accurate analytical equivalent models of inverters during short-circuit conditions for use in numerical fault studies. In addition, a concept design for a variable speed generator that does not contribute to the local fault level is presented and verified by simulation and experiment. The flexibility of control offered by the application of power electronics in distribution networks is paramount in the transition to a decentralised power system but still faces significant technical challenges to widespread integration into the incumbent utility grid. Power electronic interfaces have historically only been used in rare cases and their effect on the network has hitherto often been ignored. The uptake of energy sources such as photovoltaics, variable speed wind, fuel cells, microturbines has caused a sufficient increase in grid connection requests for inverter interfaced generators, that before long their fault behaviour can no longer be neglected. The fault response of an inverter is dictated by its control strategy, its current limiting strategy and the reference frame in which they have been implemented. Current limiting typically breaks an inverter’s outer control loop and effectively turns it into a current source. Depending on the exact method of current limiting, linear analytical equivalent models have been developed whose source and impedance values can be expressed as a function of the inverters hardware parameters and controller gains evaluated at the fundamental frequency. The resulting models are compatible with conventional network analysis techniques and have been verified by comparing the results of such an analysis with experimental results. Fault models have been developed for stand-alone and grid-connected inverters. In congested networks the connection of an additional generator can cause the substation circuit breaker ratings to be exceeded. A full inverter interface can be controlled not to contribute to the fault current but is still prohibitively expensive at higher power levels. An alternative generator based on a doubly-fed induction generator is proposed and experimentally tested. By inserting a tap in the rotor winding, the voltage-per-turn can temporarily be increased to retain control of the quickly rising fault current without having to upgrade the machine-side inverter’s ratings. A fast thyristor-based tap changer inverter is proposed and experimentally verified that performs the pulse width modulation and diverts the modulated waveform to the desired tap on the rotor winding. The tap changer can be commutated in such a way as to achieve the fastest possible rate of current transfer during a tap change whilst avoiding voltage spikes by allowing any energy stored in the rotor leakage inductance to return to the DC-link. The developed fault models and zero fault current generator are a step towards familiarising utility engineers with power electronics and how they affect the operation of the distribution network. The availability of standardised models avoids the need for expensive and time-consuming time domain simulation based fault studies for inverter connection requests. The work presented in this thesis may act as a base for the development of standardised representations of power electronics in power networks.

Recently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten years in anticipation of the tremendous increase in the penetration of Distributed Generation (DG) in distribution system. This work proposes new IDMs that rely on transient and distributed behaviors to improve integrity and performance of DGs while maintaining multi-DG islanding detection capability. In this thesis, the following questions have been addressed: How to utilize the transient behavior arising from an islanding condition to improve detectability and robust performance of IDMs in a distributive manner? How to reduce the negative stability impact of the well-known Sandia Frequency Shift (SFS) IDM while maintaining its islanding detection capability? How to incorporate the perturbations provided by each of DGs in such a way that the negative interference of different IDMs is minimized without the need of any type of communication among the different DGs? It is shown that the proposed techniques are local, scalable and robust against different loading conditions and topology changes. Also, the proposed techniques can successfully distinguish an islanding condition from other disturbances that may occur in power system networks. This work improves the efficiency, reliability and safety of integrated DGs, which presents a necessary advance toward making electric power grids a smart grid.<br>Ph.D.<br>Doctorate<br>Electrical Engineering and Computer Science<br>Engineering and Computer Science<br>Electrical Engineering

Doctor of Philosophy<br>Department of Electrical and Computer Engineering<br>Behrooz Mirafzal<br>In this dissertation, a new topology for Direct-Drive Wind Turbines (DDWTs) with a new power electronics interface and a low-voltage generator design is presented. In the presented power electronics interface, the grid - side converter is replaced by a boost Current Source Inverter (CSI) which eliminates the required dc-bus capacitors resulting in an increase in the lifetime of DDWTs. The inherently required dc-link inductor for this topology is eliminated by utilizing the inductance of the Permanent Magnet Synchronous Generator (PMSG). The proposed three-phase boost CSI is equipped with Reverse-Blocking IGBTs (RB-IGBT) and the Phasor Pulse Width Modulation (PPWM) switching pattern to provide a 98% efficiency and high boost ratios ([superscript V]LL/V[subscript dc]) up to 3.5 in a single stage. In this dissertation, Phasor Pulse Width Modulation (PPWM) pattern for the boost – CSI is also modified and verified through simulation and experimental results. In order to realize potential capabilities of the boost inverter and to assist its penetration into renewable energy systems, the boost inverter dynamic behaviors are studied in this dissertation. Then, the developed models are verified using circuit simulations and experiments on a laboratory-scale boost – CSI equipped with RB-IGBTs. The developed dynamic models are used to study the stability of the boost – CSI through root locus of small signal poles (eigenvalues) as control inputs and load parameters vary within the boost inverter's operating limits. The dynamic models are also used to design the control schemes for the boost – CSI for both stand-alone and grid-tied modes of operation. The developed controllers of the boost – CSI are verified through simulation and experimental results. In this dissertation, the boost – CSI steady-state characterization equations are also developed and verified. The developed boost – CSI is used to replace the grid - side converter in a DDWT. A reliability analysis on the power electronics interface of an existing and developed topology is presented to demonstrate the increase in the mean time between failures. The boost – CSI enables conversion of a low dc voltage to a higher line-to-line voltage enabling the implementation of a low-voltage generator. This further enables a reduction in the number poles required in DDWT generators. The feasibility of the presented low-voltage generator is investigated through finite element computations. In this dissertation, a 1.5MW low-voltage generator designed for the proposed topology is compared with an existing 1.5MW permanent magnet synchronous generator for DDWTs to demonstrate the reduction in the volume, weight, and amount of permanent magnet materials required in the generator. The feasibility of the developed system is supported by a set of MATLAB/Simulink simulations and laboratory experiments on the closed-loop stand-alone and grid-tied systems.

Nowadays islanding has become a big issue with the increasing use of distributed generators in power system. In order to effectively detect islanding after DG disconnects from main source, author first studied two passive islanding methods in this thesis: THD&VU method and wavelet-transform method. Compared with other passive methods, each of them has small non-detection zone, but both of them are based on the threshold limit, which is very hard to set. What’s more, when these two methods were applied to practical signals distorted with noise, they performed worse than anticipated. Thus, a new composite intelligent based method is presented in this thesis to solve the drawbacks above. The proposed method first uses wavelet-transform to detect the occurrence of events (including islanding and non-islanding) due to its sensitivity of sudden change. Then this approach utilizes artificial neural network (ANN) to classify islanding and non-islanding events. In this process, three features based on THD&VU are extracted as the input of ANN classifier. The performance of proposed method was tested on two typical distribution networks. The obtained results of two cases indicated the developed method can effectively detect islanding with low misclassification.

Distributed Generators (DGs) are sensible to voltage sags, so the protection devices must trip fast to disconnect the faulted part of the grid. The DG disconnection will not be desirable in the near future with a large penetration, so it will be necessary to lay down new requirements that should be based on avoiding unnecessary disconnections. Therefore, to prevent unnecessary tripping when inverter-based DGs are connected to the Medium Voltage (MV) grid, reliable and effective protection strategies need to be developed, considering the limited short-circuit current contribution of DG. The initial goal of this study is to employ different possible control strategies for a grid-connected inverter according to the Spanish grid code and to analyze the output voltage behavior during symmetrical and unsymmetrical voltage sags. The analytical development of the proposed strategies shows the impacts of the sag on currents, voltages, active and reactive powers. Another goal of this research is to propose a protection strategy based on Artificial Intelligence for a radial or ring distribution system with high DG penetration. The protection strategy is based on three different algorithms to develop a more secure, redundant, and reliable protection system to ensure supply continuity during disturbances in ring and radial grids without compromising system stability. In order to classify, locate and distinguish between permanent or transient faults, new protection algorithms based on artificial intelligence are proposed in this research, allowing network availability improvement disconnecting only the faulted part of the system. This research introduces the innovative use of directional relay based on a communication system and Artificial Neural Network (ANN). The first algorithm, Centralize algorithm (CE), collects the data from all the PDs in the grid in the centralized controller. This algorithm detects the power flow direction and calculates the positive-sequence current of all the PDs in the grid. Significant benefits of this system are that it consolidates the entire systems security into a single device, which can facilitate system security control. However, the CE will not pinpoint the exact location of the fault if there is any loss of information due to poor communication. Therefore, the systems redundancy can be improved by cooperating with a second algorithm, the Zone algorithm (ZO). ZO algorithm is based on zone control using peer-to-peer connectivity in the same line. The faulty line in that zone may be identified by combining the two PDs data on the same line. The most relevant advantage of this algorithm is its flexibility to adapt to any grid modification or disturbance, even if they are just temporary, unlike the CE, which is fixed to the existing grid configuration. The third protection algorithm, Local algorithm (LO), has been proposed without depending on the communication between the PDs; then, the protection system can work properly in case of a total loss of communication. Each PD should be able to detect if the fault is located in the protected line or another line by using only the local information of the PD. According to the type of fault and based on local measurements at each PD of abc voltages and currents, different algorithms will be applied depending on the calculation of the sequence components. The main advantage of this algorithm is the separate decision of each PD, and avoiding communication problems. In case of radial grids, both mechanical breakers and Solid State Relays (SSRs) are used to verify the protection strategies, and in the case of ring grids, mechanical breakers are used, due to the limitations in required voltage difference of SSR. The proposed protection algorithms are compared with conventional protections (Overcurrent and Differential) protections to validate the contribution of the proposed algorithms, especially in reconfigurable smart grids.<br>El objetivo inicial de este estudio es emplear diferentes estrategias de control posibles para un inversor conectado a la red segun el código de red español y analizar el comportamiento de la tensión de salida durante caídas de tensión simétricas y asimétricas. El desarrollo analítico de las estrategias propuestas muestra los impactos de los huecos de tensión en las corrientes, tensiones, potencias activas y reactivas. Otro objetivo de esta investigación es proponer una estrategia de protecclón basada en lnteligencia Artificial para una red del Sistema de Distribución, radial o en anillo, con elevada penetración de Generación Distribuida. La estrategia de protección se basa en tres algoritmos diferentes para desarrollar un sistema de protección más seguro, redundante, y fiable, que asegure la continuidad de suministro durante perturbaciones en redes radiales o en anillo sin comprometer la estabilidad del sistema. Para clasificar, localizar y distinguir entre faltas permanentes o transitorias, se proponen en este trabajo nuevos algoritmos de protección basados en inteligencia artificial, permitiendo la mejora de la disponibilidad de la red, al desconectar sólo la parte del sistema en falta. Esta investigación introduce la innovación del uso del rele direccional basado en un sistema de comunicación y Redes Neuronales Artificiales (ANN). El primer algoritmo, Algoritmo Central (CE), recibe los datos de todos los PDs de la red en un control central. Este algoritmo detecta la dirección de flujo de cargas y calcula la corriente de secuencia positiva de todos los PDs de la red. El entrenamiento de ANNs incluye variaciones en la corriente de cortocircuito y la dirección del flujo de potencia en cada PD. Los beneficios mas significativos de este sistema son que concentra la seguridad total del sistema en un único dispositivo, lo que puede facilitar el control de la seguridad del sistema. Sin embargo, el CE no determinara con precisión la localización exacta de la falta si hay alguna perdida de información debida a una pobre comunicación. Por lo tanto, la redundancia del sistema se puede mejorar cooperando con un segundo algoritmo, el algoritmo de Zona (ZO). El algoritmo ZO se basa en un control de zona usando la conectividad entre dispositivos de protección de una misma línea. La línea en falta en esa zona puede identificarse combinando los datos de los dos PDs de la misma línea.. La ventaja mas relevante de este algoritmo es su flexibilidad para adaptarse a cualquier modificación de la red o perturbación, incluso si sólo son temporales, a diferencia del CE, que se ha adaptado para la configuración de la red existente. El tercer algoritmo de protección, algoritmo Local (LO), ha sido propuesto sin dependencia de la comunicación entre PDs; por lo tanto, el sistema de protección puede operar correctamente en el caso de una pérdida total de comunicación. Cada PD debe poder detectar si la falta esta ubicada en la línea protegida o en otra línea, utilizando sóIo la información local del PD. Según el tipo de falta, y en base a medidas locales en cada PD, de tensiones y corrientes abc, se aplican diferentes algoritmos en función del cálculo de las componentes simétricas. La principal ventaja de este algoritmo es la actuación por separado de cada PD, evitando los problemas de comunicación. En el caso de las redes radiales, se utilizan tanto interruptores mecánicos como réles de estado sóIido (SSR) para verificar las estrategias de protección, y en el caso de las redes en anillo se utilizan interruptores mecánicos, debido a las limitaciones de tensión para su conexión. Los algoritmos de protección propuestos se comparan con protecciones convencionales (Sobrecorriente y Diferencial) para validar la contribución de los algoritmos propuestos, especialmente en redes inteligentes reconfigurables.<br>Enginyeria Elèctrica

The increasing utilisation of renewable energy sources (RESs) plays an important role in the modern power system. The high penetration of the RESs in the electrical power network leads to challenges to the system’s stability. Therefore, the microgrid concept is proposed to solve such problems due to its flexibility and practicality. The hybrid AC/DC microgrid configuration is compatible with AC power supplies, DC power supplies, AC loads and DC loads which is viewed as the most practical choice in the power system application. The microgrid utilises an interlinking converter for the system’s control and grid connection. In this case, the microgrid implementation provides the possibility to achieve the other power electronic device functions such as a static compensator (STATCOM) or an active power filter (APF) in addition to dealing with the RES problems. In this PhD thesis, a grid-connected-mode-based control strategy for the microgrid is proposed to regulate the power generation as well as to reduce the grid current harmonics and neutral current. A virtual synchronous generator (VSG) based control strategy is introduced for microgrid’s smooth transient performance purpose. The first contribution of this research is the combination of the notch filter and traditional grid-connected microgrid control strategy. The notch filter is introduced into a three-phase system for current harmonics detection. The obtained harmonics signals are converted into reference signals for a revised constant power control strategy so that the microgrid is able to achieve the power regulation and harmonics reduction simultaneously. The interlinking converter is designed with three transistor-based bridges and a split-capacitor-based bridge so that the system is decoupled from hardware without any internal signals interference. The second contribution of this research is the design for grid neutral current compensation. The interlinking converter is designed with another independent neutral module bridge for the neutral current compensation purpose and a controller is developed based on this. In the context, the microgrid is implemented as a traditional microgrid with STATCOM-APF functions embedded. The third contribution of this research is the introduction of an improved VSG controller with its specific pre-synchronisation module. The designed method conducts smooth transient performances for a microgrid under different scenarios. An exclusive pre-synchronisation block is designed for the improved VSG controller for the microgrid to reconnect to the utility network smoothly when there is a requirement. The final contribution of this research is the establishment of the microgrid system benchtop. The hardware setup achieves the traditional power regulation function as well as the power-sharing between two microgrids. The proposed STATCOM-APF-based grid-connected microgrid controller is also tested under different scenarios. The effectiveness is validated through experiment. Various case studies are conducted in this research to investigate the microgrid possibilities. The proposed methods are validated through simulation first. The hardware prototype also verifies the correctness of the proposed grid-connected microgrid control method. The microgrid setup finally realises the power regulation, the harmonics reduction, the neutral current compensation and the cooperative operation functions.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Eng & Built Env<br>Science, Environment, Engineering and Technology<br>Full Text

Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xvi, 209 p.; also includes graphics. Includes bibliographical references (p. 202-209). Available online via OhioLINK's ETD Center

Bien que le gouvernement cambodgien s’efforce d’augmenter sa production d’électricité pour répondre à sa demande en énergie, il reste toujours dépendant de réseau électrique existant ou de l’extension du réseau dont le coût d’investissement initial est élevé. La solution temporelle consiste à employer un système de production d'énergie distribué qui présente un coût de cycle de vie inférieur et introduit une diversité de technologies pour répondre aux applications. Minimiser les impacts environnementaux représente un objectif majeur du développement durable, compte tenu de l'épuisement des ressources et des capacités d'adaptation limitées de l'environnement. Les ressources en énergies renouvelables ont été bien comprises comme les solutions pour alimenter le développement rural et réduire les impacts environnementaux de la production d’énergie. Suivant les progrès technologiques et de la demande croissante des consommateurs, de grande quantité de déchets électriques et électroniques ont entraîné de graves conséquences pour l’environnement. Les stratégies actuelles reposent principalement sur les techniques classiques de collecte et de traitement des déchets. Ce travail de thèse proposait une solution de réutilisation des composants électroniques dans un système d'énergie renouvelable hybride isolé pour la solution d'électrification pour la zone rurale. Une configuration choisie pour le système proposé est un système de génération hybride solaire-hydroélectrique, car les ressources solaires et hydrauliques sont abondantes dans les zones rurales du Cambodge. Les composants qui sont réutilisés dans la solution comprennent des blocs d’alimentation d’un PC (PSU) pour la partie solaire, des alimentations sans interruption (UPS) et des machines asynchrone triphasées pour la partie hydraulique. Les batteries automobiles usagées sont utilisées pour le stockage d’énergie. Ce travail de thèse aborde dans une première partie l’évaluation des impacts environnementaux de la solution de réutilisation proposée. Cette étude repose sur la méthodologie de l’Analyse du Cycle de Vie (ACV) qui compare les impacts du cycle de vie de la solution proposée à ceux d’une solution conventionnelle. La deuxième partie de ce travail traite des aspects technologiques de la solution de réutilisation, à la fois en théorie et en expérimentation. La première partie de cet aspect concerne la reconversion des blocs d’alimentations usagées. Le bloc d'alimentation, qui contient généralement l'un des quelques types de convertisseurs DC-DC isolés, est réutilisé comme contrôleur de charge, qui est le composant principal du système de générateur photovoltaïque. La dernière partie de cette thèse décrit une nouvelle configuration de générateur basé sur des moteurs asynchrone triphasés. Le générateur monophasé proposé basé sur une machine triphasée est une version modifiée d'une topologie à base de l’onduleur où deux enroulements sont alimentés séparément par sources d'excitation, et l'autre enroulement est connecté à la charge. Une nouvelle modélisation est proposée. Les résultats de simulation sont comparés aux résultats expérimentaux en alimentation sinus. La comparaison met en évidence une supériorité de la nouvelle configuration par rapport à l'ancienne en termes de rendement et de minimisation de pulsations de couple<br>While the Cambodia’s government is making effort to increase electricity production for its energy demand, it still remains dependent on the existing or the expansion of the centralized grid lines which have high initial investment cost. The temporally solution is to employ a distributed energy generation system which has lower life cycle cost and provides a diversity of technologies to meet the desired applications. Minimizing environmental impacts represents a major objective of sustainable development considering resources depletion and the limited capabilities of the environment to adapt. The potential of renewable energy resources has been well understood as the solutions to power rural development and to reduce the environmental impacts of energy generation. Due to advance in technologies and increasing consumer demands, there has been a vast amount of electrical and electronic waste which introduces severe impacts on the environment. The current strategies mainly rely on conventional waste collection and processing techniques for material recovery. This thesis proposed a solution of reusing discarded components in an isolated hybrid renewable energy system as the solution for electrification of rural Cambodia. This is frugal innovation, local solution with local materials for and with local people. A suitable configuration for the proposed system is a solar-hydro hybrid generation system since solar and water resources are plentiful in rural Cambodia. The components that are reused in the solution after being discarded include computer power supply units (PSUs) for the solar part, uninterruptable power supply units (UPSs) and three phase induction machines for the electrohydro part. Used auto-mobile batteries will be used for the system storage. The thesis presents in the first part the evaluation of the environmental impacts of the proposed reuse solution for rural electrification. The study of the environmental impacts is based on Life Cycle Assessment (LCA) methodology which compares the life cycle impacts of the proposed solution to that of a conventional solution. Moreover, a sensitivity analysis is achieved in order to evaluate the impacts of uncertainties of the environmental impacts. The second part of this work deals with the technological aspects of the reuse solution in both theory and experimentation. The first part of this aspect is focused on the repurposing of used computer power supply units (PSUs), through limited modifications of the circuits in order to increase its range of operation. The PSU which usually contains one of a few types of isolated DC-DC converters is repurposed as charge controller with MPPT control in a cheap micro-controller with very good results. The last part of this thesis studies a new configuration of generators based on re-used three-phase induction motors. The proposed single-phase generator is based on a three-phase machine in a modified version of the coupling and with a rather uncommon supply. Modelling is highly investigated. An inverterassisted topology where two windings will be supplied separately by two inverters for excitation and the remaining winding is connected to load. A new modeling of the generator has been studied. The results of simulation were compared to experimental test results in open loop study. These results have demonstrated the advantages of the new configuration in comparison to the previously proposed inverter-assisted topology in term of efficiency and minimization of torqueripple

Les travaux de thèse s’inscrivent dans les problématiques des travaux de recherche de l’équipe thématique : Maitrise des Energies Renouvelables et systèmes de Stockage (MERS) du laboratoire GREAH-EA3220. Ils englobent le dimensionnement des éléments constitutifs du système et la gestion optimale de l’énergie électrique pour un système hybride (Diesel à vitesse variable, Eolien, PV et Batteries) dédié aux sites isolés. Les sources de production d'énergie alimentent des charges par le biais de convertisseurs multi-niveaux d’électronique de puissance. Le groupe électrogène comportant un moteur diesel à vitesse variable est considéré comme la principale source d’énergie utilisée pour contrôler la tension continue du point de couplage. Ce type de groupe électrogène est choisi pour optimiser la consommation du carburant. Il est sollicité pour délivrer une puissance électrique compatible avec le régime du moteur qui supporte mal les variations fréquentes et rapides. Les sources d’énergie renouvelables dont on cherche à augmenter la part d’énergie pour satisfaire la demande sont pilotées de manière à extraire instantanément le maximum de puissances disponible par les ressources (ensoleillement, vent). Celles-ci imposent ainsi leurs dynamiques et leurs intermittences au point de couplage. Le pack des batteries sert à compenser les fluctuations rapides de l’énergie provenant des sources d’énergie renouvelables par rapport à une évolution plus lente prise en charge par le groupe électrogène. La gestion des interactions au sein du système électrique hybride résultant est assurée au moyen de convertisseurs statiques multi-niveaux (AC / DC, DC / DC et DC / AC). Une approche de gestion d’énergie électrique fondée sur la répartition fréquentielle des perturbations induites au point de couplage par les sources renouvelables. Une plateforme expérimentale à échelle réduite (1/22) a été développée pour valider expérimentalement les approches théoriques et les simulations. Les résultats de simulations obtenus dans l’environnement logiciel Matlab/Simulink/SimPowerSystems et ceux issus du dispositif expérimental réalisé et piloté par dSPACE-1104 prouvent l’adéquation des méthodes de contrôle proposées<br>The thesis works are part of the research work of the thematic team: Mastery of Renewable Energies and Storage Systems (MERS) of the GREAH-EA3220 laboratory. They include the dimensioning of the constituent elements of the system and the optimal management of electrical energy for a hybrid system (Variable speed Diesel, Wind, PV and Batteries) dedicated to isolated sites. Power sources supply loads through multi-level converters of power electronics. The generator set with a variable speed diesel engine is considered to be the main source of energy used to control the DC voltage at the coupling point. This type of generator is chosen to optimize fuel consumption. It is used to deliver an electrical power compatible with the engine speed which does not tolerate frequent and rapid variations. Renewable energy sources whose share of energy is sought to meet demand are managed so as to instantly extract the maximum power available from resources (sunshine, wind). These thus impose their dynamics and their intermittences at the coupling point. The battery pack is used to compensate for rapid fluctuations in energy from renewable energy sources compared to a slower evolution supported by the generator. Interactions within the resulting hybrid electrical system are managed by means of multi-level static converters (AC / DC, DC / DC and DC / AC). An electrical energy management approach based on the frequency distribution of disturbances induced at the coupling point by renewable sources. An experimental platform on a reduced scale (1/22) has been developed to experimentally validate theoretical approaches and simulations. The results of simulations obtained in the Matlab / Simulink / SimPowerSystems software environment and those from the experimental device produced and piloted by dSPACE-1104 prove the adequacy of the proposed control methods

abstract: Energy is one of the wheels on which the modern world runs. Therefore, standards and limits have been devised to maintain the stability and reliability of the power grid. This research shows a simple methodology for increasing the amount of Inverter-based Renewable Generation (IRG), which is also known as Inverter-based Resources (IBR), for that considers the voltage and frequency limits specified by the Western Electricity Coordinating Council (WECC) Transmission Planning (TPL) criteria, and the tie line power flow limits between the area-under-study and its neighbors under contingency conditions. A WECC power flow and dynamic file is analyzed and modified in this research to demonstrate the performance of the methodology. GE's Positive Sequence Load Flow (PSLF) software is used to conduct this research and Python was used to analyze the output data. The thesis explains in detail how the system with 11% of IRG operated before conducting any adjustments (addition of IRG) and what procedures were modified to make the system run correctly. The adjustments made to the dynamic models are also explained in depth to give a clearer picture of how each adjustment affects the system performance. A list of proposed IRG units along with their locations were provided by SRP, a power utility in Arizona, which were to be integrated into the power flow and dynamic files. In the process of finding the maximum IRG penetration threshold, three sensitivities were also considered, namely, momentary cessation due to low voltages, transmission vs. distribution connected solar generation, and stalling of induction motors. Finally, the thesis discusses how the system reacts to the aforementioned modifications, and how IRG penetration threshold gets adjusted with regards to the different sensitivities applied to the system.<br>Dissertation/Thesis<br>Masters Thesis Electrical Engineering 2020