The Swedish island of Gotland , situated about 100 km from mainland Sweden in the Baltic Sea, represents a power system with a high wind power penetration. The island is connected to the mainland Sweden exclusively via two HVDC cables that provide the only source of active power and frequency control. The two cables can operate in different configurations, i.e. import or export power from or to mainland. However, in order to ensure the N-1 criterion, one of the cables currently always must import power from the mainland. This means that the available power exporting capacity is limited to the rated power of one of the cables. Therefore, in the case of having a fault on the exporting HVDC cable during low load demand and high wind power production, the power system will suffer from high active power transients that will increase the frequency above the acceptable threshold. Consequently, the protection system will trip the over-frequency relays, triggering cascading outages on the island that might eventually lead to blackout if the problem is not addressed correctly. Thus, increasing the renewable energy production on Gotland is currently considered as a risk that will increase the probability of instable over-frequency contingencies. This has led the local grid operator to cap the installed wind power capacity to its current level. Therefore, the ability to preserve the stability of the power system during islanded operations until the HVDC cables fault is cleared or the emergency reserves are online is essential for the growth of installed wind power capacity. The main objective of the thesis is to examine the capability of a centralized energy storage along with or without wind curtailment. The ESS is tested for maintaining the frequency stability during the unintentional islanding through dynamic studies using the software PSS/E. The results show that an ESS prevents frequency instabilities and provide frequency response during HVDC cables fault albeit of the absence of any form of rotating inertia. The results show that for today’s 185 MW of installed wind power capacity, an energy storage of 50 MW power capacity will reduce over-frequency instabilities in the case of HVDC cables fault from 13% to 1%. The analysis finds that the power capacity of the energy storage depends on the exported power from the HVDC cables at the instant of fault, which eventually relates to the installed wind power capacity. finally, the study shows that using wind power curtailment will significantly decrease the energy capacity of the energy storage.

Cette thèse aborde les problèmes de la modélisation et de la commande d'un micro-réseau courant continu (CC) en vue de la gestion énergétique optimale, sous contraintes et incertitudes. Le micro-réseau étudie contient des dispositifs de stockage électrique (batteries ou super-capacités), des sources renouvelables (panneaux photovoltaïques) et des charges (un système d'ascenseur motorise par une machine synchrone a aimant permanent réversible). Ces composants, ainsi que le réseau triphasé, sont relies a un bus commun en courant continu, par des convertisseurs dédies. Le problème de gestion énergétique est formule comme un problème de commande optimale qui prend en compte la dynamique du système, des contraintes sur les variables, des prédictions sur les prix, la consommation ou la production et des profils de référence.Le micro-réseau considère est un système complexe, de par l'hétérogénéité de ses composants, sa nature distribuée, la non-linéarité de certaines dynamiques, son caractère multi-physiques (électromécanique, électrochimique, électromagnétique), ainsi que la présence de contraintes et d'incertitudes. La représentation consistante des puissances échangées et des énergies stockées, dissipées ou fournies au sein de ce système est nécessaire pour assurer son opération optimale et fiable.Le problème pose est abordé via l'usage combine de la formulation hamiltonienne a port, de la platitude et de la commande prédictive économique base sur le modelé. Le formalisme hamiltonien a port permet de décrire les conservations de la puissance et de l'énergie au sein du micro-réseau explicitement et de relier les composants hétérogènes dans un même cadre théorique. Les non linéarités sont gérées par l'introduction de la notion de platitude démentielle et la sélection de sorties plates associées au modèle hamiltonien a ports. Les profils de référence sont génères a l'aide d'une para métrisation des sorties plates de telle sorte que l'énergie dissipée soit minimisée et les contraintes physiques satisfaites. Les systèmes hamiltoniens sur graphes sont ensuite introduits pour permettre la formulation et la résolution du problème de commande prédictive _économique a l'échelle de l'ensemble du micro-réseau CC. Les stratégies de commande proposées sont validées par des résultats de simulation pour un système d'ascenseur multi-sources utilisant des données réelles, identifiées sur base de mesures effectuées sur une machine synchrone. / The goals of this thesis is to propose modelling and control solutions for the optimal energy management of a DC microgrid under constraints. The studied microgrid system includes electrical storage units (e.g., batteries, supercapacitors), renewable sources (e.g., solar panels) and loads (e.g., an electro-mechanical elevator system). These interconnected components are linked to a three phase electrical grid through a DC bus and associated DC/AC converters. The optimal energy management is usually formulated as an optimal control problem which takes into account the system dynamics, cost, constraints and reference profiles.An optimal energy management for the microgrid is challenging with respect to classical control theories. Needless to say, a DC microgrid is a complex system due to its heterogeneity, distributed nature (both spatial and in sampling time), nonlinearity of dynamics, multi-physic characteristics, the presence of constraints and uncertainties. Moreover, the power-preserving structure and the energy conservation of a microgrid are essential for ensuring a reliable operation.This challenges are tackled through the combined use of port-Hamiltonian formulations, differential flatness, and economic Model Predictive Control.The Port-Hamiltonian formalism allows to explicitly describe the power-preserving structure and the energy conservation of the microgrid and to connect different components of different physical natures through the same formalism. The strongly non-linear system is then translated into a flat representation. Taking into account differential flatness properties, reference profiles are generated such that the dissipated energy and various physical constraints are taken into account. Lastly, we minimize the purchasing/selling electricity cost within the microgrid using the economic Model Predictive Control with the Port-Hamiltonian formalism on graphs.The proposed control designs are validated through simulation results.

Urban microgrids are smart and complex energy systems that help integrate renewables into our cities, turning our neighborhoods into partly energy self-sufficient hubs. Moreover, they create the space for electricity transactions between neighbors, transforming the former consumers into prosumers. The following work proposes the implementation of an urban microgrid to a neighborhood in Lisbon, Portugal. This dissertation’s objective is designing and discovering the optimal photovoltaic and storage capacity, optimal electricity dispatch, effects of distributed energy production in grid voltage and economic viability of such a system. With this purpose, a comprehensive model was elaborated, considering specific site weather data, electric loads, grid topology and utility tariffs. The self-sufficiency of Arco do Cego was found to be 66% in this study, reducing its carbon footprint by 61%. A detailed map of where to place each PV system and battery bank was generated, with specific electricity dispatch strategies. Moreover, the system was designed under real grid voltage, current and power flow constraints.

In this report, the modeling process and operation of an autonomous hybrid power system is studied. It is built based on a hypothetical case study of electrification of a remote village of 100 inhabitants in Kenya. The power demand is estimated and the costs of equipment components are specified after extensive research, so that the techno-economical design of the system can be carried out. The microgrid consists of photovoltaics, wind turbine, batteries, diesel genset, basic loads and water pumping and purification load. The system is modeled and simulated in terms of power management and its operation as well as the performance of the dispatch strategy is assessed. Problems like the management of extra power or tackling the deficit of power in the system are addressed. The model represents reliably the behavior of the microgrid and several improving actions are suggested.

The motivation of this research is to carry out the control and operation of smart inverters and voltage source converters (VSC) for distributed energy resources (DERs) such as photovoltaic (PV), battery, and plug-in hybrid electric vehicles (PHEV). The main contribution of the research includes solving a couple of issues for smart grids by controlling and implementing multifunctions of VSC and smart inverter as well as improving the operational scheme of the microgrid. The work is mainly focused on controlling and operating of smart inverter since it promises a new technology for the future microgrid. Two major applications of the smart inverter will be investigated in this work based on the connection modes: microgrid at grid-tied mode and autonomous mode. \indent In grid-tied connection, the smart inverter and VSC are used to integrate DER such as Photovoltaic (PV) and battery to provide suitable power to the system by controlling the supplied real and reactive power. The role of a smart inverter at autonomous mode includes supplying a sufficient voltage and frequency, mitigate abnormal condition of the load as well as equally sharing the total load's power. However, the operational control of the microgrid still has a major issue on the operation of the microgrid. The dissertation is divided into two main sections which are: 1- Low-level control of a single smart Inverter. 2- High-level control of the microgrid. The first part investigates a comprehensive research for a smart inverter and VSC technology at the two major connections of the microgrid. This involves controlling and modeling single smart inverter and VSC to solve specific issues of microgrid as well as improve the operation of the system. The research provides developed features for smart inverter comparing with a conventional voltage sourced converter (VSC). The two main connections for a microgrid have been deeply investigated to analyze a better way to develop and improve the operational procedure of the microgrid as well as solve specific issues of connecting the microgrid to the system. A detailed procedure for controlling VSC and designing an optimal operation of the controller is also covered in the first part of the dissertation. This section provides an optimal operation for controlling motor drive and demonstrates issues when motor load exists at an autonomous microgrid. It also provides a solution for specific issues at operating a microgrid at autonomous mode as well as improving the structural design for the grid-tied microgrid. The solution for autonomous microgrid includes changing the operational state of the switching pattern of the smart inverter to solve the issue of a common mode voltage (CMV) that appears across the motor load. It also solves the issue of power supplying to large loads, such as induction motors. The last section of the low-level section involves an improvement of the performance and operation of the PV charging station for a plug-in hybrid electric vehicle (PHEV) at grid-tied mode. This section provides a novel structure and smart controller for PV charging station using three-phase hybrid boost converter topology. It also provides a form of applications of a multifunction smart inverter using PV charging station. The second part of the research is focusing on improving the performance of the microgrid by integrating several smart inverters to form a microgrid. It investigates the issue of connecting DER units with the microgrid at real applications. One of the common issues of the microgrid is the circulating current which is caused by poor reactive power sharing accuracy. When more than two DER units are connected in parallel, a microgrid is forming be generating required power for the load. When the microgrid is operated at autonomous mode, all DER units participate in generating voltage and frequency as well as share the load's power. This section provides a smart and novel controlling technique to solve the issue of unequal power sharing. The feature of the smart inverter is realized by the communication link between smart inverters and the main operator. The analysis and derivation of the problem are presented in this section. The dissertation has led to two accepted conference papers, one accepted transaction IEEE manuscript, and one submitted IET transaction manuscript. The future work aims to improve the current work by investigating the performance of the smart inverter at real applications.

This work presents the development of a methodology to service replacement and management loads in islanded smart grid by load shedding, supported by Distributed Generation, to avoid or reduce violations of continuity indicators, subject to penalties for infringement, established in Module 8 of PRODIST, ANEEL (2015a). To adjust the power demanded by the load to the power generated during the islanding of microrrede specifies to the best loads to be rejected by Multicriteria Methodology Analytic Hierarchy Process - AHP. In applying of methodology it was considered as criteria the continuity indicators that generate compensation to consumers for violation, and also it was considered the priority of continuity of supply to loads. Thus, for the formation of the island, is obtained as a preliminary result, a classification of loads in order of need for service. The best loads classified will be reconnected to microrrede until that GD units do not support new loads or that they violate any of the restrictions, being the remaining loads rejected. In continuously, they was made a reassessment in every pre-set period of time in order to identify new possible loads shedding to be made. This revaluation occurs in two distinct scenarios, both for typical day as for critical day. Any Violations of system constraints are checked by software of load flow calculation. Thus, obtained as final result a whole of loads to be served during replacement or continuity of the service. / Este trabalho apresenta o desenvolvimento de uma metodologia para reposição de serviço e gestão de cargas em microrrede inteligente ilhada, suportada por unidades de Geração Distribuída, a fim de evitar ou atenuar violações dos indicadores de continuidade, passíveis de penalidades por violação, estabelecidos no Módulo 8 dos Procedimentos de Rede da Agência Nacional de Energia Elétrica PRODIST, ANEEL (2015a). Para adequar a potência demandada pelas cargas à potência gerada, durante o ilhamento da microrrede, definem-se as melhores cargas a serem rejeitadas, por meio da Metodologia Multicritério Analytic Hierarchy Process AHP. Na aplicação da metodologia foram considerados como critérios os indicadores de continuidade passíveis de compensações aos consumidores por violação, e também, foi considerada a prioridade de continuidade do fornecimento às cargas. Assim, para a formação da ilha, obtém-se como resultado preliminar, uma classificação das cargas em ordem de necessidade de atendimento. As cargas melhores classificadas são reconectadas à microrrede até que as unidades de GD não suportem novas cargas ou que ocorra a violação de alguma das restrições, sendo as demais cargas rejeitadas. De forma contínua, são feitas reavaliações a cada período de tempo pré-definido de forma a identificar novas possíveis rejeições ou reconexões de carga a serem realizados durante o ilhamento. Esta reavaliação ocorre em dois cenários distintos, tanto para dia típico como para dia crítico. Eventuais violações das restrições do sistema são verificadas por meio de software para cálculo de fluxo de carga. Desta forma, obtém-se como resultado final um conjunto de cargas a serem atendidas durante a reposição ou continuidade do serviço.

In Canada, more than 1.11 TWh of energy per year is generated by diesel generators in off-grid remote areas. Delivering energy to these territories always has a high cost for the local and federal governments both financially and environmentally. Substituting fossil fuels with clean energies is the solution. However, the unreliability and intermittency of renewable energies (RE) are always challenging issues that need to be solved. Zinc air flow battery (ZAFB) with decoupled power and energy capacity can bring sustainability and reliability for microgrids. In this study, an efficient model was developed for ZAFB, which is applicable for large-scale modeling, and incorporated in microgrid modeling. A bilevel optimization approach was implemented in the microgrid model to find the optimal size and control of the microgrid simultaneously over the project lifetime. Using model predictive control (MPC) and based on user-defined foresight horizon and known information like energy demand and RE resources, the control model decides the future changes in microgrid components. This tool is used to propose the best microgrid design for these communities to reduce or eliminate their dependency on fossil fuels. The functionality of this tool was evaluated by three case studies in British Columbia: Blind Channel, Hot Springs Cove and Moresby Island. Zero CO2 emission and zero fuel consumption were achieved by a 100% RE microgrid consisting of wind and tidal turbines and large ZAFB. The net present cost (NPC) of this system and cost of energy are 39 – 46 % and 55 – 60 % less than the base case costs in which diesel is the main energy source. ZAFB with a longer storage duration (50 – 60 hours) satisfies 17 – 23% of annual energy demand in these case studies. / Graduate

This thesis describes the operation , characteristics and operating conditions of microgrid with energy storage , provides insight into the benefits of using listed concepts . The first part deals with the description of microgrid systems, distribution and shows examples of its use. The second part describes individual elements of the storage systems, energy production and energy transformation used in microgrids . The third part describes the work with PSCAD software. The main goal is to design a micro grid model in PSCAD and validate its function.

Some communities in remote locations with high wind velocities and an unreliable utility supply, will typically install small diesel powered generators and wind generators to form a microgrid. Over the past few years, microgrid projects have been developed in many parts of the world, and commercial solutions have started to appear. Such systems face specific design issues, especially when the wind penetration is high enough to affect the operation of the diesel plant. The dynamic behavior of a medium penetration hybrid microgrid is investigated. It consists of a diesel generator set, a wind-generator and several loads. The diesel engine drives a 62.5 kVA synchronous generator with excitation control. The fixed-speed wind turbine drives a 60 kW cage rotor induction generator. The microgrid can be connected to the utility grid but can also run as an isolated system. The total load of the microgrid is about 100 kVA which varies during the day, and consists of static and dynamic loads, including an induction motor. The excitation controller and speed controller for the diesel’s synchronous generator are designed, as well as the power control of the wind turbine, and the controller for capacitor banks and dump load. The system is modeled and simulated using PSCAD. The study evaluates how the power generation is shared between the diesel generator set and the wind generator, the voltage regulation during load connections, and discusses the need of battery energy storage, the system ride- through-fault capability and frequency control, particularly at times when the utility is disconnected and the microgrid is run as an independent isolated power system. The results of several case studies are presented.

Nous présentons notre contribution sur la régulation et l’optimisation de la production d’électricité.La première partie concerne l’optimisation de la gestion d’un micro réseau. Nous formulons le programme de gestion comme un problème de commande optimal en temps continu, puis nous résolvons ce problème par programmation dynamique à l’aide d’un solveur développé dans ce but : BocopHJB. Nous montrons que ce type de formulation peut s’étendre à une modélisation stochastique. Nous terminons cette partie par l’algorithme de poids adaptatifs, qui permet une gestion de la batterie du micro réseau intégrant le vieillissement de celle-ci. L’algorithme exploite la structure à deux échelles de temps du problème de commande.La seconde partie concerne des modèles de marchés en réseaux, et en particulier ceux de l’électricité. Nous introduisons un mécanisme d’incitation permettant de diminuer le pouvoir de marché des producteurs d’énergie, au profit du consommateur. Nous étudions quelques propriétés mathématiques des problèmes d’optimisation rencontrés par les agents du marché (producteurs et régulateur). Le dernier chapitre étudie l’existence et l’unicité des équilibres de Nash en stratégies pures d’une classe de jeux Bayésiens à laquelle certains modèles de marchés en réseaux se rattachent. Pour certains cas simples, un algorithme de calcul d’équilibre est proposé.Une annexe rassemble une documentation sur le solveur numérique BocopHJB. / We present our contribution on the optimization and regulation of electricity produc- tion.The first part deals with a microgrid Energy Management System (EMS). We formulate the EMS program as a continuous time optimal control problem and then solve this problem by dynamic programming using BocopHJB, a solver developed for this application. We show that an extension of this formulation to a stochastic setting is possible. The last section of this part introduces the adaptative weights dynamic programming algorithm, an algorithm for optimization problems with different time scales. We use the algorithm to integrate the battery aging in the EMS.The second part is dedicated to network markets, and in particular wholesale electricity markets. We introduce a mechanism to deal with the market power exercised by electricity producers, and thus increase the consumer welfare. Then we study some mathematical properties of the agents’ optimization problems (producers and system operator). In the last chapter, we present some pure Nash equilibrium existence and uniqueness results for a class of Bayesian games to which some networks markets belong. In addition we introduce an algorithm to compute the equilibrium for some specific cases.We provide some additional information on BocopHJB (the numerical solver developed and used in the first part of the thesis) in the appendix.