Modeling, Simulation and Decentralized Control of Islanded Microgrids

Modeling, Simulation and Decentralized Control of Islanded Microgrids by Farideh Doost Mohammadi This thesis develops a comprehensive modular state-space model of microgrids containing inverter-based Distributed Energy Resources (DERs). The model is validated and then used for small signal stability enhancement and voltage and frequency control. State space models of various microgrid elements are first derived, which allow for the inclusion of any possible elements such as current controlled inverters that are missing in the literature. Then a complete state space model is obtained to complement the models that are available in the literature and whose objectives are system analysis only as compared to the purpose of this work which is stability enhancement and control design. Specifically,;1. Small signal stability is enhanced by adding current controlled inverters to the microgrid. 2. Decentralized secondary frequency and voltage control techniques are proposed.;For secondary frequency control purposes, at first, the control strategies of different kinds of inverters and storage devices are described. Then, a novel solution is introduced for islanded microgrids by decomposing the system into virtual control areas.;For the secondary voltage control an Average Consensus Algorithm (ACA) is used and applied on a network of agents which has been chosen optimally based on the required connectivity. The main purpose of the ACA is to keep the average voltage of all the buses at a desired level during islanding. Then another control strategy is proposed to improve the voltage profile. While the average voltage is kept fixed by the voltage controlled inverters, this voltage profile smoothness is obtained by dedicating zones to current controlled inverters and defining their responsibilities based on the location of the loads

Event-triggered distributed MPC for resilient voltage control of an islanded microgrid

This paper addresses the problem of distributed secondary voltage control of an islanded microgrid (MG) from a cyber-physical perspective. An event-triggered distributed model predictive control (DMPC) scheme is designed to regulate the voltage magnitude of each distributed generators (DGs) in order to achieve a better trade-off between the control performance and communication and computation burdens. By using two novel event triggering conditions that can be easily embedded into the DMPC for the application of MG control, the computation and communication burdens are significantly reduced with negligible compromise of control performance. In addition, to reduce the sensor cost and to eliminate the negative effects of non-linearity, an adaptive non-asymptotic observer is utilized to estimate the internal and output signals of each DG. Thanks to the deadbeat observation property, the observer can be applied periodically to cooperate with the DMPC-based voltage regulator. Finally, the effectiveness of the proposed control method has been tested on a simple configuration with 4 DGs and the modified IEEE-13 test system through several representative scenarios

Small signal modeling and analysis of microgrid systems

This dissertation focuses on small-signal modeling and analysis of inverter based microgrid systems. The proposed microgrid consists of two microsources placed on two different buses. The buses are connected using a distribution feeder with some impedance. The proposed microgrid can operate with the grid support, or without the grid support. When operated without the grid support, the standalone system’s microsources participate in controlling the system voltage and frequency. For a non-inertia source, such as the inverter, the load perturbations play an important role in system dynamics. In paper-I, such complex system was studied. In the grid-tied mode, the microsources share the load demand with other sources that are present in the main grid. The control algorithm for such system is much simpler than that of the islanded system. However, when aggregated in multi-bus system, prohibitively higher order state-space models are formed. In paper-II, a reduced order modeling of such systems was considered. Singular perturbation method was applied to identify the two time-scale property of the system. In paper-III, a similar approach was taken to develop a reduced order model of the islanded system that was developed in paper-I. Application of such reduced order models were illustrated by using them to simulate a modified IEEE-37 bus microgrid system. The islanded microgrids system’s stability is characterized in paper-IV by the Markov Jump Linear System Analysis. Conservative bounds on the expected value of the state were determined from a combination of the Markov process parameters, the dynamics of each linear system, and the magnitude of the impulses. The conclusions were verified with the simulation results. --Abstract, page iii

Event-triggered distributed model predictive control for resilient voltage control of an islanded microgrid

This article addresses the problem of distributed secondary voltage control of an islanded microgrid (MG) from a cyber‐physical perspective. An event‐triggered distributed model predictive control (DMPC) scheme is designed to regulate the voltage magnitude of each distributed generators (DGs) in order to achieve a better trade‐off between the control performance and communication and computation burdens. By using two novel event triggering conditions that can be easily embedded into the DMPC for the application of MG control, the computation and communication burdens are significantly reduced with negligible compromise of control performance. In addition, to reduce the sensor cost and to eliminate the negative effects of nonlinearity, an adaptive nonasymptotic observer is utilized to estimate the internal and output signals of each DG. Thanks to the deadbeat observation property, the observer can be applied periodically to cooperate with the DMPC‐based voltage regulator. Finally, the effectiveness of the proposed control method has been tested on a simple configuration with four DGs and the modified IEEE‐13 test system through several representative scenarios

Resilience-oriented control and communication framework for cyber-physical microgrids

Climate change drives the energy supply transition from traditional fossil fuel-based power generation to renewable energy resources. This transition has been widely recognised as one of the most significant developing pathways promoting the decarbonisation process toward a zero-carbon and sustainable society. Rapidly developing renewables gradually dominate energy systems and promote the current energy supply system towards decentralisation and digitisation. The manifestation of decentralisation is at massive dispatchable energy resources, while the digitisation features strong cohesion and coherence between electrical power technologies and information and communication technologies (ICT). Massive dispatchable physical devices and cyber components are interdependent and coupled tightly as a cyber-physical energy supply system, while this cyber-physical energy supply system currently faces an increase of extreme weather (e.g., earthquake, flooding) and cyber-contingencies (e.g., cyberattacks) in the frequency, intensity, and duration. Hence, one major challenge is to find an appropriate cyber-physical solution to accommodate increasing renewables while enhancing power supply resilience. The main focus of this thesis is to blend centralised and decentralised frameworks to propose a collaboratively centralised-and-decentralised resilient control framework for energy systems i.e., networked microgrids (MGs) that can operate optimally in the normal condition while can mitigate simultaneous cyber-physical contingencies in the extreme condition. To achieve this, we investigate the concept of "cyber-physical resilience" including four phases, namely prevention/upgrade, resistance, adaption/mitigation, and recovery. Throughout these stages, we tackle different cyber-physical challenges under the concept of microgrid ranging from a centralised-to-decentralised transitional control framework coping with cyber-physical out of service, a cyber-resilient distributed control methodology for networked MGs, a UAV assisted post-contingency cyber-physical service restoration, to a fast-convergent distributed dynamic state estimation algorithm for a class of interconnected systems.Open Acces

Smart PIN: performance and cost-oriented context-aware personal information network

The next generation of networks will involve interconnection of heterogeneous individual networks such as WPAN, WLAN, WMAN and Cellular network, adopting the IP as common infrastructural protocol and providing virtually always-connected network. Furthermore, there are many devices which enable easy acquisition and storage of information as pictures, movies, emails, etc. Therefore, the information overload and divergent content’s characteristics make it difficult for users to handle their data in manual way. Consequently, there is a need for personalised automatic services which would enable data exchange across heterogeneous network and devices. To support these personalised services, user centric approaches for data delivery across the heterogeneous network are also required. In this context, this thesis proposes Smart PIN - a novel performance and cost-oriented context-aware Personal Information Network. Smart PIN's architecture is detailed including its network, service and management components. Within the service component, two novel schemes for efficient delivery of context and content data are proposed: Multimedia Data Replication Scheme (MDRS) and Quality-oriented Algorithm for Multiple-source Multimedia Delivery (QAMMD). MDRS supports efficient data accessibility among distributed devices using data replication which is based on a utility function and a minimum data set. QAMMD employs a buffer underflow avoidance scheme for streaming, which achieves high multimedia quality without content adaptation to network conditions. Simulation models for MDRS and QAMMD were built which are based on various heterogeneous network scenarios. Additionally a multiple-source streaming based on QAMMS was implemented as a prototype and tested in an emulated network environment. Comparative tests show that MDRS and QAMMD perform significantly better than other approaches

Plataforma de gestão para sistemas de transportes cooperativos

The rapid evolution of technology led to increased research in domains such as smart devices. As a result, the Internet of Things technology has expanded rapidly and is being used to solve challenges needing vast quantities of data from many devices. With this, the Smart City concept became more popular with the goal of establishing a healthy ecosystem in which the functioning of the city is enhanced. The European Commission subsequently adopted Cooperative Intelligent Transport Systems (C-ITS), which enables road users and traffic controllers to share information and coordinate their actions. In addition, the Institute of Telecommunications (IT) group has placed and continues to install Road Side Units (RSUs) on Portuguese roads. These intelligent devices may have radars, cameras, or other elements that aid in determining traffic patterns. This dissertation emerges in the context of offering a C-ITS platform capable of addressing the demands of IT researchers and delivering feedback to them and regular road users on traffic behavior or alerts. For the development of a proof-of-concept system, a user-centered design approach was adopted, beginning with the identification of target users and the collection of key requirements generated from usage scenarios. The developed system implemented a micro-service architecture. The proof-of-concept is composed by several modules responsible for handling the camera stream, admin privileges, radars data, creation of alerts and several streams of data. The presented system showed to be capable of providing useful information to the users and administrators. By using the developed platform, users may see a collection of information as charts, interact with the RSUs installed on the roadways, generate and display alerts, and interact with the camera’s live stream.A rápida evolução da tecnologia levou ao aumento da investigação em domínios como dispositivos inteligentes. Como resultado, a tecnologia da Internet of Things tem-se expandido rapidamente e está a ser usada para resolver desafios que necessitam de vastas quantidades de dados de muitos dispositivos. Com isto, o conceito de Cidades Inteligentes começou a ficar mais popular tendo por objetivo estabelecer um ecosistema saudável em que o funcionamento da cidade é melhorado. A Comissão Europeia adotou posteriormente os Sistemas Inteligentes de Transporte Cooperativos (C-ITS), o que permite aos utilizadores de estrada e controladores de tráfego partilhar informações e coordenar as suas ações. Mais adiante, o grupo do Instituto de Telecomunicações (IT) colocou e continua a instalar infraestrutura de comunicações (RSUs) nas estradas portuguesas. Estes dispositivos inteligentes podem ter radares, câmaras ou outros elementos acoplados que ajudam a determinar os padrões de tráfego. Esta dissertação surge no contexto de oferecer uma plataforma C-ITS capaz de atender às necessidades dos investigadores do IT e fornecer-lhes feedback bem como aos utilizadores regulares de estrada sobre o comportamento ou alertas do tráfego. Para o desenvolvimento de um sistema como prova de conceito, uma abordagem centrada no utilizador foi adotada, começando com a identificação dos utilizadores alvo e a recolha de requisitos-chave gerados a partir de cenários de uso. O sistema desenvolvido implementou uma arquitetura baseada em micro-serviços, composto por vários módulos responsáveis por manipular o fluxo de câmaras, privilégios de administrador, dados de radares, criação de alertas e diversos fluxos de dados. O sistema apresentado mostrou-se capaz de fornecer informações úteis aos utilizadores e administradores. Através da utilização da plataforma desenvolvida, os utilizadores podem ver um conjunto de informações como gráficos, interagir com as RSUs instaladas nas rodovias, gerar e exibir alertas e interagir com a transmissão ao vivo da câmara.Mestrado em Engenharia de Computadores e Telemátic