Design and Power Management of an Offshore Medium Voltage DC Microgrid Realized Through High Voltage Power Electronics Technologies and Control

The growth in the electric power industry’s portfolio of Direct Current (DC) based generation and loads have captured the attention of many leading research institutions. Opportunities for using DC based systems have been explored in electric ship design and have been a proven, reliable solution for transmitting bulk power onshore and offshore. To integrate many of the renewable resources into our existing AC grid, a number of power conversions through power electronics are required to condition the equipment for direct connection. Within the power conversion stages, there is always a requirement to convert to or from DC. The AC microgrid is a conceptual solution proposed for integrating various types of renewable generation resources. The fundamental microgrid requirements include the capability of operating in islanding mode and/or grid connected modes. The technical challenges associated with microgrids include (1) operation modes and transitions that comply with IEEE1547 without extensive custom engineering and (2) control architecture and communication. The Medium Voltage DC (MVDC) architecture, explored by the University of Pittsburgh, can be visualized as a special type of DC microgrid. This dissertation is multi-faceted, focused on many design aspects of an offshore DC microgrid. The focal points of the discussion are focused on optimized high power, high frequency magnetic material performance in electric machines, transformers, and DC/DC power converters – all components found within offshore power system architectures. A new controller design based upon model reference control is proposed and shown to stabilize the electric motor drives (modeled as constant power loads), which serve as the largest power consuming entities in the microgrid. The design and simulation of a state-of-the-art multilevel converter for High Voltage DC (HVDC) is discussed and a component sensitivity analysis on fault current peaks is explored. A power management routine is proposed and evaluated as the DC microgrid is disturbed through various mode transitions. Finally, two communication protocols are described for the microgrid – one to minimize communication overhead inside the microgrid, and another to provide robust and scalable intra-grid communication. The work presented is supported by Asea Brown Boveri (ABB) Corporate Research Center within the Active Grid Infrastructure program, the Advanced Research Project Agency – Energy (ARPA-E) through the Solar ADEPT program, and Mitsubishi Electric Corporation (MELCO)

Projeto de sistemas de controlo auxiliado por computador usando uma abordagem de simulação com hardware-in-the-loop

A forma mais rápida, menos custosa, e segura para avaliar o desempenho de diferentes estratégias de controlo é através de um ambiente virtual simulado em tempo real, capaz de representar de forma fidedigna o comportamento das grandezas físicas que deseja-se controlar. Neste contexto, a técnica de simulação com hardware-in-the-loop (HIL), tem um importante destaque pelo facto de parte do loop de simulação ser composto por modelos puramente virtuais, enquanto as restantes partes consistem em componentes de hardware do sistema físico completo. Nesta dissertação este conceito foi aplicado utilizando como hardware um microcontrolador Arduino UNO, para o desenvolvimento de uma bancada de teste capaz de realizar técnicas de simulação em tempo real, com ênfase em 2 sistemas de atuação muito utilizados a nível industrial: motor de corrente contínua e um cilindro hidráulico de duplo efeito. Com isso, foi desenvolvida uma ferramenta computacional que permite testar o desempenho de diferentes estratégias de controlo em fases iniciais de projeto, e que pode ser facilmente adaptável para outros tipos de sistemas físicos. Para isso, foram desenvolvidos os modelos virtuais destes sistemas a partir da toolbox Simscape, pertencente ao ambiente MatLab/ Simulink, que proporciona uma visão detalhada dos componentes dos sistemas e suas interações. Para validação do conceito da plataforma, foram realizados dois casos de estudo, um para cada modelo criado. No primeiro caso, o modelo foi parametrizado sem a presença do sistema físico completo, através de informações geométricas de componentes mais gerais do sistema, e parâmetros por defeito do Simscape que só poderiam ser obtidos por via experimental. Já o segundo caso de estudo foi realizado usando um método diferente: os parâmetros do modelo foram estimados através do sistema real por métodos de optimização. Após todo o processo de parametrização e desenvolvimento do esquema de controlo, foram então realizados ensaios experimentais, no segundo caso de estudo, para validação das ferramentas assistidas por computador utilizadas neste trabalho.The fastest, cheapest, and safest way to evaluate the performance of different control strategies is through a virtual environment simulated in real time, capable of representing reliably the behavior of the physical quantities that one wishes to control. In this context, the technique of simulation technique with hardware-in-the-loop (HIL), has an important highlight due to the fact that part of the simulation loop is composed of purely virtual models, while the remaining parts consist of hardware components of the complete physical system. In this dissertation this concept was applied using an Arduino UNO microcontroller as hardware, for the development of a test bench capable of performing simulation techniques in real time, with emphasis on 2 actuating systems widely used at industrial level: DC motor and a double acting hydraulic cylinder. With this, a computational tool was developed that allows testing the performance of different control strategies in early design stages, and that can be easily adaptable to other types of physical systems. For this, the virtual models of these systems were developed from the Simscape toolbox, belonging to the MatLab/Simulink environment, which provides a detailed view of the system components and their interactions. To validate the platform concept, two case studies were performed, one for each model created. In the first case, the model was parameterized without the presence of the complete physical system, through geometric information of more general system components, and Simscape default parameters that could only be obtained experimentally. The second case study was performed using a different method: the model parameters were estimated from the real system system by optimization methods. After the whole process of parameterization and development of the control scheme, experimental tests were then performed, in the second case study, to validate the computer-aided tools used in this work.Mestrado em Engenharia Mecânic

Novel Night and Day Control of PV Solar Farm as STATCOM (PV-STATCOM) for Critical Induction Motor Stabilization and FIDVR Alleviation

Induction motors are globally used in several critical operations such as petrochemicals, mining, process control, etc., where their shutdown during faults causes significant financial loss. System faults can also lead to Fault Induced Delayed Voltage Recovery (FIDVR) causing service disruptions. Dynamic reactive power compensators such as SVC and STATCOM are conventionally employed to mitigate these issues, however, these are very expensive. PV solar plants are growing at unprecedented rate globally and are likely to be installed near such critical motors. This thesis presents several novel applications of a patented technology of utilizing PV solar plants, both during night and day, as STATCOM, termed PV-STATCOM, for mitigating above issues at about 50 times lower cost than equivalent-size STATCOMs. A reactive power modulation based PV-STATCOM control is developed to stabilize remotely located motor both during night and day in a realistic distribution feeder, even when reactive power support according to the pioneering German Grid code fails. This control was field demonstrated for first time in Canada (and perhaps in world) on the 10 kW PV solar system in the utility network of Bluewater Power, Sarnia, Ontario. Another novel control strategy based on active and reactive power modulation of PV-STATCOM is developed. MATLAB/PSCAD simulation studies show that the proposed control can stabilize remotely located motor much faster and with reduced real power curtailment than conventional strategies. A new real and reactive power control of PV-STATCOM is proposed to alleviate FIDVR. Electromagnetic Transients simulation studies on a realistic transmission network show that the proposed control on a 100 km remote solar farm can alleviate FIDVR and stabilize a cluster of motors for wide range of system parameters and operating conditions. PV-STATCOM can alleviate the need of local STATCOM for achieving the same objective. Comprehensive sensitivity and stability analysis of single and two distribution level PV-STATCOMs are performed with: i) equivalent and detailed PV-STATCOM model, and ii) PV-STATCOM control implemented at plant level and inverter level. The impact of modeling details, controller location and system parameters on controller interaction, are investigated

Metodología para la detección y localización de faltas en redes de distribución con puesta a tierra activa

pag. var.Esta tesis doctoral define y desarrolla una nueva metodología de detección y localización de faltas monofásicas, de aplicación en redes de distribución en las que se aplique un nuevo sistema de puesta a tierra activo. Esta metodología está basada en la inyección de señales de corriente homopolar, a dos frecuencias diferentes de la frecuencia fundamental, por la puesta a tierra del neutro del sistema. Estas inyecciones son realizadas tanto estando el sistema en situación de prefalta, como estando en situación de falta. Así, para la aplicación del método de detección del feeder en falta propuesto, es necesario determinar el valor de ciertas magnitudes en cada feeder, tanto en la situación de prefalta como en falta. Incluso se ha analizado el caso de que en la subestación a implantar la metodología exista la posibilidad de comunicación entre los equipos de medida y protección de los diferentes feeders, lo que añadiría una mayor fiabilidad en la detección del feeder en falta. Ya establecida la detección del feeder en falta, y conociendo previamente la fase en que se ha producido la misma, la siguiente etapa es proceder a localizar el punto de falta. Para ello, se ha realizado un análisis comparativo de resultados a medida que se modificaba el algoritmo principal, pudiendo observar como los resultados se iban optimizando hasta llegar a la versión definitiva del mismo. La verificación de todo lo anteriormente expuesto ha sido posible mediante la modelización y simulación de una red de distribución real, cuyos datos han sido facilitados por una compañía eléctrica. Dicha modelización ha sido contrastada con datos de flujo de carga facilitados por la propia compañía eléctrica