Robust Control of Power System Frequency Regulation in Islanded Microgrids

This paper reviews the work in the areas of robust control strategies for power system frequency regulation in islanded microgrids. One study delves into the challenges of accurate power sharing and voltage regulation in multi-feeder microgrid systems. It introduces an enhanced resilient control strategy that views the regulation and power balancing as a quadratic optimization problem. This strategy employs an impedance estimator and an optimal controller, focusing on voltage magnitude information transfer at each inverter’s controller. The approach is designed to be computationally efficient, especially for micro-networks with a large number of load feeders. Another area of focus is the development of a generalized central power management system and a decentralized, robust control strategy for autonomous operation of microgrids with multiple distributed energy resource (DER) units. These DER units, categorized into voltage-controlled and power-controlled units, operate based on independent internal oscillators synchronized by a GPS-based timereference signal. The power management system sets power and voltage points for each DER unit’s local controllers. A robust decentralized control system ensures fast tracking, zero steady-state error, and resilience against microgrid uncertainties. The performance of these strategies is validated through various simulation platforms and hardware-in-the-loop studies

Controle secundário aliado ao corte de carga para microrredes em condições operativas de ilhamento

The evolution of current electrical systems is notorious when compared in the last years. This evolution is mainly due to the emergence of the smart-grids concept, giving increased access to the penetration of distributed resources at the level of energy distribution. In this context, microgrids are increasingly emerging as a potential solution to combine reliability, quality, and sustainability in the supply of electricity. Since there is a possibility of a microgrid operates in isolation from the main network, special attention should be given to this issue. In this way, the MGCC plays a vital role in the survival of the system, managing all the resources of the agents to guarantee safe operation and within the standards of supply demanded by the regulatory agencies. In this Ph.D. thesis, the whole theoretical basis of microgrids is presented, giving evidence mainly to the problem of islanding regarding the variation of demand, which in many cases, can cause a point of operation unfeasible due to the inherent variability of demand. To correct the operation, a unified secondary voltage and frequency control strategy in the process of power flow convergence is proposed. In addition, taking into account the limitation of the available resources, the load shedding becomes an emergency approach, preserving the operation limits and the continuity in the supply of electricity to essential services. Finally, an analysis within the concept of voltage stability is also presented with the purpose of assisting in decision making. This analysis shows the relation of the degree of system supportability related to the converters operation mode and their generation limits, both in the connected and islanded systems operation. The results from the tools proposed here are validated and discussed based on the IEEE 37-Nodes Test Feeder system, when modifications are made to make it equivalent to a micro network. Thus, in an islanding scenario, it is expected that MGCC with the tools developed here will be to manage all resources by predicting demand variability and before the system experiences any non-feasible operating point, regardless of the load and penetration scenario. renewable resourcesÉ notória a evolução dos sistemas elétricos atuais quando comparado aos dos últimos anos. Tal evolução deve-se principalmente ao surgimento do conceito de smart-grids, dando cada vez mais abertura à penetração de recursos distribuídos ao nível de distribuição de energia. Nesse contexto, as microrredes vêm surgindo como uma potencial solução para aliar confiabilidade, qualidade e sustentabilidade no fornecimento de energia elétrica. Dada a possibilidade de uma microrrede operar de forma isolada da rede principal, especial atenção deve ser dada a esse quesito. Portanto, o MicroGrid Central Controller (MGCC) exerce papel fundamental na sobrevivência do sistema, gerenciando todos os recursos e agentes de modo a garantir uma operação segura e dentro dos padrões de fornecimento exigidos pelas agências regulatórias. Nesta tese de doutorado, toda a fundamentação teórica de microrredes é apresentada, dando evidência principalmente ao problema do ilhamento quanto à variação de demanda, o que em muitos casos, pode ocasionar um ponto de operação não factível. No intuito de corrigir a operação, uma estratégia de controle secundário unificado de tensão e frequência no processo de convergência do fluxo de potência é proposta. Ainda, prevendo a limitação dos recursos disponíveis, o corte de carga se torna uma medida emergencial, levando em consideração para isso os limites operativos e a continuidade no suprimento de energia elétrica a serviços essenciais. Por fim, uma análise dentro do conceito de estabilidade de tensão também é apresentada com o intuito de auxiliar em uma tomada de decisão. Tal análise mostra a relação do grau de suportabilidade do sistema com o modo operativo dos conversores e seus limites de geração, tanto para a operação conectada quanto ilhada. Os resultados provenientes das ferramentas aqui propostas são validados e discutidos tendo como base o sistema IEEE 37-Nodes Test Feeder, quando modificações são feitas de modo a torná-lo equivalente a uma microrrede. Assim, espera-se que em um cenário de ilhamento, o MGCC com as ferramentas aqui desenvolvidas seja capaz de gerenciar os recursos prevendo a variabilidade da demanda e antes que o sistema experimente qualquer ponto operativo não factível, independente do cenário de carga e penetração de recursos renováveis

Arquitecturas hardware avanzadas para el control de micro-redes eléctricas

El objetivo principal del presente trabajo es el diseño, implementación y evaluación de una plataforma de comunicaciones y de control para micro-redes eléctricas basado en un sistema Multi-Processor Systemon- Chip (MPSoC). Los motivos fundamentales que justifican la utilización de estos dispositivos son la gran capacidad de cómputo, el alto grado de paralelismo y la flexibilidad para adaptarse a las múltiples topologías de convertidores de potencia presentes en las micro-redes actuales. La solución planteada se basa en el desarrollo de un sistema con una arquitectura Asymmetric Multi-Processing (AMP) que proporcione la heterogeneidad necesaria para el exigente control agregado de todos los elementos, así como la introducción del concepto de virtualización para la integración de una pila software que permita una abstracción hardware y un mecanismo de aislamiento entre las tareas críticas y no críticas en los diferentes niveles de control. La plataforma propuesta se ha evaluado sobre un convertidor real Back-to-Back (B2B) de 700 kVA actuando como un sistema de emulación de red para ensayos de certificación.The main objective of this work is the design, implementation and evaluation of a communications and control platform for electrical microgrids based on Multi-Processor System-on-Chip (MPSoC). The fundamental reasons that justify the use of these devices are the high computing capacity, the high degree of parallelism and the flexibility to adapt to the multiple topologies of power electronics converters present in today’s micro-grids. The proposed solution is based on the development of a system with an Asymmetric Multi-Processing (AMP) architecture that provides the necessary heterogeneity for the demanding aggregate control of all systems, as well as the introduction of the virtualization concept for the integration of a software stack that allow a hardware abstraction and an isolation mechanism between critical and non-critical tasks at different levels of control. The proposed platform has been evaluated on a real 700 kVA Back-to-Back (B2B) converter acting as a network emulation system for certification tests.Máster Universitario en Ingeniería de Telecomunicación (M125