Protection and fault management in active distribution systems

The integration of renewable energy resources (RES), as a type of distributed generation (OG) units, is increasing in distribution, systems. This integration, changes the topology, performance and the operational aspects of conventional distribution systems. Protection is one of the main issues that are affected after the high penetration of OGs. Therefore, new protection methods are necessary to guarantee the safety and the reliability of active distribution systems. On the other hand, most RESs are interfaced with the AC grids through power-electronic devices. These interfaces consist of at least one AC/DC conversion units. Hence, using OC distribution systems can contribute to the loss/cost reduction, as some power conversion stages are eliminated. Enhancement in system stability, reduction of power losses, and power quality 1 improvement are other advantages of OC networks. For these reasons as well as the simple integration of electronic loads that are supplied by OC power, the concept of OC distribution systems has attracted a considerable attention over the last years. In 1 fact, MVOC and LVDC grids can be an important part of the future distribution systems. Furthermore, AC and OC system can contribute to construct hybrid AC/DC distribution systems. According to these significant changes in the distribution systems, it is necessary to modify the algorithm of existing protection methods or to propose new protection schemes for both active AC and OC distribution systems. Moreover, in conventional distribution systems, loads are supplied by upstream grid, i.e. transmission lines; therefore, when a fault impacts the upstream grid and the faulty part disconnected by the protection system, all loads connected to distribution systems are disconnected as well. However, in active distribution systems, DGs can support the on-outage zones if the grid equipped with an appropriate fault management system. Therefore, automatic self-healing methods can increase the network reliability and power supply continuity. To provide the self-healing capability, distribution grids should be equipped with adequate algorithms that are able to guarantee the continuous and optima! operation for the isolated section of the grid. In this thesis, differences between protection issues in OC and AC systems are investigated and analyzed. Then, based on this analyze, effective protection and fault management methods are presented far OC distribution systems and microgrids. In the other part of this thesis, a fault management and self-healing algorithm is proposed far active distribution systems. The proposed methods have been evaluated by the hardware-in-the-loop approach using real-time simulators and suitable controllers.La creciente integración de recursos energéticos renovables en el sistema eléctrico ha propiciado el aumento de sistemas de generación distribuida (DG) en los sistemas de distribución. Esta integración,influye en la topologla, el rendimiento y los aspectos operacionales de los sistemas de distribución convencionales. Su impacto sobre los sistemas de protección es uno de los principales problemas que se derivan de la alta penetración de DG. Por ese motivo es preciso diseñar nuevos métodos y sistemas de protección que sean capaces de garantizar la seguridad y la fiabilidad de los sistemas de distribución activos. Por otro lado, la mayoria de sistemas de generación basados en renovables están interconectados con la red de AC a través de convertidores electrónicos de potencia.Estas interfaces consisten en unidades de conversión DC/AC. Por lo tanto, el uso de sistemas de distribución de corriente continua puede contribuir a la reducción de las pérdidas/ costes, ya que algunas etapas de conversión de energía pueden ser eliminadas. La mejora en la estabilidad del sistema, la reducción de las pérdidas de energía,y la mejora la calidad de energía son otras de las ventajas que las redes de corriente continua pueden ofrecer. Por estos motivos, junto con la fácil integración de cargas electrónicas alimentadas en OC, el concepto de sistemas de distribución en OC ha atraido una considerable atención en los últimos anos. De hecho, los sistemas MVDC y las redes LVDC están llamados a ser una parte importante delos sistemas de distribución y transmisión en el futuro. Además, los sistemas de conversión OC y AC pueden contribuir a la construcción de sistemas de distribución de AC I DC híbridos. De acuerdo con estos cambios, significativos en los sistemas de distribución, es necesario modificar el algoritmo y los métodos de protección existentes y proponer nuevos esquemas de protección tanto para los sistemas de distribución en AC como para los de OC. Por otra parte, en los sistemas de distribución convencionales, las cargas son alimentadas por la red aguas arriba, es decir;por las lineas de transmisión; Por lo tanto, cuando una falta se produce en la red aguas arriba la parte defectuosa es desconectada por el sistema de protección, asimismo todas las cargas conectadas a los sistemas de distribución se desconectan también. Sin embargo, en los sistemas de distribución activos, los sistemas DG pueden soportar las zonas de no disponibilidad si la red está equipada con un sistema de gestión de fallos. Por lo tanto, los métodos automáticos de 'self-healing' pueden contribuir a aumentar la continuidad y la fiabilidad del suministro en ta red. Para proporcionar la capacidad de 'self-healing', las redes de distribución deben estar equipadas con algoritmos adecuados que sean capaces de garantizar el funcionamiento continuo y óptimo para la sección aislada de la red. En esta tesis, las diferencias entre tas protecciones para sistemas de OC y CA son investigadas y analizadas. Luego, en base a este analísis, se presentarán los métodos de protección y gestión de fallos adecuados para los sistemas y microrredes de distribución OC. En la otra parte de esta tesis, se propone un algoritmo de gestión de fallos y 'self-healing ' para sistemas de distribución activos. Para validar los métodos propuestos se ha trabajado con plataformas hardware-in­ the-loop avanzado utilizando simuladores en tiempo real y controladores trabajando en base a plataformas de control reales

Role of control, communication, and markets in smart building operation

This thesis explores the role of control, communication, and markets in the operation of smart buildings and microgrids. It develops models to study demand response (DR) alternatives in smart buildings using different communication and control protocols in building management systems. Moreover, it aims at understanding the extent to which smart buildings can provide regulation service reserves (RSR) by real time direct load control (DLC) or price-based indirect control approaches. In conducting a formal study of these problems, we first investigate the optimal operational performance of smart buildings using a control protocol called packetized direct load control (PDLC). This is based on the notion of the energy packet which is a temporal quantization of energy supplied to an appliance or appliance pool by a smart building operator (SBO). This control protocol is built on top of two communication protocols that carry either complete or binary information regarding the operation status of the appliances in the pool. We discuss the optimal demand side operation for both protocols and analytically derive the performance differences between them. We analyze the costs of renewable penetration to the system's real time operation. In order to strike a balance between excessive day-ahead energy reservation costs and stochastic real time operation costs, we propose an optimal reservation strategy for traditional and renewable energy for the PDLC in both the day-ahead and the real time markets to hedge the uncertainty of real time energy prices and renewable energy realization. The second part of the thesis proposes systematic approaches for smart buildings to reliably participate in power reserve markets. The problem is decomposed into two parts in the first of which the SBO starts by estimating its prior capacity of reserve provision based on characteristics of the building, the loads, and consumer preferences. We show that the building's reserve capacity is governed by a few parameters and that there is a trade off for smart buildings to provide either sustained reserve or ramping reserve. Based on the estimated capacity, we propose two real time control mechanisms to provide reliable RSR. The first is a DLC framework wherein consumers allow the SBO to directly modulate their appliances' set points within allowable ranges. We develop a feedback controller to guarantee asymptotic tracking performance of the smart building's aggregated response to the RSR signal. The second is a price controlled framework that allows consumers to voluntarily connect and consume electricity based on their instantaneous utility needs. Consumers' time varying dynamic preferences in providing RSR are studied by Monte Carlo simulation, in which such preferences are characterized by sufficient statistics that can be used in a stochastic dynamic programming (DP) formulation to solve for the optimal pricing policy

IoT Supervised PV-HVDC Combined Wide Area Power Network Security Scheme Using Wavelet-Neuro Analysis

Power system networks are one of the most widely used methods in the real world for trans- ferring large amounts of electrical energy from one location to another. At present, High Voltage Direct Current Transmission is preferred for long distances over hundreds of miles due to minimal power loss and transmission cost of transmission.Due to an increase in power demand, integration of renewable sources to minimise the voltage uctuations and compensate for power loss is necessary. This is a mandatory re- quirement to produce sophisticated protection methods for mainly smart systems under various balanced and unbalanced fault conditions. The system protection scheme must respond as quickly as possible to protect the connected devices in a smart environment. The network must be monitored and protected under var- ious weather conditions as well as electrical paramet- ric problems. The proposed research work is carried on the basis of physical monitoring with the aid of the Internet-of-Things and electrical parameters cali- brated with the help of wavelet analysis. A wavelet is a mathematical tool to investigate the behaviour of transient signals at di erent frequencies, which pro- vides important information related to the detailed analysis of faults in power networks. The ma- jor goals of this research are to analyse faults us- ing detailed coe cients of current signals through the bior-1.5 mother wavelet for fault identi cation and arti cial neural network analysis for fault localiza- tion. This proposed approach furnishes an IoT su- pervised Photovoltaic - High Voltage Direct Current (HVDC) combined wide area power network secu- rity scheme using wavelet detailed coe cients under various types of faults with Fault-Inception-Angles