Expansion planning of power distribution systems considering reliability : a comprehensive review

One of the big concerns when planning the expansion of power distribution systems (PDS) is reliability. This is defined as the ability to continuously meet the load demand of consumers in terms of quantity and quality. In a scenario in which consumers increasingly demand high supply quality, including few interruptions and continuity, it becomes essential to consider reliability indices in models used to plan PDS. The inclusion of reliability in optimization models is a challenge, given the need to estimate failure rates for the network and devices. Such failure rates depend on the specific characteristics of a feeder. In this context, this paper discusses the main reliability indices, followed by a comprehensive survey of the methods and models used to solve the optimal expansion planning of PDS considering reliability criteria. Emphasis is also placed on comparing the main features and contributions of each article, aiming to provide a handy resource for researchers. The comparison includes the decision variables and reliability indices considered in each reviewed article, which can be used as a guide to applying the most suitable method according to the requisites of the system. In addition, each paper is classified according to the optimization method, objective type (single or multiobjective), and the number of stages. Finally, we discuss future research trends concerning the inclusion of reliability in PDS expansion planning

On the explicit formulation of reliability assessment of distribution systems with unknown network topology: Incorporation of DG, switching interruptions, and customer-interruption quantification

This paper presents an original approach for the evaluation of reliability of active distribution networks with unknown topology. Built upon novel reformulations of conventional definitions for distribution reliability indices, the dependence of system-oriented reliability metrics on network topology is explicitly formulated using a set of mixed-integer linear expressions. Unlike previously reported works also modeling mathematically the relationship between reliability assessment and network topology, the proposed approach allows considering the impact of distributed generation (DG) while accounting for switching interruptions. Moreover, for the first time in the emerging closely related literature, the nonlinearity and nonconvexity of the customer average interruption duration index are precisely characterized. The proposed mixed-integer linear model is suitable for various distribution optimization problems in which the operational topology of the network is not specified a priori. Aiming to exemplify its potential applicability, the proposed formulation is incorporated into a distribution reconfiguration optimization problem. The effectiveness and practicality of the proposed approach are numerically illustrated using various test networks.Este artículo presenta un enfoque original para la evaluación de la confiabilidad de redes de distribución activas con topología desconocida. Basada en reformulaciones novedosas de definiciones convencionales para índices de confiabilidad de distribución, la dependencia de las métricas de confiabilidad orientadas al sistema en la topología de la red se formula explícitamente mediante un conjunto de expresiones lineales de enteros mixtos. A diferencia de los trabajos informados anteriormente que también modelan matemáticamente la relación entre la evaluación de la confiabilidad y la topología de la red, el enfoque propuesto permite considerar el impacto de la generación distribuida .(DG) teniendo en cuenta las interrupciones de conmutación. Además, por primera vez en la literatura emergente estrechamente relacionada, la no linealidad y la no convexidad del índice de duración promedio de interrupción del cliente se caracterizan con precisión. El modelo lineal entero mixto propuesto es adecuado para varios problemas de optimización de distribución en los que la topología operativa de la red no se especifica a priori. Con el objetivo de ejemplificar su aplicabilidad potencial, la formulación propuesta se incorpora a un problema de optimización de reconfiguración de distribución. La eficacia y la practicidad del enfoque propuesto se ilustran numéricamente utilizando varias redes de prueba

A Novel Feeder-level Microgrid Unit Commitment Algorithm Considering Cold-load Pickup, Phase Balancing, and Reconfiguration

This paper presents a novel 2-stage microgrid unit commitment (Microgrid-UC) algorithm considering cold-load pickup (CLPU) effects, three-phase load balancing requirements, and feasible reconfiguration options. Microgrid-UC schedules the operation of switches, generators, battery energy storage systems, and demand response resources to supply 3-phase unbalanced loads in an islanded microgrid for multiple days. A performance-based CLPU model is developed to estimate additional energy needs of CLPU so that CLPU can be formulated into the traditional 2-stage UC scheduling process. A per-phase demand response budget term is added to the 1st stage UC objective function to meet 3-phase load unbalance limits. To reduce computational complexity in the 1st stage UC, we replace the spanning tree method with a feasible reconfiguration topology list method. The proposed algorithm is developed on a modified IEEE 123-bus system and tested on the real-time simulation testbed using actual load and PV data. Simulation results show that Microgrid-UC successfully accounts for CLPU, phase imbalance, and feeder reconfiguration requirements.Comment: 10 pages, submitted to IEEE Transactions on Smart Gri

Dynamic Distribution System Reconfiguration to Improve System Reliability Considering Renewables and Energy Storage

O desenvolvimento económico e o crescente uso de novas tecnologias por parte dos consumidores fazem com que o fornecimento de energia, bem como a sua qualidade, se tornem uma séria preocupação. Uma forma de abordar essa preocupação é implementando sistemas de distribuição automatizados com tecnologias inteligentes para melhorar a fiabilidade e a eficiência da operação de sistema. Os sistema eléctricos actuais estão em evolução devido às novas funcionalidades que o sistema eléctrico deverá ter, nomeadamente a integração de fontes de energia renováveis em grande escala, a integração de veículos eléctricos, a implementação de tecnologias de redes inteligentes, entre outras. Neste cenário, os Sistemas de Distribuição Inteligentes (SDI) devem operar e restaurar o serviço interrompido aos consumidores. Para que o sistema ganhe esta capacidade, é necessário substituir os interruptores manuais por interruptores controlados de forma remota, melhorando a capacidade de restauração do sistema tendo em vista a implementação de redes inteligentes. Este trabalho tem como objectivo desenvolver um novo modelo, determinando o conjunto mínimo de interruptores a substituir para automatizar o sistema, juntamente com uma análise de sensibilidade sobre a posição dos novos interruptores, que podem ser colocados no mesmo local dos substituídos ou num novo local. A optimização do sistema é feita considerando a integração de fontes de energia renováveis na rede e sistemas de armazenamento de energia, simultaneamente com os requisitos económicos e funcionais do sistema. A ferramenta computacional é testada usando o sistema de teste IEEE 119 Bus, onde são considerados vários tipos de carga (residencial, comercial e industrial).The economic development and the use of more and more technologies by the consumers make the constant energy supply and quality become a critical concern. One way to address this concern is through the implementation of automated distribution systems with intelligent technologies to improve the systems reliability and efficiency in operation. The present electrical systems are evolving due to the new functionalities that the electrical system are expected to have, namely the integration of renewable energy sources in large-scale, the integration of electric vehicles, enable smart grid technologies, among others. In this scenario, Distributed Smart Systems (DSS) should operate and restore discontinued service to consumers. In order to the system gain theses ability is necessary replace the manual switches for remotely controlled switches, improving the system restoration capability having in view the Smart Grids implementation. This paper aims to develop a new model, determining the minimal set of switches to replace in order to automate the system, along with a senility analysis on the position of the new switches, whether it should be placed in the same place as the manual switch or in a new location. The optimization of the system is made considering the renewable energy sources integration in the grid, energy storage systems simultaneously with the economic and functional requirements of the system, in order to improve the system reliability. The computational tool is tested using the IEEE 119 Bus test system to validate the new tool, where different types of load are considered (residential, commercial and industrial)

A framework for reliability assessment in expansion planning of power distribution systems

This work proposes a framework that utilizes a method of analytical assessment of reliability to guide the expansion planning of power distribution systems (PDS) considering reliability criteria. The framework allows the estimation of reliability indices with and without the execution of expansion projects, thus supporting the decision-making process on investments in expansion projects. In the analytical assessment of reliability, failure rates of zones and restoration times are calculated from past data of interruptions in the primary distribution network. Additionally, the estimated reliability indices are adjusted to historical values through failure rates proportionate to the length of each zone. To test and validate the proposed framework, it was applied to a distribution network of the Roy Billinton Test System (RBTS). To validate the framework with real data of interruptions, two case studies were developed, one using a primary distribution feeder and another using a large-scale primary distribution network, both located in Southern Brazil. The results indicated that the proposed framework could help find the most attractive investments leading to improvements in reliability indices and reduction in unsupplied energy. This work formulates the impact of those alternatives of expansion that most affect reliability, namely: (i) the installation of normally closed sectionalizing switches, (ii) the installation of normally open switches with interconnection to adjacent feeders, (iii) the replacement of manual switches by remote controlled switches, and (iv) the replacement of existing bare overhead conductors by covered conductors. Nevertheless, the proposed framework allows the inclusion of other expansion alternatives. The computational performance of the adjustment processes of the estimated indices to the historical indices was evaluated for different reliability parameters, proving convergence and advantages for the chosen parameters. Finally, the proposed framework proved to be practical and useful for real-life applications by power distribution companies.Este trabalho propõe um framework que utiliza a avaliação analítica da confiabilidade para orientar o planejamento da expansão de sistemas de distribuição considerando critérios de confiabilidade. O framework proposto permite estimar indicadores de confiabilidade com e sem a execução de projetos de expansão, auxiliando assim a tomada de decisão sobre investimentos em projetos de expansão. Na avaliação analítica da confiabilidade, as taxas de falhas das zonas e os tempos de restabelecimento são calculados a partir de dados históricos de interrupções na rede de distribuição primária. Além disso, os indicadores de confiabilidade estimados são ajustados a valores históricos por meio de taxas de falhas proporcionais ao comprimento de cada zona. Para testar e validar o framework proposto, ele foi aplicado à uma rede de distribuição do Roy Billinton Test System (RBTS). Para validar o framework com dados reais de interrupções, foram desenvolvidos dois estudos de caso reais, um com um alimentador de distribuição primário e outro com um conjunto de oito alimentadores de distribuição primários de uma subestação, ambos localizados na região Sul do Brasil. Os resultados indicaram que o framework proposto pode ajudar a definir os investimentos mais atrativos levando a melhorias nos indicadores de confiabilidade e redução de energia não fornecida. Neste trabalho foi formulado o impacto das alternativas de expansão que mais afetam a confiabilidade: (i) a instalação de chaves de seccionamento normalmente fechadas (ii) a instalação de chaves normalmente abertas com interligação com alimentadores adjacentes, (iii) a substituição de chaves manuais por chaves telecomandadas, e (iv) a substituição de condutores aéreos nus de média tensão por condutores protegidos. No entanto, devido à flexibilidade do framework proposto, este permite a inclusão de outras alternativas de expansão que impactam na confiabilidade. O desempenho computacional dos processos de ajuste dos indicadores estimados aos indicadores históricos do framework foi avaliado para diferentes parâmetros de confiabilidade, provando a convergência e vantagens dos parâmetros escolhidos. Finalmente, o framework proposto provou ser prático e útil para aplicações reais por empresas de distribuição de energia

Reward-Penalty Scheme for Power Distribution Companies

In this research, we propose three Reward-Penalty algorithms, to improve the reliability of power distribution companies. The significance of this research, lies in encouraging power distribution companies, to maintain, or even improve, customer service and satisfaction, by developing the Performance Regulatory Reward-Penalty models. These models are designed to place little administrative burden, on either the regulators, or the power distribution companies, whilst providing valuable information, which will prevent degradation of service reliability

Distributed Power Generation Scheduling, Modelling and Expansion Planning

Distributed generation is becoming more important in electrical power systems due to the decentralization of energy production. Within this new paradigm, new approaches for the operation and planning of distributed power generation are yet to be explored. This book deals with distributed energy resources, such as renewable-based distributed generators and energy storage units, among others, considering their operation, scheduling, and planning. Moreover, other interesting aspects such as demand response, electric vehicles, aggregators, and microgrid are also analyzed. All these aspects constitute a new paradigm that is explored in this Special Issue

A framework for reliability assessment in expansion planning of power distribution systems

This article proposes a framework that uses analytical assessment of reliability to guide the expansion planning of power distribution systems (PDS) considering reliability criteria. The framework allows the estimation of reliability indices with and without the execution of expansion projects, thus supporting the decision-making process on investments in expansion projects. In the analytical assessment of reliability, failure rates of zones and restoration times are calculated from past data of interruptions in the primary distribution network. In addition, the estimated reliability indices are adjusted to historical values through failure rates proportionate to the length of each zone. To test and validate the proposed framework, it was applied to the distribution network at bus 5 of the Roy Billinton Test System (RBTS) and also to a real distribution feeder located in Brazil. The results indicated that the proposed framework can help define the most attractive investments leading to improvements in reliability indices and reduction in unsupplied energy. The estimation of reliability indices and energy not supplied, considered the following expansion alternatives: (i) the installation of normally-closed sectionalizing switches, (ii) the installation of normally-open switches with interconnection to adjacent feeders, (iii) the automation of switches, and (iv) the reconductoring of zones of the primary distribution network. Nevertheless, the proposed framework allows the inclusion of other expansion alternatives. Finally, the proposed framework proved to be handy and useful for real-life applications