• Energy Research

In this paper a new Software-in-the-Loop (SIL) strategy is proposed for real-time testing of Coordinated Volt/VAr Control (CVVC), through the use of the Real-Time Digital Simulator (RTDS) and Matlab® program. Such a strategy seeks to emulate, during the test, the interaction commonly established among the main layers of a Distribution Management System (DMS). To do so, a TCP/IP (Transmission Control Protocol/Internet Protocol)-based communication between the simulation module of the RTDS (RSCAD) and Matlab® is established. To prove the efficiency of the SIL strategy, an optimization technique based on Artificial Immune Systems is applied to deal with the problem of optimal CVVC in radial Distribution Networks (DNs) composed of multiple control equipment. Important aspects associated with the implementation of the test bed are discussed in this paper. Simulation results demonstrated that the proposed strategy is suited to analyzing the time domain behavior of CVVC designed for real-time operation in DNs.

Distributed energy resources have been increasingly integrated into electrical grids. Consequently, electricity markets are expected to undergo changes and become more complex. However, while there are many scientific publications on the topic, a broader discussion is still necessary. Therefore, a systematic literature review on electricity markets in the context of distributed energy resources integration was conducted in this paper to present in-depth discussions on the topic, along with shedding light on current perspectives, the most relevant sources, authors, papers, countries, metrics, and indexes. The software R and its open-source tool Bibliometrix were used to perform the systematic literature review based on the widely recognized databases Web of Science and Scopus, which led to a total of 1685 articles after removing duplicates. The results demonstrate that demand response, renewable energy, uncertainty, optimization, and smart grid are the most-used keywords. By assessing highly impactful articles on the theme, emphasis on energy storage systems becomes clear compared to distributed generation and electric vehicles. However, electric vehicles draw attention in terms of citations. Furthermore, multi-level stochastic programming is the most-applied methodology among highly impactful articles. Due to the relevance of the demand response keyword, this paper also conducts a specific review on the topic aligned with electricity markets and distributed energy resources (296 articles). The results demonstrate that virtually all high-impact publications on the topic address day-ahead or real-time pricing. Based on the literature found, this paper presents a discussion on the main challenges and future perspectives related to the field. The complexity of electrical power systems and electricity markets is increasing substantially according to what this study found. Distributed generation development is already advanced, while energy storage systems and electric vehicles are limited in many countries. Peer-to-peer electricity trading and virtual power plant are newer concepts that are currently incipient, and DR programs showcase an intermediate stage of evolution. A particular lack of research on social issues is verified, and also a lack of all-encompassing studies that address multiple interconnected topics, which should be better addressed in the future. The in-depth assessment carried out in this paper is expected to be of high value to researchers and policy-makers and facilitate future research on the topic.

An integrated electrical energy and power quality monitoring system was implemented over more than 250 location in the electric power distribution system of ELEKTRO, a utility company in the south-east of Brazil. Harmonics, short-duration voltage variation (voltage sags, voltage swells and interruptions), voltage imbalance, frequency deviation, and other power quality disturbances were monitored over more than 2 years. Measurements in substations and distribution feeders at different voltage levels (138kV, 88kV, 69kV, 34,5kV and 13,8kV) were acquired and stored in a specific energy and power quality database. Statistical analysis and characterization of typical quantities, such as magnitude and duration of phenomena as well as trends of historical indices and analysis to estimate its tendencies for the near future were the main investigation in this work. Therefore, this work contributed to broad the view of the specific electric power system behavior to power quality disturbances, with the objective of providing quick answers to customer's power quality problems and to foster the improvement of the electric distribution system performance.

While most of the research work in the field of electrical engineering was aroused by the scientific challenges to be overcome, it is fair to recognize that the practical importance of engineering hinges on its economic impact on the market, the whole society and the environment. Thus, nowadays economic modeling, analysis and optimization of the electricity market is of the utmost significance. This work presents an aggregated economic analysis of the Brazilian electricity distribution companies using an economic model of a regulated market. The fundamental agents (consumer, power utility, government, society) are represented in the TAROT—Optimized Tariff Model, which is applied to the majority of the distribution companies in Brazil, based on public real data available from ANEEL—the Brazilian electrical energy regulatory agency. This reveals the economic flows in the regulated market of each company and also presents their financial status in terms of over-investments or under-investments compared to optimal investments and positive, negative or zero economic value added of each company. Moreover, the model analysis shows the socioeconomic welfare added to society in face of different optimization objectives. This study was financed in part by the Coordenaco de Aperfeicoamento de Pessoal de Nivel Superior - Brasil (CAPES) - Finance Code 001. The authors also gratefully acknowledge the financial support in part of CNPq, INERGE, and FAPEMIG, and express gratitude for the educational support of UNIFEI, KIOS Research and Innovation Center of Excellence and Department of Electrical and Computer Engineering, University of Cyprus and Universitat Politècnica de Catalunya. Peer Reviewed

ABSTRACT Small hydroelectric power plants make up 6 GW of installed capacity in Brazil. However, electricity generation at the plants has been below their expected Assured Energy Levels (AELs) recently. This paper analyzes the flow history of 24 plants using exponential moving average control charts in an attempt to verify whether climate change or land use and occupation could have changed the average annual flow available in the basin over time. The graphs showed neither a decreasing or increasing trend in average flows, but rather showed a recurring number of out-of-control points, which proves the sensitivity of assured energy to hydrological variations and the need to evaluate the use of daily average flow rates for calculating and analyzing the energy generated by small power plants.

Abstract This paper presents a discussion about the optimum time step size and maximum simulation time in EMTP-based programs. This is of particular importance for new users of EMTP-based programs, since the user is responsible for setting up these parameters before running a simulation case. The selection of the time step size affects the precision of the simulation. The time step size depends on the maximum frequency expected in the phenomena, which is normally unknown, a priori. The calculation of eigenvalues from the state space matrix obtained from the EMTP conductance matrix and history terms algorithm formulation allows the exact ideal values for the optimal time step size and a maximum simulation time. In comparison, a general and robust algorithm is also presented here based on all the input data given for the circuit under simulation. The proposed calculation process is based on single- or multi-phase uncoupled or coupled circuits, with lumped or distributed parameters. Simulations are given demonstrating the effectiveness of the proposed rules.

This paper deals with the problem of real-time management of Smart Grids. For this sake, the energy management is integrated with the power system through a telecommunication system. The use of Multiagent Systems leads the proposed algorithm to find the best-integrated solution, taking into consideration the operating scenario and the system characteristics. The proposed technique is tested with the help of an academic microgrid, so the results may be replicated.