Análisis de armónicos variando en el tiempo en sistemas eléctricos de potencia con parques eólicos, a través de la teoría de la posibilidad

This paper focuses on the analysis of the connection of wind farms to the electric power system and their impact on the harmonic load-flow. A possibilistic harmonic load-flow methodology, previously developed by the authors, allows for modeling uncertainties related to linear and nonlinear load variations. On the other hand, it is well known that some types of wind turbines also produce harmonics, in fact, time-varying harmonics. The purpose of this paper is to present an improvement of the former method, in order to include the uncertainties due to the wind speed variations as an input related with power generated by the turbines. Simulations to test the proposal are performed in the IEEE 14-bus standard test system for harmonic analysis, but replacing the generator, at bus two, by a wind farm composed by ten FPC type wind turbines.En este trabajo se analiza el impacto de la conexión de parques eólicos, en el flujo de cargas armónicas en un sistema de potencia. Algunos generadores eólicos producen armónicos debido a la electrónica de potencia que utilizan para su vinculación con la red. Estos armónicos son variables en el tiempo ya que se relacionan con las variaciones en la velocidad del viento. El propósito de este trabajo es presentar una mejora a la metodología para el cálculo de incertidumbre en el flujo de cargas armónicas, a través de la teoría de la posibilidad, la cual fue previamente desarrollada por los autores. La mejora consiste en incluir la incertidumbre debida a las variaciones de la velocidad del viento. Para probar la metodología, se realizan simulaciones en el sistema de prueba de 14 barras de la IEEE, conectando en una de las barras un parque eólico compuesto por diez turbinas del tipo FPC. Los resultados obtenidos muestran que la incertidumbre en la velocidad del viento tiene un efecto considerable en las incertidumbres asociadas a las magnitudes de las tensiones armónicas calculadas.Fil: Romero Quete, Andrés Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Suvire, Gaston Orlando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Zini, Humberto Cassiano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Ratta, Giuseppe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentin

Combined Heat and Power Economic Dispatch for Isolated Microgrids

Microgrids (MGs) have gathered significant attention over the last decade due to their potential to integrate Renewable Energies (RE) into power systems, in a reliable and efficient way, and their ability to provide sustainable energy supply solutions for remote areas without a connection to the main grid. Microgrids used for the latter application are known as isolated MGs since they are permanently operating in stand-alone mode. Isolated MGs have specific technical features such as low inertia and a critical demand-supply balance constraint, which hinder their operation, especially in cases with high penetration of intermittent and fluctuating RE. Moreover, it is expected that Combined Heat and Power Systems (CHP) will play an important role in MGs since these systems can considerably improve the overall system efficiency. CHP systems introduce additional technical challenges mainly related to the heat-power dependency of CHP and the thermal and power demand uncertainty. Thus, in order to guarantee a reliable and economic operation of isolated MGs integrating CHP units, it is important to design adequate strategies and methods for their different control levels. In these microgrids, the Energy Management System (EMS) has the main function of optimizing their operation through the solution of optimization problems such as Unit Commitment (UC), economic dispatch and/or optimal power flow. Hence, this thesis seeks to address the aforementioned challenges by proposing a novel energy management system (EMS) approaches for isolated MGs with CHP units and high penetration of RE. First, an EMS algorithm is proposed, based on an Affine Arithmetic-based Unit Commitment (AAUC) problem for day-ahead dispatch, using uncertainty intervals of both load and RE to provide robust commitment and dispatch solutions in AA form, which are feasible for all the possible realizations within the predetermined uncertainty bounds. A real-time dispatch solution is then found by the proposed algorithm, which computes the noise symbols values of the affine forms obtained by the AAUC, based on the current and actual load, the RE power levels and the available reserves. If the actual forecast error is outside the uncertainty bounds considered in the AAUC solution process, leading to possible load and/or RE curtailment, the AAUC is recalculated with updated forecast information. The proposed AA-based EMS is tested on a modified CIGRE microgrid benchmark and is compared against day-ahead deterministic, Model Predictive Control (MPC), stochastic optimization, and stochastic-MPC approaches. The simulation results show that the proposed EMS provides robust and adequate cost-effective solutions, without the need of frequent re-calculations as with MPC-based approaches, or assumptions regarding statistical characteristics of the uncertainties as in the case of stochastic optimization. Finally, a novel approach for the optimal economic dispatch of CHP MGs is proposed, which incorporates an Affine Arithmetic-based Economic Dispatch (AAED) problem into an MPC framework. The proposed algorithm solves each ∆t minutes (e.g. 15m) an AAED problem with time steps of ∆t minutes over a time horizon T (e.g. 24h). It uses the available forecast and the current state of the system, to provide the schedule and the affine forms that represent the operation intervals of the generators and Energy Storage Systems (ESS) for the next time interval [t, t + ∆t]. Online set points for generators and ESS are then obtained by computing the noise symbols values of the affine forms, based on the most updated information of electricity and heat demands and available renewable energy power. A theoretical CHP-based MG, comprising PVs, a gas boiler, a CHP unit, a battery, and a thermal tank, is used to assess the performance of the AA-MPC approach in both connected and isolated operation modes. The method is also compared with a deterministic MPC approach. Results show the ability of the method to better address forecasting errors, resulting in more cost-effective solutions, without considerably affecting the computation performance.Resumen: El concepto de microrredes ha ganado importancia en los ´ultimos a˜nos debido a que facilita la integraci´on de energ´ıas renovables a los sistemas de potencia de forma confiable y eficiente y a que provee soluciones sostenibles de suministro de energ´ıa para ´areas remotas sin conexi´on a la red el´ectrica principal. Las microrredes utilizadas en dichas ´areas remotas se conocen como microrredes aisladas, pues funcionan permanentemente en modo aut´onomo. Estas microrredes tienen caracter´ısticas t´ecnicas espec´ıficas tales como baja inercia y restricci´on cr´ıtica de balance entre generaci´on y demanda, que dificultan su adecuada operaci´on, especialmente en casos con alta penetraci´on de energ´ıas renovables de car´acter fluctuante e intermitente. Adicionalmente, se espera que los sistemas de cogeneraci´on (CHP por sus siglas en ingl´es) jueguen un papel importante en las microrredes, pues dichos sistemas pueden mejorar considerablemente la eficiencia global del sistema. Sin embargo, los CHP introducen desaf´ıos t´ecnicos adicionales relacionados principalmente con la relaci´on que existe entre la generaci´on de electricidad y la generaci´on de calor, as´ı como la incertidumbre asociada a la demanda t´ermica. Por lo tanto, para garantizar un funcionamiento confiable y econ´omico de las microrredes aisladas con CHP, es importante dise˜nar estrategias y m´etodos adecuados para sus diferentes niveles de control. En estas microrredes, el sistema de gesti´on de la energ´ıa (EMS por sus siglas en ingl´es) tiene la funci´on principal de optimizar la operaci´on a trav´es de la soluci´on de problemas de optimizaci´on tales como el problema de compromiso de unidades (UC por sus siglas en ingl´es), el despacho econ´omico y/o el flujo de potencia ´optimo. Por lo tanto, esta tesis busca abordar los desaf´ıos mencionados, proponiendo enfoques novedosos de EMS para microrredes aisladas con sistemas de cogeneraci´on y alta penetraci´on de renovables. En primer lugar, se propone un algoritmo de EMS que integra una formulaci´on del problema de UC en donde la incertidumbre asociada a la generaci´on con renovables y a la demanda es modelada por medio de la t´ecnica matem´atica conocida como “Affine Arithmetic (AA)”. Al resolver dicho problema, nombrado aqu´ı AAUC, se obtienen soluciones robustas de despacho en el dominio de la AA, las cuales son factibles para todos los posibles escenarios dentro de los l´ımites de incertidumbre considerados. Posteriormente, haciendo uso de la informaci´on m´as reciente de demanda, potencia generada con renovables y reservas disponibles y de las predicciones de dichas variables, se calculan los valores de los “noise symbols” de las “affine forms” obtenidas en el AAUC, obteniendo as´ı soluciones de despacho en tiempo real. Si el error de predicci´on est´a fuera de los l´ımites considerados en el proceso de soluci´on del AAUC, lo que conlleva a un deslastre de carga o de generaci´on con renovables, el AAUC se recalcula con un pron´ostico actualizado. El EMS propuesto es probado en un modelo de microrred propuesto por el CIGRE y se compara con otros m´etodos disponibles en la literatura, tales como el control predictivo por modelo (MPC por sus siglas en ingl´es), la optimizaci´on estoc´astica y el m´etodo combinado estoc´astico-MPC. Los resultados de la simulaci´on muestran que el EMS propuesto ofrece soluciones de operaci´on econ´omicas y confiables, sin la necesidad de efectuar c´alculos recurrentes con un costo computacional asociado o de hacer suposiciones con respecto a las caracter´ısticas estad´ısticas de las incertidumbres, como en el caso de los enfoques basados en MPC u optimizaci´on estoc´astica. Finalmente, se presenta un nuevo enfoque para el despacho econ´omico ´optimo de CHP microrredes, el cual incorpora dentro de un esquema de MPC un problema de despacho econ´omico basado en AA, denominado AAED. El algoritmo propuesto resuelve cada ∆t minutos (ej. 15 m) un problema AAED para un horizonte de tiempo T (ej. 24 h) dividido en pasos de tiempo de ∆t minutos. Utilizando el pron´ostico disponible y el estado actual del sistema, la soluci´on de dicho problema proporciona el compromiso de unidades y las “affine forms” que representan los intervalos de operaci´on de los generadores y de los sistemas de almacenamiento de energ´ıa para el siguiente intervalo de tiempo [t, t + ∆t]. Posteriormente, con base en la informaci´on m´as actualizada disponible de demanda de electricidad y de calor y de la energ´ıa generada con renovables, se calculan los valores de los “noise symbols” de las “affine forms” con el fin de obtener las referencias de potencia en tiempo real para los controles locales de los generadores y sistemas de almacenamiento. Para validar y comparar el m´etodo propuesto, se utiliza una microrred te´orica que comprende paneles fotovoltaicos, una caldera a gas, una unidad de CHP, una bater´ıa y un tanque t´ermico. El m´etodo se compara con el enfoque determinista de MPC en los dos modos de operaci´on de la microrred: conectada y aislada. Los resultados muestran la capacidad del m´etodo propuesta para enfrentar m´as apropiadamente los errores de pron´ostico, lo que resulta en soluciones de operaci´on m´as econ´omicas, sin afectar de forma considerable el rendimiento de computo.Doctorad

Health index for power transformer condition assessment: A comparison of three different techniques

In practice, the condition state of Power Transformers (PT) is quantified by using Health Index (HI). This paper analyzes and compares three different state-of-the-art algorithms to compute HI. The first one uses a Weighted Sum Model (WSM), the second is based on a Fuzzy Inference System (FIS), and the third combines both techniques, i.e., WSM and FIS. These three approaches are tested in a PT fleet composed of 30 units. Results show that each approach produces different HI values for the same PTs. Therefore, decision making regarding the PT fleet will depend on the selected approach for HI calculation. This work proposes merging the knowledge involved in each analyzed approach by using a K-means clustering technique to overcome this drawback. This solution could help the asset manager to make adequate decisions regarding the maintenance scheduling of PT when there is uncertainty about the appropriate approach to be selected.Fil: Zaldivar Sanchez, Diego Armando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Romero Quete, Andrés Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentin

Impact of nonlinear lighting loads on the neutral conductor current of low voltage residential grids

In the last decade, mainly due to political incentives towards energy efficiency, the share of lamps with power electronic interfaces, like Compact Fluorescent Lamps (CFL) and Light Emitting Diode (LED) lamps, has significantly increased in the residential sector. Their massive use might have a substantial impact on harmonic currents and, consequently, on the current flowing in the neutral conductor. This paper analyzes the impact of modern energy-efficient lighting technologies on the neutral conductor current by using a synthetic Low Voltage residential grid. Different load scenarios reflecting the transition from incandescent lamps, via CFL, to LED lamps are compared concerning the neutral conductor current at different points in the network. The inherent randomness related to the use of lighting devices by each residential customer is considered employing a Monte Carlo simulation. Obtained results show that the use of CFL has a greater impact on the neutral conductor current of Low Voltage (LV) residential grids and that, with increasing use of LED lamps, a decreasing impact can be expected in the future.Fil: Hernández, Jairo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Romero Quete, Andrés Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Meyer, Jan. Technische Universität; AlemaniaFil: Blanco, Ana María. Technische Universität; Alemani

Harmonic load-flow approach based on the possibility theory

Harmonics in power systems are responsible for several technical problems that justify the development of models to study them. Well-established models exist to analyse the harmonic load-flow (HLF) from a deterministic point of view. Moreover, models based on the probability theory have been developed to deal with the inherent variability and random nature of loads, network configuration etc. In the last few years, possibility theory has arisen as an alternative tool that in many cases could be better suited to describe and quantify the real nature of the uncertainty involved in harmonic studies. In this study a methodology for HLF calculation based on the possibility theory is presented. Possibility distributions instead of probabilities are the input used to describe the uncertainty in the magnitude and composition of the loads. Tests presented shows that the results of the proposed model are consistent with those obtained with a probabilistic method, and that both models lead to the same ranking of the risk that the bus harmonic voltages exceed a given level. Independent possibility distributions are assumed at the development stage reported here; research is being carried out in order to overcome this constraint.Fil: Romero Quete, Andrés Arturo. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Zini, Humberto Cassiano. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; ArgentinaFil: Rattá, G.. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Dib, R.. No especifíca

Risk assessment algorithm for power transformer fleets based on condition and strategic importance

In every electric power system, power transformers (PT) play a critical role. Under ideal circumstances, PT should receive the utmost care to maintain the highest operative condition during their lifetime. Through the years, different approaches have been developed to assess the condition and the inherent risk during the operation of PT. However, most proposed methodologies tend to analyze PT as individuals and not as a fleet. A fleet assessment helps the asset manager make sound decisions regarding the maintenance scheduling for groups of PT with similar conditions. This paper proposes a new methodology to assess the risk of PT fleets, considering the technical condition and the strategic importance of the units. First, the state of the units was evaluated using a health index (HI) with a fuzzy logic algorithm. Then, the strategic importance of each unit was assessed using a weighting technique to obtain the importance index (II). Finally, the analyzed units with similar HI and II were arranged into a set of clusters using the k-means clustering technique. A fleet of 19 PTs was used to validate the proposed method. The obtained results are also provided to demonstrate the viability and feasibility of the assessment model.Fil: Zaldivar Sanchez, Diego Armando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Romero Quete, Andrés Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Rivera, Sergio R.. Universidad Nacional de Colombia; Colombi

Integración y análisis de pequeñas turbinas eólicas en entornos urbanos

En este libro podrás encontrar el análisis de pequeñas turbinas, desde el recuento histórico de las mismas, el modelado del viento que hace posible su uso en zonas urbanas hasta los elementos necesarios para su uso en zonas residenciales. Adicionalmente, se presentan los elementos necesarios para la integración de micro eólicas en la red de energía, analizando el control, las protecciones y tipologías dentro de una microrred. Finalmente, se presenta la normatividad existente en Iberoamérica para la regulación y restricciones en la implementación e interconexión fe dichos elementos de generación eólic

Frequency scan analysis supported by a possibility theory-based approach

This paper describes a procedure used to identify the states of a power system that lead to harmonic resonance. The proposed methodology results from an application of the possibility theory which aims to extend the capabilities of the classic frequency scan concept. With the proposed approach, the frequency scan provides more useful information on the harmonic behavior of a power system in contexts where load characteristics are known with uncertainty. To exemplify the potential of this proposal, a case study based on a 14-bus standard test system for harmonic analysis is presented. The states of the power system that lead to harmonic resonance are assessed within the possibility theory framework. Additionally, this paper introduces a risk measure of harmonic resonance based on possibility and necessity fuzzy measures.Fil: Romero Quete, Andrés Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Caicedo Navarro, Joaquin Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Zini, Humberto Cassiano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Ratta, Giuseppe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; Argentin

An improved methodology for the hierarchical coordination of PEV Charging

This paper proposes an improved methodology for the hierarchical coordination of daily Plug-in Electric Vehicle (PEV) charging. The aim is to limit the power supplied by the primary distribution transformer (PDT) while minimizing the energy costs of the aggregators. This methodology consists of an iterative optimization of the total aggregated power at the PDT level, considering the local power constraints of the aggregators and the PEVs with a reduced number of decision variables and constraints which only depend on the number of time intervals. Moreover, it defines the energy boundaries of the optimization problem in each iteration through a proposed method for simulating early charging and delayed charging, considering the power constraints of the aggregators. Otherwise, it evenly distributes the total power among the aggregators, and the local power of each aggregator among the PEVs, maximizing the feasible region of the optimization problem. The proposed methodology is applied to two case studies. The uncertainties related to the charging scenarios are considered by means of Monte-Carlo simulations. The results obtained show that the total power profile is effectively limited, while the profits of the aggregators are not significantly affected by the coordinated approach that is expected to be performed by the Distribution System Operator (DSO). Additionally, to demonstrate the reduction of the impact of PEV charging on the distribution system, the voltage profile, the transformer loss of life and the power and energy losses are reported.Fil: Sanchez, Angel Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Coria Pantano, Gustavo Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Romero Quete, Andrés Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Energía Eléctrica. Universidad Nacional de San Juan. Facultad de Ingeniería. Instituto de Energía Eléctrica; ArgentinaFil: Rivera, Sergio Raúl. Universidad Nacional de Colombia; Colombi

State-of-the-Art Using Bibliometric Analysis of Wind-Speed and -Power Forecasting Methods Applied in Power Systems

The integration of wind energy into power systems has intensified as a result of the urgency for global energy transition. This requires more accurate forecasting techniques that can capture the variability of the wind resource to achieve better operative performance of power systems. This paper presents an exhaustive review of the state-of-the-art of wind-speed and -power forecasting models for wind turbines located in different segments of power systems, i.e., in large wind farms, distributed generation, microgrids, and micro-wind turbines installed in residences and buildings. This review covers forecasting models based on statistical and physical, artificial intelligence, and hybrid methods, with deterministic or probabilistic approaches. The literature review is carried out through a bibliometric analysis using VOSviewer and Pajek software. A discussion of the results is carried out, taking as the main approach the forecast time horizon of the models to identify their applications. The trends indicate a predominance of hybrid forecast models for the analysis of power systems, especially for those with high penetration of wind power. Finally, it is determined that most of the papers analyzed belong to the very short-term horizon, which indicates that the interest of researchers is in this time horizon