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Publications

Publications by CPES

2017

Substations SF6 circuit breakers: Reliability evaluation based on equipment condition

Authors
Vianna, EAL; Abaide, AR; Canha, LN; Miranda, V;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
This paper presents a new methodology to define a priority scale for maintenance actions in substations, based on the development of a Composite Risk Index (CRI) associated with each device. Two auxiliary indices are built: Basic Condition (BC) and Operating Condition (OC), representing the physical and functional characteristics of the equipment that can compromise their performance and contribute to the occurrence of failures. Their evaluation is helped by a Technical Capacity Index (TCI), which evaluates how much the equipment has been affected by wear and tear, in the assessment of the Basic Condition, and the classification of the equipment defects by degrees of severity, in the assessment of the Operating Condition. Two cascading Fuzzy Inference Systems of the Mandani type are used, the first in defining the BC, and the second to obtain the equipment CRI denoting maintenance priority, which may then be used in planning maintenance actions. The methodology is verified through an SF6 circuit breaker CRI assessment, and its priority scale for maintenance planning. The method for evaluating the SF6 circuit breakers reliability is validated through a comparison with a statistical approach, using real data collected from equipment installed in Eletrobras Eletronorte Transmission System, in Rondonia, Amazon region of Brazil. (C) 2016 Published by Elsevier B.V.

2017

Merging conventional and phasor measurements in state estimation: a multi-criteria perspective

Authors
Tavares, B; Freitas, V; Miranda, V; Costa, AS;

Publication
2017 19TH INTERNATIONAL CONFERENCE ON INTELLIGENT SYSTEM APPLICATION TO POWER SYSTEMS (ISAP)

Abstract
This paper presents a new proposal for sensor fusion in power system state estimation, analyzing the case of data sets composed of conventional measurements and phasor measurements from PMUs. The approach is based on multiple criteria decision-making concepts. The equivalence of an L-1 metric in the attribute space to the results from a Bar-Shalom-Campo fusion model is established. The paper shows that the new fusion proposal allows understanding the consequences of attributing different levels of confidence or trust to both systems. A case study provides insight into the new model.

2017

Mapping the Impact of Daytime and Overnight Electric Vehicle Charging on Distribution Grids

Authors
Heymann, F; Miranda, V; Neyestani, N; Soares, FJ;

Publication
2017 IEEE VEHICLE POWER AND PROPULSION CONFERENCE (VPPC)

Abstract
Strong adoption dynamics of private passenger electric vehicles (EV) will require adjustments in the operation and planning of electrical distribution grids. This work proposes a novel approach to assess the impact of electric vehicle charging while considering EV adoption dynamics and commuting patterns. The proposed model uses Geographic Information Systems (GIS) and is applied to a real-world case study. Results suggest that clustering of EV charging will occur and underline the relevance of accurate spatial and temporal charging pattern estimations for distribution grid planning. Overloading of distribution network elements was observed even under light EV penetration rates.

2017

Forecasting and setting power system operating reserves

Authors
Matos, M; Bessa, R; Botterud, A; Zhou, Z;

Publication
Renewable Energy Forecasting: From Models to Applications

Abstract
The system operator is responsible for maintaining a constant balance between generation and load to keep frequency at the nominal value. This fundamental objective is achieved with upward (e.g., synchronized and nonsynchronized generation units) and downward (e.g., demand response, storage) reserve capacity. The system operator needs to define, in advance, the reserve capacity requirements that mitigate the risk of imbalances due to forecast errors and unplanned outages of generation units. The research trend is to apply probabilistic methodologies for setting the reserve requirements based on uncertainty forecasts for renewable generation and load, as well as a probabilistic modeling of units' outages. This chapter describes two probabilistic methods, which share a common modeling framework, for quantifying risk and reserve requirements in two types of electricity markets: (1) sequential markets with the reserves market after the energy market clearing and (2) cooptimization (or joint market clearing) of energy and reserves. Two case studies with real data are presented to illustrate the application of both methodologies.

2017

Multi-Period Modeling of Behind-the-Meter Flexibility

Authors
Pinto, R; Matos, MA; Bessa, RJ; Gouveia, J; Gouveia, C;

Publication
2017 IEEE MANCHESTER POWERTECH

Abstract
Reliable and smart information on the flexibility provision of Home Energy Management Systems (HEMS) represents great value for Distribution System Operators and Demand/flexibility Aggregators while market agents. However, efficiently delimiting the HEMS multi-temporal flexibility feasible domain is a complex task. The algorithm proposed in this work is able to efficiently learn and define the feasibility search space endowing DSOs and aggregators with a tool that, in a reliable and time efficient faction, provides them valuable information. That information is essential for those agents to comprehend the fully grid operation and economic benefits that can arise from the smart management of their flexible assets. House load profile, photovoltaic (PV) generation forecast, storage equipment and flexible loads as well as pre-defined costumer preferences are accounted when formulating the problem. Support Vector Data Description (SVDD) is used to build a model capable of identifying feasible HEMS flexibility offers. The proposed algorithm performs efficiently when identifying the feasibility of multi-temporal flexibility offers.

2017

Advanced voltage control for smart microgrids using distributed energy resources

Authors
Olival, PC; Madureira, AG; Matos, M;

Publication
ELECTRIC POWER SYSTEMS RESEARCH

Abstract
Large scale integration of distributed generation (DG), particularly based on variable renewable energy sources (RES), in low voltage (LV) distribution networks brings significant challenges to operation. This paper presents a new methodology for mitigating voltage problems in LV networks, in a future scenario with high integration of distributed energy resources (DER), taking advantage of these resources based on a smart grid type architecture. These resources include dispersed energy storage systems, controllable loads of residential clients under demand side management (DSM) actions and microgeneration units. The algorithm developed was tested in a real Portuguese LV network and showed good performance in controlling voltage profiles while being able to integrate all energy from renewable sources and minimizing the energy not supplied.

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