Aplicação de métodos de pontos interiores no fluxo de potência ótimo não-linear com utilização de processamento de alto desempenho

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico.A versão Primal-Dual do método de Pontos Interiores para programação não-linear possui a capacidade de resolver problemas de otimização não-lineares de grande porte, como os exigidos na operação dos sistemas elétricos modernos. O algoritmo inclui na sua formulação a perturbação da equação de complementaridade das condições de otimalidade de primeira ordem. Na versão convencional do método, esta perturbação requer um parâmetro empírico. A presente monografia estuda o referido parâmetro, expressando-o como a combinação linear de duas direções: de Centralização e Afim-Escala. A possibilidade de combinar estas direções permite a formulação de outras sete versões do método, com distintas características de convergência. As variantes do método de Pontos Interiores são avaliadas em sistemas teste e reais. São considerados no estudo: número de iterações até a convergência, tempo de cálculo e proximidade ao caminho central. Em geral, as versões analisadas requerem tempos de cálculo por iteração superiores ao algoritmo convencional. A vetorização da solução do sistema linear através do "caminho de fatoração" é considerada a fim de diminuir os tempos de convergência do processo de otimização

Alternatives of Revenue for Corrective Actions of Wind Generators in a Delegated Dispatch

Face to critical contingence situations, the System Operator can require wind farms output reductions. The zonal Delegated Dispatches can act as interface between the System Operator and the producers, allowing a faster and accurate answer. Three probable approaches are mathematically formulated and analyzed in the paper, separately considering the controllability and the possibility of disconnecting the wind farms. The methods are testedand compared by using a realistic test network, extracted from the Spanish national network.Publicad

On the hydropower short-term scheduling of large basins, considering nonlinear programming, stochastic inflows and heavy ecological restrictions

Large hydro basins are difficult to optimally operate, due to extended water travel times, numerous tributaries to the same reservoir, uncertainties in the water inflows and different characteristics and efficiencies of the hydro plants. Also, optimal management must consider ecological restrictions, guarantying legal and social requirements. This paper proposes an advanced optimization tool, improving economic profits while meeting European and local regulations. Nonlinear relationships between efficiency, height and stored water are represented through piecewise linear functions, without requiring integer variables. Uncertainties in the water inflow and large travel times are considered by using stochastic scenarios. The Guadalquivir Basin, in southern Spain, with 18 reservoirs, a minimum of 50 h between head and mouth of the considered section and strong flow restrictions is analyzed in the study. Results show the robustness of the model and the validity of statistical studies for short-term studies, given a large chain of reservoirs, dry circumstances and strong operation constraints

Analytical methodology for reliability assessment of distribution networks with energy storage in islanded and emergency-tie restoration modes

A wide scale deployment of energy storage systems in power networks for energy balancing applications will lead to network reliability improvements. After a fault occurs in a network, energy storage will be able to help restore supply in the network areas isolated from the primary substation or in those re-connected to adjacent feeders of limited transfer capacity by emergency-ties. The reliability improvements introduced by energy storage need to be evaluated and quantified for both restoration modes. The objective of this paper is to assess the energy storage contribution in these restoration modes and to seek analytical, less computationally intensive solutions for such evaluation. The proposed analytical technique uses a probabilistic model of energy storage to assess the charge and discharge processes over a fault duration and the related operational strategy. In this way, reliability indices are calculated by taking into account the energy storage actions during a fault as well as the time-evolution of renewable generation and demand. These features lead to more realistic modelling of energy storage in analytical techniques. The proposed analytical technique was firstly validated by using a case study where the results obtained by Monte Carlo Simulation were used as a reference. Then, the proposed technique was applied to a distribution network to assess the reliability improvement provided by energy storage and to demonstrate the effectiveness and accuracy of the proposed approach.The authors kindly acknowledge the support of Fundacion Iberdrola to SinCortes project

Optimization of the operation of a flywheel to support stability and reduce generation costs using a Multi-Contingency TSCOPF with nonlinear loads

Multi-Contingency Transient Stability Constrained Optimal Power Flow (MC-TSCOPF) models optimize the economic dispatch of power systems while ensuring their stability after a series of reference incidents. This paper proposes a MC-TSCOPF model that represents the power balance at each node of the system and at each sample time. The proposed model includes non-linear loads, synchronous generators, a windfarm, and a Flywheel Energy Storage system (FESS). The model is written on GAMS and solved using a standard Interior Point algorithm. This study focuses on the Fuerteventura-Lanzarote insular grid in Spain, where stability problems and load shedding cause high additional costs due to the low inertia of the system. A FESS has been recently installed in the system to improve its stability, taking advantage of its high-power capacity and rapid response. The proposed TSCOPF model has been applied to optimize the operation of the FESS to support stability in the event of a contingency. The results of the study show that 1) a proper model of non-linear loads is essential in TSCOPF studies; 2) the proposed MC-TSCOPF provides a tool for minimizing the generation costs while ensuring transient and frequency stability; and 3) it is possible to further reduce the generation costs by using the proposed model to calculate an optimal dynamic response of the FESS.Publicad

Optimal Curtailment of Non-Synchronous Renewable Generation on the Island of Tenerife Considering Steady State and Transient Stability Constraints

The increasing penetration of non-synchronous, renewable energy in modern power systems displaces synchronous generation and affects transient stability. This is just one of the factors that has led to preventive curtailment of renewable energy sources in an increasing number of electrical grids. Transient stability constrained optimal power flow (OPF) techniques provide a tool to optimize the dispatch of power systems while ensuring a secure operation. This work proposes a transient stability-constrained OPF model that includes non-synchronous generation with fault ride-through capability and reactive support during voltage dips. The model is applied it to the IEEE 39 Bus benchmark test case and to the power system of the Spanish island of Tenerife, and solved using the open-source library IPOPT that implements a primal-dual interior point algorithm. The solution of the model makes it possible to optimize the dispatch of conventional plants and the curtailment of non-synchronous generation, as well as to explore methods to reduce generation cost. Fault ride-through capability, synchronous inertia and fault clearing times are identified as useful tools to reduce the curtailment of non-synchronous generation, especially during periods of low load and high availability of renewable energy sources.The authors acknowledge the Ministry of Science and Technology of Spain (Project RESMART, ENE2013-48690-C2-1-R)

Reliability assessment of distribution networks with optimal coordination of distributed generation, energy storage and demand management

This article belongs to the Section F: Electrical EngineeringModern power distribution networks assume the connection of Distributed Generators (DGs) and energy storage systems as well as the application of advanced demand management techniques. After a network fault these technologies and techniques can contribute individually to the supply restoration of the interrupted areas and help improve the network reliability. However, the optimal coordination of control actions between these resources will lead to their most efficient use, maximizing the network reliability improvement. Until now, the effect of such networks with optimal coordination has not been considered in reliability studies. In this paper, DGs, energy storage and demand management techniques are jointly modelled and evaluated for reliability assessment. A novel methodology is proposed for the calculation of the reliability indices. It evaluates the optimal coordination of energy storage and demand management in order to reduce the energy-not-supplied during outages. The formulation proposed for the calculation of the reliability indices (including the modelling of optimal coordination) is described in detail. The methodology is applied to two distribution systems combining DGs, energy storage and demand management. Results demonstrate the capability of the proposed method to assess the reliability of such type of networks and emphasise the impact of the optimal coordination on reliability.This research was funded by the research program "Energy and Environment 2018" of Fundación Iberdrola, project name "SinCortes"

Simulating scenarios and prediction intervals in wind power forecasting with the Beta distribution

Proceedings of: 11th Spanish-Portuguese Conference on Electrical Engineering (XICHLIE), 1-4 Julio 2009, Zaragoza (España)A methodology for the simulation of the wind power scenario for a short term horizon (one or two days in advance) is proposed. The covariance of the historical errors and the wind power forecast are use to generate a conditional random variable that represent the power wind production as a scenario. With the information provided by the scenario simulation, the energy deviation during a period and the prediction interval for each hour are obtained. The Beta distribution is used to represent the behaviour of the wind power production due to its better performance. With the results, it is possible to quantify the uncertainty of wind energy production. Finally, comparing the covariance and correlation of the simulated errors with historical errors, the procedure of the methodology is validated.The authors thanks for the financial support granted by the Ministerio de Ciencia e Innovación of Spain, IREMEL project with reference ENE2010-16074, called "Integración de Energías Renovables en el Mercado de Electricidad"Publicad

Optimal operation of a pumped-storage hydro plant that compensates the imbalances of a wind power producer

The participation of wind energy in electricity markets requires providing a forecast for future energy production of a wind generator, whose value will be its scheduled energy. Deviations from this schedule because of prediction errors could imply the payment of imbalance costs. In order to decrease these costs, a joint operation between a wind farm and a hydro-pump plant is proposed; the hydro-pump plant changes its production to compensate wind power prediction errors. In order to optimize this operation, the uncertainty of the wind power forecast is modeled and quantified. This uncertainty is included in an optimization problem that shifts the production of the hydro-pump plant in an optimal way, aiming at reducing the imbalance costs. The result of such a method is profitable for both participants, the wind farm and the hydro-pump plant. A realistic test case is used to evaluate the proposed method.The authors thanks for the financial support granted by the Ministerio de Ciencia e Innovación of Spain, IREMEL project with reference ENE2010-16074, called “Integración de Energías Renovables en el Mercado de Electricidad” and ANEMOS.plus and Integrated Action IT2009-0063 projects.Publicad

Optimal statistical calculation of underground cable bundles positions for time-varying currents

Underground cables are intensively used, especially for transporting energy in urban areas. In general, the currents flowing in the cables change, following the loads profile. Moreover, the optimal installation of these cables must consider geometry, magnetic fields and arrangement costs. This paper proposes and analyses different statistical calculations of these optimal locations. The application of the methods to real data demonstrates the effectiveness of the statistical approaches in terms of costs and magnetic fields.Edgardo Castronuovo acknowledges the Ministry of Science and Technology of Spain (Project RESMART, 2014/00338/001)