GNOM - Grup d´Optimització Numèrica i Modelització
http://hdl.handle.net/2117/3320
Tue, 26 Jul 2016 10:27:47 GMT2016-07-26T10:27:47ZA stochastic programming model for the tertiary control of microgrids
http://hdl.handle.net/2117/87023
A stochastic programming model for the tertiary control of microgrids
Citores, Leire; Corchero García, Cristina; Heredia, F.-Javier (Francisco Javier)
In this work a scenario-based two-stage stochastic programming model is proposed to solve a microgrid’s tertiary control optimization problem taking into account some renewable energy resource’s uncertainty as well as uncertain energy deviation prices in the electricity market. Scenario generation methods for wind speed realizations are also studied. Results show that the introduction of stochastic programming represents a significant improvement over a deterministic model.
Thu, 12 May 2016 14:15:37 GMThttp://hdl.handle.net/2117/870232016-05-12T14:15:37ZCitores, LeireCorchero García, CristinaHeredia, F.-Javier (Francisco Javier)In this work a scenario-based two-stage stochastic programming model is proposed to solve a microgrid’s tertiary control optimization problem taking into account some renewable energy resource’s uncertainty as well as uncertain energy deviation prices in the electricity market. Scenario generation methods for wind speed realizations are also studied. Results show that the introduction of stochastic programming represents a significant improvement over a deterministic model.Potential externalities savings due to electric vehicle smart charge
http://hdl.handle.net/2117/86395
Potential externalities savings due to electric vehicle smart charge
Benveniste Pérez, Gabriela; Corchero García, Cristina; Cruz Zambrano, Miguel
This work focuses on the analysis developed in order to demonstrate how smart charging, using tailored control algorithms, contributes to minimize the environmental impact and economic costs associated to the electric vehicles under an LCA perspective. The analysis considers the Spanish grid mix profile and specific charging patterns.The LCA methodology adopted implies a comprehensive assessment of the impacts and costs occurring upstream and downstream the charging event. For the environmental analysis, the LCA impact categories are considered, while for the economic assessment, data regarding the costs associated to the electricity price and the pollutants generation have been adopted.
Thu, 28 Apr 2016 15:17:03 GMThttp://hdl.handle.net/2117/863952016-04-28T15:17:03ZBenveniste Pérez, GabrielaCorchero García, CristinaCruz Zambrano, MiguelThis work focuses on the analysis developed in order to demonstrate how smart charging, using tailored control algorithms, contributes to minimize the environmental impact and economic costs associated to the electric vehicles under an LCA perspective. The analysis considers the Spanish grid mix profile and specific charging patterns.The LCA methodology adopted implies a comprehensive assessment of the impacts and costs occurring upstream and downstream the charging event. For the environmental analysis, the LCA impact categories are considered, while for the economic assessment, data regarding the costs associated to the electricity price and the pollutants generation have been adopted.European electric vehicle fleet: driving and charging behaviors
http://hdl.handle.net/2117/86393
European electric vehicle fleet: driving and charging behaviors
Corchero García, Cristina
The electrification of vehicles would be a reality in the coming decades. Statistical results on real electric vehicle usage data is a key point in the development of the electro mobility. A large collection of electric vehicles and charging points have been monitored during three years and the results about the driving and charging patterns are shown in this work. These results may help to develop future policies on, for instance, charging infrastructure location, end-users incentives, or to allow different type of economic analysis such as an evaluation of the electric vehicle integration in the grid, smart-charge impact…
Thu, 28 Apr 2016 15:10:46 GMThttp://hdl.handle.net/2117/863932016-04-28T15:10:46ZCorchero García, CristinaThe electrification of vehicles would be a reality in the coming decades. Statistical results on real electric vehicle usage data is a key point in the development of the electro mobility. A large collection of electric vehicles and charging points have been monitored during three years and the results about the driving and charging patterns are shown in this work. These results may help to develop future policies on, for instance, charging infrastructure location, end-users incentives, or to allow different type of economic analysis such as an evaluation of the electric vehicle integration in the grid, smart-charge impact…A mathematical programming approach for different scenarios of bilateral bartering
http://hdl.handle.net/2117/85754
A mathematical programming approach for different scenarios of bilateral bartering
Nasini, Stefano; Castro Pérez, Jordi; Fonseca Casas, Pau
The analysis of markets with indivisible goods and fixed exogenous prices has played an important role in economic models, especially in relation to wage rigidity and unemployment. This paper provides a novel mathematical programming based approach to study pure exchange economies where discrete amounts of commodities are exchanged at fixed prices. Barter processes, consisting in sequences of elementary reallocations of couple of commodities among couples of agents, are formalized as local searches converging to equilibrium allocations. A direct application of the analysed processes in the context of computational economics is provided, along with a Java implementation of the described approaches.
Fri, 15 Apr 2016 15:03:14 GMThttp://hdl.handle.net/2117/857542016-04-15T15:03:14ZNasini, StefanoCastro Pérez, JordiFonseca Casas, PauThe analysis of markets with indivisible goods and fixed exogenous prices has played an important role in economic models, especially in relation to wage rigidity and unemployment. This paper provides a novel mathematical programming based approach to study pure exchange economies where discrete amounts of commodities are exchanged at fixed prices. Barter processes, consisting in sequences of elementary reallocations of couple of commodities among couples of agents, are formalized as local searches converging to equilibrium allocations. A direct application of the analysed processes in the context of computational economics is provided, along with a Java implementation of the described approaches.Importancia de la potencia y la hipótesis en el valor p
http://hdl.handle.net/2117/85046
Importancia de la potencia y la hipótesis en el valor p
Cortés Martínez, Jordi; Casals, Martí; Langohr, Klaus; González Alastrué, José Antonio
Los lectores de Medicina Clínica conocen bien la importancia de definir bien el denominador de una proporción para estimar una probabilidad: “No es lo mismo la probabilidad de que un católico sea Papa que la de que un Papa sea católico”. De forma similar, en un diagnóstico, no es lo mismo la probabilidad de que un enfermo dé positivo (sensibilidad), que la de que un caso que ha dado positivo esté enfermo (valor predictivo de un positivo).
El valor p (o valor de p, o p-valor, o simplemente p) guarda cierta analogía con las probabilidades diagnósticas, ya que se define como la probabilidad de obtener un resultado tan significativo o más que el observado —dar positivo en la prueba diagnóstica— asumiendo cierta una hipótesis H: el paciente está sano. No obstante, a un investigador o a un clínico le puede resultar más interesante conocer el valor positivo de una prueba: cuán probable es una hipótesis H —que el paciente esté enfermo— habiendo observado unos resultados extremos.
Fri, 01 Apr 2016 10:51:58 GMThttp://hdl.handle.net/2117/850462016-04-01T10:51:58ZCortés Martínez, JordiCasals, MartíLangohr, KlausGonzález Alastrué, José AntonioLos lectores de Medicina Clínica conocen bien la importancia de definir bien el denominador de una proporción para estimar una probabilidad: “No es lo mismo la probabilidad de que un católico sea Papa que la de que un Papa sea católico”. De forma similar, en un diagnóstico, no es lo mismo la probabilidad de que un enfermo dé positivo (sensibilidad), que la de que un caso que ha dado positivo esté enfermo (valor predictivo de un positivo).
El valor p (o valor de p, o p-valor, o simplemente p) guarda cierta analogía con las probabilidades diagnósticas, ya que se define como la probabilidad de obtener un resultado tan significativo o más que el observado —dar positivo en la prueba diagnóstica— asumiendo cierta una hipótesis H: el paciente está sano. No obstante, a un investigador o a un clínico le puede resultar más interesante conocer el valor positivo de una prueba: cuán probable es una hipótesis H —que el paciente esté enfermo— habiendo observado unos resultados extremos.Scheduling policies for multi-period services
http://hdl.handle.net/2117/84649
Scheduling policies for multi-period services
Núñez del Toro, Alma Cristina; Fernández Aréizaga, Elena; Kalcsics, Jörg; Nickel, Stefan
This paper discusses a multi-period service scheduling problem. In this problem, a set of customers is given who periodically require service over a finite time horizon. To satisfy the service demands, a set of operators is given, each with a fixed capacity in terms of the number of customers an operator can serve per period. The task is to determine for each customer the periods in which he will be visited by an operator such that the periodic service requests of the customers are adhered to and the total number of operators used over the time horizon is minimal. Two alternative policies for scheduling customer visits are considered. In the first one, a customer is visited just on time, i.e., in the period where he or she has a demand for service. The second policy allows service visits ahead of time. The rationale behind this policy is that allowing irregular visits may reduce the overall number of operators needed throughout the time horizon. To solve the problem, integer linear programming formulations are proposed for both policies and numerical experiments are presented that show the reduction in the number of operators used when visits ahead of time are allowed. As only small instances can be solved optimally, a heuristic algorithm is introduced in order to obtain good quality solutions and shorter computing times.
Thu, 17 Mar 2016 15:09:08 GMThttp://hdl.handle.net/2117/846492016-03-17T15:09:08ZNúñez del Toro, Alma CristinaFernández Aréizaga, ElenaKalcsics, JörgNickel, StefanThis paper discusses a multi-period service scheduling problem. In this problem, a set of customers is given who periodically require service over a finite time horizon. To satisfy the service demands, a set of operators is given, each with a fixed capacity in terms of the number of customers an operator can serve per period. The task is to determine for each customer the periods in which he will be visited by an operator such that the periodic service requests of the customers are adhered to and the total number of operators used over the time horizon is minimal. Two alternative policies for scheduling customer visits are considered. In the first one, a customer is visited just on time, i.e., in the period where he or she has a demand for service. The second policy allows service visits ahead of time. The rationale behind this policy is that allowing irregular visits may reduce the overall number of operators needed throughout the time horizon. To solve the problem, integer linear programming formulations are proposed for both policies and numerical experiments are presented that show the reduction in the number of operators used when visits ahead of time are allowed. As only small instances can be solved optimally, a heuristic algorithm is introduced in order to obtain good quality solutions and shorter computing times.On geometrical properties of preconditioners in IPMs for classes of block-angular problems
http://hdl.handle.net/2117/84257
On geometrical properties of preconditioners in IPMs for classes of block-angular problems
Castro Pérez, Jordi; Nasini, Stefano
One of the most efficient interior-point methods for some classes of block-angular structured problems
solves the normal equations by a combination of Cholesky factorizations and preconditioned conjugate gradient for,
respectively, the block and linking constraints. In this work we show that the choice of a good preconditioner depends on geometrical properties of the constraints structure. In particular, it is seen that the principal angles between the subspaces generated by the diagonal blocks and the linking constraints can be used to estimate ex-ante the efficiency of the preconditioner. Numerical validation is provided with some generated optimization problems. An application to the solution of multicommodity network flow problems with nodal capacities and equal flows of up to 127 million of
variables and up to 7.5 million of constraints is also presented
J. Castro, S. Nasini, On geometrical properties of preconditioners in IPMs for classes of block-angular problems, Research Report DR 2016/03, Dept. of Statistics and Operations Research, Universitat Politècnica de Catalunya, 2016.
Fri, 11 Mar 2016 18:48:48 GMThttp://hdl.handle.net/2117/842572016-03-11T18:48:48ZCastro Pérez, JordiNasini, StefanoOne of the most efficient interior-point methods for some classes of block-angular structured problems
solves the normal equations by a combination of Cholesky factorizations and preconditioned conjugate gradient for,
respectively, the block and linking constraints. In this work we show that the choice of a good preconditioner depends on geometrical properties of the constraints structure. In particular, it is seen that the principal angles between the subspaces generated by the diagonal blocks and the linking constraints can be used to estimate ex-ante the efficiency of the preconditioner. Numerical validation is provided with some generated optimization problems. An application to the solution of multicommodity network flow problems with nodal capacities and equal flows of up to 127 million of
variables and up to 7.5 million of constraints is also presentedHybrid AC-DC offshore wind power plant topology: optimal design
http://hdl.handle.net/2117/83730
Hybrid AC-DC offshore wind power plant topology: optimal design
Prada Gil, Mikel de; Igualada González, Lucía; Corchero García, Cristina; Gomis Bellmunt, Oriol; Sumper, Andreas
The aim of this paper is to present a hybrid AC-DC offshore wind power plant (OWPP) topology and to optimize its design in order to minimize the OWPP's total cost. This hybrid concept is based on clustering wind turbines and connecting each group to an AC/DC power converter installed on a collector platform which is located between the AC wind turbine array and the HVDC offshore platform. Thereby, individual power converters of each wind turbine are not required, since such AC/DC converters can provide variable speed generator control for each cluster. The optimal design for an OWPP based on the hybrid AC-DC topology is formulated as a MINLP problem. The capital costs of each component within the OWPP as well as the costs associated to the inherent losses of this topology are minimized. The optimal number of AC/DC converters and offshore collector platforms needed, as well as their locations, are determined. The cable route connecting the wind turbines between each other is also optimized. The results suggests a good potential for the hybrid AC-DC OWPP topology achieving a total cost saving of 3.76% for the case study compared to the conventional OWPP topology.
Wed, 02 Mar 2016 18:34:17 GMThttp://hdl.handle.net/2117/837302016-03-02T18:34:17ZPrada Gil, Mikel deIgualada González, LucíaCorchero García, CristinaGomis Bellmunt, OriolSumper, AndreasThe aim of this paper is to present a hybrid AC-DC offshore wind power plant (OWPP) topology and to optimize its design in order to minimize the OWPP's total cost. This hybrid concept is based on clustering wind turbines and connecting each group to an AC/DC power converter installed on a collector platform which is located between the AC wind turbine array and the HVDC offshore platform. Thereby, individual power converters of each wind turbine are not required, since such AC/DC converters can provide variable speed generator control for each cluster. The optimal design for an OWPP based on the hybrid AC-DC topology is formulated as a MINLP problem. The capital costs of each component within the OWPP as well as the costs associated to the inherent losses of this topology are minimized. The optimal number of AC/DC converters and offshore collector platforms needed, as well as their locations, are determined. The cable route connecting the wind turbines between each other is also optimized. The results suggests a good potential for the hybrid AC-DC OWPP topology achieving a total cost saving of 3.76% for the case study compared to the conventional OWPP topology.Using BCD-CTA for difficult tables: a practical experiment with a real Eurostat table
http://hdl.handle.net/2117/83503
Using BCD-CTA for difficult tables: a practical experiment with a real Eurostat table
Castro Pérez, Jordi; González Alastrué, José Antonio; Hundepool, Anco
CTA is a post-tabular perturbative approach for statistical disclosure control. Its purpose is to compute the closest safe table to the original data, using some distance.
Sensitive cells are adjusted either upwards or downwards (binary decision), and the resulting cells have to be accordingly (and minimally) modi_ed to preserve marginals. For real and large tables, CTA may result in a dicult mixed integer linear problem for some
weights in the objective function. In those situations the Block Coordinate Descent (BCD) heuristic for CTA|which is included in the Tau-Argus CTA distribution|may be used to quickly obtain a feasible, hopefully close to optimality, solution. We present a practical experiment using a large and di_cult real-world table from Eurostat. We will show that, for unitary weights, while the standard CTA can not obtain a solution in about half an hour, the BCD-CTA approach provides a solution in few seconds.
Fri, 26 Feb 2016 15:41:16 GMThttp://hdl.handle.net/2117/835032016-02-26T15:41:16ZCastro Pérez, JordiGonzález Alastrué, José AntonioHundepool, AncoCTA is a post-tabular perturbative approach for statistical disclosure control. Its purpose is to compute the closest safe table to the original data, using some distance.
Sensitive cells are adjusted either upwards or downwards (binary decision), and the resulting cells have to be accordingly (and minimally) modi_ed to preserve marginals. For real and large tables, CTA may result in a dicult mixed integer linear problem for some
weights in the objective function. In those situations the Block Coordinate Descent (BCD) heuristic for CTA|which is included in the Tau-Argus CTA distribution|may be used to quickly obtain a feasible, hopefully close to optimality, solution. We present a practical experiment using a large and di_cult real-world table from Eurostat. We will show that, for unitary weights, while the standard CTA can not obtain a solution in about half an hour, the BCD-CTA approach provides a solution in few seconds.A novel model for arc territory design: promoting Eulerian districts
http://hdl.handle.net/2117/82920
A novel model for arc territory design: promoting Eulerian districts
Garcia Ayala, Gariela; González Velarde, José Luis; Rios Mercados, Roger; Fernández Aréizaga, Elena
The problem of district design for the implementation of arc routing activities is addressed. The aim is to partition a road network into a given number of sectors to facilitate the organization of the operations to be implemented within the region. This problem arises in numerous applications such as postal delivery, meter readings, winter gritting, road maintenance, and municipal solid waste collection. An integer linear programming model is proposed where a novel set of node parity constraints to favor Eulerian districts is introduced. Series of instances were solved to assess the impact of these parity constraints on the objective function and deadhead distance. Networks with up to 401 nodes and 764 edges were successfully solved. The model is useful at a tactical level as it can be used to promote workload balance, compactness, deadhead distance reduction and parity in districts.
Mon, 15 Feb 2016 12:00:47 GMThttp://hdl.handle.net/2117/829202016-02-15T12:00:47ZGarcia Ayala, GarielaGonzález Velarde, José LuisRios Mercados, RogerFernández Aréizaga, ElenaThe problem of district design for the implementation of arc routing activities is addressed. The aim is to partition a road network into a given number of sectors to facilitate the organization of the operations to be implemented within the region. This problem arises in numerous applications such as postal delivery, meter readings, winter gritting, road maintenance, and municipal solid waste collection. An integer linear programming model is proposed where a novel set of node parity constraints to favor Eulerian districts is introduced. Series of instances were solved to assess the impact of these parity constraints on the objective function and deadhead distance. Networks with up to 401 nodes and 764 edges were successfully solved. The model is useful at a tactical level as it can be used to promote workload balance, compactness, deadhead distance reduction and parity in districts.