Departament d'Enginyeria Elèctrica
http://hdl.handle.net/2117/4007
2015-10-09T14:32:08ZDFIG-based offshore wind power plant connected to a single VSC-HVDC operated at variable frequency: Energy yield assessment
http://hdl.handle.net/2117/77414
DFIG-based offshore wind power plant connected to a single VSC-HVDC operated at variable frequency: Energy yield assessment
de Prada Gil, Mikel; Díaz González, Francisco; Gomis Bellmunt, Oriol; Sumper, Andreas
The existence of HVDC (High Voltage Direct Current) transmission systems for remote offshore wind power plants allows devising novel wind plant concepts, which do not need to be synchronized with the main AC grid. This paper proposes an OWPP (offshore wind power plant) design based on variable speed wind turbines driven by DFIGs (doubly fed induction generators) with reduced power electronic converters connected to a single VSC-HVDC converter which operates at variable frequency and voltage within the collection grid. It is aimed to evaluate the influence of the power converter size and wind speed variability within the WPP on energy yield efficiency, as well as to develop a coordinated control between the VSC-HVDC converter and the individual back-to-back reduced power converters of each DFIG-based wind turbine in order to provide control capability for the wind power plant at a reduced cost. To maximise wind power generation by the OWPP, an optimum electrical frequency search algorithm for the VSC-HVDC converter is proposed. Both central wind power plant control level and local wind turbine control level are presented and the performance of the system is validated by means of simulations using MA'FLAB/Simulink (R). (C) 2015 Elsevier Ltd. All rights reserved.
2015-06-15T00:00:00ZPromotion of concentrating solar thermal power (CSP) in Spain: Performance analysis of the period 1998–2013
http://hdl.handle.net/2117/77310
Promotion of concentrating solar thermal power (CSP) in Spain: Performance analysis of the period 1998–2013
Martín Cañadas, María Elena; Hoz Casas, Jordi de la; Velasco Quesada, Guillermo; Castilla Fernández, Miguel; García de Vicuña Muñoz de la Nava, José Luis
A thorough analysis of the Concentrating Solar Thermal Power (CSP) development in Spain in the period 1998–2013 has been carried out in order to identify the main drivers behind the bubble-like behaviour exhibited by this renewable technology. Tending a parallelism with the basic principles of the control systems theory has facilitated the identification of the main shortcomings in the design of the various control frameworks governing the CSP deployment in the studied period. The CSP disorderly proliferation propitiated by inefficient control mechanisms has resulted in an overrun cost to the electricity system that has tried to be mitigated with the application of retroactive measures seriously harmful for the investors. It is expected that the conclusions drawn from this comprehensive review of the Spanish case have a general relevance for other countries undertaking the development path of renewable technologies.
2015-10-01T00:00:00ZConvertidores smart para las redes del futuro
http://hdl.handle.net/2117/77226
Convertidores smart para las redes del futuro
Heredero Peris, Daniel; Pagès Giménez, Marc; Montesinos Miracle, Daniel
2015-06-01T00:00:00ZPermanent execution of MPPT algorithm for PV systems with energy storage
http://hdl.handle.net/2117/77202
Permanent execution of MPPT algorithm for PV systems with energy storage
Heredero Peris, Daniel; Pagès Giménez, Marc; Gross, Gabriel Igor; Montesinos Miracle, Daniel
A novel strategy for continuous execution of the
MPPT algorithm for a microgrid distributed energy resource
inverter is proposed. The exposed control strategy allows to
operate a photovoltaic inverter in both grid-connected and
grid-disconnected modes also considering local loads. The main
objective of this technique is supply power to the local loads while
extracting the maximum power during charge or discharge of the
batteries with the higher allowable current for the chosen energy
storage technology
2015-01-01T00:00:00ZCalculation of the ac to dc resistance ratio of conductive nonmagnetic straight conductors by applying FEM simulations
http://hdl.handle.net/2117/77125
Calculation of the ac to dc resistance ratio of conductive nonmagnetic straight conductors by applying FEM simulations
Riba Ruiz, Jordi-Roger
This paper analyzes the skin and proximity effects in different conductive nonmagnetic straight conductors’ configurations subjected to applied alternating currents and voltages. These effects have important consequences, including a rise of the ac resistance, which in turn increases power loss, thus limiting the rating for the conductor. The alternating current (ac) resistance is important in power conductors and bus bars for line frequency applications as well as in smaller conductors for high frequency applications. Despite the importance of this topic, it is usually not analyzed in detail in undergraduate and even in graduate studies. For this purpose, this paper compares the results provided by available exact formulas for simple geometries with those obtained by means of two-dimensional finite element method (FEM) simulations and experimental results. The paper also shows that FEM results are very accurate and more general than those provided by the formulas, since FEM models can be applied in a wide range of electrical frequencies and configurations
2015-09-01T00:00:00ZOptimization of short-circuit tests based on finite element analysis
http://hdl.handle.net/2117/77106
Optimization of short-circuit tests based on finite element analysis
Capelli, Francesca; Riba Ruiz, Jordi-Roger; González, David
One of the main problems that arises when
performing short-circuit tests to large loops involving substation
connectors is the inductive component of the loop impedance.
Transformers used to perform short-circuit tests have a
secondary winding with very few turns, producing a very low
output voltage. The increase in the reactive component of the
impedance, which is related to loop size, limits the current output
capacity, because the reactive component tends to saturate the
output of the transformer and absorbs large amounts of reactive
power. This paper analyzes a simple method to minimize the
power requirements when conducting short-circuit tests, based
on the reduction of reactive power consumption during the test.
It is based on placing a wired conductor forming a closed inner
loop concentric with the testing loop. The decrease of reactive
power is related to the effect of the mutual inductance between
the inner and outer loops. Three-dimensional finite element
method (3D-FEM) simulations are used to optimize the problem,
allowing changing the geometric and material properties of the
inner loop. Experimental results validate the simulation method
applied in this work to optimize the short-circuit tests
2015-01-01T00:00:00ZImproving time-domain EMI measurements through digital signal processing
http://hdl.handle.net/2117/77098
Improving time-domain EMI measurements through digital signal processing
Azpúrua Auyanet, Barón Marco Aurelio; Pous Solà, Marc; Cakir, S.; Silva Martínez, Fernando; Cetinta, M.
This article is intended to provide a set of recommended practices for improving of the Time-Domain EMI measurement systems by means of digital signal processing. We have focused on two major aspects: the optimal configuration settings of the direct measurement equipment and the deployment of algorithms to process the measurement result. In that sense, we believe that general purpose time-domain instruments, as oscilloscopes, can be successfully used as an alternative hardware to measure EMI, since they provide accurate and reliable results, surpassing the conventional frequency-domain approach when transient disturbances are present.
2015-07-01T00:00:00ZVector feedback homogeneity and inner layout influence on fluxgate sensor parameters
http://hdl.handle.net/2117/77097
Vector feedback homogeneity and inner layout influence on fluxgate sensor parameters
Petrucha, V; Janosek, M; Azpúrua Auyanet, Barón Marco Aurelio
Vector feedback is a concept which can significantly improve linearity and stability of a magnetic field sensor. The feedback coils effectively cancel the measured magnetic field in the inner volume of the triaxial sensor. Thus, in case of fluxgates, it suppresses one possible source of nonlinearity—cross-field sensitivity error. The triaxial sensor axes orthogonality should be primarily defined by the orientation of the feedback coils, while the sensitivities are defined by feedback coil constants. The influence of the homogeneity of the feedback field and the influence of the sensor inner layout on calibration parameters of a vectorially compensated triaxial fluxgate magnetometer are presented.
2015-05-01T00:00:00ZOptimal sizing of a hybrid grid-connected photovoltaic–wind–biomass power system
http://hdl.handle.net/2117/77078
Optimal sizing of a hybrid grid-connected photovoltaic–wind–biomass power system
González Juncà, Arnau; Riba Ruiz, Jordi-Roger; Rius Carrasco, Antoni
2015-09-18T00:00:00ZAnalysis of formulas to calculate the AC resistance of different conductors' configurations
http://hdl.handle.net/2117/77077
Analysis of formulas to calculate the AC resistance of different conductors' configurations
Riba Ruiz, Jordi-Roger
Skin and proximity effects in single- or multi-conductor systems can notoriously affect the AC
resistance in conductors intended for electrical power transmission and distribution systems and for
electronic devices. This increase of the AC resistance raises power loss and limits the conductors’ currentcarrying
capacity, being an important design parameter. There are some internationally recognized exact
and approximated formulas to calculate the AC resistance of conductors, whose accuracy and applicability
is evaluated in this paper. However, since these formulas can be applied under a wide range of
configurations and operating conditions, it is necessary to evaluate the applicability of these models. This is
done by comparing the results that they provide with experimental data and finite element method (FEM)
simulation results. The results provided show that FEM results are very accurate and more general than
those provided by the formulas, since FEM models can be applied to a wide range of conductors’
configurations and electrical frequencies
2015-10-01T00:00:00Z