http://hdl.handle.net/2117/3863 2013-06-20T06:55:56Z http://hdl.handle.net/2117/19528 Title: Dielectric, thermal, and mechanical properties of acrylonitrile butadiene styrene reinforced with used tires Authors: Mujal Rosas, Ramón María; Òrrit Prat, Jordi; Ramis Juan, Xavier; Marín Genescá, Marcos; Rahhali, Ahmed Abstract: Mass production of tires as well as their storage or elimination is a real environmental problem. Various methods for recycling of tires are currently used, such as mechanical grinding, which separates vulcanized rubber, steel, and fibers from tires. Rubber is, then, used in several industrial applications such as flooring, insulations, and footwear. This paper focuses on a new application for old used tires (ground tire rubber, GTR). Tire dust and acrylonitrile butadiene styrene (ABS) have been mixed, and the maximum accepted concentration of GTR can be attained while keeping dielectric, thermal, and mechanical properties within acceptable limits, and therefore their possible industrial application will be in manufacturing of, for example, dielectrics for capacitors, low-voltage electric fences or electrical cable pipes, and trays. Actually, tire dust with particle sizes <700 μm has been classified into three different groups depending on the particle sizes (p < 200, 200< p < 500, and p > 500 μm). Afterward, ABS has been mixed with different concentrations of GTR, i.e., 5%, 10%, 20%, 50% and 70%, to establish its properties through thermal, mechanical, and dielectric tests. Finally, the fracture surfaces of the composite samples have been evaluated by using scanning electron microscopy. Description: Cop. 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E399–E415, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21287 2013-06-07T10:39:39Z http://hdl.handle.net/2117/18053 Title: Dielectric, mechanical, and thermal characterization of high-density polyethylene composites with ground tire rubber Authors: Mujal Rosas, Ramón María; Marín Genescá, Marcos; Orrit Prat, Jordi; Rahhali, Ahmed; Colom Fajula, Xavier Abstract: The mass manufacture of tires and the difficulty in storing or disposing them constitute a serious environmental problem. At present, various recycling methods for tires are used, such as grinding, which separates the steel and fibers from the vulcanized rubber, then using the rubber in numerous industrial applications such as pavements, insulators, footwear, etc. The aim of this article focuses on finding a new application for the ground tire rubber (GTR). This would allow including GTR in industrial applications of recycled high-density polythene (HDPE). Tire dust and HDPE thermoplastic have been mixed, and the maximum accepted values of GTR concentration that can be admitted while keeping dielectric, mechanical, and thermal properties within acceptable values, as well as initial polymer microstructure, have been checked. In addition, the suitability of the compounds for antistatic applications is studied. The recycled tire dust which results from the industrial milling processes has been divided by sieve in three different categories according to the size of the particles (<200, 200–500, and >500 mm). This has then been mixed with HDPE in different GTR concentrations (0%, 5%, 10%, 20%, 40%, 50%, and 70%) in order to establish its conduct through electrical, mechanical, thermal, and microstructure tests, which will be held in a temperature range 30–120_C, and with a frequency range 1 _ 10_2 and 3 _ 106 Hz. The thermal tests determined the enthalpies and fusion temperatures which allow for the observation of changes in crystalline and microstructure of the matrix, and finally, the fracture surfaces of the compound samples have been evaluated using scanning electron microscopy 2013-03-05T10:41:14Z http://hdl.handle.net/2117/17636 Title: Study on dielectric, mechanical and thermal properties of polypropylene (PP) composites with ground tyre rubber (GTR) Authors: Mujal Rosas, Ramón María; Orrit Prat, Jordi; Ramis Juan, Xavier; Marín Genescá, Marcos; Rahhali, Ahmed 2013-02-11T14:57:40Z http://hdl.handle.net/2117/17612 Title: Aplicaciones eléctricas del acrilonitrilo butadieno estireno (ABS) reforzado con neumáticos fuera de uso (GTR) Authors: Mujal Rosas, Ramón María; Orrit Prat, Jordi; Ramis Juan, Xavier; Marín Genescá, Marcos 2013-02-08T13:57:52Z http://hdl.handle.net/2117/17281 Title: Enhanced decoupled double synchronous reference frame current controller for unbalanced grid-voltage conditions Authors: Reyes, M.; Rodríguez Cortés, Pedro; Vazquez, S.; Luna Alloza, Álvaro; Teodorescu, Remus; Carrasco, J.M. Abstract: In the last few years, restrictive grid codes have arisen to ensure the performance and stability of electrical networks, which experience amassive integration of renewable energy sources and distributed generation systems that are normally connected to the grid through electronic power converters. In these codes, the injection of positive- and negative-sequence current components becomes necessary for fulfilling, among others, the low-voltage ride-through requirements during balanced and unbalanced grid faults. However, the performance of classical dq current controllers, applied to power converters, under unbalanced grid-voltage conditions is highly deficient, due to the unavoidable appearance of current oscillations. This paper analyzes the performance of the double synchronous reference frame controller and improves its structure by adding a decoupling network for estimating and compensating the undesirable current oscillations. Experimental results will demonstrate the validity of the proposed decoupled DSRF controller 2013-01-11T13:57:37Z http://hdl.handle.net/2117/17231 Title: Evaluation of storage energy requirements for constant production in PV power plants Authors: Beltran, Hector; Bilbao, Endika; Belenguer, Enrique; Etxeberria Otadui, Ion; Rodríguez Cortés, Pedro Abstract: This paper analyzes the minimum energy capacity ratings that an energy-storage (ES) system should accomplish in order to achieve a defined constant power production in a photovoltaic (PV) power plant. ES is a key issue for the further integration of intermittent and stochastic renewable energy sources, which are not currently dispatchable due to their dependence on real-time weather conditions, as is the case of PV technology. This paper proposes and describes an energy management strategy (EMS) for operating PV power plants with ES in the future. The goal of this EMS is to endow these power plants with a constant production that can be controlled and hence traded on electricity markets. This paper presents simulated results on the percentage of time throughout the year during which a large-scale PV+ES plant operates properly with different ES ratings and according to different configurations of this EMS. Finally, a test bench was developed, and experimental results validating this EMS were obtained 2013-01-09T12:11:07Z http://hdl.handle.net/2117/17230 Title: Direct synchronous-asynchronous conversion system for hybrid electrical vehicle applications. An energy-based modeling approach Authors: Muñoz Aguilar, Raúl Santiago; Dòria Cerezo, Arnau; Puleston, Paul Abstract: This paper presents a proposal for a series hybrid electric vehicle propulsion system. This new configuration is based on a wound-rotor synchronous generator (WRSM) and a doubly-fed induction machine (DFIM). The energy-based model of the whole system is obtained taking advantage of the capabilities of the port-based modeling techniques. From the dq port-controlled Hamiltonian description of the WRSM and DFIM, the Hamiltonian model of the proposed Direct Synchronous-Asynchronous Conversion System (DiSAC) is developed. Subsequently, the bond graph models of the DiSAC and associate systems are also provided. Numerical simulations are also presented in order to validate the proposed system 2013-01-09T11:36:16Z http://hdl.handle.net/2117/17114 Title: Voltage-sensor-less synchronization to unbalanced grids by frequency-adaptive virtual flux estimation Authors: Suul, Jon Are; Luna Alloza, Álvaro; Rodríguez Cortés, Pedro; Undeland, Tore Abstract: This paper proposes a simple method for inherently frequency-adaptive virtual flux (VF) estimation intended for voltage-sensor-less grid synchronization and control of voltage source converters. The frequency-adaptive characteristics are obtained by using a second-order generalized integrator configured as a quadrature signal generator (SOGI-QSG) with the grid frequency as an explicit input variable. It is also shown how the properties of VF estimation based on SOGI-QSGs can be utilized to achieve a simple and effective synchronization technique that integrates frequency-adaptive bandpass filtering, VF estimation, and symmetrical component sequence separation into one operation. This new method avoids cascaded delays of VF estimation and sequence separation and is labeled as dual SOGI-based VF (DSOGI-VF) estimation since it is based on two parallel SOGI-QSGs. The properties and performance of the DSOGI-VF estimation are analyzed in comparison to conventional configurations of VF estimation and sequence separation, demonstrating that it is a simpler structure with improved dynamic response. In fact, similar response time as for grid synchronization based on voltage measurements is achieved. The operation and performance of the proposed DSOGI-VF estimation method have been verified by laboratory experiments in a small-scale converter setup. 2012-12-12T10:30:33Z http://hdl.handle.net/2117/16415 Title: A propagative model for simulations of electric fields produced by downward leaders Authors: Hermoso Costa, Juan Ramón; Montañá Puig, Juan; March Nomen, Víctor; Van der Velde, Oscar Arnoud; Solà de Las Fuentes, Gloria; Romero Durán, David; Hermoso Alameda, Blas; Pineda Ruegg, Nicolau Abstract: Comparisons of simulated downward negative leaders with experimental measurements are presented in this paper. In order to simplify, the leaders are considered to progress vertically and charge distributions and leader speeds can be adjusted. The results report a good agreement with Cooray’s, Golde’s and Hutler’s proposals. In the case of Dellera’s proposal (LPM) it only agrees for the last 2 km of the leader position. Eriksson’s proposal produced good agreements but closer flash distances are not consistent with the measured lightning flash. The obtained speeds ranged between 1.15􀀁106 m􀀁s-1 to 2.6􀀁104 m􀀁s-1 which are consistent with those reported in literature. 2012-09-03T10:02:57Z http://hdl.handle.net/2117/15832 Title: Local reactive power control methods for overvoltage prevention of distributed solar inverters in low-voltage grids Authors: Demirok, Erhan; Casado Gonzalez, P.; Frederiksen, K.H.B.; Sera, Dezso; Rodríguez Cortés, Pedro; Teodorescu, Remus Abstract: The main objective of this study is to increase the penetration level of photovoltaic (PV) power production in low-voltage (LV) grids by means of solar inverters with reactive power control capability. This paper underlines weak points of standard reactive power strategies which are already imposed by certain grid codes, and then, the study introduces a new reactive power control method that is based on sensitivity analysis. The sensitivity analysis shows that the same amount of reactive power becomes more effective for grid voltage support if the solar inverter is located at the end of a feeder. Based on this fundamental knowledge, a location-dependent power factor set value can be assigned to each inverter, and the grid voltage support can be achieved with less total reactive power consumption. In order to prevent unnecessary reactive power absorption from the grid during admissible voltage range or to increase reactive power contribution from the inverters that are closest to the transformer during grid overvoltage condition, the proposed method combines two droop functions that are inherited from the standard cosϕ(P) and Q(U) strategies. Its performance comparison in terms of grid losses and voltage variation with different reactive power strategies is provided by modeling and simulating a real suburban LV network. 2012-05-11T11:08:05Z http://hdl.handle.net/2117/15725 Title: Power capability investigation based on electrothermal models of press-pack IGBT three-level NPC and ANPC VSCs for multimegawatt wind turbines Authors: Senturk, Osman S.; Helle, Lars; Rodríguez Cortés, Pedro; Munk-Nielsen, Stig; Teodorescu, Remus Abstract: Wind turbine power capability is an essential set of data for both wind turbine manufacturers/operators and transmission system operators since the power capability determines whether a wind turbine is able to fulfill transmission system reactive power requirements and how much it is able to provide reactive power support as an ancillary service. For multimegawatt full-scale wind turbines, power capability depends on converter topology and semiconductor switch technology. As power capability limiting factors, switch current, semiconductor junction temperature, and converter output voltage are addressed in this study for the three-level neutral-point-clamped voltage source converter (3L-NPC-VSC) and 3L Active NPC VSC (3L-ANPC-VSC) with press-pack insulated gate bipolar transistors employed as a gridside converter. In order to investigate these VSCs’ power capabilities under various operating conditions with respect to these limiting factors, a power capability generation algorithm based on the converter electrothermal model is developed. Built considering the VSCs’ operation principles and physical structure, the model is validated by a 2MV·A single-phase 3L-ANPC-VSC test setup. The power capability investigations regarding a sample grid code’s reactive power requirement showthat 3L-ANPC-VSC results in 32% better power capability than 3L-NPC-VSC at the switching frequency of 1050 Hz. Furthermore, 3L-ANPC-VSC with 57% higher switching frequency (1650 Hz) and 33% smaller switching ripple filter can yield close power capability compared to 3L-NPC-VSC with 1050 Hz. 2012-04-11T15:01:08Z http://hdl.handle.net/2117/15207 Title: Design and analysis of a slope voltage control for a DFIG wind power plant Authors: Martinez, J.; Kjaer, P. C.; Rodríguez Cortés, Pedro; Teodorescu, Remus Abstract: This paper addresses a detailed design of a wind power plant and turbine slope voltage control in the presence of communication delays for a wide short-circuit ratio range operation. The implemented voltage control scheme is based upon the secondary voltage control concept, which offers fast response to grid disturbances, despite the communication delays, i.e., this concept is based on a primary voltage control, located in the wind turbine, which follows an external voltage reference sent by a central controller, called secondary voltage control, which is controlling the voltage at the point of connection with the grid. The performance has been tested using PSCAD/EMTDC program. The plant layout used in the simulations is based on an installed wind power plant, composed of 23 doubly fed generator wind turbines. The resulting performance is evaluated using a compilation of grid code voltage control requirements. The results show that fast response to grid disturbances can be achieved using the secondary voltage control scheme, and the fulfillment of the design requirements can be extended for a wide range of short-circuit ratios. 2012-02-17T11:47:12Z http://hdl.handle.net/2117/15204 Title: Voltage-sensor-less synchronization to unbalanced grids by frequency-adaptive virtual flux estimation Authors: Suul, Jon Are; Luna Alloza, Álvaro; Rodríguez Cortés, Pedro; Undeland, Tore Abstract: This paper proposes a simple method for inherently frequency-adaptive virtual flux (VF) estimation intended for voltage-sensor-less grid synchronization and control of voltage source converters. The frequency-adaptive characteristics are obtained by using a second-order generalized integrator configured as a quadrature signal generator (SOGI-QSG) with the grid frequency as an explicit input variable. It is also shown how the properties of VF estimation based on SOGI-QSGs can be utilized to achieve a simple and effective synchronization technique that integrates frequency-adaptive bandpass filtering, VF estimation, and symmetrical component sequence separation into one operation. This new method avoids cascaded delays of VF estimation and sequence separation and is labeled as dual SOGI-based VF (DSOGI-VF) estimation since it is based on two parallel SOGI-QSGs. The properties and performance of the DSOGI-VF estimation are analyzed in comparison to conventional configurations of VF estimation and sequence separation, demonstrating that it is a simpler structure with improved dynamic response. In fact, similar response time as for grid synchronization based on voltage measurements is achieved. The operation and performance of the proposed DSOGI-VF estimation method have been verified by laboratory experiments in a small-scale converter setup. 2012-02-17T11:06:59Z http://hdl.handle.net/2117/15167 Title: Converter structure-based power loss and static thermal modeling of the press-pack IGBT three-level ANPC VSC applied to multi-MW wind turbines Authors: Senturk, Osman S.; Helle, Lars; Munk-Nielsen, Stig; Rodríguez Cortés, Pedro; Teodorescu, Remus Abstract: Wind turbine converters demand high power density due to nacelle space limitation and high reliability due to high maintenance cost. Depending on the converter structure, the converter thermal performance determines the converter power density and reliability. To estimate the converter thermal performance, the converter structure-based power loss and thermal models are developed in this study for the medium-voltage (MV) three-level active neutral-point-clamped voltage source converter (3L-ANPC-VSC) utilizing 4500 V-1800 A press-pack insulated-gate bipolar transistor-diode pairs and interfacing a 6 MW wind turbine to a MV grid. The switching power loss models are built using the experimental switching power loss data acquired via the double-pulse tests conducted on a full-scale 3L-ANPC-VSC prototype. The converter static thermal model is developed based on the double-sided water-cooled press-pack switches. Via a single-phase test setup with two full-scale 3L-ANPC-VSC legs, the developed power loss and thermal models are validated experimentally. Employing the validated models, the 3L-ANPC-VSC's thermal performance is demonstrated on simulation for a 6 MW wind turbine grid interface. Hence, these converter structure-based models developed and validated in this study are proven to be suitable for the converter power density and reliability studies based on converter thermal performance. 2012-02-15T13:29:28Z http://hdl.handle.net/2117/15102 Title: Design and coordination of a capacitor and on-load tap changer system for voltage control in a wind power plant of doubly fed induction generator wind turbines Authors: Martinez, J.; Rodríguez Cortés, Pedro; Kjaer, P. C.; Teodorescu, Remus Abstract: In this paper, a novel coordination and control strategy for capacitor banks and on-load tap changer for a wind power plant is introduced. The capacitor banks are controlled in such way that the steady-state usage of the converters for reactive power injection is driven below to a maximum desired value of 0.1 pu. Additionally, the control transients because of the capacitor bank switching are minimized by using a suitable control structure. The tap changer control is coordinated with the plant control to decrease the impact of the capacitors reactive power in the line drop calculation, thus reducing the amount of tap operations and improving the accuracy of the line drop voltage estimation. The coordination of the central controller with the plant components is analysed and tested through electromagnetic transient program simulations. 2012-02-13T15:36:10Z