http://hdl.handle.net/2117/3936 2013-05-24T22:29:10Z http://hdl.handle.net/2117/19229 Title: Design of neutral-point voltage controller of a three-level NPC inverter with small DC-link capacitors Authors: Maheshwari, RamKrishan; Munk-Nielsen, Stig; Busquets Monge, Sergio Abstract: A neutral-point-clamped three-level inverter with small dc-link capacitors is presented in this paper. The inverter requires zero average neutral-point current for stable neutral–point voltage. The small dc-link capacitors may not maintain capacitor voltage balance, even with zero neutral-point current. This may happen due to nonlinearities present in the circuit. This requires a fast control of the neutral-point voltage. A simple carrier-based modulation strategy which allows modeling of the neutral-point voltage dynamics as a continuous function of power drawn fromthe inverter is proposed. This continuous model shows that the neutral-point current is proportional to the power drawn from the inverter, and it enables the use of a well-established classical control theory for the neutral-point voltage controller design. A simple proportional integral controller is designed for the neutral-point voltage control on the basis of the continuous model. The design method for optimum performance is discussed. The implementation of the proposed modulation strategy and the controller is very simple. The controller is implemented in a 7.5-kW induction machine-based drive with only 14 μF dc-link capacitors. Also, the experimental results show that fast and stable performance of the neutral-point voltage controller are achieved and thus verify the validity of the proposed control approach. 2013-05-15T08:29:47Z http://hdl.handle.net/2117/19217 Title: Inductor shielding strategies to protect mmW LC-VCOs from high frequency substrate noise Authors: Molina García, Marc; Aragonès Cervera, Xavier; Mateo Peña, Diego; González Jiménez, José Luis Abstract: This paper analyzes the impact of high-frequency substrate noise on two 60 GHz LC-VCOs that implement different strategies for inductor shielding, namely floating and grounded shields. An analytical model, which has previously shown very good accuracy up to 7 GHz, is used to identify the circuit parameters that determine the level of the spurs created by the noise. These parameters are individually evaluated for the two VCOs, identifying their relative responsibility for the observed noise effects. The analysis concludes that a floating inductor shield provides extra immunity compared to a grounded inductor shield, and that this advantage is essentially due to the improvement in the tank quality factor. The predictions of the analytical model are validated by comparing them with circuit simulations and measurements of the noise impact on the two VCOs manufactured in a 65 nm CMOS technology, proving its usefulness at mm-wave frequencies. 2013-05-14T17:11:01Z http://hdl.handle.net/2117/19174 Title: SIXE: An X-ray experiment for the MINISAT platform Authors: Bravo Guil, Eduardo; García-Berro Montilla, Enrique; Gutierrez Cabello, Jorge Luis; José Pont, Jordi; García Senz, Domingo; Cabestany Moncusí, Joan; Madrenas Boadas, Jordi 2013-05-13T09:46:38Z http://hdl.handle.net/2117/18984 Title: Asymptotic time domain evaluation of a multilevel multiphase PWM converter voltage quality Authors: Ruderman, Alex; Reznikov, Boris; Busquets Monge, Sergio Abstract: Voltage total harmonic distortion and quadratic voltage ripple criteria are accepted figures of merit of a multilevel pulse width modulation (PWM) converter voltage quality. The dominating frequency domain approach does not deliver simple closed-form expressions and practically requires accounting up to 40–50 switching harmonics. Assuming infinitely high switching frequency, suggested time domain approach to a multilevel multiphase PWM voltage quality evaluation provides closed-form piece-wise analytical solutions. These simple formulas clearly reveal the dependence on modulation index for arbitrary voltage level and odd phase numbers. The results are applicable to any type of multilevel converters (including interleaved, open winding and other) operated with nearest level/nearest space vector modulation and relatively high switching frequency. 2013-04-25T11:31:29Z http://hdl.handle.net/2117/18861 Title: A design method for active high-CMRR fully-differential circuits Authors: Hornero Ocaña, Gemma; Casas Piedrafita, Óscar; Spinelli, Enrique Mario; Haberman, Marcelo 2013-04-18T10:16:22Z http://hdl.handle.net/2117/18806 Title: Spatially and frequency-resolved monitoring of intradie capacitive coupling by heterodyne excitation infrared lock-in thermography Authors: León, J.; Perpiñà, Xavier; Altet Sanahujes, Josep; Vallvehi, Miquel; Jordà, Xavier Abstract: This paper combines the infrared lock-in thermography (IR-LIT) and heterodyne excitation techniques to detect high-frequency capacitive currents due to intradie electrical coupling between microelectronic devices or more complex systems. Modulating the excitation with the heterodyne approach, we drive devices or complex systems with high frequency electrical signals in such a way that they behave as low frequency heat sources, modulating their temperature field at a frequency detectable by an IR-LIT system. This approach is analytically studied and extended to a bi-dimensional scenario, showing that the thermal information at low frequency depends on the electrical characteristics of the sample at high frequency. 2013-04-15T16:09:58Z http://hdl.handle.net/2117/18574 Title: Fractional DC-DC converter in solar-powered electrical generation systems Authors: Martínez González, Rubén; Bolea Monte, Yolanda; Grau Saldes, Antoni; Martínez García, Herminio Abstract: This paper deals with the fractional modeling of a DC-DC buck-boost converter, suitable in solar-powered electrical generation systems, and the design of a fractional controller for the aforementioned switching converter. Although the modeling and design of the controller is carried out for this particular DC-DC converter, it can be easily extended to other kind of switching converter. In addition, the comparison between integer-order plan/controller and fractional-order plants/controller is carried out. The article also shows that, under the same design conditions, the fractional-order controller has a better performance and behaviour than the classical integer-order controller in both situations, that is, with integer-order plant and fractional-order plant models. 2013-04-03T12:02:03Z http://hdl.handle.net/2117/18537 Title: Biological and anthropogenic sound sources: effects and control in the European Seas Observatory Network (ESONET) Authors: André, Michel; Manuel Lázaro, Antonio; Dañobeitia, Juan José; Rolin, Jean-François; Person, Roland 2013-04-02T11:07:14Z http://hdl.handle.net/2117/18443 Title: Overmodulation of n-level three-leg DC-AC diode-clamped converters with comprehensive capacitor voltage balance Authors: Busquets Monge, Sergio; Maheshwari, RamKrishan; Munk-Nielsen, Stig Abstract: This paper presents a novel pulsewidth modulation (PWM) strategy for n-level three-leg semiconductor-clamped dc–ac converters in the overmodulation region, with dc-link capacitor voltage balance in every switching cycle. The strategy is based on the virtual-vector concept. Suitable reference vector trajectories are selected to obtain low weighted total harmonic distortion and a simple algorithm. A hexagonal-boundary compression factor is introduced to guarantee, at any operating point, dc-link capacitor voltage regulation capabilities in every switching cycle and avoid narrow gate pulses. The detailed PWMalgorithm for an easy implementation in a digital control platform is also presented. The good performance of the strategy is verified through both simulation and experiments in a three-level three-phase neutral-point clamped converter. 2013-03-20T13:47:19Z http://hdl.handle.net/2117/18372 Title: An alternative method to quantify the electromagnetic immunity based on the Weibull distribution Authors: Fernández García, Raúl; Gil Galí, Ignacio Abstract: It is accepted that the electromagnetic interference should be addressed with statistical analysis. Usually the impact of electromagnetic interference on different electronic samples is evaluated and the average immunity level is used as a reference. However, this method does not provide enough information to know the probability of failure to the electromagnetic interferences of an electronic circuit. An alternative statistical analysis based on the Weibull distribution is presented. The typical and proposed methods have been compared in order to analyse the electromagnetic immunity performance of two types of operational amplifier. The results confirm the feasibility of the proposed method. 2013-03-18T15:04:11Z http://hdl.handle.net/2117/17686 Title: Emissive properties of SiO2 thin films through photonic windows Authors: Hernández García, David; Garin Escriva, Moises; Todorov Trifonov, Trifon; Rodríguez Martínez, Ángel; Alcubilla González, Ramón 2013-02-12T18:01:52Z http://hdl.handle.net/2117/17659 Title: Real-time speaker verification system implemented on reconfigurable hardware Authors: Ramos Lara, Rafael Ramón; López García, Mariano; Canto Navarro, Enrique Fernando; Puente Rodriguez, Luis Abstract: Nowadays, biometrics is considered as a promising solution in the market of security and personal verification. Applications such as financial transactions, law enforcement or network management security are already benefitting from this technology. Among the different biometric modalities, speaker verification represents an accurate and efficient way of authenticating a person’s identity by analyzing his/her voice. This identification method is especially suitable in real-life scenarios or when a remote recognition over the phone is required. The processing of a signal of voice, in order to extract its unique features, that allows distinguishing an individual to confirm or deny his/ her identity is, usually, a process characterized by a high computational cost. This complexity imposes that many systems, based on microprocessor clocked at hundreds of MHz, are unable to process samples of voice in real-time. This drawback has an important effect, since in general, the response time needed by the biometric system affects its acceptability by users. The design based on FPGA (Field Programmable Gate Arrays) is a suited way to implement systems that require a high computational capability and the resolution of algorithms in real-time. Besides, these devices allow the design of complex digital systems with outstanding performance in terms of execution time. This paper presents the implementation of a MFCC (Mel-Frequency Cepstrum Coefficients)—SVM (Support Vector Machine) speaker verification system based on a low-cost FPGA. Experimental results show that our system is able to verify a person’s identity as fast as a high-performance microprocessor based on a Pentium IV personal computer. 2013-02-12T13:39:36Z http://hdl.handle.net/2117/17649 Title: Solution-growth and optoelectronic properties of ZnO:Cl@ZnS core-shell nanowires with tunable shell thickness Authors: Fan, Jiandong; Fábrega, Cristian; Zamani, Reza; Shavel, Alexey; Güell, Frank; Carrete, Alex; Andreu, Teresa; López Martínez, Antonio Miguel; Morante, Joan Ramón; Arbiol, Jordi; Cabota, Andreu Abstract: Arrays of vertically aligned ZnO:Cl@ZnS core–shell nanowires (NWs) were grown by a facile low-cost, high-yield and seed-free two-step process. These NWs were used to demonstrate the potential of 3D electrodes based on core–shell heterostructures to enhance charge carrier separation and transfer. With this goal in mind, the photocurrent density of ZnO:Cl@ZnS NWs was characterized as a function of the shell thickness. Although no significant variations in the absorption and photoluminescence spectra were found with the presence of the shell, the photocurrent measured from the core–shell NWs was highly enhanced with respect to bare ZnO:Cl NWs. These photocurrent variations are associated with the control of the band bending in the core–shell NW surface, which modifies the efficiency of charge carrier transfer between the NW and the electrolyte. 2013-02-12T11:47:27Z http://hdl.handle.net/2117/17609 Title: Development of a system to test somnolence detectors with drowsy drivers Authors: Lopez De la O, Jaime; Rodriguez Ibañez, Noelia; Nombela, Mario; Barrios, Jose Manuel; García González, Miguel Ángel; Ramos Castro, Juan José; Fernández Chimeno, Mireya Description: Somnolence; Semi-autonomous conduction 2013-02-08T12:43:56Z http://hdl.handle.net/2117/17606 Title: Evidence of intrinsic ambipolar charge transport in a high band gap organic semiconductor Authors: Moreno Sierra, César; Pfattner, Raphael; Mas Torrent, Marta; Puigdollers i González, Joaquim; Bromley, Stephan; Rovira, Concepcio; Veciana, Jaume; Alcubilla González, Ramón Abstract: Theoretical and experimental investigations combining in situ Kelvin probe microscopy (KPM) and macroscopic electrical studies are employed to explore the intrinsic transport in dithiophene-tetrathiafulvalene (DT-TTF) single crystal organic field-effect transistors. Our work demonstrates that ambipolar behavior is not restricted only to materials possessing a high electron affinity and thus may be a more general phenomenon. 2013-02-08T11:54:37Z