http://hdl.handle.net/2117/3653 2013-05-21T10:41:57Z http://hdl.handle.net/2117/14551 Title: Analysis of PMSM using FE analysis: a didactical approach for EMF determination and cogging torque reduction. Authors: Bargalló Perpiñá, Ramón; Sust de Rosselló, Jorge; Morón Romera, Juan; Pujolras, Joan Carles Abstract: FE analysis is a useful technique, but the interpretation of the results are sometimes confuse and dark. In this paper we shown some methods to determine the back emf in PMSM and how determine and reduce the cogging torque. Our students use these methods and comparing the obtained results, they learn about the post-processing magnitudes in FE analysis and its interpretation; probably the most difficult task in this calculation method. Additionally these results are compared to a prototype and the results are agreed with the prediction. 2012-01-16T09:50:19Z http://hdl.handle.net/2117/13442 Title: Control of power converters in distributed generation applications under grid fault conditions Authors: Rodríguez Cortés, Pedro; Luna Alloza, Álvaro; Muñoz Aguilar, Raúl Santiago; Córcoles López, Felipe; Teodorescu, Remus; Blaabjerg, Frede Abstract: The operation of distributed power generation systems under grid fault conditions is a key issue for the massive integration of renewable energy systems. Several studies have been conducted to improve the response of such distributed generation systems under voltage dips. In spite of being less severe, unbalanced fault cause a great number of disconnections, as it may produce the injection of unbalanced currents that can easily conduct to the tripping of the converter. In this paper a current control strategy for power converters able to deal with these grid conditions, without exceeding the current ratings of the converter is introduced. Moreover, a novel flexible algorithm has been proposed in order to regulate easily the injection of positive and negative currents for general purpose applications. 2011-10-05T15:05:47Z http://hdl.handle.net/2117/13282 Title: Voltage feed-forward performance in stationary reference frame controllers for wind power applications Authors: Ma, Lin; Luna Alloza, Álvaro; Rocabert Delgado, Joan; Muñoz Aguilar, Raúl Santiago; Córcoles López, Felipe; Rodríguez Cortés, Pedro Abstract: In order to improve the connected current and the response speed of the controller, stationary reference frame control strategy with proportional resonant (P-R) controller due to its high dynamic and good harmonic compensation performance characteristics was already used in many different DG applications. This paper introduced an additional stationary reference frame control strategies with voltage feed-forward method. By using this method, both the quality of grid connected current and the dynamic performance are improved, which also validated by experiments. 2011-09-21T11:10:25Z http://hdl.handle.net/2117/13281 Title: Control proposals for the operation of power converters in wind power systems Authors: Luna Alloza, Álvaro; Aguilar, Daniel; Muñoz Aguilar, Raúl Santiago; Córcoles López, Felipe; Rodríguez Cortés, Pedro Abstract: The wind turbines based on Doubly Fed Induction Generators (DFIG) represent almost the 60% of the installed windpower worldwide. Nowadays most of the existing algorithms, used for regulating the production of active and reactive power in such systems, are based on control techniques that use rotational reference frames theories, where the dq0 is maybe the most popular. Despite of its good operation under balanced conditions its behaviour depends on a good phase synchronization, otherwise the different transformations cannot be performed with enough guarantees. Of course this kind of response is becomming insuficient, as far as the windpower penetration is increasing. This paper will present a new control topology for DFIG, that are connected using back to back inverters, that is able to behave better in case of faulty grids. Besides some proposals for improving the operation of the DFIG will be presented as well. The aim of that part is to extend the possibilities that the back to back inverters are able to offer to the generator system by means of including new functionalities, as the active filtering capability or the reduction of the flicker emission that will be later discussed. 2011-09-21T10:44:36Z http://hdl.handle.net/2117/13029 Title: Experimental measurements of fluorescent lamp harmonic current emissions and their impact on neutral current Authors: Cunill Solà, Jordi; Mesas García, Juan José; Sainz Sapera, Luis 2011-07-21T12:22:08Z http://hdl.handle.net/2117/12734 Title: Experimental measurements about harmonic current mitigation of electric vehicle battery chargers Authors: Sainz Sapera, Luis; Balcells Sendra, Josep Abstract: The expected high penetration of battery chargers for electric vehicles (EV) in electric networks is foreseen as a potential problem for power quality. Battery chargers are nonlinear devices that inject harmonic currents and pollute network voltages. Thus, their harmonic emissions must be analyzed and reduced by harmonic mitigation techniques to avoid future problems. This paper analyzes and reports some real case measurements of harmonics injected by single- and three-phase battery chargers and their attenuation using line choke inductances. 2011-06-08T11:26:11Z http://hdl.handle.net/2117/12733 Title: Currents' physical components (CPC) concept in wind farm harmonic current studies Authors: Sainz Sapera, Luis; Cunill Solà, Jordi Abstract: Very little information about actual wind farm harmonic measurements is available in the literature. This paper analyzes the harmonic measurements of an 18 MW wind farm with the CPC concept to determine if they are consumed or injected by the wind farm and to study the different reactive power definitions. The CPC concept is an approach to power theory that provides a physical interpretation of power phenomena in electrical systems with linear, time-invariant (LTI) loads and harmonic generating loads (HGLs) such as wind farms. 2011-06-08T11:09:33Z http://hdl.handle.net/2117/12688 Title: Low-watt compact fluorescent lamps with electronic ballasts Authors: Cunill Solà, Jordi; Mesas García, Juan José; Sainz Sapera, Luis 2011-05-31T12:28:54Z http://hdl.handle.net/2117/12631 Title: On the square arc voltage waveform model in magnetic discharge lamp studies Authors: Molina, Julio; Sainz Sapera, Luis; Mesas García, Juan José Abstract: The current number of magnetic and electronic ballast discharge lamps in power distribution systems is increasing because they perform better than incandescent lamps. This paper studies the magnetic discharge lamp modeling. In particular, the arc voltage waveform is analyzed and the limitations of the square waveform model are revealed from experimental measurements. 2011-05-23T12:01:38Z http://hdl.handle.net/2117/12630 Title: On electric vehicle battery charger modeling Authors: Sainz Sapera, Luis; Mesas García, Juan José; Balcells Sendra, Josep Abstract: The increase of electric vehicle (EV) battery chargers connected to electric networks could lead to future harmonic problems in power systems. These loads are nonlinear devices that inject harmonic currents and pollute network voltages. Thus, battery charger modeling must be studied in detail to determine their harmonic emissions and prevent future problems. This paper investigates EV battery charger behavior, analyzes its equivalent circuit and reports a model for each conduction mode of the circuit. Experimental measurements and PSpice numerical simulations support the study. 2011-05-23T10:54:57Z http://hdl.handle.net/2117/11118 Title: Grid synchronization for advanced power processing and FACTS in wind power systems Authors: Luna Alloza, Álvaro; Rocabert Delgado, Joan; Vázquez Guzmán, Gerardo; Rodríguez Cortés, Pedro; Teodorescu, Remus; Córcoles López, Felipe Abstract: The high penetration of wind power systems in the electrical network has introduced new issues in the stability and transient operation of the grid. By means of providing advanced functionalities to the existing power converters of such power plants it is possible to enhance their performance and also to support the grid operation, as the new grid codes demand. The connection of FACTS based on power converters, such as STATCOMs, are also contributing to the integration of renewable energies improving their behavior under contingencies. However, in both cases it is needed to have a grid voltage synchronization system, able to work under unbalanced and distorted conditions. This paper presents the discrete representation and performance of three PLL’s structures, designed to work in that kind of situations. Their synchronization capability will be tested in different scenarios and their performance constraints will be established according to the Grid Code Requirements (GCRs) 2011-01-20T10:49:29Z http://hdl.handle.net/2117/10646 Title: Simulation of wound rotor synchronous machine under voltage sags Authors: Aguilar Galván, Daniel; Vázquez Guzmán, Gerardo; Rolán Blanco, Alejandro; Rocabert Delgado, Joan; Córcoles López, Felipe; Rodríguez Cortés, Pedro Abstract: This paper presents a study of the Wound Rotor Synchronous Machine (SM) stability under voltage sags (dips). Machine behavior has been analyzed by considering different magnitudes (or depths) and duration of the sag. Voltage sags cause speed variations on SM (with possible lost of synchronism), current and torque peaks and hence may cause tripping and equipment damage, which leads to financial losses. Three machines of different nominal power have been modeled and simulated with MATLAB in order to study its behavior under voltage sags. These SM’s have been analyzed operating as generator, as motor, and in both cases, working under-excited and overexcited. 2010-12-16T12:49:37Z http://hdl.handle.net/2117/8972 Title: Control of DFIG-WT under unbalanced grid voltage conditions Authors: Luna Alloza, Álvaro; Rodríguez Cortés, Pedro; Lima, Kleber; Córcoles López, Felipe; Watanabe, Edson H.; Teodorescu, R. Abstract: The voltage oriented control in the synchronous reference frame (VOC-SRF) have been extensively used for controlling wind turbines based on doubly fed induction generators (DFIG-WTs) through the rotor side converter of a back to back power processor. Although its performance is fast and accurate under balanced conditions its behaviour is not good enough when the voltage of the mains is unbalanced, unless an independent control for the positive and the negative sequence is implemented. This paper proposes a new control system able to control the DFIG-WT under unbalanced conditions using a simple algorithm, which does not need to be implemented for both symmetrical components but on the static αβ reference frame. The reliability of the presented system will be tested by means of PSCAD simulations under balanced and unbalanced grid conditions. 2010-09-20T13:54:05Z