R. Cardenas

University of Santiago, Chile, CiudadSantiago, Santiago Metropolitan, Chile

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Publications (78)164.38 Total impact

  • IEEE Transactions on Industrial Electronics 07/2015; 62(7):4630-4640. DOI:10.1109/TIE.2014.2364155 · 6.50 Impact Factor
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    ABSTRACT: This paper considers the control of a seven-leg back-to-back voltage source inverter arrangement, feeding a four-wire load from a three-phase permanent-magnet synchronous generator (PMSG) operating at variable speed. The PMSG is controlled using a sensorless model reference adaptive system to obtain the rotor position angle. The seven-leg converter is regulated using resonant controllers at the load side and self-tuning resonant controllers at the generator side. The control system is augmented by a feedforward compensation algorithm that improves the dynamic performance during transients. Experimental results, which are obtained from a prototype, are presented and discussed.
    IEEE Transactions on Industrial Electronics 07/2015; 62(7):1-1. DOI:10.1109/TIE.2015.2409803 · 6.50 Impact Factor
  • Matías Díaz, Roberto Cárdenas, Félix Rojas, Jon Clare
    IET Power Electronics 12/2014; 7(12):3116-3125. DOI:10.1049/iet-pel.2014.0065 · 1.32 Impact Factor
  • Matias Diaz, Roberto Cardenas
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    ABSTRACT: In order to avoid stability problems, LVRT requirements (Low Voltage Ride Through) demand Wind Energy Conversion Systems (WECS) to remain connected to the grid in the presence of grid voltages dips. Because 88% of the grid failures are asymmetrical, positive and negative sequence components have to be controlled to fulfill LVRT requirements. This paper present a comparison between synchronous and stationary reference frame control strategies for an active front-end converter of a grid connected WECS working under grid fault conditions. The mathematical analysis and design procedure of both control system are presented in this work. Experimental results obtained from a 3kW prototype are fully discussed in this paper. The experimental implementation is realized using a novel implementation of a voltage sag generator which is based on a 3×4 Matrix Converter.
    2014 Ninth International Conference on Ecological Vehicles and Renewable Energies (EVER); 03/2014
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    ABSTRACT: In this paper an Indirect Matrix Converter (IMC) with two output stages feeding an open-end winding induction machine is presented. The IMC has the advantage of having nobulky energy storage elements and with the two output stages up to 1.5 times the input phase voltage can be obtained across the windings of the machine, without overmodulation. A vector control scheme for the machine currents is used along with a modulation strategy for the converter two-output stages to reduce the common mode voltage and compensate the phase zero sequence currents. Simulation results showing the performance of the controlscheme and the reduction of zero sequence and common mode voltages are presented and discussed.
    2014 IEEE Applied Power Electronics Conference and Exposition - APEC 2014; 03/2014
  • Matias Diaz, Roberto Cardenas, Gustavo Soto
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    ABSTRACT: The incorporation of high power rate Wind Energy Conversion Systems (WECS) have significant influence in the stability, power quality and reliability of the electrical grid. Therefore, strict grid codes have been developed during the last years in order to enhance overall stability of the systems. Thereby Low Voltage Ride Through (LVRT) requirements is a key issue for WECS. In order to test the response of WECS under grid-voltage sag conditions, a Voltage Sag Generator (VSG) is needed. This paper presents a novel Matrix Converter based VSG Prototype in order to study the fulfilment of LVRT requirements. Voltage sags/swell of variable magnitude, duration and type can be generated for the proposed VSG without using complex modulation schemes.
    2014 Ninth International Conference on Ecological Vehicles and Renewable Energies (EVER); 03/2014
  • Roberto Cardenas, Matias Diaz, Felix Rojas, J. Clare
    IEEE Transactions on Power Delivery 01/2014; DOI:10.1109/TPWRD.2014.2373038 · 1.66 Impact Factor
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    ABSTRACT: Generators working with variable speed, rather than fixed speed, have many advantages, which are well documented in the literature. Higher efficiency, better power to size ratio and less mechanical stress in the system are some of the characteristics of variable speed generators. In particular, variable speed diesel generators can be used to provide small highly portable generation systems for emergency vehicles and military/aerospace applications. Such systems can be used to feed stand-alone linear/non-linear loads if an adequate power converter interface is provided. Four-leg matrix converters can be used as the power electronic interface between variable speed generators and stand-alone loads. The fourth leg provides a neutral point for single phase loads and a path for the circulation of zero sequence currents. When non-linear loads are connected to the matrix converter output, relatively high harmonic distortion can be produced in the load voltage unless an appropriate control system is provided. In this paper the application of a repetitive control system to improve the quality of the load voltage is presented. Experimental results obtained from a prototype are shown and fully analysed. (c) 2013 Elsevier B.V. All rights reserved.
    Electric Power Systems Research 11/2013; 104:18-27. DOI:10.1016/j.epsr.2013.05.012 · 1.60 Impact Factor
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    ABSTRACT: The Doubly-Fed Induction Generator (DFIG) is one of the most widely used generators for wind energy applications with more than 50% of installed Wind Energy Conversion Systems (WECS) using this variable speed technology. However, the conventional DFIG requires brushes and copper slip-rings to connect a power converter to the rotor windings. The use of brushes decreases the WECS’ robustness and extra maintenance is required to periodically inspect/replace these elements. In this work a new topology for a Brushless Doubly-Fed Induction Generator (BDFIG) is presented. As an alternative to conventional Voltage Source Inverters (VSI) a matrix converter is used to regulate the current supplied to the stator of the doubly-fed machine, supplying the excitation energy to the WECS. The proposed generation system is mathematically analysed in this paper and the design of the control loops is discussed. Because the power spectrum density of the wind speed is dominated by low frequency components, in this work some simplifications of the transfer functions of the system are proposed. Experimental results obtained from a 3 kW prototype of a cascaded DFIG, are presented and fully discussed.
    Electric Power Systems Research 10/2013; 103:49–60. DOI:10.1016/j.epsr.2013.04.006 · 1.60 Impact Factor
  • Roberto Cardenas, Rubén Pena, Salvador Alepuz, Greg Asher
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    ABSTRACT: Doubly fed induction generators (DFIGs), often organized in wind parks, are the most important generators used for variable-speed wind energy generation. This paper reviews the control systems for the operation of DFIGs and brushless DFIGs in wind energy applications. Control systems for stand-alone operation, connection to balanced or unbalanced grids, sensorless control, and frequency support from DFIGs and low-voltage ride-through issues are discussed.
    IEEE Transactions on Industrial Electronics 06/2013; 60(7):2776 – 2798. DOI:10.1109/TIE.2013.2243372 · 6.50 Impact Factor
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    Roberto Cardenas, Marta Molinas, J.T. Bialasiewicz
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    ABSTRACT: This "Special Section on Control and Grid Integration of Wind Energy Systems - Part II" of the IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS presents the more recent advances in the following topics: 1) HVDC systems for the connection of wind farms to the main power systems; 2) novel topologies for offshore wind energy systems; 3) control of WECSs: e.g., sensorless control of electrical generators, brushless doubly fed induction generators, new topologies of permanent-magnet generators, etc.; 4) grid issues: e.g., low-voltage ride-through (LVRT) control, frequency support using grid control, stability issues, etc.; 5) power converter topologies and control systems: e.g., multilevel power converters, parallel connection of multiple converters, modulations issues, etc.
    IEEE Transactions on Industrial Electronics 06/2013; 60(7):2774-2775. DOI:10.1109/TIE.2013.2239176 · 6.50 Impact Factor
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    ABSTRACT: A novel frequency changing conversion scheme using three cascade multilevel converters in a Π topology is presented. The scheme resembles a direct frequency converter using the cascade converter in its simplest form (series strings of H-bridge modules equipped with a dc link capacitor) as the building block of the overall converter. This yields a highly modular implementation approach which may be attractive for large power applications such as intertie connections and variable speed drives. Frequency conversion takes place in a cascade converter which connects the input and output ports. Two other converters are placed, respectively, in parallel to the input, to remove unwanted current components from the input, and the output to regulate output voltage. Operation of this topology is explained and a scheme to control all the converters is developed, including control of converter currents, capacitor voltages, and output voltage. Experimental results, using a low-power prototype, confirm the foundations of the topology and verify its overall performance operating as a power supply at typical output frequencies (25 Hz, 162/3 Hz and dc) while being fed from a 50-Hz system. Additionally, PowerSIM simulations demonstrate that the topology may be suitable for implementing high-performance, high-power ac drive systems using vector control techniques.
    IEEE Transactions on Industrial Electronics 06/2013; 60(6):2118-2130. DOI:10.1109/TIE.2012.2194971 · 6.50 Impact Factor
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    ABSTRACT: A Space Vector Modulation (SVM) strategy for an open-end load fed by an indirect matrix converter consisting on one input stage and two output stages is presented. The modulation strategy aims to reduce the instantaneous common mode voltage and dynamically compensate the phase zero sequence current.
    Power Electronics and Applications (EPE), 2013 15th European Conference on; 01/2013
  • Matias Diaz, Roberto Cardenas
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    ABSTRACT: The increased penetration of renewable energy systems (RESs) rises the concern about the stability and power quality of the utility grid. Therefore, some rather strict grid requirements for Low Voltage Ride-Through (LVRT) have been produced. In order to verify the response of RES under grid-voltage sag conditions, a Voltage Sag Generator (VSG) is needed. This paper presents a 5 kVA Matrix Converter based VSG to test RES in order to study the fulfillment of LVRT requirements. Voltage dips of variable magnitude, duration time and type can be generated with the proposed VSG.
    Ecological Vehicles and Renewable Energies (EVER), 2013 8th International Conference and Exhibition on; 01/2013
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    ABSTRACT: In this paper an Indirect Matrix Converter (IMC) with two output stages feeding an open end load is presented. The IMC has the advantage of having no bulky energy storage elements and with the two output stages up to 1.5 times the input phase voltage can be obtained across the load without overmodulation. Two pulse width modulation strategies are presented. The first one is based on space vector modulation and suppresses the zero sequence voltage in the load. The second one is a carrier-based modulation and lower distorted input current is obtained. Results are presented and discussed.
    Industrial Electronics (ISIE), 2013 IEEE International Symposium on; 01/2013
  • M. Diaz, R. Cardenas
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    ABSTRACT: LVRT requirements (Low Voltage Ride Through) demand Renewable Energy Conversion Systems (RECS) to remain connected to the grid in the presence of grid voltages dips. This paper considers an active front-end converter of a grid connected DCCS working under grid fault conditions. A novel control strategy is proposed, based in to maintain active power constant through grid-voltage dips using Resonant Controllers instead the traditional d-q axis strategies. The performance of this strategy is studied on LVRT requirements fulfillment. Experimental results obtained with a small 3kVA prototype are presented and fully analysed in this paper. The experimental results show that proposed strategy is able to achieve the LVRT requirements.
    Ecological Vehicles and Renewable Energies (EVER), 2013 8th International Conference and Exhibition on; 01/2013
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    ABSTRACT: In this paper a new control system for a 4-leg Matrix Converter (MC) feeding an isolated load is discussed. The proposed system is appropriate for wind-diesel schemes or any other application where a path for the circulation of zero sequence currents is required, e.g. wind energy conversion systems feeding isolated loads, small portable diesel generators used in ambulances and similar emergency vehicles, wind hybrid generation systems, wind-diesel schemes, etc. In this work it is assumed that the 4-leg MC is fed from a variable speed diesel-driven Permanent Magnet (PM) generator. A vector control system based in two synchronous rotating d-q axes is used to regulate the load voltage. The frames are rotating clockwise and counter-clockwise respectively in order to control the positive and negative sequence of the output signals. A separate resonant controller is used to regulate the homopolar components of the load voltage. The design of the control system is discussed in this work and experimentally validated using a prototype.
    Renewable Energy 07/2012; 43. DOI:10.1016/j.renene.2011.11.052 · 3.36 Impact Factor
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    ABSTRACT: Matrix Converters (MCs) have some advantages when compared to conventional back-to-back PWM voltage source converters. The converter may be considered more reli- able and it can be smaller because the bulky dc capacitors are eliminated from the topology. For ac to ac power conversion, the size and weight of the whole generation system can be much reduced when back-to-back converters are replaced by MCs. To supply electrical energy to an unbalanced 3Φ stand-alone load, a fourth leg is required to provide a path for the zero-sequence load current. To regulate the load voltage, closed-loop control is required. In this paper, the application of d-q controllers and resonant controllers to four-leg MCs is addressed. The design and performance issues of the controllers, for operation with balanced, highly unbalanced loads and nonlinear loads are discussed in this paper. Experimental results obtained from a small prototype are presented and analysed in detail.
    IEEE Transactions on Industrial Electronics 01/2012; 59(1):141-153. DOI:10.1109/TIE.2011.2158041 · 6.50 Impact Factor
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    ABSTRACT: Matrix converters (MC) have some advantages when compared to conventional back-to-back pulsewidth modulation voltage-source converters. The MC may be considered more reliable and is smaller because the bulky dc capacitor is eliminated from the topology. Therefore, when MCs are used in ac–ac power conversion, the size and weight of the whole generation system is reduced. To interface a MC-based generation system to an unbalanced three-phase stand-alone load, a four-leg MC is required to provide an electrical path for the zero-sequence load current. Moreover, to compensate for the voltage drops in the output filter inductances, nonlinearities introduced by the four-step commutation method and voltage drops in the semiconductor devices, closed-loop regulation of the load voltage is required. In this paper, the design and implementation of a resonant control system for four-leg MCs is presented. The application of this control methodology when the four-leg MC is feeding, a linear/nonlinear unbalanced load is also presented in this study. High-order resonant controllers are also analyzed. Experimental results, obtained from a small prototype, are discussed.
    IEEE Transactions on Power Electronics 01/2012; 27(3):1120-1129. DOI:10.1109/TPEL.2011.2128889 · 5.73 Impact Factor
  • R. Cardenas, J. Clare, P. Wheeler
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    ABSTRACT: Variable-speed diesel generation systems have advantages when compared to fixed-speed generators. For example reduced fuel consumption at some operating points, less maintenance, increased life of the engine because it is operated with a lower thermal signature. Moreover, higher power output can be obtained by operating the diesel engine at high rotational speeds, improving the power to size ratio. A 4-leg matrix converter can be used to feed a stand-alone load or isolated grid, providing a path for the circulation of the zero sequence load current. In this work the control systems appropriate for variable-speed diesel engines feeding a 4-leg matrix converter are discussed. Control systems based on two revolving axes and zero sequence controllers are discussed in this work. Experimental results obtained from a prototype are presented and fully analysed.
    IECON 2012 - 38th Annual Conference on IEEE Industrial Electronics Society; 01/2012

Publication Stats

2k Citations
164.38 Total Impact Points

Institutions

  • 2009–2014
    • University of Santiago, Chile
      CiudadSantiago, Santiago Metropolitan, Chile
  • 1995–2013
    • University of Nottingham
      • Department of Electrical and Electronic Engineering
      Nottigham, England, United Kingdom
  • 2012
    • University of Chile
      • Departamento de Ingeniería Eléctrica
      CiudadSantiago, Santiago Metropolitan, Chile
  • 2009–2010
    • University of Concepción
      Ciudad de Concepcion, Biobío, Chile
  • 1999–2009
    • University of Magallanes
      Magallanes, Magallanes, Chile