R. Cardenas

University of Santiago, Chile, CiudadSantiago, Santiago, Chile

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Publications (69)141.83 Total impact

  • [Show abstract] [Hide abstract]
    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
  • 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. · 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. · 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
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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 01/2013; 60(6):2118-2130. · 6.50 Impact Factor
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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
  • 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
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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. · 5.73 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. · 6.50 Impact Factor
  • R. Cárdenas, R. Peña, P. Wheeler, J. Clare
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    ABSTRACT: Most variable-speed AC generation systems use back-to-back converters to supply electrical energy, with fixed electrical frequency and voltage, to a stand-alone load or grid. Matrix converters (MCs) are a good alternative to back-to-back converters because they have several advantages in terms of size and weight. Therefore, MCs can be advantageously used in any variable-speed generation system where high efficiency, reliability, small size, and low weight are considered important factors. Nevertheless, to interface an MC-based generation system to an unbalanced 3φ stand-alone load, a four-leg MC is required to provide a path for the zero-sequence load current. Space-vector-modulation (SVM) algorithms for the operation of four-leg MCs have been proposed in the literature. However, these modulation methods have high computational burdens, and they are difficult to implement, even in fast DSP-based control platforms. Therefore, only simulation results have been reported in these publications. In this paper, an SVM algorithm is optimized and experimentally tested. Moreover, the harmonics produced in the input current when a four-leg MC is feeding an unbalanced or nonlinear load are also mathematically analyzed in this paper, with experimental verification being provided.
    IEEE Transactions on Industrial Electronics 05/2011; · 6.50 Impact Factor
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    ABSTRACT: Multimegawatt wind-turbine systems, often organized in a wind park, are the backbone of the power generation based on renewable-energy systems. This paper reviews the most-adopted wind-turbine systems, the adopted generators, the topologies of the converters, the generator control and grid connection issues, as well as their arrangement in wind parks.
    IEEE Transactions on Industrial Electronics 05/2011; · 6.50 Impact Factor
  • R. Cárdenas, R. Peña, J. Clare, P. Wheeler
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    ABSTRACT: In this paper, the control of a grid-connected wind energy conversion system (WECS), based on an induction machine fed by a matrix converter (MC), is presented. The MC is controlled using a space vector modulation algorithm with zero displacement factor at the input. Stability issues related to the operation of the WECS for the whole power and speed range are fully analyzed in this paper, using a simplified small-signal model. The implementation of a model reference adaptive system (MRAS) observer, for sensorless control of the proposed WECS, is also presented in this paper. The MRAS observer is implemented using the output voltage demand, avoiding the use of voltage transducers to measure the machine voltage. From the speed estimated by the MRAS observer, the electrical torque of the induction generator is regulated in order to drive the WECS to the operating point where the aerodynamic efficiency is maximized. Experimental results obtained with a 2.5-kW prototype are presented and fully discussed in this paper.
    IEEE Transactions on Energy Conversion 04/2011; · 3.35 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 and more of 50% of the installed Wind Energy Conversion Systems (WECS) are using this sort of variable speed technology. However, the machine requires brushes for the operation which increases the maintenance work. To overcome this drawback a Brushless Double Fed Induction Generator (BDFIG), composed of two cascaded doubly-fed machines with the rotor windings interconnected, could be used. In this work, the control of a BDFIG is presented using a matrix converter (MC). Matrix converters may be seen as suitable converter choice for this application instead of the standard back-to-back PWM voltage source converter topology. Results from an experimental rig are presented for operation of the BDFIG at variable speed with the machine driven by a commercial AC drive as a prime mover.
    01/2011;
  • R. Cárdenas, R. Peña, P. Wheeler, J. Clare
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    ABSTRACT: Variable speed diesel generation is a good alternative to supply electrical energy to stand-alone unbalanced loads. Operating the diesel engine at variable speed reduces the fuel consumption, increases the overall efficiency, reduces the thermal signature of the machine and increases the useful life of the engine. Moreover, to reduce the size and weight of the whole generation system, a Matrix Converter (MC) can be used. However, to interface a MC-based generation system to an unbalanced 3Φ stand-alone load, a four-leg MC is required to provide a path for the zero sequence load current. In order to regulate balanced voltages into the unbalanced load, a closed loop control system is required to compensate for the voltage drops in the output filter inductances and semiconductor devices and to compensate for the non linearities introduced by the commutation method. In this paper the design and implementation of a resonant control system for 4-leg MCs is presented. Simulation and experimental results, obtained from a prototype, are discussed.
    Industrial Electronics (ISIE), 2010 IEEE International Symposium on; 08/2010
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    ABSTRACT: In this paper a control strategy for a Doubly-Fed Induction Generator (DFIG) using an Indirect Matrix Converter (IMC), which consists of an input side matrix converter and an output side voltage source converter (VSI), is presented. The capability of the input converter to generate different virtual DC link voltage levels is exploited and commutation of the VSI using these reduced voltages is shown for operating points where the required output voltage is low in magnitude, without deteriorating the performance of machine current control. This method leads to a reduction in the commutation losses in the output converter and reduced common mode voltage. For the input converter soft switching commutation is obtained synchronizing the input and output PWM patterns. This strategy is applicable in DFIG applications because the required rotor voltage decreases as the DFIG speed gets closer to synchronous speed. The strategy is experimentally validated in a 2kW rig.
    Industrial Electronics (ISIE), 2010 IEEE International Symposium on; 08/2010
  • R. Cardenas, R. Pena, P. Wheeler, J. Clare
    [Show abstract] [Hide abstract]
    ABSTRACT: Most variable speed AC generation systems use back-to-back converters to supply electrical energy, with fixed electrical frequency and voltage, to a stand-alone load or grid. Matrix Converters (MCs) are a good alternative to back-to-back converters because they have several advantages in term of size and weight. Therefore MCs can be advantageously used in any variable speed generation system where high efficiency, reliability, small size and low weight are considered important factors. Possible applications are mobile power supply systems, variable speed diesel generation schemes and wind energy conversion systems. Nevertheless, to interface a MC-based generation system to unbalanced 3Φ stand-alone loads, a four-leg MC is required to provide a path for the zero sequence load current. However, the conventional Space Vector Modulation (SVM) algorithm used with 3×3 MCs cannot be applied to a four-leg matrix converter. Therefore, in this paper a SVM algorithm, adequate for the operation of a 3×4 MC is presented. The proposed modulation scheme is mathematically analysed and experimental results, obtained with an experimental prototype, are discussed.
    Power Electronics, Machines and Drives (PEMD 2010), 5th IET International Conference on; 05/2010
  • R. Cárdenas, R. Peña, J. Clare, P. Wheeler
    [Show abstract] [Hide abstract]
    ABSTRACT: Most variable speed AC generation systems use back-to-back converters to supply electrical energy, with fixed electrical frequency and voltage, to a stand-alone load or grid. Matrix Converters (MCs) are a good alternative to back-to-back converters because they have several advantages in term of size and weight. Therefore MCs can be advantageously used in any variable speed generation system where high efficiency, reliability, small size and low weight are considered important factors. Possible applications are mobile power supply systems, variable speed diesel generation schemes and wind energy conversion systems. Nevertheless, to interface a MC-based generation system to unbalanced 3φ stand-alone loads, a four-leg MC is required to provide a path for the zero sequence load current. In this paper a SVM algorithm, adequate for the operation of a 3×4 MC is presented. The proposed modulation scheme is mathematically analysed and experimental results, obtained with an experimental prototype, are discussed.
    Industrial Technology (ICIT), 2010 IEEE International Conference on; 04/2010
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    ABSTRACT: In this paper, a topology for a grid connected generation system based on two doubly fed induction machines is presented. The proposed scheme is implemented using an indirect matrix converter consisting of an input stage and two output stages. The input stage is connected to the grid and provides the required DC voltage for both output stages. Each of the output stages is connected to the rotor of the corresponding machine. The rotor currents of each machine are vector controlled. Space vector modulation is used for the input and output stages. The switching pattern to minimize the commutation losses of the input converter and/or reduce the ripple of the indirect matrix converter input current is selected depending on the rotational speeds of the machines. Experimental results, considering the system running at below and above synchronous speed, are presented.
    Industrial Technology (ICIT), 2010 IEEE International Conference on; 04/2010
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    ABSTRACT: In this paper, the performance of a grid-connected wind energy conversion system (WECS), based on a doubly fed induction generator (DFIG) fed by a matrix converter (MC), is presented. The MC replaces the back-to-back converters conventionally used to control a DFIG. The MC is operated with close-to-unity power factor at the grid side. Stability issues related to the operation of the MC in the proposed WECS are discussed. A small signal model is used to investigate the dynamic performance of the two control arrangements discussed in this paper. Experimental results, obtained with a 4-kW prototype, are presented and fully discussed in this paper. The performance of the system for variable speed generation is verified using the emulation of a variable speed wind turbine implemented with a digitally controlled dc machine.
    IEEE Transactions on Industrial Electronics 11/2009; · 6.50 Impact Factor
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    ABSTRACT: In this paper, a topology for a grid-connected generation system, based on two doubly fed induction machines, is presented. The proposed scheme is implemented using an indirect matrix converter (IMC) consisting of an input stage, a three-to-two matrix converter, and two output stages consisting of a pair of voltage source inverters. The input stage is connected to the grid and provides the required dc voltage for the output stages. Space vector modulation (SVM) is used for the input stage producing the maximum dc voltage, with unity power factor operation at the IMC grid-side input. Each of the output converters is connected to the rotor of a DFIM. The rotor currents of each machine are vector controlled for fast dynamic response and tight torque control. Moreover, the SVM algorithm used for the inverters is designed to provide soft switching operation in the input converter. Simulation and experimental results obtained from a 2.5-kW experimental prototype are presented. Steady-state and transient operation is discussed with the system running at below and above synchronous speed. The results demonstrate the feasibility of the proposed scheme for variable speed energy systems.
    IEEE Transactions on Industrial Electronics 11/2009; · 6.50 Impact Factor