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Online ISSN 1751-8679 Print ISSN 1751-8660

IET Electric Power Applications

Volume 6, Issue 8, September 2012

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Volume 6, Issue 8

September 2012

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    • Extended Park's vector approach-based differential protection of three-phase power transformers
      Assessing the environmental impact of induction motors using manufacturer's data and life cycle analysis
      • Author(s): M. Torrent ; E. Martinez ; P. Andrada
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 473 –483
      • DOI:  10.1049/iet-epa.2012.0021
      • Type: Article
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      • p. 473 –483 (11)
        Herein is reported development and testing of a life cycle analysis (LCA) procedure for assessing the environmental impact of induction motors. The operating conditions of a given industrial application are defined by the mechanical power required, operating hours and service life of the three-phase induction motor involved. Based on manufacturer's data mainly, different three-phase induction motors for various sets of operating conditions, including oversizing, have been selected. To quantify the environmental impact of each motor, the Methodology for the Ecodesign of Energy Using Products (MEEUP) was applied, according to the quantity of each of the motor's main constituent materials used in the production phase, and to the two operating variables that directly influence the LCA results: output power and efficiency. The procedure was applied to different three-phase induction motors representing two efficiency categories (IE1 and IE2) and considering different oversizing possibilities. The total environmental impact of each motor was determined based on the production, service life and end-of-life phases. The best motor option was identified for different operating conditions. Given the potential for energy savings in electric motors, LCA-based environmental impact assessment should be performed when different motors are being evaluated for a given industrial application.
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      Shuffled frog-leaping algorithm for parameter estimation of a double-cage asynchronous machine
      • Author(s): M. Gomez-Gonzalez ; F. Jurado ; I. Pérez
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 484 –490
      • DOI:  10.1049/iet-epa.2011.0262
      • Type: Article
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      • p. 484 –490 (7)
        This study introduces a shuffled frog-leaping algorithm based method for the estimation of induction motor double-cage model parameters from standard manufacturer data: full load torque, full load power factor, full load current, maximum torque, starting torque and starting current. The steady-state equivalent circuit is applied for the simulations. The circuit parameters are found as the result of the error minimisation function between the estimated and maker data. The suggested algorithm solves the parameter estimation problem and surpasses the solutions reached by particle swarm optimisation, genetic algorithms and classical parameter estimation method (a modified Newton method). The algorithm has been tested on three motors.
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      Theoretical and experimental analysis of a three-phase permanent magnet claw-pole synchronous generator
      • Author(s): F.N. Jurca  and  C. Martis
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 491 –503
      • DOI:  10.1049/iet-epa.2012.0075
      • Type: Article
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      • p. 491 –503 (13)
        The present study deals with the theoretical and experimental analysis of a permanent magnet claw-pole synchronous generator (PMCPSG) suited for small rating, direct-driven applications, such as small-scale wind power plants. After the computation of the machine main dimensions using an analytical algorithm, a Hooke–Jeeves optimisation procedure was implemented in order to obtain the optimal geometry of the PMCPSG. The electromagnetic field and static performances are studied, based on three-dimensional finite element analysis. A prototype of the PMCPSG is tested on a test bench for resistive and inductive loads.
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      Modelling methodology and experimental verification of the permanent-magnet-biased saturation-based fault current limiter
      • Author(s): Q. Li ; J. Xu ; L. Zou ; J. Lou
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 504 –512
      • DOI:  10.1049/iet-epa.2012.0032
      • Type: Article
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      • p. 504 –512 (9)
        Regarding the line-type permanent-magnet-biased saturation-based fault current limiter (PMFCL), flux leakage effect is introduced in the modelling scheme to justify and ameliorate the theoretical analysis. The research indicates that the current flowing through the external circuit and the flux through the saturated iron-core are two principal variables in combining the external circuit with the magnetic topology of a PMFCL. Equivalent models coupling both the electric and magnetic circuits are established, in which the PMFCL is considered as a controlled voltage source dominated by the flux through the iron-core. A macro-model for simulation is achieved with MATLAB/SIMULINK software and the wrap-to-zero module is presented to substitute the switch in the simulation model. Experiments are further conducted and are thereby compared with the simulation results, which have verified the effectiveness and the accuracy of the proposed modelling methodology.
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      Implementation of a predictive controller for a sensorless interior permanent-magnet synchronous motor drive system
      • Author(s): J.-L. Chen  and  T.-H. Liu
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 513 –525
      • DOI:  10.1049/iet-epa.2011.0242
      • Type: Article
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      • p. 513 –525 (13)
        This study proposes a predictive controller design for a sensorless interior permanent-magnet synchronous motor drive system. The controllers include a current-loop predictive controller and a speed loop predictive controller with an external load estimator. In addition, a rotor position estimator with on-line tuning stator resistance and q-axis inductance has been designed to reduce the estimating error. By using the proposed control algorithms, the closed-loop sensorless interior permanent-magnet synchronous motor drive system can achieve fast transient response, satisfactory load disturbance response and good tracking response. A digital signal processor, TMS320F2812, is used to perform the rotor position estimating algorithm and the predictive control algorithm. As a result, the hardware is very simple. The experimental results can validate the theoretical analysis and show that the predictive controllers have better performance than the proportional integral (PI) controllers.
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      Design and evaluation of voltage measurement-based sectoral diagnosis method for inverter open switch faults of permanent magnet synchronous motor drives
      • Author(s): C. Choi  and  W. Lee
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 526 –532
      • DOI:  10.1049/iet-epa.2011.0315
      • Type: Article
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      • p. 526 –532 (7)
        A sectoral diagnosis method for open switch faults of inverter-fed permanent magnet synchronous motor (PMSM) drives have been described. The proposed diagnosis method defines separate residuals for each of the six switches as a sectoral average of the difference between a reference and measured pole voltage instead of direct use of the instantaneous difference, which has varying AC quantity within one cycle of rotation. How to determine plausible thresholds is described and the effectiveness and limitation of the proposed method are analysed. Several sets of experimental results validate the detection and isolation capability of the proposed method.
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      Implementation of high-performance sensorless interior permanent-magnet synchronous motor control systems using a high-frequency injection technique
      • Author(s): J.-L. Chen ; S.-K. Tseng ; T.-H. Liu
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 533 –544
      • DOI:  10.1049/iet-epa.2011.0303
      • Type: Article
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      • p. 533 –544 (12)
        This study proposes a high-performance sensorless interior permanent-magnet synchronous motor control system using a high-frequency injection technique. A new estimation method that uses both the high-frequency d-axis current and q-axis current to estimate the rotor position is investigated. By using the proposed method, the hypothesis-synchronisation signal used in the conventional high-frequency injection method can be eliminated. A 1.25 kHz, 15 V, sinusoidal waveform voltage is injected into the d-axis synchronous frame of the motor and then the high-frequency d-axis and q-axis currents can be measured to determine the rotor position of the motor. In addition, a new compensation method is developed to reduce the estimation position error because of the mutual inductance and saturation effect of the motor. By using this new method, the estimated rotor-position error is within ±2 electrical degrees. A digital signal processor, TMS-320-F2812, is used as the estimating and control centre. The experimental results show that the proposed method can be applied in both a sensorless speed control system and a sensorless position control system. The sensorless speed control system has fast response, good load disturbance response and good tracking response.
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      Torsional vibration control of large induction motors using constant air gap flux scheme
      • Author(s): N.M.B. Abdel-Rahim  and  A. Shaltout
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 545 –552
      • DOI:  10.1049/iet-epa.2011.0129
      • Type: Article
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      • p. 545 –552 (8)
        Comprehensive analysis of the starting period of inverter-fed large induction motors reveals that these motors are subjected to additional components of pulsating torsional torque. These torque pulsations may coincide with the natural torsional frequency of the large motor system and produce hazardous shaft torque oscillations. To alleviate the torsional toque problem and limit the motor starting current, a constant air-gap flux using slip frequency control scheme is proposed to operate the motor inverter. Simulation results show that the proposed scheme is capable of drastically reducing the torsional torque oscillations and limiting the motor line current to approximately 22% of its direct online starting value without prolonging its starting period.
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      Temperature-dependant voltage regulator operation for optimal load acceptance of a diesel generator
      • Author(s): A.R. Cooper ; D.J. McGowan ; D.J. Morrow ; K.D.R. Chambers
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 553 –560
      • DOI:  10.1049/iet-epa.2011.0218
      • Type: Article
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      • p. 553 –560 (8)
        Standby diesel generator sets (gen-sets) are used worldwide to provide a backup electricity supply should the mains supply to a site be lost. The diesel engine can start rapidly and the gen-set can begin supplying power within 20–60 s. Traditional commissioning of a gen-set is performed when the engine is at its normal ‘hot’ operating temperature. Unless a jacket water heater is used, once the gen-set is shutdown the engine will cool to the ambient temperature, and following start-up the load acceptance performance will be lower than when it was in a hot operating condition. A novel voltage regulator design which utilises engine temperature as a supplementary control input is presented, providing an improvement in a gen-set's cold load acceptance performance without compromising its standard hot performance. The new voltage regulator design is tested on a commercial diesel gen-set to demonstrate the optimised load acceptance performance.
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      Behaviour of the doubly fed induction generator exposed to unsymmetrical voltage sags
      • Author(s): A. Rolán ; F. Córcoles ; J. Pedra
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 561 –574
      • DOI:  10.1049/iet-epa.2011.0226
      • Type: Article
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      • p. 561 –574 (14)
        This study analyses the dynamic behaviour of the doubly fed induction generator exposed to unsymmetrical voltage sags, providing insights into wind turbine fault ride-through capability. The sags are assumed to be caused by faults. An analytical approach assuming that the rotor-side converter can keep constant the rotor current in the synchronous reference frame during the event is used. The voltage limit of the rotor-side converter is also considered in order to determine the situations where the rotor current can be controlled. The effects of sags on grid-connected equipments depend on the sag characteristics (duration and depth), but also on the fault clearing process. In this process, the fault is not cleared instantaneously, as in the case of abrupt sags (which is the usual approach in the literature), but in the successive natural fault-current zeros, leading to a voltage recovery in several steps known as discrete sags. The effects of both abrupt and discrete sags on the doubly fed induction generator behaviour are compared. This comparison reveals that the discrete clearing process smoothes the sag effects on the generator.
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      VCM controller design with enhanced disturbance decoupling for precise automated manufacturing processes
      • Author(s): J.-K. Seok  and  S.-K. Kim
      • Source: IET Electric Power Applications, Volume 6, Issue 8, p. 575 –582
      • DOI:  10.1049/iet-epa.2011.0237
      • Type: Article
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      • p. 575 –582 (8)
        In this study, a controller design of a voice coil motor (VCM) with enhanced disturbance rejection (or disturbance input decoupling) performance, especially for precise automated manufacturing processes, is proposed. The proposed disturbance decoupling strategies are twofold: (1) a dynamic stiffness-enhanced position-velocity controller and (2) state-filter-based disturbance input decoupling in a force control mode. First, a state-feedback style position-velocity controller is designed to meet tracking requirements and improve disturbance rejection in VCM control. In this control structure, the conflict in requirements between command tracking and disturbance rejection can be considerably alleviated. This design property provides powerful insights into achieving precise position control. To enhance the force control accuracy, a disturbance state filter for force control is also applied to estimate and compensate for the varying dynamics of VCM systems, such as non-linearly variable loads and other uncertainties. The state filter estimation accuracy in the presence of system parameter errors is fully analysed. In addition, both disturbance decoupling methods are computationally efficient and robust to other parameter errors. The proposed algorithms are implemented in a developed VCM actuator and verified to be appropriate for a VCM drive system with unknown disturbances.
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