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Online ISSN 1751-8679 Print ISSN 1751-8660

IET Electric Power Applications

Volume 5, Issue 4, April 2011

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Volume 5, Issue 4

April 2011

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    • Sensorless linear induction motor speed tracking using fuzzy observers
      • Author(s): P. Liu ; C.-Y. Hung ; C.-S. Chiu ; K.-Y. Lian
      • Source: IET Electric Power Applications, Volume 5, Issue 4, p. 325 –334
      • DOI:  10.1049/iet-epa.2010.0099
      • Type: Article
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      • p. 325 –334 (10)
        In this study, the authors develop a sensorless speed controller for linear induction motors (LIMs) based on a fuzzy observer. The authors use a fifth-order non-linear LIM dynamical model with end-effects approximated by Taylor series. Then, the authors represent the LIM by a T–S fuzzy model and construct a fuzzy observer to estimate the immeasurable mover speed and secondary flux states. By computationally solving a set of linear matrix inequalities to obtain the observer gains, the authors achieve exponential convergence of estimation errors when fuzzy membership functions fit a Lipshitz-like property. Based on the fuzzy observer, the control law synthesis is carried out by using a virtual desired variable concept where a skew-symmetric property is utilised. The exponential convergence for both estimation error and tracking error is ensured by the controller design. Finally, speed tracking experiments are carried out to verify the theoretical results and show satisfactory performance.
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      Design and implementation of a passivity-based controller for sensorless synchronous reluctance motor drive systems
      • Author(s): M.-Y. Wei ; T.-H. Liu ; C.-K. Lin
      • Source: IET Electric Power Applications, Volume 5, Issue 4, p. 335 –349
      • DOI:  10.1049/iet-epa.2010.0061
      • Type: Article
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      • p. 335 –349 (15)
        This study proposes a passivity-based controller for sensorless synchronous reluctance motor drive systems. By using the proposed controller, the drive systems can achieve fast transient responses, good load disturbance responses and good tracking responses. The parameters of the controller can be derived according to the required specification of the drive systems. In addition, a new sensorless technique based on an extended flux estimator is proposed as well. The estimator provides good performance in transient and steady-state conditions. The details are discussed. A digital signal processor TMS-320F-28335 is used to execute the rotor position/speed estimation, the passivity-based control algorithm, the d–q to a–b–c coordinate transformation, and the pulse width modulation switching strategy. As a result, the hardware is very simple. Experimental results show that the proposed system can perform in a wide adjustable speed range from 1 to 2000 r/min and a precise position control with satisfactory performance.
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      Stationary state error reduction on the electrical modelling of high pressure sodium lamps
      • Author(s): R. Osorio ; N. Vázquez ; S. Pinto ; G. Martínez ; M. Ponce ; A. Padilla ; J. Prado
      • Source: IET Electric Power Applications, Volume 5, Issue 4, p. 350 –358
      • DOI:  10.1049/iet-epa.2010.0194
      • Type: Article
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      • p. 350 –358 (9)
        This study presents an improvement in the steady-state error reduction in the electrical modelling of high pressure sodium (HPS) lamps when they exhibit high non-linear behaviour. An electrical expression of the lamp is resistance could be obtained from the Saha equation, which is sufficient to represent the behaviour of several high intensity discharge lamps with low non-linear behaviour, but if the modelled lamp possess high non-linear operation, as do some HPS lamps, a large stationary error between the simulation and experimental results is obtained. Therefore an enhanced expression of lamp resistance is proposed here to reduce this error. Parameters are obtained from the measurements of electrical variables such as power, current and voltage, in the lamp. The proposal can be used to simulate the non-resonant ballast. Experimental and simulation results are shown.
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      Improved sensorless control of a permanent magnet machine using fundamental pulse width modulation excitation
      • Author(s): Y. Hua ; M. Sumner ; G. Asher ; Q. Gao ; K. Saleh
      • Source: IET Electric Power Applications, Volume 5, Issue 4, p. 359 –370
      • DOI:  10.1049/iet-epa.2010.0108
      • Type: Article
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      • p. 359 –370 (12)
        A new method to estimate the rotor position of permanent magnet synchronous motor (PMSM) drives over a wide speed range, including zero frequency is introduced. The method measures the motor current derivative in response to the standard pulse width modulation (PWM) sequence to estimate rotor position. No additional signal injection or separate test vectors are required although modification is needed when narrow PWM voltage vectors occur. Three compensation techniques are proposed to improve the quality of the position estimation and reduce current distortion when narrow vectors are used for position estimation. Experimental results for sensorless speed and position control of a 4 kW PMSM verify the effectiveness of the proposed techniques.
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      Research on stator temperature field of a hydro-generator with skin effect
      • Author(s): Y.D. Fan ; X.S. Wen ; H.M. Wang ; J.H. Seo
      • Source: IET Electric Power Applications, Volume 5, Issue 4, p. 371 –376
      • DOI:  10.1049/iet-epa.2010.0185
      • Type: Article
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      • p. 371 –376 (6)
        Finite-element method is applied to calculate the stable stator three-dimensional (3D) temperature field of a hydro-generator SF125-96/15600. First, 3D controlling equation of heat conduction and its equivalent functional equation are presented. Secondly, all the parameters for simulation such as heat conductivity coefficients of iron core and stator coils, heat convection coefficients of each surface, are calculated. Thirdly, iron and copper losses are deduced by electromagnetic analysis. Then, the stator temperature field with and without skin effect are calculated. Comparing the two kinds of simulation results with that of measured, it is verified that the simulation is effective, and that the temperature field of slot under skin effect is more uneven than that of without the effect. So, more accurate temperature distribution of the key component of hydro-generator can be got on which online stator thermal monitoring and optimum design can be carried out.
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      Electric energy recovery system for a hydraulic forklift – theoretical and experimental evaluation
      • Author(s): T. Minav ; P. Immonen ; L. Laurila ; V. Vtorov ; J. Pyrhönen ; M. Niemelä
      • Source: IET Electric Power Applications, Volume 5, Issue 4, p. 377 –385
      • DOI:  10.1049/iet-epa.2009.0302
      • Type: Article
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      • p. 377 –385 (9)
        Energy efficiency has become a major research issue in all fields of engineering. As electrical drives have fast torque response capability and high controllability, they are penetrating new fields of engineering. Opportunities of utilising electric servo drives in the control of hydraulic lifting systems and enabling energy recovery in them are studied. In this study, the control of the hydraulic lifting and lowering system is carried out directly by an electric-servomotor-driven hydraulic machine. The efficiencies of the experimental drive system and its components are determined. At maximum, 66% of the potential energy was recovered in the low-power drive and improvements could still be achieved.
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      Radio-frequency-based detection of electrical discharge machining bearing currents
      • Author(s): J. Ahola ; V. Särkimäki ; A. Muetze ; J. Tamminen
      • Source: IET Electric Power Applications, Volume 5, Issue 4, p. 386 –392
      • DOI:  10.1049/iet-epa.2010.0153
      • Type: Article
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      • p. 386 –392 (7)
        The possibility of a bearing damage caused by inverter-induced bearing currents in modern variable-speed drive systems is well recognised at present. In this study a non-intrusive method to detect and monitor the frequency of occurrence of these currents is presented. A technique of this kind makes it possible to analyse a certain drive system with respect to the appearance of inverter-induced bearing currents and to estimate the risk they might pose to the bearings. The proposed method is based on measurement of the radio frequency signal emitted by the discharge and transmitted by the machine itself. The theory behind the technique and its realisation is discussed. Exemplary measurements are presented to demonstrate the feasibility of the theory by studying the relationship between the motor shaft speed and the bearing current discharge activity for a 15 kW induction motor.
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