Online ISSN
1752-1424
Print ISSN
1752-1416
IET Renewable Power Generation
Volume 6, Issue 6, November 2012
Volumes & issues:
Volume 6, Issue 6
November 2012
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- Author(s): M.H. Wang and H.H. Tsai
- Source: IET Renewable Power Generation, Volume 6, Issue 6, p. 373 –380
- DOI: 10.1049/iet-rpg.2012.0147
- Type: Article
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p.
373
–380
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This study proposes a fault forecasting system for proton exchange membrane fuel cells (PEMFCs), which uses a set of wireless sensors to accomplish fuel cell (FC) condition monitoring. The software interface of the FC fault forecast system uses LabVIEW software. Owing to the time delay condition of FC reactions, this study first forecasts all the operation features of the FC using a Grey prediction model. Then, an extension diagnosis method uses the forecasted values of the features to forecast the future operational conditions. Thus, the complex condition monitoring and fault forecasting problem of the FC can be implemented effectively. To demonstrate the effectiveness of the proposed method, comparative studies using a multilayer neural network and k-means algorithm are conducted on 400 sets of field-test patterns of 200 W PEMFC with rather encouraging results. - Author(s): J. Puukko and T. Suntio
- Source: IET Renewable Power Generation, Volume 6, Issue 6, p. 381 –391
- DOI: 10.1049/iet-rpg.2011.0302
- Type: Article
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p.
381
–391
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A common practice in the analysis of voltage source inverters is the assumption of a voltage-type input source even in the case of renewable energy sources (RES). When a converter is supplied by an RES, such as a photovoltaic (PV) generator, the dc-link voltage is usually controlled by the inverter to extract maximum power from the source. This study presents an improved dynamic model of grid-connected three-phase renewable-energy-related inverter. For the proposed model to correspond to reality, the true nature of the input source has to be taken into account: an input-voltage-controlled converter has to be analysed so that it is supplied by a current source. Since all real sources are non-ideal, an explicit method to include the source effect on the inverter dynamics is presented, which has not been previously published in the literature. This study shows that the dynamics of the converter change completely when the operating point of a PV generator shifts from the constant current to the constant voltage region. This study shows also that assuming a voltage-type input source for a PV inverter leads to a model that cannot predict the existence of higher-order dynamics and a right-half plane zero in the control-to-output transfer function. - Author(s): K. Xie ; Y. Li ; W. Li
- Source: IET Renewable Power Generation, Volume 6, Issue 6, p. 392 –399
- DOI: 10.1049/iet-rpg.2011.0156
- Type: Article
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p.
392
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Owing to geographic relationships of wind farms, wind speeds at different wind sites show certain dependence between them, which may create a considerable impact on the reliability of power systems containing wind energy. A new technique for establishing multivariate distribution of wind speeds using copulas is presented to model wind speed dependence in the study. The separation between marginal distributions of each single wind speed and dependence structure is a basic feature of the copula method, which leads to the effectiveness and simplicity in dealing with the dependence in a multivariate distribution. The case studies using two actual wind speed data indicate that the copula model can give a valid representation of multiple wind speed series. The impact of wind speed dependence between two wind regimes on system reliability is illustrated using a commonly recognised reliability test system. The results confirm that system reliability will decrease as the wind speed dependence increases. - Author(s): C. Busada ; S. Gómez Jorge ; A.E. Leon ; J. Solsona
- Source: IET Renewable Power Generation, Volume 6, Issue 6, p. 400 –407
- DOI: 10.1049/iet-rpg.2011.0333
- Type: Article
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p.
400
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A current controller suitable for three-phase photovoltaic systems is presented. The proposed controller ensures the injection of sinusoidal and balanced currents, with high immunity to both imbalances and harmonics present in the supply voltage, without using a phase-locked loop to synthesise the reference currents to be injected. A fully digital domain controller design is proposed, that takes into account the digital signal processing delay as part of the system to stabilise. - Author(s): Y.-C. Kuo ; C.-H. Liu ; L.-J. Liu
- Source: IET Renewable Power Generation, Volume 6, Issue 6, p. 408 –413
- DOI: 10.1049/iet-rpg.2012.0136
- Type: Article
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p.
408
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In this study, a novel design tool for energy harvesting integrated circuits (IC) and system synthesis is developed with visual basic software. The proposed tool can be used to shorten the design time-to-market. A temperature compensation technique is then adopted to ensure that the circuit characteristics are stable and have low thermal sensitivity. In addition, a smart meter system is developed to measure energy harvester information by using an online system. Thus, users can obtain the proposed system information at all times. The accurate and superior performance of the proposed IC and system synthesis were confirmed by computer simulations and experimental results. - Author(s): R. Sharma ; T.W. Rasmussen ; B.B. Jensen
- Source: IET Renewable Power Generation, Volume 6, Issue 6, p. 414 –423
- DOI: 10.1049/iet-rpg.2011.0210
- Type: Article
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p.
414
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An electrical structure of a variable-speed wind turbine based on an externally excited synchronous generator; a passive diode rectifier; and a boost converter is discussed in this study. The clear advantage of such a system is its lower-semi-conductor devices count. A brief theoretical explanation of such a system is included. A boost converter normally utilies an inductor (energy storage) to boost the voltage level from its input to a higher output value. This study analyses the possibility of using the generator inductance as a boost inductor. It is discussed and verified in the study that for the given switching frequency of the boost converter (fs=1 kHz), the generator sub-transient inductance (not the synchronous inductance) appears as an equivalent inductance seen by the boost converter. The parasitic capacitors present in the generator terminals are often neglected from design issues. It is presented in the study that such capacitors can be a major issue when high-frequency switching is applied to the voltage at the generator terminals. Some major results from the experimental work are included. The experimental setup used in this work is a scaled down 7.5 kVA system. - Author(s): F. Mwasilu ; J.J. Justo ; K.-S. Ro ; J.-W. Jung
- Source: IET Renewable Power Generation, Volume 6, Issue 6, p. 424 –434
- DOI: 10.1049/iet-rpg.2012.0110
- Type: Article
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p.
424
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With the current increase in wind power penetration into the energy market, control and operation of wind turbine generators becomes a major research topic. Wind turbine based on doubly fed induction generator (DFIG), which is sensitive to grid disturbances, is widely used. Under an unbalanced grid voltage condition, oscillations of the DFIG's electromagnetic torque and instantaneous stator powers strongly affect the dynamic performance of the DFIG. In this study, a new configuration based on vector proportional–integral (VPI) controller is proposed to eliminate such oscillations. This new configuration is employed in the rotor side converter (RSC) of the DFIG. With the proposed VPI control strategy, decomposition of sequential components and mathematical complexity are reduced. Compared with the conventional field-oriented control based on the standard single PI controller, the VPI controller can successfully eliminate torque and stator power oscillations. The effectiveness of the proposed control strategy is validated through simulation results obtained on a 1.5 MW DFIG-based wind turbine system model built in MATLAB/Simulink. - Author(s): J.M. Maza-Ortega ; A. Gómez-Expósito ; M. Barragán-Villarejo ; E. Romero-Ramos ; A. Marano-Marcolini
- Source: IET Renewable Power Generation, Volume 6, Issue 6, p. 435 –445
- DOI: 10.1049/iet-rpg.2011.0246
- Type: Article
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p.
435
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This study presents and thoroughly compares different alternatives to create DC links in distribution networks by means of voltage source converters (VSC). Such links give rise to fully controllable loops in nowadays radially operated systems, allowing higher levels of distributed generation penetration. Suitable VSC-based devices are reviewed and compared from several points of view, including topologies, degrees of freedom, operating ranges and performance. Several case studies, involving actual urban and rural distribution networks, are worked out to show the potential benefits provided by the use of the proposed smart links. - Author(s): J.J. Melero ; J.J. Guerrero ; J. Beltrán ; C. Pueyo
- Source: IET Renewable Power Generation, Volume 6, Issue 6, p. 446 –454
- DOI: 10.1049/iet-rpg.2011.0288
- Type: Article
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p.
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The installation of a new wind farm requires the previous acquisition of a great amount of wind speed data in order to perform a correct wind energy assessment. These data are obtained from a meteorological mast installed at each site. Real wind measurements at the meteorological mast include many erroneous data, which must be detected and eliminated before working with them. To localise wrong data, a new method based on the Kalman filter is proposed. This filter is applied to a short-term prediction like the one used in wind power forecasting. The filter parameter tuning is based on general verification metric curves tested with real data from different sites. The filter equations are adapted to different sites depending on the intensity of turbulence and wind direction. In this study all the parameters are explained in detail and the filter is evaluated, showing nice results for wind energy assessment of candidate sites.
Fuel cell fault forecasting system using grey and extension theories
Dynamic properties of a voltage source inverter-based three-phase inverter in photovoltaic application
Modelling wind speed dependence in system reliability assessment using copulas
Phase-locked loop-less current controller for grid-connected photovoltaic systems
Synthesisable solar-harvesting integrated circuit and system
Application of a synchronous generator with a boost converter in wind turbines: an experimental overview
Improvement of dynamic performance of doubly fed induction generator-based wind turbine power system under an unbalanced grid voltage condition
Voltage source converter-based topologies to further integrate renewable energy sources in distribution systems
Efficient data filtering for wind energy assessment
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