Online ISSN
1752-1424
Print ISSN
1752-1416
IET Renewable Power Generation
Volume 3, Issue 1, March 2009
Volumes & issues:
Volume 3, Issue 1
March 2009
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- Author(s): W. Yang ; P.J. Tavner ; M.R. Wilkinson
- Source: IET Renewable Power Generation, Volume 3, Issue 1, p. 1 –11
- DOI: 10.1049/iet-rpg:20080006
- Type: Article
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p.
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Some large grid connected wind turbines use a low-speed synchronous generator, directly coupled to the turbine, and a fully rated converter to transform power from the turbine to mains electricity. The condition monitoring and diagnosis of mechanical and electrical faults in such a machine are considered, bearing in mind that it has a slow variable speed and is subject to the stochastic, aerodynamic effects of the wind. The application of wavelet transforms is investigated in the light of the disadvantages of spectral analysis in processing signals subject to such stochastic effects. The technique can be used to monitor generator electrical and drive train mechanical faults. It is validated experimentally on a wind turbine condition monitoring test rig using a three-phase, permanent-magnet, slow-speed, synchronous generator, driven by a motor controlled by a model representing the aerodynamic forces from a wind turbine. The possibility of detecting mechanical and electrical faults in wind turbines by electrical signal and particularly power analysis is heralded. - Author(s): Y. Wang ; L. Xu ; B.W. Williams
- Source: IET Renewable Power Generation, Volume 3, Issue 1, p. 12 –22
- DOI: 10.1049/iet-rpg:20080007
- Type: Article
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A control strategy for compensating AC network voltage unbalance using doubly fed induction generator (DFIG)-based wind farms is presented. A complete DFIG dynamic model containing both the rotor and grid side converters is used to accurately describe the average and ripple components of active/reactive power, electromagnetic torque and DC bus voltage, under unbalanced conditions. The principle of using DFIG systems to compensate grid voltage unbalance by injecting negative sequence current into the AC system is described. The injected negative sequence current can be provided by either the grid side or the rotor side converters. Various methods for coordinating these two converters are discussed and their respective impacts on power and torque oscillations are described. The validity of the proposed control strategy is demonstrated by simulations on a 30 MW DFIG-based wind farm using Matlab/Simulink during 2 and 4% voltage unbalances. The proposed compensation strategy can not only ensure reliable operation of the wind generators by restricting torque, DC link voltage and power oscillations, but also enable DFIG-based wind farms to contribute to rebalancing the connected network. - Author(s): S.-S. Chen ; L. Wang ; W.-J. Lee ; Z. Chen
- Source: IET Renewable Power Generation, Volume 3, Issue 1, p. 23 –38
- DOI: 10.1049/iet-rpg:20070117
- Type: Article
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A novel scheme using a superconducting magnetic energy storage (SMES) unit to perform both power flow control and damping enhancement of a large wind farm (WF) feeding to a utility grid is presented. The studied WF consisting of forty 2 MW wind induction generators (IGs) is simulated by an equivalent 80 MW IG. A damping controller of the SMES unit is designed based on the modal control theory to contribute proper damping characteristics to the studied WF under different wind speeds. A frequency-domain approach based on a linearised system model using eigen techniques and a time-domain scheme based on a nonlinear system model subject to disturbance conditions are both employed to validate the effectiveness of the proposed SMES unit with the designed SMES damping controller. It can be concluded from the simulated results that the proposed SMES unit combined with the designed damping controller is very effective in stabilising the studied large WF under various wind speeds. The inherent fluctuations of the injected active power of the WF to the power grid can also be effectively controlled by the proposed control scheme. - Author(s): J. Conroy and R. Watson
- Source: IET Renewable Power Generation, Volume 3, Issue 1, p. 39 –52
- DOI: 10.1049/iet-rpg:20070091
- Type: Article
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When the transient interaction between a large wind farm and a power system is to be studied, there are two possible approaches to wind farm modelling. It can be modelled as one or more equivalent wind turbine generators (aggregate modelling) or each wind turbine generator (WTG) can be modelled separately (detailed modelling). When a power system with many wind farms is to be simulated, the aggregate approach becomes especially attractive. A successful aggregate model will reduce the simulation time without significantly compromising the accuracy of the results in comparison to the detailed model. Here, the aggregate modelling options for a wind farm with 5 MW full-converter WTGs (FCWTGs) using permanent magnet synchronous machines are presented. A braking resistor in the DC circuit of the FCWTG's converter system is employed as a means of satisfying the latest grid code requirements. It will be shown that with a braking resistor implemented in the FCWTG there is scope for significant model simplifications, which is particularly relevant for transient stability studies of large-scale systems. - Author(s): R.D. Prasad ; R.C. Bansal ; M. Sauturaga
- Source: IET Renewable Power Generation, Volume 3, Issue 1, p. 53 –64
- DOI: 10.1049/iet-rpg:20080030
- Type: Article
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Owing to the increasing power demand and the environmental concerns of the conventional power sources, power generation from wind is receiving due attention from majority of power planners. Since wind is an intermittent energy source and to find the economic viability of wind project, a proper wind resource assessment (WRA) and analysis of the data collected is very important. An extensive literature survey on WRA is carried out and the different techniques of WRA are discussed. The methodology includes discussions on preliminary wind survey to choose the best site for installing wind data instruments, selecting the optimum wind turbine suitable for a site and the uncertainties involved in estimating the wind speed using the different WRA techniques. - Author(s): S.M. Muyeen ; R. Takahashi ; T. Murata ; J. Tamura ; M.H. Ali ; Y. Matsumura ; A. Kuwayama ; T. Matsumoto
- Source: IET Renewable Power Generation, Volume 3, Issue 1, p. 65 –74
- DOI: 10.1049/iet-rpg:20070116
- Type: Article
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The energy capacitor system (ECS), composed of power electronic devices and electric double layer capacitor to enhance the low voltage ride through (LVRT) capability of fixed speed wind turbine generator system (WTGS) during network disturbance, is discussed. Control scheme of ECS is based on a sinusoidal pulse width modulation voltage source converter and DC–DC buck/boost converter composed of insulated gate bipolar transistors. Two-mass drive train model of WTGS is adopted because the drive train system modelling has great influence on the characteristics of wind generator system during network fault. Extensive analysis of symmetrical fault is performed with different voltage dip magnitudes and different time durations. Permanent fault because of unsuccessful reclosing is also analysed, which is one of the salient features of this study. A real grid code defined in the power system is considered and LVRT characteristic of WTGS is analysed. Finally, it is concluded that ECS (20 MW) can significantly enhance the LVRT capability of grid connected WTGS (50 MW) during network disturbance, where simulations have been carried out by using PSCAD/EMTDC. - Author(s): P. Meibom ; C. Weber ; R. Barth ; H. Brand
- Source: IET Renewable Power Generation, Volume 3, Issue 1, p. 75 –83
- DOI: 10.1049/iet-rpg:20070075
- Type: Article
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Adding wind power generation in a power system changes the operational patterns of the existing units due to the variability and partial predictability of wind power production. For large amounts of wind power production, the expectation is that the specific operational costs (fuel costs, start-up costs, variable operation and maintenance costs, costs of consuming CO2 emission permits) of the other power plants will increase due to more operation time in part-load and more start-ups. The change in operational costs induced by the wind power production can only be calculated by comparing the operational costs in two power system configurations: with wind power production and with alternative wind production having properties such as conventional production, that is, being predictable and less variable. The choice of the characteristics of the alternative production is not straightforward and will therefore influence the operational costs induced by wind power production. A method is applied for calculating the change in operational costs due to wind power production using a stochastic optimisation model covering the power systems in Germany and the Nordic countries. Two cases of alternative production are used to calculate the change in operational costs, namely perfectly predictable wind power production enabling the calculation of the costs connected to partial predictability and constant wind power production enabling the calculation of the operational costs connected to variability of wind power production. A 2010 case with three different wind power production penetration levels is analysed. - Author(s): H.H. Zeineldin ; T.H.M. El-Fouly ; E.F. El-Saadany ; M.M.A. Salama
- Source: IET Renewable Power Generation, Volume 3, Issue 1, p. 84 –95
- DOI: 10.1049/iet-rpg:20080026
- Type: Article
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Wind generation is considered one of the most rapidly increasing resources among other distributed generation technologies. Recently, wind farms with considerable output power rating are installed. The variability of the wind output power, and the forecast inaccuracy could have an impact on electricity market prices. These issues have been addressed by developing a single auction market model to determine the close to real-time electricity market prices. The market-clearing price was determined by formulating an optimal power flow problem while considering different operational strategies. Inaccurate power prediction can result in either underestimated or overestimated market prices, which would lead to either savings to customers or additional revenue for generator suppliers. - Author(s): F.D. Kanellos and N.D. Hatziargyriou
- Source: IET Renewable Power Generation, Volume 3, Issue 1, p. 96 –108
- DOI: 10.1049/iet-rpg:20080023
- Type: Article
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p.
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A control method for variable speed wind turbines (VSWTs) supplying islanded parts of electrical networks is presented. Active power/frequency and reactive power/voltage droops are applied in order to determine the active, reactive power production, thus downscaling to the VSWTs the conventional control concepts of the power plants. Two types of VSWTs comprising doubly fed induction generators or synchronous generators are considered. Electrical, aerodynamic and structural detailed dynamic models were developed and combined with the proposed control strategies ensuring fast regulation of the frequency and the voltage in the islanded mode of operation. The obtained models are used for the simulation of a representative simplified distribution network supplied by VSWTs.
Condition monitoring and fault diagnosis of a wind turbine synchronous generator drive train
Compensation of network voltage unbalance using doubly fed induction generator-based wind farms
Power flow control and damping enhancement of a large wind farm using a superconducting magnetic energy storage unit
Aggregate modelling of wind farms containing full-converter wind turbine generators with permanent magnet synchronous machines: transient stability studies
Some of the design and methodology considerations in wind resource assessment
Low voltage ride through capability enhancement of wind turbine generator system during network disturbance
Operational costs induced by fluctuating wind power production in Germany and Scandinavia
Impact of wind farm integration on electricity market prices
Control of variable speed wind turbines equipped with synchronous or doubly fed induction generators supplying islanded power systems
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