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Online ISSN 1752-1424 Print ISSN 1752-1416

IET Renewable Power Generation

Volume 1, Issue 3, September 2007

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Volume 1, Issue 3

September 2007

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    • High-performance voltage control scheme for wind park integration
      • Author(s): M. El Moursi ; G. Joos ; C. Abbey
      • Source: IET Renewable Power Generation, Volume 1, Issue 3, p. 151 –159
      • DOI:  10.1049/iet-rpg:20060008
      • Type: Article
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      • p. 151 –159 (9)
        The design and implementation of a new control scheme for reactive power compensation and voltage regulation in the transmission system, as provided and controlled by a wind park is presented. It proposes an optimal tracking secondary voltage control scheme applied to doubly fed induction generator-based wind generators. The ability of the controller to regulate transmission network voltage profiles is demonstrated and compared with primary voltage control, an alternate secondary voltage control approach, and the voltage profile obtained from optimal power flow analysis. The dynamic performance of the controller is also validated in response to system contingencies, namely short circuits. The impact of communication time delays and of the short-circuit ratio on the dynamic performance of the voltage controller are considered. Results show that the controller properly regulates the voltage in steady state and performs properly during transients resulting from short circuits. Decoupling between primary and secondary loops should be applied to mitigate the effects of the time delay.
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      Investigation of the reverse power flow requirements of high penetrations of small-scale embedded generation
      • Author(s): L.M. Cipcigan  and  P.C. Taylor
      • Source: IET Renewable Power Generation, Volume 1, Issue 3, p. 160 –166
      • DOI:  10.1049/iet-rpg:20070011
      • Type: Article
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      • p. 160 –166 (7)
        The research carried out to investigate the ability of power transformers to facilitate the required power flows associated with the anticipated high penetrations of small scale embedded generation (SSEG), within small-scale energy zones (SSEZs) is described. A small-scale energy zone is defined as a section of low-voltage, network with a high penetration of SSEGs, controllable loads and energy storage units. SSEZs, coupled with active control techniques, have the potential to assist the growth of SSEGs by removing network constraints and enabling blocks of aggregated and controlled SSEGs to participate more effectively in energy markets and network operational tasks. The research focused on identifying the reverse power flow and thermal-rating constraints imposed by power transformers. The analysis was performed using an approved UK generic PSCAD/EMTDC electrical network model, with varying levels of SSEGs. Simulations were carried out examining cases with a uniform distribution of SSEGs contained within a number of SSEZs. It was observed that in some cases the reverse power flow capability of the primary transformers would exceed if each customer installed an SSEG with a rating of approximately 1 kW.
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      Distributed generation as a balancing resource for wind generation
      • Author(s): J. Kennedy ; B. Fox ; D.J. Morrow
      • Source: IET Renewable Power Generation, Volume 1, Issue 3, p. 167 –174
      • DOI:  10.1049/iet-rpg:20070017
      • Type: Article
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      • p. 167 –174 (8)
        Full exploitation of the environmental and financial benefits of wind-generated energy in a power system requires prediction of the wind energy profile well in advance of delivery. On the basis of forecast profile and associated confidence, wind energy can be included in the unit commitment/economic dispatch procedure, resulting in near-optimal commitment and loading of thermal plant, thereby saving fuel. A wind forecasting methodology, which closely resembles a commercial wind forecasting package, is adopted to illustrate the possible instances of significant over-forecasting, although rare, and exposure of the system to substantial risk. It is shown that the cost of additional spinning reserve necessary for such cases is prohibitive, and a fast, flexible generation, such as diesel gen-sets are considered as a superior mechanism to balance any such shortfalls. The Northern Ireland power system is used as a case study to demonstrate the environmental and financial benefits of using distributed diesel generation in the manner described above. The study is based on a six-month period system data, and is applied to various future scenarios of the installed wind. It is shown that the methodology can mitigate many of the problems associated with large-scale wind penetration on a synchronously islanded system.
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      Virtual inductor-based islanding detection method for grid-connected power inverter of distributed power generation system
      • Author(s): H.-L. Jou ; W.-J. Chiang ; J.-C. Wu
      • Source: IET Renewable Power Generation, Volume 1, Issue 3, p. 175 –181
      • DOI:  10.1049/iet-rpg:20070018
      • Type: Article
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      • p. 175 –181 (7)
        An islanding detection method is proposed for a distributed power generation system that comprises a DC power source and a grid-connected power inverter connected in parallel to the utility. Besides serving to generate the fundamental real power, the grid-connected power inverter also acts as a virtual inductor when the frequency is slightly higher than the fundamental voltage frequency of the utility. The distributed power generation system is the only source supplying power to the load when the utility is interrupted; consequently, the amplitude or frequency of the load voltage changes because of the operation of the virtual inductor. Hence, the proposed method can immediately detect the islanding operation. A prototype was developed and tested to demonstrate the performance of the proposed islanding detection method. Experimental results show that the proposed method can detect islanding operations effectively.
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      Low-voltage ride-through of a full converter wind turbine with permanent magnet generator
      • Author(s): J.F. Conroy  and  R. Watson
      • Source: IET Renewable Power Generation, Volume 1, Issue 3, p. 182 –189
      • DOI:  10.1049/iet-rpg:20070033
      • Type: Article
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      • p. 182 –189 (8)
        The low-voltage ride-through capability of a 2 MW full converter wind turbine with permanent magnet synchronous generator is investigated herein. A detailed description of the system, its controller options and its behaviour when subjected to a severe voltage dip, is presented. A control scheme for the turbine that allows it to withstand severe voltage dips is designed and simulated. This control scheme emphasises the regulation of the dc‐link voltage and minimisation of the drive train torque surplus. Also, the level of modelling detail required for stability analysis is analysed and discussed.
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