Online ISSN
1752-1424
Print ISSN
1752-1416
IET Renewable Power Generation
Volume 3, Issue 4, December 2009
Volumes & issues:
Volume 3, Issue 4
December 2009
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- Author(s): S.C.E. Jupe and P.C. Taylor
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 371 –386
- DOI: 10.1049/iet-rpg.2008.0029
- Type: Article
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p.
371
–386
(16)
The development stages in the output control of distributed generation (DG) for network power flow management are illustrated. The first stage requires an assessment of the location of thermally vulnerable components within the distribution network. This is achieved through the offline calculation of thermal vulnerability factors that relate component power flow sensitivity factors to component thermal limits. This directly informs Stage 2 – the installation of meteorological stations and component temperature monitoring equipment for network thermal characterisation. In Stage 3, steady-state component rating models are populated with real-time environmental information from the meteorological stations to generate component real-time thermal ratings. In Stage 4, the power flow sensitivity factors calculated in Stage 1 are embedded within a network power flow management system which, together with the component real-time thermal ratings calculated in Stage 3, is used to control the power output of DG schemes. - Author(s): F. Spinato ; P.J. Tavner ; G.J.W. van Bussel ; E. Koutoulakos
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 387 –401
- DOI: 10.1049/iet-rpg.2008.0060
- Type: Article
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p.
387
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We have investigated the reliability of more than 6000 modern onshore wind turbines and their subassemblies in Denmark and Germany over 11 years and particularly changes in reliability of generators, gearboxes and converters in a subset of 650 turbines in Schleswig Holstein, Germany. We first start by considering the average failure rate of turbine populations and then the average failure rates of wind turbine subassemblies. This analysis yields some surprising results about which subassemblies are the most unreliable. Then we proceed to consider the failure intensity function variation with time for wind turbines in one of these populations, using the Power Law Process, of three subassemblies; generator, gearbox and converter. This analysis shows that wind turbine gearboxes seem to be achieving reliabilities similar to gearboxes outside the wind industry. However, wind turbine generators and converters are both achieving reliabilities considerably below that of other industries but the reliability of these subassemblies improves with time. The paper also considers different wind turbine concepts. Then we conclude by proposing that offshore wind turbines should be subject to more rigorous reliability improvement measures, such as more thorough subassembly testing, to eliminate early failures. The early focus should be on converters and generators. - Author(s): A. Hajizadeh and M.A. Golkar
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 402 –414
- DOI: 10.1049/iet-rpg.2008.0027
- Type: Article
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p.
402
–414
(13)
An innovative control strategy is proposed of hybrid distributed generation (HDG) systems, including solid oxide fuel cell (SOFC) as the main energy source and battery energy storage as the auxiliary power source. The overall configuration of the HDG system is given, and dynamic models for the SOFC power plant, battery bank and its power electronic interfacing are briefly described, and controller design methodologies for the power conditioning units and fuel cell to control the power flow from the hybrid power plant to the utility grid are presented. To distribute the power between power sources, the fuzzy switching controller has been developed. Then, a Lyapunov based-neuro fuzzy algorithm is presented for designing the controllers of fuel cell power plant, DC/DC and DC/AC converters; to regulate the input fuel flow and meet a desirable output power demand. Simulation results are given to show the overall system performance including load-following and power management of the system. - Author(s): W. El-khattam and T.S. Sidhu
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 415 –425
- DOI: 10.1049/iet-rpg.2008.0015
- Type: Article
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p.
415
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(11)
Two approaches are proposed to solve the directional overcurrent relay coordination problem associated with the installation of distributed renewable generation (DRG) in interconnected power delivery systems (IPDS), depending on the existing system protection capability (adaptive or non-adaptive). For adaptive protection systems, the first proposed approach introduces a procedure to select the optimal minimum number of relays, their locations and new settings. This procedure is restricted by the available relay setting groups. For non-adaptive protection systems, the second proposed approach implements a practice to obtain optimal minimum fault current limiter values (FCL) to limit DRG fault currents and restore relay coordination status without altering the original relay settings. An integration of the proposed two approaches is evaluated for IPDSs possessing both protection systems. Three scenarios are assessed for different numbers of DRGs, and DRG and fault locations using an optimisation model implemented in GAMS software and a developed MatLab code. The obtained results are reported and discussed. - Author(s): G. Ramtharan ; A. Arulampalam ; J.B. Ekanayake ; F.M. Hughes ; N. Jenkins
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 426 –438
- DOI: 10.1049/iet-rpg.2008.0018
- Type: Article
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p.
426
–438
(13)
Fault ride through of fully rated converter wind turbines in an offshore wind farm connected to onshore network via either high voltage AC (HVAC) or high voltage DC (HVDC) transmission is described. Control of the generators and the grid side converters is shown using vector control techniques. A de-loading scheme was used to protect the wind turbine DC link capacitors from over voltage. How de-loading of each generator aids the fault ride through of the wind farm connected through HVAC transmission is demonstrated. The voltage recovery of the AC network during the fault was enhanced by increasing the reactive power current of the wind turbine grid side converter. A practical fault ride through protection scheme for a wind farm connected through an HVDC link is to employ a chopper circuit on the HVDC link. Two alternatives to this approach are also discussed. The first involves de-loading the wind farm on detection of the fault, which requires communication of the fault condition to each wind turbine of the wind farm. The second scheme avoids this complex communication requirement by transferring the fault condition via control of the HVDC link to the offshore converter. The fault performances of the three schemes are simulated and the results were used to assess their respective capabilities. - Author(s): A.G. Madureira and J.A. Peças Lopes
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 439 –454
- DOI: 10.1049/iet-rpg.2008.0064
- Type: Article
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p.
439
–454
(16)
This paper proposes a new methodology for coordinated voltage support in distribution networks with large integration of distributed generation and microgrids. Given the characteristics of the LV networks, it is shown that traditional control strategies using only reactive power control may not be sufficient in order to perform efficient voltage control. Therefore, microgeneration shedding must also be employed, especially in scenarios with extreme microgeneration penetration. An optimisation tool based on a meta-heuristic approach was developed to address the voltage control problem. In addition, neural networks were employed in order to decrease computational time, thus enabling the use of the tool for online operation. The results obtained revealed good performance of this control approach. - Author(s): A. Keane ; Q. Zhou ; J.W. Bialek ; Mark O'Malley
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 455 –464
- DOI: 10.1049/iet-rpg.2008.0058
- Type: Article
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p.
455
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(10)
The penetration of distributed generation (DG) is increasing on distribution networks across the world. Non-firm access to the network is now being proposed as a cost effective way to facilitate DG. However, concerns remain about the operational details of non-firm access and also with regard to the financing of DG projects, which, by their nature, are not guaranteed permission to export power at all times. Here, the pertinent planning and operational issues that arise with non-firm access are analysed. The index of coincidence is used to assess the probability of constraint breaches, through analysis of historical generation and load profiles. Further to this, a novel method is proposed, which minimises the cost to the generators of non-firm access through coordinated operation. - Author(s): Â. Mendonça and J.A. Peças Lopes
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 465 –475
- DOI: 10.1049/iet-rpg.2008.0066
- Type: Article
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p.
465
–475
(11)
This paper addresses the problem of robustly tuning power system stabilisers (PSSs) in systems with large wind power integration. PSSs installed in wind energy conversion systems, namely in doubly fed induction generators, are used in this research to provide additional damping to the electromechanical modes of oscillation. A new method that aims to reduce the computational effort required to find a robust solution that is suitable for a very large set of operating conditions is also proposed. - Author(s): A. Kornelakis and E. Koutroulis
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 476 –492
- DOI: 10.1049/iet-rpg.2008.0069
- Type: Article
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p.
476
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(17)
In this study, a methodology for the design optimisation and the economic analysis of photovoltaic grid-connected systems (PVGCSs) is presented. The purpose of the proposed methodology is to suggest, among a list of commercially available system devices, the optimal number and type of system devices and the optimal values of the photovoltaic (PV) module installation details, such that the total net economic benefit achieved during the system operational lifetime period is maximised. The decision variables included in the optimisation process are the optimal number and type of the PV modules and the DC/AC converters, the PV modules optimal tilt angle, the optimal arrangement of the PV modules within the available installation area and the optimal distribution of the PV modules among the DC/AC converters. The economic viability of the resulting PVGCS configuration is explored according to the net present value, the discounted payback period and the internal rate of return methods. The proposed method has been applied for the optimal design of a PVGCS interconnected to the electric network of an island with significant solar irradiation potential and the corresponding optimal sizing and economic analysis results are presented. - Author(s): A.M. Massoud ; K.H. Ahmed ; S.J. Finney ; B.W. Williams
- Source: IET Renewable Power Generation, Volume 3, Issue 4, p. 493 –507
- DOI: 10.1049/iet-rpg.2008.0101
- Type: Article
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p.
493
–507
(15)
A harmonic distortion-based island detection technique for inverter-based distributed generation (IBDG) is proposed. The proposed technique is classified as an active island detection technique and it is based on the voltage change at the point of common coupling (PCC) that occurs in islanding. To avoid island detection failure in case of a close matching between IBDG-generated power and load power, an active power–voltage locus is introduced to shift the reference active power for PCC voltage change, therefore breaking the IBDG-load power balance and transferring the operating point outside the non-detection zone. A new harmonic performance index, named harmonic amplification factor, is introduced to detect the island. This factor amplifies each harmonic component by its order. Besides the ability of detecting short circuit, the proposed technique can discriminate between islanding and other disturbances, as load change, grid voltage distortion and unbalance, and capacitor bank switching. The proposed technique is validated by Matlab/Simulink simulation and practically as well.
Distributed generation output control for network power flow management
Reliability of wind turbine subassemblies
Fuzzy neural control of a hybrid fuel cell/battery distributed power generation system
Resolving the impact of distributed renewable generation on directional overcurrent relay coordination: a case study
Fault ride through of fully rated converter wind turbines with AC and DC transmission systems
Coordinated voltage support in distribution networks with distributed generation and microgrids
Planning and operating non-firm distributed generation
Robust tuning of power system stabilisers to install in wind energy conversion systems
Methodology for the design optimisation and the economic analysis of grid-connected photovoltaic systems
Harmonic distortion-based island detection technique for inverter-based distributed generation
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