Online ISSN
1752-1424
Print ISSN
1752-1416
IET Renewable Power Generation
Volume 5, Issue 2, March 2011
Volumes & issues:
Volume 5, Issue 2
March 2011
-
- Author(s): Y. Ma ; T. Runolfsson ; J.N. Jiang
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 109 –116
- DOI: 10.1049/iet-rpg.2009.0005
- Type: Article
- + Show details - Hide details
-
p.
109
–116
(8)
Understanding the dynamics of power output of a wind farm is important for integration of large-scale wind energy. In a large complex dynamic system, such as a wind farm, clustering is a way to reduce the model complexity and improve the understanding of the model dynamics. This study presents a methodology for clustering wind turbines of a wind farm into different groups. A weighted graph is firstly designed to represent the complex relationships between the power outputs of wind turbines. Such graph is used to construct a Markov chain for estimation of the likelihood of wind turbines belonging to the same cluster. The spectral properties of the constructed Markov chain are analyzed to identify the number of clusters, so the elements of each cluster can be identified in a feature space. Theoretical study shows that the proposed methodology can simplify the dynamic model of power output of wind farm without compromising the overall dynamic characteristics of the original system asymptotically. The methodology of clustering is demonstrated and tested based on observations of power output of wind turbines in an actual wind farm. The methodology can be used to simplify controller design, and operation and forecast of wind farm output. - Author(s): M. Ross ; R. Hidalgo ; C. Abbey ; G. Joós
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 117 –123
- DOI: 10.1049/iet-rpg.2009.0204
- Type: Article
- + Show details - Hide details
-
p.
117
–123
(7)
A knowledge-based expert system (KBES) is proposed for the scheduling of an energy storage system (ESS) installed in a wind–diesel isolated power system. The program optimises the cost of operation by determining the diesel generation and the charging/discharging cycles of the storage system from the wind and load profiles one hour in advance. The rules created aim to minimise the use of the dump load normally associated with diesel operation. The results are compared to an offline optimisation algorithm applied to the same power system and ESS size that has a 24-h lookahead. The results obtained show that by minimising the energy wasted through the dump load with the use of the ESS and KBES controller, the required diesel generation is reduced, therefore reducing operation costs and emissions. - Author(s): M. Soliman ; O.P. Malik ; D.T. Westwick
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 124 –136
- DOI: 10.1049/iet-rpg.2009.0137
- Type: Article
- + Show details - Hide details
-
p.
124
–136
(13)
A multivariable control strategy based on model predictive control techniques for the control of variable-speed variable pitch wind energy conversion systems (WECSs) in the above-rated wind speed zone is proposed. Pitch angle and generator torque are controlled simultaneously to provide optimal regulation of the generated power and the generator speed while minimising torsional torque fluctuations in the drive train and pitch actuator activity. This has the effect of improving the power quality of the electrical power generated by the WECS and increasing the life time of the mechanical parts of the system. Furthermore, safe and acceptable operation of the system is guaranteed by incorporating most of the constraints on the physical variables of the WECS in the controller design. In order to cope with the non-linearity in the WECS and the continuous variation in the operating point, a multiple model predictive controller is suggested to provide near optimal performance within the whole operating region. - Author(s): S.A. Saleh ; M.A.S.K. Khan ; M.A. Rahman
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 137 –147
- DOI: 10.1049/iet-rpg.2010.0054
- Type: Article
- + Show details - Hide details
-
p.
137
–147
(11)
This study presents a systematic approach for modelling, analysing and evaluating steady-state performances of directly driven interior permanent magnet generators (IPMG) for wind energy conversion systems. The proposed approach for modelling and analysing the performance of PMGs is based on relating the harmonic components present in the stator currents to the harmonic components present in the terminal voltages. Three laboratory IPMG of 1, 5 and 50 kW are tested at different shaft speeds for supplying a resistive load, a rectifier and a resistive load and rectifier–inverter with a resistive load. Experimental performances of the tested IPMGs demonstrate direct relationships between terminal voltage harmonic components and harmonic components present in stator currents. Also, investigated experimental performances show significant impacts of stator currents harmonic components on the IPMG efficiency. - Author(s): C. Boccaletti ; P. Di Felice ; L. Petrucci ; E. Santini
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 148 –159
- DOI: 10.1049/iet-rpg.2010.0006
- Type: Article
- + Show details - Hide details
-
p.
148
–159
(12)
A parametric analysis of axial flux disc machines (AFDMs) is performed in order to evaluate the total harmonic distortion (THD) of output voltage depending on the shape and size of permanent magnets. In renewable energy applications of AFDM (wind generators), THD is an important issue and the proposed simulation model can be used to predict the THD of the output voltage of a machine on the basis of key parameters. A simplified but reasonably accurate mathematical model has been developed to determine the equivalent circuit parameters of AFDMs of whatever configuration. The analytical model, validated by means of FEM and experimental data, allows extremely fast (almost instantaneous) calculations with an accuracy comparable with that of much slower and complex methods. Parametric analyses have been performed on an AFDM-12 – a machine with a stator and two rotors, and one coil per pole and per phase – with different shapes and sizes of permanent magnets. The harmonic content and THD of each configuration (with trapezoidal, triangular, rectangular and circular magnets) have been calculated and compared. - Author(s): T. Goya ; E. Omine ; Y. Kinjyo ; T. Senjyu ; A. Yona ; N. Urasaki ; T. Funabashi
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 160 –166
- DOI: 10.1049/iet-rpg.2010.0083
- Type: Article
- + Show details - Hide details
-
p.
160
–166
(7)
Stand-alone ac power supply system such as isolated islands is subject to large frequency and voltage fluctuations caused by power deviations of wind turbine generator and load demand. The autonomous decentralised frequency control system of parallel operated decentralised generators based on droop characteristic is presented in this study. The conventional droop control methods proposed in past researches show slow and oscillating dynamic responses. Moreover, the conventional droop control is affected by measurement noise when the fast controllability of the system is emphasised. This study proposes the improved droop control system for load sharing of multi-operated decentralised generators by applying H∞ control theory, improving transient response of droop control and robustness against measurement noise and parameter variations. Simulation results validate the effectiveness of the proposed control system. - Author(s): X. Long ; R. Liao ; J. Zhou
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 167 –174
- DOI: 10.1049/iet-rpg.2009.0199
- Type: Article
- + Show details - Hide details
-
p.
167
–174
(8)
The development of battery-buffered photovoltaic (PV) power conditioning systems (PCSs) is challenged by its cost/W. It compels the users to optimise the system's configuration in order to maximise the power generation. An alternative solution to this problem based on a charge collector (CC), which has the ability of maximising the charge collection of battery is shown here. The design of the CC is derived from the linear approximation model resolving prior probability distribution and dynamic DC/DC topology with micro-controller to meet the low-cost application. A simulation system has been made and analysed to verify the better performances of the CC over the traditional ones, and an empirical PV PCS example based on the laboratory prototype has been conducted to highlight the CC's natures. Results from the demonstrations, including LED lighting projections of PV PCS, show that the proposed low-cost CC with 4 ms settling time has about more than 20% efficiency and less than 50% sensitivity to system's parameters compared with the simple controller. - Author(s): H.H. Zeineldin and S. Conti
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 175 –183
- DOI: 10.1049/iet-rpg.2010.0096
- Type: Article
- + Show details - Hide details
-
p.
175
–183
(9)
Among frequency drift islanding detection methods, Sandia frequency shift (SFS) is considered as one of the most effective methods in detecting islanding conditions for grid connected photovoltaic (PV) inverters. The performance of the SFS method during an islanding condition and its non-detection zone (NDZ) depends to a great extent on its parameters. Furthermore, the capability of the SFS method to detect an islanding condition deteriorates with multiple PV inverters. A mathematical formula is derived to aid protection engineers in determining the optimal setting of the SFS islanding detection parameters with multiple inverter-based distributed generation (DG), such as PV systems, to eliminate the NDZ. The derived formula is applied to multiple DG systems equipped with the over frequency/under frequency protection, active frequency drift and SFS islanding detection methods and is verified through NDZ analysis and simulation results on PSCAD/EMTDC. The derived formula provides an effective guideline for designing frequency drift methods in multi-inverter-based DG systems. - Author(s): A. Karthikeyan ; C. Nagamani ; G. Saravana Ilango ; A. Sreenivasulu
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 184 –193
- DOI: 10.1049/iet-rpg.2009.0126
- Type: Article
- + Show details - Hide details
-
p.
184
–193
(10)
This study proposes a hybrid, open-loop exciter for the wind turbine-driven induction generator for low power applications. The hybrid exciter comprises one set of fixed capacitor bank and a parallel connected three-phase fixed frequency pulse width modulation (PWM) inverter fed from a battery. This hybrid exciter inherently adapts to the changes in the rotor speed or load on the generator while maintaining a near constant voltage and frequency at the load terminals. The whole system including the PWM inverter is operated in an open loop, without the need for any sensors other than the low-speed cut-in and high-speed cut-out mechanisms on the wind turbine. Results from simulations and laboratory tests show that the dynamic reactive power compensation of the generator is inherent in the proposed open-loop system. The volt ampere (VA) rating of the inverter and the battery capacity can be minimal, depending only upon the speed and load ranges of the generator and the choice of fixed capacitor var. - Author(s): Y. Yuan ; Q. Li ; W. Wang
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 194 –201
- DOI: 10.1049/iet-rpg.2009.0107
- Type: Article
- + Show details - Hide details
-
p.
194
–201
(8)
In order to obtain maximum profits in trading of wind power for large-scale wind farms, energy storage unit (ESU) can be introduced to decrease the bid imbalance and to shift energy from the cheapest to the most expensive, so that the penalty can be reduced and energy can be traded with higher price for wind farm. As the forecast error of wind power output is a stochastic variable, stochastic programming is adopted to determine the optimal operation strategies of ESU. Mathematical model for seeking the maximum benefits of wind farm and ESU is also developed based on stochastic programming. Hybrid genetic algorithm and neural network methods are employed to solve the optimisation problem. Economic analysis is also included to illustrate the feasibility of the hybrid system. Results indicate that ESU can improve the profits of wind farm by decreasing the bid imbalance and shifting wind energy from low-price intervals to higher ones. - Author(s): V. Rajagopal ; B. Singh ; G.K. Kasal
- Source: IET Renewable Power Generation, Volume 5, Issue 2, p. 202 –213
- DOI: 10.1049/iet-rpg.2010.0081
- Type: Article
- + Show details - Hide details
-
p.
202
–213
(12)
This study deals with an implementation of an instantaneous reactive power theory-based electronic load controller (ELC) for regulating the voltage and frequency of an isolated induction generator system (IG) that can supply electricity in remote areas. This ELC provides the fundamental reactive power and compensates harmonics of load currents. The proposed ELC is a combination of voltage source converter (VSC) with a dc link capacitor, a chopper and an auxiliary load at its dc bus. It controls active and reactive powers of the small hydro plant thus regulating the voltage and frequency of IG system. This ELC also balances the currents of the IG system under unbalanced load currents and eliminates the harmonics of the load currents thereby acting both as a load balancer and a harmonic eliminator. The zigzag/star transformer optimises the dc bus voltage of VSC and acts as a neutral current compensator. The proposed IG along with its ELC is implemented on a 3.7 kW IG system.
Cluster analysis of wind turbines of large wind farm with diffusion distance method
Energy storage system scheduling for an isolated microgrid
Multiple model multiple-input multiple-output predictive control for variable speed variable pitch wind energy conversion systems
Steady-state performance analysis and modelling of directly driven interior permanent magnet wind generators
Parametric analysis of axial flux wind generators focused on total harmonic distortion evaluation
Frequency control in isolated island by using parallel operated battery systems applying H∞ control theory based on droop characteristics
Low-cost charge collector of photovoltaic power conditioning system based dynamic DC/DC topology
Sandia frequency shift parameter selection for multi-inverter systems to eliminate non-detection zone
Hybrid, open-loop excitation system for a wind turbine-driven stand-alone induction generator
Optimal operation strategy of energy storage unit in wind power integration based on stochastic programming
Electronic load controller with power quality improvement of isolated induction generator for small hydro power generation
Most viewed content for this Journal
Article
content/journals/iet-rpg
Journal
5
Most cited content for this Journal
-
Integration of renewable distributed generators into the distribution system: a review
- Author(s): T. Adefarati and R.C. Bansal
- Type: Article
-
Artificial neural network-based photovoltaic maximum power point tracking techniques: a survey
- Author(s): Lina M. Elobaid ; Ahmed K. Abdelsalam ; Ezeldin E. Zakzouk
- Type: Article
-
Improved performance low-cost incremental conductance PV MPPT technique
- Author(s): Nahla E. Zakzouk ; Mohamed A. Elsaharty ; Ahmed K. Abdelsalam ; Ahmed A. Helal ; Barry W. Williams
- Type: Article
-
Optimal operation of distributed generations in micro-grids under uncertainties in load and renewable power generation using heuristic algorithm
- Author(s): Nima Nikmehr and Sajad Najafi-Ravadanegh
- Type: Article
-
Solution to short-term frequency response of wind farms by using energy storage systems
- Author(s): Ju Liu ; Jinyu Wen ; Wei Yao ; Yao Long
- Type: Article
