Online ISSN
1752-1424
Print ISSN
1752-1416
IET Renewable Power Generation
Volume 4, Issue 1, January 2010
Volumes & issues:
Volume 4, Issue 1
January 2010
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- Author(s): S.E. Ben Elghali ; M.E.H. Benbouzid ; J.-F. Charpentier
- Source: IET Renewable Power Generation, Volume 4, Issue 1, p. 1 –11
- DOI: 10.1049/iet-rpg.2008.0118
- Type: Article
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This paper deals with the modelling and control of a variable speed doubly fed induction generator-based marine current turbine with and without tidal current speed sensor. The proposed maximum power point tracking control strategy relies on the resource and the marine turbine models that were validated by experimental data. The sensitivity of the proposed control strategy is analysed regarding the swell effect because it is considered as the most disturbing one for the resource model. Tidal current data from the Raz de Sein (Brittany, France) are used to run simulations of a 7.5-kW prototype over various flow regimes. Simulation results are presented and fully analysed. - Author(s): H. Patel and V. Agarwal
- Source: IET Renewable Power Generation, Volume 4, Issue 1, p. 12 –22
- DOI: 10.1049/iet-rpg.2008.0081
- Type: Article
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With their growing popularity as alternative to conventional fuel, photovoltaics(PV) are being increasingly employed for a wide range of applications. Power quality improvement through a PV-fed active filter (PVAF) or inverter is one such application. A PVAF can supply active and reactive power to the grid when solar radiation is available or control the reactive power during periods of low or no radiation. The advantages of PVAF as an independent active source of compensation, reduced transmission losses etc. over a conventional AF have already been highlighted in the literature. However, not much attention has been paid to the effects of the PVAF configuration on its operational performance. Similarly, the effect of control schemes used to control such filters has also not been investigated. Various configurations of PVAF (viz. string- or multiple-string- or centralised-inverter based) are possible depending upon the configuration of the PV array (source). This study compares various PVAF configurations and their control schemes in terms of their ability to compensate reactive power, harmonics and phase-imbalances caused by unbalanced linear and non-linear loads in a three-phase, four-wire distribution system. Performance parameters such as power output and power quality as described by total harmonic distortion, phase imbalance and neutral conductor current are evaluated under both uniform and non-uniform radiation (e.g. partially shaded) conditions. In particular, results are presented to highlight and compare the effects of partial shading on the control schemes and PVAF configurations. Based on this study, several critical observations and remarks are presented. - Author(s): E.B. Muhando ; T. Senjyu ; K. Uchida ; H. Kinjo ; T. Funabashi
- Source: IET Renewable Power Generation, Volume 4, Issue 1, p. 23 –35
- DOI: 10.1049/iet-rpg.2007.0132
- Type: Article
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Wind turbines have become the most cost-effective renewable energy systems available today and are now completely competitive with essentially all conventional generation systems. However, wind stochasticity results in fluctuations in output power as well as undesirable dynamic loading of the drive train during high turbulence. A model-based predictive control strategy for the field-oriented control of a doubly fed induction generator is presented. The control region is defined over two wind profiles: average wind speeds below and above equipment rating, subject to assigned constraints of the maximum allowable system frequency fluctuations and the power limit of the wind generating system. To meet the control objectives of maximising energy capture and alleviation of drive train fatigue loads, each of the WGS component blocks is modelled separately so as to explore the associated trade-offs. Simulations, carried out under a Matlab® environment, serve to verify that the proposed paradigm performs better than the classical linear proportional–integral controller in achieving the regulation of torsional dynamics while maintaining optimal operation. - Author(s): F. Liu ; Y. Kang ; Y. Zhang ; S. Duan ; X. Lin
- Source: IET Renewable Power Generation, Volume 4, Issue 1, p. 36 –42
- DOI: 10.1049/iet-rpg.2009.0019
- Type: Article
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Islanding detection is a mandatory function for grid-connected converters. The popular slip mode frequency shift (SMS) and auto phase shift active islanding detection methods are investigated and an improved (IM)-SMS strategy is proposed in this study. In the proposed method, additional phase shift is introduced to help in stimulating the action of the islanding detection and the algorithm is simplified as well. When the utility grid is disconnected, the algorithm keeps the frequency of the converter output voltage deviating until the frequency protection relay is triggered. The working principle of the method is introduced and the guidance of parameters selection and optimisation is also provided. The islanding detection performance is evaluated through theoretical analysis and verified by digital simulation and experimental results. The IM-SMS method exhibits features of simplicity, easy implementation and high reliability. - Author(s): S. Zhang ; K.J. Tseng ; S.S. Choi
- Source: IET Renewable Power Generation, Volume 4, Issue 1, p. 43 –54
- DOI: 10.1049/iet-rpg.2008.0067
- Type: Article
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The impact of wind generators on voltage control of the network has been analysed via a statistical approach. A probabilistic model was developed by taking into consideration the stochastic nature of the wind and the availability status of the network elements. The proposed statistical method estimates the voltage deviation at the point of common coupling and its probability of occurrence. An index, termed significant level of voltage deviation, has also been proposed to aid in evaluating strategies for mitigating voltage quality problems. Numerical case study is presented to illustrate the proposed method and to compare its performance against other methods. - Author(s): M. Klobasa
- Source: IET Renewable Power Generation, Volume 4, Issue 1, p. 55 –63
- DOI: 10.1049/iet-rpg.2008.0086
- Type: Article
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Demand response represents an additional option for reserve capacity as first market experiences have demonstrated. An analysis for Germany shows capacities up to 3 GW and costs starting at 30 euro/MWh in the industrial sector, 8 GW in the commercial sector and more than 20 GW in the residential sector including night storage heating. Simulations of the German power system showed that using these potentials together with improved wind power predictions can limit the additional balancing costs in Germany to below 2 euro/MWh feed-in by wind turbines with 48 GW wind power in 2020. - Author(s): T. Boehme ; G.P. Harrison ; A.R. Wallace
- Source: IET Renewable Power Generation, Volume 4, Issue 1, p. 64 –74
- DOI: 10.1049/iet-rpg.2008.0109
- Type: Article
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Before new renewable generators can be connected to the electricity network, it is necessary to carefully evaluate the impact they will have. Firm connection agreements are based on snapshot assessments of the worst-case situation of maximum generation and minimum demand, which restrict renewable capacities despite infrequent occurrence. This work describes how time series of several renewable generation technologies together with demand can be applied to examine the opportunities and challenges offered by non-firm generation connections. It applies optimal power flow to extract maximum energy from available renewable resources while using curtailment of generation to maintain the network within thermal and voltage limits. By way of a case study of potential wind, wave and tidal current development in the Orkney Islands, Scotland, the analysis provides estimates for the degree of curtailment and consequent economic impact a renewable generator operating under non-firm connection may experience. The methods described provide a first-level analysis that could facilitate appraisal of non-firm connections at the planning stage by estimating the consequences of concurrent generation and demand as well as the frequency and duration of necessary curtailments. - Author(s): A. Helander ; H. Holttinen ; J. Paatero
- Source: IET Renewable Power Generation, Volume 4, Issue 1, p. 75 –84
- DOI: 10.1049/iet-rpg.2008.0093
- Type: Article
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A study on the imbalance costs or payments that wind power producers pay on the one hand and the cost incurred for the power system on the other hand is presented. Both the producer side and the system side will be examined with case data on prediction errors, system net imbalances and the balancing costs. The up-scaled forecast errors of wind power that result in imbalances have been combined with the system real net imbalance. Comparisons and discussion about the balancing costs of wind power depending on the wind penetration are provided. The results for Finland show that a two-price system for imbalances results in higher imbalance costs than a one-price system. At low wind power penetration levels, the difference in imbalance payments is high for one- and two-price system. When wind penetration increases, there is not so much difference in the different balance settlement rules used. According to the comparison between imbalance payments and system costs, the increase in system costs because of wind power is lower than imbalance payments for wind power producers when using either average prices for up- and down-regulation or the regulation prices that increase linearly with regulation demand. - Author(s): H.C. Chiang ; T.T. Ma ; Y.H. Cheng ; J.M. Chang ; W.N. Chang
- Source: IET Renewable Power Generation, Volume 4, Issue 1, p. 85 –99
- DOI: 10.1049/iet-rpg.2009.0033
- Type: Article
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A hybrid regenerative power system including photovoltaic (PV) and wind powers and combining the functions of the grid–tie system and uninterruptible power supply (UPS) for critical load applications is presented. The proposed system employs six-arm converter topology with three arms for the rectifier–inverter, one arm for battery charging/discharging and two arms for power conversion of the PV module and wind turbine generator. The operation modes include the grid–tie mode and the UPS mode depending on the grid status. A power balance control scheme is presented, which can reduce the grid power and utilise the regenerative power in the most effective way for fulfilling the two requirements of a three-stage charging of the battery and no interruption of the load. Also, the PV and wind powers can be utilised with priority in order to provide the flexibility for adapting to local circumstances. A single-phase 1.2 kW/110 V system is designed and implemented, and the effectiveness of the proposed system and control methodology are verified with some experimental results.
Modelling and control of a marine current turbine-driven doubly fed induction generator
Investigations into the performance of photovoltaics-based active filter configurations and their control schemes under uniform and non-uniform radiation conditions
Stochastic inequality constrained closed-loop model-based predictive control of MW-class wind generating system in the electric power supply
Improved SMS islanding detection method for grid-connected converters
Statistical voltage quality assessment method for grids with wind power generation
Analysis of demand response and wind integration in Germany's electricity market
Assessment of distribution network limits for non-firm connection of renewable generation
Impact of wind power on the power system imbalances in Finland
Design and implementation of a hybrid regenerative power system combining grid–tie and uninterruptible power supply functions
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