Performance of Grid-Connected PV System Based on SAPF for Power Quality Improvement

ABSTRACT:

This paper presents the design of a shunt Active Power Filter (SAPF) for grid-connected photovoltaic systems. The proposed system injects PV power into the grid, by feeding the SAPF; to eliminate harmonics currents and compensate reactive power produced by nonlinear loads. To inject the photovoltaic power to the grid we use a boost converter controlled by a Fuzzy logic (FLC) algorithm for maximum power point tracking (MPPT). The SAPF system is based on a two-level voltage source inverter (VSI); P-Q theory algorithm is used for references harmonic currents extraction. The overall system is designed and developed using MATLAB /Simulink software. Simulation results confirm the performance of the grid-connected photovoltaic system based on SAPF. For the MPPT controller, the results show that the proposed FLC algorithm is fast in finding the MPPT than conventional techniques used for MPPT like perturbed and observed (P&O). The simulated compensation system shows its effectiveness such as the sinusoidal form of the currents and the reactive power compensation. The proposed solution has achieved a low Total Harmonic Distortion (THD), demonstrating the efficiency of the presented method. Also, the results determine the performances of the proposed system and offer future perspectives of renewable energy for power quality improvement.

KEYWORDS:   

1.      SAPF, Harmonics

2.      MPPT

3.      Reactive power

4.      P-Q theory algorithm

5.      Power quality and THD

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 The present article presents an analysis and simulation of a three-phase SAPF fed by PV systems. An MPPT fuzzy logic controller is employed to feed the grid by the maximum allowable PV power. The proposed system has been simulated in MATLAB/SIMULINK software. This system is used to eliminate harmonics and to compensate reactive power generated by nonlinear loads. Performances of the shunt APF are related to the current references quality. This method is very important because it allows harmonic currents and reactive power compensation simultaneously. Simulation results show that the current obtained after filtering and the voltage waveforms are in phase. Also, the current THD is reduced from 33.34% to 2.87% which confirms the good filtering quality of harmonic currents and the perfect compensation of reactive power which improve the power quality.

REFERENCES:

[1] J. Lu, X. Xiao, J. Zhang, Y. Lv, and C. Yuan, "A Novel Constant Active-current Limit Coordinated Control Strategy Improving Voltage Sag Mitigation for Modular Multi-level Inverter-based Unified Power Quality Conditioner," Electric Power Components and Systems, vol. 44, pp. 578-588, 2016.

[2] R. Belaidi, A. Haddouche, and H. Guendouz, "Fuzzy logic controller based three-phase shunt active power filter for compensating harmonics and reactive power under unbalanced mains voltages," Energy Procedia, vol. 18, pp. 560-570, 2012.

[3] T.-J. Park, G.-Y. Jeong, and B.-H. Kwon, "Shunt active filter for reactive power compensation," International Journal o Electronics, vol. 88, pp. 1257-1269, 2001.

[4] S. K. Jain, P. Agarwal, and H. Gupta, "A Dedicated Microcontroller based Fuzzy Controlled Shunt Active Power Filter," Intelligent Automation & Soft Computing, vol. 11, pp. 33- 46, 2005.

[5] K. Srikanth, T. K. Mohan, and P. Vishnuvardhan, "Improvement of power quality for microgrid using fuzzy based UPQC controller," in Electrical, Electronics, Signals, Communication and Optimization (EESCO), 2015 International Conference on, 2015, pp. 1-6.

Off-board electric vehicle battery chargerusing PV array

 ABSTRACT:

During the recent decade, the automobile industry is booming with the evolution of electric vehicle (EV). Battery charging system plays a major role in the development of EVs. Charging of EV battery from the grid increases its load demand. This leads to propose a photovoltaic (PV) array-based off-board EV battery charging system in this study. Irrespective of solar irradiations, the EV battery is to be charged constantly which is achieved by employing a backup battery bank in addition to the PV array. Using the sepic converter and three-phase bidirectional DC–DC converter, the proposed system is capable of charging the EV battery during both sunshine hours and non-sunshine hours. During peak sunshine hours, the backup battery gets charged along with the EV battery and during non-sunshine hours, the backup battery supports the charging of EV battery. The proposed charging system is simulated using Simulink in the MATLAB software and an experimental prototype is fabricated and tested in the laboratory and the results are furnished in this study.

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 

 In this paper, an off-board EV battery charging system fed from PV array is proposed. This paper discusses the flexibility of the system to charge the EV battery constantly irrespective of the irradiation conditions. The system is designed and simulated in Simulink environment of the MATLAB software. The hardware prototype is fabricated and tested in laboratory for the three modes of operation of the proposed charging system separately and the results are furnished. In OPAL-RT Real time simulator OP4500, experimental investigation is carried out in RCP methodology and the dynamic response of the system is furnished both in simulation and experimental investigation. Correlation between the simulation and experimental results emphasise the effectiveness of the proposed charger.

REFERENCES:

[1] Santhosh, T.K., Govindaraju, C.: ‘Dual input dual output power converter with one-step-ahead control for hybrid electric vehicle applications’, IET Electr. Syst. Transp., 2017, 7, (3), pp. 190–200

[2] Shukla, A., Verma, K., Kumar, R.: ‘Voltage-dependent modelling of fast charging electric vehicle load considering battery characteristics’, IET Electr. Syst. Transp., 2018, 8, (4), pp. 221–230

[3] Wirasingha, S.G., Emadi, A.: ‘Pihef: plug-in hybrid electric factor’, IEEE Trans. Veh. Technol., 2011, 60, pp. 1279–1284

[4] Kirthiga, S., Jothi Swaroopan, N.M.: ‘Highly reliable inverter topology with a novel soft computing technique to eliminate leakage current in grid-connected transformerless photovoltaic systems’, Comput. Electr. Eng., 2018, 68, pp. 192–203

[5] Badawy, M.O., Sozer, Y.: ‘Power flow management of a grid tied PV-battery system for electric vehicles charging’, IEEE Trans. Ind. Appl., 2017, 53, pp. 1347–1357

Solar PV Charging Station for Electric Vehicles

ABSTRACT:

Of late, electric vehicles (EVs) have attracted much attention owing to their use of clean energy. Large progress in lithium-ion battery has propelled the development of EVs.However, the challenge is that growing number of EVs leads to huge demand in electric power, which will aggravate the power grid load. This leads to an exploration for alternative and clean sources of energy to charge EVs. This project implements solar energy system to erect a charging station for EV application. The charging station employs multi-port charging by providing a constant voltage DC bus. The charging controllers are operated based on the concept of power balance, and constant current/constant voltage charging. Performance of the charging system is validated with simulation and experimental results.

KEYWORDS:

1.      Electric Vehicles

2.       Solar Power

3.      Charging station

4.      DC-DC converters

5.      MPPT

6.      CCCV battery Charging

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 Utilization of Optimization techniques in the use of renewable resources like Solar, wind, biofuel will enhance the opportunities of Electric Vehicles. Extension of the system with fast response storage scheme can be implemented for Fast charging stations. Intelligent Controllers or Machine Learning Techniques can be implemented to avoid excess loading of EV Charging stations on the grid. Hybrid charging stations incorporating more than one renewable source or a backup diesel generator will certainly increase the stability and reliability of the system.

 REFERENCES:

 [1] T. S. Biya and M. R. Sindhu, "Design and Power Management of Solar Powered Electric Vehicle Charging Station with Energy Storage System," Proceedings of 3rd International conference on Electronics, Communication and Aerospace Technology (ICECA), Coimbatore, India, 2019.

[2] K. S. Vikas, B. Raviteja Reddy, S. G. Abijith and M. R. Sindhu, "Controller for Charging Electric Vehicles at Workplaces using Solar Energy," Proceedings of International Conference on Communication and Signal Processing (ICCSP), Chennai, India, 2019.

[3] B. Revathi, A. Ramesh, S. Sivanandhan, T. B. Isha, V. Prakash and S. G., "Solar Charger for Electric Vehicles" ,Proceedings of International Conference on Emerging Trends and Innovations In Engineering And Technological Research (ICETIETR), Ernakulam, 2018, pp. 1-4.

[4] D. Oulad-abbou, S. Doubabi and A. Rachid, "Solar charging station for electric vehicles," Proceedings of 3rd International Renewable and Sustainable Energy Conference (IRSEC), Marrakech, 2015.

[5] B. Singh, A. Verma, A. Chandra and K. Al-Haddad, "Implementation of Solar PV-Battery and Diesel Generator Based Electric Vehicle Charging Station," Proceedings of IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES),2018, Chennai, India.

Electrical design of a photovoltaic-grid system for electric vehicles charging station

ABSTRACT:

This work presents a smart method for a photovoltaic grid system for electric vehicles charging station, however, it describes the flow power through a smooth algorithm using Matlab/Simulink environment. The consumption of electric vehicle battery is considered as a daily load for the charging station, indeed, it is highly recommended to predict the periodic power use in the charging station. However, the storage system is ensured through a lithium ion battery, which provides a wider operating temperature and others convenient characteristics. Additionally, the contribution of the electrical grid is also combined in this architecture as a back-up plan for mutual benefits when the photovoltaic power is unable to secure the station needs, on the one hand and on the other hand, when the battery of the charging station is fully charged and the photovoltaic system is able to inject an extra energy in the grid.

KEYWORDS:

1.      Photovoltaic-Grid System (PVGS)

2.      Electric vehicle (EV)

3.      Charging Station (CS)

4.      dc-dc Converters

5.      Maximum Power Point Tracking (MPPT)

6.      Perturb and Observe (P&O)

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

 This paper presents an intelligent process to feed a lithium ion battery in an EVCS architecture. In this regard, the effectiveness of charging the battery through numerous modes of operation has been validated by simulation results, indeed, it is interesting how fast the battery is charging under higher recharge rate. In fact, this work is inspired from a study case of a project with full specifications, for instance, the meteorological data for the PV panels design and the daily need of energy for the EVB to resize the rated capacity of the BSB. However, the contribution of the grid power remains primordial in the structure nonetheless there are some complexity issues related to the used power flow algorithms in the controller unit, and how it effects on the grid, positively and negatively both.

REFERENCES:

 

[1] I. Rahman, P. M. Vasant, B. S. M. Singh, M. Abdullah-Al-Wadud, and N. Adnan, “Review of recent trends in optimization techniques for plug-in hybrid, and electric vehicle charging infrastructures,” Renew. Sustain.Energy Rev., vol. 58, pp. 1039–1047, 2016.

[2] A. R. Bhatti, Z. Salam, M. J. B. A. Aziz, K. P. Yee, and R. H. Ashique, “Electric vehicles charging using photovoltaic: Status and technological review,” Renew. Sustain. Energy Rev., vol. 54, pp. 34–47, 2016.

[3] M. Van Der Kam and W. Van Sark, “Smart charging of electric vehicles with photovoltaic power and vehicle-to-grid technology in a microgrid ; a case study,” Appl. Energy, vol. 152, pp. 20–30, 2015.

[4] J. P. Torreglosa, P. García-Triviño, L. M. Fernández-Ramirez, and F. Jurado, “Decentralized energy management strategy based on predictive controllers for a medium voltage direct current photovoltaic electric vehicle charging station,” Energy Convers. Manag., vol. 108, pp. 1–13, 2016.

[5] P. Goli and W. Shireen, “PV powered smart charging station for PHEVs,” Renew. Energy, vol. 66, pp. 280–287, 2014.

Electric vehicles charging using photovoltaic: Status and technological review

ABSTRACT:

The integration of solar photovoltaic(PV) into the electric vehicle(EV) charging system has been on the rise due to several factors, namely continuous reduction in the price of PV modules, rapid growth in EV and concerns over the effects of green house gases. Despite the numerous review articles published on EV charging using the utility(grid) electrical supply, so far, none has given sufficient emphasis on the PV charger. With the growing interest in this subject, this review paper summarizes and update all the related aspects on PV–EV charging, which include the power converter topologies, charging mechanisms and control for both PV–grid and PV-standalone /hybrid systems. In addition, the future outlook and the challenges that face this technology are highlighted. It is envisaged that the information gathered in this paper will be a valuable one-stop source of information for researchers working in this topic.

KEYWORDS:

1.      Photovoltaic(PV)system

2.      Electric vehicle(EV)charging system

3.      State of charge(SOC)

4.      Maximum power point tracking(MPPT)

5.      MPPT dc–dc converter

6.       Bi-directional Inverter

7.       Bi-directional dc–dc charger

8.       Control algorithm

9.      EV charging algorithm

10.  Prediction models

11.  Optimization techniques

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 This paper reviews the PV–grid and PV-standalone EV charging methods proposed in various papers .It is noted ,among the two structures, the PV–grid is more popular due to its flexibility and its interruption-less operation . Also in this paper, the main hardware components, i.e. the dc–dc converter with MPPT ,bi-directional inverter and bi-directional dc charger are evaluated. Due to the rapid development, it is not possible to cover all aspects related to the EV charging infra structure in a single work. Other topics—for example , the economic and environmental impacts of PV and grid powered EV charging are addressed elsewhere [9,86]. Further- more, issues such as the stability, reliability and PV–EV interactions require detailed analysis that may not be feasible for inclusion. For the energy management systems, researchers are highly relaying optimization algorithms and soft computing. However ,it seems that the heuristic rule based charging strategies is a good solution for quick and accurate energy management as already been adopted by [92]. But, there is still a need to devise more accurate techniques for better utilization of available PV energy.

REFERENCES:

 [1]Galus MD, Anders son G. Demand management of grid connected plug-in hybrid electric vehicles(PHEV).In: Proceedings of IEEE energy 2030 con- ference,ENERGY;2008.p.1–8.

[2]Kelman C. Supporting increasing renewable energy penetration in Australia- the potential contribution of electric vehicles. In: Proceedings of 20th Australasi an universities power engineering conference (AUPEC);2010.p.1–6. [3] Barker PP, Bing JM. Advances in solar photovoltaic technology :an applications perspective .In :Proceedings of power engineering society general meeting, vol.2;2005.p.1955–60.

[4] KadarP, VargaA. PhotoVoltaic EV chargestation. In: Proceedings ofIEEE11th international symposium on applied machine intelligence and informatics (SAMI);2013.p.57–60.

[5] Branker K, Pathak MJM ,Pearce JM. Are view of solar photovoltaic levelized cost of electricity.  Renew Sustain Energy Rev2011;15:4470–82.

Electric Vehicle Charging System with PV Grid- Connected Configuration

ABSTRACT:

This paper presents an experimental control strategy of electric vehicle charging system composed of photovoltaic (PV) array, converters, power grid emulator and programmable DC electronic load that represents Li-ion battery emulator. The designed system can supply the battery at the same time as PV energy production. The applied control strategy aims to extract maximum power from PV array and manages the energy flow through the battery with respect to its state of charge and taking into account the constraints of the public grid. The experimental results, obtained with a dSPACE 1103 controller board, show that the system responds within certain limits and confirm the relevance of such system for electric vehicle charging.

 KEYWORDS:

1.      Renewable energy integration

2.      Photovoltaic

3.      Battery electric vehicles

4.      Public grid

5.      Control charging system

 SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

 Smart grid with renewable electricity integrated concerns both the utility companies as well as the end-users. In the next ten years, the smart grid could concern the residential level with house power “routers”, whose goal is to intelligently manage and supply every home appliance by minimizing and redirecting the overall consumption. The prime goal of utility companies could be the real time demand management in order to adjust their electricity generation, for end user it could be the real time control of energy use, like EV charging system.

            An experimental EV charging with PV grid-connected system control strategy was presented. The system control strategy aims to extract maximum power from PV array and manages the energy flow through the BEV, with respect to its SOC. The experimental results are obtained with a numerical modelling implemented under MATLAB-Simulink and a dSPACE 1103 controller board. In this work, a simple and quick to implement control was done. This control was not necessarily developed to improve global energy efficiency or life cycle of the BEV system. For this first approach, the goal was to verify the feasibility of the proposed system control. The results show that the system can supply a BEV at the same time as PV energy production and responds within certain limits of the PV power and public grid availability. Obtained test results indicate that the proposed control can successfully be used for buildings and car parking equipped with PV power plant.

            The further work is the modelling of the behaviour of EV charging with PV grid-connected system as an operating subsystem under the supervision device as a control-command subsystem. The chosen approach will take into account the uncertainties on PV power production, public grid availability and BEV request, in order to achieve more efficient power transfer with a minimized public grid impact.

 REFERENCES:

 [1] S. D. Jenkins, J. R. Rossmaier, and M. Ferdowsi, "Utilization and effect of plug-in hybrid electric vehicles in the United States power grid", in: Proc. IEEE Vehicle Power and Propulsion Conference, VPPC 2008.

[2] EPRI, “Environmental Assessment of Plug-In Hybrid Electric Vehicles; Volume 1: Nationwide Greenhouse Gas Emissions”, Final Report, July 2007.

[3] V. Marano and G. Rizzoni, “Energy and Economic Evaluation of PHEVs and their Interaction with Renewable Energy Sources and the Power Grid”, in: Proc. IEEE International Conference on Vehicular Electronics and Safety, 2008.

[4] Y. Gurkaynak and A. Khaligh, “Control and Power Management of a Grid Connected Residential Photovoltaic System with Plug-in Hybrid Electric Vehicle (PHEV) Load”, in Proc. IEEE Applied Power Electronics Conference and Exposition, APEC 2009.

[5] X. Li, L. A. C. Lopes, and S. S. Williamson, “On the suitability of plugin hybrid electric vehicle (PHEV) charging infrastructures based on wind and solar energy”, in: Proc. IEEE Power & Energy Society General Meeting, PES 2009

Analysis and Design of a Standalone Electric Vehicle Charging Station Supplied by Photovoltaic Energy

ABSTRACT:

Nowadays, there is a great development in electric vehicle production and utilization. It has no pollution, high efficiency, low noise, and low maintenance. However, the charging stations, required to charge the electric vehicle batteries, impose high energy demand on the utility grid. One way to overcome the stress on the grid is the utilization of renewable energy sources such as

photovoltaic energy. The utilization of standalone charging stations represents good support to the utility grid. Nevertheless, the electrical design of these systems has different techniques and is sometimes complex. This paper introduces a new simple analysis and design of a standalone charging station powered by photovoltaic energy. Simple closed-form design equations are derived, for all the system components. Case-study design calculations are presented for the proposed charging station. Then, the system is modeled and simulated using Matlab/Simulink platform. Furthermore, an experimental setup is built to verify the system physically. The experimental and simulation results of the proposed system are matched with the design calculations. The results show that the charging process of the electric vehicle battery is precisely steady for all the PV insolation disturbances. In addition, the charging/discharging of the energy storage battery responds perfectly to store and compensate for PV energy variations.

KEYWORDS:

1.      Electric vehicle

2.      Charging station;

3.      Photovoltaic

4.      Maximum power point tracking

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

 An isolated EV charging station based on a PV energy source is proposed. The system consists of PV panel, boost converter, ESS batteries, two DC/DC charging converters, and an EV battery. The control system consists of three controllers named the MPPT, the EV charger, and the storage converter controller. PI voltage and current controllers are adapted to control charging/discharging of the ESS system and the EV charger as well. The system is simulated and implemented physically. A single-chip PIC18F4550 microcontroller is utilized to realize the system controllers. New simple energy and power analyses procedure has been introduced. Hence, closed-form equations have been derived to help in the design phase. Complete design of the system, including the ESS size, the PV rating, and the filter components, has been proposed. Simulation and experimental results are very close and verify the effectiveness of the proposed system. At different insolation levels, the results show that the charging process of the EV battery is steady without any disturbance. However, the charging/discharging of the ESS battery responds perfectly to store and compensate for PV energy variations. The current and voltage controllers of the converters give good responses and track their references well. In addition, the MPPT controller tracks the peak conditions of the PV precisely.

 REFERENCES:

1. Irle, R. Global EV Sales for the 1st Half of 2019. EV Volumes. 2019. Available online: http://www.ev-volumes.com/country/ total-world-plug-in-vehicle-volumes/ (accessed on 20 November 2019).

2. Sun, X.; Li, Z.;Wang, X.; Li, C. Technology Development of Electric Vehicles: A Review. Energies 2020, 13, 90. [CrossRef]

3. Luc, Vehicles & Charging Tips. Fastned. 2019. Available online: https://support.fastned.nl/hc/en-gb/sections/115000180588 -Cars-charging-tips- (accessed on 30 March 2019).

4. Richard, L.; Petit, M. Fast charging station with a battery storage system for EV: Optimal integration into the grid. In Proceedings of the 2018 IEEE Power & Energy Society General Meeting (PESGM), Portland, OR, USA, 5–10 August 2018; pp. 1–5.

5. Chakraborty, S.; Vu, H.-N.; Hasan, M.M.; Tran, D.-D.; Baghdadi, M.E.; Hegazy, O. DC-DC Converter Topologies for Electric Vehicles, Plug-in Hybrid Electric Vehicles and Fast Charging Stations: State of the Art and Future Trends. Energies 2019, 12, 1569. [CrossRef]

Generation of Higher Number of Voltage Levels by Stacking Inverters of Lower Multilevel Structures with Low Voltage Devices for Drives

ABSTRACT

This paper proposes a new method of generating higher number of levels in the voltage waveform by stacking multilevel converters with lower voltage space vector structures. An important feature of this stacked structure is the use of low voltage devices while attaining higher number of levels. This will find extensive applications in electric vehicles since direct battery drive is possible. The voltages of all the capacitors in the structure can be controlled within a switching cycle using the switching state redundancies (pole voltage redundancies). This helps in reducing the capacitor size. Also, the capacitor voltages can be balanced irrespective of modulation index and load power factor. To verify the concept experimentally, a 9-level inverter is developed by stacking two 5-level inverters and an induction motor is run using V/f control scheme. Both steady state and transient results are presented.

KEYWORDS

1.      Induction motor drive

2.      PWM

3.      Multilevel inverter

4.      Topology

5.      CHB

6.      Flying capacitor

7.      Low voltage devices

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION

In this paper, a new method of generating higher number of voltage levels by stacking multilevel converters having lower space vector structures is presented. Here each of the stacked inverter is having only one DC supply. The proposed stacked multilevel inverter has a modular structure which is realized by stacking the FC and cascading it with series connected capacitor fed H-bridges. Since the voltage across the H-bridge switches are low, the switching loss can be further reduced. Also the H-bridges can be bypassed if it fails. Thus using this system has a improved reliable operation. Also when one of the FC fails, inverter can still be operated with reduced voltage and power levels. The concept of stacking can be generalized to obtain higher voltage levels. As the number of levels increases, blocking voltages of switches reduces and the proposed structure can be fed from low voltage battery cells. Also, higher number of voltage levels imply lower switching frequency and therefore higher efficiency, which makes it suitable for application in electric vehicles. Hysteresis based  capacitor voltage balancing algorithm is used to maintain the capacitor voltages irrespective of modulation index and load power factor. Detailed experimental results, using a stacked 9- level inverter, showing the steady state operation at different frequencies and the transient results, ensure that the proposed structure will be a viable scheme for high power applications with improved reliability.

REFERENCES

[1] A. Nabae, I. Takahashi, and H. Akagi, “A new neutral-point-clamped PWM inverter,” IEEE Trans. Ind. Appl., vol. IA-17, no. 5, pp. 518–523, Sept 1981.

[2] S. Kouro, M. Malinowski, K. Gopakumar, J. Pou, L. Franquelo, B. Wu, J. Rodriguez, M. Perez, and J. Leon, “Recent advances and industrial applications of multilevel converters,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553–2580, Aug 2010.

[3] J. Rodriguez, S. Bernet, P. Steimer, and I. Lizama, “A survey on neutralpoint- clamped inverters,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2219–2230, July 2010.

[4] P. Barbosa, P. Steimer, J. Steinke, L. Meysenc, M. Winkelnkemper, and N. Celanovic, “Active neutral-point-clamped multilevel converters,” in Proc. 2005 IEEE Power Electron. Special. Conf., June 2005, pp. 2296– 2301.

[5] T. Bruckner, S. Bernet, and H. Guldner, “The active npc converter and its loss-balancing control,” IEEE Trans. Ind. Electron., vol. 52, no. 3, pp. 855–868, June 2005.