Design, Experimentation, And Analysis Of Photovoltaic And Wind Energy Systems

Influence of Mechanical Speed on Generator Voltage

The increase in population and the pollution is the biggest issue that world is facing, the use of conventional fuels is the key problem of pollution around the world. Majority of countries ae moving to the non pollutant energy sources. The use of solar is on the top, while the use of wind is also increasing day by day. The sun is the main foundation of energy for the photovoltaic which converts heat energy into electricity. Wind is use to drive the rotor of the wind turbine which converts kinetic energy to electrical energy. Both the sources are subjected to uncertainties due to variation in atmospheric parameters. The actual output from PV and wind is dependent on the certain conditions, that is known as capacity factor. The capacity factor of WT is around 20-40% while in case of PV its around 12-15%. However it always dependent on the location, wind speed, solar irradiation and temperature of that particular location [2]. The solar power available during day time and peak during afternoon periods while the wind power is available most of the time specially during night due to high wind velocity [7]. tIntpractice,tthis impliest thet  possibility toftforming tathybrid tpowertsystemt totmediatetthetpowertimbalances,  withtthet PVtcells  tprovidingtelectricitytduring the tday tand  twindtprovidingt electricitytat night in wintertandtsummertseasons.

Efficiency of inverter is defined as the how much power from DC is converted into the AC power losttastheat,tandtalsotsometstand-bytpowertistconsumedtfor keeping the inverter in poweredtmode.tThetgeneraltefficiency formula is

The rotor current of DFIG is controllable by the dual stage converter stage, still any change in rotor current affect the stator voltage as the current in the rotor winding changes the flux of rotor and the induced voltage on stator terminal also get affected. To smoothly control the stator voltage of the DFIG the rotor fed control from converter must be implemented.

As the frequency of rotor varies the stator frequency also changes, two factor are important for stator frequency one is the mechanical speed of rotor and second is rotor frequency. Mechanical speed can be controlled by gear box arrangement still perfect control is not possible while the rotor frequency can be controllable from the converter stage. Any change in rotor frequency will leads to change in stator frequency.

The rotor current of DFIG is controllable by the dual stage converter stage, still any change in rotor current affect the stator voltage as the current in the rotor winding changes the flux of rotor and the induced voltage on stator terminal also get affected. To smoothly control the stator voltage of the DFIG the rotor fed control from converter must be implemented.

Influence of Variable Rotor Frequency on Stator Frequency

The full report is attached below designed using PVsyst utilized in evolution mode.

PVSYST V5.74		15/12/18	Page 1/3
	Grid-Connected System: Simulation parameters
Project  : Geographical Site                                                 Melbourne                                          Country    Australia
Situation	Latitude    37.5°S                             Longitude    144.6°E
Time defined	as                                           Legal Time    Time zone UT+10              Altitude    38 m Albedo     0.20
Meteo data  :	Melbourne, Synthetic Hourly data
Simulation variant  :          New simulation variant Simulation date    15/12/18 11h11
Simulation parameters
Tracking plane, two axis                               Minimum Tilt    10°                            Maximum Tilt    80° Rotation Limitations                         Minimum Azimuth    -80°                   Maximum Azimuth    80°
Horizon	Free Horizon
Near Shadings	No Shadings
PV Array Characteristics PV module                                          Si-poly            Model    VSPS-310-72-A
	Manufacturer    Voltec Solar
Number of PV modules                                           In series   1 modules                       In parallel    1 strings Total number of PV modules                           Nb. modules   1                          Unit Nom. Power    310 Wp Array global power                                        Nominal (STC)    310 Wp             At operating cond.    282 Wp (50°C) Array operating characteristics (50°C)                       U mpp    34 V                                       I mpp    8.3 A Total area                                                          Module area    2.0 m²                               Cell area    1.8 m²
Inverter	Model    YC500-SAA/EU
	Manufacturer    APS
Characteristics	Operating Voltage    22-45 V               Unit Nom. Power    0.50 kW AC
PV Array loss factors Thermal Loss factor                                              Uc (const)    20.0 W/m²K                     Uv (wind)    0.0 W/m²K /	m/s
=> Nominal Oper. Coll. Temp. (G=800 W/m²,  Tamb=20°C,  Wind=1 m/s.)                   NOCT    56 °C
Wiring Ohmic Loss                                    Global array res.    70 mOhm                  Loss Fraction    1.5 % at STC Module Quality Loss                                                                                                    Loss Fraction    0.1 % Module Mismatch Losses                                                                                            Loss Fraction    2.0 % at MPP
Incidence effect, ASHRAE parametrization                IAM =    1 – bo (1/cos i – 1)     bo Parameter    0.05
User’s needs :	Unlimited load (grid)

PVSYST V5.74		15/12/18	Page 3/3
Main system parameters                                System type    Grid-Connected PV Field Orientation                                 Tracking two axis PV modules                                                                 Model    VSPS-310-72-A                    Pnom    310 Wp PV Array                                                       Nb. of modules   1                                    Pnom total    310 Wp Inverter                                                                        Model    YC500-SAA/EU                    Pnom    500 W ac User’s needs                                         Unlimited load (grid)
Loss diagram over the whole year 1532 kWh/m²                                                    Horizontal global irradiation +41.8% Global incident in coll. plan -1.6%   IAM factor on global 2138 kWh/m² * 2 m² coll.                                  Effective irradiance on collector                           PV conversion 669 kWh                                              Array nominal energy (at STC effic.) -3.2%    PV loss due to irradiance level -8.2%      PV loss due to temperature -0.1%            Module quality loss -2.2%            Module array mismatch loss -1.2%             Ohmic wiring loss 575 kWh                                                   Array virtual energy at MPP -5.5%             Inverter Loss during operation (efficiency) 0.0%                  Inverter Loss over nominal inv. power -0.0%                 Inverter Loss due to power threshold 0.0%                  Inverter Loss over nominal inv. voltage 0.0%                  Inverter Loss due to voltage threshold 543 kWh                                                    Available Energy at Inverter Output 543 kWh                                                    Energy injected into grid

References

[1] G. Boyle, “Renewable energy,” Renewable Energy, by Edited by Godfrey Boyle, pp. 456. Oxford University Press, May 2004. ISBN-10: 0199261784. ISBN-13: 9780199261789, p. 456, 2004.

[2] O. Hafez and K. Bhattacharya, “Optimal planning and design of a renewable energy based supply system for microgrids,” Renewable Energy, vol. 45, pp. 7-15, 2012.

[3] E. J. Coster, J. M. Myrzik, B. Kruimer, and W. L. Kling, “Integration issues of distributed generation in distribution grids,” Proceedings of the IEEE, vol. 99, no. 1, pp. 28-39, 2011.

[4] A. S. Anees, “Grid integration of renewable energy sources: Challenges, issues and possible solutions,” in Power Electronics (IICPE), 2012 IEEE 5th India International Conference on, 2012, pp. 1-6: IEEE.

[5] L. Saw, Y. Ye, and A. Tay, “Electro-thermal analysis and integration issues of lithium ion battery for electric vehicles,” Applied energy, vol. 131, pp. 97-107, 2014.

[6] P. Siano, “Assessing the impact of incentive regulation for innovation on RES integration,” IEEE Transactions on Power Systems, vol. 29, no. 5, pp. 2499-2508, 2014.

[7] H. H. Fong, “Integration of herbal medicine into modern medical practices: issues and prospects,” Integrative cancer therapies, vol. 1, no. 3, pp. 287-293, 2002.

[8] T. Esram and P. L. Chapman, “Comparison of photovoltaic array maximum power point tracking techniques,” IEEE Transactions on energy conversion, vol. 22, no. 2, pp. 439-449, 2007.

[9] W. Xiao, N. Ozog, and W. G. Dunford, “Topology study of photovoltaic interface for maximum power point tracking,” IEEE transactions on Industrial Electronics, vol. 54, no. 3, pp. 1696-1704, 2007.

[10] K. Kobayashi, I. Takano, and Y. Sawada, “A study on a two stage maximum power point tracking control of a photovoltaic system under partially shaded insolation conditions,” in Power Engineering Society General Meeting, 2003, IEEE, 2003, vol. 4, pp. 2612-2617: IEEE.

[11] C. R. Sullivan and M. J. Powers, “A high-efficiency maximum power point tracker for photovoltaic arrays in a solar-powered race vehicle,” in Power Electronics Specialists Conference, 1993. PESC’93 Record., 24th Annual IEEE, 1993, pp. 574-580: IEEE.

[12] S. Silvestre and A. Chouder, “Effects of shadowing on photovoltaic module performance,” Progress in Photovoltaics: Research and applications, vol. 16, no. 2, pp. 141-149, 2008.

[13] G. Notton, V. Lazarov, and L. Stoyanov, “Optimal sizing of a grid-connected PV system for various PV module technologies and inclinations, inverter efficiency characteristics and locations,” Renewable Energy, vol. 35, no. 2, pp. 541-554, 2010.

[14] G. K. Andersen, C. Klumpner, S. B. Kjaer, and F. Blaabjerg, “A new green power inverter for fuel cells,” in Power Electronics Specialists Conference, 2002. pesc 02. 2002 IEEE 33rd Annual, 2002, vol. 2, pp. 727-733: IEEE.

[15] M. Kayikci and J. V. Milanovic, “Reactive power control strategies for DFIG-based plants,” IEEE transactions on energy conversion, vol. 22, no. 2, pp. 389-396, 2007.

[16] F. M. Hughes, O. Anaya-Lara, N. Jenkins, and G. Strbac, “A power system stabilizer for DFIG-based wind generation,” IEEE Transactions on Power Systems, vol. 21, no. 2, pp. 763-772, 2006.

[17] Y. Zhou, P. Bauer, J. A. Ferreira, and J. Pierik, “Operation of grid-connected DFIG under unbalanced grid voltage condition,” IEEE Transactions on Energy Conversion, vol. 24, no. 1, pp. 240-246, 2009.

[18] J. Ekanayake, L. Holdsworth, and N. Jenkins, “Comparison of 5th order and 3rd order machine models for doubly fed induction generator (DFIG) wind turbines,” Electric Power Systems Research, vol. 67, no. 3, pp. 207-215, 2003.

[19] L. Xu and P. Cartwright, “Direct active and reactive power control of DFIG for wind energy generation,” IEEE Transactions on energy conversion, vol. 21, no. 3, pp. 750-758, 2006.

[20] S. Xiao, G. Yang, H. Zhou, and H. Geng, “An LVRT control strategy based on flux linkage tracking for DFIG-based WECS,” IEEE Transactions on Industrial Electronics, vol. 60, no. 7, pp. 2820-2832, 2013.