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Maximum power point tracking.......saq

The electric power supplied by a photovoltaic power generation system depends on the solar radiation and temperature. Designing efficient PV systems heavily emphasizes to track the maximum power operating point.
This work develops a three-point weight comparison method that avoids the oscillation problem of the perturbation and observation algorithm which is often employed to track the maximum power point. Furthermore, a low cost control unit is developed, based on a single chip to adjust the output voltage of the solar cell array.

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Maximum power point tracking.......saq

  4. 4. PV modules still have relatively low conversion efficiency; therefore, controlling maximum power point tracking (MPPT) for the solar array is essential in a PV system. The amount of power generated by a PV depends on the operating voltage of the array. A PV’s maximum power point (MPP) varies with solar insulation and temperature.
  5. 5.  MPPT or Maximum Power Point Tracking is algorithm that included in charge controllers used for extracting maximum available power from PV module under certain conditions. The voltage at which PV module can produce maximum power is called ‘maximum power point’ (or peak power voltage). WHAT IS MPPT?
  6. 6. Equivalent circuit of solar PV array. MATHEMATICAL MODEL:
  7. 7. I= Isc – Io{exp[ q(V + RsI)/(nkTk) ]- 1} – (V+RsI)/Rsh ………………..(1) Where , Isc = Id + I The above equation is used in computer simulations to obtain the o/p characteristics of a solar cell.
  8. 8. Output characteristics of a solar cell are non- linear and are crucially influenced by a solar radiation, temperature and load condition. V-I and V-P characteristics of a solar cell:
  9. 9.  The major principle of MPPT is to extract the maximum available power from PV module by making them operate at the most efficient voltage (maximum power point).  MPPT checks output of PV module, compares it to battery voltage then fixes what is the best power that PV module can produce to charge the battery and converts it to the best voltage to get maximum current into battery. How MPPT works? MPPT is most effective under these conditions: • Cold weather, cloudy or hazy days: Normally, PV module works better at cold temperatures and MPPT is utilized to extract maximum power available from them. • When battery is deeply discharged: MPPT can extract more current and charge the battery if the state of charge in the battery is lowers.
  10. 10.  A MPPT solar charge controller is the charge controller embedded with MPPT algorithm to maximize the amount of current going into the battery from PV module.  MPPT is DC to DC converter which operates by taking DC input from PV module, changing it to AC and converting it back to a different DC voltage and current to exactly match the PV module to the battery.  Examples of DC to DC converter are • Boost converter • Buck converter  MPPT algorithm can be applied to both of them depending on system design. MPPT solar charge controller:
  11. 11. MPPT solar charge controllers are useful for off-grid solar power systems such as stand- alone solar power system, solar home system and solar water pump system, etc. MPPT solar charge controllers
  12. 12. Generalconfigurationofthe MPPT solar charge controller OOOOOOOOOOOOOOOO OOOOOOOOOOOOOO PV INPUT DC Load INVERTER AC Load
  13. 13. MPPT TECHNIQUES:  Fractional Open-CircuitVoltage  Fractional Short-Circuit Current  Perturb and Observe  Incremental Conductance
  14. 14. Fractional Open-Circuit Voltage:  VMPP ≈ k1VOC ……………….(2) Factor k1 has been reported to be between 0.71 and 0.78. Implementation of this method is simple. Its tracking efficiency is relatively low.
  15. 15. Fractional Short-Circuit Current: IMPP ≈ k2 ISC …………………(3)  k2 is not constant. It is found to be between 0.78 and 0.92.  The accuracy of the method and tracking efficiency depends on the accuracy of K2 and periodic measurement of short circuit current.
  16. 16. Perturb and Observe:  The concept behind the P&O method is to modify the operating voltage or current of the PV panel until you obtain maximum power from it.  The tracker operates by periodically incrementing or decrementing the solar array voltage.  If increasing the voltage to a panel increases the power output of the panel, the system continues increasing the operating voltage until the power output begins to decrease.
  17. 17. Flowchart for P&O algorithm
  18. 18. Incremental Conductance:  Incremental conductance considers the fact that the slope of the power-voltage curve is zero at the maximum power point, positive at the left of the MPP, and negative at the right of the MPP.  ΔI/ΔV = - I/V , at MPP  ΔI/ΔV > - I/V , left of MPP  ΔI/ΔV < - I/V , right of MPP
  19. 19. Flowchart of incremental conductance
  20. 20. SYSTEM MODELING:  The PV power system is modeled using Power System Blockset under Matlab.
  21. 21. Solar Panel
  22. 22. Digital Controller  The microcontroller provides the control in our system.  The choice of microcontroller for the system dictates much of the cost, performance, and flexibility of the entire system.
  23. 23. Circuits of the boost converter DC-DC Converter
  24. 24. ADVANTAGES:  MPPT method can extract maximum available power from the PV module.  This can increase the tracking efficiency.  If your energy use is greatest in the winter (typical in most homes) and you have cold winter weather, then you can gain a substantial boost in energy when you need it the most!
  25. 25. CONCLUSION: A PV systems are suitable for residential and/or industrial applications as it provides a regulated AC output voltage that may also track the input mains utility voltage in phase and amplitude at hundreds to thousands of watts. Thus MPPT system can be deployed to get maximum amount of power to take advantage of solar energy.
  26. 26. REFERENCES:  N. Femia, et. Al. “Optimization of Perturb and observe Maximum Power Point tracking Method,” IEEETrans. Power Electron., Vol. 20, pp. 963-973, July 2005.  E. Koutroulis; et. al , “ Development of a Microcontroller-based Photovoltaic maximum power tracking control system”, IEEETrans.On power Electron.,Vol. 16, No. 1, pp. 46-54, 2001.  J .A.Jiang et. Al. , “Maximum PowerTracking for Photovoltaic Power Systems,”Tamkang Journal of Science and Engineering,Vol. 8, No. 2, pp. 147-153, 2005.  S. Jain andV. Agarwal, “A New Algorithm for RapidTracking of Approximate Maximum Power Point in Photovoltaic Systems,” IEEE Power Electronic Letter., Vol. 2, pp. 16-19, Mar. 2004.  W. Xiao and W. G. Dunford,“A modified adaptive hill climbing MPPT method for photovoltaic power systems,” 35th. Annual IEEE Power Electron. Specialists Conf. , pp. 1957-1963, 2004.  Y. Kuo, et. Al., “Maximum power point tracking controller for photovoltaic energy conversion system,” IEEETrans. Ind. Electron.,Vol. 48, pp. 594-601, 2001.
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