Presented by…

MD SAQUIB MAQSOOD

REGD NO. 0901292238ELECTRICAL & ELECTRONICS ENGINEERING

MAXIMUM POWER POINTTRACKING………..

MAXIMUM POWER POINT TRACKING FOR PHOTOVOLTAIC SYSTEM

INTRODUCTION

MATHEMATICAL MODEL

WHAT IS MPPT

HOW IT WORKS

MPPT TECHNIQUES

SYSTEM MODELING

ADVANTAGES

CONCLUSION

PV modules still have relatively low conversionefficiency; therefore, controlling maximumpower point tracking (MPPT) for the solar arrayis essential in a PV system. The amount ofpower generated by a PV depends on theoperating voltage of the array. A PV’s maximumpower point (MPP) varies with solar insulationand temperature.

MPPT or Maximum Power PointTracking is algorithm that included incharge controllers used for extractingmaximum available power from PVmodule under certain conditions. Thevoltage at which PV module canproduce maximum power is called‘maximum power point’ (or peak powervoltage).

WHAT IS MPPT?

Equivalent circuit of solar PV array.

MATHEMATICAL MODEL:

I= Isc – Io{exp[ q(V + RsI)/(nkTk) ]- 1} – (V+RsI)/Rsh

………………..(1)

Where , Isc = Id + I

The above equation is used in computersimulations to obtain the o/p characteristics of asolar cell.

Output characteristics of a solar cell are non- linear and arecrucially influenced by a solar radiation, temperature and loadcondition.

V-I and V-P characteristics of a solar cell:

The major principle of MPPT is to extract the maximum availablepower from PV module by making them operate at the most efficientvoltage (maximum power point).

MPPT checks output of PV module, compares it to battery voltagethen fixes what is the best power that PV module can produce tocharge the battery and converts it to the best voltage to getmaximum 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 fromthem.

•When battery is deeply discharged: MPPT can extract more current andcharge the battery if the state of charge in the battery is lowers.

A MPPT solar charge controller is the charge controllerembedded with MPPT algorithm to maximize the amountof current going into the battery from PV module.

MPPT is DC to DC converter which operates by taking DCinput from PV module, changing it to AC and converting itback to a different DC voltage and current to exactlymatch 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 themdepending on system design.

MPPT solar charge controller:

MPPT solar chargecontrollers are useful foroff-grid solar powersystems such as stand-alone solar power system,solar home system andsolar water pump system,

etc.

MPPT solar charge controllers

General configuration of the MPPT solar charge controller

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PV INPUTDC Load

INVERTER AC Load

MPPT TECHNIQUES:

Fractional Open-Circuit Voltage

Fractional Short-Circuit Current

Perturb and Observe

Incremental Conductance

Fractional Open-Circuit Voltage:

VMPP ≈ k1 VOC ……………….(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.

Fractional Short-Circuit Current:

IMPP ≈ k2 ISC …………………(3)

k2 is not constant. It is found to be between 0.78and 0.92.

The accuracy of the method and tracking efficiencydepends on the accuracy of K2 and periodicmeasurement of short circuit current.

Perturb and Observe:

The concept behind the P&O method is to modifythe operating voltage or current of the PV paneluntil you obtain maximum power from it.

The tracker operates by periodically incrementingor decrementing the solar array voltage.

If increasing the voltage to a panel increases thepower output of the panel, the system continuesincreasing the operating voltage until the poweroutput begins to decrease.

Flowchart for P&O algorithm

Incremental Conductance:

Incremental conductance considers the fact that theslope of the power-voltage curve is zero at themaximum power point, positive at the left of theMPP, 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

Flowchart of incremental conductance

SYSTEM MODELING:

The PV power system is modeled using Power System Blockset under Matlab.

Solar Panel

Digital Controller

The microcontrollerprovides the control inour system.

The choice ofmicrocontroller for thesystem dictates much ofthe cost, performance,and flexibility of theentire system.

Circuits of the boost converter

DC-DC Converter

ADVANTAGES:

MPPT method can extract maximum availablepower from the PV module.

This can increase the tracking efficiency.

If your energy use is greatest in the winter (typicalin most homes) and you have cold winterweather, then you can gain a substantial boost inenergy when you need it the most!

CONCLUSION:

A PV systems are suitable for residential and/orindustrial applications as it provides a regulated ACoutput voltage that may also track the input mainsutility voltage in phase and amplitude at hundreds tothousands of watts. Thus MPPT system can bedeployed to get maximum amount of power to takeadvantage of solar energy.

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-basedPhotovoltaic maximum power tracking control system”, IEEETrans. Onpower Electron., Vol. 16, No. 1, pp. 46-54, 2001.

J .A.Jiang et. Al. , “Maximum Power Tracking for Photovoltaic PowerSystems,” Tamkang Journal of Science and Engineering, Vol. 8, No. 2,pp. 147-153, 2005.

S. Jain and V. Agarwal, “A New Algorithm for Rapid Tracking ofApproximate Maximum Power Point in Photovoltaic Systems,” IEEEPower Electronic Letter., Vol. 2, pp. 16-19, Mar. 2004.

W. Xiao and W. G. Dunford,“A modified adaptive hill climbing MPPTmethod for photovoltaic power systems,” 35th. Annual IEEE PowerElectron. Specialists Conf. , pp. 1957-1963, 2004.

Y. Kuo, et. Al., “Maximum power point tracking controller for photovoltaicenergy conversion system,” IEEETrans. Ind. Electron., Vol. 48,pp. 594-601, 2001.

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