Simulation of Maximum Power Point Tracking for Photovoltaic

Systems

Abstract:

A photovoltaic (PV) solar panels exhibit non-linear current–voltage characteristics, and according to the maximum powertransform (MPT) theory, it can produce maximum power atonly one particular operating point (OP), namely, when thesource impedance matches with the load impedance, a matchwhich cannot be guaranteed spontaneously. Furthermore, themaximum power point (MPP) changes with temperature andlight intensity variations. Therefore, different algorithms havebeen developed for maximum power point tracking (MPPT)based on offline and online methods. Evaluating theperformance of these algorithms for various PV systemsoperating under highly dynamic environments are essentials toensure a reliable, efficient, cost-effective, and highperformance systems.

CONTENTS

PROBLEM DESCRIPTION

PROBLEM SOLUTION

BLOCK DIAGRAM OF DESIGN MODEL

BLOCK DIAGRAM OF ANALYTICAL MODEL

SCHEMATIC DIAGRAM OF PV SYSTEM

PV SYSTEM MODEL

DEFINITION OF MPPT

DESCRIPTION OF MPPT

ADVANTAGES

REFERENCES

PROBLEM DEFINITION:

The development of renewable energy has been anincreasingly critical topic, due to the tremendous growth inenergy demand that is expected to climb 35% by 2030 incomparison with current energy consumption.

As a result of that an enormous pressure on existingconventional energy resources, in particular, fossil fuels suchas oil and natural gas.

Where they are currently providing more than 98% of theenergy consumed worldwide .

Dependence on fossil fuels presents a number of challenges,including: high cost, environmental damage, and lack ofsustainability.

PROBLEM SOLUTION:

The most obvious source of RE is the solar energy.

A photovoltaic (PV) solar panels exhibit non-linear

current–voltage characteristics, and according to the

maximum power transform (MPT) theory, it can

produce maximum power at only one particular

operating point (OP), namely, when the source

impedance matches with the load impedance, a match

which cannot be guaranteed spontaneously.

The role of simulation in validating a design model.

The role of simulation in validating an analytical model.

Schematic diagram of a PV system.

PV SYSTEM MODEL

A general configuration of a standard PV systemcomprises the following components:

A standalone PV panel

An MPPT composed of a DC-DC convertertopology along with its MPPT algorithm. Aninverter can be used when AC load is needed.

A battery bank as a storage device with itsassociated charger controllers.

Definition of MPPT(maximum power point tracking)

There is a need to implement an MPPT algorithm totrack changes and extract the maximum power fromthe PV solar panel, because the power generated bythe panel is significantly affected by variations inirradiation, temperature and panel voltage, revealinga non-linear characteristic.

An MPPT system can be defined as an electronicdevice that operates the PV panel in such way that itdelivers all the power it can produce.

Contd………..

The difference between MPPT system and a mechanicaltracking system is that the mechanical system physicallyorients the panel straight at the sun, while the MPPTsystem electronically control the system so it can changethe electrical OP of the panel in accordance with changesin irradiation or temperature, so that the solar panel isable to yield the maximum available power.

The MPPT plays the role of impedance matching adapter,i.e., it forces the impedance at the terminals of the PVpanel to the value that produces maximum power out ofthe panel.

ROLE OF MPPT IN PV SYSTEM

MPPT plays a big role in PV systems because itmaximize the power output from a PV system for agiven set of environment changes and loadvariations, and therefore maximize the arrayefficiency and minimize the overall system cost.

The MPP varies depending on the irradiation andcell temperature, therefore; appropriate algorithmsmust be developed to track the MPP and maintainthe operation of the system as close as possible tothis point.

Description of MPPT

Typical solar panel can only convert 30% to 40% of theincident solar irradiation into electrical energy. However,usually solar panel delivers less than that, because accordingto the MPT theorem, the actual power output of a circuitreaches its maximum when the source impedance matcheswith the load impedance, a match which is usually notguaranteed.

MPPT algorithms are used to ensure impedance match toimprove the efficiency of the solar panel in delivering itsmaximum power.

In the source side a boost converter is connected to a solarpanel in order to enhance the output voltage. By changing theduty cycle of the boost converter appropriately the sourceimpedance is matched with that of the load impedance.

Perturb and Observe (P&O) algorithm

The P&O algorithm is used due to its simplicity and easyimplementation.

The operation of P&O consists in periodically perturbingthe panel operating voltage incrementally, so that thepower output can be observed and compared atconsecutive perturbing cycles.

If the power difference is positive, further perturbation isadded to the operating voltage with the same increment,and again the output power is observed. This perturbingprocess is continued until the power difference becomesnegative.

Thus, the direction of perturbation in operating voltagemust be reversed.

Advantages:

The most obvious source of RE is the solar energy,therefore, a huge number of projects andresearches have been adopted worldwide to utilizethe indispensable sunlight as a sustainable sourceof energy.

PV solar cells have relatively low efficiency ratings;thus operating at the MPP is desired because it isat this point array will operate at the highestefficiency.

CONCLUSIONS

A MPPT controller for PV solar system is modeled in thisproject using the P&O algorithm on MATLAB software.

The simulated model demonstrated an excellent andflexible environment for studying various PV solar cellsoperating under different environments of irradianceand temperature.

Many other parameters can be modeled and investigatedusing the same model which all left for future research.

Furthermore, the same simulation approach can beequally applied to other renewable energy sources, suchas the wind energy system.

REFERENCES

[1] National Renewable Energy Laboratory and theDepartment of Energy, “Types of renewable energy”, accessedon 20th April 2013 fromhttp://www.renewableenergyworld.com/rea/tech/home .

[2] US Energy Information Administration, “Energyconsumption by primary fuel”, accessed on 2nd April 2013from http://www.eia.gov/forecasts/aeo/er/early_fuel.cfm.

[3] Internationa Energy Agency, “Tracking clean energyprogress 2013”, accessed on 2nd May 2013 fromwww.iea.org/publications/tcep_web.pdf

[4] C. Hua and C. Shen, “Comparative study of peak powertracking techniques for solar storage system”, Proceedings ofthe 13th Annual Conference on Applied Power ElectronicsConference and Exposition (APEC '98). Vol. 2, pp. 679 – 685,1998.