Maximum Power Point Tracking of Solar System

Hybrid Car

A B.Tech. Preliminary Project Report
Submitted in partial fulfillment of the requirements for the
Degree of Bachelor of Technology
Under Biju Pattnaik University of Technology

Submitted By
Sujeet Kumar Roll # EEE200825424
Goutam Mishra Roll # EEE200825443

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2011-2012

Under the guidance of
Prof. Sangram Mudali
&
Dr. Sidhartha Panda

NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY
Palur Hills, Berhampur, Orissa - 761008, India
ABSTRACT

The need for renewable energy sources is on the rise because of the acute energy crisis in the world today. India plans to produce 20 Gigawatts Solar power by the year 2020, whereas we have only realized less than half a Gigawatt of our potential till date. Solar energy is a vital untapped resource in a tropical country like ours. The main hindrance for the penetration and reach of solar PV systems is their low efficiency and high capital cost.

“Solar Panel Maximum Power Point Tracker”. As the name implied, it is a photovoltaic system that uses the photovoltaic array as a source of electrical power supply and since every photovoltaic (PV) array has an optimum operating point, called the maximum power point, which varies depending on cell temperature, the insolation level and array voltage. A maximum power point tracker (MPPT) is needed to operate the PV array at its maximum power point.

In this thesis, we examine a schematic to extract maximum obtainable solar power from a PV module and use the energy for a DC application. This project investigates in detail the concept of Maximum Power Point Tracking (MPPT) which significantly increases the efficiency of the solar photovoltaic system.

ACKNOWLEDGEMENT

Completing a job has never been an easy go for a two persons often it is the result of invaluable contributions from individuals in the surrounding in a direct or indirect manner.

I am deeply grateful to my advisor Mr. B.P. Pattnaik for having been a constant source of encouragement for our B.Tech Project Report on “Maximum Power Point Tracking Of NIST Solar Park”.

In our association with our guide for this purpose, we experienced not only his in-depth knowledge but also his affection towards us. We would like to thank all my friends who have helped me for successful completion of our project.

Last, but not the least, we give our sincere thanks to Mr. Swadhin Mishra, B. Tech Project Coordinator, for giving us the opportunity and creating a nice work environment for us to complete our B.TECH project within the stipulated period of time.

Finally I thank Prof. Sangram Mudali, for his continued drive for better quality in everything that happens at NIST. This report is a small contribution towards the greater goal.

Suresh Chandra Padhi

Kunal Kumar

TABLE OF CONTENTS

ABSTRACT i

ACKNOWLEDGEMENT ii

TABLE OF CONTENTS iii

LIST OF FIGURES iv

1. INTRODUCTION 1

2.SEMICONDUCTOR AS A PART OF PV CELL 4

2.1Photo voltaic effect 4

2.2 VI & PV Characteristic of PV cell

2.3 PV Cell technology 5

3. PHOTO VOLTAIC SYSTEM DESIGN 8

3.1 Brief Description 8

3.2PV MODULE 8

3.1 BATTERY 8

3.1 CHARGER 8

3.1 DC/DC CONVERTOR 8

3.1 LOAD 8

3.1 SHUNT 8

3.1 SWITCH CONTROL 8

4. APPROACH STRATEGY 10

REFERENCES 11
LIST OF FIGURES

Fig. 2.1 The System Architecture 4

Fig. 2.2 Detailed Block Diagram 5

1. INTRODUCTION

Solar power is an alternative technology that will hopefully lead us away from our petroleum dependent energy sources. The major problem with solar panel technology is that the efficiencies for solar power systems are still poor and the costs per kilo-watt-hour (kwh) are not competitive, in most cases, to compete with petroleum energy sources. Solar panels themselves are quite inefficient (approximately 30%) in their ability to convert sunlight to energy. However, the charge controllers and other devices that make up the solar power system are also somewhat inefficient and costly.

While solar panels are not very efficient due to their current limitations, we hope to extract the maximum amount of possible power from the solar panel with our MPPT device. The MPPT monitors the output voltage and current from the solar panel and determines the operating point that will deliver that maximum amount of power available to the batteries.

In order to enable us to complete this project in an effective manner we need to understand the solar technology and the most important aspects of it. We will look at different applications and whether or not they are even feasible at the current state of solar technology. After understanding more about the technology that solar power involves and the different applications that it is used for, we can then approach our problem for a specific application and design the best solar panel peak power tracking system.

2. ELECTRIC HYBRID CAR OVERVIEW DESIGN

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Solar power is the conversion of sunlight into electricity and can be done directly using photovoltaic (PV) systems. Photovoltaic power technology uses semiconductor cells (wafers), generally several square centimetres in size. The cell is basically a large area p-n diode with the junction positioned close to the top surface. Numerous cells are assembled in a module to generate required power [8].
Photovoltaic were initially used to power small and medium-sized applications, from the calculator powered by a single solar cell to off-grid homes powered by a photovoltaic array. The only significant problem with solar power is the installation cost [6], although cost has been decreasing in recent years due to advances in technology.
In comparing alternative cell technologies, the most important measure is the energy cost per kWh delivered. In PV technology, this is primarily based on 2 parameters:
(i) PV energy conversion efficiency and

(ii) The capital cost per watt capacity

1.3.1. Single-Crystalline Silicon
The single crystal silicon is the most widely available cell material, and has been the workhorse of this particular industry. The manufacturing process is a slow and intensive one, and results in almost half of the high raw material silicon ingot produced being wasted due to the maximising of the number of cells that can be mounted together on a rectangular panel. This material waste can be minimised by making full size round cells from round ingots (Fig. 7) instead of rectangular ones. However, this case is only

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Polycrystalline and Semicrystalline
This is a relatively fast and low cost manufacturing process that produces thick crystalline cells. Instead of drawing single crystals using seeds (as in the Single-Crystalline Silicon manufacturing process), the molten silicon is cast into ingots, and 11 forms multiple crystals. The conversion efficiency is lower, but the cost is much lower, giving a net reduction in cost per watt of power.
1.3.3. Thin Films
These are materials such as Copper Indium Diselenide, Cadmium Telluride, and Gallium Arsenide, typically a few μm or less in thickness. They can be directly deposited on glass, stainless steel, ceramic or other compatible substrate materials. This technology is less expensive per watt of power generated as it uses much less material per square area of the cell.
1.3.4. Amorphous Silicon
In this technology, amorphous silicon vapour is deposited on a couple of μm thick amorphous (glassy) films on stainless steel rolls, typically about 610m long and 0.33m wide. Compared to the crystalline silicon, this technology utilises only 1 % of the material. Its efficiency is about one-half of the crystalline silicon at present, but the cost per watt generated is projected to be significantly lower.
1.3.5. Concentrated Cells
In an attempt to improve the conversion efficiency, sunlight is concentrated into tens or hundreds of times the normal sun intensity by focusing on a small area using low cost lenses (Fig. 8). The primary advantage of this method is that these cells require a fraction of the area, compared to standard cells, to operate to a satisfactory level; thus significantly reducing the PV material requirement. However, the total module area remains the same to collect a similar amount of sunlight.

Advantages:
• Increases amount of power produced and reduces the size/number of cells.

• Cell efficiency increases under concentrated light up to a certain point.

• Smaller area cells can be employed (It‟s easier to produce high efficiency cells of smaller areas than to produce larger area cells with a comparable efficiency).

Disadvantage:
• Concentrated cells require focusing optics which adds to the overall cost.

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MPPT algorithms
In general, a PV system is operated in conjunction with a DC-DC converter, whose duty cycle is modulated in order to track the instantaneous MPP of the PV source. Several tracking schemes and algorithms have been proposed and researched:
• Perturb and Observe (P&O) or “hill – climbing” [12]-[13]

• Incremental Conductance [14]

• Short-circuit current method [15]

• Open -circuit voltage method [16]

• Ripple correlation approach [17]

Both the P&O and the Incremental Conductance methods have been researched and are discussed below. The following conclusion states which algorithm was pursued for the duration of this project and why it was chosen.
2.2.1. Perturb and Observe Method (P&O)
The P&O method is one of the most popular MPPT algorithms due to its simplicity. It has a simple control structure and few measured parameters are required for power tracking. It can also be easily applied to any PV panel as it has the advantage of not relying on the PV module characteristics in the MPPT process.
Fig. 11 shows the flow chart of the operation. After one perturb operation the current power is calculated and compared with previous value to determine the change of power ΔP. If ΔP>0, then the operation continues in the same direction of perturbation. Otherwise it reverses the perturbation direction [18].
The P&O perturbation step size plays a significant role in determining the accuracy and speed with which the operating point converges on the MPP. Larger perturbation size results in a faster convergence but induces larger oscillations around the MPP in steady-state. These oscillations reduce the effectiveness of the PV power conversion, as power is lost due to the large error of the system. A smaller perturbation size would increase the effectiveness of the PV power conversion but would take longer to converge on the MPP. So a balance needs to be sought. 18
Another very important point about the P&O method is that when atmospheric conditions are constant or change slowly, this method works to a satisfactory degree. However, when these conditions change rapidly, this method fails to track the MPP and gives rise to a waste of some of the available energy [19].

Figure 11 - Flow chart of P&O algorithm11
11 See
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