Dissertation:CONTROL OF GRID CONNECTED SOLAR PHOTOVOLTAIC SYSTEM

1

CONTROL OF GRID CONNECTED SOLAR

PHOTOVOLTAIC SYSTEM

A DISSERTATION

Submitted in partial fulfillment of the

requirements for the award of the degree

of

MASTER OF TECHNOLOGY

in

ALTERNATE HYDRO ENERGY SYSTEMS

By

ZAMEER AHMAD

ALTERNATE HYDRO ENERGY CENTRE

INDIAN INSTITUTE OF TECHNOLOGY ROORKEE

ROORKEE ― 247667 (INDIA)

JUNE, 2013

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CANDIDATE’S DECLARATION

I hereby declare that the work which is being presented in this dissertation

report entitled “Control of Grid Connected Solar Photovoltaic System” submitted

in partial fulfilment of the requirements for the award of the degree of Master of

Technology with specialization in Alternate Hydro Energy Systems, submitted in

Alternate Hydro Energy Centre, Indian Institute of Technology Roorkee is an

authentic record of my own work carried out during a period from July 2012 to June

2013 under the supervision of DR. S.N.Singh, senior scientific officer, Alternate

Hydro Energy Centre, Indian Institute of Technology Roorkee.

The matter embodied in this dissertation report has not been submitted by me

for the award of any other degree or diploma.

Date: 10 June, 2013

Place: Roorkee (Zameer Ahmad)

This is to certify that the above statement made by the candidate is correct to

the best of my knowledge.

(S.N.Singh)

Senior scientific officer,

Alternate Hydro Energy Centre,

Indian Institute of Technology Roorkee,

Roorkee-247667 (Uttarakhand)

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ACKNOWLEDGEMENT

I would like to express my deep sense of gratitude to my guide DR. S.N.Singh,

senior scientific officer, Alternate Hydro Energy Centre, Indian Institute of

Technology Roorkee, for providing me all the necessary guidance and inspirational

support throughout this dissertation work. I can never forget his caring words and

support in the difficult times. They have displayed unique tolerance and

understanding at every step of progress, without which this dissertation work would

not has been in the present shape.

I wish to express my profound gratitude to Dr. R. P. Saini, Head, Alternate

Hydro Energy centre, Indian Institute of Technology Roorkee for providing all

the facilities, which would have made it possible for me to complete this dissertation

work.

I also owe a great deal of appreciation to all faculty members and staff of

Alternate Hydro Energy Centre, Indian Institute of Technology Roorkee who

have helped me directly or indirectly for the completion of this dissertation.

I would also like to thank all my friends for their help and encouragement at the

hour of need. As a final personal note, I am most grateful to the Almighty for

showering blessings on me and my family members who are inspirational to me in

their understanding, patience and constant encouragement.

Date: 10 June, 2013 (Zameer Ahmad)

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ABSTRACT

In modern contest the world is moving from conventional energy sources to the

renewable one. It is due to its greater abundance and environment friendly

characteristics. Solar energy is one of the most promising renewable resources that

can be used to produce electric energy through photovoltaic process. A significant

advantage of photovoltaic (PV) systems is the use of the abundant and free energy

from the sun.

Power electronic devices used as interface between renewable power and its

user. It makes the power generated by renewable sources suitable for utilization.

Solar power contribution in power generation has been increasing very fast and

cost of power generated by solar photovoltaic is falling rapidly. Solar photovoltaic

cell converts solar energy directly into dc power. Power is mostly transmitted and

utilized in ac form because of advantages associated with it. To convert the dc power

into ac, a highly efficient converter is required for optimum utilization of energy.

Power electronic devices can be used for this purpose, because they are highly

efficient, light weight, small size, very fast and most reliable. Power electronic

devices used as a switch.

Power electronics devices required control signal for its operation. These

signals may require continuously or at the time of switching. There are many

controllers which generate control signal and has its own advantages and

disadvantages.

The characteristic of solar photovoltaic cell is such that it has a point on curve which

corresponds to maximum power. So it becomes necessary to design a controller which

not only convert dc power of solar to ac but convert peak power.

This work demonstrates a new method that can be used for transferring solar

energy into the grid. This consists of designing of line commutated inverter and

microcontroller based control circuit. The microcontroller has been used to design the

control circuit because of its greater reliability, flexibility and versality. Besides the

delay angle can be controlled according to requirement by just changing the program

not the hardware setup.

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CONTENTS

TITLE Page No

Candidate’s Declaration i

Acknowledgement ii

Abstract iii

Contents iv

List of Figures vii

List of Tables ix

List of abbreviations x

List of symbols xi

CHAPTER 1 INTRODUCTION 1

1.1 GENERAL 1

1.2 ENERGY CLASSIFICATION 2

1.2.1 Non-Renewable energy resources 2

1.2.2 Renewable energy resources 2

1.2.2.1 Status of renewable energy in India 3

1.3 SOLAR ENERGY 4

1.3.1 Solar photovoltaic system 4

1.3.1.1 Photovoltaic energy conversion 4

1.3.1.2 Photovoltaic technology 4

1.3.1.3 Grid-Connected PV Systems 5

1.4 8051 MICROCONTROLLER 6

1.4.1 Basic architecture of 8051 microcontroller 6

1.4.2 Features of 8051 7

1.4.3 Timers of 8051 7

1.5 POWER ELECTRONICS 8

1.5.1 Power electronic devices 8

1.5.2 Power converter topologies 9

1.6 OBJECTIVES OF DISSERTATION 10

1.7 ORGANIZATION OF DISSERTATION REPORT 10

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CHAPTER 2 LITERATURE REVIEW 11

2.1 CONTROL OF GRID CONNECTED PV SYSTEMS 11

2.2 PEAK POWER POINT TRACKING 12

CHAPTER 3 METHODOLOGY AND FLOWCHARTS 14

3.1 METHODOLOGY 14

3.1.1 Flowchart of the proposed method 15

3.2 SYNCHRONIZATION 16

3.2.2 Synchronization flowchart 16

3.2.3 Program of Synchronization 17

3.3 CONTROL PULSE OR TRIGGERING PULSE 18

3.3.1 Triggering Pulse Flowchart 18

3.3.2 Program For Triggering Pulse 19

3.4 INTERFACING 20

3.4.1 Interfacing program of ADC with 8255 20

CHAPTER 4 SOFTWARE MODEL OF SPV CELL 21

4.1 MATHEMATICAL MODELING 21

4.2 MATLAB SIMULINK MODEL 23

4.2.1 PV module characteristics 23

4.3 MAXIMUM POWER POINT TRACKING 25

CHAPTER 5 EXPERIMENTAL SETUP 32

5.1 INTRODUCTION 32

5.2 COMPLETE CIRCUIT DIAGRAM 33

5.3 DEVELOPED MODEL 35

5.4 DESCRIPTION OF CONTROL UNIT COMPONENTS 36

5.4.1 8051 advanced microprocessor development kit 36

5.4.2 Zero crossing detector 37

5.4.4 Analog to digital converter 37

5.4.5 Isolation for control pulse 38

5.5 POWER UNIT CIRCUIT DESCRIPTION 40

5.5.1 Single phase fully controlled converter 40

CHAPTER 6 RESULTS AND DISCUSSION 41

6.1 ZERO CROSSING DETECTOR 41

6.2 DELAY TIME CALCULATION 42

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6.3 SYNCHRONIZATION 43

6.4 TRINGGERING PULSES 44

6.5 OUTPUT VOLTAGE WAVEFORM 47

CHAPTER 7 CONCLUSIONS AND FUTURE SCOPE 49

7.1 CONCLUSIONS 49

7.2 FUTURE SCOPE OF THE WORK 50

LIST OF PUBLICATIONS 51

REFERENCES 52

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LIST OF FIGURES

Figure No. Description Page No.

1.1 Renewable energy resources 2

1.2 Photovoltaic energy conversions 4

1.3 Technology used for PV cells 5

1.4 Main components of grid-connected photovoltaic systems 5

1.5 Basic architecture of 8051 6

1.6 Timer registers 7

1.7 Basic power electronics system 8

1.8 Power semiconductor devices 8

1.9 Ratings of Power semiconductor devices 9

3.1 Single Phase Fully Controlled Converter with RLE load 14

3.2 Flow chart of the proposed method 15

3.3 Flowchart of the synchronization 16

3.4 Flowchart of Triggering pulses 18

4.1 Electrical equivalent circuit of PV cell 21

4.2 Model of solar photovoltaic module 23

4.3 Characteristic curve 24

4.4-4.16 I-V, P-V and dp/dv-V characteristics curves at different solar

insolation and different temperatures

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4.17 Voc vs. Vmpp 30

4.18 Actual Pmax and Pmax tracked 31

4.19 Power loss in fixed Vmpp and actually tracking of Vmpp 31

5.1 Main circuit diagram 33

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5.2 Photograph of developed model 35

5.3 Photograph of solar module used 35

5.4 8051 microcontroller kit 36

5.5 Zero crossing detector (a) circuit diagram, (b) photograph 37

5.6 Circuit diagram of ADC (a) circuit diagram, (b) photograph 38

5.7 Driver and Buffer circuit (a) circuit diagram, (b) photograph 39

5.8 Single Phase Fully Controlled Converter with RLE load 40

6.1 Output of zero crossing detector 41

6.2 Output of Zero Crossing Detector as square wave 41

6.3 Synchronized pulse 43

6.4 Triggering pulse with 5ms delay 44

6.5 Triggering pulse with 6 ms delay 45




6.9 Output Voltages and Load Current Waveform for different

Triggering angles

47

6.10 Output voltage waveform and source current waveforms 48

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LIST OF TABLES

Table No. Description Page No.

1.1 Status of renewable energy in India 3

1.2 Conversion efficiency of cell 5

1.3 Four basic types of converters 9

4.1 Parameters of ELDORA40 Solar Module 23

4.2 Major Characteristics of MPPT Tequenique 25

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LIST OF ABBREVIATIONS

Abbreviations Meaning

SPV Solar Photovoltaic

MPPT Maximum Power Point Track

DC Direct Current

AC Alternating Current

ROM Read Only Memory

RAM Random Access Memory

CPU Central Processing Unit

I/O Input Output

ADC Analog To Digital Converter

ALU Arithmetic Logic Unit

DPTR Data Pointer Register

TMOD Timer Mode

SCR Silicon Controlled Rectifier

P&O Perturb And Observe

IncCond Incremental Conductance

ZCD Zero Crossing Detector

PPI Programmable Peripheral Interface

OP-AMP Operational Amplifier

IC Integrated Circuit

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LIST OF SYMBOLS

Symbols Meaning

IA PV Array Output Current

VA PV Array Output Voltage

Iph Solar Cell Photocurrent

IRS Reverses Saturation Current

q Electron Charge

N P–N Junction Ideality Factor

k Boltzmann's Constant

TC Absolute Operating Temperature

RS Cell Intrinsic Series Resistance

KI SCC Temperature Coefficient

ISC Short Circuit Current

S Solar Insolation in W/m2

VOC Open-Circuit Voltage

R Resistance

L Inductor

E Energy Source

T Thyristor

G Gate Of Thyristor

V0 Output Voltage

Vm Peak Of Voltage

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CHAPTER-1

INTRODUCTION

1.1 GENERAL

The present day electronics world is moving towards miniaturization and low

priced equipments. At the risk of making a trite observation, the last two decade of

advances in microcontrollers, processors, and programmable logic have opened up

tremendously exciting possibilities for enhancing performance, applicability, and

economy of power electronics appliances. Thus implementing a digital circuit in place

of analog circuit attracts all the benefits associated with digital circuits.


renewable one. To overcome the problems associated with generation of electricity

from fossil fuels, renewable energy sources can be participated in the energy mix.

One of the renewable energy sources that can be used for this purpose is the light

received from the sun. This light can be converted to clean electricity through the

photovoltaic process. The use of photovoltaic (PV) systems for electricity generation

started in the seventies of the 20th

century and is currently growing rapidly worldwide.

It is due to its greater abundance and environment friendly characteristics.

Power electronic devices are working as an interface between grid and solar

power output. Power electronics refers to control and conversion of electrical power

with the help of power semiconductor devices, which used as switch. Advent of

silicon controlled rectifier led to the development of new area of applications [1].

Simple triggering circuit can be realised by R or Resistance and Capacitance

network. They are not expensive and little power required for its operation. However

the control and hence the load output voltage susceptible to device temperature

variations. Moreover feedback control incorporation is not easy.

Although RC trigger circuits are simple and economical they depend on gate

trigger characteristics of thyristers used, and they cannot be used easily in feedback

controlled systems or where automation is needed. In a controller a group of thyristers

or power semiconductor devices are required to be switched at different switching

instants for different duration and in a particular sequence. Different three phase

converters, for example dual converters, cycloconverters, and regenerative reversible

drive, may require 12 to 36 such devices [2].

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Thus switching a large number of these power devices with different control

strategy by a simple triggering circuit is almost impossible. Moreover incorporation

of feedback and/or different control approaches for same load drive system requires

an intelligent controller. Therefore the advanced triggering circuits become necessary.

1.2 CLASSIFICATION OF ENERGY RESOURCES

The energy resources are generally classified into two categories:

(i) Non-Renewable Resources of Energy

(ii) Renewable Resources of Energy

1.2.1 Non-Renewable Resources of Energy

Non-Renewable Resources are those natural resources which are exhaustible

and cannot be replaced once they are used. Non renewable resources are as follows:

(i) Coal

(ii) Petroleum

(iii) Natural gal

(iv) Uranium etc.

1.2.2 Renewable Energy resources:

Renewable sources of energy are never-ending and can be used to generate

energy again and again. Renewable energy resources are categorised as given in

Figure 1.1.

Fig.1.1: Renewable energy resources [3]

RENEWABLE ENERGY

Solar Wind Small hydro Biomass

Geothermal

Solar thermal Solar

photovoltaic

Tidal Wave Ocean thermal

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1.2.2.1 Status of Renewable Energy in India

India has a vast potential of renewable energy sources and a number of

technologies have been developed to harness them. A number of industrial bases have

been created in the country in the various renewable energy technologies such as solar

thermal, solar photovoltaics, wind, small hydro, biomass etc [5]. An aggregate

capacity of 28951 MW has been installed 0n 31-03-2013 based on these technologies

[4]. The status of renewable energy in India is given in table 1.1.

Table 1.1: Status of renewable energy in India [4]

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1.3 SOLAR ENERGY

Solar energy can be exploited in two ways:

(i) Solar thermal;

(ii) Solar photovoltaic

1.3.1 Solar Photovoltaic system

1.3.1.1Photovoltaic energy conversion

It works on the principle of simple PN junction. PV cell converts sun energy

into direct current. To get required dc power cells are connected in series and parallel

to get required power level. When cells are connected in series increases the voltage

while in parallel connection increase the current [6]. Figures 1.2 shows photovoltaic

energy conversion.

Figure 1.2: Photovoltaic energy conversions [6]

1.3.1.2 Photovoltaic technology

PV cell technology is mainly classified into two categories, namely, crystalline

silicon, as shown in Figure 1.3. Majority of PV cells are made of crystalline silicon;

and thin film technology is newer and increasing in popularity. Conversion efficiency

of cells is given in Table 1.2.

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Fig.1.3: Technology used for PV cells [7]

Table 1.2: conversion efficiency of cell [8]

PV Cell Technology Module efficiency

Mono- crystalline 20-27%

Poly-crystalline 14-18%

Copper indium gallium selenide 10-13%

Amorphous silicon 5-7%

1.3.1.3 Grid-Connected SPV Systems

The building blocks of a grid-connected photovoltaic system are shown in

Figure 1.4. The system is mainly composed of a matrix of PV arrays, which converts

the sunlight to DC power and a power conditioning unit that converts the DC power

to AC power. The generated AC power is injected into the grid and/or utilized by the

local loads. In some cases, storage devices are used to improve the availability of the

power generated by the PV system.

Fig. 1.4: Main components of grid-connected photovoltaic systems [9]

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1.4 8051 MICROCONTROLLER

A Microcontroller is a programmable digital processor with essential

peripherals. Both microcontrollers and microprocessors are complex sequential digital

circuits meant to carry out job according to the program / instructions.

Basically it is used for automatic control actions. It is used to control the function of

machine using fixed program that is stored in ROM/EPROM and that does not change

over the life time.

(i) CPU (microprocessor)

(ii) RAM

(iii) ROM

(iv) I/O ports

(v) Timer

(vi) ADC and other peripherals

1.4.1 Basic architecture of 8051 microcontroller

Pin diagram of 8051 is given in Figure 1.5.

Fig. 1.5: Basic architecture of 8051[10]

The whole configuration is obviously thought of as to satisfy the needs of the

most of the users working on development of automation devices. The fixed amount

of on-chip ROM, RAM, and number of I/O ports makes them ideal for many

applications in which cost and space are critical.

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1.4.2 Features of 8051

The silent features of 8051 microcontroller are as follows:

(i) 8 bit ALU.

(ii) 16 bit PC and DPTR.

(iii) 8 bit stacks pointer and 8 bit PSW.

(iv) 4K internal ROM

(v) 128 bytes Internal RAM.

(vi) Two 16 bit timers

(vii) Two External and three internal interrupt sources.

(viii) 0-12 MHz clock.

(ix) 40 pin DIP package [11].

1.4.3 Timers of 8051

There two basic registers of timer, which are shown in figure 1.6.

(a)

(b)

Fig.1.6: Timer registers: (a) Timer 0 Registers (b) Timer 1 Registers [12]

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1.5 POWER ELECTRONICS

Power Electronics is technology associated with efficient conversion and

control of electric power by power semiconductor devices. The goal of power

electronics is to control the flow of energy from electric source to load. Block

diagram of power electronic system is given in Figure 1.7.

Fig.1.7: Basic power electronics system [13].

Power electronics devices are very popular because of the following reasons:

(i) High efficiency: the efficiency of power electronic converter is very high. It is as

high as 99%.

(ii) Compactness: power electronic controllers are lighter in weight and occupy less

space.

(iii) High speed: power electronic controllers are very fast in comparison to other

controller.

(iv) Reliability: probability of failure is low and life is longer.

1.5.1 Power electronic devices

Power semiconductor devices are used as a switch to control the power supply

to load. Various types of power semiconductor devices are given in figure 1.8

Fig. 1.8: power semiconductor devices [14]

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Ratings of Power semiconductor devices are shown in figure 1.9.

Fig.1.9: Ratings of Power semiconductor devices [15]

1.5.2 Power Converter Topologies

There can be four basic types of converters depending upon the function

performed as given in Table 1.3.

Table 1.3: Four basic types of converters [16]

CONVERSION

FROM/TO

NAME FUNCTION

DC TO DC CHOPPER Constant to Variable DC

and Variable to Constant

DC

DC TO AC INVERTER DC to AC of Desired

Voltage and Frequency

AC TO DC CONVERTER AC to Unipolar Current

AC TO AC CYCLOCONVERTER AC of desired Frequency

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1.6 OBJECTIVES OF THE WORK

The present day electronics world is moving towards miniaturization and low

priced equipments. At the risk of making a trite observation, the last two decade of

advances in microcontrollers, processors, and programmable logic have opened up

tremendously exciting possibilities for enhancing performance, applicability, and

economy of power electronics appliances. Thus implementing a digital circuit in place

of analog circuit attracts all the benefits associated with digital circuits

Following are the objectives of the present study:

(i) Tracking the peak power of solar PV cell by developing a correlation

between Voc and Vmpp.

(ii) Design and implementation of advanced microcontroller based controller

for controlling power electronics devices.

(iii) Experimental setup to transfer the maximum solar PV power to grid.

1.7 ORGANIZATION OF DISSERTATION REPORT

To achieve the aforementioned objectives and facilitate the presentation of the

results obtained in this work, the dissertation work is organized as follows:

Chapter 2 deals with the Literature Review of the recent achievements and current

research activities in the field of the grid-connected PV systems and its control,

Maximum Power Point Tracking.

Chapter 3 deals with methodology and flowchart of the proposed system.

Chapter 4 deals with Matlab simulink based modeling of the SPV

Chapter 5 based on the review presented in Chapter 2, this chapter introduces

experimental setup of a new method that can be used to control and transfer the solar

photovoltaic energy to grid. The details of each components of the setup are also

presented in this chapter.

Chapter 6 presents the output of different circuitry of experimental setup.

Chapter 7 covers conclusion and future scope.

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CHAPTER-2

LITERATURE REVIEW

2.1 LITERATURE REVIEW OF CONTROL OF GRID CONNECTED PV

SYSTEM


renewable one. It is due to its greater abundance and environment friendly

characteristics. Control of grid connected comprised of two structures, MPPT control

and inverter control. Many methods have been proposed and discussed in literature.

Carrasco et al. [17] proposed Power-Electronic Systems for the Grid Integration of

Renewable Energy Sources and presented new trends in power electronics for the

integration of wind and photovoltaic (PV) power generators. A storage system

technology was introduced for the resources whose output changes.

Kazantzakis et al. [18] proposed a method to integrate the photovoltaic system into

distribution network operations. Distributed PV generator was used to improve the

stability of system by appropriate control. Power modulation should be such that

power quality remains within specified limit.

Magureanu et al. [19] proposed a real solution for Renewable energy sources

connection into distribution. Direct current link was proposed and simulated. A new

method for load sharing and droop control was presented.

Nayar et al. [20] presented the bi-directional inverters application in the field of PV,

diesel generators and battery storage.

Gonzalez-Moran et al. [21] proposed and described a photovoltaic direct current

source model. PV o/p could be supplied to inverters, which connected to grid.

Proposed model considered all the parameters that could affect o/p of PV.

Mei Shan Ngan et al. [22] discussed two categories of maximum power point

tracking algorithm algorithms. Also, the advantages and disadvantages of each

maximum power point tracking algorithm were reviewed. Also compared the results

obtained by the algorithms used.

Martina Calais et al. [23] presented an overview on different multilevel topologies

and investigated their suitability for single-phase grid connected photovoltaic systems.

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Magureanu,%20R..QT.&newsearch=partialPref

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Nayar,%20C.V..QT.&newsearch=partialPref

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Gonzalez-Moran,%20C..QT.&newsearch=partialPref

http://ieeexplore.ieee.org/search/searchresult.jsp?searchWithin=p_Authors:.QT.Mei%20Shan%20Ngan.QT.&newsearch=partialPref

24

Gianfranco Chicco et al [24] discussed the operation of grid connected photovoltaic

(PV) systems and provided a detailed performance comparison of different inverter

technologies for connecting the photovoltaic systems to the grid.

Massimo Aiello et al. [25] calculated total harmonic distortion theoretically and

experimentally in order to show which of the currently defined distortion factors was

best suitable to detect supply pollution.

Hirotaka Koizumi et al. [26] developed a novel microcontroller for grid-connected

photovoltaic (PV) systems. A 100-W-class module-integrated converter prototype

model composed of the proposed controller and a flyback inverter had been built and

tested.

G. Brando et al. [27] proposed an architecture that included a Power Electronic

Transformer which was practically an isolated high-frequency link AC/AC converter

that substitutes a conventional transformer. A maximum power point tracking control

technique was presented and result obtained was validated by simulation.

Javier Chavarría et al [28] presented an energy-balance control strategy for a cascaded

single-phase grid-connected H-bridge multilevel inverter linking n independent

photovoltaic (PV) arrays to the grid.

D.C. Riawan et al. [29] presented a scheme for transferring power from the

photovoltaic (PV) modules to a storage battery using a solar charge controller based

on a Cuk dc/dc converter.

2.2 PEAK POWER POINT TRACKING

The maximum power that can be delivered by a PV panel depends greatly on

the insulation level and the operating temperature. Therefore, it is necessary to track

the maximum power point all the time. Many researchers have been focused on

various MPP control algorithm to lead the operating point of the PV.

P. HUYNH et al. [30] analyzed Stability and dynamics of a series configuration peak-

power tracking (PPT) system. Analysis of multiloop control in the PPT mode was

discussed.

Yongho Kim [31] presented a new peak power tracker (PPT) which forces a

photovoltaic system to extract the maximum power from solar arrays, regardless of

the change of load demand, insolation and temperature.

25

G. Brando et al. [32] proposed a control setup to transfer the maximum power of

photovoltaic cell to the grid without use of sensor in all weather condition. The

control technique was presented and validated by simulation implemented on a

photovoltaic system with H-bridge 5-levels converter.

Theodore Amissah et al. [33] proposed an artificial neural network maximum power

point tracker (MPPT) for solar electric vehicles. The maximum peak power tracking

was based on a highly efficient boost converter with very high efficient power

electronic device insulated gate bipolar transistor (IGBT) power switch. The reference

voltage for maximum peak power tracking was obtained by artificial neural network

(ANN) with gradient descent momentum algorithm.

Eftichios Koutroulis et al. [34] developed a new maximum peak power tracking

system, consisting of a Buck-type chopper, which was controlled by a

microcontroller-based entity. The major difference between the method used in the

proposed maximum peak power tracking system and other techniques used in the past

was that the photovoltaic module output power was used to directly control the dc/dc

converter, thus it made system simple.

Verma et al. [35] a fuzzy logic controller (FLC) was utilized to extract the maximum

power point (MPP) of a photovoltaic system through control of a power electronic

device IGBT (Insulated Gate Bipolar Transistor) switch of the boost converter. This

system was used for compensation of neutral harmonic currents, current, reactive

power and to provide load balancing. Performance of the proposed fuzzy logic

controller was fast in finding the maximum peak power tracking than the conventional

techniques used for maximum peak power tracking.

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CHAPTER-3

METHODOLOGY AND FLOWCHARTS

3.1 METHODOLOGY

The main idea of the proposed method is to use fully controlled converter with

RLE load in inversion mode. When negative polarity of dc source (battery, solar

photovoltaic cell or array, etc.) is connected with cathode of thyristors 1 and 3 as

shown in fig 3.1. it act as a line commutated inverter.

The convertor operates in inversion mode only when triggering pulse is greater

than 90 degree and there is an inductive load in the output circuit.

The heart of this system is microcontroller based advanced triggering circuit.

Microcontroller is programmed to generate triggering pulses such that maximum

power of solar photovoltaic cell or array is supplying to grid.

I-V characteristic of solar photovoltaic cell is such that there is a peak power

point on the characteristic. The voltage corresponding to peak power is called

maximum power point voltage. As solar photovoltaic cell is a current source. Current

varies almost directly proportional to solar irradiation while open circuit voltage has a

weak link with solar insolation and cell temperature. So To extract the maximum

power, peak power point voltage is being tracked.

Fig.3.1: Single Phase Fully Controlled Converter with RLE load

27

3.1.1 Flowchart of Proposed Method

The general layout of the proposed method is presented in Figure 3.1.

Figure 3.2: Flow chart of the proposed method

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3.2 SYNCHRONIZATION

3.2.1 Flowchart of the synchronization

Flowchart of the synchronization is shown below.

Fig.3.3: Flowchart of the synchronization

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3.2.1 PROGRAM FOR SYNCHRONIZATION

MOV A, #90H PORT A INPUT, PORT B AND C AS OUTPUT OF 8255

MOV DPTR, #0FF03H ADDRESS FOR CONTROL WORD

MOVX @DPTR, A

MOV DPTR, #0FF00H

BACK: MOVX A, @DPTR

JZ BACK JUMP IF A=0

MOV A, #00H

INC DPTR INCREASING DPTR ADDRESS TO 0FF01H

MOVX @DPTR, A

MOV 89H, #01H TIMER0

MOV 8AH, #7DH

MOV 8CH, #0FFH

SETB 8CH TIMER START

HERE: JNB 8FH, HERE

CLR 8CH

CLR 8DH

MOV A, #0FFH

MOVX @DPTR, A

MOV 89H, #10H TIMER1

MOV 8BH, #0EDH

MOV 8DH, #0FFH

SETB 8EH TIMER1 START

HERE1: JNB 8FH, HERE1

CLR 8EH

CLR 8FH

MOV A, #00H

MOVX @DPTR, A

MOV DPTR, #0FF00H

GO: MOVX A, @DPTR

JNZ GO

LJMP BACK

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3.3 FLOWCHART OF TRIGGERING PULSES

3.3.1 Flowchart of Triggering pulses for inverter

Fig.3.4: Flowchart of Triggering pulses

31

3.3.2 Program for Flowchart of Triggering Pulses

MOV A, #90H

MOV DPTR, #0FF03H

MOVX @DPTR, A

MOV DPTR, #0FF00H

MOV A, #00H

BACK1: MOVX @DPTR, A

JZ BACK1

MOV A, #00H

INC DPTR INCREASING DPTR ADDRESS TO 0FF01H

MOVX @DPTR, A

LCALL DELAY1

MOV A, #0FFH

MOV DPTR, #0FF01H

MOVX @DPTR, A

LCALL DELAY2

MOV A, #00H

MOV DPTR, #0FF00H

BACK2: MOVX A,@DPTR

JNZ BACK2

MOV A, #00H

MOV DPTR, #0FF02H

MOVX @DPTR, A

LCALL DELAY1

MOV A, #0FFH

MOV DPTR, #0FF02H

MOVX @DPTR, A

LCALL DELAY 2

MOV A, #00H

LJMP BACK1

DELAY 1: MOV 89H, #01H

MOV 8AH, #66H

MOV 8CH, #0E6H

SETB 8CH

32

HERE1: JNB 8DH, HERE 1

CLR 8CH

CLR 8DH

RET

DELAY 2: MOV 89H, #10H

MOV 8BH, #66H

MOV 8DH, #0FCH

SETB 8EH

HERE2: JNB 8FH, HERE2

CLR 8EH

CLR 8FH

RET

3.4 INTERFACING

3.4.1 Interfacing program of ADC with 8255

MOV A, #90H ;( PA is input, PB and PC is output)

MOV DPTR, #address ; load control register; port address

MOVX @DPTR, A ; issue control word

MOV DPTR, # address ; PA address

MOVX A, @DPTR

INC DPTR INCREASING DPTR ADDRESS

MOVX @DPTR, A

INC DPTR INCREASING DPTR ADDRESS

MOVX @DPTR, A

Interfacing enables the electronic chip to work intelligently and work

accordingly as program is made. 8051mic can be interfaced in many ways such as by

means of interrupts, by means of ports of 8051 or by means of 8255 PPI in which the

chip 8255 is first interfaced and physical quantities are interfaced by means of the

ports. Using this technique as several advantages such as multiple handling of output

and input is possible. Every data used as an input has to be in digital form and output

has to be processed before giving it to the desired place. Since in our case the input is

supply signal and output is square wave so we do not need A/D converter rather a

zero crossing detector to sense the zero crossing of supply system.

33

CHAPTER 4

SOFTWARE MODEL OF SPV CELL

4.1 MATHEMATICAL MODEL OF THE SPV CELL/MODULE

Incident solar radiation produces current so it becomes effectively a current

source. Current depends on solar radiation incident. It has a PN junction so there must

be a diode. When current flow through material it encounter a resistance in its path.

This resistance is a series resistance. There will be a resistance between material and

metal. This shunt resistance is due to recombination of electron hole pairs. So the

electrical equivalent circuit can be represented as shown in figure4.1.

Fig.4.1: Electrical equivalent circuit of PV cell [8]

From Figure 4.1 output current is derived as given in equation (4.1).

INPIPHNPISexp {q(V/NS+IRS)/(NPKTCN)}-1]-(NPV/NS+IRS)/RSH (4.1)

Where:

I: PV array output current

V: PV array output voltage

Iph: Solar cell photocurrent

IRS: Solar cell reverses saturation current (aka dark current)

q: Electron charge, 1.60217733e-19

C

N: P–N junction ideality factor, between 1 and 5

k: Boltzmann's constant, 1.380658e-23

J/K

RS: Cell intrinsic series resistance

RP: Cell intrinsic shunt or parallel resistance

34

The current generated photon by Iph is in fact related with solar insolation S as:

Iph= [ISC+KI (TC-Tref)] S (4.2)

Where

KI: Cells short-circuit current temperature coefficient

ISC: short circuit current at 25 C

Tcell: cell’s temperature

S: solar insolation in W/m2

PV Cell under Varying Temperature

IS=IRS (TCell/Tr) 3

exp [qEG (1/Tr-1/TCell)/KN] (4.3)

Where

IS : cell’s saturation current

IRS: reverse saturation current

EG: band-gap energy

IRS=ISC/ [exp (qvOC/KNNSTC)-1] (4.4)

VOC: PV open-circuit voltage.

35

4.2 Simulink Model of solar photovoltaic module

The equations (4.1), (4.2), (4.3) and (4.4) have been used to develop a Matlab

simulink model of solar photovoltaic cell/module/array as given in Figure 4.2.

Fig.4.2: Model of solar photovoltaic module

4.2.1 PV MODULE CHARACTERISTICS

I–V and P–V characteristic curve are obtained by simulation of the developed

model for the parameters given in table 4.1 for ELDORA40 module is given in

Fig.4.3.

Table 4.1: Parameters of ELDORA40 Solar Module at solar radiation 1000W/sqm,

AM 1.5 and 25C cell temperature

PARAMETER VALUE

Maximum power (Pmax) 37 W

Voltage at Pmax (Vmax) 17.2V

Current at Pmax (Imax) 2.2A

Short circuit current (Isc) 2.4A

Open circuit voltage (Voc) 21V

36

Fig.4.3: Characteristic curves of the module

The results obtained by the simulation of model are same as the parameters given by

manufacturer.

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 240

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 240

2468101214161820

22242628303234363840

Pow

er

(W)

P vs V

I vs V

1000 W/sqm

700 W/sqm

400 W/sqm

100 W/sqm100 W/sqm

400 W/sqm

700 W/sqm

1000 W/sqm

37

4.3 MAXIMUM POWER POINT TRACKING

There are many algorithms for tracking of maximum power point of solar cell

as the summary is presented in Table 4.2.

Table 4.2: Main Characteristics of MPPT Tequenique [36]

38

The current and voltage characteristics of solar cell are non- linear. Maximum

power changes with change in solar insolation and cell temperature.

In this study, a relation between open circuit voltage and voltage corresponding

to maximum power has been developed. For developing relationship between Vmpp

and Voc, parameters of the solar PV module ELDORA40 as given in Table 4.1 have

been used.

The model given in Figure 4.2 is simulated for various values of solar insolations (0-

1100 W/m2) and cell temperatures and obtained results are shown in Figures 4.4-

4.16. Open circuit voltage (Voc) and corresponding maximum power point voltage is

read from the graphs.

Fig.4.4: I-V, P-V and dp/dv-V characteristics curves at 25 W/m2 solar insolation


0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 220

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 220

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

11

pow

er

(W)

I vs V

dp/dv vs V

P vs V

18 deg C

25 deg C

35 deg C

45 deg C

Vmpp

Voc

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 220

0.05

0.1

0.15

0.2

0.25

0.3

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 220

0.5

1

1.5

2

pow

er

(W)

I vs V

dp/dv vs V

P vs V

35 deg C

18 deg C

25 deg C

45 deg C

Voc

Vmpp

39




0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 220

0.05

0.1

0.15

0.2

0.25

0.3

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 220

0.5

1

1.5

2

2.5

3

3.5

pow

er

(W)

I vs V

dp/dv vs V

P vs V

18 deg C

35 deg C

VocVmpp

25 deg C

45 deg C

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 220

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

11

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 220

1

2

3

4

5

6

7

8

9

10

pow

er

(W)

I vs V

dp/dv vs V

P vs V

18 deg C

35 deg C

25 deg C

45 deg C

VmppVoc

0 2 4 6 8 10 12 14 16 18 20 22 240

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

11

Voltage (V)

Curr

ent

(A)

0 2 4 6 8 10 12 14 16 18 20 22 240

1

2

3

4

5

6

7

8

9

10

11

12

pow

er

(W)

I vs V

dp/dv vs V

P vs V

18 deg C

35 deg C

25 deg C

45 deg C

VmppVoc

40




0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 240

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 240

2

4

6

8

10

12

14

16

pow

er

(W)

I vs V

dp/dv vs V

P vs V

35 deg C

18 deg C

25 deg C

45 deg C

VocVmpp

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.80.9

1

1.1

1.2

1.3

1.4

1.5

1.6

1.71.8

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

2

4

6

8

10

12

14

16

18

20

pow

er

(W)

I vs V

dp/dv vs V

P vs V

35 deg C

Voc

18 deg C

25 deg C

45 deg C

Vmpp

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.80.9

1

1.1

1.2

1.3

1.4

1.5

1.6

1.71.8

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

2

4

6

8

10

12

14

16

18

20

22

24

pow

er

(W)

I vs V

dp/dv vs V

P vs V

35 deg C

25 deg C

18 deg C

45 deg C

VmppVoc

41




0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

0.10.20.30.40.50.60.70.80.9

11.11.21.31.41.51.61.71.81.9

22.12.22.32.4

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

2

4

6

8

10

12

14

16

18

20

22

24

pow

er

(W)

I vs V

dp/dv vs V

P vs V

35 deg C

18 deg C

Vmpp

25 deg C

45 deg C

Voc

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

pow

er

(W)

I vs V

dp/dv vs V

P vs V

35 deg C

18 deg C

25 deg C

45 deg C

Vmpp Voc

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

2

4

6

8

10

12

14

1618

20

22

24

26

28

30

32

3436

pow

er

(W)

I vs V

dp/dv vs V

P vs V

35 deg C

Vmpp Voc

18 deg C

25 deg C

45 deg C

42



As it is clear from the above characteristic curves that Voc and Vmpp depends

on solar insolations and cell temperatures.

The values of Voc and Vmpp are read from the above curves and plotted to

develop a relation as given in Figure 4.17.

Fig.4.17: Voc vs. Vmpp

The Figure 4.17 shows a linear relation between Voc and Vmpp that can be

represented by a linear equation as given in equation (4.5).

Vmpp=0.817Voc+0.0055 (4.5)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

Voltage (V)

Curr

ent

(A)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260246810121416182022242628303234363840

pow

er

(W)

I vs V

dp/dv vs V

P vs V

35 deg C

VocVmpp

18 deg C

25 deg C

45 deg C

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 260

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

3

Voltage (V)

Cur

rent

(A

)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 2602468101214161820222426283032343638404244

pow

er (

W)

I vs V

dp/dv vs V

P vs V

35 deg C

Voc

18 deg C

25 deg C

45 deg C

Vmpp

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 210

1

2

3

4

5

6

7

89

10

11

12

13

14

15

16

1718

Voc (V)

Vm

pp(V

)

43

Can be approximated as,

Vmpp=0.817Voc (4.6)

To implement this by using microcontroller two modules of similar

characteristics are required. Open circuit voltage of one module is multiplied by the

factor 0.817 and given to reference of the ADC. Now the voltage of the module

whose maximum power is being tracked is sensed and feed to one of the channel of

ADC.adc compare the voltages and sends an error signal to microcontroller.

Programming is done such that when the sensed voltage is equal to the reference

voltage a control pulse is generated.

In literature there is a fixed voltage method to track the maximum power. In

this study mp has been tracked by this method also. The Vmpp has been fixed by

using equation (4.6) by multiplying the average value of Voc.

Actual maximum power, maximum power actually tracked and maximum power

obtained by fixed Vmpp method have been shown in Figure 4.18.

Fig.4.18: Actual Pmax and Pmax tracked

Loss of power when these two methods are used is given in Figure 4.19. It can be

seen that power loss is minimum when power is tracked by implementing equation

(4.2).

Fig. 4.19: Power loss in fixed Vmpp and actually tracking of Vmpp

0 100 200 300 400 500 600 700 800 900 100002468

10121416182022242628303234363840

Actu

al m

axim

um

pow

er(

W)

0 100 200 300 400 500 600 700 800 900 10000246810121416182022242628303234363840

solar insolation (W/sqm)

Maxim

um

pow

er

tracked (

W)

0 100 200 300 400 500 600 700 800 900 10000246810121416182022242628303234363840

Actual maximum power

Maximum power tracked

maximum power by fixed Vmpp

0 100 200 300 400 500 600 700 800 900 10000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

11

Pow

er lo

ss (W

)

0 100 200 300 400 500 600 700 800 900 10000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

11

solar insolation (W/sqm)

Pow

er lo

ss (

W)

Actually trackedFixed Vmpp

44

CHAPTER-5

EXPERIMENTAL SETUP

5.1 INTRODUCTION

The main objective of this chapter is to explain the components of the

experimental setup. Brief function of each component has been described. The whole

setup is divided into two units. The one unit which is of low power and control the

power flow is called control unit and the other unit is of high power which contains

power electronic devices thyristers is known as power unit.

The experimental setup comprises of the following components:

1. 8051 advanced microcontroller kit

2. Analog to digital converter

3. Zero crossing detectors

5. Driver and buffer circuit

6. Single phase fully controlled converter

7. Solar module

The control unit which generates control pulses of desired delay to control the

flow of power are comprised of the following components:

(i) 8051 advanced microcontroller kit

(ii) Analog to digital converter

(iii) Zero crossing detectors

(iv) Driver and buffer circuit

The detail description of each component with circuit diagrams and photographs

have been discussed. The complete circuit diagram of the proposed work is given in

Figure 5.1.

45

5.2 COMPLETE CIRCUIT DIAGRAM

Fig. 5.1 (a)

46

Fig 5.1: Main circuit diagram

47

5.3 DEVELOPED MODEL

The complete experimental setup of the control of grid connected photovoltaic

system is shown in Fig.5.2 and photograph of the solar module used is given in

Fig.5.3.

Fig.5.2: (a)

Fig.5.2: (b)

Fig.5.2: Developed model of the proposed work

Fig.5.3: Solar module used in experiment

48

5.4 DESCRIPTION OF CONTROL UNIT COMPONENTS

The control unit comprises of the following components:

(i) A microcontroller kit

(ii) A/D converter

(iii) A Zero crossing detector

(iv) Driver and Buffer circuit

5.4.1 8051 Advanced Microprocessor Development Kit

The development kit has the following components:

(i) 8 bit, 12 MHz, 8051 microcontroller,

(ii) Two timers-8253: which are used to provide desired delay.

(iii)Two 8255 parallel I/O interface as photograph is shown in Figure 5.2.

Fig. 5.4: 8051 microcontroller kit

8255 PPI

TIMER

8051

CONTROL

PULSE

ADC

INTERFACE

49

5.4.2 Zero Crossing Detector

The proposed circuit of zero crossing detectors is shown in Fig.5.3. ZCD is

used to sense the zero crossing of supply voltage. It acts as a reference signal for

control pulse.

(a)

(b)

Fig.5.5: Zero crossing detector (a) circuit diagram, (b) photograph

5.4.4 Analog to Digital Converter

ADC is most widely used device for data acquisition. In physical world

everything is analog so we need ADC to convert analog signal into digital for

processing through microcontroller. Circuit diagram of ADC is shown in Figure 5.4.

TRANSFORMER

220/12V OP-AMP 741 IC-7805

OUTPU

T TO

ADC

50

(a)

(b)

Fig 5.6: Circuit diagram of ADC (a) circuit diagram, (b) photograph

5.4.5 Isolation for Control Pulse

In most of the circuits, there is a potential difference between the gates of the

various thyristers, as well as between the control circuit and thyristers. The setup will

consist of linear ICs (OPAM) and digital IC microcontroller, PPI. Basically these are

low voltage and low power circuits. The power circuits which consist of thyristor is

high power circuit. Therefore it becomes necessary for the output channel of the gate

pulse generating circuit to be isolated from one another as well as from thyristers. The

isolation can be provided either by a small high frequency transformer or by an opt-

coupler ICs. Similarly control electronics which control the conduction period of each

OUTPUT FROM

ZCD OUTPUT TO

8255 ADC

51

thyristor, gives as output of very low power. In general in most of cases output power

is not sufficient to drive the gate directly. Therefore a amplifier circuit is required.

For isolation between control and power circuit, use of pulse transformer is

common. Figure 5.5 shows a driver and buffer circuit. A high frequency positive

pulse from an oscillator is applied to an AND gate continuously. These pulses are

enabled to reach the base of transistor only when the input drive control signal is high.

Transistor basically acts as a switch to energize the primary winding of the pulse

transformer corresponding to each pulse. In secondary winding pulses of almost same

strength are produced due to transformer action.

(a)

(b)

Fig. 5.7: Driver and Buffer circuit (a) circuit diagram, (b) photograph

GATE

PULSE

ISOLATION

TRANSFORMER OSCILATOR

GATE PULSES

FROM

MICROCONTROLLER

52

5.5 POWER UNIT CIRCUIT DESCRIPTION

The power circuit, which consist thyristors, is a high voltage circuit (normally

of the order of several hundreds of volts).

Power unit comprises of the following components:

1. Line commutated inverter and

2. Solar photovoltaic

5.5.1 Single Phase Fully Controlled Converter

Single Phase Fully Controlled Converter with RLE load is shown in Figure 5.8.

(a)

(b)

Fig. 5.8: Single Phase Fully Controlled Converter with RLE load (a) circuit diagram,

(b) photograph

SCR SNUBBER

CIRCUIT

53

CHAPTER 6

RESULTS AND DISCUSSION

6.1 ZERO CROSSING DETECTOR

The output of zero crossing detector is given in figure 6.1. output of zero

crossing detector is not only detecting the zero crossing of supply but also produce a

high pulse of 5 V corresponding to the positive cycle of the supply as given in figure

6.2. Negative pulse is blocked by diode.

Fig.6.1: Output of zero crossing detector

Fig.6.2: Output of Zero Crossing Detector as square wave

54

6.2 DELAY TIME CALCULATION

Timer clock frequency FC = 1/12 of the crystal frequency FXT;

Crystal frequency=11.0592 MHz

Fc= 11.0592 MHz / 12 = 921.6 kHz.

Time period Tc = 1/921.6 kHz = 1.085us.

Delay time = number of counts × 1.085us.

Calculation of the values to be loaded into the TL and TH registers:

(i) Required delay is divided by 1.085 us

(ii) Value obtained in (i) is subtracted from 65536

(iii)Value obtained in (ii) is converted into hex as ABCD

(iv) Load TL = AB and TH = CD

55

6.3 SYNCHRONIZATION

Control pulse generated by the microcontroller must be synchronized with

supply. If control pulse is not synchronized with supply frequency the power circuit

triggered wrongly. It is clear from the output shown in figure 6.3 that pulse generated

by microcontroller is synchronized with supply frequency.

(a)

(b)

Fig.6.3: synchronized pulse (a) synchronized with +ve cycle (b) synchronized with -

ve cycle

OUPUT OF ZCD CONTROL PULSE

56

6.4 TRIGGERING PULSES

The topology of inverter used in the proposed work is fully controlled full wave

inverter. This topology of inverter has bridge of four thyristers. Four triggering pulses

are required to trigger the thyristors of this topology. The thyristers T1 and T2 are

triggered simultaneously with same type of gate pulse G1 and G2 and other two

thyristers T3 and T4 required gate pulse G3 and G4 complementary to the gate pulses

of thyristers T1 and T2.

The control or triggering pulses generated experimentally various delay time is being

depicted below.

The converter circuit work as an inverter only when thyristers are trigger after

90 degree and there is an inductive load connected to circuit. Triggering pulse of any

delay can be generated by microcontroller by feeding suitable value to timer just by

changing the program without any change in hardware. The waveform record of

control pluses generated by controller for various time delays is given in Fig. 6.4, 6.5,

6.6, 6.7 and 6.8.

(a)

(b)

Fig.6.4: control pulse with 5ms delay (a) generated by controller for G1 and G2 (b)

generated by controller for G3 and G4

57

(a)

(b)

Fig.6.5: control pulse with 6 ms delay (a) generated by controller for G1 and G2 (b)

generated by controller for G3 and G4.

(a)

(b)



58

(a)

(b)



(a)

(b)



59

6.5 OUTPUT VOLTAGE WAVEFORM

The output wave forms obtained experimentally are given in figure 6.9 and

6.10. It is clear from the negative value of output voltage wave form that power is

being transferred to grid from the solar photovoltaic panel connected to the load side.

Fig. 6.9: Output Voltages and Load Current Waveform for different Triggering

angles

OUTPUT VOLTAGE LOAD CURRENT

60

Fig.6.10: Output voltage waveform and source current waveforms

SOURCE CURRENT VOLTAGE ACROSS LOAD

61

CHAPTER-7

CONCLUSIONS AND FUTURE SCOPE

7.1 CONCLUSIONS

The use of microcontroller based control circuit provides us large number of

advantages. It reduces size and cost of controller significantly. The efficient control of

delay angle is the main advantage.

Besides this it provide more versality and greater scope for further

improvement just by changing the program but not hardware configuration.

This work is carried out by breaking it into several steps for its smooth and

successful completion.

The first stage consisted of generating control pulse which corresponds to peak

power of solar photovoltaic module.

The first stage, a synchronized control pulse for an ac to dc converter/ inverter

for the full wave was generated. After getting satisfactory results then delay program

was changed to generate a control pulse whose delay angle was adjusted beyond 90

degree to operate converter in inversion mode, at this condition the converter supplies

the energy from solar photovoltaic cell to grid.

The developed relation between open circuit voltage and voltage corresponding

to maximum power point is unique for a module. Peak power tracked by this method

is very accurate.

. The performance of controller is found satisfactory. In general switching

control mode as well as specific application mode for solar photovoltaic grid

interactive inverter. The wave form records shows accuracy of delay of control pulse

and also show the satisfactory performance of whole setup.

62

7.2 FUTURE SCOPE OF THE WORK

Following study can be carried out in future:

1. Following analysis can be carried out before field implementation:

(i) Total harmonic distortion of grid power quality

(ii) Power inversion analysis

(iii) Developed method for tracking of Pmax implement experimentally

(iv) Cost analysis

2. Programming microcontroller for the grid interactive in all weather condition for

three phase system.

3. The developed relation between Voc and Vmpp should be derived by

experimental setup.

4. Controller can be used for the control of FACTS devices by little modification.

5. This controller can be applied in HVDC transmission.

63

LIST OF PUBLICATIONS

1. Zameer Ahmad and S.N. Singh, “ Modeling and Control of Grid Connected

Photovoltaic System-A Review” International Journal of Emerging Technology

and Advanced Engineering (ISSN 2250–2459, ISO 9001:2008 Certified Journal,

Volume 3, Issue 3, March 2013).

2. Zameer Ahmad and S.N. Singh, “Extraction of the Internal Parameters of Solar

photovoltaic Module by developing Matlab / Simulink Based Model” International

Journal of Applied Engineering Research, ISSN 0973-4562 Vol.7 No.11 (2012).

3. Zameer Ahmad and S.N. Singh, “Microcontroller Based Advanced Triggering

Circuit for Converters/Inverters” (Submitted).

64

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Documents

Dissertation:CONTROL OF GRID CONNECTED SOLAR PHOTOVOLTAIC SYSTEM