ABSTRACT
Modern electrical devices such as Compact Fluorescent Lamp (CFL), many of which are non-linear loads inject harmonics into the Power Distribution Network (PDN). For the devices to operate efficiently as well as reduce electricity consumption and environmental impacts without introducing undesirable side effects, such as harmonics into the distribution network, the devices performance need to be analyzed. CFL has highest penetration level of about 80% compared to other lighting devices. The current and voltage Total Harmonics Distortion (THDi and THDv) being emitted by CFL are within the range of 90% – 200% of the fundamental current and 20% – 40% of the fundamental voltage respectively. These harmonics cause power quality problems such as overheating of Distribution Transformer (DT) and low tension conductors, mal-operation of energy meter, deterioration of protective equipment. The combined effects of these small sources are as detrimental as one large source. Mitigation of these harmonics is even harder once injected into the network due to their distributed nature. Consequently, this research work modeled and simulated compact fluorescent lamp for the analysis of harmonics injections into power distribution network. A suitable method was also developed for mitigating the harmonics emissions before they are injected into the distribution network with the view to mitigating their effects. Linear Technology Spice (LTspice) software package was used to generate voltage and current waveforms. The acquired waveforms were used to simplify the Fast Fourier Transform (FFT) harmonics analysis generic algorithm, which was found to be simpler than the generic. Analysis of the CFL harmonics was carried out using the simplified algorithm; LTspice software as well as powergui analyzer software on MATLAB R2012a. The results obtained for THDi and THDv were in relation to the CFL fundamental current and voltage: 135.50% and 35.43%; 130.13% and 33.64%; as well as 130.08% and 36.55% with simplified FFT harmonics analysis algorithm, LTspice software, and Powergui harmonics analyzer respectively. The results were
vii
observed to be in agreement with laboratory test bed results which were averagely 128.90% and 31.60% of the fundamental current and voltage for THDi and THDv respectively. These results were found to be violating the IEEE standard limits for harmonics. Analog passive series and shunt filter networks were also developed. CFL Simulink models with the series and shunt passive harmonics filters networks were developed. The FFT harmonics analyses results of the developed Simulink models were: 9.54% and 5.00% of the fundamental current and voltage for the THDi and THDv with the series filters; 3.65% and 0.05% of the fundamental current and voltage respectively were obtained with the shunt filters. It was observed that the levels of reductions of THDs of the CFL were in compliance with the IEEE 519-2014 standard harmonics limits.
TABLE OF CONTENTS
Declaration …………………………………………………………………………………………….i
Certification …………………………………………………………………………………………….ii
Dedication ………………………………………………………………………………………..iii
Acknowledgements ………………………………………………………………………………iv
Abstract ……………………………………………………………………………………………v
Table of Contents ……………………………………………………………………………………..vii
List of Figures ………………………………………………………………………………………..x
List of Tables ……………………………………………………………………………………xii
List of Plates ……………………………………………………………………………………xiii
List of Appendices………………………………………………………………………………xiv
List of Abbreviations ……………………………………………………………………………xv
CHAPTER ONE: INTRODUCTION
1.1 Background ………………………………………………………………………………………1
1.2 Problem Statement …………………………………………………………………………..6
1.3 Justification of the Research …..…….………………………………………………………7
1.4 Aim and Objectives …………..…….………………………………………………………..7
CHAPTER TWO: LITERATURE REVIEW
2.1 Review of Fundamental Concepts ……………………………………………………………8
2.1.1 Power system ……………………………………………………………………………….8
2.1.2 Harmonics in power system …………………………………………………………………..9
2.1.3 Power factor …………………………………………………………………………………11
2.1.4 Productions of harmonics …………………………………………………………………12
2.1.5 Types of harmonics …………………………………………………………………………….14
ix
2.1.6 Concept of wave distortion …………………………………………………………………….14
2.1.7 Methods of harmonics analysis ……………………………………………………………16
2.1.8 Methods of harmonics emission mitigation …………………………………………………25
2.2 Review of Similar Works …………………………………………………………………..29
CHAPTER THREE: MATERIALS AND METHODS
3.1 Introduction ……………………………………………………………………………………..35
3.2 Materials ……………………………………………………………………………………35
3.2.1 Personal computer …………………………………………………………………………35
3.2.2 Compact fluorescent lamp……………………………………………………………………35
3.2.3 Power and harmonic analyser ……………………………………………………………….36
3.2.4 Current probe ………………………………………………………………………………36
3.3 Method ………………………………………………………………………………………36
3.3.1 Acquisition of compact fluorescent lamp circuit diagram …………………………………36
3.3.2 Linear technology spice software ………………………………………………………………….36
3.3.3 Current and voltage waveform characterization …………………………………………..37
3.3.4 Fast Fourier transform harmonics analysis ………………………………………………..40
3.3.5 Development and implementation of harmonic passive filters ……………………………43
3.3.6 Experimental Fixed-bed harmonics measurements….……………………………………..50
3.4 Conclusion ………………………………………………………………………………….50
CHAPTER FOUR: RESULTS AND DISCUSSIONS
4.1 Introduction ……………………………………………………………………………………..52
4.2 Simplified FFT Algorithm CFL Harmonics Analysis Results …………………………..52
4.3 LTspice FFT Harmonics Analysis Results …………………………………………………….53
4.4 CFL Simulink Model FFT Harmonics Analysis Results ………………………………..54
x
4.5 Passive Harmonics Filters Results ………………………………………………………………55
4.5.1 Series passive harmonics filter network results ……………………………………………56
4.5.2 Shunt passive harmonics filter network results ……………………………………………57
4.6 Experimental Fixed-bed Results………………………………………………………………….59
4.7 Results Summary …………………………………………………………………………..59
4.8 Results Validation ………………………………………………………………………….60
4.9 Conclusion ………………………………………………………………………………………62
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION
5.1 Introduction …………………………………………………………………………………63
5.2 Discussions on Results ……………………………………………………………………..63
5.3 Conclusion ………………………………………………………………………………………64
5.4 Significant Contributions of the Research …………………………………………………64
5.5 Recommendations for Further Works ………………………………………………………….65
References ………………………………………………………………………………………66
Appendices …………………………………………………………………………………………71
xi
CHAPTER ONE
INTRODUCTION
1.1 Background
In recent time there has been considerable increase in the number of Compact Fluorescent Lamp CFL connected to electrical power distribution network. From the viewpoint of the electric utility industry, it is important to understand the impacts of such devices on distribution network.
Compact Fluorescent Lamp is an extension of Fluorescent Lamp (FL). CFL is designed to replace Incandescent Lamp (IL) and fit into most existing light fixtures especially those for the IL (Mansurali and Swamynathan, 2014). This is due to the following advantages of Compact fluorescent lamps (CFLs) over Incandescent Lamps (ILs) (Cunill-Solà and Salichs, 2007 and Singh and Katal, 2013):
i. CFLs are cost efficient.
ii. CFLs are energy efficient.
iii. CFL has longer lifespan (10,000hrs).
Due to the above listed advantages of CFL, the lamps are being promoted by governments and electricity supply utilities worldwide as part of energy conservation program (Jabbar et al., 2008). CFLs are increasingly being used for residential and commercial applications, retrofitting a large number of IL and other lighting devices.
One major disadvantage of CFL is that it increases level of disturbances that might affect customer as well as utility equipment on the distribution system, (Pourarab et al., 2011). This is due to the fact that it emits and injects harmonics into the power distribution network. Power System harmonic is a sinusoidal component of a periodic wave having a frequency that is an integral multiple of the power system fundamental frequency (Feng et al., 2013).
2
Figure 1.1: Block Diagram of CFL Operation Stages
CFL operates through chemical reaction unlike IL that operates through heating (Singh and Katal, 2013). Every CFL uses Electronic Ballast (EB) circuit to generate a high frequency within the range of 10 kHz to 40 kHz which in turn enables the tube to emit visible light from its inner coating (Jabbar et al., 2008). In other words, EB of the CFL uses rectifier to input power to an inverter which in turn supplies necessary AC power to the lamp, (Singh and Katal, 2013). The phenomena of ballast circuit are the major sources of harmonics in CFLs. It is responsible for rise in harmonics current injections into the electrical power distribution Network. A typical CFL consists of three main parts as in Plate 1.1. The screw base and housing which holds the unit firm in a lighting fixture, it also serves as neutral for the supply to the lamp as well as houses the electronic ballast circuit. The electronic ballast circuit which supply and maintain sufficient current in the lamp circuit. Finally, the lamp emits visible light.
Plate 1.1: CFL Three Main Parts (Oramus et al., 2013).
The operation of CFL is carried out in three main stages based on the works of Shafi et al., (2007) and Moulahoum et al., (2013) as in Figure 1.1.
AC supply
Rectification stage
Inverter stage
Output stage
3
The first stage is rectification stage. This stage consists of a full bridge diode rectifier circuit that converts AC to DC. A series resistor RF which serves as current peak limiting component and a fuse for protection is connected at the input side to this stage. The DC obtained at the stage is filtered by a capacitor CBus to provide a smooth DC voltage for the resonant inverter in the second stage known as inverter stage. The lamp in the last stage (Output stage) is powered by the inverter. The resulting frequency at this stage which self-oscillates between 10 – 40 kHz is associated with high voltage which provides an invisible light that strike the coating in the inner side of the tube. The coating emits visible light for the normal operation of the lamp. The electronic configuration of the stages is in Figure 1.2 (Shafi et al., 2007 and Moulahoum et al., 2013). A Positive Temperature Coefficient (PTC) device (Thermistor) is connected by some manufacturers across the terminals of the lamp to prolong tube life span (Oramus et al., 2013).
Figure 1.2: A Typical CFL Circuit (Shafi et al., 2007 and Moulahoum et al., 2013)
Compact fluorescent lamp generates harmonics during its operation. According to Nassif and Acharya, (2008) and Oramus et al., (2013), the current and voltage total harmonics distortion of most commercially available CFL are within the range of 90 – 200% and 20 – 45% respectively with a corresponding power factor within the range 50 – 65%. However, the current and voltage THD limits of the CFLs with electronic ballasts according to Institute of Electrical and Electronics
4
Engineers (IEEE) Std. 519-2014 and International Electro technical Commission (IEC) are 20 % and 8% (Niitsoo, 2011). Harmonics are usually a superposition of signals which are multiples integer of power system fundamental frequency (50Hz or 60Hz as the case may be); they can be voltage or currents (Jabbar et al., 2008, Elphick et al., 2010 and Ndungu et al., 2012,). The harmonics being generated by CFL are due to the conversion of the frequency from one low level to a much higher level (50 or 60 Hz to 80 kHz), (Jabbar et al., 2008 and Teodosescu et al., 2012). Therefore, proliferation of CFLs increases the harmonics level in power distribution system that could adversely affect the system as well as the consumers (Pourarab et al., 2011).
Some of the effects caused by harmonics to the power system are (Fehér and Puklus, 2007):
A. Distorted line current
i. Reduced power factor means reduced available power, increased distribution losses (exacerbated by sky and proximity effects).
ii. The third harmonics means excessive current in neutral conductor (danger of fire).
iii. Overheating of transformers and generators (copper losses).
iv. Increased audio noise, increased telephone interference.
B. Distorted Line voltage (caused by distorted line current due to the presence of distribution
impedance)
i. Overheating of transformers and generators (increased iron losses).
ii. Cogging (refusal to start smoothly) and crawling (very high slip) in induction motors;
mechanical oscillations.
iii. Overheating of Power Factor correcting capacitors (premature failure).
iv. Dielectric stress in insulation systems.
v. Resonances (overvoltage insulation failure).
vi. Impaired performance of power-line communication systems.
5
In summary, harmonics if not mitigated affect power quality of the entire distribution system through (Rawa et al., 2015):
i. Increase in voltage distortion.
ii. Equipment failure.
iii. System resonance.
iv. Increase system losses.
v. Decrease system efficiency.
Some researchers attempted to provide platform for the harmonics being generated by CFLs to be quantified for its mitigation before it is injected into the network (Molina et al., 2014). This is because, if the harmonics are not mitigated and once injected into Distribution Network (DN) is difficult to do so and this could seriously affect the performance of the Power Distribution Network (PDN) (Ingale, 2014).
Some previous works on modeling of the CFL for harmonic analysis used laboratory test bed to take measurements of the harmonic emissions of individual or grouped CFLs in order to provide platform to analyze harmonics. This method is associated with challenge of cut-off of harmonics being injected to the lamp by the distribution network through the AC current being drawn by it. This affects accuracy of the overall results. In order to clearly quantify the harmonics produced by CFLs precisely, a more appropriate procedure for modeling the lamp is required, (Rawa et al., 2014).
Other researchers carried out harmonic analysis in frequency domain. In the method of harmonic analysis in frequency domain, the principle of superposition is applied to enable each harmonic to be considered separately. The differential equations obtained are usually converted to complex algebraic equations. These equations are then represented by complex phasor either in rectangular
6
or polar form. Even though this method was said to have advantage of computational efficiency, it is complex.
In view of the above, this research modeled and simulated compact fluorescent lamp for analysis of harmonics injection into power distribution network using software packages (LTSpice and MATLAB R2012a) and developed an appropriate method of the harmonics emission reduction with the view to mitigating their injection into the power distribution network.
1.2 Problem Statement
Harmonics distortion in power systems has been attracting significant attention of researchers recently. This is largely due to the mass use of nonlinear loads such as CFL which increases problem with the network voltage and current distortion (Molina and Sainz, 2014). CFL emits and injects harmonics into the Power Distribution Network (PDN) (Molina and Sainz, 2014). Power System (PS) harmonics are multiple integer of the fundamental power system frequency. The combined effects of the wide use of CFLs can be just as detrimental as one large harmonics source (Yong et al., 2010). Moreover, mitigation of harmonic distortions caused by nonlinear load such as the CFL is very difficult once they are injected into power distribution network (Watson et al., 2007). Therefore, this research modeled and simulated compact fluorescent lamp for the analysis and mitigation of harmonics emissions before they are injected into power distribution network.
1.3 Justification of the Research
The research is carried out with the view to reducing CFL current and voltage harmonics injections into power distribution network to conform to the IEEE-519 2014 standard limits. This effort will improve power quality of the network by reducing losses, overheating of equipment, avoiding system resonance etc. It will also improve the power quality of the lamp and this will help
7
consumers making some savings for not replacing the lamp at a shorter life span as mentioned by the manufacturers.
1.4 Aim and Objectives
The aim of the research is modeling and simulation of compact fluorescent lamp for the analysis and mitigation of harmonics injection into power distribution network.
The objectives of the research are to:
i. develop CFL model and determine its current and voltage total harmonics distortions being
injected into power distribution network.
ii. develop analog passive harmonics filter network for the CFL harmonics injections mitigation.
iii. validate results obtained through comparison with measured values from experimental fixed-
bed.
IF YOU CAN'T FIND YOUR TOPIC, CLICK HERE TO HIRE A WRITER»
