HIGHER HARMONICS ANALIZE IN LED DIODE LAMPS USED TO ILLUMINATION SCENERY

ELEKTRYKA 2011 Zeszyt 1 (217) Rok LVII Łukasz PUTZ, Ryszard NAWROWSKI Instytut Elektrotechniki i Elektroniki Przemysłowej. Politechnika Poznańska HIGHER HARMONICS ANALIZE IN LED DIODE LAMPS USED TO ILLUMINATION SCENERY Summary. The paper presents the use of electroluminescence diodes (LED). The structure and principles of operation of the diodes are presented. The paper shows positive and negative aspects of LED diode operation. Main part of the paper includes presentation of preliminary study of electroluminescent light sources taking into account generation of the higher harmonics. The results provided the plots of the voltage and current harmonics contents in the phase and neutral conductors. The characteristics obtained this way have been thoroughly analyzed. Keywords: higher harmonics, LED diodes LED lamps, operation of diodes, THD ratio ANALIZA WYŻSZYCH HARMONICZNYCH W LAMPACH LED UŻYWANYCH DO OŚWIETLENIA DEKORACYJNEGO Streszczenie. W artykule zaprezentowano zastosowania diod elektroluminescencyjnych (LED). Przedstawiono budowę oraz zasadę działania takich diod. Artykuł prezentuje także pozytywne i negatywne aspekty pracy diod LED. Część główną publikacji stanowi zaprezentowanie wstępnych badań na elektroluminescencyjnych źródłach światła w zakresie generacji wyższych harmonicznych. Na podstawie wyników pomiarów zostały sporządzone wykresy zawartości harmonicznych napięcia i prądu. Następnie dokonano szerokiej analizy uzyskanych charakterystyk. Słowa kluczowe: diody LED, działanie diod, lampy LED, współczynnik THD, wyższe harmoniczne 1. INTRODUCTION The electroluminescence diodes (i.e. LED Light Emitting Diodes) are modern light sources widely introduced to lighting industry. They replace traditional bulbs, halogens and fluorescent light sources for lighting homes. They are also used at outer illumination of buildings. The present automotive vehicles are as well provided with lighting diodes, inclusive of lighting the vehicle interior and the outer road lights. At present the

100 Ł. Putz, R. Nawrowski electroluminescent light sources are used in lighting of streets, replacing to growing degree the low and high pressure gas discharge lamps [7]. 2. THE LED DIODES DESIGN AND OPERATION The electroluminescent diodes are made in the form of a p-n junction composed of semiconductors of two types: the electron excess (N-egative) and electron defect (P-ositive) ones. The current flowing through the junction causes recombination of electrons that transit from the higher to basic energetic state. While passing to lower energetic state the energy excess is transformed into the electromagnetic radiation quanta that is observed as a light of the colour depending on the type of semiconductor used for the purpose. The design and operation of electroluminescent diodes are shown in Fig. 1 [1, 10]. Fig. 1. Design and operation of LED diodes [10] Rys. 1. Budowa i działanie diod LED [10] The diodes of cold colours (white, blue, green) are obtained by proper doping of four components: aluminum, gallium, indium, and nitrogen. The warm colours (red, orange, yellow) may be obtained similarly, replacing nitrogen with phosphor. Colour of the diodes affects the pattern of its voltage-current characteristics in the conduction direction, that approximates a silicon rectifying diode. Current conduction begins at various voltage values (Fig. 2) [1, 9]: 0.5 0.7V a silicon rectifying diode, 1.3 1.5V red diode, 1.8 2.0V yellow diode, 2.0 2.2V green diode.

Higher harmonics analize 101 Fig. 2. Voltage-current characteristics of LED diodes [9] Rys. 2. Charakterystyki napięciowo-prądowe diod LED [9] 3. INTRODUCTION FEEDING SYSTEMS OF LED LAMPS For proper operation of diode light sources an appropriate feeder is required. At present such feeders are based on specialized integrated systems. An example of a control feeding system based on the SP7600 integrated system from EXAR is presented in Fig. 3. Such controllers significantly improve the operation parameters of diode lamps, growing power efficiency and power factor. Simultaneously such a feedings have a better resistance to electromagnetic interference [3]. Fig. 3. LED feeder with Exar SP7600 integrated circuit [2] Rys. 3. Zasilacz LED z układem scalonym Exar SP7600 [2]

102 Ł. Putz, R. Nawrowski 4. THE CONCEPT OF HIGHER HARMONICS The term higher harmonics is assigned to sinusoidal voltage or current patterns the frequencies of which exceed the basic frequency (50Hz). The patterns superpose together resulting in distorting the basic sinusoidal shape. The k-th voltage (current) harmonics is defined as the ratio of multiplicity of the frequency of considered pattern to the basic sinusoidal frequency [7]: where: fk harmonic frequency, f1 basic mains frequency. Connection of nonlinear receivers to the power network results in distortion of the current pattern. On the other hand, the voltage drop occurring at the network impedance causes voltage distortion in the receiver connection point. The distorted voltage (current) disadvantageously affects other receivers connected to the same network, that, in consequence, is conducive to [4]: increase in active power loss in transformers and motors; perturbations in operation of power-electric security systems; wrong operation of electric power meters; overload of capacitor batteries; difficulties in electric arc extinction in case of earth shorting; additional heat loss in the supplying line. The distorted patterns of T period caused by the higher harmonics may be presented in the form of Fourier series expansion [6]: or where:

Higher harmonics analize 103 In order to appraise the degree of the pattern deformation the synthetic indexes are used, referred to as the distortion factors of the voltage or current harmonic distortion THDU and THDI (Total Harmonic Distortion), respectively [4]: where: U1 rms value of the basic voltage harmonic component, Uk rms value of further voltage harmonic components, I1 rms value of the basic current intensity harmonic component, Ik rms value of further current intensity harmonic components. 5. THE INVESTIGATE POSITION In order to find the level of higher harmonics generation emitted by the diode light sources used in housekeeping the LED diode from APOLLO Lighting has been tested. The tested diode is marked by manufacturer as LED-E27A12-WHT. It is a diode with a E27 screw-cap, supplied with alternate voltage 230V 50Hz and 1.2W power, white light emitting. The tests have been carried out in the Theoretical Electrical Engineering Laboratory of the Institute of Electrical Engineering and Industrial Electronics of Poznan University of Technology. For the measurement purposes a high class FLUKE 434/PWR Power Quality Analyzer of harmonic contents has been used (Fig. 4). It is a complete three-phase troubleshooting tool that measures virtually every power system parameter: voltage, current, frequency, power, energy consumption or power factor (cos φ), unbalance, and harmonics and inter-harmonics [8].

104 Ł. Putz, R. Nawrowski Fig. 4. The measurement diagram with Fluke 434 meter Rys. 4. Schemat pomiaru miernikiem Fluke 434 One can use Fluke 434/PWR meter to conduct energy consumption studies and electrical load analysis, and to perform power quality logging and analysis according to PN-EN 50160. From most important advantages of power quality meter it is possible to feature [8]: Captures events like dips and swells, interruptions and rapid voltage changes, based upon ½ cycle rms values; Auto Trend function gives a fast insight into changes over time; System Monitor function gives you an overview of power system performance. It also checks that incoming power complies to norm PN-EN 50160 limits or to user own custom specifications; Detailed, user-configurable long-term recording gives the MIN, MAX and AVG readings of different parameters on all phases. Averaging time can be selected down to 0.5 seconds (or 1 minute for 1 day s recording, 10 minutes for 1 week, 30 minutes for 1 month or more; Two groups of four channels: simultaneously measure voltage and current on all three phases and neutral; Auto Scaling function: easier trend analysis with automatic scaling of the vertical axis so user will always view the waveforms on a full display; Meets the stringent 600 V CAT IV, 1000 V CAT III safety standard required for measurements at service entrance; Extensive data analysis: cursors and zoom can be used live while taking the measurements, or offline on stored measurement data; The stored measurements can also be transferred to Power Log software on the computer by the infrared port (safety connecting between computer and meter) and then widely analyzed. The meter enables measuring percent contents of particular harmonic components H (until the 50th one), the harmonic contents THD factor and voltage or current direct

Higher harmonics analize 105 component (DC). Accuracy available in case of the FLUKE 434 analyzer reaches ±2.5 per cent in the measurement range 0 100% (for THD, DC, H1..H50) [8]. According to the norm PN-EN 50160, for the lighting equipment, total harmonic distortion factor for voltage (THD U ) can t exceed 8 percent. Instead for current total harmonic distortion THD I isn t clearly precise there are given acceptable levels each harmonics: second harmonic 2 percent, third harmonic 30 φ (power factor) percent, fifth 10 percent, seventh 7 percent, ninth 5 percent, eleventh to thirty ninth 3 percent [5]. 6. FINDINGS The measurement has been made for higher harmonics range. Other parameters of electric power have not been measured. The harmonics arising in the phase and neutral conductors have been separately recorded. Afterwards, the results obtained this way have been averaged in order to minimize the errors (Table 1) and, consequently, served for making the plots of percent contents of higher voltage and current harmonics, shown in Fig. 5 (the phase conductor) and Fig. 6. (neutral conductor). Analysis of the plots allows observing clear predomination of odd harmonics, both in case of voltage and current. The THD U factor is similar both for the phase and neutral conductors, being equal to 3.7 and 3.3%, respectively. It might be said that it is a satisfying value the pattern of actual voltage value is only slightly distorted as compared to the sinusoidal shape. The contents of constant component in the voltage pattern is quite insignificant (0.1 percent). The bigger attention turns the plots of harmonic contents of current intensity. Same as in case of voltage becomes visible the domination of odd harmonics. However the basic harmonic of the phase conductor is no longer dominating, because amounts 57,5 percent (for voltage it was 99,9 percent). In effect we have a large total harmonic distortion factor of current THD I = 59,3 percent. In the neutral conductor we can see the phenomenon of the current rectification. The curve of current intensity is widely deformed from the sinusoid (THD I = 90,3%), became straight the content of constant component amount 95,9 percent. One can declare that the stabilizing structure inside the LED lamp realize his role very well. However it influence wrong on the energetic network by the generating higher harmonics of current intensity and deform the current curve.

106 Ł. Putz, R. Nawrowski Component The higher harmonics contents measuring results Percent contents of THD factor, constant component DC and each harmonics (1 50) [%] Phase conductor L1 Neutral conductor N Table 1 Voltage U Current I Voltage U Current I THD 3,7 59,3 3,3 90,3 DC 0,1 23,7 0,1 95,9 1 99,9 57,5 99,9 4,8 2 0,1 16,3 0,3 1,8 3 2,5 22,2 2,2 1,9 4 0 6,4 0,1 1,6 5 2,5 13,3 2,1 2 6 0 5,3 0 1,8 7 0,9 7,9 0,9 1,5 8 0 3,9 0,1 1,7 9 0,5 6,1 0,3 1,6 10 0 4,9 0 1,4 11 0,2 6,8 0,2 1,7 12 0 4,8 0 1,6 13 0,4 6,4 0,3 1,6 14 0 4,2 0 1,7 15 0,5 6,1 0,3 1,8 16 0 4,5 0 1,4 17 0,1 6,2 0 1,8 18 0 3,8 0 1,9 19 0,2 4,7 0,1 1,5 20 0 4,1 0 1,7 21 0,2 4,9 0,1 1,7 22 0 4,1 0 1,7 23 0 4,2 0 1,7 24 0 3,9 0 1,7 25 0,1 4 0,1 1,8 26 0 4,2 0 1,8 27 0,1 4,3 0 1,6 28 0 4,3 0 1,6 29 0 4,1 0 1,5 30 0 4,5 0 1,5 31 0 3,6 0 1,6 32 0 4,6 0 1,6 33 0 4,2 0 1,7 34 0 4,6 0 1,7 35 0 4,3 0 1,6 36 0 3,8 0 1,6 37 0 4,2 0 1,7 38 0 3,9 0 1,6 39 0 4,4 0 1,6 40 0 4,1 0 1,5 41 0 3,9 0 1,7 42 0 4 0 1,5 43 0 3,9 0 1,6 44 0 3,9 0 1,6 45 0 4,1 0 1,5 46 0 3,6 0 1,5 47 0 3,6 0 1,5 48 0 3,7 0 1,5 49 0 4,2 0 1,7 50 0 3,3 0 1,1

Higher harmonics analize 107 Fig. 5. Percent harmonics contents in the phase conductor Rys. 5. Procentowa zawartość harmonicznych w przewodzie fazowym Fig. 6. Percent harmonics contents in the neutral conductor Rys. 6. Procentowa zawartość harmonicznych w przewodzie zerowym

108 Ł. Putz, R. Nawrowski 7. SUMMARY The use of electronic systems with a view to stabilizing operation of the lighting diodes, apart from its many advantages has one important fault it generates higher harmonic component. The systems of diode lamps emit higher order harmonics to the network, giving rise to important hazard. This phenomenon would not be very significant without the fact that the electroluminescent lighting is more and more commonly used and may become soon a basic light source. In effect the distortion of voltage and current introduced to energetic network are more and more greater, causing increasing of the THD factor in points of the electrical energy distribution. It is necessary to use the special devices to reducing higher harmonics. It is also possible that using nonlinear elements, like LED lamps, will force the legislators to introduction of changes in the present norm PN-EN 50160. The tests referred to in the present paper only depict the scope of the knowledge on generation of higher harmonics by the electroluminescent light sources. The subject is very wide and requires further experiences and studies with the use of various types of the LED lamps [6]. BIBLIOGRAPHY 1. Collective Work: Technika świetlna 09. Poradnik Informator. Polish Lighting Committee of SEP. Warsaw 2009. 2. Datasheet of EXAR SP7600 Integrated Circuit. 3. Gondek J., Kordowiak S.: Cyfrowe sterowniki hybrydowe LED. Materials of XIII Scientific Conference Computer Applications in Electrical Engineering. Poznan 2008. 4. Lubierski K., Nawrowski R.: Badanie harmonicznych generowanych przez wyładowcze źródła światła. Materials of Conference Polish-Ukrainian School-Seminar. Jawor-Solina 2000. 5. Polish European Norm PN-EN 50160. 6. Putz Ł.: Generating higher harmonics in LED diode lamps used in housekeeping. Materials of XI International Conference Computational Problems of Electrical Engineering. Lazne Kynzvart 2010. 7. Putz Ł.: Oświetlenie elektroluminescencyjne a emisja wyższych harmonicznych. Materials of XV Scientific Conference Computer Applications in Electrical Engineering. Poznan 2010. 8. User Manual of FLUKE 434/PWR Power Quality Analyzer. 9. www.elektroda.pl (2011.02.01.). 10. www.en.wikipedia.org (2011.02.01.).

Higher harmonics analize 109 Wpłynęło do Redakcji dnia 20 września 2011 r. Recenzent: Prof. dr hab. inż. Marian Pasko Omówienie W artykule zaprezentowano zastosowania diod elektroluminescencyjnych (LED). Przedstawiono budowę oraz zasadę działania diod oraz pokazano przykład układu stabilizująco zasilającego dla lampy LED. Artykuł prezentuje także pozytywne i negatywne aspekty pracy diod LED. W artykule przedstawiono także podstawy teorii wyższych harmonicznych oraz skutki ich działania. Część główną publikacji stanowi zaprezentowanie wstępnych badań na elektroluminescencyjnych źródłach światła w zakresie generacji wyższych harmonicznych. Do pomiarów użyto analizatora jakości energii Fluke 434/PWR. Źródłem światła, które wykorzystano do badań, była lampa LED firmy Apollo Lighting LED- E27-A12-WHT. Na podstawie wyników pomiarów zostały sporządzone wykresy zawartości harmonicznych napięcia i prądu. Następnie dokonano analizy uzyskanych charakterystyk.