Use Of Advanced Unipolar SPWM Technique For Higher .

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2nd International Conference on Multidisciplinary Research & PracticeP a g e 161Use of Advanced Unipolar SPWM Technique forHigher Efficiency High Power ApplicationsNaman Jadhav, Dhruv ShahInstitute of Technology, Nirma UniversityAbstract—In high power applications like SONAR, PWMtechniques are essentialto control high power as well as to reduceswitching losses. The primary reason for preferring sinusoidalPWM is that our final need is a sinusoidal output. Hence, we usesinusoidal wave as reference wave. Sampling it with triangularwave of high frequency would ensure nearly sinusoidal wave onoutput side. The unipolar PWM which is one of the twocommonly used types of SPWM is better suited for theapplications mentioned. However, it faces problem of dead shortcircuit as two switches of same leg would be ON simultaneously.A modification under the name of advanced unipolar PWMtechnique is introduced and presented. The simulation andhardware implementation of same is also depicted usingMATLAB while a microcontroller board (Arduino Uno, in thiscase) is used to implement the embedded code generation. Theuse of the microcontroller board further adds to the advantageswhen compared to the conventional method. The modifiedtechnique has been explained in the paper.Keywords—Unipolar SPWM, Dead band, Advanced UnipolarPWM, Sinusoidal Pulse Width modulation, Total harmonicdistortion.I. INTRODUCTIONIn a highly competitive world of constantly improvingefficiencies and reducing costs, what may have onceseemed as revolutionary would soon seem obsolete. As aresult, the onus falls upon today's engineers to either comeup with new technologies that can outmatch their currentcounterparts or build upon the current technology toimprove their performance. Inverters, both single and threephase, have now become an indispensable part of ourhouseholds as well as industries. Thus, any scheme thatimproves the output attained and specialises it according tospecific applications will always be welcome. AdvancedUnipolar SWPM, introduced in this paper is one suchmethod.PWM is basically adjusting the on and off periods of pulses ofconstant amplitude, in order to gain inverter output voltagecontrol and to reduce its harmonic content. The main factorsfor PWM control are: Duty CycleFrequencyDuty cycle is the ratio of the high (on) time of a pulse in acycle to the total time period of that cycle. Frequency is themeasure of how quickly the PWM completes one cycle. If thefrequency and the duty cycle are high enough, the outputappears as an analog signal.In general, the longer the on period of a switch, the higher thepower supplied to the load and vice versa. A plus point forPWM is that the power lost in switching is fairly low. Whenthe switch is on, the voltage across it is ideally zero, whilewhen it is off, the current flowing through it is negligible.Thus, the product of current and voltage, which amounts tothe power loss, is almost equal to zero.PWM signals are used in a variety of control applications. It isgenerally used for DC motors, but can be used to controlvalves, pumps, fans etc. as well as in communication circuitsfor encoding to convey information. The frequency and dutycycle of the PWM signals depend on the response and thedesired performance of the application.C. Advantages of PWMII. NEED FOR PWMA. History of PWMThe advantages of using the PWM technique are: Lower power dissipation, Relative ease of implementation and control The output voltage control can be obtained withoutany additional componentsMany applications require us to control the output voltagelevels by supplying partial power from a fixed input powersource. This was conventionally accomplished by using arheostat in series to dissipate the excess power. ThisVolume III Issue Itechnique worked satisfactorily well for low powerapplications but would result in high losses for largesystems. Thus, an efficient and cheaper method was requiredfor switching that could better control an Eboard.Fig 6Hardware ImplementationThis output works as supply for gate driver IC (TLP 250 in thiscase). This IC serves two purposes. First, isolation betweenpower and control circuit. Secondly, it amplifies the signalsfrom Arduino UNO board from 5V to 15V to drive MOSFETs.One gate driver IC for each MOSFET is used. The input to gatedriver ICs are pulses from Arduino UNO board with resistor(330Ω) in series to limit the current to photo LED of TLP250.The middle section at the uppermost side is having connectorsfor pulses from Arduino UNO board. The output of gate driverIC is given across gate and source terminal of each MOSFET.In the last section i.e. Power circuit, the MOSFETs areconnected in H bridge topology. Connector is provided forinput DC voltage. Across the H bridge resistor of (100 Ω, 10W)is connected, across which output voltage waveform is observedin digital storage oscilloscope.Output voltage waveforms for different frequencies oftriangular wave are as follows.D. Hardware circuitry and Output voltage waveform (usingArduino Uno board)Here, in this hardware circuit there are basically threesections. Fig 7. For carrier frequency 600Hz and modulation index 0.9Isolated DC power supplyGate driver circuitPower circuitThe left most section is for isolated DC power supply forgate driver IC. The input is 18V AC. With use of bridgerectifier, capacitor and constant voltage IC (7815) we get15V at the output side.Fig 8.For carrier frequency 300Hz and modulation index 0.9As can be observed, these are similar to the pulses obtainedby conventional unipolar technique.Volume III Issue IIJRSIISSN 2321-2705

2nd International Conference on Multidisciplinary Research & PracticeV. APPLICATIONSAs has been mentioned, for low power applications, thepower loss and the lack of control due to inferior techniquessuch as using a rheostat or single pulse PWM do notsignificantly affect the output. Here, the main factor is thesimplicity of design and overall cost reduction.However, for sizeable applications where efficiency is one ofthe main parameters and small discrepancies in voltagecontrol can lead to large losses, accurate and efficientmethods such as advanced unipolar SPWM may be used.One such application is SONAR,[5] which is the SOundNavigation And Ranging used for underwater detection.Here, as high power tens of kilowatts are to be delivered byeach unit, this method can be particularly useful.Furthermore, the ability to control parameters like outputfrequency, voltage and power would be an added bonus.VI. CONCLUSIONSWe can now safely claim that advanced unipolar helpscombine the advantages of conventional unipolar whiletaking care of the problem of dead short circuit. Thus, forsystems that need a high level of efficiency and can affordthe extra complexity and costs, this scheme is a viableVolume III Issue IP a g e 165option.ACKNOWLEDGMENTWe would like to thank the Electrical department of Instituteof Technology, Nirma University for providing us with theequipments and technical assistance for the hardware. Wewould also like to thank our teachers, friends and family fortheir constant support and encouragement.REFERENCES[1][2][3][4][5]IJRSIP. S. Bhimbra (2006), Power Electronics, Khanna PublishersM. H. Rashid, (2012). Power Electronics. Pearsons PublicationsB. Ismail,S.Taib MIEEE, A. R Mohd Saad, M. Isa and C. M. Hadzer.“Development of a Single Phase SPWM Microcontroller-BasedInverter”. First International Power and Energy Conference on 2006,November 28-29, 2006, Putrajaya, Malaysia.Bin Wu, (2006). High-power converters and ac drives.A John Wiley &Sons, Inc., PublicationBineesh P. Chacko, V. N. Panchalai, N Sivakumar. “ModifiedUnipolar Switching Technique for PWM Controlled Digital SonarPower Amplifier” in International Journal of Engineering andInnovative Technology (IJEIT) Volume 3, Issue 5, November 2013.ISSN 2321-2705

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