Sinusoidal And Space Vector Pulse Width Modulation For .

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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013Sinusoidal and Space Vector Pulse WidthModulation for InverterK. Mounika#1, B. Kiran Babu 2#Final Year B. Tech, Dept. of EEE, KL University, Vaddeswaram, AP, IndiaAssistant professor, Dept. of EEE, KL University, Vaddeswaram, AP, IndiaAddress Abstract- Inverters inherently have the property ofcontrolling output frequency but the output voltage can’t be varied. Usually to vary output voltagewe have to vary supply voltage which is not alwayspossible for this reason PWM techniques gainedmomentum. Basic aim of PWM technique is tocontrol output voltage and harmonic reduction.Pulse-width modulation (PWM), or pulseduration modulation (PDM), is a commonly usedtechnique for controlling power to inertial electrical devices, made practical by modern electronicpower switches. Here we apply PWM techniqueslike Sinusoidal pulse width modulation (SPWM)and Space Vector Pulse width Modulation(SVPWM) to inverter and study its performance.In Sinusoidal Pulse width modulation(SPWM) we generate the gating signals by comparing a sinusoidal reference signal with a triangular carrier wave. In Space vector Modulation(SVPWM) we consider a rotating phased which isobtained by adding all the three voltages. Modulation is accomplished by switching state of an inverter. Thus by comparing these two techniqueswe study the performance of our inverter.2. External control of dc input voltage.3.Internalcontrolofinverter.In external type of control, circuit becomes bulky,costly and complicated so we go for internal controlof inverter. In internal control inverter output voltagecan be adjusted by exercising the control within theinverter itself. The two possible ways of doing ulationcontrol.Pulse-width modulation (PWM) [2] uses a rectangular pulse wave whose pulse width is modulated resulting in the variation of the average value of thewaveform. The simplest way to generate a PWMsignal is the interceptive method, which requires onlya saw tooth or a triangle waveform (easily generatedusing a simple oscillator) and a control wave. Whenthe value of the reference signal is more than themodulation waveform, the PWM signal is in the highstate, otherwise it is in the low state. The inverteroutput voltage is determined in the following: When Vcontrol Vtri, VA0 Vdc/2When Vcontrol Vtri, VA0 Vdc/2Keywords - PWM (pulse width modulation),SPWM (sinusoidal pulse width modulation) andSVPWM (space vector pulse width modulation).I. INTRODUCTIONInverter is usually a device which converts DC powerinto AC power. In many industrial applications, it isoften required to vary output voltage of inverter [1]due to the following reasons: 1.To compensate for thevariations in input voltage.2.To compensate for theregulation of inverters.3. To supply some specialloads which need variation of voltage with frequency.The various methods for the control of output voltageare: 1. External control of ac output voltage.ISSN: 2231-5381II. SINUSOIDAL PULSE WIDTH MODULATIONIn single-pulse and multiple pulse modulation techniques the width of all pulses are same but in sinusoidal pulse width modulation the width of each pulseis varied in proportion to theamplitude of a sinewave. In this technique the gating signals are generated by comparing a sinusoidal reference signal witha triangular carrier wave. The DF and LOH [3] arereduced significantly. The output voltage is obtainedfrom the mat lab results. The DF and LOH are measured by using FFT analysis. The gating signal for thehttp://www.ijettjournal.orgPage 1012

International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013inverter is obtained by taking the repeating sequence(triangular wave)as the control signal andcomparing it with the reference wave(sinusoidalwave).In order to detect or eliminate the zero sequence currents we use zero hold circuit and by comparing the with the help of greater than or equal toblocks.III.SIMULATION CIRCUIT FOR SINUSOIDALPWMV. SIMULATION CIRCUIT FOR SVPWMFig:2 circuit for svpwmVI. IMPLEMENTING SVPWMFig:1 Circuit for sinusoidal pwmIV. SPACE VECTOR PULSE WIDTH MODULATIONSpace vector modulation is a PWM control algorithm[8] for multi-phase AC generation, in which the reference signal is sampled regularly; after each sample,non-zero active switching vectors adjacent to the reference vector and one or more of the zero switchingvectors are selected for the appropriate fraction of thesampling period in order to synthesize the referencesignal as the average of the used vectors. The topology of a three-leg voltage source inverter is Because ofthe constraint that the input lines must never beshorted and the output current must always be continuous a voltage source inverter can assume onlyeight distinct topologies. Six out of these eight topologies produce a nonzero output voltage and areknown as non-zero switching states and the remaining two topologies produce zero output voltage andare known as zero switching states.ISSN: 2231-5381The SVPWM [4] can be implemented by using wither sector selection algorithm or by using a carrierbased space vector algorithm. The types of SVPWMimplementations are: a) Sector selection based spacevector modulation b) Reduced switching Space vector modulation c) Carrier based space vector modulation d) Reduced switching carrier based space vectormodulation.VII. STEPS TO IMPLEMENT SVPWM, THECONVENTIONAL METHOD1) The sector in which the tip of the reference sectoris situated is to be determined from the instantaneousphase references Va *, Vb * and Vc* Va *, Vb *, Vc * v ,v Tan-1(v /v ) - k(600) ; k such that 60 0Sector number k 12) Computation of T1 and T2; here lookup tables areneeded to know the values of Sin (600- ) and Sin 3)Determinationofswitchingvectors.4) Assert the appropriate control signals to affect therequiredswitchingaction.From this analysis, the space vector modulation taskcan be solved into following steps to make actualPWM pattern.http://www.ijettjournal.orgPage 1013

International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013Step-1: Sector identificationBy comparing the stationary frame d-q componentsof the reference voltage vector, the sector where thereference voltage vector is located is identified.Step-2: Calculating the effective timesThe imaginary switching periods Tas, Tbs and Tcs aredefined as: T T T Tas s va* ; Tbs s vb* ; Tcs s vc* Vdc Vdc Vdc Using the d-q components of the reference voltagevector, a sine loop voltage and a dc-link voltage information, the effective times T1, T2 are calculated.Instead of the sine table, to reduce the calculationtime, another look-up table which contains the corresponding to each sector number may be used.The active vector switching times T1 and T2 in sector1 may be expressed as:Step-3: Determining the switching statesT1 Tas Tbs ; T2 Tbs TcsUsing the corresponding sector information the actualswitching time for each inverter leg is generated fromthe combination of effective times and zero sequencetime. Equating volt-seconds along the -axis:( Vsr cos )* Ts Vdc* T 1 (Vdccos600 ) * TsEquating volt-seconds along the -axis:( Vdc sin600 ) * T2( Vsr sin ) * Ts Solving the above two simultaneous equations, onegets:T1 T v sr T s sin( / 3 )V dc sin( / 3 ) v sr T s sin V dc sin( / 3 ) 22Ts [v sin( / 3) v cos( / 3)]3Vdc; T2 2Tsv 3VdcSubstitutingv v 32v*a Tmax TminThe offset time, Toffset required to distribute thezero voltage symmetrically during one sampling period is given by:T0 Tmin2The actual switching times for each the inverterleg can be obtained by the time shifting operation asfollows:Tga Tas Toffset; Tgb Tbs Toffset; Tgc Tcs ToffsetVIII. DC-BUS UTILIZATION WITH SVPWMThe principal advantage of the SVPWM over SPWMis that it enhances the DC bus utilization [6] by about15%. It is instructive to evaluate the sample-averagedpole voltage of a phase, V AO for instance, to understand this fact.3( v b* v c* )2Ts (va* vb* )Ts (vb* vc* )T1 ; T2 VdcVdcISSN: 2231-5381Teff max{Tas,Tbs,Tcs} min{Tas,Tbs,Tcs}Toffset Vsr represents the length of the reference Vector and is measured from the start of the vector.T1 Extending this procedure, for the other sectors, theactive vector switching times (T1 andT2) [4] and forthe respective sectors may be expressed in terms ofthe imaginary switching times (Tas,Tbs and Tcs) for aparticular sampling interval. The effective time Teffis the time during which the active vectors areswitched in a sector and is given by (T1 T2). Thismay be determined as the difference between themaximum and minimum values among Tas, Tbs andTcs. Hence, T0 Ts - Teff.During (0 Wt 30)http://www.ijettjournal.orgPage 1014

International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013VAO,avg VBO,avgVdc / 2 T0T T1 T2 0 Ts 22 The maximum magnitude of the reference voltagespace vector corresponds to the radius of the biggestcircle that can be inscribed in the hexagon. Thus, themaximum value of the peak-phase voltage is givenbyV /2 TT dc 0 T1 T2 0 Ts 22 VCO,avg Vdc / 2 T0T T1 T2 0 Ts 22 V2 3Vph, peak,max * *Vdc dc 0.577*Vdc3 23During (30 Wt 90)VAO,avg Vdc / 2 T0T T1 T2 0 Ts 22 VBO,avg Vdc / 2 T0T T1 T2 0 Ts 22 VCO,avg Vdc / 2 T0T T1 T2 0 Ts 22 IX. OUTPUT VOLTAGE FOR SPWMINVERTERV /2 VTVAO,avg dc * sr * s 0 sin(600 ) sin TsVdcsin60 t 30 0 t 30 0 simplifyingwhenNoting that t 30when030 0 t 90 0Fig:3 output waveform of spwmsimplifyingV AO , avg Vsr3Sin ( t 30 0 )The peak value of the A-phase voltage, while theinverter is operated in the range of linear modulationis given by:Vph, peak (2 / 3) * VsrISSN: 2231-5381http://www.ijettjournal.orgPage 1015

International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013Fig:5 fft analysis of spwmX. OUTPUT VOLTAGE OF SVPWMXII. FFT ANALYSIS FOR SVPWMFig:4 output waveform of svpwmSimulation results [5] are observed by the followinganalysis.XI. FFT ANALYSIS OF SPWMFig:6 fft analysis of svpwmXIII. CONCLUSIONCompared to SPWM the Total harmonic distortion(THD) and lower order harmonics (LOH) contentsare decreased in SVPWM. It is known that the maximum value of the peak-phase voltage that can beobtained from a 3-Ph inverter with Sinusoidal PulseWidth Modulation (SPWM) technique is equal toVdc/2. It is therefore evident that SVPWM achieves abetter DC bus utilization compared to SPWM (byabout 15.4%).ISSN: 2231-5381http://www.ijettjournal.orgPage 1016

International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013XIV. LATEST IMPROVEMENTS Microprocessor-based controllers eliminate analog,potentiometer-based adjustments. Digital control capability. Built-in Power Factor correction. Radio Frequency Interference (RFI) filters. Short Circuit Protection (automatic shutdown). Advanced circuitry to detect motor rotor position bysampling power at terminals, ASD and motor circuitry combined to keep power waveforms sinusoidal,minimizing power losses. Motor Control Centers (MCC) coupled with theASD using real-time monitors to trace motor-drivesystem performance. Higher starting torques at low speeds (up to 150%running torque) up to 500 HP, in voltage sourcedrives. Load-commutated Inverters coupled with synchronous motors.REFERENCES[1]. Dr. P.S.Bimbhra “power electronics,Fourthedition,2009[2]. Muhammad H. Rashid, “Power electronic circuits, devices, and applications. Low price edition.Isbn:978-81-317-0246-8.[3]M.D.Singh, K.B.Kanchandani “Power electronics”Tata McGraw-Hill Education Private limited, Isbn:13:978-0-07-058394.[4]. Mohan, Undeland, Riobbins, “Power electronicconverters, applications and design” WILEY[6]. B.K. Bose. 1986. Power electronics and acdrives. Prentice hall Inc., Englewood Cliffs, NewJersey.[7]. Shoji Fukuda and Yoshitaka Iwaji, “Introductionof the Harmonic Distortion Determining Factor andits Application to Evaluating Real Time PWM Inverters,” IEEE transactions on Industry Applications,Vol. 31, No. 1, January/February, 1995.[8]. G. Narayanan, Harish K. Krishnamurthy, Rajapandian Ayyanar and V. T. Ranganathan, “SpaceVector Based Hybrid PWM Techniques for ReducedCurrent Ripple,” IEEE Transactions on IndustrialElectronics, Vol. 55, No. 4, April 2008.ISSN: 2231-5381BIOGRAPHIESKondapalli Mounika wasborn in India in 1991. She ispursuing B. Tech final yearin KL University in Electrical and Electronics Engineering. Her field of interestis in FACTS devices andPowerElectronics.Email Id: mouni.kondapalli99@gmail.comB. Kiran babu received theB. Tech degree from JNTUHyderabad in the year 2004,the M. Tech degree in power system engineering fromMNIT Jaipur, Rajasthan inthe year 2007. His researcharea includes distribution system reconfiguration,transmissionlossallocation.Email Id: ge 1017

Pulse-width modulation (PWM), or pulse-duration modulation (PDM), is a commonly used technique for controlling power to inertial electri-cal devices, made practical by modern electronic power switches. Here we apply PWM techniques like Sinusoidal pulse width modulation (SPWM)

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