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  1. 1. Ms. Sunitha Undrajavarapu, M. Srinivasa Rao, Mr. L. Uday Kiran/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2136-2141 Pv Fed Boost Spwm Inverter Driven Single-Phase Induction MotorMs. Sunitha Undrajavarapu *, M. Srinivasa Rao**, Mr. L. Uday Kiran*** *(Department of Electrical & Electronics Engineering, B.V.C Engineering College Odalarevu, India ** (Department of Electrical & Electronics Engineering, B.V.C Engineering College Odalarevu, India ** (Department of Electrical & Electronics Engineering, VISIT, Tadepalligudem, IndiaABSTRACTPV array is increasingly employed for water The breakthroughs experienced in each field havepumping system. In this paper, a boost converter strongly and positively influenced the evolution ofto step up the input voltage of the inverter todays various types of cost effective, efficient,interposed between the PV array and single-phase compact, and reliable high performance SPWM-VSIinduction motor is developed. The model was converters. Since they involve various disciplines ofimplemented using MATLAB/Simulink with engineering and there has always been a strongSPWM controlled inverter model. The detailed demand for them in the market, SPWM-VSImodeling of the components of proposed scheme converters have continuously drawn the attention ofhas been taken up. The developed boost converter many researchers all around the world. Therefore, insteps up the voltage produced by the PV array to parallel with this progress, a substantial amount ofa value which is suitable to run a single-phase literature relating to electric converters has beeninduction motor. The inverter converts DC to AC accumulated. In particular, the literature involvingis controlled by using sinusoidal pulse width the SPWM methods boosting of input voltage.modulation (SPWM) technique. By using a LC- Perhaps, the modern power electronics erafilter pure sine wave is obtained which can be began with the invention of the thyristor device indirectly used to drive a single-phase induction 1957. Overcoming the size, cost, efficiency,motor. Experimental investigation presented gives reliability, and performance deficiencies of thethe utility of such a drive system. previous power converter switching devices, the solid state semiconductor made thyristor gained immediate1. INTRODUCTION acceptance. In particular, its application in power The need for energy is never ending. This is converter circuits with inherent natural commutationcertainly true of electrical energy, which is a large characteristics such as cycloconverter, phasepart of total global energy consumption. The demand controlled rectifiers, and reactive powerfor electrical energy is increasing twice as fast as compensators, etc. has been the most practicaloverall energy use and is likely to rise 76% by 2030. solution to the present date. However, lacking self-Another point of concern is that in many commutation capability, the thyristor would requireoverpopulated countries, like India, there is a dearth involved commutation circuits in forced commutationof power generating resources and as a result many applications, rendering the drive bulky, expensive,cities and towns are facing constant load shedding and complex. Therefore, its utilization in forcedand black-outs. The existing centralized power commutation power electronic converters, ingeneration units are not sufficient to meet the particular in the VSI applications [2].continuously rising power demand. The wide gap Safe-commutation strategy want begeneration and distribution location lead to the implemented is to solve switching transients. So,inefficiency in supplying power to the rural areas. Insulated Gate Bipolar Transistor (IGBT) is use asThis can be eliminated by the use of advancement in switching devices. IGBT is preferable because it ispower electronics by providing instantaneous supply easy to control and low losses. Thus the IGBTto the people by providing flexibility in source by switches have become the most widely utilizedplacing the inverters [2]. devices and have revolutionized the SPWM-VSI Sinusoidal Pulse width-modulated (SPWM) converters.voltage-source inverters (VSI) are widely utilized in The switching frequency of the early powerac motor drive applications and at a smaller quantity electronic converters was typically low. For examplein controlled rectifier applications as a means of dc to a VSI would operate in the six-step mode, yielding aac power conversion devices, about three quarters of switching frequency equal to the output voltagea century of progress in the power electronics field, fundamental frequency. The intelligence involved inand about half a century of progress in the micro- generating the gate signals was not significant andelectronics/macro-electronics and control fields are the control could be implemented with analoginherited in the state of the art SPWM-VSI circuits. However, the low switching frequencyconverters. Mostly occurring at different time frames, 2136 | P a g e
  2. 2. Ms. Sunitha Undrajavarapu, M. Srinivasa Rao, Mr. L. Uday Kiran/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2136-2141would result in large amount of low frequency 1977 published the models for dc to dc convertersharmonic voltages/currents. now used today. Middle book averaged the circuit configurations for each switch state in a technique2. PHOTOVOLTAIC called state-space averaging. This simplification Photovoltaic are solid-state semiconductor reduced two systems into one. The new model led todevices that convert directly light energy into insightful design equations which helped SMPSelectricity. They are usually made of silicon with growth.traces of other elements and are first cousins totransistors, LED‟s and other electronic devices. APPLICATIONS Photovoltaic (PV) generation is becoming Battery powered systems often stackincreasingly important as a renewable source, since it batteries in series to achieve higher voltage.offers many advantages such as incurring no fuel However, stacking batteries is not possible in manycosts, not being polluting, requiring little high voltage applications due to lack of space. Boostmaintenance, and emitting no noise, among others. converters can increase the voltage and reduce theThe amazing thing about solar power is that all the number of cells. Two battery-powered applicationselectricity is generated from the material of the solar that use boost converters are hybrid electric vehiclespanels and the energy from the sun. The solar panels (HEV) and lighting systems.are mainly made out of semiconductor material, Boost converters also power devices atsilicon being the most abundantly used smaller scale applications, such as portable lightingsemiconductor. The benefit of using semiconductor systems. A white LED typically requires 4V to emitmaterial is largely due to the ability of being able to light, and a boost converter can step up the voltagecontrol its conductivity whereas insulators and from a single 1.5 V alkaline cell to power the lamp.conductors cannot be altered. The electrons of the Boost converters can also produce higher voltages tosemiconductor material can be located in one of two operate cold cathode fluorescent tubes (CCFL) indifferent bands, the conduction band or the valence devices such as LCD backlights and some flashlightsband. The valence band is initially full with all the [5].electrons that the material contains. When the energyfrom sunlight, known as photons, strikes the electrons 4. INVERTERin the semiconductor, some of these electrons will From the late nineteenth century through theacquire enough energy to leave the valence band and middle of the twentieth century, DC-to-AC powerenter the conduction band. When this occurs, the conversion was accomplished using rotary converterselectrons in the conduction band begin to move or motor-generator sets (M-G sets). In the earlycreating electricity. As soon as the electron leaves the twentieth century, vacuum tubes and gas filled tubesvalence band, a positively charged hole will remain began to be used as switches in inverter the location the electron departed. When this D. Prince was the person who invention of theoccurs, the valence band is no longer full and can earliest inverter device in 1925. He suggests thealso play a role in the current flow. This process nameinverter was given to this device for itsbasically describes how Photovoltaic (PV) systems operating characteristics are the reverse of thefunction. However, PV systems further enhance the rectifiers; instead of AC to DC voltagerate at which the electrons are sent into the transformation, DC to AC. The first practicalconduction band through the process of doping [1], application of single phase inverters is claimed to be[3]. in textiles. However, inverters did not find widespread applications until the development of the3. BOOST CONVERTER modern power electronic switches. For high efficiency, the SMPS switch mustturn on and off quickly and have low losses. The TYPES OF INVERTERSadvent of a commercial semiconductor switch in the Power inverters produce one of three1950‟s represented a major milestone that made different types of wave output:SMPSs such as the boost converter possible.  Square WaveSemiconductor switches turned on and off more  Modified Square Wave (Modified Sinequickly and lasted longer than other switches such as Wave)vacuum tubes and electromechanical relays. The  Pure Sine Wave (True Sine Wave)major dc to dc converters were developed in the The three different wave signals represent threeearly-1960s when semiconductor switches had different qualities of power output.become available. The aerospace industry‟s need for One might wonder why there are so manysmall, lightweight, and efficient power converters led types of inverters. The primary reason is cost. Somethe converter‟s rapid development [5]. types of devices won‟t work on the cheaper modifiedSwitched systems such as SMPS are a challenge to square wave of cheaper inverters and since its model depends on whether a switch is Audio/ video equipment, some computers and someopened or closed. R.D. Middle brook from Caltech in 2137 | P a g e
  3. 3. Ms. Sunitha Undrajavarapu, M. Srinivasa Rao, Mr. L. Uday Kiran/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2136-2141microwave ovens require a nearly pure (low raises the low voltage DC at the inverter input to 230distortion) sine wave input. In audio/video volts DC. The second stage is the actual inverterequipment, the higher frequency harmonics present in stage. It converts the high voltage DC into 230 volt,distorted sine waves can come through as buzzing in 50 Hz internationally The DC-to-DC converter stagethe speakers [1]. uses modern high frequency power conversion techniques that eliminate the bulky transformersSquare Wave found in inverters based on older technology. The Square wave inverters result in uneven inverter stage uses IGBT switches in a full bridgepower delivery that is not efficient for running most configuration. This gives you excellent overloaddevices. Square wave inverters were the first types of capability and the ability to operate tough reactiveinverters made and are obsolete. loads like lamp ballasts and small induction motorsSquare wave inverters works well for a resistive load [2], [1].like an incandescent light. But things get a bit morecomplicated with inductive loads APPLICATIONS Inverters are used in wide range applications such asModified Square Wave  DC Power source utilization Modified square wave (modified sine wave)  Uninterruptible power suppliesinverters deliver power that is consistent and efficient  Induction heatingenough to run most devices fine. Some sensitive  HVDC power transmissionequipment requires a sine wave, like certain medical  Variable-frequency drivesequipment and variable speed or rechargeable tools.  Electric vehicle drivesModified sine wave or quasi-sine wave inverters  The general casewere the second generation of power inverter. Theyare a considerable improvement over square waveinverters. These popular inverters represent a 5. Sinusoidal Pulse Width Modulationcompromise between the low harmonics (a measure Since voltage source inverters employof waveform quality) of a true sine wave inverter and switching devices with finite turn-on time and turn-ofthe higher cost and lower efficiency of a true sine time characteristics, inverter switching losses arewave inverter. inevitable. Because the switching losses strongly Modified sine wave inverters approximate a affect the energy efficiency, size and reliability of ansine wave and have low enough harmonics that they inverter, a modulation method with high performancedo not cause problems with household equipment. is desirable. Therefore, the modulation methodThey runs TVs, stereos, induction motors (including choice is significantly important. Of the variety ofcapacitor start), universal motors, computers, modulation methods, the carrier based SPWMmicrowave, and more quite well. The main methods are used [7].disadvantage of a modified sine wave inverter is that Now a day‟s most of the inverters availablethe peak voltage varies with the battery voltage. in the market utilizes the SPWM (Sinusoidal PulseInexpensive electronic devices with no regulation of Width Modulation) technology .The inverters basedtheir power supply may behave erratically when the on SPWM technology are superior in many factorsbattery voltage fluctuates. compared to other inverters designed using conventional technologies. The SPWM basedTrue Sine Wave inverters generally use IGBTs in the output switching True sine wave inverters represent the latest stage. In such cases the inverters are generally termedinverter technology. The waveform produced by as SPWM IGBT inverters. The inverters based onthese inverters is the same as or better than the power SPWM technology has a lot of protection and controldelivered by the utility. Harmonics are virtually circuits compared to the traditional inverters.eliminated and all appliances operate properly withthis type of inverter. They are, however, significantly 5.2 WHAT IS SPWM TECHNOLOGY? &WHYmore expensive than their modified sine wave SPWM IS USED?cousins. SPWM or Sinusoidal Pulse width For many other loads, a less than perfect Modulation is used to keep the output voltage of thesine wave is adequate. The issue then becomes a inverter at the rated voltage (110V AC / 220V AC)trade-off between cost and waveform purity. An (depending on the country) irrespective of the outputapproximation of a sine wave may be created by load. In a conventional inverter the output voltageoutputting one or more stepped square wave with the changes according to the changes in the load. Toamplitudes chosen to approximate the sine. The more nullify effect caused by the changing loads, thesteps, the more like a sine wave the output is. The SPWM inverter correct the output voltage accordingmore steps, the higher the cost. to the value of the load connected at the output .This Most inverters convert DC power in two is accomplished by changing the width of thestages. The first stage is a DC-to-DC converter that switching frequency generated by the oscillator 2138 | P a g e
  4. 4. Ms. Sunitha Undrajavarapu, M. Srinivasa Rao, Mr. L. Uday Kiran/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2136-2141section. The AC voltages at the output depend on the Elimination of Higher Order Harmonicswidth of the switching pulse. The process is achieved Harmonics are classified into two feed backing a part of the inverter output to the They are higher order harmonics and lower orderSPWM controller section (SPWM controller IC). harmonics. To eliminate higher order harmonics, weBased on this feedback voltage the SPWM controller use filter. Where the lower order harmonics arewill make necessary corrections in the pulse width of eliminated using SPWM technique.the switching pulse generated at oscillator section. Types of FiltersThis change in the pulse width of the switching pulse There are different types of filters. They arewill cancel the changes in the output voltage and the as shown below [4].inverter output will stay constant irrespective of the  L-filterload variations.  LC-filter Output voltage from an inverter can also be  LCL-filteradjusted by exercising a control within the inverter LC-Filteritself. The most efficient method of doing this is by In this project, we use LC-filter. LC-filter issinusoidal pulse-width modulation control used a second order filter and it has better filtering abilitywithin an inverter. than L-filter. This simple configuration is easy to In this method, a fixed dc input voltage is design and it works mostly without problems. Thegiven to the inverter and a controlled ac output basic block diagram of a LC-filter is as shown below.voltage is obtained by adjusting the on and offperiods of the inverter components. This is the mostpopular method of controlling the output voltage andthis method is termed as Pulse-Width Modulation(PWM) Control. If the reference signal used ingeneration of pulses, then it is called sinusoidal pulsewidth modulation [8], [9].Advantages Fig 6.1: Basic block diagram of LC-filterSPWM technique has several advantages. They are aslisted below [8]. MODELING OF LC-FILTER The output voltage control can be obtained In filter designing, the first step is finding without any additional components the best filter. The second step is calculating the Lower order harmonics can be eliminated. designed impedance from the lowest voltage (Vmin) The filtering requirements are reduced to higher divided by the highest current (Imax) where is Rd. order filters only. the third step is equating the inductor (L) and the High power handling capability. capacitor (C) values from the second step using the Efficiency up to 90%. following equation [4]. Low power consumption. The design impedance form can be SPWM generates less harmonic distortion in the calculated by using the below equation. output voltage or currents in comparison with PWM. The inductance (L) and the capacitance (C) values of the filter can be calculated by6. FILTER Need For Filter Filters play a key role in the inverter drivenloads. It is mainly used for two reasons. They are aslisted below. Calculations of L & C 1. To convert the inverter output (i.e., square The values of the inductor and capacitor that are used wave) into pure sinusoidal wave in a LC-filter are calculated as shown below. The design impedance form can be calculated as 2. To eliminate the higher order harmonics. below.Conversion of Square Wave In to Sine Wave The output of an inverter is in square wave. The values of inductance and capacitance in the LC-This output is suitable for lighting loads. But is not filter are given bysuitable for motor and other sensitive loads likeelectronic loads. Since this project is a motor drive(i.e., single-phase induction motor), it is necessary toconvert the square wave output into pure sinusoidalwave. Thus we need filter [8], [9]. 7. SINGLE-PHASE INDUCTION MOTOR The characteristics of single phase induction 2139 | P a g e
  5. 5. Ms. Sunitha Undrajavarapu, M. Srinivasa Rao, Mr. L. Uday Kiran/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2136-2141motors are identical to 3-phase induction motors 9. MATLAB RESULTSexcept that single phase induction motor has no In the analysis of the PV fed boost SPWMinherent starting torque and some special inverter driven single-phase induction motor, thearrangements have to be made for making itself resultant waveforms are used for the verification ofstarting. It follows that during starting period the the results for the desired response.single phase induction motor must be converted to atype which is not a single phase induction motor in The results includethe sense in which the term is ordinarily used and it  Boost converter output voltage,becomes a true single phase induction motor when it  SPWM wave forms for positive sequence andis running and after the speed and torque have been negative sequence operation of inverter,raised to a point beyond which the additional device  Voltage and current wave forms of inverter model,may be dispensed with. For these reasons, it is  Voltage and current wave forms of inverter modelnecessary to distinguish clearly between the starting with filter,period when the motor is not a single phase induction  Torque-Speed characteristics of single-phasemotor and the normal running condition when it is a induction motor &single phase induction motor. The starting device  Output characteristics of single-phase inductionadds to the cost of the motor and also requires more For the same output a 1-phase motor is about Voltage Wave Form Of Boost Converter30% larger than a corresponding 3-phase motor.The single phase induction motor in its simplest formis structurally the same as a poly-phase inductionmotor having a squirrel cage rotor, the onlydifference is that the single phase induction motorhas single winding on the stator which produces mmfstationary in space but alternating in time, apolyphase stator winding carrying balanced currentsproduces mmf rotating in space around the air gap Fig 9.1: Simulation output voltage of boost converterand constant in time with respect to an observer The above shown figure is the simulation outputmoving with the mmf. The stator winding of the voltage. The output voltage of boost converter is 250single phase motor is disposed in slots around the volts.inner periphery of a laminated ring similar to the 3-phase motor [7]. SPWM Wave Forms for Positive & Negative Sequence SwitchesFig 7.1: Elementary single phase induction motor8. Functional block of PV fed boost SPWMinverter driven single- phase induction motorThe below shown figure 8.1 is the implementation of Fig 9.2: SPWM waveforms for positive and negativePV fed boost SPWM inverter driven single-phase sequences Positive sequence G1 & G3, Negativeinduction motor in MATLAB/SIMULINK. sequence G2 & G4 Voltage and Current Wave Forms of Inverter Figure 9.3: Simulation output current and voltageFig 8.1: Functional block of PV fed boost SPWM without filterinverter driven single phase induction motor The above shown figure is the simulation output voltage. The output voltage and current of 2140 | P a g e
  6. 6. Ms. Sunitha Undrajavarapu, M. Srinivasa Rao, Mr. L. Uday Kiran/ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2136-2141 single phase boost SPWM inverter is 230 volts and are eliminated by using proposed LC filter. The 2.3 amps. experimental results on MATLAB/Simulink areVoltage and Current Wave Forms of Inverter with presented to validate our drive scheme. The driveFilter scheme is easy to implement economically. Future Scope In this project, “PV fed boost SPWM inverter driven single-phase induction motor” is implemented using open loop control. In open loop control system there is no scope for automatic voltage regulation and peak power tracking. In future, “PV fed boost SPWM inverter driven single-phase Figure 9.4: Simulation output current and voltage induction motor” can be implemented with a closed with filter loop control system to eliminate the above stated The above shown figure is the simulation output problem. The closed loop control can be current. The output voltage and current of single implemented using any controller like P, PI & PID. phase boost SPWM inverter is 230 volts 2.3 amps. The controller can be selected according to the Speed-Torque Waveforms of Single Phase designer requirement. Induction Motor. 10. References [1] Analog controller for Photovoltaic array fed inverter driven Single-phase induction motor, B. Santhosh Kumar, S. Arul Daniel, and H. Habeebullah Sait, Department of Electrical and Electronics Engineering, National Institute of Technology, Trichirappalli, India . [2] AzuanBin Alias:Modeling and simulation of Figure 9.5: Simulation speed-torque of single phase single phase inverter with PWM using induction motor MATLAB/SIMULINK, University of The above shown figure is the simulation output Malaysia Pahang, NOVEMBER 2007. speed and torque. The output speed and torque of [3] Eric Anderson, Chris dohan, Aaron sikora, single phase induction motor is 1500 rpm 8 N-m. Stephan J.bitar, John A.MC Neill, „Solar Output Characteristics of Single-Phase Induction panel peak power tracking system, A major Motor qualifying project of Worcester polytechnic institute, project no. MQP-SJB-1A03, 2003. [4] The Analysis of Output filter for Grid Connected Single Phase Full Bridge Inverter Based on PSpice Simulation Technique, P. Khamphakdi and W. Khan-ngern, Faculty of Engineering and Research Center for Communications and Information Technology. [5] PabloSanchis, Member IEEE: Boost DC-AC Fig 9.6: Output characteristics of single-phase Inverter: A New Control Strategy, IEEE induction motor transactions on power electronics. VOL 20, a) Total current, b) Main winding current, No.2, March 2005. c) Auxiliary winding current, d) Capacitor voltage, e) [6] Katsunori Taniguchi, Member, IEEE: PWM Rotor speed & f) Electromagnetic torque. Technique for MOSFET Inverter, IEEE transaction on power electronics. VOL 3. Conclusion NO 3. July 1988. The system descried here is a PV system for [7] Electrical Machinery by P.S. Bimbhra, water pumping, employing a single-phase boost Khanna Publishers SPWM inverter and single-phase induction motor. [8] Power Electronics by P.S. Bimbhra 3rd The boost converter is used to step up the low input Edition voltage produced by PV array. The proposed scheme [9] Power Electronics By MD Singh KB is thus successfully used to drive a single-phase Khanchandani Tata Mc Graw Hill induction motor. SPWM technique is used to control the IGBT inverter and for the effective elimination of lower order harmonics, where higher order harmonics 2141 | P a g e