closed loop controlled ac-ac converter for induction heating

8/9/2019 Closed Loop Controlled AC-AC Converter for Induction Heating

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The Ofcial Electronic Publication of the The Association of Technology, Management, and Applied Engineering www.nait.org

2009

Clse Lp Cntlle AC-ACCnvete f Inuctin Heating

By Mr. D. Kirubakaran & Dr. S. Rama Reddy

Volume 25, Number 2 - April 2009 through June 2009

Peer-Reereed ArticleApplied Papers

ElecticitElectnics

KEyword SEArCH


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Journal of Industrial Technology Volume 25, Number 2 April 2009 through June 2009 www.nait.org

Clse Lp CntlleAC-AC Cnvete fInuctin HeatingBy Mr. D. Kirubakaran & Dr. S. Rama Reddy

AbstractA single-switch parallel resonant con-verter or induction heating is simu-lated and implemented. The circuit con-sists o input LC-flter, bridge rectiferand one controlled power switch. Theswitch operates in soft commutationmode and serves as a high requencygenerator. Output power is controlledvia switching frequency. Steady stateanalysis o the converter operation

is presented.. A closed loop circuitmodel or AC to AC converted induc-tion heating system is also proposed.Experimental results are compared withsimulation results.

IntroductionStatic requency converters have beenextensively applied in industry as amedium requency power supply orinduction heating and melting installa-tions. They are applied in all brancheso the military, machine-building

industries, jewellery, smithy heating,domestic heating cooking devices andother purposes.

The ordinary circuit o an AC-ACconverter or induction heating typi-cally includes a controlled rectier anda requency controlled current sourceor a voltage source inverter. It is awell known act that the input recti-er does not ensure a sine wave inputcurrent, and is characterized by a lowpower [1-3]. Recently many studies

o high power actor rectiers with asingle switch have been made [4-5].These schemes are also characterizedby a close to sine wave input current.In addition, in [6] the scheme o theAC-AC converter or induction heat-ing is described. The input circuit othe converter is constructed similarlyto the input circuit in [4, 5], which alsoensures a high power actor. However

the inverting circuit is constructed bytraditional mode with our controlledswitches. The above literature does notdeal with closed loop modeling andembedded implementation o AC toAC converter ed induction heater. Inthe present work AC to AC converter ismodeled and it is implemented usingan atmel microcontroller. The presentproblem aims to minimize the cost oinduction heater system by using an

embedded controller.

Fig.1 Circuit Diagram

In the scheme (Fig.1) o the AC-ACconverter there are two main advantag-es: It is characterized by a high poweractor and a sine wave input current.On the other hand the inverter circuitis constructed with a single controlledswitch, which serves as a high-requen-cy generator or induction heating.

Principle O OperationThe operating principles o the circuitare illustrated by Fig.2 and the theoreti-cal waveorms

Fig.2a. Mode 1 (to-t

1)

Mr. D.Kirubakaran has obtained M.E. degreefrom Bharathidasan University in 2000. He ispresently doing his research in the area of AC-AC converters for induction heating. He has 10years of teaching experience. He is a life memberof ISTE.

Dr. S. Rama Reddy received his M.E degreefrom College of Engineering, Anna University,

Chennai, India in 1987. He received Ph.D degreein the area of Resonant Converters from Collegeof Engineering, Anna University, Chennai Indiain 1995. Presently he is working as Dean inElectrical & Electronics Dept., Jerusalem Colle-ge of Engineering, Chennai. He has worked inTata Consulting Engineers and Anna University,Chennai, India. He is fellow member of Institutionof Electronics and Telecommunication Engineers(India), Life Member of Institution of Engineers(India), Member of ISTE, Member of CSI andMember of SPE, India. He has authored textbooks on Power Electronics, Electronic Circuitsand Electromagnetic Fields. He has published 30research papers in reputed journals. His researchareas are Power Electronic Converters, Drivesand FACTS.


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Fig.2b. Mode 1I (t1-t

2)

Fig.2c. Mode 1II (t2-t

3)

Fig.2 Equivalent Circuits

are shown in Fig.3.We suppose theswitching requency is much higherthan the input line requency and in theanalysis we arbitrarily chose the timeinterval where v

in>0

Interval 1: t0


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The values o duty cycles D1

and D may

also be ound rom the approximate poly-

nomial expressions

(6)

Simulation ResultsThe AC to AC converter ed inductionheater is simulated using matlab simu-link and their results are presented here.The circuit model o AC-AC converteris shown in Fig.4a.. Scopes are con-nected to measure output voltage, driv-ing pulses and capacitor voltage.

Fig.4a. open loop Circuit

Fig.4b. Driving pulses

Fig.4c. Voltage across S1

(Vds)

Fig.4d. Current through S1

Fig.4e. AC Output Voltage

Switching pulses are shown in Fig4b.Voltage and current waveorms othe switch are shown in Fig.4c & Fig4d respectively. High requency ACoutput o converter is shown in Fig. 4e.

The closed loop circuit model o AC-AC converter is shown in Fig.4

. Scopesand displays are connected to measurethe output voltage.

Fig.4. Closed loop controlled AC-ACConverter

A disturbance is given at the input byusing two switches. Output voltageis sensed and it is compared with thereerence voltage. The error signal isgiven to the controller. The output oPI controller controls the dependentsource. Response o open loop systemis shown in g 4g.

Fig 4g. Output voltage o openloop system


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Fig 4h. Output voltage o closedloop system

The output voltage o closed loopsystem is shown in Fig 4h. The distur-bance is applied at 3.0 secs. The controlcircuit takes proper action to reduce theamplitude to the set value and settles

ater 0.5 secs. Thus the closed loopsystem reduces the steady state error.

Experimental VerifcationThe single-switch AC-AC converterwas built and tested at 230V. Experi-mental setup o AC to AC converter isshown in Fig. 5.

Fig. 5. Hardware layout

The circuit parameters are R0=60;L

0=150H; C

0=2.35F; L

r=22H;

Li=8.0mH; C

in=0.94F and the switch-

ing requency S= (62-113) x103 s-1.

The experimental waveorm o outputvoltage is shown in Fig.6.

Fig.6 Oscillogram o output voltage

The output power control was alsochecked and its dependency by switch-ing requency is shown in Fig.7. Theoutput power increases with the in-crease in switching requency.

Fig.7 Output power v/s switchingrequency

ConclusionAn AC-AC converter circuit or induc-tion heating has been simulated andtested. The converter input current ispractically sinusoidal and its power ac-tor is close to unity. The circuit topol-ogy is very simple since includes onlyone power switch. This switch oper-ates in a sot commutation mode. Theconverter provides a wide-range powercontrol. This converter has advantageslike reduced hardware, reduced stresses

and high power density. Closed loopcircuit model is developed and it is suc-cessully used or simulation studies.The limitation o this converter is pres-ence o DC component in the outputcurrent and operating requency is lim-ited to 11MHz. Simulation and experi-mental results demonstrate the actualconverter capability to control the heat.The experimental results closely agreewith the simulation results.

ReerencesBayindir, N.S.; Kukrer, O.; Yakup, M

(May 2003).: DSP-based PLL con-trolled 50100 kHz 20 kW high-requency induction heating systemor surace hardening and weldingapplications. IEE Proc.-Electr. PowerAppl., Vol. 150, No.3, pp. 365-371.

Okuno, A.; Kawano, H.; Sun, J.; Kuroka-wa, M.; Kojina,A.; Nakaoka, M.(July/August 1998) Feasible develop-ment o sot-switched SIT inverterwith load-adaptive requency-trackingcontrol scheme or induction heating.IEEE Trans. Ind. Applicat., Vol. 34,No. 4, , pp. 713-718.

Kiune, H.; Hatanaka, Y.; Nakaoka,M. (January 2004 ) Cost eectivephase shited pulse modulation sotswitching high requency inverter orinduction heating applications. IEEProc.-Electr. Power Appl., Vol. 151,

No. 1, , pp. 19-25.Ogiwara, H.; Nakaoka, M. ( March

2003) ZCS high requency inverterusing SIT or induction heatingapplications. IEE Proc.- Electr. PowerAppl., Vol. 150, No. 2, pp. 185-192.

Mollov, S.V.; Theodoridis, M.; Forsyth,A.J. (January 2004): High requencyvoltage-ed inverter with phase-shitcontrol or induction heating, IEEProc.-Electr. Power Appl., Vol. 151,No. 1, pp. 12-18.

Ogiwara, H.; Gamage, L.; Nakaoka,M.( September 2001) Quasiresonantsot switching PWM voltage-edhigh requency inverter using SIT orinduction heating applications. IEEProc.- Electr. Power Appl., Vol. 148,No. 5, pp. 385-392.

Singh, B.; Singh, B.N.; Chandra, A.; Al-Haddad, K.; Pandey, A.; Kothari, D.P(October 2003) A review o single-phase improved power quality AC-DCconverters. IEEE Trans. Ind. Electron.Vol. 50, No. 5, pp. 962-981.

Singh, B.; Singh, B.N.; handra, A.; Al-Haddad, K.; Pandey, A.; Kothari, D.P.(June 2004) A review o three-phaseimproved power quality AC-DC con-verters. IEEE Trans. Ind. Electron.,Vol. 51, No. 3, pp. 641-660.

B.Saha, K.Y. Suh, S.K. Kwon, andM.Nakaoka, (Apr. 2007) Selec-tive dual duty cycle controlled highrequency inverter using resonantcapacitor in parallel with an auxiliaryreverse blocking switch, J.PowerElecctron., vol.7, no.2, pp118-123.

closed loop controlled ac-ac converter for induction heating

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