commerical utility frequency ac to high frequency ac softw by Ryan Lian

The 30th Annual Conference of the lEEE Industrial ElectronicsSociety, November 2 - 6,2004, Busan, Korea

Commercial Utility Frequency AC to High Frequency AC Soft Switching Power Conversion Circuit with Non Smoothing DC Llnk for IH Dual Packs Heater 1

Hisayuki Sugimura, 'Tarek Ahmed, 3MohamedOrabi, *Hyun-Woo Lee, and '2Mutsuo Nakaoka,

'Division of Electrical and Electronics Engineering, The Graduate School of Science and Engineering, Yamaguchi University, Yamagucbi, Japan e-mail : supimura@me-newsl .eee.vamapchi-u.ac.jip 'The Electric Energy Saving Research Center & Technology Innovation Research Center for Production Automation, Department of Electrical and Electronics Engineering, K w g n a m University, Masan, Korea 'Elecmcal Power and Machines Department, Faculty of Engineering, South Valley University, Aswan, Egypt

Abstrucf- In this paper, a novel topology of soft switching PWM high frequency AC power conversion conditioning and processing circuit without DC smoothing Capacitor filter link from the voltage grid of utility frequency AC power supply source with 60Hz-100Vor 6OHz-ZOOV is proposed and introduced for innovative consumer induction heating OH) boiler applicationsas a hot water producer, steamer and super heated steamer. The operating principle of utility frequency AC-high frequency AC power frequency conversion circuit defined as high frequency cycloinverter is described,which can etliciently operate under a principle of zero voltage soft switching and regulate by means of positive and negative alternate asymmetrical PWM synchronized with the utility frequency single phase AC voltage. The dual mode control scheme based on high frequency PWM and commercial frequency AC voltage PDM for high frequency cycloinverter are discussed in order to extend its soft switching commutation operating range in spite of power regulation. This power frequency changer as high frequency cycloinverter is developed originally for the high frequency induction heating boiler in consumer and industrial fluid pipeline system, It is verified on the basis of experiment and simulation results in the steady state operation of the high frequency cycloinverter using IGBTs which is suitable for the business-use IH boiler using new electromagnetic induction heating dual packs fluid beater. Finally, the power regulation characteristics in addition to utility AC side line current harmonic components and power factor characteristics and power conversion effi-

trial and consumer applications is roughly classified into two; low frequency IH and high kquency IH (over 20kHz). In recent years, significant verifications of effective applications of IH have been recognized as follows: metal heat treatment process in the industry application fields, including thermal treatment process such as forging and casting, electromagnetic induction based plasma generation process, high-speed dissolution process for the new materials and melting process of semiconductor manufacturing, high fiequency induction heating soldering process with the self temperature function using magnetic alloy heating element, and induction h i o n processing of the polyethylene pipe. On the other hand, the latest technology developments of IH application products emphasized on the environment have attracted special interest in the consumer application fields as follows: IH cooking device, rice cooker and warmer, boiler, hut-water producer, floor and wall fluid heater, ti-yer, dryer, wastes treatment and soil sterilization equipment using cleaning, sterilization and drymg of atmospheric pressure super heated steamer. Under these technological requirements, research and development of circuits and control schemes of the high ftequency power supply equipment for the electromagnetic induction heating by a variety of high efficiency voltage source type series capacitor compensated and parallel capacitor compensated load resonant high fre-

ciency characteristics of this high frequency cycloinverter are evaluated and discussed from an experimental point of view. fndex fems- High kquency cycloinverter, Soft switching

PWM, Utility AC-PDM, Dual mode control strategy, Non DC smoothing capacitor DC link, Induction heating, Spiral type dual packs fluid heater

I. INTRODUCTION

In general, the electromagnetic induction heating (IH) is concemed with non-contact, high efficiency, and clean electric heating method due to the energy conversion heated device by induction eddy current based on Faraday's law of electromagnetic induction principle in addition to Joule's heating principle. Attractive IH technology used for indus-

(b) fi-Lseries equivalent circuit model Fig. 1 Equivalent circuit modeling of electromagnetic induction eddy (a) Transformer type

equivalent circuit model

current based Joule's heating load.

0-7803-8730-9/04/$20.00 02004 IEEE

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quency inverter which incorporate soft switching pulse modulation technologies (PFM, PWM, PAM, PDM, PSM) using the latest MOS gate controlled power semiconductor switching devices (IGBTs, CSTBTs) are actively proceeded from a practical point of view. However, the harmonic distortion inherently causes in the commercial AC input grid side because of rectified DC smoothing voltage link with capacitor input filter. In addition, the significant problems on power conversion efficiency, volumetric physical size, reliability and life of the electrolytic capacitor DC link power stage have actually appeared by using the electrolytic capacitor bank or assembly for the DC voltage smoothing. This paper proposes the utility frequency AC - high hquency AC power conversion circuit defined as high f?equency cycloinverter or cycloconverter, which does not include DC smoothing fdter stage. In addition, the circuit operation of the soft switching PWM AC- high fiequency (HF) AC power converter as high fkequency cycloinverter is described for the hot-water producer and steamer using new M Dual Packs Fluid Heater @PH) . Then,the circuit operation verification of high fiequency cycloinverter is carried out in experiment and simulation. Finally, the power regulation characteristics and power conversion efficiency characteristics of high fiequency cycloinverter is evaluated and discussed, along with active filtering characteristics on harmonic line current components and total harmonic power factor in utility AC power grid side. The feasible effectiveness and practicability of soR switching PWM controlled high-frequency cycloinverter treated here are substantially proved on the basis of experimental results for consumer M-DPHapplications in pipeline systems.

induction fluid heating load (DPH) discussed below is shown in Fig. 1. Figure 1 is a linear model of the induction heated load circuit represented by equivalent effective inductor Lo in series with equivalent effective resistor Ro in the input side of working coil terminals of the induction heater or IH-DPH. R, and L, are respectively determined by the self-inductance LI and internal resistance RI of the work coil, self-inductance L2 of eddy current heated device in electromagnetic induction transformer secondary side and mutual inductance M between LI and L2. It is considered that these circuit parameters in spite of output power regulation of the IH-DPH load is

[a) Top view of spiraltype dual packs heater Output nuid Bar &e.

Spin1 type heater

Eeating vessel

11. E Q U I V A L CIRCUIT E~ OF hTl"DTI0N HEATDTG LOAD AND MEASUREMEhT OF CIRCUIT PARAMETERS

The equivalent circuit modeling of the electromagnetic Indirect heatiap.

Input maid

UtilityAC power

@) spiral heater 6truCtu;e

Fig.3 Internal structure of IH spiral type dud packs heater heater.

Direct heating

Fluid heating

Fig. 2 Soft switching pulse modulaicd utility frequency AC-high fiequcncy AC power conversion circuit without electmiytic capacitor.

Fig. 4 Soft switching pulse modulated utility kquency AC-hi& frequency AC power conversion circuit without elech-olyticcapacitor.

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kept constant, when the output fkequency of high frequency AC voltage. Structures of IH load are shown in F i g 2 The metal swface hardening trpeutilizes the skin effect by high fkquency current. The indirect heating type heats the heating vessel in the induction beating. The direct heating type can heat directly heating object in which induction currents are generated such as the metal. The fluid heating type is inserted into the non-metal heating vessel in the pipeline. When high frequency current flows through working coil h m high hquency inverter, induction heater is heated quickly. Water flows through into heating vessel from lower side. After that, bot water i s outputted from upper side. Measured methods of circuit parameters Roand La in the M-DPHload are as follows. High fresuency AC voltage is provided to the IH-DPH load via, working coil by high fiequency inverter as well as high frequency cycloinverter or high fiequency linear power amplifier. The effective value V,, of hi@ fieequency (HF)AC voltage and effective value ,I of high frequency AC current with electrical angular ) , factor cost!? (cos@: difference fiequency ( w = ~ j power angle between output voltage and output current) are measured for IH-DPH load with working coil driven by high fiequency power supply. Equation (1) is obtained on the basis of the sine wave alternating current theory.

vms

-zm

cos e =

Rn2+ t m 4 1

............. (1)

she=* The impedance of the induction heating load Z,

for the

angular frequency U of output voltage and current of high frequency linear power amplifier (high ftequency inverter or high frequency cycloinverter) is calculated using the equation (1). By using measured power factor, the equivalent parameters R, and L, of IH-DPH load with working coil is estimated. In case of considering internal resistance RI of the work coil, the equivalent effective resistance value becomes R, + R I . The circuit parameters k and r expressed in Fig. 1(a) are represented as follow s by using R, and L,. 1x1. NOVELTYPE OF INDUCTION HEATING DUAI, PACKS nun,HEATER In the high frequency ZH,improvement of high frequency power supply due to AC-smoothing DC-HFAC indirect power conversion processing is required practically. The high fiequency cycloinverter due to utility fkquency AC-HPAC power conversion processing is more effective for unity power factor and sine wave current in utility AC grid high-hquency power conditioning in the IH-DPH load side. Moreover, the development and improvement of IH-DPH device With higher beating conversion efficiency are suitable for I Hheat exchanger of the fluid heating device in pipeline systems. The appearance of business use IH-DPH driven by the high hquency inverter is shown in Fig.3. This spiral IH-DPH device developed newly works as a heat exchanger of the new spiral structure with the end ring with a low resistance, which is formed spirally by the thin plate of nonmagnetic stainless steel SUS316,which is inserted into the non metal vessel. The material of the IH-DPH device as must consider the followings: temperature distribution is miformity, corrosion protection for fluid (water, vapor, gas, powder) is excellent, low pressure moving fluid in pipeline becomes clean. SUS316 is the stainless steel which is especially more excellent in corrosion protection than non-magnetic material SUS304 used most widely. The work coil uses enamel copper wire twisting together of the insulation to each other. This work coil is called litz wire for power. In this IH heating device (see Fig.3), thermally stable temperature of this wire is about 170 degrees centigrade. Table 1 Design specificationsand circuit parameters Item

Switching frequency Dead time Filter and resomnt capacitors Lossless snubbing quasi-resonant capacitor Inductance of utility AC side filter inductor Effective resistance component of IH load Effective inductance component of IH load

Fig. 5.Gate voltage pulse signal sequences of asymmetricalPWM control scheme.

Fig. 6 Utility AC kquency-based pulse density modulation control strategy (dPD,,, 4.7).

f C,,C2

2lkwz 2P 5 P

0.lpF

1.65s2

34.2pH

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Actually, the water tube part is not over 120 degrees centigrade, because tbe heat insulating material is packed in IH-DPH hot-water producer between work coil and IH heating element. Therefore, the security of enough thermally stable temperature is possible for fluid heating container made of ceramics and nitrogen resin. This M heating element is based on the mechanism, which heats the low pressure continuous movement fluid in the pipeline tube by the heat exchange action between IH heating element and fluid. Therefore, thermally stable temperature is also necessary for the pipeline tube. The fluid heating vessel tube uses the polycarbonate, and the thermally stable temperature is below 120 degrees centigrade. IV. UT"Y

FREQUENCY AC - HIGHFREQUENCY AC POWER CONVERSION CIRCUIT

A. Circuit description

The circuit structure of the AC-HFAC power converter or high frequency cycloinverter in which converts utility frequency AC into high frequency AC without the electrolytx capacitor DC link or complete DC smoothing busline is shown in Fig.4. The proposed power frequency conversion circuit as a high frequency cycloinverter is a power fiequency changing circuit topoIogy which converts the utility fiequency AC into high frequency AC voltage over 20 kHz. This circuit structure is defined as high frequency cycloinverter which is different from the conventional high frequency inverter. The main power conversion circuit structure is composed of: two power switching blocks QI ( SWl/DI ) and Q2 ( SW2/D2 ), filter inductor LI in utility AC input-side, two capacitors Cl and C2 as active clamp resonance in ac-

B. Dual mode control of asymmetrical PWMand utilip Jrequency AC PDM The gate pulse signal timing sequences for asymmetrical PWM control of the cycloinverter are shown in Fig.5. The asymmetrical PWM as control variable is defined as the equation (2). That is the duration proportion of on time Ton] of the main power switch for a high frequency cycloinverter period Tis defined as Duty Factor or Duty Cycle d p w in the alternate asymmetrical PWM control scheme exchanged synchronkinglyby the polarity of the utility AC voltage. The duration time of Toni contains a dead time T,. In addition, the gate pulse trains of the main and auxiliary power switch must be reversed to supply the desired AC power for M-DPHload, because each role of SW) and SW, is reversed in accordance with either positive or negative voltage of utility AC power source. By introducing this control strategy, the high frequency cycloinverter enables to supply of the desired output AC power for the M-DPH load.

..............................

To,, T

dPWM --

(2)

In addition to this asymmetrical P W M control strategy, the commercial utility frequency AC-PDM (Pulse Density Modulation) Z V S control scheme or commercial utility AC voltage cycle control scheme is also introduced herein. 3 y the commercial utiIity fiequency AC-ZVS-PDM control, the output HFAC effective power by changing the discrete cycle numbers of commercial utility fiequency AC voltage pulse sains in some intervals Tp~Au to the IH-DPH load. New concepts of the commercial utility hquency AC-ZVS-PDM

cordance with M-DPH load and low pass filter, lossless quasi-resonant snubber capacitor COand, induction heated DPH load. This cycloinversion circuit operation is equal to that of active clamp quasi-resonant invertr due to the capacitor C, in parallel with the induction heated DPH load. h w e of using each CJ2 in parallel with Ql and Q2,the active clamp inverter becomes the same equivalent U in Fig.4.

vQ2

iQ2 i

;

.........

----.........-..-.-

i i i i i i i i ;

d ~ ~ ~ 0 . 3

~~,,r~~~:2OO[V/div] vM:250[v/div] iQ,,io?:I OO[A/div] Time: IOb/div] Fig 8 Soft switching voltage and current waveforms in c u e of ~ P R U 4 . 5 in asymmetrical ZVS-PWM sch-.

dm+O.l

(LeR traccs:SimuIaiion, Right traces:Expeliment)

Fig.7 Input voltage and current waveforms

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control strategy are conceptually shown in Fig.6. The ZVS-based commercial utility frequency AC-PDM time ratio as a controlvariable dpDM i s defined as the equation (3). In the high fiequency cycloinverter, the quantity in a period of utility AC power source under in 1/10 periods of utility AC voltage can be regulated discretely.

The high fiequency cycloinverter circuit topology depicted in Fig.4 can adjust high-frequency AC output power on the basis of dual-mode control of asymmetrical PWM and comrnetcial frequency AC-PDM under a condition of zero voftage soft switching commutation. The zero voltage soft switching commutation operation can be realized over all the output power regulation area on the basis of dual mode control implementation in case of low power setting area using the utility frequency AC-ZVS-PDM control and the ssymmetrical PWM control in case of high power setting area. The changing point of asymmeh-ical PWM and commercial frequency AC PDM changed by in this high frequency cycloinverter is set to dpwM4 . 3 . The changing point of pulse modulation scheme is determined by time ratio which depends on IH-DPH load power and switching hquency. In all the high fiequency AC power regulation ranges, this high frequency cycloinverter operate in soft switching commutation by changing the control scheme changing point ofpulse modulation, even if the IH-DPH load might be replaced by

the different IH-DPH load.

v. SIMULATIONAND EXPERIMENTAL RESULTS The results in simulation and experiment of the high fkquency cycloinverter using IGBT module are described as follows. The design specifications and circuit parameters for experimental setup of high fiequency cydoinverter are indicated in Table 1. Figure 7 shows input voltage and current survey waveforms of the cycloinverter. When duty factor d p m=0.4,0.3, 0.2, the input current form is sine wave. Although, input current wave form is not sine wave when dpwM4 . 1 . The relevant simulation and measured operating waveforms near the peak value of utility sine wave AC as the high fiequency cycloinverter set up in case of d p m -0.5 are shown in Fig.8. Tbe typical voltage and current operation wavefonns of simulation and measured ones have a good agreement within the slight error. Therefore, it is noted that the proposed pulse modulation control scheme i s more effective for the high frequency cycloinverter.

.I e, 2.

l o

2 1. a 0

[

iQl

iQI

3 4 Duty factor ~ P W

Fig.10 Inputbutput power vs. duty factor cbaractaistics in case of asymmdrical ZVS-PWM control scheme. VQ2

VQ2

iQ3

iQ2

SRL

VRL

, " " " : " ,

v~,,Vy::200[v/diVJI vu:250[v/di~J,i@,:5O[AldivJ,i p M l [ A i d i ~ ] im: IW[Aidivj, T i m e M ~ d i v J

Pulse density mnml variable

Fig.9 Soft swilcbing voltage and current waveforms in case of utility AC frequency-based utility AC-ZVS-PDMcontrol scheme in asymmetrical ZVS-PWM scheme. (dPII1(4 . 3 , dpDu=0.S). (Left trsces:Simularion, Right traces:Experiment)

dmw

Fig. 1 I InpuVoutput power vs. ZVS-PDM characteristics in case of utility AC voltage and duty factor dpw =0.3.

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VI. CONCLUSIONS

70 I

0.5

1.5 2.0 2.5 Inputpower Pin [kwl 1.0

3.0

3.5

Fig.12 Actual power conversion efficiency vs. input powex characteristics in dual mode control and nou dual mode control schemes.

The simulation and measured operating waveforms in case of the utility frequency AC-ZVS-PDM control strategy and the asymmetrical ZVS-PWMcontrol strategy are shown in Fig.9. This figure shows the operating waveforms in case of dpm 4 . 3 and dpDM=OS. The operation waveforms of simulation and measured ones are comparatively illustrated herein. The utility fkquency AC and high-frequency AC are synchronized each other. As a result, the utility frequency AC-ZVS-PDM control can operate accurately. The input or output power vs. the duty factor charackristics of this high frequency cycloinverter is depicted in Fig.10. The input or output power vs. the pulse density modulation characteristics of this high fiequency cycloinverterincaseofdp~=O.3isshowninFig.11. InFig.lO,the high frequency cycloinverter by the asymmetrical ZVS-PWM controlor Duty Cycle control is hard switching commutation operation mode in low power setting area. However, the high hquency cycloinverter operated by the asymmetrical PWM control and the utility fiequency AC-PDM control becomes soft switching operation mode even in low power setting area. Therefore, the input power or output power of high fiequency cycloinverter can be regulated up to about 150W in the zero voltage sot? switching operation, when the utility hquency AC-ZVS-PDM control is implemented in addition to the asymmetrical ZVS-PWM. Figure 12 illustrates the power conversion efficiency characteristics of the high frequency cycloinverter (see Fig.3). In Fig. 1 1, the actual efficiency of the high frequency cycloinverter using asymmetrical ZVS-PWM control might be reduced in the low power setting area, because the high frequency cycloinverter is hard switching operation mode in low power setting area. The high conversion efficiency over 90% can be almost maintained, when the utility frequency AC-ZVS-PDM is used for low power setting area, since high fiequency cycloinverter can operate under a conhtion of the soft switching commutation in all the high fkquency power regulation areas. Therefore, the dual mode pulse modulation contra1 scheme using asymmetrical ZVS-PWM and utility fiequency AC-ZVS-PDM is more effective, which is put into practical use for the high-efficient power control implementation,

In this paper, high frequency zero voltage soft switching pulse modulated cycloinverter based on LFAC to HFAC power converter with non electrolytic capacitor DC voltage smoothing filter link was newly proposed, which can achieve compactness in a volumetric physical size and weight, low cost, high reliability, high efficiency, low noise and long life. And then, the sot? switching circuit operation principle and features of the soft switching high frequency cycloinverter were actually clarified for unique consumer induction heating applications based on new type DPH using spiral plate with copper end ring as M heat exchanger. Its high ericiency power conversion could be achieved kom an experimental point of view by using LFAC to HFAC power converter using the dual mode pulse modulation time-sharing control implementation due to asymmetrical ZVS-PWM and commercial utility frequency AC-ZVS-PDM over the wide power regulation setting areas ranging from a low power to a high power setting. In the future, the optimum circuit design method of the input filter part of the high fkquency soft switching cyclainverter treated here should be investigated, and the power loss analysis of high frequency soft switching cycloinverter using measured v-i characteristics of soft switching pulse modulated power semiconductor switching devices (IGBTs; CSTBTs) represented by piece wise h e a r characteristics should be analyzed as well as improved. The actual efficiency and conventional efficiency characteristics have to be compared and studied in experiment. Finally, the LFAC to HFAC power conversion circuit using bidirectional power switches due to reverse blocking IGBT defined as high fiequency cycloinverter.

VII. REFERENCES Hideaki TanMilsuru Kmeda, Srawouth chandhaket, M a " Aubdallha At,Mutsuo N h k a "Eddy Current Dual Packs Heater based Continuous Pipeline Fluid Heating using Soft Switching PWM High Frequency Inverter", Proceedingsof InternationalSymposium on Industtial Electronics VUE), Mexico. pp306-311, December, 2000 Hanro Taai, Hideki Sadalrata, Hideki Omti, Hidekazu Ymashita, Mutsuo Nakaoka :"High Frequency Soft Switching Inverter for Fluid-Hearing Applianm Using Induction Eddy Cumnt-based Involuted Type Heat", Pmecdings of iEEE Power Eleehonics Specialists Conference (PESC), Vo1.4, pp. 1874-1878 Caims, Australia, June,2002 Lahrath Gamage, Tarck Ahmed, Hisayuki SugimUrq Srawouth Chandhket and Mutsuo Nakoka," Series Load Resonant Phase Shifted Z V S - P W High-Frequmcy Inverter with a Single Auxiliary Edge Resonant AC Load Side Snub& for Induction Heating Super Heated Steamer", Proceedings of 2003 International Conference on Power Electronics and Drive System PEDS), no.PS-04,pp.30-37, Singapore, " % m b e r ~ ~ 3 . H i s a m Sugimura,HideMuraoka, Kouji Sousbjn, Mikiya Matsuda, and Mutsuo Nalcaoka'?)ual Mode ZVS-PWM High Frequency Load Resonant lnvertet with Auxiliary Edge resonant Snubber for Super Heated Steamer", Proceedingsof The 29*Annual Conference of the IEEE Musirial Electronics Society (IECON), pp.1679-16W4. Virginia,USA, November, 2003.

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