4466 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 47, NO. 10, OCTOBER 2019

Solid-State Bipolar Pulsed-Power Modulator Basedon a Half-Bridge Power Cell Structure

Seung-Hee Lee, Seung-Ho Song , Hyun-Bin Jo, and Hong-Je Ryoo , Member, IEEE

Abstract— This paper addresses the design of a solid-statebipolar pulsed-power modulator based on a series of stackedpower cells that realize a simple and robust structure. Eachcell is charged in parallel by an LCC resonant converterindependently of the discharging loop. A passive cell-balancingdesign is implemented. The power cell using insulated gatebipolar transistors (IGBTs) can operate in bypass mode withoutan additional component, and the circuit operation was analyzed.A simple gate driving method, which provides synchronized gatesignals without an extra power source of each gate driver usingtwo control loops and isolation transformers, is implemented forthe proposed bipolar pulsed-power modulator based on stackedcells. Moreover, an unexpected gate turn-on problem was solvedby an additional off signal. To validate the proposed structure andthe gate driving scheme, a three-cell, 1.2-kV, 110-A, 1.5- to 4-µs,3-kHz laboratory experimental prototype test was conducted. Theresults proved the reliability of the proposed solid-state bipolarpulsed-power modulator.

Index Terms— Capacitor charger, gate drive circuit, powercells, solid-state bipolar pulsed-power modulator.

I. INTRODUCTION

THE environment and sanitation have become popular top-ics in science and industrial technology in the twenty-first

century. Accordingly, interest in pulsed electric fields (PEFs)and dielectric barrier discharges (DBDs) for liquid food pas-teurization, wastewater treatment, and air purification systemsis increasing [1]–[5]. Research on the topologies of the bipolarpulsed-power modulator has been conducted actively becausethe power supply based on the bipolar topology is moresuitable for these applications than the unipolar topology.

As a method of constructing a bipolar pulse modulator,structures combining a unipolar solid-state Marx generatorand an H-bridge have been introduced [6], [7]. Because aseries stack of insulated gate bipolar transistors (IGBTs) isimplemented to generate high voltage over the rated voltage ofthe switch used in the inverter, a voltage-balancing techniquebetween the IGBTs is needed. To address this issue, a cascadebipolar arrangement of two unipolar pulsed-power modulators

Manuscript received January 2, 2019; revised March 4, 2019; acceptedApril 2, 2019. Date of publication May 1, 2019; date of current ver-sion October 9, 2019. This work was supported in part by the NationalResearch Foundation of Korea (NRF) Grant funded by the Korea Government(MSIP) under Grant NRF-2017R1A2B3004855 and in part by the Chung-Ang University Graduate Research Scholarship in 2019. The review of thispaper was arranged by Senior Editor R. P. Joshi. (Corresponding author:Hong-Je Ryoo.)

The authors are with the School of Energy Systems Engineering,Chung-Ang University, Seoul 06974, South Korea (e-mail: hjryoo@cau.ac.kr).

Color versions of one or more of the figures in this article are availableonline at http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TPS.2019.2911716

has been suggested [8]. Similarly, combinations of submoduleshave been presented to increase the output voltage [9], [10].

In a voltage-multiplier-based bipolar pulsed-power mod-ulator, only capacitors and switches have been used withlow-voltage stress [11]. However, the number of componentsis doubled and complicated charging modes are required toincrease the number of stages. A topology for the modifiedvoltage multiplier has been proposed as one of the methods toreduce the number of circuit elements [12]. In bipolar pulsed-power modulators based on a voltage multiplier, however,the power source does not charge the storage capacitor directlyand the average power is limited.

Solid-state Marx-generator structures have been adopted forseveral bipolar pulsed-power modulators [13]–[15]. In thistopology, each of the cells is charged by the input power sourceand voltage balancing can be achieved. Switches for chargingas well as switches for generating bipolar pulses are required,and each of the charging switches needs switching control.An improved structure with a reduced number of componentshas been suggested [16].

Generally, bipolar pulsed modulator based on a half-bridgeinverter is not used because it is difficult to charge bipolarhigh voltage to generate high-voltage bipolar pulses. In [17],it is tried to use half-bridge cell stacking to generate thehigh-voltage bipolar pulse. But, this topology has drawbacksthat modulations of pulse width, pulse repetition rate, and theoutput voltage level are limited.

Stacked power cells topologies need a synchronized switch-ing signal and isolated power for driving switches. The generalgate driving method to provide isolated and synchronized gatesignals needs a separate power source for each gate driver [18].To generate high-voltage pulses, the number of dischargingswitches increases and many power sources for gate drivingare required, complicating the structure and switching control.Implementing a control-loop gate driving method is a solutionto this limitation of the conventional method [19], [20]. Whengate driving with the control-loop method, ON–OFF pulsesfrom the pulse control inverter enter into a single loop andare delivered to each of the gate drivers simultaneously viasmall transformers. A 40-kV solid-state unipolar pulsed-powermodulator realizes the compact structure and simple switchingcontrol using the control-loop gate driving method [20].

In this paper, a solid-state bipolar pulsed-power modulatorbased on a series of stacked power cells is proposed with asimple scheme for minimizing the number of components. Theproposed power cell based on a half-bridge structure realizes abypass mode without an additional component. The proposed

0093-3813 © 2019 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission.See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.

LEE et al.: SOLID-STATE BIPOLAR PULSED-POWER MODULATOR BASED ON A HALF-BRIDGE POWER CELL STRUCTURE 4467

topology has achieved synchronized switching control byapplying a modified control-loop gate driving method forbipolar pulsed-power modulators. Because the control loopprovides the gate drivers with isolated and synchronizedsignals as well as power for gate driving, no additional powersource is required, simplifying the structure of the proposedmodulator. An LCC resonant converter with current sourcecharacteristics was designed as a capacitor charger. Indepen-dently of the discharging loop, storage capacitors of eachpower cell are charged in parallel via a multiwinding trans-former of the capacitor charger and a voltage-doubler rectifier,requiring no additional charging switch. Moreover, chargerdesign techniques for passive cell balancing are employed.Finally, to prove the reliability of the proposed structureand gate driving method, a laboratory prototype has beenfabricated and tested.

II. BIPOLAR CIRCUIT OPERATION

The proposed power cell, based on a typical half-bridgestructure, consists of two IGBT switches and two storagecapacitors. Both IGBT switches are designated as positiveand negative discharging switches. The storage capacitors arecharged in parallel by a capacitor charger. A positive or neg-ative pulse is generated depending on the switch beingturned on. When the same-side switches of N stacked powercells are turned on simultaneously, the cells are connectedin series and the pulse of N · Vc (where Vc is the voltageof a single capacitor) is discharged to the load. In addition,the proposed power cell realizes bypass operation withoutadditional components.

A. Operation PrincipleThe proposed bipolar pulsed-power modulator operates

basically as a positive pulse discharging mode and a negativepulse discharging mode, as shown in Fig. 1. Bypass modesessential for the series stack of power cell structure are alsoimplemented, achieving robust operation.

1) Positive Discharging Mode: Fig. 1(a) shows the opera-tion when the storage capacitors C2, C4, . . . , C2N charged inparallel are connected in series when switches S2, S4, . . . , S2N

are turned on. The N series connected capacitors generate apositive pulse, and the output pulse voltage to the load is asfollows:

Vo = +N · Vc (1)

where the voltage of a single storage capacitor is Vc. Whenthe positive pulse is generated, voltage 2Vc is applied to thecollector–emitter of the opposite-side switches that are turnedoff, which is utilized to determine the rated voltage of a singledischarging switch.

2) Positive Bypass Mode: To generate a positive pulse, allthe positive discharging switches should be turned on. Thepositive bypass mode operates when the gate signals are notwell synchronized, or a malfunction occurs in the gate driver ofthe switch. Without a bypass circuit, the sum of the voltages onthe series connected capacitors can damage the switch whichfails in synchronization. The bypass operation, in which theantiparallel diode of S3 provides the current path when S4 isnot turned on, is shown in Fig. 1(b).

Fig. 1. Operation modes of the proposed power cells. (a) Positive dischargingmode. (b) Positive bypass mode. (c) Negative discharging mode. (d) Negativebypass mode.

The opposite polarity voltage −Vc is generated in thedysfunctional cell, and, as a result, the voltage applied to theload is

Vo = +(N − 2) · Vc. (2)

The voltage across the collector–emitter of S4 is −2V c,which is below the rated voltage, and the circuit is safelyprotected. As a result, without additional bypass elements,the bypass operation increases the reliability and robustnessof the proposed pulsed-power modulator.

3) Negative Discharging Mode: The negative dischargingmode is similar to the positive discharging mode. As shownin Fig. 1(c), the serial connection of the charged storagecapacitors C1, C3, . . . , C2N−1 generates a negative pulse andthe output pulse voltage to the load is

Vo = −N · Vc. (3)

4468 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 47, NO. 10, OCTOBER 2019

4) Negative Bypass Mode: In the case of the synchro-nization failure or malfunction of the gate driver in thenegative discharging mode, similar to the positive bypassmode, the antiparallel diode of the opposite switch providesthe current path to enable bypass operation. The operation ofthe negative bypass mode when S3 is not turned on is shownin Fig. 1(d). The output pulse voltage in the negative bypassoperation is

Vo = −(N − 2) · Vc. (4)

III. DESIGN AND IMPLEMENTATION OF THE PROPOSED

BIPOLAR PULSE MODULATOR

The overall scheme of the proposed bipolar pulsed-powermodulator is shown in Fig. 2. A three-cell bipolar pulsed-power modulator, comprising a current source capacitorcharger using an LCC resonant converter and three powercells, is designed to validate the proposed topology. The LCCresonant converter comprises an LCC resonant tank (seriesresonant inductor Ls , series resonant capacitor Cs , and parallelresonant capacitor Cp), a multiwinding isolation transformer,and an H-bridge with snubber capacitors in parallel witheach switch. Also, three parallel secondary windings of themultiwinding transformer are connected in parallel with thepower cells through voltage-doubler rectifier circuits.

A. Capacitor Charger

The LCC resonant converter is used to charge the storagecapacitors independently of the discharging loop through themultiwinding isolation transformer and rectifier. Employingmultiwinding transformers for each loop provides the advan-tages of low cost and a simple structure [19]. Low conductionloss and switching loss can be obtained by using an LCCresonant converter operating in a continuous conduction mode,and the charging voltage can be controlled by adjusting theswitching frequency. In addition, the leakage inductance andparasitic capacitance of the multiwinding isolation transformerwere utilized for a part of the LCC resonant tank.

The parallel resonant capacitor (Cp) can change the currentwaveform into a trapezoidal shape, which decreases the crestfactor [21]. Also, a high resonant current can be obtainedthrough the operation to charge Cp . Before the switches areturned on, sufficient resonant current enables the completedischarge of the snubber capacitors, which is designed tominimize the turn-off loss of the switches, within the operatingfrequency range.

Under light-load operation, however, the snubber capacitorthat is incompletely discharged due to the low resonant currentcan lead to hard switching. Therefore, the operating frequencyis determined by considering both the rated operation and thefrequency range where hard switching does not occur. Theseries resonant frequency of 9 kHz and the parallel resonantfrequency of 139 kHz were set according to the operatingfrequency, and the parameters of the resonant tank weredetermined accordingly. A C2M0040120 silicon carbide (SiC)power MOSFET was selected as a semiconductor switch forthe full-bridge inverter by considering the maximum resonant

Fig. 2. Overall configuration of the proposed N -power-cell stacked bipolarpulsed-power modulator. (a) Capacitor charger and pulse generator. (b) Gatedrive circuits and double control loops.

current value and switch characteristics at high-switching-frequency operation. The specifications and design parametersof the LCC resonant converter are summarized in Table I.

B. Isolation Multiwinding Transformer and SeriesResonant Inductor

The process of designing the transformer and series resonantinductor of the resonant LCC converters is as follows. Theprimary-side turns are determined so that the transformeris not saturated by the input voltage during the minimum-switching-frequency operation. The transformer turns ratio iscalculated according to the voltage ratio between the primaryand secondary sides, and the number of secondary windingscan be easily calculated by multiplying the transformer turnsratio and the number of primary turns. In addition, a bobbindesign is implemented to ensure insulation between the pri-mary and secondary windings and between each of the threeparallel secondary windings [22]. The series resonant inductor

LEE et al.: SOLID-STATE BIPOLAR PULSED-POWER MODULATOR BASED ON A HALF-BRIDGE POWER CELL STRUCTURE 4469

TABLE I

SPECIFICATIONS AND DESIGN PARAMETERSFOR THE CAPACITOR CHARGER

is implemented so that the sum of the value of the transformerleakage inductance and the value of the inductance of theseries resonant inductor is the Ls design value of the resonanttank. The Ls design value takes into account cell balancingas explained in Section III-C. The air gap and the number ofturns of the series resonant inductor are determined so that itis not saturated by the resonant current. Furthermore, becausethe resonant LCC converter operates at a high frequencyof 85 to 240 kHz, a 0.08-mm 500 Litz wire is used as thewinding of the resonant inductor and the primary winding ofthe transformer.

C. Voltage Balancing of the Secondary Winding

Each of the three parallel secondary windings of the trans-former is connected to the two storage capacitors of the powercell through a voltage-doubler circuit, as shown in Fig. 2.When three secondary parallel windings and the primarywinding are coupled, the structural differences cause thedifference in the leakage inductances between the secondarywindings, inducing voltage unbalancing of the power cells.The voltage unbalancing becomes even worse as differencesbetween secondary parasitic elements become larger.

To solve the unbalancing of power cells, a primary-sideseries resonant inductor with an inductance factor of 20 greaterthan the differences of the secondary-side leakage inductancesis needed. The series resonant inductor significantly reducesthe influence of differences in leakage inductance, minimizingcell unbalancing.

D. Cell

The proposed power cell is based on a simple half-bridge structure consisting of two IGBTs and two capacitors.When the upper or the lower discharging switches in eachpower cell are turned on at the same time, the charged storagecapacitors are connected in series and generate a pulse. At thisinstant, the voltage across the two storage capacitors is appliedto the opposite-side switches that are not turned on. Under the

TABLE II

SPECIFICATIONS OF THE PULSE DISCHARGING SWITCH

rated condition, a single capacitor is charged to 400 V,so the 800-V voltage is applied to the switch, which is themain consideration in selecting the discharging switch. Also,an antiparallel diode of the switch for bypass operation shouldbe considered. An FGL40N120AND 1200-V NPT IGBT wasselected as the discharging switch of the power cell, and itsspecifications are summarized in Table II.

E. Control-Loop Method for Gate Driving Circuit

General topologies adopt switching control based on opticalfiber for providing an isolated and synchronized gate signal.This method needs an independent power source for each gatedriver, complicating the structure and increasing the cost [18].A gate driving circuit based on the control-loop methodeliminates this drawback [19], [20]. The ON–OFF pulse of thecontrol inverter, controlled by the pulse controller, enters thesingle control loop and is simultaneously transmitted to eachof the gate drivers via the isolation transformer. The ON–OFF

pulse is not only a switching signal but also a power source forthe gate driving circuit. Implementing this method simplifiesthe structure and minimizes the number of control components.

The conventional control-loop method was modified andapplied to the proposed bipolar pulsed-power modulator.Double control loop is used for bipolar pulse discharging,and each control loop consists of a winding and a controlinverter, as shown in Fig. 2(b). Two control inverters are drivenindependently for positive and negative pulses. In using adouble control loop, one loop is utilized for positive discharg-ing signal and the other for a negative discharging signal.The output pulse width is adjusted by the interval betweenthe ON pulse and the OFF pulse from control inverter. Also,the repetition rate of the pulse generation is adjusted by theswitching frequency of the control inverter. An overview ofthe gate driving of the pulse generator is shown in Fig. 3.

F. IGBT Turn-On Problem in the Off-State

The control inverter, the H-bridge controlled by the pulsecontroller, generates a positive voltage (ON pulse) and anegative voltage (OFF pulse), as illustrated in Fig. 3. Throughthe control loop, these outputs of the control inverter aretransmitted to the gate driver as power and the gate signalfor the gate driving circuit. When the gate driver receivesthe ON pulse from the control loop, 20 V is applied to thegate–emitter of the discharging switches until it receives anOFF signal.

During the interval of the ON–OFF pulse signal, turn-onis maintained, which generates a positive or negative output

4470 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 47, NO. 10, OCTOBER 2019

Fig. 3. Summary of the gate driving of pulse generation.

pulse (turn-on hold mode). When the OFF pulse is received,the 20-V voltage source is disconnected from the gate–emitterof the IGBT. As Cge is discharged to the ground through thepull-down resistor, the switch is turned off (turn-off mode).This system, which does not have a turn-off hold mode andis just pulled down to the ground through a resistor, causes ashort-circuit problem that both IGBTs of the power cell areturned on at the same time. The IGBT of the proposed powercell satisfies

Vce = Vcg + Vge (5)

2V c = Vp,ce + Vn,ce. (6)

The OFF-state voltage across each of the IGBTs satisfies

Vp,ce = Vn,ce = Vc (7)

if the balancing between IGBTs turned off is assumed tobe perfect.

The instant when the positive discharging mode starts isexplained as follows. When the positive discharging switchturns on, the voltages Vce of the positive and negative dis-charging switches are as follows:

Vp,ce = 0, Vn,ce = 2V c. (8)

That is, Vn,ce increases from Vc to 2V c. Vn,cg and Vn,ge arealso increased in inverse proportion to Ccg and Cge when Vn,ceis rapidly increased. Therefore, when a high voltage is appliedto the IGBT without a turn-off hold operation, the switch turnson when the voltage of Vge rises and exceeds the thresholdvoltage. In this case, the two switches of the half-bridge-based structure in the power cell are turned on at the sametime, leading to a short-circuit problem, which may damagethe circuit. In this study, additional gate-off signals are usedto avoid this problem.

G. Additional Gate-Off Signal

At the instant of positive discharging, the voltage appliedto the negative discharging IGBT rapidly increases fromVc to 2Vc, and the gate voltage (Vn,ge) of the IGBT withouta turn-off hold mode also rises above the threshold voltage.

The parasitic capacitances of the dischargingFGL40N120AND 1200-V NPT IGBT are as follows:

Cge = 3075 pF, Cce = 245 pF, Cgc = 125 pF.

Because Vc (the increment of Vce) is divided into Vcg and Vgein inverse proportion to each of the capacitances, Vn,ge underrated condition is approximately calculated as

Vn,ge ∼= Vc × Cgc

Cgc + Cge

∼= 16 V. (9)

Vn,ge above the threshold voltage is reduced via a pull-downresistor (500 �) in the gate driver, which takes a certainamount of time until it becomes lower than the thresholdvoltage. That is, when the positive discharging IGBT isturned on, the negative discharging switch is turned on fora certain period of time and the same phenomenon occurs inthe negative discharging mode. This phenomenon may damagethe circuit of the power cell.

In this paper, as shown in Fig. 3, when transmitting apulse to an IGBT for output pulse discharging, an “additionalgate-off pulse” is transmitted to the opposite switch, whichshould be turned off, preventing switch damage. Vge, which isincreased due to a sudden rise of voltage across the IGBT,is instantly reduced by the gate-off pulse, and abnormaloperation does not occur.

IV. EXPERIMENTAL RESULTS

Based on this paper, various experiments were conductedto verify the characteristics and performance of the proposedstructure and gate driving method. A laboratory prototypeof a 1.2-kV, 110-A, 1.5- to 4-μs, 3-kHz, three-cell bipolarpulsed-power modulator with a noninductive resistor load hasbeen employed for experimental verification. A YokogawaDLM2024 (2.5 GS/s and 200 MHz) was used as an oscil-loscope, a Tektronix P6015A (20 kV, 75 MHz, and 1000:1)was used as a voltage probe to measure the load voltage andcurrent, and a Pearson Electronics model 4997 (100:1) wasused as a current probe.

To verify the bypass operation, the output pulse voltage inthe discharging mode and in the bypass mode were comparedby turning off the negative discharging IGBT of the firstcell under 600-V output condition which is half of the ratedcondition, as shown in Fig. 4. In the negative bypass mode, theoutput pulse voltage is about −200 V, which is minus thetwo capacitor voltages at −600 V output pulse voltage inthe negative discharging mode. When the negative dischargingswitch of the first cell is not turned on in negative discharging,the voltage across the positive discharging IGBT of the firstcell, VCE,1p , is about 0 V. This means that the body diodeof the IGBT is forward-biased and conducts current. It isverified that the bypass mode is operated when the discharg-ing switch is not turned on. In addition, in the OFF-state,VCE,1p and VCE,1n are floated. A Yokogawa 701921 differ-ential probe (1000:1) was used to measure the voltage acrossthe discharging IGBT. To validate cell balancing, the voltagesof the three power cells were measured under 800-V chargingconditions. Fig. 5 shows that voltage differences of <±3%among the three cells were measured. A Yokogawa 701 921

LEE et al.: SOLID-STATE BIPOLAR PULSED-POWER MODULATOR BASED ON A HALF-BRIDGE POWER CELL STRUCTURE 4471

Fig. 4. Experimental results comparing bypass operation with normaloperation.

Fig. 5. Comparison of charging voltage of each cell.

Fig. 6. Voltage and current waveforms of the bipolar pulsed-power modulatorunderrated condition.

differential probe (1000:1) was used to measure the power cellvoltage.

The experimental waveforms show a single pulse at ratedoperation (1.2 kV and 110 A) in Fig. 6. To vary the chargingvoltage of the power cell, the switching frequency of thecharger was controlled by the charger controller, and theexperiment was performed over a wide range from light-loadoperation to the rated operation. The output pulse voltage wasincreased by 200 V from 400 to 1200 V, as shown in Fig. 7(a).

The pulse width can be varied by adjusting the intervalbetween the gate ON–OFF signal from the pulse controller. Theexperimental waveforms of the pulse width, which is increasedfrom 0.5 to 4 μs in steps of 0.5 μs under the rated condition,are shown in Fig. 7(b).

The repetition rate of the pulse output can be controlledby adjusting the frequency of the control inverter in thepulse controller. Fig. 7(c) shows the output pulse waveformwith a repetition rate of 3000 pulses/s. The specifications ofthe laboratory prototype of three-cell bipolar pulsed-powermodulator are summarized in Table III.

Fig. 7. Experimental waveforms. (a) Variable output pulse voltage.(b) Variable pulse width. (c) Maximum pulse repetition under 6-cell,5-kV condition.

TABLE III

THREE-POWER-CELL-STACKED BIPOLAR PULSE

MODULATOR SPECIFICATIONS

To verify the feasibility of the proposed topology in highvoltage, an experimental prototype with stacked six powercells was tested. Fig. 7(c) also shows 5-kV bipolar pulsewaveforms.

V. CONCLUSION

A bipolar pulsed-power modulator based on a series ofstacked power cells has been proposed. The proposed topol-ogy consists of series-connected power cells and a storagecapacitor charger using an LCC resonant converter. A powercell with a simple and robust structure has been suggested. Thepower cell operates in bypass mode when synchronization failswithout an additional component. A modified control-loopgate driver circuit has been applied to the proposed topology.Synchronized gate signals can be obtained without separatepower sources for each of the gate drivers, which minimizesthe number of components. Moreover, it is easy to vary the

4472 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 47, NO. 10, OCTOBER 2019

pulse width and repetition rate. In this study, the use of anadditional gate-off pulse solves the arm short problem thatboth switches are turned on. A 1.2-kV, 110-A, 3-kHz, three-power-cell stacked bipolar pulsed-power modulator was testedto validate the reliability of the proposed topology. In addition,the 5-kV test verified that the proposed half-bridge structurecan be effectively used at high voltage as well.

REFERENCES

[1] S. A. Ghani, W. I. Ibrahim, M. R. Ghazali, and N. A. Azli, “Powerelectronics converter with Marx generator configuration based PEF forliquid food sterilization,” in Proc. Int. Conf. Elect., Control Comput.Eng. (InECCE), Jun. 2011, pp. 416–419.

[2] W. Shin, J. Choi, and T. Kim, “Bidirectional pulse plasma power supplyfor treatment of air pollution,” in Proc. IEEE 37th Power Electron. Spec.Conf., Jeju, South Korea, Jun. 2006, pp. 1–6.

[3] Y. Xu, R. Zhang, C. Zhang, Z. Li, Z. Guan, and L. Wang, “Bipolarpulsed discharge in the gas-liquid-solid mixture and its application forwater treatment,” in Proc. IEEE 9th Int. Conf. Properties Appl. Dielectr.Mater., Jul. 2009, pp. 579–582.

[4] C. Wang, Q. H. Zhang, and C. Streaker, “A 12 kV solid state highvoltage pulse generator for a bench top PEF machine,” in Proc.IEEE Power Electron. Motion Control Conf., vol. 3, Aug. 2000,pp. 1347–1352.

[5] P. S. Brito, H. Canacsinh, J. P. Mendes, L. M. Redondo, andM. T. Pereira, “Comparison between monopolar and bipolar microsec-ond range pulsed electric fields in enhancement of apple juice extrac-tion,” IEEE Trans. Plasma Sci., vol. 40, no. 10, pp. 2348–2354,Oct. 2012.

[6] X. Lan, M. Long, X. Zi-Jie, X. Qin, Z. De-Qing, and Y. Zi-Kang,“A novel generator for high-voltage bipolar square pulses with appli-cations in sterilization of microorganism,” IEEE Trans. Dielectr. Electr.Insul., vol. 22, no. 4, pp. 1887–1895, Aug. 2015.

[7] S. Bae, A. Kwasinski, M. M. Flynn, and R. E. Hebner, “High-power pulse generator with flexible output pattern,” IEEE Trans. PowerElectron., vol. 25, no. 7, pp. 1675–1684, Jul. 2010.

[8] A. Elserougi, A. Massoud, and S. Ahmed, “Conceptual study of abipolar modular high voltage pulse generator with sequential charging,”IEEE Trans. Dielectr. Electr. Insul., vol. 23, no. 6, pp. 3450–3457,Dec. 2016.

[9] L. L. Rocha, J. F. Silva, and L. M. Redondo, “Multilevel high-voltagepulse generation based on a new modular solid-state switch,” IEEETrans. Plasma Sci., vol. 42, no. 10, pp. 2956–2961, Oct. 2014.

[10] A. Elserougi, A. Massoud, M. Daoud, and S. Ahmed, “A hybridboost modular multilevel converter-based bipolar high voltage pulsegenerator,” IEEE Trans. Dielectr. Electr. Insul., vol. 24, no. 5,pp. 2873–2880, Oct. 2017.

[11] A. Alijani, J. Adabi, and M. Rezanejad, “A bipolar high-voltage pulsed-power supply based on capacitor-switch voltage multiplier,” IEEE Trans.Plasma Sci., vol. 44, no. 11, pp. 2880–2885, Nov. 2016.

[12] M. R. Delshad, M. Rezanejad, and A. Sheikholeslami, “A new mod-ular bipolar high-voltage pulse generator,” IEEE Trans. Ind. Electron.,vol. 64, no. 2, pp. 1195–1203, Feb. 2017.

[13] T. Sakamoto, A. Nami, M. Akiyama, and H. Akiyama, “A repeti-tive solid state Marx-type pulsed power generator using multistageswitch-capacitor cells,” IEEE Trans. Plasma Sci., vol. 40, no. 10,pp. 2316–2321, Oct. 2012.

[14] L. M. Redondo, H. Canacsinh, and J. F. Silva, “New repetitive bipolarsolid-state Marx type modulator,” in Proc. IEEE Int. Power ModulatorsHigh-Voltage Conf., May 2008, pp. 253–256.

[15] L. M. Redondo, H. Canacsinh, and J. F. Silva, “Generalized solid-stateMarx modulator topology,” IEEE Trans. Dielectr. Electr. Insul., vol. 16,no. 4, pp. 1037–1042, Aug. 2009.

[16] H. Canacsinh, L. M. Redondo, and J. F. Silva, “Marx-type solid-statebipolar modulator topologies: Performance comparison,” IEEE Trans.Plasma Sci., vol. 40, no. 10, pp. 2603–2610, Oct. 2012.

[17] L. Gao, D. Wang, J. Qiu, and K. Liu, “All-solid-state pulse adder withbipolar high voltage fast narrow pulses output,” IEEE Trans. Dielectr.Electr. Insul., vol. 18, no. 3, pp. 775–782, Jun. 2011.

[18] S. Castagno, R. D. Curry, and E. Loree, “Analysis and comparison ofa fast turn-on series IGBT stack and high-voltage-rated commercialIGBTS,” IEEE Trans. Plasma Sci., vol. 34, no. 5, pp. 1692–1696,Oct. 2006.

[19] S.-H. Ahn, H.-J. Ryoo, J.-W. Gong, and S.-R. Jang, “Robust designof a solid-state pulsed power modulator based on modular stackingstructure,” IEEE Trans. Power Electron., vol. 30, no. 5, pp. 2570–2577,May 2015.

[20] S.-B. Ok, H.-J. Ryoo, S.-R. Jang, S.-H. Ahn, and G. Goussev, “Designof a high-efficiency 40-kV, 150-A, 3-kHz solid-state pulsed powermodulator,” IEEE Trans. Plasma Sci., vol. 40, no. 10, pp. 2569–2577,Oct. 2012.

[21] S.-R. Jang, C.-H. Yu, and H.-J. Ryoo, “Trapezoidal approximation ofLCC resonant converter and design of a multistage capacitor chargerfor a solid-state Marx modulator,” IEEE Trans. Power Electron., vol. 33,no. 5, pp. 3816–3825, May 2018.

[22] J.-W. Gong, H.-J. Ryoo, S.-H. Ahn, and S.-R. Jang, “Design andimplementation of a 40-kV, 20-kJ/s capacitor charger for pulsed-powerapplication,” IEEE Trans. Plasma Sci., vol. 42, no. 11, pp. 3623–3632,Nov. 2014.

Seung-Hee Lee received the B.S. degree in energysystems engineering from Chung-Ang University,Seoul, South Korea, in 2017, where he is currentlypursuing the M.S. degree with the Department ofEnergy Engineering.

His current research interests include high-efficiency resonant converters and solid-state high-voltage pulsed-power modulators.

Seung-Ho Song received the B.S. degree in electri-cal engineering from Kwangwoon University, Seoul,South Korea, in 2016. He is currently pursuing theM.S. and Ph.D. degrees with the Department ofEnergy Engineering, Chung-Ang University, Seoul.

His current research interests include soft-switchedresonant converter applications and high-voltagepulsed-power supply systems.

Hyun-Bin Jo received the B.S. degree in electronicengineering from Catholic University, Bucheon,South Korea, in 2016. He is currently pursuing theM.S. and Ph.D. degrees with the Department ofEnergy Engineering, Chung-Ang University, Seoul,South Korea.

His current research interests include high-voltagepulsed-power supply systems.

Hong-Je Ryoo (M’17) received the B.S., M.S.,and Ph.D. degrees in electrical engineering fromSungkyunkwan University, Seoul, South Korea,in 1991, 1995, and 2001, respectively.

From 1996 to 2015, he was a Principal ResearchEngineer with the Electric Propulsion Research Divi-sion, Korea Electrotechnology Research Institute,Changwon, South Korea, where he was a Leaderwith the Pulsed Power World Class Laboratory andthe Director of the Electric Propulsion ResearchCenter. From 2004 to 2005, he was a Visiting

Scholar with WEMPEC, University of Wisconsin–Madison, Madison, WI,USA. From 2005 to 2015, he was a Professor with the Department of EnergyConversion Technology, University of Science and Technology, Daejeon,South Korea. In 2015, he joined the School of Energy Systems Engineering,Chung-Ang University, Seoul, where he is currently a Professor. His currentresearch interests include pulsed-power systems and their applications, as wellas high-power and high-voltage conversions.

Dr. Ryoo is the Academic Director of the Korean Institute of PowerElectronics, a Senior Member of the Korean Institute of Electrical Engineers,and the Vice President of the Korean Institute of Illuminations and ElectricalInstallation Engineers.