A Modular Multilevel Based High-Voltage Pulse Generator for Water Disinfection Applications

Transcription

1 Elgenedy, Mohamed A. and Badawy, Ahmed and Ahmed, Shehab and Williams, Barry W. (26) A modular mulilevel based high-volage pulse generaor for waer disinfecion applicaions. IEEE Transacions on Plasma Science. ISSN (In Press), This version is available a hps://srahprins.srah.ac.uk/5784/ Srahprins is designed o allow users o access he research oupu of he Universiy of Srahclyde. Unless oherwise explicily saed on he manuscrip, Copyrigh and Moral Righs for he papers on his sie are reained by he individual auhors and/or oher copyrigh owners. Please check he manuscrip for deails of any oher licences ha may have been applied. You may no engage in furher disribuion of he maerial for any profimaking aciviies or any commercial gain. You may freely disribue boh he url (hps://srahprins.srah.ac.uk/) and he conen of his paper for research or privae sudy, educaional, or no-for-profi purposes wihou prior permission or charge. Any correspondence concerning his service should be sen o he Srahprins adminisraor: srahprins@srah.ac.uk The Srahprins insiuional reposiory (hps://srahprins.srah.ac.uk) is a digial archive of Universiy of Srahclyde research oupus. I has been developed o disseminae open access research oupus, expose daa abou hose oupus, and enable he managemen and persisen access o Srahclyde's inellecual oupu.

2 A Modular Mulilevel Based High-Volage Pulse Generaor for Waer Disinfecion Applicaions Mohamed A. Elgenedy, Suden Member, IEEE, Ahmed Darwish, Shehab Ahmed, Senior Member, IEEE, and Barry W. Williams Absrac The role of irreversible elecroporaion using pulsed elecric field (PEF) is o generae high volage (HV) pulses wih a predefined magniude and duraion. These HV pulses are applied o he reamen chamber unil deconaminaion of he sample is compleed. In his paper, a new opology for HV recangular pulse generaion for waer disinfecion applicaions is inroduced. The proposed opology has four arms comprised of series conneced half H-bridge modular mulilevel converer cells. The recangular pulse characerisics can be conrolled via a sofware conroller wihou any physical changes in power opology. The converer is capable of generaing boh bipolar and monopolar HV pulses wih micro-second pulse duraions a a high frequency rae wih differen characerisics. Hence, he proposed opology provides flexibiliy by sofware conrol, along wih hardware modulariy, scalabiliy, and redundancy. Moreover, a cell s capaciance is relaively small which drasically reduces he converer fooprin. The adoped charging and discharging process of he cell capaciors in his opology eliminae he need of any volage measuremens or complex conrol for cellcapaciors volage balance. Consequenly, coninuiy of converer operaion is assured under cell malfuncion. In his paper, analysis and cell-capacior sizing of he proposed opology are deailed. Converer operaion is verified using MATLAB/Simulink simulaion and scaled experimenaion. Index Terms Modular mulilevel converers (MMC), pulsed elecric field, high volage pulses, waer disinfecion. P I. INTRODUCTION ULSED elecric field (PEF) generaors are applied for elecroporaion, ha is a process in which a cell membrane is subjeced o high elecric field []. Manuscrip received April, 26; revised Augus 4, 26 and acceped Sepember 5, 26. This work was suppored by a Naional Prioriies Research Program (NPRP) gran NPRP ( ) from he Qaar Naional Research Fund (QNRF). M. A. Elgenedy is wih he Deparmen of Elecronic and Elecrical Engineering, Universiy of Srahclyde, G RD Glasgow, U.K., and also wih he Elecrical Engineering Deparmen, Faculy of Engineering, Alexandria Universiy, Alexandria 2544, Egyp ( A. Darwish, and B. W. Williams are wih he Deparmen of Elecronic and Elecrical Engineering, Universiy of Srahclyde, Glasgow GXQ, U.K. ( ahmed.mohameddarwish-badawy@srah.ac.uk barry.williams@srah.ac.uk). S. Ahmed is wih he Deparmen of Elecrical and Compuer Engineering, Texas A&M Universiy a Qaar, Doha 23874, Qaar ( shehab.ahmed@qaar.amu.edu). Usually, he argeed cell membranes are of microorganisms o be deconaminaed. This is required when bacerial deconaminaion is sough in an irreversible elecroporaion, for example in waer purificaion and in he food indusry [2]. The parameers selecion of he generaed PEF is applicaion dependen. However, volage magniude, pulse duraion, repeiion rae and pulse shape are he mos imporan parameers. Hence, he main arge of PEF generaors is o generae a pulse of high-volage (HV) across he erminals of he reamen chamber (which conains he subsance) for sufficien pulse duraion [3]. Among he differen pulse shapes, recangular pulses have high effecive pulse areas; hence hey are preferred for PEF applicaion in waer reamen [3]. The HV pulses can be monopolar and bipolar. The monopolar pulses coninuously subjec he cell membrane o an elecric field in a fixed direcion, and hus he membrane canno recover. Alernaively, bipolar pulses subjec he cell membrane o mechanical sresses in addiion o elecrical sresses, hence can expedie he lysing process [4]. For effecive lysing for waer disinfecion, he pulse volage should be a leas kv wih pulse duraion of a few microseconds (ha is, o µs) [5]. Generaing HV recangular pulses, eiher monopolar or bipolar, is an esablished opic in he lieraure. Classically, Marx generaors, pulse forming neworks, and Blumlein lines are applied in PEF applicaions [6]. However, due o he evoluion of power elecronic swiches, wih high volage wihsand and fas ON/OFF swiching operaion, numerous solid-sae based HV pulse generaors have been proposed. Examples of solid-sae pulse generaors vary from mimicking he classical generaors, such as he Marx generaor [7], o emerging new opologies and converers for generaing he HV pulses [8]-[6]. An imporan aspec in he newly developed HV pulse generaors is modulariy, which offers redundancy and robus pulse generaion operaion. In [8], he auhors uilized several capacior-diode volage muliplier modules such ha, wih proper semi-conducor swiching, he capaciors charge in parallel hen discharge in series across he load which allows generaion of HV pulses from a low volage inpu AC supply. In [9] modulariy is achieved via connecing several flyback converers in series/parallel in order o fulfill he oupu pulse

3 Arm 4 Arm requiremens. Alhough hese opologies are modular, hey are limied o monopolar pulse generaion of a predefined duraion. Exploiaion of he modulariy in modular mulilevel converers (MMC) is addressed in lieraure, where he halfbridge (HB) MMC cell, shown in Fig. a, is uilized o sequenially charge he MMC cell capaciors and hen discharge hem in series across he load []. However, exending his sysem o more han 3 kv pulses requires series connecion of he used diodes, and i is only capable of generaing monopolar pulses. In [] and [2] a modified HB- MMC cell, shown in Fig. b, is used in a wo arm opology (or, a single leg from he hree-phase based MMC converer), he modified cell allows sensorless operaion of he opology a a paricular swiching sequence of he MMC cells while generaing he HV pulses. In [] and [2] he defaul pulse generaion is bipolar, however monopolar pulse generaion is possible when changing he load ground poin. This paper proposes a opology based on he convenional HB-MMC cells ha can generae boh monopolar and bipolar HV recangular pulses. Pulse generaion is conrolled via a sofware conroller, hence no physical changes are required in he power opology. Alhough he defaul pulses generaed by his converer are bipolar and monopolar recangular pulses wih uniformly disribued null periods, he converer sofware conroller can be programmed o generae oher differen cusomised recangular pulses namely: a rain of variablefrequency recangular bipolar pulses; a rain of variableduraion bipolar recangular pulses; and a rain of variableduraion bipolar recangular pulses wih combined posiive and negaive null periods. Thus, he proposed converer provides sofware flexibiliy and hardware modulariy, scalabiliy, and redundancy. The cell capaciors are responsible for clamping he volage across he cell swiches, hus he volage sresses are equally disribued on he converer swiches. The adoped charging and discharging paerns of he cell capaciors in his opology eliminae he need of any volage measuremen or complex conrol o provide cell-capaciors volage balance. Moreover, in case of cell failure, he converer is able o coninue funcioning wihou inerruping converer operaion. The opology uilizes small cell capaciance, hence is fooprin is significanly reduced in comparison o convenional MMC converers used in HVDC ransmission applicaions. The proposed converer is inroduced in secion II, is operaion principle oulined in secion III, analysis and design given in secion IV, and simulaion and experimenal resul are presen in secions V and VI respecively. II. PROPOSED CONVERTER TOPOLOGY The proposed circui opology is shown in Fig. 2. I consiss of four MMC arms (Arm, where ) forming ogeher an H-bridge conneced o supply volage via an inducor. Each arm is formed of series conneced MMC cells, depending on he desired oupu volage magniude. Each arm comprises an arm inducor o supress he inrush curren beween he cell capaciors during heir inserion. Each cell has a capacior in series wih an auxiliary insulaed gae bipolar ransisor (IGBT) swich/diode and boh are parallel wih a main IGBT swich/diode, see Fig. 2. Depending on he swiching sequence of he complimenary swiches and, he cell-erminal volage is eiher equal o he capacior-volage or zero as illusraed in he swiching able in Fig. 2. The proposed converer is capable of generaing he bipolar ( ) and monopolar ( ) HV pulses shown in Fig. 3a and 3b respecively. The conrolling parameers are namely: he repeiion ime ( ) and he pulse duraion ( ). The generaed pulses can be defined by he ime duraions in () and (2) for bipolar and monopolar pulses respecively, see Fig. 3. () (2) where is he peak pulse volage. + V c - C c T x T m Fig.. Half-bridge modular muli-level cell: convenional and modified []. Vs Cell swiching able A V AB B Fig. 2. Proposed converer opology. Vc + - Cc Tx is Ls Tm III. OPERATING PRINCIPLE The same mehodology is used o generae monopolar and bipolar pulses. The only difference is he omission of one Cell A VAB B D iarm io S 2 C + - V c + - vo iarm4 Cell Cell Cell La Arm 2 Arm 3 S A B V AB

4 polariy during pulse generaion. Accordingly, he following discussion will consider bipolar pulse generaion o illusrae he basic concep. Addiionally, he waer under elecroporaion is modelled as a resisive load () [4]. For proper operaion, each arm should be able o wihsand he dc-link volage, herefore, each cell-capacior volage is. Table I shows he circui configuraion and summarises he operaing sequence in each period. Generally, during posiive pulse generaion Arm3 and Arm4 capaciors are insered o discharge across he load, while Arm and Arm2 are insered during negaive pulse generaion. The posiive and negaive null periods in () allow charging of he lower arms and he upper arms respecively. The uilised MMC cells in each arm are all urned ON/OFF simulaneously, herefore, each IGBT swich is subjeced only o he cell volage. Thus, he cell capacior clamps he IGBT volage and enforces a symmerical series volage disribuion. In boh charging and discharging, he arm cell capaciors are insered ogeher forming a oal capaciance of per arm. IV. ANALYSIS AND DESIGN OF THE PROPOSED CONVERTER Based on he menioned operaing principle in Table I, provided all he arm swiches are urned ON/OFF a he same ime, a picorial charging and discharging sequence of he equivalen arm capacior is shown in Fig. 4. The insananeous curren flow hrough he load ( ), he inpu inducor ( ), Arm ( ), and Arm4 ( ) are shown in Fig. 5. V v bi p T s V p Fig. 3. Generaed HV pulses: bipolar recangular pulse and monopolar recangular pulse. V v mono p T s V p 2 3 Negaive Null Negaive Pulse Posiive Null Posiive Pulse TABLE I OPERATING PRINCIPLE OF THE PULSE GENERATOR V s V s V s V s Circui configuraion L s L s L s L s C vo i C4 i C3 i o i C4 i o = i C4 C 4 C i C vo i C - 4 i o + vo i C2 + - vo C 3 i C2 i C2 C 2 C 2 i C3 C C 3 i C i o = i C3 Sequence of operaion Capaciors of Arm3 and Arm4, C 3 and C 4, are insered simulaneously while Arm and Arm2 are bypassed such ha load volage is +V s. Load curren is formed by a combinaion of hree energy sources; C 3, C 4 and L s. C 3 and C 4 discharge during his period. Capaciors of Arm2 and Arm4, C 2 and C 4, are insered, Arm and Arm3 are bypassed, and hence, he load volage is nullified. The load curren is zero. C 2 and C 4 are charged hrough L s during his period. Capaciors of Arm and Arm2, C and C 2, insered while Arm3 and Arm4 are bypassed such ha he load volage is V s. The load curren is formed by a combinaion of hree energy sources; C, C 2 and L s. C and C 2 discharge during his period. Capaciors of Arm and Arm3, C and C 3, are insered, Arm2 and Arm4 are bypassed, and hence, he load volage is nullified. The load curren is zero. C and C 3 are charged hrough L s during his period. V v o v C v C2 v C3 v C4 p V p T s Fig. 4. Cell capaciors charging and discharging sequence for generaing a bipolar pulse. V s /N V s /N V s /N V s /N Assuming he volages and currens noaion in Table I are posiive, he load curren is calculaed as = (3) while he inpu curren is = (4) During posiive pulse generaion, he load curren is supplied from hree energy sources namely: Arm3 capaciors discharge hrough Arm; Arm4 capaciors discharge hrough Arm2; and curren from he inpu inducor. In conras, during a negaive pulse duraion he load curren is formed from hree energy sources namely: Arm capaciors discharge hrough Arm3; Arm2 capaciors discharge hrough Arm4; and he inpu inducor curren. Denoing he average inpu curren as, while neglecing semi-conducor losses: (5) where and are he load rms volage and curren. Accordingly, is calculaed using Fig. 3a as:

5 A i o i Arm_ i Arm_4 p I p I s I x Since, is where is he pulse duy raio. T s.5i s.5i s Fig. 5. Curren waveforms hrough he load, he inpu inducor, Arm, and Arm4. (6) From Fig. 5 and (3), he peak pulse curren can be expressed as (7) (8) where he capaciors discharging and charging currens are denoed by and respecively. Accordingly, he capaciors curren-second balance yields (9) whereas from Fig. 5 and (3) he capacior charging curren will be () Solving (8), (9) and () yields () (2) (3) As he average charge change in any cell capacior should be zero, examinaion of eiher he charging or he discharging period is sufficien. Thus he equivalen arm capaciance can be defined as (4) where is he discharging curren duraion and is he peak o peak volage ripple. Subsiuing for variables from he previous equaions gives I s I y Inducor curren Capacior discharging Capacior charging (5) where is he percen peak o peak volage ripple of an arm capacior. Accordingly he cell capacior can be calculaed as: (6) If IGBT volage drop and he inernal resisance of are negleced, hen. Then (6) reduces o (7) where, is a safey facor o accoun for he negleced losses. Resonance beween he dc link inducor and arm capaciance during charging of eiher he wo upper arms or he wo lower arms should be avoided. Device swiching frequency should be well away from he resonance frequency of he equivalen LC circuis o avoid exciing resonance currens. Therefore, based on he calculaed equivalen arm capaciance and he repeiion ime, an esimaion of he inducance of is: (8) V. SIMULATION RESULTS The proposed opology is assessed using MATLAB/Simulink simulaions, wih he parameers given in Table II. The capaciance of he cell capaciors are calculaed based on (7) wih, and (8) is used o esimae he inpu inducance. The simulaions assess he abiliy of he converer o generae bipolar and monopolar pulses, as well as operaion wih fauly MMC cells. The simulaion resuls when generaing s bipolar HV pulses a khz are shown in Fig. 6. The generaed pulses are shown in Fig. 6a, he 4 arms capacior volages are given in Fig. 6b wih a zoomed view of arms and 3. The response of he capacior volages followed he expeced response shown in Fig. 4. As a resul, in his case for s each arm capacior is responsible of discharging across he load for s, charging for 4s while keeping heir volage unchanged for 5s. Addiionally, each capacior volage is oscillaing around V, ha is, wih less han 5% volage ripple, as expeced. The proposed converer is capable of changing he pulse shape wihou changing he converer opology, specifically via sofware. Therefore, using he same specificaion as in Table II, he proposed converer is programmed o generae s monopolar HV pulses wih monopolar posiive and negaive polariies as well as 4s bipolar and monopolar HV pulses, all a a khz repeiion rae. The simulaion resuls are shown in Figs. 7a and 7b for s monopolar pulses, Fig. 7c for 4s bipolar pulses while Fig. 7d shows he 4s posiive monopolar pulses. Moreover, generaing recangular pulses wih differen characerisics is explored in Fig. 8, where bipolar pulses wih differen posiive and negaive duraions, s and 4s respecively, are shown in Fig. 8a. Combined null periods bipolar pulses are shown in Fig. 8b such ha he posiive pulse duraion is s and ha of he negaive pulse is

6 4s. Fig. 8c shows he flexibiliy of he concep, wih bipolar pulses of a variable repeiion frequency. A rain of 4s pulses a khz is combined wih a rain of s pulses a 5 khz, wih a 2 s repeiion ime. The small volage droop in he pulse peak is due o he decrease of he capacior energy during pulse generaion, his droop is reciprocal o he cell capacior size viz. he larger he capacior size he smaller he volage droop and vice versa. - TABLE II SPECIFICATION FOR SIMULATION AND EXPERIMENTATION Parameer Simulaion Experimenaion DC inpu volage ( ) kv 25 V Inpu inducance ( ).5 mh.5 mh Number of cells/arm () 3 Repeiion ime ( ) s s Arm inducance ( ) 5 H H Load resisance () kω 5 Ω Cell capaciance ( ) F F Pulse duraion ( ) s and 4 s s and 4 s Percen volage ripple ().5.5 Safey facor () = us) Fig. 6. Simulaion resuls for bipolar HV pulses, s: oupu pulse, wih base volage kv and 4 arms capacior volages wih zoomed view on Arms and Volage, V = us) = us) Arm 3 Capaciors = us) (d) Fig. 7. Simulaion resuls for oupu HV pulses wih base volage kv: s posiive monopolar, s negaive monopolar, 4s bipolar, and (d) 4s posiive monopolar Arm Capaciors = us) = us) I should be noed ha he abiliy of he converer o generae he a wide range of recangular pulses is solely depend on he speed of seleced conroller in execuing he conrol sofware insrucions, such ha he oal sofware execuion ime is lesser han he required pulse repeiion ime. Moreover, for high repeiion raes and/or shor pulse duarions he uilisaion of fas semi-conducor swiches is mandaory. Volage. pu = us) = us) Fig. 8. Simulaion resuls for oupu HV pulses wih base volage kv: Differen duraion pulses, Combined differen duraion pulses, Variable pulse duraion and repeiion frequency Fig. 9. Simulaion resuls for oupu HV pulses when wo fauly cells in Arm, s oupu pulse, base volage kv and 4 arms capacior volages. The cell capaciors are responsible for clamping he volage across he module swiches o wihou any volage measuremens or conrol. Thus, if one or more cells are subjec o failure, he excess volage will be shared equally beween he healhy cell-capaciors. Hence, he new cell volage under failure is (9) where is he number of he fauly cells. The simulaion resuls in Fig. 9 address a cell failure case, where wo cells of Arm malfuncion while he converer sill able o generae he desired bipolar pulses, as shown in Fig. 9a. Neverheless, in his case he cell-volage of each healhy cell in Arm will be 25V increased from is normal V. Therefore, he Time: 6us/div = us) - 3 cycles of us pulses w ih 5kHz Volage, V cycles of 4us pulses w ih khz Arm Arms 2, 3 and = us)

7 volage sress is disribued beween he healhy cells o alleviae he malfuncion of he wo cells, as shown in Fig. 9b. VI. EXPERIMENTAL RESULTS The es equipmen o assess he proposed converer opology uses ulra-fas IGBT swiches (STGW3NC6WD) while he conrol algorihm is implemened on Texas Insrumens ezdsp F The experimenal parameers are given in Table II, and he scaled experimenal rig is shown in Fig.. Fig. shows he experimenal resuls for bipolar volage pulses wih µs. Volage: V/div. Fig. 2. Experimenal resuls for he oupu volage pulses: monopolar a µs and bipolar a µs. Volage: V/div. Time: 25 µs/div. Volage: V/div. 3 cycles of 4 µs pulses wih khz 3 cycles of 8 µs pulses wih 2.5 khz Time: 25 µs/div. Volage: V/div. Fig.. The scaled experimenal es rig. Time: 25 µs/div. Volage: V/div. Fig. 3. Experimenal resuls: Differen duraion pulses, Combined differen duraion pulses, Variable pulse duraion and repeiion frequency. Volage: V/div. Shifed-Zoomed view Time:25µs/div. Volage: V/div. Arm Arm 3 Fig.. Experimenal resuls, µs: oupu bipolar volage pulses, inpu curren, and a cell capacior volage in each of he 4 arms. Time: 5µs/div. Volage: 2V/div. Time: µs/div. Curren: 2mA/div. The oupu volage pulses and he inpu curren hrough are shown in Figs. a and b respecively. The volages across one capacior in each of he 4 arms are given in Fig. c wih a shifed-zoomed view of Arm and Arm3 capacior volages. Since he peak of he oupu pulse is 25V, each capacior volage should be around 83.3V, as shown in Fig.c. A µs monopolar volage pulse is shown in Fig. 2a while bipolar volage pulses wih µs are depiced a Fig. 2b. Generaing cusomised recangular pulse characerisics is explored in Fig. 3. Fig. 3a shows bipolar pulses wih posiive and negaive pulse duraions of µs and µs respecively. Combined null periods wih posiive and negaive pulse duraions of µs and µs, respecively, is shown in Fig. 3b. In Fig. 3c, a rain of 4s pulses a khz is combined wih a rain of µs pulses a 2.5 khz, for a 5s repeiion ime.

8 Arm healhy cells ACKNOWLEDGMENT The saemens made herein are solely he responsibiliy of he auhors. Volage: V/div. Fig. 4. Experimenal resuls, when a cell in Arm is fauly: oupu bipolar volage pulses wih µs, Arm cell capacior volages along wih a cell in Arm4, and a cell capacior volage in each of he 4 arms. Finally, in order o verify he performance of he proposed opology during an MMC cell malfuncion, one of he cells in Arm is deliberaely shor circuied while generaing a bipolar pulse of µs. Again he parameers in Table II are used wih an inpu volage of V. The oupu volage pulses in his case are shown in Fig. 4a. The fauly arm cell volages are shown in Fig.4b along wih a cell volage in Arm4. The healhy cell volages in Arm increase o V from 66.7V. The volage across one capacior in each arm for his case is shown in Fig. 4c. VII. CONCLUSION This paper presened a new HV pulse generaor opology based on half-bridge MMC cells. The recangular pulse characerisics are conrolled via sofware conrol wihou any physical change o he power opology. The converer can generae boh bipolar and monopolar HV pulses wih microsecond pulse duraions a a high frequency rae wih differen characerisics. Hence, he proposed opology provides flexibiliy by sofware conrol, along wih hardware modulariy, scalabiliy, and redundancy. The adoped charging and discharging process of he MMC cell capaciors assure volage balance wihou any volage measuremens or complex conrol, consequenly, coninuous operaion during cell malfuncion is gained, where he volage sress across each module is clamped o he capacior volage. Moreover, he cell capaciances are small, hereby reducing he converer s fooprin. The presened simulaions and experimenal resuls confirm he feasibiliy and he feaures of he proposed opology for waer disinfecion applicaions. Fauly cell in Arm Arm Arms 2, 3 and 4 Volage: 2V/div. Cell in Arm4 Volage: 2V/div. REFERENCES [] K. H. Schoenbach, F. E. Peerkin, R. W. Alden, and S. J. Beebe, "The effec of pulsed elecric fields on biological cells: experimens and applicaions," IEEE Trans. Plasma Sci., vol. 25, no. 2, pp , 997. [2] J. Raso and V. Heinz, Pulsed elecric fields echnology for he food indusry: fundamenals and applicaions, London, Springer, 26. [3] H. Bluhm, Pulsed power sysems: principles and applicaions, Berlin, Springer, 26. [4] K. H. Schoenbach, R. P. Joshi, R. H. Sark, F. C. Dobbs, and S. J. Beebe, "Bacerial deconaminaion of liquids wih pulsed elecric fields," IEEE Trans. Dielec. Elec. Insulaion, vol. 7, no. 5, pp , 2. [5] A. Abou-Ghazala, S. Kasuki, K. H. Schoenbach, F. C. Dobbs, and K. R. Moreira, "Bacerial deconaminaion of waer by means of pulsed-corona discharges," IEEE Trans. Plasma Sci., vol. 3, no. 4, pp , 22. [6] M. Reberšek and D. Miklavčič, "Advanages and disadvanages of differen conceps of elecroporaion pulse generaion," AuomaikaJournal for Conrol, Measuremen, Elecronics, Compuing and Communicaions, vol. 52, no., 2. [7] E. Veilleux, B. T. Ooi, and P. W. Lehn, "Marx dc-dc converer for high-power applicaion," Power Elecronics, IET, vol. 6, no. 9, pp , 23. [8] M. Rezanejad, A. Sheikholeslami, and J. Adabi, "Modular swiched capacior volage muliplier opology for pulsed power supply," IEEE Trans. Dielec. Elec. Insulaion, vol. 2, no. 2, pp , Apr. 24. [9] P. Davari, F. Zare, A. Ghosh, and H. Akiyama, "High-volage modular power supply using parallel and series configuraions of flyback converer for pulsed power applicaions," IEEE Trans. Plasma Sci., vol. 4, no., pp , Oc. 22. [] A. A. Elserougi, A. M. Massoud, and S. Ahmed, "A Modular High-Volage Pulse-Generaor wih Sequenial Charging for Waer Treamen Applicaions," IEEE Trans. Ind. Elecron., vol. PP, no. 99, pp. -, 26. [] L. Lamy Rocha, J. F. Silva, and L. M. Redondo, "Mulilevel highvolage pulse generaion based on a new modular solid-sae swich," IEEE Trans. Plasma Sci., vol. 42, no., pp , Oc. 24. [2] L. L. Rocha, J. F. Silva, and L. M. Redondo, "Seven-Level Unipolar/Bipolar Pulsed Power Generaor," IEEE Trans. Plasma Sci., vol. PP, no. 99, pp. -5, 26. [3] A. Elserougi, S. Ahmed, and A. Massoud, "High volage pulse generaor based on DC-o-DC boos converer wih capacior-diode volage mulipliers for bacerial deconaminaion," IECON 25, pp [4] S. Zabihi, F. Zare, G. Ledwich, A. Ghosh, and H. Akiyama, "A novel high-volage pulsed-power supply based on low-volage swich-capacior unis," IEEE Trans. Plasma Sci., vol. 38, no., pp , Oc. 2. [5] L. M. Redondo and J. F. Silva, "Flyback versus forward swiching power supply opologies for unipolar pulsed-power applicaions," IEEE Trans. Plasma Sci., vol. 37, no., pp. 7-78, Jan. 29. [6] S. Zabihi, F. Zare, G. Ledwich, A. Ghosh, and H. Akiyama, "A new pulsed power supply opology based on posiive buck-boos converers concep," IEEE Trans. Dielec. Elec. Insulaion, vol. 7, no. 6, pp. 9-9, Dec. 2.

9 Mohamed A. Elgenedy received he B.Sc. (wih firs-class honors) and M.Sc. degrees in Elecrical Engineering from Alexandria Universiy, Egyp in 27 and 2 respecively. Currenly he is working oward he Ph.D. degree a he Universiy of Srahclyde, Glasgow, U.K. He is also an assisan lecurer wih he Elecrical Engineering Deparmen, Faculy of Engineering, Alexandria Universiy. In 22, he was wih Spireronic LLC, Houson, TX, USA, as a Research Engineer. From 23 o 24, he was a Research Associae a Texas A&M Universiy a Qaar. His research ineress include high power elecronics, elecric machine drives, energy conversion, and renewable energy. Shehab Ahmed (SM'2) was born in Kuwai Ciy, Kuwai in July 976. He received he B.Sc. degree in Elecrical Engineering from Alexandria Universiy, Alexandria, Egyp, in 999; he M.Sc. and Ph.D. degrees from he Deparmen of Elecrical & Compuer Engineering, Texas A&M Universiy, College Saion, TX in 2 and 27, respecively. From 2 o 27, he was wih Schlumberger Technology Corporaion working on downhole mecharonic sysems. He is currenly an Assoicae Professor wih Texas A&M Universiy a Qaar, Doha, Qaar. His research ineress include mecharonics, solid-sae power conversion, elecric machines, and drives. Ahmed Darwish received he B.Sc. and M.Sc. degrees in elecrical engineering from he Faculy of Engineering, Alexandria Universiy, Alexandria, Egyp, in 28 and 22, respecively, and he Ph.D. degree in elecric engineering from he Deparmen of Elecronic and Elecrical Engineering, Universiy of Srahclyde, Glasgow, U.K., in 25. From 29 o 22, he was a Research Assisan a Texas A&M Universiy a Qaar, Doha, Qaar. He is currenly a Research Associae wih PEDEC Group a he Universiy of Srahclyde. His research ineress include dc dc converers, mulilevel converers, elecric machines, digial conrol of power elecronic sysems, energy conversion, renewable energy, and power qualiy. Barry W. Williams received he M.Eng.Sc. degree from he Universiy of Adelaide, Adelaide, Ausralia, in 978, and he Ph.D. degree from Cambridge Universiy, Cambridge, U.K., in 98. Afer seven years as a Lecurer a Imperial College, Universiy of London, London, U.K., he was appoined o a Chair of Elecrical Engineering a Herio-Wa Universiy, Edinburgh, U.K, in 986. He is currenly a Professor a he Universiy of Srahclyde, Glasgow, U.K. His eaching covers power elecronics (in which he has a free inerne ex) and drive sysems. His research aciviies include power semiconducor modeling and proecion, converer opologies, sof swiching echniques, and applicaion of ASICs and microprocessors o indusrial elecronics.