A FAST HYSTERESIS CURRENT CONTROLLED PERMANENT MAGNET SYNCHRONOUS MOTOR DRIVE BASED ON FIELD ORIENTATION

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1 Jounal of ELECTRICAL ENGINEERING, VOL 67 (216), NO2, A FAST HYSTERESIS CURRENT CONTROLLED PERMANENT MAGNET SYNCHRONOUS MOTOR DRIVE BASED ON FIELD ORIENTATION Cosmas Ogbuka Cajethan Nwosu Macel Agu A fast hysteess cuent-contolled (HCC) pemanent magnet synchonous moto(pmsm) dve based on feld oentaton s pesented. The objectves of ths eseach ae to develop and utlze HCC algothm fo feld oentaton contol (FOC) of a complete closed loop speed-contolled PMSM dve system, optmze the HCC algothm to obtan fast speed esponse wth step and amp speed nputs to examne the effectveness of cuent and toque tackng, dentfy the optmal contol vaables of the HCC on the PMSM, examne the pefomance wth amp and step efeence speed nputs. The esponse of the developed model s compaed wth the speed esponse of the standad AC6 of MATLAB Smpowe systems n tems of se tme, settlng tme and effectveness of cuent and toque tackng. Compaed to the standad AC6 of MATLAB Smpowe systems, the developed model acheved se tme and settlng tme of.18 seconds and.143 seconds espectvely whle the coespondng values fo AC6 model ae.1944 seconds and.1984 seconds espectvely. The developed model, theefoe, offeed supeo pefomance ove the AC6 model n tems of se tme, settlng tme and tackng capablty. Keywods: hysteess cuent contol, feld oentaton, PMSM, voltage souce nvete 1 INTRODUCTION Fo the same output powe, Pemanent Magnet Synchonous Motos (PMSM) offe pefomance enhancement ove the conventonal nducton and synchonous motos n tems of powe facto, effcency, powe densty and toque-to-neta ato [1]. Ths justfes the ecent concentaton of eseach effots n the desgn, analyss and contol of the PMSM as epoted n [2 7]. Recently, seveal effots have been made towad the opeatonal compason between the pemanent magnet synchonous moto and the nducton moto whch, htheto, s the wokhose of the ndusty. These compasons have favoued the PMSM both fo fxed speed and vaable speed opeatons [8, 9]. Lne-stat PMSM has also been favouably compaed wth nducton motos n the feld of sem-hemetc dves, lke n compessos, whee heavy loadng s obtaned because of good coolng [1]. Pemanent magnet mateals ae ated on the bass of enegy densty and esstance fo demagnetzaton and ths dectly nfluences the pefomance of the PMSM. Neodymum Ion Boon (Nd 2 Fe 14 B) magnets (second geneaton ae eath magnet) ae the most common ae eath magnets used n PM motos these days because of the supeo B-H chaactestcs. The ae-eath PMs have poblems such as hgh cost and ae n vey lmted supply. The unpedctablty assocated wth pocung such mateals, clealy, suggests the need fo a compettve altenatve. Seveal eseach effots ae on-gong to utlze fete magnets n place of Pemanent magnets whee the fetes ae expected to have compettve powe densty and effcency of the ae-eath PMSM [11 14]. Unlke n low pecson applcatons whee open loop fxedspeedopeatonofthe PMSMmaybetoleated,Adjustable Speed Dves (ASD), dependng on specfc load equements, sgnfcantly mpoves moto dve pefomance. Ths s the pactce n ndusty whee hgh pecson n speed and toque s desed. Faste and accuate speed esponse, qucke ecovey of speed fom any load mpact, and nsenstvty of paamete vaatons ae some of the mpotant ctea of adjustable speed dve to acheve hgh pefomance fo such applcatons lke n obotcs, ollng mlls, a condtones, a compessos, spndle dves, and othe machne tools [15]. Snce toque can be made popotonal to cuent ethe n the statonay o oto efeence fames and contol of cuent gves contol of toque and speed, cuent contol stateges ae employed n ASD to ensue that stato phase cuents tack the espectve efeence values. One of such cuent contol stateges s the Hysteess Cuent Contol (HCC). The HCC when compaed to othe cuent contol stateges offes supeo cuent tackng pefomance and elmnates the need fo feedback loop compensaton [16]. The poblems of poo load tansent esponse and egulato naccuacy have, howeve, consstently necesstated futhe eseach effots to acheve optmal dves pefomance [17 2]. In the pesent wok, a fast hysteess cuent contolled pemanent magnet synchonous moto dve based on feld oentaton was developed and optmsed to obtan fast speed esponse and effectve cuent and toque tackng. Beng a speed-contolled dve system, a compason of the dve pefomance fo step and amp speed nputs was undetaken. The esults obtaned wee then Depatment ofelectcal Engneeng,UnvestyofNgea,Nsukka,Ngea.cosmas.ogbuka@unn.edu.ng, cajethan.nwosu@unn.edu.ng, macel.agu@unn.edu.ng DOI: /jee , Pnt (tll 215) ISSN , On-lne ISSN X c 216 FEI STU

2 7 C. Ogbuka C. Nwosu M. Agu: A FAST HYSTERESIS CURRENT-CONTROLLED PERMANENT MAGNET SYNCHRONOUS... v s v ds q - axs v qs s s ds = f qs = T af d - axs Stato Refeence Fame Fg. 1. Phaso dagam of vecto contol by FOC fo PMSM compaed wth the esults of the standad AC6 of the Smpowe of MATLAB and the developed model showed supeo pefomance. 2 DYNAMIC MODEL OF PMSM The stato of the PMSM and the wound oto synchonous moto ae smla. In addton thee s no dffeence between the back emf poduced by pemanent magnet and that poduced by an excted col. Hence the mathematcal model of a PMSM s smla to that of the wound oto synchonous moto. The followng smplfyng assumptons wee made to deve the dynamc model of the PMSM n the oto efeence fame. The machne has no dampng ccuts snce t s nvete contolled and the effect of satuaton and paamete vaatons ae neglected [1, 21]. Based on these assumptons, the stato qd equatons of the PMSM, n the oto efeence fame, s deved as [ ] [ ][ v qs Rs +L = q p ω L d qs ω L q R s +L d p v ds ds The electomagnetc toque s obtaned as ] [ ] ω λ + af (1) T e = 3 P 2 2 [λ af +(L d L q ) ds] qs (2) The oto dynamc equatons ae and T e = T L +Bω +Jpω (3) θ = ω dt, (4) whee vqs,v ds =q,d axs voltage, qs, ds = q,d axs cuents, L q,l d = q,d axs nductances, R s =stato esstances, λ af =stato esstances, ω =angula oto speed, P =numbe of moto poles, p =dffeental opeato, T e =electomagnetc toque, T L =load toque, B = oto dampng coeffcent, J = neta constant. 3 FIELD ORIENTATION CONTROL (FOC) OF PMSM Vecto contol, by feld oentaton, s used to decouple the stato cuent of the PMSM nto equvalent flux and toque poducng cuent components fo ndependent and pecse contol of toque and flux lke n DC machne as shown n the phaso dagam of Fg. 1. As shown n Fg. 1, the oto flux lnkage evolves at a oto speed ω and s postoned away fom a statonay efeenceby the otoangle θ. The statocuentphaso s at angle δ fom the oto flux lnkages phaso. Feld oentatoncontolsachevedbymakng δ = 9 theeby endeng the stato flux cuent component zeo. Theefoe, Snce sn9 = 1, qs = s f = ds = s cosδ =. (5) T e = 3 P 2 2 λ af qs. (6) T e = 3 P 2 2 λ af s = K t s (7) whee K t = 3 P 2 2 λ af s the toque constant. Unde ths condton, the PMSM behaves exactly as the sepaately excted dc moto [22] as seen fom the toque expesson (7) whee the toque s poduced by the nteacton of the oto flux and the stato cuent. 4 SCHEMATIC OF THE SPEED CONTROLLED DRIVE SYSTEM The complete Schematc of the Speed-Contolled PMSM Dve System s shown n Fg. 2. It conssts ofthe PMSM, the Speed and Poston Feedback, PI Speed Contolle, Hysteess Cuent Contolle and the Thee Phase Voltage Souce Invete. All efeence o command values ae supescpted wth n the dve dagam. The oto speed sensed by the speed sensos flteed by the 1st odelow passflte. The speed eo between the actual oto speed and ts efeence (ω ω ) spocessedthoughthepispeedcontolle to nullfy the steady state eo n speed. The output of the speed contolle s the toque efeence whch s estcted to an uppe and a lowe lmt by the toque lmte theeby poducng a ealstc toque efeence Te. The toque efeence Te s dvded by the moto toque constant K t = 3 P 2 2 λ af to poduce the efeence quadatue axs cuent qs. To acheve vecto contol by feld oentaton,the efeencedect axscuent ds =. The ds and qs ae passed though the nvese pak s tansfom block to poduce the stato abc phase cuent efeences a, b, and c. Electcal oto poston θ e feedback ealsed by ntegatng the electcal oto speed

3 Jounal of ELECTRICAL ENGINEERING 67, NO2, V dc e a ds Refeence Stato Cuent Estmato (eqn. 8) qs qs Gatng Sgnal Geneaton by Hysteess Compason (Fg. 4) v g1 - vg6 3 VSI (Fg. 3) 1 s 1 3 P 2 2 af T e Toque Lmte L L L e K p + K s PI Contolle PMSM P 2 K f s st Ode Low Pass Flte N Speed Senso Fg. 2. Complete schematc of the speed-contolled PMSM dve system ω e s equed n ode to geneate the phase cuent efeences as shown n a = qs cosθ e + dssnθ e, b = qs cos( θ e 2π 3 c = qs cos ( θ e + 2π 3 ) + ds sn ( ) θ e 2π 3, ) + ds sn ( (8) ) θ e + 2π 3. Snce toque can be made popotonal to cuent ethe n the statonay o oto efeence fames and contol of cuent gves contol of speed and poston, contol of PMSM dves s execsed though cuent contol. To acheve hgh pefomance fom sevo dves, cuent contol stateges ae employed to ensue that the actual cuents flowng nto the moto ae as close as possble to the snusodal efeences usng Hysteess Cuent Contol (HCC). In ths stategy, the efeence phase cuents ( a, b and c ) and the actual phase cuents (, and ) ae compaed, by feedback, and eo sgnals geneated. At the cente of the vaable speed dve of the PMSM, and n fact all ac dves, s the thee phase nvete wth the typcal powe ccut shown n Fg. 3. The powe ccut conssts of sx self-commuted semconducto swtches S 1 to S 6 wththecoespondngantpaalleldodesused to contol the stato phase cuents. The contol logc of appendx one s employed to geneate the gatng sgnals v g1, v g2, v g3,v g4, v g5, v g6 fo the swtches of the thee phase nvete of as shown n Fg. 4. Cuent contol s acheved by the appopate fng of the powe semconducto swtches S 1 to S 6 of the thee phase nvete. The nvete s suppled by an adequately flteed dc souce V dc. The phase cuents to the moto s lmted by nducto L of 5 mh. V dc 2 V dc 2 N S 1 a S 4 D 1 D 4 S 3 b c S 6 D 3 D 6 S 5 S 2 D 5 D 2 v a v b v c Fg. 3. Powe ccut of thee-phase nvete The HCC acton s made possble by usng qs as shown n the Fg. 2 whee, n the ange of.2.5, s the hysteess wndow. Smla logc apples to the othe two phases. 5 RESULTS AND DISCUSSIONS The complete dve system s smulated fo the moto of appendx two and the esults pesented hee fo step and amp efeence speed nputs. To obtan the best

4 72 C. Ogbuka C. Nwosu M. Agu: A FAST HYSTERESIS CURRENT-CONTROLLED PERMANENT MAGNET SYNCHRONOUS... qs + - Hysteess Block S 1 S 4 Gatng Sgnals v, v g1 To Swtches S 1, S 4 g4 qs + - S 6 S 3 Gatng Sgnals v, v g3 To Swtches S 3, S 6 g6 qs + - S 2 S 5 Gatng Sgnals v, v g5 To Swtches S 5, S 2 g2 Fg. 4. Geneatng of gatng sgnals fo hysteess cuent contol Cuent +/ Refeence and Actual Speed (pm) 4 1. v g v g4-8 Ref Speed N ef.5-12 Actual Speed N Fg. 5. Phase a hysteess cuent wth S1 and S4 gatng sgnal Fg. 6. Refeence and actual oto speed fo step speed nput possble pefomance, tunng method was employed to obtan the optmal popotonal and ntegal gan values. The pocedue s to lowe the popotonal and ntegal gan values and gadually tune them up untl the best possble pefomance s acheved. Ths s the pactce n ndusty. The optmal contol vaables ae: popotonal gan = 5, ntegal gan = 1, 1st ode low pass flte tme constant = seconds, toque lmte uppe lowe = 3Nm/ 3Nm, hysteess band = Hysteess Cuent Contol Acton The gatng sgnals, vg1 and vg4, fo the complementay swtches n the fst leg of the nvete S1 and S4 ae shown n Fg. 5 usng phase a to hghlght the hysteess popety fo a naow tme band (.2914 seconds to.292 seconds) fo pupose of claty. It can be seen that the two swtches conduct altenately as eale explaned. The phase a cuent tacts the uppe bounday a+ qs (nceases) when swtch S1 s conductng and tacts the lowe bounday a qs (deceases) when swtch S4 s conductng. The hysteess cuent contol acton, whch makes the phase a cuent to tack ts efeence a, s seen as moves between a + qs to a qs as swtches S1 and S4 conduct altenately. 5.2 Step Speed Input (2 pm to 5pm to 75pm) The moto s stated at a efeence speed nput of 2pm at full load stess as shown n Fg. 6. At.9 seconds, the speed efeence s stepped-up to 5 pm. At.17 seconds, a negatve speed command of 75 pm s ssued. It s obseved that the oto speed would, afte bef tansents, catch-up and eman at the efeence speed n each case of speed change. Fgues 7(a),(b) show the efeence phase cuents and the actual phase cuents. The phase cuents esponded to two step speed changes. A close obsevaton shows that the swtchng fequency nceased by 15% as efeence speed s stepped fom 2 pm to 5pm. A 5% ncease n swtchng speed s also obseved as speed changed fom 5 pm to 75pm. The actual phase cuent effectvely tacks the efeence. Of specfc nteest s the natue of phase nveson(evesal) fom a-b-c to c-b-a that occus as speed changes fom 5 pm to 75pm. The expanded vew s shown

5 Jounal of ELECTRICAL ENGINEERING 67, NO2, Refeence Phase Cuents (A) 4 Actual Phase Cuents (A) 4 Actual Phase Cuents (A) Fg. 7. Step nput esponses: (a) phase cuents, (b) actual phase cuents, (c) cuent phase evesal (expanded) Toques (Nm) 4 T e T l 4 q - axs Cuents (A) q d - axs Cuents (A) 2 T ef 2 qef 8 d 4 def Fg. 8. Step-speed nput esponses: (a) electomagnetc toque, efeence toque and load toque fo step speed nput, (b) q-axs stato cuent, actual qs and efeence qs, and (c) d-axs stato cuent, actual ds and efeence ds and efeence qs and efeence ds Electomagnetc Toque (Nm) theta (Deg) Refeence and Actual Speed (pm) Ref Speed N ef 2 1 Actual Speed N T e Roto speed (pm) Fg. 9. Step-speed esponses: (a) toque-speed pofle, (b) oto poston θ, (c) efeence and actual oto speed at RAMP nput n Fg. 7(c). As shown n Fg. 8(a) dung statng, efeence toque and the electomagnetc toque equals the maxmum set toque capablty. Ths ensues that the oto uns-up n the shotest possble tme. As soon as the oto speed catches-up wth the efeence, the electomagnetc toque and the toque efeence settles at the load toque and the oto cuses at 2 pm. At tme.9 seconds when speed s stepped-up to 5 pm, the efeence toque agan attans the maxmum possble toque of 3 Nm. At the nstant of step speed

6 74 C. Ogbuka C. Nwosu M. Agu: A FAST HYSTERESIS CURRENT-CONTROLLED PERMANENT MAGNET SYNCHRONOUS... 4 Refeence Phase Cuents (A) 4 Actual Phase Cuents (A) 4 Actual Phase Cuents (A) Fg. 1. RAMP-speed nput esponse: (a) efeence phase cuents, (b) actual phase cuents, and (c) cuent phase evesal (expanded) 3 Toques (Nm) T e T ef T l q - axs Cuents (A) d - axs Cuents (A) 5 qef d def q Fg. 11. RAMP-speed nput esponse: (a) electomagnetc toque T e, efeence toque T ef, and load toque T l, (b) q-axs stato cuent, actual qs and efeence qs, and (c) d-axs stato cuent, actual ds and efeence ds Toque (Nm) theta (Rad) Roto speed (pm) Speed (pm) Fg. 12. RAMP-speed nput esponse: (a) toque-speed pofle, (b) oto poston θ d-axs stato cuent, actual ds and efeence ds, and (c) the se tme fo the developed model change fom 5 pm to 75 pm at.17 seconds, the efeence toque attans the mnmum value of 3 Nm. As soon as stablty s acheved afte each case of speed change, the efeence toque s estoed to 26 Nm whch s the full load toque. Snce electomagnetc toque s dectly popotonal to the q-axs stato cuent, q-axs stato cuent shown n Fg. 8(b) has exactly the same esponse chaactestcs as the electomagnetc toque; wth the actual value effectvely tackng the efeence. A deep tansent due

7 Jounal of ELECTRICAL ENGINEERING 67, NO2, Roto speed (pm) Roto speed (pm) 198 Roto speed (pm) Fg. 13. (a) the se tme - AC6 model, (b) settle tme fo the developed model, and (c) Settle tme fo the AC6 model to speed evesal s obseved n the d-axs stato cuent n Fg. 8(c). The efeence value s set at zeo whle the actual value aveages to zeo. Fgue 9(a) shows the toque-speed pofle n all fou quadants of opeaton namely: fowad motong, fowad egeneaton, evese motong, and evese egeneaton. The oto poston s zeo at stat and nceases fo as long as speed emans postve but ceates a new oentaton wth speed change. When efeence speed s made negatve, the oto eveses decton as shown n Fg. 9(b). (c) RAMP Speed Input ( pm to 5 pm to 5 pm to pm) The efeence speed nput s a amp; sng fom zeo to postve nput value of 5 pm and fallng back to negatve nput value of 5pm and then to zeo. A combned plot of the efeence speed nput and actual otospeed s shown n Fg. 9(c). As can be seen, ampng povdes a gadual speed tanston theeby enablng the actualotospeed to tace the path ofthe efeence speed nput vey closely. Just as n the case of step speed nput, phase sequence evesal also occu at the nstant of speed change fom postve to negatve as seen n Fgs. 1(a) and (b). A compason of Fg. 7(c) and Fg. 1(c), howeve, shows that excellent dynamc stablty s obtaned dung phase evesal n the case of amp nput. Ramp nput povdes smooth speed tanston. Unlke n the step nput whee the efeence toque takes ts mnmum value at the nstant of speed evesal theeby, momentaly, focng the electomagnetc toque to the negatve exteme, the toque-speed pofle dung speed ampng as shown n Fg. 12(a) s postve due to the gadual speed tanston. Electomagnetc toque and ts efeence ae equal to the load toque at steady state as shown n Fg. 11(a). 6 DRIVE SPEED RESPONSE COMPARED WITH RESPONSE OF MATLAB SIMPOWER AC6 MODEL The speed esponse of the developed dve model s compaed wth the speed esponse of the AC6 of MAT- LAB Smpowe Systems unde the same condton of opeaton (Constant efeence speed of 2 pm at no load). Emphass was pad on the se tme and settlng tme of the speed esponse. Whle the developed model acheved setme (e 98% offnaltme) n.18seconds,these tme fo AC6 model s.1944 seconds. These ae shown n Fg. 12(c) and 13(a) espectvely. Wth settlng tme defned, fo an unde damped system, as the tme tx t becomes 98% of fnal value o less fo all t tx, the settlng tme fo the developed model s.1435 seconds. The esponse fo AC6 s ctcally damped; hence the settlng tme concdes wth the fnal value tme whch s.1984 seconds. These ae shown n Fg. 13(b) and 13(c) espectvely. 7 CONCLUSION A fast hysteess cuent contolled pemanent magnet synchonous moto dve based on feld oentaton has been pesented n ths wok. The specfc eseach objectves have been acheved as shown n the esults. The coe advantage of vecto contol by Feld OentatonContol(FOC)hasbeenusednthswokto,successfully, convet the Pemanent Magnet Synchonous Moto, pefomancewse, nto equvalent sepaately excted dc moto by decouplng the stato cuent nto toque and flux poducng components fo ndependent contol of toque and flux. A complete closed loop contol system employng an oute PI speed contolle and an nne hysteess cuent contolle was mplemented to ealze ths speedcontolled dve. Snce toque can be made popotonal to cuent ethe n the statonay o oto efeence

8 76 C. Ogbuka C. Nwosu M. Agu: A FAST HYSTERESIS CURRENT-CONTROLLED PERMANENT MAGNET SYNCHRONOUS... fames and effectve contol of cuent gves effectve contol of toque, speed and poston, the HCC stategy has been used to ensue that the actual moto phase cuents tacked the espectve snusodal efeences. The HCC algothm was developed and employed fo the logcal fng of the powe semconducto swtches of the nvete. Optmzaton of the contol algothm yelded vey fast speed esponse, unde full load stess, wth the moto attanng steady state at.1 seconds wth mnmal toque pulsaton at steady state fo the step and amp efeence speed nputs. Optmal contol vaables wee dentfed wth emphass on effectve cuent and toque tackng. The dentfed optmal contol vaablesae:popotonal gan = 5, ntegal gan = 1, fst ode low pass flte tme constant = seconds, toque lmte uppe/lowe lmts = 3/ 3 Nm, and hysteess band =.5. Effectve tackng n cuent and toque was acheved confmng that the contol vaables ae optmal fo a wde ange of the PMSM atngs. Dve pefomance wth amp efeence speed nput offeed gadual speed tanston fom postve to negatve mantanng postve speed pofle compaed to the step efeence speed nput whch foced the toque efeence to the negatve lmt at the nstant of speed evesal theeby pemttng opeaton n fou quadants. Fnally, compaed to the standad AC6 of MATLAB Smpowe systems, the developed model acheved se tme and settlng tme of.18 and.143 seconds espectvely whle the coespondng values fo AC6 model ae.1944 and.1984 seconds espectvely. Ths, clealy, shows that the developed model has an enhanced speed esponse. Appendx 1: Invete Swtch Gatng Voltage Sgnal Estmaton (a) Fo nvete phase a leg If 1 < a qs OR ( 1 > a qs AND 1 < a+ qs AND da dt > ) v g1 = 1 ; v g4 = else v g1 = ; v g4 = 1 end (b) Fo nvete phase b leg If < b qs OR ( > b qs AND < b + qs AND d dt > ) v g3 = 1 ; v g6 = else v g3 = ; v g6 = 1 end (c) Fo nvete phase c leg If < c qs OR ( > c qs AND < c+ qs AND dc dt > ) v g5 = 1 ; v g2 = else v g5 = ; v g2 = 1 end Appendx 2: PMSM Ratngs Rated toque, Speed and Powe 26Nm, 3pm and 11Hp Stato Phase Resstance R s(ω).11 Stato Quadatue Axs Inductance L q(h).97 Stato Dect Axs Inductance L d (H).97 Flux Lnkage establshed by Magnet (Wb).1119 Voltage Constant (Vph/pm) Toque Constant (Nm/A-peak).6714 Ineta Constant J (kg-m 2 ).16 Vscous Fctonal Constant B.224 Numbe of Poles 8 Refeences [1] PILLAY, P. KRISHNAN, R.: Contol Chaactestcs and Speed Contolle Desgn fo a Hgh Pefomance Pemanent Magnet Synchonous Moto Dve, IEEE Tans. on Powe Electoncs 5 No. 2 (Ap 199), [2] INOUE, Y. YAMADA, K. MORIMOTO,S.;SANADA,M. : Effectveness of Voltage Eo Compensaton and Paamete Identfcaton fo Model-Based Sensoless Contol of IPMSM, IEEE Tans. on Industy Applcatons 45 No. 1 (Jan-Feb 29, [3] SAYEEF, S. FOO, G. RAHMAN, M. F.: Roto Poston and Speed Estmaton of a Vaable Stuctue Dect-Toque-Contolled IPM Synchonous Moto Dve at Vey Low Speeds Includng Standstll, IEEE Tans. on Industal Electoncs 57 No. 11 (Nov 21), [4] FOO, G. RAHMAN, M.: Sensoless Dect Toque and Flux-Contolled IPM Synchonous Moto Dve at Vey Low Speed Wthout Sgnal Injecton, IEEE Tans. on Industal Electoncs 57 No. 1 (Jan 21), [5] INOUE, Y. MORIMOTO, S. SANADA, M.: Compaatve Study of PMSM Dve Systems Based on Cuent Contol and Dect Toque Contol n Flux-Weakenng Contol Regon, IEEE Tans. on Industy Applcatons 48 No. 6 (Nov-Dec 212), [6] KSHIRSAGAR, P. BURGOS, R. JIHOON, J. LIDOZZI, A. FEI, W. BOROYEVICH, D. SEUNG-KI, S.: Implementaton and Sensoless Vecto-Contol Desgn and Tunng Stategy fo SMPM Machnes n Fan-Type Applcatons, IEEE Tans. on Industy Applcatons 48 No. 6 (Nov-Dec 212), [7] STOJAN, D. DREVENSEK, D. PLANTIC, Z. GRCAR, B. STUMBERGER, G.: Novel Feld-Weakenng Contol Scheme fo Pemanent-Magnet Synchonous Machnes Based

9 Jounal of ELECTRICAL ENGINEERING 67, NO2, on Voltage Angle Contol, IEEE Tansactons on Industy Applcatons 48 No. 6 (Nov-Dec 212), [8] MARCIC, T. STUMBERGER, B. STUMBERGER, G. HADZISELIMOVIC, M. VIRTIC, P. DOLINAR, D.: Lne- Statng Thee and Sngle Phase Inteo Pemanent Magnet Synchonous Motos: Dect Compason to Inducton Motos, IEEE Tans. on Magnetc 44 No. 11 (Nov 28), [9] MARCIC, T. STUMBERGER, B. STUMBERGER, G.: Compason of Inducton Moto and Lne-Stat IPM Synchonous Moto Pefomance n a Vaable-Speed Dve, IEEE Tans. on Industy Applcatons 48 No. 6 (Nov-Dec 212), [1] STUMBERGER, B. MARCIC, T. HADZISELIMOVIC, M.: Dect Compason of Inducton Moto and Lne-Stat IPM Synchonous Moto Chaactestcs fo Sem-Hemetc Compesso Dves, IEEE Tans. on Industy Applcatons 48 No. 6 (Nov-Dec 212), [11] SEKERAK, P. HRABOVCOVA, V. PYRHÖNEN, J. KA- LAMEN, L. RAFAJDUS, P. ONUFER, M.: Fetes and Dffeent Wndng Types n Pemanent Magnet Synchonous Moto, Jounal of Electcal Engneeng (Elektotechncky Casops) 63 No. 3 (212), [12] OBATA. M. MORIMOTO, S. SANADA, M. INOUE, Y.: Pefomance of PMASynRM wth Fete Magnets fo EV/HEV Applcatons Consdeng Poductvty, IEEE Tans. on Industy Applcatons 5 No. 4 (Dec 213), [13] SANADA, M. INOUE, Y. MORIMOTO, S.: Stuctue and Chaactestcs of Hgh-Pefomance PMASynRM wth Fete Magnets, Electcal Engneeng n Japan 187 No. 1 (214), [14] MORIMOTO, S. OOI, S. INOUE, Y. SANADA, M.: Expemental Evaluaton of a Rae-Eath-Fee PMASynRM wth Fete Magnets fo Automotve Applcatons, IEEE Tans. on Industal Electoncs 61 No. 1 (Jan 214), [15] UDDIN, M. RADWAN, T. GEORGE, G. RAHMAN, M.: Pefomance of Cuent Contolles fo VSI-Fed IPMSM Dve, IEEE Tans. on Industy Applcatons 36 No. 6 (Nov-Dec 2), [16] KAZMIERKOWSKI, M. MALESANI, L.: Cuent Contol Technques fo Thee-Phase Voltage-Souce PWM Convetes: A Suvey, IEEE Tans. on Industal Electoncs 45 No. 5 (Oct 1998), [17] RAHMAN, K. KHAN, M. CHOUDHURY, M. RAHMAN, M.: Vaable-Band Hysteess Cuent Contolles fo PWM Voltage-Souce Invetes, IEEE Tans. on Powe Electoncs 12 No. 6 (Nov 1997), [18] HYUNG-TAE, M. HYUN-S, K. MYUNG-JOONG, Y.: A dscete-tme Pedctve Cuent Contol fo PMSM, IEEE Tans. on Powe Electoncs 18 No. 1 (Jan 23), [19] RODRIGUEZ, J. PONTT, J. SILVA, C. A. CORREA, P. LEZANA, P. CORTES, P. AMMANN, U.: Pedctve Cuent Contol of a Voltage Souce Invete, IEEE Tans. on Industal Electoncs 54 No. 1 (Feb 27), [2] CORTES, P. KAZMIERKOWSKI, M. P. KENNEL, R. M. QUEVEDO, D. RODRIGUEZ, J.: Pedctve Contol n Powe Electoncs and Dves, IEEE Tans on Industal Electoncs 55 No. 12 (Dec 28), [21] KRAUSE, P. C.: Analyss of Electc Machney, McGaw-Hll, New Yok, [22] STULRAJTER, M. HRABOVCOVA, V. FRANKO, M.: Pemanent Magnets Synchonous Moto Contol Theoy, Jounal of Electcal Engneeng 58 No. 2 (27), Receved 6 Januay 216 Cosmas Ogbuka (Eng D) was bon n Umuna Ngea on 1st Apl, He eceved hs BEng (Fst Class Honos), MEng (Dstncton) and PhD n 24, 29 and 214 espectvely n the Depatment of Electcal Engneeng Unvesty of Ngea, Nsukka, whee he pesently woks as a Lectue I. Hs eseach nteests ae n Adjustable Speed Dves of Electcal Machnes: (DC and AC Electc Machne Toque/Speed Contol wth Convetes and Invetes), Electc Machnes and Powe Electoncs. He has publshed both locally and ntenatonally and attended confeences wthn and outsde Ngea. He s a membe of Ngean Socety of Engnees (NSE), Ngean Insttuton of Electcal Engnees (NIEEE), Intenatonal Assocaton of Engnees (IAENG) and s egsteed by the Councl fo the Regulaton of Engneeng n Ngea (COREN). He s pesently on a postdoctoal eseach vst at the Cha of Electcal Dves and Actuatos (EAA) Unvestät de Bundesweh München, Gemany wth Pofesso D-Ing Dete Gelng. Cajethan Nwosu (Eng D) was bon 1st Octobe He obtaned the BEng, MEng, and PhD Degees n Electcal Engneeng fom the Unvesty of Ngea, Nsukka n 1994, 24, and 215 espectvely. In 27, he undetook a thee months pe-doctoal eseach on Wnd/Sola Hybd Powe System and Renewable Enegy Resouces at the Unvesty of Technology, Delft (TU-Delft), the Nethelands. Snce 25, he has been wth the Depatment of Electcal Engneeng, Unvesty of Ngea, Nsukka, whee he s cuently a Seno Lectue. He had wtten two books and had publshed ove thty atcles both n local and ntenatonal jounals. He s an executve membe of Ngean Insttuton of Electcal and Electonc Engnees (NIEEE), Nsukka chapte. He s a membe of Powe Electoncs Socety of Insttuton of Electcal and Electonc Engneeng (PES IEEE). He s an edtoal boad membe Wold Scence Jounal of Engneeng Applcatons. Hs aeas of eseach nteest nclude powe electonc convetes, electcal dves and enewable enegy technologes. Macel Agu (Eng Pof), bon n 1947 n Ohebe-Dm Ngea, obtaned hs BSc n Electcal Engneeng n 1974 n the Unvesty of Ngea, Nsukka. He also eceved hs MASc and PhD n 1978 and 1982 espectvely n Powe Electoncs fom the Unvesty of Toonto Canada. He s a Pofesso of Powe Electonc n the Depatment of Electcal Engneeng Unvesty of Ngea, Nsukka. Hs eseach nteests ae, but not lmted to, Powe Electonc Ccuts [Sold State AC/DC and DC/DC Convetes, Invete Ccuts and Cycloconvete/nvete ccuts ], Statc Electc Moto Dves (DC and AC Electc Machne Toque/Speed Contol wth Convetes and Invetes), Analogue, dgtal and mcopocessobased electonc contol ccuts, Statc Inducton Heatng Powe Supples fo heat teatment of metals (meltng, castng, fogng, fomng, annealng, hadenng), Renewable Enegy Souces(especally n the aea of wokng wth sola photo voltac cells and panels to ealze sola lghtng, heatng, battey chagng and wate pumpng), Powe System Dstbuton fo Resdental, Commecal and Industal Aeas. He has publshed wde both n local and ntenatonal jounals.