Analysis and Modeling of Parallel Three-Phase Boost Converters Using Three-Phase Coupled Inductor

Transcription

1 J Electr Eng Technol Vol. 8, No. 5: , ISSN(Print ISSN(Online Analysis an Moeling of Parallel Three-Phase Boost Conerters Using Three-Phase Couple Inuctor Chang-Soon Lim, Kui-Jun Lee, Rae-Young Kim an Dong-Seok Hyun Abstract The main issue of parallel three-phase boost conerters is reuction of the low- an high frequency circulating currents. Most present technologies concentrate on low frequency circulating current because the circulating current controller cannot mitigate the high frequency circulating current. In this paper, analytical approach of three-phase couple inuctor applie to parallel system becomes an important objectie to effectiely reuce the low- an high frequency circulating currents. The characteristics of three-phase couple inuctor base on a structure an oltage equations are mathematically erie. The moifie oltage equations are then applie to parallel three-phase boost conerters to eelop aerage moels in stationary coorinates an rotating coorinates. Base on the aerage moeling approach, esign of the circulating current controller is presente. Simulation an experimental results emonstrate the effectieness of the analysis an moeling for the parallel threephase boost conerters using three-phase couple inuctor. Keywors: Parallel three-phase boost conerters, Circulating current, Three-phase couple inuctor. 1. Introuction Parallel three-phase boost conerters hae many aantages, such as high power uner a lower oltage or current ripple, easy moularity, fast-ynamic response, an high efficiency. Therefore, their utilization has ramatically increase in arious applications incluing uninterruptible power supplies (UPS, motor ries, an power factor correction (PFC equipment [1-3]. Howeer, one of the major concerns with parallel threephase boost conerters is the reuction of the low- an high frequency circulating currents. A low frequency circulating current may be present in the case of small unbalances between two conerters, such as ifferent line inuctances or ifferent uty cycles. A high frequency circulating current occurs when the interleae PWM is applie to the parallel three-phase boost conerters. A straightforwar solution for the low- an high frequency circulating currents is to isrupt the circulating current path. This is easily achiee using a transformer or separate power supplies on the AC sie [4-5]. This solution results in an oerall system which is heay, bulky, an high-price. To aoi these issues, seeral circulating current controllers which o not require installation of aitional harware hae been propose for the low frequency circulating current [6-8]. Howeer, these controllers are unable to mitigate the high frequency Corresponing Author: Dept. of Electrical Engineering, Hanyang Uniersity, Korea. (shyun@hanyang.ac.kr Dept. of Electrical Engineering, Hanyang Uniersity, Korea. ({reamepot, rykim}@hanyang.ac.kr FREEDM Systems Center, North Carolina State Uniersity, USA. (kuijun.lee@gmail.com Receie: December 8, 01; Accepte: April 18, 013 circulating current ue to its ientical banwih to the switching frequency. In orer to reuce the high frequency circulating current, installation of aitional system harware is unaoiable. Recently, arious methos using the wining-couple inuctor hae been presente to achiee performance improing results [9-1]. In orer to effectiely reuce low- an high frequency circulating current, this paper analyzes three-phase couple inuctor applie to parallel three-phase boost conerters, as shown in Fig. 1. In Section, the characteristics of three-phase couple inuctor connecte to three-phase AC source are mathe- Fig. 1. Parallel three-phase boost conerters incluing three-phase couple inuctor 1086

2 Chang-Soon Lim, Kui-Jun Lee, Rae-Young Kim an Dong-Seok Hyun matically erie by a structure an oltage equations. Then, the moifie oltage equation of three-phase couple inuctor is presente. Section 3 introuces aerage moels, which can simultaneously reuce low- an high frequency circulating currents, in stationary coorinates an rotating coorinates. Base on the aerage moeling approach, section 4 presents esign of circulating current controller for parallel three-phase boost conerters using three-phase couple inuctor. Section 5 shows simulation an experimental results to emonstrate the effectieness of the analysis an moeling approach. Section 6 summarizes the major contributions of this paper.. Analysis of the Three-Phase Couple Inuctor This section analyzes the three-phase couple inuctor in parallel three-phase boost conerters. The three-phase couple inuctor structure is use to examine how the three-phase couple inuctor mitigates the circulating current. Subsequently, oltage equations of the three-phase couple inuctor are examine to moel parallel threephase boost conerters incluing the three-phase couple inuctor..1 Three-phase couple inuctor structure Fig. shows a three-phase couple inuctor (i.e., the three-wining integrate magnetic eice structure with reference irections for the currents when three-phase currents i a, i b, an i c flow through wining N. In the threephase couple inuctor, the three total flux equations are φa = φaa + φba + φca = ρaa Nia + ρba Nia + ρca Nia (1 φb = φab + φbb + φcb = ρab Nib + ρbb Nib + ρ cbnib ( φ = φ + φ + φ = ρ Ni + ρ Ni + ρ Ni (3 c ac bc cc ac c bc c cc c where φ x is the total flux linking coil x in the three-phase couple inuctor, φ xx is the flux linking coil x prouce by a current in coil x in the three-phase couple inuctor, φ yx is N V Cb i b the flux linking coil y prouce by a current in coil x in the three-phase couple inuctor, ρ xx is the permeance of the space occupie by the flux φ xx in the three-phase couple inuctor, an ρ yx is the permeance of the space occupie by the flux φ yx in the three-phase couple inuctor. If the couple inuctor is in an ieal state, it is possible to assume the following: ρs = ρaa = ρbb = ρ cc = 0 (4 ρ = ρ = ρ = ρ = ρ = ρ = ρ (5 m ab ac ba bc ca cb Summing up (1-3, an using (4-5, the following equation can be erie: φ + φ + φ = ρ N( i + i + i (6 a b c m a b c Eq. (6 inicates that the net magnetic flux in the core is nearly zero uner balance conition. Howeer, uner unbalance conitions, the net magnetic flux in the core is non-zero. Specifically, if there is no circulating current, the system is not influence by the three-phase couple inuctor.. Voltage equations for three-phase couple inuctor The oltage equations for a three-phase couple inuctor are typically efine as Va = Laa ia + Lab ib + Lac ic (7 Vb = Lba ia + Lbb ib + Lbc ic (8 Vc = Lca ia + Lcb ib + Lcc ic (9 where L xx is the self-inuctance prouce by a current in coil x in the three-phase couple inuctor, an L yx is the mutual inuctance prouce by a current in coil x in the three-phase couple inuctor. Similar to (4-5, the self-inuctance an mutual inuctance can be respectiely assume to be Ls = Laa = Lbb = Lcc (10 L = L = L = L = L = L = L (11 m ab ac ba bc ca cb V Ca i a N φ a φ b Therefore, the relationship between self-inuctance an mutual inuctance can be expresse as Fig.. Simplifie structure of the three-phase couple inuctor φ c i c N V Cc Lm = kc Ls Ls = kc Ls (1 where k c is the coupling coefficient in the three-phase couple inuctor. In Fig. 1, the circulating current i z is efine as i = i = i + i + i = i = ( i + i + i (13 z z1 a1 b1 c1 z a b c 1087

3 Analysis an Moeling of Parallel Three-Phase Boost Conerters Using Three-Phase Couple Inuctor Using (10-13, three-phase couple inuctor oltage Eqs. (7-9 can be rewritten as V a Ls (1 kc ia kc Ls iz (14 V b Ls (1 kc ib kc Ls iz (15 V c Ls (1 kc ic kc Ls iz (16 where L S (1 - k c an k c L S are the leakage inuctance to the line current an the mutual inuctance to the circulating current, respectiely. The moifie oltage Eqs. (14-16 inicate that the leakage inuctance an mutual inuctance are epenent on the coupling coefficient of the three-phase couple inuctor. In other wors, the mutual inuctance to the circulating current is increase an leakage inuctance to the line current is ecrease if the coupling coefficient k c is increase. 3. Aerage Moeling Generally, a traitional moeling approach for a threephase boost conerter is to transform three-phase stationary coorinates into synchronous rotating coorinates. In this case, the zero-sequence component oes not influence the input line currents or the output irect current (DC oltages because there is no zero-sequence component. Howeer, the traitional moeling approach cannot be use for parallel three-phase boost conerters because zero-sequence components o exist. Therefore, in orer to moel the zero-sequence components in parallel threephase boost conerters, an aerage moel base on a phase-leg aeraging technique was use in [6] an [13]. In orer to preict the system ynamics an esign controller, three moels (aerage moel in stationary coorinates, aerage moel in rotating coorinates, an small-signal moel for parallel three-phase boost conerters incluing the three-phase couple inuctor will be escribe in this section. As shown in Fig. 3, the three stages are neee in orer to obtain linear time inariant (LTI moel: phase-leg aeraging technique, abc/qz transformation, an perturbation an linearization. 3.1 Aerage moel in stationary coorinates In orer to accurately reflect a three-phase couple inuctor to parallel three-phase boost conerters moel, moifie oltage Eqs. (14-16 are ae to conentional aerage moel in stationary coorinate. As a result, the Phase-leg aeraging technique abc / qz transformation Perturbation an linearization Parallel three-phase boost conerters incluing threephase couple inuctor Aerage moel in stationary coorinates Aerage moel in rotating coorinates Small signal moel nonlinear, time-ariant nonlinear, time-inariant linear, time-inariant Fig. 3. The relationship of three moeling methos. Fig. 4. Aerage moel of parallel three-phase boost conerters incluing the three-phase couple inuctor in stationary coorinates. 1088

4 Chang-Soon Lim, Kui-Jun Lee, Rae-Young Kim an Dong-Seok Hyun aerage moel of parallel three-phase boost conerters incluing three-phase couple inuctor in stationary coorinate is propose, as shown in Fig. 4. This moel can simultaneously reuce the low an high frequency circulating currents. Using the Fig. 4, the statespace equations in stationary coorinates can be easily obtaine: ia1 an + N CL1 1 i b1 = bn + N CL1 L1 + Ls1(1 kc1 ic1 cn + N CL1 a1 L + L (1 k 1 s1 c1 b1 1 ia an + N CL 1 ib = bn + N CL L + Ls( 1 kc i + c cn N CL a + b L Ls( 1 kc ia1 1 = ( [ a1 b1 c1] i b1 C i where V CL1 an V CL are an c c1 ia + [ a b ] ib RC i CL1= kc1ls1 iz1 CL = kcls iz (17 (18 (19 a b c uty cycle for three-phase i a i b i c aerage three-phase currents uring one switching perio 3. Aerage moel in rotating coorinates In orer to reuce steay-state error, the moel in the stationary coorinates is usually transforme into rotating coorinates. The transformation matrix T is efine as follows: π π cosωt cos( ωt cos( ω t+ 3 3 π π T = sinωt sin( ωt sin( ω t (0 where ω is angular frequency. The ariables in the stationary coorinates Y abc can be transforme into the rotating coorinates Y qz by using transformation matrix (0. Y qz = T Y (1 Applying Eqs. (1 to (17-19, the state-space equations in rotating coorinates can be efine as 0 ω ω abc i1 1 iq1= q L1 + Ls1( 1 kc1 iz1 z + 3( N CL1 0 ω ω i1 1 0 i q1 q1 L + 1 Ls1( 1 kc1 0 iz1 z1 i 1 iq= q L + Ls(1 kc iz z + 3(VN VCL 0 i 0 i q q L + Ls(1 kc 0 iz z i1 i 1 ( z1 z = 1 q1 i q1 q i q C i z1 i z RC where z1 an z are z1 = a1 + b1 + c1, z = a + b + c ( (3 (4 Using the Eq. (13, the state-space Eqs. (-4 can be rewritten as i ω i 1 = i L + L (1 k ω 0 i q1 1 s1 c1 q q1 L L k 1 1+ s1(1 c1 q1 i 1 0 ω i = i L + L (1 k ω 0 i q s c q q L L k + s (1 c q ( z1 z i Z= L + L + L (1+ k + L (1+ k 1 s1 c1 s c (5 (6 (7 1089

5 Analysis an Moeling of Parallel Three-Phase Boost Conerters Using Three-Phase Couple Inuctor 1 i1 i = ( 1 q1 q C + i q1 iq ( z1 z + iz (8 3 RC Unlike the single three-phase conerter system, the parallel three-phase conerters system has zero-sequence component as (7 an (8. Using the state-space Eqs. (5-8, the aerage moel of parallel three-phase boost conerters incluing the three-phase couple inuctor in rotating coorinates can be eelope, as shown in Fig Small-signal moel The aerage Eqs. (5-8 in rotating coorinate are nonlinear functions of the signals in the system. In orer to esign controller, nonlinear aerage equations must be linearize. Using the aerage small-signal moel at a quiescent operating point, the linear moel can be easily obtaine. In perturbation an linearization step, it is assume that an aerage alues are perturbe by aing the small-signal ac ariation ( at a quiescent operating point. The perturbe alue is represente as: i = I + i i = I + i q1 q1 q1 i = I + i i = I + i z z z q q q i = I + i = V + = V + = V + ( q q q = D + = D + q1 q1 q1 = D + = D + = = D + z1 z z z z q q q Assuming that the input oltage sources are ieal, then q 0 = = (30 The linearization step can be complete by neglecting the nonlinear secon-orer ac terms because each of the secon-orer terms is much smaller than the first-orer ac terms in magnitue. After the linearization step, the aerage small-signal equation of parallel three-phase boost conerters incluing three-phase couple inuctor can be erie as follows: Where X = AX + BU (31 1 D D 1 q1 D D q 0 RC C C C C D 1 0 ω α Dq 1 ω A= α D ω 0 β Dq 0 0 ω 0 0 β (3 ω ω ω ω Fig. 5. Aerage moel of parallel three-phase boost conerters incluing the three-phase couple inuctor in rotating coorinates. 1090

6 Chang-Soon Lim, Kui-Jun Lee, Rae-Young Kim an Dong-Seok Hyun Fig. 6. Aerage small-signal moel of parallel three-phase boost conerters incluing three-phase couple inuctor. X = [ i i i i i ] T (33 1 q1 q z I I 1 q1 I I q 0 C C C C V α V α B= V β V β V γ T 1 q1 q z U = where α,β, an γ are shown as follows : α= L + L (1 k 1 s1 c1 β= L + L (1 k s c γ= L + L + L (1+ k + L (1+ k 1 s1 c1 s c (34 (35 From the Eq. (31, the aerage small-signal moel of parallel three-phase boost conerters incluing three-phase couple inuctor can be eelope, as shown in Fig. 6. Since the system moel is linearize at a quiescent operating point, the controller for parallel three-phase boost conerters incluing three-phase couple inuctor can be esigne Design of the Circulating Current Controller Fig. 7 represents the one space-ector PWM pattern for the three-phase boost conerter. 1, are uty cycles for actie ectors (pnn an ppn an 0 is uty cycle for zero ectors (ppp an nnn. Therefore, the uty cycles a, b an c of S ap, S bp an S cp can be expresse as = + + a ppp 1 b = ppp + c ppp = (36 where ppp is uty cycle for zero ector ( ppp. Since this system consists of two parallel conerters, the z1 (conerter 1 an z (conerter are = + + = z1 a1 b1 c1 ppp = + + = (37 z a b c ppp 1 If two parallel conerters hae the ientical actie ectors, can be expresse as Z Fig. 7. Relationship between space-ector PWM pattern an uty cycle 1091

7 Analysis an Moeling of Parallel Three-Phase Boost Conerters Using Three-Phase Couple Inuctor Fig. 8. Simplifie zero-sequence ynamic in small-signal moel Fig. 9. Block iagram of the circulating current controller in a close loop = = 3 3 (38 Z Z1 Z ppp1 ppp As a result, one loop equation for zero-sequence ynamic in Fig. 6 can be rewritten as i z L (3 eq + Req iz = ppp1 3 ppp V (39 where an Leq an R eq are L = L + L + L (1+ k + L (1+ k eq 1 s1 c1 s c R = R + R + R + R (40 eq L1 L C1 C Fig. 10. Magnitue/phase plots of the circulating current controller loop gain for an open an close loop R L1 R L R C R C Equialent series resistors of the inuctors Equialent series resistors of the three-phase couple inuctors From the Eq. (39, the zero-sequence ynamic of smallsignal moel is simplifie, an is epicte in Fig. 8. The ac circulating current ariation i z can be expresse as the superposition of terms arising from two inputs i z 3 V 3 V = L S+ R L S+ R ppp ppp1 eq eq eq eq (41 A single circulating current controller is sufficient for controlling the low frequency circulating current since there is only one circulating current. Therefore, the block iagram of the circulating current controller can be eelope, as shown in Fig. 9. The transfer function G 1 an G are 3 V G 1 = L eq S + R eq G eq 3 V = L S+ R eq (4 The PI compensator of (43 is use for the circulating current compensator G C. Using the circuit parameter:l 1 = L =mh, L S1 =L S =1mH, k c1 =k c =0.99, R L1 =R L =0.35Ω, R C1 =R C =0.Ω, the circulating current compensator parameters are etermine. Gain an time constant in Eq. (43 are k=0.04 an T= S T Gc = k S T (43 Fig. 10 shows magnitue/phase plots of the circulating current loop gain for an open an close loop. The compensator esign results show a phase margin higher than 85 egree. The crossoer frequency is about 500Hz. 5. Simulation an Experimental Results In orer to erify the effectieness of the analysis an moeling, the prototype specifications in Table 1 were esigne, simulate, constructe an experimente. Different line inuctance parameters are applie to generate a Table 1. Parameters for experiment Parameter Input line-to-line oltage Output oltage Output power Switching frequency Line inuctor, L 1, L 3φ couple inuctor, L S1, L S Coefficient of coupling, k c1, k c IGBT moules DSP Value 0 [ V rms ] 400 [ V ] 3 [ kw ] 10 [ khz ].5.0 [ mh ] [ mh ] 0.99 BSM00GB10DLC TMS30VC33 109

8 Chang-Soon Lim, Kui-Jun Lee, Rae-Young Kim an Dong-Seok Hyun (a (b Fig.11. Photograph of the experimental prototype: (a Parallel three-phase boost conerters; (b Three-phase couple inuctor. (a (b (c ( (e (f Fig. 1. Simulate waeforms of the line currents an the circulating currents: (a Not use the circulating current controller; (b Use the circulating current controller; (c Not use the circulating current controller an the three-phase couple inuctor; ( Use the only circulating current controller; (e Use the only three-phase couple inuctor; (f Use the circulating current controller an the three-phase couple inuctor simultaneously. low frequency circulating current an a 180-egree interleae PWM is applie to generate a high frequency circulating current. Figs. 11 (a an (b show the test setup of the parallel three-phase boost conerters an three-phase couple inuctor, respectiely. The power stage consiste of two parallel three-phase boost conerters using Infineon IGBT moules, current sensors (ES100C, an isolation amplifiers (AD-0JN, which were use to generate the input line currents an the output DC-link oltage. The control algorithms were programme an translate into the TMS30VC33 DSP platform. Fig. 1 shows the simulate waeforms of the line currents an the circulating current in the parallel threephase boost conerters. There is no high frequency circulating current in Fig. 1(a an (b since interleaing PWM is not applie for the simulations. Therefore, Fig. 1(b shows that the low frequency circulating current is effectiely reuce by the circulating current controller. On the other han, Figs. 1(c to (f illustrates simultaneous high frequency an low frequency circulating currents since interleaing PWM is applie in the simulations. As a result, a certain amount of line current (i a1 +i a ripple is cancelle ue to the interleaing PWM, as can be seen by comparing Figs. 1(a to (b with Figs. 1(c to (f. As shown in Fig. 1(, the circulating current controller only reuces the low frequency circulating current. Both Figs. 1(e an (f show that the low frequency an the high frequency circulating currents are reuce by the three-phase couple inuctor. Howeer, the low frequency circulating current shown in Fig. 1(f is further reuce by applying the circulating current controller. Fig. 13 shows the experimental waeforms of the line 1093

9 Analysis an Moeling of Parallel Three-Phase Boost Conerters Using Three-Phase Couple Inuctor (a (b (c ( (e (f Fig. 13. Experimental waeforms of the line currents an the circulating currents. (a Not use the circulating current controller. (b Use the circulating current controller. (c Not use the circulating current controller an the threephase couple inuctor. ( Use the only circulating current controller. (e Use the only three-phase couple inuctor. (f Use the circulating current controller an the three-phase couple inuctor simultaneously. the structure an oltage equations were mathematically erie. It was shown that the aerage moel, which can simultaneously reuce low- an high frequency, was eelope in stationary coorinates an rotating coorinates. Base on the aerage moeling approach, the esign of the circulating current controller was presente. Simulation an experimental results emonstrate the effectieness of three-phase couple inuctor an circulating current controller in parallel three-phase boost conerters. Fig. 14. THD results of the gri currents currents an the circulating current in the parallel threephase boost conerters. Due to ientical conitions an control algorithms, the experimental results were almost similar to the simulate results. Fig. 14 shows the gri current THDs of two ifferent systems. The THD of propose system is less than the THD of conentional system. Therefore, propose system can be a goo solution to reuce the current harmonic istortion in parallel threephase boost conerters. 6. Conclusion In this paper, the analysis an moeling of the parallel three-phase boost conerters incluing three-phase couple inuctor was presente to preict system ynamics. To examine the characteristic of three-phase couple inuctor, References [1] K. Xing, F. C. Lee, D. Boroyeich, Z. Ye, an S. K. Mazumer, The circulating current in parallele three-phase boost PFC rectifiers, IEEE Trans. Power Electron., Vol. 14, No. 5, pp , Sep [] I. Takahashi an M. Yamane, Multiparallel asymmetrical cycloconerter haing improe power factor an waeforms, IEEE Trans. In. Applicat., Vol., No. 6, pp , [3] M. Baumann an J. W. Kolar, Parallel connection of two three-phase three-switch buck-type unity-powerfactor rectifier systems with DC-link current balanceing, IEEE Trans. In. Electron., Vol. 54, No. 6, pp , Dec [4] T. Kawabata an S. Higashino, Parallel operation of oltage source inerters, IEEE Trans. In. Applicat., Vol. 4, No., pp , [5] L.-P. Wong, D. K.-W. Cheng, M. H. L. Chow, an Y

10 Chang-Soon Lim, Kui-Jun Lee, Rae-Young Kim an Dong-Seok Hyun S. Lee, Interleae three-phase forwar conerter using integrate transformer, IEEE Trans. In. Electron., Vol. 5, No. 5, pp , Oct [6] Z. Ye, D. Boroyeich, J.-Y. Choi an F. C. Lee Control of circulating current in two parallel threephase boost rectifiers, IEEE Trans. Power Electron., Vol. 17, pp. 609, Sep. 00. [7] K. Xing, F. C. Lee, D. Borojeic, Z. Ye, an S. Mazumer, Interleae PWM with iscontinuous space-ector moulation, IEEE Trans. Power Electron., Vol. 14, No. 5, pp , Sep [8] C.-T. Pan an Y.-H. Liao, Moeling an coorinate control of circulating current in parallel three-phase boost rectifiers, IEEE Trans. In. Electron., Vol. 54, No., pp , Apr [9] W. S. Yu, J. -S. Lai, an S. -Y. Park, An improe zero-oltage switching inerter using two couple magnetics in one resonant pole, IEEE Trans. Power Electron., Vol. 5, No. 4, pp , Apr [10] S.-K. Changchien, T.-J. Liang, J.-F. Chen, an L.-S. Yang, Noel high step-up - conerter for fuel cell energy conersion system, IEEE Trans. In. Electron., Vol. 57, No. 6, pp , Jun [11] L. Asiminoaei, E. Aeloiza, P. N. Enjeti, an F. Blaabjerg, Shunt actie-power-filter topology base on parallel interleae inerters, IEEE Trans. In. Electron., Vol. 55, No. 3, pp , Mar [1] B. Yang, W. Li, Y. Zhao, an X. He, Design an analysis of a grionnecte photooltaic power system, IEEE Trans. Power Electron., Vol. 5, No. 4, pp , Apr [13] K. Xing, Moeling, Analysis an Design of Distribute Power Electronics System Base on Builing Block Concept, Ph.D. issertation, Virginia Polytech. Inst. an State Uni., Blacksburg, May Chang-Soon Lim He receie the B.S. egree in electronic engineering from Soongsil Uniersity, Seoul, Korea, in 009, an the M.S. egree in Electrical Engineering from Hanyang Uniersity, Seoul, Korea, in 011, where he is currently working towar the Ph.D. egree. His research interests inclue moeling an control of power conerter systems, soft switching techniques for renewable energies an battery charger. Kui-Jun Lee He receie the B.S. an Ph.D. egrees in electrical engineering from Hanyang Uniersity, Seoul, Korea, in 005 an 01, respectiely. In 01, he joine the Future Renewable Electric Energy Deliery an Management (FR-EEDM Systems Center, North Carolina State Uniersity, Raleigh. His research interests inclue power conerter system for renewable energies an soft switching techniques. Rae-Young Kim He receie the B.S. an M.S. egrees from the Hanyang Uniersity, Seoul, Korea, in 1997 an 1999, respectiely, an the Ph.D. egree from the Virginia Polytechnic Institute an State Uniersity, Blacks burg, VA, in 009, all in electrical engineering. From 1999 to 004, he was a Senior Researcher at the Hyosung Heay Inustry R&D Center, Seoul, Korea. In 009, he was a Postoctoral Researcher at National Semiconuctor Corporation, working a smart home energy management system. Since 010, he has been with the Hanyang Uniersity, Seoul, Korea, where he is currently an Assistant Professor in the Department of Electrical an Biomeical Engineering. His research interests inclue moeling an control of power conerter systems, soft switching techniques, energy management systems in smart gri applications, power conerter systems for renewable energies, an motor rie systems. Dr. Kim receie a First Prize Paper Awar in IAS 007. Since 009, He has been a Member of the IEEE Inustry Applications Society (IAS Inustry Power Conerters Committee, an also sere as a Reiewer for the IEEE Transaction on Inustrial Electronics an the IEEE Transaction on Inustry Applications. Dong-Seok Hyun He receie the B.S. an M.S. egrees from Hanyang Uniersity, Seoul, Korea, in 1973 an 1978, respectiely, an the Ph.D. egree from Seoul National Uniersity, Seoul, Korea, in 1986, all in electrical engineering. From 1976 to 1979, he was a Researcher with the Agency of Defense Deelopment, Korea. From 1984 to 1985, he was a Research Associate in the Department of Electrical Engineering, Uniersity of Toleo, Toleo, OH, an from 1988 to 1989, he was a Visiting Professor in the Department of Electrical Engineering, Technical Uniersity of Munich, Germany. Since 1979, he has been with Hanyang Uniersity, where he is currently a Professor in the Department of Electrical Engineering. He is the author of more than 650 publications concerning electric machine esign, high-power engineering, power electronics, an motor ries. His research interests inclue power electronics, motor ries, traction, an their control systems. Dr. Hyun is a member of the IEEE Power Electronics, Inustrial Electronics, Inustry Applications, an Electron Deices Societies. He is also a member of the Institution of Engineering an Technology, the Korean Institute of Power Electronics, an the Korean Institute of Electrical Engineers. 1095