THE growing penetration of ac motor drives into commercial,

Transcription

1 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 51, NO. 5, SEPTEMBER/OCTOBER Hexagon Voltage Manipulating Control (HVMC) for AC Motor Drive Operating at Voltage Limit Jul-Ki Seok, Senior Member, IEEE, and SeHwan Kim, Student Member, IEEE Abtract Thi paper propoe a hexagon voltage manipulating control (HVMC) method for ac motor drive operating at voltage limit. The command output voltage can be determined imply by the torque command and the hexagon voltage boundary in the abence of motor current-regulating proportional-integral (PI) control gain, additional flux weakening (FW) controller, and oberver for cloed-loop control. Thee attribute reduce the time and effort needed for calibration of the controller in the nonlinear voltage-limited region. The propoed HVMC accomplihe the true maximum available voltage utilization, allowing for higher efficiency than that of the current vector controller (CVC) alone in the FW domain. In addition, a voltage election rule wa propoed to determine the unique HVMC olution between two poible voltage vector. The ucceful application of the control approach wa corroborated by a graphical and analytical analyi. The propoed control approach i potentially applicable to a wide range of control deign for ac drive. Index Term AC motor drive operating at voltage limit, hexagon voltage manipulating control (HVMC), maximum available voltage utilization. I. INTRODUCTION THE growing penetration of ac motor drive into commercial, indutrial, and tranportation application ha prompted the entry of current technology into voltage contrained region. Good example of thi trend include ultrahigh-peed (> r/min), high efficiency, and high-powerdenity drive, uch a electrically aited turbo charger [1], [2], turbo compreor [3], [4], white good application [5], [6], and reduced dc-link capacitor technology for heatingventilating-air-conditioning (HVAC) ytem [7] [9]. In thee emerging application, rapid load torque change and trict torque regulation are not normally conidered becaue particular emphai of ytem operation and deign i placed on reliable high peed/high efficient operation and high-powerdenity drive control. Manucript received November 6, 2014; revied February 10, 2015; accepted March 13, Date of publication March 23, 2015; date of current verion September 16, Paper 2014-IDC-0802.R1, preented at the 2014 IEEE Energy Converion Congre and Expoition, Pittburgh, PA, USA, September 20 24, and approved for publication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONSby the Indutrial Drive Committee of the IEEE Indutry Application Society. Thi work wa upported by the 2014 Yeungnam Univerity Reearch Grant. The author are with the School of Electrical Engineering, Yeungnam Univerity, Gyeongbuk , Korea ( doljk@ynu.ac.kr; kh_8508@ ynu.ac.kr). Color verion of one or more of the figure in thi paper are available online at Digital Object Identifier /TIA The proportional-integral (PI) type current vector control (CVC) i the mot widely ued approach for achieving decoupling control of an air-gap torque and flux linkage of ac motor [10]. PI-type CVC ha a well-developed reach in technology and ha been a market ucce becaue of it robutne and implicity. Although it i excellent in the maximum-torqueper-ampere (MTPA) operation, the performance requirement are atified with the help of multiple-objective ub-control action at voltage limit, uch a the maximum-torque-pervoltage (MTPV) or flux weakening (FW) control, anti-windup control, and over-modulation cheme. A a reult, one major difficulty under the voltage-limited region arie from the fact that ub-control action conflict in ubtle way [11]. In addition, there are certain current limitation or load angle contraint that mut be conidered when deigning a MTPV tracking controller. Therefore, the CVC trategy become more complicated under voltage-limited condition becaue it require an extra control function and a tuning gain, which hould be elected carefully baed on the complex tradeoff between the drive ytem tability and the control dynamic. Furthermore, realization of the maximum voltage utilization fail becaue the voltage limit need to be conidered a a circle intead of a hexagon. Conequently, thi control methodology increae the copper lo and require multiple control law for the tranition between flux weakening and maximum voltage utilization. A an alternative, ome modified direct torque and flux control (DTFC) cheme have been exploited for high performance ac motor drive [13], [14]. Depite their improved robutne and tranient performance over claical hyteretic direct torque control algorithm, cloed loop performance degradation till remain when the controller operate at the contrained region. Thee advere conequence arie from the adherence to the control tructure uing the PI-type torque and flux regulator at the nonlinear hexagonal voltage limit. One of the main reaon for uing a PI regulator i the nonlinear cro-coupling of the voltage manipulated input, yielding both an air-gap torque and tator flux linkage, which i not olvable directly and cannot be decoupled in continuou time. Thee have a cloedloop feedback tructure to regulate the motor air-gap torque and tator flux linkage. Therefore, the control performance i influenced directly by a tator flux linkage and torque oberver deign baed on the motor model. Recently, a finite-ettling-tep DTFC (FSS-DTFC) method aociated with the inverter voltage and current contraint for interior permanent-magnet ynchronou motor (IPMSM) wa propoed [11], [12]. The FSS-DTFC ugget that the interection of the current limited ellipe and the rotating hexagon IEEE. Peronal ue i permitted, but republication/reditribution require IEEE permiion. 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2 3830 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 51, NO. 5, SEPTEMBER/OCTOBER 2015 become a feaible voltage vector at the next ampling intant. A cloed-loop Volt-ec olution can correctly decouple the nonlinear cro-coupling of the applied voltage in the dicrete time without adopting a PI-type regulator. The control law dynamically cale the voltage vector on the hexagonal voltage boundary to enure the maximum torque capabilitie under a given operating condition, while imultaneouly regulating the tator flux linkage magnitude to meet the flux weakening requirement. The automatic tranition to the FW mode wa achieved with a ingle voltage election rule. In addition to the tator flux linkage and torque oberver, a cloed-loop tator current oberver i eential for accurately tracking and etimating the change in current in each witching period. The complicated deign of multiple oberver and the need to olve the complex equation may prohibit it implementation on real indutrial drive ytem. Thi paper focue on developing a hexagon voltage manipulating control (HVMC) method for ac motor drive operating at variou voltage limit. The command voltage vector at each dicrete time tep can be determined imply by the torque command and the hexagon voltage boundary without requiring motor current-regulating PI gain, additional FW controller, and oberver for a cloed-loop torque and flux control. Thee attribute reduce the time and effort needed to calibrate the controller in the nonlinear voltage-limited region. The propoed HVMC accomplihe the true maximum available voltage utilization, allowing a higher efficiency than that of the CVC alone in the FW domain. Model-baed voltage control (MVC) or CVC i performed under the MTPA region and motor control i handed automatically over to the propoed HVMC in the voltage hortage region. The automatic tranition from the MTPA to FW mode provide new opportunitie in a mall dc-link capacitor inverter fed by diode-bridge rectifier, which experience frequent dc-bu voltage hortage. The ucceful application of the control approach ha been corroborated by graphical and analytical analyi. The propoed tructure can offer further flexibility in motor deign and ac drive control operating at variou voltage limit. II. HVMC DESIGN FOR AC MOTORS UNDER FW REGION In thi paper, an ac motor i conidered to be alient when the q-axi inductance i larger than the d-axi inductance, wherea non-alient if the d-axi inductance i identical to the q-axi inductance. A. Non-Salient PM Motor At the teady-tate, the tator voltage equation of non-alient permanent magnet (PM) motor can be expreed a v d = i d ω r L i q v q = i q + ω r L i d + ω r λ pm (1a) (1b) where v dq and i dq are the tator voltage and current vector in the ynchronou coordinate, repectively. i the tator reitance, ω r i the rotor angular velocity, λ pm i the flux Fig. 1. Voltage election principle for the HVMC operation of non-alient PM motor. linkage of the PM, and L denote the tator inductance. The q-axi tator current can be obtained a ( ) ( ) ωr L i q = R 2 + v d + ω2 r L2 R 2 + v q ω2 r L2 ω r λ pm R 2 + ωr 2 L 2. (2) The motor torque command can be decribed a a function of the rotor peed and the d-q axi voltage a follow: T e = 3 P 2 2 λ pmi q ( ) = 3 P 2 2 λ pm ωr L R v 2 d ( +ω2 r L2 ) R + R 2 +ωr 2 L v 2 q ω (3) r λ pm R 2 +ωr 2 L 2 where P denote the number of pole. Fig. 1 provide a graphical repreentation of the tator voltage olution between the torque command line and rotating hexagon in the ynchronouly rotating d-q voltage plane. The boundary of each rotating hexagon ector can be modeled a a traight line in the d-q voltage plane [11], [12] v q (k) = M n v d (k) + B n (4) where M n and B n are contant value given by the boundary of each hexagon ector. The correponding hexagon boundary and the torque command of (3) can provide two poible tator voltage olution that produce the deired output torque, a hown in Fig. 1. Here, the command voltage vector, vdq, i choen a a uitable olution at every ampling time v d = 3 2 Te P 2 λ pm vq = M n + ω r λ pm R 2 +ω 2 r L 2 ω r L R 2 +ωr 2 L 2 T e 3 P 2 2 λ pm M n B n R 2 +ωr 2 L 2 R 2 +ωr 2 L 2 + ω r λ pm R 2 +ω2 r L2 ω r L R 2 +ω2 r L2 M n B n R 2 +ω2 r L2 R 2 +ω2 r L2 +B n. (5a) (5b)

3 SEOK AND KIM: HVMC FOR AC MOTOR DRIVES OPERATING AT VOLTAGE LIMIT 3831 In the propoed HVMC method, the interection of the torque line and the rotating hexagon become the command voltage vector at the next ampling intant. B. Salient PM Motor The tator voltage equation of the alient ac motor can be expreed a v d = i d ω r L q i q v q = i q + ω r L d i d + ω r λ pm (6a) (6b) where L dq indicate the d-q axi tator inductance. From (6), the d-q axi tator current can be obtained a ( ) ( ) ω r L q i d = R 2 + ωr 2 v d + L d L q R 2 + ωr 2 v q L d L q ω2 r L q λ pm R 2 + ω2 r L (7a) ( dl q ) ( ) ω r L d i q = R 2 + ωr 2 v d + L d L q R 2 + ωr 2 v q L d L q ω r λ pm R 2 + ωr 2. (7b) L d L q The motor torque command can be decribed a a function of the rotor peed and the d-q axi voltage a follow: T e 3 P 2 2 where = λ pm (k q1 v d +k q2 v q +k q3 ) +(L d L q )(k d1 v d +k d2 v q +k d3 )(k q1 v d +k q2 v q +k q3 ) (8) ω r L q k d1 = R 2 + ω2 r L, k d2 = dl q R 2 + ω2 r L dl q k d3 = ω2 r L qλ pm ω r L d R 2 + ω2 r L, k q1 = dl q R 2 + ω2 r L dl q k q2 = R 2 + ω2 r L, and k q3 = ω r λ pm dl q R 2 + ω2 r L. dl q Fig. 2 how the tator voltage olution in the d-q voltage plane, where a torque command trajectory form a hyperbolic curve. A uitable voltage vector at the correponding interection between (4) and (8) can be obtained a follow: where v d = β β 2 4αγ 2α v q =M nv d +B n (9) α =(L d L q ) { k d1 k q1 +k d2 k q2 M 2 n +(k d1k q2 +k d2 k q1 )M n } β =(L d L q ) {2k d2 k q2 M n B n +(k d1 k q2 +k d2 k q1 )B n +k d1 k q3 +k d3 k q1 +(k d2 k q3 +k d3 k q2 )M n } + λ pm k q1 + λ pm k q2 M n γ =(L d L q )(k d2 k q2 B 2 n +(k d2k q3 +k d3 k q2 )B n +k d3 k q3 ) + λ pm k q2 B n + λ pm k q3 T e. 3 2 P 2 Fig. 2. Voltage election principle for the HVMC operation of alient PM motor. In (9), a ingle voltage olution, which fall on the hexagonal voltage boundary, can be choen a a feaible olution becaue only one olution can be achieved at the next ampling time. C. Induction Motor At the teady-tate, the motor air-gap torque and the rotor flux linkage of the rotor-flux oriented-controlled (RFO) IM can be expreed a T e = 3 2 λ dr = Lm i d P L m λ dr i q 2 L r (10a) (10b) where λ dr i the d-axi rotor flux linkage. L m and L r are the magnetizing and rotor inductance, repectively. The tator voltage equation can alo be implified a v d = i d ω e σl i q v q = i q + ω e L i d (11a) (11b) where σl i the tator tranient leakage inductance. By combining (10) and (11), the rotor flux linkage and torque command can be obtained a a function of the ynchronou peed λ ω e σl dr =L m R 2 + ωe 2 σl 2 v d +L m R 2 + ωeσl 2 2 v q (12) ( ) T e = 3 P L m ω e L λ R 2 +ωe 2 L σl v d dr R 2 2 L r +. (13) R 2 +ω 2 e L σl v q The motor torque command can be obtained a follow: T e = 3 2 P L m (k d1_im v d +k d2_im v q ) 2 L r (k q1_im v d +k q2_im v q ) (14)

4 3832 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 51, NO. 5, SEPTEMBER/OCTOBER 2015 Fig. 3. Voltage election principle for the HVMC operation of induction motor. where k d1_im =L m R 2 + ω2 e σl2 ω e σl ω e L k d2_im =L m R 2 +, k q1_im = ω2 e σl2 R 2 +, and ω2 e σl2 k q2_im = R 2 +. ω2 e σl2 Fig. 3 how the tator voltage olution in the d-q voltage plane. A feaible voltage vector can be obtained a follow: where v d = β ± β 2 4αγ 2α v q =M n v d +B n (15) α =k d1_im k q1_im +(k d1_im k q2_im +k d2_im k q1_im )M n +k d2_im k q2_im M 2 n β =(k d1_im k q2_im +k d2_im k q1_im )B n +2k d2_im k q2_im M n B n, and γ =k d2_im k q2_im B 2 n T e 3 P L m. 2 2 Lr D. Natural Flux-Weakening Operation Fig. 4 how the torque command trajectorie at 70% of the rated torque when the rotor peed travel from 100% to 150% of the bae peed. A the rotor peed i increaed, the voltage olution naturally hift to a downward q-axi direction. In other word, the voltage interection at a 1.5 p.u. peed ha a lower q-axi voltage component than that of the bae peed. It can be noticed from (1b), (6b), and (11b) that the lower q- axi voltage lead to a decreaed d-axi current, which caue a lower flux linkage at a given rotor peed. Thi ugget that an automatic flux-weakening operation and maximum voltage utilization can be achieved imultaneouly without requiring extra control function. Fig. 4. Voltage olution with the rotor peed elevation. (a) Non-alient PM motor. (b) Salient PM motor. (c) Induction motor. E. Voltage Vector Selection Principle The correponding hexagon boundary and torque command curve can provide two poible or adjacent tator voltage olution (va and v B ) that produce the deired output torque, a howninfig.5and6. Here, the command voltage vector va in the voltage plane i choen a a uitable HVMC olution becaue it require a lower tator current magnitude ( i A ), a hown in the current plane, to meet the torque requirement with a higher flux linkage magnitude in the voltage deficit region. The correponding

5 SEOK AND KIM: HVMC FOR AC MOTOR DRIVES OPERATING AT VOLTAGE LIMIT 3833 Fig. 5. Voltage election rule for PM motor. (a) Voltage plane. (b) Current plane. tator current magnitude of va and v B can be calculated uing (1), (6), and (11) at all ampling time. III. CONTROLLER DESIGN FOR AC MOTORS UNDER THE MTPA REGION Although the HVMC can achieve the minimum tator current or maximum voltage utilization operation in the FW region, it i not the optimal trategy under the uncontrained region, compared to the MTPA method. Fig. 7 how the tator current vector of a alient ac motor in the d-q current plane for a given torque requirement when the motor i operated below a bae peed (ω bae ). The tator current magnitude from a given MTPA trategy i maller than that of the HVMC. In thi regard, thi paper ugget a hybrid tructure for the minimum copper lo control over the entire operating range. Thi paper introduce an MVC for an induction motor operating in the non-limited voltage region [9]. When the tator voltage remain within V dc / 3 (circular voltage boundary), which i called the MVC operation, the interection between the contant flux linkage and deired torque command in the d- q voltage plane become the feaible voltage command at the next ampling time. Fig. 8 preent the MVC olution trajectorie of the induction motor with the rotor peed elevation. Once vdq_mvc near the circular voltage boundary, the control witche to the propoed HVMC, which generate the deired air-gap torque a cloely a poible, while imultaneouly regulating the flux linkage magnitude under the MTPA region. Fig. 6. Voltage election rule for induction motor. (a) Voltage plane. (b) Current plane. Fig. 7. Stator current vector of the MTPA and HVMC in the non-limited region. One caveat of MVC mode i that the flux level i not maintained properly when the machine-parameter drift due to magnetic aturation and initial error. On the other hand, an automatic tranition to the HVMC mode can be achieved with a ingle voltage election rule. Therefore, a tranparent and treamlined controller can be deigned under a ingle control law, and reduce the time and effort needed to calibrate the controller in the entire operating region.

6 3834 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 51, NO. 5, SEPTEMBER/OCTOBER 2015 TABLE I RATINGS AND KNOWN PARAMETERS OF 900-W IPMSM Fig. 8. Voltage trajectorie of MVC mode. TABLE II RATINGS AND KNOWN PARAMETERS OF 600-W SPMSM Fig. 9. Propoed hybrid control configuration for copper lo minimization control. When uing the CVC operation for the MTPA operation, it require additional effort for the control mode tranition. A mooth tranition between CVC and HVMC could be achieved by reetting the CVC integrator whenever mode witching occur [15]. Fig. 9 provide an example of the hybrid control configuration, where the MVC or CVC i reponible for the MTPA operation. Uing the propoed hybrid voltage control, the minimum copper lo operation i achieved over the entire operating pace. Thi deign can be effective in regulating the motor torque and flux linkage without requiring any tator current or flux linkage oberver while reducing the computational complexity. Note that the precie torque regulation in the MVC and HVMC mode can be achieved, provided there i no drift of the motor parameter. Thi i not alway the cae, in practice, and the motor parameter hould be etimated and updated in real ituation. Thi paper adopted a familiar PI-type Luenbergertyle tator current oberver controller to decouple the parameter drift effect of MVC and HVMC mode [9], [15], [16]. TABLE III RATINGS AND KNOWN PARAMETERS OF 1.5-kW IM IV. SIMULATION AND EXPERIMENTAL RESULTS The baic feaibility of the propoed controller wa verified on a 900-W alient PM motor, a 600-W non-alient PM motor which i coupled to a 1.0-kW ervo motor, and a 1.5-kW induction motor with a mall dc-link capacitor inverter fed by threephae diode front-end rectifier, a decribed in Table I III. In thi paper, the algorithm wa implemented in the inverter with a contant PWM witching frequency of 5 khz (100 μ ampling time). A TMS320VC33 DSP wa ued a a main control proceor, which operate at 120-MHz clock peed. The computational efficiency of the propoed cheme (MVC+ HVMC) againt the conventional CVC and FW method [17] i compared for the given main proceor. It can be noticed from Fig. 10 that the entire execution time of the propoed Fig. 10. Drive execution time comparion over one ampling period.

7 SEOK AND KIM: HVMC FOR AC MOTOR DRIVES OPERATING AT VOLTAGE LIMIT 3835 Fig. 12. Tet reult of the propoed HVMC for the non-alient PM motor (CVC+HVMC operation). Fig. 11. Simulated reult of the propoed HVMC for the alient PM motor (CVC+HVMC operation). algorithm take approximately 37 μ, while the conventional implementation under the voltage-limited region take 41 μ for each cycle. The propoed implementation reult in a 10% reduction in the algorithm execution time. Here, the required minimum ampling time i around 40 μ for the real implementation becaue the execution time of the whole algorithm coded in C-language i about 37 μ. The imulated tet reult for the alient PM motor i depicted in Fig. 11(a) when the rotor peed travel to 200% of the bae peed and 35% of the rated torque i regulated in the teted motor. The rotor peed, command/controlled air-gap torque, d- q axi tator current, and tator flux linkage are illutrated from the top to bottom. The air-gap torque i regulated in an average ene in the flux weakening domain while an automatic tranition occur between the MTPA (CVC) and FW (HVMC) mode. The torque ditortion are rarely found during the tranition between the CVC and HVMC mode. The x-y locu [Fig. 11(b)] how that the propoed HVMC cheme achieve the maximum voltage utilization under voltage-limited condition. To examine the tranient performance for the HVMC operation, a hown in Fig. 12(a), the rotor peed command wa varied from 0 to 130% of the bae peed while a load torque command wa increaed tepwie from zero to 70% of the rated value. In thi tet, the dc-link voltage wa et to 150 V and the advent of flux weakening occur at approximately 1350 r/min. Ditortion were rarely found in the rotor velocity and etimated tator linkage during the load torque tranition. The reult fully illuminate the fact that the propoed HVMC method achieve a reliable torque command tracking in the tranient tate. Fig. 12(b) highlight the meaured tator current trajectory correponding to Fig. 12(a). The tator current wa regulated well under the FW region without ub-control action

8 3836 IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 51, NO. 5, SEPTEMBER/OCTOBER 2015 Fig. 14. Copper lo comparion between CVC and HVMC operation. (a) Salient PM motor. (b) Non-alient PM motor. Fig. 13. Tet reult of the propoed HVMC for a non- alient PM motor (CVC+HVMC operation). for current control and with the propoed voltage election rule. The x-y locu how that the tator current follow the contant torque trajectory under the FW region. Fig. 13(a) preent a motoring tet reult for the 600 W non-alient PM motor, where the rotor peed, meaured torque, meaured d-q tator current, and etimated tator flux linkage are illutrated from the top to bottom. In thi tet, the dc-link voltage wa et to 150 V and the motor drive wa operated from 0 to 200% of the bae peed. The coupled ervo drive wa operated in peed-control mode, while 35% of the rated torque wa regulated in the teted motor. Fig. 13(b) how the elected d-q command voltage waveform of (5) in the tationary reference frame at the maximum peed. No additional ditortion wa oberved in the output phae voltage waveform. Thi wa confirmed from the x-y locu [Fig. 13(b)] in that the reulting HVMC achieve the maximum voltage utilization under the voltage limited condition. Fig. 14 how the imulated copper lo comparion reult between CVC and HVMC for two teted PM motor at 150% of the bae peed. Compared to the copper loe of the CVC mode alone, the loe of the HVMC operation are reduced by 14% (alient PM motor) and 13% (non-alient PM motor) at the rated torque level owing to the maximum voltage excitation. The reult fully illuminate the fact that the propoed method achieve the minimum copper lo operation under the FW region. Validation of the theoretical development preented above wa performed on a 1.5 kw IM drive with a 20 μf film capacitor fed by a three-phae diode rectifier through a real tet. The nominal input line-to-line voltage wa et to 210 V. Fig. 15(a) preent the tet reult in the motoring operation, where the meaured dc-link voltage, flag ignal, etimated airgap torque, and etimated rotor flux linkage are illutrated from the top to bottom. The mode_hvmc i 1 if the HVMC mode activate and 0 otherwie (MVC mode). In thi tet, the IM drive wa operated with 90% of the bae peed while the rated load torque wa applied. The dc-link voltage fluctuate with ix time the input grid voltage frequency. The flag ignal how that a mooth and rapid tranition occur between the MVC and HVMC operation while the deired torque wa wellregulated with the average value. Thi i becaue the propoed MVC and HVMC controller were deigned without integrator

9 SEOK AND KIM: HVMC FOR AC MOTOR DRIVES OPERATING AT VOLTAGE LIMIT 3837 Fig. 15. Tet reult of the propoed HVMC for an induction motor. (MVC+HVMC operation). for current control and with the ame voltage election rule. The propoed method avoid econdary upet by the control mode witching and complexity of having an additional control function or gain to be adjuted. The x-y locu [Fig. 15(b)] how that the reulting controller can achieve the maximum voltage utilization at the periodic voltage dropping region. V. C ONCLUSION Thi paper ha propoed a hexagon voltage manipulating control (HVMC) method for ac motor drive operating at voltage limit. The command output voltage can be determined imply by the torque command and the hexagon voltage boundary in the abence of control gain, additional FW controller, and oberver for cloed-loop control. Thi performance criterion i particularly important for application experiencing frequent dc-bu voltage hortage. The performance of the propoed HVMC wa illutrated in both imulation and on a real ac drive, howing the combination of graphical and analytical analyi. The propoed control approach i potentially applicable to a broad family of control deign for ac drive. REFERENCES [1] C. Bell, Maximum Boot: Deigning, Teting and Intalling Turbocharger Sytem. Cambridge, MA, USA: Bentley, [2] S. H. Kim and J. K. Seok, Comprehenive PM motor controller deign for electrically aited turbo-charger ytem, in Proc. IEEE ECCE Conf., 2013, pp [3] B. H. Bae, S. K. Sul, J. H. Kwon, and J. S. Byeon, Implementation of enorle vector control for uper high peed PMSM of turbo-compreor, IEEE Tran. Ind. Appl., vol. 39, no. 3, pp , May/Jun [4] S. Chi and L. Xu, Development of enorle vector control for a PMSM running up to rpm, inproc. IEEE IEMDC Conf., 2005, pp [5] I. Boldea, Control iue in adjutable peed, IEEE Ind. Electron. Mag., vol. 2, no. 3, pp , Sep [6] A. Tenconi, S. Vachetto, and A. 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Appl., vol. 50, no. 5, pp , Sep./Oct [12] C. H. Choi, J. K. Seok, and R. D. Lorenz, Wide-peed direct torque and flux control for interior PM ynchronou motor operating at voltage and current limit, IEEE Tran. Ind. Appl., vol. 49, no. 1, pp , Jan./Feb [13] I. Boldea, M. C. Paicu, G. D. Andreecu, and F. Blaabjerg, Active flux DTFC-SVM enorle control of IPMSM, IEEE Tran. Energy Conver., vol. 24, no. 2, pp , Jun [14] G. Foo and M. F. Rahman, Senorle direct torque and flux-controlled IPM ynchronou motor drive at very low peed without ignal injection, IEEE Tran. Ind. Appl., vol. 57, no. 1, pp , Jan [15] S. H. Kim, C. H. Choi, and J. K. Seok, Voltage diturbance tate-filter deign for precie torque-controlled interior permanent magnet ynchronou motor, in Proc. IEEE ECCE Conf., 2011, pp [16] S. H. Kim and J. K. Seok, Maximum voltage utilization of IPMSM uing modulating voltage calability for automotive application, IEEE Tran. Power Electron., vol. 28, no. 124, pp , Dec [17] S. K. Sul, Control of Electric Machine Drive Sytem. New York, NY, USA: Wiley-IEEE Pre, Jul-Ki Seok (S 94 M 98 SM 09) received the B.S., M.S., and Ph.D. degree from Seoul National Univerity, Seoul, Korea, in 1992, 1994, and 1998, repectively, all in electrical engineering. From 1998 to 2001, he wa a Senior Engineer with the Production Engineering Center, Samung Electronic, Suwon, Korea. Since 2001, he ha been a member of the faculty of the School of Electrical Engineering, Yeungnam Univerity, Gyeongan, Korea, where he i currently a Profeor. Hi pecific reearch area are motor drive, power converter control of offhore wind farm, and nonlinear ytem identification related to the power electronic field. Dr. Seok wa the recipient of the 2014 IEEE TRANSACTIONS ON IN- DUSTRY APPLICATIONS Second Place Prize Paper Award and erve a an Aociate Editor of the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS. SeHwan Kim (S 10) received the B.S. degree from Yeungnam Univerity, Gyeongan, Korea in 2010, where he i currently working toward the Ph.D. degree in the Power Converion Laboratory. Hi current reearch interet include highperformance electrical machine drive, battery voltage maximum utilization for EV/HEV, and precie torque control of PM ynchronou motor.