Integrated Inverter/Converter Circuit and Control Technique of Motor Drives With Dual-Mode Control for EV/HEV Applications

1358 IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL. 29, NO. 3, MARCH 2014

Integrated Inverter/Converter Circuit and ControlTechnique of Motor Drives With Dual-Mode

Control for EV/HEV ApplicationsYen-Shin Lai, Senior Member, IEEE, Wei-Ting Lee, Yong-Kai Lin, Member, IEEE, and Jian-Feng Tsai

AbstractA new integrated circuit for motor drives with dual-mode control for EV/HEV applications is proposed. The proposedintegrated circuit allows the permanent magnet synchronous mo-tor to operate in motor mode or acts as boost inductors of the boostconverter, and thereby boosting the output torque coupled to thesame transmission system or dc-link voltage of the inverter con-nected to the output of the integrated circuit. In motor mode, theproposed integrated circuit acts as an inverter and it becomes aboost-type boost converter, while using the motor windings as theboost inductors to boost the converter output voltage. Moreover,a new control technique for the proposed integrated circuit underboost converter mode is proposed to increase the efficiency. Theproposed control technique is to use interleaved control to signif-icantly reduce the current ripple and thereby reducing the lossesand thermal stress under heavy-load condition. In contrast, single-phase control is used for not invoking additional switching andconduction losses under light-load condition. Experimental resultsderived from digital-controlled 3-kW inverter/converter using dig-ital signal processing show the voltage boost ratio can go up to600 W to 3 kW. And the efficiency is 93.83% under full-load condi-tion while keeping the motor temperature at the atmosphere level.These results fully confirm the claimed merits for the proposedintegrated circuit.

Index TermsBoost converter, inverter, motor drives.

I. INTRODUCTION

IN PARALLEL hybrid electric vehicle (HEV) [1][3] andelectric vehicle (EV) [4], [5] system as shown in Fig. 1, theconverter is used for boosting the battery voltage to rated dcbus for an inverter to drive motor. In the multimotor drive sys-tem [6], [7], the system will use two or more motors to boosttorque, especially under low speed and high-torque region asshown in Fig. 2. For such applications, two or more inverters/converters are required. Fig. 3 shows the application of the pro-posed integrated circuit for motor drives with dual-mode controlfor EV/HEV applications. As shown in Fig. 3, the proposed inte-grated circuit allows the permanent magnet synchronous motor

Manuscript received December 24, 2012; revised March 21, 2013; acceptedApril 30, 2013. Date of current version September 18, 2013. Recommended forpublication by Associate Editor M. Ferdowsi

Y.-S. Lai and W.-T. Lee are with the Center for Power Electronics Tech-nology, National Taipei University of Technology, Taipei 106, Taiwan (e-mail:[email protected]; [email protected]).

Y.-K. Lin and J.-F. Tsai are with the Industrial Technology Research Institute,Hsinchu 31040, Taiwan (e-mail: [email protected]; [email protected]).

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TPEL.2013.2263395

Fig. 1. HEV and EV system. (a) Parallel HEV drive train. (b) EV drive train.

Fig. 2. Conventional multimotor drive system of EV/HEV.

(PMSM) to operate in motor mode or acts as boost inductorsof the boost converter, and thereby, boosting the output torquecoupled to the same transmission system or dc-link voltage ofan inverter connected to the output of the integrated circuit. Inmotor mode, the proposed integrated circuit acts as an inverterand it becomes a boost-type boost converter, while using themotor windings as the boost inductors to boost the converteroutput voltage. Therefore, the proposed integrated circuit cansignificantly reduce the volume and weight of the system.

0885-8993 2013 IEEE

LAI et al.: INTEGRATED INVERTER/CONVERTER CIRCUIT AND CONTROL TECHNIQUE OF MOTOR DRIVES 1359

Fig. 3. Proposed integrated inverter/converter for the multimotor drive systemof EV/HEV.

Fig. 4. Boost converter with and without interleaved control. (a) Single-phaseboost converter. (b) Interleaved boost converter.

The integrated circuit presented in this paper can act as an in-verter and a boost converter depending on the operation mode.For the integrated circuit, it not only can reduce the volumeand weight but also boost torque and dc-link voltage for mo-tor/converter modes, respectively. Moreover, a new control tech-nique for the proposed integrated circuit under boost convertermode is proposed to increase the efficiency.

For conventional circuit, shown in Fig. 4(a) and (b), a single-phase boost converter [8] has been widely used for boost controldue to its simplicity. However, for higher power applications,an interleaved boost converter [9][13] can reduce the currentripple and components stress and thereby reducing the lossesand thermal stress.

Based upon the interleaved control idea, a boost-control tech-nique using motor windings as boost inductors for the proposedintegrated circuit will be proposed. Under light load, the in-tegrated circuit acts as a single-phase boost converter for notinvoking additional switching and conduction losses, and func-tions as the two-phase interleaved boost converter under heavyload to significantly reduce the current ripple and thereby re-

Fig. 5. Integrated circuit for dual mode of motor drives and boost converter.

TABLE ISPECIFICATIONS OF COMPONENTS

Fig. 6. Single-phase boost mode. (a) Charge path for inductor. (b) Dischargepath for inductor.

ducing the losses and thermal stress. Therefore, the proposedcontrol technique for the proposed integrated circuit under boostconverter mode can increase the efficiency.

II. PROPOSED INTEGRATED CIRCUITAND CONTROL TECHNIQUE

A. Proposed Integrated Inverter/Converter CircuitFig. 5 shows the integrated circuit for dual-mode control. In

Fig. 5, Cin and Cout can stabilize the voltage when input andoutput voltages are disturbed by source and load, respectively.Diode (D) is used for preventing output voltage impact on theinput side. When the integrated circuit is operated in inverter


Fig. 7. Proposed interleaved boost mode. (a) Phase B : Charge; Phase C :Discharge. (b) Phase B : Discharge; Phase C : Charge.

(motor) mode, relay will be turned ON and six power devices(IGBTs in Fig. 5) are controlled by pulse width modulation(PWM) control signals. Details of the component specificationsare shown in Table I.

When the proposed integrated circuit is operated in the con-verter mode, relay is turned OFF. And a single-phase or inter-leaved control method will be applied to control of the powerdevices depending upon the load conditions.

Figs. 6 and 7 show the single-phase and two-phase interleavedboost converters. In Fig. 6, the single-phase boost converteruses power switch V , stator winding A, and winding B toboost the output voltage. In Fig. 7, two-phase interleaved boostconverter uses power switches V and W , stator winding A,winding B, and winding C to boost the output voltage andreduce the current ripple.

B. Modeling and Controller Design Under Boost ModeThis section will introduce the model of boost converter and

derive the transfer function of the voltage controller. Fig. 8shows the nonideal equivalent circuit of the boost converter, itconsiders nonideal condition of components: inductor windingresistance RL , collector-emitter saturation voltage VCE , diodeforward voltage drop VD , and equivalent series resistance ofcapacitor Resr .

Analysis of the boost converter by using the state-space av-eraging method [14], small-signal ac equivalent circuit can bederived, as shown in Fig. 9.

By Fig. 9, the transfer function of the voltage controller canbe derived as shown in (1), at the bottom of the next page.

Fig. 8. Equivalent circuit of the boost converter.

Fig. 9. Small-signal equivalent circuit.

TABLE IICONTROLLER DESIGN PARAMETERS

Substituting the parameters shown in Table II into (1) gives

Gvd(s) =6.737 105s2 + 0.06827s + 24982.004 105s2 + 0.00409s + 3.242 . (2)

Fig. 10 shows the block diagram of voltage loop, using aproportional-integral (PI) controller for the compensator.

In this paper, the switching frequency is 20 kHz and voltageloop bandwidth will be less than 2 kHz. And the phase marginshould be more than 45 to enhance the noise immunity. For thedesigned controller shown in (3), the Bode plot of the closed-loop loop gain as shown in Fig. 11, the bandwidth is 7.73 Hzand the phase margin is 91.8

C(s) =0.0248387s + 13.073

s. (3)


Fig. 10 Block diagram of voltage loop.

Fig. 11. Bode plots, voltage control, B.W. = 7.73 Hz and P.M. = 91.8.

C. Proposed Control Technique of the IntegratedInverter/Converter Circuit

Fig. 12 shows the measured efficiency of the proposed in-tegrated circuit and switching point of different voltage ratiosas it acts as a boost converter. As shown in Fig. 12(a), the ef-ficiency for interleaved control is increased as load goes morethan 2.4 kW as compared to that for single-phase control. There-fore, the boost converter is controlled by the proposed hybridcontrol method shown in Fig. 13. As shown in Fig. 13, as loadis more than the switching point of power ratio for the givenvoltage ratio shown in Fig. 12(b), the converter is controlledby interleaved mode to significantly reduce the current rippleand thereby reducing the losses. In contrast, as load is less thanthe switching point of power ratio for the given voltage ratioshown in Fig. 12 (b), the converter is controlled by the single-phase control method without invoking additional conductionand switching losses as compared to that for two-phase inter-leaved control. The transition point is determined by the loadcondition and implemented in the interrupt service routine (ISR)as shown in Fig. 13 for the flow chart of the proposed controlfor the proposed integrated circuit under boost converter mode.

Fig. 12. Measured efficiency of the proposed circuit, boost converter mode.(a) Measured efficiency of proposed circuit of voltage ratio = 3. (b) Switchingpoints of different voltage ratios.

III. EXPERIMENTAL SYSTEM AND RESULTSFig. 14 shows the block diagram of the integrated circuit

and controller. As shown in Fig. 14, phase currents and out-put voltage are sensed and fed back to the DSP (digital signalprocessing), TMS320F2808 [15]. The experimental system con-sists of a PMSM as shown in Fig. 15, the proposed integratedcircuit which acts as inverter/boost converter and DSP controlboard to give PWM control signals of inverter/converter basedupon the feedback signals and reference. The specifications ofthe integrated circuit and motor are shown in Table III.

Fig. 16(a) and (b) show the experimental results of single-phase and two-phase interleaved boost operations. The test con-ditions include: input voltage = 96 V, output voltage = 288 V,and output power = 2400 and 2430 W. As shown in Fig. 16, theoutput voltage can be controlled to agree with its reference.

Fig. 17 shows the measured current waveforms with single-phase control and interleaved control. The test conditions in-clude: input voltage = 96 V, output voltage = 288 V, and outputpower = 2400 and 2430 W. Obviously, the current ripple for

Gvd(s) =Vo(s)

d(s)=

s2 L C(R + Resr) + s[L + C RL (R + Resr) + (1D)2C R Resr ] + [(1D)2 R + RL ]s2 C R Resr L IL + s{C R Resr [(Vd + Vo VCE)(1D)RLIL ]R L IL}

+R [(Vd + Vo VCE)(1D)RLIL ](1)


Fig. 13. Flow chart of the proposed control for the proposed integrated circuitunder boost converter mode.

Fig. 14. Block diagram of the integrated circuit and controller.

two-phase control shown in Fig. 17 (b) is significantly reducedas compared to its counterpart with single-phase control shownin Fig. 17(a).

Fig. 18 shows the experimental waveforms for the transitionbetween single-phase control and two-phase interleaved control.The test conditions include: input voltage = 96 V, output voltage= 288 V, and output power = 2400 and 2430 W. As shown inFig. 18, during the transition period, the output voltage is kept

Fig. 15. Photo of the experimental motor.

Fig. 16. Experimental results, Ch1: IA , Ch2: IB , Ch3: IC , Ch4: Vout .(a) Single-phase boost, 2400 W. (b) Two-phase interleaved boost,2430 W.


TABLE IIISPECIFICATIONS OF EXPERIMENTAL INVERTER/CONVERTER AND MOTOR

Fig. 17. Measured current with and without interleaved control, Ch1: IA ,Ch2: IB , Ch3: IC , Ch4: Vout . (a). Single-phase boost, 2400 W. (b) Two-phaseinterleaved boost, 2430 W.

constant and the transition period is only 150 ms which confirmsfast dynamic response during mode transition.

Fig. 19 shows the temperature of power devices in order toconfirm the reduction of switching losses contributed by the

Fig. 18. Experimental waveforms for the transition between single-phase con-trol and two-phase interleaved control, Ch1: IA , Ch2: IB , Ch3: IC , Ch4: Vout .(a) From single-phase to two-phase interleaved modes. (b) From two-phaseinterleaved to single-phase modes.

two-phase interleaved control method. When the proposed inte-grated circuit operates in single-phase mode, the inductor cur-rent flows through the power device V and its temperature willgo up to 87.9 C as shown in Fig. 19(a). In contrast, when theproposed integrated circuit operates in two-phase interleavedmode, the inductor current flows through the power devicesV and W and their temperature will be 62 C as shown inFig. 19 (b). This comparison result confirms the merit of thecontrol method for the integrated circuit under the boost-modeoperation.

Similar results for other test conditions can be derived and willnot be included in the paper due to length limitation. Table IVshows the measured results for various power ratios and voltageratios. As shown in Table IV, under full-load condition, themaximum efficiency is more than 95% and efficiency can bemaintained at more than 91.7% for voltage ratios varies from1.25 to 3, despite of different voltage ratios. These results fullyconfirm the effectiveness of the proposed integrated circuit andcontrol technique.


TABLE IVMEASURED EFFICIENCY VERSUS POWER AND VOLTAGE RATIOS

Fig. 19. Measured temperature of power devices. (a) Single-phase control,2400 W. (b) Two-phase interleaved control, 2430 W.

IV. CONCLUSIONThe contributions of this paper include:1) proposal of a new integrated inverter/converter circuit of

motor drives with dual-mode control for EV/HEV appli-cations to significantly reduce the volume and weight;

2) proposal of a new control method for the integrated in-verter/converter circuit operating in boost converter modeto increase the efficiency;

3) verification of the proposed integrated inverter/convertercircuit;

4) verification of the proposed control method.Experimental results show that the voltage boost ratio can go

up to 3. Under full-load condition, the maximum efficiency ismore than 95% and efficiency can be maintained at more than91.7% for voltage ratios varies from 1.25 to 3. These results fully

confirm the claimed merits of the proposed integrated circuit andcontrol method.

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Yen-Shin Lai (M96SM01) received the M.S. de-gree from the National Taiwan University of Scienceand Technology, Taipei, Taiwan, and the Ph.D. degreefrom the University of Bristol, Bristol, U.K., both inelectronic engineering.

In 1987, he joined the Electrical Engineering De-partment, National Taipei University of Technology,Taipei, as a Lecturer. He has been a full Professorsince 1999 and served as the Chairperson during20032006. He was a Distinguished Professor dur-ing 20062012. He is currently a Chair Professor.

His research interests include control of motor drives, power converter, andinverter.

Dr. Lai received several National and International Awards, including theJohn Hopkinson Premium for the session 19951996 from the Institute of Elec-trical Engineers, the Technical Committee Prize Paper Award from the IEEEIAS Industrial Drives Committee for 2002, the Outstanding Paper Award, Inter-national Conference on Renewable Energy Research and Applications, 2012.He serves as the Chair of the Technical Committee for Paper Review, theIEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, the IEEE Industrial DrivesCommittee (IDC), the Vice Chair of the IDC, the IEEE Industry ApplicationSociety, and an Associate Editor of the IEEE TRANSACTIONS ON INDUSTRIALELECTRONICS and the IEEE JOURNAL OF EMERGING AND SELECTED TOPICS INPOWER ELECTRONICS. He is an AdCom Member of the Industrial ElectronicsSociety and a Board Member of the Taiwan Power Electronics Association,Taiwan.

Wei-Ting Lee received the B.S. degree in electricalengineering from the Feng Chia University, Taichung,Taiwan, in 2011. He is currently working towardthe M.S. degree in electrical engineering from theNational Taipei University of Technology, Taipei,Taiwan.

His research interests include digital control ofmotor drives and switching power converters.

Yong-Kai Lin received the B.S., M.S., and Ph.D.degrees in electrical engineering from the NationalTaipei University of Technology, Taipei, Taiwan.

He is currently an Engineer in the Mechanicaland Systems Research Laboratories, Industrial Tech-nology Research Institute, Hsinchu, Taiwan. His re-search interests include field-programmable gate ar-ray design and inverter control.

Jian-Feng Tsai was born in Kaohsiung, Taiwan,in 1976. He received the B.S. and M.S. degrees inpower mechanical engineering from National Ts-ing Hua University, Hsinchu, Taiwan, in 1999 and2001, respectively, and the Ph.D. degree in electricaland control engineering from Chiao Tung University,Hsinchu, China.

From 2008 to 2009, he was a Senior Electrical En-gineer with Delta Electronics, Inc., Taipei, Taiwan,in Display Power BU. Since 2010, he has been a Re-searcher in Industrial Technology Research Institute,

Hsinchu. His research interests include control theories and power electronics.

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Integrated Inverter/Converter Circuit and Control Technique of Motor Drives With Dual-Mode Control for EV/HEV Applications