Overview of Multi-Functional Converter Systems

Transcription

1 7 Research Report Oerie of Multi-Functional Conerter Systems Hieo Nakai, Kazunari Moriya, Hiroki Ohtani, Hiroo Fuma, Yukio Inaguma There is no oubt that hybri electric ehicles an fuel cell hybri electric ehicles contribute greatly to presering the enironment. Both of these types of ehicles use multiple electrical poer sources an the poer flos beteen these sources are generally controlle using DC/DC conerters. Therefore the DC/DC conerter is an extremely important component of both an HEV an FCHV. This paper proies an oerie of the Multi-Functional Conerter System (MFCS) stuies conucte by our laboratory. An MFCS consists of motors, inerters an aitional iring but no DC/DC conerters. The MFCS can control the poer flo beteen seeral AC or DC electrical poer sources hile, at the same Abstract time, controlling the motor torque. There are basically to types of MFCSs, the main ifference being in the location of the electrical poer sources in the circuits. One group has an electrical poer source beteen the neutral point of the motor an the DC bus line of the inerter. The secon group has one electrical poer source beteen the to neutral points of the motors. This paper escribes the basic circuit concepts an introuces their characteristic equations, the controller esign concepts, an the ifferences beteen the circuits of the to groups. Also escribe are seeral experiments that proe the aliity of the propose metho. Keyors Motor, Inerter, DC/DC conerter, Neutral point, Zero-phase current, Control R&D Reie of Toyota CRDL Vol. 39 No. 3

2 8 1. Introuction There is no oubt that hybri electric ehicles (HEV) can contribute greatly to presering the enironment. A problem ith these ehicles, hoeer, is that the olume of the HEV poertrain is greater than that of a conentional internal combustion engine (ICE) ehicle poertrain. An HEV 1) also features electrical rie equipment, hich consists of a battery, a traction motor ith an inerter an a controller, as ell as an ICE. In the poer electronics fiel, it is ell knon that the olume of a motor can be reuce if the DC oltage on the inerter DC bus line can be increase. Therefore, proie there is a conenser to supply a DC oltage to the inerter, the use of a DC/DC conerter beteen the battery an conenser offers the possibility of reucing the olume. ) Seeral methos 3-1) of connecting the ifferent electrical poer sources ithout a DC/DC conerter hae been inestigate oer the last 15 years. Since the 199s, e hae been conucting similar stuies aime specifically at HEV applications ) The basic approaches that e hae taken in our stuies are as follos: (1) Changing the iring connections in the motor an inerter system to enable the use of zero-phase current. () Using the zero-phase current, hich is the unuse thir egree-of-freeom of a conentional motor an inerter system, to realize the full potential of a DC/DC conerter in a motor an inerter system. We call the system that is base on the aboe concepts a multi-functional conerter system (MFCS). In the laboratory, e hae repeately succeee in realizing this concept. It is not possible to explain each an eery one of those stuies in this paper. Therefore, this paper concentrates on oerieing our MFCS results. Fig. 1 Higher DC h. Multi-function conerter system concept An MFCS can be classifie into one of to types accoring to the location of the electrical poer source. One, calle the one neutral-point type, has an electrical poer source beteen the neutral-point of the motor an the DC bus line of the inerter. The secon, calle the to neutral-points type, has an electrical poer source beteen the to neutralpoints of the motors.. 1 MFCS using one neutral-point Basic circuit The typical, simple MFSC circuit shon in Fig. 1 consists of a conentional motor rie system an an extra DC poer source system. The rie system has an inerter, a motor an a higher DC oltage source (HDCVS) that supplies a DC oltage to the inerter bus line. The extra system has a loer DC oltage source (LDCVS) an an aitional ire that connects the neutral-point of the three-phase motor to the inerter DC negatie bus line. In this section, e explain the equations ith a non salient-pole type motor, a battery for the HDCVS an the LDCVS. The equations can easily be extene to coer the salient-pole type, a conenser for the HDCVS, an a battery for the LDCVS.. 1. Characteristic equation This section explains the oltage equation for the MFCS. The relationships beteen the phase oltages in a three-phase motor are escribe by Eq. (1). The phase oltages gien by Eq. () take the electric potential of the neutral-point into consieration. Inerter Conentional Motor Drie System i u Neutral Point i i Motor u Aitional ire Loer DC l Extra DC Poer System Example of the one neutral-points type MFSC circuit an poer sources. R&D Reie of Toyota CRDL Vol. 39 No. 3

3 9 u 1 1 / u 1 i R i i kuh l = kuh l kh l u lai 1 Ma 3 i i i sin( θ) Φsin( θ π /3) sin( θ π /3) =.. (1) () Where θ, M a, l a, R, Φ, I n are the electric rotor angle, the main flux element of the self-inuctance, the leakage flux element of the self-inuctance, the resistance of the coil, the amplitue of the magnetic flux, an an ientity matrix ith n-imensions, respectiely. Also, i u, i, i, u,,, h, l, q are efine in Fig. 1. The sitching conitions of the inerter legs are inicate by k u, k, an k. If the upper sitch of the inerter leg turns on, then k x = 1 (x = u,, ). If the loer sitch of the inerter leg turns on, then k x = (x = u,, ). Using the transformation matrix, the i u, i, an i currents can be transforme into the irect an quarature axes (q-axes) currents i, i q, an zerophase current i. In the same ay, sitching conitions k u, k, an k can be transforme into sitching conitions k, k q, an k. The oltage equation for the q-axes is escribe by Eq. (3). t u The oltage equation for the zero-phase current an conenser oltage is escribe by Eq. (4). The 3 inuctance L a = M a l a, an the angular elocity ω = θ/t. L a La t i k = h iq kq R ωla i (3) ωla R iq ωφ i = ( R/ la ) i ( 3/ la) l ( 1/ la) k h.... (4) t Controller esign The faculty of the motor epens on Eq. (3), hile the faculty of the DC/DC conerter epens on Eq. (4). This proes that it is possible to control the motor torque an each of the poer flos beteen the HDCVS an the LDCVS. An example control iagram is shon in Fig.. In this figure, i r an i qr represent the reference currents for the q-axes. The oltage etermines only the control input k using the measure signals, l, h an i. The current an the ecoupling s etermine only the control inputs k an k q using the measure signals, i an i q. The control signal for the PWM inerter is mae by aing k to k an k q (k u *, k *, k *). To analyze the inerter sitch conition in the steay state, e assumes that k x (x = u,, ) is a continuous ariable. Gien this assumption, k u is i r - i qr - current current k k q -q u,, k * u k * k * k oltage h l u PWM inerter oltage sensor oltage sensor Higher DC Loer DC motor position sensor ecoupling i i q i -q- u,, i i θ ω angle an angular elocity calculator Fig. The controller iagram of the one neutral-point type MFCS. R&D Reie of Toyota CRDL Vol. 39 No. 3

4 3 shon using k, k q, an k in Fig. 3. Figure 3 inicates that the mean alue of k u controls the DC oltage, hile the alternatie element controls the motor torque. Here, e consier the higher an loer DC oltages in Fig. 3. Gien the efinition of k u, it is clear that h correspons to 1 on the ertical axis. Also, l is equal to the alue of B, because the oltage at the neutral-point is l. Gien that the oltage of the neutral-point is l an that of the inerter DC bus line is h, it becomes clear that h = l is a goo conition for riing the motor.. MFCS using to neutral-points.. 1 Basic circuit An MFSC circuit ith to neutral-points is shon in Fig. 4. A system using this MFSC circuit consists of to conentional motor rie systems an an extra DC poer source. The rie system has to three-phase inerters, to three-phase motors, an an HDCVS that supplies a DC oltage to the inerter bus line. The extra system consists of an LDCVS an an aitional ire that connects the neutral-point of one three-phase motor to that of the other motor... Characteristic equation The metho of introucing the equations has alreay escribe for the one neutralpoint type an is ery similar in this case. Therefore, only the results are escribe here. The oltage equation for the q-axes currents of the to motors are escribe by Eq. (5). The oltage equation for the zero-phase current an conenser oltage is escribe by Eq. (6). The q-axes inuctance, the leakage inuctance, the resistance, an the angular elocity for the to motors are L x, L qx, l ax, R x, an ω x (x = 1, ), respectiely. q Higher DC h Fig. 4 k u 1.5 Fig. 3 L x Lqx t i i x qx k = k x qx q C Rx ω xlqx ix (5) ωxlx Rx iqx ω xφx (x = 1, ) 1st Conentional Motor Drie System Inerter i u1 Inerter A = Neutral Point i 1 1 i 1 Neutral Point i n Conentional Motor Drie System B A π i u i Motor Motor 1 u1 u Loer DC l Aitional ire Extra DC Poer System Example of the to neutral-points type MFSC circuit an poer sources. B = θ A k A cos( θ α )B The representation of the inerter sitching ariable k u using the control inputs (k, k q, k ). R&D Reie of Toyota CRDL Vol. 39 No. 3

5 31 t i = q ( R1 R)( / l 1 la) ( k 1 k ) { C( la1 la) } k k i 1 1 k..... (6).. 3 Controller esign The motor torque, hich is gien by Eq. (5), can be controlle inepenently of k 1 an k. The DC oltage, hose characteristic equation is gien by (6), epens on all the control inputs. Therefore, the controller is esigne as escribe belo, base on the fact that the time constant emane for the motor torque is generally faster than that of the conenser oltage. First, the motor torque controller for hich the inputs are k x, k qx (x = 1, ) is esigne. Then, the conenser oltage controller for hich the inputs are k x (x = 1, ) is esigne, assuming the signal 'k 1 i 1 k q1 i q1 k i k q i q ' to be a isturbance. 3. Results of experiments 3 h kq1iq1 / ( la1 la) k k q q Our apparatus consiste of a synchronous motor, hich incorporate to sets of three-phase starconnecte coils an to neutral-points, to threephase inerters, a battery as the LDCVS an a conenser as the HDCVS. This apparatus is a to neutral-points type MFCS. The effectieness of the conenser oltage control as examine ithout the q-axes currents. To sets of theoretical results an one set of measure results are gien in Fig. 5. One set of the theoretical alues correspons to the case in hich the inerter i l = 5 V i i q a / 1 ea time t is µs, hile the secon shos the case here t = 1 µs. The circles inicate the alues obtaine by experiment. The alues obtaine by experiment agree ell ith the theoretical results because the t alue for this apparatus is about 1 µs. This proes that the MFCS can realize the characteristics of a DC/DC conerter. Figure 6 shos the phase currents an zero-phase current uner controlling h. This figure shos that the phase currents flo like the currents of a conentional system an that the zero-phase currents flo at the same time as the alternating current elements. Therefore, these results confirm that the MFCS can achiee the characteristics of a DC/DC conerter hile simultaneously controlling the motor-inerter system. 4. Conclusion This paper has proie an oerie of our MFCS stuies. The MFCS consists of motors, inerters an aitional iring but no DC/DC conerter. The MFCS can realize the functions of a DC/DC conerter hile simultaneously controlling the motor. We hae escribe the basic circuit concepts an their characteristic equations an controller esign concepts. The aliity of the MFCS has been confirme by experiment. The aantage of the MFCS is that it can achiee the characteristics of a DC/DC conerter an proie motor control ithout the nee for DC/DC conerter circuits. To ate, hoeer, ery fe practical examples of the MFCS hae appeare. We beliee that the MFCS ill be iely applie in the future. h =3V, l =1V, 3 rpm i Theoretical alues (t = µs) i u1 i 1 h / l Theoretical alues (t =1 µs) Experimental alues phase currents (A) A A i u i Fig. 5 (mean alue of k 1 ) - (mean alue of k ) The characteristic of DC/DC conerter. Fig. 6 time (ms) 1 ms Phase currents an zero-phase current uner controlling the higher DC oltage h. R&D Reie of Toyota CRDL Vol. 39 No. 3

6 3 Acknolegments The authors oul like to acknolege the assistance, support an efforts of Mr. S. Sasaki an other staff members of the Toyota Motor Corporation. References 1) Sasaki, S., Takaoka, T., Matsui, H. an Kotani, T. : "Toyota's Nely Deelope Electric-Gasoline Engine Hybri Poertrain System'', Proc. of EVS, 14(1997), 1-8 ) Okamura, M., Satoh, E. an Sasaki, S. : "Deelopment of Hybri Electric Drie System Using a Boost Conerter'', Proc. of EVS, (3), 1-1 3) Hotta,Y., Nakamura, H. an Tanihata, K. : Unexamine Patent Pub. H (in Japanese) 4) Ishikaa, T., Sekimori, T., Hotta, Y. an Suzuki, A. : "Deelopment of a Traction Inerter ith Charge Function", Proc. of EVS, 14(1997), ) Rippel, W. E. an Cocconi, A. G. : Unite States Patent, No , (199) 6) Kinoshita, S., Itoh, J. an Fujita, K. : Unexamine Patent Pub., H (in Japanese) 7) Kusaka, Y. an Tsuji, K. : "Noel Poer Conersion System for Cost Reuction in Vehicles With 4 V/14 V Poer Supply'', SAE Tech. Pap. Ser., No (3) 8) Caricchi, F., Crescimbini, F. an Lipo, T. A. : "Conerter Topology ith Loa-Neutral Moulation for Trapezoial-EMF PM Motor Dries'', IEEE Trans. on Poer Electron., 9-(1994), ) Itoh, J. an Fujita, K. : "Noel Unity Poer Factor Circuits Using Zero-Vector Control for Single-Phase Input Systems'', IEEE Trans. on Poer Electron., 15-1(), ) Seung-Ki, S. an Sang-Joon, L. : "An Integral Battery Charger for Four-Wheel Drie Electric Vehicle'', IEEE Trans. on In. Appl., 31-5(1995), ) Moriya, K., Inaguma, Y., Ohtani, H., Sasaki, T., Ishikaa, S. an Komatsu, M. : Unexamine Patent Pub., (in Japanese) 1) Inaguma, Y., Moriya, K., Ohtani, H., Sasaki, S., Syamoto, S. an Komatsu, M. : Unexamine Patent Pub., (in Japanese) 13) Moriya, K., Inaguma, Y., Nakai, H., Ohtani, H., Sasaki, S., Syamoto, S. an Komatsu, M. : Unexamine Patent Pub., (in Japanese) 14) Moriya, K., Nakai, H., Inaguma,Y. an Sasaki, S. : "A DC/DC Conerter Using Motor Neutral Point an its Control Metho", Proc. of National Conentional Recor IEE Japan, (4), (in Japanese) (Report receie on Jun. 4, 4) Hieo Nakai Year of birth : 1963 Diision : HV Electric Drie System Research fiels : Control, estimation an moeling of electrical poer trains, motors, inerters, ehicle suspensions, engine mounts an acoustic noise Acaemic egree : Dr. Eng. Acaemic society : Jpn. Soc. Mech. Eng., Inst. Electr. Eng. Jpn., Soc. Instrum. Control Eng. Kazunari Moriya Year of birth : 1969 Diision : HV Electric Drie System Research fiels : Control of electric motors, poer electronics topologies Acaemic society : Inst. Electr. Eng. Jpn. Hiroki Ohtani Year of birth : 1971 Diision : HV Electric Drie System Research fiels : Motor rie system Hiroo Fuma Year of birth : 1956 Diision : HV Electric Drie System Research fiels : SiC Semiconuctor, Inerter an conerter for motor Acaemic society : Inst. Electr. Eng. Jpn., Jpn. Soc. Appl. Phys. Yukio Inaguma Year of birth : 1946 Diision : HV Electric Drie System Research fiels : Poer electronics Acaemic society : Soc. Automot. Eng. Jpn., Inst. Electr. Eng. Jpn., Soc. Instrum. Control Eng. R&D Reie of Toyota CRDL Vol. 39 No. 3