Drive control apparatus for electric synchronous machine having field winding

Abstract: A drive control apparatus for an electric synchronous machine (1000) is composed of armature current control means (100) and transient operation detection means (500). When the synchronous machine (1000) is intended to increase power in a transient operation, the current control means (100) supplies the armature winding (1110) with compensation current to cancel counter-electromotive force formed when field current is supplied to the field winding (1230) through a mutual inductance of the field winding (1230) and the armature winding (1110).

Description: The present invention relates to a drive control apparatus of an electric synchronous machine having a field winding. An electric synchronous machine is composed of a three-phase armature winding and a field winding. The armature winding has three phase-windings which are supplied respectively with driving phase-current iu, iv and iw. Voltage Vf is applied across the field winding to supply field current if, thereby generating field magnetic flux. The field current may be controlled in a vector control process using d-q rectangular coordinate axes with the magnetic field component set on one of the axes. DE 3149402 discloses a controlling method that is mainly based on fundamental theoretical considerations of vector control method for a synchronous machine in the field weakening range. The controlling method provides for a machine that is able to react on rapid changes of the main magnetic flux h of a synchronous machine that is operated in connection with a grid. A synchronous electric machine disclosed in JP-A-9-74607 is mounted in a parallel hybrid vehicle together with an engine and a infinite variable transmission. The synchronous machine is not used when the vehicle is driven at a constant speed but is used only when the vehicle is in a transient operation such as is accelerated or decelerated. Preferably, the field current should be supplied only when the vehicle is accelerated or decelerated to improve the power efficiency of the hybrid vehicle. However, in the conventional drive control apparatus can not increase the field current immediately when driving power or battery charging energy of the synchronous machine is needed during the transient operation. If field voltage Vf is applied to the field winding, counter-electromotive force ef is generated as expressed in the following expression. [E1] ef = Lf (dif/dt), where Lf is an inductance of the field winding. The counter electromotive force ef impedes increase in the field current if and, in turn, increase in magnetic flux f. The invention is made in view of the above problems, and a main object of the invention is to provide an improved drive control apparatus which can improve rise-up of the field magnetic flux. In order to attain the above object, a drive control apparatus for an electric synchronous machine has detection means for detecting transient operation of the synchronous machine and current control means for supplying the armature winding with an amount of a current-component to cancel the counter-electromotive force generated in the field winding when the transient operation is detected. In other words, when the transient operation is detected, a target amount of an armature current component is provided to generate an electromotive force in the field winding to cancel the counter-electromotive force due to the self inductance of the field winding. Accordingly, the rise-up time of the field magnetic flux is improved and torque response is improved. The principle of the vector control according to the invention is described with reference to Fig. 7. In a graph of d-q rectangular axes, the magnetic field of field winding F is put on d-axis, and component id of the armature current of armature winding S is put on d-axis. A counter electromotive force ef is generated in the field winding as expressed in the following expression [E2]. [E2] ef = Lf • (dif/dt) - Mfd • (did/dt) Here, Lf is an inductance of the field winding, and Mfd is a mutual inductance between the field winding and the armature winding. Because the electromotive force Mfd•(d id /dt) acts to cancel the counter-electromotive force ef , the rise up speed of the field magnetic flux can be increased. Practically, in the drive control apparatus according to the invention, the current control means receives a torque command signal and a signal of the armature current sensor to calculate a target amount of magnetic flux, a basic amount of the armature current forming magnetic flux through the mutual inductance in the same direction as the field magnetic flux, and calculates compensation amount from a difference between the target magnetic flux and actual magnetic flux and adding the compensation amount to the basic amount of the armature current to provide a target amount of the armature current. Thus, the rise-up speed of the field magnet flux can be increased. The compensation amount can be calculated from a difference between a target field current and an actual field current. Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings: Fig. 1 is a diagram showing a structure of a drive control apparatus of an electric vehicle according to a preferred embodiment; Fig. 2 is a circuit diagram of an inverter circuit of the drive control apparatus according to the preferred embodiment; Fig. 3 is a longitudinally cross-sectional view of a motor mounted in an electric vehicle to be controlled by the drive control apparatus according to the embodiment; Fig. 4A is a cross-sectional view of the motor shown in Fig. 3 cut along line 4A-4A, and Fig. 4B is a cross-sectional view of the motor shown in Fig. 3 cut along line 4B-4B; Fig. 5 is a flow diagram of a part of a main program for a controller of the drive control apparatus according to the embodiment; Fig. 6 is a flow diagram of another part of the main program; Fig. 7 illustrates a principle of the invention; and Fig. 8 is a graph showing changes in magnetic flux with time. A drive control apparatus according to a preferred embodiment of the invention is described with reference to the appended drawings. In Fig. 1, the control apparatus is connected to synchronous motor 1000 which has three-phase armature winding 1110 and a field winding 1230. Motor 100 is mounted as a driving source in an electric vehicle. The control apparatus is composed of controller 100, inverter 200, battery unit 300 and magnetic field circuit 400. Controller 100 has a microcomputer, which receives a torque command signal, which is provided by torque command circuit 500 when an accelerator or a brake pedal is operated. Controller 100 controls motor 1000 in response to the torque command signal according to programs stored in a ROM. Controller 100 has a signal process section which detects the position of rotor 1200 according to a signal from rotor position sensor 1930. Inverter 200 is connected to controller 100, battery unit 300 and three input terminals of armature winding 1110. As shown in Fig. 2, inverter 200 has main input terminals 201, 202 connected to plus and minus terminals of battery unit 300, output terminals 203, 204, 205 connected respectively to U, V, W-phase windings of motor 1000, and input terminals 206, 207, 208, 209, 210, 211 connected to gate drive circuits (not shown) of controller 100. Inverter also has IGBT modules 212, 213, 214, current sensors 215, 216 and output terminals 217, 218 thereof. Each of IGBT modules 212, 213, 214 has two sets of an IGBT element (insulation gate type bi-polar transistors) and a flywheel diode, which are well-known. IGBT module 212 has terminal C1 connected to main input terminal 201, terminal E2 connected to main terminal 202, and terminals E1 and C2 jointly connected to output terminal 203, thereby forming a drive circuit for the U-phase winding of motor 1000. IGBT modules 213, 214 have also substantially the same components as IGBT module 212 forming drive circuits for the V-phase and W-phase windings. Current sensors 215, 216 are fixed to lead wires respectively connected to terminals 203, 205, and connected to controller 100 through terminals 217, 218. Each of current sensors 215, 216 is composed of a Hall element and is a clamp-and-non-contact type sensor. current sensors 215, 216 respectively detect output current of terminal 203, 205 and provide voltage signals. That is, current sensor 215 detects current iu of U-phase winding, and current sensor 216 detects current iw of W-phase winding. Magnetic field circuit 400 is connected to controller 100 and to field winding 1230 to control field current if supplied thereto. Inverter 200 and magnetic field circuit 400 are controlled by controller 100. As shown in Figs. 3, 4A and 4B, motor 1000 is composed of front frame 1910, end frame 1911, stator 1100 housed in frames 1910, 1911, a pair of bearings 1920, 1921, rotor 1200 respectively and rotatably supported by frames 1910, 1911 via the pair of bearings 1920, 1921, and rotor position sensor 1930. Rotor 1200 rotates at an air gap radially inner side of stator 1100. Rotor position sensor 1930 is composed of a known set of resolver rotor 1931 and resolver stator 1932 which is connected to controller 100. Controller 100 calculates rotor position  according to the signal from rotor position sensor 1930. Stator 1100 is composed of three-phase winding 1110 and stator core 1120 which is a lamination of a plurality of electric steel sheets. Stator core 1120 has a plurality of slots 1121, teeth 1122 and core back portion 1123 to accommodate three-phase armature winding 1110. Rotor 1200 is composed of rotor yoke 1210 which is a cylindrical lamination of a plurality of electric steel sheets, a pair of wheel-like rotor yokes 1220 which is a lamination of a plurality of electric steel sheet disposed opposite ends of rotor yoke 1210, and field winding 1230 disposed inside rotor yoke 1210. Cylindrical rotor yokes 1210, the pair of wheel-like rotor yokes 1220 and field winding 1230 form magnetic circuit section 1250. A pair of nonmagnetic plates 1260 is disposed on the opposite ends of magnetic circuit section 1250. In magnetic circuit section 1250, cylindrical iron core 1231 is press-fitted to shaft 1240 at a serrated portion thereof and resinous bobbin 1232 is fixed on the outer periphery of iron core 1231. Field winding 1230 is wound on bobbin 1232 in one way direction. A spline 1241 is formed on a left portion of shaft 1240 in Fig. 3. Shaft 1240 is the output shaft of motor 1000 to be connected to vehicle wheels (not shown). Field winding 1230 is supplied with field current by magnetic field circuit 400 through brush holders 1310, brushes 1320, slip rings 1330 and lead wires 1350. Lead wires 1350 are integrated with shaft 1240 by resinous insulating mold 1340. As shown in Fig. 4A, rotor yoke 1210 has twelve magnet holes 1211 on a circumference at equal intervals. Twelve permanent magnets are inserted in magnetic holes 1211 respectively. Rotor yoke 1210 also has twelve round holes 1212 formed between magnet holes 1211. As shown in Fig. 4B, rotor yoke 1220 has annular portion 1221, hub portion 1222 and six spokes 1223 connecting annular portion 1221 and hub portion 1222. In other words, spokes 1223 are spaced apart from one another at 720/12 (12 is the number of poles) or 60 degree in angle. Annular portion 1221 has twelve magnet holes 1224, as in rotor yoke 1210, on a circumference at equal intervals and round holes 1225 formed at circumferentially central portions between magnet holes 1224 adjacent to each other. Magnet holes 1211 of rotor yoke 1210 are the same in shape and size as magnet holes 1224 of rotor yoke 1220, and round holes 1212 are also the same in shape and size as round holes 1225. Accordingly, the magnet circuit section has 24 through holes extending from one axial end thereof to the other. In Fig. 3, a pair of right and left rotor yokes 1220 is assembled so that spokes 1223 of one can not circumferentially overlap with spokes 1223 of the other. Permanent magnets 1280 are inserted respectively into magnet holes 1211, 1224 in the direction perpendicular to the figure so that one circumferential side of one of permanent magnets has the same polarity as the other circumferential side of another permanent magnet adjacent thereto. Soft iron pins 1281 are also press-fitted to respective round holes 1212, 1225 to join rotor yokes 1210, 1220 together. Permanent magnets 1280 are magnetized in the circumferential direction to provide N and S poles alternately on the outer periphery of rotor 1200. The magnetic flux bypasses from the N pole of permanent magnets 1280 to the S pole thereof through N-pole-side soft iron pin 1281, N-pole-side spoke 1223, iron core 1231, S-pole-side spoke 1223, and S-pole-side soft iron pin 1281. Thus, bypassing circuits of the magnetic flux of the permanent magnets 1280 are provided. Accordingly, reluctance of the bypassing circuit can be controlled, and the effective magnetic flux that is supplied to the stator through the air gap can be controlled whether field winding 1230 is energized or not. Motor 1000 is controlled in a vector control mode according to torque command signal T* , rotor position , amounts of currents of the U-phase and W-phase windings detected by current sensors 215, 216. The main program is started when a vehicle ignition key switch is turned on. As shown in Figs. 5 and 6, controller 100 reads torque command signal T* and motor rotation speed Ωm at step S101. Torque command signal T* is generated when the accelerator pedal or brake pedal is operated. Motor rotation speed Ωm is calculated from the signal of rotor position sensor 1930. At step S102, controller 100 calculates basic amount id0 of the d-axis component of the armature current necessary to generate required output power of the motor 1000 at normal operation, target amount iq* of the q-axis component of the armature current, and target amount if* of the field current from current torque command signal T* and current motor rotation speed Ωm with reference to a map stored in a ROM. At step S103, controller 100 examine whether the vehicle is in the transient operation or not. If a level of torque command signal T* is a certain value higher than the last level thereof, it is determined that the vehicle is accelerated, decelerated, or in a transient operation. Otherwise, NO is provided at step S103, and controller 100 sets d-axis compensation amount idh to "0". That is, no compensation is made on the d-axis armature current id . Then step S108 follows. On the other hand, if the vehicle is in the transient operation, YES is provided at step S103, and controller 100 calculates compensation amount idh of the d-axis armature current in step S105-107. Target total amount 0 of the magnetic flux in the air gap is calculated at step S105. Target total amount 0 is calculated from the following expression [E3], which includes target field magnetic flux f0 supplied from field winding 1230, target armature magnetic flux d0 generated by the basic amount id0 of the d-axis component of the armature current, permanent magnet flux m supplied from permanent magnets 1280, self inductance Lf of field winding 1230, a mutual inductance between field winding 1230 and the d-axis portion of armature winding 1110, the number of turns Nf of field winding 1230, the number of turns Nd of the d-axis portion of armature winding 1110, target amount of the field current if* , and target amount of d-axis component of the armature current id*. [E3] 0 = f0 + d0 + m = (Lf/Nf) • if* + (Mfd/Nd) • id* + m Target total amount 0 of the magnetic flux can be selected from a map. At step S106, controller 100 calculates an amount of actual magnetic flux 1 in the air gap, which is given by the following expression [E4]. Here, f1 is an actual amount of the field magnetic flux supplied by field winding 1230,  d1 is an actual amount of the armature magnetic flux in the air gap generated by the d-axis component id1 of the armature current. [E4] 1 = f1 + d1 + m = (Lf/Nf) • if1 + (Mfd/Nd) • id1 + m In [E4], if1, id1 are respectively calculated from amounts of U-phase current iu and W-phase current iw. However, 1 can be detected by a sensor 1115 such as a search coil disposed between stator 1100 and rotor 1200. At step S107, controller 100 calculates d-axis compensation amount idh to reduce a difference between target magnetic flux 0 and actual magnetic flux 1. This can be carried out by a well-known feedback system, feed forward system or a combination thereof. At step S108, controller 100 adds the basic amount id0 of d-axis armature current and the compensation amount idh to obtain d-axis target amount id* . If the field current is sufficiently large, the target amount id* of the d-axis component of the armature current is controlled to induce a negative counter-electromotive force. On the other hand, if the field current is not large, the target amount id* is controlled to induce a positive counter-electromotive force. Thereafter, controller 100 reads amounts iu , iw of U-phase and W-phase armature current by current sensors 215, 216 at step S109 and reads rotor position  at step S110. At step S111, controller 100 calculates amounts id , iq of d-axis component and q-axis component of the armature current of the d-q rectangular coordinate axes from the detected amounts iu and iw . At step S112, controller 100 provides current differences εd and εq, where, εd = id* - id, εq = iq* - iq. At step 113, d-axis-component target voltage Vd* and q-axis-component target voltage Vq* are calculated from εd, εq and electric constants of motor 1000. At step S114, controller 100 calculates target phase-voltages Vu* , Vv* , and Vw* from d-axis-component target voltage Vd* and q-axis-component target voltage Vq* . Then, controller 100 calculates target field-voltage Vf* from target field current if* and the resistance of field winding 1230 at step S115. At step S116, target phase-voltages Vu* , Vv* , and Vw* and the target field voltage Vf* are modulated respectively to pulse width modulation (PWM) signals at frequency of 10 kHz, for example, and written into a PWM resistor to supply the calculated armature current and the field current. Thus, field winding 1230 is prevented from impeding rise-up of the field magnetic flux. In Fig. 8, a solid line represents the magnetic flux in the air gap according to the embodiment of the invention, and a dotted line represents the magnetic flux in the air gap of a conventional apparatus. It is clear that the magnetic flux of the embodiment of the invention rises up much faster than that of the conventional apparatus. Step S103 corresponds to the means for detecting transient operation, step S102-108 corresponds to the current control means, and steps S105-108 correspond to the compensation means. In the above embodiment, the basic amount is calculated and compensated to provide the d-axis target amount id* . However, the calculation for compensation can be replaced by a map based on changes in the magnetic flux and in the field current. The present invention is applicable other than the control system of an electric vehicle. For example, it can be applied to the control system of a hybrid vehicle or synchronous motors for use in devices other than vehicles. In the foregoing description of the present invention, the invention has been disclosed with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made to the specific embodiments of the present invention without departing from the broader scope of the invention as set forth in the appended claims. Accordingly, the description of the present invention in this document is to be regarded in an illustrative, rather than restrictive, sense.

Claims: A drive control apparatus for an electric synchronous machine (1000) having a field winding (1230) for supplying field magnetic flux (f0), a three-phase armature winding (1110), and an airgap disposed therebetween, said apparatus including current control means (100) for controlling armature current according to a torque command signal to provide necessary power, and detection means (500) for detecting operation of that synchronous machine (1000), characterized in that said detection means (500) detect transient operation of said synchronous machine (1000) said current control means (100) supply said armature winding (1110) with an amount of compensation armature current ( idh ) to form compensation magnetic flux (0-1) in said air gap through a mutual inductance between said field winding (1230) and said armature winding (1110) in the same direction as said field magnetic flux (0) for compensating the counter electromotive force (ef) which is induced in said field winding (1230) as a consequence of application of a field voltage (V f ) when said transient operation is detected. The drive control apparatus as claimed in claim 1, characterized in that said detection means (500) further includes an armature current sensor (215, 216) and a magnetic flux sensor, and said current control means (100) receives said torque command signal and a signal of said armature current sensor (215, 216) to calculate a target amount of magnetic flux (  0) in said air gap, a basic amount ( id0 ) of said armature current forming magnetic flux (  d0) in said air gap through said mutual inductance in the same direction as said field magnetic flux (f0), and calculates compensation amount ( idh ) from a difference between said target magnetic flux (0) and actual magnetic flux (1) and adding said compensation amount ( idh ) to said basic amount ( id0 ) of said armature current to provide a target amount ( id* ) of said armature current. The drive control apparatus as claimed in claim 1, characterized in that said detection means (500) comprises an armature current sensor (215, 216) and a field current sensor, and said current control means (100) receives said torque command signal and a signal of said armature current sensor (215, 216) to calculate a target amount (id*) of field current, a basic amount (id0) of said armature current forming magnetic flux ( d0) in said air gap through said mutual inductance in the same direction as said field magnetic flux (f0), and calculates compensation amount ( idh ) from a difference between said target amount ( if* ) of field current and an amount ( if ) of actual field current and adding said compensation amount ( idh ) to said basic amount ( id0 ) of said armature current to provide a target amount ( id* ) of said armature current. The drive control apparatus as claimed in claim 1, characterized in that said armature control means (100, 200) controls said compensation current component to induce a negative counter-electromotive force when said amount ( if ) of said actual field current is large enough to generate said necessary power and a positive counter-electromotive force when amount ( if ) of said field current is not large enough to generate said necessary power. A method of controlling an electric synchronous machine (1000) having a field winding (1230), an armature winding (1110) and an air gap between said field winding (1230) and said armature winding (1110) characterized to comprise the steps of: detecting a torque command signal (T*) and rotation speed (Ωm) of said machine (1000); calculating a basic amount ( id0 ) of armature current and a target amount ( if* ) of field current from said torque command signal (T*) and said rotation speed (Ωm); determining whether said synchronous machine (1000) is in transient operation or not according to said torque command signal (T*); calculating a basic amount (0) of total magnetic flux in said air gap necessary to generate necessary power according to said torque command signal 8T*) and said rotation speed (Ωm); detecting an actual amount (1) of total magnetic flux in said air gap; calculating compensation amount ( idh ) and target amount ( id* ) of armature current according to a difference between said basic amount of said total magnetic flus and said actual amount of said total magnetic flux for compensating the counter electromotive force (ef) induced in said field winding (1230) as a consequence of application of a field voltage (V f ); and supplying said target amount ( if* ) of field current to said field winding (1230) and said target armature current ( id* ) to said armature winding (1110) when said synchronous machine (1000) is determined to be in transient operation. The method as claimed in claim 5, characterized in that said basic amount ( id0 ) is an amount of a vector component of said armature current forming magnetic flux (d0) in the same direction as magnetic flux formed by said field winding (1230). The method as claimed in claim 6, characterized in that said synchronous machine (1000) is a three-phase electric rotary machine (1000), said armature winding (1110) is composed of three phase windings, and said three phase windings are supplied with respective amounts of phase current calculated from said target amount ( id* ) of armature current.

Inventors: EGAMI TSUNEYUKI, OBAYASHI KAZUYOSHI, TSUJI HIROYA, EGAMI, TSUNEYUKI, OBAYASHI, KAZUYOSHI, TSUJI, HIROYA
Applicants: DENSO CORP, DENSO CORPORATION
Application year: 1999
Main classification: H02P21
IPC codes: B60L11, H02K1, H02K19, B60L15, H02P23, H02P27, H02K11