JP2010068617A - Controller of switched reluctance electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the overall efficiency of an electric motor and an inverter, by reducing the switching loss of a drive circuit of a switched reluctance motor. <P>SOLUTION: A controller of a switched reluctance motor includes a plurality of drive circuits which are connected to each winding and start excitation of a plurality of windings at the same timing for each plurality of conduction phases. The phase of hysteresis current waveform of at least one winding from among the windings (UL1-UL4) of the same conduction phase is different from the phase of hysteresis current waveform of other winding of the same conduction phase; the amplitude of hysteresis current is equal to or larger than the amplitude, where the current frequency is equal to the drivable upper limit frequency of the switching element; and the amplitude of hysteresis current is maximized and switching loss is reduced by setting the amplitude, in a range where the current peak upper limit value (it) is equal to the drivable upper limit current of the switching element, or the current peak lower limit value becomes 0. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a controller for a switched reluctance motor having a rotor having a plurality of salient poles and a stator having a winding wound around each of the salient poles opposed to the salient poles of the rotor. .

  There is an increasing demand for miniaturization of power electronics components for electric vehicles. For this reason, not only miniaturization of individual parts but also a miniaturization structure in which a motor and an inverter, which are conventionally housed in different cases at different locations, are being studied.

  Furthermore, as an evolution of such an integrated structure, a motor / inverter integrated structure in which each winding is individually driven by an inverter arranged in the immediate vicinity of each winding of the motor has been put into practical use.

  In order to realize such integration and downsizing, it is important to reduce the loss of the motor and the inverter so that the heat generation density does not increase.

  Regarding motor loss, in the case of a motor that operates by controlling the switching element of the inverter to convert the DC voltage into a pseudo sine wave voltage, harmonic magnetic flux due to switching is generated in the magnetic body of the motor, and harmonic iron loss occurs. Therefore, it is necessary to reduce this.

As a technique for reducing harmonic iron loss, there is a technique described in Patent Document 1, for example. In this technology, two windings are wound for each stator salient pole of the motor, and separate inverter switching elements are connected to the respective windings, and the timing of switching for applying voltage to both windings is shifted. Thus, the harmonic component of the combined magnetic flux generated by the two winding currents is reduced, and the harmonic iron loss can be reduced.
JP-A-6-197593

  However, although the above-described conventional technology can reduce the harmonic iron loss, simply shifting the timing of applying the voltage to each winding does not reduce the switching loss, and the overall efficiency of the motor and the inverter is reduced. There was a problem that improvement could not be expected.

  In order to solve the above problems, the present invention provides a switched reluctance motor control device comprising a plurality of drive circuits connected to each of the stator windings, and at least one of the windings of the same energized phase. The phase of the hysteresis current waveform of one winding is different from the phase of the hysteresis current waveform of other windings in the same energized phase, and the amplitude of the hysteresis current is the amplitude that makes the current frequency equal to the drivable upper limit frequency of the switching element It is above, and it is set as the range below the amplitude from which the current peak upper limit becomes equal to the drivable upper limit current of the switching element, or below the amplitude at which the current peak lower limit becomes zero.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that the switching loss of a switched reluctance motor drive circuit can be reduced and the total efficiency of a motor and an inverter can be improved.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. Each embodiment described below is an embodiment applied to a switched reluctance motor having a three-phase inner rotor structure. However, the number of phases of the motor is not limited to three phases, and other phases such as two phases, four phases, and five phases, and the structure of the motor is not limited to the inner rotor structure, but also to the outer rotor structure. It is clear that it can be applied.

  FIG. 1 is a schematic cross-sectional view showing an example of a switched reluctance motor to which the present invention is applied. In FIG. 1, a switched reluctance motor 1 includes a stator 2 (stator) and a rotor 5 (rotor) that is rotatably supported inside the stator 2.

  Twelve stator salient poles 3 are provided every 30 ° on the inner peripheral portion of the stator 2, and a winding 4 is wound around each stator salient pole 3. Each winding 4 is divided into three energized phases such as a U-phase winding (UL1 to UL4), a V-phase winding (VL1 to VL4), and a W-phase winding (WL1 to WL4).

  Eight rotor salient poles 6 are provided on the outer peripheral portion of the rotor 5 every 45 °, and 12 stator salient poles 3 and eight rotor salient poles 6 on the circumference of 360 °. Are facing each other. The rotation angle of the rotor 5 is a rotor angle 0 when the stator salient pole 3 around which the winding UL1 is wound and a specific one of the rotor salient poles 6 face each other and have the smallest magnetic resistance.

  FIG. 2 is a circuit diagram showing a configuration of an inverter device for driving the switched reluctance motor 1. In FIG. 2, a smoothing capacitor C1 and an inverter device are connected in parallel with the DC power supply Vdc.

  The inverter device is composed of 12 sets of half-bridge circuits each having two switching elements and two diodes having the same circuit configuration. For example, the half-bridge circuit that energizes the winding UL1 includes an upper switching element USW1, a lower switching element USW2, and diodes UD1 and UD2. The twelve windings UL1 to WL4 of the switched reluctance motor 1 are respectively connected to the half bridge circuit, and each winding can be individually driven by each half bridge circuit.

  Next, a method for energizing each winding of the switched reluctance motor 1 will be described with reference to FIG. There are soft chopping and hard chopping as a method of causing a current of a desired magnitude to flow from the DC power source to the motor winding by chopping.

  FIG. 4A is a diagram showing a current path of soft chopping in the half-bridge circuit, and FIG. 4B is a diagram showing waveforms of winding voltage and winding current in soft chopping. FIG. 4C is a diagram showing a current path of hard chopping in the half-bridge circuit, and FIG. 4D is a diagram showing waveforms of winding voltage and winding current in hard chopping.

  FIGS. 4A and 4C are diagrams in which only the circuit connected to the winding UL1 is extracted from the 12 sets of half-bridge circuits. 4A and 4C, the half-bridge circuit includes an upper switching element USW1, a lower switching element USW2, and diodes UD1 and UD2.

  4B and 4D, when the rotor angle θ reaches the energization start angle θon_UL1 of the winding UL1, energization is started, and the winding current is held between the predetermined upper limit value it and the predetermined lower limit value ib. The switching elements USW1 and USW2 are turned on / off as described above. When the rotor angle θ reaches the energization end angle θoff_UL1 of the winding UL1, the energization is terminated.

  As shown in FIGS. 4A and 4B, soft chopping turns off either the switching element USW1 or the switching element USW2 after the winding current reaches the upper limit value it, and the diodes UD2, UD1 This is a chopping method in which the winding current is recirculated through one of them and when both the USW1 and USW2 switching elements are turned on again when the lower limit value ib is reached.

  As shown in FIGS. 4C and 4D, the hard chopping turns off the switching elements of both USW1 and USW2 after the winding current reaches the upper limit value it, and supplies the current through both the diodes UD1 and UD2. This is a chopping method for regeneration to the power supply side.

  In the conventional switched reluctance motor, the windings of the same phase, for example, the U-phase windings UL1 to UL4 have the same current waveform. Therefore, the switching elements USW1, USW3, USW5, USW7, USW2, USW4, USW6, USW8 Switch at the same timing. Alternatively, four U-phase windings UL1 to UL4 are connected in parallel, and the current of the U-phase winding is controlled only by the same bridge circuit (two switching elements USW1, USW2 and two diodes UD1, UD2). . In such a method, since all in-phase windings are chopped at the same timing, a large ripple current flows through the smoothing capacitor C1.

  On the other hand, in this embodiment, even if the windings have the same phase as shown in FIG. 3, for example, by changing the timing of chopping between the pair of UL1 and UL3 and the pair of UL2 and UL4, The ripple phase is shifted, and the ripple current amplitude to the smoothing capacitor C1 can be reduced.

  As an example of a method of shifting the chopping timing, in addition to the upper limit value it and the lower limit value ib, a command value of an intermediate value ia satisfying ib <ia <it is provided, and this command value is applied only to the winding currents of UL2 and UL4. There are ways to apply.

  The action of the command value of the intermediate value ia is to start energization again when the current decreases to the intermediate value ia after first reaching the upper limit value it after starting energization from the energization start angle θon of the rotor. It is. In this way, it is possible to shift the phases of the ripple currents of the UL1 and UL3 and the ripple currents of the UL2 and UL4.

  Moreover, by adjusting the intermediate value ia and setting the phase difference of the current waveform to 180 degrees, the combined value of the harmonic currents of the windings is reduced, so that the current ripple between the drive circuit and the DC power supply is reduced, and the DC power supply When the smoothing capacitor C1 provided between the drive circuits can be downsized.

  In addition, if the upper limit value it is set to a value that is equal to the driveable upper limit current of the switching elements USL1 to USW4 and the lower limit value ib is set to 0, the amplitude of the hysteresis current is maximized, so the chopping frequency decreases. The switching loss of the drive circuit can be reduced.

  In addition, when hard chopping is selected for all the drive circuits, more current is supplied to the diode having a smaller on-resistance than the switching element as compared to the current path in the drive circuit for one electrical angle cycle when soft chopping is used. Therefore, the on-loss can be reduced.

  In addition, by switching between soft chopping and hard chopping for each electrical angle of the rotor, soft chopping with a relatively low chopping frequency is periodically performed, and an increase in temperature of the switching element can be suppressed.

  In addition, the number of windings driven by hard chopping and the number of windings driven by soft chopping are set to be not equal, and the number of windings driven by soft chopping is increased to increase the temperature of the switching element. Can be suppressed.

  In addition, the ratio of the number of windings driven by hard chopping and the number of windings driven by soft chopping is switched by the effective value of the winding current, and at the time of low current, the number of windings of soft chopping and hard chopping is made equal, When the current is large, the total efficiency can be improved without reducing the torque by increasing the number of hard chopping windings than the number of soft chopping windings.

  Also, hysteresis current chopping ON / OFF switching timing of one winding of multiple windings of the same phase (excitation starts at the same timing) is used as a reference, and hysteresis current chopping ON / OFF of other windings The / off timing can be a timing obtained by inverting the timing of the reference winding.

  For example, in the U-phase, there are four windings UL1 to UL4, but any one of them, for example, on / off switching timing of hysteresis current chopping of the winding UL1 is used as a reference. The on / off timing of hysteresis current chopping of the other windings UL2 to UL4 is set to a timing obtained by inverting the timing of the winding UL1.

  By setting the timing as described above, the other switching elements (USW3, USW4, USW5, USW6, USW7, USW8) give the inverted signal to the control circuit of the switching elements (USW1, USW2) serving as the timing reference. Therefore, the cost and size of the control circuit can be reduced.

  According to the present embodiment described above, the phase of at least one of the plurality of windings having the same phase is different from the phase of the hysteresis current waveform of the other windings, and the amplitude of the hysteresis current is The amplitude is greater than or equal to the current frequency equal to the drivable upper limit frequency of the switching element, and the current peak upper limit value is equal to or smaller than the amplitude equal to the drivable upper limit current of the switching element or the current peak lower limit value is equal to or smaller than 0. As a result, the amplitude of the hysteresis current can be maximized, the chopping frequency can be lowered, and the switching loss of the drive circuit can be reduced.

  Further, according to the present embodiment, among the plurality of windings having the same phase, the phase difference between at least one hysteresis current waveform and the hysteresis current waveform of the other windings is 180 degrees. Since the composite value of the wave current is reduced, the current ripple of the current supplied from the DC power source to the drive circuit is reduced, and the smoothing capacitor can be downsized.

  Further, according to the present embodiment, since the chopping method for controlling the hysteresis comparator current selects hard chopping in all the drive circuits, the path of the current in the drive circuit for one electrical angle cycle when soft chopping is used. In comparison, the diode having a smaller on-resistance than the switching element is energized more, so that the on-loss can be reduced.

  Further, according to the present embodiment, since soft chopping and hard chopping are switched every electrical angle period of the rotor of the switched reluctance motor, the soft chopping with a relatively low chopping frequency is periodically executed, and the switching element There is an effect that an increase in temperature can be suppressed.

  In addition, according to the present embodiment, the number of windings driven by hard chopping and the number of windings driven by soft chopping are different. Therefore, by increasing the number of windings driven by soft chopping, the temperature of the switching element can be increased. There is an effect that the rise can be suppressed.

  Further, according to this embodiment, the ratio of the number of windings driven by hard chopping and the number of windings driven by soft chopping is switched by the effective value of the winding current, so that soft chopping and hard chopping are performed at low currents. By equalizing the number of windings and increasing the number of windings for hard chopping at large currents, there is an effect that overall efficiency can be improved without reducing torque.

  Furthermore, according to the present embodiment, on / off timing of hysteresis current chopping of one winding among the windings of the same energized phase, on / off timing of hysteresis current chopping of another winding Since the on / off of the reference timing is the inverted timing, the other switching elements only need to give the inverted signal to the control circuit of the switching element that is the reference of the timing. There is an effect that the cost can be reduced and the size can be reduced.

  Next, a second embodiment of the switched reluctance motor control apparatus according to the present invention will be described with reference to FIG. In this embodiment, a switched reluctance motor and its drive circuit are housed in a motor case.

  FIG. 5 is a schematic cross-sectional view showing a cross section of the switched reluctance motor 1 of the present embodiment. In FIG. 5, the switched reluctance motor 1 has the same shape as FIG. 1, but is accommodated in the motor case 10. In the motor case 10, twelve drive circuits 12 a, 12 b,..., 12 l each made up of a half bridge circuit are arranged on the outer periphery of the stator 2. Further, cooling water passages 11 are provided at the four corners of the motor case 10 as cooling structures, respectively. Each of the drive circuits 12a to 12l is connected to a winding wound around the nearest stator salient pole 3, and constitutes a circuit as shown in FIG. As a control method for each of the drive circuits 12a to 12l, the control method described in the first embodiment can be used as it is.

  In the case of such a structure, the drive circuits 12a to 12l have different distances to the cooling water channel 11, and therefore the tendency of the temperature rise of each drive circuit is different even when the same current is applied to all the windings. . That is, the shorter the distance to the cooling water channel 11, the smaller the temperature rise of the drive circuit, and the longer the distance to the cooling water channel 11, the larger the temperature rise of the drive circuit.

  Therefore, in this embodiment, the drive circuits 12b, 12c, 12e, 12f, 12h, 12i, 12k, and 12l installed at positions where the distance from the cooling water channel 11 is shorter than the predetermined length L are driven by hard chopping. Then, the drive circuits 12a, 12d, 12g, and 12j installed at positions where the distance from the cooling water channel 11 is equal to or longer than the predetermined length L are driven by soft chopping. In this way, by using hard chopping as the chopping method of the drive circuit installed at a position where the distance from the cooling water channel 11 is shorter than the predetermined length L, hard chopping having a higher chopping frequency than soft chopping is used. However, since the switching element is disposed at a site with high cooling performance, an increase in temperature of the switching element can be suppressed.

  According to the present embodiment described above, since the distance from the cooling structure installed on the outer periphery of the switched reluctance motor is driven by hard chopping only the drive circuit installed at a position shorter than a predetermined length, In addition to suppressing the temperature rise of the switching element, there is an effect that the heat generation density can be sufficiently reduced to enable a motor / inverter integrated structure.

  Next, a third embodiment of the switched reluctance motor control apparatus according to the present invention will be described with reference to FIG. In the third embodiment, the switched reluctance motor is set so that the total loss Pt = Pc + Pe + Pi including the copper loss Pc, the iron loss Pe, and the inverter loss Pi is minimized, in other words, the overall efficiency is maximized. A system for controlling the control device will be described.

  FIG. 6 is a system configuration diagram showing a configuration of a motor drive system provided with a switched reluctance motor control device of the present embodiment. 6, the motor drive system includes a current command value generation unit 101, an inverter drive signal generation unit 102, an inverter 103, a current sensor 104 that detects each phase current of the switched reluctance motor 1, and a switched A reluctance motor 1, a rotor angle sensor 106 that detects the rotor angle of the switched reluctance motor 1, and a DC power source 107 that supplies power to the inverter 103.

  The switched reluctance motor 1 is the same motor as the switched reluctance motor 1 shown in FIG.

  Based on the torque command value T *, the three-phase winding current values iu, iv, iw, the rotor angle θ, and the inverter loss Pi, the current command value generation unit 101 generates the energization start angle command value θon *, the energization end angle command. The value θoff *, the current upper limit command value it *, the current lower limit command value ib *, and the current center command value ia * are output.

  The inverter drive signal generation unit 102 includes three-phase winding current values iu, iv, iw, rotor angle θ, energization start angle command value θon *, energization end angle command value θoff *, current upper limit command value it *, and current lower limit command. Based on the value ib * and the current center command value ia *, the drive signal of each switching element of the inverter 103 and the inverter loss Pi are output.

  The current command value generation unit 101 calculates an estimated value of the motor loss (copper loss Pc, iron loss Pe) based on the three-phase winding current values iu, iv, iw and the rotor angle θ. This estimated value is calculated using a theoretical formula or a loss map stored in advance. Further, the energization start angle command value θon *, the energization end angle command value θoff *, the current upper limit command so that the total loss Pt (= Pc + Pe + Pi) combined with the inverter loss Pi calculated by the inverter drive signal generation unit 102 is minimized. The value it *, the current lower limit command value ib *, and the current center command value ia * are determined.

  These command values are set so that the control method as shown in the first embodiment can be performed. The relationship between the total loss and the command value is related using a map or the like obtained in advance through experiments.

  Further, the inverter loss Pi in the inverter drive signal generator 2 is also calculated using a theoretical formula, a map obtained experimentally in advance, or the like.

  According to the embodiment described above, the torque command value, the rotational speed of the rotor of the switched reluctance motor, the winding current, and the winding voltage are input, and the copper loss and iron loss are calculated from each input value. Since the switching loss is estimated and the amplitude of the hysteresis current is determined so that the sum of the respective losses is minimized, there is an effect that the operation with the highest overall efficiency can be performed without deteriorating the torque and the torque ripple.

It is sectional drawing explaining the example of the switched reluctance motor to which the control apparatus which concerns on this invention is applied. FIG. 3 is a circuit diagram illustrating an example of a switched reluctance motor driving inverter in the control device according to the first embodiment. 3 is a waveform diagram showing a winding current waveform in Example 1. FIG. (A) Current path explanatory diagram of soft chopping, (b) Waveform diagram showing waveform example of soft chopping, (c) Current path explanatory diagram of hard chopping, (d) Waveform diagram showing an example of waveform of hard chopping. 6 is a cross-sectional view of a switched reluctance motor of Example 2. FIG. FIG. 9 is a system configuration diagram illustrating a system configuration of Embodiment 3.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Switched reluctance motor, 2 ... Stator, 3 ... Stator salient pole, 4 ... Winding, 5 ... Rotor, 6 ... Rotor salient pole, 10 ... Motor case, 11 ... Cooling water channel (cooling structure) ), 12a to 12l... Drive circuit.

Claims (9)

In a control device for a switched reluctance motor having a rotor having a plurality of salient poles and a stator having a winding wound around each of the plurality of salient poles facing the salient poles of the rotor,
A plurality of drive circuits connected to each of the windings, and starting a plurality of windings for each of a plurality of energized phases at the same timing;
The phase of the hysteresis current waveform of at least one of the windings of the same energized phase is different from the phase of the hysteresis current waveform of other windings of the same energized phase,
The amplitude of the hysteresis current is equal to or greater than the amplitude at which the current frequency equal to the drivable upper limit frequency of the switching element, and the current peak upper limit value is equal to or smaller than the amplitude at which the drivable upper limit current of the switching element is equal, or the current peak lower limit value is 0. Switched reluctance motor control device, characterized in that the amplitude is within a range of   2. The phase difference between the hysteresis current waveform of at least one winding among the windings of the same energized phase and the hysteresis current waveform of other windings of the same energized phase is 180 degrees. Switched reluctance motor control device described in 1.   3. The switched reluctance motor control device according to claim 1, wherein the chopping method of the drive circuit selects hard chopping in all the drive circuits.   The switched chopping method of the drive circuit switches between soft chopping and hard chopping for each electrical angle of the rotor of the switched reluctance motor. Control device for reluctance motor.   3. The switched reluctance motor according to claim 1, wherein the number of windings driven by hard chopping differs from the number of windings driven by soft chopping in the chopping method of the drive circuit. Control device.   6. The switched reluctance motor control according to claim 5, wherein a ratio between the number of windings driven by hard chopping and the number of windings driven by soft chopping is switched by an effective value of winding current. apparatus.   A drive circuit for each winding and a cooling structure are provided on the outer periphery of the switched reluctance motor, and the drive circuit whose distance between the drive circuit and the cooling structure is shorter than a predetermined length is driven by hard chopping to have a predetermined length. 3. The switched reluctance motor control apparatus according to claim 1, wherein the drive circuit is driven by soft chopping.   Among the windings of the same energized phase, the hysteresis current chopping on / off switching timing of one winding is used as a reference, and the hysteresis current chopping on / off timing of the other winding is the reference timing on / off timing. The switched reluctance motor control device according to claim 1, wherein the timing is a reverse timing of / off.   Input torque command value, rotor rotation speed, winding current and winding voltage, and estimate copper loss, iron loss and switching loss from each input value so that the sum of each loss is minimized 9. The switched reluctance motor control device according to claim 1, wherein the amplitude of the hysteresis current is determined.

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