Control device

Abstract

To detect idling or slide of a wheel shaft of an induction machine.SOLUTION: A controller 1 comprises: a power converter 2 that amplifies a voltage command v and supplies power to a plurality of induction machines 101, 102, 103, and 104; a magnetic flux calculator 4 that calculates an induction machine magnetic flux φ based on the sum total current i and the voltage command v; a speed calculator 5 that calculates an induction machine speed ωm based on the induction machine magnetic flux φ and the sum total current i; a torque control unit 6 that generates the voltage command v based on the sum total current i, the induction machine speed ωm, a magnetic flux command φC, and a torque command τC; a magnetic flux square calculator 7 that calculates an induction machine magnetic flux square value φvol2 obtained by squaring the induction machine magnetic flux φ; and a magnetic flux reduction detection unit 8 that receives input of the induction machine magnetic flux square value φvol2 and a predetermined detection threshold dφX, and outputs a detection signal K indicating the presence or absence of idling or slide of a wheel shaft of at least part of the plurality of induction machines 101, 102, 103, and 104.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for performing torque control of a plurality of induction machines.

Background Art

[0002] As an example of a control device for controlling an induction machine that drives an electric vehicle (vehicle), a control device that obtains the rotational speed of the induction machine by calculation and performs torque control of the induction machine is disclosed in Patent Document 1. According to such a control device, the induction machine can be controlled according to a torque command without using a speed sensor.

[0003] FIG. 5 is a diagram showing a configuration example of a conventional control device 1A as described above. The control device 1A shown in FIG. 5 collectively controls the torques of a plurality of induction machines 101, 102, 103, 104. In the following, an example of controlling the torques of four induction machines 101, 102, 103, 104 will be used for explanation, but the present invention is not limited thereto, and the number of induction machines to be collectively controlled may be two, three, or five or more.

[0004] As shown in FIG. 5, the control device 1A includes a power converter 2, a current detector 3, a flux calculator 4, a speed calculator 5, and a torque control unit 6.

[0005] The power converter 2 amplifies the voltage command v output from the torque control unit 6 described later and supplies power to each of the plurality of induction machines 101, 102, 103, 104 that are loads.

[0006] The current detector 3 detects the total current i, which is the sum of the currents flowing through each phase of each of the induction machines 101, 102, 103, 104 connected to the power converter 2. The current detector 3 outputs the detection result of the total current to the flux calculator 4, the speed calculator 5, and the torque control unit 6.

[0007] Based on the total current i detected by the current detector 3 and the voltage command v, the magnetic flux calculator 4 calculates the induction machine magnetic flux φ according to the following formula (2).

[0008]

Number

[0009] In formula (1), R1 is the combined value of the primary resistances of the induction machines 101, 102, 103, 104, L2 is the combined value of the secondary self-inductances of the induction machines 101, 102, 103, 104, M is the combined value of the mutual inductances of the induction machines 101, 102, 103, 104, and Lek is the combined value of the leakage inductances of the induction machines 101, 102, 103, 104. The combined value of the leakage inductance Lek is given by the following formula (2).

[0010]

Number

[0011] In formula (2), L1 is the combined value of the primary self-inductances of the induction machines 101, 102, 103, 104.

[0012] The magnetic flux calculator 4 outputs the calculation result of the induction machine magnetic flux φ to the speed calculator 5.

[0013] Based on the induction machine magnetic flux φ calculated by the magnetic flux calculator 4 and the total current i detected by the current detector 3, the speed calculator 5 calculates the induction machine speed ωm according to the following formulas (3) to (5).

[0014]

Number

[0015] In formulas (3) to (5), R2 is the combined value of the secondary resistances of the induction machines 101, 102, 103, 104, and FA and FB are the components of the induction machine magnetic flux φ.

[0016] The induction machine speed ωm calculated by Equation (5) is the average value of the speeds of the induction machines 101, 102, 103, and 104, and is the value shown by the following Equation (6). ωm = (ωm1 + ωm2 + ωm3 + ωm4) / 4 Equation (6)

[0017] In Equation (6), ωm1 is the speed of the induction machine 101, ωm2 is the speed of the induction machine 102, ωm3 is the speed of the induction machine 103, and ωm4 is the speed of the induction machine 104.

[0018] The speed calculator 5 outputs the calculation result of the induction machine speed ωm to the torque control unit 6.

[0019] Based on the total current i detected by the current detector 2, the induction machine speed ωm calculated by the speed calculator 5, the torque command τC indicating the total torque of the induction machines 101, 102, 103, and 104, and the flux command φC indicating the flux of the induction machines 101, 102, 103, and 104, the torque control unit 6 generates a voltage command v for collectively controlling the torque of the induction machines 101, 102, 103, and 104. Specifically, the torque control unit 6 generates a voltage command v such that the flux and total torque of the induction machines 101, 102, 103, and 104 respectively match the flux command φC and the torque command τC. The torque control unit 6 outputs the generated voltage command v to the power converter 2 and the flux calculator 4.

[0020] According to the conventional control device 1A, with the above-described configuration, the total torque of the plurality of induction machines 101, 102, 103, and 104 can be made to follow the torque command τC.

[0021] In a vehicle, since bogie control and single-vehicle control are common, the collective control of the torques of a plurality of induction machines by the control device 1A as shown in FIG. 5 is frequently used.

Prior Art Documents

Patent Documents

[0022]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0023] In a vehicle, some of the wheel axles of the induction machines that are collectively controlled may slip, for example, the speed ωm3 of the induction machine 103 may become greater than the speeds ωm1 of the induction machine 101, ωm2 of the induction machine 102, and ωm4 of the induction machine 104. In this case, according to Equation (6), calculation errors in the induction machine speed ωm with respect to the speeds ωm1 of the induction machine 101, ωm2 of the induction machine 102, ωm3 of the induction machine 103, and ωm4 of the induction machine 104 will occur. When the slip of the induction machine 103 is large and the calculation error of the induction machine speed ωm becomes large, the induction machine 103 will enter a demagnetized state. If the slip of the induction machine 103 becomes even larger, not only the induction machine 103 but also the induction machines 101, 102, and 104 will enter a demagnetized state. Also, when the skid of the wheel axles of some of the induction machines becomes large, as in the case of slip, there is a possibility that the induction machines will enter a demagnetized state.

[0024] When the induction machines enter a demagnetized state, torque control becomes impossible, and in the worst case, overcurrent or overvoltage may lead to the destruction of the induction machines or the elements constituting the power converter 2.

[0025] Therefore, when collectively controlling the torques of a plurality of induction machines, a technique for detecting the occurrence of slip or skid of the wheel axles of the induction machines is required.

[0026] In view of the above problems, an object of the present invention is to provide a control device capable of detecting the occurrence of slip or skid of the wheel axles of induction machines when collectively controlling the torques of a plurality of induction machines.

Means for Solving the Problems

[0027] To solve the above problems, a control device according to the present invention is a control device for controlling the torque of a plurality of induction machines, comprising: a power converter that amplifies a voltage command and supplies power to each of the plurality of induction machines; a flux calculator that calculates an induction machine flux based on a sum current that is the sum of the currents flowing through each of the plurality of induction machines and the voltage command; a speed calculator that calculates an induction machine speed based on the induction machine flux and the sum current; a torque control unit that generates the voltage command for collectively controlling the torque of the plurality of induction machines based on the sum current, the induction machine speed, a flux command that indicates the fluxes of the plurality of induction machines, and a torque command that indicates the total torque of the plurality of induction machines; a flux square calculator that calculates a squared value of the induction machine flux by squaring the induction machine flux; and a flux reduction detector that inputs the squared value of the induction machine flux and a predetermined detection threshold value and outputs a detection signal indicating the presence or absence of idling or skidding of the wheel shafts of at least some of the plurality of induction machines. , the magnetic flux decrease detection unit includes a change amount calculator that calculates a magnetic flux change amount indicating a change amount of the square value of the induction machine magnetic flux, a divider that calculates a magnetic flux change rate obtained by dividing the magnetic flux change amount by the square value of the induction machine magnetic flux, and a comparator that outputs a detection signal indicating that wheel axle idling or skidding has occurred if the magnetic flux change rate is less than or equal to the detection threshold value, and outputs a detection signal indicating that wheel axle idling or skidding has not occurred if the magnetic flux change rate is greater than the detection threshold value. It has.

[0029] Further, in the control device according to the present invention, when a detection signal indicating that idling or skidding of the wheel shaft has occurred is output, the torque command is decreased, and after the decrease of the torque command, when a detection signal indicating that idling or skidding of the wheel shaft has not occurred is output, the torque command is returned to a predetermined value.

[0030] Further, in the control device according to the present invention, when a detection signal indicating that idling or skidding of the wheel shaft has occurred is output, the torque command is decreased, and after the decrease of the torque command, when the squared value of the induction machine flux becomes larger than a predetermined squared flux limit value, the torque command is returned to a predetermined value.

[0031] Further, in the control device according to the present invention, when a detection signal indicating that idling or skidding of the wheel shaft has occurred is output, the torque command is decreased, and after the decrease of the torque command, when the squared value of the induction machine flux becomes larger than a predetermined squared flux limit value, the torque command is returned to a predetermined value.

[0032] Also, in the control device according to the present invention, the change amount calculator multiplies the value obtained by differentiating the square value of the induction machine flux by the operation period dt and outputs the value as the flux change amount.

[0033] Also, in the control device according to the present invention, when the magnitude of the induction machine flux is denoted as φV, the flux command is denoted as φC, and a detection signal indicating that wheel axle idling or skidding has occurred is output, if the decrease amount of the induction machine flux magnitude φV during the operation period dt is denoted as ΔφX, the detection threshold value is -2 * ΔφX / φC.

[0034] Also, in the control device according to the present invention, the change amount calculator outputs, as the flux change amount, the difference between the square value of the induction machine flux and the first-order lag of the square value of the induction machine flux.

[0035] Also, in the control device according to the present invention, when the magnitude of the induction machine flux is denoted as φV, the time constant of the first-order lag is denoted as T, the flux command is denoted as φC, and a detection signal indicating that wheel axle idling or skidding has occurred is output, if the decrease amount of the induction machine flux magnitude φV during the time constant T is denoted as ΔφY, the detection threshold value is -2 * ΔφY / φC.

Advantages of the Invention

[0036] According to the control device of the present invention, when collectively controlling the torques of a plurality of induction machines, it is possible to detect the occurrence of idling or skidding of the wheel axles of the induction machines.

Brief Description of the Drawings

[0037]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0038] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[0039] FIG. 1 is a diagram showing a configuration example of a control device 1 according to an embodiment of the present invention. The control device 1 according to this embodiment collectively controls the torques of a plurality of induction machines 101, 102, 103, 104. In the following, an example of controlling the torques of four induction machines 101, 102, 103, 104 will be used for explanation, but the present invention is not limited to this, and the control device 1 may collectively control the torques of two, three, or five or more induction machines. In FIG. 1, the same components as those in FIG. 5 are denoted by the same reference numerals, and the description thereof is omitted.

[0040] As shown in FIG. 1, the control device 1 according to this embodiment includes a power converter 2, a current detector 3, a magnetic flux calculator 4, a speed calculator 5, a torque control unit 6, a magnetic flux squared calculator 7, and a magnetic flux decrease detector 8. The control device 1 shown in FIG. 1 is different from the control device 1A shown in FIG. 5 in that a magnetic flux squared calculator 7 and a magnetic flux decrease detector 8 are added.

[0041] The magnetic flux squared calculator 7 receives the calculation result of the induction machine magnetic flux φ by the magnetic flux calculator 4. The magnetic flux squared calculator 7 calculates an induction machine magnetic flux squared value φvol2 obtained by squaring the induction machine magnetic flux φ according to the following formula (7).

[0042]

Equation

[0043] The magnetic flux squared calculator 7 outputs the calculation result of the induction machine magnetic flux squared value φvol2 to the magnetic flux decrease detector 8.

[0044] The magnetic flux reduction detection unit 8 inputs the induced machine magnetic flux φvol2 calculated by the magnetic flux square calculator 7 and a predetermined detection threshold value dφX, and outputs a detection signal K. The detection signal K is a signal indicating the presence or absence of wheel axle idling or skidding in at least a part of the plurality of induced machines 101, 102, 103, 104 whose torque is controlled by the control device 1.

[0045] For example, among the plurality of induced machines 101, 102, 103, 104, it is assumed that the wheel axle of the induced machine 103 idles and the speed ωm3 of the induced machine 103 becomes larger than the speeds ωm1, ωm2, ωm4 of the induced machines 101, 102, 104. In this case, the speed calculation error is ωm > ωm1, ωm > ωm2, ωm > ωm4, ωm < ωm3. As a result, the actual slip of the induced machines 101, 102, 104 becomes larger and the actual slip of the induced machine 103 becomes smaller with respect to the slip command ωs expected from the torque command τC and the magnetic flux command φC.

[0046] In this state, when the torque control unit 6 performs torque control so that the sum Current i is constant, the total torque matches the torque command τC, but the magnetic flux magnitudes of the respective induced machines 101, 102, 103, 104 are different from the magnetic flux command φC. Specifically, the magnetic flux magnitudes of the induced machines 101, 102, 104 become smaller than the magnetic flux command φC. Also, the magnetic flux magnitude of the induced machine 103 becomes smaller than the magnetic flux command φC if the idling is large, depending on the degree of idling. As a result, the induced machine magnetic flux magnitude φV, which is the magnitude of the induced machine magnetic flux φ, becomes smaller than the magnetic flux command φC. The magnetic flux reduction detection unit 8 utilizes the fact that the above-described induced machine magnetic flux magnitude φV becomes smaller than the magnetic flux command φC to generate the detection signal K. Here, idling is taken as an example, but the same applies to the case of skidding.

[0047] Note that the magnetic flux reduction detection unit 8 calculates the induced machine magnetic flux magnitude φV by the following formula (8).

[0048]

Equation

[0049] FIG. 2 is a diagram showing a configuration example of the magnetic flux decrease detection unit 8.

[0050] As shown in FIG. 2, the magnetic flux decrease detection unit 8 includes a change amount calculator 81, a divider 82, and a comparator 83.

[0051] The change amount calculator 81 receives the induced machine magnetic flux squared value φvol2 calculated by the magnetic flux squared calculator 7. Based on the input induced machine magnetic flux squared value φvol2, the change amount calculator 81 calculates a magnetic flux change amount dφ2 indicating the change amount of the induced machine magnetic flux squared value φvol2 according to the following formula (9).

[0052]

Equation

[0053] In formula (9), d(φvol2) represents the change amount of the induced machine magnetic flux squared value φvol2, and d(φvol2) is taken as the magnetic flux change amount dφ2. Also, if d(φV) is taken as Δφ, formula (9) is represented by the following formula (10). In formula (10), Δφ is the change amount of the induced machine magnetic flux magnitude φV.

[0054]

Equation

[0055] The change amount calculator 81 outputs the calculation result of the magnetic flux change amount dφ2 to the divider 82.

[0056] The divider 82 receives the induced machine magnetic flux squared value φvol2 calculated by the magnetic flux squared calculator 7 and the magnetic flux change amount dφ2 calculated by the change amount calculator 81. The divider 82 calculates a magnetic flux change rate dφ according to the following formula (11).

[0057]

Equation

[0058] That is, the divider 82 calculates a magnetic flux change rate dφ obtained by dividing the magnetic flux change amount dφ2 by the square value φvol2 of the induction machine magnetic flux.

[0059] When Equation (11) is transformed, it is expressed by the following Equation (12).

[0060]

Number

[0061] Equation (12) represents the magnetic flux change rate dφ in terms of the magnitude φV of the induction machine magnetic flux and the change amount Δφ of the magnitude φV of the induction machine magnetic flux.

[0062] The divider 82 outputs the calculation result of the magnetic flux change rate dφ to the comparator 83.

[0063] The comparator 83 receives the magnetic flux change rate dφ calculated by the divider 82 and the detection threshold value dφX. If the magnetic flux change rate dφ is less than or equal to the detection threshold value dφX, the comparator 83 outputs a detection signal K indicating that wheel axle idling or skidding has occurred (turns the detection signal K ON). Also, if the magnetic flux change rate dφ is greater than or equal to the detection threshold value dφX, the comparator 83 outputs a detection signal K indicating that wheel axle idling or skidding has not occurred (turns the detection signal K OFF). Note that a negative value is set as the detection threshold value dφX.

[0064] In the field weakening operation in the voltage saturation region, although the magnitude φV of the induction machine magnetic flux changes, the change amount Δφ of the magnitude φV of the induction machine magnetic flux is 0 or a minute value (a minute negative value during acceleration and a minute positive value during deceleration). If the detection threshold value dφX is set in consideration of the change amount Δφ of the magnitude φV of the induction machine magnetic flux during the field weakening operation, the detection signal K remains OFF. The detection threshold value dφX may be determined based on a balance between the degree of idling or skidding to be detected and the change amount Δφ of the magnitude φV of the induction machine magnetic flux during the field weakening operation.

[0065] When wheel axle idling or skidding occurs in some of the plurality of induction machines 101, 102, 103, 104, the magnitude φV of the induction machine magnetic flux decreases. Therefore, the change amount Δφ of the induction machine magnetic flux magnitude φV becomes a negative value. Depending on the degree of idling or skidding, the magnitude of the change amount Δφ of the induction machine magnetic flux magnitude φV is different. The greater the degree of idling or skidding, the greater the magnitude of the change amount Δφ of the induction machine magnetic flux magnitude φV. By setting the detection threshold value dφX according to the degree of idling or skidding to be detected, the detection signal K becomes ON when the desired degree of idling or skidding is reached.

[0066] When performing an operation to reduce the magnetic flux command φC to turn off the induction machine, and if the induction machine magnetic flux φ decreases with a first-order lag of the secondary time constant L2 / R2, at the beginning of the reduction of the induction machine magnetic flux φ, the change amount Δφ of the induction machine magnetic flux magnitude φV once becomes negative, but immediately the change amount Δφ of the induction machine magnetic flux magnitude φV heads towards 0. By setting the detection threshold value dφX in consideration of the magnitude of the change amount Δφ of the induction machine magnetic flux magnitude φV at the beginning of the reduction of the induction machine magnetic flux φ, the detection signal K remains OFF. Furthermore, if a time element is inserted at the final stage (the stage after the comparator 83) of the magnetic flux reduction detection unit 8 shown in FIG. 2, the magnitude of the detection threshold value dφX can be reduced. The detection threshold value dφX may be set in consideration of the degree of idling or skidding to be detected and the change amount Δφ of the induction machine magnetic flux magnitude φV when performing an operation to reduce the magnetic flux command φC to turn off the induction machine.

[0067] As described with reference to FIGS. 1 and 2, in the control device 1 according to the present embodiment, when wheel axle idling or skidding occurs in some of the plurality of induction machines 101, 102, 103, 104, the detection signal K becomes ON, and when wheel axle idling or skidding does not occur in any of the induction machines 101, 102, 103, 104, the detection signal K becomes OFF. Also, by appropriately setting the detection threshold value dφX, it is possible to prevent false detection of wheel axle idling or skidding in some of the plurality of induction machines 101, 102, 103, 104 during field weakening operation at voltage saturation or when performing an operation to reduce the magnetic flux command φC to turn off the operation.

[0068] Regardless of whether it is applied to all or any of the induction machines 101, 102, 103, 104, wheel spin or skidding occurs when the wheel torque is too large relative to the road surface friction force. Therefore, it is necessary to reduce the wheel torque in order to control spin or skidding.

[0069] Therefore, in the control device 1 according to the present embodiment, when the detection signal K becomes ON, the torque command τC is decreased. Various methods such as step, jerk, and first-order lag can be considered as methods for reducing the torque command τC. When the road surface friction force increases, the degree of spin or skidding decreases, and the detection signal K becomes OFF. In the control device 1 according to the present embodiment, when the detection signal becomes OFF, the torque command τC is restored to a predetermined value (for example, a torque command value designed based on the acceleration / deceleration characteristics of the induction machine). Various methods such as step, jerk, and first-order lag can be considered as methods for restoring the torque command τC.

[0070] Thus, in the control device 1 according to the present embodiment, when a detection signal K indicating that wheel spin or skidding has occurred on the wheel axle is output (when the detection signal K becomes ON), the torque command τC is decreased. Also, in the control device 1 according to the present embodiment, after the decrease in the torque command τC, when a detection signal K indicating that wheel spin or skidding is not occurring on the wheel axle is output (when the detection signal K becomes OFF), the torque command τC is returned to a predetermined value. By decreasing the torque command τC when the detection signal K becomes ON, spin or skidding can be controlled. Further, after the decrease in the torque command τC, when the detection signal K becomes OFF, by returning the torque command τC to a predetermined value, it is possible to prevent the induction machines 101, 102, 103, 104 from becoming out of synchronization and to prevent the occurrence of overcurrent or overvoltage.

[0071] Also, in the control device 1 according to the present embodiment, when the road surface friction increases by reducing the torque command τC and the square value φvol2 of the induction machine magnetic flux becomes larger than a predetermined magnetic flux square limit value, the torque command τC may be restored to a predetermined value. Here, the magnetic flux square limit value is a value set according to, for example, the calculation accuracy of the speed calculator 5. By doing so, it is possible to prevent the induction machines 101, 102, 103, 104 from being out of synchronization and to prevent the occurrence of overcurrent or overvoltage. The magnetic flux square limit value may be determined by, for example, the calculation accuracy of the speed calculator 5.

[0072] FIG. 3 is a diagram showing a configuration example of the change amount calculator 81.

[0073] The change amount calculator 81 shown in FIG. 3 includes a differential calculator 811 and a multiplier 812.

[0074] The differential calculator 811 receives the square value φvol2 of the induction machine magnetic flux calculated by the magnetic flux square calculator 7. The differential calculator 811 performs the calculation shown in the above formula (9) and outputs the calculation result to the multiplier 812. That is, the differential calculator 811 differentiates the square value φvol2 of the induction machine magnetic flux and outputs it to the multiplier 812.

[0075] The multiplier 812 multiplies the output of the differential calculator 811 by the calculation period dt and outputs it as the magnetic flux change amount dφ2.

[0076] As described above, the change amount calculator 81 shown in FIG. 3 outputs, as the magnetic flux change amount dφ2, a value obtained by multiplying the value obtained by differentiating the square value φvol2 of the induction machine magnetic flux by the calculation period dt.

[0077] The magnetic flux change amount dφ2 obtained by the change amount calculator 81 shown in FIG. 3 represents the change amount of the square value φvol2 of the induction machine magnetic flux during the calculation period dt. When determining the degree of idling or skidding that turns on the detection signal K and setting the decrease amount ΔφX of the induction machine magnetic flux magnitude φV during the calculation period dt in that case, the detection threshold dφX can be calculated by the following formula (13) using the magnetic flux command φC.

[0078]

Number

[0079] That is, when the change amount calculator 81 has the configuration shown in FIG. 3, assuming that the magnitude of the induction machine flux is φV, the flux command is φC, and the detection signal K indicating that wheel axle idling or skidding has occurred is output, if the decrease amount during the calculation period dt of the induction machine flux magnitude φV is ΔφX (positive value), the detection threshold dφX is determined as -2*ΔφX / φC.

[0080] By determining the detection threshold dφX based on Equation (13), the detection signal K can be turned ON according to the degree of idling or skidding to be detected. In Equation (13), instead of the flux command φC, the magnitude φV of the induction machine flux when the detection signal K is OFF may be used. In this case, the detection threshold dφX when the detection signal K becomes ON is held, and thereafter, when the detection signal is OFF, the value of Equation (13) depends on the magnitude φV of the induction machine flux.

[0081] FIG. 4 is a diagram showing another configuration example of the change amount calculator 81.

[0082] The change amount calculator 81 shown in FIG. 4 includes a first-order lag calculator 813 and a subtractor 814.

[0083] The first-order lag calculator 813 receives the squared value φvol2 of the induction machine flux calculated by the flux squared calculator 7. The first-order lag calculator 813 applies a first-order lag with a time constant T to the squared value φvol2 of the induction machine flux and outputs it to the subtractor 814.

[0084] The subtractor 814 subtracts the output value of the first-order lag calculator 813 from the squared value φvol2 of the induction machine flux calculated by the flux squared calculator 7 and outputs it as the flux change amount dφ2.

[0085] In this way, the change amount calculator 81 shown in FIG. 4 outputs the difference between the squared value φvol2 of the induction machine flux and the first-order lag of the squared value φvol2 of the induction machine flux as the flux change amount dφ2.

[0086] The magnetic flux change amount dφ2 obtained by the change amount calculator 81 shown in FIG. 4 represents the change amount of the square value φvol2 of the induction machine magnetic flux during the time T. When determining the degree of no-load rotation or slip that turns on the detection signal K, and setting the decrease amount of the induction machine magnetic flux magnitude φV during the time T in that case as ΔφY (positive value), the detection threshold value dφX can be calculated by the following formula (14) using the magnetic flux command φC.

[0087]

Equation

[0088] That is, when the change amount calculator 81 has the configuration shown in FIG. 4, assuming the induction machine magnetic flux magnitude is φV, the time constant of the first-order lag is T, the magnetic flux command is φC, and when a detection signal K indicating that no-load rotation or slip has occurred on the wheel axle is output, setting the decrease amount of the induction machine magnetic flux magnitude φV during the time constant T as ΔφY, the detection threshold value dφX is determined as -2 * ΔφY / φC.

[0089] By determining the detection threshold value dφX based on formula (14), the detection signal K can be turned on at the degree of no-load rotation or slip to be detected. In formula (14), instead of the magnetic flux command φC, the induction machine magnetic flux magnitude φV when the detection signal K is OFF may be used. In this case, the detection threshold value dφX when the detection signal K becomes ON is held, and thereafter, when the detection signal is OFF, the value of formula (14) depends on the induction machine magnetic flux magnitude φV. Also, when the operation period dt < time constant T, if the operation period dt is the same in FIGS. 4 and 3, the change amount calculator 81 shown in FIG. 4 can reduce false detections compared to the change amount calculator 81 shown in FIG. 3.

[0090] The present invention is applicable not only when a speed calculation error occurs due to no-load rotation or slip of the wheel axle in some of the plurality of induction machines 101, 102, 103, 104 that are the objects of torque batch control, but also when a difference occurs in the shaft speeds of the plurality of induction machines 101, 102, 103, 104 that are the objects of torque batch control.

[0091] Although the above embodiments have been described as representative examples, it will be apparent to those skilled in the art that many changes and substitutions are possible within the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited by the above embodiments, and various modifications and changes are possible without departing from the scope of the claims.

Description of Reference Numerals

[0092] 1, 1A Control device 2 Power converter 3 Current detector 4 Flux calculator 5 Speed calculator 6 Torque control unit 7 Square of flux calculator 8 Flux decrease detector 81 Change amount calculator 82 Divider 83 Comparator 811 Differentiator 812 Multiplier 813 First-order lag calculator 814 Subtractor 101, 102, 103, 104 Induction machine

Claims

1. A control device for controlling the torque of a plurality of induction machines, comprising: a power converter that amplifies a voltage command and supplies power to each of the plurality of induction machines; a flux calculator that calculates an induction machine flux based on a total current that is the sum of the currents flowing through each of the plurality of induction machines and the voltage command; a speed calculator that calculates an induction machine speed based on the induction machine flux and the total current; a torque control unit that generates the voltage command for collectively controlling the torque of the plurality of induction machines based on the total current, the induction machine speed, a flux command that indicates the flux of the plurality of induction machines, and a torque command that indicates the total torque of the plurality of induction machines; a flux squared calculator that calculates a squared value of the induction machine flux by squaring the induction machine flux; a flux reduction detector that inputs the squared value of the induction machine flux and a predetermined detection threshold value, and outputs a detection signal indicating the presence or absence of idling or skidding of at least a part of the wheel shafts of the plurality of induction machines; The flux reduction detector includes: a change amount calculator that calculates a flux change amount indicating a change amount of the squared value of the induction machine flux; a divider that calculates a flux change rate by dividing the flux change amount by the squared value of the induction machine flux; a comparator that outputs a detection signal indicating that idling or skidding of the wheel shaft has occurred if the flux change rate is less than or equal to the detection threshold value, and outputs a detection signal indicating that idling or skidding of the wheel shaft has not occurred if the flux change rate is greater than the detection threshold value.

2. In the control device according to Claim 1, when a detection signal indicating that idling or skidding of the wheel shaft has occurred is output, the torque command is decreased, and when a detection signal indicating that idling or skidding of the wheel shaft has not occurred is output after the decrease of the torque command, the torque command is returned to a predetermined value.

3. In the control device according to Claim 1, when a detection signal indicating that idling or skidding of the wheel shaft has occurred is output, the torque command is decreased, and when the squared value of the induction machine flux becomes greater than a predetermined flux squared limit value after the decrease of the torque command, the torque command is returned to a predetermined value.

4. In the control device according to Claim 1, the change amount calculator outputs, as the flux change amount, a value obtained by multiplying a value obtained by differentiating the squared value of the induction machine flux by an operation period dt.

5. In the control device according to Claim 4, Let the magnitude of the induction machine flux, which is the magnitude of the induced machine flux, be φV, let the flux command be φC, and when a detection signal indicating that wheel axle idling or skidding has occurred is output, let the decrease amount of the induced machine flux magnitude φV during the calculation period dt be ΔφX. In this case, the detection threshold is -2 * ΔφX / φC, a control device.

6. In the control device according to claim 1, The change amount calculator outputs, as the magnetic flux change amount, the difference between the square value of the induction machine flux and the first-order lag of the square value of the induction machine flux, a control device.

7. In the control device according to claim 6, Let the magnitude of the induction machine flux, which is the magnitude of the induced machine flux, be φV, let the time constant of the first-order lag be T, let the flux command be φC, and when a detection signal indicating that wheel axle idling or skidding has occurred is output, if the decrease amount of the induced machine flux magnitude φV during the time constant T is ΔφY, then the detection threshold is -2 * ΔφY / φC, a control device.

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