Method and Device for Monitoring an Electric Network in a Rail Vehicle and Rail Vehicle

Abstract

The invention relates to a device and a method for monitoring an electric network in a rail vehicle. The electric network includes at least one power converter, at least one permanent magnet machine, and at least one first phase line for the electrical connection of the at least one power converter and the at least one permanent magnet machine. The first phase line is interrupted. A potential difference is determined between a machine-side part of the first phase line and a reference potential and a potential-difference-dependent variable, wherein a speed of the permanent magnet machine and, as a function of the speed, a speed-dependent reference variable are determined. A deviation of the potential-difference-dependent variable from the speed-dependent reference variable is determined, wherein a network fault is detected if the deviation is greater than a predetermined threshold value.

Claims

1.-12. (canceled)

13. A method for monitoring an electric network in a rail vehicle, wherein the electric network comprises at least one power converter, at least one permanent magnet machine, and at least one first phase line for the electrical connection of the at least one power converter and the at least one permanent magnet machine, wherein the first phase line is interrupted, wherein a potential difference between a machine-side part of the first phase line and a reference potential and a potential-difference-dependent variable are determined, wherein a speed of the permanent magnet machine and, as a function of the speed, a speed-dependent reference variable are determined, wherein a deviation of the potential-difference-dependent variable from the speed-dependent reference variable is determined, wherein a network fault is detected if the deviation is greater than a predetermined threshold value, wherein the electric network comprises three phase lines, wherein at least two of the three phase lines are interrupted, wherein a potential difference between a machine-side part of the phase line and a reference potential is determined for each phase line, wherein a speed of the permanent magnet machine and, as a function of the speed, a speed-dependent reference variable are determined for each phase line, wherein a potential-difference-dependent variable and a deviation of the potential-difference-dependent variable from the speed-dependent reference variable are determined for each phase line and a network fault is detected if at least one of the deviations is greater than a predetermined threshold value, and/or wherein a minimum potential difference of all potential differences and a variable dependent on this minimum potential difference are determined, wherein a deviation of this variable dependent on this minimum potential difference from the speed-dependent reference variable is determined and a network fault is detected if this deviation is greater than a predetermined threshold value, wherein a two-phase network fault or a three-phase network fault is determined as a function of the potential differences and/or the at least one deviation.

14. The method as claimed in claim 13, wherein upon detection of a network fault, a speed of the permanent magnet machine is reduced and/or a further interruption of the machine-side part of the phase line is carried out.

15. The method as claimed in claim 13, wherein an accuracy of the determination of the potential difference is checked in that at least one normal operating potential difference is determined in the case of an uninterrupted phase line, wherein a deviation of the normal operating potential difference from a normal operating reference value is determined, wherein a sufficient accuracy is detected if the deviation is less than or equal to a predetermined threshold value and/or in that a standstill of the permanent magnet machine is detected, wherein at least one standstill potential difference is detected in the case of an interrupted phase line, wherein a deviation of the standstill potential difference from a standstill reference value is determined, wherein a sufficient accuracy is detected if the deviation is less than or equal to a predetermined threshold value.

16. The method as claimed in claim 13, wherein the speed is assigned to one speed interval of multiple speed intervals, wherein an interval-dependent reference variable is assigned to one speed interval, wherein the speed-dependent reference variable is determined as the interval-dependent reference variable.

17. The method as claimed in claim 13, wherein the potential difference is assigned to one potential difference interval of multiple potential difference intervals, wherein an interval-dependent potential difference value is assigned to one potential difference interval, wherein the potential-difference-dependent variable is determined as a function of the interval-dependent potential difference value.

18. The method as claimed in claim 13, wherein a potential difference between a machine-side part of the phase line and a reference potential and a potential-difference-dependent variable is determined for each phase line, wherein a combined output signal is formed, wherein the combined output signal comprises a first bit sequence, which codes the potential-difference-dependent variable formed from the minimum potential difference, wherein the combined output signal comprises a further bit sequence, which codes an equality of all potential differences.

19. The method as claimed in claim 13, wherein the potential-difference-dependent variable is a maximum amplitude or an RMS value of the potential difference during a predetermined determination duration.

20. A device for monitoring an electric network in a rail vehicle, wherein the electric network comprises at least one power converter, at least one permanent magnet machine, and at least one first phase line for the electrical connection of the at least one power converter and the at least one permanent magnet machine, wherein the device comprises at least one evaluation unit, at least one determination unit, and at least one interruption unit, wherein the first phase line is interruptible by means of the interruption unit, wherein a potential difference between a machine-side part of the first phase line and a reference potential is determinable by means of the determination unit, wherein furthermore a potential-difference-dependent variable is determinable, wherein a speed of the permanent magnet machine and, as a function of the speed, a speed-dependent reference variable are determinable, wherein a deviation of the potential-difference-dependent variable from the speed-dependent reference variable is determinable by means of the evaluation unit, wherein a network fault is detectable if the deviation is greater than a predetermined threshold value, wherein the electric network comprises three phase lines, wherein at least two or all phase lines are interrupted, wherein a potential difference between a machine-side part of the phase line and a reference potential is determinable for each phase line, wherein a speed of the permanent magnet machine and, as a function of the speed, a speed-dependent reference variable are determinable for each phase line, wherein a potential-difference-dependent variable and a deviation of the potential-difference-dependent variable from the speed-dependent reference variable are determinable for each phase line and a network fault is detectable if at least one of the deviations is greater than a predetermined threshold value, and/or wherein a minimum potential difference of all potential differences and a variable dependent on this minimum potential difference are determinable, wherein a deviation of this variable dependent on this minimum potential difference from the speed-dependent reference variable is determinable and a network fault is detectable if this deviation is greater than a predetermined threshold value, wherein a two-phase network fault or a three-phase network fault is determinable as a function of the potential differences and/or the at least one deviation.

21. The device as claimed in claim 20, wherein the potential difference is determined close to the motor.

22. A rail vehicle comprising a device as claimed in claim 20.

23. A rail vehicle comprising a device as claimed in claim 21.

Description

[0065] The invention will be explained in greater detail on the basis of an exemplary embodiment. In the figures:

[0066] FIG. 1 shows a schematic circuit diagram of an electric network of a rail vehicle,

[0067] FIG. 2 shows a schematic block diagram of a device according to the invention, and

[0068] FIG. 3 shows a schematic illustration of speed intervals and voltage intervals.

[0069] Hereafter, identical reference signs identify elements having identical or similar technical features.

[0070] FIG. 1 shows an electric network 1 of a rail vehicle (not shown). The electric network 1 comprises a power converter C and a permanent magnet machine M, wherein inductors L of the permanent magnet machine M are shown by way of example. Furthermore, the electric network 1 comprises a link circuit capacitor C_k. The power converter C is connected on the input side to a link circuit capacitor C_k.

[0071] The power converter C is a three-phase power converter in this case. It comprises six electric switch elements S_C, to each of which a freewheel diode D is electrically connected in parallel. For the sake of comprehensibility, only one electric switch element S_C and one diode D of the power converter C are provided with a reference sign.

[0072] Furthermore, the electric network 1 comprises three phase lines P1, P2, P3. Furthermore, phase currents I_P1, I_P2, and I_P3, are shown, which illustrate a current flow through the corresponding phase line P1, P2, P3.

[0073] Furthermore, the electric network 1 comprises a first current sensor CS1 and a further current sensor CS3, wherein the first current sensor CS1 detects the first phase current I_P1 and the further current sensor CS3 detects the third phase current I_P3.

[0074] By means of the phase lines P1, P2, P3, the power converter C is connected on the output side to the permanent magnet machine M. The permanent magnet machine M is therefore a three-phase electric machine.

[0075] A first electric switch element S1_P1 and a second electric switch element S2_P1 are arranged in the first phase line P1. By opening and closing these two switch elements S1_P1, S2_P1, the electrical connection via the first phase line P1 between the power converter C and the permanent magnet machine M can be established or interrupted. In a closed state of the switch elements S1_P1, S2_P1, the electrical connection is established in this case. If at least one of the two switch elements S1_P1, S2_P1 is opened, the electrical connection is thus interrupted. In this case, the first switch element S1_P1 can designate a so-called motor switch. The second switch element S2_P1 can designate a further motor switch.

[0076] Accordingly, a first electric switch element S1_P2, S1_P3 and a second electric switch element S2_P2, S2_P3 are respectively also arranged in further phase lines P2, P3.

[0077] Furthermore, a first voltage sensor VS1 and a second voltage sensor VS2 are shown. The first voltage sensor VS1 detects a voltage U12, i.e., a potential difference, between the first phase line P1 and the second phase line P2. Accordingly, the second voltage sensor VS2 detects a voltage U23 between the second phase line P2 and the third phase line P3.

[0078] To monitor the electric network 1, at least one electric switch element, preferably both electric switch elements S1_P1, . . . , S2_P3, of each phase line P1, P2, P3 is/are opened. The voltages U12, U23 are then detected and a voltage U13 between the first phase line P1 and the third phase line P3 is calculated.

[0079] Furthermore, a speed d (see FIG. 2) of the permanent magnet machine M is determined.

[0080] Furthermore, a voltage-dependent variable is determined for each of the voltages U12, U23, U13, for example, a maximum absolute value during a predetermined time interval of 100 ms, which follows a determination start time, for example.

[0081] A speed-dependent reference variable is determined as a function of the speed d of the permanent magnet machine M. The reference variable corresponds in this case to the voltage-dependent variable. For example, the speed-dependent reference variable can be a minimum absolute value of an idle voltage of the permanent magnet machine M in the predetermined time interval of 100 ms.

[0082] As explained in greater detail in FIG. 2, a difference is then determined between the speed-dependent reference variable and the voltage-dependent variable and a network fault is detected if the difference is greater than a predetermined threshold value, in particular greater than zero.

[0083] FIG. 2 shows the electric network 1 from FIG. 1 and a determination unit BE and an evaluation unit AE. Reference is made in this case to the statements on FIG. 1 with respect to the design of the electric network 1.

[0084] The determination unit BE which can be designed as a microcontroller or parts thereof, for example, has a signal connection to the voltage sensors VS1, VS2. The voltage U12 between the first phase line P1 and the second phase line P2 and the voltage U23 between the second phase line P2 and the third phase line P3 form input signals for the determination unit BE. These are filtered by a filter unit F. Furthermore, it is shown that after the filtering, a difference calculation is performed to determine the voltage U13 between the first phase line P1 and the third phase line P3. In the units E, a maximum absolute value of an amplitude of the voltages U12, U23, U13 in an interval of 100 ms is determined to determine the voltage-dependent variable. In an A/D converter AD, a digitization of this voltage-dependent variable is performed. In this case, the digitalization is performed inversely proportional to a level of the voltage-dependent variables. In particular, a value of the voltage-dependent variable of zero is coded using the highest digital value. The digitization can be performed using a Gray code.

[0085] These digital values, which represent the voltage-dependent variables, form output signals of the determination unit BE and input signals of the evaluation unit AE, which has a data connection to the determination unit BE. A further input signal of the evaluation unit AE is a speed d of the permanent magnet machine M. Via a previously known relationship, which is shown by way of example in the evaluation block AB in FIG. 2, the evaluation unit AE determines a speed-dependent reference variable Vref (see FIG. 3).

[0086] Furthermore, it is determined whether the speed-dependent reference variable Vref is greater by more than a predetermined amount than each of the transmitted voltage-dependent variables. If the speed-dependent reference variable Vref is greater than at least one of the transmitted voltage-dependent variables, a fault signal FS is thus generated. It is furthermore shown in FIG. 2 that it is checked by a further evaluation block AB2 whether the permanent magnet machine M is not connected to the power converter C, for example, whether all switches S1_P1, . . . , S2_P3 are open. It can also be checked whether no feedback signal, which can also be referred to as a “life signal,” from a traction control unit (not shown) is provided. For example, it can be detected that the switches S1_P1, . . . , S2_P3 are open if such a feedback signal is not provided.

[0087] If at least one of the conditions is met, a resulting fault signal rFS is thus output by the evaluation unit AE. A corresponding protective measure can then be initiated as a function of this resulting fault signal rFS.

[0088] Furthermore, a reference signal generation unit RE is shown, which is part of the evaluation unit AE. It transmits a reference signal, for example, a step signal, to the digital converter AD. This can be performed, for example, during startup of the evaluation unit AE and the determination unit BE. A functionality of the digital converter AD can be checked in this way.

[0089] To check the functionality, it can also be checked whether a bit pattern of the digitized output signal of the determination unit DE changes by at most 1 bit, in particular if a so-called Gray code is used for the digitization.

[0090] It is not shown that a further electric network can also be monitored by the determination unit BE and the evaluation unit AE, which also comprises, for example, a power converter C, phase lines, P1, P2, P3, and a permanent magnet machine M. The determination unit BE and the evaluation unit AE can thus be used to monitor multiple electric networks, which each comprise a permanent magnet machine M for the drive of the rail vehicle. It is also conceivable that multiple permanent magnet machines of a railroad truck are monitored.

[0091] FIG. 3 schematically shows a relationship between a speed d and a speed-dependent reference variable Vref. The speed-dependent reference variable Vref can be a voltage in particular. The voltage induced at a specific speed d is approximately linearly dependent on the motor speed. However, aging influences and temperature, in particular a magnet temperature, can influence the induced voltage. Thus, for example, the speed-dependent reference variable Vref can be defined as a minimum speed-dependent voltage, which is induced at a maximum occurring magnet temperature in normal operation. Alternatively or cumulatively, the speed-dependent reference variable Vref can also be determined as a function of the age of the permanent magnet machine, wherein the speed-dependent reference variable decreases with increasing age. This relationship can be previously known, however. A reliability and a robustness of the method can advantageously be increased in this way.

[0092] Furthermore, it is shown that as a result of the digitization, the speed d can be assigned to one speed interval of multiple speed intervals, wherein the speed intervals are delimited by predetermined speeds d0, d1, d2, d3, d4, d5, d6, d7. An interval-dependent reference variable VL1, VL2, VL3, VL4, VL5, VL6, VL7 is assigned to each speed interval. For example, a first interval-dependent reference variable VL1 is assigned to a first speed interval, which lies between the first speed d0 and a second speed d1. If the speed is thus in this speed interval, the speed-dependent reference variable Vref is thus determined as this interval-dependent reference variable VL1.