METHOD FOR OPERATING A MOTOR VEHICLE, AND THE MOTOR VEHICLE

Abstract

A method for operating a motor vehicle having at least one electric machine, which is electrically coupled across a pulse inverter to a DC distribution bus of a high-voltage onboard network of the motor vehicle, includes, by means of a compensation unit electrically coupled to the DC distribution bus, feeding an electric compensation voltage to the DC distribution bus such that ripple of the electric DC voltage present in the DC distribution bus which is caused by the pulse inverter is at least partly compensated.

Claims

1. A method for operating a motor vehicle having at least one electric machine, which is electrically coupled across a pulse inverter to a DC distribution bus of a high-voltage onboard network of the motor vehicle, the method comprising: feeding, by a compensation unit electrically coupled to the DC distribution bus, an electric compensation voltage to the DC distribution bus such that ripple of the electric DC voltage present in the DC distribution bus which is caused by the pulse inverter is at least partly compensated.

2. The method according to claim 1, wherein a voltage measurement series is measured, relating to the time variation of the electric voltage in the DC distribution bus, and a control signal is generated in dependence on the voltage measurement series, by which the compensation voltage is generated.

3. The method according to claim 2, wherein, with the aid of the voltage measurement series, at least one item of ripple information is determined, the ripple information relating to at least one variable of an oscillation describing the ripple, and the control signal is generated with the aid of the ripple information.

4. The method according to claim 3 wherein the at least one variable is an amplitude, a period, and/or a phase of the oscillation describing the ripple.

5. The method according to claim 2, wherein the voltage measurement series or an adjusted voltage measurement series, which has been generated by subtracting from the measured voltage values of the voltage measurement series a constant voltage value, being a constant component of the DC voltage present in the DC distribution bus, is relayed to a phase shifting and/or inverting unit, by which a modified voltage measurement series is generated by phase-shifting the voltage measurement series by a substantially half period of the ripple or by phase-shifting or inverting the adjusted voltage measurement series by a substantially half period of the ripple, and the control signal is generated with the aid of the modified voltage measurement series.

6. The method according to claim 1, wherein at least one measurement value relating to an electric voltage and/or electric current strength present in the pulse inverter, in particular on the side with the DC distribution bus and/or on the side with the electric machine, is measured, and with the aid of the measurement value and a known switching behavior of the pulse inverter at least one item of or the ripple information is determined, relating to at least one variable of an oscillation describing the ripple, and the control signal is generated with the aid of the ripple information.

7. A motor vehicle, comprising: at least one electric machine, which is electrically coupled across a pulse inverter to a DC distribution bus of a high-voltage onboard network of the motor vehicle; and a compensation unit electrically coupled to the DC distribution bus, which is adapted and/or designed to feed an electric compensation voltage into the DC distribution bus such that ripple of the electric DC voltage present in the DC distribution bus which is caused by the pulse inverter can be at least partly compensated.

8. The motor vehicle according to claim 7, wherein the motor vehicle further comprises at least one distribution bus sensor for measuring a voltage measurement series relating to a time variation of the electric voltage in the DC distribution bus, wherein the compensation unit is adapted to generating a control signal in dependence on the voltage measurement series, and the compensation voltage can be generated using this signal.

9. The motor vehicle according to claim 8, wherein a control device of the compensation unit is adapted to generating the control signal in dependence on the voltage measurement series.

10. The motor vehicle according to claim 8, wherein at least one phase shifting and/or inverting unit is provided, which is in particular a component of the compensation unit, and which is configured and/or adapted to generating a modified voltage measurement series by phase-shifting the voltage measurement series by substantially half a period of the ripple or by phase-shifting or inverting an adjusted voltage measurement series, which has been generated by subtracting from the measured voltage values of the voltage measurement series a constant voltage value, being a constant component of the DC voltage present in the DC distribution bus, by substantially half a period of the ripple, and the compensation unit is adapted to generating the control signal in dependence on the modified voltage measurement series.

11. The motor vehicle according to claim 7, wherein the motor vehicle further comprises at least one pulse inverter sensor for measuring a measurement value relating to an electric voltage and/or electric current strength present in the pulse inverter, in particular on the side with the DC distribution bus and/or on the side with the electric machine, the compensation unit is adapted to generating the or a control signal in dependence on the measurement value, and the compensation voltage can be generated using this signal.

12. The motor vehicle according to claim 7, wherein the pulse inverter and the compensation unit are configured as a combined component.

13. The motor vehicle according to claim 7, wherein at least one DC voltage component which can be operated by a DC voltage is electrically coupled to the DC distribution bus, wherein the DC voltage component is a high-voltage battery, in which energy is stored or can be stored in order to propel the motor vehicle, and/or a component of an air conditioning system of the motor vehicle, and/or a charger, by which an electric energy accumulator of the motor vehicle can be charged.

14. The motor vehicle according to claim 13 wherein the component of the air conditioning system of the motor vehicle is a compressor or a heating component.

15. The motor vehicle according to claim 13 wherein the energy accumulator of the motor vehicle is a high-voltage battery.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0033] Further benefits, aspects and details will emerge from the following embodiments as well as the figures.

[0034] FIG. 1 shows a first embodiment of the motor vehicle.

[0035] FIG. 2 shows a first embodiment of the method regarding the motor vehicle of FIG. 1.

[0036] FIG. 3 shows a second embodiment of the motor vehicle.

[0037] FIG. 4 shows a second embodiment of the method regarding the motor vehicle of FIG. 3.

[0038] FIG. 5 shows diagrams regarding modification or evaluation of the voltage measurement series acquired in connection with the method presented in FIG. 4.

[0039] FIG. 6 shows a third embodiment of the motor vehicle.

[0040] FIG. 7 shows a third embodiment of the method regarding the motor vehicle of FIG. 6.

DETAILED DESCRIPTION

[0041] FIG. 1 shows a first embodiment of a motor vehicle 1, having a high-voltage onboard network 2. The motor vehicle further comprises an electric machine 3, which is electrically coupled across a pulse inverter 4 to a DC distribution bus 5 of the high-voltage onboard network 2. By means of the pulse inverter 4, the alternating voltage present on the side with the electric machine 3 can be transformed into a DC voltage, so that it becomes possible to feed electric energy from the electric machine 3 to the DC distribution bus 5 by means of the pulse inverter 4, and vice versa.

[0042] Multiple DC voltage components 6 which can be operated by means of a DC voltage are electrically coupled to the DC distribution bus 5. One of the DC voltage components 6 is a high-voltage battery 7 of the motor vehicle 1, in which energy is or can be stored for the propulsion of the motor vehicle 1. The high-voltage battery 7, which can also be called a traction battery, can be both a consumer and an energy source of the high-voltage onboard network 2. The high-voltage battery 7 is a consumer when the motor vehicle 1 is in a charging mode, for example when it is being charged by means of an outside current source, or when the electric machine 3 is functioning as a generator in the course of a recuperation mode of the motor vehicle 1. The high-voltage battery 7 is an electric energy source when it is feeding energy for the other DC voltage components 6 and/or for the electric machine 3 operating in motor mode to the high-voltage onboard network 2. The high-voltage battery in this case supplies a voltage of 400 Volt, for example.

[0043] Moreover, components of an air conditioning system of the motor vehicle not further shown in the figure are provided as a DC voltage component 6, namely, a compressor 8 and a heating component 9. Moreover, a charger 10 is provided as a DC voltage component 6, by means of which the high-voltage battery 7 can be charged.

[0044] One problem involving the pulse inverter 4 is that, because of its switching behavior, voltage ripple or simply ripple 38 is caused in the DC distribution bus 5. This represents harmonics, so to speak, in the electric DC voltage present in the DC distribution bus. Since the ripple 38 is detrimental to the operation of the DC voltage components 6 and in the worst case they may even be damaged by the ripple 38, it is necessary to reduce the ripple 38 as much as possible. For this purpose, a compensation unit 10 is provided, being coupled to the DC distribution bus 5. The pulse inverter 4 and the compensation unit 10 are configured as a combined component, for example, as is indicated in FIG. 1 by the dotted box 11. The combined component comprises a common housing, in which the pulse inverter 4 and the compensation unit 10 are arranged.

[0045] The compensation unit 10 is adapted to feeding an electric compensation voltage into the DC distribution bus 5, so that the ripple 38 is at least partially compensated. Details regarding this compensating process will be explained below with the aid of FIG. 2, relating to a first embodiment of the method with the aid of the motor vehicle 1 shown in FIG. 1. In order to carry out this method, there is provided a control device 12, in particular, being in the present case part of the compensation unit 10. The method shown in FIG. 2 involves the steps 13-15.

[0046] In step 13 of the method, a voltage measurement series 16 is detected or measured, relating to a temporal variation of the electric voltage in the DC distribution bus 5. Thus, pairs of values are detected, in each of which a corresponding voltage value is associated with a definite moment of time. For the detecting of the voltage measurement series 16 there is provided a distribution bus sensor 17, which in the present case is or comprises a voltmeter. The measurement detected by means of the distribution bus sensor 17 are relayed to the control device 12.

[0047] In the second step 14 of the method, ripple information 18 is ascertained by means of the control device 12 and with the aid of the voltage measurement series 16. The ripple information 18 describes multiple variables of an oscillation, by means of which the ripple 38 can be described. For example, the ripple information 18 is determined by carrying out a regression analysis with the data of the voltage measurement series 16. Specifically, a sine function is fitted to the corresponding data values, so that the variables determined in connection with the ripple information 18 are the amplitude A, the period P and the phase φ of this oscillation.

[0048] The temporal variation of the voltage values of the voltage measurement series 16 is evaluated by means of a sine function, which can be represented by the functional equation:

[00001]$U\left(t\right)=U_0+A.Math.\sin \left(\frac{2\pi }{T}t+\phi \right).$

U(t) denotes here the time-dependent values of the voltage in the DC distribution bus 5 and t denotes the time. U.sub.0 denotes a constant voltage value in the DC distribution bus 5, A is the amplitude, T is the period or duration of the oscillation, and φ is the phase of the ripple 36. This functional equation can be fitted to the measurement series by means of a χ.sup.2 minimization and in this way the ripple information 18, i.e., the values for A, T and φ, can be determined. U.sub.0 can be taken as known, or also be determined as an unknown in the context of this analysis.

[0049] In the last step 15 of the method, the ripple information 18 is used to generate a control signal 19, with the aid of which the compensation voltage is generated. For the generating of the compensation voltage, the compensation unit 10 is connected by electric connections 20 to the high-voltage battery 7. The DC voltage provided by the high-voltage battery 7 is modified by the compensation unit 10 such that the voltage imposed by means of the compensation unit 10 on the voltage in the DC distribution bus 5 comprises a voltage variation running counter to the ripple 38. Thus, the ripple 38 is attenuated by feeding the compensation voltage to the DC distribution bus 5. Since the counter oscillations of the voltage fed in are generated in the present example with the aid of a sinusoidal oscillation, yet the ripple 38 present in the DC distribution bus 5 typically does not have an ideal sine shape, the ripple 38 while not completely compensated will be significantly smoothed out.

[0050] Steps 13-15 of the method are carried out simultaneously. That is, the detecting of the voltage measurement series 16 always occurs in parallel with the feeding in of the compensation voltage, so that it is possible to respond to any changes in regard to the ripples 38. In particular, allowance is also made for the attenuation of the ripple 38 brought about by the compensation voltage. The simultaneous performance of steps 13-15 begins once the determination of the voltage measurement series 16 performed during step 13 constitutes a sufficient database to carry out the determination of the ripple information 18 with sufficient accuracy in step 14.

[0051] FIG. 3 shows a second embodiment of the motor vehicle 1, in which the same components have been given the same reference numbers in regard to the motor vehicle 1 of FIG. 1. The differences between these embodiments shall be made clear in the following explanations for FIG. 4, which shows a flow chart of a second embodiment of the method for the motor vehicle 1 shown in FIG. 3. The method explained with the aid of FIG. 4 involves the steps 21-24.

[0052] In the first step 21, the voltage measurement series 16 is determined according to the first step 13 of the method shown in FIG. 2. The top diagram 25 of FIG. 5 shows, for better comprehension, a system of coordinates in which the values of the voltage measurement series 16 have been plotted. The abscissa of this system of coordinates relates to the time and the ordinate relates to the value of the electric voltage present in the DC distribution bus 5. Even though the curve shown in the diagram 25 is a solid line, the voltage measurement series 16 comprises concrete pairs of values and therefore discrete points. The existing ripple 38 is clearly recognizable in the diagram 25, being shown exaggerated for better clarity.

[0053] In the next step 22, an adjusted voltage measurement series 26 is generated from the voltage measurement series 16. The adjusted voltage measurement series 26 is generated by subtracting a constant voltage value U.sub.0 each time from the measured voltage values of the voltage measurement series 16. The constant voltage value U.sub.0 may correspond to the predetermined and known nominal voltage of the DC distribution bus 5 or it can be determined means of the voltage measurement series 16 by forming a mean value from the measured voltage values. The adjusted voltage measurement series 26 is represented in the diagram 27 in FIG. 5. As is evident, this curve has been created by a parallel shifting of the curve represented in the diagram 25 along the y-axis by the value U.sub.0. The creation of the adjusted voltage measurement series 26 from the voltage measurement series 16 is done, for example, by the control device 12.

[0054] In the next step 23 of the method, the adjusted voltage measurement series 26 is taken to a phase shifting and/or inverting unit 27 of the control device 12. The phase shifting and/or inverting unit 27 inverts the adjusted voltage measurement series 26, that is, the magnitudes of the voltage values present in the adjusted voltage measurement series 26 are reversed.

[0055] The result is a modified, adjusted voltage measurement series 29, represented in the diagram 28 in FIG. 5. Alternatively, the modified, adjusted voltage measurement series 29 can be generated by phase-shifting the adjusted voltage measurement series 26 by a half period or 180° by means of the phase shifting and/or inverting unit 27, which in the case of a sinusoidal oscillation is the same as an inverting.

[0056] In the last step 24 of the method, the control signal 19 is generated by means of the modified voltage measurement series 29 generated in step 23 and this is used to generate the compensation voltage. The variation of the compensation voltage fed to the DC distribution bus 5 corresponds to the variation of the modified voltage measurement series 29, so that the temporal variations of the compensation voltage and the voltage present in the DC distribution bus 5 run counter to each other and cancel each other out, or at least attenuate each other. The result of this compensation is shown in the diagram 30 in FIG. 5, where the curve 31 plotted in the diagram 30 represents the voltage present in the DC distribution bus 5 as a function of time. As can be seen, the ripples 38 are clearly smoothed out by the described method.

[0057] The previous step 22 in the context of the just explained embodiment of the method regarding the generating of the adjusted voltage measurement series 26 is merely optional. Thus, in particular, it is also conceivable for the voltage measurement series 16 to be taken directly to the phase shifting and/or inverting unit 27, which generates the modified voltage measurement series 29 by means of a phase shifting, for example, by 180°. The control signal 19 can likewise depend on the values created in this way.

[0058] FIG. 6 shows a third embodiment of the motor vehicle 1, in which, apart from the following explained differences, the aspects explained in connection with the motor vehicles 1 represented in FIGS. 1 and 3 apply equally, and the same components are given the same reference numbers. The motor vehicle represented in FIG. 6 comprises, in place of the distribution bus sensor 17, a first pulse inverter sensor 32 and a second pulse inverter sensor 33. By means of the first pulse inverter sensor 32, an electric voltage which is present in the pulse inverter, namely, on the side with the DC distribution bus 5, can be detected. By means of the second pulse inverter sensor 33, an electric current strength present on the side with the DC distribution bus 5 can be detected in the pulse inverter 4. The measurement values are relayed to the control device 12. The sensors 32, 33 may alternatively be arranged in the pulse inverter 4 on the side with the electric machine 3.

[0059] A third embodiment of the method regarding the motor vehicle 1 of FIG. 6 shall be explained with the aid of the flow chart shown in FIG. 7. This method involves the steps 34-36. In the first step 34, measurement values 37 are detected by the first pulse inverter sensor 32 and the second pulse inverter sensor 33.

[0060] As in the second step 14 of the method of FIG. 2, in the second step 35 of the method of FIG. 7 the ripple information 18 is detected. However, the detecting of the ripple information 18 is not done as in the method explained with the aid of FIG. 2 by using voltage values regarding the DC distribution bus 5, but instead by using the measurement values 37 and the known switching behavior of the pulse inverter 4 for this purpose. Thus, a lookup table is kept on the side with the control device 12, in which the ripple information 18, i.e., the amplitude as well as the phase of the anticipated ripple 38, is contained as a function of the voltage and current strength in the region of the pulse inverter 4. The measurement values to be detected can therefore be detected with a shorter time resolution than that in the embodiment explained with the aid of FIG. 2, since the ripple 38 does not need to be detected explicitly and time-resolved in the method explained with the aid of FIG. 7.

[0061] By means of the ripple information 18 generated in this way, the control signal 19 is generated in the last step 36 of this method, and the details explained in connection with the last step 15 of the method explained in FIG. 2 likewise apply here.

[0062] In particular, it can also be provided that the first embodiment and the third embodiment of the motor vehicle 1 and the first embodiment and third embodiment of the method are combined. In this case, the determination of the ripple information 18 is done on the one hand with the aid of the measurement data of the distribution bus sensor 17 and on the other hand with the aid of the measurement data of the first pulse inverter sensor 32 and the second pulse inverter sensor 33. The ripple information 18 can be generated even more precisely and verified in regard to consistency by using this expanded database.

[0063] German patent application no. 10 2021 123322.4, filed Sep. 9, 2021, to which this application claims priority, is hereby incorporated herein by reference, in its entirety. Aspects of the various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.