Method and arrangement for providing electrical power to an on-board electrical system of a motor vehicle

Abstract

Method for providing electrical power to an on-board electrical system of a motor vehicle with a high-voltage battery (11) and two separate electric machines, wherein each of the two electric machines is assigned a power electronics unit (13, 14) with a DC-DC converter (13_1, 14_1), wherein the respective DC-DC converter (13_1, 14_1) is designed to reduce a high-voltage voltage of the high-voltage battery (11) to a predetermined voltage, and the two DC-DC converters (13_1, 14_1) of the two power electronics units (13, 14) are connected electrically in parallel, wherein the two DC-DC converters (13_1, 14_1) are controlled independently of each other and are set separately to different voltage values, wherein the different voltage values ​​to which the DC-DC converters are set differ by a delta value selected from a range of 0,The voltages of 5 volts to 2 volts are distinguished from each other, and one of the two DC-DC converters (14_1) is set to a voltage value of U_1 and the other of the two DC-DC converters (13_1) to a voltage value of U_2 = U_1 - delta value, whereby the vehicle electrical system is supplied by the DC-DC converter set to the voltage value of U_1, and whereby in the event of a sudden increase in the power required in the vehicle electrical system, a voltage drop to the delta value is limited.

Description

[0001] The present invention relates to a method and a corresponding arrangement for providing electrical power for an on-board network of a motor vehicle.

[0002] Electrical energy is becoming increasingly important in motor vehicles due to its versatility and excellent controllability for the implementation of innovative functions. However, a prerequisite for the use of electrical energy is its reliable and efficient supply by the vehicle's electrical system. This requires intelligent energy management to ensure that sufficient energy is available to the various consumers at all times. In particular, potential load changes in the electrical system must be manageable. This means that the energy must be provided in such a way that each consumer, depending on its importance, can be provided with sufficient energy at a given time.

[0003] An increasing number of electrical loads and a wide range of new safety and comfort features in a motor vehicle often require the use of more powerful power supplies within the vehicle. Functions such as electromechanical brakes, an electric boost function for a conventional combustion engine, or electromagnetically controlled valves require the use of loads that often can no longer be adequately supplied with a conventional 12-volt electrical system.

[0004] DE 20 2010 000 551 U1 describes a drive system for a vehicle with an electric motor controlled by an inverter, wherein the inverter is assigned a bidirectional DC / DC converter which establishes a connection between a high-voltage battery and a low-voltage battery.

[0005] US 2012 / 0 176 817 A1 teaches a DC-DC converter having at least a first and a second power converter, wherein the inputs of the power converters are connected in series so that direct current through the input of the first power converter also flows through the input of the second power converter, and the outputs of the power converters are connected in parallel.

[0006] US 6 954 365 B2 describes a power supply system in which several DC / DC converters are connected in parallel, wherein the number of DC / DC converters to be activated is changed depending on the electrical energy consumed by loads.

[0007] JP H10-191624 A describes a main circuit comprising a synchronous commutating DC / DC converter consisting solely of a constant-voltage control circuit. A slave circuit consists of a DC / DC converter including a constant-current control circuit. When the load is small, the current output by the slave circuit is fed back to an input power source via the main circuit's synchronously commutating DC / DC converter, maintaining a constant output voltage, and controlling the constant-current operation by the slave circuit.

[0008] JP 2000-184 608 A describes a redundant operating structure in which a battery on one side continues to supply power to a load on one side, even if a battery on another side fails. During battery backup, power to the load shared by the batteries is supplied solely from the main supply, while the other supplies are maintained in a no-load standby state.

[0009] JP 2004-242 371 A describes an arrangement comprising a first inverter that supplies power to a front-wheel drive motor unit; a second inverter that supplies power to a rear-wheel drive motor unit; a battery that supplies power to the first and second inverters; a first booster circuit that boosts the DC voltage from the battery and supplies the boosted DC voltage to the first inverter; and a first booster circuit that boosts the DC voltage from the battery and supplies the boosted DC voltage to the second inverter; a second booster circuit that supplies an inverter; wherein the first booster circuit includes a first reactor, and the second booster circuit includes a second reactor that is different from the first reactor.

[0010] US Pat. No. 6,154,381 A discloses a system with a plurality of parallel-connected DC-DC converters. The system proposed therein comprises a plurality of parallel DC-DC converters controlled by an input and output control signal interface using a smart controller. The proposed system includes a smart controller based on the fact that module efficiency varies with the applied load, so that an optimal operating point exists. However, this requires a rather complex control of the DC-DC converters, as synchronized control must always be ensured. This requires additional sensors and additional cabling.

[0011] For the purposes of this description, a hybrid or electric vehicle with at least two separate electric machines was considered. Both electric machines are designed as so-called three-phase synchronous machines, meaning they are supplied with 3-phase alternating current. The motor vehicle also has a high-voltage battery. This high-voltage battery serves to provide direct current. In order to operate the two electric machines, the direct current provided by the high-voltage battery must first be converted into a suitable alternating current, namely the aforementioned 3-phase alternating current. Therefore, each electric machine is assigned a power electronics unit. Each power electronics unit has an inverter to convert the direct current from the high-voltage battery into a suitable alternating current for the respective electric machine.

[0012] Against the background of the above-mentioned prior art and the problem that, due to the increasing number of electrical loads and the wide range of new safety and comfort functions, the 12-volt electrical system may not be able to adequately supply all of these functions at a certain point in time, it is now an object of the present invention to provide a way of largely avoiding an associated voltage drop in the event of a brief overload of the conventional 12-volt electrical system, but rather of continuing to provide electrical power.

[0013] To solve this problem, the invention proposes a method having the features of patent claim 1 and an arrangement having the features of patent claim 8. Further embodiments can be found in the respective subclaims.

[0014] According to the invention, a method is now provided for providing electrical power for an on-board electrical system of a motor vehicle with a high-voltage battery and two separate electric machines. In the method according to the invention, each of the two electric machines is assigned a power electronics unit, each with a DC-DC converter. The respective DC-DC converter is designed to reduce a high-voltage of the high-voltage battery to a predetermined voltage. The two DC-DC converters are further electrically connected in parallel, wherein the two DC-DC converters are set to different voltage values. The voltage value to which a respective DC-DC converter is set indicates the voltage present at the output of the corresponding DC-DC converter, i.e. to which the high-voltage is to be reduced.

[0015] In an embodiment of the method according to the invention, the vehicle electrical system is selected as a conventional 12-volt vehicle electrical system.

[0016] In a further embodiment of the method according to the invention, the different voltage values ​​to which the DC-DC converters are set differ by a delta value depending on the on-board network topology, typically in a range of 0.5 volts to 2 volts.

[0017] In the case of a 12-volt vehicle electrical system, it can be provided that one of the two DC-DC converters is set to a first voltage value, e.g., 14.5 volts, and the other of the two DC-DC converters is set to a second voltage value, e.g., the difference between the first voltage value and a delta value of e.g., 1 volt, i.e., 13.5 volts. The parallel connection of the two DC-DC converters provided according to the invention makes it possible to supply the vehicle electrical system with twice the electrical power compared to just one DC-DC converter. The control of the two DC-DC converters is set to different target voltage values.If the vehicle electrical system requires more electrical power than one of the DC-DC converters can provide, a voltage drop in the vehicle electrical system may occur without the parallel connection of the two DC-DC converters, which would no longer ensure the safe operation of electrical units in the vehicle. However, since the second DC-DC converter is electrically connected in parallel to the first DC-DC converter and set to a lower target voltage value, the voltage drop is limited to the target voltage value of the second DC-DC converter in the event of a sudden increase in the required power in the 12-volt vehicle electrical system. The resulting voltage drop, corresponding to the delta value, lies within the range of "normal" voltage fluctuations in the vehicle electrical system and can therefore be neglected.

[0018] A voltage dip in a power supply is generally referred to as a temporary drop in the supply voltage. Such a voltage dip occurs when a high current loads the vehicle electrical system. This is particularly the case when switching on high-power loads or specific motors that require a high starting current. By connecting two DC-DC converters in parallel according to the invention, which can be controlled and adjusted independently of each other, the voltage dip can be largely compensated for or at least significantly limited.

[0019] A DC / DC converter, as provided in each of the two power electronics units, is also referred to as a DC / DC converter and describes an electrical circuit that converts a DC voltage supplied at the input into a DC voltage with a higher, lower, or inverted voltage level. Within the scope of this description, each of the two DC / DC converters provided converts the high-voltage voltage of the high-voltage battery into a DC voltage with a lower voltage level. The DC voltage with a lower voltage level, which is then present at the respective output of the corresponding DC / DC converter, is typically in the range of 10 V to 16 V.

[0020] In a further embodiment of the method according to the invention, one of the two electric machines is arranged on a rear axle and the other of the two electric machines is arranged on a front axle of the motor vehicle.

[0021] As already mentioned, in a further embodiment of the method according to the invention, the two DC-DC converters are controlled independently of each other. The control of the two DC-DC converters can be carried out via a data bus, e.g., a CAN bus.

[0022] The invention further relates to an arrangement for providing electrical power for an on-board electrical system of a motor vehicle. The arrangement according to the invention comprises a high-voltage battery and two separate electric machines, each of the two electric machines being assigned a power electronics unit with a DC-DC converter. The electric machine, power electronics, and / or DC-DC converter components can each be integrated or arranged separately. A respective DC-DC converter of the two DC-DC converters is designed to reduce a high-voltage voltage of the high-voltage battery to a predetermined voltage, and the two DC-DC converters of the two power electronics units are electrically connected in parallel. The two DC-DC converters are also set to different voltage values.

[0023] The electrical system can be a 12-volt electrical system. The different voltage values ​​to which the DC / DC converters are set can differ from each other by a delta value selected from a range of 0.5 volts to 2 volts. In the case of a 12-volt electrical system, it is conceivable that one of the two DC / DC converters is set to a voltage value of 14.5 volts, while the other of the two DC / DC converters, with a delta value of 1 volt, is set to a voltage value of 13.5 volts. Of course, a different electrical system is also possible, for example, a 48-volt electrical system, with correspondingly different voltage values.

[0024] Furthermore, in a further embodiment of the arrangement according to the invention, it is conceivable that one of the two electric motors is arranged on a rear axle and the other of the two electric motors is arranged on a front axle of the motor vehicle. The two DC-DC converters are each controlled independently of one another via a data bus, e.g., a CAN bus.

[0025] The present invention further relates to the use of the arrangement according to the invention and / or the application of the method according to the invention in a hybrid vehicle.

[0026] The present invention further relates to the use of the arrangement according to the invention and / or the application of the method according to the invention in an electric vehicle.

[0027] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0028] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0029] The invention is illustrated schematically in the drawing using embodiments and is described in detail with reference to the drawing. Fig. 1 shows a possible arrangement of an embodiment of the arrangement according to the invention.

[0030] Fig.1 shows an embodiment of an arrangement 1 according to the invention, as can be provided in a motor vehicle for providing electrical energy for an on-board electrical system. The circuit 1 shown here comprises a high-voltage battery 11, which is provided for supplying an on-board electrical system of the motor vehicle (not explicitly shown here) as well as two electric machines of the motor vehicle. Each of the two electric machines is assigned a power electronics unit. The power electronics units are represented here by dashed boxes 13 and 14. The electric machines are arranged separately from one another and can be operated independently of one another. It is possible for one of the electric machines to be located on a front axle of the motor vehicle and the other electric machine to be located on a rear axle of the motor vehicle.Each of the two power electronics units has an inverter (not shown here) for converting direct current from the high-voltage battery 11 into a suitable alternating current for the respective electric machine. Furthermore, a DC-DC converter is assigned to each of the two power electronics units. A DC-DC converter 13_1 is assigned to the power electronics unit 13, and a DC-DC converter 14_1 is assigned to the power electronics unit 14. The DC-DC converters 13_1 and 14_1 are electrically connected in parallel with one another. Each of the DC-DC converters 13_1 and 14_1 is designed to convert a voltage, such as a DC voltage supplied at input 13_2 or 14_2, respectively, into a DC voltage with a lower voltage level. In the case shown here, the high-voltage battery 11 assigns the DC-DC converter 13_1 or 14_2 to a respective input 13_2 or 14_2.14_1 is supplied with a DC voltage, which is routed to the two inputs via a common high-voltage conductor 12. The DC-DC converter 13_1 converts the DC voltage supplied to it into a DC voltage with a lower voltage level. DC-DC converter 14_1 does the same; it also converts the DC voltage supplied at input 14_2 into a DC voltage with a lower voltage level, since the loads or functions to be supplied within the motor vehicle must be supplied with a lower voltage than the high voltage of the high-voltage battery 11.

[0031] According to the invention, one of the DC-DC converters is now set to a different voltage value than the corresponding other DC-DC converter. This means that the DC-DC converters 13_1 and 14_1 differ in their set voltage values, to which the high voltage supplied at the respective input 13_2 or 14_2 is reduced. The respectively set voltage values ​​thus define the voltage present at the output 13_3 or 14_3 of the respective DC-DC converter 13_1 or 14_1. The voltage present at the output 13_3 of the DC-DC converter 13_1 is set to U_2 (e.g., 13.5 volts), while the voltage present at the output 14_3 of the DC-DC converter 14_1 is set to U_1 (e.g., 14.5 volts). Thus, the voltage values ​​present at the respective outputs of the DC-DC converters differ by a delta value of U_1 minus U_2 (e.g. by 1 volt).The loads 15, which are distributed throughout the motor vehicle, are now supplied with electrical energy via a bus 16. Because the voltage of DC-DC converter 14_1 is higher than that of DC-DC converter 13_1, the on-board electrical system is initially supplied by DC-DC converter 14_1 due to the parallel connection. If DC-DC converter 14_1 is temporarily overloaded, i.e., if DC-DC converter 14_1 cannot keep the on-board electrical system stable or at U_1 on its own, the voltage drop only occurs up to the voltage of DC-DC converter 13_1 and thus within the range of negligible voltage fluctuations.

[0032] It should be emphasized that the present invention does not require any additional sensors or cabling to synchronize the DC-DC converters. To set the different setpoint voltage values ​​of the two DC-DC converters, the two DC-DC converters simply need to be adjusted separately with regard to their setpoint values ​​via a dedicated data bus, e.g., a CAN bus. To extend the service life of the DC-DC converters, a periodic or random change in the setpoint values ​​can be made between the DC-DC converters.

Claims

[1] Method for providing electrical power for an on-board network of a motor vehicle with a high-voltage battery (11) and two separate electric machines, in which each of the two electric machines is assigned a power electronics unit (13, 14) each with a DC-DC converter (13_1, 14_1), wherein the respective DC-DC converter (13_1, 14_1) is designed to reduce a high-voltage of the high-voltage battery (11) to a predetermined voltage, and the two DC-DC converters (13_1, 14_1) of the two power electronics units (13, 14) are electrically connected in parallel, wherein the two DC-DC converters (13_1, 14_1) are controlled independently of one another and are set separately to different voltage values, in which the different voltage values ​​to which the DC-DC converters are set differ by a delta value selected from a range of 0,5 volts to 2 volts from each other and one of the two DC-DC converters (14_1) is set to a voltage value of U_1 and the other of the two DC-DC converters (13_1) is set to a voltage value of U_2 = U_1 - delta value, wherein the on-board network is supplied by the DC-DC converter which is set to the voltage value of U_1, and wherein in the event of a sudden increase in the required power in the on-board network, a voltage drop is limited to the delta value. [2] Method according to claim 1, wherein the vehicle electrical system is selected as a 12-volt vehicle electrical system. [3] Method according to one of the preceding claims, in which one of the two electric machines is arranged on a rear axle and the other of the two electric machines is arranged on a front axle of the motor vehicle. [4] Method according to one of the preceding claims, in which the control of the two DC-DC converters (13_1, 14_1) is carried out via a data bus, in particular a CAN bus. [5] Arrangement for providing electrical power for an on-board network of a motor vehicle with a high-voltage battery (11) and two separate electric machines, each of the two electric machines being assigned a power electronics unit (13, 14) each with a DC-DC converter (13_1, 14_1), the respective DC-DC converter (13_1, 14_1) being designed to reduce a high-voltage of the high-voltage battery (11) to a predetermined voltage, and the two DC-DC converters (13_1, 14_1) of the two power electronics units (13, 14) being electrically connected in parallel, the two DC-DC converters (13_1, 14_1) being controllable independently of one another and being set separately to different voltage values, in which the different voltage values ​​to which the DC-DC converters (13_1, 14_1) are set differ by a value selected from a range of 0,5 volts to 2 volts from each other and one of the two DC-DC converters (14_1) is set to a voltage value of U_1 and the other of the two DC-DC converters (13_1) is set to a voltage value of U_2 = U_1 - delta value, wherein the on-board network is supplied by the DC-DC converter which is set to the voltage value of U_1, and wherein in the event of a sudden increase in the required power in the on-board network, a voltage drop is limited to the delta value. [6] Arrangement according to claim 5, wherein the electrical system is a 12-volt electrical system. [7] Arrangement according to claim 5 or 6, wherein one of the two DC-DC converters (14_1) is set to a voltage value of 14.5 volts and the other of the two DC-DC converters (13_1) is set to a voltage value of 13.5 volts. [8] Arrangement according to one of claims 5 to 7, in which one of the two electric machines is arranged on a rear axle and the other of the two electric machines is arranged on a front axle of the motor vehicle. [9] Arrangement according to one of claims 5 to 8, in which the two DC-DC converters (13_1, 14_1) are each controlled independently of one another via a data bus, in particular a CAN bus. [10] Use of an arrangement according to one of claims 5 to 9 and / or application of a method according to one of claims 1 to 4 in a hybrid vehicle. [11] Use of an arrangement according to one of claims 5 to 9 and / or application of a method according to one of claims 1 to 4 in an electric vehicle.

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