Method for operating power electronics for converting electrical energy from an on-board electrical system into heat

Abstract

The present invention relates to a method for operating power electronics (1) for converting electrical energy from an on-board electrical system (201) into heat by means of a consumer arrangement (50) consisting of two consumers (51). The power electronics (1) has three half-bridges (2, 3, 4) which are connected in parallel and each have a centre tap (9) and two switching elements (10, 11), wherein the switching elements (10, 11) are connected in such a way that they connect the consumers (51) individually to the on-board electrical system (201) and to one another. The invention also relates to a power electronics arrangement (100) having such power electronics (1) and to a computer program product for carrying out the method.

Description

[0001] R.411726

[0002] - 1 -

[0003] Description

[0004] title

[0005] Method for operating power electronics to convert electrical energy from a vehicle electrical system into heat

[0006] The present invention relates to a method for operating power electronics for converting electrical energy from the electrical system of a powertrain into heat. The invention also relates to a computer program for carrying out the method and to a power electronics arrangement with such operated power electronics.

[0007] The powertrain of a partially or fully electric vehicle typically includes an electric motor connected to the vehicle's electrical system. This system usually operates on direct current (DC). An inverter is generally located between the electrical system and the electric motor.

[0008] There may be excess electrical energy in the drivetrain that needs to be dissipated. This excess electrical energy can, for example, originate from the electric machine when it is operating in generator mode.

[0009] To dissipate excess electrical energy, power electronics can be used to supply consumers with electricity to convert the electrical energy into heat.

[0010] Such power electronics are known from WO 2023 / 036510 A1. The power electronics comprise an inverter that connects three loads to the vehicle's electrical system for converting electrical energy from the vehicle's electrical system. R.411726

[0011] - 2 -

[0012] The object of the present invention is to provide an improved or at least different method for operating power electronics for converting electrical energy from the electrical system of a drive train into heat. Furthermore, the object of the invention is to specify improved or at least different embodiments of a computer program for operating such power electronics, as well as of a power electronics arrangement comprising such power electronics.

[0013] The problem is solved using the features of the independent claims. Advantageous variants are the subject of the dependent claims.

[0014] The core idea of ​​the invention is therefore to equip a power electronics unit for converting electrical energy from the electrical system of a powertrain into heat with three half-bridges, each comprising two switching elements and a center tap. The center taps serve to connect to a consumer arrangement consisting of two consumers, and the switching elements can connect their respective center taps to the electrical system. The switching elements can connect the consumers to the electrical system either individually or in parallel. Thus, depending on the connection of the consumers to the electrical system, different amounts of energy are converted from the electrical system. This allows for flexible use of the consumers for converting electrical energy into heat and therefore for the demand-based dissipation of electrical energy from the electrical system.Consequently, the core idea leads to an adaptable conversion of electrical energy from the vehicle's electrical system into heat, while also being easy to implement.

[0015] The core idea is advantageously implemented in a method for operating such power electronics. The power electronics serve to convert electrical energy from the electrical system of a powertrain into heat by means of a consumer arrangement consisting of two loads. Thus, each load generates heat when energized. The power electronics feature three half-bridges connected in parallel. Each half-bridge has a series connection of a first switching element and a second switching element. This means that R.411726

[0016] - 3 - Each half-bridge has a first switching element and a second switching element connected in series. Furthermore, each half-bridge has a center tap between the associated switching elements for connection to the load assembly. The power electronics can be connected to the vehicle electrical system via two terminals and are connected during operation; these terminals are hereinafter also referred to as vehicle electrical system terminals or, in short, mains terminals. The first switching element connects the associated center tap to one of the mains terminals, and the second switching element connects the associated center tap to a second mains terminal. The switching elements of the half-bridges are configured in an operating mode such that only one of the loads is electrically connected to the vehicle electrical system, so that only this load receives power.This operating mode is hereinafter also referred to as the first operating mode. In another operating mode, the switching elements of the half-bridges are connected in such a way that the loads are connected in parallel and to the vehicle's electrical system, so that the loads are powered in parallel. This operating mode is hereinafter also referred to as the second operating mode.

[0017] The first switching element, when closed, establishes an electrical connection between its associated center tap and the first mains connection, and disconnects this connection when open. The second switching element, when closed, establishes an electrical connection between its associated center tap and the second mains connection, and disconnects this connection when open.

[0018] For better differentiation, the three half-bridges will subsequently be referred to as the first half-bridge, second half-bridge and third half-bridge.

[0019] The power electronics are conveniently connected to the vehicle's electrical system via the mains connections during operation / use. The switching elements selectively establish the electrical connection of the respective load to the vehicle's electrical system in order to, as described, direct a current flowing through the vehicle's electrical system through at least one load connected to the system, so that this load converts electrical energy from the vehicle's electrical system into heat. Consequently, electrical energy is converted into heat. R.411726

[0020] - 4 -

[0021] Power is consumed, and the consumed power is subsequently referred to as power consumption. In a lossless system, the power consumption P thus corresponds to the square of the voltage U of the vehicle electrical system divided by the total resistance R_total of the consumer arrangement connected to the vehicle electrical system, subsequently also referred to as total resistance. Therefore, P = U 2 / R_total. The power consumption is therefore inversely proportional to the total resistance.

[0022] If both power resistors are disconnected from the vehicle's electrical system, no conversion of electrical energy takes place via the power resistors. Therefore, no power is consumed.

[0023] In the second operating mode, the total resistance R_total is minimized, and thus the power consumption is maximized. The second operating mode can therefore also be referred to as the high-power operating mode.

[0024] In the first operating mode, the total resistance R_ges is higher compared to the second operating mode. This results in reduced power consumption in the first operating mode compared to the second. The first operating mode can therefore also be described as the average power operating mode.

[0025] In preferred embodiments, the switching elements of the half-bridges are switched in a further operating mode such that the loads are connected in series and to the vehicle electrical system, so that the loads are energized in series. This operating mode is hereinafter also referred to as the third operating mode.

[0026] In the third operating mode, the total resistance R_total is therefore lower than in the first operating mode. Consequently, the power consumption in the third operating mode is lower than in the first. The third operating mode can thus also be described as the low-power operating mode. This results in further flexibility in the consumption of electrical energy from the vehicle's electrical system. R.411726

[0027] - 5 -

[0028] The respective consumer can be of any design, provided that it generates heat when an electric current from the vehicle's electrical system flows through it, and thus consumes electrical energy. The respective consumer is therefore, in particular, an electrical load.

[0029] For example, at least one of the consumers can be a coil or at least have a coil which, when energized, inductively converts electrical energy from the vehicle electrical system into heat through eddy currents.

[0030] Likewise, at least one of the consumers could be a heating element or similar device.

[0031] In advantageous versions, at least one of the consumers, and in particular the respective consumer, is a power resistor. This leads to simple implementation and scalable heat generation in a compact design. In particular, the generated heat can thus be easily dissipated, for example, to supply another application, such as an air conditioner.

[0032] The power electronics, especially the half-bridges, can in principle be implemented in any way.

[0033] In advantageous embodiments, the power electronics are arranged within an inverter. This allows the switching elements to be switched at increased speeds and consequently higher frequencies. Furthermore, the power electronics are simplified and compact in this way.

[0034] The respective consumer preferably has two connections that allow the consumer to be powered and are hereinafter also referred to as consumer connections.

[0035] The first consumer connection of the first consumer is hereinafter also referred to as the first primary consumer connection, and a second consumer connection of the first consumer is also referred to as the second primary consumer connection. Similarly, the first consumer connection of the second consumer is hereinafter also referred to as R.411726.

[0036] - 6 - first second consumer connection and a second consumer connection of the second consumer also referred to as second second consumer connection.

[0037] In preferred variants, the second primary consumer connection is connected to the second secondary consumer connection, so that the consumers are connected in series.

[0038] Preferably, the center tap of the first half-bridge is connected to the first primary consumer connection of the first consumer. Furthermore, it is advantageous to connect the center tap of the second half-bridge to the first secondary consumer connection of the second consumer. Additionally, it is advantageous to connect the center tap of the third half-bridge to the second primary consumer connection of the first consumer and the second secondary consumer connection of the second consumer.

[0039] In preferred embodiments, in the first operating mode, the first switching element of the first half-bridge is closed and the second switching element of the first half-bridge is opened. Additionally, the first and second switching elements of the second half-bridge are opened. Furthermore, the first switching element of the third half-bridge is opened and the second switching element of the third half-bridge is closed. Thus, only the first load is energized.

[0040] Alternatively, in the first operating mode, the first and second switching elements of the first half-bridge are preferably opened. Additionally, the first switching element of the second half-bridge is closed and the second switching element of the second half-bridge is opened. Likewise, the first switching element of the third half-bridge is opened and the second switching element of the third half-bridge is closed. Thus, only the second load is energized.

[0041] In preferred embodiments, in the second operating mode, the first switching element of the first half-bridge is closed and the second switching element of the first half-bridge is opened. Furthermore, the first switching element of the second half-bridge is closed and the second switching element of the second half-bridge is opened. Also, the first switching element of the third half-bridge is opened and the second switching element of the third half-bridge is opened. R.411726

[0042] - 7 - the third half-bridge is closed. Thus, both consumers are powered in parallel.

[0043] In the third operating mode, the first switching element of the first half-bridge is preferentially closed and the second switching element of the first half-bridge is opened. Additionally, the first switching element of the second half-bridge is opened and the second switching element of the second half-bridge is closed. Furthermore, the first and second switching elements of the third half-bridge are opened. Thus, both loads are energized in series.

[0044] The switching elements of the half-bridges are advantageously controlled by pulse-width modulation. Pulse-width modulation, hereinafter also referred to as "PWM", is performed at a specific frequency and thus with a specific period. This period is hereinafter also referred to as the PWM cycle.

[0045] Preferably, the respective operating mode is repeated periodically for twice the length of the PWM cycle. The states within the respective operating mode are thus repeated periodically with a period that corresponds to twice the length of the PWM cycle. Consequently, the amplitudes of the discharge currents during switching are reduced, and the discharge currents are distributed across two PWM cycles and thus two phases of the control signal. By selecting the appropriate operating mode depending on the vehicle electrical system voltage and the required power consumption to be converted, the so-called ripple currents and voltage ripple on the vehicle electrical system are reduced. Advantageously, the control frequency is also varied to achieve an optimum for the respective operating point.Power consumption is modulated by the duty cycle, which is advantageously selected as large as possible by choosing the appropriate operating modes in order to achieve the desired effects of minimizing voltage ripple with all its associated benefits, such as reduced shield currents, EMC, eddy current losses, unwanted heating of critical components, and the like. This leads both to improved operation of the drive train and to the possibility of using smaller power electronics components, especially power electronics capacitors, while further reducing ripple currents. R.411726.

[0046] - 8 -

[0047] In preferred embodiments, the consumers are supplied with a uniform current periodically. This leads to uniform aging and / or stress on the consumers and thus to an overall increased service life of the consumer arrangement. Furthermore, heat is generated uniformly within the consumer arrangement in this way. The latter simplifies the use and / or dissipation of the generated heat. Additionally, this results in a comparatively homogeneous heat distribution within the consumer arrangement.

[0048] The power electronics can be part of an arrangement for converting electrical energy from a powertrain's electrical system into heat. This arrangement, hereinafter also referred to as the power electronics arrangement, advantageously includes a control unit for operating the power electronics, in particular for switching the switching elements, which is designed accordingly.

[0049] The power electronics arrangement can include the consumer arrangement.

[0050] It is understood that, in addition to the method for operating the power electronics, the power electronics arrangement is also part of the scope of this invention.

[0051] The procedure is preferably carried out using a computer program product.

[0052] The computer program product includes instructions that, when executed by a computer, cause the computer to perform the procedure.

[0053] The computer can be part of the control unit or be equivalent to the control unit.

[0054] It is understood that the computer program product itself is also part of the scope of this invention. R.411726

[0055] - 9 -

[0056] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0057] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0058] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0059] They show, each schematically

[0060] Fig. 1 shows a highly simplified, circuit diagram-like representation of a drive train with an on-board electrical system and power electronics for converting electrical energy from the on-board electrical system.

[0061] Fig. 2 shows a highly simplified, circuit diagram-like representation of the power electronics and the vehicle electrical system.

[0062] Fig. 3 shows a circuit diagram-like representation of the power electronics and a consumer arrangement in a first operating mode,

[0063] Fig. 4 shows the representation from Figure 3 in a second operating mode,

[0064] Fig. 5 shows the representation from Figure 3 in a third operating mode,

[0065] Fig. 6 is a diagram to illustrate the operation of the power electronics using the first operating mode,

[0066] Fig. 7 is a diagram illustrating the operation of the power electronics using the first operating mode, R.411726

[0067] - 10 -

[0068] Fig. 8 is a diagram to illustrate the operation of the power electronics using the second operating mode,

[0069] Fig. 9 is a diagram to illustrate the operation of the power electronics using the second operating mode,

[0070] Fig. 10 is a diagram to illustrate the operation of the power electronics using the third operating mode.

[0071] A power electronics unit 1, shown by way of example in Figures 1 to 5, serves to convert, in particular to reduce, electrical energy of an electric drive train 200, shown by way of example in Figures 1 and 2, of a motor vehicle 300, which is only indicated in Figure 1 and is not shown otherwise.

[0072] The electric powertrain 200, hereinafter also referred to simply as powertrain 200, has, as shown in Figures 1 and 2, an electrical system 201 that supplies power to an electric motor 202 of the powertrain 200. The power electronics 1 convert electrical energy from the electrical system 201 into heat by means of a load arrangement 50, which consists of two loads 51, namely a first load 51, 51a and a second load 51, 51b. The electrical system 201 makes it possible to supply the electric motor 202 with electricity when the electric motor 202 is operating as a motor to drive the motor vehicle 300. Furthermore, the electrical system 201 can be used to draw off electrical energy generated in the electric motor 202 when the electric motor 202 is operating as a generator.In the illustrated embodiments, the vehicle electrical system 201 is a high-voltage vehicle electrical system 201 operated with direct current / direct voltage. An inverter 203 is connected upstream of the electric machine 202. In the illustrated embodiments, the drive train 200 also includes a traction battery 204, which is connected to the electric machine 202 via the vehicle electrical system 201 and the inverter 203.

[0073] The conversion, in particular the reduction, of electrical energy by means of the power electronics 1 is carried out by connecting the consumers 51 to the vehicle electrical system 201 , R.411726

[0074] - 11 - so that a current flowing through the vehicle electrical system 201 flows through the respective consumer 51 connected to the vehicle electrical system 201. The respective consumer 51 is thus energized and generates heat, resulting in the aforementioned conversion of electrical energy into heat. In the illustrated embodiments, the consumers 51 are, purely by way of example, each configured as a power resistor 52. In the illustrated embodiments, the consumers 51 are, purely by way of example, identical components, i.e., they have, in particular, the same resistance R.

[0075] The connection of the respective consumer 51 to the vehicle electrical system 201 is effected by means of three half-bridges 2, 3, 4 of the power electronics 1, shown by way of example in Figures 1 to 5, namely a first half-bridge 2, a second half-bridge 3 and a third half-bridge 4. The half-bridges 2, 3, 4 are connected in parallel.

[0076] As can be seen in particular from Figure 2, the power electronics 1 has two connections 5 that can be connected to the vehicle electrical system 201 and are connected during operation; these are hereinafter also referred to as mains connections 5. The power electronics 1 thus has a first mains connection 5, 5a and a second mains connection 5, 5b.

[0077] The heat generated by the consumers 51 can be dissipated by means of a cooler 301 shown in Figure 2. For this purpose, the cooler 301 has fluid connections 302 so that a coolant can flow through it. The consumers 51 are fluidically separated from the coolant and, as can be seen in Figure 3, can be arranged in the cooler 301.

[0078] The power electronics 1 can be arranged inside an inverter 6. The power electronics 1, in particular the inverter 6, can have a capacitance 7, shown only in Figures 4 to 6, in the illustrated embodiments in the form of a capacitor 8.

[0079] As illustrated below with reference to Figures 3 to 5, the power electronics 1 can connect the consumers 51 individually to the vehicle electrical system 201 and to each other by means of the half-bridges 2, 3, 4, so that they are supplied with different currents. For this purpose, each half-bridge 2, 3, 4 has two switching elements R.411726.

[0080] - 12 -

[0081] The circuit consists of two switching elements, 10 and 11, in a series circuit, namely a first switching element 10 and a second switching element 11. Furthermore, each half-bridge 2, 3, 4 between the first and second switching elements has a center tap 9. The center taps 9 serve to connect to the load arrangement 50. Each switching element 10, 11 can be connected to one of the corresponding mains terminals 5. In the illustrated embodiments, the respective first switching element 10 can connect its corresponding center tap 9 to the first mains terminal 5, 5a, and the respective second switching element 11 can connect its corresponding center tap 9 to the second mains terminal 5, 5b. The respective switching element 10, 11 establishes this electrical connection when closed and disconnects it when open.

[0082] The power electronics 1 can be part of an arrangement 100, which also includes a control unit 101 for controlling the power electronics 1, in particular the half-bridges 2, 3, 4. The control unit 101 is designed accordingly. The arrangement 100 is hereinafter also referred to as the power electronics arrangement 100. The power electronics arrangement 100 can include the load arrangement 50.

[0083] Each consumer 51 has two connections 53, 54 for supplying power to the consumer 51. A first connection 53, 53a of the first consumer 51, 51a is hereinafter also referred to as the first primary consumer connection 53, 53a, and a first connection 53, 53b of the second consumer 51, 51b as the first secondary consumer connection 53, 53b. Similarly, a second connection 54, 54a of the first consumer 51, 51a is hereinafter also referred to as the second primary consumer connection 54, 54a, and a second connection 54, 54b of the second consumer 51, 51b as the second secondary consumer connection 54, 54b. The second primary consumer connection 54, 54a and the second secondary consumer connection 54, 54b are connected to each other, so that the consumers 51 are connected serially.

[0084] In the illustrated embodiments, the center taps 9 serve for connection to the consumer terminals 53, 54. In the illustrated embodiments, during operation, particularly in the power electronics arrangement 100, the center tap 9 of the first half-bridge 2 is connected to the first consumer terminal 53, 53a and the R.411726

[0085] - 13 -

[0086] The center tap 9 of the second half-bridge 3 is connected to the first secondary consumer connection 53, 53b. Furthermore, the center tap 9 of the third half-bridge 4 is connected to the second primary consumer connection 54, 54a and the second secondary consumer connection 54, 54b.

[0087] The power electronics 1, in particular the inverter 8, can be controlled by pulse-width modulation. Pulse-width modulation, hereinafter also referred to as "PWM", is performed at a frequency and thus a period C (compare Figures 6 to 10). This period C is hereinafter also referred to as the PWM cycle C.

[0088] The switching elements 10, 11 of the half-bridges 2, 3, 4 can be switched differently to operate the power electronics 1 and thus also the power electronics arrangement 100 in different operating modes 12, 13, 14. In the different operating modes 12, 13, 14, the loads 51 are connected to the vehicle electrical system 201 in different ways, so that they are supplied with different currents and thus convert more or less electrical energy from the vehicle electrical system 201 into heat. The load arrangement 50 consumes electrical energy and thus a power P, which is subsequently also referred to as power consumption P. In a lossless system, the power consumption P thus corresponds to the square of the voltage U of the vehicle electrical system 201 divided by the total resistance R_total of the load arrangement 50 connected to the vehicle electrical system 201.

[0089] In an exemplary first operating mode 12 shown in Figure 3, the switching elements 10, 11 of the half-bridges 2, 3, 4 are switched such that only one of the loads 51 is connected to the vehicle electrical system 201, so that only this load 51 is energized. In the first operating mode 12, the power consumption P is therefore P = U 2 / R.

[0090] As can be seen in Figure 3, in the illustrated embodiment, in the first operating mode 12, the first switching element 10 of the first half-bridge 2 is closed and the second switching element 11 of the first half-bridge 2 is opened. In addition, the first switching element 10 and the second switching element 11 of the second half-bridge 3 are opened. The first switching element 10 of the third half-bridge 4 R.411726 is also opened.

[0091] - 14 - opened and the second switching element 11 of the third half-bridge 4 closed. Thus, as indicated in Figure 3, only the first consumer 51 , 51 a is energized.

[0092] To implement the first operating mode 12, in a variant not shown, the first switching element 10 and the second switching element 11 of the first half-bridge 2 are opened. Additionally, the first switching element 10 of the second half-bridge 3 is closed and the second switching element 11 of the second half-bridge 3 is opened. Furthermore, the first switching element 10 of the third half-bridge 4 is opened and the second switching element 11 of the third half-bridge 4 is closed. Thus, only the second load 51, 51b will be energized.

[0093] In a second operating mode 13, shown by way of example in Figure 4, the switching elements 10, 11 of the half-bridges 2, 3, 4 are switched such that the loads 51 are connected in parallel and to the vehicle electrical system 201, so that the loads 51 are energized in parallel. Thus, the power consumption P in the second operating mode 13 is therefore P = 2U 2 / R.

[0094] As can be seen in Figure 4, in the illustrated embodiment, in the second operating mode 13, the first switching element 10 of the first half-bridge 2 is closed and the second switching element 11 of the first half-bridge 2 is opened. In addition, the first switching element 10 of the second half-bridge 3 is closed and the second switching element 11 of the second half-bridge 3 is opened. Furthermore, the first switching element 10 of the third half-bridge 4 is opened and the second switching element 11 of the third half-bridge 4 is closed.

[0095] In a third operating mode 14, shown as an example in Figure 5, the power electronics 1 can connect the loads 51 to the vehicle electrical system 201 in series, so that they are powered in series. The power consumption P in the third operating mode 14 is therefore P = U 2 / 2R.

[0096] As can be seen in Figure 5, in the illustrated embodiment, in the third operating mode 14, the first switching element 10 of the first half-bridge 2 is closed and the second switching element 11 of the first half-bridge 2 is opened. Furthermore, R.411726

[0097] - 15 - the first switching element 10 of the second half-bridge 3 is opened and the second switching element 11 of the second half-bridge 3 is closed. The first switching element 10 and the second switching element 11 of the third half-bridge 4 are also opened.

[0098] The switching elements 10, 11 can also be switched in various positions not shown, in which no power is consumed. For example, it is possible to disconnect the consumers 51 from the vehicle electrical system 201, as shown in Figure 1.

[0099] In the illustrated embodiments, and preferably, the consumers 51 are periodically and uniformly supplied with current.

[0100] The operation of the power electronics 1 is explained below using the control of the half-bridges 2, 3, 4 shown in Figures 6 to 10 as an example. Figures 6 to 10 each show a diagram in which time t is plotted along the abscissa and power consumption P along the ordinate. Figures 6 to 10 also show the power consumption P of the first load 51, 51a with a solid line L1 and the power consumption of the second load 51, 51b with a dashed line L2. More precisely, Figures 6 to 10 show the maintenance duration of the corresponding operating modes 12, 13, 14 over a period T. The PWM cycle C is indicated in Figures 6 to 10 by vertical, dashed lines.

[0101] As can be seen in Figures 6 to 10, in the illustrated embodiments, the respective operating modes 12, 13, 14 are periodically repeated for twice the duration of the PWM cycle C. The states in the respective operating modes 12, 13, 14 are thus repeated periodically with a period T, which, for example, corresponds to twice the duration of the PWM cycle C for a duty cycle of 100%. The result is reduced amplitudes of the discharge currents during switching, as well as the distribution of the discharge currents across two PWM cycles C and thus two phases of the control of the power electronics 1. The result is a reduction of the so-called ripple currents in the drive train 200 and, in particular, in the vehicle electrical system 201. In addition to improved operation of the drive train 200, components of the power electronics 1, especially the capacitor 6, can thus be operated with further reduced ripple currents.

[0102] - 16 - smaller. This results in improved operation and more compact and cost-effective training of power electronics 1.

[0103] Figures 6 and 7 show the control of the half-bridges 2, 3, 4 using the first operating mode 12. More precisely, Figures 6 and 7 show the maintenance duration of the first operating mode 12 over a period T. In these embodiments, there is no overlapping connection of the consumers 51 to the vehicle electrical system 201. This means that only one of the consumers 51 is connected to and energized by the vehicle electrical system 101 at any given time. In the illustrated embodiments, as can be seen, for example, in Figure 6, the consumers 51 are connected to the vehicle electrical system 201 alternately and at equal time intervals. In the embodiment shown in Figure 6, the consumers 51 are connected to the vehicle electrical system 201 one after the other for a connection duration that corresponds to a maximum of one-eighth of the period T, with the connection durations being evenly distributed over the period T.This results in a periodically uniform current being supplied to the consumers 51. The alternating connection of the consumers 51 to the vehicle electrical system 101 means that the electrical energy converted into heat is distributed between both consumers 51. This leads, for example, to reduced wear of the power electronics 1.

[0104] In the embodiment shown in Figure 6, the consumers 51 are alternately connected to the vehicle electrical system 201 for one-eighth of the period T and disconnected from the vehicle electrical system 101 for the following seven-eighths of the period T. In the illustrated embodiment, the first consumer 51, 51a is connected to the vehicle electrical system 201 for the first eighth of the period T and disconnected from the vehicle electrical system 201 for the following seven-eighths of the period T. Furthermore, the second consumer 51, 51b is connected to the vehicle electrical system 201 for the fifth-eighth of the period T and disconnected from the vehicle electrical system 201 for the remaining eighths of the period T.

[0105] In the embodiment shown in Figure 7, the consumers 51 are alternately connected to the vehicle electrical system 201 for one sixteenth of the period T, disconnected from the vehicle electrical system 201 for the following twelve sixteenths of the period T, and connected to the vehicle electrical system R.411726 for the following sixteenth of the period C.

[0106] - 17 -

[0107] In the illustrated embodiment, the first consumer 51, 51a is connected to the vehicle electrical system 201 for the first sixteenth and the thirteenth sixteenth of the period T and disconnected from it for the remaining sixteenth of the period T. Furthermore, the second consumer 51, 51b is connected to the vehicle electrical system 201 for the fifth and ninth sixteenth of the period T and disconnected from it for the remaining sixteenth of the period T.

[0108] In these embodiments, the converted energy E during a period T can thus be (1 / 5)TxP, where P corresponds to the power consumption of a consumer 51, i.e., the power consumption P in the first operating mode 12.

[0109] Figures 8 and 9 show an exemplary control of the half-bridges 2, 3, 4 using the second operating mode 13. In the illustrated embodiments, the loads 51 are operated in the second operating mode 13, i.e., energized in parallel, for at least six-eighths, i.e., three-quarters, of the period T. In the illustrated embodiments, each load 51 is connected to the vehicle electrical system 201 for a maximum of seven-eighths of the period T. Furthermore, the loads 51 are alternately disconnected from the vehicle electrical system 501, whereby only one of the loads 51 can be energized at a time, and thus the first operating mode 12 can be present.

[0110] In the embodiment shown in Figure 8, the respective consumer 51 is connected to the vehicle electrical system 201 for a total of seven eighths of the period T and disconnected from the vehicle electrical system 201 for the other eighth of the period T, wherein the disconnections of the consumers 51 from the vehicle electrical system 201 are equally spaced in time.

[0111] In the embodiment shown in Figure 9, each consumer 51 is connected to the vehicle electrical system 201 for a total of six-eighths of the period T and disconnected from the vehicle electrical system 201 for the other two-eighths of the period T, wherein one of the consumers 51 is disconnected from the vehicle electrical system 101 in each eighth of the period T. R.411726

[0112] - 18 -

[0113] In the control systems of the embodiments shown in Figures 8 and 9, the converted energy E during a period T can thus be (17 / 10)TxP, where P corresponds to the power consumption of a consumer 51 in the first operating mode 12.

[0114] Figure 10 shows the control of the half-bridges 2, 3, and 4 using the third operating mode 14. The third operating mode 14 is alternately activated and deactivated for a quarter of the period T, and thus for half of the PWM cycle C. In the illustrated embodiment, the third operating mode 14 is maintained for the first quarter of the period T, the consumers 2 are disconnected from the vehicle electrical system 101 for the following quarter of the period T, the third operating mode 14 is maintained for the next quarter of the period T, and so on.

[0115] When controlling the embodiment shown in Figure 10, the converted energy E during a period T can thus be (1 / 4)TxP, where P corresponds to the power consumption of a consumer 51.

[0116] The operation of the power electronics 1, and in particular the switching of the switching elements 10, 11, is preferably implemented by means of a computer program product containing corresponding instructions. Preferably, when the computer program product is executed by a computer (not shown) and / or by the control unit 101, the instructions cause the computer and / or the control unit 101 to operate the power electronics 1 as described.

Claims

R.411726 - 19 - Claims 1. Method for operating power electronics (1) for converting electrical energy from a vehicle electrical system (201) of a powertrain (200) into heat by means of a consumer arrangement consisting of two consumers (51). (50), which generate heat when energized, - with three parallel-connected half-bridges (2, 3, 4), - wherein each half-bridge (2, 3, 4) has a center tap (9) for connecting to the consumer arrangement (50) and a series connection of a first switching element (10) for connecting the center tap (9) to a first mains connection (5, 5a) for connecting to the vehicle electrical system (201) and a second switching element (11) for connecting the center tap (9) to a second mains connection (5, 5b) for connecting to the vehicle electrical system (201), - wherein the switching elements (10, 11) of the half-bridges (2, 3, 4) are switched in a first operating mode (12) such that only one of the consumers (51) is electrically connected to the vehicle electrical system (201), so that only this consumer (51) is energized, - wherein the switching elements (10, 11) of the half-bridges (2, 3, 4) are switched in a second operating mode (13) such that the consumers (51) are connected in parallel and connected to the vehicle electrical system (201), so that the consumers (51) are powered in parallel.

2. Method according to claim 1, characterized in that the switching elements (10, 11) of the half-bridges (2, 3, 4) are switched in a third operating mode (14) such that the consumers (51) are connected in series and to the vehicle electrical system (201), so that the consumers (51) be powered serially.

3. Method according to claim 1 or 2, characterized in that, R.411726 - 20 - - that the center tap (9) of a first of the half-bridges (2) is connected in operation to a first first consumer connection (53, 53a) of a first of the consumers (51 , 51 a), - that the center tap (9) of a second of the half-bridges (3) is connected in operation to a first secondary consumer connection (53, 53b) of a second of the consumers (51 , 51 b), - that the center tap (9) of a third of the half-bridges (4) is connected in operation to a second first consumer connection (54, 54a) of the first consumer (51 , 51 a) and a second second consumer connection (54, 54b) of the second consumer (51 , 51 b), - that in the first operating mode (12): • the first switching element (10) of the first half-bridge (2) is closed and the second switching element (11) of the first half-bridge (2) is opened, • the first switching element (10) and the second switching element (11) of the second half-bridge (3) are opened, • the first switching element (10) of the third half-bridge (4) is opened and the second switching element (11) of the third half-bridge (4) is closed, • or • the first switching element (10) and the second switching element (11) of the first half-bridge (2) are opened, • the first switching element (10) of the second half-bridge (3) is closed and the second switching element (11) of the second half-bridge (3) is opened, • the first switching element (10) of the third half-bridge (4) is opened and the second switching element (11) of the third half-bridge (4) is closed, - that in the second operating mode (13): • the first switching element (10) of the first half-bridge (2) is closed and the second switching element (11) of the first half-bridge (2) is opened, • the first switching element (10) of the second half-bridge (3) is closed and the second switching element (11) of the second half-bridge (3) is opened, • the first switching element (10) of the third half-bridge (4) is opened and the second switching element (11) of the third half-bridge (4) is closed. R.411726 - 21 - 4. Method according to claims 2 and 3, characterized in that in the third operating mode (14): - the first switching element (10) of the first half-bridge (2) is closed and the second switching element (11) of the first half-bridge (2) is opened, - the first switching element (10) of the second half-bridge (3) is opened and the second switching element (11) of the second half-bridge (3) is closed, - the first switching element (10) and the second switching element (11) of the third half-bridge (4) are opened.

5. Method according to any one of claims 1 to 4, characterized in that, - that the switching elements (10, 11) of the half-bridges (2, 3, 4) are controlled with a PWM signal, - that the respective operating mode (12, 13, 14) is periodically repeated for twice the length of a PWM cycle (C).

6. Method according to claim 5, characterized in that the consumers (51) are periodically supplied with a uniform current.

7. Computer program product comprising instructions which, when executed by a computer, cause the computer to operate the power electronics (1) according to any one of claims 1 to 6.

8. Power electronics arrangement (100) for converting electrical energy from a vehicle electrical system (201) of a powertrain (200) into heat by means of a consumer arrangement (50) consisting of two consumers (51) which generate heat when energized. - with three parallel-connected half-bridges (2, 3, 4), - wherein each half-bridge (2, 3, 4) has a center tap (9) for connecting to the consumer arrangement (50) and a series connection of a first switching element (10) for connecting the center tap (9) to a first R.411726 - 22 - has a mains connection (5, 5a) for connecting to the vehicle electrical system (201) and a second switching element (11) for connecting the center tap (9) to a second mains connection (5, 5b) for connecting to the vehicle electrical system (201), - with a control unit (101) connected to the power electronics (1) which is designed to operate the power electronics (1) according to the method according to one of claims 1 to 6.

9. Power electronics arrangement according to claim 8, characterized in that, - that the power electronics arrangement (100) includes the consumer arrangement (50), - that the center tap (9) of a first of the half-bridges (2) is connected to a first first consumer connection (53, 53a) of a first of the consumers (51 , 51 a), - that the center tap (9) of a second of the half-bridges (3) is connected to a first second consumer connection (53, 53b) of a second of the consumers (51 , 51 b), - that the center tap (9) of a third of the half-bridges (4) is connected to a second first consumer connection (54, 54a) of the first consumer (51 , 51 a) and a second second consumer connection (54, 54b) of the second consumer (51 , 51 b).

10. Power electronics arrangement according to claim 8 or 9, characterized in that the power electronics (1) is arranged inside an inverter (6).

11. Power electronics arrangement according to one of claims 8 to 10, characterized in that at least one of the consumers (51) is a power resistor (52).

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