WO2009098124A1 - Method for controlling an on-board power supply network and corresponding on-board power supply network - Google Patents

Abstract

The invention relates to a method for controlling an on-board supply network which comprises at least two subnetworks with different voltage levels for a motor vehicle which is supplied with power by a generator step-up chopper. In a first operating mode, the lower voltage level subnetwork is connected to the generator. In a second operating mode, at least one higher voltage level subnetwork is connected to the generator or generator step-up chopper. The invention further relates to an on-board supply network that comprises a plurality of subnetworks with different voltage levels.

Description

 15. 01. 2008

ROBERT BOSCH GMBH, 70442 STUTTGART

description

title

Method for controlling an electrical vehicle electrical system and electrical system

State of the art

The invention relates to a method for controlling an electrical system according to the preamble of claim 1 and an electrical system according to the preamble of the claim. The method is particularly applicable to a vehicle electrical system of a motor vehicle. For the supply of the consumers of the on-board network, this usually comprises a storage device for electrical energy, in particular a battery, as well as a driven by the engine of the motor vehicle generator, which converts mechanical energy into electrical energy and this provides for the electrical system. The electrical system of a modern motor vehicle includes a plurality of electrical consumers who make very different demands on the electrical system, for example, in terms of reliability, performance, voltage quality or desired voltage level. With a conventional electrical system, hereinafter referred to as the base unit network, for example, with only one nominal voltage is operated by about 14 volts, these different requirement profiles, especially from a cost point of view, are increasingly difficult to meet.

An attempt has already been made to couple modified subnetworks with a base on-board network in order to be able to meet different requirements of electrical consumers in this way. If the voltage levels of the base-board network and the coupled sub-network differ, the coupling between the named networks was carried out with the aid of DC / DC converters. However, this solution is relatively expensive and expensive. High costs and space requirements arise in particular due to the transformers and chokes used in the converters, which are large and heavy at high currents and outputs. For example, the energy-carrying inductor of a choke boost converter must be dimensioned for the maximum transient peak current that occurs.

Another known approach is to realize a free generator operation for the supply of high current loads. In this case, the generator voltage varies at least temporarily in a range of, for example, 12 V to 42 V. However, a significant disadvantage of this solution is that the voltage in free generator operation is not regulated and the electrical loads therefore have to be designed for a wide voltage range.

To generate the energy required in the motor vehicle claw pole generators are usually used today. These are three-phase generators whose output current is rectified by means of a diode bridge, since the vehicle electrical system is operated with direct current. Such a Three-phase generator comprises a field coil, which is traversed by the field current. The field current is regulated by means of a voltage regulator so that the

Output voltage of the generator is independent of the speed of the generator is approximately constant. The amount of voltage that is controlled is usually chosen to be suitable for charging the battery. Depending on various conditions, the voltage is approximately between 12 and 14.5 V. In a modern electrical system, there is the problem that a vehicle electrical system voltage of 12 V is no longer sufficient for a large number of consumers or consumers with high power requirements. In addition to a so-called base-board network with the aforementioned voltage level, therefore, sub-electrical systems are provided which operate with a higher vehicle electrical system voltage of 42 V, for example. In particular, to supply the consumers in these sub-board networks solutions are known in which a generator is controlled to a higher output voltage of, for example, around 42 volts. This higher voltage is then provided directly to the sub-board network or the consumers arranged in this sub-board network, which are designed for this higher output voltage. The lower voltage required for charging the battery and / or supplying low-voltage loads is then usually derived from the higher voltage by means of a DC-DC converter. Conventional DC / DC converters require in addition to power transistors, diodes and capacitors also inductive components and are therefore relatively expensive.

This applies to transformers with transformer and smoothing reactor and non-floating reactor with a storage choke. In a design for high current load or power requirement these are Components big heavy and expensive. For example, the energy-carrying throttle of a throttle boost converter must be dimensioned according to the maximum transient peak current occurring.

DE 198 45 569 A1 discloses a device and a method for controlling a generator, for example a claw-pole generator, with which the rectifier bridge adjoining the generator can be short-circuited for a short time, as a result of which

Ständerinduktivitäten energy is stored, which leads to higher strand voltages. By a suitable choice of the drive frequency for a transistor, which enables the short-circuiting of the diode bridge, an output voltage of the generator can be set to a desired one

Set voltage level, which is significantly higher than the conventional vehicle electrical system voltage.

Disclosure of the invention

Technical task

The invention has for its object to provide an improved electrical system, which makes it possible to reliably supply a variety of electrical consumers with different requirements and this is inexpensive to implement.

Technical solution

Based on a vehicle electrical system of the type mentioned, this object is achieved by the features mentioned in claim 1. The invention is based on the recognition that an optimal operation of a multi-subnetwork comprehensive on-board network is made possible by the choice of different operating modes, wherein in a first Operating mode only one configured for a low voltage sub-network (base board network) with the generator or generator plate and in a second operating mode, a designed for a higher voltage subnet to the generator or to the generator plate are connected.

Advantageous effects

The electrical system provided by the inventive solution allows the supply of numerous electrical consumers, some of which in a so-called

Base board network with a conventional comparatively low voltage of about 14V and which are arranged in part in at least one other sub-board network, the voltage of which differs from the base on-board network, in particular is higher than this and, for example, 42V. The solution according to the invention thus advantageously makes it possible to feed in electrical energy both into a base on-board network and into at least one further sub-board network. Notwithstanding previously known solutions, the supply of said vehicle electrical system is not done with individual DC / DC converters that provide the required voltages for the subnets, but with the help of a generator with turn-off Hochsetzfunktion. In this case, the generator provided for the energy supply can advantageously be operated as a conventional generator for the supply of the base on-board network. In addition, the generator with downstream generator plate can optionally feed electrical energy into a subnet or multiple subnets, which are designed for a higher voltage.

Another advantage is that when fed into a subnetwork whose voltage is higher than the voltage of the base-board network, the output power of the generator can be greatly increased. Another advantage is that the cost can be significantly reduced compared to a vehicle electrical system with one or more DC / DC converters, since the generator controller can take over the voltage conversion for the supply of sub-networks with higher voltage. In this case, by means of the boost function of the generator generator energy can be fed into a sub-board network with higher voltage of 42V, for example, even at very low speed of the generator. Another advantage is that the voltage can be regulated to a predefinable value when fed into a sub-board network or multiple sub-electrical systems with a higher voltage. The switchover between the different operating modes, ie the supply of the base-board network or the supply of the sub-network, takes place in an advantageous manner

Way by means of controllable switches. By interposing a low-cost voltage converter low power between a designed for a higher voltage subnet and designed for a lower voltage subnet the latter subnet can continue to be advantageous continuously supplied with energy. Particularly advantageously, a subsystem of the vehicle electrical system designed for a higher voltage level can also comprise an energy store in the form of a double-layer capacitor. This embodiment is particularly suitable for storing the energy obtained by recuperation when braking the vehicle. Further advantages will become apparent from the description, the dependent claims and the drawings.

Brief description of the drawings

Embodiments of the invention are explained below with reference to the drawing. Showing:

Figure 1 shows a vehicle electrical system for different voltages with a generator plate and a DC / DC converter; FIG. 2 shows a first exemplary embodiment of a generator actuator;

Figure 3 shows a second exemplary embodiment of a

Generator plate;

4 shows a first embodiment of a vehicle electrical system with two coupled subnets;

Figure 5 is a diagram showing the

Output power as a function of the speed of the generator actuator when fed into a subnetwork of the electrical system;

Figure 6 is another diagram showing the

Output power as a function of the speed of the generator actuator;

Figure 7 is a diagram showing the efficiency as a function of speed;

8 shows a second embodiment of a vehicle electrical system with two coupled subnets;

Figure 9 shows a third embodiment of a vehicle electrical system with three coupled subnets;

FIG. 10 shows a fourth exemplary embodiment of a vehicle electrical system with two coupled subnetworks;

Figure 11 shows a fifth embodiment of a vehicle electrical system with two coupled subnets. Embodiments of the invention

In Figure 1, the essential for understanding the invention components of a vehicle electrical system for a motor vehicle with multiple voltages and a generator are shown first. The generator G, for example a

Claw pole generator, comprising the stator inductances Ll, L2, L3 and the resistors Rl, R2, R3 representing the winding resistances. The generator G generates the line voltages US1, US2, US3, which are formed from the pole wheel voltages U, U2, U3 and the voltages across the resistors R1, R2, R3 and the stator inductances L1, L2, L3. These voltages lead to currents II, 12, 13, which are rectified via the diode bridge DB and form the output current IG of the generator G, which serves to supply the consumers in the electrical system. The regulation of

Generator G is carried out with the aid of a voltage regulator R, which controls the field current IF through the field winding F so that adjusts a predetermined voltage. The voltage regulator R input signals E are supplied, for example, different voltages and / or currents, the speed of the generator G, etc. Furthermore, the voltage regulator R is able to output output signals A, with the aid of such switches or the like can be operated. The generator G is followed by a circuit SCH, which here comprises a transistor T, a diode D and a capacitor C. The circuit SCH allows a control of the generator G by the transistor T, which is parallel to the diode bridge DB, temporarily short-circuits the diode bridge DB. The switching state of the transistor T is controlled for example by a pulse width modulation stage, which is integrated in the controller R. Short-circuiting the diode bridge DB with the aid of the transistor T causes the energy flow from the generator G to become the components of the vehicle electrical system following in the circuit interrupted. As a result, energy in the stator inductances Ll, L2, L3 of the generator G is buffered. The diode Dl prevents that current flows back and short circuits the following components in the circuit. As soon as the transistor T is controlled in the blocking state, the energy stored in the stator inductances L1, L2, L3 is released in the form of induced voltages which add to the respective pole wheel voltages Ul, U2, U3. This results in a higher output voltage of the generator G. By appropriate control of the

For example, transistor T can be regulated to an output voltage of 42V. The capacitor C at the output of the circuit SCH is used for smoothing the pulsed output current. A circuit such as the circuit SCH is also, together with the generator, as

Generator generator or generator boost converter referred. If the regulation of the generator G by means of the circuit SCH is performed, arises, as already mentioned, at the output of the circuit SCH, a voltage which is substantially increased compared to the conventional voltage of the generator G. This part of the on-board network supplies consumers R4 who are designed for this high voltage and require high power. For example, it may be the window heating of a vehicle. For the operation of consumers R5, which are designed for a conventional, low voltage of a vehicle electrical system, for example, 12V, a reduction of the higher voltage level to this lower value is necessary. This is achieved with the aid of a DC-DC converter DCW. Each voltage level of the electrical system shown here has its own battery, which are designated in Figure 1 with B42 and B12. The disadvantage here is the necessary use of a voltage converter DCW, which in particular at a high power consumption in the low-voltage part of the electrical system large and expensive. The invention now shows solutions to how this disadvantage can be overcome by an improved electrical system.

Embodiments of the invention are explained in more detail below with reference to the drawing. In this case, the embodiments of generator actuators shown in FIG. 2 and FIG. 3 will first be discussed.

Figure 2 shows a first embodiment of a

Generator controller 20. The generator controller 20 includes a generator 10. Connected to the generator 10 is a circuit arrangement 10.1 which comprises three diodes D1, D2, D3, three transistors T1, T2, T3 and a capacitor C1. The transistors are preferably MOSFET

Transistors. At the terminal A1 of the circuit arrangement, a preferably pulse-width modulated control signal can be applied, which controls the transistors Tl, T2, T3 acting as switches. The circuit 10.1 then works as a boost converter, thus enabling the generation of a higher

Voltage for the supply of a sub-board network, which requires a higher voltage level than a base-board network.

FIG. 3 shows a second exemplary embodiment of a generator actuator 30. Its design substantially corresponds to that already shown in FIG

Generator plate. A generator 10 is followed by a B6 bridge DB for the rectification of the generator current. The subsequent circuit arrangement 10.2 comprises, in addition to a diode D7 and a capacitor Cl, a transistor T4, in particular a MOSFET transistor. The transistor T4 can be controlled via a control signal applied to the terminal A1, preferably a pulse-width-modulated control signal. In the case of pulse width modulated activation of the transistor T4 by the Control signal is at the output of the circuit 10.2 a high voltage U _G for the supply of a designed for a higher voltage level sub-electrical system.

FIG. 4 shows a first exemplary embodiment of a vehicle electrical system 40 with two coupled subnetworks BBN and TBN. The subnet BBN is also referred to as the base board network. BBN is a conventional electrical system that operates at the usual voltage of UB = 14V. The simplified basic on-board network BBN comprises a starter S, a first battery Bl and electrical consumers R _v . The subsystem TBN operated at the higher voltage UT> UB comprises a second battery B2 and at least one electrical consumer RT. This electrical load RT can also be representative of a larger number of electrical consumers that are supplied via the subnet TBN. Depending on the operation and the characteristics of the electrical load RT, the battery B2 can optionally be omitted or replaced by another storage for electrical energy, such as in particular a double-layer capacitor. For the supply of the two subnets TBN and BBN a generator with generator plate is provided. The generator plate 20 shown in FIG. 2 or the generator plate 30 shown in FIG. 3 can advantageously be used as the generator plate. The generator G of the generator actuator 20, 30 may be advantageously designed as a claw pole generator. The output voltage output by the generator plate 20, 30 is designated by UG.

Subnetwork TBN is connected to the output of generator generator 20, 30 via a diode D8 polarized in the direction of flow. The coupling of the subnet BBN with the generator plate 20, 30 via a switch Sl. This switch Sl can be designed, for example, as a semiconductor switch or as a relay be .

The operation of the embodiment shown in FIG. 4 will now be described. The mode of operation is exemplary of an embodiment of Figure 2 with the

Generator plate 20 shown. For the embodiment with the generator plate 30 applies accordingly. If the selected operating strategy requires that energy be fed into the subnetwork BBN, then the output voltage UG of the generator controller 20 becomes the operating voltage UB of this

Subnet regulated. So UG = UB. The switch Sl is closed in this case. In this first operating mode BML MOSFET transistors Tl, T2, T3 provided as switching means are controlled such that they are blocked. The generator current is rectified in this case by a passive B6 bridge. The B6 bridge consists of the diodes D1, D2, D3 and the drawbacks Tl.1, T2.1, T3.1, which are not shown in the drawing, of the MOSFET transistors T1, T2, T3 which are preferably used as switching means. In one embodiment, additional diodes may be provided for the rectification, which are connected in parallel with the MOSFET transistors Tl, T2, T3. The regulation of the output voltage UG of the generator actuator 20 is advantageously carried out with the aid of the exciter current of the generator G.

If, in a second operating mode BM2, electrical energy is to be fed into the subsystem TBN, the switch S1 is opened. Furthermore, the output voltage of generator generator 20 is regulated to a voltage UG = (UT + UD) with UD> 0. At low speed of the generator G to the MOSFET transistors Tl, T2, T3 of the generator actuator 20 are controlled so that electrical energy is fed into the subnet TBN. The control of the transistors Tl, T2, T3 can thereby advantageously by a pulse width modulated signal respectively. In this operating mode, the generator plate 20 is operated in Hochsetzfunktion. If the speed of the generator G is so high that the output voltage UG of the generator G reaches the voltage UT + UD with UD> 0 even with a passive B6 bridge circuit, then the boosting function of the

Generatorstellers 20 off. The MOSFET transistors Tl, T2, T3 are controlled in this operating mode so that they lock. The value of the speed at which the switching between the boost converter operation and the B6 rectification takes place can be carried out in accordance with the selected operating strategy

Variation of the excitation current of the generator G can be changed. When the boost function is switched off, the output voltage is only regulated by the exciter current of the generator G to the setpoint. The basic course of the output power as a function of the rotational speed of the generator G when fed into a subnetwork with U = UT> UB is shown for a fixed exciter current in FIG. An essential advantage of the invention is that it is possible to increase the output power and the efficiency when feeding energy into a subnetwork. By way of example, the possible increase in available output power is shown in Figure 6, which shows the output power as a function of the speed of the generator for some selected speed values. The left-hand bar represents the output power of a generator designed for an output voltage of 14 V when operating with a passive B6 bridge. The rightmost bar represents the output power of the same generator when fed into a subnetwork with an operating voltage of 42 V. At a speed of the generator G, for example, 6000 rev / min, the output power is many times higher. FIG. 7 further shows a diagram showing the efficiency as a function of the rotational speed of the generator G. The left-hand bar in the diagram in each case represents the efficiency of the generator G when it is fed into the subnetwork BBN with the operating voltage UB = 14V. The right-hand bar represents the efficiency when fed into the sub-network TBN with the higher voltage UT. While the efficiency at a speed of n = 1800 / min, the efficiency when fed into both subnetworks BBN, TBN is about the same, the diagram shows a significant increase in efficiency with increasing speed when fed into the subnet TBN.

The illustrated in Figure 8 second embodiment of a vehicle network consisting of two coupled subnets BBN and TBN differs from the embodiment shown in Figure 4 in that instead of the diode Dl, a switch S2 is provided.

Figure 9 shows an advantageous further embodiment of the

Invention, in addition to the supply of a base on-board network BBN, the supply of multiple subnets TBNl, TBN2 allows with deviating from the voltage of the base board network BBN voltages. The structure of the base on-board network BBN again corresponds to that which has already been described in connection with the exemplary embodiments described in FIG. 4 and FIG. The subnetwork TBN1 also essentially corresponds to the subnetwork TBN already shown in FIG. 4 and FIG. As FIG. 9 shows, a second subnetwork TBN2 is additionally provided in this development of the invention. This simplified illustrated

Subnetwork TBN2 comprises, in addition to a further switch S3, a battery B3 and an electrical consumer RT2. The voltages UT1, UT2 of the subnetworks TBN1, TBN2 may be different or the same height, depending on the requirements of the electrical consumers, RT1, RT2. However, it applies here that the voltages UT1, UT2 of the subnetworks TBN1, TBN2 are greater than the voltage UB of the base on-board network BBN. The control of the respective operating modes for the supply of the subnetworks BBN, TBN1, TBN2 takes place by means of the mentioned switches S1, S2, S3.

The illustrated in Figure 10 fourth embodiment of the invention is particularly suitable for the recovery of electrical energy by recuperation in the deceleration of the vehicle. Instead of a battery B2 can advantageously be used in the subnet TBN a capacitive energy storage, in particular a double-layer capacitor DCAP. During a braking operation, the generator plate 20, 30 converts the kinetic energy produced by the braking process into electrical

Energy around and feeds them into the subnet TBN, which is operated with a higher voltage UT. As already explained with reference to FIG. 6 and FIG. 7, the return of electrical energy with high power and high efficiency takes place in this case. Therefore, a very effective recuperation of braking energy is possible with this invention. The double-layer capacitor DCAP stores the recovered energy and can thus supply consumers RT, which require a higher operating voltage UT.

An advantageous further embodiment of the invention is illustrated below with reference to FIG. In contrast to the embodiment shown in FIG. G, a DC-DC converter (DC / DC converter DC1) is additionally provided here, which is connected between both subnetworks BBN and TBN. The DC-DC converter DCl converts the higher voltage UT of the sub-network TBN into the lower voltage UB of the sub-network BBN and feeds this with electrical energy which is taken from the double-layer capacitor DCAP1. Since the energy taken from the double-layer capacitor DCAP1 can be fed into the sub-network BBN over a relatively long period of time, it is possible to use a DC / DC converter DC1 with comparatively low power, which can be produced cost-effectively. In the context of the invention, further variants are conceivable which comprise, for example, more than two subnetworks with voltages deviating from the voltage of the base on-board network BBN. The components or components for the control of various subnetworks may be arranged separately from the generator controller 20, 30 or separately from the generator G. In a particularly advantageous and space-saving embodiment, however, these components can also be arranged in close spatial proximity to the generator plate 20, 30 or the generator G, in particular structurally integrated with these.

In addition to the interconnection of the phase windings of the generator G in delta connection, an interconnection of the phase windings can be provided in star connection.

The generator G can be advantageously designed as a claw pole generator. Alternatively, however, generators can be used in other construction, such as synchronous machines. It is also possible to use generators with more than three strand windings.

Claims

15. 01. 2008ROBERT BOSCH GMBH, 70442 STUTTGART claims 1. Method of controlling at least two Subnets (BBN, TBN, TBNl, TBN2) with different voltage levels comprehensive electrical system for a motor vehicle, which is powered by a generator plate (G, 10) with downstream generator plate with energy, characterized in that in a first Operating mode (BML) the sub-network (BBN) of the lower voltage level is connected to the generator plate and supplied with a voltage lying at a lower voltage level, and that in a second operating mode (BM2) at least one sub-network (TBN, TBNl, TBN2) with a higher voltage level connected to the generator or the generator plate and is supplied with a voltage lying on a higher voltage level. 2. The method according to claim 1, characterized in that the selection of the operating mode (BMl, BM2) is demand-dependent or load-dependent. 3. The method according to any one of the preceding claims, characterized in that when selecting the second operating mode (BM2), the output voltage of the generator actuator to the higher voltage level of the second operating mode (BM2) connected to the generator actuator sub-network (TBN, TBNl, TBN2) raised becomes. 4. The method according to any one of the preceding claims, characterized in that the higher output voltage for the second operating mode (BM2) by controlling a switch provided in the generator means (transistor Tl, T2, T3, T4) is generated. 5. The method according to any one of the preceding claims, characterized in that the control of the switching means (transistor Tl, T2, T3, T4) takes place with a pulse width modulated control signal. 6. The method according to any one of the preceding claims, characterized in that the designed for a low voltage level subnet (BBN) with a Voltage of about 14V and designed for a higher voltage level subnet (TBN, TBNl, TBN2) are operated with a voltage of U> 14V. 7. Electrical system with at least two subnetworks (BBN, TBN, TBNl, TBN2) for different voltage levels and a generator (G, 10) with generator plate for the supply of the electrical system, characterized in that switching means (Sl, S2, S3) are provided , each one subnet (TBN, TBNl, TBN2) of a certain voltage level to the output of the generator or the generator plate connect. 8. Electrical vehicle electrical system according to one of the preceding claims, characterized in that provided in at least one designed for a higher voltage level than the base vehicle network (BBN) subnet (TBN, TBNl, TBN2) of the electrical system as a charge storage a double-layer capacitor (DCAP, DCAPl) or batteries are. 9. Electrical vehicle electrical system according to one of the preceding claims, characterized in that a designed for a higher voltage level subnet (TBN, TBNl, TBN2) of the electrical system via a DC-DC converter (DCl) is connected to a subsystem designed for a lower voltage level (for example, base network BBN). 10. Electrical system according to one of the preceding claims, characterized in that the generator plate controllable switching means (transistor Tl, T2, T3, T4) comprises. 11. Electrical system according to one of the preceding Claims, characterized in that the switching means (transistor Tl, T2, T3, T4) are controllable by control signals.