WO2008065067A1

WO2008065067A1 - Electronic drive system for a vehicle unit

Info

Publication number: WO2008065067A1
Application number: PCT/EP2007/062803
Authority: WO
Inventors: Elmar Dilger; Isidro Corral Patino; Roland Karrelmeyer
Original assignee: Robert Bosch Gmbh
Priority date: 2006-12-01
Filing date: 2007-11-26
Publication date: 2008-06-05
Also published as: EP2097972A1; DE102006056855A1

Abstract

The invention relates to an electric drive system for a unit of a vehicle, particularly a motor vehicle, comprising a vehicle wiring system, a controllable bridge arrangement, and an electric machine. The vehicle wiring system encompasses several redundant vehicle networks while the bridge arrangement encompasses several bridge transitions, each of which is connected to a different vehicle network. Furthermore, the electric machine is designed as a multiple polyphase machine that has several independent groups of polyphase windings, each group being connected to a different bridge transition. The invention further relates to a method for operating an electric drive system.

Description

description

Title Electronic drive system for an aggregate of a vehicle

The invention relates to an electric drive system for an aggregate of a vehicle, in particular motor vehicle, with a vehicle electrical system, a controllable bridge arrangement and an electric machine. The drive system according to the invention is used in particular for a fault-tolerant drive, for example as an electric power steering drive in motor vehicles. It is crucial that even with the occurrence of errors at least a limited operation is maintained, so that a very high level of security is given.

State of the art

From the prior art drives are known which has a voltage supply which is connected via a controllable bridge circuit with three bridge branches to an electric motor. The windings of the electric motor are connected in star, wherein the neutral point is connected to a midpoint of the power supply. In the bridge branches a total of six controllable transistors are arranged, which are operated by means of field-oriented control in the pulse width modulation method. By means of a suitable control strategy, limited motor operation is possible even if one phase fails. For particularly safety-relevant drives, however, the known arrangement is not sufficiently suitable.

Disclosure of the invention

The electrical drive system according to the invention for an aggregate of a vehicle, in particular a motor vehicle, has an on-board network system, a controllable bridge arrangement and an electrical machine, wherein the on-board network system has a plurality of redundant vehicle systems and the bridge arrangement a plurality of bridge circuits connected to the on-board network, each bridge circuit being connected to another on-board network, and wherein the electric machine is designed as a multi-phase multiple machine comprising a plurality of independent groups of polyphase windings, the groups being connected to the bridge circuits, each group being connected to a different bridge circuit. Due to the redundant vehicle electrical system, the redundant bridge circuits and the formation of the electrical machine as a multiple machine with multiple independent groups of polyphase windings extremely high reliability is realized. Even with the failure of two phases, a limited operation of the electric machine is maintained. Even if, for example, a vehicle electrical system fails, the machine can continue to be operated by means of another or the other vehicle electrical system. The operation of the multiple machine is much more efficient than the use of multiple electric machines working on a common shaft. This is a new topology of a fault-tolerant drive system. At the same time a compact design is given. The invention is particularly suitable for the use of fault-tolerant actuators, in particular in the area of break-by-wire and steer-by-wire systems.

According to a development of the invention, it is provided that the bridge arrangement has two bridge circuits. In particular, it can be provided that the multiple machine is designed as a dual machine and has two groups of polyphase windings.

Each group is preferably formed in three phases. Alternatively, however, more or less than three phases may be provided. The above-described redundancy in the on-board networks and in the bridge circuits can of course also be greater than two. In the method according to the invention more or less than three phases can also be used, in particular an asynchronous machine with four phases.

It is particularly preferred if the electrical machine is designed as an asynchronous machine. The windings of each group of the electrical machine are preferably connected in star. In particular, the star points of the groups are connected to centers of DC buses. The respective DC bus is preferably between the associated electrical system and the associated bridge circuit. Each star point is assigned a different center point.

To control the electric drive system according to the invention, the controllable bridge arrangement is connected to a field-oriented control. The controllable bridge circuit is controlled in particular by means of pulse width modulation.

Furthermore, it is advantageous if the bridge arrangement has controllable electronic links, wherein each electronic link has at least two series-connected electrical switching elements, in particular transistors. This is also a redundant power amplifier topology, that is,

Transistor shorts will have no effect on the system due to the series connection.

Brief description of the drawings

The drawings illustrate the invention with reference to an embodiment, in which:

Figure 1 is a circuit diagram of an electric drive system and an associated, designed as a dual machine

Multiple machine

2 shows a bridge arrangement with redundantly arranged bridge elements in the electronic switching elements,

FIGS. 3 to 9 diagrams,

Figures 10 and 11 diagrams and

Figures 12 and 13 diagrams. Embodiment (s) of the invention

1 shows an electric drive system 1, which is used for driving an aggregate of a vehicle, in particular a motor vehicle. The

Drive system 1 has an electrical system 2 with two electrical systems B1 and B2. The vehicle electrical systems B1 and B2 each have, among other things, a rechargeable battery.

The drive system 1 of Figure 1 further has a bridge arrangement 3, which has a bridge circuit 4 and a bridge circuit 5. Each bridge circuit 4, 5 is formed in three phases, so that in each case three bridge branches 6 and three bridge branches 7 are provided. In each of the bridge branches 6, 7 are two controllable electronic elements 8, wherein each electronic element 8 composed of two series-connected electronic switching elements 9. The switching elements 9 are formed as transistors.

The two bridge circuits 4 and 5 are each connected via a DC bus 10, 10 'to the respectively associated electrical system B1 or B2. A multiple machine 12 designed as a dual machine 11 is electrically connected to the bridge arrangement 3 with its windings U1, V1 and W1 or U2, V2 and W2. The windings U1, V1 and W1 are connected between the electronic links 8 to the corresponding bridge branches 6 of the bridge circuit 4; Accordingly, the windings U2, V2 and W2 are connected to the respective bridge branches 7 of the bridge circuit 5. There are multiphase windings, wherein the windings U1, V1 and W1 form a group 13 and the windings U2, V2 and W2 form a group 14. The windings of the groups 13 and 14 are each connected in star, wherein the neutral point S1 is connected to a center 15 of the DC bus 10 and the neutral point S2 to a center 16 of the DC bus 10 '. Furthermore, the phase lines of the two groups 13 and 14 are connected via phase current detection elements to a field-oriented regulation 17 in connection with which the individual transistors of the respective bridge circuit 4, 5 are driven. In both DC buses 10 and 10 'each have two support capacitors 18 and 19 connected to the center 15 and 16, respectively.

From the above, it can be seen that the dual-structure multiple machine 12 has two groups 13, 14 of three phases.

Preferably, this dual machine 11 is wound only in one layer. In each groove, only two strands of equal phase are routed to prevent interphase shorts in the length of the machine. Within each group 13, 14, the dual machine 11 has eight turns per phase. With this design, the machine achieves a high degree of safety, as required, for example, when used as a steer-by-wire actuator.

FIG. 2 illustrates in detail again the design of the bridge branches 6 and 7 of the two bridge circuits 4 and 5, respectively. It can be seen that each electronic element 8 is composed of two switching elements 9 connected in series. Each switching element 9 is designed as a transistor which is connected to a freewheeling diode 20. By the series connection, a redundancy is created, so that even when short circuiting of a transistor, the respective bridge circuit 4 or 5 remains fully functional.

In the following, the regulation, ie the operation of the electric drive system 1, will be discussed in more detail, and the case will be examined in which two phases fail at the same time. The peculiarity is that due to the redundant design of the overall arrangement and appropriate control strategy, the multiple machine 12 remains limited functional, so a high level of security is guaranteed.

For the application of the invention, for example, in a steer-by-wire actuator, designed as an electric motor dual machine 11 must be position-controlled, in particular by means of field-oriented control. If two phases fail, the machine can continue to operate. The following derivation clarifies this, wherein the electric machine is exemplified as a dual three-phase asynchronous machine. Since the dual machine can be considered as two groups 13, 14 of three-phase machines, there are two possibilities for the failure of two phases:

Option 1: The two failed phases belong to different phase groups (groups 13, 14).

In this case, each phase group is considered in isolation. The new angles to which the remaining current phasors are to be directed can be deduced from the separate consideration of each isolated group 13, 14, ie, from the interruption of one phase in a three-phase asynchronous machine, the angles of the remaining two phases per group become the dual Derived machine.

3 shows on the left the current phasors of a faultless, known three-phase asynchronous machine and on the right the new setpoint angles of the current phasors b and c in the event of failure of the phase a of the dual machine according to the invention. By employing these current phasors, the strength of the magnetic field (MMF) is maintained equal before and after the phase interruption. Both phasors should have a module V3 of the value before the phase break.

FIG. 4 shows on the left the current phasors for the dual machine. Group 13 is shifted 30 electrical degrees from group 14.

On the right in FIG. 4 the phasors are shown after interruption of the phases a1 and b2.

Before the phase break, the following applies to the currents in all phases:

θ = wt

The MMF generated by these streams is:

After introducing equation (7) and equation (15) into equation (13),

MMF = 3NIe ^ß (\ 6)

FIG. 4 shows, on the right, the new angles which each phase group is to adapt, namely after the failure of one phase per group. The respective angles can be derived as it was done for the general three-phase asynchronous machine. It is still missing to determine the modulus of the resulting phasors. This is derived below:

If phase a1 and b2 fail, the generated MMF is valid for the following:

To ensure a continuous Betheb, the MMF should be maintained equal:

MMF = MMF '(18;

Then:

The mathematical representation of the phasors recorded on the right in FIG. 4 can be seen in equations (20) to (25):

The currents in equation (19) are replaced by those in equations (20) - (25):

Isolating the part with e ^jθ from equation (20)

The result of equation (21) shows that the modulus of the respective phasors after interruption of one phase per group is V3 of the original normal state module. This will lead to minimum current flooding through the statoric phases.

As option 2, the two interrupted phases belong to the same phase group:

In this case, the angle and modulus of the remaining phasors are derived, which will lead to the same MMF distribution after the phase break.

As an example, the interruption of phases a1 and b1 is assumed. When equating the MMF before equation (16) and after the phase break applies:

After separating real and imaginary parts:

In equation system (23) and (24), there are four degrees of freedom. These can be reduced to two by the following assumptions:

The resulting equation system is:

Then:

FIG. 5 shows the resulting current phasors of the dual asynchronous machine; left: normal condition; right: after interruption phases a1 and b1.

Unlike for option 1, the current phasors in this case will have different modules to produce the same MMF as for the normal state. It should also be noted that the current will flow from the sum of the four remaining phases through the star point cable (variant 1). Now another variant is derived for which the current through the

Star point cable will flow and leads to an optimal power distribution in the machine.

Forcing the same modules for all streams of healthy phases: The currents in the machine are defined as follows:

Introducing the current forms from equation (33) to equation (36) in equation (14), then comparing according to equation (18) and isolating the part with e ^jθ from that with e ^"jθ .

Separating the real part from the imaginary part in equations (37) and (38):

The system of equations from (39) to (40) has four equations and five unknowns. If the angle of the single healthy phase of group 13 is kept constant, the following solution for the system is found:

FIG. 6 shows the resulting current phasors of the dual asynchronous machine for this variant. Left: Normal condition. Right: After interruption of phases a1 and b1 with optimized energy distribution in the machine.

If the current phasors are added together (FIG. 6, right), the current is determined by the star point cable whose value is 1, 9924 of the modulus of a phase for the normal state.

Now, a control takes place in case of failure of two phases of a conventional six-phase asynchronous machine:

Option 1: The two interrupted phases belong to different phase groups:

In this case, each phase group is considered in isolation, which leads exactly to the same results as in the dual machine

Option 2: The two interrupted phases belong to the same phase group:

The procedure continues as for the dual machine with the phases a1 and b1 interrupted. Then the equation system is:

The solution for the system is:

FIG. 7 shows the resulting current phasors before and after

Phase interruption for the proposed control strategy, namely, Figure 7 shows the current phasors of the conventional six-phase asynchronous machine. Left: Normal condition; Right: After interruption of phases a1 and b1 with optimized energy distribution in the machine.

The results are as follows:

Figure 8 shows the results after the onset of the control strategy in the failure of two phases of the same group for the dual machine. After 0.2 seconds, the phases a1 and d are interrupted. The small

The difference between the power modules after the control strategy has been applied to zero current at the star point can be seen in FIG.

In Figure 8, the stator currents Lstat (A), the rotor speed W _R (rad / s), the torque M _d (Nm) and the current l _s (A) through the neutral cable in the dual asynchronous machine after interruption of two phases of the same group and the zero current represented by the neutral point cable. Furthermore are still the rotor target speed ω _s (rad / s) and a load torque M _L shown.

The optimal control strategy for interrupting two phases of the same group becomes possible after the star point cable has been inserted. This results in an optimal energy distribution in the machine. FIG. 10 shows the results of the method. All phases have the same module. The current through the neutral cable is 1, 9924 greater than that through one phase of the machine for the normal state.

FIG. 9 shows the stator currents lstat (A), the rotor speed W _R (rad / s), the torque M _d (Nm) and the current l _s (A) through the star point cable in the dual ASM after interruption of two phases of the same group and the optimal energy distribution in the machine.

FIG. 10 once again shows the overall design of the system according to the invention with star point cables, wherein, with respect to FIG. 1, it is additionally indicated that the two star circuits of the dual three-phase asynchronous machine are arranged at an angle with respect to each other. In addition, a rotary encoder 21 is still shown, which passes information about rotor position and rotor speed to the controller 17.

Figure 11 shows an alternative embodiment of the proposed system employing a H-bridge inverter.

FIG. 12 shows on the left side a dual six-phase asynchronous machine, the position of the magnetic axes being illustrated. The angular offset is ττ / 6. To the right is shown an illustration of a conventional six-phase asynchronous machine in which the magnetic axes are offset by ττ / 3.

FIG. 13 illustrates the position of the magnetic axes of a four-phase asynchronous machine. Variants are shown on the left and in the middle when the machine is wound asymmetrically on a layer. Right shows symmetrical magnetic axes when the machine is wound on two layers.

Claims

claims

1. Electric drive system for an aggregate of a vehicle, in particular a motor vehicle, with an electrical system, a controllable bridge arrangement and an electric machine, characterized in that the electrical system comprises a plurality of redundant electrical systems and that the bridge arrangement comprises a plurality of bridge circuits which are connected to the vehicle electrical system, wherein each bridge circuit is connected to another electrical system, and that the electrical machine is designed as a multi-phase multiple machine having a plurality of independent groups of polyphase windings, the groups are each connected to the bridge circuits and wherein each group is connected to a different bridge circuit.

2. Drive system according to claim 1, characterized in that the bridge arrangement comprises two bridge circuits.

3. Drive system according to one of the preceding claims, characterized in that the multiple machine is designed as a dual machine and has two groups of polyphase windings.

4. Drive system according to one of the preceding claims, characterized in that each group is formed in three phases.

5. Drive system according to one of the preceding claims, characterized in that the electric machine is an asynchronous machine.

6. Drive system according to one of the preceding claims, characterized in that the windings of each group of the electric machine are connected in star.

7. Drive system according to one of the preceding claims, characterized in that the star points of the groups are connected to centers of DC buses.

8. Drive system according to one of the preceding claims, characterized in that the respective DC bus between the associated electrical system and the associated bridge circuit is located.

9. Drive system according to one of the preceding claims, characterized in that the controllable bridge arrangement is connected to a field-oriented control.

10. Drive system according to one of the preceding claims, characterized in that the controllable bridge arrangement means

Pulse width modulation is controlled.

11. Drive system according to one of the preceding claims, characterized in that the bridge arrangement has controllable electronic elements, wherein each electronic element has at least two series-connected electrical switching elements, in particular transistors.

12. A method for operating, controlling and / or regulating an electric drive system, in particular according to one or more of the preceding claims.