Method for actuating an electrical circuit arrangement comprising at least one switching element, a control unit, an electrical circuit device, and a motor vehicle

Abstract

A method for actuating an electrical circuit arrangement including at least one switching element. The switching element is actuated by a driver circuit as a function of switching-signal information for switch-on and switch-off. The switching-signal information is continuously determined and a switch-on period and signal position information are specified respectively for at least one switching-signal time window with a fixed duration. The position of the switch-on signal within the switching-signal time window is specified by the signal position information for a switch-on signal that results from a switch-on period that is less than the duration of the switching-signal time window.

Claims

1. A method for actuating an electrical circuit arrangement comprising: actuating at least one switching element by a driver circuit based on switching-signal information for switch-on and switch-off; continuously determining the switching-signal information; and specifying a switch-on period and a signal position for at least one switching-signal time window, the at least one switching-signal time window having a fixed duration; wherein the switch-on period is less than the fixed duration of the at least one switching-signal time window and the signal position describes a position of the switch-on signal relative to the at least one switching-signal time window, wherein a switching frequency of the at least one switching element driven by the driver circuit differs from a computation frequency at which the switching-signal information is continuously determined, and wherein the signal position is selected from a group of possible positions, the group of possible positions comprising: a switch-off edge position, whereby the switch-on signal begins directly at a beginning of the at least one switching-signal time window; a switch-on edge position, whereby the switch-on signal ends directly at an end of the at least one switching-signal time window; a center-synchronous position, whereby the switch-on signal is centered within the at least one switching-signal time window; and an inverse position, whereby a first part of the switch-on signal begins directly at the beginning of the at least one switching-signal time window, a second part of the switch-on signal ends directly at the end of the at least one switching-signal time window, and a switch-off phase is provided between the first part and the second part of the switch-on signal.

2. The method according to claim 1, wherein the switching-signal information contains the switch-on period and the signal position for two or more switching-signal time windows.

3. The method according to claim 1, wherein the switching frequency is lower than the computing frequency, and wherein the signal position of several successive switch-on signals is selected such that a total switch-on pulse results that is continuous over a corresponding several switching-signal time windows.

4. The method according to claim 1, wherein the switching frequency is higher than the computing frequency, and wherein several successive switch-on signals are generated, each with a central arrangement in the switching-signal time window.

5. The method according to claim 1, wherein the electrical circuit arrangement comprises several switching elements which are actuated by the driver circuit as a function of one or more pieces of switching-signal information for switch-on and switch-off.

6. The method according to claim 1, wherein the electrical circuit arrangement is a three-phase pulse-controlled inverter.

7. The method according to claim 1, wherein the switching-signal information is determined by a control unit based on at least one measured value.

8. The method according to claim 1, wherein the switching-signal information is determined based on an operating point of the electrical circuit arrangement and/or an operating point of a machine connected to the electrical circuit arrangement.

9. The method according to claim 7, wherein the at least one measured value is a stator current of an electric machine connected to the electrical circuit arrangement.

10. The method according to claim 7, wherein the at least one measured value is an angular position of an electric machine connected to the electrical circuit arrangement.

11. The method according to claim 1, wherein the switch-on period prescribes a duty cycle of the at least one switching element which defines a proportion of the at least one switching-signal time window during which the at least one switching element is switched to be conductive.

12. The method according to claim 2, wherein the switch-on period and/or the signal position of a first switching-signal time window contained in the switching-signal information differs from that of a second switching-signal time window contained in the switching-signal information.

13. The method according to claim 4, wherein the switching frequency is higher than the computing frequency, and wherein the switching-signal information contains the switch-on period and the signal position for two or more switching-signal time windows.

14. The method according to claim 13, wherein the switch-on period of a first switching-signal time window contained in the switching-signal information differs from that of a second switching-signal time window contained in the switching-signal information.

15. A control unit for actuating a driver circuit for an electrical circuit arrangement comprising at least one switching element, wherein the control unit is configured to: actuate the at least one switching element by the driver circuit based on switching-signal information for switch-on and switch-off; continuously determine the switching-signal information; and specify a switch-on period and a signal position for at least one switching-signal time window, the at least one switching-signal time window having a fixed duration; wherein the switch-on period is less than the fixed duration of the at least one switching-signal time window and the signal position describes a position of the switch-on signal relative to the at least one switching-signal time window, wherein a switching frequency of the at least one switching element driven by the driver circuit differs from a computation frequency at which the switching-signal information is continuously determined, and wherein the signal position is selected from a group of possible positions, the group of possible positions comprising: a switch-off edge position, whereby the switch-on signal begins directly at a beginning of the at least one switching-signal time window; a switch-on edge position, whereby the switch-on signal ends directly at an end of the at least one switching-signal time window; a center-synchronous position, whereby the switch-on signal is centered within the at least one switching-signal time window; and an inverse position, whereby a first part of the switch-on signal begins directly at the beginning of the at least one switching-signal time window, a second part of the switch-on signal ends directly at the end of the at least one switching-signal time window, and a switch-off phase is provided between the first part and the second part of the switch-on signal.

16. An electrical circuit device, comprising a driver circuit, an electrical circuit arrangement comprising at least one switching element, and the control unit according to claim 15.

17. A motor vehicle comprising the electrical circuit device according to claim 16.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further advantages and details of the invention result from the exemplary embodiments described below and from the drawings. These are schematic representations and show the following:

(2) FIG. 1 an exemplary embodiment of a motor vehicle according to the invention;

(3) FIG. 2 an exemplary embodiment of an electrical circuit device according to the invention, comprising a control unit according to the invention for executing an exemplary embodiment of a method according to the invention;

(4) FIG. 3 diagram for showing the different positions of a switch-on signal within a switching-signal time window;

(5) FIG. 4 diagram for showing the different positions of a switch-on signal within a switching-signal time window;

(6) FIG. 5 diagram for showing the different positions of a switch-on signal within a switching-signal time window;

(7) FIG. 6 diagram for showing the different positions of a switch-on signal within a switching-signal time window;

(8) FIG. 7 a diagram for showing a switch-on signal which describes a switching element that is permanently switched on within a switching-signal time window;

(9) FIG. 8 a diagram for showing a switch-on signal, which describes a switching element that is permanently switched off within a switching-signal time window;

(10) FIG. 9 a diagram for showing a first operating state of a switching element actuated by means of the method according to the invention;

(11) FIG. 10 a diagram for showing a second operating state of a switching element actuated by means of the method according to the invention; and

(12) FIG. 11 a diagram for showing a third operating state of a switching element actuated by means of the method according to the invention.

DETAILED DESCRIPTION

(13) FIG. 1 shows an exemplary embodiment of a motor vehicle 1. The motor vehicle 1 comprises an electrical circuit device 2 and a control unit 3, which is designed to actuate an electrical circuit arrangement 4 of the electrical circuit device 2, which electrical circuit arrangement comprises at least one switching element. The electrical circuit arrangement 4 is used to convert a direct voltage, which is provided by a traction energy storage device 5 of the motor vehicle, into a particularly three-phase alternating voltage for operating an electric traction motor 6 of the motor vehicle 1. A reverse conversion of a current in generator operation of the electric traction motor 6 is also possible. The electric traction motor can be designed, for example, as a synchronous machine or as an asynchronous machine. The traction energy storage device 5 can, for example, be a battery, for example a high-voltage battery.

(14) An electrical circuit device 2 is shown in FIG. 2. In addition to the control unit 3 and the electrical circuit arrangement 4, which is designed as a three-phase pulse-controlled inverter, the electrical circuit device 2 also comprises a driver circuit 7, which is used to actuate the switching elements S.sub.i of the circuit arrangement 4. The connections between the driver circuit 7 and the gate terminals of the switching elements S.sub.1-S.sub.6 are not shown for reasons of clarity. The switching elements S.sub.1-S.sub.6 are implemented as transistors, for example as metal-oxide-semiconductor field-effect transistors or as bipolar transistors with an insulated gate.

(15) The control unit 3 continuously determines switching-signal information, which is transmitted from the control unit 3 to the driver circuit 7 via an interface. Depending on the switching-signal information, the driver circuit 7 actuates at least some of the switching elements S.sub.i of the circuit arrangement 4. The circuit arrangement 4 is connected to the traction energy storage device 5, which is not shown here, at terminals DC.sup.+ and DC.sup.−.

(16) The control unit 3 is configured to actuate the driver circuit 7 for actuating at least one switching element S.sub.i of switching elements S.sub.1-S.sub.6 of the electrical circuit arrangement 4. The respective switching element S.sub.i is actuated by the driver circuit 7 as a function of the switching-signal information for switch-on and switch-off. The switching-signal information is continuously determined by the control unit 3 with a computing frequency. The length of time that lies between the determination of two pieces of switching-signal information is limited by the maximum possible computing frequency and thus by the computing power of the control unit 3.

(17) The control unit 3 can determine the switching-signal information, for example, as a function of at least one measured value. For this purpose, the control unit 3 can be connected, for example, to one or more measuring means, which are assigned to the circuit arrangement 4 and/or the electric machine 6. The measuring means can be, for example, a stator current measuring means 8 and/or an angular position measuring means 9, which accordingly transmit a stator current measured value or an angular position measured value to the control unit 3.

(18) The signal position information specifies a switch-on period and signal position information for at least one switching-signal time window with a fixed duration. In this case, the position of the switch-on signal within the switching-signal time window is specified by the signal position information for a switch-on signal that results from a switch-on period that is less than the duration of the switching-signal time window. The positions of a group of possible positions of a switch-on signal 10 within a first switching-signal time window 11 are shown below in FIGS. 3 to 8 by way of example. The time is shown on the abscissa and the signal level of the switch-on signal 10 is shown on the ordinate. No switch-on signal 10 is shown for the second switching-signal time window 12, which is also within the computing period T.sub.calc.

(19) A diagram is shown in FIG. 3 which represents a switch-off edge position of the switch-on signal 10. In the present exemplary embodiment, there are two switching-signal time windows 11, 12 within the computing time of the control unit 3 designated by T.sub.calc, i.e. the reciprocal of the computing frequency of the control unit 3. For the first switching-signal time window 11, a switch-on signal 10 is shown, which is in a switch-off edge position. The switch-on signal 10 begins directly at the beginning of the switching-signal time window 11. The switching signal 10 is assigned a switch-on period DC.sub.1 which, in the present example, corresponds to 75% of the duration of the switching-signal time window 11. This means that the switch-on period T.sub.e of the switch-on signal 10 corresponds to 75% of the duration of the switching-signal time window 11 or a duty cycle of 75%. Accordingly, the switch-on signal 10 is switched on at the beginning of the switching-signal time window 11 for 75% of the duration of the switching-signal window 11 in a switch-on phase, followed by a switch-off edge 13. There is a switch-off phase 14 between the switch-off edge 13 and the end of the switching-signal time window 11. The switch-on phase is formed by a first signal level of the switching signal, which differs from a second signal level that characterizes the switch-off phase 14.

(20) A switch-on edge position of the switch-on signal 10 is shown in FIG. 4. In this example, too, the switch-on period DC.sub.1 is 75% of the duration of the switching-signal time window 11. In the switch-on edge position, the switch-on signal 10 ends directly at the end of the switching-signal time window 11. At the beginning of the switching-signal time window 11, there is a switch-off phase 14, which is followed by a switch-on edge 15, and the switch-on signal 10 for the remaining duration of the switching-signal time window 11 corresponding to the switch-on period is at the first signal level, which indicates a switched-on switching element S.sub.i.

(21) FIG. 5 shows a center-synchronous position of the switch-on signal 10. In this position, the switch-on signal is in the middle of the switching-signal time window 11. In this example, too, the switch-on period is 75% of the duration of the switching-signal time window 11. There is a switch-off phase 14 after the switch-off edge 13 or before the switch-on edge 15 of the switch-on signal 10.

(22) FIG. 6 shows an inverse position of the switch-on signal 10 in the switching-signal time window 11, with a first part 16 of the switch-on signal 10 beginning directly at the start of the switching-signal time window 11 and a second part 17 of the switch-on signal 10 ending at the end of the switching-signal time window 11. There is a switch-off phase 14 between the first part 16 and the second part 17 of the switch-on signal 10. In this exemplary embodiment too, the switch-on signal is switched on for 75% of the duration of the switching-signal time window 11.

(23) There is a switch-off edge 13 of the switching signal 10 between the first part 16 and the switch-off phase 14. Accordingly, there is a switch-on edge 15 between the switch-off phase 14 and the second part 17 of the switch-on signal 10. The switch-off phase 14 lies in the middle of the switching-signal time window 11, so that overall the first part 16 and the second part 17 of the switch-on signal 10 result in the required switch-on period DC.sub.1 of 75%.

(24) The positions shown above can advantageously be numbered, as shown by way of example by value PosDC.sub.1 as a 2-bit binary number. This makes it possible for the signal position information to be transmitted from the control unit 3 to the driver circuit 7 as a numerical value PosDC.sub.1. Correspondingly, an assignment rule can be stored in the driver circuit 7, which assignment rule carries out an actuation of switching element S.sub.1, for example, according to the signal position information PosDC.sub.1 and the further transmitted switch-on period DC.sub.1.

(25) It may be provided that switching signal S.sub.4, which forms a half-bridge with switching element S.sub.1, is switched on in the switch-off phases 14 of the switch-on signal 10, thus resulting in a complementary switching operation for switching element S.sub.4. Alternatively, switching element S.sub.4 can also be switched by means of its own, assigned switching-signal information. Correspondingly, this also applies to further high-side switching elements S.sub.2 and S.sub.3 and to corresponding further low-side switching elements S.sub.5 and S.sub.6. In addition to the positions shown in FIGS. 3 to 6, a switch-on period that corresponds to 100% of the duration of the switching-signal time window and a switch-on period that corresponds to 0% of the duration of the switching-signal time window are also possible.

(26) FIG. 7 shows the case in which the switch-on period corresponds to 100% of the duration of the switching-signal time window 11. Accordingly, the switch-on signal 10 is at the switching level associated with a switched-on state of switching element S.sub.i for the complete period of the time window 11. A separate position does not have to be assigned to the switch-on signal 10 since the value of the switch-on signal is constant for the entire duration of the switching-signal time window 11. In this case, no signal position information or any signal position information can be transmitted.

(27) FIG. 8 accordingly shows a switch-on signal for a switch-on period of 0% of the duration of the switching-signal time window 11. The switch-on signal 10 is accordingly at the switching level corresponding to a switched-off state of switching element S.sub.i for the complete time duration of the switching-signal time window 11 so that no position or any position can be assigned in this case as well.

(28) As already indicated above in FIGS. 3 to 8, the switching-signal time window 11 within the computing period T.sub.Calc is followed by at least one further signal switching window 12, which can accordingly be assigned its own switch-on period DC.sub.2 and its own signal position information PosDC.sub.2 of a switch-on signal 10 within the second switching-signal time window 12. This makes it possible to combine the previously illustrated individual states of the switching signals 10 with one another in order to obtain different actuations of the at least one switching element S.sub.i.

(29) The switch-on period DC.sub.2 and the signal position information PosDC.sub.2 are determined as common switching-signal information, in particular from the same measured values of the measuring means 8, 9. In this case, it can be provided that switch-on period DC.sub.2 is equal to switch-on period DC.sub.1, as a result of which the computing effort in determining the switching-signal information for the two switching-signal time windows 11, 12 can be kept low. It is also possible to use a different switch-on period, for example according to a predetermined ratio or an assignment rule stored in the control unit 3. The same position or a position different than signal position information PosDC.sub.1 can be specified for signal position information PosDC.sub.2 of the switch-on signal 10 in the second switching-signal time window 12, resulting in different combinations of switch-on signals or switching frequencies of the switched switching element S.sub.i, as shown below.

(30) FIG. 9 shows an example of the switching of one of the switching elements S.sub.i. A center-synchronous switch-on signal 10 is output for each of the switching-signal time windows 11, 12 during a computing period T.sub.n. The switch-on signal 10 has a switch-on period of DC.sub.1 for switching-signal time window 11, and the switch-on signal 10 has a switch-on period of DC.sub.2 for second switching-signal time window 12. The respective period T.sub.S of the switch-on operation is half as long as the period T.sub.n of the computing operation in which the switching-signal information is determined. This makes it possible for two switching operations of switching element S.sub.i to be carried out for each piece of switching-signal information determined. The switching frequency f.sub.s=1/T.sub.s with which the switching element S.sub.i is switched is consequently twice as high as the frequency with which the control unit 3 calculates the switching-signal information.

(31) The switch-on signals 10 which are center-synchronous in the individual switching-signal time windows can also continue to be output as switching signals in a center-synchronous position for a subsequent computing period T.sub.n+1. A new switch-on period DC.sub.1 and/or DC.sub.2 for the switching-signal time window 11, 12 can be selected for computing period T.sub.n+1 as a function, for example, of new measured values evaluated by the control unit 3.

(32) This operating state makes it possible to carry out high switching frequencies of the switching element S.sub.i even with a low computing frequency f.sub.Calc=1/T.sub.n. Two or more successive center-synchronous pulses with the same current or angle information are calculated by the control unit 3 in one computing period. This operating state makes it possible, for example, to operate the electric machine 6 and the circuit arrangement 4 with minimal loss, which can be present particularly at high switching frequencies that can exceed the computing frequency f.sub.Calc of the control unit.

(33) Due to the illustrated doubling of the switching frequency of the switching element S.sub.i, the higher switching frequency f.sub.s can also be implemented during operation of the electric machine 6, so that losses due to harmonics or the like can be advantageously avoided, which leads to an increase in the efficiency of the electric machine 6. When using the electrical circuit device 2 in the motor vehicle 1, the range of the motor vehicle 1 in an electric driving mode, in which the electric traction motor 6 is supplied from the traction energy storage device 5, can thus advantageously be increased.

(34) The computing time T.sub.n can be 100 μs, for example, depending on the configuration of the control unit 3. It can be provided, for example, that the control unit has a load of 80% and thus calculates switching-signal information within 80 μs, with new switching-signal information being transmitted to the driver circuit 7 via the interface every 100 μs. The switching-signal information for the switching elements S.sub.i can be transmitted to the driver circuit within the computing time window of 100 μs and can be used accordingly by this driver circuit for actuating the switching elements S.sub.i. A switching frequency of 20 kHz can be achieved when two switching-signal time windows are used per computing period. In this way, a better simulation of a sinusoidal voltage curve can advantageously be achieved than would be the case with purely center-synchronous actuation in a time window that is twice as long and thus at 10 kHz. Advantageously, the frequency increase is also greater than the 12.5 kHz switching frequency, which can be achieved with an increase in utilization to 100%.

(35) FIG. 10 shows a second actuation of a switching element S.sub.i operated using the method. In this case, the switching period T.sub.S of the switching element S.sub.i is twice as long as the computing period T.sub.n or T.sub.n+1. In this actuation mode, a switch-on signal with the switch-on period DC.sub.1 is output in the first computing period T.sub.n in the first switching-signal time window 11, which switch-on period is in the switch-on edge position.

(36) A switched-on switch-on signal with DC.sub.2 equal to 100% is correspondingly output continuously in the subsequent switching-signal time window 12. Correspondingly, a permanently switched-on switch-on signal with a switch-on period of DC.sub.1 equal to 100% is output for the second computing period T.sub.n+1 for the first signal switching window 11. In the subsequent switching-signal time window 12, a switch-on signal 10 with a switch-on period DC.sub.2 of, for example, 75% is output in the switch-off edge position. This leads to a total switch-on pulse 18 being output over the two computing periods T.sub.n and T.sub.n+1. Due to the width of this pulse over a number of switching-signal time windows 11, 12, the switching frequency f.sub.s=1/T.sub.s is half the frequency f.sub.n=1/T.sub.n. The switch-on edge 15 of the total switch-on pulse 18 is set at the beginning in the first switching-signal time window 11, and the switch-off edge 13 is correspondingly set in the last switching-signal time window 12 of the second computing period T.sub.n+1.

(37) A third actuation state of one of the switching elements S.sub.i is shown in FIG. 11. In this actuation state, a switch-on signal 10 is output in the position of the switch-on edge and with a switch-on period DC.sub.1 of, for example, 40% in the first switching-signal time window 11. A switch-on signal 10 is correspondingly set in the switch-off edge position, likewise with a switch-on period DC.sub.2 of 40%, in the subsequent, second switching-signal time window 12 of the first computing period T.sub.n. A switch-on signal 10 is accordingly output in the first switching-signal time window 11 with a switch-on period DC.sub.1 in the subsequent computing period T.sub.n+1, and a further switch-on signal is output in the switch-off edge position with the switch-on period DC.sub.2 in the second switching-signal time window 12.

(38) It is possible for switch-on periods DC.sub.1 and DC.sub.2 in the second computing period T.sub.n to be equal, but to differ from periods DC.sub.1 and DC.sub.2 in the switching-signal time window 11, 12 belonging to the first computing period N. For computing period T.sub.n+1, the switching-signal information is determined on the basis of new measured values transmitted to the control unit 3, so that a different pulse width of the total switch-on pulse 19 resulting herein can result. In this exemplary embodiment, the switching frequency f.sub.s=1/T.sub.s is equal to the computing frequency f.sub.n=1/T.sub.n.

(39) This makes it possible to implement different actuation cycles using the method for actuating at least one switching element S.sub.i. In addition to a standard case in which switch-on period DC.sub.1 is equal to switch-on period DC.sub.2, the method according to the invention can also be used to generate total switch-on pulses 19 that are asymmetrical, i.e. in which a different switch-on period DC.sub.2 is provided in the second switching-signal time window 12 than provided for the first switching-signal time window 11.

(40) It is possible that further actuation operations are generated, in particular using the inverse switch-on signal shown in FIG. 6 and the permanent off state shown in FIG. 8. In this way, further actuation signals can be generated, which can be further adapted in their time profile to the optimal operating conditions of the electrical circuit arrangement 4 and/or the electric machine 6. It is also possible for three or more switching-signal time windows to be used in addition to the example in which two switching-signal time windows 11, 12 are used per computing period T.sub.n. In particular, this also enables the switching frequency f.sub.s to be increased by more than a factor of 2 compared to the computing frequency f.sub.n. The further positions of the switch-on signals 10 shown in FIGS. 3 to 6 make it possible to achieve an actuation state in such cases in which the switching frequency f.sub.s is equal to the computing frequency f.sub.n or in which the switching frequency f.sub.s is less than the switching frequency f.sub.n.

(41) In addition to the positions shown, further positions are also possible which, for example, contain more than one complete switch-on pulse, i.e. two or more pairs of switch-on edges and switch-off edges. The switch-on period for the switching-signal time window can be divided into two or more partial switch-on signals, which are combined, in particular over several switching-signal time windows, to form one overall periodic signal. An increase in the switching frequency can also be achieved within a switching-signal time window per computing period by means of one or more such positions. In such an embodiment, the number of possible positions increases, so that greater or more complex signal position information is required.

(42) The method advantageously enables the highest possible switching frequency of the switching elements S.sub.i to be achieved with a predetermined, maximum processor utilization of a processor of the control unit 3. This can advantageously avoid the need for comparatively expensive control units 3 with powerful processors to operate the circuit arrangement 4 or to energize the electric machine 6. Furthermore, it is advantageously made possible that a sufficient number, for example ten, switching operations of the switching elements S.sub.1-S.sub.6 can still be carried out per period of the fundamental wave of the alternating voltage to be generated if fundamental waves with a higher frequency are to be generated or more switching operations can be used for a given fundamental frequency of the alternating voltage.