METHOD FOR CONNECTING MULTIPLE BATTERY CELLS OF A BATTERY AND BATTERY SYSTEM HAVING A BATTERY WITH MULTIPLE BATTERY CELLS AND MULTIPLE BATTERY-CELL-MONITORING MODULES WHICH ARE RESPECTIVELY ASSIGNED TO A BATTERY CELL

Abstract

The present invention relates to a method for connecting multiple battery cells (21) of a battery (11), wherein the multiple battery cells (21) can be connected in series to one another, and a single first control variable P1 and a single second control variable P2 are predefined for all the battery cells (21). In this context, in order to generate a desired output voltage of the battery (11), each battery cell (21) is electrically coupled to the battery (11) with a corresponding first probability, defined as a function of the first control variable P1, and in each case electrically decoupled from the battery (11) with a corresponding second probability, defined as a function of the second control variable P2. In addition, a value of the first control variable P1 and a value of the second control variable P2 are respectively predefined repeatedly with an update frequency which is dependent on the desired output voltage of the battery (11) which is to be generated.

Claims

1. A method for connecting multiple battery cells (21) of a battery (11), wherein the multiple battery cells (21) are connectable in series with one another and a single first controlled variable P1 and a single second controlled variable P2 are prescribed for all battery cells (21), the method comprising: producing a desired output voltage (Us) of the battery (11) is by electrically coupling each battery cell (21) to the battery (11) with an applicable first probability, defined on the basis of the first controlled variable P1, and electrically decoupling each from the battery (11) with an applicable second probability, defined on the basis of the second controlled variable P2, wherein a value of the first controlled variable P1 and a value of the second controlled variable P2 are each repeatedly prescribed at an update frequency (AR) that is dependent on the desired output voltage (Us) to be produced from the battery (11).

2. The method as claimed in claim 1, wherein the value of the first controlled variable P1 and the value of the second controlled variable P2 are altered such that a magnitude (|ΔU|) of a control error (ΔU) that is defined as the difference between a currently produced output voltage (U) of the battery (11) and the desired output voltage (Us) to be produced from the battery (11) is minimized.

3. The method as claimed in claim 1, wherein whenever the value of the first controlled variable P1 is updated, an applicable evenly distributed random process is carried out for each battery cell (21) electrically decoupled from the battery (11), which random process interprets the present value of the first controlled variable P1 or an applicable first variable, determined on the basis of the present value of the first controlled variable P1, as the probability that is currently to be used for the applicable battery cell (21).

4. The method as claimed in claim 2, wherein the update frequency (AR) is dependent on the control error ΔU, on a frequency of an AC voltage to be produced as the desired output voltage (Us) of the battery (11), or both.

5. The method as claimed in claim 2, wherein the update frequency (AR) is a monotonously rising function of the magnitude (|ΔU|) of the control error ΔU, is a monotonously rising function of the frequency of the AC voltage to be produced as the desired output voltage (Us) of the battery (11), or both.

6. The method as claimed in claim 1, wherein the update frequency (AR) does not exceed a maximum update frequency limit value, which is the same as a maximum transmission frequency of a transmission channel (31) used for transmitting the value of the first controlled variable P1 and the value of the second controlled variable P2, does not fall below a minimum update frequency limit value, or both and wherein a minimum update frequency limit value is used that is such that a rate of change of the switching state, which is defined as the quotient between a number of switching state changes, obtained as the sum of a number of battery cells (21) from the multiple battery cells (21) that are electrically coupled to the battery (11) within a predefined period and a further number of battery cells (21) from the multiple battery cells (21) that are electrically decoupled from the battery (11) within the predefined period, and a length of the predefined period, does not fall below a minimum limit value for the rate of change of the switching state.

7. A battery system (100) having a battery (11) having multiple battery cells, wherein each battery cell (21) has a respective associated battery cell monitoring module (22) arranged in the battery (11) and the multiple battery cells (21) are connectable in series with one another by means of the associated battery cell monitoring modules (22), and a central control unit (130) arranged in the battery system (100) is designed to prescribe a single first controlled variable P1 and a single second controlled variable P2 for all battery cells (21) and to provide said controlled variables for all battery cell monitoring modules (22), wherein a desired output voltage (Us) of the battery (11) is produced by virtue of each battery cell monitoring module (22) being designed to electrically couple the associated battery cell (21) to the battery (11) with an applicable first probability, defined on the basis of the first controlled variable P1, and to electrically decouple said associated battery cell from the battery (11) with an applicable second probability, defined on the basis of the second controlled variable P2, wherein the central control unit (130) is designed to repeatedly prescribe a value of the first controlled variable P1 and a value of the second controlled variable P2 at an update frequency (AR) that is dependent on the desired output voltage (Us) to be produced from the battery (11).

8. The battery system (100) as claimed in claim 7, wherein the central control unit (130) is designed to alter the value of the first controlled variable P1 and the value of the second controlled variable P2 such that a magnitude (|ΔU|) of a control error (ΔU) that is defined as the difference between a currently produced output voltage (U) of the battery (11) and the desired output voltage (Us) to be produced from the battery (11) is minimized.

9. The battery system (100) as claimed in claim 7, wherein each battery cell monitoring module (22) is designed to carry out an applicable evenly distributed random process whenever the associated battery cell (21) is electrically decoupled from the battery (11) and the value of the first controlled variable P1 is updated, which random process interprets the present value of the first controlled variable P1 or an applicable first variable, determined on the basis of the present value of the first controlled variable P1, as the first probability that is currently to be used for the associated battery cell (21), to carry out an applicable evenly distributed further random process whenever the associated battery cell (21) is electrically coupled to the battery (11) and the value of the second controlled variable P2 is updated, or both which further random process interprets the present value of the second controlled variable P2 or an applicable second variable, determined on the basis of the present value of the second controlled variable P2, as the second probability that is currently to be used for the associated battery cell (21).

10. The battery system (100) as claimed in claim 7, wherein the update frequency (AR) used by the central control unit (130) is dependent on the control error (ΔU) on a frequency of an AC voltage to be produced as the desired output voltage (Us) of the battery (11), or both.

11. The battery system (100) as claimed in claim 7, wherein the update frequency (AR) used by the central control unit (130) is a monotonously rising, function of the magnitude (|ΔU|) of the control error (ΔU), monotonously rising function of the frequency of the AC voltage to be produced as the desired output voltage (Us) of the battery (11), or both.

12. The battery system as claimed in claim 7, wherein the update frequency (AR) used by the central control unit (130) does not exceed a maximum update frequency limit value, which is the same as a maximum transmission frequency of a transmission channel (31) used for transmitting the value of the first controlled variable P1 and the value of the second controlled variable P2, does not fall below a minimum update frequency limit value, or both, wherein the control unit (130) is designed to use a minimum update frequency limit value that is such that a rate of change of the switching state, which is defined as the quotient between a number of switching state changes, obtained as the sum of a number of battery cells (21) from the multiple battery cells (21) that are electrically coupled to the battery (11) within a predefined period and a further number of battery cells (21) from the multiple battery cells (21) that are electrically decoupled from the battery (11) within the predefined period, and a length of the predefined period, does not fall below a minimum limit value for the rate of change of the switching state.

13. The method as claimed in claim 1, wherein whenever the value of the second controlled variable P2 is updated, an applicable evenly distributed further random process is carried out for each battery cell (21) electrically coupled to the battery (11), which further random process interprets the present value of the second controlled variable P2 or an applicable second variable, determined on the basis of the present value of the second controlled variable P2, as the second probability that is currently to be used for the applicable battery cell (21)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. Like components also have the same reference symbols used for them. In the drawings:

[0024] FIG. 1 is a battery system known from the prior art,

[0025] FIG. 2 is a control engineering equivalent circuit diagram for the battery system depicted in FIG. 1,

[0026] FIG. 3 is a profile, depicted as a function of a time, of a currently produced output voltage of a battery of the battery system depicted in FIG. 1 in comparison with a further profile, depicted as a function of time, of a desired output voltage to be produced from the battery of the battery system depicted in FIG. 1,

[0027] FIG. 4 is a battery system according to a first embodiment of the invention, and

[0028] FIG. 5 is a dependency between a magnitude of a control error and an update frequency of a value of a first controlled variable and a second controlled variable, wherein the control error is predefined as a difference between a currently produced output voltage of a battery of the battery system depicted in FIG. 4 and an output voltage to be produced from said battery and wherein each battery cell of this battery is electrically coupled to the applicable battery on the basis of the first controlled variable and is electrically decoupled from the applicable battery on the basis of the second controlled variable.

DETAILED DESCRIPTION

[0029] FIG. 4 shows a battery system 100 according to the invention based on a first embodiment of the invention. Like the battery system depicted in FIG. 1 and known from the prior art, the battery system 100 according to the invention comprises a battery 11 having multiple battery cell units 20 that each comprise a battery cell 21 and a battery cell monitoring module 22 associated with the battery cell 21. In this case too, the multiple battery cells 21 are connectable in series with one another by means of the associated battery cell monitoring modules 22. Further, a central control unit 130 of the battery system 100 according to the invention is also designed to provide controlled variables P1, P2 of each battery cell monitoring module 22 of the battery 11 via a transmission channel in the form of the communication link 31 and to alter the value of the first controlled variable P1 and the value of the second controlled variable P2 such that a magnitude of a control error that is defined as a difference between a currently produced output voltage U of the battery 11 and a desired output voltage Us to be produced from the battery 11 of the battery system 100 according to the invention is minimized.

[0030] Unlike in the case of the battery system depicted in FIG. 1, the value of the first controlled variable P1 and the value of the second controlled variable P2 are repeatedly prescribed by the central control unit 130 of the battery system 100 according to the invention at a variable update frequency. Further, the central control unit 130 of the battery system 100 according to the invention is designed to use an update frequency that is a monotonously rising, linear function of the magnitude of said control error.

[0031] Even in the case of the battery system 100 according to the invention, each battery cell monitoring module 22 is designed to carry out an applicable evenly distributed random process that interprets the respective present value of the first controlled variable P1 as the present value of a first probability of the associated battery cell 21, when electrically decoupled from the battery 11, being electrically coupled to the battery 11 and that interprets the respective present value of P2 as the present value of a second probability of the associated battery cell 21, when electrically coupled to the battery 11, being electrically decoupled from the battery 11.

[0032] FIG. 5 shows a linear dependency between a variable update frequency AR used by the control unit 130 of the battery system 100 according to the invention and the magnitude |ΔU| of the aforementioned control error ΔU. FIG. 5 reveals that when the magnitude of the control error ΔU changes between a minimum magnitude value |ΔU1| of the control error ΔU and a maximum magnitude value |ΔU2| of the control error ΔU, the update rate AR changes between a minimum update rate value AR1 and a maximum update rate value AR2. In this case, the magnitude |ΔU| of the control error ΔU is a linear monotonously rising function of the update frequency AR.

[0033] Besides the written disclosure above, reference is hereby additionally made to the depiction in FIGS. 4 and 5 for further disclosure of the invention.