Method for determining a cell current limit of a traction battery and an onboard network in a motor vehicle

Abstract

A method for determining a cell current limit for a traction battery and for an onboard network that is supplied with power by the traction battery in a motor vehicle with, respectively, a cell and onboard network voltage limiter using an integral feedback loop calculating a respective integral current term. The integral feedback loops of the two voltage limiters are interdependent, the integral current terms of the cell voltage limiter being transmitted to the integral feedback loop of the network voltage limiter and the integral terms of the voltage limiter of the network being transmitted to the integral feedback loop of the cell voltage limiter so as to determine a battery current limit that is common to the two limiters.

Claims

1. A method for determining a common battery current limit on the basis of a cell current limit for a traction battery and for an onboard network that is supplied with power by the traction battery in an electric or hybrid motor vehicle with, respectively, a cell voltage limiter and an onboard network voltage limiter, the cell voltage limiter receiving, for each cell, a predetermined cell voltage limit and an actual cell voltage and the onboard network limiter receiving a predetermined network voltage limit and an actual onboard network voltage, each limiter comprising a respective integral feedback loop calculating, for a loop n being the n.sup.th loop, a respective integral current term on the basis of the difference between the voltage limit and the actual voltage that are received by the limiter, wherein the integral feedback loops of the two voltage limiters are interdependent, the integral current terms of the cell voltage limiter being transmitted to the integral feedback loop of the voltage limiter of the network and the integral terms of the voltage limiter of the network being transmitted to the integral feedback loop of the cell voltage limiter so as to determine a common current limit common to the two voltage limiters.

2. The method as claimed in claim 1, wherein, to determine a current limit for each of the two voltage limiters, a correction is calculated for each limiter, this correction being based on an error that is dependent, respectively, on the difference between the predetermined voltage limit of the cell and the actual voltage of the cell and on the difference between the predetermined network voltage limit and the actual onboard network voltage, to which correction a value that is dependent on the integral current terms of the two voltage limiters is added.

3. The method as claimed in claim 2, wherein the correction based on the error of the cell voltage limiter is, for a given cell, calculated on the basis of the difference between the predetermined voltage limit of the cell and the actual voltage of the cell divided by the resistance of the cell and the correction based on the error of the onboard network voltage limiter is calculated on the basis of the difference between the predetermined network voltage limit and the actual onboard network voltage divided by the resistance of the battery.

4. The method as claimed in claim 1, wherein the value that is dependent on the integral current terms of the two voltage limiters is the minimum integral current term out of the two integral current terms of the two voltage limiters.

5. The method as claimed in claim 4, wherein, to the correction based on the error for each of the two voltage limiters, a value that is dependent on the integral current terms of the two voltage limiters is added so as to give a revised integral correction.

6. The method as claimed in claim 5, wherein the revised integral correction is limited, in a saturation block, between two, minimum and maximum, current values, the values of the revised integral correction that are lower than the minimum value or higher than the maximum value not being taken into account and being replaced, respectively, with the minimum value or the maximum value so as to give a limited revised integral correction, the limited revised integral correction giving, respectively, the current limit for each of the two limiters.

7. The method as claimed in claim 6, wherein an auxiliary correction, different from the correction based on the error, is carried out, the possibly limited, if required, revised integral correction and the auxiliary correction being added to obtain the battery current limit for each of the two voltage limiters.

8. The method as claimed in claim 3, wherein a first voltage limiter first executes the n.sup.th loop, the first voltage limiter using the integral current terms of the two voltage limiters taken for the n1.sup.th preceding loop, the second limiter using the integral current term from the n1.sup.th preceding loop as its integral term and the integral term of the n.sup.th loop from the first voltage limiter.

9. The method as claimed in claim 1, wherein the common current limit for the two voltage limiters is the minimum value for the loop n out of the cell current limit for the traction battery and the current limit for the onboard network.

10. A control assembly including a cell voltage limiter for a traction battery and a voltage limiter for an onboard network in an electric or hybrid motor vehicle, each voltage limiter imposing a current limit and including means for implementing, in a corrector, a feedback loop that is based on the respective error between a voltage limit and an actual voltage so as to determine a respective integral current term for each of the two limiters wherein the assembly implements a determining method as claimed in claim 1 and comprises means for transmitting the integral current terms of the cell voltage limiter to the means for implementing the feedback loop of the network voltage limiter and means for transmitting the integral terms of the network voltage limiter to the means for implementing the feedback loop of the cell voltage limiter.

11. The assembly as claimed in claim 10, comprising, for each of the two limiters, a comparison module determining a minimum integral term out of the integral current term associated with the cell voltage limiter and the integral current term associated with the onboard network limiter and a summation module for adding the integral term from the integral corrector of the limiter to said minimum integral term determined by the comparison module, a saturation block limiting a revised integral correction from the summation module between two, minimum and maximum, values.

12. The method as claimed in claim 2, wherein, to the correction based on the error for each of the two voltage limiters, a value that is dependent on the integral current terms of the two voltage limiters is added so as to give a revised integral correction.

13. The method as claimed in claim 3, wherein, to the correction based on the error for each of the two voltage limiters, a value that is dependent on the integral current terms of the two voltage limiters is added so as to give a revised integral correction.

14. The method as claimed in claim 5, wherein an auxiliary correction, different from the correction based on the error, is carried out, the possibly limited, if required, revised integral correction and the auxiliary correction being added to obtain the battery current limit for each of the two voltage limiters.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features, aims and advantages of aspects of the present invention will become apparent from reading the following detailed description and with reference to the appended drawings, which are given by way of nonlimiting examples and in which:

(2) FIG. 1 is a schematic representation of an electric motor vehicle having a traction battery supplying power both to a high-voltage network and to an onboard network in the motor vehicle, the control method according to an aspect of the present invention being able to be implemented in such a motor vehicle;

(3) FIG. 2 is a schematic representation of one implementation of a method for determining a battery current limit by comparing a current limit calculated, respectively, by a cell voltage limiter for a traction battery and a voltage limiter for an onboard network in an electric or hybrid motor vehicle, this method being according to the prior art;

(4) FIG. 3 is a schematic representation of one embodiment of the implementation of a method for determining a battery current limit in a cell voltage limiter for the traction battery in an electric or hybrid motor vehicle for the purpose of determining and imposing a battery current limit, this method being according to an aspect of the present invention, the cell voltage limiter for the battery and the onboard network voltage limiter being interconnected;

(5) FIG. 4 is a schematic representation of one embodiment of the implementation of a method for determining a battery current limit in a voltage limiter for the onboard network in an electric or hybrid motor vehicle for the purpose of determining and imposing a battery current limit, this method being according to an aspect of the present invention, the cell voltage limiter for the battery and the onboard network voltage limiter being interconnected;

(6) FIG. 5 is a schematic representation of one embodiment of the implementation of the step of determining a common current limit for the battery voltage limiter shown in FIG. 3 and the onboard network voltage limiter shown in FIG. 4, this step being able to be included in a method according to an aspect of the present invention, the minimum value out of the cell current limit and the onboard network current limit then being taken as the common current limit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) With reference to all of these figures, an aspect of the present invention relates to a method for determining a cell current limit Lim I C for a traction battery 1 and for an onboard network Lim I RB that is supplied with power by the traction battery 1 in an electric or hybrid motor vehicle, via a control assembly comprising, respectively, a cell voltage limiter and an onboard network voltage limiter. This is shown in FIGS. 3 to 5 for an n.sup.th loop, in which the n or n1 in brackets refers to the loop preceding the n.sup.th loop.

(8) FIG. 3 substantially illustrates the control assembly for its portion in charge of controlling the voltage of a traction battery 1 cell, i.e. the cell voltage limiter for the battery that bears the reference CONT C in FIG. 5, and FIG. 4 substantially illustrates the control assembly for its portion in charge of controlling the voltage of the onboard network, i.e. the onboard network voltage limiter that bears the reference CONT RB in FIG. 5. In FIGS. 3 and 4, however, the interconnection between the two voltage limiters can be seen.

(9) With reference to FIG. 3, the cell voltage limiter receives, for each cell, a predetermined cell voltage limit L VC(n) and an actual cell voltage VC(n), the actual cell voltage VC(n) being subtracted from the predetermined cell voltage limit L VC(n) in a subtraction module 16 of the cell voltage limiter, for a feedback loop of order n.

(10) With reference to FIG. 4, still for a feedback loop of order n, the onboard network limiter receives a predetermined network voltage limit L VRB(n) and an actual onboard network voltage VRB(n), the actual onboard network voltage VRB(n) being subtracted from the predetermined onboard network voltage limit L VRB(n) in a subtraction module 16 of the onboard network voltage limiter.

(11) With reference to FIG. 3, a correction based on an error Ki of the cell voltage limiter is, for a given cell, calculated on the basis of the difference between the predetermined cell voltage limit L VC(n) and the actual cell voltage VC(n) divided by the resistance of the cell Rcell in a divider module 18 of the cell voltage limiter.

(12) With reference to FIG. 4, a correction based on an error Kai of the onboard network voltage limiter is calculated on the basis of the difference between the predetermined network voltage limit L VRB(n) and the actual onboard network voltage VRB(n) divided by the resistance of the battery Rbat, which operation is carried out in a divider module 18a of the onboard network voltage limiter.

(13) These two corrections based on an error Kai, Ki form the basis of an integral correction, given that a value dependent on the integral current terms LimInt RB(n1), LimInt C(n1); LimInt C(n), LimInt RB(n1) of the two voltage limiters CONT C, CONT RB is added to them.

(14) Generally, the error related to the correction Ki for the cell voltage limiter is dependent on the difference between the predetermined cell voltage limit L VC(n) and the actual cell voltage VC(n). The error related to the correction Kai for the onboard network voltage limiter is dependent on the difference between the predetermined network voltage limit L VRB(n) and the actual onboard network voltage VRB(n).

(15) With reference to FIGS. 3 and 4, respectively, each limiter therefore comprises a respective integral feedback loop performing a correction based on the error Ki, Kai with the calculation of a respective integral current term LimInt C(n1), LimInt RB(n1) on the basis of the difference between the voltage limit L VC(n), L VRB(n) and the actual voltage VC(n), VRB(n) that are received by the limiter, advantageously divided by the resistance of the cell Rcell or the resistance of the battery Rbat.

(16) A first voltage limiter, in FIG. 3, the cell voltage limiter bearing the reference CONT C in FIG. 5, but the converse is also possible, carries out the n.sup.th loop first. This first voltage limiter uses the integral current terms LimInt RB(n1), LinnInt C(n1) of the two voltage limiters taken for the n1.sup.th preceding loop. Conversely, as the second limiter, in FIG. 4, the onboard network voltage limiter, bearing the reference CONT RB in FIG. 5, works after the first limiter, it may use, in addition to its integral current term of the n1.sup.th preceding loop for its integral term LimInt RB(n1), the integral term of the n.sup.th loop LimInt C(n) from the first voltage limiter, which is then available.

(17) According to an aspect of the present invention, with reference to FIGS. 3 to 5, the integral feedback loops of the two voltage limiters CONT C, CONT RB are interdependent, the integral current terms LimInt C(n) of the cell voltage limiter being transmitted to the integral feedback loop of the network voltage limiter and the integral current terms LimInt RB(n1) of the voltage limiter of the network being transmitted to the integral feedback loop of the cell voltage limiter so as to determine a respective battery current limit Lim I C(n), Lim I RB(n) for each voltage limiter CONT C, CONT RB.

(18) In FIG. 3, an integral term LimInt RB(n1) of the onboard network voltage limiter is transmitted to the cell voltage limiter and, in FIG. 4, an integral term LimInt C(n) of the cell voltage limiter, working as the first of the two voltage limiters (but this is optional), is transmitted to the onboard network limiter. The integral current terms LimInt RB(n1), LimInt C(n1) are for the cell voltage limiter CONT C and the terms LimInt C(n), LimInt RB(n1) are for the onboard network voltage limiter CONT.

(19) The reference Z.sup.1 for the onboard network voltage limiter and for the cell voltage limiter denotes a mathematical operator for the cell voltage limiter and the onboard network voltage limiter.

(20) To determine a battery current limit Lim I C(n), Lim I RB(n) that is specific to each of the two voltage limiters CONT C, CONT RB, a correction based on the error Ki, Kai is calculated for each limiter, to which may be added a value that is dependent on the integral current terms LimInt RB(n1), LimInt C(n1); LimInt C(n), LimInt RB(n1) of the two voltage limiters CONT C, CONT RB. This may be carried out in a respective first summation module 19, which can be seen in FIGS. 3 and 4.

(21) In the preferred embodiment of an aspect of the present invention, the value that is dependent on the integral current terms LimInt RB(n1), LimInt C(n1); LimInt C(n), LimInt RB(n1) of the two voltage limiters CONT C, CONT RB may be the minimum integral current term out of the two integral current terms LimInt RB(n1), LimInt C(n1); LimInt C(n), LimInt RB(n1) of the two voltage limiters CONT C, CONT RB. This may be carried out in a comparison module 22, which may be similar for both voltage limiters CONT C, CONT RB. This minimum value is then added to the correction based on the error Ki, Kai in the first summation module 19 of the battery cell voltage limiter, shown in FIG. 3, or in the first summation module 19 of the onboard network limiter, shown in FIG. 4. A revised integral correction is thus obtained.

(22) At the output of the respective first summation module 19, the correction based on the error Ki, Kai, to which a value that is dependent on the integral current terms LimInt RB(n1), LimInt C(n1); LinnInt C(n), LimInt RB(n1) of the two voltage limiters CONT C, CONT RB has been added to give a revised integral correction, may be limited, in a saturation block 20, between two, minimum and maximum, current values.

(23) The values of the revised integral correction that are lower than the minimum value or higher than the maximum value are then not taken into account and are replaced, respectively, with the minimum value or the maximum value so as to give a revised and limited integral correction, the revised and limited integral correction giving the respective battery current limit Lim I C(n), Lim I RB(n) for each of the two voltage limiters CONT C, CONT RB.

(24) As shown in FIGS. 3 and 4, an auxiliary correction Kp, Kap, different from the correction based on the error Ki, Kai being used as the basis for an integral correction, may be carried out; in these figures a proportional correction Kp or Kap. In this case, the integral correction that is revised in the first summation module 19 by adding a value that is dependent on the integral current terms LimInt RB(n1), LimInt C(n1); LimInt C(n), LimInt RB(n1) of the two voltage limiters CONT C, CONT RB, which may be limited, if required, and the auxiliary correction Kp, Kap are added to one another to obtain the battery current limit Lim I C(n), Lim I RB(n) for a respective voltage limiter CONT C, CONT RB, which takes place in a second summation module 21.

(25) As can be seen in FIG. 3, in the cell voltage limiter, what is thus obtained, for the loop n, is a cell integral current limit LimInt C(n) obtained by the advantageously revised integral correction and a current limit LimProp C obtained by proportional correction, the possible sum of the two limits giving the cell current limit Lim I C(n). It is also possible for the cell integral current limit LimInt C(n) to give the cell current limit Lim I C(n) directly without further correction.

(26) As can be seen in FIG. 4, in the onboard network voltage limiter, what is thus obtained, for the loop n, is an onboard network integral current limit LimInt RB(n) obtained by the advantageously revised integral correction and a current limit LimProp RB obtained by proportional correction, the possible sum of the two limits giving the cell current limit Lim I RB(n). It is also possible for the onboard network integral current limit LimInt RB(n) to give the onboard network current limit Lim I RB(n) directly.

(27) FIG. 5 shows the combination of a cell voltage limiter CONT C shown in FIG. 3 with an onboard network voltage limiter CONT RB shown in FIG. 4 for calculating a common current limit for the two limiters.

(28) Depending on the cell voltage in the loop n VC(n), the cell voltage limiter CONT C gives a cell current limit Lim I C(n) and an integral cell current limit LimInt C(n).

(29) Depending on the onboard network voltage in the loop n VRB(n), the onboard network voltage limiter CONT RB gives an onboard network current limit Lim I RB(n) and an integral cell current limit LimInt RB(n1).

(30) To calculate a common current limit Lim I(n) for the two voltage limiters CONT C and CONT RB, this common current limit Lim I(n) is the minimum value for the loop n out of the cell current limit Lim I C(n) for the traction battery and the current limit for the onboard network Lim I RB(n). This is carried out in a comparator MIN bearing the reference 23 in FIG. 5.

(31) With reference to all of these figures, an aspect of the invention also relates to a control assembly including a cell voltage limiter for a traction battery 1 and a voltage limiter for an onboard network in an electric or hybrid motor vehicle fitted with a traction battery 1.

(32) Each voltage limiter imposes a battery current limit Lim I C, Lim I RB and includes means for implementing, in an integral corrector, a feedback loop for determining a respective integral current term LimInt RB(n1), LimInt C(n1); LimInt C(n), LimInt RB(n1) for each of the two limiters CONT C, CONT RB. These implementation means give, respectively, the correction based on the error Ki or Kai by being placed at the output of a respective subtraction module 16 and of a respective divider module 18, 18a, which are mentioned above, for the cell voltage limiter or the onboard network voltage limiter.

(33) According to an aspect of the present invention, to implement the determining method such as described above, the assembly comprises means for transmitting the integral current terms LimInt C(n) from the cell voltage limiter to the means for implementing the feedback loop for the onboard network voltage limiter and means for transmitting the integral terms LimInt RB(n1) from the onboard network voltage limiter to the means for implementing the feedback loop for the cell voltage limiter.

(34) In one preferred embodiment of an aspect of the present invention, the control assembly may comprise, for each of the two limiters CONT C, CONT RB, a comparison module 22 for determining a minimum integral term out of, for the cell voltage limiter, the integral current term LimInt C(n1) associated with the cell voltage limiter and the integral current term LimInt RB(n1) associated with the onboard network limiter and, for the onboard network voltage limiter, the integral current term LimInt RB(n1) associated with the onboard network limiter and the integral current term LimInt C(n) associated with the cell voltage limiter.

(35) Since it is assumed that the cell voltage limiter executes the loop first out of the two limiters, for this cell voltage limiter, the comparison module 22 compares, in FIG. 3, the respective integral terms LimInt RB(n1) and Lim C(n1). Conversely, since the onboard network voltage limiter executes the loop second, for this voltage limiter, the comparison module 22 compares, in FIG. 4, the respective integral terms LimInt RB(n1) and LimInt C(n), this last integral term already being available due to the completion of the loop n by the cell voltage limiter.

(36) Each voltage limiter may comprise a summation module 19 for adding the integral term from the integral corrector of the limiter to said minimum value determined by the comparison module 22 so as to obtain a revised integral correction. Moreover, each voltage limiter may comprise a saturation block 20 limiting the revised integral correction from the summation module 19 between two, minimum and maximum, values.

(37) The assembly for calculating a common current limit Lim I(n) for the two limiters and comprising the two voltage limiters CONT C, CONT RB, this assembly being shown in FIG. 5, may comprise a comparator 23 for determining the minimum value out of the cell current limit Lim I C(n) and the onboard network current limit Lim I RB(n) so as to calculate the common current limit Lim I(n) for the two voltage limiters CONT C, CONT RB.

(38) Lastly, an aspect of the invention relates to an electric or hybrid motor vehicle, noteworthy in that it comprises such a control assembly including a cell voltage limiter for a traction battery 1 and a voltage limiter for an onboard network.