DE102011012818A1 - Method for operating rechargeable battery that is utilized for supplying current to electromotor for driving e.g. electric car, involves determining square value of current supplied to battery, and operating battery based on square value - Google Patents

Abstract

The method involves determining a root mean square value (IRMS) of an electrical variable i.e. current (I) supplied to a battery over time, and operating the battery based on the square value. The variable is limited such that the square value is held below a predetermined threshold value (IRMSsoll). A control variable (4) is determined from a difference between the threshold value and the square value. The control variable is set to zero if the difference between the threshold and square values is positive. A resulting limit is determined from sum of the threshold and square values. An independent claim is also included for a device for operating a battery of a vehicle.

Description

The present invention relates to a method for operating a battery, which is used in particular for supplying an electric motor of a vehicle. In addition, the present invention relates to a correspondingly configured device and a suitably designed vehicle.

The DE 10 2009 006 461 A1 describes a method for determining load data of a battery for a vehicle.

The charging rate and / or discharge rate of a battery is one of the factors that influence the aging of the battery. In this case, the aging of a battery is understood to mean, in particular, the increase of the internal resistance of the battery and the reduction of the cell capacity (that is to say the reduction of the charge which can be stored by the battery).

The object of the present invention is to operate a vehicle battery in such a way that the aging of the vehicle battery is delayed compared with a prior art operation.

According to the invention, this object is achieved by a method for operating a battery for a vehicle according to claim 1, by a device for operating a battery for a vehicle according to claim 11 and by a vehicle according to claim 14. The dependent claims define preferred and advantageous embodiments of the present invention.

In the context of the present invention, a method for operating a battery for a vehicle is provided. In this case, an average value (averaged over time) of an electrical variable (in particular of a current or a power), which is supplied to or taken from the battery, is determined. The battery is operated depending on this mean value.

• 1. Die elektrische Größe wird derart begrenzt oder geregelt, dass der Mittelwert dadurch quasi zwangsläufig langfristig unterhalb des vorgegebenen Schwellenwerts gehalten wird.
• 2. Dem Fahrer des Fahrzeugs wird eine Information gegeben, wodurch der Fahrer darüber informiert ist, ob der Mittelwert unterhalb oder oberhalb des Schwellenwerts liegt. Durch diese Information (beispielsweise einer Art Bonusanzeige, falls der Mittelwert unterhalb des vorgegebenen Schwellenwerts liegt) wird der Fahrer dazu animiert, die Batterie durch ein entsprechendes ”sanftes” Fahren derart zu betreiben, dass der Mittelwert zumindest langfristig unterhalb des vorgegebenen Schwellenwerts gehalten wird.

By operating the battery as a function of the mean value, the mean value is kept as low as possible below a predetermined threshold value. In order to ensure this (that the average is kept below the threshold, at least in the long-term average), there are two possibilities according to the invention:

• 1. The electrical variable is limited or regulated in such a way that the mean value is thereby kept quasi inevitably long-term below the predetermined threshold value.
• 2. Information is given to the driver of the vehicle which informs the driver as to whether the average value is below or above the threshold. By this information (for example, a kind of bonus display, if the average is below the predetermined threshold), the driver is encouraged to operate the battery by a corresponding "soft" driving such that the average is kept below the predetermined threshold, at least in the long term.

By keeping the mean value of the electric variable in the long-term average below the predetermined threshold value, the aging of the vehicle battery is advantageously delayed accordingly compared to an operation in which care is not taken whether the average is kept below the threshold, at least in the long term. In the context of the present invention, a long-term below the threshold value Hold is understood to mean that appropriate measures for lowering the average value are taken as soon as the mean value is above the threshold value. As a result, the mean is kept long or predominantly (but not always) below the threshold.

For this purpose, the mean value for a specific time can be determined such that the electrical quantity (in particular the magnitude of the electrical variable) is determined in each case over a time interval of predetermined length, this time interval ends at the corresponding specific time in each case. Such a procedure is also known as "moving average".

In order to determine the mean value over the time interval of predetermined length, the electrical quantity can be sampled within the time interval at predetermined equidistant times, wherein in each case a respective sampling value is detected. The mean value can then be calculated, for example, as the root mean square of these samples.

In the following equation (1), the root mean square (RMS) I _{RMS of} the electric current supplied to or taken out of the battery is calculated by current samples x _i . These current samples are each sampled at times each having a fixed time interval from their predecessor current sample. In the equation (1), N stands for the number of detected current samples.

For example, if the average value is detected over a period of 600 seconds (10 minutes) by taking an equidistant sample every 100 ms, N = 6001, for example, if the first sample is detected at the beginning of the period and the last sample at the end of the period ,

By operating or regulating the operation of the battery as a function of the mean value I _RMS , the operation advantageously depends on a variable that changes only slowly and continuously (namely the I _RMS ), as long as the period in which the average value I _{RMS is} determined has been chosen long enough.

As already stated above, it is possible according to the invention to carry out the operation of the battery as a function of an average current value (eg I _RMS ). However, as already described above, it is also possible to perform the operation of the battery depending on an average power, which is supplied to the battery or removed. In this case, the mean power P _avg could be _determined, for example, by the following equation (2). The average voltage U _RMS is calculated in the same way as the mean current value I _RMS , but at the sampling times, the battery voltage U and not the current I is sampled. P _avg = I _RMS * U _RMS (equation 2)

Another possibility according to the invention consists in limiting the current which is supplied to or taken from the battery as a function of the maximum no-load voltage of the battery and / or the minimum no-load voltage of the battery, since the aging of the battery (in particular the capacity loss) occurs directly from the battery minimum discharge voltage or the maximum charging voltage depends.

According to a preferred embodiment of the invention, the electrical quantity is kept below the threshold value by means of a regulation. For this purpose, a control variable is determined as a function of a difference between the threshold value (in particular the desired value of the I _RMS ) and the mean value (in particular the actual value of the I _RMS ). The control variable is added to a predetermined limit, resulting in a resulting limit as the sum. By means of the control (for example a P-control (proportional control, ie the output is proportional to the input)), it is ensured that the electrical variable is kept below this resulting limit.

Since the control quantity is negative when the average value is greater than the threshold value, the resulting limit is advantageously smaller, the more the average value lies above the threshold value. Therefore, as the electrical quantity is kept below this resulting limit, the farther the average is above the threshold, the more the electrical quantity is lowered.

In particular, the control variable is set to the value zero if the difference between the threshold value and the mean value is positive.

This procedure ensures that the resulting limit can never be greater than the specified limit. As a result, it is advantageously ensured according to this embodiment that the electrical variable is never above the predetermined limit.

According to another preferred embodiment of the invention can be ensured that the battery always gives a minimum performance. For this purpose, a minimum value corresponding to this minimum power is introduced and the control is designed in such a way that the resulting limit is never below this minimum value.

According to this embodiment, it is ensured that the electrical quantity can also be above the predetermined limit if it is below the minimum value.

According to the invention, the threshold value can be changed manually, for example, by a workshop or by an authorized user.

As a result, the threshold value can advantageously be adapted, for example, to the current state (of the age) of the battery. It makes sense to set the threshold by the battery manufacturer. In this case, the threshold should be chosen by the manufacturer so as to ensure a predetermined battery life if this threshold is met.

In the context of the present invention, an apparatus for operating a battery for a vehicle is also provided. In this case, the device comprises a measuring device and a controller. The measuring device is configured to measure an electrical quantity (in particular, an electric current or an electric power) supplied to or taken out of the battery. The controller is configured to determine the averaged average over time of this electrical quantity. By means of the device, the battery is operated as a function of the mean value.

According to a preferred embodiment of the invention, the device further comprises a limiting device or Control apparatus. With the aid of the limiting device, the device is able to limit the electrical variable in such a way that the mean value is kept below a predetermined threshold value in the long term.

The advantages of the device according to the invention essentially correspond to the advantages of the method according to the invention, which have been carried out in detail in advance, so that a repetition is dispensed with here.

Finally, in the context of the present invention, a vehicle (in particular a hybrid vehicle or electric vehicle with an electric motor) is provided which comprises a device according to the invention.

The present invention is particularly suitable for vehicles with an electric motor for driving the vehicle. Of course, the present invention is not limited to this preferred application, since the present invention can also be applied to aircraft, ships or track-based and track-guided vehicles. At least in principle, for example, the present invention can also be used outside of a means of locomotion for the operation of a rechargeable battery, provided that in this operation, in particular the discharge current is controllable.

In the following, the present invention will be described in detail based on preferred embodiments of the invention with reference to the figures.

In 1 a basic regulation according to the invention of the charging / discharging current of a battery is shown.

In 2 an inventive control of the charging / discharging is shown in detail.

In 3 shows the time course of various measured and controlled variables when using a controller according to the invention.

4 schematically shows a vehicle according to the invention with a device according to the invention.

In 1 is a basic inventive control of a current I shown, which is supplied to a battery or the battery is removed. The purpose of the regulation is to keep a time average I _{RMS of} the current I below a predetermined threshold I _RMSsoll in the long term. This is done by means of a measuring device 2 the mean current value I _RMS determines, as described above with equation (1). The control becomes a simple P-controller 1 used, which is a control variable 4 calculated in proportion to the difference between the threshold I _RMSsoll and the mean I _RMS . This tax code 4 becomes an actuating device 5 supplied, which output side outputs a manipulated variable I _Res . By means of this manipulated variable I _Res , the current I with respect to a controlled system 7 and one the controlled system 7 influencing disturbance 6 controlled such that the mean I _{RMS is kept} long term below the threshold I _RMSsoll .

In 2 the control of the current I according to the invention is shown in detail. By means of the current measuring device 2 For example, the current I is sampled at equidistant times, the magnitude of each sample is determined, and an average I _{RMS is} calculated according to equation (1) for the respective magnitudes, with the average I _RMS from the current measuring device 2 is issued. The mean value I _RMS is, together with the current _{threshold value} I _RMSsoll, a subtraction _element or subtractor 8th fed. This subtraction element 8th _subtracts the mean I _RMS from the threshold I _RMSsoll and gives this difference as a control deviation 9 out. The deviation 9 becomes a limiter 11 supplied, which outputs as output a 0, if the control deviation 9 is positive, and otherwise as output the control deviation 9 outputs. The output of the limiter 11 becomes a multiplier together with a constant K 12 which supplies the constant K with the output of the limiter 11 multiplied and at the output a control variable 4 as the corresponding product. The tax size 4 is combined with a predetermined current limit I _max an adder 13 supplied, which at the output a resulting current limit I _Lim as the sum of the predetermined current limit I _max and the control variable 4 outputs. This resulting current limit I _Lim, in turn, together with a guaranteed current limit I _min a maximum value images 15 supplied, which at the output as a final resulting current limit I _{Limres outputs} the respective greater value of the guaranteed current limit I _min and the resulting current limit I _Lim .

An unillustrated part of the regulator ensures that the current I is always kept below the final resulting current limit I _Limres . The guaranteed current limit I _min is provided by a divider 14 supplied to which a guaranteed power P _min and the battery voltage U are supplied. The divider 14 divides the guaranteed power P _min by the battery voltage U to determine the guaranteed current limit I _min .

It makes sense that the predetermined current limit I _{max is} greater than the guaranteed current limit I _min . In this case, the final moves resulting current limit I _Limres between the guaranteed current limit I _min and the predetermined current limit I _max . Through the limiter 11 For example, the final resulting current limit I _{Limres is lowered} only as a function of the difference between the average I _RMS and the threshold I _RMSsoll if this difference is negative (ie if the mean I _{RMS is} greater than the threshold I _RMSsoll ).

Through the maximum value images 15 and by this maximum value images 15 supplied guaranteed current limit I _min is advantageously avoided that a driving performance of the vehicle with electric motor falls below a minimum value P _min .

In particular, to avoid problems at the beginning of a journey, the value of the mean I _RMS should be stored at the end of a journey and used as a starting value at the next start or at the next trip.

In 3 the curves of some variables and controlled variables are shown when using the control according to the invention.

In 3a the course of the current I is shown. Positive values mean that the current I is supplied to the battery, so the battery is charged. In contrast, negative values mean that the current I is taken from the battery, in order in particular to operate an electric motor for driving the vehicle.

In 3b the course of the average current value I _{RMS is} shown. It can be seen that the mean value increases relatively strongly over the first 600 s, since the first time interval has elapsed only after 600 s, via which the mean value I _{RMS is} formed in each case (compare equation (1) above).

In 3c is the control deviation 9 , ie the difference between the threshold I _RMSsoll and the mean I _RMS plotted. Negative values of the control deviation 9 mean that the mean I _{RMS should be} greater than the threshold I _RMSsoll . In 3d is the tax size 4 applied, which has only negative values. The tax size 4 corresponds (for negative values of the control deviation 9 ) the product of the control deviation 9 and the constant K.

In 3e the resulting current limit I _{Lim is} shown. As long as the tax size 4 is equal to 0, the resulting current limit I _Lim corresponds to the predetermined current limit I _max . Only when the tax size 4 is less than 0, the resulting current limit c reduces according to the control amount 4 ,

In 3f the guaranteed current limit I _{min is} applied. Since the guaranteed current limit I _min corresponds to the division of the guaranteed power P _min divided by the battery voltage U, the guaranteed current limit I _{min changes} depending on the battery voltage U.

In 3g is the final resulting current limit I _Limres shown, whose course substantially corresponds to the course of the resulting current limit I _Lim . Only in the cases in which the resulting current limit I _Lim falls below the guaranteed current limit I _min does the final resulting current limit I _{Limres correspond to} this guaranteed current limit I _min . In addition to a regulation of the current which is supplied to or taken from the battery, the driver can also be provided with information which informs him as to whether the mean value I _{RMS is} above or below the threshold value I _RMSsoll . By a display in the form of a bonus system, the driver can be encouraged to charge the battery by "smoother driving" only within predetermined limits. If the driver remains due to correspondingly low accelerations of the vehicle and by gently braking with the average below the threshold value, for example, a corresponding motivating display element in the driver display can be displayed in order to move the driver to a range optimization and a careful handling of the battery.

In addition, the threshold or setpoint I _RMSsoll in a sport mode of the vehicle could be increased accordingly, which would then result in a continuous increase of the current limits I _Lim , I _Limres .

In 4 is a vehicle according to the invention 10 shown, which is a battery 16 , a device according to the invention 20 and an electric motor 17 to drive the vehicle 10 includes. The device 20 in turn comprises a current measuring device 2 , a current limiter 18 and a controller 19 , The device 20 is designed such that it the current I, which of the battery 16 is removed or the battery 16 is supplied to the charging, limited such that the average current value I _{RMS is obtained in the} long term below the predetermined threshold I _RMSsoll .

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009006461 A1 [0002]

Claims (14)

Method for operating a battery ( 16 ) for a vehicle ( 10 ), wherein an average value (I _RMS ) over the time of an electrical variable (I), which of the battery ( 16 ) is determined or supplied, and wherein the battery ( 16 ) is operated as a function of the mean value (I _RMS ). A method according to claim 1, characterized in that the electrical variable (I) is limited such that the mean value (I _RMS ) below a predetermined threshold value (I _RMSsoll ) is maintained. Method according to claim 2, characterized in that a control variable ( 4 ) is determined as a function of a difference between the threshold value (I _RMSsoll ) and the mean value (I _RMS ) that a resulting limit (I _limres ) from an addition from the control variable (I 4 ) and a predetermined limit (I _max ), and that the electrical quantity (I) is kept below the resulting limit (I _limres ). Method according to Claim 3, characterized in that the control variable ( 4 ) is set to the value zero when the difference between the threshold value (I _RMSsoll ) and the mean value (I _RMS ) is positive. Method according to claim 3 or 4, characterized in that the resulting limit (I _Limres ) is not determined below a predetermined minimum value (I _min ) to obtain a minimum power output (P _min ) of the battery (P _min ). 16 ) to ensure. Method according to one of claims 2-5, characterized in that the threshold value (I _RMSsoll ) is set manually by a user. Method according to one of claims 2-6, characterized in that information of the vehicle ( 10 ) which informs the driver whether the mean (I _RMS ) is below or above the threshold (I _RMSsoll ). Method according to one of the preceding claims, characterized in that the electrical variable is a current (I) and the mean value is an average current value (I _RMS ), or that the electrical variable is a power and the mean value is a mean power value. Method according to one of the preceding claims, characterized in that the mean value (I _RMS ) is determined for a current point in time by determining the electrical variable (I) in each case for a time interval of a predetermined length which ends at the current point in time. A method according to claim 9, characterized in that the mean value (I _RMS ) is determined by sampling the electrical quantity (I) within the time interval at predetermined times, whereby sampling values are detected, and that the mean value (I _RMS ) is quadratic Mean value of the samples is calculated. Device for operating a battery ( 16 ) for a vehicle ( 10 ), the device ( 20 ) a measuring device ( 2 ) and a controller ( 19 ), the measuring device ( 2 ) for measuring an electrical quantity (I) which the battery ( 16 ) is supplied or removed, is configured, wherein the controller ( 19 ) for determining an average value (I _RMS ) of the electrical quantity (I) averaged over time, and wherein the device ( 20 ) is configured such that the device ( 20 ) the battery ( 16 ) depending on the mean (I _RMS ). Device according to claim 11, characterized in that the device ( 20 ) in addition a limiting device ( 18 ) and that the device ( 20 ) is configured such that the device ( 20 ) the electrical variable (I) by means of the limiting device ( 18 ) such that the mean value (I _RMS ) is below a predetermined threshold value (I _RMSsoll ). Device according to claim 11 or 12, characterized in that the device ( 20 ) is designed for carrying out the method according to one of claims 1-10. Vehicle with a device ( 20 ) according to any one of claims 11-13.

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