WO2018103946A1

WO2018103946A1 - Method, machine-readable storage medium and electronic control unit for operating an electrical energy storage system, and corresponding electrical energy storage system

Info

Publication number: WO2018103946A1
Application number: PCT/EP2017/077399
Authority: WO
Inventors: Joerg Schneider; Ulrich Zimmermann; Joerg Nils ILLIG
Original assignee: Robert Bosch Gmbh
Priority date: 2016-12-09
Filing date: 2017-10-26
Publication date: 2018-06-14
Also published as: CN110036528A; DE102016224551A1; CN110036528B

Abstract

A method for operating an electrical energy storage system, comprising at least one electrical energy storage unit, wherein the steps described below are performed. After a predefined first voltage threshold value (UTHR1) has been exceeded or undershot by an ascertained voltage value (UESU) of the electrical energy storage system, a counter value (TIM) is changed. After a predefined first counter threshold value is reached by the counter value (TIM), a predefined first voltage limit value (ULIM1) is changed. Thereafter, the electrical energy storage system is actuated such that the changed first voltage limit value (ULIM1) is not exceeded or undershot. Moreover, a machine-readable storage medium, an electronic control unit, an electrical energy storage system and the corresponding use thereof in electrically driven vehicles, including hybrid vehicles, in fixed electrical energy storage installations and in electrically operated hand tools are described.

Description

description

Method, machine-readable storage medium and electronic control unit for operating an electrical energy storage system and corresponding electrical energy storage system

The present invention is based on a method, a machine-readable storage medium, an electronic control unit, an electrical energy storage system and their use according to the preamble of the independent patent claims.

State of the art

As a result of the increasing electrification, in particular in the automotive or automotive sector, increasingly mobile electrical energy storage systems are being used. Strict adherence to specified limit values, for example voltage and temperature limit values, is absolutely necessary in particular in the increasingly used lithium-ion technology in order not to jeopardize the safety of the electrical energy storage system. Therefore, certain safety requirements are placed on the sensors used, for example, the measurement principles of current sensors should be designed diversified, which requires at least two current sensors.

Disclosure of the invention

Advantages of the invention

Disclosed are a method, a machine-readable storage medium, an electronic control unit, an electrical energy storage system and their use with the characterizing features of the independent claims. In the context of the disclosed method for operating an electrical energy storage system, when a predefined first voltage threshold value is exceeded or undershot by a determined voltage value of the electrical energy storage system, a counter value which, for example, is stored in an internal data memory and in particular represents a time period, is changed. After reaching a predefined first counter threshold value by the counter value, a predefined first voltage limit value is changed. Subsequently, a control of the electrical energy storage system takes place in such a way that the changed first voltage limit value is not exceeded or undershot. It is thus achieved that only a limited period of time elapses after exceeding or falling below the predefined first voltage threshold value, in which the original capacity of the electrical energy storage system is available, for which purpose no current measured values have to be determined or must be taken into account. For example, it is achieved that only a limited

Amount of energy is stored in the electrical energy storage system, without taking into account current values. The limited time span and thus also the predefined first counter threshold value can be determined by a worst case estimation on the basis of a smallest possible resistance value of the electrical energy storage unit and a maximum electrical current, wherein the largest possible electric current depends, for example, on the predefined first voltage limit value and a constant voltage charge can be determined with the first voltage limit. This estimate can be made before the actual operation of the electrical energy storage system, in which case maps are used in operation, or during operation, so to speak in real time. Thus, the safety requirements for the current sensor can be reduced, which simplifies the construction of the electrical energy storage system, whereby the safety of the electrical energy storage system can still be ensured by the disclosed method, without sacrificing performance. Alternatively, the method described can be used for further safeguarding and plausibility if other methods are already used.

Further advantageous embodiments of the present invention are the subject of the dependent claims. Expediently, the counter value is also changed after falling below or exceeding a predefined second voltage threshold value by the ascertained voltage value of the electrical energy storage system. If, for example, the counter value has been continuously increased when the predefined first voltage threshold value is exceeded, then it is reduced again after falling below the predefined second voltage threshold value. Thus, the flexibility of the method is increased, since the period in which the original, increased efficiency of the electrical energy storage system is available, can be increased again.

Expediently, the counter value does not exceed a predefined first counter limit value and does not fall below a predefined second counter limit value. If the counter value has reached the predefined first counter limit value or the predefined second counter limit value, there is no increase or decrease anymore. The predefined first counter threshold value preferably corresponds to the first predefined counter threshold or the second predefined counter threshold. Thereby, the period of time in which the original capacity of the electric energy storage system is available can be set.

It is expedient to determine at least one first temperature value and to determine a rate of change of the counter value as a function of the determined at least one first temperature value. Since the temperature generally has a great influence on the performance of the electrical energy storage system, this relationship is included in the inventive method via the dependency described and thus increases its flexibility and scope.

Advantageously, the amount of a rate of change of the counter value when increasing the counter value and the amount of a rate of change of the counter value when reducing the counter value are not the same. Thus, for example, the amount of the rate of change in decreasing the counter value may be smaller than the amount of the rate of change when the counter value is increased. Thus, the safety level with respect to the non-violation of voltage limits is still times, since already the determination of the predefined first counter threshold is based on a worst case estimate. Furthermore, the different electrical stresses, ie charging or discharging with potentially different electrical resistance values of the electrical energy storage unit, can be taken better into account, which increases the flexibility of the invention

Procedure additionally increased.

Expediently, the rate of change of the counter value depends on a first difference between the determined voltage value and the predefined first voltage limit value. Preferably, therefore, a magnitude-wide first difference leads to a smaller change in the counter value than a smaller first difference, since the greater the distance from the predefined first voltage limit value, the risk of exceeding the first voltage limit value is low. The closer the determined voltage value is now to the first voltage limit value, the greater the risk that it will be exceeded, which is to be prevented. This adaptation increases the efficiency of the electrical energy storage system.

Expediently, the first voltage threshold value and / or the second voltage threshold value depend on a determined second temperature value. As a result, the temperature dependence of the electrical performance of the electrical energy storage system or the electrical energy storage unit is mapped in the process, thereby increasing the availability of the electrical energy storage system. The determined second temperature value may be identical to the determined first temperature value or the first voltage threshold value and / or the second voltage threshold value may be dependent on the determined first temperature value. After reaching the predefined first counter threshold value, the electrical energy storage system is expediently actuated by the counter value and depending on exceeding or falling below a predefined third voltage threshold value by a determined further voltage value of the electrical energy storage system for a predefined first time space such that the electrical energy storage system is within the predefined one the first period, the amount above a predefined power limit. This ensures that no relevant voltage limits for the safety of the electrical energy storage system are violated. For example, the predefined power limit may be 0W.

Expediently, the determined voltage value and / or the determined further voltage value comprise an extreme value of the detected voltage values of the at least one electrical energy storage unit. If, for example, the electrical energy storage system comprises three electrical energy storage units, then only in rare cases do they have exactly the same voltage within the scope of the measurement accuracy. If the determined voltage value now includes an extreme value within the implementation of the method, for example the voltage value of one of the three electrical energy storage units which is closest to the predefined first voltage limit value, it is ensured that the predefined first voltage limit value is not exceeded when carrying out the method according to the invention if the electrical energy storage system comprises more than one electrical energy storage unit. By using the extreme value in conjunction with the worst-case estimation, it is ensured that the corresponding voltage values of the other electrical energy storage units also have a sufficient distance from the first voltage limit value or do not exceed it.

Furthermore, a machine-readable storage medium is described, on which a computer program is stored, wherein the computer program is set up to carry out all the steps of the method according to the invention. Thus, an easy way is provided to propagate the method according to the invention and to use it in many electrical energy storage systems.

Furthermore, an electronic control unit is described which is set up to perform all the steps of the method according to the invention. Thus, a simple way of performing the method is created.

Advantageously, under an electronic control unit, in particular an electronic control unit, which, for example, a microcontroller and / or an application-specific hardware component, for example an ASIC, can be understood, understood, but also may include a personal computer or a programmable logic controller.

Furthermore, an electrical energy storage system is described which comprises at least one electrical energy storage unit and an electronic control unit according to the invention. As a result, the method described can be carried out in the electrical energy storage system in an uncomplicated manner.

Advantageously, an electrical energy storage unit can be understood in particular to be an electrochemical battery cell and / or a battery module having at least one electrochemical battery cell and / or a battery pack having at least one battery module. For example, the electric energy storage unit may be a lithium-based battery cell or a lithium-based battery module or a lithium-based battery pack. In particular, the electrical energy storage unit may be a lithium-ion battery cell or a lithium-ion battery module or a lithium-ion battery pack. Furthermore, the battery cell may be of the type of lithium-polymer accumulator, nickel-metal hydride accumulator, lead-acid accumulator, lithium-air accumulator or lithium-sulfur accumulator or more generally an accumulator of any electrochemical composition.

Furthermore, a use of the method according to the invention or of the electrical energy storage system according to the invention in electrically driven vehicles including hybrid vehicles, in stationary electrical energy storage systems and in electrically operated hand tools is described. In the electrically operated hand tools, for example, a special mode can be provided which allows the retrieval of a higher power in the short term, this mode being monitored by the method according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Advantageous embodiments of the invention are illustrated in the figures and explained in more detail in the following description. Show it:

FIG. 1 shows a flowchart of the method according to the invention in accordance with a first embodiment;

FIG. 2 shows a flow chart of the method according to the invention in accordance with a second embodiment; FIG. 3 shows a flowchart of the method according to the invention in accordance with a third embodiment; and

Figure 4 is a schematic representation of electrical voltage and current waveforms of an electrical energy storage system including associated counter and voltage limit.

EMBODIMENTS OF THE INVENTION Identical reference symbols denote the same device components or the same method steps in all figures.

FIG. 1 shows a flowchart of the method according to the invention according to a first embodiment, which focuses on a charging process of the electrical energy storage system. After a general initialization in an upstream step SO, which includes, for example, an initialization of a counter, a check is made in a first step S1 as to whether a determined voltage value exceeds a predefined first voltage threshold value. The determination of the voltage value can also take place in the first step S1. The determined voltage value may be, for example, a total voltage value of an electrical energy storage system, ie, the sum of the voltage values of the electrical energy storage units constituting the electrical energy storage system. Preferably, the determined voltage value represents an extreme value of all individual voltage values of the electrical energy storage system. stituierenden electrical energy storage units, in the present case of charging a maximum value. If the determined voltage value exceeds the predefined first voltage threshold value, the counter is incremented in a second step S2. In a third step S3, it is then checked whether a predefined first counter threshold value is reached by the counter. If the first counter threshold value is reached by the counter, then in a fourth step S4, a predefined first voltage limit value is reduced, for example from 4.3 V to 4.2 V. In a fifth step S5, the electrical energy storage system is then activated in such a way that the modified one first voltage limit of none of the electrical energy storage system constituting electrical energy storage units is exceeded, ie the corresponding single-cell voltages do not exceed the first voltage limit. This can be done for example with a suitable power electronics, such as a suitable power converter. In the first step S 1 and the third step S 3, in each case a negative check result is branched again before the first step S 1, and a new voltage value is determined in the following first step S 1. For a discharge process, the method can also be used with slight adjustments: In the first step S1, it is checked whether a first voltage threshold value is undershot, and it is preferable to use the minimum value of all individual voltage values of the electrical energy storage units constituting the electrical energy storage system. Furthermore, in the fourth step S4, the predefined first voltage threshold is increased, for example from 2.8 V to 3.2 V, when the first counter threshold value has become. Subsequently, the electrical energy storage systems in the fifth step S5 is controlled so that the changed first voltage limit is not exceeded by any electrical energy storage unit.

FIG. 2 shows a flow chart of the method according to the invention according to a second embodiment. Here, a charging process is shown as in Figure 1. In contrast to the method illustrated in FIG. 1, in the case of not exceeding the predefined first voltage threshold value, a branch is made in a sixth step S6 in FIG. In the sixth step S6 it is checked whether the determined voltage value falls below a predefined second voltage threshold value, for example 3.9 V. If the predefined second voltage threshold is undershot, the counter will be in a seventh step S7 decrements. Subsequently, and when the predefined second voltage threshold value is not undershot, a branch is made before the first step S1 and a voltage value is again determined. For a discharge operation, the described method can also be used with slight adjustments as described above. For this purpose, in addition to the above adjustments in the sixth step S6, it is to be checked whether the determined voltage value exceeds a predefined second voltage threshold value, for example 3.8 V in the case of discharging. If the predefined second voltage threshold is now exceeded, the counter is decremented in the seventh step S7. Subsequently, and not exceeding the predefined second voltage threshold value, a voltage value is branched before the first step S1 and again a voltage value is determined.

FIG. 3 shows a flowchart of the method according to the invention in accordance with a third embodiment. Here, a charging process is shown as in Figure 2. In this case, the part of the flowchart with the steps SO, S1, S2, S3, S6, S7 corresponds to the method described in FIG. 2 and in the associated section. After the third step S3, an eighth step S8 is performed in which it is checked whether a determined further voltage value exceeds a predefined third voltage threshold value. If the predefined third voltage threshold is exceeded, a ninth step S9 is performed, in which the electrical energy storage system for a predefined first period is controlled such that the electrical energy storage system for the predefined first period does not absorb electrical power, the amount above a predefined electrical

Power limit. For example, this predefined electrical power limit may be 0 W in order to prevent further electrical power consumption. Subsequently or not exceeding the predefined third voltage threshold value, the above-described fourth and fifth steps S4, S5 are performed. In the case of adaptation to a discharge process, ie with a delivery of electrical energy which exceeds the supply of intrinsic systems of the electrical energy storage system, the predefined power limit value is preferably chosen such that the self-supply of the electrical energy storage system is ensured. Self-systems, so for example an electronic control unit and associated switching devices, such as an electromechanical contactor or an electronic circuit breaker, so are preferably further supplied with electrical energy.

Figure 4 shows a schematic representation of electrical voltage and current waveforms of an electrical energy storage system including associated

Counter and Spannungsgrenzwertverlauf in carrying out the method according to the invention. In the upper part of the figure, electrical voltage waveforms are shown. The ordinate axis represents a voltage U and the abscissa axis the time t. In addition, the first voltage threshold UTHR1, the second voltage threshold UTH R2 and the third voltage threshold

UTHR3 shown. The voltage curve U ESU reproduces the voltage at an electrical energy storage unit over time when the electrical energy storage unit is subjected to the corresponding current. The associated current profile I ESU is reproduced in the lower part of the figure over time, the associated ordinate axis being labeled I.

The voltage curve UOCV represents the not directly determinable voltage curve of an open circuit voltage of the electrical energy storage unit again. The course of the predefined first voltage limit value is represented by the voltage profile ULIM1. In the lower part of FIG. 4, a counter course TIM of a counter with a corresponding upper predefined first counter limit TLIM1 and a corresponding lower predefined second counter limit TLIM2 is furthermore illustrated. The counter value corresponds to a time span in seconds. The associated ordinate axis is specified with TIMER. Up to a point in time t 1, the electrical energy storage unit is charged with a relatively low current, for example 20 A. From the

Time tl to time t2 is a charge with an increased current, wherein the predefined first voltage limit ULIMl is not exceeded. Since the first voltage threshold UTHR1 is exceeded in this charging process, the counter value of the counter increases continuously. At a point in time t2, the electrical energy storage system and thus the electrical energy storage unit are activated such that the current delivered is at 0 A. Since the predefined second voltage threshold UTHR2 is not undershot at the time t2 in the corresponding voltage curve U ESU, the counter value continues to increase in the course of the counter TIM. At a time t3, the counter has reached a predefined first counter threshold value, in which case the predefined first counter threshold value and the predefined first counter threshold value Counter limit TLIM1 are identical and thus the counter value is not further increased. Therefore, after time t3, the predefined first voltage limit ULIM1 is reduced. From a time t4, the electrical energy storage unit is discharged. In this case, the predefined second voltage threshold value UTHR2 is undershot. Therefore, there is a reduction of the counter value, as can be seen from the associated counter profile TIM. After falling below a predefined second counter threshold value, an increase of the predefined first voltage limit value to the value before the reduction takes place at a time t5. From a point in time t6, the electrical discharge current is reduced, which, for example, leads to an increased voltage at the electrical energy storage unit due to lower losses at an electrical resistance of the electrical energy storage unit. The resulting voltage is between the predefined first voltage threshold and the predefined second voltage threshold, so that the counter is not changed. From a time t7, the discharge current increases again and the counter value is reduced. It can also be seen from the illustration that the rate of change of the counter or of the counter value is not constant over the entire time period shown and can also differ in terms of magnitude in terms of increase and decrease. For example, it is also possible to determine a temperature value, for example a minimum temperature value of the electrical energy storage unit of the energy storage system or an average temperature value, which is formed from temperature values of the electrical energy storage units, and to determine the rate of change of the counter or of the counter value as a function of this temperature value. The same is possible for the voltage threshold values UTHR1, UTHR2, UTHR3 and / or the counter threshold values.

Claims

claims

A method of operating an electrical energy storage system, comprising at least one electrical energy storage unit, wherein the following steps are performed:

a) after exceeding or falling below a predefined first voltage threshold value (UTHR1) by a determined voltage value (U ESU) of the electrical energy storage system changing a counter value (TIM);

b) after reaching a predefined first counter threshold value by the counter value (TIM), changing a predefined first voltage limit value (ULIM1);

c) driving the electrical energy storage system such that the changed first voltage limit (ULIM1) is not exceeded or undershot.

2. The method according to claim 1, further comprising the following step:

d) After falling below or exceeding a predefined second

Voltage threshold (UTHR2) due to the determined voltage value (U ESU) of the electrical energy storage system Changing the counter value (TIM).

3. The method according to any one of the preceding claims, wherein the counter value (TIM) does not exceed a predefined first counter limit value (TLIM1) and does not fall below a predefined second counter limit value (TLIM2).

4. The method according to any one of the preceding claims, further comprising the following steps:

e) determining at least a first temperature value;

f) depending on the determined at least a first temperature value setting a rate of change of the counter value (TIM);

5. The method according to any one of the preceding claims, wherein the amount of a rate of change of the counter value (TIM) when increasing the counter value (TIM) and the amount of a rate of change of the counter value (TIM) when reducing the counter value (TIM) are not equal.

6. The method according to any one of the preceding claims, wherein the rate of change of the counter value (TIM) is dependent on a first difference between the determined voltage value (U ESU) and the predefined first voltage limit value (ULIM1).

7. The method according to any one of the preceding claims, wherein the first voltage threshold value (UTHR1) and / or the second voltage threshold value (UTHR2) are dependent on a determined second temperature value.

8. Method according to one of the preceding claims, wherein in step b) after reaching the predefined first counter threshold value by the counter value (TIM) and in response to exceeding or falling below a predefined third voltage threshold value (UTHR3) by a determined further voltage value (U ESU) of the electrical energy storage system, the electrical energy storage system for a predefined first period of time is controlled such that the electrical energy storage system for the predefined first period does not absorb or emit electrical power, the amount is above a predefined electrical power limit.

9. Method according to one of the preceding claims, wherein the determined voltage value (U ESU) and / or the determined further voltage value (U ESU) comprises an extreme value of the detected voltage values (U ESU) of the at least one electrical energy storage unit.

10. A machine-readable storage medium on which a computer program is stored, wherein the computer program is set up to perform all the steps of the method according to one of claims 1 to 9.

11. Electronic control unit which is arranged to perform all the steps of the method according to one of claims 1 to 9.

12. An electrical energy storage system, comprising at least one electrical energy storage unit and an electronic control unit according to claim 11.

13. Use of a method according to any one of claims 1 to 9 or an electrical energy storage system according to claim 12 in electrically powered vehicles including hybrid vehicles, in stationary electrical energy storage systems and in electrically operated hand tools.