DE102015201628A1 - Monitoring of a battery system during control-related debounce times - Google Patents

Abstract

The invention relates to a method for monitoring operating parameters (x) of a rechargeable high-voltage battery system (11) of an electric or hybrid vehicle during control-related debounce times, wherein the high-voltage battery system (11) comprises a plurality of interconnected battery cells (15). The operating parameters (x) of the high-voltage battery system (11) or of the individual battery cells (15) are detected during the debounce times and evaluated by the comparison with permissible limit values (x0). Limit overflows are counted and stored as a number of error entries (N) for further evaluation. Furthermore, the invention relates to an electric drive train (10) of an electric or hybrid vehicle comprising a high-voltage battery system (11) and an electric machine (14), which are electrically connected to each other via a control and / or regulating unit (13). Operating parameters (x) of the high-voltage battery system (11) detected during control-related debounce times can be mathematically evaluated by the control and / or regulating unit (13).

Description

The present invention relates to electric and hybrid vehicles with rechargeable high-voltage battery systems, and more particularly to a method for monitoring operating parameters of the high-voltage battery system during derailleur-related Entprellzeiten and an electric drive train such a vehicle.

State of the art

Among other things, the automotive industry is reducing the consumption of fossil fuels through a gradual electrification of vehicle drives, so-called hybrid-electric (HEV) or battery-electric (BEV) vehicles. In addition, auxiliary and auxiliary units of such vehicles are increasingly electrified, such as the electric power steering. In order to provide the required performance in hybrid and electric vehicles, high-voltage battery systems are used as rechargeable or rechargeable energy storage. Such battery systems typically have a plurality of battery modules, which are composed of a plurality of interconnected battery cells. High voltage battery systems include, for example, nickel metal hybrid, lithium ion and sodium nickel chloride battery systems.

Lithium-ion batteries are increasingly being used, as they are characterized by their relatively high energy densities and cell voltages. However, lithium-ion batteries are relatively sensitive to both overcharging and over-discharging. The aging of lithium-ion batteries is generally highly dependent on the ambient temperature, the cell voltages and the charging currents. Therefore, it should be ensured for all lithium-ion battery cells to comply with upper and lower cell voltage limits. On the other hand, the discharge power is significantly reduced at low temperatures by the specific electrochemical cell kinetics, which manifests itself above all in an increased internal resistance of a battery cell, but also in a reduced discharge capacity, especially at high currents. The height of the charging currents should therefore be limited, especially at low temperatures. To avoid critical conditions, various operating parameters of battery cells, such as current, voltage and temperature, are continuously or periodically measured and evaluated.

Due to control processes in a vehicle and for reasons of robustness, cut-off limits for operating parameters of battery cells, such as, for example, current, voltage and temperature, are typically debounced in time. During debouncing, that is, in the debounce time, operation of battery cells outside of a predetermined operating range may occur, which is not registered by standard control and / or regulating units. If operation of battery cells outside of the predetermined operating range frequently occurs, this can lead to an accelerated and unexpected aging of the affected battery cells, which in extreme cases can pose a safety risk.

The use of debouncing for reasons of robustness, for example, from the document DE 10 2011 086 043 A1 in the context of the classification of the functionality of an energy storage cell known. Here, a plurality of debouncing factors are calculated, wherein in each case a debouncing factor of a performed determination of an internal resistance of at least one energy storage cell is assigned. The classification of the functionality of the at least one energy storage cell is carried out based on a calculated integral.

From the publication DE 10 2009 054 959 A1 For example, a method for detecting faults in a control device for controlling and / or regulating an engine in a vehicle is known, with which operating variables are monitored for the presence of fault conditions. In particular, the method also makes it possible to specify a debounce time, wherein the erroneous state is evaluated as an error after the debounce time has expired.

From the publication DE 10 2005 062 873 A1 For example, a method for operating a control and / or regulating device is known, in which debouncing is provided in order to prevent fault reactions from being triggered unnecessarily for only very short-term fault states.

Against this background, it is an object of the present invention to enable monitoring of battery cells of a battery system, which serves to drive a motor vehicle, during operational debounce times.

Disclosure of the invention

To solve the problem, a method for monitoring operating parameters a rechargeable high-voltage battery system of an electric or hybrid vehicle during control-related Entprellzeiten and an electric drive train of an electric or hybrid vehicle having proposed a control and / or regulating unit for processing and evaluation of the operating parameters.

Accordingly, the invention provides a method for monitoring operating parameters of a rechargeable high-voltage battery system of an electric or hybrid vehicle during control-related debounce times, wherein the high-voltage battery system comprises a plurality of interconnected battery cells. The operating parameters of the high-voltage battery system or of the individual battery cells are recorded during the debounce times and evaluated by comparison with permissible limit values. Limit overruns are counted and stored as a number of error entries for further evaluation.

By detecting and evaluating fault entries when limit values are exceeded for the various operating parameters, early aging of the battery cells of the battery system as well as problems in the electric powertrain of an electric or hybrid vehicle can be detected and safety risks avoided.

Compared with the prior art, the method according to the invention has the advantage that premature aging of the high-voltage battery system or of the individual battery cells can be diagnosed by an insufficient regulation of the electric drive.

In an advantageous embodiment of the invention, it is provided that the number of fault entries are compared with a predetermined reference value in order to detect premature aging of the high-voltage battery system. If the reference value is reached or exceeded, the battery system or the entire electric drive train of the electric or hybrid vehicle can be shut down or maintenance arranged.

In a further advantageous embodiment of the invention, it is provided that a temporal analysis of the number of error entries is performed, being drawn from the temporal analysis conclusions regarding the beginning and the frequency of the error entries.

This time analysis can be used to detect problems in the powertrain of a vehicle. In particular, conclusions can be drawn with this temporal analysis since when the error entries occur and whether the frequency has increased over time, ie the frequency of the error entries, and thus, whether an accelerated aging of the battery system or individual battery cells has occurred or occurs and whether the control of the drive train has deteriorated or increasingly deteriorated.

According to a preferred embodiment of the invention, it is provided that for the temporal analysis, the number of error entries over a certain period of time is recorded, the number of error entries is stored, and thus provided for later evaluation and made a division of the recorded error entries in different periods becomes.

According to a further preferred embodiment of the invention, it is provided that the number of defect entries over time is displayed graphically and the slope of the graph is used to analyze the defect entries.

It is further provided that an exponentially increasing number of fault entries early diagnosis of battery cells is diagnosed.

A further advantageous embodiment of the invention provides that the high-voltage battery system is used as a component of an electric drive train of the electric or hybrid vehicle, with an exponentially increasing number of fault entries a problem of the electric drive train is diagnosed.

A further advantageous embodiment of the invention provides that the current, the voltage, the average current and the temperature are detected during the Entprellzeiten as operating parameters.

A further advantageous embodiment of the invention provides that the evaluation of the error entries by a control or regulating unit, which is performed with the high-voltage battery system and an electric machine of the electric or hybrid vehicle.

To achieve the object mentioned above, an electric drive train of an electric or hybrid vehicle comprising a high-voltage battery system and an electric machine, which are electrically connected to each other via a control and / or regulating unit, also proposed.

Operating parameters of the high-voltage battery system detected during control-related debounce times can be mathematically evaluated by the control and / or regulating unit. Limit overruns of the operating parameters can be determined by the control and / or regulating unit and counted as a number of fault entries. By comparing the number of fault entries with a reference value and / or a time analysis of the number of fault entries, problems in the electric drive train can be diagnosed by the control and / or regulating unit.

Brief description of the drawings

Further advantageous details, features and design details of the invention are explained in more detail in connection with the exemplary embodiments illustrated in the figures. Showing:

1 in a schematic representation of a block diagram of an electric drive train of an electric or hybrid vehicle; and

2 in a schematic representation of the detection of error events over time.

In the figures, identical or functionally identical components are provided with the same reference numerals.

Embodiment (s) of the invention

In the 1 is a block diagram of an electric drive train 10 an electric or hybrid vehicle according to a possible embodiment shown. The electric drive train 10 has, among other things, a rechargeable high-voltage battery system 11 , a battery management system (BMS) 12 , a control and / or regulating unit 13 and an electric machine 14 which are electrically connected to each other. The high-voltage battery system 11 has a plurality of interconnected battery cells 15 on. High-voltage battery systems 11 For example, nickel-metal hybrid, lithium ion, and sodium nickel chloride include battery systems. The high-voltage battery system 11 is according to a possible embodiment preferably a lithium-ion battery system.

The battery management system (BMS) 12 is an electronic circuit used to monitor and control the rechargeable battery system 11 , So an accumulator system is used. The battery management system (BMS) 12 is often referred to as a battery control unit, also known as "battery control unit" (BCU) in the English language. The need for a BMS 12 results in the interconnection of multiple battery cells to the battery system 11 , The BMS 12 It should be the unavoidable production-related variations of various parameters of the battery cells 15 , such as capacity and leakage, detect, monitor and correct. In some cases, operating data is displayed or stored for service purposes.

If, for example, the vehicle is started, then a command from the control unit 13 of the vehicle to the BMS 12 sent, which then controls the condition of a drive battery and the electric machine 14 Powered in the programmed cases. If a fault occurs in the battery system during operation 11 on, this is the BMS 12 processed and sent to the control unit 13 passed. The error can now be assigned to an error category that the driver of the vehicle is informed of and / or the battery system 11 be brought into a safe condition.

Shutdown limits for operating parameters of the battery system 11 , such as current, voltage and temperature, are usually time-delayed due to vehicle control and robustness. This debouncing can damage the battery system 11 or the individual battery cells 15 be operated during the debounce time outside a prescribed operating range. In order to detect such impermissible operating times, according to a possible embodiment, the operating parameters of the individual battery cells 15 or the battery system 11 , such as the current I, the voltage U, the average current I _rms and the temperature detected during the _{Entprellzeiten} and by comparing with allowable limits, ie minimum and maximum allowable values of the current I, the voltage U, the average current I _rms and the temperature evaluated. For this purpose, various functions are applicable.

mit

N

Anzahl der Fehlereinträge

x

Spannung U, Strom I, mittlerer Strom I_rms, oder Temperatur T

x₀

Grenzwert (maximale oder minimale Spannung U, maximaler oder minimaler Strom I, maximaler oder minimaler mittlerer Strom I_rms und maximale oder minimale Temperatur T)

t

Zeit

T_end

Gesamtdauer des Zustandes außerhalb von x₀

1/60

Normierung auf Minuten

On the one hand, according to equation (1), a linear integral can be formed:

With

N

Number of error entries

x

Voltage U, current I, mean current I _rms , or temperature T

x ₀

Limit value (maximum or minimum voltage U, maximum or minimum current I, maximum or minimum average current I _rms and maximum or minimum temperature T)

t

Time

T _end

Total duration of the state outside of x ₀

1/60

Normalization to minutes

mit

N

Anzahl der Fehlereinträge

x

Spannung U, Strom I, mittlerer Strom I_rms, oder Temperatur T

x₀

Grenzwert (maximale oder minimale Spannung U, maximaler oder minimaler Strom I, maximaler oder minimaler mittlerer Strom I_rms und maximale oder minimale Temperatur T)

t

Zeit

T_end

Gesamtdauer des Zustandes außerhalb von x₀

1/60

Normierung auf Minuten

On the other hand, according to equation (2), a quadratic integral can be formed as an energy equivalent:

With

N

Number of error entries

x

Voltage U, current I, mean current I _rms , or temperature T

x ₀

Limit value (maximum or minimum voltage U, maximum or minimum current I, maximum or minimum average current I _rms and maximum or minimum temperature T)

t

Time

T _end

Total duration of the state outside of x ₀

1/60

Normalization to minutes

For both equations, normalization to minutes rather than seconds is an optional normalization. Other standards or no standardization can be used.

Every time you use the battery system 11 or individual battery cells 15 outside the specified limits, the integral is now counted up. The implementation of the integral takes place according to a possible embodiment in the control and / or regulating unit 13 discrete in time and thus as a sum, for example via the known from the prior art trapezoidal formula instead. Thus, counters are realized which reproduce the number of error entries (N) occurring during control-related debounce times.

mit

N

Anzahl der Fehlereinträge

U

Spannung

U₀

maximale oder minimale Spannung U (Grenzwert)

t

Zeit

T_end

Gesamtdauer des Zustandes außerhalb von x₀

1/60

Normierung auf Minuten

R

Referenzwert, beispielsweise R = 500 V²s

For each monitored operating parameter, a comparison with a reference value (R) or threshold value may be performed according to a possible embodiment. For example, 500 V can be ² s by the manufacturer of the battery cells 15 be allowed. This results in the following check:

With

N

Number of error entries

U

tension

U ₀

maximum or minimum voltage U (limit)

t

Time

T _end

Total duration of the state outside of x ₀

1/60

Normalization to minutes

R

Reference value, for example R = 500 V ² s

If the reference value (R) is reached or exceeded, the battery system can 11 or the entire electric drive train 10 shut down or a maintenance arranged.

By coupling the monitoring of operating parameters of the battery system 11 or the individual battery cells 15 during control-related debounce times with a limit value monitoring and a reference value comparison can critical states of the battery system 11 and the electric drive train 10 be detected early and in case of warranty evidence that the vehicle over the life of the battery system 11 , or individual battery cells 15 , has not sufficiently regulated and thus the battery cells 15 have aged faster than intended.

Should the occurrence of error entries (N) and thus the operation of the battery system 11 or the individual battery cells 15 Outside the given limits (x _{0) increase} with time, is expected from a larger problem. Therefore, according to a possible embodiment, furthermore, a diagnosis function is proposed which specifically evaluates a time-changed behavior of the number of error entries (N). This diagnostic function can be controlled by the control and / or regulating unit 13 be executed.

In addition to the comparison to a reference value (R) already described, a temporal analysis of the integral values (N) determined as described above can be carried out. Using this temporal analysis of integral values (N) can cause problems in the powertrain 10 of a vehicle. In particular, conclusions can be drawn with this temporal analysis of the integral values (N) since when the error entries occur and whether the frequency over time, ie the frequency of the error entries (N), has increased and thus whether accelerated aging of the battery system 11 or individual battery cells 15 has occurred or occurs and whether the regulation of the drive train 10 worsened or increasingly worsened.

In the 2 the detection of the number of defect entries (N) over time (t) is shown schematically. To carry out the temporal analysis of the calculated integral value or the error entries (N) and thus the limit value excesses of operating parameters of the battery system which occur during the debounce times 11 or individual battery cells 15 the following steps are proposed. First, the error entries (N), ie the limit value exceedances or integral values, over a certain period of time (T), z. From 15 days. The number of defect entries (N) is preferably stored so that it is available for later comparison. According to one possible embodiment, it is possible to divide the recorded error entries (N) into different periods (T). make. As in 2 this can be, for example, a division into periods (T) of 5 days each, ie from day 1 to 5 days, from 5 days to 10 days ago and from 10 days to 15 days ago, etc.

The evaluation of the recorded error entries (N) can, for example, be carried out in three different categories, which are shown by way of example in the characteristics a, b and c of FIG 2 are shown. Decisive for the temporal analysis of the recorded error entries (N) is the slope of the characteristic curves. The characteristic a shows a constant integral value. This means that the error occurs only sporadically and the number of error events (N) does not increase with time (t).

The characteristic curve b shows a linearly increasing integral value. Thus, a constant rate of change for the integral value is defined, e.g. B. 2 V ² s / 24 h. Exceeding indicates an increased frequency of error entries (N). With an exemplary integral value of 2V ² s, the following test can be used to check whether the occurrence of the error entries (N) increases. N (t = 0) - N (t = 0 - 5 days) / 5 days> 2V ² s (4)

The characteristic curve c shows an exponentially increasing integral value. An exponential rate of change for the integral value is defined. Exceeding can be a serious problem in the powertrain 10 show. The exponential rate of change can be determined, for example, as follows:

mit

N

Anzahl der Fehlereinträge

T

eitraum

t

Zeitpunkt

R

Referenzwert

or

With

N

Number of error entries

T

PERIOD

t

time

R

reference value

The exponential functions are relatively flat for negative values and have a steep slope in the range 0 to 1. Accordingly, a section of the exponential function according to equation (5) or (6) in which a relatively steep slope occurs is preferably used for the diagnosis. In the in the 2 Therefore, the time range T of -15 to 0 days is considered, as well as a shift by 1 and possibly a normalization to a time range. The reference value (R), z. B. 2V ² s, then controls the limit. In a table can then several values, for example, for t = -15 days, -10 days, -5 days, in the battery management system (BMS) 12 and then compared with already stored values. If exceeded, the driver may have a problem in the powertrain 10 are displayed, for. B. by activating a warning lamp.

Thus, operating parameters of a battery system can be determined using the described methods 11 or the individual battery cells 15 during control-related debounce times are monitored. By detecting and evaluating fault entries (N) in the event of limit violations of the various operating parameters, premature aging of the battery cells can take place 15 of the battery system 11 as well as problems in the electric powertrain 10 an electric or hybrid vehicle detected and safety risks are avoided.

The illustrated in the figures and explained in connection with these embodiments are illustrative of the invention and are not limiting for this.

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 102011086043 A1 [0005]
• DE 102009054959 A1 [0006]
• DE 102005062873 A1 [0007]

Claims (10)

Method for monitoring operating parameters (x) of a rechargeable high-voltage battery system ( 11 ) of an electric or hybrid vehicle during control-related Entprellzeiten, the high-voltage battery system ( 11 ) a plurality of interconnected battery cells ( 15 ), characterized in that the operating parameters (x) of the high-voltage battery system ( 11 ) or the individual battery cells ( 15 ) are detected during the debounce times and evaluated by the comparison with permissible limit values (x ₀ ), limit value overflows being counted and stored as a number of error entries (N) for further evaluation. A method according to claim 1, characterized in that the number of fault entries (N) is compared with a predetermined reference value (R), which is suitable for early aging of the high-voltage battery system ( 11 ) to recognize. Method according to one of claims 1 or 2, characterized in that a temporal analysis of the number of error entries (N) is carried out, which is suitable to draw conclusions regarding the beginning and the frequency of the error entries (N). A method according to claim 3, characterized in that for the temporal analysis, the number of error entries (N) over a certain period (T) is recorded, the number of error entries (N) is stored and thus provided for later evaluation and a division of the recorded error entries in different periods (T) is made. Method according to one of claims 3 or 4, characterized in that the number of error entries (N) over time is graphically displayed and the slope of the graph is used to analyze the error entries (N). Method according to Claim 5, characterized in that, given an exponentially increasing number of fault entries (N), premature aging of the battery cells ( 15 ) is diagnosed. Method according to claim 6, characterized in that the high-voltage battery system ( 11 ) as a component of an electric drive train ( 10 ) of the electric or hybrid vehicle is used, with an exponentially increasing number of fault entries (N) a problem of the electric drive train ( 10 ) is diagnosed. Method according to one of the preceding claims, characterized in that as an operating parameter (x) of the current (I), the voltage (U), the average current (Irms) and the temperature (T) during the debounce be detected. Method according to one of the preceding claims, characterized in that the evaluation of the error entries (N) by a control and / or regulating unit ( 13 ) connected to the high-voltage battery system ( 11 ) and an electric machine ( 14 ) of the electric or hybrid vehicle is electrically connected, is performed. Electric drive train ( 10 ) of an electric or hybrid vehicle comprising a high-voltage battery system ( 11 ) and an electric machine ( 14 ), which are controlled by a control unit ( 13 ) are electrically connected to one another, characterized in that operating parameters (x) of the high-voltage battery system (x) detected during control-related debounce times ( 11 ) from the control and / or regulating unit ( 13 ) are mathematically evaluable, wherein limit value exceedings of the operating parameters (x) of the control and / or regulating unit ( 13 ) and can be counted as a number of fault entries (N), and by comparing the number of fault entries (N) with a reference value (R) and / or a time analysis of the number of fault entries (N) problems in the electric drive train ( 10 ) from the control and / or regulating unit ( 13 ) are diagnosable.

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