DE102010003421A1 - Energy storage device operating method for e.g. hybrid car, involves determining initial sizes of energy storage voltage and current, determining two state of charge, and determining state of charge loss dependent on two state of charge - Google Patents

Abstract

The method involves determining initial sizes (U, I) of detected energy storage voltage and current, respectively. A state of charge (SOC) of an energy storage device (10) is determined depending on the initial size of detected energy storage voltage. Another state of charge (SOCi) of the energy storage device is determined depending on an initial value and the initial size of current, where the value is representative of the former state of charge at the end of a previous operation phase. A state of charge loss (deltaSOC) is determined dependent on the two state of charge. An independent claim is also included for a device for operating an energy storage device during a current operating phase.

Description

The invention relates to a method and a device for operating an energy store, in which or in which a first state of charge and a second state of charge of an energy store are determined.

Due to low CO ₂ emissions, interest in battery-powered vehicles, especially hybrid-powered vehicles, is growing rapidly. Vehicles with hybrid drive have in comparison to conventional vehicles on an additional energy storage in which recovered energy can be stored. For the function of battery-powered vehicles and hybrid vehicles, the performance of the energy storage plays an essential role. Many modern energy storage systems used in hybrid vehicles and battery vehicles, for example, have monitoring and battery management electronics.

SH Choi, J. Kim, Y. Yoon, Self-discharge analysis of LiCoCO2 for lithium batteries, Journal of Power Sources 138 (2004), pages 283 to 287 discloses an experimental determination of self-discharge of various Li / LiCoCO ₂ energy storage cells, each having different particle sizes. To determine the self-discharge, a drop in a quiescent voltage of the energy store is evaluated.

The object on which the invention is based is to provide a method and a device for operating an energy store which makes a contribution to operating the energy store reliably.

The object is solved by the features of the independent claims. Advantageous embodiments are characterized in the subclaims.

The invention is characterized by a method and a corresponding device for operating an energy store. During a current operating phase of the energy store, a first operating variable representative of a sensed energy storage voltage and a second operating variable representative of a sensed energy storage current are determined. During the current operating phase of the energy store, a first state of charge of the energy store is determined as a function of at least the first operating variable. Furthermore, depending on a predetermined first initial value and at least the second operating variable, but independent of the first operating variable, a second state of charge of the energy store is determined, wherein the first initial value is representative of the first state of charge of the energy store at the end of a previous operating phase. The previous operating phase and the current operating phase are separated by a rest phase. Depending on the first state of charge and the second state of charge, a state of charge loss is determined.

Preferably, the first state of charge is also determined depending on the second operating variable. The first operating variable is, for example, the analog-digitally converted energy storage voltage and the second operating variable the analog-digitally converted energy storage current. It is also possible for the detected energy storage voltage and the detected energy storage current to be processed further by means of a signal conditioning unit, for example by being filtered. By taking into account the first operating variable when determining the first state of charge and disregarding the first operating variable when determining the second state of charge, a state of charge loss can be determined using the knowledge that the second state of charge does not take account of charging losses during the idle phase. By comparing the first state of charge with the second state of charge, the charge state loss of the energy store during the idle phase, which lies between the preceding and the current operating phase, can thus advantageously be determined virtually without errors. For example, in the course of a vehicle life a total duration of the rest periods clearly outweighs a total duration of the operating phases. A large part of a self-discharge of the energy storage thus takes place in the resting phases. During the operating phase, for example, energy storage electronics are active and an energy storage circuit is closed via a load connected to the energy store. During the resting phase, however, the energy storage circuit is not closed via a load connected to the energy storage.

According to an advantageous embodiment of the invention, the state of charge state is determined at the earliest after a predetermined first period of time from the beginning of the current operating phase as a function of the first state of charge and the second state of charge. This allows to determine the state of charge loss taking into account possible settling times.

According to a further advantageous embodiment of the invention, the first state of charge is determined by means of a state estimator depending on the first operating variable. In the state estimation, it is assumed that at least the first operating variable has noise components and the first state of charge is estimated and determined non-deterministically. The state estimation has a settling time. Advantageously, the first time duration is selected equal to the settling time of the state estimate.

According to a further advantageous embodiment of the invention, the state estimator comprises a Kalman filter. The Kalman filter is a linear filter and allows for easy implementation.

According to a further advantageous embodiment of the invention, the second state of charge is determined depending on an integration of the second operating variable. The determination of the second state of charge as a function of the integration of the second operating variable has the advantage that a state of charge change can be easily determined by charging or discharging the energy store during the operating phase taking into account the predetermined first initial value.

According to a further advantageous embodiment of the invention, a mean self-discharge current is determined as a function of the state of charge loss and a resting phase duration, which is representative of a period of time between the current and the preceding operating phase.

Advantageously, it can be estimated with the aid of the determined average self-discharge current, how long a possible rest phase of the energy store may last at most until the energy store falls below a critical state of charge. The critical state of charge can be characterized, for example, as a state of charge, in which at least one functionality of the energy store is impaired, for example, in which it is no longer possible to start an internal combustion engine by an electric motor of a hybrid vehicle. Furthermore, an estimate of an aging state of the energy store can be carried out with the aid of the determined average self-discharge current, for example with the aid of energy storage-specific aging characteristics.

According to a further advantageous embodiment of the invention, the first state of charge is determined depending on a further operating variable. For example, the further operating variable may be representative of a measured energy storage temperature. The use of a further operating variable may contribute to reducing mis estimates of the first state of charge by the state estimator.

According to a further advantageous embodiment of the invention, the second state of charge is determined depending on the further operating variable. For example, the further operating variable may be representative of a measured energy storage temperature. As a result, for example, a contribution can be made to more accurately determine the second state of charge of the energy store.

According to a further advantageous embodiment of the invention, an energy storage temperature is determined at predetermined periods and determined during at least one operating phase in each case at the predetermined first time of state of charge loss and determined depending on the respective energy storage temperatures and the respective state of charge loss temperature-dependent self-discharge. With the help of the determined energy storage temperatures, a temperature histogram can be created, in particular for the resting phases of the energy storage. The temperature histogram has, for example for specific temperature ranges, in each case a cumulative time duration during which the energy store in each case has the specific temperature range. Advantageously, the temperature histogram is updated at the beginning of the respective operating phase. A number of the specific temperature ranges and a number of cumulative dwell phases may be specified for each application. The temperature histogram has, for example, a minimum of three to a maximum of seven specific temperature ranges and, for example, the temperature histogram is determined in each case for a minimum of three to a maximum of seven rest periods. Advantageously, such a temperature dependence of the respective self-discharge currents of the energy store can be determined during one or more rest periods. If the number of rest periods and the number of specific temperature ranges are chosen to be the same, it is very easy to calculate the temperature-dependent self-discharge currents. By knowing the temperature dependence of the self-discharge of the energy store during the rest phases, it is possible to determine the aging state and a maximum rest period of the energy storage depending on the energy storage temperatures and, for example, additionally or alternatively taking into account the respective ambient temperature.

Embodiments of embodiments of the invention are explained in more detail below with reference to schematic drawings. Show it:

1 a first embodiment of a device 100 to operate an energy storage 10 in connection with a measuring device 200 and the energy storage 10 .

2 A second embodiment of the device 100 to operate the energy storage 10 in connection with the measuring device 200 and the energy storage 10 and

3 a temperature histogram, a state of charge loss diagram and a diagram of a temperature-dependent self-discharge current ISD.

1 shows a measuring unit 200 and a device 100 to operate an energy storage 10 , The measuring unit 200 For example, it is designed to detect an energy storage voltage and an energy storage current. The measuring unit 200 For example, it may also be designed to detect further measured variables, for example an energy storage temperature Temp.

The device 100 to operate the energy storage 10 has, for example, a signal conditioning unit 105 , a state of charge unit 110 and a first evaluation unit 160 on.

The signal conditioning unit 105 For example, it is designed to determine a first operating variable U, which is representative of the measured energy storage voltage and to determine a second operating variable I, which is representative of the measured energy storage current. The signal conditioning unit 105 For example, it may include a filter for suppressing measurement noise.

The charge status unit 110 includes, for example, a state estimator 130 , an integration unit 140 , a summation unit 150 and a timer unit 120 ,

The state estimator 130 is coupled with the signal conditioning unit 105 , The state estimator 130 the first operating variable U, preferably also the second operating variable I, is supplied. The state estimator 130 is formed, depending on the first operating variable U, preferably also dependent on the second operating variable I, to determine a first state of charge SOC. The state estimator 130 For example, it can be designed as a Kalman filter. It is also possible that the state estimator 130 in addition to the first operating variable U, in addition to or as an alternative to the second operating variable I, at least one further operating variable is supplied and the first charging state SOC is determined as a function of the first operating variable U and at least the further operating variable.

The integration unit 140 is for example coupled with the signal conditioning unit 105 , The integration unit 140 the second operating variable I is supplied. The integration unit 140 is formed, depending on a predetermined first initial value and the second operating variable I, but independent of the first operating variable U, to determine a second state of charge SOCi. The initial value is, for example, the first state of charge SOC of the energy store 10 at the end of a previous operating phase, wherein the preceding operating phase and the current operating phase are separated by a rest phase. It is also possible that the integration unit 140 in addition to the second operating variable I at least one further operating variable, but not the first operating variable U, is supplied and the second state of charge SOCi is determined depending on the second operating variable I and at least the further operating variable.

The summation unit 150 is, for example, coupled with the state estimator 130 and the integration unit 140 , The summation unit 150 Thus, the first state of charge SOC and the second state of charge SOCi are supplied. The summation unit 150 For example, it is configured to determine a state of charge loss ΔSOC which is equal to the difference between the first state of charge SOC and the second state of charge SOCi. The determination of the state of charge loss ΔSOC takes place, for example, at the earliest after a predetermined first period of time from the start of the current operating phase, wherein the first time duration is a settling time of the state estimator 130 is.

The timer unit 120 For example, it is designed to determine in each case a rest period t, which is representative of a period of time between the current and the preceding operating phase.

The first evaluation unit 160 has, for example, a current calculation unit 163 on. The current calculation unit 163 is coupled to the summation unit 150 and the timer unit 120 , Of the Current calculation unit 163 In each case, the state of charge loss ΔSOC and the rest phase duration t are supplied. The current calculation unit 163 is designed, for example, to determine a mean self-discharge current ISE, depending on a ratio of the state of charge loss ΔSOC to the resting phase duration t. The first evaluation unit 160 For example, a supplementary unit that is in 1 is not shown, which is designed to determine depending on the average self-discharge current ISE, how long a possible rest phase of the energy storage can last a maximum of time until the energy storage falls below a critical state of charge. Furthermore, the supplementary unit can be designed to estimate an aging state of the energy store with the aid of the determined mean self-discharge current ISE, for example with the aid of energy-specific aging characteristics which are stored, for example, in a memory unit.

The device 100 to operate an energy storage 10 For example, it can be designed as a computer unit with a program and data memory.

2 shows a second embodiment of the device 100 to operate an energy storage 10 in conjunction with an energy storage 10 , a measurement unit 200 and a temperature measuring unit 300 ,

The temperature measuring unit 300 For example, it is designed to measure an energy storage temperature Temp at predetermined time intervals, in particular during a rest phase. For example, the energy storage temperature Temp is measured at regular intervals. If the predetermined time intervals are selected the same, this has the advantage that the time intervals do not have to be temporarily stored for the further processing of measured values. For example, it can be specified that the energy storage temperature Temp is measured every hour.

This in 2 shown second embodiment of the device 100 to operate the energy storage 10 indicates the state of charge unit 110 and a second evaluation unit 190 on. The measuring unit 200 and the state of charge unit 110 are for example analogous to that in 1 formed first embodiment shown.

The second evaluation unit has, for example, a histogram unit 191 , a vector unit 193 and a power unit 195 on.

The histogram unit 191 is coupled with the temperature measuring unit 300 , the timer unit 120 and the summation unit 150 , The histogram unit 191 is formed, depending on the respective rest period of the rest phase and the measured energy storage temperatures Temp a temperature histogram for the energy storage 10 to investigate. The temperature histogram indicates in each case a cumulative duration, how long the energy store 10 for example, has a specific temperature range during several rest periods. The determination of the temperature histogram, for example, for several consecutive periods of rest. For example, three resting phases are evaluated and given three specific temperature ranges. For this purpose, the energy storage temperature Temp is measured and stored during each resting phase in the predetermined time intervals. Subsequently, it is determined for the respective specific temperature range how long the energy store has the respective specific temperature range during the three rest phases. If the temperature histogram is updated at the beginning of the respective operating phase, this has the advantage that current values are available and storage space requirements can be kept low. Taking into account, for example, three resting phases and three specific temperature ranges, the temperature histogram can be determined using a 3 × 3 matrix according to Equation Eq. 1:

The vector unit 193 is coupled to the summation unit 150 , The vector unit 193 has, for example, a memory unit in which the state of charge losses ΔSOC of the rest phases are temporarily stored.

The power unit 195 is formed, depending on the determined state of charge losses ΔSOC during the resting phases and depending on the temperature histogram a temperature-dependent Self-discharge current ISD, for example, according to equation Eq. 2 for each specific temperature range to determine.

If the number of specific temperature ranges to be considered and the number of quiescent phases to be taken into account are the same, and thus the temperature histogram can be represented by means of a square matrix, the temperature-dependent self-discharge current ISD can be calculated according to Eq. 2 are determined. If the temperature histogram can not be represented by means of a square matrix, since the number of specific temperature ranges and the number of rest periods are different, the temperature-dependent self-discharge current ISD can be numerically calculated, for example.

3a shows an example of the temperature histogram taking into account three rest periods and three specific temperature ranges.

3b shows the determined state of charge loss ΔSOC for three periods of rest depending on a respective rest phase duration t1, t2, t3.

3c shows the cumulative for the specific temperature range over the three rest periods temperature-dependent self-discharge current ISD.

LIST OF REFERENCE NUMBERS

10

energy storage

100

Device for operating an energy store

105

Signal conditioning unit

110

SOC unit

120

Timer unit

130

Charge state estimator

140

integration unit

150

Summation unit

160

first evaluation unit

163

Stromberechungseinheit

190

second evaluation unit

191

histogram unit

193

vector unit

195

power unit

200

measuring unit

300

Temperature measurement unit

H

Temperature histogram matrix

I

second farm size

ISE

Self-discharge current

ISD

temperature-dependent self-discharge current

S

SOC loss vector

SOC

first charge state

Soci

second charge state

t

Dormancy period

Temp

Energy storage temperature

U

first farm size

.DELTA.SOC

SOC loss

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 non-patent literature

• SH Choi, J. Kim, Y. Yoon, Self-discharge analysis of LiCoCO 2 for lithium batteries, Journal of Power Sources 138 (2004), pages 283 to 287 [0003]

Claims (10)

Method for operating an energy store ( 10 ), during which during a current operating phase of the energy store ( 10 ) - a first operating variable (U) is determined, which is representative of a detected energy storage voltage, - a second operating variable (I) is determined, which is representative of a detected energy storage current, - depending on at least the first operating variable (U), a first state of charge (SOC) of the energy store ( 10 ) is determined, depending on a predetermined first initial value and at least the second operating variable (I), but independent of the first operating variable (U), a second state of charge (SOCi) of the energy store ( 10 ), wherein the first initial value is representative of the first state of charge (SOC) of the energy store ( 10 ) at the end of a previous operating phase, which is separated by a rest phase of the current operating phase, and - depending on the first state of charge (SOC) and the second state of charge (SOCi) a state of charge loss (.DELTA.SOC) is determined. Method according to Claim 1, in which the state of charge state loss (ΔSOC) is determined at the earliest after a predetermined first period of time from the beginning of the current operating phase as a function of the first state of charge (SOC) and the second state of charge (SOCi). Method according to one of claims 1 or 2, wherein the first state of charge (SOC) is determined by means of a state estimator depending on the first operating variable (U). The method of claim 3, wherein the state estimator comprises a Kalman filter. Method according to one of the preceding claims, in which the second state of charge (SOCi) is determined as a function of an integration of the second operating variable (I). A method according to any one of the preceding claims, wherein an average self-discharge current (ISE) is determined in dependence on the state of charge loss (ΔSOC) and a resting phase duration (t) which is representative of a period of time between the current and the preceding phases of operation. Method according to one of the preceding claims, in which the first state of charge (SOC) is determined as a function of a further operating variable. Method according to one of the preceding claims, in which the second state of charge (SOCi) is determined as a function of the further operating variable. Method according to one of the preceding claims, in which An energy storage temperature (Temp) is determined in predetermined time intervals, During at least one operating phase, the charge state loss (ΔSOC) is determined in each case at the predetermined first time, - Depending on the respective energy storage temperatures (Temp) and the respective state of charge losses (ΔSOC) temperature-dependent self-discharge currents (ISD) can be determined. Device for operating an energy store ( 10 ), which is formed during a current operating phase of the energy store ( 10 ), - to determine a first operating variable (U) which is representative of a detected energy storage voltage, - to determine a second operating variable (I), which is representative of a detected energy storage current, - depending on at least the first operating variable (U) a first State of charge (SOC) of the energy store ( 10 ), - depending on a predetermined first initial value and at least the second operating variable (I), but independent of the first operating variable (U), a second state of charge (SOCi) of the energy store ( 10 ), wherein the first initial value is representative of the first state of charge (SOC) of the energy store ( 10 ) at the end of a previous operating phase, which is separated by a rest phase of the current operating phase, and - depending on the first state of charge (SOC) and the second state of charge (SOCi) to determine a state of charge loss (.DELTA.SOC).

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