ELECTRICAL ENERGY STORAGE SYSTEM COMPRISING A CROSS-CONNECTION OF A PLURALITY OF PARALLEL ENERGY STORAGE STRINGS THAT IS ELECTRICALLY CONDUCTIVELY CONNECTED TO A CURRENT DETECTION MEANS VIA A DIODE, AND METHOD FOR DETECTING A CONDUCTION FAULT

Abstract

Electrical energy storage system (1), comprising at least two strings (STR1, STR2, STR3) interconnected in parallel connection, wherein the strings each have at least two electrical energy storage units (15) interconnected in series connection, characterized in that at least one first electrically conductive cross-connection (11) between electrical energy storage units (15) at an identical first electrical potential in the strings (STR1, STR2, STR3) interconnected in parallel connection is electrically conductively connected via at least one diode (12) to a means for detecting an electric current (13) and a controllable electrical energy source (14), wherein the diode (12) is not incorporated into the first electrically conductive cross-connection (11).

Claims

1. An electrical energy storage system (1), comprising: at least two strings interconnected in parallel (STR1, STR2, STR3) and are at an identical first electrical potential, the at least two strings (STR1, STR2, STR3) each comprising at least two electrical energy storage units (15) interconnected in series, wherein at least a first electrically conductive cross-connection (11), between electrical energy storage units (15) in the strings (STR1, STR2, STR3), is electrically conductively connected, via at least one diode (12), to a current sensor (13) configured to detect an electric current (13) and a controllable electrical energy source (14), wherein the diode (12) is separate from the first electrically conductive cross-connection (11).

2. The electrical energy storage system (1) as claimed in claim 1, wherein the at least one first electrically conductive cross-connection (11) is electrically conductively connected, via the at least one diode (12), to at least a second electrically conductive cross-connection (21), between electrical energy storage units (15) in the strings (STR1, STR2, STR3) which are interconnected in parallel and which are at an identical second electrical potential, wherein the first electrical potential and the second electrical potential are different.

3. The electrical energy storage system (1) according to claim 2, wherein the at least one second electrically conductive cross-connection (21), referenced to a defined reference potential, is at a higher electrical potential than the at least one first electrically conductive cross-connection (11), and the at least one diode (12) is installed in the forward direction between the at least one first electrically conductive cross-connection (11) and the at least one second electrically conductive cross-connection (21).

4. The electrical energy storage system (1) as claimed in claim 2, wherein the diode (12) and the electrically conductive connection to the current sensor (13) are situated at different ends of the second electrically conductive cross-connection (21).

5. The electrical energy storage system (1) as claimed in claim 1, wherein the controllable electrical energy source (14) is a current source.

6. A method for detecting a line fault in an electrical energy storage system (1) as claimed in claim 1 the method comprising: a) detecting at least a first current signal profile (SIG1) via the current sensor (13); b) comparing the detected at least one first current signal profile (SIG1) to a second current signal profile (SIG2) specified by the controllable electrical energy source (14); and c) generating a signal indicating a detection of a line fault in the electrical energy storage system (1) when a predefined signal deviation threshold value is exceeded.

7. The method as claimed in claim 6, wherein the controllable electrical energy source (14) generates a pulse-shaped current signal profile (SIG1, SIG2).

8. The method as claimed in claim 6, characterized in that the method is carried out for at least a predefined period (t12, t34).

9. A device, comprising an electrical energy storage system (1) comprising at least two strings interconnected in parallel (STR1, STR2, STR3) and are at an identical first electrical potential, the at least two strings (STR1, STR2, STR3) each comprising at least two electrical energy storage units (15) interconnected in series, wherein at least a first electrically conductive cross-connection (11), between electrical energy storage units (15) in the strings (STR1, STR2, STR3), is electrically conductively connected, via at least one diode (12), to a current sensor (13) configured to detect an electric current (13) and a controllable electrical energy source (14), wherein the diode (12) is separate from the first electrically conductive cross-connection (11), the device configured to a) detect at least a first current signal profile (SIG1) via the current sensor (13); b) compare the detected at least one first current signal profile (SIG1) to a second current signal profile (SIG2) specified by the controllable electrical energy source (14); and c) generate a signal indicating a detection of a line fault in the electrical energy storage system (1) when a predefined signal deviation threshold value is exceeded.

10. The electrical energy storage system (1) as claimed in claim 1, wherein the electrical energy storage system is part of an electrically driven vehicle.

11. The method as claimed in claim 6, wherein the method is carried out for an integral multiple of a period duration (t12, t34) of the second current signal.

12. The electrical energy storage system (1) as claimed in claim 1, wherein the electrical energy storage system is part of a stationary energy storage system.

13. The electrical energy storage system (1) as claimed in claim 1, wherein the electrical energy storage system is part of an electrically operated hand tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Advantageous embodiments of the present invention will be depicted in the figures and will be described in greater detail in the following description

[0019] The following are shown:

[0020] FIG. 1 shows a schematic representation of the electrical energy storage system according to the present invention, according to a first embodiment;

[0021] FIG. 2 shows a schematic representation of the electrical energy storage system according to the present invention, according to a second embodiment;

[0022] FIG. 3 shows a schematic representation of the electrical energy storage system according to the present invention, according to a third embodiment;

[0023] FIG. 4 shows a flow chart of the method according to the present invention, according to one embodiment;

[0024] FIG. 5 shows a schematic representation of the current signal profiles used within the method according to the present invention, according to a first embodiment; and

[0025] FIG. 6 shows a schematic representation of the current signal profiles used within the method according to the present invention, according to a second embodiment.

DETAILED DESCRIPTION

[0026] In all figures, identical reference numerals refer to identical device components or identical method steps.

[0027] FIG. 1 shows a schematic representation of the electrical energy storage system 1 according to the present invention, according to a first embodiment. The electrical energy storage system 1 comprises two strings STR1, STR2 interconnected in parallel, wherein the strings STR1, STR2 respectively comprise two electrical energy storage units 15 interconnected in series. A first electrically conductive cross-connection 11, between electrical energy storage units 15 in the strings STR1, STR2 which are interconnected in parallel and which are at an identical first electrical potential, is electrically conductively connected, via a diode 12, to a current sensor 13, for example, a Hall sensor or a shunt-based current sensor, and to an electrical energy source 14.

[0028] FIG. 2 shows a schematic representation of the electrical energy storage system according to the present invention 1, according to a second embodiment. The electrical energy storage system 1 comprises the two strings STR1, STR2 which are interconnected in parallel, wherein the strings STR1, STR2 have respectively been extended by one electrical energy storage unit 15, and thus comprise three electrical energy storage units 15 which are interconnected in series. The first electrically conductive cross-connection 11 is present between energy storage units 15 which are at an identical first electrical potential. The first electrically conductive cross-connection 11 is electrically conductively connected, via the diode 12, to a second electrically conductive cross-connection 21 which connects electrical energy storage units 15 which are at a second electrical potential. The second electrically conductive cross-connection 21 is connected to the current sensor 13 and the electrical energy source 14. The diode 12 and the electrically conductive connection to the current sensor 13 are situated at different ends of the second electrically conductive cross-connection 21.

[0029] FIG. 3 shows a schematic representation of the electrical energy storage system 1 according to the present invention, according to a third embodiment. Here, the electrical energy storage system 1 comprises three strings STR1, STR2, STR3 connected in parallel. The dashed lines in the depiction of the strings STR1, STR2, STR3 indicate that the principle depicted in FIG. 1 and in FIG. 2 can in principle be extended to strings comprising a more or less arbitrary number of electrical energy storage units 15. Electrically conductive cross-connections 11, 21, 31 connect the electrical energy storage units 15, which are at an identical potential. Electrical resistance elements 32 are installed in the electrically conductive cross-connections 11, 21, 31, in order to limit compensation currents potentially flowing between the electrical energy storage units 15.

[0030] FIG. 4 shows a flow diagram of the method according to the present invention, according to one embodiment. In a first step S1, a current signal profile within the circuit, which is formed by the components: electrically conductive cross-connection 11, diode 12, current sensor 13, electrical energy source 14, and a corresponding electrically conductive return connection to the electrically conductive cross-connection 11, is detected by means of the current sensor 13. In a second step S2, the detected current signal profile is compared to a current signal profile which is specified by the energy source 14. If there are no faults in the above-described circuit, these current signal profiles will be highly similar. In a third step S3, if a predefined signal deviation threshold value is exceeded, a signal indicating the detection of a line fault in the electrical energy storage system 1 or in the above-described circuit is subsequently generated, if necessary. Thus, for example, the user of the electrical energy storage system 1 may be informed of a fault in the electrical energy storage system 1.

[0031] FIG. 5 shows a schematic representation of the current signal profiles SIG1, SIG2 according to a first embodiment, which are used within the method according to the present invention. The first current signal profile SIG1 shows the current signal profile detected by the current sensor 13. The second current signal profile SIG2 shows the current signal profile specified by the electrical energy source 14, which is known, for example, because it is specified by suitable programming on an electronic control unit. Both current signal profiles proceed in a pulse-shaped manner, between a first current value I1 and a second current value I2. A time difference t12, between a first instant t1 which determines a start of a current signal period, and a second instant t2 which determines an end of the current signal period, constitutes the period duration of the second current signal. By means of the integral of the magnitude of the difference between the first current signal profile SIG1 and the second current signal profile SIG2 over a period duration of the second current signal, a signal deviation value may be calculated which is compared to a predefined signal deviation threshold value, wherein if the predefined signal deviation threshold value is exceeded, a signal indicating the detection of a line fault is generated.

[0032] FIG. 6 shows a schematic representation of the current signal profiles SIG1, SIG2 according to second embodiment, which are used within the method according to the present invention. Here, the current signal profiles are also pulse-shaped, wherein the second current value I2 is 0 mA. A difference between the two current signal profiles SIG1, SIG2 is depicted by hatched lines in FIG. 6, exactly as in FIG. 5. A time difference t34 between a third instant t3 and a fourth instant t4 determines a period duration of the first current signal. Instead of the aforementioned integral as a signal deviation value, alternatively, a Fourier transform of the first current signal profile SIG1 and the second current signal profile SIG2 may be carried out, wherein the predefined signal deviation threshold value is then determined, for example, as a quantity in the phase space of the Fourier transform, for example, a power density.