EP2862255A2

EP2862255A2 - Switching device for a battery and corresponding switching method

Info

Publication number: EP2862255A2
Application number: EP13717496.7A
Authority: EP
Inventors: Joerg Ziegler; Thomas Plum; Marcus Preissner; Johanna May
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2012-06-14
Filing date: 2013-04-18
Publication date: 2015-04-22
Also published as: DE102012209995A1; WO2013185955A3; WO2013185955A2; CN104604076B; CN104604076A

Abstract

The invention devises a switching device (10) for a battery (2), comprising: a control device (1); and a control switch (S); wherein, by means of the switch (S) activated by the control device (1), cells (Z) of the battery (2) can be wired to one another variably in such a way that a terminal voltage of the battery (2) is substantially independent of the state of charge of the cells (Z).

Description

description

title

Switching device for a battery and corresponding switching method The invention relates to a switching device for a battery. The invention further relates to a method for interconnecting cells of a battery.

PRIOR ART Nowadays, electrical energy stores are in the form of accumulators

(rechargeable batteries) to DC generators in different electrical circuit topologies with integrated.

DE 21 2008 000 035 111 discloses a high-frequency inverter for converting a DC voltage generated by at least one solar module via at least one input DC / DC converter, an intermediate circuit and an output DC / AC converter into an AC voltage for supplying consumers and or for feeding into a supply network. In this case, the input DC / DC converter is connected to a control device.

US 2004/0125618 A1 discloses a power converter system which interconnects various types of electrical power sources and provides a defined type of electrical power, for example a standard mains voltage supply for a load. Each of the electrical power sources is electrically isolated from the load and also against each other. A corresponding input transducer is connected to each power source.

Disclosure of Invention The invention provides a switching device for a battery, comprising:

a control device; and - Switch; wherein by means of the controlled by the controller switch cells of the battery can be variably interconnected such that a terminal voltage of the battery is substantially independent of a state of charge of the cells.

According to a further aspect, the invention provides a method for interconnecting cells of a battery, comprising the following steps:

Determining a state of charge of the cells; and

- Connecting the cells of the battery by means of switches such that a terminal voltage of the battery is substantially independent of a state of charge of the cells.

Preferred developments are the subject of dependent claims. Advantages of the invention

The idea underlying the present invention is that a

Terminal voltage of a battery with rechargeable cells should be substantially independent of a state of charge of the cells. By interconnecting the cells according to the invention, the battery can be better connected to an inverter of a DC voltage generator. In particular, the constancy of a DC link voltage of the inverter is favored by the constant terminal voltage of the battery. As a result, the inverter of the battery can be designed to be more power-optimized in an advantageous manner, for example, a voltage swing of the inverter can be lower. Advantageously, thereby inverter for the

DC voltage generator be less lossy and cheaper to manufacture.

An advantageous development of the switching device provides that for determining the state of charge electrical voltages of each cell of the battery are determined. Advantageously, by this direct measurement of the electrical voltages low-performance cells before a complete discharge with a negative impact on the

Lifespan be preserved. Furthermore, by discharging all cells to the minimum state of charge, a higher capacity of the battery can be used. A preferred embodiment of the switching device provides that cell modules are interconnected with at least one cell. This advantageously makes it possible to use a simplified switch mechanism, since a number of cell modules is generally smaller than a number of cells.

An advantageous development of the switching device provides that by means of the switch, a defined number of cells in series and / or can be connected in parallel. As a result, it is advantageously possible to generate very flexible switching structures or switching composites of cells, as a result of which an outwardly acting terminal voltage of the battery can be set very finely.

An advantageous development of the switching device provides that by the

Connect the terminal voltage of the battery is adapted to an intermediate circuit voltage of an inverter of a DC voltage generator. As a result, the battery is adapted to an optimal working range of the inverter, whereby the electrical converter of the battery advantageously a lower voltage swing

has to accomplish and thus can be dimensioned less powerful.

An advantageous embodiment of the switching device provides that the switching device is disposed within the battery. This is advantageous one

Uses variety of equipped with a switching device according to the invention battery increases.

A preferred embodiment of the method according to the invention provides that, for a frequency of interconnecting the cells and / or forming a switching interconnection of the cells, a state of charge of each individual cell is taken into account. This advantageously causes a balancing of the cells.

A preferred embodiment of the method provides that electrical voltages are determined by each individual cell or cell modules with a plurality of cells. As a result, on the one hand a direct measurement of the cell voltages is carried out, whereby a quality of the individual cells is determined. Alternatively, a module measurement is performed on cell modules having a plurality of cells, wherein in each case an electrical voltage of a switching group of cells is measured. From a difference of module voltages can be concluded that charge states of single cells. A preferred embodiment of the method provides that cells are cyclically removed from the switching network during interconnection and taken into the switching network. As a result, a regular exchange of charging and discharging of the cells is supported by means of a ring exchange, because no cell is completely excluded from a charge / discharge process for a longer period of time. A uniform state of charge and thus an extended operating life of the cells are supported in this way.

A preferred embodiment of the method provides that the

Taking out the cells from the switching network depending on the state of charge of the cells is performed. This advantageously further reduces one

Unequal distribution of states of charge of the cells.

An advantageous development of the method proposes that a frequency of changing the interconnection of the cells from a level of a current within the

Switching group depends. This advantageously takes into account the fact that a change in a state of charge of the cell depends on a current intensity of a charging current. As a result, charge states of the individual cells can be taken into account individually for each cell.

An advantageous development of the method provides that always a defined number of cells remains excluded from the switching network, wherein the recessed cells are exchanged cyclically. This ensures that in each case a defined number of cells is provided in the switching network, which is advantageous in conjunction with the cyclic replacement of the recessed cells, a uniform state of charge of the cells is supported.

A preferred embodiment of the method provides that the cyclic

The higher the charge / discharge flow of the cells, the quicker the cells are to be exchanged. This advantageously takes into account the fact that a

Debalancing of the cells depends to a high degree on a current strength. Thus, a debalancing of cells can be counteracted in this way.

A preferred embodiment of the method provides that the cells are connected in such a way that the cells of the switching networks comprise the largest possible number of cells. This will advantageously a maximum number of cells in the Switching group added, creating a maximum number of cells on

Loading / unloading is involved. This advantageously becomes more uniform

Charge state of the cells supported.

Further features and advantages of the present invention will be explained below with reference to embodiments with reference to the figures. All described or illustrated features, alone or in any combination form the subject matter of the invention, regardless of their summary in the claims or their dependency, as well as regardless of their formulation or representation in the description or in the figures. The figures are primarily intended to illustrate the principles essential to the invention. In the figures, like reference numerals designate the same or functionally identical elements.

Brief description of the drawings

Show it:

Fig. 1 a shows a configuration with a DC voltage generator and

Battery according to the prior art;

Fig. 1b shows a further configuration with a DC voltage generator and a battery according to the prior art;

2 shows an embodiment of a switching device according to the invention;

3a shows a configuration of a switching network according to the invention of cells of a battery;

3b shows a further configuration of a switching network according to the invention of cells of a battery; and

FIG. 4 shows a configuration of a DC power generation system, in FIG

which the switching device according to the invention is used. Embodiments of the invention

1 a is a greatly simplified, schematic representation of a conventional system with a DC voltage generator 4 and a rechargeable battery 2. The DC voltage generator 4 may be formed, for example, as a photovoltaic system with a plurality of panels which generate a DC voltage and this to a conversion into an inverter 5 feed. The inverter 5 has internally a DC / DC converter 5a (DC-DC converter) and an AC / DC converter 5b (DC / AC converter), wherein between the DC / DC converter 5a and the AC / DC converter 5b, an intermediate circuit 6 is arranged , An output voltage of the inverter 5 feeds an electrical network 8 (e.g., household AC mains) and / or supplies electrical consumers.

Furthermore, a battery 2 with rechargeable cells (not shown) is provided in the system, which feeds a DC voltage into an inverter 5, wherein an output voltage of the inverter 5 also feeds the network 8 and / or supplies electrical consumers. The inverter 5 of the battery 2 includes a bi-directional (two-way current flow possible) AC / DC converter 5 b and a DC / DC converter 5 a for setting the currently required charging or

Discharge voltage for the battery 2.

In an alternative conventional configuration according to FIG. 1 b, the battery 2 is connected directly to a DC link 6 of the inverter 5 of the DC voltage generator 4 via a DC / DC converter 5 a. In this way one needs compared to the configuration of Fig. 1 a one less transducer.

After a terminal voltage U _{k of} the battery 2 depending on the battery technology depends to a high degree on a state of charge of the individual cells of the battery 2, the DC / DC converter 5 a may have to perform high voltage strokes to a required voltage level for the intermediate circuit 6 of the inverter. 5 provide. Thus, the DC / DC converter 5a of the battery 2 with respect to a

Circuit complexity and efficiency over a work area to be able to design optimized, the most constant input and output voltage from the battery 2 is desirable. According to the invention it is therefore provided that a switching device or a

Switching mechanism is provided which provides by means of a variable, dynamic interconnection of the cells of the battery 2 as constant a terminal voltage of the battery 2.

Fig. 2 shows a first embodiment of the switching device according to the invention. The switching device 10 comprises a control device 1 (for example a microcontroller), by means of which a plurality of switches S (eg electronic switches) can be activated and operated. By means of the switches S and the control device 1, the cells Z can be variably interconnected in such a way that a terminal voltage U _{k of} the battery 2 is substantially independent of

Charge states of the cells Z is.

It is known that an electrical voltage of rechargeable battery cells depends strongly on their current state of charge. By way of example, an electrical cell voltage of a lithium-ion cell in the discharged state is approximately 2.5 V and in the charged state approximately 4.2 V. As a result, a total electrical voltage of a plurality of interconnected cells Z is disadvantageously highly dependent on the states of charge of the individual Cells Z dependent.

To counteract this fact, by means of the switch S, a switching structure or a switching network 7 of the cells Z is configured and current

Requirement adapted that a terminal voltage U _{k of} the battery 2 is as constant as possible. For this purpose, a state of charge of the individual cells Z is determined. For example, this can be done by means of a determination device (not shown), wherein electrical voltages of the individual cells Z are determined or electrical voltages of cell modules 3 having a plurality of cells Z. By way of example only two cell modules 3 are shown in FIG. As a result, the individual state of charge of each individual cell Z can be taken into account for the interconnection according to the invention. The cell modules 3 can in extreme cases consist of individual cells Z. Another extreme case is the measurement of the total voltage and a reconnection solely with this information.

The cell modules 3 are connected in parallel or in series with one another in different ways, in order thereby to come as close as possible to the terminal voltage U _{K of} the battery 2 to an optimum operating point of the DC / DC converter 5 a, or within to remain predetermined, narrow voltage limits of the DC / DC converter 5a. The entire interconnection takes place dynamically, according to the loading

For example, it may be switched in sub-second, second, minute or hourly intervals. By means of the switch S is thus an almost unlimited variety of possible

Switching structures with cells Z conceivable. For example, cells Z and / or

Cell modules 3 are connected in series and / or in parallel. By bridging cells Z by means of the switches S, cell voltages for a total voltage are not considered. By way of example only, FIG. 2 shows a parallel connection of strings having a plurality of serially connected cells Z, where Z defines a first cell in a first column, Z ₁₂ a second cell in the first column, etc.

In order to achieve a homogenization of the state of charge of the individual cells Z, it is preferably provided that individual cells Z are cyclically removed from the switching assembly 7 or taken into the switching assembly 7, respectively. In this way, none of the cells Z is permanently charged / discharged

locked out. The cyclic exchange of the cells Z should preferably be faster, the higher the charge / discharge current, because with higher currents faster debalancing of the cells Z can be set. Preferably, in each case a maximum number of cells Z should be present in the switching group 7, so that in this way as many cells Z as possible are involved in the loading / unloading processes, which favors a uniform charge state of as many cells Z as possible.

Based on two principal switching connections 7 of cells Z, the dynamic mode of operation of the switching is explained in principle with reference to FIGS. 3a and 3b, the switches S not being shown for a better overview. FIG. 3 a shows a total of six cells, which are connected in two cell modules 3 in such a way that two strings of three series-connected cells Z are connected in parallel. A single cell Z _mn is removed at periodic intervals in each case from the switching network 7 and taken back into the switching network 7.

Fig. 3b shows in principle that due to changing charge states and thereby increasing electrical voltages at the cells Z now in one

Switching step of the switching network 7 is changed such that only two cells Z are connected in series, in each case two cells Z in three parallel

Strands are arranged. A cell Z _mn is in turn cyclically out of the switching network Taken out, it being provided that the recessed cells Z _{mn are} cyclically exchanged within the switching network 7, so that in each case at periodic intervals another cell Z is taken out of the switching network 7. As a result, a very uniform state of charge of the cells Z can advantageously be achieved.

When charging, cells Z with a higher state of charge can be temporarily switched off, and in this way approach the other cells Z with the highest state of charge. The same can also be achieved during unloading by temporary removal of the least charged cells Z.

An example not shown in the figures of the interconnection according to the invention can be performed with a hundred cells Z. At a low electrical voltage, a parallel connection of ten strings to ten series-connected cells Z is performed. With increasing voltage of the switching network 7 is changed into a parallel interconnection of eleven strands, each with nine series-connected cells Z, in each case a single cell Z is switched out alternately. With further increasing voltage, twelve strings are connected in parallel to eight series-connected cells Z, with four cells being alternately switched out in each case.

Finally, fourteen strings are connected in parallel to each of seven cells connected in series, with two cells Z from the switching group 7 alternating in each case

be switched out.

It can thus be seen that a substantially constant total voltage of the switching network 7 or terminal voltage U _{k of} the battery 2 can be achieved in this way with different switching connections 7. The cyclic exchange of individual cells Z prevents individual cells Z from being charged / discharged unevenly. This ensures that all cells Z of the battery 2 remain substantially at the same voltage level and thus substantially at the same state of charge.

If the cells Z are combined to form cell modules 3 and the cell modules 3 are connected in accordance with the principles described above, it is true that under certain circumstances the same voltage constancy as with individual cells Z can not be achieved. This is due to the fact that each cell module 3 has a higher voltage than the single cell Z due to the connection of cells Z. However, in this way a number of switches S can be significantly reduced. FIG. 4 shows an overall arrangement of a DC voltage generating system in which the switching device 10 according to the invention can be used. It can be seen that a plurality of serially connected DC voltage generators 4 feed into an inverter 5, wherein the overall arrangement can be expanded in a line with further DC voltage generators 4. The DC voltage generator 4 may, for example, alternatively, as a combined heat and power.

In a conceivable variant, the DC / DC converter 5 a of the battery 2 can also be completely dispensed with, as a result of which the battery 2 is fed directly into the DC bus 6 of the battery 2

Inverter 5 feeds. For coupling the battery 2 directly to the inverter intermediate circuit 6, a constant DC link voltage is optimal from the point of view of the DC / DC converter 5a. This should correspond to the maximum permissible DC link voltage, which the power semiconductors of the converters 5a, 5b of the inverter 5 of the DC voltage generator can still reliably control (for example approximately 450 V for 600 V semiconductors). In this way, on the panel side, the maximum variability of the voltage of the DC voltage generator 4 can be ensured, since the panel voltage must always be less than or equal to the intermediate circuit voltage. In addition, an expensive intermediate circuit capacitor for the intermediate circuit 6 can advantageously be saved.

In order to keep the DC link voltage of the inverter 5 almost constant and yet to charge / discharge all cells of the battery 2 uniformly, the cells in the battery 2 are variably and dynamically connected as described above. A defined number of cells Z has a defined total voltage in the discharged state. This voltage should be kept constant during the charging / discharging of the battery 2. For this purpose, fewer cells Z are connected in series during charging. The electrical voltage of the single cell increases with the charge, whereby fewer cells must be connected in series to the defined

To maintain battery voltage. Conversely, in a discharge more cells Z are connected in series, until in the fully discharged state again all

Cells Z are connected in series and thus a defined total voltage is reached.

In a conceivable alternative, it is possible for the control device 1 to drive the DC / DC converter 5a of the DC voltage generator 4, for example by instructing the DC voltage generator 4 to provide a higher DC link voltage, thereby charging the battery 2. This way a can efficient cooperation between the switching device 10 according to the invention and the inverter 5 of the DC voltage generator 4 can be achieved.

In summary, the present invention provides improved terminal voltage stability of a battery by variably interconnecting cells of the battery. Advantageously, by means of the invention, a required output voltage of the DC / DC converter of the battery can be kept in a narrow voltage range. In this way, the inventive switching device for efficient

be used to energetic support of a DC voltage generating system and thereby increased operating life of the cells. Due to the reduced power requirements of the DC / DC converter of the battery, this can advantageously be associated with lower losses and produced in a more compact design. Advantageously, by means of the invention, an operating period-extending cell balancing (English, cell balancing, reaching the same state of charge of all cells) is carried out.

Although the present invention has been described in terms of preferred embodiments, it is not limited thereto. In particular, the aforementioned switching structures are only exemplary and not limited to the illustrated examples. The invention can also be applied to other types of batteries, for example Pb batteries or Ni metal hydride batteries.

The person skilled in the art will therefore suitably modify or combine the features of the invention without departing from the essence of the invention.

Claims

Claims 1. Switching device (10) for a battery (2), comprising:

- a control device (1); and

- switch (S); wherein by means of the control device (1) controlled switch (S) cells (Z) of the battery (2) can be variably interconnected such that a terminal voltage of the battery (2) is substantially independent of a state of charge of the cells (Z) ,

2. Switching device according to claim 1, wherein for determining the state of charge

electrical voltages of each individual cell (Z) of the battery (2) are determined.

3. Switching device according to claim 1 or 2, wherein cell modules (3) with at least one cell (Z) are interconnected.

4. Switching device according to one of claims 1 to 3, wherein by means of the switch (S) a defined number of cells (Z) in series and / or can be connected in parallel.

5. Switching device according to one of claims 1 to 4, wherein by connecting the terminal voltage of the battery (2) to an intermediate circuit voltage of an inverter (5) of a DC voltage generator (4) is adjusted.

6. Switching device according to one of claims 1 to 5, wherein the switching device (10) within the battery (2) is arranged.

7. A method for interconnecting cells (Z) of a battery (2), comprising the steps of:

- determining a state of charge of the cells (Z); and

- Connecting the cells (Z) of the battery (2) by means of switches (S) such that a terminal voltage of the battery (2) is substantially independent of a state of charge of the cells (Z).

8. The method of claim 7, wherein for a frequency of interconnecting the cells (Z) and / or forming a switching network (7) of the cells (Z), a state of charge of each cell (Z) is taken into account.

9. The method according to claim 7 or 8, wherein electrical voltages from each individual cell (Z) or cell modules (3) with a plurality of cells (Z) are determined.

10. The method according to any one of claims 7 to 9, wherein removed during the interconnection cells (Z) at cyclic intervals from the switching network (7) and taken into the switching network (7).

1 1. The method of claim 10, wherein the removal of the cells (Z) from the switching network (7) in dependence on the state of charge of the cells (Z) is performed.

12. The method according to any one of claims 7 to 1 1, wherein a frequency of a

Changing the interconnection of the cells (Z) depends on a level of a current within the switching group (7).

13. The method according to any one of claims 9 to 12, wherein always a defined number of cells (Z) is excluded from the switching network (7), wherein the recessed cells (Z) are cyclically exchanged.

14. The method according to claim 13, wherein the cyclic exchange of the cells (Z) is performed the faster, the higher a charge / discharge current of the cells (Z).

15. The method according to any one of claims 7 to 14, wherein the cells (Z) in such a way

be interconnected, that the switching network (7) as large as possible number of cells (Z).