WO2012052224A1

WO2012052224A1 - Method for controlling a battery with variable output voltage

Info

Publication number: WO2012052224A1
Application number: PCT/EP2011/065650
Authority: WO
Inventors: Ralph Schmidt; Stefan Butzmann; Holger Fink
Original assignee: Sb Limotive Company Ltd.; Sb Limotive Germany Gmbh
Priority date: 2010-10-20
Filing date: 2011-09-09
Publication date: 2012-04-26
Also published as: DE102010042718A1

Abstract

A method is proposed for controlling a battery having a plurality of battery modules (40, 60), which are connected in series to form a battery module section (70), with the load on the battery modules (40, 60) being distributed as uniformly as possible. The method has a step of production of a rising output voltage from the battery module section (70) by activation of an increasing number of battery modules (40, 60) during a first time period, and a step of production of a falling output voltage of the battery module section (70) by deactivation of an increasing number of battery modules (40, 60) during a second time period, which follows the first time period. According to the invention, a first sequence of battery modules (40, 60), in which the battery modules (40, 60) are activated during the first time period, is the same as a second sequence of battery modules (40, 60) in which the battery modules (40, 60) are deactivated during the second time period.

Description

Description title

Method for controlling a battery with variable output voltage

The present invention relates to a method of controlling a variable output voltage battery and a battery configured to perform the method.

State of the art

It is becoming apparent that in the future both in stationary applications as well as in vehicles such as hybrid and electric vehicles increased

Battery systems will be used. In order to meet the voltage and available power requirements of a particular application, a large number of battery cells are connected in series. Since the power provided by such a battery must flow through all the battery cells and a battery cell can only conduct a limited current, battery cells are often additionally connected in parallel in order to increase the maximum current. This can be done either by providing multiple cell wraps within a battery cell housing or by externally interconnecting battery cells.

The block diagram of a conventional electric drive system, as used for example in electric and hybrid vehicles or in stationary applications such as in the rotor blade adjustment of wind turbines is shown in Figure 1. A battery 10 is connected to a

DC voltage connected, which by a

Capacitor 11 is buffered. Connected to the DC voltage intermediate circuit is a pulse inverter 12, which is connected via two switchable semiconductor valves and two diodes at three outputs against each other phase-offset sinusoidal currents for the operation of an electric drive motor 13 provides. The capacitance of the capacitor 11 must be large enough to stabilize the voltage in the DC link for a period of time in which one of the switchable semiconductor valves is turned on. In a practical application such as an electric vehicle results in a high capacity in the range of mF. Because of the usually quite high voltage of the DC intermediate circuit such a large capacity can be realized only at high cost and with high space requirements.

FIG. 2 shows the battery 10 of FIG. 1 in a more detailed block diagram. A large number of battery cells are connected in series as well as optionally additionally in parallel, in order to achieve a high level of power for a particular application

Output voltage and battery capacity to achieve. Between the positive pole of the battery cells and a positive battery terminal 14, a charging and disconnecting device 16 is connected. Optionally, a separating device 17 can additionally be connected between the negative pole of the battery cells and a negative battery terminal 15. The separating and charging device 16 and the separating device 17 each include a contactor 18 and 19, respectively, which are provided to disconnect the battery cells from the battery terminals in order to disconnect the battery terminals from voltage. Because of the high

DC voltage of the series-connected battery cells is otherwise significant risk potential for maintenance personnel or the like. In addition, a charging contactor 20 with a charging resistor 20 connected in series with the charging contactor 20 is provided in the charging and disconnecting device 16. The charging resistor 21 limits a charging current for the capacitor 1 1 when the battery is connected to the DC link. For this purpose, the contactor 18 is initially left open and only the charging contactor 20 is closed. When the voltage at the positive battery terminal 14 reaches the

Voltage of the battery cells, the contactor 19 can be closed and

if necessary, the charging contactor 20 are opened. The contactors 18, 19 and the charging contactor 20 increase the cost of a battery 10 is not insignificant, since high demands are placed on their reliability and the currents to be led by them. Batteries have now been proposed in which battery modules are interconnected, which can be activated and deactivated. In the active state are the Battery cells of the battery module connected to its outputs, so that the voltage of the battery module participates in the generation of the battery voltage. In the deactivated state, however, the battery cells of a battery module are disconnected from its outputs and the outputs bridged, so that the 5 battery module voltage is zero. By now a variable number of

Battery modules is activated or deactivated, the battery voltage can be variably adjusted, so that the

DC voltage intermediate circuit, the pulse inverter and possibly also the charging contactors can be omitted. Here, however, there is the problem that the l o load should be distributed as evenly as possible on the battery modules, so that the battery cells of the battery modules are uniformly discharged and age evenly.

15 disclosure of the invention

According to the invention, therefore, a method for controlling a battery having a plurality of connected to a battery module string in series

Battery modules introduced, which distributes the load on the battery modules evenly 20 possible. Each battery module comprises at least one battery cell and a coupling unit. The at least one battery cell is connected between a first input and a second input of the coupling unit, which is designed, in response to a first control signal, the at least one battery cell between a first terminal of the battery module and a second terminal of the battery module

25 battery module to switch and on a second control signal out the first

Terminal to connect to the second terminal, leaving a

Battery module voltage of the battery module assumes a voltage dependent on the first and second control signal voltage value. The method has at least one step of generating a rising output voltage

30 of the battery module string by outputting the first control signal to an increasing number of battery modules during a first time period and a step of generating a falling output voltage of the battery module string by outputting the second control signal to an increasing number of battery modules during a second time period following the first time period , According to the invention, a first sequence of battery modules in which the first control signal to the Battery modules during the first time period is output, similar to a second order of battery modules, in which the second control signal is output to the battery modules during the second period of time.

By the order in which the individual battery modules are activated to produce an increasing output voltage of the battery module string, the same as the order in which the individual battery modules are subsequently deactivated to a falling output voltage of the battery module

Battery module string is the time during which a single battery module to generate the output voltage of the

Battery module string participates, largely aligned.

Preferably, the first control signal is continuously output to a respective battery module from a respective first output timing during the first time period until the second control signal is output to the respective battery module at a respective second output timing during the second time period. This minimizes losses due to switching operations.

The first output time of a first battery module may be prior to the first output time of a second battery module, wherein the second output time of the first battery module is before the second output time of the second battery module.

Alternatively or additionally, the first and the second output time of a third battery module can be simultaneously with the first and second

Be issuing time of a fourth battery module. By simultaneously activating and deactivating the third and fourth battery modules, a larger increase or decrease of the output voltage of the

Battery module string can be achieved, both battery modules experience an equal load.

A earliest second output time of the second output time is also preferable to a latest first time of the first output time. Particularly preferably, the rising output voltage of

Battery module string and the falling output voltage of the

Battery module strand on a sinusoidal course. As a result, the battery can be connected directly to a consumer that is designed for operation in an AC voltage network. By "sinusoidal" is meant here also a gradual course, which approximates a sine.

The sinusoidal profile of the output voltage preferably has a predefinable frequency. As a result, for example, by adjusting the frequency in the context of a control system, the output voltage with a

Voltage of a utility network are synchronized.

Within the scope of the method, a plurality of sinusoidal output voltages, preferably three sinusoidal output voltages, are preferably generated, wherein each of the sinusoidal output voltages is phase-shifted with respect to the remaining sinusoidal output voltages. This allows electrical machines to be powered directly from the battery. If three sinusoidal output voltages are generated, machines designed for a three-phase utility network can be modified or modified without modification

Intermediate components are connected to the battery.

A second aspect of the invention introduces a battery having a plurality of battery modules connected in series to a battery module string and a control unit. Each battery module comprises at least one battery cell and a coupling unit, wherein the at least one battery cell connected between a first input and a second input of the coupling unit and the coupling unit is formed on a first control signal towards the at least one battery cell between a first terminal of the battery module and a second Terminal of the battery module to switch and on a second control signal to connect the first terminal to the second terminal, so that a

Battery module voltage of the battery module assumes a voltage dependent on the first and second control signal voltage value. The control unit is configured to generate and output the first and second control signals to the battery modules and to perform the method according to one of

previous claims. The coupling unit may have a first output and be configured to connect to the first control signal either the first input or the second input to the output. The output is connected to one of the terminals of the battery module and one of the first or second input to the other of the terminals of the battery module. Such

Coupling unit with the use of only two switches, preferred

Semiconductor switches such as MOSFETs or IGBTs can be realized.

Alternatively, the coupling unit may have a first output and a second output and be configured to connect the first input to the first output and the second input to the second output in response to the first control signal. In this case, the coupling unit is also

configured to separate the first input from the first output and the second input from the second output and to connect the first output to the second output to the second control signal. This embodiment requires a slightly higher circuit complexity (usually three switches), but decouples the battery cells of the battery module at its two poles, so that switched off in an impending deep discharge or damage to a battery module whose battery cells and thus replaced safely in the continuous operation of the overall arrangement can.

In a further alternative embodiment, the coupling unit may comprise a first input, a second input, a first output and a second output and configured to connect the first input to the first output and the second input to the second output in response to a first control signal and connect, in response to a second control signal, the first input to the second output and the second input to the first output. Although this embodiment requires a somewhat higher circuit complexity (usually four switches or two

Changeover switch), but has the advantage that an output voltage of a selectable polarity can be applied to the outputs of the coupling unit or the battery module. This can be bipolar

Output voltages are generated, covering a twice as large voltage range with the same number of battery modules. In extreme cases, each battery module has only one battery cell or only a parallel connection of battery cells. In this case, the

Output voltage of a battery module string are set the finest. As is generally preferred within the scope of the invention,

Lithium-ion battery cells used, which have a cell voltage between 2.5 and 4.2 V, the output voltage of the battery could be adjusted accordingly. The more accurate the output voltage of the battery is adjustable, the smaller the problem of electromagnetic compatibility, because the radiation caused by the battery current decreases with its high-frequency components. However, this is an elevated

Compared to circuitry, which also brings increased power losses in the switches of the coupling units due to the large number of switches used. A third aspect of the invention relates to a motor vehicle with an electric

Drive motor for driving the motor vehicle and one with the

electric drive motor connected battery according to the preceding aspect of the invention.

drawings

Embodiments of the invention will be explained in more detail with reference to the drawings and the description below, wherein like reference numerals designate like or functionally similar components. Show it:

1 shows an electrical drive system according to the prior art,

2 shows a block diagram of a battery according to the prior art,

Figure 3 shows a first embodiment of a coupling unit for use in the

battery according to the invention,

Figure 4 shows a possible circuit implementation of the first

Embodiment of the coupling unit, FIGS. 5 and 6 show two embodiments of a battery module with the first embodiment of the coupling unit,

FIG. 7 shows a second embodiment of a coupling unit for use in the battery according to the invention,

FIG. 8 shows a possible circuit implementation of the second and third embodiments of the coupling unit,

Figure 9 shows a possible circuit implementation of the third

Embodiment of the coupling unit,

FIG. 10 shows an embodiment of a battery module with the second or third embodiment of the coupling unit,

FIG. 11 shows a first embodiment of the battery according to the invention,

FIG. 12 shows a drive system with a further embodiment of the

battery according to the invention, and

Figure 13 shows a time course of an output voltage of

battery according to the invention and control signals for a number of

Battery modules according to the inventive method.

Embodiments of the invention

FIG. 3 shows a first embodiment of a coupling unit 30 for use in the battery according to the invention. The coupling unit 30 has two inputs 31 and 32 and an output 33 and is designed to connect one of the inputs 31 or 32 to the output 33 and to decouple the other.

FIG. 4 shows a possible circuit implementation of the first embodiment of the coupling unit 30, in which a first and a second switch 35 or 36 are provided. Each of the switches is between one of the inputs 31 and 32 and the output 33 connected. This embodiment has the advantage that both inputs 31, 32 can be decoupled from the output 33, so that the output 33 becomes high-impedance, which may be useful, for example, in the case of repair or maintenance. In addition, the switches 35, 36 simply as

Semiconductor switches such. As MOSFETs or IGBTs can be realized.

Semiconductor switches have the advantage of a low price and a high switching speed, so that the coupling unit 30 can respond to a control signal or a change of the control signal within a short time and high switching rates can be achieved. Compared to a conventional pulse inverter, which generates a desired voltage shape by appropriate choice of a duty cycle between maximum and minimum DC voltage (pulse width modulation), the invention has the advantage that the switching frequencies of the switches contained in the coupling units is much lower, as in principle, each switch only once each period of the output voltage to be generated is closed and reopened. As a result, the electromagnetic compatibility (EMC) is improved and it can be made lower demands on the switch.

Figures 5 and 6 show two embodiments of a battery module 40 with the first embodiment of the coupling unit 30. A plurality of

Battery cells 11 is connected between the inputs of the coupling unit 30 in series. However, the invention is not limited to such a series connection of battery cells 11, it can also be provided only a single battery cell 1 1 or a parallel connection or mixed-serial-parallel circuit of battery cells 1 1. In the example of Figure 5, the output of Coupling unit 30 with a first terminal 41 and the negative pole of

Battery cells 11 connected to a second terminal 42. However, an almost mirror-image arrangement as in FIG. 6 is possible in which the positive pole of the battery cells 11 is connected to the first terminal 41 and the output of the coupling unit 30 to the second terminal 42.

FIG. 7 shows a second embodiment of a coupling unit 50 for use in the battery according to the invention. The coupling unit 50 has two inputs 51 and 52 and two outputs 53 and 54. It is formed, either the first input 51 to the first output 53 and the second input 52 to the connect either the first input 51 to the second output 54 and the second input 52 to the first output 53 or to connect the first output 53 to the second output 54 (and thereby the inputs 51 and / or Disconnect 52). In certain embodiments of the coupling unit, this can also be designed to separate both inputs 51, 52 from the outputs 53, 54 and also to decouple the first output 53 from the second output 54. However, it is not intended to connect both the first input 51 to the second input 52.

FIG. 8 shows a possible circuit implementation of the second embodiment of the coupling unit 50, in which a first, a second and a third switch 55, 56 and 57 are provided. The first switch 55 is connected between the first input 51 and the first output 53, the second switch 56 is connected between the second input 52 and the second output 54 and the third switch 57 between the first output 53 and the second output 54.

Figure 9 shows a possible circuit implementation of the third

Embodiment of the coupling unit 50, in which a first, a second, a third and a fourth switch 55, 56, 58 and 59 are provided. The first switch 55 is connected between the first input 51 and the first output 53, the second switch 56 is between the second input 52 and the second output 54, the third switch 58 between the first input 51 and the second output 54 and the fourth Switch 59 connected between the second input 52 and the first output 53.

The embodiments of Figures 8 and 9 also offer the advantage that the switches 55, 56 and 57 and 55, 56, 58 and 59 simply as a semiconductor switch such. B. MOSFETs (Metal Oxide Semiconductor Field Effect

Transistor) or IGBTs (Insulated Gate Bipolar Transistor) can be realized. Semiconductor switches have the advantage of a low price and a high switching speed, so that the coupling unit 50 within a short time to a control signal or a change in the

Control signal can respond and high switching rates are achievable. FIG. 10 shows an embodiment of a battery module 60 with the second or third embodiment of the coupling unit 50. A plurality of

Battery cells 11 is connected in series between the inputs of a coupling unit 50. This embodiment of the battery module 60 is not limited to such a series connection of battery cells 11, it may again be provided only a single battery cell 11 or a

Parallel connection or mixed-serial-parallel connection of battery cells 1 1. The first output of the coupling unit 50 is connected to a first terminal 61 and the second output of the coupling unit 40 to a second terminal 62. The battery module 60 offers over the battery module 40 of FIGS

6 either the advantage that the battery cells 11 can be disconnected on both sides by the coupling unit 50 of the rest of the battery, which allows a safe replacement during operation, as at any pole of the battery cells 11, the dangerous high sum voltage of the rest

Battery module is applied to the battery or that both the positive and the negative battery module voltage can be connected to the outputs.

FIG. 11 shows a first embodiment of the battery according to the invention, which has n battery module strings 70-1 to 70-n. Everyone

Battery module string 70-1 to 70-n has a plurality of battery modules 40 or 60, preferably each battery module string 70-1 to 70-n the same number of battery modules 40 or 60 and each battery module 40 or 60 the same number of battery cells 1 1 in more identical Contains way interconnected. One pole of each battery module string 70-1 to 70-n may be connected to a corresponding pole of the other battery module strings 70-1 to 70-n, which is indicated by a dashed line in FIG. Generally, one battery module string 70-1 to 70-n may include any number of battery modules 40 or 60 greater than 1 and one battery each number of battery module strings 70-1 to 70-n. Also, at the poles of the battery module strings 70-1 to 70-n, additional charging and disconnecting devices and disconnecting devices may be provided as in FIG. 2, if safety regulations so require. However, such separators are not necessary according to the invention, because a

Decoupling of the battery cells 11 can be done by the battery terminals by the coupling units 30 or 50 contained in the battery modules 40 or 60. FIG. 12 shows a drive system with a further embodiment of the battery according to the invention. In the example shown, the battery has three battery module strings 70-1, 70-2 and 70-3, which are each connected directly to an input of a drive motor 13. Since most available electric motors are designed for three-phase operation, the battery of the invention preferably has exactly three battery module strings. The battery of the invention has the further advantage that the functionality of a pulse inverter is already integrated in the battery. By a control unit of the battery, a variable number of battery modules 40 or 60 of a

Battery module string enabled (or disabled), stands at the output of the battery module string to the number of activated battery modules 40 or 60 proportional voltage, which is between 0 V and the full

Output voltage of the battery module string may be available. The control unit realizes the control method according to the invention, whereby the loads of the battery cells 11 of the individual battery modules 40 or 60 are matched to one another as far as possible.

FIG. 13 shows an exemplary time profile of an output voltage of the battery according to the invention and control signals for a number of battery modules according to the method according to the invention. The

Output voltage of the battery (or a battery module line) V is plotted over the time t. Reference numeral 80-b is a desired (ideal) sine for an exemplary application

applied, but only has voltage values greater than or equal to zero. The ideal sine is approximately generated by the battery according to the invention by a value-discrete voltage curve 80-a. The deviations of the discrete-value voltage curve 80-a from the ideal curve 80-b depend on the size of the number of battery cells 11, which are connected in series in a battery module 40 or 60. The fewer battery cells 1 1 are connected in series in a battery module 40 or 60, the more accurately the value-discrete voltage curve 80-a can follow the idealized curve 80-b. In usual applications, the relatively low affect

However, deviations do not affect the function of the overall system. Compared to a conventional pulse inverter, which can connect an output terminal only with two different potentials, the deviations are significantly reduced anyway. In the example shown, eight battery modules are one

Battery module strand interconnected. The battery modules have a uniform battery module voltage V _M , so that a total of nine different voltage levels between 0 V and 8 * V _M result in the diagram.

Of course, a much larger number of battery modules can be used.

The lower part of the diagram shows (binary) control signals M1 to M8 for the eight battery modules. In this case, a high voltage level mean the

Outputting a first control signal that activates a given battery module and a low voltage level outputting a second control signal that disables the given battery module. In the example of FIG. 13, the battery modules are activated in ascending order from the first battery module (control signal M1) to the last battery module (control signal M8), resulting in an increasing output voltage 80-a of the battery. The

Turn-on times are chosen so that a sinusoidal curve results. In the regions around the zero-crossing of the sinusoidal waveform, which is here due to the fact that only positive battery voltages are output, at the voltage 4 * V _M , the slope in the example shown is so large that in each case two battery modules are activated simultaneously. However, a better voltage curve can be achieved if the battery modules are basically activated individually, but this places high demands on the temporal resolution of the control method, because the battery modules are then activated at a very short time interval.

After the output voltage 80-a has reached its maximum with the activation of the last battery module (control signal M8), the battery modules are deactivated in the same order in which they were activated. First, therefore, the control signal M 1 is set to a low voltage level, then the control signal M2 and so on. As a result, each battery module is activated half a period and half a period is deactivated so that identical loads of the individual battery modules result and the switching frequencies of the switches of the coupling units of the individual battery modules are minimized. In addition to the advantages already mentioned, the invention has the advantages of reducing the number of high-voltage components, of plug connections and offers the possibility of a cooling system of the battery with that of the

Pulse inverter to combine, with a coolant that is used to cool the battery cells, then for cooling the components of the pulse inverter (ie the coupling units 40 or 60) can be used, since these usually reach higher operating temperatures and by the already heated by the battery cells coolant can still be cooled sufficiently. It also makes it possible to combine the control units of the battery and the pulse inverter and so on to save effort. The coupling units offer an integrated safety concept for pulse inverters and battery and increase the reliability and availability of the

Overall system and battery life.

Another advantage of the battery with integrated pulse inverter is that it is very simple modular of individual battery modules with integrated

Coupling unit can be constructed. As a result, the use of identical parts (modular principle) is possible.

Claims

A method of controlling a battery having a plurality of battery modules (40, 60) connected in series to a battery module string (70), each comprising at least one battery cell (11) and a coupling unit (30, 50), the at least one battery cell (11) between a first input (31, 51) and a second input (32, 52) of

Coupling unit (30, 50) connected and the coupling unit (30, 50) is formed on a first control signal towards the at least one battery cell (11) between a first terminal (41, 61) of the battery module (40, 60) and a second terminal (42, 62) of the battery module (40, 60) and to connect the first terminal (41, 61) to the second terminal (42, 62) in response to a second control signal, so that a battery module voltage of the battery module (40, 60 ) assumes a voltage value dependent on the first and second control signals, the method comprising at least the following steps:

Generating a rising output voltage of the battery module string (70) by outputting the first control signal to an increasing number of battery modules (40, 60) during a first time period; and

Generating a falling output voltage of the battery module string (70) by outputting the second control signal to an increasing number of battery modules (40, 60) during a second time period following the first time period, characterized

a first sequence of battery modules (40, 60) in which the first control signal is output to the battery modules (40, 60) during the first time period is equal to a second order of battery modules (40, 60) in which the second control signal is output to the battery modules (40, 60) during the second time period. The method of claim 1, wherein the first control signal is applied to a respective battery module (40, 60) of a respective first battery module (40, 60) Output timing during the first time period is continuously output until at a respective second output time during the second time period, the second control signal to the respective battery module (40, 60) is output.

The method of claim 2, wherein the first dispense time of a first battery module (40, 60) is prior to the first dispense time of a second battery module and the second dispense time of the first battery module (40, 60) is prior to the second dispense time of the second battery module.

The method according to claim 2 or 3, wherein the first output timing of a third battery module (40, 60) is simultaneous with the first output timing of a fourth battery module and the second output timing of the third battery module (40, 60) is concurrent with the second Output time of the fourth battery module is.

The method according to one of claims 2 to 4, wherein an earliest second output time of the second output time is after a latest first time of the first output time.

The method according to one of the preceding claims, wherein the rising output voltage of the battery module string (70) and the falling output voltage of the battery module string (70) have a sinusoidal profile.

The method of claim 6, wherein the sinusoidal waveform of the output voltage has a predetermined frequency.

The method according to one of claims 6 or 7, wherein a

Plurality of sinusoidal output voltages, preferably three sinusoidal output voltages, each of the sinusoidal output voltages being out of phase with the remaining sinusoidal output voltages.

9. A battery having a plurality of battery modules (40) connected in series battery modules (40, 60), each comprising at least one battery cell (1 1) and a coupling unit (30, 50), wherein the at least one battery cell ( 1 1) between a first input (31, 51) and a second input (32, 52) of the coupling unit (30, 50) and the coupling unit (30, 50) is formed, on a first control signal towards the at least one battery cell ( 1 1) between a first terminal (41, 61) of the battery module (40, 60) and a second terminal (42, 62) of the

Battery module (40, 60) to switch and on a second control signal, the first terminal (41, 61) to the second terminal (42, 62) to connect, so that a battery module voltage of the battery module (40, 60) one of the first and second control signal dependent voltage value, characterized by a control unit which is adapted to generate the first and second control signals and output to the battery modules (40, 60) and the method according to one of the preceding

Perform claims.

A motor vehicle having an electric drive motor (13) for driving the motor vehicle and a battery connected to the electric drive motor (13) according to the preceding claim.