WO2013143771A1

WO2013143771A1 - Method for heating up energy storage cells of an energy storage device and heatable energy storage device

Info

Publication number: WO2013143771A1
Application number: PCT/EP2013/052985
Authority: WO
Inventors: Peter Feuerstack
Original assignee: Robert Bosch Gmbh
Priority date: 2012-03-29
Filing date: 2013-02-14
Publication date: 2013-10-03
Also published as: DE102012205095A1; CN104335412B; CN104335412A

Abstract

The invention relates to a method for heating up energy storage cells of an energy storage device having a plurality of energy storage modules which are connected in series in an energy supply chain and which each comprise an energy storage cell module which has at least one energy storage cell and a coupling device having coupling elements which are designed to connect or to bypass the energy storage cell modules selectively into the energy supply chain. The method comprises the steps of coupling the output terminals of the energy storage device to an intermediate DC circuit, driving the coupling devices of at least one first energy storage module to connect the respective energy storage cell modules into the energy supply chain for a first predetermined time interval, and driving the coupling devices of at least one second energy storage module to connect the respective energy storage cell modules into the energy supply chain for a second predetermined time interval after the first predetermined time interval has elapsed.

Description

Description title

A method for heating energy storage cells of an energy storage device and heatable energy storage device

The invention relates to a method for heating energy storage cells of an energy storage device and a heatable energy storage device, in particular an energy storage device with a modular battery system for an electrically operated vehicle.

State of the art

It is becoming apparent that in the future both stationary applications, e.g. Wind turbines or solar systems, as well as in vehicles such as hybrid or

Electric vehicles, increasingly electronic systems are used, which combine new energy storage technologies with electric drive technology.

The feeding of multiphase electricity into an electric machine becomes

Usually accomplished by a converter in the form of a pulse inverter. For this purpose, one provided by a DC voltage intermediate circuit

DC voltage in a multi-phase AC voltage, for example, a three-phase AC voltage to be reversed. The DC link is fed by a string of serially connected battery modules. In order to meet the power and energy requirements of a particular application, multiple battery modules are often connected in series in a traction battery.

The publications DE 10 2010 027 857 A1 and DE 10 2010 027 861 A1 disclose modularly connected battery cells in energy storage devices, which can be selectively connected or disconnected via a suitable control of coupling units in the strand of serially connected battery cells. Systems of this type are known as the Battery Direct Converter (BDC). Such systems include DC sources in an energy storage module string connected to a DC link for electrical power supply an electrical machine or an electrical network via a pulse inverter can be connected.

The energy storage module strand has a plurality of energy storage modules connected in series, each energy storage module having at least one energy storage module

Battery cell and an associated controllable coupling unit, which allows depending on control signals to bridge the respectively associated at least one battery cell or to switch the respectively associated at least one battery cell in the respective energy storage module string. Optionally, the coupling unit can be designed such that it additionally allows the respectively associated at least one battery cell with inverse polarity in the respective

Energy storage module strand to switch or the respective

Interrupt energy storage module string. BDCs usually have higher efficiency and higher

Reliability against conventional systems. The reliability is ensured, inter alia, that defective, failed or not fully efficient battery cells by suitable bridging control of the

Coupling units can be switched out of the power supply line. The total output voltage of the energy storage module string can by

corresponding activation of the coupling units varies and in particular be set in stages. The gradation of the output voltage results from the

Voltage of a single energy storage module, the maximum possible

Total output voltage by the sum of the voltages of all

Energy storage modules of the energy storage module string is determined.

To set an output voltage of an energy storage module, a pulse width modulated (PWM) control of the coupling units can take place. This makes it possible to output a desired mean value as energy storage module voltage by specific variation of the on or off times.

When used in electrically powered vehicles such as electric cars or hybrid vehicles, it may happen that the temperatures of the battery cells of such BDCs are very low, for example when starting the vehicle in the winter. Since typically used battery cells are temperature dependent

Internal resistance, which increases with decreasing temperature, it may be that the battery cells can not provide full power at low temperatures. There is therefore a need for a method which fully exploits the

To ensure battery cells even at low temperatures, without the need for elaborate heating elements or a time and energy-intensive external heating process must be used.

Disclosure of the invention

According to one aspect, the present invention provides a method for heating energy storage cells of an energy storage device having a plurality of energy storage modules connected in series in a power supply strand, each comprising an energy storage cell module having at least one energy storage cell and a coupling device with coupling elements, which are designed to selectively switch or bypass the energy storage cell module into the power supply string. The method has the steps of Koppeins the

Output terminals of the energy storage device with a

DC voltage intermediate circuit, the driving of the coupling devices of at least one first energy storage module for switching the respective

Energy storage cell modules in the power supply line for a first

predetermined period of time, and the driving of the coupling means of at least one second energy storage module for switching the respective

Energy storage cell modules in the power supply line for a second predetermined period of time after the first predetermined period of time has elapsed.

In a further aspect, the present invention provides a system having a plurality of energy storage devices in a power supply string

Series switched energy storage modules, each one

Energy storage cell module, which has at least one energy storage cell, and a coupling device comprising coupling elements, which are adapted to selectively connect or bypass the energy storage cell module in the power supply line. The system further comprises a DC intermediate circuit, which is coupled to output terminals of the energy storage device, a pulse inverter, which is coupled to the DC intermediate circuit and which is fed from the DC voltage intermediate circuit with an input voltage, an electric machine which is coupled to the pulse inverter, and which of the pulse inverter is supplied with a phase voltage, and a control device, which is coupled to the coupling devices, and which is adapted to the coupling means of the energy storage device for Providing a total output voltage of the energy storage device to selectively drive and perform a method according to the invention.

Advantages of the invention

It is idea of the present invention, a modular design

Energy storage device with in a power supply line connected in series battery cells by high-frequency, alternating transfer of electrical energy from one energy storage module into another energy storage module to heat. This strategy makes use of the knowledge that through the

Transferring electrical energy from one energy storage module to another energy storage module Waste heat due to power dissipation when feeding the energy storage module

Energy storage cells is created, which can heat the energy storage cells locally. This has the advantage that energy storage cells which have an undesirably high internal resistance at low temperatures can be brought back to an operating temperature without additional heating measures or heating components, in which the energy storage cells have full or almost complete performance. According to an embodiment of the method according to the invention, the duration of the second predetermined period of time may be dependent on an amount of the voltage in the

DC link dependent. According to an alternative

Embodiment of the method according to the invention may be the duration of the second predetermined period of time dependent on an amount of current flow through the respective energy storage cell modules. In both cases, the second

Energy storage modules are charged as long as cached electrical energy is available in the DC voltage intermediate circuit.

According to a further embodiment of the method according to the invention, further selection of the first and second energy storage modules of the

Power supply line for providing the supply voltage for the DC intermediate circuit. This has the advantage that only a portion of the energy storage modules must be heated for operating situations in which only a low input voltage for the electrical machine is needed. These heated energy storage modules can then in such operating situations, for example when starting an electrically operated vehicle, for the provision of

Supply voltage are used, while the remaining, not yet heated energy storage modules must be heated later. According to a further embodiment of the method according to the invention, the method can be carried out when the temperature of the energy storage cells falls below a first predetermined limit value. This procedure is particularly advantageous at low temperatures at which the internal resistance of the energy storage cells is particularly high.

According to a further embodiment of the method according to the invention, the steps of driving the coupling devices of at least one first

Energy storage module and the driving of the coupling devices of at least one second energy storage module are alternated until the temperature of the energy storage cells of the energy storage modules involved a second

exceeds predetermined limit. This high-frequency transfer of electrical energy between energy storage modules can be generated by the resulting power loss until the internal resistance of the

Energy storage cells is sufficiently low again.

In accordance with a further embodiment of the method according to the invention, the step of coupling the output terminals of the energy storage device to a DC voltage intermediate circuit can take place via a coupling inductance.

According to one embodiment of the system according to the invention, the

Coupling devices comprise coupling elements in full bridge circuit. Alternatively, the coupling devices may comprise coupling elements in a half-bridge circuit.

According to a further embodiment of the system according to the invention, the energy storage cells may comprise lithium-ion accumulators. This kind of

Energy storage cells is particularly affected by the increased internal resistance at low temperatures.

Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

Brief description of the drawings

Show it: Fig. 1 is a schematic representation of a system with a

Energy storage device according to an embodiment of the present invention;

Fig. 2 is a schematic representation of an embodiment of a

Energy storage module of an energy storage device according to Fig. 1;

Fig. 3 is a schematic representation of another embodiment of a

Energy storage module of an energy storage device according to Fig. 1; and

Fig. 4 is a schematic representation of a method for heating of

Energy storage cell of an energy storage device in a system according to another embodiment of the present invention. 1 shows a system 100 for voltage conversion of DC voltage provided by energy storage modules 3 into an n-phase AC voltage. The system 100 comprises an energy storage device 1 with energy storage modules 3, which are connected in series in a power supply train. The power supply line is coupled between two output terminals 1 a and 1 b of the energy storage device 1, which are each coupled to a DC voltage intermediate circuit 2b.

By way of example, the system 100 in FIG. 1 is used to supply a three-phase electric machine 6. However, provision may also be made for the energy storage device 1 to be used for generating electrical current for a power supply network 6.

For this purpose, the energy storage device 1 via a coupling inductance 2a with the

DC intermediate circuit 2b coupled. The coupling inductance 2a can

For example, be a selectively connected between the DC voltage intermediate circuit 2b and the output terminal 1a of the energy storage device 1 inductive throttle. Alternatively, it may also be possible for the coupling inductance 2 a to be present through parasitic inductances in the interconnection that are present anyway

Energy storage device 1 and DC intermediate circuit 2b is formed.

The DC voltage intermediate circuit 2b feeds a pulse inverter 4, which from the DC voltage of the DC intermediate circuit 2b a three-phase

AC voltage for the electric machine 6 provides. The system 100 may further include a controller 8, which is connected to the energy storage device 1, and by means of which the

Energy storage device 1 can be controlled to the desired

Total output voltage of the energy storage device 1 to the respective

Output terminals 1 a, 1 b provide. In addition, the control device 8 can be designed to charge the energy storage cells during charging

Energy storage device 1 to control the respective coupling elements or active switching elements of the energy storage device 1. The power supply line of the energy storage device 1 has at least two energy storage modules 3 connected in series. By way of example, the number of energy storage modules 3 in FIG. 1 is four, but any other number of

Energy storage modules 3 is also possible. The energy storage modules 3 each have two output terminals 3a and 3b, via which a

Module output voltage of the energy storage modules 3 can be provided. Since the energy storage modules 3 are primarily connected in series, add up the

Module output voltages of the energy storage modules 3 to the

Total output voltage, which at the output terminals 1 a, 1 b the

Energy storage device 1 is provided.

Two exemplary construction forms of the energy storage modules 3 are shown in greater detail in FIGS. 2 and 3. The energy storage modules 3 each comprise a coupling device 7 with a plurality of coupling elements 7a, 7c and 7b and 7d. The

Energy storage modules 3 furthermore each comprise an energy storage cell module 5 with one or more energy storage cells 5a to 5k connected in series.

The energy storage cell module 5 can have, for example, series-connected cells 5a to 5k, for example lithium-ion cells or accumulators. In this case, the number of energy storage cells 5a to 5k in the energy storage modules 3 shown in FIG. 2 and FIG. 3 is by way of example two, but any other number of energy storage cells 5a to 5k is likewise possible. The

Energy storage cell modules 5 have a terminal voltage of U _M and are connected via connecting lines with input terminals of the associated coupling device 7. At the input terminals of the associated coupling device 7 so the voltage U _{M is applied} .

In Fig. 2, the series-connected coupling elements 7a and 7c, the center tap is connected to the output terminals 3a, the so-called left branch of Full bridge and it form the series-connected coupling elements 7b and 7d, whose center tap is connected to the output terminal 3b, the so-called right branch of the full bridge. The coupling device 7 is formed in Fig. 2 as a full bridge circuit with two coupling elements 7a, 7c and two coupling elements 7b, 7d. The

Coupling elements 7a, 7b, 7c, 7d can each have an active switching element, for example a semiconductor switch, and a free-wheeling diode connected in parallel therewith. It may be provided that the coupling elements 7a, 7b, 7c, 7d are designed as MOSFET switches, which already have an intrinsic diode. The coupling elements 7a, 7b, 7c, 7d can be controlled in such a way, for example with the aid of the control device 9 shown in FIG

Energy storage cell module 5 is selectively connected between the output terminals 3a and 3b or that the energy storage cell module 5 is bridged. For example, referring to FIG. 2, the energy storage cell module 5 may be connected in the forward direction between the output terminals 3a and 3b by turning on the active power cell module 5

Switching element of the coupling element 7d and the active switching element of the coupling element 7a are placed in a closed state, while the other two active switching elements of the coupling elements 7b and 7c are set in an open state. In this case, the voltage U _M is present between the output terminals 3a and 3b of the coupling device 7. A lock-up state can be set, for example, by putting the two active switching elements of the coupling elements 7a and 7b in the closed state, while keeping the two active switching elements of the coupling elements 7c and 7d in the open state. A second

Bridging state, for example, be set by the two active switches of the coupling elements 7c and 7d are placed in the closed state, while the active switching elements of the coupling elements 7a and 7b are kept in the open state. In both bridging states, the voltage 0 is present between the two output terminals 3a and 3b of the coupling device 7. Similarly, the energy storage cell module 5 in the reverse direction between the

Output terminals 3a and 3b of the coupling device 7 are switched by the active switching elements of the coupling elements 7b and 7c are placed in the closed state, while the active switching elements of the coupling elements 7a and 7d are set in the open state. In this case, the voltage -U _M is applied between the two output terminals 3a and 3b of the coupling device 7.

By suitable activation of the coupling devices 7 can therefore individual

Energy storage cell modules 5 of the energy storage modules 3 targeted in the

Series connection of the power supply line to be integrated. This can be done by a targeted control of the coupling devices 7 for selectively switching the

Energy storage cell modules 5 of the energy storage modules 3 in the

Power supply line, a total output voltage can be provided, which depends on the individual output voltages of the energy storage cell modules 5 of the

Energy storage modules 3 is dependent. The total output voltage can be set in each case in stages, wherein the number of stages with the number of

Energy storage modules 3 scaled. For a number of n energy storage modules 3, the total output voltage of the power supply string can be set in 2n + 1 stages between -n-U _M , ..., 0, ..., + «· U _M.

Fig. 3 shows a schematic representation of another exemplary

Embodiment for an energy storage module 3. In this case, the coupling device 7 comprises only the coupling elements 7a and 7c, the half-bridge circuit as the

Energy storage cell module 5 can be switched either in a bridging state or a switching state in the forward direction in the power supply line. Incidentally, similar control rules apply as explained in connection with FIG. 3 for the energy storage module 3 shown in full bridge circuit.

The internal resistance of the energy storage cells 5 a to 5 k is temperature-dependent: With lithium-ion batteries, the internal resistance at a temperature of -10 ° C can be increased up to ten times the internal resistance at a temperature of + 25 ° C. As a result, the performance of the energy storage cells 5a to 5k can drop sharply. Especially for situations in electric drive systems where high currents are required, for example start-up situations of electrically operated vehicles, it is desirable because of the high current load

Energy storage cells 5a to 5k with a low internal resistance to supply the electric machine 2 use.

To avoid having to provide expensive, expensive, space-consuming and / or heavy heating elements or heaters for the energy storage cells 5a to 5k, the fact can be exploited that in a transfer of electrical energy from one energy storage module 3 to another

Energy storage module 3 of the power supply line by the current load a power loss occurs in the form of waste heat. This waste heat can be used to locally and temporarily heat the respective energy storage modules 3. For this type of heating no additional heating components are necessary because only a certain control strategy for the coupling devices 7 must be selected to electrical energy between two energy storage modules 3 back and forth

transfer.

4 shows a schematic illustration of a method 10 for heating energy storage cells of an energy storage device, for example of energy storage cells 5 a to 5 k of the energy storage device 1 in FIG. 1. The method 10 is suitable in particular for use in electrically operated vehicles which have an electric motor as electrical Machine 6 have. Energy storage devices 1 with energy storage cells 5 a to 5 k used in such vehicles are exposed to low temperatures, for example in winter or at night, so that starting the electrically operated vehicle is accelerated and simplified by method 10. Due to the high frequency transfer of energy between

Energy storage cells 5a, 5k of the energy storage device 1, the participating energy storage cells 5a, 5k are heated by the resulting charging power loss, so that their internal resistance decreases and their performance is improved. The method 10 can preferably be carried out when the temperature of the energy storage cells 5 a, 5 k falls below a first predetermined limit value. This first predetermined limit value can be based, for example, on a temperature below which the internal resistance of the energy storage cells 5 a, 5 k of the energy storage device 1 exceeds a maximum permissible or desired value.

The method 10 may include, as a first step 11, coupling the

Output terminals 1 a, 1 b of the energy storage device 1 with a

DC intermediate circuit 2b include. For example, the connection can take place via an inductive component 2 a, such as, for example, a storage throttle 2 a. In this case, the storage throttle 2a and the capacity of the

DC intermediate circuit 2b together as a boost converter, so that the

Voltage that can be provided to an energy storage module 3 in the power supply string by boosting the in the DC voltage intermediate circuit

2b existing voltage in the storage inductor 2a can be increased. The inductive component 2 a may generally be a coupling inductance 2 a, which, for example, is also present as a parasitic inductance at the output of the energy storage device 1. For temporarily storing electrical energy in the DC voltage intermediate circuit 2b, in a second step 12, a driving of the coupling devices 7 of at least one first energy storage module 3 for switching the respective

Energy storage cell modules 5 in the power supply line for a first predetermined period of time. As a result, electrical energy is transferred from the first energy storage modules 3 into the DC voltage intermediate circuit 2b and stored there temporarily. The energy cached in such a way can then be transferred into at least one second energy storage module 3 of the energy supply line. For this purpose, in a third step 13, a control of the coupling devices 7 of the at least one second energy storage module 3 for switching the respective

Energy storage cell modules 5 are made in the power supply line for a second predetermined period of time after the first predetermined period of time has elapsed.

If the voltage in the DC intermediate circuit 2b is high enough, the step 13 can be connected directly to the step 12, that is, the voltage in the DC intermediate circuit 2b is then also to the second

Energy storage modules 3 on. As a result, the second energy storage modules 3 are charged. The reloading can in this case also take place clocked, that is, the second energy storage modules 3 can be intermittently connected in the power supply line to a set Stro mg limit value for the

Energy storage cell modules 5 not to be exceeded. The duration of the second

predetermined period of time may be at the level of the voltage in the

Orient DC voltage intermediate circuit 2b, that is, when the voltage in the

DC intermediate circuit 2b has dropped below a certain level, the second energy storage modules 3 can be switched off again, and a re iteration of step 12 done. However, when the voltage in the DC voltage intermediate circuit 2b is too low, that is, lower than the voltage of the second energy storage modules 3, the

Storage choke 2a can be used as coupling inductance of a boost converter. For this purpose, the power supply string is first switched to short circuit, so that the capacity of the DC intermediate circuit 2b, the storage inductor 2a charges. After a short short-circuit period, the second energy storage modules 3 can then be switched to the energy supply line in step 13. If the current from the storage inductor 2a has dropped to zero, a re-iteration of step 12 can take place, that is, the duration of the second predetermined time period can be based on the amount of current flow from the storage inductor 2a.

The steps 12 and 13 can be alternated until the temperature of the energy storage cells 5 a, 5 k of the energy storage modules 3 involved exceeds a second predetermined limit value. This second predetermined limit may be for example, at a temperature above which the internal resistance of the energy storage cells 5 a, 5 k of the energy storage device 1 falls below a desired value.

In a step 14, then selecting the first and second

Energy storage modules 3 of the power supply line for providing the

Supply voltage for the DC voltage intermediate circuit 2b done. In particular, in an operating situation that requires only a low input voltage for the electric machine 6, such as a startup of an electric vehicle, those energy storage modules 3 can be selectively selected, which have already been heated to the supply voltage for the

DC intermediate circuit 2b provide. Only in a later

Operating stage then the other energy storage modules 3 are switched on, for example, if a later heating of these energy storage modules 3 is done, either by heating by the method 10 or an automatic heating by the driving operation of the electrically operated vehicle.

Claims

Method (10) for heating energy storage cells (5a, 5k) of a

Energy storage device (1) having a plurality of in one

Power supply string connected in series energy storage modules (3), each comprising:

an energy storage cell module (5) which has at least one energy storage cell (5a, 5k), and

a coupling device (7) with coupling elements (7a, 7b; 7c, 7d), which are designed to selectively load the energy storage cell module (5) into the

Switching or bridging power supply line,

the method (10) comprising the steps of:

Coupling (11) of the output terminals (1 a, 1 b) of the energy storage device (1) with a DC intermediate circuit (2b);

Driving (12) of the coupling devices (7) at least a first

Energy storage module (3) for switching the respective energy storage cell modules (5) in the power supply line for a first predetermined period of time; and driving (13) of the coupling devices (7) of at least one second

Energy storage module (3) for switching the respective energy storage cell modules (5) in the power supply line for a second predetermined period of time after the first predetermined period of time has elapsed.

The method (10) of claim 1, wherein the duration of the second predetermined

Period of an amount of voltage in the DC intermediate circuit (2b) is dependent.

The method (10) of claim 1, wherein the duration of the second predetermined

Time span from an amount of current flow through the respective

Energy storage cell modules (5) is dependent.

The method (10) according to any one of claims 1 to 3, further comprising the step:

Selecting (14) the first and second energy storage modules (3) of the

Power supply line for providing the supply voltage for the DC intermediate circuit (2b).

5. The method according to claim 1, wherein the method is carried out when the temperature of the energy storage cells falls below a first predetermined limit value. 6. The method as claimed in claim 1, wherein the steps of driving the coupling devices of at least one first energy storage module and of driving the coupling devices of at least one second energy storage module. 3) to be alternated until the temperature of the

Energy storage cells (5a, 5k) of the participating energy storage modules (3) exceeds a second predetermined limit.

7. The method (10) according to any one of claims 1 to 6, wherein the step of Koppeins (1 1) of the output terminals (1 a, 1 b) of the energy storage device (1) with the

DC intermediate circuit (2b) via a coupling inductance (2a).

8. System (100), with:

an energy storage device (1) having a plurality of in one

an energy storage cell module (5), which at least one energy storage cell

(5a, 5k), and

Switching or bridging power supply line;

a DC intermediate circuit (2b) which is coupled to output terminals (1 a, 1 b) of the energy storage device (1);

a pulse inverter (4) which is coupled to the DC intermediate circuit (2b) and which is fed from the DC intermediate circuit (2b) with an input voltage;

an electric machine (6) which is coupled to the pulse inverter (4) and which is supplied by the pulse inverter (4) with a phase voltage; and

a control device (8) which is coupled to the coupling devices (7) and which is designed to selectively control the coupling devices (7) of the energy storage device (1) for providing a total output voltage of the energy storage device (1) and a method (10) to carry out any of claims 1 to 6.

9. System (100) according to claim 8, wherein the coupling devices (7) comprise coupling elements (7a; 7b; 7c; 7d) in full-bridge connection.

10. System (100) according to claim 8, wherein the coupling devices (7)

Coupling elements (7a, 7c) in half-bridge circuit include.

1 1. A system (100) according to any one of claims 8 to 10, wherein the

Energy storage cells (5a, 5k) include lithium-ion batteries.