Patent Application
20160001674
This application claims the priority of German Patent Application, Serial No. 10 2014 212 935A, filed Jul. 3, 2014, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.
The present invention relates to an apparatus for supplying an electric voltage with a battery system having at least two serially-connected battery modules.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Apparatuses for providing an electric voltage usually include an electric energy store, which can be embodied as a battery system for example. Such battery systems can be used to supply electric loads, for example electric machines, with energy. Such electric machines can be disposed in motor vehicles for example and serve to drive the motor vehicle. Electric energy stores can also be used as buffer stores for electric energy. In such cases electric energy is provided by an electric machine in generator mode and is buffered in the electric energy store. Such electric energy stores are known for example from wind power systems or hybrid vehicles.
In the possible applications given above the battery systems are generally designed as high-voltage batteries which provide a high voltage as the battery system voltage. High-voltage here is to be understood as a voltage greater than 60 volts, especially greater than 120 volts. One or more loads can be connected to such an electric energy store, which are supplied by the battery with electric energy. Since the voltage provided by the battery is not equally suitable for all electric loads, the electric energy from the battery is usually transmitted via one or more voltage converters to the electric load or loads.
A circuit arrangement according to the prior art is shown in
The battery system 10 provides a battery system voltage US which is provided to the voltage converter modules 20 via an inductance L. The battery system voltage US is divided up between the voltage converter modules 20 such that, at each of the voltage converter modules 20 a partial voltage UT of the battery system voltage US drops. The battery system voltage US is thus divided serially between a plurality of voltage converter modules 20, wherein the voltage converter modules 20 are connected in a series circuit to the battery system 10. The respective partial voltage UT is thus dependent on the number of connected voltage converter modules 20 and is scaled via this number of voltage converter modules 20. The partial voltage UT falling at a voltage converter module 20 is converted by means of the voltage converter module 20 into a voltage suitable for the electric component 30.
The disadvantage of the circuit arrangement according to FIG. 1—and thus of the prior art—is that the partial voltage UT of each individual voltage converter module 20 is only scaled by the number of serially-connected and above all similar voltage converter modules 20, which brings with it restrictions in the scope of possible applications of the circuit arrangement.
It is also disadvantageous that a simultaneous operation of the battery system 10 as source or sink with the circuit arrangement according to the prior art is not possible. This means that it is not possible for example to provide a generator mode in which energy is fed back into the battery with the individual voltage converter modules 20 and simultaneously provide a motor mode with the remaining voltage converters 20, in which electric loads connected to the voltage converter modules can be supplied with energy.
A significant further disadvantage of the circuit arrangement according to the prior art is that the power output of each voltage converter module 20 must be approximately the same. To this end the voltage converter modules 20 coupled serially to one another are as a rule of identical design. In such cases each voltage converter module 20 is designed for a specific part voltage, also called intermediate circuit voltage. If the maximum permissible intermediate circuit voltage for each voltage converter module 20 is exceeded the voltage converter module will be destroyed. The maximum permissible intermediate circuit voltage per submodule will always be exceeded if the differences in the power output (motor mode) or power consumption (generator mode) respectively of the individual voltage converter modules 20 become very large. This means the intermediate circuit voltages of the individual voltage converter modules 20 can no longer be regulated if the sinks or sources of the individual voltage converter modules 20 deviate too greatly from one another.
Further disadvantages of the prior art emerge as a result of the restrictions in the current dimensioning of the batteries. A battery system or battery string or energy storage module is generally constructed by connecting battery modules one after the other, said arrangement usually comprising serial and/or parallel connected battery cells. The battery modules are always necessarily charged or discharged in this arrangement with the same current. The reason for this is that the individual battery modules are connected into a system with a higher voltage, i.e. into an energy storage module inflexibly in series and only the overall energy storage module can be accessed. Only the current which flows through the entire energy storage module can be regulated in such cases. The battery system voltage is proportional to the number of battery modules connected in series. High battery system voltages thus demand a large number of battery modules or cells connected in series and thereby make optimal battery design more difficult, which can lead to over-dimensioning and an additional increase in battery costs and system complexity. Furthermore the series connection makes greater demands on a battery management system (BMS), on safety and on energy storage module design, which again leads to increased costs.
On the other hand a pure parallel connection of the battery modules requires operation with low battery system voltage, which however, with high powers, leads to large battery currents and thus to higher power losses between battery and the loads. Realization is technically complex and expensive. Furthermore no scaling effects are produced here. The battery modules continue to represent a large and complex overall system. The redundancy and thus possible fault tolerance of the system is not increased by mere parallel connection of the battery modules.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved apparatus for supplying electric energy for one or more electric components in an especially cost-effective and optimized manner by using a redundant system that can be flexibly adapted to the power requirements of the electric components.
According to one aspect of the present invention, an apparatus for supplying an electric voltage includes a battery system supplying a battery voltage and having at least two serially-connected battery modules, with each of the battery modules supplying a battery module voltage, and at least two voltage converter modules, with each of the voltage converter modules being electrically connected to a respective one of the at least two battery modules and receiving at an input the battery module voltage and supplying at an output electric power to a connected electric component.
In the apparatus, a battery module and a voltage converter module electrically connected to this battery module form a submodule. The partial voltage which is now present at the voltage converter module is no longer scaled in this case via the number of voltage converter modules connected to the battery system. In each submodule the voltage which is present at the voltage converter module is defined by the connected battery module. Each submodule thus forms a separate module voltage supply apparatus. The advantage produced by this is that the apparatus is embodied especially reliably with a high availability. On failure of a voltage converter module or of a battery module, i.e. of an individual submodule, the remaining voltage converter modules in combination with the associated battery modules, i.e. the remaining submodules, can continue to be operated without problems and can provide energy for at least one connected electric component. In addition the apparatus according to the invention can be scaled in any given way in its power, since the apparatus can be expanded by further submodules for increasing the power without influencing the submodules already present, especially the battery module voltage of the submodules, in doing so. Thus a low-cost, efficiency-optimized, redundant and flexible power supply can be realized with the apparatus.
According to an advantageous feature of the present invention, each battery module may include at least one battery cell or may include a series circuit or a parallel circuit of a plurality of battery cells. Thus each battery module can provide a different voltage from another battery module and can thus scale the battery system voltage. Each individual battery module can thus be dimensioned so that the connected voltage converter module can be operated at its optimum efficiency. Submodules with different voltage classes are thus able to be realized and loaded independently of one another. This obviates the need for a central control, which insures the even adaptation of the partial voltage to the respective voltage converter module.
According to another advantageous feature of the present invention, the apparatus may include at least one switching device which is disposed between the two battery modules for electrical connection and/or disconnection of the battery modules. When the battery modules and the switching device are electrically connected to one another a serial connection of the submodules can be made possible. The battery modules, and thus the submodules, can however also be galvanically isolated from one another if undesired coupling-in of electrical noise should occur between the submodules. The ability for the individual battery modules to be galvanically isolated from one another during operation enables the apparatus according to the invention to be especially flexibly disposed as regards space.
According to another advantageous feature of the present invention, the voltage converter module may have at least one voltage converter element which has a boost converter and/or a buck converter. Boost converters and buck converters, referred to generally as synchronous converters, are DC converters. A boost converter converts an input-side voltage into an output-side voltage of which the amount is larger than that of the input-side voltage. A buck converter converts an input-side voltage into an output-side voltage of which the amount is smaller than that of the input-side voltage. In particular each voltage converter element for each submodule can be designed to meet its demand and be embodied for a specific power requirement adapted to the submodule. This means that each voltage converter module and thus each submodule is flexibly designed and can provide a suitable voltage for an electric load or the electric component connected to the submodule.
According to another advantageous feature of the present invention, the voltage converter module may have at least two voltage converter elements which are connected electrically in parallel. This enables a submodule to be formed which has a battery module and a voltage converter module with at least two parallel-switched voltage converter elements. Through the parallel switching of the at least two voltage converter elements the current is summed at an output side of the voltage converter module, to which an electric load is able to be connected. This increased current can be provided to an electric load able to be connected thereto with higher power requirements for example. This produces a greater flexibility in current scaling and thus also the power scaling of the submodules, which can be achieved by the parallel connection of a number of voltage converter elements to a battery module.
According to another advantageous feature of the present invention, the at least one voltage converter element may have a power-electronic inverter for converting the battery module voltage into an AC voltage. This enables the battery module voltage provided by a battery module which is converted by means of a boost converter or a buck converter into a higher or lower output DC voltage compared to the battery module voltage present on the input side, to be transformed by the power electronic converter into an AC voltage. Thus an electric motor can be operated with a submodule for example.
According to another advantageous feature of the present invention, the power electronic converter may include an H-bridge and/or a two-stage converter. This enables an AC voltage with variable frequency, variable amplitude to be generated from a DC voltage. The inverter can be suitably selected for the requirements of each submodule. The submodules thus produced are thus decoupled such that they can be loaded independently of one another and can operate electric components, for example motors, with different power requirements.
According to another advantageous feature of the present invention, the battery module voltage which is present at the respective battery module may be less than 120 volts or preferably less than 60 volts. A DC voltage which is less than 120 volts or preferably less than 60 volts is generally no longer regarded as a high voltage but as a low voltage. This enables the requirements for (high-voltage) safety according to the relevant known standards to be dispensed with. Thus the use of special high-voltage connectors, of cables with high insulation strength as well as high-voltage interlock mechanisms and further safety measures are irrelevant. The high-voltage interlock is generally a monitoring facility of high-voltage plug-in connectors and is used for shock hazard protection. Likewise, with battery module voltages of less than 120 volts or preferably less than 60 volts, lower-cost components and protection concepts for lower voltages can be employed. Inter alia this makes possible the use of semiconductor switches for simple switching off of the individual 60 volt-based battery modules. This enables expensive and large relays to be dispensed with which are needed for switching higher powers at high voltage. Likewise in the event of damage, for example an accident, no “splitting up” of the batteries into subunits of lower voltage is necessary since all voltage converter modules already have voltages in the range of the safe low voltage. This is a measure often required specifically in the automobile industry, which however has not been able to be implemented satisfactorily to date.
According to another aspect of the present invention, a drive arrangement includes at least one apparatus according to the invention and at least one electric component which is connected electrically to the at least one apparatus according to the invention.
According to another advantageous feature of the present invention, the drive arrangement may include a control device designed to control the at least one switching device of the apparatus. The electric component may be embodied as an electric machine.
According to another advantageous feature of the present invention, when the electric component operates in a motor mode, at least one of the battery modules supplies electric energy to the respective electric component, and wherein when the electric component operates in a generator mode, the respective electric component supplies electric energy to the at least one battery module for charging the at least one battery module.
Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:
Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.
Turning now to the drawing, and in particular to
The DC voltage provided by the battery system 10, which is divided up as a partial voltage UT serially to the connected voltage converter modules 20, is converted upwards in each case via a voltage converter element 21 into a voltage suitable for an electric motor and is converted into an AC voltage. To this end the partial voltage UT is applied via a choke inductance L to a boost converter 22.
The circuit topology of a boost converter 22 is shown in
If the boost converter 22 from
To supply energy to the electric machines 30 the serial stack converter or the apparatus 2 has a battery system 10, especially a high-voltage battery. The layout of the battery system 10 is shown in
The battery system 10 with the battery modules 13 and the switching devices are 17 according to
A voltage converter module 20 is thus expanded by its own battery module 13. A submodule 40 produced in this way is thus decoupled from the other, similarly-embodied submodules, such that the individual submodules 40 can be loaded independently of one another. Switching devices 17 which are able to be controlled via the control device 11 are disposed between the individual battery modules 13. Via the switching devices 17 the battery modules 13, and thus also the submodules 40 can be connected to one another electrically, wherein in the closed state of the switching devices 17 a series circuit of the individual submodules 40 is provided. The submodules 40 can however also be separated galvanically from one another by the switching devices 17, should undesired coupling-in of noise between the submodules 40 occur.
In addition the submodules 40 can be operated independently of one another. For example one submodule 40 can be in a generator mode. Then for example energy is provided in a charge mode by the connected electric component 30 which in this case is operated as a generator, which is supplied via the voltage converter module 20, which especially allows a bidirectional energy flow, to the connected battery module 13 to charge the battery module 13. Meanwhile another submodule 40 can be in a motor mode, wherein the electric component 30 of this submodule 40 is supplied with energy via the submodule 40. Through this high flexibility the battery system voltage US can be adapted to any given charging voltage without having to make large changes to the overall drive system. This leads to the development times and development costs of the drive arrangement 1 being greatly reduced.
The voltage converter modules 20, as described in
In order to achieve any given power scaling of the serial stack converter or of the apparatus 2, the number of battery modules 13 in combination with voltage converter modules 20 can be varied. In particular a redesign of the entire serial stack converter or the apparatus 2 is not necessary since the serial stack converter, for power scaling, can merely be expanded by “standardized” submodules 40.
It is especially advantageous for the battery module voltage UM (or the voltage potential in relation to bodywork of the motor vehicle) to always be less than 60 volts. If there is no charging mode the switching devices 17, which can be controlled via the electronic control device 11, are open in this case. If the switching devices 17 can remain permanently opened and charging of the individual battery modules 13 with below 60 volts can be guaranteed, then the requirements for high-voltage safety, in accordance with ISO 6469 for example, also do not apply. The disadvantage of a possible battery module partial voltage UM which is too low is compensated for in that the boost converter 22 disposed in the voltage converter element 21 boosts the intermediate circuit voltage of the inverter 23 to the desired voltage value or regulates it according to operating point and thus optimized for efficiency.
Within the upper submodule 40′ the voltage converter module 20 includes a number of parallel-connected voltage converter elements 21, to which an electric component 30′, especially an electric motor, is connected. The parallel connection of the voltage converter elements 21 is used for current scaling. If the voltage converter elements 21, which—as described in
In the present exemplary embodiment a single electric component 30 is connected to the two central submodules 40. Through this the electric component 30 is supplied with twice the battery module voltage UM. The serial connection of the submodules 40, to which the electric component 30 is connected, serves to scale the voltage.
The lower submodule 40″ supplies an electric component 30″, which is referred to here as the DC load, with energy. The voltage converter element 21 of the voltage converter module 20 is embodied here for example as a synchronous converter, especially as a boost converter. There is no provision for a conversion of the DC voltage provided by the battery system 10 into an AC voltage within the submodule 40″, since the DC load is supplied with a DC voltage.
The apparatus 2 or the serial stack converter, of which typical forms of embodiment are shown in the drive arrangement 1 from
Thus an apparatus 2 can be provided the form of the serial stack converter, which is used for diverse topologies and can meet a wide diversity of performance and voltage requirements. Thus for example, as well as the use of drive arrangement with such a stack converter in a motor vehicle, there can also be provision for use in a wind power system. In addition such a drive arrangement can be flexibly scaled with standardized submodules. Through the standardization the advantages of low-cost repairs for an end customer, a high redundancy of the drive arrangement 1, a high robustness through use of proven components from proven production processes as well as a marked reduction in manufacturing costs with increased quality and flexibility are also produced.
While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.
What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein:
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2014 212 935.4 | Jul 2014 | DE | national |
