System for coupling at least one alternating current source to a controllable energy storage device and associated operating method

Abstract

System for coupling at least one alternating current source (9) to a controllable energy storage device (2) with - the controllable energy store (2), which serves to control and supply electrical energy to an n-phase electrical machine (1), with n ≥ 1, wherein the controllable energy store (2) has n parallel energy supply branches (3-1, 3-2, 3-3), which ▪ on the one hand can be connected to a reference rail (T-) and ▪ on the other hand, are connectable to a respective phase (U, V, W) of the electrical machine (1), and - at least one n-phase alternating current source (9) which can be coupled to the individual power supply branches (3-1, 3-2, 3-3), wherein the energy supply branches (3-1, 3-2, 3-3) of the controllable first energy storage device (2) each have at least two series-connected energy storage modules (4), each comprising at least one electrical energy storage cell (5) with an associated controllable coupling unit (6) which, depending on control signals, bridges the respectively associated energy storage cells (5) or switches the respectively associated energy storage cells (5) into the respective energy supply branch (3-1, 3-2; 3-3), wherein the at least one alternating current source (9) is connectable to a respective connection point (A1; A2; A3) in the respective energy supply branch (3-1; 3-2; 3-3), which is located between two energy storage modules (4) of the respective energy supply branch (3-1; 3-2; 3-3), and wherein the coupling unit (6) of at least one energy storage module (4) located between the respective connection point (A1; A2; A3) and the reference rail (T-) is used as a controllable switching element, and wherein the connection points (A1; A2; A3) are each located on the side of the energy storage module (4-1m; 4-2m; 4-3m) directly connected to the reference rail (T-) facing away from the reference rail (T-).

Description

[0001] The invention relates to a system for coupling at least one alternating current source to a controllable energy storage device and to a method for operating the system according to the invention. State of the art

[0002] US 2009 / 0 102 288 A1 describes a power supply with a plurality of power supply modules and a method for operating such a power supply, wherein the state of individual power supply modules is monitored in order to prevent the modules from operating outside a predetermined range.

[0003] US Patent No. 7,964,990 B2 describes an uninterruptible power supply unit with a switch connected between a power source and a load. A combination of the outputs of two types of single-phase inverters is intended to compensate for system voltage fluctuations and supply the load with a predetermined voltage after a system voltage drop.

[0004] DE 197 36 414 A1 describes a battery block set for an electric vehicle with a battery control unit for controlling an equalization charging of the battery blocks in the battery block set.

[0005] It is becoming apparent that in the future, electronic systems that combine new energy storage technologies with electric drive technology will be increasingly used in both stationary applications such as wind turbines and vehicles such as hybrid or electric vehicles. In conventional applications, an electrical machine, designed as a rotating field machine, for example, is controlled via a converter in the form of an inverter. A characteristic of such systems is a so-called DC link, via which an energy storage device, usually a battery, is connected to the DC side of the inverter. In order to meet the power and energy requirements of a specific application, several battery cells are connected in series.Since the current provided by such an energy storage device must flow through all battery cells and a battery cell can only conduct a limited current, additional battery cells are often connected in parallel to increase the maximum current.

[0006] Connecting multiple battery cells in series not only results in a high overall voltage but also brings with it the problem that if a single battery cell fails, the entire energy storage system will fail because the battery current can no longer flow. Such a failure of the energy storage system can lead to a failure of the entire system. In a vehicle, a failure of the drive battery can cause the vehicle to break down. In other applications, such as the rotor blade adjustment of wind turbines, unfavorable conditions such as strong winds can even lead to safety-threatening situations. Therefore, a high level of reliability of the energy storage system should always be strived for, whereby "reliability" refers to the ability of a system to operate fault-free for a specified period of time.

[0007] The older applications DE 10 2010 027 857 A1 and DE 10 2010 027 861 A1 describe batteries with multiple battery module strings that can be connected directly to an electrical machine. The battery module strings have a plurality of battery modules connected in series, each battery module having at least one battery cell and an associated controllable coupling unit that allows the respective battery module string to be interrupted, or the respective associated at least one battery cell to be bridged, or the respective associated at least one battery cell to be connected to the respective battery module string, depending on control signals. By appropriately controlling the coupling units, e.g. using pulse width modulation, suitable phase signals for controlling the electrical machine can also be provided, so that a separate pulse-width inverter can be dispensed with.The pulse-controlled inverter required to control the electric machine is thus, so to speak, integrated into the battery. For the purposes of disclosure, these two earlier applications are incorporated in their entirety into the present application.

[0008] If such batteries are to be used in electric vehicles, for example, it should be noted that the battery technologies available today significantly limit the range of electric vehicles. Disclosure of the invention

[0009] The present invention provides a system for coupling at least one alternating current source to a controllable energy storage device, which serves to control and supply electrical energy to an n-phase electrical machine, where n ≥ 1. The controllable energy storage device has n parallel power supply branches, which can be connected to a reference rail on the one hand and to a respective phase of the electrical machine on the other. At least one n-phase alternating current source is provided for supplying electrical energy, which can be coupled to the individual power supply branches.

[0010] The present invention also provides a method for operating a system according to the invention, wherein the at least one alternating current source is coupled to the individual energy supply branches of the controllable energy storage device to support the energy supply of the electrical machine and / or to charge the controllable energy storage device. Advantages of the invention

[0011] By coupling an additional AC source to the controllable energy storage device according to the invention, it is possible to provide additional electrical energy and thus, for example, significantly extend the range of an electric vehicle. Depending on the current operating state of the controllable energy storage device and the electric machine, the provided energy can be used either to charge energy storage cells of the controllable energy source or to support the controllable energy source in supplying power to the electric machine. The system according to the invention is characterized in particular by a simple and thus cost-effective circuit topology.

[0012] In order to enable operation of the electrical machine and the controllable energy storage device even without the support of the alternating current source, according to one embodiment of the invention, controllable switching elements are provided, with the aid of which the at least one alternating current source can be coupled to the individual energy supply branches.

[0013] According to one embodiment of the invention, the alternating current source can be connected in parallel to the power supply branches of the controllable energy storage device, particularly with the aid of controllable switching elements. If the current required by the electric machine exceeds the value provided by the alternating current source, the controllable energy storage device compensates for the difference. In the opposite case, the controllable energy storage device absorbs the difference, whereby energy storage cells of the controllable energy storage device are charged by the alternating current source.

[0014] A similar effect can be achieved if the at least one alternating current source can be connected in series, rather than in parallel, to the power supply branches of the controllable energy storage device, particularly with the aid of controllable switching elements. The difference between the desired phase voltage at the electrical machine and the voltage provided by the alternating current source is adjusted via energy storage cells of the controllable energy storage device. This allows the controllable energy storage device to support the alternating current source, or the energy storage cells of the controllable energy storage device to be charged using the alternating current source. The phase voltages of the electrical machine can differ from the phase voltages of the alternating current source in terms of both amplitude and frequency.

[0015] Particularly efficient energy supply with high availability can be achieved if the AC power source includes a range extender with an AC generator driven by an internal combustion engine.

[0016] Alternatively or additionally, any other AC power source, such as any three-phase network, in particular the public network, can be used.

[0017] The energy supply branches of the controllable energy storage device each comprise at least two series-connected energy storage modules, each comprising at least one electrical energy storage cell with an associated controllable coupling unit that, depending on control signals, bridges the respectively associated energy storage cells or connects the respectively associated energy storage cells to the respective energy supply branch. Such a design allows the dual function of the controllable energy storage device—namely, controlling and supplying energy to the electrical machine—to be implemented in a particularly simple and efficient manner.

[0018] The alternating current source can be connected to a connection point in each power supply branch, with the respective connection points being located between two energy storage modules of the respective power supply branch. The coupling unit of at least one energy storage module located between the respective connection point and the reference rail can be used as a controllable switching element for the respective power supply branch. The common connection of the power supply branches can be broken using these coupling units, thus connecting the alternating current source in series with the energy storage modules located above it. This series connection also represents a coupling of the alternating current source to the individual power supply branches within the meaning of the application.

[0019] Since in this embodiment the alternating current source is only connected in series with the energy storage modules located between the respective connection point and the phases of the electrical machine, the connection points are each provided on the side of the energy storage module directly connected to the reference rail facing away from the reference rail, so that when the alternating current source is connected per energy supply branch only a single energy storage module becomes ineffective.

[0020] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings. Short description of the drawings

[0021] They show: Fig. 1 a schematic representation of a first embodiment of a system according to the invention for coupling at least one alternating current source to a controllable energy storage device and Fig. 2 a schematic representation of a second embodiment of a system according to the invention for coupling at least one alternating current source to a controllable energy storage device.

[0022] The Fig. 1 and Fig. 2 show schematic representations of embodiments of a system according to the invention for coupling at least one alternating current source to a controllable energy storage device. A controllable energy storage device 2 is connected to a three-phase electrical machine 1. The controllable energy storage device 2 comprises three energy supply branches 3-1, 3-2, and 3-3, which are connected on the one hand to a reference potential T- (reference rail), which carries a low potential in the illustrated embodiments, and on the other hand to individual phases U, V, W of the electrical machine 1. Each of the energy supply branches 3-1, 3-2, and 3-3 has m series-connected energy storage modules 4-11 to 4-1m, 4-21 to 4-2m, and 4-31 to 4-3m, where m ≥ 2.The energy storage modules 4, in turn, each comprise a plurality of series-connected electrical energy storage cells, which, for reasons of clarity, are provided with reference numerals 5-31 to 5-3m only in the energy supply branch 3-3 connected to phase W of the electrical machine 1. The energy storage modules 4 furthermore each comprise a coupling unit, which is assigned to the energy storage cells 5 of the respective energy storage module 4. For reasons of clarity, the coupling units are also provided with reference numerals 6-31 to 6-3m only in the energy supply branch 3-3. In the illustrated embodiments, the coupling units 6 are each formed by four controllable switching elements 7-311, 7-312, 7-313 and 7-314 to 7-3m1, 7-3m2, 7-3m3 and 7-3m4, which are connected in the form of a full bridge. The switching elements can be power semiconductor switches, e.g.in the form of IGBTs (Insulated Gate Bipolar Transistors) or as MOSFETs (Metal Oxide Semiconductor Field-Effect Transistors).

[0023] The coupling units 6 make it possible to interrupt the respective power supply branch 3 by opening all switching elements 7 of a coupling unit 6. Alternatively, the energy storage cells 5 can either be bridged by closing two of the switching elements 7 of a coupling unit 6, e.g., closing switches 7-312 and 7-314, or switched into the respective power supply branch 3, e.g., closing switches 7-312 and 7-313.

[0024] The total output voltages of the power supply branches 3-1 to 3-3 are determined by the respective switching state of the controllable switching elements 7 of the coupling units 6 and can be adjusted in stages. The gradation depends on the voltage of the individual energy storage modules 4. Assuming the preferred embodiment of similarly designed energy storage modules 4, a maximum possible total output voltage results from the voltage of a single energy storage module 4 times the number m of energy storage modules 4 connected in series per power supply branch 3.

[0025] The coupling units 6 thus allow the phases U, V, and W of the electrical machine 1 to be connected to either a high reference potential or a low reference potential and can therefore also fulfill the function of a known inverter. Thus, with appropriate control of the coupling units 6, the power and operating mode of the electrical machine 1 can be controlled by the controllable energy storage device 2. The controllable energy storage device 2 thus fulfills a dual function, serving both to supply electrical energy and to control the electrical machine 1.

[0026] The electric machine 1 has stator windings 8-U, 8-V and 8-W, which are interconnected in a star connection in a known manner.

[0027] In the illustrated embodiments, the electric machine 1 is designed as a three-phase AC machine, but can also have fewer or more than three phases. The number of power supply branches 3 in the controllable energy storage device 2 naturally also depends on the number of phases of the electric machine.

[0028] In the illustrated embodiments, each energy storage module 4 has a plurality of energy storage cells 5 connected in series. However, the energy storage modules 4 may alternatively each have only a single energy storage cell or energy storage cells connected in parallel.

[0029] In the illustrated embodiments, the coupling units 6 are each formed by four controllable switching elements 7 in the form of a full bridge, which also offers the possibility of voltage reversal at the output of the energy storage module. However, the coupling units 6 can also be implemented by more or less controllable switching elements, as long as the necessary functions (bridging the energy supply cells and switching the energy supply cells into the energy supply branch) can be realized. In particular, the coupling units can also be designed in the form of Hall bridges. Such embodiments are exemplified by the older applications DE 10 2010 027 857 A1 and DE 10 2010 027 861 A1.

[0030] To support the energy supply of the electrical machine 1 and / or to charge energy storage cells 5 of the controllable energy storage device 2, an alternating current source 9 can be connected to the individual energy supply branches 3-1, 3-2, 3-3 of the controllable energy storage device.

[0031] The alternating current source 9 comprises a range extender 13, which is known per se, with an alternating current generator 15 driven by an internal combustion engine 14. Alternatively or in addition to the range extender 13, any other alternating current sources, such as an n-phase network, in particular the public network, can be connected to the energy supply branches 3-1, 3-2, 3-3.

[0032] According to a Fig. In the first embodiment of the invention shown in Figure 1, the phases of the alternating current source 9 are connected via controllable switching elements 16-1, 16-2, and 16-3 to the connecting lines between the power supply branches 3-1, 3-2, and 3-3 of the controllable energy storage device 2 and the phases U, V, and W of the electrical machine 1. By closing the switching elements 16, a parallel connection of the alternating current source 9 with the power supply branches 3 of the controllable energy storage device 2 is achieved.

[0033] The speed of the alternating current generator 15 is controlled synchronously with the electric machine 1 via the combustion engine 14. If the current required by the electric machine 1 exceeds a value provided by the alternating current source 9, the controllable energy storage device 2 compensates for the difference. In the opposite case, the controllable energy storage device 2 absorbs the difference, whereby energy storage cells 5 of the controllable energy storage device 2 are charged by the alternating current source 9. By connecting the individual phases of the alternating current source 9 to one of the energy supply branches 3-1, 3-2, 3-3 of the controllable energy storage device, it is thus possible, on the one hand, to support the energy supply of the electric machine 1 and, on the other hand, to charge the controllable energy storage device 2.

[0034] According to a second embodiment of the invention, which is Fig.2, the phases of the alternating current source 9 are each connected to a connection point A1, A2, and A3 in the respective energy supply branch 3-1, 3-2, and 3-3, respectively. The connection points A1, A2, and A3 are each located on the side of the energy storage module 4-1m, 4-2m, and 4-3m directly connected to the reference rail T, facing away from the reference rail T. By appropriately controlling the switching elements 7 of the coupling units 6 assigned to these energy storage modules 4-1m, 4-2m, and 4-3m, e.g., opening all switching elements 7, the common connection of the energy supply branches 3-1, 3-2, and 3-3 can be broken. As a result, the alternating current source 9 is connected in series to the energy storage modules 4-11 to 4-1(m-1) or 4-21 to 4-2(m-1) or 4-22 to 4-2(m-1) located between the connection points A1, A2, A3 and the respective phases U or V or W of the electrical machine 1.4-31 to 4-3(m-1), which represents a coupling of the alternating current source 9 with the individual power supply branches 3.

[0035] The difference between a desired phase voltage at the electrical machine 1 and a voltage provided by the alternating current source 9 is adjusted via the energy storage cells 5 of the energy storage modules 4 connected in series with the alternating current source 9. Thus, the controllable energy storage device 2 can support the alternating current source 9 in supplying energy to the electrical machine 1, or the energy storage cells 5 of the controllable energy storage device 2 can be charged using the alternating current source 9.

[0036] In principle, it is also possible to provide the connection points A1, A2, and A3 at a different location in the respective power supply branch 3-1, 3-2, or 3-3. If the alternating current source 9 is also to be decoupled from the power supply branches 3, it is only necessary to ensure that the connection points A1, A2, A3 are each located between two energy storage modules 4 of the respective power supply branch 3, so that at least one energy storage module 4 is located between the connection point A and the reference rail T-, the coupling unit 6 of which can be used as a controllable switching element for coupling the alternating current source 9 to the power supply branches 3, i.e., for disconnecting the common connection of the power supply branches 3-1, 3-2, and 3-3.

[0037] In a further embodiment not specifically shown, it is also possible to connect the phases of the alternating current source 9 at the lower end of the energy supply branches 3-1, 3-2, and 3-2, i.e., in an area between the reference rail T- and the energy storage modules 4-1m, 4-2m, and 4-3m directly connected thereto. In this case, similar to the first embodiment, additional controllable switching elements can be provided, which allow the alternating current source 9 to be coupled to the energy supply branches 3, but also to be separated from them, so that operation without support from the alternating current source 9 is also possible.

Claims

[1] System for coupling at least one alternating current source (9) to a controllable energy storage device (2) with - the controllable energy store (2), which serves to control and supply electrical energy to an n-phase electrical machine (1), with n ≥ 1, wherein the controllable energy store (2) has n parallel energy supply branches (3-1, 3-2, 3-3), which ▪ on the one hand can be connected to a reference rail (T-) and ▪ on the other hand, are connectable to a respective phase (U, V, W) of the electrical machine (1), and - at least one n-phase alternating current source (9) which can be coupled to the individual power supply branches (3-1, 3-2, 3-3), wherein the energy supply branches (3-1, 3-2, 3-3) of the controllable first energy storage device (2) each have at least two series-connected energy storage modules (4), each comprising at least one electrical energy storage cell (5) with an associated controllable coupling unit (6) which, depending on control signals, bridges the respectively associated energy storage cells (5) or switches the respectively associated energy storage cells (5) into the respective energy supply branch (3-1, 3-2; 3-3), wherein the at least one alternating current source (9) is connectable to a respective connection point (A1; A2; A3) in the respective energy supply branch (3-1; 3-2; 3-3), which is located between two energy storage modules (4) of the respective energy supply branch (3-1; 3-2; 3-3), and wherein the coupling unit (6) of at least one energy storage module (4) located between the respective connection point (A1; A2; A3) and the reference rail (T-) is used as a controllable switching element, and wherein the connection points (A1; A2; A3) are each located on the side of the energy storage module (4-1m; 4-2m; 4-3m) directly connected to the reference rail (T-) facing away from the reference rail (T-). [2] System according to claim 1, wherein the at least one alternating current source can be coupled to the individual power supply branches (3-1, 3-2, 3-3) by means of controllable switching elements (16). [3] System according to one of claims 1 or 2, wherein the at least one alternating current source can be switched in parallel to the energy supply branches (3-1, 3-2, 3-3) of the controllable energy storage device (2). [4] System according to one of claims 1 or 2, wherein the at least one alternating current source is connectable in series with the energy supply branches (3-1, 3-2, 3-3) of the controllable energy storage device (2). [5] System according to one of claims 1 to 4, wherein the at least one alternating current source (9) is designed as a range extender (13) with an alternating current generator (15) driven by an internal combustion engine (14). [6] System according to one of claims 1 to 4, wherein an n-phase network, in particular the public network, serves as the alternating current source (9). [7] Method for operating a system according to one of claims 1 to 6, wherein, in order to support the energy supply of the electrical machine (1) and / or to charge the controllable energy storage device (2), the at least one alternating current source (9) is coupled to the individual energy supply branches (3-1, 3-2, 3-3) of the controllable energy storage device (2).

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