Device and method for the voltage equalisation of a plurality of two-terminal networks, and DC power distribution system

Abstract

The invention describes a device (1) for the voltage equalisation of a plurality n of at least two (n≥2) two-terminal networks (P1, P2, P3). The device comprises a current-limiting component (10) with an input (10.1) and an output (10.2), and n connection pairs (A) each having a first connection (A1) and a second connection (A2) for connecting the n two-terminal networks (P1, P2, P3). Two or more of the first connections (A1) are each connected to the input (10.1) via a first switch (S1) or directly. In addition, two or more of the first connections (A1) are each connected to the output (10.2) via a second switch (S2). The second connections (A2) are connected to a common reference potential GND or are connected in a switchable manner. The device (1) is designed to set switching states of the first switch (S1) and of the second switch (S2) by means of a control unit (9) and / or by means of voltages applied to the first connections (A1) in such a manner that the current-limiting component (10) consumes power in its input (10.1) and not in its output (10.2), and the current-limiting component (10) outputs power from its output (10.2) and not its input (10.1). The invention also describes a method for the voltage equalisation of n two-terminal networks (P1, P2, P3) that can be carried out with the device (1), and a DC power distribution system.

Description

[0001] Device and method for voltage equalization of multiple two-poles, as well as DC power distribution system

[0002] Technical field of the invention

[0003] The invention relates to a device and a method for voltage equalization of several two-terminal networks. The two-terminal networks can, in particular, be two-terminal networks designed to be interconnected in a direct current (DC) circuit. The two-terminal networks can include one or more two-terminal networks that operate in a power-outputting manner during voltage equalization. However, it is also possible for them to have one or more two-terminal networks that operate in a power-consuming manner, particularly during voltage equalization. The invention further relates to a DC power distribution system with such a device.

[0004] State of the art

[0005] Many electrical and electronic devices contain a capacitance effective at their terminals and / or exhibit capacitive behavior at their terminals. Such devices must be pre-charged with a limited current before they begin normal operation, particularly when connecting the terminals to a voltage source. For example, inverters with an uncharged high-capacity direct current (DC link) cannot simply be connected to a battery on the DC side. In this case, the battery would feed into the initially uncharged DC link and generate a high inrush current, at least briefly, which could damage components of the inverter, e.g. semiconductor switches and / or DC link capacitors. The same applies to devices with a high capacitance effective at their terminal that are connected to the DC side of the inverter.Here, the charged capacitance of the devices can act as a voltage source, at least briefly, and generate a high inrush current on the inverter's DC link. A similar problem would arise in the opposite direction, namely if the DC side of an inverter, which includes a charged DC link, is connected to a terminal of an electrical device that has an uncharged effective capacitance at its terminal. Devices with a correspondingly high capacitance could include electrolyzers or DC buses of direct current (DC) grids, for which the connected capacitances are sometimes unknown.Even if the inverter is connected to an AC voltage source, for example an AC grid, high inrush currents can be generated on the initially uncharged DC link via freewheeling diodes in a bridge circuit of the inverter, which can damage the freewheeling diodes or other components of the inverter located in the path of the inrush current.

[0006] To prevent such damage, it is known to precharge devices with an initially uncharged capacitance via a precharge resistor or an actively controlled current-limiting component, such as a DC / DC converter, before connecting them to a low-impedance voltage source. This allows for a controlled equalization of the voltages of the device and the voltage source, suppressing high inrush current.

[0007] In complex electrical DC power distribution systems, several devices, each with a large capacity, often have to be connected and thus pre-charged simultaneously or sequentially. In order to use the devices as flexibly as possible, it may also be desirable to provide different pre-charging paths for a device. In concrete terms, for example, it may be desired to be able to pre-charge the DC link of an inverter at one time via the DC side and at another time via the AC side of the inverter. To meet all of these requirements, one or more separate pre-charging resistors can be provided for each of the devices, although this would result in significantly high costs overall. Furthermore, it is possible that individual devices, particularly in the case of voltage equalization that takes place in several stages, operate by consuming power at one time and outputting power at another time.In this case, an actively controlled current-limiting component would have to be designed for a bidirectional power flow, which also entails increased costs compared to a unidirectionally operating current-limiting component.

[0008] Document EP 2760096 A1 discloses an electrical storage system that operates with only a small number of current-limiting resistors. The storage system includes a charger that supplies energy from an external power source to an electrical storage device and energy from the electrical storage device to an external device. A first main relay and a second main relay enable a connection of a positive electrode terminal and a negative electrode terminal of the electrical storage device to a load. A third main relay is connected in series with a current-limiting resistor and, together with the current-limiting resistor, is connected in parallel with the first main relay. A first charging relay and a second charging relay enable a connection of the positive and negative electrode terminals of the electrical storage device to the charger.A third charging relay is connected in series with the current-limiting resistor and, together with the current-limiting resistor, is connected in parallel with the first charging relay. This requires that power flow through the current-limiting resistor occurs in two opposite directions, i.e., bidirectionally. Replacing the current-limiting resistor with a unidirectional current-limiting component is not possible here.

[0009] The document DE 10 2011 083741 A1 discloses a circuit arrangement for the variable interconnection of energy sources and energy consumers, comprising a bidirectional AC / DC converter, a DC / DC converter, at least four electrical switches and a control device for controlling the switches and the converters.

[0010] The document DE 10 2011 088457 A1 discloses a circuit arrangement for converting an input voltage into an output voltage, comprising an input voltage pole pair for connecting a voltage source, an output voltage pole pair for tapping an output voltage, and a half-bridge with two controllable switching elements and a choke connected to a half-bridge tap arranged between the controllable switching elements. The half-bridge is connectable by means of a switch arrangement to at least either the first input voltage pole or the first output voltage pole, wherein the choke is or can be connected to the input or the output.

[0011] US 2014 / 0009106 A1 discloses a battery and load balancing circuit for preventing an inrush current surge when initially connecting batteries and / or loads in parallel. Various techniques are used, such as charging and discharging using DC / DC converters, to balance charges between batteries and between batteries and capacitive loads.

[0012] Object of the invention

[0013] The object of the invention is to provide a device and a method for voltage equalization of several two-terminal networks, in particular for pre-charging and / or discharging one or more of the two-terminal networks. Implementation of the method and also of the device should be as cost-effective as possible. In particular, the device and the method should be suitable for bringing about voltage equalization of several two-terminal networks with the smallest possible number of current-limiting components. This should also enable the simplest and most cost-effective design of the current-limiting components, in particular in a case where the current-limiting component is actively controlled. A further object of the invention is to provide a DC power distribution system suitable for carrying out the method.

[0014] Solution

[0015] The object of providing a device for voltage equalization of the type mentioned at the outset is achieved according to the invention with the features of independent claim 1. The object of providing a method for voltage equalization of the type mentioned at the outset is achieved according to the invention with the features of independent claim 13. The object of providing a DC power distribution system suitable for implementing the method is achieved according to the invention with the features of independent claim 19. Advantageous embodiments of the device are mentioned in claims 2 to 12, advantageous embodiments of the method in claims 14 to 18, and advantageous embodiments of the DC power distribution system in claims 20 to 21. Description of the invention

[0016] The device according to the invention is designed to perform voltage equalization of a plurality n of at least two (n>2) two-terminal networks (P1, P2, P3). At least one, and possibly several, of the two-terminal networks can have a capacitance or capacitive behavior effective on the connection side. The device comprises: a current-limiting component with an input and an output, and n terminal pairs, each with a first terminal and a second terminal for connecting the n two-terminal networks.

[0017] Two or more of the first terminals are each connected via a first switch or directly to the input of the current-limiting component. As a result, these two or more of the n terminal pairs are designed to be connected to a two-terminal network that operates at least temporarily to output power. Furthermore, two or more of the first terminals are each connected via a second switch to the output of the current-limiting component, as a result of which these two or more of the n terminal pairs are each designed to be connected to a two-terminal network that operates at least temporarily to consume power. The second terminals of the n terminal pairs are connected directly or switchably to one another and to a common reference potential GND.The device is designed to set switching states of the first switches and the second switches by means of a control unit and / or by means of voltages applied to the first terminals relative to the reference potential - and thus also relative to the second terminals - in such a way that power is input by the current-limiting component from one or more of the first terminals via one or more of the first switches or the direct connection to the input of the current-limiting component, but not via one or more of the second switches, and power is output by the current-limiting component to one or more of the first terminals via one or more of the second switches, but not via one or more of the first switches.Furthermore, the switching states of the first and second switches only enable a unidirectional power flow through the current-limiting component, namely from the input of the current-limiting component to its output, whereas a power flow directed from the output to the input, and thus a bidirectional power flow through the current-limiting component, is suppressed. Switching states that do not match this suppression can be avoided by appropriately controlling the first and second switches or can be excluded from the outset by using a unidirectional switch as the first switch and / or as the second switch.By means of the device, a power flow can thus be enabled from one or more of the first terminals, each associated with a power-emitting two-terminal network, along a path via the current-limiting component, to one or more of the first terminals, each associated with a power-consuming two-terminal network. If necessary, however, a power flow between two or more of the first terminals can be at least temporarily suppressed by means of the switching states of the first and second switches, bypassing the current-limiting component. For this purpose, it is also possible and advantageous to design the switches as unidirectional switches.

[0018] In this description, power consumption or output at individual contacts is always to be understood relative to the reference potential GND. This means that the power consumption in a contact is the current into the contact multiplied by the voltage between the contact and the reference potential GND. Correspondingly, power output from a contact is the current out of the contact multiplied by the voltage between the contact and the reference potential GND. A power flow through a component means that it absorbs power at one contact and outputs power at another contact. In the sense of this description, a contact can be understood in particular as the first connection or the second connection of a two-terminal network. In addition, the term “contact” can also refer to the input or output of the current-limiting component.Finally, the contact can also be a contact of one of the switches in the first and second switch.

[0019] A method according to the invention enables voltage equalization of a plurality n of at least two (n>2) two-terminal networks, at least one of which contains a terminal-side effective capacitance or exhibits a terminal-side effective capacitive behavior. The method can be carried out using the device according to the invention and comprises the following steps:

[0020] Connecting the n two-poles to one of the terminal pairs of the device, if these are not already connected, so that two or more of the n two-poles are each connected in a single-pole manner directly, or via a first switch, to the input of the current-limiting component and two or more of the n two-poles are each connected in a single-pole manner via a second switch to the output of the current-limiting component,

[0021] Bringing about the voltage equalization by setting the switching states of the first switches and the second switches by means of the control unit and / or by means of voltages applied to the first terminals such that power is input by the current-limiting component from one or more of the first terminals via one or more of the first switches or the direct connection to the input of the current-limiting component, but not via one or more of the second switches, and that power is output by the current-limiting component to one or more of the first terminals via one or more of the second switches, but not via one or more of the first switches, so that a unidirectional power flow via the current-limiting component from the input to the output is enabled,and a reverse power flow from the output to the input - and thus also a bidirectional power flow via the current-limiting component - is prevented.

[0022] In the method, the switching states of the first and second switches shift the power input of the current-limiting component to its input and not to its output, while the power output of the current-limiting component always occurs at its output and not at its input. This results in a unidirectional power flow directed from the input to the output of the current-limiting component, which emanates from one or more of the n two-terminal networks operating in a power-emitting manner and runs along a path via the same current-limiting component to one or more of the n two-terminal networks operating in a power-absorbing manner. If desired, a power flow between two or more of the n two-terminal networks can be suppressed, or at least temporarily suppressed, bypassing the current-limiting component.

[0023] A voltage equalization between a plurality of two-terminal networks can be carried out exclusively using the method according to the invention. Alternatively, however, it is also possible for the method to be combined with other known methods of voltage equalization. For example, two of the first connections can be connected or switchably connected via a further path that does not lead via the current-limiting component in addition to the path that leads via the current-limiting component. Specifically, for example, the first connections of two two-terminal networks can be connected or switchably connected via a further impedance, for example a further pre-charging resistor. This is particularly advantageous if a large power flow is required to equalize the voltage of the two two-terminal networks in question, which power flow exceeds the current-carrying capacity of the current-limiting component.

[0024] A two-terminal network within the meaning of the invention can only contain two poles. Alternatively, however, it is also possible for the two-terminal network to have more than two, for example four or more poles. In this case, individual poles can be considered as a two-terminal network in pairs. For example, a DC side of an AC / DC converter can be a two-terminal network within the meaning of the invention. The same applies to an input side as well as an output side of a DC / DC converter. A power-outputting two-terminal network can, but does not necessarily have to, operate in a power-outputting manner at all times. Rather, it is possible for a two-terminal network or individual two-terminal networks to operate in a power-outputting and power-consuming manner during voltage equalization, provided this occurs at different times. For example, such a two-terminal network can operate in a power-outputting manner at one time and a power-consuming manner at another time.Such behavior can occur particularly in multi-stage voltage equalization. The same applies analogously to a power-consuming two-terminal network. This network, too, can operate in a power-outputting mode at one time and a power-consuming mode at another during voltage equalization.

[0025] Voltage equalization within the scope of the invention can, in particular, comprise pre-charging a previously uncharged or only partially charged two-terminal network or several previously uncharged or only partially charged two-terminal networks connected to the device. The two-terminal networks that are pre-charged during voltage equalization can each operate in a power-consuming manner. Alternatively, the voltage equalization can also comprise a complete or partial discharge of a previously charged two-terminal network or several previously charged two-terminal networks connected to the device. The two-terminal networks that are to be discharged during voltage equalization can each operate in a power-emitting manner.

[0026] During voltage equalization, the voltage of one or more of the two-terminal systems involved in the power flow can change over time. This is particularly the case for two-terminal systems that contain a capacitance on the connection side, i.e. between their two poles, or that exhibit capacitive behavior at their poles. Specifically, a voltage between the poles of a power-emitting two-terminal system can decrease over time. Correspondingly, a voltage between the poles of a power-consuming two-terminal system can increase over time. In addition to two-terminal systems that change their voltages over time, there can also be two-terminal systems that have a time-invariant voltage. This is the case, for example, for two-terminal systems in which power flowing out of the poles is compensated by an energy source that is part of the two-terminal system or that is connected to a third and a fourth pole of the two-terminal system.In any case, the voltage equalization process results in a change in the voltages of at least one two-terminal network, and possibly also of several two-terminal networks, such that the voltages of the power-emitting two-terminal networks and the voltages of the power-consuming two-terminal networks equalize each other.

[0027] The optional suppression of power flow by bypassing the current-limiting component between two or more first terminals, each assigned to a power-supplying two-terminal network, does not necessarily have to be permanent. Rather, it may be sufficient if this occurs during the voltage equalization process at least until the voltages of the corresponding first terminals are sufficiently equalized, so that they only differ slightly from each other. The same applies to the optional suppression of power flow by bypassing the current-limiting component between those first terminals, each assigned to a power-supplying two-terminal network.

[0028] During voltage equalization using the device according to the invention, as well as using the method according to the invention, the switching states of the first switch are used to set which of the two-terminal networks, which are essentially intended for power output, operates in a power-emitting manner at a specific time. The switching states of the second switch are used to set which of the two-terminal networks, which are essentially intended for power input, operates in a power-consuming manner at a specific time. Therefore, the switching states of the first and second switches can also be used to set which of the power-emitting two-terminal networks is connected to which of the power-consuming two-terminal networks at a specific time. The power flow from one or more power-emitting two-terminal networks to one or more power-consuming two-terminal networks always occurs via the same current-limiting component.This therefore only needs to be provided once, and not separately for each two-terminal device, or even for each pair of two-terminal devices between which voltage equalization is to take place, which means enormous cost savings, particularly as the number of two-terminal devices increases. In addition, the switching states of the first and second switches specify a unidirectional power flow via the current-limiting component from its input to its output. Specifically, the first switches only output power from two-terminal devices currently operating in a power-emitting manner to the input of the current-limiting component. Furthermore, the second switches only input power from two-terminal devices currently operating in a power-consuming manner from the output of the current-limiting component.It is therefore sufficient to design the current-limiting component itself only for a unidirectional power flow. It can therefore also be implemented more cost-effectively than a current-limiting component designed for a bidirectional power flow. This is particularly the case when it is an actively controllable current-limiting component, for example a DC / DC converter. If a DC / DC converter designed as a buck converter is desired for voltage equalization, it is sufficient that it can only operate in one direction, for example from the input to the output. It does not have to be additionally designed to operate in a buck-converting manner from the output to the input, since such a directed power flow is suppressed via the switching states of the first and second switches.Furthermore, it is generally sufficient if the DC / DC converter can conduct current in only one direction, so that, for example, a buck converter can be designed with only one active switch and does not have to be constructed as a half-bridge. Overall, the use of the device according to the invention, as well as the method according to the invention, results in a simple and cost-effective voltage equalization of several two-terminal networks. Advantageous embodiments of the invention are specified in the following description and the dependent claims, the features of which can be used individually and in any desired combination.

[0029] In principle, it is possible for the device to be designed to equalize the voltage of only two two-terminal networks, i.e., where n=2. In this case, the device has only two pairs of connections, with the first terminals of both pairs being connected to the input of the current-limiting component via a first switch and to the output of the current-limiting component via a second switch. In this case, both two-terminal networks are designed to operate, in principle, i.e., at different times, both in a power-output and a power-consumption manner.

[0030] In a preferred embodiment, however, the device can be designed for voltage equalization of three or more (n>3) two-terminal networks and, for this purpose, can have three or more terminal pairs. At least three, possibly more, and optionally all of the first terminals—and the two-terminal networks connected to them—can participate simultaneously in the power flow via the current-limiting component, at least temporarily. The cost advantage of both the method and the device increases with the number of two-terminal networks involved in the voltage equalization, since each newly added two-terminal network can utilize the existing current-limiting component.Even in a case where the device is designed for voltage equalization of more than just two two-terminal networks (n>3), one two-terminal network / multiple two-terminal networks can operate, for example in the case of multi-stage voltage equalization, in a power-emitting manner at one time and a power-consuming manner at another time. Therefore, in this case too, it is possible for a first terminal or several of the first terminals to be switchably connected to the input of the current-limiting component via a first switch and to the output of the current-limiting component via a second switch. In this case, one or more bridge branches are formed which are each assigned to the first terminals and which each have a series connection of the first switch assigned to the first terminal and the second switch assigned to the first terminal.The first terminals are connected to their assigned bridge branches via branch taps, each of which is located within the bridge branches between the first and second switches. Thus, each of the corresponding first terminals can be conductively connected to the input via a closed first switch when the connected two-terminal network is in power-output mode, and can be connected to the output of the current-limiting component via a closed second switch when the connected two-terminal network is in power-consumption mode. This ensures that the power flow is always unidirectional from the input to the output of the current-limiting component, regardless of whether a particular two-terminal network is currently operating in power-consumption or power-output mode.

[0031] In the device, at least one of the first switches and / or at least one of the second switches can each have a diode D or can each be designed as a diode D. In this case, a forward conducting and reverse blocking behavior can be impressed on the at least one first switch and / or the at least one second switch via the diode comprised by the switch. In this context, a forward conducting behavior can be understood in the case of a first switch as a conducting behavior that enables a power flow out of the two-terminal network assigned to the first switch, whereas in the case of a second switch it refers to a conducting behavior that enables a power flow into the two-terminal network assigned to the second switch.Accordingly, a reverse blocking behavior in this context can be understood for a first switch as a blocking behavior that blocks a power flow into the two-terminal network associated with the first switch, while for a second switch it refers to a blocking behavior that blocks a power flow out of the two-terminal network associated with the second switch.

[0032] In this way, undesired switching states, i.e. switching states which conflict with the desired unidirectional power flow through the current-limiting component, can be suppressed via the reverse-blocking behavior of the corresponding first switch and / or second switch. The switching states of the corresponding first and / or second switches, which each have a diode or are each designed as a diode, can be set by the voltages applied to the first terminals relative to the GND potential, i.e. the respective voltages of the two-terminal networks, and it is not necessary to control the switching states via a control unit. With a large number of first switches, each designed as a diode, the diode which always assumes a conductive switching state is the one in which the two-terminal network assigned to the diode has a maximum voltage or a minimum voltage compared to the other two-terminal networks.The same applies to the second switches, each of which is designed as a diode. Therefore, a control unit can be omitted entirely, for example if each of the first switches and second switches is designed as a diode, or a control unit required for other reasons can be designed more simply because it has to process fewer functions, which has a beneficial effect on the costs incurred for a corresponding device. In addition, a diode is usually less expensive than an actively controllable semiconductor switch, which likewise generates a cost advantage for the corresponding device. It goes without saying that the device can also have several diodes, possibly even each of the first switches, or can be designed as a diode.Alternatively or cumulatively, several of the second switches, if appropriate each of the second switches, can each have a diode or be designed as a diode.

[0033] In one embodiment, each of the first switches and each of the second switches of the device can be designed as a diode. In this case, the diodes can be designed as ready-made diode bridges, resulting in further space and cost savings. The suppression of temporarily undesired power flows within the device is possible via third switches. Alternatively or cumulatively, however, it is also possible for at least one, possibly several, of the first switches and / or at least one, possibly several, of the second switches to each comprise a switch controllable by the control unit. This can in particular be a semiconductor switch or an electromechanical switch. In such a case, it goes without saying that the device comprises a control unit for controlling the corresponding first and / or second switch.Thus, a switch controlled by the control unit can be controlled independently of a voltage applied to its assigned first terminal relative to the reference potential GND, allowing a greater degree of freedom in implementing the method. In this case, a unidirectional power flow through the current-limiting component can be set via the control unit by means of suitable switching states of the first and second switches.

[0034] Alternatively or in addition to the aforementioned cases, it is also possible to suppress a bidirectional power flow through the current-limiting component by having one, several, or each of the first switches and / or one, several, or each of the second switches comprise a unidirectional switch. A unidirectional switch within the meaning of the application is a switch with at least one control state that is designed to enable a power flow in one direction and to suppress it in the opposite direction. Such a unidirectional switch thus exhibits a reverse-blocking and forward-conducting behavior in the respective control state—similar to a diode. A distinction must be made between the control state and the switching state of the unidirectional switch. A control state can thus comprise multiple switching states.For example, the above-mentioned control state in question, which is characterized by forward conducting and reverse blocking behavior, comprises two switching states, namely the "closed" or "conducting" switching state for a forward-directed power flow and the "open" or "blocking" switching state for a reverse-directed power flow. To assume the control states, the unidirectional switch can comprise or be constructed from several different switches. A unidirectional switch can, but does not necessarily have to, be actively controllable and, for this purpose, have a control terminal for assuming the control state. A unidirectional switch that is not actively controllable has only a single control state. An actively controllable unidirectional switch, on the other hand, can have additional control states that can be advantageously used during operation of the device.The following are examples of unidirectional switches, not limiting ones:

[0035] • a series circuit of an electromechanical switch and a diode,

[0036] • a series circuit of a bidirectionally conductive semiconductor switch and a diode

[0037] • a parallel circuit of a reverse blocking semiconductor switch and a diode,

[0038] • a reverse blocking semiconductor switch, e.g. a reverse blocking IGBT,

[0039] • a diode, and

[0040] • a thyristor.

[0041] Some unidirectional switches and their advantageous properties for the operation of the device are described in more detail in Fig. 4a - 4c.

[0042] In the device, at least one of the first switches can be designed as a unidirectional switch which, in the respective control state, behaves like a diode whose flow direction is oriented such that a power flow from the first terminal assigned to the first switch to the input of the current-limiting component is enabled, but a power flow from the input of the current-limiting component to the respective first terminal is suppressed. In this way, in the respective control state, a power flow via the first switch into the assigned first terminal, and thus also a direct power flow from another two-terminal network into the two-terminal network connected to the respective first terminal, is prevented, bypassing the current-limiting component.

[0043] Accordingly, in the device, at least one of the second switches can be designed as a unidirectional switch which, at least in the respective control state, behaves like a diode whose flow direction is oriented such that a power flow from the output of the current-limiting component to the first terminal assigned to the second switch is enabled, but a power flow from the corresponding first terminal to the output of the current-limiting component is suppressed. In this way, in the respective control state, a power flow via the second switch from the first terminal assigned to it, and thus also a direct power flow from the two-terminal network connected to the first terminal into another two-terminal network, bypassing the current-limiting component, is prevented.

[0044] If advantageously all first and second switches of the device are designed as unidirectional switches, it can be ensured, at least when all these switches assume the respective control state, that a power flow neither occurs in an undesired direction via the current-limiting component nor directly between two two-poles.

[0045] Further control states of a unidirectional first and / or second switch can be used

[0046] • to reduce the forward voltage and thus the power loss of the corresponding unidirectional switch, such as in a normally-off MOSFET, where the channel can be switched on in parallel with a body diode

[0047] • after completion of the voltage equalization, to establish a direct connection between the first terminals of two two-poles

[0048] • temporarily suppress unwanted power flows through the unidirectional switch, for example by arranging an electromechanical or semiconductor switch in series with the diode.

[0049] In an advantageous embodiment, the current-limiting component can comprise an ohmic resistor RVL, a thermistor, for example a hot-wire resistor (NTC) or a cold-wire resistor (PTC), and / or a semiconductor switch TVL that can be actively controlled by the control unit. It is also possible for the current-limiting component to comprise a series connection of two different ones of these components. In a further embodiment, the current-limiting component can be designed as a DC / DC converter, in particular as a step-down DC / DC converter from the input to the output. Relative to an ohmic resistor as the current-limiting component, this enables the power flow through the current-limiting component to be controlled in a more finely tuned manner, resulting in a greater degree of freedom when implementing the voltage equalization method.

[0050] Advantageously, the device can additionally comprise a switching unit for the switchable low-impedance connection of two or more of the first terminals to one another, as well as a control unit for controlling the switching unit. The control unit of the switching unit can be the same one that is also used to control the first and second switches. In this case, the control unit can be designed to connect two or more of the first terminals to one another in a low-impedance manner depending on a voltage prevailing between the respective first terminals. Specifically, for example, two first terminals, more than two first terminals, or all first terminals of the n two-terminal networks can be connected to one another in a low-impedance manner by means of the switching unit when an absolute value of a voltage present between the respective first terminals reaches or falls below a voltage threshold value UTH.For this purpose, it is possible to detect the voltage from each of the first terminals separately. Alternatively, however, it is also possible for the device to comprise one, in particular only one, voltage sensor for detecting a voltage U applied to the current-limiting component, i.e., a voltage U applied between the input and the output of the current-limiting component. The control unit is designed to operate the switching unit depending on the voltage U applied to the current-limiting component. In this way, the number of required voltage sensors and thus the cost of the device can be further reduced.

[0051] The switching unit for the switchable, low-impedance connection of two or more of the first terminals of the n two-terminal networks to one another can also be formed via two or more of the first switches controllable by the control unit or via two or more of the second switches controllable by the control unit. This can be advantageous for cost reasons if actively controllable first and / or second switches are already present and their current-carrying capacity is sufficiently dimensioned. Alternatively, however, it is also possible to provide additional separate switches for the switching unit. The switching unit can be designed such that it comprises a plurality of switches, such that each first terminal can be separately connected to each of the other remaining first terminals in a low-impedance manner.

[0052] In a further embodiment, the device can have one or more third switches controllable by the control unit, wherein each of the third switches is arranged between the first connection and the first switch assigned to it and / or between the first connection and the second switch assigned to it. In this way, if desired, individual two-terminal networks can be decoupled from voltage equalization in order to carry out voltage equalization with them, if necessary at a later time, and if necessary with other two-terminal networks connected to the device. In particular, the voltage equalization process can thus be largely automated by embodying all first and second switches as diodes, and only those two-terminal networks that would disrupt the desired temporal sequence of the method are temporarily disconnected. In this way, only a minimal number of controllable switches is required.It is then sufficient to implement only the third switches as actively controllable switches.

[0053] In one embodiment of the method, two or more power-emitting two-terminal networks with initially different voltages can be connected to the device. In this case, power output can initially be enabled for the two-terminal network whose absolute voltage, i.e. the magnitude of the voltage between its first terminal and the reference potential GND, is maximum. The power outputs for the other two-terminal networks can then be enabled with a time delay, for example, depending on a voltage between their assigned first terminal and the input of the current-limiting component. Such behavior can occur, for example, if the power-emitting two-terminal networks each have a capacitance effective on the terminal side, which discharges at least partially over time depending on the power output of the two-terminal networks.In a further embodiment, two or more power-consuming two-terminal networks with different voltages can be connected to the device, alternatively or cumulatively, with power consumption being enabled first for the two-terminal network whose absolute voltage, i.e., the magnitude of the voltage between its first terminal and the reference potential GND, is minimal. The power consumptions for the other two-terminal networks can then be enabled with a time delay, for example, depending on a voltage between their assigned first terminal and the output of the current-limiting component. This behavior can occur, for example, if the power-consuming two-terminal networks each have a terminal-side effective capacitance that is at least partially charged depending on the power consumption of the two-terminal networks.In the device as well as the method, it is possible for the positive poles of the two-pole network to be or be connected to one of the first terminals and the negative poles of the two-pole network to be or be connected to one of the second terminals of the device. In this case, the common reference potential GND is formed by the negative poles of the two-pole network. Alternatively, however, it is also possible for the negative poles of the two-pole network to be or be connected to one of the first terminals and the positive poles of the two-pole network to be or be connected to one of the second terminals of the device. In this case, the common reference potential GND is formed by the positive poles of the two-pole network. This is particularly advantageous when the current-limiting component is designed as a special DC / DC converter, such as a buck converter.Here, an actively controllable switch, as a so-called low-side switch of the DC / DC converter, can have a quiescent emitter potential or source potential, which - as explained in more detail in Fig. 3c - enables simpler control of the actively controllable switch.

[0054] A DC power distribution system according to the invention with voltage-adjustable two-terminal lines comprises a device according to the invention for voltage adjustment of at least two two-terminal lines, as well as the plurality n (n>2) of the at least two two-terminal lines connected to the device. The DC power distribution system is designed and configured to carry out the method. This results in the advantages already explained in connection with the device and the method.

[0055] In one embodiment of the DC power distribution system, at least one of the n two-poles comprises one or more of the following elements:

[0056] - a DC connection of an inverter having an intermediate circuit capacitance and / or an input capacitance,

[0057] - an electrolyzer,

[0058] - a battery,

[0059] - a DC network with a capacitance coupled to it,

[0060] - a DC output of a rectifier connected to an AC network, and

[0061] - a charging cable for an electric vehicle.

[0062] A further embodiment of the DC power distribution system can comprise a power-emitting but non-regenerative two-terminal network, one of whose terminals is directly connected to the input of the current-limiting component and the other of its terminals to the reference potential GND, or is switchably connected. For this purpose, it is connected to one of the terminal pairs whose first terminal is directly connected to the input of the current-limiting component. In contrast, a power-emitting but in principle regenerative two-terminal network is connected to a terminal pair whose first terminal is connected to the input of the current-limiting component via a first switch. In this way, the regenerative feeding of electrical power into the two-terminal network can be prevented if necessary.

[0063] Short description of the characters

[0064] The invention is illustrated below with the aid of figures, of which

[0065] Fig. 1 shows a first embodiment of a voltage equalization device according to the invention, which is connected to a plurality of n two-terminal networks;

[0066] Fig. 2a shows a second embodiment of a voltage equalization device according to the invention;

[0067] Fig. 2b shows a third embodiment of a voltage equalization device according to the invention;

[0068] Fig. 3a shows a first embodiment of a flow-limiting component of the device;

[0069] Fig. 3b shows a second embodiment of a current-limiting component of the device; and

[0070] Fig. 3c shows a third embodiment of a flow-limiting component of the device;

[0071] Fig. 4a shows a first embodiment of a unidirectional switch;

[0072] Fig. 4b shows a second embodiment of a unidirectional switch; and

[0073] Fig. 4c a third embodiment of a unidirectional switch; Fiqurenbeschreibung

[0074] Fig. 1 shows a first embodiment of a device 1 according to the invention for voltage equalization of a plurality n of at least two (n>2) two-terminal networks. In addition, Fig. 1 also illustrates a DC power distribution system 50 which corresponds to a combination of the device 1 and the two-terminal networks P1, P2, P3 connected to the device 1. By way of example and not by way of limitation, the device 1 in Fig. 1 is designed for operation of three two-terminal networks P1, P2, P3, which are each connected to a first terminal A1 and a second terminal A2 of a different one of the three terminal pairs A. Two of the first terminals A1, in Figure 1 by way of example the terminals of the two-terminal networks P1 and P2, are each connected to an input 10.1 of a current-limiting component 10 via a first switch S1 and a common first connection point 6.1.Furthermore, the first terminals A1 of two terminal pairs A are each connected to an output 10.2 of the current-limiting component 10 via a second switch S2 and a common second connection point 6.2. The second terminals A2 of the terminal pairs A are connected to each other with low resistance and to a common reference potential GND. The connection of the second terminals A2 to the reference potential GND is shown in Fig. 1 as a direct connection. Alternatively, however, it is also possible for the connection to be switchable for one or more of the second terminals A2, optionally also for all second terminals A2.

[0075] In Figure 1, one of the two-terminal networks P1, P2, P3 (here: P2) is designed to operate in a power-emitting mode at one time and a power-consuming mode at another. For this purpose, the first terminal A1 assigned to it is connected both via one of the first switches S1 to the input 10.1 and via one of the second switches S2 to the output 10.2 of the current-limiting component 10. The first switch S1 and the second switch S2 are connected in series in a bridge branch 5.2, with a branch tap 3.2 of the bridge branch 5.2 being connected to the first terminal A1 assigned to the two-terminal network P2.

[0076] The device 1 has a voltage sensor 8 which is connected to a control unit 9 of the device 1. The voltage sensor 8 is designed to detect a voltage U applied to the current-limiting component 10. The control unit 9 can - as also explicitly shown in Fig. 1 - be connected to the current-limiting component 10 for control purposes. This can be the case in particular if the current-limiting component 10 contains actively controllable components, for example an actively controllable semiconductor switch. Alternatively, the control of a semiconductor switch of the current-limiting component can also take place autonomously and without a connection to a voltage sensor 8. This is the case, for example, with current regulation, in particular regulation of the output current of the current-limiting component 10. In general, control-related connections are shown in Fig. 1, as well as in Figs.2a and 2b are each symbolized by a dashed line. The device 1 further includes a switching unit 7, which comprises a plurality of switches S12, S13, S23 for the low-impedance connection of individual first terminals A1 to one another. The control unit 9 is designed to control the switching unit 7, in particular its switches S12, S13, S23, as a function of the voltages prevailing between the first terminals A1 and / or the voltage U dropping across the current-limiting component 10. The first terminals A1 of individual two-terminal networks (P1 and P3, for example, in Fig. 1) are additionally each connected to the first switches S1 and second switches S2 assigned to them via an actively controllable third switch S3.The third switch S3 can be used to decouple the corresponding two-terminal network P1, P3, if necessary, with regard to its output or input of a power flow during voltage equalization. This is equivalent to a temporary activation or deactivation of the corresponding two-terminal network P1, P3 during voltage equalization. The third switch, connected to the first terminal of the first two-terminal network, is connected to the first connection point 6.1 via a diode, so that the combination of the third switch and the diode has the same effect as a first switch designed as a unidirectional switch.

[0077] As shown in Fig. 1, the first terminals A1 of two two-terminal networks (here: the two-terminal networks P2 and P3) can optionally also be connected, in particular switchably connected, via an additional impedance in the form of a further pre-charging resistor RVL,2. This is particularly advantageous when a current flow required to equalize the voltage of the respective two-terminal networks P2, P3 exceeds a current-carrying capacity of the current-limiting component 10. Since the further pre-charging resistor RVL,2 is an optional component, it is shown in dashed lines in Fig. 1. A possible embodiment of a method for operation is explained below using the example of device 1.For this purpose, it is assumed, as an example, that the two-terminal network P1 represents a DC connection of a low-power power supply, i.e., in the simplest case, a rectifier, the two-terminal network P2 represents a DC side of a bidirectional AC / DC converter with high power, and the two-terminal network P3 represents a DC input of an electrolyzer. In the initial state, all third switches S3 and all switches S12, S13, S23 of the switching unit 7 are open. One DC side of the bidirectional AC / DC converter (i.e., the two-terminal network P2) is voltage-free, since the AC / DC converter is not yet connected with its AC side to an AC network (not shown in Fig. 1). The two-terminal network P3 representing the electrolyzer is also voltage-free. Within the framework of a multi-stage voltage adjustment, first the DC side of the bidirectional AC / DC converter (i.e., the two-terminal network P2) is to be connected to the two-terminal network P1, and then the DC input of the electrolyzer (i.e.,the two-terminal P3) must be charged for its normal operation by the two-terminal P2:.

[0078] For this purpose, the third switch S3 assigned to the first two-terminal network P1 is first closed. Due to the voltages U(P1), U(P2) of the first two-terminal network P1 and the second two-terminal network P2, the first switch S1 assigned to the first two-terminal network P1 and the second switch S2 assigned to the second two-terminal network P2 are put into a conductive switching state. This results in a power flow P via the current-limiting component 10 from the first terminal A1 of the first two-terminal network P1 to the first terminal A1 of the second two-terminal network P2, which charges the second two-terminal network P2 and causes its voltage U(P2) to equalize with the voltage U(P1) of the first two-terminal network P1. The high-power bidirectional AC / DC converter is then synchronized with the AC grid and connected to it. This completes the first stage of the multi-stage voltage equalization of the three two-terminal networks P1, P2, and P3.For the subsequent second stage of voltage equalization, the third switch S3 assigned to the electrolyzer (two-terminal P3) is closed. The voltages of the first P1 and the second two-terminal P2 are almost equal and greater than the voltage U(P3) of the third two-terminal P3, i.e., U(P1)«U(P2) > U(P3) now applies. Due to the voltage ratios, the first switches S1 of the first P1 and the second two-terminal P2, as well as the second switch S2 of the third two-terminal P3, are now switched to the conductive state or maintained in the conductive state. This results in a power flow P via the current-limiting component 10 from the now power-emitting two-poles P1, P2 to the now power-absorbing two-pole P3, whereby the DC input of the electrolyzer is charged and its voltage U(P3) approaches the voltages U(P1), U(P2) of the two-poles P1, P2.Additionally, a power flow through the optional pre-charging resistor RVL,2 can support voltage equalization. If the absolute value of the difference between the two voltages of the two-terminal terminals P2 and P3 reaches or falls below a voltage threshold UTH, i.e., |U(P3) - U(P2)| < UTH, then their first terminals A1 can be connected to each other with low resistance by switching unit 7, or more precisely, its switch S23. This completes the second stage of voltage equalization and thus also the multi-stage voltage equalization as such.

[0079] Both the first switch S1 and the second switch S2 are embodied in Figure 1, for example, as diodes D, whose switching states are adjusted depending on the voltages applied to the corresponding first terminals A1 and A2, specifically depending on the voltages applied to the two-terminal circuits P1, P2, P3. Alternatively, however, it is also possible for one or more of the first switch S1 to be embodied as actively controllable switches.

[0080] Fig. 2a shows a second embodiment of a device 1 according to the invention, which is similar in many respects to the first embodiment already explained in Fig. 1. Therefore, only the differences from the embodiment in Fig. 1 are described below. For the identical features, reference is made to the description of Fig. 1.

[0081] In contrast to the first embodiment shown in Figure 1, in the embodiment of Figure 2a all of the two-terminal networks P1, P2, P3 are designed for both power-consuming and power-emitting operation. This can be the case, for example, if each of the two-terminal networks P1, P2, P3 is to be not only charged (i.e. its voltage U(P1), U(P2), U(P3) is to be increased) by means of the device 1 via the current-limiting component 10, but also discharged (i.e. its voltage U(P1), U(P2), U(P3) is to be reduced). Therefore, each of the two-poles P1, P2, P3 is connected via a branch tap 3.1, 3.2, 3.3 of a respective bridge branch 5.1, 5.2, 5.3, and is thus connected both via a first switch S1 to the input 10.1 and via a second switch S2 to the output 10.2 of the current-limiting component 10. The bridge branches 5.1, 5.2, 5.3 are each arranged parallel to the current-limiting component 10 and together form a bridge 5 with a first connection point 6.1, via which the first switches S1 are connected to the input 10.1, and a second connection point 6.2, via which the second switches S2 are connected to the output 10.2 of the current-limiting component 10.

[0082] Fig. 2b shows a third embodiment of the device 1 according to the invention. This is also similar in many respects to the first embodiment already explained in Fig. 1, which is why only the differences from the embodiment explained in Fig. 1 will be discussed below.

[0083] In Figures 1 and 2a, the positive (+) poles of the two-poles P1, P2, P3 are each connected to one of the first terminals A1 and the negative (-) poles of the two-poles P1, P2, P3 are each connected to one of the second terminals A2 of the device 1. In contrast, in the embodiment according to Fig. 2b, the positive (+) poles of the two-poles P1, P2, P3 are each connected to one of the second terminals A2 and the negative (-) poles of the two-poles P1, P2, P3 are each connected to one of the first terminals A1 of the device 1. The reference potential GND is formed here by the positive poles of the two-poles P1, P2, P3. By way of example, in the bridge branches 5.1 - 5.3 only some of the first switches S1 (here: those of the bridge branches 5.1 and 5.2) and the second switch S2 are designed as diode D (here: those of the bridge branches 5.1 and 5.3), while the others are designed as actively controllable switches.The flow direction of the first and second switches, designed as diodes D, is opposite to the embodiment shown in Fig. 2a, resulting in the same forward conducting and reverse blocking behavior with respect to the power flows. As will be described in more detail in connection with Fig. 3c, this type of connection of the two-terminal terminals P1, P2, P3 to the terminal pairs A results in a particularly simple implementation of the current-limiting component 10. Specifically, a current-limiting component 10 designed as a special DC / DC converter, namely a DC / DC converter with a low-side switch, can be controlled and operated more easily.

[0084] Fig. 3a shows a first embodiment of a current-limiting component 10, such as can be used in device 1. The direction of current 1 and power P flow are schematically symbolized by arrows in Fig. 3a (as well as in the following Figs. 3b, 3c). For better understanding, the first S1 and second switches S2 of device 1, designed as diodes D (see, for example, Fig. 2a), are also shown again to clarify their connection to input 10.1 and output 10.2.

[0085] For the following explanation of Fig. 3a (as well as Fig. 3b), it is assumed that the positive (+) poles of the two-pole networks P1, P2, P3 are each connected to one of the first terminals A1, while their negative (-) poles are each connected to one of the second terminals A2 - and thus to the reference potential GND. In order to generate a unidirectional power flow P from the input 10.1 to the output 10.2 in this case, the diodes D of the first switches S1 are each connected by their cathode to the input 10.1 and the diodes D of the second switches S2 are each connected by their anode to the output 10.2. The current flow I and the power flow P flow through the current-limiting component 10 in the same direction. In the first embodiment, the current-limiting component 10 can comprise only one component. The component can be designed as an ohmic resistor RVL.The ohmic resistor RVL can be a thermistor, such as an NTC thermistor. Alternatively or cumulatively (i.e., in series with the ohmic resistor RVL), the current-limiting component 10 can also include a transistor TVL that can be controlled by the control unit 9. The transistor TVL can be controlled such that it operates in its linear range during the power flow P. Advantageously, however, it can be controlled in a clocked manner.

[0086] Fig. 3b shows a second embodiment of the current-limiting component 10, which is designed as a DC / DC converter. This is, in particular, a step-down DC / DC converter from the input 10.1 to the output 10.2. The second embodiment can be used in a case in which the positive (+) poles of the two-pole networks P1, P2, P3 are each connected to one of the first terminals A1, while the negative (-) poles are each connected to one of the second terminals A2 - and thus to the reference potential GND. The DC / DC converter includes a series circuit of a transistor T and an inductor Lw, the connection point of which is connected to the reference potential GND of the device 1 via a diode Dw. Although only one specific topology of a step-down DC / DC converter is shown here as an example, the use of other known topologies of step-down DC / DC converters is also possible.However, due to the purely unidirectional power flow specified by the first switch S1 and second switch S2, the DC / DC converter can be implemented in a simple and therefore cost-effective manner. Specifically, it is also sufficient to design the current-limiting component 10 as a DC / DC converter that only bucks in one direction and not as a DC / DC converter that bucks in both directions. By designing the current-limiting component as a buck converter, it is possible that a current flowing through the input 10.1 and a current flowing through the output 10.2 may have different current intensities (not shown in Fig. 3b). However, both currents can be limited by suitable control of the buck converter in a way that is appropriate for the function of the current-limiting component.

[0087] Fig. 3c shows a third embodiment of the current-limiting component 10, which is also designed as a step-down DC / DC converter from the input 10.1 to the output 10.2. The third embodiment can be used in a case in which the negative (-) poles of the two-pole networks P1, P2, P3 are each connected to one of the first terminals A1, while the positive (+) poles of the two-pole networks P1, P2, P3 are each connected to one of the second terminals A2 - and thus to the reference potential GND. In order to generate a power flow from the input 10.1 to the output 10.2 in this case, the diodes D of the first switch S1 are each connected by their anode to the input 10.1. Correspondingly, the diodes D of the second switch S2 are each connected by their cathode to the output 10.2. In this case, the current flow I is opposite to the power flow P. Both potentials, that of the input 10.1 and that of the output 10.2, are here smaller (i.e., more negative) than or equal to the reference potential GND formed by the positive (+) poles of the two-terminal circuits P1, P2, and P3. However, the output 10.2 is at a more positive potential relative to the input 10.1, which generates the current flow I from the output 10.2 to the input 10.1, although the power flow P is still directed from the input 10.1 to the output 10.2.

[0088] Similar to the embodiment of Fig. 3b, the DC / DC converter of Fig. 3c also contains a series circuit consisting of a transistor T and an inductor Lw, the junction of which is connected to the reference potential GND via a diode Dw. During operation, the transistor Tw is a so-called low-side switch, whose emitter or source connection has a quiescent potential. A gate-source voltage is required to control the transistor T. Compared to a quiescent emitter or source potential, the required gate-source voltage can be generated much more easily than with an emitter or source potential which - as would be the case with a high-side switch, for example - depends on the switching state of the transistor Tw and would therefore jump with the switching process of the transistor Tw. A driver to provide the required gate-source voltage can therefore be used for the device shown in Fig.The low-side switch shown in Figure 3c can be implemented more easily and cost-effectively.

[0089] Fig. 4a shows a first embodiment of a unidirectional switch 60, such as can be used as the first switch S1 and / or as the second switch S2 within the device 1 in Figs. 1, 2a and 2b. The unidirectional switch 60 has a series circuit comprising a diode 62 and a switch which, in its closed state, is bidirectionally conductive, i.e., is designed for bidirectional power flow. In Fig. 4a, the switch which is bidirectionally conductive in the closed state is shown by way of example as an electromechanical switch 61. As an alternative to the electromechanical switch 62, another switch which is bidirectionally conductive in the closed state, for example a MOSFET, is also possible. The relevant control state, in which the unidirectional switch 60 in Fig. 4a behaves like a diode, corresponds to the closed state of the electromechanical switch 61 (or alternatively the MOSFET).Another control state of the unidirectional switch 60 occurs when the electromechanical switch 61 is open. In this case, the power flow is suppressed in both directions. This can be used, for example, to temporarily suppress a power flow that is intended in principle but not permanently desired.

[0090] Fig. 4b shows a second embodiment of a unidirectional switch 60, which corresponds to a parallel circuit of a diode 64 and a switch that is bidirectionally conductive in the closed state, which is illustrated here by way of example as an electromechanical switch 63. The control state of the unidirectional switch 60, in which the unidirectional switch 60 in Fig. 4b behaves like a diode, i.e., allows power flow in one direction and blocks it in the other direction, corresponds in Fig. 4b to the open state of the electromechanical switch 63. Another control state of the unidirectional switch 60 according to Fig. 4b results when the electromechanical switch 63 is closed. The further control state can be used to reduce a forward voltage of the unidirectional switch, and thus a power loss of the diode 64 caused by the power flow.It can also be used to temporarily enable a bidirectional power flow via the unidirectional switch 60. Here, too, instead of the electromechanical switch 63 shown as an example, it is also possible to use a semiconductor switch that conducts bidirectionally when closed. If a MOSFET is used for this purpose, it generally already includes a body diode, so a separate diode 64 can be omitted. In other words, the unidirectional switch 60 can be designed as a MOSFET according to Fig. 4b.

[0091] Fig. 4c shows a third embodiment of a unidirectional switch 60, in which the unidirectional switch 60 is designed as a thyristor 65. The control state in which the unidirectional switch 60 in Fig. 4c behaves like a diode, i.e., allows power flow in one direction and blocks it in the other direction, results after a firing pulse has been applied to the thyristor. The control state is terminated by current quenching, i.e., a decay of the current I flowing through the unidirectional switch 60. After the current quenching and in the absence of a firing pulse, the unidirectional switch 60 formed by the thyristor 65 assumes a further control state, which is characterized by a bidirectional suppression of a power flow. This can be used for the temporary suppression of a power flow that is intended in principle but not permanently desired.

[0092] List of reference symbols

[0093] 1 device

[0094] 3.1 - 3.3 Branch tap

[0095] 5.1 - 5.3 Bridge branch

[0096] 6.1 , 6.2 Connection point

[0097] 7 Switching unit

[0098] 8 Voltage sensor

[0099] 9 Control unit

[0100] 10 Current-limiting component

[0101] 10.1 Entrance

[0102] 10.2 Exit

[0103] 50 DC power distribution system

[0104] 60 unidirectional switch

[0105] 61 , 63 electromechanical switch

[0106] 62, 64 diodes

[0107] 65 Thyristor

[0108] A connection pair

[0109] A1, A2 connection

[0110] P1 , P2, P3 Two pole

[0111] S1 first switch

[0112] S2 second switch

[0113] S3 third switch

[0114] S12, S13, S23 switches

[0115] D-diode

Claims

Patent claims Device (1) for voltage equalization of a plurality n of at least two (n>2) two-poles (P1, P2, P3) comprising: - a flow-limiting component (10) with an input (10.1) and an output (10.2), - n terminal pairs (A), each with a first terminal (A1) and a second terminal (A2) for connecting the n two-terminal networks (P1, P2, P3), wherein two or more of the first terminals (A1) are each connected via a first switch (S1) or directly to the input (10.1) of the current-limiting component (10), and furthermore two or more of the first terminals (A1) are each connected via a second switch (S2) to the output (10.2) of the current-limiting component (10), and wherein the second terminals (A2) are connected or switchably connected to a common reference potential GND, characterized in that the device (1) is designed to set switching states of the first switches (S1) and the second switches (S2) by means of a control unit (9) and / or by means of voltages applied to the first terminals (A1),that a power input of the current-limiting component (10) from one or more of the first terminals (A1) occurs via one or more of the first switches (S1) or the direct connection, but not via one or more of the second switches (S2), and a power output of the current-limiting component (10) to one or more of the first terminals (A1) occurs via one or more of the second switches (S2), but not via one or more of the first switches (S1), so that a unidirectional power flow via the current-limiting component from the input (10.1) to the output (10.2) is enabled and a reverse power flow from the output (10.2) to the input (10.1) is suppressed. Device (1) according to claim 1, characterized in that the device (1) is designed for voltage equalization of three or more (n>3) two-terminal networks (P1, P2, P3) and for this purpose has three or more terminal pairs (A).optionally at least temporarily at least three of the first connections (A1 ), are simultaneously involved in a power flow via the current-limiting component (10). Device (1) according to one of claims 1 and 2, characterized in that one or more of the first connections (A1) is / are each switchably connected to the input (10.1) via a first switch (S1) and also switchably connected to the output (10.2) of the current-limiting component (10) via a second switch (S2), whereby one or more bridge branches (5.1, 5.2, 5.3) are formed, each of which is assigned to the first connections (A1), each of which has a series connection of the respective first switch (S1) and the respective second switch (S2), and whose branch taps (3.1, 3.2, 3.3) are connected to the first connections (A1) assigned to them.Device (1) according to one of the preceding claims, characterized in that at least one of the first switches (S1) and / or at least one of the second switches (S2) comprises a unidirectional switch (60). Device (1) according to one of claims 1 to 4, characterized in that at least one of the first switches (S1) and / or at least one of the second switches (S2) has a diode (D) or is designed as a diode (D). Device (1) according to one of the preceding claims, characterized in that the device (1) comprises a control unit (9), and in that at least one of the first switches (S1) and / or one of the second switches (S2) comprises a switch that can be controlled by the control unit (9), in particular a semiconductor switch or an electromechanical switch.Device (1) according to one of the preceding claims, wherein the current-limiting component (10) comprises an ohmic resistor RVL, a thermistor, or an actively controllable semiconductor switch TVL as a component, or wherein the current-limiting component (10) comprises a series connection of two different components. Device (1) according to one of claims 1 to 7, characterized in that the current-limiting component (10) is designed as a DC / DC converter, in particular as a. a step-down DC / DC converter is designed from the input (10.1) to the output (10.2). Device according to one of the preceding claims, additionally comprising a switching unit (7) for the switchable, low-impedance connection of two or more of the first terminals (A1) to one another, and a control unit (9) for controlling the switching unit (7), wherein the control unit (9) is designed to connect two or more of the first terminals (A1) to one another in a low-impedance manner depending on a voltage prevailing between the respective first terminals (A1).Device (1) according to one of the preceding claims, wherein the switching unit (7) is formed for the switchable, low-impedance connection of two or more of the first terminals (A1) of the n two-terminal networks (P1, P2, P3) to one another via two or more of the first switches (S1) controllable by the control unit (9) or via two or more of the second switches (S2) controllable by the control unit (9). Device (1) according to one of the preceding claims, additionally comprising a voltage sensor (8) for detecting a voltage U applied to the current-limiting component (10), wherein the control unit (9) is designed to operate the switching unit (7) as a function of the voltage U applied to the current-limiting component (10).Device (1) according to one of the preceding claims, further comprising one or more third switches (S3) controllable by the control unit (9), wherein each of the third switches (S3) is arranged between the first terminal (A1) and the first switch (S1) assigned to it and / or between the first terminal (A1) and the second switch (S2) assigned to it. Method for voltage equalization of a plurality n of at least two (n>2) two-terminal networks (P1, P2, P3) with a device (1) according to one of the preceding claims and the steps:. - connecting the n two-poles (P1, P2, P3) to one of the terminal pairs (A) of the device (1), if these are not already connected, so that two or more of the n two-poles (P1, P2, P3) are each single-pole switchable via a first switch (S1) or directly connected to an input (10.1) of the current-limiting component (10) and two or more of the n two-poles (P1, P2, P3) are each single-pole switchable via a second switch (S2) to an output (10.2) of the current-limiting component (10), Bringing about the voltage equalization by setting switching states of the first switches (S1) and the second switches (S2) by means of the control unit (9) and / or by means of voltages applied to the first terminals (A1) in such a way that a power input of the current-limiting component (10) from one or more of the first terminals (A1) takes place via one or more of the first switches (S1) or the direct connection, but not via one or more of the second switches (S2), and a power output of the current-limiting component (10) to one or more of the first terminals (A1) takes place via one or more of the second switches (S2), but not via one or more of the first switches (S1), so that a unidirectional power flow via the current-limiting component (10) from the input (10.1) to the output (10.2) is enabled and a reverse power flow from the output (10.2) to the input (10.1) is suppressed.Method according to claim 13, wherein two first terminals (A1), more than two first terminals (A1) or all first terminals (A1) of the n two-terminal networks are connected to one another in a low-impedance manner by means of a switching unit (7) when an absolute value of a voltage applied between the respective first terminals (A1) reaches or falls below a voltage threshold value UTH. Method according to claim 13 or 14, wherein two or more power-emitting two-terminal networks (P1, P2, P3) with different voltages are connected to the device (1), wherein power output is initially enabled for that two-terminal network whose absolute voltage is maximum, and wherein the power outputs for the further two-terminal networks are offset in time, in particular depending on a voltage between the first one assigned to them. Connection (A1) and the input (10.1) of the current-limiting component (10). Method according to one of claims 13 to 15, wherein two or more power-consuming two-terminal networks (R1, P2, P3) with different voltages are connected to the device (1), wherein power consumption is initially enabled for that two-terminal network whose absolute voltage is minimal, and wherein the power consumptions for the further two-terminal networks (P1, P2, P3) are enabled with a time delay, in particular depending on a voltage between the first connection (A1) assigned to them and the output (10.2) of the current-limiting component (10). Method according to one of claims 13 to 16, wherein the positive poles of the two-poles (P1, P2, P3) are each connected to one of the first terminals (A1) and the negative poles of the two-poles (P1, P2, P3) are each connected to one of the second terminals (A2) of the device (1).Method according to one of claims 13 to 16, wherein the negative poles of the two-pole systems (P1, P2, P3) are each connected to one of the first terminals (A1) and the positive poles of the two-pole systems (P1, P2, P3) are each connected to one of the second terminals (A2) of the device (1). DC energy distribution system (50) with two-pole systems (P1, P2, P3) that can be connected in a voltage-matching manner, comprising a device (1) according to one of claims 1 to 12 and a plurality n (n>2) of at least two two-pole systems (P1, P2, P3). DC energy distribution system (50) according to claim 19, wherein at least one of the n two-pole systems (P1, P2, P3) comprises one or more of the following elements: - a DC connection of an inverter having an intermediate circuit capacitance and / or an input capacitance, - an electrolyzer, in particular its DC input - a battery - a DC network with a capacitance coupled to it - a DC output of a rectifier connected to an AC network, and - a charging cable for an electric vehicle. DC energy distribution system (50) according to one of claims 19 and 20, additionally comprising a power-emitting and non-regenerative two-pole (P1, P2, P3), which is connected or switchably connected with one of its poles directly to the input (10.1) of the current-limiting component (10) and with the other of its poles to the reference potential GND.

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