Power flow control system with series compensator for use in an electrical grid

Abstract

The invention relates to a control module for a power flow control system (90), configured for use in an electrical grid (12) and configured for adjusting the voltage and / or the current in at least one line (20) of the grid (12), comprising at least two line connections (60, 62) for serial connection to the line (20) of the grid (12), a plurality of switch elements (64), an energy store (68) and two energy connections (70) for connection to a voltage supply unit (40), wherein the first line connection (60) and the second line connection (62) are designed to switch the control module (30) electrically in series with the line (20); two of the switch elements (64) are connected in series and are connected in parallel to the energy store (68), the control module (30) is connected such that there is a galvanically defined connection to a voltage supply unit which can be controlled such that the potential of the control module (30) follows the potential of the line (20) of the grid (12) in a predefined manner; and the switch elements (64) are designed to increase or reduce the amplitude of the voltage in the line (20) in order to adjust the voltage in order to displace the phase of the voltage or to correspondingly control the current flow in the line (20).

Description

[0001] Power flow control system with series compensator for use in an electrical network

[0002] The present invention relates to a control module for a power flow control system, configured for use in an electrical network and configured to adjust the voltage and / or current in at least one line of the network. The application further relates to a power flow control system for use in an electrical network, comprising a control module and a voltage supply unit.

[0003] The utilization of electrical power grids, particularly medium-voltage and low-voltage grids, has been steadily increasing in recent years. Distributed power generation and decentralized power feed-in from solar systems on the one hand, and the increasing number of charging stations for electric vehicles on the other, are leading to this changing utilization. Individual outgoing feeders of a local grid station in a residential or industrial area are therefore frequently overloaded. Laying new lines with larger cross-sections and the associated civil engineering work should be avoided. Therefore, voltage regulation can be achieved, for example, using controllable local grid transformers. However, these can only change the load flow in the outgoing feeders to a limited extent.

[0004] EP 3 413 422, for example, proposes a distribution substation with a three-winding transformer to supply two separate busbars, each with a separate low-voltage winding. This allows for a response to a change in the power flow in the individual busbars.

[0005] Alternatively, variable-voltage transformers are known, but these require major modifications and an additional measuring unit for measuring the voltage in the busbar of the low-voltage network and the current at the feeder. However, a variable-voltage transformer still cannot provide selective control of individual supply lines.

[0006] In the meshed structures of low-voltage local grids, current flows through the individual inputs cannot be controlled. They adjust passively depending on the load. To change the voltage level of an outgoing network line, mesh current controllers are used to raise or lower the voltage amplitude. The energy for the change is usually drawn from the grid itself. A change in voltage in a grid segment can be compensated by distributing the load between the various inputs. A mesh current controller is therefore a suitable means of actively shifting the load within a mesh. A mesh current controller therefore represents a voltage source connected in series with one or more phases of the grid, allowing uncontrollable current flows via the individual inputs in the individual meshes due to various loads to be regulated.However, the known mesh current regulators require a power transformer for series coupling to provide a voltage between the conductor and ground potential and to change the voltage amplitude. Such transformers, however, are structurally large and expensive.

[0007] The transformers used also lead to unwanted losses at higher frequency components, even though they are well suited for low frequencies. However, to compensate for unwanted distortions in the grid, such as harmonics, higher frequencies must be fed in or extracted to improve grid quality. However, the known mesh controllers are not suitable for this purpose. DE 102021 111 860 A1 discloses a power flow control module for use in an AC electrical power grid. The control module is wired in such a way that it is at the potential of the grid line and galvanically isolated from ground potential or another grid line. Thus, the power flow control module is at the same potential as the line to which it is connected in series.Although the power flow control module floats with the line voltage, it cannot be actively controlled and is dependent on changes in the line voltage of the grid.

[0008] Document CN 106099937A describes a control unit for controlling the charging electronics of a control module of a power flow control system, comprising at least one controller for regulating the common-mode current and at least one controller for regulating the differential-mode current. The currents to the individual submodules and the submodule voltages are monitored. Active control is not possible.

[0009] There is therefore still a need for cost-effective solutions that can improve network quality in meshed networks and adjust load distribution.

[0010] The present object is achieved by a control module for a power flow control system, set up for use in an electrical network and for adjusting the voltage and / or the current in at least one of the lines of the network, having the features of claim 1, by a power flow control system, set up for use in an electrical network, having the features of claim 2, and by a network segment of an electrical network, having the features of claim 19. The object is likewise achieved by a control unit for controlling the charging electronics of a control module of a power flow control system, having the features of claim 20. In a first aspect, the present invention relates to a control module for a power flow control system, set up for use in an electrical network and set up for adjusting the voltage and / or the current in at least one line of the network. The voltage is adjusted orthe current through the line.

[0011] The control module comprises at least two line connections for serial connection to the network line, several switching elements, an energy storage device and two energy connections for connection to a power supply unit.

[0012] For the purposes of this invention, a line is understood as a phase of the network. A three-phase network therefore has three lines, with a control module being provided for the serial connection of one of the phases of the network or one of the lines of the network.

[0013] The first line connection of the control module and the second line connection of the control module are designed to electrically connect the control module in series with the line. Two of the switching elements are connected in series with each other and in parallel with the energy storage device included in the control module. The control module is wired in such a way that a galvanically defined connection is established with a power supply unit, which can be controlled such that the potential of the control module follows the potential of the network line in a predefined manner.

[0014] The control module's switching elements are designed to increase or decrease the amplitude of the voltage in the line, to adjust the voltage, to shift the phase of the voltage, or to control the current flow in the line accordingly. The switching elements are designed for low voltages, e.g., up to 10% of the mains voltage, and high currents, e.g., greater than 10 A.

[0015] A galvanically defined connection of the power supply within the meaning of this invention is to be understood as a connection of the power supply unit to the network or line to which the control modules and, via the control modules, the power supply unit are connected. A galvanically defined connection to the power supply can mean, in particular, that current can flow from a control module, e.g., the positive or negative supply rail of the control module, to the power supply unit without a compensating return current necessarily having to flow from the power supply unit to the control module.Accordingly, this current between a power supply unit and an associated control module can be a common-mode current, which contrasts with a differential-mode current that can charge or discharge a capacitor connected to the positive and negative supply rails in the control module. Such common-mode currents are possible, for example, if a power supply unit is not galvanically isolated from a control module by a transformer or high-frequency transformer. Common-mode currents can also flow from the power supply unit to an electrical element that is either ground or has a fixed electrical potential relative to ground, such as a line in the electrical network.This possibility can be given, for example, if a power supply unit further has a galvanically defined connection to the electrical network, for example via an active front end or a mains rectifier, which preferably further comprises a power factor correction stage.

[0016] Preferably, a galvanically defined connection in the present sense allows common-mode direct currents, i.e., constant common-mode currents in contrast to common-mode alternating currents, whose time average disappears, across the galvanically defined connection. Capacitor connections or parasitic capacitances to ground, for example, generally do not allow continuous, constant common-mode currents. Common-mode currents via the galvanically defined connection to the power supply unit preferably charge the capacitance of the respective control module to ground (common-mode capacitance), causing the electrical potential of the control module (to ground) to rise or fall, provided no other common-mode inflows or outflows are present (for example, approximately given when the power switches or transistors of the respective control module are electrically open).For example, by appropriately generating a time-varying common-mode current, the electrical potential of a control module can be adjusted with or parallel to the line voltage of a conductor of the electrical network.

[0017] Preferably, a common-mode current is actively controlled via a control loop, for example to approximately 0 or on average to 0 or in such a way that the electrical potential of the associated control module runs temporally parallel to the voltage of a conductor of an electrical network.

[0018] Preferably, in addition to a galvanically defined connection of a control module to a power supply unit, there is also a galvanically defined connection of the control module to a line of an electrical network. In this case, ring or circular currents are also possible due to the at least two parallel galvanically defined connections to ground, to a potential with a fixed voltage condition relative to ground, or, for example, to a conductor of an electrical network.

[0019] A galvanically defined connection can exist, for example, if a power supply unit is electrically designed as a voltage source (so-called voltage-source inverter, which can also be regulated as a current source), which, in addition to a voltage between the power connections, can also set an electrical potential or a voltage of the power connections to earth or another potential with a fixed reference to earth.

[0020] According to another aspect, the invention relates to a power flow control system that is designed for use in an electrical network and is designed to adjust the voltage and / or current in at least one line of the network. The power flow control system comprises a control module, as described above, and a voltage supply unit for supplying the control module with electrical energy. A galvanically defined connection exists between the control module and the voltage supply unit. The voltage supply unit is controllable such that the potential of the control module follows the potential of the line of the network in a predefined manner. The potential of the control module is thus preferably proportional to the potential of the line of the network.This has the advantage that, to regulate the voltage across the line, only the difference in voltage required for regulation or compensation needs to be applied, rather than the entire voltage relative to ground. This allows much smaller voltages to be generated, ultimately making the power flow control system unit small and compact.

[0021] According to a further aspect, the invention relates to a network segment of an electrical network comprising a line connected to a network transformer and to which several consumers and / or feed-in points are connected. The network segment has a power flow control system as described above.

[0022] According to a further aspect, the invention relates to a control unit for controlling the charging electronics of a control module of a power flow control system, as described above. The control unit comprises an ammeter for measuring the current of the connections between the charging electronics, for example the power supply unit or a part thereof, and the power connections of the control module. The control unit further comprises a voltmeter for measuring the voltage between a positive rail of the control module and a negative rail of the control module. The control unit comprises at least one controller for regulating the common-mode current and at least one controller for regulating the differential-mode current. Thus, the control unit can be used to compensate for voltage fluctuations or changes in a line or phase of the network. Common regulators can be used as regulators, possibly after adaptation.

[0023] Within the scope of the invention, it was recognized that a power electronics solution only needs to have a very low rated power in order to be able to serve a grid segment with a very high power. With the arrangement and circuit according to the invention, it is possible to separate locations in a grid with high voltage requirements, i.e. grid voltage such as low voltage, medium voltage or high voltage, from locations with high current requirements, i.e. with currents of several amperes, and to keep reactive power out of such a circuit. The solution according to the invention has the advantage that it dispenses with any power transformers, which are large and heavy. High-frequency transformers, which despite the increased frequency still take up a relatively large installation space and require extensive and cost-intensive wiring with additional passive power components, such as transistors, are also not used.

[0024] According to the invention, the entire power exchange between the series-connected control modules and the power supply is galvanically connected. The parallel tap or the power supply or voltage supply (unit) has components that meet high voltage requirements, for example, for the mains voltage, but only have to comply with low current requirements, for example, only a few amperes. Preferably, mains rectifiers or inverters with mains filters and semiconductors with corresponding characteristics can be used for this purpose. For example, low-power silicon IGBTs (insulated gate bipolar transistors) or super-junction silicon FETs (field-effect transistors) or silicon carbide FETs can be used, each of which requires only low current.

[0025] The control module for the power flow system, on the other hand, has the advantage that only components can be used that only need to be able to process very low voltages, for example a few volts, generally less than 100 volts at low voltage, preferably < 60 volts, particularly preferably < 20 volts, very preferably < 10 volts. However, the components used can process large currents, which can sometimes be in the range of several tens of amperes or several hundred amperes up to several kiloamperes. The control module in the power flow control system is used in a quasi-floating manner with the mains voltage, which in the context of the present invention means that the voltage of the mains line, in which a control module is used in series, primarily determines the electrical potential of the control module.A control module preferably has no ground reference or connection to the other phases of the network, i.e., to the other lines in the network. A potential reference can preferably be established via a power supply unit. The potential of the modules moves accordingly with the voltage of their phase or line, creating only a small voltage difference between the input and output. While in a low-voltage network, the phase voltage can, for example, be 325 volts peak at 50 or 60 hertz, the voltage difference is usually < 10 volts. Since the modules only operate between the input and output, they do not "see" the total voltage amplitude, but only the maximum voltage difference that can be set. This allows the use of low-voltage semiconductor components that can still conduct several hundred amperes of current in a very small space.A separate control module is provided for each phase (line) to be processed—for example, three lines. Furthermore, the intermediate circuit of each control module is maintained at very low voltages, for example, < 60 volts, < 30 volts, or sometimes < 15 volts in low-voltage networks.

[0026] Contrary to all previous assumptions in the state of the art, the control modules, which move with the phase voltage, can be supplied galvanically (bidirectionally). If, for example, converters are used in the power supply unit to which the control module is coupled, these converters are galvanically connected and their outputs must always follow the potential of the associated control module and be able to cover the entire electrical potential range of the control module. This can be achieved using various circuits. A preferred circuit for a power supply unit resembles a type of "2-phase inverter." The two AC phases operate largely in parallel. Each of the two output phases follows the potential of the mains voltage, or more precisely, one of the DC voltage rails of the corresponding control module.

[0027] In a preferred embodiment of the line flow control system, the power supply unit has a grid interface and a quasi-converter unit. The quasi-converter unit is connected to the power terminals of the control module and is connected between the control module and the grid interface.

[0028] A preferred embodiment provides that the power supply unit has exactly one grid interface and one quasi-converter unit for each line of the grid. In a three-phase grid with three lines, one grid interface and three quasi-converter units are preferably required for the power flow control system according to the invention.

[0029] Preferably, the quasi-converter unit of the voltage supply unit has an inverter circuit with at least one inverter. An inverter circuit with at least two inverters is particularly preferred. It has proven advantageous for each inverter to comprise two transistors.

[0030] A further preferred embodiment provides that the quasi-converter unit of the voltage supply unit comprises an inverter circuit, which preferably has four interconnected transistors. Particularly preferably, the four transistors are connected in half-bridges. The four transistors can also be connected in parallel-connected half-bridges.

[0031] In a further preferred embodiment, the quasi-converter unit of the voltage supply unit comprises a balancing unit, which preferably has four transistors connected in series. The balancing unit preferably has two half-bridges of transistors connected in series, particularly preferably two transistors each. Optionally, the balancing unit can comprise a module intermediate circuit formed by a capacitor.

[0032] A preferred embodiment has a quasi-converter unit comprising two inverters, preferably two transistors, forming a half-bridge whose terminal is connected to the balancing unit. The quasi-converter unit can thus comprise a balancing unit and two inverters.

[0033] A further preferred embodiment of the power flow control system has a quasi-converter unit comprising a balancing unit with two inductors and an inverter circuit with two inverters, wherein the inverters preferably each have two transistors.

[0034] The quasi-converter unit comprises, for example, either an inverter and a balancing unit or at least two inverters with only an optional balancing unit, with a quasi-converter unit provided for each control module. The quasi-converter unit is galvanically defined by the converter and balancing units.

[0035] A preferred embodiment of the power flow control system is designed such that the quasi-converter unit, which is galvanically connected to the control module, follows the potential of the grid interface and covers the entire potential range of the grid interface. The quasi-converter unit thus follows the potential of the grid interface with its outputs.

[0036] The quasi-converter unit preferably comprises an inverter circuit, for example, with two inverters, which has two DC voltage rails. Each of the two DC voltage rails of the inverter circuit of the quasi-converter unit follows the potential of the mains voltage of the grid. Preferably, the DC voltage existing between the DC voltage rails is a control voltage of the control module. This DC voltage thus serves to compensate for and / or regulate voltage fluctuations in the grid for one phase of the grid.

[0037] According to a preferred embodiment, one of the two DC voltage rails of the control module, preferably the positive rail of the control module, follows one AC voltage phase of the converter or the inverter circuit, while the other of the two DC voltage rails, preferably the negative rail of the control module, follows the other AC voltage phase of the converter or the inverter circuit.

[0038] According to a preferred variant of the power flow control system, the grid interface of the power supply unit comprises an inverter circuit. Particularly preferably, the inverter circuit comprises a grid inverter or a rectifier. The grid interface is thus constructed, for example, from a coupling of several inverters, which can be connected in half-bridges, for example.

[0039] Preferably, the moving potential of the control module remains within the inverter voltage generated between the positive rail of the grid interface and the negative rail of the grid interface. The potential of the control module essentially moves with the potential of the voltage. It can be controllable. Preferably, the potential of the control module or the common-mode voltage of the inverter is lower than the inverter circuit; preferably, it is less than 50%, preferably less than 25%, and particularly preferably less than 10% of the instantaneous grid voltage of the line.

[0040] The voltage supply unit of the power flow control system is preferably designed to have a quasi-converter unit for each line of the network or each phase of the network. In a three-phase network, the voltage supply unit has three quasi-converter units.

[0041] In a preferred embodiment, the voltage provided by the control module for varying the line amplitude is at most one-third of the nominal grid peak voltage, preferably at most one-fifth, very preferably at most one-tenth of the nominal grid peak voltage. Likewise preferred embodiments can provide that the control voltage for varying the line amplitude is at most one-fifteenth or particularly preferably at most one-twentieth of the nominal grid peak voltage. The lower the control voltage, the greater the selection of components to be used and the cheaper the components and thus the control module can be. This allows for the construction of a very cost-effective power flow control system.

[0042] According to a preferred embodiment of the power flow control system, the voltage supply unit is electrically connected in parallel to the lines of the network and is supplied with power from the electrical network.

[0043] The power supply unit can preferably comprise a line filter that connects to the line of the mains. The line filter can, for example, be a PI filter formed from inductors, such as an LCL.

[0044] A preferred embodiment of the power flow control system for a low-voltage network, for example, with a 3 x 400 volt line-to-line voltage, has a control module in which the voltage provided by the control module for changing the line amplitude is a maximum of 100 volts. The control voltage, i.e., the voltage provided by the control module, is preferably a maximum of 50 volts, very preferably a maximum of 20 volts. Other embodiments have a control module with a control voltage of a maximum of 20 volts, preferably a maximum of 15 volts, and particularly preferably a maximum of 10 volts, whereby the latter can be used in particular for regulating only small voltage fluctuations.

[0045] If a power flow control system is used in a medium-voltage network, which may, for example, have 10 kV, 20 kV or 30 kV, the control voltage in the control module is preferably not greater than 10% of the effective line-to-line voltage, particularly preferably not greater than 7% or 5%.

[0046] The data given for the low-voltage network refers to a three-phase network with 400 volts effective line voltage, i.e. 230 volts effective star voltage or approximately 325 volts peak voltage.

[0047] For a power flow control system used in such a low-voltage network, switching elements of the control module can be used that are designed for low voltages with a magnitude of < at most 100 volts, preferably < at most 25 volts. At the same time, these switching elements or components are designed for high currents of > 1 ampere, preferably > 2 amperes, more preferably > 5 amperes, or more preferably > 10 amperes. Special designs include switching elements or transistors for the control module that are designed for currents of > 15 amperes, > 25 amperes, or > 50 amperes. If the system is also intended for use in medium-voltage networks, switching elements or transistors can be used that are designed for currents of > 100 amperes, preferably > 200 amperes. The voltages in a medium-voltage network are correspondingly higher, namely up to approximately 3 kV, preferably 2 kV, very preferably 1 kV.

[0048] The switching elements or inverters of the control module are preferably connected as half-bridges, preferably as two half-bridges. They are preferably designed as transistors or power transistors, whereby low-voltage transistors or ultra-low-voltage transistors can preferably be used. The use of low-voltage trench transistors or field-effect transistors (FETs) is particularly preferred.

[0049] One embodiment of the power flow control system can provide a voltage supply unit comprising an inverter circuit and powered by the electrical network in which it is used. The voltage supply unit is preferably connected to the network lines. The inverter circuit can, for example, comprise semiconductors or semiconductor components that must meet a high voltage requirement, preferably on the order of magnitude of the network voltage, while simultaneously requiring only a low current requirement. The semiconductors are preferably designed for currents of no more than 20 amperes, more preferably no more than 10 amperes, and very preferably no more than 5 amperes. Further embodiments can comprise components, semiconductors, or transistors designed for currents < 2 amperes or currents < 1 ampere.Preferably, the currents are so low that the product of current and voltage is less than 1 / 10 or even 1 / 20 of the product of the grid voltage (star voltage) and phase current, i.e., the power controlled via a control module. Such components are inexpensive, allowing a cost-effective power flow control system to be constructed.

[0050] Preferred embodiments of the invention are defined in the dependent claims. It is understood that the features mentioned above and those to be explained below can be applied not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the present invention.

[0051] The invention is described and explained in more detail below using a few selected exemplary embodiments in conjunction with the accompanying drawings. Reference is made here to a low-voltage local network or low-voltage grid as a possible example of an electrical AC network, without restricting the generality of a voltage network or local network. The low-voltage local network is one possible embodiment of a network with an effective line voltage of 3x400 volts.

[0052] They show:

[0053] Figures 1 a and 1 b show a schematic diagram of a network segment with three lines and a power flow control module;

[0054] Figures 2a, 2b show a more detailed sketch of the network segment from Figure 1;

[0055] Figures 3a, 3b show an alternative embodiment of the power flow control module;

[0056] Figure 4 is a schematic diagram explaining the voltage levels within the control system;

[0057] Figures 5 to 10 show further alternative embodiments of the control system; Figure 11 illustrates the power flow control system for three phases;

[0058] Figure 12 shows a further alternative embodiment;

[0059] Figure 13 shows a schematic diagram of a control system for controlling the charging electronics of the power flow control system; and

[0060] Figure 14 shows an alternative embodiment of a local network segment with a power flow control module for constructing a low-voltage energy router.

[0061] Figures 1a and 1b show a three-phase network segment 10 of an electrical network 12 with three lines 20. This electrical network 12 is, for example, a low-voltage local network. A control module 30 is connected in series in each line 20. The control module 30 has an AC section 32 and a DC section 34. Optional line filters 36, which can be in the form of inductors or PI filters, are arranged between the control module 30 and the line 20.

[0062] Each line 20 has its own control module 30, with each control module connected to a power supply unit 40 configured as a power supply, the other output of which is isolating as shown in Figure 1a and can be supplied with any voltage or energy source. An AC part 42 of the power supply can be connected to an energy source (not shown in Figure 1a), which can be arranged at terminals 46.

[0063] According to Figure 1 b, the power supply unit is connected with its terminals 46 to the lines 20 of the network 12.

[0064] A connection exists between a DC part 44 of the voltage supply unit 40 and the control module 30, in particular to the DC part 34 of the control module 30, by means of two conductors 48. Figures 1a and 1b show that the voltage at an input side 22 of the network 12, relative to the control module 30, has a different shape, for example a different amplitude, than the output voltage at an output side 24, which prevails "behind" the control module 30.

[0065] Figure 2 shows the network segment 10 from Figure 1 in detail. The control module 30 is also shown in detail, although only one line 20 of the three-phase network segment 10 is shown.

[0066] The control module has a module connection 60 connected to the line 20 at an input side 22. The control module 30 has a second module connection 62 connected to the output side 24 of the line 20. The optional line filters 36 from Figure 1a can be arranged between the line 20 and the respective module connections 60, 62.

[0067] The control module 30 comprises a plurality of switching elements 64, which can be implemented, for example, as low-voltage field-effect transistors or as silicon FETs. In the example shown, the switching elements 64 implemented as transistors are connected as two half-bridges, between which an energy storage device 68 in the form of a capacitor 69 is arranged.

[0068] Figure 2a also shows the voltage supply unit 40 in detail. The voltage supply unit 40, together with the control module 30, forms a power flow control system 90, which is configured to adjust the voltage across the line and / or adjust the current through the line 20. Thus, fluctuations in the electrical network 12 can be compensated for with the power flow control system 90.

[0069] The voltage supply unit 40 comprises a grid interface 400 and a quasi-converter unit 500. The quasi-converter unit 500 can, for example, as shown in Figure 2, comprise an inverter circuit 510 and a balancing unit 520. While the voltage supply unit 40 for a three-phase grid 12 comprises only one grid interface 400, there is a quasi-converter unit 500 for each phase or line 20. However, for reasons of clarity, only one line 20 is shown in Figure 2, and therefore only one quasi-converter unit 500.

[0070] The grid interface 400 can, for example, be a single-phase or preferably a three-phase rectifier and / or comprise a plurality of inverters 420, which, as shown in Figure 2, are connected as half-bridges 422. The inverters 420 can, for example, be diodes or transistors.

[0071] An interface circuit 410 is designed as an inverter or as a rectifier, for example in the form of a diode circuit with several diodes 408 connected as half bridges 422.

[0072] The inverters 420, designed here as a half-bridge, form the interface circuit 410, which has two DC rails, a positive DC rail 412 and a negative DC rail 414. A capacitor 416 arranged between the two DC rails forms an inverter intermediate circuit 418.

[0073] The inverter circuit 510 of the quasi-converter unit 500 comprises at least one inverter 512, in Figures 2 and 3 two inverters 512 each with two transistors 514, which are connected to form half-bridges.

[0074] The balancing unit 520 comprises four transistors 522, which are connected together to form two series-connected half-bridges 524. Furthermore, the balancing unit 520 comprises two inductors 526, which are connected to the outputs of the inverter circuit 510. A capacitor 528 forms the balancing intermediate circuit, the ends of which are connected to the two power terminals 70.

[0075] Figure 3a shows a similar embodiment of the power flow control system 90, wherein the grid interface 400 is formed from transistors 424 and not from diodes 508, as in the embodiment of Figure 2.

[0076] The transistors of the grid interface 400 and the inverter circuit 510 must be able to withstand the full voltage of the grid 12. They must therefore be suitable for correspondingly high voltages, for example, at least 400 volts effective for low-voltage grids. However, these transistors only need to be suitable for relatively low currents of < 10 amperes, preferably < 1 ampere.

[0077] The transistors 522 of the balancing unit 520, on the other hand, preferably only need to withstand low voltages, for example, voltages below 50 volts in low-voltage networks. However, they must be able to carry high currents, currents > at least 10 amperes, but also, for example, > 20 amperes. In the cases shown in Figures 2a and 3a, however, the full voltage blocking capability of the transistors 522 is preferably required.

[0078] The transistors 66 of the control module must have the same characteristics as the transistors 522 of the balancing unit 520.

[0079] The voltage of the intermediate circuit of the control module(s) 30 in three-phase networks can be set almost independently of the voltage of the intermediate circuits of the quasi-converter unit 500, allowing bidirectional energy exchange. The electrical potential of both the positive rail 312 and the negative rail 314 of the intermediate circuit of the control module 30 may be above the positive DC rail 412, between the positive DC rail 412 and the negative DC rail 414, and also below the negative DC rail 414 of the inverter circuit 510. However, eight transistors are then required for the energy exchange: four transistors 514 of the inverter circuit 510 and four transistors 525 of the balancing unit 520.

[0080] The balancing unit 520 can furthermore—as shown in Figures 2b and 3b—be designed such that the transistors 522 only have to block, and thus be able to withstand, a voltage lower than the voltage of the inverter circuit 510. For this purpose, at least one decoupling capacitor 599 preferably separates the ground or other comparatively fixed potentials from the balancing unit 520. Preferably, according to these embodiments, a decoupling capacitor 599 is connected with at least one terminal to the common electrical connection between at least two of the transistors 522 of the balancing unit, particularly preferably to a common electrical connection having at least two series-connected transistors 522 on each side.

[0081] At least one further terminal of a decoupling capacitor 599 is preferably connected to ground or another largely stable electrical potential. A decoupling capacitor 599 can, for example, allow a constant voltage between ground or a largely stable electrical potential and the balancing unit 520 and prevent direct currents through the decoupling capacitor, while alternating currents can flow, for example, for the balancing process and / or the generation of alternating-mode potentials.

[0082] The capacitance of such a decoupling capacitor 599 can be selected so that the transistors 522 can have a lower voltage withstand capability. For this purpose, the capacitance of such a decoupling capacitor 599 should generally be selected large enough for the switching rate of the transistors 522, with faster switching rates of the transistors 522 usually reducing the required capacitance. Such a decoupling capacitor can, in particular, absorb the currents with which the transistors 522 electrically and magnetically charge and discharge inductors 526.

[0083] For example, the transistor 522 which is electrically connected by at least one first terminal to the decoupling capacitor 599 and by a second terminal to a circuit node which in turn can be optionally connected to a positive rail of the intermediate circuit of a control module via a further transistor 522 preferably charges the decoupling capacitor 599 via an inductance 526, while a further transistor 522 which is preferably electrically connected by a first terminal to the coupling capacitor 599 and by a second terminal to a circuit node which in turn can be connected to a negative rail of the intermediate circuit of a control module via a further transistor 522 preferably charges the decoupling capacitor 599 negatively.Preferably, the two states are operated such that the charge of the coupling capacitor 599 is constant on average over time and is positively charged by one of the transistors 522 with an absolutely identical charge and negatively charged by the other transistor 522 with a negative charge. These two charging processes can preferably occur simultaneously, overlapping in time, or sequentially. During simultaneous operation, the currents preferably balance each other out, so that the coupling capacitor 599 can have a lower capacitance to compensate only for the slight temporal differences in the charge.

[0084] Further transistors 522, however, are each electrically conductive at times when the first-mentioned transistors 522 are off. These further transistors 522 preferably allow at least one inductor 526 to be temporarily electrically connected to a positive or a negative rail of the intermediate circuit of a control module. These latter transistors 522 are preferably operated cyclically but alternately with the first-mentioned transistors 522 in order to electromagnetically and magnetically charge the inductors 526 via the first-mentioned transistors 522 and to discharge them via the latter transistors 522 into the positive and / or negative rail of the intermediate circuit of a control module.

[0085] In a preferred embodiment, capacitor 599 is purely parasitic coupled to ground and is not implemented by a separate electrical component. In this case, the capacitance can be less than 1 nF, preferably less than 10 pF, and particularly preferably less than 1 pF. Positive and / or negative rails of the intermediate circuit of a control module are preferably power terminals 70 in the present invention.

[0086] The voltage potential of the DC rails of the grid interface in relation to the possible voltage potential of the positive and negative rails of the intermediate circuit of the control module are shown in Figure 4.

[0087] The eight transistors of the quasi-converter unit can be reduced to just four transistors, as shown in the particularly preferred embodiment in Figure 5. However, this requires compliance with boundary conditions relating to the voltage between the two intermediate circuits. These voltage conditions must be enforced, for example, by open-loop or closed-loop control.

[0088] The electrical potential of the positive rail 312 of the intermediate circuit of the control module 30 must never exceed the potential of the positive DC rail 412 of the interface circuit 410. Furthermore, the electrical potential of the negative rail 314 of the intermediate circuit of the control module 30 must never be below the potential of the negative DC rail 414 of the intermediate circuit of the interface circuit 410. Consequently, all potentials and voltages of the control module must always be within the range of the positive DC rail 412 and the negative DC rail 414 of the grid interface 400 or the corresponding intermediate circuit. Furthermore, it should be noted that the floating control modules 30 cyclically move up and down with the grid voltage and its frequency, typically 50 Hertz or 60 Hertz, of their respective associated phases.Together with the intermediate circuit voltage of the floating control modules 30, this covers, for example, a range in European low-voltage grids from approximately +325 volts plus the voltage at the intermediate circuit of the control module to approximately -325 volts minus the voltage at the intermediate circuit of the control module 30. In principle, the grid voltage of the grid 12 may also fluctuate, so that, for example, an additional 10% voltage could be added.

[0089] According to Figure 5, it can be seen that the quasi-converter unit 500 is now formed only from the inverter circuit 510 as well as the inductors 526 and the capacitor 528.

[0090] The series-connected control modules 30 are each supplied via a galvanically non-isolated DC-DC converter that dynamically follows the floating control module 30. This converter is formed from the two inverters of the inverter circuit 510 connected to form a half-bridge and can, for example, be of the buck or step-down type. Instead of the transmitters used in the prior art, i.e., a type of transformer, only simple inductors 526 are required here, which can be coupled to one another, as shown, for example, in Figures 8 or 9.

[0091] Consequently, the electrical potential of the positive and negative rails of the floating control module 30 must always be less than (or equal to) the positive potential and greater than (or equal to) the negative potential of the inverter intermediate circuit 418, which also feeds the DC-DC converter of the power supply unit 40. This can be achieved, for example, by a mains inverter with suitable regulation of the DC-DC link voltage, such as by slightly boosting the mains voltage.

[0092] The transistors of this DC-DC converter are designed for high voltages, preferably at least sufficient for the intermediate circuit voltage. They are only designed for small currents (e.g., less than 10 A at low voltage), which is sufficient for the present application. This is in contrast to the components of the floating control module 30, which are designed for low voltages and high currents.

[0093] Figure 6 shows an embodiment of a power flow control system 90 for use in a network 12, which, in addition to the three phases (lines 20), also has an N conductor 21. Each of the four lines is connected to the network interface 400, which is formed from four inverters 420 connected to half-bridges 422. However, the basic structure corresponds to the network interface of the previous figures. By means of this power flow control system 90, symmetry errors with respect to the N conductor 21 or ground can also be compensated. For this purpose, a control module 30 is also provided for the N conductor 21 and connected accordingly to the other conductors.

[0094] Figure 7 shows an alternative embodiment in which the balancing unit 520 comprises two series-connected half-bridges 524 made up of transistors 522. The inverter circuit 510 is formed from only two transistors 514, which are also connected to form a half-bridge. The network interface corresponds to the network interface according to the embodiments of Figures 2, 3, and 5.

[0095] The embodiment shown in Figure 7 comprises a quasi-DC-DC converter 500 with two stages, a first stage comprising an inverter circuit 510 designed as a transistor half-bridge with an intermediate output, which can thus only carry a voltage relative to ground, and a second stage which is designed as a balancing unit 520 and comprises four series-connected transistors 522, which form two series-connected half-bridges 524, which can each boost via an intermediate inductance and thus increase the voltage (upper half-bridge) or decrease it (lower half-bridge).

[0096] In contrast to the embodiment with an inverter circuit comprising 2x2 transistors 514 and an additional balancing unit 520 with four series transistors 522, this embodiment preferably features a clear division of tasks. The inverter circuit 510 with a transistor half-bridge approximately follows the AC voltage of the corresponding phase of the grid interface 400 and outputs a voltage level. The subsequent balancing unit 520 then "spreads" this voltage to the voltage for the positive supply rail 312 of the control module 30 and the negative supply rail 314 of the control module 30. Preferably, the splitting or spreading is symmetrical. In principle, the splitting could also be asymmetrical, at least to a certain extent, with the more positive (upper) output of the balancing unit 520 being closer to the output of the inverter circuit 510 than the more negative (lower) output of the balancing unit 520.What is crucial here, however, is that the balancing unit generates the DC voltage as the difference between the outputs, while the inverter circuit 510 approximately follows the electrical potential of the associated control module, preferably an electrical potential between that of the positive supply rail or the negative supply rail of the control module, for example, the center. This does not have to be exact, as long as the remaining deviation from the target potentials of the positive and negative supply rails of the associated control module 30 lies within the operating range of the balancing unit 520.

[0097] Preferably, the inverter circuit of the quasi-DC-DC converter relatively precisely generates the instantaneous AC voltage of the associated phase, i.e., the common-mode component (of the supply voltage provided to the control module via at least two electrical connections), and the balancing unit 520 generates the voltage of the intermediate circuit capacitor in the control module 30, i.e., the differential-mode component or the difference between the two outputs of the quasi-converter unit 500. The clear division of tasks between the inverter circuit 510 and the balancing unit 520 allows for corresponding division and decoupling during control. In the embodiment, for example, according to Figure 5 with an inverter circuit 510 with 2x2 transistors 514 per control module 30 in the quasi-converter unit 500, these two tasks are performed by a single circuit part, namely the inverter circuit 510. A balancing unit is not provided according to Figure 5.

[0098] Figure 8 shows an alternative embodiment of the power flow control system 90, in which the balancing unit is omitted. Only the capacitor 528 of the intermediate circuit is present. In this embodiment, the inverter circuit 510 of the quasi-converter unit 500 is formed by two inverters 512, each with two transistors 514, connected in parallel to form half-bridges. The inverter circuit further comprises two simple inductors 526, which, as shown here, can be magnetically coupled. Thus, the inverter circuit 510 represents a DC-DC converter that is not galvanically isolated and dynamically follows the floating control module 30.

[0099] The magnetic coupling is preferably such that currents flowing in parallel from inverters to the module (common mode) experience a high inductance; those flowing in one direction through one of the two coupled inductances and in the opposite direction through the other (push-mode), on the other hand, experience a low inductance.

[0100] The embodiment according to Figure 9 differs in that two inductance pairs with inductances 516 are provided in the inverter circuit 510, which are each coupled to one another.

[0101] A further embodiment according to Figure 10 also has a quasi-converter unit 500, which has an inverter circuit 510 with two inverters 512 connected to form half-bridges. A balancing unit is not provided.

[0102] In this case, the mains interface 400 is formed from a combination of diodes 408 and transistors 424. Consequently, a mains rectifier with an integrated power factor correction stage is constructed. In this case, the PFC (power factor correction) stage is designed as an active front end. The components are designed for high voltages but low currents.

[0103] Figure 11 now shows a three-phase network 12, in which all control modules 30 for the respective lines 20 are shown. The voltage supply unit 40 comprises a network interface 400, which in the present case is constructed by three inverters 420 comprising transistors connected to form half-bridges 422. A separate quasi-converter unit 500 is provided for each line 20 or each control module 30, whereby an embodiment without a balancing unit is shown here. The quasi-converter unit 500 is formed from the inverter circuit 510 and the inductor 526 as well as the capacitor 528. Figure 12 shows an abstract representation of a network segment 10 with a power flow control system 90. Each of the lines 20 has its own control module 30, whereby optional line filters 36 can be provided upstream and downstream of the control modules 30.

[0104] For each phase or line 20, a separate floating control module 30 is provided. This module is essentially a two-phase inverter with its two AC terminals connected in series to the respective phase. The DC voltage input is supplied bidirectionally by the power supply unit 40.

[0105] Between the three quasi-converter units 500 (one for each phase) of the power supply unit 40 and the control modules 30, three DC supply lines are provided, each with an electrical potential that follows the control modules 30. Depending on the grid inverter used in the grid interface 400, control is bidirectional. Four quadrants can be influenced in the respective lines 20, meaning that the voltage can be increased or decreased for both power flow directions.

[0106] The power supply unit 40 consists of a grid interface and three quasi-converter units 500, one for each line. A DC intermediate circuit is formed between the grid interface 400, which functions as a grid inverter, and the quasi-converter units 500. Depending on the capacitance, this DC intermediate circuit may pulsate slightly. The voltage must be greater than the grid peak voltage plus half the control module intermediate circuit voltage; preferably, the voltage is greater than the grid peak voltage plus the control module intermediate circuit voltage.

[0107] The mains filters between the mains interface 400 can be formed by inductors, PI filters, LCL, etc.

[0108] The floating control modules 30 (series modules) can be powered in several ways. If the module capacitance is small (also compared to the connection inductance from the supply unit to the control modules), the power supply to each control module can be voltage-controlled. The voltage of the control module is then measured and regulated to the reference or target value, for example, using a PID controller. If necessary, the controller must have the smallest possible dynamic range (bandwidth) to avoid oscillations.

[0109] However, with large control module capacities, voltage control alone is potentially problematic because very high currents can flow, especially inrush currents, when the capacity has a significantly lower voltage than the target value. In this case, current control is recommended. Either pure current control with a reference current value for each phase or line is used, with the current reference value preferably being calculated from the grid conditions or the grid segment and the desired feed-in.

[0110] Alternatively, a cascaded controller can be used, in which an internal current controller keeps the current within acceptable limits and dynamics, while an external voltage controller regulates the intermediate circuit voltage of the floating control modules to their target value. The internal current controller preferably regulates with two-sided limits, i.e., with a positive and a negative limit.

[0111] With a cascaded control system, it should be noted that the series feed-in modules (control modules 30) of each phase (line 20) move up and down in terms of their electrical potential with the phase voltage. Accordingly, in a preferred control system, more than just one controller is used. Preferably, a distinction is made between common mode (CM) and differential mode (DM) currents and voltages. Each component is preferably controlled separately. The DC voltage of the control modules should remain relatively constant, although the potential of the control modules moves around earth (earth potential) with the line frequency and the line voltage. The DC charging voltage of the control modules, as the difference between the electrical potential of the positive supply rail and the negative supply rail of the control module, is therefore essentially a differential mode voltage. The oscillation of both potentials around earth is a common mode voltage.The same applies to the currents: Only the differential-mode current charges the module, while the common-mode current, on the other hand, leads to feeds into the respective phase, which may be desired in individual cases. At higher frequencies, the common-mode current potentially leads to undesirable electromagnetic interference. With suitable hardware in the control unit, the common-mode current can also be additionally suppressed with coupled inductors, so-called common-mode chokes. Such common-mode chokes were already shown in the exemplary embodiments shown in Figures 8 and 9.

[0112] Accordingly, a control unit 600 according to Figure 13 is configured to use the differential mode current to charge the modules 30 and to keep the common mode current as low as possible. Alternatively, the common mode current can be regulated to a certain reference value if feeding is desired.

[0113] An embodiment of the control unit 600 is shown in Figure 13 together with a control module 30 and an inverter circuit 510 for a line 20. The inverter circuit 510 forms a charging electronics 610 that serves to compensate for voltage fluctuations in the line 20.

[0114] The control unit 600 comprises two ammeters 620, which are integrated on the lines 48 between the inverter 510 and the control module 30. The ammeters 620 measure a positive current or a negative current, from which a common-mode current IcM.m and a differential-mode current Mm are formed by appropriate superposition. The measured common-mode current IcM.m is subtracted from a setpoint value of the common-mode current ICM and fed to a first controller 630, which can be designed, for example, as a PI or PR controller. The difference between the setpoint value ICM and the measured common-mode current IcM.m represents the common-mode error current ICM,error, which is fed to the controller 630.

[0115] A voltmeter 640 of the control unit 600 measures the voltage in the control module 30 between the positive rail and the negative rail. The measured voltage V m is applied to a reference voltage V ref negatively superimposed, so that an error reference voltage V re f, error is formed, which is fed to another controller 630b, which can also be designed as a PI controller. An optional limiting unit 650 can be provided between the controller 630 and an adder 660 to limit the output signal of the controller 630b. The output signal is then superimposed at a superposition point (adder 660) with the negative measured differential mode current Mm, whereupon a differential mode error current IDM, error is generated, which is fed to another controller 630c. The controller 630c can also be designed as a PI controller.

[0116] The outputs of controllers 630a and 630c are further processed, and two superposition elements 670 form the sum and the difference of the two controlled variables doM and dcM. These are the input signals for the charging electronics 610 and the inverter circuit 510, respectively. The common-mode voltage at the output of controller 630a specifies the movement of the control module 30 around the Earth. This allows the positive and negative rails to be generated by summing and subtracting, respectively, in the superposition elements 670.

[0117] Figure 14 shows an embodiment in which multiple network segments can be interconnected to form a low-voltage energy router. In principle, the control modules 30 can have multiple inputs and outputs, as shown in Figure 14. In this case, the modules can distribute power like a switch between n inputs and m outputs by generating any voltage gradient between the n x m taps. For low voltages, for example, this can be within the intermediate circuit voltage levels of the control modules 30, for example, a maximum of + / -48 volts for 48-volt systems or a maximum of + / -24 volts for 24-volt systems.

[0118] It is particularly preferred that, due to symmetry, it is no longer possible to distinguish between inputs and outputs in the control modules 30. This turns the compact power electronics mesh flow controller, i.e., the power flow control system 90, into a type of gateway or router, more commonly known from packet distribution in data networks. However, it is important that there is preferably no galvanic connection to the other phases (lines) or even to ground, and that the inputs and outputs are very close to one another in phase. The phase systems therefore have a fixed phase relationship with only a few degrees (preferably less than 10°, particularly preferably less than 5°) difference. Each additional pair has only a small voltage difference and can be processed by the floating control modules 30.

[0119] While several three-phase input lines are present, twice as many phases can be output to the individual control modules 30.

[0120] The solutions shown may provide some or more of the following features:

[0121] Raising or lowering the voltage amplitude at the fundamental frequency, typically 50 Hertz or 60 Hertz, of a network segment 10 by building up a voltage difference across the power flow control system 90.

[0122] Reactive power compensation (power factor correction) via the parallel tap (of the power supply unit 40), but also via the serial tap, i.e. via the control module 30.

[0123] Since the use of large power transformers with their high-frequency losses is avoided, it is possible to enable the injection or absorption of harmonic or transient distortions via the parallel tap or also via the series tap.

[0124] The power flow control system 90 can, within certain limits, not only continuously change the voltage amplitude between inputs and outputs, thus introducing or removing voltage distortions, but also shift the phase between input and output. This can occur in both positive and negative directions. Thus, a network segment 10 or a mesh can be operated offset by a few degrees relative to the supply. The limit for this is again the intermediate circuit voltage of the floating control modules 30. The phase shift between input and output must not lead to a voltage difference above the intermediate circuit voltage.

[0125] Overall, not only single-phase but also multi-phase solutions can be implemented using the power flow control system.

[0126] The invention has been comprehensively described and explained with reference to the drawings and the description. The description and explanation are to be understood as exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other embodiments or variations will become apparent to those skilled in the art upon use of the present invention and upon careful analysis of the drawings, the disclosure, and the following claims.

[0127] In the patent claims, the words "comprising" and "having" do not exclude the presence of further elements or steps. The undefined article "a" or "an" does not exclude the presence of a plurality. Furthermore, other numerals do not exclude a higher number. A single element or unit can perform the functions of several of the units mentioned in the patent claims. An element, unit, device, and system can be implemented partially or entirely in hardware and / or software. For example, parts of the control unit or the entire control unit can be implemented entirely or partially in software. The software or the corresponding computer program can be stored / distributed on a non-volatile data carrier, for example on an optical memory, a flash memory, even within a microprocessor, or on a solid-state drive (SSD).A computer program can be distributed together with hardware and / or as part of hardware, for example, via the Internet. The mere mention of some measures in several different dependent patent claims should not be understood to mean that a combination of these measures cannot also be used advantageously. Reference signs in the patent claims are not to be understood as limiting.

[0128] Reference symbol

[0129] 10 network segment

[0130] 12 Network

[0131] 20 Line

[0132] 22 Entrance page

[0133] 24 Exit page

[0134] 30 control module

[0135] 32 AC part

[0136] 34 DC part

[0137] 36 line filters

[0138] 40 Power supply unit

[0139] 42 AC part

[0140] 44 DC part

[0141] 46 Energy connection

[0142] 48 conductors

[0143] 56 line filters

[0144] 60 first module connection

[0145] 62 second module connection

[0146] 64 switching element

[0147] 66 transistors

[0148] 68 energy storage

[0149] 69 Capacitor

[0150] 70 Energy connection

[0151] 90 Power flow control system

[0152] 312 positive rail of 30

[0153] 314 negative rail of 30

[0154] 400 network interface

[0155] 408 Diode

[0156] 410 interface circuit

[0157] 412 positive DC rail

[0158] 414 negative DC rail

[0159] 416 Capacitor 418 Inverter intermediate circuit

[0160] 420 inverters

[0161] 422 Half Bridge

[0162] 424 transistors

[0163] 500 quasi-converter unit

[0164] 510 inverter circuit

[0165] 512 inverters

[0166] 514 transistors

[0167] 516 Inductance

[0168] 520 balancing unit

[0169] 522 transistors

[0170] 524 Half Bridge

[0171] 526 Inductance

[0172] 528 Capacitor

[0173] 599 Decoupling capacitor

[0174] 600 control unit

[0175] 610 charging electronics

[0176] 620 ammeter

[0177] 630 (ad) Controller

[0178] 640 voltmeter

[0179] 650 limiting unit

[0180] 660 Addition element

[0181] 670 superposition element

Claims

Patent claims 1. Control module for a power flow control system (90), designed for use in an electrical network (12) and designed to adjust the voltage and / or the current in at least one line (20) of the network (12), comprising at least two line connections (60, 62) for serial connection to the line (20) of the network (12), a plurality of switching elements (64), an energy store (68) and two energy connections (70) for connection to a voltage supply unit (40), wherein the first line connection (60) and the second line connection (62) are designed to electrically connect the control module (30) in series with the line (20);two of the switching elements (64) are connected in series and are connected in parallel to the energy storage device (68), the control module (30) is connected in such a way that a galvanically defined connection exists with a voltage supply unit which is controllable in such a way that the potential of the control module (30) follows the potential of the line (20) of the network (12) in a predefined manner; and the switching elements (64) are designed to increase or reduce the amplitude of the voltage in the line (20) in order to adjust the voltage, to shift the phase of the voltage or to control the current flow in the line (20) accordingly.

2. A power flow control system, designed for use in an electrical network (12) and designed to adjust the voltage and / or current in at least one line (20) of the network (12), comprising a control module (30) according to claim 1 and a voltage supply unit (40) for supplying the control module (30), wherein there is a galvanically defined connection between the control module (30) and the voltage supply unit (40) and the voltage supply unit (40) is controllable such that the potential of the control module (30) follows the potential of the line (20) of the network (12) in a predefined manner.

3. Power flow control system according to the preceding claim, characterized in that the voltage supply unit (40) has a network interface (400) and a quasi-converter unit (500), wherein the quasi-converter unit (500) is connected to the energy connections (70) of the control module (30) and is connected between the control module (30) and the network interface (400).

4. Power flow control system according to claim 3, characterized in that the voltage supply unit (40) has exactly one network interface (400) and one quasi-converter unit (500) for each line (20) of the network (12).

5. Power flow control system according to claim 3 or 4, characterized in that the quasi-converter unit (500) of the voltage supply unit (40) comprises an inverter circuit (510) with an inverter (512), preferably an inverter circuit (510) with at least two inverters (512), wherein each inverter (512) preferably comprises two transistors (514).

6. Power flow control system according to one of claims 3 to 5, characterized in that the quasi-converter unit (500) of the voltage supply unit (40) comprises an inverter circuit (510), preferably with four interconnected transistors (514), which are preferably interconnected in half-bridges, particularly preferably in parallel-connected half-bridges.

7. Power flow control system according to one of claims 3 to 6, characterized in that the quasi-converter unit (500) of the voltage supply unit (40) comprises a balancing unit (520), which preferably comprises four series-connected transistors (522), particularly preferably two series-connected half-bridges (524) of transistors (522).

8. Power flow control system according to the preceding claim, characterized in that the quasi-converter unit (500) comprises two inverters (512), preferably two transistors (514), which form a half-bridge (524), the terminal of which is connected to the balancing unit (520).

9. Power flow control system according to one of the preceding claims 3 to 5, characterized in that the quasi-converter unit (500) comprises a balancing unit (520) with two inductors (526) and an inverter circuit (510) with two inverters (512), preferably with two transistors (514) each.

10. Power flow control system according to one of the preceding claims, characterized in that the quasi-converter unit (500) galvanically connected to the control module (30) follows the potential of the network interface (400) and covers the entire potential range of the network interface (400).

11. Power flow control system according to claim 9, characterized in that the inverter circuit (510) has two DC voltage rails and each of the two DC voltage rails of the inverter circuit (510) of the quasi-converter unit (500) follows the potential of the mains voltage, wherein the DC voltage existing between the DC voltage rails is preferably a control voltage of the control module (30).

12. Power flow control system according to the preceding claim, characterized in that one of the two DC voltage rails of the control module (30), preferably the positive rail (312) of the Control module (30) which follows one AC voltage phase and the negative rail (314) of the control module (30) of the other AC voltage phase of the converter.

13. Power flow control system according to one of the preceding claims, characterized in that the network interface (400) of the voltage supply unit (40) comprises an inverter circuit (510), which preferably has a network inverter or rectifier.

14. Power flow control system according to the preceding claim, characterized in that the moving potential of the control module (30) remains within the inverter voltage between the positive rail of the grid interface (400) and the negative rail of the grid interface (400).

15. Power flow control system according to the preceding claim, characterized in that the voltage supply unit (40) comprises a quasi-converter unit (500) for each line (20) of the network (12).

16. Power flow control system according to one of the preceding claims, characterized in that the voltage provided by the control module (30) for changing the amplitude of the line (20) amounts to at most one third of the nominal network peak voltage, preferably at most one fifth, very preferably at most one tenth, further preferably at most one fifteenth, particularly preferably at most one twentieth.

17. Power flow control system according to one of the preceding claims, characterized in that the voltage supply unit (40) is electrically connected in parallel to the lines (20) of the network (12) and is supplied with power from the electrical network (12), wherein the voltage supply unit (40) preferably comprises a network filter (50) which is coupled to the lines (20) of the network (12).

18. Power flow control system according to one of the preceding claims, characterized in that the voltage provided by the control module (30) for changing the amplitude of the line (20) in a low-voltage network with 3 x 400 V phase-to-phase voltage is at most 100 volts, preferably at most 50 volts, very preferably at most 25 volts, further preferably at most 20 volts, further preferably at most 15 volts, particularly preferably at most 10 volts.

19. Network segment of an electrical network (12) with a line (20) which is connected to a network transformer and to which a plurality of consumers and / or feed-in sources are connected, and with a power flow control system (90) according to one of the preceding claims.

20. Control unit for controlling the charging electronics (610) of a control module (30) of a power flow control system (90), comprising an ammeter (620) for measuring the current of the connections between the charging electronics (610) and power connections of the control module (30) and a voltmeter (640) for measuring the voltage between a positive rail (312) of the control module (30) and a negative rail (314) of the control module (30), and comprising at least one regulator (630) for regulating the common-mode current and at least one regulator (630) for regulating the differential-mode current.

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