Power converter having multiple converter modules

Abstract

The application discloses a power converter (30) having three or more converter modules (10a, 10b) each comprising: - a housing (16), - a converter circuit (12a-12d) having at least one semiconductor switch (14a-14d) controlled in a clocked manner, - a power terminal (22a-22d) for receiving and / or delivering an electrical power, - a DC link terminal (18a-18d), and a capacitance (20a-20d) connected to the DC link terminal (18a-18d). The three or more converter modules (10a-10d) are each connected by way of their DC link terminal (18a-18d) to a joint DC bus (19). The power converter (30) is characterized in that it comprises multiple two-party pairs of converter modules (10a-10d), in each of which pairs at least one decoupling inductance (40a-40e) is arranged in a current path (50), passing via the DC bus (19), between the capacitance (20a) of a first converter module (10a) associated with the respective two-party pair and the capacitance (20b) of the second converter module (10b) associated with the respective two-party pair. The application furthermore relates to a device having multiple power converters (30) connected in parallel with one another to an energy source and / or an energy sink.

Description

[0001] POWER CONVERTER WITH MULTIPLE CONVERTER MODULES

[0002] Technical field of the invention

[0003] The invention relates to a power converter comprising a plurality of converter modules, each of which has a direct current (DC) intermediate circuit connection and a capacitor connected to the DC intermediate circuit connection, and which are connected to a common DC bus via their respective DC intermediate circuit connection. The invention further relates to a power conversion device comprising a plurality of such power converters.

[0004] State of the art

[0005] Power converters with high nominal power in the MW range often have a modular design. They contain multiple converter modules connected to a common DC link. To adapt the power converter to individual customer requirements, it is desirable to combine multiple DC-DC converter modules with each other, multiple DC-AC converter modules with each other, as well as DC-DC converter modules with DC-AC converter modules. In this way, by selecting suitable converter modules, various energy sources (e.g., photovoltaics, wind, fuel cells, batteries, AC grid) can be flexibly combined with different energy sinks (fuel cells, batteries, AC grid, AC island loads) via a standardized power converter.

[0006] The modular design of the power converter not only allows the type of required power conversion, for example, DC-DC power conversion, DC-AC power conversion, AC-DC power conversion, or AC-AC power conversion, to be specified by appropriately selecting its various converter modules. The nominal power of the power converter can also be scaled by varying the number of its respective converter modules.

[0007] The individual converter modules can each have capacitances connected to their DC link connection. In this way, the effective capacitance for the DC link is calculated from the sum of the individual capacitances of all converter modules connected in parallel to the DC link. In other words, as the number of converter modules connected to the DC link increases, the effective capacitance of the DC link increases.

[0008] A problem that occurs particularly in DC intermediate circuits arranged far apart from one another is high-frequency interference currents that can develop between individual converter modules during operation of the power converter. These interference currents are superimposed on the power converter's useful current and result in the power converter's total nominal power no longer being available for converting its useful current. To compensate for this, the power converter can be oversized with respect to the nominal power required for the application, which, however, leads to increased costs.

[0009] An alternative solution to the problem aims at a suitable reduction of the interference currents. To date, it has been established to connect the individual converter modules to the common DC link with as low an inductance as possible. In previous power converters, this not only reduced the unwanted interference currents, but also reduced the overall energy loss between individual converter modules connected in parallel to the common DC link. However, with the use of new materials for the semiconductor switches in the converter modules, e.g. silicon carbide (SiC), and increasing clock rates of the semiconductor switches, this approach becomes complex, since individual precautions to suppress interference currents must be taken for the different applications and designs of the power converter.These individual adaptations make it difficult to design the power converter in a standardized and modular manner.

[0010] From WO 2015 / 165658 A1, it is known to couple multiple converter modules via a common DC link. This results in a flexibly combinable variety of components.

[0011] A low-inductance connection of converter modules to a common DC busbar is disclosed, for example, in the document WO 2023 / 006371 A1.

[0012] The document DE 10 042 624 B4 discloses a three-level inverter

[0013] A device comprising a converter for converting power from an AC power source into DC power, an inverter for supplying the converted DC power as AC power, and a DC link for connecting the converter and the inverter. The DC link includes a bus with a positive polarity potential, a bus with a negative polarity potential, and a bus with an intermediate potential. The positive polarity potential bus and the negative polarity potential bus each have a reactor inserted therein for resonance control.

[0014] US 2010 / 0207560 A1 discloses a power conversion device comprising a converter unit for converting AC power into DC power, and an inverter unit that converts the DC power into a specified AC power and supplies the specified AC power to an electric motor. The power conversion device has a magnetic core for suppressing a resonance current flowing between the converter unit and the inverter unit.

[0015] Document EP 2 631 104 A1 discloses a DC link decoupling circuit in combination with two inverters connected in parallel to a common DC power supply line, each driving a different traction motor. A switching device is provided for each of the two inverters to disconnect the corresponding inverter from the supply line in the event of a failure. The DC link decoupling circuit has means for damping resonant oscillations in the form of an RL filter. Document JP H 11 355 909 A discloses a power conversion device comprising a PWM converter, to whose output side a first capacitor is connected, and a PWM inverter, to whose input side a second capacitor is connected. An impedance element is connected in series between the first capacitor and the second capacitor.

[0016] The document DE 102010 050282 B4 discloses a method for avoiding electrical resonance in a vehicle having a high-voltage motor generator unit (MGU) and a high-voltage direct current bus shared by a first and a second power electronics converter device. The object of the invention

[0017] The invention is based on the object of demonstrating an improved power converter for converting electrical energy that can be easily and flexibly configured for various applications. In particular, the power converter should have a modular design with several converter modules connected in parallel to a common DC link. The interference currents occurring between individual converter modules should be suppressed as effectively as possible. This suppression should be particularly effective for new semiconductor materials such as SiC and increased clock rates of the semiconductor switches. It should function as standardized as possible and, if possible, without individual adaptations, even for different power converter configurations. It is also an object to disclose a device for power conversion with several power converters.

[0018] Solution

[0019] The object of providing an improved power converter with multiple converter modules of the type mentioned above is achieved according to the invention with the features of independent patent claim 1. Advantageous embodiments of the power converter are recited in claims 2 to 17. A device for power conversion with multiple power converters is described according to the invention by the features of claim 18.

[0020] Description of the invention

[0021] A power converter according to the invention comprises three or more converter modules. Each of the converter modules comprises: a housing, a converter circuit with at least one clocked semiconductor switch, a power connection for receiving and / or delivering electrical power, an intermediate circuit connection, and a capacitor connected to the DC intermediate circuit connection.

[0022] The three or more converter modules are each connected to a common DC bus via their DC link connection. The power converter is characterized in that it further comprises several pairs of converter modules, in particular several different pairs of adjacent converter modules. The several pairs of converter modules each comprise at least one decoupling inductance arranged in a current path leading via the DC bus between the capacitance of a first converter module of the respective pair of converter modules and the capacitance of a second converter module of the respective pair of converter modules.

[0023] The decoupling inductance is to be understood as a separate component that is incorporated into the circuit. It thus differs from a parasitic inductance of an electrical line, for example, a cable or a busbar, which is naturally present and typically depends on the length of the electrical line and its geometry. Rather, the decoupling inductance of the present application is a component that is additionally arranged on an electrical conductor, for example, mounted on it and / or connected in series with the electrical conductor, in order to locally and specifically modify, in particular increase, an otherwise existing inductance of the respective electrical conductor.

[0024] The converter modules can each have an internal control device for controlling their converter circuits, in particular their at least one semiconductor switch. The power converter can have a higher-level control device for the coordinated control of the converter modules. This can be connected to the internal control devices of the converter modules for control purposes and for data exchange, for example via wired or wireless communication links. The higher-level control device of the power converter can be a separate control device. Alternatively, however, it is also possible for the higher-level control device of the power converter to be fully or at least partially integrated into one or more internal control devices of the converter modules.

[0025] Because the three or more converter modules are each connected to the common DC bus with their DC link connection, and each of the DC link connections has a capacitance, this results in several different pairs of two converter modules, each containing a first converter module and a second converter module. During operation of the power converter, each of the several pairs of two converter modules forms an oscillating system together with the DC bus. For example, a high-frequency ripple voltage is generated at the capacitance of the first converter module of each pair of two by a clocked current draw. This ripple voltage then excites a high-frequency interference current, which flows along the current path via the DC bus and the capacitance of the second converter module of the respective pair of two.Each of the multiple pairs of two thus forms an inductive-capacitive-resistive (LCR) resonant circuit that exhibits resonant behavior. The resonant behavior is influenced by the values ​​of capacitance C, inductance L, and ohmic resistance R effective in the respective current path. While converter modules of conventional power converters in the respective power class typically have lower clock rates (e.g., approximately 3 kHz), the clock frequencies occurring there are usually lower than a resonant frequency fRes that characterizes the resonant behavior. Connecting the converter modules to the DC bus with as little inductance as possible leads to an increase in the distance between the clock frequency fciock that excites the interference current in the current path and the resonant frequency fRes. However, the converter modules in question here typically feature semiconductor switches made of SiC or GaN, which can be operated at a significantly higher clock frequency.For example, the clock frequency fciock in the converter modules in question here is at least 5 kHz, in some cases at least 8 kHz or higher. With the higher clock frequencies of the semiconductor switches, the excitation frequency for the unwanted interference current also changes, and the distance between the excitation frequency and the resonance frequency fRes is reduced. In other words, with conventional approaches to suppressing the interference current (i.e., connecting the converter modules to the DC bus with the lowest possible inductance), increasing the clock frequency fciock brings the resonance frequency fRes closer to the resonance frequency and thus increases the unwanted interference current. Although the converter modules in question here typically have semiconductor switches made of SiC or GaN, it cannot be ruled out that one or more, or possibly even all, converter modules of the power converter may have semiconductor switches made of Si.

[0026] By deliberately arranging a decoupling inductance in the current path between the first and second converter modules of the respective pair of two, according to the invention, this has two significant effects: Firstly, in each of the multiple pairs of two, the resonance frequency fRes effective in the current path is shifted to smaller values ​​by increasing the inductance in the current path. Specifically, the resonance frequency fRes can be shifted by means of the decoupling inductance so that it is lower than the clock frequency of the converter module that excites the interference current. In this case, an increase in the capacitance in the converter module also leads to an increase in the distance between the clock frequency fciock that excites the interference current and the resonance frequency fRes. By increasing the capacitance value of a converter module, the interference current that occurs can thus be further minimized.This behavior is the opposite of the case where the clock frequency fciock exciting the interference current lies below the resonant frequency fRes effective in the current path. This is particularly advantageous for the design of the converter module—and thus the power converter—with regard to a higher nominal power. Specifically, an increase in capacitance is desired or necessary anyway when the nominal power is increased. This now results in lower interference currents under otherwise comparable conditions. Furthermore, interference currents still present in the current path can also be significantly attenuated by the additional decoupling inductance.For example, the interference currents can cause eddy currents and magnetization reversal processes in the decoupling inductance, which generate power loss in the decoupling inductance and thus exert a damping effect on the high-frequency interference currents between the two converter modules assigned to a respective pair.

[0027] The behavior described above was explained using a pair of two converter modules consisting of a first converter module and a second converter module as an example. However, the power converter according to the invention contains three, four, five, or more converter modules, which may also differ from one another. The number of pairs of two converter modules, each of which forms an oscillating system, increases rapidly. Specifically, with three converter modules, there are three pairs of two, but with four converter modules, there are already six different pairs of two. Each of the pairs of two forms an oscillating system in its own right. The interference currents generated by all pairs of two overlap, so that a converter module in a particular pair of two also "feels" the interference currents of all other converter modules connected to the common DC bus. As the number of converter modules, especially different ones, increases, the complexity of all interference currents quickly becomes significant and difficult to manage.However, by providing at least one decoupling inductance for each of several pairs of two, the complex interference currents of all converter modules can be significantly reduced, while the power converter remains manageable.

[0028] In summary, in a power converter with three or more converter modules, the at least one additional decoupling inductor between the capacitances of the two converter modules of each pair of two results in effective suppression of all interference currents within the power converter. The decoupling inductor can be manufactured in large quantities as a standardized component. Fine-tuning with regard to the shift in the resonant frequency fRes can be achieved by inserting several decoupling inductors arranged serially in the current path, in particular of the same type and in particular of identical construction. The principle can be applied both to different combinations of converter modules within the power converter and to a change in the number of converter modules within the power converter.This results in a modular power converter for a wide range of applications, especially for high power classes, with significantly reduced interference currents between its converter modules.

[0029] In an advantageous embodiment of the power converter, in at least one of the several pairs of converter modules, optionally in each pair of converter modules, an inductance value of the at least one decoupling inductance can be selected such that a resonant frequency fRes of the current path, which originates from the capacitance of the first converter module of a respective pair of converter modules and leads via the capacitance of the second converter module of the respective pair of converter modules, is below a clock frequency fciock of the first converter module of the respective pair of converter modules and / or below a clock frequency fciock of the second converter module of the respective pair of converter modules. In this way, an increase in the clock frequency fciock, which may be desired for other reasons, simultaneously leads to an increase in the distance between the clock frequency fciock and the resonant frequency fRes.Furthermore, an otherwise necessary, particularly low-inductance connection of the individual converter modules to the shared DC bus can be dispensed with. This low-inductance connection, which is usually associated with considerable effort, would be necessary if the resonance frequency fRes were above the clock frequency fciock of the first converter module, or even above the clock frequencies fciock of both converter modules in the respective pair. Further advantages resulting from this, particularly for power converters with high nominal power, have already been mentioned: For example, an increase in the capacitance of a converter module, which is necessary anyway when increasing its nominal power, simultaneously also results in an increase in the distance between the resonance frequency fRes and the clock frequency fciock of the first converter module, and possibly also of the second converter module, which likewise results in a reduction in the interference current.

[0030] Advantageously, in at least one of the several pairs of two converter modules, optionally in each pair of two converter modules, the resonance frequency fRes of the current path can be at least a factor of 2, preferably at least a factor of 3, below a clock frequency fciock of the first converter module or the second converter module of the respective pair of two. In particular, the following can therefore apply to each of the two converter modules of the pair of two: 2 * fRes < fciock, and preferably 3 * fRes < fciock. Optionally, it can also be a factor of 2, preferably also a factor of 3, below a minimum value of the clock frequencies fciock of both converter modules of the respective pair of two. This results in particularly effective attenuation of the unwanted interference current.

[0031] In an advantageous embodiment of the power converter, in at least one of the multiple pairs of converter modules, a clock frequency fciock of the first converter module assigned to the respective pair of converter modules can be at least 5 kHz, preferably at least 8 kHz, optionally at least 11 kHz. This can optionally also apply in the same way to a clock frequency fciock of the second converter module of the respective pair of converter modules. At such clock frequencies fciock, SiC and GaN semiconductor switches with lower switching losses and higher blocking voltages can be used in the converter modules.In addition, at a clock frequency fciock above the resonance frequency fRes assigned to the current path, the distance between the clock frequency fciock and the resonance frequency fRes effective in the current path between the two converter modules also increases with increasing clock frequency fciock, which also reduces the interference current between the converter modules.

[0032] In one embodiment of the power converter, in at least one of the multiple pairs of converter modules, the current path between the capacitance of the first converter module of the respective pair and the capacitance of the second converter module of the respective pair can have exactly one decoupling inductance. This typically results in particularly low component costs for the respective power converter, since the total number of decoupling inductances installed in the power converter is small. However, it may be necessary to maintain decoupling inductances with several different inductance values, which in turn can result in higher component costs for each of the individual decoupling inductances.In an alternative embodiment of the power converter, it is therefore possible for at least one of the multiple pairs of converter modules to have a plurality of decoupling inductors in the current path between the capacitance of the first converter module of the respective pair of two and the capacitance of the second converter module of the respective pair of two. The plurality of decoupling inductors can be arranged at different locations in the current path and in series with one another. This results in a higher total number of decoupling inductors installed in the power converter. On the other hand, however, it is sufficient to provide a maximum of one or a few decoupling inductors with different inductance values ​​as standard components and to implement the respective inductance value desired for the current path in the form of several decoupling inductors that are as identical as possible.

[0033] In a first embodiment of the power converter, in which, in a respective pair of converter modules, the at least one decoupling inductance arranged in the current path between the capacitance of the first converter module and the capacitance of the second converter module now comprises exactly one decoupling inductance, the exactly one decoupling inductance can be arranged in the housing of the first converter module of the respective pair of two or in the housing of the second converter module of the respective pair of two.In a second embodiment of the power converter, in which, for a respective pair of converter modules, the at least one decoupling inductance arranged in the current path between the capacitance of the first converter module and the capacitance of the second converter module comprises a plurality of decoupling inductances, one or more of the at least one decoupling inductances can be arranged in the housing of the first converter module of the respective pair of converter modules or in the housing of the second converter module of the respective pair of converter modules. In this case, it is particularly possible for each of the converter modules to comprise one or more decoupling inductances.By having one or more converter modules each comprise one or more decoupling inductors arranged in their housing, their inductance values ​​can be matched to the corresponding converter module, so that replacing one converter module with another converter module does not result in any additional effort, or at least only a small additional effort with respect to an additional replacement of decoupling inductors in the power converter.

[0034] Alternatively or additionally to an arrangement of one or more decoupling inductors within the housings of the converter modules, the power converter can, in at least one pair of two converter modules, have one or more decoupling inductors of the at least one decoupling inductor, which is / are arranged outside the housings of the converter modules in the current path extending from the capacitance of the first converter module of the corresponding pair, via the DC bus, the capacitance of the second converter module of the corresponding pair, and back to the capacitance of the first converter module of the corresponding pair. This one decoupling inductor can / these several decoupling inductors can be arranged in particular on the DC bus or on the electrical connections between the converter modules of the corresponding pair and the common DC bus.

[0035] In a pair of two converter modules with a plurality of decoupling inductors arranged in the current path between the capacitance of the first converter module and the capacitance of the second converter module, a first number of the plurality of decoupling inductors can be assigned to the first converter module of the respective pair of two and, in combination, have a first inductance value. The first inductance value can be selected such that it depends on the capacitance and clock frequency fciock of the first converter module of the respective pair of two, but not on the capacitance and clock frequency of the second converter module of the respective pair of two. Furthermore, a second number of the plurality of decoupling inductors can be assigned to the second converter module of the respective pair of two and, in combination, have a second inductance value.The second inductance value can be selected such that it depends on the capacitance and clock frequency fciock of the second converter module of the respective pair of two, but not on the capacitance and clock frequency of the first converter module of the respective pair of two. In particular, the first inductance value can be different from the second inductance value. In this way, one or more decoupling inductances are assigned to each of the two converter modules. The resulting inductance values ​​from the first and second inductance values ​​are characteristic of the respectively assigned converter module. In this way, each of the converter modules can be designed to be self-sufficient and independent of the other converter modules connected to the common DC bus. For the design of the decoupling inductance or decoupling inductance assigned to a converter module.In particular, a second current path can be used as a basis for decoupling inductances, which results from the DC link connections of the respective converter module being connected – i.e., essentially short-circuited – via the number of decoupling inductances assigned to the respective converter module. In the resulting second current path, the inductance value of the respective decoupling inductance(s) can be selected such that the resonant frequency fRes of this second current path is below the clock frequency fciock, in particular by a factor of 2 or a factor of 3 below the clock frequency fciock of the respective converter module. This type of design ensures that all possible combinations of converter modules connected to one another via the common DC bus remain manageable in a simple manner.This applies in particular when more than just two converter modules are connected together to the common DC bus. In particular, it is no longer necessary to change the decoupling inductances of the converter modules previously connected to the DC bus when adding just one further converter module to the common DC bus. In one embodiment of the power converter, one or more of the at least one decoupling inductance of a respective pair of two, which is / are arranged in the current path leading via the DC bus between the capacitances of the first converter module and the second converter module of the respective pair of two, can each have a core enclosing a busbar. The core can be wound from a metal strip and have several layers. Alternatively, it can be designed as a laminated core and have several laminates arranged parallel to one another.Furthermore, the core can have one or more gaps to suppress saturation at high currents flowing through the busbar. The busbar can be a busbar of the DC bus, a busbar of an electrical connection between the converter module and the DC bus, or a busbar within one of the converter modules of the respective pair. Alternatively to the busbar, the decoupling inductance, in particular its core, can also be arranged on an electrical cable and enclose it at least largely along its circumference.

[0036] In one embodiment, the power converter can comprise more than just three converter modules, for example 4 converter modules, 5 converter modules, or more than 5 converter modules, each having a DC link connection and a capacitance connected to the DC link connection, and which are connected to the common DC bus via their respective DC link connection. In principle, the power converter can also comprise at least one pair of two converter modules, in which no decoupling inductance is arranged in a current path leading via the DC bus between the capacitances of the converter modules of the at least one pair of two. In an advantageous embodiment, however, for each pair of two converter modules, at least one decoupling inductance is arranged in a current path leading via the DC bus between the capacitances of the converter modules of the respective pair of two.It is understood that the at least one decoupling inductance can optionally also comprise multiple decoupling inductances. An inductance value of the at least one decoupling inductance can be selected such that the following applies to all pairs of converter modules: A resonant frequency fRes of the current path leading via the DC bus, which originates from the capacitance of a first converter module of the respective pair of converter modules and leads via the capacitance of a second converter module of the respective pair of converter modules, is below a clock frequency fciock of the first converter module and / or below a clock frequency fciock of the second converter module of the respective pair of converter modules. This allows the power converter in question to be designed to simultaneously carry out a multitude of different applications.

[0037] In one embodiment, one of the converter modules of the power converter can comprise a DC / DC converter, in particular a bidirectional DC / DC converter. The DC / DC converter can have a 2-level topology. It is understood that several of the converter modules can each be designed as a DC / DC converter, in particular as a bidirectional DC / DC converter. In particular, several of the DC / DC converters can each have a 2-level topology. Alternatively or cumulatively, one of the converter modules of the power converter can comprise a DC / AC converter, in particular a bidirectional DC / AC converter. The DC / AC converter can have a 2-level topology. Of course, the power converter can also contain several converter modules, each designed as a DC / AC converter, in particular as a bidirectional DC / AC converter. In particular, several of the DC / AC converters can each have a 2-level topology.The power converter can also further comprise at least one connection module connected to one of the converter modules or directly to the DC bus. The at least one connection module can be designed to connect at least one element from a group formed by a battery, an electrolyzer, an electric vehicle (EV) charger, and a fuel cell. Different connection modules can each be designed for an individual element of the group and contain components that are exclusively required for operation with the corresponding element. In addition, they can contain switching devices, fuses, and / or components for system protection, for example, for overvoltage protection. The at least one connection module allows the power converter to be easily configured for an individual application.

[0038] A power conversion device according to the invention comprises a plurality of power converters whose power terminals are connected in parallel to one another to a common energy sink and / or a common energy source. The power converters can be of identical or different construction with regard to the converter modules they contain. In identically constructed power converters, the number and type of converter modules of the respective power converters are identical. In differently constructed power converters, the number and / or type of converter modules of the respective power converters are different. This results in the advantages already mentioned in connection with the power converter.

[0039] Advantageous embodiments of the invention are specified in the following description and the subclaims, the features of which can be used individually and in any combination with one another.

[0040] Short description of the characters

[0041] The invention is illustrated below with the aid of figures, of which

[0042] Fig. 1 shows a first embodiment of a power converter according to the invention;

[0043] Fig. 2 is a schematic representation of possible arrangements of decoupling inductors in the power converter of Fig. 1;

[0044] Fig. 3 shows a decoupling inductance in one embodiment;

[0045] Fig. 4a shows a power converter according to the invention in a second embodiment;

[0046] Fig. 4b shows a power converter according to the invention in a third embodiment.

[0047] Figure description

[0048] Fig. 1 shows a first embodiment of a power converter 30 according to the invention. The first embodiment comprises three or more converter modules, of which only two converter modules 10a, 10b are explicitly shown. The other converter modules are symbolized by dots in Fig. 1. The following explanation is based on the example of the pair of converter modules shown in Fig. 1, which includes the converter modules 10a and 10b.

[0049] Each of the converter modules 10a, 10b has a power connection 22a, 22b, a converter circuit 12a, 12b with semiconductor switches 14a, 14b, a control device 24 controlling the semiconductor switches 14a, 14b, and a housing 16. The converter modules 10a, 10b are connected to a common DC bus 19 via respective intermediate circuit connections 18a, 18b. Since the power converter 30 is designed for a high nominal power—and thus also for high currents—the electrical conductors of the DC bus 19 are typically implemented in the form of busbars 51. This also applies to the electrical connections 23 between the converter modules 10a, 10b and the DC bus 19, as well as to the power-carrying electrical connections within the converter modules 10a, 10b. However, this does not mean that the DC bus 19 and the electrical connections 23 only have busbars 51.Rather, where additional flexibility is required, this can also be provided via a suitable electrical cable. Depending on the composition of the power converter 30, the DC bus 19 can assume a large spatial extent. Therefore, the DC bus 19 can have several busbars 51 of the same polarity, which are electrically and mechanically connected to one another via connecting elements 25, for example suitable screw connections, whereby the DC bus 19 can be extended. The connecting elements 25 shown as examples at the ends of the DC bus 19 in Fig. 1 are optional components and are therefore shown in dashed lines in Fig. 1.

[0050] The converter modules 10a, 10b each have a capacitance 20a, 20b connected in parallel to the respective DC link connection 18a, 18b. Thus, the capacitances 20a, 20b of the two converter modules 10a, 10b connected to the DC bus 19 provide the total effective capacitance for the DC bus 19. The power converter 30 further comprises a higher-level control device 27, which is connected to the control devices 24 of the respective converter modules 10a, 10b via communication connections 26 to control its converter modules 10a, 10b. The communication connections 26 can be wired communication connections (e.g., based on electrical cables or fiber optic cables). Alternatively, however, it is also possible for the communication between the higher-level control device 27 and the internal control devices 24 of the converter modules 10a, 10b to be wireless, e.g.via radio and the communication connections 26 are designed as radio-based communication connections. The converter modules 10a, 10b can each be, for example, a DC / DC converter or a DC / AC converter. They can each be designed for a unidirectional, or alternatively, for a bidirectional power flow. By high-frequency clocking of the semiconductor switches 14a, 14b, a high-frequency ripple voltage is generated at the capacitors 20a, 20b. Each of these capacitors 20a, 20b thus also represents a voltage source, which in each case results in superimposed high-frequency interference currents between the capacitors 20a, 20b of the two converter modules 10a, 10b in a current path leading via the DC bus 19 (cf. Fig. 2). The superposition of the two interference currents results in the interference current effectively flowing between the capacitors in the current path.The high-frequency interference current is undesirable because it disrupts the operation of the converter modules 10a, 10b and reduces the power available for a useful current of the converter modules 10a, 10b.

[0051] In order to effectively reduce the high-frequency interference current, at least one decoupling inductance is arranged in the current path leading via the DC bus 19 between the capacitances of the converter modules 10a, 10b. For this purpose, in Fig. 1, each converter module 10a, 10b has a decoupling inductance 40a, 40b in one of its electrical connections to its respective DC link connection 18a, 18b. The at least one decoupling inductance here thus comprises, by way of example, exactly as many decoupling inductances as converter modules, of which only the decoupling inductances 40a, 40b of the converter modules 10a, 10b are shown in detail in Fig. 1. As explained in connection with Fig.2, both decoupling inductances 40a, 40b are located in a current path leading via the DC bus 19, from the capacitance 20a of the first converter module 10a, via the capacitance 20b of the second converter module 10b and back again to the capacitance 20a of the first converter module 10a. The inductance value of the two decoupling inductances 40a, 40b is now selected such that a resonance frequency fRes of the current path determined by the decoupling inductances 40a, 40b and the capacitances 20a, 20b lies below a clock frequency fciock of the semiconductor switches 14a, 14b, and at different clock frequencies fciock of the converter modules 10a, 10b below the smaller of the two clock frequencies fciock.Instead of two decoupling inductors 40a, 40b in the converter modules, the same reduction in interference current can also be achieved with just one decoupling inductor, or more than two decoupling inductors in the current path assigned to the respective pair of two, provided that the resulting overall inductance value of just one decoupling inductor or of the multiple decoupling inductors in combination with the capacitances 20a, 20b leads to the aforementioned resonant frequency fRes. The behavior explained in Fig. 1 as an example for the pair of two converter modules 10a, 10b can in principle also be transferred to the other pairs of two converter modules of the power converter 30 connected to the common DC bus 19. However, it should be noted that in such a case, multiple superposition of interference currents also occurs.Specifically, for each of the converter modules, the interference currents of all other converter modules must be considered, i.e., all pairs of two that contain the converter module in question. It has been shown that for more complex power converters with more than two converter modules, special requirements arise when selecting the inductance value of the respective decoupling inductors. Specifically, it is advantageous if the decoupling inductors are used to generate a resonant frequency of the current path in question that is significantly lower than the clock frequency of the respective converter module, in particular by at least a factor of 2, particularly advantageously by at least a factor of 2.5 or at least a factor of 3. This can also apply in particular to a second current path that results from the DC link connections 18a, 18b of the converter module in question being connected via the number of...

[0052] Decoupling inductors 40a, 40b are connected - i.e., short-circuited.

[0053] Fig. 2 schematically shows possible arrangements of the at least one decoupling inductance in a current path 50 leading via the DC bus 19 between the capacitors 20a, 20b of the two converter modules 10a, 10b of the pair of converter modules from Fig. 1. The two converter modules 10a, 10b are each schematically symbolized by their respective housings 16. Further converter modules of the power converter 30 are symbolized by dots in Fig. 2.

[0054] Fig. 2 shows possible positions of decoupling inductors in the current path 50, at each of which a decoupling inductor can be present, but does not necessarily have to be present. It is important that the current path 50 as a whole has at least one of the decoupling inductors 40a - 40e. Specifically, it is possible, for example, for one or more decoupling inductors 40a to be arranged within a housing 16 of the first converter module 10a. These can each be arranged in an electrical connection from the capacitor 20a to the intermediate circuit connection 18a of the first converter module. Analogously, it is also possible for one or more decoupling inductors 40b to be arranged within a housing 16 of the second converter module 10b, for example, each in an electrical connection from the capacitor 20b to the DC intermediate circuit connection 18b of the second converter module.Alternatively or cumulatively, it is possible for a decoupling inductance 40a, 40b / multiple decoupling inductances 40a, 40b to be arranged outside a housing 16 of the converter modules 10a, 10b in the current path 50. For example, a decoupling inductance 40a can be arranged in an electrical connection 23 between the DC link connection 18a of the first converter module 10a and the DC bus 19. It is also possible for a decoupling inductance 40b to be arranged in an electrical connection 23 between the DC link connection 18b of the second converter module 10b and the DC bus 19. Finally, the DC bus 19, in particular a busbar 51 with positive polarity and / or a busbar 51 with negative polarity within the DC bus 19, can also have a decoupling inductance 40e.

[0055] Fig. 3 shows an embodiment of a decoupling inductor, such as can be used as a decoupling inductor 40a-40d in a power converter 30 according to Figs. 1, 4a or 4b. The decoupling inductor 40a-40e has a core 41 that surrounds an electrical conductor, here: exemplarily a busbar 51, at least largely along its circumference and is fastened to the electrical conductor (here: busbar 51) by means of a fastening element - here: a screw 43. The core 41 can comprise a winding core wound from a thin metal foil. Alternatively, however, it can also be composed of metal sheets arranged parallel to one another. The metal sheets can be screwed together or fixed in some other way. The core 41 can have one or more gaps (not explicitly shown in Fig. 3) in order to suppress magnetic saturation of the core 41.This can be an air gap. At the very least, it is a gap that is free of ferromagnetic material. A distributed gap is also possible. The core 41 can be electrically connected to the electrical conductor (here: the busbar 51) and have (at least approximately) the same potential with it. Alternatively, it is also possible for the core 41 and the busbar 51 to be electrically insulated from one another. This can be the case, for example, if the core 41 is a winding core made of metal foil that is wound on a plastic carrier and attached to the busbar 51 via this. In this case, the plastic carrier provides electrical insulation between the core 41 and the busbar 51.

[0056] The high-frequency currents in the busbar 51 and the resulting magnetic flux generate remagnetization processes and eddy currents in the core 41. These effects heat the core material and thus lead to a power loss, which is extracted from the high-frequency interference current flowing in the busbar 51 and dampens it.

[0057] Fig. 4a shows a second embodiment of a power converter 30 according to the invention, together with the energy sources and energy sinks connected to it. The power converter is similar in many respects to the power converter 30 already presented in Fig. 1, which is why reference is made to the description in Fig. 1 for the same points. For reasons of clarity, some elements, for example, those that were already labeled in Fig. 1, have been omitted in Fig. 4a. The following primarily describes the differences from the power converter 30 in Fig. 1.

[0058] The second embodiment of the power converter 30 in Fig. 4a includes a total of four converter modules 10a-10d, each having a housing 16. They are connected to a common DC bus 19 via their respective DC link connections 18a-18d. The first and second converter modules 10a, 10b are each designed as unidirectional DC / DC converters, whose power connections 22a, 22b are each connected to a DC energy source, here a PV generator 32. The third and fourth converter modules 10c, 10d are each designed as DC / AC converters, whose power connections 22c, 22d are connected in parallel to an alternating voltage (AC) network 34, optionally via a transformer (not shown in Fig. 4a). The DC bus 19 contains a flexibly designed area which, for example, has electrical cables 28 instead of busbars 51.The electrical cables 28 are connected via connecting elements 25 to the associated busbars 51 of the common DC bus 19. The power converter 30 from Fig. 4a operates, by way of example, as a high-performance photovoltaic (PV) inverter, for example for a PV power plant, which converts electrical DC power from the PV generators 32 into AC power and feeds it into the AC grid 34. To effectively suppress the interference current, a decoupling inductance 40a, 40b is arranged in the respective housings 16 of the converter modules 10a, 10b designed as DC / DC converters. There, it is located in an electrical connection between the capacitor 20a, 20b and the positive pole of the DC link connection 18a, 18b. The converter modules 10c, 10d designed as DC / AC converters have, for example, a lower clock frequency fciock of their semiconductor switches 14c, 14d.In order to nevertheless maintain a sufficient distance between the clock frequency fciock of these converter modules 10c, 10d and a resonant frequency fRes in a current path leading via the DC bus 19 between the capacitors 20c, 20d, the converter modules 10c, 10d designed as DC / AC converters each contain two decoupling inductors 40c, 40d in their respective housings 16. Of these, one decoupling inductor 40c, 40d is located in a positive electrical connection and the other decoupling inductor 40c, 40d is located in a negative electrical connection between the capacitor 20c, 20d and the corresponding pole of the DC link connection 18c, 18d.In this way, the inductance value in the circuit leading via the DC bus 19 between the third and fourth converter modules 10c, 10d is increased, and its resonance frequency fRes is reduced, so that a sufficient distance between the clock frequency fciock of the converter modules 10c, 10d and the resonance frequency fRes is maintained.

[0059] Furthermore, a decoupling inductance 40e is arranged in a busbar 51 of the DC bus 19 between the second converter module 10b and the third converter module 10c. It leads to a reduction in the resonant frequency fRes in a current path leading via the DC bus 19 between the second and third converter modules 10b, 10c, so that a sufficient distance is maintained between the resonant frequency fRes and the clock frequency fciock of the third converter module 10c, i.e., the converter module with the lower clock frequency fciock of the converter modules 10b, 10c.

[0060] Fig. 4b shows a third embodiment of a power converter 30 according to the invention, together with energy sources and energy sinks connected thereto, which corresponds in many respects to the second embodiment from Fig. 4a. With regard to the same points, reference is therefore made to the description of Fig. 4a. In contrast to the second embodiment, however, the power converter 30 in Fig. 4b is now connected to other energy sources and sinks. Specifically, the first converter module 10a is designed as a unidirectional DC / DC converter and is connected to a PV generator 32. The second converter module 10b is designed as a bidirectional DC / DC converter and is connected to an energy storage device 36—here, for example, a battery. In this way, it is designed to charge and discharge the energy storage device 36 from the DC bus 19. The third and fourth converter modules 10c, 10d are each designed as bidirectionally operating DC / AC converters.The third converter module 10c is connected to an AC network 34, and the fourth converter module 10d is connected to an AC consumer—here, for example, to a motor 38. In this way, the third converter module 10c is designed to transfer electrical power from the DC bus 19 to the AC network 34 and vice versa. The fourth converter module 10d can drive the motor 38 via a power transfer from the DC bus 19 to the motor 38 and, when the motor 38 is braked, transfer the released electrical power to the DC bus 19. In contrast to the embodiment according to Fig. 4a, the DC bus 19 is constructed solely by means of busbars 51. A flexible region 28 realized via electrical cables 28 has been omitted here. Instead, the DC bus 19 has a decoupling inductance 40e in each of its busbars between the second converter module 10b and the third converter module 10c.The arrangement of the decoupling inductors 40a-40d in the housings 16 of the converter modules 10a-10d is identical to the arrangement of the decoupling inductors 40a-40d in Fig. 4a.

[0061] List of reference symbols a - 10d converter module a - 12d converter circuit a - 14d semiconductor switch

[0062] Housing a - 18d DC link connection a - 20d Capacity a - 22d Power connection

[0063] Electrical connection

[0064] Control device (converter module)

[0065] connecting element

[0066] Communication connection of higher-level control device (power converter)

[0067] Cable

[0068] Power converter

[0069] Photovoltaic (PV) generator

[0070] Alternating current (AC) network

[0071] Energy storage (battery, capacitor bank)a - 40e decoupling inductance

[0072] core

[0073] clamp

[0074] Fastening

[0075] Current path

[0076] Busbar

Claims

Patent claims 1 . Power converter (30), with three or more converter modules (10a-1 Od), each comprising: - a housing (16), - a converter circuit (12a-12d) with at least one clocked semiconductor switch (14a-14d), - a power connection (22a-22d) for receiving and / or delivering electrical power, - a DC link connection (18a-18d), and a capacitor (20a-20d) connected to the DC link connection (18a-18d), - wherein the three or more converter modules (10a-10d) are each connected to a common DC bus (19) via their DC intermediate circuit connection (18a-18d), characterized in that - the power converter (30) further comprises a plurality of pairs of converter modules (10a-10d), in each of which at least one decoupling inductance (40a-40e) is arranged in a current path (50) leading via the DC bus (19) between the capacitance (20a) of a first converter module (10a) of the respective pair of two and the capacitance (20b) of a second converter module (10b) of the respective pair of two.

2. Power converter (30) according to claim 1, characterized in that in at least one of the plurality of pairs of converter modules (10a-10d) an inductance value of the at least one decoupling inductance (40a, 40b, 40e) is selected such that a resonance frequency fRes of the current path (50), which starts from the capacitance (20a) of the first converter module (10a) of the respective pair of two and leads via the capacitance (20b) of the second converter module (10b) of the respective pair of two, is below a clock frequency fciock of the first converter module (10a) and / or the second converter module (10b) of the respective pair of two.

3. Power converter (30) according to claim 2, characterized in that in at least one of the plurality of pairs of converter modules (10a-10d) the resonance frequency fRes of the current path (50) is at least a factor of 2, preferably at least a factor of 3, below a clock frequency fciock of the first converter module (10a) of the respective pair of two and / or the second converter module (10b) of the respective pair of two.

4. Power converter (30) according to one of the preceding claims, characterized in that in at least one of the plurality of pairs of converter modules (10a-10d), a clock frequency fciock of the first converter module (10a) of the respective pair of two, optionally also a clock frequency fciock of the second converter module (10b) of the respective pair of two, is at least 5 kHz, preferably at least 8 kHz, optionally at least 11 kHz.

5. Power converter (30) according to one of the preceding claims, characterized in that in at least one of the plurality of pairs of converter modules (10a-10d), the current path (50) between the capacitance (20a) of the first converter module (10a) of the respective pair of two and the capacitance (20b) of the second converter module (10b) of the respective pair of two has exactly one decoupling inductance (40a, 40b, 40e).

6. Power converter (30) according to one of claims 1 to 4, characterized in that in at least one of the plurality of pairs of converter modules (10a-10d), the current path (50) between the capacitance (20a) of the first converter module (10a) of the respective pair of two and the capacitance (20b) of the second converter module (10b) of the respective pair of two has a plurality of decoupling inductances (40a, 40b, 40e).

7. The power converter (30) of claim 6, wherein a first number of the plurality of decoupling inductors (40a) is associated with the first converter module (10a) of the respective pair of two and, in combination, has a first inductance value, wherein a second number of the plurality of decoupling inductors (40b) is associated with the second converter module (10b) of the respective pair of two and, in combination, has a second inductance value, and wherein the first inductance value is different from the second inductance value.

8. Power converter (30) according to one of the preceding claims, characterized in that in at least one of the plurality of pairs of Converter modules (10a-10d) each having exactly one decoupling inductance (40a, 40b, 40e) or at least one of the plurality of decoupling inductances (40a - 40e) each having a core (41) enclosing a busbar (51) of the DC bus (19).

9. Power converter (30) according to one of the preceding claims, characterized in that in at least one of the plurality of pairs of converter modules (10a-10d), one or more decoupling inductors (40a - 40d) of the at least one decoupling inductor (40a - 40d), which is / are arranged in the current path (50) between the capacitance (20a) of the first converter module (10a) of the respective pair of two and the capacitance (20b) of the second converter module (10b) of the respective pair of two, is / are arranged in the housing (16) of the first converter module (10a) or in the housing (16) of the second converter module (10b) of the respective pair of two.

10. Power converter (30) according to claim 9, characterized in that each of the converter modules (10a, 10b) of the plurality of pairs of two comprises one decoupling inductance (40a - 40d) or several decoupling inductances (40a - 40d).

11. Power converter (30) according to one of the preceding claims, characterized in that in at least one pair of converter modules (10a-10d), one or more decoupling inductors (40a - 40d) of the at least one decoupling inductor (40a - 40d), which is / are arranged in the current path (50) between the capacitance (20a) of the first converter module (10a) of the at least one pair of two and the capacitance (20b) of the second converter module (10b) of the at least one pair of two, is / are arranged outside the housings (16) of the converter modules (10a, 10b) of the at least one pair of two, in particular on the DC bus (19).

12. Power converter (30) according to one of the preceding claims, characterized in that one of the converter modules (10a-10d) comprises a DC / DC converter, in particular a bidirectional DC / DC converter.

13. Power converter (30) according to one of the preceding claims, characterized in that one of the converter modules (10a-10d) comprises a DC / AC converter, in particular a bidirectional DC / AC converter.

14. Power converter according to one of claims 12 and 13, characterized in that the DC / DC converter and / or the DC / AC converter each has a 2-level topology.

15. Power converter (30) according to one of the preceding claims, further comprising at least one connection module for connecting at least one element from a group formed by a battery, an electrolyzer, an EV charger and a fuel cell, wherein the connection module is connected to one of the converter modules (10a-10d) or directly to the DC bus (19).

16. Power converter (30) according to one of the preceding claims, characterized in that for each pair of converter modules (10a-10d), at least one decoupling inductance (40a-40e) is arranged in a current path (50) leading via the DC bus (19) between the capacitances (20a-20d) of the converter modules (12a-12d) assigned to the respective pair of converter modules.

17. Power converter (30) according to one of the preceding claims as far as related back to claim 6, wherein a first number of the plurality of decoupling inductances (40a) is assigned to the first converter module (10a) of the respective pair of two and in their combination have a first inductance value, wherein a second number of the plurality of decoupling inductances (40b) is assigned to the second converter module (10b) of the respective pair of two and in their combination have a second inductance value, wherein the first inductance value and / or the second inductance value is / are selected such that a resonance frequency fRes of a second current path emanating from the capacitance (20a, 20b) of the converter module (10a, 10b) assigned to the respective inductance value and is created by the DC intermediate circuit connections (18a, 18b) of the respective converter module (10a, 10b) being connected via the respective Converter module (10a,10b) a respective assigned number of decoupling inductors (40a, 40b) are short-circuited, is below a clock frequency fciock of the converter module (10a, 10b) assigned to the respective inductance value, 18. Device for power conversion with a plurality of power converters (30) according to one of the preceding claims, which are connected in parallel to one another to a common energy sink and / or a common energy source.

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