Method and system for increasing the lifetime of a converter switch

Abstract

The present application relates to a method for increasing the service life of a converter switch (Q1, Q2, Q3, Q4) in a system (10), which system comprises an energy source (PV) which is jointly attached to a DC bus (DC+, DC-) with a DC / DC converter (12) which comprises the converter switch (Q1, Q2, Q3, Q4). The method comprises the following steps: determining a system state in which electrical power of the energy source (PV) is available for use, for which electrical power no transmission via the DC / DC converter (12) is provided and no output to a further participant of the DC bus (DC+, DC-) is provided; operating the DC / DC converter (12) during the determined system state in such a way that a loss power is generated in the DC / DC converter (12) without transmitting power via the DC / DC converter (12). Furthermore, the present application relates to a system (10) with an energy source (PV) and a DC / DC converter (12) which has a converter switch (Q1, Q2, Q3, Q4), and to an energy generation facility with such a system.

Description

Technical Field

[0001] The present invention relates to a method for increasing the service life of a converter switch and a system having a generator and a DC / DC converter having a converter switch. Background Technology

[0002] The following power converters are used in energy generation facilities, especially PV facilities (PV: Photovoltaic): These power converters may have clockwise controlled semiconductor switches, so-called converter switches. For such semiconductor switches, temperature fluctuations lead to a reduced lifespan.

[0003] EP2600510A1 describes a method in which an electric power converter is manipulated such that, in addition to the output current, a current is generated that does not affect the output current and simultaneously heats the converter switch to a predetermined target temperature. Summary of the Invention

[0004] This application is based on the objective of increasing the lifespan of converter switches.

[0005] This task is solved by a method having the features of claim 1, a system having the features of independent claim 8, and an energy generation facility according to claim 14. Preferred embodiments are given in the dependent claims.

[0006] In the system, an energy source, particularly a generator, is connected to a DC bus along with a DC converter. The energy source is, for example, a PV generator. The DC / DC converter has converter switches in the form of semiconductor switches. For example, the DC / DC converter is configured to transfer electrical power from the DC bus to a DC energy storage device, such as a battery, or vice versa. For example, a DC memory may be configured to receive and store electrical energy generated by the energy source. A method for increasing the lifespan of the converter switches in a DC / DC converter includes the following steps:

[0007] The following system state is defined: in which the electrical power of the energy source is available for use, and for the electrical power, there is no transmission via the DC / DC converter and no output to other participants on the DC bus.

[0008] The DC / DC converter is operated in such a way during the defined system state that power loss occurs in the DC / DC converter, rather than power is transferred through the DC / DC converter.

[0009] That is, the determined system state involves a system state in which no electrical energy is configured to be transferred to the DC memory via a DC / DC converter. This could be, for example, if the battery is fully charged. Another participant in the DC bus could be an inverter configured to transfer electrical energy from the DC bus to an AC network. For example, the AC network could be an AC supply network. Another participant in the DC bus could be a separate DC load. Typically, the DC bus has two conductors at different potentials, and a DC bus voltage is applied between the conductors.

[0010] That is, this method enables the DC / DC converter to operate during a defined system state such that power loss occurs within the DC / DC converter, for example, through loop current flowing within the DC / DC converter, without power transfer via the DC / DC converter, and the converter switch is held in a heated state relative to the inactive state. In this application, DC (Direct Current) represents direct current / direct voltage. In this application, AC (Alternating Current) represents alternating current / alternating voltage.

[0011] For example, a system state (in which the electrical power of the energy source is available for use, with no transmission via a DC / DC converter and no output to other participants in the DC bus) can be a system state where the battery is fully charged, there is no feed-in of the currently available power to the AC network via an inverter attached to the DC bus, or at least no full feed-in, and simultaneously no other participants in the DC bus, such as other DC loads, are available to receive electrical energy. In such a state, the electrical energy of the energy source can be used unused and can be used in the method according to the invention without disadvantage.

[0012] During favorable weather periods for the PV facility, such as on a sunny day (from afternoon to evening), the batteries have already been charged earlier in the day by the PV generator, and the PV generator can generate more electrical energy than is set to supply the DC bus due to the ever-present sunlight. Here, the method enables the determination of such operating conditions and simultaneously enables the operation of the DC / DC converter, where energy is not transferred via the DC / DC converter (e.g., in the direction of the DC memory), but rather the DC / DC converter only receives energy to keep the converter switch warm through the internal current flow within the DC / DC converter. This warming is achieved through the current flow within the DC / DC converter and the resulting power loss in the form of heat.

[0013] In one embodiment, the DC / DC converter includes a first half-bridge having a first switch and a second switch connected in series. Preferably, the first and second switches are implemented as semiconductor switches. The first and second switches are converter switches of the DC / DC converter. The first half-bridge is arranged between attachment terminals on the output side of the DC / DC converter. For example, the attachment terminals on the output side are configured for attachment to a DC memory. Furthermore, the DC / DC converter has a second half-bridge having a third switch and a fourth switch connected in series. The third and fourth switches are converter switches of the DC / DC converter and are preferably implemented as semiconductor switches. The second half-bridge is arranged between attachment terminals on the input side of the DC / DC converter, attached to the DC bus. The center attachment terminals of the first and second half-bridges are interconnected via a drossel. The center attachment terminals of the first and second half-bridges are respectively arranged between the two switches. The drossel can be considered an electrical drossel, i.e., implemented as an inductor. The first and fourth switches have a common attachment terminal, which can be connected, for example, to one of the conductors of the DC bus.

[0014] Now, in one embodiment of this method, for such a DC / DC converter, during the defined system state, the second switch is permanently closed and the first switch is permanently open. This effectively prevents power flow through the DC / DC converter. During the defined system state, the third switch is subjected to clockwise control. Clockwise control means manipulating the switch such that it is sometimes open and sometimes closed.

[0015] This control of the switch allows electrical energy to be drawn from the DC network and flow within the DC / DC converter as a current that generates power loss. The flowing current generates power loss, which heats the switch. Here, with the third switch closed, the current flows through the third and second switches and via the choke. With the third switch open, the current flows through the second and fourth switches. Depending on the switching state of the fourth switch, the current flows either through a freewheeling diode arranged in parallel with the fourth switch or through the closed fourth switch.

[0016] In one implementation, to operate the DC / DC converter, the third and fourth switches are tactilely controlled during a defined operating state. In another implementation, the third and fourth switches are tactilely controlled in a complementary manner. Complementary tactile control means that the fourth switch is open during the period when the third switch is closed, and vice versa. It is also possible that the fourth switch is kept open during the defined system state, since the desired current flow for heating the converter switch can also be achieved via the freewheeling diode of the fourth switch.

[0017] In one embodiment of this method, the tactile control of the third switch is performed with a duty cycle such that the allowable nominal current (Nennstrom) of the DC / DC converter is not exceeded. For example, the third switch is operated in a current-regulating manner, and for instance, the third switch is opened if a turn-off threshold below the nominal current is exceeded, and closed again if the current is below the turn-on threshold. In this method, the current flowing through the DC / DC converter is determined by the duty cycle of the third switch, since power is only drawn from the DC network when the third switch is closed. However, when the fourth switch is tactilely controlled in a complementary manner, the fourth switch is tactilely controlled with a corresponding duty cycle in a manner complementary to that of the third switch.

[0018] In one embodiment of the method, the cycle control of the third switch is performed with a duty cycle that is related to the temperature measured in the DC / DC converter. For example, the duty cycle can be selected such that a predetermined target temperature is achieved in the DC / DC converter. Alternatively, if the temperature in the DC / DC converter is low, the current flow is increased accordingly in a defined system state to still achieve the desired heating of the converter switch. For example, the aforementioned turn-off threshold and / or turn-on threshold can be determined as a function of the measured temperature. Here, the duty cycle can also, of course, be related to other influencing factors, such as the DC bus voltage.

[0019] Instead of measuring the temperature within the DC / DC converter, or in addition to the temperature measured within the DC / DC converter, the cycle control of the third switch or the power loss generated by the method according to the invention can be determined based on the temperature detected outside the DC / DC converter. For this purpose, determining the system state includes detecting the temperature of a component in which the DC / DC converter is in thermal contact, but which is not itself part of the DC / DC converter, and whose temperature should not drop below a predetermined value. In one embodiment, this could be, for example, a battery that is charged and discharged via the DC / DC converter. Commonly used types of batteries have the characteristic that they cannot or should not be charged below a critical charging temperature, even though they can be discharged at such low temperatures. Here, the resulting power loss can be used to raise the temperature of the battery in thermal contact with the DC / DC converter or to maintain that temperature above the aforementioned temperature. Here, this power loss can also be obtained entirely or partially from the battery, and for this purpose, the fourth switch can be cycle-controlled with a suitable duty cycle.

[0020] In an advantageous embodiment of this method, the system state is determined based on the voltage of the DC bus. The system state to be determined (in a system state in which no acquisition is performed via another participant on the DC bus and no power transfer is performed via the DC / DC converter) can be obtained from the voltage on the DC bus. The voltage on the DC bus is determined, for example, by an inverter on the DC bus, another load on the DC bus, and / or an energy source.

[0021] In another embodiment of the method, a determination of the system state is displayed to the DC / DC converter via an input signal. This embodiment can be applied, for example, if the system state is determined by a control device and then transmitted to the DC / DC converter, in which case the control unit of the DC / DC converter operates the converter switch according to the described method. Here, the control device of the DC / DC converter can be understood as part of the control device of the system. This embodiment can also be applied, for example, if the system state is determined based on voltage measurements on the DC bus and transmitted to the DC / DC converter, in which case the control unit of the DC / DC converter then operates the converter switch according to the method. The control device can be a computing unit having at least one processor, memory, and communication interface.

[0022] The system includes a power source and a DC / DC converter. The power source and DC / DC converter are each attached to a DC bus. The DC / DC converter has a converter switch that can be operated to open and close for power conversion via the DC / DC converter. A control device is also provided, configured and set to implement one of the methods described above. This control device may be located, for example, within the DC / DC converter and / or on other computing units of the system. The control device may also be distributed, for example, on one or more computing units of the DC / DC converter and the system, or located remotely from the system. The control device may also be additionally designed to operate other participants in the DC / DC converter and / or the DC bus.

[0023] In one embodiment of the system, the first switch is thermally coupled to at least one of the second, third, and / or fourth switches. In this method, a current generated to produce power loss flows through the second, third, and fourth switches. That is, these switches can be heated by the power loss. Through the coupling of the first switch with the second, third, and / or fourth switches, the first switch can also be heated to increase its service life.

[0024] In one embodiment, the first switch is thermally coupled to a choke that serves as a heat storage device. In this embodiment of the method, the current used to generate power loss flows through the choke of the DC / DC converter. To heat the first switch, it is thermally coupled to the choke, which acts as a heat storage device. This also achieves heating of the first switch.

[0025] In one embodiment, the converter switch and the choke are thermally coupled to a common cooling body. This common cooling body ensures uniform heat exchange between the converter switch and the choke, thus enabling uniform heating of the converter switch.

[0026] In one implementation of this system, the energy source is a PV generator. This method is particularly advantageous for systems with PV generators because solar energy generated by the PV generator can exist if the system is determined to be in a state where network feeding or full network feeding of power generated by the energy source is not possible or expected, and the batteries attached to the system are fully charged or not set for further charging. This solar energy can then be used to heat the converter switch and thus extend the lifespan of the converter switch.

[0027] Similarly, it is also possible to continuously or occasionally check whether the following condition is still met during the implementation of the method according to the invention: there are no other applications providing power for heating the DC / DC converter. If this is not the case, heating can be stopped or the power used for heating can be reduced.

[0028] In one embodiment of the system, the DC / DC converter has first and second sub-converters. The two sub-converters are each connected to the DC bus at their input sides. Given the system configuration, the two sub-converters are interconnected at their output sides via optional coupling switches, such that power flows of equal magnitude but opposite magnitude are transmitted through the two sub-converters. However, the sub-converters can also be permanently interconnected at their output sides without coupling switches. Due to the equal but opposite power flows, power loss occurs in the sub-converters via converter switches, thus keeping the converter switches in a heated state. This occurs without total power transmission through the DC / DC converter, i.e., without outputting electrical power via the output attachments of the DC / DC converter. Advantageously, the two sub-converters are operated in parallel while transmitting power via the DC / DC converter. This means that, in order to transmit total power via the DC / DC converter, the two sub-converters are attached to the DC bus at their input sides, and the two sub-converters are attached to the output attachments of the DC / DC converter at their output sides. Then, in the determined system state, the output sides of the sub-converters are connected via coupling switches such that the sub-converters transmit power flows of the same magnitude but opposite to each other. Alternatively, the sub-converters can be permanently connected in parallel at their output sides.

[0029] Furthermore, this application relates to an energy generation facility having one of the systems described above and an inverter attached to a DC bus for feeding power generated by an energy source into an AC current network. Preferably, the AC current network is an AC supply network. Attached Figure Description

[0030] The present application will now be illustrated in more detail by way of example with reference to the accompanying drawings. The drawings show:

[0031] Figure 1 A schematic diagram illustrating one implementation of a system having an energy source and a DC / DC converter;

[0032] Figure 2 A method for increasing the lifespan of converter switches is illustrated schematically.

[0033] Figure 3A schematic diagram illustrating one implementation of a system is shown, which includes an energy source and a DC / DC converter.

[0034] In the accompanying drawings, the same reference numerals are used for the same or similar elements. Detailed Implementation

[0035] exist Figure 1 An embodiment of system 10 is schematically shown, comprising a DC bus DC+, DC-, an energy source PV with voltage U_PV, and a DC / DC converter 12 attached to the DC bus. The DC bus DC+, DC- has two conductors, DC+ and DC-, located at different potentials. A DC bus voltage U_Bus is applied between the two conductors of the DC bus DC+, DC-. A DC / DC converter 12 may be attached to the DC bus DC+, DC-. Figure 1 Other DC bus participants not shown. These other DC bus participants may be, for example, inverters configured to feed electrical power generated by an energy source PV into the AC supply network.

[0036] DC / DC converter 12 is configured to obtain electrical power from DC buses DC+ and DC-, convert the electrical power, and transfer the electrical power, for example, to a DC memory Bat attached to the output attachments 12A+ and 12A- of the DC bus, so that the power can be provided to the DC bus again at a later time. The DC memory Bat has a voltage U_Bat between its attachments. The DC / DC converter has a series connection of first and second semiconductor switches Q1 and Q2 between its output attachments 12A+ and 12A-. A capacitor is arranged in parallel with the series connection of the first and second semiconductor switches Q1 and Q2. DC / DC converter 12 has a series connection of third and fourth semiconductor switches Q3 and Q4 between its input attachments 12E+ and 12E-. A capacitor is arranged in parallel with the series connection of the third and fourth semiconductor switches Q3 and Q4 between the input attachments 12E+ and 12E- of the DC / DC converter. Semiconductor switches Q1, Q2, Q3, and Q4 correspond to the converter switches of the DC / DC converter 12 and may have inherent freewheeling diodes, or the freewheeling diodes may be connected in reverse parallel with the semiconductor switches. The two series connections of switches Q1, Q2 and Q3, Q4 correspond to the two half-bridges of the DC / DC converter 12. The two half-bridges are connected at the center between the two switches via a choke D. A current meter A is arranged in series with the choke D. The second switch Q2 and the fourth switch Q4 are interconnected, for example, via the conductor DC- of the DC bus.

[0037] Figure 2A method for increasing the lifespan of converter switches Q1, Q2, Q3, and Q4 is illustrated schematically. Figure 1 or Figure 3 In the system 10 shown (which has a DC / DC converter 12 and an energy source PV, both attached to DC buses DC+ and DC-), electrical energy generated by the energy source PV can be fed into the DC buses DC+ and DC-. The energy source PV has a PV voltage U_PV existing between its attachment terminals. The DC / DC converter 12 can obtain electrical power from the DC buses DC+ and DC- and can output this electrical power, for example, to a DC memory Bat via its output attachment terminals 12A+ and 12A-.

[0038] In this method, a system state is determined in step S1 where the electrical power of the energy source PV is used by the DC buses DC+ and DC-. This system state is determined if there is no transmission of electrical power via the DC / DC converter 12 and no output of electrical power to other participants in the DC buses DC+ and DC-. Other participants in the DC buses DC+ and DC- can be, for example, other DC loads (not shown) and / or an inverter (not shown). The inverter can be configured to, for example, feed electrical power into the AC supply network. Now, a system state can be generated where the energy source PV can generate electrical power, but there is no transmission of the generated power via the inverter, or at least no complete transmission. This situation can be caused, for example, by management reasons. It is also possible that there is no transmission to the DC memory Bat, for example, because the DC memory Bat is already full. This is an example of a system state determined in step S1.

[0039] Now, in step S2, after determining the system state, the DC / DC converter 12 is operated such that power loss occurs within the DC / DC converter 12 without power transmission through it. This results in the converter switches Q1, Q2, Q3, and Q4 of the DC / DC converter 12 being held in a heated state relative to their inactive state. This heated state is caused by the switching process and by the current flowing through the DC / DC converter 12 and the resulting power loss.

[0040] The system state that can be determined in step S1 can be achieved, for example, by measuring the voltage U_Bus of the DC bus DC+ and DC-. To operate the DC / DC converter 12 in step S2, the first switch Q1 can now be permanently open. The second switch Q2 can be permanently closed. The third switch Q3 is clock-controlled. The fourth switch Q4 can, for example, be permanently open. It is also possible that if the third switch Q3 is open, the fourth switch Q4 is closed. That is, the third and fourth switches Q3 and Q4 can be clock-controlled in a complementary manner. If the fourth switch Q4 opens during the time the third switch Q3 is closed, the third and fourth switches Q3 and Q4 can also be clock-controlled in a less complementary manner. A possible clock-control of the third switch Q3 is an on-time of 30 μs at a clock frequency of 100 Hz.

[0041] In step S2, with the third switch Q3 closed, current flows through the third switch Q3 via the choke D and the second switch Q2. Then, if the third switch Q3 is opened, the current can continue to flow back to the second switch Q2 via the choke D through the switch Q4. Here, depending on the switch type, the current flow through the fourth switch Q4 can be achieved either through a freewheeling diode arranged in reverse parallel with or inherent to the fourth switch Q4, or, if the switch Q4 is closed, directly through the closed switch Q4. Thus, current flows through the third, second, and fourth switches Q3, Q2, and Q4, but the current does not flow through the output terminals 12A+ and 12A- of the DC / DC converter 12. This current flow generates power loss, which heats the converter switches Q1, Q2, Q3, and Q4. Since there is no direct current flow through the first switch Q1, the first switch can be heated, for example, via a choke D that serves as a common heat storage unit or a common cooling body having the choke D and switches Q2, Q4, and Q3. However, it is also conceivable that the converter switch Q1 is mounted together with the converter switch Q2 in a module and is thus thermally coupled to and heated by the converter switch Q2.

[0042] exist Figure 3In the system 10 shown, the DC / DC converter 12 has two sub-converters 14 and 16. The first sub-converter 14 and the second sub-converter 16 are connected to the DC bus DC+ and DC- respectively at their input terminals. The input terminals 14E+ of the first sub-converter 14 and 16E+ of the second sub-converter 16 are connected to the input terminal 12E+ of the DC / DC converter 12. The input terminals 14E- of the first sub-converter 14 and 16E- of the second sub-converter 16 are connected to the input terminal 12E- of the DC / DC converter 12. Here, the two sub-converters 14 and 16 also correspond to the DC / DC converter. During normal operation, i.e., when the DC / DC converter 12 draws power from the DC bus DC+ and DC- and transfers it to the DC memory Bat, the sub-converters 14 and 16 are connected in parallel at their input terminals, as shown below. Figure 3 As shown in the diagram. On the output side, the DC / DC converter 12 has separate output attachment terminals 12A+ and 12A- for each sub-converter 14, 16, to which the battery can be attached respectively. Optionally, a coupling switch 18 may be provided between output attachment terminals 14A+ and 16A+ and / or between output attachment terminals 14A- and 16A- to enable temporary, parallel connection of sub-converters 14, 16 on the output side, or to separate these sub-converters from each other on the output side using a single-pole or all-pole connection. However, it is also conceivable that the output attachment terminals 12A+ and 12A- of the sub-converters are connected to the same battery, thereby permanently connecting sub-converters 14, 16 in parallel on the output side.

[0043] In step S2 of the method, if the sub-converters were not originally permanently connected in parallel, they are now connected in parallel on the output side via an optional coupling switch. The electrical power output by one of the sub-converters 14 and 16 is the same in magnitude, but is received by the other sub-converters, so that the power is not exchanged via the output terminals 12A+ and 12A- of the DC / DC converter 12. Although power is received via the input terminals 12E+ and 12E- in state S2, further power flow operates entirely within the DC / DC converter 12 and does not exchange power via the output terminals 12A+ and 12A-.

[0044] List of reference numerals

[0045] 10 System

[0046] 12 DC / DC converters

[0047] Output terminals of 12A+ and 12A- DC / DC converters

[0048] Input terminals of 12E+ and 12E- DC / DC converters

[0049] 14 First Sub-converter

[0050] 14A+, 14A- Output attachments of the first sub-converter

[0051] Input attachments of the 14E+ and 14E- first sub-converters

[0052] 16 Second Sub-converter

[0053] 16A+, 16A- Output attachment terminals of the second sub-converter

[0054] Input attachment terminals of the 16E+ and 16E- second sub-converters

[0055] 18. Coupling switch

[0056] A current meter

[0057] DC+, DC- DC bus

[0058] U_Bus DC bus voltage

[0059] Bat Battery

[0060] U_Bat battery voltage

[0061] PV energy source

[0062] U_PV PV voltage

[0063] D Choke

[0064] Q1, Q2, Q3, Q4 converter switches

Claims

1. A method for increasing the service life of converter switches (Q1, Q2, Q3, Q4) in a system (10), said system including a generator (PV) connected together with a DC / DC converter (12) on a DC bus (DC+, DC-), said DC / DC converter including said converter switches (Q1, Q2, Q3, Q4), wherein, The method includes the following steps: The following system state is determined: in this system state, the electrical power of the generator (PV) is available for use, and for this electrical power, there is no transmission via the DC / DC converter (12) and no output to any other participant in the DC bus (DC+, DC-). The DC / DC converter (12) is operated in such a way that power loss occurs in the DC / DC converter (12) without power transmission via the DC / DC converter (12) during the defined system state.

2. The method according to claim 1, wherein, The DC / DC converter (12) includes a first half-bridge and a second half-bridge. The first half-bridge has a first switch (Q1) and a second switch (Q2) connected in series. The first switch and the second switch are arranged between the attachment terminals (12A+, 12A-) on the output side of the DC / DC converter (12). The second half-bridge has a third switch (Q3) and a fourth switch (Q4) connected in series. The third switch and the fourth switch are arranged between the attachment terminals (12E+, 12E-) on the input side of the DC / DC converter (12) attached to the DC bus (DC+, DC-). The center attachment terminals of the first half-bridge and the second half-bridge are interconnected via a choke (D), and the second switch (Q2) and the fourth switch (Q4) share a common attachment terminal. During the defined system state, the DC / DC converter (12) permanently closes the second switch (Q2) and permanently opens the first switch (Q1), while the third switch (Q3) is controlled by a clock.

3. The method according to claim 2, wherein, The third switch (Q3) and the fourth switch (Q4) are controlled by a clock cycle.

4. The method according to claim 2 or 3, wherein, The cycle control of the third switch (Q3) is performed with a duty cycle such that it does not exceed the allowable nominal current of the DC / DC converter (12).

5. The method according to claim 2 or 3, wherein, The cycle control of the third switch (Q3) is performed with the following duty cycle: the duty cycle is selected such that the temperature measured in the DC / DC converter (12) is adjusted to the target temperature.

6. The method according to any one of claims 1 to 3, wherein, The system state is determined based on the voltage of the DC bus (DC+, DC-).

7. The method according to any one of claims 1 to 3, wherein, The system state is determined by the input signal to the DC / DC converter (12).

8. A system (10) comprising a generator (PV) and a DC / DC converter (12) comprising converter switches (Q1, Q2, Q3, Q4), the generator and the DC / DC converter being commonly attached to a DC bus (DC+, DC-), the system comprising a control device configured and set to perform the method according to any one of claims 1 to 7.

9. The system according to claim 8, wherein, The DC / DC converter (12) includes a first half-bridge and a second half-bridge. The first half-bridge has a first switch (Q1) and a second switch (Q2) connected in series. The first switch and the second switch are arranged between the attachment terminals (12A+, 12A-) on the output side of the DC / DC converter (12). The second half-bridge has a third switch (Q3) and a fourth switch (Q4) connected in series. The third switch and the fourth switch are arranged between the attachment terminals (12E+, 12E-) on the input side of the DC / DC converter (12) attached to the DC bus (DC+, DC-). The center attachment terminals of the first half-bridge and the second half-bridge are interconnected via a choke (D), and the second switch (Q2) and the fourth switch (Q4) have a common attachment terminal.

10. The system according to claim 9, wherein, The first switch (Q1) is thermally coupled to at least one of the second, third and / or fourth switches (Q2, Q3, Q4).

11. The system according to claim 9 or 10, wherein, The first switch (Q1) is thermally coupled to the choke (D) which serves as a heat storage unit.

12. The system according to claim 9 or 10, wherein, The converter switches (Q1, Q2, Q3, Q4) and the choke (D) are thermally coupled to a common cooling body.

13. The system according to any one of claims 8 to 10, wherein, The generator (PV) is a PV generator (PV).

14. The system according to any one of claims 8 to 10, wherein, The DC / DC converter (12) includes a first sub-converter (14) and a second sub-converter (16), the first sub-converter and the second sub-converter being connected to the DC bus (DC+, DC-) respectively on the input side (14E+, 14E-, 16E+, 16E-), and the first sub-converter and the second sub-converter being configured to transmit power flows that are the same in magnitude but opposite to each other in a state of parallel connection on the output side when the system state is determined, such that the converter switches (Q1, Q2, Q3, Q4) of the first and second sub-converters (14, 16) are kept in a heated state without total power transmission of the DC / DC converter (12).

15. The system according to claim 14, wherein, The system is configured to achieve a parallel connection on the output side via a coupling switch (18) arranged between the output attachments (14A+, 14A-) of the first sub-converter (14) and the output attachments (16A+, 16A-) of the second sub-converter (16).

16. An energy generation facility comprising a system (10) according to any one of claims 8 to 15 and an inverter attached to a DC bus (DC+, DC-), the inverter being used to feed power generated by a generator (PV) into an alternating current network.

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