Method and circuit arrangement for detecting a characteristic curve of a PV generator

Abstract

The present application relates to a method for detecting a characteristic curve of a PV generator (2) to be scanned among a plurality of PV generators (2) in an energy generation system (10), wherein each of the PV generators (2) is connected on the output side via an associated DC / DC converter (12) in parallel or as a series circuit to an intermediate circuit (14) as an input element of a DC / AC converter (20). The method comprises: a) reducing the cumulative output power (KA) of the DC / DC converter (12) of the PV generator (2) to be scanned, which is not configured for detecting the characteristic curve, based on the expected maximum output power (Pscan) of the DC / DC converter (12) connected to the PV generator (2) to be scanned, so as to ensure that the sum of the cumulative output power (KA) and the expected maximum power (Pscan) does not exceed the nominal power (PN) of the DC / AC converter (20); b) subsequently detecting the characteristic curve of the PV generator (2) to be scanned; c) wherein, during the detection of the characteristic curve, the voltage (UZK) of the intermediate circuit (14) and the current of the series circuit of the DC / DC converter (12) are kept constant by the DC / AC converter (20). The application also relates to a circuit arrangement for detecting the characteristic curve of the PV generator (2) to be scanned.

Description

Technical Field

[0001] The present application relates to a method and a circuit arrangement for detecting a characteristic curve of a photovoltaic generator (PV generator for short), as well as an energy generation system having such a circuit arrangement. Detecting the characteristic curve of a PV generator may also be referred to as scanning the characteristic curve of the PV generator or scanning the PV generator. Background Art

[0002] In energy generation plants, PV generators can be connected to a power converter via a DC / DC converter (direct current voltage converter). A PV generator can include multiple PV strings, which can be interconnected in series and / or in parallel. A PV string can, in turn, include multiple PV modules. The power converter can, in particular, be a DC / AC converter (inverter), which is connected to an AC power grid, in particular an AC supply network, in order to exchange electrical power with the AC grid and, in particular, to feed electrical power into the AC grid.

[0003] PV generators have a voltage-current characteristic curve (UI characteristic curve for short), which represents the dependence of the DC current generated by the PV generator on the PV voltage present at the PV generator. It may be desirable to detect the UI characteristic curve of the PV generator during operation. In particular, in derated energy generation systems, as is known from WO 2014 / 118059 A1 and US 2020 / 0220357 A1, when the UI characteristic curves of individual DC / DC converters of the energy generation system deviate, the resulting fluctuations in the total power are compensated by compensating control of one or more other DC / DC converters of the energy generation system, thereby keeping the total power as constant as possible. This compensating control places increased demands on the regulation and communication of the energy generation system.

[0004] For example, US Pat. No. 11171489 B2 describes a method for detecting the UI characteristic curve of a PV generator in an energy generation system, wherein converters not involved in detecting the UI characteristic curve compensate for power variations of the converter that detects the UI characteristic curve. In an extreme case, it is also disclosed that the power of the converter not involved in the detection is reduced to zero during the characteristic curve detection. The present application is based on the object of providing an improved method for detecting the characteristic curve of a PV generator. Furthermore, a circuit arrangement for detecting the characteristic curve of a PV generator is to be described. Summary of the Invention

[0005] This object is achieved by a method according to the invention for detecting a characteristic curve of a PV generator to be scanned among a plurality of PV generators in an energy generation system, or by a further method according to the invention for detecting a characteristic curve of a PV generator to be scanned among a plurality of PV generators in an energy generation system. This object is further achieved by a circuit arrangement according to the invention for detecting a characteristic curve of a PV generator to be scanned among a plurality of PV generators in an energy generation system, or by a further circuit arrangement according to the invention for detecting a characteristic curve of a PV generator to be scanned among a plurality of PV generators in an energy generation system. Preferred embodiments are described below.

[0006] In an energy generation system with multiple PV generators, each PV generator is connected to a DC / AC converter via an associated DC / DC converter. The DC / DC converter is connected on the output side to an intermediate circuit, which serves as the input element of the DC / AC converter. A PV generator has at least one PV string, preferably multiple PV strings. The multiple PV strings of a PV generator can be interconnected in parallel, in series, or in a combination of series and parallel connections. Accordingly, the DC / DC converter can be connected on its input side to one PV string or to multiple PV strings, which can be connected to the DC / DC converter in parallel, in series, or in a combination thereof.

[0007] The PV generators can be connected in parallel via their respective associated DC / DC converters with the intermediate circuit as the input element of the DC / AC converter. Alternatively, the PV generators can be connected in series via their respective associated DC / DC converters with the intermediate circuit as the input element of the DC / AC converter.

[0008] The characteristic curve of a PV generator can be detected by performing a so-called scan, which can also be referred to as scanning the PV generator. During scanning of the PV generator, for example, different voltage values ​​are set at the output of the PV generator via an associated DC / DC converter, and the current supplied by the PV generator is measured at the set voltage values. Alternatively, the current flowing through the PV generator can be set and the resulting voltage measured. By plotting the measured current values ​​against the set voltage values, the UI characteristic curve of the PV generator can be detected.

[0009] A method for detecting a characteristic curve of a PV generator to be scanned among a plurality of PV generators in such an energy generation system comprises:

[0010] a) Based on the maximum output power expected from the DC / DC converter connected to the PV generator to be scanned during detection of the characteristic curve of the PV generator to be scanned, reducing the cumulative output power of the DC / DC converter whose associated PV generator is not configured for detecting the characteristic curve, so as to ensure that the sum of the reduced cumulative output power and the expected maximum power of the PV generator to be scanned does not exceed the rated power of the DC / AC converter.

[0011] b) The characteristic curve of the PV generator to be scanned is then detected.

[0012] In an energy generation plant having a DC / DC converter connected in parallel at the input of the DC / AC converter, the method further comprises:

[0013] c) During the characteristic curve detection: The voltage of the intermediate circuit is kept constant by the DC / AC converter. The voltage of the intermediate circuit corresponds to the voltage at the output of the DC / DC converter. The value of the intermediate circuit voltage in this step preferably corresponds to a value greater than or equal to the idling voltage of the PV generator to be scanned, which is ensured when a step-up chopper is used as the DC / DC converter. This constant maintenance is preferably achieved by controlling clocked semiconductor switches of the DC / AC converter.

[0014] In an energy generation plant in which a DC / DC converter is connected in series with an intermediate circuit at the input of a DC / AC converter, the method comprises:

[0015] c1) During the detection of the characteristic curve: the current flowing through the series circuit of the DC / DC converter is kept constant by the DC / AC converter. This is preferably achieved by actuating clocked semiconductor switches of the DC / AC converter.

[0016] The method according to the invention is characterized by its ease of implementation and the minimal loss of producible power caused by the scanning. At the same time, overloading of the DC / AC converter is avoided, which is particularly dangerous in systems where the possible nominal power of the installed PV generator is significantly higher than the nominal power of the DC / AC converter, so that these systems are regularly operated at the nominal power of the DC / AC converter, and therefore also immediately before the method according to the invention is carried out.

[0017] When scanning one of the PV generators, the output power of the PV generator being scanned changes because different points of the UI characteristic curve are traversed, each with a different output power of the PV generator being scanned. The changing output power of the PV generator being scanned has a maximum power at the maximum power point (MPP) on the UI characteristic curve of the PV generator being scanned. Overall, the sum of the output power of the PV generator being scanned and the cumulative output power of the remaining PV generators should not exceed the rated power of the DC / AC converter to avoid damage to the DC / AC converter and to ensure network compatibility with the AC power grid.

[0018] The expected maximum power of the PV generators participating in the scan can be determined using this method before reducing the cumulative output power. The expected maximum power can be based on empirical values ​​(e.g., from previous scans or other known maximum powers of PV generators not participating in the scan) and can also depend on or be determined from temperature, sunlight exposure, and similar environmental factors.

[0019] This is achieved by the method described above because the cumulative output power of the PV generators not participating in the scan is reduced during the scan to a level where the sum of the output powers of all PV generators does not exceed the nominal power of the DC / AC converter during the scan. At the same time, it is possible to continue to generate as much electrical power as possible in one of the PV generators and output it via the DC / AC converter during the characteristic curve scan. This is advantageous because it allows the generation of electrical power to continue to be maintained at an acceptable level. Maintaining such a large distance from the nominal power of the DC / AC converter allows the characteristic curve of the PV generator being scanned to be traversed as completely as possible. It is even possible that the output power of each DC / DC converter and the associated PV generator not participating in the scan need not be reduced, or significantly reduced.

[0020] The advantage of this method is that it is easy to implement since the cumulative output power of the DC / DC converters not involved in the scan does not have to be changed during the scan, but can be kept at a constant level and still generate electrical active power at an acceptable level and be able to supply this electrical active power to the AC grid.

[0021] According to the present invention, during the characteristic curve acquisition, the individual output power of the DC / DC converters whose associated PV generators are not configured for characteristic curve acquisition is kept constant. The individual output power can be reduced relative to the output power at the respective maximum power point of the associated PV generator in order to reduce the cumulative output power of the DC / DC converters not participating in the acquisition. However, these PV generators still generate further electrical power, albeit at a reduced level. Keeping the individual output power constant has the advantage of simplifying the method and reducing the control effort.

[0022] In one embodiment of the method, the characteristic curve of the PV generator to be scanned is detected during controlled operation of a DC / DC converter associated with the PV generator to be scanned. Controlled operation has the following advantages over regulated operation: a control loop with feedback can be omitted, and the method is simpler and faster. Compared to regulated operation (in which, for example, voltage values ​​are specifically adjusted, including feedback of the voltage value present at the PV generator), controlled operation involves, for example, only adjustments without feedback. For example, at least one parameter of the DC / DC converter can be adjusted and, therefore, controlled. For the scan, this adjustment or parameter is then continuously varied to detect the characteristic curve, for example, by varying the parameter to change and measure the voltage present at the PV generator and the current output by the PV generator when this voltage is present. This parameter can, in particular, be the duty cycle, which is used to control the DC / DC converter. Particularly preferably, the parameter or duty cycle varies according to a predetermined temporal profile, thereby improving the reproducibility of the scan and simplifying subsequent correction calculations.

[0023] In one embodiment of the method, controlled operation includes current limiting to prevent the permitted input current of the DC / DC converter associated with the PV generator to be scanned from being exceeded. Current limiting serves to protect the DC / DC converter and can be implemented, for example, as a protective circuit or as a superimposed, limiting control system. The protective circuit is activated or the superimposed control system intervenes in a limiting manner only when the permitted input current of the DC / DC converter is exceeded. Otherwise, current limiting has no effect on the scanning process. In response to activation, scanning can be interrupted and subsequently continued, for example with modified control, to prevent reactivation of the protective circuit or superimposed control system.

[0024] In one embodiment of the method, the controlled parameter is the duty cycle of the DC / DC converter. Thus, during controlled operation, the duty cycle of the DC / DC converter associated with the PV generator to be scanned is controlled and continuously varied. The scanning for detecting the characteristic curve can be performed, in particular, using a predetermined profile of the duty cycle.

[0025] In one embodiment, the method, after detecting the characteristic curve of the PV generator to be scanned, comprises:

[0026] d) Ending the reduction of the cumulative output power of the DC / DC converter whose associated PV generator is not provided for detecting the characteristic curve.

[0027] This makes it possible to reduce the output power only during the scan and, after the scan is complete, to resume non-reduced power output.

[0028] A circuit arrangement for detecting a characteristic curve of a PV generator to be scanned among a plurality of PV generators in an energy generation plant is provided and configured to:

[0029] - depending on the maximum output power expected of the DC / DC converter connected to the PV generator to be scanned during the detection of the characteristic curve of the PV generator to be scanned, adjusting the DC / DC converter of the associated PV generator not configured for detecting the characteristic curve so that the cumulative output power of the DC / DC converter is reduced in order to ensure that the sum of the cumulative output power and the expected maximum power of the PV generator to be scanned does not exceed the nominal power of the DC / AC converter,

[0030] - Detecting the characteristic curve of the PV generator to be scanned.

[0031] In a first embodiment of an energy generation device, in which each of the PV generators is connected in parallel on the output side to an intermediate circuit as an input element of a DC / AC converter via an associated DC / DC converter, the circuit arrangement is arranged and configured to keep constant the voltage of the intermediate circuit and the individual output power of the associated PV generator (2) which is not configured for detecting the characteristic curve, during the detection of the characteristic curve.

[0032] In a second embodiment of the energy generation device, in which each of the PV generators is connected in series on the output side via an associated DC / DC converter to an intermediate circuit as an input element of a DC / AC converter, the circuit arrangement is arranged and configured to keep constant the current through the series circuit of the DC / DC converters and the individual output power of the associated PV generator (2) which is not configured for detecting the characteristic curve during the detection of the characteristic curve.

[0033] The expected maximum power of the DC / DC converters involved in the scan can be determined by the circuit arrangement before reducing the accumulated output power. The expected maximum power can be based on empirical values ​​(e.g., from previous scans) and can also depend on temperature, sunlight exposure, and similar environmental factors. The required reduction can also be conservatively determined from the nominal variables of the DC / DC converters being scanned (e.g., nominal current or nominal power).

[0034] In one embodiment, the circuit arrangement is arranged in a DC / AC converter and / or a DC / DC converter and is particularly designed and configured to additionally detect regulation and / or control tasks of the DC / AC converter and / or the DC / DC converter. In particular, the circuit arrangement can be designed as at least one computing unit, which is arranged in the DC / AC converter and / or the DC / DC converter. The at least one computing unit can then optionally be configured and constructed to additionally perform regulation and / or control tasks of the DC / AC converter and / or the DC / DC converter.

[0035] An energy generation system having a DC / AC converter and multiple PV generators can include the aforementioned circuit arrangement, wherein the PV generators are each connected in parallel or in series on the output side via an associated DC / DC converter to an intermediate circuit serving as an input element of the DC / AC converter. The PV generators can be scanned using one of the aforementioned methods. After scanning one PV generator, another of the multiple PV generators can be scanned using the described method. It is also possible to sequentially scan some or all of the multiple PV generators in the energy generation system using the described method. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present application is further illustrated and described below with reference to the embodiments shown in the accompanying drawings.

[0037] Figure 1 A method for detecting a characteristic curve of a PV generator is schematically shown,

[0038] Figure 2 Schematic representation of the course of characteristic electrical variables in an energy generation system,

[0039] Figure 3 schematically shows an example of an energy generation device with DC / DC converters connected in parallel, and

[0040] Figure 4 An example of an energy generation device with DC / DC converters connected in series is schematically shown. DETAILED DESCRIPTION

[0041] Figure 1 A method for detecting a characteristic curve of a PV generator 2 to be scanned among a plurality of PV generators 2 in an energy generation system 10 is schematically shown. The method comprises:

[0042] a) Reduce the cumulative output power KA of the DC / DC converter 12 whose associated PV generator 2 is not configured for characteristic curve detection. This reduction is performed based on the expected maximum output power Pscan of the DC / DC converter 12 connected to the PV generator 2 to be detected during the detection of the characteristic curve of the PV generator 2 to be detected. This reduction is selected so that the sum of the cumulative output power KA and the expected maximum power Pscan does not exceed the nominal power PN of the DC / AC converter 20.

[0043] b) The characteristic curve of the PV generator 2 to be scanned is then detected.

[0044] If the energy generating device 10 is Figure 3 The configuration shown in Figure 3 Each of the PV generators 2 is connected in parallel on the output side via an associated DC / DC converter 12 to an intermediate circuit 14 as an input element of a DC / AC converter 20.

[0045] c) During the detection of the characteristic curve, the voltage U ZK of the intermediate circuit 14 is kept constant by the DC / AC converter 20 .

[0046] If, in an alternative embodiment, the energy generating device is Figure 4 The configuration shown in Figure 4 The PV generators 2 are connected in series on the output side via an associated DC / DC converter 12 with an intermediate circuit 14 as an input element of a DC / AC converter 20.

[0047] c1) During the detection of the characteristic curve, the current of the series circuit of the DC / DC converter 12 is kept constant by the DC / AC converter 20 .

[0048] In this case, the voltage of c) or the current of c1) can be kept constant by means of a circuit arrangement 16 , which can optionally be designed as a regulating unit of a DC / AC converter 20 .

[0049] After detecting the characteristic curve of the PV generator to be scanned,

[0050] d) Ending the reduction of the cumulative output power KA of the DC / DC converter 12 whose associated PV generator 2 is not provided for detecting the characteristic curve.

[0051] As a result, after scanning, the same power output as before the scanning process can be restored.

[0052] exist Figure 2 , electrical variables in the energy generation system 10 are shown by way of example before, during and after the scanning process. The scanning process of the PV generator begins at time t1 and ends at time t2.

[0053] At the top, the nominal power PN of DC / AC converter 20 is plotted. Below this, the cumulative output power KA of DC / DC converter 12, which does not participate in the scanning process because its associated PV generator is not configured for scanning, is shown. During the scanning process, i.e., between t1 and t2, the cumulative output power KA decreases and is held constant at this decreased value.

[0054] The DC / DC converters involved in the scanning are preferably operated in a controlled manner, i.e. their duty cycle is varied in such a way that the voltage at the connected PV generator to be scanned changes in such a way that the characteristic curve can be detected. In particular, the duty cycle can be varied in a ramp-like manner. During the scanning, the current Iscan output by the PV generator is Figure 2 The power Pscan output by the DC / DC converters involved in the scan is shown in the lower part of Figure 2 , is plotted above the cumulative output power KA in the upper part of . It can be seen that the decrease in the cumulative output power KA is selected so that the sum of the maximum power of the output power Pscan of the PV generators 2 participating in the scan and the cumulative output power remains below the nominal power PN of the DC / AC converter 20 during the scan process.

[0055] For one embodiment of the energy generating plant 10, as in Figure 3 As shown in , the intermediate circuit voltage UZK is kept constant during the scanning process. Figure 2 The intermediate circuit voltage UZK preferably corresponds to the idling voltage of the PV generator 2 to be scanned.

[0056] For one embodiment of the energy generating plant 10, as in Figure 4As shown in , the current flowing through the series-connected DC / DC converters is kept constant during the scanning process.

[0057] Figure 3 An embodiment of an energy generation system 10 is shown, which includes a DC / AC converter 20 and a plurality of PV generators 2, each of which includes a plurality of PV modules 4 connected in series. The PV generators 2 are connected in parallel on the output side via a respectively assigned DC / DC converter 12 to an intermediate circuit 14, which serves as an input element of the DC / AC converter 20. The energy generation system 10 feeds electrical power into an AC power grid 30 via the DC / AC converter 20. The energy generation system 10 includes a circuit arrangement 16, which is designed and configured to carry out the above-described method.

[0058] In particular, circuit arrangement 16 is designed and configured to, based on the expected maximum output power Pscan of a DC / DC converter 12 connected to the PV generator 2 to be scanned during the detection of the characteristic curve of the PV generator 2 to be scanned, adjust the DC / DC converter 12 of the associated PV generator 2, which is not configured for characteristic curve detection, so that the cumulative output power KA of the DC / DC converter is reduced to ensure that the sum of the cumulative output power KA and the expected maximum power Pscan does not exceed the nominal power PN of the DC / AC converter 20. Furthermore, circuit arrangement 16 is designed and configured to detect the characteristic curve of the PV generator 2 to be scanned by controlling the DC / DC converter associated with the PV generator 2 to be scanned so that the duty cycle remains the same over multiple clock cycles. This results in a voltage at the PV generator 2 to be scanned, and the associated measured value, namely the current output by the PV generator 2 to be scanned, can be determined in a targeted manner. Thereafter, the duty cycle can be changed, maintained for multiple clock cycles, and the next measured value of the characteristic curve can be determined. This process can be repeated until the entire characteristic curve from the idling point to the short-circuit point has been traversed.

[0059] exist Figure 3 In the energy generating plant 10 , the circuit arrangement 16 is furthermore provided and configured to keep the voltage of the intermediate circuit constant during the detection of the characteristic curve.

[0060] Figure 4An embodiment of an energy generation system 10 is shown, which includes a DC / AC converter 20 and a plurality of PV generators 2, each of which includes a plurality of PV modules 4 connected in series. The PV generators 2 are connected in series on the output side via their respective associated DC / DC converters to an intermediate circuit 14, which serves as an input element of the DC / AC converter 20. The energy generation system 10 feeds electrical power into an AC power grid 30 via the DC / AC converter 20. The energy generation system 10 includes a circuit arrangement 16, which is designed and configured to implement the above-described method. In particular, the circuit arrangement 16 is designed and configured to, based on the expected maximum output power Pscan of the DC / DC converter 12 connected to the PV generator 2 to be scanned during the characteristic curve of the PV generator 2 to be scanned, adjust the DC / DC converter 12 of the associated PV generator 2, which is not configured for characteristic curve detection, so that the cumulative output power KA of the DC / DC converter is reduced to ensure that the sum of the cumulative output power KA and the expected maximum power Pscan does not exceed the nominal power PN of the DC / AC converter 20. Furthermore, the circuit arrangement 16 is designed and configured to detect the characteristic curve of the PV generator 2 to be scanned. Figure 3 Proceed in a similar manner as described.

[0061] exist Figure 4 In the energy generating plant 10 of FIG. 1 , the circuit arrangement 16 is furthermore provided and configured to keep a current through the series circuit of the DC / DC converter constant during the detection of the characteristic curve.

[0062] It is possible that, as in Figure 3 and Figure 4 The circuit arrangement 16 shown in FIG is designed as a separate unit, such as a computing unit, and exchanges information with the DC / AC converter 20 and the DC / DC converter, for example, via a communication line. It is also possible to arrange the circuit arrangement 16 in the DC / AC converter 20 and / or the DC / DC converter 12. In particular, the circuit arrangement 16 can be designed and configured to additionally sense regulation and / or control tasks of the DC / AC converter 20 and / or the DC / DC converter 12. In particular, the circuit arrangement 16 can be designed as at least one computing unit, which is arranged in the DC / AC converter 20 and / or the DC / DC converter 12. This at least one computing unit can, for example, be designed as a regulating unit of the DC / AC converter 20 or as part thereof. The circuit arrangement 16 can, in particular, be configured and configured to additionally carry out regulation and / or control tasks of the DC / AC converter 20 and / or the DC / DC converter 12.

[0063] The scanning of the plurality of PV generators 2 of the energy generation system 10 can be performed sequentially in each PV generator. In this case, it is possible to scan some or all of the plurality of PV generators of the energy generation system 10 sequentially using the described method.

[0064] Reference Signs List

[0065] t time

[0066] t1 starts scanning

[0067] t2 End of scan

[0068] Nominal power of PN DC / AC converter

[0069] KA cumulative output power

[0070] UZK intermediate circuit voltage

[0071] Iscan Output current of the PV generator to be scanned

[0072] Pscan Output power during scanning

[0073] 2 PV generators

[0074] 4 PV modules

[0075] 10 Energy generation equipment

[0076] 12 DC / DC converters

[0077] 14 Intermediate circuit

[0078] 16 Circuit Devices

[0079] 20 DC / AC converters

[0080] 30 AC grid

[0081] a), b), c), d) Method steps

Claims

1. A method for detecting a characteristic curve of a PV generator (2) to be scanned among a plurality of PV generators (2) in an energy generation system (10), wherein: Each of the PV generators (2) is connected in parallel on the output side via an associated DC / DC converter (12) to an intermediate circuit (14) as an input element of a DC / AC converter (20), the method comprising: a) reducing the cumulative output power (KA) of the DC / DC converter (12) of the PV generator (2) to be scanned, which is not configured for detecting the characteristic curve, based on the expected maximum output power (Pscan) of the DC / DC converter (12) connected to the PV generator (2) to be scanned during the detection of the characteristic curve of the PV generator (2) to be scanned, so as to ensure that the sum of the reduced cumulative output power (KA) and the expected maximum power (Pscan) of the PV generator (2) to be scanned does not exceed the nominal power (PN) of the DC / AC converter (20), b) subsequently detecting the characteristic curve of the PV generator (2) to be scanned, c) wherein, during the detection of the characteristic curve, the voltage (UZK) of the intermediate circuit (14) is kept constant by the DC / AC converter (20), and d) wherein, during the detection of the characteristic curve, the individual output power of the DC / DC converter (12) of the PV generator (2) to which it is assigned is not provided for detecting the characteristic curve is kept constant.

2. A method for detecting a characteristic curve of a PV generator (2) to be scanned among a plurality of PV generators (2) in an energy generation system (10), wherein: The PV generators (2) are each connected in series on the output side via an associated DC / DC converter (12) to an intermediate circuit (14) as an input element of a DC / AC converter (20). The method comprises: a) reducing the cumulative output power (KA) of the DC / DC converter (12) of the PV generator (2) to be scanned, which is not provided for detecting the characteristic curve, based on the expected maximum output power (Pscan) of the DC / DC converter (12) connected to the PV generator (2) to be scanned during the detection of the characteristic curve of the PV generator (2) to be scanned, so as to ensure that the sum of the cumulative output power (KA) and the expected maximum power (Pscan) of the PV generator (2) to be scanned does not exceed the nominal power (PN) of the DC / AC converter (20), b) subsequently detecting the characteristic curve of the PV generator (2) to be scanned, c1) wherein, during detection of the characteristic curve, the current of the series circuit of the DC / DC converter (12) is kept constant by the DC / AC converter (20), and d) wherein, during the detection of the characteristic curve, the individual output power of the DC / DC converter (12) of the PV generator (2) to which it is assigned is not provided for detecting the characteristic curve is kept constant.

3. The method according to claim 1 or 2, wherein: The characteristic curve of the PV generator (2) to be scanned is detected during controlled operation of a DC / DC converter (12) associated with the PV generator (2) to be scanned.

4. The method according to claim 3, wherein: The controlled operation includes current limiting in order to avoid exceeding a permissible input current of a DC / DC converter (12) associated with the PV generator (2) to be scanned.

5. The method according to claim 3, wherein: The controlled operation comprises controlling the duty cycle of a DC / DC converter (12) associated with the PV generator (2) to be scanned, wherein the scanning for detecting the characteristic curve is performed using the course of the duty cycle.

6. The method according to claim 1 or 2, wherein: The method comprises, after detecting the characteristic curve of the PV generator (2) to be scanned: d) ending the reduction of the cumulative output power (KA) of the DC / DC converter (12) of the associated PV generator (2) which is not provided for detecting the characteristic curve.

7. A circuit arrangement for detecting a characteristic curve of a PV generator (2) to be scanned among a plurality of PV generators (2) in an energy generation system (10), wherein: Each of the PV generators (2) is connected in parallel on the output side via an associated DC / DC converter (12) to an intermediate circuit (14) as an input element of a DC / AC converter (20), wherein the circuit arrangement is provided and configured for: According to the maximum output power (Pscan) expected from the DC / DC converter (12) connected to the PV generator (2) to be scanned during detection of the characteristic curve of the PV generator (2) to be scanned, the PV generator (2) to be scanned is adjusted so that the DC / DC converter (12) is not set to detect the characteristic curve, so that the cumulative output power (KA) of the DC / DC converter is reduced, so as to ensure that the sum of the reduced cumulative output power (KA) and the expected maximum power (Pscan) does not exceed the nominal power (PN) of the DC / AC converter (20), Detecting the characteristic curve of the PV generator (2) to be scanned, and During the detection of the characteristic curve, the voltage (UZK) of the intermediate circuit (14) and the individual output power of the DC / DC converter (12) of the associated PV generator (2) which is not provided for detecting the characteristic curve are kept constant.

8. A circuit arrangement for detecting a characteristic curve of a PV generator (2) to be scanned among a plurality of PV generators (2) in an energy generation system (10), wherein: The PV generators (2) are each connected in series on the output side via an associated DC / DC converter (12) to an intermediate circuit (14) as an input element of a DC / AC converter (20), wherein the circuit arrangement is provided and configured for: According to the maximum output power (Pscan) expected from the DC / DC converter (12) connected to the PV generator (2) to be scanned during detection of the characteristic curve of the PV generator (2) to be scanned, the PV generator (2) to be scanned is adjusted so that the DC / DC converter (12) is not set to detect the characteristic curve, so that the cumulative output power (KA) of the DC / DC converter is reduced, so as to ensure that the sum of the reduced cumulative output power (KA) and the expected maximum power (Pscan) does not exceed the nominal power (PN) of the DC / AC converter (20), Detecting the characteristic curve of the PV generator (2) to be scanned, and During the detection of the characteristic curve, the current through the series circuit of the DC / DC converter (12) and the individual output power of the DC / DC converter (12) of the associated PV generator (2) not provided for detecting the characteristic curve are kept constant.

9. The circuit arrangement according to claim 7 or 8, wherein: The circuit arrangement is arranged in the DC / AC converter (20) and / or the DC / DC converter (12).

10. The circuit arrangement according to claim 7 or 8, wherein: The circuit arrangement is arranged and configured for controlling and / or regulating the DC / AC converter (20) and / or the DC / DC converter (12).

11. An energy generation plant (10) having a DC / AC converter (20) and a plurality of PV generators (2), wherein: The PV generators (2) are each connected in parallel or in series on the output side via an associated DC / DC converter (12) to an intermediate circuit (14) as an input element of the DC / AC converter (20), and the energy generation system (10) has a circuit arrangement according to any one of claims 7 to 9.

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