Method for operating an energy generation system and an energy generation system including said method - Patents.com

Abstract

The present application relates to an energy generation system including a plurality of DC sub-generators (5.1 to 5.n) connected in parallel with each other and connected to a shared DC load (20) via a DC / DC converter (4.1 to 4.n) in each case. Each of the DC sub-generators (5.1 to 5.n) includes a DC power source (2.1 to 2.n) connected to a specific DC / DC converter (4.1 to 4.n) assigned to the corresponding DC sub-generator (5.1 to 5.n) via at least one fuse (9.1 to 9.n) connected in series with the DC power source (2.1 to 2.n). The method includes a step of monitoring the DC sub-generators (5.1 to 5.n) for faults (30), in particular short-circuit faults, and if the monitoring of the DC sub-generators (5.1 to 5.n) indicates a faulty DC sub-generator (5.1), the DC / DC converters (4.2 to 4.n) not assigned to the faulty DC sub-generator (5.1) are configured to supply a common total current I corresponding to a default value. Rest The present application also relates to an energy generation system (1) designed and configured to carry out the method.

Description

[Technical field]

[0001] The present invention relates to a method for operating an energy generating system (EEA). The invention particularly relates to the operation of an EEA when a fault in the EEA is detected and its damaging effects on components of the EEA are avoided, but at least reduced. The EEA may in particular be a renewable EEA with several DC sub-generators connected in parallel with each other and in each case connected to and supplying a shared DC load via a DC / DC converter. Fault cases may exist in particular when one, possibly several DC sub-generators are faulty, for example a short circuit fault. The invention further relates to an EEA designed and configured for such a method. [Background technology]

[0002] In the so-called power-to-gas method, electrical energy is converted by an electrolyzer into a gaseous energy carrier, in particular hydrogen. The electrical energy can advantageously be renewable electrical energy. In such a method, the electrolyzers and the renewable EEA supplying them can be interconnected in the form of an island network that is not connected at all or only temporarily to a public power grid (EVN) operating at AC voltage.

[0003] Many renewable energy sources are often designed essentially as DC power sources. Since electrolyzers operate as DC consumers, it is advantageous in terms of avoiding conversion losses if the island network is also designed as a DC network. For example, an EEA in an island network can have several DC sub-generators designed as photovoltaic (PV) sub-generators, which are connected in parallel with each other to the input of the electrolyzer or to another DC load, in each case via a DC / DC converter. The voltage of the DC sub-generators can be decoupled from the voltage of the input of the electrolyzer via the DC / DC converter. Each DC sub-generator can thus operate at its respective maximum power point (MPP), but still supply the electrolyzer with the same output voltage with all DC / DC converters. The operating point of the electrolyzer, and in particular its power consumption, can be set via the output voltage of the DC / DC converter. In particular, a higher level control unit can control the output voltage of the DC / DC converter in such a way that on the one hand there is always an equilibrium between the total power generated and the total power consumed in the island network, and on the other hand the maximum possible power of the renewable energy of the PV sub-generators can be obtained at any time.

[0004] Now, in case of a fault in one or possibly more of the PV sub-generators operating as DC sub-generators, for example in case of a short circuit fault or double insulation fault, the fault-free operating DC sub-generators will supply their power to one faulty DC sub-generator (or, if applicable, to several faulty DC sub-generators). Typically, a DC sub-generator comprises one or more DC power sources. The DC power sources of the DC sub-generators are connected to the DC / DC converter assigned to the DC sub-generator via one or more fuses, depending on the size of the EEA. However, in case of a suspected fault in the EEA, the resulting current from the fault-free DC source of the EEA to the faulty DC source may not be high enough to blow at least one of the fuses to which the faulty DC source is relayed and connected to the assigned DC / DC converter. Thus, in case of a fault, there is a risk that the generated faulty current will not be sufficient without additional measures to isolate the faulty DC source from the remaining DC sources operating without faults by blowing a fuse downstream of the faulty DC source. The resulting current, representing a fault current, will not be reliably interrupted and, depending on the current strength and the duration of the fault current, may damage or destroy further components of the EEA, in particular the associated DC / DC converter.

[0005] The patent application WO 2005 / 023333 discloses a method and a device for supplementary supply of current from at least one power source to a final power network having several consumption points. The final power network is connected to a higher level power source, the consumption points being protected from the higher level power source via at least one overcurrent fuse. A control unit detects the current flowing from the higher level power source and the current flowing from the power source to the final power network. An instantaneous sum formed from the currents is compared with a predefined maximum current in order to reduce the current flowing from the current source if the maximum current is exceeded. In this way overload conditions of the final power network can be prevented.

[0006] Patent document 2 discloses a PV system with an inverter connected to the power grid via an AC disconnecting means and at least one PV sub-generator, each having at least one PV string, connected to the DC connection area of ​​the inverter via a DC line. A DC separator close to the generator, a DC short-circuit switch downstream in the energy flow direction during feeding for short-circuiting at least one PV string, and a reverse current protection downstream of the DC short-circuit switch in the energy flow direction are assigned to the PV sub-generator. Furthermore, an AC short-circuit switch is arranged upstream of the AC disconnecting means in the energy flow direction.

[0007] A photovoltaic (PV) system with an arc detection device is known from US Pat. No. 5,399,633. In the PV system, a PV string is connected to a power converter via a first power line, a DC-DC converter and another power line. The arc detection device includes a capacitor forming a bypass current path for the DC-DC converter and a current sensor arranged in one of the other power lines between the DC-DC converter and the power converter.

[0008] US Pat. No. 5,399,633 describes a method of operating a maximum power point tracking controller (MPPT controller), which is designed to transfer power between an input terminal and an output terminal, and includes the following steps:

[0009] A first operating mode of the MPPT controller includes operating a first switching device of the MPPT controller with a fixed duty cycle.

[0010] A second operating mode of the MPPT controller causes a regulating switching device of the MPPT controller to repeatedly switch between conducting and non-conducting states to maximize the power available from the PV device electrically connected to the input terminals.

[0011] US Patent Publication 5,333,636 discloses a PV string having a plurality of PV modules electrically connected in series and having a first end and a second end. A power line with a first string protection unit is electrically connected to the first end, and a return line with a second string protection unit is connected to the second end. One of the string protection units includes a plurality of protection devices selected from overcurrent protection, arc fault protection, reverse current protection, and earth fault protection. The other string protection unit includes a plurality of protection devices selected from overcurrent protection, arc fault protection, reverse current protection, earth fault protection, and a remote controlled switch in series with the power line or the return line.

[0012] A PV system with several PV modules and their assigned DC / DC converters, connected in parallel to one another on the output side to a central inverter, is known from US Pat. No. 6,399,666. The inverter converts the DC link voltage of the intermediate circuit, generated by the DC / DC converters, into a sinusoidal AC voltage. The PV modules are galvanically decoupled by the individual DC / DC converters. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] German Patent Application Publication No. 102015007443A1 [Patent Document 2] German Patent Application Publication No. 102013111869A1 [Patent Document 3] US Patent Application Publication No. 2018 / 210022 [Patent Document 4] German Patent No. 112012007202T5 [Patent Document 5] US Patent Application Publication No. 2016181781A1 [Patent Document 6] DE 10136147 A1 Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the invention is to identify a method of operating an EEA with several DC sub-generators connected in parallel with each other, which ensures that damage to the EEA is avoided in the event of a fault. The object is specifically to isolate the faulty DC power source of the DC sub-generator from the remaining DC power sources operating in a fault-free manner, possibly by blowing a fuse. However, the resulting faulty currents must be controlled so that damage to components of the EEA that are sensitive to overcurrents is precluded, even if the fuse cannot be blown. Furthermore, the object of the invention is to identify an EEA suitable for carrying out the method. [Means for solving the problem]

[0015] For a method of the type mentioned at the outset, the object is achieved according to the invention with the features of independent claim 1. Advantageous embodiments of the method are given in claims 2 to 7. The object of specifying an energy generating system suitable for carrying out the method is achieved according to the invention with the features of independent claim 8. Advantageous embodiments of the energy generating system are given in claims 9 to 13.

[0016] The method according to the invention is intended for the operation of an energy generating system (EEA) having a number of DC sub-generators connected in parallel with one another and in each case connected via a DC / DC converter to a shared DC load. Each of the DC sub-generators has at least one DC power source connected to a DC / DC converter assigned to the respective DC sub-generator via at least one fuse connected in series with the DC power source. The method comprises: monitoring each of the DC sub-generators for faults, in particular for short circuit faults; If DC sub-generator monitoring indicates a faulty DC sub-generator, The DC / DC converters that are assigned to the non-faulty DC sub-generators and not to the faulty DC sub-generators will have a common total current I Rest Works with.

[0017] Each of the DC sub-generators may have one DC power source or several DC power sources connected in parallel to the corresponding DC / DC converter. The fuses may in each case be arranged between the DC power source and the DC / DC converter in relation to the direction of power flow during normal operation of the EEA. The fuses may not only be one fuse, but several fuses, which are usually arranged in series connection between the DC power source and the DC / DC converter. Only one pole of the DC power source may be connected to the corresponding DC / DC converter via one fuse or several fuses connected in series. However, it is also within the scope of the invention that each of the two poles of the DC power source is connected to the assigned DC / DC converter via one fuse or several fuses connected in series. Thus, each of the DC / DC converters may be connected only to one DC power source on the input side. Alternatively, however, it is also possible that one, several or even each of the DC / DC converters are connected on the input side to several DC power sources connected in parallel to each other. In particular, if at least one of the DC / DC converters is connected on the input side to several DC power sources, the power flows of the DC power sources may be combined in a cascaded manner within the corresponding DC sub-generator in several stages. Each individual stage can have a separate fuse. For example, a so-called main string fuse can protect a generator box which in each case includes several so-called string fuses. In this way, several fuses of different types can be connected in series between the DC source and the DC / DC converter. Here, the blowout threshold of the fuses can be increased with increasing distance from the DC source and with decreasing distance to the DC / DC converter.

[0018] Monitoring each of the DC sub-generators for faults can be done in that the electrical parameters of the DC sub-generator, in particular the current and / or voltage, are detected in a time-sequential manner. In this case, it is not necessary to monitor each of the DC sources in the DC sub-generator individually. In particular, if several DC sources connected in parallel with each other are connected to a shared DC / DC converter as one DC sub-generator, it is sufficient to group the DC sources together, or in other words to monitor the corresponding DC sub-generator. During monitoring, it can be detected, for example, whether a return current flows through a faulty DC sub-generator that is subject to a short-circuit fault. The monitoring does not directly generate a faulty DC source, but a DC sub-generator that includes a faulty DC source.

[0019] The invention makes use of the effect that in the event of a fault, in particular in the event of a short-circuit fault of one of the DC sources, the voltage of the faulty DC source as well as the voltage of the DC sub-generators including the faulty DC source will drop, resulting in a return current being generated from the non-faulty DC sources. The dropped voltage is applied on the input side to the DC-DC converter assigned to the faulty DC source, so that this DC-DC converter can no longer provide a voltage on its output side that corresponds to the voltage on the output side of the remaining DC / DC converters that are not connected to the faulty DC source or to the faulty DC sub-generator on the input side. This causes a resulting total current I Rest to the faulty DC sub-generator, in particular to the faulty DC power source of the faulty DC sub-generator. The total current I Rest flows back through the freewheeling diodes of the DC / DC converter assigned to the faulty DC sub-generator, i.e. in the opposite direction to the current direction during normal operation of the EEA.

[0020] A failure of a DC source can also affect the EEA, not only causing a voltage drop at the output of the DC / DC converter assigned to the faulty DC source. Instead, the voltage drop may be more or less strongly present at the output of all other DC / DC converters. In this case, the voltage drops to a smaller voltage value across the DC bus of the EEA. However, in this case, the voltage drop is usually more pronounced at the DC / DC converter assigned to the faulty DC source than at the remaining DC / DC converters not assigned to the faulty DC source, so that the already explained total current I Rest also occurs here.

[0021] According to the invention, only the DC / DC converters that are not assigned to the faulty DC sub-generator can supply their common total current I Rest The coordinated control operates with the aim of corresponding to a default value. This can be done by controlling in a coordinated manner the DC / DC converters that are not assigned to the faulty DC sub-generator. The coordinated control can be performed by a control unit acting on all DC / DC converters. In the case of coordinated control, the adjusted default value must be taken into account by the control device. The control unit may further comprise the individual currents of all DC / DC converters involved in the coordinated control. However, this is not absolutely necessary. Rather, in addition to the adjusted default value, the control unit may determine the common total current I Rest It is sufficient to have a common total current I Rest may also optionally include a portion flowing from the DC load in the direction of the DC / DC converter assigned to the faulty DC sub-generator. Since fewer values ​​need to be measured and / or communicated during the coordinated control, the coordinated control can be simplified overall and the corresponding control units need not be as sophisticated. Thus, the total current I Rest The faulty current corresponding to does not flow in an uncontrolled manner, but the total current IRest corresponds to a default value. The default value may be selected to preclude damage to overcurrent-sensitive components of the EEA, in particular of the DC / DC converters assigned to the faulty DC sub-generator or, in other words, of the DC / DC converters assigned to the faulty DC source. The overcurrent-sensitive components may in particular be the freewheeling diodes of the corresponding DC / DC converter. On the one hand, the total current I Rest can be limited upwards using a default value. However, on the other hand, the common total current I Rest The total current I Rest is simultaneously limited downwards. In particular, the default value can be selected to ensure that the fuse connected in series with the DC / DC converter and the faulty DC source, or one or more fuses connected in series with the DC / DC converter and the faulty DC source, in case of several fuses, blows. In the case of a DC sub-generator with several DC sources connected in parallel with each other, the fuse closest to the faulty DC source will usually have, on the one hand, a relatively low blowing threshold with respect to the other fuses in the DC sub-generator, and, on the other hand, a higher blowing threshold with respect to the total current I generated outside the faulty DC sub-generator. Rest However, the fault current generated within the faulty DC sub-generator is generally larger than the total current I generated outside the faulty DC sub-generator. Rest Both currents add up, thus assisting in the desired blowing of the fuse in the event of a fault.

[0022] Total current I Rest The current intensity of the total current I RestWith the proper operation of the DC / DC converters contributing to the faulty DC sub-generator, the current flowing through the DC / DC converters can be adjusted or set to a default value. For this purpose, the current flowing through the DC / DC converters can be sensed in all DC / DC converters and transmitted to a higher level control unit. The higher level control unit can sum up the sensed currents of the DC / DC converters not assigned to the faulty DC sub-generator and from there derive the present total current I Rest The total current I Rest By comparing it with the default value, the control unit calculates the total current I Rest The associated DC / DC converter can be controlled so that the total corresponds to a default value. current I Rest If the default value is exceeded or is in danger of being exceeded, at least one current (I 2 ~I n However, in return, the total current I Rest To set the default value, some or all of the currents (I 2 ~I n ) can be reduced. Conversely, the total current I Rest If at least one current (I 2 ~I n ) can be boosted by a respective one of the DC / DC converters, and optionally some or all of the currents can be boosted by a respective one of the DC / DC converters that is not assigned to the faulty DC sub-generator.

[0023] In an advantageous embodiment of the method, when monitoring for faults in the DC sub-generators, the current flowing through the DC / DC converters can be detected for all DC / DC converters in each case. If the current flowing from the DC / DC converter assigned to the DC sub-generator in the direction of the DC load exceeds the current threshold ITH below 0 V, or if the current flowing in the direction of the DC load from the DC / DC converter assigned to the DC sub-generator changes its current direction. In this case, the current flowing in the direction of the DC load from the DC / DC converter is evaluated as a positive current, and the current flowing in the direction of the DC load to the DC / DC converter is evaluated as a negative current. According to this definition, a negative current flowing in the direction of the DC load through the DC / DC converter also indicates that a faulty DC sub-generator is connected on the input side to the associated DC / DC converter. Detecting the current flowing through the DC / DC converter allows the detection of the input or output current of the DC / DC converter.

[0024] Instead of detecting the current flowing through the DC / DC converter, or cumulatively, it is equally possible to detect the voltage of the DC subgenerator in each case in order to monitor for faults in the DC subgenerator. In this case, the voltage detected on the DC subgenerator is equal to the voltage threshold U TH below which a faulty DC sub-generator is indicated. The voltage can advantageously be detected at the input of the DC / DC converter assigned to the respective DC sub-generator. Alternatively, however, the output voltage of the DC / DC converter can also be detected. Advantageously, measuring units already available in the DC / DC converter can be used during the detection of the voltage as well as the detection of the current.

[0025] In one variation of this method, the default value is the sum current I Rest can be selected such that the time integral formed from exceeds the i2t value of the overcurrent sensitive components of the DC / DC converter assigned to the faulty DC source, or in other words, of the DC / DC converter assigned to the faulty DC sub-generator. This prevents the overcurrent sensitive components of the DC / DC converter(s) from being damaged as the overcurrent sensitive components. Furthermore, the default value is a sum current I Restcan advantageously be selected such that the time integral formed from preferably exceeds the i2t value of a fuse connected in series between the faulty DC source and the DC / DC converter assigned to the faulty DC source. The selection of such a default value is aimed at blowing the fuse and thus isolating the faulty DC source from the remaining non-faulty DC sources within the faulty DC sub-generator as well as from the remaining non-faulty DC sources outside the faulty DC sub-generator.

[0026] In case of a fault within the EEA, a situation may arise where the selection of such default values ​​does not result in the blowing of the fuses connected in series with the faulty DC source. This may be facilitated, for example, by component tolerances in combination with the i2t values ​​of overcurrent sensitive components and fuses in close proximity to each other. However, even in such cases, the faulty DC sub-generator can be easily isolated from the shared DC loads and thus from the remaining non-faulty DC sub-generators. In particular, if the selected default values ​​do not result in the blowing of fuses, the DC / DC converters not assigned to the faulty DC sub-generator can be deactivated to reduce the total current I Rest can be set to a current value of 0A. In this way, a zero current condition occurs between the DC / DC converters, in which the faulty DC source or the faulty DC sub-generator can be electrically isolated from the shared DC load via electromechanical switching elements. Such switching elements are usually already present in the EEA in question. However, since the switching operation takes place in the zero current condition, it is not necessary for the switching elements to be equipped with absolute arc extinguishing means. They can therefore be designed in a significantly more cost-effective manner.

[0027] In an advantageous embodiment of the method, faults indicated during monitoring of the DC sub-generator, and optionally also the successful or unsuccessful blowing of the fuse, can be signalled by the EEA. This can be done, for example, by a communication unit of the EEA. In this way, an operator of the EEA can be notified accordingly in a timely manner of the fault and the correspondingly necessary repair measures. The operator can thus take preventive measures in advance in order to carry out the repair of the faulty DC power supply or the EEA as efficiently as possible.

[0028] The energy generating system according to the invention comprises a number of DC sub-generators connected in parallel with one another and in each case connected via a DC / DC converter to a shared DC load. Each of the DC sub-generators has a DC power source, which is connected to a DC / DC converter assigned to the respective DC sub-generator via at least one fuse connected in series with the DC power source. As a characteristic configuration, the energy generating system further comprises a control unit designed and configured to carry out the method according to the invention. The control unit can be an individually designed control unit of the EEA. However, it is also possible, alternatively or cumulatively, for the control unit to be included in one control unit of the DC / DC converter or in several control units of the DC / DC converter. In other words, the control unit can thus also be distributed to the control units of several DC / DC converters of the EEA. Advantages have already been mentioned in connection with the results of the method.

[0029] In an advantageous embodiment of the EEA, the DC sub-generators each have a number of DC power sources connected in parallel with one another via at least one fuse to a DC / DC converter assigned to the respective DC sub-generator. The DC power sources can also be connected respectively via a series connection of a number of fuses to a DC / DC converter assigned to the respective DC sub-generator. In this case, the value of the fuse melting threshold or i2t value can be increased the further the series-connected fuses are from the DC power source, or in other words the closer the series-connected fuses are arranged to the corresponding DC / DC converter. In a further embodiment of the EEA, the DC power sources of the one or more DC sub-generators can include photovoltaic (PV) strings and / or batteries. Furthermore, the shared DC load can in particular include an electrolyzer.

[0030] The EEA may include a step-down converter as a DC / DC converter. In particular, the DC / DC converter, the plurality of, or possibly all, DC / DC converters of the EEA may each include a step-down converter and / or a DC / DC converter with step-down function, i.e. designed and configured to convert an input voltage to a smaller output voltage. The overcurrent-sensitive component of the DC / DC converter assigned to the faulty DC power source, or in other words the DC / DC converter assigned to the faulty DC sub-generator, may include a separate freewheeling diode connected in parallel with the semiconductor switch of the DC / DC converter. Alternatively, the overcurrent-sensitive component of the DC / DC converter may also include the semiconductor switch of the DC / DC converter, in particular the body diode of the semiconductor switch. [Brief description of the drawings]

[0031] The invention is illustrated below with the aid of the figures:

[0032] [Figure 1] 1 shows an EEA according to the present invention in a first embodiment. [Diagram 2] 2 shows an EEA according to the present invention in a second embodiment. [Diagram 3] 1 shows a flow chart of a method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Fig. 1 shows an EEA 1 according to the invention in a first embodiment. The EEA 1 comprises a number of DC sub-generators 5.1-5.n connected in parallel with one another and in each case via DC / DC converters 4.1-4.n connected to a shared DC load 20, illustrated here for example as an electrolyser 21. The EEA 1 further comprises a control unit 15 for controlling the DC / DC converters 4.1-4.n. The control unit 15 is configured to receive and analyze measured values ​​of the current and / or voltage detected by the measuring units of the DC / DC converters 4.1-4.n. The control unit 15 furthermore controls, alone or in combination with the control units present in the DC / DC converters 4.1-4.n, the individual ones of the DC / DC converters 4.1-4.n to be connected to a common total current I generated by the individual ones of the DC / DC converters 4.1-4.n. Rest are configured to control the inputs U10.1-10.n in order to correspond to default values. The DC / DC converters 4.1-4.n are shown by way of example in FIG. 1 as step-down converters with respective inputs 10.1-10.n, input capacitances 8.1-8.n connected to the inputs 10.1-10.n, two semiconductor switches 6.1-6.n and inductances 7.1-7.n connected to the outputs 11.1-11.n of the DC / DC converters 4.1-4.n. However, according to the invention, the DC / DC converters 4.1-4.n are provided with a step-down function, i.e. the input voltage U applied to the inputs 10.1-10.n is controlled by the inputs U10.1-10.n. 1 ~U nIt is also possible to use any DC / DC converter capable of converting the input voltage Ua of the DC sub-generator 5.1-5.n to a smaller output voltage Ua applied to the output 11.1-11.n. In the embodiment according to Fig. 1, each of the DC sub-generators 5.1-5.n comprises only one DC power source 2.1-2.n, which is connected via fuses 9.1-9.n to the input 10.1-10.n of the DC / DC converter 4.1-4.n to which it is assigned. Each of the DC power sources 2.1-2.n is shown as a photovoltaic (PV) string 3.1-3.n by way of example. However, one or more of the DC power sources 2.1-2.n can also be designed as batteries.

[0034] During normal operation of the EEA 1, the DC sources 2.1 to 2.n, designated as PV strings 3.1 to 3.n, are operated at their respective maximum power points (MPP). Here, the voltage U 1 ~U n is the shared output voltage U a The electrolytic cell 21 as the shared DC load 20 has an output voltage U a This ensures that the maximum possible renewable power is always converted by the EEA 1 and supplied to the DC loads 20.

[0035] During normal operation of the EEA 1, the DC sub-generators 5.1 to 5.n are monitored for possible faults 30, for example possible short-circuit faults. The monitoring is carried out according to FIG. 1, such that measuring devices (not shown in FIG. 1) already present in the DC / DC converters 4.1 to 4.n are used. In each case, the measuring device is used to measure the voltage U applied to the inputs 10.1 to 10.n of the DC / DC converters 4.1 to 4.n. 1 ~U n and / or the current I flowing through the outputs 11.1-11.n of the DC / DC converters 4.1-4.n in the direction of the DC load 20 1 The voltage U applied to inputs 10.1 to 10.n can be detected.1 ~U n One of the voltage thresholds U TH and / or the current I flowing in the direction of the DC load 20 via the output of the DC / DC converters 4.1 to 4.n 1 ~I n One of the current thresholds I TH If the detected current I of the control unit 15 of the higher level is exceeded, the corresponding DC / DC converter 4.1 to 4.n notifies the control unit 15 of this. 1 ~I n and voltage U 1 ~U n It is also possible for the device to transmit the value of , which it itself evaluates and detects indications of a fault 30 .

[0036] FIG. 1 shows, by way of example, a fault 30 in the form of a short circuit fault in the DC power source 2.1 of one of the DC sub-generators 5.1 to 5.n, here the DC sub-generator 5.1. Due to the short circuit fault, the voltage U 1 drops to a very small absolute value. In this case, unlike the remaining DC / DC converters 4.2 to 4.n, the DC / DC converter 4.1 assigned to the faulty DC sub-generator 5.1, or in other words the DC / DC converter 4.1 assigned to the faulty DC source 2.1, does not receive the voltage U applied to its input side. 1 Share the value U a Instead, the shared value U aAn output voltage significantly smaller than that of the DC / DC converter 4.1 assigned to the faulty DC source 2.1 is also applied here to the output of the DC / DC converter 4.1 assigned to the faulty DC source 2.1. In some cases, a drop may occur not only in the output voltage of the DC / DC converter 4.1 assigned to the faulty DC source 2.1. It may also be possible, instead, that in response to one faulty DC source 2.1, a voltage drop occurs across the DC bus of the EEA 1, i.e. there may also be a voltage drop in the DC / DC converters 4.2 - 4.n that are not assigned to the faulty DC source 2.1. However, the drop in the output voltage at the DC / DC converter 4.1 assigned to the faulty DC source 2.1 is somewhat more noticeable than the voltage drop at the other DC / DC converters 4.2 - 4.n. An at least slightly more noticeable drop in voltage at the output 11.1 of the DC / DC converter 2.1 is in any case in the direction of the DC / DC converter 2.1 assigned to the faulty DC source 2.1, and in the direction of the I of the DC / DC converters 4.2 - 4.n assigned to the faulty DC sub-generators 5.2 - 5.n. Rest =I 2 +I 3 +…+I n According to the total current I Rest Without further measures, the total current I Rest can assume values ​​that can irreversibly damage overcurrent-sensitive components of the DC / DC converter 2.1 involved, especially if the fuse 9.1 connected in series with the faulty DC power source 2.1 does not blow or does not blow in time to interrupt the faulty current.

[0037] According to the present invention, the fault 30 is detected by the detected current I 1 ~I n and / or voltage U 1 ~U n Based on this, the control unit 15 detects the common total current I generated by the DC / DC converters 4.2 to 4.n assigned to the non-faulty DC sub-generators 5.2 to 5.n. Rest I Rest =I 2 +I3 +…+I n In this case, not only the default value itself but also the respective currents I contributed by the individual DC / DC converters 4.2 to 4.n to achieve the shared default value are also operated by the control unit 15 for the purpose of taking the default value according to 2 ~I n can also be pre-determined from the beginning. The default value is selected such that, on the one hand, damage to overcurrent-sensitive components of the DC / DC converter 4.1 connected to the faulty DC sub-generator 5.1 is precluded. In particular, the default value can be selected to be smaller than the value of the overcurrent-sensitive components of the corresponding DC / DC converter 2.1. On the other hand, the default value is selected (higher) such that, if possible, the fuse 9.1 downstream of the faulty DC source 2.1 is reliably blown, thus isolating the faulty DC source 2.1 from the remaining non-faulty DC sources 2.2-2.n. Since the DC / DC converters 4.1-4.n of the EEA 1 are DC / DC converters designed and configured for step-down functionality, the DC / DC converters 4.2-4.n are required to generate a sufficiently high total current I at their output even in the case of a relatively low irradiation of the DC sources 2.2-2.n configured as PV strings 3.1-3.n. Rest If the fuse 9.1 downstream of the faulty DC source 2.1 does not blow before the i2t value of the overcurrent sensitive components of the associated DC / DC converter 4.1 is exceeded, damage to the overcurrent sensitive components will occur only if the total current I Restis avoided in that the remaining DC / DC converters 4.2 - 4.n are set to a value of 0 A by properly operating them. In particular, in this case the remaining DC / DC converters 4.2 - 4.n can be deactivated. The faulty DC sub-generator 5.1 can be permanently and electrically isolated in a zero current state from the shared DC load 20 and the remaining non-faulty DC sub-generators 5.2 - 5.n via a DC separator not shown in Fig. 1 (similar to the DC separators 13.1 - 13.n shown in Fig. 2). The EEA 1 can then be operated further without the defective DC sub-generator 5.1 and with the remaining non-faulty DC sub-generators 5.2 - 5.n. The disconnected DC sub-generator 5.1 or its faulty DC source 2.1 can be repaired without risk and then reconnected to the EEA 1.

[0038] Although Figure 1 shows only one faulty DC sub-generator 5.1, this method can also be applied when there are multiple faulty DC sub-generators present at the same time, at least as long as the number of non-faulty DC sub-generators exceeds the number of faulty DC sub-generators.

[0039] Figure 2 shows a second embodiment of an EEA 1 according to the invention, which is similar in many configurations to the EEA 1 shown in Figure 1. Therefore, for the sake of clarity, only the differences from the first embodiment of the EEA 1 will be mentioned and reference will be made to the description of Figure 1 for identical configurations.

[0040] The EEA 1 shown in Fig. 2 also comprises a number of DC sub-generators 5.1-5.n, which are connected in parallel with each other and connected to a shared DC load 20 via DC / DC converters 4.1-4.n, respectively. However, in contrast to Fig. 1, each of the DC sub-generators 5.1-5.n in Fig. 2 comprises a number of DC power sources 2.1-2.n, each of which is connected in parallel with each other and connects in each case via a series connection of a number of fuses 9.1-9.n to a DC / DC converter 4.1-4.n assigned to the respective DC sub-generator 5.1-5.n. Here, the i2t value of the fuses 9.1-9.n in each of the series connections increases as the distance of the fuses 9.1-9.n from the DC power source 2.1-2.n assigned to it increases. Furthermore, a DC separator 13.1-13.n may be arranged between each of the DC sub-generators 5.1-5.n and the DC / DC converter 4.1-4.n assigned thereto, by means of which the corresponding DC sub-generator 5.1-5.n may be electrically isolated from the DC / DC converter 4.1-4.n assigned thereto. The DC separators 13.1-13.n may advantageously dispense with means for extinguishing arcs and may therefore be designed in a relatively cost-effective manner.

[0041] Also, in Fig. 2, the current I 1 ~I n and / or voltage U 1 ~U n is detected by a measuring unit of the DC / DC converters 4.1 to 4.n (not shown in FIG. 2) and transmitted to the control unit 15. 1 ~I n and / or voltage U 1 ~U n One of them is threshold I TH , U TH, this indicates a fault 30 of the corresponding DC sub-generator 5.1-5.n. Figure 2 shows, by way of example, a fault 30 in the form of a short circuit fault in the upper DC sub-generator 5.1, in which the lower one of the DC sources 2.1 is shown. Here too, the input voltage of the DC / DC converter 4.1 assigned to the faulty DC source 2.1 and thus assigned to the faulty DC sub-generator 5.1, or in other words connected to it on the input side, drops. The associated DC / DC converter 4.1 then produces at its output 10.1 the same output voltage U as the other DC / DC converters 4.2-4.n. a instead, the voltage also drops there. As a result, the fault-free DC / DC converters 5.2 to 5.n now only supply a total current I Rest to one faulty DC / DC converter 5.1.

[0042] Analogously to the method already described in connection with FIG. 1, the fault 30 is detected by the control unit 15 which monitors the DC sub-generators 5.1 to 5.n. In response, the remaining DC / DC converters 4.2 to 4.n, which are assigned in each case to the fault-free DC sub-generators 5.2 to 5.n, are operated via the control unit 15 to reduce the total current I generated by them. REST is intended to take a default value. Also in FIG. 2, the default value is selected (low) such that, on the one hand, the overcurrent-sensitive components of the DC / DC converter 4.1 assigned to the faulty DC sub-generator 5.1 are protected and their damage is avoided. However, on the other hand, it is also selected (high) such that the fuse 9.1 located in the series connection of fuses 9.1 between the faulty DC source 2.1 and the downstream DC / DC converter 4.1 blows. Since the i2t value of the fuse 9.1 in the series connection decreases with decreasing distance from the faulty DC source 2.1, there is a large probability of blowing exactly the fuse connected immediately downstream of the faulty DC source 2.1. Advantageously, this fuse is also usually the most cost-effective of the fuses 9.1 in the series connection.

[0043] FIG. 3 shows a variant of the method according to the invention in the form of a flow chart, as it can be executed with the EEA 1 according to FIG. 1 or with the EEA 1 according to FIG. 2. In a first step S1, the method starts with the MPP operation of all fault-free DC sub-generators 5.1 to 5.n. At the beginning of the method, by way of example, it is assumed that there are no faulty DC sources 2.1 and thus no faulty DC sub-generators 5.1, so that the number of all fault-free DC sub-generators initially corresponds to the number of all available DC sub-generators 5.1 to 5.n of the EEA 1. In a second step S2, all DC sub-generators 5.1 to 5.n of the EEA 1 that are currently operating are monitored for faults 30. The monitoring is carried out by monitoring the voltage U of any one of the DC sub-generators 5.1 to 5.n. 1 ~U n and / or the current I flowing in the direction of the DC load 20 via the outputs 11.1-11.n of the DC / DC converters 4.1-4.n 1 ~I n is detected and transmitted to the control unit 15. In a third step S3, the control unit 15 detects the detected voltage U 1 ~U n One of the voltage thresholds U TH and / or the detected current I 1 ~I n One of the current thresholds I TH If not, the method returns to the first step S1. However, if the detected voltage U 1 ~U n One of the voltage thresholds U TH If the detected currents I1 to In fall below the current threshold I TH If the voltage falls below the undershoot voltage U k and / or undershoot current I kAccording to this method, the DC sub-generators 5.1 to 5.n with (k=1...n) are shown to be the faulty DC sub-generator 5.k with the faulty DC source 2.k. In this case, the method can be used to determine the total current I Rest The control unit 15 then jumps to a fourth step S4, in which all remaining operational DC / DC converters 4.1 to 4.n that are not assigned to the faulty DC sub-generator 5.k are operated via the control unit 15 with the aim of taking on a default value for the total current I Rest is limited both above and below. The fifth step S5 is to limit the total current I Rest checks whether it has been possible to blow the fuse 9.k connected downstream of the faulty DC source 2.k. This is done, for example, by checking whether the current I k and / or voltage U k This can be checked by detecting whether the current Ik flowing in the direction of the DC load through the output 11.k of the DC / DC converter 4.k exceeds the current threshold I TH and / or the voltage U applied to input 11.k of DC / DC converter 4.k k is the voltage threshold U THIf the threshold voltage continues to remain below 0.5 V, it can be assumed that the fuse 9.k has not blown. If, however, this is not the case, it is assumed that the fuse 9.k connected downstream of the faulty DC source 2.k has blown, resulting in the faulty DC source 2.k being isolated from the shared DC load 20. Once the fuse 9.k has blown, the DC sub-generator 5.k previously indicated as a faulty DC sub-generator now indicates only the non-faulty DC source 2.k, i.e. can again be called a non-faulty DC sub-generator, and can continue to operate. Thus, once the fuse 9.k has been blown, the method returns to the first step S1 where all non-faulty DC sub-generators operate again at the MPP. The number of DC sub-generators continues to correspond to the total number of sub-generators of the EEA 1. However, the DC sub-generator 5.k previously identified as faulty now has at least one less DC source 2.k. However, if in the fifth step S5 it is concluded that the fuse 9.k connected downstream of the faulty DC source 2.k did not blow, then all remaining DC / DC converters 4.1 to 4.n that are not assigned to the faulty DC sub-generator 5.k are deactivated in a sixth step S6, so that their total current I Rest takes on the value 0A. Then, in a seventh step S7, the faulty DC sub-generator 5.k is electrically isolated from the shared DC load 20 and the remaining non-faulty DC sub-generators via the DC separator 13.k assigned to it. The method then jumps to the first step S1 where all non-faulty DC sub-generators operate again at their respective MPPs. However, the EEA 1 now continues to operate without the DC sub-generator 5.k previously identified as faulty, in this case the number of non-faulty sub-generators has been reduced by one. [Explanation of symbols]

[0044] 1 Energy Generation System (EEA) 2.1~2.n DC power supply 3.1~3.n Photovoltaic (PV) strings 4.1~4.n DC / DC Converters 5.1~5.n DC Sub-Generators 6.1~6.n Semiconductor switches 7.1~7.n Inductance 8.1~8.n Input capacitance 9.1~9.n Fuse 10.1~10.n Input 11.1~11.n Output 12.1~12.n Fuse 13.1~13.n DC separator 15 Control Unit 20 DC load 21 Electrolytic cell 30 Disability S1~S7 Method steps

Claims

1. A method for operating an energy generation system (EEA; 1) comprising a plurality of DC sub-generators (5.1 to 5.n) connected in parallel with each other and each connected to a shared DC load (20) via a DC / DC converter (4.1 to 4.n), each of said DC sub-generators (5.1 to 5.n) comprising a DC power source (2.1 to 2.n) connected to said DC / DC converter (4.1 to 4.n) assigned to each of said DC sub-generators (5.1 to 5.n) via at least one fuse (9.1 to 9.n) connected in series to said DC power source (2.1 to 2.n), monitoring each of said DC sub-generators (5.1 to 5.n) for short circuit faults; If monitoring of the DC sub-generators (5.1 to 5.n) indicates a faulty DC sub-generator (5.1), The DC / DC converters (4.2 to 4.n) that are not assigned to the faulty DC sub-generator (5.1) will have a common total current I Ｒｅｓｔ It is operated by The method, wherein the default value is selected such that a time integral formed from the total current I Rest exceeds the i2t value of one of the fuses (9.1) or one of the fuses (9.1) connected in series between a faulty DC power source (2.1) and a DC / DC converter (4.1) assigned to the faulty DC power source (2.1) in order to blow the fuse (9.1).

2. A method for operating an energy generation system (EEA; 1) comprising a plurality of DC sub-generators (5.1 to 5.n) connected in parallel with each other and each connected to a shared DC load (20) via a DC / DC converter (4.1 to 4.n), each of said DC sub-generators (5.1 to 5.n) comprising a DC power source (2.1 to 2.n) connected to said DC / DC converter (4.1 to 4.n) assigned to each of said DC sub-generators (5.1 to 5.n) via at least one fuse (9.1 to 9.n) connected in series to said DC power source (2.1 to 2.n), monitoring each of said DC sub-generators (5.1 to 5.n) for short circuit faults; If monitoring of the DC sub-generators (5.1 to 5.n) indicates a faulty DC sub-generator (5.1), The DC / DC converters (4.2 to 4.n) not assigned to the faulty DC sub-generator (5.1) are operated with a common total current I Rest corresponding to a default value; The method, wherein said default value is selected such that a time integral formed from said total current I Rest is below the i2t value of an overcurrent sensitive component of said DC / DC converter (4.1) assigned to a faulty DC power source (2.1).

3. In monitoring the DC sub-generators (5.1 to 5.n), a current (I １ ~I ｎ ) is detected in each case and the current (I １ ) is the current threshold I ＴＨ In particular, the current (I １ ) changes its current direction, a faulty DC power source (2.1) is indicated; and / or In monitoring the DC sub-generators (5.1 to 5.n), a voltage (U １ ~U ｎ ) is detected in each case, and the detected voltage U １ is the voltage threshold U ＴＨ 3. The method according to claim 1 or 2, wherein if the DC sub-generator (5.1) is indicated, then a faulty DC sub-generator (5.1) is indicated.

4. The input current or output current of the DC / DC converter (4.1 to 4.n) is the detected current (I １ ~I ｎ 4. The method of claim 3, wherein the signal is detected as

5. The total current I Ｒｅｓｔ the default value is selected such that a time integral formed from exceeds the i2t value of one of the fuses (9.1) or one of the fuses (9.1) connected in series between the faulty DC power source (2.1) and a DC / DC converter (4.1) assigned to the faulty DC power source (2.1) in order to blow the fuse (9.1); The method according to any one of claims 1 to 4, wherein if the blowing of the fuse (9.1) at the selected default value does not occur, the DC / DC converters (4.2 to 4.n) not assigned to the faulty DC sub-generator (5.1) are deactivated to set the total current I Rest to a current value of 0 A, and optionally the faulty DC sub-generator (5.1) is isolated from the shared DC load (20) via a DC isolation device (13.1).

6. The method according to any one of claims 1 to 5, wherein faults (30) indicated during monitoring of the DC sub-generators (5.1 to 5.n), and optionally also the success or failure of blowing the fuse (9.1), are signalled by the EEA (1), in particular by a communication unit of the EEA (1).

7. An energy generation system (EEA;1) comprising a plurality of DC sub-generators (5.1 to 5.n) connected in parallel with each other and connected to a shared DC load (20) via respective DC / DC converters (4.1 to 4.n), each of the DC sub-generators (5.1 to 5.n) comprising a DC power source (2.1 to 2.n) connected to the DC / DC converter (4.1 to 4.n) assigned to each of the DC sub-generators (5.1 to 5.n) via at least one fuse (9.1 to 9.n) connected in series to the DC power source (2.1 to 2.n), The energy generating system (EEA; 1), characterized in that the energy generating system (1) further comprises a control unit (15) designed and configured to carry out the method according to any one of claims 1 to 6.

8. The energy generation system (1) according to claim 7, wherein each of the DC sub-generators (5.1 to 5.n) comprises a plurality of DC power sources (2.1 to 2.n) connected in parallel to one another via at least one fuse to the DC / DC converter (4.1 to 4.n) assigned to each of the DC sub-generators (5.1 to 5.n).

9. The energy generation system (1) according to claim 7 or 8, wherein the DC power sources (2.1-2.n) comprise photovoltaic (PV) strings (3.1-3.n) and / or batteries.

10. The energy generation system (1) according to any one of claims 7 to 9, wherein the shared DC load (20) comprises an electrolyser (21).

11. The energy generation system (1) according to any one of claims 7 to 10, wherein the DC / DC converters (4.1 to 4.n) comprise step-down converters and / or the DC / DC converters (4.1 to 4.n) are designed and configured for a step-down function.

12. An energy generation system (EEA;1) comprising a plurality of DC sub-generators (5.1 to 5.n) connected in parallel with each other and connected to a shared DC load (20) via respective DC / DC converters (4.1 to 4.n), each of said DC sub-generators (5.1 to 5.n) comprising a DC power source (2.1 to 2.n) connected to said DC / DC converter (4.1 to 4.n) assigned to each of said DC sub-generators (5.1 to 5.n) via at least one fuse (9.1 to 9.n) connected in series to said DC power source (2.1 to 2.n), The energy generating system (1) further comprises a control unit (15) designed and configured to carry out the method according to claim 2, The overcurrent sensitive component of the DC / DC converter (4.1) assigned to the faulty DC power source (2.1) is connected in parallel with a semiconductor switch (6.1) of the DC / DC converter (4.1) or includes a separate freewheeling diode, including a semiconductor switch (6.1) of the DC / DC converter (4.1), in particular a body diode of the semiconductor switch (6.1).

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