Method for operating a power generation system and power generation system using the method

Abstract

The present application describes a method for operating an electric power generation system (EEA; 1) having a plurality of DC sub-generators (5.1-5.n) which are connected in parallel to each other and are connected to a common DC load (20) via a DC / DC converter (4.1-4.n). Each DC sub-generator (5.1-5.n) comprises a DC source (2.1-2.n), which is connected to a DC / DC converter (4.1-4.n) via at least one fuse (9.1-9.n) connected in series with the DC source (2.1-2.n), and the DC / DC converter (4.1-4.n) is assigned to the corresponding DC sub-generator (5.1-5.n). The method comprises the following steps: monitoring each DC sub-generator (5.1-5.n) for a fault (30), in particular a short-circuit fault, wherein, when the monitoring of the DC sub-generator (5.1-5.n) indicates a faulty DC sub-generator (5.1), a common total current I corresponding to a preset value is supplied to the DC sub-generator (5.1-5.n). Rest Those DC / DC converters (4.2-4.n) which are not assigned to the faulty DC sub-generator (5.1) are operated. The application also relates to a power generation system (1) designed and arranged to carry out the method.

Description

[0001] Technical field of the invention

[0002] The present invention relates to a method of operating an electrical power generation system (EEA). In particular, the present invention relates to the operation of an EEA, wherein faults within the EEA are identified and their destructive effects on components of the EEA are avoided in addition to at least reducing their destructive effects on components of the EEA. In particular, the EEA may be a regenerative EEA having a plurality of DC sub-generators which are connected in parallel to each other and are respectively connected to a common DC load via a DC / DC converter to supply it. In particular, a fault situation may exist when one DC sub-generator, and possibly also a plurality of DC sub-generators, has a fault, such as a short circuit fault. The present invention also relates to an EEA designed and arranged for use with such a method. Prior art

[0003] In the so-called power-to-gas process, electrical energy is converted into a gaseous energy carrier, in particular hydrogen, by an electrolyser. Advantageously, the electrical energy can be regeneratively produced electrical energy. In such a method, the electrolyser and the regenerative EEA supplying the electrolyser can be connected to one another in the form of an independent grid which is not connected at all to the public energy supply network (EVN) operating at alternating voltage or is only temporarily connected thereto.

[0004] Many renewable energy sources are usually designed as DC sources in nature. Since the electrolysis device is operated as a DC consumer, it is advantageous to avoid conversion losses if the independent power grid is also designed as a DC grid. For example, the EEA can have multiple DC sub-generators designed as photovoltaic (PV) sub-generators in the independent power grid, and these DC sub-generators are connected to the input of the electrolysis device or another DC load in parallel with each other through DC / DC converters. The voltage of the DC sub-generator can be decoupled from the voltage at the input of the electrolysis device via the DC / DC converter. Therefore, each DC sub-generator can be operated at its respective maximum power point (MPP=Maximum Power Point) and still provide the electrolysis device with the same output voltage for all DC / DC converters. Here, the working point of the electrolysis device, in particular its power consumption, can be set by the output voltage of the DC / DC converter. Specifically, the superior control unit can adjust the output voltage of the DC / DC converter so that on the one hand, a balance is always maintained between the total power generated and consumed in the independent power grid, and on the other hand, the maximum possible power can always be harvested on the power generated by the regeneration of the PV sub-generator.

[0005] If a PV sub-generator, or possibly a plurality of PV sub-generators, operating as a DC sub-generator, fails, for example, due to a short circuit or double insulation fault, the DC sub-generator operating without fault feeds its power into the faulty DC sub-generator (or possibly into a plurality of faulty DC sub-generators). The DC sub-generator usually comprises one or more DC sources. Here, depending on the size of the EEA, the DC sources of the DC sub-generators are connected to the DC / DC converters assigned to the DC sub-generators via one or more fuses. However, if a fault occurs within the EEA, it may happen that the current flowing from the fault-free DC sources of the EEA into the faulty DC source is not high enough to trigger at least one fuse, via which the faulty DC source is connected to the DC / DC converter assigned to it. Therefore, there is the risk that in the event of a fault, the generated fault current is not sufficient to separate the faulty DC source from the remaining fault-free DC sources by triggering the fuses connected downstream of the faulty DC source without further measures. The resulting current, which is representative of the fault current, cannot be reliably interrupted and, depending on the current strength and duration of the fault current, it may damage or even destroy other components of the EEA, in particular the associated DC / DC converter.

[0006] Document DE 10 2015 007 443 A1 discloses a method and a device for supplementing the feeding of current from at least one current source to a terminal network having a plurality of consumption points. The terminal network is connected to a superior power supply, wherein the consumption points are protected from the influence of the superior power supply via at least one overcurrent protection device. A control unit detects the current flowing in from the superior power supply and the current flowing from the current source into the terminal network. The instantaneous sum value formed by the current is compared with a predetermined maximum current, so that the current flowing out of the current source is reduced when the maximum current is exceeded. The method can be used to prevent the terminal network from overloading.

[0007] Document DE 10 2013 111 869 A1 discloses a PV device, which has an inverter and at least one PV sub-generator, the inverter is connected to an energy supply network via an AC disconnect mechanism, each PV sub-generator has at least one PV string and is connected to the DC connection area of ​​the inverter via a DC line. The PV sub-generator is assigned a DC disconnect unit near the generator, a DC short-circuit switch connected downstream of the DC disconnect unit in the energy flow direction during feeding, and a reverse current fuse connected downstream of the DC short-circuit switch in the energy flow direction, the DC short-circuit switch being used to short-circuit at least one PV string. In addition, the AC short-circuit switch is arranged upstream of the AC disconnect mechanism in the energy flow direction.

[0008] A photovoltaic (PV) device with an arc detection device is known from document US2018 / 210022 A. In the PV device, the PV string is connected to a power converter via a first power line, a DC-DC converter and other power lines. The arc detection device includes a capacitor forming a bypass current path for the DC-DC converter and a current sensor arranged on one of the other power lines between the DC-DC converter and the power converter.

[0009] Document DE 11 2012 007 202 T5 describes a method for operating a regulator for maximum power point tracking (MPPT-Regler), which is designed to transfer power between an input port and an output port by means of the following steps:

[0010] - in a first operating mode of the MPPT regulator: operating a first switching device of the MPPT regulator at a fixed duty cycle; and

[0011] - In a second operating mode of the MPPT regulator: causing the regulating switching device of the MPPT regulator to repeatedly switch between its conducting and non-conducting states to maximize the power extracted from the PV device electrically connected to the input port.

[0012] Document US2016 181781A1 discloses a PV string having a plurality of PV modules electrically connected in series, the PV string having a first end and a second end. A power line having a first string protection unit is electrically connected to the first end, and a return line having a second string protection unit is electrically connected to the second end. One of the string protection units includes a plurality of safety devices selected from the following items: overcurrent protection, arc fault protection, reverse current protection, and ground fault protection. Another string protection unit includes a plurality of safety devices selected from the following items: overcurrent protection, arc fault protection, reverse current protection, ground fault protection, and a remote control switch connected in series with the power line or the return line.

[0013] Document DE 101 36 147 A1 discloses a PV system with a plurality of PV modules and their associated DC / DC converters, which are connected in parallel with each other on the output side to a central inverter. The inverter converts the DC link voltage generated by the DC / DC converter into a sinusoidal AC voltage. In this case, the PV modules are electrically decoupled by their individual DC / DC converters.

[0014] Invention Task

[0015] The object of the present invention is to provide a method for operating an EEA having a plurality of DC sub-generators connected in parallel with each other, by which method damage to the EEA can be reliably avoided in the event of a fault. Specifically, the faulty DC source of the DC sub-generator should be separated from the remaining fault-free DC sources as far as possible by triggering the fuse. However, the generated fault current should be controlled in such a way that under no circumstances - even if the fuse cannot be triggered - overcurrent-sensitive components of the EEA are damaged. The object of the present invention is also to specify an EEA suitable for implementing this method.

[0016] Description of the invention

[0017] The method according to the invention is intended to operate an electric power generation system (EEA) having a plurality of DC sub-generators, which are connected in parallel to each other and to a common DC load via a DC / DC converter. Here, each DC sub-generator has at least one DC source, which is connected to the DC / DC converter assigned to the corresponding DC sub-generator via at least one fuse connected in series with the DC source. The method comprises the following steps:

[0018] Monitor each DC sub-generator for faults, especially short circuit faults,

[0019] When the monitoring of the DC sub-generator indicates a faulty DC sub-generator, the common sum current I corresponding to the preset value is Rest Operation is performed on those DC / DC converters which are not allocated to the faulty DC sub-generator but are allocated to the non-faulty DC sub-generator.

[0020] Each DC sub-generator may have one DC source or more DC sources connected in parallel with the corresponding DC / DC converter. Here, the fuse device may be arranged between the DC source and the DC / DC converter respectively relative to the power flow direction during normal operation of the EEA. The fuse device may be only one fuse device, but it may also be generally multiple fuse devices, which are arranged in a series circuit between the DC source and the DC / DC converter. Here, only one pole of the DC source may be connected to the corresponding DC / DC converter through one fuse device or multiple fuse devices connected in series. However, within the scope of the present invention, each of the two poles of the DC source may also be connected to the assigned DC / DC converter through one fuse device or multiple fuse devices connected in series. Therefore, each DC / DC converter may be connected to only one DC source on the input side. However, alternatively, one, more or each of the DC / DC converters may be connected to multiple DC sources connected in parallel with each other on the input side. In particular, when at least one of the DC / DC converters is connected to multiple DC sources on the input side, the power flow of the DC source may be combined in multiple stages in a cascade manner in the corresponding DC sub-generator. Each stage can have a separate fuse. For example, a so-called main string fuse can protect a generator box, each generator box containing a plurality of so-called string fuses. In this way, a plurality of fuses of different types can be connected in series between the DC source and the DC / DC converter. Here, the triggering threshold of the fuse increases with increasing distance from the DC source and decreasing distance from the DC / DC converter.

[0021] The fault of each DC sub-generator can be monitored in the following manner, that is, the electrical parameters of the DC sub-generator, in particular the current and / or voltage, are continuously detected over time. Here, it is not necessary to monitor each DC source within the DC sub-generator individually. In particular, when a plurality of DC sources connected in parallel to each other as DC sub-generators are connected to a common DC / DC converter, it is sufficient to monitor the DC sources combined in groups, in other words, it is sufficient to monitor the corresponding DC sub-generators. In the monitoring, for example, it can be detected whether a reverse current flows into a faulty DC sub-generator affected by a short-circuit fault. Although the monitoring does not directly provide a faulty DC source, a DC sub-generator containing a faulty DC source is provided.

[0022] The present invention utilizes the effect that, in the event of a fault, in particular a short-circuit fault in one of the DC sources, the voltage of the faulty DC source and the voltage of the DC sub-generator containing the faulty DC source collapse, and a reverse current is caused from the non-faulty DC source. The collapsed voltage is applied to the DC / DC converter assigned to the faulty DC source on the input side, and the DC / DC converter is therefore no longer able to provide a voltage on the output side that corresponds to the output-side voltage of the remaining DC / DC converters that are not connected to the faulty DC source or the faulty DC sub-generator on the input side. Therefore, the generated total current I of the DC / DC converters that are not assigned to the faulty DC sub-generator, i.e., those that are not connected to the faulty DC sub-generator on the input side, is Rest Into the faulty DC sub-generator and there in particular into the faulty DC source of the faulty DC sub-generator. In this case, the total current I Rest The current flows back via the freewheeling diode of the DC / DC converter assigned to the faulty DC sub-generator, ie in the opposite direction to the current flow in normal operation of the EEA.

[0023] The failure of a DC source can also have an effect in the EEA, so that a voltage drop does not only occur at the output of the DC / DC converter assigned to the faulty DC source. Instead, the voltage drop can also be more or less pronounced at the output of all other DC / DC converters. In this case, the voltage in the entire DC bus of the EEA will drop to a small voltage value. However, in this case, the voltage drop at the DC / DC converter assigned to the faulty DC source is slightly more pronounced than the voltage drop at the remaining DC / DC converters not assigned to the faulty DC source, so that here also the above-described total current I from the non-faulty DC sub-generator to the faulty DC sub-generator is caused. Rest .

[0024] According to the invention, those DC / DC converters which are not assigned to the faulty DC sub-generator are now operated with the aim of making the common sum current I Rest corresponds to the preset value. This can be done via coordinated regulation of those DC / DC converters which are not assigned to the faulty DC sub-generator. The coordinated regulation can be carried out with the aid of a control unit acting on all DC / DC converters. In the coordinated regulation, the control unit takes into account the preset value to be regulated. In addition, the currents of all DC / DC converters participating in the coordinated regulation can be provided to the control unit in detail. However, this is not mandatory. More precisely, in addition to the preset value to be regulated, the control unit has a common sum current I of the DC / DC converters participating in the coordinated regulation. Rest Here, the common sum current I RestIf necessary, the portion of the current from the DC load to the DC / DC converter assigned to the faulty DC sub-generator can also be included. Since fewer values ​​must be measured and / or transmitted during the coordinated control, the coordinated control can be simplified overall and the corresponding control unit can be designed more simply. Thus, corresponding to the total current I Rest The fault current does not flow in an uncontrolled manner, but its current intensity is specifically controlled so that the total current I Rest corresponds to a preset value. Here, the preset value can be selected so as to exclude damage to overcurrent-sensitive components of the EEA, in particular to a DC / DC converter assigned to the faulty DC sub-generator (which also means assigned to the faulty DC source). In particular, the overcurrent-sensitive component can be a freewheeling diode of the corresponding DC / DC converter. On the one hand, the sum current I can be limited upwards by the preset value Rest Since the purpose of regulating the relevant DC / DC converter is to make the common sum current I Rest corresponds to the preset value, so the total current I Rest At the same time, it is also limited downward. Specifically, the preset value can be selected so that the fuse connected in series with the DC / DC converter and the faulty DC source is reliably triggered, or in the case of multiple fuses, so that one or more fuses connected in series with the DC / DC converter and the faulty DC source are reliably triggered. Here, for circuit reasons, it is advantageous that in a DC sub-generator having multiple DC sources connected in parallel, the fuse closest to the faulty DC source is triggered first, because compared with other fuses in the DC sub-generator, this fuse usually has a relatively low triggering threshold on the one hand, and on the other hand, is not only triggered by the total current I generated outside the faulty DC sub-generator Rest Flows through, and additionally also flows through the fault current generated inside the faulty DC sub-generator. However, the fault current generated inside the faulty DC sub-generator is usually significantly lower than the total current I generated outside the faulty DC sub-generator Rest The two currents are added together, thus enabling the desired triggering of the fuse in the event of a fault.

[0025] By appropriate operation, the total current I Rest Those DC / DC converters that contribute can convert the total current I Rest The current intensity is adjusted or set to a preset value. For this purpose, the current flowing through the DC / DC converter can be detected for all DC / DC converters and transmitted to the superordinate control unit. The superordinate control unit can add up the detected currents of those DC / DC converters which are not assigned to the faulty DC sub-generator and thereby determine the currently existing total current I Rest By dividing the sum of the current IRest Compared with the preset value, the control unit can control the relevant DC / DC converter to make the total current I Rest Corresponds to the preset value. Here, if the sum value I Rest If the current exceeds or is about to exceed the preset value, at least one current (I2-I n ). Alternatively, however, several or all currents (I2-I n ) to convert the total current I Rest Set to the preset value. On the contrary, when the sum value I Rest When the current I2-I3 is lower than or about to be lower than a preset value, at least one current (I2-I3) can be increased by a corresponding DC / DC converter among the DC / DC converters not assigned to the faulty DC sub-generator. n ), if necessary, several or all currents can also be increased by corresponding DC / DC converters in the DC / DC converter.

[0026] In an advantageous embodiment of the method, when monitoring the DC sub-generators for faults for all DC / DC converters, the current flowing through the DC / DC converters is detected respectively. Here, when the current flowing from the DC / DC converters assigned to the DC sub-generators in the direction of the DC load is below a current threshold I TH When, or in particular when a current flowing from a DC / DC converter assigned to a DC sub-generator in the direction of a DC load changes its current direction, a faulty DC sub-generator can be indicated. Here, a current flowing from a DC / DC converter in the direction of a DC load is evaluated as a positive current, while a current flowing from a DC load in the direction of a DC / DC converter is evaluated as a negative current. According to this definition, a negative current flowing through a DC / DC converter in the direction of a DC load also indicates that a faulty DC sub-generator is connected to the input side of the DC / DC converter involved. When detecting a current flowing through a DC / DC converter, an input current or an output current of the DC / DC converter can be detected.

[0027] As an alternative or additional method to detecting the current flowing through the DC / DC converter, the voltage of the DC sub-generator can also be detected separately to monitor the fault of the DC sub-generator. In this case, when the voltage detected at the DC sub-generator is lower than the voltage threshold U TH, a faulty DC sub-generator is indicated. In this case, the voltage can advantageously be detected on the input side of a 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, when detecting the voltage as well as the current, measuring units that are available in any case in the DC / DC converter can be used.

[0028] In a variant of the method, the preset value can be selected so that in the sum value I Rest The time integral formed on the sum value I is lower than the limit load integral of the overcurrent sensitive component assigned to the DC / DC converter of the faulty DC source (which also means the DC / DC converter assigned to the faulty DC sub-generator). In this way, the overcurrent sensitive component of the DC / DC converter or the DC / DC converter as the overcurrent sensitive component is prevented from being damaged. In addition, the preset value can be advantageously selected so that in the sum value I Rest The time integral formed on the faulty DC source exceeds the limit load integral of the fuse connected in series between the faulty DC source and the DC / DC converter assigned to the faulty DC source as much as possible. The selection of such a preset value is intended to trigger the fuse, thereby separating the faulty DC source from the remaining non-faulty DC sources within the faulty DC sub-generator and from the remaining non-faulty DC sources outside the faulty DC sub-generator.

[0029] In the event of a fault within the EEA, a situation may arise in which the triggering of the fuse connected in series with the faulty DC source does not occur even if the preset value is selected in this way. For example, component tolerances related to overcurrent-sensitive components and the limit load integral of the fuse that are close to each other may favor this situation. However, even in this case, the faulty DC sub-generator can be easily separated from the common DC load and thus from the remaining non-faulty DC sub-generators. In particular, if the fuse does not trigger at the selected preset value, those DC / DC converters that are not assigned to the faulty DC sub-generator can be disabled to reduce the total current I Rest The current value is set to 0A. In this way, a power-off state is formed between the DC / DC converters, in which the faulty DC source or the faulty DC sub-generator can be electrically separated from the common DC load by an electromechanical switching mechanism. Such a switching mechanism is usually present in the EEA in question anyway. However, since the switching operation is carried out in the power-off state, the switching mechanism does not absolutely need to have an arc extinguishing device. Therefore, the design cost of the switching mechanism is significantly lower.

[0030] In an advantageous embodiment of the method, faults indicated during monitoring of the DC sub-generators, and optionally also successful or unsuccessful triggering of the fuses, can be signaled by the EEA. This can be done, for example, by means of a communication unit of the EEA. In this way, the operator of the EEA can be informed of faults and the corresponding required repair measures in good time. In this way, he can take preventive measures in advance in order to repair the faulty DC source or the EEA as efficiently as possible.

[0031] The power generation system according to the present invention comprises a plurality of DC sub-generators, which are connected in parallel to a common DC load via a DC / DC converter. Here, each DC sub-generator has a DC source, which is connected to a DC / DC converter assigned to the corresponding DC sub-generator via at least one fuse connected in series with the DC source. As a characterizing feature, the power generation system also has a control unit, which is designed and arranged to perform the method according to the present invention. The control unit can be a separately designed control unit of the EEA. Alternatively or additionally, the control unit can also be included in a control unit of the DC / DC converter or in multiple control units of the DC / DC converter. In other words, the control unit can therefore also be distributed in the control units of multiple DC / DC converters of the EEA. The advantages mentioned in conjunction with the method are obtained.

[0032] In an advantageous embodiment of the EEA, the DC sub-generators each have a plurality of DC sources, which are connected in parallel to each other via at least one fuse to a DC / DC converter assigned to the corresponding DC sub-generator. Here, the DC sources can also be connected to the DC / DC converters assigned to each DC sub-generator via a series circuit of a plurality of fuses. In this case, the farther the fuses in the series circuit are from the DC source, or also means the closer the fuses in the series circuit are to the corresponding DC / DC converter, the greater the triggering threshold or limit load integral of the fuses may be. In another embodiment of the EEA, the DC sources of one or more DC sub-generators may include photovoltaic (PV) strings and / or batteries. In particular, the common DC load may also include an electrolytic device.

[0033] The EEA may include a buck converter as a DC / DC converter. Specifically, one DC / DC converter, more DC / DC converters or possibly all DC / DC converters of the EEA may respectively include a buck converter and / or respectively include a DC / DC converter with a buck function, i.e., it is designed and arranged to convert an input voltage into a smaller output voltage. The overcurrent sensitive component of the DC / DC converter assigned to the faulty DC source (or also means 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 a semiconductor switch of the DC / DC converter, in particular a body diode of the semiconductor switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention is described below with the aid of the accompanying drawings.

[0036] Figure 1 shows an EEA according to the present invention in a first embodiment;

[0037] Figure 2 shows an EEA according to the present invention in a second embodiment;

[0038] Figure 3 A flow chart of a method according to the invention is shown.

[0039] Description of the drawings

[0040] exist Figure 1 In the figure, an EEA 1 according to the invention is shown in a first embodiment. The EEA 1 comprises a plurality of DC sub-generators 5.1-5.n, which are connected in parallel with each other via respective DC / DC converters 4.1-4.n to a common DC load 20, which is here exemplarily shown as an electrolysis device 21. The EEA 1 also comprises a control unit 15 for controlling the DC / DC converters 4.1-4.n. The control unit 15 is arranged to receive and evaluate measured values ​​of currents and / or voltages detected by measuring units of the DC / DC converters 4.1-4.n. The control unit 15 is also arranged to regulate the individual DC / DC converters 4.1-4.n alone or together with the control units present in the DC / DC converters 4.1-4.n, with the aim of regulating the common sum current I generated by the individual DC / DC converters 4.1-4.n Rest corresponds to the preset value. The DC / DC converters 4.1-4.n Figure 11 is a step-down converter, wherein each DC / DC converter 4.1-4.n has an input terminal 10.1-10.n, an input capacitor 8.1-8.n connected to the input terminal 10.1-10.n, two semiconductor switches 6.1-6.n and an inductor 7.1-7.n connected to the output terminal 11.1-11.n of the DC / DC converter 4.1-4.n. However, according to the present invention, any device having a step-down function (i.e., the input voltage U1-U2 applied to the input terminal 10.1-10.n) may be used. n Converted into a smaller output voltage U applied to the output terminals 11.1-11.n a ) can be used as DC / DC converters 4.1-4.n. Figure 1 In the embodiment of the invention, each DC sub-generator 5.1-5.n comprises only one DC source 2.1-2.n, which is connected to the input terminal 10.1-10.n of the DC / DC converter 4.1-4.n assigned to the DC source 2.1-2.n via a fuse 9.1-9.n. Each DC source 2.1-2.n is exemplarily shown as a photovoltaic (PV) string 3.1-3.n. However, one or more DC sources 2.1-2.n can also be designed as batteries.

[0041] In normal operation of the EEA 1, the DC sources 2.1-2.n designed as PV strings 3.1-3.n operate at their respective maximum power points (MPP=Maximum Power Point). Here, the voltages U1-U2 of the DC sources 2.1-2.n associated with the respective MPPs are n is converted into a common output voltage U a , these voltages U1-U n Applied to the input terminals 10.1-10.n of the DC / DC converters 4.1-4.n assigned to the DC sources 2.1-2.n. With output voltage U a The electrolysis device 21 is supplied as a common DC load 20. In this way it is ensured that the maximum possible regenerative power is always converted by the EEA 1 and fed to the DC load 20.

[0042] During normal operation of the EEA 1, the DC sub-generators 5.1-5.n are monitored for possible faults 30 (e.g. possible short circuit faults). Figure 1 The monitoring is carried out in such a way that the measuring device ( Figure 1 The voltages U1-U2 applied to the input terminals 10.1-10.n of the DC / DC converters 4.1-4.n can be detected by means of the measuring device. nand / or currents I1-I flowing through the output terminals 11.1-11.n of the DC / DC converters 4.1-4.n in the direction of the DC load 20 n If the voltage U1-U applied to the input terminals 10.1-10.n n One is below the voltage threshold U TH and / or currents I1-I flowing toward the DC load 20 via the output terminals of the DC / DC converters 4.1-4.n. n Below the current threshold I TH , the corresponding DC / DC converter 4.1-4.n sends a signal to the control unit 15. Additionally or alternatively, the detected current I1-I n and voltage U1-U n The value of is transmitted to the superordinate control unit 15 , which then evaluates it and recognizes the indication of a fault 30 .

[0043] exist Figure 1 , a fault 30 designed as a short-circuit fault at the DC source 2.1 of one of the DC sub-generators 5.1-5.n (here the DC sub-generator 5.1) is shown by way of example. Due to the short-circuit fault, the voltage U1 of the faulty DC source 2.1 drops to a very small absolute value. In this case, the DC / DC converter 4.1 associated with the faulty DC sub-generator 5.1 or the DC / DC converter 4.1 assigned to the faulty DC source 2.1 can no longer convert the voltage U1 applied on the input side to the common value U1 as the remaining DC / DC converters 4.2-4.n do. a Instead, a voltage which is significantly smaller than the common value U t is now also present at the output of the DC / DC converter 4 . 1 which is assigned to the faulty DC source 2 . 1 . a output voltage. Sometimes it may happen that not only the output voltage of the DC / DC converter 4.1 assigned to the faulty DC source 2.1 drops. Rather, it is also possible that, in response to the faulty DC source 2.1, a voltage drop is formed on the entire DC bus of the EEA 1, i.e., a voltage drop is also formed on those DC / DC converters 4.2-4.n that are not assigned to the faulty DC source 2.1. However, here, the voltage drop of the output voltage at the DC / DC converter 4.1 assigned to the faulty DC source 2.1 is slightly more pronounced than the voltage drops at the other DC / DC converters 4.2-4.n. Since the voltage drop at the output terminal 11.1 of the DC / DC converter 4.1 is at least slightly more pronounced, in the direction of the DC / DC converter 4.1 assigned to the faulty DC source 2.1, according to the I of the DC / DC converters 4.2-4.n respectively assigned to the non-faulty DC sub-generators 5.2-5.n. Rest =I2+I3+…+I nThe total current I Rest Without further measures, the total current I Rest The value of may irreversibly damage overcurrent-sensitive components of the relevant DC / DC converter 4.1. This is the case in particular when the fuse 9.1 connected in series with the faulty DC source 2.1 is not triggered or is not triggered in time to interrupt the fault current.

[0044] According to the present invention, the control unit 15 detects the current I1-I n and / or voltage U1-U n In response to this, the DC / DC converters 4.2-4.n assigned to the DC sub-generators 5.2-5.n that are not faulty are operated by the control unit 15 in order to make the common sum current I generated by these DC sub-generators Rest According to I Rest =I2+I3+…+I n Here, not only the preset value itself, but also the corresponding current I2-I of the individual DC / DC converters 4.2-4.n contribute to the realization of the common preset value. n can all be predetermined from the outset. Here, the preset value is selected so that, on the one hand, damage to the overcurrent-sensitive components of the DC / DC converter 4.1 connected to the faulty DC sub-generator 5.1 is excluded. Specifically, the preset value can be selected so that it is smaller than the limit load integral of the overcurrent-sensitive components of the corresponding DC / DC converter 4.1. On the other hand, the preset value is selected to be as high as possible so that the fuse 9.1 connected downstream of the faulty DC source 2.1 is reliably triggered, thereby separating 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 arranged for the step-down function, the DC / DC converters 4.2-4.n are able to provide a sufficiently high total current I at their output ends even if the radiation on the DC source 2.2-2.n designed as a PV string 3.2-3.n is relatively low. Rest If the fuse 9.1 connected downstream of the faulty DC source 2.1 fails to trip before the load limit integral of the overcurrent-sensitive components of the relevant DC / DC converter 4.1 is exceeded, the total current I Rest The value of 0A is set to avoid damage to overcurrent sensitive components. In particular, the remaining DC / DC converters 4.2-4.n can be disabled. The faulty DC sub-generator 5.1 can then be switched off in the power-off state by Figure 1 The DC separation unit not shown in FIG. Figure 2The DC separation unit 13.1-13.n) shown in FIG. 1 is permanently electrically separated from the common DC load 20 and the remaining non-faulty DC sub-generators 5.2-5.n. The EEA 1 can then continue to operate without the faulty DC sub-generator 5.1, but using the remaining non-faulty DC sub-generators 5.2-5.n. In this case, the separated DC sub-generator 5.1 or its faulty DC source 2.1 can be repaired without risk and then reconnected to the EEA 1.

[0045] although Figure 1 Only one faulty DC sub-generator 5.1 is shown in FIG. 1 , but the method can also be applied to the case where there are multiple faulty DC sub-generators at the same time. This is at least applicable to the case where the number of non-faulty DC sub-generators exceeds the number of faulty DC sub-generators.

[0046] exist Figure 2 In FIG. 1 , a second embodiment of the EEA 1 according to the invention is shown, which is similar in many features to the Figure 1 For the sake of brevity, only the differences from the first embodiment of the EEA 1 will be discussed, while reference will be made to the first embodiment of the EEA 1 for similar features. Figure 1 Description.

[0047] Figure 2 The EEA 1 shown in FIG. 1 also has a plurality of DC sub-generators 5.1-5.n, which are connected in parallel to a common DC load 20 via DC / DC converters 4.1-4.n. Figure 1 compared to, Figure 2 Each DC sub-generator 5.1-5.n in the embodiment includes a plurality of DC sources 2.1-2.n, which are connected in parallel to each other and are connected to the DC / DC converter 4.1-4.n assigned to the corresponding DC sub-generator 5.1-5.n through a series circuit of a plurality of fuses 9.1-9.n. Here, the limit load integral of the fuses 9.1-9.n in each series circuit increases as the distance between the fuses 9.1-9.n and the DC source 2.1-2.n assigned to it increases. A DC separation unit 13.1-13.n is also arranged between each DC sub-generator 5.1-5.n and the DC / DC converter 4.1-4.n assigned to it, through which the corresponding DC sub-generator 5.1-5.n can be electrically separated from the DC / DC converter 4.1-4.n assigned to it. Advantageously, the DC separation units 13 . 1 - 13 . n can be designed without means for extinguishing the arc and are therefore relatively inexpensive.

[0048] Also in Figure 2In the case of DC / DC converters 4.1-4.n (in Figure 2 The measuring unit (not shown) detects the current I1-I of the DC sub-generators 5.1-5.n. n and / or voltage U1-U n , and transmits it to the control unit 15. If the current I1-I n One and / or voltage U1-U n One of them is lower than the corresponding threshold I TH , U TH , which indicates that the corresponding DC sub-generator 5.1-5.n has a fault 30. Figure 2 , a fault 30 in the form of a short-circuit fault in the upper DC sub-generator 5.1 and in the lower DC source 2.1 shown is shown by way of example. Here, the input voltage of the DC / DC converter 4.1 assigned to the faulty DC source 2.1 and therefore also to the faulty DC sub-generator 5.1 (or in other words connected thereto on the input side) also drops sharply. The relevant DC / DC converter 4.1 can no longer provide the same output voltage U at its output 11.1 as the other DC / DC converters 4.2-4.n. a , instead, the voltage also drops sharply at the output terminal 11.1. As a result, the fault-free DC / DC converters 5.2-5.n also add the total current I Rest Feeds the faulty DC / DC converter 5.1.

[0049] Similar to already combined Figure 1 In the method described, the control unit 15 detects a fault 30 by monitoring the DC sub-generators 5.1-5.n. In response, the remaining DC / DC converters 4.2-4.n assigned to the DC sub-generators 5.2-5.n without the fault are operated by the control unit 15 in order to make the total current I generated by these DC sub-generators Rest Use the default value. Figure 2 In the example, the preset value (low) is selected so 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. On the other hand, the preset value (high) is selected so that the fuse 9.1 arranged in the series circuit of fuses 9.1 between the faulty DC source 2.1 and the DC / DC converter 4.1 connected downstream is triggered. Since the limit load integral of the fuse 9.1 in the series circuit decreases with decreasing distance from the faulty DC source 2.1, the fuse that is most likely to be triggered is the fuse connected directly downstream of the faulty DC source 2.1. Advantageously, this is usually also the least expensive fuse 9.1 in the series circuit.

[0050] Figure 3A variation of the method according to the invention is shown in the form of a flow chart, which can be used according to Figure 1 EEA 1 or under Figure 2 1. The method is performed by the EEA 1 of FIG. 1. In a first step S1, the method starts with the MPP operation of all fault-free DC sub-generators 5.1-5.n. Since it is assumed at the beginning of the method that there is no faulty DC source 2.1 and therefore no faulty DC sub-generator 5.1, the number of all fault-free DC sub-generators at the beginning also corresponds to the number of all available DC sub-generators 5.1-5.n of the EEA 1. In a second step S2, all currently operating DC sub-generators 5.1-5.n of the EEA 1 are monitored for faults 30. The monitoring is performed by the following steps: The voltages U1-U2 of the DC sub-generators 5.1-5.n are respectively detected. n and / or currents I1-I2 flowing to the DC load 20 via the output terminals 11.1-11.n of the DC / DC converters 4.1-4.n. n and transmits it to the control unit 15. In a third step S3, the control unit 15 checks the detected voltage U1-U n Is one of them below the voltage threshold U TH and / or the detected current I1-I n Is one of them lower than the current threshold I TH If this is not the case, the method jumps back to the first step S1. If, on the other hand, the detected voltage U1-U n One is below the voltage threshold U TH and / or the detected current I1-I n One is lower than the current threshold I TH , then according to this method the indication has an undervoltage U k and / or undercurrent I k The DC sub-generator 5.1-5.n (k=1...n) is a faulty DC sub-generator 5.k, which has a faulty DC source 2.k. In this case, the method jumps to the fourth step S4, in which all the remaining DC / DC converters 4.1-4.n in operation (which are not assigned to the faulty DC sub-generator 5.k) are operated by the control unit 15, in order to reduce the total current I Rest The preset value is adopted. Therefore, the total current I Rest In the fifth step S5, the total current I Rest Whether the fuse 9.k connected downstream of the faulty DC source 2.k can be triggered. This can be done, for example, by detecting the current I of the DC / DC converter 4.k assigned to the faulty DC sub-generator 5.k k and / or voltage Uk Here it can be assumed that when the current I flows to the DC load via the output terminal 11.k of the DC / DC converter 4.k k Continue to be below the current threshold I TH and / or the voltage U applied to the input terminal 10.k of the DC / DC converter 4.k k Continue to be below the voltage threshold U TH , the fuse 9.k is not triggered. If this is not the case, however, the method assumes that the fuse 9.k connected downstream of the faulty DC source 2.k has been triggered and that the faulty DC source 2.k is therefore separated from the common DC load 20. The DC sub-generator 5.k previously indicated as a faulty DC sub-generator has a non-faulty DC source 2.k again after the triggering of the fuse 9.k and can therefore be referred to as a non-faulty DC sub-generator and can also continue to operate. Accordingly, in the event of the triggering of the fuse 9.k, the method jumps back to the first step S1 in which all non-faulty DC sub-generators are again operated in their MPP. The number of DC sub-generators continues to correspond to the total number of existing sub-generators of the EEA 1. However, the DC sub-generator 5.k previously identified as a faulty one now has at least one less DC source 2.k. If, on the other hand, it is concluded in the fifth step S5 that the fuse 9.k connected downstream of the faulty DC source 2.k has not been triggered, then in a sixth step S6 all remaining DC / DC converters 4.1-4.n which are not assigned to the faulty DC sub-generator 5.k are disabled, so that their total current I Rest The value of is 0A. Then, in a seventh step S7, the faulty DC sub-generator 5.k is electrically separated from the common DC load 20 and the remaining non-faulty DC sub-generators by the DC separation unit 13.k assigned to it. Then, the method jumps to the first step S1, in which all non-faulty DC sub-generators are operated again in their respective MPPs. However, the EEA 1 now continues to operate without the DC sub-generator 5.k previously identified as faulty, in which case the number of non-faulty sub-generators is reduced by one.

[0051] Reference Mark List 1. Electricity Generation System (EEA) 2.1-2.n DC Source

[0052] 3.1-3.n Photovoltaic (PV) strings

[0053] 4.1-4.n DC / DC Converter

[0054] 5.1-5.n DC sub-generator

[0055] 6.1-6.n Semiconductor switches

[0056] 7.1-7.n Inductor

[0057] 8.1-8.n Input Capacitance

[0058] 9.1-9.n Safety devices

[0059] 10.1-10.n Input

[0060] 11.1-11.n Output

[0061] 12.1-12.n Safety device

[0062] 13.1-13.n DC separation unit

[0063] 15 Control Unit

[0064] 20 DC load

[0065] 21. Electrolysis Device 30 Failure S1-S7 Method steps.

Claims

1. A method for operating an electric power generation system EEA (1) having a plurality of DC sub-generators (5.1-5.n), said DC sub-generators (5.1-5.n) being connected in parallel with each other and connected to a common DC load (20) via a DC / DC converter (4.1-4.n), wherein: Each DC sub-generator (5.1-5.n) has a DC source (2.1-2.n), which is connected to the DC / DC converter (4.1-4.n) assigned to the corresponding DC sub-generator (5.1-5.n) via at least one fuse (9.1-9.n) connected in series with the DC source (2.1-2.n), The method comprises the following steps: monitoring each DC sub-generator (5.1-5.n) for faults (30), When the monitoring of the DC sub-generators (5.1-5.n) indicates a faulty DC sub-generator (5.1), a common sum current I corresponding to a preset value is Rest operating those DC / DC converters (4.2-4.n) which are not assigned to said faulty DC sub-generator (5.1), Among them, select the preset value: So that the total current I Rest The time integral formed on the overcurrent is lower than the baseline load integral of the overcurrent sensitive component of the DC / DC converter (4.1) assigned to the faulty DC source (2.1) to prevent damage to the overcurrent sensitive component; or So that the total current I Rest The time integral formed on the load exceeds the limit load integral of a fuse (9.1) connected in series between the faulty DC source (2.1) and a DC / DC converter (4.1) assigned to the faulty DC source (2.1), so as to trigger the fuse (9.1).

2. The method according to claim 1, wherein: The fault (30) is a short circuit fault.

3. The method according to claim 1 or 2, wherein: When monitoring the DC sub-generators (5.1-5.n), the currents (I1-I2) flowing through the DC / DC converters (4.1-4.n) are detected respectively. n ), and wherein, when the current (I1) flowing from the allocated DC / DC converter (4.1) to the common DC load (20) is lower than the current threshold I TH or when the current (I1) flowing from the distributed DC / DC converter (4.1) to the common DC load (20) changes its current direction, indicating a faulty DC source (2.1), and / or The voltages (U1-U2) of the DC sub-generators (5.1-5.n) are detected respectively. n ) to monitor the DC sub-generator (5.1-5.n), and wherein, when the detected voltage (U1) of the DC sub-generator (5.1) is lower than the voltage threshold U TH , it indicates a faulty DC sub-generator (5.1).

4. The method according to claim 3, wherein: Detecting the input current or output current of the DC / DC converter (4.1-4.n) as the detected current (I1-I2) flowing through the DC / DC converter (4.1-4.n) n ).

5. The method according to claim 1, wherein: If the fuse (9.1) is not triggered at the selected preset value, the DC / DC converters (4.2-4.n) not assigned to the faulty DC sub-generator (5.1) are disabled to reduce the total current I Rest Set the current value to 0A.

6. The method according to claim 5, wherein: The faulty DC sub-generator (5.1) is separated from the common DC load (20) by a DC separation device (13.1).

7. The method according to any one of claims 1-2 and 4-6, wherein: A fault (30) indicated in the monitoring of the DC sub-generators (5.1-5.n) is signaled by the EEA (1).

8. The method according to claim 3, wherein: A fault (30) indicated in the monitoring of the DC sub-generators (5.1-5.n) and a successful or unsuccessful triggering of the fuse (9.1) are signaled by the EEA (1).

9. The method according to claim 7, wherein: The signaling is performed by the communication unit of the EEA (1).

10. The method according to claim 8, wherein: The signaling is performed by the communication unit of the EEA (1).

11. A power generation system (1) having a plurality of DC sub-generators (5.1-5.n), wherein the DC sub-generators (5.1-5.n) are connected in parallel to a common DC load (20) via DC / DC converters (4.1-4.n), wherein each DC sub-generator (5.1-5.n) has at least one DC source (2.1-2.n), and the at least one DC source (2.1-2.n) is connected to the DC / DC converter (4.1-4.n) assigned to the corresponding DC sub-generator (5.1-5.n) via at least one fuse (9.1-9.n) connected in series with the at least one DC source (2.1-2.n). It is characterized in that The power generation system (1) further comprises a control unit (15) which is designed and arranged to execute the method according to any one of claims 1-10.

12. The power generation system (1) according to claim 11, wherein: The at least one DC source (2.1-2.n) is a plurality of DC sources which are connected in parallel to each other via at least one fuse to a DC / DC converter (4.1-4.n) assigned to the corresponding DC sub-generator (5.1-5.n).

13. The power generation system (1) according to claim 11, wherein: The at least one DC source (2.1-2.n) comprises a photovoltaic (PV) string (3.1-3.n) and / or a battery.

14. The power generation system (1) according to claim 12, wherein: The at least one DC source (2.1-2.n) comprises a photovoltaic (PV) string (3.1-3.n) and / or a battery.

15. The power generation system (1) according to any one of claims 11 to 14, wherein: The common DC load (20) comprises an electrolysis device (21).

16. The power generation system (1) according to any one of claims 11 to 14, wherein: The DC / DC converter (4.1-4.n) comprises a buck converter and / or wherein the DC / DC converter (4.1-4.n) is designed and arranged for a buck function.

17. The power generation system (1) according to claim 15, wherein: The DC / DC converter (4.1-4.n) comprises a buck converter and / or wherein the DC / DC converter (4.1-4.n) is designed and arranged for a buck function.

18. The power generation system (1) according to any one of claims 11 to 14 and 17, wherein: The overcurrent-sensitive component of the DC / DC converter (4.1) assigned to the faulty DC source (2.1) comprises a separate freewheeling diode connected in parallel with a semiconductor switch (6.1) of the DC / DC converter (4.1) or comprises a semiconductor switch (6.1) of the DC / DC converter (4.1).

19. The power generation system (1) according to claim 15, wherein: The overcurrent-sensitive component of the DC / DC converter (4.1) assigned to the faulty DC source (2.1) comprises a separate freewheeling diode connected in parallel with a semiconductor switch (6.1) of the DC / DC converter (4.1) or comprises a semiconductor switch (6.1) of the DC / DC converter (4.1).

20. The power generation system (1) according to claim 16, wherein: The overcurrent-sensitive component of the DC / DC converter (4.1) assigned to the faulty DC source (2.1) comprises a separate freewheeling diode connected in parallel with a semiconductor switch (6.1) of the DC / DC converter (4.1) or comprises a semiconductor switch (6.1) of the DC / DC converter (4.1).

21. The power generation system (1) according to claim 18, wherein: The overcurrent-sensitive component of the DC / DC converter (4.1) assigned to the faulty DC source (2.1) comprises the body diode of the semiconductor switch (6.1).

22. The power generation system (1) according to claim 19 or 20, wherein: The overcurrent-sensitive component of the DC / DC converter (4.1) assigned to the faulty DC source (2.1) comprises the body diode of the semiconductor switch (6.1).

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