Method for operating a power supply system, power supply system, and load connection module

Abstract

The invention is based on a method for operating a power supply system (10), comprising multiple DC generator units (12, 14), each designed as a fuel cell system (16, 18) comprising one or more fuel cell stacks (20), at least one load connection module (22), in particular grid connection module, having at least one inverter (24) for converting a current generated by the DC generator units (12, 14) into a preferably grid-compatible AC voltage, and an electrical intermediate circuit (26) via which the multiple DC generator units (12, 14) are connected to the load connection module (22). The invention proposes for a load connection module individual voltage to be measured by the load connection module (22) connected to the electrical intermediate circuit (26) and for an associated DC generator individual voltage to be measured by each of the DC generator units (12, 14) connected to the electrical intermediate circuit (26), wherein a voltage-measuring system (28, 30, 32) that ascertains these individual voltages is selected as a reference measuring system (34), which uses at least one individual voltage measurement as a reference measurement by way of which measured values from other voltage-measuring systems (28, 30), from which the other individual voltages are ascertained, are compared with one another, in particular continuously.

Description

[0001] R.414134

[0002] - 1 -

[0003] Description

[0004] Procedure for operating an energy supply system, energy supply system and load connection module

[0005] State of the art

[0006] A method for operating an energy supply system has already been proposed, comprising several DC generator units, each designed as a fuel cell system with one or more fuel cell stacks, at least one load connection module, which has at least one inverter for converting a current generated by the DC generator units into an AC voltage, and an electrical intermediate circuit through which the several DC generator units are connected to the load connection module.

[0007] Fuel cells are seen as a solution for the necessary further development of the power supply system within the framework of the energy transition. Fuel cell systems have the advantage that, in their smallest configuration, they exhibit a relatively low electrical output compared to systems with similar electrical efficiency, for example, 20 kW. This allows for flexible scaling to power supply systems with higher total output by connecting several such 20 kW fuel cell systems. Further intermediate stages are introduced in this scaling process; for example, five 20 kW fuel cell systems form a power supply system with 100 kW. These power supply systems can, in turn, be interconnected if even higher outputs are required. Within such a power supply system, necessary functions can be bundled to reduce costs.An example of this is the conversion of the fuel cell systems R.414134.

[0008] - 2 - the supplied direct current is converted into alternating current by a DC / AC converter. In the example of the 100kW power supply system, this DC / AC converter can be implemented as a single large 100kW DC / AC converter or as five smaller 20kW converters. Of course, further intermediate stages are possible, or an oversized DC / AC converter could be used. A necessary aspect of the conversion to alternating current is buffering or additional consumption of electrical energy to meet the power control requirements (minimum power, speed of power adjustment) demanded by a consumer or grid connection rules (so-called grid codes), as the fuel cell systems can otherwise be a limiting factor. In particular, the control speed, but also the minimum power, represent limitations of fuel cell systems. To circumvent this, storage systems (e.g.,Batteries or capacitors / supercapacitors) and / or additional loads such as heating resistors are installed. Due to varying measurement inaccuracies, e.g., of loads and power supplies connected to a DC bus, each fuel cell system typically measures a different voltage. In the DC networks of known power supply systems with multiple fuel cell systems, no voltage matching takes place, and the inaccuracies in voltage measurement and the resulting power measurement, along with their potentially negative effects on wear, power regulation, etc., are accepted.

[0009] Disclosure of the invention

[0010] The invention relates to a method for operating an energy supply system comprising several DC generator units, each configured as a fuel cell system with one or more fuel cell stacks, at least one load connection module, in particular a grid connection module, which has at least one inverter for converting a current generated by the DC generator units into an AC voltage, preferably grid-compatible, and an electrical intermediate circuit through which the several DC generator units are connected to the load connection module. R.414134

[0011] - 3 -

[0012] It is proposed that a load connection module voltage be measured from the load connection module connected to the electrical intermediate circuit, and that a corresponding DC generator voltage be measured from each of the DC generator units connected to the electrical intermediate circuit. A voltage measurement system determining one of these individual voltages is selected as a reference measurement system, from which at least one individual voltage measurement is used as a reference measurement. Measured values ​​from other voltage measurement systems, from which the other individual voltages are determined, are then compared, particularly continuously, with each other. This allows advantageous operating characteristics for the power supply system to be achieved. Advantageously, voltage-balanced operation of the fuel cell systems of the power supply system can be achieved.Advantageously, this enables particularly precise calculation of relative individual power output and / or absolute total power output. It also allows for more uniform wear of the fuel cell systems within the energy supply system. Furthermore, it is advantageous not only to compensate for initial deviations between interconnected fuel cell systems, but also to compensate for voltage deviations between individual fuel cell systems within the energy supply system caused by temperature drift and / or long-term drift. Additionally, voltage balancing allows for the advantageous measurement of smaller voltage differences, enabling the overall system to communicate via a DC link voltage, allowing components connected to the DC link to react according to a predefined control strategy.Furthermore, a cost-effective method for increasing measurement accuracy can be advantageously provided, especially compared to providing high-precision voltage measuring devices on each component or fuel cell system of the energy supply system.

[0013] The energy supply system is, in particular, a power system formed from several interconnected fuel cell systems for generating electrical energy. Preferably, the electrical energy is provided by the energy supply system in the form of alternating current. The energy supply system can, for example, be used in a photovoltaic park with R.414134

[0014] - 4 -

[0015] The system can be used with multiple power generators in a network. The energy supply system can, for example, be an island-capable DC system with multiple power generators. The fuel cell stacks can be SOFC (Solid Oxide Fuel Cell) stacks or stacks of another fuel cell type. The load connection module can also be referred to as a grid module. The inverter of the load connection module is designed to operate according to predefined grid regulations. For example, the inverter of the load connection module is able to disconnect from the public power grid, connect to the public power grid, and / or react to frequency or voltage changes, e.g., in the public power grid. The load connection module is specifically designed to convert the electrical energy generated by the DC generators so that it can be used by a consumer (load).Preferably, the load connection module is designed to convert the electrical energy generated by the DC generator units so that it can be fed into the public power grid. The intermediate circuit is, in particular, an electrical circuit that connects the DC generator units to the load connection module.

[0016] The load connection module individual voltage is, in particular, the measured value for a voltage, especially a DC voltage, that is determined by a voltage measuring system assigned to the load connection module as being applied to the load connection module, preferably to a DC side of the inverter of the load connection module. The DC generator individual voltage is, in particular, the measured value for a voltage, especially a DC voltage, that is determined by a voltage measuring system assigned to one of the DC generator units of the power supply system as being applied to the respective DC generator unit. Preferably, each DC generator unit and the load connection module is assigned at least one, preferably exactly one, separate voltage measuring system. The voltage measuring systems are preferably voltage measuring devices / voltmeters, especially DC voltage measuring systems / DC voltmeters.In particular, the measured values ​​of the other voltage measurement systems, from which the other individual voltages are determined, are continuously compared and / or adjusted relative to the instantaneous measured value of the reference measurement. R.414134.

[0017] - 5 -

[0018] Furthermore, it is proposed that the voltage measurement system with the highest measurement precision for voltage measurements be selected as the reference system from all the voltage measurement systems of the load connection module and the DC generator units. This allows for particularly precise voltage balancing and / or highly accurate measured values ​​for all components of the power supply system to which the calibrated voltage measurement systems are assigned. Advantageously, only one voltage measurement system from all the voltage measurement systems in the power supply system needs to have enhanced precision. This also ensures that all other, less precise voltage measurement systems still exhibit very high relative and / or absolute measurement accuracy. This approach advantageously enables particularly cost-effective yet precise and comprehensive voltage monitoring.In particular, the voltage measurement system with the highest measurement precision is a (DC) precision voltage measurement system. Specifically, this (DC) precision voltage measurement system is based on precision components or methods such as delta-sigma ADCs, guarding techniques, four-wire measurements, and / or low-drift amplifiers, etc., while the other voltage measurement systems are preferably designed without such precision components. The other voltage measurement systems with lower measurement precision can, for example, be low-cost voltmeters.

[0019] Furthermore, it is proposed that the voltage measurement system of the load connection module be selected as the reference measurement system. This would advantageously simplify maintenance and / or replacement of the voltage measurement system. Alternatively, one of the voltage measurement systems of one of the DC generator units could also be selected as the reference measurement system. The reference measurement system could be integrated into and / or designed as a high-precision power supply unit.

[0020] Furthermore, it is proposed that, for the purpose of adjusting the other individual voltages, an individual correction factor is applied to the respective measured value of each of these other individual voltages, in particular the currently determined value, whereby the respective individual correction factor for the R.414134

[0021] - 6 -

[0022] The reference measurement system for each of the various voltage measurement systems is formed by a quotient of a measured value of the individual voltage of the reference measurement system and a measured value of the respective other individual voltage, which was measured at the time of the reference measurement by the respective other voltage measurement system that also measures the other individual voltage to be calibrated, in particular the current voltage. This allows advantageous operating characteristics for the power supply system to be achieved. Advantageously, voltage-balanced operation of the fuel cell systems of the power supply system can be achieved. Advantageously, voltage balancing can be enabled in a particularly simple manner. The reference measurement can be performed, for example, during the commissioning of the power supply system.Alternatively, the reference measurement can also be performed at a different time, for example, at any point during normal operation of the power supply system. It is conceivable that the reference measurement is carried out with a special measurement program of the reference measurement system with increased measurement precision. Preferably, the reference measurement is performed during an operating time of the power supply system when no or only small currents are flowing. Preferably, the reference measurement is performed in an operating state of the power supply system in which no or only small currents are flowing (e.g., an idle operating state). This advantageously minimizes the voltage drop across lines, current components, busbars, etc., of the power supply system and any resulting effect on the reference measurements.It is also conceivable that the reference measurement is repeated once, several times, or regularly, particularly to check the individual correction factors and / or to update them. The correction factor of the nth voltage measurement system different from the reference measurement system k. n This preferably corresponds to the formula kn ~ Um,n / Um,ref, where U m ,n is the (DC) voltage detected at the time of the reference measurement by the nth voltage measurement system at its associated component (load connection unit or preferably fuel cell system) and wherein R.414134

[0023] - 7 -

[0024] U m , r ef is the (DC) voltage recorded by the reference measurement system at its associated component (fuel cell system or, preferably, load connection unit) at the time of the reference measurement. The recorded (DC) voltages are preferably transmitted between the components by a higher-level communication system of the power supply system, in particular at least between the reference measurement system and the other voltage measurement systems. The higher-level communication system can, for example, be an edge controller of the power supply system. Alternatively, however, it is also conceivable that the communication system that facilitates communication between the components involved is only added (once or repeatedly) to the power supply system for carrying out the reference measurement and calculating the correction factors, and is then removed from the power supply system again.In particular, the voltage measurement systems and the reference measurement system must at least be capable of transmitting voltage values ​​to the communication system. Additionally, the voltage measurement systems and the reference measurement system may be capable of receiving voltage values ​​or correction factors via the communication system.

[0025] To determine the balanced instantaneous individual voltage of a component of the power supply system / the nth component of the power supply system / the nth fuel cell system U n , kon- then the currently measured actual voltage U n of the nth voltage measurement system by the correction factor k n of the nth voltage measurement system.

[0026] U n ,corr = Ul / kl

[0027] If the individual correction factors are periodically re-determined and recalculated, a particularly high degree of precision and / or reliability can be achieved. Furthermore, this allows for the advantageous consideration of drifts or other effects on the stresses.

[0028] Alternatively or additionally, the individual correction factors for different operating temperatures of the DC generator units, especially before and after a warm-up phase or any other phase with R.414134

[0029] - 8 - By determining and calculating significant temperature changes in a fuel cell system of the DC generator units, particularly high precision and / or reliability can be advantageously achieved. Furthermore, drifts or other effects on the voltages caused by temperature changes can be advantageously taken into account. A "significant temperature change" shall be understood to mean, in particular, a temperature change of at least 10 K, preferably at least 15 K, and preferably at least 20 K.

[0030] Additionally, it is proposed that the measured values ​​of the other individual voltages to be calibrated be calculated by averaging them over a definable measurement period. This advantageously further increases the precision of the calibrated measured values. Measurement disturbances (e.g., due to EMC interference or other measurement artifacts) can also be advantageously prevented. For example, averaging could be performed over one second or several seconds. Preferably, the measurement period is selected such that averaging is performed over a sufficient number of individual measurements (e.g., at least 30 or at least 50), particularly to cover individual outlier values.

[0031] Furthermore, it is proposed that an intermediate circuit voltage for the electrical DC link be determined from the balanced individual voltages, particularly by averaging. This allows the overall system to advantageously communicate via the DC link voltage. Consequently, the components connected to the electrical DC link can respond advantageously according to a predefined control strategy. This can advantageously optimize the operation of the power supply system and / or increase its efficiency.

[0032] In a further aspect of the invention, which can be considered on its own or in combination with at least one, in particular in combination with one, in particular in combination with any number of the other aspects of the invention, a method for operating the energy supply system is provided, comprising the several DC generator units, the at least one load connection module, and the electrical intermediate circuit, as well as further comprising at least one storage system for storing R.414134

[0033] - 9 - electrical energy, such as a battery or a capacitor / supercapacitor, to which an instantaneous state-of-charge parameter can be assigned at any given time, whereby an intermediate circuit voltage of the electrical intermediate circuit is set and / or regulated depending on the instantaneous state-of-charge parameter. This advantageously allows the energy supply system to be independent of higher-level communication systems. In known energy supply systems with the components mentioned above, communication for setting a currently correct power setpoint at the fuel cell systems takes place via a higher-level communication system. If this system fails, the power setpoint is no longer updated and the storage system can run empty or full, so that the entire energy supply system can no longer respond and has to be shut down.This problem can be advantageously prevented by the proposed invention. Advantageously, a high availability of the energy supply system can be achieved. Advantageously, it can be particularly well-suited for island grids / grids that must operate autonomously. Advantageously, it could even be advantageous to completely dispense with higher-level communication systems in the energy supply system. This could advantageously result in cost savings and / or a reduction in system complexity. Furthermore, improved cybersecurity can be advantageously achieved, especially since no vulnerable higher-level communication system exists and / or since a physical quantity (the DC link voltage) serves as / is sufficient as the communication medium for controlling the state-of-charge parameter.

[0034] The storage system is specifically designed to compensate for fluctuations in energy demand or energy production in the power supply unit / fuel cell systems. Preferably, the storage system is responsive and / or has sufficient storage capacity, for example, comparable to 1 F to 20 F. In particular, the storage system serves to counteract the inertia of the fuel cell systems during load fluctuations, to prevent high wear of fuel cell stacks due to frequent switching on, off, and / or off of the respective fuel cell systems, to improve system efficiency by supporting the start-up of fuel cell systems, and to reduce the start-up time of R.414134.

[0035] - 10 -

[0036] The storage system is designed to bridge gaps in fuel cell systems, cover peak loads, and / or compensate for fluctuations in the operation of fuel cell systems in conjunction with non-constant energy sources such as wind or solar. Preferably, the storage system provides power regulation capacity required by a consumer or a grid connection controller for the energy supply system. For example, if a higher power output than that currently supplied by the energy supply system is quickly requested, the storage system steps in and supplies part of the difference until the fuel cell systems, which are slow to respond, have adjusted. Conversely, if a lower power output than that currently supplied by the energy supply system is quickly requested, the storage system steps in and absorbs part of the difference until the fuel cell systems, which are slow to respond, have adjusted.The state-of-charge parameter can be, for example, the state-of-charge value / charge level of a battery or the voltage of a capacitor / supercapacitor. "Designed" and / or "configured" should be understood to mean specifically programmed, designed, and / or equipped. The fact that an object is designed or configured for a specific function should be understood to mean, in particular, that the object fulfills and / or performs this specific function in at least one application and / or operating state.

[0037] Furthermore, it is proposed that the DC link voltage be set and / or regulated according to a predetermined DC link voltage-state-of-charge parameter characteristic curve, in particular a DC link voltage-state-of-charge parameter characteristic curve, wherein the DC link voltage-state-of-charge parameter characteristic curve preferably has an increasing slope, apart from possible deadband regions. This enables particularly advantageous control of the power supply system. Advantageously, a power control variable of the DC generator units can be controlled depending on the remaining buffer capacity available. Advantageously, the smoothest possible continued operation can be achieved in the event of a failure of a higher-level communication system. In the DC link voltage-state-of-charge parameter characteristic curve, the DC link voltage is specifically related to the state-of-charge parameter, preferably the state of charge of the R.414134.

[0038] - 11 -

[0039] The graph shows the DC link voltage and state-of-charge parameter characteristic curve of the energy storage system. The described upward slope of the DC link voltage and state-of-charge parameter characteristic curve means, in particular, that a lower DC link voltage is set / regulated at low state-of-charge parameters / charge levels. Conversely, the described upward slope of the DC link voltage and state-of-charge parameter characteristic curve means, in particular, that a higher DC link voltage is set / regulated at higher state-of-charge parameters / charge levels. Lowering the DC link voltage when the energy storage system is discharging can, in particular, help to reduce system load, increase efficiency, extend the discharge time of the energy storage system, and / or prevent damage to components.Lowering the DC link voltage during a discharging energy storage system preferably ensures better matching of energy output to the remaining available energy and protects the power supply system from overload, especially when only a small amount of electrical energy remains in the storage system. A deadband region is, in particular, a region of a characteristic curve in which small changes in an input signal have no effect on the output. The DC link voltage-state-of-charge parameter characteristic curve can also be referred to as the DC link voltage-state-of-charge parameter droop. Characteristic curve regions outside of deadband regions can be linear or non-linear, preferably increasing.In particular, the DC link voltage-charge state parameter characteristic ensures that power control variables of the energy supply system are adjusted slowly, especially to avoid oscillations of current and / or voltage and preferably to ensure stability.

[0040] Additionally, it is proposed that the operating power of the power supply system, in particular the DC generator units of the power supply system, be adjusted and / or regulated at least in one operating state of the power supply system in which the DC link voltage of the electrical DC link is set and / or regulated as a function of the current state-of-charge parameter, preferably as a function of the power control variable-DC link voltage characteristics of the DC generator units. This allows for a particularly advantageous control of R.414134

[0041] - 12 -

[0042] Energy supply systems are enabled. Advantageously, at least temporary independence from higher-level communication systems / control units can be achieved. Greater autonomy / suitability for stand-alone solutions can be advantageously achieved. Apart from possible deadband regions, the power control variable-DC link voltage characteristic curve exhibits a downward slope with increasing DC link voltage. This means, in particular, that at higher DC link voltages, significantly more power is delivered by the respective fuel cell systems, and that at lower DC link voltages, less power is delivered by the fuel cell systems.

[0043] Furthermore, it is proposed that the adjustment and / or regulation of the DC link voltage and / or the adjustment and / or regulation of the operating power of the power supply system be performed by a component connected to the DC link and independently of a higher-level control unit, such as an edge controller. This enables particularly advantageous control of the power supply system. Advantageously, at least temporary independence from higher-level communication systems / control units can be achieved. Advantageously, greater autonomy / suitability for off-grid solutions can be achieved. In particular, the load connection module (co-located with the fuel cell systems), preferably a control unit of the load connection module, is provided for the adjustment and / or regulation. The load connection module is preferably DC grid-forming.The load connection module preferably has a control function for the state of charge of the storage system. The storage system is preferably part of the load connection module. Alternatively, however, the storage system could also be designed separately from the load connection module. The DC generator units are preferably current-controlled. Alternatively, a separate control unit and / or regulation unit located locally in the intermediate circuit and / or one or more control units and / or regulation units of one or more of the fuel cell systems could be provided for adjustment and / or regulation. In particular, it is conceivable that the load connection module and / or the fuel cell systems or one of the control units detects when no higher-level communication is (or is no longer) possible or available, and R.414134.

[0044] - 13 - automatically switch to an operating mode in which they behave according to the power-control variable-DC-circuit voltage characteristic curve, in particular the power-DC-circuit voltage characteristic curve, of the power supply system, in particular the fuel cell system. A "control and / or regulating unit" shall be understood to mean, in particular, a unit with at least one control electronics unit. A "control electronics unit" shall be understood to mean, in particular, a unit with a processor unit and a memory unit, as well as an operating program stored in the memory unit. The higher-level control and / or regulating unit may be part of the power supply system or be arranged and / or designed separately from it.

[0045] Furthermore, the energy supply system is proposed, comprising the multiple DC generator units, each configured as a fuel cell system with one or more fuel cell stacks, the at least one load connection module, in particular a grid connection module, which includes at least one inverter for converting the current generated by the DC generator units into an AC voltage, preferably grid-compatible, and the electrical intermediate circuit through which the multiple DC generator units are connected to the load connection module, or the load connection module for the energy supply system, wherein the load connection module is provided for carrying out the method described above. This allows advantageous operating characteristics to be achieved for the energy supply system.Advantageously, a voltage-balanced operation of the fuel cell systems in the energy supply system can be achieved. Advantageously, a particularly precise calculation of relative individual power output and / or absolute total power output can be enabled.

[0046] The methods, energy supply system, and load connection module according to the invention are not intended to be limited to the application and embodiment described above. In particular, the methods, energy supply system, and load connection module according to the invention can be combined with a number of individual elements, components, and units as specified herein to achieve a functionality described herein.

[0047] - 14 -

[0048] The number of process steps may differ. Furthermore, for the value ranges specified in this disclosure, values ​​lying within the stated limits shall also be considered disclosed and freely usable.

[0049] drawing

[0050] Further advantages will become apparent from the following description of the drawing. The drawing illustrates an embodiment of the invention. The drawing, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0051] They show:

[0052] Fig. 1 shows a schematic representation of an energy supply system,

[0053] Fig. 2 shows a schematic flowchart of a procedure for operating the energy supply system,

[0054] Fig. 3 shows a DC link voltage-state of charge parameter characteristic curve used in the method and

[0055] Fig. 4 shows a power control variable-intermediate circuit voltage characteristic curve used in the method.

[0056] Description of the exemplary embodiment

[0057] Figure 1 shows a schematic representation of a power supply system 10. The power supply system 10 is connected to a public power grid 48. The power supply system 10 is connected to a load 50 that is separate from the public power grid 48. The power supply system 10 comprises several DC generator units 12, 14, in particular, among others, a first DC generator unit 12 and a second DC generator unit 14, which can represent further DC generator units. The DC generator units 12, R.414134

[0058] - 15 -

[0059] The 14 units are each configured as fuel cell systems 16 and 18. Each fuel cell system 16 and 18 includes at least one fuel cell stack 20. The DC generator units 12 and 14 each comprise a voltage measurement system 28 and 30, respectively. The voltage measurement systems 28 and 30 are each configured as DC voltmeters. The voltage measurement system 28 of a first DC generator unit 12 of the power supply system 10 is configured to determine a measured value of a DC voltage (output) of a first fuel cell system 16 of the first DC generator unit 12. The voltage measurement system 30 of a second DC generator unit 14 of the power supply system 10 is configured to determine a measured value of a DC voltage (output) of a second fuel cell system 18 of the second DC generator unit 14.

[0060] The power supply system 10 includes a load connection module 22. The load connection module 22 forms a grid connection module for connection to the public power grid 48. Furthermore, the load connection module 22 is designed to connect loads 50, which are not connected to the public power grid 48, to the power supply system 10. The load connection module 22 includes an inverter 24. The inverter 24 is designed to convert direct current generated by the direct current generator units 12, 14 into a grid-compatible or other alternating current. The power supply system 10 includes a storage system 36. The storage system 36 is designed as part of the load connection module 22. The storage system 36 is designed to store electrical energy. The storage system 36 is designed to release electrical energy in a controlled manner, e.g., to load 50 or to the public power grid 48.The storage system 36 is exemplified as a supercapacitor system. It could also include a battery or alternatively be configured as a battery. A (momentary) state-of-charge parameter, in particular a state of charge (SoC) or charging voltage, can be assigned to the storage system 36 at any given time. The load connection module 22 includes a DC-DC converter 52. The DC-DC converter 52 is designed to adjust the voltage level of the DC voltage before it is fed into the storage system 36 and / or after it is output from the storage system 36. The load connection module 22 includes a generator circuit breaker (GCB) 54, which is an R.414134.

[0061] - 16 -

[0062] The electrical connection of the load connection module 22 to the public power grid 48 is also secured by a circuit breaker 56 in a known manner. The switching on and off of the energy supply system 10 from the load 50 and / or the public power grid 48 is made possible.

[0063] The load connection module 22 includes a voltage measurement system 32. The voltage measurement system 32 of the load connection module 22 is designed to determine a measured value of a DC voltage (an input) of the load connection module 22. The voltage measurement system 32 of the load connection module 22 forms a reference measurement system 34 of the power supply system 10, particularly for the procedure described below. Alternatively, one of the other voltage measurement systems 28, 30, 32 could also be selected as the reference measurement system 34. However, in the exemplary case shown in the present figures, the voltage measurement system 32 of the load connection module 22 has the highest measurement precision for voltage measurements, especially for DC voltage measurements in the voltage range of the intermediate circuit 26 (here, for example, approximately 800 V), and is therefore selected as the reference measurement system 34.

[0064] The power supply system 10 has an electrical intermediate circuit 26. The electrical intermediate circuit 26 connects the several DC generator units 12, 14 to the load connection module 22. The electrical intermediate circuit 26 includes a switching unit 58, which allows individual fuel cell systems 16, 18 to be connected to and disconnected from the electrical intermediate circuit 26. The fuel cell systems 16 also each have a DC converter 60, which connects the fuel cell stacks 20 to the intermediate circuit 26.

[0065] The energy supply system 10 can also be connected to a higher-level control and / or regulation unit 46. The higher-level control and / or regulation unit 46 can be designed to influence the fuel cell systems 16, 18 and / or the load connection module 22. However, a configuration without the higher-level control and / or regulation unit 46 is also conceivable. In addition, the fuel cell systems 16, 18 and / or the load connection module 22 can each have their own local control.

[0066] - 17 - and / or control units (not shown) which may either be subordinate to the superior control and / or regulation unit 46, or may act independently, in particular in the absence or failure of the superior control and / or regulation unit 46.

[0067] Figure 2 shows a schematic flowchart of a method for operating the power supply system 10. The method comprises a first process part 62, which could also be a standalone step. In the first process part 62, DC voltages dropping across components of the power supply system 10 / the electrical intermediate circuit 26 are equalized. In at least one process step 100, which in particular initiates a reference measurement, a command, e.g., a broadcast message, is sent by the higher-level control and / or regulation unit 46 or by an external control and / or regulation system temporarily connected to the power supply system 10. This command instructs the components of the electrical intermediate circuit 26, in particular the voltage measurement systems 28, 30, 32 of the fuel cell systems 16, 18 and the load connection module 22, to measure the current measured values ​​of the voltages Ui, L, ..., U. n and U mto be stored. In at least one further process step 110, the load connection module individual voltage U is then measured by the voltage measuring system 32 of the load connection module 22 connected to the electrical intermediate circuit 26. m Furthermore, in process step 110, the voltage measuring systems 28, 30 measure the respective individual DC generator voltage Ui, L , ..., U of each of the DC generator units 12, 14 connected to the electrical intermediate circuit 26. n measured. In at least one further process step 120, the voltage measurement system 32 of the load connection module 22 is defined as the reference measurement system 34. The measurement of the load connection module individual voltage U m This is selected as the reference measurement. The selected load connection module individual voltage U m This is then used as the reference voltage U mThe reference voltages used / determined are the individual DC generator voltages Ui, U2, ..., U, which were also determined during the reference measurement. n are considered the values ​​U m ,i, U m ,2, ..., U m ,n stored and used for a continuous voltage adjustment of the future DC generator individual voltages Ui, U2, ..., U, as explained below. n used. R.414134

[0068] - 18 -

[0069] From the stresses determined in the reference measurement, an individual correction factor k is then calculated in at least one further process step 130. nThe correction factor is determined for each of the voltage measurement systems 28, 30, 32, which are different from the reference measurement system 34. The correction factor is calculated as a quotient of the measured value of the individual voltage of the reference measurement system 34 during the reference measurement and the measured value of the respective other individual voltage, which was measured by the corresponding other voltage measurement system 28, 30 at the time of the reference measurement. The individual correction factors can be periodically re-determined and recalculated. For this purpose, procedural steps 100 to 130 are repeated. The individual correction factors can also be determined and calculated for different operating temperatures of the DC generator units 12, 14, in particular before and after a warm-up phase or another phase with significant temperature changes of a fuel cell system 16, 18 of the DC generator units 12, 14.For this purpose, process steps 100 to 130 are carried out for the different temperatures. In at least one further process step 130, the corresponding individual correction factor ki, kz, ..., k is applied to adjust the other individual voltages. n based on the currently determined respective measured value Ui, Uz, ..., U n Each of these individual stresses is applied. The individual correction factors ki, kz, ..., k nThe values ​​can be managed and stored centrally, e.g., in the higher-level control and / or regulation unit 46, or managed and stored locally, e.g., in the components of the electrical DC link 26 themselves, or all together in the load connection module 22. The measured values ​​of the individual voltages to be balanced are calculated by averaging them over a definable measurement period. In at least one further process step 140, a DC link voltage for the electrical DC link 26 is determined from the balanced individual voltages.

[0070] The procedure comprises a second procedure part 64. The second procedure part 64 is based on the determined intermediate circuit voltage. However, if the intermediate circuit voltage is determined by other means, e.g., via individual high-precision voltage measuring devices, the second procedure part 64 could also be carried out independently of the first procedure part 62. Hence R.414134

[0071] - 19 - the second part of the process 64 could also be used independently. The purpose of the second part of the process 64 is to adjust and / or regulate the intermediate circuit voltage of the electrical intermediate circuit 26 as a function of the current state of charge parameter of the storage system 36. This results in the adjustment and / or regulation of a power control variable of the energy supply system 10 / the fuel cell systems 16, 18. The second part of the process 64 can be used either when the higher-level control unit 46 fails, is not present, or is not to be used for any reason, or when island operation is planned (circuit breaker 56 open).

[0072] In at least one optional process step 200, the power supply system 10, in particular the components of the power supply system 10, detects that no higher-level communication is present / available. It then switches to a DC link control mode, which is explained below. In at least one process step 210, the DC link voltage is set and / or regulated according to a predefined DC link voltage-state-of-charge parameter characteristic curve 38 (see Fig. 3). The DC link voltage-state-of-charge parameter characteristic curve 38 is a DC link voltage-state-of-charge characteristic curve. The DC link voltage-state-of-charge parameter characteristic curve 38 corresponds to a plot of the DC link voltage (DC) of the DC link 26 against the state of charge (SoC) of the storage system 36. Apart from a central deadband region 40, the DC link voltage-state-of-charge parameter characteristic curve 38 has an upward slope 42.When the charge level is low (<40%), the DC link voltage is regulated to a low DC link voltage (<800 V). For example, according to the exemplary DC link voltage-state-of-charge parameter characteristic curve 38 of Fig. 3, a charge level of 20% is regulated to a DC link voltage of approximately 770 V. When the charge level is high (>60%), the DC link voltage is regulated to a high DC link voltage (>800 V). For example, according to the exemplary DC link voltage-state-of-charge parameter characteristic curve 38 of Fig. 3, a charge level of 80% is regulated to a DC link voltage of approximately 820 V. The deadband range 40, in which no change in the DC link voltage occurs, extends in this example approximately between charge levels of 40% and 60%. R.414134.

[0073] - 20 -

[0074] In at least one further process step 220, in the operating state of the power supply system 10 in which the intermediate circuit voltage of the electrical intermediate circuit 26 is set and / or regulated as a function of the current state-of-charge parameter, an operating power of the power supply system 10, in particular of the DC generator units 12, 14 of the power supply system 10, is set and / or regulated as a function of the intermediate circuit voltage previously regulated and / or set in process step 210. This setting and / or regulation is carried out as a function of a power control variable-intermediate circuit voltage characteristic curve 44 of the DC generator units 12, 14 (see Fig. 4).The setting and / or adjustment of the DC link voltage of process step 210 and the setting and / or adjustment of the operating power of the power supply system 10 of process step 220 are each carried out by a component connected to the DC link 26 and independently of the higher-level control and / or regulation unit 46, which may, for example, be designed as an edge controller.

[0075] The power control variable-DC link voltage characteristic curve 44 corresponds to a plot of a power control variable (P) of the power supply system 10 / the fuel cell systems 16, 18 against the DC link voltage (DCV) of the DC link 26. Apart from a central deadband region 66, the power control variable-DC link voltage characteristic curve 44 exhibits a downward slope 68. When the DC link voltage is low (<790 V), the power supply system 10 / the fuel cell systems 16, 18 are driven at a high power (> 65% of P). ma x). For example, according to the exemplary power control variable-DC link voltage characteristic curve 44 of Fig. 4, at a DC link voltage of approximately 770 V, the system is regulated to nearly 100% of Pmax. If the DC link voltage is high (>810 V), then the power supply system 10 / the fuel cell system 16, 18 is regulated to a low power output (<65% of P). max) adjusted. For example, according to the exemplary power control variable-DC link voltage characteristic curve 44 of Fig. 4, a DC link voltage of approximately 820 V results in a power output of approximately 30% of P. max Set in place. The deadband area 66 in which no change R.414134

[0076] - 21 - the power control variable extends in this example between intermediate circuit voltages of approximately 790 V to 810 V.

Claims

R.414134 - 22 - Claims 1. Procedure for operating an energy supply system (10), comprising: - several DC generator units (12, 14), each configured as a fuel cell system (16, 18) with one or more fuel cell stacks (20), - at least one load connection module (22), in particular a grid connection module, which has at least one inverter (24) for converting a current generated by the DC generator units (12, 14) into an AC voltage, preferably grid-compatible, and - an electrical intermediate circuit (26) via which the several DC generator units (12, 14) are connected to the load connection module (22), characterized in that a load connection module individual voltage is measured from the load connection module (22) connected to the electrical intermediate circuit (26) and an associated DC generator individual voltage is measured from each of the DC generator units (12, 14) connected to the electrical intermediate circuit (26), wherein a voltage measuring system (28, 30, 32) determining one of these individual voltages is selected as a reference measuring system (34), from which at least one individual voltage measurement is used as a reference measurement, by means of which measured values ​​of other voltage measuring systems (28, 30), from which the other individual voltages are determined, are compared to each other, in particular continuously.

2. Method according to claim 1, characterized in that from all voltage measurement systems (28, 30, 32) of the load connection module (22) and the DC generator units (12, 14) the one which has the highest measurement precision for voltage measurements is selected as the reference measurement system (34). R.414134 - 23 - 3. Method according to claim 1 or 2, characterized in that a voltage measurement system (32) of the load connection module (22) is selected as a reference measurement system (34).

4. Method according to one of the preceding claims, characterized in that, for the purpose of adjusting the other individual voltages, an individual correction factor is applied to the respective measured value of each of these other individual voltages, in particular the currently determined value, wherein the correction factor is formed by a quotient of a measured value of the individual voltage of the reference measuring system (34) measured in the reference measurement and a measured value of the respective other individual voltage, which was measured at the time of the reference measurement by the respective other voltage measuring system (28, 30), which also measures the other individual voltage to be adjusted, in particular the current value.

5. Method according to claim 4, characterized in that the individual correction factors are periodically re-determined and recalculated.

6. Method according to claim 4 or 5, characterized in that the individual correction factors for different operating temperatures of the DC generator units (12, 14), in particular before and after a warm-up phase or another phase with significant temperature changes of a fuel cell system (16, 18) of the DC generator units (12, 14), are determined and calculated.

7. Method according to one of the preceding claims, characterized in that the measured values ​​of the other individual voltages to be adjusted are formed by averaging over a definable measurement period.

8. Method according to one of the preceding claims, characterized in that an intermediate circuit voltage for the R.414134 - 24 - electrical intermediate circuit (26) is determined.

9. Method at least according to the preamble of claim 1, preferably according to claim 8, further comprising at least one storage system (36) for storing electrical energy, such as an accumulator or a capacitor / supercapacitor, to which an instantaneous state-of-charge parameter can be assigned at any time, characterized in that an intermediate circuit voltage of the electrical intermediate circuit (26) is set and / or regulated as a function of the instantaneous state-of-charge parameter.

10. Method according to claim 9, characterized in that the intermediate circuit voltage is set and / or adjusted according to a predetermined intermediate circuit voltage-state of charge parameter characteristic curve (38), in particular intermediate circuit voltage-state of charge characteristic curve, wherein the intermediate circuit voltage-state of charge parameter characteristic curve (38) preferably has an increasing profile (42), apart from possible deadband areas (40).

11. Method according to claim 9 or 10, characterized in that an operating power of the power supply system (10), in particular of the DC generator units (12, 14) of the power supply system (10), is set and / or regulated at least in an operating state of the power supply system (10) in which the DC link voltage of the electrical DC link (26) is set and / or regulated as a function of the instantaneous state of charge parameter, preferably as a function of power control variable-DC link voltage characteristics (44) of the DC generator units (12, 14).

12. Method according to one of claims 9 to 11, characterized in that the setting and / or regulation of the DC link voltage and / or the setting and / or regulation of the operating power of the power supply system (10) is carried out by a component connected to the DC link and independently of a higher-level control system. R.414134 - 25 - and / or control unit (46), such as an Edge Controller.

13. Energy supply system (10), comprising several DC generator units (12, 14), each of which is a fuel cell system (16, 18) are equipped with one or more fuel cell stacks (20), at least one load connection module (22), in particular a grid connection module, which has at least one inverter (24) for converting a current generated by the DC generator units (12, 14) into an AC voltage, preferably grid-compatible, and an electrical intermediate circuit (26) via which the several DC generator units (12, 14) are connected to the load connection module (22), or load connection module (22) for the power supply system (10), characterized in that the load connection module (22) is provided for carrying out a method according to one of the preceding claims.

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