Method for characterising a first power unit of an energy system

Abstract

The invention relates to a method for characterising a first power unit of an energy system, wherein the energy system has a plurality of power units for providing electrical power; and wherein the power unit has a fuel cell system and / or an electrical energy store, and wherein the energy system is electrically coupled to an electrical load; and the energy system is designed to provide the electrical load with dynamic power for operation, comprising: determining (S1) a current power requirement of the electrical load; providing (S2) a power operating point for the first power unit during the characterisation; providing (S3) the current power requirement of the load by means of the plurality of power units, wherein the first power unit is controlled to provide the electrical power of the power operating point in a stationary manner; and characterising (S4) the first power unit, wherein the first unit provides the electrical power in a stationary manner in accordance with the power operating point.

Description

[0001] Description

[0002] title

[0003] Method for characterizing a first power unit of an energy system

[0004] The invention relates to a method for characterizing a first power unit, wherein the first power unit comprises a fuel cell stack, in particular with a BoP system, and an electrical energy storage device.

[0005] State of the art

[0006] Vehicles with a fuel cell drive system (FCV = Fuel Cell Vehicle) are operated taking into account a variety of requirements and / or objectives. This can, for example, be the minimization of fuel consumption, such as hydrogen. The functionality of such a drive system must be ensured over a wide (global) operating range, including freezing starts, driving in hot climates, driving uphill, and driving with a trailer. The operation of the drive system must take into account that the functionality can be ensured in both new and aged states. This can particularly affect the aging and / or degradation of a fuel cell stack in the fuel cell system.In addition, such a fuel cell system typically comprises at least one electrical energy storage device, for example in the form of an HV battery, and other components, such as air compressors, in which aging and / or degradation are to be minimized.

[0007] Disclosure of the invention In applications of fuel cell systems for driving mobile platforms, such as civil vehicles and especially long-haul trucks, objectives such as failure safety, reliability, availability, robustness to errors and avoidance of breakdowns can be of great importance.

[0008] For this purpose, the fuel cell system can have a plurality of fuel cell stacks (multi-stack system), in particular with corresponding BoP systems (BoP = balance of plant), ie auxiliary units for individual fuel cell stacks and / or auxiliary units for a plurality of fuel cell stacks, so that increased reliability can be provided based on a redundancy of several fuel cell stacks.

[0009] Both a fuel cell stack, in particular with at least one BoP system for its supply, and an electrical energy storage device, such as HV batteries, of an energy system are electrochemical energy converters or energy storage devices that are subject to system-inherent degradation processes. Both reversible and irreversible degradation processes occur. An energy system for driving mobile platforms can have a plurality of power units, wherein a power unit can comprise a fuel cell stack, in particular having at least one BoP system and / or an electrical energy storage device.

[0010] For an optimized or adaptive operating strategy of an energy system, it can be advantageous to diagnose the current states of the fuel cell stacks and / or the electrical energy storage systems as accurately as possible using diagnostic procedures.

[0011] In a dynamic operation of the energy system, with time-varying consumer loads, corresponding to a mobile vehicle application, it can be difficult to carry out a diagnosis as accurately as possible, or only uncertain results with regard to reversible and irreversible degradation can be derived from a dynamic behavior.

[0012] According to aspects of the invention, a method for characterizing a first power unit of an energy system and a control unit for carrying out the method according to the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description. According to one aspect, a method for characterizing a first power unit of an energy system is proposed, wherein the energy system has a plurality of power units for providing electrical power, and wherein the energy system is electrically coupled to at least one electrical consumer; and the energy system, in particular by means of the plurality of power units, is configured to provide the electrical consumer with dynamic power for operation.

[0013] In one step of the method, a current, in particular dynamic, power requirement of the consumer is determined. In a further step, a power operating point for the first power unit is provided and / or determined during characterization. In a further step, the current power requirement of the consumer is provided and / or generated by means of the plurality of power units, wherein the first power unit is controlled, set up, and / or configured to provide the electrical power of the power operating point in a steady-state manner, i.e., in particular, at a constant time.

[0014] In a further step, the first power unit is characterized, in particular by means of an electrical test method and / or a test method for media systems of the fuel cell stack, wherein the first unit provides the electrical power in a stationary manner, corresponding to the power operating point.

[0015] The characterization of the first power unit may include electrical tests and / or power electronic tests and / or tests of signals and / or measured variables and / or thermodynamic tests and / or tests of flows of a media supply of the fuel cell stack and / or tests regarding chemical reactions and / or electrochemical tests.

[0016] The characterization may include a power electronic assessment and / or an electrical, signal-based assessment and / or an assessment of measured variables.

[0017] BoP systems can be systems that include fuel cell stacks for supplying power and connecting a fuel cell stack to the vehicle electrical system.

[0018] Such BoP systems can also be considered auxiliary units and include media systems, in particular an air system for supplying and / or operating the fuel cell stack cathode path; and / or a fuel and anode system for supplying and / or operating the fuel cell stack anode path; and / or a coolant system for controlling the temperature of the fuel cell stack (stack coolant paths); and / or an electrical system, in particular a DC / DC converter. The BoP systems can be implemented both individually for each stack and across all stacks.

[0019] BoP systems can require significant power for operation, which can also be referred to as auxiliary power or parasitic power, which must be additionally supplied by the fuel cell stack. The useful power of energy converters, such as fuel cell stacks, can thus be determined based on the gross power of the fuel cell stack minus the BoP power. This means that a fuel cell stack can generate a gross power, with the useful power of an energy converter path (fuel cell stack) being determined from the fuel cell stack's gross power minus the BoP power.

[0020] A stack gross power should cover a power of parasitic consumers, or an auxiliary power or a BoP power, where the BoP power can be up to 25% of the stack gross power, which can depend on an operating point of the fuel cell stack.

[0021] Example: if an energy system has a fuel cell system with a power of 2x100kW FCS power (net useful power) and a battery that can boost 50kW, then with a consumer demand of 210kW the operating point of the stack to be tested cannot be below a limit of 60kW

[0022] (Limit: 21 kW - 50 kW battery - 100 kW = 60 kW) to provide the necessary power to operate the consumer. A higher operating point may also be necessary because the battery cannot provide 50 kW for an unlimited period of time.

[0023] A fuel cell system and / or a fuel cell stack and / or a power unit may in particular comprise a BoP system.

[0024] The characterization of the respective power aggregate of the process can take into account those power flows that are required for the operation of BoP systems.

[0025] A fuel cell system can comprise a plurality of fuel cell stacks, in particular including the respective balance of power (BoP) systems for supplying a fuel cell stack and connecting the fuel cell stacks. The BoP systems can be individual to each fuel cell stack, such as an air system per fuel cell stack, and / or stack-spanning, such as an air system that supplies two fuel cell stacks.

[0026] An energy system can include energy converters, such as fuel cell stacks, and energy storage devices, such as HV batteries.

[0027] The load, which can be operated with the energy system and electrically coupled to the energy system, can comprise a mobile platform, such as various vehicle classes: on-road, off-road, commercial vehicles, or buses. In particular, the method for operating the energy system can be used in CV applications with multi-stack systems to increase the reliability and resilience of an overall system comprising a fuel cell system and an electrical energy storage system.

[0028] The method can be used in vehicles, various vehicle classes on-road, off-road, commercial vehicles, buses, etc., with energy systems, especially in CV applications that require high reliability, robustness and lifetime-optimized systems with appropriate monitoring / diagnostics, etc.

[0029] This characterization can be initiated by a trigger signal ("C.trigTest"). This means that a test mode for characterizing the fuel cell stack can be implemented without restrictions regarding the power requirements of a mobile platform or vehicle and its consumers.

[0030] Such a duration for characterizing (dt_test) a power aggregate, in particular an energy system, can be adaptively adjusted according to a current situation of an energy management of the energy system.

[0031] The duration of the characterization can also be determined individually, depending on the respective fuel cell stack, and in particular its BoP systems, and / or depending on the respective electrical energy storage device. In particular, the characterization method can be carried out successively with differently provided power operating points. Alternatively or additionally, the characterization of the respective power unit can be carried out during a consecutively changing course of operating points, each of which is set to a stationary state. The start of the method for characterizing a respective power unit can be initiated by an energy management system of the energy system and / or the mobile platform, in particular by means of a carrier.

[0032] The start of the characterization procedure can alternatively or additionally be carried out periodically and / or depending on certain events and / or depending on the results of the characterization of the respective power unit.

[0033] The time interval between characterizations of a respective power unit can be determined and performed depending on the respective state of the respective power unit and / or the states of the other power units. In particular, the time interval between characterizations can be determined based on the operating time of the respective power unit. Thus, in the event of a significant degradation of the performance of a respective power unit, the respective power unit can be characterized more frequently.

[0034] A higher-level system controller, such as an energy management system and / or a multistack manager, can determine the power unit to be characterized, particularly taking into account the characterization of all power units within a defined period of time. This can be done to prevent two power units from being characterized in parallel.

[0035] The method may provide for the interruption of a current characterization of a power unit if external conditions, such as a driving situation and / or a power demand from the electrical consumer, require it. The corresponding characterization may then be discarded.

[0036] Advantageously, the method allows the total power of all power units of the energy system (power sources PelSources) to remain the same with or without a currently performed characterization, so that the characterization of the first power unit has no influence on the overall power balance of the consumer, such as a mobile platform and / or a vehicle and its consumers. In particular, the method can also be carried out when not all fuel cell stacks are active by adapting it accordingly to perform the compensation only with active and / or available fuel cell stacks, and in particular their BoP systems. In particular, the method can be carried out as described if some fuel cell stacks are malfunctioning and / or can no longer be started or are not allowed to be started.Furthermore, the method can advantageously be used to characterize an electrical energy storage device such as a high-voltage battery.

[0037] The power operating points can also include special operating modes, e.g., an inerted stack with power output OkW.

[0038] Alternatively or additionally, the method for characterizing a first power unit can be carried out with other defined power curves instead of with stationary power operating points, such as in particular with a defined power ramp, which can have different power gradients.

[0039] In other words, the method can be used to integrate a first power unit, such as a fuel cell stack, and in particular its BoP systems, and / or an HV battery into a test

[0040] Operating mode, preferably controlled in a stationary operating mode, while the other fuel cell stacks and / or other energy storage devices (battery^)) assume the dynamic requirements of a consumer (power compensation). This means that an affected fuel cell stack and / or HV battery can be characterized and / or tested without affecting the overall performance of all power units (power sources).

[0041] The steady-state operating state can also include several specific stationary points, e.g., following a target trajectory, and can be used for both defect-related purposes (diagnosis, aging assessment) and prophylactic or predictive purposes (targeted recovery functions at defined operating points).

[0042] The system controller or multi-stack manager (MSM) addresses the stack or battery to be tested, ensures sequencing (i.e., the DefTest can also be performed on other stacks at a different time interval), and triggers the test phases (at adaptive or operating-situation-dependent intervals) for a limited / appropriate test time. In multi-stack systems, power compensation can also be performed without the HV battery, using only the other stacks.

[0043] Prediction is preferably used to plan the respective test phases and to compensate for the missing performance with the other performance sources.

[0044] Advantageously, the method can be used to carry out improved aging assessment / diagnosis / SOH determination, etc. of the power units, particularly since the total power provided by the power units is not affected by the characterization method, so that there is no loss of dynamics and comfort of a mobile platform operated with the energy system. However, the power unit to be characterized is operated at a defined power operating point, and thus the characterization can be improved, particularly with a test method. Additionally or alternatively, the improved characterization of the power units can enable improved operational management and / or optimization of an operating strategy through more precise information about the condition of the power units (power sources).Thus, operating objectives for the energy system can be achieved and / or improved.

[0045] According to one aspect, it is proposed that the plurality of power units, without the first power unit, be controlled in such a way that a respective current, in particular dynamic, power requirement of the electrical consumer is compensated in such a way that the first power unit continues to provide and / or generate the electrical power of the power operating point, in particular in a stationary manner.

[0046] According to one aspect, it is proposed that the power operating point for the first unit is determined and / or provided during the characterization based on a power trajectory and / or range and / or route planning for the electrical consumer.

[0047] In other words, the method can be implemented using predictive operation, meaning the duration of the respective test (dt_test) and the power level during the test (Pel_test) can be predictively planned accordingly. For example, a battery SOC can be prepared or the number of required active stacks for the test procedure can be ensured. This can be ensured, in particular, by activating an additional fuel cell stack, etc. Using this prediction, a suitable section of a journey can be selected for characterization, for example, by ensuring that the power spread does not become too large during characterization.

[0048] By means of a trigger (trigTest[n]) that is scheduled and / or set by an energy management system of the mobile platform and / or by a multi-stack manager at appropriate times to perform the procedure.

[0049] In particular, it can be considered that the characterization is not carried out during an operating phase with maximum power demand for the energy system, since compensation by the other power units cannot always be ensured in this case. However, as a special case, the characterization can be carried out with the energy system operating at maximum power.

[0050] According to one aspect, it is proposed that the first power unit is controlled, based on the power trajectory and / or range and / or route planning, to provide the electrical power of the power operating point in a stationary manner in order to characterize the first unit.

[0051] According to one aspect, it is proposed that the plurality of power units comprise at least one fuel cell stack and / or at least one electrical energy storage device.

[0052] An electrical energy storage device can be an electrical battery or a plurality of electrical batteries that have a significant power capacity and / or a significant energy content. These can be, for example, high-voltage batteries (HV batteries) and / or supercapacitors. The electrical energy storage device can comprise a plurality of electrical energy storage devices to store and / or provide electrical energy. For example, long-haul trucks can have multiple electrical energy storage devices installed. The state of charge of each electrical energy storage device can be quantified by a state of charge (SOC).

[0053] According to one aspect, it is proposed that the energy system has a first fuel cell stack and a second fuel cell stack, and the first power unit is the first fuel cell stack; and the respective current power requirement of the consumer is compensated by means of the second fuel cell stack in order to provide the power of the power operating point in a stationary manner using the first fuel stack. According to one aspect, it is proposed that the first power unit is the first fuel cell stack; and the respective current power requirement of the consumer is compensated by means of the electrical energy storage device in order to provide the power of the power operating point in a stationary manner using the first fuel stack.

[0054] According to one aspect, it is proposed that the first power unit is the electrical energy storage device; and the respective current power requirement of the consumer is compensated by means of the at least one fuel cell stack in order to provide the power of the power operating point in a stationary manner by means of the electrical energy storage device.

[0055] According to one aspect, it is proposed that the first power unit be characterized by means of a test method; and in particular, the test method comprises a diagnosis of the first unit; and / or a plausibility check of a functionality of the first unit; and / or an assessment of a degradation of the first unit.

[0056] While the corresponding power unit is operating at steady-state operating point, diagnostic functions (diagnoses, plausibility checks, etc.) and evaluations can be performed (e.g., impedance spectroscopy (EIS) or HFR, CVM (cell-specific voltage measurement), etc.). This can be used to assess degradation, SOH (state of health), and other factors for the respective energy converter or energy storage device. These findings can be used to optimize and adapt operating strategies. For example, recovery functions can also be triggered for the respective stack to reverse reversible degradation.

[0057] According to one aspect, it is proposed that the test method comprises predictive functions and / or prophylactic functions for minimizing aging of the first aggregate and / or for checking recovery functions.

[0058] A control unit with an interface and a computing unit is proposed, wherein the interface is configured to couple the control unit to the plurality of power units. The control unit is configured and configured based on the computing unit to carry out one of the methods described above. Exemplary embodiments of the invention are explained in more detail below with reference to schematic representations in Figures 1 to 5.

[0059] Here they show:

[0060] Figure 1 outlines a flowchart of a method for characterizing a first power unit of an energy system;

[0061] Figure 2 outlines the power provided by a fuel cell stack and an electrical energy storage device, characterising the fuel cell stack;

[0062] Figure 3 outlines the power provided by the first fuel cell stack according to Figure 1 with and without a stationary curve for characterization;

[0063] Figure 4 outlines the power provided by a first fuel cell stack, a second fuel cell stack and an electrical energy storage device, wherein the first fuel cell stack is characterized; and

[0064] Figure 5 outlines the power provided according to Figure 3 of the first fuel cell stack with and without the stationary curve for characterization.

[0065] Figure 1 outlines a flowchart of a method for characterizing a first power unit of an energy system, wherein the energy system has a plurality of power units for providing electrical power, and wherein the energy system is electrically coupled to an electrical load. The energy system is configured to provide the electrical load with dynamic power for operation. In a step S1, a current power requirement of the electrical load can be determined. In a further step S2, a power operating point for the first unit can be provided during the characterization.

[0066] In a further step S3, the current power requirement of the consumer is provided by means of the plurality of power units, wherein the first power unit is controlled such that the electrical power of the power operating point is provided in a stationary manner. In a further step S4, the first unit is characterized, wherein the first unit provides the electrical power in a stationary manner, corresponding to the power operating point. Figure 2 schematically outlines, with a diagram 200 in which the output power is plotted over time, the power provided by a fuel cell stack 210 and an electrical energy storage device 220, wherein the fuel cell stack is operated in a stationary manner at a power operating point in order to characterize the fuel cell stack. A sum of the power provided by the fuel cell stack and the electrical energy storage device, orgenerated are shown by the curve of the total energy 230. From the curve of the total energy 230, it can be seen that the electrical power provided by the energy system with the fuel cell stack and the electrical energy storage device is dynamic, i.e., time-dependent, according to a consumer's demand, although the curve of the power provided by the fuel cell stack 210 at the points marked by the arrows shows that the curve of the power provided by the fuel cell stack is stationary. Furthermore, it can be seen from the curve of the power provided by the electrical energy storage device 220 that the electrical energy storage device compensates for the power requested by the electrical consumer by the electrical energy storage device releasing or absorbing energy.

[0067] In other words, the fuel cell stack is characterized at a power operating point at intervals of time, which are condensed here for clarity, by keeping the power supplied by the fuel cell stack constant at the power operating point. The electrical energy storage device (e.g., a battery) is controlled so that the power supplied by the electrical energy storage device compensates for any resulting differences in the total power required by the energy system. This makes it possible to meet the electrical consumer's demand for dynamically varying power despite the stationary operation of the fuel cell stack.

[0068] To illustrate the steady-state operation of the fuel cell stack, in particular having a BoP system, during the characterization according to Figure 2, Figure 3 shows an electrical power plotted against time using diagram 300. The power provided by the fuel cell stack 310 and a simulated power provided by the fuel cell stack 320 with temporary characterizations during steady-state provision of electrical power at the respective power operating point are plotted one above the other. The periods marked with arrows illustrate steady-state operation compared to dynamically controlled operation of the fuel cell stack.

[0069] Figure 4 schematically outlines, with a diagram 400 in which power curves are plotted over time, the power provided by a first fuel cell stack 510, a second fuel cell stack 511 and an electrical energy storage device 520, wherein the first fuel cell stack is operated in a stationary manner at a respective power operating point in order to characterize the first fuel cell stack.

[0070] The sum of the powers provided or generated by the fuel cell stack and the electrical energy storage device is represented by the curve of the total energy 530. It can be seen from the curve of the total energy 530 that the electrical power provided by the energy system with the fuel cell stack and the electrical energy storage device is dynamic, i.e., time-dependent according to a consumer's demand, although the curve of the power provided by the fuel cell stack 510 indicates that the power provided by the fuel cell stack is stationary at the points marked with arrows.Furthermore, it can be seen from the curve of the provided power of the second fuel cell stack 511 that the second fuel cell stack compensates for the requested power of the electrical consumer by the second fuel cell stack providing additional power or providing a lower power.

[0071] In other words, the fuel cell stack is characterized at a respective power operating point at time intervals, which are condensed here for clarity, by keeping the power provided by the first fuel cell stack constant at the respective power operating point. The second fuel cell stack is controlled such that the respective power provided by the second fuel cell stack compensates for any resulting differences from the total power required by the energy system. This makes it possible to meet a demand from the electrical consumer for dynamically varying power despite the stationary operation of the first fuel cell stack.

[0072] In other words, the power provided by the first fuel cell stack can be balanced by the second fuel cell stack to maintain the same total power (PelSources). The power provided by the electrical energy storage device continues to be dynamic, without contributing to compensating for the power provided by the first fuel cell stack. In particular, in the method, the power provided by the first fuel cell stack can be compensated by the electrical energy storage device in addition to the power provided by the second fuel cell stack.

[0073] To illustrate the steady-state operation of the first fuel cell stack during characterization according to Figure 4, Figure 5 shows a curve of electrical power over time using diagram 500. The power provided by the first fuel cell stack 510 and the second fuel cell stack 511 is plotted superimposed on a simulated power provided by the first fuel cell stack 512 and the second fuel cell stack 513, respectively, with temporary characterizations during steady-state provision of electrical power at the respective power operating point of the first fuel cell stack. The time periods marked with arrows illustrate the steady-state operation of the first fuel cell stack compared to dynamically controlled operation of the second fuel cell stack and the corresponding compensation by controlling the second fuel cell stack.

[0074] Alternatively or additionally, in an energy system comprising a first fuel cell stack and a second fuel cell stack and an electrical energy storage device, the described compensation of the power provided by the respective power unit, which is to be characterized at a power operating point, can be carried out using the other power units. Such a modified method enables greater flexibility and, in particular, a larger power range when compensating for negative and / or positive power, since the electrical energy storage device, in particular, is configured to absorb and / or release electrical energy.

[0075] Alternatively or additionally, in an energy system with a first fuel cell stack and a second fuel cell stack and a first electrical energy storage device and a second electrical energy storage device, the method can be carried out accordingly by using all other power units to compensate for the respective power provided by the power unit that is to be compensated. Thus, the power compensation can be carried out during characterization by fuel cell stacks and / or electrical energy storage devices. In particular, the electrical energy storage device can also be characterized using the method. In other words, at time intervals - initiated by a trigger "trigTestBat" - the electrical energy storage device, such as an HV battery, can be held at one or more defined stationary operating points and the fuel cell stack orA plurality of fuel cell stacks can be controlled in such a way that a necessary difference is compensated so that a power curve of a total power of all power units of the energy system (power sources) can provide a dynamic power that corresponds to a dynamic power when all power units are operated dynamically.

Claims

Claims 1. A method for characterizing a first power unit of an energy system, wherein the energy system has a plurality of power units for providing electrical power; and wherein the power unit has a fuel cell system and / or an electrical energy storage device, and wherein the energy system is electrically coupled to an electrical consumer; and the energy system is configured to provide the electrical consumer with dynamic power for operation, comprising: determining a current power requirement of the electrical consumer (S1); providing a power operating point for the first power unit during the characterization (S2); Providing the current power requirement of the consumer by means of the plurality of power units (S3), wherein the first power unit is controlled to provide the electrical power of the power operating point in a stationary manner; and Characterizing the first power unit (S4), wherein the first unit provides the electrical power in a stationary manner, according to the power operating point.

2. The method according to claim 1, wherein the plurality of power units, without the first power unit, are controlled such that a respective current power requirement of the electrical consumer is compensated such that the first power unit provides the electrical power of the power operating point in a stationary manner.

3. The method according to claim 1 or 2, wherein the power operating point for the first unit is determined and / or provided during the characterization based on a power trajectory and / or range and / or route planning for the electrical consumer.

4. The method according to claim 3, wherein the first power unit is controlled, based on the power trajectory and / or range and / or route planning, to provide the electrical power of the power operating point in a stationary manner in order to characterize the first unit.

5. The method according to one of the preceding claims, wherein the plurality of power units comprise at least one fuel cell stack, in particular comprising a BoP system (balance of plant system), and / or at least one electrical energy storage device.

6. The method according to claim 5, wherein the energy system comprises a first fuel cell stack and a second fuel cell stack, and the first power unit is the first fuel cell stack; and the respective current power demand of the consumer is compensated by means of the second fuel cell stack in order to provide the power of the power operating point in a stationary manner by means of the first fuel stack.

7. The method according to claim 5, wherein the first power unit is the first fuel cell stack; and the respective current power requirement of the consumer is compensated by means of the electrical energy storage device in order to provide the power of the power operating point in a stationary manner by means of the first fuel stack.

8. The method according to claim 5, wherein the first power unit is the electrical energy storage device; and the respective current power requirement of the consumer is compensated by means of the at least one fuel cell stack in order to provide the power of the power operating point in a stationary manner by means of the electrical energy storage device.

9. The method according to one of the preceding claims, wherein the first power unit is characterized by means of a test method; and in particular, the test method comprises a diagnosis of the first unit; and / or a plausibility check of a functionality of the first unit; and / or an assessment of a degradation of the first unit.

10. A control unit comprising: an interface for coupling the control unit to the plurality of power units; and a computing unit; wherein the control unit, based on the computing unit, is configured to perform one of the methods 1 to 9.

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