DE102020100600A1 - Method for the optimized operation of a fuel cell system and fuel cell system - Google Patents

Abstract

The invention relates to a method for the optimized operation of a fuel cell system comprising a control device (134), which has a DC voltage converter (100) with an integrated load regulator (130) for regulating load requirements on a fuel cell unit (102) electrically connected on the input side to the DC voltage converter (100) comprises a traction network (106) connected or connectable on the output side for providing power to a traction motor, the DC / DC converter (100) having a memory (136) in which at least one parameter set of the load regulator (130) for regulating the load requirements on the fuel cell unit (102) is temporarily storable, comprising the steps of selecting, determining or compiling a parameter set required for an optimized operating mode by means of the control device (134), transmitting the parameter set by means of a communication interface (132) between Chen the control unit (134) and the DC voltage converter (100), the loading of the parameter set into the memory (136) of the DC voltage converter (100) and the regulation of the load requirement on the fuel cell unit (102) with the load regulator (130) using the parameter set. The invention also relates to a fuel cell system.

Description

The invention relates to a method for the optimized operation of a fuel cell system comprising a control device and to a fuel cell system which is designed to carry out the method. In order to regulate the output power of the fuel cell device, in particular of the fuel cell stack comprising a plurality of fuel cells connected in series, a control and regulating device is necessary, which is present in particular as a fuel cell control unit (FCU for "Fuel Cell Control Unit") equipped with a power regulator is. In addition, an actuator is necessary in order to regulate the desired output, the voltage to be supplied by the fuel cell device or the setpoint current to be supplied typically being selected as the reference variable. The current flow is usually the control variable in the fuel cell control unit.

It is also known to integrate the fuel cell device in a hybrid system via a DC voltage converter into a common on-board network with a battery, the on-board network being electrically connected to a traction motor for driving a motor vehicle. Such hybrid systems with battery and fuel cell are from the publications US 2017/0141 419 A1 , CN 101 786 413 A and CN 105 253 139 A known. Especially in the CN 101 786 413 A an energy management system of this hybrid structure of fuel cell device and battery is described, with energy models being able to be stored in an energy management controller through which the output power of the fuel cell device but also the state of charge of the battery can be predefined based on models.

In such systems, in the worst case, the power regulator of the control unit of the fuel cell device can swing up internally against the regulator provided by the DC voltage converter. This is particularly the case when an attempt is made to use a rule set that is generally valid for a wide variety of operating states in the DC / DC converter in order to cover all operating states with this rule set. Such a generally valid set of control parameters is not adapted to the given operating states (for example normal start / air-air start / cold operation / hot operation / air-depleted operation / normal operation / sport mode etc.) and therefore restricts the overall performance of the fuel cell system in its areas Dynamics, consumption, noise emissions and aging of the fuel cell system.

It is therefore the object of the present invention to provide a method for the optimized operation of a fuel cell system comprising a control device and a fuel cell system itself which take into account at least one of the disadvantages mentioned above.

This object is achieved by a method with the features of claim 1 and by a fuel cell system with the features of claim 10. Advantageous configurations with expedient developments of the invention are specified in the dependent claims.

The method according to the invention is based on a fuel cell system provided with a control device, which comprises a DC voltage converter with an integrated load regulator for regulating load requirements on a fuel cell unit electrically connected to the DC voltage converter on the input side. On the output side, a traction network is connected or can be connected to a traction motor to provide power. The DC / DC converter has a memory in which at least one parameter set of the load regulator for regulating the load requirements on the fuel cell unit can be stored at least temporarily, in particular permanently. The method comprises in particular the steps of selecting, determining or compiling a parameter set required for an optimized operating mode by means of the control device, transmitting the parameter set by means of a communication interface between the control device and the DC / DC converter, loading the parameter set into the memory of the DC / DC converter and the regulation of the load requirement on the fuel cell unit with the load regulator using the parameter set.

This has the advantage that the regulators of the control device of the fuel cell system and the load regulator of the DC voltage converter do not oscillate towards one another. The optimized setting of the control parameters results in optimal dynamics of the fuel cell system across all of its operating states, so that optimized aging and consumption properties can also be achieved when operating the fuel cell system on the basis of optimal current or voltage gradients.
In fuel cell systems, so-called air-air starts can also cause damage to the fuel cell stack, with air-air starts when air or oxygen is present both in the anode area and in the cathode area of the fuel cell stack during start-up. When hydrogen is supplied during start-up, a hydrogen air front occurs, which sweeps over the electrochemically active surface of the anodes. Thus are immediately available The front and immediately after the front face different levels of potential, since the fuel cell is already operating the electrolysis in one area and not yet in another area. This leads to damage or degradation of the fuel cell, in particular to corrosion of the catalyst or its carrier material. In order to reduce damage to the fuel cell systems and to enable the fuel cell systems to have a long service life, it is therefore necessary to prevent air-air starts or to reduce their number. It is also important to avoid excessive voltage peaks, as these also contribute to degradation. The time in which the hydrogen can be kept in the anode area, i.e. the time after the fuel cell system has been switched off, in which hydrogen is still present in the anode area, is generally also referred to as hydrogen protection time. If this hydrogen protection time is exceeded, i.e. air diffuses into the anode area, the conditions for an air-air start are again given and methods are known to remove the air from the fuel cell stack as quickly as possible, which often occurs unevenly for structural reasons.

For this reason, it is possible to provide a starting voltage model which, based on the shutdown time of the fuel cell system, influences the U-I behavior, which corresponds to the controlled system function when the fuel cell system is started. It is therefore advantageous if the control device records the shutdown time since the system was shut down and takes into account the recorded shutdown time at the time of restart of the fuel cell system when selecting, determining or compiling the parameter set. In this way, an optimized set of controller parameters can be determined, with which an optimized operating mode of the fuel cell system can be achieved.

It is advantageous here if the parameter sets stored in the control device are defined by means of a starting voltage model which includes a plurality of U-I characteristics and is dependent on the shutdown time. In this way it can be achieved that there are no voltage peaks that go beyond the maximum voltage of the fuel cell system and that the fuel cell system unintentionally ages.

It is advantageous if the parameter set is also selected, determined or compiled as a function of a selected operating mode of the fuel cell system, since the different operating modes such as "cold operation", "hot operation", "air-depleted operation", "normal operation", " Sport mode ”etc., can be taken into account.

In this context, it is therefore advantageous if a plurality of fuel cell system models influencing the functional behavior are stored in the control unit of the fuel cell device, from which the optimized parameter set is selected, determined or compiled before it is then transferred to the DC voltage converter. Fuel cell system models can relate to information about the dynamics, consumption or noise emissions of the fuel cell system. In this case, parameters are specified which also relate to the auxiliary units of the fuel cell system, for example the compressor, the humidifier, the coolant pump of a cooling circuit, the recirculation fan or the like.

Those of a serial bus system have proven to be advantageous as reliable communication interfaces, with the use of a CAN interface, or a LIN interface or a FlexRay interface, in particular, having proven to be useful.

The advantages and advantageous configurations relating to the fuel cell system according to the invention are the same as those of the method according to the invention. The fuel cell system with its control device is thus designed to carry out the method explained above. The fuel cell system comprises a control device and a DC voltage converter with an integrated load regulator for regulating load requirements for a fuel cell unit, in particular a fuel cell stack, which is electrically connected to the DC voltage converter on the input side. In addition, a traction network is connected on the output side of the DC voltage converter to provide the electrical power to a traction motor, the DC voltage converter having a memory in which at least one parameter set for regulating the load requirements on the fuel cell unit can be temporarily, preferably permanently, stored. The control unit of the fuel cell device is designed to select, determine or compile a parameter set required for an optimized operating mode, to transmit the parameter set by means of a communication interface between the control unit and the DC voltage converter, and to load the parameter set into the memory of the DC voltage converter and thus the load regulator to cause the parameter set to be used to regulate the load requirement on the fuel cell unit.

The features and feature combinations mentioned above in the description as well as those mentioned below in the description of the figures and / or shown alone in the figures Features and combinations of features can be used not only in the respectively specified combination, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also to be regarded as encompassed and disclosed by the invention, which are not explicitly shown or explained in the figures, but which emerge and can be generated from the explained embodiments by means of separate combinations of features.

• 1 eine schematische Darstellung eines Brennstoffzellensystems mit einer Spannungswandleranordnung, die die Brennstoffzelleneinheit mit einem eine Batterie umfassenden Traktionsnetz elektrisch verbindet, an welches zwei Verbraucher angeschlossen sind, und
• 2 eine zeitabhängige Darstellung der von der Brennstoffzelleneinheit generierten Spannung (U) für vier unterschiedliche lange Abstellzeiten, wobei A den Spannungsverlauf für eine Abstellzeit von weniger als 5 Minuten, B den Spannungsverlauf für eine Abstellzeit von ca. 10 Stunden, C den Spannungsverlauf für eine Abstellzeit von ca. 20 Stunden und D den Spannungsverlauf für eine Abstellzeit von deutlich mehr als 20 Stunden beschreibt.

Further advantages, features and details of the invention emerge from the claims, the following description of preferred embodiments and on the basis of the drawings. Show:

• 1 a schematic representation of a fuel cell system with a voltage converter arrangement, which electrically connects the fuel cell unit with a traction network comprising a battery, to which two consumers are connected, and
• 2 a time-dependent representation of the voltage (U) generated by the fuel cell unit for four different long shutdown times, where A is the voltage curve for a shutdown time of less than 5 minutes, B the voltage curve for a shutdown time of approx. 10 hours, C the voltage curve for a shutdown time of approx. 20 hours and D describes the voltage curve for a shutdown time of significantly more than 20 hours.

In 1 is a schematic representation of a fuel cell system is shown, which is a fuel cell unit 102 includes. This fuel cell unit 102 is on connections 114 , 116 a pair of connections on the input side of a DC / DC converter 100 connected, which is designed, for example, as a (modified) DC / DC converter. The DC / DC converter 100 is with its two connections 118 , 120 , therefore with its output-side connection pair, with a traction network 106 (On-board network) electrically connected, in which a high-voltage battery 104 is present. This on-board network is used for the electrical supply of a first consumer 122 and a second consumer 124 . The traction network 106 but can preferably also supply other consumers not shown in detail with electrical energy.

The consumer 122 includes a drive unit 128 , which is in the form of an electrical machine. This electrical machine can typically be operated by means of a three-phase alternating current and is preferably designed as a traction motor for a motor vehicle. Because in the traction network 106 a high DC voltage and a DC current is present to the consumer 122 an additional inverter 126 assigned, which converts the direct current into a three-phase alternating current. In a further training of the consumer 122 can the drive unit 128 can also be used as a generator, so that, for example, during braking by the drive unit 128 generated energy of the high-voltage battery 104 via the inverter 126 can be fed back.

The second consumer 124 can also be connected to the traction network, which can be formed, for example, as one of the auxiliary units of the fuel cell system such as a compressor, a recirculation fan, a jet pump or the like. It is also possible that the consumer 124 as a charger, a twelve-volt DC-DC converter, a high-voltage heater, an electric air conditioning compressor, or the like.

The structure of the DC-DC converter is explained below 100 received.

The DC / DC converter 100 is with an integrated load regulator 130 equipped to regulate load requirements on the input side of the DC / DC converter 100 electrically connected fuel cell unit 102 . Also includes the DC-DC converter 100 a memory 136 , in which at least one parameter set of the load regulator 130 for regulating the load requirements on the fuel cell unit 102 is temporarily, preferably permanently, storable.

The DC / DC converter 100 is by means of a communication interface 132 with the control unit 134 of the fuel cell system, which also contains a power regulator, so that this power regulator is also connected to the fuel cell device 102 can interact.

The control unit 134 is designed to select, determine or compile a parameter set required for an optimized mode of operation, and to transfer the parameter set to the memory by means of the communication interface formed, for example, as a CAN interface, as a LIN interface or as a FlexRay interface 136 of the DC / DC converter 100 to transmit, and the load regulator 130 of the DC / DC converter 100 to cause the parameter set required for the optimized mode of operation to regulate the load requirements on the fuel cell unit 102 to use.

In 2 four different voltage curves are shown that can result when starting the fuel cell system after shutdown times of different lengths. The start time is indicated by a vertical dotted line marked. It can be seen that with a shutdown time of less than 5 minutes (curve A), there are no significant voltage peaks that could damage the fuel cells of the fuel cell device 102 can lead, as this remains well below the maximum voltage (U max). Only with longer shutdown times of, for example, 10 hours (curve B) does a significant increase in the voltage curve occur, with the maximum voltage (U max) being exceeded, especially at shutdown times of 20 hours (curve C), and especially at significantly more than 20 hours for the Shutdown time Voltage peaks occur that lead to undesirable greater degradation.

Because of this, the control unit is 134 designed to detect the shutdown time since the shutdown of the fuel cell system and to take into account the acquired shutdown time at the time of restarting the fuel cell system when selecting, determining or compiling the parameter set. It is in the control unit 134 a plurality of UI characteristics comprising parameter sets that are dependent on the shutdown time are available in the form of a starting voltage model. The parameter set can be established as a function of a selected operating mode of the fuel cell system or of the motor vehicle using the fuel cell system. At the same time, in the control unit 134 a plurality of fuel cell system models influencing the functional behavior, for example with regard to dynamics, with regard to consumption or with regard to noise emissions, can be stored, from which the optimized parameter set for the DC voltage converter 100 selected, determined or compiled.

As a result, the method according to the invention and the fuel cell system according to the invention are distinguished by an improved mode of operation of the fuel cell system, which is subject to less aging, less consumption during operation and less noise.

List of reference symbols

100

DC voltage converter

102

Fuel cell unit

104

High voltage battery

106

Transaction network

108

Measuring unit

110

Comparison unit

112

Control unit

114

Connection (input-side connection pair)

116

Connection (input-side connection pair)

118

Connection (pair of connections on the output side)

120

Connection (pair of connections on the output side)

122

consumer

124

(second) consumer

126

Inverter

128

Drive unit

130

Load regulator

132

Communication interface

134

Control unit

136

Storage

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 2017/0141419 A1 [0002]
• CN 101786413 A [0002]
• CN 105253139 A [0002]

Claims (10)

Method for the optimized operation of a fuel cell system comprising a control device (134), which has a DC voltage converter (100) with an integrated load regulator (130) for regulating load requirements on a fuel cell unit (102) electrically connected on the input side to the DC voltage converter (100) and an output side connected or comprises connectable traction network (106) for providing power to a traction motor, the DC / DC converter (100) having a memory (136) in which at least one parameter set of the load regulator (130) for regulating the load requirements on the fuel cell unit (102) can be temporarily stored, comprising the steps of selecting, determining or compiling a parameter set required for an optimized operating mode by means of the control device (134), transmitting the parameter set by means of a communication interface (132) between the control device (134) and the DC voltage converter (100), loading the parameter set into the memory (136) of the DC voltage converter (100) and regulating the load requirement on the fuel cell unit (102) with the load regulator (130) using the parameter set. Procedure according to Claim 1 , characterized in that the control device (134) detects the shutdown time since the shutdown of the fuel cell system and takes into account the recorded shutdown time at the time of restart of the fuel cell system when selecting, determining or compiling the parameter set. Procedure according to Claim 2 , characterized in that the parameter sets stored in the control device (134) are determined by means of a starting voltage model which includes a plurality of UI characteristics and is dependent on the shutdown time. Method according to one of the Claims 1 to 3 , characterized in that the parameter set is also selected, determined or compiled as a function of a selected operating mode of the fuel cell system. Method according to one of the Claims 1 to 4th , characterized in that a plurality of fuel cell system models influencing the functional behavior are stored in the control device (134), from which the optimized parameter set is selected, determined or compiled. Method according to one of the Claims 1 to 5 , characterized in that the communication interface (132) is part of a serial bus system. Procedure according to Claim 6 , characterized in that the communication interface (132) is formed as a CAN interface. Procedure according to Claim 6 , characterized in that the communication interface (132) is formed as a LIN interface. Procedure according to Claim 6 , characterized in that the communication interface (132) is formed as a FlexRay interface. Fuel cell system with a control unit (134) and a DC voltage converter (100) with an integrated load regulator (130) for regulating load requirements on a fuel cell unit (102) electrically connected on the input side to the DC voltage converter (100) and with a fuel cell unit (102) connected on the output side to the DC voltage converter (100) Traction network (106) for providing power to a traction motor, the DC / DC converter (100) having a memory (136) in which at least one parameter set of the load controller (130) for regulating the load requirements on the fuel cell unit (102) can be temporarily stored, and wherein the control unit (134) is designed: - select, determine or compile a parameter set required for an optimized operating mode; - to transmit the parameter set by means of a communication interface (132) between the control device (134) and the DC voltage converter (100), and - Load the parameter set into the memory (136) of the DC / DC converter (100) and thus cause the load regulator (130) to use the parameter set to regulate the load requirement on the fuel cell unit (102).

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