DE102007031070A1 - Adaptation circuit for a fuel cell system of a vehicle, drive system and method for operating a drive or the drive system - Google Patents

Abstract

The invention has for its object to provide a matching circuit for a fuel cell system, a drive system for a vehicle and a method for operating a drive system for a vehicle, which enables an economical operation of the fuel cell system. This object is achieved by an adaptation circuit (8) for a fuel cell system (2) of a vehicle (1) having an input interface (9) for connecting an output voltage (US) of a fuel cell arrangement (6) of the fuel cell system (2) to a drive output interface (13 ) for supplying a power train (3) for a drive motor (5) with a drive voltage (UA) and with a supply output interface (10) for supplying a supply bus (11) for peripheral components (12) with a supply voltage (UV), wherein the matching circuit ( 8) can be switched to a special operating state, in which the supply voltage (UV) is greater in magnitude than the drive voltage (UA) is formed.

Description

The The invention relates to a matching circuit for a fuel cell system a vehicle having an input interface for connecting an output voltage a fuel cell assembly of the fuel cell system and with a drive output interface for supplying a power line for a drive motor with a drive voltage. Further The invention relates to a corresponding drive system and a Method for operating the drive system.

Fuel cell systems put in an electro-chemical process a fuel, usually hydrogen, with an oxidant, mostly ambient air, around and walk in the frame the process of chemical energy into electrical energy, the z. B. a vehicle provided as drive energy becomes. In addition to supplying the vehicle with drive power is a part of the converted energy usually for self-supply used so that peripheral components, such as compressors, Heaters, valves or the like also with by the Fuel cell system generated energy to be supplied.

each Fuel cell system has a plurality, usually more than 100, Fuel cells, which are usually connected in series are such that one formed by the plurality of fuel cells Fuel cell assembly an output voltage of about 100V provides. The individual fuel cells contribute to this Output voltage each with a cell voltage between about 0.2V and 0.7V at, with cell voltage strongly dependent from the operating state of the fuel cells. As a consequence, that depending on the operating condition of the fuel cells Also, the output voltage of the fuel cell assembly varies widely. To compensate for this variation, matching circuits are known, which the fluctuating output voltage of the fuel cell assembly convert, so that a DC voltage is provided, which over a minimum required operating voltage for the drive motor of the vehicle and for a supply bus for the peripheral components is located.

For example, the document discloses US Pat. No. 6,428,918 81 a fuel cell supply system having a converter that converts the energy generated by a fuel cell assembly with fluctuating output voltage so that the output energy is provided at a substantially constant voltage amplitude.

The Publication PAJ 20032003663 A (publication number), probably the Next state of the art forms, also shows a fuel cell supply device with a DC / DC converter, which is controlled by a control device and the like is connected at the output of the DC / DC converter, a predetermined Output value is present.

Of the Invention is based on the object, a matching circuit for a fuel cell system, a drive system for a Vehicle and a method for operating a drive system to propose for a vehicle which is an economic Operation of the fuel cell system allows.

These The object is achieved by a matching circuit for a fuel cell system with the features of claim 1, a drive system for a vehicle with the features of claim 10 and with a Method for operating a drive system for a vehicle with a fuel cell system having the features of the claim 11 solved. Preferred or advantageous embodiments The invention will become apparent from the dependent claims, the following description and / or the figures.

According to the invention a matching circuit or a device with this matching circuit proposed which for a fuel cell system of a Vehicle is suitable and / or trained.

On the input side the matching circuit has an input interface which for connecting a fuel cell arrangement of the fuel cell system trained, interconnected and / or interconnected, wherein in operation the fuel cell system, an output voltage of the fuel cell assembly is present at the input interface. The fuel cell assembly preferably comprises one or more fuel cell stacks, each with multiple fuel cells, especially with hydrogen be operated from a tank or from a reformer. Especially is the output voltage of the fuel cell assembly as the common Voltage of all fuel cells in the fuel cell system and / or the fuel cell assembly defined.

On the output side the matching circuit has a drive output interface, which supply a power train for a drive motor formed with a drive voltage, interconnected and / or interconnected is. The power train preferably ends in a DC / AC converter, which converts the drive voltage into an AC voltage for converts the drive motor.

In the context of the invention, a supply output interface of the matching circuit proposed, which is designed to supply a supply bus for peripheral components of the fuel cell assembly with a supply voltage, interconnected and / or interconnected. The supply bus is designed in particular as a high-voltage bus, preferably with a supply voltage greater than 150 V, in particular greater than 170 V, in particular greater than 180 V. The peripheral components of the fuel cell assembly are used to supply the fuel cells with the operating materials, such. As fuel, oxidant, water, and / or to ensure operating conditions such. Operating pressure or temperature of the working gases or supplies, and preferably include any selection of the following devices: compressors, valves, dehumidifiers, humidifiers, fans, etc.

The Matching circuit is according to the invention in a special operating condition switchable, in which the supply voltage in terms of amount greater than the drive voltage is formed.

In This special mode is the power line and the supply bus supplied with different voltages, the voltage difference preferably over a longer period of time at least 5 seconds, preferably at least 30 seconds, in particular maintained for at least 2 minutes and / or greater as 5 V, preferably greater than 15 V, in particular greater than 25 V is formed.

A consideration The invention is that special operating conditions of the fuel cell system can occur where it is desirable the operating voltages of the fuel cells and thus the output voltage to keep the fuel cell assembly low. For example, occurs Such a special operating state at a cold or freeze start a fuel cell system during which the fuel cell system a temperature well below the normal operating temperature having. In this special operating state, the task arises the fuel cell system from the temperature below normal Operating temperature, in particular below 0 ° C, on the normal operating temperature of z. B. to bring 80 ° C. This could be achieved by the fuel cells be operated with a very low operating voltage, as the emitted heat or heat loss of the fuel cell assembly inversely proportional to the operating voltage of the fuel cells or the output voltage of the fuel cell assembly is. Usually In this procedure, then a matching circuit is used to the output voltage of the fuel cell assembly to a voltage whose minimum amplitude is due to the requirements of the Vehicle is determined.

at On the other hand, the invention recognizes that it is not necessary to but to convert the entire drive energy to a common voltage that it is advantageous to supply the supply voltage for Supply bus and the drive voltage for the power train different or independently to the needs to adapt to the respective assigned consumer. The drive motor is capable, in particular at low speeds, of with a smaller drive voltage sufficient torque to create.

Consequently it was found that - even at low output voltage the fuel cell assembly - the drive voltage is not necessarily by means of a matching circuit with respect to the output voltage must be increased. It is in the special mode consequently possible, the fuel cell assembly with a low output voltage, for example less than 50% or 30% of the maximum output voltage, operate and only the supply voltage for the peripheral components, the drive voltage However, to leave at the level of the output voltage.

This leads to the advantage that the matching circuit for this special operating condition only for adjusting the voltage for designed a part of the output of the fuel cell assembly have to be. After the bulk of the output of the Fuel cell assembly out in the power train is, the matching circuit can be correspondingly small and therefore cost fail. The matching circuit may, for example, be less than 40% preferably less than 25%, in particular less than 10% of Maximum power of the fuel cell assembly to be designed.

at a preferred embodiment of the invention is the Matching circuit designed so that in the special operating state the drive voltage of the output voltage of the fuel cell assembly equivalent. In particular, the time averaged correspond in each case or smoothed amplitudes. In this embodiment is preferably between the drive output interface and the input interface or between the power train and the Fuel cell arrangement no DC / DC converter interposed, which has a boost functionality.

Preferably, it is provided in the special operating state that the drive voltage and / or the output voltage is sufficiently designed to supply the drive motor for a driving operation. This condition allows the reduction of the voltage generated by a single fuel cell to values less than 0.3 V, preferably less than 0.2 V per cell. In this way it is also possible in the special operating state that the vehicle can be moved while driving with the energy of the fuel cell system. At least an emergency or a limited power operation is possible thereby.

at a constructive realization, the matching circuit has a converter module which is used to convert the output voltage into the supply voltage is formed and / or interconnected. The converter module is preferred formed as a DC / DC converter, which in particular as a DC chopper, DC / DC controller and / or clocked voltage controller is formed. In particular, the converter module is designed as a boost converter or includes a boost converter.

at A preferred embodiment is the converter module exclusively assigned to the supply bus, or the Matching circuit has only the exclusively assigned to the supply bus Converter module.

Especially to switch from the special mode to a normal one To allow operating state, the converter module is preferred self-bridging and / or with an activatable Bypass formed for bridging the converter module. A separate activatable bypass is preferably used, if the converter module does not bridge itself, as soon as the applied output voltage increases as the required supply voltage for the supply bus is.

at a preferred embodiment, the matching circuit a control device, which for activating the special operating state is trained. The activation of the special operating state takes place in particular, as soon as the output voltage falls below one, in particular adjustable minimum supply voltage for the supply bus falls. This minimum supply voltage is greater or equal to the minimum voltage requirement of the peripheral components. For example, at least one, some, or all of the peripheral components operable only over the minimum voltage requirement.

Preferably the control device is designed such that the special operating state is activated as soon as a cold or freeze start of the fuel cell system is determined or reported. A cold or freeze starts in particular before, when the operating temperature of the fuel cell is below normal Operating temperature, for example 80 ° C and in particular, when the operating temperature is less than 0 ° C is.

One Another object of the invention relates to a drive system for a vehicle with a fuel cell system, which according to the invention a Matching circuit, as previously described or after one of the preceding claims. The matching circuit is intended with the fuel cell assembly, with the power line and connected to the supply bus.

One Another object of the invention relates to a method of operation a drive system for a vehicle having a fuel cell system in a special operating condition, especially in a cold or Freezing start, wherein preferably the previously described matching circuit and / or the drive system described above or in each case according to one of previous claims is used.

In the special operating state is the operating voltage of one or Fuel cell arrangement in terms smaller in size as a minimum predetermined supply voltage of one or the supply bus for peripheral components. It becomes an energy strand for one or the drive motor with the output voltage of the fuel cell assembly as drive voltage and the supply bus with a converted Output voltage supplied as a supply voltage, wherein the converted Output voltage greater in magnitude as the minimum supply voltage and / or as the drive voltage is trained.

Further Features, advantages and effects of the inventions emerge the following description of an embodiment the invention and the accompanying figures. Showing:

1 a block diagram of a drive system in a vehicle as an embodiment of the invention;

2 the block diagram in 1 with further, optional details.

each other corresponding components are in each of the two figures provide the same reference numerals.

The 1 shows a highly schematic representation of a vehicle 1 with a fuel cell system 2 and an energy strand 3 , The energy strand 3 includes a DC / AC converter 4 which converts a drive voltage UA, which is designed as a DC voltage, into an AC voltage and thus a drive motor 5 supplied, so that this the vehicle 1 can drive while driving.

The fuel cell system 2 has a fuel cell assembly 6 with a plurality of fuel cells 7 in one or more fuel cell stacks. The fuel cell assembly 6 Provides a voltage US at its power output.

A matching circuit 8th of the fuel cell system 2 is via input interfaces 9 with the fuel cell assembly 6 , in particular the power output, electrically conductively connected, so that the output voltage US of the fuel cell assembly 6 at the matching circuit 8th as input voltage US is present.

On the output side, the matching circuit 8th Supply output interface 10 on where a utility bus 11 for peripheral components 12 is arranged so that it is supplied with a supply voltage UV. The supply bus 11 is for example designed as a high voltage bus with a voltage UV> 170V. The peripheral components are also known by the term BOP (Balance-Of-Plant) and include components that are in operation and supply to the fuel cell assembly 6 , such as compressors, fans, fans, heaters and the like are necessary.

At a drive output interface 13 the matching circuit is the drive voltage UA, wherein drive output interface 13 with the energy strand 3 is conductively connected.

In a normal operating condition, the fuel cell system becomes 2 operated or controlled so that at the supply output interface 10 and at the drive output interface 13 each the same or substantially the same voltage (UA = UV) abut.

In special operating conditions, for example during a cold or freeze start of the fuel cell assembly 6 however, is the output voltage US of the fuel cell assembly 6 smaller than the minimum necessary supply voltage UV formed. The minimum supply voltage UV is defined by the smallest voltage with which some, all or all necessary peripheral components 12 are still operable.

To the functionality of the peripheral components 12 To ensure the output voltage US is converted via a DC / DC converter, so that the supply voltage UV> US and at the same time greater than the minimum necessary supply voltage UV is formed. The drive voltage UA, however, remains unconverted and corresponds or substantially corresponds to the output voltage US. With this over the normal operating condition of the fuel cell system 2 reduced drive voltage UA, it is still possible, the drive motor 5 to provide sufficient and a reduced-power operation, especially light or emergency operation of the vehicle 1 to reach.

The matching circuit 8th is designed so that only a maximum of 10% or a maximum of 20% of the total power of the fuel cell assembly 6 can be converted in the normal operating state or in the special operating state. This allows the matching circuit 8th be formed with comparatively low-power conversion components and at the same time very good properties of the fuel cell system 2 even during a cold or freeze start.

The 2 shows the vehicle 1 with the fuel cell system 2 in the same representation as in 1 , but with an optional circuit design of the matching circuit 8th is shown. As can be seen from the presentation in the 2 results, the output voltage US through the matching circuit 8th looped through so that to the drive output interface 13 as the drive voltage UA, the output voltage US is applied. In contrast, however, is between the input interface 9 and the utility exit interface 10 a DC / DC booster 14 interposed, which converts the conversion of the output voltage US in the higher supply voltage UV. In the event that the output voltage UA is greater than the minimum necessary supply voltage UV, has the matching circuit 8th a switchable bypass 15 on, the circuitry parallel to the DC / DC booster 14 is arranged and bridges this when activated. Often, however, already indicates the DC / DC booster 14 a self-bypass function, so the bypass 15 can be omitted.

1

vehicle

2

The fuel cell system

3

power train

4

DC / AC converter

5

drive motor

6

A fuel cell assembly

7

fuel cells

8th

matching

9

Input interfaces

10

Supply output interface

11

supply bus

12

peripherals

13

Drive output interface

14

DC / DC Booster

15

bypass

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 642891881 [0004]

Claims (12)

Matching circuit ( 8th ) for a fuel cell system ( 2 ) of a vehicle ( 1 ) with an input interface ( 9 ) for connecting an output voltage (US) of a fuel cell arrangement ( 6 ) of the fuel cell system ( 2 ), with a drive output interface ( 13 ) for supplying an energy train ( 3 ) for a drive motor ( 5 ) with a drive voltage (UA), characterized by a supply output interface ( 10 ) for supplying a supply bus ( 11 ) for peripheral components ( 12 ) with a supply voltage (UV), wherein the matching circuit ( 8th ) can be switched to a special operating state, in which the supply voltage (UV) is greater in magnitude than the drive voltage (UA) is formed. Matching circuit ( 8th ) according to claim 1, characterized in that the matching circuit ( 8th ) is formed such that in the special operating state, the drive voltage (UA) corresponds to the output voltage (US) of the fuel cell assembly. Matching circuit ( 8th ) according to claim 1 or 2, characterized in that the drive voltage (UA) sufficient for the supply of the drive motor ( 5 ) is for a driving operation. Matching circuit ( 8th ) according to one of the preceding claims, characterized by a converter module ( 14 ), which is designed to convert the output voltage (US) into the supply voltage (UV) and / or connected. Matching circuit ( 8th ) according to claim 4, characterized in that the converter module ( 14 ) is designed as a DC / DC converter, which exclusively to the supply bus ( 11 ) assigned. Matching circuit ( 8th ) according to one of claims 4 or 5, characterized in that the converter module as a boost module ( 14 ) is trained. Matching circuit ( 8th ) according to one of claims 4 to 6, characterized by an activatable bypass ( 15 ), which in terms of circuitry parallel to the converter module ( 14 ) and is arranged to bridge it. Matching circuit ( 8th ) according to one of the preceding claims, characterized by a control device which is designed to activate the special operating state as soon as the output voltage (US) falls below a minimum supply voltage (UV). Matching circuit ( 8th ) according to one of the preceding claims, characterized by one or the control device, which is designed to activate the special operating state, as soon as a cold start of the fuel cell system is determined. Drive system for a vehicle ( 1 ) with a fuel cell system ( 2 ), characterized by a matching circuit ( 8th ) according to any one of the preceding claims. Method for operating a drive system for a vehicle ( 1 ) with a fuel cell system ( 2 ) in a special operating state, preferably using a matching circuit ( 8th ) and / or the drive system according to any one of the preceding claims, wherein in the special operating state, the output voltage (US) of a fuel cell assembly ( 6 ) smaller than a minimum supply voltage (UV) of a supply bus ( 11 ) for peripheral components ( 12 ), wherein an energy strand ( 3 ) for a drive motor ( 5 ) with the output voltage (US) as the drive voltage (UA) and with the supply bus ( 11 ) is supplied with a converted output voltage, wherein the converted output voltage is greater in magnitude than the minimum supply voltage (UV) and / or as the drive voltage (UA) is formed. Method according to claim 11, characterized in that that the special operating condition designed as a cold or freeze start is.