Electrical arrangement for a fuel cell system

Abstract

The invention relates to an electrical arrangement for a fuel cell system (7), comprising: an electrical power section (10) designed to electrically connect a fuel cell (5) to an application (1); a DC-to-DC converter (4) designed to convert an input voltage to an output voltage, wherein the DC-to-DC converter (4) has a first connection (41) which is designed to be connected to the fuel cell (5); a bidirectional, galvanic isolation device (3) designed to electrically isolate the electrical power section (10), wherein the bidirectional galvanic isolation device (3) has a second connection (30) which is designed to be electrically connected to the application (1); a connection line (8) which electrically connects the DC-to-DC converter (4) to the isolation device (3); and a branching point (9) from which a branch line (90) branches off at the connection line (8), wherein the branch line (90) is designed to be connected to an auxiliary component system (6) of the fuel cell system (7).

Description

[0001] Electrical arrangement for a fuel cell system

[0002] Description

[0003] The present invention relates to an electrical arrangement for a fuel cell system with an improved electrical power train with a bidirectional galvanic isolation device, a fuel cell system with such an electrical arrangement, and a use of such a fuel cell system, particularly in a maritime, automotive, and / or heavy-duty application.

[0004] Fuel cell systems are known in various configurations from the prior art. The fuel cell system can be implemented as a single stack or as an interconnection of several individual stacks. Typically, all components of the fuel cell system, especially the fuel cell and auxiliary component systems (balance-of-plant components), are arranged on a common DC bus system, such as the application. In this configuration, the fuel cell stack is not isolated from the DC bus system, which can frequently lead to undesirable leakage currents to ground at the application or other electrical disturbances. Particularly if the application includes a battery with a highly sensitive battery management system, undesirably high loads can occur on the battery management system, which in extreme cases can lead to the failure of the battery management system and / or other systems within the application.US 11329484 B2 generally shows a power supply device with several utility units connected in series.

[0005] It is therefore an object of the present invention to provide an electrical arrangement for a fuel cell system and a fuel cell system which, with simple construction and simple, cost-effective manufacturing, prevent a significant reduction of disturbances in an application. This object is achieved by an electrical arrangement with the features of claim 1, a fuel cell system with the features of claim 14, and the use of a fuel cell system according to claim 15. The dependent claims each describe preferred embodiments of the invention.

[0006] The electrical arrangement according to the invention for a fuel cell system with the features of claim 1 has the advantage that an electrical power train of the fuel cell system, which is configured to establish an electrical connection between a fuel cell and an application, comprises a bidirectional galvanic isolation device. Such bidirectional galvanic isolation devices have not previously been used in fuel cell systems. A major advantage of the bidirectional galvanic isolation device is that galvanic isolation between the fuel cell system and the application is possible. Thus, disturbances from the fuel cell system have no influence on components of the application, in particular a DC bus of the application and components arranged thereon, and conversely, disturbances from the application have no influence on the fuel cell.This allows, in particular, the avoidance of conducted interference coupling into components of the application. This results in a significantly reduced load on the application components, which, through appropriately adapted design of the individual components, can lead to substantial cost advantages. According to the invention, this is achieved by the electrical arrangement comprising an electrical power train configured for electrically connecting a fuel cell to an application. Furthermore, the electrical arrangement includes a DC-DC converter in the power train, configured to perform a voltage conversion from an input voltage to an output voltage, the DC-DC converter having a first terminal. The first terminal is configured to be connected to the fuel cell.The electrical arrangement further comprises the bidirectional galvanic isolation device in the power train, configured for electrical isolation of the electrical power train from the application, wherein the bidirectional galvanic isolation device has a second terminal configured to be connected to the application. The electrical arrangement further comprises a connecting line which has a branch line. The connecting line connects the DC-DC converter to the bidirectional galvanic isolation device. At the branch point, the branch line is arranged on the connecting line, wherein the branch line is configured to be connected to an auxiliary component system of the fuel cell system.The auxiliary system (balance-of-plant (BOP) system) comprises all auxiliary systems of the fuel cell except the fuel cell itself and the power train, in particular the air and water supply, pumps, compressors, cooling devices, control units, etc. The bidirectional galvanic isolation device between the components of the fuel cell system and the application further reduces losses, resulting in a higher overall efficiency of the fuel cell system. This results in, in particular, reduced interference from the fuel cell system to the outside, as well as reduced interference from the application to components of the fuel cell system. Furthermore, the bidirectional galvanic isolation device also enables energy transfer in both directions, i.e., from the fuel cell to the application and from the application, especially if it includes a battery storage system or similar, to the fuel cell.In particular, this enables energy transmission at the same voltage level in both directions.

[0007] Preferably, the bidirectional galvanic isolation device has a first voltage monitoring system on one side of the fuel cell and / or a second voltage monitoring system on one side of the application. The voltage monitoring systems are preferably connected to a control unit which is configured to control the bidirectional galvanic isolation device based on the values ​​of the monitored voltages.

[0008] Preferably, the auxiliary component system of the electrical arrangement is configured to exchange energy and / or data and / or signals with the fuel cell, comprising in particular devices for supplying the fuel cell with air and water, pumps, compressors, cooling devices and control units.

[0009] This allows for the exchange of energy and / or data and / or signals, especially commands, in both directions between the fuel cell and the auxiliary components. The auxiliary components can also be interconnected.

[0010] The bidirectional galvanic isolation device preferably includes insulation monitoring. This monitoring is preferably located on the fuel cell side. If a predetermined electrical insulation threshold is exceeded, the fuel cell system can be disconnected from the application.

[0011] Preferably, the bidirectional galvanic isolation device comprises a primary-side filter, a primary-side power stage, a resonant path with a transformer, a secondary power stage, and a secondary filter. The bidirectional galvanic isolation device is thus preferably configured as a mirror image of the resonant path.

[0012] Preferably, the power train further comprises a disconnect unit (DCU). The disconnect unit is arranged in the electrical power train between the galvanic isolation device and the application. The disconnect unit is preferably arranged directly in series with the bidirectional galvanic isolation device. The disconnect unit is an electrical component that connects or disconnects the electrical DC power train of the fuel cell system from the application. In particular, all-pole isolation of the fuel cell system and the application on a DC bus can be enabled. Furthermore, defined connection with pre-charging and protection of all trains against overcurrent can be enabled.

[0013] The interruption unit preferably includes a device for monitoring insulation resistance. This allows an insulation measurement to be performed on the application-facing side, and the interruption unit to be controlled based on the measurement result. The insulation resistance monitoring device is preferably located on the fuel cell side of the interruption unit.

[0014] Preferably, the interruption unit has several sensors, in particular a temperature sensor and / or a voltage sensor and / or a current sensor.

[0015] In a preferred embodiment, the interruption unit has its own control unit. The control unit of the interruption unit is preferably arranged directly on the interruption unit itself.

[0016] Preferably, the DC-DC converter also includes a plurality of sensors, in particular a temperature sensor, a voltage sensor, and / or a current sensor. The DC-DC converter is preferably a boost converter, especially with freewheeling diodes. Preferably, the boost converter has several boost stages, wherein the boost stages are further preferably operated out of phase. In particular, the boost converter enables the voltage of the fuel cell potential to be increased to an application potential. The boost converter can also preferably enable power control.

[0017] According to a further preferred embodiment of the invention, at least two electrical arrangements are arranged in parallel. Particularly preferred are exactly six electrical arrangements arranged in parallel to one another. Each electrical arrangement has the same construction and its own bidirectional galvanic isolation device. Preferably, each electrical arrangement is connected to a DC bus of the application.

[0018] Furthermore, the present invention relates to a fuel cell system comprising at least one fuel cell and at least one electrical arrangement according to the invention. Particularly preferably, several fuel cell systems are combined to form a fuel cell module. The present invention further relates to the use of a fuel cell system in an application. The application is preferably a maritime application, an automotive application, or a heavy-duty application, in particular a railway application.

[0019] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawing. The drawing shows:

[0020] Fig. 1 A schematic representation of a fuel cell system with an electrical arrangement according to a first embodiment of the invention,

[0021] Fig. 2 is a schematic enlarged partial representation of Figure 1 ,

[0022] Fig. 3 is a schematic representation of a bidirectional galvanic isolation device of the fuel cell system of Figure 1, Fig. 4 is a schematic view of an interruption unit (DCU) of the fuel cell system of Figure 1,

[0023] Fig. 5 is a schematic representation of a DC / DC converter of the fuel cell system of Figure 1.

[0024] Fig. 6 shows a schematic sectional view of the electronic arrangement of Figure 1 and

[0025] Fig. 7 shows a schematic representation of a bidirectional galvanic isolation device according to a second embodiment of the invention.

[0026] Below, with reference to Figures 1 to 6, we describe in detail a fuel cell system 7 with an electrical arrangement with an electrical power train 10 according to a preferred embodiment of the invention.

[0027] The electrical power train 10 is set up to establish an electrical connection between a fuel cell 5 and an application 1, e.g. a maritime or automotive application.

[0028] Fuel cell 5 is a fuel cell stack and forms the electrical source of the system. Energy is provided in the fuel cell by converting chemical energy from hydrogen into electrical energy. The number of fuel cell cells and the operating point essentially determine the resulting output voltage. The resulting output current is determined, in particular, by the size of the active cell area.

[0029] The electrical arrangement 10 comprises a DC-DC converter 4, which is configured to perform a voltage conversion from an input voltage to an output voltage. The DC-DC converter 4 has a first terminal 41, via which the DC-DC converter 4 is connected to the fuel cell 5 (see Figure 2).

[0030] In this embodiment, the DC-DC converter 4 is a boost converter, which in particular increases the voltage of the fuel cell potential to an application potential. The DC-DC converter 4 can also include sensors for temperature, voltage, and current. Furthermore, the DC-DC converter 4 regulates the electrical power of the fuel cell 5.

[0031] The electrical arrangement 10 further comprises a bidirectional galvanic isolation device 3. The bidirectional galvanic isolation device 3 is configured for the electrical isolation of the electrical power train 10, wherein the isolation device 3 has a second connection 30. The second connection 30 is configured to be connected to the application 1.

[0032] As can be seen from Figures 1 and 2, a connecting line 8 is also provided, which connects the DC-DC converter 4 to the bidirectional galvanic isolation device 3. A branch point 9 is arranged in the connecting line 8, from which a branch line 90 extends from the connecting line 8. An electrical connection is made via the branch line 90 to an auxiliary component system 6 (balance-of-plant system) of the fuel cell system 7.

[0033] The auxiliary component system 6 comprises all other components of the fuel cell system 7, in particular pumps, compressors, sensors, heat exchangers, seals, coolers and / or humidifiers, etc. The auxiliary component system 6 is shown schematically in Figures 1 and 2.

[0034] Figure 3 shows the bidirectional galvanic isolation device 3 in detail. As shown in Figure 3, the main components of the isolation device 3 are a primary-side filter 31, a primary-side power section 32, a resonant path 33 with transformer, a secondary power section 34, and a secondary filter 35. The components are arranged in series as shown in Figure 3. A main function of the isolation device 3 is to provide galvanically isolated power transmission from the primary side, characterized by PRI+ and PRI-, to the secondary side, characterized by SEC+ and SEC-, and vice versa, at the same voltage level. The primary side is connected to the DC-DC converter 4 via the connecting line 8, and the secondary side is electrically connected to a disconnect unit 2 (DCU).

[0035] The bidirectional galvanic isolation device 3 has a first voltage monitoring 14 and a second voltage monitoring 15 (see Figure 2).

[0036] The interruption unit 2 is an electrical component that connects or disconnects the electrical power train 10 of the fuel cell system 7 from the application 1. The interruption unit 2 enables all-pole connection and disconnection between the fuel cell system 7 and the application 1 on a DC bus. This allows for defined connection with pre-charging and protection of all electrical train sets against potential overcurrent. Furthermore, insulation monitoring 21 can perform insulation measurements, particularly on the side of the interruption unit 2 facing the fuel cell 5, and sensors for measuring temperature, voltage, and current can be provided.

[0037] The interruption unit 2 is shown in detail in Figure 4. As shown in Figure 4, the all-pole disconnection is achieved by a disconnecting device on each pole. The interruption unit 2 comprises a main contactor S1 for disconnecting the positive path and a main contactor S2 for disconnecting the negative path. Parallel to the positive main contactor S1 is an additional disconnecting device S3 with a resistive load R1 connected in series. A further optional disconnecting device S4 with a resistive load R2 connected in series can be arranged in parallel. A voltage measurement U2 upstream of the main contactors S1 and S2 on the application side and a voltage measurement U1 downstream of the main contactors S1 and S2 on the fuel cell side can be provided.

[0038] Furthermore, as shown in Figure 4, a current measurement A2 is provided on a DC path on the application side and a current measurement A1 on the DC path on the fuel cell side. Within the interruption unit 2, several temperature sensors, schematically labeled T in Figure 4, can be arranged, particularly to measure an internal temperature. Insulation monitoring R_ISO 1 and R_ISO 2 are also arranged on the fuel cell side. In this embodiment, a connection to the application 1 is provided on the application side for each pole, consisting of multiple fused strands, with the designations F1, F2, F3, and F4 for the positive strand and F5, F6, F7, and F8 for the negative strand.

[0039] On the fuel cell side, the power is split into several strings. Each string preferably terminates in a module. Each string is also separately fused. The positive string is designated F9, F10, F11, and F12, and the negative string is designated F13, F14, F15, and F16.

[0040] The interruption unit 2 is further configured to connect a DC bus of the fuel cell system 7 to the DC bus of the application 1 according to the following steps:

[0041] First, the main contactor S2 of the negative main winding closes. A pre-charging phase then begins, during which contactor S3 closes as a pre-charging contactor, allowing a defined current, limited by the resistive load R1, to pre-charge the components of the fuel cell system. After a defined time, contactor S4 (another pre-charging contactor) closes, and together with the resistive load R2, increases the pre-charging current. This reduces the potential difference between the two potentials U1 and U2. Finally, the positive main contactor S1 closes, followed by the opening of contactors S3 and S4.

[0042] The interruption unit 2 comprises, as schematically shown in Figure 2, its own control unit 20 and an insulation monitoring device 21. The insulation monitoring device is located on the combustion chamber side, and the control unit 20 is located on the application side. Thus, the interruption unit 2 enables all-pole isolation of the DC bus to the application 1, allowing, in particular, the measurement of voltage, current, and temperature, as well as insulation monitoring. Furthermore, it enables defined pre-charging of all electrical power components in the fuel cell system 7 and protection of all strings both towards the fuel cell and towards the application.

[0043] Figure 5 shows an example of the sliding voltage converter 4 in the form of a boost converter. The fuel cell 5 is arranged on the input side of the DC-DC converter 4, labeled IN+ and IN-. On the input side, a capacitor C1 is connected in series with an inductor L1. This inductor leads to a center tap of a half-bridge consisting of switches S11 and S12. Antiparallel freewheeling diodes, which are not shown in Figure 5, can be arranged in parallel with switches S11 and S12. A capacitor C2 is located on one output side. The output side is labeled OUT+ and OUT-. A stage as shown in Figure 5 can be used multiple times, particularly due to higher currents, and can be operated in phase-shifted (interleaved) mode. Filters and measuring circuits are not shown in detail.If the DC-DC converter 4 is configured as a boost converter, its function within the fuel cell system is to increase the voltage of the fuel cell 5 to the voltage of the application 1. Internal current control or power control can also be implemented. The voltage is specified by the application 1 and can vary within a predefined range. Since the fuel cell 5 can exhibit a highly variable voltage characteristic depending on its operating range, the boost converter can compensate for this fluctuating voltage. Thus, the fuel cell 5, the DC-DC converter 4, the bidirectional galvanic isolation device 3, and the interruption unit 2 are connected in series, as shown in Figure 1. The auxiliary component system 6 is arranged on the connecting line 8 within the fuel cell system 7.In a parallel connection of several fuel cell systems 7, 7' (see Figure 1), the inventive concept ensures that requirements and limit values ​​regarding insulation resistance are met over the lifetime of the electrical arrangement 10. Since each fuel cell system has its own bidirectional galvanic isolation device 3, a stable and high insulation resistance can be ensured regardless of the number of individual fuel cell systems 7, 7'. Thus, the reduced overall insulation resistance resulting from the parallel connection of the fuel cell systems 7, 7' can be compensated for, thereby ensuring that the insulation resistance limits are met over the lifetime.

[0044] Preferably, the components, in particular the fuel cell 5, the DC-DC converter 4, and the bidirectional galvanic isolation device 3, are each controlled by their own logic (control unit). Preferably, a higher-level control unit is provided to which information and data from the individual components and measuring circuits, excluding the interruption unit 2, are supplied. The isolation devices of the interruption unit 2 are preferably controlled by a separate control unit of the interruption unit 2. Data from the sensors regarding voltage, current, and temperature are evaluated by this control unit of the interruption unit 2.

[0045] Figure 6 shows a schematic partial sectional view of a gate driver control. A sandwich design is used, which allows electronic components 108 of the gate driver control 102 to be directly connected to a cooling structure 101 from below and also enables electrical connection to module control pins 104. A sandwich design was also used for the connection between power semiconductor modules 105 and DC capacitors 109 and the power board 103. The DC link capacitors 109 are thermally connected to the cooling structure 101 from below and electrically connected to the semiconductor modules 105 via the power board 103 from above. Above the power board 3 is a busbar 106 which leads to the input and output of the device. Thus, the busbar 106, the power board 103, and, if necessary, the power module 109 can be connected to the power module 105 via a single contact point, namely a screw in a module pin 107.The various measuring circuits, a DC capacitor 109, and the power semiconductor module 105 itself are electrically connected. This allows for a particularly low-inductance design, which is intended to introduce no significant disturbances into the fuel cell system 7.

[0046] Furthermore, the arrangement of the insulation monitoring device 21 on the input side allows for the continuous determination and transmission of information on the insulation resistance of the fuel cell 5. A DC bus 11 of the auxiliary component system 6 connects all auxiliary components of the auxiliary component system 6. This can also include a battery 12.

[0047] The parallel-connected fuel cell systems 7' are constructed in the same way as the fuel cell system 7, which is shown in Figure 1 by the dashed line with the reference numerals 2', 3', 4', 5' and 6'.

[0048] The invention thus enables an arrangement of any number of parallel connected fuel cell systems 7, 7' without having a significant influence on the system insulation resistance.

[0049] Figure 7 shows an alternative embodiment of a bidirectional galvanic isolation device 3. On the input side (PRI-, PRI+), which is connected to the DC-DC converter 4, an input capacitor C1 is arranged to smooth the DC bus voltage of the fuel cell system 7. This is followed by a full bridge, comprising two half-bridges, with four power semiconductor switches S1, S2, S3, S4 arranged in an H-shape. Two switches are always arranged in series between the positive and negative DC bus potentials.

[0050] A center tap is located between the semiconductors. Following the center tap of one half-bridge (S1, S3) are resonant capacitors C3 connected in series. These resonant capacitors are connected on the other side to the primary winding of a high-frequency transformer T1. The other terminal of the primary side of the high-frequency transformer T1 is connected to the center tap of the second half-bridge (S2, S4).

[0051] On the secondary side of the high-frequency transformer T1 is a full-wave rectifier comprising four diodes D1, D2, D3, and D4. Two diodes are connected in series between the positive and negative DC bus potentials. A center tap between any two diodes of a branch D1 / D3 or D2 / D4 connects to a terminal on the secondary side of the high-frequency transformer T1.

[0052] On the output side, there is another capacitor C2 followed by a filter 35. Additionally, measuring circuits are located within the bidirectional galvanic isolation device 3, with a voltage measurement and monitoring unit U1 on the input side and another voltage measurement and monitoring unit U4 on the output side. Further voltage measurements U2 and U3 are used for zero-voltage switching (ZVS) detection. Reference numeral A1 describes an overcurrent detection unit on the secondary side, which is labeled SEC+ and SEC- in Figure 7. A temperature sensor 13 is shown in Figure 7 as an example of a possible sensor within the component. Thus, this embodiment enables detailed insulation monitoring 21 on the input side of the isolation device 3.

[0053] The isolating device 3 shown in Figure 7 thus enables a one-to-one voltage conversion from the input side to the output side. On the input side, the DC current from the full bridge is chopped by switches S1, S2, S3, and S4. Switches S1, S2, S3, and S4 are always driven diagonally. This, together with the resonant circuit formed by the resonant capacitance C3 and the leakage inductance of the high-frequency transformer T1, results in a sinusoidal waveform for the primary-side current of the high-frequency transformer T1. Due to the one-to-one turns ratio, this current is transferred to the secondary side. Rectification takes place there using diodes D1, D2, D3, and D4.

Claims

Patent claims 1. Electrical arrangement for a fuel cell system (7) comprising: . an electrical power train (10) configured for electrically connecting a fuel cell (5) to an application (1 ), . a DC-DC converter (4) configured to convert an input voltage to an output voltage, wherein the DC-DC converter (4) has a first terminal (41) configured to be connected to the fuel cell (5), . a bidirectional galvanic isolation device (3) configured for electrical isolation of the electrical power train (10), wherein the bidirectional galvanic isolation device (3) has a second terminal (30) configured to be electrically connected to the application (1), . a connecting line (8) which electrically connects the DC voltage converter (4) to the isolating device (3), and . a branch point (9) from which a branch line (90) branches off at the connecting line (8), wherein the branch line (90) is configured to be connected to an auxiliary component system (6) of the fuel cell system (7).

2. Electrical arrangement according to claim 1, wherein the bidirectional galvanic isolation device (3) has a first voltage monitoring (14) on a side facing the fuel cell (5) and / or a second voltage monitoring (15) on a side facing the application (1).

3. Electrical arrangement according to one of the preceding claims, wherein the auxiliary component system (6) is configured to exchange energy and / or data and / or signals with the fuel cell, wherein the Auxiliary component system (6) includes in particular devices for supplying the fuel cell with air and water, pumps, compressors, cooling devices and control units.

4. Electrical arrangement according to one of the preceding claims, wherein the bidirectional galvanic isolation device (3) has an insulation monitoring device (21), in particular on the side facing the fuel cell (5).

5. Electrical arrangement according to one of the preceding claims, wherein the bidirectional galvanic isolation device (3) comprises a primary-side filter (31), a primary-side power section (32), a resonant path (33) with transformer, a secondary-side power section (34) and a secondary-side filter (35).

6. Electrical arrangement according to one of the preceding claims, wherein the power train (10) further comprises an interruption unit (2) which is arranged in the electrical power train (10) between the bidirectional galvanic isolation device (3) and the application (1).

7. Electrical arrangement according to claim 6, wherein the interruption unit (2) comprises a device for monitoring insulation resistances.

8. Electrical arrangement according to claim 7, wherein the device for monitoring insulation resistances in the interruption unit (2) is arranged on the side facing the fuel cell (5).

9. Electrical arrangement according to one of claims 6 to 8, wherein the interruption unit (2) has sensors for temperature, voltage and / or current.

10. Electrical arrangement according to one of claims 6 to 9, wherein the interruption unit (2) has its own control unit (20).

11. Electrical arrangement according to one of the preceding claims, wherein the DC voltage converter (4) has sensors for temperature, voltage and / or current.

12. Electrical arrangement according to one of the preceding claims, wherein the DC voltage converter (4) is a boost converter, wherein the boost converter in particular has several boost stages which are operated out of phase.

13. Electrical arrangement according to any one of the preceding claims, wherein two or more electrical arrangements are connected in parallel.

14. Fuel cell system comprising: . a fuel cell (5) and . an electrical arrangement (10) according to any one of the preceding claims.

15. Use of a fuel cell system (7) according to claim 15 in a maritime device or an automotive device or a heavy-duty application, in particular a railway application.

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