JP2011003288A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a specific arrangement of an internal structure of a converter boosting an output from a cell stack and the cell stack.SOLUTION: The cell stack 3 including a plurality of laminated cells 2 and the converter 150 boosting the cell stack 3 are integrated, a heating part of the converter 150 is arranged to one end or both ends of an end cell 2e of the cell stack 3, and the cell stack 3 is connected to the converter 150 via a bus 4. As the heating part, for example, a reactor L1 of the converter 150 is arranged to one end or both ends of the end cell 2e, and an IPM 154 is arranged to a negative electrode side. The cell stack 3 and the converter 150 are preferably housed in the same frame.

Description

  The present invention relates to a fuel cell system. More specifically, the present invention relates to improvements in the structure of fuel cells and the like within a fuel cell system.

  In general, a cell stack (cell stack) of a fuel cell (for example, a polymer electrolyte fuel cell) is configured by stacking a plurality of cells each having an electrolyte sandwiched between separators. Further, as a fuel cell system including such a fuel cell, a fuel cell system including a converter (DC / DC converter) for boosting the output of the cell stack is used (for example, see Patent Document 1).

JP 2007-207582 A

  However, in the fuel cell system including the converter as described above, conventionally, the specific configuration of the internal structure of the converter and the specific arrangement of the cell stack has not been sufficiently studied.

  Therefore, an object of the present invention is to provide a fuel cell system in which the internal configuration of a converter that boosts the output of a cell stack and the specific arrangement of the cell stack are improved.

  In order to solve this problem, the present inventor has made various studies. First, focusing on the electrical connection between the fuel cell and the converter, it is necessary to absorb the position error and fluctuation of the member that electrically connects the cell stack and the converter. These are connected using, for example, (see FIG. 10), and as a result, the structure may be too complicated. In addition, it is necessary to provide a noise shield or waterproof cover for the braided busbar to ensure the degree of freedom of deformation of the braided busbar, and also to ensure shielding and waterproofing, but this is difficult and increases the number of parts. Sometimes invited. In particular, in the case of an on-vehicle fuel cell system, it is essential to ensure the waterproofness of the bus bar and to reduce radio noise and control signal noise, and these problems are likely to become remarkable. In addition, in a fuel cell system for vehicle use, all the power is supplied by the fuel cell, so that a large current (for example, 500 A class) can be passed, position errors and fluctuations can be absorbed, and vibrations can be absorbed. It is desirable to have a waterproof (water-resistant) and noise-shielding bus that can absorb relative position fluctuations due to secular change, but there is no bus that satisfies all of these requirements. It is a fact.

  Next, the inventor paid attention to the end cells of the cell stack. In a cell stack composed of a plurality of cells, the temperature of the end cell is difficult to rise, and even after breaking through freezing by rapid warm-up, the temperature may fall below freezing and the water may freeze. Even if the water does not freeze, flooding is likely to occur because the saturated vapor pressure is low, which may cause a decrease in output, a cell voltage, and a deterioration of the fuel cell. In general cell stacks, there is no heat accumulation or heat interference between cells, and it is difficult to raise the temperature particularly in the end cells where heat easily escapes to the outside, and the saturated water vapor pressure does not rise and water tends to exist. is there. If water is present in the end cells in this way, it becomes difficult to supply oxygen and hydrogen, and the cell voltage is lowered.

  Based on the examination contents as described above, the present inventor conceived and studied to integrate the cell stack and the converter in order to solve these problems having different viewpoints. In such a case, it is possible to raise the temperature of the end cell without using a conventional bus bar and by bringing the heat generating component (reactor or IPM) of the converter close to or in contact with the end cell. However, in order to integrate the cell stack and the converter, it is important to optimize the component layout. In particular, in order to avoid flooding and avoid cell voltage drop, the knowledge that converter components should be placed near the end cells Got. In addition, when integrating the cell stack and the converter, we also learned that it is important to reduce the size (especially the common use of the stack case) and simplify the connection bus in consideration of cost reduction.

  In the present invention based on such knowledge, a cell stack formed by laminating a plurality of cells and a converter for boosting the cell stack are integrated, and a heat generating component of the converter is disposed at one end or both ends of an end cell of the cell stack. The cell stack and the converter are connected by a bus. By integrating the cell stack and the converter in this way, it is possible to connect the cell stack and the converter using a bus having a simplified structure, instead of a conventional bus such as a braided bus bar. In addition, the heat generated from the converter can be used to raise the temperature of the end cells, and in particular, the warm-up performance at the cold start can be improved.

  Such a fuel cell system preferably has a structure in which the cell stack and the converter are mounted on the same frame. By eliminating the relative displacement between the cell stack and the converter, a conventionally required apparatus for absorbing displacement can be omitted.

  Moreover, in such a fuel cell system, it is preferable that the heat generating components of the converter are arranged in contact with the end cells. In this case, since the end cell is heated, the heat generated from the converter can be used more effectively.

  Furthermore, it is preferable that a cooling device for cooling the heat generating component is provided on the side opposite to the end cell as viewed from the heat generating component.

  In the fuel cell system according to the present invention, the converter reactor is disposed at one or both ends of the end cell, and the IPM is disposed at the negative electrode side of the end cell.

  According to the present invention, it is possible to improve the specific arrangement of the internal configuration of the converter that boosts the output of the cell stack and the cell stack.

It is a block diagram of the fuel cell system in one Embodiment of this invention. It is the figure which illustrated the structure of the single phase circuit for 1 phase of the converter which pressure | voltage-rises the output of a cell stack. It is the figure which illustrated the relationship between the input voltage of an inverter and the output terminal voltage of a fuel cell when the request | requirement power of load has a fluctuation | variation. It is a figure which shows the outline of the structure of the integrated cell stack and a converter. It is a figure which shows the outline of a structure at the time of making arrangement | positioning of heat-emitting components different in the integrated cell stack and a converter. It is a perspective view which shows the outline of the whole cell stack and converter which were integrated. It is a perspective view of a converter in the state where a built-in reactor is visible. It is a perspective view of a converter in the state where built-in IPM can be seen. It is a perspective view of a converter in the state where a built-in capacitor can be seen. It is a perspective view which shows the conventional structure of the integrated cell stack and converter as a reference.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  1 to 9 show an embodiment of a fuel cell system 100 according to the present invention. Hereinafter, as an application example of the fuel cell system 100, a fuel cell vehicle (FCHV) on which the fuel cell system 100 is mounted will be described. The fuel cell system 100 of the present embodiment has a configuration in which a DC / DC converter (hereinafter referred to as a battery converter) 180 is provided between the battery 120 and the inverter 140 (see FIG. 1).

  The fuel cell 1 is, for example, a polymer electrolyte fuel cell including a cell stack (cell stack) 3 in which a plurality of cells (power generation cells) 2 are stacked. The fuel cell 1 is provided with a voltage sensor for detecting the output terminal voltage Vfc from the cell stack 3 and a current sensor (both not shown) for detecting the output current (FC current).

  The cell 2 includes an electrolyte membrane composed of an ion exchange membrane and a membrane-electrode assembly (MEA) composed of a pair of electrodes sandwiching the electrolyte membrane from both sides, and a pair of separators sandwiching the membrane-electrode assembly from the outside. , Is composed of. The separator is, for example, a conductor based on metal, and has a fluid flow path for supplying an oxidant gas such as air and a fuel gas such as hydrogen gas to each electrode, and is supplied to the cells 2 adjacent to each other. To block the mixing of dissimilar fluids. With this configuration, an electrochemical reaction occurs in the membrane-electrode assembly of the cell 2 to obtain an electromotive force. Although not shown, the separator is formed with manifolds (oxidizing gas manifold, fuel gas manifold, refrigerant manifold) for flowing oxidizing gas, fuel gas, and refrigerant in the cell stacking direction.

  A converter (hereinafter also referred to as FC converter) 150 that boosts the output from the cell stack 3 of the fuel cell 1 plays a role of controlling the output terminal voltage Vfc of the fuel cell 1, and is on the primary side (input side: fuel). The FC output terminal voltage Vfc input to the battery 1 side) is converted to a voltage value different from the primary side (step-up or step-down) and output to the secondary side (output side: inverter 140 side). This is a bidirectional voltage conversion device that converts a voltage input to the secondary side into a voltage different from the secondary side and outputs the converted voltage to the primary side. The FC converter 150 controls the output terminal voltage Vfc of the fuel cell 1 to be a voltage corresponding to the target output (that is, the target output terminal voltage vfc).

  The FC converter 150 is, for example, a step-up converter, and has a circuit configuration as a three-phase parallel converter composed of a three-phase operation method, specifically a U-phase 151, a V-phase 152, and a W-phase 153. ing. In the present embodiment, non-insulated boost converters are arranged in three phases in parallel to reduce the current flowing in one phase, thereby reducing the size and loss of components.

  FIG. 2 is a configuration diagram of a load driving circuit in which a circuit for one phase of the FC converter 150 is extracted. In the following description, a voltage before boosting input to the FC converter 150 is referred to as an input voltage Vin, and a voltage after boosting output from the FC converter 150 is referred to as an output voltage Vout.

  As shown in FIG. 2, the FC converter 150 (for one phase) includes a reactor L1, a rectifying diode D1, and a switching element SW1 including an IGBT (Insulated Gate Bipolar Transistor). As will be described later, the reactor L1 is disposed in the vicinity of an end cell of the fuel cell 1 (indicated by reference numeral 2e in FIG. 4 and the like). Further, the end of the reactor L1 is connected to the collector of the switching element SW1. Here, the electric current which flows into the reactor L1 is detected by the current sensors I1-I3 (refer FIG. 1) which detect the reactor current of each phase. The switching element SW1 is connected between the power supply line of the inverter 140 and the earth line. Specifically, the collector of the switching element SW1 is connected to the power supply line, and the emitter is connected to the earth line. In such a configuration, first, when the switch SW1 is turned ON, a current flows from the fuel cell 1 → the reactor L1 → the switch SW1, and at this time, the reactor L1 is DC-excited to accumulate magnetic energy.

  Subsequently, when the switch SW1 is turned OFF, the induced voltage due to the magnetic energy accumulated in the reactor L1 is superimposed on the FC voltage (input voltage Vin) of the fuel cell 1, and an operating voltage (output voltage Vout) higher than the input voltage Vin is generated. While being output from the reactor L1, an output current is output through the diode D1. The controller 160 obtains a desired output voltage Vout by appropriately changing the ON / OFF duty ratio (described later) of the switch SW1. The input current of FC converter 150 (that is, the output current of fuel cell 1) is detected by current sensor 156, and the input voltage of FC converter 150 (that is, the output voltage of fuel cell 1) is detected by a voltage sensor (not shown). Detected). In this embodiment, the current sensor 156 is arranged in front of the reactor L1 in order to improve the control performance (see FIG. 2).

  Returning to FIG. 1, the battery (power storage device) 120 is connected in parallel to the fuel cell 1 with respect to the load 130, and is a surplus power storage source, a regenerative energy storage source during regenerative braking, acceleration of the fuel cell vehicle, or Functions as an energy buffer when the load fluctuates due to deceleration. As the battery 130, for example, a secondary battery such as a nickel / cadmium storage battery, a nickel / hydrogen storage battery, or a lithium secondary battery is used.

  The battery converter 180 plays a role of controlling the input voltage Vin of the inverter 140 and has, for example, a circuit configuration similar to that of the FC converter 150. In this embodiment, when the required power of the load 130 changes abruptly (hereinafter assumed to increase), first, the input voltage Vin of the inverter 140 is set to the set target input voltage Vtin (see Δ in FIG. 3). ) Until the battery converter 180 is controlled. Then, after the input voltage Vin of the inverter 140 reaches the target input voltage Vtin, the FC converter 150 is controlled until the output terminal voltage Vfc of the fuel cell 1 becomes the set target output terminal voltage Vtfc. As described above, when the required power for the fuel cell 1 is rapidly increased, the output voltage Vfc of the fuel cell 1 is controlled by the FC converter 150 after the input voltage Vin of the inverter 140 is controlled by the battery converter 180. Thus, stable converter control can be realized. Note that the circuit configuration of the battery converter 180 is not limited to the above, and any configuration capable of controlling the input voltage Vin of the inverter 140 can be employed.

  The inverter 140 is, for example, a PWM inverter that is driven by a pulse width modulation method, and converts DC power output from the fuel cell 1 or the battery 120 into three-phase AC power in accordance with a control command from the controller 160, thereby obtaining a traction motor The rotational torque of 131 is controlled.

  The traction motor 131 is the main power of the vehicle, and generates regenerative power during deceleration. The differential 132 is a reduction device that reduces the high-speed rotation of the traction motor 131 to a predetermined number of rotations and rotates the shaft on which the tire 133 is provided. The shaft is provided with a wheel speed sensor or the like (not shown), thereby detecting the vehicle speed or the like of the vehicle. In the present embodiment, all devices (including the traction motor 131 and the differential 132) that can operate by receiving power supplied from the fuel cell 1 are collectively referred to as a load 130.

  The controller 160 is a computer system for controlling the FCHV system 100 and includes, for example, a CPU, a RAM, a ROM, and the like. The controller 160 receives various signals supplied from the sensor group 170 (for example, a signal indicating the accelerator opening, a signal indicating the vehicle speed, a signal indicating the output current of the fuel cell 1 and the output terminal voltage, etc.) and the load. The required power of 130 (that is, the required power of the entire system) is obtained.

  The required power of the load 130 is, for example, the total value of the vehicle running power and the auxiliary machine power. Auxiliary power includes power consumed by in-vehicle auxiliaries (humidifiers, air compressors, hydrogen pumps, cooling water circulation pumps, etc.), and equipment required for vehicle travel (transmissions, wheel control devices, steering devices, and suspensions) Power consumed by a device, etc., and power consumed by a device (such as an air conditioner, a lighting fixture, and audio) disposed in the passenger space.

  Then, the controller (control device) 160 determines the distribution of output power between the fuel cell 1 and the battery 120 and calculates a power generation command value. When the controller 160 obtains the required power for the fuel cell 1 and the battery 120, the controller 160 controls the operation of the FC converter 150 and the battery converter 180 so that the required power is obtained. Then, the controller 160 outputs, for example, each U-phase, V-phase, and W-phase AC voltage command value as a switching command to the inverter 140 so that a target torque corresponding to the accelerator opening is obtained, and the traction motor The output torque of 131 and the rotation speed are controlled.

  Furthermore, when the required power for the fuel cell 1 satisfies a predetermined condition (here, when the required power has increased rapidly), the controller 160 first inputs the input voltage of the inverter 140 in order to realize stable converter control. The battery converter 180 is controlled until Vin reaches the set target input voltage (setting required voltage) Vtin (see Δ in FIG. 3). Then, after the input voltage Vin of the inverter 140 reaches the target input voltage Vtin, the FC converter 150 is controlled until the output terminal voltage Vfc of the fuel cell 1 becomes the set target output terminal voltage (output required voltage) Vtfc. Processing (hereinafter referred to as converter stabilization processing) is performed.

  Here, the predetermined conditions described above can be arbitrarily set and changed. For example, when the rate of change of the required power for the fuel cell 1 exceeds a set threshold (first condition), the input side of the FC converter 150, The converter stabilization process may be executed when the sum of the voltage change rates on the output side exceeds a set threshold (second condition). Each threshold value to be set may be obtained in advance by experiments or the like and stored in a memory (not shown) or the like. Further, the threshold value may be a fixed value, but may be set / changed as appropriate according to operating conditions, user operations, and the like.

  Next, a structure for integrating the cell stack 3 and the FC converter 150 in the fuel cell system 100 of the present embodiment will be described (see FIG. 4 and the like).

  The fuel cell system 100 of this embodiment has a structure in which the cell stack 3 and the FC converter 150 are mounted on the same frame 10 as described above. A preferred example of the frame 10 here is a plate-like member having a predetermined rigidity (see FIG. 6), but is not limited to this, and for example, a part of the stack case 5 is used to connect the cell stack 3 and the FC. Both converters 150 may be supported and integrated (see FIGS. 4 and 5). By integrating the cell stack 3 and the FC converter 150 as illustrated here, it is possible to eliminate relative displacement between the two. According to this, a device for absorbing displacement between the two, which has been required in the past (for example, a member for giving flexibility to the bus bar connecting the cell stack 3 and the FC converter 150), is omitted. Can do.

  Further, in the fuel cell system 100, the cell stack 3 and the FC converter 150 are arranged so that the heat generating components of the FC converter 150 are close to or in contact with the end cell 2e of the cell stack 3 (FIG. 4, FIG. 4). (See FIG. 5). In such an arrangement, the end cell 2e can be heated using heat from the heat-generating component, and is particularly useful in that it is possible to improve the warm-up performance during cold start. It is. For example, in the present embodiment, the reactor L1 and the IPM (Intelligent Power Module) 154 of the FC converter 150 are brought close to the end cell 2e of the cell stack 3 so that these heats can be used to raise the temperature of the end cell 2e. (See FIGS. 4, 7, and 8). In such a configuration, the heat insulation effect (the effect of making it difficult for the heat of the end cell 2 to escape to the outside) by the air layer between the reactor L1 and the IPM 154 and the end cell 2e of the cell stack 3 can be achieved. . Further, from the viewpoint of more effectively using heat from the heat-generating component, it is also preferable that the reactor L1 and the IPM 154 are in contact with the end cell 2e. In this case, the end cell 2e can be directly heated.

  In addition, in the fuel cell system 100, it is possible to connect the cell stack 3 and the FC converter 150 using a bus having a simpler structure than the conventional one. That is, conventionally, a flexible bus bar or the like has been used because it is necessary to absorb relative positional errors and fluctuations between the cell stack 3 and the FC converter 150, but in the present embodiment, these cell stacks 3 and Since the FC converter 150 is integrated, there are no conventional conditions and restrictions on the bus. For this reason, it is possible to reduce cost and size by using a bus (wiring) having a simpler structure.

  Further, in the fuel cell system 100, it is preferable that heat generating components are arranged at one end or both ends of the end cell 2e of the cell stack 3 so that bus wiring can be simplified. For example, in this embodiment, the bus wiring is simplified by arranging the reactor L1 and the IPM 154 on the positive electrode side (the side indicated by + in the drawing) of the cell stack 3. Specifically, in FIG. 2, the wiring portions indicated by reference numerals (1), (2), (3), (4), and (5) are shown with corresponding reference numerals in FIG. By configuring the bus (wiring), the bus wiring is simplified as a whole. In general, if the bus bar becomes long and complicated due to complicated wiring or poor layout, the size of the stack case 5 becomes large in order to secure the clearance, the wiring inductance increases, and surge voltage increases. It may become high and the reactor L1 etc. may be destroyed. In this respect, according to the present embodiment in which the bus wiring is simplified, such a situation can be suppressed.

  However, the above-described is merely an example of a suitable arrangement. In addition, for example, the reactor L1 is provided on the positive electrode side of the cell stack 3 and the negative electrode side (the side indicated by-in the figure) of the cell stack 3. Each IPM 154 may be arranged to simplify the bus wiring (see FIG. 5). Moreover, when it is set as such an arrangement | positioning, it is possible to heat up the cell 2e on both the positive electrode side and the negative electrode side of the cell stack 3 by the heat generating component.

  It is also preferable to provide a cooling device 6 for cooling the heat generating component on the side opposite to the end cell 2e when viewed from the heat generating component such as the reactor L1 (see FIGS. 4 and 5). While the heat-generating component such as the reactor L1 needs to be cooled in principle, the heat-generating component can be effectively used to raise the temperature of the end cell 2e by using the above-described method. Therefore, it is possible to maintain the performance of each component by suppressing the temperature from rising excessively. As the cooling device 6, for example, a cooling plate provided with a heat radiating plate, a water cooling device for circulating cooling water, or the like can be used. In addition, in FIG. 5, the water cooling apparatus which represented the circulation example of the cooling water with the imaginary line is illustrated.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the present embodiment, the reactor L1 and the IPM 154 are exemplified as the heat generating components in the FC converter 150 (see FIGS. 7 and 8), but it is natural that the capacitor 155 and the like constituting the FC converter 150 may be used as the heat generating components. It is possible (see FIG. 9).

  In the above-described embodiment, the case where the fuel cell system 100 is applied to a fuel cell vehicle has been described. However, the application range is not limited to this, and the fuel cell system 100 can be used for various mobile objects (for example, ships, airplanes, etc.). ) And a robot, etc., and can be applied as a stationary power generation system.

  The present invention is suitably applied to a tank having an FRP layer, and further to a cylindrical body such as a long object or a structure.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Cell, 2e ... End cell, 3 ... Cell stack, 4 ... Bus, 6 ... Cooling device, 10 ... Frame, 100 ... Fuel cell system, 150 ... FC converter (converter), 154 ... IPM (Heat generation component) 155 ... Condenser (Heat generation component), L1 ... Reactor (Heat generation component)

Claims (5)

  A cell stack formed by laminating a plurality of cells and a converter for boosting the cell stack are integrated, and heat generating components of the converter are disposed at one end or both ends of an end cell of the cell stack. A fuel cell system in which the converter and the converter are connected by a bus.   The fuel cell system according to claim 1, wherein the cell stack and the converter are mounted on the same frame.   The fuel cell system according to claim 1, wherein the heat generating component of the converter is disposed in contact with the end cell.   The fuel cell system according to any one of claims 1 to 3, wherein a cooling device that cools the heat generating component is provided on a side opposite to the end cell as viewed from the heat generating component.   The fuel cell system according to any one of claims 1 to 4, wherein a reactor of the converter is disposed at one end or both ends of the end cell, and an IPM is disposed on the negative electrode side of the end cell.

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