JP2018156743A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system which can be operated smoothly by detecting a rotational state of a pump, without using an expensive pump including a sensor for detecting a rotational position.SOLUTION: A fuel cell system includes a hydrogen pump 44 being provided in a hydrogen circulation passage 42 connected with a fuel cell 2 and a hydrogen gas supply passage 41, and feeding unreacting hydrogen gas in off-gas from the fuel cell 2 to the hydrogen supply passage 41 by rotating in a prescribed direction, a gas-liquid separator 45 for separating liquid from the off-gas and storing the liquid, an exhaust drain valve 46 provided in the gas-liquid separator 45, and a voltage sensor 21 for measuring an output voltage of the fuel cell 2. A control section 6 opens the exhaust drain valve 46, and, when a voltage difference V2-V1 before and after valve opening, measured based on a detection value from the voltage sensor 21, is below a preset value Vs, determines that the hydrogen pump 44 is rotating in a direction opposite to the prescribed direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel cell system.

  The fuel cell system has a hydrogen circulation path in which unreacted hydrogen gas in the off-gas discharged from the fuel cell is sent again to the fuel cell and used as fuel by driving the pump. As a fuel cell system having this hydrogen circulation path, there is a fuel cell system that uses a pump driven by a sensorless electric motor that does not have a sensor for detecting a rotational position such as a resolver and avoids control failure due to sensor deterioration (for example, Patent Document 1). reference).

JP 2004-152729 A

  By the way, since a pump driven by a sensorless electric motor does not have a sensor for detecting a rotational position, when controlling this type of pump, the number of rotations required for controlling a motor in the pump is estimated. As a method of estimating the rotation speed, there is a method of performing an estimation calculation using an induced electromotive force due to the rotation of the motor. However, in a pump on the assumption that the rotation of the motor is in one direction, the estimated value is a positive value. In general, the rotation direction cannot be determined. For this reason, it may be difficult to detect the rotation state such as whether the pump is rotating in reverse and to smoothly control the circulation of hydrogen gas.

  The present invention has been made in view of the above circumstances, and is a fuel cell system that can smoothly operate by detecting the rotational state of a pump without using an expensive pump having a sensor that detects a rotational position. The purpose is to provide.

In order to achieve the above object, the fuel cell system of the present invention comprises:
A fuel cell;
A supply path for supplying fuel gas to the fuel cell;
A circulation path connected to the fuel cell and the supply path;
A pump that is provided in the circulation path and that feeds the unreacted fuel gas in the off-gas discharged from the fuel cell to the supply path by rotating in a predetermined direction;
A gas-liquid separator that is provided in the circulation path and separates and stores the liquid from the off-gas;
An exhaust / drain valve that is provided in the gas-liquid separator and discharges at least a part of the stored liquid and the off-gas by being opened;
A voltage sensor for measuring the output voltage of the fuel cell;
A fuel cell system comprising:
By opening the exhaust drain valve, the voltage difference of the output voltage of the fuel cell before and after opening the exhaust drain valve is measured based on the detection value from the voltage sensor, and the voltage difference is preset. A controller that determines that the pump is rotating in a direction opposite to the predetermined direction when the value is equal to or less than the predetermined value.

  According to the fuel cell system of this configuration, the control unit opens the exhaust drainage valve, so that the voltage difference before and after opening the exhaust drainage valve is set based on the detected value from the voltage sensor. When it is below, it is determined that the pump is rotating in the reverse direction. Thus, since the control unit determines the reverse rotation of the pump based on the detection value of the voltage sensor originally provided for detecting the output voltage of the fuel cell, an expensive pump having a sensor for detecting the rotational position Without using the pump, it is possible to detect the rotational state of the pump and operate smoothly.

  According to the fuel cell system of the present invention, it is possible to provide a fuel cell system capable of detecting the rotational state of the pump and operating smoothly without using an expensive pump having a sensor for detecting the rotational position.

1 is a schematic configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a flowchart explaining the rotation state determination process by a control part. It is a graph which shows the change of the output voltage by opening and closing of the exhaust drain valve when the hydrogen pump is rotating backward.

  Next, an embodiment of a fuel cell system according to the present invention will be described. Hereinafter, the case where this fuel cell system is applied to an in-vehicle power generation system of a fuel cell vehicle will be described. However, the present invention is not limited to such an application example, and is applicable to all moving objects such as ships, airplanes, trains, and walking robots. For example, the present invention can be applied to a stationary power generation system in which a fuel cell is used as a power generation facility for a building (house, building, etc.).

FIG. 1 is a schematic configuration diagram of a fuel cell system according to an embodiment of the present invention.
As shown in FIG. 1, a fuel cell system 1 according to the present embodiment includes a fuel cell 2 that generates electric power by an electrochemical reaction upon receiving supply of an oxidizing gas that is a reactive gas and a hydrogen gas that is a fuel gas. It has an oxidizing gas piping system 3 that supplies air as gas to the fuel cell 2, a hydrogen gas piping system 4 that supplies hydrogen gas as fuel gas to the fuel cell 2, and a control unit 6 that performs overall control of the entire system. .

  The fuel cell 2 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell has a cathode electrode (air electrode) on one surface of an electrolyte made of an ion exchange membrane, an anode electrode (fuel electrode) on the other surface, and further sandwiches the cathode electrode and anode electrode from both sides. It has the structure which has a pair of separator. In this case, hydrogen gas is supplied to the hydrogen gas flow path of one separator, oxidizing gas is supplied to the oxidizing gas flow path of the other separator, and electric power is generated by the chemical reaction of these reaction gases.

  The oxidizing gas piping system 3 includes a compressor 31 that takes in and compresses the oxidizing gas in the atmosphere, sends it out, an air supply path 32 for supplying the oxidizing gas to the fuel cell 2, and the oxidation exhausted from the fuel cell 2. And an air discharge path 33 for discharging off-gas.

  The hydrogen gas piping system 4 includes a hydrogen supply path (supply path) 41 for supplying hydrogen gas from a fuel supply source such as a hydrogen tank to the fuel cell 2, and a hydrogen supply path 41 for supplying hydrogen off-gas discharged from the fuel cell 2. A hydrogen circulation path (circulation path) 42 for returning to

  An injector 48 is provided in the hydrogen supply path 41. The supply amount of hydrogen gas from the fuel supply source to the fuel cell 2 is adjusted by opening and closing the valve of the injector 48. The hydrogen supply path 41 is provided with a pressure sensor 43 that detects the supply pressure of hydrogen gas to the fuel cell 2. The pressure sensor 43 is provided at a position downstream of the hydrogen circulation path 42 in the hydrogen supply path 41 by being disposed on the fuel cell 2 side of the connection position of the hydrogen circulation path 42 in the hydrogen supply path 41. The hydrogen supply path 41 may be provided with a pressure regulating valve instead of the injector 48, and the opening and closing control of the pressure regulating valve may adjust the amount of hydrogen gas supplied from the fuel supply source to the fuel cell 2. Good.

  The hydrogen circulation path 42 is provided with a hydrogen pump (pump) 44 that pressurizes the hydrogen off gas and sends it to the hydrogen supply path 41 side. In addition, a discharge path 47 is connected to the hydrogen circulation path 42 via a gas-liquid separator 45 and an exhaust drain valve 46. The gas-liquid separator 45 collects and stores the liquid from the hydrogen off gas. The exhaust / drain valve 46 discharges (purges) at least a part of the liquid stored in the gas-liquid separator 45 and the off-gas in accordance with a command from the control unit 6. Exhaust gas discharged from the exhaust drain valve 46 merges with the oxidizing off gas in the air discharge path 33.

  The hydrogen pump 44 provided in the hydrogen circulation path 42 is a sensorless pump whose drive source is an electric motor that does not include a sensor for detecting the rotational position of a resolver or the like. By using this sensorless hydrogen pump 44, it is possible to reduce the cost and avoid control failure due to deterioration of the sensor.

  The control unit 6 detects an operation amount of an acceleration operation member (accelerator or the like) provided in the fuel cell vehicle, and provides control information such as an acceleration request value (for example, a required power generation amount from a power consumption device such as a traction motor). In response, the operation of various devices in the system is controlled. In addition to the traction motor, the power consuming device includes, for example, an auxiliary device (for example, the compressor 31 and the hydrogen pump 44) necessary for operating the fuel cell 2, and various devices (shifts) that are involved in traveling of the vehicle. Actuators, wheel control devices, steering devices, suspension devices, etc.), passenger space air conditioners (air conditioners), lighting, audio, and the like.

  The control unit 6 is connected to the compressor 31, the hydrogen pump 44, the exhaust drain valve 46, the injector 48, and the like. The control unit 6 includes the compressor 31, the hydrogen pump 44, the exhaust drain valve 46, the injector 48, and the like. Control. The control unit 6 is connected to a pressure sensor 43 and a voltage sensor 21 that detects the output voltage of the fuel cell 2, and a detection signal is transmitted from the pressure sensor 43 and the voltage sensor 21 to the control unit 6. .

  In the fuel cell system 1 having the above-described configuration, the control unit 6 controls the opening and closing of the injector 48 according to a request, thereby adjusting the supply amount of hydrogen gas from the fuel supply source and supplying it to the fuel cell 2. To generate electricity.

  Further, when the fuel cell system 1 controls the sensorless hydrogen pump 44, the control unit 6 drives the sensorless hydrogen pump 44 by estimating, for example, the number of revolutions necessary for the control. The number of rotations of the hydrogen pump 44 is calculated and estimated based on, for example, an induced electromotive force due to rotation of the electric motor. However, since this rotational speed estimation method is based on only one direction of rotation (positive value), it is impossible to determine the rotational state such as whether the rotational direction is reverse.

  For this reason, in the fuel cell system 1 according to the present embodiment, the controller 6 determines the rotational state of the hydrogen pump 44 by performing the following rotational state determination process based on the detection signal from the voltage sensor 21.

FIG. 2 is a flowchart for explaining the rotation state determination processing by the control unit.
First, based on the detection signal from the voltage sensor 21, the output voltage of the fuel cell 2 is measured, and this measured value is set as the output voltage V1 before opening the valve (step SP1).

  Next, the exhaust / drain valve 46 is driven to open (step SP2).

  After the exhaust / drain valve 46 is opened, the output voltage of the fuel cell 2 is measured based on the detection signal from the voltage sensor 21, and this measured value is set as the output voltage V2 after the valve is opened (step SP3).

  A voltage difference determination is made as to whether or not the voltage difference V2-V1 between the output voltage V2 after opening the exhaust / drain valve 46 and the output voltage V1 before opening is equal to or less than a predetermined value Vs that is a predetermined threshold ( Step SP4). That is, it is determined whether V2−V1 ≦ Vs.

  As a result of the voltage difference determination (step SP4), if the voltage difference V2-V1 is larger than the predetermined value Vs (V2-V1> Vs) (step SP4: No), it is assumed that the hydrogen pump 44 is not rotating in reverse, and the exhaust drainage The valve 46 is closed (step SP5), and the rotational state determination process is terminated.

  As a result of the voltage difference determination (step SP4), when the voltage difference V2-V1 is equal to or less than the predetermined value Vs (V2-V1 ≦ Vs) (step SP4: Yes), it is determined that reverse rotation has occurred in the hydrogen pump 44. (Step SP6).

  If it is determined that reverse rotation has occurred in the hydrogen pump 44 (step SP6), the exhaust drain valve 46 is closed (step SP7) and the fuel cell system 1 is stopped (step SP8).

Here, the determination of the rotation direction of the hydrogen pump 44 in the voltage difference determination (step SP4) will be described.
FIG. 3 is a graph showing a change in output voltage due to opening / closing of the exhaust / drain valve when the hydrogen pump rotates in the reverse direction.

  In the fuel cell system 1, when the rotation direction of the hydrogen pump 44 is normal, hydrogen gas is supplied to the fuel cell 2 through the injector 48. Unreacted hydrogen gas discharged from the fuel cell 2 (hydrogen gas that has not been consumed) is circulated by the hydrogen pump 44, merged with the hydrogen gas supplied through the injector 48, and supplied to the fuel cell 2 again. Further, since the off gas discharged from the fuel cell 2 includes components other than hydrogen gas (water vapor and nitrogen), these components other than hydrogen gas are discharged by opening and closing the exhaust drain valve 46 at an appropriate timing. ing.

  On the other hand, when the hydrogen pump 44 rotates in the reverse direction, the hydrogen gas supplied through the injector 48 is sucked into the hydrogen circulation path 42 by the hydrogen pump 44. The hydrogen gas sucked into the hydrogen circulation path 42 is supplied to the fuel cell 2 when the exhaust drain valve 46 is closed, but is exhausted before being supplied to the fuel cell 2 when the exhaust drain valve 46 is opened. .

  Therefore, as shown in FIG. 3, when the hydrogen pump 44 is rotating in the reverse direction, the exhaust drain valve 46 is opened, so that the hydrogen gas supplied to the fuel cell 2 is insufficient, and the fuel cell 2 During steady operation where the output current is constant, the total output voltage and the cell output voltages of the stacked cells constituting the fuel cell 2 are reduced to cause variations. Therefore, it is possible to determine the rotation state of the hydrogen pump 44 by using the total output voltage of the fuel cell 2 or a specific cell output voltage among a plurality of cells as a determination target. The specific cell to be determined is, for example, a cell with the lowest cell output voltage, such as a cell on the back side of the stack that is easily affected when hydrogen gas is reduced.

  As described above, according to the fuel cell system 1 according to the present embodiment, the control unit 6 opens the exhaust drain valve 46 so that the exhaust drain valve 46 is based on the detected value from the voltage sensor 21. When the voltage difference V2-V1 before and after the opening is equal to or less than a predetermined value Vs set in advance, it is determined that the hydrogen pump 44 is rotating in reverse. Thus, since the control part 6 determines reverse rotation of the hydrogen pump 44 based on the detected value of the voltage sensor 21 originally provided for detecting the output voltage of the fuel cell 2, the rotational position is detected. Without using an expensive hydrogen pump equipped with a sensor, the rotation state of the hydrogen pump 44 can be detected and smoothly operated.

  The rotation state determination process is preferably performed at a timing at which the output voltage fluctuation is small except during the transition of the fuel cell 2 where the output voltage varies greatly. That is, it is preferable to perform the rotation state determination process immediately after the start of the fuel cell system 1 before the user starts the driving operation or during steady power generation in which the output voltage is stable.

  In addition, since it is considered that the normally rotating hydrogen pump 44 does not suddenly start reverse rotation, the rotation state determination process may be performed only once at the above timing, and the battery clear determination may be performed. You may carry out about once at any of the above timings only later.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Fuel cell 6 Control part 21 Voltage sensor 41 Hydrogen supply path (supply path)
42 Hydrogen circulation path (circulation path)
44 Hydrogen pump (pump)
45 Gas-liquid separator 46 Exhaust drain valve

Claims (1)

A fuel cell;
A supply path for supplying fuel gas to the fuel cell;
A circulation path connected to the fuel cell and the supply path;
A pump that is provided in the circulation path and that feeds the unreacted fuel gas in the off-gas discharged from the fuel cell to the supply path by rotating in a predetermined direction;
A gas-liquid separator that is provided in the circulation path and separates and stores the liquid from the off-gas;
An exhaust / drain valve that is provided in the gas-liquid separator and discharges at least a part of the stored liquid and the off-gas by being opened;
A voltage sensor for measuring the output voltage of the fuel cell;
A fuel cell system comprising:
By opening the exhaust drain valve, the voltage difference of the output voltage of the fuel cell before and after opening the exhaust drain valve is measured based on the detection value from the voltage sensor, and the voltage difference is preset. A fuel cell system comprising: a controller that determines that the pump is rotating in a direction opposite to the predetermined direction when the predetermined value is equal to or less than the predetermined value.