JP2013069489A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately grasp an abnormal deviation between a detection value of a sensor which detects an output voltage from a fuel cell and a detection value of a sensor which detects an input voltage to a booster converter.SOLUTION: A fuel cell system includes: a fuel cell 12 which generates electric power by electrochemical reaction of a fuel gas and an oxidant gas; a booster converter 14 for boosting an output power of the fuel cell 12; an output voltage sensor 12a for detecting an output voltage of the fuel cell 12; an input voltage sensor 35 for detecting an input voltage to the booster converter 14; and a determining section 41 for determining an abnormal deviation when the state of an absolute value of a deviation between a detection voltage value of the output voltage sensor 12a and a detection voltage value of the input voltage sensor 35 exceeding a predetermined threshold value is continued for a predetermined time.

Description

  The present invention relates to a fuel cell system including a fuel cell and a boost converter that boosts the output of the fuel cell, and in particular, between a sensor detection value for an output voltage from the fuel cell and a sensor detection value for an input voltage to the boost converter. It relates to anomaly judgment of deviation.

  A fuel cell system that uses a fuel cell that generates power by an electrochemical reaction of a reaction gas (fuel gas and oxidizing gas) as an energy source is provided with a cell voltage monitor that detects an output voltage from the fuel cell. Various control of the system is performed based on the detection result of the cell voltage monitor (for example, see Patent Document 1).

JP 2008-209357 A

  In the fuel cell system, lower limit determination means for determining whether or not the cell voltage detected by the cell voltage monitor is equal to or lower than the lower limit cell voltage detectable by the cell voltage monitor, and the cell voltage detected by the cell voltage monitor When the lower limit determination means determines that the voltage is lower than the lower limit cell voltage, the cell voltage monitor fails when the cell voltage detected in the past by the cell voltage monitor and stored in the storage means is greater than the determination cell voltage. Therefore, the failure determination of the cell voltage monitor can be performed.

  However, some fuel cell systems include a boost converter that boosts the output at the subsequent stage of the fuel cell. In such a fuel cell system, an input voltage sensor that detects an input voltage to the boost converter is further provided. In this case, it is difficult to accurately grasp the abnormal deviation between the detected voltage value of the input voltage sensor and the detected voltage value of the cell voltage monitor.

  The present invention has been made in view of the above circumstances, and accurately detects an abnormal deviation between a detection value of a sensor that detects an output voltage from a fuel cell and a detection value of a sensor that detects an input voltage to a boost converter. It aims at providing the fuel cell system which can be grasped | ascertained.

  In order to achieve the above object, a fuel cell system of the present invention includes a fuel cell that generates electric power by an electrochemical reaction between a fuel gas and an oxidizing gas, a boost converter that boosts the output power of the fuel cell, and an output of the fuel cell. An absolute value of a deviation between an output voltage sensor that detects a voltage, an input voltage sensor that detects an input voltage to the boost converter, and a detected voltage value of the output voltage sensor and a detected voltage value of the input voltage sensor is And a determination unit that determines that the deviation is abnormal when the state exceeding the predetermined threshold continues for a predetermined time or longer.

  In the fuel cell system of the present invention, when the fuel cell has a stack structure in which a plurality of single cells are stacked, the output voltage sensor can detect a voltage for each single cell or for each plurality of cells. A simple cell monitor may be used.

  In the fuel cell system of the present invention, the determination unit may perform a process of aligning the detection range of the output voltage sensor and the detection range of the input voltage sensor as pre-processing of the determination. In addition, the determination unit may perform a smoothing process on the detected voltage values of the output voltage sensor and the input voltage sensor as preprocessing for the determination.

  In the fuel cell system of the present invention, when the determination unit continues the state where the absolute value of the deviation between the detected voltage values of the output voltage sensor and the input voltage sensor is equal to or less than the predetermined threshold for the predetermined time or more. In addition, it may be determined that the deviation is normal.

  The determination by the determination unit may be prohibited under a condition in which normal operations of the determination unit, the output voltage sensor, and the input voltage sensor are not guaranteed.

  According to the fuel cell system of the present invention, it is possible to accurately grasp the abnormal deviation between the detection value of the sensor that detects the output voltage from the fuel cell and the detection value of the sensor that detects the input voltage to the boost converter. It becomes possible.

1 is a schematic circuit diagram of a fuel cell system according to an embodiment of the present invention. It is a flowchart which shows an example of the determination process which control ECU of FIG. 1 implements.

  Hereinafter, an embodiment of a fuel cell system according to the present invention will be described with reference to the accompanying drawings. This embodiment demonstrates the case where the fuel cell system which concerns on this invention is used as a vehicle-mounted power generation system of a fuel cell vehicle (FCHV; Fuel Cell Hybrid Vehicle).

First, the configuration of the fuel cell system in the present embodiment will be described with reference to FIG.
As shown in FIG. 1, the fuel cell system 11 includes a fuel cell 12 that generates electric power by an electrochemical reaction between an oxidizing gas that is a reactive gas and the fuel gas.

  The fuel cell 12 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 an air electrode on one surface of an electrolyte composed of an ion exchange membrane, a fuel electrode on the other surface, and a structure having a pair of separators so as to sandwich the air electrode and the fuel electrode from both sides. It has become. In this case, hydrogen gas is supplied to the hydrogen gas flow path of one separator, and air, which is an 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 fuel cell 12 is provided with a cell monitor (output voltage sensor) 12a for measuring the voltage of each cell constituting the fuel cell stack. The cell monitor 12a provides the total voltage of all the cells as well as each cell. It is possible to monitor the voltage or the voltage of each cell.

  The fuel cell 12 is connected to a drive motor (drive source, load) 13 for running the vehicle, and supplies power to the drive motor 13. An FC boost converter (boost converter) 14, a capacitor 15, and a drive inverter 16 are connected to the power supply path from the fuel cell 12 to the drive motor 13 in order from the fuel cell 12 side.

  Thus, in the fuel cell system 11, the electric power generated by the fuel cell 12 is boosted by the FC boost converter 14 and supplied to the drive motor 13 via the drive inverter 16.

  The FC boost converter 14 is a multiphase converter that is a multiphase converter, and includes a plurality (four in this example) of conversion units 31a to 31d. Each of the conversion units 31a to 31d includes a reactor 32, a transistor 33, and a diode 34.

  The drive motor 13 is, for example, a three-phase AC motor, and the drive inverter 16 to which the drive motor 13 is connected converts a direct current into a three-phase alternating current and supplies it to the drive motor 13.

  The fuel cell system 11 includes a battery 21 that can discharge power to the drive motor 13 and can charge power from the fuel cell 12. A battery boost converter 23 is connected to the power supply path from the battery 21 to the drive motor 13. The fuel cell system 11 according to the present invention may be configured not to include the battery boost converter 23.

  The power supply path of the battery 21 is connected to the power supply path of the fuel cell 12, and the power from the battery 21 can be supplied to the drive motor 13.

  The battery boost converter 23 of the present embodiment is a DC voltage converter, and has a function of adjusting a DC voltage input from the battery 21 and outputting the same to the drive motor 13 side, and an input from the fuel cell 12 or the drive motor 13. And a function of adjusting the direct-current voltage and outputting it to the battery 21. By such a function of the battery boost converter 23, charging / discharging of the battery 21 is realized.

  The fuel cell system 11 includes a control ECU (hereinafter referred to as ECU) 41 having a volatile memory 40. The ECU 41 is connected to the fuel cell 12, the FC boost converter 14, the battery 21, the battery boost converter 23, the drive inverter 16, and the drive motor 13. The ECU 41 includes the fuel cell 12, the FC boost converter 14, the battery. 21, controls the battery boost converter 23, the drive inverter 16, and the drive motor 13.

  As shown in FIG. 1, the fuel cell system 11 is provided with an input voltage sensor 35 that detects an input voltage to the FC boost converter 14 on the upstream side of the FC boost converter 14. This input voltage sensor 35 is connected to the ECU 41. The ECU 41 is also connected to a cell monitor 12 a provided in the fuel cell 12, and the detection result of the cell monitor 12 a is also transmitted to the ECU 14. Then, the ECU 14 performs various controls of the fuel cell system 11 using detected voltage values from the cell monitor 12a and the input voltage sensor 35.

  The ECU 41 also has a function as a determination unit according to the present invention, and performs a determination process shown in the flowchart of FIG. 2 as a specific function. In this process, first, the detection voltage value V1 (total voltage of all cells) of the cell monitor 12a and the detection voltage value V2 of the input voltage sensor 35 are acquired (step S1).

  Note that voltage detection by the cell monitor 12a of this embodiment is performed at intervals of 100 (ms), and voltage detection by the input voltage sensor 35 is performed at intervals of 1 (ms). In the cell monitor 12a, when the number of cells is 300, a maximum time of about 90 (ms) is required for voltage detection of all channels. The detected voltage value of the cell monitor 12a is transmitted to the ECU 41 at intervals of 100 (ms), and the detected voltage value of the input voltage sensor 35 is transmitted to the ECU 41 at intervals of 8 (ms).

  Next, signal processing which will be described in detail later is performed on these detection voltage values V1 and V2 (step S3). Thereafter, the presence or absence of an abnormal deviation is determined based on the deviation of the detected voltage values V1 and V2 subjected to signal processing (step S5).

  In this abnormal deviation determination step, whether or not the absolute value of the deviation of the detected voltage values V1 and V2 signal-processed in step S3 has exceeded a predetermined threshold, and such a state has continued for a predetermined time or more. It is determined whether or not (step S5). As a result of the determination, when the state where the absolute value of the deviation exceeds a predetermined threshold continues for a predetermined time or longer (“Yes” in step S5), the detection voltage value V1 of the cell monitor 12a and the detection voltage of the input voltage sensor 35 are detected. It is determined that there is a deviation abnormality with respect to the value V2, and the abnormality counter is set and the normal counter is cleared (step S7).

  On the other hand, if “No” is determined in step S5, whether or not the absolute value of the deviation between the detected voltage values V1 and V2 signal-processed in step S3 is equal to or smaller than a predetermined threshold value, and such It is determined whether or not the state has continued for a predetermined time (step S11). As a result of the determination, when the state where the absolute value of the deviation is equal to or less than the predetermined threshold continues for a predetermined time or longer (“Yes” in step S11), the detection voltage value V1 of the cell monitor 12a and the detection voltage of the input voltage sensor 35 are detected. There is no abnormal deviation with respect to the value V2, in other words, it is determined as a normal deviation, and the normal counter is set and the abnormal counter is cleared (step S13).

Next, the “predetermined threshold” and “predetermined time” used in steps S5 and S11 will be described in detail.
The predetermined threshold value Vth is obtained by the following equation (1). That is, the sensor error deviation A (formula (4)) defined by the larger value of ΔVx obtained by the following formula (2) and ΔVy obtained by the following formula (3), and the cell monitor 12a And the detected voltage values V1 and V2 of the input voltage sensor 35 are defined by the total value (ie, Vth = deviation A + deviation B) that can occur when the signal processing in step S3 is performed.

Vth = deviation A + deviation B (1)
ΔVx = Va1-Va2 (2)
ΔVy = Va1−Vb1 (3)
Deviation A = max (ΔVx, ΔVy) (4)

ΔVx in the above formula (2) is when the detected voltage value (clamp value) of the cell monitor 12a is Va1, the actual voltage at that time is Var, and the detected voltage value of the input voltage sensor 35 with respect to this actual voltage Var is Va2. This is a value obtained by subtracting Va2 from Va1.
ΔVy in the above equation (3) is the same Va1 as the detected voltage value (clamp value) of the input voltage sensor 35 as in the above equation (1), the actual voltage at that time is Vbr, and the cell monitor 12a detects this actual voltage Vbr. When the voltage value is Vb1, it is a value obtained by subtracting Vb1 from Va1.

  The signal processing in step S3 is performed on each detected voltage value in order to suppress communication delay of each detected voltage value of the cell monitor 12a and the input voltage sensor 35, sudden change, and influence on erroneous determination due to voltage ripple. In this embodiment, it consists of a clamping process and an annealing process.

  In the clamping process, for example, the upper and lower limit voltage of the fuel cell 12 measured by the cell monitor 12a is in the range of 100V to 360V, and the upper and lower limit voltage of the fuel cell 12 measured by the input voltage sensor 35 is in the range of 80V to 320V. In addition, the common part of these ranges, that is, the range of 100V to 320V is unified. In the present embodiment, the detection voltage values of the cell monitor 12a and the input voltage sensor 35 are clamped to 0V to 360V.

  In the annealing process, a primary filter is applied to the detection voltage value of the cell monitor 12a and the detection voltage value of the input voltage sensor 35 clamped by the clamping process according to a predetermined time constant. It is possible to avoid misjudgment due to temporary sudden fluctuations in value.

  While the output voltage of the fuel cell 12 fluctuates on the order of about 10 (ms) during normal operation, in the present embodiment, as described above, the voltage detection of the cell monitor 12a is performed at a cycle of 100 (ms), and the input voltage sensor. Since the voltage detection of 35 is performed in a cycle of 1 (ms), if the detected voltage values of the cell monitor 12a and the input voltage sensor 35 are compared without performing the annealing process, no abnormal deviation occurs. Nevertheless, there is a possibility that the deviation between the detected voltage values instantaneously increases and it is erroneously determined that an abnormal deviation has occurred.

Therefore, in order to avoid such erroneous determination, in the present embodiment, the annealing process is performed on the detected voltage values of the cell monitor 12a and the input voltage sensor 35.
In this embodiment, the detection delay of each detected voltage value (that is, the deviation between the actual voltage and the detected voltage value) caused by performing this annealing process is obtained based on, for example, the results of experiments or simulations. The value is set as the deviation B.

  The time constant used for the annealing process takes into account the difference between the communication time from the cell monitor 12a to the ECU 41 and the communication time from the input voltage sensor 35 to the ECU 41, even when such a difference occurs at the maximum. A value that does not cause the erroneous determination is set based on, for example, an experiment or a simulation result. In this setting, as the time constant is increased, it is possible to avoid erroneous determination when the detected voltage value fluctuates greatly temporarily. The point of being invited is also considered.

  The “predetermined time” determines whether or not the state where the absolute value of the deviation between the detected voltage values V1 and V2 signal-processed in step S3 exceeds a predetermined threshold or is not more than the predetermined threshold is occurring. This is a determination reserve time for the purpose of preventing misjudgment due to temporary abnormal deviation or normal deviation.

  The “predetermined time” is set to, for example, a time that is about 100 times the time required for voltage detection of all channels in the cell monitor 12a (in this embodiment, about 90 (ms)), or 10 times the value of the time constant. Although it is possible to set the time to about twice, it is not limited to these numerical values, and can be set to any time within a range not departing from the purpose of reserved reservation.

  As described above, according to the fuel cell system 11 according to the present embodiment, is there an abnormal deviation between the detected voltage value of the cell monitor 12a and the detected voltage value of the input voltage sensor 35 due to the determination process performed by the ECU 41? It is possible to accurately determine whether or not. Therefore, it is possible to suppress inappropriate control of each part such as the FC boost converter 14 using the voltage value detected by the cell monitor 12a and / or the input voltage sensor 35 in a state where such an abnormal deviation occurs.

  When the predetermined determination prohibition condition is satisfied, that is, when normal operation of the ECU 41, the cell monitor 12a, and the input voltage sensor 35 is not guaranteed, the execution of the determination process of FIG. 2 may be prohibited.

  The determination prohibition conditions include, for example, abnormalities in the ECU 41 and the drive inverter 16, abnormalities in the power supply source for the ECU 41, the cell monitor 12a, and the input voltage sensor 35 (for example, voltage drop), and signals from the cell monitor 12a and the input voltage sensor 35. This corresponds to a case where an abnormality is detected or a predetermined time (for example, 0.3 seconds) after the ECU 41 is activated. In such a case, it is possible to prevent erroneous determination by the ECU 41 by prohibiting the determination processing of FIG.

DESCRIPTION OF SYMBOLS 11 ... Fuel cell system, 12 ... Fuel cell, 12a ... Cell monitor (output voltage sensor), 14 ... FC boost converter, 35 ... Input voltage sensor, 41 ... ECU (determination part)

Claims (6)

A fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidizing gas;
A boost converter that boosts the output power of the fuel cell;
An output voltage sensor for detecting an output voltage of the fuel cell;
An input voltage sensor for detecting an input voltage to the boost converter;
Determination that an abnormal deviation is determined when a state where an absolute value of a deviation between a detection voltage value of the output voltage sensor and a detection voltage value of the input voltage sensor exceeds a predetermined threshold continues for a predetermined time or more. A fuel cell system. The fuel cell has a stack structure in which a plurality of single cells are stacked,
The fuel cell system according to claim 1, wherein the output voltage sensor includes a cell monitor capable of detecting a voltage for each single cell or a plurality of cells.   3. The fuel cell system according to claim 1, wherein the determination unit performs a process of aligning a detection range of the output voltage sensor and a detection range of the input voltage sensor as preprocessing of the determination.   The fuel cell system according to any one of claims 1 to 3, wherein the determination unit performs a smoothing process on each detection voltage value of the output voltage sensor and the input voltage sensor as preprocessing of the determination.   The determination unit determines that the deviation is a normal deviation when a state in which an absolute value of a deviation of each detection voltage value between the output voltage sensor and the input voltage sensor is equal to or less than the predetermined threshold continues for the predetermined time or more. The fuel cell system according to any one of claims 1 to 4.   The fuel cell system according to any one of claims 1 to 5, wherein the determination by the determination unit is prohibited under a condition in which normal operation of the determination unit, the output voltage sensor, and the input voltage sensor is not guaranteed.

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