Voltage estimation device and voltage estimation method

Abstract

When a fuel cell stack includes dummy cells that do not generate electricity, along with unit cells that can generate electricity, a decrease in the cell voltage of each unit cell may be falsely detected. To eliminate this cell voltage drop, a voltage estimation device is provided that suppresses the activation of control operations that would otherwise be unnecessary. [Solution] The voltage estimation device 10 includes a voltage acquisition unit 30 that acquires the output voltage V1 of a first cell group G1 in which one or more unit cells capable of generating electricity using fuel gas and oxidizer gas and one or more dummy cells that do not generate electricity are connected in series, and a voltage estimation unit 32 that estimates the cell voltage for each unit cell based on the output voltage V1, the dummy cells, and the amount of voltage drop per unit cell.

Description

Technical Field

[0001] The present disclosure relates to a voltage estimation device and a voltage estimation method.

Background Art

[0002] In recent years, research and development on fuel cells that contribute to energy efficiency have been carried out to enable more people to secure access to affordable, reliable, sustainable and advanced energy. International Publication No. 2013 / 108369 discloses a fuel cell system including a cell monitor capable of detecting a group voltage for each of a plurality of cells.

Prior Art Literature

Patent Literature

[0003]

Patent Literature 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] If a fuel cell stack includes a non-power-generating dummy cell together with power-generatable unit cells, a decrease in cell voltage in each unit cell may be erroneously detected. In such a case, an originally unnecessary control operation is activated to eliminate the cell voltage decrease.

[0005] The present disclosure aims to solve the above-described problem and thereby contributes to energy efficiency.

Means for Solving the Problem

[0006] A first aspect of the present disclosure is a voltage estimation device comprising: a voltage acquisition unit that acquires the output voltage of a first cell group in which one or more unit cells capable of generating electricity using a fuel gas and an oxidizer gas and one or more dummy cells that do not generate electricity are connected in series; and a voltage estimation unit that estimates the cell voltage of each unit cell based on the output voltage and the unit amount of voltage drop per dummy cell.

[0007] A second aspect of the present disclosure is a voltage estimation method comprising: a voltage acquisition step of acquiring an output voltage from a first cell group in which one or more unit cells capable of generating electricity using a fuel gas and an oxidizer gas and one or more dummy cells that do not generate electricity are connected in series; and a voltage estimation step of estimating the cell voltage for each unit cell based on the output voltage and the amount of voltage drop per dummy cell. [Effects of the Invention]

[0008] According to this disclosure, the activation of unnecessary control operations in the fuel cell stack is suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a diagram illustrating the cell groups of a fuel cell stack and a voltage estimation device that estimates the cell voltage for each individual cell. [Figure 2] Figure 2 is a diagram illustrating the estimation of the cell voltage for each unit cell. [Figure 3] Figure 3 is a flowchart illustrating the processing steps for a voltage estimation method that estimates the cell voltage for each unit cell. [Figure 4] Figure 4 is a diagram illustrating the acquisition of the current value of the generated current. [Figure 5] Figure 5 is an example of a setting table in which the unit amount of voltage drop is set. [Figure 6] Figure 6A is a diagram illustrating the cell groups of the fuel cell stack. Figure 6B is a diagram illustrating the estimation of the cell voltage for each individual cell. [Figure 7] Figure 7A is a diagram illustrating the cell groups of the fuel cell stack. Figure 7B is a diagram illustrating the estimation of the cell voltage for each individual cell. [Modes for carrying out the invention]

[0010] Figure 1 is a diagram illustrating the cell group G of the fuel cell stack F and the voltage estimation device 10 that estimates the cell voltage Vc for each unit cell C. A closed circuit is formed including the fuel cell stack F and the load device L to supply the power consumed by the load device L. The generated current I of the fuel cell stack F flows through this closed circuit. When the fuel cell stack F is mounted on a vehicle, the load device L is, for example, a motor.

[0011] The fuel cell stack F includes a plurality of cells. The plurality of cells include unit cells C that can generate electricity using fuel gas and oxidizer gas, and dummy cells D that do not generate electricity. The plurality of dummy cells D are arranged at both ends of the fuel cell stack F. That is, one or more dummy cells D are arranged at one end of the fuel cell stack F, and one or more dummy cells D are also arranged at the other end. When a plurality of dummy cells D are arranged at each end of the fuel cell stack F, the plurality of dummy cells D arranged at each end are equivalent to a plurality of electrical resistances connected in series with each other.

[0012] Multiple unit cells C are positioned between dummy cells D located at both ends of the fuel cell stack F. The multiple unit cells C are connected in series with each other. The dummy cells D, positioned at both ends of the fuel cell stack F, perform the following functions: First, the dummy cells D block moisture from entering the fuel cell stack F from outside the stack F via the fuel gas or oxidizer gas flow paths, before reaching the unit cells C. Second, the dummy cells D maintain the temperature inside the fuel cell stack F, which rises due to the power generation by the unit cells C.

[0013] In the example shown in Figure 1, two dummy cells D are placed at each end of the fuel cell stack F. Two dummy cells D11 and D12, connected in series, are placed at one end of the fuel cell stack F. Two dummy cells D21 and D22, connected in series, are placed at the other end of the fuel cell stack F. Five unit cells C11, C31, C32, C41, and C42 are placed between the two dummy cells D11 and D12 and the two dummy cells D21 and D22. That is, an odd number of unit cells C are connected in series.

[0014] The fuel cell stack F includes multiple cell groups G. Each cell group G includes the multiple cells described above. The multiple cell groups G include a first cell group G1 and a second cell group G2. The first cell group G1 includes one or more unit cells C and one or more dummy cells D. In the first cell group G1, one or more unit cells C and one or more dummy cells D are connected in series. The second cell group G2 includes only multiple dummy cells D. In the second cell group G2, multiple dummy cells D are connected in series.

[0015] The aforementioned cell groups G may include other cell groups G that are different from the first cell group G1 and the second cell group G2. These other cell groups G contain only multiple unit cells C. In these other cell groups G, the multiple unit cells C are connected in series. The third cell group G3 and the fourth cell group G4, described later, both correspond to the aforementioned other cell groups G.

[0016] In the example shown in FIG. 1, the cell group G includes two cells. As described above, an odd number of unit cells C are connected in series. Therefore, among the plurality of cell groups G included in the fuel cell stack F, a first cell group G1 in which one unit cell C and one dummy cell D are connected in series is included. Further, among the plurality of cell groups G, a second cell group G2 in which only two dummy cells D are connected in series is included. Furthermore, among the plurality of cell groups G, a third cell group G3 and a fourth cell group G4 in which only two unit cells C are connected in series are included.

[0017] In the first cell group G1, a unit cell C11 and a dummy cell D11 are connected in series. In the second cell group G2, dummy cells D21 and D22 are connected in series. In the third cell group G3, unit cells C31 and C32 are connected in series. In the fourth cell group G4, unit cells C41 and C42 are connected in series.

[0018] A voltage measurement unit Mv measures a voltage for each cell group G of the fuel cell stack F. When a cell group G includes one or more unit cells C, such as the first cell group G1 and the other cell groups G described above, the voltage measurement unit Mv measures the output voltage from the cell group G. When a cell group G includes only dummy cells D, such as the second cell group G2, the voltage measurement unit Mv measures the voltage drop across the cell group G.

[0019] In the example shown in FIG. 1, the cell group G includes two cells. Therefore, the voltage measurement unit Mv, which measures a voltage for each cell group G, measures the voltage for every two cells. Specifically, the voltage measurement unit Mv measures the voltage across both ends of the first cell group G1. Thereby, the output voltage V1 from the first cell group G1 is measured. The voltage measurement unit Mv measures the voltage across both ends of the second cell group G2. Thereby, the voltage drop V2 across the second cell group G2 is measured.

[0020] The voltage measurement unit Mv measures the voltage across the third cell group G3. Accordingly, the output voltage V3 from the third cell group G3 is measured. The voltage measurement unit Mv measures the voltage across the fourth cell group G4. Accordingly, the output voltage V4 from the fourth cell group G4 is measured.

[0021] In the example shown in Fig. 1, the first cell group G1 includes one unit cell C and one dummy cell D. Therefore, the output voltage V1 from the first cell group G1 is lower than the cell voltage Vc of the unit cell C. In this case, there is a risk that an abnormality in which the cell voltage Vc of the unit cell C included in the first cell group G1 decreases may be erroneously detected.

[0022] Along with such erroneous detection, there is a possibility that a predetermined control operation may be activated in the fuel cell stack F. As a normal cause for a decrease in the cell voltage Vc of the unit cell C, for example, a state where moisture has entered the fuel cell stack F can be considered. Therefore, as the aforementioned predetermined control operation, for example, a control operation for increasing the supply amount of oxidant gas to the fuel cell stack F can be activated. Increasing the supply amount of oxidant gas is expected to remove moisture.

[0023] However, the cause of the low output voltage V1 from the first cell group G1 is not moisture entering the fuel cell stack F. The cause lies in that the first cell group G1 includes the dummy cell D together with the unit cell C. Therefore, activation of the aforementioned predetermined control operation is unnecessary. For this reason, as will be described later, the voltage estimation device 10 estimates the cell voltage Vc for each unit cell C. This suppresses activation of unnecessary control operations in the fuel cell stack F.

[0024] Figure 1 shows a block diagram illustrating the configuration of the voltage estimation device 10. The voltage estimation device 10 includes a calculation unit 20 and a storage unit 22. The calculation unit 20 is a computer and includes a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). In other words, the calculation unit 20 includes processing circuitry.

[0025] The storage unit 22 is a computer-readable recording medium. The storage unit 22 includes volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory) or flash memory. The volatile memory is used as the processor's working memory. The non-volatile memory stores the computer program executed by the processor and other necessary data.

[0026] Computer programs (computer software) executed by a processor can also be called computer program products. Computer program products are not limited to computer programs stored on recording media, but also include computer programs transmitted, distributed, or downloaded via the internet, etc.

[0027] The calculation unit 20 includes a voltage acquisition unit 30 and a voltage estimation unit 32. The calculation unit 20 executes a computer program stored in the storage unit 22 to realize the voltage acquisition unit 30 and the voltage estimation unit 32. At least a portion of the voltage acquisition unit 30 and the voltage estimation unit 32 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array), or by an electronic circuit including discrete devices.

[0028] The voltage acquisition unit 30 acquires the output voltage V1 from the first cell group G1 from the voltage measurement unit Mv. In this embodiment, the voltage acquisition unit 30 further acquires the voltage drop V2 from the second cell group G2 and the output voltages from the other cell groups G described above from the voltage measurement unit Mv. In the example shown in Figure 1, the output voltages V3 and V4 from the third cell group G3 and the fourth cell group G4 are acquired as output voltages from the other cell groups G.

[0029] The voltage estimation unit 32 estimates the cell voltage Vc for each unit cell C based on the output voltage V1 from the first cell group G1, the dummy cell D, and the unit voltage drop per cell. As will be described later using Figure 2, the unit voltage drop is obtained by dividing the voltage drop V2 from the second cell group G2 by the number of dummy cells D included in the second cell group G2. This allows for accurate correction of the output voltage V1 from the first cell group G1, which includes the unit cells C and dummy cells D, and enables the estimation of the cell voltage Vc of the unit cells C included in the first cell group G1.

[0030] The voltage estimation unit 32 obtains a correction amount by multiplying the voltage drop unit amount by the number of dummy cells D included in the first cell group G1. The voltage estimation unit 32 obtains a corrected voltage by adding this correction amount to the output voltage V1 obtained by the voltage acquisition unit 30. The voltage estimation unit 32 estimates the cell voltage Vc using this corrected voltage and the number of unit cells C included in the first cell group G1. The cell voltage Vc is obtained by dividing the corrected voltage by the number of unit cells C included in the first cell group G1. The estimation of the cell voltage Vc in the example shown in Figure 1 will be described later with reference to Figure 2.

[0031] In other words, the voltage estimation device 10 estimates the cell voltage Vc of each unit cell C by correcting the output voltage V1 from the first cell group G1 using a unit amount of voltage drop. Therefore, the possibility of erroneously detecting an abnormality in which the cell voltage Vc of a unit cell C included in the first cell group G1 decreases is reduced. This suppresses the activation of unnecessary control operations in the fuel cell stack F.

[0032] The voltage estimation device 10 further divides the output voltage of another cell group G, which contains only unit cells C, by the number of unit cells C included in that cell group G. This allows the voltage estimation device 10 to estimate the cell voltage Vc for each unit cell C.

[0033] Specifically, the voltage estimation device 10 estimates the cell voltage Vc by dividing the output voltage V3 from the third cell group G3 by the number of unit cells C included in the third cell group G3, which is 2. The voltage estimation device 10 also estimates the cell voltage Vc by dividing the output voltage V4 from the fourth cell group G4 by the number of unit cells C included in the fourth cell group G4, which is 2. In this way, the voltage estimation device 10 estimates the cell voltage Vc for each unit cell C included in the fuel cell stack F.

[0034] Figure 2 is a diagram illustrating the estimation of the cell voltage Vc for each unit cell C. Here, the estimation of the cell voltage Vc is explained using the example shown in Figure 1. The first cell group G1 shown in Figure 1 contains one unit cell C11 and one dummy cell D11. That is, the number of unit cells C and dummy cells D in the first cell group G1 is 1 each. The second cell group G2 shown in Figure 1 contains two dummy cells D. That is, the number of dummy cells D in the second cell group G2 is 2.

[0035] The voltage drop unit amount described above is obtained by dividing the voltage drop V2 due to the second cell group G2 by 2, which is the number of dummy cells D included in the second cell group G2. Therefore, the voltage drop unit amount is V2 / 2. The correction amount described above is obtained by multiplying the voltage drop unit amount by 1, which is the number of dummy cells D included in the first cell group G1. Therefore, the correction amount is V2 / 2. The correction voltage described above is obtained by adding this correction amount to the output voltage V1. Therefore, the correction voltage is V1 + V2 / 2.

[0036] The cell voltage Vc is obtained by dividing the correction voltage by 1, which is the number of unit cells C included in the first cell group G1. Therefore, the cell voltage Vc is V1 + V2 / 2. This allows for accurate correction of the output voltage V1 from the first cell group G1, which includes unit cells C and dummy cells D, and enables estimation of the cell voltage Vc of the unit cells C included in the first cell group G1.

[0037] Furthermore, if the first cell group G1 includes one unit cell C11 and one dummy cell D11, the voltage estimation unit 32 may estimate the cell voltage Vc by adding a voltage drop unit amount V2 / 2 to the output voltage V1. With such a configuration, the cell voltage Vc of the unit cell C included in the first cell group G1, which includes one unit cell C and one dummy cell D, can be easily estimated.

[0038] Figure 3 is a flowchart illustrating the processing procedure for a voltage estimation method that estimates the cell voltage Vc for each unit cell C. This processing procedure is performed by the calculation unit 20 executing a computer program stored in the storage unit 22 of the voltage estimation device 10. When this processing procedure is started, in step S1, the voltage acquisition unit 30 acquires the output voltage from a cell group G in which a unit cell C and a dummy cell D are connected in series. In the example shown in Figure 1, the voltage acquisition unit 30 acquires the output voltage V1 from the first cell group G1.

[0039] In step S2, the voltage estimation unit 32 obtains the voltage drop unit amount for each dummy cell D. In step S3, the voltage estimation unit 32 obtains the correction amount described above based on the voltage drop unit amount. The voltage estimation unit 32 obtains a corrected voltage based on the output voltage obtained in step S1 (output voltage V1 from the first cell group G1) and the correction amount.

[0040] In step S4, the voltage estimation unit 32 estimates the cell voltage Vc for each unit cell C in the cell group G (first cell group G1) which includes unit cells C and dummy cells D, based on the corrected voltage obtained in step S3. The voltage estimation unit 32 further estimates the cell voltage Vc for each unit cell C in other cell groups G which include only unit cells, based on the output voltage of the cell group G. Once the processing in step S4 is completed, this processing procedure ends.

[0041] The embodiments described above may be modified as follows. In the following modifications, explanations that overlap with the embodiments described above will be omitted.

[0042] (Variation 1) In the embodiment described above, the voltage drop V2 due to the second cell group G2 is measured by the voltage measurement unit Mv. The voltage acquisition unit 30 acquires the voltage drop V2 from the voltage measurement unit Mv. The voltage estimation unit 32 acquires the unit amount of voltage drop per dummy cell D. However, the acquisition of the unit amount of voltage drop is not limited to this. The unit amount of voltage drop may also be acquired using the current value of the generated current I of the fuel cell stack F. Figure 4 is a diagram illustrating the acquisition of the current value of the generated current I.

[0043] As described above, the generated current I from the fuel cell stack F flows through a closed circuit including the fuel cell stack F and the load device L. In the example shown in Figure 4, a current measuring unit Ma is provided in the closed circuit to measure the current value of the generated current I.

[0044] The calculation unit 20 of the voltage estimation device 10 further includes a current acquisition unit 34 in addition to the voltage acquisition unit 30 and voltage estimation unit 32 described above. The current acquisition unit 34 is also realized by the calculation unit 20 executing a computer program stored in the storage unit 22. The current acquisition unit 34 may also be realized by an integrated circuit such as an ASIC or FPGA, or by an electronic circuit including discrete devices. The current acquisition unit 34 acquires the current value of the generated current I of the fuel cell stack F, which includes multiple cell groups G.

[0045] Figure 5 illustrates a setting table in which the voltage drop unit amount is set. This setting table is stored in the memory unit 22 in advance. The generated current I of the fuel cell stack F described above flows through the second cell group G2, which contains only dummy cells D. The number of dummy cells D included in the second cell group G2 is predetermined. Also, as described above, since the dummy cells D are equivalent to electrical resistance, the resistance value of the electrical resistance that causes the voltage drop by the second cell group G2 is predetermined.

[0046] Therefore, the voltage drop unit amount per dummy cell D can be calculated in advance according to the current value of the generated current I. The voltage drop unit amount calculated in this advance is associated with the generated current I and set in the setting table shown in Figure 5. In the example shown in Figure 5, the voltage drop unit amount Va is set for the current value Ia of the generated current I. Also, the voltage drop unit amount Vb is set for the current value Ib of the generated current I. The voltage estimation unit 32 obtains the voltage drop unit amount per dummy cell D from the setting table based on the current value of the generated current I obtained by the current acquisition unit 34.

[0047] The voltage estimation unit 32 estimates the cell voltage Vc of a unit cell C included in the first cell group G1 based on the voltage drop unit amount obtained from the setting table and the output voltage V1 obtained by the voltage acquisition unit 30. The fuel cell stack F is usually equipped with a current measurement unit Ma for measuring the current value of the generated current I. Because this current measurement unit Ma is used, there is no need to provide a voltage measurement circuit in the voltage measurement unit Mv for measuring the voltage drop V2 caused by the second cell group G2, which includes only dummy cells D.

[0048] (Modification 2) In the embodiment described above, cell group G includes two cells. The voltage measurement unit Mv measures the voltage for each cell group G, so it measures the voltage of two cells at a time. However, cell group G may include three or more cells. The voltage measurement unit Mv measures the voltage for each cell group G, so it measures the voltage for each cell in the cell group G. This modified example 2 describes an example where cell group G includes three cells, but the same applies to examples where cell group G includes more than three cells.

[0049] Figure 6A is a diagram illustrating the cell group G of the fuel cell stack F. In the example shown in Figure 6A, three dummy cells D are placed at each end of the fuel cell stack F. Three dummy cells D11, D12, and D13, connected in series, are placed at one end of the fuel cell stack F. Three dummy cells D21, D22, and D23, connected in series, are placed at the other end of the fuel cell stack F. Four unit cells C11, C31, C32, and C33 are placed between the three dummy cells D11, D12, and D13 and the three dummy cells D21, D22, and D23.

[0050] The fuel cell stack F includes multiple cell groups G. Each cell group G includes three cells. The multiple cell groups G include a first cell group G1 and a second cell group G2. The first cell group G1 includes one or more unit cells C and one or more dummy cells D. In the example shown in Figure 6A, in the first cell group G1, one unit cell C11 and two dummy cells D11 and D12 are connected in series. The second cell group G2 includes only multiple dummy cells D. In the example shown in Figure 6A, in the second cell group G2, three dummy cells D21, D22 and D23 are connected in series.

[0051] The aforementioned cell groups G of the fuel cell stack F further include a third cell group G3. The third cell group G3 contains only multiple unit cells C. In the example shown in Figure 6A, three unit cells C31, C32, and C33 are connected in series in the third cell group G3.

[0052] As described above, cell group G contains three cells. Therefore, the voltage measurement unit Mv, which measures the voltage for each cell group G, measures the voltage of three cells at a time. Specifically, the voltage measurement unit Mv measures the voltage across the first cell group G1. This measures the output voltage V1 from the first cell group G1. The voltage measurement unit Mv measures the voltage across the second cell group G2. This measures the voltage drop V2 from the second cell group G2. The voltage measurement unit Mv measures the voltage across the third cell group G3. This measures the output voltage V3 from the third cell group G3.

[0053] In the example shown in Figure 6A, the third cell group G3 contains 3 unit cells C. The first cell group G1 contains 1 unit cell C. Therefore, the output voltage V1 from the first cell group G1 is lower than the output voltage V3 from the third cell group G3.

[0054] Figure 6B is a diagram illustrating the estimation of the cell voltage Vc for each unit cell C. Here, the estimation of the cell voltage Vc is explained using the example shown in Figure 6A. The first cell group G1 shown in Figure 6A contains one unit cell C11 and two dummy cells D11 and D12. That is, the number of unit cells C and dummy cells D in the first cell group G1 is 1 and 2, respectively. The second cell group G2 shown in Figure 6A contains three dummy cells D. That is, the number of dummy cells D in the second cell group G2 is 3.

[0055] The voltage drop unit amount described above is obtained by dividing the voltage drop V2 due to the second cell group G2 by 3, which is the number of dummy cells D included in the second cell group G2. Therefore, the voltage drop unit amount is V2 / 3. The correction amount described above is obtained by multiplying the voltage drop unit amount by 2, which is the number of dummy cells D included in the first cell group G1. Therefore, the correction amount is 2 × V2 / 3. The correction voltage described above is obtained by adding this correction amount to the output voltage V1. Therefore, the correction voltage is V1 + 2 × V2 / 3.

[0056] The cell voltage Vc is obtained by dividing the correction voltage by 1, which is the number of unit cells C included in the first cell group G1. Therefore, the cell voltage Vc is V1 + 2 × V2 / 3. This allows for accurate correction of the output voltage V1 from the first cell group G1, which includes unit cells C and dummy cells D, and enables estimation of the cell voltage Vc of the unit cells C included in the first cell group G1.

[0057] Figure 7A is a diagram illustrating the cell group G of the fuel cell stack F. In the example shown in Figure 7A, three dummy cells D are placed at each end of the fuel cell stack F. Three dummy cells D11, D12, and D13, connected in series, are placed at one end of the fuel cell stack F. Three dummy cells D21, D22, and D23, connected in series, are placed at the other end of the fuel cell stack F.

[0058] Five unit cells C11, C12, C31, C32, and C33 are placed between three dummy cells D11, D12, and D13 and three dummy cells D21, D22, and D23.

[0059] The fuel cell stack F includes multiple cell groups G. Each cell group G includes three cells. The multiple cell groups G include a first cell group G1 and a second cell group G2. The first cell group G1 includes one or more unit cells C and one or more dummy cells D. In the example shown in Figure 7A, in the first cell group G1, two unit cells C11 and C12 and one dummy cell D11 are connected in series. The second cell group G2 includes only multiple dummy cells D. In the example shown in Figure 7A, in the second cell group G2, three dummy cells D21, D22, and D23 are connected in series.

[0060] The aforementioned cell groups G of the fuel cell stack F further include a third cell group G3. The third cell group G3 contains only multiple unit cells C. In the example shown in Figure 7A, three unit cells C31, C32, and C33 are connected in series in the third cell group G3.

[0061] As described above, cell group G contains three cells. Therefore, the voltage measurement unit Mv, which measures the voltage for each cell group G, measures the voltage of three cells at a time. The details of the voltage measurement by the voltage measurement unit Mv are the same as described above using Figure 6A. In this way, the voltage measurement unit Mv measures the output voltage V1 from the first cell group G1, the voltage drop V2 from the second cell group G2, and the output voltage V3 from the third cell group G3.

[0062] In the example shown in Figure 7A, the third cell group G3 contains 3 unit cells C. The first cell group G1 contains 2 unit cells C. Therefore, the output voltage V1 from the first cell group G1 is lower than the output voltage V3 from the third cell group G3.

[0063] Figure 7B is a diagram illustrating the estimation of the cell voltage Vc for each unit cell C. Here, the estimation of the cell voltage Vc is explained using the example shown in Figure 7A. The first cell group G1 shown in Figure 7A contains two unit cells C11 and C12 and one dummy cell D11. That is, the number of unit cells C and dummy cells D included in the first cell group G1 is 2 and 1, respectively. The second cell group G2 shown in Figure 7A contains three dummy cells D. That is, the number of dummy cells D included in the second cell group G2 is 3.

[0064] The voltage drop unit amount described above is obtained by dividing the voltage drop V2 due to the second cell group G2 by 3, which is the number of dummy cells D included in the second cell group G2. Therefore, the voltage drop unit amount is V2 / 3. The correction amount described above is obtained by multiplying the voltage drop unit amount by 1, which is the number of dummy cells D included in the first cell group G1. Therefore, the correction amount is V2 / 3. The correction voltage described above is obtained by adding this correction amount to the output voltage V1. Therefore, the correction voltage is V1 + V2 / 3.

[0065] The cell voltage Vc is obtained by dividing the correction voltage by 2, which is the number of unit cells C included in the first cell group G1. Therefore, the cell voltage Vc is (V1 + V2 / 3) / 2. This allows for accurate correction of the output voltage V1 from the first cell group G1, which includes unit cells C and dummy cells D, and enables estimation of the cell voltage Vc of the unit cells C included in the first cell group G1.

[0066] With regard to the embodiments and modifications described above, the following additional information is disclosed.

[0067] (Note 1) The voltage estimation device (10) of this disclosure includes a voltage acquisition unit (30) that acquires an output voltage (V1) from a first cell group (G1) in which one or more unit cells (C) capable of generating electricity using a fuel gas and an oxidizer gas and one or more dummy cells (D) that do not generate electricity are connected in series, and a voltage estimation unit (32) that estimates the cell voltage (Vc) for each unit cell based on the output voltage and the unit amount of voltage drop per dummy cell. With such a configuration, the activation of unnecessary control operations in the fuel cell stack is suppressed.

[0068] (Note 2) The voltage estimation device described in Appendix 1 may be obtained by dividing the voltage drop (V2) by the number of dummy cells included in the second cell group (G2), in which only a plurality of dummy cells are connected in series. With such a configuration, the output voltage of a cell group including a unit cell and dummy cells can be accurately corrected to estimate the cell voltage of a unit cell included in the cell group.

[0069] (Note 3) A voltage estimation device as described in Appendix 1 or 2, wherein the first cell group includes a plurality of dummy cells, and the voltage estimation unit estimates the cell voltage using a correction voltage, which is the output voltage plus a correction amount obtained by multiplying the number of the plurality of dummy cells included in the first cell group by the unit amount of voltage drop, and the number of the unit cells included in the first cell group. With such a configuration, the output voltage of the first cell group can be accurately corrected and the cell voltage of the unit cells included in the first cell group can be estimated.

[0070] (Note 4) The voltage estimation device described in Appendix 1 or 2, wherein the first cell group includes one unit cell and one dummy cell, and the voltage estimation unit estimates the cell voltage by adding the voltage drop unit amount to the output voltage. With such a configuration, the cell voltage of a unit cell included in a cell group including one unit cell and one dummy cell can be easily estimated.

[0071] (Note 5) The voltage estimation device described in Appendix 1 further comprises a current acquisition unit (34) that acquires the current value of the generated current (I) of a fuel cell stack (F) including the first cell group, and a setting table in which the voltage drop unit amount is set in advance according to the current value of the generated current, wherein the voltage estimation unit acquires the voltage drop unit amount from the setting table based on the current value of the generated current acquired by the current acquisition unit. With such a configuration, there is no need to provide a voltage measurement circuit for measuring the voltage drop by a cell group including only dummy cells.

[0072] (Note 6) The voltage estimation method of this disclosure includes a voltage acquisition step of acquiring the output voltage of a first cell group in which one or more unit cells capable of generating electricity using a fuel gas and an oxidizer gas and one or more dummy cells that do not generate electricity are connected in series, and a voltage estimation step of estimating the cell voltage for each unit cell based on the output voltage and the unit amount of voltage drop per dummy cell. With such a configuration, the activation of unnecessary control operations in the fuel cell stack is suppressed.

[0073] (Note 7) The voltage estimation method described in Appendix 6, wherein the first cell group includes one unit cell and one dummy cell, and in the voltage estimation step, the cell voltage may be calculated by adding the voltage drop unit amount to the output voltage. With such a configuration, the cell voltage of a unit cell included in a cell group including one unit cell and one dummy cell can be easily estimated.

[0074] While this disclosure has been described in detail, it is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, partially deleted, etc., in any way that does not depart from the gist of this disclosure or from the spirit of this disclosure derived from the claims and their equivalents. These embodiments can also be implemented in combination. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. [Explanation of Symbols]

[0075] 10...Voltage estimation device 20...Calculation unit 22...Memory unit 30...Voltage acquisition unit 32...Voltage estimation unit 34...Current acquisition unit

Claims

1. A voltage acquisition unit acquires the output voltage of a first cell group in which one or more unit cells capable of generating electricity using a fuel gas and an oxidizer gas are connected in series with one or more dummy cells that do not generate electricity. A voltage estimation unit estimates the cell voltage for each unit cell based on the output voltage and the unit amount of voltage drop per dummy cell. A voltage estimation device equipped with the following features.

2. A voltage estimation device according to claim 1, The voltage drop unit amount is obtained by dividing the voltage drop due to a second cell group, in which only a plurality of the dummy cells are connected in series, by the number of dummy cells included in the second cell group, in a voltage estimation device.

3. A voltage estimation device according to claim 1 or 2, The first cell group includes a plurality of the dummy cells, The voltage estimation unit is a voltage estimation device that estimates the cell voltage using a correction voltage, which is the output voltage plus a correction amount obtained by multiplying the number of dummy cells included in the first cell group by the unit amount of voltage drop, and the number of unit cells included in the first cell group.

4. A voltage estimation device according to claim 1 or 2, The first cell group includes one unit cell and one dummy cell, The voltage estimation unit is a voltage estimation device that estimates the cell voltage by adding the voltage drop unit amount to the output voltage.

5. A voltage estimation device according to claim 1, A current acquisition unit that acquires the current value of the power generation current of the fuel cell stack including the first cell group, A setting table in which the unit amount of voltage drop is set in advance according to the current value of the generated current, Furthermore, The voltage estimation unit is a voltage estimation device that obtains the voltage drop unit amount from the setting table based on the current value of the generated current obtained by the current acquisition unit.

6. A voltage acquisition step to acquire the output voltage of a first cell group in which one or more unit cells capable of generating electricity using a fuel gas and an oxidizer gas are connected in series with one or more dummy cells that do not generate electricity, A voltage estimation step in which the cell voltage for each unit cell is estimated based on the output voltage and the unit amount of voltage drop per dummy cell, A voltage estimation method, including the following.

7. A voltage estimation method according to claim 6, The first cell group includes one unit cell and one dummy cell, A voltage estimation method in which, in the voltage estimation step, the cell voltage is calculated by adding the voltage drop unit amount to the output voltage.

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