Power supply system and power distribution control method for fuel cell and secondary battery in power supply system

Abstract

To provide a power supply system capable of more surely attaining improvement of fuel consumption efficiency or improvement of durability by controlling power distribution of a fuel cell and a secondary battery, and a power distribution control method.SOLUTION: A power supply system including a fuel cell FC and a secondary battery BAT as power supply sources comprises: a power distribution control section A which distributes output power of the batteries for supplying requested power to an electric load; an impedance acquisition section B for acquiring impedance (R1) in a plurality of frequencies regarding the fuel cell; and an arithmetic section C for extracting material transport resistance (R2) of the fuel cell on the basis of the impedance (R1) and calculating power (P2) that the fuel cell should supply and power (P3) that the secondary battery should supply by specific arithmetic based on a magnitude of the resistance (R2). The power distribution control section A controls the output of the batteries based on an arithmetic result of the arithmetic section C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply system and a method for controlling power distribution between a fuel cell and a secondary battery in the power supply system. [Background technology]

[0002] In recent years, attention has been focused on the application of power supply systems that use fuel cells and secondary batteries as a power supply source for electrical loads such as electric mobility. In such power supply systems, secondary batteries are used in combination with fuel cells to improve their efficiency and durability, due to the following characteristics of fuel cells:

[0003] That is, fuel cells generally have the following characteristics: when the power required by the load (required power: load power) is small and the output power is low, the operating voltage increases, resulting in high power generation efficiency; conversely, when the load power is large and the output power is high, the operating voltage decreases, resulting in low power generation efficiency. Fuel cells also have the characteristic of deteriorating with use, resulting in a decrease in their current-voltage characteristics (IV characteristics). Such fuel cell degradation is primarily caused by fluctuations in the fuel cell's voltage. For this reason, when fuel cells are applied to electrical loads such as motors for electric mobility vehicles, which have large load fluctuations, a power supply system combining a fuel cell and a secondary battery (hybrid power supply system) is used to reduce this degradation.

[0004] In such power supply systems, power is supplied by allocating (sharing) the output power from the fuel cell and the secondary battery according to the power required by the electrical load to which the power is supplied. However, how to allocate power between the fuel cell and the secondary battery is a particularly important issue from the perspective of improving the fuel efficiency (fuel economy) and durability of the power supply system. Generally, if a constant power is generated (output) from the fuel cell to maintain a constant fuel cell voltage in order to improve durability, the secondary battery must compensate for any shortfall in the required power due to load fluctuations. This increases the number of charge / discharge cycles of the secondary battery, resulting in a loss of battery performance in the secondary battery, and as a result, the fuel efficiency and durability of the power supply system (hybrid power supply system) decrease. On the other hand, the more the fuel cell is forced to follow fluctuations in the power required by the electrode load of the power supply system, the more the fuel cell voltage fluctuates, reducing the durability of the fuel cell and the durability of the power supply system (hybrid power supply system). Considering these points, it is believed that there is no simple optimal method for distributing (sharing) the output power from fuel cells and secondary batteries, and distribution methods have been studied from various perspectives in order to optimize power distribution. However, the methods that have been studied so far are not necessarily sufficient in terms of distributing (sharing) the output power from fuel cells and secondary batteries to improve fuel efficiency and durability with high precision, and there is a need for the emergence of a new power distribution control method that can improve fuel efficiency and durability with high precision.

[0005] For example, Japanese Patent Application Laid-Open No. 2007-324140 (Patent Document 1) discloses a method of determining the power generation resistance at the start-up of a fuel cell when power generation begins using an AC impedance method, and controlling the target value of the current to be generated based on the determined power generation resistance, thereby avoiding a drop in the fuel cell voltage. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-324140 Summary of the Invention [Problem to be solved by the invention]

[0007] Here, even if the method for avoiding voltage drops in fuel cells described in Patent Document 1 is considered for application to a power supply system (hybrid power supply system), it is still not necessarily sufficient in terms of improving power generation efficiency or durability with high precision, for reasons that will be explained later. Thus, simply applying the technology described in Patent Document 1 makes it difficult to improve fuel efficiency or durability with high precision.

[0008] The present invention has been made in consideration of the problems associated with the prior art, and aims to provide a power supply system that controls the power distribution between a fuel cell and a secondary battery, thereby more reliably improving fuel efficiency and durability; and a method for controlling the power distribution between a fuel cell and a secondary battery in a power supply system, which more reliably improves the fuel efficiency and durability of the power supply system. [Means for solving the problem]

[0009] The inventors first considered the problems of the prior art and studied the technology described in Patent Document 1. In the method described in Patent Document 1, the impedance value at a single frequency is measured to measure the power generation resistance at startup, and information about the internal state of the fuel cell is obtained based on that value. However, because the response speed of the same reaction inside the fuel cell varies depending on the environment, even if the reaction is the same, measuring the internal state at a single frequency may not always accurately predict or understand the internal state, making it difficult to accurately improve fuel efficiency and durability. Therefore, through further research, the inventors came to the conclusion that it would be effective to analyze the impedance measurement results at multiple frequencies and reflect the results in a power distribution method. Patent Document 1 does not even mention measuring impedance at multiple frequencies, and does not particularly mention or suggest how to analyze such impedance at multiple frequencies.

[0010] Then, in order to achieve the above-mentioned object, the inventors conducted further research taking into consideration the above-mentioned viewpoints, and as a result, they discovered that in order to grasp the internal state of a fuel cell, including the state of reactions depending on the environment, with higher accuracy, the impedance R1 of the fuel cell is obtained at a plurality of different frequencies, and based on the data on the plurality of impedances R1, a resistance R2 related to material transport in the fuel cell (material transport resistance R2) is extracted, and this material transport resistance R2 is used as data indicating the internal state of the fuel cell, and based on this resistance R2, in a power supply system comprising a fuel cell and a secondary battery as a power supply source to an electrical load, the ratio (distribution ratio) of the power that each battery should share with respect to the required power is corrected, and the power output from each battery is controlled based on this corrected value (corrected distribution ratio), thereby making it possible to more reliably improve fuel efficiency and durability, and thus completed the present invention.

[0011] That is, the present invention provides the following aspects.

[0012] [1] A power supply system including a fuel cell and a secondary battery as a power supply source for an electrical load, a power distribution control unit (A) that distributes the output power of each of the batteries in order to supply the required power P1 to the electrical load; an impedance acquisition unit (B) for acquiring an impedance R1 of the fuel cell at a plurality of different frequencies; a calculation unit (C) that extracts a resistance R2 related to substance transport in the fuel cell based on data on the plurality of impedances R1 obtained by the impedance acquisition unit (B), and calculates, based on the magnitude of the resistance R2, the distribution of power (power distribution ratio) among the cells when the required power P1 is output from the power supply system, thereby determining the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; and The power supply system, wherein the power distribution control unit (A) controls the distribution of power output from each battery based on the calculation result of the calculation unit (C).

[0013] [2] The power supply system described in [1], wherein when extracting the resistance R2 related to material transport in the fuel cell, an equivalent circuit is assumed and the resistance R2 related to material transport is determined based on data on multiple impedances R1.

[0014] [3] In a power supply system having a fuel cell and a secondary battery as a power supply source for an electric load, a method for controlling power distribution of each battery with respect to a required power P1 of the electric load, comprising: an impedance acquisition step (S1) of acquiring an impedance R1 of the fuel cell at a plurality of different frequencies; a calculation step (S2) of extracting a resistance R2 related to material transport in the fuel cell based on the data of the plurality of impedances R1 obtained in the step (S1); a calculation step (S3) of calculating the power distribution (power distribution ratio) of each battery when the power required by the electric load P1 is output from the power supply system based on the magnitude of the resistance R2 calculated in the step (S2), thereby calculating the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; a power distribution control step (S4) of controlling the power output from each battery so that the power output from the fuel cell and the power output from the secondary battery are distributed to the power P2 and the power P3 calculated in the step (S3); A method for controlling power distribution between a fuel cell and a secondary battery in a power supply system, comprising:

[0015] [4] A power distribution control method according to [3], wherein in the calculation step (S2) of extracting the resistance R2 related to material transport in the fuel cell, an equivalent circuit is assumed and the resistance R2 related to material transport is calculated based on data on multiple impedances R1. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a power supply system that controls the power distribution between a fuel cell and a secondary battery, thereby more reliably improving fuel efficiency and durability; and a method for controlling the power distribution between a fuel cell and a secondary battery in a power supply system that more reliably improves the fuel efficiency and durability of the power supply system. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram schematically illustrating a preferred embodiment of the configuration of a power supply system of the present invention. [Figure 2] FIG. 1 is a graph of a typical impedance of a fuel cell, and is a Bode plot consisting of a graph (solid line) showing the relationship between the logarithm of frequency and the absolute value of impedance, and a graph (dotted line) showing the relationship between frequency and phase. [Figure 3]FIG. 2 is a Nyquist diagram of a typical impedance graph for a fuel cell, showing the relationship between the real component Zre and the imaginary component Zim of the impedance. [Figure 4] FIG. 1 is a diagram of a series circuit, which is one form of an equivalent circuit of a fuel cell. [Figure 5] FIG. 1 is a diagram of a parallel circuit, which is one form of an equivalent circuit of a fuel cell. [Figure 6] 10 is a flowchart showing one embodiment of a procedure (flow) that can be suitably employed as a method for extracting mass transport resistance R2. [Figure 7] 1 is a graph showing an example of a Nyquist diagram of impedance for each magnitude of substance transport resistance (gas transport resistance). [Figure 8] 8 is a graph of a distributed relaxation time (DRT) waveform obtained by performing a DRT analysis on the Nyquist diagram of FIG. 7. [Figure 9] 1 is a graph showing the relationship between the gas transport resistance (R2) and the current-voltage characteristics of a fuel cell. [Figure 10] 10 is a flowchart showing an embodiment of a calculation procedure (flow) in a power distribution calculation unit. [Figure 11] 10 is a flowchart showing an embodiment of a procedure (flow) for controlling power distribution between a fuel cell and a secondary battery. [Figure 12] 12(a) is a graph showing the relationship between time and each element (P1(t); R2(t); P2(t); P2'(t); P3(t); P3'(t); FC current(t); FC voltage(t); and fuel consumption (t)) determined by simulation in Example 1 and Comparative Example 1. FIG. 12(a) is a graph showing the relationship between time and P1(t); FIG. 12(b) is a graph showing the relationship between time and R2(t); FIG. 12(c) is a graph showing the relationship between time and P2(t) and P2'(t); FIG. 12(d) is a graph showing the relationship between time and P3(t) and P3'(t); FIG. 12(e) is a graph showing the relationship between time and FC current(t); FIG. 12(f) is a graph showing the relationship between time and FC voltage(t); and FIG. 12(d) is a graph showing the relationship between time and the integrated amount of fuel consumption (fuel consumption (t)). [Figure 13] 1 is a graph showing the relationship between the electrochemical area (deterioration index) of the catalyst and time, which was determined by simulation in Example 1 and Comparative Example 1. [Figure 14] 1 is a graph comparing fuel efficiency and durability between Example 1 and Comparative Example 1 (a graph of relative evaluation in which the simulation value of Comparative Example 1 is set to 1). DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description and drawings, the same or corresponding elements are designated by the same reference numerals, and redundant description will be omitted.

[0019] FIG. 1 is a schematic diagram (block diagram) showing a preferred embodiment of the configuration of a power supply system of the present invention. The power supply system of the embodiment shown in FIG. 1 includes a secondary battery (BAT) 10, a fuel cell (FC) 11, a power distribution control unit 12 (power distribution control unit (A)), an impedance acquisition unit (impedance acquisition unit (B)) 13, and a control unit 14. The control unit 14 includes a calculation unit (C) consisting of an impedance analysis unit 141 and a power distribution calculation unit 142. Such a power supply system is electrically connected so as to supply power to an external electrical load (not shown). Such a power supply system can be applied, for example, to an electric vehicle or a ship that runs on a fuel cell as a power source. The electrical load to which power is supplied is not particularly limited as long as it is a device that operates when supplied with voltage (electric power).

[0020] The secondary battery (BAT) 10 is used to temporarily store the power (surplus power) generated by the fuel cell (FC) 11 or the power obtained during regeneration, or to supply the stored power to a power consumption source. The structure of such a BAT 10 is not particularly limited, and may be the same as that of a known secondary battery, and an optimum structure may be selected depending on the purpose, the type of electrical load, etc.

[0021] Furthermore, the fuel cell (FC) 11 is not particularly limited and may be a known one, for example, a polymer electrolyte fuel cell. The structure of such FC 11 is not particularly limited and may be the same as the design of a known fuel cell, and the optimum structure may be selected appropriately depending on the purpose, the type of electrical load, etc.

[0022] The power distribution control unit 12 (power distribution control unit (A)) controls the output from each battery so as to distribute the output power of each battery in order to supply the required power P1 to the electrical load. In the present invention, the power distribution control unit 12 controls the output from the BAT 10 and FC 11 based on the calculation results of a calculation unit (C) in the control unit 14 (described below) (for example, input of calculation result data or input of a control command value based on the calculation results input from the calculation unit (C)), and controls the distribution of power output from each battery so as to supply the required power P1 (so that the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery are distributed and output). In this way, the power distribution control unit 12 is configured to be used to control the distribution of the output power of the BAT 10 and FC 11 to be supplied to an electrical load (for example, a motor) based on the calculation results (power distribution ratio) of the calculation unit (C) in the control unit 14. The device (power distribution control unit 12) for performing such power distribution control can be configured similarly to known devices, except that it controls the outputs from BAT 10 and FC 11 based on the calculation results of a control unit 14 (which includes a calculation unit (C)) described below. For example, the power distribution control unit 12 may be configured to include an inverter that converts DC power generated by the FC 11 into AC power (e.g., three-phase AC power) and supplies it to a power load, and a DC / DC converter that adjusts the output power of the FC 11 and controls the distribution of the supply power output from the FC 11 and the secondary battery 10.

[0023] The impedance acquisition unit (impedance acquisition unit (B)) 13 is not particularly limited as long as it can acquire the impedance R1 of the FC 11 at multiple (at least two or more) different frequencies, and any known impedance measurement means can be used as appropriate. For example, if the FC 11 has a structure (fuel cell stack: FC stack) in which multiple unit cells are stacked, each of which is composed of a membrane electrode assembly (MEA) in which catalyst layers are bonded to both sides of an electrolyte membrane, and a current collector (separator) equipped with a gas diffusion and gas flow path, an impedance measurement device connected in parallel to the FC stack can be used as the impedance acquisition unit 13. Also, any known impedance measurement means can be used as appropriate, such as a device that measures impedance using an AC impedance method. Furthermore, instead of using a dedicated impedance measurement device, for example, a device with a configuration similar to the impedance measurement unit described in JP 2021-180076 A (a measurement unit that measures by superimposing a sine wave on a power converter such as a DC / DC converter) can be used as the impedance acquisition unit 13. As described above, the configuration of the impedance acquisition unit 13 is not particularly limited, and the design thereof may be changed as appropriate depending on the type of electrical load and the type of FC 11. In the present invention, impedance is used as an index of the electrical frequency characteristics of the FC 11.

[0024] The control unit 14 also includes a calculation means (calculation unit (C)) that extracts resistance R2 related to material transport in the fuel cell based on data on impedance R1 at multiple different frequencies obtained by the impedance acquisition unit 13, and calculates the power distribution (power distribution ratio) of each battery when the required power P1 is output from the power supply system based on the magnitude of resistance R2 to calculate power P2 to be supplied by the fuel cell and power P3 to be supplied by the secondary battery. Such calculation means (calculation unit (C)) is made up of an impedance analysis unit 141 and a power distribution calculation unit 142. That is, the impedance analysis unit 141 and power distribution calculation unit 142 in the control unit 14 constitute the calculation means (calculation unit (C)) that performs calculations to determine material transport resistance R2.

[0025] The impedance analysis unit 141 analyzes data on the impedance R1 of the FC 11 at multiple different frequencies measured by the impedance acquisition unit, and performs an analysis to extract the resistance (mass transport resistance) R2 related to material transport in the fuel cell. The method of analyzing impedance to determine such material transport resistance R2 will be described later. Furthermore, the power distribution calculation unit 142 calculates the power distribution (power distribution ratio) of each battery when the power required by the external load P1 is output from the power supply system based on the magnitude of the resistance (mass transport resistance) R2, and performs a calculation to determine the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery. The method of such calculation will be described later.

[0026] The calculation unit (C) in the control unit 14 is electrically connected to the power distribution control unit 12 so that the calculation result (value for a control command) can be input to the power distribution control unit 12, in order to have the power distribution control unit 12 (power distribution control unit (A)) allocate the output power of each battery according to the calculation result. Note that such a calculation unit (C) inputs the calculation result to the power distribution control unit 12 as a control command value (which may be the calculated P2 and P3 themselves), and therefore can also be said to be a calculation device for a control command value.

[0027] Furthermore, such a calculation unit (C) may be any device capable of performing the above-mentioned control and calculation. For example, it may be a computer configured by appropriately combining known peripheral devices such as a necessary CPU, ROM, RAM, and programs required for various calculations required for control (such programs may be stored in the ROM or may be stored on a separate recording medium). The specific configuration is not particularly limited, and it may include hardware such as a CPU and memory, and a computer program (software) stored (installed) in memory for executing the necessary calculations. Examples of such a CPU include a central processing unit, processing unit, arithmetic unit, processor, microprocessor, microcomputer, DSP (Digital Signal Processor), etc. Furthermore, for example, when the power supply system is installed in a vehicle, a computer in a so-called engine control unit (ECU) for controlling the driving state of the automobile motor (electrical load) may be used as the control unit 14, and a part of it (part of the ECU computer) may be configured to function as the calculation unit (C). The control unit 14 may be configured to consist of only the calculation unit (C), and in that case, the control unit 14 may be configured as a unit (another computer, etc.) separate from the ECU, etc.

[0028] <Analysis of impedance R1 data> Below, we will explain a preferred embodiment of a method in which the impedance analysis unit 141 of the calculation unit 14 analyzes data on the impedance R1 of the fuel cell (FC) 11 at multiple different frequencies measured by the impedance acquisition unit 13, and extracts the resistance R2 related to material transport of the FC 11 (material transport resistance: reaction resistance related to material transport: gas transport resistance).

[0029] Here, typical impedance graphs for a fuel cell when the impedance R1 is obtained at a plurality of different frequencies are shown in Figures 2 and 3. Figure 2 is a Bode plot consisting of a graph (solid line) showing the relationship between the logarithm of frequency and the absolute value of impedance, and a graph (dotted line) showing the relationship between frequency and phase, and Figure 3 is a Nyquist plot consisting of a graph showing the relationship between the real component Zre and the imaginary component Zim of impedance.

[0030] In the present invention, data on multiple impedances R1 measured at multiple different frequencies (for example, data such as those shown in FIGS. 2 and 3) is analyzed to determine the resistance components within the electrochemical cell, and the resistance R2 related to material transport in the fuel cell (FC) 11 (material transport resistance: reaction resistance related to material transport: gas transport resistance) is extracted. A suitable method for extracting this resistance R2 is to assume an equivalent circuit and determine the resistance R2 related to material transport based on data on multiple impedances R1. A suitable method for determining the resistance R2 related to material transport based on this equivalent circuit is described below.

[0031] Examples of such equivalent circuits include an equivalent circuit consisting of a series circuit as shown in Fig. 4 and an equivalent circuit consisting of a parallel circuit as shown in Fig. 5. Regarding the symbols in the equivalent circuits shown in Figs. 4 and 5, R ohm denotes the DC resistance, and R cl denotes the charge transfer resistance, and C cl indicates the electric double layer capacitance (electric double layer capacitor: capacitance), R2 indicates the mass transport resistance (reaction resistance related to mass transport: gas transport resistance), and C mt represents the apparent capacitance associated with the mass transport resistance. Here, the equivalent circuit shown in Figures 4 and 5 is mt >C cl The following condition must be satisfied. There are no particular limitations on the method for setting (assuming) such an equivalent circuit of impedance, and an equivalent circuit model may be appropriately determined using a known method according to the design of the battery, etc. In this way, an equivalent circuit of a fuel cell (for example, an equivalent circuit such as that shown in FIG. 4 or FIG. 5) can be determined and used using a known method.

[0032] In a method for determining the mass transport resistance R2 based on such an equivalent circuit, it is preferable to perform parameter fitting of each resistance component, etc., from measured impedance R1 data to the assumed equivalent circuit to obtain information on each component of the equivalent circuit, and extract the mass transport resistance R2 of the fuel cell (FC) 11. Thus, a preferred method for determining the resistance R2 is to assume an equivalent circuit, fit impedance R1 data at multiple frequencies to the equivalent circuit (circuit parameter fitting), analyze the reaction components of the fuel cell (FC), and extract the "mass transport resistance R2" from the parameter set of each component of the obtained equivalent circuit. It is believed that such resistance R2 is a component that causes a sudden drop in voltage (efficiency) when the required power (power demand) increases.

[0033] Here, there are no particular limitations on the method for assuming an equivalent circuit, obtaining information on each component of the equivalent circuit from the measured impedance R1 data, and extracting the resistance (mass transport resistance) R2 related to mass transport in the fuel cell (FC) 11, and any known method can be used as appropriate. Note that, if the technical idea of ​​determining the mass transport resistance R2 of the fuel cell (FC) 11 from the impedance R1 data is clear, an equivalent circuit can be set, and commercially available software can be used to perform curve fitting using the complex nonlinear least squares method from the measurement data to determine information on each component of the equivalent circuit, and the mass transport resistance R2 can be calculated (extracted) as appropriate.

[0034] A preferred example (preferable embodiment) of a method that can be used to extract the mass transport resistance R2 will be described below with reference to the flowchart shown in Figure 6. The flow (procedure) shown in Figure 6 is a preferred procedure for extracting the mass transport resistance R2 by setting (assuming) the equivalent circuit shown in Figure 5. In addition, prior to the extraction of such resistance R2, it is necessary to measure the mass transport resistance R2 at N different frequencies f n(n is a natural number from 1 to N), the impedance R1 n (n is a natural number from 1 to N) data is measured and used. n The measured impedance at is the impedance R1 n (n is f n and R1 n (The same value is obtained for both.)

[0035] f n = f1, f2, f3 f N R1 n = R11, R12, R13...R1 N .

[0036] In the flowchart shown in FIG. 6, first, in step S101, a set of parameters (parameter set) P determined from the assumed equivalent circuit (the equivalent circuit shown in FIG. 5 in this embodiment) and each frequency fn are used as a function to calculate a theoretical impedance value R sim Formula R to find sim (f n ,P), where the set of parameters P is as follows from Figure 5: P={R2, R ohm , R cl , C cl , C mt}.

[0037] And the required R sim (f n ,P) is calculated using the following formula (1):

[0038]

number

[0039] As is clear from the formula (1), in this embodiment, the theoretical value of impedance R sim is its real component R sim,r and its imaginary component jR sim,i(where j represents the imaginary unit).

[0040] Next, in step S102, N different frequencies f n (f n = f1, f2, f3 f N ) measured at R1n (R1n = R11, R12, R13...R1 N ) to calculate the cost function J based on the root mean square error. cost (f n , P) is calculated using the following formula (2):

[0041]

number

[0042] The formula is expressed as follows. Note that R1 in formula (2) r denotes the real component of impedance R1, and R1 i indicates the imaginary component.

[0043] Next, in step S103, an optimization method is used to find a set of parameters P that minimizes the cost function. mt and C cl But under the following conditions: C mt >C cl The set of parameters P is determined within a range that satisfies the following formula (3):

[0044]

number

[0045] Then, in step S104, the mass transport resistance R2 is extracted from the set of parameters P that have been found, thereby making it possible to find the mass transport resistance R2.

[0046] Above, we have explained a suitable example of the procedure for extracting the mass transport resistance R2 using the flowchart shown in Figure 6, but the method for extracting the mass transport resistance R2 is not limited to the above method, and other methods may be adopted as appropriate.

[0047] Another suitable method for determining the mass transport resistance R2 is to use the distribution of relaxation times (DRT) analysis to determine the mass transport resistance (reaction resistance related to mass transport) from measurements of impedance R1 at multiple different frequencies. Examples of such DRT analysis methods include known methods (such as those reported in the paper in Electrochimica Acta, 2015, 184, pp. 483-499 (URL: https: / / doi.org / 10.1016 / j.electacta.2015.09.097)). This method involves performing an inverse Fourier transform on the impedances (spectra) at multiple frequencies to determine the relaxation time distribution function (DRT waveform, DRT spectrum), and then separating each component of the equivalent circuit to determine the mass transport resistance R2. For reference, Figure 7 shows an example of the Nyquist diagrams obtained by measuring impedance R1 at multiple different frequencies at the timing when it can be determined that gas transport is inhibited and mass transport resistance (gas transport resistance) is increasing, the timing when gas transport is not inhibited and mass transport resistance is decreasing, and the timing between these. Figure 8 shows the DRT waveforms obtained by performing distributed relaxation time (DRT) analysis on the Nyquist diagrams. As is clear from these measurement diagrams, the response frequency changes as the gas transport resistance increases or decreases. If measurements are taken at a single frequency, it becomes difficult to accurately estimate each parameter at low frequencies. Therefore, it is necessary to measure impedance at multiple different frequencies in order to perform a highly accurate analysis. Note that the peak on the high frequency side of Figure 8 corresponds to the charge transfer resistance R cl This is the peak for.

[0048] Above, we have explained a preferred embodiment regarding the analysis of impedance R1 data (extraction of mass transport resistance R2). Below, we will explain a preferred embodiment of a method for calculating power allocation (power distribution ratio) based on such mass transport resistance R2.

[0049] <Calculation of power distribution (power distribution ratio) for each battery> Here, we will explain how the power distribution calculation unit 142 of the calculation unit 14 calculates the power distribution (power distribution ratio) of each battery when the required power P1 is output from the power supply system based on the magnitude of the resistance R2, and determines the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery.

[0050] Note that, taking the example of a case where a power supply system is used in a hybrid vehicle (where the electrical load is a hybrid vehicle (motor)), the required power of the hybrid vehicle at a certain time t (required load: required power P1) is generally supplied from the fuel cell (FC) 11 and the battery (BAT) 10 so that the sum of the output (power P2) from the fuel cell (FC) 11 at that time t and the output (power P3) from the secondary battery (BAT) 10 at that time t is equal to the required power (required power P1). Here, when supplying power from the FC 11 and the battery (BAT) 10 to the electrical load, from the viewpoint of improving system efficiency and durability, it is preferable to maximize the power generation efficiency of the FC 11 and restrict the power distribution of the battery (BAT) 10 to achieve optimization. As a method for such optimization, various methods for optimizing power distribution (power distribution control methods) and power distribution control programs for executing these methods have been researched.

[0051] In the present invention, when performing such power distribution, the distribution ratio (the proportion of each battery's output shared) is calculated by correcting it using the mass transport resistance R2 extracted (calculated) as described above, thereby achieving improved fuel efficiency and durability. Correction of the distribution ratio using resistance R2 is preferably performed based on a conventional power distribution optimization method (power distribution control method). Examples of such conventional power distribution control methods include those described in JP 2020-147256 A. That is, the present invention may also be a method for further optimizing power distribution by using mass transport resistance R2, which is an index indicating the difficulty of oxidizing gas reaching the catalyst surface at a specific usage time t, to correct the distribution ratio of power output from FC 11 and BAT 10.

[0052] Generally, to use the FC 11 with maximum efficiency, it is preferable to generate power at an operating point that maximizes system efficiency. However, once the current-voltage characteristics (IV characteristics) of the fuel cell are determined, its output power P2 is uniquely determined, and the difference from the required power P1 will increase or decrease the power P3 output from the BAT 10. However, if the output power P2 is uniquely determined in this way, the number of times the BAT 10 is charged and discharged will increase, resulting in a decrease in system efficiency. Furthermore, the BAT 10 needs to be able to operate at a point that maximizes system efficiency by controlling the remaining energy (SOC BAT ) needs to be charged when it decreases, so for efficient operation of the system, the remaining energy (SOC) of the BAT10 during use BAT ) must also be taken into consideration. Therefore, in the past, when controlling power distribution, it was necessary to consider the remaining energy (SOC) of the BAT10 during use, assuming how the system would be used when the electric load was actually operating. BAT ) is preferably adopted, and for example, the relational equations for feedforward control (power distribution parameter equations: P1 and SOC BAT Expression f as a function FF (P1,SOC BAT)) and used it for control. The relational expression f FF (P1,SOC BAT ) can be determined by a known method (for example, the method described in JP 2020-147256 A) depending on the type of electrical load, etc.

[0053] P2=f FF (P1,SOC BAT ) (10) P3 = P1 - P2 (11).

[0054] The calculation formula (10) is based on P1 (required power at a certain time t) and SOC BAT This is a calculation formula that uses (the remaining energy amount of BAT at a certain time t) as a function, for example, the following formula (10-1): f FF (P1,SOC BAT ) = P1 × γ1 + (γ2 - SOC BAT )×γ3 (10-1) Such a control formula may be obtained by calculating the remaining battery charge (SOC) while determining the amount of P2 to be distributed based on P1 at a certain time and the distribution ratio γ1. BAT This is general control that performs power feedback so as to maintain γ at a specific value γ2, and γ1 to γ3 are all adaptation coefficients. When general control is performed based on the above-mentioned formula (10-1), such adaptation coefficients can be appropriately determined using a known method (general method) (for example, they can be determined with reference to the method described in JP 2020-147256 A).

[0055] In contrast to such conventional control, in the present invention, when the power distribution (power distribution ratio) of each battery is calculated to determine the power P2 to be supplied by the FC (fuel cell) 11 and the power P3 to be supplied by the BAT (secondary battery) 10, the distribution ratio is corrected based on the magnitude of the mass transport resistance R2, and the power distribution (power distribution ratio) of each battery relative to the required power P1 is calculated to determine the power P2 to be supplied by the FC (fuel cell) 11 and the power P3 to be supplied by the BAT (secondary battery) 10.

[0056] Here, when mass transport resistance R2, which is an index (gas transport resistance) indicating the difficulty of oxidizing gas reaching the catalyst surface of FC11, is large, the voltage of FC11 tends to decrease significantly on the high current side (high power side). Therefore, it is preferable to control P2 to be small when resistance R2 is large. This is because by suppressing the power P2 shared by FC11 when resistance R2 is large, it is possible to avoid FC11 operation in a region where resistance R2 is large and power generation efficiency is low, thereby improving the fuel efficiency of the system. Furthermore, controlling the magnitude of P2 based on R2 in this way also makes it possible to avoid FC11 operation in a region where voltage drops, thereby efficiently suppressing voltage fluctuations that cause FC11 degradation. From this perspective, in the present invention, the distribution ratio (such as the magnitude of P2) is corrected based on the magnitude of mass transport resistance R2, the power distribution (power distribution ratio) of each battery relative to the required power P1 is calculated, and the output from each battery is controlled based on the calculation results, thereby making it possible to improve the fuel efficiency and durability of the system.

[0057] FIG. 9 shows a graph of the relationship between the gas transport resistance R2 and the current-voltage characteristics of a typical fuel cell. In the graphs shown in FIG. 9, the magnitude of R2 increases in the order of 1 to 4, with graph 1 showing the case where R2 is minimum and graph 4 showing the case where R2 is maximum. As shown in FIG. 9, when the resistance R2 is a large value, the voltage of FC11 generally drops significantly on the high current side (high power side). From the graph shown in FIG. 9, it can be said that when the resistance R2 is a large value, it is preferable to control the power output of each battery in the system so that the power P2 output from the fuel cell is reduced and the power P3 output from the secondary battery is increased.

[0058] In the present invention, for example, the relational expression f of the feedforward control FF When control is performed using the relational expression of the parameters for power distribution, the relational expression fFF It is preferable to adopt a calculation method for power allocation (power distribution ratio) that corrects whether or not the mass transport resistance R2 is used based on the magnitude of the mass transport resistance R2. A preferred embodiment of such a calculation method is, for example, a method in which power P2 is corrected to decrease when the mass transport resistance R2 determined by impedance analysis is greater than a specific threshold. A preferred method for limiting power P2 when the resistance R2 is greater than a specific threshold and calculating power P2 and power P3 is, for example, to calculate power P2 (the amount of power allocated to FC11) based on one of the following equations (13) to (14) depending on the case, and then calculate power P3 (the amount of power allocated to BAT10) using equation (15). In such a method, a threshold R2 for switching control of mass transport resistance R2 is set. th is calculated in advance, and the resistor R2 is set to the threshold R2 th greater than and f FF (P1,SOC BAT ) is the power limit value P2 lim If P2 is greater than the value calculated by the following formula (13) (power limit value P2 lim ), otherwise, it is preferable to control the power distribution amount of each battery so that P2 becomes the value calculated by the following formula (14). The formula used for such control is shown below.

[0059] [R2>R2 th and f FF (P1,SOC BAT )>P2 lim Formula for calculating power P2 when the condition is satisfied: P2=P2 lim (13) [Formula for calculating power P2 in other cases] P2=f FF (P1,SOC BAT ) (14) [Formula for calculating power P3 after calculating power P2] P3 = P1 - P2 (15).

[0060] By controlling the magnitude of P2 based on the resistance R2 using such equations (13) and (14), when the resistance R2 is large, the power P2 shared by FC11 is suppressed, making it possible to avoid operation of FC11 in a region where the resistance R2 is large and power generation efficiency is low, thereby increasing the fuel efficiency of the system.Furthermore, when the magnitude of P2 is controlled based on R2 using equations (13) and (14), it is also possible to avoid operation of FC11 in a region where the voltage drops, making it possible to efficiently suppress voltage fluctuations that cause deterioration of FC11, thereby improving the durability of the system.

[0061] Here, the power allocation calculation unit 142 included in the control unit 14 calculates the formula f FF FIG. 10 shows a preferred embodiment of a calculation flow (procedure) that can be employed in the calculation unit 142 when the calculation unit 142 is configured to calculate the power allocation (power distribution ratio) by correcting the use or non-use of the mass transport resistance R2 based on the magnitude of the mass transport resistance R2, and is configured to perform the calculation based on the above equations (13) to (15) (equipped with hardware consisting of a CPU, memory, etc., and a program stored in the memory, etc., for executing the necessary calculations).

[0062] When calculating the power distribution (required values ​​of P2 and P3) based on the calculation flow shown in FIG. 10, the power distribution calculation unit 142 first calculates the required power P1 of the electric load and the remaining energy (SOC) of the BAT 10 in step S201. BAT: charging rate) is acquired. For example, when the electric load is a hybrid vehicle, the required electric power P1 may be obtained by detecting the accelerator opening and vehicle speed, inputting the data to the control unit 14, and calculating the electric power P1 required to output the power required by the vehicle from the obtained data in the control unit 14, or may be obtained via the electric power distribution control unit 12. The calculation of the required electric power, required power, etc. can be obtained by appropriately adopting a known method (for example, the method described in JP 2020-147256 A, etc.). In addition, the remaining energy (SOC) of the BAT 10 is calculated. BAT ) can be acquired by, for example, separately providing a remaining energy quantification means that can quantify the remaining energy of the BAT 10 by a known method (for example, by using known analysis software or the like and appropriately connecting a detection means or the like to the secondary battery so that necessary data can be obtained, thereby making it possible to quantify the remaining energy), and constructing a system in which the data quantified by the remaining energy quantification means is input to the power allocation calculation unit 142, so that the power allocation calculation unit 142 automatically calculates the remaining energy SOC. BAT This may be achieved by making it possible to obtain the

[0063] Next, the process proceeds to step S202, where the value of resistance R2 related to material transport in the fuel cell (FC) 11 (material transport resistance: reaction resistance related to material transport) is obtained, which is calculated by the impedance analysis unit 141. The resistance R2 can be acquired by configuring the impedance analysis unit 141 to calculate the resistance R2 and then input the calculation result to the power allocation calculation unit 142, and there are no particular limitations on the method for acquiring the value of R2 (extracted value).

[0064] Next, the process proceeds to step S203, and in step S203, the resistor R2 is set to a value equal to or lower than the threshold value R2 th It is determined whether the threshold R2 is greater than the threshold R2. th The setting method is not particularly limited, but may be set appropriately according to the specifications of the fuel cell, and the following conditions are set: R2 th <{(0.8 / current)-R ohm -Rcl} It is preferable to appropriately set the range so as to satisfy the following conditions: R2 th <{(0.4 / current)-R ohm -R cl} It is more preferable to set the resistor R2 appropriately within a range that satisfies the above. th If it is greater than the threshold value R2, the process proceeds to step S204. th If it is smaller than , the process proceeds to step S206.

[0065] In step S204, P1 and SOC obtained in step S201 are BAT Based on the data, the relation f for feedforward control is FF (P1,SOC BAT ) and calculate the calculated f FF (P1,SOC BAT ) is the power limit value (output limit value of generated power) P2 lim Here, it is determined whether the power limit value P2 lim The magnitude of the power limit value P2 is not particularly limited and may be determined by a known method (for example, the method described in JP 2020-147256 A). The power limit value P2 is a current upper limit value of the power generation power that is determined by calculating various parameters that indicate the current state of the FC11. lim Furthermore, from the viewpoint of improving durability and fuel economy, the power limit value P2 lim The following equation (13-1) is a function of R2: P2 lim (R2) = γ4 - (γ5 × R2) (13-1) In addition, γ4 and γ5 in such an equation are compatibility coefficients, and such compatibility coefficients can be appropriately calculated by adopting a known method (for example, the method described in JP 2020-147256 A). FF (P1,SOC BAT ) is the calculated power limit value P2 limIf it is greater than the value determined linearly based on the above formula (13-1), for example, proceed to step S205 to set P2, and on the other hand, f FF (P1,SOC BAT ) is the power limit value P2 lim If it is smaller than P2, the process proceeds to step S206 and P2 is set.

[0066] In addition, steps S205 and S206 are steps for setting P2. When the flow shown in FIG. 10 is adopted, P2 is determined based on the determination results in steps S203 and S204 (the value of R2 and f FF (P1,SOC BAT If the process proceeds to step S205 as a result of the determination in steps S203 to S204, the power limit value (output limit value of generated power) P2 lim is set as P2 as it is, and if the process proceeds to step S206 as a result of the determination in steps S203 to S204, then f FF (P1,SOC BAT ) is set as P2. After setting P2 in steps S205 and S206, the process proceeds to step S207, where power P3 to be output from the BAT (secondary battery) 10 is calculated based on equation (15). That is, in step S207, power P3 to be output from the BAT (secondary battery) 10 is also calculated from the difference between P1 and P2. In this way, the calculation unit 142 can calculate power P2 to be output from the FC 11 and power P3 to be output from the BAT 10 with respect to the required power P1. Note that in the flow shown in FIG. 10, steps S203 and S204 are performed in this order, but the order of these steps is not particularly limited, and they may be performed in reverse or simultaneously.

[0067] Also, the parameter relation f for feedforward control FF (P1,SOC BATThe calculation method of the power allocation (power distribution ratio) that corrects whether or not the mass transport resistance R2 is used based on the magnitude of the mass transport resistance R2 is not limited to the above method, and other methods may be adopted. Preferred methods (embodiments) as such other methods will be described below with reference to examples. For convenience, the preferred methods as such calculation methods will be referred to as embodiments (A) to (E) below.

[0068] <Regarding another preferred embodiment of the calculation method (embodiment (A))> Another preferred embodiment of the calculation method is, for example, a parameter relational expression f that determines the optimum value of the power share P2 from the fuel cell and secondary battery according to the magnitude of the resistance R2 based on the relationship between the magnitude of the required power P1, the magnitude of the resistance R2, the output from the fuel cell, the output from the secondary battery, fuel efficiency, etc. FF An example of a method (embodiment (A)) is to obtain a map of correction ratios (relationship between R2 and C1) for correcting the value of R2 in advance, and then calculate the distribution of power from each battery (power distribution ratio) using the correction ratio C1 calculated from the map (relationship C1(R2)) according to the magnitude of the resistance R2.

[0069] When adopting the embodiment (A) using such a correction ratio map (correction map), it is preferable to calculate the power distribution (power distribution ratio) by, for example, calculating the power P2 (the amount of power distributed to FC11) based on one of the following equations (16) to (17) depending on the case, and then calculating the power P3 (the amount of power distributed to BAT10) using equation (18). In such a method, the threshold value R2 for switching control for the mass transport resistance R2 is set. th is calculated in advance, and the resistor R2 is set to the threshold R2 th If P2 is greater than , it is preferable to control P2 to the value calculated by the following formula (16), and otherwise to control the power allocation of each battery so that P2 is the value calculated by the following formula (17). A suitable example of a formula to be used when performing the calculation of embodiment (A) is shown below.

[0070] [R2>R2 thFormula for calculating power P2 when the condition is satisfied: P2 = C1(R2) × f FF (P1,SOC BAT ) (16) [Formula for calculating power P2 in other cases] P2=f FF (P1,SOC BAT ) (17) [Formula for calculating power P3 after calculating power P2] P3 = P1 - P2 (18).

[0071] In other words, embodiment (A) using such a correction ratio map is a method in which, in the calculation unit 142, based on the magnitude of material transport resistance R2, a correction ratio C1 is calculated from a pre-calculated correction map when R2 is greater than a threshold, and power P2 to be output from FC11 is calculated; when R2 is less than the threshold, power P2 to be output from FC11 is calculated based on a parameter relational expression for feedforward control, and power P3 to be output from the secondary battery is calculated from the difference between P1 and P2. When using such a correction ratio map, it is desirable to calculate relational expression C1(R2) so that the value of C1 decreases as the value of resistance R2 increases. This allows control so that power P2 decreases when R2 increases, and operation of FC11 in a range where power generation efficiency is low can be suppressed, resulting in greater benefits in terms of improving fuel efficiency. There are no particular limitations on the method for determining such relational expression C1 (R2). For example, a method may be adopted in which the relationship between R2 and fuel efficiency is experimentally obtained in advance, and the relational expression C1 that maintains a certain level of fuel efficiency or higher is experimentally determined.

[0072] <Regarding another preferred embodiment of the calculation method (embodiment (B))> In another preferred embodiment of the calculation method, for example, the resistor R2 is set to a threshold value R2 th If the resistance R2 is greater than the threshold R2, the power generation of the FC11 is stopped and the output power P2 is set to 0 (embodiment (B)).th It is preferable to calculate the power allocation by selecting the formula to be used from the following formulas (19) and (20) depending on whether the power distribution is greater than or equal to . A suitable example of the formula to be used when performing the calculation of embodiment (B) is shown below.

[0073] [R2>R2 th Formula for calculating power P2 when the condition is satisfied: P2=0 (19) [Formula for calculating power P2 in other cases] P2=f FF (P1,SOC BAT ) (20) [Formula for calculating power P3 after calculating power P2] P3 = P1 - P2 (21).

[0074] In addition, such embodiment (B) can be said to be a method of setting the output P2 from the fuel cell to 0 when R2 is greater than the threshold value, and operating the fuel cell intermittently or stopping it (when P2 is set to 0, P3 becomes equal to P1).

[0075] <Regarding another preferred embodiment of the calculation method (embodiment (C))> In another preferred embodiment of the calculation method, for example, a relational expression C2(R2) is calculated in advance to find an upper limit setting value C2 of power P2 that is determined in relation to R2 so that power P2 output from the fuel cell according to the magnitude of resistance R2 becomes an optimum value based on the relationship between the magnitude of required power P1, the magnitude of resistance R2, the output from the fuel cell, the output from the secondary battery, fuel efficiency, etc. When resistance R2 is larger than a threshold value, the upper limit setting value calculated by expression C2(R2) is adopted as P2, and when R2 is smaller than the threshold value, the upper limit setting value calculated by expression f FF (P1,SOC BAT ) and calculate P3 as the difference between P1 and P2 (embodiment (C)). When using the method described in embodiment (C), the resistor R2 is set to a value lower than the threshold R2 thIt is preferable to calculate the power allocation by selecting the formula to be used from the following formulas (22) and (23) depending on whether the power distribution is greater than . A suitable example of a formula to be used when performing the calculation of embodiment (C) is shown below.

[0076] [R2>R2 th Formula for calculating power P2 when the condition is satisfied: P2=C2(R2) (22) [Formula for calculating power P2 in other cases] P2=f FF (P1,SOC BAT ) (twenty three) [Formula for calculating power P3 after calculating power P2] P3=P1-P2 (24).

[0077] In addition, in equation (23), it is desirable to find a relational expression so that the larger R2 is, the smaller the calculated value of C2(R2) becomes. Also, in embodiment (C), equation C2(R2) is used to find the upper limit of power, but it is also desirable to find a relational expression that finds the upper limit of current or voltage based on R2, and use the data obtained from that equation to find the resistance R2 relative to the threshold R2 th If the value of P2 is larger than 1, the formula or control method may be modified to find P2.

[0078] <Regarding another preferred embodiment of the calculation method (embodiment (D))> Another preferred embodiment of the calculation method is, for example, to determine in advance a formula C3(R2) for determining a ratio C3 (where C3 satisfies the condition that C3 is 1 or less) that optimizes the power P2 output from the fuel cell according to the resistance R2, based on the relationship between the magnitude of the required power P1, the magnitude of the resistance R2, the output from the fuel cell, the output from the secondary battery, fuel efficiency, etc., and when the resistance R2 is greater than a threshold value, the value obtained by multiplying P1 by the ratio C3 determined by formula C3(R2) is adopted as P2, and when R2 is smaller than the threshold value, the value obtained by multiplying P1 by the ratio C3 determined by formula f FF (P1,SOC BAT), and then calculate P3 as the difference between P1 and P2 (embodiment (D)). If P2 is calculated by multiplying P1 by a ratio C3, P3 will be the same as P1 multiplied by (1-C3). A suitable example of an equation to be used when performing the calculation of embodiment (D) is shown below.

[0079] [R2>R2 th Formula for calculating power P2 when the condition is satisfied: P2 = P1 × C3(R2) (25) [Formula for calculating power P2 in other cases] P2=f FF (P1,SOC BAT ) (26) [Formula for calculating power P3 after calculating power P2] P3=P1-P2 (27) In addition, in equation (25), it is desirable to find a relational expression such that the larger R2 is, the smaller the calculated value of C3(R2) becomes.

[0080] <Regarding another preferred embodiment of the calculation method (embodiment (E))> Another preferred embodiment of the calculation method is, for example, to determine in advance a relational expression C4(R2) for determining a time constant C4 of a low-pass filter such that the power P2 output from the fuel cell according to the magnitude of the resistance R2 is an optimum value, based on the relationship between the magnitude of the required power P1, the magnitude of the resistance R2, the output from the fuel cell, the output from the secondary battery, fuel efficiency, etc., and when the resistance R2 is greater than a threshold value, the power P2 is calculated using a low-pass filter with a time constant C4 determined according to the resistance R2 when the required power P1 is input, and when R2 is smaller than the threshold value, the power P2 is calculated using the expression f FF (P1,SOC BAT ) and then calculate P3 as the difference between P1 and P2 (embodiment (E)). The formula used when performing the calculation of embodiment (E) is shown below.

[0081] [R2>R2 thFormula for calculating power P2 when the condition is satisfied: P2 = (calculated value of low-pass filter with time constant C4 (R2)) (28) [Formula for calculating power P2 in other cases] P2=f FF (P1,SOC BAT ) (29) [Formula for calculating power P3 after calculating power P2] P3 = P1 - P2 (30).

[0082] In equation (28), it is desirable to determine the relational expression so that the larger R2 is, the smaller the calculated value of C4(R2) becomes. The relational expression C4(R2) for determining such time constant C4 can be determined by experimental fitting during system design. There are no particular restrictions on the specific method of calculation using a low-pass filter; a known program for calculation using a low-pass filter may be used to calculate an optimal value as appropriate.

[0083] As described above, the parameter relation f for feedforward control has been explained by exemplifying the embodiments (A) to (E). FF (P1,SOC BAT Although a preferred embodiment of a method for calculating power allocation (power distribution ratio) that corrects whether or not the mass transport resistance R2 is used based on the magnitude of the mass transport resistance R2 has been described, the method for calculating such power allocation is not limited to the above method, and other methods can be appropriately adopted. Note that in the present invention, the power allocation calculation unit 142 may be configured as any device capable of performing such calculations, and may be configured, for example, as a computer or the like that includes a memory in which a program for performing the above calculations is stored.

[0084] While preferred embodiments of the configuration of the power supply system of the present invention have been described above using Figures 1 to 10, the power supply system of the present invention is not limited to the above embodiments and may include a power supply system having a fuel cell and a secondary battery as a power supply source for an electric load, the power supply system including: a power distribution control unit (A) that distributes the output power of each of the batteries to supply a required power P1 to the electric load; an impedance acquisition unit (B) that acquires an impedance R1 of the fuel cell at a plurality of different frequencies; and a calculation unit (C) that extracts a resistance R2 related to mass transport in the fuel cell based on data on the plurality of impedances R1 obtained by the impedance acquisition unit (B), and calculates, based on the magnitude of the resistance R2, the distribution of power (power distribution ratio) of each battery when the required power P1 is output from the power supply system to obtain the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; and the power distribution control unit (A) controls the distribution of power output from each battery so as to supply the required power P1 based on the calculation results of the calculation unit (C). For example, in the above embodiment, the parameter relation f for feedforward control is FF (P1,SOC BAT ), the power supply system of the present invention is not limited to the above embodiment. For example, the power supply system of the present invention may be configured in a manner similar to that of the embodiment described above. BAT and charge / discharge amount (△SOC BAT ) on the premise that control is performed based on feedback.

[0085] Next, a preferred embodiment of the method for controlling power distribution between a fuel cell and a secondary battery of the present invention will be described. The method for controlling power distribution between a fuel cell and a secondary battery of the present invention is a method for controlling power distribution between the fuel cell and the secondary battery in a power supply system including a fuel cell and a secondary battery as a power supply source for an electric load, in response to the power required by the electric load, and includes the following steps: an impedance acquisition step (S1) of acquiring an impedance R1 of the fuel cell at a plurality of different frequencies; a calculation step (S2) of extracting a resistance R2 related to material transport in the fuel cell based on the data of the plurality of impedances R1 obtained in the step (S1); a calculation step (S3) of calculating the power distribution (power distribution ratio) of each battery when the power required by the electric load P1 is output from the power supply system based on the magnitude of the resistance R2 calculated in the step (S2), thereby calculating the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; a power distribution control step (S4) of controlling the power output from each battery so that the power output from the fuel cell and the power output from the secondary battery are distributed to the power P2 and the power P3 calculated in the step (S3); The method is characterized by comprising:

[0086] A preferred embodiment of the power distribution control method of the present invention will be described below using an example in which the fuel cell system of the embodiment shown in Figure 1 is used. In the embodiment described below, it is assumed that the electric load is a hybrid vehicle and the control unit in Figure 1 is the ECU of the hybrid vehicle. That is, when a power supply system is used for a hybrid vehicle, a preferred embodiment of the power distribution control method of the present invention will be described below using an example in which the power required by the hybrid vehicle at a certain time t (required load: required power P1) is supplied from the FC 11 and the BAT 10. Note that the preferred embodiment of the power distribution control method of the present invention will be described below based on the flowchart shown in Figure 11.

[0087] FIG. 11 shows a preferred example (preferable embodiment) of the procedure for controlling the power distribution between the fuel cell and the secondary battery when the fuel cell system of the embodiment shown in FIG. 1 is used.

[0088] 11, first, in step S301, required power P1, which is data required to calculate the allocation of power output from each battery, is input to power allocation calculation unit 141. For example, when the electric load is a hybrid vehicle, such required power P1 may be obtained by detecting the accelerator opening, vehicle speed, etc., inputting the data to control unit 14 (ECU), and calculating the power P1 required to output the power required by the vehicle from the obtained data within control unit 14 (ECU).

[0089] Next, in step S302, the impedance acquisition unit 13 measures data on the impedance R1 at multiple frequencies to acquire multiple impedances R1 (this is a preferred embodiment of the impedance acquisition step (S1)). In this measurement, when the required power P1 is the required power of the hybrid vehicle at a certain time t, it is desirable to measure data on the impedance R1 at the same time, and it is desirable to perform steps S301 and S302 simultaneously. The multiple frequencies may be two or more different frequencies, and are not particularly limited. For example, two or more frequencies (more preferably, 6 to 30 frequencies) are desirable. Furthermore, the measurement of the impedance at multiple frequencies may be performed by a method of measuring impedance at multiple frequencies, for example, by measuring 10 points per decade in a frequency range of 1 to 1 kHz, or may be automated using commercially available software or the like. The method of measuring the impedance R1 is not particularly limited, and for example, an AC impedance method or the like may be adopted.

[0090] Next, after executing step S302, the process proceeds to step S303, where the acquired impedance R1 data for the multiple frequencies is input to the impedance analysis unit 13. In response to the input of this R1 data, the impedance analysis unit 13 extracts (calculates) the mass transport resistance R2 in step S304 (a preferred embodiment of the calculation step (S2)). The extraction of this resistance R2 is preferably performed by assuming an equivalent circuit and fitting the multiple impedance R1 data to the equivalent circuit (circuit parameter fitting) to determine the "mass transport resistance R2" of each component of the equivalent circuit. The aforementioned method for analyzing the impedance R1 data (the aforementioned method for determining R2) can be appropriately adopted to extract the resistance R2.

[0091] Next, after extracting the resistance R2, in step S305, the calculated value (extracted value) of the resistance R2 is input to the power allocation calculation unit 142. In response to the input of the data for R2, in step S306, the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery are calculated based on the magnitude of the resistance R2. That is, in step S306, based on the magnitude of the resistance R2 calculated in step S304, the power allocation (power allocation ratio: magnitude of P2 and P3) of each battery when the power required by the electrical load P1 is output from the power supply system is calculated, and the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery are determined (this is a preferred embodiment of the calculation step (S3)). Note that this calculation is not particularly limited, and the method described above in the "Method for calculating power allocation (power allocation ratio) corrected based on the magnitude of mass transport resistance R2" or the like can be appropriately adopted.

[0092] In this way, the power allocation (such as the ratio of P2) is corrected based on the magnitude of the resistance R2 (gas transport resistance) related to material transport. This is because, as is clear from the graph shown in Figure 9, fuel efficiency can be increased by suppressing the power (output power) shared by FC11 when resistance R2 is large (high), while setting a threshold value for resistance R2 makes it possible to efficiently avoid operation in a region where the voltage of FC11 drops, efficiently suppress voltage fluctuations that cause deterioration of FC11, and improve the durability of FC11. Furthermore, operating the system while correcting the power allocation (such as the ratio of P2) based on the magnitude of resistance R2 (gas transport resistance) in this way ultimately makes it possible to improve the fuel efficiency and durability of the entire system.

[0093] Furthermore, in step S306, after the power distribution calculation unit 142 calculates the magnitude of the power P2 and power P3 to be output from each battery, the process proceeds to step S307, where the calculated power distribution result is input to the power distribution control unit 12. Thereafter, upon receiving the input of this power distribution calculation result (for example, input of a control command value for outputting P2 and P3 calculated by calculation), in step S308, the power distribution control unit 12 controls the power output from each battery in accordance with the calculation result of the power distribution (the power P2 and the power P3) so that the power output by the FC (fuel cell) 11 and the power output by the BAT (secondary battery) 10 are distributed (this is a preferred embodiment of the power distribution control step (S4)). As a method for controlling the power output from FC11 and BAT10 in accordance with the calculation results of the power distribution (the power P2 and the power P3), other than using the calculation results, any known distribution control method employed in known power supply systems can be appropriately adopted.

[0094] A preferred embodiment of the power distribution control method of the present invention has been described above based on Figures 1 and 11, etc., but the power distribution control method of the present invention may be any method that includes the above steps (S1) to (S4), and is not limited to the above embodiment. [Example]

[0095] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0096] (Example 1 and Comparative Example 1) A power supply system including a fuel cell and a secondary battery was used as a power supply source. The system was operated under the WHVC (Worldwide Harmonized Vehicle Cycle) pattern, which is a pattern used to evaluate commercial vehicles. The relationship between fuel consumption and time was simulated (estimated) to evaluate the fuel economy of the system when each control method was adopted. The relationship between the electrochemical area and time was also simulated (estimated) using a specific degradation model, assuming that similar control (two different types of control) were performed. The electrochemical area of ​​the catalyst was calculated as an index of durability during driving under the WHVC pattern, and the durability of the system when each control method was adopted was evaluated. Each simulation method is described in detail below.

[0097] <Simulation of the relationship between fuel consumption and time for an electricity supply system> First, a simulation of the relationship between fuel consumption and time was performed using Comparative Example 1, which assumes that the control for distributing the required power (P1: required power) at time t between the power (P2) output from the fuel cell (FC) and the power (P3) output from the secondary battery (BAT) is performed using a conventional control method based on the following equations (I) to (III).

[0098] [Formula (I) for calculating P2(t) when the required power P1(t) at a certain time t satisfies the condition P1(t)>0] P2(t) = P1(t) × γa + (γb - SOC BAT (t))×γc (I) [Formula (II) for calculating P2(t) when P1(t) satisfies other conditions] P2(t)=0 (II) [Formula (III) for calculating P3(t)] P3(t) = P1(t) - P2(t) (III).

[0099] The power distribution control (Comparative Example 1) based on such equations (I) to (III) determines the distribution amount of power P2(t) at time (t) based on the magnitude of the required power P1(t) at that time (t) and the distribution ratio γa, while determining the remaining battery charge (SOC) at that time (t). BAT This is a general control method that uses power feedback to maintain the power consumption (t)) at γb, where γa to γc are adaptation coefficients, and similar coefficients were used in both the example and the comparative example (for the simulation, these coefficients were "γa: 0.7, γb: 50, γc: 0.8").

[0100] On the other hand, when the value of the mass transport resistance R2(t) at time t is large, the upper limit P2 of the power to be output from the fuel cell (FC) at that time t is set to a small value (the output power from the FC in the embodiment is denoted as "P2'(t)" for convenience). lim A simulation of the relationship between fuel consumption and time was performed using Example 1, which is an assumption that (t) is specified and control is performed using the following equations (IV) to (VII) (for convenience, the output power from the BAT in Example 1 is denoted as "P3'(t)").

[0101] [Upper limit P2 lim (t) Desired formula (IV)] P2 lim (t) = γd - (γe × R2(t)) (IV) [P2(t) calculated by the above formula (I) is P2 lim (t) is greater than (P2(t)>P2 lim (t) (if the condition (t) is satisfied) Formula (V) for calculating P2'(t) P2'(t)=P2 lim (t) (V) [P2(t) calculated by the above formula (I) is P2 lim (t) or less, formula (VI) for calculating P2'(t)] P2'(t)=P2(t) (VI) (P2(t) in formula (VI) is the value calculated by formula (I).) [Equation (VII) for determining P3'(t)] P3'(t) = P1(t) - P'2(t) (VII).

[0102] The power distribution control based on such equations (IV) to (VII) (used in Example 1) uses a limit value P2 that is linearly calculated based on the magnitude of the mass transport resistance R2(t) at that time (t). lim (t) (in other words, the limit value P2 obtained linearly based on equation (IV) as a function of the mass transport resistance R2(t) at time (t) lim In other words, the power distribution control based on equations (IV) to (VII) employed in Example 1 is a control that utilizes mass transport resistance R2(t) to correct the conventional control method (the control method of Comparative Example 1) performed using equations (I) to (III). Here, γd and γe are adaptation coefficients (these coefficients were adopted as "γd: 67, γe: -5" in the simulation).

[0103] In Example 1 (power distribution control based on formulas (IV) to (VII)) and Comparative Example 1 (power distribution control based on formulas (I) to (III)), a WHVC (Worldwide harmonized vehicle cycle) pattern, which is an evaluation pattern for commercial vehicles, was used, and the remaining battery charge (SOC) before and after the simulation was measured to fairly compare the differences in control. BAT ) to match the initial SOC BATBy adjusting the magnitude of and performing the control as described above, graphs (time series charts) showing the relationship between time and P1(t); R2(t); P2(t); P2'(t); P3(t); P3'(t); fuel cell (FC) current (FC current (t)); fuel cell (FC) voltage (FC voltage (t)); and the accumulated amount of fuel consumption (fuel consumption (t)) were obtained by simulation.

[0104] In this simulation, the required power P1(t) is calculated by multiplying the running resistance under vehicle conditions assuming a typical bus by the WHVC vehicle speed pattern, and the mass transport resistance R2(t) is assumed to be a value generated by a random walk function. BAT The change in (t) was calculated by dividing the integrated value of P3 (or P3') by the battery capacity. The fuel cell (FC) current (FC current (t)) and fuel cell (FC) voltage (FC voltage (t)) were assumed to have the characteristics shown in Figure 9, and the fuel consumption (t) was calculated by multiplying the fuel cell current by the number of layers and dividing by Faraday's constant. The results obtained from this simulation are shown in Figure 12.

[0105] 12(a) shows a graph (time series chart) of the relationship between P1(t) and time, FIG. 12(b) shows a graph (time series chart) of the relationship between R2(t) and time, FIG. 12(c) shows a graph (time series chart) of the relationship between P2(t) and P2'(t) and time, FIG. 12(d) shows a graph (time series chart) of the relationship between P3(t) and P3'(t) and time, FIG. 12(e) shows a graph (time series chart) of the relationship between FC current(t) and time, FIG. 12(f) shows a graph (time series chart) of the relationship between FC voltage(t) and time, and FIG. 12(d) shows a graph (time series chart) of the relationship between the integrated amount of fuel consumption (fuel consumption amount(t)) and time.

[0106] <Durability simulation> Next, we evaluated the durability of the WHVC pattern during driving using a fuel cell (FC) degradation model (a degradation model that predicts changes in the particle number and particle size distribution of catalyst particles supported on the cathode) described in Reference 1 (Darling, RM and JP Meyers, “Kinetic model of platinum dissolution in PEMFCs”, Journal of the Electrochemical Society, 2003, 150(11), A1523-A1527) and Reference 2 (Shinobu Sekine et al., “PtCo Catalyst Dissolution and Oxidation Modeling for Durability Improvement of Automotive Fuel Cell” ECS transaction, 2020). For this evaluation, the electrochemical area of ​​the catalyst was calculated by summing the total particle surface area per unit electrode area based on the particle number and particle size distribution predicted by the degradation model for each case where the fuel cell (FC) current and voltage were controlled over time as shown in Figure 12 (for each of Example 1 and Comparative Example 1) while the load fluctuations were changed by running the WHVC pattern. Here, the catalyst degradation parameters were calculated using the values ​​described in Reference 2. It is known that the durability of a fuel cell (FC) is largely determined by catalyst degradation, which is determined by a decrease in the electrochemical area of ​​the catalyst used in the cathode. Therefore, it is clear that durability can be evaluated by comparing the electrochemical area predicted using the FC degradation models described in References 1 and 2. Therefore, to compare the electrochemical areas predicted by the degradation models, the relationship between the size of the catalyst electrochemical area and time was determined for each of the control cases of Example 1 and Comparative Example 1. A graph showing the relationship between the electrochemical area of ​​the catalyst (an index of degradation) and time obtained in this way is shown in Figure 13.

[0107] 13, the electrochemical area volume corresponding to the life of a fuel cell used in a vehicle (assuming the amount generally considered to be the life of a fuel cell) is shown by a dashed-dotted line. The time at which the electrochemical areas of the fuel cells of Example 1 and Comparative Example 1 intersect with the dashed-dotted line in the figure was determined as the endurance time. That is, the time at each of the intersection points (D) of the dashed-dotted line in the figure with the graph of the electrochemical area volume when control of Comparative Example 1 (conventional control) was performed, and the intersection point (D') of the dashed-dotted line in the figure with the graph of the electrochemical area volume when control of Example 1 was performed was determined as the endurance time.

[0108] [Simulation results] FIG. 14 shows a graph showing the magnitude of the reciprocal of the accumulated amount of fuel consumption (accumulated amount) of Example 1 when the reciprocal of the accumulated amount calculated in Comparative Example 1 is set to 1 for the fuel consumption (accumulated amount) shown in FIG. 12, and a graph showing the magnitude of the endurance time of Example 1 when the endurance time of Comparative Example 1 shown in FIG. 13 is set to 1.

[0109] As is clear from the results shown in Fig. 14, Example 1 (an example employing the power distribution control method of the present invention) improves fuel efficiency by 1.1 times and durability by 3 times compared to Comparative Example 1 (an example employing a conventional power distribution control method). When examining this point using the time series chart shown in Fig. 12, in Example 1, as is clear from the above control equation, the power output from the fuel cell (FC power) P'2(t) is controlled as shown in Fig. 12(c), and the power output from the secondary battery (BAT power) P'3(t) is controlled as shown in Fig. 12(c), based on the magnitude of P1(t) shown in Fig. 12(a) and R2(t) shown in Fig. 12(b). On the other hand, in Comparative Example 1, the FC power and BAT power are controlled regardless of the magnitude of R2(t), and FC power P2(t) is controlled as shown in Fig. 12(c), and BAT power P3(t) is controlled as shown in Fig. 12(c). Here, compared to Comparative Example 1 (which employs a conventional control method), in Example 1 (which employs the power distribution control method of the present invention), the magnitude of FC power P'2(t) is limited when R2 is a high value (see FIGS. 12(b) and 12(c)). As a result, it can be seen that the fuel cell current (FC current) is suppressed when R2 is a high value (FIG. 12(e)), and fluctuations in fuel cell voltage are reduced (FIG. 12(f)). From the results shown in FIG. 12, it can be seen that, according to the control method employed in Example 1, the amount of power generated by the FC (FC operation) is controlled at the timing (operating point) when the power generation efficiency of the fuel cell (FC) becomes low (because control is performed to avoid FC operation in a region where resistance R2 is large and power generation efficiency becomes low), and therefore, the amount of fuel consumed (integrated value) after driving is reduced compared to Comparative Example 1 (conventional control) (FIG. 12(g)). Furthermore, since the amount of power generated by the fuel cell (FC) is controlled at the timing (operating point) when the power generation efficiency of the FC becomes low, in Example 1, the fluctuations in FC voltage that cause deterioration of the fuel cell are controlled to be less than in the comparative example, and it is believed that durability has been improved by three times. [Industrial Applicability]

[0110] As described above, the present invention provides a power supply system that controls power distribution between a fuel cell and a secondary battery to more reliably improve fuel efficiency and durability, and a method for controlling power distribution between a fuel cell and a secondary battery in a power supply system that more reliably improves fuel efficiency and durability of the power supply system. Therefore, the power supply system of the present invention is useful as a power supply source for supplying power to electrical loads such as motors of electric mobility vehicles that have large load fluctuations. [Explanation of symbols]

[0111] 10... Secondary battery (BAT), 11... Fuel cell (FC), 12... Power distribution control unit, 13... Impedance acquisition unit, 14... Control unit (having a calculation unit (C)), 141... Impedance analysis unit, 142... Power distribution calculation unit.

Claims

1. A power supply system including a fuel cell and a secondary battery as a power supply source for an electrical load, a power distribution control unit (A) that distributes the output power of each of the batteries in order to supply the required power P1 to the electrical load; an impedance acquisition unit (B) for acquiring an impedance R1 of the fuel cell at a plurality of different frequencies; a calculation unit (C) that extracts a resistance R2 related to material transport in the fuel cell based on data on the plurality of impedances R1 obtained by the impedance acquisition unit (B), and calculates the distribution of power among the cells when the required power P1 is output from the power supply system based on the magnitude of the resistance R2, thereby determining the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; and the power distribution control unit (A) controls the distribution of power output from each battery based on the calculation result of the calculation unit (C); A power supply system characterized by:

2. The power supply system of claim 1, characterized in that when extracting the resistance R2 related to material transport in the fuel cell, an equivalent circuit is assumed and the resistance R2 related to material transport is determined based on data on multiple impedances R1.

3. A method for controlling power distribution among fuel cells and secondary batteries in a power supply system having a fuel cell and a secondary battery as power supply sources for an electric load, with respect to a required power P1 of the electric load, comprising: an impedance acquisition step (S1) of acquiring an impedance R1 of the fuel cell at a plurality of different frequencies; a calculation step (S2) of extracting a resistance R2 related to material transport in the fuel cell based on the data of the plurality of impedances R1 obtained in the step (S1); a calculation step (S3) of calculating the distribution of power among the cells when the power required by the electrical load P1 is output from the power supply system based on the magnitude of the resistance R2 calculated in the step (S2), thereby calculating the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; a power distribution control step (S4) of controlling the power output from each battery so that the power output from the fuel cell and the power output from the secondary battery are distributed to the power P2 and the power P3 calculated in the step (S3); 1. A power distribution control method for a fuel cell and a secondary battery in a power supply system, comprising:

4. The power distribution control method according to claim 3, characterized in that in the calculation step (S2) of extracting the resistance R2 related to material transport in the fuel cell, an equivalent circuit is assumed and the resistance R2 related to material transport is calculated based on data on multiple impedances R1.

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