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

Abstract

This power supply system is provided with a fuel cell (11) and a secondary battery (10) as power supply sources. The power supply system comprises: a power distribution control unit (A) (12) for distributing the output power of each of the batteries in order to supply required power P1 to an electric load; an impedance acquisition unit (B) (13) for acquiring an impedance R1 at a plurality of frequencies for the fuel cell (11); and an arithmetic unit (C) for extracting a material transport resistance R2 of the fuel cell (11) on the basis of the specific impedance R1, and performing a specific calculation based on the magnitude of the resistance R2 to obtain power P2 to be supplied by the fuel cell (11) and power P3 to be supplied by the secondary battery (10). The power distribution control unit (A) controls the output of each of the batteries on the basis of the calculation result of the arithmetic unit (C).

Description

Power supply system and power distribution control method for fuel cells and secondary batteries in the power supply system

[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.

[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 deterioration in their current-voltage characteristics (IV characteristics). Such fuel cell degradation is primarily caused by fluctuations in the fuel cell's voltage. Therefore, when fuel cells are used for 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 the power between the fuel cell and the secondary battery is a particularly important issue from the perspective of improving the fuel efficiency (fuel efficiency) 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 from the secondary battery, and as a result, the fuel efficiency and durability of the power supply system (hybrid power supply system) are reduced. 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 allocating (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 allocating (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 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 for 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.

[0006] JP 2007-324140 A

[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. In this way, 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.

[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, when measuring the power generation resistance at startup, the impedance value at a single frequency is measured 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, it is possible to obtain the impedance R1 of the fuel cell at a plurality of different frequencies, extract the resistance R2 related to material transport in the fuel cell (material transport resistance R2) based on the data on the plurality of impedances R1, and use this material transport resistance R2 as data indicating the internal state of the fuel cell, and in a power supply system comprising a fuel cell and a secondary battery as a power supply source to an electrical load, correct the ratio (distribution ratio) of the power that each battery should share with respect to the required power based on this resistance R2, and control the power output from each battery based on this corrected value (corrected distribution ratio), thereby more reliably improving 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 comprising a fuel cell and a secondary battery as a power supply source for an electric load, the power supply system comprising: a power distribution control unit (A) that distributes the output power of each of the batteries in order to supply a required power P1 to the electric load; an impedance acquisition unit (B) that acquires an impedance R1 for the fuel cell at a plurality of different frequencies; and 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, based on the magnitude of the resistance R2, a power distribution ratio for each battery 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 wherein the power distribution control unit (A) controls the distribution of power output from each battery based on the calculation results of the calculation unit (C).

[0013] [2] A power supply system as described in [1], in which 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] A method for controlling power distribution among the cells in a power supply system having a fuel cell and a secondary battery as a power supply source for an electric load in response to a power P1 required by the electric load, comprising: an impedance acquisition step (S1) of acquiring an impedance R1 for 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 data on the plurality of impedances R1 obtained in the step (S1); a calculation step (S3) of calculating a power distribution (power distribution ratio) among the cells when the power required by the electric load P1 is output from the power supply system based on the magnitude of the resistance R2 obtained in the step (S2), thereby determining the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; and a power distribution control step (S4) of controlling the power output from the cells so that the power output by the fuel cell and the power output by the secondary battery are distributed to the power P2 and the power P3 obtained 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.

[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.

[0017] 7 is a block diagram schematically illustrating a preferred embodiment of the configuration of a power supply system of the present invention. It is a graph of typical impedance of a fuel cell, which is a Bode plot consisting of a graph (solid line) showing the relationship between the logarithm of frequency and the impedance absolute value, and a graph (dotted line) showing the relationship between frequency and phase. It is a graph of typical impedance of a fuel cell, which is a Nyquist diagram consisting of a graph showing the relationship between the real component Zre and the imaginary component Zim of the impedance. It is a diagram of a series circuit, which is one form of an equivalent circuit of a fuel cell. It is a diagram of a parallel circuit, which is one form of an equivalent circuit of a fuel cell. It is a flowchart showing an embodiment of a procedure (flow) that can be suitably adopted as a method for extracting mass transport resistance R2. It is a graph showing an example of a Nyquist diagram of impedance for each magnitude of mass transport resistance (gas transport resistance). It is a graph of a distributed relaxation time (DRT) waveform obtained by performing DRT analysis on the Nyquist diagram of FIG. 7. It is a graph showing the relationship between gas transport resistance (R2) of a fuel cell and current-voltage characteristics. It is a flowchart showing an embodiment of a procedure (flow) for calculation in a power distribution calculation unit. It is a flowchart showing an embodiment of a procedure (flow) for controlling power distribution between a fuel cell and a secondary battery. 12A and 12B are graphs (time series charts) 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, where FIG. 12A is a graph showing the relationship between P1(t) and time, and FIG. 12B is a graph showing the relationship between R2(t) and time. 12(c) is a graph showing the relationship between P2(t) and P2'(t) and time, FIG. 12(d) is a graph showing the relationship between P3(t) and P3'(t) and time, FIG. 12(e) is a graph showing the relationship between FC current (t) and time, FIG. 12(f) is a graph showing the relationship between FC voltage (t) and time, and FIG. 12(d) is a graph showing the relationship between the integrated amount of fuel consumption (fuel consumption (t)) and time.

[0043] FIG. 12 is a graph showing the relationship between the electrochemical area (indicator of deterioration) of the catalyst and time, as determined by simulation in Example 1 and Comparative Example 1.1 is a graph comparing fuel efficiency and durability of Example 1 and Comparative Example 1 (a graph of relative evaluation in which the simulation value of Comparative Example 1 is set to 1);

[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) illustrating a preferred embodiment of the configuration of a power supply system of the present invention. The power supply system of the embodiment illustrated 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 to an external electrical load (not shown) so as to supply power to the external electrical load. Such a power supply system can be applied, for example, to an electric vehicle or a ship powered by a fuel cell. The electrical load to which power is supplied may be any device that operates when supplied with voltage (electric power), and is not particularly limited.

[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, and in the present invention, the power distribution control unit 12 is a device that controls the output from 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 result 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 usable for controlling the distribution of the output power of BAT 10 and FC 11 to be supplied to an electrical load (for example, a motor, etc.) 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 the BAT 10 and the 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 is capable of acquiring the impedance R1 of the FC11 at multiple (at least two or more) different frequencies, and any known impedance measurement means can be used as appropriate. For example, if the FC11 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 a gas flow path, an impedance measurement device connected in parallel to the FC stack may be used as the impedance acquisition unit 13. Also, any known impedance measurement means, such as a device that measures impedance using an AC impedance method, may be used as appropriate. Furthermore, even without 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) may be used as the impedance acquisition unit 13. As described above, the configuration of the impedance acquisition unit 13 is not particularly limited, and its design 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 a resistance R2 related to material transport in the fuel cell based on data on the impedance R1 at a plurality of different frequencies obtained by the impedance acquisition unit 13, and calculates, based on the magnitude of the resistance R2, the power distribution (power distribution ratio) of each battery when the required power P1 is output from the power supply system, thereby calculating the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery. This 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 the power distribution calculation unit 142 in the control unit 14 constitute the calculation means (calculation unit (C)) that performs the calculation to determine the material transport resistance R2.

[0025] The impedance analysis unit 141 analyzes the impedance R1 data 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 impedance analysis method for determining the material transport resistance R2 will be described later. Furthermore, the power allocation calculation unit 142 calculates the power allocation (power allocation ratio) of each battery when the power supply system outputs the power P1 required by the external load 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 calculation method 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 so that the power distribution control unit 12 (power distribution control unit (A)) can allocate the output power of each battery according to the calculation result. Since the 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), it 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 to perform various calculations required for control (such programs may be recorded in the ROM or may be recorded 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] <Regarding 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 resistance R2 related to material transport in the FC11 (material transport resistance: reaction resistance related to material transport: gas transport resistance).

[0029] Typical impedance graphs obtained for a fuel cell when the impedance R1 is measured 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 (e.g., data such as those shown in Figures 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, ｏｈｍ denotes the DC resistance, and R ｃｌ denotes the charge transfer resistance, and C ｃｌ represents the electric double layer capacitance (electric double layer capacitor: capacitance), R2 represents 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 FIGS. 4 and 5 has the following characteristics: C 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 depending on 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 by assuming such an equivalent circuit, it is preferable to perform parameter fitting of each resistance component, etc., from the 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 group 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 data on the measured impedance R1, and extracting the resistance (mass transport resistance) R2 related to the mass transport of 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 data on the impedance R1 is clear, an equivalent circuit can be set, and commercially available software or the like 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. Furthermore, prior to this extraction of the resistance R2, it is necessary to measure the frequency f at N points (N is a natural number of 2 or more) different frequencies. ｎ (n is a natural number from 1 to N), impedance R1 ｎ(n is a natural number from 1 to N) data is measured and used. ｎ The measured impedance at ｎ (n is f ｎ and R1 ｎ (The same value is obtained for both.)

[0035] f ｎ = f １ , f ２ , f ３ ...f Ｎ R1 ｎ = R1 １ , R1 ２ , R1 ３ ...R1 Ｎ .

[0036] In the flowchart shown in FIG. 6, first, in step S101, a set of parameters (parameter set) P determined from an 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 FIG. 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]

[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 (fｎ = f １ , f ２ , f ３ ...f Ｎ ) R1n (R1n = R1 １ , R1 ２ , R1 ３ ...R1 Ｎ ) to calculate the cost function J based on the root mean square error. ｃｏｓｔ (f ｎ , P) is calculated by the following calculation formula (2):

[0041]

[0042] The formula is expressed by the following formula. 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 The following conditions are met: C ｍｔ >C ｃｌ The set of such parameters P is determined within a range that satisfies the following formula (3):

[0044]

[0045] Then, in step S104, the mass transport resistance R2 can be obtained by extracting the mass transport resistance R2 from the set of the obtained parameters P.

[0046] The above describes a preferred 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 used as appropriate.

[0047] Another suitable method for determining the mass transport resistance R2 is to use the relaxation time distribution (DRT) analysis method to determine the mass transport resistance (reaction resistance related to mass transport) from measurements of impedance R1 at multiple different frequencies. Examples of such a DRT analysis method include known methods (such as the method 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, FIG. 7 shows an example of Nyquist diagrams obtained by measuring impedance R1 at multiple different frequencies at a time when it can be determined that gas transport is inhibited and mass transport resistance (gas transport resistance) is increasing, a time when gas transport is not inhibited and mass transport resistance is decreasing, and intermediate times. FIG. 8 shows the DRT waveforms obtained by performing a distribution of relaxation times (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 performed 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. The peaks on the high frequency side of FIG. 8 correspond to the charge transfer resistance R ｃｌ This is the peak for.

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

[0049] <Calculation of power allocation (power allocation ratio) for each battery> Here, a method will be described in which the power allocation calculation unit 142 of the calculation unit 14 calculates the power allocation (power allocation ratio) for 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] Taking the example of a power supply system 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 secondary 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). When supplying power from the FC 11 and the BAT 10 to the electrical load, it is preferable to maximize the power generation efficiency of the FC 11 and restrict the power distribution of the BAT 10 to optimize the supply, from the viewpoint of improving system efficiency and durability. Various methods for optimizing power distribution (power distribution control methods) and power distribution control programs for implementing these methods have been studied.

[0051] In the present invention, when performing such power distribution, the distribution ratio (the proportion of output shared by each battery) is calculated by correcting it with the mass transport resistance R2 extracted (calculated) as described above, thereby achieving improved fuel efficiency and durability. Correction of the distribution ratio using such 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 FC11 and BAT10.

[0052] Generally, in order to use the FC11 with maximum efficiency, it is preferable to generate power at an operating point that maximizes the system efficiency. However, once the current-voltage characteristics (IV characteristics) of the fuel cell are determined, the output power P2 is uniquely determined, and the difference from the required power P1 will increase or decrease the power P3 output from the BAT10. However, if the output power P2 is uniquely determined in this way, the number of times the BAT10 is charged and discharged will increase, resulting in a decrease in the system efficiency. Furthermore, the BAT10 needs to calculate 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 BAT 10 during use ＢＡＴ Therefore, in the past, when controlling the power distribution, it was necessary to consider the remaining energy (SOC) of the BAT 10 during use, assuming how the system would be used when the electric load was actually operating. ＢＡＴ ) and the like are preferably adopted. For example, a relational expression for feedforward control (power distribution parameter expression: P1 and SOC ＢＡＴ The formula f is a function ＦＦ (P1, SOC ＢＡＴ )) and used it for control.ＦＦ (P1, SOC ＢＡＴ ) The optimal formula can be determined by a known method (for example, the method described in JP-A-2020-147256) 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 (remaining energy amount of BAT at a certain time t) is a function, for example, the following formula (10-1): f ＦＦ (P1, SOC ＢＡＴ )=P1×γ1+(γ2−SOC ＢＡＴ )×γ3 (10-1) Note that this control formula determines the amount of P2 distributed based on P1 at a certain time and the distribution ratio γ1, while calculating the remaining battery charge (SOC ＢＡＴ This is general control that performs power feedback to maintain a specific value γ2, where γ1 to γ3 are all adaptation coefficients. Such adaptation coefficients can be appropriately determined using a known method (general method) when performing general control based on the above-mentioned formula (10-1) (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 with respect 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, when resistance R2 is large, it is preferable to control P2 to be small. This is because by suppressing the power P2 shared by FC11 when resistance R2 is large, it is possible to avoid operation of FC11 in a region where 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 in this manner, it is possible to avoid operation of FC11 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 graph shown in FIG. 9, the magnitude of R2 increases in the order of 1 to 4, with graph 1 representing the case where R2 is minimum and graph 4 representing the case where R2 is maximum. As shown in FIG. 9, when the resistance R2 is large, the voltage of the 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 large, 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 f ＦＦIt is preferable to employ a calculation method for power allocation (power distribution ratio) that corrects the use or non-use of mass transport resistance R2 based on the magnitude of 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 mass transport resistance R2 determined by impedance analysis is greater than a specific threshold. A preferred method for limiting power P2 when 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 value R2 for switching control of mass transport resistance R2 is set. ｔｈ is calculated in advance, and the resistance R2 is set to the threshold value R2 ｔｈ is greater than 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 met: P2 = P2 ｌｉｍ (13) [Formula for calculating power P2 in other cases] P2 = f ＦＦ (P1, SOC ＢＡＴ ) (14) [Formula for finding P3 after finding 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 the FC11 can be suppressed, thereby avoiding operation of the FC11 in a region where the resistance R2 is large and power generation efficiency is low, thereby making it possible to increase 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 the FC11 in a region where the voltage drops, making it possible to efficiently suppress voltage fluctuations that cause deterioration of the FC11 and thereby improving the durability of the system.

[0061] Here, the power allocation calculation unit 142 of 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 employing a known method (for example, the method described in JP 2020-147256 A). In addition, the remaining energy (SOC) of the BAT 10 is calculated.ＢＡＴ ) can be obtained by, for example, separately providing a remaining amount 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, 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 amount), and constructing a system so that the data quantified by the remaining amount quantification means is input to the power distribution calculation unit 142, and the power distribution calculation unit 142 automatically calculates the remaining amount 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 obtained 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 obtaining 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 R2 may be set appropriately according to the specifications of the fuel cell, and the setting method is not particularly limited. ｔｈ <{(0.8 / current)-R ｏｈｍ -R ｃｌ It is preferable to appropriately set the range so as to satisfy the following condition: R2 ｔｈ <{(0.4 / current)-R ｏｈｍ -R ｃｌ} In step S203, the resistor R2 is set to a value that satisfies the threshold value R2 ｔｈ If the resistance R2 is greater than the threshold 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 areＢＡＴ Based on the data, the relation f for feedforward control is ＦＦ (P1, SOC ＢＡＴ ) is calculated, and 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 Japanese Patent Application Laid-Open No. 2020-147256). The power limit value P2 is the upper limit of the current power generation power, which is determined by calculating various parameters indicating the current state of the FC11. ｌｉｍ Furthermore, from the viewpoint of improving durability and fuel economy, the power limit value P2 ｌｉｍ is expressed as the following equation (13-1) using R2 as a function: P2 ｌｉｍ (R2) = γ4 - (γ5 × R2) (13-1) where γ4 and γ5 are compatibility coefficients, which can be determined appropriately by using a known method (for example, the method described in JP 2020-147256 A). ＦＦ (P1, SOC ＢＡＴ ) is the power limit value P2 ｌｉｍ If it is greater than (for example, a value linearly determined based on the above formula (13-1)), the process proceeds 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] 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 ＢＡＴIf the process proceeds to step S205 as determined in steps S203 and 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 and 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 manner, 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 in response 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 is not particularly limited, and these steps may be performed in reverse or simultaneously.

[0067] Also, the parameter relation f for feedforward control ＦＦ (P1, SOC ＢＡＴ The calculation method for 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 used. Preferred methods (embodiments) as such other methods are described below using examples. For convenience, these preferred methods are hereinafter referred to as embodiments (A) to (E).

[0068] <Regarding another preferred embodiment of the calculation method (embodiment (A))> As another preferred embodiment of the calculation method, for example, a parameter relational expression f is calculated 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, and fuel efficiency, etc., so that the power share P2 from the fuel cell and the secondary battery becomes an optimal value according to the magnitude of the resistance R2. ＦＦA method (embodiment (A)) can be exemplified in which a map of correction ratios (relationship between R2 and C1) for correcting the value of R2 is obtained in advance, and the allocation of power from each battery (power distribution ratio) is calculated using a correction ratio C1 calculated from the map (relationship C1(R2)) according to the magnitude of resistance R2.

[0069] When adopting the embodiment (A) using such a correction ratio map (correction map), it is preferable to use a method for calculating the power distribution (power distribution ratio) in which, for example, power P2 (the amount of power distributed to FC11) is calculated based on one of the following formulas (16) to (17) depending on the case, and then power P3 (the amount of power distributed to BAT10) is calculated using formula (18). In such a method, the threshold value R2 for switching control for the mass transport resistance R2 is set to ｔｈ is calculated in advance, and the resistance R2 is set to the threshold value R2 ｔｈ If the power consumption of each battery is greater than 100%, it is preferable to control P2 so that it becomes the value calculated by the following formula (16), and otherwise control the power consumption of each battery so that P2 becomes 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 ｔｈ Formula for calculating power P2 when the condition is satisfied: P2 = C1 (R2) x f ＦＦ (P1, SOC ＢＡＴ ) (16) [Formula for calculating power P2 in other cases] P2 = f ＦＦ (P1, SOC ＢＡＴ ) (17) [Formula for finding P3 after finding power P2] P3 = P1 - P2 (18).

[0071] In other words, embodiment (A) using such a correction ratio map is a method in which the calculation unit 142 calculates the correction ratio C1 from a pre-calculated correction map based on the magnitude of material transport resistance R2 when R2 is greater than a threshold value, thereby calculating the power P2 to be output from the FC11; when R2 is less than the threshold value, the calculation unit 142 calculates the power P2 to be output from the FC11 based on a parameter relational expression for feedforward control, and then calculates the power P3 to be output from the secondary battery from the difference between P1 and P2. When using such a correction ratio map, it is desirable to calculate the 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, thereby suppressing operation of the FC11 in a range where power generation efficiency is low, 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 relational expression C1 that maintains a certain level of fuel efficiency or higher is experimentally determined.

[0072] <Another Preferred Embodiment of the Calculation Method (Embodiment (B))> In addition, as another preferred embodiment of the calculation method, for example, 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 an equation to be used from the following equations (19) and (20) depending on whether the power distribution is greater than or equal to 1. A suitable example of an equation 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 finding P3 after finding 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))> Another preferred embodiment of the calculation method is, for example, to obtain a relational expression C2(R2) for obtaining an upper limit setting value C2 of power P2, which is obtained in advance in relation to R2, so that power P2 to be output from the fuel cell becomes an optimum value according to the magnitude of resistance R2, from the relationships 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., and when resistance R2 is larger than a threshold value, the upper limit setting value obtained by expression C2(R2) is adopted as P2, and when R2 is smaller than the threshold value, 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 equal to or larger than the threshold R2 ｔｈ It is preferable to calculate the power allocation by selecting an equation to be used from the following equations (22) and (23) depending on whether the power distribution is greater than or equal to . A suitable example of an equation 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 ) (23) [Formula for finding P3 after finding power P2] P3 = P1 - P2 (24).

[0077] In addition, in the formula (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 the embodiment (C), the formula C2(R2) for finding the upper limit of the power is used, but it is also desirable to find a relational expression so that the upper limit of the current or voltage can be found based on R2, and from the data obtained from that formula, it is possible 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))> As another preferred embodiment of the calculation method, for example, a formula C3(R2) is calculated in advance to find a ratio C3 (where C3 satisfies the condition that C3 is 1 or less) that will optimize the power P2 output from the fuel cell depending on 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 calculated by formula C3(R2) is used as P2, and when R2 is smaller than the threshold value, the value obtained by multiplying P1 by the ratio C3 calculated by formula f ＦＦ (P1, SOC ＢＡＴ ) and then calculate P3 as the difference between P1 and P2 (embodiment (D)). Note that if P2 is calculated by multiplying P1 by the ratio C3, P3 will be the same as P1 multiplied by (1-C3). A suitable example of a formula 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 P3 after calculating power P2] P3 = P1 - P2 (27) In addition, in formula (25), it is desirable to determine the relational formula so that the calculated value of C3(R2) becomes smaller as R2 becomes larger.

[0080] <Regarding another preferred embodiment of the calculation method (embodiment (E))> As another preferred embodiment of the calculation method, for example, a relational expression C4(R2) for finding a time constant C4 of a low-pass filter that optimizes the power P2 output from the fuel cell according to the resistance R2 is previously determined from 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 found 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 ｔｈ Formula for calculating power P2 when the condition that P2 = f 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 finding P3 after finding 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. The specific method of calculation using a low-pass filter is not particularly limited, and it is sufficient to apply a known program or the like for calculation using a low-pass filter so that an optimal value can be calculated 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 ＢＡＴAlthough a preferred embodiment of a method for calculating a 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 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; a power distribution control unit (A) that distributes the output power of each of the batteries in order 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 material 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 of each battery when the required power P1 is output from the power supply system (power distribution ratio), thereby determining the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; and wherein 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, and may be any other system that controls power distribution based on, for example, a measured SOC ＢＡＴ and charge / discharge amount (△SOC ＢＡＴ ) and control the power distribution on the premise that control is performed based on feedback.

[0085] Next, a preferred embodiment of the power distribution control method for fuel cells and secondary batteries according to the present invention will be described. The power distribution control method for a fuel cell and a secondary battery of the present invention is a method for controlling power distribution among the cells in a power supply system equipped with a fuel cell and a secondary battery as a power supply source for the electric load, for controlling power distribution among the cells in response to the power required by the electric load, and includes: an impedance acquisition step (S1) of acquiring an impedance R1 for 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 data on the plurality of impedances R1 obtained in step (S1); a calculation step (S3) of calculating a power distribution (power distribution ratio) among the cells when the power required by the electric load P1 is output from the power supply system based on the magnitude of the resistance R2 obtained in step (S2), thereby determining the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; and a power distribution control step (S4) of controlling the power output from the cells so that the power output by the fuel cell and the power output by the secondary battery are distributed to the power P2 and the power P3 obtained in step (S3). The method includes:

[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 electrical 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, the 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, if the electrical load is a hybrid vehicle, required power P1 may be determined by detecting the accelerator opening, vehicle speed, etc., inputting the data to control unit 14 (ECU), and calculating 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, if 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. Here, the multiple frequencies may be two or more different frequencies, and are not particularly limited. For example, it is desirable to use two or more frequencies (more preferably, 6 to 30 frequencies). 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)). 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 resistance R2 is input to the power allocation calculation unit 142. In response to the input of the R2 data, 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 supply system outputs the required power P1 of the electrical load 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" and the like can be appropriately adopted.

[0092] In this manner, the power allocation (e.g., 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 efficiently avoids operation in a region where the voltage of FC11 drops, efficiently suppressing voltage fluctuations that would cause deterioration of FC11, and improving the durability of FC11. Furthermore, operating the system while correcting the power allocation (e.g., the ratio of P2) based on the magnitude of resistance R2 (gas transport resistance) in this manner ultimately makes it possible to improve the fuel efficiency and durability of the entire system.

[0093] Furthermore, after the power distribution calculation unit 142 calculates the magnitudes of the power P2 and power P3 to be output from each battery in step S306, 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 the calculated power distribution result (e.g., input of a control command value for outputting P2 and P3 calculated by the calculation), in step S308, the power distribution control unit 12 controls the power output from each battery in accordance with the calculated power distribution result (the power P2 and the power P3) so that the power output from the FC (fuel cell) 11 and the power output from 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 (power P2 and 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.

[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. It was assumed that the vehicle was driven in a WHVC (Worldwide Harmonized Vehicle Cycle) pattern, which is an evaluation pattern for commercial vehicles. Two different types of control (controls of Example 1 and Comparative Example 1) were performed during power supply, as described below. The relationship between fuel consumption and time was simulated (estimated), and the fuel economy performance of the system was evaluated when each control method was adopted. Furthermore, assuming that similar control (two different types of control) was performed, a specific degradation model was used to simulate (estimate) the relationship between electrochemical area and time. The electrochemical area of ​​the catalyst was calculated as an index of durability during driving in the WHVC pattern, and the durability of the system when each control method was adopted was evaluated. Each simulation method is described below in detail.

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

[0098] [Formula (I) for determining 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 conditions other than those above] 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 (in 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 output from the fuel cell (FC) at time t is set so that the power to be output at that time t (the output power from the FC in the embodiment is denoted as "P2'(t)" for convenience) becomes a small value. ｌｉｍ A simulation of the relationship between fuel consumption and time was performed using Example 1, where it is assumed 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) Formula (IV) to be determined] 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) ｌｉｍ Formula (V) for calculating P2'(t) when the condition (t) is satisfied: 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).) [Formula (VII) for calculating P3'(t)] P3'(t) = P1(t) - P'2(t) (VII).

[0102] The power distribution control (adopted in Example 1) based on such equations (IV) to (VII) is a linearly calculated limit value P2 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 control that utilizes mass transport resistance R2(t) to correct the conventional control method (control method of Comparative Example 1) performed using equations (I) to (III). Here, γd and γe are compatibility coefficients (in the simulation, these coefficients were "γd: 67, γe: -5").

[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 in order to fairly compare the differences in control, the remaining battery charge (SOC) before and at the end of the simulation was measured. ＢＡＴ ) so that the initial SOC ＢＡＴ By adjusting the magnitude of R, 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); the fuel cell (FC) current (FC current (t)); the fuel cell (FC) voltage (FC voltage (t)); and the integrated 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. ＢＡＴThe 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, the durability of the system during running of the WHVC pattern was evaluated based on the results of reference 1 (Darling, R. M. and J. P. 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 Durability during WHVC driving was evaluated using a fuel cell (FC) degradation model (a degradation model that predicts changes in the number and particle size distribution of catalyst particles supported on the cathode) described in "Automotive Fuel Cell," ECS transaction, 2020. In 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 the cases in which the current and voltage of the fuel cell (FC) were controlled over time as shown in FIG. 12 (for each of Example 1 and Comparative Example 1) when load fluctuations changed due to driving in the WHVC pattern. Here, the values ​​described in Reference 2 were used as catalyst degradation parameters. Note that 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 areas predicted using the FC degradation models described in References 1 and 2. Therefore, in order to compare the electrochemical areas predicted by the degradation model, the relationship between the size of the electrochemical area of ​​the catalyst 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 (degradation index) obtained in this manner and time is shown in Figure 13.

[0107] 13, the electrochemical area capacity 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 and the graph of the electrochemical area capacity when Comparative Example 1 (conventional control) was performed, and the intersection point (D') of the dashed-dotted line and the graph of the electrochemical area capacity when Example 1 was performed was determined as the endurance time.

[0108] [Regarding the results of the simulation] FIG. 14 shows a graph illustrating the magnitude of the reciprocal of the accumulated amount of fuel consumption (accumulated amount) of Example 1, where 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 illustrating the magnitude of the endurance time of Example 1, where the endurance time of Comparative Example 1 shown in FIG. 13 is set to 1.

[0109] As is clear from the results shown in Figure 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). Regarding this point, when examining the time series chart shown in Figure 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 Figure 12(c), and the power output from the secondary battery (BAT power) P'3(t) is controlled as shown in Figure 12(c), based on the magnitudes of P1(t) shown in Figure 12(a) and R2(t) shown in Figure 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 Figure 12(c), and BAT power P3(t) is controlled as shown in Figure 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, 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, with the control method employed in Example 1, the amount of FC power generation (FC operation) is controlled at the timing (operating point) when the fuel cell (FC) power generation efficiency is low (because control is performed to avoid FC operation in a region where resistance R2 is large and power generation efficiency is 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.

[0110] As described above, the present invention makes it possible to provide 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 electric loads such as motors of electric mobility vehicles that have large load fluctuations.

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

Claims

1. A power supply system comprising a fuel cell and a secondary battery as a power supply source for an electric load, the power supply system comprising: a power distribution control unit (A) that distributes the output power of each of the batteries in order to supply a required power P1 to the electric load; an impedance acquisition unit (B) that acquires the impedance R1 of the fuel cell at a plurality of different frequencies; and 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 to each of the batteries 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 results of the calculation unit (C).

2. The power supply system according to claim 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 found based on data on a plurality of impedances R1.

3. A method for controlling power distribution between a fuel cell and a secondary battery in a power supply system equipped with a fuel cell and a secondary battery as a power supply source for the electric load, for controlling power distribution between the cells in response to a power P1 required by the electric load, the method comprising: an impedance acquisition step (S1) of acquiring an impedance R1 for 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 data on the plurality of impedances R1 obtained in step (S1); a calculation step (S3) of calculating the distribution of power between the cells when the power required by the electric load P1 is output from the power supply system based on the magnitude of the resistance R2 obtained in step (S2), to determine the power P2 to be supplied by the fuel cell and the power P3 to be supplied by the secondary battery; and a power distribution control step (S4) of controlling the power output from the cells so that the power output by the fuel cell and the power output by the secondary battery are distributed to the power P2 and the power P3 obtained in step (S3).

4. A power distribution control method as described in claim 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 determined based on data on multiple impedances R1.

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