JP6753289B2 - Fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system.

The fuel cell system generates electricity from the fuel cell and outputs the target electric power in response to an external load such as a motor or an auxiliary machine inside the system. The fuel cell system incorporates a control system that boosts the output voltage of the fuel cell using a converter in order to stably output the output power of the fuel cell to an external load and accessories. The converter is composed of, for example, a reactor which is an inductance element and a switching element which controls the flow of a current (hereinafter, referred to as “reactor current”) with respect to the reactor. Such boost control is performed by feedback controlling the duty ratio indicating the ratio between the on-time and the off-time of the switching element based on the average value of the reactor current. In general, the reactor current repeats rising and falling as the switching element is periodically turned on and off. Patent Document 1 discloses a technique of calculating a value obtained by multiplying the value of the midpoint of the reactor current at the on-time of the switching element by a predetermined coefficient as the average value of the reactor current.

International Publication No. 2013/098999

However, the technique described in Patent Document 1 is based on the premise that the amount of increase in the reactor current value during the on-time of the switching element is equal to the amount of decrease in the reactor current value during the off-time of the switching element. For example, when the target power changes significantly in a short time, the amount of increase and decrease of the reactor current value may differ. In this case, if the method for calculating the average value of the reactor current described in Patent Document 1 is used, the error of the calculated average value of the reactor current may become large. Therefore, there is a demand for a technique for accurately calculating the average value of the reactor current even when the amount of increase and decrease of the reactor current value are different.

The present invention has been made to solve at least a part of the above-mentioned problems, and can be realized as the following forms.

(1) According to one embodiment of the present invention, a fuel cell system is provided. This fuel cell system is a fuel cell system having a reactor and including a converter that controls the output voltage of the fuel cell based on the current value flowing through the reactor, and is an average for calculating the current average value IL _avg of the reactor. A value calculation unit; a switching element connected to the reactor and switching on / off of the current output from the reactor; after the current value rises by controlling the on / off of the switching element based on the current average value. The output voltage control unit that controls the output voltage so as to continuously decrease; and the average value calculation unit; the current value IL ₁ and the current value IL ₁ at an arbitrary time t ₁ during the increase period during which the current value increases. The current value IL _{2 at} the time t ₂ after the time t ₁ and the current value IL _{3 at the} time t ₃ at which the current value is not zero at any time during the falling period in which the current value falls. Based on the time t ₁ , the time t ₂ , the current value IL _1, and the current value IL ₂ , the rising period is used by using a linear interpolation method. the current IL ₄ at the time of a start time t ₄ and said time t _4, the current value IL ₅ at the end time and the start time for a period of time of the falling period t ₅ and said time t ₅ of the rising period, Is calculated, and based on the time t ₃ , the time t ₅ , the current value IL _3, and the current value IL ₅ , the end time of the descending period is calculated by using a linear interpolation method. the current IL ₆ at time _{t 6} and said time _{t 6,} a calculation unit for calculating an; has to calculate the current average value _{IL avg} using equation (1).

The fuel cell system of this embodiment, a current value IL ₄ in the time which is the start time of the rising period t ₄ and said time t _4, the start time of the end time and the falling period of the rising period time t ₅ and the calculating a current value IL ₅ at time _{t 5,} the current value IL ₆ at the end time for a period of time _{t 6} and said time _{t 6} of the falling period, is calculated, and using this information the current average value _{IL avg} Therefore, even when the amount of increase and decrease of the reactor current value IL are different, the current average value IL _avg can be calculated accurately.

The present invention can also be realized in various forms. For example, it can be realized in a vehicle equipped with a converter, a power control method in a converter system, an on / off control method of a switching element, and the like.

It is explanatory drawing which shows the electric structure of the fuel cell system in embodiment of this invention. It is a block diagram which shows the detailed structure of a fuel cell converter. It is explanatory drawing which shows an example of the time change of the reactor current value in a continuous mode. It is explanatory drawing for demonstrating the calculation method of the current average value in a continuous mode. It is explanatory drawing which shows an example of the time change of the reactor current value in a discontinuous mode. It is explanatory drawing for demonstrating the calculation method of the current average value in a discontinuous mode.

A. Embodiment:
A1. Overall configuration of fuel cell system:
FIG. 1 is an explanatory diagram showing an electrical configuration of the fuel cell system 100 according to the embodiment of the present invention. The fuel cell system 100 is mounted on the fuel cell vehicle and generates a driving force of the fuel cell vehicle in response to a driver's request. The fuel cell system 100 includes a fuel cell 10, a fuel cell converter 11, a secondary battery 15, a secondary battery converter 16, a drive motor 20, a DC / AC inverter 21, a first voltage detection unit 31, and the like. A second voltage detection unit 32 and a control unit 50 are provided.

The fuel cell 10 is a power source of the fuel cell system 100, and is a polymer electrolyte fuel cell that generates electricity by receiving hydrogen gas and air as reaction gases. The fuel cell 10 is not limited to the polymer electrolyte fuel cell, and various types of fuel cells can be adopted. For example, as the fuel cell 10, a solid oxide fuel cell may be adopted instead of the polymer electrolyte fuel cell. The fuel cell 10 is connected to the input terminal of the fuel cell converter 11 via the first DC lead wire 1.

The fuel cell converter 11 is a step-up converter that boosts the voltage input from the fuel cell 10 to a target voltage and outputs the voltage in response to an instruction from the control unit 50. Specifically, the fuel cell converter 11 controls the output voltage of the fuel cell 10 based on the current value (hereinafter, referred to as “reactor current value IL”) flowing through the reactor (reactor 61 described later). The output terminal of the fuel cell converter 11 is connected to the DC terminal of the DC / AC inverter 21 via the second DC lead wire 2. The fuel cell converter 11 transmits the reactor current value IL to the control unit 50. The detailed configuration of the fuel cell converter 11 will be described later.

The secondary battery 15 is composed of, for example, a lithium ion battery, and functions as a power source of the fuel cell system 100 together with the fuel cell 10. The secondary battery 15 is connected to the input terminal of the secondary battery converter 16 via the third DC lead wire 3.

The secondary battery converter 16 adjusts the input voltage (voltage in the second DC lead wire 2) of the DC / AC inverter 21 in cooperation with the fuel cell converter 11 in response to an instruction from the control unit 50. Further, the secondary battery converter 16 controls charging and discharging of the secondary battery 15. The secondary battery converter 16 is a step-up converter having the same configuration as the fuel cell converter 11. The output terminal of the secondary battery converter 16 is connected to the second DC lead wire 2 via the fourth DC lead wire 4.

The drive motor 20 is a power source for driving the wheels of a fuel cell vehicle, and is composed of, for example, a three-phase AC motor. The drive motor 20 is connected to the AC terminal of the DC / AC inverter 21 via an AC lead wire.

The DC / AC inverter 21 drives by converting DC power supplied from the fuel cell 10 and the secondary battery 15 via the second DC lead wire 2 into three-phase AC power in response to an instruction from the control unit 50. It is supplied to the motor 20. Further, the DC / AC inverter 21 converts the regenerative power generated in the drive motor 20 into DC power and outputs it to the second DC lead wire 2.

The first voltage detection unit 31 is connected to the first DC lead wire 1 and measures the input voltage of the fuel cell converter 11. The second voltage detection unit 32 is connected to the second DC lead wire 2 and measures the output voltage of the fuel cell converter 11. The first voltage detection unit 31 and the second voltage detection unit 32 output the measured value VL of the input voltage and the measured value VH of the output voltage to the control unit 50, respectively. The input voltage and output voltage of the fuel cell converter 11 correspond to the input voltage and output voltage of the reactor (reactor 61 described later) in the fuel cell converter 11.

The control unit 50 controls the outputs of the fuel cell 10 and the secondary battery 15 by controlling the fuel cell converter 11, the secondary battery converter 16, and the DC / AC inverter 21, and requests an output from the outside. A driving force corresponding to the above is generated in the drive motor 20. The control unit 50 is electrically connected to the fuel cell converter 11, the secondary battery converter 16, and the DC / AC inverter 21. The control unit 50 uses the reactor current value IL received from the fuel cell converter 11 to control the fuel cell converter 11. In the present embodiment, the control unit 50 is composed of a computer. The CPU of the control unit 50 functions as an output voltage control unit 51 and an average value calculation unit 52 by executing a control program stored in advance in the memory in the control unit 50. The average value calculation unit 52 includes a current value acquisition unit 53 and a calculation unit 54.

The output voltage control unit 51 controls the output voltage of the fuel cell 10 based on the average value of the reactor current value IL. Specifically, this is performed by controlling the duty ratio indicating the ratio between the turn-on time and the turn-off time of the switching element 63. Such a duty ratio is feedback controlled based on the average value of the reactor current value IL.

The average value calculation unit 52 has a reactor current value IL (calculated value) based on the reactor current value IL (actual measurement value) acquired by the current value acquisition unit 53 and the reactor current value IL (calculated value) calculated by the calculation unit 54. (Hereinafter, referred to as "current average value IL _avg ") is calculated. The details of the calculation method of the current average value IL _avg will be described later.

The current value acquisition unit 53 acquires the reactor current value IL (actual measurement value) flowing through the reactor (reactor 61 described later) of the fuel cell converter 11.

Based on the reactor current value IL (actual measurement value) acquired by the current value acquisition unit 53, the calculation unit 54 sets the start time of the increase period (hereinafter, simply referred to as “increased period”) in which the reactor current value IL increases. The reactor current value IL at the end time and the reactor current value IL at the end time of the falling period in which the reactor current value IL falls (hereinafter, simply referred to as “falling period”) are calculated.

A2. Detailed configuration of fuel cell converter:
FIG. 2 is a block diagram showing a detailed configuration of the fuel cell converter 11. In FIG. 2, the third DC lead wire 3 and the fourth DC lead wire 4 are not shown. The fuel cell converter 11 includes four voltage conversion circuits (first voltage conversion circuit 11U, second voltage conversion circuit 11V, third voltage conversion circuit 11W, and fourth voltage conversion circuit 11X) connected in parallel with each other. It includes a current sensor (first current sensor 67U, second current sensor 67V, third current sensor 67W and fourth current sensor 67X), and a smoothing capacitor 66.

The voltage conversion circuits 11U to 11X are connected to the power supply line 5 and the ground line 6. The power supply line 5 is a common power supply line for the fuel cell 10 and the DC / AC inverter 21. The grounding line 6 is a common grounding line for the fuel cell 10 and the DC / AC inverter 21. A smoothing capacitor 66 is inserted between the power supply line 5 and the ground line 6 in the subsequent stage of each voltage conversion circuit 11U to 11X. The smoothing capacitor 66 reduces voltage fluctuations between the power supply line 5 and the ground line 6.

Each voltage conversion circuit 11U to 11X includes a reactor 61, an output diode 62, and a switching element 63. The reactor 61 of each voltage conversion circuit 11U to 11X is connected to the power supply line 5 via the current sensors 67U to 67X. The current sensors 67U to 67X measure the current value of the current flowing through the reactor 61 of each voltage conversion circuit 11U to 11X, and transmit the measured values IL _U, IL _v, IL _W, and IL _x to the control unit 50. In this specification, for convenience, the measured values IL _U, IL _v, IL _W and IL _x of the reactor currents of the voltage conversion circuits 11U to 11X are collectively referred to as “reactor current value IL”.

The output diodes 62 of the voltage conversion circuits 11U to 11X are interposed between the output side of the reactor 61 and the power supply line 5 in the forward direction. The switching element 63 is interposed between the output side of the reactor 61 and the ground line 6. Each switching element 63 is composed of a transistor 64 and a protection diode 65.

The transistors 64 of the voltage conversion circuits 11U to 11X are npn type transistors, and are composed of, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOS (Metal Oxide Semiconductor) transistor for power, and a bipolar transistor for power. The transistor 64 is connected with the reactor 61 side as a collector and the ground line 6 side as an emitter. The protection diode 65 is connected between the collector and the emitter of the transistor 64 in the direction opposite to the direction in which the collector current flows.

Control signals SU, SV, SW, and SX generated based on the duty ratio set by the control unit 50 are input from the control unit 50 to the base terminals of the transistors 64 of the voltage conversion circuits 11U to 11X. In this specification, for convenience, the control signals SU, SV, SW and SX of the voltage conversion circuits 11U to 11X are collectively referred to as "control signal S" without distinction. The switching element 63 of each voltage conversion circuit 11U to 11X repeats turn-on and turn-off according to the control signal S.

When the switching element 63 is turned on, a current starts to flow from the fuel cell 10 to the switching element 63 via the reactor 61, and magnetic energy due to direct current excitation is stored in the reactor 61. When the switching element 63 is turned off, the magnetic energy stored in the reactor 61 during the turn-on period is output to the DC / AC inverter 21 via the output diode 62 and the power supply line 5.

Magnetic energy is stored in the reactor 61 while the switching element 63 is turned on and a current is flowing through the reactor 61, and the stored magnetic energy is released while the switching element 63 is turned off. Therefore, the switching element 63 can control the energy stored in the reactor 61 by switching the current output from the reactor 61 on and off, and the current flowing on the reactor 61 of each voltage conversion circuit 11U to 11X on average. (Effective current) can be controlled.

A control signal S is transmitted to the voltage conversion circuits 11U to 11X so that the switching elements 63 of the voltage conversion circuits 11U to 11X are sequentially and repeatedly turned on. Therefore, the output voltages of the voltage conversion circuits 11U to 11X are sequentially higher than the output voltage of the fuel cell 10, and the voltage input to the DC / AC inverter 21 is maintained higher than the output voltage of the fuel cell 10. Therefore, the output voltage control unit 51 described above controls the turn-on / turn-off timing of the switching element 63 based on the current average value IL _avg of the reactor 61 to control the output voltage of the fuel cell 10. By the above operation, the fuel cell converter 11 boosts the voltage input from the fuel cell 10 to the target voltage and inputs it to the DC / AC inverter 21.

A3. Operation mode of the fuel cell converter 11:
As described above, when the switching element 63 is turned on, the reactor current value IL starts to increase, and when the switching element 63 is turned off, the reactor current value IL starts to decrease. In other words, the reactor current value IL increases during the period when the switching element 63 is turned on (hereinafter, referred to as “on period _Ton ”), and increases during the period when the switching element 63 is turned off (hereinafter, “off period”). It descends to (called " _Toff "). Therefore, within one cycle of the switching element 63 (hereinafter, referred to as “T for one cycle”), the reactor current value IL rises and then falls continuously.

Here, as the operation mode of the fuel cell converter 11, the "continuous mode" in which the current continues to flow in the reactor 61 and the current in the reactor 61 according to the ratio of the on period _Ton and the off period _Tof of the switching element 63 are used. There is a "discontinuous mode" that flows intermittently. In the following description, a method of calculating the current average value IL _avg of the reactor 61 will be described in each of the continuous mode and the discontinuous mode.

A4. Calculation method of current average value IL _avg in continuous mode:
FIG. 3 is an explanatory diagram showing an example of a time change of the reactor current value IL in the continuous mode. In FIG. 3, the vertical axis represents the reactor current value IL, and the horizontal axis represents time. FIG. 3 shows the time change of the reactor current value IL for about two cycles in the continuous mode. In FIG. 3, the time change of the on period _Ton and the off period To _off of the switching element 63 is also shown at the upper part of the figure showing the time change of the reactor current value IL. As shown in FIG. 3, when the switching element 63 is turned on at the time t ₀ , the reactor current value IL starts to increase from the time t ₄ after the response delay d. When the switching element 63 is turned off, after the response delay d, the descent of the reactor current IL from time t ₅ to begin. As shown in FIG. 3, the end time of the rising period, the start time of the falling period, both of which coincide with the time t _5. Lowering of the reactor current IL starts at time t _5, at time t _6, along with the falling period of the first cycle of the reactor current IL is finished, the rising period of the second cycle is started.

In the present embodiment, the time t ₀ and the on period _Ton are managed by the control unit 50. Further, the response delay d is a response delay due to feedback control, and is a value determined by design measurement, actual measurement, or the like.

The current average value IL _avg of the reactor current value IL can be expressed by the following equation (2).

In the formula (2), the area of S1 is meant the sum of the charges accumulated in the reactor 61 in the on-period T _on. The area of S2 means the sum of the charges accumulated in the reactor 61 during the off period To _off . As shown in FIG. 3, since S1 and S2 each have a trapezoidal shape, the current average value IL _avg can be expressed by the following equation (3).

Therefore, in order to calculate the current average value IL _avg shown in the above equation (3), the time t ₄ and the time t ₅ which are two vertices in the trapezoid S1 and the time t ₆ which are one vertices in the trapezoid S2 are used. , The reactor current values IL ₄ , IL ₅ and IL _{6 at} each time t ₄ , t ₅ and t ₆ may be calculated. Here, two vertices in trapezoidal S1 is, in other words, the start time t ₄ increasing period, a start time t ₅ of the end time and the falling period of the rising period. Further, one vertex in the trapezoid S2 is, in other words, the end time t ₆ of the descending period. Rise period start time t ₄ and reactor current value IL _{4 at} that time, rise period end time and fall period start time t ₅ and reactor current value IL _{5 at that} time and fall period end time t ₆ and time The reactor current value IL ₆ in the above can be calculated as follows.

FIG. 4 is an explanatory diagram for explaining a method of calculating the current average value IL _avg in the continuous mode. In FIG. 4, the vertical axis represents the reactor current value IL, and the horizontal axis represents time. FIG. 4 shows a time change of the reactor current value IL similar to the time change of the reactor current value IL shown in FIG. Further, as in FIG. 3, the time change of the on period _Ton and the off period To _off of the switching element 63 is shown at the upper part of the figure showing the time change of the reactor current value IL.

Start time t ₄ of the rising period is calculated as follows. As shown in FIG. 4, the time t ₄ is a time later than the time t ₀ by the response delay d. Therefore, the time t ₄ can be calculated by the following equation (4). As described above, the time t ₀ , the on period _Ton, and the response delay d are known values, respectively.

Start time t ₅ of the end time and the falling period of the rising period is calculated as follows. As shown in FIG. 4, the time t _5, a value obtained by adding the response delay d and the on-period T _on which starting from time t _0. Therefore, the time t ₅ can be calculated by the following equation (5).

The reactor current value IL _{4 at} the start time t ₄ of the ascending period and the reactor current value IL _{5 at} the end time of the ascending period and the start time t ₅ of the descending period are calculated as follows. First, the current value acquisition unit 53 has a reactor current value IL ₁ (actual measurement value) at an arbitrary time t ₁ during the rise period and a reactor current value IL _{2 at} a time t ₂ after the time t ₁ during the rise period. (Actual measurement value) and are obtained respectively. Specifically, the current value acquisition unit 53 acquires the reactor current value IL acquired from each of the current sensors 67U to 67X by AD conversion. In FIG. 4, the reactor current value IL ₁ (actual measurement value) and the reactor current value IL ₂ (actual measurement value) are indicated by black circles, respectively.

As shown in FIG. 4, the straight line showing the increase in the reactor current value IL has a constant slope. Therefore, the use of linear interpolation, the relationship between the reactor current IL ₁ in the reactor current value IL ₄ and the time _{t 1} at time _{t 4,} the reactor current in the reactor current value IL ₁ and the time _{t 2} at time _{t 1} As for the relationship with the value IL ₂ , the relationship of the following equation (6) is established.

By modifying the equation (6), the reactor current value IL _{4 at} the time t ₄ can be expressed by the following equation (7).

Similarly for reactor current IL ₅ at time _{t 5,} the use of linear interpolation, the relationship between the reactor current IL ₁ in the reactor current value IL ₅ and the time _{t 1} at time _{t 5,} the reactor at time _{t 1} As for the relationship between the current value IL ₁ and the reactor current value IL _{2 at} time t ₂ , the relationship of the following equation (8) is established.

By modifying the equation (8), the reactor current value IL _{5 at} the time t ₅ can be expressed by the following equation (9).

In FIG. 4, the reactor current value IL ₄ and the reactor current value IL ₅ calculated by the linear interpolation method are indicated by white circles, respectively.

End time t ₆ of the falling period is calculated as follows. First, the time t ₇ shown in FIG. 4 is calculated. As shown in FIG. 4, the time t ₇ is the time during which T has elapsed for one cycle after the response delay d has occurred from the time t ₀ . Therefore, the time t ₇ can be calculated by the following equation (10).

The reactor current value IL _{7 at} time t ₇ can be calculated by using the linear interpolation method in the same manner as the reactor current value IL ₄ and the reactor current value IL ₅ described above. Specifically, the current value acquisition unit 53 acquires the reactor current value IL ₃ (actual measurement value) at an arbitrary time t ₃ during the falling period. In the present embodiment, the time t ₃ selects the time when the reactor current value IL is not zero. In FIG. 4, the reactor current value IL ₃ (measured value) is indicated by a black circle.

As shown in FIG. 4, the straight line indicating the decrease in the reactor current value IL has a constant slope, similarly to the straight line indicating the increase in the reactor current value IL. Further, as described above, the start time of the falling period, the end time of the rising period, i.e., the same as the time t _5. Therefore, the use of linear interpolation, the relationship between the reactor current value IL ₅ in reactor current value IL ₇ and time _{t 5} at time _{t 7,} the reactor current in the reactor current value IL ₃ and the time _{t 5} at time _{t 3} As for the relationship with the value IL ₅ , the relationship of the following equation (11) is established.

By modifying the equation (11), the reactor current value IL _{7 at} the time t ₇ can be expressed by the following equation (12).

Here, in the continuous mode, the reactor current value IL ₇ takes a value of 0 or more. Therefore, when the reactor current value IL ₇ is 0 or more, the time t ₇ and the time t ₆ and the reactor current value IL ₇ and the reactor current value IL ₆ are the same as in the continuous mode. Will be done. Therefore, in the above equation (12), the reactor current value IL ₆ is expressed by the following equation (13) by replacing the time t ₇ with the time t ₆ and the reactor current value IL ₇ with the reactor current value IL _6. be able to.

Was calculated by the above procedure, the reactor current IL ₄ at the start time of the rising period t ₄ and said time t _4, the reactor current IL at the start time of the end time and the falling period of the rising period t ₅ and said time t _{5 By} substituting ₅ and the reactor current value IL _{6 at} the end time t ₆ of the descending period and the time t ₆ into the above equation (3), the current average value IL _avg can be calculated.

A5. Calculation method of current average value IL _avg in discontinuous mode:
FIG. 5 is an explanatory diagram showing an example of a time change of the reactor current value IL in the discontinuous mode. In FIG. 5, the vertical axis represents the reactor current value IL, and the horizontal axis represents time. FIG. 5 shows the time change of the reactor current value IL for about two cycles in the discontinuous mode. Further, similarly to FIG. 3, the time change of the on period _Ton and the off period To _off of the switching element 63 is also shown at the upper part of the figure showing the time change of the reactor current value IL. As described above, the discontinuous mode is a state in which a current flows intermittently through the reactor 61.

As shown in FIG. 5, when the switching element 63 is turned on, as in the continuous mode described above, after the response delay d, the increase of the reactor current IL from time t ₄ to start. When the switching element 63 is set to turn off after a response delay d, and starts lowering of the reactor current IL at the time t _5, the reactor current IL becomes zero at time t _6. After that, unlike the case of the continuous mode described above, when the switching element 63 is turned on again after the state where the reactor current value IL is zero continues for a predetermined time, the reactor current value IL rises again after the response delay d. To start.

Current average value _{IL avg} in the discontinuous mode can be calculated by the same method of calculating the current average value _{IL avg} in the continuous mode. Specifically, the current average value IL _avg can be expressed by the above equation (2). As shown in FIG. 5, since S1 and S2 each have a triangular shape, the current average value IL _avg can be expressed by the following equation (14).

In the discontinuous mode, as shown in FIG. 5, the reactor current value IL _{4 at} the start time t ₄ of the rising period and the reactor current value IL _{6 at} the end time t ₆ of the falling period are zero, respectively. Therefore, the following equation (15) holds.

In the above equation (14), when the reactor current value IL ₄ and the reactor current value IL ₆ are replaced by the equation (15), the above equation (3) is obtained. Therefore, the current average value IL _avg in the discontinuous mode can also be calculated from the same equation (3) as the current average value IL _avg in the continuous mode. Therefore, similarly to the method of calculating the current average value IL _avg in the case of the above-described continuous mode, the reactor current value IL ₄ at the start time of the rising period t ₄ and said time t _4, the end time and the falling period of the rising period the reactor current value IL ₅ at the start time _{t 5} and said time _{t 5,} the reactor current value IL ₆ at the end time of the falling period _{t 6} and said time _{t 6,} when the calculated, a current average value _{IL avg} It will be possible to calculate.

FIG. 6 is an explanatory diagram for explaining a method of calculating the current average value IL _avg in the discontinuous mode. In FIG. 6, the vertical axis represents the reactor current value IL, and the horizontal axis represents time. FIG. 6 shows a time change of the reactor current value IL similar to the time change of the reactor current value IL shown in FIG. Further, as in FIG. 5, the time change of the on period _Ton and the off period To _off of the switching element 63 is also shown at the upper part of the figure showing the time change of the reactor current value IL. Here, the reactor current value IL ₄ at the start time of the rising period t ₄ and said time t _4, the reactor current value IL ₅ at the start time t ₅ and said time t ₅ of the end time and the falling period of the rising period, the Since each calculation procedure is the same as the calculation procedure in the case of the continuous mode, detailed description thereof will be omitted. In the following description, the procedure for calculating the reactor current value IL ₆ at the end time t ₆ of the descending period and the time t ₆ will be described.

As in the case of the continuous mode described above, first, the reactor current value IL ₇ at the time t ₇ shown in FIG. 6 is calculated. The reactor current value IL ₇ is represented by the above equation (12). Here, in the discontinuous mode, the reactor current value IL _{6 at} the end time t ₆ of the descending period is zero. Therefore, when the reactor current value IL ₇ is smaller than 0, the reactor current value IL ₆ is set to zero, assuming that the mode is discontinuous. Therefore, the reactor current value IL ₆ can be expressed by the following equation (16).

End time t ₆ of the falling period is calculated as follows. Here, the time t ₆ must be the time when the reactor current value IL ₆ is zero. Therefore, in this case, the use of linear interpolation, the relationship between the reactor current value IL ₅ in reactor current value IL ₆ and the time _{t 5} at time _{t 6,} the reactor current value IL ₃ and the time _{t 5} at time _{t 3} The relationship of the following equation (17) is established with the relationship with the reactor current value IL ₅ .

By transforming the equation (17), the time t ₆ can be expressed by the following equation (18).

Was calculated by the above procedure, the reactor current IL ₄ at the start time of the rising period t ₄ and said time t _4, the reactor current IL at the start time of the end time and the falling period of the rising period t ₅ and said time t _{5 By} substituting ₅ and the reactor current value IL _{6 at} the end time t ₆ of the descending period and the time t ₆ into the above equation (3), the current average value IL _avg can be calculated.

Described above, according to the fuel cell system of this embodiment, a current value IL ₄ in the time which is the start time of the rising period t ₄ and said time t _4, is the start time of the end time and the falling period of the rising period calculating a current value IL ₅ at time t ₅ and said time t _5, the current value IL ₆ at the end time for a period of time t ₆ and said time t ₆ of the falling period, the mean current by using the information Since the value IL _avg is calculated, the current average value IL _avg can be calculated accurately even when the amount of increase and decrease of the reactor current value IL are different.

B. Modification:
B1. Modification 1:
In the above embodiment, the arbitrary time t ₁ and t ₂ during the ascending period and the arbitrary time t ₃ during the descending period are not limited to the examples shown in FIGS. 4 and 6. For example, in FIG. 4, any time t ₃ during the descent period may be any time within the response delay d during the descent period. Even in such a configuration, since the time t ₃ is an arbitrary time during the descending period and the reactor current value IL is not zero, the same effect as that of the above embodiment is obtained. That is, generally, the time t _1, t ₂ and t _3, respectively, any time during the rise period t _1, the time t ₂ is later than said time t _1, be any time during the falling period the reactor When the current value IL is the time t ₃ which is not zero, the same effect as that of the above embodiment is obtained.

The present invention is not limited to the above-described embodiments and modifications, and can be realized with various configurations without departing from the spirit of the present invention. For example, the embodiments corresponding to the technical features in each of the embodiments described in the column of the outline of the invention, the technical features in the modified examples are used to solve some or all of the above-mentioned problems, or the above-mentioned above. It is possible to replace or combine them as appropriate to achieve some or all of the effects. If the technical features are not described as essential in the present specification, they can be deleted as appropriate.

S, SU, SV, SW, SX ... Control signal T _off ... Off period _Ton ... On period VH ... Output voltage value VL ... Input voltage value 1 ... 1st DC lead wire 2 ... 2nd DC lead wire 3 ... 3rd DC lead wire 4 ... 4th DC lead wire 5 ... Power supply line 6 ... Grounding line 10 ... Fuel cell 11 ... Fuel cell converter 11U ... 1st voltage conversion circuit 11V ... 2nd voltage conversion circuit 11W ... 3rd voltage conversion circuit 11X ... 4th voltage conversion Circuit 15 ... Secondary battery 16 ... Secondary battery converter 20 ... Drive motor 21 ... DC / AC inverter 31 ... First voltage detection unit 32 ... Second voltage detection unit 50 ... Control unit 51 ... Output voltage control unit 52 ... Average value Calculation unit 53 ... Current value acquisition unit 54 ... Calculation unit 61 ... Reactor 62 ... Output diode 63 ... Switching element 64 ... Transistor 65 ... Protection diode 66 ... Smoothing capacitor 67U ... First current sensor 67V ... Second current sensor 67W ... 3rd current sensor 67X ... 4th current sensor 100 ... Fuel cell system IL, IL ₁ , IL ₂ , IL ₃ , IL ₄ , IL ₅ , IL ₆ , IL ₇ ... Reactor current value IL _avg ... Current average value T ... 1 Between cycles t ₀ , t ₁ , t ₂ , t ₃ , t ₄ , t ₅ , t ₆ , t ₇ ... hours

Claims (1)

A fuel cell system having a reactor and a converter that controls the output voltage of the fuel cell based on the current value flowing through the reactor.
An average value calculation unit that calculates the current average value IL _avg of the reactor, and
A switching element that is connected to the reactor and switches the current output from the reactor on and off.
An output voltage control unit that controls the output voltage so that the current value rises and then continuously falls by controlling the on / off of the switching element based on the current average value IL _avg .
With
The average value calculation unit
The current IL ₂ at time t ₂ is later than the current value IL ₁ and said time t ₁ at any time t ₁ during the rising period of the current value increases, any descending period in which the current value is lowered The current value acquisition unit for acquiring the current value IL _{3 at the} time t ₃ during which the current value is not zero, respectively.
Based on the time t ₁ , the time t ₂ , the current value IL _1, and the current value IL ₂ , using a linear interpolation method, the time t ₄ which is the start time of the rising period and the time t ₄ and the the current IL ₄ at time t _4, the current value IL ₅ at the end time and the start time for a period of time of the falling period t ₅ and said time t ₅ of the rising period, and calculates a said time t ₃ , and the time t _5, and the current value IL _3, and the current value IL _5, based on using linear interpolation, the current in the which is the end time of the falling period time t ₆ and said time t ₆ A calculation unit that calculates the value IL ₆ and
To calculate the current average value IL _avg using the formula (1).
Fuel cell system.

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