Fuel cell system

Abstract

To provide a fuel cell system that can level out the frequency of reactor use and extend the life of the entire system.SOLUTION: A fuel cell system 1 includes an FC stack 11, a motor 30, a multi-phase converter 17, and a control device 50 that controls the multi-phase converter 17. The control device 50 calculates a stress value for each phase of the multi-phase converter 17 on the basis of the drive output and travel distance of each phase of the multi-phase converter 17 during the previous trip, and determines, on the basis of the stress values of each phase of the multi-phase converter 17, to use the drive phase with the lowest stress value in the next trip.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to fuel cell systems. [Background technology]

[0002] Patent Document 1 describes a technology that prevents a decrease in the durability of switching elements by calculating an accumulated temperature stress value, which is the accumulated value of the temperature stress of each of multiple switching elements that a boost converter has, and determining which of the multiple switching elements should be driven based on this accumulated temperature stress value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-103350 Summary of the Invention [Problem to be solved by the invention]

[0004] The boost converter has four phases, namely, a U-phase unit circuit, a V-phase unit circuit, a W-phase unit circuit and an X-phase unit circuit, each of which is made up of a reactor, a diode and a MOSFET.

[0005] However, in the above-mentioned Patent Document 1, the switching element to be driven from among a plurality of switching elements is determined based on the accumulated temperature stress value. However, since the U phase to the X phase are fixed to the first to fourth phases in order, the U phase is always used, which causes a problem that the U phase set as the first phase is prone to failure, and there is room for improvement.

[0006] The present disclosure has been made in view of the above, and has an object to provide a fuel cell system that can level out the frequency of reactor use and extend the life of the entire system. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the objectives, the fuel cell system of the present disclosure is a fuel cell system comprising: a fuel cell that supplies electric power; a load device that operates by receiving electric power supplied from the fuel cell; a multi-phase converter that is provided between the fuel cell and the load device and controls the output voltage of the fuel cell; and a control device that controls the multi-phase converter, wherein the control device calculates a stress value for each phase based on the drive output and mileage of each phase of the multi-phase converter during the previous trip, and determines, based on the stress values ​​of each phase, to use the drive phase with the lowest stress value in the next trip. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to achieve an effect of leveling out the frequency of reactor use and thereby extending the life of the entire system. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing the functional configuration of a fuel cell system according to one embodiment. [Figure 2] FIG. 2 is a diagram illustrating an outline of the control of switching the number of drive phases of the unit circuits by the control device 50 according to one embodiment. [Figure 3] FIG. 3 is a flowchart outlining a process for allocating each phase in the FC boost converter, which is executed by the control device 50 according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, fuel cell systems according to embodiments of the present disclosure will be described with reference to the drawings. Note that the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical. Furthermore, the drawings referred to in the following description merely show a schematic representation of the shape, size, and positional relationship to the extent that the contents of the present disclosure can be understood. In other words, the present disclosure is not limited to only the shape, size, and positional relationship illustrated in each drawing.

[0011] [Configuration of fuel cell system] Fig. 1 is a block diagram showing the functional configuration of a fuel cell system according to one embodiment. The fuel cell system 1 shown in Fig. 1 is mounted on a vehicle such as an FCEV (Fuel Cell Electric Vehicle). The fuel cell system 1 includes a power supply device 10 having an FC (Fuel Cell) stack 11 as a fuel cell, a multi-phase converter 12, and a relay circuit 13, a drive inverter 20, a drive motor 30, a meter 40, and an ECU (Electronic Control Unit) 50 functioning as a control device. The fuel cell system 1 supplies electric power generated by the power supply device 10 to the drive motor 30 via the relay circuit 13 and the drive inverter 20, thereby driving the drive motor 30 to rotate.

[0012] The FC stack 11 is a solid polymer electrolyte cell stack configured by stacking a plurality of unit cells in series.

[0013] The multi-phase converter 12 is provided between the FC stack 11 and the motor 30, and controls the output voltage of the FC stack 11 to a voltage and current corresponding to a target output. The multi-phase converter 12 has four phases of unit circuits, each consisting of a reactor, a diode, and a MOSFET. Specifically, the multi-phase converter 12 has a U-phase unit circuit, a V-phase unit circuit, a W-phase unit circuit, and an X-phase unit circuit. The output voltage and output current of the multi-phase converter 12 can be detected by voltage sensors and current sensors (not shown).

[0014] The relay circuit 13 is turned on and off under the control of the ECU 60 to electrically connect the power supply device 10 and the drive inverter 20 .

[0015] The drive inverter 20 is configured using, for example, a PWM inverter driven by a pulse width modulation method, and under the control of the ECU 60, converts the DC power supplied from the power supply device 10 into three-phase AC power and controls the rotational torque of the drive motor 30.

[0016] The motor 30 operates by receiving power supplied from the FC stack 11. The motor 30 generates rotational torque that powers the vehicle and generates regenerative power during deceleration. The rotational torque of the drive motor 30 is transmitted to the tires via a shaft (not shown). In one embodiment, the motor 30 functions as a load device.

[0017] The meter 40 is configured using, for example, an odometer, measures the total distance traveled by the vehicle (accumulated distance), and outputs the measurement result to the control device 50.

[0018] The control device 50 includes an ECU (Electronic Control Unit) 60 and drive circuits 61, 62, 63, and 64 that drive the MOSFETs of each unit circuit. The ECU 60 is implemented using a processor having memory and hardware. The hardware includes, for example, a memory, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), and an FPGA (Field-Programmable Gate Array). The ECU 60 changes the number of drive phases of the four-phase unit circuits according to the output current from the FC stack 11 in order to reduce overall loss in the multi-phase converter 12.

[0019] [Switching control of the number of driving phases by the control device] Next, we will explain the control of switching the number of drive phases of the unit circuits by the control device 50. Figure 2 is a diagram illustrating an overview of the control of switching the number of drive phases of the unit circuits by the control device 50. In Figure 2, the horizontal axis represents the FC current [A], and the vertical axis represents the switching current of each phase.

[0020] 2, the control device 50 performs control to switch the number of drive phases used in the multi-phase converter 12 based on the current value required for vehicle running. Specifically, the control device 50 performs control to increase the number of phases used in the multi-phase converter 12 as the FC current increases.

[0021] [Processing by the control device] Next, a description will be given of the process of allocating each phase in the FC boost converter executed by the control device 50. Fig. 3 is a flowchart outlining the process of allocating each phase in the FC boost converter executed by the control device 50. Note that, in the following, the ECU 60 executes the process when the ignition switch of the vehicle is turned on.

[0022] 3, the ECU 60 calculates the mileage of the previous trip (step S101). Specifically, the ECU 60 acquires the ODD value at the end of the previous trip (hereinafter simply referred to as "odd1") and the ODD value at the start of the previous trip (hereinafter simply referred to as "odd0") from the meter 40, and calculates the mileage (odd) of the previous trip by subtracting the ODD value at the start of the previous trip from the ODD value at the end of the previous trip. Specifically, the ECU 60 calculates the mileage (odd) of the previous trip using the following equation (1): odd=odd1-odd0 (1)

[0023] Next, the ECU 60 updates the ODD value at the start of the previous trip to the ODD value at the start of the current trip (step S102). Specifically, the ECU 60 updates the ODD value at the start of the previous trip to the ODD value at the start of the current trip using the following equation (2). odd_0=ODD (2)

[0024] Thereafter, ECU 60 calculates the usage index of each phase by multiplying the phase number by the distance traveled during the previous trip (step S103), and updates the cumulative value of each phase (step S104). For example, in the case of the U phase, ECU 60 calculates the U phase usage index during the previous trip (hereinafter simply referred to as "stress_U") using the following equation (3), and updates the cumulative value of the U phase usage index (hereinafter simply referred to as "STRESS_U") using the following equation (4). stress_U=(5-n_U)×odd ···(3) STRESS_U=STRESS_U+stress_U ···(4) Here, (5-n_U) is the phase number of the U phase in the previous trip. Similarly, ECU 60 calculates a usage index for each phase number (U to X) and updates the cumulative value of the usage index for each phase number (U to X). In one embodiment, the phase usage index for each phase (U to X) during the previous trip corresponds to the drive output of each phase, and the cumulative value of the usage index for each phase (U to X) corresponds to the stress value.

[0025] Next, the ECU 60 assigns a phase number to each of the STRESS_U to STRESS_X in ascending order of the accumulated value based on the accumulated value (step S105).

[0026] Thereafter, the ECU 60 stores the current ODD value in odd_1 at the end of the previous trip (step S106). After step S106, the ECU 60 repeats steps S101 to S106 described above until the ignition switch of the vehicle is turned off.

[0027] According to the embodiment described above, ECU 60 calculates the stress value of each phase based on the drive output and mileage of each phase of multi-phase converter 17 during the previous trip, and determines to use the drive phase with the lowest stress value in the next trip based on the stress value of each phase. As a result, by using the ODD information from meter 40, the frequency of use of the reactors of each phase in multi-phase converter 12 can be equalized, thereby extending the life of fuel cell system 1 as a whole.

[0028] (Other forms) Further advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0029] Although some of the embodiments of the present application have been described in detail above with reference to the drawings, these are merely examples, and the present invention can be implemented in other forms that have undergone various modifications and improvements based on the knowledge of those skilled in the art, including the aspects described in the disclosure of the present invention. [Explanation of symbols]

[0030] 1. Fuel cell system 10 Power supply 11 FC stack 12 Multiphase Converter 13 Relay Circuit 17 Multiphase Converter 20 Drive inverter 30 motor 40 meters 50 Control device 60 ECU 61, 62, 63 Drive circuit

Claims

[Claim 1] a fuel cell for supplying power; a load device that operates by receiving power supplied from the fuel cell; a multi-phase converter provided between the fuel cell and the load device and configured to control an output voltage of the fuel cell; a control device for controlling the multi-phase converter; Equipped with 1. A fuel cell system, comprising: The control device Calculating a stress value for each phase based on the driving output and travel distance of each phase of the multi-phase converter during a previous trip; Based on the stress values ​​of the phases, it is determined that the drive phase having the lowest stress value is to be used in the next trip. Fuel cell system.

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