JP2018032580A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system which can improve climbing performance by preventing overvoltage, when traveling alone with the power of fuel cell upon occurrence of abnormality in a secondary battery.SOLUTION: A fuel cell system 11 includes a step-up converter 15 having a capacitor, and supplying the voltage outputted from a fuel cell 12, while boosting, to the auxiliary machinery of the fuel cell 12 and drive motors 13, 14, a battery step-up converter 22 having a capacitor, and boosting the voltage outputted from a secondary battery 20, and a control section 30. When the accelerator opening of a vehicle is larger than 0, and the number of revolution of the drive motors 13, 14 on the opposite side to the direction of travel of the drive motors 13, 14 is larger than the slip-down number of revolution, the control section 30 permits regenerative power generation of the drive motors 13, 14, and supplies regenerative electric power to the auxiliary machinery.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel cell system.

  A fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas has attracted attention. The fuel cell controls the supply amount of fuel gas and outputs electric power according to the request from the drive motor, but due to the delay in response of the gas supply amount, the responsiveness of the output power may be low, A secondary battery may be mounted for compensation. This secondary battery stores the regenerative energy generated when the drive motor decelerates and the electric power generated by the fuel cell, compensates for a decrease in the responsiveness of the fuel cell, and increases the output of the entire fuel cell system. For this purpose, the stored energy is discharged.

  In the fuel cell system in which the fuel cell and the secondary battery are connected in parallel, the output voltage of the fuel cell and the output voltage of the secondary battery are converted by the respective converters, so that both are used together. A snubber capacitor (hereinafter referred to as a capacitor) is provided in parallel with the switch element in order to reduce the loss caused by the switching operation of the switch element of the converter, so-called switching loss.

  By the way, in the fuel cell system described above, a converter for a secondary battery that plays a buffer role with respect to load fluctuations is configured to control the input voltage to the inverter. For this reason, if an abnormality such as a failure occurs in the secondary battery and the power supply path between the secondary battery and the inverter is interrupted, the input voltage to the inverter cannot be controlled, and only the fuel cell This makes it difficult to operate the load stably.

  A technique intended to solve this problem is disclosed in Patent Document 1 below. That is, in Patent Document 1 below, when an abnormality occurs in the secondary battery, the two converters are controlled even from the fuel cell alone to stably supply power to the first load and the second load. Further, it is disclosed that the electric power traveling of the fuel cell is possible. In addition, when such a secondary battery abnormality occurs and the secondary battery is disconnected, it is not possible to store power even if the motor is regenerated. It is disclosed in Patent Document 1.

International Publication No. 2013-090909

  By the way, during the uphill traveling with the secondary battery disconnected, the motor may rotate in the reverse direction, and in this case, the following problem may occur due to regenerative power generation of the motor. That is, the motor performs regenerative power generation, but the fuel cell can only perform discharge, so the generated power accumulates in the capacitor and an overvoltage occurs. In addition, since the fuel cell adjusts the fuel supply amount according to the required power, the fuel supply amount is suppressed at a low vehicle speed, and as a result, the climbing performance decreases.

  The present invention has been made in view of such problems, and its purpose is to prevent overvoltage and improve climbing performance when the fuel cell is running alone when an abnormality occurs in the secondary battery. An object of the present invention is to provide a fuel cell system that can be made to operate.

  In order to solve the above problems, a fuel cell system according to the present invention is a fuel cell system including a fuel cell and a secondary battery as a power supply source to a drive motor that drives a vehicle, and includes a capacitor, A first boost converter that boosts a voltage output from the fuel cell and supplies the boosted voltage to the auxiliary device of the fuel cell and the drive motor; a second boost converter that includes a capacitor and boosts the voltage output from the secondary battery; A control unit that controls the regenerative operation of the drive motor, wherein the control unit has an accelerator opening of the vehicle that is greater than 0, and the rotational speed on the opposite side of the traveling direction of the drive motor is lower than the rotational speed. Is larger, the regenerative power generation of the drive motor is permitted and the regenerative power is supplied to the auxiliary machine.

  In the fuel cell system according to the present invention, when the vehicle slips, the fuel cell is generated by driving the auxiliary device of the fuel cell by the regenerative electric power of the motor. Therefore, a necessary torque is output based on the generated power. You can drive uphill. Further, since the regenerative power is consumed by the auxiliary device of the fuel cell, the overvoltage of the capacitor can be suppressed.

  According to the present invention, it is possible to provide a fuel cell system capable of preventing an overvoltage and improving a climbing performance when the fuel cell is traveling alone when an abnormality occurs in the secondary battery. .

It is a block diagram of the fuel cell system in embodiment of this invention. It is a flowchart which shows one control example of the control part at the time of abnormality occurrence of a secondary battery.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the following description of the preferred embodiment is merely an example, and is not intended to limit the present invention, its application, or its use.

  FIG. 1 is a configuration diagram of a fuel cell system according to the present embodiment. This embodiment demonstrates the case where a fuel cell system is used as a vehicle-mounted power generation system of a fuel cell vehicle.

  As shown in FIG. 1, the fuel cell system 11 according to this embodiment includes a fuel cell 12 and a secondary battery 20 as power supply sources for the drive motors 13 and 14.

  The fuel cell 12 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell has an air electrode on one surface of an electrolyte composed of an ion exchange membrane, a fuel electrode on the other surface, and a structure having a pair of separators so as to sandwich the air electrode and the fuel electrode from both sides. It has become. Then, hydrogen gas as a fuel gas is supplied to the hydrogen gas channel of one separator, and air as an oxidizing gas is supplied to the oxidant gas channel of the other separator. Will occur.

  The fuel cell 12 and a drive motor (first load) 13 for running the vehicle are connected via a power supply path (fuel cell power supply path) A. In this power supply path A, an FC boost converter (first converter) 15 and a drive inverter 16 are provided in this order from the fuel cell 12 side.

  The FC boost converter 15 is a DC voltage converter, and adjusts the DC voltage input from the fuel cell 12 and outputs it to the drive inverter 16 side. The drive inverter 16 converts a direct current into a three-phase alternating current and supplies it to a drive motor 13 (for example, a three-phase alternating current motor). The FC boost converter 15 and the drive inverter 16 each include a capacitor (not shown).

  A power supply path (first secondary battery power supply path) B is connected to the power supply path A. A connection point X between the power supply path A and the power supply path B is located between the FC boost converter 15 and the drive inverter 16. A secondary battery 20 is connected to one end of the power supply path B. Between the secondary battery 20 and the connection point X, a relay (circuit breaker) 21 and a battery boost converter are sequentially provided from the secondary battery 20 side. A (second converter) 22 is provided.

  The secondary battery 20 charges the surplus output power of the fuel cell 12 and the regenerative power of the drive motor 13 based on a control signal from the control unit 30, or power necessary for driving the drive motors 13 and 14. On the other hand, when the output power of the fuel cell 12 is insufficient, it is possible to replenish the shortage of power or supply power to the auxiliary motors 25 and 26 described later.

  The battery boost converter 22 is a DC voltage converter, and functions to adjust the DC voltage input from the secondary battery 20 and output it to the drive motors 13 and 14, and input from the fuel cell 12 or the drive motor 13. And a function of adjusting the DC voltage and outputting it to the secondary battery 20 and / or the auxiliary motors 25 and 26. The charge / discharge of the secondary battery 20 is realized by such a function of the battery boost converter 22. Battery boost converter 22 includes a capacitor (not shown).

  Further, the function of the battery boost converter 22 controls the input voltage to the drive inverter 16 and the auxiliary inverter 17 during the normal operation of the fuel cell system 11, while the relay 21 to be described later causes for some reason. When the secondary battery 20 is disconnected from the fuel cell system 11 (when the secondary battery is abnormal), power can be supplied from the fuel cell 12 to the auxiliary motors 25 and 26. .

  A power supply path (fuel cell power supply path) C is connected to the high voltage side of the power supply path B. A connection point Y between the power supply path B and the power supply path C is located between the connection point X and the battery boost converter 22. A drive motor (first load) 14 is connected to one end of the power supply path C. The drive motor 14 is, for example, a three-phase AC motor, and is a drive motor for an air compressor that pumps air (oxidizing gas) to the fuel cell 12. An auxiliary inverter 17 is provided between the drive motor 14 and the connection point Y. The auxiliary inverter 17 converts a direct current into a three-phase alternating current and supplies it to the drive motor 14.

  A power supply path D (second secondary battery power supply path) is connected to the low voltage side (secondary battery 20 side) of the power supply path B. A connection point Z between the power supply path B and the power supply path D is located between the battery boost converter 22 and the relay 21. The power supply path D is bifurcated, and auxiliary inverters 23 and 24 and auxiliary motors 25 and 26 are provided at the branch destinations, respectively.

  The auxiliary motor 25 is a motor that drives a hydrogen pump for recirculating the hydrogen off gas discharged from the hydrogen gas flow path of the fuel cell 12 to the fuel cell 12. The auxiliary motor 26 is a motor that drives a cooling water pump for circulating cooling water used for temperature control of the fuel cell 12. Auxiliary machine inverters 23 and 24 convert the direct current into three-phase alternating current and supply it to auxiliary machine motors 25 and 26, respectively.

  Note that a vehicle equipped with the fuel cell system 11 shown in FIG. 1 includes a shift position sensor that detects the shift position of the vehicle, an accelerator opening sensor that detects the accelerator opening, a brake sensor that detects the presence or absence of a brake, and the like. Is provided.

  The control unit 30 is a computer system for integrated control of the fuel cell system 11 and includes, for example, a CPU, a RAM, a ROM, and the like. The control unit 30 detects an operation amount (for example, accelerator opening) of an acceleration operation member (accelerator) provided in the fuel cell vehicle by a sensor (for example, accelerator opening sensor) or shifts the shift position of the vehicle. Detected by the position sensor and receives control information for acceleration request values (for example, traction motor speed, wheel speed, compressor and hydrogen pump motor speed, etc.) and controls the operation of various devices in the system .

  Note that the control unit 30 of the present embodiment can also detect the occurrence of an abnormality such as a failure of the secondary battery 20 based on a signal supplied from the secondary battery 20 or sensors provided in the vicinity thereof. It is.

  As loads other than the drive motors 13 and 14 and the auxiliary motors 25 and 26, power consumed by devices (transmission, wheel control device, steering device, suspension device, etc.) necessary for vehicle travel, There is power consumed by the devices (air conditioners, lighting fixtures, audio, etc.) to be arranged.

  The control unit 30 determines the distribution of each output power of the fuel cell 12 and the secondary battery 20 and calculates a power generation command value. More specifically, when the required power for the fuel cell 12 and the secondary battery 20 is calculated, the control unit 30 controls the operations of the FC boost converter 15 and the battery boost converter 22 so as to obtain these required powers.

  The control unit 30 controls the FC boost converter 15 to control the output voltage of the fuel cell 12 during normal operation including when no abnormality occurs in the secondary battery 20, and causes the battery boost converter 22 to drive the drive motor 13, The output voltage to the 14 side, in other words, the input voltage to the drive inverter 16 and the auxiliary machine inverter 17 is controlled. The operation performed by the control unit 30 when an abnormality occurs in the secondary battery 20 will be described in detail with reference to FIG.

  FIG. 2 is a flowchart illustrating one control example of the control unit when an abnormality occurs in the secondary battery. When the control unit 30 detects a failure (abnormality) of the secondary battery 20, the relay 21 of the secondary battery 20 is disconnected (battery failure). Thereby, the secondary battery 20 is disconnected from the fuel cell system 11.

(Step S10)
First, the control unit 30 determines whether or not the accelerator opening is larger than 0 and the rotational speed on the opposite side of the traveling direction of the drive motors 13 and 14 is greater than the rotational speed. Specifically, the accelerator opening is detected by an accelerator opening sensor provided in the vehicle, and when the accelerator opening is larger than 0, it is determined that the user intends to move forward. The shift position sensor detects the shift position of the vehicle and determines the forward direction of rotation (positive rotation at the drive position (D) and negative rotation at the reverse (R)). Based on the information that the motor speed is traveling in the backward direction, the controller 30 determines whether the controller 30 falls. As a result of the determination, if it is determined that the accelerator opening is larger than 0 and the rotational speed on the opposite side of the traveling direction of the drive motors 13 and 14 is greater than the rotational speed (step S10 (YES)), step The process proceeds to S30, and if not (step S10 (NO)), the process proceeds to step S20.

(Step S20)
If the condition shown in step S10 (accelerator opening is larger than 0 and the rotational speed on the opposite side of the traveling direction of the drive motors 13 and 14 is greater than the rotational speed), the drive motor is determined in step S20. Based on the required power of 13 and 14, the generated power of the fuel cell 12 is calculated.

(Step S30)
When the condition shown in step S10 (accelerator opening is greater than 0 and the rotational speed on the opposite side of the driving direction of the drive motors 13 and 14 is greater than the rotational speed), the motor moves forward in step S30. Regenerative power generation is performed with directional torque applied.

(Step S40, Step S50)
Next, the regenerative electric power is consumed by the auxiliary equipment of the fuel cell (air compressor, hydrogen pump, cooling water pump, etc.) (step S40). Since the auxiliary machine is driven, fuel can be supplied to the fuel cell 12, so that the generated electric power of the fuel cell 12 is used to shift to motor control of positive rotation and positive torque (step S 50). ).

  As described above, according to the fuel cell system of the present embodiment, when the accelerator opening of the vehicle is greater than 0 and the rotational speed on the opposite side of the traveling direction of the motor is lower than the rotational speed, the motor regenerative power generation is performed. And supply regenerative power to the fuel cell auxiliaries. When the vehicle slips down, the fuel cell is generated to move the auxiliary device of the fuel cell by the regenerative power of the motor, and a necessary torque can be output based on the generated power of the fuel cell to travel uphill. Further, since the regenerative power is consumed by the auxiliary device of the fuel cell, the overvoltage of the capacitor can be suppressed.

  The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. In other words, those specific examples that have been appropriately modified by those skilled in the art are also included in the scope of the present invention as long as they have the characteristics of the present invention.

11: Fuel cell system 12: Fuel cell 13, 14: Drive motor 15: Boost converter (first boost converter)
16: Drive inverter 17: Auxiliary inverter 20: Secondary battery 21: Relay 22: Battery boost converter (second boost converter)
23, 24: Auxiliary machine inverter 25, 26: Auxiliary machine motor 30: Control unit

Claims (1)

A fuel cell system including a fuel cell and a secondary battery as a power supply source to a drive motor for driving a vehicle,
A first boost converter having a capacitor and boosting a voltage output from the fuel cell and supplying the boosted voltage to the auxiliary device of the fuel cell and the drive motor;
A second boost converter having a capacitor and boosting a voltage output from the secondary battery;
A control unit for controlling the regenerative operation of the drive motor,
The controller is
When the accelerator opening of the vehicle is greater than 0 and the rotational speed on the opposite side of the traveling direction of the drive motor is greater than the rotational speed, the regenerative power generation of the drive motor is permitted and the regenerative power is sent to the auxiliary machine. Supply fuel cell system.

Images