WO2013030933A1 - Fuel cell system and fuel cell vehicle - Google Patents

Abstract

[Problem] A fuel cell system provided with a converter, wherein control at a high voltage in a normal-temperature environment is achieved while an increase in manufacturing cost is suppressed. [Solution] A fuel cell system (1) having a fuel cell converter (10) provided between a fuel cell (2) and a load device (5), wherein the fuel cell system is provided with a threshold value switching means (7) for switching the overvoltage threshold value of the fuel cell converter (10) according to the temperature of the cooling water cooling the fuel cell converter (10). The threshold value switching means (7) increases the overvoltage threshold value as the temperature of the cooling water increases.

Description

Fuel cell system and fuel cell vehicle

The present invention relates to a fuel cell system and a fuel cell vehicle.

Conventionally, there has been proposed a fuel cell vehicle in which a fuel cell that generates power by receiving a supply of reaction gas (fuel gas and oxidizing gas) is mounted on a vehicle together with a secondary battery such as a storage battery. In such a fuel cell vehicle, a converter for converting a DC voltage supplied from a fuel cell or a secondary battery into a larger DC voltage is generally employed.

Currently, a technique has been proposed in which the temperature of a switching element of a converter is detected, and the number of switching elements to be driven and the switching target switching element are determined based on the detected element temperature (see, for example, Patent Document 1). By adopting such a technique, it is said that the useless operation (switching loss) of driving all the switching elements even when the load is low can be eliminated, and the power conversion efficiency of the converter can be improved.

JP 2011-19338 A

By the way, it is known that the withstand voltage performance of the switching element of the converter changes as the temperature changes. For this reason, in the conventional technique as described in Patent Document 1, the converter is designed so that the actual voltage does not exceed the withstand voltage even in a low temperature environment where the withstand voltage of the switching element is the lowest in the specification. The overvoltage threshold of the boosted voltage was set to the minimum value. However, if the overvoltage threshold is set to the minimum value in advance as described above, the boosted voltage of the converter is controlled too low even in a room temperature environment, and as a result, the vehicle running performance (drivability) may be reduced. was there.

On the other hand, it is also possible to employ an expensive switching element having a high withstand voltage performance that allows control at a high voltage that does not deteriorate the vehicle running performance in a low temperature environment. However, when such an expensive switching element is employed, a new problem arises that the manufacturing cost of the converter (and thus the entire system) increases.

The present invention has been made in view of such circumstances, and an object of the present invention is to realize control at a high voltage in a normal temperature environment while suppressing an increase in manufacturing cost in a fuel cell system including a converter. .

In order to achieve the above object, a fuel cell system according to the present invention is a fuel cell system including a fuel cell converter provided between a fuel cell and a load device, and a temperature of cooling water for cooling the fuel cell converter. And a threshold value switching means for switching the overvoltage threshold value of the fuel cell converter.

When such a configuration is adopted, the overvoltage threshold of the fuel cell converter can be switched according to the temperature of the cooling water that cools the fuel cell converter. Therefore, for example, in a low temperature environment where the temperature of the cooling water is lower than the normal temperature, the switching element can be protected by setting the overvoltage threshold of the fuel cell converter to a small value. For this reason, since it is not necessary to employ an expensive switching element having high withstand voltage performance even in a low temperature environment, an increase in manufacturing cost of the fuel cell converter (and thus the entire system) can be suppressed. In addition, when the temperature of the cooling water is normal, control at a high voltage can be realized by setting the overvoltage threshold of the fuel cell converter to a large value.

Further, in the fuel cell system according to the present invention, the battery, the battery converter provided between the battery and the load device, and limit value switching for switching the boost target voltage limit value of the battery converter according to the temperature of the cooling water Means. In such a case, it is possible to employ threshold switching means for switching the overvoltage threshold of the fuel cell converter in synchronization with switching of the boost target voltage limit value of the battery converter.

If such a configuration is adopted, the boost target voltage limit value of the battery converter can be switched according to the temperature of the cooling water, and the overvoltage threshold value of the fuel cell converter can be switched in synchronization with the switching of the boost target voltage limit value. .

The fuel cell vehicle according to the present invention is equipped with the fuel cell system.

When such a configuration is adopted, when the temperature of the cooling water is normal, control at a high voltage can be realized by setting the overvoltage threshold of the fuel cell converter to a large value. As a result, high running performance can be ensured.

According to the present invention, in a fuel cell system provided with a converter, it is possible to realize control at a high voltage in a normal temperature environment while suppressing an increase in manufacturing cost.

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. It is a graph which shows the relationship between the cooling water temperature of the fuel cell system which concerns on embodiment of this invention, and an overvoltage threshold value.

Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. The fuel cell system 1 according to the present embodiment is a power generation system mounted on a fuel cell vehicle.

As shown in FIG. 1, the fuel cell system 1 rotates the traction motor 5 by supplying electric power generated by the fuel cell 2 and the battery 3 to the traction motor 5 via the inverter 4. . The fuel cell system 1 includes an FC (fuel cell) converter 10 provided between the fuel cell 2 and the inverter 4, a battery converter 6 provided between the battery 3 and the inverter 4, and a controller for integrated control of the entire system. 7 etc.

The fuel cell 2 is a solid polymer electrolyte cell stack configured by stacking a plurality of single cells in series. In the fuel cell 2, an oxidation reaction of the following formula (1) occurs in the anode electrode, and a reduction reaction of the following formula (2) occurs in the cathode electrode, and the fuel cell 2 as a whole has the following formula (3). An electrical reaction occurs.

H ₂ → 2H ⁺ + 2e ⁻ (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

A unit cell constituting the fuel cell 2 is a separator for supplying a fuel gas and an oxidizing gas to a membrane / electrode assembly (MEA) formed by sandwiching a polymer electrolyte membrane between two electrodes, an anode electrode and a cathode electrode. It has a structure sandwiched between. The fuel cell 2 is provided with a fuel gas supply system for supplying fuel gas to the anode electrode, an oxidizing gas supply system for supplying oxidizing gas to the cathode electrode, and a cooling system for supplying cooling liquid into the separator. By controlling the supply amount of the fuel gas and the supply amount of the oxidizing gas in accordance with the control signal from the control signal, it is possible to generate desired power.

The FC converter 10 functions to control the output voltage of the fuel cell 2. As shown in FIG. 1, the FC converter 10 in the present embodiment is a multiphase converter in which four phases of a U-phase converter 11, a V-phase converter 12, a W-phase converter 13, and an X-phase converter 14 are connected in parallel. The FC converter 10 uses one phase driving that uses only one phase (for example, U phase) and two phases (for example, U phase and V phase) according to the load (required power) of a load device such as the traction motor 5. The drive phase can be switched such as two-phase drive, three-phase drive using three phases (for example, U phase, V phase, and W phase) and four-phase drive using all drive phases. .

The FC converter 10 controls the output voltage of the fuel cell 2 so as to be a voltage corresponding to the target output (voltage after boosting). Note that the output voltage (voltage after boosting) and output current of the FC converter 10 can be detected by a voltage sensor and a current sensor (not shown).

The types of switching elements used for each drive phase (U phase, V phase, W phase, X phase) of the FC converter 10 include, for example, a junction Schottky diode, a pin / Schottky composite diode, and a MOS barrier. Diodes such as Schottky diodes, current control transistors such as bipolar junction transistors (BJT) and Darlington, thyristors such as normal thyristors and GTO (Gate Turn Off) thyristors, MOS field effect (FET) transistors, insulated gate bipolar type Examples thereof include a voltage control type transistor such as a transistor (IGBT) and an injection promotion type insulated gate transistor (IEGT). Of these, thyristors and voltage-controlled transistors are preferable.

In the present embodiment, a cooling device (not shown) that circulates cooling water to cool the FC converter 10 and the like, and a temperature sensor 10a that detects the temperature of the cooling water of the cooling device are provided. The temperature of the cooling water detected by the temperature sensor 10a is input to the controller 7 and used for overvoltage threshold switching control described later.

The battery 3 is connected in parallel to the fuel cell 2 with respect to the traction motor 5 and has a function of storing surplus power and regenerative energy during regenerative braking, and at the time of load fluctuation accompanying acceleration or deceleration of the fuel cell vehicle. It functions as an energy buffer. As the battery 3, for example, a secondary battery such as a nickel / cadmium storage battery, a nickel / hydrogen storage battery, or a lithium secondary battery can be employed.

The battery converter 6 fulfills the function of controlling the input voltage of the inverter 4. For example, a battery converter having a circuit configuration similar to that of the FC converter 10 can be adopted. As the battery converter 6, a step-up converter may be employed, but instead, a step-up / step-down converter capable of a step-up operation and a step-down operation may be employed, and the input voltage of the inverter 4 can be controlled. Any configuration can be adopted.

The inverter 4 can employ, for example, a PWM inverter driven by a pulse width modulation method, and converts DC power supplied from the fuel cell 2 or the battery 3 into three-phase AC power in accordance with a control command from the controller 7. Thus, the rotational torque of the traction motor 5 is controlled.

The traction motor 5 generates rotational torque as power for the fuel cell vehicle, and is also configured to generate regenerative power during deceleration. The rotational torque of the traction motor 5 is transmitted to the tire 9 through the shaft 8a after being decelerated to a predetermined rotational speed by the reduction gear 8. In the present embodiment, all devices (including the traction motor 5 and the speed reduction device 8) that operate by receiving power supplied from the fuel cell 2 are collectively referred to as a load device.

The controller 7 is a computer system for integrated control of the fuel cell system 1 and includes, for example, a CPU, a RAM, a ROM, and the like. The controller 7 receives inputs of signals (for example, a signal indicating the accelerator opening, a signal indicating the vehicle speed, a signal indicating the output current and output voltage of the fuel cell 2) supplied from various sensors, and loads the load on the load device. (Required power) is calculated.

The load of the load device is, for example, the total value of the vehicle traveling power and the auxiliary power. Auxiliary power is the power consumed by in-vehicle auxiliaries (air compressors, hydrogen pumps, cooling water circulation pumps, etc.), and equipment required for vehicle travel (transmissions, wheel control devices, steering devices, suspension devices, etc.) Power consumed, power consumed by devices (air conditioners, lighting fixtures, audio, etc.) arranged in the passenger space are included.

Then, the controller 7 determines the distribution of output power between the fuel cell 2 and the battery 3 and calculates a power generation command value. When the controller 7 calculates the required power for the fuel cell 2 and the battery 3, the controller 7 controls the operations of the FC converter 10 and the battery converter 6 so that these required powers are obtained.

Further, the controller 7 receives the input of the temperature of the cooling water detected by the temperature sensor 10a and switches the target voltage limit value (boost target voltage limit value) of the output voltage (voltage after boost) of the battery converter 6 or not. The boost target voltage limit value is switched according to the detected temperature so that the boost target voltage limit value increases as the detected temperature increases. That is, the controller 7 functions as limit value switching means in the present invention.

Specifically, as shown in FIG. 2, when the detected temperature is lower than T2 (° C.) (eg, T1 (° C.)), the controller 7 sets the boost target voltage limit value of the battery converter 6 to V _B1 (V). Keep it. Then, the controller 7 switches the boost target voltage limit value of the battery converter 6 from V _B1 (V) to V _B2 (V) when the detected temperature rises to T2 (° C.) or more, and detects the detected temperature. Is kept at V _B2 (V) in the temperature range of T2 (° C.) or more and less than T4 (° C.) (eg, T3 (° C.)). Thereafter, the controller 7 switches the boost target voltage limit value of the battery converter 6 from V _B2 (V) to V _B3 (V) when the detected temperature rises to T4 (° C.) or higher.

On the other hand, when the detected temperature rises to be equal to or higher than T4 (° C.), the controller 7 sets the boost target voltage limit value of the battery converter 6 to V until the detected temperature decreases and becomes lower than T3 (° C.). _B3 (V) is maintained. Then, the controller 7 switches the boost target voltage limit value of the battery converter 6 from V _B3 (V) to V _B2 (V) when the detected temperature falls below T3 (° C.), and detects the detected temperature. Is kept at V _B2 (V) in the temperature range of T1 (° C.) or more and less than T3 (° C.) (eg, T2 (° C.)). Thereafter, the controller 7 switches the boost target voltage limit value of the battery converter 6 from V _B2 (V) to V _B1 (V) when the detected temperature falls below T1 (° C.).

Further, the controller 7 receives an input of the temperature of the cooling water detected by the temperature sensor 10a, determines whether or not to switch the overvoltage threshold of the output voltage (post-boost voltage) of the FC converter 10, and the detected temperature is high. The overvoltage threshold is switched according to the detected temperature so as to increase the overvoltage threshold as the time goes. That is, the controller 7 functions as threshold switching means in the present invention. At this time, the controller 7 performs control to switch the overvoltage threshold of the FC converter 10 in synchronization with the switching of the boost target voltage limit value of the battery converter 6.

Specifically, as shown in FIG. 2, when the detected temperature is lower than T2 (° C.) (for example, T1 (° C.)), the controller 7 maintains the overvoltage threshold of the FC converter 10 as V _FC1 (V). To do. The controller 7 switches the overvoltage threshold of the FC converter 10 from V _FC1 (V) to V _FC2 (V) when the detected temperature rises to T2 (° C.) or higher, and the detected temperature is T2 ( The overvoltage threshold is maintained at V _FC2 (V) in the temperature region of not less than T4 (° C) (eg, T3 (° C)). Thereafter, the controller 7 switches the overvoltage threshold of the FC converter 10 from V _FC2 (V) to V _FC3 (V) when the detected temperature rises to T4 (° C.) or higher.

On the other hand, when the detected temperature rises to be equal to or higher than T4 (° C.), the controller 7 sets the overvoltage threshold of the FC converter 10 to V _FC3 (V) until the detected temperature thereafter decreases to less than T3 (° C.). ). The controller 7 switches the overvoltage threshold of the FC converter 10 from V _FC3 (V) to V _FC2 (V) when the detected temperature falls below T3 (° C.), and the detected temperature is T1 ( The overvoltage threshold is maintained as V _FC2 (V) in the temperature region of not less than T 3 (° C.) (eg, T 2 (° C.)). Thereafter, the controller 7 switches the overvoltage threshold value of the FC converter 10 from V _FC2 (V) to V _FC1 (V) when the detected temperature falls below T1 (° C.).

That is, in the process of increasing the detected temperature, when the detected temperature is less than T2 (° C.) (for example, T1 (° C.)), the boost target voltage limit value of the battery converter 6 and the overvoltage threshold of the FC converter 10 are V _B1 ( V) and V _FC1 (V) are maintained, and when the detected temperature reaches T2 (° C.) or more, the boost target voltage limit value of the battery converter 6 and the overvoltage threshold value of the FC converter 10 are V _B2 (V), respectively. And V _FC2 (V) at the same time. In the temperature region where the detected temperature is T2 (° C.) or higher and lower than T4 (° C.) (eg, T3 (° C.)), the boost target voltage limit value of the battery converter 6 and the overvoltage threshold value of the FC converter 10 are V _B2 (V). And V _FC2 (V), and when the detected temperature reaches T4 (° C.) or higher, the boost target voltage limit value of the battery converter 6 and the overvoltage threshold value of the FC converter 10 are V _B3 (V) and V V, respectively. It will be switched simultaneously to _FC3 (V).

On the other hand, in the decreasing process of the detected temperature, the boost target voltage limit value of the battery converter 6 and the overvoltage threshold value of the FC converter 10 are V _B3 (V) and V _FC3 (V), respectively, until the detected temperature becomes lower than T3 (° C.). When the detected temperature becomes less than T3 (° C.), the boost target voltage limit value of the battery converter 6 and the overvoltage threshold value of the FC converter 10 become V _B2 (V) and V _FC2 (V), respectively. It can be switched at the same time. In the temperature region where the detected temperature is T1 (° C.) or more and less than T3 (° C.) (eg, T2 (° C.)), the boost target voltage limit value of the battery converter 6 and the overvoltage threshold value of the FC converter 10 are V _B2 (V). And V _FC2 (V), and when the detected temperature becomes less than T1 (° C.), the boost target voltage limit value of the battery converter 6 and the overvoltage threshold value of the FC converter 10 are V _B1 (V) and V _{FC1, respectively.} Switching to (V) is performed at the same time.

In the fuel cell system 1 according to the embodiment described above, the overvoltage threshold of the FC converter 10 can be switched according to the temperature of the cooling water that cools the FC converter 10 and the like. Therefore, in a low temperature environment where the temperature of the cooling water is lower than room temperature (for example, less than T2 (° C.)), the switching element is set by setting the overvoltage threshold of the FC converter 10 to a small value (V _FC1 (V)). Can be protected. For this reason, since it is not necessary to employ an expensive switching element having a high withstand voltage performance even in a low temperature environment, an increase in manufacturing cost of the FC converter 10 (and thus the entire system) can be suppressed. Further, when the temperature of the cooling water is normal temperature (for example, T4 (° C.)), the overvoltage threshold of the FC converter 10 is set to a large value (V _FC3 (V)), thereby realizing a high voltage control. Can be made.

In the fuel cell system 1 according to the embodiment described above, the boost target voltage limit value of the battery converter 6 can be switched according to the temperature of the cooling water, and is synchronized with the switching of the boost target voltage limit value. The overvoltage threshold of the FC converter 10 can be switched.

Further, the fuel cell vehicle according to the embodiment described above sets the overvoltage threshold of the FC converter 10 to a large value (V _FC3 (V)) when the temperature of the cooling water is normal temperature (for example, T4 (° C.)). Thus, since the fuel cell system 1 that can realize control at a high voltage is provided, high running performance can be ensured.

In the above-described embodiment, an example in which the fuel cell system according to the present invention is mounted on a fuel cell vehicle has been shown. Such a fuel cell system can also be mounted. Further, the fuel cell system according to the present invention may be applied to a stationary power generation system used as a power generation facility for a building (house, building, etc.). Furthermore, the present invention can be applied to a portable fuel cell system.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... Battery, 5 ... Traction motor (load apparatus), 6 ... Battery converter, 7 ... Controller (threshold value switching means, limit value switching means), 10 ... FC converter (fuel cell) converter).

Claims (4)

1. A fuel cell system comprising a fuel cell converter provided between a fuel cell and a load device,
   A threshold value switching means for switching an overvoltage threshold value of the fuel cell converter according to a temperature of cooling water for cooling the fuel cell converter;
   Fuel cell system.
2. The threshold switching means increases the overvoltage threshold as the temperature of the cooling water increases.
   The fuel cell system according to claim 1.
3. Battery,
   A battery converter provided between the battery and the load device;
   Limit value switching means for switching the boost target voltage limit value of the battery converter according to the temperature of the cooling water,
   The threshold value switching means switches the overvoltage threshold value of the fuel cell converter in synchronization with the switching of the boost target voltage limit value of the battery converter.
   The fuel cell system according to claim 1 or 2.
4. The fuel cell system according to any one of claims 1 to 3 is provided.
   Fuel cell vehicle.
   

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