JP2003187841A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which hardly exerts adverse influence on power generating characteristics of a fuel cell and on the charging/ discharging characteristics of a capacitor. <P>SOLUTION: A charging current, flowing from the fuel cell 21 to a capacitor 25, and a regenerative current from a motor drive circuit 29 to the capacitor 25 are controlled by a switching device 28A and an HBC controller 33. Herewith, even although the fuel cell 21 and capacitor 25 are separately connected in parallel to the motor drive circuit 29, the discharge current and regenerative current flowing from the fuel cell 21 and motor drive circuit 29 to the capacitor 25 can be restricted. Thereby, this fuel cell system hardly exerts adverse influence on the power generating characteristics of the fuel cell 21 and on the charging/discharging characteristics of the capacitor 25. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell system including a fuel cell and a capacitor connected in parallel to a motor drive circuit, and more particularly to a fuel cell system suitable for an electric vehicle.

[0002]

2. Description of the Related Art Conventionally, as a fuel cell system used in an electric vehicle or the like, a system in which a fuel cell and a capacitor are connected in parallel has been proposed, and regenerative electric power generated during braking by a regenerative brake is concerned. The capacitor is used to store electricity, and the electric energy stored in the condenser can be used to compensate for the shortage of electrical energy supplied from the fuel cell only when the load is high such as during acceleration.

As such a capacitor, a large capacity electric double layer capacitor or the like is usually used and is connected in parallel to a fuel cell or a motor drive circuit via a switch or the like.

[0004]

However, when a large-capacity capacitor is connected in parallel to the fuel cell or the motor drive circuit as described above, the following two problems occur. (1) If the amount of charge stored in the capacitor is extremely low, such as close to 0%, the potential difference between the capacitor and the fuel cell is large, and it takes some time for full charge. Immediately after connecting the capacitor and the fuel cell, a phenomenon may occur in which a large current exceeding the supply capacity of the fuel cell rapidly flows from the fuel cell to the capacitor. At this time, the supply of oxygen necessary for a chemical reaction to generate electricity is insufficient, and an undesired chemical reaction (for example, hydrogen reacts with carbon that constitutes the electrode) occurs at the electrode, which deteriorates the electrode. Therefore, there is a problem that the power generation characteristics of the fuel cell may be adversely affected.

(2) Further, since the fuel cell and the motor drive circuit are connected in parallel to the capacitor, when the surplus power by the fuel cell or the regenerative power by the motor drive circuit is generated, the electric energy is Although it can be supplied to the capacitor, in such a case, if the supply exceeds the scheduled charging capacity of the capacitor and the supply is continued, there is a problem that the charge / discharge characteristics of the capacitor may be affected such that the electrolyte in the capacitor is decomposed. is there.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel cell system in which the power generation characteristics of a fuel cell and the charge / discharge characteristics of a capacitor are less likely to be adversely affected. Especially.

[0007]

[Means for Solving the Problems and Actions and Effects of the Invention]
In order to achieve the above object, the fuel cell system according to claim 1 is a fuel cell system including a fuel cell and a capacitor that are respectively connected in parallel to a motor drive circuit, and a charging current flowing from the fuel cell to the capacitor. And a current control means for controlling the regenerative current flowing from the motor drive circuit to the capacitor.

According to the first aspect of the invention, the current control means controls the charging current flowing from the fuel cell into the capacitor and the regenerative current flowing from the motor drive circuit into the capacitor. Accordingly, even if the fuel cell and the capacitor are connected in parallel to the motor drive circuit, the charging current and the regenerative current flowing from the fuel cell and the motor drive circuit to the capacitor are limited. Therefore, for example, even when the amount of charge stored in the capacitor is extremely reduced such that it is close to 0%, the charging current flowing from the fuel cell into the capacitor can be suppressed,
Further, even when the surplus power generated by the fuel cell or the regenerative power generated by the motor drive circuit is supplied to the capacitor, the charging current and the regenerative current flowing into the capacitor within the expected charging capacity of the capacitor. Can be suppressed. Therefore, there is an effect that the power generation characteristics of the fuel cell and the charge / discharge characteristics of the capacitor are hardly adversely affected.

In the fuel cell system according to claim 2,
In claim 1, the technical feature is that the current control means is composed of a semiconductor element.

According to the second aspect of the invention, since the current control means is made of a semiconductor element, it is possible to suppress energy loss in current control more than that of a passive element such as a resistor. As a result, the current can be efficiently controlled, and the electric energy generated in the fuel cell or the like can be stored in the capacitor as lean as possible. Therefore, in addition to the effect that the power generation characteristics of the fuel cell and the charge / discharge characteristics of the capacitor are less likely to be adversely affected, there is an effect of suppressing wasteful consumption of clean energy.

Further, in the fuel cell system according to claim 3, in claim 1 or 2, the current control means is:
A technical feature is that when the voltage between the terminals of the capacitor is lower than a first predetermined voltage value, the charging current flowing from the fuel cell into the capacitor is suppressed to a first predetermined current value or less.

According to the third aspect of the invention, the current control means suppresses the charging current flowing from the fuel cell into the capacitor to the first predetermined current value or less when the inter-terminal voltage of the capacitor is lower than the first predetermined voltage value. To do. This allows
The charging current flowing from the fuel cell to the capacitor is suppressed when the conditions that may adversely affect the power generation characteristics of the fuel cell are satisfied based on the voltage between the terminals of the capacitor, otherwise it is not suppressed. It is possible to perform current control according to the charged state. Therefore, there is an effect that the power generation characteristics of the fuel cell are less likely to be adversely affected.

Furthermore, in the fuel cell system according to claim 4, in claim 1 or 2, the current control means is configured to operate from the fuel cell when the inter-terminal voltage of the capacitor is higher than a second predetermined voltage value. A technical feature is that the charging current flowing into the capacitor and / or the regenerative current flowing from the motor drive circuit into the capacitor is suppressed to a second predetermined current value or less.

According to the fourth aspect of the present invention, the current control means causes the charging current flowing from the fuel cell to the capacitor and / or the motor driving circuit to flow into the capacitor when the inter-terminal voltage of the capacitor is higher than the second predetermined voltage value. The regenerative current is suppressed below the second predetermined current value. That is, when the voltage between the terminals of the capacitor is higher than the second predetermined voltage value, the current control means causes the charging current to flow from the fuel cell to the capacitor and the regenerative current from the motor drive circuit to the capacitor, or the fuel cell to the capacitor. The charging current that flows in or the regenerative current that flows into the capacitor from the motor drive circuit is suppressed to a second predetermined current value or less. This suppresses the charging current and / or the regenerative current flowing from the fuel cell and / or the motor drive circuit to the capacitor when the conditions that may adversely affect the charge / discharge characteristics of the capacitor are satisfied based on the voltage between the terminals of the capacitor. It is possible to perform current control according to the charged state of the capacitor, which is not suppressed in other cases. Therefore, there is an effect that the charge / discharge characteristics of the capacitor are less likely to be adversely affected.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a fuel cell system of the present invention will be described below with reference to the drawings. In addition, in each of the following embodiments, an example in which the fuel cell system of the present invention is applied to an electric vehicle will be described.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
The functional block diagram showing the main functional composition of fuel cell system 20 concerning an embodiment is shown. As shown in the figure,
The fuel cell system 20 mainly includes a fuel cell 21, an output control current adjusting unit 23, a capacitor 25,
A fuel cell 21 and a capacitor 25 each of which is composed of a protection current adjusting unit 28, a load 29, a system controller 31 and the like, and is connected in parallel to the load 29.
Equipped with. Therefore, the structure of the fuel cell system 20 is also called a hybrid circuit. The broken lines shown in FIG. 1 indicate the flow of information signals exchanged between the functional blocks.

FIG. 2 is a circuit diagram showing the electrical configuration of the fuel cell system 20, and more specifically shows the configuration contents of the fuel cell system 20 than the functional block diagram of FIG. Hereinafter, referring to FIG. 2, the fuel cell system 20
The configuration of will be described. The broken lines shown in FIG. 2 indicate the flow of information signals exchanged between the functional blocks or functional parts.

The fuel cell 21 can take out electric energy by reacting hydrogen and oxygen, and is one of the energy sources of an electric vehicle in which wheels are driven by a motor. Therefore, the fuel cell 21 is supplied with hydrogen and oxygen (or air), and the supply amount thereof is controlled by a fuel cell / motor controller (hereinafter referred to as “FC / M controller”) 35, which will be described later. The output power is being controlled. The fuel cell 21 is generally
The fuel cell system according to the present invention can be applied to any of various types depending on the type of hydrogen storage, reforming catalyst, etc., as long as hydrogen and oxygen react to generate electricity.

The fuel cell 21 has its terminal voltage (hereinafter referred to as "FC voltage") Vfc detected by a voltage sensor 22. That is, between the output terminals of the fuel cell 21,
The voltage sensor 22 is connected, and the voltage sensor 22
The FC voltage Vfc detected by is output to the FC / M controller 35. As a result, the output voltage of the fuel cell 21 (FC voltage V
Since fc) can be monitored as appropriate, output control of the fuel cell 21 based on this can be performed.

Contactors CN-a and CN-b are connected to the output terminal of the fuel cell 21. That is, the fuel cell 2
A contactor CN-a is provided on the positive electrode terminal side of 1, and a fuel cell 2
Contactors CN-b are connected to the negative electrode terminal side of No. 1 respectively. These contactors CN-a and CN-b have a mechanical switch circuit such as a relay, and are used to turn on / off the switch circuit by a control signal input from the outside of the system controller 31 such as an ignition switch. It is configured so that it can be controlled in each state.

As a result, the input / output of the fuel cell 21 can be cut off by the operation of cutting off the switch circuit by either one of the contactors CN-a or CN-b. Since the contactors are connected to both terminals, even if one contactor CN-a (or contactor CN-b) fails, the other contactor CN-b (or contactor CN-a) causes the input / output of the fuel cell 21. Can be shut off. Therefore, the fuel cell 21 can be electrically disconnected from the external circuit when an abnormality occurs in the fuel cell 21 or when a vehicle equipped with the fuel cell system 20 detects a large impact such as a collision.

The output control current adjusting unit 23 is used for the fuel cell 2
It controls the amount of current output from the device 1, and is represented by a switching element 23A in FIG. This includes, for example, IGBT (insulated gate bipolar transistor)
or; an insulated gate bipolar transistor) or the like is used as a power semiconductor switching element, and its base terminal or gate terminal is connected to the FC / M controller 35.

As a result, FC / M based on the fuel cell current (hereinafter referred to as "FC current") Ifc detected by the current sensor 24 capable of measuring the input / output current of the fuel cell 21.
The switching control by the controller 35 can be performed on the switching element 23A. Therefore, the fuel cell 21 output through the switching element 23A
FC current Ifc of F is detected by the current sensor 24.
The FC current Ifc is input to the C / M controller 35.
The switching control of the switching element 23A is performed based on the value of. That is, since the closed loop negative feedback control system including the switching element 23A, the current sensor 24, and the FC / M controller 35 can be configured, it is possible to control the output of the fuel cell 21 targeting a predetermined current value.

The capacitor 25 is a large-capacity capacitor capable of storing electric charges of several F to several hundred F, and for example, an electric double layer capacitor is used. The fuel cell 21 is connected to the fuel cell 21 via the protection current adjusting unit 28.
And the motor drive circuit 29A are connected in parallel. Therefore, electric energy (charging current) generated by the electric power generated by the fuel cell 21 and electric energy (regenerative current) generated by the regenerative electric power generated by the motor drive circuit 29A are stored.
That is, it can be charged.

Like the fuel cell 21, this capacitor 25 also has a voltage sensor 26 detecting the voltage Vec between its terminals (hereinafter referred to as "capacitor voltage"). That is, the voltage sensor 26 is provided between the output terminals of the capacitor 25.
Are connected, and the capacitor voltage Vec detected by the voltage sensor 26 is output to a hybrid circuit controller (hereinafter referred to as “HBC controller”) 33 described later. As a result, the HBC controller 33
Output voltage of the capacitor 25 (capacitor voltage V
ec) is monitored accordingly.

The output terminal of the capacitor 25 has contactors CN-c and CN-d similar to the contactor CN-a described above.
Are connected. That is, the contactor CN-c is connected to the positive electrode terminal side of the capacitor 25, and the contactor CN-d is connected to the negative electrode terminal side of the capacitor 25. These contactors CN-c and CN-d are also configured so that the switch circuit can be controlled to be in a conductive / interrupted state by a control signal input from the outside of the system controller 31 such as an ignition switch.

As a result, one of the contactors CN-c and CN-d operates to cut off the switch circuit, so that the input / output of the capacitor 25 can be cut off, and both terminals of the capacitor 25 can be cut off. Since the contactor is connected to, even if one contactor CN-c (or contactor CN-d) fails, the other contactor CN-d (or contactor CN-c) cuts off the input and output of the capacitor 25. be able to. Therefore, the capacitor 25
When an abnormality occurs in the vehicle or when a vehicle equipped with the fuel cell system 20 detects a large impact such as a collision, the capacitor 25 can be electrically disconnected from the external circuit.

A current sensor 27 is connected to the contactor CN-c. This current sensor 27 includes a capacitor 25
Current input to the capacitor 25, that is, the amount of charging current or regenerative current flowing into the capacitor 25 is detected,
While detecting the amount of discharge current output from,
The HBC controller 33 detects the detected capacitor current Iec.
Is output to.

The protection current adjusting unit 28 controls the charging current flowing from the fuel cell 21 to the capacitor 25 and the regenerative current flowing from the motor drive circuit 29A to the capacitor 25. As shown in FIG. Is represented. Similar to the switching element 23A described above, a power semiconductor switching element such as an IGBT is used for this, and its base terminal or gate terminal is connected to the HBC controller 33. This switching element 28A is an HBC
By the capacitor management control process by the controller 33, current control according to the capacitor current Iec of the current sensor 27 is performed.

The protective current adjusting section 28 (switching element 28A) constitutes a functional element corresponding to "current control means" in the claims, together with an HBC controller 33 which will be described later.

The motor drive circuit 29A constitutes a part of the load connected in parallel to the fuel cell 21 and the capacitor 25, and is, for example, an inverter circuit for driving the vehicle AC motor M. As the load 29, in addition to the vehicle AC motor M driven by the motor drive circuit 29A, electric components such as a pump and a fan (not shown) for supplying hydrogen and oxygen (air) to the fuel cell 21 are also included in the load 29. Can be included in.

The system controller 31 is a control device composed of a microprocessor, a memory, an input / output interface and the like (not shown). The system controller 31 is connected to the HBC controller 33 and the FC / M controller 35, and the contactor CN-a described above. , CN-b, CN-c, CN-d are also connected. As a result, various control by the HBC controller 33 and the FC / M controller 35, control of the entire fuel cell system 20 such as processing, etc. can be performed, and the HBC controller 33 and the FC / M controller 3 can be performed.
Based on the information input from 5, contactors CN-a to CN
It is also possible to output a conduction / cutoff control signal for -d.

Like the system controller 31, the HBC controller 33 is also a control device composed of a microprocessor, a memory, an input / output interface and the like (not shown), and includes the system controller 31 and the voltage sensor 2.
6, the current sensor 27, and the switching element 28A, respectively. As a result, predetermined information can be transferred to and from the system controller 31, and the capacitor voltage Vec input from the voltage sensor 26 can be transferred.
Of the capacitor current Iec input from the current sensor 27, the capacitor management control process described later, that is, the switching control of the switching element 28A can be executed.

Like the system controller 31, the FC / M controller 35 is a control device including a microprocessor, a memory, an input / output interface and the like (not shown), and includes the system controller 31, the fuel cell 21, the voltage sensor 22, and the switching element. 23A, current sensor 2
4, each of which is connected to the motor drive circuit 29A.
This makes it possible to transfer predetermined information to the system controller 31, control the supply amount of hydrogen or the like supplied to the fuel cell 21, or control the motor drive circuit 29A. FC input from the voltage sensor 22
The switching of the switching element 23A can be controlled based on the information on the voltage Vfc and the information on the FC current Ifc input from the current sensor 24.

By configuring the fuel cell system 20 in this way, the fuel cell 2 can be connected to the motor drive circuit 29A.
Even if 1 and the capacitor 25 are connected in parallel, the charging current and the regenerative current flowing from the fuel cell 21 and the motor drive circuit 29A into the capacitor 25 can be limited. Therefore, for example, the capacitor 25
Even if the amount of electric charge stored in is extremely low such that it is close to 0%, the charging current flowing from the fuel cell 21 to the capacitor 25 can be suppressed and generated by the fuel cell 21. Even when the surplus power or the regenerative power generated by the motor drive circuit 29A is supplied to the capacitor 25, the charging current and the regenerative current flowing into the capacitor 25 are suppressed within the range of the scheduled charging capacity of the capacitor 25. You can Therefore, there is an effect that the power generation characteristics of the fuel cell 21 and the charge / discharge characteristics of the capacitor 25 are hardly adversely affected.

Even if the contactor CN-a shown in FIG. 2 is removed and the fuel cell 21 and the switching element 23A are directly connected, the switching element 23A replaces the function of the contactor CN-a. The number of parts can be reduced. That is, the switching element 2
By performing the control for cutting off the conduction by the gate control of 3A, it is possible to substitute the switching element 23A for the circuit cutting function by the contactor CN-a, so that the fuel cell 21 can be provided without the contactor CN-a. The fuel cell 21 can be electrically disconnected from the external circuit when an abnormality occurs in the vehicle or when a vehicle equipped with the fuel cell system 20 detects a large impact such as a collision. It is also possible to replace the contactor CN-b with a switching element similar to the switching element 23A.

Next, when the electric vehicle equipped with the fuel cell system 20 is started, or when the electric energy stored in the capacitor 25 is mainly supplied to the AC motor M when the output demand of the AC motor M is low. HBC in etc.
The flow of capacitor management control processing by the controller 33 will be described with reference to FIGS. 3 and 4.

As shown in FIG. 3, in the capacitor management control process at the time of starting the electric vehicle, first, step S1 is performed.
A process of reading the capacitor voltage Vec by 01 from the voltage sensor 26 is performed. Then, it is determined whether or not the capacitor voltage Vec read from the voltage sensor 26 in step S103 is lower than a preset first predetermined voltage value C_LV0.

That is, in step S103, it is determined whether or not the amount of electric charge stored in the capacitor 25 is extremely reduced such that it is close to 0%. The process of determining is performed.

When it is determined in step S103 that the capacitor voltage Vec is lower than the first predetermined voltage value C_LV0 (Yes in S103), the amount of charge stored in the capacitor 25 is extremely small and the fuel cell 21 may adversely affect the power generation characteristics. That is, the capacitor 25 whose input impedance is extremely low
By directly connecting the fuel cell 21 to the fuel cell 21, more electric energy can be extracted from the fuel cell 21 than expected, which may adversely affect the power generation characteristics of the fuel cell 21 thereafter. Therefore, the fuel cell 21 corresponds to the capacitor voltage Vec read by the voltage sensor 26.
Charging current value (1st
(Predetermined current value of) is set. This charging current value setting is
It is determined by the map in the next step S105.

In step S105, a process of reading a predetermined charging current value is performed according to a map as shown in FIG. 4, for example. In the map, a predetermined charging current value is mapped in advance corresponding to the range of the capacitor voltage detected by the voltage sensor 26 (C_LV0>C_LV1> C_L).
V2> C_LV3, C_CC1 <C_CC2 <C_CC3). For example, the range of the capacitor voltage C_LV is C_LV0 (for example, 290V) ≧
If C_LV ≧ C_LV1 (eg 210V), the charging current is set to C_CC1 (eg 75A), and if C_LV1 (eg 210V)> C_LV ≧ C_LV2 (eg 190V) the charging current is set to C_CC2 (eg 240A). It Further, if the range of the capacitor voltage C_LV is C_LV2 (for example 190V)> C_LV ≧ C_LV3 (for example 0V), the charging current is set to C_CC3 (for example 270A).

When a predetermined charging current value is set in step S105, a process of reading the capacitor current Iec from the current sensor 27 is performed in subsequent step S107.
That is, the charging current flowing into the current capacitor 25 is detected as the capacitor current Iec, and based on the detected charging current, the capacitor current Iec is read in order to perform the control process of the switching element 28A in the next step S109.

In step S109, a current control process for the switching element 28A is performed. That is, step S107
And the capacitor current Iec read by step S10
The charging current set by 5 is compared, and the gate control of the switching element 28A is performed so that they match.
Then, when this processing ends, the processing is returned to step S101 again.

On the other hand, when it cannot be determined in step S103 that the capacitor voltage Vec is lower than the first predetermined voltage value C_LV0 (No in S103), the capacitor 25
Since there is a high possibility that the electric charge amount is stored to some extent, the process proceeds to step S111 to control the switching element 28A to be in the continuous conduction state. That is, without controlling the current to the capacitor 25, the fuel cell 21
The electric energy that can be supplied from the capacitor is supplied to the capacitor 25. Then, in step S113, the steady operation control is activated, and the series of capacitor management control processes at the time of starting the electric vehicle is ended.

As described above, according to the fuel cell system 20 of the first embodiment, the switching elements 28A and H are provided.
When the capacitor voltage Vec of the capacitor 25 is lower than the first predetermined voltage value C_LV0 by the BC controller 33 (Yes in S103), the charging current flowing from the fuel cell 21 to the capacitor 25 is suppressed to the first predetermined current value C_CC1 or less. (S105, S107, S109). As a result, when the conditions that may adversely affect the power generation characteristics of the fuel cell 21 based on the capacitor voltage Vec of the capacitor 25 are satisfied (Yes in S103), the charging current flowing from the fuel cell 21 to the capacitor 25 is suppressed ( S10
5, S107, S109), otherwise (S1
It is possible to perform the current control according to the stored state of the capacitor 25, that is, No in 03) or not suppressed (S111). Therefore, there is an effect that the power generation characteristics of the fuel cell 21 are less likely to be adversely affected.

Next, the HBC controller 3 during steady operation of the electric vehicle equipped with the fuel cell system 20
The flow of the capacitor management control process according to No. 3 will be described with reference to FIGS.

As shown in FIG. 5, the capacitor management control processing at the time of steady operation of the electric vehicle is a modification of the flow of the capacitor management control processing at the time of starting described with reference to FIG. Note that steps S101, S107, S109, and S111 shown in FIG. 3 correspond to steps S201, S207, S209, and S211 shown in FIG. 5, respectively, and perform similar processing.

In the capacitor management control process during steady operation or the like, first, in step S201, the capacitor voltage Vec is read from the voltage sensor 26, and then the read capacitor voltage Vec is lower than the preset second predetermined voltage value C_HV0. Step S2 for determining whether or not it is high
03.

That is, in step S203, it is determined whether or not the electric charge is stored in the capacitor 25 close to the predetermined charging capacity, based on the capacitor voltage Vec which is the terminal voltage of the capacitor 25.

When it is determined in this step S203 that the capacitor voltage Vec is higher than the second predetermined voltage value C_HV0 (Yes in S203), the electric charge is already stored in the capacitor 25 to the extent that it is close to its charging capacity. Therefore, the charging / discharging characteristics of the capacitor 25 may be adversely affected by causing the normal charging current to flow. Therefore, a predetermined charging current value (second predetermined current value) that is unlikely to adversely affect the charge / discharge characteristics of the capacitor 25 is set corresponding to the capacitor voltage Vec read by the voltage sensor 26. This charging current value is set in the next step S2.
It is determined by the map according to 05.

In step S205, a process of reading a predetermined charging current value is performed according to the map as shown in FIG. 6, for example. In the map, a predetermined charging current value is mapped in advance corresponding to the range of the capacitor voltage detected by the voltage sensor 26 (C_HV0 <C_HV1, C_C.
C4 <C_CC5). For example, the range of the capacitor voltage C_HV is C_HV0 (for example, 369V) ≦ C_HV <C_HV1 (for example, 4
If it is 10V, the charging current is set to C_CC4 (for example, 5A), and if C_HV1 (for example, 410V) ≦ C_HV, the charging current is set to C_CC5 (for example, 0A).

In the above description, the grounds for specific numerical values are as follows. The maximum allowable voltage value of the capacitor having the laminated structure of the single cell is 410V, and this is set as C_HV1. The maximum allowable voltage of a capacitor is usually determined by the maximum allowable voltage of a single cell (maximum value at which the electrolyte in the cell does not decompose) × the number of stacked layers. Also, C_HV0 is due to the rapid inflow of current into the capacitor,
The maximum allowable voltage value (C_HV1) of the capacitor is 90 as a value at which the voltage of a specific single cell in the capacitor may exceed the maximum allowable voltage value due to a temporary local bias of the voltage.
% Value. Further, under the voltage of C_HV0, the value of C_CC4 is set to 5 A as a current inflow amount that does not cause a temporary local bias of the voltage between the cells in the capacitor. When the voltage of the capacitor is higher than the maximum allowable voltage value C_HV1, further attempting to charge the capacitor will cause the electrolyte to start to be decomposed in all cells in the capacitor, which may cause serious damage to the capacitor. 0
It was set to A.

When a predetermined charging current value is set in step S205, a process of reading the capacitor current Iec from the current sensor 27 is performed in subsequent step S207,
The read capacitor current Iec is compared with the charging current set in step S205, and the gate control of the switching element 28A is performed in step S2 so that they match.
09.

On the other hand, when it cannot be determined in step S203 that the capacitor voltage Vec is higher than the second predetermined voltage value C_HV0 (No in S203), the capacitor 25
There is a high possibility that there is still room to store the amount of charge, so
The process proceeds to step S211, and the switching element 2
8A is controlled to be continuously conductive. That is, the capacitor 2
The electric energy that can be supplied from the fuel cell 21 or the motor drive circuit 29A during regenerative braking is supplied to the capacitor 25 without controlling the current for the capacitor 5.

Step S209 or step S211
When the process by is finished, the series of capacitor management control processes is finished.

Thus, according to the fuel cell system 20 of the first embodiment, the switching elements 28A and H
When the capacitor voltage Vec of the capacitor 25 is higher than the second predetermined voltage value C_HV0 by the BC controller 33 (Yes in S203), the charging current flowing from the fuel cell 21 to the capacitor 25 and / or the motor drive circuit 29A to the capacitor 25 is changed. The regenerative current that flows in is suppressed to a second predetermined current value C_CC3 or less. As a result, when the conditions that may adversely affect the charge / discharge characteristics of the capacitor 25 are satisfied based on the capacitor voltage Vec of the capacitor 25 (Yes in S203), the fuel cell 21 and / or
Alternatively, the charging current and / or the regenerative current flowing from the motor drive circuit 29A to the capacitor 25 is suppressed, and otherwise (No in S203), the current is controlled according to the state of charge of the capacitor 25. You can Therefore, there is an effect that the charge / discharge characteristics of the capacitor 25 are less likely to be adversely affected.

It is also preferable that the circuit configuration described in this embodiment is modified as follows, for example. (1) A diode for preventing current backflow is added to the output side of the fuel cell 21. In this case, the direction of the diode is the direction in which the current output from the fuel cell 21 passes (the fuel cell 21
Anode, capacitor 25, motor drive circuit 29A on the side
Cathode on the side). It is desirable to dispose this location directly at any terminal of the switching element 23A in the circuit of FIG. 2 or between the contactor CN-a and the fuel cell 21. By disposing this diode, it becomes possible to prevent current from flowing into the fuel cell 21 from the capacitor 25 or the motor drive circuit 29A. (2) A current adjusting unit that controls the emission current from the capacitor 25 is installed. The arrangement location is connected in series to any terminal of the switching element 28A in the circuit of FIG. 2, for example. More specifically, a semiconductor element equivalent to the switching element 28A is arranged in series with any terminal of the switching element 28A in the direction of controlling the current in the opposite direction to the switching element 28A. (3) It is also preferable not to arrange the switching element 23A in FIG. By doing so, the circuit configuration can be simplified and the cost of the fuel cell system 20 as a whole can be reduced.

[Second Embodiment] Next, a fuel cell system 40 according to a second embodiment of the present invention will be described with reference to FIGS. 7 to 9. FIG. 7 is a circuit diagram showing the electrical configuration of the fuel cell system 40 according to the second embodiment of the present invention, which is substantially the same as the fuel cell system 20 according to the first embodiment described above. The same reference numerals are given to the components. The broken lines shown in FIG. 7 indicate the flow of information signals exchanged between the functional blocks.

Fuel cell system 4 according to the second embodiment
0 is a motor drive circuit 29 during braking of the electric vehicle
It is characterized by the control when the regenerative electric power by A is supplied to the capacitor 25, that is, the regenerative braking control. Therefore, as can be seen by comparing FIG. 2 and FIG. 7, in the fuel cell system 40 according to the second embodiment, the circuit element in which the discharge resistor 41 and the switching element 42 are connected in series is connected in parallel with the motor drive circuit 29A. Is different from the fuel cell system 20 according to the first embodiment in that the brake mechanism 53 provided in the AC motor M is controlled by the brake controller 51. Therefore,
The configuration and operation of the fuel cell system 40 will be described focusing on these differences.

As shown in FIG. 7, the fuel cell system 40
Is the discharge resistor 4 in parallel with the motor drive circuit 29A.
1 and a switching element 42 are connected in series, and a voltage sensor 43 connected in parallel to the motor drive circuit 29A detects the input / output voltage (inverter voltage) Viv of the motor drive circuit 29A. Is configured to get. Further, the brake mechanism 53 is provided in the motor drive circuit 29A, and the system controller 31
The brake mechanism 53 is configured to be controlled by the brake controller 51 connected to the. It should be noted that the brake controller 51 is configured so that brake depression amount information can be input from the outside.

Next, the regenerative braking control process in the fuel cell system 40 thus constructed will be described with reference to the flowcharts shown in FIGS. 8 and 9. The regenerative braking control process is performed by the system controller 31. In addition, this regenerative braking control process, when detecting the depression of the brake pedal by the depression amount sensor,
An interrupt signal is generated for the system controller 31 and is started as an interrupt process. Therefore, while the brake pedal is being depressed,
The regenerative braking control process is repeatedly executed, and the required braking force Brq described below is updated according to the change in the depression amount. Further, the regenerative braking force Bre is updated at any time according to the number of revolutions of the AC motor M which changes with the deceleration of the vehicle speed.

As shown in FIG. 8, in the regenerative braking control process by the system controller 31, first, in step S301.
Thus, it is determined whether or not the brake pedal is depressed based on the brake depression amount information input from the outside. The brake depression amount information is detected by a depression amount sensor (not shown) attached to the brake pedal.

When it is determined in step S301 that the brake pedal is depressed (Yes in S301),
In a succeeding step S303, processing for detecting the depression amount from the inputted brake depression amount information is performed. On the other hand, if it is not determined in step S301 that the brake pedal is depressed (No in S301), braking by the brake does not occur, and thus the regenerative braking control process ends (RETURN).

When the depression amount is detected in step S303, the braking force to be realized, that is, the required braking force Brq is calculated from the depression amount of the brake pedal in step S305. The required braking force Brq may be a value proportional to the amount of depression of the brake pedal, or may be obtained by a predetermined function or map in which the amount of depression of the brake pedal is input and the required braking force Brq is output. For example, when the depression amount (input) is large, the required braking force Brq corresponding to the proportional depression is output. It may also be based on the depression speed of the brake pedal.

Subsequently, in step S307, the braking force that can be achieved by the regenerative power generated at the current motor speed, that is, the regenerative braking force Bre is calculated from the characteristics of the AC motor M and the motor drive circuit 29A. Here, the "regenerated electric power" means the counter electromotive force generated from the electric motor when the output shaft of the electric motor is forcibly rotated by an external force. The regenerative braking force is the sum of the torque generated by the back electromotive force and the viscous resistance of the electric motor. Further, these can be calculated from various characteristics of the electric motor and its drive circuit (inverter circuit or the like).

In step S309, the braking force to be achieved by the mechanical brake, that is, the mechanical braking force Bme is calculated. The mechanical braking force Bme corresponds to the required braking force Brq minus the regenerative braking force Bre (Bme = Brq−Bre).

Then, the mechanical braking force Bme calculated in step S309 is output from the system controller 31 to the brake controller 51 in step S311 as an output command value to the brake controller 51, and a series of regenerative braking control processing ends. As a result, the brake mechanism 53 that receives the output command value Bme from the brake controller 51 executes mechanical braking based on the command value.

On the other hand, almost simultaneously with this, the capacitor management control process at the time of regenerative braking shown in FIG. 9 is executed by the HBC controller 33, so this capacitor management control process will be described with reference to FIG. This capacitor management control process at the time of regenerative braking is always executed by the HBC controller 33 in parallel with the above-described regenerative braking control process, and as shown in FIG.
Calls the capacitor management control processing as a subroutine. That is, the capacitor management control process at the time of steady operation described in FIG. 5 of the first embodiment is executed.

Then, in step S403, during regeneration, the motor drive circuit 29 detected by the voltage sensor 43 is detected.
It is monitored whether the inverter voltage Viv of A is equal to or higher than the allowable value. When the inverter voltage Viv is equal to or higher than the allowable value (Yes in S403), step S40
In order to shift the processing to step 5 and consume the surplus of the regenerative electric power in the discharge resistor 41, control for making the switching element 42 conductive, that is, processing for giving a trigger signal to the gate or base of the switching element 42 is performed.

On the other hand, when it is not determined in step S403 that the inverter voltage Viv is equal to or higher than the allowable value (No in S403), the series of capacitor management control processes is ended, and the process waits until it is activated again.

As described above, according to the fuel cell system 40 of the second embodiment, it is monitored whether the inverter voltage Viv of the motor drive circuit 29A detected by the voltage sensor 43 is equal to or more than the allowable value, and the inverter voltage Viv is If it is equal to or more than the allowable value (Yes in S403), step S4
The processing shifts to 05 to cause the discharge resistor 41 to consume the surplus of regenerative power. As a result, the surplus of regenerative power that cannot be fully charged by the capacitor 25 is consumed by the discharge resistor 41, so that it is possible to prevent the capacitor 25 from being supplied with electric energy exceeding the scheduled charging capacity of the capacitor 25. Therefore, also in the second embodiment, there is an effect that the charge / discharge characteristics of the capacitor 25 are less likely to be adversely affected.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing a main functional configuration of a fuel cell system according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an electrical configuration of the fuel cell system according to the first embodiment.

FIG. 3 is a flowchart showing a flow of a capacitor management control process at the time of starting an electric vehicle equipped with the fuel cell system of the first embodiment.

FIG. 4 is an explanatory diagram showing an example of a “capacitor voltage-charging current map” used in the capacitor management control process shown in FIG. 3.

FIG. 5 is a flowchart showing a flow of capacitor management control processing during steady operation of an electric vehicle equipped with the fuel cell system of the first embodiment.

FIG. 6 is an explanatory diagram showing an example of a “capacitor voltage-charging current map” used in the capacitor management control process shown in FIG. 5.

FIG. 7 is a circuit diagram showing an electrical configuration of a fuel cell system according to a second embodiment of the present invention.

FIG. 8 is a flowchart showing a flow of regenerative braking control processing by the fuel cell system according to the second embodiment.

FIG. 9 is a flowchart showing a flow of capacitor management control processing by the fuel cell system according to the second embodiment.

[Explanation of symbols]

20, 40 Fuel Cell System 21 Fuel Cell 23 Output Control Current Adjusting Section 23A Switching Element 25 Capacitor (Capacitor) 28 Protection Current Adjusting Section (Current Control Means) 28A Switching Element (Current Control Means) 29 Load 29A Motor Driving Circuit 31 System controller 33 HBC controller (current control means) 35 FC / M controller M motor Vec capacitor voltage (capacitor terminal voltage) Vfc FC voltage C_LV0 first predetermined voltage value C_CC1 first predetermined current value C_HV0 second predetermined voltage Value C_CC4 Second predetermined current value

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masao Ando             2-19-12 Sotokanda, Chiyoda-ku, Tokyo Stock             Inside the company Equus Research (72) Inventor Munehisa Horiguchi             2-19-12 Sotokanda, Chiyoda-ku, Tokyo Stock             Inside the company Equus Research (72) Inventor Tetsuhiro Ishikawa             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Hiroshi Sugiura             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. F-term (reference) 5H027 AA02 DD01 KK54 MM26                 5H115 PA15 PC06 PG04 PI16 PI18                       PO01 PO06 PO17 PU01 PV03                       PV09 PV23 QE10 QI04 QN11                       SE06 TI05 TI06 TO12 TO13                       TU02

Claims (4)

[Claims] 1. A fuel cell system comprising a fuel cell and a capacitor, which are connected in parallel to a motor drive circuit, respectively, wherein a charging current flowing from the fuel cell to the capacitor is controlled and the motor drive circuit controls the charging current. A fuel cell system comprising a current control means for controlling a regenerative current flowing into the fuel cell system. 2. The fuel cell system according to claim 1, wherein the current control means comprises a semiconductor element. 3. The current control means suppresses a charging current flowing from the fuel cell into the capacitor to a first predetermined current value or less when the inter-terminal voltage of the capacitor is lower than a first predetermined voltage value. The fuel cell system according to claim 1 or 2, wherein. 4. The current control means, when the terminal voltage of the capacitor is higher than a second predetermined voltage value, the charging current flowing from the fuel cell to the capacitor and / or the motor drive circuit to the capacitor. 3. The fuel cell system according to claim 1, wherein the regenerative current that flows in is suppressed to a second predetermined current value or less.