JP2002044807A - Power supply for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply for an electric vehicle, which suppresses deterioration of a fuel cell by preventing the fuel cell from supplying excessive current when the power demand abruptly increases from the drive motor. SOLUTION: The power supply has a first power supply having a DC/DC converter 5 at the output of a fuel cell 2 and a second power supply consisting of a secondary battery 3, both parallel connected to the vehicle drive motor 1. Further it has a control means 20a to control the power from the first power supply by controlling the output instruction signal to the above DC/DC converter 5 and supplies power to the drive motor from the first and/or the second power supply to meet the demand from the above motor 1. The above control means 20a changes the output instruction signal to the above DC/DC converter 5 to increase the current when the load demand increases from the motor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for an electric vehicle, and more particularly to a power supply device for an electric vehicle comprising a hybrid power supply in which a fuel cell and a secondary battery are combined.

[0002]

2. Description of the Related Art In an electric vehicle using a fuel cell as a power source for a vehicle driving motor, a secondary battery is mounted on the vehicle together with the fuel cell in order to supplement the electric power of the fuel cell and increase the responsiveness to a required load. A hybrid electric vehicle that drives a motor using these two power sources has been developed. By thus using the secondary battery together, it is possible to reduce the weight and volume of the fuel cell mounted on the vehicle, cope with a case where a large amount of power is required, and cover the responsiveness of the fuel cell.

In such a hybrid electric vehicle, the power supply distribution from the fuel cell and the secondary battery is changed according to the load required by the motor, and the motor is driven at an optimum sharing ratio corresponding to the load, the battery capacity, and the like. Is thought to be. For example, as shown in FIG. 8 (A), when the peak load exceeds the maximum power of the fuel cell (FC), the excess of the required load a is compensated for by the discharge from the secondary battery. When the power is lower than the power, the secondary battery is charged with the surplus power. Also, as shown in FIG. 4B, when the required load a always exceeds the maximum power of the fuel cell, the electric power is always supplied to the motor by discharging the fuel cell and the secondary battery without charging the secondary battery. Supply. When the required load is always smaller than the maximum power of the fuel cell, the secondary battery is charged with the surplus power while driving the motor only with the fuel cell, as shown in FIG.

In such a hybrid electric vehicle, in order to control the ratio of the amount of electric power supplied from the fuel cell to the total required load, DC / DC is applied to the output of the fuel cell.
A converter is provided, and this D
By changing the output command value of the C / DC converter,
Adjusting the distribution of power from the fuel cell supplied to the motor via the DC / DC converter has been considered.

[0005] In this case, the fuel cell has a rated power value at which a proper allowable maximum output is obtained. If an overload operation exceeding this value is performed, an overcurrent flows and an abnormal voltage drop occurs, deteriorating the fuel cell. . Therefore, it is necessary to operate the fuel cell so as not to exceed an appropriate allowable value.

On the other hand, an auxiliary power supply for preventing an abnormal voltage drop of a fuel cell is described in Japanese Patent Application Laid-Open No. H11-154520. The power supply for auxiliary equipment described in this publication is an auxiliary power supply that can supply a part of the electric power generated by the fuel cell to the auxiliary equipment necessary for independent power generation of the fuel cell in a fuel cell configured to be able to generate power independently. DC / D for converting the voltage of a part of the electric power generated by the fuel cell
The configuration includes a C converter, a battery charged by the output of the DC / DC converter, and an input current limiting mechanism for controlling power from the fuel cell passing through the DC / DC converter. With such a configuration, an object is to smoothly start the fuel cell without causing a voltage drop or the like of the fuel cell main body.

[0007]

However, in the above-described hybrid electric vehicle, when sudden acceleration or other sudden increase in load occurs, when the remaining capacity of the secondary battery is small, when the energy density is small, or when the battery is used. When the battery is deteriorated, a sudden load is applied to the fuel cell, and the current for the suddenly increased load flows from the fuel cell,
Due to the increase in the load current, the voltage of the fuel cell is extremely reduced, and a normal power generation function may be impaired, and the electrode plate and the like may be deteriorated.

On the other hand, the power supply for auxiliary equipment described in the above-mentioned publication stops power supply from the fuel cell to the auxiliary equipment and supplies electric power from the secondary battery to the auxiliary equipment at the time of low voltage of the fuel cell at the initial stage of startup. When the voltage of the fuel cell reaches a predetermined value, electric power is supplied only to the auxiliary device from the fuel cell. The ratio of the amount of power supply from the fuel cell to the auxiliary equipment in the initial stage of the start is DC / DC
Control is performed by changing the duty ratio of the converter. Therefore, no consideration is given to a response to a sudden increase in the required load from the drive motor in the normal operation state after startup. For this reason, the fuel cell may deteriorate as described above when the load suddenly increases.

The present invention has been made in consideration of the above-mentioned prior art, and prevents excessive electric power from being supplied from a fuel cell when a required load from a vehicle drive motor suddenly increases, thereby preventing deterioration of the fuel cell. It is an object of the present invention to provide a suppressed power supply device for an electric vehicle.

[0010]

In order to achieve the above object, according to the present invention, a first power supply having a DC / DC converter on the output side of a fuel cell and a second power supply comprising a secondary battery are connected in parallel. Connected to the vehicle drive motor, and the DC / DC
Control means for controlling an output command signal to a converter to control the output from the first power supply, and supplying power to the motor from the first power supply and / or the second power supply in accordance with a required load from the motor In the electric vehicle power supply apparatus, the control means changes an output command signal of the DC / DC converter according to an increase in load current when a required load from the motor increases. Provide a supply device.

According to this configuration, in a hybrid electric vehicle having two power sources using the fuel cell as the first power source and the secondary battery as the second power source, when the load suddenly increases during normal driving, etc. When the output command signal value to the variable DC / DC converter for adjusting the output voltage of the fuel cell rises with an increase in the load, the output of the fuel cell is monitored and the fuel cell output exceeds a predetermined allowable value. When this happens, the output command signal value of the DC / DC converter is subtracted according to the load increase, thereby preventing excessive power supply from the fuel cell and suppressing deterioration of the fuel cell.

In a preferred configuration example, a current sensor and a voltage sensor are provided on the output side of the DC / DC converter,
The control means includes an efficiency characteristic map of the DC / DC converter, and calculates an output of the fuel cell based on the efficiency characteristic map from detected values of current and voltage on the output side of the DC / DC converter. The output command signal of the DC / DC converter is changed according to the calculated fuel cell output.

[0013] According to this configuration, the DC / DC converter outputs the DC / DC converter data based on the DC / DC converter efficiency characteristic map obtained in advance through experiments or the like from the output side data from the current sensor and the voltage sensor provided on the output side. The power on the input side of the DC converter, that is, the output of the fuel cell is calculated. When the output of the fuel cell obtained by this calculation becomes larger than a predetermined allowable value, the output command signal value of the DC / DC converter is reduced to maintain the output of the fuel cell at a predetermined rated value or less. As a result, the output from the fuel cell on the input side can be calculated and estimated from the output side data of the DC / DC converter without directly monitoring the output of the fuel cell, thereby reducing the number of parts and simplifying the structure. Can be

In another preferred embodiment, a current sensor and a voltage sensor are provided between the fuel cell and the DC / DC converter, and the control means controls the fuel cell based on detection signals from the current sensor and the voltage sensor. Of the DC / DC according to the calculated fuel cell output.
It is characterized in that the output command signal of the converter is changed.

According to this configuration, the current and voltage of the fuel cell are directly detected from the current sensor and the voltage sensor provided on the output side of the fuel cell, and the output of the fuel cell is calculated based on the detected data. Is larger than a predetermined allowable value, the output command signal value of the DC / DC converter is reduced to maintain the output of the fuel cell at or below a predetermined rated value. Thus, the fuel cell output can be directly processed on the basis of the detection data on the fuel cell output side without preparing the efficiency characteristic map of the DC / DC converter, thereby simplifying the calculation processing program.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the entire power supply device for an electric vehicle to which the present invention is applied.

This embodiment is, for example, a power supply device for a motorcycle. A fuel cell 2 and a secondary battery 3 serving as a power source of a vehicle driving motor 1 connected to a rear wheel (not shown) of the vehicle are connected to a controller 4 shown by a two-dot chain line via an interface (IF). D on the output side of the fuel cell 2
The C / DC converter 5 is connected and forms a first power supply. A secondary battery 3 serving as a second power supply is connected to the motor 1 in parallel with the first power supply. The DC / DC converter 5 is of a variable output type, and converts a voltage from the fuel cell 2 into a voltage required for driving the motor in accordance with an output command signal and supplies power to the motor 1. This DC / DC converter 5
Thereby, the distribution of the power supplied from the first power supply and the second power supply to the motor 1 is adjusted and controlled according to the operating state, the capacity of the secondary battery, and the like.

The configuration of the fuel cell 2 will be briefly described. This fuel cell 2 supplies hydrogen as a fuel to an anode, supplies air as an oxidant to a cathode, and performs an electrochemical reaction by a catalyst. It generates electricity. A polymer ion exchange membrane is interposed between the two electrodes. Water is supplied to the ion-exchange membrane in order to secure the permeability of hydrogen ions and to make the ion-exchange membrane wet and smooth. A cell is configured using such an electrode pair as a unit, and a plurality of cells are combined to form an FC unit having a predetermined output obtained by summing the electromotive forces of the cells. The heat generated by the electromotive reaction of the cell is:
Cooling is performed by flowing air or water around each cell.

Hydrogen serving as a fuel is mixed with water, for example, with methanol as a primary fuel, heated and evaporated, and decomposed into hydrogen and carbon dioxide by a catalytic reaction of a reformer. The hydrogen gas is supplied to the anode electrode of the cell of the fuel cell after the concentration of the carbon monoxide slightly generated in the reformer is reduced through the reformer. Alternatively, hydrogen gas may be supplied directly from a cylinder.

Air for power generation is supplied to the cathode electrode by an air pump (not shown). The fuel cell 2 includes a heater 6 for preventing water in the FC unit from freezing,
A cooling fan 7 is provided for making the heating temperature uniform and for cooling during power generation.

The user switch 8 sets an operation mode such as a night charging mode. Main switch 9 is O
When set to N, this is detected by the main switch detection unit 10 in the controller 4, and the power of the controller power supply 12, the DC / DC converter 5, and the motor controller 13 is turned on via the system power supply control unit 11. The power supply control of the entire system becomes possible.

The timer time calculating unit 14 calculates a timer time for driving the heater 6 or the fuel cell 2 itself in order to prevent freezing of water in the fuel cell 2 at a low temperature at night or the like. Even when the power is OFF, the power is turned ON via the system power control unit 11 to perform the warm-up operation.
This warm-up operation is performed based on the temperatures detected by the outside air temperature detector 16 and the cell temperature detector 17.
Is determined, the heater control unit 19 or the FC output control unit 2
0 drives the heater 6 or the fuel cell 2. When the heater 6 is driven, the cooling fan 7 is also driven via the cooling fan control unit 21 to make the temperature uniform. Also,
Even when driving the fuel cell 2, the cooling fan 7 is driven according to the cell temperature.

The motor output calculator 22 includes a throttle 23
The power supply to the motor 1 is calculated from the throttle opening signal by the operation of (1). At this time, the secondary battery protection control unit 24 limits the power sharing ratio between the fuel cell 2 and the secondary battery 3 to protect the secondary battery according to the remaining capacity and temperature of the secondary battery. A motor control signal is sent to the motor controller 13 in consideration of the value.

The state-of-charge detecting unit 25 determines whether the secondary battery 3 is in a charged state or a discharged state, and in the case of charging, also determines whether the state is due to a fuel cell or a regenerative current.
That is, the current detection signal from the current sensor 26 of the secondary battery 3 is determined by the current detection unit 27 in the charging direction or the discharging direction, and the regenerative current is flowing to the secondary battery side by the current sensor 28 of the motor 1. Is detected to determine the state of charge.

The capacity calculation unit 29 calculates the capacity of the secondary battery 3 based on the detection signals and the current detection data from the voltage detection unit 30 and the temperature detection unit 31 of the secondary battery 3, and calculates the capacity of the secondary battery 3 as described above. Send to battery protection control unit 24
The power is sent to the output control unit 20 to control the power distribution of the fuel cell 2 according to the secondary battery capacity.

The FC output control unit 20 includes a D / A converter 32
The voltage command value is sent to the DC / DC converter 5 via the.
This voltage command value controls the electric power supplied from the fuel cell 2 to the motor 1 via the DC / DC converter 5. In this case, when an abnormality of the fuel cell, for example, an out-of-fuel condition or an abnormal cell temperature occurs, the detected data is sent to the abnormal data receiving unit 33. This abnormal data is sent to the FC start / stop determining unit 3 via the FC output control unit 20.
4 and determines whether or not the fuel cell 2 can be driven, and sends an ON / OFF signal for the fuel cell 2.

FIG. 2 is a block diagram showing a main part of the first embodiment of the present invention in the hybrid electric vehicle. FIG. 2 shows a main part of FIG. 1, and the same components as those of FIG. 1 are denoted by the same reference numerals, and the configuration of a portion not shown is the same as that of FIG.

In this embodiment, a voltage sensor 35 and a current sensor 36 are provided on the output side of the DC / DC converter 5, and the detection data is supplied to the FC output control unit 20 (through a current detection unit 37 and a voltage detection unit 38, respectively). It is sent to the DC / DC output control unit 20a in FIG. The DC / DC output control unit 20a converts the current data and the voltage data into a DC / D signal based on a map 40 of the efficiency characteristic data of the DC / DC converter 5 as described later.
Power on the input side of the C converter 5 (output of the fuel cell 2) is obtained by calculation. The DC / DC converter 5 is connected via the D / A converter 32 in accordance with the fuel cell output obtained by this calculation.
To the motor 1 from the fuel cell 2
To control the power supplied to the

The fuel cell outputs electric power corresponding to the required load of the motor, for example, according to the throttle opening. In this case, the voltage and the current of the secondary battery 3 are detected by the voltage sensor 39 and the current sensor 26, respectively.
DC through a current detection unit 27 and a voltage detection unit 30
/ DC output control section 20a. Based on these data, the capacity and state of charge of the secondary battery 3 are determined, the power supply amount to be shared by the fuel cell 2 is determined in consideration of these, and an output command signal to the DC / DC converter 5 is transmitted. I do.

As an operation mode when the required load to be driven by the motor is increased, the amount of power supplied from the fuel cell 2 is increased in response to the increase in the required load, or the fuel cell 2 always has a predetermined rated power value. The power supply is controlled so that the secondary battery 3 bears the increase in the required load.
Such power supply control is performed by the DC / DC output control unit 20a as described above. In this case, for example, when the required load suddenly increases, if the fuel cell 2 supplies power exceeding the allowable limit of its output, the load current increases and the voltage drops abnormally, deteriorating the fuel cell. In this embodiment,
In order to prevent the operation of the fuel cell exceeding the allowable value, the output of the fuel cell is obtained by calculating the output of the fuel cell from the current and voltage data on the output side of the DC / DC converter 5. It is to estimate whether or not.

FIGS. 3, 4 and 5 are explanatory diagrams of the arithmetic processing of the first embodiment. FIG. 3A shows an example of the output characteristics of the fuel cell. As the output power increases, the output current increases and the output voltage decreases. In this case, power = current × voltage. When the current value further increases and exceeds a certain value, the voltage sharply decreases. It is necessary to reduce the output power before this sudden voltage drop occurs. For this purpose, it is necessary to lower the output command value for the DC / DC converter 5.

FIG. 3B is a diagram showing the amount of subtraction of the output command value. The horizontal axis shows the increase in current with increasing load,
The vertical axis indicates the subtraction amount of the output command value (control voltage). As shown in the figure, when the current is increasing, the amount of subtraction of the output command value is increased in proportion to the increasing amount. As a result, for example, a sudden increase in the output of the fuel cell when the output value exceeds the limit value can be suppressed. When the current corresponding to the load has not increased (when the current on the horizontal axis is negative), there is no need to lower the output command value, and the operation with the current output command value is continued.

FIG. 3C is a graph showing the output characteristics of the DC / DC converter 5. The horizontal axis is the output command value (control voltage), and the vertical axis is the output voltage. The output voltage increases as the output command value increases. For example, it is assumed that when the control voltage of the DC / DC converter is v1 and the output at that time is driven at V1, the increase in the load current in (B) is A1 due to a sudden increase in the load. At this time, the output command value is subtracted by Δv1 from FIG. As a result, the control voltage decreases from Δv1 to Δv2 as shown in FIG. 3 (C), and as a result, the output of the DC / DC converter decreases from V1 to V2. In this way, the output command value is reduced in accordance with the increase in the load current, whereby the power supply from the fuel cell side can be suppressed.

Based on such an operation principle, the power supply from the fuel cell is controlled as follows. As shown in FIG. 4, when the required load 41 to be driven by the motor increases (for example, when the throttle 23 (FIG. 1) is opened), DC /
Voltage (Vdc) and current (Idc) are detected by a voltage sensor 35 and a current sensor 36 provided on the output side of the DC converter 5, respectively. The detection data of these voltages and currents is sent to the DC / DC output control unit 20a, where it is subjected to arithmetic processing as described below to obtain the output of the fuel cell.

Fuel cell output = DC / DC converter input = (DC / DC converter output) × (DC / DC converter efficiency) = (Vdc × Idc) × ηdc where Vdc and Idc are detection data, and ηd
c is read from the map 40.

Based on the fuel cell output obtained in this way, as shown in FIG. 5A, the fuel cell output (FC output b) is always a predetermined limit value regardless of the increase in the motor required load a. The output of the DC / DC converter (DC / DC output c) is controlled as follows.

The DC / DC output control is performed by controlling an output command value to the DC / DC converter as shown in FIG. F obtained by the above-described arithmetic processing
The C output value is monitored, and the DC / DC output command value is subtracted when the value exceeds the range of the predetermined limit section. This subtraction value corresponds to the increase in the load current of the fuel cell, as shown in FIG.

By subtracting the DC / DC output command value in this way, the FC output value decreases with a certain time delay. More specifically, in a control cycle (usually several milliseconds) in a control program, an increase in load current and an FC output are calculated from the current and voltage detection data on the output side of the DC / DC converter.
If the output exceeds the limit section, the DC / DC output command value is decreased in the next control cycle in accordance with the increase in the load current. As a result, the FC output value can be reduced and operation can be performed within an appropriate allowable range, thereby suppressing deterioration of the fuel cell.

FIGS. 6 and 7 are a main part configuration diagram and a control operation explanatory diagram of the second embodiment of the present invention. In this embodiment, as shown in FIG. 6, the output side (D
The voltage sensor 42 and the current sensor 43 are provided on the input side of the C / DC converter 5), and the power is obtained by directly detecting the output side of the fuel cell 2. That is, as shown in FIG. 7, the voltage Vdc and the current I
dc is detected, and the output value (Vdc × Idc) of the fuel cell 2 is directly obtained from the detected data without using a data map of the efficiency characteristics. The other configuration and operation and effect are the same as those of the above-described embodiment.

[0040]

As described above, according to the present invention, in a hybrid electric vehicle having a fuel cell as a first power source and a secondary battery as a second power source and having two motor driving power sources, a sudden load during normal driving is obtained. When the output command signal value to the variable DC / DC converter that adjusts the output voltage from the fuel cell increases with an increase in load, for example, when the load of the fuel cell increases, the output of the fuel cell is reduced by the DC / DC converter. This fuel cell output is monitored by calculating from the detection data on the output side or directly obtained from the detection data on the output side of the fuel cell. When the fuel cell output exceeds a predetermined allowable value, DC / The output command signal value of the DC converter is subtracted according to the load increase, so that excessive power supply exceeding the rated output from the fuel cell can be prevented. Thus, early deterioration of the fuel cell in the hybrid electric vehicle can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an entire electric vehicle to which the present invention is applied.

FIG. 2 is a main part configuration diagram of a power supply device according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of output characteristics of a fuel cell and a DC / DC converter.

FIG. 4 is an explanatory diagram of an operation of a control process according to the embodiment of FIG. 2;

FIG. 5 is an explanatory view of an output in the control processing of the embodiment in FIG. 2;

FIG. 6 is a main part configuration diagram of another embodiment of the present invention.

FIG. 7 is an explanatory diagram of the operation of the control processing according to the embodiment of FIG. 6;

FIG. 8 is an explanatory diagram of a hybrid power supply.

[Explanation of symbols]

1: motor for driving a vehicle, 2: fuel cell, 3: secondary battery,
4: controller, 5: DC / DC converter, 6: heater, 7: cooling fan, 8: user switch, 9: main switch, 10: main switch detector, 11: system power controller, 12: controller power, 13 : Motor controller, 14: timer time control unit, 16: temperature detection unit, 17: temperature detection unit, 18: warm-up operation control unit, 1
9: heater control unit, 20: FC output control unit, 23: throttle, 24: secondary battery protection control unit, 25: charge state detection unit, 26: current sensor, 27: current detection unit, 28: current sensor, 29 : Capacity calculator, 30: voltage detector, 3
1: temperature detector, 32: D / A converter, 33: data receiver, 34: FC start / stop determiner, 35: voltage sensor, 36: current sensor, 37: current detector, 38: voltage detector , 39: voltage sensor, 40: map of efficiency characteristic data, 41: required load, 42: voltage sensor, 43: current sensor.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H02J 7/34 ZHV H02J 7/34 ZHVK F-term (Reference) 5G003 AA05 BA01 CA01 CA11 CC02 DA07 DA15 DA18 FA06 GB03 GC05 5G065 AA00 BA02 DA01 DA07 EA02 EA04 GA09 HA01 HA09 HA16 JA07 LA01 LA02 MA10 5H027 AA00 DD03 KK51 MM26 5H115 PA15 PG04 PI16 PI18 PO10 PU01 QE01 QH01 QN03 QN08 SE03 SE06 SE10 TO05 TO12 TO13 TR19 TR20 TU02

Claims (3)

[Claims] 1. A first power supply having a DC / DC converter on the output side of a fuel cell and a second power supply comprising a secondary battery are connected in parallel to a vehicle driving motor, and are connected to the DC / DC converter. Control means for controlling the output command signal from the first power supply to control the output from the first power supply, and supplying electric power from the first power supply and / or the second power supply to the motor in accordance with a load required from the motor. In the power supply device for a vehicle, the control unit is configured to increase a required load from the motor.
An electric power supply device for an electric vehicle, wherein an output command signal of the DC / DC converter is changed according to an increase in load current. A current sensor and a voltage sensor are provided on an output side of the DC / DC converter, and the control means includes an efficiency characteristic map of the DC / DC converter;
The output of the fuel cell is calculated based on the efficiency characteristic map from the detected values of the current and the voltage on the output side of the DC / DC converter, and the DC / DC converter is calculated according to the calculated fuel cell output.
The power supply device for an electric vehicle according to claim 1, wherein an output command signal of the DC converter is changed. 3. A current sensor and a voltage sensor are provided between the fuel cell and a DC / DC converter, and the control means calculates an output of the fuel cell based on detection signals of the current sensor and the voltage sensor. The power supply device for an electric vehicle according to claim 1, wherein an output command signal of the DC / DC converter is changed according to the calculated fuel cell output.