JPS6345765A - Fuel cell power source system - Google Patents

Abstract

PURPOSE:To prevent the overdischarge and overcharge of a secondary battery by installing a fuel cell current detector, in which a measured signal is outputted according to output current, and a controller, in which a setting signal and the measured signal are inputted and a control signal is outputted and the output current of a fuel cell is feedbackcontrolled by a power converter. CONSTITUTION:When a secondary battery 3 is discharged and the quantity of electricity Q of the battery is decreased, a setting signal 12a and output voltage V2 are increased to retard decrease in the Q, or adequate charge current flows to the battery 3 to recover the Q. When output current If of a fuel cell 1 is increased than a value corresponding to the signal 12, a controller 14 outputs a control signal 14a to decrease the voltage V2 and the current If to the value corresponding to the signal 12 and the overdischarge of the battery 3 can be prevented. When the battery 3 is charged and the quantity of electricity Q is increased, the setting signal 12a and the output voltage V2 are decreased to retard increase in the Q or charge current of the battery 3 to recover the Q to an adequate value. Therefore, the overcharge of the battery can be prevented. Even when the load 4 is increased, the overdischarge of the battery and sharp voltage drop in the load 4 can be prevented.

Description

[Detailed description of the invention] [Technical field to which the invention belongs] The present invention connects a secondary battery such as a lead-acid battery to a fuel cell in parallel, and uses a floating photovoltaic battery to connect the secondary battery to the fuel cell. It is possible to supply load VC power and reduce this insufficient power to the secondary battery when the output power of the fuel cell is insufficient, such as when starting up the fuel cell or at peak load. Concerning configuration.

[Prior art and its problems]

In a fuel cell, for example, when starting an electric motor as a load, a large load current is required as the starting current of the motor, so fuel consumption at the electrodes of the fuel cell increases rapidly, but hydrogen-rich gas or air etc. Since it takes time to supply this amount of fuel to the electrodes, the fuel cell will run out of fuel and its output voltage will drop. Furthermore, in a hydrogen-oxygen fuel cell system using a fuel reformer that obtains hydrogen-rich gas from methanol and water, the fuel hydrogen generated in the reformer and guided to the fuel cell electrode is The unreacted surplus, so-called off-gas, is returned to the reformer and used as part of the fuel used in the vaporizer tube heating burner in the reformer.

When a sudden increase in hydrogen fuel occurs at the electrodes of a fuel cell, the burner misfires due to a lack of off-gas. For this reason, in a power supply device using a fuel cell, a secondary battery such as a lead-acid battery is connected in parallel to the fuel cell, and when the fuel cell is started, the desired amount of power is extracted from the secondary battery, and the steady state after the fuel cell is started. During operation, the secondary battery is floatingly charged by the fuel cell, and the secondary battery compensates for the shortfall in fuel cell output power that occurs during heavy loads.

However, in such a fuel cell power supply device, if the average power consumption at the load is higher than the average output power of the fuel cell, the amount of electricity remaining in the secondary battery will decrease over time (Natsu The output voltage of the fuel cell power supply decreases,
There is a problem that the secondary W1 battery may eventually become over-discharged and be damaged.

Also, if the average power consumption in the load is less than the average output power of the fuel cell, the secondary battery will become overcharged and the water in the battery will be electrolyzed, resulting in damage to the secondary battery's electrode plate. There is also the problem of having something to do.

[Purpose of the invention]

The present invention solves the problems of conventional power supply devices as described above, and provides a fuel cell power supply device in which the secondary battery does not become over-discharged or overcharged, and the output voltage does not drop extremely. The purpose is to provide.

[Key points of the invention]

In order to achieve the above object, the present invention detects the amount of remaining electricity in the secondary battery and controls the output current of the fuel cell according to this amount of remaining electricity, thereby preventing the secondary battery from being in an over-discharged state or an overcharged state. This is to provide a fuel cell power supply device that does not suffer from excessive drop in output type EE.

[Embodiments of the invention]

FIG. 1 is a block diagram of an embodiment of the present invention. In Figure 1, 1 is fuel cell% and 2 is fuel cell! The primary power P outputted by the controller and the control signal 14a are input, and the primary power P,
3 is a power conversion unit that converts DC secondary power P and VC having a voltage V according to a control signal 14a, and 3 is a secondary battery for backup for the fuel cell I, which is floatingly charged by the secondary power P. 4 was connected in parallel to the secondary battery 3.

(Electric motor). R is the resistance existing in the conductive path from the output terminal 2a of the conversion valve 20 to the terminal 3aK of the secondary battery 3. 5 is a secondary battery 3 f) Voltage V.

A secondary battery 1 that detects the voltage and outputs a voltage signal 5a corresponding to this voltage! 6 is the discharge current sd of the secondary battery 3.
The signals 5a and 6a are input to the calculation part 7, where the calculations described below are performed and the two are output. It is configured such that a charge signal 7a corresponding to the remaining charge in the next battery 3 is output.

FIG. 2 is an explanatory diagram illustrating the amount of remaining electricity in the secondary battery 31F described above, and this figure is based on experimental results. It is clear from the diagram that the one in five diagram is the secondary battery 3f1 voltage vs.
It shows the relationship between the electric current flowing through this battery and the amount of remaining electricity Q. Electricity tQ is expressed in yen, and is Q÷100.
C%) indicates that the battery 3 is charged to the rated state. It is clear from this figure that if the voltage Vs and the current s are known, the remaining electricity quantity Q can be determined. The group is stored, and furthermore, the calculation unit 7
When the signal 5a and the signal 6a are inputted, it is configured to output a charge signal 7a corresponding to the charge Q determined by the two input signals and the group of temporal lines.

FIG. 1 will be explained again. In the figure, reference numeral 8 denotes a remaining electricity amount detection unit consisting of a secondary battery voltage detection unit 5, a secondary battery current detection unit 6, and a calculation unit 7. Since each part of this detection unit operates as described above, it is ultimately detected. This means that the section 8 detects the remaining amount of electricity -Q of the secondary battery 3 and outputs the amount of electricity signal 7a corresponding to the amount of electricity Qvc. 9 indicates the discharge current I represented by this signal when the current signal 6a is input.
sd is a predetermined value f] Upper limit current value Ih and predetermined lower limit current value I
It is determined whether the current is between It<t5.
d(Ih) is a current determination unit that sets the binary output signal 9a to H level; 10 is a current determination unit to which a signal 9m is input, and this signal remains at H level for a predetermined period of time, for example, 3 seconds; This is a time determination section that outputs a first signal tOa when the time has elapsed.The current determination section 9, the time determination section IO, and the current detection section 6 constitute a current state detection section 11.
The signal 10a is a binary signal output from the time determining section 10 and is expressed as an H level state. Current state detection section 1
1 is configured as described above, so in the end it is this detection section! l detects the discharge current ISd of the secondary battery 3, and detects the current I
When a predetermined state of the current Isd appears, in which the current Isd is within a predetermined current value range and the current value Q is within the current value range for a predetermined period or longer, the first signal 1
This is a detection unit that outputs 0B.

12, when the coulometric signal 7a and the output signal of the time determining section 10 are input and the first signal 10a is output from the one hour determining section 10, the coulometric signal 7a is determined by the characteristic line input shown in FIG. 13 is a fuel cell current detection section that detects the output current If of the fuel cell l and outputs a measurement signal 13a corresponding to this current. Setting signal 12a and measurement signal 13a
is inputted to the control unit 14Vc, and the control unit 14 performs a predetermined adjustment operation based on the deviation between the signal 12a and the signal 13a, and outputs a control signal 14a according to the result.
With this signal 14a, the output voltage of the converter 2 is V! It has a function of changing the fuel cell output current If by adjusting or subtracting the deviation from the fuel cell to zero. In other words, 14 receives the setting signal 12a and the measurement signal 13a, outputs the control signal 14a, and connects the fuel cell l to the power converter 2Vc.
This is a control section that performs feedback control of the output current If.
' In FIG. 1, each part is configured as described above, but furthermore, the calculation part 7 calculates the discharge current "sd is I t
It is configured to output a highly accurate coulometric signal 7a only when the condition <I sd <I hen is satisfied.

This is because there is a limit to the storage capacity of the calculation unit 7 for Vs-I and characteristic details using the electrical quantity Q as a parameter. Now, since the calculation section 7 is configured as described in r) above, the amount of electricity signal 7a when the first signal 10a is output from the current state detection section 11 is the amount of electricity Q remaining in the secondary battery 3&f at this time. accurately represented. Further, the fuel cell output current I (is a current value according to the setting signal 128 due to the operation of the control unit 14 and the conversion unit 2. However, in this case,
The characteristic line A in FIG. 3 where the signal conversion unit 12 performs signal conversion is as follows:
Converter 2F) Output that prevents excessive discharge current from being generated in the battery 3 or allows an appropriate charging current to flow in when the remaining electricity Q in the secondary battery 3Vc is in the state represented by the signal 7a. The voltage V is expressed by the current I corresponding to the g'1 voltage. Therefore, the first
In the figure, when the secondary battery 3 is discharged due to the load 47F') and the remaining electricity tQ decreases, the setting signal 12a increases, and as a result, the output voltage V increases, thereby suppressing the decrease in Q. Alternatively, an appropriate charging current flows into the battery 3, and one quantity of electricity Q is recovered. σ) Naturally, the secondary power P! Since P becomes larger, the primary power P also becomes larger, and as a result, the fuel cell output current If also becomes larger. If If becomes greater than the value corresponding to signal 128, control 1! Since B14 reduces the voltage V by the control signal 141, If also becomes smaller and finally matches the value corresponding to the signal 1zavc. As a result, over-discharge of the battery 3 is prevented. In FIG. 1, contrary to the above, when the secondary battery 3 is charged and the amount of electricity Q increases, the setting signal 12a becomes smaller, so the output voltage V becomes smaller.
As a result, the increase in Q in the battery 3 is suppressed, or the discharge current of the battery 3 increases, and the quantity of electricity Q is restored to its proper value. Therefore, in this case, the battery 3 will not be overcharged. In Fig. 1, the 6th section operates as above 0 to 5, so when the load 4 becomes large, the secondary battery 3 becomes over-discharged! The voltage applied to the load 4 does not drop significantly due to IK.

In FIG. 1, the calculation section 7 is configured to use the signals 5a and 6a to output the signal 7a according to the remaining electricity tQ, but in addition to the illustrated sections, there is also a A temperature detection section for detecting the temperature is provided, and the calculation section 7 receives the output signal in addition to the signals 5a and 6a, and outputs the tt signal 7a with a higher [ff] than in the above case. If the VC is configured like this, there is no problem.

In FIG. 1, it is convenient to use a single power supply unit σ) by providing a display section to which the IEi-signal 7a is input and to display the quantity of electricity tQ. Note that the current state detection section 11 described above
is not necessarily necessary, and if this detection section j1 is omitted, the signal conversion section 12 will be configured as a VC so that it always performs a signal conversion operation on the twit signal 7aK.

〔Effect of the invention〕

As described above, in the present invention, the amount of remaining electricity of the fuel cell backup secondary battery that is floatingly charged by the fuel cell is detected, and the output current of the fuel cell is controlled according to this amount of electricity. , the secondary battery does not become over-discharged or over-charged, and the fuel cell power supply device (G)
This has the effect that the output voltage does not drop extremely.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the amount of remaining electricity of the secondary battery in FIG. 1, and FIG. 3 is an explanatory diagram of the signal conversion characteristics of the signal converter in FIG. 1. be. 1...fuel cell, 2...power conversion section,
3... Secondary battery, 7a... Electricity signal, 8... Residual electricity amount detection unit, 12...
Signal converter, 12a...Setting signal, 13...
... fuel cell current detection section, 13a ... measurement signal, 14 ... control section, 14a ... control signal, P ... primary power, Pt...Secondary power, If...Fuel cell output current. 0 Nini missing It3', ffL(I
s) Note 2 Prison note 3 j

Claims (1)

[Claims] a fuel cell, a power converter that receives a control signal and primary power output from the fuel cell and converts the primary power into DC secondary power having a voltage according to the control signal; a secondary battery that is float-charged, a residual electricity detection unit that detects the remaining electricity of the secondary battery and outputs a electricity signal corresponding to the remaining electricity; a signal conversion unit that detects the output current of the fuel cell and outputs a measurement signal corresponding to the output current; A fuel cell power supply device comprising: a control section that receives a measurement signal, outputs the control signal, and performs feedback control of the output current of the fuel cell by the power conversion section.