JPH0636367B2 - Fuel cell power supply - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel cell, in which a secondary battery is connected in parallel, and the secondary battery is floatingly charged by the fuel cell while supplying power to a load. The present invention relates to a fuel cell power supply device in which a secondary battery compensates for insufficient power when the output power of the fuel cell is insufficient, such as during startup or during peak load, and more particularly to a device configuration capable of reducing the capacity of the secondary battery.

[Prior art and its problems]

Since the fuel cell cannot follow the fuel supply for a short-term load change, it is normally operated so as to output the rated current even when there is a load change, and therefore, the fuel cell is backed up. The secondary battery is generally selected to have the same capacity as the fuel cell in order to bear the overload exceeding the rated current. Therefore, the fuel cell power supply device including the fuel cell and the secondary battery as described above has a problem that the secondary battery becomes large.

[Object of the Invention]

The present invention solves the problems in the conventional fuel cell power supply device as described above, and can reduce the capacity of the secondary battery, and as a result, provide a fuel cell power supply device that can be downsized. The purpose is to do.

[Main points of the invention]

In order to achieve the above-mentioned object, the present invention provides a fuel cell power supply device comprising a fuel cell provided with a DC converter and a backup battery for the fuel cell connected in parallel to the fuel cell. A fuel cell current detection unit that detects a fuel cell current output by the fuel cell and outputs a voltage proportional to the fuel cell current; a load current flowing through a load of the fuel cell is detected, and a voltage proportional to the load current is detected. A load current detection unit that outputs as a detection signal; a voltage generator that outputs a voltage equal to the voltage output by the fuel cell detection unit when the fuel cell current reaches a rated current value as a first setting signal; A comparator which receives the first setting signal and the first detection signal and outputs a binary signal of H level when the latter is larger than the former and L level when the latter is smaller than the former; A first amplifier that outputs a voltage proportional to the first detection signal when the output signal of the first amplifier is at the H level and the time when the output signal of the first amplifier is input and the signal at the H level continues A time signal generator for generating a predetermined time signal which is less than or equal to and which is larger as the signal of the first amplifier is smaller, and the first signal is input while the time signal is input and the time signal continues. A second amplifier that outputs a voltage proportional to the output signal of the amplifier as a second setting signal; and an adder that adds the output voltage of the second amplifier and the first setting signal and outputs the added voltage A deviation amplifier that inputs the output voltage of the adder and a voltage proportional to the fuel cell current output from the fuel cell current detection section and outputs a deviation signal according to the difference between the two voltages; Before the deviation signal becomes zero A control unit for controlling the DC converter is provided. With such a configuration, when the load current becomes an overcurrent exceeding the rated current, a predetermined amount of electricity is supplied to the control unit. Then, the fuel cell is forced to output the current in the above-mentioned overcurrent state, and as a result, the secondary battery has a capacity smaller than that of the conventional fuel cell power supply device in which all the overcurrent is borne by the secondary battery. The next battery can be used.

Example of Invention

FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, 1 is a fuel cell, 2 is a secondary cell which is connected in parallel to the fuel cell 1 and which backs up the shortage of the fuel cell current _If output from the fuel cell 1, 3 is a deviation signal 4 input The DC converter is configured to adjust the magnitude of the battery current _If according to the signal 4. 5 is a load such as an electric motor driven by the fuel cell 1 and the secondary cell 2,
Reference numeral 6 is a load switch for connecting or disconnecting the load 5 to or from the batteries 1 and 2. When the rated output voltage of each of the batteries 1 and 2 is, for example, 30 volts and 100 volts,
Normally, the converter 3 receives the input output voltage 30 of the fuel cell 1.
It is configured to output a direct current voltage of approximately 100 volts. 7 detects the current I _f and detects this current I _f
A fuel cell current detection unit that outputs a voltage signal 7a proportional to the magnitude of _f , 8 detects a load current I ₁ flowing through the load 5, and has a voltage V _la equal to A · I ₁ where A is a proportional constant. The load current detector 1 outputs the detection signal 8a, and the first 9 sets the voltage V _r equal to the voltage value of the signal 7a output from the detector 7 when the fuel cell current _If reaches the rated current value I _r. A voltage generator 10 that outputs as a signal 9a is a binary signal 10 that is at an H level when the first detection signal 8a and the first setting signal 9a are input and the former becomes larger than the latter.
It is a comparator that outputs a.

The first detection signal 8a and the output signal 10a of the comparator 10 are input, and 11 outputs a voltage signal having a value of V _lb = B · V _la with B being a predetermined constant when the signal 10a is at the H level. 1st amplifier which outputs as 11a, 12
Is an input of the output signal 11a of the amplifier and performs a time calculation based on the output signal V _1bo immediately after the rising time when the output signal 10a of the comparator rises from the L level to the H level. 12a is a time signal generator for generating a time signal of 12a. The time T is determined so that the time is shorter when the signal of the first amplifier is greater than or equal to the time when the H-level signal continues and is larger.

For example, the time of T is determined by the following equation (1).

T = a + b (1 / V _1bo ) (1) where a and b are constants, and the smaller V _1bo is, the larger T is, but the time when the H-level signal continues is exceeded. The upper limit is set so that nothing happens. a and b are appropriately selected according to the specifications of the fuel cell.

For example, if the time unit for which the H-level signal continues is 1 second and a and b are 0.2 and 0.5, the minimum value of T is
The maximum value of 0.2 seconds is 1 second because the upper limit is set so as not to exceed the duration of the H-level signal.

Reference numeral 13 in FIG. 1 is inputted with the output signal 11a of the amplifier and the output signal 12a of the signal generator, and the signal 12a is H level.
When the level is C, a second amplifier that outputs a voltage signal having a value of V _lc = C · V _lb as an output signal 13a with C as a predetermined constant, and 14 performs addition of the first setting signal 9a and the output signal 13a. , An adder for outputting the voltage V _{s of the} addition result as a set voltage, and 15 for inputting the output voltage signal 7a of the fuel cell current detection unit 7 and the set voltage V _s and outputting a deviation signal 4 according to the difference between the two. In the deviation amplifier, the DC converter 3 adjusts the fuel cell current _If so that the deviation signal 4 becomes zero. 16 is a voltage generator 9, a comparator 10, amplifiers 11 and 13, a time signal generator 12 and an adder 14.
In the setting unit 16, each unit is configured as described above.
Detection signal 8a is inputted, and outputs the value V _la of the detection signal 8a from the adder 14 as it is as the set voltage V _s of the first setting signal 9a which does not change over time when not exceeding a predetermined voltage V _r, also detected When the value V _{la of the} signal 8a exceeds the predetermined voltage V _r , the signal 1 having the magnitude V _lc proportional to the value of the detection signal 8a is generated for the time T corresponding to the value of the detection signal 8a at this time.
This means that the adder 14 has a function of outputting the voltage (V _lc + V _r ) obtained by adding 3a as the second setting signal to the first setting signal 9a as the setting voltage V _s . The output voltage signal 7 a of the fuel cell current detection unit 7 and the set voltage V _s as the output signal of the setting unit 16 are input to the unit 17 to set the voltage V _s.
Is used as a set value to control the magnitude of the fuel cell current _If .
It is a control unit including a DC converter 3 and a deviation amplifier 15.

Next, the operation of the fuel cell power supply device shown in FIG. 1 will be described with reference to the waveform diagram of the main part of FIG. That is, assuming that the load current I ₁ is zero until the time t ₁ , the voltage V _la of the first detection signal 8a is smaller than the voltage of the first setting signal V _r. Therefore, the output signal 10a of the comparator is at the L level, which results in the voltage V _lb of the output signal 11a of the first amplifier.
Is zero, the output signal 12a of the signal generator is at L level, and therefore the voltage V _lc of the output signal 13a of the second amplifier is
Is also zero. Therefore, until the time t ₁ , the adder 14
The magnitude of the set voltage V _s output from is equal to the voltage value V _r of the first set signal 9a that does not change over time, and therefore the magnitude of the battery current _If is controlled by the control unit 17 to the rated current. Is equal to the value I _r , and at this time the load current I
_l is the charging current of the current I _f all secondary batteries 2 because it is zero. I _b is a current flowing through the secondary battery 2.

It is assumed that at time t ₁ , the load current I ₁ has a current value I _l1 larger than the current value I _r , and the current value I _l1 changes stepwise such that it continues for a time W ₁ . In this case, since the main part is configured such that the voltage V _la1 of the first detection signal 8a proportional to the load current I _l1 is larger than the voltage V _r of the first setting signal 9a, at time t ₁ . The output signal 10a of the comparator becomes H level, and the signal 11a having a voltage of V _lb1 = B · V _la1 is output from the amplifier 11. When the signal 11a having the voltage of V _lb1 is output from the first amplifier 11, the output signal 12a of the time signal generator 12 is
Time T ₁ calculated by the equation (1), that is, T ₁ = a
_High level only during + b (1 / V _lb1 ) and first
Since the output signal 11a of the amplifier continues to have the magnitude of the voltage V _lb1 during the time W ₁ , if T ₁ <W ₁ in this case, the magnitude of V _lc1 = C · V _lb1 from the second amplifier 13 is _obtained. The voltage signal 13a is output only during the time T ₁ . Therefore, the magnitude of the set voltage V _s output from the adder 14 from time t ₁ to time T ₁ becomes V _lc1 + V _r , so that the fuel cell current _If is the time when time T _{1 has} elapsed from time t ₁ Up to t ₂ , the magnitude I _f1 corresponding to the set voltage V _lc1 + V _r
become. In this case, since the relevant main part is configured such that I _f1 = I _l1 , the current I _b in the secondary battery 2 becomes zero.

The state in which the battery current _If becomes I _f1 continues until time t _2, but since the set voltage V _s returns to the magnitude of V _r after the time t _{2, the} current _If also returns to the magnitude of I _r. and, on the other hand the time _{t 2} time _{t 3} when passed from further time _{t 1} by a time _{T 1}
Since the load current I _l continues to have the magnitude of I _l1 ,
From the time t ₂ to the time t ₃ , the secondary battery 2 to I _b =
So that the magnitude of the current I _l1 -I _r is discharged.

Assuming that the load current I _l reaches a value I _l2 smaller than the rated current value I _r at time t ₃ , the output signal 1 of the comparator 1
Since 0a becomes L level, the output signal 11a of the first amplifier
There becomes zero, the output signal 13a of a result the second amplifier is a fuel cell current I _f so continuing zero continues the magnitude of I _r. Since this case is _{I l2 <I r, (I} r -I l2)
The secondary battery 2 is charged with a current of the magnitude.
If the load current I ₁ becomes zero at time t ₄ , the state of each part is the state before time t _1, so the secondary battery 2 is charged again with the current _If having the magnitude of I _r. .

Atsuta load current I _l at zero, from time t ₅ to time t ₆ has elapsed by the time W _3, the larger I _r is assumed that the abrupt change in the I _l3 of I _l1 smaller current value, the time During this period, the output signal 10a of the comparator becomes H level, and the signal 11a having the voltage of V _lb3 is output from the amplifier 11. As a result, the signal generator 12 outputs the H signal for the time T ₃ equal to a + b (1 / V _lb3 ). Since the signal 12a which becomes the level is output, the voltage V equal to C · V _lb3 is output from the amplifier 13.
_The signal 13a having _lc3 is output. In this case when the size of the first detection signal 8a and _{V la3 V la3 = A · I} l3
And the voltage V _lb3 output from the amplifier 11 is V _lb3
= B · V _la3 . In the figure, it is assumed that W ₃ = T ₃ happens to occur.
In V _LB3 <V _lb1 because in this case I _l3 <I _l1,
Therefore, T ₃ > T ₁ . Since the set voltage V _s becomes (V _r + V _lc3 ) from the time t ₅ to the time t ₆ , the fuel cell current _If is set to the set voltage (V _r + V
becomes the current value I _f3 corresponding to _LC3), from main portion such that I _f3 = I _l3 is composed, from time t ₅ t ₆
Until then, the secondary battery current I _b becomes zero. Assuming that the load current I _l has a current value I _l4 smaller than the rated current value I _r from the time t ₆ to the time t ₇ , the secondary battery 2 has I _b = I _r −I _l4 during this time. Charging current flows.

Since the power supply device of FIG. 1 operates as described above, when an overload current of a magnitude exceeding the rated current value I _r of the fuel cell 2 flows through the load 5, an overcurrent of the same magnitude from the fuel cell 1 is generated. Since it is output and supplied to the load 5, the output time of this overcurrent is limited to the time T calculated by the equation (1), so in this case, in this case, a certain amount of electricity is the overcurrent value in the state of the fuel cell. 1 to the load 5. Therefore, the first
In the fuel cell power supply device shown in the figure, when an overload occurs, a part of this overload is borne by the fuel cell 1. The capacity of the secondary battery 2 can be made smaller than that of the battery power supply device, and thus the secondary battery 2 can be formed in a small size in such a power supply device.

〔The invention's effect〕

As described above, in the present invention, in the fuel cell power supply device comprising the fuel cell provided with the DC converter and the backup secondary battery of the fuel cell connected in parallel to the fuel cell, the fuel cell A fuel cell current detection unit that detects a fuel cell current output by the fuel cell and outputs a voltage proportional to the fuel cell current; a load current flowing through a load of the fuel cell is detected, and a voltage proportional to the load current is first detected. A load current detection unit that outputs as a signal; a voltage generator that outputs a voltage equal to the voltage output by the fuel cell detection unit when the fuel cell current reaches a rated current value as a first setting signal; A comparator that receives a 1-setting signal and the first detection signal and outputs a binary signal of H level when the latter becomes larger than the former and L level when the latter becomes smaller; A first amplifier that inputs an output signal and outputs a voltage proportional to the first detection signal when the signal is at the H level, and a time equal to or less than the time when the output signal of the first amplifier is input and the H level signal continues And a time signal generator for generating a predetermined time signal such that the larger the signal of the first amplifier, the shorter the time, and the first amplifier for inputting the time signal and maintaining the time signal. A second amplifier that outputs a voltage proportional to the output signal of the second setting signal as a second setting signal, and an adder that adds the output voltage of the second amplifier and the first setting signal and outputs the added voltage. A setting unit; a deviation amplifier that inputs the output voltage of the adder and a voltage proportional to the fuel cell current output from the fuel cell current detection unit, and outputs a deviation signal according to the difference between the two voltages; So that the signal becomes zero Since the control section for controlling the flow converter is provided, by such a configuration, when the load current becomes an overcurrent exceeding the rated current, a predetermined amount of electricity is generated in the control section. As a result of the forced output from the fuel cell in the state of the overcurrent, the size of the secondary battery is smaller than in the case of the conventional fuel cell power supply device in which all the overcurrent is borne by the secondary battery. There is the effect that it can be of capacity.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is a waveform diagram of a main part in FIG. 1 ... Fuel cell, 2 ... Secondary battery, 5 ... Load, 7 ...
Fuel cell current detector, 8 ... Load current detector, 8a
1st detection signal, 9a ... 1st setting signal, 13a ... 2nd
Setting signal, 16 ... Setting section, 17 ... Control section.

Claims (1)

[Claims] 1. A fuel cell power supply device comprising a fuel cell having a DC converter and a backup secondary battery for the fuel cell connected in parallel to the fuel cell, wherein the fuel cell outputs the fuel cell. A fuel cell current detection unit that detects a current and outputs a voltage proportional to the fuel cell current; a load that detects a load current flowing through a load of the fuel cell and outputs a voltage proportional to the load current as a first detection signal A current detector; a voltage generator that outputs a voltage equal to the voltage output by the fuel cell detector when the fuel cell current reaches a rated current value as a first setting signal; A first detection signal is input, and a comparator that outputs a binary signal of H level when the latter becomes larger than the former and an L level when the latter becomes smaller, and a signal that receives the output signal of the comparator A first amplifier that outputs a voltage proportional to the first detection signal when it is at the H level; and a first amplifier that is equal to or less than the time during which the output signal of the first amplifier is input and the signal at the H level continues A time signal generator for generating a predetermined time signal such that the larger the signal is, the shorter the time signal is, and a voltage proportional to the output signal of the first amplifier while the time signal is input and the time signal continues. A second amplifier that outputs as a second setting signal and an adder that adds the output voltage of the second amplifier and the first setting signal and outputs the added voltage; And a deviation amplifier that inputs a voltage proportional to the fuel cell current output from the fuel cell current detection unit and outputs a deviation signal according to the difference between the two voltages, so that the deviation signal becomes zero. Controls the DC converter The fuel cell power supply device characterized by comprising a; and control unit.