JP2520963B2 - Fuel cell DC parallel operation system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power supply system for converting a DC output of a fuel cell into a voltage by a DC power supply device to supply power to a load, and particularly to a commercial power supply according to load fluctuation. Alternatively, the present invention relates to a fuel cell DC parallel operation system for sharing a load with a rectifier output having an engine generator as an input to effectively use a fuel cell.

[Prior Art] Conventionally, positive and negative electrodes are opposed to each other through an electrolyte, and an oxidizer and a fuel (reducing agent) are continuously supplied to each electrode to generate electricity without burning the chemical energy of the fuel. Fuel cells are known that chemically directly convert to electrical energy. Unlike the primary and secondary batteries, which have a limited discharge capacity, this fuel cell has the advantage of being able to discharge continuously as long as the supply of oxidant and fuel from the outside continues, and the energy conversion efficiency. It has the advantage of being expensive.

FIG. 6 is a block diagram of a conventional fuel cell power supply system. Reference numeral 1 is a fuel cell (fuel cell), 2 is a DC power supply device, 3 is a fuel cell power supply composed of these fuel cell 1 and DC power supply device 2, and 10 is a load. Fuel cell 1
Since DC power is generated by an electrochemical reaction between hydrogen and oxygen, DC power can be directly supplied to a DC load. However, in general, it is often necessary to convert the voltage of the fuel cell output, and in that case, as shown in FIG. 6, the power supply to the load 10 is a DC power supply device using the output of the fuel cell 1 as an input. The voltage conversion is performed at 2. At this time, if the power consumption of the load 10 is constant regardless of time, the fuel cell power source 3 can be effectively used by adjusting the output capacity of the fuel cell power source 3 and the power consumption of the load 10.

[Problems to be Solved by the Invention] However, in the fuel cell power supply system according to the above-mentioned conventional technique, the power consumption of the load 10 normally fluctuates with time as shown in FIG. If the output capacity of the fuel cell power supply 3 is determined according to the value, most of the time, the fuel cell power supply 3 will be operated at a partial load while leaving a considerable surplus in output, and the fuel that is expensive to establish will be expensive. There is a problem that the battery cannot be effectively used.

The present invention was devised to solve the above problems, and an object of the present invention is to provide a fuel cell DC parallel operation system for effectively utilizing a fuel cell that is expensive to establish.

[Means for Solving the Problems] The configuration of the fuel cell DC parallel operation system of the present invention for achieving the above object is to provide a DC power supply device having a fuel cell and an output voltage control means using the output of the fuel cell as an input. And a rectifier for rectifying a commercial power source or another power source, the output of the fuel cell power source and the output of the rectifier are connected in parallel, and a DC power supply device for the fuel cell power source The output voltage control means controls the output voltage according to the variation of the load to control the load sharing ratio of the output of the fuel cell power source.

[Operation] The present invention controls the output voltage of the DC power supply device in which the output of the fuel cell is input, and the output is connected in parallel with the output of the rectifier whose input is a commercial power supply or an engine generator, by the output voltage control circuit, By adjusting the ratio of load sharing with the rectifier, the output capacity of the fuel cell is not adjusted to the peak value of the power consumption of the fluctuating load, but is, for example, less than or equal to the minimum value of the power consumption or between the peak value and the minimum value. The fuel cell power supply always operates at almost the rated output, and the part exceeding the output of the fuel cell power supply is the DC output power supply of another system, for example, the output of the rectifier with the commercial power supply or the engine generator etc. as the input. Power will be supplied from the fuel cell to make effective use of the fuel cell, which is expensive to establish.

Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the basic configuration of the present invention. In FIG. 1, members and elements having the same functions as those of the conventional example of FIG. 6 are designated by the same reference numerals. 1 is a fuel cell (Fu
el Cell), 2 is a DC power supply device, and 3 is a fuel cell power supply composed of these fuel cell 1 and DC power supply device 2. The DC power supply device 2 of this embodiment includes a DC power supply device main circuit 2-1 and an output voltage control circuit 2-2. The DC power supply device main circuit 2-1 has a function of converting the output of the fuel cell 1 into an input and converting it into a voltage suitable for a load. The output voltage control circuit 2-2 detects the output voltage of the DC power supply main circuit 2-1 and performs processing such as comparison with a desired output voltage and operational amplification to determine the DC power supply main circuit 2-1. It has a function of controlling the DC power supply device main circuit 2-1 so that the output voltage, that is, the output voltage of the DC power supply device 2 becomes a desired output voltage. Reference numeral 4 is, for example, a commercial power source, 5 is a rectifier for rectifying the commercial power source 4, and 10 is a load. The output of the fuel cell power supply 3, that is, the output of the DC power supply main circuit 2-1 is the rectifier 5
It is connected in parallel with the output of to supply the load 10.

The operation and action of the basic configuration of the present invention configured as described above will be described. FIG. 2 is an explanatory diagram of load sharing between the DC power supply device 2 and the rectifier 5. I ₀ is the output of the fuel cell power supply 3,
That is, the output current and the output of the DC power supply apparatus 2 rectifier 5 fuel cell DC parallel operation system due to the load sharing of the output of, as indicated by the solid line in FIG. 2, of the output current I _0, the DC power supply apparatus 2 There the I _1, the rectifier 5 is shared with I _2. Therefore, I ₀ = I ₁ + I ₂ . As shown by the broken line in FIG. 2, by changing the output voltage characteristic of the DC power supply device 2, the load sharing of the DC power supply device 2 and the rectifier 5 can be set at an arbitrary ratio (I ₁ + ΔI: I ₂ −ΔI). ) Can be changed to That is, when the current flowing through the load 10 changes or the output voltage of the rectifier 5 changes due to the fluctuation of the commercial power supply 4, the load sharing ratio of the DC power supply device 2 and the rectifier 5 changes, and the DC power supply device 2 Output changes, but output voltage control circuit 2
It is possible to control the load sharing ratio of the output of the DC power supply device 2, that is, the output of the fuel power supply 3 by changing the output voltage of the DC power supply device 2 by controlling -2 by an appropriate means. This makes it possible to regulate the output capacity of the fuel cell 1 to be less than or equal to the peak load value. That is, the output capacity of the fuel cell 1 is selected to be equal to or less than the minimum value of the power consumption of the fluctuating load 10 or between the peak value and the minimum value, and
By changing the output voltage characteristics of the DC power supply device 2 as shown by the broken line and solid line in FIG. 2 according to the fluctuation of the power consumption (current) of 10, the fuel cell power supply 3 is always operated at almost the rated output. For the portion exceeding the rated output of the fuel cell power source 3, power is supplied from a DC output power source of another system, for example, the output of a rectifier having a commercial power source or an engine generator as an input. It can be effectively used.

FIG. 3 is a diagram for explaining one embodiment of the present invention, and is a block diagram of a fuel cell DC parallel operation system showing one control method of the output voltage of the DC power supply device 2. In this embodiment, members and elements having the same functions as those of the basic structure shown in FIG. 1 are designated by the same reference numerals. In this embodiment, the fuel cell 1
And the output of the fuel cell power source 3 composed of the DC power source 2 having the DC power source main circuit 2-1 and the output voltage control circuit 2-2 as inputs and the output of the rectifier 5 rectifying the commercial power source 4. In the basic configuration of FIG. 1 in which power is supplied to the load 10 by connecting them in parallel, the load is applied to the output voltage control circuit 2-2.
As an appropriate means for giving a control command in accordance with the power consumption of 10, the load current / power detection means 6 coupled to the power supply line to the load 10 and the DC power supply output current connected to the output line of the DC power supply 2 / a power detection unit 7, the load current / power direct-current power supply 3 is a current value to be shared from the detection output I _L of the detecting means 6 (I _L or I _L max) DC power supply output current / power setting means for setting a 8 and its set current value (I _L or I _L
max) and the detected output I _{d of the} DC power supply output current / power detection means 7 and outputs the output voltage control signal VQ corresponding to the error to the output voltage control circuit 2-2. It is provided with a voltage control signal output means 9.

FIG. 4 is a circuit diagram showing a configuration example of an output voltage control circuit 2-2 for changing the output voltage of the DC power supply device 2 by the output signal VQ of the DC power supply device output voltage control signal output means 9. Is. The operational amplifier 11, the input resistor 12 connected to one of the inputs, and the output feedback resistor 13 form an error amplifier. One input of this error amplifier,
That is, the reference voltage composed of the resistor 14 and the Zener diode 15 is connected to the input via the resistor 12 via the reverse current blocking diode 16, and the output voltage of the DC power supply device 2 is divided by the resistors 17 and 18 to the other input. Press to connect. Reference numeral 20 denotes a drive control circuit including a pulse width modulation circuit, which receives the output of the error amplifier and stabilizes the output voltage of the DC power supply main circuit 2-1.

The operation and action of the embodiment configured as described above will be described. The load current or power is detected by the load current / power detection means 6, and the signal value corresponding to the load current or power is detected.
I _L is sent to the DC power supply output current / power setting means 8. In direct-current power supply output current / power setting means 8 compares the signal value I _L corresponding to a predetermined set upper limit value I _L max and the load current or power, greater than I _L is I _L max I _L If I _L is smaller than I _L max, I _L is sent to the DC power supply device output voltage control signal output means 9. In the DC power supply output voltage control signal output means 9, the signal I _d corresponding to the output current or power of the DC power supply 2 output from the DC power supply output current / power detection means 7 and the DC power supply output current / Signal sent from power setting means 8
It is compared with I _L or I _L max, and a signal VQ corresponding to the error is sent to the output voltage control circuit 2-2.

In the output voltage control circuit 2-2, the output signal VQ of the DC power supply output voltage control signal output means 9 is connected to the reference voltage input side of the error amplifier via the reverse current blocking diode 19 according to the configuration example of FIG. By doing so, the output voltage of the DC power supply device 2 can be changed by the output signal VQ. That is, by increasing the level of the output signal VQ, the output voltage of the DC power supply device main circuit 2-2 can be increased, and thereby the proportion of the load current or the power sharing of the DC power supply device 2 can be increased. it can. The upper limit value of the signal VQ, that is, the upper limit value of the output voltage of the DC power supply device 2 can be suppressed by providing the clamp zener diode 21 as necessary. Further, a feedback loop including the DC power supply output current / power detection means 7, the DC power supply output voltage control signal output means 9, the output voltage control circuit 2-2, and the DC power supply main circuit 2-1 is configured. Therefore, the signal I _d corresponding to the output current or power of the DC power supply 2 output from the DC power supply output current / power detection means 7 is output from the DC power supply output current / power setting means 8. It is possible to make it equal to I _L or I _L max. That is, the output current or power of the DC power supply device 2 can be matched with the load current or power corresponding to the value set by the DC power supply device output current / power setting means 8. However, when the output voltage of the DC power supply device 2 is set to be higher than the voltage of the rectifier 5 even though the output signal VQ is not sent, the output current of the DC power supply device 2 or The power is
The DC power supply device will be supplied in excess of the load current or power corresponding to the upper limit value I _L max set by the output current / power setting means 8.

From the operation as described above, if the set upper limit value _IL max determined by the DC power supply output current / power setting means 8 is set to a value corresponding to the rated output current or power of the fuel cell power supply 3, the load current Alternatively, the electric power is fuel cell power source 3
If the load current or power exceeds the rated output current or power of the fuel cell power supply 3, all the load current or power is supplied from the fuel cell power supply 3 if the load current or power is less than the rated output current or power of the fuel cell power supply 3. Can supply at least its rated output current or power.

In the above description, the load current / power detection means 6 and the DC power supply output current / power detection means 7 detect the same current or power, that is, the case where the same current is detected. / Power detection means 6
There is no need to match the detection targets in the DC power supply output current / power detection means 7. For example, the load current / power detection means 6 detects the power and outputs the DC power supply output current /
The power setting means 8 or the DC power supply output voltage control signal output means 9 has some method (for example, the output voltage of the DC power supply 2 is detected by means not shown in FIG. If the power detected by the current / power detection means 6 is converted into a current by
This is because there is no problem in detecting the current in the DC power supply current / power detection means 7.

FIG. 5 is a view for explaining another embodiment of the present invention,
It is a block diagram of a fuel cell DC parallel operation system showing one control method of the output voltage of a DC power supply device. Those having the same reference numerals as those in FIG. 3 have the same functions. The embodiment of FIG. 5 differs from the embodiment of FIG. 3 in that the method for detecting the current or power supplied to the load 10 by the fuel cell DC parallel operation system is the output current or power of the DC power supply 2 and the rectifier. The output current or the power of 5 is detected individually, and the two are added to form a load current / power detection means. That is,
Reference numeral 61 is a rectifier output current / power detection means for detecting an output current or power of the rectifier 5, and 62 is an output detected by the detected output current or output power and the aforementioned DC power supply output current / power detection means 7. It is an adder that adds the current or the power and sends it to the above-mentioned DC power supply output current / power setting means 8 as a detection output of the load current or the power consumption of the load. Even with such a configuration, it is clear that the same operation and the same operation as those of the embodiment of FIG. 3 described above are performed.

The commercial power supply 4 in the above embodiments may be another generator such as an engine generator.

Further, the means for controlling the output voltage control circuit 2-2 is not limited to the above-mentioned embodiment, and the point is that the control signal can be changed according to the fluctuation of the load current (or the power consumption of the load). Anything is fine. As described above, the present invention can be applied in various ways in accordance with its gist and take various embodiments.

[Effects of the Invention] As is clear from the above description, according to the fuel cell DC parallel operation system of the present invention, the fuel cell power supply for converting the DC output of the fuel cell into the voltage by the DC power supply device and supplying the load to the load, When applied to a power source with a fluctuating load, the fuel cell shares the entire load if the load current or power is within the rating of the fuel cell power source, and if the load current or power exceeds the rating of the fuel cell power source, the fuel cell power source Since at least the rated output current or the electric power is shared by the load, it becomes possible to effectively use the fuel cell which is expensive to establish.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention, FIG. 2 is an explanatory diagram of load sharing of a DC power supply device and a rectifier that constitute a fuel cell power source, and FIG. 3 is a block diagram showing an embodiment of the present invention. FIG. 4 is a circuit diagram showing a configuration example of the output voltage control circuit of the above embodiment, FIG. 5 is a block diagram showing another embodiment of the present invention, and FIG. 6 is a block diagram of a conventional fuel cell power supply system. FIG. 7 and FIG. 7 are views showing the time change of the power consumption of the load. 1 ... Fuel cell, 2 ... DC power supply device, 2-1 ... DC power supply device main circuit, 2-2 ... Output voltage control circuit, 3 ...
Fuel cell power source, 4 ... Commercial power source, 5 ... Rectifier, 6 ...
Load current / power detection means, 7 ... DC power supply output current / power detection means, 8 ... DC power supply output current / power setting means, 9 ... DC power supply output voltage control signal output means, 10 ... Load, 11 ... Operational amplifier, 12, 13, 14, 17, 18 ...
… Resistance, 15 …… Zener diode, 16,19 …… Diode, 20 …… Drive control circuit including pulse width modulation circuit, 21
... Zener diode for clamp, 61 ... Rectifier output current / power detection means, 62 ... Adder.

Claims (2)

(57) [Claims] 1. A fuel cell power supply comprising a fuel cell and a DC power supply having an output of the fuel cell as an input and having an output voltage control means, and a rectifier for rectifying a commercial power supply or another power generation source. The output of the fuel cell power supply is obtained by connecting the output of the battery power supply and the output of the rectifier in parallel, and controlling the output voltage of the DC power supply device of the fuel cell power supply according to the fluctuation of the load by the output voltage control means. A fuel cell DC parallel operation system characterized by controlling the load sharing ratio of the fuel cell. 2. The fuel cell DC parallel operation system according to claim 1, wherein the output voltage control means includes load current / power detection means for detecting load current or power supplied to the load by the fuel cell DC parallel operation system. A DC power supply output current / power detection means for detecting an output current or power of the DC power supply and outputting a signal corresponding thereto; and a load current or power received by the load current / power detection means. When the load current or power is below a predetermined current or power, a signal corresponding to the load current or power is output, and when the load current or power exceeds a predetermined current or power, a signal corresponding to the predetermined current or power is output. DC power supply output current / power setting means, the signal output from the DC power supply output current / power detection means, and the direct current Current source / output power / power setting means, comparing the output current or power of the DC power supply to the load current or power within the range of the predetermined current or power, A DC power supply output voltage control signal for controlling such that the output voltage of the DC power supplied from the DC power supply to the load is output at a voltage equal to or higher than the output voltage of the DC power supplied from the rectifier to the load. And a DC power supply output voltage control signal output means for outputting the output voltage control circuit of the DC power supply, when the load current or power is below the predetermined current or power, the DC power supply output voltage control DC power supplied from the DC power supply to the load by the DC power supply output voltage control signal output from the DC signal output means. Output voltage of the rectifier is controlled to be output at a voltage equal to or higher than the output voltage of the DC power supplied to the load, and most or all of the load current or power is supplied from the DC power supply, and the load current or When the electric power exceeds the predetermined current or the electric power, the direct current supplied from the direct current power supply to the load by the direct current power supply output voltage control signal output from the direct current power supply output voltage control signal output means. With respect to the output voltage of the DC power supplied from the rectifier to the load, the output voltage of the power is at least the predetermined current or the power is output by the DC power supply device at a voltage shared by the load and supplied to the load. A fuel cell DC parallel operation system characterized in that