JPH05101840A - Power supply device using fuel cell - Google Patents

Abstract

PURPOSE:To provide possibility of using a commercially available inverter to be supplied with the power from AC mains by sinking the voltage impressed on the inverter below the rated voltage value by a voltage adjusting means, or by dividing the fuel cell output voltage with a resistance so as to become below the rated voltage value, as long as the fuel cell output voltage lies higher than the rated voltage value. CONSTITUTION:A series circuitry of resistances R1 and R2 is furnished on a DC power supply line 6 tying a fuel cell 1 to an inverter 4 and is connected to with the internal resistance Ri of the inverter 4 in series. The resistances R1, R2 are fitted with relays K1, K2 in respective parallel states, and the supply current I from the fuel cell 1 is sensed by a current sensor 5 installed on the cell 1 side of the supply line 6, and according to this current obtained, a control device 7 makes control via the relays K1, K2 to switch from the condition, that current is fed to the resistances R1, R2, to the condition out of current feed, and vice versa. Otherwise, diodes D1, D2 connected in regular direction are provided in lieu of resistances R1, R2, and these diodes are connected serially with the internal resistance Ri, or a separate voltage adjusting means is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power supply device having an inverter for converting direct current output from a fuel cell into alternating current.

[0002]

2. Description of the Related Art The output voltage / current characteristics of a fuel cell have a drooping characteristic in which the open circuit voltage is very high and the output voltage sharply decreases as the output current increases. The output voltage in the load range is extremely higher than the rated voltage. (For example, in a phosphoric acid fuel cell, the open circuit voltage is about twice as high as the rated voltage.) Therefore, conventionally, as an inverter for a power supply device using such a fuel cell, the output voltage of the fuel cell is rated. In order to consider the low load range which is higher than the voltage, it is necessary to make the input withstand voltage considerably higher than the rated voltage (for example, about twice the rated voltage for phosphoric acid fuel cells). There is
In addition, the semiconductor elements used in the inverter are in the high voltage range.
It was necessary to use a high voltage type.

[0003]

Therefore, conventionally, it is necessary to design and manufacture a special dedicated inverter for a power supply device using a fuel cell, which results in a considerably high cost of the inverter, and as a result, the device as a whole. There is room for improvement in terms of cost, because the cost of will be high. The present invention has been made in view of the above circumstances, and an object thereof is to reduce the cost of a power supply device using a fuel cell by rationally improving a method of supplying output power from a fuel cell to an inverter. There is a point.

[0004]

A first characteristic configuration of a power supply device using a fuel cell according to the present invention is that a voltage adjusting means for adjusting a voltage value applied to the inverter to a set value or less is provided. is there. A second characteristic configuration is that the voltage adjusting means connects the fuel cell with the inverter in series with the inverter, a detector that detects an output current or an output voltage of the fuel cell, and a detector thereof. The output DC power from the fuel cell is configured to be switched between a state in which the resistor is energized and a state in which the resistor is not energized based on the detection information of 1.

[0005]

According to the first characteristic configuration, the voltage applied to the inverter is equal to or lower than a predetermined set value (for example, rated voltage) even in a low load range where the output voltage of the fuel cell is higher than the rated voltage. Since the input withstand voltage of the inverter only needs to consider the rated voltage, the inverter input withstand voltage must be considerably higher than the rated voltage in consideration of the low load range. You don't have to. According to the second characteristic configuration, on the basis of the detected current information or the detected voltage information of the detector, in the low load range, the output DC power from the fuel cell is brought into a state where the resistance is energized to change the output voltage of the fuel cell. By dividing the voltage with a resistor, the voltage applied to the inverter is set to a specified value (eg rated voltage).
Adjust the following and, except in the low load range, make sure that the output DC power from the fuel cell does not pass through the resistor and applies the entire output voltage of the fuel cell to the inverter. Need only consider the rated voltage.

[0006]

According to the first characteristic configuration, it is not necessary to design and manufacture a special dedicated inverter as in the prior art, and it is possible to use a commercially available inexpensive power source for general commercial power sources. Since an inverter can be used, it is possible to provide a power supply device using a fuel cell, which is advantageous in terms of cost. According to the second characteristic configuration, only a very simple improvement is carried out by using a general commercial inexpensive ordinary component such as a resistor, a current detector or a voltage detector, and an energization switching means. Since it becomes possible to use a commercially available inexpensive inverter used for the above, the cost of the entire device can be reduced, and a power supply device using a fuel cell that is advantageous in terms of cost can be provided.

[0007]

Embodiments of the present invention will be described below with reference to FIGS.

First, a schematic structure of a power supply device using a fuel cell will be described. The fuel cell 1 reforms a supplied fuel gas such as natural gas into a reformed gas containing hydrogen as a main component in the reforming unit 2, and contains hydrogen in the reformed gas and oxygen separately supplied such as air. The power generation unit 3 reacts with oxygen in the gas to generate DC power. The output DC power from the fuel cell 1 is converted into AC in the inverter 4, and the output AC power from the inverter 4 is supplied to the external load.

In the figure, 5 is a current detector for detecting the output current I of the fuel cell 1. Resistors R1 and R2 are connected in series with an internal resistance Ri of the inverter 4 on a DC power supply line 6 that connects the fuel cell 1 and the inverter 4, and relays K1 and K2 are connected to the resistors R1 and R2, respectively. Are connected in parallel. Reference numeral 7 denotes a control device that opens and closes each of the relays K1 and K2 based on the detection current I of the current detector 5, and the control device 7 and the relay K1.
And K2, the output DC power from the fuel cell 1 is converted into resistors R1 and R2 based on the detected current value of the current detector 5.
A switching device C that switches between a state in which each of them is energized and a state in which they are not energized is configured.

The current detector 5, the resistors R1 and R2, and the switching device C constitute a voltage adjusting device S which adjusts the voltage value applied to the inverter 4 to a set value or less.

FIG. 2 is a diagram showing the output voltage-current characteristics of the fuel cell 1, showing a drooping characteristic in which the open circuit voltage value Va is extremely high and the output voltage V sharply decreases as the output current I increases. In the low load range (generally, the output current I of the fuel cell 1 is from Ia (= 0) to Ic), the output voltage V is higher than the rated voltage Vd. However, when the output current I is Ic is when the output voltage Vc at that time is equal to or close to the rated voltage Vd.

Next, the method of setting the resistance values of the resistors R1 and R2 with respect to the resistance value of the internal resistance Ri of the inverter 4 will be described with reference to FIG. That is, the resistors R1 and R
2, and the voltages V1, V2 applied to the internal resistance Ri, respectively.
Vi is the output voltage V when the output current is Ia (= 0)
a (= open circuit voltage of the fuel cell 1) is divided by the resistors R1 and R2 and the internal resistor Ri, and the output voltage Vb when the output current is a predetermined set value Ib is divided into the resistor R2 and the internal resistor Ri. When the voltage is divided by, the resistances of the resistors R1 and R2 are set so that the voltage Vi applied to the internal resistance Ri becomes a value Vc that is equal to or close to the output rated voltage Vd of the fuel cell 1, as shown in FIG. The value is set with respect to the resistance value of the internal resistance Ri of the inverter 4.

Next, a method of controlling the voltage value applied to the inverter 4 will be described. First, the control device 7 causes the detected current value I of the current detector 5 to be Ia (= 0, that is,
From the state in which the power consumption in the external load is zero) to the predetermined set value Ib, the relays K1 and K2 are maintained in the open state, and the output current is equal to the resistances R1 and R2 and the internal resistance R2.
i is in a state of flowing. Therefore, since the output voltage of the fuel cell 1 is divided by the resistors R1 and R2 and the internal resistance Ri of the inverter 4, the voltage Vi applied to the internal resistance Ri is always kept lower than Vc. You can

Subsequently, the controller 7 controls the current detector 5
When the detected current value I of I becomes Ib, the relay K2 closes the relay K1 while maintaining the open state, and by maintaining the state until the detected current value I becomes Ic,
The output current is relay K1, resistor R2, and internal resistor Ri.
Put it in a state of flowing through. Therefore, since the output voltage of the fuel cell 1 is divided by the resistor R2 and the internal resistance Ri of the inverter 4, the voltage V applied to the internal resistance Ri
i can always be kept lower than Vc.

Further, when the detected current value I of the current detector 5 becomes Ic by the control device 7, both the relays K1 and K2 are closed by closing the relay K2, and the output currents of the relays K1, K2, Also, the internal resistance Ri is made to flow. Therefore, the output voltage of the fuel cell 1 is entirely applied to the internal resistance Ri, but the voltage Vi applied to the internal resistance Ri does not exceed Vc as the output current I increases from Ic.

By controlling as described above, the output voltage V of the voltage Vi applied to the inverter 4 is the rated voltage Vd.
Even in the low load range (generally, the output current value I of the fuel cell 1 is from Ia (= 0) to Ic) in a higher state, it is possible to always maintain the value equal to or lower than the predetermined set value Vc. However, Vc can be set arbitrarily such as equal to or close to the rated voltage Vd.

[Other Embodiment] Instead of the resistors R1 and R2 of the above embodiment, a diode D1 is used as shown in FIG.
And D2 may be connected in a forward direction in series with the internal resistance Ri of the inverter 4, and the output voltage of the fuel cell 1 may be divided by the forward resistances of the diodes D1 and D2.

Two or more resistors that are connected in series with the internal resistance Ri of the inverter 4 are connected, and a relay is connected in parallel to each resistance, and the fuel cell 1
The voltage division by the resistance of the output voltage may be further subdivided.

Instead of the current detector 5 of the above embodiment, a voltage detector is provided, and the control device 7 is configured to open and close each of the relays K1 and K2 based on the detected voltage value of the voltage detector. You may.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a power supply device using a fuel cell.

[Figure 2] Output voltage / current characteristic diagram of fuel cell

FIG. 3 is a configuration diagram of a power supply device using a fuel cell according to another embodiment.

[Explanation of symbols]

 1 Fuel Cell 4 Inverter 5 Detector C Switching Means R1, R2 Resistance S Voltage Adjusting Means

Claims (2)

[Claims] 1. A power supply device using a fuel cell, comprising an inverter (4) for converting direct current output from a fuel cell (1) into alternating current, wherein a voltage value applied to the inverter (4) is a set value or less. A power supply device using a fuel cell, which is provided with a voltage adjusting means (S) for adjusting to. 2. The resistors (R1), (R2) connected to the fuel cell (1) in series with the inverter (4), and the fuel cell (1). )
(5) for detecting the output current or output voltage of the fuel cell, and based on the detection information of the detector (5), the output DC power from the fuel cell (1) is the resistances (R1), (R2).
2. The power supply device using a fuel cell according to claim 1, further comprising a switching means (C) for switching between energizing and non-energizing states.