JPS63110922A - Feeding system employing fuel cell - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a power supply system using a fuel cell, which is suitable for application to an AC power supply system in which frequent changes in load are expected.

(Prior Art) Conventionally, as a power supply system for independently operating a fuel cell, the one shown in FIG. 4 is known.

That is, in FIG. 4, 21 is a fuel cell, 22 is a voltage source inverter, 23 is a transformer, 24 is a switch, and 25
In this power supply system, DC power from a fuel cell 21 is converted into AC power by an inverter 22, and power is supplied to a plurality of loads 25 via a transformer 23.

Therefore, in this power supply system, when the load 25 is increased or decreased by turning on the switch 24 or releasing the DI.

As a result, a situation occurs in which the output current 1tc of the fuel cell 21 suddenly changes as shown in FIG. However, fuel cell 21
In general, it is desirable to avoid sudden changes in output as much as possible from the viewpoint of lifespan, strength, etc., and a system like the one shown in FIG. 4 cannot meet this requirement. For this reason, there is a system in which this type of power supply system is linked to a large-capacity power grid, and the fuel cell is always operated at an optimal constant output so that even if the load increases or decreases, the influence does not spread to the fuel cell. Proposed.

However, in general, power supply systems using fuel cells demonstrate their usefulness only when used in remote areas or remote islands where there is no stable large-scale power grid due to their ease of handling and maintenance, and they are inevitably used independently. In many cases, they are used for operation or linked operation with weaker power systems using diesel generators, etc.

Therefore, as long as the conventional example shown in FIG. 4 is operated alone or in conjunction with a weak system, it is impossible to prevent the sudden change in output as described above.

For this reason, a system is constructed in which a power storage device that absorbs changes in the output of a power supply circuit consisting of a fuel cell 21, an inverter 22, etc. is connected in parallel to the power supply circuit, thereby suppressing sudden changes in the output of the fuel cell 21. is proposed.

That is, FIG. 6 shows an example thereof, and is constructed by adding a power storage device 26 surrounded by a dashed line in the figure to the example of FIG. 4. The power storage device 26 includes a storage battery 27 that stores and releases power, a smoothing capacitor 28, and a voltage type inverter 29 that performs orthogonal conversion and control of power between these and the load 25 side. The AC reactor 31 increases the output impedance of the power supply circuit including the fuel cell 21 and suppresses changes in its output.

In this power supply system, power is supplied or stored in the power storage device 26 before the power supply circuit when the load 25 increases or decreases, thereby suppressing sudden changes in the output current Itc of the power supply circuit, that is, the fuel cell 21. It is.

(Problems to be Solved by the Invention) However, according to the conventional example shown in FIG. 2
It is necessary to make the speed faster than 2, and the inverter 29
It is necessary to take steps such as setting the inductance of the AC reactor 31 to a large value in anticipation of sudden changes in the load 25 that cannot be achieved by power control. Therefore, there is a problem in that selection of these control constants and main circuit constants is quite complicated.

Furthermore, even if the number of rooms is optimized,
Especially when a sudden change in the load 25 occurs, the fuel cell 21
A part of this change spreads to the side, and the output current Ire
There was a risk that the situation could suddenly change.

The present invention was proposed to solve the above problems, and its purpose is to increase the AC output impedance by using the inverter on the power supply circuit side as a current type, thereby increasing the output of the power supply system as the load increases or decreases. Changes are efficiently absorbed by a separate power storage device, preventing sudden changes in the output of the fuel cell, thereby preventing shortening of the fuel cell's lifespan, and enabling independent operation in remote areas or linked operation with weak power systems. The aim is to provide a power supply system that

(Means for Solving the Problems) In order to achieve the above object, the present invention connects a load to the output side of a power supply circuit that has a fuel cell and an inverter that converts the output DC power into AC power. In the power supply system, the inverter is configured with a current source inverter, and when the load is increased or decreased, 1. A power storage device equipped with a power storage element such as a voltage source inverter capable of supplying or storing a portion of the output power of the power supply circuit, a storage battery, and an electric motor with a flywheel is connected in parallel to the power supply circuit. It is characterized by being connected.

(Function) In the present invention, a part of the output power of the power supply circuit that should be decreased in proportion to the decrease in load is stored in the power storage device, and a part of the output power of the power supply circuit that should be increased in proportion to the increase in load is stored in the power storage device. By supplying a portion of the power from the power storage device, changes in the output of the power supply circuit when the load increases or decreases are slowed down, thereby preventing sudden changes in the output current of the fuel cell. Sudden changes in the output current of the fuel cell are automatically suppressed by prioritizing and absorbing ζ on the power storage device side with low output impedance over the power supply circuit side of the fuel cell.

(Example) The present invention will be described in detail below with reference to FIG.

First, FIGS. 1 and 2 show a first embodiment of the present invention. In FIG. 1 showing the circuit configuration, 5 is a power supply circuit, and this power supply circuit 5 connects the fuel cell 1 and the DC current. It is composed of a DC reactor 2 for smoothing that suppresses changes in the voltage, a current source inverter 3 made of a GTO or the like, and a transformer 4. In addition, a switch 6 is placed on the output side of the transformer 4.
A plurality of loads 7 are connected via.

Next, reference numeral 8 denotes a power storage device formed almost similarly to the power storage device 26 in FIG. 6 described above, and the power storage device 8 includes a storage battery 9 as a power storage element, a smoothing capacitor 10, A voltage source inverter 11 consisting of a GTO and a feedback diode.

The output side of the transformer 12 is connected to the output side of the transformer 4, and the power supply circuit 5 and the power storage device 8 are connected in parallel. Here, the inverter 11 converts the DC power of the ¥5ffi pond 9 into AC power and supplies it to the load 7 side, and converts the AC power on the load 7 side to DC power with a feedback diode and can regenerate it to the storage battery 9. In addition, the inverter 11 sets the output AC voltage to the load 7 side to match, for example, the commercial voltage.

Next, the operation when the load 7 increases or decreases in this power supply system will be described with reference to FIG. 2. In addition, the first
In the figure and FIG. 2, PI is the power taken by the load 7, Ps
t indicates the output power of the power storage device 8, Pfc indicates the output power of the power supply circuit 5, and it is assumed that the direction of the arrow in FIG. 1 is the positive direction. First, if a certain load 7 is removed by opening the switch 6 at time t1 in FIG. 2, the electric power P decreases rapidly as shown. Now, power storage device 8
If not, this decrease in power Pi will directly affect the output power Ptc of the power supply circuit 5 as shown by the broken line in the figure.

However, in this embodiment, since the AC output impedance of the current source inverter 3 constituting the power supply circuit 5 is high, a sudden decrease in the surplus power Plc due to the removal of the load 7 does not occur on the power supply circuit 5 side; The change in power P1 is shared at the rate of change allowed by the fuel cell 1. That is, a part of the surplus power Pfc is supplied as negative output power Pst to the power storage device 8 side, which has a relatively low output impedance, as shown by diagonal lines in the figure, and is stored in the storage battery 9. , correspondingly, the output power Ptc
The decrease will also be slower. Therefore, the output current Ice of the fuel cell 1 also decreases slowly without suddenly decreasing.

Further, at a subsequent time t2, the switch 6 is turned on,
If a new load 7 is added, the electric power Pl increases rapidly as shown in the figure. However, at this time as well, the positive output power Pst from the power storage device 8 side with low output impedance is supplied to the load 7 side so as to share a part of the increase in power, and the power supply circuit 5 Since the increase in power PI is shared at the rate of change, a sudden increase in power PI does not immediately affect the output power Pfc of the power supply circuit 5, and the increase in output power Ptc becomes slow as shown in the figure.

Therefore, even when the load 7 suddenly increases, the output current of the fuel cell 1 is 1 t.
c increases slowly.

Next, FIG. 3 shows a second embodiment of the present invention. In this embodiment, an electric motor 13 with a flywheel is used as the power storage element, and the electric motor 13 and the converter 14 . Voltage source inverter 15° smoothing capacitor 16.17. The reactor 18 and transformer 12 constitute a power storage device 8A. However, in this embodiment, a part of the surplus power Ptc when the load 7 suddenly decreases is taken into the power storage device 8A as negative power Pst, and this power is converted into the rotational energy of the flywheel and stored. By discharging the rotational energy applied when the load 7 suddenly increases before the power supply circuit 5, it is possible to absorb the change in the electric power Pl and slow down the change in the output current Ifc as in the first embodiment.

(Effects of the Invention) As detailed above, according to the present invention, the power storage device connected in parallel to the power supply circuit having the current source inverter acts to buffer changes in the output of the power supply circuit. It is possible to prevent a sudden change in the output current of the fuel cell, thereby preventing a reduction in its lifespan, and it is also possible to perform independent operation or linked operation with a weak system without any problems in remote areas or remote islands.

Furthermore, it is extremely economical because there is no need to worry about setting circuit constants as in the prior art, and the system can be configured by only making slight changes to the conventional circuit configuration.

[Brief explanation of the drawing]

Figures 1 and 2 show a first embodiment of the present invention, with Figure 1 being a single line diagram of the circuit configuration, and Figure 2 explaining the state of change in each power depending on whether the load is turned on or off. FIG. 3 is a single-line circuit diagram showing the second embodiment of the present invention, and FIG.
The figure is a circuit configuration diagram using a single line diagram showing a conventional example. Figure 5 is a diagram explaining the state of change in the fuel cell output current according to load on/off in the conventional example. Figure 6 is a single line diagram showing another conventional example. FIG. 2 is a diagram showing a circuit configuration. 1...Fuel cell 2...DC reactor 3...Current source inverter 5...Power supply circuit 7...
・Load 8,8A...Power storage device 9・
... Storage battery 11.15 ... Voltage type inverter 13 ... Electric motor with flywheel 14 ... Converter patent applicant Fuji Electric Co., Ltd. Fig. 1 8' Fig. 2 5 Fig. 3 8'A Fig. 4 Figure 5 Figure 6

Claims (1)

[Claims] In a power supply system in which a load is connected to the output side of a power supply circuit having a fuel cell and an inverter that converts the output DC power into AC power, the inverter is configured with a current source inverter, and the load is increased or decreased. A power storage device including a voltage source inverter and a power storage element capable of supplying or storing part of the output power of the power supply circuit is connected in parallel to the power supply circuit. Power supply system using fuel cells.