JP2002135982A - Uninterruptible power supply switchable to independent operation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive but reliable uninterruptible power supply which can reduce the interrupted period when switching from link operation to independent operation covering the momentary interruption completely. SOLUTION: This uninterruptible power supply switchable to independent operation is provided with an inverter to invert the dc power from the main fuel cell into ac power, a power feed point to send the surplus of the above power to an ac power system excepting the power consumed in the load equipment, a first high speed breaker to cut off the connection of the above feed point and the above ac power system without momentary interruption, an abnormality detector quickly detecting an abnormality in the ac power system, a second breaker which can quickly connect the above load equipment to another ac power supply system independent of the above ac power system without momentary interruption, and a controller which automatically switch the supply power for the above load equipment to the best power supply by operating the above first and second breakers upon receiving the signal from the abnormality detector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an instantaneous interruption independent transition power generation system that switches system power without interruption when a system abnormality occurs in a system interconnection operation of a fuel cell or the like.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a configuration diagram of a fuel cell power generation system as an example of an instantaneous interruption-free independent power generation system described in Japanese Patent Publication No. 20; 6, reference numeral 2 denotes a fuel cell main body, 3 denotes an inverter, 4 denotes a load device connected to the output side of the fuel cell main body 2 via the inverter 3, 10 denotes an AC system, and 15 denotes current detection means. . 31 is a supply generation adjustment equipment, 38 is a changeover switch for switching a power supply source to an independent load from the AC system to the inverter output side, 40 is a control device, 41 is a setting function, 42 is an adjustment control system, 43 is a signal changeover switch, and 44 is a current setting device.

Next, the operation of this conventional example will be described. Raw fuel composed of city gas, natural gas, or the like is converted into hydrogen by the supply generation adjustment facility 31, and supplied to the fuel cell body 2 together with air. The fuel cell body 2 generates DC power, and the DC power is converted into AC power by the inverter 3. The single load 4 has a changeover switch 3
The power is supplied from the AC system 10 or the AC output of the inverter 3 by the AC system 8.

The control device 40 specifies the adjustment value of the adjustment control system 42 by the setting function 41 to maintain the current value detected by the current detection means 15 at the current value set by the current setting device 44, 31 raw fuels are controlled.

[0005] The raw fuel gas and air are supplied to the feed generation and regulation equipment 31, and the DC output from the fuel cell main body 2 is input to the inverter 3. Power. During such operation, the feed generation adjustment equipment 31, the fuel cell body 2,
When an abnormality occurs in the DC detection means 15, the inverter 3, and the controller 40 and the AC system 10 is normal, the power supply to the load 4 is controlled by the changeover switch 38 so that the output of the inverter 3 is To the AC system 10.

When power is supplied from the AC system 10 to the single load 4 through the changeover switch 38, any of the supply generation adjustment equipment 31, the fuel cell main body 2, the DC detection means 15, the inverting device 3, and the control device 40 are used. Is normal, and if an abnormality occurs in the AC system 10, the power supply to the single load 4 is switched by the changeover switch 38 to the AC system 1.
The output is switched from 0 to the output of the inverse converter 3.

In order to switch the power supply to the single load 4 from the AC system 10 to the output of the inverter 3 without an instantaneous interruption, the state where the fuel cell main body 2 can start power generation at a very high speed is maintained. Therefore, it is necessary to generate fuel cell power at all times and keep the switch 18 of the changeover switch bypass circuit 17 closed at all times.
When the abnormality occurs, the switch 18 is disconnected at a high speed, and the changeover switch 38 is switched from the AC system 10 to the output of the inverter 3.

[0008]

In the conventional control method,
Since it is necessary to maintain a state in which the fuel cell body 2 can start power generation at a very high speed, the inverter 3 always outputs the fuel cell output, as in a conventional example called a twin inverter shown in FIG. Inverter dedicated to grid-connected operation for reverse power flow to the AC system 10 through the changeover switch bypass circuit 17, and reverse converter 3B dedicated to isolated operation that supplies the output of the fuel cell to the single load 4 through the changeover switch 38
It is necessary to incorporate the two inverse converters, and the changeover switch 38 and the changeover switch bypass circuit 1
Two switches of the switch 18 for 7 were required.

Both switches use a thyristor switch or the like in order to realize high-speed switching and switching. However, the thyristor switch is expensive and the current loss of the switch section is larger than that of a vacuum circuit breaker. The cost was increased as a whole of the high-speed switching system.

In addition, since the operation of the thyristor switch requires a cut-off time of about half a cycle, the conventional high-speed switching system has an instantaneous interruption time of half a cycle or more, and the small-capacity electromagnetic relays and the like have the thyristor switch of the conventional system. For example, it was impossible to completely compensate for instantaneous power failure for some control devices. In order to compensate for momentary power failure even for some control equipment that cannot withstand a momentary power failure of more than half a cycle, an always-on backup type uninterruptible power supply (UPS) that does not involve switching at the momentary power failure is introduced. Needed. However, uninterruptible power supplies are generally short-term compensation means of several minutes to several hours, depending on the capacity of the battery installed in the equipment. To do so requires an enormous amount of batteries, which is very expensive.

In order to cope with a long-term power outage, a power supply such as a gas turbine generator or a diesel generator is disconnected from the AC system and always operates independently. Then, stable power supply to a single load can be performed, but the initial cost increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is intended to reduce AC current conduction loss in a changeover and cutoff switch section, and to shorten a cutoff time for switching between interconnected operation and isolated operation. The purpose of the present invention is to provide an instantaneous interruption-free transition system that can completely compensate for momentary power failures, is inexpensive, has high reliability, and can continue to operate important loads even if a long-term power failure occurs .

[0013]

According to the present invention, there is provided a non-instantaneous interruption independent transition system according to the present invention, comprising: a fuel cell main body for generating DC power by gas supplied from a gas supply facility; A device, an AC generation current measuring means for measuring an AC current output from the inverting device, a supply gas flow control means for adjusting a supply gas flow rate corresponding to the AC current, and an AC output from the inverting device. A load device that consumes power, a transmission point that transmits a surplus of the AC output power excluding power consumption by the load device to an AC system, and disconnects the transmission point and the AC system without an instantaneous interruption. A possible first high-speed cutoff means, a means for using the AC output power as an operation power supply for the first high-speed cutoff means, a system abnormality detection means for instantaneously detecting an abnormality in the AC system, Control means for receiving a detection signal from the abnormality detection means and issuing a disconnection command to the first high-speed cutoff means to switch the operation mode of the inverter from constant power control to constant voltage control; and A second high-speed cutoff means that can be turned on so as to connect another AC system to the load device without an instantaneous interruption; and wherein the control device performs the first and second high-speed cutoffs in response to the system abnormality signal. Activating the means to automatically switch the power supply source to the load device to an optimum power supply source.
Further, the instantaneous interruption-free autonomous transition system according to the present invention further includes a control stabilization circuit for stabilizing the control when the inverter operation mode is switched, and the control stabilization circuit is configured to perform the inverse conversion after switching the power generation control mode. An overcurrent limiter control circuit is provided which keeps the operation of the inverting device continued for a certain period of time even if an overcurrent occurs in the output of the device, and then makes the device self-sustained. Further, the instantaneous interruption-free transition system according to the present invention includes a fuel cell main body that generates DC power using gas supplied from a gas supply facility, an inverter that converts the DC power into AC power, and the inverter. AC generation current measurement means for measuring the output AC current, supply gas flow control means for adjusting the supply gas flow rate corresponding to the AC current, and a load device for consuming AC output power from the inverting device. A power transmission point for transmitting a surplus of the AC output power excluding power consumption by the load device to an AC system, and a high-speed cutoff unit capable of disconnecting the power transmission point and the AC system without instantaneous interruption, Means for using the AC output power as an operation power supply of the high-speed cutoff means,
A system abnormality detecting means for instantaneously detecting an abnormality of the AC system, and receiving a detection signal of the system abnormality detecting means, issuing a disconnection command to the high-speed cutoff means, and changing an operation mode of the inverter from constant power control. Control means for switching to constant voltage control, and a control stabilization circuit for stabilizing the control when the inverter operation mode is switched, the control stabilization circuit,
Even if an overcurrent occurs in the output of the inverter after the switching of the power generation control mode, an overcurrent limiter control circuit is provided that allows the operation of the inverter to continue for a certain period of time and then shifts to an independent state. It is. Still further, the instantaneous interruption-free independent transition system according to the present invention is characterized in that the system abnormality detection means is configured by a control device having a low instantaneous power failure tolerance, such as a failure due to a short-time power failure. Further, the instantaneous interruption independent transition system according to the present invention includes:
A fuel cell main body for generating DC power by gas supplied from a gas supply facility, an inverter for converting the DC power to AC power, and an AC generation current measuring means for measuring an AC current output from the inverter. Supply gas flow rate control means for adjusting a supply gas flow rate corresponding to the AC current, a load device consuming AC output power from the inverter, and a power consumption by the load device among the AC output power. A transmission point for transmitting the surplus removed to the AC system,
High-speed cutoff means capable of disconnecting the power transmission point and the AC system without instantaneous interruption, means for using the AC output power as an operation power supply for the high-speed cutoff means, and instantaneously detecting an abnormality in the AC system System abnormality detection means, and control means for receiving a detection signal of the system abnormality detection means, issuing a disconnection command to the high-speed cutoff means, and switching an operation mode of the inverter from constant power control to constant voltage control. Wherein the system abnormality detection means is configured by a control device having a low instantaneous power failure resistance, such as a failure due to a short-time power failure.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, a case where the instantaneous interruption-free transition system according to the present invention is applied to a fuel cell power plant will be described. Embodiment 1 FIG. FIG. 1 is a flowchart of a fuel cell power plant according to Embodiment 1 of the present invention. In FIG. 1, this fuel cell power plant includes a gas supply facility 1, a fuel cell main body 2, an inverter 3, a load device 4, a first high-speed cutoff unit, or simply a high-speed cutoff unit (the second and later embodiments described later). And a high-speed cutoff switch 5 and the like. The fuel cell power plant further includes an inverter control circuit 6, a system abnormality detection circuit 6a, a power generation output power control circuit 6,
b, Inverter abnormality detection circuit 6c, high-speed cutoff switch operating power supply 8, gas supply amount control circuit 9, AC system 10, protection circuit breaker 11, system voltage measurement device 12, generation voltage measurement device 1
3. A generated current measuring device 15 is provided. In addition, a circuit for supplying power to the load device 4 from a system 10a different from the AC system 10 is provided. This circuit also has a high-speed cutoff switch 5 as a second high-speed cutoff device, similar to the high-speed cutoff switch 5.
The high-speed cutoff switch 5a is supplied with power from a high-speed cutoff switch operating power supply 8a. Further, the inverse conversion device control circuit 6 includes an inverse conversion device abnormality detection circuit (not shown) for detecting an abnormality of the inverse conversion device 3.

Next, the operation of the first embodiment will be described with reference to FIG.
A description will be given based on FIG. In FIG. 1, the fuel cell 2 generates DC power by hydrogen gas and oxygen gas supplied from a gas supply facility 1, and the DC power is converted into AC power by an inverter 3. The power output of the inverter 3 is supplied to the load device 4 through the protection circuit breaker 11, and the excess power output of the power output minus the power consumed by the load device 4 is divided into the high-speed cutoff switch 5 and the protection circuit breaker. It is output to the system 10 through 11. That is, when the system 10 is normal, the fuel cell power generation system is in a system interconnection operation state.

In the system interconnection operation, the inverter control circuit 6
Performs an interconnected synchronous operation in which the voltages of the system voltage measuring device 12 and the generated voltage measuring device 13 are synchronized, and controls the generated power of the inverter 3 by the generated voltage measuring device 13 and the generated current measuring device 15, The gas supply amount control circuit 9 calculates the gas amount required for the generated current value measured by the generated current measuring device 15, and adjusts the gas amount supplied from the gas supply equipment 1 to the fuel cell 2 main body.

FIG. 2 shows a method of detecting an instantaneous system interruption in the system abnormality detection circuit 6a and the operation control mode switching timing of the inverter 3. For example, when the system voltage abnormal level is set to the system voltage ± 25% for each phase voltage, the system voltage value measured by the system voltage measuring device 12 is set to a predetermined system voltage shortage level (system normal voltage × 75%). )
When the power is below the threshold, the system abnormality detection circuit 6a sends a system abnormality signal to the power generation output power control circuit 6b, and the power generation output power control circuit 6b sends a cutoff signal to the high-speed cutoff switch 5,
The output of the power converter is switched from the constant power control to the constant voltage control in accordance with the timing of the high-speed cutoff switch disconnection, and the power is continuously supplied to the load device 4 without interruption. That is, the system 10 is switched from the grid-connected operation in which the system 10 is in a normal state to the isolated operation state in which the fuel cell output is disconnected from the system 10 without any interruption. When the measured system voltage measured by the generated voltage measuring device 13 exceeds a preset system voltage excess level (system normal voltage × 125%), the system abnormality detection circuit 6a sends a system abnormality to the generation output power control circuit 6b. A signal is sent out, and the operation is instantaneously interrupted and self-sustained in the same operation as in the case of the instantaneous power outage. Also in the case of other system abnormality detection such as islanding operation detection, under-frequency, over-frequency, over-current, etc., the instantaneous interruption independent transition is performed by the same operation as in the case of the system instantaneous stop. AC system 1
0, when an abnormality occurs in both the inverters 3, a system abnormality signal of the system abnormality detector 6a and an inverter abnormality detector circuit (not shown) built in the inverter controller 6
Output power control circuit 6b based on the abnormality detection signal of
As a result, the high-speed switch 5a installed between the AC separate system 10a and the load device 4 is turned on without an instantaneous interruption, and the power to the load device 4 is continued.

As in the case of a general electric circuit breaker, a power supply for operating the high-speed cutoff switches 5, 5a is required, and a part of the power generated by the inverter 3 is supplied. Specifically, in order to use a high-speed cutoff switch as described in JP-A-11-111123, an AC power supply to the DC power supplies 8 and 8a is required as a charging device.

Embodiment 2 FIG. 3 is a flowchart of the fuel cell power plant according to Embodiment 2 of the present invention. In FIG. 3, 1 to 15 are the same as in FIG. 1, but the circuit for supplying power to the load device 4 from the separate system 10a in FIG. 1 is omitted, and the inverter control circuit 6 switches the inverter operation mode. A control stabilization circuit that stabilizes the control at times, and the control stabilization circuit includes an overcurrent limiter control circuit 6c that interrupts an output signal supplied from the generated current measuring device 15 to the generated output power control circuit 6b for a predetermined time. Have. FIG. 4 is a diagram for explaining the operation of the second embodiment.

Next, the operation of the second embodiment will be described with reference to FIG.
It will be described based on. In FIG. 3, the gas supply operation and the power generation operation in the system interconnection operation and the single operation are the same as those in the first embodiment in FIG. In FIG. 3, when a system abnormality occurs and the inverter 3 switches from constant power control to constant voltage control without instantaneous interruption, when the switching timing shown in FIG. 4 is reached, the high-speed cutoff switch 5 is closed. Since the AC system 10 and the inverter 3 are not disconnected, a timing for performing the constant voltage control occurs.
When there is a difference between the voltage target value in the constant voltage control of the inverter 3 and the system voltage, and an instantaneous interruption occurs in the system 10 and the system voltage is lower than the constant voltage control target of the inverter 3 In this case, the inverter control is performed in the direction in which the overcurrent increases. However, in the period from 1 cycle to 1.5 cycles, even if there is a difference between the system voltage and the inverting device constant voltage control target value, the rate of increase of the overcurrent is small, so that the overcurrent substantially hardly flows. For this reason, in the second embodiment, the overcurrent limiter control (the output cutoff of the generated current measuring device 15) by the overcurrent limiter control circuit 6c is performed for a predetermined time (about 20 ms) and the overcurrent limiter is still in the overcurrent state. Only in such a case, the power generation output power control circuit 6b causes the reverse conversion device 3 to make an emergency stop.

In the second embodiment, the circuit for supplying power from the separate system 10a to the load device 4 has been described. However, in the first embodiment, the overcurrent limiter control circuit 6c of the second embodiment is also used. May be provided.

Embodiment 3 FIG. FIG. 5 is a flow chart of a fuel cell power plant according to Embodiment 3 of the present invention. In FIG. 5, 1 to 15 are the same as those in FIG. 1, and 6z is a system instantaneous power failure detector. That is, in the third embodiment, the circuit for supplying power to the load device 4 from the separate system 10 a in FIG. 1 is omitted, and a system abnormality is detected from the output of the system voltage measuring device 12. A system instantaneous interruption detector 6z for interrupting (opening) the high-speed interruption switch 5 is provided.

Next, the operation of the third embodiment will be described with reference to FIG.
It will be described based on. In FIG. 5, the gas supply operation and the power generation operation in the system interconnection operation and the single operation are the same as those in the first embodiment in FIG. In FIG. 5, a device having the lowest system power failure tolerance is used as a system voltage shortage detector. For example, a small-capacity electromagnetic relay that goes down when the voltage is 75% or less of a normal value and continues for about 3 ms or more is replaced with a high-speed undervoltage. Used for detection. Specifically, the tap value of the system voltage measuring instrument (transformer) 12 is set to a normal value (440 V / 110
V), the direction in which the secondary voltage slightly decreases (440 /
105V). The electromagnetic relay or the like is connected to the secondary side of the system voltage measuring device (transformer) 12 as the system momentary power failure detector 6z.
In the state of V (100%), the electromagnetic relay has 105
V (95.45% of the normal value of 110 V) is applied, so that the normal value (110 V) of the electromagnetic relay is 95.45%.
This means that a voltage of 45% (105 V) is applied.
That is, when 78.58% of the system voltage of 440 V (voltage of the electromagnetic relay is 110 V × 75% or less) continues for about 3 ms, the electromagnetic relay goes down first and sends a cutoff command to the high-speed cutoff switch 5. The following is the first embodiment.
Performs the same operation as above, and achieves self-sustained transition without any interruption.

In the first and second embodiments, the instantaneous power failure detector 6z of the third embodiment may be provided. In this case, the same as in the third embodiment is provided. Needless to say, the effect of the invention can be obtained.

[0025]

As described above, according to the present invention, the following effects can be obtained. According to the first aspect of the present invention, the capacity of the inverter can be reduced to one rated power generation output, the initial cost of the inverter can be suppressed, and the configuration of the inverter can be simplified, The reliability of the converter can be improved, and the running cost can be suppressed by adopting a high-speed cutoff switch having a vacuum valve structure in which the conduction loss is very close to zero. In addition, when a momentary power failure occurs, the power failure time of the load supply power is extremely short (about 2 msec), which is shorter than that of the conventional system. Compensation is also possible. Furthermore, even if the system abnormality continues during the isolated operation and the inverter becomes abnormal, the power supply to the load device is switched from the inverter output to a system different from the abnormal system without instantaneous interruption. It is possible to improve the continuity of the operation of the load equipment. Therefore, it is possible to transmit a stable power generation output to the load device and the grid. According to the second or third aspect of the present invention, when a system abnormality occurs and a self-sustained shift occurs without an instantaneous interruption, a signal transmission delay between the inverter and the high-speed cutoff switch or an operation delay of the high-speed cutoff switch occurs. In a state in which the control system of the inverter is switched from the interconnected operation mode constant power control to the self-parallel operation mode constant voltage control in a state where the system has not been disconnected, without performing overcurrent detection for a short time,
Since the overcurrent limiter control circuit controls the operation to continue even in an overcurrent state, it is possible to improve the continuous power supply to the load device without unnecessarily stopping the inverter in an emergency. According to the invention of claim 4 or 5, since an inexpensive electromagnetic relay or the like can be used as a system abnormality detector, an inexpensive detection system can be constructed without providing a high-speed detection logic for each system.

[Brief description of the drawings]

FIG. 1 is a flowchart of a fuel cell power plant according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a system abnormality detection method according to the first embodiment.

FIG. 3 is a flowchart of a fuel cell power plant according to Embodiment 2 of the present invention.

FIG. 4 is a diagram for explaining an operation of the second embodiment.

FIG. 5 is a flowchart of a fuel cell power plant according to Embodiment 3 of the present invention.

FIG. 6 is a flowchart showing a conventional fuel cell power plant.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 gas supply facility, 2 fuel cell main body, 3 inverter, 4 load device, 5 high-speed cutoff switch (first high-speed cutoff means, high-speed cutoff means), 5 a high-speed cutoff switch (second high-speed cutoff means), 6 Control circuit, 6a system abnormality detection circuit, 6b power generation output power control circuit, 6c overcurrent limiter control circuit, 6z system momentary power failure detector, 8, 8a DC power supply for high-speed cutoff switch operation, 9 gas supply amount control circuit, 10 AC System, 10a separate AC system, 11 protection circuit breaker, 12 transmission voltage detector, 13 generation voltage detector, 15 generation current detector.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Takeda 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsubishi Electric Corporation (72) Inventor Kenji Morishita 3-2-2 Nakanoshima, Kita-ku, Osaka-shi, Osaka No. Kansai Electric Power Company F-term (reference) 5G015 FA13 GA05 HA15 JA05 JA21 JA32 JA64 5G066 HA01 HA06 HB07 5H027 BA01 DD01 KK51 MM01 MM26 5H420 BB12 BB14 CC03 DD03 EA03 EA37 EA47 EB13 EB39 FF03 FF04 LL10

Claims (5)

[Claims] 1. A fuel cell main body that generates DC power using gas supplied from a gas supply facility, an inverter that converts the DC power into AC power, and measures an AC current that is output from the inverter. AC generation current measurement means, supply gas flow rate control means for adjusting a supply gas flow rate corresponding to the AC current, a load device consuming AC output power from the inverter, and the load of the AC output power A power transmission point for transmitting a surplus amount excluding power consumption by the device to the AC system, and a first power source capable of disconnecting the power transmission point and the AC system without an instantaneous interruption.
High-speed cutoff means, means for using the AC output power as an operating power supply for the first high-speed cutoff means, system abnormality detection means for instantaneously detecting abnormality in the AC system, and detection of the system abnormality detection means Control means for receiving a signal and issuing a disconnection command to the first high-speed cutoff means to switch the operation mode of the inverter from constant power control to constant voltage control; and another AC system independent of the AC system. A second high-speed cutoff unit that can be turned on so as to be connected to the load device without an instantaneous interruption. The control device operates the first and second high-speed cutoff units according to the system abnormality signal. A power supply source for the load device is automatically switched to an optimum power supply source. 2. The system according to claim 1, further comprising a control stabilization circuit for stabilizing the control at the time of switching the operation mode of the inverter, wherein the control stabilization circuit is provided after the switching of the power generation control mode. Even if an overcurrent occurs in the output of the inverting device, an overcurrent limiter control circuit for continuing the operation of the inverting device for a certain period of time, and then performing an independence transition, characterized in that it is provided with an instantaneous interruption independence transition system . 3. A fuel cell main body that generates DC power using gas supplied from a gas supply facility, an inverter that converts the DC power into AC power, and measures an AC current that is output from the inverter. AC generation current measurement means, supply gas flow rate control means for adjusting a supply gas flow rate corresponding to the AC current, a load device consuming AC output power from the inverter, and the load of the AC output power A power transmission point for transmitting a surplus amount excluding power consumption by the device to the AC system; a high-speed cutoff unit capable of disconnecting the power transmission point and the AC system without instantaneous interruption; and Means for utilizing AC output power; system abnormality detection means for instantaneously detecting abnormality in the AC system; and receiving a detection signal from the system abnormality detection means and issuing a disconnection command to the high-speed cutoff means. Control means for switching the operation mode of the inverter from constant power control to constant voltage control; anda control stabilization circuit for stabilizing the control when the inverter operation mode is switched. Even if an overcurrent occurs in the output of the inverter after the switching of the power generation control mode, an overcurrent limiter control circuit is provided that allows the operation of the inverter to continue for a certain period of time and then shifts to an independent state. Instantaneous interruption independent transition system. 4. The system according to claim 1, wherein the system abnormality detection unit is configured by a control device having a low tolerance to instantaneous interruption such as a short-time power interruption. An instantaneous interruption independent transition system characterized by the following. 5. A fuel cell main body for generating DC power by gas supplied from a gas supply facility, an inverter for converting the DC power into AC power, and measuring an AC current output from the inverter. AC generation current measurement means, supply gas flow rate control means for adjusting a supply gas flow rate corresponding to the AC current, a load device consuming AC output power from the inverter, and the load of the AC output power A power transmission point for transmitting a surplus amount excluding power consumption by the device to the AC system; a high-speed cutoff unit capable of disconnecting the power transmission point and the AC system without instantaneous interruption; and Means for utilizing AC output power; system abnormality detection means for instantaneously detecting abnormality in the AC system; and receiving a detection signal from the system abnormality detection means and issuing a disconnection command to the high-speed cutoff means. Control means for switching the operation mode of the inverting device from constant power control to constant voltage control; andthe system abnormality detecting means is configured by a control device having a low tolerance to instantaneous power failure such as a short-time power failure. An instantaneous interruption independent transition system characterized by the following.