JP2015186408A - Operation method for fuel cell system, and fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten time until operation switching at the time of power failure or power recovery of a system power supply. During independent operation, the generated power of the fuel cell is set to a constant independent generated power that is smaller than the rated maximum power and larger than the idling power required to drive the auxiliary machine. In the event of a power failure of the grid power supply, the power generated by the fuel cell is consumed during the stand-alone time by consuming or storing surplus power other than the idling power without supplying power to the external load during the standby time until the start of autonomous operation. Maintain generated power. At the time of power recovery of the system power supply, during the standby time until the output according to the demand power, the generated power according to the demand power is maintained by the same method. [Selection] Figure 4

Description

  The present invention relates to an operation method of a fuel cell system, and in particular, when a power failure of a system power source or a power recovery, any one of an interconnection operation linked to the system power source or a self-sustained operation disconnected from the system power source. The present invention relates to an operation method for shortening the switching time when switching from one to the other.

As a related technique, there is a technique described in Patent Document 1.
In the technology described in Patent Document 1, while the power to the external load is shut off at the time of a power failure of the system power supply, the generated power before the occurrence of the power failure is maintained, and surplus power other than the idling power necessary for driving the auxiliary machine is generated. Consumed by the heater. Therefore, if the power outage duration is short, the generated power before the occurrence of the power outage is maintained until power is restored. If the power outage duration exceeds a predetermined time, the generated power is reduced to idling power at that time, and the power recovery is awaited.

JP 2009-272158 A

The fuel cell system is operated in conjunction with the system power supply. However, when the power supply of the system power supply is interrupted, the fuel cell system is switched to the independent operation, so that an external load, particularly an emergency specific load (supplied in advance during the autonomous operation) It is possible to supply electric power to the load determined in (1).
The generated power during the self-sustained operation is set to a constant self-generated power (for example, 450 W) that is smaller than the rated maximum power (for example, 800 W) and greater than the idling power (for example, 100 W) necessary for driving the auxiliary machine. This self-sustained power generation power is power generation power capable of self-sustaining operation that can cover the power demand of an emergency specific load and that can stably supply power even if an inrush current occurs.

  In general control of a conventional fuel cell system, when a power failure of the system power supply is detected, the system power supply is disconnected and the output to the system-side general load is shut off. At the same time, the generated power is instantaneously reduced to idling power. Then, after a predetermined standby time (for example, a power failure determination time for confirming a power failure) elapses, the generated power is increased from the idling power to the self-generated power. Then, when the power generated during the self-sustaining operation is reached, the self-sustaining operation is started, that is, the power supply to the specific load by the self-sustaining operation is started.

However, the rate of increase in generated power in the fuel cell system is limited by a delay in the reforming response of the fuel, and it takes time (for example, about 3 to 5 minutes) to increase from idling power to power generated during stand-alone operation. . Therefore, it takes time from the power failure to the start of independent operation, and it is desired to shorten this time.
Note that the technique described in Patent Document 1 waits for power recovery by reducing the generated power to idling power when the power outage duration is long, in other words, when power is not recovered within a predetermined standby time. However, it is not disclosed to shift to self-sustained operation.

  Similarly, when the system power supply is restored, it takes time from the restoration to the output in accordance with the demand power, and it is desired to shorten this time.

  The present invention has been made in view of the above situation, and shortens the time until the start of self-sustaining operation at the time of power failure of the system power supply or the time to output corresponding to the demand power at the time of power recovery of the system power supply The task is to do.

The present invention relates to a fuel for switching from one of the grid operation connected to the grid power supply or the independent operation disconnected from the grid power supply to the other at the time of a power failure or power recovery of the grid power supply. This provides a battery system operation method, and during self-sustained operation, the power generated by the fuel cell is set to a constant self-generated power that is smaller than the rated maximum power and greater than the idling power required to drive the auxiliary equipment. Assuming
Here, the present invention consumes or stores surplus power other than the idling power without supplying power to the external load during a standby time until the start of operation after switching at the time of power failure or power recovery of the system power supply. By doing so, the power generation power of the fuel cell is maintained at the self-sustained power generation power or the power generation power that matches the demand power.

According to the present invention, in the event of a power failure of the system power supply, by maintaining the generated power at the self-sustained power generation for a predetermined standby time, the self-sustained operation (power supply in the self-sustained operation) immediately after the standby time elapses. The time from a power failure to the start of independent operation can be shortened.
Also, when the grid power supply is restored, the generated power is maintained at the generated power that matches the demand power for a predetermined standby time. Supply) can be started, and the time from power recovery to the start of grid operation can be shortened.

The block diagram of the fuel cell system which shows one Embodiment of this invention Flow chart of fuel cell system operation control (Part 1) Flow chart of fuel cell system operation control (part 2) Diagram showing changes in power generated during a power outage Diagram showing changes in power generated during power recovery The block diagram of the fuel cell system which shows other embodiment of this invention

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a configuration diagram of a fuel cell system showing an embodiment of the present invention. The home (stationary) fuel cell system includes a power generation unit and a hot water storage unit that stores hot water using exhaust heat generated during power generation as a cogeneration system, but only the power generation unit is shown in the figure. ing.

  The fuel cell system (power generation unit) of this embodiment includes a fuel cell 1, a power conditioner 2, and a control device 100.

The fuel cell 1 is an assembly (cell stack) of a plurality of fuel cells. Each fuel cell has a fuel electrode (anode), an oxidant electrode (cathode), and an electrolyte layer disposed therebetween. A hydrogen-containing fuel is supplied to the fuel electrode, and air (including oxygen) is supplied to the oxidant electrode as an oxidant.
Accordingly, in the fuel cell 1, hydrogen is supplied to the fuel electrode on one end side of the electrolyte layer, and oxygen is supplied to the oxidant electrode on the other end side of the electrolyte layer, thereby causing an electrochemical reaction between hydrogen and oxygen. Generates power (generates DC power).

  In order to supply a hydrogen-containing fuel to the fuel electrode, generally, a hydrocarbon-based fuel (for example, city gas, LPG, kerosene, methanol, biofuel, etc.) is subjected to a steam reforming reaction using a reforming catalyst. A fuel reformer that reforms by a partial oxidation reaction, an autothermal reforming reaction, or the like to generate a hydrogen-rich reformed gas is used, but the illustration is omitted. However, when a fuel that does not require reforming treatment (for example, pure hydrogen gas, hydrogen-enriched gas, hydrogen storage agent, etc.) is used as the fuel, the fuel reformer itself can be omitted.

  The power conditioner 2 extracts DC power generated in the fuel cell 1 and converts the DC power into AC power. Accordingly, the power conditioner 2 includes a DC / DC converter 3 that extracts and boosts the DC power generated in the fuel cell 1, and a DC / AC inverter 4 that converts the DC power into AC power at the subsequent stage. .

The output side of the power conditioner 2 (the output side of the inverter 4) is connected to the system power supply 6 through the system interconnection relay 5. A grid interconnection line L1 branched from between the grid interconnection relay 5 and the grid power supply 6 is connected to the home load 7.
Therefore, at the time of grid connection (when the grid connection relay 5 is turned on), the generated power of the fuel cell 1 is supplied to the home load 7 via the DC / DC converter 3 and the DC / AC inverter 4, and the fuel cell. When the generated power of 1 is less than the demand power of the household load 7, the grid power from the grid power supply 6 is supplied to the household load 7 as a shortage.

  The power conditioner 2 further includes a DC / DC converter 8 interposed in a branch line from between the DC / DC converter 3 and the DC / AC inverter 4.

  The DC / DC converter 8 is a step-down converter for driving an auxiliary machine, and its output side is connected to various auxiliary machines 9 of the fuel cell system. Thereby, the auxiliary machine 9 can be driven by the fuel cell 1. Auxiliary machine 9 includes equipment on the power generation unit side (fuel supply pump, air supply pump, etc.) and equipment for exhaust heat recovery (pump that circulates hot water for heat recovery between the power generation unit and hot water storage unit, etc. ) Is also included.

The power conditioner 2 is also connected to a surplus power heater 11 as an internal load for surplus power consumption. The surplus power heater 11 may be either a DC heater or an AC heater, but an AC heater is illustrated here. The surplus power heater (AC heater) 11 of this example is connected to the output side of the DC / AC inverter 4 via a self-sustained output relay 16 described later and further via a phase control type SSR (solid state relay) 10. . The surplus power heater 11 can also consume surplus power to prevent reverse power flow. The surplus power heater 11 is used to convert surplus power into heat and warm hot water in a hot water storage unit (not shown). However, heat utilization is not limited to this.
When a DC heater is used as the surplus power heater, it is connected to the output side of the DC / DC converter 3 via a step-down DC / DC converter.

  The control device 100 is constituted by a microcomputer, and includes a CPU, ROM, RAM, an input / output interface, and the like, and controls the generated power of the fuel cell 1 in accordance with the demand power of the household load 7 during grid connection. In accordance with this, the power conditioner 2 (DC / DC converter 3, DC / AC inverter 4, etc.) is controlled. Data can be transmitted to and received from the power conditioner 2.

The control by the control device 100 uses a current / voltage measuring instrument 12 that measures the current / voltage output from the fuel cell 1 in order to detect the power generated by the fuel cell 1.
The control by the control device 100 further includes a current / voltage measuring device 13 for measuring the current / voltage output from the DC / AC inverter 4, a voltage measuring device 14 for measuring the voltage of the system power supply 6, and the generated power as the system power supply. In FIG. 6, a current measuring device 15 or the like for detecting that no reverse flow is present is used.

  Control of the generated power by the control device 100 is performed by controlling the amount of fuel and air supplied to the fuel cell 1. In many cases, since a fuel reformer is provided, the control of the fuel supply amount controls the amount of fuel supplied to the fuel reformer.

  Therefore, the control device 100 controls the supply amounts of fuel and air according to the generated power target value of the fuel cell 1 set according to the demand power of the household load 7 (so as to obtain the generated power target value). Thus, the generated power of the fuel cell 1 is controlled.

  The control device 100 also controls the power conditioner 2 in parallel with the control of the power generated by the fuel cell 1. Specifically, based on the generated power target value of the fuel cell 1, the current taken out from the fuel cell 1 is set and controlled. More specifically, the target value of power generated by the fuel cell 1 is divided by the output voltage of the fuel cell 1, a current target value is set, and the current (sweep current) taken out from the fuel cell 1 is controlled according to this current target value. .

  In the fuel cell system of this embodiment, in the event of a power failure of the system power supply 6, the independent operation (system solution) from the system power supply 6 is disconnected from the system operation (system connection operation) connected to the system power supply 6. Column operation).

  For the independent operation, the power conditioner 2 has an independent output line L2 for supplying power from the DC / AC inverter 4 to the specific load 18 via the independent output relay 16 and the independent load relay 17 as an output line during the independent operation. Provided. The specific load 18 is a dedicated load used during the independent operation.

  During the self-sustained operation, the generated power of the fuel cell 1 is lower than the rated maximum power (for example, 800 W) and is larger than the idling power (for example, 100 W) required for driving the auxiliary machine 9, and the constant power generation power (for example, 450 W). Set to. This self-sustained power generation power is power generation power capable of self-sustained operation that can cover the power demand of an emergency specific load and can avoid an overload state even if an inrush current occurs.

Next, the process of switching from the grid operation to the independent operation at the time of a power failure of the system power supply 6 will be described with reference to the operation control flowchart of FIG.
In the interconnected operation (S1), the generated power of the fuel cell 1 is controlled according to the demand power. Therefore, as long as the demand power exceeds the rated maximum power (for example, 800 W) of the fuel cell 1, the generated power of the fuel cell 1 is controlled to the rated maximum power (for example, 800 W), and the shortage is supplied from the system power supply 6. .
During the interconnection operation, it is monitored whether or not a power failure has occurred (S2).

When the system power supply 6 fails, the system voltage disappears. This is detected by the voltage meter 14.
Upon detection of a power failure (S2), the grid interconnection relay 5 is turned off to disconnect from the grid power supply 6 (S3). And it transfers to standby operation (S4).
The standby operation (S4) is performed for a predetermined time (standby time) in order to confirm a power failure.

In the standby operation (S4), the power generated by the fuel cell 1 is controlled to the power generated during the independent operation (for example, 450 W). At this time, the self-sustained output relay 16 is turned on, but the self-supporting load relay 17 is in an off state, power is not supplied to the specific load 18, and surplus power other than idling power necessary for driving the auxiliary machine 9 is surplus power heater. 11 is consumed.
During standby operation, it is monitored whether or not power has been restored and whether or not a power failure determination time has elapsed (S5, S6).

  When power is restored during the standby time (for example, when there is a momentary power failure), the process proceeds to power recovery processing (S10) at that time. In the power recovery process, the grid interconnection relay 5 is turned on at an appropriate timing, the grid operation is restarted, and the generated power of the fuel cell 1 is gradually increased.

If the power failure judgment time (standby time) has elapsed and the power is in a power failure state, the power failure is confirmed. When the power failure is confirmed, the self-supporting load relay 17 is turned on (S7). And it transfers to a self-sustained operation (S8).
In the self-sustained operation (S8), the power generated by the fuel cell 1 is controlled to the power generated during self-sustaining (for example, 450 W). At this time, since the self-supporting load relay 17 is on, power is supplied to the emergency specific load 18. That is, by switching to the self-sustained operation, the generated power of the fuel cell 1 can be supplied to a self-supporting outlet and the various external loads connected thereto can be operated. At this time, since it is disconnected from the system power supply 6, there is no worry of reverse power flow to the system, and there is no need for frequency synchronization with the system.

  In the self-sustained operation (S8), when the demand power exceeds the power generated during the self-sustaining, that is, in the case of an overload, in principle, the power supply to the external load is stopped. That is, the self-supporting load relay 17 is turned off, and power supply to a self-supporting outlet is stopped. At this time as well, power generation with constant power continues and all surplus is consumed by the surplus power heater 11 in the system.

During the independent operation, it is monitored whether or not the power is restored (S9).
If power is restored during the self-sustained operation, the process proceeds to power restoration processing according to the operation control flowchart of FIG. This will be described later.

FIG. 4 shows the transition of the power generated by the fuel cell 1 when a power failure occurs. (A) is a conventional case, and (B) is a case of this embodiment.
Before the occurrence of a power failure, the power generated by the fuel cell 1 is controlled to the rated maximum power (for example, 800 W).

  When a power failure occurs, the grid interconnection relay 5 is turned off and the operation shifts to standby operation, and power supply to the external load is lost. For this reason, conventionally, as shown in FIG. 4A, simultaneously with the occurrence of a power failure, the power generated by the fuel cell is instantaneously reduced to idling power (for example, 100 W) necessary for driving the auxiliary machine.

  On the other hand, in this embodiment, as shown in FIG. 4B, simultaneously with the occurrence of a power failure, the power generated by the fuel cell is reduced, but is maintained at the power generated during the self-sustaining operation (for example, 450 W). . Excess power other than idling power (hatched portion in FIG. 4B) is consumed by the surplus power heater 11.

  When the predetermined standby time (power failure determination time) ends, conventionally, as shown in FIG. 4A, the generated power of the fuel cell increases from idling power (for example, 100 W) to self-generated power (for example, 450 W). Is done. However, the rate of increase in generated power in the fuel cell system is limited, and it takes time (for example, about 3 to 5 minutes) to increase from idling power to self-generated power. Then, when the power generated during the self-sustaining operation is reached, the self-sustaining operation becomes possible. Accordingly, the time from the power failure to the start of independent operation is T1 in the figure, which takes time.

  On the other hand, in the present embodiment, as shown in FIG. 4B, when the predetermined standby time ends, the generated power of the fuel cell is maintained at the self-generated power (for example, 450 W). When the standby time ends, the autonomous operation becomes possible. Therefore, the time from the power failure to the self-sustained operation becomes T2 in the figure, and can be greatly shortened.

In other words, when switching from grid operation to independent operation in the event of a power failure, conventionally, the standby time for confirming that there is a power failure and the power to raise the generated power of the fuel cell from idling power to independent power generation Ascending time is required, and waiting time of about several minutes was required from the actual power failure to the start of independent operation (start of power supply in independent operation).
On the other hand, in this embodiment, only the standby time for confirming that there is a power outage is necessary, and the power increase time is not required, so the self-sustained operation starts from the actual power outage (power supply starts in the self-sustained operation). It is possible to greatly shorten the time until the time.

  According to the control as described above, in the present embodiment, it is possible to shorten the time until the start of independent operation at the time of power failure of the system power supply. As a result, for example, even if there is no electricity at the time of a power outage at night, you can get self-sustained power immediately and get a light, or if an earthquake etc. occurs, turn on the television early, etc. Will be able to obtain.

Next, the process of switching from the independent operation to the interconnected operation when the system power supply 6 is restored will be described with reference to the flowchart of FIG. 3 following the flowchart of FIG.
During the self-sustained operation (S8), it is monitored whether or not the power has been restored (S9), and when power is restored, it is monitored whether or not the power restoration judgment time for confirming the power restoration has passed (S11). . During the power recovery determination time, the self-sustained operation (S8) with the power generated at the time of self-sustaining (for example, 450 W) is continued.

If the power recovery determination time has elapsed and the power recovery status is established, power recovery is determined. When the power recovery is confirmed, the self-supporting load relay 17 is turned off (S12). And it transfers to standby operation for power recovery (S13).
The standby operation for power recovery (S13) is performed for a predetermined time (standby time; approximately 3 minutes). This time is typically a certain period of time after power recovery determined by an agreement (an agreement between electric utilities) between a provider supplying grid power and a provider supplying distributed power such as a fuel cell system. Is the shut-off time.

In the standby operation (S13), the generated power of the fuel cell 1 is gradually increased from the self-generated power (for example, 450 W) at a system-specific speed, and finally the generated power (demand power is adjusted to the demand power). If the rated maximum power is exceeded, the rated maximum power is maintained at 800 W). At this time, the grid interconnection relay 5 remains off, and power is not supplied to the grid interconnection line L1, and surplus power other than idling power required for driving the auxiliary machine 9 is supplied to the surplus power heater 11 and consumed. Is done.
During standby operation, it is monitored whether or not a predetermined shut-off time has elapsed (S14).

  When the predetermined shut-off time has elapsed, at that time, the DC / AC inverter 4 is instantaneously switched to the grid connection and the grid connection relay 5 is turned on (S15). And it transfers to a grid operation (S1 of FIG. 2).

FIG. 5 shows the transition of the power generated by the fuel cell 1 at the time of power recovery.
In the self-sustained operation before power recovery, the power generated by the fuel cell 1 is controlled to the power generated during self-sustaining (for example, 450 W).

When power recovery is detected, a power recovery determination time is reached. During the power recovery determination time, the self-sustained operation with the self-generated power (for example, 450 W) is continued.
When the power recovery determination time has elapsed and power recovery is confirmed, the self-sustained load relay 17 is turned off, and a transition is made to standby operation.
Conventionally, in order to synchronize the frequency of the output power of the fuel cell system with the frequency of the system power when connecting to the system power at the time of power recovery, the output of the DC / AC inverter 4 in the power conditioner 2 is temporarily stopped and compensated. An operation for reducing the idling power necessary for driving the machine 9 is required.
In the present embodiment, the generated power of the fuel cell 1 at this time is gradually increased from the self-generated power (for example, 450 W) at a system-specific speed without being reduced to idling power. The generated power matched to the power is maintained (800 W which is the rated maximum power if the demand power exceeds the rated maximum power). Surplus power other than idling power at this time (hatched portion in FIG. 5) is consumed by the surplus power heater 11.

  When a predetermined shut-off time elapses, the interconnected operation becomes possible. In this embodiment, since the generated power of the fuel cell is maintained at the generated power corresponding to the demand power when the predetermined cutoff time has elapsed, the DC / AC is instantaneously generated when the predetermined cutoff time ends. By switching the inverter 4 to grid connection and turning on the grid connection relay 5, the grid operation can be performed.

On the other hand, conventionally, since the generated power of the fuel cell is controlled to idling power during the predetermined shut-off time, the generated power is increased after the predetermined shut-off time has elapsed, and then the operation is switched to the grid operation. Become.
Therefore, in the present embodiment, it is possible to shorten the time to output corresponding to the demand power at the time of power recovery.

Next, another embodiment of the present invention will be described.
FIG. 6 is a configuration diagram of a fuel cell system showing another embodiment of the present invention, and only parts different from FIG. 1 will be described.

  In the embodiment of FIG. 1, surplus power other than idling power is supplied to the surplus power heater 11 without supplying power to the external load during the standby time until the operation switching at the time of power failure or power recovery of the system power supply 6. As a result, the generated power of the fuel cell 1 is maintained at the self-sustained generated power or the generated power that matches the demand power.

On the other hand, in the embodiment of FIG. 6, surplus power other than the idling power is supplied to the DC / DC without supplying power to the external load during the standby time until the operation switching at the time of power failure or power recovery of the system power supply 6. By supplying and storing the storage battery 22 via the DC converter 21, the power generated by the fuel cell 1 is maintained at the power generated during the self-sustaining operation or the power demand.
That is, instead of supplying the surplus power to the surplus power heater 11 and consuming it, the surplus power is supplied to the storage battery 22 and stored.

When the surplus power heater 11 is used for consumption, the surplus power can be used for heat. On the other hand, when the storage battery 22 is used for storage, the power stored in the storage battery 22 can be used as it is.
Therefore, a bidirectional converter is used as the DC / DC converter 21 interposed in the front stage of the storage battery 22.

The fuel cell system according to the present invention includes a fuel cell 1, a power conditioner 2 that takes out the power generated by the fuel cell 1 and supplies it to a load in connection with a system power supply 6, and a control that controls the fuel cell 1 and the power conditioner 2. The device 100 is configured to be capable of switching between an interconnection operation linked to the system power supply 6 and a stand-alone operation disconnected from the system power supply 6. The electric power is set to a constant self-generated power (for example, 450 W) that is smaller than the rated maximum power (for example, 800 W) and larger than the idling power (for example, 100 W) necessary for driving the auxiliary machine 9.
Here, the fuel cell system according to the present invention further includes a device (power heater 11 or storage battery 22) that consumes or stores surplus power. The control device 100 consumes surplus power other than the idling power without supplying power to the external load during the standby time until the start of operation after switching at the time of power failure or power recovery of the system power supply 6. Alternatively, a standby operation control unit that maintains the generated power of the fuel cell at the self-sustained generated power or the generated power that matches the demand power by storing power is provided.
Therefore, the control device 100 includes an interconnection operation control unit, an independent operation control unit, and a standby operation control unit.
2 corresponds to the interconnection operation control unit, S8 in FIG. 2 corresponds to the self-sustaining operation control unit, and S4 in FIG. 2 and S13 in FIG. 3 correspond to standby operation control. It corresponds to the part.

In the above description, the generated power, time, and the like have been described with numerical values, but this is for ease of understanding and is not intended to limit the numerical values.
The illustrated embodiments are merely examples of the present invention, and the present invention includes various improvements and modifications made by those skilled in the art within the scope of the claims in addition to those directly shown by the described embodiments. Needless to say, it is included.

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Power conditioner 3 DC / DC converter 4 DC / AC inverter 5 System interconnection relay 6 System power supply 7 Domestic load 8 DC / DC converter 9 Auxiliary machine 10 Phase type SSR
11 Surplus power heater (AC heater)
12 to 15 Measuring instrument 16 Self-supporting output relay 17 Self-supporting load relay 18 Specific load 21 DC / DC converter 22 Storage battery 100 Control device

Claims (6)

Operation of the fuel cell system when switching from one of the grid operation with the grid power supply or the independent operation with the grid power supply disconnected during a power failure or recovery of the grid power supply A method,
When setting the power generated by the fuel cell to a certain level of self-sustained power generation, which is smaller than the rated maximum power and greater than the idling power required to drive the auxiliary machine, during self-sustaining operation.
During the power failure or power recovery of the system power supply, the surplus power other than the idling power is consumed or stored without supplying power to the external load during the standby time until the start of operation after switching. A method of operating a fuel cell system, characterized in that the generated power is maintained at the self-sustained generated power or generated power that matches demand power. A method of operating a fuel cell system when switching from a grid-operated operation linked to a system power supply to a self-sustained operation disconnected from the system power supply at the time of a power failure of the system power supply,
When setting the power generated by the fuel cell to a certain level of self-sustained power generation, which is smaller than the rated maximum power and greater than the idling power required to drive the auxiliary machine, during self-sustaining operation.
During the standby time until the start of autonomous operation, during the power failure of the system power supply, the surplus power other than the idling power is consumed or stored without supplying power to the external load. A method for operating a fuel cell system, characterized by maintaining generated power. An operation method of the fuel cell system when switching from a self-sustained operation disconnected from the system power supply to an interconnected operation connected to the system power supply when the system power supply is restored,
When setting the power generated by the fuel cell to a certain level of self-sustained power generation, which is smaller than the rated maximum power and greater than the idling power required to drive the auxiliary machine, during self-sustaining operation.
Demand for power generated by the fuel cell is consumed by consuming or storing surplus power other than the idling power without supplying power to the external load during the standby time until the start of grid operation when the grid power is restored. A method of operating a fuel cell system, characterized by maintaining the generated power in accordance with the power.   The surplus power during the standby time is supplied to a surplus power consumption heater and consumed, and the operating method of the fuel cell system according to any one of claims 1 to 3.   The method of operating a fuel cell system according to any one of claims 1 to 3, wherein the surplus power during the standby time is supplied to and stored in a storage battery. Comprising a fuel cell, a power conditioner that takes out the generated power of the fuel cell and supplies it to the load in linkage with the system power supply, and a control device that controls the fuel cell and the power conditioner,
It is possible to switch between grid operation connected to the grid power supply and independent operation disconnected from the grid power supply. During the stand-alone operation, the generated power of the fuel cell is smaller than the rated maximum power and A fuel cell system that is set to a constant self-generated power that is greater than the idling power required for driving,
Further comprising a device that consumes or stores surplus power,
The control device consumes or stores surplus power other than the idling power without supplying power to an external load during a standby time until the start of operation after switching at the time of power failure or power recovery of the system power supply. The fuel cell system further comprises a standby operation control unit that maintains the generated power of the fuel cell at the self-sustained generated power or the generated power matched to the demand power.