JP7513137B1 - Power generation system and method for controlling power generation system - Google Patents

Abstract

[Problem] To provide a technology for efficiently operating a reverse conversion unit in a power generation system equipped with a plurality of fuel cell units. [Solution] The power generation system includes a plurality of fuel cell units and a plurality of reverse conversion units, the outputs of the plurality of fuel cell units being connected in parallel to a first node, and the inputs of the plurality of reverse conversion units being connected in parallel from a second node that is connected to the first node. [Selected Figure] Figure 1

Description

This disclosure relates to a power generation system and a method for controlling the power generation system.

Patent Document 1 discloses a fuel cell power generation system that includes a first fuel cell power generation system and a second fuel cell power generation system. Patent Document 1 discloses that each of the first fuel cell power generation system and the second fuel cell power generation system includes a fuel cell and an inverter that converts the direct current power generated by the fuel cell into alternating current power.

JP 2021-089886 A

In a fuel cell, there are cases where the output is stopped to perform a refresh. In a power generation system having multiple fuel cell units, when any of the multiple fuel cell units is stopped for a refresh, it is required to efficiently operate the reverse conversion unit that converts the DC power from the fuel cell unit to AC power.

This disclosure provides technology for efficiently operating a reverse conversion unit in a power generation system equipped with multiple fuel cell units.

According to one aspect of the present disclosure, there is provided a power generation system comprising a plurality of fuel cell units and a plurality of reverse conversion units, wherein the outputs of each of the plurality of fuel cell units are connected in parallel to a first node, and the inputs of each of the plurality of reverse conversion units are connected in parallel from a second node connected to the first node, and further comprising a storage unit connected to the first node, and a control unit for controlling each of the plurality of fuel cell units, each of the plurality of reverse conversion units, and the storage unit, wherein the control unit controls to start up only a first fuel cell unit of any of the plurality of fuel cell units when starting up at least two of the fuel cell units of the plurality of fuel cell units from a state in which all of the plurality of fuel cell units are stopped, and after the first fuel cell unit has started up, controls to start up the fuel cell units other than the first fuel cell unit in the plurality of fuel cell units .

According to the present disclosure, in a power generation system equipped with multiple fuel cell units, the reverse conversion unit can be operated efficiently.

FIG. 1 is a diagram showing an outline of a power generation system according to this embodiment. FIG. 2 is a diagram illustrating the output of the fuel cell unit in the power generation system according to this embodiment. FIG. 3 is a diagram illustrating the output of the inverter in the power generation system according to this embodiment. FIG. 4 is a diagram illustrating the output of the power generation system according to this embodiment. FIG. 5 is a flow diagram illustrating a first example of a start-up procedure for the fuel cell unit in the power generation system according to this embodiment. FIG. 6 is a flow diagram illustrating a first example of a start-up procedure for the fuel cell unit in the power generation system according to this embodiment. FIG. 7 is a diagram for explaining the operation at the start-up of the fuel cell unit in the power generation system according to this embodiment. FIG. 8 is a flow diagram illustrating a second example of the start-up procedure of the fuel cell unit in the power generation system according to this embodiment. FIG. 9 is a flow diagram illustrating a second example of the start-up procedure of the fuel cell unit in the power generation system according to this embodiment. FIG. 10 is a diagram for explaining the operation at the start-up of the fuel cell unit in the power generation system according to this embodiment. FIG. 11 is a flow diagram illustrating an example of a procedure for reducing the output of the fuel cell unit in the power generation system according to this embodiment. FIG. 12 is a flow diagram illustrating an example of a procedure for reducing the output of the fuel cell unit in the power generation system according to this embodiment. FIG. 13 is a diagram for explaining the operation in reducing the output of the fuel cell unit in the power generation system according to this embodiment. FIG. 14 is a diagram showing an outline of a power generation system according to a reference example. FIG. 15 is a diagram illustrating the output of an inverter in a power generation system of a reference example.

Hereinafter, the embodiments will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope of the claims.

In addition, with regard to the description of the specification and drawings relating to each embodiment, components having substantially the same or corresponding functional configurations may be given the same reference numerals to avoid redundant explanation. Also, to facilitate understanding, the scale of each part in the drawings may differ from the actual scale.

In directions such as parallel, right-angled, orthogonal, horizontal, vertical, up-down, left-right, and front-back, deviations are permitted to the extent that they do not impair the effects of the embodiment. The shape of the corners is not limited to right angles and may be rounded. Parallel, right-angled, orthogonal, horizontal, and vertical may include approximately parallel, approximately right-angled, approximately orthogonal, approximately horizontal, and approximately vertical, respectively.

For example, "approximately parallel" means that even if two lines or two surfaces are not completely parallel to each other, they can be treated as parallel to each other as long as it is within the range of manufacturing tolerance. As with "approximately parallel," the other terms "approximately right angle," "approximately perpendicular," "approximately horizontal," and "approximately vertical" are also intended to fall under the respective terms as long as the relative positions of the two lines or two surfaces are within the range of manufacturing tolerance.

The power generation system according to this embodiment will be described. Figure 1 is a diagram showing an outline of power generation system 1, which is an example of the power generation system according to this embodiment.

The power generation system according to this embodiment is a power generation system that uses a fuel cell. The power generation system according to this embodiment supplies the generated power to an AC power system. The power generation system according to this embodiment includes multiple fuel cell units and multiple reverse conversion units. For example, power generation system 1, which is an example of the power generation system according to this embodiment, includes four fuel cell units and three reverse conversion units. The power generation system 1 supplies the generated power to the AC power system ACPG.

The fuel cell unit generates electricity by chemically reacting hydrogen and oxygen. The inverter unit converts the DC power output from the fuel cell unit into AC power.

More specifically, the power generation system 1 includes a fuel cell unit 10A, a fuel cell unit 10B, a fuel cell unit 10C, and a fuel cell unit 10D. The power generation system 1 also includes a reverse conversion unit 20A, a reverse conversion unit 20B, and a reverse conversion unit 20C.

In the power generation system according to this embodiment, the number of fuel cell units may be the same as or different from the number of reverse conversion units. Also, the number of reverse conversion units may be one.

In the power generation system according to this embodiment, the outputs of the fuel cell units are connected in parallel to a first node. By connecting the outputs of the fuel cell units in parallel to the first node, the outputs of the fuel cell units are combined in parallel. For example, in power generation system 1, which is an example of a power generation system according to this embodiment, the outputs of fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D are all connected in parallel to node ND1. Node ND1 is an example of the first node.

Note that when something is connected in parallel to node ND1, it does not necessarily mean that everything is connected in parallel at node ND1. For example, a case where some of the components are connected before being connected to node ND1, and then all of the components are finally connected at node ND1, is also included in the case of being connected in parallel to node ND1.

In addition, in the power generation system according to this embodiment, the inputs of the multiple reverse conversion units are connected in parallel to a second node that is connected to the first node. By connecting the inputs of the multiple reverse conversion units in parallel to a second node that is connected to the first node, the output obtained by combining the outputs of the multiple fuel cell units is distributed to the multiple reverse conversion units. For example, in power generation system 1, which is an example of the power generation system according to this embodiment, the inputs of reverse conversion unit 20A, reverse conversion unit 20B, and reverse conversion unit 20C are connected in parallel to node ND2. Node ND2 is connected to node ND1 via wiring WL. Node ND2 is an example of the second node.

Note that when something is connected in parallel to node ND2, it does not necessarily mean that everything is connected in parallel at node ND2. For example, a case where some of the components are connected before being connected to node ND2, and then all of the components are finally connected at node ND2, is also included in the case of being connected in parallel to node ND2.

The power generation system according to this embodiment also includes a power storage unit connected to the first node. The power storage unit charges with power from the first node and discharges power to the first node depending on the voltage at the first node. For example, power generation system 1, which is an example of the power generation system according to this embodiment, includes a power storage unit 40 connected to node ND1.

Furthermore, the power generation system according to this embodiment includes a control unit that controls each of the fuel cell units, each of the reverse conversion units, and the power storage unit. For example, the power generation system 1, which is an example of the power generation system according to this embodiment, includes a control unit 50. The control unit 50 controls each of the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D. The control unit 50 also controls each of the reverse conversion unit 20A, the reverse conversion unit 20B, and the reverse conversion unit 20C. The control unit 50 also controls the power storage unit 40.

The power generation system according to this embodiment also includes a transformer between each of the multiple inverter units and the AC power system. The power generation system according to this embodiment includes multiple transformers. Each of the multiple inverter units in the power generation system according to this embodiment is connected to one of the multiple transformers. For example, the power generation system 1, which is an example of the power generation system according to this embodiment, includes transformers 30A, 30B, and 30C. The output of the inverter unit 20A is connected to the transformer 30A. The output of the inverter unit 20B is connected to the transformer 30B. The output of the inverter unit 20C is connected to the transformer 30C. The outputs of the transformers 30A, 30B, and 30C are connected in parallel to the node ND3 and connected to the AC power system ACPG.

Next, the details of the fuel cell unit, reverse conversion unit, and control unit provided in the power generation system according to this embodiment will be described using power generation system 1, which is an example of the power generation system according to this embodiment.

[Fuel cell unit]
Each of the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D generates electricity by chemically reacting hydrogen with oxygen. Each of the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D includes a fuel cell 11.

The fuel cell 11 generates electricity by chemically reacting supplied hydrogen with oxygen contained in the air. The fuel cell 11 is, for example, a polymer electrolyte fuel cell (PEFC). The fuel cell 11, which is a polymer electrolyte fuel cell, has a stack structure in which many single cells are stacked.

The unit cell of the fuel cell 11, which is a polymer electrolyte fuel cell, includes a membrane electrode assembly (MEA) that includes a polymer electrolyte membrane and a pair of electrodes provided on both sides of the polymer electrolyte membrane. The polymer electrolyte membrane selectively transports hydrogen ions. Each electrode is formed of a porous material. Each of the pair of electrodes includes a catalyst layer that is mainly composed of carbon powder that supports a platinum-based metal catalyst (electrode catalyst), and a gas diffusion layer that is both breathable and electronically conductive. Furthermore, the unit cell includes a pair of separators that sandwich the membrane electrode assembly (MEA) from both sides.

The electricity generated by the fuel cell 11 is boosted by a boost converter and output from each of the fuel cell units 10A, 10B, 10C, and 10D.

The fuel cell 11 generates heat when generating electricity. The fuel cell 11 needs to be cooled because the temperature rises due to the heat generated. The fuel cell 11 is cooled by a coolant supplied from outside each of the fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D.

[Reverse conversion unit]
The reverse conversion unit 20A, the reverse conversion unit 20B, and the reverse conversion unit 20C convert the DC power output from the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D, respectively, into AC power. The reverse conversion unit 20A, the reverse conversion unit 20B, and the reverse conversion unit 20C are so-called inverters. The inverter is, for example, a power conditioning system (PCS) or a grid-connected inverter.

[Transformer]
The transformer 30A converts the voltage of the AC power output from the inverter unit 20A and provides insulation between the AC power system ACPG and the inverter unit 20A. The transformer 30A is a so-called insulating transformer. The transformers 30B and 30C are similar to the transformer 30A.

[Electricity storage unit]
The power storage unit 40 is charged with power from the node ND1 and discharges power to the node ND1. The power storage unit 40 is a secondary battery. The power storage unit 40 is, for example, a lithium ion battery, a lithium ion capacitor, or an electric double layer capacitor. The power storage unit 40 may include, for example, a plurality of batteries connected in series or in parallel.

The power storage unit 40 compensates for fluctuations in the fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D, and the reverse conversion unit 20A, reverse conversion unit 20B, and reverse conversion unit 20C by charging and discharging. For example, the power storage unit 40 suppresses fluctuations due to load fluctuations or start-stop in each of the fuel cell units and reverse conversion units.

In the power generation system 1, the shortage of power is discharged from the power storage unit 40, and the surplus power is charged to the power storage unit 40, thereby responding to output fluctuations in the power generation system 1.

The capacity of the power storage unit 40 will be explained. The voltage in the power storage unit 40 fluctuates depending on the start/stop of the fuel cell unit and changes in the load. For example, when the fuel cell unit starts up, it uses the power stored in the power storage unit 40. Therefore, when the fuel cell unit starts up, the voltage in the power storage unit 40 drops. Also, if the fuel cell unit is stopped before the reverse conversion unit, the voltage in the power storage unit 40 drops. On the other hand, if the reverse conversion unit is stopped before the fuel cell unit, the voltage in the power storage unit 40 rises.

Therefore, for example, when multiple fuel cell units are started up at the same time, the voltage in the power storage unit 40 drops quickly. Therefore, as described below, when starting up a fuel cell unit using only the power storage unit 40, multiple units are not started up at the same time, but only one unit is started up. Therefore, the capacity of the power storage unit 40 is set to be larger than the minimum startup capacity at which any of the multiple fuel cell units can be started up, but smaller than twice the minimum startup capacity. When starting up a fuel cell unit using only the power storage unit 40, starting up only one unit reduces the capacity of the power storage unit 40, thereby reducing costs.

The capacity of the power storage unit 40 is determined on the premise that it will be within the range of the power storage unit in the event of start-stop, load changes, emergency stop, etc. For example, if a lithium ion capacitor is used as the power storage unit 40, the capacity is determined so that the power storage unit 40 can operate for about two seconds even if it suddenly stops from a state of outputting 60 kilowatts.

[Controller unit]
The control unit 50 controls the fuel cell units 10A, 10B, 10C, and 10D, the reverse conversion units 20A, 20B, and 20C, and the power storage unit 40.

The functions of the control unit 50 (the processing performed by the control unit 50) are realized, for example, by a processor such as a CPU (Central Processing Unit) operating according to a program stored in memory. The functions of the control unit 50 may also be realized by an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

<Power generation system operation>
Next, the operation of the power generation system according to this embodiment will be described using the power generation system 1.

Stationary power generation systems using fuel cells require stable, continuous output. When using a polymer electrolyte fuel cell as the fuel cell, the fuel cell is stopped intermittently to be refreshed. Refreshing the fuel cell prevents deterioration of the fuel cell and maintains its performance.

The power generation system of this embodiment uses multiple fuel cell modules, which alternate between operating and stopping to obtain a constant, continuous output.

Figure 2 shows an example of the operation of each of fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D in power generation system 1. Figure 2 is a diagram explaining the output of the fuel cell units in power generation system 1, which is an example of a power generation system according to this embodiment.

The horizontal axis of FIG. 2 represents time, and the vertical axis represents the output of each of fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D.

In FIG. 2, fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D stop generating power in sequence to refresh. In the example shown in FIG. 2, fuel cell unit 10A stops first, and fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D operate. The outputs of fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D are controlled to be equal. Next, fuel cell unit 10A starts up and fuel cell unit 10B stops. Then, fuel cell unit 10B stops, and fuel cell unit 10A, fuel cell unit 10C, and fuel cell unit 10D operate. After that, fuel cell unit 10C and fuel cell unit 10D stop in that order, and the same operation is repeated.

The operation of the reverse conversion unit 20A, the reverse conversion unit 20B, and the reverse conversion unit 20C when the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D are operating as shown in FIG. 2 will be described. FIG. 3 is a diagram illustrating the output of the reverse conversion device in the power generation system 1, which is an example of a power generation system according to this embodiment.

The horizontal axis of FIG. 3 represents time, and the vertical axis represents the output of inverse transformation unit 20A, inverse transformation unit 20B, and inverse transformation unit 20C.

In FIG. 3, each of the inverse conversion unit 20A, the inverse conversion unit 20B, and the inverse conversion unit 20C operates at a constant output. According to the power generation system 1, as shown in FIG. 3, each of the inverse conversion unit 20A, the inverse conversion unit 20B, and the inverse conversion unit 20C can operate with a constant output.

The power output from the power generation system 1 to the AC power system ACPG is shown in FIG. 4. FIG. 4 is a diagram illustrating the output of the power generation system 1, which is an example of a power generation system according to this embodiment.

The horizontal axis of Figure 4 indicates time, and the vertical axis indicates the output of power generation system 1. In Figure 4, power generation system 1 operates at a constant output. With power generation system 1, a stable output can be obtained, as shown in Figure 4.

For example, when the power generation system 1 operates to output 100 kilowatts of power, the power generation system 1 outputs a total of 100 kilowatts of power from three of the four fuel cell units that are not undergoing refresh operation. Therefore, the control unit 50 controls each of the three fuel cell units to output 33.3 kilowatts evenly. The control unit 50 also controls each of the three reverse conversion units to output 33.3 kilowatts evenly.

For example, if one of the three inverter units fails, the control unit 50, which is constantly monitoring the operating status of the inverter units, immediately switches to operation using the two inverter units. Similarly, for the fuel cell units, if an abnormality occurs in one of the multiple fuel cell units, operation is switched to using the remaining fuel cell unit.

In the above example, the output is allocated equally to each of the multiple fuel cell units, and the output is allocated equally to each of the multiple reverse conversion units, but the output allocation is not limited to being equal. For example, the output allocation may be different for each of the multiple fuel cell units. Similarly, the output allocation may be different for each of the multiple reverse conversion units.

Here, we will explain a reference example in which the fuel cell unit and the reverse conversion unit are connected in a one-to-one relationship. Figure 14 is a diagram showing an outline of the power generation system 1z of the reference example.

Like the power generation system 1, the power generation system 1z includes a fuel cell unit 10A, a fuel cell unit 10B, a fuel cell unit 10C, and a fuel cell unit 10D. The fuel cell unit 10A in the power generation system 1z is connected to a reverse conversion unit 20A and a power storage unit 40A. The reverse conversion unit 20A in the power generation system 1z is connected to the AC power system ACPG via a transformer 30A.

Similarly, the fuel cell unit 10B in the power generation system 1z is connected to the reverse conversion unit 20B and the power storage unit 40B. The reverse conversion unit 20B in the power generation system 1z is connected to the AC power system ACPG via a transformer 30B. The fuel cell unit 10C in the power generation system 1z is connected to the reverse conversion unit 20C and the power storage unit 40C. The reverse conversion unit 20C in the power generation system 1z is connected to the AC power system ACPG via a transformer 30C. The fuel cell unit 10D in the power generation system 1z is connected to the reverse conversion unit 20D and the power storage unit 40D. The reverse conversion unit 20D in the power generation system 1z is connected to the AC power system ACPG via a transformer 30D.

For details about each component, please refer to the explanation for power generation system 1; we will not repeat the explanation here.

In the power generation system 1z, the case where the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D are each operated as shown in FIG. 2 will be described. In the power generation system 1z, the reverse conversion unit 20A operates in synchronization with the operation of the fuel cell unit 10A. That is, when the fuel cell unit 10A stops operating, the reverse conversion unit 20A also stops operating. Then, when the fuel cell unit 10A starts operating, the reverse conversion unit 20A also starts operating. Each of the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D operates in the same manner as the fuel cell unit 10A.

Figure 15 is a diagram explaining the output of the inverter in the power generation system 1z of the reference example. As shown in Figure 15, in the power generation system 1z of the reference example, each of the inverter unit 20A, the inverter unit 20B, the inverter unit 20C, and the inverter unit 20D repeatedly operates and stops.

In the power generation system 1z of the reference example, the durability of each of the multiple reverse conversion units included in the power generation system 1z may decrease due to frequent repetition of operation and shutdown.

The power generation system according to this embodiment can operate without fluctuating the output of each of the multiple reverse conversion units, which helps prevent a decrease in durability.

In addition, the power generation system 1z of the reference example has a one-to-one connection between the fuel cell unit and an inverter unit of the same capacity. Therefore, the total capacity of the multiple inverter units included in the power generation system 1z is greater than the required output and is excessive. In addition, in the power generation system 1z of the reference example, the operating rate of the multiple inverter units decreases when some of the multiple inverter units stop.

The power generation system according to this embodiment allows the total capacity of the multiple reverse conversion units connected to the multiple fuel cell units to be selected to suit the power generation system. In addition, the power generation system according to this embodiment allows for greater freedom in selecting the multiple reverse conversion units to be connected to the multiple fuel cell units.

Furthermore, in the power generation system 1z of the reference example, the fuel cell unit and the reverse conversion unit must be wired and controlled in a one-to-one relationship. Therefore, in the power generation system 1z of the reference example, when multiple fuel cell units are used in parallel, the wiring and control become complicated. Also, in the power generation system 1z of the reference example, the number of storage units, which are the basis for output, increases proportionally.

The power generation system according to this embodiment can simplify wiring and control. For example, in FIG. 1, by connecting nodes ND1 and ND2 with a single wire WL, the wiring can be simplified even when the fuel cell unit and the reverse conversion unit are installed at a distance. Furthermore, the power generation system according to this embodiment can reduce the number of storage units to be connected.

<Start-up of a fuel cell unit in a power generation system>
[First Example]
A first example of the start-up of the fuel cell unit in the power generation system according to this embodiment will be described using the power generation system 1. The start-up of the fuel cell unit in the power generation system according to this embodiment will be described to explain the steps included in the control method for the power generation system. Each of Figs. 5 and 6 is a flow diagram explaining a first example of the start-up procedure of the fuel cell unit in the power generation system 1, which is an example of the power generation system according to this embodiment. Fig. 7 is a diagram explaining the operation in the start-up of the fuel cell unit in the power generation system 1, which is an example of the power generation system according to this embodiment.

The horizontal axis of Figure 7 represents time, and the vertical axis represents the output of each of the multiple fuel cell units, the voltage of the power storage unit, and the output of each of the multiple inverter units.

The first example is an example in which the fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D in the power generation system 1 are started up one by one. In other words, only one of the fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D is started up. Then, after only one of the fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D has been started up, the fuel cell units other than the started fuel cell unit are started up one by one.

Initially, it is assumed that all of the fuel cell units 10A, 10B, 10C, and 10D in the power generation system 1 are stopped. In other words, it is assumed that all of the fuel cell units in the power generation system 1 are stopped. Here, as an example, a case is shown in which the fuel cell units 10A, 10B, 10C, and 10D are started up in that order. Note that the order of start-up is not limited to the above and may be changed as appropriate. Also, when starting up at least two fuel cell units, the fuel cell unit 10A, 10B, 10C, and 10D, the same process is carried out for the fuel cell units to be started up.

(Step S10)
The control unit 50 instructs the fuel cell unit 10A, which is to be started first, to output at the minimum output value. The fuel cell unit 10A, which has been instructed by the control unit 50 to output at the minimum output value, starts up and starts output. As illustrated in Figure 7, at time t1, the fuel cell unit 10A starts output.

(Step S20)
Next, the control unit 50 calculates the output of one reverse conversion unit from the required outputs of all the fuel cell units, i.e., fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D. Note that in step S20, since fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D have not yet started up, the control unit 50 calculates the output of one reverse conversion unit based on the required output of fuel cell unit 10A.

Specifically, the control unit 50 divides the required output of the fuel cell unit 10A by the number of reverse conversion units to calculate the output of one reverse conversion unit. Since the power generation system 1 has three reverse conversion units, namely, reverse conversion unit 20A, reverse conversion unit 20B, and reverse conversion unit 20C, the control unit 50 divides the required output of the fuel cell unit 10A by three to calculate the output of one reverse conversion unit.

(Step S30)
Next, the control unit 50 instructs each of the multiple reverse conversion units to output the output of one reverse conversion unit calculated in step S20. Specifically, the control unit 50 instructs each of the reverse conversion units 20A, 20B, and 20C to output the output of one reverse conversion unit calculated in step S20. Each of the reverse conversion units 20A, 20B, and 20C instructed by the control unit 50 converts the DC power from the fuel cell unit into AC power.

(Step S40)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within a predetermined range, in other words, whether the voltage at the power storage unit 40 has converged within the predetermined range.

For example, when the fuel cell unit 10A is started, the power storage unit 40 discharges to compensate for the output of the fuel cell unit 10A, causing the voltage to gradually decrease. Therefore, while the fuel cell unit 10A is started, it is determined whether the power storage unit 40 has charged the amount that was discharged.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S40), the control unit 50 returns to step S20 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S40), the control unit 50 proceeds to step S50.

The processing in step S40 allows the next fuel cell unit to be started after the voltage in the power storage unit 40 has converged to within a predetermined range.

(Step S50)
Next, the control unit 50 determines whether the output of the fuel cell unit 10A is equal to or greater than the minimum output value. If the output of the fuel cell unit 10A is equal to or greater than the minimum output value, the control unit 50 determines that the start-up of the fuel cell unit 10A is complete.

If the output of the fuel cell unit 10A is less than the minimum output value (NO in step S50), the control unit 50 returns to step S20 and repeats the process. If the output of the fuel cell unit 10A is equal to or greater than the minimum output value (YES in step S50), the control unit 50 proceeds to step S110.

As shown in FIG. 7 from time t1 to time t2, the output of the fuel cell unit 10A gradually increases until it reaches the minimum output value. Then, as shown in FIG. 7 from time t2 to time t3, the voltage in the power storage unit 40 can be gradually increased to bring the voltage of the power storage unit 40 within a predetermined range.

Next, as an example, start up the fuel cell unit 10B.

(Step S110)
The control unit 50 instructs the next fuel cell unit 10B to output at the minimum output value. The fuel cell unit 10B, which has been instructed by the control unit 50 to output at the minimum output value, starts up and starts output. As illustrated in Figure 7, at time t3, the fuel cell unit 10B starts output.

(Step S120)
Next, the control unit 50 calculates the output of one reverse conversion unit from the required outputs of all the fuel cell units, i.e., fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D. Note that in step S120, since fuel cell unit 10C and fuel cell unit 10D have not yet started up, the control unit 50 calculates the output of one reverse conversion unit based on the required outputs of fuel cell unit 10A and fuel cell unit 10B.

Specifically, the control unit 50 divides the sum of the required outputs of the fuel cell unit 10A and the fuel cell unit 10B by the number of reverse conversion units to calculate the output of one reverse conversion unit.

(Step S130)
Next, the control unit 50 instructs each of the multiple reverse conversion units to output the output of one reverse conversion unit calculated in step S120. Specifically, the control unit 50 instructs each of the reverse conversion units 20A, 20B, and 20C to output the output of one reverse conversion unit calculated in step S120. Each of the reverse conversion units 20A, 20B, and 20C instructed by the control unit 50 converts the DC power from the fuel cell unit into AC power.

(Step S140)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within a predetermined range, similar to step S40.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S140), the control unit 50 returns to step S120 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S140), the control unit 50 proceeds to step S150.

(Step S150)
Next, the control unit 50 determines whether the output of the fuel cell unit 10B is equal to or greater than the minimum output value, as in step S50. If the output of the fuel cell unit 10B is equal to or greater than the minimum output value, the control unit 50 determines that the start-up of the fuel cell unit 10B is complete.

If the output of the fuel cell unit 10B is less than the minimum output value (NO in step S150), the control unit 50 returns to step S120 and repeats the process. If the output of the fuel cell unit 10B is equal to or greater than the minimum output value (YES in step S150), the control unit 50 proceeds to step S210.

The same process is then performed when starting up fuel cell unit 10C and fuel cell unit 10D.

(Step S210)
The control unit 50 instructs the next fuel cell unit 10C to output at the minimum output value. The fuel cell unit 10C, which has been instructed by the control unit 50 to output at the minimum output value, starts up and starts output. As illustrated in Figure 7, at time t5, the fuel cell unit 10C starts output.

(Step S220)
Next, the control unit 50 calculates the output of one reverse conversion unit from the required outputs of all the fuel cell units, i.e., fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D. Note that in step S220, since fuel cell unit 10D has not yet started up, the control unit 50 calculates the output of one reverse conversion unit based on the required outputs of fuel cell unit 10A, fuel cell unit 10B, and fuel cell unit 10C.

(Step S230)
Next, the control unit 50 instructs each of the multiple inverse conversion units to output the amount of output for one inverse conversion unit calculated in step S220.

(Step S240)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within a predetermined range, similar to step S40.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S240), the control unit 50 returns to step S220 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S240), the control unit 50 proceeds to step S250.

(Step S250)
Next, the control unit 50 determines whether the output of the fuel cell unit 10C is equal to or greater than the minimum output value, similar to step S50. If the output of the fuel cell unit 10C is equal to or greater than the minimum output value, the control unit 50 determines that the start-up of the fuel cell unit 10C is complete.

If the output of the fuel cell unit 10C is less than the minimum output value (NO in step S250), the control unit 50 returns to step S220 and repeats the process. If the output of the fuel cell unit 10C is equal to or greater than the minimum output value (YES in step S250), the control unit 50 proceeds to step S310.

(Step S310)
The control unit 50 instructs the next fuel cell unit 10D to output at the minimum output value. The fuel cell unit 10D, which has been instructed by the control unit 50 to output at the minimum output value, starts up and starts output. As illustrated in FIG 7, at time t7, the fuel cell unit 10D starts output.

(Step S320)
Next, the control unit 50 calculates the output of one inverter unit from the required outputs of all the fuel cell units, that is, the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D.

(Step S330)
Next, the control unit 50 instructs each of the multiple inverse conversion units to output the amount of output for one inverse conversion unit calculated in step S320.

(Step S340)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within a predetermined range, similar to step S40.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S340), the control unit 50 returns to step S320 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S340), the control unit 50 proceeds to step S350.

(Step S350)
Next, the control unit 50 determines whether the output of the fuel cell unit 10D is equal to or greater than the minimum output value, similar to step S50. If the output of the fuel cell unit 10D is equal to or greater than the minimum output value, the control unit 50 determines that the start-up of the fuel cell unit 10D is complete.

If the output of the fuel cell unit 10D is less than the minimum output value (NO in step S350), the control unit 50 returns to step S320 and repeats the process. If the output of the fuel cell unit 10D is equal to or greater than the minimum output value (YES in step S350), the control unit 50 ends the process.

At time t9 in FIG. 7, the startup of fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D in power generation system 1 is completed.

The processing of steps S20 and S30, steps S120 and S130, steps S220 and S230, and steps S320 and S330 can change the output of each of the multiple reverse conversion units depending on the number of activated fuel cell units.

[Second Example]
A second example of the start-up of the fuel cell unit in the power generation system according to this embodiment will be described using the power generation system 1. The start-up of the fuel cell unit in the power generation system according to this embodiment will be described to explain the steps included in the control method for the power generation system. Each of Figs. 8 and 9 is a flow diagram explaining a second example of the start-up procedure of the fuel cell unit in the power generation system 1, which is an example of the power generation system according to this embodiment. Fig. 10 is a diagram explaining the operation in the start-up of the fuel cell unit in the power generation system 1, which is an example of the power generation system according to this embodiment.

The horizontal axis of FIG. 10 represents time, and the vertical axis represents the output of each of the multiple fuel cell units, the voltage of the power storage unit, and the output of each of the multiple inverter units.

The second example is an example in which fuel cell unit 10A in power generation system 1 is started, and then fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D are started simultaneously.

Initially, it is assumed that fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D in power generation system 1 are all in a stopped state. Here, as an example, a case is shown in which fuel cell unit 10A is started first. Note that the fuel cell unit that is started first is not limited to fuel cell unit 10A, and may be changed as appropriate.

Steps S10, S20, S30, S40, and S50 are the same as those in the first example, so the explanation will be omitted here and the first example will be referred to. Note that in step S50, if the output of the fuel cell unit 10A is equal to or greater than the minimum output value (YES in step S50), the control unit 50 proceeds to step S410.

(Step S410)
The control unit 50 instructs the fuel cell unit 10A on the command output values required to simultaneously start up each of the other fuel cell units, namely, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D. The fuel cell unit 10A, which has been instructed by the control unit 50 to output at the command output value, changes its output so that it becomes the command output value. As illustrated in Figure 10, at time t4, the fuel cell unit 10C starts outputting so that it becomes the command output value.

(Step S420)
Next, the control unit 50 calculates the output of one reverse conversion unit from the required outputs of all the fuel cell units, i.e., fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D. Note that in step S420, since fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D have not yet started up, the control unit 50 calculates the output of one reverse conversion unit based on the required output of fuel cell unit 10A.

Specifically, the control unit 50 divides the required output of the fuel cell unit 10A by the number of reverse conversion units to calculate the output of one reverse conversion unit.

(Step S430)
Next, the control unit 50 instructs each of the multiple reverse conversion units to output the output of one reverse conversion unit calculated in step S420. Specifically, the control unit 50 instructs each of the reverse conversion units 20A, 20B, and 20C to output the output of one reverse conversion unit calculated in step S420. Each of the reverse conversion units 20A, 20B, and 20C instructed by the control unit 50 converts the DC power from the fuel cell unit into AC power.

(Step S440)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within a predetermined range, similar to step S40.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S440), the control unit 50 returns to step S420 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S440), the control unit 50 proceeds to step S450.

(Step S450)
Next, the control unit 50 determines whether the output of the fuel cell unit 10A is equal to or greater than the command output value. If the output of the fuel cell unit 10A is equal to or greater than the command output value, the control unit 50 determines that the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D are each capable of being started simultaneously.

If the output of the fuel cell unit 10A is less than the command output value (NO in step S450), the control unit 50 returns to step S420 and repeats the process. If the output of the fuel cell unit 10A is equal to or greater than the command output value (YES in step S450), the control unit 50 proceeds to step S510.

(Step S510)
The control unit 50 instructs the fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D, which are to be started up simultaneously next, to use their minimum output values. Each of the fuel cell units 10B, 10C, and 10D, which have been instructed by the control unit 50 to output at their minimum output values, starts up and starts output. As illustrated in Figure 10, at time t6, each of the fuel cell units 10B, 10C, and 10D starts output.

(Step S520)
Next, the control unit 50 calculates the output of one inverter unit from the required outputs of all the fuel cell units, that is, the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D.

(Step S530)
Next, the control unit 50 instructs each of the multiple inverse conversion units to output the amount of output for one inverse conversion unit obtained in step S520.

(Step S540)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within a predetermined range, similar to step S40.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S540), the control unit 50 returns to step S520 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S540), the control unit 50 proceeds to step S550.

(Step S550)
Next, the control unit 50 determines whether the output of each of the fuel cell units 10B, 10C, and 10D is equal to or greater than the minimum output value. If the output of each of the fuel cell units 10B, 10C, and 10D is equal to or greater than the minimum output value, the control unit 50 determines that the start-up of each of the fuel cell units 10B, 10C, and 10D is complete.

If the outputs of fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D are less than the minimum output value (NO in step S550), control unit 50 returns to step S520 and repeats the process. If the outputs of fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D are equal to or greater than the minimum output value (YES in step S550), control unit 50 ends the process. At time t7 in FIG. 10, start-up of the fuel cell system in power generation system 1 is completed.

Note that while the first and second examples above are examples of starting up a fuel cell unit when all fuel cell units are stopped, they can also be applied to cases where some fuel cell units are operating and the number of operating fuel cell units is to be increased.

<Reducing the output of a fuel cell unit in a power generation system>
An example of output reduction of the fuel cell unit in the power generation system according to this embodiment will be described using the power generation system 1. By explaining the output reduction of the fuel cell unit in the power generation system according to this embodiment, the steps included in the control method of the power generation system will be described. Each of Figs. 11 and 12 is a flow diagram explaining an example of the output reduction procedure of the fuel cell unit in the power generation system 1, which is an example of the power generation system according to this embodiment. Fig. 13 is a diagram explaining the operation in the output reduction of the fuel cell unit in the power generation system 1, which is an example of the power generation system according to this embodiment.

The horizontal axis of FIG. 13 represents time, and the vertical axis represents the output of each of the multiple fuel cell units, the voltage of the power storage unit, and the output of each of the multiple inverter units.

This example is an example in which the output of each of fuel cell units 10A, 10B, 10C, and 10D in the power generation system 1 is reduced in sequence.

First, it is assumed that all of the fuel cell units 10A, 10B, 10C, and 10D in the power generation system 1 are outputting a predetermined output. In other words, it is assumed that all of the multiple fuel cell units in the power generation system 1 are operating. Here, as an example, a case is shown in which the output is reduced in the order of the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D. In this example, the power generation system 1 reduces the output of the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D one by one in sequence. In other words, in the power generation system according to this embodiment, when reducing the output of at least two of the multiple fuel cell units, the control unit controls to reduce the output of only one of the multiple fuel cell units. Then, after reducing the output of the fuel cell unit, the control unit controls to reduce the output of the other fuel cell units in the multiple fuel cell units.

The order in which the output is reduced is not limited to the above and may be changed as appropriate. In addition, when reducing the output of at least one of the fuel cell units 10A, 10B, 10C, and 10D, the same process is performed for the fuel cell unit whose output is to be reduced.

(Step S610)
The control unit 50 instructs the fuel cell unit 10A, which is to reduce its output first, to a reduced output value that is lower than the current output. The fuel cell unit 10A, which has been instructed by the control unit 50 to output at the reduced output value, begins to reduce its output. As illustrated in Figure 13, at time t1, the fuel cell unit 10A begins to reduce its output.

(Step S620)
Next, the control unit 50 calculates the output of one inverter unit from the required outputs of all the fuel cell units, that is, the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D.

Specifically, the control unit 50 calculates the output of one reverse conversion unit from the required output of all fuel cell units, i.e., fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D.

(Step S630)
Next, the control unit 50 instructs each of the multiple reverse conversion units to output the output of one reverse conversion unit calculated in step S620. Specifically, the control unit 50 instructs each of the reverse conversion units 20A, 20B, and 20C to output the output of one reverse conversion unit calculated in step S620. Each of the reverse conversion units 20A, 20B, and 20C instructed by the control unit 50 converts the DC power from the fuel cell unit into AC power.

(Step S640)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within a predetermined range, in other words, whether the voltage at the power storage unit 40 has converged within the predetermined range.

For example, when the output of the fuel cell unit 10A is reduced, the power storage unit 40 charges the output of the fuel cell unit 10A, and the voltage gradually increases. Therefore, while the output of the fuel cell unit 10A is being reduced, it is determined whether the power storage unit 40 has discharged the amount that it had charged.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S640), the control unit 50 returns to step S620 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S640), the control unit 50 proceeds to step S650.

The processing in step S640 allows the output of the next fuel cell unit to be reduced after the voltage in the power storage unit 40 has converged to within a predetermined range.

(Step S650)
Next, the control unit 50 determines whether the output of the fuel cell unit 10A is equal to or lower than the reduced output value. If the output of the fuel cell unit 10A is equal to or lower than the reduced output value, the control unit 50 determines that the output reduction of the fuel cell unit 10A is complete.

If the output of the fuel cell unit 10A is greater than the reduced output value (NO in step S650), the control unit 50 returns to step S620 and repeats the process. If the output of the fuel cell unit 10A is equal to or less than the reduced output value (YES in step S650), the control unit 50 proceeds to step S710.

As shown in FIG. 13 from time t1 to time t2, the output of the fuel cell unit 10A gradually decreases until it reaches the reduced output value. Then, as shown in FIG. 12 from time t2 to time t3, the voltage of the power storage unit 40 can be gradually decreased to bring the voltage of the power storage unit 40 within a predetermined range.

Next, as an example, the output of fuel cell unit 10B is reduced.

(Step S710)
The control unit 50 instructs the fuel cell unit 10B, which is to be next to reduce its output, to a reduced output value that is lower than the current output. The fuel cell unit 10B, which has been instructed by the control unit 50 to output at a reduced output value, begins to reduce its output. As illustrated in Figure 13, at time t3, the fuel cell unit 10B begins to reduce its output.

(Step S720)
Next, the control unit 50 calculates the output of one inverter unit from the required outputs of all the fuel cell units, that is, the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D.

(Step S730)
Next, the control unit 50 instructs each of the multiple reverse conversion units to output the output of one reverse conversion unit calculated in step S720. Specifically, the control unit 50 instructs each of the reverse conversion units 20A, 20B, and 20C to output the output of one reverse conversion unit calculated in step S720. Each of the reverse conversion units 20A, 20B, and 20C instructed by the control unit 50 converts the DC power from the fuel cell unit into AC power.

(Step S740)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within the predetermined range, similarly to step S640.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S740), the control unit 50 returns to step S720 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S740), the control unit 50 proceeds to step S750.

(Step S750)
Next, the control unit 50 determines whether the output of the fuel cell unit 10B is equal to or lower than the reduced output value, as in step S650. If the output of the fuel cell unit 10B is equal to or lower than the reduced output value, the control unit 50 determines that the output reduction of the fuel cell unit 10B is complete.

If the output of the fuel cell unit 10B is greater than the reduced output value (NO in step S750), the control unit 50 returns to step S720 and repeats the process. If the output of the fuel cell unit 10B is equal to or less than the reduced output value (YES in step S750), the control unit 50 proceeds to step S810.

The same process is then performed when reducing the output of fuel cell unit 10C and fuel cell unit 10D.

(Step S810)
The control unit 50 instructs the fuel cell unit 10C, which is to be next to reduce its output, to a reduced output value that is lower than the current output. The fuel cell unit 10C, which has been instructed by the control unit 50 to output at a reduced output value, begins to reduce its output. As illustrated in Figure 13, at time t5, the fuel cell unit 10C begins to reduce its output.

(Step S820)
Next, the control unit 50 calculates the output of one inverter unit from the required outputs of all the fuel cell units, that is, the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D.

(Step S830)
Next, the control unit 50 instructs each of the multiple inverse conversion units to output the amount of output for one inverse conversion unit calculated in step S820.

(Step S840)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within the predetermined range, similarly to step S640.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S840), the control unit 50 returns to step S820 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S840), the control unit 50 proceeds to step S850.

(Step S850)
Next, the control unit 50 determines whether the output of the fuel cell unit 10C is equal to or lower than the reduced output value, similar to step S650. If the output of the fuel cell unit 10C is equal to or lower than the reduced output value, the control unit 50 determines that the output reduction of the fuel cell unit 10C is complete.

If the output of the fuel cell unit 10C is greater than the reduced output value (NO in step S850), the control unit 50 returns to step S820 and repeats the process. If the output of the fuel cell unit 10C is equal to or less than the reduced output value (YES in step S850), the control unit 50 proceeds to step S910.

(Step S910)
The control unit 50 instructs the fuel cell unit 10D, which is to reduce its output next, to use a reduced output value. The fuel cell unit 10D, which has been instructed by the control unit 50 to output at a reduced output value, begins reducing its output. As illustrated in Figure 13, at time t7, the fuel cell unit 10D begins reducing its output.

(Step S920)
Next, the control unit 50 calculates the output of one inverter unit from the required outputs of all the fuel cell units, that is, the fuel cell unit 10A, the fuel cell unit 10B, the fuel cell unit 10C, and the fuel cell unit 10D.

(Step S930)
Next, the control unit 50 instructs each of the multiple inverse conversion units to output the amount of output for one inverse conversion unit calculated in step S920.

(Step S940)
Next, the control unit 50 determines whether the voltage of the power storage unit 40 is within the predetermined range, similarly to step S640.

If the voltage of the power storage unit 40 is not within the predetermined range (NO in step S940), the control unit 50 returns to step S920 and repeats the process. If the voltage of the power storage unit 40 is within the predetermined range (YES in step S940), the control unit 50 proceeds to step S950.

(Step S950)
Next, the control unit 50 determines whether the output of the fuel cell unit 10D is equal to or lower than the reduced output value, as in step S650. If the output of the fuel cell unit 10D is equal to or lower than the reduced output value, the control unit 50 determines that the output reduction of the fuel cell unit 10D is complete.

If the output of the fuel cell unit 10D is greater than the reduced output value (NO in step S950), the control unit 50 returns to step S920 and repeats the process. If the output of the fuel cell unit 10D is equal to or less than the reduced output value (YES in step S950), the control unit 50 ends the process.

At time t9 in FIG. 13, the output reduction of each of fuel cell unit 10A, fuel cell unit 10B, fuel cell unit 10C, and fuel cell unit 10D included in power generation system 1 is completed.

In addition, by processing steps S620 and S630, steps S720 and S730, steps S820 and S830, and steps S920 and S930, the output of each of the multiple reverse conversion units can be changed according to the output of the operating fuel cell unit.

In the above example, a reduced output value was instructed for each of the fuel cell units, but this can also be applied to the case where the power generation system 1 is stopped by instructing each of the fuel cell units to have zero output as the reduced output value.

<Summary>
According to the power generation system of this embodiment, the reverse conversion unit can be operated efficiently. According to the power generation system of this embodiment, even if any of the multiple fuel cell units is stopped for refresh, the reverse conversion unit can be operated continuously without being stopped, so that the reverse conversion unit can be operated efficiently.

According to the power generation system of this embodiment, multiple fuel cell units are connected in parallel and distributed to multiple inverters, allowing the connection of an inverter unit independent of the output of the fuel cell unit. Therefore, in a power generation system equipped with multiple fuel cell units, the number of types of inverter units that can be connected can be increased. Also, in a power generation system equipped with multiple fuel cell units, the degree of freedom for expansion can be increased.

In addition, according to the power generation system of this embodiment, by connecting multiple fuel cell units in parallel and distributing them to multiple inverter devices, the number of inverter units, power storage units, and transformers can be reduced. Furthermore, according to the power generation system of this embodiment, the number of times the inverter unit is operated and stopped can be reduced. By reducing the number of times the inverter unit is operated and stopped, the durability of the inverter unit can be improved.

For example, when a fuel cell unit, a reverse conversion unit, a transformer, and a storage battery are connected in a one-to-one ratio, the respective capacities of the fuel cell unit, the reverse conversion unit, the transformer, and the storage battery may not match the capacity on the demand side. Also, when a fuel cell unit and a reverse conversion unit are connected in a one-to-one ratio, the control of each of the fuel cell unit and the reverse conversion unit may become complicated.

In the power generation system according to this embodiment, the control can be simplified and the configuration can be simplified by connecting a different number of reverse conversion units to the fuel cell units compared to the number of fuel cell units.

The above operation example is an example of the operation of the power generation system according to this embodiment, and the power generation system according to this embodiment is not limited to the above operation. Furthermore, the numerical values shown in the above operation example are numerical values used as examples to explain the operation of the power generation system according to this embodiment, and the operation of the power generation system according to this embodiment is not limited to these numerical values.

Although the power generation system has been described above using an embodiment, the present invention is not limited to the above embodiment. Various modifications and improvements, such as combinations or substitutions with part or all of other embodiments, are possible within the scope of this disclosure.

Reference Signs List 1 Power generation system 10 Control device 10A, 10B, 10C, 10D Fuel cell unit 11 Fuel cell 20A, 20B, 20C Inverse conversion unit 30A, 30B, 30C Transformer 40 Power storage unit 50 Control unit ACPG AC power system ND1, ND2 Node

Claims (9)

A plurality of fuel cell units;
A plurality of inverse transformation units;
Equipped with
the outputs of each of the plurality of fuel cell units are connected in parallel to a first node;
The inputs of the plurality of inverse transformation units are connected in parallel from a second node connected to the first node ;
a power storage unit connected to the first node;
a control unit that controls each of the plurality of fuel cell units, each of the plurality of reverse conversion units, and the power storage unit;
Further comprising:
when starting up at least two of the fuel cell units from a state in which all of the fuel cell units are stopped, the control unit controls to start up only a first fuel cell unit of the plurality of fuel cell units, and after the first fuel cell unit has started up, controls to start up the fuel cell units other than the first fuel cell unit in the plurality of fuel cell units.
Power generation system. A plurality of fuel cell units;
A plurality of inverse transformation units;
Equipped with
the outputs of each of the plurality of fuel cell units are connected in parallel to a first node;
The inputs of the plurality of inverse transformation units are connected in parallel from a second node connected to the first node;
a power storage unit connected to the first node;
a control unit that controls each of the plurality of fuel cell units, each of the plurality of reverse conversion units, and the power storage unit;
Further comprising:
when starting up at least two of the fuel cell units from a state in which all of the fuel cell units are stopped, the control unit controls to start up only a first fuel cell unit of the plurality of fuel cell units, and after the first fuel cell unit has started up and the voltage at the power storage unit has converged within a predetermined range, controls to start up the fuel cell units other than the first fuel cell unit in the plurality of fuel cell units.
Power generation system. the control unit sequentially starts up the fuel cell units that are not yet started, one by one, among the plurality of fuel cell units, after the first fuel cell unit has been started up.
The power generation system according to claim 1 . the control unit simultaneously starts up a plurality of the fuel cell units that are not yet started, after the first fuel cell unit has been started up;
The power generation system according to claim 1 . 2. The power generation system according to claim 1 , wherein the capacity of the power storage unit is greater than a minimum startup capacity capable of starting any one of the plurality of fuel cell units and is smaller than twice the minimum startup capacity. the control unit changes the output of each of the plurality of reverse conversion units in accordance with the number of activated fuel cell units among the plurality of fuel cell units.
The power generation system according to claim 1 . A plurality of fuel cell units;
A plurality of inverse transformation units;
Equipped with
the outputs of each of the plurality of fuel cell units are connected in parallel to a first node;
The inputs of the plurality of inverse transformation units are connected in parallel from a second node connected to the first node;
a power storage unit connected to the first node;
a control unit that controls each of the plurality of fuel cell units, each of the plurality of reverse conversion units, and the power storage unit;
Further comprising:
the control unit, when reducing the output of at least two of the fuel cell units of the plurality of fuel cell units, controls to reduce the output of only a second fuel cell unit of any of the plurality of fuel cell units, and after reducing the output of the second fuel cell unit, controls to reduce the output of the fuel cell units other than the second fuel cell unit of the plurality of fuel cell units.
Power generation system. Further comprising a plurality of transformers;
Each of the plurality of inverter units is connected to one of the plurality of transformers.
The power generation system according to any one of claims 1 to 7 . A plurality of fuel cell units;
A plurality of inverse transformation units;
A power storage unit;
Equipped with
the outputs of each of the plurality of fuel cell units are connected in parallel to a first node;
The inputs of the plurality of inverse transformation units are connected in parallel from a second node connected to the first node;
A method for controlling a power generation system, wherein the power storage unit is connected to the first node,
When starting up at least two of the fuel cell units from a state in which all of the fuel cell units are stopped,
a step of controlling so as to start up only a first fuel cell unit of the plurality of fuel cell units;
after the first fuel cell unit is started up, starting up the fuel cell units other than the first fuel cell unit in the plurality of fuel cell units;
including,
A method for controlling a power generation system.

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