JP2014103092A - Fuel cell unit and parallel operation system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a parallel operation system of a fuel cell unit which can ensure a large power generation output, by operating a plurality of fuel cell units efficiently.SOLUTION: In a parallel operation system of a fuel cell unit for operating a plurality of fuel cell units 2A-2D while connecting in parallel, the fuel cell units 2A-2D include a fuel cell 4 and power generation output control means 6 for controlling the power generation output thereof, respectively. First current converters 36A-36D and second current converters 38A-38D are provided corresponding to the fuel cell units 2A-2D, the first current converters 36A-36D detect a current flowing through a commercial power line 30, and the second current converters 38A-38D detects a current flowing through the power generation output lines 8A-8D. Power generation output control means for the fuel cell units 2A-2D controls the power generation output of the fuel cell 4, based on the detection currents of the first current converters 36A-36D and second current converters 38A-38D.

Description

  The present invention relates to a fuel cell unit that generates power by a fuel cell reaction and a parallel operation system of fuel cell units that connect a plurality of them in parallel to obtain a large power generation output.

  In recent years, home fuel cell systems that are installed and used in detached houses and the like have been put into practical use. This household fuel cell system is configured to cover power consumption consumed at home, and its power generation output is as small as 700 to 1000 W, for example. Therefore, development has been advanced to obtain a power output of medium output (for example, 3 to 5 kW) using such a home fuel cell system, and a plurality of fuel cell systems are connected in parallel to obtain a power output. A parallel operation system has been proposed (see, for example, Patent Document 1).

  This known fuel cell system (fuel cell unit) has a configuration as shown in FIG. 29, for example. In this known example, four fuel cell systems (fuel cell units) 102A to 102D are connected in parallel, and their power generation output lines 104A to 104D are connected to the power load 108 via the power supply line 106. Yes. Each of the fuel cell systems 102A to 102D includes a fuel cell 110, a power generation output control means 112 for controlling the power generation output of the fuel cell 110, and a DC power generated from the fuel cell 110 for converting into AC power. DC / AC converters 113 </ b> A to 113 </ b> D are provided, and sub-breakers 114 are provided in the power generation output lines 104 </ b> A to 104 </ b> D, and AC power from the fuel cell systems 102 </ b> A to 102 </ b> D is supplied to the power load 108.

  The commercial power supply 116 is connected to the power supply line 106 via the commercial power line 118, and a power meter 120 for measuring the power flowing through the commercial power line 118 is disposed on the commercial power line 118. Yes. The commercial power line 118 is provided with current converters 122A to 122D corresponding to the fuel cell systems (fuel cell units) 102A to 102D, and each of the current converters 122A to 122D flows through the commercial power line 118. And the electric power (so-called purchased electric power) flowing through the commercial power line 118 is measured using the detected current. Further, a main breaker 117 is disposed in the commercial power line 118, and the power generation output lines 104A to 104D from the fuel cell systems 102A to 102D are connected to the power supply line 106 on the downstream side of the main breaker 117. .

  The detected current from each of the current converters 122A to 122D is supplied to the power generation output control means 112 of the corresponding fuel cell system (fuel cell unit) 102A to 102D, and each power generation output control means 112 corresponds to the corresponding current converter 122A to 122A. Based on the detected current from 122D, the power generation output of the fuel cell 110 is controlled, and by this control, the fuel cell systems 102A to 102D generate a reverse flow (also referred to as “reverse power”) to the commercial power supply 116. While being prevented, the power generation output according to the size of the power load 108 is sent to the power load 108.

Japanese Patent Laid-Open No. 9-275637

  However, in such a parallel operation system, the following problems may occur. When all the fuel cell systems 102A to 102D are operated at the rated power generation output, the fuel cell systems 102A to 102D can be stably operated, but the partial load of the fuel cell systems 102A to 102D is less than the rated power output. When operating in this state, the operation of each of the fuel cell systems 102A to 102D may become unstable. For example, when four fuel cell systems 102A to 102D having a rated power output 700W are operated in parallel and the power load is 1500W, for example, one fuel cell system 102A is 500W, for example, another fuel cell system 102B is 400W, for example, the remaining The two fuel cell systems 102C and 102D may have an imbalance of 300W.

  When a plurality of fuel cell systems are operated in parallel, generally only the same fuel cell system can be supported, and fuel cell systems having different power generation output characteristics (for example, fuel cell systems having different manufacturers) are combined. Could not be operated in parallel. Even in the same fuel cell system, the system must be modified in order to operate in parallel, and if the cost is increased or if one unit fails, the remaining fuel cell system generates power output. There is also a problem that it is necessary to raise the power generation operation so that it can be continued automatically.

  An object of the present invention is to provide a fuel cell unit parallel operation system capable of efficiently operating a plurality of fuel cell units and obtaining a large power generation output.

  Another object of the present invention is to provide a fuel cell unit that can be advantageously used for both parallel operation and single operation.

A fuel cell unit parallel operation system according to claim 1 of the present invention is a fuel cell unit parallel operation system that operates by connecting a plurality of fuel cell units in parallel to each other,
The plurality of fuel cell units includes a fuel cell that generates power by a fuel cell reaction, and a power generation output control unit that controls a power generation output of the fuel cell, and corresponds to each of the power generation output control units of the plurality of fuel cell units. And a first current converter for detecting a current flowing through a commercial power line of a commercial power source, and a second current converter corresponding to each of the fuel cells of the plurality of fuel cell units. A current converter is provided, the second current converter detects a current flowing through a power generation output line of the corresponding fuel cell, and the power generation output control means of each of the plurality of fuel cell units includes the corresponding first The power generation output of the corresponding fuel cell is controlled based on the detected currents of the first and second current converters.

  Further, in the fuel cell unit parallel operation system according to claim 2 of the present invention, the second current converter corresponding to each of the plurality of fuel cell units corresponds to the corresponding first current converter. It is characterized by being electrically reversely connected in parallel.

  In the fuel cell unit parallel operation system according to claim 3 of the present invention, a current transformer is provided corresponding to the second current converter corresponding to the fuel cell of each of the plurality of fuel cell units. The current transformer is transformed so that a current flowing through the power generation output line of the corresponding fuel cell becomes small, and the second current converter converts the current transformed by the corresponding current transformer. It is characterized by detecting.

  In the fuel cell unit parallel operation system according to claim 4 of the present invention, the current transformer ratio of each of the current transformers of each of the plurality of fuel cell units is 1 to 100.

  In the fuel cell unit parallel operation system according to claim 5 of the present invention, the second current converter and the current transformer of each of the plurality of fuel cell units are integrally configured. Features.

According to a sixth aspect of the present invention, a fuel cell unit includes a fuel cell that generates power by a fuel cell reaction, and a power generation output control unit that controls a power generation output of the fuel cell, and corresponds to the power generation output control unit. A first current converter is provided, the first current converter detects a current flowing through a commercial power line of a commercial power source, and a second current converter is provided corresponding to the fuel cell, and the second current converter is provided. The current converter detects a current flowing through the power generation output line of the fuel cell, and in addition to the second current converter, switch means is provided,
When used in parallel operation, the switch means allows the detection current to be supplied from the second current converter to the power generation output control means, and the power generation output control means includes the first and second currents. When the power generation output of the fuel cell is controlled based on the detected current of the converter and used for single operation, the switch means supplies the detected current from the second current converter to the power generation output control means. The power generation output control means controls the power generation output of the fuel cell based on the detected current of the first current converter.

  Furthermore, in the fuel cell unit according to claim 7 of the present invention, the first and second output terminals of the first current converter are connected to the first of the power generation output control means via the first and second current lines, respectively. And the second current converter is electrically connected in reverse to the first current converter, and the first output terminal of the second current converter is connected to the first input terminal. Electrically connected to the second current line via a three current line, and a second output terminal of the second current converter is electrically connected to the first current line via a fourth current line, The switch means is disposed in the third and fourth current lines of the second current converter, and when used for parallel operation, the switch means is kept closed, and when used for single operation, The switch means is held in an open state. That.

  According to the fuel cell unit parallel operation system of the first aspect of the present invention, the first current conversion for detecting the current flowing through the commercial power line corresponding to each of the power generation output control means of the plurality of fuel cell units. And a second current converter for detecting a current flowing through the power generation output line of the fuel cell corresponding to each of the fuel cells of the plurality of fuel cell units. The power generation output control means controls the power generation output of the corresponding fuel cell based on the detected currents of the corresponding first and second current converters. The power generation output of the fuel cell unit can be output stably. In addition, by controlling in this way, the present invention is also applied to parallel operation of fuel cell units having different power generation outputs (for example, fuel cell units having different manufacturers) without special modification of a plurality of fuel cell units. be able to.

  In particular, when a plurality of fuel cell units having the same rated power generation output are used, the power generation output of the fuel cells of each fuel cell unit can be made uniform and stably output. As a result, the plurality of fuel cell units as a whole Power generation efficiency can be increased, and a plurality of fuel cell units can be operated in parallel with high efficiency.

  According to the fuel cell unit parallel operation system of the second aspect of the present invention, the second current converter corresponding to each of the plurality of fuel cell units is electrically connected to the corresponding first current converter. Therefore, the detection signal (detection current) sent to the corresponding power generation output control means is the difference between the detection current of the first current converter and the detection current of the second current converter. By using this difference signal to control the power generation output of the fuel cell, it is possible to stably output the power generation output of a plurality of fuel cell units with a simple configuration, A plurality of fuel cell units can be operated in parallel with high efficiency.

  According to the fuel cell unit parallel operation system of the third aspect of the present invention, a current transformer is provided corresponding to each of the second current converters, and the current transformer is connected to the corresponding fuel cell. Since the current flowing through the power generation output line is reduced so that the second current converter detects the current converted by the current transformer, the total power generation output and the power load of the plurality of fuel cell systems are detected. Operation can be performed so that the difference is reduced.

  In the fuel cell unit parallel operation system according to claim 4 of the present invention, the current transformer ratio of each of the current transformers of the plurality of fuel cell units is 1 to 100. Even if they are different from each other, the difference between the total power generation output of the fuel cell system and the power load can be suppressed to be small and the power generation output can be stably performed.

  According to the fuel cell unit parallel operation system of the fifth aspect of the present invention, since the second current converter and the current transformer of each of the plurality of fuel cell units are integrally configured, the system The entire configuration can be simplified.

  According to the fuel cell unit of the present invention, the first current converter for detecting the current flowing through the commercial power line is provided corresponding to the power generation output control means of the fuel cell unit. In correspondence with the fuel cell, a second current converter for detecting a current flowing through the power generation output line of the fuel cell is provided, and a switch means is provided in association with the second current converter. . When used in parallel operation, the switch means allows the detection current to be supplied from the second current converter to the power generation output control means, so that the power generation output control means can be used for the first and second current converters. The power generation output of the fuel cell is controlled on the basis of the detected current. Therefore, when the parallel operation is performed, the fuel cell unit can be operated with high power generation efficiency. In addition, when used for isolated operation, the switch means cuts off the supply of the detected current from the second current converter to the power generation output control means, so the power generation output control means uses the detected current of the first current converter. Based on this, the power generation output of the fuel cell is controlled, so that it can be operated independently as desired.

  Furthermore, according to the fuel cell unit of the seventh aspect of the present invention, the second current converter is electrically reversely connected in parallel with the first current converter, and the first output of the second current converter is The terminal is electrically connected to the second current line from the first current converter via the third current line, and the second output terminal of the second current converter is connected to the first current converter via the fourth current line. Since the switch means are disposed on the third and fourth current lines of the second current converter, the second current converter is held in the closed state by being electrically connected to the first current line from the second current converter. The detected current from the current converter is sent to the power generation output control means, the fuel cell unit can be applied to parallel operation and operated with high power generation efficiency, and the switch means is kept open, Generation of detected current from the second current converter Is feed is shut off to the force control unit, it can be applied to the desired islanding.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified diagram showing a first embodiment of a fuel cell unit parallel operation system according to the present invention; The block diagram which shows simply the fuel cell unit and the structure relevant to it in the parallel operation system of FIG. The flowchart which shows the flow of the output control of the fuel cell unit of FIG. The figure which shows the relationship between the electric power generation output of the fuel cell of a fuel cell system, and electric power generation efficiency. The figure which shows the determination result of the power generation efficiency when four fuel cell units are operated. FIGS. 6A and 6B are diagrams showing the relationship between the elapsed time when four fuel cell units are operated and the power generation output of the fuel cell. FIG. 6A shows a current transformation ratio of 1, and FIG. FIG. 6C shows the relationship when the ratio is 100, FIG. 6C shows the current transformation ratio of 1000, and FIG. 6D shows the current transformation ratio being infinite. The figure which shows the relationship between a current transformation ratio when four fuel cell units are operated, and a total power generation output. The figure which shows the relationship between the elapsed time when four fuel cell units are operated with a rated power generation output, and the power generation output of a fuel cell. FIG. 9 is a diagram showing the relationship between the elapsed time and the power generation output of the fuel cell when four fuel cell units (units having the same output increase speed and different output decrease speeds) are operated with partial loads; FIG. 9A shows the relationship when the current transformation ratio is 100, and FIG. 9B shows the relationship when the current transformation ratio is 30. FIG. It is a figure which shows the relationship between the elapsed time when a power load is fluctuate | varied, and the electric power generation output of four fuel cell units, Comprising: Fig.10 (a) is a current transformation ratio, FIG.10 (b) is a current transformation ratio. The figure which shows the relationship when is 30. The figure which shows the relationship between the elapsed time when one fuel cell unit trips, and the electric power generation output of the remaining three fuel cell units. FIG. 12A is a diagram showing the relationship between the elapsed time and the power generation output of the fuel cell when the power generation outputs of the four fuel cell units fluctuate by ± 2 W. FIG. ) Shows the relationship when the current transformation ratio is 30, FIG. 12C shows the current transformation ratio of 10, and FIG. 12D shows the current transformation ratio of 3. FIG. 13A is a diagram showing the relationship between the elapsed time and the fuel cell power generation output when two fuel cell units having different rated power generation outputs are operated. FIG. 13A shows a power load of 800 W, and FIG. FIG. 13C shows the relationship when the power load is 1000 W, FIG. 13C is the power load 1200 W, and FIG. 13D is the power load 1400 W. FIGS. 14A and 14B are diagrams showing the relationship between the elapsed time and the power generation output of the fuel cell when two fuel cell units are operated, in which FIG. Is a diagram showing the relationship when the current transformation ratio is 1000. FIG. FIG. 15A is a diagram showing the relationship between the elapsed time and the power generation output of the fuel cell when the power generation outputs of the two fuel cell units fluctuate by ± 2 W. FIG. ) Shows the relationship when the current transformation ratio is 100, and FIG. 15C shows the relationship when the current transformation ratio is 1000. FIGS. 16A and 16B are diagrams showing the relationship between the elapsed time and the power generation output of the fuel cell when two fuel cell units having different output characteristics are operated. FIG. FIG. 16C shows the relationship when the power load is 1000 W, FIG. 16C is the power load 1200 W, and FIG. 15D is the power load 1400 W. FIGS. 17A and 17B are diagrams showing the relationship between the elapsed time and the power generation output of the fuel cell when two fuel cell units are operated, in which FIG. Is a diagram showing the relationship when the current transformation ratio is 1000. FIG. FIG. 18A is a diagram showing the relationship between the elapsed time and the power generation output of the fuel cell when the power generation outputs of the two fuel cell units fluctuate by ± 2 W. FIG. ) Shows the relationship when the current transformation ratio is 100, and FIG. 18C shows the relationship when the current transformation ratio is 1000. The figure which shows the electric power generation output of each fuel cell and the electric power generation efficiency of the whole system when changing the current transformation ratio of a current transformer in the case of load electric power 800W. The figure which shows the electric power generation output of each fuel cell and the electric power generation efficiency of the whole system when changing the current ratio of a current transformer in the case of load electric power 1600W. The figure which shows the electric power generation output of each fuel cell when the current transformation ratio of a current transformer is fluctuated in the case of load electric power 2400W, and the electric power generation efficiency of the whole system. The figure which shows the electric power generation output of each fuel cell when changing the current transformation ratio of a current transformer when load electric power is 3000 W or more. The figure which shows the relationship between the electric power generation output of the whole system when the current ratio of a current transformer is changed, and the electric power generation efficiency of the whole system. The figure which shows the power generation efficiency when operating the whole system (four fuel cell units) and the power generation efficiency when operating one fuel cell unit (the power generation output is quadrupled). . The simplification figure which shows 2nd Embodiment of the parallel operation system of the fuel cell unit according to this invention. The simplification figure which shows 3rd Embodiment of the parallel operation system of the fuel cell unit according to this invention. The block diagram which shows simply the fuel cell unit and the structure relevant to it in the parallel operation system of FIG. The block diagram which shows a part of 4th Embodiment of the parallel operation system of the fuel cell unit according to this invention simply. The figure which shows simply the parallel operation system of the conventional fuel cell system.

  Hereinafter, various embodiments of a parallel operation system for fuel cell units according to the present invention will be described with reference to FIGS.

[First embodiment of parallel operation system of fuel cell units]
First, with reference to FIGS. 1-3, 1st Embodiment of the parallel operation system of a fuel cell unit is described. 1 and 2, the fuel cell unit parallel operation system shown in the figure uses a plurality (four in the embodiment) of fuel cell units 2A to 2D, and the plurality of fuel cell units 2A to 2D are mutually connected. They are arranged in parallel. Each of the fuel cell units 2A to 2D has substantially the same configuration, the fuel cell 4 that generates power by a fuel cell reaction, the power generation output control means 6 for controlling the power generation output of the fuel cell 4, and the fuel cell And a DC / AC converter 11A (11B, 11C, 11D) for converting the generated DC power from AC 4 into AC power. The fuel cell 4 is, for example, a solid oxide fuel cell known per se. Consists of

  The power generation output from each of the fuel cell units 2A to 2D is sent to the power supply line 10 via the power generation output lines 8A to 8D, and is sent to the power load 12 via this power supply line 10. Sub-breakers 14A (14B, 14C, 14D) are arranged on the power generation output lines 8A (8B, 8C, 8D) from the fuel power generation units 2A (2B, 2C, 2D), and the fuel cell units 2A (2B, 2C, 2D, 2D) is supplied to the power load 12 via the auxiliary breaker 14A (14B, 14C, 14D). Further, the auxiliary breaker 14A (14B, 14C, 14D) is for safety. When the auxiliary breaker 14A (14B, 14C, 14D) is turned off, the fuel cell unit 2A (2B, 2C, 2D) Supply of the power generation output to the power supply line 10 is stopped.

  Here, the fuel cell unit 2A (2B, 2C, 2D) will be described. The fuel cell 4 (for example, a solid oxide fuel cell) in the fuel cell unit 2A (2B, 2C, 2D) is formed by stacking fuel cells. A fuel cell stack 16, and further a fuel gas supply pump 18 for supplying fuel gas (for example, city gas), an air supply blower 20 for supplying air, and reformed water for supplying reformed water A supply pump 22 is included. When the power generation output of the fuel cell 4 is increased, the rotational speeds of the fuel gas supply pump 18, the air supply blower 20 and the reforming water supply pump 22 are increased, and the fuel gas and air to the fuel cell stack 16 and the reformer ( When the amount of reforming water supplied to the fuel cell 4 increases and the power generation output of the fuel cell 4 decreases, the rotational speeds of the fuel gas supply pump 18, the air supply blower 20, and the reforming water supply pump 22 decrease. The supply amount of fuel gas and air to the fuel cell stack 16 and reforming water to the reformer are reduced.

  Further, the power generation output control means 6 in the fuel cell unit 2A (2B, 2C, 2D) is composed of, for example, a microprocessor, and includes a power value calculation means 24 and an operation control means 26. The power value calculating means 24 calculates the power value of the commercial power line 30 using a current value described later, and the operation control means 26 is based on the calculated power value of the power value calculating means 24, the fuel gas supply pump 18, The air supply blower 20 and the reforming water supply pump 22 are controlled to operate as described later.

  In this embodiment, the commercial power supply 28 is connected to the power supply line 10 via the commercial power line 30, and the commercial power (for example, 100 V, 60 Hz AC power) from the commercial power supply 28 is supplied to the commercial power line 30 and the power. It is supplied to the electric power load 12 through the supply line 10. The commercial power line 30 is provided with a main breaker 32. When the main breaker 32 is turned off, supply of commercial power from the commercial power supply 28 to the power supply line 10 is stopped. Further, a power meter 34 is disposed in the commercial power line 30 (specifically, a portion upstream of the main breaker 32), and the power meter 34 measures the power flowing through the commercial power line 30.

  The parallel operation system including the fuel cell units 2A to 2D is configured as follows in order to prevent the power generation output from the fuel cell units 2A to 2D from flowing backward to the commercial power source 28. . That is, when the power load 12 is equal to or smaller than the total power (2800 W) of the rated power generation output (for example, 700 W) of the four fuel cell units 2A to 2D, the power from the fuel cell units 2A to 2D Since the power load 12 can be covered by the power generation output, the power generation output from the fuel cell units 2A to 2D is sent to the power load 12 through the power generation output lines 8A to 8D and the power supply line 10, and the power load 12 is consumed. On the other hand, when the power load 12 is larger than the total power (2800 W) of the rated power output (for example, 700 W) of the four fuel cell units 2A to 2D, this power load is generated with the power output from the fuel cell units 2A to 2D. 12, in this case, the power generation output from the fuel cell units 2 </ b> A to 2 </ b> D is sent to the power load 12 through the power generation output lines 8 </ b> A to 8 </ b> D and the power supply line 10, and from the commercial power supply 28. Commercial power is supplied to the power load 12 through the commercial power line 30 and the power supply line 10, and power from both is consumed by the power load 12.

  In general, the power generation outputs of the fuel cells 4 of the fuel cell units 2A to 2D are not constant, and some fluctuations occur. For example, the fuel cell units 2A to 2A It is configured to purchase an extra 2 to 5% of the rated power output of 2D (in other words, when the power load 12 is 2800 W, for example, 14 to 35 W of commercial power is purchased). Thus, description will be made by applying to the case where control is performed in consideration of fluctuations in the power generation output.

  In this embodiment, in order to control the power generation output of the fuel cell 4 of the fuel cell units 2A to 2D, the first current converters 36A to 36D correspond to the power generation output control means 6 of each fuel cell unit 2A to 2D. Is provided. The first current converters 36 </ b> A to 36 </ b> D are disposed in the commercial power line 30 (specifically, a portion between the power meter 34 and the main breaker 32) and detect a current flowing through the commercial power line 30. The first current converters 36 </ b> A to 36 </ b> D have a current transformation ratio of, for example, 3000: 1 (so-called current transformation ratio: 3000), and when the current of 3 A flows through the commercial power line 30, for example, A current of 1 mA flows through each of the current converters 36A to 36D. Detection signals (detection currents) from the first current converters 36A to 36D are supplied to the power generation output control means 6 of the corresponding fuel cell units 2A to 2D.

  In addition, second current converters 38A to 38D are provided corresponding to the respective fuel cells 4 of the fuel cell units 2A to 2D, and these second current converters 38A to 38D are connected to the power generation output lines of the corresponding fuel cells 4. Current flowing through 8A to 8D (AC current converted into AC power by DC / AC converters 11A to 11D) is detected. The second current converters 38A to 38D can be configured, for example, from the same ones as the first current converters 36A to 36D described above, and the current transformation ratio is configured to 3000: 1.

  Furthermore, current transformers 40A to 40D are provided corresponding to the second current converters 38A to 38D corresponding to the fuel cell units 2A to 2D, respectively. The current transformers 40A to 40D are arranged downstream of the fuel cell units 2A to 2D, and reduce the alternating current flowing through the power generation output lines 8A to 8D of the fuel cell units 2A to 2D with a predetermined current transformation ratio. For example, one having a current transformation ratio of 1 to 100: 1 can be advantageously used. For example, when a current ratio of 10: 1 (so-called current ratio: 10) is used, the current flowing through the power generation output lines 8A to 8D of the fuel cell units 2A to 2D is transformed to 1/10. The second current converters 38 </ b> A to 38 </ b> D detect currents transformed by the corresponding current transformers 40 </ b> A to 40 </ b> D. Detection signals (detection currents) from the second current converters 38A to 38D are sent to the power generation output control means 6 of the corresponding fuel cell units 2A to 2D. Note that the current transformers 40A to 40D can be omitted. When the current transformers 40A to 40D are omitted, the current transformer ratio in the following description is 1.

  The first current converters 36A to 36D and the second current converters 38A to 38D corresponding to the fuel cell units 2A to 2D are electrically connected to the power generation output control means 6 as shown in FIG. The k-side output terminal (first output terminal) of the first current converter 36A (36B, 36C, 36D) is connected to the K-side input terminal (first output terminal) of the power generation output control means 6 via the current line 42 (first current line). And its l-side output terminal (second output terminal) is connected to the L-side input terminal (second input terminal) of the power generation output control means 6 via the current line 44 (second current line). The The second current converter 38A (38B, 38C, 38D) is electrically arranged in parallel with the first current converter 36A (36B, 36C, 36D), and its l-side output terminal (first output) 4 output terminal) is connected to the K side input terminal (first input terminal) of the power generation output control means 6 via the current line 42, and the k side output terminal (third output terminal) is generated via the current line 44. The output control means 6 is connected to the L side input terminal (second input terminal).

  Since the first current converter 36A (36B, 36C, 36D) and the second current converter 38A (38B, 38C, 38D) are connected in this way, the power generation of the fuel cell unit 2A (2B, 2C, 2D) The current input to the output control means 6 is the difference in detection current between the detection current of the first current converter 36A (36B, 36C, 36D) and the detection current of the second current converter 38A (38B, 38C, 38D) ( The power generation output control means 6 controls the power generation output of the corresponding fuel cell 4 as follows using this difference signal.

  The power (so-called purchased power Z) flowing through the commercial power line 30 can be calculated using the detected current of the first current converter 36A (36B, 36C, 36D). For example, the actual current value flowing through the commercial power line 30 can be obtained by multiplying the current value of the first current converter 36A (36B, 36C, 36D) by, for example, 3000, and the voltage is the power generation output of the fuel cell 4. It can be obtained from the line 8A (8B, 8C, 8D), and the power (purchased power Z) flowing through the commercial power line 30 can be obtained from the current value and the voltage value.

  Further, the electric power flowing through the power generation output line 8A (8B, 8C, 8D) using the detected current of the second current converter 38A (38B, 38C, 38D), that is, the fuel cell unit 2A (2B, 2C, 2D). The power generation output PA (PB, PC, PD) of the fuel cell 4 can be calculated. In this case, the current flowing through the power generation output line 8A (8B, 8C, 8D) is 1 / X times (current transformation ratio: X) by the current transformer 40A (40B, 40C, 40D). The calculated power using the detected current of the second current converter 38A (38B, 38C, 38D) is 1 / X times the power PA / X (PB / P) of the power generation output PA (PB, PC, PD) of the fuel cell 4. X, PC / X, PD / X). For example, by multiplying the current value of the second current converter 38A (38B, 38C, 38D) by, for example, 3000, a current value 1 / X times the actual current flowing through the power generation output line 8A (8B, 8C.8D) is obtained. Further, the voltage can be obtained from the power generation output line 8A (8B, 8C, 8D) of the fuel cell 4, and 1 / X times the current value and the voltage value, 1 / X of the power generation output of the fuel cell 4 can be obtained. X times the power PA / X (PB / X, PC / X, PD / X) can be obtained.

  In this embodiment, since the first current converter 36A (36B, 36C, 36D) and the second current converter 38A (38B, 38C, 38D) are reversely connected, the first current converter 36A (36B, 36C, 38D) and the power QA (QB, QC.QD) calculated based on the detected currents of the second current converter 38A (38B, 38C, 38D) are 1 of the purchased power Z and the power generation output of the fuel cell 4. / X times the power PA / X (PB / X, PC / X, PD / X) and the difference power (QA = Z-PA / X) [(QB = Z-PB / X), (QC = Z- PC / X), (QD = Z-PD / X)].

  In this way, the power (purchased power Z) of the commercial power line 30 and the power generation outputs PA, PB, PC, PD of the plurality of fuel cell units 2A, 2B, 2C, 2D are monitored to control the power generation output of the fuel cell 4. As a result, the power generation outputs of the plurality of fuel cell units 2A, 2B, 2C, 2D can be output substantially uniformly and stably, and the power generation efficiency of the plurality of fuel cell systems 2A to 2D as a whole can be increased. Can do.

[Simulation for parallel operation]
Next, referring to FIG. 4 and FIG. 5, the power generation efficiency of the entire system is better when operation control is performed so that the power generation outputs of a plurality (four in this embodiment) of fuel cell units 2A to 2D are equal. Explain that it will be higher. FIG. 4 shows the relationship between the power generation output and the power generation efficiency when, for example, a solid oxide fuel cell with a rated power output of 700 W is used as the fuel cell 4, and four fuel cell systems are used with reference to FIG. The simulation results of the power generation efficiency when the power generation outputs of 2A to 2D are dispersed and when the power generation outputs are equalized as in the above-described embodiment are as shown in FIG. In FIG. 5, when the power generation outputs of the fuel cell units 2A to 2D are dispersed, the average power generation efficiency obtained by averaging the power generation efficiencies of the fuel cell units 2A to 2D and the power generation outputs of the fuel cell units 2A to 2D are equalized. When the power generation efficiency at the average power generation output of each of the fuel cell units 2A to 2D is compared and equalized, the power generation efficiency is higher as a whole system. ".

  For example, in the first stage of FIG. 5, the power generation output of the fuel cell unit 2A (2B, 2C, 2D) is 83W (564W, 153W, 696W), and the power generation efficiency at this time is 15.40% (44.01). %, 24.10%, 46.03%), the average power generation efficiency of the entire system is 37.71%. Further, the average power generation output of the fuel cell units 2A to 2D at this time is 374.00 W, and the power generation efficiency of each of the fuel cell units 2A to 2D at this time is 37.97%. It shows that the power generation efficiency is higher by 0.26% when the power generation outputs of the fuel cell systems 2A to 2D are equalized.

  Such a simulation of the comparison of power generation efficiency was analyzed a plurality of times using 100 patterns of random number data, and FIG. 5 shows a part of the analysis result. Summarizing the analysis results, as shown in the determination column, the power generation efficiency increases with a probability of approximately 70% (71% in the simulation result) when the power generation outputs of the fuel cell systems 2A to 2D are equalized. The result was obtained. Based on this result, as described above, based on the detected currents of the first current converters 36A to 36D and the second current converters 38A to 38D, the power generation output of the corresponding fuel cell 4 is controlled to be equal. Thus, the power generation efficiency of the whole of the plurality of fuel cell systems 2A to 2D can be increased.

  Here, with reference to FIG.6 and FIG.7, current transformation ratio (X) of current transformer 40A-40D is examined. 6A to 6D, a solid line F indicates a change in the power load 12, a solid line T indicates a change in the total power generation output of the fuel cell units 2A to 2D, and a solid line A (B, C, D). Indicates changes in the power generation output of the fuel cell unit 2A (2B, 2C, 2D). In this simulation, the performance of the fuel cell unit 2D, the fuel cell unit 2C, the fuel cell unit 2B, and the fuel cell unit 2A is high in order (highest performance: 2D> 2C> 2B> 2A) (that is, the output increases) Fast).

  As understood from FIG. 6, when the current transformation ratio X of the current transformers 40 </ b> A to 40 </ b> D affects the power generation output of the fuel cell units 2 </ b> A to 2 </ b> D and the current transformation ratio X of the current transformers 40 </ b> A to 40 </ b> D increases. The total power generation output T of the fuel cell units 2A to 2D reaches almost the power load F [(see FIGS. 6 (b), (c) and (d))], but the current transformation ratio X is small. Then, the total power generation output T of the fuel cell units 2A to 2D does not reach the power load F [see FIG. 6 (a)], the operating efficiency of the entire system is deteriorated, and the purchased power Z through the commercial power line 30 is reduced. Will increase. On the other hand, if the current transformation ratio X of the current transformers 40A to 40D increases, the power generation output of the fuel cell unit becomes very unstable (see FIG. 6C), or if this current transformation ratio X further increases, The power generation outputs of the two low performance fuel cell units 2A and 2B become almost zero (see FIG. 6D), and the power generation outputs of the four fuel cell units 2A to 2D can be made equal. However, when the current transformation ratio X becomes smaller, the power generation output of the fuel cell unit becomes stable (see FIGS. 6A and 6B), and the power generation output of the four fuel cell units 2A to 2D. Becomes even.

  Here, paying attention to the total power generation output T of the fuel cell units 2A to 2D, and simulating the relationship between the current transformation ratio X of the current transformers 40A to 40D and the total power generation output T, the result as shown in FIG. became. As can be seen from FIG. 7, when the current transformation ratio X of the current transformers 40A to 40D is reduced, the total power output T of the four fuel cell units 2A to 2D is somewhat reduced.

  From the results shown in FIGS. 6 and 7, the current transformation ratio X of the current transformers 40A to 40D is 1 to 100 unless some decrease in the total power output T of the plurality of fuel cell units 2A to 2D is considered. (1 ≦ X ≦ 100) is desirable, and considering the slight decrease in the total power generation output T, it is desirable that the range is 3 to 100 (3 ≦ X ≦ 100).

  FIG. 8 shows the relationship between the elapsed time when the power load 12 is sufficient (for example, power load: 3000 W) and the change state of the power generation output of the four fuel cell units 2A to 2D, as shown in FIG. Finally, it was confirmed that all of the four fuel cell units 2A to 2D were finally in the rated power generation output operation (power generation output: 700 W).

  FIGS. 9A and 9B show simulation results when the output increase speeds of the four fuel cell units 2A to 2D are the same and there is a difference in the output decrease speed. In this simulation, it is assumed that the output descending speed increases in the order of the fuel cell unit 2D, the fuel cell unit 2C, the fuel cell unit 2B, and the fuel cell unit 2A (in descending order of the output descending speed: 2D> 2C> 2B> 2A).

  As is clear from FIG. 9, the power output of the fuel cell unit is higher when the output lowering speed is smaller (see FIG. 9A), and the current transformation ratio of the current transformers 40A to 40D is smaller. It was found that the difference in power generation output between the fuel cell units 2A to 2D was small.

  FIGS. 10A and 10B show simulation results of the behavioral states of the fuel cell units 2A to 2D when the load state of the electric load 12 fluctuates. As is clear from FIGS. 10A and 10B, the four fuel cell units 2A to 2D operate so that their power generation outputs follow the load fluctuation, and the current transformation of the current transformers 40A to 40D. When the ratio X was 100 and when the current transformation ratio X was 30, it was confirmed that the behavior of these fuel cell units 2A to 2D was almost the same.

  FIG. 11 shows a simulation result when one of the four fuel cell units 2A to 2D trips. In this example, the output state of the power generation output of the remaining three fuel cell units 2B to 2D when the fuel cell unit 2A trips at an elapsed time of 500 s is shown. In this simulation, it is assumed that the fuel cell unit 2D, the fuel cell unit 2C, the fuel cell unit 2B, and the fuel cell unit 2A have higher performance (in order of higher performance: 2D> 2C> 2B> 2A).

  As is clear from FIG. 11, for example, when the fuel cell unit 2A trips, the power generation outputs of the remaining three fuel cell units 2B to 2D increase, and the total power generation output of these fuel cell units 2B to 2D is the power load. It was confirmed that the fuel cell unit 2A can be operated without any problem even when the fuel cell unit 2A is tripped.

  FIGS. 12A to 12D show simulation results when the power generation outputs of the fuel cell units 2A to 2D fluctuate vertically within ± 2 W (so-called fluctuation occurs). In this simulation as well, the performance of the fuel cell unit 2D, the fuel cell unit 2C, the fuel cell unit 2B, and the fuel cell unit 2A is assumed to be higher in order (higher performance: 2D> 2C> 2B> 2A).

  As apparent from FIGS. 12A to 12D, when the current transformation ratio X of the current transformers 40A to 40D is 100, the power generation output of the fuel cell units 2A to 2D is affected by the fluctuation of the power generation output. Becomes unstable, and when the current transformation ratio X becomes 30, the influence of this fluctuation is reduced, and the instability of the power generation output of the fuel cell units 2A to 2D is solved to some extent. When it is lowered to 10, the influence of this fluctuation is almost eliminated, and the power generation outputs of the fuel cell units 2A to 2D become stable. For this reason, when considering fluctuations in the power generation output of the fuel cell units 2A to 2D, the current transformation ratio X of the current transformers 40A to 40D is preferably 30 or less (X ≦ 30).

  The power generation output of each fuel cell 4 of the fuel cell units 2A to 2D described above is similarly controlled by the corresponding power generation output control means 6 as shown in FIG. Referring to FIG. 3 together with FIG. 1 and FIG. 2, for example, control of the power generation output of the fuel cell unit 2A (2B, 2C, 2D) will be described. The first current converter 36A detects the current flowing through the commercial power line 30. (Step S1), the second current converter 38A detects the current flowing through the power generation output line 8A of the fuel cell 4 (Step S2). In this embodiment, the first current converter 36 </ b> A detects a current value that is 1/3000 times the actual current flowing through the commercial power line 30. The current flowing through the power generation output line 8A of the fuel cell 4 is transformed into a current value of 1 / X times (X: current transformation ratio) by the current transformer 40A, and the second current converter 38A is a current transformer. A current value 1/3000 times the current value transformed by 40A, that is, a current value 1 / 3000X times the actual current value of the current flowing through the power generation output line 8A is detected.

  The detected currents from the first and second current converters 36A and 38A are supplied to the power generation output control means 6. At this time, since the first current converter 36A and the second current converter 38A are electrically connected in parallel and reversely connected, the difference current between the first and second current converters 36A and 38A (so-called difference signal) ) Is sent to the power generation output control means 6. Then, the power value calculation means 24 of the power generation output control means 6 calculates a power value, that is, [power generation output (PA / X) multiplied by purchased power (Z) -1 / X] based on this difference signal ( Step S3).

  Thereafter, the operation control means 26 determines whether to prevent reverse power flow based on the power value [purchased power (Z) -1 / X times power generation output (PA / X)] calculated by the power value calculation means 24 (step S4). ).

  In this determination, determination is made based on whether (Z-PA / X) is larger or smaller than Y (where Z: purchased power, PA: power generation output of the fuel cell unit 2A, X: current transformer 40A) Current ratio, Y: reverse power flow prevention judgment value).

  If this determination result is (Z−PA / X)> Y, it is determined that the power generation output of the fuel cell unit 2A (ie, the fuel cell 4) is small and the purchased power Z is large, and in this case, step S5. From step S6, the power generation output control means 6 controls the fuel cell 4 so that the power generation output increases. That is, the operation control means 26 controls the fuel gas supply pump 18, the air supply blower 20, and the reforming water supply pump 22 so that the number of revolutions increases, and thus controls the fuel cell stack 16. The amount of reformed water supplied to the fuel gas and air and the reformer (not shown) increases, and the power generation output of the fuel cell 4 increases.

  On the other hand, if this determination result is (Z−PA / X) <Y, it is determined that the power generation output of the fuel cell unit 2A (ie, the fuel cell 4) is large and the purchased power Z is small. The process proceeds from step S5 to step S7 to step S8, where the power generation output control means 6 controls the fuel cell 4 so that the power generation output decreases. That is, the operation control means 26 controls the fuel gas supply pump 18, the air supply blower 20, and the reforming water supply pump 22 so that the number of revolutions is reduced, and thus controls the fuel cell stack 16. The amount of reformed water supplied to the fuel gas and air and the reformer (not shown) is reduced, the power generation output of the fuel cell 4 is reduced, and the occurrence of reverse power flow is prevented.

  If this determination result is (Z−PA / X) = Y, it is determined that the power generation output of the fuel cell unit 2A (that is, the fuel cell 4) is appropriate in relation to the purchased power Z. Then, the process proceeds from step S5 to step S9 through step S7, and the power generation output control means 6 controls the fuel cell 4 so that the power generation output is maintained. That is, the operation control means 26 maintains the rotational speeds of the fuel gas supply pump 18, the air supply blower 20 and the reforming water supply pump 22 as they are, thereby maintaining the power generation output of the fuel cell 4.

  By controlling the fuel cell unit 2A (2B, 2C, 2D) in this way, reverse power flow can be prevented even if the power generation output fluctuates with the purchased power Z being constant.

  The embodiment of the fuel cell unit parallel operation system according to the present invention has been described above. However, the present invention is not limited to such an embodiment, and various changes or modifications can be made without departing from the scope of the present invention. Is possible.

  For example, in the above-described embodiment, the present invention is applied to a parallel operation system using four fuel cell units 2A to 2D having substantially the same configuration (for example, a solid oxide fuel cell having a rated power output of 700 W as the fuel cell 4). Although described, the present invention is not limited to such a configuration, and the present invention can be similarly applied to a parallel operation system using two, three, or five or more fuel cell units having substantially the same configuration.

  In addition, such a parallel operation system is similarly applied to a system in which two or three or more fuel cell units are combined in different types (for example, different rated power output or different fuel cell types). be able to.

[Simulation when two units are operated in parallel]
Next, a simulation result applied to a parallel operation system using two fuel cell units 2G and 2H having different rated power generation outputs will be described. This simulation is applied to a parallel operation system using a fuel cell unit 2G having a fuel cell with a rated power output 700W and a fuel cell unit 2H having a fuel cell with a rated power output 500W.

  13A to 13D, a solid line F indicates a change in the power load 12, a solid line T indicates a change in the total power generation output of the fuel cell units 2G and 2H, and a solid line G (H) indicates a fuel cell unit. A change in the power generation output of 2G (2H) is shown. In this simulation, it is assumed that the current transformation ratio X of the current transformer is 10 and the output increase speeds of the fuel cells of the two fuel cell units 2G and 2H are the same. This condition is shown in FIGS. The same is true for the simulation results shown.

  As is clear from FIG. 13, when the current transformation ratio X is 10, the power generation output of the fuel cell units 2G and 2H is very stable when the load is constant. When the load is small, the power generation outputs of the two fuel cell units 2G and 2H are the same (see FIGS. 13 (a) and (b)), and the load increases and one fuel cell unit 2H becomes It has been found that when the rated power output (500 W) is reached, the power generation output of the other fuel cell unit 2G increases until the rated power output (700 W) is reached for load fluctuations exceeding that [FIG. 13 (c). And (d)].

  FIGS. 14A to 14C show the simulation results when the current transformer ratio X of the current transformer is changed in the state of the power load 800W. As understood from FIG. 14, even when the current transformation ratio X is changed to 1, 100, and 1000, the power generation outputs of the fuel cell units 2G and 2H are the same as when the current transformation ratio is 10 (simulation result of FIG. 13). Even and stable (the power generation outputs of the two fuel cell units 2G and 2H in FIGS. 14A to 14C overlap), the current transformation ratio increases (for example, the current transformation ratio X is 1000). The total power output of the two fuel cell units 2G and 2H increases and approaches the power load (see FIG. 14C), but the current transformer ratio X is 1 In some cases, it was found that the total power output of the two fuel cell units 2G and 2H is smaller than the power load, and the operation efficiency of the entire system is lowered.

  FIGS. 15A to 15C show simulation results when the power generation outputs of the fuel cell units 2G and 2H fluctuate up and down within ± 2 W (so-called fluctuation occurs). As is apparent from FIGS. 15A to 15C, when the current transformer ratio X of the current transformer is 1000, the power generation output of the fuel cell units 2G and 2H is extremely affected by the fluctuation of the power generation output. However, when the current transformation ratio X is reduced to 100, the influence of this fluctuation is reduced, and the instability of the power generation output of the fuel cell units 2G and 2H is resolved to some extent. When 1, the influence of this fluctuation is eliminated and the power generation output of the fuel cell units 2G and 2H becomes stable. For this reason, when considering fluctuations in the power generation output of the two fuel cell units 2G and 2H having different power generation outputs, the current transformation ratio X of the current transformer is preferably 100 or less.

  FIG. 16 shows the power generation of two fuel cell units 2G and 2H using a fuel cell unit 2G having a fuel cell with a rated power output 700W and a fuel cell unit 2H having a fuel cell with a rated power output 500W. The simulation results are shown when the output increase speed is different (in this example, the fuel cell unit 2G has a higher power generation output increase speed than the other fuel cell units 2H). 17 and 18 also have the same conditions as described above.

  16A to 16D, a solid line F indicates a change in the power load 12, a solid line T indicates a change in the total power generation output of the fuel cell units 2G and 2H, and a solid line G (H) indicates a fuel cell unit. A change in the power generation output of 2G (2H) is shown. In this simulation, the variation ratio X of the current transformer is 10.

  As is clear from FIG. 16, when the current transformation ratio X is 10, the power generation outputs of the fuel cell units 2G and 2H are very stable when the load is constant, as in the simulation result of FIG. Yes. When the load is small, the power generation outputs of the two fuel cell units 2G and 2H are the same (see FIGS. 16 (a) and (b)), and the load increases so that one fuel cell unit 2H When the rated power generation output (500 W) is reached, the power generation output of the other fuel cell unit 2G rises until the rated power generation output (700 W) is reached for load fluctuations exceeding that [FIGS. 16 (c) and (d). reference〕.

  FIGS. 17A to 17C show simulation results when the current transformation ratio X of the current transformer is changed. As can be understood from FIG. 17, when the current transformation ratio X is 1 and 100, the power generation outputs of the fuel cell units 2G and 2H are stable, but the current transformation ratio increases (for example, the current transformation ratio X is 1000), the power generation outputs of the two fuel cell units 2G and 2H become very unstable (see FIG. 17C), and the power generation outputs of the two fuel cell units 2G and 2H are not equal. For this reason, the current transformer ratio X of the current transformer is desirably 100 or less. When the current transformation ratio X of the current transformer is 1, the power generation outputs of the two fuel cell units 2G and 2H are equal as in the simulation result of FIG. 14, but these fuel cell units 2G , 2H total power generation output becomes smaller than the load, and the operating efficiency of the entire system is reduced.

  FIGS. 18A to 18C show simulation results when the power generation outputs of the fuel cell units 2G and 2H fluctuate up and down within ± 2 W (so-called fluctuation occurs). As is clear from FIGS. 18A to 18C, when the current transformer ratio X of the current transformer is 1000, the power generation output of the fuel cell units 2G and 2H is extremely affected by the fluctuation of the power generation output. However, when the current transformation ratio X is reduced to 100, the influence of this fluctuation is reduced, and the instability of the power generation output of the fuel cell units 2G and 2H is resolved to some extent. When 1, the influence of this fluctuation is eliminated and the power generation output of the fuel cell units 2G and 2H becomes stable. For this reason, when considering fluctuations in the power generation output of the fuel cell units 2G and 2H, the current transformer ratio X of the current transformer is preferably 100 or less.

[Demonstration experiment when four units are operated in parallel]
Next, in order to confirm the simulation results described above, the following demonstration experiment was performed using the parallel operation system shown in FIGS. 1 and 2. As the fuel cell units 2K to 2N, four solid oxide fuel cell units having a rated power output of 700 W (the power generation outputs fluctuate up and down within a few W) are used, and each of the fuel cell units 2K to 2N is used. Two types of current transformers 40A to 40D having a current transformation ratio of 10 and a current transformation ratio of 100 are used. For those having a current transformation ratio of 10, the secondary side is short-circuited with a conductor so that CT can be clipped up to 3 turns. In the case of a current transformation ratio of 100, the secondary side was short-circuited with a conductor so that it could be clipped up to 5 turns. The used fuel cell units 2K to 2N had higher system performance in the order of the fuel cell unit 2K, the fuel cell system 2L, the fuel cell system 2M, and the fuel cell system 2N (2K>2L>2M> 2N).

  For the current transformers 40A to 40D having a current transformation ratio of 10, these are attached to the distribution board of the parallel operation system, and the CTs of the current transformers 40A to 40D are turned 1 turn (current transformation ratio: 10), 2 turns (current transformation) Ratio: 5) and 3 turns (current transformation ratio: 3.3) were clipped in order to obtain various data. Moreover, about the current transformers 40A-40D of the current transformation ratio 100, it replaces with the thing of 10 current transformation ratios, attaches to a distribution board, CT of current transformer 40A-40D is 1 turn (current transformation ratio: 100), Various data were obtained by sequentially clipping 2 turns (current transformation ratio: 50), 3 turns (current transformation ratio: 33) and 5 turns (current transformation ratio: 20). In the case of the current transformation ratio 1, data is acquired by clipping the CT directly to the power generation output line (8A-8D) without going through the current transformers 40A-40D, and in the case of the current transformation ratio ∞. The data was acquired by disconnecting the secondary side line (detection current line) of CT of the current transformers 40A to 40D from the circuit.

  The various acquired data when the power load is set to 800 W is as shown in FIG. 19, and the various acquired data when the power load is set to 1600 W (or 2400 W) is shown in FIG. 20 (or FIG. 21). The obtained data when the power load is set to a value exceeding 3800 W (3500 W, 3000 W, 4000 W) was as shown in FIG. 19 to 22, a solid line F indicates a change in the power load 12, a solid line T indicates a change in the total power generation output of the fuel cell units 2K to 2N, a solid line J indicates a power generation efficiency of the system, and a solid line K, L, M, and N indicate changes in the power generation output of the fuel cell units 2K, 2L, 2M, and 2N.

  As a result of this demonstration experiment, as apparent from FIGS. 19 to 21, when the power load 12 is smaller than 2800 W (the total power generation output of the rated power generation output), the current transformation ratio of the current transformers 40 </ b> A to 40 </ b> D is smaller than 33. The power generation outputs of the four fuel cell units 2K to 2N are substantially uniform, and the power generation efficiency of the entire system can be maintained high. However, when the current transformation ratio exceeds 50, the power load 12 decreases as the power load 12 decreases. It was confirmed that the power generation output of each of the fuel cell units 2K to 2N greatly deviated and the power generation efficiency of the entire system was lowered. When the current transformation ratio of the current transformers 40A to 40D is 1, the power generation outputs of the four fuel cell units 2K to 2N are substantially uniform, but the total power generation output of the four fuel cell units 2K to 2N is As a result, the power generation efficiency of the entire system was lowered, and the same experimental results as the simulation results described above were obtained.

  When the power load 12 exceeds 2800 W (total power generation output of the rated power generation output), as is apparent from FIG. 22, the four fuel cell units 2K to 2N have the current ratio of the current transformers 40A to 40D. It operated with the rated power output (700W) without being affected.

  FIG. 23 shows the relationship between the power generation output of the system (total power generation output) and the power generation efficiency of the system using the result of the verification experiment described above. As is clear from FIG. 23, in order to operate the system with high power generation efficiency even when the power load 12 fluctuates, the current transformation ratio of the current transformers 40A to 40D is preferably in the range of 3.3 to 33. The current transformation ratio is more preferably in the range of 3.3 to 20, and the results of the demonstration experiment almost coincide with the simulation results described above.

  FIG. 24 shows the relationship between the power load 12 and the power generation efficiency of the system when the current transformation ratio is 10, and the solid line KP shows the power generation efficiency when the four fuel cell units 2K to 2N are operated in parallel. The solid line KS indicates the relationship with the power generation efficiency when the power generation output when the fuel cell unit is operated alone is quadrupled. As is apparent from FIG. 24, when the current transformation ratio of the current transformers 40A to 40D is set to 10 (in other words, a range of around 10), the fuel cell units 2K to 2N are almost alone in the total power generation output. It is higher than the power generation efficiency of the fuel cell system at the time of operation (power generation efficiency at a power generation output obtained by quadrupling the power output of the single operation). Accordingly, the power generation outputs of the four fuel cell units 2K to 2N are substantially equal, and the power generation efficiency of the four fuel cell units 2K to 2N is higher than the power generation efficiency of the single operation in almost all power generation output regions. Considering that it is high, it can be seen that the optimum current transformation ratio of the current transformers 40A to 40D is around 10.

[Second Embodiment of Parallel Operation System of Fuel Cell Units]
Next, a second embodiment of the fuel cell unit parallel operation system will be described with reference to FIG. In FIG. 25, in the parallel operation system of the second embodiment, the second current converters 52A to 52D provided corresponding to the fuel cell units 2A to 2D are improved, and the second current converter A current transformer (not shown) is incorporated in 52A to 52D, and the second current converters 52A to 52D in this embodiment are the same as the second current converters 38A to 38D in the embodiment of FIGS. The devices 40A to 40D are integrally configured. Even if such second current converters 52 </ b> A to 52 </ b> D are used, the same effect as described above can be achieved.

[Third embodiment of parallel operation system of fuel cell units]
Next, with reference to FIG.26 and FIG.27, 3rd Embodiment of the parallel operation system of a fuel cell unit is described. In the parallel operation system of the third embodiment, the fuel cell systems 2A to 2D are configured to be applicable to both parallel operation and single operation.

  26 and 27, in the parallel operation system of the third embodiment, switch means 62A to 62D are provided in relation to the second current converters 38A to 38D of the fuel cell units 2A to 2D. The second current converter 38A (38B, 38C, 38D) is arranged on the U-phase line 64 and the V-phase line 65 of the power generation output line 8A (8B, 8C, 8D) of the fuel cell unit 2A (2B, 2C, 2D). It is installed. In relation to this, the first current converter 36 </ b> A (36 </ b> B, 36 </ b> C, 36 </ b> D) is disposed on the U-phase line 66 and the V-phase line 67 of the commercial power line 30. The configurations of the fuel cell units 2A to 2D, the first current converters 36A to 36D, and the second current converters 38A to 38D are substantially the same, and hereinafter, a set of these configurations, that is, the fuel cell unit 2A (2B To 2D), the first current converter 36A (36B, 36C, 36D) and the second current converter 38A (38B, 38C, 38D) will be described.

  The k-side output terminal (first output terminal) of the first current converter 36AU (or 36AV) disposed on the U-phase line 66 (or V-phase line 67) of the commercial power line 30 is the first current line 70 (or 71) and is electrically connected to the K-side input terminal (first input terminal) of the power generation output control means 6 via its 1-side output terminal (second output terminal) through the second current line 72 (or 73). To the L-side input terminal (second input terminal) of the power generation output control means 6.

  Further, the k-side output terminal (first output terminal) of the second current converter 38AU (or 38AV) disposed in the U-phase line 64 (or V-phase line 65) of the power generation output line 8A is the third current line 74. (Or 75) is electrically connected to the second current line 72 (or 73) from the first current converter 36AU (or 36AV), and its l-side output terminal (second output terminal) is the fourth current. It is electrically connected to the first current line 70 (or 71) from the first current converter 36AU (or 36AV) via the line 76 (or 77). Accordingly, also in this embodiment, as described above, the second current converter 38AU (or 38AV) disposed in the U-phase line 64 (or V-phase line 65) of the power generation output line 8A is not connected to the commercial power line. The first current converter 36AU (or 36AV) disposed on the 30 U-phase lines 66 (or V-phase lines 67) is electrically connected in reverse in parallel.

  In this embodiment, as the second current converters 38A to 38D, the one used in the embodiment shown in FIG. 25 (that is, the one in which a current transformer is incorporated in advance) is used. May be used (that is, a current transformer is not incorporated and it is necessary to provide a separate current transformer), and in this case, it may be used in the same manner as described above. it can.

  In this embodiment, the switch means 62A (62B, 62C, 62D) includes the third current lines 74, 75 and the fourth current from the second current converters 38AU, 38AV (38BU, 38BV, 38CU, 38CV, 38DU, 38DV). The lines 76 and 77 are disposed. As shown in FIGS. 26 and 27, the switch means 62A (62B, 62C, 62D) is held in the closed state (on state) when the plurality of fuel cell units 2A to 2D are operated in parallel, and the fuel means When one of battery units 2 </ b> A to 2 </ b> D is operated independently, it is held in an open state (off state). Other configurations of the third embodiment are substantially the same as those of the first embodiment described above.

  In the third embodiment, when the switch means 62A (62B, 62C, 62D) is held in the closed state for parallel operation, the second current converters 38AU, 38AV (38BU, 38BV) as understood from FIG. , 38CU, 38CV, 38DU, 38DV) is supplied to the generated power control means 6 through the third current lines 74, 75 and the fourth current lines 76, 77, and accordingly, the plurality of fuel cell units 2A to 2A to 2D is detected current of the first current converters 36AU, 36AV (36BU, 36BV, 36CU, 36CV, 36DU, 36DV) and the second current converters 38AU, 38AV (38BU, 38BV, 38CU, 38CV, 38DU, 38DV). Based on this, the operation is controlled (that is, the power generation output is controlled), whereby the fuel cell unit 2A Power output of the 2D) is operated controlled so as to be substantially uniform, can be operated to increase the power generation efficiency of the entire system.

  On the other hand, when the switch means 62A (62B, 62C, 62D) is opened for independent operation, the detection current of the second current converters 38AU, 38AV (38BU, 38BV, 38CU, 38CV, 38DU, 38DV) is generated. Therefore, the fuel cell unit 2A (or 2B, 2C, 2D) is operated and controlled based on the detected current from the first current converter 36A (or 36B, 36C, 36D) (ie, the fuel cell unit 2A (or 2B, 2C, 2D)). Power generation output is controlled) and can be operated independently as required.

  In this way, by providing the switch means 62A to 62D in relation to the second current converters 38A to 38D of the fuel cell units 2A to 2D, the fuel cell units 2A to 2B can be operated independently and in a plurality of units without improving the fuel cell units 2A to 2B. It can be applied to parallel operation by.

[Fourth Embodiment of Fuel Cell Unit Parallel Operation System]
Next, a fourth embodiment of the fuel cell unit parallel operation system will be described with reference to FIG. In the parallel operation system of the fourth embodiment, two switch means, that is, first and second switch means are provided.

  In FIG. 28, in the fourth embodiment, the first switch means 62A (62B, 62C, 62D) is similar to the third embodiment in that the second current converters 38AU, 38AV (38BU, 38BV, 38CU) , 38CV, 38DU, 38DV) from the third current line 74, 75 and the fourth current line 76, 77. In addition, the third current lines 74 and 75 and the fourth current lines 76, on the second current converter 38 A (38 B, 38 C, 38 D) side from the arrangement part of the first switch means 62 A (62 B, 62 C, 62 D). Connection lines 84 and 85 are provided to connect to 77, and second connection means 82A (82B, 82C and 82D) are provided on the connection lines 84 and 85. Other configurations of the fourth embodiment are substantially the same as those of the third embodiment described above.

  In the fourth embodiment, when the plurality of fuel cell units 2A to 2D are operated in parallel, as shown in FIG. 28, the first switch means 62A to 62D of the fuel cell units 2A to 2D are closed (ON state). ) And the second switch means 82A to 82D are held in the open state (off state). In this connected state, the detected currents of the second current converters 38AU to 38DU, 38AV to 38DV are sent to the power generation output control means 6 via the third current lines 74 and 75 and the fourth current lines 76 and 77, Therefore, the power generation output control means 6 generates the power generation outputs of the fuel cell units 2A to 2D based on the detected currents of the first current converters 36AU to 36DU, 36AV to 36DV and the second current converters 38AU to 38DU, 38AV to 38DV. Thus, the operation is performed so that the power generation outputs of the plurality of fuel cell units 2A to 2D become substantially equal, and the power generation efficiency of the entire system can be increased.

  On the other hand, when one of the fuel cell units 2A to 2D is operated independently, the first switch means 62A to 62D are held in the open state and the second switch means 82A to 82D are held in the closed state. In this connection state, the third current lines 74 and 75 and the fourth current lines 76 and 77 are short-circuited, and the detected currents from the second current converters 38AU to 38DU and 38AV to 38DV are sent to the power generation output control means 6. Accordingly, the fuel cell unit 2A (or 2B, 2C, 2D) is operated and controlled based on the detected current from the first current converter 36A (or 36B, 36C, 36D), and is operated as required. can do.

  As described above, also in the fourth embodiment, it is possible to achieve the same effect as that of the third embodiment described above. In addition, when used alone, the third current lines 74 and 75 and the fourth current lines 76 and 77 are short-circuited via the connection lines 84 and 85, so that the electric currents of the second current converters 38A to 38D are obtained. Damage can be prevented. In the embodiment shown in FIG. 26 and FIG. 27, the second switch means 82A to 82D are not provided. However, this is the second current converter 38A to 38D, and the secondary circuit is opened (open). This is because a semiconductor device with a built-in breakage preventing semiconductor for preventing breakage when used is used, and the second current converters 38A to 38A- The circuit configuration related to 38D can be simplified.

2A, 2B, 2C, 2D, 2G, 2H Fuel cell unit 4 Fuel cell 6 Power generation output control means 8A, 8B, 8C, 8D Power generation output line 12 Power load 30 Commercial power line 36A, 36AU, 36BV, 36B, 36BU, 36BV 36C, 36CU, 36CV, 36D, 36DU, 36DV First current converter 38A, 38AU, 38AV, 38B, 38BU, 38BV, 38C, 38CU, 38CV, 38D, 38DU, 38DV Second current converter 40A, 40B , 40C, 40D Current transformer 62A, 62B, 62C, 62D Switch means (first switch means)
70, 71 First current line 72, 73 Second current line 74, 75 Third current line 76, 77 Fourth current line 82A, 82B, 82C, 82D Second switch means

Claims (7)

A fuel cell unit parallel operation system that operates by connecting a plurality of fuel cell units in parallel to each other,
The plurality of fuel cell units includes a fuel cell that generates power by a fuel cell reaction, and a power generation output control unit that controls a power generation output of the fuel cell, and corresponds to each of the power generation output control units of the plurality of fuel cell units. And a first current converter for detecting a current flowing through a commercial power line of a commercial power source, and a second current converter corresponding to each of the fuel cells of the plurality of fuel cell units. A current converter is provided, the second current converter detects a current flowing through a power generation output line of the corresponding fuel cell, and the power generation output control means of each of the plurality of fuel cell units includes the corresponding first A parallel operation system for fuel cell units, wherein the power generation output of the corresponding fuel cell is controlled based on the detected currents of the first and second current converters.   2. The second current converter corresponding to each of the plurality of fuel cell units is electrically reversely connected in parallel to the corresponding first current converter. Fuel cell unit parallel operation system.   A current transformer is provided corresponding to the second current converter corresponding to the fuel cell of each of the plurality of fuel cell units, and the current transformer flows through the power generation output line of the corresponding fuel cell. 3. The parallel fuel cell unit according to claim 1, wherein the current is reduced so that the current is reduced, and the second current converter detects the current that has been changed by the corresponding current transformer. 4. Driving system.   4. The fuel cell unit parallel operation system according to claim 3, wherein a current transformation ratio of the current transformer of each of the plurality of fuel cell units is 1 to 100. 5.   5. The fuel cell unit parallel operation system according to claim 3, wherein the second current converter and the current transformer of each of the plurality of fuel cell units are integrally configured. 6. A fuel cell that generates power by a fuel cell reaction; and a power generation output control unit that controls a power generation output of the fuel cell, wherein a first current converter is provided corresponding to the power generation output control unit, and the first current converter Detects a current flowing through a commercial power line of a commercial power source, and a second current converter is provided corresponding to the fuel cell, and the second current converter detects a current flowing through a power generation output line of the fuel cell. In addition, a switch means is provided in relation to the second current converter,
When used in parallel operation, the switch means allows the detection current to be supplied from the second current converter to the power generation output control means, and the power generation output control means includes the first and second currents. When the power generation output of the fuel cell is controlled based on the detected current of the converter and used for single operation, the switch means supplies the detected current from the second current converter to the power generation output control means. The fuel cell unit is characterized in that the power generation output control means controls the power generation output of the fuel cell based on the detected current of the first current converter. The first and second output terminals of the first current converter are electrically connected to the first and second input terminals of the power generation output control means through first and second current lines, respectively, and the second current The converter is electrically reverse connected in parallel to the first current converter, and the first output terminal of the second current converter is electrically connected to the second current line via a third current line. And a second output terminal of the second current converter is electrically connected to the first current line via a fourth current line, and the switch means includes the third and fourth switches of the second current converter. The switch means is disposed in a current line and is kept closed when used for parallel operation, and the switch means is kept open when used for independent operation. 7. The fuel cell unit according to 6.

Images