JP2012248503A - Power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generation system which makes it possible to prevent the degradation of fuel cells while also adding general-purpose utility to a power conditioner.SOLUTION: In a power generation system 1 equipped with a fuel cell device 2, a power conditioner 4 includes no step-up converter, and the fuel cell device 2 is provided with a step-up converter 6 instead. Furthermore, the fuel cell device 2 is provided with an AC/DC converter 7 which converts AC power supplied from a system A into DC power and applies converted power to the output part of the converter. When the output voltage of the converter 6 is equal to or below a prescribed voltage, the AC/DC converter 7 is activated and driven until voltage at the output part of the converter 6 is raised to a target voltage. Then, the output of the AD/DC converter 7 is lowered, and while so doing, the output of the converter 6 is raised.

Description

  The present invention relates to a power generation system, and more particularly to a power generation system in which a converter that boosts an output voltage is mounted on a fuel cell device including a fuel cell as a power generation unit.

  Recently, a power generation system using a combination of power generation by a fuel cell (fuel cell power generation) and power generation by a solar cell (solar power generation) has been provided in a household power generation system.

  This type of power generation system includes a power conditioner that is an inverter device that converts DC power into AC power so that DC power generated by a fuel cell or solar cell can be used in a household power load. However, in the conventional power generation system, as shown in FIG. 5, since the power conditioner c is connected to each of the solar cell a and the fuel cell b, the power conditioners c and c are almost the same. There has been a waste of redundantly providing the inverter e and the display unit f having functions.

  On the other hand, the converter d to which the solar cell a and the fuel cell b are connected is preferably selected according to the output characteristics of these power generation facilities. Recently, there are various types other than the solar cell a and the fuel cell b. In order to be able to connect such various types of power generation equipment to the power conditioner c (in other words, to make the inverter device versatile), It is required to employ a configuration in which the boost converter d is separated from the power conditioner c.

JP 2011-50191 A

  FIG. 6 shows a configuration in which the converter d is separated from the power conditioner c in response to such a request. In the power generation system shown in FIG. 6, each of the solar cell a and the fuel cell b is used for boosting. The converter d is separated from the power conditioner c, and the inverter e and the display unit f are shared by the solar cell a and the fuel cell b, thereby eliminating duplication of the inverter and the like.

  However, the configuration shown in FIG. 6 has the following problems and needs to be improved.

  That is, since the fuel cell b deteriorates when a current exceeding the power generation amount is output, the conventional power generation system shown in FIG. 5 uses an inverter as a control for preventing an inrush current so that no overcurrent flows when the converter d is started. When the converter d is operated after e is operated reversely to increase the output voltage of the converter d (see, for example, Patent Document 1), the power conditioner c has versatility as shown in FIG. If the configuration in which the inverter e and the converter d are separated is employed, the converter d and the inverter e do not have communication means, and therefore, the method of preventing the inrush current by operating the inverter e in the reverse direction cannot be employed. That is, the inrush current at the time of starting the converter cannot be prevented for the fuel cell b, and the fuel cell b may be deteriorated.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a power generation system capable of preventing the deterioration of the fuel cell while giving the power conditioner versatility. There is.

  In order to achieve the above object, a power generation system according to a first aspect of the present invention includes a fuel cell device including a fuel cell as a power generation unit, and an inverter that connects DC power output from the fuel cell device to a system. The fuel cell device includes: a converter that boosts DC power generated by the power generation unit; and AC power supplied from the system is converted to DC power and An AC / DC converter that applies power to the output unit of the converter, and a control unit that controls the AC / DC converter. When the output voltage of the converter is equal to or lower than a predetermined voltage, the control unit To increase the voltage at the output of the converter to a predetermined target voltage, and then reduce the output of the AC / DC converter while reducing the output of the AC / DC converter. And performing control for increasing the output of the converter.

  That is, in the power generation system according to the first aspect, the converter that boosts the DC power generated by the fuel cell is separated from the grid interconnection inverter device (power conditioner) and provided in the fuel cell device. . The fuel cell device is provided with an AC / DC converter that converts AC power supplied from the system into DC power and applies power to the output of the converter, and the output voltage of the converter is below a predetermined voltage. In some cases, that is, when the fuel cell is not generating power and the charge is not accumulated at the output of the converter, the AC / DC converter is operated to increase the voltage at the output of the converter to a predetermined target voltage. Therefore, the output of the converter is increased while decreasing the output of the AC / DC converter. For this reason, the current output from the fuel cell gradually increases with the operation of the converter, and the current output from the fuel cell is prevented from increasing rapidly, and the fuel cell may be deteriorated due to overcurrent. Is prevented.

  The power generation system according to claim 2 of the present invention is the power generation system according to claim 1, wherein the control unit is configured to provide the AC / DC on condition that the power generation amount of the power generation unit is equal to or greater than a predetermined value. A control structure for stopping the operation of the converter is provided.

  That is, in the power generation system according to claim 2, the AC / DC converter stops its operation when the power generation amount of the power generation unit becomes a predetermined value or more, and therefore when the power generation unit starts power generation normally. No voltage is applied from the AC / DC converter to the output of the converter.

  A power generation system according to a third aspect of the present invention is the power generation system according to the first or second aspect, wherein the fuel cell device and the inverter device are configured separately.

  According to the present invention, the converter for boosting the DC power generated by the fuel cell is separated from the grid interconnection inverter device (power conditioner) and is provided in the fuel cell device. You can have it.

  Moreover, the fuel cell device includes an AC / DC converter that converts AC power supplied from the system into DC power and applies power to the output of the converter, and the output voltage of the converter is equal to or lower than a predetermined voltage. Sometimes, the AC / DC converter is operated to boost the voltage at the output of the converter to a predetermined target voltage, and then the output of the converter is increased while the output of the AC / DC converter is decreased. A sudden increase in the current output from the fuel cell is avoided, and the fuel cell is prevented from deteriorating due to overcurrent.

It is a circuit block diagram which shows an example of schematic structure of the electric power generation system which concerns on this invention. It is a flowchart which shows the starting procedure of the converter of the fuel cell apparatus in the power generation system. It is a flowchart which shows the procedure which applies electric power with respect to the output part of a converter in the starting procedure of the converter. It is explanatory drawing which shows an example of the voltage change of the output part of the converter at the time of the converter starting. It is a circuit block diagram which shows schematic structure of the conventional electric power generation system. FIG. 6 is a circuit block diagram illustrating a modified example of the power generation system illustrated in FIG. 5.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a schematic configuration of a power generation system to which the present invention is applied. This power generation system 1 is a home power generation system that operates DC power generated by a power generation unit in linkage with a system composed of an AC power source such as a commercial power source. As shown in FIG. The battery device 2, the solar cell panel 3, and the power conditioner (inverter device) 4 are provided as main parts.

  The fuel cell device 2 is a power generation facility including a converter that boosts DC power generated by the power generation unit, and includes a power generation unit 5 and a converter that boosts DC power generated by the power generation unit 5 to a desired voltage. (DC / DC converter) 6, AC / DC converter 7 that converts AC power (for example, AC 200 V) supplied from system A into DC power, and FC control unit 8 that controls each part of the fuel cell device 2 are mainly used. It is configured as a part. Note that “FC” in the FC control unit is an abbreviation for “Fuel Cell”.

  The power generation unit 5 is configured by a fuel cell that supplies a fuel gas containing hydrogen such as natural gas and an oxidant gas containing oxygen such as air, and obtains DC power by chemically reacting hydrogen and oxygen. For example, a solid oxide fuel cell (SOFC) or a polymer electrolyte fuel cell (PEFC) is employed as the power generation unit 5.

  The converter 6 is composed of a DC-DC converter that boosts the DC power generated by the power generation unit 5 so that the power conditioner 4 can convert the DC power into AC power having a voltage (for example, AC 200 V) that can be connected to the system A. The DC power boosted by the converter 6 is input to the power conditioner 4. Here, the specific configuration / control of the converter 6 is determined according to the output characteristics of the power generation unit 5. Specifically, since a fuel cell is connected to the converter 6, a converter suitable for the fuel cell, for example, an insulating type and input current control converter is used.

  As described above, the AC / DC converter 7 converts AC power supplied from the system A into DC power, and its input unit is connected to the system A (specifically, the system A via the power line 9). Connected to a switchboard (not shown) that receives supply of AC power from an output terminal of the converter 6 and the output section of the converter 6. That is, the AC / DC converter 7 is configured to convert AC power supplied from the system A into DC power and apply power to the output unit of the converter 6.

  The FC control unit 8 is a control device that controls the operation of each unit of the fuel cell device 2 and includes a microcomputer (not shown) as a control center, and performs power generation control of the power generation unit 5 as well as the converter 6 and the AC. / DC converter 7 is configured to perform operation control (details will be described later).

  The solar cell panel 3 includes a plurality of solar cells (not shown) as a power generation unit, and is a power generation facility formed by connecting and arranging these solar cells in a panel shape, and converts solar energy into DC power. It is configured as follows.

  The solar cell panel 3 is attached with a converter (DC / DC converter) 10 that boosts the DC power generated by the solar cell panel 3, and the DC power generated by the solar cell panel 3 is converted to this converter. 10 is input to the power conditioner 4 through the terminal 10. Here, the specific configuration and control of the converter 10 are also determined in accordance with the output characteristics of the power generation unit in the same manner as the converter 6 of the fuel cell device 2 described above. As the converter 10 in which a solar cell is used as the power generation unit, for example, a non-insulated or insulated converter and a maximum power point tracking control (MPPT control) converter is used.

  The power conditioner 4 is an inverter device that converts the DC power generated by the fuel cell device 2 and the solar cell panel 3 into AC power that can be linked to the system A. As shown in FIG. In the embodiment, an inverter 11 and a PC control unit 12 that controls each part of the power conditioner 4 are provided as main parts. Note that “PC” in the PC control unit is an abbreviation of “Power Conditioner”.

  The inverter 11 is formed of a DC / AC inverter that converts the DC power boosted by the converter 6 and the converter 10 into voltage / frequency AC power (for example, a single-phase three-wire system 200V) that can be linked to the system A. ing. The DC link section (not shown) constituting the input section of the inverter 11 is connected to the output sections of the converter 6 and the converter 10, and the DC power boosted by the converters 6 and 10 is supplied to the inverter 11. It is supplied to the DC link unit.

  The PC control unit 12 is a control device that controls the operation of each unit of the power conditioner 4 and includes a microcomputer (not shown) as a control center. The PC control unit 12 is configured to control the output of the inverter 11 so that the input voltage becomes constant when the input voltage of the inverter 11 becomes a certain value or more.

  Thus, the power conditioner 4 shown in the present embodiment is not provided with a DC / DC converter that boosts the DC power supplied from the fuel cell device 2 or the solar cell panel 3, and is exclusively used for the fuel cell device 2 or Only DC power supplied from the solar cell panel 3 is converted into AC power. In other words, the power conditioner 4 receives DC power boosted to a desired voltage and does not include a converter that is selected according to the output characteristics of the power generation section. This is a versatile inverter device that can connect various power generation units without being affected by the above.

  In relation to this, the fuel cell device 2, the solar cell panel 3 and the power conditioner 4, which are often installed outdoors, are all configured separately, and the fuel cell device 2 The FC control unit 8 and the PC control unit 12 of the power conditioner 4 are not connected for communication. That is, the fuel cell device 2, the solar cell panel 3, and the power conditioner 4 all function independently.

  Therefore, in this power generation system 1, when at least one of the fuel cell device 2 and the solar cell panel 3 starts power generation, the PC control unit 12 uses the input voltage (voltage of the DC link unit) of the power conditioner 4 to generate fuel. It is determined that at least one of the battery device 2 or the solar battery panel 3 is generating power, and the PC control unit 12 operates the inverter 11 to convert the supplied DC power into AC power. It is designed to be connected.

  Next, protection (overcurrent prevention) of the power generation unit 5 in the fuel cell device 2 in the power generation system 1 will be described in detail with reference to FIGS.

  In the power generation system 1 configured as described above, the fuel cell device 2 (power generation unit 5) and the solar cell panel 3 both stop generating power, that is, the output unit of the converter 6 of the fuel cell device 2. If the power generation unit 5 of the fuel cell device 2 starts power generation in a state in which no electric charge is accumulated in the battery, current may suddenly flow from the power generation unit 5 (overcurrent) and the power generation unit 5 may be deteriorated. In the power generation system 1 of the present invention, in order to prevent such overcurrent, the FC control unit 8 of the fuel cell device 2 is configured to perform the following control.

  That is, the FC control unit 8 operates the converter 6 when the power generation unit 5 starts power generation. If there is an operation request for this converter 6 (Yes in step S1 in FIG. 2), the output voltage of the converter 6 (in other words, Then, it is determined whether or not the potential at the output end is equal to or less than a certain value (threshold value X) (see step S2 in FIG. 2). Here, for example, in the case where the solar cell panel 3 is generating power, the output voltage of the converter 6 is higher than the threshold value X because the electric charge is accumulated in the converter 6. If neither battery panel 3 is generating power, the output voltage of the converter 6 is equal to or lower than the threshold value X, the determination in step S2 of FIG. 2 becomes affirmative, and the FC control unit 8 proceeds to step S3 of FIG.

  When the output voltage of the converter 6 is equal to or lower than the threshold value X, the FC control unit 8 starts a process of boosting the voltage of the output unit of the converter 6 to a predetermined target voltage Y (charging of the output unit of the converter 6). (Refer to step S3 in FIG. 2).

  Here, the charging of the output section of the converter 6 is performed according to the procedure shown in FIG. That is, when starting the charging of the output unit of the converter 6, the FC control unit 8 operates the AC / DC converter 7 to convert the AC power supplied from the system A into DC power, and the converted DC power is converted to DC power. Applied to the output of the converter 6. Thereby, the voltage of the output part of converter 6 rises (refer Step S1 of Drawing 3).

  Therefore, the FC control unit 8 determines whether or not the output voltage of the converter 6 is equal to or higher than the predetermined target voltage Y (see step S2 in FIG. 3), and when the output voltage of the converter 6 is equal to or higher than the target voltage Y, The operation of the converter 6 is started (see step S3 in FIG. 3). At this time, the FC control unit 8 controls the converter 6 so that the boosting operation by the converter 6 is performed slowly, instead of performing the boosting operation by the converter 6 abruptly. That is, the converter 6 is controlled so as to gradually increase the output of the converter 6.

  In parallel with the operation of the converter 6, the FC control unit 8 slowly decreases the output of the AC / DC converter 7 to the output unit of the converter 6 (see step S4 in FIG. 3). That is, the FC control unit 8 gradually increases the output of the converter 6 while gradually decreasing the output of the AC / DC converter of the AC / DC converter 7.

  The FC control unit 8 operates the AC / DC converter 7 when the power generation amount in the power generation unit 5 becomes equal to or greater than the predetermined value Z (that is, when the power generation unit 5 starts power generation normally). Is stopped (see step S5 in FIG. 3). That is, the application of power to the output unit of the converter 6 by the AC / DC converter 7 is stopped.

  FIG. 4 shows changes in the output voltage (output terminal potential) of the converter 6 in a series of these operations. As shown in this figure, in the power generation system 1 of the present invention, the converter 6 of the fuel cell device 2 is When starting up, the AC / DC converter 7 first increases the output voltage of the converter 6 to the target voltage Y, and then increases the output of the converter 6 while decreasing the output of the AC / DC converter 7. The AC / DC converter 7 is stopped and output is performed only by the converter 6.

  Therefore, in the power generation system 1 of the present invention, the current output from the power generation unit 5 gradually increases with the operation of the converter 6, and it is avoided that the current output from the power generation unit 5 increases rapidly. The power generation unit 5 is prevented from deteriorating due to overcurrent.

  In the power generation system 1 of the present invention, the power conditioner 4 and the converter 6 (fuel cell device 2) are configured separately, and no communication means is provided between them, so that the converter 6 side Although the operating state of the inverter 11 cannot be grasped, the AC / DC converter 7 is gradually stopped after the AC / DC converter 7 increases the voltage at the output of the converter 6. Can absorb fluctuations due to

  On the other hand, when the operation request of the converter 6 is made, for example, when the output voltage of the converter 6 is higher than the threshold value X, such as when the solar battery panel 3 is generating power (No in step S2 in FIG. 2). In this case, the FC control unit 8 does not charge the output unit of the converter 6 described above, and operates the converter 6 as usual to control the input current of the converter 6 (see step S4 in FIG. 2).

  And when the stop request | requirement of the converter 6 is made, such as when stopping the power generation in the power generation unit 5 (see step S5 in FIG. 2), the FC control unit 8 stops the operation of the converter 6 (step S6 in FIG. 2). reference).

  As described above, in the power generation system 1 according to the present invention, even when the boost converter 6 is separated from the power conditioner 4, the power generation unit 5 in the fuel cell device 2 connected to the power conditioner 4 is used. A sudden current is prevented from flowing through the power generation unit 5 and the power generation unit 5 is prevented from deteriorating.

  The above-described embodiments show preferred embodiments of the present invention, and the present invention is not limited to these, and various design changes can be made within the scope of the invention.

  For example, in the above-described embodiment, the case where the fuel cell device 2 and the solar cell panel 3 are used as the power generation equipment connected to the power conditioner 4 has been described. However, the power generation system 1 according to the present invention includes the power conditioner 4. It is also possible to connect a direct current power source (direct current power generation facility) such as a storage battery instead of the solar cell panel 3 or in combination with the solar cell panel 3 as a power generation facility connected to. Moreover, it is also possible to comprise only the fuel cell device 2 and the power conditioner 4.

DESCRIPTION OF SYMBOLS 1 Power generation system 2 Fuel cell apparatus 3 Solar cell panel 4 Power conditioner (inverter apparatus)
5 Power generation section (fuel cell)
6 Converter 7 AC / DC converter 8 FC control unit (control unit of fuel cell device)
11 Inverter 12 PC control part (control part of power conditioner)

Claims (3)

A power generation system having a fuel cell device including a fuel cell as a power generation unit, and an inverter device including an inverter that connects DC power output from the fuel cell device to a system,
The fuel cell device includes: a converter that boosts DC power generated by a power generation unit; an AC / DC converter that converts AC power supplied from the system into DC power and applies power to an output unit of the converter; And a control unit for controlling these,
When the output voltage of the converter is equal to or lower than a predetermined voltage, the control unit operates the AC / DC converter to boost the voltage of the output unit of the converter to a predetermined target voltage, and then the AC / DC converter A power generation system that performs control to increase the output of the converter while decreasing the output of the converter.   2. The power generation according to claim 1, wherein the control unit includes a control configuration that stops the operation of the AC / DC converter on condition that the power generation amount of the power generation unit is equal to or greater than a predetermined value. system.   The power generation system according to claim 1, wherein the fuel cell device and the inverter device are configured separately.

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