JP2006172769A - Fuel cell system and method of controlling fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which can reduce the amount of losses of kinetic energy accompanying the transformation of an electric power. <P>SOLUTION: The fuel cell system includes a plurality of fuel cells 40 a-p which distributes and is provided in each of thermal load 56 a-p provided in a distinct position that the quantity of heat should be supplied, a series circuit 61 a-d which connects the fuel cell 40 a-p in series, an orthogonal conversion apparatus 60 a-d to an electric power load 58 a-p which consumes the ac power by converging a dc power obtained by the series circuit 61 a-d into the ac power, and a fuel cell switching part 50 which stops the amount of deteriorations of a dc voltage inputted into the orthogonal conversion apparatus 60 a-d, and a fuel cell switching part 50 which suppresses the amount of deteriorations of a dc voltage inputted into the orthogonal conversion apparatus 60 a-d by connecting a fuel cell 40 a-p new to the series circuit in series when the fuel cell of one of the fuel cell 40 a-p is removed from the series circuit. The fuel cell switching part 50 selects the fuel cell 40 a-p as a thermal load 56 a-p which is the most insufficient of the quantity of heat to need for the quantity of heat and a power generation is made to start, and connects the fuel cell 40 a-p to the series circuit 61 a-d. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system and a fuel cell system control method. In particular, the present invention relates to a fuel cell system and a fuel cell system control method for suppressing a decrease in the DC voltage input to an orthogonal transformation device by connecting a plurality of fuel cells in series.

In a cogeneration system using a fuel cell, for example, DC power generated by the fuel cell is converted into AC power using an inverter connected to the fuel cell and supplied to an AC load. (For example, refer to Patent Document 1).
JP-A-8-306376

  In general, the conversion efficiency of power from direct current to alternating current in an inverter decreases as the input voltage to the inverter decreases. Therefore, when power is supplied to an AC load that requires an AC voltage of 100 V using a fuel cell with an output voltage of about several tens of volts, the amount of energy loss associated with power conversion in the inverter increases. was there.

  On the other hand, the conversion efficiency in an inverter can be improved by using the fuel cell which has many power generation cells connected in series. However, a system in which each fuel cell has a large number of power generation cells is not preferable because the equipment cost increases. In such a system, if one power generation cell of the fuel cell fails, the entire fuel cell in which the power generation cell has failed cannot be used. In this case, many other normal power generation cells are not used and are wasted, and the inverter connected to the fuel cell in which the power generation cell has failed is not used and is not preferred.

  In order to solve such a problem, the fuel cell system according to the first aspect of the present invention includes a plurality of fuel cells provided in a distributed manner so as to supply heat to each of thermal loads provided at different positions, and a plurality of fuel cells. A series circuit that connects the fuel cells in series, an orthogonal conversion device that converts DC power obtained by the series circuit into AC power, and supplies the AC power to a power load, and one of a plurality of fuel cells When the fuel cell is removed from the series circuit, a new fuel cell is connected in series to the series circuit, thereby reducing the amount of decrease in the DC voltage input to the orthogonal transformation device. For this reason, the amount of energy loss accompanying the conversion of power in the orthogonal transform device can be reduced.

  The fuel cell switching unit selects a fuel cell that can supply heat to the heat load that requires the least amount of heat as a new fuel cell, starts power generation, and places the fuel cell in a series circuit. Connecting. For this reason, it can prevent that the calorie | heat amount which a heat load requires is insufficient.

  The fuel cell switching unit selects a fuel cell that produces more heat than the heat required by the heat load, removes the selected fuel cell from the series circuit, and stops power generation of the selected fuel cell. . For this reason, it is possible to reduce waste of energy due to the fuel cell generating excessive heat.

  The fuel cell system according to this embodiment further includes a failure detection unit that detects a failure of the fuel cell, and the fuel cell switching unit removes the failed fuel cell from the series circuit when the failure detection unit detects the failure. For this reason, even when the fuel cells connected in series fail, it is possible to continue supplying power to the power load.

  When the fuel cell user stops the power generation of the fuel cell, the fuel cell switching unit removes the fuel cell from the series circuit, and supplies the heat load to the heat load that requires the least amount of heat. The fuel cell that can be used is selected as a new fuel cell to start power generation, and the fuel cell is connected to the series circuit. For this reason, even when the fuel cells connected in series stop operating, it is possible to continue supplying power by connecting other fuel cells.

  In the fuel cell system according to this embodiment, the DC voltage output from each of the fuel cells is smaller than the peak value of the AC voltage output from the orthogonal transformation device, and the voltage obtained by the series circuit is the AC output from the orthogonal transformation device. More than the peak voltage value. For this reason, compared with the case where each uses a fuel cell with a high output voltage, the voltage input into an orthogonal transformation device can be raised at lower cost.

  Further, in the fuel cell system according to the present embodiment, the fuel cell switching unit supplies the amount of power required by the power load, and the power generation efficiency of the plurality of fuel cells connected to the series circuit and the conversion efficiency of the orthogonal transform device When one fuel cell is removed from the series circuit, the energy efficiency when a new fuel cell is connected to the series circuit does not connect the new fuel cell to the series circuit. A new fuel cell is connected to the series circuit on the condition that it is higher than the energy efficiency of the time. For this reason, the amount of reduction in energy efficiency of the entire system can be reduced.

  The fuel cell switching unit is configured such that when the energy efficiency when one fuel cell is removed from the series circuit is higher than the energy efficiency when the one fuel cell is not removed from the series circuit, the one fuel cell is removed from the series circuit. except for. For this reason, even when the amount of power consumed by the power load is reduced and the fuel cell is in partial load operation, the amount of reduction in the energy efficiency of the entire system can be reduced.

  A plurality of orthogonal transformation devices are provided, and a series circuit is provided for each orthogonal transformation device. The series circuit includes a connection switch that inserts each of the plurality of fuel cells into the series circuit and connects them in series, and a plurality of fuels. A bypass switch that bypasses each of the batteries without inserting them into the series circuit. When removing one fuel cell from the series circuit, the fuel cell switching unit opens a connection switch that connects the one fuel cell to the series circuit in series and closes a bypass switch that bypasses the one fuel cell. The bypass switch for bypassing the new fuel cell without inserting it into the series circuit is opened, and the connection switch for connecting the new fuel cell in series with the series circuit is closed. For this reason, it is possible to control the connection of the fuel cell to the series circuit with a simple configuration. Further, the fuel cell can be connected to the series circuit by any combination of fuel cells.

  The fuel cell switching unit selects a series circuit to which one fuel cell is connected when one fuel cell stops power generation, removes one fuel cell from the selected series circuit, and installs a new fuel cell. Connect in series. For this reason, the amount of energy loss accompanying the fall of the power conversion efficiency of an orthogonal transformation device can be reduced, and electric power can be efficiently supplied to a power load.

  The fuel cell switching unit stops the operation of one orthogonal transformation device and stops each of the fuel cells connected to the orthogonal transformation device when a predetermined number of fuel cells stop generating power. The fuel cells connected in series are connected in series. For this reason, in the whole of a plurality of orthogonal transform apparatuses, the amount of energy loss due to a decrease in power conversion efficiency can be reduced.

  A fuel cell system according to another embodiment of the present invention includes a plurality of fuel cells provided in a distributed manner so as to supply heat to each of thermal loads provided at different positions, and a series circuit that connects the plurality of fuel cells in series. In the case where the direct current power obtained by the series circuit is converted into alternating current power and supplied to the power load that consumes alternating current power, and one fuel cell of the plurality of fuel cells is removed from the series circuit A fuel cell is removed from the series circuit when power can be supplied without increasing the power generated by the remaining fuel cells connected to the series circuit without connecting the new fuel cell to the series circuit. Energy loss obtained by increasing the power generated by the remaining fuel cells due to the increase in energy loss caused by the decrease in conversion efficiency of the orthogonal transformation device On condition that less than the amount of decrease, including a fuel cell switching unit to suppress the decrease of the DC voltage to be input to the orthogonal transform unit by connecting in series with the series circuit of the new fuel cell. For this reason, the increase amount of the energy loss in the whole fuel cell system can be reduced.

  A fuel cell system control method according to another aspect of the present invention includes a step of connecting a plurality of fuel cells provided in a distributed manner to supply heat to each of thermal loads provided at different positions using a series circuit. Converting DC power obtained by the series circuit into AC power using an orthogonal transformation device and supplying the AC power to a power load that consumes AC power; and one fuel cell of the plurality of fuel cells from the series circuit In the case of removing the fuel cell, a fuel cell switching step is provided in which a new fuel cell is connected in series to the series circuit to suppress a decrease in the DC voltage input to the orthogonal transformation device.

  In the fuel cell switching step, a fuel cell that can supply heat to the heat load that requires the least amount of heat is selected as a new fuel cell to start power generation, and the fuel cell is put into a series circuit. Connecting. In the fuel cell switching step, a fuel cell that produces an excessive amount of heat compared to the amount of heat required by the heat load is selected, and the selected fuel cell is removed from the series circuit.

  In the fuel cell system control method according to the present embodiment, a plurality of orthogonal transformation devices are provided, and a series circuit is provided for each orthogonal transformation device. The series circuit inserts each of the plurality of fuel cells into the series circuit. A connection switch for connecting in series and a bypass switch for bypassing each of the fuel cells without inserting them into the series circuit, and the step of switching the fuel cell is to remove one fuel cell from the series circuit. Open the connection switch that connects the battery in series with the series circuit, close the bypass switch that bypasses one fuel cell, and open the bypass switch that bypasses the new fuel cell without inserting it into the series circuit. Close the connection switch that connects the new fuel cell in series to the series circuit.

  The fuel cell switching step selects a series circuit to which one fuel cell is connected when one fuel cell stops power generation, removes one fuel cell from the selected series circuit, and installs a new fuel cell. Connect in series. In the fuel cell switching step, when more than a predetermined number of fuel cells stop generating power, the operation of one orthogonal transform device is stopped, and each fuel cell connected to the orthogonal transform device is Are connected in series to each of the series circuits to which the fuel cells having been stopped are connected.

  The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

  ADVANTAGE OF THE INVENTION According to this invention, the amount of energy loss accompanying conversion of electric power can be reduced.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the claimed invention, and all the combinations of features described in the embodiments are not included in the invention. It is not always essential for development means.

  FIG. 1 shows an example of the configuration of a fuel cell system 30 according to an embodiment of the present invention. An object of the present embodiment is to provide a fuel cell system capable of reducing the amount of energy loss accompanying power conversion.

  The fuel cell system 30 supplies power and heat to a plurality of dwellings (42a to 42p, hereinafter collectively referred to as 42). Here, the fuel cell system 30 may supply electric power and heat to a single building in which a plurality of residences 42 are provided, and the residence 42 provided in each of the plurality of buildings provided in different regions. It may supply power and heat.

  The fuel cell system 30 includes a plurality of residences 42, a plurality of series circuits (61a to 61d, hereinafter collectively referred to as 61), a plurality of orthogonal transformation devices (60a to 60d, hereinafter collectively referred to as 60), and a failure detection unit 52. , A power network 44, a power meter 46, and a fuel cell switching unit 50.

  The residence 42a includes a fuel cell 40a, a power load 58a, a hot water tank 54a, and a heat load 56a. The dwellings (42b to 42p) have the same components as the dwelling 42a, and identify which dwelling 42 is a component by attaching the symbols b to p at the end of the symbols of the components. .

  Hereinafter, operation | movement of each component of the residence 42a is demonstrated. The fuel cell 40a consumes hydrogen to generate power. The fuel cell 40 is, for example, a polymer electrolyte fuel cell (PEFC). The fuel cell 40 may generate electricity using hydrogen gas obtained by reforming city gas, propane gas, or the like, or may generate electricity using hydrogen gas supplied from the outside as fuel. . The power generated by the fuel cell 40 is supplied to the power network 44 through the series circuit 61 and the orthogonal transformation device 60. The power load 58 a receives power from the power network 44 and operates. The hot water storage tank 54a circulates the cooling water for cooling the fuel cell 40a, receives the exhaust heat accompanying the power generation of the fuel cell 40a, and stores hot water generated by the received amount of heat. The hot water stored in the hot water tank 54a is supplied to the heat load 56a and consumed by the heat load 56a.

  The operation of each component of the dwelling 42a has been described above, but the operation of each component of any other dwelling 42 is the same as the operation of each component of the dwelling 42a.

  The series circuit 61 is provided for each orthogonal transformation device 60 and inputs DC power obtained by connecting the fuel cells 40 in series to the orthogonal transformation device 60. The orthogonal transform device 60 is an inverter that converts input DC power into AC power and outputs the AC power, and converts the DC power obtained by the series circuit 61 into AC power and supplies it to the power network 44.

  In the fuel cell system of the present embodiment, as an example, the rated value of the input voltage to the orthogonal transformation device 60 is 200V, and the rated value of each output voltage of the fuel cell 40 is 50V. The series circuit 61 inputs 200V DC power obtained by connecting four fuel cells 40 in series to the orthogonal transformation device 60. The orthogonal transform device 60 converts the 200V DC power input from the series circuit 61 into 100V AC power and supplies it to the power network 44. In general, an inverter can increase the power conversion efficiency by increasing the input DC voltage. Therefore, by connecting the fuel cells 40 in series by the series circuit 61 and increasing the DC voltage input to the orthogonal transformation device 60, the efficiency is higher than when one fuel cell is input to the orthogonal transformation device 60. The orthogonal transformation device 60 can be operated. Further, it is possible to supply power by converting the voltage into a voltage required by the power load 58 without providing a boosting circuit for boosting the fuel cell 40.

  The series circuit 61a includes a plurality of bypass switches (62a to 62p, hereinafter collectively referred to as 62) and a plurality of connection switches (64a to 64p and 65a to 65p, hereinafter collectively referred to as 64 and 65, respectively). The series circuit 61b, the series circuit 61c, and the series circuit 61d have the same components as the series circuit 61a, and any series can be obtained by adding the symbols b, c, and d to the end of the symbols of the respective components. Whether it is a component of the circuit 61 is identified.

  Hereinafter, the operation of each component of the series circuit 61a will be described. The connection switch 64 and the connection switch 65 are each connected to the output terminal of the fuel cell 40, and each of the fuel cells 40 is inserted into the series circuit 61 and connected in series. The bypass switch 62 bypasses each fuel cell 40 without inserting it into the series circuit 61a.

  The operation of each component of the series circuit 61a has been described above, but the operation of each component of any other series circuit 61 is the same as the operation of each component of the series circuit 61a, and thus the description thereof is omitted. .

  In this way, each of the series circuits 61 included in the orthogonal transformation device 60 can connect any of the fuel cells 40 in series. Further, the fuel cell 40 can be connected to each of the series circuits 61 in any combination.

  The fuel cell switching unit 50 selects the fuel cell 40 connected to the series circuit 61 by controlling opening and closing of the bypass switch 62 and the connection switches (64, 65). When the fuel cell 40 is removed from the series circuit 61, the fuel cell switching unit 50 connects the new fuel cell 40 to the series circuit 61 in series. In this way, the fuel cell switching unit 50 can suppress the amount of decrease in the DC voltage input to the orthogonal transformation device 60 when the fuel cell 40 is removed from the series circuit 61, so that the energy associated with power conversion can be reduced. Loss amount can be reduced.

  The failure detection unit 52 notifies the fuel cell switching unit 50 of the failed fuel cell 40 when detecting a failure of the fuel cell 40. The failure detection unit 52 monitors the voltage of each power generation cell of each fuel cell 40, and determines that the fuel cell 40 has failed when the voltage falls below a predetermined voltage value. Information for identifying the fuel cell 40 is notified to the fuel cell switching unit 50. In addition, the failure detection unit 52 monitors the ratio of the amount of generated power to the amount of fuel consumed for each of the fuel cells 40, and the fuel cell 40 has failed when the ratio falls below a predetermined value. Is determined, and information for identifying the failed fuel cell 40 is notified to the fuel cell switching unit 50. When the failure detection unit 52 is notified of the failure of the fuel cell 40, the fuel cell switching unit 50 removes the failed fuel cell from the series circuit 61.

  The fuel cell switching unit 50 also removes the fuel cell 40 from the series circuit even when power generation of the fuel cell 40 is stopped by the user of the fuel cell 40. For example, when the user of the fuel cell 40 turns off the operation switch of the fuel cell 40, the fuel cell 40 is removed from the series circuit.

  Thus, even when the fuel cell 40 whose power generation has been stopped due to a failure or the fuel cell 40 whose power generation has been stopped by a user is connected in series to the series circuit 61, the orthogonal transformation device to which the series circuit 61 is connected 60 can continue to supply power.

  In addition, the fuel cell switching unit 50 selects the hot water storage tank 54 in which the amount of heat of the hot water stored in the hot water storage tank 54 is excessive as compared with the amount of heat consumed by the heat load 56 and supplies the heat storage tank 54 with the heat amount. The fuel cell 40 to be removed is removed from the series circuit 61 and the power generation of the fuel cell 40 is stopped. Accordingly, it is possible to prevent waste of energy due to the fuel cell 40 generating excessive heat. Further, since the hot water tank 54 can be prevented from being filled with hot water, the fuel cell 40 can be prevented from being stopped due to the cooling water of the fuel cell 40 being unable to be cooled.

  In addition, the fuel cell switching unit 50 manages the history of the amount of power generated by the fuel cell 40 and the amount of heat consumed by the thermal load 56, and based on the history and the amount of heat of hot water currently stored in the hot water tank 54. Then, it is determined whether the amount of heat of the hot water stored in the hot water storage tank 54 is excessive as compared with the amount of heat required by the heat load 56. In this way, the fuel cell switching unit 50 can determine in advance whether or not an excessive amount of heat is supplied to the hot water tank 54. Then, the fuel cell 40 that generates power can be selected and connected to the series circuit 61 so that the amount of heat of the hot water stored in the hot water tank 54 does not become excessive or insufficient.

  The fuel cell switching unit 50 is connected to the fuel cell 40, the hot water tank 54, the connection switches (64, 65), the bypass switch 62, and the orthogonal transformation device 60 through a communication network such as Ethernet (registered trademark). Yes. The fuel cell switching unit 50 acquires information indicating the respective states from the fuel cell 40 and the hot water tank 54 through the communication network, and the fuel cell 40, the connection switches (64, 65), the bypass switch 62, and the orthogonal transformation. The operation of the device 60 is controlled.

  FIG. 2 is a diagram illustrating an example of an open / close state of the bypass switch 62 and the connection switches (64, 65). As an example, FIG. 2 shows that DC power obtained by connecting fuel cells (40a, 40b, 40c) in series is input to an orthogonal transformation device 60a, and the electric power of other fuel cells 40 is orthogonal transformation device 60a. It is a figure which shows the open / close state of each of the bypass switch 62 and the connection switch (64, 65) in the series circuit 61a when not inputting into. The bypass switches (62a, 62b, 62c) of the series circuit 61a are open, and the connection switches (64a, 64b, 64c, 65a, 65b, 65c) are closed. Thus, the fuel cells (40a, 40b, 40c) are connected in series.

  Further, the connection switches (64d to 64p, 65d to 65p) of the series circuit 61a are opened, and the bypass switches (62d to 62p) are closed. Thus, the fuel cells (40d to 40p) are not connected to the series circuit 61, and only the fuel cells (40a, 40b, 40c) are connected in series to form a circuit for inputting power to the orthogonal transformation device 60a.

  Thus, when the fuel cell 40 is removed from the series circuit 61, the fuel cell switching unit 50 opens the connection switches (64, 65) that connect the fuel cell 40 in series to the series circuit 61, and The bypass switch 62 that bypasses the fuel cell 40 is closed. When the fuel cell switching unit 50 inserts the fuel cell 40 into the series circuit 61, the fuel cell switching unit 50 opens the bypass switch 62 that bypasses the fuel cell 40 without inserting the fuel cell 40 into the series circuit 61. The connection switches (64, 65) that connect 40 to the series circuit 61 in series are closed.

  The fuel cell switching unit 50 stops the operation of one orthogonal transform device 60 when a predetermined number or more of the fuel cells 40 stop generating power, and the fuel cell switching unit 50 is connected to the orthogonal transform device 60. Each is connected in series to each of the series circuits 61 to which the stopped fuel cells 40 were connected. Then, the fuel cell switching unit 50 switches the stop of the orthogonal transformation device 60 and the connection of the fuel cell 40 to the series circuit 61 so that the number of the fuel cells 40 not connected to the series circuit 61 falls below a predetermined number.

  In the fuel cell system of the present embodiment, the standard connection number of the fuel cells 40 connected to each of the series circuits 61 of the orthogonal transformation device 60 is determined in advance, and the fuel cell switching unit 50 is equal to or greater than the standard connection number. When the fuel cell 40 stops the power generation, the orthogonal transformation device 60 is stopped and the connection of the fuel cell 40 to the series circuit 61 is switched. For example, the number of connected fuel cells 40 that maximizes the power conversion efficiency of the orthogonal transformation device 60 within a range not exceeding the rated value of the input voltage of the orthogonal transformation device 60 is defined as the standard connection number. In the fuel cell system of this embodiment, the DC power of the fuel cell 40 with a rated voltage of 50V is input in series to the orthogonal transformation device 60 with a rated value of the input voltage of 200V, so the standard number of connections is four.

  FIG. 3 is a flowchart illustrating a procedure in which the fuel cell switching unit 50 stops the orthogonal transformation device 60 and switches the connection of the fuel cell 40. The fuel cell switching unit 50 determines whether or not the total number of the fuel cells 40 removed from the series circuit 61 is equal to or greater than a predetermined number (S122). In step S122, the fuel cell switching unit 50 obtains a difference between the number of standard connections and the number of fuel cells 40 that are actually connected for each of the series circuits 61 of the orthogonal transformation device 60 that are operating, and calculates the difference. Is the total number of fuel cells removed from the series circuit 61. Note that the prescribed number in the determination of S122 is set to the same value as the standard connection number, for example. The fuel cell switching unit 50 ends the process when the total number of the fuel cells 40 removed from the series circuit 61 in S122 is less than a predetermined number.

  When the total number of fuel cells 40 removed from the series circuit 61 is greater than or equal to a predetermined number in S122, the fuel cell switching unit 50 is connected to the connected orthogonal transformation device 60 in the operating orthogonal transform device 60. One of the orthogonal transformation devices 60 with the smallest number of batteries 40 is stopped (S124). Further, the fuel cell switching unit 50 determines whether or not there is a fuel cell 40 that is connected to the orthogonal transformation device 60 stopped in S124 and is generating power (S126).

  When there is a fuel cell 40 that is connected to the stopped orthogonal transformation device 60 and is generating power in S126, the fuel cell switching unit 50 removes the fuel cell 40 that is generating power from the series circuit 61 (S128). . Then, the fuel cell switching unit 50 selects the series circuit 61 of the other orthogonal transformation device 60 in operation, and connects the fuel cell 40 removed from the series circuit 61 in S128 to the selected series circuit 61 (S130). ). In addition, when the fuel cell switching unit 50 selects the series circuit 61 to which the fuel cell 40 is connected in S130, the fuel cell switching unit 50 of the connected fuel cell 40 is included in the series circuit 61 of the orthogonal transformation device 60 in operation. A series circuit 61 having a smaller number than the standard connection number and the largest number of connected fuel cells 40 is sequentially selected. After the process of S130, the fuel cell switching unit 50 moves the process to the determination of S122. In S126, when there is no fuel cell 40 that is connected to the stopped orthogonal transform device 60 and is generating power, the process proceeds to S122.

  Thus, the fuel cell switching unit 50 stops the operation of one orthogonal transform device 60 and connects to the orthogonal transform device 60 when the predetermined number or more of the fuel cells 40 stop generating power. Since each of the existing fuel cells 40 is connected in series to each of the series circuits 61 to which the stopped fuel cells 40 were connected, energy loss due to a reduction in power conversion efficiency in the whole of the plurality of orthogonal transform devices 60 is reduced. Can be reduced.

  FIG. 4 is a diagram illustrating an example of a connection state of the fuel cell 40 to the orthogonal transformation device 60. When the fuel cells (40b, 40e, 40g, 40k, 40o) of the fuel cells 40 stop generating power, the stopped fuel cells 40 are removed from the series circuit 61 by the fuel cell switching unit 50. The fuel cell switching unit 50 connects the four fuel cells 40 of the fuel cells (40a, 40f, 40c, 40d) to the orthogonal transformation device 60a in order to satisfy the standard connection number of the series circuit 61a. Further, the fuel cell switching unit 50 connects the four fuel cells 40 of the fuel cells (40i, 40j, 40l, 40h) to the orthogonal transformation device 60c in order to satisfy the standard connection number of the series circuit 61c. The fuel cell switching unit 50 connects the three fuel cells 40 of the remaining fuel cells (40 m, 40 n, 40 p) that are generating power to the orthogonal transformation device 60 d. Then, the fuel cell switching unit 50 stops the operation of the orthogonal transformation device 60b without connecting any of the fuel cells 40 to the series circuit 61b.

  Thus, when the fuel cell 40 stops generating power, the fuel cell switching unit 50 selects the series circuit 61 to which the fuel cell 40 that has stopped generating power is connected, and the fuel cell 40 is selected from the selected series circuit 61. And a new fuel cell 40 is connected in series. For this reason, it is possible to efficiently supply power to the power load 58 by reducing the amount of energy loss associated with a decrease in power conversion efficiency in the orthogonal transform device 60.

  When the fuel cell 40 is removed from the series circuit 61, the fuel cell switching unit 50 determines whether or not another fuel cell 40 is newly connected to the series circuit 61. Judgment is made by comparing the energy efficiency when the fuel cell is connected to the fuel cell and the energy efficiency when the other fuel cell 40 is not newly connected.

  In general, the power generation efficiency of the fuel cell 40 depends on the power generated by the fuel cell 40, and the higher the power generation power, the higher the power generation efficiency. Therefore, when any one of the fuel cells 40 connected to one series circuit 61 is operated at a rated output or less, the number of fuel cells 40 connected to the series circuit 61 is reduced to generate power from the fuel cell 40. The power generation efficiency can be increased by increasing the power. However, the amount of energy loss accompanying power conversion in the orthogonal transform device 60 increases as the number of fuel cells 40 connected to the series circuit 61 decreases.

  FIG. 5 is a flowchart showing an operation procedure when the fuel cell switching unit 50 is removed from the series circuit 61. The fuel cell switching unit 50 removes the fuel cell 40 whose power generation has been stopped from the series circuit (S212). Then, the fuel cell switching unit 50 determines whether the energy efficiency is higher when another fuel cell 40 is newly connected to the series circuit 61 than when not newly connected (S214).

  In S214, the fuel cell switching unit 50 stores in advance the conversion efficiency and the number of connected units, the amount of energy loss caused by the decrease in the conversion efficiency of the orthogonal transform device 60 when one fuel cell 40 is removed from the series circuit 61. The amount of increase in the amount of energy loss in the orthogonal transformation device 60 is determined based on the above relationship. In addition, the fuel cell switching unit 50 stores in advance the amount of energy lost when the power generated by the remaining fuel cells 40 is increased without newly connecting another fuel cell 40 to the series circuit 61. Calculation is made based on the relationship between the efficiency and the generated power, and the amount of reduction in energy loss in the entire fuel cell 40 connected to the orthogonal transformation device 60 is determined. The fuel cell switching unit 50 determines that the increase in the amount of energy loss caused by the decrease in the conversion efficiency of the orthogonal transformation device 60 due to the removal of one fuel cell 40 from the series circuit 61 is the power generation of the remaining fuel cells 40. If the amount of loss of energy when the power to be increased is less than the amount of decrease in energy loss, the energy efficiency is higher when the other fuel cell 40 is newly connected to the series circuit 61 than when it is not newly connected. to decide.

  When the fuel cell switching unit 50 determines in S214 that the energy efficiency is higher when the new fuel cell 40 is connected to the series circuit 61 than when the fuel cell switching unit 50 is not connected, the future heat storage in each of the hot water tanks 54 is performed. The amount is predicted (S216). At this time, the fuel cell switching unit 50 predicts the amount of heat accumulated in the hot water storage tank 54 over a period from the present to 6 hours later. Then, the fuel cell switching unit 50 determines the hot water storage tank 54 with the shortest heat storage amount among the hot water storage tanks 54 to which the fuel cells 40 that are not generating power supply heat (S218). At this time, the fuel cell switching unit 50 sets the hot water storage tank 54 in which the heat storage amount predicted in S216 is predicted to fall below the predetermined lower limit value of the heat storage amount at the earliest time as the hot water storage tank 54 with the shortest heat storage amount. decide. Then, the fuel cell switching unit 50 connects the fuel cell 40 that supplies hot water to the hot water tank 54 determined in S218 to the series circuit 61 (S220), and ends the process. If the fuel cell switching unit 50 determines in S214 that the energy efficiency is lower when the new fuel cell 40 is connected to the series circuit 61 than when it is not connected, the process is terminated.

  As described above, when the fuel cell switching unit 50 newly connects the fuel cell 40 to the series circuit 61, the fuel cell 40 can supply the heat amount to the heat load 56 in which the required heat amount is most insufficient. Is selected to start power generation, and the fuel cell 40 is connected to the series circuit 61. For this reason, it can prevent that the calorie | heat amount which the heat load 56 requires is insufficient. Further, when the fuel cell switching unit 50 removes the fuel cell 40 from the series circuit 61, the energy efficiency when another fuel cell 40 is newly connected to the series circuit 61, and the fuel cell newly added to the series circuit 61. Compared with the energy efficiency when not connecting 40, it is determined whether or not the fuel cell 40 is newly connected to the series circuit 61. Therefore, the energy of the entire system when the fuel cell 40 is removed from the series circuit 61 is determined. The amount of decrease in efficiency can be reduced.

  When there is a series circuit 61 in which the input voltage to the orthogonal transformation device 60 is lower than a predetermined voltage value, the fuel cell switching unit 50 newly connects the fuel cell 40 to the series circuit 61. You may control. For example, the number of fuel cells 40 connected to the series circuit 61 is increased so that the input voltage to the orthogonal transformation device 60 is equal to or higher than the peak value of the AC voltage required by the power load 58. In the fuel cell system 30 of the present embodiment, the fuel cells connected to the series circuit 61 are controlled so that the number of the fuel cells 40 connected to one series circuit 61 is three or more.

  In this way, power can be supplied to the power load 58 using the fuel cell 40 having a power generation voltage lower than the peak value of the AC voltage required by the power load 58. For this reason, the fuel cell system 30 can be constructed at a low cost by using a fuel cell having a power generation voltage lower than the peak voltage output from the orthogonal transformation device 60. Also, AC power can be supplied at a voltage required by the power load 58 without installing a booster circuit or the like for increasing the input voltage to the orthogonal transform device 60.

  In addition, the fuel cell switching unit 50 removes the fuel cell 40 from the series circuit 61 when the overall energy efficiency is increased by removing the fuel cell 40 from the series circuit 61 based on the power consumed by the power load 58. Except for this, power generation is stopped.

  FIG. 6 is a flowchart illustrating a procedure in which the fuel cell switching unit 50 controls connection of the fuel cell 40 based on power consumption. The fuel cell switching unit 50 acquires the amount of power consumed by the power load 58 from the wattmeter 46 (S232). The fuel cell switching unit 50 calculates the overall energy efficiency of the fuel cell 40 and the orthogonal transformation device 60 (S234). In S234, the fuel cell switching unit 50 calculates the energy efficiency by calculating the amount of energy lost when the fuel cell 40 is removed from the series circuit 61 and when the fuel cell 40 is not removed, in the same procedure as described in S214. To do. Then, the fuel cell switching unit 50 determines whether or not the energy efficiency when the orthogonal transformation device 60 outputs the power required by the power load 58 is increased by removing the fuel cell 40 from the series circuit 61. (S236).

  When the fuel cell switching unit 50 determines that the energy efficiency is increased by removing the fuel cell 40 from the series circuit 61 in S236, the fuel cell switching unit 50 predicts the future heat storage amount in each of the hot water tanks 54 (S238). At this time, the fuel cell switching unit 50 predicts the amount of heat accumulated in the hot water storage tank 54 over a period from the present to 6 hours later. And the fuel cell switching part 50 determines the hot water storage tank 54 from which the heat storage amount becomes the most surplus among the hot water storage tanks 54 to which the fuel cell 40 which is generating electric power supplies heat (S240). At this time, the fuel cell switching unit 50 replaces the hot water storage tank 54 in which the heat storage amount predicted in S238 is predicted to exceed the predetermined upper limit value of the heat storage amount at the earliest time, and the hot water storage tank 54 in which the heat storage amount becomes the most excessive Determine as. And the fuel cell switching part 50 removes the fuel cell 40 which supplies warm water to the hot water storage tank 54 determined by S240 from the series circuit 61 (S242), stops the electric power generation of the said fuel cell 40, and complete | finishes a process. If the fuel cell switching unit 50 determines that the energy efficiency is lowered by removing the fuel cell 40 from the series circuit 61 in S236, the process is terminated.

  As described above, the fuel cell switching unit 50 has a higher energy efficiency when the one fuel cell 40 is removed from the series circuit 61 than when the fuel cell 40 is not removed from the series circuit 61. One fuel cell 40 is removed from the series circuit 61. For this reason, even when the amount of power consumed by the power load 58 is reduced and the fuel cell 40 is in partial load operation, the amount of reduction in the energy efficiency of the entire system can be reduced.

  In S216 of FIG. 5 and S238 of FIG. 6, the fuel cell switching unit 50 performs hot water to be stored in each hot water storage tank 54 in the future based on the history of the amount of power generated by the fuel cell 40 and the amount of heat consumed by the thermal load 56. Predict the amount of heat.

  FIG. 7 is a flowchart illustrating a procedure in which the fuel cell switching unit 50 predicts the amount of heat stored in the hot water tank 54. The fuel cell switching unit 50 calculates the integrated value (Q1) of the amount of heat consumed by the heat load 56 in the future based on the history of the amount of heat consumed by the heat load 56 (S252). Furthermore, the fuel cell switching unit 50 calculates an integrated value (Q2) of the amount of heat supplied to the hot water tank 54 based on the history of the amount of power generated by the fuel cell 40 (S254). Further, the fuel cell switching unit 50 calculates the sum of the integrated value (Q2) of the heat amount to be supplied to the hot water storage tank 54 in the future and the heat amount currently stored in the hot water storage tank 54, and supplies this to the hot water storage tank 54. The accumulated heat storage amount (Q3) is set (S256). Further, the fuel cell switching unit 50 calculates a value obtained by subtracting the integrated value (Q1) of the heat amount that the thermal load 56 will consume in the future from the accumulated heat amount (Q3) to the hot water tank 54, and uses this value as the future hot water tank. The amount of heat (Q4) accumulated in 54 is set (S258).

  The fuel cell switching unit 50 calculates the amount of heat consumed by the heat load 56 based on the amount of hot water supplied from the hot water tank 54 to the heat load 56 and the temperature of the hot water. The fuel cell switching unit 50 calculates the amount of heat stored in the hot water storage tank 54 based on the amount of hot water stored in the hot water storage tank 54 and the temperature of the hot water. The fuel cell switching unit 50 stores in advance a relationship between the amount of heat received from the fuel cell 40 and the amount of power generated by the fuel cell 40, and calculates the amount of heat supplied to the hot water tank 54 based on the relationship.

  The fuel cell switching unit 50 has a history table that stores past histories of the amount of heat consumed by the thermal load 56 and the amount of power generated by the fuel cell 40, and is stored in the future hot water tank 54 with reference to the history table. Calculate the amount of heat (Q4).

  FIG. 8 is a diagram illustrating an example of a history table managed by the fuel cell switching unit 50. The fuel cell switching unit 50 stores, in the history table for each residence 42, the average value for each predetermined number of days of heat consumption and generated power for each hour of the hour from 1 o'clock to 24 o'clock of the day. Store. Further, the fuel cell switching unit 50 creates a history table for each of weekdays and Saturdays or Sundays.

  The fuel cell switching unit 50 refers to the history table corresponding to the day of the week derived based on the date information from the history table managed by the fuel cell switching unit 50, and thereby the amount of heat consumed and the fuel of the heat load 56 on that day. The time development of the amount of power generated by the battery 40 is obtained. Then, when the fuel cell switching unit 50 determines whether or not the amount of heat accumulated in the hot water storage tank 54 is excessive as compared with the amount of heat required by the heat load 56, the time evolution of the amount of power generated by the fuel cell 40 is developed. This is determined based on the time evolution of the amount of heat generated by the fuel cell 40 calculated from the above, the time evolution of the amount of heat consumed by the heat load 56, and the amount of heat currently stored in the hot water tank 54.

  For example, the fuel cell switching unit 50 predicts the amount of heat accumulated in each of the hot water tanks 54 over a period from the present to 6 hours later. Then, when the predicted amount of heat is predicted to fall below a predetermined lower limit value of the stored heat amount, it is determined that the amount of heat required by the thermal load 56 is insufficient. Further, when it is predicted that the predicted heat amount exceeds the predetermined upper limit value of the heat storage amount, it is determined that the heat amount required by the thermal load 56 is excessive.

  In addition, when the difference between the generated power amount stored in the history table and the actual generated power amount is larger than the predetermined power amount, the actual generated power amount is compared with the actual generated power amount with respect to the generated power amount. The future power generation amount is calculated by correcting to match the power generation amount. For example, the difference between the actual generated power amount in the hour immediately before the current time and the generated power amount stored in the history table is calculated, and the difference between the generated power amount and the generated power amount stored in the history table is calculated. The sum is calculated as the amount of power generated in the future. Similarly, when the difference between the heat consumption amount stored in the history table and the actual heat consumption amount is larger than the predetermined heat amount, the actual heat consumption amount is compared with the heat consumption amount stored in the history table. Calculate future heat consumption by correcting to match.

  In general, the amount of heat consumed by the heat load 56 and the amount of power generated by the fuel cell 40 vary greatly depending on whether it is a weekday, Saturday or Sunday. The fuel cell switching unit 50 can appropriately determine the amount of heat consumed and the amount of generated power based on the day of the week based on a history table in which past histories of the amount of heat consumed by the thermal load 56 and the amount of power generated by the fuel cell 40 are stored. Therefore, the fuel cell switching unit 50 can appropriately determine whether or not the amount of heat in the hot water storage tank 54 becomes excessive.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements are also included in the technical scope of the present invention.

1 shows an exemplary configuration of a fuel cell system 30 according to an embodiment of the present invention. An example of the open / close state of the bypass switch 62 and the connection switches (64, 65) is shown. 7 is a flowchart showing a procedure in which the fuel cell switching unit 50 stops the orthogonal transformation device 60 and switches the connection of the fuel cell 40. An example of the connection state of the fuel cell 40 to the orthogonal transformation device 60 is shown. 6 is a flowchart showing an operation procedure when the fuel cell switching unit 50 is removed from the series circuit 61. 4 is a flowchart showing a procedure for controlling connection of the fuel cell 40 based on power consumption by the fuel cell switching unit 50. 4 is a flowchart showing a procedure in which the fuel cell switching unit 50 predicts the amount of heat stored in the hot water tank 54. It is a figure which shows an example of the log | history table which the fuel cell switching part 50 manages.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 40 ... Fuel cell, 42 ... Dwelling, 44 ... Electric power network, 46 ... Wattmeter, 50 ... Fuel cell switching part, 52 ... Failure detection part, 54 ... Hot water storage tank 56 ... Thermal load, 58 ... Power load, 60 ... Orthogonal transformation device, 61 ... Series circuit, 62 ... Bypass switch, 64, 65 ... Connection switch

Claims (18)

A plurality of fuel cells provided in a distributed manner to supply heat to each of the thermal loads provided at different positions;
A series circuit connecting the plurality of fuel cells in series;
An orthogonal transformation device that converts direct current power obtained by the series circuit into alternating current power and supplies it to a power load that consumes alternating current power;
When one fuel cell of the plurality of fuel cells is removed from the series circuit, the amount of decrease in the DC voltage input to the orthogonal transformation device by connecting a new fuel cell in series to the series circuit A fuel cell system comprising: a fuel cell switching unit that suppresses fuel consumption.   The fuel cell switching unit selects a fuel cell that can supply heat to the heat load that requires the least amount of heat as the new fuel cell, and starts power generation. The fuel cell system according to claim 1, wherein the fuel cell system is connected to the series circuit.   The fuel cell switching unit selects a fuel cell that produces more heat than the heat load requires, removes the selected fuel cell from the series circuit, and generates power from the fuel cell. The fuel cell system according to claim 2, which is stopped. A failure detector for detecting failures of the plurality of fuel cells;
The fuel cell system according to claim 2, wherein the fuel cell switching unit removes a failed fuel cell from the series circuit when the failure detection unit detects a failure.   The fuel cell switching unit removes the one fuel cell from the series circuit when the power generation of the one fuel cell is stopped by a user of the plurality of fuel cells, and requires the least amount of heat. The fuel cell system according to claim 2, wherein a fuel cell capable of supplying heat to the thermal load is selected as the new fuel cell to start power generation, and the fuel cell is connected to the series circuit. . The DC voltage output from each of the plurality of fuel cells is smaller than the peak value of the AC voltage output from the orthogonal transform device,
The fuel cell system according to claim 1, wherein a voltage obtained by the series circuit is equal to or higher than the peak value.   The fuel cell switching unit includes the power generation efficiency of the whole of the plurality of fuel cells connected to the series circuit and the conversion efficiency of the orthogonal transform device for supplying the amount of power required by the power load. When the one fuel cell is removed from the series circuit, the energy efficiency when the new fuel cell is connected to the series circuit is equal to the new fuel cell in the series circuit. 2. The fuel cell system according to claim 1, wherein the new fuel cell is connected to the series circuit on condition that the energy efficiency is higher than the energy efficiency when not connected.   The fuel cell switching unit, when the energy efficiency when the one fuel cell is removed from the series circuit is higher than the energy efficiency when the one fuel cell is not removed from the series circuit, The fuel cell system according to claim 7, wherein the one fuel cell is excluded from the series circuit. A plurality of the orthogonal transformation devices are provided, and the series circuit is provided for each orthogonal transformation device,
Each of the series circuits includes a connection switch that inserts each of the plurality of fuel cells into the series circuit and connects them in series, and a bypass that bypasses each of the plurality of fuel cells without being inserted into the series circuit. A switch,
When the one fuel cell is removed from the series circuit, the fuel cell switching unit opens the connection switch that connects the one fuel cell in series to the series circuit and bypasses the one fuel cell. Closing the bypass switch, and further opening the bypass switch for bypassing the new fuel cell without inserting it into the series circuit, and connecting the connection switch for connecting the new fuel cell in series with the series circuit. The fuel cell system according to claim 3.   The fuel cell switching unit selects the series circuit to which the one fuel cell is connected when one fuel cell stops power generation, and removes the one fuel cell from the selected series circuit. The fuel cell system according to claim 9, wherein the new fuel cells are connected in series.   The fuel cell switching unit stops the operation of one orthogonal transform device when a predetermined number of fuel cells stop generating power, and generates power for each of the fuel cells connected to the orthogonal transform device. The fuel cell system according to claim 10, wherein the fuel cell system is connected in series to each of the series circuits to which the fuel cells having been stopped are connected. A plurality of fuel cells provided in a distributed manner to supply heat to each of the thermal loads provided at different positions;
A series circuit connecting the plurality of fuel cells in series;
An orthogonal transformation device that converts direct current power obtained by the series circuit into alternating current power and supplies the alternating current power to a power load;
When one fuel cell of the plurality of fuel cells is removed from the series circuit, a new fuel cell is added to the series circuit by increasing the power generated by the remaining fuel cells connected to the series circuit. When the one fuel cell is removed from the series circuit when the electric power can be supplied without being connected to, the increase in the amount of energy loss caused by the decrease in the conversion efficiency of the orthogonal transform device is the remaining amount. The new fuel cell is input to the orthogonal transformation device by connecting the new fuel cell in series to the series circuit on condition that the amount of energy loss obtained by increasing the power generated by the fuel cell is less than the reduction amount. A fuel cell system comprising a fuel cell switching unit that suppresses a decrease in DC voltage. Connecting a plurality of fuel cells provided in a distributed manner to supply heat to each of the heat loads provided at different positions in series with a series circuit;
Converting DC power obtained by the series circuit into AC power using an orthogonal transformation device and supplying the AC power to a power load that consumes AC power;
When one fuel cell of the plurality of fuel cells is removed from the series circuit, the amount of decrease in the DC voltage input to the orthogonal transformation device by connecting a new fuel cell in series to the series circuit A fuel cell system control method comprising:   In the fuel cell switching step, a fuel cell that can supply heat to the thermal load having the least amount of heat required is selected as the new fuel cell to start power generation. The fuel cell system control method according to claim 13, wherein the fuel cell system control method is connected to the series circuit.   The fuel cell according to claim 14, wherein the fuel cell switching step selects a fuel cell that produces an excessive amount of heat compared to the amount of heat required by the thermal load, and removes the selected fuel cell from the series circuit. System control method. A plurality of the orthogonal transformation devices are provided, and the series circuit is provided for each orthogonal transformation device,
The series circuit includes a connection switch that inserts each of the plurality of fuel cells into the series circuit and connects them in series, and a bypass switch that bypasses each of the fuel cells without being inserted into the series circuit. And
In the fuel cell switching step, when the one fuel cell is removed from the series circuit, the connection switch for connecting the one fuel cell in series to the series circuit is opened and the one fuel cell is bypassed. Closing the bypass switch, and further opening the bypass switch for bypassing the new fuel cell without inserting it into the series circuit, and connecting the connection switch for connecting the new fuel cell in series with the series circuit. The fuel cell system control method according to claim 15.   In the fuel cell switching step, when one fuel cell stops power generation, the series circuit to which the one fuel cell is connected is selected, and the one fuel cell is removed from the selected series circuit. The fuel cell system control method according to claim 16, wherein the new fuel cells are connected in series.   In the fuel cell switching step, when more than a predetermined number of fuel cells stop generating power, the operation of one orthogonal transform device is stopped, and each of the fuel cells connected to the orthogonal transform device generates power. The fuel cell system control method according to claim 17, wherein the fuel cell system is connected in series to each of the series circuits to which the fuel cells having been stopped are connected.

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