JP2015211507A - Power control system, power controller, and power control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve load followability by gradually reducing a power generation amount of a fuel power generator depending on a power storage amount.SOLUTION: A power control system 1 comprises: a fuel power generator 33 for generating power during the course of a current sensor 40 detecting a forward power flow; a storage battery 12; a power controller 20 for controlling the fuel power generator and the storage battery so as to link with each other; and a pseudo output unit 50. The power controller 20 outputs generation power based on current in the forward power flow direction detected by the current sensor 40. The power controller 20 monitors a power storage amount of the storage battery 12; and, when the power storage amount exceeds a threshold, reduces current in the forward power flow direction detected by the current sensor 40 by adjusting pseudo current to make generation power of the fuel power generator 33 gradually reduce while charging the storage battery 12 with the generation power.

Description

  The present invention relates to a power control system, a power control device, and a power control method.

  Conventionally, as a power storage power conditioner of a power storage system including a power storage facility such as a storage battery that is charged by a commercial power system (hereinafter abbreviated as “system”), a grid connection that outputs AC power connected to the system There has been known one that enables operation and independent operation that outputs AC power regardless of the system (see, for example, Patent Document 1).

  In addition, a fuel cell that generates electric power by a fuel cell reaction, a storage battery that stores electric power, and a control means for controlling the operation of the fuel cell and the storage battery, the control is performed when the operating temperature of the fuel cell exceeds a set temperature. As a means, there is known a fuel cell system that limits the power generation output of the fuel cell and discharges the storage battery (see, for example, Patent Document 2).

JP 2008-253033 A JP 2006-344488 A

  However, if the power generation amount of the fuel cell decreases rapidly, for example, if the power load suddenly becomes zero during the independent operation disconnected from the power system and the load following operation, the temperature of the fuel cell rapidly decreases. There was a risk of damaging the fuel cell. In addition, when the fuel cell completely stops power generation, it takes time to resume operation, and there is a problem that it cannot immediately follow the load.

  An object of the present invention made in view of such circumstances is a power control system, a power control device, and a power that can improve load followability while slowly reducing the amount of power generation when stopping the fuel power generation device. It is to provide a control device method.

  In order to solve the above problems, a power control system according to the present invention includes a fuel power generation device that generates power while a current sensor detects a forward power flow, a storage battery, and a power control device that controls each of them in cooperation with each other. And a pseudo output unit for generating a pseudo current detected by the current sensor, wherein the power control device outputs generated power based on a forward current detected by the current sensor, and the power The control device monitors the amount of electricity stored in the storage battery, and when the amount of electricity stored exceeds a first threshold value, adjusts the pseudo current to reduce the current in the forward flow direction detected by the current sensor, and The generated power of the power generation device is gradually reduced, and the generated power is gradually charged in the storage battery.

  Furthermore, in the power control system according to the present invention, the current sensor detects a differential current obtained by subtracting a charging current flowing from the fuel power generation device to the storage battery from the pseudo current as a current in a forward power flow direction. .

  Furthermore, in the power control system according to the present invention, the power control device controls the pseudo current and the differential current becomes zero when the charged amount exceeds a second threshold larger than the first threshold. It is characterized by adjusting as follows.

  Further, in the power control system according to the present invention, the pseudo output unit includes a power adjustment unit that converts supplied power, and a branch unit that shunts a current output from the power adjustment unit, One output current is set as the pseudo-current, and the power control device controls the pseudo-current by controlling an output voltage of the power adjustment unit.

  Furthermore, the power control system according to the present invention is characterized in that the power adjustment unit makes the output voltage variable by PWM control.

  Furthermore, in the power control system according to the present invention, a resistor is connected to each of the branch portions.

  The power control apparatus according to the present invention is a power control apparatus used in a power control system that controls a fuel power generation apparatus and a storage battery that generate power while a current sensor detects a forward power flow. A pseudo output unit that generates a pseudo current detected by a sensor, and when the fuel power generation device performs a self-sustained operation, the pseudo output unit outputs a pseudo current, monitors a storage amount of the storage battery, and When the amount exceeds a threshold value, the current of the pseudo-output unit is controlled to adjust the differential current obtained by subtracting the charging current flowing through the storage battery from the pseudo-current from the fuel power generator, and the generated power of the fuel power generator Is gradually reduced, and the storage battery is gradually charged with the generated power.

  The power control method according to the present invention is a power control method for a power control apparatus that controls a fuel power generation apparatus and a storage battery that generate power while a current sensor detects a forward power flow. Includes a pseudo output unit that generates a pseudo current detected by the current sensor, and outputs a pseudo current from the pseudo output unit when the fuel power generation device performs a self-sustaining operation; and a storage amount of the storage battery When the amount of stored electricity exceeds a threshold value, the pseudo current is controlled to adjust a differential current obtained by subtracting the charging current flowing from the fuel power generator to the storage battery from the pseudo current, and the fuel power generator Gradually reducing the generated power, and gradually charging the generated battery with the generated power.

  According to the present invention, the power generation amount of the fuel power generation device can be gradually reduced according to the amount of stored electricity, so that the rate of temperature drop in the fuel battery cell becomes gradual and the life of the fuel battery cell can be extended. It becomes. In addition, when the fuel power generation device completely stops power generation, the temperature of the fuel cell is low. Therefore, when power is generated again, it takes time to resume power generation, and load follow-up operation cannot be performed immediately. However, according to the present invention, since the power generated by the fuel power generator is gradually reduced before the storage battery is fully charged, the frequency at which power generation is completely stopped is reduced, and the load followability can be improved.

1 is a block diagram of a power control system according to an embodiment of the present invention. It is a figure which shows the wiring regarding the pseudo output part in the electric power control system which concerns on one Embodiment of this invention. It is a figure which shows the example of control at the time of the grid operation of the electric power control system which concerns on one Embodiment of this invention. It is a figure which shows the electric power supply to the pseudo | simulation output part at the time of the independent operation of the electric power control system which concerns on one Embodiment of this invention. It is a figure which shows the electric power generation of the fuel electric power generating apparatus at the time of the independent operation of the electric power control system which concerns on one Embodiment of this invention. It is a figure which shows the electric power generation amount at the time of the electric power generation stop process of the fuel electric power generating apparatus in the electric power control system which concerns on one Embodiment of this invention. It is a flowchart which shows the power control method in the power control system which concerns on one Embodiment of this invention. It is a figure which shows the structural example of the pseudo output part in the electric power control system which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, a power control system according to an embodiment of the present invention will be described. The power control system according to the present embodiment includes a distributed power source that supplies power that cannot be sold in addition to power supplied from the grid. The distributed power source that supplies electric power that cannot be sold is, for example, a storage battery that can charge and discharge electric power, a fuel cell such as an SOFC (Solid Oxide Fuel Cell), or a power generator that generates electric power using gas fuel. In the present embodiment, an example in which a storage battery and a fuel power generation device are provided as a distributed power source that supplies power that cannot be sold is shown. Moreover, you may further provide the distributed power supply which supplies the electric power which can be sold. A distributed power source that supplies power that can be sold is a system that supplies power by, for example, solar power generation.

  FIG. 1 is a block diagram showing a schematic configuration of a power control system according to an embodiment of the present invention. The power control system 1 according to the present embodiment includes a storage battery 12, a fuel power generation device 33, a power control device (power conditioner) 20, and a pseudo output unit 50. The power control device 20 is connected to the fuel power generation device 33 and the load 32 via the distribution board 31. A current sensor 40 is disposed between the system and the distribution board 31. A solar cell may be connected in parallel with the storage battery 12.

  The power control system 1 normally performs an interconnection operation with the grid, and supplies the load 32 with the power supplied from the grid and the power from the distributed power supply (the storage battery 12 and the fuel power generation device 33). In addition, when there is no power supply from the system, such as during a power failure, the power control system 1 disconnects the storage battery 12 and the fuel power generation device 33 from the system and performs independent operation, and the power from the fuel power generation device 33 is supplied to the load 32. Supply. In addition, when the power control system 1 performs independent operation, each distributed power source is disconnected from the system, and when the power control system 1 performs interconnected operation, each distributed power source is parallel to the system. It becomes a state.

  In FIG. 1, a line without an arrow connecting each functional block represents a wiring through which power flows, and a line with an arrow connecting each functional block represents a flow of a control signal or information to be communicated. Communication indicated by a line without an arrow may be wired communication or wireless communication. Various methods can be adopted for communication of control signals and information including each layer. For example, communication by a short-range communication method such as ZigBee (registered trademark) can be employed. In addition, various transmission media such as infrared communication and power line communication (PLC) can be used. In addition, various protocols such as ZigBee SEP 2.0 (Smart Energy Profile 2.0), ECHONET Lite (registered trademark), etc. are defined on lower layers including the physical layer suitable for each communication. A communication protocol may be operated.

  The storage battery 12 includes a storage battery such as a lithium ion battery or a nickel metal hydride battery. The storage battery 12 can supply electric power by discharging the charged electric power. In addition to the power supplied from the grid, the storage battery 12 can charge the power supplied from the fuel power generation device 33 as described later.

  The power control device 20 is a device that controls the storage battery 12, the fuel power generation device 33, and the pseudo output unit 50 in cooperation with each other. The power control device 20 is supplied from the direct current power supplied from the storage battery 12 and the system and the fuel power generation device 33. Conversion with alternating current power, and switching control between interconnected operation and independent operation. The power control device 20 includes a power conversion unit (inverter) 21, interconnection operation switches 22 and 23, a self-sustaining operation switch 24, and a control unit 25 that controls the entire power control device 20. The interconnecting operation switch 23 may be configured to go out of the power control device 20.

  The power conversion unit 21 is a bidirectional inverter, converts DC power supplied from the storage battery 12 into AC power, and converts AC power supplied from the system and the fuel power generation device 33 into DC power. Convert. Note that a converter that boosts the DC power from the storage battery 12 to a certain voltage may be provided before the power conversion unit 21.

  The interconnecting operation switches 22 and 23 and the independent operation switch 24 are each configured by a relay, a transistor, and the like, and are on / off controlled. As illustrated, the self-sustaining operation switch 24 is disposed between the fuel power generation device 33 and the storage battery 12. The interconnecting operation switches 22 and 23 and the independent operation switch 24 are switched synchronously so that both are not simultaneously turned on (or off). More specifically, when the interconnection operation switches 22 and 23 are turned on, the autonomous operation switch 24 is turned off synchronously, and when the interconnection operation switches 22 and 23 are turned off, the autonomous operation switch 24 is turned on synchronously. It becomes. Synchronous control of the interconnection operation switches 22 and 23 and the independent operation switch 24 is realized by hardware by branching the wiring of the control signal to the interconnection operation switches 22 and 23 to the independent operation switch 24. Needless to say, the ON and OFF states for the same control signal can be set separately for each switch. Further, the synchronous control of the interconnection operation switches 22 and 23 and the independent operation switch 24 can be realized by software by the control unit 25.

  The control unit 25 is configured by a microcomputer, for example, and controls the operation of each unit such as the power conversion unit 21, the interconnection operation switches 22 and 23, and the self-sustained operation switch 24 based on a state such as a rise in system voltage or a power failure. Control. The control unit 25 switches the interconnection operation switches 22 and 23 on and the independent operation switch 24 off during the interconnection operation. Moreover, the control part 25 switches the interconnection operation switches 22 and 23 off and the autonomous operation switch 24 on during the independent operation.

  The distribution board 31 distributes the power supplied from the grid during the grid operation to a plurality of branches and distributes it to the load 32. In addition, the distribution board 31 distributes the power supplied from the plurality of distributed power sources (the storage battery 12 and the fuel power generation device 33) to the plurality of branches and distributes it to the load 32. Here, the load 32 is a power load that consumes power. For example, various electric appliances such as air conditioners, microwave ovens, and televisions used in homes, air conditioners and lighting equipment used in commercial and industrial facilities, and the like. Machine, lighting equipment, etc.

  The fuel power generation device 33 includes a fuel cell 34 that generates direct-current power through a chemical reaction with oxygen in the air using hydrogen, and a power conversion unit 36 that converts the generated direct-current power into 100V or 200V AC power. The control unit 35 that controls the fuel cell 34 and the power conversion unit 36 and other auxiliary devices are provided. Here, the fuel power generation device 33 is a device that enables supply of AC power to the load 32 without going through the power control device 20, and is not necessarily designed assuming connection to the power control device 20. The device may be versatile. The fuel power generation device 33 may be a gas generator that generates power with a gas engine using a predetermined gas or the like as fuel.

  The fuel power generation device 33 generates power while the current sensor 40 detects a forward current (current in the power purchase direction), and performs load following operation that follows the power consumption of the load 32 during power generation, and a predetermined rated power value. Perform rated operation with. The tracking range during load following operation is, for example, 200 to 700 W, and the rated power value during rated operation is, for example, 700 W. Note that the fuel power generation apparatus 33 may perform load following operation that follows the power consumption of the load 32 during the interconnected operation, and may perform load following operation or rated operation based on the rated power value during the independent operation. The electric power generated by the fuel power generation device 33 is determined based on the forward flow flowing toward the distribution board 31 and the fuel power generation device 33 in the current sensor 40, and when the forward flow becomes zero or negative, the generation stop process is started.

  The current sensor 40 is provided to detect a reverse power flow (current in the power selling direction) to the system side of the fuel power generation apparatus 33 stipulated as being unable to sell power, and flows between the system and the fuel power generation apparatus 33. Detect current. When the current sensor 40 detects reverse power flow, the fuel power generation device 33 stops power generation. On the other hand, while the current sensor 40 detects a forward power flow, the fuel power generation apparatus 33 performs power generation in a load following operation or a rated operation on the assumption that power can be supplied to the load 32 from itself.

  Here, the power control system 1 according to the present embodiment is in a self-sustaining operation state in which the fuel power generation device 33 and the storage battery 12 are disconnected from the grid, and the current sensor 40 has the same direction as the pseudo forward flow through the pseudo output unit 50. A current (pseudo current) is supplied. As a result, the fuel power generation device 33 can be rated and the power generated by the fuel power generation device 33 can be stored in the storage battery 12. Hereinafter, power storage by the pseudo current through the pseudo output unit 50 will be described in detail.

  The pseudo output unit 50 can supply a pseudo current that is a current in the same direction as the forward power flow to the current sensor 40, and includes a pseudo current load 51, a synchronous switch 52, and a pseudo current control switch 53. . As will be described later, by providing the pseudo output unit 50 and flowing the pseudo current, the fuel power generation apparatus 33 can be operated independently. The pseudo output unit 50 is supplied with power from the outside or is supplied with power from the power control device 20. In order to show that power is supplied to the pseudo output unit 50, a block of “power supply source” is shown in the drawing.

  FIG. 2 is a diagram illustrating wiring related to the pseudo output unit 50 when the pseudo output unit 50 is supplied with power from the power control device 20. In FIG. 2, the system is a single-phase three-wire of 200V. In this case, one of the voltage lines and the neutral line are connected to the pseudo output unit 50. As shown in the drawing, the connection line to the pseudo output unit 50 is wired so as to pass through the current sensors 40 installed in the two voltage lines. The pseudo output unit 50 may be configured integrally with the power control device 20 or may be configured independently of the power control device 20.

  The pseudo current load 51 is a load provided for current adjustment in the pseudo output unit 50. As the pseudo current load 51, a load outside the pseudo output unit 50 may be used. The synchronous switch 52 is for supplying a part of the electric power supplied to the pseudo output unit 50 to the current sensor 40 as a pseudo current in the same direction as the forward power flow. The pseudo current control switch 53 is for preventing unnecessary power generation due to the pseudo current. The synchronous switch 52 and the pseudo-current control switch 53 are configured by independent relays, transistors, and the like, and are independently controlled on / off by the control unit 25 of the power control device 20.

  The synchronization switch 52 is ON / OFF controlled in synchronization with the autonomous operation switch 24 of the power control device 20. That is, the synchronous switch 52 is turned off during the interconnected operation and is turned on during the autonomous operation, like the autonomous operation switch 24. More specifically, the synchronous switch 52 is a switch that synchronizes the disconnection / parallel switching with the system and the switching timing, and allows a pseudo current to flow at the time of disconnection and does not flow a pseudo current at the time of parallel. The synchronous control of the independent operation switch 24 and the synchronous switch 52 is realized by hardware by branching the wiring of the control signal to the independent operation switch 24 to the synchronous switch 52. The synchronous control of the independent operation switch 24 and the synchronous switch 52 can also be realized by software by the control unit 25.

  The pseudo current control switch 53 is turned off when charging of the storage battery 12 is completed, and is turned on when charging is not completed. Here, the case where the charging of the storage battery 12 is completed indicates a case where the storage battery 12 is charged with electric power of a predetermined value or more. Note that the control unit 25 may be configured to determine whether or not charging is completed through communication with the storage battery 12. When charging of the storage battery 12 is completed and the pseudo-current control switch 53 is turned off during the self-sustaining operation, the pseudo-current does not flow through the current sensor 40, so that unnecessary power generation by the fuel power generator 33 can be stopped.

  Hereinafter, a control example in the power control system 1 according to the present embodiment will be described in detail with reference to the drawings.

  FIG. 3 is a diagram illustrating a control example of the power control system 1 during the interconnected operation. In this case, each switch of the power control device 20 is controlled such that the grid operation switches 22 and 23 are on and the self-sustaining operation switch 24 is off. In addition, each switch of the pseudo output unit 50 is controlled so that the synchronous switch 52 is turned off and the pseudo current control switch 53 is turned on or off according to the charge amount of the storage battery 12.

  At the time of the interconnection operation, as indicated by the thick arrow, AC 100 V (or 200 V) is supplied from the system and is supplied to the load 32. When the charging of the storage battery 12 is not completed, the power control device 20 converts the AC power from the system into DC power and charges the storage battery 12. The power control device 20 has a configuration capable of outputting the power from the grid and the power of the storage battery 12 to the pseudo output unit 50. However, since the synchronous switch 52 is off during the interconnection operation, the power control device 20 simulates the current sensor 40. No current is supplied.

  A forward flow (current in the power purchase direction) flows from the system and the power control device 20 to the current sensor 40. The fuel power generation device 33 receives information on the current detected by the current sensor 40. When a forward current flows through the current sensor 40, the fuel power generation device 33 generates power and supplies power to the load 32 through the distribution board 31. As the fuel power generation device 33 increases the output, the load 32 eventually stops receiving power from the system and the power control device 20. Then, since the current does not flow to the current sensor 40, the fuel power generation device 33 reduces the output, and if it decreases too much, this time, power is input from the system and the power control device 20, and as a result, a forward current flows to the current detection unit, The fuel power generation device 33 increases the output. In this way, the fuel power generation device 33 performs load following by changing the output so that no current flows through the current sensor 40.

  Next, a control example of the power control system 1 during the independent operation will be described with reference to FIGS. 4 and 5, it is assumed that charging of the storage battery 12 is not completed. In this case, each switch of the power control apparatus 20 is controlled such that the interconnection operation switches 22 and 23 are turned off and the independent operation switch 24 is turned on. Each switch of the pseudo output unit 50 is controlled such that the synchronous switch 52 is on and the pseudo current control switch 53 is on.

  FIG. 4 is a diagram illustrating power supply to the pseudo output unit 50 during the autonomous operation. During the independent operation, the electric power control device 20 outputs the electric power of the storage battery 12 via the independent operation switch 24 to the pseudo output unit 50. Alternatively, power may be supplied to the pseudo output unit 50 from the outside.

  FIG. 5 is a diagram illustrating the power generation of the fuel power generation apparatus 33 by the pseudo current during the independent operation. As shown in FIG. 4, during the independent operation, the control unit 25 controls the switches 22, 23, and 24 to supply electric power from the power control device 20 to the pseudo output unit 50. Alternatively, the control unit 25 instructs the pseudo output unit 50 to supply power from the outside. The power generation power of the fuel power generation device 33 is determined based on the forward flow flowing toward the distribution board 31 and the fuel power generation device 33 in the current sensor 40. When the forward flow decreases, the generated power is reduced and the forward flow is zero or If negative, the power generation stop process is started. During the self-sustaining operation, a differential current I-i obtained by subtracting the current i flowing from the fuel power generation device 33 to the storage battery 12 from the pseudo current I becomes a forward current.

  By controlling the pseudo-current so that the forward flow is positive, the fuel power generation apparatus 33 performs power generation in the load following operation or the rated operation. The distribution board 31 supplies the power generated by the fuel power generation apparatus 33 to the load 32 and supplies surplus power exceeding the power consumption of the load 32 to the power control apparatus 20. The surplus power is converted into DC power by the power converter 21 through the self-sustained operation switch 24 in the power control device 20 and charged to the storage battery 12.

  When charging of the storage battery 12 is completed, control is performed so that the pseudo current amount becomes a current amount that cancels the forward power flow. As a result, since the forward flow from the system is not detected by the current sensor 40, the fuel power generation apparatus 33 stops power generation. Therefore, no more current than necessary is output to the storage battery 12. Thus, according to the present embodiment, it is possible to prevent unnecessary power generation by the fuel power generation apparatus 33.

  Here, when there is no load 32 or when the power consumed by the load 32 is small, it is assumed that the power generated by the fuel power generation apparatus 33 cannot be consumed by the load 32 and the storage battery 12 is fully charged. When the storage battery 12 is fully charged, the fuel power generation apparatus 33 starts a power generation stop process. Hereinafter, the power generation stop process of the fuel power generation apparatus 33 will be described.

  FIG. 6 is a diagram showing the power generation amount during the power generation stop process of the fuel power generation apparatus 33. When the fuel power generation device 33 sharply decreases the amount of power generation, the temperature in the cell of the fuel cell 34 increases and decreases, causing damage to the fuel cell. Therefore, the fuel power generation device 33 gradually reduces the amount of power generation in order to reduce damage to the fuel cells. When power generation is completely stopped as shown in FIG. 6 (a), when power is generated again, the amount of power generation must be gradually increased, so that it becomes impossible to follow the load quickly.

  Therefore, in the present embodiment, the control unit 25 monitors the amount of electricity stored in the storage battery 12, and as shown in FIG. 6B, the amount of electricity stored at time t1 is a first threshold (for example, 80% of full charge). Is exceeded, by adjusting the differential current obtained by subtracting the charging current flowing from the fuel power generation device 33 to the storage battery 12 from the pseudo current, the generated power of the fuel power generation device 33 is gradually reduced and the generated power is gradually transferred to the storage battery 12. Let it charge. That is, when the storage amount exceeds the first threshold, the control unit 25 gradually decreases the generated power of the fuel power generation apparatus 33 by gradually decreasing the pseudo current and gradually decreasing the differential current. The information received from the storage battery 12 by the control unit 25 may be information indicating the storage amount, for example, the current storage amount (power amount) of the storage battery 12 or the ratio of the current storage amount to full charge. Note that the control unit 25 can also monitor the generated power of the fuel power generation apparatus 33 to control the generated power with high accuracy.

  As shown in FIG. 6, the fuel power generation apparatus 33 continues power generation for a predetermined time even after the start of the power generation stop process. In this case, if the power generation is continued after the storage battery 12 is fully charged, the generated power after the full charge cannot be charged and is wasted. In FIG. 6 (b), after the power generation stop process is started at time t2, the generated power until time t3 when power generation is completely stopped is wasted. Therefore, as shown in FIG. 6C, the control unit 25, when the charged amount exceeds a second threshold value (for example, 90% of full charge) larger than the first threshold value at time t4, that is, full charge. Before the above, the current of the pseudo output unit 50 may be controlled and adjusted so that the differential current becomes zero. When the differential current becomes zero, the fuel power generation device 33 starts a power generation stop process. By adjusting the second threshold value, the storage battery 12 can be fully charged at time t5 when power generation is completely stopped, and waste of power generation can be prevented.

  FIG. 7 is a flowchart showing a power control method during the independent operation in the power control system 1. During the independent operation, the control unit 25 performs control so that power is supplied from the outside or the power control device 20 to the pseudo output unit 50 (step S101). The pseudo output unit 50 causes a pseudo current to flow through the current sensor 40 when electric power is supplied. When the pseudo current flows through the current sensor 40, the fuel power generation device 33 starts power generation and charges the storage battery 12 with the generated power. When starting the power generation, the fuel power generation device 33 outputs the generated power based on the differential current I-i obtained by subtracting the charging current i flowing from the fuel power generation device 33 to the storage battery 12 from the pseudo current I (step S102).

  The control unit 25 determines whether or not the charged amount exceeds the first threshold (step S103), and when the charged amount exceeds the first threshold (step S103-Yes), controls the pseudo current. By gradually reducing the differential current, the generated power is gradually reduced (step S104). On the other hand, when the charged amount is equal to or less than the first threshold (step S103-No), the process returns to step S102.

  Next, the control unit 25 determines whether it is necessary to supply power to the load 32 following the power consumption of the load 32 (step S105). When it is necessary to follow the load (step S105-Yes), the fuel power generation apparatus 33 performs the load following operation (step S107). On the other hand, when there is no need to follow the load (step S105-No), it is determined whether or not the charged amount exceeds the second threshold (step S106). When the amount of stored electricity exceeds the second threshold (step S106-Yes), the power generation stop process is started by controlling the pseudo current to set the differential current to zero (step S108). On the other hand, when the charged amount is equal to or smaller than the second threshold (No at Step S106), the process returns to Step S105.

  The pseudo output unit 50 can change the amount of pseudo current flowing through the current sensor 40 by, for example, using the pseudo current load 51 as a variable resistor such as a digital potentiometer. Moreover, as shown in FIG. 8, it is good also as a structure which can change the amount of pseudo currents by changing a voltage.

  FIG. 8 is a diagram illustrating a configuration example of the pseudo output unit 50. In this configuration, the pseudo output unit 50 includes a diversion unit 60. The diversion unit 60 includes a power adjustment unit 61, a control unit 62, and a branching unit 63. The power adjustment unit 61 is, for example, an AC / AC converter, and converts and outputs a voltage supplied from the outside or the power conversion device 20. The voltage output from the power adjustment unit 61 can be made variable by PWM control. In order to control the power adjustment unit 61, the control unit 62 outputs a gate signal to a switching element included in the power adjustment unit 61 based on an instruction from the control unit 25 of the power control device 20. In PWM control, the pulse width of the gate signal is determined by comparing the triangular wave with the voltage command. The control unit 62 may be provided outside the pseudo output unit 50, or may be directly controlled by the control unit 25 of the power control apparatus 20 without the control unit 62.

  The branching unit 63 divides the current output from the power adjustment unit 61. The branch part 63 is connected to pseudo-current loads (resistors) 51 and 54, and the current flowing through the pseudo-current load 51 becomes a pseudo-current. The dynamic range of the pseudo current is determined by a combination of the output voltage of the power adjustment unit 61 and the resistance values of the pseudo current loads 51 and 54. By connecting the pseudo current loads 51 and 54 in parallel, a change in the combined resistance value with respect to a change in the resistance value of the pseudo current loads 51 and 54 can be suppressed. That is, since the fluctuation of the output impedance viewed from the power adjustment unit 61 is reduced, the pseudo current loads 51 and 54 can be easily selected.

  As described above, according to the present embodiment, the power output control device 20 performs the simulation in which the simulated output unit 50 is a current in the same direction as the forward power flow during the self-sustaining operation in which the fuel power generation device 33 and the storage battery 12 are disconnected from the system. Since the current flows through the current sensor 40, the fuel power generation apparatus 33 can generate power. In addition, since the power generation of the fuel power generation device 33 is controlled using a pseudo current to the current sensor 40, there is an advantage that a general-purpose power generation device can be diverted without requiring special changes to the fuel power generation device 33 itself. .

  Further, according to the present embodiment, when the storage amount of the storage battery 12 exceeds the first threshold, the differential current obtained by subtracting the charging current from the pseudo current is adjusted, and the generated power of the fuel power generation apparatus 33 is gradually reduced. Since the generated power is gradually charged in the storage battery 12, the rate of temperature decrease in the fuel battery cell becomes gradual, and the life of the fuel battery cell can be extended. Further, when the fuel power generation device 33 completely stops power generation, the temperature of the fuel cell is low, so it takes time to generate power again, and load follow-up operation cannot be performed immediately. According to the embodiment, since the power generated by the fuel power generation device 33 is gradually reduced before the storage battery 12 is fully charged, the frequency at which power generation is completely stopped is reduced, and load followability can be improved. At this time, since the generated power has been lowered in advance, the time from when the power generation stop process is started until power generation is completely stopped is shortened.

  In addition, according to the present embodiment, when the storage amount of the storage battery 12 exceeds a second threshold value that is larger than the first threshold value, the pseudo current of the pseudo output unit 50 is controlled to adjust the differential current to zero. Therefore, the power generation stop process is started before the storage battery 12 is fully charged, and the storage battery 12 can be fully charged at the timing when power generation is completely stopped, so that waste of power generation can be prevented.

  Further, according to the present embodiment, the synchronous switch 52 is a switch that synchronizes the switching / parallel switching with the system and the switching timing, and allows a pseudo current to flow at the time of disconnection and does not flow a pseudo current at the time of parallel. As a result, a pseudo current flows through the current sensor 40 during the independent operation disconnected from the system, while a pseudo current does not flow through the current sensor 40 during the parallel operation in parallel with the system. No reverse flow from 33 will occur.

  Further, according to the present embodiment, the self-sustained operation switch 24 is turned off during the interconnected operation and is turned on during the self-sustained operation by the distributed power source, and is disposed between the fuel power generation apparatus 33 and the storage battery 12. Thereby, it is possible to store in the storage battery 12 surplus power that is generated by the fuel power generation device 33 during the self-sustained operation and exceeds the power consumption of the load 32, for example.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each component block, each step, etc. can be rearranged so that there is no logical contradiction, and a plurality of component blocks, steps, etc. can be combined into one or divided. It is.

1 Power Control System 12 Storage Battery 20 Power Control Device (Power Conditioner)
21 Power converter (inverter)
22, 23 Interconnection operation switch 24 Autonomous operation switch 25 Control unit 31 Distribution board 32 Load 33 Fuel power generation device 34 Fuel cell 35 Control unit 40 Current sensor 50 Pseudo output unit 51, 54 Pseudo current load 52 Synchronous switch 53 Pseudo current control Switch 60 Shunt unit 61 Power adjustment unit 62 Control unit 63 Branch unit

Claims (8)

A power control system comprising a fuel power generation device that generates power while a current sensor detects a forward power flow, a storage battery, and a power control device that controls the battery in cooperation with each other,
Including a pseudo output unit that generates a pseudo current detected by the current sensor;
The power control device
Output the generated power based on the current in the forward current direction detected by the current sensor,
The power control device monitors the storage amount of the storage battery, and when the storage amount exceeds a first threshold, adjusts the pseudo current to reduce a forward current detected by the current sensor, A power control system characterized by gradually reducing the generated power of the fuel power generator and gradually charging the storage battery with the generated power.   2. The power control system according to claim 1, wherein the current sensor detects a differential current obtained by subtracting a charging current flowing from the fuel power generation device to the storage battery from the pseudo current as a current in a forward power flow direction.   The power control device adjusts the differential current to be zero by controlling the pseudo current when the charged amount exceeds a second threshold value that is larger than a first threshold value. Item 3. The power control system according to Item 2. The pseudo output unit includes a power adjustment unit that converts supplied power, and a branch unit that diverts a current output from the power adjustment unit,
One of the currents output from the branch is the pseudo current,
4. The power control system according to claim 1, wherein the power control device controls the pseudo current by controlling an output voltage of the power adjustment unit. 5.   The power control system according to claim 4, wherein the power adjustment unit makes the output voltage variable by PWM control.   The power control system according to claim 4, wherein a resistor is connected to each of the branch portions. A power control device used in a power control system for controlling a fuel power generation device and a storage battery in cooperation with each other while detecting a forward power flow,
Including a pseudo output unit that generates a pseudo current detected by the current sensor;
When the fuel power generator performs a self-sustained operation, a pseudo current is output from the pseudo output unit,
When the storage amount of the storage battery is monitored, and the storage amount exceeds a threshold value, the current of the pseudo output unit is controlled, and the differential current obtained by subtracting the charging current flowing through the storage battery from the pseudo-current from the fuel power generation device The power control device is characterized by gradually reducing the generated power of the fuel power generation device, and gradually charging the storage battery with the generated power. A power control method for a power control device that controls a fuel power generation device and a storage battery that generate power while a current sensor detects a forward power flow, respectively,
The power control device includes a pseudo output unit that generates a pseudo current detected by the current sensor,
A step of outputting a pseudo current from the pseudo output unit when the fuel power generation device performs a self-sustaining operation;
Monitoring the storage amount of the storage battery, and when the storage amount exceeds a threshold, the pseudo current is controlled to adjust a differential current obtained by subtracting the charging current flowing from the fuel power generation device to the storage battery from the pseudo current, Gradually reducing the generated power of the fuel power generator, and gradually charging the storage battery with the generated power;
A power control method comprising:

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