JP5481760B2 - Power system - Google Patents

Description

The present invention relates to operational techniques for distributed power generation device such as a fuel cell, in particular, it relates to a power supply system provided with a self driving support equipment to support the autonomous operation of the distributed power generation device in such time of stopping of the system power source.

  In recent years, fuel cells have been deployed as distributed generators (hereinafter referred to as “distributed power sources”) at the locations of power consumers (customers), and the power from the fuel cells and the system power sources (commercial power sources) of electric power companies. The distributed power supply system that combines the power from the power source to cover the power consumption of the power consumers is attracting attention. In this case, the DC power generated by the distributed power source is converted into AC power, and is distributed to the load in the home of the power consumer by being superimposed on the AC power of the system power source. For this reason, an inverter for converting DC power to AC power is used to link the fuel cell to the system power supply. The inverter outputs AC power whose frequency and voltage match those of the power from the system power supply. In addition, when the system power supply fails, in order to ensure safety on the distribution network side of the system power supply, the operation of the distributed power supply is stopped and the distributed power supply is electrically disconnected from the system power supply (disconnection) To do).

  By the way, a fuel cell used as a distributed power source cannot cope with a sudden change in load due to its operating principle and structural features. A fuel cell is a power source that cannot easily adjust its output with respect to a load demand input. For example, if a fuel cell is operated at a certain output power and the load supplied with power from the fuel cell consumes power commensurate with the output of the fuel cell, the load may suddenly increase power consumption. The output power of the fuel cell cannot be increased at such a rapid change rate. Of course, when the fuel cell is operating at its rated output, no more power can be obtained from the fuel cell. Even if the power consumption in the load decreases rapidly, the output power of the fuel cell cannot be reduced so rapidly. When the power consumption of the load is rapidly reduced, problems such as overvoltage and temperature rise in the fuel cell may occur unless power corresponding to the difference between the output of the fuel cell and the power consumption is separately consumed. For stable operation of the fuel cell, the output power cannot be reduced below a certain value. In addition, the power generation cost per amount of generated power in a distributed power source such as a fuel cell is lowest when the distributed power source is operated at its rated output.

  Therefore, when using a distributed power source such as a fuel cell connected to the system power source, the rated output should be such that the power consumption on the load side does not fall below that value for a certain length of time. In general, a distributed power source is configured, and a portion of the difference between the output of the distributed power source and power consumption, that is, a large fluctuation is expected, is covered by a system power source. In the time zone where the power consumption is expected to be extremely low, such as at night or on holidays, the operation of the distributed power supply is stopped to cover the power consumption with only the system power supply.

  A distributed power source should be able to operate as a self-sustained power source from the system power source, so it can be used as an emergency power source when the system power source is interrupted in the event of a disaster or where the system power source cannot be obtained In recent years, a self-sustained operation system that can be used as a power source for power supplies and can cope with power outages such as disasters using a distributed power source is spreading in many fields. Normally, when using a distributed power source connected to the system power source as an emergency power source, the power source is disconnected from the system power source and operates as described above when a power failure of the system power source is detected. Then, change the connection in the distribution line or switchboard so that power is supplied only to the load that should be supplied in an emergency, restart the distributed power supply, and supply power to those loads. Will be supplied.

  When a distributed power source, in particular, a fuel cell is operated independently, it is necessary to be able to cope with a sudden load fluctuation. To start the fuel cell, power is supplied to the fuel cell before starting power generation, for example, to raise the temperature of the fuel cell to a predetermined temperature and to operate a pump that supplies fuel to the fuel cell. There is a need to. In addition, the distributed power source connected to the system power source is generally configured to generate AC power based on the frequency and phase of the AC power of the system power source, so when AC power from the system power source is interrupted, AC power with appropriate frequency and phase cannot be generated. Therefore, it is difficult to operate the distributed power supply independently by making it independent from the system power supply in the event of a power failure of the system power supply, etc., simply because there is a distributed power supply that consists of fuel cells and the like and is connected to the system power supply. .

  Therefore, there is a demand for a system that can support a self-sustained operation of a distributed power source that can cope with a sudden change in load and that supports a distributed power source that requires power when starting up, such as a fuel cell. In particular, it is desirable to have a system that can operate a distributed power source in the event of a power failure of the system power supply, without changing the device of the distributed power supply itself, with respect to the existing distributed power supply connected to the system power supply. It is rare.

  When connected to the grid, single-phase three-wire AC power may be supplied from the distributed power supply, but it is desired to supply power from the distributed power supply to the three-phase three-wire load during independent operation. , Sometimes.

The purpose of the present invention, with distributed power sources such as fuel cells, to provide a power supply system capable of self-sustaining operation of the distributed power supply such as in case of power failure of the system power source.

The power supply system of the present invention includes a distribution board provided between the system power supply and the load, and a disconnection board provided between the system power supply and the distribution board that transitions to a shut-off state when a power failure of the system power supply is detected. A power supply device that includes a switch, a fuel cell stack, and a power conditioner that connects DC power from the fuel cell stack to the system power supply, and that is connected to a distribution board and outputs AC power synchronized with the frequency of the system power supply in normal times A power storage device that outputs DC power, an output that is connected between the distribution board and the power supply device, and converts the DC power from the power storage device into AC power of a predetermined frequency, and the power supply device operates independently. and control means for storing controlled release be released from the allowed or power storage device stored in the power storage device to excess or deficiency of the electric power consumption and the power supply in the load occurs at the time that, the grid electricity During the power failure, and still load regulator for stabilizing the operation of the consumer to the power supply the power to be surplus by the accumulation controlled release, directly connected to the distribution board for generating an AC power, it can operate at partial load conditions possess Do the auxiliary power unit, and the AC power from the auxiliary power unit, the power supply in case of power failure of the system power source starts autonomous operation is started, and the load variation of the power supply device Ru is leveled.

  Since the present invention is configured as described above, according to the present invention, it is possible to realize a self-supporting power supply system that can cope with load fluctuations even when a power failure occurs in a system without requiring extensive modification of the distributed power supply system itself. be able to. In addition, when a fuel cell is used as a distributed power source, it is possible to supply power at startup. Furthermore, it can be used as an operation test device for a distributed power source before grid connection.

It is a block diagram which shows the fundamental structure of the whole power supply system containing the self-sustained operation assistance apparatus of one Embodiment of this invention. It is a block diagram which shows the structural example of an autonomous driving assistance apparatus. It is a flowchart which shows the process from a system power supply stop to the self-sustained operation of a fuel cell and the return of a system power supply. It is a graph which shows the relationship between the fluctuation | variation of the power consumption of load, the output electric power of a fuel cell system, and charging / discharging of an electrical storage apparatus. It is a block diagram which shows the detailed structure of an example of the power supply system containing an autonomous driving assistance apparatus.

  Next, a preferred embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a basic configuration of an entire power supply system including an autonomous driving support device according to an embodiment of the present invention. This power supply system has a fuel cell system 12 linked to a system power supply (commercial power supply) 11 as a distributed power supply. In normal times, the power from the fuel cell system 12 and the power from the system power supply 11 are superimposed. In addition to being supplied to the load 13, at the time of a power failure of the system power supply 11, the fuel cell 12 can be operated independently to supply power to the load 13. AC power is generally supplied from the system power supply 11 in a single-phase three-wire system or a three-phase three-wire system.

  The fuel cell system 12 includes a fuel cell stack 21 that generates DC power as a fuel cell body, and a power conditioner 22 that converts DC power from the fuel cell stack 21 into AC power linked to a system power source. The output of the power conditioner 22 becomes the output of the fuel cell system 12. The power conditioner 22 includes a circuit for detecting a power failure on the system power supply 11 side and disconnecting the fuel cell system 12 in addition to an inverter circuit for DC / AC conversion. A distribution board 14 is provided, and the distribution board 14 is connected to the system power supply 11 via the disconnect switch 15, and the fuel cell system 12 and the load 13 are connected. The system power supply 11 and the fuel cell system AC power from 12 is supplied to the load 13. A self-sustaining operation support device 16 to be described later for supporting the self-sustained operation of the fuel cell system 12 is connected to a distribution line connecting the distribution board 14 and the fuel cell system 12. A disconnect switch 17 for disconnecting the fuel cell system 12 in the event of a power failure of the system power supply 11 is also provided in the distribution board 14. In this power supply system, when a power failure of the system power supply 11 is detected, the disconnect switch 15 and the disconnect switch 17 are once cut off. Thereafter, when the fuel cell system 12 is restarted in the self-sustained operation mode, the disconnect switch 17 is turned on while the disconnect switch 15 is kept in the disconnected state, and only the AC power from the fuel cell system 12 is supplied to the load 13. To be able to supply.

  The autonomous operation support device 16 supplies power necessary for starting the fuel cell system 12 to the fuel cell system 12 in a state where the system power supply is interrupted, and when the fuel cell system 12 is operating autonomously. This is to cope with a sudden change in load.

  The autonomous driving support device 16 includes a connection point 31 for the distribution line between the fuel cell system 12 and the distribution board 14, a voltage-controlled inverter 32 whose output is connected to the connection point 31, and an inverter 32. Connected to the power storage device 33 for storing the DC power supplied to the power supply device 33 and the connection point 31, and connected to the connection point 31, and the load regulator 34 that consumes excess power of the AC power generated by the fuel cell system 12. And a charging converter 35 that converts AC power taken in from the connection point 31 into DC power and supplies it to the power storage device 33 for charging. The output of charging converter 35 is connected to a connection point 36 between power storage device 33 and inverter 32. In addition, when the DC power from the power storage device 33 alone cannot cover the power required for starting the fuel cell system 12 or when the power consumption at the load 13 cannot be dealt with rapidly, the solar power is supplied to the connection point 36. You may make it connect auxiliary power supply devices 37, such as a power generator and an engine generator.

  As described in the “Background Art” section, the fuel cell system 12 cannot cope with a rapid change in power consumption of a load and requires power to start up. Therefore, in the self-sustaining operation support device 16, when the power generated by the fuel cell system 12 is more than the power consumption generated by the load 13 during the self-sustained operation of the fuel cell system 12, the surplus power is stored in the power storage device 33. When the power generated by the fuel cell system 12 is insufficient as compared with the power consumption of the load, the shortage is compensated by the DC power stored in the power storage device 33. Further, when the system power supply is operating normally, DC power can be stored in the power storage device 33 by converting the AC power taken from the connection point 31 into DC by the charging converter 35. Therefore, the DC power stored in the power storage device 33 can be used as the power necessary for restarting the fuel cell system 12 after the power failure of the system power supply 11 occurs. What is necessary is just to add and use the electric power from the power supply device 37. FIG.

  In the present embodiment, the power storage device 33 is capable of accumulating electric power supplied from the outside and has a function of releasing the accumulated electric power, and changes the output current in accordance with a fluctuating load. It is something that can be done. Such a power storage facility 33 is intended to be able to cope with sudden load fluctuations that the fuel cell system 12 cannot cope with. Examples of the power storage device 33 include various secondary batteries such as a lithium ion secondary battery, a lead storage battery, a nickel-cadmium battery, and a nickel-hydrogen battery, or a large-capacity capacitor (capacitor) such as an electric double layer capacitor. used. A secondary battery with a relatively large capacity is provided to cope with moderately slow load fluctuations, and an electric double layer capacitor is installed in parallel with the secondary battery to cope with sudden load fluctuations in a short time. The power storage device 33 is preferably connected.

  While it is preferable that the fuel cell be operated without load fluctuation in the vicinity of a predetermined rated output power, the auxiliary power supply device 37 operates at an output power lower than the rated output power (so-called partial load state). There are no obstacles to this, and those that can cope with rapid load fluctuations are used. As such an auxiliary power device 37, in addition to the above-described solar power generation device (solar cell) and engine generator, a wind power generation facility, a large secondary battery, and the like can be used. When the auxiliary power supply 37 is used only for starting the fuel cell system 12, the auxiliary power supply 37 is not connected to the connection point 36, but an auxiliary is provided to the pump and heater of the fuel cell stack 21 of the fuel cell system 12. The power supply device 37 may be connected.

  In this embodiment, the fuel cell system 12 is operated at its rated output as much as possible. However, depending on the state of the load 13, the fuel cell system 12 is generated even when the power required for power storage in the power storage device 33 is taken into consideration. Some parts of the AC power that is used may not be consumed. The load regulator 34 consumes such surplus power, thereby preventing the occurrence of problems associated with load fluctuations in the fuel cell system 12. As the load adjuster 34, for example, an (electric) resistor that converts surplus power into heat can be used. In the present embodiment, when the system power supply 11 is operating, the load fluctuation is covered by the power from the system power supply, and the fuel cell system 12 is stopped when the power consumption is too small. In operation, such a load regulator 34 need not be connected to the connection point 31.

  When the fuel cell system 12 that can be operated with variable output (load) is used, or as a power supply device to be operated independently, output fluctuation within the maximum rating is allowed. When using one, the load regulator 34 controls the amount of charge to the power storage device 33 and the amount of power consumed by the resistance so that the output of the fuel cell system 12 does not exceed at least the load demand input. Alternatively, a command value for the output power value may be generated for the fuel cell system 12 according to the power demand, and the command value may be fed back. Specifically, the fuel cell system 12 can follow the load fluctuation and the charge amount of the power storage device 33 is maintained within the required charge amount range that maintains the start-up or adjustment capability. A command value for the output power of the battery system 12 is generated.

  In the present embodiment, the inverter 32 does not have a function of simply generating AC power and supplying it to the load 13. The voltage waveform of the AC power generated by the inverter 32 is also supplied to the fuel cell system 12 that is operating independently through the connection point 31, and the power conditioner 22 of the fuel cell system 12 receives the voltage of the AC power from the inverter 32. AC power is output based on the waveform. That is, the inverter 32 serves as a reference for the frequency and phase in the AC power generated by the fuel cell system 12. Therefore, AC power having an accurate frequency and phase can be generated by using the voltage control type inverter 32. Note that after the fuel cell system 12 is started, the electric power generated by the fuel cell system 12 is supplied to the inverter 32, whereby AC power having an accurate frequency and phase is permanently generated. become. The AC power from the inverter 32 is also used as power for starting the fuel cell system 12 via the power conditioner 22.

  FIG. 2 shows a specific connection configuration of the autonomous driving support device 16 when the fuel cell system 12 outputs single-phase three-wire AC power. Corresponding to the single-phase three-wire system, two inverters 32 sharing a neutral point are provided.

  Next, the operation of this power supply system will be described with reference to FIG. Assuming that the system power supply 11 is operating normally (step 101), when the system power supply is down, that is, when a power failure occurs (step 102), the disconnect switch 15 and the disconnect switch 17 are cut off. Thereafter, the disconnection switch 17 is turned on to operate the autonomous driving support device 16 to restart the fuel cell system 12 (step 103). At this time, there is a case where the fuel cell system 12 cannot be restarted due to power shortage or the like. In this case, the auxiliary power supply device 37 is connected and the fuel cell system 12 is started up by the power from the auxiliary power supply device 37 (step 104). ).

  When the fuel cell system 12 is activated, it switches to a disaster prevention operation mode in which power is connected only to a load (emergency load) to which power is to be supplied even during a power failure of the system power supply (step 105), and power is supplied only to the emergency load. The connection in the distribution board is changed so as to be supplied (step 106), and electric power is supplied to these emergency loads by the autonomous operation of the fuel cell system 12 (step 107).

  Thereafter, when the system power supply is restored (step 108), the operation of the fuel cell system 12 is once stopped (step 109), and power is supplied to loads other than the emergency load. Is switched back to the original state (step 110), and the operation of the fuel cell system 12 is started so as to connect the system switch 11 with the disconnection switch 15 in the conductive state (step 111). Thereby, the operation of the entire system is returned to the state before the power failure of the system power supply 11.

  Next, a response to a sudden change in power consumption of the load during the autonomous operation of the fuel cell system 12 will be described. FIG. 4 shows a relationship among fluctuations in power consumption of the load 13, output power of the fuel cell system 12, and charging / discharging of the power storage device 33. The fuel cell system 12 is continuously operated substantially at its rated power A as shown in the figure. On the other hand, the power consumption P of the load 13 changes greatly as shown by the bold line in the figure, but when P <A, the power corresponding to A−P of the difference passes through the charging converter 35. The power storage device 33 is used for charging. Further, when P> A, the difference P-A power is covered by AC power supplied from the power storage device 33 via the inverter 32. Thereby, in this embodiment, the fuel cell system 12 comes to be able to endure the rapid fluctuation | variation of load. When P> A and the power storage device 33 is almost fully charged, the surplus power PA is consumed by the load regulator 34.

  As described above, in the power supply system shown in FIG. 1, by using the self-sustained operation support device 16, it is not necessary to modify the fuel cell system 12 itself that is a distributed power supply system. A self-supporting power supply system that can cope with In addition, even when the system power supply is blacked out, it is possible to supply the fuel cell system 12 with power necessary for starting the fuel cell system 12. Such a self-sustained operation support device 16 can also be used as an operation test device for the fuel cell system 12 before grid connection.

  Next, as a specific example of the present invention, a detailed configuration of a power supply system including an autonomous driving support device will be described. The power supply system shown in FIG. 5 has the same configuration as that of the power supply system shown in FIG. 1, and two types of AC power of a single-phase three-wire system (1φ3W) and a three-phase three-wire system (3φ3W) are supplied from the system power supply 11. Has been. However, the auxiliary power unit 37 is different from that of FIG. 1 in that a single-phase three-wire type AC power is generated and directly connected to the distribution board.

  As a load, there is provided a load (important load) 13A to which single-phase three-wire AC power is to be supplied even during a power failure of the system power supply, and a three-phase three-wire load 13B to which power is not supplied during a power failure of the system power supply. Yes. As the distribution board, two of the distribution board 14A for the fuel cell provided between the distribution board 14A, the distribution board 14A, and the fuel cell system 12 in which the system power supply 11 and the loads 13A and 13B are accommodated. The disconnect switch 17 is provided in the fuel cell distribution board 14B. The fuel pump of the fuel cell system 12 is configured to operate with single-phase AC power. The fuel cell system 12 includes a fuel cell stack 21, and as a power conditioner, a boost converter 22A that boosts the output DC power of the fuel cell stack 21, and a DC power output from the boost converter 22A is a single-phase three-wire power. A grid interconnection inverter 22B for converting to a grid power supply and linking to the grid power supply is provided.

  A charge / discharge relay control panel 40 is connected to the system distribution board 14A. The charge / discharge relay control panel 40 monitors the voltage and current of each device and performs analog-to-digital conversion. By numerical control and process control, each switch and relay connect and disconnect each device to control charge / discharge. And a start / stop sequence (for example, a sequence as shown in FIG. 3) at the time of the autonomous operation of the fuel cell system 12 is executed.

  Further, the charge / discharge relay control panel 40 is a warning light or the like indicating that surplus power is wasted by a load regulator or the like when power is supplied from a power source that is inferior in output adjustment capability such as the fuel cell system 12. It may be possible to notify the user by this means, or it may be able to warn the user in advance of the occurrence of an unstable event such as excessive power consumption as a load. Further, in an emergency in which the amount of power supplied from the power source cannot catch up with the demand (load power), the system distribution board 14A may be controlled so that a part of the load can be disconnected.

  As the power storage device 33, an electric double layer capacitor is provided. For charging the power storage device 33, the rectifier 41 that converts the single-phase power supplied from the fuel cell distribution board 14B into direct current and the rectifier 41 A DC-DC converter 42 that converts DC power of 280 to 340 V into DC power having a voltage suitable for the power storage device 33 is provided. The rectifier 41 and the DC-DC converter 42 correspond to a charging converter in the system shown in FIG. Note that the DC-DC converter 42 controls the power supplied to the power storage device 33 when the power storage device 33 is charged, and controls the power converted from the power storage device 33 into alternating current by the inverter 32 when the power storage device 33 is discharged. Discharge current limiting function is provided. This charge / discharge current control function allows the power storage device 33 to be charged or taken out from the power storage device 33 only as much as the excess or deficiency between the steady power generated in the fuel cell system 12 and the power consumption of the load. It is a function.

  The inverter 32 converts the DC power stored in the power storage device 33 into AC power, similar to the inverter in FIG. 1, and the output thereof, together with the output of the fuel cell system 12, is a fuel cell distribution board. 14B is commonly connected. The load adjuster includes an LR load 34A composed of resistance and reactance, and an AC load device 34B that is connected to the output of the fuel cell system 12 and supplies surplus power to the LR load 34A.

  As the auxiliary power supply device 37 that generates single-phase three-wire AC power, a power generator or a battery and an inverter is used. When the auxiliary power supply device 37 has a battery, the battery is charged by the DC-DC converter 42 described above. The AC power from the auxiliary power supply device is supplied to the fuel cell distribution board 14B, and is used as the power necessary for starting up the fuel cell system 12 and further when the power at the load 13A is increased. It will be.

DESCRIPTION OF SYMBOLS 11 System power supply 12 Fuel cell system 13, 13A, 13B Load 14 Distribution board 14A System distribution board 14B Fuel cell distribution board 15 Disconnect switch 16 Self-sustained operation support device 17 Disconnection switch 21 Fuel cell stack 22 Power conditioner 22A Booster Converter 22B Grid-connected inverter 31, 36 Connection point 32 Inverter 33 Power storage device 34 Load regulator 34A LR load 34B AC load device 35 Charging converter 40 Charging / discharging relay control panel 41 Rectifier 42 DC-DC converter

Claims (8)

A distribution board provided between the system power supply and the load;
A disconnect switch that is provided between the system power supply and the distribution board, and transitions to a shut-off state when a power failure of the system power supply is detected,
DC power from the fuel cell stack and the fuel cell stack and a power conditioner for interconnection to the system power supply, connected to the distribution board power during normal for outputting AC power synchronized with the frequency of the power grid Equipment,
A power storage device that outputs DC power ;
An output is connected between the distribution board and the power supply device, and an inverter that converts DC power from the power storage device into AC power of a predetermined frequency;
Control means for performing accumulation / release control for causing the power storage device to store or release the excess or deficiency of the power consumption in the load and the power generated by the power supply device when the power supply device is operating independently. When,
During a power outage of the system power supply, a load regulator still stabilize the operation of the consuming power of the surplus the power supply device by the accumulation release control,
Auxiliary power supply device that is directly connected to the distribution board and generates AC power, operable in a partial load state,
I have a,
A power supply system in which the power supply is activated and starts a self-sustained operation and the load fluctuation of the power supply is leveled by the AC power from the auxiliary power supply when a power failure occurs in the system power supply. 2. The power supply system according to claim 1 , wherein the inverter is a voltage-controlled inverter , and the power supply device outputs AC power synchronized with AC power output from the inverter during the independent operation . The control means, the power supply is in a range capable of following the load fluctuation, and so as to maintain a required charge quantity range required for the charged amount of the power storage device to implement the load adjustment, fed back to generate a command value of the output value to the power supply, the power supply system according to claim 1 or 2. Warning means for warning that surplus power generated by the power supply device is consumed wastefully and / or for warning in advance of occurrence of an unstable event in which load power consumption exceeds a rated value of the power supply device further comprising power supply system according to any one of claims 1 to 3. Comprising a load disconnecting means to disconnect the portion of said load by controlling the distribution board in an emergency from the distribution board comprising when the load demand is excessive, according to any one of claims 1 to 4 Power system. The power supply according to any one of claims 1 to 5, further comprising a converter connected to a point between the power supply device and the inverter and capable of supplying power from the point to the power storage device. system. The power storage system according to claim 1, wherein the power storage device includes at least one of a secondary battery and a capacitor. The power supply system according to any one of claims 1 to 7, wherein the auxiliary power supply device includes at least one of a solar power generation device and an engine generator.

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