JP2005039951A - Thermoelectricity feeding system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectricity feeding system that does not exert an unfavorable influence upon a distribution system and can perform high-efficiency power feeding, in an aggregate or in a region composed of a plurality of consumers including at least one consumer that has a load and a generating set. <P>SOLUTION: A special distribution system 71 having power quality of which the range is different form a voltage variation range and a frequency range of the distribution system 11 is additionally arranged to the distribution system 11 that mainly undertakes the power feeding to the load 21. The special distribution system 71 is made to mainly undertake power collection from the generating set 31, and the special distribution system 71 and the distribution system 11 are connected via a linkage inverter 41 (or a linkage bidirectional inverter) that has a function for adjusting a difference between the power qualities of both the systems 11, 71. By the power quality adjusting function carried by the linkage inverter 41 (or the linkage bidirectional inverter), the operation of the generating set 31 connected below the special distribution system 71 is made possible irrespective of the power quality of the distribution system 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a combined heat and power system in an assembly or a region composed of a plurality of consumers in which a cogeneration type power generator and a load coexist.

  A consumer as used herein is defined as a consumption or a supplier of energy such as electric power or heat, which refers to an independent minimum economic unit with respect to payment of compensation for the consumption of energy or delivery of compensation for supply. .

  As a specific example, in the case of a tenant building, it means each tenant, and in the case of an apartment house, it means each individual dwelling unit. In addition, those who have only a load and do not have a power generation device include the above economic units in the definition of consumers.

"Distributed power supply next-generation system establishment verification test (1993 research report / NEDO-NP-9312)" New Energy and Industrial Technology Development Organization, March 1994, pages 204-205 6.3- 1 figure JP 2002-233077 A

  2. Description of the Related Art Conventionally, as an effective energy utilization means, a combined heat and power (cogeneration) system that uses exhaust heat from a power generation device to simultaneously generate heat and electricity has been actively used.

  FIG. 6 is a connection example of a combined heat and power generation apparatus in a consumer in which a conventional load and a combined heat and power generation apparatus that are generally employed coexist (for example, FIG. 6-3-1 in Non-Patent Document 1). a)).

  In FIG. 6, 1 is a power distribution system, 3 is a power generator, and 4 is a grid interconnection inverter. The power output of the power generator 3 is connected to the power distribution system 1 in an aggregate (or region) 61 composed of a plurality of consumers by the grid interconnection inverter 4, and is distributed to necessary locations (elevator, lighting, air conditioning, etc.) by alternating current. Is done. Although the heat supply system is not exemplified in the original text, it is a so-called centralized heat supply system in which heat generated at one place is supplied to each necessary place through piping.

  In the case of such a centralized heat supply system, the length of a heat supply pipe, for example, a hot water supply pipe, is often several hundred meters, and the heat dissipation loss from the pipe is very large. In addition, in order to supply hot water when needed while avoiding a drop in the temperature of the hot water in the piping, it is necessary to circulate hot water as close as possible to the required location regardless of whether hot water is needed or not. Therefore, the power consumption for the pump power is also very large. This has caused the problem that as the building becomes taller or larger in scale, the heat supply piping and the necessary pump head increase, and both heat dissipation loss and circulating power increase.

  In order to solve such problems, it is better to generate hot water by saving at the final consumption place. Specifically, a small-sized fuel cell having a required capacity is installed at a place where heat is required, and a distributed heat supply system for supplying hot water and electric power is adopted.

  However, the final consumption place of hot water described above is the end when viewed from the electric power system, and is easily affected by the start / stop of the power generation device and the fluctuation of the power generation output. In particular, in the case of household fuel cells, the DDS (Daily Start & Shutdown or Stop) operation method that starts in the morning and stops at night is often adopted, and there is a high possibility of causing the same fluctuation all at once in a certain region. It was happening.

  In this way, when power generation devices that are likely to cause similar output fluctuations at once are concentrated in the distribution system at the end that is far from the substation and has a small power supply capacity, the distribution system will show fluctuations in the power flowing into the distribution system. According to the standards relating to power quality such as the voltage range determined by the distribution system, for example, according to Article 26 of the Electricity Business Act, the voltage range is 101V ± 6V, 202V at the consumer end in the low voltage system of 100V or 200V. Although it is supposed to be maintained at ± 20 V, it will be difficult to maintain ("Basic study for the configuration of the demand area system-Examination of the configuration of the demand area system from the viewpoint of voltage fluctuation") No. T99042).

  This phenomenon applies not only to the distribution system installed by general electric utilities but also to the distribution system in the building. For example, the same problem is caused when a fuel cell or a solar power generation device is installed in each house arranged at a close distance as in an apartment house.

  In addition, power generators are installed individually for each consumer, but each power generator has a power output, operation time, etc. depending on the consumer's own convenience, such as the amount of heat required by the consumer and the time at home. Therefore, it is not easy to implement a controlled power generation plan that takes into account the impact on the power system.

  Furthermore, in order to link the power generation output to the AC distribution system, when a large number of interconnected inverters are arranged at a short distance, there is a problem that the harmonic rate is deteriorated due to mutual interference between the inverters.

  As described above, when the distributed combined heat and power generation apparatus is introduced in the conventional distribution system, it is necessary to limit the number of installed units, and heat cannot be efficiently supplied to a necessary portion.

  In order to mitigate the adverse effect on the distribution system by the distributed power generation device, various solutions have been proposed (see Patent Document 1).

  FIG. 7 shows an example of a solar cell that undergoes output fluctuations due to weather as a power generation device, and the solar cell 111 may be read as a fuel cell that fluctuates due to individual reasons.

  In FIG. 7, the photovoltaic power generation system 100 includes a plurality of power generation load units 110 and a single control center 120 to which these power generation load units 110 are connected.

  The power generation load unit 110 has a predetermined power generation capacity and generates power according to sunlight, an orthogonal transformation unit 112 connected to the solar cell 111 to convert DC power into AC power, and connected to the orthogonal transformation unit 112. And an AC load 113 to which AC power is supplied from the orthogonal transform unit 112.

  The control center 120 actually includes a power storage control unit 121 connected to the orthogonal transformation unit 112 of each power generation load unit 110, a common storage battery 122 connected to the power storage control unit 121, an external commercial power supply 130, and power storage control. The system link part 123 which connects the part 121 and transmits / receives electric power between these, and the system control part 124 which controls the whole photovoltaic power generation system 100 are provided.

  The orthogonal transformation unit 112 converts the DC power generated by the solar cell 111 into AC power and supplies the AC power to the AC load 113 or the power storage control unit 121. Further, the orthogonal transform unit 112 opens and closes in response to an instruction from the system control unit 124 of the control center 120 to supply all the electric power generated by the solar cell 111 to the AC load 113 or to supply a part of the electric power to the control center. 120 is supplied as surplus power to the power storage controller 121 of 120, or conversely, power is supplied to the AC load 113 from the power storage controller 121 of the control center 120.

  In this manner, the control center 120 is provided and the solar cell 111 is provided as a power storage device, and fluctuations in the output of the solar cell 111 are alleviated and then connected to the power distribution system via the grid interconnection unit 123.

  However, fluctuation mitigation using only power storage increases the cost of equipment due to an increase in the required power storage capacity and an increase in the number of charge / discharge cycles of the battery, which has an effect on the life. Problems due to mutual interference of inverters remain. Further, the functions of the original control center have no concept of output adjustment of the power generation device, operation on the power generation device, and stop command.

  Further, power generation devices such as solar cells and fuel cells generate direct current. Furthermore, even in the case of an AC load, there are many that are used after rectifying and converting AC to DC.

  Thus, although there are not a few cases where both the power generation device and the load are direct current, the power network is alternating current. For example, in order to supply power from the power generation device to the load, the direct current is once converted into alternating current. Then, it is necessary to perform the operation of returning the alternating current to the direct current again, and a loss occurs in the conversion process between the direct current and the alternating current.

  As a method for avoiding this problem, as shown in FIG. 8, a power supply system using commercial frequency / DC hybrid wiring has been proposed (see Non-Patent Document 1, FIG. 6-3-1 (c)).

  This is because when power is sent from a generator that is originally output in direct current, such as a fuel cell or solar power, to a load that is ultimately consumed in direct current, such as an inverter-controlled elevator, power is directly supplied in direct current. By sending, the DC / AC conversion and AC / DC conversion are omitted, and the efficiency is increased.

However, since it is not assumed that fuel cells are dispersedly arranged for each consumer, the problem of deviation from the voltage fluctuation range of the DC distribution system to which the fuel cells are connected is not mentioned.
Further, although not shown in the original text, a connection converter is required for connection of the fuel cell to the DC power distribution system. In the case of direct current, for example, if a large number of interconnected converters are connected at a close distance while keeping the voltage fluctuation range as strict as it is, it will not be possible to send output due to voltage increase, or the autonomous control of the converter will cause comprehensive interference and oscillation. Or voltage hunting. Furthermore, it does not assume unified control of fuel cells individually arranged in different consumers, that is, power generation apparatuses having different ownership rights.

  In order to solve the above problems, the present invention is highly efficient in an aggregate or region composed of a plurality of consumers including at least one consumer having a load and a power generation device without adversely affecting the distribution system. An object of the present invention is to provide a cogeneration system capable of supplying thermoelectric power.

  The present invention relates to a power distribution system for connecting a load to an assembly or a region composed of a plurality of consumers including at least one consumer having a load and a combined heat and power generation device, and the power distribution system has a voltage fluctuation. A special distribution system having at least one of a range, a frequency, or a frequency fluctuation range, and the special distribution system is connected to a plurality of power generators, and the special distribution system is connected to a connected inverter or a connected bidirectional inverter. And operating the operating state of the power generation device by a control center connected to the power generation device.

  Here, the interconnected inverter or interconnected bidirectional inverter matches the so-called power quality difference such as the voltage fluctuation range or frequency or frequency fluctuation range between the special distribution system and the distribution system, and allows the interchange of power between the two systems It has the function to make and the system protection function for grid connection. In addition, the power generator is connected to the special power distribution system via an inverter or converter. This is to adjust the power generator output so that it matches the operating conditions of the special power distribution system. This is similar to the input inverter, but is different in that the restriction condition such as the voltage range is moderate or the adjustment parameter is small when the output is sent.

  The present invention relates to monitoring of the power distribution system, the special power distribution system, or the power generation device whether the total power generation amount of the power generation device managed by the control center is a predetermined planned value, not the power demanded by individual consumers The gist is that, based on the information, the control center controls the output, the number of operating units, or the operating time zone of each power generator so as to obtain an appropriate output.

  The gist of the present invention is that a special load having a durability that can be used under the condition of the voltage fluctuation range or frequency or frequency fluctuation range of the special distribution system is connected to the special distribution system.

  The gist of the present invention is that the special power distribution system is a direct current.

  Moreover, this invention makes it a summary to connect the power storage device to the predetermined position of the said special power distribution system.

  Furthermore, the gist of the present invention is to connect the power storage device to the control center and control charging / discharging of the power storage device.

  The combined heat and power system of the present invention is provided with a special power distribution system having a power quality different from the voltage fluctuation range and frequency range of the power distribution system for the power distribution system mainly responsible for power supply to the load. Connect the special power distribution system to the power distribution system via a grid-connected inverter or a grid-connected bidirectional inverter that has the function of adjusting the difference in power quality between the two systems. ing.

  As a result, the power generation device connected under the special power distribution system can be operated without being constrained by the power quality of the power distribution system by the power quality adjustment function of the power grid inverter or the grid bidirectional inverter.

  For example, by setting the voltage fluctuation range and frequency fluctuation range of the special power distribution system wider than those of the power distribution system, the degree of freedom regarding the installation density of the power generation devices is improved. In addition, since it is possible to select a unique frequency, it is also possible to reduce the volume of the reactor or the transformer by setting the frequency high, for example.

  In addition, it is possible to alleviate voltage fluctuations in the special power distribution system by providing a control center and controlling power generators installed in different consumers in a unified manner, and reduce restrictions on the number of power generators installed. In addition, it is possible to improve the facility operation rate by systematically controlling the amount of power generated per hour in the entire combined heat and power system.

  In addition, the present invention can prevent an increase in harmonic rate due to mutual interference between interconnection inverters by consolidating a plurality of power generation devices under a special distribution system and reducing the number of interconnection points to the distribution system. . Furthermore, it is not always necessary to limit the connection point to the power distribution system to an aggregate or region composed of a plurality of consumers having power generation devices, and it is possible to select a point where the power distribution system capacity is less affected and is large. . For example, by setting the installation point as a point having a large load capacity like a 22 KV extra high distribution system, the influence of the power generation device on the distribution system can be further reduced.

  In addition, the present invention uses power in the vicinity of a power generation device by directly connecting a special load having a proof strength that can be used under conditions of voltage fluctuation range or frequency or frequency fluctuation range of the special power distribution system to the special power distribution system. And distribution loss can be reduced.

  In addition, the present invention eliminates the restrictions on interconnection caused by AC such as power factor, phase, frequency, waveform distortion, etc. In addition to simplifying the configuration of the inverter and converter for connecting to the power distribution system, it is possible to eliminate restrictions on the operation of the power generation apparatus and restrictions on the number of installed units and installation positions. Also, by directly using the DC power generated by the power generator with a special load, the conversion loss for converting the power generation output to AC and the rectification loss for converting the AC to DC inside the special load are eliminated. Can do.

  Furthermore, the present invention can absorb the fluctuation of demand and the output fluctuation of the power generator due to the special load or the load by connecting the power storage device at a predetermined position of the special power distribution system. In addition, it is possible to more easily generate power during the period of less demand due to loads and special loads, and to improve the operating rate of the power generator.

  Moreover, the present invention connects the power storage device to the control center and controls charging / discharging of the power storage device by the control center, thereby increasing the degree of freedom of power generation plan control and further improving the facility operation time and economy. The improvement of property can be realized.

  FIG. 1 is a block diagram of a composite distribution type electric power network showing a first embodiment of a combined heat and power system of the present invention. In FIG. 1, 6 is a consumer, 11 is a power distribution system, 21 is its load, 31 is a power generation device, 41 is an interconnected inverter (or interconnected bidirectional inverter), 411 is an inverter (or converter), 61 is a plurality of An aggregate (or region) made up of consumers 6, 71 is a special power distribution system, and 81 is a control center.

  A distribution system 11 mainly connecting a load 21 to an aggregate (or region) 61 composed of a plurality of predetermined consumers 6 and at least one of a voltage variation range or a frequency or a frequency variation range is a distribution system 11 A different special power distribution system 71 is provided, the power generation device 31 is connected to the special power distribution system 71 via an inverter (or converter) 411, and the special power distribution system is connected via a connected inverter (or connected bidirectional inverter) 41. 71 and the power distribution system 11 are connected.

  In addition, a control center 81 is provided and connected to the power generation device 31, and operating conditions such as operation / stop of each power generation device 31, operation time, and power generation output are controlled from the control center 81.

  Here, the power distribution system 11 is mainly responsible for supplying power to the load 21. The power distribution system 11 may be an existing power distribution system or a new power distribution system. Further, the distribution system is not limited to a distribution system under the direction of a general electric company, and may be any of a distribution system to a specific consumer 6, a distribution system in a specific establishment, and a power supply system in a building.

  The special power distribution system 71 is mainly responsible for collecting power from the power generator 31. Here, the so-called power quality typified by the voltage fluctuation range or frequency or frequency fluctuation range of the special distribution system 71 takes a unique value without being bound by the regulations relating to the power quality of the distribution system 11. For example, the output of the power generator can be easily fed into the special power distribution system 71 by setting the voltage fluctuation range sufficiently wide without being restricted by the conventional specified values (101V ± 6V, 202V ± 20V) described above. it can.

  In this case, matching of power quality for interconnection with the distribution system 11 is handled by the interconnection inverter (or interconnection bidirectional inverter) 41. In addition, the point where the special power distribution system 71 is connected to the power distribution system 11 via the interconnection inverter (or the interconnection bidirectional inverter) 41 is not particularly defined, and an aggregate (or region) composed of a plurality of consumers 6. It does not matter whether it is 61 or outside. Further, the control center 81 is based on a predetermined power generation plan, for example, monitors the voltage of the special power distribution system 71 or the power distribution system 11, and the operation conditions such as operation / stop, operation time, power generation output for each power generation device 31. Command is output.

  In addition, as monitoring information at this time, in addition to the voltage of each system described above, the input / output power value or input / output current value of the interconnected inverter (or interconnected bidirectional inverter) 41, the output power value of each power generator 31 Alternatively, if the current value and voltage value, the special distribution system 71 is an alternating current, the phase angle of each power generation device 31 with respect to the special distribution system 71, and if the power generation device 31 has a reservoir, the amount of remaining hot water Such information can be considered. The communication means between the power generation device 31 and the control center 81 may be either wireless or wired. Further, the voltage of the special power distribution system 71 and the power distribution system 11 or the above-described measuring device for obtaining monitoring information may be provided with a dedicated monitoring device, or the power generation device 31 or the interconnection inverter (or the interconnection bidirectional). Information may be obtained from each device such as an inverter 41.

  FIG. 2 shows a second embodiment of the combined heat and power system of the present invention, (a) is a comparative graph showing the relationship between the operation time of each power generator and a control command for power generation output, and (b) is a power generation plan and total power generation system. It is a comparative graph figure which shows the relationship with the control result of electric power generation amount. The system itself is the same as that shown in FIG.

  In order to match the total power generation output for each time zone with the planned value, the power generation time zone, the power generation output, and the number of operating power generation devices are controlled based on a command from the control center 81 in consideration of the necessary heat amount of each consumer 6. Here, it does not matter whether the command method is a real-time method or a method for instructing each generator in advance with a power generation plan. In addition, it is not necessary for the amount of generated power to match the demand of each individual consumer 6, and the operating rate of the power generation device 31 is improved by allowing mutual interchange through the special power distribution system 71 and the power distribution system 11. Can do. For example, the power generation output of a consumer 6 that has a large amount of required heat but a small amount of required power or whose power required time zone does not coincide with the power generation time zone is to be interchanged with other required consumers 6. Further, as shown by the power generators A to E in FIG. 2A, by shifting the power generation time zone of each power generator 31, the influence on the power distribution system 11 is alleviated, or conversely, the power rate is set high. It is also possible to charge the outside by operating the power generation device 11 intensively during a certain time zone.

  FIG. 3 is a block diagram of a composite distribution type power network showing a third embodiment of the combined heat and power system of the present invention. In FIG. 3, 6 is a consumer, 11 is a power distribution system, 21 is its load, 211 is a special load, 31 is a power generation device, 41 is an interconnected inverter (or interconnected bidirectional inverter), and 411 is an inverter (or converter). , 61 is an aggregate (or region) made up of a plurality of consumers 6, 71 is a special power distribution system, and 81 is a control center.

  In FIG. 3, the special power distribution device 71 is connected to a special load 211 having a proof strength that can be used even with power quality represented by voltage fluctuation or frequency or frequency fluctuation of the special power distribution device 71.

  Here, the special load 211 means that, for example, many of the loads shown in FIG. 2 may cause malfunction or failure when the power supply voltage fluctuates beyond a specified value (101V ± 6V, 202V ± 20V). However, the special load 211 means a load capable of normal operation even with a larger voltage fluctuation than the above. As an example in the case where the voltage range is expanded, for example, there are some power adapters and the like of notebook personal computers compatible with overseas power supplies that can operate between 90V and 260V.

  The special load 211 can not only directly use the output of the power generator 31 in the consumer 6 but also receive the interchange of the output of the power generator 31 of another consumer 6 via the special power distribution system 71. it can. In addition, when the interconnecting inverter (or interconnecting bidirectional inverter) 41 is a bidirectional type, the power supply may be received from the closed circuit meter 11 or the like 11 via the interconnecting bidirectional inverter 41 via the special power distribution system 71. It becomes possible.

  By the way, it is also possible to make the special power distribution system 71 a direct current with respect to the first embodiment or the third embodiment described above. In this case, the interconnection inverter (or interconnection bidirectional inverter) 41 has a conversion function between direct current and alternating current. Further, the inverter or converter 411 outputs to the special power distribution system 71 with a direct current. Further, the special load 211 is a load that can be used with direct current.

  Here, the fuel cell is also connected to the DC distribution system as described in the prior art, but as described above, the limitation on the number of installed power generators due to the power quality such as the voltage fluctuation range is considered. The present invention is different from the present invention in that there is no policy for uniformly controlling the power generation output of power generation devices of different consumers, that is, different responsible entities.

  FIG. 4 is a block diagram showing Embodiment 5 of the combined heat and power system of the present invention. In FIG. 4, 6 is a consumer, 11 is a power distribution system, 21 is its load, 211 is a special load, 31 is a power generation device, 41 is a linked inverter (or linked bidirectional inverter), and 411 is an inverter (or converter). , 51 is a power storage device, 61 is an aggregate (or region) composed of a plurality of consumers 6, 71 is a special power distribution system, and 81 is a control center.

  In the fifth embodiment, the power storage device 51 is connected to a predetermined position of the special power distribution system 71 with respect to those shown in the first to fourth embodiments.

  The power storage device 51 can absorb or mitigate fluctuations by charging and discharging according to the output of the power generation device 31 and the fluctuations of the special load 211 or the load 21. Here, the power storage device 51 may be any device that has a function of accumulating and re-releasing a predetermined capacity of power with a secondary battery, a flywheel generator, a condenser, a SMES (superconducting power storage device), or the like. The type is not limited.

  FIG. 5 is a block diagram showing Embodiment 6 of the combined heat and power system of the present invention. In FIG. 5, 6 is a consumer, 11 is a power distribution system, 21 is its load, 211 is a special load, 31 is a power generator, 41 is a connected inverter (or a connected bidirectional inverter), and 411 is an inverter (or converter). , 51 is a power storage device, 61 is an aggregate (or region) composed of a plurality of consumers 6, 71 is a special power distribution system, and 81 is a control center.

  In the sixth embodiment, the power storage device 51 is connected to a predetermined position of the special power distribution system 71 and the power storage device 51 and the control center 81 are connected to those shown in the first to fourth embodiments. Thus, the charging / discharging time zone, charging power, or discharging power of the power storage device 51 is controlled.

It is a block diagram which shows Example 1 of the cogeneration system of this invention. Fig. 2 shows a second embodiment of the combined heat and power system of the present invention, (a) is a comparative graph showing the relationship between the operation time of each power generator and a control command for power generation output, and (b) is a power generation plan and control of the total power generation amount. It is a comparative graph figure which shows the relationship with a result. It is a block diagram which shows Example 3 of the cogeneration system of this invention. It is a block diagram which shows Example 5 of the cogeneration system of this invention. It is a block diagram which shows Example 6 of the cogeneration system of this invention. It is a system block diagram of the example of a connection of the combined heat and power generator in the consumer in which the conventional load and the combined heat and power generator coexist. It is a system block diagram in the case of the solar cell which receives an output fluctuation | variation by the weather as a conventional power generation device. It is a system block diagram of the electric power supply system by the conventional commercial frequency and direct-current hybrid wiring.

Explanation of symbols

6 ... Consumer 11 ... Distribution system 21 ... Load 211 ... Special load 31 ... Power generation device 41 ... Interconnection inverter (or interconnection bidirectional inverter)
411 ... Inverter (or converter)
51 ... Power storage device 61 ... Aggregate (or region) consisting of a plurality of consumers
71 ... Special power distribution system 81 ... Control center

Claims (6)

A power distribution system for connecting a load to a group or area composed of a plurality of consumers including at least one consumer having a load and a combined heat and power generation device, and the distribution system is a voltage fluctuation range or frequency or A special power distribution system with at least one of the frequency fluctuation ranges is different,
The special power distribution system is connected to a plurality of power generators, and the special power distribution system is connected to the power distribution system via a connected inverter or a connected bidirectional inverter, and the power generating device is connected to the power generator by a control center. A combined heat and power system characterized by operating the operating state of the battery.   Based on the monitoring information of the power distribution system, the special power distribution system, or the power generation device, whether the total power generation amount of the power generation device managed by the control center is a predetermined plan value, not the power consumed by individual consumers The combined heat and power system according to claim 1, wherein the control center controls the output, the number of operating units, or the operating time zone of each power generator so as to obtain an appropriate output.   3. The special distribution system according to claim 1 or 2, wherein a special load having a proof stress that can be used under conditions of a voltage fluctuation range or a frequency or a frequency fluctuation range of the special distribution system is connected to the special distribution system. Combined heat and power system.   The cogeneration system according to any one of claims 1 to 3, wherein the special power distribution system is a direct current.   The combined heat and power system according to any one of claims 1 to 4, wherein a power storage device is connected to a predetermined position of the special power distribution system. The combined heat and power system according to claim 5, wherein the power storage device is connected to the control center to control charging and discharging of the power storage device.

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