Patent Publication Number: US-9836032-B2

Title: Power control device and power control method

Description:
TECHNICAL FIELD 
     The present invention relates to a power control device and a power control method applied to control of storage and supply of a power storage device equipped in a home, for example. 
     BACKGROUND ART 
     In recent years, suppression of energy consumption has been required in factories, offices (buildings), and homes. According to statistical data of the energy consumption, the proportion of the energy consumption in homes is relatively high in total energy consumption. Therefore, the suppression of the energy consumption in homes is an issue to be addressed. A technology of controlling energy in homes is called a “home energy management system” (HEMS). The conventional HEMS implements measures for energy conservation including on/off control of electrical appliances such as an air conditioner, collection of logs of power consumption, and the like. 
     Meanwhile, power generation using renewable energy in place of fossil fuel is being put to practical use, and it is expected, in the future, this tendency becomes stronger. As the power generation using the renewable energy, solar power generation, wind power generation, biomass power generation, wave activated power generation, and the like have been developed. Actually, it has been spread that a solar panel is disposed on a roof, a wall, and the like, and the solar power generation is performed in each home. 
     It can be considered that power by the solar power generation is stored in a storage battery disposed in each home and the power is supplied to a load in the home. In this case, the power consumed by electrical appliances in the home is mixed power from an existing power supply network and from the storage battery. The storage battery is charged with the power by the renewable energy or with the power from the power supply network. Further, even the power from the power supply network is mixed power generated by different power generation methods such as thermal power generation, nuclear power generation, and the like. 
     The conventional measurements to suppress consumed electric energy in the home do not focus on the origin of the power, and therefore, have a problem of not necessarily leading to the reduction of a CO2 (carbon dioxide) emission amount. As disclosed in Patent Document 1, a system of managing the CO2 emission amount is proposed. In Patent Document 1, the CO2 emission amount is obtained for each site, the CO2 emission amount of each site is collected by a management device, and whether the CO2 emission amount is a target value or less by each device group in each site is determined. 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Application Laid-Open No. 2009-199495 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     The invention disclosed in Patent Document 1 manages the CO2 emission amount in a manufacturing factory of semiconductor devices. It is difficult to apply the invention disclosed in Patent Document 1 to CO2 emission amount management in a home and the storage battery provided in the home. 
     Therefore, a purpose of the present invention is to provide a power control device and a power control method based on a CO2 emission amount that can be applied to a home and the like provided with a storage battery. 
     Further, another purpose of the present invention is to provide a power control device and a power control method based on a power rate that can be applied to a home and the like provided with a storage battery. 
     Solution to Problems 
     The present disclosure provides a power control device, including: 
     a storage device of power; 
     a carbon emission strength information acquisition device configured to acquire information of carbon emission strength of the power; and 
     a control device, 
     wherein the control device controls whether the storage device stores the power or supplies the power in accordance with change of the information of carbon emission strength. 
     The power control device preferably further includes: 
     a rate information acquisition device configured to acquire information of a power rate of the power to be supplied, 
     wherein the control device controls whether the storage device stores the power or supplies the power in accordance with the change of the information of carbon emission strength and change of the information of a power rate. 
     The power control device preferably further includes a generation device of the power. 
     The present disclosure provides a power control method, including the steps of: 
     storing power in a storage device; 
     supplying the power from the storage device; 
     acquiring information of carbon emission strength of the power; and 
     controlling whether the storage device stores the power or supplies the power in accordance with change of the information of the carbon emission strength. 
     The power control method preferably further includes the steps of: 
     acquiring information in relation to a power rate of the power; and 
     controlling whether the storage device stores the power or supplies the power in accordance with the change of the information of carbon emission strength or change of the information in relation to a power rate. 
     Effects of the Invention 
     According to at least one of embodiments, an amount of CO2 emission emitted from a home can be reduced. 
     According to at least one of embodiments, a cost required for storing power in the home can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram showing a power system of an embodiment of a power control system according to the present invention. 
         FIG. 2  is a block diagram showing a communication system of an embodiment of the power control system according to the present invention. 
         FIG. 3  is a block diagram used for conceptual description of the power system according to the embodiment of the present invention. 
         FIG. 4  is an outline diagram showing a display on a display according to the embodiment of the present invention. 
         FIG. 5  is a block diagram used for description of a power conditioner connected to a solar panel and a storage device. 
         FIG. 6  is a status transition diagram used for description of a process of controlling charging/discharging of the storage device. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the present invention will be described. Note that the description will be given in the following order. 
     1. Embodiment 
     2. Modifications 
     Note that an embodiment to be described herein is a preferred specific example of the invention, and technically preferred various limitations are applied. However, the scope of the invention is not limited to the embodiment unless otherwise specifically described. 
     &lt;1. Embodiment&gt; 
     [An Example of a Power Control System] 
     An example of a power control system in a divided area, for example, a power control system in a home will be described with reference to  FIG. 1 .  FIG. 1  shows a supply channel of power and  FIG. 2  shows a transmission path of information data, a control signal, and the like. Further,  FIG. 3  is used for showing a concept of a home power network. Direct current (DC) and alternate current (AC) are shown as the type of power. For example, alternate current power of 220 V (60 Hz) flows in the home power network. 
     The power generated by a power plant is introduced through a power supply network  1  to the home via a power meter  2  in the home. The power plant includes a thermal power plant, a nuclear power plant, and the like. A CO2 emission amount of the power supplied to the home through the power supply network  1  differs depending on a power generation method. Further, a power rate of the power bought by a householder, the power being supplied from the power supply company, varies depending on the time of day. For example, the power rate at nighttime when a demand for power is small is set to be relatively reasonable compared with the power rate at daytime. 
     As shown in  FIG. 2 , a power meter  2  is connected to a gateway  4  in the home power network through a wireless local area network (LAN), for example. Devices connected through the wireless LAN are authenticated by mutual authentication. Further, to ensure security, data communicated through the wireless LAN is encrypted. The path in a solid line in  FIG. 2  shows a communication path of a cable LAN and the path in a broken line shows a communication path of the wireless LAN. 
     The power meter  2  performs accurate measurement of the power supplied to the home through the power supply network  1  with a predetermined period, and transmits a measured value to the gateway  4  in the home power network by a communication unit through the wireless LAN. In this case, a measured time is transmitted as a time stamp along with the measured value. The time is time information common to the power network. For example, a reference time source is provided on the power network. 
     Commercial power supply introduced to the home through the power meter  2  is supplied to a plug strip  3 . The plug strip  3  is an appliance having a plurality of power supply plugs in order to supply alternate current power. The alternate current power is supplied from the plug strip  3  to the gateway  4  and an appliance monitor  5 . The alternate current power is supplied through the appliance monitor  5  to home electrical appliances including a television device  6 , an illumination  7 , and a hair dryer  8 , for example. Note that these electrical appliances are examples, and in reality, more various types of electrical appliances are used in the home. 
     The appliance monitor  5  measures power consumption of each electrical appliance connected thereto with a predetermined period, for example, with a period of one second. Information of measured consumed power of each electrical appliance and a time stamp indicating a measured time are transmitted from the appliance monitor  5  to the gateway  4  via wireless communication. 
     Direct current power generated by a solar panel  9  configured from a solar cell is supplied to a solar module  10 . Alternate current power synchronized with the alternate current power in the home is generated by the solar module  10 . The generated alternate current power is supplied to the plug strip  3 . In the plug strip  3 , the alternate current power from the power meter  2  and the alternate current power from the solar module  10  are added and used as the power in the home. Not only the solar panel  9  but also a wind power generation device or the like that generates electricity by renewable energy may be used as a power generation device. 
     The solar module  10  is connected with the gateway  4  through the wireless LAN. The solar module  10  measures the direct current power generated by the solar panel  9  and the alternate current electric energy resulting from conversion of the direct current power and supplied to the power network. The measured value and the time stamp indicating the measured time are transmitted from the solar module  10  to the gateway  4  via the wireless communication. 
     As the power storage device in the home, a storage device  11  including three batteries  12   a ,  12   b , and  12   c  is equipped, for example. The batteries  12   a  to  12   c  are, for example, lithium-ion batteries. The storage device  11  may employ an electrical double layer. A battery center  13  is provided in order to manage operations such as charging/discharging of the batteries  12   a ,  12   b , and  12   c  in the storage device  11 , and to convert the direct current power stored in the storage device  11  into the alternate current power. The storage device  11  and the battery center  13  are connected by a cable interface. For example, a serial peripheral interface (SPI) can be used. The alternate current power from the battery center  13  is supplied to the plug strip  3 . 
     The battery center  13  is equipped with a plurality of sockets as physical connection units. The batteries  12   a ,  12   b , and  12   c  are respectively inserted into/disconnected from the sockets. The batteries  12   a ,  12   b , and  12   c  can employ different types. For example, a lithium-ion battery, a capacitor, a fuel cell, a micro cogenerator, and the like can be used. Each of the batteries can be uniquely identified by a secure battery identifier (battery ID). Even if the types of the batteries are different, all of the batteries can be inserted into the standardized sockets. 
     The socket secures physical connection and an interface between the batteries  12   a ,  12   b , and  12   c  and the battery center  13 . The battery center  13  manages the status of the batteries  12   a ,  12   b , and  12   c  and monitors safety and reliability. The battery center  13  is connected with the gateway  4  through the wireless LAN. The gateway  4  receives information from the battery center  13  and transmits a control signal in relation to the batteries  12   a  to  12   c  to the battery center  13 . 
     As shown in  FIG. 3 , the gateway  4  is connected with a battery profile server  17  on an internet  16  through an asymmetric digital subscriber line (ADSL)  15 . The gateway  4  receives a battery ID and storage information corresponding thereto from the server  17 , so that the batteries can be safely and properly charged. Further, information of use result of the batteries (the number of charging, trouble, and the like) is transmitted from the gateway  4  to the server  17 , and storage information in a database in the server  17  is renewed into latest information. 
     As shown in  FIG. 3 , each of the batteries is configured to be detachable from the battery center  13  and is detached and used for other purpose of use. That is, the battery is used as a power source of an electric device, for example, a power-assisted bicycle  18  or a power tool  19 . As described above, the battery can be used as power supply other than the household storage battery, and the control and the charging device are common to the several types of batteries, whereby the household storage battery can be configured at a low cost without deteriorating safety. 
     A display  14  is connected to the gateway  4  through the wireless LAN, and display information is transmitted from the gateway  4  to the display  14 . The display  14  displays information or a part of the information exemplarily shown below to a user in the home.
     The power supplied from the power supply network  1  to the home   The power supplied from the solar panel  9     Net power flowing into the battery center  13     The status of a battery on the battery center  13     The power consumed by an electrical appliance in the home   The proportions of green power and non-green power in used energy   The carbon emission strength of used power in real time   A carbon footprint of the power consumed by the home power network
 
(For example, a value obtained by integrating emitted greenhouse effect gas (carbon emission strength) for one month is displayed as the carbon footprint, so that the carbon emission amount is visualized.)
   

     The above-described information to be displayed on the display  14  may also be displayed on a mobile display  20  on the internet  16 . Examples of the mobile display  20  include a mobile phone and a mobile personal computer. Further, a control signal for controlling the power network can be transmitted to the gateway  4  in the home using these mobile terminals. 
     [A Time Stamp Associated with Measured Data] 
     The above-described information to be displayed on the display  14  is generated such that a measured value (with a time stamp) transmitted from the power meter  2 , the appliance monitor  5 , the solar module  10 , and the battery center  13  through the wireless LAN is processed by the gateway  4 . In the gateway  4 , used electric energy is synchronized with each other by the time stamp. Further, an integrated value of the used electric energy in a time direction is calculated. As a power measuring instrument, an instrument that satisfies a predetermined specification is used in order to secure accuracy. Further, accurate measurement in relation to the power serves as a base of a function to inform a householder of numerical value data that is obtained by adjusting/converting energy consumed in the home into a carbon dioxide emission amount with accuracy. 
     A typical example of monitoring the status of use of the energy in the home is to integrate and display, on a display, a total energy amount consumed during a specific period (time). As described above, the measured value is data associated with a time stamp that indicates a measured time. Therefore, assuming that two measured values are obtained, instant power P can be obtained by dividing a difference between the two measured values E 1  and E 2  of the energy by a difference between the times T 1  and T 2 .
 
 P =( E   2   −E   1 )/( T   2   −T   1 )
 
     Information can be secured by obtaining the integrated value of data even if breakdown of devices and the like due to power failure occurs. In a system that treats data as power, even if only one data is missing, the integration that includes a period in which the measurement could not be carried out becomes a speculation. Therefore, the conversion/adjustment of the total energy amount becomes inaccurate. If it is a system based on information in association with a time stamp that indicates a measured time, recovery of the breakdown and accuracy of the conversion can be realized. 
     [Control of a Power Control System from an Outdoor] 
     Further, remote control of the storage device  11  from an outdoor with a mobile terminal on a network through the internet  16  and the gateway  4  is possible. A simple example of an application fully using this merit is that the householder operates the power storage device from the outdoor to flexibly change an operation of the system in accordance with the action of the householder. In a case where larger power consumption than usual is expected when the householder goes out and next comes back home, the householder can give an instruction of storing energy in advance to the storage device  11  from the outdoor. Further, for example, when the householder leaves a house on vacation and the like, it is possible to make a long-term contract to entrust control of the storage of the power to the public utility company (power company). 
     [Control of a Storage Device Based on the Carbon Emission Strength of Energy to be Used] 
     When obtaining the carbon emission strength, it may be possible to access a server on the internet  16 , more specifically, an application program interface (API), to transmit information of consumed power and the like in the home to the API, and to calculate the carbon emission strength in the API. An example of the API includes an avoiding mass extinctions engine (AMEE)  21 . The AMEE  21  collects energy data all around the world and stores various forms of energy consumption data collected for long periods. According to a profile defined by the AMEE  21 , the gateway  4  can obtain information in relation to the CO2 emission amount of the home where the gateway  4  is located. 
     The gateway  4  can control when to store the energy in the storage device  11  as the power and when to supply the energy from the storage device  11  based on the carbon emission strength calculated on its own or by the API. Further, the gateway  4  can control allocation of the storage and the supply. 
     An example of a rule of the control based on the carbon emission strength will be described. This rule is an algorithm for minimizing the total carbon emission strength by the power consumption. The above-described power control system is set to store the power in the storage device  11  only when the carbon emission strength of supplied energy is lower than a certain threshold value. When the carbon emission strength is high, the power is supplied from the storage device  11 . Such a power control system enables the householder to consume the energy with a lower carbon emission amount. 
     In the power control system, the carbon emission strength of energy to be used can be obtained as net carbon emission strength based on the energy generated by a power generator (solar panel  9 ) disposed in the home in addition to the energy supplied from outside (power company). The carbon emission strength varies depending on how the energy has been generated. The energy stored in the storage device  11  with lower carbon emission strength is more favorable. Information in relation to the carbon emission strength of the energy supplied from the power company can be obtained not only from the power company but also from the above-described AMEE. 
     There are two costs for storing the power in the power control system. The first cost is a cost of the power to be stored itself. The second cost is a cost caused by durable years (deterioration) of a battery used for storing the power. When determining the rule about when to charge and what rate to charge, both aspects of the costs: the power and an exchange of the battery should be considered. According to the power control system, by quickly storing the energy when the carbon emission strength is low, an unnecessary cost caused by the deterioration of the battery due to the quick charging can be canceled out. 
     [Control of a Storage Device Based on a Buying Power Rate] 
     When the storage device  11  is controlled, a buying power rate of energy is considered. The buying power rate of energy (power) varies depending on the time of day, the season, and the like. The power control system calculates the storage of power in the home and the buying power rate of energy presented by the power company. The buying power rate changes due to adjustment of the demand and supply balance of power by the power company and a spot price in the power market. 
     Information of the buying power rate can be obtained by a consumer from the power company. The power control system defines the rule of when to store the energy as the power and when to supply the energy. Further, the allocation of the storage and the supply can be controlled. The power control system is set to store the power only when the buying power rate by the consumer to whom the energy is supplied is lower than a certain threshold value. Such a power control system is effective in enabling the householder to minimize the cost of the energy consumed in the home. 
     The rule of determining when to store the energy as the power and what rate to charge is determined considering both of the cost of the storage, that is, the cost of the power itself, and the life of the battery. According to the power control system, when the buying power rate by the consumer is low, an unnecessary cost caused by the deterioration of the battery due to quick charging can be canceled out by rapidly storing the energy. 
     [An Example of a Display on a Display] 
     An example of a display on the display  14  will be described with reference to  FIG. 4 . The display on the display  14  is a color display. A mark of a house is displayed in a nearly center of a display area. The mark of the house is divided into two, and a display  31 A indicating an amount of the power supplied from the power supply network  1  to the home is displayed on the left half of the mark facing the drawing. Usually, this power is the non-green power (power with relatively high carbon emission strength) and is therefore indicated in red. However, when the green power (power with relatively low carbon emission strength) exists in the power supplied from the power supply network  1 , a display  31 B (green) corresponding to an amount of the green electric energy is displayed as shown in the broken line. These displays  31 A,  31 B, and  32  are animation displays changing in real time. 
     The display  32  corresponding to an amount of the green power generated by the solar panel  9  (shown by an icon  33  in  FIG. 4 ) is displayed on the right half of the mark facing the drawing. Further, icons  34   a ,  34   b , and  34   c  corresponding to the three batteries that constitute the storage device  11  and indicating respective stored amounts are displayed. Further, an area  35  that indicates electrical appliances in the home is provided, and respective icons of working electrical appliances in the area  35  and current consumed power are displayed. A display  36  indicating current total consumed electric energy is displayed. 
     Further, an indicator  37  is displayed. The position pointed by a pointer mark of the indicator  37  shows the degree of greenness (cleanness) of the electric energy currently supplied to the home. A left hand icon  38   a  on the indicator  37  shows the most favorable position and a right hand icon  38   b  shows the worst position. Therefore, the more left the pointer mark points at, the more favorable the degree of greenness is, whereas the more right the pointer mark points at, the worse the degree of greenness is. 
     Further, a display  39  of a carbon footprint is displayed on a lower part of the display area. The carbon footprint is a value resulting from conversion of the total power consumed in the home during a predetermined period such as one month into the CO2 emission amount. As described above, when obtaining the CO2 emission amount, the carbon footprint is obtained considering the carbon emission strength of each power in accordance with a generation method. 
     A display  40  of my score card is displayed on a lowermost part of the display area. A score displayed on the display  40  of my score card is a meaningful value for the user&#39;s (householder&#39;s) interests. For example, the score is a base of an environmental subsidy supplied by the government. Alternatively, it serves as a transaction object in a transaction market of a CO2 emission amount. 
     [Regarding a Scale of the Degree of Greenness (Greenness Gauge)] 
     As described above, the total carbon emission strength of the power consumed in the home is displayed on the display  14 . The total carbon emission strength is shown in a form of a scale (gauge). The calculation of a variable for obtaining this scale can consider the energy generated by a solar cell disposed in each home, or by a combined heat and power (CHP) facility and the like, as well as the energy supplied from outside (power company). For example, the scale is calculated with the following formula. “E” represents an energy amount and “C” represents a carbon cost.
 
 G=ΣE (supply), E (solar), E (CHP), E (battery)/Σ C (supply), C (CHP), C (battery)
 
     In this calculation, it is assumed that a “carbon cost” to the power obtained by the solar cell is zero or is a “carbon cost” caused in the implementation. The “carbon cost” of the power supplied from a battery may be a “carbon cost” of the power for charging, or may be integration of a specific “carbon cost” in each use of the battery and/or a proportion of the specific “carbon cost” in each use of the battery to a total cost. 
     Further, this scale (gauge) may include information of total consumed power. In this way, this scale (gauge) can serve as an indicator showing whether the home uses carbons in an efficient manner. Another formula of calculating the scale is shown below.
 
 G=ΣE (supply), E (solar), E (CHP), E (battery)/Σ E (supply), E (solar), E (CHP), E (battery)+Σ C (supply), C (CHP), C (battery)
 
     With the display on the above-described display  14 , in the home, the householder can immediately get to know a balance between the energy supplied from outside (power company) and the energy generated in each home. 
     [Power Conditioner] 
     A first power conditioner and a second power conditioner provided in each of the solar module  10  and the battery center  13  will be described with reference to  FIG. 5 .  FIG. 5  shows a partial configuration of the battery center  13 . 
     A direct current voltage generated in the solar panel  9  is supplied to a DC-DC converter  51  and is output as a predetermined direct current voltage. The output voltage from the DC-DC converter  51  is supplied to a DC-AC inverter  52 . The DC-AC inverter  52  is, for example, configured to be a grid tie inverter (GTI) and outputs alternate current power in synchronization with alternate current power of the power supply network at an output side. 
     Power generation by the solar panel  9  varies depending on the weather, the time of day, and the like. Therefore, when an output voltage of the solar panel  9  is supplied to the DC-AC inverter  52 , the DC-DC converter  51  is used in order to stabilize an input voltage of the DC-AC inverter  52 . Further, the DC-DC converter  51  is configured to adjust the impedance of an output in accordance with the impedance of the solar panel under any input light at any given time. This characteristic of following a maximum value of a load on the solar panel  9  is known as “maximum peak point tracking” (MPPT, a maximum power point tracking control function that follows a point at which output power of the solar panel is maximized). 
     Further, the DC-DC converter  51  and the DC-AC inverter  52  configured to be a GTI require an assumption that an AC line obtains the power from other power supply before the transmission of power. The reason is to ensure the safety of an engineer who works in the wiring network. Because of such a characteristic, a certain amount of delay occurs during a period from a DC input timing to an AC output timing in the DC-AC inverter  52 . 
     Alternate current power from the power meter  2  is converted into direct current power by a rectifier circuit  53  of the battery center  13 . The direct current power from the DC-DC converter  51  of the solar module  10  and/or the direct current power from the rectifier circuit  53  of the battery center  13  are supplied to a charger  54 . A battery of the storage device  11  is charged by the charger  54 . 
     The storage device  11  is similar to a solar panel in generation of the direct current power, and a power conditioner is also connected to an output of the storage device  11 . That is, the direct current power generated by the storage device  11  is supplied to a DC-DC converter  55 . Predetermined direct current power from the DC-DC converter  55  is supplied to a DC-AC inverter  56 . Alternate current power output from the DC-AC inverter  56  is supplied to a home alternate current power system. The DC-AC inverter  56  is configured to be a GTI. 
     As described above, when each battery is configured to be detachable from the battery center  13 , authentication is performed between the battery center  13  and the battery before the charging and discharging of the battery is performed, and only when the authentication is established, the charging and discharging are processed. In the authentication process, an ID of each battery is used. 
     For such an authentication process and charging and discharging operations, a controller  57  and a wireless communication unit (not shown) are provided in the battery center  13  in order to control each part of the battery center  13 . The controller  57  is configured from a microcomputer. The above-described DC-DC converter  55  and the DC-AC inverter  56  constitute a first power conditioner and the DC-DC converter  51  and the DC-AC inverter  52  of the solar module  10  constitute a second power conditioner. As each circuit block that constitutes these power conditioners, an identical configuration is used for the reason of consistency of control, ease of access, and the like. 
     An example of control of a charging/discharging process by the controller  57  will be described with reference to  FIG. 6 . In  FIG. 6 , three types of the status: “charging”, “off”, and “supply (allocation)” are shown. 
     A condition of a transition S 1  from “off” to “charging” 
     (A solar panel output≧150 W) and (the charging status&lt;90%) 
     A condition of a transition S 2  from “charging” to “off” 
     (A solar panel output&lt;150 W) or (the charging status≧90%) 
     A condition of a transition S 3  from “off” to “supply” 
     (An electrical appliance load≧50 W) and (the charging status≧25%), or (a solar panel output≧150 W) and (the charging status&lt;90%) 
     A condition of a transition S 4  from “supply” to “off” 
     (An electrical appliance load&lt;50 W) or (the charging status&lt;25%) 
     The above-described control of a charging/discharging process is an example of a control of charging the storage device  11  only by an output from the solar panel. Other control method may be available when the storage device  11  is chargeable with an output from the above-described rectifier circuit  53 . Further, the numerical values of the threshold values for determination are mere examples and various values can be set. 
     As described above, the DC-DC converter  51  and the DC-AC inverter  52  have a certain amount of delay during the period of the DC input timing to the AC output timing in the DC-AC inverter  52 . However, the output voltage from the storage device  11  is desired to instantly supply the power as demanded. 
     To satisfy such a demand, the DC-DC converter  55  is configured to have two output voltages. The first output voltage is a stand-by voltage. The stand-by voltage is lower than the threshold value when the DC-AC inverter  56  begins to supply the power to outside, and is a sufficient voltage for the DC-AC inverter  56  to operate. The second voltage is a voltage with which the DC-AC inverter  56  begins to supply the power to outside. In this way, the DC-DC converter  56  outputs the first voltage at which the DC-AC inverter  56  stands by in order to instantly transfer to a supply mode. 
     The DC-DC converter  51  includes, as described above, the maximum power point tracking control function. Similarly, the DC-DC converter  55  into which the output voltage from the storage device  11  is input includes the maximum power point tracking control function. The storage device  11  has an output characteristic that is different from the solar panel. Therefore, when the DC-DC converter  55  connected to the storage device  11  includes the maximum power point tracking control function, the storage device  11  causes a system (power supply to the AC line) to be unstable. Therefore, the DC-DC converter  55  is configured to dynamically change the output impedance in such a way that the output impedance traces a load curve of the solar panel. 
     Note that, in a system in which one DC-AC inverter (GTI) is included for a plurality of batteries and a plurality of DC-DC converters, this load curve simulation means that a plurality of outputs of a plurality of DC-DC converters is merely connected in parallel. 
     &lt;2. Modification&gt; 
     As described above, an embodiment of the present invention has been specifically described. However, the present invention is not limited to the above-described embodiment, and various modifications based on technical ideas of the present invention are possible. For example, a power controller system can be applied to a divided area besides a home. 
     REFERENCE SIGNS LIST 
     
         
           1  Power supply network 
           2  Power meter 
           4  Gateway 
           5  Appliance monitor 
           9  Solar panel 
           10  Solar module 
           11  Storage device 
           13  Battery center 
           14  Display 
           51  and  55  DC-DC converter 
           52  and  56  DC-AC inverter