JPWO2010082506A1 - DC power supply system - Google Patents

Abstract

Provided is a direct current power supply system capable of effectively using a power storage device for backup while maintaining high backup reliability in the event of a power failure. Always connected in parallel to the first DC load 14 and supplies the minimum DC power for backup to the first DC load 14 when the AC power 11 drops momentarily or stops instantaneously. The first power storage device 16 having a power storage capacity that can be connected, and can be connected in parallel to the first power storage device 16 and the first DC load 14. The power storage capacity is higher than that of the first power storage device 16. The second power storage device 17, the first switch SW1 provided in the circuit connecting the power conversion device 13 and the second power storage device 17, the second power storage device 17 and the second DC load. 50, the second switch SW2 provided in the circuit connecting the power supply 50, the power failure detection means 21 for detecting the supply stop of the AC power 11 to the power converter 13, and the DC power stored in the second power storage device 17 Supply to second DC load 50 When the first switch SW1 is turned off and the second switch SW2 is turned on, and the power failure detection means 21 detects the supply stop of the AC power 11 to the power converter 13, it is given priority. And a circuit switching means 20 for turning on the first switch SW1 and turning off the second switch Sw2.

Description

  The present invention relates to a DC power supply system that reduces power loss, and more particularly, to a DC power supply system that can effectively use a power storage device for backup while maintaining high reliability of backup for a load in the event of a power failure.

  Some power supply systems supply power to a communication device as a load. In a power supply system for communication, DC power is supplied to a load such as an exchange or a transmission device. On the other hand, many data centers and companies adopt an AC power feeding method. In the case of the AC power feeding method, it is necessary to perform power conversion a plurality of times before power is supplied to a load such as an IT device, and there is a problem that power loss increases.

  In order to reduce power loss, data centers and the like are planned to introduce a DC power supply system that supplies DC power to a load. FIG. 11 shows an example of a data center 1 that employs a DC power supply system. As shown in FIG. 11, commercial power 2 as AC power is supplied to the data center 1, and the commercial power 2 is supplied to a power converter (rectifier) 4 via a distribution board 3. Further, AC power can be supplied to the power conversion device 4 from the generator 7 when the commercial power 2 is interrupted.

  The power conversion device 4 converts the commercial power 2 into DC power and supplies the DC power to the server 5 and the like. A power storage device 6 is connected to the output side of the power conversion device 4 for load backup during a power failure. In the case of direct current power supply, the server 5 is designed as a direct current specification, so that direct current power can be supplied to the server 5, and the direct current power supplied to the server 5 is adjusted by a built-in DC-DC converter 5a. Thereafter, it is sent to the CPU 5b and the like. Thus, in the case of direct current power supply, since the load is a direct current device, it is only necessary to convert the alternating current power 2 supplied from the electric power company into direct current power by the power conversion device 4, and to suppress power loss to a small amount. it can.

  In a power supply system that supplies power to a communication device or the like, a power storage device for backup of a load in the event of a power failure is essential, and energy saving is required by leveling the power load. In view of this, a power supply system has been proposed in which the DC power supply system is backed up, and at the same time, loads such as air conditioning are leveled to reduce daytime power consumption (see, for example, Patent Document 1).

Japanese Patent No. 3695641

  By the way, in the supply of commercial power, an instantaneous voltage drop of about 0.1 seconds called instantaneous drop and an instantaneous power failure called instantaneous interruption occupy most of the problems. Since the capacity of the device is set in consideration of the assumed maximum power failure time, a large-capacity power storage device is required for a facility having a large-scale communication device, and a large amount of capital investment is required. In other words, in the conventional power supply system, a large amount of investment is required to introduce a large-capacity power storage device in order to reliably avoid the effects of momentary power failure, but the power storage device functions only in the event of a power failure. Since it is not used effectively in normal times, there is a problem from the viewpoint of the operating rate of the apparatus. Even in the power supply system of Patent Document 1, since power supply control is performed only for the same load, there remains a problem from the viewpoint of effective use of the storage battery.

  A power storage device such as a secondary battery has a feature that allows the stored power to be discharged at a stretch. Therefore, the power storage device is optimal for power supply for rapid charging of an electric vehicle. If rapid charging is possible, electric vehicles can be promoted and spread without newly installing large-scale substation facilities for rapid charging.

  In addition, with the development of information and communication technology in recent years, ultra-small mobile phone base stations called femtocells have been installed in ordinary households, and they have high reliability against power outages in ordinary households. Moreover, it is desired to introduce a DC power supply system with little power loss.

  Accordingly, an object of the present invention is to provide a DC power supply system that can effectively use a power storage device for backup while maintaining high reliability of backup in the event of a power failure.

  In order to achieve the above object, the first aspect of the present invention provides a first DC load that is charged by a power converter that converts AC power into DC power and that is supplied with DC power from the power converter. Always connected in parallel, and supplies the minimum DC power for backup to the first DC load when the AC power supplied to the power converter drops momentarily or stops instantaneously The first power storage device that can be used, and the power conversion device that is charged by the power conversion device and that can be connected in parallel to the first power storage device and the first DC load, and that is stored A circuit that connects the power converter and the second power storage device, and a second power storage device that can supply the direct-current power from the second power source to the second DC load and has a larger capacity than the first power storage device Established in A first switch, a second switch provided in a circuit connecting the second power storage device and the second DC load, and a power failure detecting a supply stop of the AC power to the power converter When supplying the DC power stored in the detection unit and the second power storage device to the second DC load, the first switch is turned off and the second switch is turned on. A circuit switching means for preferentially turning on the first switch and turning off the second switch when detecting a supply stop of the AC power to the power converter by the power failure detection means; A direct current power supply system comprising:

  According to the present invention, when an instantaneous voltage drop or power failure occurs, the DC power stored in the first power storage device is instantaneously supplied to the first DC load, and the AC power is detected by the power failure detection means. When the supply stop is detected, the power supply circuit is switched by the circuit switching means, and the power supply from the second power storage device to the first DC load is also started. At times other than the occurrence of a power failure, the first DC load and the second power storage means are electrically disconnected by the circuit switching means, and the DC power stored in the second power storage means is, for example, the first electric vehicle or the like 2 can be supplied to the DC load.

  According to a second aspect of the present invention, in the DC power supply system according to the first aspect, the first power storage device is constituted by a capacitor.

  According to a third aspect of the present invention, in the DC power supply system according to the first or second aspect, the second power storage device includes a secondary battery.

  According to a fourth aspect of the present invention, in the DC power supply system according to any one of the first to third aspects, the power conversion device is configured by an AC-DC converter using at least a SiC semiconductor element. It is characterized by.

  According to a fifth aspect of the present invention, in the DC power supply system according to any one of the first to fourth aspects, the first DC load includes an information communication device.

  According to a sixth aspect of the present invention, in the DC power supply system according to any one of the first to fifth aspects, the second DC load uses pure DC power supplied from the second power storage device. Thus, it is an electric mobile body having a quick charging function for performing quick charging.

  According to a seventh aspect of the present invention, in the DC power supply system according to any one of the first to sixth aspects, the circuit switching means turns on the first switch only in a specific time period and turns on the second It has a function of turning off the switch and a function of turning off the second switch when the remaining power storage amount of the second power storage device becomes a predetermined value or less.

  According to an eighth aspect of the present invention, in the DC power supply system according to any one of the first to seventh aspects, the first power storage device, the second power storage device, and the first DC load In addition, at least DC power from a solar cell or DC power from a fuel cell can be supplied.

  According to the first aspect of the present invention, it is possible to supply power from the first power storage device that is always connected to the first DC load for an instantaneous voltage drop or power failure, and a relatively long power failure. In contrast, since the power supply from the second power storage device to the first DC load is possible, the reliability of the system against the occurrence of a power failure can be maintained at a high level, and the operation of the second power storage device during a time other than the time of the power failure can be maintained. The rate can be significantly increased. As a result, the DC power stored for backup can be effectively used, and the capital investment can be easily recovered even if a large amount of capital investment is made in the power storage device.

  In addition, since the first switch is turned off when supplying power to the second DC load, the first DC load is electrically disconnected from the second DC load, and the second DC load side It is possible to prevent noise from entering. That is, even if the first DC load is an important information communication facility or the like, noise generated by the second DC load such as an electric vehicle is blocked by the first switch that is turned off. Noise from the DC load will not adversely affect the first DC load.

  According to the second aspect of the present invention, since the first power storage device is composed of the capacitor, the charging / discharging reaction speed is very fast, and the instantaneous voltage drop or the instantaneous power failure continues. Even if it occurs, the first DC load can be backed up reliably. In addition, since the capacitor is hardly deteriorated by charging and discharging, high performance can be maintained for a long time, and the running cost can be reduced.

  According to the third aspect of the invention, since the second power storage device is constituted by a secondary battery, it is possible to store power using a secondary battery having a high energy density such as a lithium ion battery. This makes it possible to reliably back up the first DC load even for a long-time power outage. Moreover, since the 2nd electrical storage apparatus can discharge | release the stored big electric power at a stretch, even if it is the 2nd DC load which requires large electric power for a short time, it can respond.

  According to the fourth aspect of the present invention, since the power conversion device is composed of an AC-DC converter using a SiC semiconductor element, the power conversion efficiency is higher than that of a conventional AC-DC converter using a silicon semiconductor element. The power loss when converting commercial power to DC power can be significantly reduced.

  According to the invention described in claim 5, since the first DC load is composed of the information communication device, it is installed not only in the information communication device of the data center owned by the company but also in a general home called a femtocell, for example. It is possible to improve the reliability of backup in the event of a power failure even for an information communication device of an ultra-small mobile phone base station.

  According to the sixth aspect of the present invention, the second DC load is an electric mobile body having a quick charging function for performing quick charging using pure DC power supplied from the second power storage device. In addition, it is possible to quickly charge an electric vehicle in a company or a home by effectively utilizing a power storage device for backup. As a result, infrastructure for rapid charging of electric vehicles can be promoted, and the spread of electric vehicles can be promoted.

  According to the seventh aspect of the present invention, the circuit switching means has a function of turning on the first switch and turning off the second switch only in a specific time zone. Utilizing this, DC power is stored in the second power storage device, and power can be supplied to the second DC load. The circuit switching means has a function of turning off the second switch when the remaining power storage amount of the second power storage device becomes a predetermined value or less. It can store a minimum amount of power for power outages.

According to the eighth aspect of the present invention, at least DC power from the solar cell or DC power from the fuel cell can be supplied to the first power storage device, the second power storage device, and the first DC load. Therefore, it is possible to use electric power other than commercial electric power and contribute to prevention of global warming by reducing CO ₂ .

1 is a schematic diagram of a DC power supply system according to Embodiment 1 of the present invention. It is a front view which shows the outline | summary of the quick charge of the electric vehicle using the DC power supply system of FIG. FIG. 2 is an electric circuit diagram showing a connection relationship between the DC power supply system of FIG. 1 and an electric vehicle. It is a flowchart which shows the operation | movement procedure at the time of a power failure and the normal time in the direct-current power supply system of FIG. It is a flowchart which shows the operation | movement procedure of the circuit switching means in the DC power supply system of FIG. It is a schematic diagram of the DC power supply system concerning Embodiment 2 of this invention. It is a schematic diagram of the DC power supply system concerning Embodiment 3 of this invention. It is a schematic diagram of the direct-current power feeding system concerning Embodiment 4 of this invention. It is a schematic diagram of the direct-current power supply system concerning Embodiment 5 of this invention. It is a schematic diagram of the DC power feeding system concerning Embodiment 6 of this invention. It is a schematic diagram showing an example of a direct current power supply system.

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

(Embodiment 1)
1 to 5 show Embodiment 1 of the present invention, and particularly show a case where it is applied to a data center. In FIG. 1, commercial power 11 from an electric power company is supplied to a data center 10. The commercial power 11 is three-phase AC power, and the voltage is, for example, 6600V. The commercial power 11 is supplied to the power conversion device 13 via the switchboard 12 installed in the data center 10. An emergency generator 25 is disposed outside the data center 10, and AC power can be supplied from the generator 25 to the power converter 13. The generator 25 has a function of supplying power to the power conversion device 13 in place of a second power storage device 17 described later when the power failure time is very long. The power circuit of the data center 10 is connected to a smart grid (next generation power transmission network).

  The power conversion device 13 has a function of converting alternating current power into direct current power, and is composed of, for example, an AC-DC converter. The AC-DC converter has a function of converting AC power input by switching control into DC power. The AC-DC converter is manufactured using a SiC (silicon carbide) semiconductor element in order to increase the conversion efficiency when converting from AC power to DC power. Since the SiC semiconductor element is suitable for controlling a large current and has heat resistance, the cooling structure of the AC-DC converter can be simplified. Moreover, the AC-DC converter which comprises the power converter device 13 is good also as a structure using the GaN (gallium nitride) semiconductor element which has the same advantage as a SiC semiconductor element. The power converter 13 has a function of converting, for example, input AC power having a voltage of 6600 V into DC power having a voltage of 380 V.

  A server 14 as a first DC load is connected to the output side of the power conversion device 13. The server 14 is one of information communication devices, and here means a high-performance and high-reliability computer for business use. The server 14 includes two DC-DC converters 14a and 14c, a CPU (Central Processing Unit) 14b, and an HHD (Hybrid Hard Disk) 14d. The DC-DC converter 14a has a function of controlling the DC power from the power conversion device 13 to a voltage suitable for the CPU 14b. The DC-DC converter 14c has a function of controlling the DC power from the power conversion device 13 to a voltage suitable for the HHD 14d. In addition, a lighting device 15 as a first DC load is connected to the output side of the power conversion device 13. The lighting device 15 includes a DC-DC converter 15a and an LED (light emitting diode) 15b. The DC-DC converter 15a has a function of controlling the DC power from the power converter 13 to a voltage suitable for the LED 15b. The LED 15 b is a semiconductor element that emits light by direct current power, and is used as illumination of the data center 10.

  A first power storage device 16 is connected to the output side of the power conversion device 13. The first power storage device 16 is always connected in parallel to the server 14 and the lighting device 15 that are the first DC load, and is charged by the DC power from the power conversion device 13. The first power storage device 16 is composed of an electric double layer capacitor as a capacitor. The output voltage of first power storage device 16 is set to 380 V, which is substantially the same as that of power conversion device 13. The first power storage device 16 is a minimum for backup to the server 14 and the lighting device 15 when the voltage of the AC power 11 supplied to the power conversion device 13 drops momentarily or stops momentarily. It has a power storage capacity capable of supplying the direct current power. The electric double layer capacitor has a very fast charging / discharging reaction speed compared to the secondary battery, and reacts instantaneously to an instantaneous voltage drop or power failure. Backup can be performed reliably. In addition, since the electric double layer capacitor does not use a chemical reaction for charging and discharging, there is almost no deterioration of the substance due to use, and high performance can be maintained over a long period of time. In the first embodiment, the capacitor is configured as an electric double layer capacitor, but the capacitor may be configured from a lithium ion capacitor. A lithium ion capacitor has a structure in which a negative electrode of a lithium ion battery and a positive electrode of an electric double layer capacitor are combined, and has a higher energy density than an electric double layer capacitor.

  A second power storage device 17 is connected to the power conversion device 13 via the first switch SW1. The first switch SW1 has a function of turning on and off the circuit based on a plurality of input control signals. The second power storage device 17 can be connected in parallel to the first power storage device 16 and the server 14 and the lighting device 15 as the first DC load via the first switch SW1. The second power storage device 17 is charged with DC power from the power conversion device 13 via the first switch SW1. The second power storage device 17 can supply the stored DC power from the power conversion device 13 to the electric vehicle 50 that is the second DC load, and the power storage capacity is significantly larger than that of the first power storage device 16. ing.

  The 2nd electrical storage apparatus 17 is comprised from secondary batteries, such as a lead storage battery and a lithium ion battery, for example. The output voltage of the second power storage device 17 is set to 380 V, which is the same as that of the power conversion device 13. A secondary battery such as a lithium ion battery has a higher energy density than a capacitor, and thus can store a large amount of power. This makes it possible to reliably back up the server 14 that is the first DC load even for a long-time power failure. An information communication device such as the server 14 is the heart of information communication as described above, and power supply is not allowed to stop. However, by securing a large power storage capacity of the second power storage device 17, Even if there is a power failure, it is possible to reliably perform backup. In addition, since the second power storage device 17 having a high energy density can supply DC power to the second DC load except during a power failure, even if the second DC load uses a large amount of power. It becomes possible to supply electric power for a long time.

  A second switch SW <b> 2 is connected to the second power storage device 17. The second switch SW2 has a function of turning on and off the circuit based on a plurality of input control signals. As shown in FIG. 1, the second switch SW <b> 2 is connected in parallel to the first switch SW <b> 1 and the second power storage device 17. Each of the first switch SW1 and the second switch SW2 has an opening / closing function of supplying or stopping DC power, and is composed of a semiconductor element or an electromagnetic contactor. The first switch SW1 and the second switch SW2 have a function of suppressing the generation of arcs when cutting off high-voltage DC power of 380V.

  In the data center 10, circuit switching means 20 for switching circuits in the DC power supply system is arranged. A power failure detection means 21 is connected to the circuit switching means 20. When supplying the DC power stored in the second power storage device 17 to the electric vehicle 50 as the second DC load, the circuit switching unit 20 turns off the first switch SW1 and the second switch It has a function to turn on SW2. In addition, when the power failure detection unit 21 detects the supply stop of the commercial power 11 to the power conversion device 13, the circuit switching unit 20 preferentially turns on the first switch SW1 and the second switch It has a function to turn off SW2. Between the first switch SW1 and the second switch SW2, capacity calculation means 22 for calculating the remaining capacity of the second power storage device 17 is provided. The circuit switching means 20 is input with a signal S6 indicating the calculation result of the remaining capacity of the second power storage device 17 from the capacity calculating means 22.

  FIG. 2 shows a state of charge of the electric vehicle 50 having a quick charge function of performing quick charge using pure DC power supplied from the second power storage device 17. As shown in FIG. 2, the second switch SW2 is connected in series with a third switch SW3 as an opening / closing means. The third switch SW3 is accommodated in the charging stand 26 arranged outside the data center 10. To the output side of the third switch SW3, an electric vehicle 50, which is one of the electric mobile bodies as the second DC load, can be connected. The charging stand 26 includes a display unit 27 and an operation unit 28. A charging cable 29 constituting a part of the charging circuit is connected to the third switch SW3 housed in the charging stand 26. The third switch SW3 has a function of turning on and off the charging circuit based on a plurality of input control signals. The charging cable 29 is held on the side surface of the charging stand 26 at times other than charging, and extends toward the electric vehicle 50 as an electric mobile body during charging. A charging plug 30 that can be connected to a charging connector (not shown) of the electric vehicle 50 is provided at the tip of the charging cable 29.

  FIG. 3 shows the connection relationship between the charging stand 26 and the electric vehicle 50 during charging. The charging plug 30 of the charging cable 29 is connected to the electric vehicle 50 side. Pure DC power from the second power storage device 17 is supplied to the electric vehicle 50 via the second switch SW2 and the third switch SW3. The third switch SW3 is opened and closed by a signal from the operation unit 28 of the charging stand 26 or a signal from the electric vehicle 50, and supplies or stops pure DC power from the second power storage device 17 to the electric vehicle 50. Has the function to perform.

  Signals S10, S11, and S20 from the charging control means 80 of the electric vehicle 50 can be input to the third switch SW3 side. In addition to the charging control means 80, various devices are mounted on the electric vehicle 50. Pure DC power supplied to the electric vehicle 50 is controlled to a predetermined voltage and current by the charging control means 80 and then supplied to the secondary battery 85. The secondary battery 85 is composed of a lithium ion battery in which a large number of cells are connected in series. The DC power stored in the secondary battery 85 can be supplied to the travel motor 87 via the controller 86, and the electric vehicle 50 can travel using the travel motor 87 as a drive source. The electric vehicle 50 is equipped with a cooling unit 60 for cooling the heat generating part in the charging system.

  The charge control means 80 has a quick charge control function for controlling pure DC power from the second power storage device 17 to a charge voltage and a charge current suitable for the secondary battery 85. The charging control means 80 includes a DC-DC converter and a current control circuit having a DC chopper circuit (DC chopper circuit using a step-up chopper circuit and a step-down chopper circuit in combination). The charge control means 80 has a function of chopper-controlling (switching control) pure DC power supplied from the second power storage device 17 and charging the secondary battery 85 with an optimum charging voltage. Regarding the charging of the lithium ion battery, a high control accuracy is particularly required with respect to the charging voltage. Therefore, the charging control means 80 performs a high-accuracy charging control considering this. The charging circuit in the charging control means 80 is not limited to the DC chopper circuit, and may have a circuit configuration using other methods.

  Since the DC-DC converter of the charge control means 80 has a DC chopper circuit that uses both a step-up chopper circuit and a step-down chopper circuit, the voltage of the second power storage device 17 gradually increases due to the discharging of the electric vehicle 50 when the electric vehicle 50 is charged. Even if the voltage drops, the secondary battery 85 can be charged with the optimum voltage by controlling the voltage of the pure DC power from the second power storage device 17 by the DC chopper circuit. Therefore, the change in the output voltage of the second power storage device 17 during the quick charging does not affect the charging of the secondary battery 85. Thus, a charging program for performing optimal charging control on the secondary battery 85 is input in advance to the charging control means 80.

  The electric vehicle 50 includes a charging history storage unit 80 a that stores a charging history of the secondary battery 85 by the charging control unit 80. The charging history storage unit 80a is connected to the charging control unit 80, and stores a charging result (charging voltage, charging current, charging time, etc. at the time of charging) for each charging of the secondary battery 85 by the charging control unit 80. It has become. The electric vehicle 50 can estimate the lifetime of the secondary battery 85 by grasping the number of times of charging through the charging history storage unit 80a. The data center 10 can receive information from the charging history storage means 80a mounted on the electric vehicle 50 via wireless or the like, and grasp the life of the secondary battery 85 based on this information. It has become. Thereby, the owner of the electric vehicle 50 can know from the information from the data center 10 that the replacement time of the secondary battery 85 is imminent.

  As shown in FIG. 3, a large number of signals are input and output to the charging control means 80. At the start of charging, a signal S12 from a voltage measurement sensor (not shown) provided on the third switch SW3 side is input to the charging control means 80. When the output voltage (open voltage) of the second power storage device 17 is within a predetermined range, the charge control means 80 outputs a signal S11 indicating that the electric vehicle 50 can be rapidly charged to the third switch SW3 side. The

  As shown in FIG. 3, the electric vehicle 50 includes a lock sensor 71, a driving start confirmation sensor 72, a parking brake sensor 73, a charge amount indicator 74, a charge end alarm 75, a current sensor 76, and a temperature sensor 77. Is provided. The lock sensor 71 has a function of confirming that the charging plug 30 is connected to the electric vehicle 50 side. Before the start of charging, a signal S17 from the lock sensor 71 is input to the charging control means 80. The driving activation confirmation sensor 72 has a function of confirming activation of the electric vehicle 50. Before the start of charging, the signal S13 from the operation start confirmation sensor 72 is input to the charging control means 80.

  The parking brake sensor 73 has a function of confirming that the parking brake is operating so that the electric vehicle 50 does not move during charging. Before the start of charging, the signal S14 from the parking brake sensor 73 is input to the charging control means 80. The charge amount indicator 74 has a function of displaying the remaining power amount of the secondary battery 85. During charging, the charge control means 80 outputs a signal S18 to the charge amount indicator 74. In the vicinity of the secondary battery 85, a temperature sensor 77 for detecting the temperature of the secondary battery 85 is provided. From the temperature sensor 77, a signal S15 corresponding to the measured temperature is input to the charge control means 80.

  The charge end alarm 75 has a function of notifying the driver 88 that the secondary battery 85 has reached full charge. At the time of charging, the charging current flowing to the secondary battery 85 is measured by the current sensor 76, and based on the signal S16 from the current sensor 76, the charging control means 80 determines whether or not the secondary battery 85 has reached full charge. . When it is determined that the secondary battery 85 has reached full charge, the charge control means 80 outputs a signal S19 to the charge end alarm 75. The charging end alarm 75 has a function of notifying the mobile phone 89 owned by the driver 88 that charging has ended by radio. If an abnormality is confirmed in the charging function of the electric vehicle 50 during charging, a signal S20 is output from the charging control means 80 to the opening / closing means SW3, and charging of the electric vehicle 50 is stopped.

  Next, the control procedure and operation of the DC power supply system in the first embodiment will be described.

  In the direct current power supply system, when the commercial power 11 is momentarily reduced or momentarily interrupted, power is supplied from the first power storage device 16 to the server 14 and the lighting device 15. In other words, since the first power storage device 16 is always connected to the server 14 and the lighting device 15, there is no need to switch circuits, and power is instantaneously transferred from the first power storage device 16 to the server 14 and the lighting device 15. Can be supplied. Here, since the first power storage device 16 is composed of an electric double layer capacitor, the charge / discharge reaction speed is very fast, and it reacts instantaneously to an instantaneous voltage drop or power failure. The server 14 that is the heart of the communication device can be backed up reliably.

  FIG. 4 shows an operation procedure of control in the circuit switching means 20. In step 101 of FIG. 4, whether or not the commercial power 11 is supplied to the power converter 13 is monitored by the power failure detection means 21. In step 102, it is determined based on information from the power failure detection means 21 whether or not a power failure has occurred (whether or not instantaneous interruption continues). In this state, as shown in step 103, the supply of power from the first power storage device 16 to the server 14 and the lighting device 15 is continued. If it is determined in step 102 that a power failure has occurred, the power failure signal S5 from the power failure detection means 21 is input to the circuit switching means 20. As a result, a circuit switching command is issued by the circuit switching means 20, and in step 104, the circuit switching means 20 outputs an off command signal S4 to the second switch SW2, and the second switch SW2 is turned off. Next, the process proceeds to step 105, where the ON command signal S1 is output from the circuit switching means 20 to the first switch SW1, and the first switch SW1 is turned ON.

  Thus, when a power failure occurs, the first switch SW1 is preferentially turned on and the second switch SW2 is turned off. Therefore, in step 106, the direct current stored in the second power storage device 17 is stored. Electric power is supplied to the server 14 and the lighting device 15. Here, the first power storage device 16 has a power storage capacity for supplying power to the server 14 and the lighting device 15 even after power supply from at least the second power storage device 17 is started. The server 14 that is the heart of the information communication apparatus can be backed up reliably. The second power storage device 17 has a significantly larger power storage capacity than the first power storage device 16 and is composed of a secondary battery such as a lithium ion battery having a high energy density. Therefore, it is possible to continue supplying DC power to the server 14 and to back up the server 14 and the lighting device 15 for a long time.

  Here, the output voltage of the second power storage device 17 gradually decreases by supplying DC power to the server 14 and the lighting device 15, but the server 14 includes DC-DC converters 14a and 14c. And since the illuminating device 15 has the DC-DC converter 15a, the fall of the output voltage of the 2nd electrical storage apparatus 17 does not become a problem. That is, since the DC-DC converter 14a has a function of converting the DC power from the second power storage device 17 into a voltage suitable for the CPU 14b, the decrease in the output voltage of the second power storage device 17 is caused by the CPU 14b. Does not affect operation. Similarly, the DC-DC converter 14c converts the voltage to a voltage suitable for the HDD 14d, and the DC-DC converter 15a converts the voltage to a voltage suitable for the LED 15b. Therefore, the decrease in the output voltage of the second power storage device 17 is affected by the HDD 14d. And does not affect the operation of the LED 15b.

  In step 107, it is determined whether or not the power failure has ended. Here, when it is determined that the power failure has not ended, the process returns to step 106 and the supply of DC power from the second power storage device 17 to the server 14 and the lighting device 15 is continued. If it is determined in step 107 that the power failure has ended, the process proceeds to step 108, where the second switch SW2 is maintained off, and the process proceeds to step 109, where the first switch SW1 is maintained on. Thereby, in step 110, charging of the second power storage device 17 is continued by supplying DC power from the power conversion device 13. In addition, when the power failure ends, the server 14 and the lighting device 15 operate by supplying DC power from the power conversion device 13.

  Next, when it is determined in step 102 that a power failure has not occurred, the process proceeds to step 111 to determine whether or not the electric vehicle 50 that is the second DC load needs to be quickly charged. Here, if it is determined that the rapid charging of the electric vehicle 50 is not necessary, the process proceeds to step 108 and step 109, and the second power storage device 17 is supplied with the DC power from the power conversion device 13 in step 110. Charging continues.

  If it is determined in step 111 that the electric vehicle 50 needs to be quickly charged, the process proceeds to step 112 where the opening / closing means SW3 of the charging stand 26 is turned on as shown in FIG. 2, and charging from the opening / closing means SW3 is performed. The request signal S7 is input to the circuit switching means 20. As a result, in step 113, the circuit switching means 20 outputs an off command signal S2 to the first switch SW1, and the first switch SW1 is turned off. Next, proceeding to step 1114, based on the charge request signal S7, an on command signal S3 is output from the circuit switching means 20 to the second switch SW2, and the second switch SW2 is turned on. In step 115, the DC power stored in the second power storage device 17 is supplied to the electric vehicle 50, which is the second DC load, and the electric vehicle 50 is started to be quickly charged.

  The second power storage device has a remarkably large power storage capacity than the first power storage device, and is composed of a secondary battery such as a lithium ion battery having a high energy density. The electric vehicle 50 can be discharged in a very short time. Here, the second power storage device 17 supplies DC power to the electric vehicle 50, so that the output voltage gradually decreases. However, the charging control means 80 of the electric vehicle 50 includes a DC-DC converter. Therefore, the change in the output voltage of the second power storage device 17 does not affect the charging control of the secondary battery 85 mounted on the electric vehicle 50.

  Further, since the electric power supplied from the second power storage device 17 to the electric vehicle 50 is pure DC power, supplying high-quality electric power called pure DC power to the electric vehicle 50 is supplied with high-quality electric power. Therefore, the electric control circuit of the electric vehicle 50 can be designed. Therefore, in the rapid charging of the electric vehicle 50 by the electric power from the second power storage device 17, it is necessary to consider almost ripple, noise, and surge for the DC power supplied from the second power storage device 17 to the electric vehicle 50. Therefore, the design of the electric control circuit of the electric vehicle 50 can be facilitated, and the reliability of the electric control function of the electric vehicle 50 can be improved.

  When charging of the electric vehicle 50 is completed, the routine proceeds to step 116, where the opening / closing means SW3 is turned off. Thereafter, the process proceeds to step 108, where the second switch SW2 is turned off, and in step 109, the first switch SW1 is turned on. Thereby, the second power storage device 17 is charged by the power supply from the power conversion device 13.

  The circuit switching means 20 has a function of turning on the first switch SW1 and turning off the second switch SW2 only in the nighttime period (for example, the time from 22:00 on the previous day to 7:00 on the next day), and the second power storage device 17 When the remaining power storage amount becomes equal to or less than a predetermined value, the second switch SW2 is turned off. FIG. 5 shows a control procedure of the first switch SW1 and the second switch SW2 in the circuit switching means 20. As shown in FIG. 5, in step 181, the circuit switching means 20 determines whether or not it is a nighttime zone based on its own timer function. Here, when it is determined that it is the nighttime zone, the process proceeds to step 182, and power is supplied from the power conversion device 13 to the second power storage device 17. That is, the second power storage device 17 is charged by supplying power from the power conversion device 13 only in the nighttime.

  If it is determined in step 181 that it is not a nighttime zone, the process proceeds to step 183, and based on the remaining capacity signal S6 from the capacity calculating means 22, it is determined whether or not the remaining capacity of the second power storage device 17 is equal to or less than a predetermined value. To be judged. If it is determined that the remaining capacity of the second power storage device 17 is sufficient, the process proceeds to step 184, where the first switch SW1 is turned off and the power supply to the second power storage device 17 is stopped. If it is determined in step 183 that the remaining capacity of the second power storage device 17 is equal to or less than a predetermined value based on the calculation signal S6 from the capacity calculation means 22, the process proceeds to step 182 to turn on the first switch SW1. Power is supplied to the second power storage device 17.

  In this way, by using the circuit switching means 20 to turn on and off the first switch SW1 and the second switch SW2 according to the time zone, inexpensive nighttime electricity stored in the second power storage device 17 is used. The electric vehicle 50 can be rapidly charged. In addition, the circuit switching means 20 turns off the second switch Sw2 when the remaining power storage amount of the second power storage device 17 becomes a predetermined value or less, so that the second power storage device 17 has a power failure. The minimum amount of power provided can be stored.

  As described above, in the first embodiment, for a momentary voltage drop or power outage, the first power storage device 16 that is always connected to the server 14 or the lighting device 15 that is the first DC load. Power supply is possible, and power supply from the second power storage device 17 to the server 14 and the lighting device 15 is possible for a relatively long power failure, so that the reliability of the system against the occurrence of a power failure can be maintained high. In addition, the operation rate of the second power storage device 17 other than during a power failure can be significantly increased. As a result, the DC power stored for backup can be effectively used, and the capital investment can be easily recovered even if a large amount of capital investment is made in the power storage device.

  In addition, since the first power storage device 16 is composed of an electric double layer capacitor, there is almost no deterioration due to charge and discharge, and high performance can be maintained over a long period of time, so that the running cost can be reduced. As in the first embodiment, in the data center 10 that employs a DC power supply system, power loss can be greatly reduced by reducing the number of power conversions compared to the conventional AC power supply system, so that energy saving can be achieved. .

  When power is supplied to the electric vehicle 50 that is the second DC load, the first switch SW1 is turned off, so that the server 14 that is the first DC load is electrically disconnected from the electric vehicle 50. Further, it is possible to prevent the noise or the like generated in the electric vehicle 50 from entering the first DC load side. That is, even if the first DC load is an important information communication facility such as the server 14, noise generated from the second DC load side such as the electric vehicle 50 is cut off by the first switch SW1 that is turned off. Therefore, noise generated on the electric vehicle 50 side does not adversely affect the server 14 which is the heart of information communication. Moreover, since the capacity of the second power storage device 17 has a very large capacity compared to the capacity of the secondary battery 85 of the electric vehicle 50, for example, the second power storage device 17 is an equivalent circuit of the storage battery. It has a very large capacitance (capacitance). Thereby, for example, noise generated from the charging control means 80 of the electric vehicle 50 can be sufficiently absorbed by the very large capacitance of the second power storage device 17.

  Further, in the DC power supply system, the DC load has a DC-DC converter that converts the voltage to an appropriate voltage according to the load, so that power is supplied to various DC loads with one power converter 13. Can do. Therefore, in the case of the electric vehicle 50 as well, since a DC-DC converter corresponding to the mounted secondary battery 85 is incorporated in the charging control means 80, various types of electricity having different charging voltages depending on the second power storage device 17 are used. The vehicle 50 can be quickly charged. As described above, the electric vehicle 50 includes a DC-DC converter that can convert the supplied power into a voltage suitable for charging the secondary battery 85, so that direct current power can be supplied. Regardless, rapid charging is possible anywhere in the world, and standardization of charging power can be achieved. Then, by incorporating the electric vehicle 50 into the charging control means 80 corresponding to the charging of the secondary battery 85, the electric vehicle 50 is incorporated into the other electric vehicle 50 (charging control means 80 using the electric power from one electric vehicle 50. Fast charging to other mobile electric bodies (including other electric mobile bodies) is also possible, and flexibility can be provided for quick charging of mobile bodies.

(Embodiment 2)
FIG. 6 shows a second embodiment of the present invention. The difference between the second embodiment and the first embodiment is that a fuel cell 33 is adopted instead of the emergency generator 25, and the configuration of the other parts is the same as that of the first embodiment. The description of the equivalent parts is omitted by attaching the same reference numerals to. The description of the conforming part is the same in other embodiments described later.

  A fuel cell 33 and an inverter 34 are arranged outside the data center 10. The fuel cell 33 uses hydrogen obtained by reforming fossil fuel as a fuel, and has a function of outputting DC power. The fuel cell 33 includes a thermoelectric generator 33a that can generate electricity using heat generated during operation, and improves power generation efficiency. The output side of the fuel cell 33 can be connected to the power conversion device 13 or the inverter 34 via the fourth switch SW4. The output voltage of the fuel cell 33 is set to 380 V, which is the same as the output voltage of the power converter 13. The fuel cell 33 is connected to the inverter 34 via the fourth switch SW4 except during a power failure of the commercial power 11. The inverter 34 has a function of converting DC power from the fuel cell 33 into AC power and supplying the AC power to the commercial power system. The generator 25 in FIG. 1 operates only at the time of a power failure and remains stopped daily, but the fuel cell 33 always operates regardless of day and night, and supplies power to the commercial power system.

  In the second embodiment configured as described above, when the supply of the commercial power 11 is stopped, the power failure signal S5 from the power failure detection means 21 is input to the circuit switching means 20. As a result, an off command signal S4 is output from the circuit switching means 20 to the second switch SW2, and the second switch SW2 is turned off. Next, based on the power failure signal S5 from the power failure detection means 21, the on-command signal S1 is output from the circuit switching means 20 to the first switch SW1, and the first switch SW1 is turned on. As a result, the DC power stored in the second power storage device 17 is supplied to the server 14 and the lighting device 15 that are the first DC load.

  When the power supply from the second power storage device 17 to the server 14 and the lighting device 15 as the first DC load is continued, the remaining capacity of the second power storage device 17 gradually decreases. When the remaining capacity of the second power storage device 17 falls below a predetermined value, the circuit switching means 20 sends the capacity reduction signal S8 to the fourth switch SW4 based on the remaining capacity signal S6 from the capacity calculating means 22. Output. As a result, the fourth switch SW4 is switched, and the power from the fuel cell 33 is supplied to the server 14 and the lighting device 15 that are the first DC load. Therefore, the server 14 and the lighting device 15 are backed up by the power supply from the fuel cell 33, and backup for a long time is possible.

Further, since it is possible to supply power from the fuel cell 33 to the commercial power system through the inverter 34 except during a power failure, the operating rate of the fuel cell 33 can be increased and the earth can be reduced by reducing CO _2. It can contribute to the prevention of global warming.

(Embodiment 3)
FIG. 7 shows Embodiment 3 of the present invention. In the third embodiment, a smart meter 31 is attached to the data center 10, and power control of the DC load in the data center 10 is performed by the smart meter 31. Here, the smart meter 31 is an electronic control device having a plurality of functions such as a communication function, a power consumption control function, and a power measurement function, and is used as a necessary element for enabling demand control. Is. For example, when the power consumption of the data center 10 exceeds a predetermined value, the smart meter 31 has a function of controlling power consumption of devices with lower priority in operation. In addition, the smart meter 31 supplies the power E from the second power storage device 17 converted into alternating current by the power conversion device (inverter) 32 to the power transmission system of the power company (reverse power flow) according to a command from the power company. It has a function to do. As described above, by using the smart meter 31, it is possible to efficiently operate electronic devices and air conditioners in the data center 10, and to significantly reduce CO ₂ emission from the data center 10. it can.

In the data center 10, a stable power supply control device 35 for stabilizing the amount of power in a specific area is provided. The stable power supply control device 35 monitors the amount of power used by a factory or household in a specific area based on a signal ES1 from a smart meter (not shown) provided in the factory or general house. The stable power supply control device 35 has a function of outputting a signal ES2 for controlling the amount of power used toward a smart meter in a factory or a general house in order to balance supply and demand and supply of power in a specific area. . As described above, even in factories and ordinary houses, by using smart meters, it is possible to efficiently operate various electric devices and air conditioning devices, and CO ₂ emissions can be greatly reduced.

(Embodiment 4)
FIG. 8 shows a fourth embodiment of the present invention, and shows a charging method of the electric vehicles 50 and 51 using the second power storage device 17. In the first to third embodiments, the electric vehicle 50 has the charge control means 80 that can rapidly charge the secondary battery 85 with the optimum voltage and current. However, in the fourth embodiment, the charge control is performed. The electric vehicle 51 not equipped with the means 80 can be rapidly charged.

  As shown in FIG. 8, the electric vehicle 51 is equipped with a secondary battery 85 </ b> B for supplying power to the travel motor 87. In the charging stand 26, charging control means 48 for rapidly charging the secondary battery 85B is provided. The charging control means 48 has a function capable of rapid charging based on the type of the secondary battery 85B, and is charged with the charging voltage and charging current optimum for the secondary battery 85B by the command signal K2 from the electric vehicle 51. It has a function of rapidly charging the battery 85B. For example, when the type of the electric vehicle 51 is different, the charging control unit 48 determines the vehicle type based on the command signal K2, and performs optimal charging control for quick charging of the secondary battery 85B mounted on the electric vehicle 51. It is like that.

  The charging stand 26 charging cable 29 can be used for quick charging of the electric vehicle 50 and the electric vehicle 51. When the charging cable 29 is connected to the electric vehicle 50, the third switch SW3 of the control unit 26a is turned on based on the command signal K1 from the electric vehicle 50, and the charging control means 48 of the charging stand 26 stops its function. To do. That is, the charging control means 48 operates only when charging the electric vehicle 51 that does not include the charging control means 80.

(Embodiment 5)
FIG. 9 shows a fifth embodiment of the present invention. In the first and second embodiments, the example applied to the data center 10 has been described. However, the fifth embodiment shows a case where the present invention is applied to a house.

  In the fifth embodiment, the power conversion device 13 has a function of converting, for example, input AC power with a voltage of 100 V or 200 V into DC power with a voltage of 380 V. On the output side of the power conversion device 13, a server 41 as a first DC load, a lighting device 42, and a digital television 43 are connected. The server 41 is one of information communication apparatuses that constitute a home communication base station called a femtocell, and here means a high-performance and high-reliability computer for home use. The server 14 includes two DC-DC converters 41a and 41c, a CPU (central processing unit) 41b, and an HHD (hybrid hard disk) 41d. The DC-DC converter 41a has a function of controlling the DC power from the power conversion device 13 to a voltage suitable for the CPU 14b. The DC-DC converter 41c has a function of controlling the direct-current power from the power converter 13 to a voltage suitable for the HHD 41d.

Further, an illumination device 42 and a digital television 43 as a first DC load are connected to the output side of the power conversion device 13. The lighting device 42 includes a DC-DC converter 42a and an LED 42b. The DC-DC converter 42a has a function of controlling the DC power from the power converter 13 to a voltage suitable for the LED 42b. The LED 42 b is a semiconductor element that emits light by direct current power, and is used as indoor lighting of the house 40.
The digital television 43 includes a DC-DC converter 43a and an FPD (flat panel display) 43b. The DC-DC converter 43a has a function of controlling the direct-current power from the power converter 13 to a voltage suitable for the FPD 43b.

  A solar battery 46 is attached to the roof 40 a of the house 40. The solar cell 46 is always connected to the output side of the power converter 13. The voltage of the DC power output from the solar cell 46 is set to 380 V, which is the same as the output voltage of the power converter 13. In the house 40, a high output electric heater 45 as a second DC load is installed. The high output electric heater 45 is connected to the output side of the second switch SW2 via the fifth switch SW5. The high-power electric heater 45 outputs a large amount of heat energy in a very short time, and is used as, for example, a cooking electric heater, a water heater, or a heating device. The high output electric heater 45 uses only Joule heat, and has an advantage of not emitting electromagnetic waves unlike an electromagnetic cooker using induction heating.

  In the fifth embodiment configured as described above, when the high-power electric heater 45 is used, the use signal S9 is output to the circuit switching unit 20 by turning on the fifth switch SW5. As a result, an off command signal S2 is output from the circuit switching means 20 to the first switch SW1, and the first switch SW1 is turned off. Next, an on command signal S3 is output from the circuit switching means 20 to the second switch SW2 based on the use signal S9, and the second switch SW2 is turned on. As a result, the DC power stored in the second power storage device 17 is supplied to the high-output electric heater 45 that is the second DC load. Therefore, the high-power electric heater 45 becomes a high temperature in a very short time, and cooking with high heating power is possible.

In the fifth embodiment, in addition to the rapid charging of the electric vehicle 50 described above, the high-power electric heater 45 can also be used using the electric power stored in the second power storage device 17, and the second power storage device 17. The utility value of can be increased. Moreover, since the DC power from the solar battery 46 can be supplied to the first power storage device 16, the second power storage device 17, the server 41, the lighting device 42, and the digital television 43, the power from the renewable energy is always used. And can contribute to the prevention of global warming by reducing CO ₂ .

(Embodiment 6)
FIG. 10 shows a sixth embodiment of the present invention. The sixth embodiment shows a case where a smart meter 31 and a HEMS (Home Energy Management System) 55 are applied to a general household. HEMS55 comprehensively grasps the situation of power supply and demand of the entire house in a solar cell 46, fuel cell 47, and a house equipped with a power storage function, and efficiently operates home appliances. Realizes energy saving. The HEMS 55 has a function of monitoring and displaying the usage state of the home appliance in the house 40 and a function of remotely operating the home appliance. The HEMS 55 has a function of controlling not only a direct current load but also an alternating current load 49 in the house 40 that operates on the commercial power supply 11.

On the outside of the house 40, a charging control means 48 connected to the second power storage device 17 is provided. As described with reference to FIG. 8, the charging control unit 48 is configured by a DC-DC converter, and can charge the electric vehicle 51 that does not include the charging control unit 80. The charging control means 48 is connected in parallel with the third switch SW3 for rapidly charging the electric vehicle 50. Thereby, in the house 40, two types of quick charging with different charging methods are possible. The output power from the charging control means 48 can be supplied to other DC loads via, for example, a DC power system. In the sixth embodiment configured as described above, it becomes possible to efficiently operate home appliances and the like by the HEMS 55, and CO ₂ emissions can be greatly reduced.

  As described above, the first to sixth embodiments of the present invention have been described in detail. However, the specific configuration is not limited to these embodiments, and there are design changes and the like within a range not departing from the gist of the present invention. However, it is included in this invention. For example, the DC power supply system of the present invention has been described as being applied to the data center 10 or the house 40. However, the DC power supply system is also applicable to a building using a large amount of power such as a large three-dimensional parking lot or a large refrigerated warehouse that can charge an electric vehicle. Is possible. When a large refrigerated warehouse is laid near a harbor, it is possible to quickly charge a ship using a large storage battery of the large refrigerated warehouse.

  The first DC load may be a device other than the servers 14 and 41 constituting the information communication device, and the information communication device may be wired communication or wireless communication. Furthermore, the second DC load is not limited to an electric vehicle such as the electric vehicle 50 that requires a large amount of power in a short time, and includes a cooking electric heater, a water heater, a nursing robot, and the like. In the above-described first to third embodiments, the output voltage of the DC power output from the power conversion device 13 is 380 V, but is not limited to this voltage value. For example, in the case of the data center 10, 360 V or It may be set to 400V, or in the case of a general house 40, for example, 48V. Even in the general house 40, when using an electrical device or the like that can ensure sufficient safety against a high voltage, a high voltage of 360 to 400V can be used.

  As the second power storage device 17 used in the house 40 of FIGS. 9 and 10, the second power storage device 17 mounted on the electric vehicles 50 and 51 can be reused. That is, since the secondary batteries 85 and 85B used in the electric vehicles 50 and 51 are normally replaced with a capacity remaining, the used batteries can be used for a long time in applications other than automobiles. Therefore, by reusing the secondary batteries 85 and 85B mounted on the electric vehicles 50 and 51 as the power storage device of the house 40, the investment cost of the DC power supply system in the house 40 can be reduced.

10 Data center 11 Commercial power (AC power)
13 Power Converter 14 Server (First DC Load)
15 Lighting device (first DC load)
Reference Signs List 16 First power storage device 17 Second power storage device 20 Circuit switching means 21 Power failure detection means 22 Capacity calculation means 33 Fuel cell 34 Inverter 40 Housing 43 Digital television (first DC load)
45 High-power electric heater (second DC load)
46 Solar cell 50 Electric vehicle (second DC load)
SW1 first switch SW2 second switch

Claims (8)

AC power that is charged by a power conversion device that converts AC power into DC power and that is always connected in parallel to a first DC load to which DC power from the power conversion device is supplied and supplied to the power conversion device A first power storage device capable of supplying a minimum DC power for backup to the first DC load when the voltage drops momentarily or stops instantaneously;
Charged by the power conversion device and connectable in parallel to the first power storage device and the first DC load, and supplies the stored DC power from the power conversion device to the second DC load A second power storage device capable of being larger in capacity than the first power storage device;
A first switch provided in a circuit connecting the power conversion device and the second power storage device;
A second switch provided in a circuit connecting the second power storage device and the second DC load;
A power failure detection means for detecting a supply stop of the AC power to the power converter;
When supplying the DC power stored in the second power storage device to the second DC load, the first switch is turned off and the second switch is turned on. Circuit switching means for preferentially turning on the first switch and turning off the second switch when detecting the supply stop of the AC power to the power converter;
A direct current power supply system comprising:   The DC power feeding system according to claim 1, wherein the first power storage device includes a capacitor.   The DC power supply system according to claim 1 or 2, wherein the second power storage device is configured by a secondary battery.   The DC power feeding system according to any one of claims 1 to 3, wherein the power converter is configured by an AC-DC converter using at least a SiC semiconductor element.   5. The DC power supply system according to claim 1, wherein the first DC load is configured by an information communication device. 6.   The second DC load is an electric mobile body having a quick charging function for performing quick charging using pure DC power supplied from the second power storage device. The DC power supply system according to any one of the above.   The circuit switching means has a function of turning on the first switch and turning off the second switch only during a specific time period, and a case where a remaining power storage amount of the second power storage device becomes a predetermined value or less. 7 has a function of turning off the second switch. 7. The DC power feeding system according to claim 1, wherein the second switch is turned off.   The DC power from a solar cell or DC power from a fuel cell can be supplied to the first power storage device, the second power storage device, and the first DC load. The DC power supply system according to any one of 1 to 7.

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