Network connection system, connection control device and network connection method

Abstract

Network connection system (100) for an electricity network, characterized in that it has: a storage battery (11); a current conversion device that converts current from the storage battery (11) into alternating current; and a connection control device (36) that supplies power from a mains power supply to a consumer and supplies power from the power conversion device to the consumer when the mains power supply fails, wherein, when the mains power supply is restored, the current conversion device (21) synchronizes a voltage phase of current supplied by the current conversion device (21) to the consumer with a voltage phase of current from the mains power supply, the current conversion device (21) matches a frequency of current supplied by the current conversion device (21) to a frequency of current from the mains power supply, and After matching the frequencies of the currents, the current conversion device (21) aligns a zero crossing point of the current supplied by the current conversion device (21) to the consumer with a zero crossing point of the current from the mains power supply. and after the voltage phase of the current supplied from the current conversion device (21) to the consumer is synchronized with the voltage phase of the current from the mains power supply, the connection control device (36) starts the supply of current from the mains power supply to the consumer, and the connection control device (36) stops the supply of current from the current conversion device to the consumer after the supply of current from the mains power supply to the consumer has been started.

Description

AREA

[0001] The present invention relates to a network connection system, a connection control device and a network connection method for supplying power from a storage battery in the event of a power failure and for resuming the supply of power from a mains power supply at the time of power restoration. BACKGROUND

[0002] The transition from gasoline-powered or hybrid vehicles to electrically powered vehicles such as plug-in hybrid electric vehicles (PHEVs) or electric vehicles (EVs) is progressing in the market. Japanese patent publication JP 2018-61432A discloses a vehicle-to-home (V2H) device that connects such an electrically powered vehicle to an electrical device used in a house, allowing a storage battery in the electric vehicle to be used as an emergency power supply in an emergency such as a natural disaster.

[0003] However, a power distribution service from the storage battery to the power grid is not limited to V2H and extends from general households to V2X, which is a general term for Vehicle-to-Building (V2B), Vehicle-to-Grid (V2G), etc., and refers to a service for larger end users or power grids. DEPICTION

[0004] A grid connection system supplies power from a storage battery to a consumer when the grid power supply fails. When the grid power supply is restored, the grid connection system also resumes supplying power from the grid to the consumer. In a conventional grid connection system, when the grid power supply is restored, the supply of power from the storage battery to the consumer is stopped, and then the supply of power from the grid to the consumer is started. Therefore, a problem arises in that the supply of power to the consumer is interrupted.

[0005] The present disclosure was made in light of such circumstances, and it is a task to specify a network connection system, a connection control device, and a network connection method that can prevent the supply of electricity from being interrupted at the time of power restoration.

[0006] A grid connection system for a power grid according to one aspect of the present disclosure is characterized in that it comprises: a storage battery; a current conversion device which converts current from the storage battery into alternating current; and a connection control device which supplies current from a grid power supply to a consumer and supplies current from the current conversion device to the consumer when the grid power supply fails, wherein, when the grid power supply is restored, the current conversion device synchronizes a voltage phase of current supplied from the current conversion device to the consumer with a voltage phase of current from the grid power supply, and the current conversion device synchronizes a frequency of the current supplied from the current conversion device to the consumer with a frequency of the current from the grid power supply.and after matching the frequencies of the currents, the current conversion device aligns a zero-crossing point of the current supplied from the current conversion device to the consumer with a zero-crossing point of the current from the mains power supply, and after the voltage phase of the current supplied from the current conversion device to the consumer is synchronized with the voltage phase of the current from the mains power supply, the connection control device starts the supply of current from the mains power supply to the consumer, and the connection control device stops the supply of current from the current conversion device to the consumer after the supply of current from the mains power supply to the consumer has been started.

[0007] In the network connection system according to one aspect of the present disclosure, it is characterized in that the current conversion device determines whether a voltage and a frequency of the current from the mains power supply are within a predetermined range or not; if the voltage and the frequency are within the predetermined range, the current conversion device synchronizes the voltage phase of the current supplied by the current conversion device to the consumer with the voltage phase of the current from the mains power supply; and if the voltage or the frequency is not within the predetermined range, the current conversion device waits for a phase synchronization process and continues to supply current to the consumer.

[0008] A network connection system for an electricity network according to one aspect of the present disclosure is characterized by having the following features: a storage battery; a current conversion device that converts current from the storage battery into alternating current; and a connection control device that supplies power from a mains power supply to a consumer and supplies power from the power conversion device to the consumer when the mains power supply fails, wherein, when the mains power supply is restored, the current conversion device determines whether the voltage and frequency of the current from the mains power supply are within a predetermined range or not; if the voltage and frequency are within the predetermined range, the current conversion device synchronizes the voltage phase of the current supplied by the current conversion device to the load with the voltage phase of the current from the mains power supply; and if the voltage or frequency is not within the predetermined range, the current conversion device waits for a phase synchronization process and continues to supply current to the load until the voltage and frequency fall within the predetermined range, and after the voltage phase of the current supplied by the current conversion device to the load,The connection control device starts the supply of current from the mains power supply to the consumer when the voltage phase of the current from the mains power supply is synchronized with the current phase of the mains power supply, and the connection control device stops the supply of current from the current conversion device to the consumer after the supply of current from the mains power supply to the consumer has been started.

[0009] The grid connection system according to one aspect of the present disclosure is characterized in that it further comprises: a charging and discharging station for an electrically powered vehicle. If the grid power supply fails, the connection control device supplies current from the power conversion device and the charging and discharging station to the consumer.

[0010] In one aspect of the present disclosure, the network connection system further includes a charging and discharging station for an electric vehicle. In the event of a power failure, the connection control device supplies power from the power conversion device and the charging and discharging station to the consumer. This makes it possible to use the electric vehicle as an emergency power supply.

[0011] The network connection system according to one aspect of the present disclosure is characterized in that, when the network power supply fails, the connection control device supplies current from the current conversion device to a specific consumer, and when the network power supply is restored, the connection control device starts supplying current from the network power supply to the specific consumer.

[0012] In one aspect of the present disclosure, the grid connection system, in the event of a power outage, supplies power to the specific consumer and switches the power supply source for the specific consumer to the grid supply without interrupting the power supply at the time the power is restored. By primarily supplying power to a critical specific consumer, such as an emergency elevator, it is possible to minimize the power to be supplied in the event of a grid power outage and to extend the time during which power can be supplied.

[0013] In a connection control device according to one aspect of the present disclosure, which supplies current to a consumer of a current conversion device that converts energy from a storage battery into alternating current when a mains power supply fails, wherein the linking control device is operable in order to to initiate the power conversion device when the mains power supply is restored, to synchronize a voltage phase of current supplied by the current conversion device to the consumer with a voltage phase of current from the mains power supply by matching a frequency of the current supplied by the current conversion device to a frequency of the current from the mains power supply, and by, After matching the frequencies of the currents, a zero crossing point of the current supplied by the current conversion device to the consumer is aligned with a zero crossing point of the current from the mains power supply, starting the supply of current from the mains power supply to the consumer after the voltage phase of the current supplied by the current conversion device (21) to the consumer is synchronized with the voltage phase of the current from the mains power supply, and stopping the supply of current to the current conversion device after the supply of current from the mains power supply to the consumer has been started.

[0014] According to one aspect of the present invention, a connection control device is provided, wherein the current is supplied to a consumer of a current conversion device, which converts energy from a storage battery into alternating current when a mains power supply fails, wherein the connection control device is operable to to cause the current conversion device, when the mains power supply is restored, to determine whether the voltage and frequency of the current from the mains power supply are within a predetermined range or not, If the voltage and frequency are within the specified range, the current conversion device is to be synchronized with the voltage phase of the current supplied by the current conversion device to the consumer, and If the voltage or frequency is not within the specified range, the current conversion device is to be instructed to wait for a phase synchronization process and to continue supplying current to the load until the voltage and frequency fall within the specified range. Starting the supply of electricity from the mains power supply to the consumer after the voltage phase of the current supplied by the current conversion device to the consumer has been synchronized with the voltage phase of the current from the mains power supply, and Stopping the supply of power from the power conversion device after the supply of power from the mains power supply to the consumer has started.

[0015] A grid connection method for a power grid according to one aspect of the present disclosure is characterized in that it comprises: using a storage battery and a current conversion device for converting current from the storage battery into alternating current, supplying current from a grid power supply to a consumer; supplying current from the current conversion device to the consumer when the grid power supply fails;Causing the current conversion device to synchronize a voltage phase of current supplied by the current conversion device to the consumer with a voltage phase of current from the mains power supply when the mains power supply is restored, by matching a frequency of current supplied by the current conversion device to the consumer with a frequency of current from the mains power supply, and by matching, after matching between the frequencies of the currents, a zero crossing point of current supplied by the current conversion device to the consumer with a zero crossing point of current from the mains power supply; Starting the supply of electricity from the mains power supply to the consumer, after the voltage phase of the current supplied by the Power conversion device supplied to the consumer, synchronized with the voltage phase of current from the mains power supply; and stopping the supply of current from the power conversion device to the consumer after the supply of current from the mains power supply to the consumer has been started.

[0016] In one aspect of the present revelation it

[0017] A network connection method for an electricity network, characterized by the fact that it includes the following features: using a storage battery and a power conversion device to convert current from the storage battery into alternating current, supplying current from a mains power supply to a consumer; Supplying electricity from the power conversion device to the consumer when the mains power supply fails; to cause the current conversion device, when the mains power supply is restored, to determine whether the voltage and frequency of the current from the mains power supply are within a predetermined range or not, If the voltage and frequency are within the specified range, the current conversion device is to be synchronized with the voltage phase of the current supplied by the current conversion device to the consumer, and If the voltage or frequency is not within the specified range, the current conversion device is to be instructed to wait for a phase synchronization process and to continue supplying current to the load until the voltage and frequency fall within the specified range.

[0018] Starting the supply of electricity from the mains power supply to the consumer after the voltage phase of the current supplied by the current conversion device to the consumer is synchronized with the voltage phase of electricity from the mains power supply; and stopping the supply of electricity from the current conversion device to the consumer after the supply of electricity from the mains power supply to the consumer has been started.

[0019] The present disclosure exhibits excellent effects, such as being able to resume the supply of electricity from the grid power supply to the consumer without interrupting the supply of electricity to the consumer when the grid power supply is restored. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic view showing an example of the optical appearance of a network connection system according to a first embodiment; Fig. Figure 2 is a schematic representation illustrating an example of the circuit configuration of the network connection system according to the first embodiment; Fig. Figure 3 is a block diagram showing an example of a communication connection type of a connection cabinet, a storage battery PCS, and a charging and discharging station, and internal configuration examples of the storage battery PCS and the charging and discharging station according to the first embodiment; Fig. Figure 4 is a schematic representation showing a first example of a network connection through the network connection system according to the first embodiment, when a power network is normal; Fig. Figure 5 is a schematic representation showing a second example of a network connection through the network connection system according to the first embodiment, when a power grid is normal; Fig. Figure 6 is a schematic representation showing an example of independent operation in an emergency through the network connection system according to the first embodiment; Fig. Figure 7 is a flowchart showing an example of the process for starting independent operation by the network connection system according to the first embodiment in the event of a power failure; Fig. Figure 8 is a flowchart illustrating an example of the sequence of a process carried out by the network connection system according to the first embodiment at the time of power restoration; Fig. 9 is a flowchart illustrating an example of the sequence of a phase synchronization process performed by the storage battery PCS according to the first embodiment; Fig. 10 is a schematic representation illustrating an example of a grid connection at the time of power restoration by the grid connection system according to the first embodiment; Fig. Figure 11 is a schematic representation illustrating an example of the circuit configuration of a network connection system according to a second embodiment; Fig. Figure 12 is a block diagram illustrating an example of a communication connection type of a connection cabinet and a storage battery PCS according to the second embodiment and an example of the internal configuration of the storage battery PCS; Fig. Figure 13 is a schematic representation that provides an example of a network connection through the network connection system according to the second embodiment when a power grid is normal; Fig. 14 is a schematic representation showing an example of independent operation in an emergency through the network connection system according to the second embodiment; Fig. Figure 15 is a flowchart showing an example of the process for starting independent operation by the network connection system according to the second embodiment in the event of a power failure; Fig. Figure 16 is a flowchart showing an example of the sequence of a process carried out by the network connection system according to the second embodiment at the time of power restoration; Fig. 17 is a schematic representation showing an example of a grid connection at the time of power restoration by the grid connection system according to the second embodiment; Fig. Figure 18 is a schematic representation showing an example of the circuit configuration of a network connection system according to a third embodiment; Fig. Figure 19 is a schematic representation showing a first example of a network connection through the network connection system according to the third embodiment when a power grid is normal; Fig. Figure 20 is a schematic representation showing a second example of a network connection through the network connection system according to the third embodiment when a power grid is normal; Fig. Figure 21 is a schematic representation showing an example of independent operation in an emergency through the network connection system according to the third embodiment; Fig. Figure 22 is a flowchart showing an example of the process for initiating independent operation by the network connection system according to the third embodiment in the event of a power failure; and Fig. Figure 23 is a flowchart showing an example of the sequence of a process carried out by the network connection system according to the third embodiment at the time of power restoration. DETAILED DESCRIPTION

[0020] The present DISCLOSURE will below be described in more detail with reference to the illustrations that depict embodiments of the present invention. (First embodiment)

[0021] Fig. Figure 1 is a schematic view illustrating an example of the optical appearance of a network connection system 100 according to a first embodiment. In the example from Fig. In Figure 1, the grid connection system 100 is installed in a parking lot, which has parking spaces for five cars. The grid connection system 100 comprises charging and discharging stations 41, 42, 43, 44, and 45, which are installed in the parking space for electric vehicles (51, 52, 53, 54, and 55), and a grid connection unit, which is installed in the parking lot. The grid connection system 100 can be configured as a business continuity management (BCP) device. The grid connection unit includes a storage battery cabinet 10, which houses a storage battery; a power conversion cabinet 20, which houses a storage battery power conditioning system (PCS); and a connection cabinet 30, which houses a connection control device for grid connection to a power grid. The number of charging and discharging stations is not limited to five.The storage battery, the storage battery PCS, and the connection control device are in . Fig. Figure 1 is not illustrated. The storage battery PCS corresponds to a power conversion device.

[0022] The electrically powered vehicle is a plug-in hybrid electric vehicle (PHEV) or an electric vehicle (EV), which is also referred to as PHEV or EV in this description. The charging and discharging stations 41 to 45 can charge and discharge the battery (vehicle-integrated storage battery) mounted on the electrically powered vehicle. The storage battery PCS, housed in the power conversion cabinet 20, can convert current in both directions from alternating current (AC) to direct current (DC) and from DC to AC, thus enabling the charging and discharging of the storage battery housed in the storage battery cabinet 10. When the power grid is functioning normally, the connection control device, housed in the connection cabinet 30, performs a grid connection operation between the power grid, the storage battery PCS, and the charging and discharging stations 41 to 45.

[0023] The connection control device enables independent operation by the storage battery PCS and the charging and discharging stations 41 to 45 when the power grid is abnormal due to a natural disaster or similar event, such as a power outage. Even if all or some of the electric vehicles are not parked in the parking area, the grid connection unit can supply the required power to the grid consumer by supplying power from the storage battery to the consumer using the storage battery PCS. Consumers are various electrical devices. For example, a consumer is an electrical device located in a facility where a parking area is installed.

[0024] Fig. Figure 2 is a schematic representation illustrating an example of the circuit configuration of the network connection system 100 according to the first embodiment. A stationary storage battery 11, a control device (not illustrated), a cooling device, a heating device, and the like are housed in the storage battery cabinet 10. A storage battery PCS 21 and a cooling device (not illustrated) for heat dissipation from the storage battery PCS 21 are housed in the current transformation cabinet 20. The storage battery PCS 21 includes a control device (not illustrated), a cooling device, and the like. The connection cabinet 30 includes a connection control device 36, a remote I / O 31, a vacuum circuit breaker (VCB) 32 as an opening and closing unit, a transformer 33, an undervoltage relay (UVR) 34, a voltage transformer 35, and the like.

[0025] The junction box 30 has terminals 101 and 102, a disconnecting device 37, and switches 103, 104, and 111 to 115. Terminal 101 is located on the electrical line (high-voltage power supply line) on the high-voltage input side. This means that a power line from the secondary side of a step-down transformer 85 of the power grid and a power line from the primary side of a step-down transformer 86, which is connected to a general-purpose load, are connected to terminal 101. The step-down transformer 85 is connected to a mains power supply and transforms the voltage from the mains power supply to a lower level. Examples of general-purpose loads include electrical devices that have relatively little impact on others, even if the power is interrupted in the event of a natural disaster.

[0026] Terminal 102 is located on the high-voltage supply line of the electrical line. In other words, a power line from the primary side of a step-down transformer 87, which is connected to a critical load, is connected to terminal 102. A critical load is one that requires a continuous power supply even in the event of an anomaly such as a natural disaster. Examples of critical loads include an emergency elevator, an electrical device that must operate continuously, building lighting, or air conditioning equipment.

[0027] An electrode of the VCB 32, the UVR 34, and the voltage transformer 35 are connected to the terminal block 101 by the disconnecting device 37. The VCB 32 is a circuit breaker whose electrodes are contained in a high-vacuum chamber and which extinguishes an arc by diffusion of substances that form an arc discharge, which occurs between the electrodes when a current is interrupted, in a high vacuum.

[0028] The voltage transformer 35 measures the voltage and frequency of the current from the mains power supply and inputs the measured value to the UVR 34. The UVR 34 can detect an anomaly, such as a short circuit on the mains side or a power outage. If an anomaly is detected, the UVR 34 outputs a control signal to the VCB 32 to disconnect its electrical circuit.

[0029] Furthermore, a current monitoring unit 80 is provided for monitoring the current on the primary side of the step-down transformer 85 in a building for which power demand management is implemented using the grid connection system. The current monitoring unit 80 is not always strictly necessary. If the step-down transformer 85 is not installed, the location monitored by the current monitoring unit 80 is appropriately determined. The current monitoring unit 80 comprises an overvoltage grounding relay (OVGR) 81, a reverse current relay (RPR) / undercurrent relay (UPR) 82, and a current sensor 83. The OVGR 81 continuously detects ground faults in the power grid. The RPR / UPR 82 can detect an anomaly such as reverse current flow to the grid side or a short circuit.Even if an anomaly is detected by the OVGR 81 or the RPR / UPR 82, the electrical line of the VCB 32 is disconnected.

[0030] The remote input / output I / O 31 is an analog-to-digital converter (ADC) that converts the current (analog value) detected by the current sensor 83 into a digital value. The remote I / O 31 outputs the converted current (digital value) to the connection control device 36.

[0031] The transformer 33 (specifically a first winding 331) is separated from the other electrode of the VCB 32 by the electrical conductor. The transformer 33 has the first winding 331, a second winding 332 which is connected to the switch 103 by the electrical conductor, and a third winding 333 which is connected to the switches 111 to 115 by the electrical conductor.

[0032] In other words, transformer 33 can be a three-phase, three-winding transformer. The voltage and power (apparent power) on the side of the first winding 331 can be, for example, 6600 V and 50 kVA, respectively. The voltage and power on the side of the second winding 332 can be, for example, 300 V and 50 kVA, respectively. The voltage and power on the side of the third winding 333 can be, for example, 210 V and 50 kVA, respectively. The voltage and current are not limited to these values. Using transformer 33 as a three-winding transformer allows for space savings and weight reduction compared to using two transformers.

[0033] The storage battery PCS 21 is connected to the switch 103. The storage battery PCS 21 can convert current in both directions from AC to DC and from DC to AC, making it possible to charge and discharge the stationary storage battery 11.

[0034] The electrical line from one phase of these three phases of the third winding 333 is connected to the switch 104. For example, a voltage of 105 V to 210 V is supplied as a power supply for the control device and the cooling device contained in the storage battery PCS 21, and further as a power supply for the control device, the cooling device and the heating device in the storage battery cabinet 10.

[0035] Power lines from charging and discharging stations 41 to 45 are connected to switches 111 to 115. Charging and discharging stations 41 to 45 include converter circuits capable of converting power in both directions from AC to DC and from DC to AC, thus enabling the charging and discharging of the batteries installed in the electric vehicles 51 to 55.

[0036] Fig. Figure 3 is a block diagram illustrating a communication connection type between the connection cabinet 30, the storage battery PCS 21, and the charging and discharging station 41, as well as internal configuration examples of the storage battery PCS 21 and the charging and discharging station 41 according to the first embodiment. The connection cabinet 30 includes a communication unit 38, which communicates with the storage battery PCS 21 and the charging and discharging station 41. The communication unit 38 is connected to the connection control device 36 via a communication line. The communication unit 38 is also connected to the storage battery PCS 21 and the charging and discharging station 41 via a communication line. The connection control device 36 sends signals to the storage battery PCS 21 and the charging and discharging station 41 and receives signals from them via the communication unit 38.

[0037] The storage battery PCS 21 comprises a control unit 211, a current conversion unit 212, and a communication unit 213. The control unit 211 controls the operation of each unit of the storage battery PCS 21. The current conversion unit 212 performs AC-to-DC and DC-to-AC conversions. The communication unit 213 is connected to the communication unit 38 via a communication line. The storage battery PCS 21 sends signals to the connection control device 36 and receives signals from it via the communication unit 213. The connection cabinet 30 also includes a display unit 301. For example, the display unit 301 is a display. The display unit 301 shows information relating to the operations of the storage battery PCS 21 and the charging and discharging station 41, as well as information about the mains voltage and the like.

[0038] The charging and discharging station 41 comprises a control unit 411, a charging and discharging unit 412, a communication unit 413, and a notification unit 414. The control unit 411 controls the operation of each unit of the charging and discharging station 41. The charging and discharging unit 412 performs charging and discharging of the battery of the electric vehicle 51. The communication unit 413 is connected to the communication unit 38 via a communication line. The charging and discharging station 41 sends signals to the connection control device 36 and receives signals from it via the communication unit 413.

[0039] The notification unit 414 provides notification of information regarding the charging and discharging of the battery of the electric vehicle 51. The notification unit 414 can be, for example, a display panel or a warning light, or it can transmit information via radio communication to an end device used by a user, administrator, or the like. The charging and discharging information can include, for example, information on operating states such as charging or discharging in preparation, preparation complete, charging or discharging, and charging or discharging complete; the battery's state of charge (SOC); the time required for full charge; the time remaining until full charge; the amount of charge that can be discharged; and the charge for charging or discharging.Therefore, it is possible to obtain information regarding the charging and discharging of the electric vehicle in a timely manner.

[0040] The configurations of charging and discharging stations 42 to 45 are the same as those of charging and discharging station 41. Similar to charging and discharging station 41, each of the charging and discharging stations 42 to 45 is connected to the communication unit 38 via a communication line. Communication units 38, 213, and 413, and the communication units contained within charging and discharging stations 42 to 45, are gateways, for example.

[0041] Next, the network connection procedure in the network connection system 100 according to the first embodiment is described. Fig. Figure 4 is a schematic representation illustrating a first example of a network connection through the network connection system 100 according to the first embodiment when the power grid is normal. Fig. Figure 4 illustrates the flow of a portion of the current with arrows. When the power grid is normal and a charging mode is selected, the connection control device 36 supplies current from the grid power supply to the charging and discharging stations 41 to 45, and the electric vehicles 51 to 55 can be charged by the charging and discharging stations 41 to 45. Therefore, the grid connection system 100 can be used as a fast charging station for electric vehicles.

[0042] Although not shown, when the power grid is functioning normally, electricity is also supplied from the grid to the critical consumer. When the power grid is functioning normally, electricity is also supplied from the grid to the general consumer.

[0043] By dividing the electricity grid into two systems—a general consumer and a critical consumer—the amount of electricity required in the event of an anomaly, such as a natural disaster, can be minimized to ensure a continuous supply of electricity to the critical consumer, and the duration for which electricity can be supplied to the critical consumer can be extended. The critical consumer corresponds to a specific consumer.

[0044] Fig. Figure 5 is a schematic representation illustrating a second example of a network connection through the network connection system 100 according to the first embodiment when the power grid is normal. Fig. Figure 5 illustrates the flow of a portion of the current with arrows. When the power grid is normal and the current at the power pickup point at a predetermined location is equal to or greater than a threshold in a state where a power management mode is set—for example, when the current detected by the current sensor 83 is equal to or greater than a threshold—the interconnection control device 36 supplies current from the charging and discharging stations 41 to 45 to the critical load and the general load, so that the pickup point current becomes equal to or less than the threshold. Alternatively, the interconnection control device 36 causes the storage battery PCS 21 to supply current to the critical load and the general load. This enables peak current shedding.If the current at the power pickup point at the specified position is equal to or less than a threshold value, current from the power grid can be supplied to the charging and discharging stations 41 to 45 or the storage battery PCS 21 within a range without exceeding the threshold value.

[0045] Fig. Figure 6 is a schematic representation illustrating an example of independent operation in an emergency by the network connection system 100 according to the first embodiment. Fig. Figure 6 illustrates the current flow with arrows. If the power grid is abnormal, i.e., if the grid power supply fails, the connection control device 36 disconnects the electrical line of the VCB 32 to disconnect the grid power supply from the critical load. In this state, independent operation by the connection control device 36 is possible by supplying power from the charging and discharging stations 41 to 45 or the storage battery PCS 21. If the power grid is abnormal, the connection control device 36 can supply power to the critical load from at least either the charging and discharging stations 41 to 45 or the storage battery PCS 21.

[0046] Fig. Figure 7 is a flowchart illustrating an example of the process for initiating independent operation by the grid connection system 100 according to the first embodiment in the event of a power failure. This step is abbreviated as S below. The UVR 34 detects a power failure of the grid power supply based on a voltage from the grid power supply (S11). When the voltage from the grid power supply, measured by the voltage transformer 35, is applied and the input voltage drops below a predetermined voltage, the UVR 34 detects a power failure of the grid power supply and outputs a control signal to disconnect the electrical line to the VCB 32. In response to the control signal, the VCB 32 disconnects the electrical line, so that the grid connection system 100 disconnects the grid power supply and the general load from the critical load (S12).

[0047] Then, the connection control device 36 stops the storage battery PCS 21 (S13). At S13, the connection control device 36 issues a control signal to stop the storage battery PCS 21, and the storage battery PCS 21 stops in response to the control signal. Subsequently, the connection control device 36 stops the charging and discharging stations 41 to 45 (S14). At S14, the connection control device 36 issues a control signal to stop the charging and discharging stations 41 to 45, and the charging and discharging stations 41 to 45 stop in response to the control signal. If the mains power supply fails, the storage battery PCS 21 and the charging and discharging stations 41 to 45 may have stopped themselves due to a fault.Even if the storage battery PCS 21 or the charging and discharging stations 41 to 45 stop themselves, the connection control device 36 reliably outputs a control signal in S13 and S14 to stop the storage battery PCS 21 and the charging and discharging stations 41 to 45.

[0048] The connection control device 36 then operates the storage battery PCS 21 (S15). In S15, the connection control device 36 outputs a control signal to the storage battery PCS 21 to start operation in independent operating mode, and the storage battery PCS 21 starts operation in response to the control signal. The storage battery PCS 21 then operates independently. The connection control device 36 receives signals indicating the detection of a power failure by the UVR 34, the disconnection of the electrical line by the VCB 32, and the stopping of the storage battery PCS 21. After receiving all these signals, the connection control device 36 performs the processing from S15. Due to the storage battery PCS 21 starting to operate, power is supplied from the storage battery PCS 21 to the charging and discharging stations 41 to 45.

[0049] The connection control device 36 then operates the charging and discharging stations 41 to 45 (S16). In S16, the connection control device 36 outputs a control signal to start operation to the charging and discharging stations 41 to 45, and the charging and discharging stations 41 to 45 begin operation in response to the control signal. The network connection system 100 then terminates the process of starting independent operation.

[0050] Once the grid connection system 100 starts independent operation, power from the storage battery PCS 21 and the charging and discharging stations 41 to 45 is supplied to the important consumer, as shown in Fig. Figure 6 illustrates this. When the connection control device 36 operates independently, the storage battery PCS 21 performs voltage control by acting as a voltage source. The current required to obtain the necessary power or current is generated by connecting the charging and discharging stations 41 to 45 to the storage battery PCS 21, which, in turn, acts as a current source. Even if the required current cannot be supplied to the critical load from the charging and discharging stations 41 to 45 in the event of a power outage, current can be supplied to the critical load from the storage battery PCS 21. Therefore, the grid connection system 100 as a whole can supply the required current to the critical load in the power grid.

[0051] If the power grid is abnormal and the current from the charging and discharging stations 41 to 45 exceeds the capacity of the major consumer, the connection control device 36 more precisely directs excess current from the charging and discharging stations 41 to 45 to the storage battery PCS 21. Therefore, when the electric vehicle is parked in the parking space, the electric vehicle's power can be used effectively.

[0052] If the power grid is abnormal and the current that can be supplied by the charging and discharging stations 41 to 45 is less than the capacity of the critical load, the connection control device 36 supplies current to the critical load from both the charging and discharging stations 41 to 45 and the storage battery PCS 21. For example, if the capacity of the critical load is 50 kVA and the total power that can be supplied from the charging and discharging stations 41 to 45 is 30 kVA, then 20 kVA of power is supplied from the storage battery PCS 21, so that the remaining 50 kVA is supplied to the critical load from the high-voltage side of the transformer 33. If the capacity of the critical load changes, only the current or power suitable for the critical load's capacity can be supplied.If all or some of the required number of electrically powered vehicles are not parked in the parking lot, the missing or insufficient current or power can be supplied by the storage battery PCS 21, so that the required current or power can be supplied to the important consumer of the power grid.

[0053] When the mains power supply is restored from the power outage, the network connection system 100 resumes supplying power from the mains power supply to the critical consumer. Fig. Figure 8 is a flowchart illustrating an example of the process performed by the grid connection system 100 according to the first embodiment at the time of power restoration. The UVR 34 detects the power restoration of the grid power supply based on a voltage from the grid power supply (S21). When the voltage from the grid power supply, measured by the voltage transformer 35, is applied and the input voltage exceeds a predetermined voltage, the UVR 34 detects the power restoration and outputs a control signal to the connection control device 36 in response to the power restoration detection.In response to the control signal from the UVR 34, the interconnection control device 36 instructs the storage battery PCS 21 to start synchronizing the voltage phase of the current from the storage battery PCS 21 and the voltage phase of the current from the mains power supply (S22). For example, in S22, the interconnection control device 36 sends a control signal, which is used to issue an instruction to start phase synchronization, through the communication unit 38 to the storage battery PCS 21. In response to the control signal from the interconnection control device 36, the storage battery PCS 21 performs a phase synchronization process to synchronize the voltage phase of the current from the storage battery PCS 21 and the voltage phase of the current from the mains power supply.

[0054] Fig. Figure 9 is a flowchart illustrating an example of the phase synchronization process performed by the storage battery PCS 21 according to the first embodiment. The following process is primarily carried out by the control unit 211. The storage battery PCS 21 determines whether or not an instruction to start phase synchronization is present (S301). When a control signal to issue an instruction to start phase synchronization is received by the communication unit 213, the storage battery PCS 21 determines that an instruction to start phase synchronization exists.If a control signal to initiate phase synchronization is not received by communication unit 213, or if a control signal to terminate phase synchronization is received by communication unit 213, the storage battery PCS 21 determines that there is no instruction to initiate phase synchronization. If there is no instruction to initiate phase synchronization (S301: NO), the storage battery PCS 21 terminates the phase synchronization process. After the phase synchronization process is complete, the storage battery PCS 21 resumes independent operation and repeats the processing from S301 at any time.

[0055] If there is an instruction to start phase synchronization (S301: YES), the storage battery PCS 21 waits for the phase synchronization process to complete for a specified time and then resumes independent operation (S302). The waiting time (the predetermined time) is preset. For example, the waiting time is 300 seconds. The storage battery PCS 21 then obtains the voltage and frequency of the current from the mains power supply (S303). In S303, the storage battery PCS 21 receives the voltage and frequency measured by the voltage transformer 35. The storage battery PCS 21 can measure the voltage and frequency of the current from the mains power supply.

[0056] The storage battery PCS 21 then determines whether the voltage and frequency of the current from the mains power supply are within a predefined range (S304). For example, the storage battery PCS 21 determines whether the voltage of the current from the mains power supply exceeds a predefined lower limit voltage and is less than a predefined upper limit voltage. Additionally, the storage battery PCS 21 determines whether the frequency of the current from the mains power supply exceeds a predefined lower frequency limit and is less than a predefined upper frequency limit. The voltage and frequency ranges are the ranges of the voltage and frequency of the current that can be stably supplied from the mains power supply when the power grid is operating normally, and are predefined. For example, the lower voltage limit is the same as the voltage that triggers the operation of the UVR 34.

[0057] If the voltage or frequency of the mains power supply is not within the specified range (S304: NO), the storage battery PCS 21 displays information indicating "out of synchronization range" on the display unit 301 (S305). For example, the storage battery PCS 21 sends information indicating "out of synchronization range" from the communication unit 213 to the display unit 301, and the display unit 301 receives the information from the storage battery PCS 21 through the communication unit 38 and displays a character image of "out of synchronization range". The storage battery PCS 21 then determines whether or not there is an instruction to start phase synchronization (S306). If there is no instruction to start phase synchronization (S306: NO), the storage battery PCS 21 terminates the phase synchronization process.After the phase synchronization process is complete, the storage battery PCS 21 continues independent operation and repeats the processing from S301 at any time.

[0058] If there is an instruction to start phase synchronization (S306: YES), the storage battery PCS 21 resets the process to S303. By repeating the processing from S303 to S306, the storage battery PCS 21 waits for phase synchronization to complete until the voltage or frequency of the current from the mains power supply is within a predefined range and then resumes independent operation. While in independent operation, the storage battery PCS 21 continues to supply power to the critical load. At this time, the storage battery PCS 21 maintains the frequency of the current from the storage battery PCS 21 while in independent operation. If the mains power supply is unstable, the voltage or frequency of the current from the mains power supply will deviate from the predefined range, even after the power is restored.When the power grid stabilizes while the storage battery PCS 21 awaits phase synchronization and continues independent operation, the voltage and frequency of the mains power supply can be stabilized within the specified range. Because the storage battery PCS 21 waits for phase synchronization and continues independent operation, it prevents the mains power supply from being connected to the critical load in an unstable state, thus ensuring a stable power supply to the critical load.

[0059] If the voltage and frequency of the current from the mains power supply are within the specified range (S304: YES), the storage battery PCS 21 determines whether the difference between the zero crossing point of the mains voltage and the zero crossing point of the voltage from the storage battery PCS 21 is equal to or less than a threshold value (S307). The zero crossing point is the moment when the AC voltage becomes zero and the moment when the positive and negative sides of the AC voltage reverse. In S305, for example, the storage battery PCS 21 measures times at the zero crossing point and calculates the difference between the measured times. The threshold value is predefined.

[0060] If the difference between the zero crossing points exceeds the threshold (S307: NO), the storage battery PCS 21 determines whether the frequency of the mains power supply is lower than the fundamental frequency (S308). The fundamental frequency is preset. For example, the fundamental frequency is 50 Hz or 60 Hz.

[0061] If the frequency of the mains power supply is lower than the fundamental frequency (S308: YES), the storage battery PCS 21 increases the frequency of the current from the storage battery PCS 21 by a predetermined amount relative to the frequency of the mains power supply (S309). The predetermined amount for increasing the frequency is set in advance to a value sufficiently lower than the fundamental frequency. For example, the predetermined amount is 0.02 Hz. Because the frequency of the mains power supply is relatively low, the storage battery PCS 21 slightly increases the frequency of the current from the storage battery PCS 21 by processing S309, so that the frequency does not deviate from the predetermined range.

[0062] If the frequency of the mains power supply is equal to or higher than the fundamental frequency (S308: NO), the storage battery PCS 21 reduces the frequency of the current from the storage battery PCS 21 by a predetermined amount relative to the mains power supply frequency (S310). The predetermined amount for reducing the frequency is preset to a value sufficiently lower than the fundamental frequency, for example, 0.02 Hz. Because the mains power supply frequency is relatively high, the storage battery PCS 21 slightly reduces the frequency of the current from the storage battery PCS 21 through processing from S310, so that the frequency does not deviate from the predetermined range. After the processing from S309 or S310 is complete, the storage battery PCS 21 resets the process to S306.

[0063] If the difference between the zero crossing points is equal to or less than the threshold value (S307: YES), the storage battery PCS 21 synchronizes the frequency of the current from the storage battery PCS 21 with the frequency of the current from the mains power supply (S311). Then, the storage battery PCS 21 synchronizes the zero crossing point of the voltage from the storage battery PCS 21 with the zero crossing point of the voltage from the mains power supply (S312). The control unit 211 pre-stores a table that defines the time-dependent voltage variation, forming a sine wave. In S312, the storage battery PCS 21 reads data corresponding to the zero crossing point in the table at the time of the zero crossing point of the voltage from the mains power supply and locks the zero crossing point of the voltage from the storage battery PCS 21 to the zero crossing point of the voltage from the mains power supply.

[0064] If the zero-crossing points are brought to coincide in a state where the difference between the zero-crossing point of the voltage from the mains power supply and the zero-crossing point of the voltage from the storage battery PCS 21 is large, a phase shift occurs. During processing S307 to S312, by aligning the zero-crossing points in a state where the difference between them is small, the occurrence of a phase shift is prevented, and the voltage phase of the current from the storage battery PCS 21 and the voltage phase of the current from the mains power supply can be synchronized. Furthermore, the phase shift occurs even if the frequency of the current from the mains power supply and the frequency of the current from the storage battery PCS 21 differ significantly.When processing from S311 and S312, the occurrence of a phase shift is prevented by aligning the zero-crossing points after aligning the frequencies of the currents with each other, and the voltage phase of the current from the storage battery-PCS 21 and the voltage phase of the current from the mains power supply can be synchronized with each other.

[0065] The storage battery PCS 21 then notifies the connection control device 36 that phase synchronization has been completed (S313). For example, the storage battery PCS 21 sends a signal indicating the completion of phase synchronization from the communication unit 213 to the connection control device 36. The storage battery PCS 21 then sets the input gain of a voltage regulator, which regulates the voltage input to the current conversion unit 212, to 0 (S314).

[0066] During standalone operation, the storage battery PCS 21 performs voltage control via the voltage regulator. When power is supplied from the mains supply, the mains voltage is fixed. In S314, the storage battery PCS 21 stops voltage control by setting the input gain of the voltage regulator to 0. This prevents the voltage control by the storage battery PCS 21 from going out of control by forcing the storage battery PCS 21 to control or regulate the fixed voltage. Because the processing from S314 is carried out after phase synchronization is complete, there is no significant difference between the voltage from the storage battery PCS 21 and the voltage from the mains supply due to the cessation of voltage control. The storage battery PCS 21 then completes the phase synchronization process.

[0067] According to S22, the connection control device 36 determines whether phase synchronization has been completed or not (S23). For example, if a signal indicating the completion of phase synchronization is received by the communication unit 38, the connection control device 36 determines that phase synchronization has been completed. If the signal indicating the completion of phase synchronization is not received, the connection control device 36 determines that phase synchronization has not been completed. If phase synchronization has not been completed (S23: NO), the connection control device 36 determines whether the UVR 34 has detected a power failure in the mains supply (S24). For example, if a signal indicating a power failure is received by the UVR 34, the connection control device 36 determines that the UVR 34 has detected a power failure in the mains supply.If no power failure has been detected (S24: No), the link control device 36 resets the process to S23.

[0068] If a power failure is detected (S24: YES), the interconnection control device 36 cancels the instruction to start phase synchronization that is to be given to the storage battery PCS 21 (S25). In S25, for example, the interconnection control device 36 stops the transmission of a control signal to give an instruction to start phase synchronization or sends a control signal to cancel the start of phase synchronization to the storage battery PCS 21 via the communication unit 38. In response to the processing from S25, the storage battery PCS 21 cancels the phase synchronization process. After the processing from S25, the interconnection control device 36 terminates the process without resuming the supply of power from the mains power supply.If another power outage occurs while the storage battery PCS 21 is performing the phase synchronization process, the connection control device 36 causes the storage battery PCS 21 to stop the phase synchronization process. In this case, the supply of power from the mains power supply is not resumed, and the mains connection system 100 continues independent operation.

[0069] Once phase synchronization is complete (S23: YES), the connection control device 36 stops the charging and discharging stations 41 to 45 (S26). In S26, the connection control device 36 sends a control signal to stop the charging and discharging stations 41 to 45 via the communication unit 38. The charging and discharging stations 41 to 45 stop in response to the control signal.

[0070] Then, the connection control device 36 switches on the VCB 32 to connect the mains power supply to the critical load (S27). In S27, the connection control device 36 outputs a control signal to connect the electrical line to the VCB 32. The VCB 32 connects the electrical line in response to the control signal. By connecting the electrical line using the VCB 32, the mains power supply is connected to the critical load. Then, the connection control device 36 stops the storage battery PCS 21 (S28). In S28, the connection control device 36 outputs a control signal to stop the storage battery PCS 21 via the communication unit 38. The storage battery PCS 21 stops in response to the control signal. Subsequently, the mains connection system 100 terminates the process at the time of power restoration.

[0071] Fig. Figure 10 is a schematic representation illustrating an example of a grid connection at the time of power restoration by the grid connection system 100 according to the first embodiment. The grid connection system 100 connects the grid power supply to the critical load at the time of power restoration, so that power from the grid power supply is supplied to the critical load. During the processing of S21 to S28, the grid connection system 100 connects the grid power supply to the critical load while supplying power from the storage battery PCS 21 to the critical load, and then stops the storage battery PCS 21. Therefore, the supply of power to the critical load is not interrupted.In other words, the state in which power is supplied from the storage battery PCS 21 to the critical load is seamlessly switched to the state in which power is supplied from the mains supply. In this way, the supply of power from the mains supply to the critical load is resumed.

[0072] Furthermore, in processing steps S21 to S28, the mains power supply is connected to the critical load after phase synchronization is performed. When the mains power supply is connected to the critical load while power from the storage battery PCS 21 is being supplied to the critical load, the power from the storage battery PCS 21 and the mains power supply are supplied to the critical load simultaneously. By performing phase synchronization, it is possible to connect the mains power supply without subjecting the critical load to a load such as voltage fluctuations. By stopping the storage battery PCS 21 while both currents are being supplied to the critical load simultaneously, it is possible to switch the power source for the critical load without interrupting the power supply.

[0073] After the processing of S21 to S28 is complete, the connection control device 36 can restart the charging and discharging stations 41 to 45 and the storage battery PCS 21 to establish a grid connection. The storage battery PCS then proceeds to establish the grid connection. The grid connection system 100 can then establish the grid connection as described in [reference to...]. Fig. 4 and Fig. 5 described. In this process, during the processing of S21 to S28, the charging and discharging stations 41 to 45 are stopped before the supply of power from the grid power supply to the important consumer has been started; however, the connection control device 36 can carry out the process at the time of power restoration without carrying out the process of stopping the charging and discharging stations 41 to 45.

[0074] In this case, the power supply source for the important consumer is switched without stopping the charging and discharging stations 41 to 45.

[0075] The present embodiment shows an example where the connection to the power grid is made at a high voltage of 6600 V. However, the grid connection system 100 can also be used for a low-voltage connection. In the case of a low voltage, the power or current must be less than 50 kVA. Therefore, the voltage and power (apparent power) on the side of the first winding 331 of the transformer 33 can be, for example, 210 V and 49 kVA, the voltage and power (apparent power) on the side of the second winding 332 can be, for example, 300 V and 49 kVA, and the voltage and power (apparent power) on the side of the third winding 333 can be, for example, 210 V and 49 kVA. Furthermore, the transformer is not limited to a three-winding transformer and can be configured to include two-winding transformers.

[0076] In this configuration, the grid connection system 100 can have a power supply method such as a solar cell instead of, or in addition to, the charging and discharging stations 41 to 45. Furthermore, in this form, the grid connection system 100 can supply power from the storage battery PCS 21 to the critical load in the event of a power outage and can switch the power supply source for the critical load without interrupting the power supply at the time the power is restored. (Second embodiment)

[0077] In a second embodiment, the network connection system 100 does not include the charging and discharging stations 41 to 45 as shown. Although the first embodiment shows an example of the network connection system 100 installed in the parking lot, the network connection system 100 according to the second embodiment is, for example, installed in a building.

[0078] Fig. Figure 11 is a schematic representation showing an example of the circuit configuration of the network connection system 100 according to the second embodiment. The network connection system 100 does not have the charging and discharging columns 41 to 45 compared to the first embodiment. The connection cabinet 30 does not have the switches 111 to 115 compared to the first embodiment. Furthermore, the connection cabinet 30 does not have the transformer 33, which is a three-winding transformer, but instead has a transformer 302 and a transformer 303, which are two-winding transformers. The high-voltage side of the transformer 302 is connected to the VCB 32 via the electrical line. The low-voltage side of the transformer 302 is connected to the switch 103 via the electrical line. The transformer 303 is connected between the high-voltage side of the transformer 302 and the switch 104.The current supplied to and from the storage battery PCS 21 is transformed by the transformer 302. The current transformed by the transformer 303 is supplied as power to the control device and the cooling device contained in the storage battery PCS 21, and further supplied as power to the control device, the cooling device and the heating device in the storage battery cabinet 10.

[0079] The configuration of the remaining parts of the junction box 30 is the same as that of the first embodiment. The configurations of the storage battery cabinet 10, the current conversion cabinet 20, the current monitoring unit 80, and the step-down transformers 85, 86, and 87 are the same as those in the first embodiment. A consumer is an electrical device installed in a building. A general consumer is, for example, an electrical device with a relatively low impact, even if the power is cut off in the event of a natural disaster. A critical consumer is an electrical device that requires a continuous power supply, even in the event of an anomaly such as a natural disaster. For example, a critical consumer is an emergency elevator or an electrical device that requires continuous or uninterrupted operation.

[0080] Fig. Figure 12 is a block diagram showing an example of a communication connection type between the connection cabinet 30 and the storage battery PCS 21 according to the second embodiment, and an example of the internal configuration of the storage battery PCS 21. Similar to the first embodiment, the connection cabinet 30 includes the communication unit 38. The communication unit 38 is connected to the connection control device 36 via a communication line and is also connected to the storage battery PCS 21 via a communication line. The configuration of the storage battery PCS 21 is the same as in the first embodiment.

[0081] Fig. Figure 13 is a schematic representation illustrating an example of a network connection through the network connection system 100 according to the second embodiment when the power grid is normal. Fig. Figure 13 illustrates the flow of a portion of the current with arrows. When the power grid is normal, the connection control device 36 can supply current from the grid power supply to the storage battery PCS 21 to charge the storage battery PCS 21 with the stationary storage battery 11. If the current at the power pickup point at a predetermined location is equal to or greater than a threshold value, the connection control device 36 causes the storage battery PCS 21 to supply current to a critical load and a general load so that the current at the power pickup point is equal to or less than the threshold value. If the current at the power pickup point at a predetermined location is equal to or less than the threshold value, current can be supplied from the grid to the storage battery PCS 21 within a range that does not exceed the threshold value.In addition, the network connection system 100 can establish a network connection so that electricity from the grid power supply is supplied to the general consumer and the important consumer when the power grid is normal.

[0082] Fig. Figure 14 is a schematic representation illustrating an example of independent operation in an emergency through the network connection system 100 according to the second embodiment. Fig. Figure 14 illustrates the flow of current with arrows. If the power grid is abnormal, i.e., if the mains power supply fails, the connection control device 36 disconnects the electrical line of the VCB 32 to disconnect the mains power supply from the critical load. Therefore, independent operation by the connection control device 36 becomes possible. The connection control device 36 supplies current from the storage battery PCS 21 to the critical load when the power grid is abnormal.

[0083] Fig. Figure 15 is a flowchart illustrating an example of the process for initiating independent operation by the grid connection system 100 according to the second embodiment in the event of a power failure. The UVR 34 detects a power failure of the grid power supply based on a voltage to or from the grid power supply (S41). The UVR 34 outputs a control signal to disconnect the electrical line to the VCB 32, and the VCB 32 disconnects the electrical line, so that the grid connection system 100 disconnects the grid power supply and the general load from the critical load (S42).

[0084] Then, the connection control device 36 stops the storage battery PCS 21 (S43). In S43, the connection control device 36 outputs a control signal to stop the storage battery PCS 21, and the storage battery PCS 21 stops in response to the control signal. Then, the connection control device 36 operates the storage battery PCS 21 (S44). In S44, the connection control device 36 outputs a control signal to start operation in independent operating mode to the storage battery PCS 21, and the storage battery PCS 21 starts operation in response to the control signal. After that, the storage battery PCS 21 operates independently. The connection control device 36 receives signals indicating the detection of a power failure by the UVR 34, the disconnection of the electrical line by the VCB 32, and the stopping of the storage battery PCS 21.After receiving all these signals, the connection control device 36 performs the processing from S44. The network connection system 100 completes the process of starting independent operation.

[0085] Once the network connection system 100 starts independent operation, power from the storage battery PCS 21 is supplied to the critical load, as shown in Fig. Figure 14 illustrates this. When the connection control device 36 operates independently, the storage battery PCS 21 performs voltage control to function as a voltage source. In this way, the network connection system 100 can supply the required current to the critical load by drawing power from the storage battery PCS 21 in the event of a power outage.

[0086] Fig. Figure 16 is a flowchart of an example of the sequence of a process performed by the grid connection system 100 according to the second embodiment at the time of power restoration. The UVR 34 detects the power restoration of the grid power supply based on a voltage from the grid power supply (S51). The UVR 34 outputs a control signal to the connection control device 36 upon detection of the power restoration, and the connection control device 36 instructs the storage battery PCS 21 to start synchronizing between the voltage phase of the current from the storage battery PCS 21 and the voltage phase of the current from the grid power supply (S52). The storage battery PCS 21 performs a phase synchronization process to synchronize the voltage phase of the current from the storage battery PCS 21 and the voltage phase of the current from the grid power supply.The content of the phase synchronization process is the same as in the first embodiment. When the phase synchronization is complete, the storage battery PCS 21 notifies the connection control device 36 that the phase synchronization has been completed.

[0087] According to S52, the connection control device 36 determines whether phase synchronization has been completed or not (S53). If a signal indicating the completion of phase synchronization is received by the communication unit 38, the connection control device 36 determines that phase synchronization has been completed. If phase synchronization has not been completed (S53: NO), the connection control device 36 determines whether the UVR 34 has detected a power failure in the mains power supply (S54). If no power failure has been detected (S54: NO), the connection control device 36 resets the process to S53.

[0088] If a power failure is detected (S54: YES), the interconnection control device 36 cancels the instruction to start phase synchronization that is to be given to the storage battery PCS 21 (S55). In response to the processing of S55, the storage battery PCS 21 cancels the phase synchronization process. After processing S55, the interconnection control device 36 terminates the process without resuming power from the grid supply. Therefore, if another power failure occurs while the storage battery PCS 21 is performing the phase synchronization process, power from the grid supply is not resumed, and the grid interconnection system 100 continues independent operation.

[0089] Once phase synchronization is complete (S53: YES), the connection control device 36 switches on the VCB 32 to connect the mains power supply to the critical load (S56). In S56, the connection control device 36 issues a control signal to connect the electrical line to the VCB 32, and the VCB 32 connects the electrical line. As a result, mains power is connected to the critical load. Subsequently, the connection control device 36 stops the storage battery PCS 21 (S57). Then, the mains connection system 100 terminates the process at the time of power restoration.

[0090] Fig. Figure 17 is a schematic representation illustrating an example of a grid connection at the time of power restoration by the grid connection system 100 according to the second embodiment. The grid connection system 100 connects the grid power supply to the critical load at the time of power restoration, so that power is supplied from the grid power supply to the critical load. During the processing of S51 to S57, the grid connection system 100 seamlessly switches from the state in which power is supplied from the storage battery PCS 21 to the state in which power is supplied from the grid power supply to the critical load. In this way, the supply of power from the grid power supply to the critical load is resumed.

[0091] After the processing from S51 to S57 is complete, the connection control device 36 can restart the storage battery PCS 21 to establish the network connection. The storage battery PCS 21 then proceeds to establish the network connection. The network connection system 100 can then establish the network connection as described in [reference to...]. Fig. Perform as described in section 13.

[0092] As described above in the second embodiment, the grid connection system 100 can supply power from the storage battery PCS 21 to the critical load in the event of a power outage and can switch the power supply source for the critical load without interrupting the power supply when the power is restored. In this second embodiment, a three-winding transformer can be provided instead of the two-winding transformers 302 and 303. Furthermore, the grid connection system 100 can include a plurality of storage battery cabinets 10 and a plurality of power conversion cabinets 20, so that power is supplied from a plurality of storage battery PCS 21. (Third embodiment)

[0093] A third embodiment shows an example of the network connection system 100 for industrial use. The network connection system 100 according to the third embodiment forms part of a factory energy management system (FEMS). The network connection system 100 is installed in a factory.

[0094] Fig. Figure 18 is a schematic diagram showing an example of the circuit configuration of the network connection system 100 according to the third embodiment. The configurations of the connection cabinet 30, the storage battery cabinet 10, the current transformation cabinet 20, the current monitoring unit 80, and the step-down transformers 85 and 87 are the same as those in the second embodiment. The network connection system 100 does not include the step-down transformer 86 compared to the second embodiment. The step-down transformer 87 is connected to a load 88. The load 88 is an electrical device provided in the factory. For example, the load 88 is factory equipment or lighting.

[0095] The communication connection type of the connection cabinet 30 and the storage battery PCS 21, and the internal configuration of the storage battery PCS 21, are the same as those in the second embodiment. When the storage battery PCS 21 is operating, a signal indicating that the storage battery PCS 21 is operating is transmitted by the communication unit 213. The connection control device 36 receives a signal indicating that the storage battery PCS 21 is operating from the communication unit 38.

[0096] Fig. Figure 19 is a schematic representation illustrating a first example of a network connection through the network connection system 100 according to the third embodiment when the power grid is normal. Fig. Figure 19 illustrates the flow of a portion of the current with arrows. The connection control device 36 establishes a grid connection so that current from the grid power supply is supplied to the consumer 88 when the power grid is normal.

[0097] Fig. Figure 20 is a schematic representation showing a second example of the network connection through the network connection system 100 according to the third embodiment when the power grid is normal. Fig. Figure 20 illustrates the flow of a portion of the current with arrows. The connection control device 36 causes the storage battery PCS 21 to supply current to the load 88. Additionally, the connection control device 36 can supply current from the mains power supply to the storage battery PCS 21 to charge the storage battery PCS 21 with the stationary storage battery 11.

[0098] Fig. Figure 21 is a schematic representation showing an example of independent operation in an emergency through the network connection system 100 according to the third embodiment. Fig. Figure 21 illustrates the current flow with arrows. If the power grid is abnormal, or if the mains power supply fails, the connection control device 36 disconnects the electrical line of the VCB 32 to disconnect the mains power supply from the critical load. Therefore, independent operation is enabled by the connection control device 36. The connection control device 36 supplies current from the storage battery PCS 21 to the critical load when the power grid is abnormal.

[0099] Fig. Figure 22 is a flowchart illustrating an example of the process for initiating independent operation by the network connection system 100 according to the third embodiment in the event of a power failure. The UVR 34 detects a power failure of the mains power supply based on a voltage from the mains power supply (S61). The UVR 34 outputs a control signal to disconnect the electrical line to the VCB 32, and the VCB 32 disconnects the electrical line, so that the network connection system 100 disconnects the mains power supply from the consumer 88 (S62).

[0100] Then, the connection control device 36 stops the storage battery PCS 21 (S63). In S63, the connection control device 36 outputs a control signal to stop the storage battery PCS 21, and the storage battery PCS 21 stops in response to the control signal. Then, the connection control device 36 operates the storage battery PCS 21 (S64). In S64, the connection control device 36 outputs a control signal to start operation in independent mode to the storage battery PCS 21, and the storage battery PCS 21 starts operation in response to the control signal. After that, the storage battery PCS 21 operates independently. The connection control device 36 receives signals indicating the detection of a power failure by the UVR 34, the disconnection of the electrical line by the VCB 32, and the stopping of the storage battery PCS 21.After receiving all these signals, the connection control device 36 performs the processing from S64. The network connection system 100 completes the process to start independent operation.

[0101] After the network connection system 100 starts independent operation, power from the storage battery PCS 21 is supplied to the consumer 88, as shown in Fig. Figure 21 illustrates this. When the connection control device 36 operates independently, the storage battery PCS 21 performs voltage control by operating a voltage source. In this way, the network connection system 100 can supply the required current to the consumer 88 by drawing power from the storage battery PCS 21 in the event of a power outage. Therefore, even in the event of a power outage, power can be supplied to the consumer 88 in the factory, thus preventing a shutdown of factory operations.

[0102] Fig. Figure 23 is a flowchart illustrating an example of the process performed by the grid connection system 100 according to the third embodiment at the time of power restoration. The UVR 34 detects the restoration of the grid power supply based on a voltage from the grid power supply (S71). Then, the connection control device 36 instructs the storage battery PCS 21 to start synchronizing the voltage phase of the current from the storage battery PCS 21 and the voltage phase of the current from the grid power supply (S72). The storage battery PCS 21 performs a phase synchronization process to synchronize the voltage phase of the current from the storage battery PCS 21 and the voltage phase of the current from the grid power supply. The content of the phase synchronization process is the same as in the first and second embodiments.When phase synchronization is complete, the storage battery PCS 21 notifies the connection control device 36 that phase synchronization has been completed.

[0103] Following S72, the interconnection control device 36 determines whether phase synchronization has been completed (S73). If phase synchronization has not been completed (S73: NO), the interconnection control device 36 determines whether the UVR 34 has detected a power outage (S74). If no power outage has been detected (S74: NO), the interconnection control device 36 resets the process to S73. If a power outage has been detected (S74: YES), the interconnection control device 36 cancels the instruction to start phase synchronization that is to be given to the storage battery PCS 21 (S75). In response to the processing of S75, the storage battery PCS 21 cancels the phase synchronization process. After processing from S75, the interconnection control device 36 terminates the process without resuming power from the mains supply.If another power outage occurs during the phase synchronization process, the supply of power from the grid will not be resumed, and the grid connection system 100 will continue independent operation.

[0104] Once phase synchronization is complete (S73: YES), the connection control device 36 switches on the VCB 32 to connect the mains power supply to the load 88 (S76). In S76, the VCB 32 connects the electrical line, thus connecting the mains power supply to the load 88. The connection control device 36 then stops the storage battery PCS 21 (S77). Finally, the mains connection system 100 terminates the process upon power restoration.

[0105] After the process ends, at the time of power restoration, as in Fig. As illustrated in Figure 19, the mains power supply is connected to the load 88, so that current from the mains power supply is supplied to the load 88. During the processing of S71 to S77, the mains connection system 100 switches seamlessly from the state in which current is supplied from the storage battery PCS 21 to the state in which current is supplied from the mains power supply to the load 88. In this way, the supply of current from the mains power supply to the load 88 is resumed.

[0106] After the processing of S51 to S57 is complete, the connection control device 36 can restart the storage battery PCS 21 to establish the network connection. The storage battery PCS 21 then proceeds to establish the network connection. The network connection system 100 can then establish the network connection as described in [reference to...]. Fig. Perform as described in section 20.

[0107] As described above, in the third embodiment, the network connection system 100 can also supply power from the storage battery PCS 21 to the consumer 88 in the event of a power outage and can switch the power supply source for the consumer 88 without interrupting the power supply at the time the power is restored. Therefore, at the time the power is restored, the power supply to the consumer 88 in the factory is not interrupted, thus preventing any interruption to factory operations. In this third embodiment, a three-winding transformer can be provided instead of the two-winding transformers 302 and 303.In addition, the network connection system 100 can have a large number of storage battery cabinets 10 and a large number of power conversion cabinets 20, so that the power is supplied from a large number of storage battery PCS 21. [List of reference symbols] 10 storage battery cabinet 11 stationary storage battery 20 power conversion cabinets 21 Storage battery power conversion device (PCS) 30 Connection cabinet 32 VCB 33 Transformer 34 UVR 36 Connection control device 41, 42, 43, 44, 45 Charging and unloading station 51, 52, 53, 54, 55 Electrically powered vehicle 100 network connection system

Claims

[1] Network connection system (100) for an electricity network, characterized by , that it exhibits: a storage battery (11); a current conversion device that converts current from the storage battery (11) into alternating current; and a connection control device (36) that supplies power from a mains power supply to a consumer and supplies power from the power conversion device to the consumer when the mains power supply fails, wherein, when the mains power supply is restored, the current conversion device (21) synchronizes a voltage phase of current supplied by the current conversion device (21) to the consumer with a voltage phase of current from the mains power supply, the current conversion device (21) matches a frequency of current supplied by the current conversion device (21) to a frequency of current from the mains power supply, and After matching the frequencies of the currents, the current conversion device (21) aligns a zero crossing point of the current supplied by the current conversion device (21) to the consumer with a zero crossing point of the current from the mains power supply. and after the voltage phase of the current supplied from the current conversion device (21) to the consumer is synchronized with the voltage phase of the current from the mains power supply, the connection control device (36) starts the supply of current from the mains power supply to the consumer, and the connection control device (36) stops the supply of current from the current conversion device to the consumer after the supply of current from the mains power supply to the consumer has been started. [2] Network connection system (100) according to claim 1, characterized by , that The current conversion device determines whether the voltage and frequency of the current from the mains power supply lie within a predetermined range or not. If the voltage and frequency are within the specified range, the current conversion device synchronizes the voltage phase of the current supplied by the current conversion device to the consumer with the voltage phase of the current from the mains power supply, and If the voltage or frequency is not within the specified range, the current conversion device waits for a phase synchronization process and continues supplying current to the consumer. [3] Network connection system (100) for an electricity network, characterized by , that it exhibits: a storage battery (11); a current conversion device that converts current from the storage battery (11) into alternating current; and a connection control device (36) that supplies power from a mains power supply to a consumer and supplies power from the current conversion device (21) to the consumer when the mains power supply fails, wherein, when the mains power supply is restored, the current conversion device (21) determines whether a voltage and frequency of the current from the mains power supply are within a predetermined range or not, If the voltage and frequency are within the specified range, the current conversion device (21) synchronizes the voltage phase of the current supplied by the current conversion device (21) to the consumer with the voltage phase of the current from the mains power supply, and If the voltage or frequency is not within the specified range, the current conversion device (21) waits for a phase synchronization process and continues to supply current to the load until the voltage and frequency fall within the specified range, and after the voltage phase of the current supplied from the current conversion device (21) to the consumer is synchronized with the voltage phase of the current from the mains power supply, the connection control device (36) starts the supply of current from the mains power supply to the consumer, and the connection control device (36) stops the supply of current from the current conversion device to the consumer after the supply of current from the mains power supply to the consumer has been started. [4] Network connection system (100) according to one of claims 1 to 3, characterized by , that it further exhibits: a charging and discharging station (41, 42, 43, 44, 45) for an electrically powered vehicle (51, 52, 53, 54, 55), wherein, in the event of a power failure, the connection control device (36) supplies power from the power conversion device and the charging and discharging station (41, 42, 43, 44, 45) to the consumer. [5] Network connection system (100) according to any one of claims 1 to 4, characterized by , that when the mains power supply fails, the connection control device supplies current from the current conversion device (21) to a specific consumer, and When the mains power supply is restored, the connection control device (36) starts the supply of power from the mains power supply to the specific consumer. [6] Connection control device (36) which supplies current to a consumer of a current conversion device (21) which converts energy from a storage battery (11) into alternating current when a mains power supply fails, wherein the connection control device (36) is operable to to cause the current conversion device (21), when the mains power supply is restored, to synchronize a voltage phase of current supplied by the current conversion device (21) to the consumer with a voltage phase of current from the mains power supply by matching a frequency of the current supplied by the current conversion device (21) to a frequency of the current from the mains power supply, and by, After matching the frequencies of the currents, a zero crossing point of the current supplied by the current conversion device (21) to the consumer is matched with a zero crossing point of the current from the mains power supply, Starting the supply of electricity from the mains power supply to the consumer after the voltage phase of the current supplied by the current conversion device (21) to the consumer has been synchronized with the voltage phase of the current from the mains power supply, and Stopping the supply of current from the current conversion device (21) after the supply of current from the mains power supply to the consumer has been started. [7] Connection control device (36) which supplies current to a consumer of a current conversion device (21) which converts energy from a storage battery (11) into alternating current when a mains power supply fails, wherein the connection control device (36) is operable to to cause the current conversion device (21) to determine, when the mains power supply is restored, whether a voltage and frequency of the current from the mains power supply are within a predetermined range or not, if the voltage and frequency are within the specified range, to cause the current conversion device (21) to synchronize the voltage phase of the current supplied by the current conversion device (21) to the consumer with the voltage phase of the current from the mains power supply, and If the voltage or frequency is not within the specified range, the current conversion device (21) is to be instructed to wait for a phase synchronization process and to continue supplying current to the consumer until the voltage and frequency fall within the specified range. Starting the supply of electricity from the mains power supply to the consumer after the voltage phase of the current supplied by the current conversion device (21) to the consumer has been synchronized with the voltage phase of the current from the mains power supply, and Stopping the supply of current from the current conversion device (21) after the supply of current from the mains power supply to the consumer has been started. [8] Network interconnection methods for an electricity network, characterized by , that it includes: using a storage battery (11) and a current conversion device for converting current from the storage battery (11) into alternating current, supplying current from a mains power supply to a consumer; Supplying electricity from the power conversion device to the consumer when the mains power supply fails; Causing the current conversion device (21) to synchronize a voltage phase of current supplied by the current conversion device (21) to the consumer with a voltage phase of current from the mains power supply when the mains power supply is restored, by matching a frequency of the current supplied by the current conversion device (21) to a frequency of the current from the mains power supply, and by After matching the frequencies of the currents, a zero crossing point of the current supplied by the current conversion device (21) to the consumer is matched with a zero crossing point of the current from the mains power supply; Starting the supply of electricity from the mains power supply to the consumer after the voltage phase of the current supplied by the current conversion device to the consumer has been synchronized with the voltage phase of current from the mains power supply; and Stopping the supply of electricity from the power conversion device to the consumer after the supply of electricity from the mains power supply to the consumer has started. [9] Network interconnection method for an electricity network, characterized by , that it includes: using a storage battery (11) and a current conversion device for converting current from the storage battery (11) into alternating current, supplying current from a mains power supply to a consumer; Supplying electricity from the power conversion device to the consumer when the mains power supply fails; to cause the current conversion device (21) to determine, when the mains power supply is restored, whether a voltage and frequency of the current from the mains power supply are within a predetermined range or not, if the voltage and frequency are within the specified range, to cause the current conversion device (21) to synchronize the voltage phase of the current supplied by the current conversion device (21) to the consumer with the voltage phase of the current from the mains power supply, and If the voltage or frequency is not within the specified range, the current conversion device (21) is to be instructed to wait for a phase synchronization process and to continue supplying current to the consumer until the voltage and frequency fall within the specified range. Starting the supply of electricity from the mains power supply to the consumer after the voltage phase of the current supplied by the current conversion device to the consumer has been synchronized with the voltage phase of current from the mains power supply; and Stopping the supply of electricity from the power conversion device to the consumer after the supply of electricity from the mains power supply to the consumer has started.

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