Charging and discharging system for electric vehicles, power control system, and method for charging electric vehicles

Abstract

To achieve control for stably maintaining connection between a power control system and an EV without troubling a user.SOLUTION: A charging / discharging system for an electric vehicle includes: a connector for connecting to an electric vehicle; an EV charging / discharging circuit for performing charging / discharging of an in-vehicle storage battery under a state in which the connector is connected to the electric vehicle; and a charging / discharging control circuit for controlling the EV charging / discharging circuit. The charging / discharging control circuit acquires information including a discharging lower limit charging amount, which is a lower limit value at which discharging from the in-vehicle storage battery is allowed, from the electric vehicle, sequentially acquires a charging amount of the in-vehicle storage battery to compare it with a discharging stop threshold value that is larger than the discharging lower limit charge amount by a predetermined value, and stops discharging from the in-vehicle storage battery and enters a standby state when it is determined that the charging amount acquired during discharging from the in-vehicle storage battery is equal to or less than the discharging stop threshold value.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a charge / discharge system for an electric vehicle, a power control system, and a method for charging an electric vehicle, and more particularly to maintaining connection with an electric vehicle via a connector.

Background Art

[0002] Plug-in hybrid vehicles and electric vehicles have been put into practical use and are expected to become more widespread in the future. In this specification, these are collectively referred to as EVs (abbreviation for Electric Vehicle) or electric vehicles. EVs assume charging from an external power source. Many EV owners install a charging device for EVs at home to charge their vehicles. Also, a V2H system that uses the power of a large-capacity in-vehicle battery mounted on an EV as domestic power is known. The V2H system is a power system that discharges and supplies the power stored in the in-vehicle battery of an EV, i.e., Vehicle to Home, to a power load such as a house or a stationary battery. Charging and discharging between an EV and a V2H system are standardized, and charging and discharging are performed via a connector conforming to the standard. There are several standards for charging and discharging between an EV and a V2H system, such as Tesla, GB / T, CHAdeMO, etc., and it is also possible to connect an EV and a charging device of a different standard via an adapter. Most of the EVs sold in Japan conform to the CHAdeMO standard.

[0003] When charging and discharging an EV, especially when performing rapid charging and discharging, it is necessary to perform charging and discharging in accordance with the standards and guidelines. According to those standards and guidelines, it is stipulated that communication be carried out with the vehicle before starting charging and discharging to obtain vehicle information and detect the connection of the connector. When a V2H system's power converter charges and discharges an electric vehicle, it is necessary to keep the charging cable connected to the electric vehicle regardless of whether it is day or night. A technology is known that provides a vehicle power converter that is excellent in both safety and security when charging and discharging (see, for example, Patent Document 1). An embodiment of Patent Document 1 discloses a procedure in which a charge / discharge control unit connects a charging connector having a charging connector latch to the vehicle inlet to charge and discharge an electric vehicle.

[0004] Furthermore, a technology has been proposed that exhibits high responsiveness while suppressing degradation, even while following a predetermined procedure according to the charge / discharge method (see, for example, Patent Document 2). Switching between charging and discharging operation and stopping of an EV requires following a predetermined procedure that includes opening and closing relays (DC relays) on the vehicle side, DC relays and disconnection relays on the charge / discharge device side, but conventionally, it has been difficult to meet the high-speed response demands from the EMS (Energy Management System). Also, if charging and discharging operation and stopping are repeated, there is a risk of degradation due to the frequent opening and closing of the relays. This technology aims to solve that problem. According to Patent Document 2, the control unit of the charge / discharge device to which the vehicle is connected acquires vehicle information, including the charge rate of the vehicle's energy storage device, from the vehicle's onboard charge / discharge control device.

[0005] The energy storage device can be charged and discharged at a level below a first charge level (corresponding to the upper limit charge level described later) that is close to full charge, and above a second charge level (corresponding to the lower limit discharge charge level described later) that is a state where the remaining capacity has decreased. The control unit then determines whether the charge level is below the second charge level at which discharge is deemed impossible. If the charge level falls below the second charge level, the control unit turns on the disconnection relay to start or continue charging the energy storage device with minimum power and transmits the charging current value to the on-board charge / discharge control device. When the charge level of the energy storage device reaches the third charge level through this charging, the control unit turns off the disconnection relay to end charging at minimum power. However, it sends a message to the on-board charge / discharge control device indicating the minimum charging current value. After ending charging at minimum power, when the charge level of the energy storage device falls below the second charge level again, the control unit turns on the disconnection relay as described above and starts charging the energy storage device with minimum power. In this way, the control unit opens and closes the disconnection relay to maintain the charge level of the energy storage device at a state between the second charge level and the third charge level, and waits for instructions from the EMS while waiting until the upper limit time is reached. When the upper time limit is reached, the termination sequence is initiated. In this way, the control unit maintains a ready state with the vehicle and enables a quick response to instructions. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2017 / 072895 [Patent Document 2] Japanese Patent Publication No. 2020-191774 [Overview of the project] [Problems that the invention aims to solve]

[0007] For example, when charging and discharging in accordance with the CHAdeMO standard and guidelines, EVs have pre-set upper charge limit (maximum chargeable value for EVs) and lower discharge limit (minimum discharge limit for EVs), depending on the manufacturer or vehicle model. Charging of the onboard battery is prohibited when the charge level exceeds the upper charge limit. Similarly, discharging from the onboard battery is prohibited when the charge level falls below the lower discharge limit. Therefore, if the onboard battery's charge level reaches the aforementioned lower discharge limit during discharge, the EV's discharge must be stopped. The connection between the connector and the EV must then be disconnected. Furthermore, when connecting a connector to an EV to receive power using a V2H system, if the onboard battery is below the lower discharge limit, discharge from the EV is not permitted, and the connection between the connector and the EV must be disconnected. Charging of the EV cannot be started once the connection between the connector and the EV is disconnected. For example, in order to start charging an EV when it becomes possible to charge it using surplus electricity during the day, the user needs to manually reconnect the connector to the EV.

[0008] Patent Document 2 maintains the charge level of the energy storage device at a state between a second charge level and a third charge level to prevent the ready state between the vehicle and the device from being canceled. However, if the charge level of the energy storage device falls below the second charge level, the on-board charge / discharge control device turns off the DC relay, making charging and discharging impossible. Therefore, if the response time from when the control circuit recognizes that the charge level of the energy storage device has fallen below the second charge level until charging at a minimum power level or higher is slow, the on-board charge / discharge control device may turn off the DC relay. Also, if the second charge level and the third charge level are close, the disconnection relay may be opened and closed multiple times while the ready state is being maintained (according to the numerical example in Patent Document 2, the second charge level is 10% and the third charge level is 15%). Patent Document 2 assumes that control instructions from the EMS require a fast response. In contrast, this invention focuses on maintaining the connection between the power control system and the EV so that the EV can be charged during times when surplus power is generated in the power control system, and so that power can be supplied from the EV to the power control system in the event of an unexpected power outage. This invention was made in consideration of the above circumstances, and it is possible to realize a control system that can stably maintain the connection between the power control system and the EV without requiring any intervention from the user. [Means for solving the problem]

[0009] This invention provides an electric vehicle charging and discharging system comprising a connector for connecting to an electric vehicle, an EV charging and discharging circuit for charging and discharging the on-board battery of the electric vehicle while the connector is connected to the electric vehicle, and a charging and discharging control circuit for controlling the EV charging and discharging circuit, wherein the charging and discharging control circuit acquires information from the electric vehicle, including a minimum discharge charge amount which is the lower limit value at which discharge from the on-board battery is permitted, sequentially acquires the charge amount of the on-board battery and compares it with a discharge stop threshold which is a predetermined value greater than the minimum discharge charge amount, and stops discharging from the on-board battery when it is determined that the charge amount acquired during discharge from the on-board battery is less than or equal to the discharge stop threshold.

[0010] Furthermore, this invention provides a power control system comprising the aforementioned electric vehicle charging and discharging system, a solar module related to solar power generation, a grid connection unit connected to a power grid, and an equipment connection unit to which power-consuming equipment is connected, wherein the charging and discharging control circuit controls the charging and discharging control to charge the on-board battery with the surplus power generated by the solar power generation.

[0011] Furthermore, from a different perspective, this invention provides a method for charging and discharging an electric vehicle, comprising: a charge / discharge control circuit for EVs that charges and discharges an on-board battery of an electric vehicle while a connector for connecting an electric vehicle is connected to the electric vehicle, the circuit control circuit obtaining information from the electric vehicle including a minimum discharge charge amount which is the lower limit value at which discharge from the on-board battery is permitted; a step of sequentially obtaining the charge amount of the on-board battery and comparing it with a discharge stop threshold which is a predetermined value greater than the minimum discharge charge amount; and a step of stopping the discharge from the on-board battery when it is determined that the charge amount obtained during discharge from the on-board battery is less than or equal to the discharge stop threshold. [Effects of the Invention]

[0012] In the electric vehicle charging and discharging system according to this invention, the charging and discharging control circuit acquires information including the minimum discharge charge amount from the electric vehicle, sequentially acquires the charge amount of the onboard battery, compares it with a discharge stop threshold that is a predetermined value greater than the minimum discharge charge amount, and stops discharging from the onboard battery when it is determined that the acquired charge amount is less than or equal to the discharge stop threshold. This allows for stable maintenance of the connection between the power control system and the EV without requiring any action from the user. Consequently, it avoids the loss of charging and discharging opportunities, such as when the connector connection is disconnected and the charging and discharging of the onboard battery cannot be continued unless the user reconnects the connector. The power control system and the charging / discharging method for electric vehicles according to this invention also produce similar effects. [Brief explanation of the drawing]

[0013] [Figure 1]This is an explanatory diagram showing an example configuration of a power control system according to Embodiment 1. [Figure 2] Figure 1 is an explanatory diagram showing an example of the operation screen displayed on the remote controller. [Figure 3] Figure 1 is an explanatory diagram showing an example of the V2H operation screen displayed on the remote controller. [Figure 4] Figure 1 is an explanatory diagram illustrating an example of the charging and discharging process performed by the V2H system according to the state of the on-board battery. [Figure 5] Figure 1 shows the first flowchart illustrating an example of the charging and discharging process of an on-board battery performed by the PCS control circuit. [Figure 6] Figure 1 shows a second flowchart illustrating an example of the charging and discharging process of an on-board battery performed by the PCS control circuit. [Modes for carrying out the invention]

[0014] The invention will be described in further detail below with reference to the drawings. The following description is illustrative in all respects and should not be construed as limiting the invention. (Embodiment 1) Figure 1 is an explanatory diagram showing an example configuration of a power control system according to Embodiment 1 of the present invention. The power control system 10 shown in Figure 1 is illustrated as an example of a house that receives power from a power grid 15 via a distribution board 15B. The distribution board 15B also serves as a grid connection section connecting the power control system 10 and the power grid 15. The power control system 10 in Figure 1 includes a solar power generation system 11, a stationary battery storage system 12, and a V2H system 13. The solar power generation system 11 generates electricity using sunlight. The stationary battery storage system 12 can store electricity generated by the solar power generation system 11, electricity from the on-board battery 14B of the EV 14, or electricity from the power grid 15 in the stationary battery 12B. Furthermore, the electricity stored in the stationary battery 12B can be supplied to power-using equipment 16 connected to the distribution board 15B, which corresponds to the equipment connection section, or to the EV 14 described later, or it can be sold back to the power grid 15. The stationary battery 12B is a battery installed in a house. The EV 14 is equipped with a socket 14S, an on-board battery 14B, and an on-board charge / discharge control circuit 14C. Furthermore, the V2H system 13 is a charge / discharge system for electric vehicles that controls the charging and discharging of the on-board battery 14B. As shown in Figure 1, with the EV connected to the V2H system 13, it is possible to supply power from the EV 14's on-board battery 14B to the stationary battery system 12 or power-using equipment 16, or to sell the power to the power grid 15. Conversely, the EV 14's on-board battery 14B can be charged with power supplied from the solar power generation system 11, the stationary battery system 12, or the power grid 15.

[0015] As shown in FIG. 1, the photovoltaic power generation system 11 includes a photovoltaic module 11S, a power conditioner 11P (also called PCS, Power Conditioning System), and a remote controller 11R. The power conditioner 11P includes a PCS control circuit 11C, a converter 11D for photovoltaic power generation, a bidirectional inverter 11V, and a remote controller 11R. The main body of the power conditioner 11P and the remote controller 11R are physically separated but connected by communication. The power conditioner 11P is also connected to the HEMS controller 17 by communication. The HEMS controller 17 communicates with a HEMS server 17S outside the house via a router 17R and a network. The power conditioner 11P and the remote controller 11R are not only components of the photovoltaic power generation system 11 but also components of the stationary battery system 12 and the V2H system 13.

[0016] The photovoltaic module 11S is a power generation device including a plurality of solar cells, which generates a DC voltage by receiving sunlight and causes a DC current due to the voltage to flow through a circuit. The converter 11D for photovoltaic power generation of the power conditioner 11P is a circuit that receives an instruction from the PCS control circuit 11C and converts the DC voltage generated by the photovoltaic module 11S into a predetermined DC voltage. The bidirectional inverter 11V of the power conditioner 11P is a circuit that receives an instruction from the PCS control circuit 11C, converts the DC voltage output by the converter 11D for photovoltaic power generation into an AC voltage, and outputs it to an electric power consuming device 16 connected to a socket or an electric power system 15. Conversely, it is a circuit that converts an AC voltage from the electric power system 15 into a DC voltage and outputs it to a battery converter 12D, an in-vehicle battery 14B of an EV 14 connected to the V2H system 13, or an EV converter 13D.

[0017] The stationary battery system 12 includes a stationary battery 12B, a battery converter 12D, and a PCS control circuit that controls the battery converter 12D. It also includes a power conditioner 11P and a remote controller 11R, as described above. In this embodiment, the PCS control circuit that controls the battery converter 12D is the PCS control circuit 11C. The battery converter 12D is a charging and discharging circuit for the stationary battery, and the PCS control circuit that controls the battery converter 12D is a charging and discharging control circuit for the stationary battery. The stationary battery 12B is a rechargeable secondary battery that can be repeatedly charged and discharged, and is connected to the power conditioner 11P via the battery converter 12D. The battery converter 12D receives instructions from the PCS control circuit 11C, converts the DC voltage from the power conditioner 11P to a predetermined DC voltage, and outputs it to the stationary battery 12B to charge the stationary battery 12B. Conversely, the DC voltage from the stationary battery 12B is converted to a predetermined DC voltage and output to the power conditioner 11P. In this way, power from the stationary battery 12B is supplied to power-using equipment 16 connected to the distribution board 15B and to the power grid 15. In addition, the DC voltage from the stationary battery 12B is converted to a predetermined DC voltage and output to the power conditioner 11P, and power is supplied to the on-board battery 14B via the EV converter 13D for charging.

[0018] The V2H system 13 includes a connector 13C for EV connection and a converter 13D for EV. The connector 13C includes a connector latch 13L. Further, as described above, it includes a power conditioner 11P and a remote controller 11R. The converter 13D for EV is an EV charge / discharge circuit, which receives an instruction from the PCS control circuit 11C and converts the DC voltage from the power conditioner 11P into a predetermined DC voltage. Then, in a state where the connector 13C is connected to the socket 14S of the EV 14, it supplies power to the in-vehicle battery 14B for charging. Conversely, it converts the DC voltage output from the in-vehicle battery 14B via the socket 14S and the connector 13C into a predetermined DC voltage and supplies it to the power conditioner 11P. By doing so, the power stored in the in-vehicle battery 14B is supplied to the power-consuming device 16 connected to the distribution board 15B, the stationary battery 12B, and the power system 15. The connector latch 13L is switched between a locked and an unlocked state by the PCS control circuit 11C. In the locked state, the connector latch 13L physically fixes the connection between the connector 13C and the socket 14S to prevent the connector 13C from coming off. For the user to unplug the connector 13C from the socket 14S, the connector latch 13L needs to be in the unlocked state. When the connector latch 13L is in the unlocked state, the in-vehicle battery 14B cannot be charged or discharged. In this specification, when the connector 13C is connected to the socket 14S of the EV 14 and the connector latch 13L is locked, it is said that the EV 14 and the V2H system 13 are connected. Also, when the connector latch 13L is unlocked, it is said that the connection between the EV and the V2H system is released. Further, the state where the connector 13C is connected to the socket 14S of the EV 14 and the connector latch 13L is locked is called the state where the connector is connected to the EV, and unlocking the connector latch 13L is called releasing the connection between the connector and the EV.

[0019] The power-consuming equipment 16 is a household electrical appliance such as an air conditioner, cooking appliance, or information equipment, and is a load that consumes power. The stationary storage battery 12B and EV 14 are also power loads when they are being charged. The remote controller 11R includes a display device that displays information related to the power controlled by the PCS control circuit 11C and an operation device that receives user input.

[0020] The PCS control circuit 11C is a charge / discharge control circuit of the power control system 10, and includes a processor, memory, input / output circuits, communication circuits, etc. The PCS control circuit 11C is communicatively connected to the solar power converter 11D, the bidirectional inverter 11V, the battery converter 12D, and the EV converter 13D. The PCS control circuit 11C acquires information on whether the EV 14 is connected via connector 13C and the charge status of the EV 14's onboard battery 14B (charge power value, remaining capacity, etc.) and displays it on the display device of the remote controller 11R. It also accepts user operations via the remote controller 11R regarding settings related to the charging and discharging of the EV 14. Furthermore, the PCS control circuit 11C acquires information on the charge status (charge power value, remaining capacity, etc.) of the stationary battery 12B of the stationary battery system 12 and displays it on the display device of the remote controller 11R. It also accepts user operations via the remote controller 11R regarding settings related to the charging and discharging of the stationary battery 12B.

[0021] When charging the EV14, the user connects connector 13C to socket 14S provided on the EV14. This connects a power line between the EV converter 13D of the V2H system 13 and the on-board battery 14B, and a communication line between the EV converter 13D and the on-board charge / discharge control circuit 14C. Then, the processor of the PCS control circuit 11C and the on-board charge / discharge control circuit 14C become able to communicate, making it possible to supply power to the on-board battery 14B while exchanging information with the EV14. The on-board charge / discharge control circuit 14C includes a processor, memory, input / output circuits, communication circuits, etc., and controls communication with the V2H system 13 and the charging and discharging of the on-board battery 14B.

[0022] The PCS control circuit 11C may not only display the charge and discharge amounts to the on-board battery 14B of the EV 14 connected to the connector 13C on the remote controller 11R, as well as the charge and discharge amounts to the stationary battery 12B, but may also display information related to power control by the power control system 10 executed by the power conditioner 11P. For example, it may display information such as voltage values, current values, and power values ​​related to the power transmitted to and from the power grid 15, which is detected by a smart meter (not shown in Figure 1). It may also display the amount of electricity or energy purchased by the power control system 10 from the power grid 15, or the amount of electricity or energy sold to the power grid 15. Furthermore, it may display the amount of power generated by the solar module 11S, the amount of energy stored in the stationary battery 12B and the on-board battery 14B, the state of charge (SOC), the charge amount and discharge amount, or the charge power and discharge power.

[0023] The HEMS controller 17 communicates with the solar power generation system 11, the stationary battery storage system 12, and the V2H system 13 to control the power of the power control system 10. Specifically, the HEMS controller 17 communicates with the remote controller 11R of the power conditioner 11P. The HEMS controller 17 also communicates with the user's smartphone or other information device 17D to provide information related to power control and to accept user settings related to power control. The remote controller 11R may also perform the functions of the information device 17D, communicating with the HEMS controller 17 to provide the aforementioned information related to power control and to accept user settings related to power control. Conversely, the portable information device may also perform the functions of the remote controller 11R. In the example shown in Figure 1, the battery converter 12D and the EV converter 13D are separate devices from the power conditioner 11P, but some or all of them may be included in the power conditioner 11P.

[0024] ≪Operating the V2H System≫ This section describes an example of a procedure in which a user operates the V2H system 13 to instruct the charging and discharging of the on-board battery 14B of the EV 14 in the power control system 10 shown in Figure 1. Figure 2 is an explanatory diagram showing an example of an operation screen displayed on the display device of the remote controller 11R shown in Figure 1. The operation screen shown in Figure 2 is an example of a top screen that provides comprehensive information of the power control system 10. The PCS control circuit 11C causes the remote controller 11R to display the top screen 20 as shown in Figure 2. From the left end to the right end of the top screen 20, the solar power generation information display area 21, the V2H information display area 22, the stationary battery information display area 23, and the power consumption / sales power display area 24 are arranged in order, each enclosed in a dashed line frame.

[0025] The solar power generation information display area 21 provides information such as the power generated by the solar power generation system 11. The V2H information display area 22 provides information such as the charge and discharge status of the on-board battery 14B. The stationary battery information display area 23 provides information such as the charge and discharge status of the stationary battery 12B. The power consumption / sale power display area 24 provides information about the power consumption of the power control system 10, the status of selling or buying electricity, and information related to that electricity. A [V2H operation] button 25 is located in the V2H information display area 22. When the user touches the [V2H operation] button 25, the PCS control circuit 11C responds to that operation by switching the top screen 20 to the V2H operation screen 30 shown in Figure 3.

[0026] The V2H operation screen 30 includes a [Manual Charge] button 31, an [Automatic Operation] button 32, a [Charge from Stationary Battery] button 33, a [Discharge to Stationary Battery] button 34, and an [EV Disconnect] button 35. When the EV 14 and the V2H system 13 are not connected, the [EV Disconnect] button 35 changes its display to an [EV Connect] button. When the [EV Connect] button is touched, the connector latch 13L is locked, and the connector is connected to the EV. When the [EV Disconnect] button is touched, the connector latch 13L is unlocked, and the connection between the connector and the EV is disconnected. The operating mode of the V2H system 13 is also displayed in the V2H mode information 36.

[0027] With connector 13C connected to socket 14S of EV14, when the user touches the [Manual Charge] button 31, the PCS control circuit 11C responds to the operation and starts charging the onboard battery. Also, when the [Automatic Drive] button 32 is touched, the PCS control circuit 11C responds to the operation and starts charging and discharging the onboard battery in the mode set on the operation screen (not shown). When the [Charge from Stationary Battery] button 33 is touched, the PCS control circuit 11C responds to the operation and starts charging the onboard battery 14B from the stationary battery 12B. On the other hand, when the [Discharge to Stationary Battery] button 34 is touched, the PCS control circuit 11C responds to the operation and starts discharging the onboard battery 14B to the stationary battery 12B. The PCS control circuit 11C selectively displays the [Manual Charge] button 31 and the two buttons [Charge from Stationary Battery] button 33 and [Discharge to Stationary Battery] button 34. When the power control system 10 is operating in grid-connected mode, the [Manual Charge] button 31 is displayed, but the [Charge from Stationary Battery] button 33 and the [Discharge to Stationary Battery] button 34 are not displayed. On the other hand, when the power control system 10 is operating independently, the [Charge from Stationary Battery] button 33 and the [Discharge to Stationary Battery] button 34 are displayed, but the [Manual Charge] button 31 is not displayed.

[0028] The [Charge from Stationary Battery] button 33 and the [Discharge to Stationary Battery] button 34 are intended to be operated when the power grid 15 is experiencing a power outage and the power control system 10 is operating independently. Specifically, the [Charge from Stationary Battery] button 33 is intended for use when electricity generated by the solar power generation system 11 during the daytime while the system is operating independently is stored in the stationary battery 12B, and that electricity is then supplied to the EV 14. The [Discharge to Stationary Battery] button 34 is intended for use when the EV 14 is moved to an area without a power outage to charge the on-board battery 14B, and then the EV 14 is connected to the V2H system 13 to supply the electricity stored in the on-board battery 14B to the stationary battery 12B.

[0029] Furthermore, if the connector latch 13L is locked and the [EV Disconnect] button 35 is touched, the PCS control circuit 11C responds to the operation by stopping the charging and discharging of the onboard battery 14B as appropriate and unlocking the connector latch 13L.

[0030] ≪V2H System Control≫ Next, we will describe the charging and discharging process of the onboard battery 14B, which is performed by the PCS control circuit 11C of the V2H system 13 in accordance with user instructions via the V2H operation screen described above and the state of the onboard battery. Figure 4 is an explanatory diagram showing an example of the charging and discharging process performed by the PCS control circuit 11C of the V2H system shown in Figure 1. In this embodiment, the charging and discharging process is controlled using the charge rate [%] as the charge amount of the onboard battery 14B, but it may also be controlled using the stored energy [kWh].

[0031] In Figure 4, the three horizontal divisions indicate the types of user instructions or settings via the V2H operation screen. The leftmost division shows the state of discharging from the on-board battery 14B. This state corresponds to when the [Discharge to Stationary Battery] button 34 is operated to receive a discharge instruction, or when the [Automatic Driving] button 32 is operated to receive a discharge instruction from the PCS control circuit 11C during automatic driving. The center division shows the state of charging the on-board battery 14B. This state corresponds to when the [Manual Charging] button 31 or the [Charge from Stationary Battery] button 33 is operated to receive a charging instruction, or when the [Automatic Driving] button 32 is operated to receive a charging instruction from the PCS control circuit 11C during automatic driving.

[0032] The far right indicates the state where automatic driving is set. When automatic driving is set, the PCS control circuit 11C issues charging and discharging instructions according to the situation. Therefore, it indicates that the state will be either discharged (far left) or charged (center) according to the instructions. When automatic driving is set, the PCS control circuit 11C performs charging and discharging of the on-board battery in the mode set on the operation screen (not shown). For example, in the automatic driving mode shown in Figure 4, during the day, if there is surplus power, charging is performed with surplus power, and if there is no surplus power, power is supplied (discharged) to the power-using equipment. At night, charging is performed from the power grid. Here, a situation where there is surplus power is when the power generated by solar power generation exceeds the power consumption of the power-using equipment 16, and the excess power is surplus power. The power generated by solar power generation is preferentially supplied to the power-using equipment 16, and the surplus power is either used to charge the stationary battery 12B or the on-board battery 14B, or sold to the power grid 15. In this operating mode, the surplus power is used to charge the on-board battery 14B. A situation where there is no surplus power is one in which the power generated by solar power generation is less than the power consumed by the power-using equipment 16. The power generated by solar power generation is preferentially supplied to the power-using equipment 16, and any power shortage is supplied to the power-using equipment 16 by discharging from the stationary battery 12B or the vehicle-mounted battery 14B, or by purchasing power from the power grid 15. In this operating mode, any power shortage is supplied to the power-using equipment 16 by discharging from the vehicle-mounted battery 14B. As a different operating mode, a mode that prioritizes selling surplus power during the daytime when there is a surplus power may be set. The automatic operation mode is not essential, so further explanation is omitted.

[0033] In Figure 4, the vertical axis represents the charge level of the onboard battery 14B, with higher values ​​indicating a greater charge level. A charge level of 100% corresponds to a fully charged state, while a charge level of 0% corresponds to an empty state of the onboard battery 14B. The onboard charge / discharge control circuit 14C of the EV14 stores predetermined upper and lower charge limits for the EV14. For example, the lower charge limit is 15%, and the upper charge limit is 95%. When the EV14 is connected to the V2H system 13 via connector 13C, the onboard charge / discharge control circuit 14C transmits this information to the V2H system 13. The V2H system 13 uses the information received from the EV14 to charge and discharge the onboard battery 14B according to a predetermined sequence. Here, the upper limit of the charge rate may be considered as a fully charged state of 100%, and the lower limit of the discharge rate may be considered as a completely discharged state of 0%. For example, the charge rate displayed on the remote controller 11R may be displayed as 100% (fully charged) when the charge rate is 95%, and as 0% when the charge rate is 15%.

[0034] The sequence described above stipulates that when the vehicle's battery charge level exceeds the upper limit charge level, charging of the vehicle's battery will stop and the connector latch 13L will be unlocked. Furthermore, when the vehicle's battery charge level falls below the lower limit discharge charge level, discharging of the vehicle's battery will stop and the connector latch 13L will be unlocked. Therefore, if the vehicle's battery charge level reaches the upper limit charge level during charging, the connector latch 13L will be unlocked, preventing further charging of the vehicle's battery. Similarly, if the vehicle's battery charge level reaches the lower limit discharge charge level during discharging, the connector latch 13L will be unlocked, preventing further discharging of the vehicle's battery.

[0035] Even if the discharge of the on-board battery is stopped, if time passes without charging the on-board battery 14B while the EV14 is connected to the V2H system 13, the charge level of the on-board battery 14B will gradually decrease due to natural discharge, etc. If the charge level is slightly above the minimum discharge charge level and left uncharged, it may eventually fall below the minimum discharge charge level. The PCS control circuit 11C of the V2H system 13 sequentially acquires the state of the on-board battery 14B of the EV14 connected via the connector 13C. The state of the on-board battery 14B acquired by the PCS control circuit 11C also includes the EV-SOC. SOC stands for State of Charge and generally refers to the charge level of the battery. When the EV-SOC (charge level) falls below the minimum discharge charge level, the PCS control circuit 11C stops the discharge of the on-board battery 14B and unlocks the connector latch 13L according to the sequence described above. When unlocked, charging and discharging of the onboard battery 14B cannot be resumed unless the user inputs a connection command to the system again, connecting connector 13C to EV14. However, especially in scenarios where autonomous driving is enabled, the connection between EV14 and the V2H system 13 is maintained, and power is exchanged between EV14 and the V2H system 13, with surplus power used for charging when there is surplus power, discharge when there is no surplus power, and charging from the power grid. Therefore, if the connection between connector 13C and EV14 is disconnected, the opportunity for charging and discharging of the onboard battery 14B is lost. Furthermore, the CHAdeMO standard prohibits EV14 from transitioning from a disconnected state to a connected state without a connection command from the user, which would inconvenience the user. Therefore, it is desirable to avoid a state where the connection between connector 13C and EV14 is disconnected.

[0036] Therefore, in this embodiment, the PCS control circuit 11C performs charge and discharge control according to the EV-SOC so that the charge level of the onboard battery 14B does not fall below the minimum discharge charge level when the EV 14 is connected to the V2H system 13. When the PCS control circuit 11C obtains the minimum discharge charge level from the EV 14, it sets a discharge stop threshold that is 5% greater than the minimum discharge charge level. In the example shown in Figure 4, the discharge stop threshold is a charge level of 20%, which is 5% greater than the minimum discharge charge level. This value is just an example. Preferably, the PCS control circuit 11C further sets a priority charge threshold that is 1% greater than the minimum discharge charge level but smaller than the discharge stop threshold. In the example shown in Figure 4, the priority charge threshold is a charge level of 16%, which is 1% greater than the minimum discharge charge level and 4% smaller than the discharge stop threshold. This value is also just an example.

[0037] Then, when the onboard battery 14B is in a discharge state, i.e., the state shown on the far left of Figure 4, the PCS control circuit 11C performs the following processing according to the EV-SOC. First, when the EV-SOC is below the upper charge limit and above the discharge stop threshold, i.e., in the discharge processing area 41 shown in Figure 4, the onboard battery 14B is discharged. However, when the EV-SOC falls below the discharge stop threshold, i.e., in the standby processing area 42 shown in Figure 4, the discharge is stopped. The system then enters a standby state where neither charging nor discharging occurs. On the other hand, when the onboard battery 14B is in a charging state, i.e., the state shown in the center of Figure 4, the PCS control circuit 11C charges the onboard battery 14B if the EV-SOC is below the upper charge limit. Charging is performed not only when the EV-SOC is above the discharge stop threshold, but also when it is below the discharge stop threshold. In other words, in the charging processing area 43 shown in Figure 4, the onboard battery 14B is charged.

[0038] In a preferred embodiment, the PCS control circuit 11C charges the onboard battery 14B even when discharging is in progress, if the EV-SOC falls below the priority charging threshold while in the discharge state shown on the far left of Figure 4. Similarly, charging is performed when the EV-SOC falls below the priority charging threshold while in the charging state shown in the center of Figure 4. The state in which the charge rate of the onboard battery 14B falls below the priority charging threshold corresponds to the priority charging processing area 44 shown in Figure 4. When the charge rate of the onboard battery 14B drops to the priority charging processing area 44, charge and discharge control of the onboard battery 14B is performed. By performing this control, even if the connection between the EV 14 and the V2H system 13 is maintained for several days, and the discharge state shown on the far left of Figure 4 continues for a long time, for example due to the setting of automatic driving, the charge rate of the onboard battery 14B is controlled so that it does not drop to the lower limit of discharge charge rate during that time.

[0039] Flowchart An example of the charge / discharge process performed by the PCS control circuit 11C described above will be explained using a flowchart. Figures 5 and 6 are flowcharts showing an example of the charge / discharge process of the on-board battery 14B performed by the PCS control circuit 11C shown in Figure 1. As shown in Figure 5, when a connection instruction is input to the system by the user, the PCS control circuit 11C performs a predetermined sequence for connector connection to establish communication with the on-board charge / discharge control circuit 14C (step S11). As part of this sequence, information including the lower limit discharge charge rate and the upper limit charge charge rate for the on-board battery 14B is obtained from the on-board charge / discharge control circuit 14C. The determination in step S13 of Figure 5 will be described later. User input of a connection instruction includes button operation on the remote controller 11R, and the CHAdeMO standard prohibits the EV14 from transitioning from a disconnected state to a connected state without a user connection instruction.

[0040] Next, the state of the on-board battery 14B, including its charge rate at that time, i.e., the EV-SOC, is obtained from the on-board charge / discharge control circuit 14C (step S17). Then, it is determined whether or not it is time to discharge the on-board battery (step S19). The situation in which it is time to discharge the on-board battery refers to the state shown on the far left of Figure 4. That is, when the [Discharge to Stationary Battery] button 34 is touched and the discharge process from the on-board battery 14B to the stationary battery 12B is being performed, or when the [Automatic Driving] button 32 is touched and the PCS control circuit 11C has instructed the system to discharge during automatic driving.

[0041] If the situation does not warrant discharging the onboard battery (No in step S19), the PCS control circuit 11C then determines whether or not the situation warrants charging the onboard battery (step S21). The situation warranting charging the onboard battery refers to the state shown in the center of Figure 4. That is, when the [Manual Charging] button 31 or the [Charging from Stationary Battery] button 33 is touched and charging from the stationary battery 12B is in progress, or when the [Automatic Driving] button 32 is touched and the PCS control circuit 11C has instructed the vehicle to charge during automatic driving. The processing when the result of the determination in step S21 is Yes and the processing when the result is No will be described later.

[0042] If the determination in step S19 indicates that the vehicle battery should be discharged (Yes in step S19), then it is determined whether the charge level is above the discharge stop threshold (step S35 shown in Figure 6). Here, the discharge stop threshold is a threshold calculated by the PCS control circuit 11C by adding a predetermined charge level to the lower limit discharge charge level obtained from the EV 14 in a predetermined sequence related to the processing in step S11, as described above. The state in which the charge level of the vehicle battery 14B is above the discharge stop threshold corresponds to the discharge processing area 41 shown in Figure 4. If the charge level is above the discharge stop threshold (Yes in step S35), the PCS control circuit 11C controls the EV converter 13D to start or continue discharging from the vehicle battery 14B (step S37). Then, the process returns to step S13 shown in Figure 5, and it is determined whether the connection between the connector 13C and the EV 14 can be continued. If it is determined that the connection between connector 13C and EV14 cannot be maintained (No in step S13), the PCS control circuit 11C executes a predetermined sequence for disconnecting the connector (step S15) and terminates the process. The state in which the connection between connector 13C and EV14 cannot be maintained is, for example, the state in which the charge rate of the onboard battery 14B has reached the aforementioned lower discharge charge rate. On the other hand, if it is determined that the connection between connector 13C and EV14 can be maintained (Yes in step S13), the PCS control circuit 11C repeats the process from step S17 onwards described above.

[0043] If, as determined in step S35, the charge rate is not equal to or greater than the discharge stop threshold (No. in step S35), the PCS control circuit 11C then compares the charge rate with the discharge lower limit charge rate (step S39). However, in a preferred embodiment, the charge rate is compared with the priority charge threshold instead of the discharge lower limit charge rate. The preferred embodiment is shown by a dashed line in Figure 6. Here, the priority charge threshold is a threshold smaller than the discharge stop threshold, calculated by the PCS control circuit 11C by adding a predetermined charge rate to the discharge lower limit charge rate obtained from the EV14 in a predetermined sequence related to the processing in step S11, as described above. The state in which the charge rate of the onboard battery 14B is greater than the priority charge threshold and less than or equal to the discharge stop threshold corresponds to the standby processing area 42 shown in Figure 4.

[0044] If the determination in step S39 is that the charge level is below the minimum discharge charge level, the PCS control circuit 11C controls the EV converter 13D to charge the onboard battery 14B (step S41). Then, the process returns to step S13 as shown in Figure 5. On the other hand, if the determination is that the charge level is greater than the minimum discharge charge level (No in step S39), that is, if the charge level is below the discharge stop threshold but above the minimum discharge charge level, the PCS control circuit 11C controls the EV converter 13D to stop discharging from the onboard battery 14B (step S43). Then, the process returns to step S13 as shown in Figure 5.

[0045] In a preferred embodiment, if the determination in step S39 determines that the charge rate is below the priority charging threshold, charging of the on-board battery 14B is initiated (step S41). That is, charging is started before the charge rate of the on-board battery 14B drops to the lower discharge limit charge rate. The state in which the charge rate of the on-board battery 14B is below the priority charging threshold corresponds to the priority charging processing area 44 shown in Figure 4. On the other hand, if it is determined that the charge rate is greater than the priority charging threshold (No in step S39), that is, if the charge rate is below the discharge stop threshold but greater than the priority charging threshold, the PCS control circuit 11C controls the EV converter 13D to stop discharging from the on-board battery 14B (step S43). Then, the process returns to step S17 shown in Figure 5. The state in which the charge rate of the on-board battery 14B is below the discharge stop threshold and greater than the priority charging threshold corresponds to the standby processing area 42 shown in Figure 4.

[0046] If the determination in step S21 of Figure 5 above indicates that the vehicle battery 14B should be charged (Yes in step S21), the PCS control circuit 11C determines whether the charge level of the vehicle battery 14B is below the upper limit charge level (step S23). If the charge level is not below the upper limit charge level (No in step S23), the PCS control circuit 11C controls the EV converter 13D to stop charging the vehicle battery 14B and put it into standby mode (step S25). Then, the process returns to step S13. On the other hand, if the determination in step S23 indicates that the charge level is below the upper limit charge level (Yes in step S23), the PCS control circuit 11C controls the EV converter 13D to start or continue charging the vehicle battery 14B (step S27). Then, the process returns to step S13. The state in which the charge level of the vehicle battery 14B is below the upper limit charge level corresponds to the charging processing area 43 shown in Figure 4.

[0047] On the other hand, if the determination in step S21 above determines that it is not a situation in which the onboard battery 14B should be charged (No in step S21), that is, if it is determined that the system is in a standby state where neither discharge nor charge is performed, the PCS control circuit 11C proceeds to step S39 shown in Figure 6. That is, the charge rate of the onboard battery 14B is continuously monitored during standby, and charging is started when it falls below the discharge lower limit charge rate. In a preferred embodiment, charging is started when the charge rate during standby falls below the priority charging threshold. The above is an example of the charge and discharge process performed by the PCS control circuit 11C.

[0048] (Embodiment 2) Embodiment 1 described an example in which the power control system 10 includes a stationary battery storage system 12, but this invention is not limited to that embodiment. The invention is similarly applicable to embodiments in which the power control system 10 does not include a stationary battery storage system 12, but includes a solar power generation system 11 and a V2H system 13. Furthermore, even in the case of a power control system 10 that does not include a solar power generation system 11, the PCS control circuit 11C can control the charging and discharging of the on-board battery 14B as shown in Figure 4. Alternatively, even in the case where neither the solar power generation system 11 nor the stationary battery storage system 12 is included, but only a V2H system 13 is provided, the PCS control circuit 11C can control the charging and discharging of the on-board battery 14B as shown in Figure 4.

[0049] (Embodiment 3) In Embodiment 1, a configuration was shown in which discharge control was performed by setting a first charge level higher than the lower limit charge level so that the charge level of the on-board battery 14B would not fall below the lower limit charge level. Similarly, the upper limit charge level may also be set to a third charge level lower than that, and charge control may be performed. That is, when the PCS control circuit 11C is charging the on-board battery 14B shown in the center of Figure 4, charging may be stopped if the EV-SOC reaches the third charge level or higher. The system may then be put into standby mode. When the on-board battery 14B exceeds the upper limit charge level, the PCS control circuit 11C unlocks the connector latch 13L according to the sequence, so this configuration controls charging to stop when the charge level approaches the upper limit charge level to prevent it from being unlocked.

[0050] As stated above, (i) The electric vehicle charging and discharging system according to the present invention comprises a connector for connecting to an electric vehicle, an EV charging and discharging circuit for charging and discharging an on-board battery of the electric vehicle while the connector is connected to the electric vehicle, and a charging and discharging control circuit for controlling the EV charging and discharging circuit, wherein the charging and discharging control circuit acquires information from the electric vehicle including a minimum discharge charge amount which is the lower limit value at which discharge from the on-board battery is permitted, successively acquires the charge amount of the on-board battery and compares it with a discharge stop threshold which is a predetermined value greater than the minimum discharge charge amount, and stops discharging from the on-board battery when it is determined that the charge amount acquired during discharge from the on-board battery is less than or equal to the discharge stop threshold.

[0051] In this invention, the connector is for connecting an electric vehicle charging / discharging system to an electric vehicle to charge and discharge the vehicle's onboard battery, and includes a power line for charging and discharging the onboard battery and a communication line for communicating about charging and discharging between the electric vehicle and the power line. Specific examples include connectors conforming to standards such as CHAdeMO, GB / T, and Tesla. Each standard specifies not only the physical specifications of the connector but also the communication and power transmission procedures during connection and disconnection. Furthermore, the EV charging / discharging circuit is a circuit for charging and discharging the on-board battery. The EV converter in the aforementioned embodiment corresponds to the EV charging / discharging circuit of this invention. Furthermore, the charge / discharge control circuit is a circuit that controls the EV charge / discharge circuit. The charge / discharge control circuit sends charging, discharging, and standby instructions to the EV charging circuit. The PCS control circuit in the above-described embodiment may correspond to the charge / discharge control circuit of this invention. Standards such as CHAdeMO require that when the charge level of an on-board battery installed in an electric vehicle falls below the minimum discharge charge level, the discharge of the on-board battery be stopped and the connection between the connector and the electric vehicle is disconnected. In this invention, since the discharge is stopped at a charge level greater than the minimum discharge charge level, the disconnection of the connector and the electric vehicle can be avoided and the connection between the connector and the electric vehicle can be maintained.

[0052] Furthermore, preferred embodiments of this invention will be described. (ii) The charge / discharge control circuit may sequentially acquire the charge amount of the on-board battery while it is discharging, in standby mode, or charging the on-board battery, compare it with a priority charge threshold that is greater than the lower limit charge amount and less than the discharge stop threshold, and charge the on-board battery when the acquired charge amount is less than or equal to the priority charge threshold. According to this embodiment, the on-board battery is charged when its charge level falls below a priority charging threshold that is greater than the minimum discharge charge level. This allows for stable maintenance of the connection between the power control system and the EV without requiring any user intervention. Furthermore, even if the discharge of the on-board battery is stopped when its charge level is slightly above the minimum discharge charge level, leaving it uncharged could eventually cause the charge level to fall below the minimum discharge charge level. However, since the on-board battery is charged when its charge level falls below a priority charging threshold that is greater than the minimum discharge charge level, the charge level can be maintained above the minimum discharge charge level.

[0053] (iii) The connector has a communication line for communicating with the electric vehicle and a connector latch for fixing and releasing the physical connection with the electric vehicle, and the charge / discharge control circuit may communicate with the electric vehicle, fix the connector latch, and then perform a discharge, and stop the discharge and release the connector latch when the amount of charge obtained from the onboard battery falls below the lower limit of discharge charge. According to this embodiment, when the charge level falls below the minimum discharge charge level, the discharge from the onboard battery is stopped and the connector latch is released (set to an unlocked state). However, since the discharge from the onboard battery is stopped when it is determined that the charge level of the onboard battery is below the minimum discharge charge level, the release of the connector latch (set to an unlocked state) can be avoided.

[0054] (iv) One aspect of the present invention comprises the above-mentioned electric vehicle charging and discharging system, a solar module for solar power generation, a grid connection unit connected to a power grid, and an equipment connection unit to which power-using equipment is connected, wherein the charging and discharging control circuit includes a power control system that controls the charging and discharging control circuit to charge the on-board battery with the surplus power generated by the solar power generation. Here, surplus power refers to the power generated by solar power generation minus the power supplied to power-using equipment. In the above embodiment, the distribution board corresponds to both the grid connection section and the equipment connection section.

[0055] (v) The charge / discharge control circuit may charge the on-board battery with power from the power grid. According to this embodiment, the vehicle's battery can be reliably charged not only with surplus electricity generated by solar modules but also with electricity from the power grid. When charging the vehicle's battery with electricity from the power grid, the charging may be set to take place during times when electricity rates are set lower.

[0056] (vi) The charge / discharge control circuit may supply power from the onboard battery to the power-using equipment via the equipment connection section when no surplus power is generated by solar power generation. According to this embodiment, when no surplus power is generated, the amount of electricity purchased from the power grid can be reduced by supplying power from the onboard battery to power-consuming equipment.

[0057] (vii) The power control system according to this invention may further include a stationary battery for storing power, a stationary battery charge / discharge circuit for charging and discharging the stationary battery, and a stationary battery charge / discharge control circuit for sending instructions related to charging and discharging to the stationary battery charge / discharge circuit to control the charging and discharging of the stationary battery.

[0058] (viii) One aspect of the present invention includes an electric vehicle charging and discharging system comprising a connector for connecting an electric vehicle, an EV charging and discharging circuit for charging and discharging an on-board battery of an electric vehicle while the connector is connected to the electric vehicle, and a charging and discharging control circuit for controlling the charging and discharging of an on-board battery of an electric vehicle, the charging and discharging system comprising the steps of: obtaining information from the electric vehicle, including a minimum discharge charge amount which is the minimum value at which discharge from the on-board battery is permitted, while the charging and discharging connector is connected to the electric vehicle; sequentially obtaining the charge amount of the on-board battery and comparing it with a discharge stop threshold which is a predetermined value greater than the minimum discharge charge amount; and stopping the discharge from the on-board battery and putting it into standby mode when it is determined that the charge amount obtained during discharge from the on-board battery is less than or equal to the discharge stop threshold. In other words, a charging and discharging control circuit for an EV that charges and discharges an on-board battery of an electric vehicle while a connector for connecting to the electric vehicle is connected to the electric vehicle includes the steps of: acquiring information from the electric vehicle including a minimum discharge charge amount, which is the lower limit value at which discharge from the on-board battery is permitted; successively acquiring the charge amount of the on-board battery and comparing it with a discharge stop threshold that is a predetermined value greater than the minimum discharge charge amount; and stopping the discharge from the on-board battery when it is determined that the charge amount acquired during discharge from the on-board battery is less than or equal to the discharge stop threshold.

[0059] The embodiments of this invention also include combinations of any of the embodiments described above. In addition to the embodiments described above, various modifications of this invention are possible. These modifications should not be considered outside the scope of this invention. This invention should encompass the meaning of the claims and equivalents, as well as all of the aforementioned modifications. [Explanation of Symbols]

[0060] 10: Power control system, 11: Solar power generation system, 11P: Power conditioner, 11C: PCS control circuit, 11D: Solar power converter, 11R: Remote controller, 11S: Solar module, 11V: Bidirectional inverter, 12: Stationary battery storage system, 12B: Stationary battery, 12D: Battery converter, 13: V2H system, 13C: Connector, 13D: EV converter, 13L: Connector latch, 14: EV, 14B: On-board battery, 14C: On-board charge / discharge control circuit, 14S: Socket, 15: Power grid, 15B: Distribution board, 16: Power-consuming equipment, 17: HEMS controller, 17D: Information equipment, 17R: Router, 17S: HEMS server, 20: Top screen, 21: Solar power generation information display area, 22: V2H information display area, 23: Stationary battery information display area, 24: Power consumption / sales power display area, 25: [V2H operation] button, 30: V2H operation screen, 31: [Manual charging] button, 32: [Automatic operation] button, 33: [Charge from stationary battery] button, 34: [Discharge to stationary battery] button, 35: [Disconnect EV] button, 36: V2H mode information, 41: Discharge processing area, 42: Standby processing area, 43: Charging processing area, 44: Priority charging processing area

Claims

1. A connector for connecting to an electric vehicle, With the connector connected to the electric vehicle, an EV charge / discharge circuit performs charging and discharging of the electric vehicle's onboard battery, The system includes a charge / discharge control circuit that controls the aforementioned EV charge / discharge circuit, The aforementioned charge / discharge control circuit is Information including the discharge limit charge amount, which is the lower limit value at which discharge from the on-board battery is permitted, is obtained from the electric vehicle. A charging and discharging system for electric vehicles that sequentially acquires the charge amount of the on-board battery and compares it with a discharge stop threshold that is a predetermined value greater than the discharge lower limit charge amount, and stops discharging from the on-board battery when it is determined that the charge amount acquired during discharge from the on-board battery is less than or equal to the discharge stop threshold, and charges the on-board battery when it is determined that the charge amount acquired is greater than the discharge lower limit charge amount and less than the discharge stop threshold, and charges the on-board battery.

2. The connector has a communication line for communicating with the electric vehicle, and a connector latch for fixing and releasing the physical connection with the electric vehicle. The charge / discharge control circuit communicates with the electric vehicle, controls the discharge after fixing the connector latch, stops the discharge and releases the connector latch when the amount of charge obtained from the on-board battery falls below the lower limit of discharge charge, according to claim 1.

3. A charging and discharging system for electric vehicles according to claim 1 or 2, Solar modules related to solar power generation, A grid connection part that connects to the power grid, It includes an equipment connection section to which power-consuming equipment that uses electricity is connected, The charge / discharge control circuit is a power control system that controls the charging of the vehicle's battery with surplus power generated by solar power generation when such surplus power is generated.

4. The power control system according to claim 3, wherein the charge / discharge control circuit charges the on-board battery with power from the power grid.

5. The power control system according to claim 3, wherein the charge / discharge control circuit supplies power from the vehicle battery to the power-using equipment via the equipment connection section when no surplus power is generated by solar power generation.

6. Stationary batteries for storing electricity, A charging and discharging circuit for a stationary battery that performs charging and discharging of the aforementioned stationary battery, The stationary battery charge / discharge control circuit further comprises sending instructions related to charging and discharging to the aforementioned stationary battery charge / discharge circuit to control the charging and discharging of the stationary battery. The power control system according to claim 3.

7. A charge / discharge control circuit for EVs that charges and discharges the onboard battery of an electric vehicle, while a connector for connecting to an electric vehicle is connected to the electric vehicle, The steps include obtaining information from the electric vehicle, including the discharge limit charge amount, which is the lower limit value at which discharge from the on-board battery is permitted, The steps include sequentially acquiring the charge amount of the on-board battery and comparing it with a discharge stop threshold that is a predetermined value greater than the discharge lower limit charge amount, The steps include stopping the discharge from the vehicle battery when it is determined that the amount of charge acquired during the discharge from the vehicle battery is less than or equal to the discharge stop threshold, A step of comparing the discharge lower limit charge amount with a priority charge threshold that is greater than the discharge stop threshold, A method for charging and discharging an electric vehicle, comprising the step of charging the vehicle battery when it is determined that the amount of charge acquired during discharge from the vehicle battery is less than or equal to the priority charging threshold.

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