JP7801682B2 - Charging and discharging system - Google Patents

Description

This disclosure relates to a charging and discharging system for electric vehicles.

In recent years, electric vehicles (EVs), plug-in hybrid vehicles (PHVs), and other electrically powered vehicles have become increasingly popular. Accordingly, V2H (Vehicle to Home) devices for transferring electricity between electric vehicles and homes have also become increasingly popular.

One example of a power conversion system with V2H equipment is the multi-input power conversion system shown in Figure 2 (details will be described later). Multiple DC power sources (vehicle storage batteries, solar cells, stationary storage batteries) are connected to a high-voltage DC bus via their respective DC/DC converters, and then to a grid-connected bidirectional inverter. During grid-connected operation, power generated by the solar cells is supplied to, for example, loads outside the inverter or to stationary storage batteries connected via the DC bus. It is also possible to perform peak-shift operation, whereby the stationary storage batteries are charged from the commercial power grid (hereinafter simply referred to as the grid) at night when electricity rates are low, and discharged during the day when household load consumption increases.

Each converter controls the input and output of power between each DC power source (vehicle battery, solar cell, stationary battery) and the DC bus. The inverter controls the input and output of power between the grid and the DC bus. Power is controlled in the desired direction through coordinated or distributed control of these controls.

The power conversion system with V2H shown in Figure 2 complies with the V2H Guidelines (Guidelines for Charging and Discharging Systems for Electric Vehicles, V2H DC Edition, EVPS-002) (hereafter simply referred to as the V2H Guidelines) established by the CHAdeMO Council. By using the drive battery of an electric vehicle as a stationary storage battery, it can assist in the supply of power to the household load by charging surplus electricity or discharging when the household load increases.

In addition to the main circuit, the electric vehicle and EV power conversion equipment share the signal and communication lines specified in the V2H guidelines. A sequence circuit is also installed in the EV power conversion equipment, and sequence control is performed to handle operation requests, charging and discharging, and operation shutdown.

It's important to note that, unlike stationary batteries, when using a drive battery for an electric vehicle, the drive battery and the main circuit of the EV power conversion device are only electrically connected after sequence control has been completed by the EV power conversion device. In other words, the drive battery for an electric vehicle and the main circuit of the EV power conversion device are not electrically connected via a contactor (relay) until sequence control has progressed to a certain extent. This is because, unlike stationary batteries, the connection between the drive battery for an electric vehicle and the EV power conversion device is not fixed and must be connected by the end user using a movable cable. Therefore, the connection is made only after safety verification is performed to ensure the reliability of the electrical connection and to check for short circuits, ground faults, etc. In other words, unlike stationary batteries, the drive battery for an electric vehicle cannot be used to power the start-up power of the EV power conversion device. EV power conversion devices basically need to be started using power within a power conversion system with V2H (which can be power taken from the grid).

When the grid is healthy, or when power can be received from solar cells or stationary storage batteries even during a power outage, there is no problem starting up the power conversion equipment for EVs. In contrast, if the entire power conversion system including V2H loses power (when there is a power outage and power cannot be received from solar cells or stationary storage batteries, hereafter referred to as a total power loss state for the system), startup power cannot be obtained from the drive batteries of the electric vehicles. Therefore, problems arise when starting up the power conversion equipment for EVs.

This type of total power loss typically occurs during long-term power outages following disasters such as typhoons or heavy snowfall. During long-term power outages following disasters, stationary storage batteries are likely to become depleted. Furthermore, bad weather can easily cause solar panels to run out of power. Even in such environments, a V2H power conversion system that allows an electric vehicle to disconnect from the power conversion system, drive itself to a non-disaster area, charge its drive storage battery, then drive itself back to the power conversion system and connect to it offers a significant advantage in terms of resilience. It goes without saying that it can also accept electric vehicles from outside the non-disaster area as emergency power sources.

In order to start up an EV power conversion device in a total power loss situation, possible methods include installing a start-up battery within the power conversion device or drawing accessory power from the accessory socket of the electric vehicle. Accessory power is supplied from an auxiliary battery (e.g., a 12V lead-acid battery) installed in the electric vehicle separately from the drive battery.

Patent Document 1 discloses a method for starting a power conversion system with V2H equipment during a power outage when the power conversion system does not have a power source, by using the vehicle's auxiliary battery as the startup power source. This corresponds to the use example of a vehicle's auxiliary battery established in the V2H guidelines. However, Patent Document 1 assumes that startup power will be drawn from the auxiliary battery installed in the electric vehicle (hereinafter referred to as the oncoming vehicle) that is equipped with the drive storage battery to be connected.

As an example of a circuit configuration recommended in the V2H guidelines, an external startup power supply input cable (hereinafter referred to as the external power supply cable) is shown to connect the accessory socket of an electric vehicle to the external startup power supply input unit (hereinafter referred to as the external power supply input unit) of the power conversion system (hereinafter referred to as the charge/discharge system, as appropriate) (see Figure 3 (details will be explained later)). The external power supply cable does not have a negative wire, and the vehicle ground and the charge/discharge system ground are connected via the ground wire of the charge/discharge cable.

When an oncoming vehicle and the charging/discharging system are connected via a charging/discharging cable, completing sequence control, including turning on the first relay D1 and the second relay D2, enables charging/discharging operation in the main circuit. When an oncoming vehicle is connected via an external power cable to extract startup power from the oncoming vehicle's auxiliary battery to activate the sequence circuit, if the vehicle's ground and the external input are connected via the negative conductor of the external power cable, if the ground conductor running through the charging/discharging cable is disconnected due to damage to the charging/discharging cable, the negative conductor of the external power cable will act as a bypass ground conductor. As a result, the safety stop function provided in the signal circuit and sequence in the V2H guidelines will not function on either the charging/discharging system side or the vehicle side, resulting in a design that fails to meet the shutdown requirements based on the detection of a disconnected ground conductor. For this reason, the system is designed not to connect the vehicle's ground and the external input side via the negative conductor of the external power cable. In other words, the safety stop functions of turning off the first relay D1 and the second relay D2 and turning off the operation permission signal are based on the assumption that there is a single ground conductor.

JP 2017-143710 A

There may be cases where it is not possible to draw power from the auxiliary battery of an oncoming vehicle. For example, this may occur if the oncoming vehicle does not come equipped with an accessory socket that outputs 12V accessory power as standard, or if the accessory socket is equipped but cannot be used with the charge/discharge connector connected (when using CHAdeMO for charging and discharging). Furthermore, in bad weather conditions such as a typhoon that causes a total power loss, it can be difficult to connect an external power cable to the accessory socket inside the vehicle, remove the external power cable from a window or door, and connect it to the charge/discharge system.

To address these issues, one possible solution is to draw power from an accessory socket on a vehicle other than the oncoming vehicle, or from a portable power source capable of outputting 12V. Hereinafter, in this specification, devices other than the oncoming vehicle that can supply power to the charging/discharging system from an external source, including vehicles other than the oncoming vehicle, as well as portable power sources and generators other than those in the vehicle, will be collectively referred to as "non-oncoming vehicles."

As mentioned above, assuming a circuit configuration in which the vehicle's accessory socket and the charging/discharging system's external power input are not connected with a negative wire, even if an external power cable is connected to an external power source other than that of an oncoming vehicle, the negative pole will not be conductive, so no current will flow and power cannot be extracted.

However, if a negative wire is added to the external power cable, when power is drawn from the auxiliary battery of an oncoming vehicle, the generation of sneak current and the multiplexing of ground wires will prevent proper detection of breaks in the ground wire running through the charge/discharge cable, resulting in a design that does not comply with the V2H guidelines.

This disclosure has been made in light of these circumstances, and its purpose is to provide a charging/discharging system that can extract startup power from an external power source other than an auxiliary battery installed in the vehicle that is equipped with the drive storage battery to be connected, and that does not impede the safety shutdown function of the sequence circuit.

In order to solve the above problems, one aspect of the charging/discharging system disclosed herein is a charging/discharging system capable of charging/discharging a drive battery of an electric vehicle via a charge/discharge cable, and includes a DC/DC converter for charging/discharging the drive battery, a sequence circuit for executing a charge/discharge sequence with the electric vehicle, a control unit for controlling the DC/DC converter and the sequence circuit, an external power input unit for receiving power from an external source, and a control power generation unit that generates control power to be supplied to the sequence circuit and the control unit based on power obtained from the power line to which the DC/DC converter is connected or from the external power input unit. The charging/discharging system is designed so that when an external power cable is connected to the external power input unit, the ground wire between the electric vehicle and the system is not duplicated during charging/discharging.

This disclosure makes it possible to realize a charging/discharging system that can extract startup power from an external power source other than an auxiliary battery installed in a vehicle equipped with a drive storage battery to be connected, and that does not impede the safety shutdown function of the sequence circuit.

1 is a diagram for explaining a first example of a configuration of a charging/discharging device according to an embodiment; FIG. 10 is a diagram for explaining a second example of the configuration of the charging/discharging device according to the embodiment. 1 is a diagram showing the internal configuration of an electric vehicle and a charging/discharging device according to a first embodiment; FIG. 10 is a diagram showing the internal configuration of an electric vehicle and a charging/discharging device according to a second embodiment. FIG. 1 is a diagram illustrating a first example of a configuration of a sneak current prevention circuit. FIG. 10 is a diagram illustrating a second example of the configuration of a sneak current prevention circuit. FIG. 10 is a diagram illustrating an example of the location of a current detection circuit provided in a sequence circuit. FIG. 10 is a diagram illustrating a third example of a configuration of a sneak current prevention circuit. 9A and 9B are diagrams showing a first example of the configuration of an external power cable. FIG. 10 is a diagram illustrating a second example of the configuration of an external power cable.

(Configuration Example 1)
1 is a diagram illustrating a first example configuration of a charging/discharging device 10 according to an embodiment. The charging/discharging device 10 is a V2H device for connecting an electric vehicle 20 with a power receiving point of a grid 2 within a home or a load 4. The charging/discharging device 10 has a charging/discharging interface and sequence that comply with the V2H guidelines.

The charging/discharging device 10 includes a DC/DC converter 11, an inverter 12, a sequence circuit 13, and a control unit 14. The DC/DC converter 11 and the inverter 12 form the main power circuit. The charging/discharging device 10 and the electric vehicle 20 are connected by a DC charging/discharging cable 30. The charging/discharging cable 30 has a charging/discharging connector that connects to the sequence circuit 13 and the main power circuit, and is fixedly connected to the charging/discharging device 10. A gun connector 30a is attached to the end of the charging/discharging cable 30; the user connects the charging/discharging device 10 and the electric vehicle 20 by inserting the gun connector 30a into the inlet of the electric vehicle 20.

One end of the DC/DC converter 11 is connected to the electric vehicle 20 via a charge/discharge cable 30, and the other end of the DC/DC converter 11 is connected to the inverter 12. The DC/DC converter 11 is a bidirectional DC/DC converter for charging and discharging the drive battery mounted on the electric vehicle 20.

The inverter 12 is a bidirectional inverter connected between the DC/DC converter 11 and the distribution board 3. The inverter 12 converts the DC power input from the DC/DC converter 11 into AC power and outputs the converted AC power to the distribution board 3. The distribution board 3 is connected to the grid 2 and the load 4. The load 4 is a general term for the loads within the home. The inverter 12 can also convert the AC power supplied from the grid 2 via the distribution board 3 into DC power and output the converted DC power to the DC/DC converter 11.

The sequence circuit 13 is a circuit for executing a charge/discharge sequence with the electric vehicle 20, and is a circuit that complies with the V2H guidelines. The sequence circuit 13 includes signal circuits and communication circuits for operating the start/stop, power amount, current direction, etc. of the drive battery mounted on the electric vehicle 20 while handshaking. The control unit 14 controls the entire charging/discharging device 10 in an integrated manner. The detailed configurations of the sequence circuit 13 and control unit 14 will be described later.

(Configuration Example 2)
2 is a diagram illustrating a second configuration example of the charging/discharging device 10 according to the embodiment. In the first configuration example, the charging/discharging device 10 includes the inverter 12 and is directly connected to the distribution board 3, but in the second configuration example, the charging/discharging device 10 does not include the inverter 12 and is connected to the distribution board 3 via a hybrid power storage system (also referred to as a generation/storage linked system). The charging/discharging device 10 and the hybrid power storage system are DC-coupled to form a power conversion system having a charge/discharge interface and sequence that comply with the V2H guidelines.

The hybrid power storage system includes a solar cell 6, a stationary storage battery 7, and a power conversion device 40. The power conversion device 40 is a power conditioner for the solar cell 6 and the stationary storage battery 7, and includes a DC/DC converter 41 for the solar cell 6, a DC/DC converter 42 for the stationary storage battery 7, an inverter 43, and a control unit 44.

The solar cell 6 includes multiple solar cell modules (solar panels) connected in series. Each solar cell module includes multiple solar cell modules connected in series. The solar cell utilizes the photovoltaic effect to directly convert light energy into DC power. Solar cell types that can be used include heterojunction solar cells, polycrystalline silicon solar cells, single-crystalline silicon solar cells, thin-film silicon solar cells, and compound solar cells.

The solar cell 6 is connected to a DC/DC converter 41 and outputs the generated power to the DC/DC converter 41. The DC/DC converter 41 is connected between the solar cell 6 and the DC bus Bdc and adjusts the voltage of the DC power output from the solar cell 6 and outputs it to the DC bus Bdc. For example, it may be configured as a step-up chopper.

The stationary storage battery 7 is capable of charging and discharging DC power and includes a storage battery such as a lithium-ion storage battery, a nickel-metal hydride storage battery, or a lead-acid battery. Instead of a storage battery, a capacitor such as an electric double-layer capacitor or a lithium-ion capacitor may also be included.

The stationary storage battery 7 is connected to a DC/DC converter 42, and charging and discharging are controlled by the DC/DC converter 42. The DC/DC converter 42 is a bidirectional DC/DC converter connected between the stationary storage battery 7 and the DC bus Bdc.

The inverter 43 is a bidirectional inverter connected between the DC bus Bdc and the distribution board 3. The inverter 43 can convert DC power input from the DC bus Bdc into AC power and output the converted AC power to the distribution board 3. The inverter 43 can also convert AC power supplied from the system 2 via the distribution board 3 into DC power and output the converted DC power to the DC bus Bdc. In addition, during a power outage, the inverter 43 can convert DC power input from the DC bus Bdc into AC power and output it to the AC outlet 5 in an autonomous manner.

The control unit 44 provides overall control of the power conversion device 40. The control unit 44 can be realized by a combination of hardware and software resources, or by hardware resources alone. Hardware resources can include analog circuits, logic circuits, microcontrollers, DSPs, ROMs, RAMs, ASICs, FPGAs, and other LSIs. Software resources can include programs such as firmware.

The control unit 44 can perform MPPT (Maximum Power Point Tracking) control of the DC/DC converter 41 so that the output power of the solar cell 6 is maximized. The control unit 44 generates a voltage command value to maximize the output power of the solar cell 6 based on the relationship between the output voltage and output power of the solar cell 6.

The control unit 44 searches for the maximum output operating point, for example, by changing the operating voltage in predetermined step widths using a hill-climbing method. Specifically, the control unit 44 generates a voltage command value to shift the current operating voltage toward the higher voltage side on the low-voltage side of the maximum output operating point of the solar cell module's P-V curve, and generates a voltage command value to shift the current operating voltage toward the lower voltage side on the high-voltage side of the maximum output operating point. Once the maximum output operating point is captured, the control unit 44 generates a voltage command value to maintain the maximum output operating point. The DC/DC converter 41 performs switching operation in response to a drive signal based on the generated voltage command value.

The control unit 44 controls the DC/DC converter 42 to charge and discharge the stationary storage battery 7. The DC/DC converter 42 performs constant current (CC) discharge, constant voltage (CV) discharge, constant current charging, or constant voltage charging of the stationary storage battery 7 based on the current command value or voltage command value set by the control unit 44. When operating the stationary storage battery 7 to track at least one of the power generation amount of the solar cell 6 and the power consumption amount of the load 4, the control unit 44 generates a current command value for the DC/DC converter 42 according to the voltage of the DC bus Bd.

The control unit 44 controls the inverter 43 as its basic control so that the voltage of the DC bus Bdc maintains a target value. Specifically, the control unit 44 detects the voltage of the DC bus Bdc and generates a current command value to match the detected bus voltage to the target value. If the voltage of the DC bus Bdc is higher than the target value, the control unit 44 generates a current command value to increase the output power of the inverter 43, and if the voltage of the DC bus Bdc is lower than the target value, the control unit 44 generates a current command value to decrease the output power of the inverter 43. The inverter 43 performs switching operation in response to a drive signal based on the generated current command value.

It is desirable to set the target voltage of DC bus Bdc to a value higher than and close to the voltage of system 2. The smaller the difference between the input voltage and output voltage of inverter 43, the higher the conversion efficiency of inverter 43. For example, if the voltage of system 2 is AC 200V, the target voltage of DC bus Bdc is set to approximately DC 330-360V.

The control unit 44 of the power conversion device 40 and the control unit 14 of the charging/discharging device 10 are connected by a communication line. The control unit 44 of the power conversion device 40 can transmit a current command value or a voltage command value for charging/discharging the drive storage battery installed in the electric vehicle 20 to the control unit 14 of the charging/discharging device 10.

In Figure 2, the charging/discharging device 10 is shown connected to the distribution board 3 via a hybrid power storage system, but it may also be connected to the distribution board 3 via a solar power generation system (not including the stationary storage battery 7 and DC/DC converter 42) rather than a hybrid power storage system. It may also be connected to the distribution board 3 via a power storage system (not including the solar cell 6 and DC/DC converter 41).

Figure 3 shows the internal configuration of an electric vehicle 20 and a charging/discharging device 10 according to the first embodiment. The electric vehicle 20 includes a drive battery 21, a control unit 22, an auxiliary battery 23, a contactor Rc, a drive relay Rd, an inlet 26, an accessory socket 27, and a vehicle-side sequence circuit. The vehicle-side sequence circuit includes a first photocoupler PC1, a second photocoupler PC2, a transistor Q1, a first resistor R1 to a fourth resistor R4, a connection detection circuit 24, and a CAN (Controller Area Network) communication unit 25. Figure 3 shows only the components of the electric vehicle 20 that are related to charging and discharging the drive battery 21.

In addition to the DC/DC converter 11, sequence circuit 13, and control unit 14, the charging/discharging device 10 further includes a control power supply generation unit 15, an external power supply input unit 16, and an operation unit 18. The sequence circuit 13 includes a first relay D1, a second relay D2, a third photocoupler PC3, a fifth resistor R5, a sixth resistor R6, a connection detection circuit 13a, and a CAN communication unit 13b. The control unit 14 includes a connection control unit 14a and a charging/discharging control unit 14b.

The control unit 22 of the electric vehicle 20 and the control unit 14 of the charging/discharging device 10 can each be realized by a combination of hardware and software resources, or by hardware resources alone. Hardware resources can include analog circuits, logic circuits, microcontrollers, DSPs, ROMs, RAMs, ASICs, FPGAs, and other LSIs. Software resources can include programs such as firmware.

The connection control unit 14a controls the charge/discharge sequence between the charging/discharging device 10 and the electric vehicle 20 via the charge/discharge cable 30. The charge/discharge control unit 14b controls charging/discharging between the drive storage battery 21 mounted on the electric vehicle 20 and the in-home power source or load 4. For example, the charge/discharge control unit 14b can set a current command value in the DC/DC converter 11 to control the charging current to the drive storage battery 21 or the discharging current from the drive storage battery 21.

The drive battery 21 is a rechargeable battery containing multiple cells, and is primarily used as a power source for driving the traction motor. The cells may be lithium-ion battery cells, nickel-metal hydride battery cells, or other types of cells. Capacitors such as electric double-layer capacitors and lithium-ion capacitors may also be used instead of batteries. It is also possible to use a power source that can only discharge, such as a fuel cell or Stirling engine, or a combination of these power sources and the drive battery 21. When the electric vehicle 20 and the charging/discharging device 10 are connected by the charging/discharging cable 30, the drive battery 21 is connected to the DC/DC converter 11 of the charging/discharging device 10 via the contactor Rc.

The auxiliary battery 23 is a power source that primarily supplies power to the auxiliary equipment within the electric vehicle 20, and is typically a 12V lead battery. Meanwhile, the 12V DC voltage used by the sequence circuit 13 on the charging/discharging device 10 side is generated by the control power supply generation unit 15.

The control power supply generation unit 15 includes a first buck converter, a boost converter, and a second buck converter. In the case of configuration example 1 of the charging/discharging system, the first buck converter steps down the voltage obtained from the power line L0 (specifically, the voltage obtained from the high-voltage DC bus between the inverter 12 and the DC/DC converter 11, the high-voltage DC circuit between the electric vehicle 20 and the DC/DC converter 11, or the AC circuit on the grid 2 side of the parallel-off relay provided in the inverter 12) to generate a control voltage (e.g., a DC voltage of 25 V). In the case of configuration example 2 of the charging/discharging system, the first buck converter steps down the voltage obtained from the power line L0 (specifically, the voltage obtained from the high-voltage DC bus Bdc between the inverter 43 and the DC/DC converter 11, the high-voltage DC circuit between the electric vehicle 20 and the DC/DC converter 11, or the AC circuit on the grid 2 side of the parallel-off relay provided in the inverter 43) to generate a control voltage (e.g., a DC voltage of 25 V).

When the accessory socket 27 of the electric vehicle 20 and the external power input unit 16 of the charging/discharging device 10 are connected via an external power cable 50, the boost converter boosts the 12V DC voltage supplied from the auxiliary battery 23 to generate a control voltage (e.g., 23V DC voltage). The second buck converter steps down the control voltage supplied from the first buck converter or boost converter to 12V DC voltage. The control power generation unit 15 supplies the 12V DC voltage to the sequence circuit 13.

The control power supply generation unit 15 also includes another step-down converter that steps down the voltage to a DC voltage other than 12V. For example, if 5V is used as the power supply voltage for the control unit 14, the step-down converter generates a 5V DC voltage and supplies it to the control unit 14.

In the case of configuration example 1 of the charging/discharging system, when the system is connected to the grid, startup power is obtained from outside the inverter 12, and in response to a user's driving request (such as operating a button on the operation unit 18), the inverter 12 starts up, and then the DC/DC converter 11 and sequence circuit 13 start up. The sequence circuit 13 starts a sequence with the sequence circuit of the electric vehicle 20, and partway through the sequence, the contactor Rc of the electric vehicle 20 closes and the main circuit of the charging/discharging device 10 becomes conductive. From this state, power can be drawn from the DC bus between the inverter 12 and DC/DC converter 11, or from the DC circuit between the electric vehicle 20 and the DC/DC converter 11.

In the case of configuration example 2 of the charging/discharging system, when the system is connected to the grid, startup power is obtained from outside the inverter 43. In response to a user's driving request (such as a button operation on the operation unit 18), the inverter 43 starts up and controls the boost of the DC bus Bdc. As a result, the charging/discharging device 10 draws power from the DC bus Bdc, and the DC/DC converter 11, sequence circuit 13, and control unit 14 start up. The sequence circuit 13 starts a sequence with the sequence circuit of the electric vehicle 20, and the contactor Rc of the electric vehicle 20 closes midway through the sequence, bringing the main circuit of the charging/discharging device 10 into conduction. From this state, power can also be drawn from the DC circuit between the electric vehicle 20 and the DC/DC converter 11. Note that a control power line can be connected from the housing of the power conversion device 40 to the housing of the charging/discharging device 10, and the charging/discharging device 10 can be started up using power supplied via the control power line.

In both charging/discharging system configuration examples 1 and 2, if power is taken in from a high-voltage DC bus or DC circuit, even if a voltage drop or power outage occurs in system 2, the control power supply can be maintained with power from the distributed DC power sources (solar cells 6, stationary storage battery 7, drive storage battery 21). Therefore, the power conversion and protection functions of charging/discharging device 10 can be safely controlled.

The charge/discharge cable 30 connecting the electric vehicle 20 and the charge/discharge device 10 includes a power line L0, a first operation start/stop line L1, a second operation start/stop line L2, a connector connection confirmation line L3, an operation enable/disable line L4, a ground line L5, and a CAN communication line L6. The CAN communication line L6 is composed of a twisted pair wire.

The basic circuit configuration and sequence of the sequence circuit 13 are defined in the V2H guidelines.

The first operation start/stop line L1 is a signal line used by the charging/discharging device 10 to notify the electric vehicle 20 of a request to start operation, and by the electric vehicle 20 receiving the notification to start its own charge/discharge sequence. Specifically, the first operation start/stop line L1 connects the control power supply (12V DC) generated by the control power supply generation unit 15 of the charging/discharging device 10 to the ground of the electric vehicle 20 via the first relay D1 on the charging/discharging device 10 side, and the first resistor R1 and the diode of the first photocoupler PC1 on the electric vehicle 20 side. The transistor of the first photocoupler PC1 is connected to the control unit 22, which can detect whether the diode of the first photocoupler PC1 (i.e., the first operation start/stop line L1) is conductive.

The second operation start/stop line L2 is a signal line that notifies the electric vehicle 20 of a request to start charging/discharging from the charging/discharging device 10, and allows the electric vehicle 20 to receive the notification and determine whether to close the contactor Rc. In addition, it is used to open the contactor Rc in response to a request to stop operation from the charging/discharging device 10.

The second operation start/stop line L2 connects the branch point between the first relay D1 and first resistor R1 of the first operation start/stop line L1 to the ground of the charging/discharging device 10 via the diode of the second photocoupler PC2 and the second resistor R2 on the electric vehicle 20 side, and the second relay D2 on the charging/discharging device 10 side. The transistor of the second photocoupler PC2 is connected to the control unit 22, which can detect whether the diode of the second photocoupler PC2 (i.e., the second operation start/stop line L2) is conductive.

Both ends of the drive coil of contactor Rc are connected to the first operation start/stop line L1 and the second operation start/stop line L2, respectively. A drive relay Rd is connected between the drive coil and the second operation start/stop line L2.

The connector connection confirmation line L3 is a signal line used primarily on the electric vehicle 20 side to detect whether the connector is connected to prevent the vehicle from accidentally starting while the charging/discharging connector is connected. Note that the charging/discharging device 10 side may also detect whether the connector is connected.

The connector connection confirmation line L3 connects the auxiliary battery 23 of the electric vehicle 20 to the ground of the charging/discharging device 10 via a connection detection circuit 24 and a third resistor R3 on the electric vehicle 20 side, and a fifth resistor R5 and a connection detection circuit 13a on the charging/discharging device 10 side. The connection detection circuit 24 on the electric vehicle 20 side can be composed of a photocoupler, for example. The transistor of the photocoupler is connected to the control unit 22. The control unit 22 can determine whether or not there is a physical and electrical connection between the electric vehicle 20 and the charging/discharging device 10 by detecting whether or not the diode of the photocoupler (i.e., the connector connection confirmation line L3) is conductive.

The connection detection circuit 13a on the charging/discharging device 10 side can be composed of, for example, a photocoupler. The transistor of the photocoupler is connected to the connection control unit 14a. The connection control unit 14a can determine whether or not there is a physical and electrical connection between the electric vehicle 20 and the charging/discharging device 10 by detecting whether or not the diode of the photocoupler (i.e., the connector connection confirmation line L3) is conductive. Note that the connection detection circuit 13a on the charging/discharging device 10 side can be omitted.

The operation permission/prohibition line L4 is a signal line that is used by the electric vehicle 20 to notify the charging/discharging device 10 of operation permission or operation prohibition while driving based on the first photocoupler PC1 and the vehicle status (shift position, power-on mode, battery status, etc.).

Operation permission/prohibition line L4 connects the control power supply (12V DC) generated by control power supply generation unit 15 of charging/discharging device 10 to the ground of electric vehicle 20 via the diode of third photocoupler PC3 and sixth resistor R6 on the charging/discharging device 10 side, and via fourth resistor R4 and transistor Q1 on the electric vehicle 20 side. Control unit 22 can control the conduction/non-conduction of operation permission/prohibition line L4 by controlling the on/off of transistor Q1.

The CAN communication line L6 connects the CAN communication unit 25 on the electric vehicle 20 side to the CAN communication unit 13b on the charging/discharging device 10 side, and is a communication line used to exchange specification values, status values, etc. between the electric vehicle 20 and the charging/discharging device 10.

The ground line L5 serves as a common ground line for the various signal lines mentioned above. On the electric vehicle 20 side, it is connected to the negative potential of the auxiliary battery 23 (the same potential as the chassis ground) and the control power ground of the sequence circuit. On the charging/discharging device 10, it is connected to the control power ground and protective ground line of the sequence circuit 13.

The V2H guidelines require that if the ground line L5 is broken, the electric vehicle 20 and the charging/discharging device 10 each passively detect this and stop charging/discharging operations. They also require that a pseudo-ground line not be formed. If a pseudo-ground line is formed, a detour path for various signals will be created even if the ground line L5 is broken, leading to malfunctions.

For example, when the first relay D1 and the second relay D2 are closed, if the ground line L5 is disconnected but a pseudo-ground line is formed, current flows through the first operation start-stop line L1 and the second operation start-stop line L2, and the operation permitted state continues. Also, when the transistor Q1 is on, if the ground line L5 is disconnected but a pseudo-ground line is formed, current flows through the operation permit/prohibit line L4, and the current-carrying state continues. In other words, the electric vehicle 20 determines that the operation permitted state continues, and the charging/discharging device 10 also determines that the operation permitted state continues, resulting in neither of them determining to stop.

The external power supply input unit 16 of the charging/discharging device 10 is an inlet for obtaining startup power from the auxiliary battery 23 of the electric vehicle 20 or other external power sources in the event that all distributed power sources, including the emergency storage battery in the power conversion system, and the grid 2 are lost. The accessory socket (accessory power socket) 27 of the electric vehicle 20 is a 12V supply interface commonly used in vehicles.

The external power cable 50 is a detachable cable that can be attached to both the electric vehicle 20 and the charging/discharging device 10, and is used to start the charging/discharging device 10 in emergencies such as power outages. By connecting the external power input unit 16 and the accessory socket 27 of the electric vehicle 20 with the external power cable 50, startup power for the charging/discharging device 10 can be drawn from the auxiliary battery 23 of the electric vehicle 20 in emergencies.

The external power input unit 16 is not a required element in the V2H guidelines, but is optional. The V2H guidelines assume that the accessory socket 27 and the external power input unit 16 will be connected using only the positive wire. This is thought to be intended to prevent the negative wire between the accessory socket 27 and the external power input unit 16 from becoming a pseudo-ground wire and providing a detour path for various signals. In Example 1, this requirement can be met by using an external power cable 50b with a non-conductive negative pole as shown in Figure 9(b) (described below), or an external power cable 50 with a switchable negative pole as shown in Figure 10 (described below).

The connection control unit 14a controls the signal reading, signal setting, and CAN communication transmission and reception in the sequence circuit 13 according to a specified sequence. The charge/discharge control unit 14b controls the DC/DC converter 11 and sequence circuit 13 according to each step of the sequence, and controls the charging and discharging of the drive storage battery 21. In configuration example 1 shown in Figure 1, the charge/discharge control unit 14b can also control the inverter 12.

Figure 4 is a diagram showing the internal configuration of an electric vehicle 20 and a charging/discharging device 10 according to a second embodiment. In the second embodiment, any type of external power cable 50 may be used. The positive and negative poles of the external power input unit 16 are coupled to the control power generation unit 15 via a sneak current prevention circuit 17. In this way, the sneak current prevention circuit 17 is connected between the external power input unit 16 and the sneak current prevention circuit 17, preventing the formation of a pseudo-ground line between the electric vehicle 20 and the charging/discharging device 10.

The negative pole of the sneak current prevention circuit 17 is connected to ground via at least one of a rectifier circuit or a switch (a switchgear (relay), semiconductor switch, etc.). The ground potential is the same as the potential of the ground line L5 and also the same potential as the chassis ground of the electric vehicle 20. The positive pole of the sneak current prevention circuit 17 is connected to the control power supply generation unit 15 via at least one of a rectifier circuit or a switch.

As described above, the control power generation unit 15 is designed so that, when power can be obtained from the power line L0, the power from the power line L0 takes priority over the power from the external power input unit 16. When power cannot be obtained from the power line L0, the control power generation unit 15 generates startup power for the charging/discharging device 10 using power from the external power input unit 16.

Figure 5 shows a first configuration example of the sneak current prevention circuit 17. A first rectifier circuit is connected to the positive line, and a second rectifier circuit is connected to the negative line. The first and second rectifier circuits are circuits that restrict the direction of current. In the example shown in Figure 5, a first diode Di1 is used as the first rectifier circuit, and a second diode Di2 is used as the second rectifier circuit.

The first diode Di1 inserted into the positive line of the sneak current prevention circuit 17 has its anode connected to the positive pole of the external power supply input unit 16 and its cathode connected to the positive pole of the control power supply generation unit 15, and rectifies the current flowing through the positive line of the sneak current prevention circuit 17 so that it flows from an external power supply such as the drive storage battery 21 toward the charge/discharge device 10.

The second diode Di2 inserted in the negative line of the sneak current prevention circuit 17 has its anode connected to the negative pole of the control power supply generation unit 15 and its cathode connected to the negative pole of the external power supply input unit 16, and rectifies the current flowing in the negative line of the sneak current prevention circuit 17 so that it flows from the charge/discharge device 10 to an external power supply such as the drive storage battery 21.

This prevents the formation of a pseudo-ground line between the electric vehicle 20 and the charging/discharging device 10 (current returning from the electric vehicle 20 to the charging/discharging device 10 in the ground line). It also prevents the generation of sneak current, which would cause current to flow from the control power supply generation unit 15 through an unintended path and cause the sequence circuit 13 to malfunction. Configuration example 1 of the sneak current prevention circuit 17 has a simple circuit configuration and can be implemented at low cost.

Figure 6 shows a second configuration example of the sneak current prevention circuit 17. A first switch RY1 is connected to the positive line, and a second switch RY2 is connected to the negative line. The control unit 14 controls at least one of the first switch RY1 or the second switch RY2 to open under conditions or conditions in which a pseudo-ground line or sneak current circuit may occur. By opening the current path, the path of the pseudo-ground line or sneak current circuit can be reliably blocked.

The control unit 14 may open at least one of the first switch RY1 and the second switch RY2 when multiple power sources are present that may generate a pseudo-ground line or sneak circuit, i.e., immediately after the main circuit of the charging/discharging device 10 is started up.

If a dual-drive relay is used for the first switch RY1 and the second switch RY2, the first switch RY1 and the second switch RY2 can only simultaneously control the positive and negative poles. On the other hand, if two single-drive relays are used for the first switch RY1 and the second switch RY2, the first switch RY1 and the second switch RY2 can be individually controlled for each pole.

In an emergency, the user connects one end of the external power cable 50 to the external power input unit 16 of the charging/discharging device 10 and the other end of the external power cable 50 to the accessory socket 27 of the electric vehicle 20 (oncoming vehicle). The user operates the power switch or the like of the electric vehicle 20 to extract 12V power from the accessory socket 27. In addition, the user connects the charging/discharging cable 30 to the inlet 26 of the electric vehicle 20 to enable charging and discharging operations between the electric vehicle 20 and the charging/discharging device 10.

The control power generation unit 15 of the charging/discharging device 10 is powered by an external power supply connected via the external power cable 50. When the control power generation unit 15 is powered by the 12V voltage supplied from the external power supply, the necessary power supply is secured for the control unit 14, and the microcomputer and operation unit 18 (including buttons, pilot lamps, displays, etc.) required for starting up the charging/discharging device 10 become operational. When the pilot lamp lights up, indicating that the device is now operational, the user can easily tell that it is operational. At this time, the ground wire L5 of the charging/discharging cable 30 and the negative wire of the external power cable 50 are both at the same potential, essentially resulting in a dual-ground state for the electric vehicle 20.

The control unit 14 of the charging/discharging device 10 receives a power supply voltage from the control power generation unit 15 and closes the first relay D1 to notify the electric vehicle 20 of a request to start operation. Upon receiving the request to start operation, the control unit 22 on the electric vehicle 20 conducts the operation permission/prohibition line L4 to permit operation. The control unit 14 of the charging/discharging device 10 closes the first relay D1 to notify the electric vehicle 20 of a request to operate charging/discharging. Upon receiving the request to start operation, the control unit 22 on the electric vehicle 20 closes the contactor Rc to supply power from the drive battery 21 to the main circuit.

As a result, power is supplied from power line L0 to control power generation unit 15, which then steps down this power to generate 12V control power. It is at this point (the point at which power line L0 becomes conductive) that control power appears on both the electric vehicle 20 and the charging/discharging device 10 sides, forming a circuit that makes it impossible to stop charging and discharging. Therefore, when contactor Rc is closed in the sequence and control power is secured, control unit 14 opens first switch RY1 and second switch RY2, preventing the formation of a pseudo-ground wire or sneak circuit.

Note that the charging/discharging device 10 cannot be started from an external power source unless the first switch RY1 and the second switch RY2 are closed before startup. Therefore, normally closed relays are used for the first switch RY1 and the second switch RY2. Before external power is supplied to the charging/discharging device 10, the microcomputer in the control unit 14 is not started, so a normally closed relay must be used. A normally closed relay is closed in a standby state where no current flows through the drive coil.

In addition, once the contactor Rc is closed and control power can be secured from the main circuit, the external power source is disconnected, and power is not continuously supplied from the auxiliary battery 23 after the charge/discharge state is entered, preventing over-discharge of the auxiliary battery 23 (i.e., dead battery). The same applies when connected to an external power source installed in an oncoming vehicle.

In this way, by disconnecting the external power supply as soon as control power can be secured from the main circuit, it is possible to reliably cut off the path of the pseudo-ground wire or sneak circuit at the required timing. Furthermore, it is possible to prevent overlooking a ground wire break during high-voltage charging/discharging. It is also possible to prevent unnecessary battery drain.

In another control example, the control unit 14 opens the first switch RY1 when multiple power sources that may generate a pseudo-ground wire or sneak circuit are present, i.e., immediately after starting up the main circuit of the charging/discharging device 10. The control unit 14 determines whether the connection is to an oncoming vehicle or a non-oncoming vehicle based on the user's startup operation, and, depending on the determination result, immediately after startup, decides whether to keep the second switch RY2 closed or open it.

When the connection destination is a non-oncoming vehicle, there is no connection process between the non-oncoming vehicle and the charging/discharging device 10 in the sequence circuits of both, so even if there are multiple power sources, a bypass circuit that could lead to malfunction is not formed. Therefore, there is little need to open the negative pole immediately after startup. Furthermore, until the control power supply generation unit 15 generates 12V control power, if there is no connection to the external power supply of the non-oncoming vehicle, the microcomputer in the control unit 14 will stop and the sequence will not be able to continue. When the connection destination is a non-oncoming vehicle, there is no particular need to open the second switch RY2, so it may remain closed, or it may be opened at the same time as the positive pole.

On the other hand, if the connection is with an oncoming vehicle, the switch is immediately opened by the user's activation operation. For example, the operation unit 18 is provided with an identification button or interface such as "Start operation with startup power from oncoming vehicle" or "Start operation with startup power from non-oncoming vehicle." If the user selects "Start operation with startup power from oncoming vehicle" between the time external power is taken in and the start of operation, the control unit 14 opens the second switch RY2.

When the second switch RY2 is opened, the ground wire L5 of the charge/discharge cable 30 is used as the single ground wire. This means that a break in the single ground wire L5 can be detected immediately after the sequence starts, before the charge/discharge state is reached, allowing for a safer shutdown if the ground wire L5 is broken. This allows for earlier detection of a break in the single ground wire L5 than when a dual-drive relay is used and the first switch RY1 and second switch RY2 are controlled simultaneously.

Furthermore, in an operating environment where the negative pole is always closed, unnecessary power consumption from the external power supply and battery drain can be prevented by opening the first switch RY1 when the control power supply generation unit 15 is started. After the main circuit is started, the control power supply can be generated using power from the power line L0, so there is no problem even if the external power supply is disconnected. In addition, costs can be reduced because the current detection circuit and current sensor described below are not required. Furthermore, since there is no time required for automatic determination processing, operation can be started quickly.

In yet another control example, the control unit 14 opens the first switch RY1 when multiple power sources that may generate a pseudo-ground wire or sneak circuit are present, i.e., immediately after the main circuit of the charging/discharging device 10 is started. The control unit 14 automatically determines whether the connection is to an oncoming vehicle or a non-oncoming vehicle, and, depending on the determination result, immediately after start-up, decides whether to keep the second switch RY2 closed or open it.

The control unit 14 determines whether the ground line is duplicated or single based on the synchronicity and magnitude of the two current changes flowing through the negative wire of the external power cable 50 and the ground wire L5 of the charge/discharge cable 30 when the control load is started (load fluctuation) when the charge/discharge device 10 is started from an external power source. The microcomputer in the control unit 14 and the operation unit 18 can be used as the control load when the charge/discharge device 10 is started. The synchronicity of the two current changes refers to the synchronicity of the currents detected by current detection circuits installed in the paths of the ground wire and the negative wire.

A state in which the ground wire is doubled refers to a state in which the external power cable 50 is connected to an oncoming vehicle and the negative wire of the external power cable 50 forms a pseudo-ground wire. A state in which the ground wire is single refers to a state in which the external power cable 50 is connected to a non-oncoming vehicle and the negative wire of the external power cable 50 does not form a pseudo-ground wire.

Figure 7 is a diagram showing an example of the installation location of the current detection circuit provided in the sequence circuit 13. In Figure 7, the first current detection circuit 19a is installed on the negative line connecting the sneak current prevention circuit 17 and the control power generation unit 15. Note that the first current detection circuit 19a may be installed anywhere on the negative line between the negative pole of the external power input unit 16 and the negative pole of the control power generation unit 15 (the ground potential of the sequence circuit 13). The second current detection circuit 19b is installed on the ground line L5.

The current detection circuit need only be able to detect the current level, and does not need to be a current sensor. The current detection circuit may be composed of, for example, a shunt resistor or Hall element, a current-to-voltage conversion circuit, and a comparator. For example, the comparator outputs a low level if the current flowing through the negative line or ground line L5 is greater than a certain current, and a high level if it is below that certain current. When using a current detection circuit, the circuit can be constructed with a simpler design and at lower costs than when using a current sensor.

Until the user's operation is permitted, the control unit 14 turns a relatively large load on and off. For example, it flashes the pilot lamp on the operation unit 18 to periodically switch the load on the operation unit 18 between light and heavy. The control unit 14 chronologically monitors whether the output results of the first current detection circuit 19a and the second current detection circuit 19b are high or low. If the output results of both the first current detection circuit 19a and the second current detection circuit 19b change to the expected high or low level at the same timing when the pilot lamp is controlled, the control unit 14 determines that the ground wire L5 of the charging/discharging cable 30 and the negative wire of the external power cable 50 are in a duplicated state. Changes in the output results of the first current detection circuit 19a and the second current detection circuit 19b correspond to load fluctuations on the pilot lamp.

In this way, the control unit 14 determines that the two current changes are synchronized if the difference in the timing of the changes in the output results of the first current detection circuit 19a and the second current detection circuit 19b is within a predetermined range. If the two current changes are synchronized, the control unit 14 determines that the ground wire L5 of the charge/discharge cable 30 and the negative wire of the external power cable 50 are in a duplicated state, and determines that the connection is to an oncoming vehicle.

Only one of the first current detection circuit 19a and the second current detection circuit 19b may be installed within the sequence circuit 13. In this case, the control unit 14 activates a known load in advance, and if the current is lower than the expected current, determines that the current is being shunted and that the connection is to an oncoming vehicle.

If the external power cable 50 is connected to an oncoming vehicle, the control unit 14 opens the second switch RY2. This eliminates the need for redundant ground lines even before a request to start operation of the charging/discharging device 10 is made, ensuring that sequence control can be passively stopped if the ground line L5 is broken.

Next, the user operates the operation unit 18 of the charging/discharging device 10 (for example, by pressing the "emergency discharge operation button") to request discharge operation to supply power from the drive storage battery 21 of the electric vehicle 20 to a load 4 (for example, a refrigerator, lighting, or other home appliance).

When the connection control unit 14a accepts a user operation, it turns on the first relay D1 of the sequence circuit 13 and requests the oncoming vehicle to start driving (i.e., start the vehicle-side sequence). When the control unit 22 of the electric vehicle 20 receives the request to start driving, it starts CAN communication and the specification values and status are mutually confirmed between the electric vehicle 20 and the charging/discharging device 10. If the confirmation is successful, the control unit 22 of the electric vehicle 20 makes the operation permission/prohibition line L4 conductive. When the operation permission/prohibition line L4 is conductive, the connection control unit 14a of the electric vehicle 20 turns on the second relay D2, putting the contactor Rc into a closable state, so that the charging/discharging device 10 can charge and discharge the drive storage battery 21.

When the second relay D2 is turned on, causing the second operation start/stop line L2 to become conductive, the control unit 22 of the electric vehicle 20 turns on the contactor Rc. This connects the drive storage battery 21 and the charging/discharging device 10 via a DC circuit. On the charging/discharging system side, when the power line L0 becomes conductive, the voltage of the DC bus between the DC/DC converter 11 and the inverter 12/43 rises, enabling the inverter 12/43 to operate. The charging/discharging control unit 14b controls the DC/DC converter 11 and the inverter 12/43 to perform charging and discharging operations.

When the voltage of the DC bus rises and a control voltage can be generated using power from power line L0, the control power generation unit 15 generates a control voltage to be supplied to the control unit 14 and sequence circuit 13 using power from power line L0. As described above, by making the control voltage generated from power from power line L0 higher than the control voltage generated from power from the external power source, it is possible to prevent current from flowing from the external power source to the control power generation unit 15 even when the external power cable 50 is connected. In addition, because the first diode Di1 is connected to the positive line of the sneak current prevention circuit 17, current also does not flow from the control power generation unit 15 to the auxiliary battery 23.

Furthermore, it is known that during a step in the sequence, the DC bus voltage rises and power from the power line L0 is used to generate the control power supply. Opening the first switch RY1 of the sneak current prevention circuit 17 during a specific step in the sequence also helps prevent the battery from running out due to continued connection to the auxiliary battery 23.

In the above example, the control power supply is generated using power from outside system 2 or from the DC bus, but the control power supply may also be generated using power from the DC circuit between the electric vehicle 20 and the DC/DC converter 11. In this case, the control power supply can be obtained before the voltage on the DC bus rises. In this way, power may be obtained from any position on the power line L0 as the source of the control power supply.

The above method automatically determines whether the external power cable 50 is connected to an oncoming vehicle, eliminating the need for redundant ground lines during charging and discharging operations, and eliminates this problem when a request to start driving is made. It also prevents the auxiliary battery 23 of the oncoming vehicle from running out of power.

If the external power cable 50 is connected to a non-oncoming vehicle, the control unit 14 keeps the second switch RY2 closed and accepts the user's request to start driving. This is because the ground line is not duplicated and a sneak circuit is not formed, and opening the first switch RY1 would result in a loss of control power for starting driving.

When a sequence is initiated in response to a user's request to start driving, the DC circuit between the electric vehicle's 20 drive storage battery 21 and the charging/discharging device 10 is connected, and the control power supply generation unit 15 is able to generate control power using power from the power line L0. In this state, the control unit 14 opens both the first switch RY1 and the second switch RY2. Even if the vehicle is connected to a non-oncoming vehicle via the external power cable 50, no sneak current is generated in the oncoming vehicle. However, maintaining the connection with the non-oncoming vehicle could result in the battery of the non-oncoming vehicle running out and wasteful power consumption, so the connection with the non-oncoming vehicle is terminated.

The above method makes it possible to detect a break in the single ground line L5 immediately after the sequence begins, before the charging/discharging state is reached, allowing for a safer shutdown if the ground line L5 breaks. Compared to examples where the connection is determined based on user operation to determine whether the vehicle is an oncoming or non-oncoming vehicle, the circuit design is more complex, but since no user operation is required, there is no risk of human error.

In the above example, the automatic determination of whether the external power cable 50 is connected to an oncoming vehicle or a non-oncoming vehicle is performed using a current detection circuit, but this determination may also be performed using a current sensor. In this case, a current sensor is provided on at least one of the ground wire L5 of the charge/discharge cable 30 or the negative wire of the external power cable 50.

If a current sensor is provided on the ground line L5, when the load of the operation unit 18 is operated, the control unit 14 determines that the connection is a non-oncoming vehicle if current is detected, and determines that the connection is an oncoming vehicle if no current is detected. If a current sensor is provided on the negative line of the external power cable 50, the control unit 14 determines that the connection is an oncoming vehicle if the current detected when the load of the operation unit 18 is operated is smaller than the known current, because the current is also shunted to the ground line L5. If the detected current is equal to or greater than the known current, the control unit 14 determines that the connection is a non-oncoming vehicle because the current is not shunted to the ground line L5.

When a dual-in-one-drive relay is used for the first switch RY1 and the second switch RY2, the first switch RY1 and the second switch RY2 open simultaneously. In this case, the opening timing of the second switch RY2 is delayed compared to when the first switch RY1 and the second switch RY2 are controlled individually and the second switch RY2 opens immediately after it is determined that the connected vehicle is an oncoming vehicle. In other words, the opening timing of the second switch RY2 is delayed from before the start of operation request to the point at which control power begins to be generated using power from the power line L0 just before charging and discharging begins. However, after charging and discharging begins, the redundancy of the ground line is eliminated, and a situation in which it becomes difficult to stop the charging and discharging state due to a ground line break does not occur. In this way, when a dual-in-one-drive relay is used, safety can be ensured while keeping component costs low.

Figure 8 shows configuration example 3 of the sneak current prevention circuit 17. Configuration example 3 of the sneak current prevention circuit 17 is a combination of configuration example 1 of Figure 5 and configuration example 2 of Figure 6, and can more reliably prevent sneak current between multiple power sources.

Figures 9(a) and 9(b) show a first example configuration of an external power cable 50. The external power cable 50a for non-oncoming vehicles shown in Figure 9(a) has two internal wires, a positive wire 50p and a negative wire 50n, with both the positive and negative poles conducting. The external power cable 50b for oncoming vehicles shown in Figure 9(b) has only the positive pole conducting. The user can choose between the two external power cables 50a and 50b depending on whether the connection is to an oncoming vehicle or a non-oncoming vehicle.

When connected to an oncoming vehicle using the oncoming vehicle external power cable 50b, there is no physical connection between the auxiliary battery 23 of the oncoming vehicle and the negative terminal. Note that, because making the cable diameter smaller increases the risk of damage, the cable itself is not limited to a single wire, the positive wire 50p. It is also acceptable to have a negative wire that is not electrically conductive. In any case, it is sufficient as long as the system does not electrically conduct the negative terminal. This can be determined from the standpoint of cost and durability.

The specifications and sales format for the external power cable 50a for non-oncoming vehicles and the external power cable 50b for oncoming vehicles are determined from the perspective of cost and durability. For example, if marketing data indicates that most users obtain emergency startup power from oncoming vehicles, the external power cable 50b for oncoming vehicles may be the cable that comes standard with the product, with the external power cable 50a for non-oncoming vehicles being sold separately as an option. In other words, the decision as to which is the standard product and which is the optional product can be made based on the proportion of use cases. Note that the cables and plugs of the external power cable 50a for non-oncoming vehicles and the external power cable 50b for oncoming vehicles may be color-coded to make it easier to distinguish between the two.

Providing an external power cable 50a for non-oncoming vehicles and an external power cable 50b for oncoming vehicles is the simplest way to prevent sneaking, and it easily prevents the user from accidentally doubling up the ground wire. In other words, when connecting to an oncoming vehicle, sneaking can be prevented by using an external power cable 50b that does not physically connect the negative pole of the cable itself. On the other hand, when connecting to a non-oncoming vehicle, using an external power cable 50a that has conductivity at both the positive and negative poles allows startup power to be obtained from the non-oncoming vehicle.

By providing an external power cable 50a for non-oncoming vehicles as an optional cable, the user will inevitably be able to avoid confusion when operating the operation unit 18. It is also possible to omit the automatic oncoming/non-oncoming vehicle discrimination function and the user start-driving request reception function that are implemented within the charging/discharging device 10.

Figure 10 is a diagram showing a second configuration example of the external power cable 50. In this second configuration example of the external power cable 50, two wires, a positive wire 50p and a negative wire 50n, are installed inside. The positive wire 50p is always conductive, while the negative wire 50n can be switched between conductive and non-conductive using a manual switch SW1. The manual switch SW1 may be located on the cable, on the cigarette lighter plug on the vehicle side, or on the plug on the charging/discharging device 10 side. There are no restrictions on the location of the manual switch SW1, as long as it is in a location that is easily visible so that the user does not forget to set it.

In configuration example 2 of the external power cable 50, one type of external power cable 50 can be used for both oncoming and non-oncoming vehicles. This is particularly effective when there is no marketing data indicating whether the connection destination for obtaining startup power is an oncoming vehicle or a non-oncoming vehicle.

As described above, this embodiment makes it possible to realize a charging/discharging system that can extract starting power from both oncoming and non-oncoming vehicles, does not form a pseudo-ground wire or sneak circuit, and does not impede the safe shutdown function of the sequence circuit 13.

The present disclosure has been described above based on embodiments. The embodiments are merely examples, and those skilled in the art will understand that various modifications are possible in the combination of each component and each processing process, and that such modifications are also within the scope of the present disclosure.

The configuration of Example 1 can be adopted when an environment is in place that allows the user to fully understand how to use the external power cable 50a for non-oncoming vehicles and the external power cable 50b for oncoming vehicles, or how to switch the manual switch SW1 on the external power cable 50. When this environment is in place, adopting the configuration of Example 2 can more reliably prevent the formation of a pseudo-ground wire or sneak circuit.

In addition, embodiments may be specified by the following items:

[Item 1]
A charging/discharging system (10) capable of charging/discharging a drive storage battery (21) of an electric vehicle (20) via a charging/discharging cable (30),
a DC/DC converter (11) for charging and discharging the drive storage battery (21);
a sequence circuit (13) for executing a charge/discharge sequence with the electric vehicle (20);
a control unit (14) that controls the DC/DC converter (11) and the sequence circuit (13);
an external power supply input unit (16) for receiving power from an external source;
a control power generation unit (15) that generates a control power supply to be supplied to the sequence circuit (13) and the control unit (14) based on power obtained from a power line to which the DC/DC converter (11) is connected or from the external power supply input unit (16),
A charging/discharging system (10) characterized in that, when an external power cable (50) is connected to the external power input unit (16), the grounding wire between the external power input unit (16) and the electric vehicle (20) is not duplicated during charging/discharging.
This makes it possible to prevent the formation of a pseudo-ground line or sneak circuit no matter what kind of startup power source is connected to the external power input section (16).
[Item 2]
The power supply device further includes a sneak current prevention circuit (17) connected between the external power supply input unit (16) and the control power supply generation unit (15),
The sneak current prevention circuit (17)
a first rectifier circuit (Di1) that rectifies current so that it flows from an external power source connected to the positive line via the external power cable (50) to the charge/discharge system (10);
The charging/discharging system (10) according to item 1, further comprising a second rectifier circuit (Di2) in the negative line that rectifies current so that it flows from the charging/discharging system (10) to the external power supply.
This makes it possible to prevent the formation of a pseudo-ground line or sneak circuit simply and at low cost.
[Item 3]
The power supply device further includes a sneak current prevention circuit (17) connected between the external power supply input unit (16) and the control power supply generation unit (15),
The sneak current prevention circuit (17)
2. The charging/discharging system (10) according to item 1, characterized in that it has switches (RY1, RY2) connected to the positive and negative wires, respectively.
According to this, by making it possible to open the current path, it is possible to reliably cut off the path of the pseudo-ground line or sneak circuit.
[Item 4]
Item 4. The charging/discharging system (10) according to item 3, wherein the control unit (14) turns off the switches (RY1, RY2) when the power line is electrically connected to the drive storage battery (21).
This allows the path of the pseudo-ground line or sneak circuit to be cut off at the required timing.
[Item 5]
The control unit (14)
The switch (RY1) connected to the positive line is turned off when the power line is electrically connected to the drive storage battery (21),
A switch (RY2) connected to the negative line,
When the external power source is an auxiliary battery (23) mounted on the electric vehicle (20), it is turned off when the power line is electrically connected to the drive storage battery (21),
Item 3. The charging/discharging system (10) according to item 3, characterized in that, when the external power source is an external power source other than an auxiliary battery (23) mounted on the electric vehicle (20), the charging/discharging system (10) maintains an ON state or turns OFF in synchronization with a switch connected to the positive line.
This makes it possible to detect a disconnection of the ground line (L5) immediately after the start of the charge/discharge sequence, and also prevents unnecessary battery drain in the external power supply.
[Item 6]
Item 6. The charging/discharging system (10) according to item 5, wherein the control unit (14) determines whether the external power source is an auxiliary battery (23) mounted on the electric vehicle (20) based on an output result of a current detection circuit (19 a, 19 b) provided on at least one of the ground line (L5) or the negative line, or based on a user operation.
This allows the timing to cut off the current path to be determined appropriately. When the connection destination is determined based on the output result of the current detection circuit (19a, 19b), an erroneous operation by the user does not occur.
[Item 7]
The power supply further includes a sneak current prevention circuit (17) connected between the external power supply input unit (16) and the control power supply generation unit (15),
The sneak current prevention circuit (17)
a first rectifier circuit (Di1) that rectifies current so that it flows from an external power source connected to the positive line via the external power cable (50) to the charge/discharge system (10);
a second rectifier circuit (Di2) that rectifies the current so that it flows from the charging/discharging system (10) to the negative line toward the external power supply;
Switches (RY1, RY2) connected to the positive line and the negative line, respectively;
2. The charging/discharging system (10) according to item 1, comprising:
This makes it possible to more reliably prevent the formation of a pseudo-ground line or sneak circuit.
[Item 8]
The external power cable (50)
an external power cable (50b) with an insulated negative pole to be used when the external power source for starting is an auxiliary battery (23) mounted on the electric vehicle (20);
8. The charging/discharging system (10) according to any one of items 1 to 7, characterized in that two types of external power cables (50 a) having conductive negative poles are provided to be used when the external power source is an external power source other than an auxiliary battery (23) mounted on the electric vehicle (20).
This makes it possible to prevent the formation of a pseudo-ground line or sneak circuit in a simple manner.
[Item 9]
The charging/discharging system (10) according to any one of items 1 to 7, wherein the external power cable (50) has a switch (SW1) capable of switching between conduction and non-conduction of the negative pole.
This allows one type of cable to be used with any external power source.

2 System, 3 Distribution board, 4 Load, 5 AC outlet, 6 Solar cell, 7 Stationary storage battery, 10 Charging/discharging device, 11 DC/DC converter, 12 Inverter, 13 Sequence circuit, 13a Connection detection circuit, 13b CAN communication unit, 14 Control unit, 14a Connection control unit, Bdc DC bus, 14b Charging/discharging control unit, 15 Control power generation unit, 16 External power supply input unit, 17 Sneak current prevention circuit, 18 Operation unit, 19a First current detection circuit, 19b Second current detection circuit, 20 Electric vehicle, 21 Drive storage battery, 22 Control unit, 23 Auxiliary battery, 24 Connection detection circuit, 25 CAN communication unit, 26 Inlet, 27 Accessory socket, 30 Charging/discharging cable, 40 Power conversion device, 41, 42 DC/DC converter, 43 Inverter, 44 Control unit, 50 External power cable, 50p Positive wire, 50n Negative wire, L0 Power line, L1 First operation start/stop wire, L2 Second operation start/stop wire, L3 Connector connection confirmation wire, L4 Operation enable/disable wire, L5 Ground wire, L6 CAN communication wire, D1 First relay, D2 Second relay, Rc Contactor, Rd Drive relay, PC1 First photocoupler, PC2 Second photocoupler, PC3 Third photocoupler, Q1 Transistor, R1 First resistor, R2 Second resistor, R3 Third resistor, R4 Fourth resistor, R5 Fifth resistor, R6 Sixth resistor, Di1 First diode, Di2 Second diode, RY1 First switch, RY2 Second switch, SW1 Manual switch.

Claims (8)

A charging/discharging system capable of charging/discharging a drive storage battery of an electric vehicle via a charging/discharging cable,
a DC/DC converter for charging and discharging the drive storage battery;
a sequence circuit for executing a charge/discharge sequence for the electric vehicle;
a control unit that controls the DC/DC converter and the sequence circuit;
an external power input section for receiving power from an external source by connecting an external power cable ;
a control power generation unit that generates a control power supply to be supplied to the sequence circuit and the control unit based on power obtained from a power line to which the DC/DC converter is connected or from the external power supply input unit;
a sneak current prevention circuit connected between the external power supply input unit and the control power supply generation unit ,
The sneak current prevention circuit includes:
a first rectifier circuit that rectifies a current so that the current flows from an external power supply connected to the positive line via the external power supply cable toward the charging/discharging system;
a second rectifier circuit for rectifying a current in a negative line so that the current flows from the charging/discharging system to the external power supply . A charging/discharging system capable of charging/discharging a drive storage battery of an electric vehicle via a charging/discharging cable,
a DC/DC converter for charging and discharging the drive storage battery;
a sequence circuit for executing a charge/discharge sequence for the electric vehicle;
a control unit that controls the DC/DC converter and the sequence circuit;
an external power input section for receiving power from an external source by connecting an external power cable;
a control power generation unit that generates a control power supply to be supplied to the sequence circuit and the control unit based on power obtained from a power line to which the DC/DC converter is connected or from the external power supply input unit;
a sneak current prevention circuit connected between the external power supply input unit and the control power supply generation unit,
The sneak current prevention circuit includes:
A charging/ discharging system having switches connected to the positive and negative wires, respectively. 3. The charging/discharging system according to claim 2 , wherein the control unit turns off the switch when the power line is electrically connected to the driving storage battery. The control unit
a switch connected to the positive line is turned off when the power line is electrically connected to the drive storage battery;
A switch connected to the negative line,
When the external power supply is an auxiliary battery mounted on the electric vehicle, the auxiliary battery is turned off when the power line is electrically connected to the drive storage battery,
3. The charging/discharging system according to claim 2, wherein when the external power source is an external power source other than an auxiliary battery mounted on the electric vehicle, the charging/discharging system maintains an on state or turns off in synchronization with a switch connected to the positive line . 5. The charging/discharging system according to claim 4, wherein the control unit determines whether the external power source is an auxiliary battery mounted on the electric vehicle based on an output result of a current detection circuit provided in at least one of a ground wire or the negative wire between the external power source and the electric vehicle , or based on a user operation. A charging/discharging system capable of charging/discharging a drive storage battery of an electric vehicle via a charging/discharging cable,
a DC/DC converter for charging and discharging the drive storage battery;
a sequence circuit for executing a charge/discharge sequence for the electric vehicle;
a control unit that controls the DC/DC converter and the sequence circuit;
an external power input section for receiving power from an external source by connecting an external power cable;
a control power generation unit that generates a control power supply to be supplied to the sequence circuit and the control unit based on power obtained from a power line to which the DC/DC converter is connected or from the external power supply input unit;
a sneak current prevention circuit connected between the external power supply input unit and the control power supply generation unit,
The sneak current prevention circuit includes:
a first rectifier circuit that rectifies a current so that the current flows from an external power supply connected to the positive line via the external power supply cable toward the charging/discharging system;
a second rectifier circuit that rectifies the current so that the current flows from the charging/discharging system to the negative line toward the external power supply;
switches connected to the positive and negative wires, respectively;
A charging and discharging system comprising: The external power cable may include:
an external power cable with an insulated negative pole to be used when the external power source for startup is an auxiliary battery mounted on the electric vehicle; and
7. The charging/discharging system according to claim 1, wherein two types of external power cables, each having a conductive negative pole, are provided to be used when the external power source is an external power source other than an auxiliary battery mounted on the electric vehicle. A charging/discharging system capable of charging/discharging a drive storage battery of an electric vehicle via a charging/discharging cable,
a DC/DC converter for charging and discharging the drive storage battery;
a sequence circuit for executing a charge/discharge sequence for the electric vehicle;
a control unit that controls the DC/DC converter and the sequence circuit;
an external power input section for receiving power from an external source by connecting an external power cable;
a control power supply generating unit that generates a control power supply to be supplied to the sequence circuit and the control unit based on power obtained from a power line to which the DC/DC converter is connected or from the external power supply input unit,
A charging/ discharging system characterized in that the external power cable has a switch that can switch between conductive and non-conductive states of the negative pole.