Charging system for electric vehicle, and control method of charging system for electric vehicle

Abstract

The purpose of the present invention is to provide a charging system for an electric vehicle that achieves welding detection and ground fault detection at low cost.　This charging system for an electric vehicle includes an AC / DC converter, a DC / DC converter, and a charging stand for charging an electric vehicle with an output current from the DC / DC converter, includes a switch between the DC / DC converter and the charging stand, further includes a detection substrate, and has an integrated control device that controls the DC / DC converter, the switch, and the detection substrate. The detection substrate includes a plurality of first voltage dividing resistors, and a ground point provided in the middle of the plurality of first voltage dividing resistors, and performs ground fault determination by comparing voltage differences between the plurality of first voltage dividing resistors.

Description

Electric vehicle charging system and control method for electric vehicle charging system

[0009] , , ,

[0010]

[0001] The present invention relates to an electric vehicle charging system and a control method for an electric vehicle charging system.

[0002] Centering on electric vehicles, electric vehicle chargers or electric vehicle charging systems have begun to spread widely. Along with this, the importance of safety measures for electric vehicle chargers or electric vehicle charging systems is also increasing.

[0003] Patent Document 1 discloses welding detection and ground fault detection in an electric vehicle charging device. Patent Document 2 discloses welding diagnosis of a power receiving device.

[0004] Japanese Patent Application Laid-Open No. 2015-23717 Japanese Patent Application Laid-Open No. 2020-78150

[0005] Patent Document 1 discloses welding detection circuits 41 and 42 and a ground fault detection circuit 43 in paragraph 0032 and others. And as disclosed in FIG. 5 and others, welding detection is performed by current, and ground fault detection is performed by current. In Patent Document​​​​​​​​​​​​​​An electric vehicle charging system comprising an AC / DC converter, a DC / DC converter, a charging station for charging an electric vehicle with the output current from the DC / DC converter, a switch between the DC / DC converter and the charging station, a detection board, and a control unit for controlling the DC / DC converter, the switch and the detection board, the detection board comprising a plurality of first voltage divider resistors and a ground point provided in the middle of the plurality of first voltage divider resistors, and a ground fault detection system for comparing the voltage difference between the plurality of first voltage divider resistors.

[0011] According to the present invention, it is possible to provide an electric vehicle charging system that enables welding detection and ground fault detection at low cost, and a control method for the electric vehicle charging system.

[0012] Further means and effects of the present invention will become apparent throughout the entire specification below.

[0013] This is a schematic diagram of the configuration of an electric vehicle charging system. This is an example of a ground fault detection circuit diagram. This is the current path under normal conditions in Figure 2. This is the current path under abnormal conditions in Figure 2. This is the current path under normal conditions when welding is detected. This is the current path under abnormal conditions when welding is detected. This is a circuit for detecting open circuits in protective conductors. This is the current path under normal conditions in Figure 7. This is the current path under abnormal conditions in Figure 7. This is an example of a circuit diagram that realizes ground fault detection, welding detection, and open circuit detection of protective earth conductors together. This is an example of applying the circuit diagram in Figure 10 to the charging system in Figure 1. This is an example of an inspection flowchart.

[0014] Embodiments of the present invention will be described below with reference to the drawings.

[0015] Figure 1 is a schematic diagram of the configuration of an electric vehicle charging system. Alternating current (AC) from power grid 1 is input to AC / DC converter 2 via power line 8. AC / DC converter 2 converts the AC to direct current (DC). The converted DC is supplied to DC / DC converter 4 via DC bus 9.

[0016] The AC / DC converter 2 is controlled by the AC / DC converter control device 3.

[0017] The DC / DC converter 4 converts direct current (DC) to DC using a converter or the like. The DC / DC converter 4 is controlled by the DC / DC converter control device 7. DC / DC conversion typically converts to DC of different voltages.

[0018] The DC power output from the DC / DC converter 4 is supplied to the charging station 5 via the switch 11. From the charging station 5, power for charging is supplied to the electric vehicle via the charging cable 21.

[0019] The present invention is characterized by having a detection substrate 20.

[0020] This detection board 20 can, for example, be built into the charging stand 5. It can also be built into the DC / DC converter 4, or it can be installed independently.

[0021] The AC / DC converter control device 3, the DC / DC converter control device 7, and the detection board 20 are controlled, for example, by control signals transmitted from the overall control device 12 via the signal transmission means 10.

[0022] Note that Figure 1 shows an example where multiple DC / DC converters 4 are connected in parallel. However, it also includes the case where only one DC / DC converter 4 is used.

[0023] Figure 2 is an example of a ground fault detection circuit diagram. The DC / DC converter 4 is provided with resistors R11 and R12. R11 and R12 have the same resistance value, for example, 540 kohms. One end of R11 is connected to the positive electrode wire 300, and the other end is connected to R12. One end of R12 is connected to R11, and the other end is connected to the negative electrode wire 301.

[0024] The DC / DC converter 4 and the detection board 20 are electrically connected by a positive electrode wire 300 and a negative electrode wire 301.

[0025] At the midpoint of R11 and R12, the circuit is electrically grounded to the chassis potential FG. The chassis potential FG can also be called the frame ground.

[0026] A positive electrode switch SW-P is provided in the middle of the positive electrode wire 300. A negative electrode switch SW-N is provided in the middle of the negative electrode wire 301. In Figure 1, SW-P and SW-N from Figure 2 are combined and represented as switch 11. In other words, in Figure 1, for the sake of simplicity, the combined description of both the positive and negative electrode sides is omitted. However, in reality, as shown in Figure 2, there is a positive electrode side and a negative electrode side.

[0027] The DC / DC converter 4 has a capacitor C11 between the positive electrode wire 300 and the negative electrode wire 301. For example, it has a capacitance of 150 microfarads.

[0028] The detection board 20 is provided with resistors R32 and R33. R32 and R33 have the same resistance value, for example, 10 kohms. One end of R32 is connected to the positive electrode wire 300, and the other end is connected to R33. One end of R33 is connected to R32, and the other end is connected to the negative electrode wire 301.

[0029] The midpoint between resistors R32 and R33 is electrically grounded to the chassis potential FG. The chassis potential FG can also be called the frame ground, or it can also mean functional grounding.

[0030] There are capacitors C21 before and after R32. The voltage across R32, or the voltage across capacitor C21, is called Vp. There are capacitors C22 before and after R33. The voltage across R33, or the voltage across capacitor C22, is called Vn.

[0031] In this case, a resistor R31 may be present between resistor R32 and positive electrode wire 300. Similarly, a resistor R34 may be present between resistor R33 and negative electrode wire 301.

[0032] In this case, resistors R31 and R34 should have the same resistance value. For example, 490 kΩ.

[0033] In this way, by making the values ​​of R32 and R33 sufficiently small compared to R31 and R34, for example to one-tenth or less, the values ​​of Vp and Vn can be reduced to small values ​​that are easy to measure. More preferably, by reducing them to one-twentieth or less, even more preferably to one-thirtieth or less, and practically optimally to one-fortieth or less, the values ​​of Vp and Vn can be reduced to even smaller values ​​that are easy to measure.

[0034] The reason for this large reduction is that the DC / DC converter 4 typically increases the voltage even further than the grid voltage of 100V or 200V for power supply to electric vehicles. The purpose is to achieve high-voltage, short-time charging.

[0035] Figure 3 shows the current path under normal conditions as shown in Figure 2. This explains the current path when no ground fault is present, under conditions where ground fault detection is performed.

[0036] Both the positive terminal switch SW-P and the negative terminal switch SW-N are in the ON state, i.e., they are conducting.

[0037] The DC / DC converter 4 supplies a circuit diagnostic voltage VDC between the positive electrode 300 and the negative electrode 301. In normal conditions, i.e., when there is no ground fault, current flows through the current path 100. Then, Vp and Vn have the same voltage value.

[0038] In other words, if Vp = Vn, it can be determined that the system is in a normal state and that there is no ground fault.

[0039] It should be noted that some degree of numerical variation is unavoidable in resistance values. Therefore, throughout this specification, "the same resistance value" means that the values ​​are the same within a range of variation, or that they are the same as the set value of the resistance.

[0040] Furthermore, even if R32 and R33 have the same resistance value, a small difference may occur between Vp and Vn due to variations in physical resistance values. Therefore, in practice, it is desirable to set a certain threshold and consider them identical if they fall within that threshold range. Throughout this specification, "Vp and Vn are the same" includes cases where the difference between them falls within the set threshold range.

[0041] Figure 4 shows the current path during abnormal conditions in Figure 2. It explains the current path when a ground fault occurs in the situation of detecting a ground fault.

[0042] In Figure 4, for example, it shows the case where a ground fault occurs in the DC / DC converter 4 and a short circuit occurs to the housing or other parts via the ground fault resistance R20.

[0043] The DC / DC converter 4 supplies the circuit diagnostic voltage VDC between the positive line 300 and the negative line 301. In case of an abnormality, that is, when a ground fault occurs, in addition to the current path 100, a current path 101 occurs from the midpoint between R32 and R33 via FG and then back to the DC / DC converter from the ground fault part. Therefore, Vp and Vn have different voltage values.

[0044] That is, if Vp and Vn are different, it can be determined that an abnormal state, a state where a ground fault has occurred, exists.

[0045] Note that it is inevitable that there is a certain degree of numerical variation physically in resistors. Therefore, throughout this specification, when the resistance values are the same, it means that they are the same within the range of variation or the same as the set value of the resistor.

[0046] Also, for example, even if R32 and R33 have the same resistance value, in reality, due to the physical variation of the resistance values, there may be a slight deviation between Vp and Vn. Therefore, for actual determination, it is desirable to set a certain threshold value and determine that Vp and Vn are different if it exceeds the range of that threshold value. Throughout this specification, when Vp and Vn are different, it also includes the case where the difference between the two exceeds the set threshold value range.

[0047] Also, the ground fault detection based on the principle described in Figure 4 can be detected even if it occurs at any position between the secondary side of the DC / DC converter 4 and the electric vehicle.

[0048] Figure 5 shows the current path in a normal state during welding diagnosis. As a circuit diagram, it is basically the same as Figure 2. The difference is that the switch SW - P and the switch SW - N are open, or in the OFF state.

[0049] Furthermore, the voltage VDC used for circuit diagnostics in Figure 3 is not supplied. This can also be described as the VDC output being shut off.

[0050] In the welding diagnosis shown in Figure 5, the residual voltage VDO generated by the charge accumulated in capacitor C11 is used.

[0051] If there is no welding between switches SW-P and SW-N, that is, if they are normally open or OFF, current flows through the current path 102. As can be seen from Figure 5, in this case, no current flows to the detection substrate 20. Therefore, no voltage appears in either Vp or Vn.

[0052] Therefore, by turning off switches SW-P and SW-N, and observing that neither Vp nor Vn is detected, it can be determined that no welding has occurred between switches SW-P and SW-N.

[0053] Figure 6 shows the current path during welding diagnosis, in an abnormal state. The circuit diagram is basically the same as in Figure 2. The difference is that switches SW-P and SW-N are open or OFF. To explain the difference from Figure 5, we will use the case where welding 700 occurs on SW-N as an example.

[0054] Similar to Figure 5, the residual voltage VDO generated by the charge accumulated in capacitor C11 is used. In Figure 5, a current path 102 is created. In Figure 6, an additional current path 103 is created due to the presence of welding 700.

[0055] The current path 103 is a current path that flows from the midpoint between R11 and R12, through FG, through the midpoint between R32 and R33, and through the negative electrode wire 301. Due to the welding 700 that has occurred on SW-N, the current path 103 flows to the DC / DC converter 4.

[0056] The current path 103 is generated, causing a voltage to be generated in Vn. Therefore, by measuring the voltage Vn, it can be determined that welding 700 has occurred in SW-N.

[0057] Similarly, if welding 700 occurs on SW-P, it can be determined that welding 700 has occurred on SW-P by measuring the voltage Vp.

[0058] In this way, the polarity to which the welded switch belongs can also be determined by whether a voltage is generated at Vp or Vn.

[0059] As described above, according to the technical concept disclosed in this embodiment, it is possible to detect both ground faults and welding using the same circuit.

[0060] Therefore, it is possible to provide an electric vehicle charging system that enables welding detection and ground fault detection at low cost, as well as a control method for the electric vehicle charging system.

[0061] This embodiment, in addition to or independently of Embodiment 1, enables the detection of a break in the protective earth conductor.

[0062] Figure 7 shows a circuit for detecting a break in the protective earth conductor 50. In the example shown in Figure 7, the circuit for detecting a break in the protective earth conductor is provided on the detection board 20.

[0063] Protective earthing is a type of installation that prevents electric shock by ensuring that current is reliably discharged to ground potential in the event of a leakage current, as stipulated by safety standards such as JIS (Japanese Industrial Standards). It is sometimes referred to as PE (Protective Earth).

[0064] There are resistors R41 and R42 between the positive electrode wire 300 and the negative electrode wire 301. Resistors R41 and R42 are set to the same value. For example, one value is 200 kohms.

[0065] It should be noted that some degree of numerical variation is unavoidable in resistance values. Therefore, throughout this specification, "the same resistance value" means that the values ​​are the same within a range of variation, or that they are the same as the set value of the resistance.

[0066] A protective earth conductor 50 is connected at the midpoint between resistors R41 and R42, and is connected to protective earth PE. PE is a connection to the physical earth potential, grounding to earth, or a specially provided earthing wire.

[0067] This protective earth conductor is an important means of preventing electric shock in the event of a ground fault, and is therefore directly connected by cables, wiring, busbars, etc.

[0068] A control power supply P15 is connected to the midpoint between resistors R41 and R42 via a current-limiting resistor R43.

[0069] For example, the current-limiting resistor R43 is 10 kΩ.

[0070] Electric vehicle charging systems use high voltage, boosted to over 200V, for the purpose of rapid charging. Therefore, if this high voltage leaks and flows through a person's body, it could pose a serious danger to human health.

[0071] Therefore, in electric vehicle charging systems, especially those using high voltage boosted to over 200V, it is necessary to detect breaks in the protective earth conductor before starting to charge the electric vehicle.

[0072] Furthermore, the detection of breaks in this protective earth conductor is neither disclosed nor suggested in Patent Documents 1 and 2.

[0073] Figure 8 shows the current path under normal conditions, as in Figure 7. This is the case when there is no break in the protective earth conductor 50.

[0074] SW-P and SW-N are open or OFF. This also represents the state before power is supplied from the electric vehicle charging system to the electric vehicle.

[0075] At this time, voltage is supplied from the control power supply P15. In this case, current flows from the control power supply P15 to FG via the current path 200, through the protective earth conductor 50.

[0076] If there is no break in the protective earth conductor 50, no voltages will be generated in terms of Vp and Vn. Therefore, the absence of voltages in Vp and Vn allows us to determine that there is no break in the protective earth conductor 50.

[0077] It should be noted that some degree of numerical variation is unavoidable in resistance values. Therefore, throughout this specification, "the same resistance value" means that the values ​​are the same within a range of variation, or that they are the same as the set value of the resistance.

[0078] Furthermore, even if R41 and R42 have the same resistance value, small potentials may actually occur in Vp and Vn due to variations in physical resistance. Therefore, in actual testing, a certain threshold is set, and if the values ​​fall within that threshold, it is determined that no voltage is present in Vp or Vn.

[0079] Figure 9 shows the current path during an abnormal situation as in Figure 7. This is the case when a break 400 occurs in the protective earth conductor 50.

[0080] Voltage is supplied from the control power supply P15. In this case, unlike in Figure 8, the current path 200 does not occur due to the open circuit 400.

[0081] Instead, a current path 311 is created, through R43 and R41, from the positive electrode wire through R32 to FG. Similarly, a current path 312 is created, through R43 and R42, from the negative electrode wire through R33 to FG.

[0082] Therefore, if a break in the protective earth conductor 50 occurs (400), voltages Vp and Vn will be generated.

[0083] Therefore, the presence of voltages in Vp and Vn indicates that a break has occurred in the protective earth conductor 50.

[0084] Furthermore, even if R41 and R42, and R32 and R33 have the same resistance value, in reality, due to variations in physical resistance values, a small potential may be generated in Vp and Vn even if there is no break in the protective earth conductor 50. Therefore, in actual judgment, a certain threshold is set, and it is determined that a voltage has been generated in Vp and Vn when the value exceeds the range of that threshold.

[0085] As described above, this embodiment enables the detection of breaks in the protective earth conductor with a simple circuit configuration. Therefore, safety measures for electric vehicle charging systems can be implemented at low cost.

[0086] This embodiment combines the configurations of both Embodiment 1 and Embodiment 2.

[0087] Figure 10 is an example of a circuit diagram that simultaneously implements ground fault detection, welding detection, and detection of breakage in the protective earth conductor.

[0088] This can also be described as a circuit configuration that combines elements of both Figure 2 and Figure 7.

[0089] According to this embodiment, a ground fault detection circuit, welding detection, and disconnection detection of the protective earth conductor can be realized simultaneously with a simple configuration.

[0090] This method allows for the detection of open circuits in protective earth conductors using the same voltage detectors as those used for ground fault and welding diagnostics, such as isolation amplifiers and voltage measurement ICs. It also offers the advantage of standardizing onboard components.

[0091] In addition to detecting breaks in the protective earth conductor, the power supply used by the control board may also be standardized to allow for simultaneous diagnosis of power supply abnormalities such as overvoltage.

[0092] Furthermore, since ground fault detection, welding detection, and protective earth conductor disconnection detection can all be performed by detecting the voltages Vp and Vn, an even simpler circuit or device configuration can be realized.

[0093] Therefore, it is possible to provide an electric vehicle charging system that can implement ground fault detection, welding detection, and protective earth conductor break detection all at a low cost.

[0094] This embodiment is an example in which the circuit configuration of Embodiments 1 to 3 is applied to a configuration having multiple DC / DC converters 4 in parallel.

[0095] Figure 11 shows an example of applying the circuit diagram of Figure 10 to the charging system of Figure 1.

[0096] As shown in Figure 1, when the DC / DC converters 4 are in parallel, the outputs from the multiple DC / DC converters 4 are aggregated between SW-P and SW-N and the detection board 20, as shown in Figure 11.

[0097] With this configuration, even when there are multiple DC / DC converters 4, the effects of Examples 1 to 3 can be achieved individually or in combination.

[0098] This embodiment describes an example of a detection routine, such as in Example 3 or Example 4.

[0099] This is a flowchart for safely operating an electric vehicle charging system. It also outlines a control method for safely operating an electric vehicle charging system.

[0100] Figure 12 shows an example of an inspection flowchart.

[0101] While it is desirable to perform all steps in the flowchart in Figure 12, this does not exclude the possibility of performing only some of them.

[0102] First, the electric vehicle charging system receives a charging instruction (S1).

[0103] This process can be initiated, for example, by a direct or indirect charging request from a user to a charging station.

[0104] Next, the control power is supplied to the test board (S2). In the circuit of Figure 10, this means that the detection board 20 receives voltage from the control power supply P15. At this time, SW-P and SW-N are in the open or OFF state.

[0105] Then, as described in Example 2, a break in the protective earth conductor is detected.

[0106] After the control power is supplied to the test board, it is determined whether or not a voltage is generated at Vp or Vn (S3).

[0107] As detailed in Example 2, if a voltage is present in Vp or Vn, it means that there is a break in the protective earth conductor. In this state, the safety of the charging system cannot be ensured, so the operation of the charging system is terminated as an initial diagnostic abnormality (S4).

[0108] If necessary, the charging station will display a message indicating that the station is out of order and instruct users to use another charging station. Furthermore, the charging station manager will be notified of the malfunction via communication lines, etc., to encourage repairs.

[0109] If no voltage is present at Vp or Vn, the protective earth conductor is considered not to be broken and is judged to be normal. When normal is determined, the detection of breaks in the protective earth conductor is terminated, and the control power is turned off.

[0110] As described above, steps S2 and S3 are steps for detecting a break in the protective earth conductor.

[0111] If there is no break in the protective earth conductor, that is, if the detection of breaks in the protective earth conductor is successful, proceed to the next step.

[0112] In the next step, for example, SW-P and SW-N in Figure 10 are set to the closed or ON state. This is the switch ON state (S5). The transition of the switch to the closed or ON state is performed by transmitting an ON drive control signal from the control unit 12 in Figure 1 to the switch 11.

[0113] Next, the DC / DC converter 4 enters a standby state (S6). This may also be called the ready state. It is in a state where it is waiting to output a voltage when it receives a command for the value of the circuit diagnostic voltage VDC from the control unit.

[0114] When the value of the circuit diagnostic voltage VDC is commanded from the control unit, voltage is supplied to the positive electrode wire 300 and the negative electrode wire 301, as explained in Figure 2 (S7). That is, the circuit diagnostic voltage VDC is output between the positive electrode wire 300 and the negative electrode wire 301. This voltage is, for example, the maximum voltage that can be expected during normal operation.

[0115] Then, as detailed in Example 1, ground fault detection is performed. Alternatively, this can be called circuit insulation diagnosis.

[0116] As detailed in Example 1, the voltages Vp and Vn are evaluated. If Vp and Vn have different values, it means that a ground fault has occurred in a part of the electric vehicle charging system, as explained in Figure 4. In this case, a ground fault abnormality is detected, and a ground fault abnormality stop (S9) occurs, terminating the operation of the charging system.

[0117] If necessary, the charging station will display a message indicating that the station is out of order and instruct users to use another charging station. Furthermore, the charging station manager will be notified of the malfunction via communication lines, etc., to encourage repairs.

[0118] If Vp and Vn have the same value, as explained in Figure 3, it is determined that there is no ground fault and that the circuit's insulation is in a normal state. When it is determined that the circuit is normal, the output of the circuit diagnostic voltage VDC is stopped (S10). Then, the DC / DC converter 4 is stopped once (S11).

[0119] As described above, steps S5 to S11 are steps for detecting ground faults or diagnosing circuit insulation.

[0120] In the next step, for example, SW-P and SW-N in Figure 10 are set to the open or OFF state. This is the switch OFF state (S12). The transition of the switch to the open or OFF state is performed by transmitting an OFF drive control signal from the control unit 12 in Figure 1 to the switch 11.

[0121] In this case, for example, in the circuit diagram of Figure 10, the capacitor C11 has accumulated charge due to the circuit diagnostic voltage VDC. This charge generates a residual voltage VDO, as shown in Figure 5.

[0122] Because the switch is OFF, under normal conditions, only the current path 102 is formed. Therefore, no voltage is generated at Vp and Vn.

[0123] However, if welding occurs, for example as shown in Figure 6, a current path is formed via FG, such as current path 103. Therefore, as detailed in Figure 6 in Example 1, a voltage is generated at either Vp or Vn. Thus, it is determined whether or not a voltage has been generated at either Vp or Vn (S13). If a voltage has been generated at either Vp or Vn, a welding abnormality is detected, and the welding abnormality is stopped (S14), ending the operation of the charging system.

[0124] If necessary, the charging station will display a message indicating that the station is out of order and instruct users to use another charging station. Furthermore, the charging station manager will be notified of the malfunction via communication lines, etc., to encourage repairs.

[0125] If no voltage is detected at Vp and Vn, it is a normal state in which welding has not occurred, as explained in Figure 5.

[0126] As described above, steps S12 to S14 are steps for performing a welding diagnosis.

[0127] It is desirable to perform the ground fault detection or circuit insulation diagnosis in S5-S11 and the welding diagnosis in S12-S14 in this order. This is because charge accumulation to capacitor C11, which is necessary in S12-S14, is performed in S5-S11. If a separate power supply is used instead of the VDO formed by capacitor C11, it is possible to reverse the order of S5-S11 and S12-S14. However, this would lead to an increase in circuit size and complexity, so it is highly desirable to perform the ground fault detection or circuit insulation diagnosis in S5-S11 and the welding diagnosis in S12-S14 in this order.

[0128] If the system is deemed normal, the system safety check is completed (S15).

[0129] As a result, the safety of charging electric vehicles from charging stations is fully ensured in accordance with user requests.

[0130] Therefore, the process will proceed to charging, in response to the user's request.

[0131] The DC / DC converter is started to operate, and charging of the electric vehicle begins (S16). The operation of the electric vehicle charging system and the charging method in S16 may be any of the various methods already known or various methods that will be standardized in the future. This is because S16 is not the main focus of this invention.

[0132] As described above, the electric vehicle charging system according to this embodiment can provide an electric vehicle charging system that realizes welding detection and ground fault detection at low cost.

[0133] Furthermore, since it can also detect breaks in the protective earth conductor, it is possible to provide an electric vehicle charging system that reliably ensures safety.

[0134] The above descriptions of each embodiment were based on an electric vehicle charging system. However, this does not exclude cases where the object to be charged is something other than an electric vehicle.

[0135] Furthermore, control methods for electric vehicle charging systems based on the technical concepts described in each of the above embodiments are also included within the scope of this application.

[0136] Each of the above embodiments can be applied individually or in combination. In such cases, it is still within the scope of the disclosure of this application.

[0137] Insofar as the technical concept disclosed in this specification is used, equivalent configurations obtained by modification, substitution, etc., are also within the scope of the disclosure in this application.

[0138] Furthermore, an example of the present invention described using the above embodiments can also be expressed as follows.

[0139] <1> An electric vehicle charging system comprising an AC / DC converter, a DC / DC converter, and a charging station for charging an electric vehicle with the output current from the DC / DC converter, wherein a switch is provided between the DC / DC converter and the charging station, and further comprising a detection board, wherein the DC / DC converter, the switch, and the detection board are controlled by a control unit, the detection board comprising a plurality of first voltage divider resistors and a ground point provided in the middle of the plurality of first voltage divider resistors, and a ground fault determination is made by comparing the voltage difference between the plurality of first voltage divider resistors. <2> The electric vehicle charging system according to <1>, wherein the ground fault determination is made by turning on the switch, supplying a circuit diagnostic voltage lower than that during normal operation from the DC / DC converter, and determining a ground fault if a voltage difference occurs between the plurality of first voltage divider resistors. <3> The electric vehicle charging system according to <2>, wherein the DC / DC converter comprises a plurality of second voltage divider resistors and a ground point provided in the middle of the plurality of second voltage divider resistors, and welding determination is made based on the voltage between the plurality of first voltage divider resistors. <4> The DC / DC converter has a capacitor provided between the positive and negative electrodes, and the welding determination is made when a voltage is generated between any of the plurality of first voltage divider resistors after the DC / DC converter has been stopped and the switch has been turned OFF, thereby determining welding. <5> The detection board has a plurality of third voltage divider resistors, a control power supply connected to the middle of the plurality of third voltage divider resistors via a current limiting resistor, and a protective earth conductor connecting the middle of the plurality of third voltage divider resistors to a ground point, and the break in the protective earth conductor is determined when a voltage is generated between the plurality of first voltage divider resistors, thereby determining a break in the protective earth conductor, as described in <4>. <6> The break in the protective earth conductor is determined when the switch has been turned OFF, the control power supply has been turned ON, and a voltage is generated between the plurality of first voltage divider resistors, as described in <5>. <7> An electric vehicle charging system according to any one of <1> to <6>, comprising a plurality of DC / DC converters, wherein the output currents from the plurality of DC / DC converters are integrated to charge the electric vehicle from the charging station.<Part 8> A control method for an electric vehicle charging system comprising an AC / DC converter, a DC / DC converter, and a charging station for charging an electric vehicle with the output current from the DC / DC converter, a switch between the DC / DC converter and the charging station, a detection board, and a control unit for controlling the DC / DC converter, the switch and the detection board, the detection board comprising a plurality of first voltage divider resistors and a ground point provided in the middle of the plurality of first voltage divider resistors, and determining whether a ground fault test has passed or failed by comparing the voltage difference between the plurality of first voltage divider resistors. <Part 9> The control method for an electric vehicle charging system according to <Part 8>, wherein the ground fault determination is made by turning on the switch, supplying the maximum voltage that can be considered during normal operation from the DC / DC converter, and determining a ground fault abnormality when a voltage difference occurs between the plurality of first voltage divider resistors. <10> The DC / DC converter has a plurality of second voltage divider resistors and a ground point provided in the middle of the plurality of second voltage divider resistors, and the pass / fail judgment of the welding inspection is made based on the voltage between the plurality of first voltage divider resistors, as described in <9>. <11> The DC / DC converter has a capacitor provided between the positive and negative electrodes, and the welding judgment is made by stopping the drive of the DC / DC converter, turning the switch OFF, and determining if there is a welding abnormality if a voltage is generated between any of the plurality of first voltage divider resistors, as described in <10>. <12> The detection board has a plurality of third voltage divider resistors, a control power supply connected to the middle of the plurality of third voltage divider resistors via a current limiting resistor, and a protective earth conductor connecting the middle of the plurality of third voltage divider resistors and the ground point, and the connection state of the protective earth conductor is determined to be abnormal if a voltage is generated between the plurality of first voltage divider resistors, as described in <11>. <Part 13> The control method for an electric vehicle charging system as described in <Part 12>, wherein the abnormality is determined to be a wire break abnormality when the switch is turned OFF, the control power is turned ON, and a voltage is generated between the plurality of first voltage divider resistors.<14> A control method for an electric vehicle charging system according to any one of <8> to <13>, comprising having a plurality of DC / DC converters, and integrating the output currents from the plurality of DC / DC converters to charge the electric vehicle from the charging station. <Part 15> The device has an AC / DC converter, a DC / DC converter, and a charging station for charging an electric vehicle with the output current from the DC / DC converter, a switch between the DC / DC converter and the charging station, and a detection board, and a control unit that controls the DC / DC converter, the switch and the detection board, the DC / DC converter has a plurality of second voltage divider resistors and a ground point provided in the middle of the plurality of second voltage divider resistors, and the DC / DC converter has a capacitor provided between the positive and negative electrodes, the detection board has a plurality of first voltage divider resistors and a ground point provided in the middle of the plurality of first voltage divider resistors, the detection board has a plurality of third voltage divider resistors, a control power supply connected to the middle of the plurality of third voltage divider resistors via a current limiting resistor, and a protective earth conductor connecting the middle of the plurality of third voltage divider resistors and the ground point, the control power supply is turned on with the switch in the OFF state, and a break in the protective earth conductor is diagnosed by whether or not a voltage is generated in the plurality of first voltage divider resistors, An electric vehicle charging system in which, with the switch in the ON state, the DC / DC converter outputs a test voltage lower than the rated voltage, and a ground fault diagnosis is performed based on whether the voltages generated across the plurality of first voltage divider resistors are different, and the DC / DC converter is stopped, the switch is turned OFF, and a welding diagnosis is performed based on whether or not a voltage is generated between the plurality of first voltage divider resistors.

[0140] 1: Power system 2: AC / DC converter 3: AC / DC converter control unit 4: DC / DC converter 5: Charging station 6: Electric vehicle 7: DC / DC converter control unit 8: Power line 9: DC bus 10: Signal transmission means 11: Switch 12: Main control unit 20: Detection board 21: Charging cable 50: Protective installation conductor 100, 102, 103, 200, 311, 312: Current path 300: Positive electrode wire 301: Negative electrode wire 400: Disconnection 700: Welding Vp: Positive electrode side potential Vn: Negative electrode side potential HGD: Protective installation conductor FG: Enclosure potential

Claims

1. An electric vehicle charging system comprising an AC / DC converter, a DC / DC converter, and a charging station for charging an electric vehicle with the output current from the DC / DC converter, a switch between the DC / DC converter and the charging station, and a detection board, and a control unit for controlling the DC / DC converter, the switch and the detection board, the detection board comprising a plurality of first voltage divider resistors and a ground point provided in the middle of the plurality of first voltage divider resistors, and a ground fault determination by comparing the voltage difference between the plurality of first voltage divider resistors.

2. The electric vehicle charging system according to claim 1, wherein the ground fault determination is made by turning on the switch, supplying a circuit diagnostic voltage lower than that during normal operation from the DC / DC converter, and determining a ground fault when a voltage difference occurs between the plurality of first voltage divider resistors.

3. The electric vehicle charging system according to claim 2, wherein the DC / DC converter has a plurality of second voltage divider resistors and a ground point provided in the middle of the plurality of second voltage divider resistors, and welding is determined by the voltage between the plurality of first voltage divider resistors.

4. The electric vehicle charging system according to claim 3, wherein the DC / DC converter has a capacitor provided between the positive and negative electrodes, and the welding determination is made when a voltage is generated between any of the plurality of first voltage divider resistors after the drive of the DC / DC converter is stopped and the switch is turned OFF.

5. The electric vehicle charging system according to claim 4, wherein the detection board has a plurality of third voltage divider resistors, a control power supply connected to the middle of the plurality of third voltage divider resistors via a current limiting resistor, and a protective earth conductor connecting the middle of the plurality of third voltage divider resistors to a ground point, and a break in the protective earth conductor is determined when a voltage is generated between the plurality of first voltage divider resistors.

6. The electric vehicle charging system according to claim 5, wherein the determination of a break in the protective earth conductor is made by turning the switch OFF, turning on the control power supply, and determining that a break is made if a voltage is generated between the plurality of first voltage divider resistors.

7. An electric vehicle charging system according to any one of claims 1 to 6, comprising a plurality of DC / DC converters, wherein the output currents from the plurality of DC / DC converters are integrated to charge the electric vehicle from the charging station.

8. A control method for an electric vehicle charging system comprising an AC / DC converter, a DC / DC converter, and a charging station for charging an electric vehicle with the output current from the DC / DC converter, a switch between the DC / DC converter and the charging station, and a detection board, and a control unit for controlling the DC / DC converter, the switch and the detection board, the detection board comprising a plurality of first voltage divider resistors and a ground point provided in the middle of the plurality of first voltage divider resistors, and determining whether a ground fault inspection has passed by comparing the voltage difference between the plurality of first voltage divider resistors.

9. The control method for an electric vehicle charging system according to claim 8, wherein the ground fault determination is made by turning on the switch, supplying the maximum voltage that can be expected during normal operation from the DC / DC converter, and determining a ground fault abnormality when a voltage difference occurs between the plurality of first voltage divider resistors.

10. The control method for an electric vehicle charging system according to claim 9, wherein the DC / DC converter has a plurality of second voltage divider resistors and a ground point provided in the middle of the plurality of second voltage divider resistors, and the pass / fail determination of a welding inspection is made based on the voltage between the plurality of first voltage divider resistors.

11. The control method for an electric vehicle charging system according to claim 10, wherein the DC / DC converter has a capacitor provided between the positive and negative electrodes, and the welding determination is made if a voltage is present between any of the plurality of first voltage divider resistors after the driving of the DC / DC converter is stopped and the switch is turned OFF, thereby determining that there is a welding abnormality.

12. The control method for an electric vehicle charging system according to claim 11, wherein the detection board has a plurality of third voltage divider resistors, a control power supply connected to the middle of the plurality of third voltage divider resistors via a current limiting resistor, and a protective earth conductor connecting the middle of the plurality of third voltage divider resistors to a ground point, and the connection state of the protective earth conductor is determined to be abnormal when a voltage is generated between the plurality of first voltage divider resistors.

13. The control method for an electric vehicle charging system according to claim 12, wherein the abnormality is determined to be a wire break abnormality when the switch is turned OFF, the control power supply is turned ON, and a voltage is generated between the plurality of first voltage divider resistors.

14. A control method for an electric vehicle charging system according to any one of claims 8 to 13, comprising having a plurality of DC / DC converters, and integrating the output currents from the plurality of DC / DC converters to charge the electric vehicle from the charging station.

15. The device comprises an AC / DC converter, a DC / DC converter, and a charging station for charging an electric vehicle with the output current from the DC / DC converter, a switch between the DC / DC converter and the charging station, and a detection board, and a control unit for controlling the DC / DC converter, the switch and the detection board, the DC / DC converter having a plurality of second voltage divider resistors and a ground point located between the plurality of second voltage divider resistors, and the DC / DC converter having a capacitor located between the positive and negative electrodes, the detection board having a plurality of first voltage divider resistors and a ground point located between the plurality of first voltage divider resistors, the detection board having a plurality of third voltage divider resistors, a control power supply connected to the plurality of third voltage divider resistors via a current limiting resistor, and a protective earth conductor connecting the middle of the plurality of third voltage divider resistors to the ground point, the control power supply is turned on with the switch in the OFF state, and a break in the protective earth conductor is diagnosed based on whether or not a voltage is generated across the plurality of first voltage divider resistors. An electric vehicle charging system in which, with the switch in the ON state, the DC / DC converter outputs a test voltage lower than the rated voltage, and a ground fault diagnosis is performed based on whether the voltages generated across the plurality of first voltage divider resistors are different, and the DC / DC converter is stopped, the switch is turned OFF, and a welding diagnosis is performed based on whether or not a voltage is generated between the plurality of first voltage divider resistors.

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