Power system

Abstract

To secure detection accuracy of a ground fault without providing a relay in series in a ground fault detection circuit.SOLUTION: A power system includes: first and second connectors which can be respectively connected to an electric vehicle; first and second power supply units which are connected to the first and second connectors via first and second power lines; a third power supply unit; first and second relays which connect and disconnect the first and second power lines and the third power supply unit; first and second ground fault detection circuits which detect first and second ground fault currents flowing between the first and second power lines and ground; and a controller which controls the first and second relays and determines whether or not there is a ground fault based on the first and second ground fault currents. The control device turns off one of the first and second relays (on side) when ground fault current flows in both of the first and second ground fault detection circuits while one of the first and second relays is on.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to power systems. [Background technology]

[0002] A conventional technique for this type of system is a DC power supply circuit in which multiple DC power supply devices, each consisting of a storage battery and a charger, are connected in parallel to a main bus and power is supplied from the DC power supply devices to a load via the main bus (see, for example, Patent Document 1). In this DC power supply circuit, each charger is provided with a ground fault detection circuit and a relay between the ground fault detection circuit and a ground point, and when multiple DC power supply devices are in operation, only one of the ground fault detection circuits of the multiple chargers is grounded via the relay. This prevents the shunting of the ground fault current. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-136264 A Summary of the Invention [Problem to be solved by the invention]

[0004] If a relay is provided between the ground fault detection circuit and the ground point, the number of relays will increase. Also, when multiple DC power supply equipment are in operation, if the relay is periodically switched on and off to ground only one ground fault detection circuit via a relay, the number of times the relay is turned on and off will increase, which may shorten the life of the relay. For these reasons, there is a demand for a configuration that can ensure the accuracy of ground fault detection without providing a relay in series with the ground fault detection circuit.

[0005] The main objective of the power system disclosed herein is to ensure the accuracy of ground fault detection without providing a relay in series with the ground fault detection circuit. [Means for solving the problem]

[0006] The power system of the present disclosure employs the following measures to achieve the above-mentioned main objective.

[0007] The power system disclosed herein is a power system including first and second connectors each connectable to an electric vehicle, first and second power supply units connected to the first and second connectors via first and second power lines, a third power supply unit, first and second relays connecting and disconnecting the first and second power lines from the third power supply unit, first and second earth fault detection circuits detecting first and second earth fault currents flowing between the first and second power lines and ground, and a control device controlling the first and second relays and determining the presence or absence of a ground fault based on the first and second earth fault currents, wherein the control device turns off one of the first and second relays when one of the first and second relays is on and earth fault currents are flowing in both the first and second earth fault detection circuits.

[0008] In the power system of the present disclosure, when one of the first and second relays is on and a ground fault current flows through both the first and second ground fault detection circuits, one of the first and second relays (the one that is turned on) is turned off. Here, a case where a ground fault current flows through both the first and second ground fault detection circuits may be when one of the first and second relays is on and the other is stuck on (welded), and the first and second power lines are electrically connected. In this case, the ground fault current flows in a branched manner through the first and second ground fault detection circuits, and the first and second ground fault currents are relatively small, making it difficult to accurately determine whether a ground fault exists. Based on this, in this case, by turning off one of the first and second relays (the one that is turned on) and electrically cutting off the first and second power lines, it is possible to make the ground fault current flow only to one of the first and second ground fault detection circuits (eliminating the division of the ground fault current), and it is possible to increase either the first or second ground fault current (specifically, the ground fault current flowing to the ground fault detection circuit corresponding to the power line in which the ground fault has occurred). This makes it possible to ensure the accuracy of ground fault detection without providing a relay in series with the ground fault detection circuit. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a power system 20 according to an embodiment. [Diagram 2] 10 is a flowchart illustrating an example of a processing routine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a power system 20 according to an embodiment of the present disclosure. The power system 20 according to the embodiment is configured as a multi-outlet type power device having two connectors 22A and 22B, and when an electric vehicle (electric vehicle, hybrid vehicle, or fuel cell vehicle) is connected to at least one of the connectors 22A and 22B, the power system 20 is capable of converting AC power of a power system 10 into DC power, adjusting the power, and supplying it to the electric vehicle. As shown in the figure, the power system 20 includes, in addition to the two connectors 22A and 22B, four converters 24A-24D, six relays 41-46, two ground fault detectors 50A and 50B, and an electronic control unit (hereinafter referred to as "ECU") 70.

[0011] The connectors 22A and 22B are configured so as to be connectable to connectors of an electric vehicle, and are connected to the positive lines 31p and 32p and the negative lines 31n and 32n of the power lines 31 and 32, respectively.

[0012] Converters 24A to 24D are respectively connected to power system 10 and positive lines 33p to 36p and negative lines 33n to 36n of power lines 33 to 36, and are capable of converting AC power from power system 10 into DC power and adjusting the power to supply it to power lines 33 to 36.

[0013] The positive relays 41p, 42p and negative relays 41n, 42n of the relays 41, 42 respectively connect and cut off the positive lines 31p, 32p and negative lines 31n, 32n of the power lines 31, 32 and the positive lines 33p, 34p and negative lines 33n, 34n of the power lines 33, 34 by being turned on and off. The positive relays 43p, 44p and negative relays 43n, 44n of the relays 43, 44 respectively connect and cut off the positive lines 33p, 34p and negative lines 33n, 34n of the power lines 33, 34 and the positive line 35p and negative line 35n of the power line 35 by being turned on and off. The positive relays 45p, 46p and negative relays 45n, 46n of the relays 45, 46 respectively connect and disconnect the positive lines 33p, 34p and negative lines 33n, 34n of the power lines 33, 34 to the positive line 36p and negative line 36n of the power line 36 by being turned on and off.

[0014] The ground fault detection devices 50A and 50B each include a resistive element 51A, 51B, a resistive element 52A, 52B, and a ground fault detection circuit 53A, 53B. The resistive elements 51A and 51B are connected to the positive lines 31p, 32p of the power lines 31, 32 and to ground lines 54A, 54B connected to the ground. The resistive elements 52A and 52B are connected to the negative lines 31n, 32n of the power lines 31, 32 and to the ground lines 54A, 54B. The ground fault detection circuits 53A and 53B each detect the ground fault currents Ig1, Ig2 that flow through the ground lines 54A, 54B (flowing between the ground and the positive lines 31p, 32p or the negative lines 31n, 32n). It should be noted that when no ground fault occurs in power lines 31, 32 and the parts electrically connected to power lines 31, 32, ground fault currents Ig1, Ig2 have a value of 0.

[0015] The ECU 70 includes a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, etc. The ECU 70 receives the ground fault currents Ig1 and Ig2 from the ground fault detection circuits 53A and 53B of the ground fault detection devices 50A and 50B. The ECU 70 outputs control signals for the converters 24A-24D and control signals for the relays 41-46 (positive relays 41p-46p and negative relays 41n-46n) via the output port.

[0016] In the power system 20 of the embodiment configured in this manner, the converters 24A-24D and the relays 41-46 are controlled according to first to third modes. The first mode is a mode in which power is supplied only to electric vehicle A connected to connector 22A of connectors 22A, 22B. The second mode is a mode in which power is supplied only to electric vehicle B connected to connector 22B of connectors 22A, 22B. The third mode is a mode in which power is supplied to both electric vehicles A and B connected to connectors 22A, 22B.

[0017] In the first mode, converters 24A, 24C, 24D are driven with relays 41, 43, 45 turned on and relays 42, 44, 46 turned off, thereby supplying power from converters 24A, 24C, 24D to electric vehicle A via power lines 33, 31 and connector 22A. In the second mode, converters 24B, 24C, 24D are driven with relays 42, 44, 46 turned on and relays 41, 43, 45 turned off, thereby supplying power from converters 24B, 24C, 24D to electric vehicle B via power lines 34, 32 and connector 22B. In the third mode, converters 24A, 24B, 24C, 24D are driven with relays 41, 42, 43, 46 turned on and relays 44, 45 turned off, so that power from converters 24A, 24C is supplied to electric vehicle A via power lines 33, 31 and connector 22A, and power from converters 24B, 24D is supplied to electric vehicle B via power lines 34, 32 and connector 22B.

[0018] In the first and third modes, when the ground fault current Ig1 from the ground fault detection circuit 53A of the ground fault detection device 50A is equal to or greater than the threshold value Igref and the ground fault current Ig2 from the ground fault detection circuit 53B of the ground fault detection device 50B is less than the threshold value Igref, it is determined that a ground fault has occurred in the power line 31 or a portion connected to the power line 31 (for example, the positive electrode line 33p of the power line 33), and power supply from the connector 22A is prohibited. In this case, the converters 24A, 24C, and 24D are stopped in the first mode, and the converters 24A and 24C are stopped in the third mode, thereby stopping the power supply to the electric vehicle A connected to the connector 22A. Note that when the power supply to the electric vehicle A is stopped in the third mode, the drive of the converters 24B and 24D may be continued, and the power supply to the electric vehicle B connected to the connector 22B may be continued.

[0019] In the second and third modes, when the ground fault current Ig2 from the ground fault detection circuit 53B of the ground fault detection device 50B is equal to or greater than the threshold value Igref and the ground fault current Ig1 from the ground fault detection circuit 53A of the ground fault detection device 50A is less than the threshold value Igref, it is determined that a ground fault has occurred in the power line 32 or a portion connected to the power line 32 (for example, the positive electrode line 34p of the power line 34), and power supply from the connector 22B is prohibited. In this case, the converters 24B, 24C, and 24D are stopped in the second mode, and the converters 24B and 24D are stopped in the third mode, thereby stopping the power supply to the electric vehicle B connected to the connector 22B. Note that when the power supply to the electric vehicle B is stopped in the third mode, the drive of the converters 24A and 24C may be continued, and the power supply to the electric vehicle A connected to the connector 22A may be continued.

[0020] Next, an operation of the power system 20 of the embodiment, particularly a process performed when a ground fault occurs in any of the power lines 31 to 34 in the third mode, will be described. Fig. 2 is a flowchart showing an example of a process routine executed by the ECU 70. This routine is repeatedly executed in the third mode.

[0021] When the processing routine of Fig. 2 is executed, the ECU 70 first determines whether or not the ground fault currents Ig1, Ig2 flow through both the ground fault detection circuits 53A, 53B of the ground fault detection devices 50A, 50B (steps S100, S102). As described above, in the third mode, the relays 41, 42, 43, 46 are turned on, so that the power lines 31, 33, 35 are electrically connected to each other and the power lines 32, 34, 36 are electrically connected to each other, and the power lines 31, 33, 35 and the power lines 32, 34, 36 are electrically disconnected from each other. However, if at least one of the relays 44, 45 is stuck on (welded), the power lines 31, 33, 35 and the power lines 32, 34, 36 are electrically connected to each other. Therefore, when a ground fault occurs in any of the power lines 31 to 34 and at least one of the relays 44, 45 is stuck on, the ground fault currents Ig1, Ig2 are shunted to flow through both the ground fault detection circuits 53A, 53B. At this time, the ground fault currents Ig1, Ig2 are both relatively small (less than the threshold value Igref), and it may be difficult to accurately determine whether or not a ground fault exists.

[0022] When it is determined in steps S100 and S102 that the ground fault currents Ig1 and Ig2 are not flowing through one or both of the ground fault detection circuits 53A and 53B, this routine is terminated. Note that the operation when one of the ground fault currents Ig1 and Ig2 is equal to or greater than the threshold value Igref has been described above.

[0023] When it is determined in steps S100 and S102 that the ground fault currents Ig1 and Ig2 flow through both the ground fault detection circuits 53A and 53B, the relays 43 and 46 are turned off (step S110). As a result, even if at least one of the relays 44 and 45 is stuck on, the power lines 31 and 33 and the power lines 32 and 34 can be electrically disconnected, so that the ground fault current flows only through one of the ground fault detection circuits 53A and 53B (the side where the ground fault occurs between the power lines 31 and 33 and the power lines 32 and 34) (the shunting of the ground fault current is eliminated), and one of the ground fault currents Ig1 and Ig2 can be increased and the other can be reduced (set to a value of 0). Before the relays 43 and 46 are turned off, the converters 22C and 22D are stopped.

[0024] Next, using the ground fault currents Ig1 and Ig2, it is determined whether a ground fault has occurred in the power lines 31 and 33 or in the power lines 32 and 34 (steps S120 and S122). This process can be performed by comparing the ground fault currents Ig1 and Ig2 with the above-mentioned threshold value Igref.

[0025] If it is determined in steps S120 and S122 that a ground fault has occurred in the power lines 31 and 33, power supply from the connector 22A is prohibited and power supply from the connector 22B is permitted (step S130), and this routine ends. In this case, power supply to the electric vehicle B connected to the connector 22B is performed (continues) by driving the converter 24B. Also, the repeated execution of this routine ends.

[0026] If it is determined in steps S120 and S122 that a ground fault has occurred in the power lines 32 and 34, power supply from the connector 22B is prohibited and power supply from the connector 22A is permitted (step S140), and this routine ends. In this case, power supply to the electric vehicle A connected to the connector 22A is performed (continues) by driving the converter 24A. Also, the repeated execution of this routine ends.

[0027] In the power system 20 of the present embodiment described above, in the third mode, that is, when the converters 24A, 24B, 24C, 24D are driven with the relays 41, 42, 43, 46 turned on and the relays 44, 45 turned off, when the ground fault currents Ig1, Ig2 flow through both the ground fault detection circuits 53A, 53B of the ground fault detection devices 50A, 50B, the relays 43, 46 are turned off. This makes it possible to electrically cut off the power lines 31, 33 and the power lines 32, 34, so that the ground fault current flows only through one of the ground fault detection circuits 53A, 53B (the side where the ground fault occurs between the power lines 31, 33 and the power lines 32, 34) (the shunting of the ground fault current is eliminated), and one of the ground fault currents Ig1, Ig2 can be increased and the other can be reduced (to a value of 0). As a result, it is possible to ensure the accuracy of the detection of the ground fault. In other words, the accuracy of detecting a ground fault can be ensured without providing a relay in series with the ground fault detection circuit.

[0028] Furthermore, in power system 20 of the present embodiment, when a ground fault is detected in power lines 31, 33 after ground fault currents Ig1, Ig2 flow through both ground fault detection circuits 53A, 53B in the third mode and relays 43, 46 are turned off, converter 24B is driven. This makes it possible to perform (continue) power supply to electric vehicle B connected to connector 22B. Furthermore, when a ground fault is detected in power lines 32, 34, converter 24A is driven. This makes it possible to supply power to electric vehicle A connected to connector 22A.

[0029] In the above-described embodiment, the ground fault detection devices 50A and 50B are connected to the power lines 31 and 32, respectively, but may be connected to the power lines 33 and 34, respectively.

[0030] In the above-described embodiment, power system 20 includes converter 24C and relays 43, 44, and converter 24D and relays 45, 46. That is, two sets of a converter and two relays that connect and disconnect power lines 33, 34 to and from the converter are provided. However, only one set or three or more sets may be provided.

[0031] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be described. In the embodiment, connectors 22A and 22B correspond to the "first and second connectors", converter 24A corresponds to the "first power supply unit", converter 24B corresponds to the "second power supply unit", converters 24C and 24D correspond to the "third power supply unit", relays 43 and 45 correspond to the "first relay", relays 44 and 46 correspond to the "second relay", ground fault detection circuits 53A and 53B correspond to the "first and second ground fault detection circuits", and ECU 70 corresponds to the "control device".

[0032] The above describes embodiments for implementing the present disclosure, but the present disclosure is not limited to these embodiments, and it goes without saying that the present disclosure can be implemented in various forms without departing from the gist of the present disclosure. [Industrial Applicability]

[0033] The present disclosure is applicable to the power system manufacturing industry and the like. [Explanation of symbols]

[0034] 20 Power system, 22A, 22B connectors, 24A~24D converter, 31~36 Power lines, 41~46 Relays, 53A, 53B Ground fault detection circuit, 70 ECU.

Claims

[Claim 1] a control device that controls the first and second relays and determines whether a ground fault exists based on the first and second ground fault currents, the control device comprising: a first connector and a second connector that are connectable to an electric vehicle, a first power supply unit and a second power supply unit that are connected to the first connector and the second connector via a first power line and a second power line; a third power supply unit; a first relay and a second relay that connect and disconnect the first and second power lines and the third power supply unit; the control device turns off one of the first and second relays when a ground fault current flows through both the first and second ground fault detection circuits while one of the first and second relays is on; Power system.

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