Converter unit

Abstract

To identify a location where a ground fault has occurred when the ground fault is detected.SOLUTION: A converter unit provided between a first DC circuit and a second DC circuit having a lower voltage than the first DC circuit comprises a converter circuit, a relay, a voltage sensor, and a control device. The control device performs a process of opening the relay when a ground fault is detected on the side of the second DC circuit relative to the converter circuit, a process of determining that the ground fault has occurred inside the converter unit when a detection voltage detected by the voltage sensor exceeds a predetermined lower limit value for a predetermined period of time after the process of opening the relay, and a process of determining that the ground fault has occurred outside the converter unit when the detection voltage falls below the lower limit value before the lapse of the predetermined period of time after the process of opening the relay.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a converter unit, and more particularly to a converter unit provided between a first DC circuit and a second DC circuit having a lower voltage than the first DC circuit. [Background technology]

[0002] Patent Document 1 describes a converter unit including a converter circuit that converts voltage between a first DC circuit and a second DC circuit that has a lower voltage than the first DC circuit, a first relay provided between the converter circuit and the first DC circuit, a second relay provided between the converter circuit and the second DC circuit, and a fault detection device that detects faults in the converter circuit. When a ground fault is detected, the control device opens the first relay and the second relay. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-104106 Summary of the Invention [Problem to be solved by the invention]

[0004] In the converter unit described above, suppose a ground fault is detected on the second DC circuit side of the converter circuit. In this case, it is impossible to determine whether the ground fault occurs inside the converter unit or outside the converter unit (i.e., in the second DC circuit). This is because there is no significant difference in the behavior of the voltage drop detected as a result of the ground fault, regardless of whether the ground fault occurs inside or outside the converter.

[0005] In view of the above circumstances, this specification provides a technique for identifying the location of a ground fault when a ground fault is detected. [Means for solving the problem]

[0006] The technology disclosed in this specification is embodied in a converter unit provided between a first DC circuit and a second DC circuit having a lower voltage than the first DC circuit. The converter unit includes: a converter circuit for converting voltage between the first DC circuit and the second DC circuit; a relay for electrically connecting and disconnecting the converter circuit and the second DC circuit; a voltage sensor provided on the second DC circuit side of the relay and measuring the voltage of the second DC circuit; and a control device for controlling the operation of the converter circuit and the relay and connected to the voltage sensor. When a ground fault is detected on the second DC circuit side of the converter circuit, the control device performs the following operations: opening the relay; determining that the ground fault has occurred inside the converter unit if the voltage detected by the voltage sensor exceeds a predetermined lower limit value for a predetermined time after opening the relay; and determining that the ground fault has occurred outside the converter unit if the detected voltage falls below the lower limit value before the predetermined time has elapsed after opening the relay.

[0007] In the converter unit described above, when a ground fault is detected on the second DC circuit side of the converter circuit, the relay is opened, electrically disconnecting the converter circuit from the second DC circuit. If a ground fault occurs inside the converter unit, the voltage sensor and the second DC circuit are insulated from the location of the ground fault. As a result, the voltage of the second DC circuit is maintained, and this voltage is detected by the voltage sensor. On the other hand, if a ground fault occurs outside the converter unit (i.e., in the second DC circuit), the second DC circuit remains grounded even if the relay is opened. As a result, the voltage of the second DC circuit drops rapidly, and this voltage is detected by the voltage sensor. Based on this, after the relay is opened, the location of the ground fault can be identified by comparing the voltage detected by the voltage sensor with a predetermined lower limit. That is, if the voltage detected by the voltage sensor exceeds the lower limit for a predetermined period of time, it can be determined that a ground fault has occurred inside the converter unit. On the other hand, if the voltage detected by the voltage sensor falls below the lower limit before the lapse of the predetermined time, it can be determined that a ground fault has occurred outside the converter unit. With this configuration, when a ground fault is detected, the location of the ground fault can be identified. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a schematic configuration of a converter unit 10 according to an embodiment and a vehicle 100 on which the converter unit 10 is mounted. [Figure 2] 4 is a flowchart for explaining a fault location identification process executed by the control device 16. DETAILED DESCRIPTION OF THE INVENTION

[0009] A converter unit 10 according to an embodiment and a vehicle 100 equipped with the converter unit 10 will be described with reference to the drawings. The vehicle 100 is an electric vehicle such as a hybrid electric vehicle (HEV) or a battery electric vehicle (BEV).

[0010] 1, a vehicle 100 includes a three-phase AC circuit including a motor 102, a first DC circuit 112 including a main battery 104, and a second DC circuit 114 including an auxiliary battery 108 and one or more auxiliary devices 110. An inverter 106 is provided between the AC circuit and the first DC circuit 112, and a converter unit 10 is provided between the first DC circuit 112 and the second DC circuit 114.

[0011] The motor 102 is a traction motor that drives the wheels of the vehicle 100, and is, for example, a three-phase motor generator having a U-phase, a V-phase, and a W-phase. The main battery 104 is a battery that supplies power to the motor 102. The main battery 104 is a secondary battery in which multiple battery cells are connected in series. The inverter 106 converts DC power from the main battery 104 into three-phase AC power and supplies it to the motor 102, and also converts the three-phase AC power from the motor 102 into DC power and supplies it to the main battery 104.

[0012] The auxiliary battery 108 is a battery that supplies power to the auxiliary device 110. The auxiliary battery 108 is a secondary battery in which a plurality of battery cells are connected in series. The auxiliary battery 108 is electrically connected to the auxiliary device 110 and can supply power to the auxiliary device 110. The auxiliary device 110 operates using power supplied from the auxiliary battery 108. The rated voltage of the auxiliary battery 108 is lower than the rated voltage of the main battery 104. As an example, the rated voltage of the auxiliary battery 108 is 12 V, and the rated voltage of the main battery 104 is 200 V to 600 V. The auxiliary battery 108 is, for example, a lead-acid battery. The auxiliary device 110 is, for example, a room lamp or a car navigation device.

[0013] As described above, the converter unit 10 is provided between the first DC circuit 112 and the second DC circuit 114. The converter unit 10 includes the converter circuit 12. The converter circuit 12 electrically connects the first DC circuit 112 and the second DC circuit 114. The first DC circuit 112 is a high-voltage DC circuit including the main battery 104, and the second DC circuit 114 is a low-voltage DC circuit including the auxiliary battery 108. The converter circuit 12 is a so-called DC-DC converter, and can step down the DC power supplied from the first DC circuit 112 and supply it to the second DC circuit 114. The converter circuit 12 can also step up the DC power supplied from the second DC circuit 114 and supply it to the first DC circuit 112.

[0014] 1, the converter unit 10 further includes a relay 14. The relay 14 is interposed between the converter circuit 12 and the second DC circuit 114. Therefore, the converter circuit 12 is electrically connected to and disconnected from the second DC circuit 114 by closing and opening the relay 14.

[0015] 1, the converter unit 10 further includes a control device 16. The control device 16 is a computer device having a processor, memory, etc. The control device 16 is communicatively connected to the converter circuit 12 and the relay 14 and controls their operations.

[0016] As shown in FIG. 1 , the converter unit 10 further includes a ground fault detection device 18. The ground fault detection device 18 is connected to the converter circuit 12 and detects the occurrence of a ground fault. In particular, the ground fault detection device 18 is configured to detect a ground fault occurring on the second DC circuit 114 side of the converter circuit 12. Note that the specific method for detecting a ground fault is not particularly limited. For example, the ground fault detection device 18 can detect the occurrence of a ground fault by monitoring the voltage and / or current on the second DC circuit 114 side of the converter circuit 12. The detection result by the ground fault detection device 18 is transmitted to the control device 16. Note that the ground fault detection device 18 may be substituted by a voltage sensor 20. That is, the control device 16 may detect the occurrence of a ground fault based on the voltage detected by the voltage sensor 20.

[0017] 1, the converter unit 10 further includes a voltage sensor 20. The voltage sensor 20 is provided closer to the second DC circuit 114 than the relay 14, and measures the voltage of the second DC circuit 114. The control device 16 is communicatively connected to the voltage sensor 20, and can monitor the voltage detected by the voltage sensor 20.

[0018] Next, the fault location identification process executed by the control device 16 will be described with reference to Fig. 2. By executing the fault location identification process, the control device 16 determines that the location where the ground fault has occurred is either inside or outside the converter unit 10.

[0019] 2, when a ground fault is detected (YES in S12) while the converter circuit 12 is operating (YES in S10), the control device 16 opens the relay 14 (S14), thereby electrically disconnecting the converter circuit 12 from the second DC circuit 114.

[0020] Then, the control device 16 determines whether the voltage detected by the voltage sensor 20 exceeds a predetermined lower limit VL for a predetermined time (S16, S18). Here, the predetermined lower limit VL means the lowest voltage value maintained by the auxiliary battery 108 provided in the second DC circuit 114 when no ground fault has occurred outside the converter unit 10 and the relay 14 is open. The predetermined lower limit VL may be determined taking into account a detection error by the voltage sensor 20, etc.

[0021] If a ground fault occurs inside the converter unit 10, the voltage sensor 20 and the second DC circuit 114 are insulated from the location of the ground fault. As a result, the voltage of the second DC circuit 114 is maintained, and this voltage is detected by the voltage sensor 20. On the other hand, if a ground fault occurs outside the converter unit 10 (i.e., in the second DC circuit 114), the second DC circuit 114 remains grounded even if the relay 14 is opened. As a result, the voltage of the second DC circuit 114 drops rapidly, and this voltage is detected by the voltage sensor 20.

[0022] Therefore, if the voltage detected by the voltage sensor 20 exceeds the lower limit value VL for a predetermined time (YES in S16), the control device 16 determines that a ground fault has occurred inside the converter unit 10 (S20). On the other hand, if the detected voltage falls below the lower limit value VL before the predetermined time has elapsed (NO in S16), the control device 16 determines that a ground fault has occurred outside the converter unit 10 when the predetermined time has elapsed (YES in S18) (S22).

[0023] In this way, after the relay opening process (S14), the location of the ground fault can be identified by comparing the voltage detected by the voltage sensor 20 with the predetermined lower limit value VL. Therefore, in the converter unit 10 described above, when a ground fault is detected, the location where the ground fault has occurred can be identified.

[0024] Although several specific examples have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility either alone or in combination. [Explanation of symbols]

[0025] 10: Converter unit, 12: Converter circuit, 14: Relay, 16: Control device, 18: Ground fault detection device, 20: Voltage sensor, 100: Vehicle, 102: Motor, 104: Main battery, 106: Inverter, 108: Auxiliary battery, 110: Auxiliary device, 112: First DC circuit, 114: Second DC circuit

Claims

[Claim 1] a converter unit provided between a first DC circuit and a second DC circuit having a lower voltage than the first DC circuit, a converter circuit that converts voltage between the first DC circuit and the second DC circuit; a relay that electrically connects and disconnects the converter circuit and the second DC circuit; a voltage sensor that is provided closer to the second DC circuit than the relay and that measures a voltage of the second DC circuit; a control device that controls operation of the converter circuit and the relay and is connected to the voltage sensor; Equipped with The control device a process of opening the relay when a ground fault is detected on the second DC circuit side of the converter circuit; a process of determining that the ground fault has occurred inside the converter unit when the voltage detected by the voltage sensor exceeds a predetermined lower limit value for a predetermined time after the process of opening the relay; a process of determining that the ground fault has occurred outside the converter unit if the detected voltage falls below the lower limit value before the predetermined time has elapsed after the process of opening the relay; To run the converter unit.

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