JP2022053559A - Power conversion device - Google Patents

Abstract

To safely diagnose the connection status of an AC wiring connected between an inverter and a load.SOLUTION: An inverter 1 converts DC power supplied from a high voltage battery 5 into AC power, and outputs the AC power to a motor 2 which is a load via an AC wiring 3. One end of shielded wires 33U to 33W of the AC wiring 3 is electrically connected to a frame ground 8 of the motor 2. In a diagnostic control circuit 13, the other end side of the shielded wire 33U to 33W and a diagnostic power supply 10 are conducted by diagnostic switching elements 17U to 17 W, and the state of the AC wiring 3 is diagnosed on the basis of the energized state of the shielded wires 33U to 33W when the other end side of 33U to 33W and a frame ground 7 of the inverter 1 are cut off by the grounding switching element 18U to 18W.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power conversion device.

The following Patent Document 1 is known as a background technique in this technical field. In Patent Document 1, a DC voltage generating means, an inverter device, a shield wire for electrically connecting the load of the inverter device, the DC voltage generating means, the inverter device, and the load, and one end of an output are described. Disclosed is an electrical connection diagnostic method that includes a grounded power supply, the shielded portion of the shielded wire is grounded at a location other than the inverter device, and the shielded portion is energized from the power supply to diagnose the connection of the shielded wire. Has been done.

Japanese Unexamined Patent Publication No. 2006-21593

In the technique of Patent Document 1, the shielded wire is grounded via a capacitor on the inverter device side, while the shielded wire is directly grounded without a capacitor on the load side. Therefore, when electric charge is accumulated in the capacitor on the inverter device side, the equipotential between the inverter device and the load may not be maintained, and a voltage may be applied to the shielded wire. In this case, there is a risk of electric shock if a person touches the shielded wire while it is broken.

An object of the present invention is to safely diagnose the connection state of the AC wiring connected between the inverter and the load in order to solve the above problems.

The power conversion device according to the present invention converts DC power supplied from a high-voltage power supply into AC power, and outputs the AC power to a load via an AC wiring formed by surrounding a core wire with a shielded wire. One end side of the shielded wire is electrically connected to the frame ground of the load, and the power conversion device keeps the conduction state between the other end side of the shielded wire and the diagnostic power supply. The first switching element to be switched, the second switching element for switching the conduction state between the other end side of the shielded wire and the frame ground of the power conversion device, and the other end side of the shielded wire by the first switching element. The energized state of the shielded wire when the current is conducted between the diagnostic power supply and the other end side of the shielded wire and the frame ground of the power conversion device are cut off by the second switching element. A control circuit for diagnosing the state of the AC wiring based on the above.

According to the present invention, it is possible to safely diagnose the connection state of the AC wiring connected between the inverter and the load.

It is a block diagram of the motor drive system which concerns on 1st Embodiment of this invention. It is a figure which shows an example of the timing chart of each signal when the AC wiring is a normal state. It is a figure which shows an example of the timing chart of each signal when the AC wiring is an abnormal state. It is sectional drawing which shows the structural example of the AC wiring which concerns on 1st Embodiment of this invention. It is a block diagram of the motor drive system which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the structural example of the AC wiring which concerns on 2nd Embodiment of this invention.

(First Embodiment)
FIG. 1 is a configuration diagram of a motor drive system according to the first embodiment of the present invention. The motor drive system shown in FIG. 1 is mounted on a vehicle such as an automobile and used, and is configured by connecting an inverter 1 and a motor 2 via an AC wiring 3.

The inverter 1 corresponds to the power conversion device according to the embodiment of the present invention, and is a power supply circuit 11, a power conversion control circuit 12, a diagnostic control circuit 13, a smoothing capacitor 14, and a power conversion switching element 15U, 15V, 15W, 16U. , 16V and 16W, diagnostic switching elements 17U, 17V and 17W, ground switching elements 18U, 18V and 18W, and current detectors 19U, 19V and 19W.

The power supply circuit 11 is connected to the low voltage battery 4, and uses the DC power supplied from the low voltage battery 4 to generate a plurality of types of power supplies used in the inverter 1. The power supply generated by the power supply circuit 11 includes the operating power supply of the power conversion control circuit 12 and the diagnostic control circuit 13, as well as the diagnostic power supply 10 connected to the AC wiring 3 via the diagnostic switching elements 17U to 17W. Is done. The diagnostic power supply 10 is a power supply used when the diagnostic control circuit 13 diagnoses the AC wiring 3, and the connection state with the AC wiring 3 is switched according to the switching operation of the diagnostic switching elements 17U to 17W. Be done. For short-circuit protection, it is preferable that the power supply circuit 11 has a current limiting function and that the power supply circuit 11 performs a predetermined safe operation when any of the power supplies is short-circuited.

The power conversion control circuit 12 operates by receiving power supply from the power supply circuit 11 and controls the switching states of the power conversion switching elements 15U to 16W, respectively, to drive the power conversion from DC power to AC power. Generate a signal. The power conversion control circuit 12 determines the timing at which the power conversion switching elements 15U to 16W are turned on and off, respectively, by PWM control based on a torque request value input from a higher-level controller (not shown), and drives signals according to the timing. To generate. The drive signal generated by the power conversion control circuit 12 is output to the power conversion switching elements 15U to 16W, respectively.

The diagnostic control circuit 13 operates by receiving power supply from the power supply circuit 11, generates switching signals for controlling the switching states of the diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W, and also generates switching signals. Diagnose the state of the AC wiring 3. The switching signal generated by the diagnostic control circuit 13 is output to the diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W, respectively. The diagnostic control circuit 13 is configured by using, for example, a microcomputer that executes a predetermined program, an FPGA, or the like. The method of generating the switching signal by the diagnostic control circuit 13 and the method of diagnosing the AC wiring 3 will be described in detail later.

The power conversion switching elements 15U to 16W convert the DC power supplied from the high voltage battery 5 into three-phase AC power by performing a switching operation according to the drive signal input from the power conversion control circuit 12. It is output to the motor 2 which is a load via the AC wiring 3. The power conversion switching elements 15U and 16U are for the U phase of three-phase AC power, the power conversion switching elements 15V and 16V are for the V phase of three-phase AC power, and the power conversion switching elements 15W and 16W are for three-phase AC power. It corresponds to each W phase. For the power conversion switching elements 15U to 16W, for example, an IGBT or MOSFET can be used.

The high voltage battery 5 is connected to the power conversion switching elements 15U to 16W via the contactor 6. When the contactor 6 is turned on by the host controller (not shown), the supply of DC power from the high voltage battery 5 is started. A smoothing capacitor 14 is connected in parallel with the power conversion switching elements 15U to 16W to the high voltage battery 5, and the DC power from the high voltage battery 5 is smoothed by the smoothing capacitor 14.

The AC wiring 3 is composed of cables 31U, 31V, and 31W corresponding to the U phase, the V phase, and the W phase, respectively. The U-phase cable 31U is connected to power conversion switching elements 15U and 16U, and U-phase AC power generated by being converted from DC power by these switching operations is transmitted from the inverter 1 to the motor 2. The V-phase cable 31V is connected to power conversion switching elements 15V and 16V, and the V-phase AC power generated by being converted from DC power by these switching operations is transmitted from the inverter 1 to the motor 2. The W-phase cable 31W is connected to power conversion switching elements 15W and 16W, and the W-phase AC power generated by being converted from DC power by these switching operations is transmitted from the inverter 1 to the motor 2.

The cable 31U has a core wire 32U connected between the power conversion switching elements 15U and 16U and a U-phase winding (not shown) included in the motor 2, and a shielded wire 33U surrounding the core wire 32U. One end side of the shielded wire 33U, that is, the motor 2 side is electrically connected to the frame ground 8 of the motor 2. The other end side of the shielded wire 33U, that is, the inverter 1 side is connected to the diagnostic power supply 10 via the diagnostic switching element 17U and the current detector 19U, and the frame ground of the inverter 1 is connected via the grounding switching element 18U. It is electrically connected to 7.

The cable 31V has a core wire 32V connected between the power conversion switching elements 15V and 16V and a V-phase winding (not shown) included in the motor 2, and a shielded wire 33V surrounding the core wire 32V. One end side of the shielded wire 33V, that is, the motor 2 side is electrically connected to the frame ground 8 of the motor 2. The other end side of the shielded wire 33V, that is, the inverter 1 side is connected to the diagnostic power supply 10 via the diagnostic switching element 17V and the current detector 19V, and the frame ground of the inverter 1 is connected via the grounding switching element 18V. It is electrically connected to 7.

The cable 31W has a core wire 32W connected between the power conversion switching elements 15W and 16W and a W-phase winding (not shown) included in the motor 2, and a shielded wire 33W surrounding the core wire 32W. One end side of the shielded wire 33W, that is, the motor 2 side is electrically connected to the frame ground 8 of the motor 2. The other end side of the shielded wire 33W, that is, the inverter 1 side is connected to the diagnostic power supply 10 via the diagnostic switching element 17W and the current detector 19W, and the frame ground of the inverter 1 is connected via the grounding switching element 18W. It is electrically connected to 7.

It is preferable that the frame ground 7 of the inverter 1 and the frame ground 8 of the motor 2 are electrically connected to each other. For example, when the motor drive system of FIG. 1 is mounted on a vehicle and used, they can be electrically connected to each other by connecting them to the body of the vehicle. This prevents a potential difference from occurring in the shielded wires 33U to 33W when one end side of the shielded wires 33U to 33W is connected to the frame ground 8 of the motor 2 and the other end side is connected to the frame ground 7 of the inverter 1. can.

The diagnostic switching element 17U, the grounding switching element 18U, and the current detector 19U are provided corresponding to the shielded wire 33U, respectively. The diagnostic switching element 17U switches the conduction state between the other end side of the shielded wire 33U and the diagnostic power supply 10 according to the switching signal input from the diagnostic control circuit 13. The grounding switching element 18U switches the conduction state between the other end side of the shielded wire 33U and the frame ground 7 of the inverter 1 according to the switching signal input from the diagnostic control circuit 13. The current detector 19U detects the current flowing through the shielded wire 33U via the diagnostic switching element 17U when the shielded wire 33U and the diagnostic power supply 10 are in a conductive state, and outputs the detection result to the diagnostic control circuit 13. The diagnostic control circuit 13 diagnoses the state of the U-phase cable 31U based on the current detection result by the current detector 19U.

The diagnostic switching element 17V, the grounding switching element 18V, and the current detector 19V are provided corresponding to the shielded wire 33V, respectively. The diagnostic switching element 17V switches the conduction state between the other end side of the shielded wire 33V and the diagnostic power supply 10 according to the switching signal input from the diagnostic control circuit 13. The grounding switching element 18V switches the conduction state between the other end side of the shielded wire 33V and the frame ground 7 of the inverter 1 according to the switching signal input from the diagnostic control circuit 13. The current detector 19V detects the current flowing through the shielded wire 33V via the diagnostic switching element 17V when the shielded wire 33V and the diagnostic power supply 10 are in a conductive state, and outputs the detection result to the diagnostic control circuit 13. The diagnostic control circuit 13 diagnoses the state of the V-phase cable 31V based on the current detection result by the current detector 19V.

The diagnostic switching element 17W, the grounding switching element 18W, and the current detector 19W are provided corresponding to the shielded wire 33W, respectively. The diagnostic switching element 17W switches the conduction state between the other end side of the shielded wire 33W and the diagnostic power supply 10 according to the switching signal input from the diagnostic control circuit 13. The grounding switching element 18W switches the conduction state between the other end side of the shielded wire 33W and the frame ground 7 of the inverter 1 according to the switching signal input from the diagnostic control circuit 13. The current detector 19W detects the current flowing through the shielded wire 33W via the diagnostic switching element 17W when the shielded wire 33W and the diagnostic power supply 10 are in a conductive state, and outputs the detection result to the diagnostic control circuit 13. The diagnostic control circuit 13 diagnoses the state of the W-phase cable 31W based on the current detection result by the current detector 19W.

The motor 2 acts as a load of the inverter 1 by receiving AC power transmitted from the inverter 1 via the AC wiring 3 to rotate and drive a rotor (not shown). The rotary drive of the motor 2 is used, for example, as a driving force for driving the vehicle to travel.

Current sensors 9U, 9V, 9W are arranged between the inverter 1 and the motor 2. The current sensor 9U detects the U-phase alternating current flowing through the cable 31U, and outputs the detection result to the power conversion control circuit 12. The current sensor 9V detects the V-phase AC current flowing through the cable 31V, and outputs the detection result to the power conversion control circuit 12. The current sensor 9W detects the W-phase AC current flowing through the cable 31W, and outputs the detection result to the power conversion control circuit 12. The power conversion control circuit 12 uses these detection results to generate a drive signal to be output to the power conversion switching elements 15U to 16W.

Next, a method of generating a switching signal by the diagnostic control circuit 13 and a method of diagnosing the AC wiring 3 will be described with reference to FIGS. 2 and 3. 2 and 3 are diagrams showing an example of a timing chart of each signal related to the diagnosis of the AC wiring 3. FIG. 2 shows an example when the AC wiring 3 is in a normal state, and FIG. 3 shows an example when the AC wiring 3 is in an abnormal state.

In FIGS. 2 and 3, (a) shows the ignition signal of the vehicle, (b) shows the on / off state of the contactor 6, and (c) shows the DC power supplied from the high voltage battery 5 to the inverter 1. It shows the voltage. (D) shows the on / off state of the upper switch to which the shielded wires 33U to 33W are connected in the inverter 1, that is, the diagnostic switching elements 17U to 17W, and (e) shows the on / off state of the shielded wires 33U to 33W in the inverter 1. The on / off states of the lower switches connected to each other, that is, the grounding switching elements 18U to 18W are shown. (F) shows the shielded current flowing through the shielded wires 33U to 33W, respectively, and (g) shows the status signal output from the diagnostic control circuit 13 as the diagnostic result of the AC wiring 3.

When the AC wiring 3 is in the normal state, when the ignition signal changes from off to on at time t1 as shown in FIG. 2A, the power of the inverter 1 is turned on accordingly, and the diagnosis is made by the power supply circuit 11. The generation of the power supply 10 is started. At this time, as shown in (d), the diagnostic switching elements 17U to 17W are in the off state, and the shielded wires 33U to 33W and the diagnostic power supply 10 are cut off. On the other hand, as shown in (e), the grounding switching elements 18U to 18W are in the ON state, and the shielded wires 33U to 33W and the frame ground 7 of the inverter 1 are conductive.

When the generation of the diagnostic power supply 10 is started at time t1, the diagnostic control circuit 13 switches the grounding switching elements 18U to 18W from on to off as shown in (e) at time t2, so that the shielded wire 33U It cuts off between ~ 33W and the frame ground 7 of the inverter 1. After that, as further shown in (d), by switching the diagnostic switching elements 17U to 17W from off to on, the shielded wires 33U to 33W and the diagnostic power supply 10 are made conductive. At this time, the diagnostic control circuit 13 sets a predetermined dead time period td in which both of the grounding switching elements 18U to 18W are turned off until the diagnostic switching elements 17U to 17W are turned on. It is provided to generate and output switching signals for the diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W.

As described above, switching control of the diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W is performed, and the diagnostic control circuit 13 uses the current detectors 19U to 19W to connect the shielded wires 33U to 33W, respectively. Detects the flowing shielded current. At this time, if the AC wiring 3 is in a normal state and the shielded wires 33U to 33W are normally connected to the inverter 1 and the motor 2, the frame of the motor 2 is connected from the diagnostic power supply 10 via the shielded wires 33U to 33W. Since the current flows through the ground 8, the shielded current as shown in FIG. 2 (f) is detected.

The diagnostic control circuit 13 sets a predetermined diagnostic determination period tj as shown in (f) corresponding to the timing when the diagnostic switching elements 17U to 17W are on. Then, the AC wiring 3 is diagnosed by comparing the shield current detected in this diagnosis determination period tj with the predetermined determination threshold value th. In the case of FIG. 2, since the shield current in the diagnosis determination period tj is equal to or greater than the determination threshold value th, the diagnostic control circuit 13 diagnoses that the AC wiring 3 is normal. In this case, as shown in FIG. 2 (g), the diagnostic control circuit 13 outputs the status signal to the host controller (not shown) without changing the status signal at the L level.

Further, the diagnostic control circuit 13 switches the diagnostic switching elements 17U to 17W from on to off as shown in (d) when a predetermined on period tun has elapsed after turning on the diagnostic switching elements 17U to 17W. Then, the shielded wires 33U to 33W and the diagnostic power supply 10 are cut off again. After that, at the time t3 when the predetermined dead time period td has elapsed, the shielded wires 33U to 33W and the frame ground 7 of the inverter 1 are switched from off to on by switching the grounding switching elements 18U to 18W as shown in (e). Conducts again between and.

Upon receiving the above status signal from the diagnostic control circuit 13, the host controller determines that the diagnostic result of the AC wiring 3 is normal, and switches the contactor 6 from off to on at time t4 as shown in FIG. 2 (b). .. As a result, as shown in (c), the voltage of the DC power supplied from the high voltage battery 5 to the inverter 1 rises, and the power conversion operation from the DC power to the AC power by the inverter 1 is started.

On the other hand, when the AC wiring 3 is in an abnormal state, when the ignition signal changes from off to on at time t1 as shown in FIG. 3A, the power of the inverter 1 is turned on accordingly, and the power supply circuit 11 Starts the generation of the diagnostic power supply 10. The switching states of the diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W at this time are the same as those in FIG. That is, as shown in (d), the diagnostic switching elements 17U to 17W are in the off state, and the shielded wire 33U to 33W and the diagnostic power supply 10 are cut off. On the other hand, as shown in (e), the grounding switching elements 18U to 18W are in the ON state, and the shielded wires 33U to 33W and the frame ground 7 of the inverter 1 are conductive.

When the generation of the diagnostic power supply 10 is started at time t1, the diagnostic control circuit 13 switches the diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W, respectively, at the same timing as in FIG. That is, the grounding switching elements 18U to 18W are switched from on to off at time t2, and the diagnostic switching elements 17U to 17W are switched from off to on after the lapse of a predetermined dead time period td. Then, the current detectors 19U to 19W are used to detect the shielded currents flowing through the shielded wires 33U to 33W, respectively. Further, when a predetermined on period tun elapses after the diagnostic switching elements 17U to 17W are turned on, the shielded wires 33U to 33W and the diagnostic power supply 10 are switched by switching the diagnostic switching elements 17U to 17W from on to off. Shut off again. After that, at the time t3 when the predetermined dead time period td has elapsed, the shielded wires 33U to 33W and the frame ground 7 of the inverter 1 are reconducted by switching the grounding switching elements 18U to 18W from off to on. ..

Here, when at least one of the shielded wires 33U to 33W in the AC wiring 3 is not electrically connected to the frame ground 8 of the motor 2, even if the diagnostic switching elements 17U to 17W are turned on, it is for diagnosis. No current flows from the power supply 10 to the frame ground 8 of the motor 2 via the shielded wire. Therefore, as shown in FIG. 3 (f), a shield current that remains 0 and does not change is detected.

When the shielded wires 33U to 33W are not electrically connected to the frame ground 8 of the motor 2, for example, the connectors attached to the U-phase, V-phase, and W-phase cables 31U, 31V, and 31W are used. This corresponds to the case where the cable is disconnected from the inverter 1 or the motor 2, or the case where the shielded wires 33U to 33W of each cable are pulled out from the connector while the connector is fixed to the inverter 1 or the motor 2. Further, the case where each cable is completely broken, that is, the case where both the core wires 32U to 32W and the shielded wires 33U to 33W are broken is also applicable. When such an abnormal state occurs in the AC wiring 3, even if the shielded wires 33U to 33W and the diagnostic power supply 10 are made conductive by the diagnostic switching elements 17U to 17W, as shown in FIG. 3 (f). Shielded current does not flow.

The diagnostic control circuit 13 diagnoses the AC wiring 3 by comparing the shield current detected in the preset predetermined diagnostic determination period tj with the predetermined determination threshold value th, as described with reference to FIG. conduct. In the case of FIG. 3, since the shield current in the diagnosis determination period tj is less than the determination threshold value th as shown in (f), the diagnostic control circuit 13 diagnoses that the AC wiring 3 is abnormal. In this case, the diagnostic control circuit 13 changes the status signal from the L level to the H level as shown in (g), and outputs the status signal to an upper controller (not shown).

Upon receiving the above status signal from the diagnostic control circuit 13, the host controller determines that the diagnostic result of the AC wiring 3 is abnormal, and leaves the contactor 6 off as shown in FIG. 3 (b). As a result, as shown in (c), the supply of DC power from the high voltage battery 5 to the inverter 1 can be prevented in advance, and the inverter 1 and the motor 2 can be kept in a safe state where no high voltage is applied. can.

Further, after the diagnosis of the AC wiring 3 by the diagnostic control circuit 13 is completed, the shielded wires 33U to 33W and the diagnostic power supply 10 are cut off by the diagnostic switching elements 17U to 17W, and the grounding switching elements 18U to 18U. The shielded wires 33U to 33W are electrically connected to the frame ground 7 of the inverter 1 by 18W. Therefore, the voltage of the shielded wires 33U to 33W with respect to the frame ground 7 of the inverter 1 and the frame ground 8 of the motor 2 can be set to 0, so that even if a person touches the shielded wires 33U to 33W while the shielded wires 33U to 33W are disconnected, an electric shock will occur. The danger can be avoided.

As described above, when the AC wiring 3 is diagnosed, by turning on the diagnostic switching elements 17U to 17W, a shielded current flows through the shielded wires 33U to 33W via the diagnostic switching elements 17U to 17W. Therefore, in order to prevent an excessive shield current from flowing, the diagnostic switching elements 17U to 17W need to have a certain resistance value when in the ON state. On the other hand, except at the time of diagnosis of the AC wiring 3, by turning on the grounding switching elements 18U to 18W, the shielded wires 33U to 33W are electrically connected to the frame ground 7 of the inverter 1 via the grounding switching elements 18U to 18W. Connected to. Therefore, in order to reduce the grounding resistance, the grounding switching elements 18U to 18W preferably have a resistance value as small as possible in the on state, and at least the resistance value in the on state is smaller than that of the diagnostic switching elements 17U to 17W. Is preferable.

FIG. 4 is a cross-sectional view showing a structural example of the AC wiring 3 according to the first embodiment of the present invention. In the present embodiment, the cables 31U, 31V, and 31W constituting the AC wiring 3 each have a structure as shown in FIG. That is, the central portion where the conductor is covered with the insulating layer corresponds to the core wire 32U, 32V, 32W, and this is surrounded by the electric shield layer corresponding to the shielded wire 33U, 33V, 33W. The outside of the electric shield layer is covered with a sheath to protect and insulate each cable.

According to the first embodiment of the present invention described above, the following effects are exhibited.

(1) The inverter 1 converts the DC power supplied from the high voltage battery 5 into AC power, and AC power is passed through the AC wiring 3 formed by the core wires 32U to 32W surrounded by the shield wires 33U to 33W. Is output to the motor 2 which is a load. One end of the shielded wires 33U to 33W is electrically connected to the frame ground 8 of the motor 2. Inverter 1 includes diagnostic switching elements 17U to 17W that switch the conduction state between the other end of the shielded wires 33U to 33W and the diagnostic power supply 10, and the other end of the shielded wires 33U to 33W and the frame ground of the inverter 1. It is provided with a grounding switching element 18U to 18W for switching the conduction state between the 7 and the diagnostic control circuit 13. In the diagnostic control circuit 13, the other end side of the shielded wire 33U to 33W is conducted by the diagnostic switching elements 17U to 17W and the diagnostic power supply 10, and the shielded wire 33U to 33W is connected by the grounding switching element 18U to 18W. The state of the AC wiring 3 is diagnosed based on the energized state of the shielded wires 33U to 33W when the other end side of the shielded wire 33U and the frame ground 7 of the inverter 1 are cut off. Since this is done, the voltage of the shielded wires 33U to 33W with respect to the frame ground 7 of the inverter 1 and the frame ground 8 of the motor 2 can be set to 0 except when the AC wiring 3 is diagnosed, so that the shielded wires 33U to 33W are disconnected. Even if a person touches it while doing so, the risk of electric shock can be avoided. Therefore, the connection state of the AC wiring 3 connected between the inverter 1 and the motor 2 can be safely diagnosed.

(2) The AC wiring 3 includes a plurality of core wires 32U to 32W for transmitting each of U-phase, V-phase, and W-phase AC power, and a plurality of shielded wires 33U to 33W surrounding each of the core wires 32U to 32W. Have. The diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W are provided for each shielded wire 33U to 33W, respectively. Since this is done, the connection state of each of the cables 31U, 31V and 31W constituting the AC wiring 3 can be safely diagnosed.

(3) The diagnostic control circuit 13 is provided with a dead time period td in which both the diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W are turned off, and the diagnostic switching elements 17U to 17W and the grounding switching element are provided. Switching control from 18U to 18W is performed. Since this is done, it is possible to prevent a short circuit between the diagnostic power supply 10 and the frame ground 7 in the inverter 1 and improve safety.

(4) The inverter 1 further includes a power supply circuit 11 that generates a diagnostic power supply 10. As described with reference to FIGS. 2 and 3, the diagnostic control circuit 13 is set between the time when the power supply circuit 11 starts generating the diagnostic power supply 10 and the time when the high voltage battery 5 starts supplying DC power, that is, the time. Between t1 and time t4, the other end of the shielded wires 33U to 33W and the diagnostic power supply 10 are conducted (diagnosis switching elements 17U to 17W are on), and the shielded wires 33U to 33W and others. Switching control between the diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W is performed so that the connection between the end side and the frame ground 7 of the inverter 1 is cut off (grounding switching elements 18U to 18W are turned off). Then, the AC wiring 3 is diagnosed. Since this is done, it is possible to prevent the supply of DC power from the high voltage battery 5 to the inverter 1 in advance when the connection state of the AC wiring 3 is abnormal. Therefore, the inverter 1 and the motor 2 can be kept in a safe state in which a high voltage is not applied.

(5) Further, the diagnostic control circuit 13 shields before the time t1 when the power supply circuit 11 starts generating the diagnostic power supply 10 and after the time t4 when the high voltage battery 5 starts supplying DC power. The other end of the wires 33U to 33W and the diagnostic power supply 10 are cut off (the diagnostic switching elements 17U to 17W are off), and the other end of the shielded wires 33U to 33W and the frame ground 7 of the inverter 1 Switching control between the diagnostic switching elements 17U to 17W and the grounding switching elements 18U to 18W is performed so that the intervals between the two are conducted (the grounding switching elements 18U to 18W are turned on). Since this is done, the voltage of the shielded wires 33U to 33W with respect to the frame ground 7 of the inverter 1 and the frame ground 8 of the motor 2 is surely set to 0 except when the AC wiring 3 is diagnosed, and the risk of electric shock is avoided. be able to.

(6) It is preferable that the grounding switching elements 18U to 18W have a smaller resistance value in the on state than the diagnostic switching elements 17U to 17W. By doing so, it is possible to prevent an excessive shield current from flowing in the shielded wires 33U to 33W at the time of diagnosing the AC wiring 3, and to reduce the grounding resistance of the shielded wires 33U to 33W.

(Second embodiment)
FIG. 5 is a block diagram of a motor drive system according to a second embodiment of the present invention. The motor drive system shown in FIG. 5 is mounted on, for example, a vehicle such as an automobile and used in the same manner as the motor drive system of FIG. 1 described in the first embodiment, and the inverter 1A and the motor 2 are AC. It is configured by being connected via the wiring 3A.

In the AC wiring 3A, as compared with the AC wiring 3 described in the first embodiment, the core wires 32U, 32V, 32W corresponding to the U phase, the V phase, and the W phase are integrated into one cable 31. The difference is that the cable 31 is provided with one shielded wire 33. Further, the inverter 1A is replaced with the diagnostic switching elements 17U to 17W, the grounding switching elements 18U to 18W, and the current detectors 19U to 19W in FIG. 1 as compared with the inverter 1 described in the first embodiment. The difference is that the diagnostic switching element 17, the grounding switching element 18, and the current detector 19 are provided for each shielded wire 33.

The diagnostic control circuit 13 performs switching control of the diagnostic switching element 17 and the grounding switching element 18 at a predetermined timing by the same procedure as described in the first embodiment, and uses the current detector 19. The shield current flowing through the shielded wire 33 is detected. Then, by comparing the detected shield current with a predetermined determination threshold value th, it is diagnosed whether the AC wiring 3 is normal or abnormal, and the diagnosis result is output to a higher-level controller (not shown). Thereby, as in the first embodiment, the connection state of the AC wiring 3A connected between the inverter 1A and the motor 2 can be safely diagnosed.

FIG. 6 is a cross-sectional view showing a structural example of the AC wiring 3A according to the second embodiment of the present invention. In the present embodiment, the cable 31 constituting the AC wiring 3A has a structure as shown in FIG. That is, one electric shield layer corresponding to the shielded wire 33 collectively surrounds the three core wires 32U, 32V, 32W each formed by covering the conductor with an insulating layer. The outside of this electric shield layer is covered with a sheath for protecting and insulating the cable 31.

According to the second embodiment of the present invention described above, the AC wiring 3 has a plurality of core wires 32U to 32W and core wires 32U to 32W for transmitting each of U-phase, V-phase, and W-phase AC power. It has one shield wire 33 which collectively surrounds the shield wire 33. The diagnostic switching element 17 and the grounding switching element 18 are provided for one shielded wire 33, respectively. Since this is done, the connection state of the AC wiring 3 can be safely diagnosed while reducing the number of diagnostic switching elements and grounding switching elements.

The embodiments and various modifications described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired. Further, although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects considered within the scope of the technical idea of the present invention are also included within the scope of the present invention.

1,1A: Inverter 2: Motor 3,3A: AC wiring 4: Low voltage battery 5: High voltage battery 6: Contactor 7: Frame ground 8: Frame ground 9U, 9V, 9W: Current sensor 10: Diagnostic power supply 11: Power supply circuit 12: Power conversion control circuit 13: Diagnostic control circuit 14: Smoothing capacitor 15U, 15V, 15W, 16U, 16V, 16W: Power conversion switching element 17, 17U, 17V, 17W: Diagnostic switching element 18, 18U, 18V, 18W: Grounding switching element 19, 19U, 19V, 19W: Current detector 31, 31U, 31V, 31W: Cable 32U, 32V, 32W: Core wire 33, 33U, 33V, 33W: Shielded wire

Claims (7)

A power conversion device that converts DC power supplied from a high-voltage power supply into AC power and outputs the AC power to a load via AC wiring formed by surrounding a core wire with a shielded wire.
One end side of the shielded wire is electrically connected to the frame ground of the load.
The power converter is
A first switching element that switches the conduction state between the other end of the shielded wire and the diagnostic power supply,
A second switching element that switches the conduction state between the other end of the shielded wire and the frame ground of the power conversion device, and
The other end side of the shielded wire and the diagnostic power supply are conducted by the first switching element, and the other end side of the shielded wire and the frame ground of the power conversion device are connected by the second switching element. A power conversion device comprising a control circuit for diagnosing the state of the AC wiring based on the energized state of the shielded wire when the space is cut off. The power conversion device according to claim 1.
The AC wiring has a plurality of core wires for transmitting each of the plurality of phases of the AC power, and a plurality of shielded wires surrounding each of the plurality of core wires.
The first switching element and the second switching element are power conversion devices provided for each of the plurality of shielded wirings. The power conversion device according to claim 1.
The AC wiring has a plurality of core wires for transmitting each of the plurality of phases of the AC power, and one shielded wire that collectively surrounds the plurality of core wires.
The first switching element and the second switching element are power conversion devices provided for the one shielded wiring, respectively. The power conversion device according to any one of claims 1 to 3.
The control circuit is a power conversion device that controls switching between the first switching element and the second switching element by providing a dead time period in which both the first switching element and the second switching element are turned off. The power conversion device according to any one of claims 1 to 3.
Further equipped with a power supply circuit for generating the diagnostic power supply,
The control circuit includes the other end of the shielded wire and the diagnostic power supply between the time when the power supply circuit starts generating the diagnostic power supply and the time when the high voltage power supply starts supplying the DC power. The switching control between the first switching element and the second switching element is performed so that the connection between the first switching element and the frame ground of the power conversion device is cut off from the other end side of the shielded wire. A power conversion device that diagnoses the AC wiring. The power conversion device according to claim 5.
The control circuit includes the other end of the shielded wire and the diagnostic power supply before the power supply circuit starts generating the diagnostic power supply and after the high voltage power supply starts supplying the DC power. The switching control between the first switching element and the second switching element is performed so that the space between the two is cut off and the other end side of the shielded wire and the frame ground of the power conversion device are conducted. Power converter. The power conversion device according to any one of claims 1 to 3.
The second switching element is a power conversion device having a smaller resistance value in the on state than the first switching element.

Images