Winding switching system, control device, control method, and computer program

Abstract

This winding switching system comprises a winding switching unit, a measuring unit, and an abnormality detection unit. The winding switching unit switches the connection status of a plurality of windings in an AC motor, which includes the plurality of windings on a stator of each phase. The measuring unit measures a physical quantity relating to rotation of the AC motor. The abnormality detection unit assesses, on the basis of the physical quantity measured by the measuring unit, whether current flowing in each phase of the AC motor is balanced.

Description

Winding switching system, control device, control method, and computer program

[0001] This application claims priority to Japanese Patent Application No. 2023-004994, filed on January 17, 2023, and incorporates by reference all of the contents of that application.

[0002] Patent Document 1 discloses a diagnostic system for a variable characteristic vehicle motor that changes the switching characteristics of the windings using a switch. The diagnostic system detects abnormalities using a switch state sensor that detects abnormalities in the switch, and if an abnormality is determined, it discloses that an emergency action such as cutting off the power supply is taken.

[0003] International Publication No. 2016 / 088265

[0004] A winding switching system according to one aspect of the present disclosure includes a winding switching unit that switches the connection state of a plurality of windings of an AC motor having a stator for each phase; a measurement unit that measures a physical quantity related to the rotation of the AC motor; and an abnormality detection unit that determines whether or not the currents flowing through each phase of the AC motor are balanced based on the physical quantity measured by the measurement unit.

[0005] The present disclosure can be realized not only as a winding switching system having the above-described characteristic configuration, but also as a control device included in the winding switching system, or as a control method for a vehicle motor in which characteristic processing steps in the control device are performed. The present disclosure can be realized as a computer program that causes a computer to function as the control device, or as a semiconductor integrated circuit in which part or all of the control device is implemented.

[0006] FIG. 1 is a diagram illustrating an example of the configuration of a winding switching system according to a first embodiment. FIG. 2 is a block diagram illustrating an example of the hardware configuration of a control device. FIG. 3 is a circuit diagram illustrating an example of the configuration of a winding switching device according to the first embodiment. FIG. 4 is a diagram for explaining an example of an unbalanced state of a motor. FIG. 5 is a diagram illustrating a relay failure pattern. FIG. 6 is an example of a simulation of phase currents, relay currents, and d- and q-axis currents when a motor is in an unbalanced state. FIG. 7 is an example of a simulation of phase currents, relay currents, and d- and q-axis currents when a motor is in an unbalanced state. FIG. 8 is an example of a simulation of phase currents, relay currents, and d- and q-axis currents when a motor is in an unbalanced state. FIG. 9 is a flowchart illustrating an example of a winding switching process performed by a control device according to the first embodiment. FIG. 10 is a circuit diagram illustrating an example of the configuration of a winding switching device according to a second embodiment. FIG. 11 is a flowchart illustrating an example of a winding switching process performed by a control device according to the second embodiment. FIG. 12 is a flowchart illustrating an example of a winding switching process performed by a control device according to the third embodiment. FIG. 13 is a circuit diagram illustrating an example of a configuration of a winding switching system according to a fourth embodiment. Fig. 14 is a flowchart showing an example of winding switching processing by the control device according to the fourth embodiment. Fig. 15 is a circuit diagram showing an example of the configuration of a winding switching system according to the fifth embodiment. Fig. 16 is a circuit diagram showing an example of the configuration of a winding switching system according to the sixth embodiment. Fig. 17 is a flowchart showing an example of winding switching processing by the control device according to the sixth embodiment. Fig. 18 is a circuit diagram showing an example of the configuration of a modified example of the winding switching device.

[0007] <Problem to be Solved by the Invention> When an abnormality occurs in the switch that switches the windings, the diagnostic system disclosed in Patent Document 1 detects the abnormality using a switch status sensor that detects the switch abnormality and takes emergency action such as cutting off the power supply. For this reason, it is necessary to provide a separate switch status sensor. <Effects of the Invention>

[0008] According to the present disclosure, abnormalities such as a stuck relay that switches windings can be detected based on the equilibrium state of the motor.

[0009] <Outline of Embodiments of the Present Disclosure> Below, an outline of embodiments of the present disclosure will be listed and described.

[0010] (1) A winding switching system according to this embodiment includes a winding switching unit that switches the connection state of a plurality of windings of an AC motor having a stator for each phase, a measurement unit that measures a physical quantity related to the rotation of the AC motor, and an abnormality detection unit that determines whether or not the currents flowing through each phase of the AC motor are balanced based on the physical quantity measured by the measurement unit. This makes it possible to detect an abnormality in the winding switching unit that switches the windings based on the balanced state of the motor.

[0011] (2) In the above (1), the winding switching unit may switch the connection states of the plurality of windings using a plurality of relays. This makes it possible to detect an abnormality in the winding switching unit that switches the windings using relays based on the equilibrium state of the motor.

[0012] (3) In the above (2), the abnormality detection unit may detect an abnormality occurring in the plurality of relays by determining whether or not the currents flowing through the respective phases of the AC motor are balanced. This makes it possible to detect an abnormality in a winding switching unit that switches windings using relays by determining whether or not the currents flowing through the respective phases of the motor are balanced.

[0013] (4) In any one of the winding switching systems (1) to (3), the measurement unit may include a current sensor that measures the current flowing through each of the phases, and the abnormality detection unit may determine that the currents flowing through each of the phases are not balanced when the currents measured by the current sensors exceed a threshold value. This allows the currents measured by the current sensors to be determined to be in an unbalanced state when they exceed the threshold value, and based on this, an abnormality in the winding switching unit can be detected.

[0014] (5) In the above (4), the current sensors may measure phase currents flowing through the stators of the respective phases. In this way, when the phase currents measured by the current sensors exceed a threshold value, it is determined that an unbalanced state exists, and based on this, an abnormality in the winding switching unit can be detected.

[0015] (6) In the above (4), at least one of the plurality of relays may be a relay that is set to ON in a first connection state and set to OFF in a second connection state, and the current sensor may measure a current (relay current) flowing through the relay that is set to ON. In this way, when the relay current measured by the current sensor exceeds a threshold, it is determined that an unbalanced state has occurred, and based on this, an abnormality in the winding switching unit can be detected.

[0016] (7) In any one of (4) to (6) above, the AC motor may be a drive motor that drives wheels of a vehicle, and the abnormality detection unit may change the threshold value based on an output required of the AC motor. In this way, by changing the threshold value based on the output required of the motor, which is determined by an accelerator opening, a required speed, a required torque, etc., it is possible to appropriately determine the equilibrium state of the motor and detect an abnormality in the winding switching unit.

[0017] (8) In any one of (1) to (3) above, the measurement unit may include a current sensor that measures phase currents flowing through a stator of each phase, and measure d-axis currents and q-axis currents flowing through the AC motor based on the phase currents, and the abnormality detection unit may compare a target d-axis current that is a target value of the d-axis current and a target q-axis current that is a target value of the q-axis current with a measured d-axis current that is a measurement of the d-axis current and a measured q-axis current that is a measurement of the q-axis current, and determine that the currents flowing through each phase are out of balance when at least one of a first condition that a difference between the target d-axis current and the measured d-axis current is equal to or greater than a first threshold and a second condition that a difference between the target q-axis current and the measured q-axis current is equal to or greater than a second threshold is satisfied. This makes it possible to determine the balanced state of the motor even in cases where it is difficult to determine the balanced state of the motor based on the phase currents or the relay current.

[0018] (9) In the above (8), the AC motor may be a drive motor that drives wheels of a vehicle, and the abnormality detection unit may change at least one of the first threshold value and the second threshold value based on an output required of the AC motor. In this way, the threshold value is changed based on the output required of the motor, which is determined by an accelerator opening, a required speed, a required torque, etc., so that the equilibrium state of the motor can be appropriately determined.

[0019] (10) In the above (8), the anomaly detection unit may determine that the currents flowing through the phases are not balanced when at least one of the period during which the first condition is satisfied and the period during which the second condition is satisfied exceeds a reference value. This makes it possible to eliminate erroneous determinations and properly determine the balanced state of the motor, even in a situation where noise suddenly enters, by determining that an unbalanced state exists when a situation in which the difference is equal to or greater than a threshold continues for a predetermined period of time or longer.

[0020] (11) In the above (10), the abnormality detection unit may change the reference value based on the rotation speed of the rotor of the AC motor. This makes it possible to appropriately determine the balanced state of the motor even when the rotation speed of the rotor decreases and the measured d-axis and q-axis currents fluctuate slowly.

[0021] (12) In any one of (1) to (3) above, the measurement unit may include a voltage sensor that measures voltages of the plurality of windings, thereby making it possible to determine a balanced state of the motor based on the voltages of the windings.

[0022] (13) In any one of (1) to (3) above, the measurement unit may include a sensor that measures the output torque or rotation speed of the AC motor. This makes it possible to determine the equilibrium state of the motor based on the torque or rotation speed of the motor.

[0023] (14) In any one of (1) to (13) above, the winding switching system may further include a restoration unit that restores the winding switching unit to the connection state before switching when the abnormality detection unit determines that the currents flowing through the phases of the AC motor are not balanced in response to the winding switching unit switching the connection state. In this way, when an abnormality is detected in the winding switching unit that switches the windings, the winding switching unit is restored to the connection state before switching, and the motor can continue to operate.

[0024] (15) In any one of (1) to (14) above, the winding switching system may further include a notification unit that notifies a user of the occurrence of an abnormality when the abnormality detection unit determines that the currents flowing through the phases of the AC motor are not balanced, thereby allowing the user of the motor to know that the motor is unbalanced.

[0025] (16) A winding switching system according to this embodiment includes a winding switching unit that switches the connection states of multiple windings of an AC motor capable of switching the connection states of the multiple windings included in a stator of each phase, a measurement unit that measures a physical quantity related to the rotation of the AC motor and an equilibrium determination unit that determines whether or not currents flowing through each phase of the AC motor are balanced based on the physical quantity measured by the measurement unit, and a restoration unit that switches the connection state from the second state to the first connection state when the determination by the equilibrium determination unit changes from that the currents flowing through each phase are balanced to that the currents flowing through each phase are not balanced in response to the connection state being switched from a first connection state to a second connection state. Thus, when an abnormality is detected in the winding switching unit that switches the windings, the winding switching unit is restored to the connection state before switching, allowing the motor to continue operating.

[0026] (17) A control device according to this embodiment includes a winding switching unit that switches the connection state of a plurality of windings of an AC motor that includes a stator for each phase, a measurement unit that includes a sensor that measures a physical quantity related to the rotation of the AC motor, and an abnormality detection unit that determines whether the currents flowing through each phase of the AC motor are balanced based on the physical quantity measured by the measurement unit. This allows the motor to return to a balanced state and continue operating even if a failure such as a stuck relay that switches the windings occurs and the motor becomes unbalanced. This makes it possible to detect an abnormality in the winding switching unit that switches the windings based on the balanced state of the motor.

[0027] (18) A control method for a winding switching device according to this embodiment includes a winding switching step of switching connections of a plurality of windings of an AC motor having a stator for each phase, a measurement step of measuring a physical quantity related to the rotation of the AC motor, and an abnormality detection step of determining whether or not currents flowing through each phase of the AC motor are balanced based on the physical quantity measured in the measurement step. This makes it possible to detect an abnormality in a winding switching unit that switches windings based on the balanced state of the motor.

[0028] (19) A computer program according to this embodiment is a computer program used by a control device that controls a winding switching device, and causes a computer to execute a winding switching step of switching the connection states of multiple windings of an AC motor that is capable of switching the connection states of the multiple windings included in a stator of each phase, a measurement step of measuring a physical quantity related to the rotation of the AC motor, and an abnormality detection step of determining whether or not currents flowing through each phase of the AC motor are balanced based on the physical quantity measured in the measurement step. This makes it possible to detect an abnormality in the winding switching unit that switches the windings based on the balanced state of the motor.

[0029] <Details of Embodiments of the Present Disclosure> Hereinafter, details of embodiments of the present disclosure will be described with reference to the drawings. Note that at least some of the embodiments described below may be combined in any manner.

[0030] [1. First Embodiment] [1-1. Winding Switching System] FIG. 1 is a diagram showing an example of the configuration of a winding switching system according to a first embodiment.

[0031] The winding switching system 10 is mounted on a vehicle (hereinafter referred to as an "electric vehicle") that is propelled by a motor, such as an electric vehicle, a plug-in hybrid vehicle, etc. The winding switching system 10 includes a motor 20, a power converter 30, a battery 40, a control device 50, and a winding switching device 100.

[0032] The motor 20 is a traction motor that generates propulsion force for the electric vehicle. In other words, the motor 20 is connected to the wheels 60 and is a drive motor that drives the wheels 60. The motor 20 is driven by three-phase AC power. The motor 20 is a non-commutator AC motor that does not have a commutator and drives a stator to generate a rotating magnetic field, which then rotates the rotor. Examples of non-commutator AC motors include synchronous motors, reluctance motors, and induction motors.

[0033] The battery 40 is a battery that supplies power to drive the motor 20. The battery 40 is a secondary battery, such as a lithium ion battery.

[0034] The power converter 30 is an inverter that converts DC power supplied from the battery 40 into three-phase AC power. The power converter 30 may have a function of converting three-phase AC power output when the motor 20 functions as a generator into DC power and charging the battery 40.

[0035] The power converter 30 includes U-phase, V-phase, and W-phase legs. The U-phase leg includes switches 31u and 32u, the V-phase leg includes switches 31v and 32v, and the W-phase leg includes switches 31w and 32w. The switches 31u, 32u, 31v, 32v, 31w, and 32w perform switching to convert DC power into three-phase AC power. The switches 31u, 32u, 31v, 32v, 31w, and 32w are, for example, insulated gate bipolar transistors (IGBTs) or metal oxide semiconductor field-effect transistors (MOSFETs).

[0036] A power line 35u corresponding to the U phase extends from the U-phase leg, a power line 35v corresponding to the V phase extends from the V-phase leg, and a power line 35w corresponding to the W phase extends from the W-phase leg. In the power converter 30, a current sensor 33u is provided on the power line 35u, a current sensor 33v is provided on the power line 35v, and a current sensor 33w is provided on the power line 35w. The current sensor 33u detects the current value of the U-phase current Iu. The current sensor 33v detects the current value of the V-phase current Iv. The current sensor 33w detects the current value of the W-phase current Iw. The current sensors 33u, 33v, and 33w can detect the current values ​​of the currents Iu, Iv, and Iw flowing through the power lines 35u, 35v, and 35w, including DC and AC components. The current sensors 33u, 33v, and 33w are, for example, DC current sensors (direct current sensors) that use Hall sensors or shunt resistors.

[0037] The winding switching device 100 is disposed between the motor 20 and the power converter 30. The power converter 30 and the winding switching device 100 are connected by power lines 35u, 35v, and 35w, and the winding switching device 100 and the motor 20 are connected by a plurality of power lines 25. The winding switching device 100 switches the connection state of a plurality of windings of the motor 20. The configuration of the winding switching device 100 will be described later. Three-phase AC currents Iu, Iv, and Iw output from the power converter 30 are supplied to the motor 20 via the winding switching device 100.

[0038] The measuring device 26 measures physical quantities related to the rotation of the motor 20. Examples of physical quantities related to the rotation of the motor include, but are not limited to, the current flowing through each winding of the motor 20, the voltage of each winding, and the torque of the output shaft of the motor 20. The measuring device 26 is provided at a location corresponding to the measurement target. When measuring the current or voltage of the power line connecting the winding switching device 100 and the motor 20, the measuring device 26 is provided on the power lines 212u, 221u, 212v, 221v, 212w, and 221w connecting the winding switching device 100 and the motor 20. When measuring the torque and rotation speed of the output shaft of the motor 20, the measuring device 26 is provided on the output shaft of the motor 20. The current is measured by a current sensor. The current sensor is, for example, a DC current sensor using a Hall sensor. The voltage is measured by a voltage sensor. The voltage sensor is, for example, an AD converter. A first terminal of the winding and a reference voltage point (the vehicle body) are connected to a first terminal and a second terminal of the input terminal of the AD converter, respectively. If the processor 501 described below has a built-in AD converter, the first and second terminals of the winding may be connected to the first and second input terminals of the AD converter of the processor 501. The torque is measured by a torque sensor, such as a strain gauge.

[0039] The control device 50 controls the motor 20. Specifically, the control device 50 controls the power converter 30 and the winding switching device 100 to control the motor 20. A signal line extends from the control device 50 to each of the switches 31u, 32u, 31v, 32v, 31w, and 32w, and the control device 50 controls the on / off timing of the switches 31u, 32u, 31v, 32v, 31w, and 32w. A signal line extends from the control device 50 to the winding switching device 100, and the control device 50 outputs a switching command signal to the winding switching device 100 to command the switching of the connection state of the windings.

[0040] The control device 50 may be configured to perform vector control of the motor 20. Vector control is a method of decomposing the current flowing through the U-, V-, and W-phases of an AC motor stator into a current component that generates magnetic flux and a current component that generates torque, and independently controlling each current component. This allows the direction and magnitude of the magnetic flux of the rotating magnetic field of the motor to be controlled as a vector quantity. The current component that generates magnetic flux is sometimes called the d-axis current, and the current component that generates torque is sometimes called the q-axis current. The currents flowing through the U-, V-, and W-phases of the motor stator can be measured, and the d-axis current and q-axis current can be calculated based on the measured currents. For example, the control device 50 compares a target d-axis current, which is a target value of the d-axis current, and a target q-axis current, which is a target value of the q-axis current, with a measured d-axis current, which is a measured value of the d-axis current, and a measured q-axis current, which is a measured value of the q-axis current, and controls the power converter 30 so that the measured d-axis current and the measured q-axis current become the target d-axis current and the target q-axis current, respectively. The target d-axis current and the target q-axis current are determined based on the output (rotational speed, torque) required of the motor 20, for example.

[0041] The control device 50 is connected to a sensor 71 that detects the amount of depression of the brake pedal 70, and receives a detection signal output from the sensor 71. The control device 50 is connected to a sensor 81 that detects the amount of depression of the accelerator pedal 80, and receives a detection signal output from the sensor 81.

[0042] A rotation sensor 201 that detects the rotation speed of the motor 20 and a torque sensor 202 that detects the output torque of the motor 20 are attached to the output shaft of the motor 20. The rotation sensor 201 and the torque sensor 202 are connected to the control device 50. The control device 50 receives a detection signal output from the rotation sensor 201 and a detection signal output from the torque sensor 202.

[0043] The control device 50 is connected to a gear shift indicator 90. The gear shift indicator 90 is an input device through which the driver inputs a gear shift instruction. The gear shift indicator 90 is, for example, a shift lever. In another example, the gear shift indicator 90 is a switch through which the driver instructs the driver to shift up or down. The gear shift indicator 90 outputs a gear shift instruction signal in response to an operation by the driver. The control device 50 receives the gear shift instruction signal output from the gear shift indicator 90.

[0044] 2 is a block diagram showing an example of the hardware configuration of the control device 50. The control device 50 includes a processor 501, a non-volatile memory 502, a volatile memory 503, and an interface (I / F) 504.

[0045] The volatile memory 503 is a semiconductor memory such as a static random access memory (SRAM) or a dynamic random access memory (DRAM). The non-volatile memory 502 is a flash memory, a hard disk, a read-only memory (ROM), or the like. The non-volatile memory 502 stores a motor control program 510, which is a computer program, and data used to execute the motor control program 510. The functions of the control device 50 are realized when the motor control program 510 is executed by the processor 501. The motor control program 510 can be stored in a recording medium such as a flash memory, a ROM, or a CD-ROM. The processor 501 controls the power converter 30 and the winding switching device 100 using the motor control program 510.

[0046] The processor 501 is, for example, a CPU (Central Processing Unit). However, the processor 501 is not limited to a CPU. The processor 501 may be a GPU (Graphics Processing Unit). The processor 501 is, for example, a multi-core processor. The processor 501 may be a single-core processor. The processor 501 may be, for example, an ASIC (Application Specific Integrated Circuit) or a programmable logic device such as a gate array or FPGA (Field Programmable Gate Array). In this case, the ASIC or programmable logic device is configured to be able to execute the same processing as the motor control program 510.

[0047] The I / F 504 is connected to the rotation sensor 201, the torque sensor 202, the sensor 71, the sensor 81, and the gear shift indicator 90. The I / F 504 is, for example, an input / output interface or a communication interface. The I / F 504 receives a detection signal indicating the rotation speed of the motor 20 output from the rotation sensor 201. The I / F 504 receives a detection signal indicating the output torque of the motor 20 output from the torque sensor 202. The I / F 504 receives a detection signal indicating the brake pedal depression amount output from the sensor 71. The I / F 504 receives a detection signal indicating the accelerator pedal depression amount output from the sensor 81. The I / F 504 receives the gear shift indicator signal output from the gear shift indicator 90.

[0048] [1-2. Configuration of the Winding Switching Device] Figure 3 is a circuit diagram showing an example of the configuration of the winding switching device according to the first embodiment. The motor 20 includes a plurality of windings 21u, 22u, 21v, 22v, 21w, and 22w. The windings 21u and 22u correspond to the U phase, the windings 21v and 22v correspond to the V phase, and the windings 21w and 22w correspond to the W phase. However, the number of windings for each phase is not limited to two and may be three or more. The windings 22u, 22v, and 22w are connected at a neutral point 23.

[0049] The winding switching device 100 switches the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w for each phase between a two-winding series-connected state and a single-winding connected state. The winding switching device 100 includes control circuits 103u, 103v, and 103w and switching circuits 104u, 104v, and 104w. Hereinafter, the two-winding series-connected state may be referred to as the series state, and the single-winding connected state may be referred to as the single state.

[0050] The switching circuits 104u, 104v, and 104w switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w between a series state and an independent state under control of the control device 50. The series state is an example of a first connection state, and the independent state is an example of a second connection state.

[0051] The following describes the connection relationship between the winding switching device 100, the power line 35u, and the motor 20 for the U phase. The same applies to the V and W phases, so a description thereof will be omitted.

[0052] The power line 35u is connected to a first terminal of the winding 21u. A power line 212u extends from a second terminal of the winding 21u. A power line 221u extends from a first terminal of the winding 22u.

[0053] The switching circuit 104u includes a relay 111u and a relay 112u. The relays 111u and 112u are, for example, mechanical (electromagnetic) relays, but are not limited to these and may also be semiconductor relays. The relays are divided into an input side and an output side. The output side of the relay includes a switch that controls current on or off, and the switch is set on / off by inputting a predetermined control signal to the input side. In the case of a mechanical relay, for example, the input side is composed of an electromagnetic coil. The output side is composed of a mechanical switch including a movable segment and a fixed segment. The movable segment and the fixed segment each have contacts. The movable segment is attracted in one direction by an elastic body such as a spring and in the other direction by the electromagnetic coil. In the case of an A-contact relay, the contacts are configured to be conductive when the electromagnetic coil attracts the movable segment in the other direction. In the case of a semiconductor relay, for example, the input side is composed of a light-emitting diode, and the output side is composed of a light-receiving element, MOSFET, and IGBT.

[0054] The power line 35u is drawn into the winding switching device 100. Within the winding switching device 100, the power line 35u branches off at a midpoint and is connected to a first terminal of a relay 111u. A second terminal of the relay 111u is connected to a first terminal of a relay 112u. The power lines 212u, 221u, and 222u extend from the motor 20 and are drawn into the winding switching device 100. A power line 221u extending from the winding 22u is connected to a connection point between the second terminal of the relay 111u and the first terminal of the relay 112u. A power line 212u extending from the winding 21u is connected to a second terminal of the relay 112u.

[0055] When the relay 111u is in the OFF state and the relay 112u is in the ON state, the winding 21u and the winding 22u are in a series state. When the relay 111u is in the ON state and the relay 112u is in the OFF state, the winding 21u is in an isolated state.

[0056] A signal line extending from the control circuit 103u is connected to each of the input sides (electromagnetic coil sides) of the relay 112u and the relay 111u. A signal line extending from the control device 50 is connected to the control circuit 103u. The signal line communicates instructions indicating which connection state of the windings to set. This signal is sometimes called a switching instruction. For example, a LOW level of the signal line indicates a series state, and a HIGH level indicates a standalone state. Alternatively, data communication may be performed via the signal line to send and receive information indicating which relay to set on or off.

[0057] The control circuit 103u controls the on / off of the relays 112u and 111u by individually applying control signals to the input sides of the relays 112u and 111u. Specifically, when the control circuit 103u receives an instruction from the control device 50 to switch the connection state of the windings 21u and 22u from a series state to an independent state, the control circuit 103u sets the relay 111u to an on state and sets the relay 112u to an off state. When the control circuit 103u receives an instruction from the control device 50 to switch the connection state of the windings 21u and 22u from a series state to an independent state, the control circuit 103u sets the relay 111u to an off state and sets the relay 112u to an on state.

[0058] The control circuit 103u is configured, for example, by a plurality of logic circuits (AND circuits, NOT circuits, latch circuits, etc.). In another example, the control circuit 103u is configured by a processor. For example, the control circuit 103u is configured by a one-chip microcomputer. The control circuit 103u may also be configured by a programmable logic device such as an ASIC or FPGA.

[0059] The measuring device 26 is provided, for example, on the power line connecting the winding switching device 100 and the motor 20. The measuring device 26 includes, for example, a phase current sensor and a relay current sensor. The phase current sensor 261u is provided on the power line 221u, and the relay current sensor 262u is provided on the power line 212u. The phase current sensor 261u measures the current flowing through the U phase when the windings 21u and 22u are in a series state and an isolated state. Hereinafter, the current measured by the phase current sensor may be referred to as the phase current. The phase current sensor 261u sends a signal or information indicating the value of the measured current to the control device 50.

[0060] The relay current sensor 262u measures the current flowing through the power line 212u connected to the second terminal of the relay 112u. When the connection state of the windings 21u and 22u is switched from the series state to the independent state, the relay current sensor 262u measures the current in the power line 212u that the relay 112u, which is set to off, is about to interrupt. Hereinafter, the current measured by the relay current sensor may be referred to as the relay current. The relay current sensor 262u sends a signal or information indicating the value of the measured current to the control device 50.

[0061] Similarly, for the V phase, a phase current sensor 261v is provided on the power line 221v, and a relay current sensor 262v is provided on the power line 212v. For the W phase, a phase current sensor 261w is provided on the power line 221w, and a relay current sensor 262w is provided on the power line 212w. Note that, although the example has been described in which measuring device 26 is provided on the power line connecting winding switching device 100 and motor 20, measuring device 26 may be provided inside winding switching device 100 or inside motor 20.

[0062] 1, the functions of the control device 50 will be described. The control device 50 has the functions of a winding switching unit 511, a measurement unit 512, and an abnormality detection unit 513. The processor 501 executes the motor control program 510, thereby realizing the functions of the winding switching unit 511, the measurement unit 512, and the abnormality detection unit 513.

[0063] [1-3-1. Winding Switching Unit] The winding switching unit switches the connection states of multiple windings of an AC motor including multiple windings in a stator for each phase. The winding switching unit also switches the connection states of the multiple windings using multiple relays. At least one of the multiple relays is set to on in a first connection state and set to off in a second connection state.

[0064] Specifically, the winding switching unit 511 switches the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w for each phase between a state in which two windings are connected in series and a state in which one winding is connected. The winding switching device 100 includes control circuits 103u, 103v, and 103w and switching circuits 104u, 104v, and 104w. The winding switching unit 511 causes the switching circuits 104u, 104v, and 104w to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w between a series state and a single state. Specifically, the winding switching unit 511 transmits switching instructions to the control circuits 103u, 103v, and 103w. For example, a low level of the switching instruction indicates a series state, and a high level indicates a single state.

[0065] [1-3-2. Measurement Unit] The measurement unit 512 measures a physical quantity related to the rotation of the AC motor. An example of a physical quantity related to the rotation of the motor is the current flowing through each phase of the motor 20. The measurement unit 512 includes a current sensor, and measures the current flowing through each phase using the current sensor. The current sensor then measures the phase current flowing through the stator of each phase. Specifically, in the U-phase, the phase current sensor 261u measures the current flowing through the power line 221u, and the measurement unit 512 measures the phase current flowing through the stator of the U-phase.

[0066] The current sensor measures the current flowing through the relay switch. Specifically, in the U-phase, the relay current sensor 262u measures the current flowing through the power line 212u, and the measurement unit 512 measures the relay current of the U-phase.

[0067] Then, the phase current sensor 261u and the relay current sensor 262u send signals or information indicating the measured current values ​​to the control device 50. The measurement unit 512 of the control device 50 receives the signals or information indicating the measured current values ​​and measures physical quantities related to the rotation of the AC motor. The same applies to the V phase and the W phase.

[0068] [1-3-3. Abnormality Detection Unit] The abnormality detection unit 513 determines whether the currents flowing through the phases of the AC motor are balanced based on the physical quantities measured by the measurement unit 512. The currents flowing through the phases of the motor 20 are not balanced when this state is defined as a state in which the balance of the currents flowing through the U, V, and W phases differs from one another. The state in which the currents flowing through the phases of the motor 20 are not balanced is sometimes referred to as an unbalanced state, and the state in which the currents flowing through the phases of the motor 20 are balanced is sometimes referred to as a balanced state.

[0069] [Unbalanced State of the Motor] Figure 4 is a diagram illustrating an example of an unbalanced state of the motor 20. The U-phase windings 21u and 22u and relays 111u and 112u necessary for the explanation are shown. The state before the winding switching device 100 switches the winding connection state is considered to be the isolated state. At this time, the relay 111u is set to ON, and the relay 112u is set to OFF (Figure 4, isolated state). Next, when the winding switching device 100 switches the winding connection state from the isolated state to the series state, the relay 111u is set to OFF, and if the relays are normal, the relay 112u is set to ON (Figure 4, series state).

[0070] However, if relay 111u fails and sticks, for example, and is fixed in the on position, relay 112u is set to on, but relay 111u is not set to off and remains in the on state (FIG. 4, abnormal state). As a result, both ends of winding 21u are short-circuited. Then, because the rotor of motor 20 is rotating, winding 21u functions as a generator, and an abnormally large current flows through winding 21u. Based on this abnormally large current, abnormality detection unit 513 determines that motor 20 is in an unbalanced state.

[0071] Figure 5 is a diagram showing types of relay failures. Possible relay failure patterns include when the output contacts stick, leaving them in a connected state (fixed ON), and when the relay's electromagnetic coil breaks, leaving them in an open state (fixed OFF). In Figure 5, OFF is represented by "0" and ON is represented by "1." Figure 5 shows the cases when the winding connection state is switched from an isolated state to a series state and when the winding connection state is switched from a series state to an isolated state. Figure 5 also shows the state of the relay current and the states of the d- and q-axis currents.

[0072] When the connection state of the windings is switched from the isolated state to the series state, the following types of faults may occur: (1) when the relay 111u is fixed on, and the relays 111u and 112u are both set on, causing the winding 21u to be short-circuited; (2) when the relay 112u is fixed off, and the relays 111u and 112u are both set off, causing no current to flow through the U-phase windings 21u and 22u; or (3) when the relay 111u is fixed on, and the relay 112u is fixed off, causing the V-phase and W-phase windings to be switched to the series state, but the U-phase remains in the isolated state.

[0073] When the connection state of the windings is switched from a series state to an isolated state, the following types of faults may occur: (1) relay 112u is fixed on, relays 111u and 112u are both set on, and winding 21u is short-circuited; (2) relay 111u is fixed off, relays 111u and 112u are both set off, and no current flows through U-phase windings 21u and 22u; or (3) relay 111u is fixed off, relay 112u is fixed on, and although the V-phase and W-phase windings have switched to the isolated state, the U-phase remains in the series state.

[0074] 6, 7, and 8 show examples of simulations of the phase currents, relay currents, and d- and q-axis currents when one of the relays that changes the winding connection state fails and the motor 20 becomes unbalanced. In all cases, the winding connection state is switched at 0.015 seconds on the time axis. Each current shows a normal state from 0 seconds to 0.015 seconds on the time axis, but after 0.015 seconds on the time axis, one of the currents becomes abnormal.

[0075] When a relay fails and the motor 20 becomes unbalanced, any of the relay current, phase current, and d-axis and q-axis currents will have an abnormal value. The abnormality detection unit 513 detects this abnormal value and determines that the motor 20 is unbalanced.

[0076] [In the case of phase current or relay current] Figure 6 shows a case where the U-phase relays 112u and 111u are both turned on when the connection state changes from the single state to the series state. In this case, as described above, both ends of the winding 21u are short-circuited and the rotor of the motor 20 is rotating, so the winding 21u functions as a generator and a large current flows circulating through the winding 21u. This large current is larger than the relay current that flows under normal conditions. Under normal conditions, the windings 21u and 22u are connected in series, so the relay current and the phase current flow approximately equal.

[0077] 7 shows a case where the U-phase relays 112u and 111u are both turned off when the connection state changes from the single state to the series state. In this case, no phase current or relay current flows through the U-phase. On the other hand, currents larger than those flowing normally flow through the V-phase and W-phase.

[0078] The abnormality detection unit 513 determines whether the currents flowing through the phases of the motor 20 are in a balanced state based on the signal indicating this large current measured by the measurement unit 512. Specifically, the abnormality detection unit 513 determines that the currents flowing through the phases are not balanced when the currents measured by the current sensors exceed a threshold value.

[0079] For example, if the phase current measured by phase current sensor 261v or phase current sensor 261w exceeds a threshold, or if the relay current measured by relay current sensor 262v or relay current sensor 262w exceeds a threshold, it is determined that motor 20 is in an unbalanced state. Note that, because no current flows through U-phase under normal conditions, abnormality detection unit 513 may determine that motor 20 is in an unbalanced state based on this current.

[0080] Furthermore, the abnormality detection unit 513 may change the threshold value based on the output required of the motor 20. This is because the current that flows during normal operation increases in accordance with the required motor output. This allows the equilibrium state of the motor 20 to be appropriately determined. If the motor 20 is a drive motor that drives the wheels of a vehicle, the required output is determined based on, for example, the accelerator opening, the speed required by the vehicle, and the torque required by the vehicle.

[0081] In this way, the abnormality detection unit 513 determines whether the currents flowing through the phases are balanced.

[0082] [Case of using d- and q-axis currents] Figure 8 shows a case where the U-phase relay 111u is turned on and the relay 112u is turned off when the connection state changes from an isolated state to a series state. In this state, the V- and W-phases are in a series state, but only the U-phase is in an isolated state. In this case, the phase currents flowing through the U-, V-, and W-phases are substantially the same as those flowing under normal conditions. For this reason, it is difficult to determine whether the motor 20 is in a balanced state based on the phase currents alone. Meanwhile, the d- and q-axis currents flow with currents that are clearly different from those flowing under normal conditions. This makes it possible to determine whether an unbalanced state exists based on the d- and q-axis currents calculated from the phase currents flowing through the U-, V-, and W-phases.

[0083] Specifically, the abnormality detection unit 513 compares a target d-axis current, which is a target value for the d-axis current, and a target q-axis current, which is a target value for the q-axis current, with a measured d-axis current, which is a measured value for the d-axis current, and a measured q-axis current, which is a measured value for the q-axis current, and determines that the currents flowing through each phase are not balanced when at least one of the following conditions is met: a first condition that the difference between the target d-axis current and the measured d-axis current is equal to or greater than a first threshold; and a second condition that the difference between the target q-axis current and the measured q-axis current is equal to or greater than a second threshold. The first threshold and the second threshold may be the same value or different values.

[0084] When the measured d-axis current and the measured q-axis current are calculated based on the U-phase, V-phase, and W-phase currents measured by the measurement unit 512, there is a risk that the measured d-axis current and the measured q-axis current may suddenly exceed a threshold value. Therefore, if at least one of the periods during which the first condition is satisfied and the period during which the second condition is satisfied exceeds a reference value, it may be determined that the currents flowing through each phase are not balanced. If the d-axis current or the q-axis current exceeds the threshold value for a period longer than a predetermined period, the abnormality detection unit 513 determines that the motor 20 is in an unbalanced state, thereby more appropriately determining the balanced state of the motor 20.

[0085] The reference value may also be changed based on the rotation speed of the rotor of the motor 20. Since the d- and q-axis currents fluctuate in response to the rotation of the rotor, the d- and q-axis currents fluctuate slowly as the rotation speed of the rotor of the motor 20 decreases. For this reason, it is preferable to lengthen the predetermined period as the rotation speed of the rotor decreases. This allows the balanced state of the motor 20 to be appropriately determined.

[0086] The first threshold value and the second threshold value may be changed, for example, according to the output required of the motor 20. This is because the current flowing during normal operation increases in accordance with the required motor output. This allows the equilibrium state of the motor 20 to be appropriately determined. If the motor 20 is a drive motor that drives the wheels of a vehicle, the required output is determined based on, for example, the accelerator opening, the speed required by the vehicle, and the torque required by the vehicle.

[0087] In this way, the abnormality detection unit 513 determines whether the currents flowing through the phases are balanced.

[0088] [1-4. Operation of the Winding Switching System] Next, a description will be given of the operation of the winding switching device 100. The control device 50 executes the winding switching process by causing the processor 501 to execute the motor control program 510.

[0089] FIG. 9 is a flowchart showing an example of a winding switching process performed by the control device according to the first embodiment.

[0090] [1-4-1. When the Relays are Fixed to ON] In this case, for example, assume that at the start of the winding switching process, windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in an isolated state. When the connection state is in the isolated state, relays 112u, 112v, and 112w are set to OFF, and relays 111u, 111v, and 111w are set to ON. Therefore, depending on the type of failure of relays 111u and 112u, for example, if relay 111u is stuck, it is set to ON, which is the same as when normal, so as long as motor 20 operates in an isolated state, motor 20 operates normally. Below, it is assumed that V-phase and W-phase relays 111v, 111w, 112v, and 112w can be set to ON / OFF normally.

[0091] [Step S101] First, the winding switching unit 511 switches the connection state of multiple windings of an AC motor including multiple windings in the stator of each phase (step S101). For example, the winding switching unit 511 switches the connection state of the windings from an isolated state to a series state. Specifically, the winding switching unit 511 transmits a switching instruction to the control circuits 103u, 103v, and 103w to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from an isolated state to a series state. Upon receiving the switching instruction to switch the connection state from an isolated state to a series state, the control circuit 103u sets the relay 112u on and the relay 111u off. Similarly, the control circuit 103v sets the relay 112v on and the relay 111v off. The control circuit 103w sets the relay 112w on and the relay 111w off. Then, the process proceeds to step S102.

[0092] In this example, the relay 111u is stuck, so the relays 111u and 112u are set to ON, which shorts both ends of the winding 21u, causing a large relay current to flow circulating through the winding 21u, as shown in FIG.

[0093] [Step S102] Next, the measurement unit 512 measures physical quantities related to the rotation of the AC motor (step S102). Specifically, the phase current sensor 261u measures the phase current and transmits a signal indicating the phase current value to the control device 50. The relay current sensor 262u measures the relay current and transmits a signal indicating the relay current value to the control device 50. In this example, the relay current sensor 262u measures a large current circulating through the winding 21u and transmits a signal indicating the value of this current. When the control device 50 receives this signal, the measurement unit 512 measures the phase current and relay current, which are physical quantities related to the rotation of the motor 20. Then, the process proceeds to step S103.

[0094] [Step S103] Next, the abnormality detection unit 513 determines whether the currents flowing through each phase of the motor 20 are balanced based on the physical quantities measured by the measurement unit 512. Specifically, the abnormality detection unit 513 compares the phase currents or relay currents measured by the measurement unit 512 with a threshold value (step S103). If the threshold value is exceeded (YES in step S103), the process proceeds to step S104. On the other hand, if the threshold value is not exceeded (NO in step S103), the process proceeds to step S105.

[0095] In this example, the control device 50 receives a signal indicating a large current value circulating through the winding 21u. The abnormality detection unit 513 of the control device 50 compares the received relay current value with a threshold value. Since the relay current value indicates a large current value, it exceeds the threshold value, and the abnormality detection unit 513 determines that the motor 20 is in an unbalanced state.

[0096] [Step S104] If the phase current or relay current exceeds the threshold, the abnormality detection unit 513 determines that the currents flowing through the phases of the motor 20 are not balanced (step S104), and then ends the winding switching process.

[0097] [Step S105] On the other hand, if the phase current and the relay current do not exceed the threshold value, the abnormality detection unit 513 determines that the currents flowing through the phases of the motor 20 are balanced (step S105), and then ends the winding switching process.

[0098] In this way, the equilibrium state of the motor can be determined.

[0099] [1-4-2. When the Relay is Fixed to Off] For example, let us say that the electromagnetic coil of the relay 111u is disconnected or the like and fixed to the off state. In this case, the motor 20 operates normally as long as the windings are connected in series. In the series state, the relay 112u is set to on and the relay 111u is set to off, but this is because, focusing on the relay 111u, there is no difference between a faulty state and a normal state. As an initial state, the windings are connected in series.

[0100] [Step S101] Next, assume that the winding switching unit 511 switches the winding connection state from a series state to an independent state (step S101). The relay 112u is set to OFF, and the relay 111u is set to ON. If the relays 112u and 111u are normal, a predetermined current flows through the U-phase winding 22u. However, since the relay 111u is fixed to OFF, the U-phase relays 112u and 111u are both set to OFF, and no current flows through the U-phase winding. Meanwhile, as shown in FIG. 7, a large current flows through the V-phase and W-phase windings 22v and 22w.

[0101] [Step S102] Next, the measurement unit 512 measures the phase currents of the U-phase, V-phase, and W-phase of the motor 20 using the phase current sensors 261u, 261v, and 261w. Specifically, the phase current sensor 261u sends a signal indicating that the current value is zero to the control device 50. The phase current sensors 261v and 261w send signals indicating large current values ​​in the V-phase and W-phase to the control device 50. When the control device 50 receives these signals, the measurement unit 512 measures the phase currents. Then, the process proceeds to step S103.

[0102] [Step S103] Next, the abnormality detection unit 513 determines whether the currents flowing through each phase of the motor 20 are balanced based on the physical quantities measured by the measurement unit 512. The value of the V-phase phase current indicates a large current and therefore exceeds the threshold (YES in step S103), and the abnormality detection unit 513 determines that the motor 20 is in an unbalanced state (step S104). Alternatively, the abnormality detection unit 513 may make this determination based on the W-phase phase current. Alternatively, the abnormality detection unit 513 may make this determination based on the U-phase phase current. As described above, the U-phase phase current is zero, and therefore the current value indicated by the signal output by the phase current sensor 261u exceeds the threshold, and the abnormality detection unit 513 determines that the motor 20 is in an unbalanced state. On the other hand, if the current does not exceed the threshold (NO in step S103), the abnormality detection unit 513 determines that the motor 20 is in a balanced state (step S105).

[0103] [1-4-3. When two relays fail] In this case, for example, let us assume that relay 111u is stuck and fixed to ON. In addition, let us assume that the electromagnetic coil of relay 112u is disconnected and fixed to OFF. In this case, the motor 20 will operate normally as long as the winding connection state is in the isolated state. In the isolated state, relay 111u is set to ON and relay 112u is set to OFF, because there is no difference between a fault and a normal state. As the initial state, the winding connection state is in the isolated state.

[0104] [Step S101] Next, the winding switching unit 511 switches the winding connection state from the isolated state to the series state (step S101). The control circuit 103u sets the relay 112u on and attempts to set the relay 111u off. However, because the relay 112u is fixed off and the relay 111u is fixed on, the U-phase winding connection state does not switch to the series state and remains in the isolated state. Meanwhile, the V-phase and W-phase winding connection states are switched to the series state. In this connection state, as shown in Figure 8, the phase current or relay current does not become significantly large. Meanwhile, when focusing on the d- and q-axis currents, they fluctuate significantly. Then, the process proceeds to step S102.

[0105] [Step S102] Next, the measurement unit 512 measures the phase currents of the U-phase, V-phase, and W-phase of the motor 20 using the phase current sensors 261u, 261v, and 261w, and outputs a signal indicating the measured phase currents. When the control device 50 receives this signal, the measurement unit 512 measures the phase currents (step S102). Then, the process proceeds to step S103.

[0106] [Steps S103 to S105] Next, the abnormality detection unit 513 compares the target d-axis current (the target value of the d-axis current) and the target q-axis current (the target value of the q-axis current) with the measured d-axis current (the measured value of the d-axis current) and the measured q-axis current (the measured value of the q-axis current). If at least one of the following conditions is met (a first condition that the difference between the target d-axis current and the measured d-axis current is equal to or greater than a first threshold) and (a second condition that the difference between the target q-axis current and the measured q-axis current is equal to or greater than a second threshold) (YES in step S103), the abnormality detection unit 513 determines that the currents flowing through the phases are not balanced (step S104). On the other hand, if the thresholds are not exceeded (NO in step S103), the abnormality detection unit 513 determines that the motor 20 is in a balanced state (step S105).

[0107] Specifically, the control device 50 receives signals indicating the U-, V-, and W-phase currents from the phase current sensors 261u, 261v, and 261w, and calculates the measured d-axis current and the measured q-axis current based on the received U-, V-, and W-phase currents. The control device 50 then calculates the difference between the target d-axis current and the measured d-axis current, and the difference between the target q-axis current and the measured q-axis current. If the difference in the d-axis current exceeds a first threshold value or the difference in the q-axis current exceeds a second threshold value (YES in step S103), the abnormality detection unit 513 determines that the motor 20 is in an unbalanced state (step S104). If neither the first condition nor the second condition is met (NO in step S103), the abnormality detection unit 513 determines that the motor 20 is in a balanced state (step S105).

[0108] In addition, the abnormality detection unit 513 may determine that the currents flowing through the phases are not balanced if at least one of the period during which the first condition is met and the period during which the second condition is met exceeds a reference value.

[0109] Specifically, first, the abnormality detection unit 513 determines whether the period during which the difference between the target d-axis current and the measured d-axis current is equal to or greater than a first threshold is longer than a predetermined period. Second, the abnormality detection unit 513 determines whether the period during which the difference between the target q-axis current and the measured q-axis current is equal to or greater than a second threshold is longer than a predetermined period. If at least one of the first and second determinations is true (YES in step S103), the abnormality detection unit 513 determines that the motor 20 is in an unbalanced state (step S104). On the other hand, if neither the first nor the second determination is true (NO in step S103), the abnormality detection unit 513 determines that the motor 20 is in a balanced state (step S105).

[0110] [2. Second Embodiment] The measurement unit of a winding switching system according to a second embodiment includes a voltage sensor, which measures the voltages of multiple windings. The second embodiment differs from the first embodiment in the configuration of the measurement device 26, but the other configurations are the same. Explanation of the same configuration as the first embodiment will be omitted, and only the different parts will be explained, with the same reference numerals used for the same configuration.

[0111] [2-1. Configuration of the Winding Switching Device] Figure 10 is a circuit diagram showing an example of the configuration of a winding switching device according to the second embodiment. While only the U phase is shown in detail, the V phase and W phase are similarly configured. In this example, a voltage Vpu between a power line 212u connecting the winding 21u and the relay 112u and a reference voltage point and a voltage Vru between a power line 221u connecting the relay 112u and the winding 22u and a reference voltage point are measured. The reference voltage point is, for example, the body of the vehicle. The measurement points are the same as those in the first embodiment, but are not limited to this.

[0112] The voltage is measured by a voltage sensor. The voltage sensor is, for example, an AD converter. A first terminal of the input of the AD converter is connected to the power line 212u, and a second terminal is connected to a reference voltage point. The voltage sensor is not limited to an AD converter, and may be a photocoupler or the like.

[0113] 2-2. Operation of the Winding Switching Device Next, a description will be given of the operation of the winding switching device 100. The control device 50 executes the winding switching process by the processor 501 executing the motor control program 510.

[0114] FIG. 11 is a flowchart showing an example of a winding switching process performed by the control device according to the second embodiment.

[0115] In this case, for example, assume that at the start of the winding switching process, windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in an isolated state. When the connection state is in the isolated state, relays 111u, 111v, and 111w are set to on, and relays 112u, 112v, and 112w are set to off. Therefore, even if relay 112u or 111u fails, for example, if the electromagnetic coil of relay 112u is broken and fixed to the off state, the relay remains set to off, which is the same as in normal operation. Therefore, as long as motor 20 operates in the isolated state, motor 20 operates normally. Hereinafter, it is assumed that V-phase and W-phase relays 111v, 111w, 112v, and 112w can be set to on / off normally.

[0116] [Step S201] First, the winding switching unit 511 switches the connection state of the windings from the single state to the series state. Specifically, the control device 50 transmits a switching instruction to the control circuits 103u, 103v, and 103w to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from the single state to the series state (step S201). The control circuit 103u, which has received the switching instruction to switch the connection state from the single state to the series state, sets the relay 112u on and the relay 111u off. Similarly, the control circuit 103v sets the relay 112v on and the relay 113v off. The control circuit 103w sets the relay 112w on and the relay 113w off. Then, the process proceeds to step S202.

[0117] In this example, relay 112u is fixed to OFF, so relays 112u and 111u are set to OFF. Under normal circumstances, relay 112u is set to ON, and windings 21u and 22u are connected in series. Vpu or Vru, which is the voltage at the midpoint of series-connected windings 21u and 22u, is approximately half the voltage of power line 35u and neutral point 23. However, because relay 112u is fixed to OFF, Vpu or Vru becomes a voltage that is completely different from that under normal circumstances. For example, if the rotor is a permanent magnet, a voltage generated by the rotating permanent magnet will be generated in windings 21u and 22u, and this voltage will be completely different from that under normal circumstances.

[0118] In addition, under normal conditions, the relay 112u is set to ON, so the voltage between the first and second terminals on the output side (contact side) of the relay 112u is zero. However, because the relay 112u is fixed to OFF, a voltage greater than zero is generated between the first and second terminals on the output side (contact side) of the relay 112u.

[0119] [Step S202] Next, the measurement unit 512 measures a physical quantity related to the rotation of the motor 20 (step S202). In the second embodiment, the measurement unit 512 measures the physical quantity related to the rotation using a voltage sensor that measures the voltages of multiple windings. The voltage sensor measures Vpu and Vpr and transmits signals indicative of Vpu and Vpr to the control device 50. When the control device 50 receives these signals, the measurement unit 512 measures Vpu and Vpr. Then, the process proceeds to step S203.

[0120] [Steps S203 to S205] Next, the abnormality detection unit 513 determines the balanced state of the motor 20 (steps S203 to S205).

[0121] Specifically, the abnormality detection unit 513 compares Vpu and Vpr measured by the measurement unit 512 with threshold values, and if the threshold values ​​are exceeded (YES in step S203), it determines that the motor 20 is unbalanced (step S204), and then ends the winding switching process.

[0122] On the other hand, if the threshold value is not exceeded (NO in step S203), it is determined that the motor 20 is in a balanced state (step S205), and the winding switching process is terminated.

[0123] In this example, Vpu and Vpr are completely different from normal values, so they exceed the thresholds, and the abnormality detection unit 513 determines that the motor 20 is unbalanced. Note that the determination may also be based on the difference between Vpu and Vru. In this case, the voltage across the relay 112u is measured. When the relay 112u is set to on, the voltage across the relay 112u is zero. On the other hand, when the relay 112u is set to off, the voltage across the relay 112u is greater than zero.

[0124] As described above, the balanced state of the motor can be determined by the voltage sensor.

[0125] [3. Third Embodiment] The measurement unit of a winding switching system according to a third embodiment measures the torque or rotational speed of the output shaft of an AC motor using a sensor that measures torque or rotational speed. The third embodiment differs from the first embodiment in the configuration of the measurement device 26, but the other configurations are the same. Descriptions of configurations that are the same as those in the first embodiment will be omitted, and only different parts will be described, with the same reference numerals used for the same configurations. The case of a torque sensor will be described below.

[0126] 3-1. Operation of the Winding Switching Device Next, a description will be given of the operation of the winding switching device 100. The control device 50 executes the winding switching process by the processor 501 executing the motor control program 510.

[0127] FIG. 12 is a flowchart showing an example of a winding switching process performed by the control device according to the third embodiment.

[0128] In this case, for example, assume that at the start of the winding switching process, windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in an isolated state. When the connection state is in the isolated state, relays 112u, 112v, and 112w are set to off, and relays 111u, 113v, and 113w are set to on. Therefore, even if relay 112u or 111u fails, for example, if the electromagnetic coil of relay 112u is broken and fixed to the off state, the relay remains set to off, which is the same as normal, and motor 20 operates normally as long as it operates in the isolated state. Hereinafter, it is assumed that V-phase and W-phase relays 112v, 112w, 113v, and 113w can be set to on and off normally.

[0129] [Step S301] First, the winding switching unit 511 switches the connection state of the windings from the single state to the series state. Specifically, the control device 50 transmits a switching instruction to the control circuits 103u, 103v, and 103w to switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from the single state to the series state (step S301). Upon receiving the switching instruction to switch the connection state from the single state to the series state, the control circuit 103u sets the relay 112u on and the relay 111u off. Similarly, the control circuit 103v sets the relay 112v on and the relay 113v off. The control circuit 103w sets the relay 112w on and the relay 113w off. Then, the process proceeds to step S302.

[0130] In this example, relay 112u is fixed to the off position, so relays 112u and 111u are set to the off position. As a result, no current flows through U-phase windings 21u and 22u. On the other hand, V-phase and W-phase windings are in series and a large current flows through them, but they are excited. As a result, the rotating magnetic field generated by the U-phase, V-phase, and W-phase windings is distorted, and the torque generated by the rotor, which receives torque from the rotating magnetic field, fluctuates greatly. For example, the torque pulsates greatly in synchronization with the rotation of the rotor.

[0131] [Step S302] Next, the measurement unit 512 measures the state of the motor 20 (step S302). Specifically, the torque of the output shaft of the motor 20 is measured by the torque sensor 202, and a signal indicating the torque is sent to the control device 50. In this example, a signal indicating, for example, a large pulsating torque is sent. When the control device 50 receives this signal, the measurement unit 512 measures the torque. Then, the process proceeds to step S303.

[0132] [Steps S303 to S305] Next, the abnormality detection unit 513 determines whether the motor 20 is in a balanced state.

[0133] Specifically, the measurement unit 512 receives a signal indicating the torque of the output shaft of the motor 20, output by the torque sensor. The abnormality detection unit 513 compares the value of the signal indicating the torque measured by the measurement unit 512 with a threshold value (step S303), and if the value exceeds the threshold value (YES in step S303), determines that the motor 20 is unbalanced (step S304). Then, the winding switching process ends.

[0134] On the other hand, if the threshold value is not exceeded (NO in step S303), it is determined that the motor 20 is in a balanced state (step S305), and the winding switching process is terminated.

[0135] Specifically, the torque exhibits a constant value under normal conditions. On the other hand, under abnormal conditions, the torque pulsates significantly at a frequency corresponding to the rotation speed of the motor 20. For example, a frequency component corresponding to the rotation speed is extracted from the measured torque value, and its intensity is measured. This intensity is then compared with a threshold value. If the threshold value is exceeded, the abnormality detection unit 513 may determine that the motor 20 is unbalanced.

[0136] As described above, the torque sensor can determine the balanced state of the motor and detect an abnormality in the winding switching section that switches the windings.

[0137] Although the above description is given using a torque sensor, a physical quantity related to the rotation of the motor 20 may be measured by a rotation sensor 201 that measures the rotation speed of the output shaft of the motor 20. This is because when the torque pulsates significantly in synchronization with the rotation of the rotor, the rotation speed of the output shaft of the motor 20 also fluctuates during one rotation of the output shaft.

[0138] 4. Fourth Embodiment A winding switching system according to a fourth embodiment further includes a restoration unit. When the abnormality detection unit determines that the currents flowing through the phases of the AC motor are not balanced in response to the winding switching unit switching the connection state, the restoration unit restores the winding switching unit to the connection state before switching.

[0139] 13 is a circuit diagram showing an example of the configuration of a winding switching system according to a fourth embodiment. The fourth embodiment differs from the first embodiment in that a return unit 514 is further provided, but the other configurations are the same. Explanation of the configurations that are the same as those in the first embodiment will be omitted, and only the different parts will be explained, with the same reference numerals used for the same configurations.

[0140] [4-1. Function of the Restoration Unit] For example, suppose that the motor 20 was operating normally before the connection state was switched, and the winding switching unit 511 switched the connection state from the single state to the series state. At this time, if the abnormality detection unit 513 determines that the motor 20 is unbalanced, the restoration unit 514 causes the winding switching unit 511 to switch back to the single state before the switch. Conversely, if the abnormality detection unit 513 determines that the motor 20 is unbalanced when the winding switching unit 511 switches the connection state from the series state to the single state, the restoration unit 514 causes the winding switching unit 511 to switch the connection state back to the series state before the switch.

[0141] In other words, motor 20 operates normally when in the connection state before the connection state is switched. Therefore, by having return unit 514 return the connection state of the windings to the connection state before the connection state is switched, motor 20 continues to operate even if some kind of failure occurs in the relay. If motor 20 is a drive motor that drives the wheels of a vehicle, the vehicle can continue to run.

[0142] 14 is a flowchart showing an example of the winding switching process by the control device according to the fourth embodiment. Steps S401 to S405 are the same as steps S101 to S105 in the first embodiment, and therefore a description thereof will be omitted. It is assumed that the winding is connected in a single state.

[0143] [Step S406] If the anomaly detection unit determines that the currents flowing through the phases of the AC motor are not balanced in response to the winding switching unit switching the connection state, the recovery unit 514 recovers the winding switching unit to the state before the connection state was switched. For example, if the winding switching unit 511 attempts to switch from the single-phase state to the series-phase state and the anomaly detection unit 513 determines that the motor 20 is unbalanced (YES in step S403), the process proceeds to step S404, and then the recovery unit 514 recovers the winding switching unit 511 to the state before the connection state was switched (step S406). The winding switching process then ends.

[0144] In this example, the winding switching unit 511 was attempting to switch the winding connection state from the isolated state to the series state, so the connection state before the switch was the isolated state. Therefore, the reset unit 514 causes the winding switching unit 511 to return the connection state to the isolated state. Even if the relay 111u had stuck in the isolated state, the return to the isolated state sets the relay 112u to off, and the large current flowing through the winding 21u stops. The V and W phases also return to the isolated state, and the U, V, and W phases all return to the isolated state, so the motor 20 is in a balanced state and continues to operate normally. If the motor 20 were installed in a vehicle, the vehicle would be able to continue running.

[0145] 5. Fifth Embodiment The winding switching system according to the fourth embodiment further includes a notification unit 516. When the abnormality detection unit 513 determines that the currents flowing through the phases of the AC motor are not balanced, the notification unit 516 notifies the user of the occurrence of an abnormality.

[0146] 15 is a circuit diagram showing an example of the configuration of a winding switching system according to the fifth embodiment. The signal notified by the notification unit 516 may be, for example, sound, light, or radio wave. The sound may be notified, for example, by a speaker. The light may be notified, for example, by a light-emitting diode. Alternatively, the notification may be made by a liquid crystal display. The radio wave may be notified, for example, by a wireless device. The wireless device communicates with a smartphone and notifies via the smartphone. The speaker, light-emitting diode, liquid crystal display, and wireless device may be provided in the vehicle, for example.

[0147] If the winding switching system is installed in a vehicle, the user of the vehicle can be notified by sound, light, or smartphone that the motor 20 is in an unbalanced state. The user who knows that the motor 20 is in an unbalanced state can take appropriate measures, such as inspecting and repairing the motor.

[0148] [6. Sixth Embodiment] A winding switching system according to a sixth embodiment includes a winding switching unit that switches connection states of a plurality of windings of an AC motor that is capable of switching connection states of the plurality of windings included in a stator of each phase; a measurement unit that measures a physical quantity related to rotation of the AC motor; an equilibrium determination unit that determines whether or not currents flowing through each phase of the AC motor are balanced based on the physical quantity measured by the measurement unit; and a return unit that causes the winding switching unit to switch the connection state from the second state to the first connection state when the determination by the equilibrium determination unit changes from that the currents flowing through each phase are balanced to that the currents flowing through each phase are not balanced in response to the connection state being switched from a first connection state to a second connection state.

[0149] 16 is a circuit diagram showing an example of the configuration of a winding switching system according to a sixth embodiment. The sixth embodiment differs from the first embodiment in that an equilibrium determination unit 515 is provided instead of the abnormality detection unit 513, and a recovery unit 514 is also provided, but the other configurations are the same. Explanation of the configurations that are the same as those in the first embodiment will be omitted, and only the different parts will be described, with the same reference numerals used for the same configurations.

[0150] [6-1. Functions of the balance determination unit] The balance determination unit 515 determines whether the currents flowing through the phases of the AC motor are balanced based on the physical quantities measured by the measurement unit. The abnormality detection unit 513 of the first embodiment detects an abnormality occurring in the winding switching device 100 by determining whether the currents flowing through the phases of the AC motor are balanced. On the other hand, the balance determination unit 515 of this embodiment is not configured to detect an abnormality. Furthermore, the recovery unit 514 is the same as the recovery unit 514 of the fourth embodiment.

[0151] 17 is a flowchart showing an example of the winding switching process by the control device according to the sixth embodiment. Steps S501 to S502 are the same as steps S101 to S102 in the first embodiment, and therefore a description thereof will be omitted. It should be noted that the initial state is assumed to be a single winding connection state.

[0152] [Step S503] The balance determination unit 515 determines whether the currents flowing through each phase of the motor 20 are balanced based on the physical quantities measured by the measurement unit 512. For example, the balance determination unit 515 compares the received signals indicating the phase current values ​​output by the phase current sensors 261u, 261v, and 261w and the received signals indicating the relay current values ​​output by the relay current sensors 262u, 262v, and 262w with a threshold value (step S503). If the received signals exceed the threshold value (YES in step S503), the balance determination unit 515 determines that the motor 20 is unbalanced. Then, the process proceeds to step S504. On the other hand, if the received signals do not exceed the threshold value (NO in step S503), the balance determination unit 515 determines that the motor 20 is in a balanced state. Then, the winding switching process ends.

[0153] [Step S504] When the balance determination unit 515 determines that the currents flowing through the phases are unbalanced in response to the connection state being switched from the first connection state to the second connection state, the recovery unit 514 causes the winding switching unit 511 to switch the connection state from the second connection state to the first connection state (step S504). For example, when the winding switching unit 511 attempts to switch from the single connection state to the series connection state and the balance determination unit 515 determines that the motor 20 is unbalanced (YES in step S503), the recovery unit 514 causes the winding switching unit 511 to switch the connection state to the first connection state. Then, the winding switching process ends.

[0154] In this example, the winding switching unit 511 was attempting to switch the winding connection state from the isolated state to the series state, so the connection state before the switch was the isolated state. Therefore, the reset unit 514 resets the connection state to the isolated state. Even if the relay 111u had stuck in the isolated state, the return to the isolated state sets the relay 112u to off, and the large current flowing through the winding 21u stops. The V and W phases also return to the isolated state, and the U, V, and W phases all return to the isolated state, so the motor 20 is in a balanced state and continues to operate normally. If the motor 20 were installed in a vehicle, the vehicle would be able to continue running.

[0155] [7. Modifications] Figure 18 shows a modification of the winding switching device 100. While Figure 18 only shows the U-phase, the VW-phase is similar. Compared to the first embodiment, a relay 113u has been added. The relay 113u is set to on / off at the same timing as the relay 111u. The addition of the relay 113u allows the windings 21u and 22u to be connected in parallel. Hereinafter, the parallel connection may be referred to as the parallel state. When connected in parallel, the relays 111u and 113u are set on, and the relay 112u is set off. On the other hand, when connected in series, the relays 111u and 113u are set off, and the relay 112u is set on.

[0156] The winding switching device 100 switches the connection state of the windings of the motor 20 from a series state to a parallel state, or from a parallel state to a series state. When the windings are switched from a series state to a parallel state and the abnormality detection unit 513 determines that the motor 20 is unbalanced, the restoration unit 514 restores the winding connection state to the series state. On the other hand, when the windings are switched from a parallel state to a series state and the abnormality detection unit 513 determines that the motor 20 is unbalanced, the restoration unit 514 restores the winding connection state to the parallel state.

[0157] Although the restoration unit 514 previously restored the motor 20 to the parallel or series state when the abnormality detection unit 513 determined that the motor 20 was in an unbalanced state, it may also restore the motor to the single state. For example, the restoration unit 514 may be configured to restore the motor to the single state if the motor imbalance is not resolved even when the motor is switched to either the parallel or series state. To restore the motor to the single state, the relay 112u is set to OFF, and one of the relays 111u and 113u is set to ON. Furthermore, if the imbalance of the motor 20 is not resolved even when one of the relays 111u and 113u is set to ON, the other relay may be set to ON.

[0158] [6. Supplementary Note] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not the above-described embodiments, and includes meanings equivalent to the claims and all modifications within the scope thereof.

[0159] 10 Winding switching system 20 Motor (drive motor) 21u, 22u, 21v, 22v, 21w, 22w Winding 23 Neutral point 25 Power line 26 Measuring device 30 Power converter 31u, 32u, 31v, 32v, 31w, 32w Switch 33u, 33v, 33w Current sensor 35u, 35v, 35w Power line 40 Battery 50 Control device 501 Processor 502 Non-volatile memory 503 Volatile memory 504 Interface (I / F) 510 Motor control program 511 Winding switching unit 512 Measuring unit 513 Abnormality detection unit 514 Recovery unit 515 Balance determination unit 516 Notification unit 60 Wheel 70 Brake pedal 71 Sensor 80 Accelerator pedal 81 Sensor 90 Speed ​​change indicator 100 Winding switching device 103u, 103v, 103w Control circuit 104u, 104v, 104w Switching circuit 111u, 112u, 113u, 111v, 112v, 113v, 111w, 112w, 113w Relay 201 Rotation sensor 202 Torque sensor 212u, 221u, 212v, 221v, 212w, 221w, Power line 24u, 25u, 24v, 25v, 24w, 25w Windings 261u, 261v, 261w Phase current sensor 262u, 262v, 262w Relay current sensor

Claims

1. a winding switching unit for switching a connection state between a first winding and a second winding of an AC motor including a stator for each phase; a measurement unit that measures a first current flowing through the first winding and a second current flowing through the second winding; an abnormality detection unit that determines whether or not the currents flowing through the phases of the AC motor are balanced based on the first current and the second current measured by the measurement unit; Equipped with Winding switching system.

2. The winding switching unit a plurality of relays are used to switch the connection state between the first winding and the second winding; The winding switching system according to claim 1 .

3. The abnormality detection unit detecting an abnormality occurring in the plurality of relays by determining whether or not the currents flowing through the respective phases of the AC motor are balanced; The winding switching system according to claim 2 .

4. the measurement unit includes a current sensor, and measures the first current and the second current flowing through each of the phases by the current sensor; the abnormality detection unit determines that the currents flowing through the phases are not balanced when at least one of the first current and the second current measured by the current sensor exceeds a threshold value. The winding switching system according to claim 2 or 3.

5. A winding switching system as described in Claim 4, wherein either the first current or the second current is a phase current flowing through the stator of each phase.

6. At least one of the plurality of relays is set to ON in a first connection state and set to OFF in a second connection state, the first current is a current flowing through the relay when it is set to on; The winding switching system according to claim 4 .

7. the AC motor is a drive motor that drives wheels of a vehicle, The abnormality detection unit The winding switching system according to claim 4 , wherein the threshold value is changed based on an output required for the AC motor.

8. the measurement unit measures a d-axis current and a q-axis current flowing through the AC motor based on the first current and the second current; The abnormality detection unit 4. The winding switching system according to claim 1, wherein a target d-axis current that is a target value of the d-axis current and a target q-axis current that is a target value of the q-axis current are compared with a measured d-axis current that is a measurement value of the d-axis current and a measured q-axis current that is a measurement value of the q-axis current, and determines that the currents flowing through the phases are not balanced when at least one of a first condition that a difference between the target d-axis current and the measured d-axis current is equal to or greater than a first threshold and a second condition that a difference between the target q-axis current and the measured q-axis current is equal to or greater than a second threshold is satisfied.

9. the AC motor is a drive motor that drives wheels of a vehicle, The abnormality detection unit 9. The winding switching system according to claim 8, wherein at least one of the first threshold value and the second threshold value is changed based on an output required for the AC motor.

10. The abnormality detection unit 9. The winding switching system according to claim 8, wherein the currents flowing through the phases are determined to be unbalanced when at least one of a period during which the first condition is satisfied and a period during which the second condition is satisfied exceeds a reference value.

11. The abnormality detection unit The winding switching system according to claim 10 , wherein the reference value is changed based on the number of rotations of a rotor of the AC motor.

12. An AC motor including a first winding and a second winding in a stator of each phase, a winding switching unit that switches a connection state between the first winding and the second winding; a measurement unit that measures a voltage across the first winding and a voltage across the second winding; an abnormality detection unit that determines whether or not the currents flowing through the phases of the AC motor are balanced based on the voltages of the first winding and the second winding measured by the measurement unit; Equipped with Winding switching system.

13. An AC motor including a first winding and a second winding in a stator of each phase, a winding switching unit that switches a connection state between the first winding and the second winding; a measurement unit that measures an output torque of the AC motor; an abnormality detection unit that determines whether or not the currents flowing through the phases of the AC motor are balanced based on the output torque measured by the measurement unit; Equipped with Winding switching system.

14. The winding switching system is a return unit that returns the winding switching unit to the connection state before switching when the abnormality detection unit determines that the currents flowing through the phases of the AC motor are not balanced in response to the winding switching unit switching the connection state; Further comprising: The winding switching system according to claim 1 .

15. The winding switching system includes:

2. The winding switching system according to claim 1, further comprising a notification unit that notifies a user that the currents flowing through the phases of the AC motor are not balanced when the abnormality detection unit determines that the currents flowing through the phases of the AC motor are not balanced.

16. a winding switching unit that switches a connection state of a first winding and a second winding included in a stator of each phase of an AC motor, and that switches a connection state of the plurality of windings; a measurement unit that measures a first current flowing through the first winding and a second current flowing through the second winding; an equilibrium determination unit that determines whether or not the currents flowing through the phases of the AC motor are balanced based on the first current and the second current measured by the measurement unit; a return unit that switches the connection state from the second connection state to the first connection state when the balance determination unit determines that the currents flowing through the phases are not balanced, in response to the connection state being switched from the first connection state to the second connection state; and Including, Winding switching system.

17. a winding switching unit for switching a connection state of a plurality of windings of an AC motor including a first winding and a second winding in a stator of each phase; a measurement unit including a sensor that measures a first current flowing through the first winding and a second current flowing through the second winding; an abnormality detection unit that determines whether or not the currents flowing through the phases of the AC motor are balanced based on the first current and the second current measured by the measurement unit; Equipped with Control device.

18. a winding switching step of switching a connection state between a first winding and a second winding of an AC motor including a first winding and a second winding in a stator of each phase; a measuring step of measuring a first current through the first winding and a second current through the second winding; an abnormality detection step of determining whether or not the currents flowing through the phases of the AC motor are balanced based on the first current and the second current measured in the measurement step; Including, A method for controlling a winding switching device.

19. A computer program used by a control device that controls a winding switching device, On the computer, a winding switching step of switching a connection state between a first winding and a second winding of an AC motor capable of switching a connection state between the first winding and the second winding included in a stator of each phase; a measuring step of measuring a first current through the first winding and a second current through the second winding; an abnormality detection step of determining whether or not the currents flowing through the phases of the AC motor are balanced based on the first current and the second current measured in the measurement step; In order to execute Computer program.