Control device, winding switching system, control method, and control program

Abstract

To suppress the occurrence of surge voltage even when the amplitude of the current flowing through the AC motor is small.SOLUTION: A control device for controlling an AC motor that can switch the connection state of multiple windings between a first connection state and a second connection state, includes a determination unit that determines whether a specific condition related to the AC motor is met, a current control unit that increases the amplitude of the winding current flowing through the windings when the determination unit determines that the specific condition is met, and an instruction unit that instructs a winding switching device that switches the connection state of the multiple windings to perform zero-crossing switching, which switches from the first connection state to the second connection state, when the winding current reaches a zero-crossing point, after the current control unit has increased the amplitude of the winding current.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a control device, a winding switching system, a control method, and a control program. [Background technology]

[0002] For example, some motors installed in electric vehicles can switch between a low-speed, high-torque operating state and a high-speed, low-torque operating state by switching the connections of multiple windings. Patent Document 1 discloses a device that identifies a period during which the AC motor current is below a predetermined value and switches the windings during the identified period in order to prevent surge voltages. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-072632 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the amplitude of the motor current is small, the influence of noise can make it difficult to accurately identify the period during which the motor current is below a predetermined value. If the period during which the motor current is below a predetermined value is incorrectly identified, it becomes difficult to prevent the occurrence of a surge voltage. [Means for solving the problem]

[0005] A control device according to one embodiment of the present disclosure is a control device for controlling an AC motor capable of switching the connection state of multiple windings between a first connection state and a second connection state, and includes: a determination unit that determines whether a specific condition related to the AC motor is met; a current control unit that increases the amplitude of the winding current flowing through the windings when the determination unit determines that the specific condition is met; and an instruction unit that instructs a winding switching device that switches the connection state of the multiple windings to perform zero-crossing switching, switching from the first connection state to the second connection state, when the winding current reaches a zero-crossing point, after the current control unit has increased the amplitude of the winding current. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to reduce the occurrence of surge voltages. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a winding switching system according to the first embodiment. [Figure 2] FIG. 2 is a circuit diagram showing an example of the configuration of the winding switching device according to the first embodiment. [Figure 3] FIG. 3 is a circuit diagram showing an example of the configuration of the control circuit. [Figure 4] FIG. 4 is a timing chart showing an example of transition of the states of the signals of the winding switching device according to the first embodiment. [Figure 5] FIG. 5 is a block diagram illustrating an example of a hardware configuration of the control device according to the first embodiment. [Figure 6] FIG. 6 is a functional block diagram showing an example of functions of the control device according to the first embodiment. [Figure 7A] FIG. 7A is a graph showing an example of the change in winding current over time when the amplitude of the winding current is large. [Figure 7B] FIG. 7B is a graph showing an example of the change in winding current over time when the amplitude of the winding current is small. [Figure 8]FIG. 8 is a graph showing a first example of the relationship between the output torque and the phase of the winding current of the motor according to the first embodiment. [Figure 9] FIG. 9 is a graph showing a second example of the relationship between the output torque and the phase of the winding current of the motor according to the first embodiment. [Figure 10] FIG. 10 is a flowchart showing an example of a winding connection switching control process performed by the control device according to the first embodiment. [Figure 11] FIG. 11 is a flowchart showing an example of the first switching control by the control device according to the first embodiment. [Figure 12] FIG. 12 is a circuit diagram showing an example of the configuration of a winding switching device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Summary of Embodiments of the Present Disclosure> The following provides an outline of embodiments of the present disclosure.

[0009] (1) A control device according to this embodiment is a control device for controlling an AC motor capable of switching the connection state of multiple windings between a first connection state and a second connection state, and includes: a determination unit that determines whether a specific condition related to the AC motor is satisfied; a current control unit that increases the amplitude of a winding current flowing through the winding when the determination unit determines that the specific condition is satisfied; and an instruction unit that instructs a winding switching device that switches the connection state of the multiple windings to perform zero-crossing switching, switching from the first connection state to the second connection state when the winding current reaches a zero-crossing point, after the current control unit has increased the amplitude of the winding current. By increasing the amplitude of the winding current, the influence of noise can be reduced and the zero-crossing point can be accurately identified. Therefore, the occurrence of surge voltage can be reduced.

[0010] (2) In the above (1), the current control unit may not change the amplitude of the winding current flowing through the winding when the determination unit determines that the specific condition is not met, and the instruction unit may instruct the switching device to perform the zero-crossing switching when the determination unit determines that the specific condition is not met. This makes it possible to switch the connection state at the zero-crossing point without changing the winding current, for example, when the system is not susceptible to noise.

[0011] (3) In the above (1) or (2), the specific condition may be that the amplitude of the winding current is smaller than a first threshold. In this way, when the winding current is smaller than the first threshold and the influence of noise becomes large, the generation of surge voltage can be reduced by performing the above-described connection state switching control.

[0012] (4) In any one of (1) to (3) above, when the determination unit determines that the specific condition is met, the current control unit may increase the amplitude of the winding current until the amplitude of the winding current exceeds a second threshold value. In this way, by increasing the winding current until it exceeds the second threshold value, the influence of noise can be reduced.

[0013] (5) In any one of (1) to (4) above, the current control unit may increase the amplitude of the winding current and change the phase of the winding current. By changing the phase of the winding current, the output torque of the AC motor can be controlled.

[0014] (6) In the above (5), the current control unit may change the phase of the winding current so that the output torque of the AC motor maintains a target value, thereby suppressing fluctuations in the output torque of the AC motor.

[0015] (7) In the above (5) or (6), the current control unit may increase the amplitude of the winding current by ramp control, thereby enabling the winding current to be changed gradually.

[0016] (8) In any one of (1) to (7) above, the current control unit may reduce the amplitude of the winding current after the zero-crossing switching is performed, thereby returning the current to its original state after the connection state of the winding is switched.

[0017] (9) A winding switching system according to this embodiment includes an AC motor capable of switching the connection state of multiple windings between a first connection state and a second connection state, a power converter that converts power output from a power source into AC power and supplies the AC power to the AC motor, a winding switching device for switching the connection state of the multiple windings, and a control device. The control device includes a determination unit that determines whether a specific condition related to the AC motor is met, a current control unit that increases the amplitude of a winding current flowing through the winding when the determination unit determines that the specific condition is met, and an instruction unit that, after the current control unit increases the amplitude of the winding current, instructs the winding switching device to perform zero-crossing switching, switching from the first connection state to the second connection state when the winding current reaches a zero-crossing point. By increasing the winding current, the influence of noise can be reduced and the zero-crossing point can be accurately identified. Therefore, the occurrence of surge voltage can be reduced.

[0018] (10) A control method according to this embodiment is a control method for controlling an AC motor capable of switching the connection states of multiple windings between a first connection state and a second connection state, and includes the steps of: determining whether a specific condition related to the AC motor is satisfied; increasing the amplitude of a winding current flowing through the winding when it is determined that the specific condition is satisfied; and instructing a winding switching device that switches the connection states of the multiple windings to perform zero-crossing switching, switching from the first connection state to the second connection state when the winding current reaches a zero-crossing point, after increasing the amplitude of the winding current. By increasing the winding current, the influence of noise can be reduced and the zero-crossing point can be accurately identified. Therefore, the occurrence of surge voltage can be reduced.

[0019] (11) A control program according to this embodiment is a control program for controlling an AC motor capable of switching the connection states of multiple windings between a first connection state and a second connection state. The control program causes a computer to execute the following steps: determining whether a specific condition related to the AC motor is satisfied; increasing the amplitude of a winding current flowing through the winding when it is determined that the specific condition is satisfied; and instructing a winding switching device that switches the connection states of the multiple windings to perform zero-crossing switching, switching from the first connection state to the second connection state when the winding current reaches a zero-crossing point, after increasing the amplitude of the winding current. By increasing the winding current, the influence of noise can be reduced and the zero-crossing point can be accurately identified. Therefore, the occurrence of surge voltage can be reduced.

[0020] The present disclosure can be realized not only as a control device having the above-described characteristic configuration, a winding switching system including the control device, a control method having steps representing characteristic processes in the control device, and a control program for causing a computer to execute the characteristic processes, but also as a semiconductor integrated circuit that realizes part or all of the control device.

[0021] <Details of the embodiment of the present disclosure> DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. At least some of the following preferred embodiments may be combined in any desired manner.

[0022] [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 the first embodiment.

[0023] 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 or a plug-in hybrid vehicle. 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.

[0024] The motor 20 is a traction motor that generates propulsion power for the electric vehicle. The motor 20 is driven by three-phase AC power. An example of the motor 20 is a permanent magnet synchronous motor.

[0025] The battery 40 is a battery for supplying power to drive the motor 20. The battery 40 is a secondary battery, for example, a lithium ion battery.

[0026] 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 the three-phase AC power output when the motor 20 functions as a generator into DC power and charging the battery 40.

[0027] 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 power metal oxide semiconductor field-effect transistors (MOSFETs).

[0028] 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 the DC and AC components. The current sensors 33u, 33v, and 33w are, for example, DCCTs (direct current transformers) or shunt resistors.

[0029] The winding switching device 100 is disposed between the motor 20 and the power converter 30. However, the position of the winding switching device 100 is not limited to 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 multiple power lines 25. The winding switching device 100 switches the connection state of multiple 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.

[0030] The control device 50 controls the power converter 30 and the winding switching device 100. Specifically, signal lines extend 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.

[0031] [1-2. Configuration of the winding switching device] 2 is a circuit diagram showing an example of the configuration of a 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.

[0032] The winding switching device 100 switches the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w for each phase between a series connection state and a parallel connection state. The series connection state is a high-torque connection state in which the output torque of the motor 20 is high, and the parallel connection state is a high-rotation connection state in which the rotation speed of the motor 20 is high. The winding switching device 100 includes current sensors 101u, 101v, and 101w, zero-cross detection circuits 102u, 102v, and 102w, control circuits 103u, 103v, and 103w, and switching circuits 104u, 104v, and 104w.

[0033] The zero-crossing detection circuits 102u, 102v, and 102w detect zero-crossing points in the measured values ​​of the current sensors 101u, 101v, and 101w. In a more specific example, the zero-crossing detection circuits 102u, 102v, and 102w compare the output voltages from the current sensors 101u, 101v, and 101w with zero voltage and detect the zero-crossing points when the output voltages from the current sensors 101u, 101v, and 101w match the zero voltage. The zero voltage is an example of a reference voltage. The reference voltage is a voltage corresponding to the output voltages of the current sensors 101u, 101v, and 101w when the currents flowing through the windings 21u, 22u, 21v, 22v, 21w, and 22w become zero, and is not limited to zero voltage. The zero-crossing detection circuits 102u, 102v, and 102w are an example of a detection unit.

[0034] The switching circuits 104u, 104v, and 104w switch the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w between a series connection state and a parallel connection state when the zero-crossing detection circuits 102u, 102v, and 102w detect a zero-crossing point. The switching circuits 104u, 104v, and 104w are an example of a switching unit. The series connection state is an example of a first connection state, and the parallel connection state is an example of a second connection state.

[0035] 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 the description will be omitted.

[0036] Power line 35u is connected to one end of winding 21u. Power line 212u extends from the other end of winding 21u. Power line 221u extends from one end of winding 22u, and power line 222u extends from the other end.

[0037] The switching circuit 104u includes semiconductor relays 111u, 112u, and 113u. The semiconductor relays 111u, 112u, and 113u are, for example, IGBTs or power MOSFETs.

[0038] The power line 35u is drawn into the winding switching device 100. Inside the winding switching device 100, the power line 35u branches off at a midpoint and is connected to a first terminal of a semiconductor relay 111u. A second terminal of the semiconductor relay 111u is connected to a first terminal of a semiconductor relay 112u. A power line 221u extending from the winding 22u is connected to a connection point between the second terminal of the semiconductor relay 111u and the first terminal of the semiconductor relay 112u.

[0039] A second terminal of the semiconductor relay 112u is connected to a first terminal of the semiconductor relay 113u. A power line 212u extending from the winding 21u is connected to the connection point between the second terminal of the semiconductor relay 112u and the first terminal of the semiconductor relay 113u. A power line 222u extending from the winding 22u is connected to a second terminal of the semiconductor relay 113u.

[0040] When the semiconductor relays 111u and 113u are in the OFF state and the semiconductor relay 112u is in the ON state, the windings 21u and 22u are connected in series. When the semiconductor relays 111u and 113u are in the ON state and the semiconductor relay 112u is in the OFF state, the windings 21u and 22u are connected in parallel.

[0041] Signal lines extending from the control circuit 103u are connected to the gate terminals of the semiconductor relays 111u, 112u, and 113u, respectively.

[0042] The power lines 212u, 221u, and 222u extend from the motor 20 and are drawn into the winding switching device 100. A current sensor 101u is attached to the power line 221u. However, the current sensor 101u may be attached to the power lines 35u, 212u, or 222u instead of the power line 221u. The current sensor 101u detects a U-phase current flowing through the power line 221u. The current sensor 101u is, for example, an ACCT that detects only the AC component of the current.

[0043] A signal line extending from the current sensor 101u is connected to the zero-cross detection circuit 102u. A signal line transmitting an output signal of the zero-cross detection circuit 102u (hereinafter referred to as a "zero-cross detection signal") extends from the zero-cross detection circuit 102u to the control circuit 103u. Furthermore, a signal line extending from the control device 50 is connected to the control circuit 103u.

[0044] The zero-crossing detection circuit 102u detects zero-crossing points of the winding current flowing through the power line 221u measured by the current sensor 101u. The zero-crossing detection circuit 102u is a comparator. For example, the inverting input of the comparator is set to a zero reference voltage, and the output signal of the current sensor 101u is applied to the non-inverting input. As a result, the output of the comparator changes from low to high at the point when the AC signal output from the current sensor 101u crosses the zero reference voltage (the zero-crossing point).

[0045] 3 is a circuit diagram showing an example of the configuration of the control circuit 103u. The control circuit 103u includes AND circuits 131 and 133, a NOT circuit 132, and a latch circuit 120. A signal line extending from the zero-crossing detection circuit 102u is connected to a first input terminal of the AND circuit 131 and a first input terminal of the AND circuit 133. A signal line extending from the control device 50 is connected to a second input terminal of the AND circuit 131. Furthermore, a signal line from the control device 50 is connected to an input terminal of the NOT circuit 132. A signal line extending from an output terminal of the NOT circuit 132 is connected to a second input terminal of the AND circuit 133.

[0046] The latch circuit 120 is an RS flip-flop. The output terminal of the AND circuit 131 is connected to the input S (set) of the RS flip-flop 120. The output terminal of the AND circuit 133 is connected to the input R (reset) of the RS flip-flop 120. The RS flip-flop 120 includes two NOT circuits 121 and 123 and two NAND circuits 122 and 124. However, the RS flip-flop 120 may also be configured by two NOR circuits.

[0047] The output Q of the RS flip-flop 120 is connected to the gates of the semiconductor relays 111u and 113u, and the output Q bar of the RS flip-flop 120 is connected to the gate of the semiconductor relay 112u.

[0048] [1-3. Zero-cross switching of winding switching device] Next, the zero-crossing switching of the winding switching device 100 will be described. Zero-crossing switching is an operation for switching the connection states of the windings 21u, 22u, 21v, 22v, 21w, and 22w between a series connection state and a parallel connection state at the zero-crossing points of the winding currents Iu, Iv, and Iw. Note that the following description will focus on the operation for switching the connection states of the windings 21u and 22u for the U phase. The same applies to the V and W phases, so their descriptions will be omitted.

[0049] FIG. 4 is a timing chart showing an example of transition of the states of the signals of the winding switching device 100 according to the first embodiment.

[0050] The current sensor 101u measures the winding current Iu flowing through the power line 221u. The zero-crossing detection circuit 102u detects zero-crossing points in the measured value of the winding current Iu. That is, the zero-crossing detection signal output from the zero-crossing detection circuit 102u is low when the winding current Iu is not zero and goes high when the winding current Iu becomes zero. In FIG. 4, the zero-crossing detection signal is low under normal conditions and high at times T1, T2, T3, and T4.

[0051] The control device 50 sets the value of the switching command signal to Low when windings 21u, 22u, 21v, 22v, 21w, and 22w of motor 20 are connected in series, and sets the value of the switching command signal to High when windings 21u, 22u, 21v, 22v, 21w, and 22w are connected in parallel. In Figure 4, the switching command signal is initially Low and changes to High at a certain point between times T1 and T2. The switching command signal changes again to Low at a certain point between times T3 and T4.

[0052] The zero-crossing detection signal and the switching command signal are input to an AND circuit 131. The AND circuit 131 outputs a low signal when the zero-crossing detection signal and the switching command signal are a combination of (low, low), (low, high), and (high, low). The AND circuit 131 outputs a high signal when the zero-crossing detection signal and the switching command signal are a combination of (high, high). That is, a low signal is input to S of the RS flip-flop 120 under normal circumstances, and a high signal is input when a zero-crossing point of the winding current Iu is detected and a parallel connection command for the windings 21u, 22u, 21v, 22v, 21w, and 22w is given. In FIG. 4, the input signal to S is high at times T2 and T3.

[0053] The zero-crossing detection signal and an inverted signal of the switching command signal (the output signal of the NOT circuit 132) are input to the AND circuit 133. The AND circuit 133 outputs a low signal when the zero-crossing detection signal and the switching command signal are combined as (low, low), (high, low), or (high, high). The AND circuit 133 outputs a high signal when the zero-crossing detection signal and the switching command signal are combined as (high, low). That is, a low signal is input to R of the RS flip-flop 120 under normal circumstances, and a high signal is input when a zero-crossing point of the winding current Iu is detected and a command to connect the windings 21u, 22u, 21v, 22v, 21w, and 22w in series is given. In FIG. 4, the input signal to R is high at times T1 and T4.

[0054] The RS flip-flop 120 holds the previous output values ​​of Q and Q-bar when the inputs S and R are Low and Low. When the inputs S and R are Low and High, the RS flip-flop 120 outputs Low and High for Q and Q-bar, and when the inputs S and R are High and Low, the RS flip-flop 120 prohibits the combination of High and High for the inputs S and R.

[0055] 4, Q is low and Q is high until time T2. Therefore, until time T2, the semiconductor relays 111u and 113u are in the off state and the semiconductor relay 112u is in the on state. Therefore, the windings 21u and 22u are connected in series.

[0056] At time T2, Q changes from low to high, and Q changes from high to low. Therefore, the semiconductor relays 111u and 113u change from off to on, and the semiconductor relay 112u changes from on to off. As a result, the connection state of the windings 21u and 22u switches from a series connection state to a parallel connection state.

[0057] From time T2 to T4, Q is high and Q is low. Therefore, from time T2 to T4, the semiconductor relays 111u and 113u are maintained in the on state, and the semiconductor relay 112u is maintained in the off state. As a result, the windings 21u and 22u are maintained in a parallel connection state.

[0058] At time T4, Q changes from High to Low, and Q changes from Low to High. Therefore, the semiconductor relays 111u and 113u change from the ON state to the OFF state, and the semiconductor relay 112u changes from the OFF state to the ON state. As a result, the connection state of the windings 21u and 22u switches from the parallel connection state to the series connection state.

[0059] After time T4, Q is low and Q is high. Therefore, until time T2, the semiconductor relays 111u and 113u remain off and the semiconductor relay 112u remains on. As a result, the windings 21u and 22u are maintained in a series connection state.

[0060] As described above, the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w can be switched between a series connection state and a parallel connection state at the timing of the zero-crossing points of the winding currents Iu, Iv, and Iw. This prevents surge voltages from occurring. Furthermore, complex processing such as identifying the period during which the winding currents Iu, Iv, and Iw are below a predetermined value is not required, and the winding switching device 100 can be configured without using a processor such as a CPU, FPGA, or ASIC.

[0061] [1-4. Hardware configuration of the control device] 5 is a block diagram showing an example of the hardware configuration of the control device according to the first embodiment. The control device 50 includes a processor 501, a non-volatile memory 502, a volatile memory 503, and an interface (I / F) 504.

[0062] 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.

[0063] 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.

[0064] The I / F 504 is connected to the winding switching device 100 and the power converter 30. The I / F 504 is, for example, an input / output interface or a communication interface. For example, the I / F 504 is connected to current sensors 33u, 33v, and 33w provided in the power converter 30 and can acquire the current value of the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw. For example, the I / F 504 is connected to each of the switches 31u, 32u, 31v, 32v, 31w, and 32w of the power converter 30 and can control the on / off of the switches 31u, 32u, 31v, 32v, 31w, and 32w. For example, the I / F 504 is connected to the control circuits 103u, 103v, and 103w of the winding switching device 100 and can output a switching command signal to the control circuits 103u, 103v, and 103w.

[0065] [1-5. Functions of the control device] FIG. 6 is a functional block diagram showing an example of functions of the control device according to the first embodiment.

[0066] When the processor 501 executes the motor control program 510, the control device 50 executes the functions of a determination unit 521, an instruction unit 522, and a current control unit 523.

[0067] The determination unit 521 determines whether a specific condition regarding the motor 20 is met.

[0068] The specific condition is, for example, that the currents (winding currents Iu, Iv, Iw) flowing through the windings 21u, 22u, 21v, 22v, 21w, 22w become smaller than a first threshold value T1. The first threshold value T1 can be determined based on, for example, the rated current of the motor 20. For example, the first threshold value T1 is a value that is a predetermined percentage (e.g., 10%) of the rated current of the motor 20. As another example, the first threshold value T1 may be determined based on a surge voltage that occurs when the winding currents Iu, Iv, Iw are momentarily interrupted so as not to exceed the withstand voltages of the semiconductor relays 111u, 112u, 113u, 111v, 112v, 113v, 111w, 112w, 113w, etc.

[0069] Fig. 7A is a graph showing an example of the change in winding current over time when the amplitude of the winding current is large, and Fig. 7B is a graph showing an example of the change in winding current over time when the amplitude of the winding current is small. In Fig. 7A and Fig. 7B, the vertical axis represents the current value, and the horizontal axis represents time.

[0070] 7A and 7B, the winding current fluctuates slightly due to noise. Even if the amplitude of the winding current changes, the magnitude of the noise does not change. Therefore, when the amplitude of the winding current is small, the noise becomes larger relative to the amplitude compared to when the amplitude of the winding current is large (FIG. 7A).

[0071] The top of each of Figures 7A and 7B shows the results of zero-crossing point detection. The points plotted on the horizontal axis are the detection times of the zero-crossing points. When the amplitude of the winding current is large, the zero-crossing points are accurately detected without being affected by noise. In contrast, when the amplitude of the winding current is large, it can be seen that the zero-crossing points are erroneously detected due to the influence of noise.

[0072] The winding switching system according to this embodiment increases the winding current before performing zero-crossing switching when the zero-crossing point detection accuracy is low and the winding current amplitude is small. On the other hand, when the zero-crossing point detection accuracy is high and the winding current amplitude is large, the winding switching system according to this embodiment performs zero-crossing switching without increasing the winding current. This reduces the occurrence of surge voltages caused by switching the connection states of the windings 21u, 22u, 21v, 22v, 21w, and 22w at times other than the zero-crossing points. Hereinafter, the control for switching the connection states of the windings 21u, 22u, 21v, 22v, 21w, and 22w by increasing the winding current before performing zero-crossing switching is also referred to as “first switching control,” and the control for switching the connection states of the windings 21u, 22u, 21v, 22v, 21w, and 22w by performing zero-crossing switching without increasing the winding current is also referred to as “second switching control.”

[0073] Returning to FIG. 6 , for example, the determination unit 521 acquires the detection values ​​of the current sensors 33u, 33v, and 33w. The determination unit 521 identifies (detects) the amplitude and phase of each of the currents Iu, Iv, and Iw based on the detection values ​​of each of the current sensors 33u, 33v, and 33w. The determination unit 521 compares the amplitude of each of the currents Iu, Iv, and Iw with a first threshold T1, and determines that the specific condition is met if the amplitude is smaller than the first threshold T1. In this case, the determination unit 521 may determine that the specific condition is met if the amplitudes of all of the currents Iu, Iv, and Iw are smaller than the first threshold T1, or may determine that the specific condition is met if the amplitude of at least one of the currents Iu, Iv, and Iw is smaller than the first threshold T1.

[0074] Instead of comparing the amplitudes of the currents Iu, Iv, and Iw with the first threshold T1, the judgment unit 521 may calculate the effective values ​​(root mean square) of the currents Iu, Iv, and Iw and compare the calculated effective values ​​with the first threshold T1.

[0075] When the determining unit 521 determines that the specific condition is met, the current control unit 523 increases the amplitudes of the currents Iu, Iv, and Iw.

[0076] In a specific example, when the determination unit 521 determines that the specific condition is met, the current control unit 523 increases the amplitudes of the currents Iu, Iv, and Iw until the amplitudes of the currents Iu, Iv, and Iw exceed a second threshold T2. The second threshold T2 is greater than the first threshold T1. The second threshold T2 is a value corresponding to the amplitudes of the currents Iu, Iv, and Iw at which zero-crossing points of the currents Iu, Iv, and Iw can be detected without being affected by noise. For example, the second threshold T2 can be determined based on the first threshold T1. In a specific example, the second threshold T2 can be set to a predetermined multiple (e.g., 1.5 times) of the first threshold T1.

[0077] For example, the current control unit 523 increases the amplitudes of the currents Iu, Iv, and Iw, and also changes the phases of the currents Iu, Iv, and Iw.

[0078] Fig. 8 is a graph showing a first example of the relationship between the output torque of the motor according to the first embodiment and the phase of the winding current. Fig. 8 shows the torque-current characteristics of motor 20 in a high-speed connection state (parallel connection state). In Fig. 8, the vertical axis represents the output torque of motor 20, and the horizontal axis represents the phases of currents Iu, Iv, and Iw.

[0079] Here, the first switching control when switching the connection state of the motor 20 from a parallel connection state to a series connection state will be described. That is, the parallel connection state corresponds to the "first connection state," and the series connection state corresponds to the "second connection state." Note that the same first switching control as described below is also performed when switching the connection state of the windings 21u, 22u, 21v, 22v, 21w, and 22w from the series connection state to the parallel connection state. In this case, the series connection state corresponds to the "first connection state," and the parallel connection state corresponds to the "second connection state."

[0080] In the parallel connection state, the current control unit 523 changes the phases of the currents Iu, Iv, and Iw so that the output torque of the motor 20 maintains the target value TT. For example, the target value TT of the output torque is the output torque value of the motor 20 at a point in time before the amplitudes of the currents Iu, Iv, and Iw are increased. The arrows in FIG. 8 indicate that the amplitudes of the currents Iu, Iv, and Iw change from I1 (the graph shown by the dashed line in FIG. 8) to I2 (the graph shown by the broken line in FIG. 8) and the phases of the currents Iu, Iv, and Iw change from θ1 to θ2 so that the output torque maintains the target value TT. In FIG. 8, I1 <I2<I3であり、I1<T2<I2である。

[0081] The control device 50 controls the currents Iu, Iv, and Iw using maximum torque per amp (MTPA) control except when the first switching control is being executed. Maximum torque control is a control method that controls the current phase so as to maximize the torque at the current amplitude at that time. On the other hand, the first switching control changes the amplitude and phase of the currents Iu, Iv, and Iw as shown by the arrows in FIG. 8. This makes it possible to increase the amplitude of the currents Iu, Iv, and Iw while maintaining the output torque of the motor 20, thereby preventing sudden torque fluctuations.

[0082] At the start of the first switching control (i.e., the time when the determination unit 521 determines that the specific condition is met), the current control unit 523 calculates the output torque of the motor 20 at that time (the present time) from the amplitude and phase of the currents Iu, Iv, and Iw determined from the detection values ​​of the current sensors 33u, 33v, and 33w, and sets the calculated output torque as a target value TT. The current control unit 523 performs ramp control on the amplitudes of the currents Iu, Iv, and Iw. That is, the current control unit 523 determines the amplitudes (target amplitudes) of the currents Iu, Iv, and Iw after a short time (e.g., a control cycle period) has elapsed by adding a small value (e.g., a predetermined value) to the amplitudes of the currents Iu, Iv, and Iw at the present time. The current control unit 523 calculates a current phase that generates the target value TT of the output torque at the determined target amplitude, and sets the calculated current phase as the target phase. The current control unit 523 switches the switches 31u, 32u, 31v, 32v, 31w, and 32w so that the amplitudes and phases of the currents Iu, Iv, and Iw match the target amplitudes and target phases. Hereinafter, the above current control will also be referred to as "current amplitude increase control." The current control unit 523 executes the current amplitude increase control in each control cycle until the amplitudes of the currents Iu, Iv, and Iw reach I2 (i.e., until the amplitudes of the currents Iu, Iv, and Iw exceed the second threshold T2). When the amplitudes of the currents Iu, Iv, and Iw reach I2, the current control unit 523 stops increasing the amplitudes of the currents Iu, Iv, and Iw.

[0083] In the first switching control, the output torque of the motor 20 does not have to maintain the target value TT while the amplitudes of the currents Iu, Iv, and Iw increase. For example, the output torque may be allowed to fluctuate within a certain range centered on the target value TT (for example, within a range of ±10% of the target value TT). In another example, the phases of the currents Iu, Iv, and Iw do not have to change while the amplitudes of the currents Iu, Iv, and Iw increase.

[0084] Returning to FIG. 6 , the instructing unit 522 instructs the winding switching device 100 to execute zero-crossing switching after the current control unit 523 increases the amplitudes of the currents Iu, Iv, and Iw. That is, in the above example, when the amplitudes of the currents Iu, Iv, and Iw reach I2, the instructing unit 522 instructs the winding switching device 100 to execute zero-crossing switching. The instruction to execute zero-crossing switching is performed by outputting a switching command signal to the control circuits 103u, 103v, and 103w. That is, as described above, when the switching command signal is input to the control circuits 103u, 103v, and 103w, a zero-crossing detection signal is output from the zero-crossing detection circuits 102u, 102v, and 102w at the time of detection of the next zero-crossing point, and zero-crossing switching is executed.

[0085] The current control unit 523 reduces the amplitudes of the currents Iu, Iv, and Iw after the zero-crossing switch is performed.

[0086] In a specific example, when the judgment unit 521 determines that a specific condition is met, the current control unit 523 reduces the amplitude of the currents Iu, Iv, and Iw until the amplitude of the currents Iu, Iv, and Iw becomes smaller than the second threshold T2.

[0087] For example, the current control unit 523 reduces the amplitudes of the currents Iu, Iv, and Iw, and also changes the phases of the currents Iu, Iv, and Iw.

[0088] Fig. 9 is a graph showing a second example of the relationship between the output torque of the motor according to the first embodiment and the phase of the winding current. Fig. 9 shows the torque-current characteristics of motor 20 in a high-torque connection state (series connection state). In Fig. 9, the vertical axis represents the output torque of motor 20, and the horizontal axis represents the phases of currents Iu, Iv, and Iw.

[0089] The current control unit 523 changes the phases of the currents Iu, Iv, and Iw so that the output torque of the motor 20 maintains a target value TT. For example, the target value TT of the output torque is the same as the target value TT in the current amplitude increase control. The arrows in FIG. 9 indicate that the amplitudes of the currents Iu, Iv, and Iw change from I2 (the graph indicated by the dashed line in FIG. 9) to I4 (the graph indicated by the two-dot chain line in FIG. 9) and the phases of the currents Iu, Iv, and Iw change from θ3 to θ4 so that the output torque maintains the target value TT. Before and after the zero-crossing switching, the phases of the currents Iu, Iv, and Iw change from θ2 to θ3. That is, θ3 is the phase of the currents Iu, Iv, and Iw immediately after the connection states of the windings 21u, 22u, 21v, 22v, 21w, and 22w are switched. The current control unit 523 changes the phases of the currents Iu, Iv, Iw from θ3 to θ4 so as to maintain the target value TT of the output torque while reducing the amplitudes of the currents Iu, Iv, Iw to the minimum amplitude I4 of the currents Iu, Iv, Iw that generates the target value TT of the output torque. That is, I4 and θ4 are the amplitudes and phases of the currents Iu, Iv, Iw at which the output torque of the motor 20 becomes the target value TT under MTPA control.

[0090] The current control unit 523 reduces the amplitudes of the currents Iu, Iv, and Iw using the target value TT of the output torque used in the current increase control. The current control unit 523 ramp-controls the amplitudes of the currents Iu, Iv, and Iw. That is, the current control unit 523 determines the amplitudes (target amplitudes) of the currents Iu, Iv, and Iw after a short time (e.g., a control cycle period) has elapsed by subtracting a small value (e.g., a predetermined value) from the current amplitudes of the currents Iu, Iv, and Iw. The current control unit 523 calculates a current phase that generates the target value TT of the output torque at the determined target amplitude, and sets the calculated current phase as the target phase. The current control unit 523 switches the switches 31u, 32u, 31v, 32v, 31w, and 32w so that the amplitudes and phases of the currents Iu, Iv, and Iw match the target amplitudes and target phases. Hereinafter, the above current control will also be referred to as "current amplitude reduction control." The current control unit 523 executes the current amplitude reduction control in each control cycle until the amplitudes of the currents Iu, Iv, and Iw reach I4 (i.e., the amplitudes that generate the target value TT of the output torque when the MTPA control is executed). When the amplitudes of the currents Iu, Iv, and Iw reach I4, the current control unit 523 stops reducing the amplitudes of the currents Iu, Iv, and Iw.

[0091] 6, when the determination unit 521 determines that the specific condition is not met, the current control unit 523 does not increase the amplitudes of the currents Iu, Iv, and Iw. In other words, when the specific condition is not met, the first switching control is not executed.

[0092] When the determining unit 521 determines that the specific condition is not met, the instructing unit 522 instructs the winding switching device 100 to perform zero-crossing switching during a period in which the amplitudes of the currents Iu, Iv, and Iw are not increasing. In a specific example, when the determining unit 521 determines that the specific condition is not met, the instructing unit 522 immediately instructs the winding switching device 100 to perform zero-crossing switching.

[0093] [1-6. Operation of the control device] Next, a description will be given of the operation of the control device 50. The control device 50 executes a winding connection switching control process by the processor 501 executing the motor control program 510.

[0094] FIG. 10 is a flowchart showing an example of a winding connection switching control process performed by the control device according to the first embodiment.

[0095] The control device 50 controls the motor 20 by, for example, MTPA control.

[0096] The current sensors 33u, 33v, and 33w detect the current values ​​of the winding currents Iu, Iv, and Iw. Detection signals from the current sensors 33u, 33v, and 33w are input to the control device 50. The current sensors 33u, 33v, and 33w detect current values ​​continuously over time. The processor 501 identifies the amplitudes and phases of the currents Iu, Iv, and Iw based on the outputs of the current sensors 33u, 33v, and 33w (step S101).

[0097] The processor 501 determines whether or not a specific condition is met (step S102). That is, the processor 501 determines whether or not the amplitudes of the winding currents Iu, Iv, and Iw are smaller than a first threshold value T1.

[0098] If the specific condition is met (YES in step S102), processor 501 executes the first switching control (step S103).

[0099] FIG. 11 is a flowchart showing an example of the first switching control by the control device according to the first embodiment.

[0100] The processor 501 calculates the output torque of the motor 20 at the current time point, and sets the calculated output torque as a target value TT (step S201).

[0101] The processor 501 performs switching control of the switches 31u, 32u, 31v, 32v, 31w, and 32w of the power converter 30, and changes the phase while increasing the amplitude of the currents Iu, Iv, and Iw so that the output torque maintains the target value TT (step S202).

[0102] The processor 501 determines whether the amplitudes of the currents Iu, Iv, and Iw exceed the second threshold T2 (step S203).

[0103] If the amplitudes of the currents Iu, Iv, and Iw do not exceed the second threshold T2 (NO in step S203), the processor 501 returns to step S202.

[0104] If the amplitudes of the currents Iu, Iv, and Iw exceed the second threshold T2 (YES in step S203), the processor 501 instructs the winding switching device 100 to perform zero-cross switching (step S204). That is, the processor 501 outputs a switching command signal to each of the control circuits 103u, 103v, and 103w of the winding switching device 100. This causes the zero-cross switching to be performed.

[0105] The processor 501 calculates the minimum amplitude of the currents Iu, Iv, and Iw that generates the target value TT of the output torque (step S205).

[0106] The processor 501 performs switching control of the switches 31u, 32u, 31v, 32v, 31w, and 32w of the power converter 30, and changes the phase while reducing the amplitude of the currents Iu, Iv, and Iw so that the output torque maintains the target value TT (step S206).

[0107] The processor 501 determines whether the amplitudes of the currents Iu, Iv, and Iw have reached the calculated minimum amplitudes (step S207).

[0108] If the amplitudes of the currents Iu, Iv, and Iw have not reached the minimum amplitude (NO in step S207), the processor 501 returns to step S206.

[0109] If the amplitudes of the currents Iu, Iv, and Iw have reached the minimum amplitude (YES in step S207), the first switching control ends.

[0110] Returning to FIG. 10, when the first switching control ends, the processor 501 ends the winding connection switching control process.

[0111] On the other hand, if the specific condition is not met (NO in step S102), the processor 501 executes the second switching control (step S104). That is, the processor 501 instructs the winding switching device 100 to perform zero-crossing switching. This ends the winding connection switching control process.

[0112] [2. Second Embodiment] The winding switching device according to the second embodiment switches the connection state of a plurality of windings of a motor between a full connection state in which all of the plurality of windings are connected and a partial connection state in which only a portion of the plurality of windings are connected. The full connection state is a high-torque connection state, and the partial connection state is a high-speed rotation connection state.

[0113] 12 is a circuit diagram showing an example of the configuration of a winding switching device according to the second embodiment. Motor 20A includes multiple windings 24u, 25u, 24v, 25v, 24w, and 25w. Windings 24u and 25u correspond to the U phase, windings 24v and 25v correspond to the V phase, and windings 24w and 25w correspond to the W phase. However, the number of windings for each phase is not limited to two and may be three or more.

[0114] The winding switching device 100A switches the connection states of the windings 24u, 25u, 24v, 25v, 24w, and 25w for each phase between a fully connected state and a partially connected state. The winding switching device 100A includes current sensors 131u, 131v, and 131w, zero-crossing detection circuits 102u, 102v, and 102w, control circuits 103u, 103v, and 103w, and switching circuits 140u, 140v, and 140w.

[0115] The zero-cross detection circuits 102u, 102v, and 102w detect zero-cross points of the measurement values ​​of the current sensors 131u, 131v, and 131w. The configurations of the zero-cross detection circuits 102u, 102v, and 102w are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0116] The switching circuits 140u, 140v, and 140w switch the connection states of the windings 24u, 25u, 24v, 25v, 24w, and 25w between a full connection state and a partial connection state when the zero-crossing detection circuits 102u, 102v, and 102w detect a zero-crossing point. The switching circuits 140u, 140v, and 140w are an example of a switching unit. The full connection state is an example of a first connection state, and the partial connection state is an example of a second connection state.

[0117] Power line 35u is connected to one end of winding 24u. The other end of winding 24u and one end of winding 25u are connected to each other, and power line 241u extends from the midpoint between winding 24u and winding 25u. Power line 241u branches into power lines 242u and 243w. Power line 251u extends from the other end of winding 25u. Power line 251u branches into power lines 252u and 253w.

[0118] Power line 35v is connected to one end of winding 24v. The other end of winding 24v and one end of winding 25v are connected to each other, and power line 241v extends from the midpoint between windings 24v and 25v. Power line 241v branches into power lines 242v and 243u. Power line 251v extends from the other end of winding 25v. Power line 251v branches into power lines 252v and 253u.

[0119] Power line 35w is connected to one end of winding 24w. The other end of winding 24w and one end of winding 25w are connected to each other, and power line 241w extends from the midpoint between windings 24w and 25w. Power line 241w branches into power lines 242w and 243v. Power line 251w extends from the other end of winding 25w. Power line 251w branches into power lines 252w and 253v.

[0120] The switching circuit 140u includes semiconductor relays 141u and 142u. The switching circuit 140v includes semiconductor relays 141v and 142v. The switching circuit 140w includes semiconductor relays 141w and 142w. The semiconductor relays 141u, 142u, 141v, 142v, 141w, and 142w are, for example, IGBTs or power MOSFETs.

[0121] In the switching circuit 140u, a first terminal of a semiconductor relay 141u is connected to a power line 242u, and a second terminal is connected to a power line 243u. A first terminal of a semiconductor relay 142u is connected to a power line 252u, and a second terminal is connected to a power line 253u. The connection relationship between the switching circuits 140v and 140w is the same as that of the switching circuit 140u, so a description thereof will be omitted.

[0122] When semiconductor relays 141u, 141v, and 141w are in the OFF state and semiconductor relays 142u, 142v, and 142w are in the ON state, a fully connected state is achieved in which all of windings 24u, 25u, 24v, 25v, 24w, and 25w are connected. When semiconductor relays 141u, 141v, and 141w are in the ON state and semiconductor relays 142u, 142v, and 142w are in the OFF state, a partially connected state is achieved in which only windings 24u, 24v, and 24w are connected among windings 24u, 25u, 24v, 25v, 24w, and 25w.

[0123] The power line 35u is drawn into the winding switching device 100. A current sensor 131u is attached to the power line 35u. The current sensor 131u detects the U-phase current flowing through the power line 35u. The current sensor 131u is, for example, an ACCT that detects only the AC component of the current. A signal line extending from the current sensor 131u is connected to the zero-crossing detection circuit 102u. The same applies to the V-phase and W-phase.

[0124] The output Q of the RS flip-flop 120 of the control circuit 103u is connected to the gate of the semiconductor relay 141u. The output Q bar of the RS flip-flop 120 is connected to the gate of the semiconductor relay 142u. The same applies to the V-phase and W-phase.

[0125] Other configurations of the winding switching device 100A according to the second embodiment are similar to those of the winding switching device 100 according to the first embodiment, so the same components are given the same reference numerals and descriptions thereof will be omitted.

[0126] In the second embodiment, the control device 50 sets the value of the switching command signal to Low when windings 24u, 25u, 24v, 25v, 24w, and 25w of the motor 20 are to be fully connected, and sets the value of the switching command signal to High when windings 24u, 25u, 24v, 25v, 24w, and 25w are to be partially connected.

[0127] When the windings are in the fully connected state, output Q goes low and output Q goes high at the timing when both the zero-crossing detection signal and the switching command signal go high. Therefore, semiconductor relay 141u changes from the on state to the off state, and semiconductor relay 142u changes from the off state to the on state. The same applies to the V-phase and W-phase. Therefore, the connection states of windings 24u, 25u, 24v, 25v, 24w, and 25w change from the fully connected state to the partially connected state.

[0128] When the windings are in the partially connected state, the zero-crossing detection signal goes high and the switching command signal goes low, causing output Q to go high and output Q bar to go low. Therefore, semiconductor relay 141u changes from the off state to the on state, and semiconductor relay 142u changes from the on state to the off state. The same applies to the V-phase and W-phase. Therefore, the connection states of windings 24u, 25u, 24v, 25v, 24w, and 25w switch from the partially connected state to the fully connected state.

[0129] As described above, the connection states of the windings 21u, 22u, 21v, 22v, 21w, and 22w can be switched between a fully connected state and a partially connected state at the timing of the zero crossing points of the winding currents Iu, Iv, and Iw.

[0130] The configurations and operations of the power converter 30 and the control device 50 according to the second embodiment are similar to those of the power converter 30 and the control device 50 according to the first embodiment, and therefore will not be described.

[0131] [3. Supplementary Notes] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims rather than the above-described embodiments, and includes meanings equivalent to the claims and all modifications within the scope thereof. [Explanation of symbols]

[0132] 10 Winding switching system 20 Motor 21u, 22u, 21v, 22v, 21w, 22w winding 23 Neutral point 25 Power Lines 30 Power Converter 31u, 32u, 31v, 32v, 31w, 32w switches 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 521 Judgment section 522 Instruction section 523 Current control section 100 Winding switching device 101u, 101v, 101w current sensor 102u, 102v, 102w zero cross detection circuit 103u, 103v, 103w control circuit 104u, 104v, 104w switching circuit 111u, 112u, 113u, 111v, 112v, 113v, 111w, 112w, 113w solid state relays 212u,221u,222u,212v,221v,222v,212w,221w,222w power line 131,133 AND circuit 132 NOT circuit 120 Latch circuit (RS flip-flop) 121,123 NOT circuit 122,124 NAND circuits 20A motor 24u, 25u, 24v, 25v, 24w, 25w winding 100A winding switching device 131u, 131v, 131w current sensor 140u, 140v, 140w switching circuit 141u, 142u, 141v, 142v, 141w, 142w solid state relays 241u,242u,243u,251u,252u,253u,241v,242v,243v,251v,252v,253v,241w,242w,243w,251w,252w,253w power line T1 First threshold T2 Second threshold I_1, I_2, I_3, I_4 amplitude θ1,θ2,θ3,θ4 phase

Claims

1. A control device for controlling an AC motor capable of switching a connection state of a plurality of windings between a first connection state and a second connection state, a determination unit that determines whether a specific condition related to the AC motor is established; a current control unit that increases an amplitude of a winding current flowing through the winding when the determination unit determines that the specific condition is met; an instruction unit that instructs a winding switching device that switches the connection states of the plurality of windings to execute zero-crossing switching to switch from the first connection state to the second connection state when the winding current reaches a zero-crossing point after the current control unit increases the amplitude of the winding current; Equipped with Control device.

2. the current control unit does not change the amplitude of the winding current flowing through the winding when the determination unit determines that the specific condition is not satisfied, the instruction unit instructs the switching device to perform the zero-cross switching when the determination unit determines that the specific condition is not satisfied. The control device according to claim 1 .

3. the specific condition is that the amplitude of the winding current is smaller than a first threshold value; The control device according to claim 1 .

4. the current control unit increases the amplitude of the winding current until the amplitude of the winding current exceeds a second threshold value when the determination unit determines that the specific condition is met. The control device according to claim 1 .

5. the current control unit increases the amplitude of the winding current and changes the phase of the winding current; The control device according to claim 1 .

6. the current control unit changes the phase of the winding current so that the output torque of the AC motor maintains a target value. The control device according to claim 5 .

7. the current control unit increases the amplitude of the winding current by ramp control; The control device according to claim 5 .

8. the current control unit reduces the amplitude of the winding current after the zero-crossing switching is performed. The control device according to any one of claims 1 to 7.

9. an AC motor capable of switching a connection state of a plurality of windings between a first connection state and a second connection state; a power converter that converts power output from a power supply into AC power and supplies the AC power to the AC motor; a winding switching device for switching the connection state of the plurality of windings; a control device; Equipped with The control device a determination unit that determines whether a specific condition related to the AC motor is established; a current control unit that increases an amplitude of a winding current flowing through the winding when the determination unit determines that the specific condition is met; an instruction unit that instructs the winding switching device to perform zero-crossing switching to switch from the first connection state to the second connection state when the winding current reaches a zero-crossing point after the current control unit increases the amplitude of the winding current; and Including, Winding switching system.

10. A control method for controlling an AC motor capable of switching a connection state of a plurality of windings between a first connection state and a second connection state, comprising: determining whether a specific condition related to the AC motor is met; increasing an amplitude of a winding current flowing through the winding when it is determined that the specific condition is met; after increasing the amplitude of the winding current, instructing a winding switching device that switches the connection states of the plurality of windings to execute zero-crossing switching, which switches the connection state from the first connection state to the second connection state, at a time point when the winding current reaches a zero-crossing point; Including, Control method.

11. 1. A control program for controlling an AC motor capable of switching a connection state of a plurality of windings between a first connection state and a second connection state, On the computer, determining whether a specific condition related to the AC motor is met; increasing an amplitude of a winding current flowing through the winding when it is determined that the specific condition is met; after increasing the amplitude of the winding current, instructing a winding switching device that switches the connection states of the plurality of windings to execute zero-crossing switching, which switches the connection state from the first connection state to the second connection state, at a time point when the winding current reaches a zero-crossing point; In order to execute Control program.

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