Dual inverter system

Abstract

To provide a technology that transitions to protective control while avoiding a battery short circuit using the same procedure in a dual inverter system, regardless of whether it is in single mode or dual mode.SOLUTION: A dual inverter system disclosed in the present specification includes a first inverter connected to one end of a motor's stator coil and a second inverter connected to the other end. A controller can operate in a dual mode, in which the motor is driven by two inverters, or in a single mode, in which the motor is driven by only one inverter. When the voltage at the DC end of the first inverter exceeds a threshold voltage, the controller closes all of the upper switching elements of the first and second inverters, opens all of the lower switching elements, and closes the connecting switch. Alternatively, the controller closes all of the lower switching elements of the first and second inverters, opens all of the upper switching elements, and closes the connecting switch.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a dual inverter system including two inverters and one open-winding motor. [Background technology]

[0002] Patent Document 1 discloses an example of a dual inverter system. In a dual inverter system, one end of a motor's stator coil is connected to the AC end of a first inverter, and the other end of the stator coil is connected to the AC end of a second inverter. Synchronizing the on / off switching elements of the first and second inverters allows twice the voltage to be applied to the motor compared to when the motor is driven by a single inverter, thereby achieving high torque. When high torque is not required, the other ends of multiple stator coils are connected to each other to create a neutral point, and the motor is driven by only the first inverter. For convenience, in this specification, driving a motor with two inverters is referred to as dual mode, and driving a motor with only one inverter is referred to as single mode.

[0003] Furthermore, when the voltage at the DC end of the inverter exceeds a predetermined threshold voltage, protective control is executed to consume the current generated by the induced electromotive force of the stator coil while rotating the motor by inertia. Patent Document 2 discloses an example of protective control. The device disclosed in Patent Document 2 is a device that drives a motor using a single inverter. Patent Document 2 also discloses protective control that turns off one of the upper and lower switching elements and turns on the other after a predetermined waiting time. Control that closes one of the upper and lower switching elements to circulate the current generated by the induced electromotive force of the stator coil is called active short circuit control (or zero vector control) (Patent Document 2). For convenience of explanation, in this specification, control that closes one of the upper and lower switching elements to circulate the current generated by the induced electromotive force of the stator coil is abbreviated as ASC control (active short circuit control). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-014829 [Patent Document 2] Japanese Patent Application Publication No. 2016-025776 Summary of the Invention [Problem to be solved by the invention]

[0005] In a dual inverter system, battery short circuit must be avoided when switching from single mode or dual mode to ASC control. This specification provides a technology that can switch to ASC control (recirculating current to the stator coil for consumption) while avoiding battery short circuit using the same procedure in both single mode and dual mode in a dual inverter system. [Means for solving the problem]

[0006] The dual inverter system disclosed in this specification includes a first inverter, a second inverter, a motor, a coupling switch, and a controller. The DC terminal of the first inverter is connected to a battery, and each of a plurality of AC terminals is connected to one end of each of a plurality of stator coils of the motor. Each of a plurality of AC terminals of the second inverter is connected to the other end of each of the plurality of stator coils. The coupling switch connects the DC terminal of the second inverter to the battery or disconnects the DC terminal of the second inverter from the battery. The controller can execute a dual mode in which the coupling switch is closed to drive the motor using both the first inverter and the second inverter, and a single mode in which the coupling switch is opened to drive the motor using only the first inverter.

[0007] As is well known, an inverter includes a plurality of series circuits in which upper and lower switching elements are connected in series. The plurality of series circuits are connected in parallel between the positive and negative poles of the DC terminal of the inverter. The midpoint of each series circuit is connected to each of the plurality of AC terminals of the inverter. When the voltage at the DC terminal of the first inverter exceeds a predetermined threshold voltage, the controller executes one of the following upper short-circuit control and lower short-circuit control. In the upper short-circuit control, the controller closes all upper switching elements of the first and second inverters, opens all lower switching elements, and closes the connecting switch. In the lower short-circuit control, the controller closes all lower switching elements of the first and second inverters, opens all upper switching elements, and closes the connecting switch.

[0008] In top short circuit control, the current generated by the induced electromotive force in the stator coil circulates through the top switching elements of the first and second inverters. In bottom short circuit control, the current generated by the induced electromotive force in the stator coil circulates through the bottom switching elements of the first and second inverters. In either dual mode or single mode, by switching to top short circuit control (or bottom short circuit control), it is possible to consume current by circulating it to the stator coil without shorting out the battery.

[0009] The controller executes the upper short-circuit control when the load on the upper switching element is smaller than the load on the lower switching element, and executes the lower short-circuit control when the load on the lower switching element is smaller than the load on the upper switching element. By selectively using the upper short-circuit control and the lower short-circuit control in this way, the cumulative loads on the upper switching element and the lower switching element are equalized.

[0010] As a protective control, the controller may return current in the following procedure: (1) the controller opens the coupling switch; (2) the controller closes the upper switching elements connected to each end of at least one stator coil and opens the lower switching elements, and also opens the upper switching elements connected to each end of the remaining stator coil and closes the lower switching elements; and (3) the controller closes the coupling switch.

[0011] According to the above procedure, current flows back through the loop that closes the upper switching element, and also flows back through the loop that closes the lower switching element. This results in greater power loss in the stator coil than in the above-mentioned upper short-circuit control and lower short-circuit control, and the current decays more quickly.

[0012] Details and further improvements of the technology disclosed in this specification are described in the following "Description of Embodiments of the Invention." [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a circuit diagram of a dual inverter system according to a first embodiment. [Figure 2] FIG. 10 is a circuit diagram showing the current flow during upper short-circuit control. [Figure 3] FIG. 10 is a circuit diagram showing a current flow during bottom short-circuit control. [Figure 4] FIG. 10 is a diagram showing the flow of a return current in the dual inverter system of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] (First embodiment) A dual inverter system 2 of a first embodiment will be described with reference to Figures 1-3. Hereinafter, for convenience of explanation, the "dual inverter system" may be abbreviated as the "DI system." Figure 1 shows a circuit diagram of the DI system 2. The DI system 2 includes a battery 3, a first inverter 10, a second inverter 20, a motor 30, coupling switches 40p and 40n, and a controller 50. The DI system 2 is mounted on, for example, an electric vehicle, and the motor 30 drives the axles.

[0015] The first inverter 10 has DC terminals (positive electrode 10p and negative electrode 10n) and AC terminals 10u, 10v, and 10w. The DC terminals are connected to the battery 3, and the AC terminals are connected to the motor 30.

[0016] The first inverter 10 includes three series circuits 11u, 11v, and 11w. The series circuit 11u is configured by a series-connected circuit of an upper switching element 12u and a lower switching element 13u. Hereinafter, for convenience of explanation, the "switching element" may be abbreviated to "SW element." A diode is connected in antiparallel to each of the upper SW element 12 and the lower SW element 13. The diode hardware may be separate from the SW element, or may be incorporated into the substrate of the SW element.

[0017] The series circuit 11u is connected between the positive electrode 10p and the negative electrode 10n of the DC terminal of the first inverter 10. The upper switching element 12u is connected to the positive electrode 10p, and the lower switching element 13u is connected to the negative electrode 10n. The midpoint of the series circuit 11u, i.e., the midpoint of the series connection circuit of the upper switching element 12u and the lower switching element 13u, is connected to the AC terminal 10u of the first inverter 10.

[0018] Series circuit 11v is composed of a series-connected circuit of upper switching element 12v and lower switching element 13v. Series circuit 11w is composed of a series-connected circuit of upper switching element 12w and lower switching element 13w. Series circuits 11v and 11w have the same structure as series circuit 11u. Hereinafter, upper switching elements 12u, 12v, and 12w may be collectively referred to as upper switching elements 12, and lower switching elements 13u, 13v, and 13w may be collectively referred to as lower switching elements 13.

[0019] A temperature sensor 14 is associated with each of the upper switching elements 12, and a temperature sensor 15 is associated with each of the lower switching elements 13. A system main relay 4 is connected between the DC terminals 10p, 10n of the first inverter 10 and the battery 3. When the system main relay 4 is closed, the first inverter 10 (and the second inverter 20) is connected to the battery 3. When the system main relay 4 is opened, the first inverter 10 (and the second inverter 20) is disconnected from the battery 3. A capacitor 5 is connected between the positive terminal 10p and the negative terminal 10n of the DC terminal of the first inverter 10, and a voltage sensor 6 is provided to measure the voltage across the capacitor 5 (the voltage at the DC terminal of the first inverter 10).

[0020] For ease of explanation, the three series circuits 11u, 11v, and 11w may be collectively referred to as the series circuit 11. The three series circuits 11 are connected in parallel between the positive pole 10p and negative pole 10n of the DC terminals of the first inverter 10. The midpoints of the three series circuits 11 are connected to the AC terminals 10u, 10v, and 10w, respectively. The upper switching element 12 and the lower switching element 13 are driven by a controller 50. When the controller 50 alternately turns on and off the upper switching element 12 and the lower switching element 13 at a predetermined duty ratio, an AC current flows through each of the three AC terminals 10u, 10v, and 10w.

[0021] The second inverter 20 has the same structure as the first inverter 10 and includes three series circuits 21u, 21v, and 21w. The same generic names are used for the second inverter 20 as for the first inverter 10. For example, the three series circuits 21u, 21v, and 21w will be hereinafter collectively referred to as series circuits 21. The same generic names are used for the upper switching elements 22u, 22v, and 22w and the lower switching elements 23u, 23v, and 23w.

[0022] The three series circuits 21 are connected in parallel between the positive electrode 20p and the negative electrode 20n of the DC terminal of the second inverter 20. Each of the series circuits 21 is composed of a series-connected circuit of an upper switching element 22 and a lower switching element 23. A diode is connected in anti-parallel to each of the upper switching element 22 and the lower switching element 23. The upper switching element 22 is connected to the positive electrode 20p, and the lower switching element 23 is connected to the negative electrode 20n. The midpoint of the series-connected circuit of the upper switching element 22 and the lower switching element 23 is connected to the AC terminal. The midpoint of the series circuit 21u (21v, 21w) is connected to the AC terminal 20u (20v, 20w).

[0023] A temperature sensor 24 is associated with each of the plurality of upper switching elements 22, and a temperature sensor 25 is associated with each of the plurality of lower switching elements 23.

[0024] The motor 30 includes three stator coils 31u, 31v, and 31w. One end of each of the three stator coils 31u, 31v, and 31w (the left end of the stator coil in FIG. 1) is connected to three AC terminals 10u, 10v, and 10w, respectively, of the first inverter 10. The other end of each of the three stator coils 31u, 31v, and 31w (the right end of the stator coil in FIG. 1) is connected to three AC terminals 20u, 20v, and 20w, respectively, of the second inverter 20. Hereinafter, the stator coils 31u, 31v, and 31w may be collectively referred to as stator coil 31.

[0025] Motor 30 is a three-phase AC motor. The subscripts "u," "v," and "w" in the symbols refer to the respective phases (u-phase, v-phase, and w-phase) of the three-phase AC. SW elements 12u, 13u, 22u, and 23u are connected to stator coil 31u. Similarly, SW elements 12v, 13v, 22v, and 23v are connected to stator coil 31v, and SW elements 12w, 13w, 22w, and 23w are connected to stator coil 31w.

[0026] In a typical motor, one end of each of the multiple stator coils is connected to each of the multiple AC terminals of the inverter, and the other ends of the multiple stator coils are connected to each other. The point where the other ends of the multiple stator coils are connected to each other is called the neutral point. In the motor 30, one end of each of the multiple stator coils 31 is connected to the AC terminals 10u, 10v, and 10w of the first inverter 10, and the other ends are connected to the AC terminals 20u, 20v, and 20w of the second inverter 20. A motor 30 that does not have a neutral point is called an open winding type.

[0027] The DC terminals 20p, 20n of the second inverter 20 are connected to the battery 3 via the connecting switches 40p, 40n. Specifically, the positive electrode 20p is connected to the positive electrode 3p of the battery 3 via the connecting switch 40p, and the negative electrode 20n is connected to the negative electrode 3n of the battery 3 via the connecting switch 40n. When the connecting switches 40p, 40n are closed, the second inverter 20 is connected to the battery 3, and when at least one of the connecting switches 40p, 40n is opened, the second inverter 20 is disconnected from the battery 3.

[0028] The controller 50 can drive the motor 30 using both the first inverter 10 and the second inverter 20. Specifically, the controller 50 closes the coupling switches 40p and 40n. The upper SW element 12u and the lower SW element 13u of the series circuit 11u are alternately turned on and off. The upper SW element 22u of the series circuit 21u is turned on and off in the opposite phase to the upper SW element 12u, and the lower SW element 23u is turned on and off in the opposite phase to the lower SW element 13u. The same applies to the other series circuits 11v / 21v (11w / 21w). The controller 50 turns on and off the SW elements of the first inverter 10 and the SW elements of the second inverter 20 in a linked manner.

[0029] When the SW elements of the first inverter 10 and the second inverter 20 are driven in opposite phases as described above, twice the voltage can be applied to the stator coil 31 compared to when the motor is driven by a single inverter. In other words, driving the motor 30 by two inverters (the first inverter 10 and the second inverter 20) produces high torque. Driving the motor 30 by the first inverter 10 and the second inverter 20 with the coupling switches 40p and 40n closed is hereinafter referred to as dual mode.

[0030] The controller 50 can also open the connecting switches 40p and 40n to drive the motor 30 using only the first inverter 10. In this case, a neutral point is created in the second inverter 20. The controller 50 opens the connecting switch 40p, closes all of the upper switching elements 22 of the second inverter 20, and opens all of the lower switching elements 23. This shorts the other ends of the multiple stator coils 31 (the right ends of the stator coils 31 in FIG. 1 ) via the upper switching elements 22. In other words, the other ends of the multiple stator coils 31 are connected to the neutral point. In this state, the controller 50 appropriately turns on and off the switching elements of the first inverter 10. The motor 30 is driven as a normal motor with a neutral point. Hereinafter, the operation of the controller 50 to create a neutral point using the second inverter 20 and drive the motor 30 using only the first inverter 10 is referred to as single mode.

[0031] The controller 50 can create a neutral point in the following two ways. In one method, as described above, the controller 50 closes all of the upper switching elements 22 and opens all of the lower switching elements 23 of the second inverter 20. In the other method, the controller 50 closes all of the lower switching elements 23 of the second inverter 20 and opens all of the upper switching elements 22. The right ends of the multiple stator coils 31 are short-circuited via the lower switching elements 23. In addition, in single mode, the controller 50 opens the connecting switches 40p and 40n.

[0032] If any malfunction occurs in the first inverter 10 or the second inverter, the voltage at the DC terminal of the first inverter 10 (the voltage between the positive electrode 10p and the negative electrode 10n) may become higher than the battery voltage. A capacitor 5 is connected to the DC terminal (the positive electrode 10p and the negative electrode 10n). If the DC terminal becomes overvoltage, the capacitor 5 and the switching elements may be damaged. In such a case, the controller 50 performs protective control. In this specification, protective control refers to control in which the current generated by the induced electromotive force in the stator coil 31 is returned to the stator coil through the inverter's switching elements while being consumed. When switching from dual mode or single mode to protective control, a short circuit between the positive electrode 3p and the negative electrode 3n of the battery 3 must be avoided.

[0033] When the voltage at the DC end of the first inverter 10 exceeds a predetermined threshold voltage, the controller 50 executes one of the following protective controls: upper short-circuit control or lower short-circuit control. In upper short-circuit control, the controller 50 closes all upper SW elements 12 and 22 of the first inverter 10 and the second inverter 20, opens all lower SW elements 13 and 23, and closes the connecting switches 40p and 40n. In lower short-circuit control, the controller 50 closes all lower SW elements 13 and 23 of the first inverter 10 and the second inverter 20, opens all upper SW elements 12 and 22, and closes the connecting switches 40p and 40n.

[0034] Figure 2 shows the current flow during upper short-circuit control. The current generated by the induced electromotive force in the stator coil 31 flows back to the stator coil 31 through the upper SW elements 12 and 22 and the connecting switch 40p. The current decays over time. As a result, the voltage at the DC end (the voltage between the positive electrode 10p and the negative electrode 10n) drops.

[0035] Figure 3 shows the current flow during bottom short-circuit control. The current generated by the induced electromotive force in the stator coil 31 flows back to the stator coil 31 through the bottom SW elements 13 and 23 and the connecting switch 40n. The current decays over time. As a result, the voltage at the DC end (the voltage between the positive electrode 10p and the negative electrode 10n) drops.

[0036] 2 and 3, neither the top short circuit control nor the bottom short circuit control short-circuits the positive electrode 3p and the negative electrode 3n of the battery 3. In particular, when transitioning from the dual mode to the top (bottom) short circuit control, and when transitioning from the single mode to the top (bottom) short circuit control, a short circuit of the battery 3 is avoided in both cases.

[0037] The controller 50 compares the loads on the upper switching elements 12 and 22 with the loads on the lower switching elements 13 and 23, and executes upper short-circuit control if the loads on the upper switching elements 12 and 22 are small, and executes lower short-circuit control if the loads on the lower switching elements 13 and 23 are small. The cumulative loads on the upper switching elements 12 and 22 and the lower switching elements 13 and 23 are leveled. The loads on the switching elements are determined based on the temperature, driving time, and number of driving times of the switching elements.

[0038] (Second embodiment) Figure 4 shows a circuit diagram of a DI system 102 of a second embodiment. The circuit configuration of the DI system 102 is the same as that of the DI system 2 shown in Figure 1. The reference numerals assigned to the components in Figure 2 are the same except for the reference numeral of the controller. The DI system 102 differs from the DI system 2 in terms of protection control. Therefore, the controller of the DI system 102 is given the reference numeral 150.

[0039] As mentioned above, the circuit configuration of the DI system 102 is the same as that of the DI system 2, so a description of the circuit will be omitted.

[0040] When the voltage at the DC end of the first inverter 10 exceeds a predetermined threshold voltage, the controller 150 of the DI system 102 performs protective control in the following procedure: (1) The controller 150 opens the coupling switches 40p and 40n. (2) The controller 150 closes the upper SW elements 12 and 22 connected to the respective ends of at least one stator coil 31 and opens the lower SW elements 13 and 23, and also opens the upper SW elements 12 and 22 connected to the respective ends of the remaining stator coils 31 and closes the lower SW elements 13 and 23. (3) The controller 150 closes the coupling switches 40p and 40n.

[0041] FIG. 4 shows an example of current flow during protection control of the DI system 102. In the example of FIG. 4, the upper switching elements 12u, 12v, 22u, and 22v connected to the respective ends of the stator coils 31u and 31v are closed, and the lower switching elements 13u, 13v, 23u, and 23v are open. The upper switching elements 12w and 22w connected to the respective ends of the stator coil 31w are open, and the lower switching elements 13w and 23w are closed. The current generated in the stator coils 31u and 31v flows back through the upper switching elements 12u, 12v, 22u, and 22v and the connecting switch 40p. Meanwhile, the current generated in the stator coil 31w flows back through the lower switching elements 13w and 23w and the connecting switch 40n.

[0042] According to the above procedure, current flows back in the loop where the upper SW element is closed, and also flows back in the loop where the lower SW element is closed. Compared to the above-mentioned upper short-circuit control and lower short-circuit control, the power loss in the connecting switches 40p and 40n is larger, and the current decays more quickly.

[0043] When the loads on the upper switching elements 12 and 22 are smaller than the loads on the lower switching elements 13 and 23, the controller 150 closes the upper switching elements 12 and 22 and opens the lower switching elements 13 and 23. When the loads on the upper switching elements 12 and 22 are larger than the loads on the lower switching elements 13 and 23, the controller 150 opens the upper switching elements 12 and 22 and closes the lower switching elements 13 and 23. The controller 150 makes this determination for each of the u-phase, v-phase, and w-phase. This process also equalizes the cumulative loads on the upper switching elements and the cumulative loads on the lower switching elements. As in the first embodiment, the loads on the switching elements are determined based on the temperature, driving time, and number of driving times of the switching elements.

[0044] In the protection control of the DI system 102 of the second embodiment, the connecting switches 40p and 40n are opened before opening or closing the SW elements. This process makes it possible to avoid a short circuit of the battery 3 when transitioning from the dual mode or single mode to the protection control.

[0045] In the protection control (upper short-circuit control and lower short-circuit control) of the DI system 2 of the first embodiment, the processes of opening and closing the SW elements and closing the connecting switch may be performed in any order. Even if they are performed in any order, a short circuit of the battery 3 can be avoided. In this respect, the DI system 2 of the first embodiment is advantageous.

[0046] Furthermore, the DI system 2, 102 has the advantage that it can transition to protective control while avoiding battery short circuit using the same procedure whether in dual mode or single mode.

[0047] Here are some points to note regarding the technology described in the embodiment. If the DC end and AC end of the first inverter 10 are referred to as the first DC end and the first AC end, respectively, and the DC end and AC end of the second inverter 20 are referred to as the second DC end and the second AC end, respectively, the circuit of the DI system 2 in the embodiment can be expressed as follows:

[0048] The DI system 2 includes a motor 30 having a plurality of stator coils 31, a first inverter 10, a second inverter 20, coupling switches 40p, 40n, and a controller 50. The first inverter 10 has a first DC terminal and a plurality of first AC terminals, the first DC terminal is connected to the battery 3, and each of the plurality of first AC terminals is connected to one end of each of the stator coils 31. The second inverter 20 has a second DC terminal and a plurality of second AC terminals, the second DC terminal is connected to the battery 3, and each of the plurality of second AC terminals is connected to the other end of each of the stator coils 31.

[0049] The coupling switches 40p and 40n connect or disconnect the second DC terminal to the battery 3. The controller 50 can execute a dual mode in which the coupling switches 40p and 40n are closed to drive the motor 30 using the first inverter 10 and the second inverter 20, and a single mode in which the coupling switches 40p and 40n are opened to drive the motor 30 using only the first inverter 10.

[0050] The first inverter 10 includes a plurality of series circuits 11 connected in parallel to a first DC terminal. Each series circuit 11 includes a series-connected circuit of an upper switching element 12 and a lower switching element 13. The midpoint of the series-connected circuit is connected to the second AC terminal.

[0051] The second inverter 20 includes a plurality of series circuits 21 connected in parallel to the second DC terminal. Each series circuit 21 includes a series-connected circuit of an upper SW element 22 and a lower SW element 23. The midpoint of the series-connected circuit is connected to the second AC terminal.

[0052] Another way to express the configuration of the inverters is as follows: Each of the first inverter 10 and the second inverter 20 includes a plurality of series circuits 11 (21) connected in parallel between the positive electrode 3p and the negative electrode 3n of the battery 3. Each series circuit includes an upper switching element 12 (22) and a lower switching element 13 (23) connected in series between the positive electrode 3p and the negative electrode 3n of the battery 3, and the midpoint of the series connection is connected to the AC end.

[0053] As a protective control when the voltage at the first DC end exceeds the threshold voltage, the controller 50 executes one of the following: an upper short-circuit control in which all upper SW elements of the first and second inverters are closed, all lower SW elements are opened, and the connecting switch is closed; and a lower short-circuit control in which all lower SW elements of the first and second inverters are closed, all upper SW elements are opened, and the connecting switch is closed.

[0054] The purpose of the protective control is to attenuate the current generated by the induced electromotive force in the stator coil while rotating the motor 30 by inertia. By implementing the protective control, it is possible to protect each component of the DI system from damage.

[0055] The technology disclosed in this specification is also applicable to a DI system having four or more series circuits and four or more stator coils.

[0056] In this specification, the expression "turning on a switching element" means making both ends of a switching element conductive, and the expression "turning off a switching element" means electrically disconnecting both ends of a switching element. However, because a diode is connected in antiparallel to the switching element, current is allowed to return via the diode even when the switching element is turned off.

[0057] The expression "turning on a switching element" is equivalent to the expression "closing a switching element," and the expression "turning off a switching element" is equivalent to the expression "opening a switching element."

[0058] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives alone is technically useful. [Explanation of symbols]

[0059] 2, 102: Dual inverter system 3: Battery 4: System main relay 5: Capacitor 6: Voltage sensor 10, 20: Inverter 11, 21: Series circuit 12, 13, 22, 23: Switching element (SW element) 14, 15, 24, 25: Temperature sensor 30: Motor 31: Stator coil 40: Link switch 50, 150: Controller

Claims

1. a motor having a plurality of stator coils; a first inverter having a DC end connected to a battery and a plurality of AC ends each connected to one end of each of the stator coils; a second inverter having a DC end connected to the battery and a plurality of AC ends each connected to the other end of the stator coil; a connecting switch connected between the DC end of the second inverter and the battery; a controller capable of executing a dual mode in which the coupling switch is closed to drive the motor with the first inverter and the second inverter, and a single mode in which the coupling switch is opened to drive the motor with only the first inverter, When the voltage at the DC end of the first inverter exceeds a predetermined threshold voltage, the controller executes one of an upper short-circuit control for closing all upper switching elements of the first and second inverters, opening all lower switching elements, and closing the connecting switch, and a lower short-circuit control for closing all lower switching elements of the first and second inverters, opening all upper switching elements, and closing the connecting switch. Dual inverter system.

2. 2. The dual inverter system of claim 1, wherein the controller executes the upper short-circuit control when a load on the upper switching element is smaller than a load on the lower switching element, and executes the lower short-circuit control when a load on the lower switching element is smaller than a load on the upper switching element.

3. a motor having a plurality of stator coils; a first inverter having a DC end connected to a battery and a plurality of AC ends each connected to one end of each of the stator coils; a second inverter having a DC end connected to the battery and a plurality of AC ends each connected to the other end of the stator coil; a connecting switch connected between the DC end of the second inverter and the battery; a controller capable of executing a dual mode in which the coupling switch is closed to drive the motor with the first inverter and the second inverter, and a single mode in which the coupling switch is opened to drive the motor with only the first inverter, When the voltage at the DC end of the first inverter exceeds a predetermined threshold voltage, the controller (1) Open the connecting switch; (2) closing the upper switching elements connected to the respective ends of at least one of the stator coils and opening the lower switching elements, and opening the upper switching elements connected to the respective ends of the remaining stator coils and closing the lower switching elements; (3) closing the coupling switch; Dual inverter system.

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