Motor driving system

Abstract

To provide a motor driving system that can reduce surge voltage to a switching element at the occurrence of motor lock.SOLUTION: A motor driving system 1 comprises a first inverter 10, a second inverter 20, and an ECU 50. When motor lock occurs in an open winding motor 30, the ECU 50 distributes current to two arms of the first inverter 10 other than a current concentration phase via the open winding motor 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a motor drive system. [Background technology]

[0002] Patent Document 1 discloses a technology that prevents overheating of the inverter's power converter by reducing the switching frequency of the switching elements when the motor locks up. This technology switches the switching frequency based on the inverter temperature and torque command value when the motor locks up. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-134990 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned Patent Document 1, if a surge voltage to the switching element increases when the motor is locked, there is a risk that the switching element may be damaged.

[0005] The present disclosure has been made in view of the above, and has an object to provide a motor drive system that can reduce surge voltage to switching elements when the motor locks. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the motor drive system of the present disclosure is a motor drive system comprising a motor, a first inverter including a plurality of switching elements corresponding to each winding of the motor, a second inverter including a plurality of switching elements corresponding to each winding of the motor and having a current capacity smaller than that of the first inverter, and a processor that controls the first inverter and the second inverter, wherein when a motor lock occurs in the motor, the processor distributes current via the motor to two arms of the first inverter other than the current-concentrated phase. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to reduce the surge voltage to the switching element when the motor is locked. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit schematic diagram showing an example of a motor drive system using a dual inverter according to an embodiment. [Figure 2] FIG. 2 is a flowchart showing an outline of the processing executed by the motor drive system according to one embodiment. [Figure 3] FIG. 3 is a circuit schematic diagram of a motor drive system according to one embodiment in a dual inverter mode when the motor drive system is in high torque. [Figure 4] FIG. 4 is a diagram showing the relationship between time and each current value in each phase of the motor drive system according to one embodiment. [Figure 5] FIG. 5 is a circuit schematic diagram of a motor drive system 1 in single inverter mode according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A motor drive system using a dual inverter according to an embodiment of the present disclosure will be described below with reference to the drawings. Note that the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical. Furthermore, the drawings referred to in the following description merely show a schematic representation of the shape, size, and positional relationship to the extent that the contents of the present disclosure can be understood. In other words, the present disclosure is not limited to the shape, size, and positional relationship illustrated in each drawing.

[0010] [Motor drive system configuration] Fig. 1 is a circuit schematic diagram showing an example of a motor drive system using a dual inverter according to one embodiment. The motor drive system 1 shown in Fig. 1 is mounted on an EV (electric vehicle). The motor drive system 1 is a system in which two independent inverters, a first inverter 10 and a second inverter 20, are electrically connected to a three-phase (U-phase, V-phase, and W-phase) open-winding motor 30, and the open-winding motor 30 is driven by the first inverter 10 and the second inverter 20.

[0011] Furthermore, the motor drive system 1 includes a switch 40 for driving only the first inverter 10 of at least the first inverter 10 and the second inverter 20, and an ECU (Electronic Control Unit) 50 for controlling the switch 40. Furthermore, the motor drive system 1 includes an ammeter 60 provided in each of the three-phase paths, and the detection results of each ammeter 60 (current value Iu, current value Iv, current value Iw) are output to the ECU 50. A battery 70 and a smoothing capacitor 80 are electrically connected to the first inverter 10.

[0012] The first inverter 10 is composed of six power elements 11 to 16, which are repeatedly turned on and off under the control of the ECU 50. The second inverter 20 is composed of six power elements 21 to 26, which are repeatedly turned on and off under the control of the ECU 50. The first inverter 10 and the second inverter 20 supply AC power to the open-winding motor 30 under the control of the ECU 50. Furthermore, the power elements 11 to 16 of the first inverter 10 are configured to have a larger current capacity than the power elements 21 to 26 of the second inverter 20. In one embodiment, the power elements 11 to 16 and 21 to 26 function as switching elements.

[0013] The switch 40 is capable of electrically connecting the first inverter 10 and the second inverter 20, and is turned on or off (open) under the control of the ECU 50.

[0014] The ECU 50 is implemented using a processor having a memory and hardware. The hardware may be, for example, a memory, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), and an FPGA (Field-Programmable Gate Array). When a motor lock occurs in the open winding motor 30, the ECU 50 distributes current to two arms of the first inverter 10 other than the current concentration phase via the open winding motor 30. Specifically, when a motor lock occurs in the open winding motor 30, the ECU 50 turns the switch 40 off (open state) and distributes current to two arms of the first inverter 10 other than the current concentration phase via the open winding motor 30. In one embodiment, the ECU 50 functions as a processor.

[0015] [Motor drive system processing] Next, a description will be given of the processing executed by the motor drive system 1. Fig. 2 is a flowchart showing an outline of the processing executed by the motor drive system 1.

[0016] As shown in FIG. 2, when a normal high torque is required for the open-winding motor 30, the ECU 50 drives the open-winding motor 30 in dual inverter mode using the first inverter 10 and the second inverter 20 by turning on the switch 40 (step S101). FIG. 3 is a circuit schematic diagram of the motor drive system 1 in dual inverter mode during high torque. As shown in FIG. 3, the ECU 50 drives the open-winding motor 30 using the first inverter 10 and the second inverter 20 by turning on the switch 40 (dual inverter mode drive). In this case, as shown in FIG. 3, the ECU 50 drives the open-winding motor 30 in dual inverter mode by turning on the power elements 11, 15, and 16 of the first inverter 10 in an ON-duty state (ON_Duty state) and turning on the power elements 22, 23, and 24 of the second inverter 20 in an ON-duty state (ON_Duty state), thereby driving the motor in dual inverter mode so that the current in the U-phase is the highest among the three phases, U-phase, V-phase, and W-phase.

[0017] Next, the ECU 50 determines whether or not a motor lock has occurred in the open winding motor 30 based on the detection results of each of the ammeters 60 (step S102). Specifically, the ECU 50 determines whether the current values ​​Iu, Iv, and Iw detected by the ammeters 60 for each of the three phases, i.e., the U phase, the V phase, and the W phase, are fixed at constant values, and if the current values ​​are fixed at constant values, the ECU 50 determines that a motor lock has occurred in the open winding motor 30. If a motor lock has occurred in the open winding motor 30 (step S102: Yes), the ECU 50 proceeds to step S103. On the other hand, if the ECU 50 determines that a motor lock has not occurred in the open winding motor 30 (step S102: No), the motor drive system 1 ends this process.

[0018] In step S103, the ECU 50 determines whether or not each of the current values ​​Iu, Iv, and Iw detected by the ammeter 60 exceeds a threshold value αA. FIG. 4 is a diagram showing the relationship between each current value in each phase and time. In FIG. 4, the horizontal axis represents time, and the vertical axis represents the current value I (A). In FIG. 4, the curve L U indicates the U-phase current value Iu, and curve L V indicates the V-phase current value Iv, and curve L W The curve L in Figure 4 indicates the W-phase current value Iw. U , curve L V and curve L W As shown in Fig. 1, the ECU 50 determines whether each of the current values ​​Iu, Iv, and Iw detected by the ammeters 60 exceeds a threshold value αA. Here, the threshold value αA is a value determined by the power element rating constraints of the second inverter 20. If the ECU 50 determines that each of the current values ​​Iu, Iv, and Iw detected by the ammeters 60 exceeds the threshold value αA (step S103: Yes), the motor drive system 1 proceeds to step S104. On the other hand, if the ECU 50 determines that each of the current values ​​Iu, Iv, and Iw detected by the ammeters 60 does not exceed the threshold value αA (step S103: No), the motor drive system 1 ends this process.

[0019] In step S104, the ECU 50 drives the open winding motor 30 in single inverter mode by driving it with the first inverter 10 by turning the switch 40 off (open state) (step S104). FIG. 5 is a circuit schematic diagram of the motor drive system 1 in single inverter mode. As shown in FIG. 5, the switch 40 is turned off (open state) to drive it with the first inverter 10, thereby driving the open winding motor 30 in single inverter mode (single inverter mode drive). In this case, as shown in FIG. 5, the ECU 50 keeps the switch 40 open and the power elements 22, 23, and 24 of the second inverter 20 always on, thereby distributing current via the open winding motor 30 to two arms (V phase and W phase) other than the current concentration phase (U phase) of the first inverter 10. This allows the motor drive system 1 to avoid current concentration in the power element 24 of the second inverter 20. Furthermore, the motor drive system 1 can simultaneously reduce loss, heat generation, and motor ripple in the second inverter 20. Furthermore, the size of the power element 24 of the second inverter 20 can be designed to be small, thereby optimizing the cost and size of the product. After step S104, the motor drive system 1 ends this process.

[0020] According to the embodiment described above, when motor lock occurs in the open winding motor 30, the ECU 50 distributes current to the two arms of the first inverter 10 other than the current concentration phase via the open winding motor 30. This eliminates the need to switch the switching frequency when the motor locks, thereby reducing the surge voltage to the power element 11 of the first inverter 10 and the power element 24 of the second inverter 20.

[0021] Furthermore, according to one embodiment, when motor lock occurs in the open winding motor 30, the ECU 50 turns the switch 40 off (open state) to drive the open winding motor 30 in single inverter mode by driving it with the first inverter 10, thereby simultaneously reducing loss and heat generation in the second inverter 20 and reducing motor ripple.

[0022] Furthermore, according to one embodiment, when motor lock occurs in the open winding motor 30 and each of the current values ​​Iu, Iv, and Iw detected by the ammeter 60 exceeds the threshold value αA, the ECU 50 turns the switch 40 off (open state) to drive the open winding motor 30 using the first inverter 10, thereby driving the open winding motor 30 in single inverter mode. This allows the power element 24 of the second inverter 20 to be designed to be small, thereby optimizing the cost and shape of the product.

[0023] (Other forms) Further advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0024] Although some of the embodiments of the present application have been described in detail above with reference to the drawings, these are merely examples, and the present invention can be implemented in other forms that have undergone various modifications and improvements based on the knowledge of those skilled in the art, including the aspects described in the disclosure of the present invention. [Explanation of symbols]

[0025] 1. Motor drive system 10 First inverter 11~16, 21~26 Power elements 20 Second inverter 30 Open Winding Motor 40 Switch 50 ECU 60 ammeter 70 Battery 80 smoothing capacitor

Claims

1. A motor; a first inverter including a plurality of switching elements corresponding to the respective windings of the motor; a second inverter including a plurality of switching elements corresponding to the respective windings of the motor and having a current capacity smaller than that of the first inverter; a processor that controls the first inverter and the second inverter; A motor drive system comprising: The processor: When a motor lock occurs in the motor, current is distributed to two arms other than the current concentration phase of the first inverter via the motor. Motor drive system.

2. 2. The motor drive system according to claim 1, further comprising a switch capable of electrically connecting the first inverter and the second inverter; The processor: When a high torque is required from the motor, the switch is turned on to drive the motor using the first inverter and the second inverter; When a motor lock occurs in the motor, the switch is turned off, and current is distributed via the motor to two arms other than the current concentration phase of the first inverter. Motor drive system.

3. 3. The motor drive system according to claim 2, further comprising an ammeter for detecting a current value in each winding of the motor; The processor: When a motor lock occurs in the motor and the current value in each winding of the motor detected by the ammeter exceeds a threshold, the switch is turned off, and current is distributed via the motor to two arms of the first inverter other than the current concentration phase. Motor drive system.

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