Motor control method and motor system

Abstract

To provide a motor control method capable of increasing torque of a motor while protecting components without enlarging a system, and a motor system.SOLUTION: Provided is a motor control method in a motor system comprising an open winding type motor and an inverter that converts and supplies electric power to the motor. The motor control method includes superposing an N-th order harmonic current, which generates a zero-phase magnetic field, on a fundamental wave current, which generates a rotary magnetic field, in a current supplied to the motor. In a case where (n) is defined as a natural number equal to or more than 1, the harmonic wave order N of the N-th order harmonic wave current satisfies either one of the following formulas (1) or (2), and the 90° phase of the fundamental wave current is matched with the 270° phase of the N-th order harmonic current.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a motor control method and a motor system. [Background technology]

[0002] Patent Document 1 discloses a motor system including a motor and an inverter. In this system, a harmonic current that generates a zero-phase magnetic field is superimposed on a fundamental current that generates a rotating magnetic field, and the motor current is increased, thereby increasing the motor torque. This makes it possible to increase the motor torque without changing the size of the system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7181817 Summary of the Invention [Problem to be solved by the invention]

[0004] In the motor system described in Patent Document 1, the current is increased by superimposing harmonic current, but if the current exceeds the limit value, the inverter may be damaged due to an increase in heat caused by the increase in current. In addition, output is limited to protect the inverter components, which may cause anxiety to passengers in a vehicle equipped with the motor system.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a motor control method and a motor system that are capable of increasing the torque of a motor while protecting components and without increasing the size of the system. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided a motor control method for a motor system including an open-winding N-phase motor and an inverter that converts power and supplies it to the motor. This motor control method superimposes an N-th harmonic current that generates a zero-phase magnetic field on a fundamental current that generates a rotating magnetic field in a current supplied to the motor, and the harmonic order of the N-th harmonic current and the number of motor phases N, where n is a natural number equal to or greater than 1, satisfy either of the following formulas (1) or (2):

number

[0007] According to the present invention, in the current supplied to the N-phase motor, the 90° phase of the fundamental current and the 270° phase of the N-th harmonic current that does not contribute to the torque of the motor are matched and superimposed, so that the positive peak of the fundamental current and the negative peak of the N-th harmonic current, and the negative peak of the fundamental current and the positive peak of the N-th harmonic current, are in phase. Therefore, the peak of the current waveform after superimposition can be made smaller than the peak of the fundamental current without reducing the torque. Therefore, by raising the peak of the phase current of the motor after superimposition to the peak of the fundamental current before superimposition, the current supplied to the motor can be increased without raising the peak of the phase current above the peak of the fundamental current. In other words, the torque can be increased without raising the peak of the current waveform more than before superimposition. Therefore, the torque of the motor can be increased while protecting the components. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of a motor system to which a motor control method according to a first embodiment of the present invention is applied. [Diagram 2] FIG. 2 is a diagram showing phase current waveforms when a third harmonic current is superimposed. [Diagram 3] FIG. 3 is a diagram showing phase current waveforms when a fifth harmonic current is superimposed. [Figure 4] FIG. 4 is a diagram showing phase current waveforms when the amplitude of the fundamental wave current is increased. [Diagram 5] FIG. 5 is a flowchart illustrating motor torque control in the motor control method according to the first embodiment. [Figure 6] FIG. 6 is a flowchart illustrating motor torque control in a motor control method according to a modification of the first embodiment. [Figure 7] FIG. 7 is a diagram showing phase current waveforms in the motor control method according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] [First embodiment] 1 is a schematic diagram of a motor system 100 to which a motor control method according to a first embodiment of the present invention is applied. The motor system 100 according to this embodiment is, for example, a system for driving an electrically-driven vehicle such as an electric vehicle or a hybrid vehicle, but is not necessarily limited to this.

[0011] As shown in FIG. 1, the motor system 100 includes a motor 10, a first inverter 21, a second inverter 22, a battery 30, a cooler 40, and a controller 50.

[0012] The motor 10 is an open winding type electric motor (open winding motor). The open winding motor is a motor that does not have a so-called neutral point, has independent stator windings of multiple phases, and is driven by two inverters: a first inverter 21 connected to one end of the stator winding, and a second inverter 22 connected to the other end of the stator winding.

[0013] In this embodiment, the motor 10 (open winding motor) is a three-phase AC motor having three-phase stator windings of UVW phases. The motor 10 is controlled by a first inverter 21 and a second inverter 22.

[0014] The first inverter 21 is an inverter connected to one end of the stator windings U, V, W. The second inverter 22 is an inverter connected to the other end of the stator windings U, V, W. The first inverter 21 and the second inverter 22 are connected to a battery 30, which is a power source, via a smoothing capacitor 31 (input capacitor). The first inverter 21 and the second inverter 22 include a plurality of semiconductor switching elements, and convert DC power output by the battery 30 into AC power by switching the semiconductor switching elements on / off, and supply the AC power to the stator windings U, V, W of the motor 10. In this way, the motor 10 is driven. Hereinafter, the first inverter 21 and the second inverter 22 are collectively referred to as the inverter 20. The operation of the inverter 20 is controlled by a controller 50, which will be described later.

[0015] The motor 10 is provided with a current sensor (not shown) and detects the three-phase AC current i supplied from the inverter 20 to the motor 10. u ,i v ,i w (hereinafter, also referred to as phase current I) is detected by a current sensor. The phase current I detected by the current sensor is transmitted to the controller 50. In addition, the inverter 20 is provided with a semiconductor temperature T s The semiconductor temperature T s is transmitted to the controller 50. In this embodiment, the semiconductor temperature T s is acquired by a temperature sensor, but is not limited to this, and the semiconductor temperature T s may be obtained by using any known method. For example, the semiconductor temperature T s may be estimated.

[0016] The battery 30 is a power source for supplying power to the motor 10, and is, for example, a laminated lithium ion battery. The battery 30 outputs DC power. The battery 30 outputs a DC voltage (hereinafter, referred to as a power supply voltage V dc The power supply voltage V dc is transmitted to the controller 50.

[0017] The cooler 40 cools the semiconductor switching elements of the inverter 20. The cooler 40 is, for example, configured with a water jacket for supplying cooling water to the semiconductor switching elements to cool them. The cooler 40 also includes a water jacket for supplying cooling water to the semiconductor switching elements to cool them. w The cooling water temperature T detected by the cooling water temperature sensor is provided. w is transmitted to the controller 50. In this embodiment, the cooling water temperature T w The coolant temperature sensor is provided in the cooler 40 to detect the temperature T w The coolant temperature sensor may be installed anywhere as long as it is located in a position where the temperature can be obtained.

[0018] The controller 50 is configured by a computer equipped with a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface) and programmed to be able to execute each process described below. The controller 50 can also be configured by multiple computer hardware that executes each process in a distributed manner.

[0019] The controller 50 controls the operation of the inverter 20. Specifically, the controller 50 receives the required torque of the motor 10, which is an electric load, as an input and generates a PWM signal for defining the switching pattern (duty ratio) of each semiconductor switching element of the inverter 20. More specifically, the controller 50 calculates a current command value (a command value of a current supplied to the inverter 20) that realizes a desired required torque according to an external required load (such as an operation amount of an accelerator pedal in the case of a vehicle), calculates a control voltage (a voltage command value) that makes the deviation between the current command value and the actual current of the motor 10 zero, and generates a PWM signal to realize the calculated voltage command value. The controller 50 outputs the generated PWM signal to the inverter 20. As a result, the inverter 20 operates based on the PWM signal, a voltage according to the voltage command value is applied to the motor 10, and a current according to the current command value flows through each phase of the motor 10.

[0020] Here, the current flowing through each phase of the motor 10 includes a fundamental current that generates a rotating magnetic field and a zero-phase current that generates a zero-phase magnetic field. The fundamental current is a current component for controlling the torque, rotation speed, etc. of the motor 10. On the other hand, the zero-phase current is a harmonic current that flows in phase with each phase in a multi-phase unbalanced AC circuit, and is a current component that circulates through each stator winding of the motor 10 and the inverter 20 and does not contribute to torque. In this embodiment, in the case of an N-phase motor, the controller 50 executes motor torque control including harmonic superposition control that superimposes an N-th harmonic current (zero-phase current) on the fundamental current. As described later, by executing harmonic superposition control, it is possible to reduce the peak (absolute value of the peak value) of the current waveform without reducing the torque of the motor 10.

[0021] In addition, when there is a request to increase the torque of the motor 10 (hereinafter also referred to as a torque increase request), the controller 50, in addition to the harmonic superposition control, determines whether it is possible to increase the current supplied to the motor 10 so as to increase the torque until the torque increase request is satisfied, and if so, executes torque increase control to increase the current and increase the torque.

[0022] In this embodiment, the controller 50 includes a CPU and the like, but is not necessarily limited to this, and may be, for example, an FPGA that allows the configuration of a logic circuit to be programmed.

[0023] The harmonic superposition control will be described in detail below.

[0024] As described above, in this embodiment, in the current supplied to the N-phase motor 10, an N-order harmonic current that generates a zero-phase magnetic field is superimposed on a fundamental current that generates a rotating magnetic field.

[0025] FIG. 2 is a diagram showing phase current waveforms of the motor 10 when a third harmonic current is superimposed on a fundamental current.

[0026] As shown in Fig. 2, in the harmonic superposition control of this embodiment, the 90° phase of the fundamental current and the 270° phase of the Nth (third) harmonic current are controlled to coincide. The phase of the fundamental current is the phase of any one of the phases of the motor 10, and Fig. 2 shows the phase of the fundamental current of the U phase. By matching the 90° phase of the fundamental current and the 270° phase of the Nth (third) harmonic current, the positive peak of the fundamental current of each phase and the negative peak of the Nth (third) harmonic current, and the negative peak of the fundamental current of each phase and the positive peak of the Nth harmonic current, are in phase. Therefore, the positive and negative peaks (absolute value of the peak value) of the phase current waveform of the motor 10 after the Nth (third) harmonic current is superimposed are reduced.

[0027] As described above, the number of phases of motor 10 and the order N of the harmonic current to be superimposed need only satisfy formula (1) or (2), and do not have to be three phases. For example, as shown in Fig. 3, even if a fifth harmonic current is superimposed on the fundamental current of a five-phase motor, the positive peak of the fundamental current and the negative peak of the fifth harmonic current, and the negative peak of the fundamental current and the positive peak of the fifth harmonic current, will be in phase. That is, the positive and negative peaks (absolute values ​​of peak values) of the phase current waveform of motor 10 after the fifth harmonic current is superimposed will be smaller.

[0028] As described above, in the harmonic superposition control of this embodiment, the fundamental current is superposed with a 90° phase coincident with the Nth (third) harmonic current. This causes the positive peak of the fundamental current to be in phase with the negative peak of the Nth harmonic current, and the negative peak of the fundamental current to be in phase with the positive peak of the Nth harmonic current. This makes it possible to make the peak of the current waveform after superposition (absolute value of the peak value) lower than the peak of the fundamental current (absolute value of the peak value) without reducing the torque.

[0029] Incidentally, in a motor system, when there is a request to increase the torque of a motor (hereinafter also referred to as a torque increase request), the torque can be increased by increasing the current supplied to the motor. Here, in order to protect inverter components such as semiconductor switching elements, the motor system is usually provided with a current limit value, which is the maximum current that can be output to the motor, taking into consideration the heat resistance of the components. When the current supplied to the motor reaches the current limit value, the output is limited to protect the components. If the fundamental current is increased in response to a torque increase request, the current supplied to the motor may exceed the current limit value, which may damage the inverter due to an increase in heat, or the output may be limited unintentionally, causing anxiety to passengers of a vehicle equipped with the motor system. Furthermore, if the current supplied to the motor is suppressed so as not to exceed the current limit value, there is a risk that the torque increase request cannot be met.

[0030] In contrast, in this embodiment, the Nth harmonic current is superimposed on the fundamental current so that the peak (absolute value of the peak value) of the current waveform of the phase current I is lower than the peak (absolute value of the peak value) of the fundamental current. That is, the peak (absolute value of the peak value) of the current waveform of the phase current I is made smaller than the peak (absolute value of the peak value) of the fundamental current without reducing the torque. Therefore, by raising the peak of the phase current I to the peak of the fundamental current before the superposition after the Nth harmonic current is superimposed, the current supplied to the motor 10 can be increased without raising the peak of the phase current I above the peak of the fundamental current. That is, the torque can be increased without raising the peak of the current waveform more than before the superposition. Therefore, the torque of the motor 10 can be increased while protecting the components.

[0031] Next, the amplitude of the superimposed Nth-order harmonic current will be described.

[0032] In the harmonic superposition control of this embodiment, the amplitude of the Nth harmonic current superimposed on the fundamental current of an N-phase motor is controlled to match the difference value ΔI between the current value at phase 90° of the fundamental current and the current value at phase (90+360 / N*4)°, where N is the number of phases of the windings of the motor 10. For example, since the windings of the motor 10 in this embodiment are three-phase, as shown in FIG. 2, the amplitude of the superimposed third harmonic current is controlled to match the current value I b1 and the current value I at phase 120° b2 Difference ΔI (1―2) For example, when the windings of the motor 10 are five-phase and a fifth-order harmonic current is superimposed, as shown in FIG. 3, the amplitude of the fifth-order harmonic current to be superimposed is a current value I b3 and the current value I at phase 108° b4 Difference ΔI (3―4) The control is performed so that

[0033] In this way, by controlling the amplitude of the Nth harmonic current to be the difference value ΔI between the current value at phase 90° of the fundamental current and the current value at phase (90+360 / N*4)°, the peak of the phase current I after the Nth harmonic current is superimposed has a flat shape without any protruding parts as shown in Figures 2 and 3. That is, the peak of the phase current waveform after the Nth harmonic current is superimposed becomes substantially minimum, and the peak of the phase current I can be substantially minimized without reducing the torque of the motor 10. Therefore, the current supplied to the motor 10 can be increased without increasing the peak of the phase current I beyond the peak of the fundamental current, and the range of torque that can be increased without exceeding the current limit value becomes larger.

[0034] Next, the torque increase control that is executed when there is a request for torque increase will be described in detail.

[0035] Fig. 4 is a diagram showing phase current waveforms when the amplitude of the fundamental wave current of the motor 10 is increased. As described above, a motor system is usually provided with a current limit value, which is the maximum value of the current that can be output to the motor. As shown in Fig. 4, the motor system 100 of this embodiment also has a current limit value I lim When the phase current I is increased in response to a torque increase request, the controller 50 determines whether the peak value of the phase current I of the motor 10 exceeds the current limit value I lim Control so as not to exceed.

[0036] Specifically, the maximum amplitude of the fundamental wave current of the motor 10 is increased within the range of the following formula (3).

number

[0037] Here, depending on the amount of increase, the amplitude of the fundamental current may increase until the peak value of the fundamental current exceeds the current limit value I lim However, due to the above-mentioned harmonic superposition control, the absolute value of the peak value of the phase current I after the harmonic current superposition is limited to the current limit value I lim is less than or equal to the absolute value of

[0038] Incidentally, the current limit value is determined mainly by the temperature of the semiconductor switching elements, which rises due to the surge voltage and loss when switching the inverter. For example, it is possible to suppress the surge voltage by slowing down the switching speed, but in this case, the loss increases and the temperature of the semiconductor switching elements rises. For this reason, even if the switching speed is slowed down, there is a risk that the maximum value (peak) of the phase current that can be output cannot be sufficiently increased. In contrast, in this embodiment, the fundamental current is increased without increasing the peak of the phase current I, so that the phase current I can be increased and the torque can be increased without increasing the switching loss.

[0039] As described above, when the torque of the motor 10 is increased, the amplitude of the fundamental wave current is increased within the range of the formula (3).

[0040] However, when the phase current I is increased to satisfy a torque increase request, the amplitude of the fundamental current may exceed the range of the formula (3). Therefore, in this embodiment, when there is a torque increase request, it is determined whether it is possible to increase the current supplied to the motor 10 so as to increase the torque in response to the torque increase request, and the current supplied to the motor 10 is increased only if it is possible.

[0041] Specifically, in this embodiment, even if the current supplied to the motor 10 is increased, the semiconductor temperature T s is a given value (threshold T sth ) or less, it is determined that the current can be increased, and the current supplied to the motor 10 is increased. sth is determined from the viewpoint of protecting the semiconductor components, and is set to, for example, the upper limit of the heat resistance temperature of the semiconductor. s is the threshold T sth Whether or not the current and semiconductor temperature T s It is possible to estimate the correlation between the

[0042] In this way, even if the current is increased in response to a torque increase request, the semiconductor temperature T s is the threshold T sth Since the current supplied to the motor 10 is increased only when the following condition is met, damage to semiconductor components and output restrictions can be prevented.

[0043] In this embodiment, the semiconductor temperature T s Whether or not it is possible to increase the current supplied to the motor 10 in response to the torque increase request is determined based on the semiconductor temperature T s For example, the cooling water temperature T w is a given value (threshold T wth) In the following cases, it is determined that it is possible to increase the current, and the current supplied to the motor 10 is increased. wth is the cooling water temperature T w , semiconductor temperature T s , and the correlation between the current and the torque. However, the threshold T wth Also, for example, the power supply voltage V of the battery 30 may vary. dc is a given value (threshold V dcth ) or less, it is determined that the current can be increased, and the current supplied to the motor 10 may be increased. dcth is the power supply voltage V dc , semiconductor temperature T s However, the threshold value V dcth The cooling water temperature T w or power supply voltage V dc When determining whether it is possible to increase the current supplied to the motor 10 based on the semiconductor temperature T s Since there is no need to obtain a reference number, the number of parts can be reduced.

[0044] 5 is a flowchart explaining the motor torque control in the motor control method of this embodiment. The motor torque control includes harmonic superposition control and torque increase control. The following process is repeatedly executed at a predetermined cycle by the controller 50. The controller 50 also appropriately acquires detection values ​​obtained by various sensors.

[0045] When the motor system 100 is started, for example by turning on the ignition switch of the vehicle in which the motor system 100 is mounted, the motor torque control starts.

[0046] In step S101, the controller 50 determines whether or not there is a torque increase request. If there is a torque increase request, the controller 50 executes the process of step S102. On the other hand, if there is no torque increase request, the controller 50 executes the process of step S104.

[0047] If there is no torque increase request, in step S104, the controller 50 executes normal control to maintain or decrease the torque of the N-phase motor 10 based on the requested torque, and ends the motor torque control. Note that since the Nth harmonic current does not contribute to the torque of the motor 10, in the normal control, harmonic superposition control may be executed to superimpose the Nth harmonic current on the fundamental current.

[0048] If there is a torque increase request, in step S102, the controller 50 determines whether it is possible to increase the current supplied to the motor 10 so as to satisfy the torque increase request. Specifically, the controller 50 determines whether the semiconductor temperature T s The estimated semiconductor temperature T s is the threshold T sth Determine whether the following occurs:

[0049] In step S102, the estimated semiconductor temperature T s is the threshold T sth If the estimated semiconductor temperature T s is the threshold T sth If it is greater, the controller 50 executes the process of step S105.

[0050] In this embodiment, in step S102, the estimated semiconductor temperature T s is the threshold T sth However, the present invention is not limited to this. For example, the cooling water temperature T w is the threshold T wth In this case, the controller 50 may determine whether the cooling water temperature Tw is the threshold T wth In the following cases, the process of step S103 is performed. w is the threshold T wth If it is greater than the power supply voltage V dc is the threshold V dcth In this case, the controller 50 may determine whether the power supply voltage V dc is the threshold V dcth In the following cases, the process of step S103 is performed. dc is the threshold V dcth If it is greater, the process of step S104 is executed.

[0051] Estimated semiconductor temperature T after torque increase s is the threshold T sth If the torque increase request is satisfied, in step S103, the controller 50 increases the fundamental current so as to satisfy the torque increase request, and executes harmonic superposition control to superimpose the Nth-order harmonic current on the fundamental current. This makes it possible to increase the torque of the motor 10 (torque boost) while controlling the peak value of the phase current I of the motor 10 to be equal to or less than the current limit value. Once the torque of the motor 10 is increased, the controller 50 ends the motor torque control.

[0052] On the other hand, the estimated semiconductor temperature T s is the threshold T sth If it is greater, in step S105, the controller 50 does not increase the torque of the motor 10, but maintains the torque of the motor 10. After executing the process of maintaining the torque of the motor 10, the controller 50 ends the motor torque control.

[0053] In this embodiment, in step S105, the torque of the motor 10 is maintained. However, this is not limited to this. In step S105, the controller 50 executes harmonic superposition control in which the N-th harmonic current is superposed on the fundamental current, and the current limit value I limThe current supplied to the motor 10 may be increased to increase the torque, provided that the current does not exceed the limit.

[0054] According to the motor control method of the first embodiment described above, the following effects can be obtained.

[0055] According to the motor control method of the present embodiment, in the current supplied to the N-phase motor 10, the 90° phase of the fundamental current that generates a rotating magnetic field and the 270° phase of the N-th harmonic current that does not contribute to the torque of the motor 10 that generates a zero-phase magnetic field are matched and superimposed. As a result, the positive peak of the fundamental current and the negative peak of the N-th harmonic current, and the negative peak of the fundamental current and the positive peak of the N-th harmonic current, are in phase with each other. Therefore, the peak of the current waveform after superimposition can be made smaller than the peak of the fundamental current without reducing the torque. Therefore, by raising the peak of the phase current I to the peak of the fundamental current before superimposition after superimposition of the N-th harmonic current, the current supplied to the motor 10 can be increased without raising the peak of the phase current I more than the peak of the fundamental current. That is, the torque can be increased without raising the peak of the current waveform more than before superimposition. Therefore, the torque of the motor 10 can be increased while protecting the components.

[0056] According to the motor control method of this embodiment, when the number of phases of the windings of the motor 10 is N, the amplitude of the Nth-order harmonic current is made to coincide with the difference value ΔI between the current value at phase 90° of the fundamental current and the current value at phase (90+360 / N*4)°. This makes the peak of the phase current waveform after the Nth-order harmonic current is superimposed substantially minimum, and the peak of the phase current I can be substantially minimized without reducing the torque of the motor 10. Therefore, the current supplied to the motor 10 can be increased without making the peak of the phase current I higher than the peak of the fundamental current, and the current limit value I lim The range in which the torque can be increased without exceeding the limit is larger.

[0057] According to the motor control method of the present embodiment, when the torque of the motor 10 is increased, the amplitude of the fundamental wave current is increased within the range of the formula (3). As a result, the peak value of the phase current I of the motor 10 is increased to the current limit value Ilim That is, damage to the semiconductor parts and output restrictions can be prevented.

[0058] According to the motor control method of this embodiment, when there is a request to increase torque, it is determined whether it is possible to increase the current supplied to the motor 10 so as to increase the torque in response to the request, and the current supplied to the motor 10 is increased only if it is possible. This prevents the current supplied to the motor 10 from exceeding the current limit value. In other words, it is possible to prevent damage to semiconductor components and output restrictions.

[0059] According to the motor control method of the present embodiment, when there is a request for an increase in torque, even if the current supplied to the motor 10 is increased, the semiconductor temperature T s is the threshold (predetermined value) T sth The current supplied to the motor 10 is increased only when the current supply to the motor 10 reaches the current limit value I lim That is, damage to the semiconductor parts and output restrictions can be prevented.

[0060] As in this embodiment, it is preferable to make the amplitude of the Nth harmonic current equal to the difference ΔI between the current value at phase 90° of the fundamental current and the current value at phase (90+360 / N*4)° of the fundamental current, but this is not necessarily limited to this. If the peak of the current waveform after superimposition is smaller than the peak of the fundamental current, even if the amplitude of the Nth harmonic current does not satisfy the above condition, it is possible to increase the torque to a certain extent without increasing the peak of the current waveform compared to before superimposition.

[0061] [Modification of the first embodiment] A motor control method according to a modified example of the first embodiment will be described with reference to Fig. 6. Note that the same elements as those in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

[0062] This modified example differs from the first embodiment in that even if it is determined that it is not possible to increase the current supplied to the motor 10 when there is a request to increase the torque of the motor 10, it may be re-determined that it is possible to increase the current when there is a mandatory request to increase the current.

[0063] Specifically, when there is a torque increase request, the estimated semiconductor temperature T s is the threshold T sth If it is determined that it is not possible to increase the current supplied to the motor 10, such as to make the current larger than the threshold voltage, the control unit 11 determines whether or not there is an essential requirement for increasing the current. A case where there is an essential requirement for increasing the current refers to a case where there is a strong requirement for an increase in torque, such as when a vehicle equipped with the motor system 100 runs on an uphill road or makes a sudden start, and it is therefore essential to increase the current supplied to the motor 10.

[0064] When there is an essential demand for an increase in current, it is judged whether or not it is possible to reduce the switching frequency of the semiconductor switching elements of the inverter 20 in consideration of the current controllability. In other words, it is judged whether or not the frequency will be lower than the minimum switching frequency required for the phase current I of the motor 10 even if the switching frequency is reduced. In addition to judging whether or not the switching frequency can be reduced, it is also judged whether or not the semiconductor temperature T s is the threshold T sth Then, it is determined whether the switching frequency can be reduced and the semiconductor temperature T of the semiconductor switching element when the switching frequency is reduced. s is the threshold T sth If the temperature of the semiconductor device becomes lower than the threshold, the control circuit 11 determines again that it is possible to increase the current supplied to the motor 10, and reduces the switching frequency while increasing the current supplied to the motor 10. When the switching frequency is reduced, the switching loss is reduced and the semiconductor temperature T s In other words, when the torque increase request is strong, a switching frequency lower than the normal switching frequency is selected, and the semiconductor temperature T sThis realizes an increase in torque while suppressing the increase in torque.

[0065] FIG. 6 is a flowchart illustrating motor torque control in a motor control method according to a modification of the first embodiment.

[0066] Steps S101 to S102 and step S104 are similar to those in the first embodiment, and therefore the description thereof will be omitted.

[0067] In step S102, the estimated semiconductor temperature T s is the threshold T sth If it is greater than the predetermined value, the controller 50 determines in step S115 whether or not it is possible to reduce the switching frequency of the semiconductor switching elements of the inverter 20. If it is possible to reduce the switching frequency, the controller 50 executes the process of step S116. On the other hand, if it is impossible to reduce the switching frequency, the controller 50 does not increase the torque of the motor 10 in step S105, but maintains the torque of the motor 10, and ends the motor torque control.

[0068] In step S116, the controller 50 calculates the semiconductor temperature T s is the threshold T sth Determine whether the semiconductor temperature T after the switching frequency change is s is the threshold T sth In the following cases, the controller 50 executes the process of step S103.

[0069] As described above, the process of step S103 is the same as that of the first embodiment, and therefore the description will be omitted. After executing the process of step S103, the controller 50 ends the motor torque control.

[0070] On the other hand, the semiconductor temperature T s is the threshold T sthIf it is greater, the controller 50 executes the process of step S105. In step S105, the controller 50 maintains the torque of the motor 10 without increasing the torque of the motor 10, and ends the motor torque control.

[0071] As described above, in this modified example, when the torque increase request is strong, the switching frequency is set lower than the normal switching frequency if possible. s It is possible to realize an increase in torque while suppressing an increase in the torque.

[0072] [Second embodiment] A motor control method according to the second embodiment will be described with reference to Fig. 7. Elements similar to those in the other embodiments are given the same reference numerals, and descriptions thereof will be omitted.

[0073] 7 is a diagram showing phase current waveforms in a motor control method according to the second embodiment. This embodiment differs from the other embodiments in that the waveform of the Nth harmonic current superimposed on the fundamental current is a triangular wave.

[0074] Specifically, in this embodiment, the Nth harmonic current superimposed on the fundamental current is controlled to be a value obtained by multiplying the sum of the maximum and minimum instantaneous values ​​of the phase currents (fundamental currents) of all phases (U, V, and W phases in this embodiment) of the motor 10 by half. For example, in the case of the phase p 1 In the above, the N-th harmonic current is the maximum instantaneous value of the phase current (fundamental current) of all phases of the motor 10, i u1 and the minimum value i w1 The sum of and multiplied by 1 / 2 N1 By controlling the Nth harmonic current as described above, the waveform of the Nth harmonic current becomes a triangular wave.

[0075] In this way, even if the Nth harmonic current is a triangular wave, the peak of the fundamental current can be reduced by superimposing the Nth harmonic current on the fundamental current as shown in Fig. 7. That is, even if the Nth harmonic current is not made sinusoidal but is simply generated as a triangular wave and superimposed, the peak of the current waveform after superimposition can be made smaller than the peak of the fundamental current without reducing the torque.

[0076] Although the embodiments of the present invention have been described above, the above-mentioned embodiments merely show some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above-mentioned embodiments.

[0077] Although the above-described embodiments have been described as separate embodiments, they may be combined as appropriate. [Explanation of symbols]

[0078] 10: Motor, 20: Inverter, 30: Battery, 40: Cooler, 50: Controller, 100: Motor system

Claims

1. A motor control method for a motor system including an open-winding N-phase motor and an inverter that converts power and supplies it to the motor, comprising: In the current supplied to the motor, an N-th harmonic current that generates a zero-phase magnetic field is superimposed on a fundamental current that generates a rotating magnetic field; The harmonic order of the N-th harmonic current and the number of motor phases N satisfy either of the following formulas (1) or (2), where n is a natural number of 1 or more: [0010] The fundamental current is matched in phase with 90° of the N-th harmonic current, and the N-th harmonic current is matched in phase with 270° of the N-th harmonic current. Motor control methods.

2. 2. A motor control method according to claim 1, comprising: The amplitude of the N-th harmonic current is made to coincide with the difference between the current value at a phase of 90° of the fundamental current and the current value at a phase of (90+360 / N*4)° of the fundamental current. Motor control methods.

3. 2. A motor control method according to claim 1, comprising: The N-th harmonic current is set to a value obtained by multiplying the sum of the maximum and minimum instantaneous values ​​of the phase currents of all phases of the motor by half. Motor control methods.

4. 2. A motor control method according to claim 1, comprising: When increasing the torque of the motor, the amplitude of the fundamental wave current is increased within the range of Equation (3) so that the peak value of the phase current of the motor does not exceed a current limit value that is a maximum value of a current that can be output to the motor. [0025] (where ΔA is the maximum amplitude of the fundamental current) Motor control methods.

5. 5. A motor control method according to claim 4, comprising: If there is a demand to increase the torque of the motor, determining whether it is possible to increase the current supplied to the motor to increase torque; Increase the current only when possible, Motor control methods.

6. 6. A motor control method according to claim 5, comprising: an inverter of the motor system includes a semiconductor switching element; if the temperature of the semiconductor of the semiconductor switching element remains equal to or lower than a predetermined value even when the current supplied to the motor is increased, it is determined that the current supplied to the motor can be increased. Motor control methods.

7. 6. A motor control method according to claim 5, comprising: determining that it is possible to increase the current supplied to the motor when the temperature of the cooling water for cooling the inverter is equal to or lower than a predetermined value; Motor control methods.

8. 6. A motor control method according to claim 5, comprising: determining that it is possible to increase the current supplied to the motor when the voltage of a power source for supplying power to the motor is equal to or lower than a predetermined value; Motor control methods.

9. A motor control method according to any one of claims 6 to 8, comprising the steps of: an inverter of the motor system includes a semiconductor switching element; Even if it is determined that it is not possible to increase the current supplied to the motor, if there is an essential request for an increase in current, a determination is made as to whether or not it is possible to reduce the switching frequency of the semiconductor switching element based on the required current, and if the semiconductor temperature of the semiconductor switching element when the switching frequency is reduced is equal to or lower than a predetermined value, a determination is made again that it is possible to increase the current supplied to the motor. Motor control methods.

10. an open winding type N-phase motor; an inverter that converts electric power and supplies it to the motor; A controller for controlling the operation of the inverter; A motor system comprising: the controller controls, in a current supplied to the motor, a fundamental current of a current that generates a rotating magnetic field, to be superimposed with an N-th harmonic current that generates a zero-phase magnetic field, and controls so that a 90° phase of the fundamental current and a 270° phase of the N-th harmonic current coincide with each other; The harmonic order of the N-th harmonic current and the number of motor phases N satisfy either of the following formulas (4) or (5), where n is a natural number of 1 or more: [0030] Motor system.

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