Motor control device

Abstract

To provide a motor control device in which loss in an AC motor can be suppressed and its output can be improved.SOLUTION: A motor control device for controlling a motor that is driven with AC power includes: a pulse control unit that generates a drive pulse based on a voltage phase of the motor; and a power converter that converts DC power to AC power in accordance with the drive pulse generated by the pulse control unit and outputs the AC power to the motor. The pulse control unit generates, as the drive pulses, a primary component suppressing pulse which suppresses a primary component of a voltage harmonic wave and a secondary component suppressing pulse which suppresses a secondary component of a voltage harmonic wave, and outputs the primary component suppressing pulse or the secondary component suppressing pulse by selective switching.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electric motor control device. [Background technology]

[0002] BACKGROUND ART In recent years, AC motors have been used in a wide range of applications, such as home appliances, infrastructure, and in-vehicle equipment, and control devices that meet the increasing demand for energy saving, compact size, and high power density have been applied.

[0003] One known drive control method for AC motors is PWM control, which creates a modulation signal based on a voltage command signal corresponding to the voltage applied to the AC motor, compares the modulation signal with a carrier to generate a PWM pulse signal that turns on and off the switching elements of a power conversion device, and then converts DC power into AC power that drives the AC motor based on the PWM pulse signal, thereby enabling control of the AC motor.

[0004] On the other hand, PWM control generates AC power by repeatedly turning on and off the switching elements of the power converter at high speed, so the voltage applied to the AC motor from the power converter is pulsed, which means that the current flowing through the AC motor contains harmonic components, which cause noise and loss.

[0005] A technique for reducing losses in an AC motor caused by the on / off switching of switching elements in such a power conversion device is known, for example, from the person described in Patent Document 1. Patent Document 1 discloses a motor drive system including a PWM signal control unit that generates pulse-width-modulated gate pulse signals from voltage command signals for each of three phases, an inverter controlled by the pulse-width-modulated gate signals, and a motor driven by the inverter, in which the PWM signal control unit generates the gate pulse signals in each of the three phases by inserting one or more on-state and one or more off-state operations of a pulse signal in a phase region including and near a zero-cross point of a fundamental wave voltage command based on the voltage command signal, and by inserting one or more on-state and one or more off-state operations of the pulse signal in a phase region including and near a positive and negative peak point of the fundamental wave voltage command, and by maintaining the pulse signal in an on state or an off state in other phase regions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2015-053824 Summary of the Invention [Problem to be solved by the invention]

[0007] In the above-mentioned conventional technology, the harmonic components of the voltage applied to the AC motor are suppressed by switching between PWM pulses and square-wave pulses for a pulse-width-modulated gate signal depending on the magnet temperature, thereby reducing losses in the AC motor. However, because the on / off period for the PWM pulse is set based on the pulse-width-modulated gate signal, harmonic components are generated in the frequency component of the carrier wave that is the source of the pulse-width modulation. Furthermore, no consideration is given to suppressing magnet losses and magnet temperature rise caused by current harmonics in the magnet direction that occur when the AC motor is a permanent magnet synchronous motor.

[0008] The present invention has been made in view of the above, and an object of the present invention is to provide a motor control device that can suppress losses in an AC motor and improve output. [Means for solving the problem]

[0009] The present application includes multiple means for solving the above-mentioned problems. One example is a motor control device that controls an electric motor driven by AC power, which includes a pulse control unit that generates drive pulses based on the voltage phase of the electric motor, and a power converter that converts DC power to AC power based on the drive pulses generated by the pulse control unit and outputs the AC power to the electric motor, wherein the pulse control unit generates, as the drive pulses, a primary component suppression pulse that suppresses the primary component of voltage harmonics and a secondary component suppression pulse that suppresses the secondary component of voltage harmonics, and selectively switches between the primary component suppression pulse and the secondary component suppression pulse for output. [Effects of the Invention]

[0010] According to the present invention, loss in an AC motor can be suppressed and output can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a functional block diagram schematically showing an electric motor control device according to a first embodiment together with related configurations. [Figure 2] FIG. 2 is a functional block diagram schematically showing the processing functions of a pulse control unit. [Figure 3] FIG. 10 is a diagram showing an example of a pulse waveform of a first-order component suppression pulse. [Figure 4] 10A and 10B are diagrams showing phase current waveforms when an AC motor is driven by a primary component suppression pulse. [Figure 5] FIG. 5 is a diagram showing the results of an order analysis of the current waveform in FIG. 4. [Figure 6] FIG. 10 is a diagram showing an example of a pulse waveform of a second-order component suppression pulse. [Figure 7]10A and 10B are diagrams showing phase current waveforms when an AC motor is driven by a secondary component suppression pulse. [Figure 8] FIG. 8 is a diagram showing the results of an order analysis of the current waveform in FIG. 7. [Figure 9] FIG. 10 is a functional block diagram schematically showing an electric motor control device according to a second embodiment together with related configurations. [Figure 10] FIG. 1 is a diagram illustrating a case where the motor control device is applied to an electric vehicle. [Figure 11] 10A and 10B are diagrams illustrating an example of waveforms of a carrier wave, a modulated signal, and a pulse in PWM control shown as a comparative example. [Figure 12] FIG. 10 is a diagram showing an example of a pulse waveform of a PWM pulse shown as a comparative example. [Figure 13] FIG. 10 is a diagram showing phase current waveforms when an AC motor is driven by PWM pulses shown as a comparative example. [Figure 14] FIG. 14 is a diagram showing the results of an order analysis of the current waveform in FIG. 13. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] First Embodiment A first embodiment of the present invention will be described with reference to FIGS.

[0014] Fig. 1 is a functional block diagram showing a motor control device according to the present embodiment together with related configurations, and Fig. 2 is a functional block diagram showing a processing function of a pulse control unit.

[0015] In FIG. 1, the motor control device 100 controls an AC motor 1, such as a permanent magnet synchronous motor (PMSM), that is driven by AC power, and includes a pulse control unit 2 that generates drive pulses 22a based on the voltage phase of the AC motor 1, and an inverter 3 as a power converter that converts DC power supplied from a DC power supply 7 into AC power based on the drive pulses 22a generated by the pulse control unit 2 and outputs the AC power to the AC motor 1.

[0016] The pulse control unit 2 has a vector control unit 21 that generates and outputs a modulation factor command value 21 a based on the detection result from a current detection circuit 4 that detects the current supplied from the inverter 3 to the AC motor 1 and the detection result from a position sensor 5 that detects the position of the rotor of the AC motor 1, and a pulse generation unit 22 that outputs a drive pulse 22 a based on the modulation factor command value 21 a output from the vector control unit 21 and a selection signal 6 a from a pulse selection device 6.

[0017] As shown in FIG. 2, the pulse generating unit 22 has a primary component suppression pulse generating unit 221 that generates a drive pulse (primary component suppression pulse) that suppresses the primary component of the voltage harmonics, a secondary component suppression pulse generating unit 222 that generates a drive pulse (secondary component suppression pulse) that suppresses the secondary component of the voltage harmonics, and a pulse switching unit 223 that selectively switches between the primary component suppression pulse generated by the primary component suppression pulse generating unit 221 and the secondary component suppression pulse generated by the secondary component suppression pulse generating unit 222 based on a selection signal 6a from a pulse selecting device 6 and outputs the switched pulse as a drive pulse 22a.

[0018] In this embodiment, the case where the pulse selection device 6 is arranged outside the pulse control unit 2 is described as an example, but this is not limited to this. For example, the function of the pulse selection device 6 may be arranged as a pulse selection unit inside the pulse control unit 2, and the drive pulse 22a output from the pulse generation unit 22 may be selectively switched by a selection signal output from the pulse selection unit depending on the drive conditions of the AC motor 1.

[0019] Fig. 3 is a diagram showing an example of the pulse waveform of a first-order component suppression pulse, showing a U-phase pulse as an example of the pulse waveform. Fig. 4 is a diagram showing the phase current waveform when an AC motor is driven by the drive pulse (first-order component suppression pulse) shown in Fig. 3 under continuous rated maximum output conditions, and Fig. 5 is a diagram showing the results of order analysis of the current waveform. Note that in a permanent magnet motor, a dq fixed coordinate system is generally set with the magnet magnetic flux direction as the d-axis and the direction perpendicular to the d-axis as the q-axis. Therefore, Fig. 5 shows the results of order analysis of the dq-axis current waveform obtained by dq-transforming the phase current waveform of Fig. 4.

[0020] As shown in Figure 3, the drive pulse (first-order component suppression pulse) that suppresses the first-order component of the voltage harmonics is generated so that the pulses are spaced at irregular intervals. For example, the pulses are generated so that the pulse intervals become shorter in each of the voltage phase regions of 0 degrees, 90 degrees, 180 degrees, and 270 degrees.

[0021] Fig. 6 is a diagram showing an example of the pulse waveform of a second-order component suppression pulse, illustrating a U-phase pulse as the pulse waveform. Fig. 7 is a diagram showing the phase current waveform when an AC motor is driven by the drive pulse (second-order component suppression pulse) shown in Fig. 6 under continuous rated maximum output conditions, and Fig. 8 is a diagram showing the results of order analysis of the current waveform. Fig. 8 also shows the results of order analysis of the dq-axis current waveform obtained by dq-transforming the phase current waveform of Fig. 7.

[0022] As shown in Figure 6, the drive pulse (first-order component suppression pulse) for suppressing the first-order component of the voltage harmonics is generated so that the pulses are spaced at irregular intervals. For example, the pulses are generated so that the pulse intervals become shorter in the voltage phase range of 180 degrees to 270 degrees.

[0023] The effects of the present embodiment configured as above will be described.

[0024] First, as a comparative example of this embodiment, a PWM control method, which is one of the general methods for controlling an AC motor, will be described.

[0025] Figure 11 shows an example of the waveforms of the carrier wave, modulation signal, and pulse in PWM control. As shown in Figure 11, the PWM control method compares the modulation signal with the carrier wave, outputting an on pulse when the modulation signal is large and an off pulse when the modulation signal is small. In this way, PWM control generates a pulse waveform (drive pulse) that controls the power converter by comparing the sinusoidal modulation signal with the carrier wave. In other words, the PWM control method generates a pulse waveform based on the carrier wave, so it outputs an on-off pulse for each carrier period. The example shown in Figure 11 shows an example of a 15-pulse synchronous waveform, where 15 on-off pulses occur per period. For this reason, the PWM control method generates voltage harmonics with components proportional to the number of synchronous pulses.

[0026] For example, permanent magnet synchronous motors (PMSMs), which are capable of achieving high power density, are often used as automotive AC motors. When PWM control of such PMSMs is performed, applying drive pulses (PWM pulses) such as those shown in Figure 12 under the continuous rated maximum output condition results in the phase current waveforms shown in Figure 13. With 15 synchronous pulses, the on-off cycle repeats 15 times per voltage cycle. The 15th-order component of the number of synchronous pulses per voltage cycle is called the first-order component of the voltage harmonic, and the 30th-order component per voltage cycle is called the second-order component of the voltage harmonic. In this case, as shown in the order analysis results in Figure 14, the q-axis current component (dashed line) is generated as the first-order sideband of the 15th-order ±3rd-order voltage harmonics. Furthermore, the d-axis current component (solid line) is generated as the second-order component of the 30th-order voltage harmonic.

[0027] In this way, in the PWM control method, on-off pulses are generated based on a carrier wave, so voltage harmonic components are concentrated at frequency components proportional to the number of synchronous pulses. Current harmonic components are the cause of increased torque ripple in AC motors and increased harmonic losses in motors.

[0028] In contrast to this, in this embodiment, a motor control device 100 that controls an AC motor 1 (e.g., PMSM) driven by AC power includes a pulse control unit 2 that generates a drive pulse 22a based on the voltage phase of the AC motor 1, and a power converter (e.g., inverter 3) that converts DC power to AC power based on the drive pulse 22a generated by the pulse control unit 2 and outputs it to the AC motor 1. The pulse control unit 2 is configured to generate, as the drive pulse 22a, a primary component suppression pulse that suppresses the primary component of the voltage harmonics and a secondary component suppression pulse that suppresses the secondary component of the voltage harmonics, and to selectively switch between the primary component suppression pulse and the secondary component suppression pulse and output them to the power converter.

[0029] For example, when AC motor 1 is driven by the drive pulse (primary component suppression pulse) shown in Fig. 3 as drive pulse 22a under continuous rated maximum output conditions, the phase current waveform shown in Fig. 4 is obtained. Comparing the phase current waveform in PWM control (Fig. 12) exemplified as the prior art with the phase current waveform in control using the primary component suppression pulse of this embodiment (Fig. 4), it can be seen that the current ripple near the current zero crossing is finer in control using the primary component suppression pulse.

[0030] Comparing the order analysis results for PWM control (FIG. 13) with the order analysis results for control using the first-order component suppression pulse in this embodiment (FIG. 5), it can be seen that the control using the first-order component suppression pulse suppresses the q-axis current harmonics of the first-order component sidebands (15th±3rd) of the voltage harmonics. On the other hand, the d-axis current harmonics of the second-order component (30th) of the voltage harmonics have a lower frequency and a larger peak value.

[0031] That is, when the first-order component suppression pulse of this embodiment is applied as a drive pulse under the continuous rated maximum output condition, it is possible to suppress the total dq-axis current harmonics, which are the sum of the dq-axis current harmonic components. Furthermore, with regard to the dq-axis components, the q-axis current harmonic is significantly reduced, while the d-axis current harmonic component is increased.

[0032] More specifically, control using this type of primary component suppression pulse is effective in reducing motor loss throughout the PSMS when the magnet temperature is low, output is low, or other conditions where there is little possibility of demagnetization due to a rise in magnet temperature. Therefore, depending on these drive conditions, the primary component suppression pulse is selected as a drive pulse that reduces the overall dq-axis current harmonic components under continuous rated maximum output conditions. This makes it possible to suppress harmonic losses such as motor iron loss caused by dq-axis current harmonics, thereby suppressing loss and temperature rise throughout the motor.

[0033] Furthermore, control using the primary component suppression pulse is effective in suppressing overall motor loss and temperature rise, even when magnet loss and magnet temperature rise due to eddy current loss do not need to be considered. Some PMSMs use magnets that do not generate eddy current loss. Drive systems that drive AC motors without magnets are also known. With such PMSMs and AC motors, magnet loss and magnet temperature rise due to eddy current loss do not need to be considered. Therefore, the primary component suppression pulse is selected as a drive pulse that reduces the dq-axis total current harmonic components under continuous rated maximum output conditions. This suppresses harmonic losses, such as motor iron loss due to dq-axis current harmonics, even in PMSMs that do not generate eddy current loss or AC motors that do not use magnets, thereby suppressing overall motor loss and temperature rise.

[0034] Furthermore, when AC motor 1 is driven by the drive pulse (secondary component suppression pulse) shown in Fig. 6 as drive pulse 22a under continuous rated maximum output conditions, the phase current waveform is as shown in Fig. 7. Comparing the phase current waveform in PWM control (Fig. 12) exemplified as the prior art with the phase current waveform in control using the secondary component suppression pulse of this embodiment (Fig. 7), it can be seen that the current ripple near the current peak is finer in control using the secondary component suppression pulse.

[0035] At this time, comparing the order analysis results for PWM control (Fig. 13) with the order analysis results for control using second-order component suppression pulses in this embodiment (Fig. 8), we see that in control using second-order component suppression pulses, in addition to the q-axis current harmonics of the first-order component sidebands (15th ±3rd) of the voltage harmonics, 6th, 24th, etc. components are generated. On the other hand, the d-axis current harmonic of the second-order component (30th) of the voltage harmonics becomes higher frequency and its peak value becomes smaller.

[0036] That is, when the second-order component suppression pulse of this embodiment is applied as a drive pulse under the continuous rated maximum output condition, it is possible to suppress the dq-axis total current harmonic components. Furthermore, with regard to the dq-axis components, the q-axis current harmonic increases and the d-axis current harmonic decreases.

[0037] More specifically, control using this type of second-order component suppression pulse is effective in suppressing eddy current loss caused by d-axis current harmonic components, which are in the direction of the magnet magnetic flux, in the magnets used in PMSMs. It is also effective in suppressing magnet demagnetization caused by magnet temperature rise when increasing the power density of PMSMs. Therefore, depending on these drive conditions, a second-order component suppression pulse is selected as a drive pulse that reduces the d-axis current harmonic components under continuous rated maximum output conditions. This makes it possible to suppress eddy current loss caused by d-axis current harmonics, and also suppress magnet loss and magnet temperature rise.

[0038] As described above, in this embodiment, the drive pulse 22a is configured to generate a primary component suppression pulse that suppresses the primary component of voltage harmonics and a secondary component suppression pulse that suppresses the secondary component of voltage harmonics, and to selectively switch between the primary component suppression pulse and the secondary component suppression pulse. This allows the AC motor 1 to be controlled by the primary component suppression pulse or the secondary component suppression pulse, and allows the dq-axis total current harmonic components to be suppressed. Furthermore, since the AC motor 1 can be controlled by switching between the primary component suppression pulse and the secondary component suppression pulse, it is possible to change the current harmonic components to be suppressed. In other words, loss in the AC motor can be suppressed, and output can be improved.

[0039] <Second embodiment> A second embodiment of the present invention will be described with reference to FIG.

[0040] This embodiment shows a case where a PWM pulse can be selected as a drive pulse in addition to a first-order component suppression pulse and a second-order component suppression pulse.

[0041] In this embodiment, only the differences from the first embodiment will be described, and the same members as those in the first embodiment will be given the same reference numerals and descriptions thereof will be omitted as appropriate.

[0042] FIG. 9 is a functional block diagram schematically showing the processing functions of the pulse control unit according to this embodiment.

[0043] As shown in FIG. 9, the pulse generating unit 22A has a primary component suppression pulse generating unit 221 that generates a drive pulse (primary component suppression pulse) that suppresses the primary component of the voltage harmonics, a secondary component suppression pulse generating unit 222 that generates a drive pulse (secondary component suppression pulse) that suppresses the secondary component of the voltage harmonics, a PWM pulse generating unit 224 that generates a drive pulse (PWM pulse) that performs PWM control, and a pulse switching unit 223A that selectively switches between the primary component suppression pulse generated by the primary component suppression pulse generating unit 221, the secondary component suppression pulse generated by the secondary component suppression pulse generating unit 222, and the PWM pulse generated by the PWM pulse generating unit based on a selection signal 6a from a pulse selecting device 6, and outputs the result as a drive pulse 22a.

[0044] The other configurations are the same as those in the first embodiment.

[0045] The present embodiment configured as above can also achieve the same effects as the first embodiment.

[0046] Furthermore, in cases where motor current harmonics can be sufficiently reduced by increasing the carrier frequency, such as when using an inverter capable of low rotation speed conditions or high-speed switching operation, the computational load on the pulse generation unit 22A can be reduced by making it possible to select a PWM pulse based on the carrier wave.

[0047] <Other embodiments> FIG. 10 is a diagram showing a case where the motor control device shown in the first embodiment or the second embodiment is applied to an electric vehicle.

[0048] As shown in FIG. 10, an electric vehicle 1000 according to this embodiment includes an AC motor 1 as a prime mover that supplies driving force to the wheels, and an electric motor control device 100 that controls the AC motor 1.

[0049] In this way, by applying the motor control device 100 to an electric vehicle 1000 that uses an AC motor 1 as the main on-board motor, it is possible to provide a highly efficient electric vehicle with reduced current harmonic components and harmonic losses.

[0050] <Additional Notes> The present invention is not limited to the above-described embodiments, and includes various modifications and combinations within the scope of the gist thereof. Furthermore, the present invention is not limited to those including all of the configurations described in the above-described embodiments, and includes those in which some of the configurations are omitted. Furthermore, the above-described configurations, functions, etc. may be realized in part or in whole by designing them as, for example, integrated circuits. Furthermore, the above-described configurations, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function. [Explanation of symbols]

[0051] 1...AC motor, 2...pulse control unit, 3...inverter, 4...current detection circuit, 5...position sensor, 6...pulse selection device, 6a...selection signal, 7...DC power supply, 21...vector control unit, 21a...modulation factor command value, 22, 22A...pulse generation unit, 22a...drive pulse, 100...motor control device, 221...primary component suppression pulse generation unit, 222...secondary component suppression pulse generation unit, 223, 223A...pulse switching unit, 224...PWM pulse generation unit, 1000...electric vehicle

Claims

1. 1. An electric motor control device that controls an electric motor driven by AC power, a pulse control unit that generates a drive pulse based on a voltage phase of the electric motor; a power converter that converts DC power into AC power based on the drive pulse generated by the pulse control unit and outputs the AC power to the electric motor; The pulse control unit generates, as the drive pulse, a primary component suppression pulse that suppresses the primary component of voltage harmonics and a secondary component suppression pulse that suppresses the secondary component of voltage harmonics, and selectively switches between the primary component suppression pulse and the secondary component suppression pulse and outputs the pulse.

2. 2. The motor control device according to claim 1, The pulse control unit selects and outputs a drive pulse that suppresses d-axis current harmonics from the primary component suppression pulse and the secondary component suppression pulse depending on the drive conditions of the motor.

3. 2. The motor control device according to claim 1, The pulse control unit selects and outputs a drive pulse that suppresses dq-axis total current harmonics from the primary component suppression pulse and the secondary component suppression pulse depending on the drive conditions of the motor.

4. 2. The motor control device according to claim 1, The pulse control unit selects and outputs drive pulses that suppress dq-axis overall current harmonics when the magnet of the motor does not generate eddy current loss or when no magnet is used in the motor.

5. 2. The motor control device according to claim 1, The pulse control unit generates, in addition to the primary component suppression pulse and the secondary component suppression pulse, a PWM pulse that performs PWM control based on a carrier wave as the drive pulse based on a carrier wave, and selectively switches and outputs the primary component suppression pulse, the secondary component suppression pulse, and the PWM pulse.

6. an electric motor as a prime mover that supplies driving force to the wheels; the electric motor control device according to claim 1, which controls the electric motor; An electric vehicle comprising:

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