Motor drive system and motor drive method

Abstract

The present invention relates to a motor drive system and a motor drive method. The motor drive system includes a power converter, a state detector, a frequency calculator, a frequency correction instruction generator, a drive amount limiter, and a speed controller. The power converter drives the motor by PWM control. The state detector detects the drive state of the motor. The frequency calculator uses an index value indicating the drive state to detect the magnitude of a specific frequency component that varies in relation to the drive state. The frequency correction instruction generator generates a correction instruction for the carrier frequency used in the PWM control based on the detection result of the periodic variation of the drive state. The drive amount limiter limits the drive amount of the motor. When searching in the direction of increasing the carrier frequency, the drive amount limiter adjusts the upper limit value of the magnitude of the current flowing in the motor coil to be lower than a predetermined upper limit current value. The speed controller generates a current reference based on the speed command value and the rotor speed of the motor according to the above limitation.

Description

Technical Field

[0001] Embodiments of the present invention relate to a motor drive system and a motor drive method. Background Art

[0002] In a motor drive system in which a power conversion device is combined with a motor (rotary electric machine) to drive the motor, depending on the relationship between the control state of the power conversion device and the natural frequency of the motor, unwanted noise and vibration may sometimes be generated from the motor. In a motor drive system, it is desirable not to generate such vibration. After installing the motor drive system, in order not to cause the above vibration in the motor, adjustment is sometimes performed by mechanical or electrical methods, but it is sometimes difficult to implement.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-68666 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a motor drive system and a motor drive method that suppress the generation of noise and vibration caused by driving a motor.

[0008] Means for Solving the Problems

[0009] The motor drive system according to the embodiment includes a power converter, a state detector, a frequency calculator, a frequency correction command generator, a drive amount limiter, and a speed controller. The power converter drives the motor by PWM control. The state detector detects the drive state of the motor. The frequency calculator uses an index value representing the drive state to detect the magnitude of a specific frequency component that varies in relation to the drive state. The frequency correction command generator generates a correction command for the carrier frequency for the PWM control based on the detection result of the periodic variation of the drive state. The drive amount limiter limits the drive amount of the motor. The drive amount limiter adjusts the upper limit value of the magnitude of the current flowing in the coil of the motor in a direction lower than a predetermined upper limit current value when searching in a direction to increase the carrier frequency. The speed controller generates a current reference based on a speed command value and the rotor speed of the motor according to the limitation. Brief Description of the Drawings

[0010] Figure 1 is a block diagram illustrating a motor drive system according to the first embodiment.

[0011] Figure 2This is a diagram for explaining the derating of the output current corresponding to the carrier frequency in the first embodiment.

[0012] Figure 3A This is a flowchart of the process related to speed control in the first embodiment.

[0013] Figure 3B This is a flowchart of the process related to speed control in the first embodiment.

[0014] Figure 3C This is a flowchart of the process related to speed control in the first embodiment.

[0015] Figure 3D This is a flowchart of the process related to speed control in the first embodiment.

[0016] Figure 3E This is a flowchart of the process related to speed control in the first embodiment.

[0017] Figure 4 This is a block diagram illustrating the motor drive system of the second embodiment.

[0018] Figure 5 This is a block diagram illustrating the motor drive system of the third embodiment. Detailed Embodiments

[0019] Hereinafter, the motor drive system and the motor drive method of the embodiment will be described with reference to the accompanying drawings.

[0020] In addition, the accompanying drawings are schematic or conceptual diagrams, and the functional allocation of each part is not necessarily the same as the actual situation.

[0021] In addition, in this application specification and each drawing, components having the same or similar functions are labeled with the same reference numerals. And sometimes the repeated description of these components is omitted.

[0022] In the embodiment, "connection" includes electrical connection. "Based on XX" means "at least based on XX", and also includes the case where other elements are also based on in addition to XX. In addition, "based on XX" is not limited to the case of directly using XX, and also includes the case based on the result obtained by operating and processing XX. "XX or YY" is not limited to the case of either XX or YY, and also includes the case of both XX and YY. This is the same in the case where there are three or more selectable elements. "XX" and "YY" are arbitrary elements (for example, arbitrary information). "Power converter" is a power converter that outputs alternating current, and includes, for example, an inverter, an AC / AC converter, etc. "Motor" is a rotating electric machine driven by alternating current power, and speed control is performed by VVVF control or the like.

[0023] (First Embodiment)

[0024] Figure 1 It is a block diagram illustrating the motor drive system 1 of the first embodiment.

[0025] In Figure 1 , in addition to the configuration of the vibration suppression control device 30, the configuration of the motor speed control device 20 is also shown. Additionally, the vibration suppression control device 30 can be housed in the same housing or disk as the motor speed control device 20, or can be housed in other physically separated housings, etc. For example, the motor drive system 1 includes a motor speed control device 20 and a vibration suppression control device 30.

[0026] As Figure 1 shown, the motor speed control device 20 is connected to the motor 2, the speed detector 4, and the vibration suppression control device 30. The motor speed control device 20 controls the motor 2 so that the actual speed of the motor 2 detected by the speed detector 4 coincides with a separately supplied speed command value. The motor speed control device 20 sets operation parameters based on the correction value supplied from the vibration suppression control device 30, thereby being able to suppress vibrations caused by resonance of the motor 2 and the mechanical load driven by the motor 2 and operate. Hereinafter, the resonance generated in the motor 2 and the mechanical load driven by the motor 2 will be simply referred to as the resonance of the motor 2. The resonance generated in the motor 2 and the mechanical load driven by the motor 2 may also include the resonance of the shaft torsional vibration system via the connected shaft. The operation parameters adjusted by correction will be described later.

[0027] The rotating shaft of the motor 2 and the mechanical load are connected by a connecting shaft. The driving torque of the motor 2 is transmitted to the mechanical load via the connecting shaft. The motor speed control device 20 performs variable speed control on the motor 2 for driving. For example, the motor 2 is a motor driven by alternating current power and is an induction motor, a synchronous motor, etc. For example, the motor speed control device 20 is an inverter device that drives an induction motor, a synchronous motor, etc.

[0028] The motor speed control device 20 includes a speed controller 5, a current controller 6, and a power converter 7.

[0029] The speed controller 5 multiplies the speed deviation between the speed command value and the speed detected by the speed detector 4 of the motor 2 by a prescribed speed response gain to generate a command value for the driving torque. For example, the speed command value is supplied from a higher-level control device such as a programmable logic controller (PLC). A limiter is provided in the speed controller 5, and this limiter limits the output value in order to limit the overmodulation state of the subsequent PWM control. The limit value based on the limiter is an example of an operation parameter that can be adjusted by control. The more specific configuration of the speed controller 5 will be described later.

[0030] The current controller 6 is connected to the output of the speed controller 5. The current controller 6 outputs a control amount generated based on the difference between the command value of the drive torque supplied from the speed controller 5 and the torque current component supplied to the motor 2.

[0031] The power converter 7 is connected to the output of the current controller 6. For example, the power converter 7 includes a PWM controller 7PWM and a converter main body 7INV. The power converter 7 controls the converter main body 7INV through PWM control based on the PWM controller 7PWM. Thus, the power converter 7 can drive the motor through PWM control. The power converter 7 can also output the voltage and current for driving the motor 2 according to the control amount generated by the current controller 6.

[0032] For example, current transformers 7CT for detecting the phase current of each phase are provided on the wiring connected to the output of the power converter 7. The current transformers 7CT can also be provided on at least two of the phase wirings of the three-phase AC. The power converter 7 obtains the instantaneous value of the phase current detected by the current transformers 7CT and supplies the detection result to the current controller 6 and the vibration suppression control device 30. The current transformers 7CT and the power converter 7 are an example of a state detector.

[0033] The vibration suppression control device 30 determines whether the motor 2 generates resonance based on the data of the instantaneous value of the supplied phase current. When the motor 2 generates resonance, the vibration suppression control device 30 corrects the limit value of the speed controller 5 or corrects the carrier frequency of the PWM control of the power converter 7.

[0034] The configuration of the vibration suppression control device 30 will be described in detail.

[0035] The vibration suppression control device 30 includes, for example, a frequency calculator 9 (fluctuation detector), a resonance determiner 10, a drive amount limiter 11, a frequency correction command generator 12, and a response characteristic determiner 13.

[0036] The input of the frequency calculator 9 is connected to the power converter 7. The frequency calculator 9 uses the index value representing the drive state supplied from the power converter 7 to detect the magnitude of a specific frequency component that varies related to the drive state. For example, the frequency calculator 9 converts the data of the phase current in the time domain detected by the power converter 7 into data in the frequency domain. The frequency calculator 9 is, for example, an FFT (Fast Fourier Transform) analyzer. In addition, the frequency calculator 9 is not limited thereto, and can also be configured to include a filter bank for detecting the magnitude of the signal components in each frequency band.

[0037] The resonance detector 10 is connected to the output of the frequency calculator 9. The resonance detector 10 determines whether the motor 2 generates vibration caused by resonance (hereinafter, also simply referred to as generating resonance) based on the data in the frequency domain.

[0038] For example, the resonance detector 10 has a threshold T0 related to the phase current that is independent of frequency. When the data of the phase current in the frequency domain is equal to or greater than the threshold T0, the resonance detector 10 determines that resonance is generated.

[0039] For example, the resonance detector 10 uses the carrier frequency of the power converter 7 and its harmonic components as the frequencies for determination. For example, when the carrier frequency of the power converter 7 is fc and the operating frequency of the motor 2 is f0, the frequency for determination fn is set to n×(fc±f0), where n = 1, 2, 3,... (natural numbers). The resonance detector 10 presets a threshold Tn for each frequency for determination fn.

[0040] In addition, the setting of the frequency for determination fn is not limited to the above situation and can be set appropriately. The frequency fn can also be set to, for example, further expand the range in the form of n×(fc±k×f0) (k>1) relative to n×(fc±f0). In addition, in the case where fc>>f0, etc., the frequency fn can also be set to fn = n×fc.

[0041] The resonance detector 10 can also be such that when the data of the phase current equal to or greater than the set threshold Tn is detected at any of the frequencies fn, it is determined that resonance is generated due to the pulsation of the phase current based on the carrier frequency. The resonance detector 10 is such that when the data of the phase current equal to or greater than the set threshold Tn is not detected at any of the frequencies fn, it is determined that resonance is not generated due to the speed response gain.

[0042] The output of the resonance detector 10 is respectively connected to a drive amount limiter 11 and a frequency correction command generator 12.

[0043] First, the drive amount limiter 11 will be described. When the resonance detector 10 determines that resonance is generated, it supplies a first enable signal to the drive amount limiter 11. The first enable signal is a signal for notifying the drive amount limiter 11 of the occurrence of resonance and activating the drive amount limiter 11 to adjust the limit value. The drive amount limiter 11 generates a new correction value of the drive amount limit value according to the value of the first enable signal and supplies the correction value to the speed controller 5, thereby limiting the drive amount of the motor 2.

[0044] More specifically, when searching in the direction of increasing the carrier frequency fc according to the specified rules, the drive amount limiter 11 can also adjust the upper limit value of the magnitude of the current (phase current) flowing through the coil of the motor 2 in a direction lower than the previously determined upper limit current value.

[0045] From the standard value of the carrier frequency fc (referred to as the standard carrier frequency fc0) to the lower limit carrier frequency, there is no need to limit the output current of the power converter 7. In contrast, when the carrier frequency fc is increased from the standard value, the switching losses in the power converter 7 increase. Therefore, it is necessary to limit the output current to use the power converter 7. Assuming that in a state where the rated output current is output without limiting the output current of the power converter 7, when the carrier frequency fc is increased from the standard value, the power converter 7 may be damaged. Therefore, in the present embodiment, when the frequency adjustment amount from the standard carrier frequency fc0 to the carrier frequency fc is represented by Δfc, the upper limit value (limit value) of the output current of the power converter 7 is generated according to the ratio (Δfc / fc0), and the upper limit value of the output current of the power converter 7 is adjusted based on this. As a result, the upper limit value of the output current of the power converter 7 can be automatically reduced.

[0046] Refer to Figure 2 An example of the derating of the output current related thereto will be described. Figure 2 It is a diagram for explaining the derating of the output current corresponding to the carrier frequency in the first embodiment.

[0047] In Figure 2 In the shown curve graph, the relationship between the ratio of the carrier frequency (fc) to the standard carrier frequency (fc0) (carrier frequency ratio: horizontal axis) and the ratio of the output current to the standard output current (output current ratio: vertical axis) is shown.

[0048] For example, the output current ratio in the range where the carrier frequency ratio is 100% or less is set to 100%, but when the carrier frequency ratio exceeds 100%, the derating is set to decrease according to the magnitude of the carrier frequency ratio. By setting such derating, the losses of the semiconductor switches constituting the power converter 7 generated when adjusted in the direction of increasing the carrier frequency can be reduced.

[0049] Return Figure 1 Continue the description.

[0050] When the resonance determiner 10 determines that resonance occurs, it supplies the second enable signal to the frequency correction command generator 12. The second enable signal is a signal that activates the frequency search of the frequency correction command generator 12. The frequency correction command generator 12 that receives the second enable signal generates a new correction value of the carrier frequency and supplies it to the power converter 7.

[0051] More specifically, the frequency correction instruction generator 12 can adjust the carrier frequency fc so that the response performance of the motor 2 converges within a range that satisfies a predetermined criterion when searching in the direction of further decreasing the carrier frequency fc.

[0052] The response characteristic determiner 13 infers the response performance (current response) when driving the motor 2 and notifies the frequency correction instruction generator 12 of whether there is a change in the response performance.

[0053] For example, the input to the response characteristic determiner 13 supplies a speed command value, the speed detected by the speed detector 4 of the motor 2, and the detected value (instantaneous value) of the phase current. The response characteristic determiner 13 obtains the response waveform (transient response characteristic) of the phase current relative to the change in the speed command value through transient response analysis based on these. For example, based on the time constant shown by the transient response characteristic of the phase current, the current response performance when driving the motor 2 is inferred. The response characteristic determiner 13 can also compare the above time constant with a reference value. If the deviation is within a specified range, it is determined that the responsiveness has not changed and is allowed. If the deviation is outside the specified range, it is determined that the responsiveness has changed and is not allowed. The frequency correction instruction generator 12 receives this determination result and can obtain a determination result as to whether the current response performance when driving the motor 2 is within the allowable range. Hereinafter, the above processing is sometimes simply referred to as collecting the current response.

[0054] Next, the operation of the vibration suppression control device 30 of the present embodiment will be described.

[0055] The resonance determiner 10 compares the data of the phase current at all supplied frequencies with a certain threshold value T0 common to all frequencies. For example, the resonance determiner 10 determines that no resonance has occurred when the data of the phase current at all frequencies fn is less than the threshold value T0. The motor speed control device 20 maintains the current operation.

[0056] The resonance determiner 10 compares the data of the phase current at each frequency fn with the threshold value Tn set for each frequency fn when the data of the phase current is equal to or greater than the threshold value T0. The frequency fn for which the threshold value is set is set based on the carrier frequency of the power converter 7. For example, this frequency fn is n×(fc±f0). Here, n is a natural number, fc is the carrier frequency, and f0 is the operating frequency of the motor 2.

[0057] Threshold values T1, T2,... are set for f1, f2,... respectively. The threshold values T1, T2,... can be different values, or some or all of them can be the same value. For example, the threshold value Tn is set based on values measured through experiments or the like, values obtained through simulations or the like.

[0058] When the phase current data is above the threshold value Tn at any frequency fn, the resonance determiner 10 supplies an enable signal to the frequency correction command generator 12.

[0059] The frequency correction command generator 12 generates a corrected value of the carrier frequency fc. For example, the value of the carrier frequency fc is obtained from the power converter 7 and multiplied by a preset coefficient α (0 < α < 1) to generate a corrected value of the carrier frequency fc. α is set to 1% (0.01), for example. For example, the frequency correction command generator 12 uses the coefficient α to calculate a new carrier frequency (1 + α) × fc. The calculated new carrier frequency is supplied to the power converter 7. In addition, the frequency correction command generator 12 also supplies the new carrier frequency to the frequency calculator 9 and the resonance determiner 10, and the resonance determiner 10 updates the frequency fn for determination together with the new carrier frequency.

[0060] The power converter 7 updates the value of the carrier frequency to (1 + α) × fc and restarts or continues to operate using the updated carrier frequency.

[0061] The above operation is repeated until the phase current data is below the threshold value at all frequencies n × (fc ± f0).

[0062] It is also possible to preset an upper limit of the carrier frequency that can be updated. In the case where the phase current data is not below the threshold value Tn even when the upper limit value is reached, the carrier frequency is corrected so that the new carrier frequency is decreased in the manner of (1 - α) × fc with respect to the initial value. Furthermore, it is possible to preset a lower limit of the correction value. In the case where the phase current data is not below the threshold value even when the lower limit value is reached, the frequency correction command generator 12 issues an alarm.

[0063] The upper limit value and the lower limit value of the correction range of the carrier frequency are set to, for example, ±5% (±0.05) based on the standard value (center frequency). By setting the upper and lower limits of the correction range of the carrier frequency, it is possible to avoid a decrease in the efficiency of the power converter 7 and an increase in noise generation.

[0064] Next, refer to Figures 3A to 3E The processing related to speed control in the embodiment will be described. Figures 3A to 3E It is a flowchart of the processing related to speed control in the first embodiment.

[0065] As Figure 3A shown, the motor speed control device 20 drives the motor at a constant speed according to each frequency (set operating frequency) corresponding to the speed command value (step S11). Driving the motor at a constant speed means determining a certain target speed for control so as to become the speed based on the speed command value.

[0066] The frequency calculator 9 performs arithmetic processing related to FFT analysis (step S12), and appends the data of the result of the FFT analysis to the storage device. The resonance determiner 10 determines whether the amplitude level shown by the result of the FFT analysis satisfies the determination value (step S13).

[0067] In the case where the amplitude level shown by the result of the FFT analysis in step S13 does not satisfy the determination value, the response characteristic determiner 13 may also collect the current response (step S14). In the case where the result of collecting the current response is not good, the process proceeds to step S30( Figure 3B ).

[0068] When the result of collecting the current response by the resonance determiner 10 is good, it determines whether the carrier frequency fc is the lower limit value (step S15). In the case where the carrier frequency fc is the lower limit value, the process proceeds to step S30( Figure 3B ). On the contrary, in the case where the carrier frequency fc is not the lower limit value, the frequency correction instruction generator 12 adjusts the correction amount in a manner of decreasing from the current carrier frequency (step S16), and performs the process from step S11.

[0069] In the case where the amplitude level shown by the result of the FFT analysis in step S13 satisfies the determination value, the resonance determiner 10 determines whether the carrier frequency has been changed (step S21).

[0070] In the case where the carrier frequency has been changed, the response characteristic determiner 13 collects the current response (step S22).

[0071] The resonance determiner 10 determines whether the difference between the current response at the current carrier frequency fc and the current response at the standard carrier frequency fc0 is within the specified value (step S23). In the case where the difference from the current response is not within the specified value, the process proceeds to step S30( Figure 3B ). On the contrary, in the case where the difference from the current response in step S23 is within the specified value, the frequency correction instruction generator 12 adjusts the correction amount in a manner of increasing from the current carrier frequency fc (step S24), and ends a series of processes.

[0072] Here, refer to Figure 3C A more specific example of the process of adjusting the correction amount in a manner of increasing from the current carrier frequency fc will be described.

[0073] The frequency correction instruction generator 12 adjusts the correction amount in such a way as to increase the frequency by a specified proportional amount of the frequency after the last change (step S241). For example, the above-mentioned specified ratio can be set to (1 / 2) times. The motor speed control device 20 drives the motor at a certain speed according to each set operating frequency (step S242). The frequency calculator 9 performs arithmetic processing related to FFT analysis (step S243). The resonance determiner 10 determines whether the magnitudes of the respective frequency components satisfy the determination value based on the result of the FFT analysis in step S243 (step S244). When the magnitudes of the respective frequency components satisfy the determination value, the processing from step S241 is performed. In contrast, when the magnitudes of the respective frequency components do not satisfy the determination value, a series of processing is ended.

[0074] Refer to Figure 3B Continue to describe the processing related to speed control.

[0075] In the above Figure 3A After the determinations in steps S15 and S23 shown above, and step S41 described later, the frequency correction instruction generator 12 adjusts the correction amount in such a way as to increase the frequency from the standard carrier frequency according to the set ratio (step S30). The motor speed control device 20 drives the motor at a certain speed according to each set operating frequency (step S31). The frequency calculator 9 performs arithmetic processing related to FFT analysis (step S32). The resonance determiner 10 determines whether the magnitudes of the respective frequency components satisfy the determination value based on the result of the FFT analysis in step S32 (step S33). When the magnitudes of the respective frequency components do not satisfy the determination value, the processing proceeds to step S41. In contrast, as a determination result in step S33, when the magnitudes of the respective frequency components satisfy the determination value, the frequency correction instruction generator 12 adjusts the correction amount in such a way as to decrease from the current carrier frequency fc (step S34), and a series of processing is ended.

[0076] Here, refer to Figure 3D A more specific example of the processing of adjusting the correction amount in such a way as to decrease from the current carrier frequency fc will be described.

[0077] The frequency correction instruction generator 12 adjusts the correction amount in such a way as to reduce the frequency by a specified proportional amount from the frequency after the last change (step S341). For example, the above-mentioned specified ratio is set to (1 / 2) times. The motor speed control device 20 drives the motor at a constant speed according to each set operating frequency (step S342). The frequency calculator 9 performs arithmetic processing related to FFT analysis (step S343). The resonance determiner 10 determines whether the magnitude of each frequency component satisfies the determination value based on the result of the FFT analysis in step S343 (step S344). When the magnitude of each frequency component satisfies the determination value, the processing from step S341 is carried out. In contrast, when the magnitude of each frequency component does not satisfy the determination value, a series of processing is ended.

[0078] Refer to Figure 3B Continue to describe the processing related to speed control.

[0079] After the determination in step S33, the resonance determiner 10 determines whether the carrier frequency fc is the upper limit value (step S41). When the carrier frequency fc is not the upper limit value, the processing proceeds to step S30. In contrast, when the carrier frequency fc is the lower limit value, the frequency correction instruction generator 12 adjusts the correction amount in such a way as to change the current carrier frequency to a region lower than the standard value (step S42), and ends a series of processing according to the conditions.

[0080] Here, refer to Figure 3E A more specific example of the processing of changing the current carrier frequency to a region lower than the standard value will be described.

[0081] The resonance determiner 10 selects the frequency with the minimum magnitude of its component from each frequency based on the FFT analysis result (referred to as the selected frequency.) (step S421), and determines whether the selected frequency is lower than the standard carrier frequency (step S422). When the selected frequency is lower than the standard carrier frequency, the response characteristic determiner 13 acquires the current response (step S423). The resonance determiner 10 determines whether the difference between the current response at the selected frequency and the current response at the standard carrier frequency is within the specified value (step S424). When the difference from the current response is not within the specified value, the frequency correction instruction generator 12 deletes the FFT result of the current carrier frequency fc, sets the selected frequency as the new carrier frequency fc, and advances the processing to step S421.

[0082] In the determination in step S422 above, when the selected frequency is lower than the standard carrier frequency, and in the determination in step S424, when the difference from the current response is within the specified value, a series of processing is ended.

[0083] The effects of the motor drive system 1 of this embodiment will be described.

[0084] The motor drive system 1 includes a power converter 7, a state detector, a frequency calculator 9, a frequency correction command generator 12, a drive amount limiter 11, and a speed controller 5. Therefore, based on the limitations under predetermined conditions, it can generate a current reference based on the speed command value and the rotor speed of the motor 2, and drive the motor 2 through PWM control. At this time, the converter 7CT (state detector) detects the drive state of the motor 2. The frequency calculator 9 uses an index value representing the drive state to detect the magnitude of a specific frequency component that varies in relation to the drive state. The frequency correction command generator 12 generates a correction command for the carrier frequency used in PWM control based on the detection result of the periodic variation of the drive state. The drive amount limiter 11 limits the drive amount of the motor. When searching in the direction of increasing the carrier frequency, the drive amount limiter 11 adjusts the upper limit value of the magnitude of the current flowing through the coil of the motor 2 in a direction lower than the predetermined upper limit current value. Thereby, the generation of noise and vibration caused by driving the motor 2 can be suppressed.

[0085] In addition, when searching in the direction of further reducing the carrier frequency, the frequency correction command generator 12 can also adjust the carrier frequency so that the response performance of the motor 2 converges within a range that satisfies a predetermined standard. The above range that satisfies the predetermined standard can also be determined based on the response performance of the motor 2 as a reference. The response performance of the motor 2 can also be specified based on the change amount of the rotor speed of the motor 2 relative to the change amount of the current reference.

[0086] For example, a part of the motor drive system 1 can also be implemented by hardware such as a CPU (Central Processing Unit) that expands a program stored in a storage device or sequentially reads out each step of the program. A part or all of the above-described constituent elements are part of a program executed by the CPU. For example, when the operation of the motor speed control device 20 is implemented by being executed by the CPU, the program of the vibration suppression control device 30 can also be executed by the CPU of the motor speed control device 20.

[0087] The motor drive system 1 can also be implemented by a sequencer (referred to as a PLC (programmable logic controller)). The vibration suppression control device 30 can be implemented as part of the program of the PLC that supplies the speed command value to the motor speed control device 20, or can also be implemented by another PLC.

[0088] By controlling the motor drive system 1 as described above, there is no need to worry about a decrease in control accuracy that may be caused by reducing the carrier frequency. By making the carrier frequency variable to avoid the operating speeds at which the motor 2 generates noise and vibration, it is possible to adjust the avoidance of the operating speeds that need to be avoided based on control without manual adjustment.

[0089] The motor drive system 1 may also notify an external device of the generation status of torque pulsations associated with the noise and vibration of the motor 2.

[0090] Depending on the structure of the motor, etc., even if an attempt is made to adjust in the direction of further reducing the carrier frequency, resonance may sometimes not be avoidable. Even in such a case, through the above control, the motor drive system 1 can adjust in the direction of further increasing the carrier frequency and search for a carrier frequency that satisfies the conditions.

[0091] The change in the carrier frequency affects the response performance of the control system. To avoid this, the motor drive system 1 may also adjust the operation parameters to appropriate values so that the dynamic characteristics of the system can be maintained. When adjusting the operation parameters, the stability and responsiveness of the system can be determined as conditions and set to values that satisfy these conditions. As such an adjustment method, there is no limitation to applying known methods or adaptive control based on the carrier frequency, and an appropriate selection can be made.

[0092] (Second Embodiment)

[0093] The second embodiment will be described.

[0094] As data for determining the presence or absence of resonance in the motor 2, parameters other than the detected value of the phase current detected by the converter 7CT can be applied. For example, in the second embodiment, an example is given of using the magnitude of the AC voltage as the above parameter.

[0095] Figure 4 It is a block diagram illustrating the motor drive system 1A of the second embodiment.

[0096] As Figure 4 shown, the motor drive system 1A of Embodiment 2 uses the detected value of the voltage detected by the instrument transformer 7VT instead of the detected value of the phase current detected by the converter 7CT.

[0097] The motor speed control device 20A and the vibration suppression control device 30A correspond to the above-mentioned motor speed control device 20 and vibration suppression control device 30.

[0098] The motor speed control device 20A includes a power converter 7A instead of the power converter 7 in the motor speed control device 20.

[0099] On the wiring connected to the output of the power converter 7A, an instrument transformer 7VT for detecting the phase voltage is further provided. The instrument transformer 7VT detects the voltage between the wirings of the three-phase AC output (line voltage). The power converter 7A obtains the instantaneous value of the line voltage detected by the instrument transformer 7VT and supplies it to the vibration suppression control device 30A. The instrument transformer 7VT and the power converter 7A are examples of state detectors. In addition, the instrument transformer 7VT may detect the phase voltage instead of the line voltage.

[0100] Based on the data of the instantaneous value of the supplied line voltage, the vibration suppression control device 30A determines whether the motor 2 generates resonance.

[0101] Instead of the frequency calculator 9 of the vibration suppression control device 30, the vibration suppression control device 30A includes a frequency calculator 9A.

[0102] The frequency calculator 9A is connected to the power converter 7A. The frequency calculator 9A converts the data of the line voltage in the time domain detected by the power converter 7A into data in the frequency domain.

[0103] The motor drive system 1A configured as described above can perform speed control in the same order as the above-described motor drive system 1, and can suppress the generation of noise and vibration caused by driving the motor 2 in the same manner as in the first embodiment.

[0104] (Third Embodiment)

[0105] The third embodiment will be described.

[0106] In the third embodiment, an example is illustrated in which the magnitudes of the alternating current and the alternating voltage are used as the above parameters.

[0107] Figure 5 It is a block diagram illustrating the motor drive system 1B of the third embodiment.

[0108] As Figure 5 shown, the motor drive system 1B of the second embodiment also uses the detected value of the voltage detected by the instrument transformer 7VT on the basis of the detected value of the phase current detected by the converter 7CT.

[0109] The motor speed control device 20B and the vibration suppression control device 30B correspond to the above-described motor speed control device 20 and vibration suppression control device 30.

[0110] Instead of the power converter 7 in the motor speed control device 20, the motor speed control device 20B includes a power converter 7B.

[0111] An instrument transformer 7VT for detecting the phase voltage is further provided on the wiring connected to the output of the power converter 7B. The power converter 7B further obtains the instantaneous value of the line-to-line voltage detected by the instrument transformer 7VT, and supplies it together with the instantaneous value of the phase current detected by the current transformer 7CT to the vibration suppression control device 30B. The current transformer 7CT, the instrument transformer 7VT, and the power converter 7A are examples of state detectors.

[0112] Based on the data of the instantaneous value of the supplied phase current and the instantaneous value of the line-to-line voltage, the vibration suppression control device 30B determines whether the motor 2 generates resonance.

[0113] The vibration suppression control device 30B includes a frequency calculator 9B instead of the frequency calculator 9 of the vibration suppression control device 30, and further includes a magnetic flux calculator 14 and a torque calculator 15.

[0114] The magnetic flux calculator 14 is connected to the power converter 7. The magnetic flux calculator 14 obtains the data of the voltage and current output by the power converter 7B from the power converter 7B. For example, this voltage is based on the line-to-line voltage detected by the instrument transformer 7VT. This current is based on the phase current detected by the current transformer 7CT. The magnetic flux calculator 14 calculates the magnetic flux based on the data of the voltage and current output by the power converter 7B and the coil resistance value of the motor 2. The coil resistance value of the motor 2 is preset by actual measurement or the like.

[0115] The torque calculator 15 is connected to the output of the magnetic flux calculator 14. The torque calculator 15 calculates the value of the shaft torque based on the value of the magnetic flux calculated by the magnetic flux calculator 14. The calculated value of the shaft torque is supplied to the frequency calculator 9B. The calculated torque value includes pulsation (torque pulsation) caused by resonance. Thus, speed control can be implemented in the same order as the above-described motor drive system 1, and generation of noise and vibration caused by driving the motor 2 can be suppressed in the same manner as in the first embodiment.

[0116] (First modification of the third embodiment)

[0117] In the above-described third embodiment, an example of using the torque inference value has been described. However, instead of this, in the first modification, the detected value of the torque detected by using a shaft torque detector may be used. The detected value of the above torque includes pulsation (torque pulsation) caused by resonance. The same processing can also be applied to the detected value of the torque.

[0118] (Second modification of the third embodiment)

[0119] In the above-described third embodiment, an example of using the torque inference value has been described. However, instead of this case, the power value based on the above voltage and current may be used in the second modification. The calculated power value includes pulsation (power pulsation) caused by resonance. The same processing can also be applied using the power value.

[0120] According to at least one of the embodiments described above, the motor drive system includes a power converter, a state detector, a frequency calculator, a frequency correction instruction generator, a drive amount limiter, and a speed controller. The power converter drives the motor by PWM control. The state detector detects the drive state of the motor. The frequency calculator uses an index value representing the drive state to detect the magnitude of a specific frequency component that varies in relation to the drive state. The frequency correction instruction generator generates a correction instruction for the carrier frequency for PWM control based on the detection result of the periodic variation of the drive state. The drive amount limiter limits the drive amount of the motor. When searching in the direction of increasing the carrier frequency, the drive amount limiter adjusts the upper limit value of the magnitude of the current flowing in the motor coil in a direction lower than a predetermined upper limit current value. The speed controller generates a current reference based on the speed command value and the rotor speed of the motor according to the limitation. Thus, a motor drive system and a motor drive method capable of suppressing the generation of noise and vibration caused by driving the motor can be achieved.

[0121] As described above, several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof. In addition, the above-described embodiments can be implemented in combination with each other.

[0122] Description of reference symbols

[0123] 1, 1A, 1B: Motor drive system; 2: Motor; 4: Speed detector; 5: Speed controller; 6: Current controller; 7, 7A, 7B: Power converter; 7CT: Converter; 7VT: Instrument transformer; 9, 9A, 9B: Frequency calculator; 10: Resonance determiner; 11: Drive amount limiter; 12: Frequency correction instruction generator; 13: Response characteristic determiner; 14: Flux calculator; 15: Torque calculator; 20, 20A, 20B: Motor speed control device; 30, 30A, 30B: Vibration suppression control device.

Claims

1. (Modified) A motor drive system comprising: A power converter that drives a motor by PWM control; A state detector that detects the driving state of the motor based on the current flowing in the coils of the motor, i.e., the phase current, or based on the phase current and the AC voltage applied to the motor; A frequency calculator that uses an index value representing the driving state to detect the magnitude of a specific frequency component that varies in relation to the driving state; A frequency correction instruction generator that generates a correction instruction for the carrier frequency used in the PWM control in such a way that the carrier frequency becomes a frequency at which the motor does not resonate, based on the detection result of the periodic variation of the driving state; A drive amount limiter that limits the drive amount of the motor; And A speed controller that generates a current reference based on a speed command value and the rotor speed of the motor according to the above limitation, The drive amount limiter, when searching in the direction of increasing the carrier frequency, adjusts the upper limit value of the magnitude of the current flowing in the coils of the motor in a direction lower than a predetermined upper limit current value.

2. (Modified) The motor drive system according to claim 1, wherein The frequency correction instruction generator is When searching in the direction of decreasing the carrier frequency compared to the frequency before adjustment and no appropriate carrier frequency is found within the range of the decrease direction, it searches in the direction of increasing the carrier frequency compared to the frequency before adjustment, When searching in the direction of decreasing the carrier frequency compared to the frequency before adjustment, it adjusts the carrier frequency so that the response performance of the motor converges within a range that satisfies a predetermined criterion.

3. The motor drive system according to claim 2, wherein The range that satisfies the predetermined criterion is determined based on the response performance of the motor as a reference.

4. The motor drive system according to claim 1, wherein The response performance of the motor is defined based on the change amount of the rotor speed of the motor relative to the change amount of the current reference.

5. (Modified) A motor drive method for driving a motor by PWM control, comprising: Detecting the driving state of the motor based on the current flowing in the coils of the motor, i.e., the phase current, or based on the phase current and the AC voltage applied to the motor, Using an index value representing the driving state to detect the magnitude of a specific frequency component that varies in relation to the driving state, Generating a correction instruction for the carrier frequency used in the PWM control in such a way that the carrier frequency becomes a frequency at which the motor does not resonate, based on the detection result of the periodic variation of the driving state, A step of limiting the drive amount of the motor; And A step of adjusting the upper limit value of the magnitude of the current flowing in the coils of the motor in a direction lower than a predetermined upper limit current value when searching in the direction of increasing the carrier frequency.

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