Asynchronous motor voltage oscillation correction method and device based on high and low frequency filtering

Abstract

The invention provides an asynchronous motor voltage oscillation correction method and device based on high and low frequency filtering, and relates to the technical field of asynchronous motor voltage oscillation processing, and the method comprises the steps of bus voltage sampling, high-frequency low-pass filtering, low-frequency low-pass filtering, difference calculation, superposition feedback and the like. According to bus voltage fluctuation, the problem of light-load oscillation of the asynchronous motor under VF control can be solved by sampling direct-current bus voltage, utilizing two low-pass filters with different cut-off frequencies and performing subtraction to generate voltage oscillation correction, superposing the voltage oscillation correction to the given voltage under VF control, adjusting the given voltage and maintaining system energy balance, and the method has the advantages that the problem of low-load oscillation of the asynchronous motor under VF control is solved; the method does not need to depend on parameters such as motor resistance and inductance, can avoid a complex parameter adjustment process, and simply and efficiently suppresses oscillation.

Description

Technical Field

[0001] The present invention relates to the technical field of asynchronous motor voltage oscillation processing, and in particular to a method and device for correcting voltage oscillation of an asynchronous motor based on high and low frequency filtering. Background Art

[0002] When unloaded or lightly loaded, asynchronous motors are prone to oscillation in the low- to medium-frequency band (especially around 20Hz) below the V / f open-loop control base frequency, which manifests as continuous current oscillation, which may damage the power module and may also cause torque pulsation and speed fluctuations to damage the machinery. The high-order nonlinearity of the motor, its parameters, inverter dead zone effect, DC bus capacitor quality, and energy exchange imbalance (active / reactive power fluctuations) may all excite oscillations.

[0003] Since the factors that cause oscillation are complex and diverse, in the motor oscillation phenomenon, the power factor angle and current (reactive and active parts) will fluctuate violently. There are several existing solutions for motor oscillation:

[0004] 1. By introducing the differential negative feedback control mechanism of active current into the output current, the output voltage frequency can be accurately controlled, thereby effectively stabilizing the torque. However, in actual application, the parameter adjustment process of this scheme is relatively complicated and may lead to an increase in the harmonic content in the output current.

[0005] 2. By introducing negative feedback to the fluctuation of reactive current, the inverter given voltage is adjusted to suppress motor oscillation. However, this solution is difficult to debug in engineering in actual application and it is not easy to obtain good results.

[0006] 3. Introduce voltage and current dual closed-loop control to keep reactive current constant, but this solution requires debugging multiple sets of voltage loop and current loop parameters and is highly dependent on motor parameters.

[0007] Based on this, the present invention is proposed. Summary of the invention

[0008] The purpose of the present invention is to provide a voltage oscillation correction method and device for an asynchronous motor based on high and low frequency filtering, which can solve the light load oscillation problem of the asynchronous motor under VF control, and has no dependence on motor parameters, avoids complex parameter adjustment process, and realizes oscillation suppression simply and efficiently.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] In a first aspect, the present invention provides a voltage oscillation correction method for an asynchronous motor based on high and low frequency filtering, comprising:

[0011] Bus voltage sampling: real-time sampling to obtain DC bus voltage signal;

[0012] High-frequency low-pass filtering is performed to filter out the noise in the DC bus voltage signal, retain the oscillation component and the DC component, and output a high-frequency filtered signal;

[0013] Low-frequency low-pass filtering is performed to filter out the noise and oscillation component in the DC bus voltage signal, retain the DC component, and output a low-frequency filtered signal;

[0014] Difference calculation is carried out to subtract the output low-frequency filtered signal from the high-frequency filtered signal to obtain a voltage oscillation correction amount;

[0015] Superposition feedback is carried out to superimpose the voltage oscillation correction amount on the given voltage of VF control.

[0016] In a first aspect of the present invention, a preferred solution is provided. Before the superposition feedback step, it further includes: amplitude limiting adjustment, performing amplitude limiting on the voltage oscillation correction amount, and taking the set amplitude for superposition for the voltage oscillation correction amount exceeding the set amplitude; the voltage oscillation correction amount after amplitude limiting adjustment is superimposed on the given voltage of VF control.

[0017] In a first aspect of the present invention, a preferred solution is provided, and the value of the set amplitude is 4% to 6% of the given voltage

[0018] In a first aspect of the present invention, a preferred solution is provided, where the high frequency and low frequency respectively refer to the high cut-off frequency f1 and the low cut-off frequency f2, and f1 >> f2.

[0019] In a first aspect of the present invention, a preferred solution is provided, and the method further includes: inverter output, generating an SVPWM drive signal according to the superimposed voltage, controlling the output of the inverter bridge to drive an asynchronous motor.

[0020] In a second aspect of the present invention, a voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering is provided for performing the above method, including:

[0021] A bus voltage sampler for sampling and obtaining the DC bus voltage signal in real time;

[0022] A high-frequency low-pass filter for filtering out the noise and oscillation component in the DC bus voltage signal, retaining the DC component, and outputting a low-frequency filtered signal;

[0023] A low-frequency low-pass filter for filtering out the noise and oscillation component in the DC bus voltage signal and retaining the DC component;

[0024] A difference calculation module for subtracting the results obtained by the high-frequency low-pass filter and the low-frequency low-pass filter to obtain a voltage correction oscillation amount;

[0025] A superposition feedback module for superimposing the voltage oscillation correction amount on the given voltage of VF control.

[0026] In a second aspect, the present invention provides a preferred solution. The device further includes: a clipping adjustment module for limiting the amplitude of the voltage oscillation correction amount, and taking the set amplitude for the voltage oscillation correction amount exceeding the set amplitude for superposition.

[0027] In a second aspect, the present invention provides a preferred solution. High frequency and low frequency respectively refer to the high cut-off frequency f1 of the high-pass filter and the low cut-off frequency f2 of the low-pass filter, and f1 >> f2.

[0028] In a second aspect, the present invention provides a preferred solution. The high-pass filter and the low-pass filter have the same proportionality coefficient.

[0029] In a second aspect, the present invention provides a preferred solution. The device further includes: an inverter output module for generating an SVPWM drive signal according to the superimposed voltage, controlling the output of the inverter bridge to drive an asynchronous motor.

[0030] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0031] According to the bus voltage fluctuation, the present invention samples the DC bus voltage, uses two low-pass filters with different cut-off frequencies, generates a voltage oscillation correction amount after taking the difference, superimposes the voltage oscillation correction amount on the given voltage of the VF control, adjusts the given voltage, and maintains the system energy balance, which can solve the light-load oscillation problem under the VF control of the asynchronous motor, does not rely on parameters such as the motor resistance and inductance, can avoid the complex parameter adjustment process, and simply and efficiently suppresses the oscillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0033] Figure 1 It is a flowchart of the voltage oscillation correction method for an asynchronous motor based on high and low frequency filtering provided in Embodiment 1 of the present invention;

[0034] Figure 2 It is a block diagram of the voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering provided in Embodiment 1 of the present invention;

[0035] Figure 3 It is a flowchart of the voltage oscillation correction method for an asynchronous motor based on high and low frequency filtering provided in Embodiment 2 of the present invention;

[0036] Figure 4 It is a module diagram of the voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering provided in Embodiment 2 of the present invention;

[0037] Figure 5 It is a signal transmission diagram after the actual application of the voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering provided in Embodiment 2 of the present invention. Specific implementation manners

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Embodiment 1

[0040] Please refer to Figure 1 , in a preferred implementation manner, a voltage oscillation correction method for an asynchronous motor based on high and low frequency filtering is provided, which is mainly implemented through the following steps:

[0041] S10. Bus voltage sampling, and the DC bus voltage signal is sampled in real time;

[0042] S21. High-frequency low-pass filtering, filtering out the noise in the DC bus voltage signal, retaining the oscillation component and the DC component, and outputting a high-frequency filtered signal;

[0043] S22. Low-frequency low-pass filtering, filtering out the noise and oscillation component in the DC bus voltage signal, retaining the DC component, and outputting a low-frequency filtered signal;

[0044] S30. Difference calculation, subtracting the output high-frequency filtered signal from the low-frequency filtered signal to obtain a voltage oscillation correction amount;

[0045] S40. Superposition feedback, superimposing the voltage oscillation correction amount on the given voltage of the VF control.

[0046] Please refer to Figure 2, correspondingly, to implement the above method, this embodiment provides a voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering, which mainly consists of the following devices and modules: a bus voltage sampler 1 for real-time sampling to obtain a DC bus voltage signal; a high-frequency low-pass filter 2 for filtering out noise and oscillation components in the DC bus voltage signal, retaining the DC component, and outputting a low-frequency filtered signal; a low-frequency low-pass filter 2 for filtering out noise and oscillation components in the DC bus voltage signal and retaining the DC component; a difference calculation module 4 for taking the difference between the results obtained by the high-frequency low-pass filter and the low-frequency low-pass filter to obtain a voltage correction oscillation amount; and a superposition feedback module 5 for superimposing the voltage oscillation correction amount on the given voltage of the VF control.

[0047] In this embodiment, high frequency and low frequency respectively refer to the high cut-off frequency f1 of the high-frequency low-pass filter and the low cut-off frequency f2 of the low-frequency low-pass filter, where f1 >> f2. In this embodiment, the low frequency refers to about 100 Hz, and the high frequency is above 1 kHz. The high-frequency low-pass filter and the low-frequency low-pass filter have the same proportionality coefficient and adopt the same Kp for engineering adjustment. By processing the bus voltage signal with two low-pass filters with different cut-off frequencies and taking the difference, the core principle lies in frequency domain separation and energy balance feedback. The specific mechanism is as follows: 1. Division of labor between high and low frequency filters: The high-frequency low-pass filter filters out noise, mainly filtering out high-frequency interferences such as switching noise (such as noise above 1 kHz generated by the inverter switching action), retaining the oscillation component and the DC component. The low-frequency low-pass filter filters out noise and oscillation components and retains the DC component. Subtracting the two results gives the oscillation component. f1 >> f2 (for example, f1 = 10 kHz, f2 = 100 Hz), ensuring that the output signals of the two filters cover different ranges in the frequency domain. 2. The essence of the difference operation: Signal difference: Subtracting the output of the high cut-off filter (including the oscillation component + DC component) from the output of the low cut-off filter (only including the DC component) can separate the oscillation component. Mathematical expression:

[0048] ΔV = V 高频滤波 - V 低频滤波

[0049] where V 高频滤波 includes the oscillation component and the DC component, and V 低频滤波 only contains the DC component. After taking the difference, the DC component is cancelled out, and the pure oscillation component ΔV is obtained.

[0050] In this embodiment, a low-pass filter with a relatively high cut-off frequency is used to filter out the high-frequency noise contained in the bus voltage. Another low-pass filter with a relatively low cut-off frequency can obtain the high-frequency noise and oscillation part in the bus voltage, and it is required that the high cut-off frequency is much higher than the low cut-off frequency. The results obtained by these two filters with the same proportionality coefficient are subtracted from each other to obtain a voltage correction oscillation quantity, which is superimposed on the given voltage of VF to achieve oscillation voltage correction. Briefly speaking, the high-frequency low-pass filter filters out the noise and retains the oscillation component and the DC component. The low-frequency low-pass filter filters out the noise and the oscillation component and retains the DC component. The difference between the two is subtracted to obtain the oscillation component. In short, in this embodiment, the oscillation component is extracted by subtracting the two filters, and the voltage is dynamically adjusted to directly intervene in the energy exchange imbalance process that causes oscillation, so as to achieve efficient and stable oscillation suppression. This method avoids the dependence on motor parameters in the traditional scheme, simplifies the system complexity, and has significant technical advantages.

[0051] Embodiment 2

[0052] Please refer to Figure 3 , in a more preferred embodiment, a method for correcting the voltage oscillation of an asynchronous motor based on high and low frequency filtering is provided, which is mainly implemented through the following steps:

[0053] S10. Sampling the bus voltage to obtain the DC bus voltage signal in real time.

[0054] S21. High-frequency low-pass filtering, filtering out the noise in the DC bus voltage signal, retaining the oscillation component and the DC component, and outputting a high-frequency filtered signal.

[0055] S22. Low-frequency low-pass filtering, filtering out the noise and the oscillation component in the DC bus voltage signal, retaining the DC component, and outputting a low-frequency filtered signal.

[0056] S30. Difference calculation, subtracting the output high-frequency filtered signal from the low-frequency filtered signal to obtain a voltage oscillation correction quantity.

[0057] S31. Limiting adjustment, limiting the amplitude of the voltage oscillation correction quantity, and taking the set amplitude for superposition of the voltage oscillation correction quantity exceeding the set amplitude.

[0058] S41. Superposition feedback, superimposing the voltage oscillation correction quantity after amplitude limiting adjustment on the given voltage of VF control.

[0059] S50. Inverter output, generating an SVPWM drive signal according to the superimposed voltage to control the output of the inverter bridge to drive the asynchronous motor.

[0060] Please refer to Figure 4, correspondingly, to implement the above method, this embodiment provides a voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering, which mainly consists of the following devices and modules: a bus voltage sampler 1 for real-time sampling to obtain a DC bus voltage signal; a high-frequency low-pass filter 2 for filtering out noise and oscillation components in the DC bus voltage signal, retaining the DC component, and outputting a low-frequency filtered signal; a low-frequency low-pass filter 2 for filtering out noise and oscillation components in the DC bus voltage signal and retaining the DC component; a difference calculation module 4 for subtracting the results obtained by the high-frequency low-pass filter and the low-frequency low-pass filter to obtain a voltage correction oscillation amount; a limit adjustment module 6 for limiting the amplitude of the voltage oscillation correction amount, and taking the set amplitude for superposition for the voltage oscillation correction amount exceeding the set amplitude; a superposition feedback module 5 for superimposing the voltage oscillation correction amount after amplitude limit adjustment on the given voltage of VF control; an inverter output module 7 for generating an SVPWM drive signal according to the superimposed voltage to control the output of the inverter bridge to drive the asynchronous motor. Through limit adjustment, the amplitude of the correction amount is limited to avoid overshoot causing system instability. In a preferred embodiment, the value of the set amplitude is 4% to 6% of the given voltage, and 5% is preferred in this embodiment.

[0061] Please refer to Figure 5 , in combination with devices such as an SVPWM signal generator and an inverter bridge, a practical application solution for the oscillation correction method and device of the present invention is given. In the traditional VF control mode, a given reference frequency generates a given voltage through a V / f curve. At the same time, the frequency is integrated through an integrator to generate a voltage vector angle, which is input to the SVPWM signal generator together with the given voltage to generate six-channel pulse signals to drive the inverter (inverter bridge) to make the motor run. Based on the method of the above embodiment of the present invention, the value of the DC bus is sampled by a bus voltage sampler, passed through two filters with different cut-off frequencies respectively, and after output difference and amplitude limit output, it is superimposed on the given voltage.

[0062] In Embodiment 2, after the obtained voltage correction oscillation amount is limited and adjusted on the basis of Embodiment 1 and added to the given voltage of VF, the maximum value of the correction amount is limited to avoid violent fluctuations in the output voltage caused by too large an amplitude of the feedback signal, and prevent the system from entering an overshoot state. At the same time, through the setting of the limit threshold, it is ensured that the correction amount is within the physical range that the motor and the inverter can withstand, avoiding hardware damage or control failure. Moreover, the limit adjustment can filter out abnormal correction amounts caused by high-frequency noise or signal mutations, avoid misoperation, and improve the control accuracy. Retain the dynamic change of the correction amount within the safe amplitude, so that the system can not only quickly respond to oscillation fluctuations, but also will not lag due to excessive adjustment.

[0063] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification. Moreover, the above embodiments only express several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention. For those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A voltage oscillation correction method for an asynchronous motor based on high and low frequency filtering, characterized in that, Including: Bus voltage sampling, which samples in real time to obtain the DC bus voltage signal; High-frequency low-pass filtering, which filters out the noise in the DC bus voltage signal, retains the oscillation component and the DC component, and outputs a high-frequency filtered signal; Low-frequency low-pass filtering, which filters out the noise and oscillation component in the DC bus voltage signal, retains the DC component, and outputs a low-frequency filtered signal; Difference calculation, which subtracts the output high-frequency filtered signal from the low-frequency filtered signal to obtain a voltage oscillation correction amount; Superposition feedback, which superimposes the voltage oscillation correction amount on the given voltage of the VF control.

2. The method for correcting voltage oscillation of an asynchronous motor based on high and low frequency filtering according to claim 1, characterized in that, Before the step of superposition feedback, it further includes: amplitude limiting adjustment, which limits the amplitude of the voltage oscillation correction amount, and takes the set amplitude for superposition for the voltage oscillation correction amount exceeding the set amplitude; the voltage oscillation correction amount after amplitude limiting adjustment is superimposed on the given voltage of the VF control.

3. The voltage oscillation correction method for an asynchronous motor based on high and low frequency filtering according to claim 2, characterized in that, The value of the set amplitude is 4% to 6% of the given voltage.

4. The voltage oscillation correction method for an asynchronous motor based on high and low frequency filtering according to claim 1, characterized in that The high frequency and the low frequency respectively refer to the high cut-off frequency f1 and the low cut-off frequency f2, and f1 >> f2.

5. The voltage oscillation correction method for an asynchronous motor based on high and low frequency filtering according to claim 1, characterized in that, It also includes: Inverter output, which generates an SVPWM drive signal according to the superimposed voltage, controls the output of the inverter bridge to drive an asynchronous motor.

6. A voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering, which is used to execute the method described in any one of the above claims 1-5, and is characterized in that, Including: A bus voltage sampler for sampling in real time to obtain the DC bus voltage signal; A high-frequency low-pass filter for filtering out the noise and oscillation component in the DC bus voltage signal, retaining the DC component, and outputting a low-frequency filtered signal; A low-frequency low-pass filter for filtering out the noise and oscillation component in the DC bus voltage signal, retaining the DC component; A difference calculation module for subtracting the results obtained by the high-frequency low-pass filter and the low-frequency low-pass filter to obtain a voltage correction oscillation amount; A superposition feedback module for superimposing the voltage oscillation correction amount on the given voltage of the VF control.

7. The voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering according to claim 6, characterized in that, It also includes: An amplitude limiting adjustment module for limiting the amplitude of the voltage oscillation correction amount, and taking the set amplitude for superposition for the voltage oscillation correction amount exceeding the set amplitude.

8. The voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering according to claim 6, characterized in that, The high frequency and the low frequency respectively refer to the high cut-off frequency f1 of the high-frequency low-pass filter and the low cut-off frequency f2 of the low-frequency low-pass filter, and f1 >> f2.

9. The voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering according to claim 6, characterized in that The high-frequency low-pass filter and the low-frequency low-pass filter have the same proportional coefficient.

10. The voltage oscillation correction device for an asynchronous motor based on high and low frequency filtering according to claim 6, characterized in that, It also includes: An inverter output module for generating an SVPWM drive signal according to the superimposed voltage, controlling the output of the inverter bridge to drive an asynchronous motor.

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