Filtering method and device, frequency converter and storage medium

Abstract

This invention provides a filtering method, apparatus, frequency converter, and storage medium. The filtering method includes: obtaining a filtering capacitor based on the cable length between the frequency converter and the motor; obtaining a filtering inductor based on the motor's rated parameters; and filtering the voltage signal to be output to the motor using the filtering inductor, the filtering capacitor, and a pulse width modulation waveform determined based on both, to obtain a filtered voltage signal. This invention improves the accuracy of filtering parameter calculation, reduces computational complexity, lowers the waveform distortion rate and phase voltage amplitude of the input voltage signal at the motor end, and reduces harmonics in the voltage signal.

Description

Technical Field

[0001] This invention relates to the field of data processing technology, and in particular to a filtering method, device, frequency converter, and storage medium. Background Technology

[0002] In the process of oilfield development, submersible motors are key equipment, and their performance directly affects oil production efficiency and production costs.

[0003] A frequency converter (VDC) is a power control device that utilizes frequency conversion technology and microelectronics, primarily used to control the speed and output frequency of AC motors. The voltage from the power grid needs to be filtered before being output to the submersible motor. When the VDC outputs a voltage signal, the high-frequency pulse components in the signal are transmitted through the cable between the VDC and the submersible motor. Due to the low-pass filtering effect of the cable on high-frequency signals, the voltage signal waveform is severely distorted during transmission, and reflections and superposition occur at the motor end, causing the peak phase voltage to be much higher than the rated voltage, thus affecting the control of the submersible motor. Therefore, a method that balances accuracy and computational efficiency is urgently needed to achieve long-distance cable filtering and submersible motor control. Summary of the Invention

[0004] In view of this, the present invention proposes a filtering method, device, frequency converter and storage medium, which solves the problems of severe voltage waveform distortion and phase voltage peak value being much higher than the rated voltage value when the voltage signal output by the frequency converter is transmitted to the motor end through the cable.

[0005] On one hand, embodiments of the present invention provide a filtering method, the filtering method comprising: The filter capacitor is obtained by measuring the length of the cable between the frequency converter and the motor. The filter inductance is obtained from the motor's rated parameters; The voltage signal to be output to the motor is filtered by using a filter inductor and a filter capacitor, as well as a pulse width modulation wave determined by the two, to obtain the filtered voltage signal.

[0006] In some implementations, the filter inductance is obtained from the motor's rated parameters, including: The filter inductance is obtained by using the motor's rated frequency and rated voltage from the motor's rated parameters.

[0007] In some implementations, the filter inductor is obtained from the motor's rated frequency and rated voltage in the motor's rated parameters, including: The filter inductance is obtained by using a pre-configured adjustment factor, motor rated frequency, and motor rated voltage.

[0008] In some implementations, the voltage signal to be output to the motor is filtered using a filter inductor and a filter capacitor, along with a pulse width modulation waveform determined by both, to obtain a filtered voltage signal, including: The cutoff frequency is obtained by using the filter inductor, filter capacitor, and motor winding capacitor; Performance evaluation indicators are obtained based on the cutoff frequency and the inverter switching frequency. Based on the performance evaluation indicators, the corresponding pulse width modulation wave is selected, and based on the selected pulse width modulation wave, filter inductor and filter capacitor, the voltage signal to be output to the motor is filtered to obtain the filtered voltage signal.

[0009] In some implementations, the cutoff frequency is obtained through a filter inductor, a filter capacitor, and a motor winding capacitor, including: The cutoff frequency can be obtained using the following formula.

[0010] in, f o Indicates the cutoff frequency. L Indicates the filter inductance. C Indicates the filter capacitor. C o This indicates the capacitance of the motor windings.

[0011] In some implementations, the performance evaluation index is calculated as cutoff frequency / inverter switching frequency.

[0012] In some implementations, the corresponding pulse width modulation wave is selected based on performance evaluation metrics, including: If the performance evaluation index is less than or equal to the first threshold, the first type of pulse width modulation wave is selected.

[0013] In some implementations, the corresponding pulse width modulation wave is selected based on performance evaluation metrics, including: If the first threshold < performance evaluation index ≤ second threshold, then the second type of pulse width modulation wave is selected, where the first threshold < the second threshold.

[0014] In some implementations, the filter inductance is obtained from the motor's rated parameters, including obtaining the filter inductance from the motor's rated parameters and an adjustment factor. The corresponding pulse width modulation wave is selected based on performance evaluation indicators, including: If the performance evaluation index is greater than the second threshold, adjust the adjustment factor and return to the step of obtaining the filter inductance through the motor rated parameters and the adjustment factor.

[0015] In some implementations, the above filtering method further includes: The filtered voltage signal is output to the motor.

[0016] On the other hand, embodiments of the present invention also provide a filtering device, which includes: The filter capacitor calculation unit is configured to calculate the filter capacitor based on the cable length between the inverter and the motor. A filter inductance calculation unit is configured to obtain the filter inductance from the motor's rated parameters. The filtering unit is configured to filter the voltage signal to be output to the motor through a filter inductor and a filter capacitor, as well as a pulse width modulation wave determined by the two, to obtain a filtered voltage signal.

[0017] On the other hand, embodiments of the present invention also provide a frequency converter that includes the filtering device described above.

[0018] On the other hand, embodiments of the present invention also provide a computer storage medium, which stores a computer program that, when executed by a processor, performs the steps of the method described in any of the above embodiments.

[0019] The present invention has at least the following beneficial effects: This invention provides a filtering method, apparatus, frequency converter, and storage medium. The filtering method, apparatus, frequency converter, and storage medium provided by this invention allow the filter capacitor to be obtained using the cable length and cable parameters between the frequency converter and the motor. The filter inductance can be obtained using the motor's rated parameters. Using the obtained filter inductance and filter capacitor, and selecting any pulse width modulation waveform to filter the voltage signal output to the motor, a filtered voltage signal is obtained. This reduces the waveform distortion rate and phase voltage amplitude of the input voltage signal at the motor end, reduces harmonics, lowers computational complexity, and improves the accuracy of the filter parameter calculation. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0021] Figure 1 A flowchart of a filtering method provided in an embodiment of the present invention; Figure 2 A flowchart of a filtering method provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a filtering device provided in an embodiment of the present invention; Figure 4This is a schematic diagram of the structure of a frequency converter provided in an embodiment of the present invention; Figure 5 A schematic diagram of a filtering system provided in an embodiment of the present invention; Figure 6 An equivalent circuit for the cable between a frequency converter and a submersible motor is provided in an embodiment of the present invention; Figure 7 A comparison diagram of the filtering method flow provided in the embodiments of the present invention and the filtering method flow in related technologies; Figure 8 A schematic diagram of the structure of a computer storage medium provided in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0023] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0024] A frequency converter is a power control device that applies frequency conversion technology and microelectronics technology. It is mainly used to control the speed and output frequency of AC motors. The voltage in the power grid needs to be regulated by the frequency converter before it can be output to the submersible motor. When the frequency converter outputs a voltage signal, the high-frequency pulse component of the voltage signal is transmitted in the cable between the frequency converter and the submersible motor. Due to the low-pass filtering effect of the cable on high-frequency signals, the waveform of the voltage signal is severely distorted during transmission, and reflections and superposition occur at the motor end, causing the peak phase voltage to be much higher than the rated voltage value, thus affecting the performance of the submersible motor.

[0025] Extensive theoretical and practical studies have shown that when the cable length exceeds 1km and the inverter switching frequency is higher than 2kHz, the amplitude of the motor terminal phase voltage can reach 1.5 to 2 times the rated voltage. When the motor operates under this phase voltage, it will accelerate the aging of the insulation material in the motor, increase the probability of winding breakdown, and reduce the reliability and lifespan of the motor.

[0026] To improve the waveform distortion and phase voltage amplitude of the voltage signal output by the frequency converter when it reaches the motor, related technologies employ passive filtering, active filtering, digital filtering, and software filtering.

[0027] Passive filtering refers to using passive components such as inductors and capacitors to form filter circuits to filter signals in cables, but the filtering effect is limited. Active filtering involves introducing active devices such as amplifiers in addition to passive components to enhance the filtering effect, but due to the long cable length, the filtering effect still cannot meet the requirements. Digital filtering refers to filtering signals in cables through digital signal processing technology; however, digital filtering requires high computing power and storage space, and its computational efficiency decreases as the motor remains underground for longer periods. Software filtering can be divided into two main categories: classical filtering and modern filtering. Classical filtering is mainly based on Fourier analysis and transform, using circuits or algorithms to selectively allow or attenuate signal frequency components. Modern filtering uses more complex mathematical theories and algorithms, such as Kalman filtering and Wiener filtering, to achieve more precise signal processing. Software filtering has high computational complexity and is time-consuming.

[0028] Among the filtering methods described above, passive and active filtering are not very effective in improving voltage waveforms and phase voltage amplitudes. Digital filtering has low computational efficiency. Software filtering has high computational complexity and is time-consuming.

[0029] In view of this, in order to solve at least one of the above-mentioned technical problems, a first aspect of the present invention provides a filtering method. For example... Figure 1 As shown, the filtering method may include steps S10 to S12.

[0030] S10. The filter capacitor is obtained by measuring the length of the cable between the frequency converter and the motor.

[0031] S11. Obtain the filter inductance through the rated parameters of the motor.

[0032] S12. The voltage signal to be output to the motor is filtered by the filter inductor and filter capacitor and the pulse width modulation wave determined by the two to obtain the filtered voltage signal.

[0033] The pulse width modulation wave can be any one of the following: square wave (PWM wave), sinusoidal pulse width modulation wave (SPWM wave), and space vector pulse width modulation wave (SVPWM wave).

[0034] The voltage signal to be output to the motor refers to the voltage signal that is obtained after the grid voltage is input into the frequency converter and converted by the frequency converter according to the motor's usage requirements.

[0035] In this embodiment of the invention, the filter capacitor can be obtained using the cable length and cable parameters (e.g., cable distributed capacitance) between the frequency converter and the motor. The filter inductor can be obtained using the motor's rated parameters (e.g., rated frequency and rated voltage, or rated current and rated frequency). Using the obtained filter inductor and filter capacitor, and selecting any pulse width modulation waveform to filter the voltage signal to be output to the motor, a filtered voltage signal is obtained. This reduces the waveform distortion rate and phase voltage amplitude of the input voltage signal at the motor end, reduces harmonics, has low computational complexity, and high accuracy in calculating the filter parameters.

[0036] In some embodiments of the present invention, such as Figure 1 In addition to steps S10-S12, the filtering method shown may also include outputting the filtered voltage signal to the motor. This optimizes motor operating efficiency, extends motor lifespan, and improves motor operational stability.

[0037] In some embodiments of the present invention, such as Figure 1 Step S10, as shown, obtaining the filter capacitor based on the cable length between the frequency converter and the motor can be achieved in the following way: The following high-frequency lumped parameter model for the cable is established: C = C O × l (1) in, C This is the total capacitance. C O This refers to the capacitance per unit length of the cable (i.e., the distributed capacitance of the cable). l This refers to the cable length.

[0038] In this embodiment of the invention, by considering the influence of the resistance-capacitance distribution of a unit cable, a simple high-frequency lumped parameter model of the cable is established, and the capacitor parameters for filtering are optimized, thereby providing an accurate basis for subsequent optimization of filtering performance.

[0039] In some embodiments of the present invention, such as Figure 1 Step S11 shown, obtaining the filter inductor through the motor's rated parameters, may include: obtaining the filter inductor through the motor's rated frequency and rated voltage in the motor's rated parameters.

[0040] Specifically, the filter inductance can be obtained using the formulas for inductance, voltage, and power, based on the motor's rated frequency and rated voltage.

[0041] In this embodiment of the invention, the filtering performance is improved by using a filter inductor and an optimized filter capacitor. This reduces the distortion rate of the input voltage waveform at the motor end and the phase voltage amplitude, reduces harmonics, lowers computational complexity, and improves the accuracy of the filter parameter calculation.

[0042] In some embodiments of the present invention, obtaining the filter inductance using the motor's rated frequency and rated voltage from the motor's rated parameters may include: obtaining the filter inductance using a pre-configured adjustment factor, the motor's rated frequency, and the motor's rated voltage.

[0043] Specifically, the filter inductance can be calculated using the following formula: (2) Among them, P n U represents the rated power of the motor. n Here, k represents voltage, k represents adjustment factor, and L represents filter inductance. The value of the adjustment factor can be set empirically.

[0044] By constructing a fast tuning formula for the filter inductor and introducing an adjustment factor to simplify the calculation of the filter inductor, the applicable range of filtering is improved. This overcomes the shortcomings of complex and highly customized correlation filtering methods, reduces computational complexity, and improves the accuracy of filter parameter calculation.

[0045] In one specific implementation, the value of the adjustment factor can be set in the range of 0.1 to 0.5 to optimize the filter inductor. By adjusting the optimized filter inductor and filter capacitor, the filtering performance can be improved, the distortion rate of the input voltage waveform at the motor end and the phase voltage amplitude can be reduced, and harmonics can be reduced.

[0046] In some embodiments of the present invention, such as Figure 1 Step S12, as shown, filters the voltage signal to be output to the motor using a filter inductor, a filter capacitor, and a pulse width modulation wave determined by both, to obtain a filtered voltage signal, which may include, for example... Figure 2 The steps S20~S22 are shown.

[0047] S20. The cutoff frequency is obtained by using the filter inductor, filter capacitor, and motor winding capacitor.

[0048] In one specific implementation, the cutoff frequency can be obtained using the following formula: (3) in, f o Indicates the cutoff frequency. L Indicates the filter inductance. C Indicates the filter capacitor. C oThis indicates the capacitance of the motor windings.

[0049] S21. Performance evaluation indicators are obtained based on the cutoff frequency and the inverter switching frequency.

[0050] In one specific implementation, the performance evaluation index of this invention can be obtained by the following formula: (4) in, η Indicates performance evaluation indicators, f o Indicates the cutoff frequency. f c This indicates the switching frequency of the frequency converter.

[0051] S22. Select the corresponding pulse width modulation wave based on the performance evaluation index, and filter the voltage signal to be output to the motor based on the selected pulse width modulation wave, filter inductor and filter capacitor to obtain the filtered voltage signal.

[0052] Performance evaluation indicators obtained from calculation It can match the corresponding pulse width modulation wave, such as SPWM or SVPWM wave, thereby realizing the intelligent selection of filtering mode and achieving a better balance in suppressing voltage distortion, reducing cost, and reducing electromagnetic interference.

[0053] This invention establishes a simplified high-frequency lumped parameter model for cables based on the influence of cable distributed capacitance to calculate the total capacitance (i.e., filter capacitance). Then, by integrating the motor's rated parameters, a fast tuning formula for the filter inductor is constructed, introducing an adjustment factor to flexibly adapt to different operating conditions. Based on this, a comprehensive performance evaluation index is defined. ,pass Value-based hierarchical criteria are used to achieve multi-objective optimization; finally, by leveraging... The value enables intelligent selection of PWM modulation mode, achieving good results in suppressing voltage distortion, reducing costs, and minimizing electromagnetic interference.

[0054] In one specific implementation, the cutoff frequency is 0.5 to 1.0 times the inverter's switching frequency, and the cable length is 0.5 km to 10 km. The filtering method of this embodiment, when the inverter's filtering cutoff frequency is 0.5 to 1.0 times the inverter's switching frequency and the cable length is 0.5 km to 10 km, can further improve filtering performance, reduce the distortion rate of the motor terminal input voltage waveform and the phase voltage amplitude, and optimize motor performance.

[0055] In some embodiments of the present invention, the present invention is as follows: Figure 2In step S23 of the illustrated embodiment, selecting the corresponding pulse width modulation wave based on the performance evaluation index may include: selecting a first type of pulse width modulation wave when the performance evaluation index is less than or equal to a first threshold.

[0056] In some embodiments of the present invention, the present invention is as follows: Figure 2 In step S23 of the embodiment shown, selecting the corresponding pulse width modulation wave based on the performance evaluation index may further include: selecting a second type of pulse width modulation wave when the first threshold < performance evaluation index ≤ second threshold.

[0057] In this embodiment of the invention, a comprehensive performance evaluation index is defined. η ,pass η The value classification criterion enables multi-objective optimization, thereby achieving intelligent selection of PWM modulation mode, improving filtering performance, reducing voltage waveform distortion rate and phase voltage amplitude when the filtered voltage signal reaches the motor end, and reducing cost and electromagnetic interference while improving filtering performance.

[0058] In some embodiments of the present invention, such as Figure 1 Step S11 shown, obtaining the filter inductance through the motor's rated parameters, may include: obtaining the filter inductance through the motor's rated parameters and the adjustment factor.

[0059] The present invention is as follows Figure 2 In step S23 of the illustrated embodiment, selecting the corresponding pulse width modulation wave based on the performance evaluation index may include: adjusting the adjustment factor when the performance evaluation index is greater than the second threshold, and returning to the step of obtaining the filter inductor through the motor rated parameters and the adjustment factor.

[0060] In this embodiment of the invention, when the performance evaluation index is greater than the second threshold, the value of the adjustment factor is reduced. The performance evaluation index is updated by adjusting the smaller adjustment factor to ensure that the updated performance evaluation index can match the corresponding pulse width modulation wave, thereby improving the filtering performance and reducing the voltage waveform distortion rate and phase voltage amplitude when the filtered voltage signal reaches the motor end.

[0061] In a specific implementation, when η When ≤0.1, select SVPWM modulation; when 0.1 < η When the value is ≤0.2, SPWM modulation is selected. This improves the filtering performance of the frequency converter and reduces the voltage waveform distortion rate and phase voltage amplitude when the filtered voltage signal reaches the motor.

[0062] In one specific implementation, the value of the adjustment factor k can be determined based on the filter performance indicators. η Make a judgment when ηWhen the value converges to 0.1~0.2 and the filter inductance L is as small as possible, the adjustment factor k is better.

[0063] Based on the same inventive concept, according to another aspect of the present invention, embodiments of the present invention also provide a filtering device, such as... Figure 3 As shown, the filter device 30 includes: The filter capacitor calculation unit 31 is configured to obtain the filter capacitor by measuring the cable length between the frequency converter and the motor.

[0064] The filter inductance calculation unit 32 is configured to obtain the filter inductance from the rated parameters of the motor.

[0065] The filtering unit 33 is configured to filter the voltage signal to be output to the motor through the filtering inductor and the filtering capacitor, as well as the pulse width modulation wave determined based on the two, to obtain the filtered voltage signal.

[0066] In this embodiment of the invention, the filter capacitor can be obtained using the cable length and cable parameters between the frequency converter and the motor. The filter inductance can be obtained using the motor's rated parameters. Using the obtained filter inductance and filter capacitor, and selecting any pulse width modulation waveform to filter the voltage signal to be output to the motor, a filtered voltage signal is obtained. Thus, when the filtered voltage signal reaches the motor, the waveform distortion rate and phase voltage amplitude of the voltage signal are reduced.

[0067] Based on the same inventive concept, according to another aspect of the present invention, embodiments of the present invention also provide a frequency converter, such as... Figure 4 As shown, the frequency converter 40 includes the filter device 30 as described above.

[0068] In this embodiment of the invention, the voltage signal to be output to the motor is filtered by a filtering device to obtain a filtered voltage signal. When the filtered voltage signal reaches the motor end, the waveform distortion rate and phase voltage amplitude of the voltage signal are reduced, thereby improving the filtering performance of the frequency converter.

[0069] The frequency converter provided in this embodiment of the invention can be applied to submersible motors.

[0070] In one specific implementation, such as Figure 5 As shown, after the grid voltage is input to the frequency converter, it is regulated and filtered by the frequency converter before being output to the submersible motor.

[0071] Specifically, the frequency converter unit in the inverter is used to regulate the 380V, 50HZ grid voltage into a voltage signal to be input to the submersible motor.

[0072] The filter capacitor calculation unit in the filter device has a high-frequency lumped parameter model of the cable. The high-frequency lumped parameter model of the cable is used to model the electrical parameters, the capacitance distribution of the long cable, and the relationship between the resistance and capacitance values ​​and the unit cable length, so as to simulate the actual underground cable conditions.

[0073] Figure 6 This invention provides an equivalent circuit diagram of the cable between a frequency converter and a submersible motor, as shown in the embodiment of the invention. R in the figure... C L represents the resistance per unit length of the cable. C and C C These represent the inductance and capacitance between the two wires of a unit length of cable, respectively.

[0074] By combining the electrical parameters, capacitance distribution, and resistance distribution in the equivalent circuit with the unit length of the long underground cable, a corresponding high-frequency lumped parameter model of the cable is constructed. This model can more realistically simulate the working conditions of underground equipment and improve the accuracy of the next step of filter parameter optimization.

[0075] Since the cable capacitance has a significant impact on filtering, while other factors have a relatively small impact on filtering, the high-frequency lumped parameter model of the cable based on the equivalent circuit is simplified to obtain the simplified high-frequency lumped parameter model of the cable, as shown in formula (1).

[0076] By adjusting the required filtering parameters of the LC filter unit in real time, problems such as distortion of PWM wave, SVPWM wave or SPWM wave modulation can be resolved in a timely manner.

[0077] The processed voltage waveform is then output to the submersible motor. Figure 6 The arrows indicate the circuit flow and show the information transmission path between units. The entire system achieves a complete closed-loop control from the grid voltage to the submersible motor, effectively solving the impact of the cable on the downhole motor and improving the operating efficiency of the submersible motor.

[0078] Figure 7 A comparison diagram of the filtering method flow provided in the embodiments of the present invention and the filtering method flow in related technologies. Figure 7 The upper part is a flowchart of the filtering method provided in an embodiment of the present invention. Figure 7 The lower half is a flowchart of filtering methods in related technologies.

[0079] like Figure 7 As shown in the lower part, after the grid voltage is connected, the controller is controlled by a single SVPWM strategy after passing through a series LC filter. The values ​​of the capacitor and inductor in the LC filter are set based on experience, which has poor accuracy.

[0080] like Figure 7As shown in the upper part, the filtering method flow provided by the embodiment of the present invention is as follows: 1) After connecting to the power grid, calculate the distributed parameters of the long cable and establish a high-frequency lumped parameter model of the cable based on the distributed parameters of the long cable.

[0081] 2) Introduce adjustment factor k to simplify the calculation formula of filter inductance and improve the filtering applicability of frequency converter.

[0082] 3) Introduce comprehensive performance evaluation indicators η The filter parameter matching is improved through multi-level criteria and closed-loop optimization strategies.

[0083] 4) Incorporate comprehensive performance evaluation indicators η The value is combined with SVPWM and SPWM modulation methods, using The value enables intelligent selection of PWM modulation mode, ultimately achieving control of the submersible motor.

[0084] The embodiments of the present invention will be specifically described below through specific examples.

[0085] The submersible motor has a rated power of 250kW and a rated voltage of 1140V. The inverter has a switching frequency of 4kHz and a dead time of 2μs. The connection between the inverter and the motor is made of 3*95mm wire. 2 A certain type of cable, with an actual length of 1.5km to 4.5km, has an estimated distributed capacitance of 0.02μF to ground for the motor windings. The specific process for controlling the motor input voltage waveform using the filtering method provided in this embodiment is as follows: Step 1: Look up the table to obtain the unit capacitance of a certain type of cable as 0.02μF / km, and substitute it into the high-frequency lumped parameter model of the cable. C = C O × l From this, the filter capacitor can be obtained. C =0.26× l .

[0086] Step 2: Substitute the adjustment factor k and the rated parameters of the motor into formula (2) to obtain the filter inductance L. The optimal value of the adjustment factor k has been proven to be 0.3 through a large number of experiments.

[0087]

[0088] Step 3: When the motor winding capacitance C o =0.02 Then, substitute the filter capacitor obtained in step 1 and the filter inductor obtained in step 2 into formula (3) to obtain the filter cutoff frequency. f o .

[0089] Indicates performance evaluation indicators, f o Indicates the cutoff frequency. f c This indicates the switching frequency of the frequency converter.

[0090] Step 4: When the inverter switching frequency f c When the frequencies are 2.5 kHz and 4 kHz respectively, substitute them into formula (6) to calculate the comprehensive performance index. η .

[0091] The comprehensive performance indicators obtained by using filter design parameters under different cable lengths and switching frequencies η The filtering performance is shown in Table 1.

[0092] Table 1

[0093] As can be seen from Table 1, the smaller... η The higher the value, the stronger the ability to suppress interference from the switching frequency and its harmonics, and the better the filtering performance.

[0094] Table 2 also provides the comprehensive performance indicators and filtering performance under different cable lengths and switching frequencies.

[0095] Table 2

[0096] Through Tables 1 and 2, and extensive analysis and verification, it can be seen that: when η When the value is ≤0.1, the filtering efficiency is optimal, the motor terminal voltage distortion rate (THD) is ≤5%, the overvoltage multiple (VR) is ≤1.1, and the harmonic attenuation (Att) is ≥30dB.

[0097] When 0.1 < η When the value is ≤0.2, the filtering efficiency is second best, the motor terminal voltage distortion rate is 5%<THD≤8%, the overvoltage multiple is 1.1<VR≤1.2, and the harmonic attenuation is 20dB<Att≤30dB.

[0098] when η When the value is greater than 0.2, the filtering efficiency is poor, the motor terminal voltage distortion rate (THD) is greater than 8%, the overvoltage multiple (VR) is greater than 1.2, and the harmonic attenuation (Att) is less than 20dB.

[0099] when η When the value is greater than 0.2, the adjustment factor needs to be adjusted using a recursive algorithm. After adjustment, the factor is recalculated using formulas (2), (3), and (4). η ,until η ≤0.2.

[0100] Step 5: The intelligent selection rule for PWM modulation mode is: when η When ≤0.1, SVPWM modulation is used to improve voltage quality; when 0.1 < η When the voltage is ≤0.2, SPWM modulation is used to improve voltage quality. The motor is then driven by the modulated waveform.

[0101] Table 3 shows the filtering effects obtained by the filtering method based on the embodiments of the present invention, the filtering method based on fixed LC, and the filtering method based on empirically set filtering parameters under different cable lengths and switching frequencies.

[0102] Table 3

[0103] As can be seen from Table 3, under different cable lengths and carrier frequencies, the embodiments of the present invention can achieve a better overall filtering effect than traditional fixed LC filtering and empirical parameter setting methods. THD The average improvement rate exceeded 70%. VR Reduced by more than 30%, Att Increased by more than 1.5 times.

[0104] Based on the same inventive concept, according to another aspect of the present invention, such as Figure 8 As shown, an embodiment of the present invention also provides a computer storage medium 800, which stores a computer program 810 that executes the above method when executed by a processor.

[0105] Finally, it should be noted that those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium for the program can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc. The above computer program embodiments can achieve the same or similar effects as any of the corresponding foregoing method embodiments.

[0106] Those skilled in the art will also understand that the various exemplary logic blocks, modules, circuits, and algorithm steps described in conjunction with the disclosure herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability between hardware and software, the functionality of various illustrative components, blocks, modules, circuits, and steps has been generally described. Whether this functionality is implemented as software or as hardware depends on the specific application and the design constraints imposed on the system as a whole. Those skilled in the art can implement the functionality in various ways for each specific application, but such implementation decisions should not be construed as departing from the scope of the embodiments disclosed herein.

[0107] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. The sequence numbers of the disclosed embodiments of this invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0108] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0109] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A filtering method, characterized in that, include: The filter capacitor is obtained by measuring the length of the cable between the frequency converter and the motor. The filter inductance is obtained from the motor's rated parameters; The voltage signal to be output to the motor is filtered by the filter inductor, the filter capacitor, and the pulse width modulation wave determined by the two, to obtain the filtered voltage signal.

2. The method according to claim 1, characterized in that, The process of obtaining the filter inductor from the motor's rated parameters includes: The filter inductor is obtained from the motor's rated frequency and rated voltage in the motor's rated parameters.

3. The method according to claim 2, characterized in that, The process of obtaining the filter inductor using the motor's rated frequency and rated voltage from the motor's rated parameters includes: The filter inductance is obtained by using a pre-configured adjustment factor, the rated frequency of the motor, and the rated voltage of the motor.

4. The method according to claim 1, characterized in that, The process of filtering the voltage signal to be output to the motor using the filter inductor, the filter capacitor, and the pulse width modulation wave determined by both, to obtain the filtered voltage signal, includes: The cutoff frequency is obtained by using the filter inductor, the filter capacitor, and the motor winding capacitor. Performance evaluation indicators are obtained based on the cutoff frequency and the inverter switching frequency. Based on the performance evaluation indicators, a corresponding pulse width modulation wave is selected, and based on the selected pulse width modulation wave, the filter inductor, and the filter capacitor, the voltage signal to be output to the motor is filtered to obtain the filtered voltage signal.

5. The method according to claim 4, characterized in that, The process of obtaining the cutoff frequency using the filter inductor, the filter capacitor, and the motor winding capacitor includes: The cutoff frequency can be obtained using the following formula. in, f o Indicates the cutoff frequency. L This refers to the filter inductor. C This refers to the filter capacitor. C o This refers to the capacitance of the motor windings.

6. The method according to claim 4, characterized in that, The performance evaluation index = the cutoff frequency / the inverter switching frequency.

7. The method according to claim 4, characterized in that, The step of selecting the corresponding pulse width modulation wave based on the performance evaluation index includes: If the performance evaluation index is less than or equal to the first threshold, the first type of pulse width modulation wave is selected.

8. The method according to claim 7, characterized in that, The step of selecting the corresponding pulse width modulation wave based on the performance evaluation index includes: If the first threshold < the performance evaluation index ≤ the second threshold, then the second type of pulse width modulation wave is selected, where the first threshold < the second threshold.

9. The method according to claim 8, characterized in that, The step of obtaining the filter inductance through the motor's rated parameters includes: obtaining the filter inductance through the motor's rated parameters and an adjustment factor; The step of selecting the corresponding pulse width modulation wave based on the performance evaluation index includes: If the performance evaluation index is greater than the second threshold, adjust the adjustment factor and return to the step of obtaining the filter inductor through the motor rated parameters and the adjustment factor.

10. A filtering device, characterized in that, include: The filter capacitor calculation unit is configured to calculate the filter capacitor based on the cable length between the inverter and the motor. A filter inductance calculation unit is configured to obtain the filter inductance from the motor's rated parameters. The filtering unit is configured to filter the voltage signal to be output to the motor using the filtering inductor and the filtering capacitor, as well as a pulse width modulation wave determined based on the two, to obtain a filtered voltage signal.

11. A frequency converter, characterized in that, Includes the filtering device as described in claim 10.

12. A computer storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it performs the steps of the method as described in any one of claims 1 to 9.

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