Harmonic suppression method, harmonic extraction method, harmonic extraction system, and related components

Abstract

This application discloses a harmonic suppression method, a harmonic extraction method, a harmonic extraction system, and related components, relating to the field of PWM converters, for processing harmonics. The harmonic extraction method includes: acquiring a grid voltage signal in real time; passing the grid voltage signal through a first bandpass filter for a preset harmonic to obtain a preliminary harmonic corresponding to the preset harmonic; determining the upper and lower envelopes of the preliminary harmonic, and determining a center offset fluctuation curve based on the upper and lower envelopes; subtracting the voltage value of the preliminary harmonic from the voltage value of the center offset fluctuation curve at the same time to obtain the processed harmonic corresponding to the preset harmonic. This application removes the influence of the center offset fluctuation curve from the preliminary harmonic, thereby obtaining a more accurate processed harmonic. This process does not require high accuracy of the preliminary harmonic; therefore, a filter with a faster convergence speed can be selected as the first bandpass filter, so that the processed harmonic simultaneously meets the requirements of both accuracy and convergence speed.

Description

Technical Field

[0001] This invention relates to the field of PWM converters, and in particular to a harmonic suppression method, a harmonic extraction method, a harmonic extraction system, and related components. Background Technology

[0002] Currently, harmonic voltages and currents in the power grid can easily damage electrical equipment. To protect electrical equipment connected to the power grid from harmonic interference, various countries have formulated regulations to limit harmonics. The conventional approach to suppressing harmonics is to detect harmonic signals and then perform compensation control. Bandpass filters can extract specific harmonic voltages in the power grid, and by compensating for these specific harmonic voltages, the impact of harmonic voltages on current can be effectively reduced, thereby improving power grid performance.

[0003] For bandpass filters that extract harmonic voltages, a higher quality factor Q (i.e., a lower bandwidth) results in a stronger ability to extract specific harmonics, but a slower convergence speed. Conversely, a lower quality factor in a bandpass filter leads to faster convergence, but reduces filtering capability and the ability to filter out other frequency signals near the center frequency.

[0004] In practical systems, users expect bandpass filters to have both high harmonic extraction accuracy and fast convergence speed. However, the harmonic extraction capability and convergence speed of bandpass filters are inherently contradictory, resulting in an unsatisfactory harmonic suppression effect.

[0005] Therefore, how to provide a solution to the above-mentioned technical problems is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a harmonic suppression method, a harmonic extraction method, a harmonic extraction system, and related components that simultaneously ensure accuracy and convergence speed. The specific solution is as follows:

[0007] A harmonic extraction method, comprising:

[0008] The grid voltage signal is acquired in real time, and the grid voltage signal is passed through a first bandpass filter of a preset subharmonic to obtain the preliminary harmonic corresponding to the preset subharmonic;

[0009] The upper and lower envelopes of the preliminary harmonics are determined, and the center offset fluctuation curve is determined based on the upper and lower envelopes.

[0010] Subtract the voltage value of the initial harmonic at the same moment from the voltage value corresponding to the center offset fluctuation curve to obtain the processed harmonic corresponding to the preset subharmonic.

[0011] Preferably, the process of determining the upper and lower envelopes of the preliminary harmonics and determining the center offset fluctuation curve based on the upper and lower envelopes specifically includes:

[0012] The voltage value of the upper envelope corresponding to the time interval from the peak of the preliminary harmonic in each cycle to the peak of the next cycle is determined as the voltage value of the peak of the current cycle.

[0013] The voltage value of the lower envelope corresponding to the time period from the trough of the preliminary harmonic in each cycle to the trough of the next cycle is determined as the voltage value of the trough in the current cycle.

[0014] The voltage value of the upper envelope and the voltage value of the lower envelope at the same time are averaged to obtain the voltage value of the center offset fluctuation curve at the same time.

[0015] Preferably, after obtaining the processed harmonic corresponding to the preset subharmonic, the method further includes:

[0016] The processed harmonics are input into a second bandpass filter to obtain smoothed harmonics;

[0017] The smoothed harmonics are then subjected to filter angle compensation.

[0018] Preferably, the process of determining the voltage value of the upper envelope corresponding to the time interval from the peak of the preliminary harmonic in each cycle to the peak of the next cycle as the voltage value of the peak of the current cycle includes:

[0019] The voltage values ​​of all sampling points of the initial harmonic entering the sampling follow-up window are compared using a sampling follow-up window with the current time as the endpoint and a preset time period as the length.

[0020] When there is a maximum value among the voltage values ​​of all the sampling points, and the maximum value is not at the end of the sampling follow window, the maximum value is determined as the voltage value of the peak of the current period, and is used as the voltage value of the upper envelope corresponding to the time period from the peak of the initial harmonic in each period to the peak of the next period.

[0021] Accordingly, the process of determining the voltage value of the lower envelope corresponding to the time interval from the trough of the preliminary harmonic in each cycle to the trough of the next cycle as the voltage value of the trough in the current cycle includes:

[0022] When a minimum value exists among the voltage values ​​of all the sampling points, and the minimum value is not at the end of the sampling follow-up window, the minimum value is determined as the voltage value of the trough of the current cycle, and is used as the voltage value of the lower envelope corresponding to the time period from the trough of each cycle to the trough of the next cycle for the preliminary harmonic.

[0023] Preferably, the process of determining the maximum value as the voltage value of the current period's peak when a maximum value exists among the voltage values ​​of all the sampling points, and the maximum value is not at the end of the sampling follow-up window, includes:

[0024] When there is a maximum value among the voltage values ​​of all the sampling points, and the maximum value is not at the end of the sampling follow-up window, the voltage value of the sampling point is differentiated to obtain a local maximum value, and the local maximum value is determined as the voltage value of the peak of the current period.

[0025] Accordingly, the process of determining the minimum value as the voltage value of the trough of the current period when a minimum value exists among the voltage values ​​of all the sampling points, and the minimum value is not at the end of the sampling follow-up window, includes:

[0026] When a local minimum exists among the voltage values ​​of all the sampling points, and the local minimum is not at the end of the sampling follow-up window, the voltage values ​​of the sampling points are differentiated to obtain a local minimum, and the local minimum is determined as the voltage value of the trough of the current period.

[0027] Preferably, the harmonic extraction method further includes:

[0028] The processed harmonics are then compensated for with a delay angle.

[0029] Accordingly, this application also discloses a harmonic suppression method, including:

[0030] Acquire the grid voltage signal;

[0031] According to any of the harmonic extraction methods described above, determine the processed harmonic of the power grid voltage signal corresponding to the preset subharmonic;

[0032] Voltage compensation is performed on the modulated voltage output by the controller based on the processed harmonics.

[0033] Accordingly, this application also discloses a harmonic extraction system, comprising:

[0034] The preliminary filtering module is used to acquire the grid voltage signal in real time. The grid voltage signal passes through a first bandpass filter with a preset subharmonic to obtain the preliminary harmonic corresponding to the preset subharmonic.

[0035] The calculation module is used to determine the upper and lower envelopes of the preliminary harmonics, and to determine the center offset fluctuation curve based on the upper and lower envelopes.

[0036] The offset removal module is used to subtract the voltage value of the initial harmonic at the same moment from the voltage value corresponding to the center offset fluctuation curve to obtain the processed harmonic corresponding to the preset subharmonic.

[0037] Accordingly, this application also discloses a harmonic extraction device, comprising:

[0038] Memory, used to store computer programs;

[0039] A processor for executing the computer program to implement the steps of the harmonic extraction method as described in any of the above.

[0040] Accordingly, this application also discloses a readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the harmonic extraction method as described in any of the above claims.

[0041] This application discloses a harmonic extraction method, comprising: acquiring a grid voltage signal in real time; passing the grid voltage signal through a first bandpass filter for a preset subharmonic to obtain a preliminary harmonic corresponding to the preset subharmonic; determining the upper and lower envelopes of the preliminary harmonic, and determining a center offset fluctuation curve based on the upper and lower envelopes; subtracting the voltage value of the preliminary harmonic at the same time from the voltage value corresponding to the center offset fluctuation curve to obtain a processed harmonic corresponding to the preset subharmonic. This application uses a first bandpass filter to extract the preliminary harmonic, and then removes the influence of the center offset fluctuation curve from the preliminary harmonic to obtain a more accurate processed harmonic. This process does not require high accuracy of the preliminary harmonic; therefore, a filter with a fast convergence speed can be selected as the first bandpass filter, so that the processed harmonic simultaneously meets the requirements of both accuracy and convergence speed. Attached Figure Description

[0042] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0043] Figure 1 This is a flowchart illustrating the steps of a harmonic extraction method according to an embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the waveform of the preliminary harmonic of the 5th harmonic in an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of the waveform of the preliminary harmonic of the 7th harmonic in an embodiment of the present invention;

[0046] Figure 4 This is a flowchart of the sub-steps of a harmonic extraction method in an embodiment of the present invention;

[0047] Figure 5 This is a waveform diagram of a harmonic extraction method according to an embodiment of the present invention;

[0048] Figure 6 This is a schematic diagram of the smoothed harmonic waveform of the 5th harmonic in an embodiment of the present invention;

[0049] Figure 7 This is a schematic diagram of the waveform of the smoothed harmonic of the 7th harmonic in an embodiment of the present invention;

[0050] Figure 8 This is a schematic flowchart of a harmonic extraction method according to an embodiment of the present invention;

[0051] Figure 9 This is an actual control block diagram of a harmonic suppression method in an embodiment of the present invention;

[0052] Figure 10 This is a waveform comparison diagram of a harmonic suppression method in an embodiment of the present invention;

[0053] Figure 11 This is a structural distribution diagram of a harmonic extraction system according to an embodiment of the present invention. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] In practical systems, users expect bandpass filters to have both high harmonic extraction accuracy and fast convergence speed. However, the harmonic extraction capability and convergence speed of bandpass filters are inherently contradictory, resulting in an unsatisfactory harmonic suppression effect.

[0056] This application uses a first bandpass filter to extract preliminary harmonics, and then removes the influence of the center offset fluctuation curve from the preliminary harmonics to obtain more accurate processed harmonics. This process does not require the accuracy of the preliminary harmonics, so a filter with a faster convergence speed can be selected as the first bandpass filter, so that the processed harmonics can meet the requirements of both accuracy and convergence speed.

[0057] This invention discloses a harmonic extraction method, see [link to relevant documentation]. Figure 1 As shown, it includes:

[0058] S1: Real-time acquisition of grid voltage signal, the grid voltage signal is passed through a first bandpass filter of preset subharmonic to obtain the preliminary harmonic of the corresponding preset subharmonic;

[0059] S2: Determine the upper and lower envelopes of the preliminary harmonics, and determine the center offset fluctuation curve based on the upper and lower envelopes;

[0060] S3: Subtract the voltage value of the initial harmonic at the same moment from the voltage value corresponding to the center offset fluctuation curve to obtain the processed harmonic corresponding to the preset subharmonic.

[0061] It is understood that the grid voltage signal can be obtained by sampling the grid line voltage. Let the three phases of the grid be R phase, S phase and T phase, and the grid voltage signal can be obtained by taking two line voltages Ust and Urs. Each line voltage can be used as an independent grid voltage signal to obtain the processed harmonics corresponding to the preset harmonics of each line voltage by the harmonic extraction method of this embodiment.

[0062] Understandably, harmonic extraction is commonly used to extract the 5th, 7th, and 11th harmonics, but it can also be used to extract harmonics of other orders besides the 5th, 7th, and 11th harmonics. The following simulation test uses the 5th and 7th harmonics as examples. In the test environment, the mains voltage signals are set as two mains voltage signals, Ust and Urs, each containing 5% of the 5th harmonic (19V) and 5% of the 7th harmonic (19V), with an amplitude of 380V. The extraction of the first harmonic can be shown below:

[0063] See Figure 2 As shown, taking the 5th harmonic as a preset subharmonic as an example, a first bandpass filter with a center frequency of 250Hz and a bandwidth of 80Hz is selected. Passing the grid voltage signals Ust and Urs through the first bandpass filter respectively yields the preliminary harmonics Ust-harm5th-Aout and Urs-harm5th-Aout corresponding to the 5th harmonic. Figure 2 The original reference harmonics Ust-harm5th-ref and Urs-harm5th-ref of the 5th harmonic in the power grid voltage signal are also added. It can be seen that the phase difference between the initial harmonic and the original reference harmonic is not large, but the amplitude is offset. Therefore, the center offset fluctuation curve in the initial harmonic is determined by step S2, and removed from the initial harmonic by step S3, so as to obtain a more accurate processed harmonic corresponding to the 5th harmonic.

[0064] Similarly, see Figure 3As shown, taking the 7th harmonic as a preset subharmonic as an example, a first bandpass filter with a center frequency of 350Hz and a bandwidth of 100Hz is selected. Passing the grid voltage signals Ust and Urs through the first bandpass filter respectively yields the preliminary harmonics Ust-harm7th-Aout and Urs-harm7th-Aout corresponding to the 7th harmonic. Figure 3 The original reference harmonics Ust-harm7th-ref and Urs-harm7th-ref of the 7th harmonic in the power grid voltage signal are also added. It can be seen that the phase difference between the initial harmonic and the original reference harmonic is not large, but the amplitude is offset. Therefore, the center offset fluctuation curve in the initial harmonic is determined by step S2, and removed from the initial harmonic by step S3, so as to obtain a more accurate processed harmonic corresponding to the 7th harmonic.

[0065] Furthermore, step S2 involves the upper and lower envelopes of the preliminary harmonics. In the field of electronic information, the line connecting all the peaks of a high-frequency amplitude-modulated signal is the upper envelope, and the line connecting all the troughs is the lower envelope. By averaging the upper and lower envelopes at the same time, the value of the center offset fluctuation curve at that time can be obtained. Therefore, the complete center offset fluctuation curve can be determined based on the complete upper and lower envelopes. However, considering that steps S1-S3 in the harmonic extraction process do not execute all the data of one step before executing the next step, but rather execute steps S1-S3 on the data of the current sampling period, the reference data is incomplete, and it is impossible to obtain an absolutely accurate and complete upper envelope, lower envelope, and center offset fluctuation curve. When only the current sampling period and historical sampling periods are available for reference, the determination of the upper and lower envelopes can be based on the envelope trend at times other than the peak / trough of the initial harmonics, or the trend of the lower envelope can be predicted based on the trend of the upper envelope. If the prediction result is not accurate enough, it may cause the post-processing filtering in step S3 to have an offset. The accuracy of post-processing filtering can be improved by filtering again, angle compensation, etc.

[0066] Understandably, harmonic extraction methods also include:

[0067] Delay angle compensation is applied to the processed harmonics.

[0068] It is understandable that this delay angle compensation is to compensate for the phase angle shift caused by the sampling delay and the transmission delay in the hardware circuit. The specific compensation amount can be obtained through calculation or experimental testing.

[0069] This application discloses a harmonic extraction method, comprising: acquiring a grid voltage signal in real time; passing the grid voltage signal through a first bandpass filter for a preset subharmonic to obtain a preliminary harmonic corresponding to the preset subharmonic; determining the upper and lower envelopes of the preliminary harmonic, and determining a center offset fluctuation curve based on the upper and lower envelopes; subtracting the voltage value of the preliminary harmonic at the same time from the voltage value corresponding to the center offset fluctuation curve to obtain a processed harmonic corresponding to the preset subharmonic. This application uses a first bandpass filter to extract the preliminary harmonic, and then removes the influence of the center offset fluctuation curve from the preliminary harmonic to obtain a more accurate processed harmonic. This process does not require high accuracy of the preliminary harmonic; therefore, a filter with a fast convergence speed can be selected as the first bandpass filter, so that the processed harmonic simultaneously meets the requirements of both accuracy and convergence speed.

[0070] This invention discloses a specific harmonic extraction method. Compared to the previous embodiment, this embodiment further explains and optimizes the technical solution. For details, see... Figure 4 As shown:

[0071] Step S2 involves determining the upper and lower envelopes of the preliminary harmonics and, based on these envelopes, determining the center offset oscillation curve. This process specifically includes:

[0072] S21: The voltage value of the upper envelope corresponding to the time interval from the peak of the initial harmonic in each cycle to the peak of the next cycle is determined as the voltage value of the peak of the current cycle.

[0073] S22: Determine the voltage value of the lower envelope corresponding to the time interval from the trough of the initial harmonic in each cycle to the trough of the next cycle as the voltage value of the trough in the current cycle.

[0074] S23: Calculate the average of the voltage value of the upper envelope and the voltage value of the lower envelope at the same time to obtain the voltage value corresponding to the center offset fluctuation curve at the same time.

[0075] It is understandable that the period of the initial harmonic is not the same as the sampling period. Taking the 5th harmonic of a 50Hz grid voltage signal as an example, its period is 1 / 250 of a second, and there must be a peak and a trough within this period. However, the sampling period of the hardware circuit is much shorter than the period of the initial harmonic. As mentioned above, in the actual harmonic extraction process, only the data of the current sampling period and historical data can be used as references. Therefore, when determining the upper and lower envelopes, over time, for one cycle of the initial harmonic, the initial harmonic is sampled in each sampling period. The data sampled in each sampling period will experience a process of rising, reaching a peak, falling, reaching a trough, rising again, and entering the next cycle. Therefore, based on the data of the current sampling period and the data of the historical sampling periods, it can be determined whether the current data has reached a new peak / trough, and then the upper and lower envelopes are updated. For example, if the current sampling period has not reached the current peak / trough, the sampling period will be adjusted accordingly. At the peak of a harmonic cycle, the voltage value of the upper envelope remains the same as the previous peak. After reaching the peak, the voltage value of the upper envelope is updated. Similarly, when the current sampling period has not reached the trough of the current harmonic cycle, the voltage value of the lower envelope remains the same as the previous trough. After reaching the trough, the voltage value of the lower envelope is updated. From the time axis, this can be seen as follows: for the initial harmonic corresponding to the current sampling period, the voltage value of the peak is set as the voltage value of the upper envelope during the time interval from the peak to the next peak, and the voltage value of the trough is set as the voltage value of the lower envelope during the time interval from the trough to the next trough. At this time, the upper envelope, lower envelope, and center offset fluctuation curve are all stepped waves, such as... Figure 5 As shown, Aout is the initial harmonic, MAX is the upper envelope, MIN is the lower envelope, and X is the center offset oscillation curve.

[0076] Specifically, when determining the peak and trough of the harmonic period, the voltage value of the sampling point can be directly selected, or the curve can be fitted again based on the voltage value of the sampling point to find the derivative or extreme value, thereby obtaining a more accurate peak and trough voltage value.

[0077] Therefore, S21, the process of determining the voltage value of the upper envelope corresponding to the time interval from the peak of the initial harmonic in each cycle to the peak of the next cycle as the voltage value of the peak of the current cycle, includes:

[0078] The voltage values ​​of all sampling points that the initial harmonics enter the sampling follow-up window are compared using a sampling follow-up window with the current time as the endpoint and a preset time period as the length.

[0079] When there is a maximum value among the voltage values ​​of all sampling points, and the maximum value is not at the end of the sampling follow-up window, the maximum value is determined as the voltage value of the peak of the current cycle, and is used as the voltage value of the upper envelope corresponding to the time period from the peak of each cycle to the peak of the next cycle of the preliminary harmonic.

[0080] Accordingly, S22 defines the voltage value of the lower envelope corresponding to the time interval from the trough of the initial harmonic in each cycle to the trough of the next cycle as the voltage value of the trough in the current cycle, including:

[0081] When a minimum value exists among the voltage values ​​of all sampling points, and the minimum value is not at the end of the sampling follow-up window, the minimum value is determined as the voltage value of the trough of the current cycle, and is used as the voltage value of the lower envelope corresponding to the time period from the trough of each cycle to the trough of the next cycle for the preliminary harmonic.

[0082] Understandably, this method directly compares the voltage values ​​at sampling points within the sampling follow-up window and uses these sampling point voltage values ​​directly as the peak or trough voltage values. The minimum length of its sampling follow-up window can be three sampling periods, comparing only the voltage values ​​V at three consecutive sampling points corresponding to these three consecutive sampling periods t1, t2, and t3. t1 V t2 and V t3 This allows us to determine whether a maximum or minimum value exists. Specifically:

[0083] When V t1 <V t2 V t2 >V t3 Then there exists a maximum value and the maximum value is V. t2 ;

[0084] When V t1 >V t2 V t2 <V t3 Then there exists a minimum value and the minimum value is V. t2 ;

[0085] In addition, considering the possibility that the actual local extrema of the initial harmonic may lie between two sampling points, resulting in the two consecutive sampling points being equal, in order to accurately understand the changing trend of the sampling points, the minimum length of the sampling following window can be 4 sampling periods. The voltage values ​​V of the 4 consecutive sampling points corresponding to the 4 consecutive sampling periods t1, t2, t3, and t4 are compared. t1 V t2 V t3 and V t4 If V exists at this time t1 <V t2 And V t3 >V t4 Then there exists a maximum value, and the maximum value is V. t2 and V t3 The larger value between, if V exists t1 >V t2 And V t3 <V t4Then there exists a local minimum, and the local minimum is V. t2 and V t3 The smaller of the two values.

[0086] Furthermore, when it is determined that there is a maximum or minimum value within the current sampling and following window, the voltage values ​​of the sampling points within the sampling and following window can be used again for curve fitting and differentiation to obtain a more accurate local extremum. Specifically:

[0087] The process of determining the maximum value as the voltage peak of the current period when a maximum value exists among all the voltage values ​​sampled, and the maximum value is not at the end of the sampling follow-up window, includes:

[0088] When there is a maximum value among all the voltage values ​​of the sampling points, and the maximum value is not at the end of the sampling follow-up window, the local maximum value is obtained by taking the derivative of the voltage value of the sampling point, and the local maximum value is determined as the voltage value of the peak of the current period.

[0089] Correspondingly, when a minimum value exists among the voltage values ​​of all sampling points, and the minimum value is not at the end of the sampling follow-up window, the process of determining the minimum value as the voltage value of the trough of the current period includes:

[0090] When a local minimum exists among the voltage values ​​of all sampling points, and the local minimum is not at the end of the sampling follow-up window, the voltage values ​​of the sampling points are differentiated to obtain the local minimum, and the local minimum is determined as the voltage value of the trough of the current period.

[0091] It is understandable that step S3 subtracts the voltage value of the initial harmonic at the same moment from the voltage value corresponding to the center offset fluctuation curve to obtain the processed harmonic of the corresponding preset harmonic. Since the center offset fluctuation curve is a stepped wave in this embodiment, the processed harmonic obtained after subtracting the initial harmonic from the center offset fluctuation curve is not smooth enough. Therefore, after obtaining the processed harmonic of the corresponding preset harmonic in step S3, it may also include:

[0092] The processed harmonics are input into the second bandpass filter to obtain smoothed harmonics;

[0093] Filtering angle compensation is applied to smooth harmonics.

[0094] Understandably, the processed harmonics are passed through a second bandpass filter to obtain the smoothed harmonic Bout, for example... Figure 2 The first harmonic corresponding to the 5th harmonic and Figure 3 The first harmonic corresponding to the 7th harmonic, when processed using the method described in this embodiment, will yield the smoothed harmonics Ust-harm5th-Bout and Urs-harm5th-Bout of the 5th harmonic, as shown below. Figure 6As shown, similarly, the smoothed harmonics Ust-harm7th-Bout and Urs-harm7th-Bout of the 7th harmonic are obtained, as follows: Figure 7 As shown, the waveform of the smoothed harmonic is basically close to that of the real harmonic, but there is a partial delay in phase. This delay is caused by the second bandpass filter smoothing the processed harmonic. Therefore, the smoothed harmonic can be compensated by the filtering angle to eliminate this delay. The specific compensation phase amount can be obtained by calculation or experimental testing.

[0095] It is understood that the complete flowchart of the harmonic extraction method in this embodiment can be shown as follows: Figure 8 As shown, Input is the grid voltage signal, filter1 is the first bandpass filter, filter2 is the second bandpass filter, angle compensation 1 is the delay angle compensation, angle compensation 2 is the filter angle compensation, and further angle compensation 1 and angle compensation 2 can be combined into one step. Ucomp is the finally extracted harmonic, which can be applied to various PWM rectifiers or active filter devices such as APF.

[0096] Accordingly, this application also discloses a harmonic suppression method, including:

[0097] Acquire the grid voltage signal;

[0098] According to the harmonic extraction method described in any of the above embodiments, the processed harmonic corresponding to the preset subharmonic of the power grid voltage signal is determined;

[0099] Voltage compensation is performed on the modulated voltage output by the controller based on the processed harmonics.

[0100] It is understood that the specific details regarding the harmonic extraction method can be found in the description of the above embodiments, and will not be repeated here.

[0101] Furthermore, the actual control block diagram of the harmonic suppression method in this embodiment can be referred to... Figure 9 As shown, the grid voltage signal is u u u v and u w Since the harmonic suppression process typically occurs during voltage modulation and is generally situated within the α-β coordinate system, the processed harmonic Ucomp obtained using the harmonic extraction method described in the above embodiment is generally decomposed into u α comp and u β comp, and correspondingly, the modulation voltage output by the controller is u. * α and u * β The process of using the processed harmonics to compensate for the modulated voltage is as follows: Figure 9As shown in the dashed block diagram, this achieves harmonic suppression of the grid-connected voltage.

[0102] In this embodiment, the harmonic suppression method can be used in various PWM methods, such as DPWM and SVPWM.

[0103] The simulation test will still use the 5th and 7th harmonics as examples. In the test environment, the grid voltage signal is set to a three-phase grid voltage signal with an amplitude of 380V, including 5% of the 5th harmonic (19V) and 5% of the 7th harmonic (19V). See [link to relevant documentation]. Figure 10 As shown, the three small figures respectively represent the input voltage without harmonic suppression, the input voltage with harmonic suppression using only a bandpass filter, and the input voltage with harmonic suppression using the method in this embodiment, as well as the harmonic content THDi. It is clear that by using the method in this embodiment, the harmonic content will be further reduced, and the waveform of the grid voltage signal will be more ideal.

[0104] Accordingly, this application also discloses a harmonic extraction system, see [link to relevant documentation]. Figure 11 As shown, it includes:

[0105] The preliminary filtering module 01 is used to acquire the grid voltage signal in real time. The grid voltage signal passes through the first bandpass filter of the preset subharmonic to obtain the preliminary harmonic corresponding to the preset subharmonic.

[0106] Calculation module 02 is used to determine the upper and lower envelopes of the preliminary harmonics, and to determine the center offset fluctuation curve based on the upper and lower envelopes;

[0107] The offset removal module 03 is used to subtract the voltage value of the initial harmonic at the same moment from the voltage value corresponding to the center offset fluctuation curve to obtain the processed harmonic corresponding to the preset subharmonic.

[0108] In this embodiment, a first bandpass filter is used to extract the initial harmonics, and then the influence of the center offset fluctuation curve is removed from the initial harmonics to obtain a more accurate processed harmonics. This process does not require the accuracy of the initial harmonics, so a filter with a faster convergence speed can be selected as the first bandpass filter, so that the processed harmonics can meet the requirements of both accuracy and convergence speed.

[0109] In some specific embodiments, the calculation module 02 is specifically used for:

[0110] The voltage value of the upper envelope corresponding to the time interval from the peak of the preliminary harmonic in each cycle to the peak of the next cycle is determined as the voltage value of the peak of the current cycle.

[0111] The voltage value of the lower envelope corresponding to the time period from the trough of the preliminary harmonic in each cycle to the trough of the next cycle is determined as the voltage value of the trough in the current cycle.

[0112] The voltage value of the upper envelope and the voltage value of the lower envelope at the same time are averaged to obtain the voltage value of the center offset fluctuation curve at the same time.

[0113] In some specific embodiments, after the offset removal module 03 obtains the processed harmonic corresponding to the preset subharmonic, it further includes:

[0114] The processed harmonics are input into a second bandpass filter to obtain smoothed harmonics;

[0115] The smoothed harmonics are then subjected to filter angle compensation.

[0116] In some specific embodiments, the calculation module 02 is specifically used to: compare the voltage values ​​of all sampling points of the preliminary harmonic entering the sampling follow-up window through a sampling follow-up window with the current time as the endpoint and a preset time period as the length;

[0117] When there is a maximum value among the voltage values ​​of all the sampling points, and the maximum value is not at the end of the sampling follow window, the maximum value is determined as the voltage value of the peak of the current period, and is used as the voltage value of the upper envelope corresponding to the time period from the peak of the initial harmonic in each period to the peak of the next period.

[0118] When a minimum value exists among the voltage values ​​of all the sampling points, and the minimum value is not at the end of the sampling follow-up window, the minimum value is determined as the voltage value of the trough of the current cycle, and is used as the voltage value of the lower envelope corresponding to the time period from the trough of each cycle to the trough of the next cycle for the preliminary harmonic.

[0119] In some specific embodiments, the process by which the calculation module 02 determines the voltage value of the peak of the current period when there is a maximum value among the voltage values ​​of all the sampling points, and the maximum value is not at the end of the sampling follow-up window, includes:

[0120] When there is a maximum value among the voltage values ​​of all the sampling points, and the maximum value is not at the end of the sampling follow-up window, the voltage value of the sampling point is differentiated to obtain a local maximum value, and the local maximum value is determined as the voltage value of the peak of the current period.

[0121] Accordingly, the process of determining the minimum value as the voltage value of the trough of the current period when a minimum value exists among the voltage values ​​of all the sampling points, and the minimum value is not at the end of the sampling follow-up window, includes:

[0122] When a local minimum exists among the voltage values ​​of all the sampling points, and the local minimum is not at the end of the sampling follow-up window, the voltage values ​​of the sampling points are differentiated to obtain a local minimum, and the local minimum is determined as the voltage value of the trough of the current period.

[0123] In some specific embodiments, the offset removal module 03 is also used for:

[0124] The processed harmonics are then compensated for with a delay angle.

[0125] Accordingly, this application also discloses a harmonic extraction device, comprising:

[0126] Memory, used to store computer programs;

[0127] A processor for executing the computer program to implement the steps of the harmonic extraction method as described in any of the above.

[0128] Accordingly, this application also discloses a readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the harmonic extraction method as described in any of the above claims.

[0129] The specific details of the harmonic extraction method in this embodiment can be found in the relevant descriptions in the embodiments above, and will not be repeated here.

[0130] In this embodiment, the harmonic extraction device and the readable storage medium have the same technical effects as the harmonic extraction method in the above embodiment, and will not be described again here.

[0131] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0132] The above provides a detailed description of the harmonic suppression method, harmonic extraction method, harmonic extraction system, and related components provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A harmonic extraction method, characterized in that, include: The grid voltage signal is acquired in real time, and the grid voltage signal is passed through a first bandpass filter of a preset subharmonic to obtain the preliminary harmonic corresponding to the preset subharmonic; wherein, a filter with fast convergence speed is selected as the first bandpass filter. By using a sampling follow-up window with the current time as the endpoint and a preset time period as the length, the voltage values ​​of all sampling points of the preliminary harmonic entering the sampling follow-up window are compared to determine the peaks and troughs, thereby determining the upper and lower envelopes of the preliminary harmonic, and determining the center offset fluctuation curve based on the upper and lower envelopes. The voltage value of the initial harmonic at the same time is subtracted from the voltage value corresponding to the center offset fluctuation curve to correct the amplitude offset of the initial harmonic, thereby obtaining the processed harmonic corresponding to the preset subharmonic. The processed harmonic is then input into the second bandpass filter to obtain the smoothed harmonic.

2. The harmonic extraction method according to claim 1, characterized in that, The process of determining the upper and lower envelopes of the preliminary harmonics, and determining the center offset fluctuation curve based on the upper and lower envelopes, specifically includes: The voltage value of the upper envelope corresponding to the time interval from the peak of the preliminary harmonic in each cycle to the peak of the next cycle is determined as the voltage value of the peak of the current cycle. The voltage value of the lower envelope corresponding to the time period from the trough of the preliminary harmonic in each cycle to the trough of the next cycle is determined as the voltage value of the trough in the current cycle. The voltage value of the upper envelope and the voltage value of the lower envelope at the same time are averaged to obtain the voltage value of the center offset fluctuation curve at the same time.

3. The harmonic extraction method according to claim 2, characterized in that, After obtaining the smoothed harmonics, the method further includes: The smoothed harmonics are then subjected to filter angle compensation.

4. The harmonic extraction method according to claim 2, characterized in that, The process of determining the voltage value of the upper envelope corresponding to the time interval from the peak of the preliminary harmonic in each cycle to the peak of the next cycle as the voltage value of the peak of the current cycle includes: The voltage values ​​of all sampling points of the initial harmonic entering the sampling follow-up window are compared using a sampling follow-up window with the current time as the endpoint and a preset time period as the length. When there is a maximum value among the voltage values ​​of all the sampling points, and the maximum value is not at the end of the sampling follow window, the maximum value is determined as the voltage value of the peak of the current period, and is used as the voltage value of the upper envelope corresponding to the time period from the peak of the initial harmonic in each period to the peak of the next period. Accordingly, the process of determining the voltage value of the lower envelope corresponding to the time interval from the trough of the preliminary harmonic in each cycle to the trough of the next cycle as the voltage value of the trough in the current cycle includes: When a minimum value exists among the voltage values ​​of all the sampling points, and the minimum value is not at the end of the sampling follow-up window, the minimum value is determined as the voltage value of the trough of the current cycle, and is used as the voltage value of the lower envelope corresponding to the time period from the trough of each cycle to the trough of the next cycle for the preliminary harmonic.

5. The harmonic extraction method according to claim 4, characterized in that, The process of determining the maximum value as the voltage value of the current period's peak when a maximum value exists among the voltage values ​​of all the sampling points, and the maximum value is not at the end of the sampling follow-up window, includes: When there is a maximum value among the voltage values ​​of all the sampling points, and the maximum value is not at the end of the sampling follow-up window, the voltage value of the sampling point is differentiated to obtain a local maximum value, and the local maximum value is determined as the voltage value of the peak of the current period. Accordingly, the process of determining the minimum value as the voltage value of the trough of the current period when a minimum value exists among the voltage values ​​of all the sampling points, and the minimum value is not at the end of the sampling follow-up window, includes: When a local minimum exists among the voltage values ​​of all the sampling points, and the local minimum is not at the end of the sampling follow-up window, the voltage values ​​of the sampling points are differentiated to obtain a local minimum, and the local minimum is determined as the voltage value of the trough of the current period.

6. The harmonic extraction method according to any one of claims 1 to 5, characterized in that, Also includes: The processed harmonics are then compensated for with a delay angle.

7. A harmonic suppression method, characterized in that, include: Acquire the grid voltage signal; According to any one of claims 1 to 6, the harmonic extraction method determines the processed harmonic of the power grid voltage signal corresponding to the preset subharmonic; Voltage compensation is performed on the modulated voltage output by the controller based on the processed harmonics.

8. A harmonic extraction system, characterized in that, include: A preliminary filtering module is used to acquire the grid voltage signal in real time. The grid voltage signal passes through a first bandpass filter with a preset subharmonic to obtain the preliminary harmonic corresponding to the preset subharmonic. The filter with a fast convergence speed is selected as the first bandpass filter. The calculation module is used to compare the voltage values ​​of all sampling points of the preliminary harmonic entering the sampling follow-up window through a sampling follow-up window with the current time as the endpoint and a length of a preset time period, so as to determine the peak and trough, and then determine the upper envelope and lower envelope of the preliminary harmonic, and determine the center offset fluctuation curve based on the upper envelope and the lower envelope. The offset removal module is used to subtract the voltage value of the initial harmonic at the same moment from the voltage value corresponding to the center offset fluctuation curve in order to correct the amplitude offset of the initial harmonic and obtain the processed harmonic corresponding to the preset subharmonic. The processed harmonic is then input into the second bandpass filter to obtain the smoothed harmonic.

9. A harmonic extraction device, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the steps of the harmonic extraction method as described in any one of claims 1 to 6 when executing the computer program.

10. A readable storage medium, characterized in that, The readable storage medium stores a computer program that, when executed by a processor, implements the steps of the harmonic extraction method as described in any one of claims 1 to 6.

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