Repetitive control method and device for active power filtering device

Abstract

The invention discloses a repetitive control method and device for an active power filtering device, and the method comprises the steps: carrying out the adjustment of the harmonic frequency of a controller according to a harmonic signal obtained from a main circuit of the active power filtering device, calculating the harmonic signal through a harmonic detection module of the adjusted controller, obtaining a fixed delay parameter, and carrying out the calculation of the fixed delay parameter. And calculating according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop to obtain a delay parameter so as to judge whether the harmonic signal needs to be compensated or not, if so, calculating a corresponding compensation parameter according to the delay parameter, and outputting a corresponding compensation current according to the compensation parameter to compensate the harmonic signal. Corresponding parameters of the controller are adjusted according to the harmonic frequency of the harmonic signal, adaptive adjustment of different harmonic scenes is achieved, and adaptability and universality to the different harmonic scenes are improved; through the repetitive control method, repetitive tracking control is carried out on the harmonic signals, and signal delay, storage resource waste and repetitive control operation complexity are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of active power filter current control, and in particular to a repeated control method and device of an active power filter device. Background Art

[0002] Repetitive control is based on the internal model principle and can track or eliminate fundamental frequency and multiple frequency harmonic signals without static error. It is often used in active power filter devices to achieve harmonic control functions. At present, with the high proportion of distributed renewable energy and nonlinear power electronic loads connected to the power system, the harmonic currents in the power system have become complicated, and the grid frequency is prone to fluctuations. Due to parameter limitations, repetitive control cannot adapt to some complex harmonic conditions, and the fixed internal model parameters cannot adapt to frequency changes, which will lead to an increase in the harmonic components of the grid-connected current and the steady-state error. Therefore, in order to ensure high-quality grid-connected current, it is particularly important to design an active power filter control strategy that can adaptively select harmonic frequencies, considering the currents of different harmonic frequencies and the control requirements under variable frequency conditions.

[0003] At present, the existing repetitive control technology can only track harmonic signals of fixed frequency due to the single internal model delay parameter. When tracking complex harmonic signals, it will cause partial delay and waste of memory resources, and the frequency adaptive structure of the repetitive control is relatively complex. The existing technology can realize the tracking of all odd harmonic currents, and the repetitive tracking control technology suitable for the harmonic characteristics of three-phase three-wire systems. Although it has improved the dynamic response capability of the controller, it is not universal for different harmonic scenarios. Summary of the invention

[0004] The present invention provides a repetitive control method and device for an active power filter device, so as to achieve the technical effect of improving the applicability of a repetitive controller to different harmonic scenarios while reducing the complexity of a repetitive control frequency adaptive structure.

[0005] In order to solve the above technical problems, an embodiment of the present invention provides a repetitive control method of an active power filter device, comprising the following steps:

[0006] Acquire a harmonic signal of a main circuit of an active power filter device, and adjust the harmonic frequency of a preset controller according to the harmonic signal;

[0007] The harmonic signal is calculated by the harmonic detection module of the controller to obtain a fixed delay parameter of the controller, a delay parameter is calculated according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop, and then whether the harmonic signal needs to be supplemented is determined according to the delay parameter;

[0008] When it is determined that the harmonic signal needs to be compensated, a compensation parameter is calculated based on the delay parameter, and the compensation parameter is output to the active power filter device through the compensator of the controller, so that the harmonic signal is compensated.

[0009] The repetitive control method provided by the present invention first needs to obtain the harmonic signal of the main circuit of the active power filter device, that is, collect the real-time harmonic signal of the power grid, and adjust the harmonic frequency of the controller, that is, the system, according to the harmonic frequency of the collected harmonic signal, that is, adjust the parameters of the system so that the adjusted system is more in line with the current harmonic frequency, and then realize adaptive adjustment to different harmonic scenarios, thereby improving the adaptability to different harmonic scenarios and the versatility of the repetitive control structure in different harmonic scenarios.

[0010] After the system completes the harmonic frequency adjustment of the controller, the harmonic signal is further analyzed and calculated through the frequency-adjusted controller to obtain the fixed delay parameters of the harmonic signal, providing a data basis for the subsequent calculation of the delay parameters. After determining the fixed delay parameters, the system will also calculate and determine the delay parameters of the collected harmonic signal based on the voltage frequency determined by the grid phase-locked loop and the fixed delay parameters, that is, the reference data for determining whether the harmonic signal needs to be compensated. By comparing the calculated delay parameters, it can be determined whether the collected harmonic signal needs to be compensated, and repeated tracking of the harmonic signal is achieved. At the same time, the calculated delay parameters can also be used as parameter data for the system to repeatedly track and control the harmonic signal.

[0011] When it is determined that the harmonic signal needs to be compensated, the compensation parameter is determined according to the delay parameter calculation, and the active power filter device is compensated according to the compensation parameter, that is, the harmonic signal is compensated by the compensation current output by the compensation parameter. The controller that adaptively adjusts the harmonic frequency repeatedly tracks and controls the harmonic signals of different frequencies, thereby reducing the delay of the harmonic signal and the waste of storage resources. At the same time, the repeated tracking and control of the harmonic signal is realized by the above method, and the operation complexity is also reduced compared with the prior art.

[0012] As a preferred example, adjusting the harmonic frequency of the preset controller according to the harmonic signal includes:

[0013] The harmonic signal is analyzed to obtain the original harmonic frequency corresponding to the harmonic signal, and the pole parameters of the open-loop transfer function of the controller are adjusted according to the original harmonic frequency so that the frequency response of the adjusted controller matches the original harmonic frequency.

[0014] By adjusting the pole value of the open-loop transfer function of the controller, the harmonic frequency of the controller is adjusted, and then the adjusted controller is more consistent with the harmonic signal frequency collected from the main circuit of the active power filter device, so as to achieve zero-error tracking of the original harmonic signal. According to the target frequency of the collected harmonic signal, the pole value of the open-loop transfer function of the controller is adjusted accordingly, and the tracking control of different target harmonics can be achieved, which improves the versatility and adaptability of the controller in different harmonic scenarios, and at the same time, the stability of the adjusted controller in the system is also improved.

[0015] The controller after adjusting the pole value has higher adaptability to the original harmonic signal, realizes zero-static-error tracking of the harmonic signal, reduces the delay of the harmonic signal and the waste of storage resources, and improves the space utilization of the controller and the repeated tracking control effect.

[0016] As a preferred example, the harmonic detection module of the controller calculates the harmonic signal to obtain a fixed delay parameter of the controller, including:

[0017] The harmonic signal is analyzed and extracted by the harmonic detection module to obtain a discretized signal, and the discretized signal is fractionally processed according to the open-loop transfer function of the controller to obtain the fixed delay parameter.

[0018] Since in actual application, the controller performs repeated tracking control of harmonic signals in digital form, the system will first discretize the harmonic signals when calculating the harmonic signals, so as to obtain the harmonic signals in digital form, and then determine the digital implementation of the harmonic signal delay link. Therefore, the system processes the discretized signals through the open-loop transfer function of the controller to obtain the repeated control transfer function under discrete conditions, and thereby determine the fixed delay parameters of the controller, providing data support for the subsequent calculation of the delay parameters of the harmonic signals.

[0019] As a preferred example, the delay parameter is calculated based on the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop, including:

[0020] Performing phase-locking processing on the active power filter device through the grid phase-locked loop to obtain grid frequency information, and parsing the grid frequency information to obtain the voltage frequency;

[0021] The fixed delay parameter and the voltage frequency are calculated by a preset fractional-order algorithm to obtain a fractional-order delay parameter, and the fractional-order delay parameter is output as the delay parameter.

[0022] The system analyzes the voltage frequency information output by the power grid phase-locked loop to obtain the voltage frequency, and then calculates the voltage frequency and fixed delay parameters through a fractional-order algorithm to obtain the delay parameters of the corresponding harmonic signal. The calculation process of the delay parameters is simplified by calculating the delay parameters through a fractional-order algorithm, the calculation efficiency of the delay parameters is improved, and the calculation burden of the digital system is reduced.

[0023] As a preferred example, judging whether the harmonic signal needs to be supplemented according to the delay parameter includes:

[0024] Comparing the delay parameter with a preset delay threshold to obtain a comparison result;

[0025] If the comparison result is that the delay parameter is greater than or less than the delay threshold, it is determined that the harmonic signal needs to be compensated;

[0026] If the comparison result is that the delay parameter is equal to the delay threshold, it is determined that the harmonic signal does not need to be compensated.

[0027] After the system calculates the delay parameter of the harmonic signal, it compares it with the preset delay threshold and determines whether the harmonic signal needs to be compensated based on the comparison result. That is, based on the comparison result between the delay parameter and the delay threshold, it determines whether the harmonic signal has a delay problem and needs compensation current for compensation.

[0028] According to the comparison results, the harmonic signal does not need to be compensated only when the delay parameter is equal to the delay threshold. Regardless of whether the delay parameter is greater than or less than the delay threshold, that is, when the harmonic signal is not equal to the delay threshold, it means that the harmonic signal needs to be compensated. That is, the system needs to calculate and output the corresponding compensation current according to the delay parameter to compensate for the harmonic signal, so as to achieve harmonic control of different harmonic frequencies.

[0029] Correspondingly, an embodiment of the present invention further provides a repetitive control device for an active power filter device, the repetitive control device comprising a harmonic signal acquisition module, a signal delay judgment module and a compensation signal output module; wherein:

[0030] The harmonic signal acquisition module is used to acquire the harmonic signal of the main circuit of the active power filter device and adjust the harmonic frequency of the preset controller according to the harmonic signal;

[0031] The signal delay judgment module is used to calculate the harmonic signal through the harmonic detection module of the controller to obtain the fixed delay parameter of the controller, calculate the delay parameter according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop, and then judge whether the harmonic signal needs to be supplemented according to the delay parameter;

[0032] The compensation signal output module is used to calculate the compensation parameter according to the delay parameter when it is determined that the harmonic signal needs to be supplemented, and output the compensation parameter to the active power filter device through the compensator of the controller, so that the harmonic signal is compensated.

[0033] As a preferred example, the harmonic signal acquisition module adjusts the harmonic frequency of the preset controller according to the harmonic signal, including:

[0034] The harmonic signal is analyzed to obtain the original harmonic frequency corresponding to the harmonic signal, and the pole parameters of the open-loop transfer function of the controller are adjusted according to the original harmonic frequency so that the frequency response of the adjusted controller matches the original harmonic frequency.

[0035] As a preferred example, the signal delay determination module calculates the harmonic signal through the harmonic detection module of the controller to obtain the fixed delay parameter of the controller, including:

[0036] The harmonic signal is analyzed and extracted by the harmonic detection module to obtain a discretized signal, and the discretized signal is fractionally processed according to the open-loop transfer function of the controller to obtain the fixed delay parameter.

[0037] As a preferred example, the signal delay judgment module calculates the delay parameter according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop, including:

[0038] Performing phase-locking processing on the active power filter device through the grid phase-locked loop to obtain grid frequency information, and parsing the grid frequency information to obtain the voltage frequency;

[0039] The fixed delay parameter and the voltage frequency are calculated by a preset fractional-order algorithm to obtain a fractional-order delay parameter, and the fractional-order delay parameter is output as the delay parameter.

[0040] As a preferred example, the signal delay judgment module judges whether the harmonic signal needs to be supplemented according to the delay parameter, including:

[0041] Comparing the delay parameter with a preset delay threshold to obtain a comparison result;

[0042] If the comparison result is that the delay parameter is greater than or less than the delay threshold, it is determined that the harmonic signal needs to be compensated;

[0043] If the comparison result is that the delay parameter is equal to the delay threshold, it is determined that the harmonic signal does not need to be compensated. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 : A flow chart of an embodiment of a repetitive control method of an active power filter device provided by the present invention;

[0045] Figure 2 : A structural diagram of an embodiment of a repetitive control device for an active power filter device provided by the present invention;

[0046] Figure 3 : A flow chart of the frequency adaptive operation process of the controller provided by the present invention;

[0047] Figure 4 : A structural diagram of a repetitive control structure with selectable harmonic frequency provided by the present invention;

[0048] Figure 5 : A structural diagram of a digital implementation method for repetitive control of selectable harmonic frequencies provided by the present invention;

[0049] Figure 6 : A structural diagram of the Newton fractional order approximate structure provided by the present invention;

[0050] Figure 7 : An overall structural diagram of the adaptive repetitive control process with selectable harmonic frequency provided by the present invention;

[0051] Figure 8 : A schematic structural diagram of a three-phase active power filter control system model provided by the present invention;

[0052] Fig. 9 : A three-phase current and harmonic spectrum diagram of the SRC control strategy under 49.5 Hz working condition provided by the present invention;

[0053] Fig.10 : The three-phase current and harmonic spectrum diagram of the FA-SRC control strategy under 49.5Hz working condition provided by the present invention;

[0054] Fig.11 : A three-phase current and harmonic spectrum diagram of the SRC control strategy under 50.5 Hz working condition provided by the present invention;

[0055] Fig.12 : The three-phase current and harmonic spectrum diagram of the FA-SRC control strategy under 50.5Hz working condition provided by the present invention. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] Embodiment 1

[0058] Please refer to Figure 1 , a flowchart of an embodiment of a repetitive control method of an active power filter device is provided, comprising steps 101 to 103, each of which is specifically as follows:

[0059] Step 101: obtaining a harmonic signal of a main circuit of an active power filter device, and adjusting the harmonic frequency of a preset controller according to the harmonic signal.

[0060] The repetitive control method provided in the embodiment of the present invention first needs to obtain the harmonic signal of the main circuit of the active power filter device, that is, collect the real-time harmonic signal of the power grid, and adjust the harmonic frequency of the controller, that is, the system, according to the harmonic frequency of the collected harmonic signal, that is, adjust the parameters of the system so that the adjusted system is more in line with the current harmonic frequency, and then realize adaptive adjustment to different harmonic scenarios, thereby improving the adaptability to different harmonic scenarios and the versatility of the repetitive control structure in different harmonic scenarios.

[0061] In this embodiment, adjusting the harmonic frequency of the preset controller according to the harmonic signal includes:

[0062] The harmonic signal is analyzed to obtain the original harmonic frequency corresponding to the harmonic signal, and the pole parameters of the open-loop transfer function of the controller are adjusted according to the original harmonic frequency so that the frequency response of the adjusted controller matches the original harmonic frequency.

[0063] By adjusting the pole value of the open-loop transfer function of the controller, the harmonic frequency of the controller is adjusted, and then the adjusted controller is more consistent with the harmonic signal frequency collected from the main circuit of the active power filter device, so as to achieve zero-error tracking of the original harmonic signal. According to the target frequency of the collected harmonic signal, the pole value of the open-loop transfer function of the controller is adjusted accordingly, and the tracking control of different target harmonics can be achieved, which improves the versatility and adaptability of the controller in different harmonic scenarios, and at the same time, the stability of the adjusted controller in the system is also improved.

[0064] The controller after adjusting the pole value has higher adaptability to the original harmonic signal, realizes zero-static-error tracking of the harmonic signal, reduces the delay of the harmonic signal and the waste of storage resources, and improves the space utilization of the controller and the repeated tracking control effect.

[0065] Step 102: The harmonic signal is calculated by the harmonic detection module of the controller to obtain a fixed delay parameter of the controller, a delay parameter is calculated based on the fixed delay parameter and the voltage frequency output by the grid phase-locked loop, and then whether the harmonic signal needs to be supplemented is determined based on the delay parameter.

[0066] After the system completes the harmonic frequency adjustment of the controller, the harmonic signal is further analyzed and calculated through the frequency-adjusted controller to obtain the fixed delay parameters of the harmonic signal, providing a data basis for the subsequent calculation of the delay parameters. After determining the fixed delay parameters, the system will also calculate and determine the delay parameters of the collected harmonic signal based on the voltage frequency determined by the grid phase-locked loop and the fixed delay parameters, that is, the reference data for determining whether the harmonic signal needs to be compensated. By comparing the calculated delay parameters, it can be determined whether the collected harmonic signal needs to be compensated, and repeated tracking of the harmonic signal is achieved. At the same time, the calculated delay parameters can also be used as parameter data for the system to repeatedly track and control the harmonic signal.

[0067] Specifically, in this embodiment, the harmonic detection module of the controller calculates the harmonic signal to obtain the fixed delay parameter of the controller, including:

[0068] The harmonic signal is analyzed and extracted by the harmonic detection module to obtain a discretized signal, and the discretized signal is fractionally processed according to the open-loop transfer function of the controller to obtain the fixed delay parameter.

[0069] Since in actual application, the controller performs repeated tracking control of harmonic signals in digital form, the system will first discretize the harmonic signals when calculating the harmonic signals, so as to obtain the harmonic signals in digital form, and then determine the digital implementation of the harmonic signal delay link. Therefore, the system processes the discretized signals through the open-loop transfer function of the controller to obtain the repeated control transfer function under discrete conditions, and thereby determine the fixed delay parameters of the controller, providing data support for the subsequent calculation of the delay parameters of the harmonic signals.

[0070] Specifically, the method of calculating and obtaining the delay parameter according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop in this embodiment includes:

[0071] Performing phase-locking processing on the active power filter device through the grid phase-locked loop to obtain grid frequency information, and parsing the grid frequency information to obtain the voltage frequency;

[0072] The fixed delay parameter and the voltage frequency are calculated by a preset fractional-order algorithm to obtain a fractional-order delay parameter, and the fractional-order delay parameter is output as the delay parameter.

[0073] The system analyzes the voltage frequency information output by the power grid phase-locked loop to obtain the voltage frequency, and then calculates the voltage frequency and fixed delay parameters through a fractional-order algorithm to obtain the delay parameters of the corresponding harmonic signal. The calculation process of the delay parameters is simplified by calculating the delay parameters through a fractional-order algorithm, the calculation efficiency of the delay parameters is improved, and the calculation burden of the digital system is reduced.

[0074] Furthermore, the step of judging whether the harmonic signal needs to be supplemented according to the delay parameter in this embodiment includes:

[0075] Comparing the delay parameter with a preset delay threshold to obtain a comparison result;

[0076] If the comparison result is that the delay parameter is greater than or less than the delay threshold, it is determined that the harmonic signal needs to be compensated;

[0077] If the comparison result is that the delay parameter is equal to the delay threshold, it is determined that the harmonic signal does not need to be compensated.

[0078] After the system calculates the delay parameter of the harmonic signal, it compares it with the preset delay threshold and determines whether the harmonic signal needs to be compensated based on the comparison result. That is, based on the comparison result between the delay parameter and the delay threshold, it determines whether the harmonic signal has a delay problem and needs compensation current for compensation.

[0079] According to the comparison results, the harmonic signal does not need to be compensated only when the delay parameter is equal to the delay threshold. Regardless of whether the delay parameter is greater than or less than the delay threshold, that is, when the harmonic signal is not equal to the delay threshold, it means that the harmonic signal needs to be compensated. That is, the system needs to calculate and output the corresponding compensation current according to the delay parameter to compensate for the harmonic signal, so as to achieve harmonic control of different harmonic frequencies.

[0080] Step 103: When it is determined that the harmonic signal needs to be supplemented, a compensation parameter is calculated according to the delay parameter, and the compensation parameter is output to the active power filter device through the compensator of the controller, so that the harmonic signal is compensated.

[0081] When it is determined that the harmonic signal needs to be compensated, the compensation parameter is determined according to the delay parameter calculation, and the active power filter device is compensated according to the compensation parameter, that is, the harmonic signal is compensated by the compensation current output by the compensation parameter. The controller that adaptively adjusts the harmonic frequency repeatedly tracks and controls the harmonic signals of different frequencies, thereby reducing the delay of the harmonic signal and the waste of storage resources. At the same time, the repeated tracking and control of the harmonic signal is realized by the above method, and the operation complexity is also reduced compared with the prior art.

[0082] Embodiment 2

[0083] As a specific example of the repetitive control method provided in Example 1, see Figure 3 , Figure 3 This is a flow chart of the controller frequency adaptive operation process provided by the second embodiment of the present invention. Figure 3 As shown, Figure 3 The controller frequency adaptive operation process provided specifically includes:

[0084] First, based on the highest possible frequency in the power grid, the system will calculate the corresponding minimum fixed integer delay parameter, namely N i =f s / f max The higher the frequency, the smaller the corresponding integer delay parameter. If the calculated fixed integer delay parameter is a decimal, the system will round down to obtain the corresponding fixed integer delay parameter.

[0085] Secondly, the fractional-order delay parameter d is calculated based on the grid frequency information obtained by the grid phase-locked loop, that is, the delay parameter described in Example 1, and the delay threshold is compared with the calculated fractional-order delay parameter, that is, whether d ≥ 0 is established. If it is determined that d is not equal to 0, d is digitally processed, that is, Figure 3 As shown, the parameter d is retained to two decimal places and is inverted, that is, it is converted to the corresponding d N .

[0086] Finally, according to d N The parameters are fed back to the Newton fractional-order approximation structure to realize the whole process of adaptive frequency adjustment.

[0087] Figure 3 The whole process of frequency adaptive adjustment shown is a simplified process of the controller frequency adaptive digital implementation process. At the same time, this embodiment also provides a simplified specific process for the simplified process. The simplified process is as follows:

[0088] In the first step, the system needs to build a repetitive control structure that can select harmonic frequencies. The structure is as follows: Figure 4 As shown, Figure 4The structure diagram of the repetitive control structure with selectable harmonic frequency provided by the present invention. Figure 4 , which is the same as step 101 in the first embodiment, the system will adjust the poles of the open-loop transfer function of the repetitive control to s=j(nk+p)ω according to the internal model principle of the repetitive control, where n and p are integers and n is not zero. The new controller constructed by adjusting the poles can generate high gain at the nk+pth harmonic frequency point, and thus can achieve tracking of the nk+pth harmonic without static error. The open-loop transfer function of the correspondingly adjusted controller can be expressed as:

[0089]

[0090] Among them, e -sT / n is the controller delay link, which is used to track the nkth harmonic signal; T is the fundamental frequency period, and the input signal is converted into the output signal after the period T / n. The choice of n determines the dynamic response capability of the controller; e jpωT / n is a complex gain that allows the selection of a pth harmonic signal to change the frequency response of the controller, where 0≤p<n-1.

[0091] The controller after the pole adjustment is a repetitive controller with selectable harmonic frequency. It can realize tracking control of different target harmonics by changing the n and p parameter values ​​according to the harmonic working conditions in the actual power grid system. For example, when n=6 and p=1, the 6k+1 positive-sequence odd-order harmonic component can be tracked; when n=6 and p=-1, the 6k-1 negative-sequence odd-order harmonic component can be tracked; when n=2 and p=0, the 2k even-order harmonic component can be tracked.

[0092] In addition, when the harmonic working conditions are complex, the system can connect multiple repetitive controllers with selectable harmonic frequencies in parallel to achieve simultaneous tracking of positive and negative sequence harmonics or harmonics of different periods. Figure 4 As shown, ko, k1 and ki are the gains of the parallel controller. In order to ensure the stability of the system, ko, k1 and ki need to meet the following conditions: k0+k1+…+k i =1.

[0093] In the second step, since the above controller is usually executed in digital form in practical applications, the digital implementation of the delay link in the controller needs to be discretized as described in step 102 of the first embodiment. The specific discretization formula is e -sT / n =Z -N / n , where N is the sampling point in the discrete domain, and the calculation formula is N = T / T s , Ts is the sampling period of the system.

[0094] The digital realization of the complex gain link requires converting the complex power into a complex operation according to Euler's formula, that is, e-jpωT / n =e -j2πp / n =cos(2πp / n)-jsin(2πp / n), the calculation burden of the digital system can be reduced by pre-calculating the trigonometric function value. In order to improve the steady-state accuracy and robustness of the controller, this embodiment will add a low-pass filter Q(z) in the internal model feedback branch, and its specific expression is Q(z)=0.25z -1 +0.5+0.25z. Based on the GSRC(s) transfer function form in the first step and combined with the above discretization expression, the expression of the repetitive control transfer function with selectable harmonic frequency under discrete conditions can be obtained as follows:

[0095]

[0096] For the vector operation of the above transfer function, the system will use Clark transformation to construct the vector signal corresponding to the input signal, that is, transform the three-phase grid signal into two-phase orthogonal signals of α and β axes. The transformation expression is as follows:

[0097]

[0098] In the αβ coordinate system, the β axis leads the α axis by 90 degrees, so the complex number j on the α axis can be represented by the β axis, and similarly the complex number on the β axis can also be represented by the α axis, which can further realize the vector operation of the transfer function.

[0099] See Figure 5 , Figure 5 The structure diagram of the digital implementation method of the repetitive control of the selectable harmonic frequency provided by the present invention. Figure 5 As shown in the figure, the overall digital implementation of the repetitive control of the selectable harmonic frequency occupies 4N / n system memory space and the dynamic response time is T / n. Through coordinate transformation and vector operation, the controller only needs two controllers in the three-phase system to track the harmonic signal. Therefore, the selection of harmonic characteristics will make the controller occupy less memory space, have faster dynamic response capabilities, and be universal under complex harmonic conditions.

[0100] In the third step, the sampling period Ts is generally a fixed value, but when the grid frequency fluctuates, the power frequency period T will change. Therefore, the value of the delay parameter N in the second step transfer function GSRC(z) under a fixed sampling period will become a fraction, and the fractional delay parameter cannot be realized in the digital system. Therefore, the system records the fractional delay parameter as N d , then there exists an expression N d =N i +d, where N i is the integer delay part, d is the fractional delay part, d∈[0,1].

[0101] Therefore, the controller frequency can be adapted by approximating the fractional-order delay parameter d. The classic Farrow structure can approximate the fractional-order delay parameter. The matrix form of the transfer function under this structure is as follows:

[0102] H Farrow (d,z)=D T CZ

[0103] where D = [1, d, d 2 ,...,d M-1 ] T , M is the approximate order, Z = [1, z -1 ,z -2 ,...,z -(M-1) ], C is the coefficient matrix.

[0104] The approximate calculation formula for the fractional-order delay parameter d using Newton's generalized binomial theorem is as follows:

[0105]

[0106] Referring to the HFarrow(d,z) expression, combined with the above delay calculation method, let d = -dN, we can further form the transfer function matrix form of Newton fractional order approximation:

[0107]

[0108] in, Z N =[1,1-z -1 ,(1-z -1 ) 2 ,…,(1-z -1 ) M-1 ], C N is the Newton coefficient matrix. By comparing H Farrow (d,z) and H Newton The relationship between the parameters (d, z) can be further constructed to obtain the conversion formula from the Farrow structure to the Newton fractional order approximate structure:

[0109]

[0110] In the above conversion formula, T d and T z is the transformation matrix; where D N =T d D, Z N =T z Z,

[0111] Transformation Matrix T d The calculation formula is Td =T d2 ×T d1 ,in, Therefore, according to d N The relationship between D and d can be transformed into and Therefore, the system can further Convert to D N .

[0112] The transformation matrix T z Convert Z to ZN, the conversion formula is:

[0113] After determining the approximate order through the above formula, the transformation matrix T can be calculated d and T z , and then calculate the Newton fractional order approximation coefficient matrix based on the coefficient matrix of the Farrow structure. Among them, since the approximation order determines the complexity and accuracy of the adaptation, the fractional approximation order M of this embodiment is preferably 4, and the Farrow fractional order calculation coefficient matrix under the Lagrange interpolation calculation method is:

[0114]

[0115] According to the conversion formula, C Farrow Calculate the Newton fractional approximation coefficient matrix:

[0116]

[0117] Compare the above two matrices C Farrow and C Netwon It can be seen that the coefficient matrix determines the complexity of the fractional-order approximation calculation, and the coefficient matrix of the Newton fractional-order approximation structure provided in this embodiment is a diagonal matrix with low complexity. Therefore, the fractional-order algorithm provided in this embodiment greatly reduces the computational burden of the digital system.

[0118] The fourth step is to use the matrix C in the third step Netwon and H Newton The calculation method of (d,z) and the calculation formula of the Newton fractional-order approximate structure for the fractional-order delay parameter are as follows:

[0119]

[0120] The digital implementation process of the above structure is as follows Figure 6 As shown, Figure 6 The structural diagram of the Newton fractional order approximation structure provided by the present invention. Figure 6 It can be seen that the above structure consists of 8 adders, 3 multipliers and 3 unit delays, and the fractional order approximation structure is based on the parameter d NThe value of d N The value of is further calculated based on the frequency information obtained by the grid phase-locked loop.

[0121] In this embodiment, the fractional delay parameter requirement is |d N |≤1. Therefore, when |d N When |>1 and is an integer, according to the calculation formula of F(z), That is, when dN is 2, F2(z)=z -2 ; When dN is 3, F3(z)=z -3 .

[0122] Therefore, the system transforms the requirement of dN into |d N |≥0, and when |d N |>1, That is, when dN is 2.5, F 2.5 (z) = z -2 F 0.5 (z). Through the above fractional-order calculation characteristics, the system can simplify the digital implementation process of the controller frequency adaptation, that is, obtain the following Figure 3 A simplified flow chart of the digital implementation of controller frequency adaptation is shown.

[0123] According to Figure 3 The simplified flow chart shown here combines the transfer function GSRC(z) of the second step with the above F dN (z) calculation method, the overall structure of adaptively selective harmonic frequency repetitive control (FA-SRC) is as follows Figure 7 As shown, Figure 7 The overall structure diagram of the adaptive repetitive control process with selectable harmonic frequency provided by the present invention. Figure 7 , Figure 7 The transfer function of the overall structure diagram shown is:

[0124]

[0125] in, is the minimum fixed integer delay, is the fractional order approximate delay. In summary, the FA-SRC control provided in this embodiment has a frequency adaptive function and can ensure accurate tracking of harmonic signals under different frequency conditions.

[0126] Through the first to fourth steps above, a repetitive control structure capable of adaptively selecting harmonic frequencies can be constructed. This embodiment also provides an active power filter control system model to analyze and verify the repetitive control structure constructed in the above steps. Figure 8 , Figure 8This is a schematic structural diagram of the three-phase active power filter control system model provided by the present invention.

[0127] like Figure 8 As shown, the main circuit of the active power filter device is the controlled object, U dc is the DC side capacitor voltage, C1 and C2 are the upper and lower filter capacitors, S1-S12 are insulated gate bipolar transistors (IGBT), L is the inverter AC side filter inductor, and R is the AC side damping resistor. The controlled object provided in this embodiment, that is, the parameters of the main circuit of the active power filter device are shown in the following table:

[0128]

[0129] According to the parameters in the above table, the transfer function of the main circuit of the active power filter device can be constructed as follows:

[0130]

[0131] It can be obtained that the repetitive control structure capable of adaptively selecting harmonic frequency is the current control link of the active power filter device, which is composed of Figure 8 It can be obtained that the controller provided in this embodiment calculates the harmonic signal to be compensated through the harmonic detection module, and realizes tracking control of the harmonic signal to be compensated through the above-mentioned repetitive control structure that can adaptively select the harmonic frequency, and then generates a switching signal to drive the main circuit through the PWM generator, and finally controls the conduction of the main circuit switch tube, and generates a harmonic current to be compensated for the output to the main circuit, that is, the compensation current described in Example 1.

[0132] Combining the controlled object, i.e., the main circuit of the active power filter device and the transfer function of the repeated control that can adaptively select the harmonic frequency, the overall control closed-loop transfer function of the system can be determined as:

[0133]

[0134] Among them, Gc(z) is a control system compensator, which is used to compensate the amplitude and phase of the system. Through simulation debugging, the phase compensation provided in this embodiment preferably adopts the lead compensation z5, and the amplitude compensation preferably adopts the proportional coefficient k=0.7, that is, Gc(z)=0.7·z5.

[0135] In order to further verify the harmonic compensation effect of the repetitive control method provided in this embodiment and the first embodiment, this embodiment also analyzes the current three-phase waveform and current spectrum of the active power filter device under different frequency conditions. The analysis results are as follows: Figures 9 to 12As shown in the figure, the current waveform reflects the quality of the current waveform at the grid connection point, and the current spectrum reflects the total distortion rate of the current waveform. The higher the waveform quality, the smaller the corresponding distortion rate, and the better the corresponding active power filter application effect.

[0136] join Figures 9 to 12 ,in, Fig. 9 and Fig.10 They are the three-phase current diagram and harmonic spectrum diagram after the SRC control strategy and FA-SRC control strategy are respectively adopted under the 49.5Hz working condition provided by the present invention, and Fig.11 and Fig.12 The three-phase current diagram and harmonic spectrum diagram after the SRC control strategy and FA-SRC control strategy are respectively adopted under the 50.5Hz working condition. Through the above four comparison diagrams, it can be determined that the current distortion degree is large and the harmonic distortion rate is high after the harmonic compensation of the SRC control strategy without frequency adaptation; while the FA-SRC with frequency adaptive structure provided by the embodiment of the present invention has good harmonic tracking ability under different frequency working conditions, high quality of three-phase current waveform, and harmonic distortion rate is below 5% after harmonic tracking compensation, which improves the application effect of active power filter device under different frequency working conditions.

[0137] In order to better illustrate the working principle and step flow of the repetitive control method and device of an active power filter device of the present invention, reference may be made to, but is not limited to, the relevant records above.

[0138] Accordingly, see Figure 2 , Figure 2 This is a structural diagram of an embodiment of a repetitive control device for an active power filter device provided by the present invention. Figure 2 As shown, the repetitive control device includes a harmonic signal acquisition module 201, a signal delay judgment module 202 and a compensation signal output module 203; wherein:

[0139] The harmonic signal acquisition module 201 is used to acquire the harmonic signal of the main circuit of the active power filter device and adjust the harmonic frequency of the preset controller according to the harmonic signal.

[0140] Furthermore, the harmonic signal acquisition module 201 adjusts the harmonic frequency of the preset controller according to the harmonic signal, including:

[0141] The harmonic signal is analyzed to obtain the original harmonic frequency corresponding to the harmonic signal, and the pole parameters of the open-loop transfer function of the controller are adjusted according to the original harmonic frequency so that the frequency response of the adjusted controller matches the original harmonic frequency.

[0142] The signal delay judgment module 202 is used to calculate the harmonic signal through the harmonic detection module of the controller to obtain the fixed delay parameter of the controller, calculate the delay parameter according to the fixed delay parameter and the voltage frequency output by the grid phase-locked loop, and then judge whether the harmonic signal needs to be supplemented according to the delay parameter.

[0143] Furthermore, the signal delay determination module 202 calculates the harmonic signal through the harmonic detection module of the controller to obtain a fixed delay parameter of the controller, including:

[0144] The harmonic signal is analyzed and extracted by the harmonic detection module to obtain a discretized signal, and the discretized signal is fractionally processed according to the open-loop transfer function of the controller to obtain the fixed delay parameter.

[0145] Furthermore, the signal delay determination module 202 calculates the delay parameter according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop, including:

[0146] The active power filter device is phase-locked by the grid phase-locked loop to obtain grid frequency information, and the grid frequency information is parsed to obtain the voltage frequency; the fixed delay parameter and the voltage frequency are calculated by a preset fractional-order algorithm to obtain a fractional-order delay parameter, and the fractional-order delay parameter is output as the delay parameter.

[0147] Furthermore, the signal delay determination module 202 determines whether the harmonic signal needs to be supplemented according to the delay parameter, including:

[0148] The delay parameter is compared with a preset delay threshold to obtain a comparison result; if the comparison result is that the delay parameter is greater than or less than the delay threshold, it is determined that the harmonic signal needs to be compensated; if the comparison result is that the delay parameter is equal to the delay threshold, it is determined that the harmonic signal does not need to be compensated.

[0149] The compensation signal output module 203 is used to calculate the compensation parameter according to the delay parameter when it is determined that the harmonic signal needs to be compensated, and output the compensation parameter to the active power filter device through the compensator of the controller, so that the harmonic signal is compensated.

[0150] In summary, the embodiment of the present invention provides a repetitive control method and device for an active power filter device, wherein the controller is adjusted for harmonic frequency according to the harmonic signal obtained from the main circuit of the active power filter device, and the harmonic signal is calculated by the harmonic detection module of the adjusted controller to obtain a fixed delay parameter, and the delay parameter is calculated according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop to determine whether the harmonic signal needs compensation processing. If necessary, the corresponding compensation parameter is calculated according to the delay parameter, and the corresponding compensation current is output according to the compensation parameter to compensate the harmonic signal. The corresponding parameters of the controller are adjusted according to the harmonic frequency of the harmonic signal to achieve adaptive adjustment to different harmonic scenarios, thereby improving the adaptability and versatility to different harmonic scenarios; the harmonic signal is repeatedly tracked and controlled by the above-mentioned repetitive control method, thereby reducing signal delay, storage resource waste and the complexity of repetitive control operations.

[0151] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A repetitive control method for an active power filter device, characterized in that: The following steps are involved: Acquire a harmonic signal of a main circuit of an active power filter device, and adjust the harmonic frequency of a preset controller according to the harmonic signal; The harmonic signal is calculated by the harmonic detection module of the controller to obtain a fixed delay parameter of the controller, a delay parameter is calculated according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop, and then whether the harmonic signal needs to be supplemented is determined according to the delay parameter; When it is determined that the harmonic signal needs to be compensated, a compensation parameter is calculated based on the delay parameter, and the compensation parameter is output to the active power filter device through the compensator of the controller, so that the harmonic signal is compensated.

2. The repetitive control method of an active power filter device according to claim 1, characterized in that: The step of adjusting the harmonic frequency of the preset controller according to the harmonic signal comprises: The harmonic signal is analyzed to obtain the original harmonic frequency corresponding to the harmonic signal, and the pole parameters of the open-loop transfer function of the controller are adjusted according to the original harmonic frequency so that the frequency response of the adjusted controller matches the original harmonic frequency.

3. The repetitive control method of an active power filter device according to claim 1, characterized in that: The calculating the harmonic signal by the harmonic detection module of the controller to obtain the fixed delay parameter of the controller includes: The harmonic signal is analyzed and extracted by the harmonic detection module to obtain a discretized signal, and the discretized signal is fractionally processed according to the open-loop transfer function of the controller to obtain the fixed delay parameter.

4. The repetitive control method of an active power filter device according to claim 1, characterized in that: The step of calculating the delay parameter according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop comprises: Performing phase-locking processing on the active power filter device through the grid phase-locked loop to obtain grid frequency information, and parsing the grid frequency information to obtain the voltage frequency; The fixed delay parameter and the voltage frequency are calculated by a preset fractional-order algorithm to obtain a fractional-order delay parameter, and the fractional-order delay parameter is output as the delay parameter.

5. The repetitive control method of an active power filter device according to claim 1, characterized in that: The determining whether the harmonic signal needs to be supplemented according to the delay parameter includes: Comparing the delay parameter with a preset delay threshold to obtain a comparison result; If the comparison result is that the delay parameter is greater than or less than the delay threshold, it is determined that the harmonic signal needs to be compensated; If the comparison result is that the delay parameter is equal to the delay threshold, it is determined that the harmonic signal does not need to be compensated.

6. A repetitive control device for an active power filter device, characterized in that: The repetitive control device includes a harmonic signal acquisition module, a signal delay judgment module and a compensation signal output module; wherein: The harmonic signal acquisition module is used to acquire the harmonic signal of the main circuit of the active power filter device and adjust the harmonic frequency of the preset controller according to the harmonic signal; The signal delay judgment module is used to calculate the harmonic signal through the harmonic detection module of the controller to obtain the fixed delay parameter of the controller, calculate the delay parameter according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop, and then judge whether the harmonic signal needs to be supplemented according to the delay parameter; The compensation signal output module is used to calculate the compensation parameter according to the delay parameter when it is determined that the harmonic signal needs to be supplemented, and output the compensation parameter to the active power filter device through the compensator of the controller, so that the harmonic signal is compensated.

7. The repetitive control device of an active power filter device as claimed in claim 6, characterized in that: The harmonic signal acquisition module adjusts the harmonic frequency of the preset controller according to the harmonic signal, including: The harmonic signal is analyzed to obtain the original harmonic frequency corresponding to the harmonic signal, and the pole parameters of the open-loop transfer function of the controller are adjusted according to the original harmonic frequency so that the frequency response of the adjusted controller matches the original harmonic frequency.

8. The repetitive control device of an active power filter device as claimed in claim 6, characterized in that: The signal delay determination module calculates the harmonic signal through the harmonic detection module of the controller to obtain a fixed delay parameter of the controller, including: The harmonic signal is analyzed and extracted by the harmonic detection module to obtain a discretized signal, and the discretized signal is fractionally processed according to the open-loop transfer function of the controller to obtain the fixed delay parameter.

9. The repetitive control device of an active power filter device as claimed in claim 6, characterized in that: The signal delay judgment module calculates the delay parameter according to the fixed delay parameter and the voltage frequency output by the power grid phase-locked loop, including: Performing phase-locking processing on the active power filter device through the grid phase-locked loop to obtain grid frequency information, and parsing the grid frequency information to obtain the voltage frequency; The fixed delay parameter and the voltage frequency are calculated by a preset fractional-order algorithm to obtain a fractional-order delay parameter, and the fractional-order delay parameter is output as the delay parameter.

10. The repetitive control device of an active power filter device as claimed in claim 6, characterized in that: The signal delay judgment module judges whether the harmonic signal needs to be supplemented according to the delay parameter, including: Comparing the delay parameter with a preset delay threshold to obtain a comparison result; If the comparison result is that the delay parameter is greater than or less than the delay threshold, it is determined that the harmonic signal needs to be compensated; If the comparison result is that the delay parameter is equal to the delay threshold, it is determined that the harmonic signal does not need to be compensated.

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