LCL inverter robust control method and device, electronic equipment and storage medium

Abstract

The application provides a robust control method for an LCL inverter, wherein according to filter parameters and a critical frequency, the anti-resonance frequency is adjusted through the filter parameters until the anti-resonance frequency is less than the preset critical frequency, and the phase crossover frequency is configured as the anti-resonance frequency; after the anti-resonance frequency is less than the preset critical frequency, the phase crossover frequency is uniquely determined through a controller factor value; the controller factor value is modified to make the phase crossover frequency to the anti-resonance frequency, and a proportional coefficient is adjusted; according to a cutoff frequency point and an amplitude margin point, an equal amplitude margin curve and an equal cutoff frequency curve are generated, an intersection of the equal amplitude margin curve and the equal cutoff frequency curve and a controller factor point are determined; the intersection or the controller factor point is input to a phase margin compensator, the phase margin of a control system is compensated, and the phase margin of the control system is improved. In the case that the crossover frequency and the cutoff frequency are not changed, the system can stably work and is not affected by the change of grid inductance.

Description

Technical Field

[0001] This invention relates to the field of power electronic control technology, and in particular to a robust control method, device, electronic equipment, and storage medium for an LCL inverter. Background Technology

[0002] Because the actual grid inductance fluctuates, it increases, causing the actual LCL filter resonant frequency to shift to the lower frequency range. This can result in the resonant frequency falling below the critical frequency, leading to instability in the grid-side current feedback single-loop control. However, current technology designs inverters with resonant frequencies above the critical frequency, requiring the addition of an active damping control inner loop. This active damping control inner loop is affected by digital control delays and is complex to design. Even when the resonant frequency is above the critical frequency, the control system still faces the risk of instability due to changes in grid inductance. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a robust control method, device, electronic device, and storage medium for LCL inverters, enabling LCL inverters to operate stably while ignoring the fluctuations in grid inductance.

[0004] In a first aspect, embodiments of the present invention provide a robust control method for an LCL inverter, applied to an LCL inverter, wherein the LCL inverter includes a phase margin compensator, and the robust control method for the LCL inverter includes:

[0005] Based on the filtering parameters and the critical frequency, the anti-resonance frequency is adjusted by the filtering parameters until the anti-resonance frequency is less than the preset critical frequency. When the anti-resonance frequency is less than the preset critical frequency, the phase crossover frequency is configured as the anti-resonance frequency.

[0006] When the anti-resonance frequency is less than the preset critical frequency, the phase crossover frequency is uniquely determined by the controller factor value, wherein the phase crossover frequency is configured after the controller factor value is adjusted.

[0007] The controller factor value is modified to bring the phase crossover frequency to the anti-resonant frequency, and the proportional coefficient is tuned after the crossover frequency reaches the anti-resonant frequency;

[0008] Based on the preset cutoff frequency and amplitude margin, the cutoff frequency point is obtained based on the cutoff frequency, and the amplitude margin point is obtained based on the amplitude margin.

[0009] Based on the cutoff frequency point and the gain margin point, generate an equal gain margin curve and an equal cutoff frequency curve, determine the intersection point of the equal gain margin curve and the equal cutoff frequency curve, and the controller factor point on the equal cutoff frequency curve;

[0010] The intersection point or the controller factor point is input to the phase margin compensator, which compensates for the phase margin of the control system to improve the phase margin of the control system.

[0011] In some embodiments of the present invention, configuring the phase crossover frequency as an anti-resonant frequency is obtained by the following formula:

[0012]

[0013] Where, ω g Where ω is the phase crossover frequency, T is the sampling period, and ω is the sampling frequency. n ω is the fundamental angular frequency. cn The cutoff frequency of the control device. In some embodiments of the present invention, determining the controller factor by phase crossover frequency after the anti-resonant frequency is less than the preset critical frequency includes:

[0014] Determine the controller factor value; once the controller factor value is determined, determine the proportional coefficient.

[0015] The resonance coefficient is calculated based on the controller factor and the proportional coefficient.

[0016] In some embodiments of the present invention, the step of obtaining a cutoff frequency point based on the cutoff frequency and an amplitude margin point based on the preset cutoff frequency and amplitude margin after the crossover frequency reaches the anti-resonant frequency includes:

[0017] Determine the cutoff frequency and gain margin values;

[0018] Based on the cutoff frequency value and the gain margin value, the adjustment ratio coefficient is used to obtain the equal cutoff frequency line and the equal gain margin line.

[0019] In some embodiments of the present invention, the phase margin compensator is provided with a first frequency transition point, a second frequency transition point, a third frequency transition point, and a fourth frequency transition point. The phase margin compensator compensates for the phase margin of the control system to improve the phase margin of the control system. The structure of the phase margin compensator is derived from the following formula:

[0020]

[0021] Among them, K Cα is the gain value of the phase margin compensator, β is the ratio of the phase crossover frequency to the cutoff frequency, β is the ratio of the second frequency inflection point to the first frequency inflection point, and also the ratio of the fourth frequency inflection point to the third frequency inflection point, and s is the complex frequency.

[0022] In some embodiments of the present invention, the phase margin compensator gain value is used to keep the phase crossover frequency unchanged, the crossover frequency being the geometric midpoint between the second frequency inflection point and the third frequency inflection point, and the phase margin compensator gain value is derived by the following formula:

[0023]

[0024] Wherein, α is the ratio of the phase crossover frequency to the cutoff frequency, and β is the ratio of the second frequency inflection point to the first frequency inflection point, and also the ratio of the fourth frequency inflection point to the third frequency inflection point.

[0025] In some embodiments of the present invention, the phase margin compensator compensates for the phase margin of the control system to improve the phase margin of the control system, and the compensation angle is derived from the following formula:

[0026]

[0027] In a second aspect, embodiments of the present invention provide a robust control device for an LCL inverter, including at least one control processor and a memory for communicatively connecting to the at least one control processor; the memory stores instructions executable by the at least one control processor, which, when executed by the at least one control processor, enable the at least one control processor to perform the LCL inverter phase compensation method as described in the first aspect above.

[0028] Thirdly, embodiments of the present invention provide an electronic device including an LCL inverter robust control device as described in the second aspect above.

[0029] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing computer-executable instructions for performing the robust control method for an LCL inverter as described in the first aspect above.

[0030] The robust control method for LCL inverters according to embodiments of the present invention has at least the following beneficial effects:

[0031] Based on the filter parameters and critical frequency, the anti-resonance frequency is adjusted by the filter parameters until it is lower than a preset critical frequency. When the anti-resonance frequency is lower than the preset critical frequency, the phase crossover frequency is configured as the anti-resonance frequency. When the anti-resonance frequency is lower than the preset critical frequency, the phase crossover frequency is uniquely determined by the controller factor value, wherein the phase crossover frequency is configured after the controller factor value is adjusted. The controller factor value is modified to make the phase crossover frequency reach the anti-resonance frequency. When the crossover frequency reaches the anti-resonance frequency, the proportional coefficient is tuned. Based on the preset cutoff frequency and gain margin, the cutoff frequency point is obtained based on the cutoff frequency, and the gain margin point is obtained based on the gain margin. An equal gain margin curve and an equal cutoff frequency curve are generated based on the cutoff frequency point and the gain margin point. The intersection point of the equal gain margin curve and the equal cutoff frequency curve, as well as the controller factor point of the controller factor value on the equal cutoff frequency curve, are determined. The intersection point or controller factor point is input to the phase margin compensator, which compensates for the phase margin of the control system to improve the phase margin of the control system. By changing the controller factor value, the phase crossover frequency is configured at the anti-resonant frequency. At the same time, the gain margin and cutoff frequency are obtained by tuning the proportional coefficient. Based on the gain margin and cutoff frequency, equal gain margin curves and equal cutoff frequency curves are obtained. The intersection value of the equal gain margin curve and equal cutoff frequency curve or the intersection value corresponding to the controller factor value is input into the phase margin compensator to accurately compensate for the phase angle margin without changing the crossover frequency and cutoff frequency, so that the system can work stably and is not affected by changes in grid inductance. Attached Figure Description

[0032] Figure 1 This is a flowchart of an LCL inverter phase compensation method provided in one embodiment of the present invention;

[0033] Figure 2 This is a model diagram of an LCL-type inverter provided in one embodiment of the present invention;

[0034] Figure 3 This is a model diagram and control block diagram of an LCL inverter provided in one embodiment of the present invention;

[0035] Figure 4 This is a flowchart of obtaining the resonant coefficient of an LCL inverter according to an embodiment of the present invention;

[0036] Figure 5 This is a flowchart of obtaining equal cutoff frequency lines and equal amplitude margin lines provided in one embodiment of the present invention;

[0037] Figure 6 This is a Bode plot of a phase margin compensator provided in one embodiment of the present invention;

[0038] Figure 7This is a waveform diagram of the grid-connected current when the amplitude of the command current suddenly increases when the series inductance is 0mH, according to an embodiment of the present invention.

[0039] Figure 8 This is a waveform diagram of the grid-connected voltage when the amplitude of the command current suddenly increases when the series inductance is 0mH, according to an embodiment of the present invention.

[0040] Figure 9 This is a waveform diagram of the grid-connected current when the amplitude of the command current suddenly increases when the series inductance is 4mH, according to an embodiment of the present invention.

[0041] Figure 10 This is a waveform diagram of the grid-connected voltage when the amplitude of the command current suddenly increases when the series inductance is 4mH, according to an embodiment of the present invention.

[0042] Figure 11 This is a structural diagram of an LCL inverter phase compensation device provided in one embodiment of the present invention;

[0043] Figure 12 A diagram showing the relationship between controller factor and proportional coefficient provided in one embodiment of the present invention. Detailed Implementation

[0044] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0045] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0046] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0047] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0048] This invention provides a robust control method for an LCL inverter, applied to an LCL inverter, which includes a phase margin compensator. The robust control method for the LCL inverter includes:

[0049] Based on the filter parameters and critical frequency, the anti-resonance frequency is adjusted by the filter parameters until it is lower than a preset critical frequency. When the anti-resonance frequency is lower than the preset critical frequency, the phase crossover frequency is configured as the anti-resonance frequency. When the anti-resonance frequency is lower than the preset critical frequency, the phase crossover frequency is uniquely determined by the controller factor value, wherein the phase crossover frequency is configured after the controller factor value is adjusted. The controller factor value is modified to make the phase crossover frequency reach the anti-resonance frequency. When the crossover frequency reaches the anti-resonance frequency, the proportional coefficient is tuned. Based on the preset cutoff frequency and gain margin, the cutoff frequency point is obtained based on the cutoff frequency, and the gain margin point is obtained based on the gain margin. An equal gain margin curve and an equal cutoff frequency curve are generated based on the cutoff frequency point and the gain margin point. The intersection point of the equal gain margin curve and the equal cutoff frequency curve, as well as the controller factor point of the controller factor value on the equal cutoff frequency curve, are determined. The intersection point or controller factor point is input to the phase margin compensator, which compensates for the phase margin of the control system to improve the phase margin of the control system.

[0050] By changing the controller factor value, the phase crossover frequency is configured at the anti-resonant frequency. At the same time, the gain margin and cutoff frequency are obtained by tuning the proportional coefficient. Based on the gain margin and cutoff frequency, equal gain margin curves and equal cutoff frequency curves are obtained. The intersection value of the equal gain margin curve and equal cutoff frequency curve or the intersection value corresponding to the controller factor value is input into the phase margin compensator to accurately compensate for the phase angle margin without changing the crossover frequency and cutoff frequency, so that the system can work stably and is not affected by changes in grid inductance.

[0051] The control method of the present invention will be further described below with reference to the accompanying drawings.

[0052] Reference Figure 1 , Figure 1 This invention provides a flowchart of an LCL inverter phase compensation method, which includes, but is not limited to, the following steps:

[0053] Step S11: According to the filter parameters and the critical frequency, the anti-resonance frequency is adjusted by the filter parameters until the anti-resonance frequency is less than the preset critical frequency. When the anti-resonance frequency is less than the preset critical frequency, the phase crossover frequency is configured as the anti-resonance frequency.

[0054] Step S12: When the anti-resonance frequency is less than the preset critical frequency, the phase crossover frequency is uniquely determined by the controller factor value, wherein the phase crossover frequency is configured after the controller factor value is adjusted.

[0055] Step S13: Modify the controller factor value to make the phase crossover frequency reach the anti-resonant frequency, and adjust the proportional coefficient after the crossover frequency reaches the anti-resonant frequency;

[0056] Step S14: Based on the preset cutoff frequency and gain margin, obtain the cutoff frequency point based on the cutoff frequency and the gain margin point based on the gain margin.

[0057] Step S15: Generate equal gain margin curves and equal cutoff frequency curves based on the cutoff frequency point and gain margin point, determine the intersection of the equal gain margin curves and equal cutoff frequency curves, and the controller factor point on the equal cutoff frequency curve.

[0058] Step S16: Input the intersection point or controller factor point to the phase margin compensator. The phase margin compensator compensates for the phase margin of the control system to improve the phase margin of the control system.

[0059] It should be noted that the phase crossover frequency is an indicator describing the frequency characteristics of the system, that is, the frequency at which the system phase crosses (2k+1)π; the cutoff frequency is the preset frequency range of the inverter output signal. Within the preset frequency range, the amplitude of the inverter output signal will gradually decrease and tend to zero.

[0060] Design the LCL filter parameters according to the following formula:

[0061]

[0062] Specifically, refer to Figure 1 , Figure 2 and Figure 3 The phase crossover frequency of the LCL inverter is configured as the anti-resonant frequency, and the anti-resonant frequency is modified as a filter parameter so that the anti-resonant frequency ωL1C = 1 / sqrt(L1C) of the inverter's first inductor and filter capacitor C is less than the critical frequency ωcrti (equal to 1 / 6 times the sampling frequency ωs), and the phase crossover frequency is configured at ωL1C. Further, referring to... Figure 2 , Figure 2 This is a model of an LCL-type grid-connected inverter with single-loop control based on grid-side current feedback, u dc, u g are the DC bus voltage and grid-connected voltage of the inverter respectively; L1 is the inverter-side inductor, L2 is the grid-side filter inductor; C is the filter capacitor; Gc(s) refers to the designed phase margin compensator, D(s) refers to the current controller; Gd(s) refers to the digital control delay link.

[0063] Figure 2 is a control block diagram of an LCL-type grid-connected inverter, wherein: Kpwm is the inverter gain, obtained from Figure 3 it is obtained that the transfer function of the LCL grid-connected inverter control device can be expressed by the following first formula:

[0064]

[0065] wherein: G plant (s) represents the filter model of the LCL inverter; ω r is the resonant frequency of the LCL inverter, and its calculation formula is ω r = sqrt((L1+L2) / (L1L2C)).

[0066] D(s) is the control device, which can be expressed by the following second formula:

[0067]

[0068] wherein, m is the controller factor value of the control device, which is obtained from the ratio of the resonance coefficient K r to the proportional coefficient K p , that is, m = Kr / Kp;

[0069] Through the phase lag effect of the control device, specifically, the control device of the present solution uses a PR controller, and configures the phase crossing frequency ω g of the transfer function Gsys(s) at the resonant frequency ω L1C formed by L1 and C, that is, ω g = ω L1C , so as to ensure the robustness of the control system to grid inductance variation. Since the controller factor value m of the PR controller must be greater than 0 to effectively pull the phase crossing frequency to the left and lower it; otherwise, if -1<m<0 is set, the PR controller is equivalent to a notch filter, which can neither track the 50Hz power frequency command current nor lower the phase crossing frequency. After setting m<-1, the PR controller exhibits non-minimum phase characteristics, which causes the frequency characteristic curve of the system to undergo a process of negatively crossing the -180° phase angle at 50Hz, resulting in instability of the control system. Therefore, it is necessary to adjust m to configure ω g = ω L1CTo improve the system's robustness to changes in grid inductance and ensure m > 0 to guarantee the stability of the control system, the filter parameters of the LCL inverter should be designed to ensure the resonant frequency ω formed by the inverter-side inductor L1 and filter capacitor C. L1C Below the critical frequency ω crit .

[0070] Actual grid inductance L g L cannot be ignored 2g To integrate L g The inverter grid-side filter inductor, i.e., L 2g =L2+L g The filter model G of the LCL inverter plant Should be

[0071]

[0072] The resonant frequency should be ω. r =sqrt((L1+L 2g ) / (L1L 2g C)); L g As the frequency increases from 0mH to ∞, the corresponding resonant frequency decreases from sqrt((L1+L2) / (L1L2C)) to a minimum value ω. r (min) = 1 / sqrt(L1C), as shown below.

[0073]

[0074] Due to the actual grid inductance L g Since ω is a finite value, r >ω L1C This holds true. Configure ω g =ω L1C This always ensures that the stability condition ωr>ωg holds true.

[0075] G plant The magnitude of (jω) at ωL1C

[0076]

[0077] From the fifth formula, |G plant (jωL1C)| is a constant, meaning it is unaffected by the grid inductance L. g The impact of change.

[0078] Therefore, at ωL1C, G plantThe magnitude of (jω) is unaffected by Lg and is always sqrt(C / L1). Since Gc(s) and Gd(s) do not change the magnitude margin of the control system, by configuring ωg=ωL1C, the single-loop control stability condition ωg<ωr will always hold regardless of how the grid inductance Lg changes, and the magnitude margin of the control system will always remain constant.

[0079] It's worth noting that LCL inverters reduce the resonant peak value and amplitude in the output voltage through filter inductors and capacitors, thereby lowering the harmonic content in the bus voltage, improving output voltage ripple and harmonic distortion, ensuring stable voltage output, and reducing grid interference. By filtering out resonances in the output voltage, LCL inverters reduce their impact on grid voltage quality, ensuring that the inverter's output AC current is synchronized with the grid current, meeting the grid's power quality requirements. The current controller, by setting a target value for the output current, enables the inverter to provide the required current on demand. Precise control of the inverter's output current can be achieved by accurately setting the target value; the gain value is a parameter in the current controller used to adjust the system's response speed and stability.

[0080] Specifically, according to the first formula, the phase angle of the system at ωg should satisfy the following sixth formula:

[0081]

[0082] In the formula, φ PR (ω g The hysteresis angle provided by the PR controller, and has

[0083]

[0084] The sixth formula can be simplified to φPR(ω) g )=1.5ω g T-0.5π; Substituting the seventh formula into the simplified sixth formula, and applying the tangent to both sides of the equation, we obtain the eighth formula:

[0085]

[0086] As can be seen from the eighth formula, the phase crossover frequency ωg of the control system can be uniquely determined by tuning the controller factor m; combined with step 1, the phase crossover frequency is configured at ωL1C by tuning the controller factor m.

[0087] Additionally, in one embodiment, reference is made to Figure 4 ,exist Figure 1 Step S13 of the illustrated embodiment also includes, but is not limited to, the following steps:

[0088] S31, Determine the controller factor value. Once the controller factor value is determined, determine the proportional coefficient.

[0089] S32, determine the resonance coefficient based on the controller factor and proportional coefficient.

[0090] Modify the proportional coefficient Kp to design the cutoff frequency ω c (exp) and gain margin GM(exp)

[0091] The modified scaling factor Kp and the design gain margin GM(exp) can be obtained using the following ninth formula:

[0092]

[0093] Modify the scaling factor K p Design cutoff frequency ω c The method for (exp) can be derived from the following tenth formula:

[0094]

[0095] Wherein, KPWM is the inverter gain value.

[0096] By controlling the factor m and the cutoff frequency ω c The mathematical relationship between the gain margin GM and the equal gain margin line and equal cutoff frequency line are plotted on the m-Kp plane; the points corresponding to the anti-resonant frequency ωL1C are marked on the equal cutoff frequency line by the controller factor m and the phase crossing frequency ωg.

[0097] Additionally, in one embodiment, reference is made to Figure 5 ,exist Figure 1 Step S14 of the illustrated embodiment also includes, but is not limited to, the following steps:

[0098] S41, determine the cutoff frequency value and the gain margin value;

[0099] S42, based on the cutoff frequency value and the gain margin value, is tuned to obtain the equal cutoff frequency line and the equal gain margin line.

[0100] Specifically, in this embodiment of the invention, the proportionality coefficient is tuned using the following method:

[0101] Tuning Scheme 1: The coordinates of the intersection point of the equal cutoff frequency line and the equal gain margin line are used as the controller factor m and proportional coefficient Kp. This scheme is suitable for strong power grids, enabling the inverter control system to accurately obtain the cutoff frequency and gain margin. Specifically, it corresponds to the intersection point 1 of the equal cutoff frequency line and the equal gain margin line; this scheme allows the control system to obtain the desired cutoff frequency (10ωn) and gain margin (8dB). This scheme is suitable for strong power grid conditions, i.e., when the equivalent inductance of the power grid is small.

[0102] Adjustment scheme two, refer to Figure 12 , Figure 12 The diagram illustrates the relationship between the controller factor and the proportional gain. The coordinates of the points corresponding to the anti-resonant frequencies marked on the constant cutoff frequency line are used as the controller factor m and the proportional gain Kp. This scheme is suitable for weak grids. The inverter control system can accurately obtain the desired cutoff frequency, and the gain margin remains constant and positive regardless of changes in grid inductance. The phase crossover frequency ωg is configured at the resonant frequency ωL1C formed by the inverter-side filter inductor L1 and filter capacitor C. This controller factor tuning method can obtain the desired cutoff frequency with a gain margin no lower than the desired value. This further ensures the robustness of the inverter control system to grid inductance, meaning that the gain margin of the control system remains constant regardless of changes in grid inductance. This scheme is suitable for weak grid conditions, i.e., situations where the grid equivalent inductance is large and fluctuates significantly.

[0103] Furthermore, such as Figure 6 As shown, the phase margin compensator is provided with a first frequency inflection point, a second frequency inflection point, a third frequency inflection point and a fourth frequency inflection point. The geometric midpoint between the second frequency inflection point and the third frequency inflection point is the phase crossover frequency. When the phase margin compensator performs compensation, the cutoff frequency and the phase crossover frequency remain unchanged.

[0104] The phase margin compensator can be expressed by the following eleventh formula:

[0105]

[0106] In the formula, Kc is the gain of the phase margin compensator, α is the ratio of the phase crossover frequency to the cutoff frequency, and β is the ratio of the second frequency inflection point to the first frequency inflection point. To ensure that the system cutoff frequency remains unchanged, the gain Kc of the phase margin compensator can be expressed by the following twelfth formula:

[0107]

[0108] Phase margin compensation angle φG c (ω c The phase margin compensation angle can be flexibly adjusted by the ratio β of the second frequency inflection point and the first frequency inflection point, and is expressed by the following thirteenth formula:

[0109]

[0110] Specifically, the phase margin compensator does not change the system's phase crossover frequency. The geometric midpoint between the second and third frequency inflection points of the phase margin compensator is the phase crossover frequency, i.e., ω. g =αω c Therefore, the phase margin compensator at ω g The phase angle contribution at point φ Gc(ω g = 0°; the cutoff frequency remains unchanged. At the cutoff frequency, the amplitude contribution of the phase margin compensator is L. Gc (jω c ) = 0dB; Phase margin compensation angle φ Gc (ω c The ratio β between the second frequency inflection point and the first frequency inflection point can be flexibly adjusted.

[0111] The following is a specific example proposed in this invention:

[0112] This manual verifies the feasibility of the GCF single-loop control method using a 2.2kV single-phase LCL inverter prototype. The filter capacitor is selected as C = 4.4μF, meaning the inverter operates under the extreme condition of ωr = ωcrit.

[0113] The inverter parameters, controller parameters, and phase margin compensator parameters are the same as those in Tables 1 and 2, respectively.

[0114]

[0115] Table 1 Electrical and Control Parameters of the Inverter

[0116]

[0117] Table 2. PR controller tuning parameters and actual performance indicators of the control system

[0118] 1. No additional series inductor is added to the inverter grid side (L) g =0mH);

[0119] The inverter command current amplitude is set to suddenly increase from 7A to 14A, and the grid-connected current i g Grid-connected voltage u g Experimental waveforms, such as Figure 7 and Figure 9 As shown.

[0120] Tuning scheme 1 is adopted, that is, the cutoff frequency of the system is set to 10ω. n The gain margin is 8dB. A phase margin compensator G is also introduced. c (s) Furthermore, by setting β = 6.5, the system phase margin increased to 45.1°; this scheme ensured high-quality grid connection of the inverter and good dynamic performance of the control system. Experimental results are shown in […]. Figure 8 As shown.

[0121] The second tuning scheme is adopted, which sets the system phase crossover frequency ω. g =1 / sqrt(L1C) and introduce a phase margin compensator (set β=6.5), this scheme can also ensure that the inverter has good stability and grid-connected current quality. Experimental results are as follows. Figure 8As shown.

[0122] 2. An additional inductor (L) is connected in series on the grid side of the inverter. g =4mH)

[0123] To verify whether tuning schemes 1 and 2 can ensure the robustness of the inverter control system to changes in grid impedance, an additional inductor (L) is connected in series on the grid side of the LCL inverter. g =4mH); Similarly, the current amplitude of the LCL inverter command suddenly increases from 7A to 14A, and the grid-connected current i g Grid-connected voltage u g Experimental waveforms are as follows Figure 10 As shown.

[0124] Using tuning scheme 1, such as Figure 9 As shown, grid inductance fluctuations severely impair the stability of the inverter control system. When L g When the current is 4mH, there are severe harmonic currents in the grid-connected current, and the grid-side voltage waveform is distorted. Therefore, the LCL inverter cannot achieve high-quality grid connection.

[0125] Adopting tuning scheme 2, such as Figure 10 As shown, the stability of the LCL inverter is almost unaffected by fluctuations in the grid inductance. When the additional series inductor L... g When the current is 4mH, the sinusoidal degree of the grid-connected current is still very high, and the steady-state grid-connected current i g The THD remains very low (2.72%); the amplitude margin and phase margin of the control system remain sufficient, so the LCL inverter can still operate with high quality in grid connection.

[0126] like Figure 9 and Figure 10 As shown: By setting the phase crossover frequency at the resonant frequency of the grid-side inductor L1 – filter capacitor C, the LCL inverter is not affected by the additional series inductor L. g The changes have an impact, and the PM will not decrease, only the cutoff frequency will narrow. The control system is robust to a wide range of fluctuations in the grid inductance.

[0127] like Figure 11 As shown, Figure 11 This is a structural diagram of an LCL inverter phase compensation device according to an embodiment of the present invention. The present invention also provides an LCL inverter phase compensation device, comprising:

[0128] The processor 1101 can be implemented using a general-purpose central processing unit (CPU), microprocessor, application specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this application.

[0129] The memory 1102 can be implemented as a read-only memory (ROM), static storage device, dynamic storage device, or random access memory (RAM). The memory 1102 can store the operating system and other applications. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 1102 and is called and executed by the processor 1101 to execute the LCL inverter phase compensation method of the embodiments of this application.

[0130] Input / output interface 1103 is used to implement information input and output;

[0131] The communication interface 1104 is used to enable communication and interaction between this device and other devices. Communication can be achieved through wired means (such as USB, network cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.).

[0132] Bus 1105 transmits information between various components of the device (e.g., processor 1101, memory 1102, input / output interface 1103, and communication interface 1104);

[0133] The processor 1101, memory 1102, input / output interface 1103 and communication interface 1104 are connected to each other within the device via bus 1105.

[0134] This application also provides an electronic device, including the LCL inverter phase compensation device described above.

[0135] This application embodiment also provides a storage medium, which is a computer-readable storage medium, storing a computer program that, when executed by a processor, implements the above-described LCL inverter phase compensation method.

[0136] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof. The device embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separate, and may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0137] It will be understood by those skilled in the art that all or some of the steps and systems in the methods disclosed above can be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components can be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application-specific integrated circuit. Such software can be distributed on a computer-readable medium, which can include computer storage media (or non-transitory media) and communication media (or transient media). As is known to those skilled in the art, the term computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tape, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer. Furthermore, as is known to those skilled in the art, communication media typically include computer-readable instructions, data structures, program modules, or other data in modulated data signals such as carrier waves or other transmission mechanisms, and may include any information delivery medium.

[0138] The above provides a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of the present invention.

Claims

1. A robust control method for an LCL inverter, characterized in that, Applied to an LCL inverter, the LCL inverter including a phase margin compensator, the robust control method of the LCL inverter includes: Based on the filtering parameters and the critical frequency, the anti-resonance frequency is adjusted by the filtering parameters until the anti-resonance frequency is less than the preset critical frequency. When the anti-resonance frequency is less than the preset critical frequency, the phase crossover frequency is configured as the anti-resonance frequency. When the anti-resonance frequency is less than the preset critical frequency, the phase crossover frequency is uniquely determined by the controller factor value, wherein the phase crossover frequency is configured after the controller factor value is adjusted. The controller factor is modified to bring the phase crossover frequency to the anti-resonant frequency, and the proportional coefficient is tuned after the phase crossover frequency reaches the anti-resonant frequency. Based on the preset cutoff frequency and amplitude margin, the cutoff frequency point is obtained based on the cutoff frequency, and the amplitude margin point is obtained based on the amplitude margin. Based on the cutoff frequency point and the gain margin point, generate an equal gain margin curve and an equal cutoff frequency curve, determine the intersection point of the equal gain margin curve and the equal cutoff frequency curve, and the controller factor point on the equal cutoff frequency curve; The intersection point or the controller factor point is input to the phase margin compensator, which compensates for the phase margin of the control system to improve the phase margin of the control system. The phase margin compensator is provided with a first frequency transition point, a second frequency transition point, a third frequency transition point, and a fourth frequency transition point. The phase margin compensator compensates for the phase margin of the control system to improve the phase margin of the control system. The structure of the phase margin compensator is derived from the following formula: ； Among them, K C α is the gain value of the phase margin compensator, β is the ratio of the phase crossover frequency to the cutoff frequency, β is the ratio of the second frequency inflection point to the first frequency inflection point, and also the ratio of the fourth frequency inflection point to the third frequency inflection point, and s is the complex frequency.

2. The robust control method for LCL inverters according to claim 1, characterized in that, The configuration of the phase crossover frequency as the anti-resonant frequency is obtained by the following formula: ； in, ω g Where T is the phase crossover frequency, and T is the sampling period. ω n The fundamental angular frequency, ω cn This is the cutoff frequency of the control device.

3. The robust control method for LCL inverters according to claim 1, characterized in that, Modifying the controller factor to bring the phase crossover frequency to the anti-resonant frequency, and then tuning the proportional coefficient after the phase crossover frequency reaches the anti-resonant frequency, including: Determine the controller factor value; once the controller factor value is determined, determine the proportional coefficient. The resonance coefficient is calculated based on the controller factor and the proportional coefficient.

4. The robust control method for LCL inverters according to claim 1, characterized in that, When the crossover frequency reaches the anti-resonance frequency, the step of obtaining the cutoff frequency point based on the preset cutoff frequency and amplitude margin, and obtaining the amplitude margin point based on the amplitude margin, includes: Determine the cutoff frequency and gain margin values; Based on the cutoff frequency value and the gain margin value, the constant cutoff frequency line and the constant gain margin line are obtained by tuning.

5. The robust control method for an LCL inverter according to claim 1, characterized in that, The phase margin compensator gain value is used to keep the phase crossover frequency unchanged. The crossover frequency is the geometric midpoint between the second frequency inflection point and the third frequency inflection point. The phase margin compensator gain value is derived from the following formula: ； Wherein, α is the ratio of the phase crossover frequency to the cutoff frequency, and β is the ratio of the second frequency inflection point to the first frequency inflection point, and also the ratio of the fourth frequency inflection point to the third frequency inflection point.

6. The robust control method for an LCL inverter according to claim 1, characterized in that, The phase margin compensator compensates for the phase margin of the control system to improve the phase margin of the control system. The compensation angle is obtained by the following formula: 。 7. A robust control device for an LCL inverter, characterized in that, It includes at least one control processor and a memory for communicatively connecting to the at least one control processor; the memory stores instructions executable by the at least one control processor, which, when executed by the at least one control processor, enable the at least one control processor to perform the LCL inverter phase compensation method as described in any one of claims 1 to 6.

8. An electronic device, characterized in that, Includes the robust control device for LCL inverters as described in claim 7.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions for causing a computer to perform the robust control method for an LCL inverter as described in any one of claims 1 to 6.

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