Voltage feed-forward control method and system for grid-connected inverter

Abstract

The invention discloses a voltage feed-forward control method and system for a grid-connected inverter. The method comprises the following steps: firstly, constructing a proportional weighted differential feedforward function; constructing an auxiliary function based on system parameters and dividing frequency intervals according to the auxiliary function; deducing a constraint condition of a weighting coefficient lambda in a frequency band through a passivity condition, and solving a common value range of the lambda; and selecting an optimal lambda value in the range, substituting the optimal lambda value into a feed-forward function, forming a final control law, and applying the final control law to the inverter. According to the invention, through accurate design of lambda, on the premise of ensuring the full-band passivity (system stability) of the output admittance of the inverter, the suppression capability of the common connection point voltage harmonic wave (especially the intermediate frequency harmonic wave) is obviously enhanced, the collaborative optimization of the stability and the electric energy quality is realized, the hardware cost does not need to be increased, and the engineering practicability is strong.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy grid-connected control, and particularly relates to a voltage feedforward control method and system for a grid-connected inverter. BACKGROUND

[0002] With large-scale grid connection of distributed energy such as photovoltaic and energy storage, the performance of a grid-connected inverter as a core device for energy conversion is crucial. In actual operation, the voltage at a point of common coupling (PCC) often contains background harmonics, which can be coupled into the grid-connected current through the control loop of the inverter, resulting in current distortion and reducing power quality. In addition, the grid impedance (especially the large inductance characteristic under weak grid conditions) can interact with the output impedance of the inverter, possibly causing resonance and even system instability.

[0003] Voltage feedforward is a widely used control technology to suppress the direct impact of PCC voltage disturbance. Traditional schemes mainly fall into two categories: one is simple unit proportional feedforward, which can suppress some harmonics, but has limited suppression ability for mid-frequency harmonics; the other is proportional and differential feedforward, which can improve the suppression effect of mid-frequency harmonics, but the introduction of pure differential term can severely weaken the impedance passivity of the system in the high-frequency band, bringing stability risks. Therefore, the existing technology cannot simultaneously achieve excellent harmonic suppression ability and robust stability (i.e., passivity in the full frequency band) in a wide frequency range.

[0004] Passivity is an important theoretical tool for judging system stability. If the output admittance of the grid-connected inverter meets the passivity condition (i.e., the real part is non-negative) in the frequency band of interest, the system can remain stable regardless of the changes in grid impedance. Existing feedforward control schemes often have to make a choice: enhancing harmonic suppression (reducing admittance amplitude) may destroy passivity (resulting in negative real part of admittance) in some frequency bands, thereby causing oscillation under certain grid impedance.

[0005] Therefore, there is an urgent need for a new voltage feedforward control method that can synergistically optimize harmonic suppression performance and full-frequency passivity, fundamentally improving the adaptability of the grid-connected inverter to complex grid environments without increasing additional hardware costs. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a voltage feedforward control method and system for a grid-connected inverter. The method achieves significant improvement in the suppression of PCC voltage harmonics (especially mid-frequency harmonics) while ensuring the full-frequency passivity of the inverter output admittance (i.e., ensuring system stability) by designing a proportional and weighted differential feedforward structure and scientifically determining its key parameters (weighting coefficient λ).

[0007] In a first aspect, the present application provides a voltage feedforward control method for a grid-connected inverter, comprising: Obtain the system parameters of the grid-connected inverter, including inverter-side inductance, filter capacitor, total system delay time caused by control delay, and inverter gain; Based on the total system delay time and inverter gain, a proportionally weighted differential feedforward function is constructed, with the following expression: , In the formula, It is a proportionally weighted differential feedforward function. For inverter gain, These are weighting coefficients. This represents the total system delay time. For the Laplace operator; An auxiliary function for analyzing the passive conditions of the system is constructed based on the inverter-side inductance, the filter capacitor, and the total system delay time. The expression is: , In the formula, This is an auxiliary function used to analyze the passivity conditions of a system. Angular frequency, For filtering capacitors, For the inverter side inductor, For grid-side inductance; Within a preset frequency range, the auxiliary function is calculated and determined. The corresponding first frequency range, and the auxiliary function The corresponding second frequency range; Based on the preset passivity condition, the weighting coefficients are derived respectively. The first constraint condition and the weighting coefficient within the first frequency range The second constraint condition within the second frequency range; Find the weighting coefficients that simultaneously satisfy both the first and second constraints. The common range of values ​​is determined, and a specific value is selected from the common range as the weighting coefficient. The final design value is then substituted into the proportional weighted differential feedforward function to form a complete feedforward control law. The feedforward control law is applied to the common coupling point voltage feedforward channel of the grid-connected inverter to suppress grid background harmonics and ensure that the inverter output admittance meets the passive condition within the preset frequency range.

[0008] In a second aspect, the present invention provides a voltage feedforward control system for a grid-connected inverter, comprising: an acquisition module configured to acquire system parameters of the grid-connected inverter, the system parameters comprising an inductor on the inverter side, a filter capacitor, a total system delay time caused by a control delay, and an inverter gain; a first construction module configured to construct a proportionally-weighted differential feedforward function based on the total system delay time and the inverter gain, expressed as: , wherein, is the proportionally-weighted differential feedforward function, is the inverter gain, is a weighting coefficient, is the total system delay time, is a Laplace operator; a second construction module configured to construct an auxiliary function for analyzing a system passivity condition based on the inductor on the inverter side, the filter capacitor, and the total system delay time, expressed as: , wherein, is the auxiliary function for analyzing the system passivity condition, is an angular frequency, is the filter capacitor, is the inductor on the inverter side, is an inductor on the grid side; a determination module configured to calculate and determine, within a preset frequency range, a first frequency interval corresponding to the auxiliary function and a second frequency interval corresponding to the auxiliary function ; a derivation module configured to derive, according to a preset passivity condition, a first constraint condition of the weighting coefficient in the first frequency interval and a second constraint condition of the weighting coefficient in the second frequency interval, respectively; a solution module configured to solve a common value range of the weighting coefficient that satisfies the first constraint condition and the second constraint condition simultaneously, and select a specific numerical value from the common value range as a final design value of the weighting coefficient , and substitute the final design value into the proportionally-weighted differential feedforward function to form a complete feedforward control law; a control module configured to apply the feedforward control law to a common connection point voltage feedforward channel of the grid-connected inverter, to suppress grid background harmonics and ensure that an inverter output admittance satisfies a passivity condition within the preset frequency range.

[0009] Thirdly, an electronic device is provided, comprising: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the steps of a voltage feedforward control method for a grid-connected inverter according to any embodiment of the present invention.

[0010] Fourthly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the program instructions are executed by a processor, the processor performs the steps of the voltage feedforward control method for a grid-connected inverter according to any embodiment of the present invention.

[0011] This application discloses a voltage feedforward control method and system for grid-connected inverters. First, a proportionally weighted differential feedforward function is constructed. An auxiliary function is then constructed based on system parameters, and frequency intervals are defined accordingly. The constraints on the weighting coefficient λ in the h(ω)>0 and h(ω)<0 frequency bands are derived through passive conditions, and the common range of λ values ​​is solved. The optimal λ value within this range is selected and substituted into the feedforward function to form the final control law, which is then applied to the inverter. This invention, through precise design of λ, significantly enhances the suppression capability of voltage harmonics (especially intermediate frequency harmonics) at the point of common coupling (PCC) while ensuring the passive nature of the inverter's output admittance across the entire frequency band (system stability). This achieves synergistic optimization of stability and power quality without increasing hardware costs, making it highly practical for engineering applications. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 A flowchart of a voltage feedforward control method for a grid-connected inverter provided in an embodiment of the present invention; Figure 2 A schematic diagram of the grid-connected inverter control structure is provided for a specific embodiment of the present invention; Figure 3 To illustrate an embodiment of the present invention, we provide Bode plots of proportional differential feedforward and unit feedforward admittances for a specific embodiment. Figure 4 A specific embodiment of the present invention is provided. A diagram illustrating the positive and negative ranges; Figure 5 This diagram illustrates the feasible range of the weighting coefficient λ in a specific embodiment of the present invention. Figure 6 A Bode plot of admittance corresponding to different weighting coefficients λ of a specific embodiment of the present application is provided for an embodiment of the present application; Figure 7 A design flow diagram of a voltage feedforward control method of a specific embodiment of the present application is provided for an embodiment of the present application; Figure 8 A schematic diagram of intermediate frequency passivity experimental results of a specific embodiment of the present application is provided for an embodiment of the present application; Figure 9 A schematic diagram of high frequency passivity experimental results of a specific embodiment of the present application is provided for an embodiment of the present application; Figure 10 A schematic diagram of voltage distortion experiments of a specific embodiment of the present application is provided for an embodiment of the present application; Figure 11 A structural block diagram of a voltage feedforward control system for a grid-connected inverter of an embodiment of the present application is provided for an embodiment of the present application; Figure 12 A structural diagram of an electronic device of an embodiment of the present application is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0014] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0015] Please refer to Figure 1 , which shows a flowchart of a voltage feedforward control method for a grid-connected inverter.

[0016] As Figure 1 shown, the voltage feedforward control method for the grid-connected inverter specifically includes the following steps: Step S101, acquiring system parameters of the grid-connected inverter, the system parameters including an inverter-side inductance, a filter capacitance, a total system delay time generated by a control delay, and an inverter gain.

[0017] Step S102, constructing a proportional-weighted differential feedforward function based on the total system delay time and the inverter gain.

[0018] In this step, the expression of the proportional-weighted differential feedforward function is: , In the formula, is the proportional-weighted differential feedforward function, is an inverter gain, is a weighting coefficient, is a system total delay time, is a Laplacian operator; Step S103, constructing an auxiliary function for analyzing a system passivity condition according to the inverter-side inductance, the filter capacitance, and the system total delay time.

[0019] In this step, the expression of the auxiliary function is: , wherein, is an auxiliary function for analyzing a system passivity condition, is an angular frequency, is a filter capacitance, is an inverter-side inductance, is a grid-side inductance.

[0020] Step S104, calculating and determining the auxiliary function corresponding to a first frequency interval, and the auxiliary function corresponding to a second frequency interval.

[0021] Step S105, deriving the weighting coefficient a first constraint condition in the first frequency interval and the weighting coefficient a second constraint condition in the second frequency interval.

[0022] In this step, the preset passivity condition is that the real part of the output admittance of the grid-connected inverter is greater than 0, and the expression of the real part of the output admittance of the grid-connected inverter is: , wherein, is a controller proportional gain.

[0023] The weighting coefficient a first constraint condition in the first frequency interval is expressed as: , The weighting coefficient a second constraint condition in the second frequency interval is expressed as: , wherein, is a controller proportional gain.

[0024] Step S106, solving the weighting coefficient a common value range of the weighting coefficient λ, and selecting a specific value from the common value range of the weighting coefficient λ as the weighting coefficient λ a final design value of the weighting coefficient λ, and substituting the final design value of the weighting coefficient λ into the proportional-differential feedforward function to form a complete feedforward control law.

[0025] In this step, the weighting coefficient λ The expression of the common value range of the weighting coefficient λ is: , In the formula, is the proportional gain of the controller.

[0026] Step S107, applying the feedforward control law to the common connection point voltage feedforward channel of the grid-connected inverter to suppress the grid background harmonics and ensure that the inverter output admittance meets the passivity condition in the preset frequency range.

[0027] In summary, the method of the present application firstly accurately associates the design of the weighting coefficient λ with the passivity condition of the inverter output admittance through strict mathematical derivation, forms a theoretical design boundary that ensures that the system meets the passivity condition in the full frequency range (from low frequency to Nyquist frequency), thereby providing a solid stability guarantee for the inverter to access a weak power grid with any impedance characteristic, and completely eliminates the risk of mid-high frequency oscillation caused by the introduction of feedforward. Secondly, under the hard constraint of ensuring the above full frequency stability, by optimizing the selection of the λ value close to the upper limit of the allowed range, the suppression ability of the feedforward control on the mid-frequency common connection point voltage harmonics is significantly enhanced. Finally, the entire method is based on closed-loop design of explicit system parameters, the steps are clear, the parameters are determined, and the method is completely realized through control algorithm software without adding any hardware sensors or filter circuits. While improving the robustness and performance of the system, the method maintains the engineering advantages of low cost and easy implementation, and provides key technical support for the safe and stable operation of the power grid under high proportion of new energy access.

[0028] In a specific embodiment, the voltage feedforward control method for the grid-connected inverter specifically comprises: Step 1: Propose a proportional-differential feedforward control Figure 2 The control structure of the grid-connected inverter is shown in the figure. In the figure, the grid voltage is denoted as , the inverter DC side voltage is defined as , the common connection point voltage is , the capacitor voltage is denoted as , the grid current and its reference current are denoted as and respectively, the feedforward module adopts a unit feedforward design, and its transfer function is . The filter part is composed of the inverter side inductance grid-side inductor and filter capacitor constitute a PR controller. The transfer function of the PR controller is represented as , and the gain parameters of the inverter itself are . represents the equivalent inductance of the grid, is the reactive compensation capacitor configured at the grid side. In view of the delay effect in the control process, a mathematical model is established by using , wherein the delay time caused by the zero-order holder and the digital control is , and the corresponding delay time is 1.5 sampling periods. The relationship between the sampling period T and the sampling angular frequency is .

[0029] According to the inverter control structure shown in (b) of Figure 1 , when the capacitor voltage is regarded as a disturbance input, the system output and the same satisfy the following relationship: , (1) wherein the open-loop transfer function of the system and the output admittance are respectively: , (2) , (3) In the above two formulas, the expression of the controller is: , (4) wherein and are the proportional gain and the resonant gain of the controller respectively.

[0030] The PR controller is ignored and approximated as a proportional link, and the output admittance is redefined as: , (5) In order to improve the non-passive area in the output admittance of the grid-connected inverter side and improve the suppression ability of the PCC voltage harmonics, the numerator of the admittance is set to zero, that is, , at this time, the impedance gain of the inverter tends to infinity in the full frequency band, and the ideal feedforward condition is derived as: , (6) Since belongs to the prediction link, it is difficult to realize in the physical system, and therefore it is approximated by the first-order Taylor expansion: , (7) Substituting formula (7) into formula (6), the following formula is obtained: The cubic differential form. Ultimately, to reduce algorithm complexity, [the algorithm is]... Approximating the proportional-differential form, its expression is: (8) Step 2: Optimization of the Proportional-Derivative Feedforward Structure To verify the actual effect of adding a proportional-derivative term, admittance Bode plots were compared and plotted under proportional-derivative feedforward and unit feedforward, as shown below. Figure 3 As shown in the figure. The results indicate that, compared to unity feedforward, proportional-derivative feedforward significantly reduces admittance gain in the low-to-mid frequency range, i.e., increases equivalent impedance, thereby enhancing harmonic suppression capability in this frequency band. From a passive perspective, its passive performance is significantly reduced in the mid-to-high frequency range.

[0031] pass Figure 3 A comparison of unit feedforward and proportional-derivative feedforward reveals that the passive region in the mid-to-high frequency band is mainly caused by the differential term. To preserve the harmonic suppression effect of the differential term in the mid-frequency band while satisfying the passivity requirement, a weighting coefficient λ is introduced before the differential term. The feedforward function can then be expressed as: (9) Step 3: Calculation of the real part of the admittance and positive / negative analysis under proportional weighted differential feedforward According to equation (5), Write in complex frequency domain form By simplifying and organizing, we can obtain The expression for the real part is: (10) As can be seen from equation (10), the real part of the output admittance is... The denominator is the sum of two squared terms, which is always non-negative. Therefore, its sign characteristic is entirely determined by the numerator. When the admittance numerator is greater than 0, the real part of the output admittance is always non-negative. Therefore, the condition for the real part of the admittance to be greater than 0 is: (11) Step 4: Design of weighting coefficients λ make The expression is: (12) To ensure admittance Since the real part of is always positive, by rearranging and changing the sign of the corresponding inequality in equation (11), and by explicitly separating the weighting coefficient λ, we can obtain that the parameter λ must satisfy the following condition: 1) In Within the corresponding frequency band, λ must satisfy: (13) 2) In Within the corresponding frequency band, λ must satisfy: (14) From equations (13) and (14), it can be seen that in order to ensure that the following conditions are met at all frequencies ω... λ must simultaneously satisfy the constraints corresponding to all frequencies, that is, in In all frequency bands, λ must be greater than the maximum value of the expression on the right side of equation (13) in that frequency band. Within all frequency bands, λ must be less than the minimum value of the expression on the right side of equation (14) within that frequency band. Therefore, the range of λ is the interval formed by these two extreme values, i.e.: (15) This range of values ​​fundamentally ensures that the real part of the output admittance of the grid-connected inverter is non-negative across the entire frequency band, realizing the global passivity of the system and providing a theoretical boundary for parameter tuning for the coordinated optimization of system passivity design and harmonic suppression.

[0032] The graph was drawn from equation (12). In the positive and negative range of the entire frequency band, such as Figure 4 As shown in the figure. From the graph, it can be seen that in the frequency bands [0Hz, 1667Hz] and [3182Hz, 5000Hz]... In the [1667Hz, 3182Hz] frequency band .

[0033] based on Figure 4 middle Divide the positive and negative frequency bands and plot the amplitude curves of the expressions on the right side of equations (13) and (14) in the corresponding frequency ranges (e.g., Figure 5 (As shown). Among them, in In the frequency band ([1667Hz, 3182Hz]), since the amplitude of the expression on the right side of equation (13) is always less than 0, and considering that λ needs to satisfy non-negativity in practical applications, the lower limit constraint corresponding to λ is 0; The frequency bands ([0Hz, 1667Hz] and [3182Hz, 5000Hz]) show a trend of first decreasing and then increasing with frequency, with a minimum value of 0.45. Therefore, the upper limit constraint corresponding to λ is 0.45. In summary, according to equation (15), the range of λ is λ∈(0,0.45). From the perspective of performance synergy, the larger λ is, the stronger the proportional weighted differential feedforward's ability to suppress mid-frequency grid voltage harmonics. Therefore, under the premise of ensuring the passivity of the system across the entire frequency band, a value close to the upper limit of the range should be selected as much as possible. Considering the balance between stability and harmonic suppression effect, this patent ultimately selects λ=0.45.

[0034] To verify the accuracy of the parameter design method, admittance Bode plots were plotted for different weighted differential feedforward coefficients (see...). Figure 6 ).Depend on Figure 6 It can be seen that when λ=0.7, although the mid-frequency admittance amplitude is low (equivalent impedance is large), it has a certain effect on suppressing PCC voltage harmonics. However, non-passive regions appear in both the mid-frequency and high-frequency bands, which cannot meet the system's full-band passivity requirements and poses a stability risk. When λ=0.55, the mid-frequency harmonic suppression capability is still superior to that of low λ value scenarios, and the attenuation of admittance amplitude is sufficient to weaken some PCC voltage harmonic interference. However, non-passive regions still remain in the mid-frequency band, and the system is susceptible to grid impedance fluctuations in this band, so the stability risk is not completely eliminated. When λ=0.45, not only does the mid-frequency admittance amplitude maintain a reasonable reduction, effectively weakening the impact of PCC voltage harmonics on the grid-connected current, but the non-passive regions in the full-band also completely disappear, and the real part of the admittance always meets the requirements. It achieves full-band passivity and realizes synergistic optimization of harmonic suppression effect and system operation stability.

[0035] Figure 7 This demonstrates the core design flow of the invention: Step 1: Determine the inverter system parameters.

[0036] Step 2: Determine the feedforward form according to equation (9).

[0037] Step 3: Determine according to equation (12) Positive and negative range.

[0038] Step 4: Judgment Still <0, when When, take the maximum value on the right side of equation (13), when When, take the minimum value on the right side of equation (14). Step 5: Determine the range of values ​​for λ according to equation (15) to provide the theoretical boundary for parameter tuning.

[0039] Step 6: Use formula (5) to draw the admittance Bode plot to determine whether the passivity condition is met. If the condition is not met, start tuning again from step 2; if the condition is met, the tuning ends.

[0040] To verify the effectiveness of the passive admittance enhancement and harmonic suppression strategy for grid-connected inverters based on proportionally weighted differential voltage feedforward, this embodiment constructs a 4.8 kVA single-phase grid-connected inverter simulation experimental platform, and conducts tests focusing on two core indicators: passivity (system stability) and harmonic suppression (power quality). The core parameters of the inverter used in the experiment are shown in Table 1, ensuring that the test conditions are consistent with actual engineering application scenarios.

[0041] Table 1 Inverter Parameters , Experiment 1: To verify the accuracy of the weighting coefficient selection method, passive verification (weak grid stability) was conducted for different weighting coefficient values. The equivalent admittance of the grid was simulated using series inductors or parallel capacitors, and the tests were conducted in two groups: 1) Intermediate frequency passive property test ( ),Depend on Figure 8 It can be seen that when λ=0.7, the grid-connected current exhibits periodic oscillations and amplitude divergence. According to the parameter design method, this coefficient exceeds the mid-frequency passive design range, resulting in a negative real part of the mid-frequency admittance. The experimental waveform also proves that this coefficient does not meet the design requirements. When λ=0.55, the grid-connected current also exhibits periodic oscillations and amplitude divergence, indicating that this coefficient also does not meet the mid-frequency passive design conditions set by the parameter design method, resulting in the existence of a non-passive region in the mid-frequency range, which also does not meet the design requirements. However, when λ=0.45, the grid-connected current waveform is smooth and stable without any oscillations. This result completely matches the derivation conclusion of the parameter design method, verifying the accuracy of the coefficient selected by this design method.

[0042] 2) High-frequency passive property testing ( , ),Depend on Figure 9 It can be seen that: when λ=0.7, the grid-connected current rapidly exhibits periodic oscillations with divergent amplitudes. According to the proposed parameter design method, this coefficient exceeds the high-frequency passive design range, resulting in a negative real part of the high-frequency admittance. The experimental waveform directly proves that this coefficient does not meet the design requirements. When λ=0.55, the grid-connected current waveform is smooth and stable without any oscillation, indicating that this coefficient is consistent with the high-frequency passive design conditions of the parameter design method proposed in this patent. When λ=0.45, the grid-connected current waveform is also consistently smooth and stable without any signs of oscillation. This result perfectly matches the derivation conclusion of the parameter design method, further verifying the accuracy of the selected design method.

[0043] Experiment 2: Harmonic suppression capability verification (for power quality). The distortion voltage was set to the fundamental frequency superimposed with the 3rd, 5th, 7th, 11th, 13th, 15th and 21st harmonics (amplitudes of 10%, 5%, 3%, 3%, 2%, 2% and 1% respectively). The three operating conditions were no feedforward (a), unit feedforward (b) and the feedforward proposed in this paper (c).

[0044] Depend on Figure 10 The grid-connected current under three different operating conditions can be obtained. The THD values ​​are as follows: No voltage feedforward condition: Current THD = 9.45%, traditional unit feedforward current THD = 4.08%, Scheme of the present invention: Current THD=2.1%. The grid-connected current power quality corresponding to the scheme of the application is optimal. Secondly, according to the corresponding harmonic spectrum, the suppression effect of the scheme of the application on 3, 5, 7 and other main harmonics is remarkable, and the amplitude of each harmonic is lower than that of the traditional feedforward, proving that the admittance gain in the medium and low frequency band is effectively reduced (the equivalent impedance is increased).

[0045] In summary, the experimental results show that the control system using the proportional weighted differential feedforward of the application ensures the passivity in the Nyquist frequency range, realizes the efficient isolation of the grid-connected current from the background harmonics of the PCC voltage, and ensures the strong robust stability and high power quality of the grid-connected inverter based on the PCC voltage feedforward strategy.

[0046] Referring to Figure 11 , a structural block diagram of a voltage feedforward control system for a grid-connected inverter is shown.

[0047] As Figure 11 shown, the voltage feedforward control system 200 includes an acquisition module 210, a first construction module 220, a second construction module 230, a determination module 240, a derivation module 250, a solving module 260 and a control module 270.

[0048] The acquisition module 210 is configured to acquire system parameters of the grid-connected inverter, including the inductance on the inverter side, the filter capacitance, the total system delay time caused by the control delay and the inverter gain. The first construction module 220 is configured to construct a proportional weighted differential feedforward function based on the total system delay time and the inverter gain, and the expression is as follows: , In the formula, is the proportional weighted differential feedforward function, is the inverter gain, is the weighted coefficient, is the total system delay time, is the Laplace operator; The second construction module 230 is configured to construct an auxiliary function for analyzing the system passivity condition according to the inductance on the inverter side, the filter capacitance and the total system delay time, and the expression is as follows: , In the formula, is the auxiliary function for analyzing the system passivity condition, is the angular frequency, is the filter capacitance, is the inductance on the inverter side, is the inductance on the grid side; The module 240 is configured to calculate and determine the auxiliary function within a preset frequency range. The corresponding first frequency range, and the auxiliary function The corresponding second frequency range; The derivation module 250 is configured to derive the weighting coefficients based on preset passivity conditions. The first constraint condition and the weighting coefficient within the first frequency range The second constraint condition within the second frequency range; Solver module 260 is configured to solve for the weighted coefficients that simultaneously satisfy the first constraint and the second constraint. The common range of values ​​is determined, and a specific value is selected from the common range as the weighting coefficient. The final design value is then substituted into the proportional weighted differential feedforward function to form a complete feedforward control law. The control module 270 is configured to apply the feedforward control law to the common coupling point voltage feedforward channel of the grid-connected inverter to suppress grid background harmonics and ensure that the inverter output admittance meets the passive condition within the preset frequency range.

[0049] It should be understood that Figure 11 The modules and references described in the document Figure 1 The steps described in the text correspond to those in the method described above. Therefore, the operations, features, and corresponding technical effects described above also apply to the method described in the text. Figure 2 The various modules in the document will not be described in detail here.

[0050] It is worth noting that the modules in the embodiments of this disclosure are not intended to limit the solutions of this disclosure. For example, the judgment module can be described as a module that determines whether the interactive state contains surgical instrument information when the device is in an interactive state. In addition, related functional modules can also be implemented by hardware processors. For example, the judgment module can also be implemented by a processor, which will not be elaborated here.

[0051] In other embodiments, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the program instructions are executed by a processor, the processor performs the voltage feedforward control method for a grid-connected inverter in any of the above method embodiments. In one embodiment, the computer-readable storage medium of the present invention stores computer-executable instructions, which are configured as follows: Obtain the system parameters of the grid-connected inverter, including inverter-side inductance, filter capacitor, total system delay time caused by control delay, and inverter gain; constructing a proportional plus differential feedforward function based on the total system delay time and the inverter gain, expressed as: , wherein, is the proportional plus differential feedforward function, is the inverter gain, is the weighting coefficient, is the total system delay time, is the Laplace operator; constructing an auxiliary function for analyzing the passivity condition of the system according to the inverter-side inductance, the filter capacitance and the total system delay time, expressed as: , wherein, is the auxiliary function for analyzing the passivity condition of the system, is the angular frequency, is the filter capacitance, is the inverter-side inductance, is the grid-side inductance; calculating and determining the first frequency interval corresponding to the auxiliary function and the second frequency interval corresponding to the auxiliary function in a preset frequency range; deriving the first constraint condition of the weighting coefficient in the first frequency interval and the second constraint condition of the weighting coefficient in the second frequency interval according to the preset passivity condition; solving the common value range of the weighting coefficient that satisfies the first constraint condition and the second constraint condition at the same time, and selecting a specific numerical value from the common value range as the final design value of the weighting coefficient , and substituting the final design value into the proportional plus differential feedforward function to form a complete feedforward control law; applying the feedforward control law to the point of common coupling voltage feedforward channel of the grid-connected inverter to suppress the grid background harmonics and ensure that the inverter output admittance satisfies the passivity condition in the preset frequency range.

[0052] Computer-readable storage media may include a stored program area and a stored data area, wherein the stored program area may store an operating system and an application program required for at least one function; the stored data area may store data created based on the use of the voltage feedforward control system for the grid-connected inverter, etc. Furthermore, the computer-readable storage medium may include high-speed random access memory, and may also include memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, the computer-readable storage medium may optionally include memory remotely disposed relative to a processor, which can be connected via a network to the voltage feedforward control system for the grid-connected inverter. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0053] Figure 12 This is a schematic diagram of the structure of the electronic device provided in the embodiment of the present invention, such as... Figure 12 As shown, the device includes a processor 310 and a memory 320. The electronic device may also include an input device 330 and an output device 340. The processor 310, memory 320, input device 330, and output device 340 can be connected via a bus or other means. Figure 12 Taking a bus connection as an example, the memory 320 is the computer-readable storage medium described above. The processor 310 executes various server functions and data processing by running non-volatile software programs, instructions, and modules stored in the memory 320, thereby implementing the voltage feedforward control method for grid-connected inverters described in the above method embodiments. The input device 330 can receive input digital or character information and generate key signal inputs related to user settings and function control of the voltage feedforward control system for grid-connected inverters. The output device 340 may include a display device such as a screen.

[0054] The aforementioned electronic device can execute the method provided in the embodiments of the present invention, and has the corresponding functional modules and beneficial effects for executing the method. Technical details not described in detail in this embodiment can be found in the method provided in the embodiments of the present invention.

[0055] In one implementation, the aforementioned electronic device is applied in a voltage feedforward control system for a grid-connected inverter, for a client, and includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to: Obtain the system parameters of the grid-connected inverter, including inverter-side inductance, filter capacitor, total system delay time caused by control delay, and inverter gain; constructing a proportional plus differential feedforward function based on the total system delay time and the inverter gain, expressed as: , wherein, is the proportional plus differential feedforward function, is the inverter gain, is the weighting coefficient, is the total system delay time, is the Laplace operator; constructing an auxiliary function for analyzing the system passivity condition according to the inverter-side inductance, the filter capacitance and the total system delay time, expressed as: , wherein, is the auxiliary function for analyzing the system passivity condition, is the angular frequency, is the filter capacitance, is the inverter-side inductance, is the grid-side inductance; calculating and determining the first frequency interval corresponding to the auxiliary function and the second frequency interval corresponding to the auxiliary function within a preset frequency range; deriving the first constraint condition of the weighting coefficient within the first frequency interval and the second constraint condition of the weighting coefficient within the second frequency interval according to the preset passivity condition; solving the common value range of the weighting coefficient that satisfies the first constraint condition and the second constraint condition at the same time, and selecting a specific numerical value from the common value range as the final design value of the weighting coefficient , and substituting the final design value into the proportional plus differential feedforward function to form a complete feedforward control law; applying the feedforward control law to the point of common coupling voltage feedforward channel of the grid-connected inverter to suppress the grid background harmonics and ensure that the inverter output admittance satisfies the passivity condition within the preset frequency range.

[0056] Those skilled in the art can clearly understand the implementation of the various embodiments by means of software and necessary general hardware platforms through the description of the above embodiments, and of course, the embodiments can also be implemented by hardware. Based on such understanding, the above technical solutions, essentially or in other words, the part of the prior art that makes a contribution, can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, and the like, and includes a number of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods of the various embodiments or some parts of the embodiments.

[0057] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. A voltage feedforward control method for a grid-connected inverter, characterized in that, include: Obtain the system parameters of the grid-connected inverter, including inverter-side inductance, filter capacitor, total system delay time caused by control delay, and inverter gain; Based on the total system delay time and inverter gain, a proportionally weighted differential feedforward function is constructed, with the following expression: ， In the formula, It is a proportionally weighted differential feedforward function. For inverter gain, These are weighting coefficients. This represents the total system delay time. For the Laplace operator; An auxiliary function for analyzing the passive conditions of the system is constructed based on the inverter-side inductance, the filter capacitor, and the total system delay time. The expression is: ， In the formula, This is an auxiliary function used to analyze the passivity conditions of a system. Angular frequency, For filtering capacitors, For the inverter side inductor, For grid-side inductance; Within a preset frequency range, the auxiliary function is calculated and determined. The corresponding first frequency range, and the auxiliary function The corresponding second frequency range; Based on the preset passivity condition, the weighting coefficients are derived respectively. The first constraint condition and the weighting coefficient within the first frequency range The second constraint condition within the second frequency range; Find the weighting coefficients that simultaneously satisfy both the first and second constraints. The common range of values ​​is determined, and a specific value is selected from the common range as the weighting coefficient. The final design value is obtained and substituted into the proportional weighted differential feedforward function to form a complete feedforward control law; The feedforward control law is applied to the common coupling point voltage feedforward channel of the grid-connected inverter to suppress grid background harmonics and ensure that the inverter output admittance meets the passive condition within the preset frequency range.

2. The voltage feedforward control method for a grid-connected inverter according to claim 1, characterized in that, in, The preset passive condition is that the real part of the output admittance of the grid-connected inverter is greater than 0, and the expression for the real part of the output admittance of the grid-connected inverter is: ， In the formula, This is the proportional gain of the controller.

3. The voltage feedforward control method for a grid-connected inverter according to claim 1, characterized in that, The weighting coefficients The expression for the first constraint condition within the first frequency range is: ， The weighting coefficients The expression for the second constraint condition within the second frequency range is: ， In the formula, This is the proportional gain of the controller.

4. The voltage feedforward control method for a grid-connected inverter according to claim 1, characterized in that, The weighting coefficients The expression for the common range of values ​​is: ， In the formula, This is the proportional gain of the controller.

5. A voltage feedforward control system for a grid-connected inverter, characterized in that, include: The acquisition module is configured to acquire the system parameters of the grid-connected inverter, including the inverter-side inductance, filter capacitor, total system delay time caused by control delay, and inverter gain. The first construction module is configured to construct a proportionally weighted differential feedforward function based on the total system delay time and inverter gain, with the expression being: ， In the formula, It is a proportionally weighted differential feedforward function. For inverter gain, These are weighting coefficients. This represents the total system delay time. For the Laplace operator; The second construction module is configured to construct an auxiliary function for analyzing the passive conditions of the system based on the inverter-side inductance, the filter capacitor, and the total system delay time. The expression is: ， In the formula, This is an auxiliary function used to analyze the passivity conditions of a system. Angular frequency, For filtering capacitors, For the inverter side inductor, For grid-side inductance; The module is configured to calculate and determine the auxiliary function within a preset frequency range. The corresponding first frequency range, and the auxiliary function The corresponding second frequency range; The derivation module is configured to derive the weighting coefficients based on preset passivity conditions. The first constraint condition and the weighting coefficient within the first frequency range The second constraint condition within the second frequency range; The solver module is configured to solve for the weighted coefficients that simultaneously satisfy both the first and second constraints. The common range of values ​​is determined, and a specific value is selected from the common range as the weighting coefficient. The final design value is obtained and substituted into the proportional weighted differential feedforward function to form a complete feedforward control law; The control module is configured to apply the feedforward control law to the common coupling point voltage feedforward channel of the grid-connected inverter to suppress grid background harmonics and ensure that the inverter output admittance meets the passive condition within the preset frequency range.

6. An electronic device, characterized in that, include: At least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method described in any one of claims 1 to 4.

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