Wide-frequency-domain adaptive admittance control method and system considering frequency coupling effect

Abstract

The invention relates to the technical field of grid-connected equipment impedance control, in particular to a wide-frequency-domain self-adaptive admittance control method and system considering the frequency coupling effect, and the method comprises the steps: building a wide-area admittance remodeling control loop considering the frequency coupling effect, comprising a virtual impedance control branch, a DC voltage loop control branch, a current loop forward control branch and two virtual impedance feed-forward branches. Selecting a reference virtual resistor based on a converter fundamental wave reactance coefficient, and determining a maximum variable admittance remolding adjustment coefficient and a numerical range of a reference virtual inductor through grid-connected converter GCC self-stability constraint; the variable admittance remolding adjustment coefficient is automatically adjusted based on the total harmonic distortion (THD) of the voltage component, the value of the amplification coefficient is determined based on the constraint of the maximum adjustment coefficient, and the admittance self-adaptive control of the converter is realized. And the method also has the advantages of broadband adjustment characteristic, simple admittance parameter setting, adaptive admittance adjustment and the like.

Description

Technical Field

[0001] This invention relates to the field of impedance control technology for grid-connected equipment, and in particular to a wide-frequency adaptive admittance control method and system that considers frequency coupling effects. Background Technology

[0002] In recent years, as the proportion of renewable energy power plants in the power grid has gradually increased, the power system has exhibited the "dual high" characteristics of high proportion of new energy and high power electronics. This has made the interaction between new energy grid-connected equipment and the power grid increasingly complex, triggering a series of broadband oscillation problems that seriously threaten the safe and stable operation of the power grid. Against this backdrop, improving the damping performance of new energy power generation equipment, thereby enhancing its broadband oscillation suppression capability, has become a key issue that urgently needs to be addressed in power electronic power systems.

[0003] The numerous power electronic converters in new energy power generation systems are a major cause of broadband oscillations. To suppress these oscillations, various active damping methods have been proposed. Compared to installing dedicated damping converters in the system, modifying existing converters is more economical and flexible. Therefore, using impedance reshaping control technology to modify the control of existing grid-connected converters to enhance system damping and suppress broadband oscillations has become the most promising solution.

[0004] Existing impedance optimization control methods mainly include phase angle compensation control, voltage feedforward, virtual impedance, and series / parallel additional damping. While these damping control methods can improve the stability of grid-connected systems to some extent, they are mostly customized for specific scenarios, typical modes, and oscillation frequency bands, lacking a unified design concept with strong universality and wide applicability. If the application scenario and operating conditions change, the damping control may be affected or even fail. Therefore, there is an urgent need to find a converter wide-area admittance reshaping control method with adaptive adjustment capabilities.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a wideband adaptive admittance control method and system that considers frequency coupling effects, thereby effectively solving the problems in the background art.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a wideband adaptive admittance control method and system considering frequency coupling effects, comprising the following steps:

[0008] Considering the frequency coupling effect, a wide-area admittance reshaping control loop is constructed, including a virtual impedance control branch, a DC voltage loop control branch, a current loop forward control branch, and two virtual impedance feedforward branches.

[0009] The reference virtual resistance is selected based on the fundamental reactance coefficient of the converter, and the numerical range of the maximum variable admittance reshaping adjustment coefficient and the reference virtual inductance is determined by the self-stability constraint of the grid-connected converter GCC.

[0010] Adaptive control of converter admittance is achieved by autonomously adjusting the variable admittance reshaping adjustment coefficient based on the total harmonic distortion (THD) of the voltage component and determining the value of the amplification coefficient based on the constraint of the maximum adjustment coefficient.

[0011] Furthermore, the construction of the wide-area admittance reshaping control loop considering frequency coupling effects includes:

[0012] Considering the frequency coupling introduced by the DC voltage loop and the phase-locked loop, the virtual admittance Y is... ad It is shaped into an adaptive, flexible, and variable admittance;

[0013] The equivalent feedforward gain is distributed across the virtual impedance control branch, the DC voltage loop control branch, the current loop forward control branch, and the two virtual impedance feedforward branches.

[0014] Furthermore, the virtual impedance control branch is used to simulate the effect of virtual impedance. The input signal is a three-phase voltage signal, which is converted into a two-phase voltage signal after abc / αβ conversion.

[0015] The two-phase voltage signals pass through a notch filter G. NF (s), and then through the variable virtual admittance Y ad (s) obtains the virtual current signal, G NF (s) is represented as:

[0016] ;

[0017] In the formula, ω1 and ζ are the fundamental frequency and the notch filter damping ratio, respectively.

[0018] Furthermore, the two virtual impedance feedforward branches are used to cancel the coupling introduced by the power parameter inductance. The input signal of the first feedforward branch is a virtual current signal, which is processed by the differentiating controller G. f1 (s) After that, the αβ axis modulated additional signal can be obtained; the input signal of the second feedforward branch is the dq axis virtual current signal, which is filtered by a high-pass filter G. H (s) and integral controller G f2 (s) then obtains the dq-axis modulated additional signal;

[0019] G f1 (s), G f2(s) and G H (s) is represented as:

[0020] ;

[0021] In the formula, L f For filter inductance, V dc For DC voltage, k sp C is the modulation coefficient. dc M1 is the DC capacitor, M1 is the steady-state amplitude of the modulation signal, and ω n ξ and ξ represent the cutoff frequency and damping ratio of the high-pass filter, respectively.

[0022] Furthermore, the forward control branch of the current loop is used to simulate virtual admittance, and the input signal is a signal filtered by a high-pass filter G. H The virtual current signal of the dq axis after (s) is directly superimposed on the current loop output given signal.

[0023] Furthermore, the DC voltage loop control branch is used to achieve decoupling control in the admittance simulation process, and its input signal is a signal passed through a high-pass filter G. H The d-axis signal of the virtual current after (s) passes through the controller G. vi (s) then obtains the additional DC voltage signal;

[0024] G vi (s) is represented as:

[0025] .

[0026] Furthermore, the selection of the reference virtual resistance based on the fundamental reactance coefficient of the converter includes:

[0027] The reference virtual admittance is set to the circuit form of RL, specifically as follows:

[0028] ;

[0029] In the formula, R viB and L viB As a reference for virtual resistance and inductance;

[0030] Reshaped variable virtual admittance Y ad With reference virtual admittance Y viB The relationship is:

[0031] ;

[0032] In the formula, k vi This is the variable admittance remodeling adjustment coefficient. The larger the value, the greater the depth of admittance remodeling adjustment.

[0033] Furthermore, determining the numerical range of the maximum variable admittance reshaping regulation coefficient and the reference virtual inductance through the self-stability constraint of the grid-connected converter GCC includes:

[0034] Set the reference virtual admittance according to the per-unit value, and set the reference virtual resistance R. viB Given one times the fundamental reactance, we have:

[0035] ;

[0036] In the formula, U B and S B Z represents the rated voltage and capacity of the GCC. B For fundamental frequency reactance;

[0037] The numerical ranges of the maximum regulation coefficient and the virtual inductance are determined by using GCC self-stability constraints.

[0038] Furthermore, the value of the variable admittance reshaping adjustment coefficient based on the total harmonic distortion (THD) of the voltage component and the value of the amplification coefficient determined by the constraint based on the maximum adjustment coefficient include:

[0039] The magnitude of the adjustment coefficient is determined by the harmonic content in the voltage component:

[0040] ;

[0041] In the formula, v αh v βh These represent the harmonic components along the α and β axes excluding the fundamental frequency, respectively; V1 is the amplitude of the fundamental voltage; and G... dz For dead zone components, k h G is the magnification factor. L This is a low-pass filter, and its cutoff frequency is set the same as that of a high-pass filter.

[0042] The dead zone is set according to the THD threshold of the low-voltage power grid, and the amplification factor is designed with constraints based on the maximum regulation factor.

[0043] The present invention also includes a wideband adaptive admittance control system considering frequency coupling effects, using the method described above, wherein the system comprises:

[0044] The wide-area admittance reshaping control unit is used to construct a wide-area admittance reshaping control loop considering frequency coupling effects. It includes a virtual impedance control branch, a DC voltage loop control branch, a current loop forward control branch, and two virtual impedance feedforward branches.

[0045] The virtual admittance design unit is used to select a reference virtual resistance based on the fundamental reactance coefficient of the converter, and to determine the numerical range of the maximum variable admittance reshaping adjustment coefficient and the reference virtual inductance through the self-stability constraint of the grid-connected converter GCC.

[0046] Admittance adaptive control unit is used to autonomously adjust the variable admittance reshaping adjustment coefficient based on the total harmonic distortion (THD) of the voltage component and determine the value of the amplification coefficient based on the constraint of the maximum adjustment coefficient, so as to realize the adaptive control of the converter admittance.

[0047] The beneficial effects of the present invention are as follows: The admittance reshaping control scheme of the present invention simulates the parallel virtual admittance of the port device through active control, fully considers the frequency coupling introduced by the DC voltage loop and the phase-locked loop, and can accurately simulate the passive admittance characteristics. It can not only avoid introducing additional power loss, but also has the advantages of wide frequency regulation characteristics, simple admittance parameter tuning and adaptive admittance adjustment. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a flowchart of the method in Example 1;

[0050] Figure 2 This is a schematic diagram of the system structure in Example 1;

[0051] Figure 3 This is a block diagram of the topology and control structure of a typical grid-connected inverter in Example 2;

[0052] Figure 4 This is a typical grid-connected converter control block diagram in Example 2;

[0053] Figure 5 The grid-connected converter circuit with adaptive variable admittance after adopting the present invention in Example 2;

[0054] Figure 6 This is the equivalent control block diagram of the grid-connected converter with adaptive variable admittance in Example 2;

[0055] Figure 7 This is a structural diagram of the standardized admittance reshaping controller after adopting the present invention in Example 2;

[0056] Figure 8 The relationship between the maximum adjustment coefficient and the virtual admittance-to-inductance ratio under different output conditions in Example 2;

[0057] Figure 9 This refers to the adaptive admittance control structure in Example 2;

[0058] Figure 10The relationship between grid-connected voltage THD and regulation coefficient in Example 2;

[0059] Figure 11 The frequency response of Case 1 and Case 2 in Example 2 without adaptive admittance control;

[0060] Figure 12 The frequency response of Case 1 and Case 2 in Example 2 after adopting adaptive admittance control;

[0061] Figure 13 This is a schematic diagram of the structure of the computer device of the present invention. Detailed Implementation

[0062] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0063] Example 1:

[0064] like Figure 1 As shown: A wideband adaptive admittance control method and system considering frequency coupling effects, comprising the following steps:

[0065] Considering the frequency coupling effect, a wide-area admittance reshaping control loop is constructed, including a virtual impedance control branch, a DC voltage loop control branch, a current loop forward control branch, and two virtual impedance feedforward branches.

[0066] The reference virtual resistance is selected based on the fundamental reactance coefficient of the converter, and the numerical range of the maximum variable admittance reshaping adjustment coefficient and the reference virtual inductance is determined by the self-stability constraint of the grid-connected converter GCC.

[0067] Adaptive control of converter admittance is achieved by autonomously adjusting the variable admittance reshaping adjustment coefficient based on the total harmonic distortion (THD) of the voltage component and determining the value of the amplification coefficient based on the constraint of the maximum adjustment coefficient.

[0068] By simulating the parallel virtual admittance of port devices through active control, and fully considering the frequency coupling introduced by the DC voltage loop and phase-locked loop, the passive admittance characteristics can be accurately simulated. This not only avoids the introduction of additional power loss, but also has the advantages of wideband adjustment characteristics, simple admittance parameter tuning, and adaptive admittance adjustment.

[0069] In this embodiment, a wide-area admittance reshaping control loop is constructed considering frequency coupling effects, including:

[0070] Considering the frequency coupling introduced by the DC voltage loop and the phase-locked loop, the virtual admittance Y is... ad It is shaped into an adaptive, flexible, and variable admittance;

[0071] The equivalent feedforward gain is distributed across the virtual impedance control branch, the DC voltage loop control branch, the current loop forward control branch, and the two virtual impedance feedforward branches.

[0072] The virtual impedance control branch is used to simulate the effect of virtual impedance. The input signal is a three-phase voltage signal, which is converted into a two-phase voltage signal after abc / αβ conversion.

[0073] Two-phase voltage signals pass through notch filter G NF (s), and then through the variable virtual admittance Y ad (s) obtains the virtual current signal, G NF (s) is represented as:

[0074] ;

[0075] In the formula, ω1 and ζ are the fundamental frequency and the notch filter damping ratio, respectively.

[0076] Two virtual impedance feedforward branches are used to cancel the coupling introduced by the power parameter inductance. The input signal of the first feedforward branch is a virtual current signal, which is then processed by the differentiating controller G. f1 (s) After that, the αβ axis modulated additional signal can be obtained; the input signal of the second feedforward branch is the dq axis virtual current signal, which is filtered by a high-pass filter G. H (s) and integral controller G f2 (s) then obtains the dq-axis modulated additional signal;

[0077] G f1 (s), G f2 (s) and G H (s) is represented as:

[0078] ;

[0079] In the formula, L f For filter inductance, V dc For DC voltage, k sp C is the modulation coefficient. dc M1 is the DC capacitor, M1 is the steady-state amplitude of the modulation signal, and ω n ξ and ξ represent the cutoff frequency and damping ratio of the high-pass filter, respectively.

[0080] The forward control branch of the current loop is used to simulate the virtual admittance, and the input signal is a signal filtered by a high-pass filter G. H The virtual current signal of the dq axis after (s) is directly superimposed on the current loop output given signal.

[0081] The DC voltage loop control branch is used to achieve decoupling control in the admittance simulation process. Its input signal is a signal passed through a high-pass filter G. HThe d-axis signal of the virtual current after (s) passes through the controller G. vi (s) then obtains the additional DC voltage signal;

[0082] G vi (s) is represented as:

[0083] .

[0084] In this embodiment, the reference virtual resistance is selected based on the fundamental reactance coefficient of the converter, including:

[0085] The reference virtual admittance is set to the circuit form of RL, specifically as follows:

[0086] ;

[0087] In the formula, R viB and L viB As a reference for virtual resistance and inductance;

[0088] Reshaped variable virtual admittance Y ad With reference virtual admittance Y viB The relationship is:

[0089] ;

[0090] In the formula, k vi This is the variable admittance remodeling adjustment coefficient. The larger the value, the greater the depth of admittance remodeling adjustment.

[0091] Among them, the numerical ranges of the maximum variable admittance reshaping regulation coefficient and the reference virtual inductance are determined by the self-stability constraint of the grid-connected converter GCC, including:

[0092] Set the reference virtual admittance according to the per-unit value, and set the reference virtual resistance R. viB Given one times the fundamental reactance, we have:

[0093] ;

[0094] In the formula, U B and S B Z represents the rated voltage and capacity of the GCC. B For fundamental frequency reactance;

[0095] The numerical ranges of the maximum regulation coefficient and the virtual inductance are determined by using GCC self-stability constraints.

[0096] The values ​​of the amplification factor are determined based on the total harmonic distortion (THD) of the voltage component, the variable admittance reshaping adjustment coefficient, and the constraint determination of the maximum adjustment coefficient, including:

[0097] The magnitude of the adjustment coefficient is determined by the harmonic content in the voltage component:

[0098] ;

[0099] In the formula, v αh v βh These represent the harmonic components along the α and β axes excluding the fundamental frequency, respectively; V1 is the amplitude of the fundamental voltage; and G... dz For dead zone components, k h G is the magnification factor. L This is a low-pass filter, and its cutoff frequency is set the same as that of a high-pass filter.

[0100] The dead zone is set according to the THD threshold of the low-voltage power grid, and the amplification factor is designed with constraints based on the maximum regulation factor.

[0101] like Figure 2 As shown, this embodiment also includes a wideband adaptive admittance control system considering frequency coupling effects. Using the method described above, the system includes:

[0102] The wide-area admittance reshaping control unit is used to construct a wide-area admittance reshaping control loop considering frequency coupling effects. It includes a virtual impedance control branch, a DC voltage loop control branch, a current loop forward control branch, and two virtual impedance feedforward branches.

[0103] The virtual admittance design unit is used to select a reference virtual resistance based on the fundamental reactance coefficient of the converter, and to determine the numerical range of the maximum variable admittance reshaping adjustment coefficient and the reference virtual inductance through the self-stability constraint of the grid-connected converter GCC.

[0104] Admittance adaptive control unit is used to autonomously adjust the variable admittance reshaping adjustment coefficient based on the total harmonic distortion (THD) of the voltage component and determine the value of the amplification coefficient based on the constraint of the maximum adjustment coefficient, so as to realize the adaptive control of the converter admittance.

[0105] Example 2:

[0106] This embodiment provides a wideband adaptive admittance control method considering frequency coupling effects. It includes the derivation of a wideband admittance reshaping controller considering frequency coupling effects, a virtual admittance design method based on the fundamental reactance coefficient of the converter, and adaptive converter admittance control based on grid-connected point harmonic voltage constraints. The admittance reshaping control scheme proposed in this embodiment simulates the parallel virtual admittance of port devices through active control, fully considering the frequency coupling introduced by the DC voltage loop and phase-locked loop. It can accurately simulate passive admittance characteristics, not only avoiding the introduction of additional power losses but also possessing advantages such as wideband regulation characteristics, simple admittance parameter tuning, and adaptive admittance adjustment.

[0107] To achieve the above objectives, this embodiment includes the following steps:

[0108] 1. Derivation of a wide-area admittance reshaping controller for converters considering frequency coupling effects;

[0109] In grid-connected converters with virtual admittance control, the DC voltage loop affects the frequency through its dynamic adjustment of active power; while the phase-locked loop (PLL), by tracking the grid frequency and phase, transmits and amplifies the power disturbances caused by the DC voltage loop, ultimately leading to frequency coupling in the grid-connected converter under virtual admittance control. Traditional virtual admittance control often ignores coupling characteristics for simplicity, resulting in a significant difference between the virtual admittance and the physical admittance. Therefore, it is mostly used for admittance reshaping in the mid-to-high frequency range. To extend virtual admittance control to a wider frequency band, this embodiment proposes a wideband admittance reshaping control that considers the frequency coupling effect. It fully considers the frequency coupling introduced by the DC voltage loop and the PLL, enabling accurate simulation of passive admittance over a wider frequency band.

[0110] Figure 3 This is a block diagram of the topology and control structure of a typical grid-connected inverter. Based on the principle of harmonic linearization modeling, the admittance coefficient matrix of the grid-connected inverter can be expressed as:

[0111]

[0112] Among them, Y o It is a 5×5 matrix.

[0113] Based on the mathematical model of ordered admittance, the following can be derived: Figure 4 The matrix form of the grid-connected converter equivalent model is shown in the figure, P v The gain matrix is ​​related to the AC voltage. The other transfer function matrices in the figure are as follows:

[0114]

[0115] In the formula, Q and E are the gain matrices related to AC voltage and DC voltage, respectively, and Y... f and Z c The filters are L and L respectively. f and DC capacitor C dc The steady-state harmonic matrices are given by M and I, respectively, representing the steady-state harmonic matrices of the modulation signal and grid-connected current, and e is the identity matrix. All of these matrices are 5×5 matrices. sp is the modulation coefficient.

[0116] To fully simulate the passive admittance characteristics, this method takes into account both the original converter control and the frequency coupling introduced by the DC voltage loop and phase-locked loop, while also incorporating the virtual admittance Y. ad Shaped into an adaptive, flexible, variable admittance (its equivalent circuit is as follows) Figure 5As shown, this is to meet the damping requirements in different scenarios.

[0117] according to Figure 5 and combined Figure 4 The equivalent control block diagram after parallel admittance can be obtained as follows: Figure 6 As shown in (a), to convert the variable admittance into active control, the variable admittance can be transformed into a feedforward control branch according to the control block diagram transformation, and its equivalent block diagram is shown below. Figure 6 As shown in (b), P in the figure ad The equivalent feedforward gain matrix for variable admittance can be expressed as:

[0118]

[0119] Because of P ad The expression is too complex to be implemented through active control, therefore P is... ad To achieve reasonable simplification and avoid affecting the fundamental frequency control, a notch filter and a high-pass filter need to be added to the controller. The simplified equivalent feedforward gain matrix is ​​expressed as follows: , It is a 5×5 matrix, where all elements except the (1,3)th and (3,3)th elements are zero. The two non-zero elements are:

[0120]

[0121] Where M1 is the steady-state amplitude of the modulation signal, For the steady-state grid-connected voltage phase, G NF and G H2 These are a notch filter and a high-pass filter, respectively, and s1 = s – jω1.

[0122] According to the formula It can be seen that the equivalent feedforward gain consists of four parts, therefore the equation can be expressed as follows: The control functions are distributed across different control branches. In summary, we can obtain the following... Figure 7 The diagram shows a standardized admittance reshaping controller. It mainly includes the following control branches:

[0123] (1) Virtual Impedance Control Branch. This control branch is designed to simulate the effect of virtual impedance. The input signal is a three-phase voltage signal, which is converted from abc / αβ to obtain a two-phase voltage signal. To avoid adverse effects on the fundamental frequency function, the two-phase voltage signal needs to pass through a notch filter G. NF (s), and then through the variable virtual admittance Y ad (s) obtains the virtual current signal. G NF (s) can be expressed as:

[0124]

[0125] In the formula, ω1 and ζ are the fundamental frequency and the notch filter damping ratio, respectively.

[0126] (2) Feedforward branches ① and ②. Corresponding equations respectively. The first two terms of the positive sequence component are intended to cancel the coupling introduced by the power parameter inductance. The input signal of the feedforward branch ① is a virtual current signal, which is processed by the differentiating controller G. f1 (s) After this, the αβ-axis modulated additional signal can be obtained. The input signal of the feedforward branch ② is the dq-axis virtual current signal, which is filtered by the high-pass filter G. H (s) and integral controller G f2 (s) then yields the dq-axis modulated additional signal. G f1 (s), G f2 (s) and G H (s) can be expressed as:

[0127]

[0128] In the formula, L f For filter inductance, V dc For DC voltage, k sp C is the modulation coefficient. dc M1 is the DC capacitor, M1 is the steady-state amplitude of the modulation signal, and ω n ξ and ξ represent the cutoff frequency and damping ratio of the high-pass filter, respectively.

[0129] (3) Current-controlled branch ③. Corresponding formula The third term of the orthogonal component ( Figure 7 China and Israel i dqvi3 This represents the feedback quantity, and its function is to simulate virtual admittance. The input signal is passed through a high-pass filter G. H The virtual current signal of the dq axis after (s) is directly superimposed on the current loop output given signal.

[0130] (4) DC voltage control branch ④. Corresponding formula The fourth term of the orthogonal component ( Figure 7 China and Israel v dcvi4 This represents the feedback quantity, and its function is to achieve decoupling control in the admittance simulation process. Its input signal is passed through a high-pass filter G. H The d-axis signal of the virtual current after (s) passes through the controller G. vi (s) then a DC voltage additional signal is obtained. G vi (s) can be expressed as:

[0131]

[0132] With the control of multiple branches, accurate simulation of passive admittance can be ensured over a wide frequency band.

[0133] 2. Virtual admittance design method based on converter fundamental reactance coefficient;

[0134] To address the difficulty in virtual admittance tuning, this embodiment simplifies virtual admittance design by setting a virtual admittance reference. The reference virtual admittance can be configured as an RL circuit, specifically as follows:

[0135]

[0136] In the formula, R viB and L viB The reference virtual resistor and inductor.

[0137] In this embodiment, the reshaped variable virtual admittance Y ad With reference virtual admittance Y viB The relationship is:

[0138]

[0139] In the formula, k vi This is the variable admittance reshaping adjustment coefficient; a larger value indicates a greater depth of admittance reshaping adjustment. The following section calculates the tuning of the baseline virtual admittance parameters.

[0140] To ensure the universality of this method, this embodiment sets the reference virtual admittance according to per-unit values ​​and sets the reference virtual resistance R. viB Given one times the fundamental reactance, we have:

[0141]

[0142] In the formula, U B and S B Z represents the rated voltage and capacity of the GCC. B This is the fundamental reactance.

[0143] Next, a reference dummy inductance is selected. For GCC, after adding admittance reshaping control, it is necessary to ensure its own stability. In addition, the maximum value of the variable admittance reshaping adjustment coefficient also varies for different dummy inductance values. Therefore, in order to facilitate the determination of the parameter range of the adjustment coefficient and the dummy inductance, this embodiment determines the numerical range of the maximum adjustment coefficient and the dummy inductance through GCC self-stability constraints.

[0144] In practical systems, the converter's output condition (steady-state operating point) affects the effectiveness of admittance reshaping control. Generally, 50% and 100% output conditions are commonly used for converter operation testing. Therefore, considering general principles... Figure 8 The figure illustrates the relationship between the maximum adjustment coefficient and different impedance-inductance ratios under different output conditions. It can be observed from the figure that the virtual admittance exhibits a significant nonlinear characteristic with respect to the impedance-inductance ratio and the maximum adjustment coefficient. Under typical operating conditions, the maximum adjustable capability of admittance reshaping decreases as the GCC output and impedance-inductance ratio increase. Therefore, a compromise must be made regarding the selection coefficient of the impedance ratio.

[0145] 3. Converter admittance adaptive control;

[0146] against Figure 7 The variable admittance design in the middle is as follows Figure 9 The adaptive admittance control structure is shown. Studies have shown that waveform quality is positively correlated with stability margin sensitivity; therefore, node voltage harmonic content can be considered as the control medium. Figure 7 and Figure 9 It can be seen that the magnitude of the adjustment coefficient is determined by the harmonic content in the voltage component, that is...

[0147]

[0148] In the formula, v αh v βh These represent the harmonic components along the α and β axes excluding the fundamental frequency, respectively; V1 is the amplitude of the fundamental voltage; and G... dz For dead zone components, k h G is the magnification factor. L This is a low-pass filter, and its cutoff frequency is set the same as that of a high-pass filter.

[0149] According to the definition of voltage harmonic distortion rate in IEEE 519-2014, the formula... It can be written as:

[0150]

[0151] To prevent the reshaping stage from responding to harmonic voltages in the system, the dead time can be set according to IEEE 519-2014, where the THD of low-voltage power grids should not exceed 8%, and the amplification factor can be constrained by the maximum regulation factor. Figure 9 As the principle shows, the admittance adjustment coefficient has a linear relationship with the THD of the voltage component; that is, the larger the THD of the voltage component, the larger the adjustment coefficient and the stronger the admittance regulation capability, thus realizing the automatic admittance control of the converter. However, due to the limitation of the maximum regulation capability, the amplification factor k... h The tuning needs to take into account the maximum adjustment coefficient k.vimax Limitations. Assuming that when the grid-connected voltage THD exceeds 20%, a severe oscillation is considered to have occurred in the system, requiring the converter to perform admittance reshaping control at its maximum regulation capacity. To meet these operational requirements, the amplification factor must satisfy:

[0152]

[0153] according to Figure 8 Under the constraint of the maximum adjustment coefficient, k can be calculated. h The relationship between voltage THD and the regulation coefficient is as follows: Figure 10 As shown.

[0154] The present embodiment will be further described below with reference to the accompanying drawings and specific examples.

[0155] Tables 1 and 2 show the operating parameters for the two working conditions:

[0156] Table 1

[0157] Table 2

[0158] Before adopting the control scheme described in this embodiment, the frequency responses of Cases 1 and 2 were as follows: Figure 11 As shown. Analysis Figure 11 It can be seen that the stability margins of Cases 1 and 2 are -3.86° and -13.05°, respectively, corresponding to oscillation frequencies of 98.3Hz (coupling frequency of 1.7Hz) and 88.9Hz (coupling frequency of 11.1Hz), indicating that the system cannot operate stably under these two conditions. The control scheme in this embodiment is used to shape the impedance of this system.

[0159] 1. Derivation of a standardized wide-area admittance reshaping controller for converters;

[0160] (1) Virtual Impedance Control Branch. This control branch is designed to simulate the effect of virtual impedance. The input signal is a three-phase voltage signal, which is converted from abc / αβ to obtain a two-phase voltage signal. To avoid adverse effects on the fundamental frequency function, the two-phase voltage signal needs to pass through a notch filter G. NF (s), and then through the variable virtual admittance Y ad (s) obtains the virtual current signal. G NF (s) can be expressed as:

[0161]

[0162] In the formula, ω1 and ζ are the fundamental frequency and the notch filter damping ratio, respectively.

[0163] (2) Feedforward branches ① and ②. Corresponding equations respectively. The first two terms of the positive sequence component are intended to cancel the coupling introduced by the power parameter inductance. The input signal of the feedforward branch ① is a virtual current signal, which is processed by the differentiating controller G. f1 (s) After this, the αβ-axis modulated additional signal can be obtained. The input signal of the feedforward branch ② is the dq-axis virtual current signal, which is filtered by the high-pass filter G. H (s) and integral controller G f2 (s) then yields the dq-axis modulated additional signal. G f1 (s), G f2 (s) and G H (s) can be expressed as:

[0164]

[0165] In the formula, L f For filter inductance, V dc For DC voltage, k sp C is the modulation coefficient. dc M1 is the DC capacitor, M1 is the steady-state amplitude of the modulation signal, and ω n ξ and ξ represent the cutoff frequency and damping ratio of the high-pass filter, respectively.

[0166] (3) Current-controlled branch ③. Corresponding formula The third term of the orthogonal component ( Figure 7 China and Israel i dqvi3 This represents the feedback quantity, and its function is to simulate virtual admittance. The input signal is passed through a high-pass filter G. H The virtual current signal of the dq axis after (s) is directly superimposed on the current loop output given signal.

[0167] (4) DC voltage control branch ④. Corresponding formula The fourth term of the orthogonal component ( Figure 7 China and Israel v dcvi4 This represents the feedback quantity, and its function is to achieve decoupling control in the admittance simulation process. Its input signal is passed through a high-pass filter G. H The d-axis signal of the virtual current after (s) passes through the controller G. vi (s) then a DC voltage additional signal is obtained. G vi (s) can be expressed as:

[0168]

[0169] Since grid-connected converters typically do not generate low-frequency oscillations (oscillation frequency of 0.1~2.5Hz), this paper selects a notch filter bandwidth of 2.5Hz to avoid adverse effects on the fundamental frequency control. Calculations show that the notch filter damping ratio ζ = 0.1, and the high-pass filter ω... n = 5π, the damping ratio ξ of the high-pass filter can be set to 0.707.

[0170] 2. Virtual admittance design method based on converter fundamental reactance coefficient;

[0171] The purpose of the virtual admittance design method is to design the parallel admittance Y in admittance reshaping control. ad The virtual resistance and virtual inductance are tuned based on the fundamental reactance coefficient. The specific calculation is as follows:

[0172] Set the reference virtual resistance R viB Given one times the fundamental reactance, we have:

[0173]

[0174] In the formula, U B and S B Z represents the rated voltage and capacity of the GCC. B This is the fundamental reactance.

[0175] Next, the numerical ranges of the maximum regulation coefficient and the virtual inductance are determined using GCC self-stability constraints. Figure 8 As can be seen, the virtual admittance exhibits a significant nonlinear characteristic with respect to the resistance-to-inductance ratio and the maximum adjustment coefficient. Under typical operating conditions, the maximum adjustable capability of admittance reshaping decreases as the GCC output power and resistance-to-inductance ratio increase. To balance the admittance reshaping capability under different GCC output conditions, a virtual resistance-to-inductance ratio of 5 can be selected, i.e., L... viB = R viB / 5, at which point the maximum variable adjustment coefficient can be set to 4.65.

[0176] 3. Converter admittance adaptive control;

[0177] Depend on Figure 7 and Figure 9 It can be seen that the magnitude of the adjustment coefficient is determined by the harmonic content in the voltage component, that is...

[0178]

[0179] In the formula, v αh v βh These represent the harmonic components along the α and β axes excluding the fundamental frequency, respectively; V1 is the amplitude of the fundamental voltage; and G... dz For dead zone components, kh G is the magnification factor. L This is a low-pass filter, and its cutoff frequency is set the same as that of a high-pass filter.

[0180] According to the definition of voltage harmonic distortion rate in IEEE 519-2014, the formula... It can be written as:

[0181]

[0182] To prevent the reshaping stage from responding to harmonic voltages in the system, the dead time can be set according to IEEE 519-2014, where the THD of low-voltage power grids should not exceed 8%, while the amplification factor can be constrained by the maximum regulation factor. Figure 9 As can be seen from the principle, the admittance adjustment coefficient has a linear relationship with the THD of the voltage component; that is, the larger the THD of the voltage component, the larger the adjustment coefficient and the stronger the admittance adjustment capability, thus realizing the automatic admittance control of the converter. However, due to the limitation of the maximum adjustment capability, the amplification factor k... h The tuning needs to take into account the maximum adjustment coefficient k. vimax Limitations. Assuming that when the grid-connected voltage THD exceeds 20%, a severe oscillation is considered to have occurred in the system, requiring the converter to perform admittance reshaping control at its maximum regulation capacity. To meet these operational requirements, the amplification factor must satisfy:

[0183]

[0184] according to Figure 8 Under the constraint of the maximum adjustment coefficient, k can be calculated. h = 23.25.

[0185] After incorporating the control scheme of this embodiment, the admittance adjustment coefficients of converters 3 and 5 are set as follows: In Case 1, k vi3 and k vi5 The values ​​are 0.2 and 0.16 respectively. In Case 2, k vi3 and k vi5 The values ​​are 0.48 and 0.4, respectively. The stability analysis results of the system under these conditions are as follows: Figure 12 As shown, the system stability margins are 3.32° and 7.45°, respectively.

[0186] Please see Figure 13The diagram shows a structural schematic of a computer device provided in an embodiment of this application. An embodiment of this application provides a computer device 400, including a processor 410 and a memory 420. The memory 420 stores a computer program executable by the processor 410. When the computer program is executed by the processor 410, it performs the method described above.

[0187] This application embodiment also provides a storage medium 430, on which a computer program is stored, and the computer program is executed by a processor 410 to perform the above method.

[0188] The storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0189] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. "A plurality of" means two or more, unless otherwise explicitly specified.

[0190] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0191] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0192] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0193] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0194] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0195] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0196] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A wideband adaptive admittance control method considering frequency coupling effects, characterized in that, Includes the following steps: Considering the frequency coupling effect, a wide-area admittance reshaping control loop is constructed, including a virtual impedance control branch, a DC voltage loop control branch, a current loop forward control branch, and two virtual impedance feedforward branches. The reference virtual resistance is selected based on the fundamental reactance coefficient of the converter, and the numerical range of the maximum variable admittance reshaping adjustment coefficient and the reference virtual inductance is determined by the self-stability constraint of the grid-connected converter GCC. Adaptive control of converter admittance is achieved by autonomously adjusting the variable admittance reshaping adjustment coefficient based on the total harmonic distortion (THD) of the voltage component and determining the value of the amplification coefficient based on the constraint of the maximum adjustment coefficient.

2. The wideband adaptive admittance control method considering frequency coupling effects according to claim 1, characterized in that, The construction of the wide-area admittance reshaping control loop considering frequency coupling effects includes: Considering the frequency coupling introduced by the DC voltage loop and the phase-locked loop, the virtual admittance Y is... ad It is shaped into an adaptive, flexible, and variable admittance; The equivalent feedforward gain is distributed across the virtual impedance control branch, the DC voltage loop control branch, the current loop forward control branch, and the two virtual impedance feedforward branches.

3. The wideband adaptive admittance control method considering frequency coupling effects according to claim 2, characterized in that, The virtual impedance control branch is used to simulate the effect of virtual impedance. The input signal is a three-phase voltage signal, which is converted from abc / αβ to obtain a two-phase voltage signal. The two-phase voltage signals pass through a notch filter G. NF (s), and then through the variable virtual admittance Y ad (s) obtains the virtual current signal, G NF (s) is represented as: ； In the formula, ω1 and ζ are the fundamental frequency and the notch filter damping ratio, respectively.

4. The wideband adaptive admittance control method considering frequency coupling effects according to claim 3, characterized in that, The two virtual impedance feedforward branches are used to cancel the coupling introduced by the power parameter inductance. The input signal of the first feedforward branch is a virtual current signal, which is processed by the differentiating controller G. f1 (s) After that, the αβ axis modulated additional signal can be obtained; the input signal of the second feedforward branch is the dq axis virtual current signal, which is filtered by a high-pass filter G. H (s) and integral controller G f2 (s) then obtains the dq-axis modulated additional signal; G f1 (s), G f2 (s) and G H (s) is represented as: ； In the formula, L f For filter inductance, V dc For DC voltage, k sp C is the modulation coefficient. dc M1 is the DC capacitor, M1 is the steady-state amplitude of the modulation signal, and ω n ξ and ξ represent the cutoff frequency and damping ratio of the high-pass filter, respectively.

5. The wideband adaptive admittance control method considering frequency coupling effects according to claim 4, characterized in that, The forward control branch of the current loop is used to simulate virtual admittance, and the input signal is a signal filtered by a high-pass filter G. H The virtual current signal of the dq axis after (s) is directly superimposed on the current loop output given signal.

6. The wideband adaptive admittance control method considering frequency coupling effects according to claim 5, characterized in that, The DC voltage loop control branch is used to achieve decoupling control in the admittance simulation process, and its input signal is a signal passed through a high-pass filter G. H The d-axis signal of the virtual current after (s) passes through the controller G. vi (s) then a DC voltage additional signal is obtained; G vi (s) is represented as: 。 7. The wideband adaptive admittance control method considering frequency coupling effects according to claim 1, characterized in that, The selection of the reference virtual resistance based on the fundamental reactance coefficient of the converter includes: The reference virtual admittance is set to the circuit form of RL, specifically as follows: ； In the formula, R viB and L viB As a reference for virtual resistance and inductance; Reshaped variable virtual admittance Y ad With reference virtual admittance Y viB The relationship is: ； In the formula, k vi This is the variable admittance remodeling adjustment coefficient. The larger the value, the greater the depth of admittance remodeling adjustment.

8. The wideband adaptive admittance control method considering frequency coupling effects according to claim 7, characterized in that, The determination of the numerical range of the maximum variable admittance reshaping regulation coefficient and the reference virtual inductance through the self-stability constraint of the grid-connected converter GCC includes: Set the reference virtual admittance according to the per-unit value, and set the reference virtual resistance R. viB Given one times the fundamental reactance, we have: ； In the formula, U B and S B For the rated voltage and capacity of GCC, Z B For fundamental frequency reactance; The numerical ranges of the maximum regulation coefficient and the virtual inductance are determined by using GCC self-stability constraints.

9. The wideband adaptive admittance control method considering frequency coupling effects according to claim 1, characterized in that, The values ​​of the variable admittance reshaping adjustment coefficient based on voltage component-based total harmonic distortion (THD) and the amplification coefficient determined by constraint based on the maximum adjustment coefficient include: The magnitude of the adjustment coefficient is determined by the harmonic content in the voltage component: ； In the formula, v αh v βh These represent the harmonic components along the α and β axes excluding the fundamental frequency, respectively; V1 is the fundamental voltage amplitude; and G... dz For dead zone components, k h G is the magnification factor. L This is a low-pass filter, and its cutoff frequency is set the same as that of a high-pass filter. The dead zone is set according to the THD threshold of the low-voltage power grid, and the amplification factor is designed with constraints based on the maximum regulation factor.

10. A wideband adaptive admittance control system considering frequency coupling effects, characterized in that, Using the method of any one of claims 1 to 9, the system comprises: The wide-area admittance reshaping control unit is used to construct a wide-area admittance reshaping control loop considering frequency coupling effects. It includes a virtual impedance control branch, a DC voltage loop control branch, a current loop forward control branch, and two virtual impedance feedforward branches. The virtual admittance design unit is used to select a reference virtual resistance based on the fundamental reactance coefficient of the converter, and to determine the numerical range of the maximum variable admittance reshaping adjustment coefficient and the reference virtual inductance through the self-stability constraint of the grid-connected converter GCC. Admittance adaptive control unit is used to autonomously adjust the variable admittance reshaping adjustment coefficient based on the total harmonic distortion (THD) of the voltage component and determine the value of the amplification coefficient based on the constraint of the maximum adjustment coefficient, so as to realize the adaptive control of the converter admittance.

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