A wind power grid-connected system oscillation suppression method, device, equipment and storage medium

Abstract

The present application relates to the technical field of wind power grid-connected system control, and particularly relates to a wind power grid-connected system oscillation suppression method, device, equipment and storage medium, which eliminates the frequency coupling effect of SVG admittance by introducing a decoupling factor, and introduces a compensation factor in the SVG voltage feedforward path, so that the SVG admittance presents positive damping characteristics in the full frequency band, thereby offsetting the negative damping of the wind turbine admittance, and effectively reducing the oscillation risk of the wind power grid-connected system. The method does not need to modify the existing wind turbine, and only optimizes the SVG control to systematically improve the weak grid adaptability and grid-connected stability of the wind farm, not only simplifies the control strategy, but also significantly improves the robustness of the system in the frequency time-varying and wide frequency oscillation scene.

Description

Technical Field

[0001] This invention relates to the field of wind power grid-connected system control technology, and in particular to a method, apparatus, equipment and storage medium for suppressing oscillations in wind power grid-connected systems. Background Technology

[0002] The installed capacity and grid connection ratio of clean energy, represented by wind power and photovoltaics, have continued to increase rapidly. However, this high proportion of new energy access has made the power grid exhibit weak grid characteristics, resulting in a decrease in the inertia and damping level of the power system, which significantly exacerbates the risk of subsynchronous, supersynchronous, and even high-frequency oscillations.

[0003] Existing research on wind farm oscillations mainly focuses on two aspects: First, improving the wind turbine's own controller, such as active damping and impedance reshaping. For example, patent application CN121618642A discloses a method for suppressing low-frequency oscillations in offshore wind farms connected to the grid via synchronous generators, which involves configuring a damping controller and superimposing damping power commands. However, this method requires modifying a large number of wind turbines individually, resulting in high costs and a large engineering workload. Second, utilizing the widely deployed SVG (Static Var Generator) for additional control in wind farms, such as voltage feedforward filtering and phase compensation. For example, patent application CN118783473A provides a method and system for suppressing doubly-fed wind farm oscillations based on improved SVG impedance, avoiding oscillations through voltage feedforward control with additional filtering. However, this method suffers from problems such as complex strategies, susceptibility to high-frequency noise, limitation to specific frequency bands, and insufficient adaptability and robustness.

[0004] In summary, existing wind farm oscillation suppression methods still suffer from problems such as complex control strategies, easy introduction of high-frequency noise, and difficulty in adapting to scenarios with both time-varying frequencies and wideband oscillations. Summary of the Invention

[0005] The main objective of this invention is to propose a method, apparatus, device, and storage medium for suppressing oscillations in wind power grid-connected systems, aiming to solve the technical problems of complex control strategies and low robustness in existing wind farm oscillation solutions.

[0006] To achieve the above objectives, the present invention provides a method, apparatus, device, and storage medium for suppressing oscillations in wind power grid-connected systems.

[0007] In a first aspect, the present invention provides a method for suppressing oscillations in a wind power grid-connected system. The method includes:

[0008] Step S1: Obtain the status data of the wind power grid-connected system;

[0009] Step S2: Obtain the PWM control signal of the SVG based on the state data and the SVG reshaped admittance model; the SVG reshaped admittance model is the SVG admittance model reshaped based on the decoupling factor and the compensation factor.

[0010] Step S3: Drive the IGBT of the SVG in the wind power grid-connected system to work according to the PWM control signal.

[0011] Furthermore, the decoupling factor includes a phase-locked loop (PLL) decoupling factor, a first decoupling factor, and a second decoupling factor. The expression for the PLL decoupling factor is as follows:

[0012]

[0013] The expression for the first decoupling factor is:

[0014]

[0015] The expression for the second decoupling factor is:

[0016]

[0017] In the formula, This is the decoupling factor for the phase-locked loop. This is the first decoupling factor. This is the second decoupling factor. The transfer function for SVG phase-locked loop PI control. For the Laplace operator, The d-axis component of the steady-state voltage operating point at the point of common connection (PCC) in the dq coordinate system. The d-axis component of the SVG AC side output current at the steady-state operating point in the dq coordinate system. The q-axis component of the SVG AC side output current at the steady-state operating point in the dq coordinate system. Let be the transfer function of the SVG DC voltage loop. This is the reactive power loop coefficient. This represents the steady-state operating point of the SVG DC voltage. The filter capacitor is located on the DC side of the SVG; the expression for the compensation factor is:

[0018]

[0019] In the formula, The compensation factor is... This is the proportional gain coefficient.

[0020] Furthermore, the expression for the SVG phase-locked loop PI control transfer function is:

[0021]

[0022] The expression for the transfer function of the SVG DC voltage loop is:

[0023]

[0024] The expression for the reactive power loop coefficient is:

[0025]

[0026] In the formula, k ppll1 k is the proportional gain of the SVG phase-locked loop. ipll1 For the integral coefficients of the SVG phase-locked loop, For the Laplace operator, This is the filter capacitor on the DC side of the SVG. This represents the steady-state operating point of the DC-side voltage of the SVG.

[0027] Furthermore, the range of values ​​for the proportional gain coefficient is as follows:

[0028]

[0029] In the formula, Y gsc_pp_1pu Y is the positive sequence admittance when the GSC active power output is 1.0 pu. gsc_nn_1pu The negative sequence admittance is given when the active power output of the GSC is 1.0 pu. The gain coefficients of the reshaped admittance model of the SVG.

[0030] Furthermore, the expression for the SVG reshaped admittance model is:

[0031]

[0032] In the formula, Reshape the admittance model for the SVG. This is the decoupling matrix for the inner current loop. Let be the transfer function matrix of the current inner-loop PI controller. This is the gain matrix from the outer loop to the inner current loop. The transfer function matrix of the DC voltage loop of the SVG. This is the current matrix used for power calculation. Main circuit impedance matrix, The voltage matrix used for power calculation. , and Both are small-signal matrices of coordinate transformation caused by phase-locked loops. To reshape the d-axis self-admittance of the admittance model for SVG The d-axis coupled admittance of the SVG reconstructed admittance model is given. The q-axis coupled admittance of the SVG reconstructed admittance model is given. q-axis self-admittance of the SVG reconstructed admittance model For the filter inductor on the AC side of the SVG, Here is the transfer function of the SVG current inner loop PI controller. This is the PI transfer function for the outer loop of the SVG DC voltage.

[0033] Furthermore, the expression for the GSC admittance model in a wind power grid-connected system is as follows:

[0034]

[0035]

[0036] In the formula, This represents the GSC admittance model. The d-axis coupled admittance of the GSC admittance model to the q-axis; The q-axis coupled admittance of the GSC admittance model to the d-axis; This represents the q-axis self-admittance of the GSC admittance model. and These represent the d-axis and q-axis components of the GSC AC output current at the steady-state operating point, respectively. This is the transfer function of the GSC current inner loop PI controller. For GSC DC-side filter capacitors, This is the steady-state operating point of the GSC DC voltage. For GSC AC side filter inductor, This is the transfer function of the GSC voltage outer loop PI controller. The transfer function of the GSC phase-locked loop PI controller. and These are the d-axis and q-axis components of the voltage at the point of common coupling (PCC) at the steady-state operating point, respectively. and These are the d-axis and q-axis components of the GSC AC side output voltage in the system coordinate system, representing the steady-state operating point.

[0037] Furthermore, the status data includes grid-side status data, point of common coupling status data, SVG-side status data, GSC-side status data, and system fixed parameters.

[0038] Secondly, the present invention also provides an oscillation suppression device for a wind power grid-connected system. The device includes:

[0039] The status data acquisition module is used to acquire status data of the wind power grid-connected system;

[0040] The PWM control signal generation module is used to obtain the PWM control signal of the SVG based on the state data and the SVG reshaped admittance model; the SVG reshaped admittance model is the SVG admittance model reshaped based on the decoupling factor and the compensation factor.

[0041] The IGBT driver module is used to drive the IGBT of the SVG to work according to the PWM control signal.

[0042] Thirdly, the present invention also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to perform the following steps:

[0043] Step S1: Obtain the status data of the wind power grid-connected system;

[0044] Step S2: Obtain the PWM control signal of the SVG based on the state data and the SVG reshaped admittance model; the SVG reshaped admittance model is the SVG admittance model reshaped based on the decoupling factor and the compensation factor.

[0045] Step S3: Drive the IGBT of the SVG to work according to the PWM control signal.

[0046] Fourthly, the present invention also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, performs the following steps:

[0047] Step S1: Obtain the status data of the wind power grid-connected system;

[0048] Step S2: Obtain the PWM control signal of the SVG based on the state data and the SVG reshaped admittance model; the SVG reshaped admittance model is the SVG admittance model reshaped based on the decoupling factor and the compensation factor.

[0049] Step S3: Drive the IGBT of the SVG to work according to the PWM control signal.

[0050] The aforementioned oscillation suppression method, device, equipment, and storage medium for wind power grid-connected systems eliminate the frequency coupling effect of SVG admittance by introducing a decoupling factor and a compensation factor in the SVG voltage feedforward path, enabling the SVG admittance to exhibit positive damping characteristics across the entire frequency band. This counteracts the negative damping of the wind turbine admittance, effectively reducing the oscillation risk of the wind power grid-connected system. This method requires no modification to existing wind turbines; simply optimizing SVG control can systematically improve the wind farm's adaptability to weak grids and its grid-connected stability. It not only simplifies the control strategy but also significantly improves the system's robustness in time-varying frequency and wideband oscillation scenarios. Attached Figure Description

[0051] 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 of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the wind power grid connection system according to an embodiment of the present invention;

[0053] Figure 2 This is a flowchart illustrating the oscillation suppression method for wind power grid-connected systems according to an embodiment of the present invention;

[0054] Figure 3 This is a schematic diagram illustrating the relationship between the system coordinate system and the controller coordinate system in an embodiment of the present invention;

[0055] Figure 4 This is a schematic diagram of the small-signal model of the SVG converter according to an embodiment of the present invention;

[0056] Figure 5 Bode plots of the GSC output admittance under different active power conditions according to an embodiment of the present invention;

[0057] Figure 6 This is a schematic diagram of the small-signal model of the SVG converter after adding compensation and decoupling factors in an embodiment of the present invention;

[0058] Figure 7 The control block diagram of the SVG converter after adding compensation and decoupling factors in the embodiments of the present invention;

[0059] Figure 8 This is a Bode plot of the gain coefficients in the SVG reshaped admittance model of this invention embodiment;

[0060] Figure 9 Bode plots of the wind farm sequence admittance model before and after reshaping in an embodiment of the present invention;

[0061] Figure 10 This is a schematic diagram of the experimental apparatus according to an embodiment of the present invention;

[0062] Figure 11 This is a schematic diagram of the grid-connected current waveform using the conventional method;

[0063] Figure 12 This is a schematic diagram of the grid-connected current waveform of the wind power grid-connected system oscillation suppression method according to an embodiment of the present invention;

[0064] Figure 13 This is a schematic diagram of the structure of the oscillation suppression device for a wind power grid-connected system according to an embodiment of the present invention.

[0065] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0066] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] Example 1

[0068] The oscillation suppression method for wind power grid-connected systems provided in this embodiment can be applied to, for example... Figure 1 In the wind power grid-connected system shown, the SVG side can be controlled by either an SVG controller or an independent oscillation suppression device on the SVG side. Specifically, the wind power grid-connected system includes a grid-side converter (GSC) of an equivalent direct-drive wind turbine, a static var generator (SVG), a point of common coupling (PCC), and an AC grid. The GSC and SVG are connected in parallel to the PCC, and the PCC is connected to the AC grid via grid impedance. The GSC control system includes a phase-locked loop (PLL2), DC voltage control, and an inner current loop control; the SVG control system includes a phase-locked loop (PLL1), an outer voltage loop control, an inner current loop control, and an outer constant var control.

[0069] Specifically, such as Figure 2 As shown, the oscillation suppression method for wind power grid-connected systems in this embodiment specifically includes the following steps:

[0070] Step S1: Obtain the status data of the wind power grid-connected system.

[0071] The status data includes grid-side status data, point of common coupling status data, SVG-side status data, GSC-side status data, and system fixed parameters. Specifically, the grid-side status data includes the AC grid equivalent impedance L. g Three-phase grid-connected current i gabc AC grid voltage u gabc Common coupling point status data includes the common coupling point voltage u. abc SVG side status data includes the SVG AC side output voltage u. cabc1 SVG DC side voltage u dc1 SVG AC side output current i abc1 And SVG AC side filter inductor L1; GSC side status data includes GSC AC side output voltage u cabc2 GSC DC side voltage u dc2and GSC AC side output current i abc2 And GSC AC side filter inductor L2; system fixed parameters include system rated frequency ω0.

[0072] Step S2: Obtain the PWM control signal of the SVG based on the state data and the SVG reconstructed admittance model.

[0073] The SVG reshaped admittance model is a reshaped SVG admittance model based on decoupling and compensation factors. The decoupling and compensation factors are designed based on the GSC admittance model and the SVG admittance model. Specifically, this embodiment simplifies the wind power grid-connected system as follows: Figure 1 The “wind turbine-SVG-equivalent grid” system shown is used in which the direct-drive wind farm is equivalent to a direct-drive wind turbine. The impedance of the connecting lines is ignored, and the wind turbine model only considers the grid-side converter (GSC) for modeling and analysis.

[0074] Since the SVG achieves synchronization with the power grid through a phase-locked loop (PLL), there are two different dq-synchronous rotating coordinate systems in the system: one is the system coordinate system (superscript s) oriented based on the actual grid voltage vector; the other is the controller coordinate system (superscript c) oriented based on the PLL output phase. The relative angular relationship between the two is as follows: Figure 3 As shown. The conversion relationship between voltage and current small-signal quantities in the two coordinate systems is shown in equation (1):

[0075] (1)

[0076] In the formula, and These represent the small-signal disturbances of the SVG common connection point voltage along the d and q axes in the controller coordinate system. and These represent the small-signal disturbances of the SVG common coupling point voltage along the d and q axes in the system coordinate system. and These represent the d-axis and q-axis components of the PCC voltage at its steady-state operating point in the system coordinate system. This is the closed-loop transfer function of the SVG phase-locked loop; and These represent the small-signal disturbances of the SVG AC side output voltage along the d and q axes in the controller coordinate system. and These represent the small-signal disturbances of the SVG AC side output voltage along the d and q axes in the system coordinate system. and These are the d-axis and q-axis components of the steady-state operating point of the AC side output voltage of the SVG in the system coordinate system. and These represent the small-signal disturbances of the SVG AC side output current along the d and q axes in the controller coordinate system. and These represent the small-signal disturbances of the SVG AC side output current along the d and q axes in the system coordinate system. and These are the d-axis and q-axis components of the steady-state operating point of the AC output current of the SVG in the system coordinate system. The transfer function of the PI controller for the SVG phase-locked loop (PLL1) is expressed as shown in equation (2). For the Laplace operator, The steady-state d-axis component of the PCC voltage in the system coordinate system is given.

[0077] H PIpll1 =k ppll1 +k ipll1 / s (2)

[0078] In the formula, k ppll1 k is the proportional gain of the SVG phase-locked loop. ipll1 The integral coefficients of the SVG phase-locked loop.

[0079] Furthermore, in Figure 1 In the AC main circuit of the SVG shown, the voltage and current satisfy Kirchhoff's voltage law. The relationship under small-signal disturbance is shown in equation (3). The relationship between the small-signal state variables in the SVG control system is shown in equation (4):

[0080] (3)

[0081] (4)

[0082] In the formula, This represents the small-signal disturbance of the DC-side voltage of the SVG. This represents the small-signal disturbance of SVG reactive power. Let be the transfer function matrix of the current inner-loop PI controller. This is the decoupling matrix for the inner current loop (used to eliminate cross-coupling between the d and q axes). This is the gain matrix from the outer loop (DC voltage loop and reactive power loop) to the inner current loop. Let be the PI transfer function of the outer loop of the SVG DC voltage, and its expression is shown in equation (5). Let be the PI transfer function of the SVG reactive power outer loop, and its expression is shown in equation (6).

[0083] H PIu1 =k pu1 +k iu1 / s (5)

[0084] In the formula, kpu1 k is the proportional coefficient of the outer loop of the SVG DC voltage. iu1 This represents the integral coefficient of the outer loop of the SVG DC voltage.

[0085] H PIQ =k pq1 +k iq1 / s (6)

[0086] In the formula, k pq1 k is the proportional coefficient of the outer loop of SVG reactive power. iq1 This is the integral coefficient of the outer loop of the SVG reactive power.

[0087] Based on the instantaneous power balance of the AC and DC sides of the SVG, a relationship can be established between DC voltage and reactive power and AC side voltage and current. Its small-signal form is as follows:

[0088] (7)

[0089] In the formula, The transfer function matrix of the DC voltage loop. For the voltage matrix used in power calculations, voltage perturbations are converted into power perturbations. For the current matrix used in power calculations, current disturbances are converted into power disturbances. Let be the transfer function of the SVG DC voltage loop. This is the reactive power loop coefficient. This is the filter capacitor on the DC side of the SVG. This represents the steady-state operating point of the DC-side voltage of the SVG.

[0090] Small-signal model of SVG converter, such as Figure 4 As shown. Combining equations (1) to (7) and Figure 4 The small-signal structure diagram shown can be used to eliminate intermediate variables and obtain the output admittance model Y of the SVG grid-connected converter as shown in equations (8)-(12). svg .

[0091] (8)

[0092] (9)

[0093] (10)

[0094] (11)

[0095] (12)

[0096] In the formula, , and All are small signal matrices of coordinate transformation caused by phase-locked loops, and their specific expressions are shown in equation (1). The transfer function of the SVG current inner loop PI controller is given by equation (13). For SVG DC-side filter capacitor; This represents the steady-state operating point of the SVG DC voltage. It is a second-order identity matrix; This is the impedance matrix of the main circuit.

[0097] H PIi1 =k pi1 +k ii1 / s (13)

[0098] In the formula, k pi1 k is the proportional gain of the SVG inner loop PI controller. ii1 The integral coefficient of the SVG current inner loop PI controller.

[0099] Through the above steps, a complete SVG small-signal admittance model was established, providing a theoretical basis for subsequent analysis of the oscillation characteristics of wind power grid-connected systems and design of admittance remodeling suppression methods.

[0100] Based on the SVG admittance model, the admittance model of the grid-side converter (GSC) of the direct-drive wind turbine is further established. Considering the phase-locked loop, the DC voltage outer loop, the current inner loop, etc., the GSC admittance model shown in equation (14) is derived in the synchronous rotating coordinate system, and its specific expansion form is shown in equation (15).

[0101] (14)

[0102] (15)

[0103] In the formula, Represents the GSC admittance model; For GSC AC side filter inductor; The d-axis self-admittance of the GSC admittance model; The d-axis coupled admittance of the GSC admittance model to the q-axis; The q-axis coupled admittance of the GSC admittance model to the d-axis; The q-axis self-admittance of the GSC admittance model; For GSC DC-side filter capacitors; The transfer function of the GSC current inner loop PI controller is given by equation (16). The transfer function of the outer loop PI controller of the GSC voltage is given by equation (17). This represents the steady-state operating point of the GSC DC voltage. and These are the d-axis and q-axis components of the voltage at the point of common coupling (PCC) at the steady-state operating point, respectively. The transfer function of the GSC phase-locked loop (PLL2) PI controller is given by equation (18). and These are the d-axis and q-axis components of the GSC AC side output current at the steady-state operating point, respectively. and These are the d-axis and q-axis components of the GSC AC side output voltage in the system coordinate system, representing the steady-state operating point.

[0104] H PIi2 =k pi2 +k ii2 / s (16)

[0105] In the formula, k pi2 k is the proportional gain of the GSC current inner loop PI controller. ii2 The integral coefficient of the GSC current inner loop PI controller.

[0106] H PIu2 =k pu2 +k iu2 / s (17)

[0107] In the formula, k pu2 k is the proportional gain of the outer loop PI controller of the GSC voltage controller. iu2 For the GSC voltage outer loop PI controller, the integral coefficient is denoted as .

[0108] H PIpll2 =k ppll2 +k ipll2 / s (18)

[0109] In the formula, k ppll2 k is the proportional gain of the GSC phase-locked loop PI controller. ipll2 For the integral coefficients of the GSC phase-locked loop PI controller.

[0110] Based on the parallel connection between the direct-drive wind turbine and the SVG at the point of common coupling (PCC), the wind farm admittance model Y of the direct-drive wind power grid-connected system containing the SVG can be obtained. s As shown in Equation (19), this model provides a theoretical basis for subsequent analysis of the impact of wind turbine output on system stability and for designing SVG admittance reshaping control.

[0111] (19)

[0112] Furthermore, based on the system parameters given in Table 1 and the wind farm admittance model shown in equation (19) in this embodiment, the following was obtained: Figure 5 The Bode plots of the GSC output admittance are shown below for different active power values ​​(0.4 pu, 0.67 pu, 1 pu). From... Figure 5 As can be seen from this, within the subsynchronous frequency band, Y gscqq The phase of Y is located outside the first and fourth quadrants, indicating that it has negative damping characteristics, and its amplitude increases with the active power of the wind turbine. This suggests that the higher the power output of the wind farm, the greater the risk of subsynchronous oscillation. Meanwhile, Y... gscqq Within this frequency band, the susceptance is greater than 0, exhibiting capacitive behavior, and easily interacts with the inductive grid impedance, inducing oscillations. In the mid-to-high frequency band, Y... gscdd The phase is also located outside the first and fourth quadrants, and its real part is negative, exhibiting negative damping characteristics, indicating that the system is at risk of oscillation in the mid-to-high frequency range.

[0113] Table 1

[0114] GSC control system SVG control system AC phase voltage / V 110 110 Grid frequency / Hz 50 50 Rated capacity / VA 6000 1200 Filter inductor / H 5e-3 5e-3 DC filter capacitor / F 1.36e-3 1.36e-3 DC voltage reference value / V 400 400 q-axis current reference value / A 0 / Switching frequency / kHz 10 10 Voltage outer loop control parameters <![CDATA[k pu2 =2,k iu2 =12]]> <![CDATA[k pu1 =0.016,k iu1 =0.3]]> Current inner loop control parameters <![CDATA[k pi2 =25,k ii2 =1973.9]]> <![CDATA[k pi1 =4.44,k ii1 =1973.9]]> PLL control parameters <![CDATA[k ppll2 =6,k ipll2 =112.1]]> <![CDATA[k ppll1 =0.473,k ipll1 =63.06]]> Reactive power outer loop control parameters / <![CDATA[k pq1 =0.016,k iq1 =0.3]]>

[0115] As can be seen from the above SVG admittance model expression, although the main diagonal elements of the original SVG admittance matrix are equal, the antidiagonal elements are not opposites, indicating a frequency coupling effect. To eliminate this coupling and simplify the system model, this embodiment introduces a decoupling factor. , and The SVG admittance model is reshaped into an SVG decoupling admittance model. The expression for the decoupling factor is shown in equation (20). The SVG decoupling admittance model Y... 2svg The expression for is shown in equation (21).

[0116] (20)

[0117] (twenty one)

[0118] SVG decoupled admittance model Y 2svg It has a symmetrical anti-diagonal structure with zero elements on the main diagonal, which eliminates the frequency coupling effect and facilitates the design of subsequent compensation factors.

[0119] Furthermore, due to the decoupling admittance model Y of SVG 2svg The main diagonal elements are 0, while the negative damping characteristics of the wind turbine GSC are mainly reflected in the main diagonal elements of its admittance matrix (i.e., Y). gscdd and Y gscqq Therefore, this embodiment introduces a compensation factor in the voltage feedforward path of the SVG. This ensures that the admittance diagonal elements of the SVG have positive real parts (positive damping). Specifically, the compensation factor... The expression is shown in equation (22):

[0120] (twenty two)

[0121] In the formula, This is the proportional gain coefficient. Those skilled in the art can adjust the value of the proportional gain coefficient according to actual needs.

[0122] Add decoupling factor , and and compensation factors The small signal structure diagram of the post-SVG is as follows: Figure 6 As shown, the corresponding control block diagram is as follows: Figure 7 As shown. According to Figure 6 The expression of the SVG admittance model after reshaping based on the decoupling factor and the compensation factor is shown in equation (23).

[0123] (twenty three)

[0124] In the formula, Y 3svg The admittance model is reshaped for SVG, where F is the gain coefficient and R is the coupling coefficient.

[0125] As can be seen from equation (23), the adjustment compensation factor The proportional gain coefficient in the SVG can directly change the amplitude of the main diagonal element of the SVG admittance, thereby adjusting the magnitude of the positive damping it provides and compensating for the negative damping of the main diagonal element of the GSC.

[0126] Finally, based on the GSC admittance model shown in Equation (14) and the SVG remodeled admittance model shown in Equation (23), the wind farm admittance model shown in Equation (24) is constructed.

[0127] (twenty four)

[0128] In the formula, This represents the admittance model of a wind farm.

[0129] PWM control signal according to Figure 7 The resulting control voltage is generated. Specifically, based on the SVG reconstructed admittance model and the state data of the wind power grid-connected system collected in real time in step S1, the current response required by the SVG is calculated under the voltage disturbance at the point of common coupling. For example... Figure 7 As shown, this current response serves as the reference value for the inner current loop. The current reference value generated via the outer voltage loop and the constant reactive power loop is compared with the feedback current, and then processed by the PI regulator in the inner current loop. and cross-decoupling terms The voltage control increments on the d and q axes are obtained, then corrected by the proportional gain coefficient m and superimposed with the feedforward voltage to finally obtain the modulated wave reference voltage in the dq coordinate system. and The reference voltage is transformed to a three-phase stationary coordinate system and then fed into a space vector pulse width modulation (SVPWM) stage to generate the corresponding PWM control signal.

[0130] Furthermore, based on the transformation relationship between dq admittance and positive and negative sequence admittance, the SVG reconstructed admittance model can be converted into the corresponding sequence admittance model, as shown in Equation (25).

[0131] (25)

[0132] in, The value is independent of the steady-state operating point of the SVG and is not affected by changes in the SVG's operating conditions. The amplitude is much greater than The amplitude is practically negligible. For example, Figure 8 Given The Bode plot shows that its phase is always located in the first and fourth quadrants (i.e., −90° to +90°), indicating that... It inherently possesses positive damping characteristics.

[0133] By adjusting the proportional gain coefficient, the amplitude of the SVG sequence admittance can be changed, thereby offsetting the negative damping in the GSC, so that the positive and negative sequence admittance phases of the entire wind farm fall within the positive damping region of [-90°, 90°]. It should be noted that if the value of m is too large, it may reduce the grid-connected current quality when there are background harmonics in the grid; if the value of m is too small, it will not be enough to suppress the negative damping of the wind turbine. Therefore, the value of m needs to be designed reasonably. The selection principle is to make the positive and negative sequence admittance phases of the wind farm located in the passive region (i.e., the positive damping region). In a preferred embodiment, when the active power output of the GSC is 1.0 pu, the range of m is as shown in equation (26):

[0134] (26)

[0135] Among them, Ygsc_pp_1pu and Ygsc_nn_1pu are the positive and negative sequence admittances of GSC under an active power output of 1.0pu, respectively.

[0136] The final compensated wind farm sequence admittance model is shown in equation (27).

[0137] (27)

[0138] Figure 9 Bode plots of the wind farm sequence admittance model before and after reshaping were drawn. From Figure 9It can be seen that before reshaping, the positive sequence admittance of the wind farm is negative real in the low frequency band and the susceptance is greater than 0. Its impedance characteristics exhibit capacitive negative damping, which is prone to interacting with the grid impedance and causing subsynchronous / supersynchronous oscillations of the wind farm. However, after reshaping by the method provided in this embodiment, the phases of both the positive and negative sequence admittances are corrected to the positive damping range of [-90°, 90°], thereby significantly reducing the risk of subsynchronous / supersynchronous oscillations of the wind farm under weak grid conditions.

[0139] Step S3: Drive the IGBT of the SVG to work according to the PWM control signal.

[0140] The PWM control signal, after being amplified and electrically isolated by the drive module, is sent to the gates of each Insulated Gate Bipolar Transistor (IGBT) in the SVG. By continuously driving the IGBTs according to the switching timing determined by the modulation wave, the converter can track the given command of the inner current loop in real time, enabling the SVG to output the required compensation current. The entire drive process forms a closed-loop control, ultimately achieving stable operation of the wind power grid-connected system under weak grid conditions and suppressing wideband oscillations.

[0141] To more clearly illustrate the actual effect of the wind power grid-connected system oscillation suppression method proposed in this embodiment, the following explanation is based on specific experiments.

[0142] This embodiment is based on Figure 1 The topology shown is used to build a structure like this. Figure 10 The experimental setup shown is illustrated, and the experimental parameters are listed in Table 1. Figure 10 In this system, the energy transmission path is as follows: DC power is converted to AC via a GSC converter and connected to the point of common coupling (PCC) through an inductor; the SVG is connected in parallel to the same PCC via its filter inductor; the AC power simulates the power grid. The information interaction path is as follows: the controller collects voltage and current signals, generates PWM to drive the IGBT in the SVG; the oscilloscope monitors the grid-connected current waveform in real time; and the host computer is used for parameter setting and data recording. Under the conditions of Pgsc=0.67pu ​​and Qsvg=0.8pu, the equivalent impedance of the power grid is increased from 8mH (short-circuit ratio SCR=2.36) to 12mH (SCR=1.57). Comparative experiments are conducted using conventional control methods and the system oscillation suppression method proposed in this invention. The experimental results are as follows: Figure 11 and Figure 12 As shown, when using conventional methods, the grid-connected current waveform is significantly distorted and unstable; however, when using the system oscillation suppression method proposed in this invention, the current waveform remains sinusoidally stable without any oscillation.

[0143] The above experiments verified the accuracy of the wind farm admittance model established in this invention, as well as the effectiveness and practicality of the proposed SVG admittance reshaping method. It is evident that this invention can significantly improve the adaptability and grid connection stability of wind farms under weak grid conditions, and effectively suppress broadband oscillation risks.

[0144] The oscillation suppression method for wind power grid-connected systems in this embodiment first establishes the dq admittance models of SVG and GSC of direct-drive wind turbines based on linearization methods, constructing an overall admittance model of the wind farm. By analyzing the admittance characteristics of GSC under different active power outputs, the negative damping characteristics of the wind farm across the entire frequency band and the law that the higher the active power, the higher the resonance risk are revealed are disclosed. Then, a decoupling factor is introduced to reshape the SVG admittance into a form where the main diagonal elements are equal and the antidiagonal elements are opposites of each other, eliminating the frequency coupling effect and simplifying the system model. Furthermore, a compensation factor is introduced into the SVG voltage feedforward path to enable the SVG admittance to obtain positive damping characteristics across the entire frequency band. By adjusting the proportional coefficient of the compensation factor, the positive damping amplitude can be flexibly adjusted to achieve full-band compensation and cancellation of the negative damping of GSC. After reshaping, the overall equivalent output admittance of the wind farm exhibits positive damping, and the positive and negative sequence admittance phases are located in the passive region, significantly reducing the risk of subsynchronous, supersynchronous, and high-frequency oscillations. Experiments show that the grid-connected current remains sinusoidally stable under weak grid conditions using this method, and there is no need to modify existing wind turbines. Only by optimizing SVG control can the adaptability of wind farms to weak grids and grid-connected stability be systematically improved, which has low implementation cost and high economic efficiency.

[0145] Example 2

[0146] Based on the same inventive concept, this embodiment also provides a wind power grid-connected system oscillation suppression device for implementing the wind power grid-connected system oscillation suppression method described above. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations in this device embodiment can be found in the limitations of the wind power grid-connected system oscillation suppression method described above, and will not be repeated here.

[0147] like Figure 13 As shown, this embodiment provides a wind power grid-connected system oscillation suppression device, including a state data acquisition module, a PWM control signal generation module, and an IGBT drive module, wherein:

[0148] The status data acquisition module is used to acquire status data of the wind power grid-connected system;

[0149] The PWM control signal generation module is used to obtain the PWM control signal of the SVG based on the state data and the SVG reconstructed admittance model; the SVG reconstructed admittance model is the SVG admittance model reconstructed based on the decoupling factor and the compensation factor;

[0150] The IGBT driver module is used to drive the IGBTs of the SVG to operate according to the PWM control signal.

[0151] Each module in the aforementioned wind power grid-connected system oscillation suppression device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the computer device's memory as software, so that the processor can call and execute the corresponding operations of each module.

[0152] Example 3

[0153] This embodiment provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps in Embodiment 1 above.

[0154] Example 4

[0155] This embodiment provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in Embodiment 1 above.

[0156] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for suppressing oscillations in a wind power grid-connected system, characterized in that, The method includes: Step S1: Obtain the status data of the wind power grid-connected system; Step S2: Obtain the PWM control signal of the SVG based on the state data and the SVG reshaped admittance model; the SVG reshaped admittance model is an SVG admittance model reshaped based on decoupling factors and compensation factors, wherein the decoupling factors include a phase-locked loop decoupling factor, a first decoupling factor, and a second decoupling factor, and the expression of the phase-locked loop decoupling factor is: The expression for the first decoupling factor is: The expression for the second decoupling factor is: In the formula, This is the decoupling factor for the phase-locked loop. This is the first decoupling factor. This is the second decoupling factor. The transfer function for SVG phase-locked loop PI control. For the Laplace operator, Let d be the steady-state operating point of the voltage at the point of common connection in the dq coordinate system. The d-axis component of the SVG AC side output current at the steady-state operating point in the dq coordinate system. The q-axis component of the SVG AC side output current at the steady-state operating point in the dq coordinate system. Let be the transfer function of the SVG DC voltage loop. This is the reactive power loop coefficient. This represents the steady-state operating point of the SVG DC voltage. This is the filter capacitor on the DC side of the SVG; The expression for the compensation factor is: In the formula, The compensation factor is... This is the proportional gain coefficient; The expression for the SVG reshaped admittance model is: In the formula, Reshape the admittance model for the SVG. This is the decoupling matrix for the inner current loop. Let be the transfer function matrix of the current inner-loop PI controller. This is the gain matrix from the outer loop to the inner current loop. The transfer function matrix of the DC voltage loop of the SVG. This is the current matrix used for power calculation. Main circuit impedance matrix, The voltage matrix used for power calculation. , and Both are small-signal matrices of coordinate transformation caused by phase-locked loops. To reshape the d-axis self-admittance of the admittance model for SVG The d-axis coupled admittance of the SVG reconstructed admittance model is given. The q-axis coupled admittance of the SVG reconstructed admittance model is given. q-axis self-admittance of the SVG reconstructed admittance model For the filter inductor on the AC side of the SVG, Here is the transfer function of the SVG current inner loop PI controller. The PI transfer function for the outer loop of the SVG DC voltage. It is a second-order identity matrix; Step S3: Drive the IGBT of the SVG to work according to the PWM control signal.

2. The oscillation suppression method for wind power grid-connected systems according to claim 1, characterized in that, The expression for the transfer function of the SVG phase-locked loop PI control is: The expression for the transfer function of the SVG DC voltage loop is: The expression for the reactive power loop coefficient is: In the formula, k ppll1 k is the proportional gain of the SVG phase-locked loop. ipll1 For the integral coefficients of the SVG phase-locked loop, For the Laplace operator, This is the filter capacitor on the DC side of the SVG. This represents the steady-state operating point of the DC-side voltage of the SVG.

3. The oscillation suppression method for wind power grid-connected systems according to claim 1, characterized in that, The range of values ​​for the proportional gain coefficient is: In the formula, Y gsc_pp_1pu Y is the positive sequence admittance when the GSC active power output is 1.0 pu. gsc_nn_1pu The negative sequence admittance is given when the active power output of the GSC is 1.0 pu. The gain coefficients of the reshaped admittance model of the SVG.

4. The oscillation suppression method for wind power grid-connected systems according to claim 1, characterized in that, The expression for the GSC admittance model in the wind power grid-connected system is: In the formula, This represents the GSC admittance model. The d-axis coupled admittance of the GSC admittance model to the q-axis; The q-axis coupled admittance of the GSC admittance model to the d-axis; This represents the q-axis self-admittance of the GSC admittance model. and These represent the d-axis and q-axis components of the GSC AC output current at the steady-state operating point, respectively. This is the transfer function of the GSC current inner loop PI controller. For GSC DC-side filter capacitors, This is the steady-state operating point of the GSC DC voltage. For GSC AC side filter inductor, This is the transfer function of the GSC voltage outer loop PI controller. Here is the transfer function of the GSC phase-locked loop PI controller. and These are the d-axis and q-axis components of the voltage at the point of common coupling (PCC) at the steady-state operating point, respectively. and ω0 represents the steady-state operating point d-axis and q-axis components of the GSC AC side output voltage in the system coordinate system, respectively, and ω0 is the system rated frequency.

5. The oscillation suppression method for wind power grid-connected systems according to claim 1, characterized in that, The status data includes grid-side status data, point of common coupling status data, SVG-side status data, GSC-side status data, and system fixed parameters.

6. A wind power grid-connected system oscillation suppression device, characterized in that, The device includes: The status data acquisition module is used to acquire status data of the wind power grid-connected system; The PWM control signal generation module is used to obtain the PWM control signal of the SVG based on the state data and the SVG reshaped admittance model. The SVG reshaped admittance model is an SVG admittance model reshaped based on decoupling factors and compensation factors. The decoupling factors include a phase-locked loop decoupling factor, a first decoupling factor, and a second decoupling factor. The expression for the phase-locked loop decoupling factor is: The expression for the first decoupling factor is: The expression for the second decoupling factor is: In the formula, This is the decoupling factor for the phase-locked loop. This is the first decoupling factor. This is the second decoupling factor. The transfer function for SVG phase-locked loop PI control. For the Laplace operator, Let d be the steady-state operating point of the voltage at the point of common connection in the dq coordinate system. The d-axis component of the SVG AC side output current at the steady-state operating point in the dq coordinate system. The q-axis component of the SVG AC side output current at the steady-state operating point in the dq coordinate system. Let be the transfer function of the SVG DC voltage loop. This is the reactive power loop coefficient. This represents the steady-state operating point of the SVG DC voltage. This is the filter capacitor on the DC side of the SVG; The expression for the compensation factor is: In the formula, The compensation factor is... This is the proportional gain coefficient; The expression for the SVG reshaped admittance model is: In the formula, Reshape the admittance model for the SVG. This is the decoupling matrix for the inner current loop. Let be the transfer function matrix of the current inner-loop PI controller. This is the gain matrix from the outer loop to the inner current loop. The transfer function matrix of the DC voltage loop of the SVG. This is the current matrix used for power calculation. Main circuit impedance matrix, The voltage matrix used for power calculation. , and Both are small-signal matrices of coordinate transformation caused by phase-locked loops. To reshape the d-axis self-admittance of the admittance model for SVG The d-axis coupled admittance of the SVG reconstructed admittance model is given. The q-axis coupled admittance of the SVG reconstructed admittance model is given. q-axis self-admittance of the SVG reconstructed admittance model For the filter inductor on the AC side of the SVG, Here is the transfer function of the SVG current inner loop PI controller. The PI transfer function for the outer loop of the SVG DC voltage. It is a second-order identity matrix; The IGBT driver module is used to drive the IGBT of the SVG to work according to the PWM control signal.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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