Multi-strategy broadband oscillation suppression method, device and equipment for wind power flexible direct current grid-connected system and medium

Abstract

The invention relates to the technical field of stability control of wind power flexible direct current grid-connected systems, in particular to a multi-strategy broadband oscillation suppression method, device and equipment for a wind power flexible direct current grid-connected system and a medium, and the method comprises the steps: building a harmonic state space impedance model of the wind power flexible direct current grid-connected system under different broadband oscillation suppression strategies; determining the optimal installation position of the broadband oscillation suppression strategy meeting the phase angle difference margin constraint; according to the method, a suitable multi-strategy cooperative broadband oscillation suppression strategy combination scheme is selected, so that the phase angle difference margin of the wind power flexible direct current grid-connected system is improved under different working conditions, it is ensured that the system obtains suitable stability margins in a target frequency band and a non-target frequency band, and therefore the overall stability of the wind power flexible direct current grid-connected system is enhanced; according to the strategy combination method, it is ensured that the wind power flexible direct current grid-connected system has a large phase angle difference margin in a broadband range, so that the overall stability margin of the system in different frequency bands is improved, and the stability and robustness of the wind power flexible direct current grid-connected system are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of stability control of a wind power flexible direct current grid-connected system, and in particular to a multi-strategy wideband oscillation suppression method, device, equipment and medium for a wind power flexible direct current grid-connected system. Background Art

[0002] In actual operation, the wind power flexible direct current grid-connected system is easily affected by oscillations in different frequency bands, resulting in reduced system stability. Traditional oscillation suppression strategies generally achieve the system oscillation suppression effect by improving the damping of the unstable frequency band. However, due to the coupling relationship between the damping of different frequency bands, while improving the damping of the target frequency band, it may cause the deterioration of the damping of the non-target frequency band and even cause system instability. To address this problem, two types of oscillation suppression strategies are currently used: active oscillation suppression strategy and passive oscillation suppression strategy.

[0003] The active oscillation suppression strategy improves the damping effect by adjusting the system control parameters to change the port external characteristics, but its effect is easily limited by factors such as control bandwidth and link delay; the passive oscillation suppression strategy relies on hardware devices to reshape the impedance characteristics of the system, but its parameter adjustment is not flexible enough and it is difficult to adapt to changing operating conditions. In addition, the control bandwidth and deployment location of different strategies are different, resulting in interactive coupling in their control effects. When suppressing oscillations in a specific frequency band, oscillations in other frequency bands may be stimulated. For example, in the Chongqing-Hubei DC back-to-back interconnection project, after low-pass filtering was used to suppress the 1810Hz high-frequency oscillation, although the high-frequency oscillation was controlled, it triggered the appearance of 700Hz medium-frequency oscillation. This shows that a single oscillation suppression strategy is difficult to achieve wide-band oscillation suppression of low, medium and high frequencies.

[0004] The existing multi-strategy wide-band oscillation suppression method for wind power flexible direct current grid-connected systems has the following problems: when suppressing the oscillation of the target frequency band, each strategy is difficult to effectively avoid the excessive reduction of the phase difference margin of the non-target frequency band, thereby affecting the overall stability of the system. Therefore, there is an urgent need for a multi-strategy collaborative method that can coordinate multiple strategies and provide robust oscillation suppression effects in different frequency bands to improve the overall stability of the system.

[0005] The information disclosed in this background technology section is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0006] The present invention provides a multi-strategy wide-band oscillation suppression method, device, equipment and medium for a wind power flexible direct current grid-connected system, thereby effectively solving the problems in the background technology.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system, comprising the following steps:

[0008] Establish the harmonic state space impedance model of the wind power flexible direct current grid-connected system under different wide-band oscillation suppression strategies, analyze the impedance characteristics of each wide-band oscillation suppression strategy in different frequency bands, and obtain the frequency band response behavior of the system in different frequency bands;

[0009] Based on the harmonic state space impedance model, the phase difference margins of the non-target frequency band and the target frequency band under different installation positions are calculated, and the optimal installation position of the wide-band oscillation suppression strategy that meets the phase difference margin constraint is determined to ensure that the phase difference margin of the non-target frequency band is not lower than a preset threshold;

[0010] Based on the optimal installation position, the effects of various wide-band oscillation suppression strategies are analyzed for different operating conditions, and an applicable multi-strategy coordinated wide-band oscillation suppression strategy combination scheme is selected to improve the phase difference margin of the wind power flexible direct current grid-connected system under different operating conditions, ensuring that the system obtains appropriate stability margins in both target frequency bands and non-target frequency bands, thereby enhancing the overall stability of the wind power flexible direct current grid-connected system.

[0011] Furthermore, a harmonic state space impedance model of the wind power flexible direct current grid-connected system under different broadband oscillation suppression strategies is established, and the steps include:

[0012] Establish a single broadband oscillation suppression strategy and a single broadband state space model of the wind power flexible direct current grid-connected system;

[0013] Based on the single broadband state-space model, the influence of different broadband oscillation suppression strategies on the dynamic response of the system at different installation positions is analyzed, state-space models of different broadbands and different installation positions are established, and the influence of different installation positions on the dynamic response of the system is analyzed;

[0014] Based on the state space models of different broadbands and different installation locations, a linearized state space model of the wind power flexible direct current grid-connected system is established to simplify the dynamic characteristics of the system and facilitate subsequent analysis;

[0015] Based on the linearized state space model, a harmonic linearized state space model of the wind power flexible direct current grid-connected system is established to analyze the impact of each order of harmonics on the system stability;

[0016] Based on the harmonic linearization state space model, a harmonic linearization state space impedance model of the wind power flexible direct current grid-connected system is established to describe the impedance response of the system to oscillations in different frequency bands, providing a basis for the implementation of subsequent optimization strategies.

[0017] Furthermore, the single broadband state-space model comprises:

[0018]

[0019] In the formula, d represents the differential, x act_i is the state variable of the i-th broadband oscillation suppression strategy, t is time, A act_i is the state matrix of the i-th wideband oscillation suppression strategy, B act_i is the input matrix of the i-th broadband oscillation suppression strategy, u act_i is the input variable of the i-th wide-band oscillation suppression strategy.

[0020] Furthermore, the establishing of the state space model of different installation positions includes:

[0021]

[0022] In the formula, x sysact_i-w,c,v is the state variable of the wind power flexible direct current grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible direct current converter respectively, A sysact_i-w,c,v is the state matrix of the wind power flexible direct current grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible direct current converter respectively, B sysact_i-w,c,v is the input matrix of the wind power flexible DC grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible DC converter respectively, u sysact_i-w,c,v are the input variables of the wind power flexible DC grid-connected system when the i-th wide-band oscillation suppression strategy is installed on the wind turbine converter, busbar and flexible DC converter respectively.

[0023] Furthermore, the establishment of a linearized state space model of the wind power flexible direct current grid-connected system includes:

[0024]

[0025] In the formula, A sysact_i-w,c,v is the state matrix of the wind power flexible DC grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible DC converter, Δx sysact_i-w,c,v Represents x sysact_i-w,c,v increment.

[0026] Furthermore, the establishment of a harmonic linearization state space model of a wind power flexible direct current grid-connected system includes:

[0027] sΔX sysact_i-w,c,v =(A Tsysact_i-w,c,v -N)ΔX sysact_i-w,c,v ;

[0028] Where s is the Laplace operator, ΔX sysact_i-w,c,vA represents the vector of harmonics of each order after adding the wide-band oscillation suppression strategy. Tsysact_i-w,c,v is the Toeplitz matrix for frequency domain convolution calculation after adding the wide-band oscillation suppression strategy, and N is the diagonal matrix reflecting the frequency information.

[0029] Furthermore, a harmonic linearized state space impedance model of the wind power flexible direct current grid-connected system is established, including:

[0030] Based on the harmonic linearization state space model of the wind power flexible DC grid-connected system, the harmonic linearization state space impedance of the flexible DC and the harmonic linearization state space impedance of the wind turbine are extracted when the broadband oscillation suppression strategy is not added.

[0031] Based on the harmonic linearization state-space model of the wind power flexible DC grid-connected system, the harmonic linearization state-space impedance of the flexible DC and the harmonic linearization state-space impedance of the wind turbine are extracted when the wide-band suppression strategy is added, and the harmonic linearization state-space impedance model of the wind power flexible DC grid-connected system is obtained.

[0032] Further, the phase difference margins of the non-target frequency band and the target frequency band under different installation positions are calculated, and the optimal installation position of the wide-band oscillation suppression strategy that meets the phase difference margin constraint is determined. The steps include:

[0033] Based on the impedance characteristics of the wind power flexible direct current grid-connected system and wind turbines, the impedance amplitude-phase diagram when the wide-band oscillation suppression strategy is not added, and the impedance amplitude-phase diagram when the wide-band oscillation suppression strategy is added are obtained to determine the frequency response characteristics of the system in the low-frequency band, medium-frequency band, and high-frequency band;

[0034] In the impedance amplitude-phase diagram, the amplitude intersection point of the impedance curves of the flexible DC converter and the wind turbine is identified, the phase angle difference when the wide-band oscillation suppression strategy is not added is calculated, and the phase angle difference is subtracted from 180 degrees to obtain an initial phase angle difference margin;

[0035] Based on the initial phase difference margin, under the action of different wide-band oscillation suppression strategies, respectively calculate the phase difference margin changes of the low-frequency band, the medium-frequency band and the high-frequency band to obtain the phase difference margin after adding the wide-band oscillation suppression strategy;

[0036] Based on the phase difference margin after adding the wide-band oscillation suppression strategy, analyzing the phase difference margin changes of different frequency bands; when the phase difference margin change of a certain frequency band is positive, the frequency band is defined as a target frequency band, and the remaining frequency bands are non-target frequency bands;

[0037] Set the constraint condition that the phase difference margin of the wide-band oscillation suppression strategy in the non-target frequency band must be greater than zero, and the constraint condition that the change of the phase difference margin in the target frequency band must not be less than the preset value;

[0038] It is respectively determined whether the non-target frequency band phase angle difference margin is greater than zero and whether the target frequency band phase angle difference margin variation satisfies the preset value under the wide-band oscillation suppression strategy at the wind turbine converter, busbar and flexible DC converter positions:

[0039] If the non-target frequency band phase angle difference margin is less than zero, or the target frequency band phase angle difference margin variation is less than the preset value, the installation position of the wide-band oscillation suppression strategy is an unselectable position;

[0040] If the non-target frequency band phase angle difference margin is greater than zero, and the target frequency band phase angle difference margin variation is greater than or equal to the preset value, then the installation position is an optional position;

[0041] The installation position where the change in the target frequency band phase angle difference margin is the largest is selected as the optimal installation position for the wide-band oscillation suppression strategy.

[0042] Furthermore, the effects of various broadband oscillation suppression strategies are analyzed according to different operating conditions, and an applicable multi-strategy coordinated broadband oscillation suppression strategy combination scheme is selected. The steps include:

[0043] All operating conditions of the wind power flexible direct current grid-connected system are set to the active power output of the wind farm within the preset range;

[0044] For different operating conditions of the active power output of the wind farm within a preset range, respectively determining whether the non-target frequency band phase angle difference margins are all greater than zero after adding the wide-band oscillation suppression strategy;

[0045] If the phase angle difference margin of the non-target frequency band is greater than zero under all operating conditions, multi-strategy coordinated suppression is not required;

[0046] If the phase angle difference margin of the non-target frequency band is less than zero under the operating conditions, multiple strategies are needed to coordinate wide-band oscillation suppression;

[0047] When the j-th wide-band oscillation suppression strategy is added, if the non-target frequency band phase difference margin is negative, k strategy combinations are selected from the m wide-band oscillation suppression strategies, so that after the synergy of multiple strategies, the non-target frequency band phase difference margin is increased to a stable value not less than zero;

[0048] The change in the non-target frequency band phase angle difference margin before and after the k wide-band oscillation suppression strategies cooperate with the j-th wide-band oscillation suppression strategy is calculated. When the change takes the maximum value, the corresponding n combinations of the k wide-band oscillation suppression strategies cooperate with the j-th wide-band oscillation suppression strategy to obtain the combination scheme of the selected wide-band oscillation suppression strategy.

[0049] Further, the non-target frequency band phase angle difference margin change ΔPM before and after the k-th wide-band oscillation suppression strategy and the j-th wide-band oscillation suppression strategy work together is calculated. sys_marge_n (n=1,2,k-1) models, including:

[0050]

[0051] In the formula, is the non-target frequency band phase angle difference margin after selecting n combinations of k wide-band oscillation suppression strategies and cooperating with the j-th wide-band oscillation suppression strategy, α wvj is the phase difference margin of the non-target frequency band after the j-th wide-band oscillation suppression strategy is added.

[0052] The present invention also includes a multi-strategy broadband oscillation suppression device for a wind power flexible direct current grid-connected system, using the above method, including:

[0053] The impedance model building module is used to establish the harmonic state space impedance model of the wind power flexible direct current grid-connected system under different wide-band oscillation suppression strategies, analyze the impedance characteristics of each wide-band oscillation suppression strategy in different frequency bands, and obtain the frequency band response behavior of the system within different frequency bands;

[0054] An installation position calculation module is used to calculate the phase difference margins of the non-target frequency band and the target frequency band under different installation positions based on the harmonic state space impedance model, and determine the optimal installation position of the wide-band oscillation suppression strategy that meets the phase difference margin constraint to ensure that the non-target frequency band phase difference margin is not lower than a preset threshold;

[0055] The strategy combination selection module is used to analyze the effects of various wide-band oscillation suppression strategies for different operating conditions based on the optimal installation position, and select an applicable multi-strategy coordinated wide-band oscillation suppression strategy combination scheme to improve the phase difference margin of the wind power flexible direct current grid-connected system under different operating conditions, ensure that the system obtains a suitable stability margin in both the target frequency band and the non-target frequency band, thereby enhancing the overall stability of the wind power flexible direct current grid-connected system.

[0056] The present invention also includes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method described above is implemented.

[0057] The present invention also includes a storage medium on which a computer program is stored. When the computer program is executed by a processor, the method described above is implemented.

[0058] The beneficial effects of the present invention are:

[0059] 1. The present invention analyzes the phase difference margin variation of different wide-band oscillation suppression strategies at different installation locations (wind turbine converter, busbar, flexible DC converter), considers the non-target frequency band phase difference margin constraint and the target frequency band phase difference margin variation constraint, and proposes a wide-band oscillation suppression strategy installation location selection method; this method avoids the situation where the non-target frequency band phase difference margin is negative under the current working condition after the installation of a single oscillation suppression strategy, resulting in system instability;

[0060] 2. The present invention obtains the change in phase difference margin before and after adding different wide-band oscillation suppression strategies under different operating conditions through multi-strategy coordination, selects a combination of multi-strategy coordinated wide-band oscillation suppression strategies, and proposes a method for selecting a combination of multi-strategy coordinated wide-band oscillation robust suppression strategies for a wind power flexible direct current grid-connected system. The method can realize that the wind power flexible direct current grid-connected system has a large phase difference margin in a wide band, thereby ensuring that the wind power flexible direct current grid-connected system has a large stability margin in a wide band. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0062] Figure 1 This is a flow chart of a multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system;

[0063] Figure 2 This is the structural diagram of the wind power flexible direct current grid-connected system;

[0064] Figure 3 This is a schematic diagram of the structure of a multi-strategy broadband oscillation suppression device for a wind power flexible direct current grid-connected system;

[0065] Figure 4 A schematic diagram of the structure of a computer device. DETAILED DESCRIPTION

[0066] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0067] like Figure 1 A method for suppressing wide-band oscillations in a wind power flexible direct current grid-connected system with multiple strategies comprises the following steps:

[0068] S10: Establish the harmonic state space impedance model of the wind power flexible direct current grid-connected system under different wide-band oscillation suppression strategies, analyze the impedance characteristics of each wide-band oscillation suppression strategy in different frequency bands, and obtain the frequency band response behavior of the system in different frequency bands;

[0069] S20: Based on the harmonic state space impedance model, the phase difference margins of the non-target frequency band and the target frequency band under different installation positions are calculated, and the optimal installation position of the wide-band oscillation suppression strategy that meets the phase difference margin constraint is determined to ensure that the phase difference margin of the non-target frequency band is not lower than the preset threshold, thereby avoiding the system from becoming unstable due to the decrease in stability of the non-target frequency band;

[0070] S30: Based on the optimal installation position, analyze the effects of various wide-band oscillation suppression strategies for different operating conditions, and select an applicable multi-strategy coordinated wide-band oscillation suppression strategy combination scheme to improve the phase difference margin of the wind power flexible direct current grid-connected system under different operating conditions, ensure that the system obtains a suitable stability margin in both the target frequency band and the non-target frequency band, thereby enhancing the overall stability of the wind power flexible direct current grid-connected system.

[0071] like Figure 2 As shown, the wind power flexible direct current grid-connected system mainly includes: wind turbines, collector lines, flexible direct current (flexible direct current transmission is referred to as flexible direct current) system, using this method;

[0072] Considering the problem that the wideband oscillation suppression strategy may make the phase difference margin of the non-target frequency band negative and the system unstable while improving the phase difference margin of the target frequency band of the wind power flexible DC grid-connected system, a multi-strategy coordinated wideband oscillation robust suppression strategy for wind power flexible DC grid-connected system is proposed. After the wideband oscillation suppression strategy is added, any frequency band has an appropriate positive phase difference margin, which improves the stability of the wind power flexible DC grid-connected system from a wide-band range and avoids the problem of system instability caused by excessive reduction of the phase difference margin of the non-target frequency band.

[0073] By analyzing the impact of different wide-band oscillation suppression strategies on the phase difference margin at different installation locations such as wind turbine converters, busbars and flexible DC converters, a method for selecting the installation location of a wide-band oscillation suppression strategy based on the phase difference margin is proposed. When selecting the installation location, this method fully considers the constraints of the non-target frequency band phase difference margin and the requirements for the change of the target frequency band phase difference margin, thereby avoiding the problem of system instability caused by a single oscillation suppression strategy causing a negative non-target frequency band phase difference margin under certain operating conditions.

[0074] Through the coordination of multiple strategies, the changes in the phase difference margin of different wide-band oscillation suppression strategies before and after adding are analyzed according to different operating conditions, and a suitable combination of multi-strategy coordinated wide-band oscillation suppression strategies is selected. This strategy combination method ensures that the wind power flexible direct-current grid-connected system has a large phase difference margin within a wide-band range, thereby improving the overall stability margin of the system in different frequency bands and ensuring the stability and robustness of the wind power flexible direct-current grid-connected system.

[0075] By establishing a harmonic state space impedance model of the wind power flexible direct current grid-connected system under different wide-band oscillation suppression strategies, this technical solution can deeply analyze the impedance characteristics and frequency band response behaviors of each oscillation suppression strategy in different frequency bands, thereby providing basic data support for the subsequent installation location selection. In this way, the system can achieve effective oscillation suppression in the target frequency band while ensuring that the phase difference margin of the non-target frequency band meets the stability requirements, avoiding the system instability problem caused by a single suppression strategy in certain frequency bands in the background technology.

[0076] By calculating the phase difference margin between the non-target frequency band and the target frequency band under different installation positions, the optimal installation position of the wide-band oscillation suppression strategy is determined, and the non-target frequency band phase difference margin is not lower than the preset safety threshold, thereby reducing or avoiding the system instability caused by the low non-target frequency band phase difference margin in the background technology. This position optimization strategy effectively solves the problem of deterioration of non-target frequency band damping caused by coupling of different frequency bands in the background technology, and improves the robustness and operational reliability of the system.

[0077] Under different operating conditions, the scheme can obtain a higher phase difference margin in different frequency bands by selecting and combining applicable multi-strategy coordinated wide-band oscillation suppression strategies, thereby effectively improving the overall stability of the system within the wide band. Compared with the limitations of the background technology that a single suppression strategy is difficult to cover the wide band and may stimulate oscillations in other frequency bands, the present invention solves the problem of stability control in the wide band through multi-strategy coordinated suppression, ensuring that the system obtains sufficient stability margin in each target band and non-target band.

[0078] As a preferred embodiment of the above, in step S10, a harmonic state space impedance model of a wind power flexible direct current grid-connected system under different broadband oscillation suppression strategies is established, and the steps include:

[0079] S11: Establish a single broadband oscillation suppression strategy and a single broadband state space model of the wind power flexible direct current grid-connected system to characterize the impact of the suppression strategy on the system frequency response;

[0080] S12: Based on a single broadband state space model, analyze the impact of different broadband oscillation suppression strategies on the system dynamic response at different installation positions, establish state space models with different broadbands and different installation positions, and analyze the impact of different installation positions on the system dynamic response;

[0081] S13: Based on the state space models of different broadbands and different installation locations, a linearized state space model of the wind power flexible direct current grid-connected system is established to simplify the dynamic characteristics of the system and facilitate subsequent analysis;

[0082] S14: Based on the linearized state space model, a harmonic linearized state space model of the wind power flexible direct current grid-connected system is established to analyze the impact of each order of harmonics on the system stability;

[0083] S15: Based on the harmonic linearization state space model, a harmonic linearization state space impedance model of the wind power flexible direct current grid-connected system is established to describe the impedance response of the system to oscillations in different frequency bands, providing a basis for the implementation of subsequent optimization strategies.

[0084] The harmonic linearized state-space impedance model finally established can intuitively describe the system's impedance response to oscillations in different frequency bands, providing data support for subsequent strategy optimization. It not only improves the system's suppression effect in the target frequency band, but also effectively avoids the risk of system instability caused by the reduction of the phase angle difference in the non-target frequency band.

[0085] In step S11, there are m types of broadband oscillation suppression strategies (i=1, 2, ..., m), and a single broadband state space model includes:

[0086]

[0087] In the formula, d represents the differential, x act_i is the state variable of the i-th broadband oscillation suppression strategy, t is time, A act_i is the state matrix of the i-th wideband oscillation suppression strategy, B act_i is the input matrix of the i-th broadband oscillation suppression strategy, u act_i is the input variable of the i-th wide-band oscillation suppression strategy.

[0088] Through a single state-space model, the impact of the i-th wide-band oscillation suppression strategy on the system frequency response can be accurately characterized, including the changes in state variables and the effects of external inputs. Compared with traditional analysis methods, the state-space model can clearly describe the dynamic characteristics of the system in mathematical form, making it easier to analyze the effects of different strategies.

[0089] Step S12: Based on a single broadband state space model, analyzing the impact of different broadband oscillation suppression strategies on the system dynamic response at different installation positions, establishing state space models of different broadbands and different installation positions, and analyzing the impact of different installation positions on the system dynamic response;

[0090] The interface relationship between the wind power flexible direct current grid-connected system and the wind power flexible direct current grid-connected system is established when m kinds of wide-band oscillation suppression strategies are installed in the wind turbine converter, busbar, and flexible direct current converter respectively:

[0091]

[0092] The above formula represents the interface relationship between the wind power flexible direct current grid-connected system and the i-th wide-band oscillation suppression strategy when it is installed in the wind turbine converter, busbar, and flexible direct current converter respectively;

[0093] In the formula, the variable subscript -w indicates that the broadband oscillation suppression strategy is installed on the wind turbine converter, -c indicates that the broadband oscillation suppression strategy is installed on the busbar, and -v indicates that the broadband oscillation suppression strategy is installed on the flexible DC converter;

[0094] U act_i-w,c,v is the voltage variable when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible DC converter, U wv is the voltage variable of the wind power flexible direct current grid-connected system, O actU_i-w,c,v I represents the voltage interface variable between the wind power flexible direct current grid-connected system and the wind power flexible direct current grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible direct current converter, respectively. act_i-w,c,v is the current variable when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible DC converter, I wv is the current variable of the wind power flexible direct current grid-connected system, O actI_i-w,c,v represents the variable of the current interface between the wind power flexible direct current grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible direct current converter respectively; ψ act_i-w,c,v represents the coordinate system of the i-th broadband oscillation suppression strategy installed in the wind turbine converter, busbar, and flexible DC converter, ψ wv is the coordinate system of the wind power flexible direct current grid-connected system, R act_i-w,c,v The variable representing the interface between the coordinate system of the i-th wide-band oscillation suppression strategy installed in the wind turbine converter, busbar, and flexible DC converter and the coordinate system of the wind power flexible DC grid-connected system.

[0095] In this embodiment, in step S12, state space models of different installation positions are established, including:

[0096]

[0097] In the formula, x sysact_i-w,c,v is the state variable of the wind power flexible direct current grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible direct current converter respectively, A sysact_i-w,c,v is the state matrix of the wind power flexible direct current grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible direct current converter respectively, B sysact_i-w,c,v is the input matrix of the wind power flexible DC grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible DC converter respectively, u sysact_i-w,c,v are the input variables of the wind power flexible DC grid-connected system when the i-th wide-band oscillation suppression strategy is installed on the wind turbine converter, busbar and flexible DC converter respectively.

[0098] By establishing separate state-space models at different installation locations such as wind turbine converters, busbars and flexible DC converters, the impact of each installation location on the dynamic response of the wind power flexible DC grid-connected system can be accurately described, ensuring that the effect of each wide-band oscillation suppression strategy at different locations is analyzed in more detail, providing more accurate frequency band response characteristics.

[0099] Step S13: Based on the state space models of different broadbands and different installation locations, a linearized state space model of the wind power flexible direct current grid-connected system is established to simplify the dynamic characteristics of the system and facilitate subsequent analysis;

[0100] Establish the state space model of the wind power flexible direct current grid-connected system, including:

[0101]

[0102] In the formula, x wv is the state variable of the wind power flexible direct current grid-connected system, A wv is the state matrix of the wind power flexible direct current grid-connected system, B wv is the input matrix of the wind power flexible direct current grid-connected system, u wv It is the input variable of the wind power flexible direct current grid-connected system.

[0103] The above model is linearized to establish the linearized state space model of the wind power flexible direct current grid-connected system:

[0104]

[0105] Where Δx represents the increment of x.

[0106] wv

[0107] As a preferred embodiment of the above, in step S13, the state space models of different installation positions are linearized to establish a linearized state space model of the wind power flexible direct current grid-connected system, including:

[0108]

[0109] In the formula, A sysact_i-w,c,v is the state matrix of the wind power flexible DC grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible DC converter, Δx sysact_i-w,c,v Represents x sysact_i-w,c,v increment.

[0110] By linearizing the state space models of different installation positions, the complex nonlinear dynamic characteristics are simplified into linear models, making the dynamic analysis process of the system more concise and efficient. The linearization process significantly reduces the computational complexity and provides a basis for rapid calculation for subsequent control optimization, thereby improving the overall system operation efficiency.

[0111] Step S14: Based on the linearized state space model, a harmonic linearized state space model of the wind power flexible direct current grid-connected system is established to analyze the influence of each order harmonic on the system stability;

[0112] Any periodic time-varying signal can be expressed as a sum of Fourier series if it satisfies the Dirichlet condition; the periodic signal Δu(t) can be expressed as a sum of Fourier series;

[0113]

[0114] Where n is the harmonic order, Δu n With θ n (n=0, 1, 2, ...) represent the amplitude and initial phase angle of the nth harmonic respectively, t is the time, and ω1 is the fundamental angular frequency of the system.

[0115] Using Euler's formula cosθ=0.5(e jθ +e -jθ ) deforms the periodic signal Δu(t);

[0116]

[0117] In the formula, ΔU n is the Fourier coefficient of the nth harmonic, which is a complex number containing the signal amplitude and the initial phase angle, and Z is the set of harmonic orders;

[0118] The input variable for frequency domain analysis of linear time-varying models is defined as a periodic signal modulated by complex exponential modulation;

[0119]

[0120] Where s is the Laplace operator;

[0121] Obtain the state variables and their derivatives of the wind power flexible direct current grid-connected system;

[0122]

[0123] In the formula, j is an imaginary unit; e st is the complex exponential signal of the wind power flexible direct current grid-connected system, x wv (t) is the function of the state variables of the wind power flexible direct current grid-connected system with respect to time, Δx wv (t) represents x wv (t) increment; = Δx wv The derivative of (t) with respect to time, x n is the state variable under the nth harmonic, Δx n Represents x n The increment of

[0124] Transform the above expression into:

[0125]

[0126] In the formula, A is expanded into a Fourier series at the nth harmonic;

[0127] wv

[0128] The above formula describes the relationship between the Fourier coefficients of the state variable, input variable and output variable. Since it contains convolution operations, it is not easy to analyze and calculate. In order to facilitate calculation, the Toeplitz matrix is ​​introduced;

[0129]

[0130] In the formula, A T The Toeplitz matrix for frequency domain convolution calculation of the wind power flexible direct current grid-connected system, A T The subscripts of the elements in represent the harmonic orders;

[0131] By combining the harmonic state equations and expressing them in the form of a Toeplitz matrix, the harmonic linearized state space model of the wind power flexible direct current grid-connected system can be obtained.

[0132] sΔX=(A T -N)ΔX;

[0133] Where ΔX is a vector containing harmonics of each order; N is a diagonal matrix reflecting frequency information.

[0134] In this embodiment, in step S14, a harmonic linearization state space model of the wind power flexible direct current grid-connected system is established, including:

[0135] sΔX sysact_i-w,c,v =(A Tsysact_i-w,c,v -N)ΔX sysact_i-w,c,v ;

[0136] Where s is the Laplace operator, ΔX sysact_i-w,c,v A represents the vector of harmonics of each order after adding the wide-band oscillation suppression strategy. Tsysact_i-w,c,v is the Toeplitz matrix for frequency domain convolution calculation after adding the wide-band oscillation suppression strategy, and N is the diagonal matrix reflecting the frequency information.

[0137] By establishing a harmonic linearization state space model and using the vectors of harmonics of each order to describe the response characteristics of the system at different frequency orders after the addition of a wide-band oscillation suppression strategy, the dynamic changes of the system at each harmonic frequency can be accurately captured, providing a more comprehensive understanding of the frequency characteristics of the system and providing data support for optimizing harmonic suppression.

[0138] In step S14, a harmonic linearized state space impedance model of the wind power flexible direct current grid-connected system is established, including:

[0139] Based on the harmonic linearization state space model of the wind power flexible DC grid-connected system, the flexible DC harmonic linearization state space impedance Z is extracted when the broadband oscillation suppression strategy is not added. mmc and wind turbine harmonic linearization state space impedance Z pmsg ;

[0140] Based on the harmonic linearization state space model of the wind power flexible DC grid-connected system, the flexible DC harmonic linearization state space impedance Z is extracted when the broadband suppression strategy is added. sysact_mmc and wind turbine harmonic linearization state space impedance Z sysact_pmsg , and the harmonic linearized state space impedance model of the wind power flexible DC grid-connected system is obtained.

[0141] By extracting the harmonic linearized state space impedance of flexible DC and wind turbines respectively in two states, without and with the wide-band oscillation suppression strategy, it is possible to compare the impedance change characteristics of the system under different states. The differentiated extraction method effectively reveals the specific impact of the wide-band suppression strategy on the harmonic characteristics of the system, providing a scientific comparison basis for subsequent optimization.

[0142] As a preference of the above embodiment, according to the above content, in step S20, the phase difference margins of the non-target frequency band and the target frequency band under different installation positions are calculated, and the optimal installation position of the wide-band oscillation suppression strategy that satisfies the phase difference margin constraint is determined, and the steps include:

[0143] S21: Based on the impedance characteristics of the wind power flexible direct current grid-connected system and wind turbines, obtain the impedance amplitude-phase diagram when the wide-band oscillation suppression strategy is not added, and the impedance amplitude-phase diagram when the wide-band oscillation suppression strategy is added, so as to determine the frequency response characteristics of the system in the low-frequency band, medium-frequency band and high-frequency band;

[0144] S22: In the impedance amplitude-phase diagram, identify the amplitude intersection point of the impedance curves of the flexible DC converter and the wind turbine, calculate the phase angle difference when the wide-band oscillation suppression strategy is not added, and subtract the phase angle difference from 180 degrees to obtain the initial phase angle difference margin;

[0145] S23: Based on the initial phase difference margin, under the action of different wide-band oscillation suppression strategies, respectively calculate the phase difference margin changes of the low-frequency band, the medium-frequency band and the high-frequency band, and obtain the phase difference margin after adding the wide-band oscillation suppression strategy;

[0146] S24: Based on the phase difference margin after adding the wide-band oscillation suppression strategy, the phase difference margin changes of different frequency bands are analyzed; when the phase difference margin change of a certain frequency band is positive, the frequency band is defined as a target frequency band, and the remaining frequency bands are non-target frequency bands;

[0147] S25: setting a constraint condition that the wideband oscillation suppression strategy must have a phase difference margin greater than zero in a non-target frequency band, and a constraint condition that a change in the phase difference margin in a target frequency band must not be less than a preset value;

[0148] S26: Determine whether the non-target frequency band phase angle difference margin is greater than zero and whether the target frequency band phase angle difference margin variation satisfies a preset value in the wide-band oscillation suppression strategy at the wind turbine converter, busbar and flexible DC converter positions respectively:

[0149] If the non-target frequency band phase angle difference margin is less than zero, or the target frequency band phase angle difference margin change is less than a preset value, the installation position of the wide-band oscillation suppression strategy is an unselectable position;

[0150] If the non-target frequency band phase angle difference margin is greater than zero, and the target frequency band phase angle difference margin variation is greater than or equal to a preset value, then the installation position is an optional position;

[0151] S27: Select the installation position with the largest change in the target frequency band phase angle difference margin as the optimal installation position for the wide-band oscillation suppression strategy.

[0152] The change of phase difference margin in different frequency bands after adding the wide-band oscillation suppression strategy α sysact_l_i-w,c,v -α wv_l , α sysact_m_i-w,c,v -α wv_m , α sysact_h_i-w,c,v -α wv_hThe frequency band corresponding to the positive time is the target frequency band of the wide-band oscillation suppression strategy, and the remaining frequency bands are non-target frequency bands; the phase difference margin of the non-target frequency band of the wide-band oscillation suppression strategy needs to satisfy the constraint of being greater than 0, and the change in the phase difference margin of the target frequency band needs to satisfy the constraint of being no less than |Δα act_0 |constraints; respectively judge the relationship between the non-target frequency band phase difference margin and 0 of the wind power flexible direct current grid-connected system under the wide-band oscillation suppression strategy installed in the wind turbine converter, busbar, and flexible direct current converter, as well as the relationship between the change in the target frequency band phase difference margin and |Δα act_0 |; if the non-target frequency band phase angle difference margin is less than 0 or the target frequency band phase angle difference margin change is less than |Δα act_0 |, then the installation position of the wide-band oscillation suppression strategy cannot be selected; if the non-target frequency band phase difference margin is greater than 0 and the target frequency band phase difference margin change is greater than or equal to |Δα act_0 |, then the installation position of the wide-band oscillation suppression strategy is selectable, and the installation position of the wide-band oscillation suppression strategy corresponding to the maximum change in the target frequency band phase angle difference margin is selected;

[0153] The change of phase difference margin in different frequency bands after adding the wide-band oscillation suppression strategy α sysact_l_i-w,c,v -α wv_l , α sysact_m_i-w,c,v -α wv_m , α sysact_h_i-w,c,v -α wv_h The frequency band corresponding to the positive time is the target frequency band of the wide-band oscillation suppression strategy, and the remaining frequency bands are non-target frequency bands; the phase difference margin of the non-target frequency band of the wide-band oscillation suppression strategy needs to satisfy the constraint of being greater than 0, and the change in the phase difference margin of the target frequency band needs to satisfy the constraint of being no less than |Δα act_0 |constraints; respectively judge the relationship between the non-target frequency band phase difference margin and 0 of the wind power flexible direct current grid-connected system under the wide-band oscillation suppression strategy installed in the wind turbine converter, busbar, and flexible direct current converter, as well as the relationship between the change in the target frequency band phase difference margin and |Δα act_0 |; if the non-target frequency band phase angle difference margin is less than 0 or the target frequency band phase angle difference margin change is less than |Δα act_0 |, then the installation position of the wide-band oscillation suppression strategy cannot be selected; if the non-target frequency band phase difference margin is greater than 0 and the target frequency band phase difference margin change is greater than or equal to |Δα act_0 |, then the installation position of the wide-band oscillation suppression strategy is selectable, and the installation position of the wide-band oscillation suppression strategy corresponding to the maximum change in the target frequency band phase angle difference margin is selected.

[0154] By calculating the phase difference margin between the non-target frequency band and the target frequency band at different installation positions, the most suitable installation position can be accurately selected to maximize the suppression effect of the wide-band oscillation suppression strategy in the target frequency band. At the same time, it ensures that the stability of the non-target frequency band is not negatively affected, thereby improving the overall suppression effect and stability of the system.

[0155] The constraint condition that the phase difference margin of the non-target frequency band is greater than zero is set to ensure that while improving the stability of the target frequency band, the instability problem of the non-target frequency band is not caused. The constraint condition design effectively prevents the frequency band coupling problem that may be caused by a single suppression strategy, and helps to maintain the relative stability of each frequency band of the system.

[0156] By calculating the phase difference margin changes of low-frequency band, medium-frequency band and high-frequency band in frequency bands, this method can identify the target band and non-target band in a targeted manner. The design of frequency band segmentation calculation can adapt to the oscillation suppression needs within different frequency bands and meet the multi-strategy coordination needs within a wide frequency band, thus enhancing the system's adaptability to multi-band oscillations.

[0157] By calculating the change in the phase difference margin, the best installation position can be quickly screened out, greatly reducing the number of trial and error times during the design and debugging process. The optimization method based on mathematical calculations improves the design efficiency of the suppression strategy, making the implementation of the suppression strategy faster and more effective.

[0158] In this embodiment, in step S30, the effects of various broadband oscillation suppression strategies are analyzed according to different operating conditions, and an applicable multi-strategy coordinated broadband oscillation suppression strategy combination scheme is selected. The steps include:

[0159] S31: Set all working conditions of the wind power flexible direct current grid-connected system to the active power output of the wind farm within the preset range P e ={0.1pu, 0.2pu, 0.3pu, 0.4pu, 0.5pu, 0.6pu, 0.7pu, 0.8pu, 0.9pu, 1.0pu}; pu represents the per-unit value of the output active power;

[0160] S32: for different operating conditions of the active power output of the wind farm within a preset range, respectively determining whether the non-target frequency band phase angle difference margins are all greater than zero after the wide-band oscillation suppression strategy is added;

[0161] If the phase angle difference margin of the non-target frequency band is greater than zero under all operating conditions, multi-strategy coordinated suppression is not required;

[0162] If the phase angle difference margin of the non-target frequency band is less than zero under the operating conditions, multiple strategies are needed to coordinate wide-band oscillation suppression;

[0163] S33: When the jth (j=1, 2, ..., m) wide-band oscillation suppression strategy is added, if the non-target frequency band phase difference margin is negative, k strategy combinations (k≤m) are selected from the m wide-band oscillation suppression strategies, so that the non-target frequency band phase difference margin is increased to a stable value not less than zero after the synergy of multiple strategies; wherein the target frequency band of the k suppression strategies corresponds to the non-target frequency band of the jth suppression strategy;

[0164] S34: Calculate the change in the non-target band phase angle difference margin before and after the k wide-band oscillation suppression strategies work together with the j-th wide-band oscillation suppression strategy. When the change takes the maximum value, the corresponding n combinations of the k wide-band oscillation suppression strategies work together with the j-th wide-band oscillation suppression strategy to form the combination scheme of the selected wide-band oscillation suppression strategy.

[0165] By analyzing the phase difference margin of non-target frequency bands under different operating conditions, it is possible to determine in real time whether multi-strategy coordinated suppression is needed, thereby improving the stability of the system under different operating conditions. Through precise analysis of each operating condition, it avoids the waste of resources when coordination is not required, and effectively improves the operating efficiency of the system.

[0166] By calculating and analyzing the phase difference margin between non-target frequency bands and target frequency bands, the method can clearly identify the impact of different strategies on specific frequency bands, thereby maximizing the effect of each wide-band oscillation suppression strategy. This method of accurately identifying the target frequency band ensures that when suppressing the oscillation of the target frequency band, instability of other frequency bands is not caused, thus avoiding interference between frequency bands.

[0167] When a single strategy cannot meet the stability requirements, this method combines different wide-band oscillation suppression strategies to ensure that the phase difference margin of the non-target frequency band reaches a stable state after synergy. This collaborative selection method improves the suppression effect of the target frequency band while enabling the system to obtain a higher stability margin within the wide-band range.

[0168] This method can flexibly switch and coordinate between different suppression strategies, adapt to changing operating conditions and harmonic frequency changes, enhance the robustness of the suppression strategy, and achieve higher fault tolerance of the system through a combination of multiple strategies, so that the wind power flexible direct-current grid-connected system can operate stably under various complex conditions.

[0169] In step S34, the non-target frequency band phase angle difference margin change ΔPM before and after the k-th wide-band oscillation suppression strategy and the j-th wide-band oscillation suppression strategy work together is calculated. sys_marge_n (n=1,2,k-1) models, including:

[0170]

[0171] In the formula, is the non-target frequency band phase angle difference margin after selecting n combinations of k wide-band oscillation suppression strategies and cooperating with the j-th wide-band oscillation suppression strategy, α wvj is the phase difference margin of the non-target frequency band after the j-th wide-band oscillation suppression strategy is added.

[0172] By calculating the change in the non-target frequency band phase difference margin before and after coordination through a formula, the coordinated suppression effect of multiple wide-band suppression strategies can be intuitively quantified. This quantitative model provides a clear data basis for selecting the optimal strategy combination, so that the effects of different strategy combinations can be directly compared, thereby greatly improving the design efficiency of the suppression strategy.

[0173] The present invention also includes a multi-strategy broadband oscillation suppression device for a wind power flexible direct current grid-connected system, using the above method, such as Figure 3 As shown, including:

[0174] The impedance model building module is used to establish the harmonic state space impedance model of the wind power flexible direct current grid-connected system under different wide-band oscillation suppression strategies, analyze the impedance characteristics of each wide-band oscillation suppression strategy in different frequency bands, and obtain the frequency band response behavior of the system within different frequency bands;

[0175] An installation position calculation module is used to calculate the phase difference margins of non-target frequency bands and target frequency bands under different installation positions based on the harmonic state space impedance model, and determine the optimal installation position of the wide-band oscillation suppression strategy that meets the phase difference margin constraint to ensure that the phase difference margin of the non-target frequency band is not lower than a preset threshold;

[0176] The strategy combination selection module is used to analyze the effects of various wide-band oscillation suppression strategies based on the optimal installation position and different operating conditions, and select an applicable multi-strategy coordinated wide-band oscillation suppression strategy combination scheme to improve the phase difference margin of the wind power flexible direct current grid-connected system under different operating conditions, ensuring that the system obtains appropriate stability margins in both target frequency bands and non-target frequency bands, thereby enhancing the overall stability of the wind power flexible direct current grid-connected system.

[0177] See also Figure 4 A computer device 400 provided in an embodiment of the present application includes: a processor 410 and a memory 420, wherein the memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, the above method is executed.

[0178] The embodiment of the present application further provides a storage medium 430 on which a computer program is stored. When the computer program is run by the processor 410, the above method is executed.

[0179] Among them, 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, disk or optical disk.

[0180] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0181] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0182] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations 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 one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0183] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0184] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic devices), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways if necessary, and then stored in a computer memory.

[0185] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0186] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0187] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system, characterized in that: The method comprises the following steps: Establish the harmonic state space impedance model of the wind power flexible direct current grid-connected system under different wide-band oscillation suppression strategies, analyze the impedance characteristics of each wide-band oscillation suppression strategy in different frequency bands, and obtain the frequency band response behavior of the system in different frequency bands; Based on the harmonic state space impedance model, the phase difference margins of the non-target frequency band and the target frequency band under different installation positions are calculated, and the optimal installation position of the wide-band oscillation suppression strategy that meets the phase difference margin constraint is determined to ensure that the phase difference margin of the non-target frequency band is not lower than a preset threshold; Based on the optimal installation position, the effects of various wide-band oscillation suppression strategies are analyzed for different operating conditions, and an applicable multi-strategy coordinated wide-band oscillation suppression strategy combination scheme is selected to improve the phase difference margin of the wind power flexible direct current grid-connected system under different operating conditions, ensuring that the system obtains appropriate stability margins in both target frequency bands and non-target frequency bands, thereby enhancing the overall stability of the wind power flexible direct current grid-connected system.

2. The multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system according to claim 1 is characterized in that: The harmonic state space impedance model of the wind power flexible direct current grid-connected system under different broadband oscillation suppression strategies is established, and the steps include: Establish a single broadband oscillation suppression strategy and a single broadband state space model of the wind power flexible direct current grid-connected system; Based on the single broadband state-space model, the influence of different broadband oscillation suppression strategies on the dynamic response of the system at different installation positions is analyzed, state-space models of different broadbands and different installation positions are established, and the influence of different installation positions on the dynamic response of the system is analyzed; Based on the state space models of different broadbands and different installation locations, a linearized state space model of the wind power flexible direct current grid-connected system is established to simplify the dynamic characteristics of the system and facilitate subsequent analysis; Based on the linearized state space model, a harmonic linearized state space model of the wind power flexible direct current grid-connected system is established to analyze the impact of each order of harmonics on the system stability; Based on the harmonic linearization state space model, a harmonic linearization state space impedance model of the wind power flexible direct current grid-connected system is established to describe the impedance response of the system to oscillations in different frequency bands, providing a basis for the implementation of subsequent optimization strategies.

3. The multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system according to claim 2 is characterized in that: The single broadband state-space model comprises: In the formula, d represents the differential, x act_i is the state variable of the i-th broadband oscillation suppression strategy, t is time, A act_i is the state matrix of the i-th wideband oscillation suppression strategy, B act_i is the input matrix of the i-th broadband oscillation suppression strategy, u act_i is the input variable of the i-th wide-band oscillation suppression strategy.

4. The multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system according to claim 2 is characterized in that: The establishing of state space models of different installation positions comprises: In the formula, x sysact_i-w,c,v is the state variable of the wind power flexible direct current grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible direct current converter respectively, A sysact_i-w,c,v is the state matrix of the wind power flexible direct current grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible direct current converter respectively, B sysact_i-w,c,v is the input matrix of the wind power flexible DC grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible DC converter respectively, u sysact_i-w,c,v are the input variables of the wind power flexible DC grid-connected system when the i-th wide-band oscillation suppression strategy is installed on the wind turbine converter, busbar and flexible DC converter respectively.

5. The multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system according to claim 2 is characterized in that: The linearized state space model of the wind power flexible direct current grid-connected system is established, including: In the formula, A sysact_i-w,c,v is the state matrix of the wind power flexible DC grid-connected system when the i-th wide-band oscillation suppression strategy is installed in the wind turbine converter, busbar, and flexible DC converter, Δx sysact_i-w,c,v Represents x sysact_i-w,c,v increment.

6. The multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system according to claim 2 is characterized in that: The establishment of a harmonic linearization state space model of a wind power flexible direct current grid-connected system includes: sΔX sysact_i-w,c,v =(A Tsysact_i-w,c,v -N)ΔX sysact_i-w,c,v ; Where s is the Laplace operator, ΔX sysact_i-w,c,v A represents the vector of harmonics of each order after adding the wide-band oscillation suppression strategy. Tsysact_i-w,c,v is the Toeplitz matrix for frequency domain convolution calculation after adding the wide-band oscillation suppression strategy, and N is the diagonal matrix reflecting the frequency information.

7. The multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system according to claim 2 is characterized in that: The harmonic linearized state space impedance model of the wind power flexible direct current grid-connected system is established, including: Based on the harmonic linearization state space model of the wind power flexible DC grid-connected system, the harmonic linearization state space impedance of the flexible DC and the harmonic linearization state space impedance of the wind turbine are extracted when the broadband oscillation suppression strategy is not added. Based on the harmonic linearization state-space model of the wind power flexible DC grid-connected system, the harmonic linearization state-space impedance of the flexible DC and the harmonic linearization state-space impedance of the wind turbine are extracted when the wide-band suppression strategy is added, and the harmonic linearization state-space impedance model of the wind power flexible DC grid-connected system is obtained.

8. The multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system according to claim 1 is characterized in that: Calculating the phase difference margins of the non-target frequency band and the target frequency band under different installation positions, and determining the optimal installation position of the wide-band oscillation suppression strategy that meets the phase difference margin constraint, the steps include: Based on the impedance characteristics of the wind power flexible direct current grid-connected system and wind turbines, the impedance amplitude-phase diagram when the wide-band oscillation suppression strategy is not added, and the impedance amplitude-phase diagram when the wide-band oscillation suppression strategy is added are obtained to determine the frequency response characteristics of the system in the low-frequency band, medium-frequency band, and high-frequency band; In the impedance amplitude-phase diagram, the amplitude intersection point of the impedance curves of the flexible DC converter and the wind turbine is identified, the phase angle difference when the wide-band oscillation suppression strategy is not added is calculated, and the phase angle difference is subtracted from 180 degrees to obtain an initial phase angle difference margin; Based on the initial phase difference margin, under the action of different wide-band oscillation suppression strategies, respectively calculate the phase difference margin changes of the low-frequency band, the medium-frequency band and the high-frequency band to obtain the phase difference margin after adding the wide-band oscillation suppression strategy; Based on the phase difference margin after adding the wide-band oscillation suppression strategy, analyzing the phase difference margin changes of different frequency bands; when the phase difference margin change of a certain frequency band is positive, the frequency band is defined as a target frequency band, and the remaining frequency bands are non-target frequency bands; Set the constraint condition that the phase difference margin of the wide-band oscillation suppression strategy in the non-target frequency band must be greater than zero, and the constraint condition that the change of the phase difference margin in the target frequency band must not be less than the preset value; It is respectively determined whether the non-target frequency band phase angle difference margin is greater than zero and whether the target frequency band phase angle difference margin variation satisfies the preset value under the wide-band oscillation suppression strategy at the wind turbine converter, busbar and flexible DC converter positions: If the non-target frequency band phase angle difference margin is less than zero, or the target frequency band phase angle difference margin variation is less than the preset value, the installation position of the wide-band oscillation suppression strategy is an unselectable position; If the non-target frequency band phase angle difference margin is greater than zero, and the target frequency band phase angle difference margin variation is greater than or equal to the preset value, then the installation position is an optional position; The installation position where the change in the target frequency band phase angle difference margin is the largest is selected as the optimal installation position for the wide-band oscillation suppression strategy.

9. The multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system according to claim 1, characterized in that: Analyze the effects of various broadband oscillation suppression strategies according to different operating conditions, and select an appropriate combination of multi-strategy coordinated broadband oscillation suppression strategies. The steps include: All operating conditions of the wind power flexible direct current grid-connected system are set to the active power output of the wind farm within the preset range; For different operating conditions of the active power output by the wind farm within a preset range, determining whether the non-target frequency band phase angle difference margins are all greater than zero after adding the wide-band oscillation suppression strategy; If the phase angle difference margin of the non-target frequency band is greater than zero under all operating conditions, multi-strategy coordinated suppression is not required; If the phase angle difference margin of the non-target frequency band is less than zero under the operating conditions, multiple strategies are needed to coordinate wide-band oscillation suppression; When the j-th wide-band oscillation suppression strategy is added, if the non-target frequency band phase difference margin is negative, k strategy combinations are selected from the m wide-band oscillation suppression strategies, so that after the synergy of multiple strategies, the non-target frequency band phase difference margin is increased to a stable value not less than zero; The change in the non-target frequency band phase angle difference margin before and after the k wide-band oscillation suppression strategies cooperate with the j-th wide-band oscillation suppression strategy is calculated. When the change takes the maximum value, the corresponding n combinations of the k wide-band oscillation suppression strategies cooperate with the j-th wide-band oscillation suppression strategy to obtain the combination scheme of the selected wide-band oscillation suppression strategy.

10. The multi-strategy broadband oscillation suppression method for a wind power flexible direct current grid-connected system according to claim 9, characterized in that: Calculate the non-target frequency band phase angle difference margin change ΔPM before and after the k-th wide-band oscillation suppression strategy and the j-th wide-band oscillation suppression strategy work together sys_marge_n (n=1,2,k-1) models, including: In the formula, is the non-target frequency band phase angle difference margin after selecting n combinations of k wide-band oscillation suppression strategies and cooperating with the j-th wide-band oscillation suppression strategy, α wvj is the phase difference margin of the non-target frequency band after the j-th wide-band oscillation suppression strategy is added.

11. A multi-strategy broadband oscillation suppression device for a wind power flexible direct current grid-connected system, characterized in that: Use of the method according to any one of claims 1 to 10, comprising: The impedance model building module is used to establish the harmonic state space impedance model of the wind power flexible direct current grid-connected system under different wide-band oscillation suppression strategies, analyze the impedance characteristics of each wide-band oscillation suppression strategy in different frequency bands, and obtain the frequency band response behavior of the system within different frequency bands; An installation position calculation module is used to calculate the phase difference margins of the non-target frequency band and the target frequency band under different installation positions based on the harmonic state space impedance model, and determine the optimal installation position of the wide-band oscillation suppression strategy that meets the phase difference margin constraint to ensure that the non-target frequency band phase difference margin is not lower than a preset threshold; The strategy combination selection module is used to analyze the effects of various wide-band oscillation suppression strategies for different operating conditions based on the optimal installation position, and select an applicable multi-strategy coordinated wide-band oscillation suppression strategy combination scheme to improve the phase difference margin of the wind power flexible direct current grid-connected system under different operating conditions, ensure that the system obtains a suitable stability margin in both the target frequency band and the non-target frequency band, thereby enhancing the overall stability of the wind power flexible direct current grid-connected system.

12. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 10 is implemented.

13. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 10 is implemented.

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