Transient oscillation characteristic analysis method, system, equipment and medium

Abstract

The invention relates to the technical field of electrical engineering, and discloses a transient oscillation characteristic analysis method, system and device and a medium, and the method comprises the steps: obtaining the inertia characteristic of a receiving-end converter station, and building a small-signal control model of a DC power flow controller based on the inertia characteristic of the receiving-end converter station; performing first conversion operation on the small signal control model; solving the transfer function matrix, and obtaining the transient characteristics of the DC power flow controller according to the solving result; the method effectively solves the problem that transient oscillation analysis of the DC power flow controller is inaccurate due to the fact that inertia characteristics of a receiving end converter station are ignored in traditional analysis. Through accurate modeling and analysis, the influence of the parameters of the direct current power flow controller on transient oscillation under different system working conditions and parameters can be comprehensively evaluated, and powerful support is provided for stable operation of a power system.

Description

Technical Field

[0001] This invention relates to the field of electrical engineering technology, and in particular to a method, system, device and medium for analyzing transient oscillation characteristics. Background Technology

[0002] The energy revolution, which systematically replaces fossil fuels, is driving a profound transformation of the power structure, and the large-scale development of zero-carbon electricity such as photovoltaic and wind power has become a global consensus. To adapt to the needs of new power system construction, the distribution network is undergoing structural reshaping. The increasing complexity of load structures and the large-scale integration of distributed energy resources have given rise to multi-energy flow coupling characteristics, posing a challenge to the system due to the combined effects of intermittent power output and peak-valley load fluctuations. Simultaneously, the increasing proportion of power electronic equipment has weakened the grid's inertia support capacity. As a core technology supporting the construction of new power systems, flexible DC transmission, with its adaptive power regulation mechanism, can effectively mitigate the fluctuations in renewable energy generation and enhance the grid's dynamic regulation capabilities in multiple dimensions.

[0003] Flexible DC transmission systems with multi-terminal interconnection architecture provide crucial support for the high-proportion penetration of new energy sources. By constructing a DC grid mode with multi-source coordination, the carrying capacity of new power systems to handle fluctuating power sources can be significantly enhanced. However, in DC grids with multi-node interconnection, the unique power distribution characteristics of the ring network architecture may lead to transmission channel congestion and equipment overstress risks. Deploying a modular multi-port DC power flow controller (DCPFC) in the DC ring network can achieve dynamic adjustment of the power flow in each branch, thereby enhancing the system's adaptive control capability to random power fluctuations and improving the stability margin of the flexible DC grid. By adopting the transient oscillation characteristic analysis method of DCPFC that takes inertia into account, the system's resonant weak points can be accurately identified within the frequency domain analysis framework. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a method, system, device, and medium for analyzing transient oscillation characteristics, which can solve the transient oscillation problem of DC power grids under the high penetration of new energy sources and improve the stability and security of the system.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a method for analyzing transient oscillation characteristics, comprising:

[0008] The inertia characteristics of the receiving-end converter station are obtained, and a small-signal control model of the DC power flow controller is established based on the inertia characteristics of the receiving-end converter station.

[0009] Perform a first transformation operation on the small-signal control model;

[0010] The first transformation operation is used to convert the small-signal control model into a transfer function matrix;

[0011] Solve the transfer function matrix and obtain the transient characteristics of the DC power flow controller based on the solution results;

[0012] The transient characteristics include the influence of DC power flow controller parameters on transient oscillations under different system operating conditions and parameters.

[0013] As a preferred embodiment of the transient oscillation characteristic analysis method of the present invention, the step of obtaining the inertia characteristics of the receiving-end converter station includes:

[0014] Embed virtual inertia control voltage equations with droop characteristics at the receiving-end converter station;

[0015] The inertia and damping characteristics of the load in a photovoltaic-storage-DC-flexible system are simulated by changing the port voltage output of the receiving-end converter station.

[0016] A small-signal control model for the DC power flow controller is established based on the inertia and damping characteristics of the simulated photovoltaic-storage DC-flexible system load.

[0017] This preferred scheme can more accurately reflect the dynamic response characteristics of the actual system. Especially under the high penetration of new energy sources, the transient oscillation problem of DC grid is more complex. By simulating the inertia and damping characteristics of the load of the photovoltaic-storage-DC-flexible system, the transient characteristics of the DC power flow controller under different operating conditions and parameters can be analyzed more effectively, providing a more reliable theoretical basis for system design and optimization.

[0018] As a preferred embodiment of the transient oscillation characteristic analysis method of the present invention, the step of establishing a small-signal control model for the DC power flow controller based on the inertia and damping characteristics of the simulated photovoltaic-storage DC-flexible system load includes:

[0019] A first state variable is introduced, which is a variable that considers inertia and damping characteristics and is introduced into the small-signal control model of the initial DC power flow controller.

[0020] The small-signal control model of the DC power flow controller after introducing the first state variable is denoted as the extended model.

[0021] As a preferred embodiment of the transient oscillation characteristic analysis method of the present invention, the small-signal control model of the DC power flow controller established based on the inertia characteristics of the receiving-end converter station includes:

[0022] Modal space modeling is performed on the extended model to obtain the state space equations;

[0023] The state-space equations are denoted as the small-signal control model of the final DC power flow controller.

[0024] As a preferred embodiment of the transient oscillation characteristic analysis method of the present invention, the first conversion operation includes:

[0025] The small-signal control model of the final DC power flow controller is dynamically segmented.

[0026] The transient reduced-order model in the small-signal control model of the final DC power flow controller after dynamic segmentation is converted into a transfer function matrix.

[0027] As a preferred embodiment of the transient oscillation characteristic analysis method of the present invention, the dynamic segmentation operation includes:

[0028] By determining whether the state variables in the small-signal control model of the final DC power flow controller are completely controlled by the PI loop, the small-signal control model of the final DC power flow controller is divided into two parts: a controllable model and a transient reduced-order model.

[0029] If it is completely controllable, it is classified as a controllable model.

[0030] As a preferred embodiment of the transient oscillation characteristic analysis method of the present invention, the step of solving the transfer function matrix includes: performing singular value decomposition on the transfer function matrix.

[0031] Secondly, the present invention provides a transient oscillation characteristic analysis system, comprising:

[0032] The model building module is used to obtain the inertia characteristics of the receiving-end converter station and to build a small-signal control model of the DC power flow controller based on the inertia characteristics of the receiving-end converter station.

[0033] The operation module is used to perform a first transformation operation on the small signal control model;

[0034] The first transformation operation is used to convert the small-signal control model into a transfer function matrix;

[0035] The solution module is used to solve the transfer function matrix and obtain the transient characteristics of the DC power flow controller based on the solution results.

[0036] The transient characteristics include the influence of DC power flow controller parameters on transient oscillations under different system operating conditions and parameters.

[0037] Thirdly, the present invention provides an electronic device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0038] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described above.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention proposes a transient oscillation characteristic analysis method to obtain the inertia characteristics of the receiving-end converter station, and establishes a small-signal control model of the DC power flow controller based on the inertia characteristics of the receiving-end converter station; performs a first transformation operation on the small-signal control model; solves the transfer function matrix, and obtains the transient characteristics of the DC power flow controller based on the solution results;

[0040] First, by acquiring the inertia characteristics of the receiving-end converter station, this invention can more accurately simulate the actual situation of the power system, improving the accuracy of the analysis. Second, establishing a small-signal control model of the DC power flow controller provides a foundation for subsequent conversion and solution operations, making the analysis process more systematic. Third, performing a first conversion operation on the small-signal control model to convert it into a transfer function matrix simplifies the analysis process of complex systems and improves computational efficiency. Finally, by solving the transfer function matrix, this invention can intuitively obtain the transient characteristics of the DC power flow controller, providing an important basis for the optimal design and fault diagnosis of the power system. This method effectively solves the problem of inaccurate transient oscillation analysis of the DC power flow controller caused by neglecting the inertia characteristics of the receiving-end converter station in traditional analysis. Through precise modeling and analysis, this invention can comprehensively evaluate the impact of DC power flow controller parameters on transient oscillations under different system operating conditions and parameters, providing strong support for the stable operation of the power system. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a flowchart of a transient oscillation characteristic analysis method provided in one embodiment of the present invention.

[0043] Figure 2 This is a block diagram of an inertia control method with drooping characteristics, provided as an embodiment of the present invention for analyzing transient oscillation characteristics.

[0044] Figure 3 This is a schematic diagram of the DCPFC working sub-mode 1, which takes into account the inertia characteristics, as provided in an embodiment of the present invention for analyzing transient oscillation characteristics.

[0045] Figure 4 This is a schematic diagram of the DCPFC working sub-mode 2, which takes into account the inertia characteristics, as provided in an embodiment of the present invention for analyzing transient oscillation characteristics.

[0046] Figure 5 This is a schematic diagram of the maximum singular values ​​of the transfer function at each frequency point in a transient oscillation characteristic analysis method provided in an embodiment of the present invention.

[0047] Figure 6 This diagram illustrates the maximum singular values ​​of the transfer function at various frequency points under different line resistances, as provided in an embodiment of the present invention for a transient oscillation characteristic analysis method.

[0048] Figure 7 This invention provides a transient oscillation characteristic analysis method under different line current reference values, which represents the maximum singular value of the transfer function at each frequency point.

[0049] Figure 8 A schematic diagram of a three-terminal medium-voltage DC transmission system for a transient oscillation characteristic analysis method provided in an embodiment of the present invention.

[0050] Figure 9 A transient oscillation characteristic analysis method provided in one embodiment of the present invention provides a common inductor L current i under different line resistances. L Transient waveform diagram.

[0051] Figure 10 A transient oscillation characteristic analysis method provided in one embodiment of the present invention provides a method for analyzing the voltage u of capacitor C2 under different line resistances. C2 Transient waveform diagram.

[0052] Figure 11 A transient oscillation characteristic analysis method provided in one embodiment of the present invention provides a common inductor current i under different line current reference values. L Transient waveform diagram.

[0053] Figure 12 The transient oscillation characteristic analysis method provided in one embodiment of the present invention provides a method for analyzing the voltage u of capacitor C2 under different line current reference values. C2 Transient waveform diagram.

[0054] Figure 13 This is an internal structural diagram of an electronic device for a transient oscillation characteristic analysis method provided in one embodiment of the present invention. Detailed Implementation

[0055] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail 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 should fall within the protection scope of the present invention.

[0056] Example 1, referring to Figures 1-7 This is the first embodiment of the present invention, which provides a method for analyzing transient oscillation characteristics, including:

[0057] In existing related technologies, there are some problems. For example, in power systems with a high proportion of new energy penetration, the transient oscillation problem of DC grids is becoming increasingly prominent. Traditional analysis methods often ignore the inertia characteristics of receiving-end converter stations, resulting in inaccurate analysis results and failing to provide a reliable basis for the optimization design and fault diagnosis of power systems.

[0058] This invention provides a method that can effectively solve the problems mentioned above. The following will describe in detail how to implement this transient oscillation characteristic analysis method with reference to several embodiments.

[0059] Figure 1 A flowchart of a transient oscillation characteristic analysis method is shown, including:

[0060] S101, Obtain the inertia characteristics of the receiving-end converter station, and establish a small-signal control model for the DC power flow controller based on the inertia characteristics of the receiving-end converter station.

[0061] It should be noted that, in the construction of mathematical models for DCPFCs considering inertia characteristics, most existing studies only focus on small-signal modeling of the differential terms of the DCPFC circuit and control loop, and further conduct transient steady-state analysis based on the small-signal model. There is currently no research on DCPFCs considering inertia characteristics based on transfer functions. Regarding transient oscillation analysis of DCPFCs considering inertia characteristics, there is currently no literature on dynamic segmentation methods based on modal space modeling or singular value analysis to study the transient characteristics of DCPFCs.

[0062] It should be noted that in order to realize the transient oscillation characteristic analysis of the DC power flow controller taking into account the inertia characteristics, it is necessary to ensure that the DC power flow controller has inertia characteristics, and the inertia characteristics need to be expressible or calculable. Therefore, this invention needs to obtain the inertia characteristics of the receiving-end converter station and establish a small-signal control model of the DC power flow controller based on the inertia characteristics of the receiving-end converter station.

[0063] In this embodiment of the invention, obtaining the inertia characteristics of the receiving-end converter station includes:

[0064] Embed virtual inertia control voltage equations with droop characteristics at the receiving-end converter station;

[0065] The inertia and damping characteristics of the load in a photovoltaic-storage-DC-flexible system are simulated by changing the port voltage output of the receiving-end converter station.

[0066] A small-signal control model for a DC power flow controller is established based on the inertia and damping characteristics of a simulated photovoltaic-storage DC-flexible system load.

[0067] It should be noted that the above operations cannot guarantee that the inertia characteristic can be expressed, so it is necessary to introduce a variable that can necessarily be expressed as the representation of the inertia characteristic.

[0068] In this embodiment of the invention, the small-signal control model for the DC power flow controller, established based on the inertia and damping characteristics of the simulated photovoltaic-storage DC-flexible system load, includes:

[0069] A first state variable is introduced, which is a variable that considers inertia and damping characteristics and is introduced into the small-signal control model of the initial DC power flow controller.

[0070] The small-signal control model of the DC power flow controller after introducing the first state variable is denoted as the extended model.

[0071] In this embodiment of the invention, the small-signal control model for the DC power flow controller, based on the inertia characteristics of the receiving-end converter station, includes:

[0072] Modal space modeling is performed on the extended model to obtain the state space equations;

[0073] The state-space equations are denoted as the small-signal control model of the final DC power flow controller.

[0074] In some specific implementations, the receiving-end VSC (Voltage Source Converter) modifies the voltage output at the receiving-end VSC port by embedding a virtual inertia control voltage equation with droop characteristics to simulate the inertia and damping characteristics of the load in a photovoltaic-storage DC-flexible system.

[0075] The block diagram of inertia control with drooping characteristics is as follows: Figure 2 As shown. The voltage equation (per unit value) for virtual inertia control can be expanded as follows:

[0076]

[0077] in, u represents the per-unit value of variable x. 33This represents the voltage drop between the actual and ideal voltage at the receiving-end converter station port under inertia characteristics. R3 represents the droop coefficient, J represents the inertia coefficient, D represents the damping coefficient, s is the Laplace coefficient, D indicates that the variable signal is a small signal, and P3 represents the actual power absorbed by converter station VSC3. The per-unit equation is transformed into a nominal equation as follows:

[0078]

[0079] Where K represents the per-unit value to nominal value conversion coefficient, u 3ref R represents the reference value for voltage control at the VSC3 port of the converter station. load This represents the local load of converter station VSC3. L This represents the current flowing through the common inductor L of the DCPFC. For ease of modal space modeling, P3 is linearized as follows:

[0080]

[0081] In some specific implementations, the modal space modeling method is applied. Based on the original small-signal model of the DC power flow controller without inertia characteristics, a state variable u3 needs to be added, and a differential equation is added as shown below. The DC power flow controller model that takes into account the virtual inertia voltage control of the receiving end VSC is an eleventh-order small-signal model.

[0082]

[0083] In some specific implementations, the differential equations related to u3 are as follows:

[0084]

[0085] Among them, L 13 L 23 These represent the inductors of line 13 and line 23 of the DCPFC circuit, respectively. 13 i 23 These represent DCPFC lines respectively. 13 ,line 23 Current. u1 and u2 are the voltages at the VSC1 and VSC2 ports of the converter station, respectively. R 13 R 23 These represent the resistances of line 13 and line 23 of the DCPFC circuit, respectively. C1 u C2 These represent the voltages across capacitors C1 and C2, respectively.

[0086] In some specific implementations, within a complete power flow control cycle, the DCPFC, taking inertia characteristics into account, includes two operating sub-modes, such as... Figure 3 and Figure 4 As shown. Based on the operating principle of each sub-mode, the state-space equations can be written as equations (7) and (8) using the modal space modeling method:

[0087]

[0088] Where D represents a small-signal perturbation of the variable. and

[0089] These represent the differentials of the current in line 13, the voltage across capacitor C1, the differential term of the PI current loop, the differential of the common inductor current, the differential of the current in line 12, the differential of the current in line 23, the differential of the voltage across capacitor C1, the differential of the voltage across capacitor C2, the differential of the voltage at port VSC1 of the voltage source converter, and the differential of the voltage at port VSC2 of the voltage source converter. d is the dynamic duty cycle of switch Q1. A represents the DC power flow controller system matrix considering inertia characteristics, B represents the system input matrix, C represents the system output matrix, and X represents the system state variables. Let represent the derivative of the system state variable, u represent the system input variable, and Y represent the system output variable.

[0090] It should be noted that obtaining the inertia characteristics of the receiving-end converter station and establishing a small-signal control model of the DC power flow controller based on these characteristics can accurately obtain the transient oscillation characteristics of the DC power flow controller, providing a reliable foundation for subsequent transient oscillation characteristic analysis. By performing modal space modeling and singular value analysis on the small-signal control model of the DC power flow controller, the oscillation modes of the DC power flow controller and their corresponding eigenvalues ​​can be obtained, thereby determining the stability of the system and providing a reliable basis for the optimal design and fault diagnosis of the power system.

[0091] S102, Perform the first transformation operation on the small-signal control model;

[0092] In some specific implementations, the first transformation operation is to dynamically segment the small-signal control model of the final DC power flow controller and convert the transient reduced-order model in the dynamically segmented final small-signal control model of the DC power flow controller into a transfer function matrix.

[0093] It should be noted that this process includes determining whether the state variables in the final small-signal control model of the DC power flow controller are completely controlled by the PI loop, thus dividing the final small-signal control model of the DC power flow controller into two parts: a controllable model and a transient reduced-order model. If the state variables are completely controllable, they are classified into the controllable model. This transformation simplifies the analysis process of complex systems, improves computational efficiency, and allows for a direct understanding of the transient characteristics of the DC power flow controller, providing important basis for the optimal design and fault diagnosis of power systems.

[0094] In some specific implementations, the first transformation operation can employ frequency domain analysis tools such as Fourier transform to convert the time-domain small-signal model to the frequency domain for analysis. This method helps to identify the system's frequency response characteristics and its stability.

[0095] In some specific implementations, the first transformation operation can also be performed using linear algebra, directly starting from the state-space equations and obtaining the system's transfer function by solving the state transition matrix. This method does not involve model partitioning but performs calculations directly based on the original state-space model.

[0096] In some specific implementations, the first conversion operation can also be simulated using MATLAB / Simulink or other simulation software to simulate the small-signal model. By inputting different types of excitation signals (such as step, pulse or sine wave), the output response of the system can be observed, thereby indirectly deriving the transfer function or frequency response characteristics of the system.

[0097] However, in this embodiment of the invention, although frequency domain analysis tools such as Fourier transform can provide the frequency response characteristics of the system, they generally assume that the system is linear and time-invariant. However, in the context of high penetration of new energy sources, many dynamic behaviors in power systems are nonlinear and vary with operating conditions. Therefore, simple frequency domain analysis may not accurately capture these complex dynamic characteristics. While the direct conversion method of state-space representation can directly calculate the transfer function from the state-space equations, direct solution may encounter problems of numerical stability and computational efficiency for highly complex and large-scale systems. Furthermore, it does not consider the accurate modeling of inertia characteristics specific to this invention, which is crucial when evaluating the impact of the DC power flow controller (DCPFC) on transient oscillations. Although tools such as MATLAB / Simulink can provide an intuitive understanding of the system response through simulation, they often rely on numerous simulation experiments to explore different operating conditions and parameter settings. This approach is not only time-consuming but also makes it difficult to systematically identify all potential transient oscillation modes and their influencing factors.

[0098] Therefore, the present invention does not use the above-described method for the first conversion operation.

[0099] In this embodiment of the invention, the first transformation operation is used to convert the small-signal control model into a transfer function matrix;

[0100] In this embodiment of the invention, the first conversion operation includes:

[0101] The small-signal control model of the final DC power flow controller is dynamically segmented.

[0102] The transient reduced-order model in the small-signal control model of the final DC power flow controller after dynamic segmentation is converted into a transfer function matrix.

[0103] In this embodiment of the invention, the dynamic segmentation operation includes:

[0104] By determining whether the state variables in the small-signal control model of the final DC power flow controller are completely controlled by the PI loop, the small-signal control model of the final DC power flow controller is divided into two parts: a controllable model and a transient reduced-order model.

[0105] If it is completely controllable, it is classified as a controllable model.

[0106] In this embodiment of the invention, the small-signal model of the DC power flow controller, which takes inertia characteristics into account, is dynamically segmented based on whether it is completely controlled by the PI loop, and divided into two parts: a controllable model and a transient reduced-order model. Since the state variable i 13 u C1 If x1 and x2 are completely controlled by the PI loop, then these four state variables can be classified into the controllable model, while the other state variables are classified into the transient reduced-order model. The state variable vectors of the controllable model and the transient reduced-order model can then be represented as shown in equations (9) and (10), respectively:

[0107] ΔX1=[Δi 13 Δu C1 Δξ1 Δξ2] T (9)

[0108] ΔX2=[Δi L Δi 12 Δi 23 Δu C2 Δu1 Δu2 Δu 33 ] T (10)

[0109] Among them, D X1 D represents the state variable vector of a controllable model. X2 Let represent the state variable vector of the transient reduced-order model. The state-space equations of the controllable model and the transient reduced-order model can be expressed as shown in equations (11) and (12), respectively:

[0110]

[0111] Where A1 represents the system matrix of the controllable model, B1 represents the input matrix of the controllable model, and u1 represents the input variable vector of the controllable model. A2 represents the system matrix of the transient reduced-order model, B2 represents the input matrix of the transient reduced-order model, and u2 represents the input variable vector of the transient reduced-order model.

[0112] Since in the transient order reduction model, the three main input variables are Δd, Δi 13 and Δu C1 These three variables can be uniformly categorized into the input variable vector Δu of the transient reduced-order model. 22 As shown below

[0113] Δu 22 =[Δd Δi 13 Δu C1 ] T (13)

[0114] Therefore, the small-signal model of the transient reduced-order model can be expressed as shown in equation (14):

[0115]

[0116] Among them, B 22 Δu 22 It can be broken down as shown in equation (15):

[0117]

[0118] Let any state variable be the output variable of the transient reduced-order model, then the output variable is defined as shown in equation (16):

[0119] ΔY 22_i =C 22_i ΔX2,(i=0,1,2...,7) (16)

[0120] Where ΔY 22_i C represents the output variable of the transient reduced-order model. 22_i Let represent the output matrix of the transient reduced-order model, and be a row vector where the i-th element is 1 and the rest are 0. Therefore, the following seven expressions for the transfer function and input / output variables can be listed as shown in equations (17) to (23):

[0121] Δi L =G 11 Δd+G 12 Δi 13 +G 13 Δu C1 (17)

[0122] Δi 12 =G 21 Δd+G 22 Δi 13 +G 23 Δu C1 (18)

[0123] Δi 23 =G 31 Δd+G 32 Δi 13 +G 33 Δu C1 (19)

[0124] Δu C2 =G 41 Δd+G 42 Δi 13 +G 43 Δu C1 (20)

[0125] Δu1=G 51 Δd+G 52 Δi 13 +G 53 Δu C1 (twenty one)

[0126] Δu2=G 61 Δd+G 62 Δi 13 +G 63 Δu C1 (twenty two)

[0127] Δu 33 =G 71 Δd+G 72 Δi 13 +G 73 Δu C1 (twenty three)

[0128] Among them, G i1 (i = 0, 1, 2, ..., 7) is the input d and the output Y. 22 The transfer function, Gi2 (i = 0, 1, 2, ..., 7), is given by input i13 and output Y. 22 The transfer function, G i3 (i = 0, 1, 2, ..., 7) represents the input u C1 The output is Y 22 The transfer function.

[0129] Equations (17) to (23) can be expressed in matrix form as shown in equation (24):

[0130]

[0131] It should be noted that performing the first transformation operation on the small-signal control model can improve the system's analysis efficiency, simplifying the originally complex transfer function relationships and more intuitively showing the relationship between each input and the output Y. 22 The first transformation operation allows this invention to integrate multiple transfer functions into a single matrix, facilitating subsequent calculations and processing. This transformation not only improves the accuracy of calculations but also significantly shortens analysis time, making the study of transient oscillation characteristics more efficient and convenient.

[0132] S103, solve for the transfer function matrix, and obtain the transient characteristics of the DC power flow controller based on the solution results;

[0133] In one specific implementation, the transfer function matrix can be solved by decomposing it into a sum of multiple simple fractions, each representing an independent dynamic characteristic or mode of the system. This approach helps to more clearly analyze the impact of each mode on the overall system behavior.

[0134] In one specific implementation, the transfer function matrix can also be solved indirectly by designing a state feedback controller or observer, directly based on the original state-space model. This method can be used not only to solve transfer functions but also directly for the design of control systems.

[0135] In one specific implementation, for some complex systems that are difficult to solve analytically, numerical integration techniques (such as the Runge-Kutta method) can be used to approximate the response of the transfer function matrix. This is particularly useful when dealing with nonlinear or time-varying systems.

[0136] In this embodiment of the invention, transient characteristics include the influence of DC power flow controller parameters on transient oscillations under different system operating conditions and parameters.

[0137] In this embodiment of the invention, solving the transfer function matrix includes performing singular value decomposition on the transfer function matrix.

[0138] Specifically, the transfer function matrix G has 3 input signals and 7 output signals. Discretizing and sampling G(jw) yields G(jw) k (k = 1, 2, ..., N), where N represents the number of discretized sampling points. At a given frequency w... k The point can be decomposed by SVD as shown in equation (25):

[0139] G(jω k )=U k ∑ k V k T (25)

[0140] Among them, G(jw k ) is a given frequency w k The transfer function matrix at point U k and V k Let Σk represent the input and output singular vector matrices, respectively, where Σk is the matrix containing the singular value σ. i (ω k The diagonal matrix of ). For an input vector v i The system at frequency w k The output response can be calculated as shown in equation (26):

[0141] G(jω k )v i =σ i (ω k )u i (26)

[0142] Where, row vector u i With column vector v i Let s be the system's output and input vectors. i These are the system's singular values. Find σ in the singular value spectrum. max The peak frequency w of (ω) p This frequency corresponds to the dominant oscillation frequency of the transient response. The peak value of the singularity is σ. max (ω) represents the maximum amplitude of transient oscillations, reflecting the system's gain strength at that frequency. Singular value decomposition is performed on the transfer function matrix, and frequency sweeping yields the maximum singular values ​​at each frequency point, thus characterizing the peak response of the autonomous system's state variables that can be excited by the input variables of the single-loop inter-line DC power flow controller system. The frequency sweep results are as follows: Figure 5 As shown.

[0143] The line parameters and control commands of a DCPFC with inertia characteristics have a significant impact on the transient oscillation characteristics of the system. Increasing the line resistance affects the change in the system's maximum singular value (see [reference needed]). Figure 6 The change in the system's maximum singular value after reducing the line current reference command is as follows: Figure 7 .Depend on Figure 6 and Figure 7 It is evident that the greater the line resistance, the more effectively the DCPFC transient oscillation is suppressed. Conversely, the smaller the line current reference command, the more effectively the DCPFC transient oscillation is suppressed.

[0144] In summary, this invention proposes a transient oscillation characteristic analysis method to obtain the inertia characteristics of the receiving-end converter station and establish a small-signal control model of the DC power flow controller based on the inertia characteristics of the receiving-end converter station; perform a first transformation operation on the small-signal control model; solve the transfer function matrix, and obtain the transient characteristics of the DC power flow controller based on the solution results;

[0145] First, by acquiring the inertia characteristics of the receiving-end converter station, this invention can more accurately simulate the actual situation of the power system, improving the accuracy of the analysis. Second, establishing a small-signal control model of the DC power flow controller provides a foundation for subsequent conversion and solution operations, making the analysis process more systematic. Third, performing a first conversion operation on the small-signal control model to convert it into a transfer function matrix simplifies the analysis process of complex systems and improves computational efficiency. Finally, by solving the transfer function matrix, this invention can intuitively obtain the transient characteristics of the DC power flow controller, providing an important basis for the optimal design and fault diagnosis of the power system. This method effectively solves the problem of inaccurate transient oscillation analysis of the DC power flow controller caused by neglecting the inertia characteristics of the receiving-end converter station in traditional analysis. Through precise modeling and analysis, this invention can comprehensively evaluate the impact of DC power flow controller parameters on transient oscillations under different system operating conditions and parameters, providing strong support for the stable operation of the power system.

[0146] Example 2, refer to Figures 8-12 In a preferred embodiment, in such a way Figure 8 The transient oscillation analysis method of DCPFC considering inertia characteristics is verified in the three-terminal medium-voltage DC transmission system shown. The DCPFC is placed in lines 13 and 23 of the three-terminal medium-voltage DC transmission system. By changing the line resistance and line current reference commands, the effectiveness of the DCPFC transient oscillation method considering inertia characteristics in characterizing the actual oscillation situation is verified. The initial parameters of the system are shown in Table 1.

[0147] Table 1: Parameters of Three-Terminal Medium-Voltage DC Transmission System Considering Inertia Characteristics

[0148]

[0149] Table 2: Experimental parameters for increasing line resistance

[0150]

[0151] Table 3: Experimental Parameters for Increasing Line Current (Reference Instructions)

[0152]

[0153] Set the line current reference command to 3.5A, and gradually increase the total line resistance. The line resistance parameters are shown in Table 2. After 1 second, connect the DCPFC to the medium-voltage DC transmission system. Figure 9 and Figure 10 It can be seen that the transient oscillations of the main state variables iL and uC2 in the transient reduced-order model decrease as the line resistance increases.

[0154] The total line resistance R is set to 3.0W, and the line current reference command is gradually increased. The line current reference command is shown in Table 3. After 1 second, the DCPFC is connected to the medium-voltage DC transmission system. Figure 11 and Figure 12 It can be seen that the larger the reference value of the line current, the greater the transient oscillation of the main state variables iL and uC2 in the transient reduced-order model.

[0155] In summary, the DCPFC transient oscillation method, which takes into account inertia characteristics, can effectively characterize actual oscillation conditions.

[0156] Example 3, referring to Figure 13 This embodiment also provides a transient oscillation characteristic analysis system, including:

[0157] The model building module is used to obtain the inertia characteristics of the receiving-end converter station and to build a small-signal control model of the DC power flow controller based on the inertia characteristics of the receiving-end converter station.

[0158] The operation module is used to perform the first transformation operation on the small-signal control model;

[0159] The first transformation operation is used to convert the small-signal control model into a transfer function matrix;

[0160] The solver module is used to solve the transfer function matrix and obtain the transient characteristics of the DC power flow controller based on the solution results.

[0161] Transient characteristics include the influence of DC power flow controller parameters on transient oscillations under different system operating conditions and parameters.

[0162] The above-mentioned unit modules can be embedded in the processor of the electronic device in hardware form or independent of it, or they can be stored in the memory of the electronic device in software form, so that the processor can call and execute the corresponding operations of the above modules.

[0163] This embodiment also provides an electronic device, which can be a terminal, and its internal structure diagram can be as follows: Figure 13As shown, the electronic device includes a processor, memory, communication interface, display screen, and input device connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage medium. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a transient oscillation characteristic analysis method. The display screen can be a liquid crystal display (LCD) or an e-ink display. The input device can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the device's casing, or an external keyboard, touchpad, or mouse.

[0164] This embodiment also provides a computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, it performs the following steps:

[0165] Obtain the inertia characteristics of the receiving-end converter station, and establish a small-signal control model for the DC power flow controller based on the inertia characteristics of the receiving-end converter station.

[0166] Perform the first transformation operation on the small-signal control model;

[0167] The first transformation operation is used to convert the small-signal control model into a transfer function matrix;

[0168] Solve for the transfer function matrix and obtain the transient characteristics of the DC power flow controller based on the solution results;

[0169] Transient characteristics include the influence of DC power flow controller parameters on transient oscillations under different system operating conditions and parameters.

[0170] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0171] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The embodiments of the present invention can be implemented using various computer languages.

[0172] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0173] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0174] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0175] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0176] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for analyzing transient oscillation characteristics, characterized in that, include: The inertia characteristics of the receiving-end converter station are obtained, and a small-signal control model of the DC power flow controller is established based on the inertia characteristics of the receiving-end converter station. Perform a first transformation operation on the small-signal control model; The first transformation operation is used to convert the small-signal control model into a transfer function matrix; Solve the transfer function matrix and obtain the transient characteristics of the DC power flow controller based on the solution results; The transient characteristics include the influence of DC power flow controller parameters on transient oscillations under different system operating conditions and parameters.

2. The transient oscillation characteristic analysis method as described in claim 1, characterized in that, The acquisition of the inertia characteristics of the receiving-end converter station includes: Embed virtual inertia control voltage equations with droop characteristics at the receiving-end converter station; The inertia and damping characteristics of the load in a photovoltaic-storage-DC-flexible system are simulated by changing the port voltage output of the receiving-end converter station. A small-signal control model for the DC power flow controller is established based on the inertia and damping characteristics of the simulated photovoltaic-storage DC-flexible system load.

3. The transient oscillation characteristic analysis method as described in claim 2, characterized in that, The small-signal control model for the DC power flow controller, established based on the inertia and damping characteristics of the simulated photovoltaic-storage DC-flexible system load, includes: A first state variable is introduced, which is a variable that considers inertia and damping characteristics and is introduced into the small-signal control model of the initial DC power flow controller. The small-signal control model of the DC power flow controller after introducing the first state variable is denoted as the extended model.

4. The transient oscillation characteristic analysis method as described in claim 3, characterized in that, The small-signal control model for the DC power flow controller based on the inertia characteristics of the receiving-end converter station includes: Modal space modeling is performed on the extended model to obtain the state space equations; The state-space equations are denoted as the small-signal control model of the final DC power flow controller.

5. The transient oscillation characteristic analysis method as described in claim 4, characterized in that, The first conversion operation includes: The small-signal control model of the final DC power flow controller is dynamically segmented. The transient reduced-order model in the small-signal control model of the final DC power flow controller after dynamic segmentation is converted into a transfer function matrix.

6. The transient oscillation characteristic analysis method as described in claim 5, characterized in that, The dynamic segmentation operation includes: By determining whether the state variables in the small-signal control model of the final DC power flow controller are completely controlled by the PI loop, the small-signal control model of the final DC power flow controller is divided into two parts: a controllable model and a transient reduced-order model. If it is completely controllable, it is classified as a controllable model.

7. The transient oscillation characteristic analysis method as described in claim 6, characterized in that, Solving the transfer function matrix includes performing singular value decomposition on the transfer function matrix.

8. A transient oscillation characteristic analysis system, using the method described in any one of claims 1 to 7, characterized in that, include: The model building module is used to obtain the inertia characteristics of the receiving-end converter station and to build a small-signal control model of the DC power flow controller based on the inertia characteristics of the receiving-end converter station. The operation module is used to perform a first transformation operation on the small signal control model; The first transformation operation is used to convert the small-signal control model into a transfer function matrix; The solution module is used to solve the transfer function matrix and obtain the transient characteristics of the DC power flow controller based on the solution results. The transient characteristics include the influence of DC power flow controller parameters on transient oscillations under different system operating conditions and parameters.

9. An electronic 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 transient oscillation characteristic analysis method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the transient oscillation characteristic analysis method according to any one of claims 1 to 7.

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