Frequency response analysis method for converter type power supply hybrid system, terminal equipment and storage medium

Abstract

The invention discloses a converter type power supply hybrid system frequency response analysis method, a terminal device and a storage medium, and the method comprises the steps: calculating a node susceptance matrix of a power system based on the grid topology and basic electrical parameters of the power system, and building a network electromagnetic power-node phase angle equation of the power system; based on a network electromagnetic power-node phase angle equation of the power system, calculating an unbalanced power distribution matrix, an inter-generator oscillation matrix and the like of each node of the power system; constructing a frequency response model of power electronic interface resources including a network-following converter and a network-constructing converter, a traditional synchronous machine, a load and other power supplies, wherein the frequency response model is used for participating in the frequency response process of the system; and establishing a multi-machine multi-node frequency response model of the converter type power supply hybrid system, and solving a frequency dynamic response curve of each node in the system. By adopting the method, the time-space distribution characteristics of the frequency of the converter type power supply hybrid system can be accurately reflected.

Description

Technical Field

[0001] The present invention relates to the technical field of power system frequency stability analysis and control, and particularly to a method for analyzing the frequency response of a converter-based power hybrid system, a terminal device, and a storage medium. Background Art

[0002] With the large-scale grid connection of clean and low-carbon energy sources such as wind power and photovoltaic power, and UHVDC, the penetration rate of renewable energy power generation has been continuously increasing. The power system mainly composed of synchronous machines is gradually evolving into a power system mainly based on new energy, showing an increasingly obvious low-inertia trend. After an active power disturbance, the frequency response ability of the system is weakened; the continuous expansion of the system scale and the increasing complexity also lead to the uneven spatial distribution of frequency regulation resources. After being disturbed, the frequency response shows a transient process, showing increasingly significant spatio-temporal distribution characteristics, and the frequency stability faces severe challenges.

[0003] In addition, due to different regions facing different frequency stability situations, key indicators such as the maximum frequency change rate and the maximum frequency deviation in different regions after being disturbed may show quite large differences. At this time, if the spatio-temporal distribution characteristics of the frequency are still ignored, and only the COI results obtained by the traditional frequency response models (SFR, ASF) based on the inertial center frequency and their improved models are used for frequency stability analysis and control, the following two problems may occur: 1) Using the inertial center frequency as the analysis basis may cause the frequency to exceed the limit or even be misjudged at some unknown positions. 2) Adopting a unified frequency response as the control basis may cause some generators to be tuned too low or even misoperate. Both of these situations may bring inestimable safety risks to the system. Therefore, it is crucial to formulate specific control strategies according to the respective frequency stabilities of different regions, and the basis is to model in detail the distributed frequency response model that retains the spatio-temporal distribution characteristics. Studying the spatio-temporal distribution characteristics of the frequency in a high-proportion new energy power system is of great significance for improving the system frequency stability, reasonably planning the grid connection of new energy units, and adopting frequency regulation strategies. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for analyzing the frequency response of a converter-based power hybrid system, a terminal device, and a storage medium, aiming at the deficiencies of the prior art, and accurately predicting the frequency dynamics of each node in the power system.

[0005] To solve the above technical problem, the technical solution adopted by the present invention is: a method for analyzing the frequency response of a converter-based power hybrid system, including the following steps:

[0006] S1. For the i-th generator node, obtain the general node power response by using the DC modulation response of the grid-connected new energy unit and the energy storage power response;

[0007] Superimpose the general node power response and the disturbance response between generator nodes to obtain the electromagnetic power change ΔP corresponding to the i-th generator node during the frequency regulation process g,i ;

[0008] S2. Subtract the primary frequency regulation power increment ΔP of the i-th generator node m,i from the electromagnetic power change ΔP corresponding to the i-th generator node during the frequency regulation process g,i , and divide the difference by the inertia / damping response of the i-th power source to obtain the frequency change Δf of the i-th generator node g,i ;

[0009] S3. Use the frequency change Δf of the i-th generator node g,i to update the disturbance response between generator nodes, the primary frequency regulation power increment of the i-th generator node, and the electromagnetic power change corresponding to the i-th generator node during the frequency regulation process, and return to step S2;

[0010] S4. When the frequency change of the i-th generator node no longer changes, end.

[0011] The present invention not only retains the partial influence of the network, but also considers the frequency response characteristics of frequency regulation resources such as converter-type interface power sources, synchronous power sources, and loads, can accurately predict the frequency dynamic information at the node level, and better analyze the system operation characteristics.

[0012] In step S1, the general node power response is expressed as:

[0013]

[0014] where k represents the total number of nodes participating in the general node power response, and B d,ik represents the element in the i-th row and k-th column of B d , B gl , B ll are submatrices of the node susceptance matrix B, and ΔP l,k represents the response power at the k-th general node. In step S1, the acquisition process of the disturbance response ΔP osc,i between generator nodes includes:

[0015] Multiply by 1 / s to obtain the first result; N is the number of generator nodes; B s,ij is the element in the i-th row and j-th column of B s , B gg , B gl , B lg , B llis a sub-matrix of the nodal susceptance matrix B, Δf g,j has an initial value of 0;

[0016] Multiply the frequency change of the i-th generator node by 1 / s, and multiply the product by B s,ii to obtain a second result; B s,ii represents the element in the i-th row and i-th column of the oscillation matrix B between generators s ;

[0017] The third result or the fourth result is the incremental primary frequency regulation power of the updated i-th generator node; if the power source at the i-th generator node is a synchronous unit, the third result is the incremental primary frequency regulation power of the updated i-th generator node; if the power source at the i-th generator node is a network-forming converter, the fourth result is the incremental primary frequency regulation power of the updated i-th generator node;

[0018] where K G,i is the gain coefficient of the i-th synchronous unit, G i (s) is the transfer function corresponding to the prime mover-governor, K GFM，i is the gain coefficient of the i-th network-forming converter, T GFM，i is the time constant of the i-th network-forming converter, and s is the Laplace operator.

[0019] The calculation process of the general node power response and the disturbance response between generator nodes in the present invention considers the power transfer and change at the node level, and has higher calculation accuracy.

[0020] In step S2, the inertia / damping response is expressed as: is the column vector of the damping coefficients of each generator node considering the load frequency response coefficient correction, D is the square matrix of the diagonal elements composed of the damping coefficients D i of each generator node, H i represents the inertia constant of the i-th power source, λ is the frequency divider matrix calculated from the sub-block of the nodal susceptance matrix B, B gl 、B lg 、B ll are sub-matrices of the nodal susceptance matrix B, D l is the column vector composed of the load frequency response coefficients.

[0021] The present invention considers the inertia and damping responses of network-forming converters and the frequency modulation effect of loads, is more in line with the actual power system situation, and contains more comprehensive information and higher accuracy than traditional models.

[0022] In step S3, the frequency change Δf of the i-th generator node is used g,i The specific implementation process of updating the primary frequency regulation power increment of the i-th generator node includes:

[0023] Multiply the frequency change of the i-th generator node by K G,i G i (s) to obtain a third result;

[0024] Multiply the frequency change of the i-th generator node by K GFM，i / (1 + T GFM，i s) to obtain a fourth result;

[0025] The third result or the fourth result is the updated primary frequency regulation power increment of the i-th generator node;

[0026] Among them, K G,i is the gain coefficient of the i-th synchronous unit, G i (s) is the transfer function of the corresponding prime mover-governor, K GFM，i is the gain coefficient of the i-th network-forming converter, T GFM，i is the time constant of the i-th network-forming converter, and s is the Laplace operator.

[0027] F H,i is the power ratio of the high-pressure cylinder of the i-th synchronous unit; T R,i is the reheat time constant of the i-th synchronous unit.

[0028] The present invention incorporates the frequency response model of the network-forming converter, which better adapts to the form of the new energy power system.

[0029] As an inventive concept, the present invention also provides a terminal device, including a memory, a processor, and a computer program stored on the memory; the processor executes the computer program to implement the steps of the above method.

[0030] As an inventive concept, the present invention also provides a computer-readable storage medium, on which a computer program / instructions are stored; when the computer program / instructions are executed by the processor, the steps of the above method are implemented.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. The present invention not only retains the partial influence of the network, but also considers the frequency response characteristics of frequency regulation resources such as converter-type interface power sources, synchronous power sources, and loads, and can accurately predict the frequency dynamic information at the node level, and better analyze the system operation characteristics;

[0033] 2. The present invention takes into account the inertia and damping responses of the network-forming converter and the frequency modulation effect of the load, which is more in line with the actual power system situation;

[0034] 3. In the calculation process of the general node power response and the disturbance response between generator nodes of the present invention, the power transfer and change at the node level are considered, and the calculation accuracy is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is an application environment diagram of a frequency response analysis method for a converter-type power source hybrid system reflecting the spatio-temporal distribution characteristics of frequency provided in an embodiment of the present application;

[0036] Figure 2 It is a schematic flow diagram of a frequency response analysis method for a converter-type power source hybrid system reflecting the spatio-temporal distribution characteristics of frequency provided in an embodiment of the present application;

[0037] Figure 3 It is a schematic structural diagram of a frequency response analysis method for a converter-type power source hybrid system reflecting the spatio-temporal distribution characteristics of frequency provided in an embodiment of the present application;

[0038] Figure 4 It is a schematic diagram of the frequency response model of the grid-following new energy unit provided in an embodiment of the present application;

[0039] Figure 5 It is a schematic diagram of an improved IEEE-10 machine 39-node example system topology provided in an embodiment of the present application;

[0040] Figure 6 It is a schematic diagram of the result of the frequency dynamic curves of each generator node calculated according to the example system provided in an embodiment of the present application;

[0041] Figure 7 It is a comparison diagram of the generator frequency curve obtained according to the process of the present application and the actual power system frequency curve provided in an embodiment of the present application;

[0042] Figure 8 It is an internal structure diagram of a computer device provided in an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] Embodiment 1

[0045] The frequency response analysis method of the converter - type power hybrid system reflecting the frequency spatio - temporal distribution characteristics provided by the embodiment of the present application can be applied to the application environment as shown in Figure 1 As shown. Among them, the terminal 102 communicates with the server 104 through the network. The data storage system can store the data that the server 104 needs to process. The data storage system can be integrated on the server 104, or placed in the cloud or other network servers. The server 104 calculates the node susceptance matrix of the power system based on the grid topology and basic electrical parameters of the power system, and establishes the network electromagnetic power - node phase angle equation of the power system; based on the network electromagnetic power - node phase angle equation of the power system, calculates the unbalanced power distribution matrix of each node of the power system, the oscillation matrix between generators, etc.; constructs the frequency response models of power sources such as power electronic interface resources including grid - following converters and grid - forming converters, traditional synchronous machines, loads, etc. to participate in the frequency response process of the system; finally, establishes a multi - machine and multi - node frequency response model of the converter - type power hybrid system, solves the frequency dynamic response curves of each node, and displays the frequency dynamic response curves of each node through the terminal 102. Among them, the terminal 102 can be, but is not limited to, various personal computers, laptop computers, smart phones, tablet computers, Internet of Things devices, and portable wearable devices. The Internet of Things devices can be smart speakers, smart TVs, smart air conditioners, smart in - vehicle devices, etc. The portable wearable devices can be smart watches, smart bracelets, head - mounted devices, etc. The server 104 can be implemented by an independent server or a server cluster composed of multiple servers.

[0046] In an exemplary embodiment, as shown in Figure 2 a frequency response analysis method of the converter - type power hybrid system reflecting the frequency spatio - temporal distribution characteristics is provided. Taking the server 104 in Figure 1 as an example for illustration, it may include the following steps:

[0047] S1. Calculate the node susceptance matrix of the power system based on the grid topology and basic electrical parameters of the power system, and establish the network electromagnetic power - node phase angle equation of the power system.

[0048] In the power system, the power flow equation of the branch connected between nodes i and j is:

[0049]

[0050] Where: P ij is the active power flow of branch ij, V i and V j are the voltage magnitudes of nodes i and j respectively, and θ ijis the voltage phase angle difference between node i and node j, G ij and B ij are the mutual conductance and mutual susceptance between node i and node j respectively, Q ij is the reactive power flow of branch ij.

[0051] When there are active power disturbances such as load shedding and grid connection disconnection in the power system, if there are no problems with power angle stability and voltage stability, the decoupling of active power - frequency dynamics and reactive power - voltage dynamics can be achieved. Under the assumption that the voltage is constant, the active power flow in the initial operating state can be calculated through the DC power flow network modeling, which can greatly reduce the computational amount while still ensuring high accuracy.

[0052] Converting the non - linear power flow equation into a linear equation without iterative calculation is the basic idea of DC power flow. DC power flow only cares about the active power distribution and does not calculate the voltage magnitudes and reactive powers of each node. The following assumptions and simplifications are made for the power network:

[0053] 1) By default, when operating normally, the node voltage is near the rated voltage, approximately V i = V j = 1.

[0054] 2) The phase angle difference between the two ends of the branch is very small, and it is approximately considered that sinθ ij = θij, cosθ ij = 1.

[0055] 3) For ultra - high - voltage power networks, the line resistance is much smaller than the reactance, and it is approximately considered that the line resistance r ij = 0.

[0056] Based on the above three assumptions, Equation (1) is simplified to:

[0057]

[0058] Rewrite the non - linear power flow equation shown in Equation (1) into the network electromagnetic power - node phase angle equation shown in Equation (2), and represent it in matrix form:

[0059] P = Bθ (3)

[0060] Where: P and θ are the column vectors composed of the network electromagnetic powers of each node and the column vectors composed of the voltage phase angles of each node respectively. P ij represents the difference between the i - th element P i and the j - th element P j in the column vector P, and the relationship between θ ij and the column vector θ is the same as above; B is the node susceptance matrix. For a specific element B ij , it represents the element located at the i - th row and j - th column of the matrix B.

[0061] S2. Calculate the unbalanced power distribution matrix of each node in the power system, the oscillation matrix between generators, etc. based on the network electromagnetic power-node phase angle equation of the power system.

[0062] According to the network topology structure of the power system, the node susceptance matrix B can be formed, which can be divided into N generator nodes (subscript g) and M general nodes (subscript l) according to the type. The relationship between the phase angle change of each node and the electromagnetic power change can also be described by the network electromagnetic power-node phase angle equation after partitioning:

[0063]

[0064] In the formula: ΔP g , ΔP l are the column vectors of the electromagnetic power changes of the generator nodes and general nodes respectively; Δδ g , Δθ l are the column vectors of the phase angle changes of the generator nodes and general nodes respectively; B gg , B gl , B lg , B ll are submatrices of the node susceptance matrix B.

[0065] Eliminating Δθ l in formula (4), we can get

[0066] ΔP g =ΔP coi +ΔP osc =B d ΔP l +B s Δδ g (5)

[0067] Where

[0068]

[0069] As shown in formula (5), at the initial moment of the disturbance, the unbalanced power ΔP l propagates from the disturbance position to each generator according to the unbalanced power distribution matrix B d . Each generator in the system will bear a part of the initial distributed power ΔP coi . Subsequently, due to the differences in the frequency modulation characteristics of each generator, these differences will generate the oscillation power ΔP s between generators according to the oscillation matrix B osc between generators, and ΔP osc will drive the frequencies of all generators to synchronize. Therefore, ΔP l can be regarded as the sum of ΔP coi and ΔPosc The linear combination. Since the oscillation matrix B in the generator room s reflects the electrical connection between generator nodes, it is a symmetric matrix, and the sum of any row and column is 0, that is

[0070]

[0071] S3. Build a frequency response model of power electronic interface resources including grid-following converters and grid-forming converters, traditional synchronous machines, loads and other power sources to participate in the frequency response process of the system.

[0072] (1) The fundamental reason for the change in system frequency is the imbalance of active power, which is manifested in the rotor motion equation of the synchronous generator, that is, the change in generator speed depends on the primary frequency modulation power output P SG and the electromagnetic power input P g The balance relationship between them.

[0073] The rotor motion equation is a second-order differential equation, and its solution provides information on rotor angle dynamics and the generator's response to disturbances. Therefore, the frequency response process of the i-th synchronous generator can be expressed by the swing equation:

[0074]

[0075] In the formula: s is the Laplace operator, Δf g,i is the frequency change of the i-th generator node in the system, Δδ g,i is the phase angle change of the i-th generator node, H SG,i is the rotor inertia constant of the i-th unit, D SG,i is the corresponding damping coefficient, K G,i is the corresponding gain coefficient, G i (s) is the transfer function of the corresponding prime mover-governor, ΔP SG,i is the primary frequency modulation-mechanical power increment of the corresponding prime mover during the frequency modulation process of the i-th generator node, ΔP g,i is the change in electromagnetic power corresponding to the i-th generator node during the frequency modulation process.

[0076] (2) The grid-forming converter can achieve stable synchronization with the external power grid better and has been widely used in new energy grid connection in recent years. Different from the grid-following converter (GFL), the grid-forming converter (GFM) adopts voltage control, presents voltage source characteristics to the power grid, and can generate an internal reference voltage waveform. Therefore, it does not require a phase-locked loop to measure the phase angle and frequency of the power grid and has an independent power angle characteristic. Relying on virtual synchronous generator (VSG) control and droop control, the grid-forming inverter can autonomously adjust power to achieve synchronization with the power grid. Among them, the droop control enables the inverter equipment to have the ability to participate in primary frequency modulation control, while the VSG enables the inverter to have inertia and damping similar to that of a synchronous machine in frequency dynamics. Different from the synchronous machine with fixed inertia and damping, the VSG can flexibly change the size of the virtual inertia and virtual damping. The process of new energy units adopting the grid-forming frequency modulation strategy to participate in the system frequency response is similar to that of a synchronous machine, and its grid connection point can also be regarded as a generator node:

[0077]

[0078] In the formula: H GFM,j (H i ) and are the virtual inertia time constant and virtual damping coefficient of the j-th grid-forming converter in the system, T GFM,j is the corresponding converter time constant, K GFM,j is the corresponding gain coefficient, ΔP GFM,j is the primary frequency modulation power increment in response to the droop link, and Δf g,j is the frequency change of the grid connection point of the grid-forming converter.

[0079] (3) The new energy power source connected to the grid through the grid-following converter also has the ability to participate in the frequency control of the power system. However, since the grid-following converter does not have a power angle characteristic, it will not participate in the distribution of unbalanced power at the moment of disturbance occurrence and will not be regarded as a generator node in the DC power flow network model. During the process of the system experiencing frequency disturbance, the grid-following inverter will dynamically adjust the output power according to the system frequency measured by the phase-locked loop (PLL), and the generated frequency modulation power will also be regarded as power disturbance and distributed to each generator through the unbalanced power distribution matrix of its node.

[0080] Since the frequency of each node in the power system is determined by the frequency at the generator, the frequency of each general node can be approximately regarded as a linear combination of the frequencies of the generator nodes. Therefore, the node frequency measured by the grid-following converter through the PLL can be calculated based on the frequency divider matrix. Thus, during the frequency response process, the frequency regulation power of the grid-following converter can also be analytically calculated and distributed to each generator to form a closed loop. Specifically:

[0081]

[0082] In the formula, λ is the frequency divider matrix calculated from the sub-block of the node susceptance matrix B, and Δf l,k is the frequency change at the k-th general node, and H GFL,k and D GFL,k are the virtual inertia time constant and virtual damping coefficient of the k-th grid-following converter, respectively.

[0083] T GFL,k is the converter time constant obtained by equivalent its inherent delay link, and ΔP GFL,k is the frequency regulation power increment generated by the grid-following converter in response to the frequency change, and Δf g is the column vector composed of the frequencies of each generator node in the system, and the corresponding Δf g,i represents the i-th element in this column vector; Δf l is the column vector composed of the frequencies of each general node in the system, and the corresponding Δf l,k represents the k-th element in this column vector.

[0084] (4) Ignoring the influence of voltage on load power, that is, the load composition of the power system is only static constant-power load, then the load frequency response characteristic on the general node can be approximately expressed as:

[0085] ΔP l = D l Δf l (11)

[0086] In the formula, D l is the column vector composed of load frequency response coefficients.

[0087] Since the solution target of this application is the frequency dynamics of the generator node, the general node variables in the network electromagnetic power-node phase angle equation can be eliminated, and the power disturbance occurring on the general node can be equivalently distributed to the generator node to correct the damping coefficient D i in the form to represent the influence of the static constant-power load on the system. Specifically:

[0088]

[0089] In the formula, is the column vector of the damping coefficient of each generator node corrected by the load frequency response coefficient. According to the type of power source, it can be divided into the damping coefficient of the synchronous unit Damping coefficient of grid-connected converter It represents the i-th element in the column vector; D is the damping coefficient of each generator node D i A square matrix of diagonal elements.

[0090] (5) Fast frequency modulation resources that perform step response based on preset power reference values, including energy storage power stations, DC FLC modulation, etc. Grid-following / grid-building converters-electrochemical energy storage units are important entities for coordinating the operation and control of new energy grid-connected due to their fast adjustment speed; DC FLC modulation can suppress the change of electromagnetic power of the generator through the fast controllable function of DC power, reduce the deviation between it and mechanical power, and improve the frequency characteristics. When there are energy storage power stations and DC FLC modulation that are actively connected to the grid using grid-following or grid-building control strategies in the power system, similar processing can be performed according to the above modeling methods, which will not be repeated here.

[0091] S4, the frequency response model of various frequency modulation resources obtained in step S3 (including equations (8), (9), (10), (12)) and the network electromagnetic power-node phase angle equation obtained in step S2 (including equation (5)) are combined. Specifically: ΔP in equation (5) g The column vector representing the electromagnetic power variation of each generator node in the frequency response, ΔP in equation (8) g,i and ΔP in equation (9) g,j represents the i-th or j-th specific element in the column vector; ΔP in formula (8) SG,i and ΔP in equation (9) GFM,j They represent the power increment of the primary frequency regulation link of the synchronous unit and the droop link of the grid-type converter respectively. The power supply at the generator node can be the synchronous unit SG or the grid-type converter GFM. For the same generator node, only one of the two can be selected. The transfer function modules of the synchronous unit and the grid-type converter have been Figure 3 The power increment of the primary frequency modulation of the two is uniformly symbolized by ΔP m express.

[0092] Taking the i-th generator node in the system as an example, after the disturbance, the primary frequency modulation power increment ΔP m,i With ΔP g,i Subtract, and then divide by the corresponding power supply (H i and They represent the inertia constant and damping coefficient of the ith power source, respectively, and are related to the type of power source. i The meaning of refers to formula (8) and formula (9), The meaning is referred to Equation (12). Specifically, when the power source is a synchronous unit, H i and can be further written as H SG,i and When the power source is a network-forming converter, H i and can be further written as H GFM,i and ) to obtain the frequency change Δf g,i , which is the specific idea of calculating the frequency of the model proposed in this application. Since the load frequency regulation characteristics are considered, according to Equation (12), the damping coefficient D of the power source at each generator node is replaced with the corrected D. From Equations (8), (9) and (12), we can get:

[0093]

[0094] SG and GFM represent synchronous units and network-forming converters respectively. From the above formula, for the i-th generator node, its electromagnetic power increment ΔP g,i , primary frequency regulation power increment ΔP m,i are all related to the node frequency Δf g,i , that is, the power increment will change with the change of Δf g,i , and the change of the power increment as feedback will cause the frequency to change, and so on, iterating until the system frequency returns to stability.

[0095] The frequency response model and transfer function block diagram of the network-connected converter are as Figure 4 shown. Its basic principle is based on Equation (10). For the general node where the k-th network-connected converter is located, the input of the network-connected converter is the frequency change Δf l,k of the general node where it is located, and the output is the frequency regulation power ΔP GFL,k . Specifically, Δf l,k is multiplied by the response link and (2H GFL, k s + D GFL,k ) to obtain ΔP GFL,k .

[0096] Figure 3 represents the specific structure at the i-th generator node in the proposed model. Specifically, Figure 3 The model framework shown is mainly divided into three modules: network-electromagnetic power response module, inertia / damping response module, and primary frequency regulation power response module.

[0097] The network-electromagnetic power response module represents the propagation of the unbalanced power generated by each general node (generated by loads, grid-connected converters, DC modulation, energy storage, etc.) and the electromagnetic oscillation power generated between each generator node. The basic principle is referred to Equation (5). The output of this module is ΔP g,i , and the input consists of the response power ΔP coi,i of the general node and the disturbance response power ΔP osc,i between the generator nodes. The input of this module involves a total of 2 summation operations, namely the summation of the power responses of each general node and the summation of the disturbance responses between the generator nodes. The sum of these two items together constitutes the output ΔP g,i of the i-th network-electromagnetic power response module. The general formula for the response power of the general node is B d,ik ΔP l,k , where B d,ik represents the element in the i-th row and k-th column of the matrix B d in Equation (6), and ΔP l,k represents the k-th element in the column vector ΔP l in Equation (5), that is, the response power at the k-th general node. For example, if the response power is generated by a grid-connected converter, then ΔP l,k can be further written as ΔP GFL,k , as shown in Equation (10). k represents the total number of nodes participating in the power response of the general node. Summing the power responses of the general nodes is to sum up the above general formula from the first item to the k-th item. The general formula for the disturbance response between the generator nodes is B s,ij Δf g,j , where B s,ij represents the element in the i-th row and j-th column of the B s matrix in Equation (6), and Δf g,j represents the frequency change of the j-th generator node. Summing up the above general formula from the first item to the N-th item, where N is the total number of generator nodes, and then through the integral operation in the frequency domain, the disturbance response power between the generator nodes can be obtained.

[0098] The primary frequency regulation power response module represents the power support provided by the power source (synchronous unit or network-forming converter) at the i-th generator node in the primary frequency regulation link of the system frequency response (the primary frequency regulation power support ΔP SG,i of the synchronous unit is provided by the prime mover-governor, and the primary frequency regulation power support ΔP GFM,i of the network-forming converter is provided by the droop link), referring to Equation (8) and Equation (9) respectively. At the output end of this link, the primary frequency regulation power increments of the two types of power sources are uniformly represented by ΔP m,i . The input of this module is the frequency change Δf g,i of the i-th generator node, and the output is the primary frequency regulation response power ΔP m,i, the transfer function modules of the synchronous generator set and the network-forming converter have been given in Figure 3 .

[0099] The inertia / damping response module represents the inertia and damping support provided by the power source (synchronous generator set or network-forming converter) at the i-th generator node to the system. The output ΔP g,i of the network-electromagnetic power response module and the output ΔP m,i of the primary frequency regulation power response module are subtracted to form the input of this module, and the output of this module is the frequency change Δf g,i at the i-th generator node. H i and represent the inertia constant and damping coefficient of the i-th power source respectively, which are related to the type of power source. The meaning of H i refers to Equations (8) and (9), and the meaning of refers to Equation (12). Specifically, when the power source is a synchronous generator set, H i and can be further written as H SG,i and When the power source is a network-forming converter, H i and can be further written as H GFM,i and

[0100] The output of the inertia / damping response module is the frequency change Δf g,i at the i-th generator node, which is also used as the input of the network-electromagnetic power response module and the primary frequency regulation power response module. New power increments and frequency increments are generated through iterative cycles. The above process is repeated until no new power increments and frequency increments are generated, that is, the system returns to stability. The dynamic information of the frequency increments obtained during the iterative process is the solution target of the model proposed in this application.

[0101] The proposed model can calculate the frequency dynamic response curves of each node, and accurately depict the spatio-temporal distribution characteristics of the node frequencies in the converter-based hybrid power system under the background of uneven distribution of inertia and frequency regulation resources.

[0102] As Figure 5 (Liu Jiahao, Wang Cheng, Bi Tianshu. Node equivalent inertia index and its application for spatio-temporal dynamics of frequency in new energy power systems [J]. Proceedings of the CSEE, 2023, 43(20): 7773-7789. DOI: 10.13334 / j.0258-8013.pcsee.220146.) shows, the IEEE 39-node system is respectively built on the DSP-BPA and Matlab / Simulink simulation platforms for testing. Figure 5Among them, the numbers 1 to 39 represent the serial numbers of each node and its relative position in the figure; G1 to G8 represent the serial numbers and positions of 8 synchronous machines and grid-forming converters, where G2 represents the grid-forming converter, and the rest represent synchronous generator sets; PV represents the access position of the grid-following converter, and there is DC injection at node 21. The reference frequency is 50 Hz, including 8 synchronous generator sets and 2 new energy power stations, and the calculation results are as Figure 6 and Figure 7 shown, where Figure 6 is the frequency dynamic curve calculated by the method provided in this application after the system is disturbed, Figure 7 is the comparison chart of the generator frequency curve obtained according to the process of this application and the actual frequency curve in DSP-BPA.

[0103] From Figure 6 and Figure 7 it can be seen that the method proposed in this application can accurately calculate the frequency dynamic curves of all generator nodes in the system. Compared with the traditional analysis method based on the inertial center frequency (f COI ), the advantages are as follows: 1. In the initial stage of frequency response, it can accurately reflect the respective frequency change rates of all generator nodes; 2. During the process of the frequency of each node dropping to the lowest point, it can accurately reflect the time difference of the frequency of each generator node reaching the lowest point and the amplitude difference of the maximum frequency deviation; 3. It can accurately reflect the system frequency oscillation phenomenon caused by the spatio-temporal distribution characteristics of frequency under the background of the access of converter-type resources, providing an important basis and reference for the frequency stability analysis of the converter-type power hybrid system.

[0104] Embodiment 2

[0105] Embodiment 2 of the present invention provides a terminal device corresponding to Embodiment 1 above. The terminal device can be a processing device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of the above embodiment.

[0106] The terminal device of this embodiment includes a memory, a processor, and a computer program stored on the memory; the processor executes the computer program on the memory to implement the steps of the method of Embodiment 1 above.

[0107] In an exemplary embodiment, a computer device is provided. The computer device can be a server, and its internal structure diagram can be as Figure 8As shown in the figure. The computer device includes a processor, a memory, an input / output interface (Input / Output, abbreviated as I / O), and a communication interface. Among them, the processor, the memory, and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database of the computer device is used to store power system data. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals through a network connection. When the computer program is executed by the processor, it realizes a frequency response analysis method for a converter-type power hybrid system that reflects the spatio-temporal distribution characteristics of frequency.

[0108] It should be noted that the information (including but not limited to power system information, power system equipment information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in this application are all information and data that have been fully authorized by all parties, and the collection, use, and processing of relevant data need to comply with relevant regulations.

[0109] In some implementations, the memory can be a high-speed random access memory (RAM: Random Access Memory), and may also include non-volatile memory, such as at least one disk memory.

[0110] In other implementations, the processor can be various types of general-purpose processors such as a central processing unit (CPU), a digital signal processor (DSP), etc., which are not limited here.

[0111] Embodiment 3

[0112] Embodiment 3 of the present invention provides a computer-readable storage medium corresponding to Embodiment 1 above, on which computer programs / instructions are stored. When the computer programs / instructions are executed by the processor, the steps of the method in Embodiment 1 above are realized.

[0113] A computer-readable storage medium can be a tangible device that holds and stores instructions used by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination of the above.

[0114] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application 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 solutions in the embodiments of the present application can be implemented using various computer languages. For example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript, etc.

[0115] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing devices, such that a series of operation steps are executed on the computer or other programmable devices to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable devices provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0117] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0118] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these changes and modifications.

Claims

1. A frequency response analysis method for a converter type power hybrid system, characterized in that: The following steps are involved: S1. For the i-th generator node, the DC modulation response and energy storage power response of the grid-following new energy unit are used to obtain the general node power response; The general node power response and the disturbance response between generator nodes are superimposed to obtain the electromagnetic power change ΔP corresponding to the i-th generator node during the frequency modulation process. g,i ; S2, the primary frequency modulation power increment ΔP of the i-th generator node m,i The electromagnetic power change ΔP corresponding to the i-th generator node during the frequency modulation process g,i Subtract the difference and divide it by the inertia / damping response of the ith power source to obtain the frequency change Δf of the ith generator node g,i ; S3, using the frequency change Δf of the i-th generator node g,i Update the disturbance response between the generator nodes, the primary frequency modulation power increment of the i-th generator node, and the electromagnetic power change corresponding to the i-th generator node during the frequency modulation process, and return to step S2; S4. When the frequency variation of the i-th generator node stops changing, the process ends.

2. The frequency response analysis method of a converter type power supply hybrid system according to claim 1, characterized in that: In step S1, the general node power response is expressed as: Where k represents the total number of nodes participating in the general node power response, B d,ik Indicates B d The element in the i-th row and k-th column of B gl , B ll is a sub-matrix of the node susceptance matrix B, ΔP l,k represents the response power at the kth general node.

3. The frequency response analysis method of a converter type power supply hybrid system according to claim 1, characterized in that: In step S1, the disturbance response between the generator nodes ΔP osc,i The acquisition process includes: Will Multiply by 1 / s to get the first result; N is the number of generator nodes; B s,ij For B s The element in the i-th row and j-th column of B gg , B gl , B lg , B ll is a sub-matrix of the node susceptance matrix B, Δf g,j The initial value of is 0; Multiply the frequency change of the i-th generator node by 1 / s, and add the product to B s,ii Multiply them to get the second result; B s,ii Denotes the inter-generator oscillation matrix B s The element in the i-th row and i-th column of ; Add the first result and the second result to obtain the inter-node disturbance response ΔP of the generator. osc,i .

4. The frequency response analysis method of a converter type power supply hybrid system according to claim 1, characterized in that: In step S2, the inertia / damping response is expressed as: is the column vector of the damping coefficient of each generator node after considering the load frequency response coefficient correction, and D is the damping coefficient of each generator node D i The square matrix of diagonal elements, H i represents the inertia constant of the ith power supply, λ is the divider matrix calculated by sub-block solution of node susceptance matrix B, λ = -B ll -1 B lg , B gl , B lg , B ll is a sub-matrix of the node susceptance matrix B, D l is a column vector consisting of load frequency response coefficients.

5. The frequency response analysis method of a converter type power supply hybrid system according to claim 1, characterized in that: In step S3, the frequency change Δf of the i-th generator node is used g,i The specific implementation process of updating the primary frequency regulation power increment of the i-th generator node includes: The frequency change of the i-th generator node and K G,i G i (s) are multiplied to obtain a third result; The frequency change of the i-th generator node and K GFM，i / (1+T GFM，i s) are multiplied to obtain a fourth result; The third result or the fourth result is the updated primary frequency modulation power increment of the i-th generator node; if the power supply at the i-th generator node is a synchronous unit, the third result is the updated primary frequency modulation power increment of the i-th generator node; if the power supply at the i-th generator node is a grid-type converter, the fourth result is the updated primary frequency modulation power increment of the i-th generator node; Among them, K G,i is the gain coefficient of the ith synchronous unit, G i (s) is the transfer function corresponding to the prime mover-speed regulator, K GFM，i is the gain coefficient of the i-th grid-connected converter, T GFM，i is the time constant of the ith grid-connected converter, and s is the Laplace operator.

6. The frequency response analysis method of a converter type power supply hybrid system according to claim 5, characterized in that: F H,i is the power ratio of the high-pressure cylinder of the ith synchronous unit, T R,i is the reheat time constant of the i-th synchronous unit.

7. A terminal device comprising a memory, a processor and a computer program stored in the memory; characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program / instruction stored thereon; characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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