A power low-frequency cut flexible load control method, system, device and medium

Abstract

The present application belongs to the technical field of power system load control, and discloses a power low-frequency flexible load shedding control method, system, device and medium, which comprises the following steps: establishing a power system node frequency model; solving the node frequency based on the power system node frequency model to obtain node frequency weight matrix information; constructing a load shedding model of a new energy power system, and solving the load shedding model of the new energy power system to obtain the expected flexible load power of the power system to be cut off; and the local flexible load device of each node controls the flexible load according to the optimization distribution result. The present application establishes frequency models of synchronous machines, loads and new energy sources from the mechanism of the time and space distribution characteristics of system frequency, explains the main indexes affecting the node frequency, and proposes a low-frequency flexible load shedding strategy for reducing the system frequency deviation and improving the system stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system load control, in particular to a power low-frequency cut flexible load control method, system, device and medium. BACKGROUND

[0002] At present, intermittent renewable energy such as wind and light and photovoltaic will gradually change from the secondary energy in the power system to the main energy, and a large number of synchronous generators on the power supply side are gradually replaced by power electronic devices. Compared with traditional synchronous machines, new energy such as wind power basically does not provide inertia, which leads to the deterioration of frequency dynamics of new power system after suffering serious power disturbance, and has a bad influence on the safe and stable and economic operation of power grid.

[0003] As the third line of defense of the power system, low-frequency load shedding is an effective method to suppress frequency drop and maintain system frequency stability. The traditional low-frequency load shedding scheme adopts a successive approximation calculation method, and according to the action frequency of each round, the pre-set load is cut off to ensure the balance between demand and power generation, thereby ensuring system stability and restoring the frequency to the allowed range. However, due to the decrease of system inertia, the probability of low-frequency load shedding triggering increases, and the above research cannot fundamentally reduce the economic loss of low-frequency load shedding measures to the power grid.

[0004] Flexible load, such as air conditioner and other constant temperature load, can reduce the average power consumption through on / off control, thereby providing frequency support for the power grid in a short time. However, due to the dispersion characteristics of flexible load, the determination of cut-off location and cut-off amount still needs further research.

[0005] Due to factors such as grid structure, generator set distribution, unit parameters and load type, the system frequency presents time and space distribution characteristics. Especially, the uneven distribution of system inertia caused by the access of new energy makes the time and space distribution characteristics of system frequency increasingly significant. Many domestic and foreign experts and scholars have carried out related research on this, and have proposed some characterization and quantification methods of system frequency response characteristics, and have carried out inertia evaluation and inertia configuration according to the time and space distribution characteristics of the system, thereby improving the frequency stability of each node in the whole system. However, few literatures consider the time and space characteristics of system frequency after load shedding. In fact, due to the cut-off of loads at different positions, it will have a new impact on the system frequency, and some nodes may further increase the frequency deviation, which will have a new adverse effect on the stability of the system.

[0006] Therefore, how to provide a power low-frequency cut flexible load control method, system, device and medium is a problem to be solved at present. SUMMARY

[0007] The embodiments of the present application provide a power low-frequency cut flexible load control method, system, device and medium to solve the problems in the prior art.

[0008] The following presents a simplified summary of some aspects of the disclosed embodiments in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of the embodiments and is intended neither to identify key / critical elements of these embodiments nor to delineate the scope of the embodiments. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0009] According to a first aspect of embodiments of the present application, there is provided a power low frequency cut flexible load control method, system, device and medium.

[0010] In one embodiment, the power low frequency cut flexible load control method comprises the following steps:

[0011] Obtaining power data of a power system, and establishing a power system node frequency model based on a power system node frequency generation mechanism; solving the node frequency based on the power system node frequency model to obtain node frequency weight matrix information;

[0012] Performing initial allocation of electromagnetic power based on the electrical distance between the power source and the disturbance occurrence location, constructing a load cut-off model of the new energy power system according to the initial allocation result and in combination with the time and space distribution characteristics of the frequency, and solving the load cut-off model of the new energy power system to obtain the expected flexible load power to be cut off of the power system;

[0013] Optimizing the allocation of the flexible load cut-off power according to the node frequency weight matrix information and the expected flexible load power to be cut off of the power system, and transmitting the optimized allocation result to each node flexible load on-site device; the on-site device controls the flexible load according to the optimized allocation result.

[0014] In one embodiment, the solving of the node frequency based on the power system node frequency model to obtain the node frequency weight matrix information comprises:

[0015] Differential processing the expression of the power system node frequency model with respect to time, and performing Laplace transform on the differential processing result to obtain a relationship function between the node frequency and the synchronous power source speed;

[0016] In the synchronous alternating current power system, the node frequency is solved according to the relationship between the rotor angle and the speed of the synchronous power source and the relationship between the node voltage phase angle and the node frequency, in combination with the relationship function between the node frequency and the synchronous power source speed, and the node frequency weight matrix information is determined according to the node frequency.

[0017] In one embodiment, the initial allocation of electromagnetic power based on the electrical distance between the power source and the disturbance occurrence location comprises:

[0018] According to the frequency response characteristics similar to the grid-connected new energy and the load, an equivalent load active power column vector is calculated;

[0019] According to the frequency response characteristics similar to the grid-connected new energy and the synchronous machine, an equivalent power active power column vector is calculated;

[0020] Based on the equivalent load active power column vector, the equivalent power active power column vector and the node frequency model of the power system, the change amount of the instantaneous electromagnetic power of the synchronous power source is calculated, and the change amount of the instantaneous electromagnetic power of the synchronous power source is taken as the initial distribution disturbance power.

[0021] In one embodiment, according to the initial distribution result, and in combination with the time and space distribution characteristics of the frequency, a load shedding model of the new energy power system is constructed, and the expected flexible load power to be cut off of the power system is obtained by solving the load shedding model of the new energy power system, including the following steps:

[0022] According to the initial distribution result, and in combination with the time and space distribution characteristics of the frequency, a target function and a power constraint condition are established, in which the difference between the initial distribution disturbance power of the equivalent synchronous power source and the disturbance power distributed according to the inertia size of the equivalent synchronous power source is minimized;

[0023] According to the target function and the power constraint condition, the expected flexible load power to be cut off of the power system is solved.

[0024] According to the second aspect of the embodiment of the present application, a power low-frequency cut flexible load control system is provided.

[0025] In one embodiment, the power low-frequency cut flexible load control system comprises:

[0026] A node frequency weight matrix information calculation module is configured to obtain power data of the power system, and establish a node frequency model of the power system based on a node frequency generation mechanism of the power system; and based on the node frequency model of the power system, the node frequency is solved to obtain node frequency weight matrix information;

[0027] An expected flexible load power to be cut off calculation module is configured to perform initial distribution of electromagnetic power based on the electrical distance between the power source and the disturbance occurrence site, construct a load shedding model of the new energy power system according to the initial distribution result and in combination with the time and space distribution characteristics of the frequency, and solve the load shedding model of the new energy power system to obtain the expected flexible load power to be cut off of the power system.

[0028] The just-in-place power control module is used for optimizing and distributing the flexible load shedding power according to the node frequency weight matrix information and the flexible load power expected to be cut off by the power system, and transmitting the optimized distribution result to each node flexible load just-in-place device; and each node flexible load just-in-place device controls the flexible load just-in-place according to the optimized distribution result.

[0029] In one embodiment, the node frequency weight matrix information is obtained by solving the node frequency based on the node frequency model of the power system, including:

[0030] The expression of the node frequency model of the power system is differentiated with respect to time, and Laplace transform is performed on the differentiated result to obtain a relationship function between the node frequency and the rotating speed of the synchronous power source;

[0031] In the synchronous alternating current power system, the node frequency is solved according to the relationship between the rotor angle and the rotating speed of the synchronous power source and the relationship between the node voltage phase angle and the node frequency, and in combination with the relationship function between the node frequency and the rotating speed of the synchronous power source, and the node frequency weight matrix information is determined according to the node frequency.

[0032] In one embodiment, the initial distribution of the electromagnetic power is based on the electrical distance between the power source and the disturbance occurrence site, including:

[0033] According to the similar frequency response characteristics of the grid-connected new energy and the load, an equivalent load active power output column vector is calculated;

[0034] According to the similar frequency response characteristics of the grid-constructing new energy and the synchronous machine, an equivalent power source active power output column vector is calculated;

[0035] Based on the equivalent load active power output column vector, the equivalent power source active power output column vector and the node frequency model of the power system, the change amount of the instantaneous electromagnetic power of the synchronous power source is calculated, and the change amount of the instantaneous electromagnetic power of the synchronous power source is taken as the disturbance power of the initial distribution.

[0036] In one embodiment, according to the initial distribution result, and in combination with the time and space distribution characteristics of the frequency, a load shedding model of the new energy power system is constructed, and the flexible load power expected to be cut off by the power system is obtained by solving the load shedding model of the new energy power system, including:

[0037] According to the initial distribution result, and in combination with the time and space distribution characteristics of the frequency, a target function and a power constraint condition are established, which minimize the difference between the disturbance power of the equivalent synchronous power source initial distribution and the disturbance power of the equivalent synchronous power source according to the inertia size thereof;

[0038] The flexible load power expected to be cut off by the power system is solved according to the target function and the power constraint condition.

[0039] According to a third aspect of the embodiments of the present application, a computer device is provided.

[0040] In some embodiments, the computer device comprises a memory and a processor, the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0041] According to a fourth aspect of the embodiments of the present application, a computer readable storage medium is provided.

[0042] In one embodiment, the computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the above method.

[0043] The technical solutions provided by the embodiments of the present application can include the following beneficial effects:

[0044] The embodiments of the present application establish frequency models of synchronous machines, loads, new energy, etc. from the mechanism of the space-time distribution characteristics of system frequency, explain the main indicators affecting the size of node frequency, and propose a low-frequency cut flexible load strategy to reduce the system frequency deviation and improve the system stability.

[0045] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0046] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the present application.

[0047] Figure 1 is a flowchart of a power low-frequency cut flexible load control method according to an exemplary embodiment;

[0048] Figure 2 is a principle block diagram of a power low-frequency cut flexible load control system according to an exemplary embodiment;

[0049] Figure 3 is a structural schematic diagram of a computer device according to an exemplary embodiment;

[0050] Figure 4 is a typical system model schematic diagram containing new energy in a power low-frequency cut flexible load control method according to an exemplary embodiment;

[0051] Figure 5 is a low-frequency cut flexible load control flow in a power low-frequency cut flexible load control method according to an exemplary embodiment;

[0052] Figure 6is a power low frequency cut flexible load control method according to an exemplary embodiment shown in a IEEE39 example system wiring diagram;

[0053] Figure 7 is a power low frequency cut flexible load control method according to an exemplary embodiment shown in a load shedding power distribution scheme schematic diagram;

[0054] Figure 8 is a power low frequency cut flexible load control method according to an exemplary embodiment shown in a node frequency comparison schematic diagram;

[0055] Figure 9 is a power low frequency cut flexible load control method according to an exemplary embodiment shown in a node frequency rate of change comparison schematic diagram;

[0056] Figure 10 is a power low frequency cut flexible load control method according to an exemplary embodiment shown in a comparison of the maximum frequency deviation of each node after load shedding schematic diagram;

[0057] Figure 11 is a power low frequency cut flexible load control method according to an exemplary embodiment shown in a comparison of the maximum frequency rate of change of each node;

[0058] Figure 12 is a power low frequency cut flexible load control method according to an exemplary embodiment shown in a comparison of the simulation results of the speed of each synchronous machine schematic diagram. DETAILED DESCRIPTION

[0059] The following description and drawings are illustrative of specific embodiments thereof and are not intended to limit the scope of the embodiments. Parts and features of some embodiments can be included or substituted in or for parts and features of other embodiments. The scope of the embodiments encompassed herein includes the whole scope of the claims together with all available equivalents of the claims. In this document, the terms "first", "second", etc. are used merely to distinguish one element from another, and do not require or imply any actual relationship or order between the elements. In fact, the first element can be referred to as the second element, and vice versa. Also, the terms "comprises", "comprising", or any other variations thereof are intended to cover a non-exclusive inclusion, such that a structure, device, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such structure, device, or apparatus. Without further limitation, an element defined by an "includes a" statement does not exclude the presence of additional identical elements in the structure, device, or apparatus that includes the element. Various embodiments are described in progressive stages, each of which focuses on the differences from other embodiments, and the same or similar parts between various embodiments can be referred to each other.

[0060] In this document, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship shown in the drawings, and are used only for the convenience of description and simplification of the description herein, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In the description herein, unless otherwise specified and limited, the terms "mount", "connect", "connection" should be interpreted broadly, for example, it can be a mechanical connection or an electrical connection, it can be a communication between two elements inside, it can be a direct connection or an indirect connection through an intermediate medium, and the specific meaning of the above terms can be understood by the person skilled in the art according to the specific circumstances.

[0061] In this document, the term "multiple" means two or more, unless otherwise specified.

[0062] In this document, the character " / " represents an "or" relationship between the objects before and after it. For example, A / B means A or B.

[0063] In this document, the term "and / or" is a description of the relationship between the objects, which means that there can be three relationships. For example, A and / or B means that there are three relationships of A or B, or A and B.

[0064] It should be understood that although the steps in the flowchart are shown in a sequential order, the steps are not necessarily performed in the order shown by the arrows. Unless explicitly stated otherwise, the steps can be performed in other orders. Moreover, at least some of the steps can include multiple sub-steps or multiple stages, which are not necessarily performed at the same time, but can be performed at different times, and the order of the sub-steps or stages can not be sequential, but can be interleaved or alternated with at least some of the other steps or sub-steps or stages of other steps.

[0065] The modules in the device or system of the present application can be implemented wholly or partially by software, hardware, and combinations thereof. The modules can be embedded in or independent of the processor in the computer device in hardware form, or stored in the memory in the computer device in software form, so as to be called and executed by the processor to perform the operations corresponding to the modules.

[0066] In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0067] Figure 1 An embodiment of the power low-frequency cut flexible load control method of the present application is shown.

[0068] In this alternative embodiment, the power low-frequency cut flexible load control method comprises the following steps:

[0069] Step S101, acquiring power data of a power system, and establishing a power system node frequency model based on a power system node frequency generation mechanism; solving the node frequency based on the power system node frequency model to obtain node frequency weight matrix information;

[0070] Step S103, performing initial allocation of electromagnetic power based on the electrical distance between the power source and the disturbance occurrence location, constructing a load cut-off model of the new energy power system according to the initial allocation result and in combination with the time and space distribution characteristics of the frequency, and obtaining the expected flexible load power to be cut off of the power system by solving the load cut-off model of the new energy power system;

[0071] Step S105, optimizing the allocation of the flexible load cut-off power according to the node frequency weight matrix information and the expected flexible load power to be cut off of the power system, and transmitting the optimized allocation result to each node flexible load on-site device; the on-site device controls the flexible load according to the optimized allocation result.

[0072] In this alternative embodiment, the expression of the power system node frequency model is:

[0073] B EG (δ EG -θ)-P ELN (I+K EL f)-P CL =B0θ

[0074] In the formula, B EG δ represents the diagonal array of internal susceptance of the equivalent power source. EG P represents the equivalent power source rotor angle column vector, θ represents the voltage phase angle vector of each node in the power system, and P represents the equivalent power source rotor angle column vector. ELN This represents the column vector of rated active power absorbed by the equivalent load, where I represents a unit vector, and K... EL This represents the column vector of equivalent load active power regulation effect coefficients, where f represents the node frequency and P... CL B0 represents the active power actually absorbed by the flexible load, and B0 represents the power system node susceptance matrix.

[0075] In this optional embodiment, when solving for the node frequency based on the power system node frequency model to obtain the node frequency weight matrix information, the expression of the power system node frequency model can be differentiated with respect to time, and the result of the differentiation can be subjected to a Laplace transform to obtain the relationship function between the node frequency and the synchronous power source speed. In a synchronous AC power system, the node frequency is solved based on the relationship between the rotor angle and speed of the synchronous power source and the relationship between the node voltage phase angle and the node frequency, combined with the relationship function between the node frequency and the synchronous power source speed, and the node frequency weight matrix information is determined based on the node frequency.

[0076] In this optional embodiment, when initially allocating electromagnetic power based on the electrical distance between the power source and the disturbance location, the equivalent load active power output column vector can be calculated based on the frequency response characteristics similar to those of grid-connected renewable energy and loads; the equivalent power source active power output column vector can be calculated based on the frequency response characteristics similar to those of grid-connected renewable energy and synchronous machines; based on the equivalent load active power output column vector, the equivalent power source active power output column vector, and the power system node frequency model, the instantaneous electromagnetic power change of the synchronous power source is calculated, and the instantaneous electromagnetic power change of the synchronous power source is used as the initial allocated disturbance power.

[0077] In this optional embodiment, the formula for calculating the change in instantaneous electromagnetic power of the synchronous power supply is:

[0078] ΔP EG =W T ΔP CL

[0079] In the formula, ΔP EG W represents the instantaneous change in electromagnetic power of the synchronous power source. T ΔP represents the transpose of the weight matrix representing the node frequencies.CL This represents the flexible load disturbance vector.

[0080] In this optional embodiment, when constructing a load shedding model for the new energy power system based on the initial allocation results and the spatiotemporal distribution characteristics of the frequency, and solving the load shedding model of the new energy power system to obtain the expected flexible load power to be shedding by the power system, an objective function and power constraint condition can be established based on the initial allocation results and the spatiotemporal distribution characteristics of the frequency, minimizing the difference between the disturbance power initially allocated by the equivalent synchronous power source and the disturbance power allocated by the equivalent synchronous power source according to its inertia; and the expected flexible load power to be shedding by the power system can be solved based on the objective function and power constraint condition.

[0081] In this optional embodiment, the objective function and power constraint for minimizing the difference between the initial disturbance power allocated by the equivalent synchronous power source and the disturbance power allocated by the equivalent synchronous power source according to its inertia are expressed as follows:

[0082]

[0083] ΔP CLimin ≤ΔP CLi ≤ΔP CLimax i = 1, 2, ..., n

[0084]

[0085] In the formula, ΔP EGj Let ΔP represent the initial disturbance power allocated to the j-th equivalent synchronous power source. Hj Let ΔP represent the disturbance power distributed by the j-th equivalent synchronous power source according to its inertia, m represent the number of equivalent synchronous power sources in the power system, and ΔP CLimin and ΔP Climax Let ΔP represent the minimum and maximum power adjustments for the ith node in the power system, respectively, where n represents the number of nodes in the power system. CLi P represents the flexible up / down adjustment power of the i-th node in the power system. exp This represents the amount of flexible load power that the power system expects to cut off.

[0086] To facilitate understanding of the above technical solutions of the present invention, the following further describes the above technical solutions of the present invention from the perspectives of architecture and principle, as follows:

[0087] The application proposes a low-frequency flexible load control strategy considering the space-time distribution characteristics: firstly, the system node frequency model is established from the generation mechanism of the frequency space-time distribution characteristics; then, considering the influence of disturbance position on the initial power distribution of each synchronous machine, a low-frequency load shedding strategy is proposed by adjusting the size of the load at different positions to reduce the frequency space-time distribution characteristics; finally, the IEEE39 model is simulated using power system simulation software (such as DlgSILENT\PowerFactory software), and the simulation results prove the superiority of the strategy.

[0088] 1. From the mechanism of node frequency generation, a simplified model of network, power supply and load is established to provide a theoretical basis for the analysis in the subsequent chapters.

[0089] a. Network model

[0090] In order to analyze the construction mechanism of the instantaneous frequency of the power system, the power system frequency response analysis method based on DC power flow is used, and the network model can be simplified as:

[0091] P=Bθ

[0092] In the formula, P represents the net active power injection vector of each node, B represents the admittance matrix of the power system, and θ represents the voltage phase angle vector of each node.

[0093] From the principle of frequency divider, in a synchronous AC power system, the frequency of each node is generated by the speed of each synchronous power source, that is, the active-angle network equation can be expressed as:

[0094] PG-PL=B0θ

[0095] In the formula, P G represents the active power output column vector of the synchronous power source, P L represents the active power output column vector of the load, B represents the admittance matrix of the power system, and θ represents the voltage phase angle vector of each node.

[0096] b. Synchronous machine model

[0097] The external characteristic of the synchronous machine is a voltage source, and the external characteristic of the synchronous machine is a voltage source. The stator winding resistance and the salient pole effect of the synchronous power source are ignored. Assuming that the internal potential and the terminal voltage of the synchronous machine are 1.0, the active power P G of the synchronous machine can be expressed as:

[0098] P G =B G (δ-θ)

[0099] In the formula, P G represents the active power output column vector of the synchronous power source, B Gwhere δ represents the rotor angle of the synchronous machine; and θ represents the phase angle vector of the terminal voltage of the machine.

[0100] c. Load model

[0101] The static active power model of the load simplified model only considers the frequency regulation effect of the load and can be expressed as:

[0102] P L = P LN (1 + K L Δf)

[0103] In the formula, P L represents the actual active power absorbed by the load, P LN represents the active power absorbed by the load at the rated voltage and frequency, K L represents the active power regulation effect coefficient of the load, and Δf represents the frequency deviation.

[0104] The power of the flexible load is adjusted according to the user temperature, and in order to simplify the calculation, the frequency regulation effect thereof can be ignored in this paper, and the equivalent constant power load model is obtained, that is, K L = 0, which can be expressed as:

[0105] P CL = P CLN

[0106] In the formula, P CL represents the actual active power absorbed by the flexible load, and P CLN represents the active power absorbed by the flexible load at the rated voltage and frequency.

[0107] d. New energy equivalent model

[0108] (1) Grid-following new energy

[0109] For grid-following new energy, the external characteristic thereof is a current source, and therefore the simplified model thereof can be expressed as:

[0110] P GFL = P GFLN (1 - K GFL Δf)

[0111] In the formula, P GFL represents the actual output of the grid-following power source, P GFLN represents the rated output of the grid-following power source, K GFL represents the active power regulation effect coefficient of the grid-following power source, and Δf represents the frequency deviation of the node where the grid-following power source is located.

[0112] (2) Grid-forming new energy

[0113] For grid-forming new energy, the external characteristic thereof is a voltage source, and therefore the simplified model thereof can be expressed as:

[0114] P GFM =B GFM (δ GFM -θ)

[0115] In the formula, P GFM Indicates the actual output of the grid-connected power supply, δ GFM B represents the virtual rotor angle of the network configuration. GFM θ represents the virtual internal susceptance of a grid-connected power source, and θ represents the node voltage phase angle.

[0116] Therefore, as Figure 4 As shown, the network equations for a typical system node frequency model containing new energy sources can be expressed as:

[0117] P G +P GFM +P GFL -P L -P CL =B0θ

[0118] In the formula, P G P represents the column vector of active power output of the synchronous power source. GFM P represents the actual output of a grid-connected power supply. GFL Indicates the actual output of the network power supply, P L P represents the actual active power absorbed by the load. CL B0 represents the active power actually absorbed by the flexible load, B0 represents the power system node susceptance matrix, and θ represents the voltage phase angle vector of each node in the power system.

[0119] Figure 4 In this context, GFL represents a grid-connected power supply, GFM represents a network-connected power supply, L represents a normal load, CL represents a controllable load, G represents a synchronous machine, and B represents a synchronous machine. 12 B 23 B represents the susceptance between nodes 1 and 2 and between nodes 2 and 3, respectively. G B GFM These represent the internal susceptance of a synchronous machine and the equivalent internal susceptance of a grid-type power supply, respectively.

[0120] Among them, the power system node susceptance matrix B0 is:

[0121]

[0122] Furthermore, from the expressions of the simplified load model and grid-connected renewable energy sources, it can be seen that grid-connected renewable energy sources and loads have similar frequency response characteristics. To simplify the calculation, they can be combined to obtain the equivalent load active power output column vector, which can be expressed as:

[0123] P EL =PL -P GFL = P ELN (I + K EL f)

[0124]

[0125] where P EL represents the equivalent load active power output column vector, P L represents the actual active power absorbed by the load, P GFL represents the actual output of the grid-connected type power source, P ELN represents the equivalent load absorbed rated active power column vector, I represents the unit vector, K EL represents the equivalent load active power regulation effect coefficient column vector, and f represents the node frequency.

[0126] Similarly, according to the synchronous machine model expression and the grid-connected type new energy expression, it can be seen that the grid-connected type new energy and the synchronous machine have similar frequency response characteristics, in order to simplify the calculation, they can be combined, and the equivalent power active output column vector P EG is expressed as:

[0127] P EG = P G + P GFM = B EG (δ EG - θ)

[0128]

[0129] where P EG represents the equivalent power active output column vector, P G represents the synchronous power active output column vector, P GFM represents the actual output of the grid-connected type power source, B EG represents the equivalent power internal inductance diagonal matrix, δ EG represents the equivalent power rotor angle column vector, θ represents the voltage phase angle vector of each node of the power system, B EG,j represents the jth equivalent power internal inductance diagonal matrix, B G,j represents the jth synchronous machine internal inductance diagonal matrix, B GFM,j represents the jth grid-connected type power source virtual internal inductance diagonal matrix, δ EG,j represents the jth equivalent power rotor angle column vector, δ j represents the jth synchronous machine rotor angle column vector, δ GFM,j represents the jth grid-connected type power source virtual rotor angle column vector.

[0130] The equivalent load active power column vector expression and the equivalent power active power column vector expression are substituted into the network equation of the typical system node frequency model containing new energy, and the network equation of the optimized typical system node frequency model containing new energy can be obtained:

[0131] P EG -P EL -P CL =B0θ

[0132] B EG (δ EG -θ)-P ELN (I+K EL f)-P CL =B0θ

[0133] In the formula, P EG represents the equivalent power active power column vector, P CL represents the active power actually absorbed by the flexible load, P EL represents the equivalent load active power column vector, B0represents the node admittance matrix of the power system, θ represents the voltage phase angle vector of each node of the power system, B EG represents the equivalent power internal admittance diagonal matrix, δ EG represents the equivalent power rotor angle column vector, P ELN represents the equivalent load active power column vector, I represents the unit vector, K EL represents the equivalent load active power adjustment effect coefficient column vector, f represents the node frequency, P CL represents the active power actually absorbed by the flexible load.

[0134] In a synchronous alternating current power system, the rotor angle δ of the synchronous power and the speed f G , and the node voltage phase angle θ and the node frequency f satisfy the following relationship:

[0135]

[0136] The network equation of the optimized typical system node frequency model containing new energy is differentiated with respect to time and subjected to Laplace transform, and the relationship expression between the node frequency and the synchronous power speed is obtained as follows:

[0137] f(s)=W(s)f EG (s)

[0138] W(s)=(B0+B EG +sK EL P ELN ) -1 B EG

[0139]

[0140] where W represents the weight matrix of node frequency, w ij represents the weight of the power source at node j on the frequency of node i, f(s) represents the frequency domain expression of node frequency, W(s) represents the frequency domain form of the weight matrix of node frequency, f EG (s) represents the frequency domain expression of the equivalent power source speed, B0represents the admittance matrix of the power system node, B EG represents the equivalent power source internal admittance diagonal matrix, K EL represents the equivalent load active power adjustment effect coefficient column vector, P ELN represents the equivalent load absorbed rated active power column vector, s represents the complex variable in Laplace transform.

[0141] Specifically, by performing Laplace inverse transform on the expression of the relationship between node frequency and synchronous power speed, the time domain expression of node frequency can be obtained.

[0142] 2. Based on the above theoretical analysis, by considering the time and space distribution characteristics of frequency, a load shedding model of new energy power system is built, including an optimization objective function for reducing node frequency deviation, a flexible load shedding power distribution method and an optimization solving process.

[0143] 2.1 Initial disturbance distribution

[0144] When the system is disturbed, the initial disturbance is distributed according to the electrical distance between the power source and the disturbance occurrence site, and the specific expression is as follows: by substituting the equivalent power source active power output column vector expression into the network equation of the optimized node frequency model of the typical system containing new energy, the following equation can be obtained:

[0145]

[0146] By substituting the above formula into the equivalent power source active power output column vector expression, the following equation is obtained:

[0147] P EG =P G +P GFM

[0148] =B EG [I-(B0+B EG ) -1 B EG ]δ EG

[0149] +B EG (B0+B EG ) -1 (P EL +P CL )

[0150] =BEG (I-W)δ EG +W T (P EL +P CL )

[0151] Therefore, when the system flexible load generates a disturbance of ΔP CL , the change of the instantaneous electromagnetic power of the synchronous power source at this time ΔP EG is:

[0152] ΔP EG = W T ΔP CL

[0153] In the formula, ΔP EG represents the change of the instantaneous electromagnetic power of the synchronous power source, W T represents the transpose matrix of the weight matrix of the node frequency, ΔP CL represents the flexible load disturbance vector.

[0154] It is shown by the above formula that when the power system generates a power disturbance, the unbalanced electromagnetic power will be distributed according to the frequency weight of the synchronous power source at the node where the disturbance occurs.

[0155] 2.2, According to the analysis of 2.1, the process of low-frequency cutting flexible load can be equivalent to the disturbance of load reduction, and the initial power distribution of each synchronous power source will be according to the expression of the change of the instantaneous electromagnetic power of the synchronous power source. According to the mechanism of the frequency space-time characteristics, because the proportion of the inertia size of the synchronous power source does not match the distribution proportion of the node frequency weight matrix W, a large deviation of the node frequency is finally caused. Therefore, this paper will optimize the above problems, reasonably distribute the cutting power of the flexible load at different positions, reduce the deviation between the two proportions, and the objective function can be represented as:

[0156]

[0157]

[0158] In the formula, ΔP EGj represents the initial disturbance power of the jth equivalent synchronous power source, ΔP Hj represents the disturbance power of the jth equivalent synchronous power source according to its inertia size, m represents the number of equivalent synchronous power sources in the power system, w ij represents the influence weight of the power source at node j on the frequency of node i, n represents the number of nodes in the power system, ΔP CLi represents the up and down power of the flexible load at the ith node in the power system, H j represents the inertia size of the jth equivalent synchronous power source.

[0159] where ΔP CLi The power constraints need to be satisfied, which can be expressed as:

[0160] ΔP CLimin ≤ ΔP CLi ≤ ΔP CLimax i = 1, 2, …, n

[0161]

[0162] ΔP CLimin and ΔP Climax represent the minimum and maximum power of the i-th node in the power system, respectively, n represents the number of nodes in the power system, and ΔP CLi represents the up and down power of the i-th node in the power system, P exp represents the expected flexible load power to be cut off in the power system.

[0163] where the expected flexible load power to be cut off in the power system can be calculated by the following formula:

[0164]

[0165] In the formula, P exp represents the expected flexible load power to be cut off in the power system, κ L represents the equivalent load frequency regulation coefficient of the power system, Δf * represents the unit value of the deviation between the frequency stability value after load shedding and the rated frequency, f ss and f N represent the frequency stability value after load shedding and the rated frequency, respectively, ΔP L represents the disturbance size, P LN represents the total active power of the system load, κ i represents the equivalent load frequency regulation coefficient, and P LNi represents the power size of the i-th load.

[0166] where the disturbance size ΔP L can be obtained by the center frequency estimation of the system inertia:

[0167]

[0168] In the formula, H COI and f COI represent the COI inertia and COI frequency, respectively, ΔP L represents the disturbance size, and m represents the number of equivalent synchronous power sources in the system. H j represents the inertia size of the j-th equivalent synchronous power source, and f ifj(t) represents the frequency of the jth equivalent synchronous power node, t represents time.

[0169] In an ideal state, after flexible load shedding, the synchronous power should be shared according to the inertia proportion, i.e. EG = ΔP H Substituting it into the expression of the change of the instantaneous electromagnetic power of the synchronous power, we have:

[0170] ΔP H = W T ΔP CL

[0171] In the formula, ΔP H represents, W T represents the transpose matrix of the weight matrix of the node frequency, ΔP CL represents the flexible load disturbance vector.

[0172] 3. Control strategy of low-frequency flexible load shedding

[0173] The control strategy flow of low-frequency flexible load shedding is shown in Figure 5 It adopts a double-layer control architecture, the upper layer is a load control center, and the lower layer is a local load control device.

[0174] The upper layer load control center realizes the solution of the node frequency by receiving the system susceptance matrix, power data, load data and other information, obtains the node frequency weight matrix information; through the solution of the power inertia and the COI frequency, the expected load shedding amount is calculated through the expression of the expected flexible load shedding power of the power system, then the load control center optimizes the flexible load shedding power according to the node frequency weight matrix, the expected load shedding amount, the expected load shedding amount of each node flexible load, and other information, and distributes the distribution results to each node flexible load local device.

[0175] The main functions of the lower layer load local control device include flexible load running situation awareness, adjustable power evaluation and power control. The flexible load running situation awareness refers to that the load local control device realizes real-time monitoring of indoor and outdoor temperature, weather, load running power, rated power, node frequency and other information through the measurement device; the adjustable power evaluation refers to that the load local control device evaluates the adjustable power of the flexible load according to the monitored data, taking into account user comfort and economic operation and other factors, and sends the evaluation results to the upper layer load control center regularly; the load power control is that the load local control device controls the local power of the flexible load according to the power instruction issued by the upper layer load control center.

[0176] The communication between the load control center and the on-site control device is realized through a 4G / 5G cloud platform. Since the state information such as indoor and outdoor temperature, weather, and load operation power will not change suddenly in a short time, the load adjustable power evaluation period can be set relatively long, and in this paper, it is set to 5 minutes. When a disturbance occurs, the load control center can calculate according to the evaluation result of the last period to improve the calculation efficiency. The node frequency and load reduction amount instructions have high real-time requirements, and the 4G / 5G cloud platform can meet the requirements of the control in this paper.

[0177] 4、To verify the effectiveness of the low-frequency cut flexible load proposed in this paper, simulation verification is carried out in DIgSILENT\PowerFactory using IEEE39 model. On the basis of the original standard model, the synchronous machines of nodes 33 and 38 are replaced by equal-capacity grid-following power sources, and the synchronous machine of node 39 is replaced by an equal-capacity grid-forming power source. The system wiring diagram is shown in Figure 6 , wherein 1-39 represents 39 bus nodes, WT1 represents a grid-forming power source, WT2 and WT3 represent grid-following power sources, and G2, G3, G5, G6, G7, G8 and G10 represent synchronous machines.

[0178] The present application adopts load surge to demonstrate the frequency change in the transient process of the example system. When the time domain simulation is 2s, the load power of node 4 is suddenly increased by 500MW, Figure 7 Two load shedding schemes are given as follows:

[0179] (1) Scheme 1: Concentratedly cut off the high-power load of node 20.

[0180] (2) Scheme 2: Based on the load shedding scheme proposed in this paper: The flexible load on nodes 8, 16, 20 and 29 is evaluated, and the flexible load adjustment power is set with the minimum frequency deviation of each node as the optimization target.

[0181] The comparison of system node frequency simulation results is shown in Figures 8-11 , wherein Figure 8 is the comparison of the frequency change of each node, Figure 9 is the comparison of the maximum frequency change rate of each node, Figure 10 is the comparison of the maximum frequency deviation of each node after load shedding, Figure 11 is the comparison of the maximum frequency change rate of each node after load shedding. From Figures 8-9It can be seen that after the same size load is cut off, the frequency deviation and the frequency change rate deviation of each node caused by the concentrated load cutting of scheme 1 are larger, and the maximum frequency change rate deviation of the node after the load is cut off is higher than the deviation caused by the disturbance, which has a bad impact on the system; and after the node space-time distribution characteristics are considered in scheme 2, the frequency deviation and the frequency change rate deviation of each node caused are significantly reduced, and the steady-state frequency of the system caused by scheme 2 is 49.91 Hz, while that of scheme 1 is 49.88 Hz, which proves the superiority of scheme 2.

[0182] By Figures 10-11 It can be further compared that the maximum frequency deviation of each node in scheme 2 is reduced by 65.01% than that in scheme 1, the maximum frequency change rate deviation of each node is reduced by 54.39%, the frequency space-time distribution characteristics are obviously weakened, the greater impact of the load cutting on the system frequency is prevented, and the frequency stability of the system is improved.

[0183] At the same time, the rotational speeds of each synchronous machine are compared and analyzed, as shown in the table. Figure 12 The rotational speed deviation of each synchronous machine after the load is cut off in scheme 1 is obvious, especially the minimum rotational speed of part of the synchronous machines is lower than that before the load is cut off, which brings a more serious impact on the synchronous machines; and the rotational speed deviation of each synchronous machine in scheme 2 is obviously reduced, and the minimum rotational speed is higher than that before the load is cut off, which is beneficial to the safe and stable operation of the synchronous machines.

[0184] In summary, the present application establishes the frequency models of synchronous machines, loads, new energy and the like from the mechanism of the system frequency space-time distribution characteristics, explains the main indexes affecting the node frequency size, and proposes a low-frequency flexible load cutting strategy for reducing the system frequency deviation and improving the system stability. The conclusions are as follows:

[0185] (1) The node frequency size is obtained by superimposing the rotational speed changes of each synchronous machine according to the weight matrix, and is only related to the network topology.

[0186] (2) The initial node power disturbance is distributed according to the electrical distance, and the mismatch between the synchronous machine inertia size causes the deviation of each node frequency.

[0187] (3) The low-frequency flexible load cutting strategy proposed in the present application can greatly reduce the secondary impact of the load cutting measure on the system frequency, improve the consistency of each node frequency, and the effectiveness and superiority of the strategy are verified through simulation.

[0188] Figure 2 An embodiment of the power low-frequency flexible load cutting control system of the present application is shown.

[0189] In this optional embodiment, the power low-frequency flexible load cutting control system comprises:

[0190] The node frequency weight matrix information calculation module 201 is configured to acquire power data of the power system, and establish a power system node frequency model based on a power system node frequency generation mechanism; and perform node frequency solving based on the power system node frequency model to obtain node frequency weight matrix information.

[0191] The expected flexible load power to be cut off calculation module 203 is configured to perform initial allocation of electromagnetic power based on electrical distances between power sources and disturbance occurrence locations, construct a load cutting-off model of the new energy power system according to the initial allocation result and in combination with time-space distribution characteristics of frequency, and obtain flexible load power to be cut off by the power system by solving the load cutting-off model of the new energy power system.

[0192] The on-site power control module 205 is configured to perform optimized allocation of flexible load cutting-off power according to the node frequency weight matrix information and the flexible load power to be cut off by the power system, and transmit the optimized allocation result to on-site devices of flexible loads of nodes; and the on-site devices of flexible loads of nodes perform on-site power control on the flexible loads according to the optimized allocation result.

[0193] In this optional embodiment, the expression of the power system node frequency model is as follows:

[0194] B EG (δ EG -θ)-P ELN (I+K EL f)-P CL =B0θ

[0195] In the formula, B EG represents an equivalent power source internal susceptance diagonal matrix, δ EG represents an equivalent power source rotor angle column vector, θ represents a voltage phase angle vector of each node of the power system, P ELN represents an equivalent load absorbed rated active power column vector, I represents a unit vector, K EL represents an equivalent load active power adjustment effect coefficient column vector, f represents a node frequency, and P CL represents actual active power absorbed by the flexible load, and B0 represents a node susceptance matrix of the power system.

[0196] In this optional embodiment, the node frequency solving based on the power system node frequency model to obtain the node frequency weight matrix information includes:

[0197] The expression of the power system node frequency model is differentiated with respect to time, and Laplace transformation is performed on the differentiated result to obtain a relationship function between the node frequency and the synchronous power source rotating speed.

[0198] In the synchronous alternating current power system, according to the relationship between the rotor angle and the rotating speed of the synchronous power source and the relationship between the node voltage phase angle and the node frequency, and in combination with the relationship function between the node frequency and the rotating speed of the synchronous power source, the node frequency is solved, and the node frequency weight matrix information is determined according to the node frequency.

[0199] In the optional embodiment, the initial allocation of the electromagnetic power based on the electrical distance between the power source and the disturbance occurrence location comprises:

[0200] According to the similar frequency response characteristics of the grid-connected new energy and the load, the equivalent load active power output column vector is calculated.

[0201] According to the similar frequency response characteristics of the grid-connection new energy and the synchronous machine, the equivalent power source active power output column vector is calculated.

[0202] Based on the equivalent load active power output column vector, the equivalent power source active power output column vector and the power system node frequency model, the change amount of the synchronous power source instantaneous electromagnetic power is calculated, and the change amount of the synchronous power source instantaneous electromagnetic power is taken as the disturbance power of the initial allocation.

[0203] In the optional embodiment, the calculation formula of the change amount of the synchronous power source instantaneous electromagnetic power is:

[0204] ΔP EG =W T ΔP CL

[0205] In the formula, ΔP EG represents the change amount of the synchronous power source instantaneous electromagnetic power, W T represents the transpose matrix of the weight matrix of the node frequency, ΔP CL represents the flexible load disturbance vector.

[0206] In the optional embodiment, according to the initial allocation result and in combination with the time and space distribution characteristics of the frequency, the load shedding model of the new energy power system is constructed, and the expected flexible load power of the power system is obtained by solving the load shedding model of the new energy power system.

[0207] According to the initial allocation result and in combination with the time and space distribution characteristics of the frequency, the objective function and the power constraint condition are established, in which the difference between the disturbance power of the equivalent synchronous power source initial allocation and the disturbance power of the equivalent synchronous power source according to the inertia size is minimized;

[0208] According to the objective function and the power constraint condition, the expected flexible load power of the power system is solved.

[0209] In the optional embodiment, the expression of the objective function of minimizing the difference between the initial allocated disturbance power of the equivalent synchronous power source and the disturbance power allocated according to the inertia size of the equivalent synchronous power source and the power constraint condition is:

[0210]

[0211] ΔP CLimin ≤ΔP CLi ≤ΔP CLimax ,i=1,2,…,n

[0212]

[0213] In the formula, ΔP EGj represents the initial allocated disturbance power of the jth equivalent synchronous power source, ΔP Hj represents the disturbance power allocated according to the inertia size of the jth equivalent synchronous power source, m represents the number of equivalent synchronous power sources in the power system, ΔP CLimin and ΔP Climax respectively represent the minimum power and the maximum power of the ith node flexibility in the power system, n represents the number of nodes in the power system, ΔP CLi represents the up and down power of the ith node flexibility in the power system, P exp represents the expected flexible load power to be cut off in the power system.

[0214] In an embodiment, a computer device, which can be a server, can have an internal structure diagram as shown in Figure 3 The computer device includes a processor, a memory and a network interface connected through a system bus. 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, a computer program and a database. The internal memory provides an environment for the operating system and the computer program in the non-volatile storage medium to run. The database of the computer device is used to store static information and dynamic information data. The network interface of the computer device is used to communicate with external terminals through network connection. The computer program is executed by the processor to implement the steps in the above method embodiments.

[0215] Those skilled in the art can understand that Figure 3 the structure shown in the figure is only a block diagram of part of the structure related to the scheme of the present application, and does not constitute a limitation on the computer device to which the scheme of the present application is applied. The specific computer device can include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0216] In addition, the present application further provides a computer device, comprising a memory and a processor, the memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0217] In addition, the present application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the steps in the above method embodiments.

[0218] A person of ordinary skill in the art can understand that all or part of the processes in the above method embodiments can be completed by a computer program instructing related hardware, and the computer program can be stored in a non-volatile computer readable storage medium. When the computer program is executed, the computer program can include the processes of the above embodiments. Any reference to memory, storage, database or other medium in each embodiment of the present application can include at least one of non-volatile and volatile memory. The non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory. The volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, the RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0219] The present application is not limited to the structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A method for controlling low-frequency flexible load shedding in power systems, characterized in that, The method includes the following steps: The power system acquires power data and establishes a power system node frequency model based on the power system node frequency generation mechanism; the node frequencies are solved based on the power system node frequency model to obtain the node frequency weight matrix information. The electromagnetic power is initially allocated based on the electrical distance between the power source and the disturbance location. Based on the initial allocation results and combined with the spatiotemporal distribution characteristics of the frequency, a load shedding model of the new energy power system is constructed. By solving the load shedding model of the new energy power system, the expected flexible load power to be shedding by the power system is obtained. Based on the node frequency weight matrix information and the power of flexible loads to be cut off by the power system, the power of flexible loads to be cut off is optimized and allocated, and the optimized allocation results are transmitted to the local flexible load devices at each node; the local flexible load devices at each node perform local power control on the flexible loads according to the optimized allocation results.

2. The power low-frequency flexible load shedding control method according to claim 1, characterized in that, The expression for the power system node frequency model is: B EG (d EG -i)-P ELN (I+K EL f)-P CL =B0θ In the formula, B EG δ represents the diagonal array of internal susceptance of the equivalent power source. EG P represents the equivalent power source rotor angle column vector, θ represents the voltage phase angle vector of each node in the power system, and P represents the equivalent power source rotor angle column vector. ELN This represents the column vector of rated active power absorbed by the equivalent load, where I represents a unit vector, and K... EL This represents the column vector of equivalent load active power regulation effect coefficients, where f represents the node frequency and P... CL B0 represents the active power actually absorbed by the flexible load, and B0 represents the power system node susceptance matrix.

3. The power low-frequency flexible load shedding control method according to claim 2, characterized in that, The process of solving for the node frequency based on the power system node frequency model to obtain the node frequency weight matrix information includes the following steps: The expression of the power system node frequency model is differentiated with respect to time, and the result of the differentiation is subjected to a Laplace transform to obtain the relationship function between the node frequency and the synchronous power source speed. In a synchronous AC power system, the node frequency is calculated based on the relationship between the rotor angle and speed of the synchronous power source and the relationship between the node voltage phase angle and the node frequency, combined with the relationship function between the node frequency and the speed of the synchronous power source. The node frequency weight matrix information is then determined based on the node frequency.

4. The power low-frequency flexible load shedding control method according to claim 1, characterized in that, The initial allocation of electromagnetic power based on the electrical distance between the power source and the location of the disturbance includes the following steps: Based on the frequency response characteristics similar to those of grid-connected new energy sources and loads, the equivalent load active power output column vector is calculated. Based on the similar frequency response characteristics of grid-type new energy sources and synchronous machines, the active power output column vector of the equivalent power source is calculated. Based on the equivalent load active power output column vector, the equivalent power source active power output column vector, and the power system node frequency model, the change in instantaneous electromagnetic power of the synchronous power source is calculated, and the change in instantaneous electromagnetic power of the synchronous power source is used as the initial allocated disturbance power.

5. The power low-frequency flexible load shedding control method according to claim 4, characterized in that, The formula for calculating the change in instantaneous electromagnetic power of the synchronous power supply is: ΔP EG =W T ΔP CL In the formula, ΔP EG W represents the instantaneous change in electromagnetic power of the synchronous power source. T ΔP represents the transpose of the weight matrix representing the node frequencies. CL This represents the flexible load disturbance vector.

6. The power low-frequency flexible load shedding control method according to claim 1, characterized in that, The process of constructing a load shedding model for the new energy power system based on the initial allocation results and the spatiotemporal distribution characteristics of frequency, and then solving the load shedding model to obtain the expected flexible load power to be shedding by the power system includes the following steps: Based on the initial allocation results and combined with the spatiotemporal distribution characteristics of the frequency, an objective function and power constraint conditions are established to minimize the difference between the disturbance power initially allocated by the equivalent synchronous power source and the disturbance power allocated by the equivalent synchronous power source according to its inertia. Based on the objective function and power constraints, the desired flexible load power to be removed from the power system is determined.

7. The power low-frequency flexible load shedding control method according to claim 6, characterized in that, The objective function and power constraint for minimizing the difference between the initial disturbance power allocated by the equivalent synchronous power source and the disturbance power allocated by the equivalent synchronous power source according to its inertia are expressed as follows: ΔP CLimin ≤ΔP CLi ≤ΔP CLimax ,i=1,2,…,n In the formula, ΔP EGj Let ΔP represent the initial disturbance power allocated to the j-th equivalent synchronous power source. Hj Let ΔP represent the disturbance power distributed by the j-th equivalent synchronous power source according to its inertia, m represent the number of equivalent synchronous power sources in the power system, and ΔP CLimin and ΔP Climax Let ΔP represent the minimum and maximum power adjustments for the ith node in the power system, respectively, where n represents the number of nodes in the power system. CLi P represents the flexible up / down adjustment power of the i-th node in the power system. exp This represents the amount of flexible load power that the power system expects to cut off.

8. A power low-frequency flexible load shedding control system, characterized in that, The system includes: The node frequency weight matrix information calculation module is used to acquire power data of the power system and establish a power system node frequency model based on the power system node frequency generation mechanism; based on the power system node frequency model, the node frequency is solved to obtain the node frequency weight matrix information. The module for calculating the expected flexible load power to be cut off is used to initially allocate electromagnetic power based on the electrical distance between the power source and the location where the disturbance occurs. Based on the initial allocation results and combined with the spatiotemporal distribution characteristics of the frequency, a load shedding model of the new energy power system is constructed. By solving the load shedding model of the new energy power system, the expected flexible load power to be cut off by the power system is obtained. The local power control module is used to optimize the allocation of flexible load shedding power based on the node frequency weight matrix information and the power of flexible loads to be shelved by the power system, and transmit the optimized allocation results to the local flexible load devices at each node; the local flexible load devices at each node perform local power control on the flexible loads based on the optimized allocation results.

9. The power low-frequency flexible load shedding control system according to claim 8, characterized in that, The expression for the power system node frequency model is: B EG (d EG -i)-P ELN (I+K EL f)-P CL =B0θ In the formula, B EG δ represents the diagonal array of internal susceptance of the equivalent power source. EG P represents the equivalent power source rotor angle column vector, θ represents the voltage phase angle vector of each node in the power system, and P represents the equivalent power source rotor angle column vector. ELN This represents the column vector of rated active power absorbed by the equivalent load, where I represents a unit vector, and K... EL This represents the column vector of equivalent load active power regulation effect coefficients, where f represents the node frequency and P... CL B0 represents the active power actually absorbed by the flexible load, and B0 represents the power system node susceptance matrix.

10. The power low-frequency flexible load shedding control system according to claim 9, characterized in that, The node frequency calculation based on the power system node frequency model yields the following node frequency weight matrix information: The expression of the power system node frequency model is differentiated with respect to time, and the result of the differentiation is subjected to a Laplace transform to obtain the relationship function between the node frequency and the synchronous power source speed. In a synchronous AC power system, the node frequency is calculated based on the relationship between the rotor angle and speed of the synchronous power source and the relationship between the node voltage phase angle and the node frequency, combined with the relationship function between the node frequency and the speed of the synchronous power source. The node frequency weight matrix information is then determined based on the node frequency.

11. The power low-frequency flexible load shedding control system according to claim 8, characterized in that, The initial allocation of electromagnetic power based on the electrical distance between the power source and the location of the disturbance includes: Based on the frequency response characteristics similar to those of grid-connected new energy sources and loads, the equivalent load active power output column vector is calculated. Based on the similar frequency response characteristics of grid-type new energy sources and synchronous machines, the active power output column vector of the equivalent power source is calculated. Based on the equivalent load active power output column vector, the equivalent power source active power output column vector, and the power system node frequency model, the change in instantaneous electromagnetic power of the synchronous power source is calculated, and the change in instantaneous electromagnetic power of the synchronous power source is used as the initial allocated disturbance power.

12. The power low-frequency flexible load shedding control system according to claim 11, characterized in that, The formula for calculating the change in instantaneous electromagnetic power of the synchronous power supply is: ΔP EG =W T ΔP CL In the formula, ΔP EG W represents the instantaneous change in electromagnetic power of the synchronous power source. T ΔP represents the transpose of the weight matrix representing the node frequencies. CL This represents the flexible load disturbance vector.

13. The power low-frequency flexible load shedding control system according to claim 8, characterized in that, Based on the initial allocation results and combined with the spatiotemporal distribution characteristics of frequency, a load shedding model for the new energy power system is constructed. By solving the load shedding model of the new energy power system, the expected flexible load power to be shedding by the power system is obtained, including: Based on the initial allocation results and combined with the spatiotemporal distribution characteristics of the frequency, an objective function and power constraint conditions are established to minimize the difference between the disturbance power initially allocated by the equivalent synchronous power source and the disturbance power allocated by the equivalent synchronous power source according to its inertia. Based on the objective function and power constraints, the desired flexible load power to be removed from the power system is determined.

14. The power low-frequency flexible load shedding control system according to claim 13, characterized in that, The objective function and power constraint for minimizing the difference between the initial disturbance power allocated by the equivalent synchronous power source and the disturbance power allocated by the equivalent synchronous power source according to its inertia are expressed as follows: ΔP CLimin ≤ΔP CLi ≤ΔP CLimax ,i=1,2,…,n In the formula, ΔP EGj Let ΔP represent the initial disturbance power allocated to the j-th equivalent synchronous power source. Hj Let ΔP represent the disturbance power distributed by the j-th equivalent synchronous power source according to its inertia, m represent the number of equivalent synchronous power sources in the power system, and ΔP CLimin and ΔP Climax Let ΔP represent the minimum and maximum power adjustments for the ith node in the power system, respectively, where n represents the number of nodes in the power system. CLi P represents the flexible up / down adjustment power of the i-th node in the power system. exp This represents the amount of flexible load power that the power system expects to cut off.

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

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

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