Optimal frequency control method and device for improving power supply level of extreme weather

Abstract

The application discloses an optimal frequency control method and device for improving power supply level of extreme weather, and the method comprises the following steps: constructing a frequency response model of an island power grid containing frequency modulation of thermal power generating units and frequency modulation of network-type energy storage; constructing a frequency safety constraint according to the frequency response model of the island power grid; the frequency safety constraint comprises constraints of maximum frequency deviation, steady-state frequency deviation and maximum frequency change rate; determining an out-of-limit condition according to the frequency safety constraint when a load disturbance occurs; when the maximum frequency deviation or the steady-state frequency deviation is out of limit, obtaining an equivalent droop coefficient range of the network-type energy storage according to the constraint of the steady-state frequency deviation and starting droop control; when the maximum frequency change rate is out of limit, obtaining an equivalent inertia coefficient range of the network-type energy storage according to the constraint of the maximum frequency change rate and starting inertia control; and performing frequency control according to the equivalent droop coefficient range and the equivalent inertia coefficient range in combination with the frequency response model of the island power grid.

Description

Technical Field

[0001] This invention relates to the field of power supply level regulation, and in particular to an optimal frequency control method and apparatus for improving power supply levels during extreme weather. Background Technology

[0002] In the event of an emergency grid failure, islanded grids can be constructed using renewable energy sources to provide power to critical loads in designated areas, thereby reducing the scope of power outages and enhancing the grid's resilience to extreme disasters. However, the establishment of an islanded grid can cause a step power surge, and the resulting frequency instability may prevent the safe establishment of the islanded grid.

[0003] Currently, scholars both domestically and internationally have conducted extensive research on frequency support for isolated systems under extreme weather conditions. Grid-based energy storage, based on virtual synchronous machine technology, synchronizes with the grid by simulating the characteristics of conventional frequency-regulating units. It can provide inertial support and damping regulation with high precision and without delay, serving as an auxiliary resource for frequency regulation in isolated grids. Some scholars have proposed a control method for grid-based energy storage to assist wind farms in participating in rapid frequency response, enabling them to possess good frequency regulation capabilities under various wind conditions. Others have proposed frequency dead-zone design ideas for grid-based energy storage under different synchronization methods, enhancing the frequency response speed and stability of grid-based energy storage while reducing its frequency regulation output. Still others have applied grid-based energy storage to rapid frequency support in an actual regional isolated grid, significantly improving the overall frequency regulation performance of the system in different simulation cases. Although the above research fully verifies the frequency regulation advantages of grid-based energy storage, due to current technological limitations, its capacity is relatively small, its frequency regulation cost is high, and it is prone to overcharging and over-discharging, affecting subsequent frequency regulation capabilities. Furthermore, most research methods derive frequency response patterns through time-domain simulation or complex models, making it difficult to quickly and accurately obtain key frequency safety indicators such as maximum frequency deviation, and thus failing to meet the rapid frequency support requirements for isolated systems under extreme weather conditions.

[0004] Therefore, a new technical solution is urgently needed to address the technical problem of how to meet the high-frequency support requirements of isolated power grids under extreme weather conditions. Summary of the Invention

[0005] This invention provides an optimal frequency control method and apparatus for improving power supply levels in extreme weather, in order to solve the technical problem of how to meet the rapid frequency support requirements of isolated power grids under extreme weather conditions.

[0006] To achieve the above objectives, the present invention provides an optimal frequency control method for improving power supply levels during extreme weather, comprising:

[0007] Construct a frequency response model for an islanded power grid that includes frequency regulation by thermal power units and frequency regulation by grid-connected energy storage; construct frequency safety constraints based on the islanded power grid frequency response model; the frequency safety constraints include constraints on maximum frequency deviation, steady-state frequency deviation, and maximum rate of frequency change; determine the over-limit situation based on the frequency safety constraints during load disturbances;

[0008] When the maximum frequency deviation or steady-state frequency deviation exceeds the limit, the equivalent droop coefficient range of the grid-type energy storage is obtained according to the constraint of the steady-state frequency deviation, and droop control is initiated; when the maximum frequency change rate exceeds the limit, the equivalent inertia coefficient range of the grid-type energy storage is obtained according to the constraint of the maximum frequency change rate, and inertia control is initiated; frequency control is performed based on the equivalent droop coefficient range and the equivalent inertia coefficient range combined with the islanded power grid frequency response model.

[0009] Preferably, the frequency response model for an islanded power grid that includes frequency regulation by thermal power units and frequency regulation by grid-based energy storage includes:

[0010] Using thermal power units as conventional frequency regulating units and considering grid-based energy storage, a frequency response model for an islanded power grid is constructed. :

[0011] ;

[0012] ;

[0013] in, Power disturbance for isolated power grids; This refers to the frequency regulation power of thermal power units; Frequency regulation power for grid-type energy storage; and These are the equivalent inertia coefficient and damping coefficient of an isolated power grid, respectively. and The first in the isolated power grid The inertia coefficient and damping coefficient of each thermal power unit; For the first The capacity of each thermal power unit; For the Laplace operator; This represents the total number of thermal power units.

[0014] Preferably, the frequency regulation power of the thermal power unit includes:

[0015] ;

[0016] ;

[0017] in, For the first Unit frequency regulation power of each thermal power unit; For the first The response transfer function of a thermal power unit; For the speed controller transfer function; For the first The response time constant of each thermal power unit; For the transfer function of the reheat turbine; , and These represent the time constants of the steam turbine, governor, and reheat steam turbine in a thermal power unit, respectively. , and This represents the percentage of total turbine power allocated to the three turbine stages: high-pressure, medium-pressure, and low-pressure.

[0018] Preferably, the frequency regulation power of grid-type energy storage includes:

[0019] ;

[0020] in, For frequency regulation power under droop control of grid-type energy storage; Frequency regulation power under inertial control of grid-type energy storage; For the first The response transfer function of a grid-type energy storage system; For the first The time constant of a grid-type energy storage system; For the first The droop coefficient of individual grid-type energy storage; and The first The inertia coefficient and damping coefficient of individual grid-type energy storage; The equivalent inertia coefficient for grid-type energy storage; The equivalent damping coefficient for grid-type energy storage; This represents the total number of grid-type energy storage systems.

[0021] Preferably, the steady-state frequency deviation and the maximum rate of frequency change include:

[0022] The maximum rate of change of frequency is obtained according to the initial value theorem. According to the final value theorem, the steady-state frequency deviation is obtained. :

[0023] .

[0024] Preferably, the maximum frequency deviation includes:

[0025] The increase in the frequency regulation power of thermal power units is approximated as linearly equivalent, and when the frequency regulation power of thermal power units... Equal to disturbance When the frequency reaches its lowest value, the equivalent frequency regulation power of the thermal power unit is... Represented as:

[0026] ;

[0027] in, The time it takes for the frequency to reach its lowest point;

[0028] Equivalent frequency regulation power of the joint thermal power unit and isolated power grid frequency response model Ignoring the effect of damping on frequency, if the grid-type energy storage in the islanded power grid does not participate in frequency regulation, the frequency time-domain equation of the islanded power grid is obtained. :

[0029] ;

[0030] in, Let be the integral variable, representing time 0 to 1. Any time between moments;

[0031] Pick = and to Differentiating both ends simultaneously yields:

[0032] ;

[0033] Further combined with the frequency regulation power of thermal power units The expression for the system's total frequency response is obtained. :

[0034] ;

[0035] When the frequency reaches its lowest point, the frequency regulation power of the thermal power unit equals the system power disturbance, and at this time, the first relationship exists:

[0036] ;

[0037] in, Indicates to [ Perform the inverse Laplace transform; express System power disturbance at any given time;

[0038] Solving the first relation, we get The value; according to The value yields the maximum frequency deviation. :

[0039] .

[0040] Preferably, the range of equivalent droop coefficients for grid-type energy storage, obtained based on the constraint of steady-state frequency deviation, includes:

[0041] Based on steady-state frequency deviation The expression yields the equivalent droop coefficient of the grid-type energy storage. Scope:

[0042] ;

[0043] in, It is the minimum equivalent droop coefficient.

[0044] Preferably, the range of equivalent inertia coefficients for grid-type energy storage, obtained based on the constraint of the maximum rate of change of frequency, includes:

[0045] Based on the maximum frequency change rate The expression yields the equivalent inertia coefficient of the grid-type energy storage. Scope:

[0046] ;

[0047] in, It is the smallest equivalent inertia coefficient.

[0048] Preferably, frequency control based on the droop coefficient range and the equivalent inertia coefficient range, combined with the islanded power grid frequency response model, includes:

[0049] Based on the range of droop coefficient and equivalent inertia coefficient, the frequency regulation power of grid-type energy storage is further expressed as:

[0050] ;

[0051] in, This indicates the droop control trigger signal; This indicates the inertial control trigger signal;

[0052] The state-of-charge (SOC) update methods for grid-based energy storage include:

[0053] ;

[0054] in, State of charge for grid-connected energy storage; This is the initial frequency modulation time; This refers to the rated capacity of the energy storage. This refers to the cumulative charge and discharge energy of grid-type energy storage.

[0055] The present invention also provides an optimal frequency control device for improving power supply levels in extreme weather, and the device for the method of the present invention includes a first module, a second module, a third module and a fourth module;

[0056] The first module is used to construct the frequency response model of an islanded power grid that includes frequency regulation by thermal power units and frequency regulation by grid-type energy storage.

[0057] The second module is used to construct frequency security constraints based on the islanded power grid frequency response model; the frequency security constraints include constraints on maximum frequency deviation, steady-state frequency deviation, and maximum rate of frequency change;

[0058] The third module is used to determine the over-limit situation based on frequency safety constraints during load disturbances; when the maximum frequency deviation or steady-state frequency deviation exceeds the limit, the droop coefficient range of each grid-type energy storage is obtained based on the steady-state frequency deviation constraint and droop control is initiated; when the maximum frequency change rate exceeds the limit, the equivalent inertia coefficient range of the grid-type energy storage is obtained based on the maximum frequency change rate constraint and inertia control is initiated.

[0059] The fourth module is used for frequency control based on the range of droop coefficients or equivalent inertia coefficients, combined with the islanded power grid frequency response model.

[0060] The present invention has the following beneficial effects:

[0061] The optimal frequency control method for improving power supply levels during extreme weather, as described in this invention, constructs a frequency response model of an islanded power grid containing grid-type energy storage. This model allows for detailed analysis of the frequency response characteristics of grid-type energy storage participating in an islanded power system. Based on the constructed islanded power grid frequency response model, analytical expressions for the maximum frequency change rate, steady-state frequency deviation, and maximum frequency deviation are derived. Furthermore, the optimal frequency change trajectory and frequency regulation coefficient are adaptively determined according to specific over-limit situations. This method can simultaneously satisfy the frequency security constraints and state of charge optimization of the islanded power system, demonstrating significant potential for widespread application.

[0062] The optimal frequency control device for improving power supply levels in extreme weather, as described in this invention, has the same beneficial effects as the method of this invention.

[0063] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0064] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0065] Figure 1 This is a schematic diagram of the method flow of a preferred embodiment of the present invention.

[0066] Figure 2 This is a schematic diagram of the frequency response model of an islanded power grid according to a preferred embodiment of the present invention.

[0067] Figure 3This is a schematic diagram of the initial state topology of a preferred embodiment of the present invention.

[0068] Figure 4 This is a topological diagram of a preferred embodiment of the present invention at time 2s.

[0069] Figure 5 This is a schematic diagram comparing the data of various methods in a preferred embodiment of the present invention; wherein, (a) is a comparison diagram of the frequency deviation of each method, (b) is a comparison diagram of the frequency change rate of each method, (c) is a comparison diagram of the grid-type energy storage power of each method, and (d) is a comparison diagram of the state of charge of the grid-type energy storage of each method. Detailed Implementation

[0070] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0071] See Figure 1 In a preferred embodiment of the present invention, an optimal frequency control method for improving power supply levels during extreme weather is provided, comprising:

[0072] S1. Construct a frequency response model for an islanded power grid that includes frequency regulation by thermal power units and frequency regulation by grid-connected energy storage. S1 specifically includes:

[0073] Islanded power systems mainly consist of various frequency-regulating generators and motor loads. Their generation, transmission, distribution, and consumption are tightly coupled, and the effects of frequency spatiotemporal distribution and network structure can be ignored. Frequency deviations are often caused by power differences resulting from power disturbances within the regional system. Therefore, see [link to relevant documentation]. Figure 2 Using thermal power units as conventional frequency regulating units and considering grid-based energy storage, a frequency response model for an islanded power grid is constructed. :

[0074] ;

[0075] ;

[0076] in, Power disturbance for isolated power grids; This refers to the frequency regulation power of thermal power units; Frequency regulation power for grid-type energy storage; and These are the equivalent inertia coefficient and damping coefficient of an isolated power grid, respectively. and The first in the isolated power grid The inertia coefficient and damping coefficient of each thermal power unit; For the first The capacity of each thermal power unit; For the Laplace operator; This represents the total number of thermal power units.

[0077] In a preferred embodiment of the present invention, the thermal power unit is used as a conventional frequency regulating unit, and its dynamic frequency response characteristics are mainly determined by the governor transfer function. and reheat turbine transfer function Characterized by the fact that when a frequency deviation occurs in the system, the thermal power unit participates in frequency regulation through droop control, and the frequency regulation power of the thermal power unit includes:

[0078] ;

[0079] ;

[0080] in, For the first Unit frequency regulation power of each thermal power unit; For the first The response transfer function of a thermal power unit; For the speed controller transfer function; For the first The response time constant of each thermal power unit; For the transfer function of the reheat turbine; , and These represent the time constants of the steam turbine, governor, and reheat steam turbine in a thermal power unit, respectively. , and This represents the percentage of total turbine power allocated to the three turbine stages: high-pressure, medium-pressure, and low-pressure.

[0081] Typically, grid-connected energy storage uses virtual synchronous machine control, possesses the ability to form an independent grid, and can respond to grid frequency signals without delay. During frequency regulation, it can precisely output power to simulate inertia and damping, providing frequency-regulated power to the power system under inertial control. Furthermore, considering that the virtual synchronous machine control also includes a virtual speed governor, the droop control of a thermal power unit can be used as a substitute, with the output droop control frequency regulation power... .

[0082] In a preferred embodiment of the present invention, the frequency regulation power of the grid-type energy storage includes:

[0083] ;

[0084] in, For frequency regulation power under droop control of grid-type energy storage; Frequency regulation power under inertial control of grid-type energy storage; For the first The response transfer function of a grid-type energy storage system; For the first The time constant of a grid-type energy storage system; For the first The droop coefficient of individual grid-type energy storage; and The first The inertia coefficient and damping coefficient of individual grid-type energy storage; The equivalent inertia coefficient for grid-type energy storage; The equivalent damping coefficient for grid-type energy storage; This represents the total number of grid-type energy storage systems.

[0085] S2. Construct frequency security constraints based on the islanded power grid frequency response model. Frequency security constraints include constraints on maximum frequency deviation, steady-state frequency deviation, and maximum rate of frequency change. Disturbance The islanded power grid must meet these three types of frequency security constraints.

[0086] In a preferred embodiment of the present invention, the steady-state frequency deviation and the maximum rate of frequency change include:

[0087] The maximum rate of change of frequency is obtained according to the initial value theorem. According to the final value theorem, the steady-state frequency deviation is obtained. :

[0088] .

[0089] In a preferred embodiment of the present invention, the maximum frequency deviation includes:

[0090] Because the frequency deviation and the total output power of the primary frequency regulation of the system are coupled, their frequency domain expressions cannot be derived. Therefore, the maximum frequency deviation is difficult to obtain directly. In order to derive the frequency domain expressions for the frequency deviation and the frequency regulation power respectively, and to simulate the maximum frequency deviation, a frequency response model of the islanded power grid is constructed. Open-loop processing is performed to decouple the speed control system from the inertial damping element of the disturbed system, specifically including:

[0091] Because the time it takes for the frequency to drop to its lowest point is very short, the increase in the frequency regulation power of thermal power units is approximated as linearly equivalent, and when the frequency regulation power of thermal power units... Equal to disturbance When the frequency reaches its lowest value, the equivalent frequency regulation power of the thermal power unit is... Represented as:

[0092] ;

[0093] in, The time it takes for the frequency to reach its lowest point;

[0094] Equivalent frequency regulation power of the joint thermal power unit and isolated power grid frequency response model Ignoring the effect of damping on frequency, if the grid-type energy storage in the islanded power grid does not participate in frequency regulation, the frequency time-domain equation of the islanded power grid is obtained. :

[0095] ;

[0096] in, Let be the integral variable, representing time 0 to 1. Any time between moments;

[0097] Pick = and to Differentiating both ends simultaneously yields:

[0098] ;

[0099] From the above formula, it can be seen that the rate of change of frequency is The derivative is 0 at time t, which corresponds to the lowest point of the frequency drop, confirming the frequency time-domain equation. The rationality of equivalent methods.

[0100] Further combined with the frequency regulation power of thermal power units The expression for the system's total frequency response is obtained. :

[0101] ;

[0102] When the frequency reaches its lowest point, the frequency regulation power of the thermal power unit equals the system power disturbance, and at this time, the first relationship exists:

[0103] ;

[0104] in, Indicates to [ Perform the inverse Laplace transform; express System power disturbance at any given time;

[0105] Solving the first relation, we get The value; according to The value yields the maximum frequency deviation. :

[0106] .

[0107] S3. When the load is disturbed, determine the over-limit situation according to the frequency safety constraints, and determine the equivalent droop coefficient range and equivalent inertia coefficient range of the grid-type energy storage.

[0108] Specifically, when the maximum frequency deviation or steady-state frequency deviation exceeds the limit, the equivalent droop coefficient range of the grid-type energy storage is obtained based on the constraint of the steady-state frequency deviation, and droop control is initiated; when the maximum frequency change rate exceeds the limit, the equivalent inertia coefficient range of the grid-type energy storage is obtained based on the constraint of the maximum frequency change rate, and inertia control is initiated. This includes:

[0109] If the remaining thermal power units within the isolated power plant are insufficient to meet frequency security constraints, grid-based energy storage must participate in frequency regulation. As the frequency security constraints indicate, with the equivalent inertia coefficient... and equivalent droop coefficient With the increase of , the maximum frequency deviation and the maximum frequency change rate will be significantly improved. The maximum frequency change rate is greatly affected by the inertia coefficient, and the maximum frequency deviation is also greatly affected by the inertia coefficient, while the steady-state frequency deviation is only affected by the droop coefficient. Therefore, for a specific frequency index exceeding the limit, inertia, droop, or a combination of inertia and droop control can be selected to achieve optimal frequency control. The determination process of frequency modulation parameters under each control mode will be described in detail below.

[0110] From the maximum frequency deviation It can be seen that the maximum frequency regulation power of grid-type energy storage is This can occur at the beginning of the frequency drop period and at the end of the frequency recovery period, and can be represented as:

[0111] ;

[0112] As shown in the above equation, the values ​​of the inertia and droop coefficients of grid-type energy storage are crucial. Traditional methods, to ensure frequency control performance, typically use conservative, fixed constants for the frequency regulation coefficient of grid-type energy storage to meet frequency safety constraints under large power disturbances. While this adequately guarantees frequency stability, in islanded power systems where frequency is supported solely by grid-type energy storage, the frequency regulation capacity is insufficient, and the available capacity easily reaches the limit, leading to shutdown. Therefore, in the preferred embodiment of this invention, an optimal frequency change trajectory is planned, and based on this, an adaptive method for determining the frequency regulation coefficient of grid-type energy storage is proposed to maintain its state of charge while meeting frequency safety requirements. The optimal frequency change trajectory includes two cases:

[0113] Scenario 1: The frequency safety boundary will not be crossed under load disturbance. In this case, grid-type energy storage will not participate in frequency regulation.

[0114] Scenario 2: Under load disturbance, a certain frequency index will exceed the limit. In this case, grid-type energy storage needs to determine the minimum frequency regulation coefficient based on the frequency safety boundary and implement the minimum frequency regulation output to meet the frequency regulation requirements. Let the droop and inertial control trigger signals be signD and signI, respectively, which can be expressed as:

[0115] ;

[0116] in, , and Disturbance The maximum frequency deviation, maximum rate of frequency change, and steady-state frequency deviation under these conditions; , and These are the given frequency safety thresholds.

[0117] As shown in the above equation, when both signD and signI are not 0, the frequency modulation control method and frequency modulation coefficients need to be adaptively determined based on frequency security constraints, including:

[0118] When the maximum frequency deviation or steady-state frequency deviation exceeds the limit, the equivalent droop coefficient range of the grid-type energy storage is obtained based on the constraint of the steady-state frequency deviation, and droop control is initiated:

[0119] Based on steady-state frequency deviation The expression yields the equivalent droop coefficient of the grid-type energy storage. Scope:

[0120] ;

[0121] in, It is the minimum equivalent droop coefficient.

[0122] When the maximum frequency change rate exceeds the limit, the equivalent inertia coefficient range of the grid-type energy storage is obtained based on the constraint of the maximum frequency change rate, and inertial control is initiated:

[0123] Based on the maximum frequency change rate The expression yields the equivalent inertia coefficient of the grid-type energy storage. Scope:

[0124] ;

[0125] in, It is the smallest equivalent inertia coefficient.

[0126] When the inertia and droop coefficient of the grid-type energy storage are and At the same time, the frequency index is effectively controlled to be within the boundary of the safe zone, avoiding the additional output of grid-type energy storage that would damage its state of charge.

[0127] S4. Frequency control is performed based on the equivalent droop coefficient range and the equivalent inertia coefficient range, combined with the islanded power grid frequency response model. S4 specifically includes:

[0128] Based on the range of droop coefficient and equivalent inertia coefficient, the frequency regulation power of grid-type energy storage is further expressed as:

[0129] ;

[0130] in, This indicates the droop control trigger signal; This indicates the inertial control trigger signal;

[0131] The state-of-charge (SOC) update methods for grid-based energy storage include:

[0132] ;

[0133] in, State of charge for grid-connected energy storage; This is the initial frequency modulation time; This refers to the rated capacity of the energy storage. This refers to the cumulative charge and discharge energy of grid-type energy storage.

[0134] When the next frequency regulation cycle arrives, determine whether the energy storage power command has been fully responded to. If not, repeat the process.

[0135] The optimal frequency control method for improving power supply levels during extreme weather, as described in this invention, constructs a frequency response model of an islanded power grid containing grid-type energy storage. This model allows for detailed analysis of the frequency response characteristics of grid-type energy storage participating in an islanded power system. Based on the constructed islanded power grid frequency response model, analytical expressions for the maximum frequency change rate, steady-state frequency deviation, and maximum frequency deviation are derived. Furthermore, the optimal frequency change trajectory and frequency regulation coefficient are adaptively determined according to specific over-limit situations. This method can simultaneously satisfy the frequency security constraints and state of charge optimization of the islanded power system, demonstrating significant potential for widespread application.

[0136] In a preferred embodiment of the present invention, an optimal frequency control device for improving power supply levels in extreme weather is also provided. The device, used in the method of the present invention, includes a first module, a second module, a third module, and a fourth module.

[0137] The first module is used to construct the frequency response model of an islanded power grid that includes frequency regulation by thermal power units and frequency regulation by grid-type energy storage.

[0138] The second module is used to construct frequency security constraints based on the islanded power grid frequency response model; the frequency security constraints include constraints on maximum frequency deviation, steady-state frequency deviation, and maximum rate of frequency change;

[0139] The third module is used to determine the over-limit situation based on frequency safety constraints during load disturbances; when the maximum frequency deviation or steady-state frequency deviation exceeds the limit, the droop coefficient range of each grid-type energy storage is obtained based on the steady-state frequency deviation constraint and droop control is initiated; when the maximum frequency change rate exceeds the limit, the equivalent inertia coefficient range of the grid-type energy storage is obtained based on the maximum frequency change rate constraint and inertia control is initiated.

[0140] The fourth module is used for frequency control based on the range of droop coefficients or equivalent inertia coefficients, combined with the islanded power grid frequency response model.

[0141] The optimal frequency control device for improving power supply levels in extreme weather, as described in this invention, has the same beneficial effects as the method of this invention.

[0142] Verification section:

[0143] To verify the feasibility of this invention, an IEEE 10-unit 39-node system was built in the MATLAB / Simulink environment. The parameters of each thermal power unit and the parameters of each grid-type energy storage were set to be consistent. The simulation parameters are shown in Table 1.

[0144] Table 1

[0145] ;

[0146] See Figure 3 A grid-type energy storage system with a rated capacity of 0.5 MWh is connected at node 38. The initial state of charge (SFC) of the energy storage unit is set to 0.5, and the damping coefficient of each energy storage unit is set to 0.1. (See also...) Figure 4 At 2 seconds, due to a power grid failure in other areas caused by heavy rain, nodes 1, 17, and 39 were disconnected under dispatch control, changing the topology of the entire system. The area where the grid-type energy storage was located became a local island, resulting in a power deficit of 0.12 pu. Figures 3 to 4 In the diagram, 1 to 39 represent nodes, and G1 to G10 are all thermal power units.

[0147] The method of this invention is compared with frequency regulation methods for thermal power units only and constant coefficient frequency regulation methods for grid-type energy storage. The energy storage power, frequency deviation, frequency change rate, and energy storage state of charge under different methods are as follows: Figure 5 Conventional frequency regulation units alone are insufficient to meet frequency regulation requirements, resulting in the largest rate and magnitude of frequency drops in the system. Compared to the fixed-coefficient frequency regulation method for grid-type energy storage, the method of this invention adaptively determines the action signals and action depth of inertial and droop control by calculating the values ​​of the maximum frequency deviation and the rate of frequency change. Figure 5 (a) and Figure 5 As shown in (b), the maximum predicted frequency deviation exceeds the given threshold of -19.07 under a perturbation of 0.12 pu. 10⁻⁴ p.u., less than -6.66 10⁻⁴ p.u., while the rate of change of frequency is not, at -19.88. 10⁻⁴ p.u., greater than 20 10⁻⁴ p.u. Therefore, grid-type energy storage only needs to participate in droop control to ensure system frequency stability, and the droop coefficient calculated based on the frequency deviation threshold is 13.35. Figure 5 (c) and Figure 5 As shown in (d), the method of the present invention can significantly reduce the frequency regulation power and fully maintain its state of charge in a better operating state. The steady-state state of charge is improved by 39.29% compared with the grid-type energy storage.

[0148] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An optimal frequency control method for improving power supply levels during extreme weather, characterized in that, include: Construct a frequency response model for an islanded power grid that includes frequency regulation by thermal power units and frequency regulation by grid-connected energy storage; and construct frequency security constraints based on the islanded power grid frequency response model. The frequency safety constraints include constraints on maximum frequency deviation, steady-state frequency deviation, and maximum rate of frequency change; when the load is disturbed, the exceeding of limits is determined based on the frequency safety constraints; When the maximum frequency deviation or steady-state frequency deviation exceeds the limit, the equivalent droop coefficient range of the grid-type energy storage is obtained according to the constraint of the steady-state frequency deviation, and droop control is initiated; when the maximum frequency change rate exceeds the limit, the equivalent inertia coefficient range of the grid-type energy storage is obtained according to the constraint of the maximum frequency change rate, and inertia control is initiated; frequency control is performed based on the equivalent droop coefficient range and the equivalent inertia coefficient range in combination with the islanded power grid frequency response model. Steady-state frequency deviation and maximum rate of frequency change include: The maximum rate of change of frequency is obtained according to the initial value theorem. According to the final value theorem, the steady-state frequency deviation is obtained. : ； Maximum frequency deviation includes: The increase in the frequency regulation power of thermal power units is approximated as linearly equivalent, and when the frequency regulation power of thermal power units... Equal to disturbance When the frequency reaches its lowest value, the equivalent frequency regulation power of the thermal power unit is... Represented as: ； in, t n The time it takes for the frequency to reach its lowest point; Equivalent frequency regulation power of the joint thermal power unit And isolated power grid frequency response model Ignoring the effect of damping on frequency, if the grid-type energy storage in the islanded power grid does not participate in frequency regulation, the frequency time-domain equation of the islanded power grid is obtained. : ； in, Let be the integral variable, representing time 0 to 1. t Any time between moments; Pick t = t n and to Differentiating both ends simultaneously yields: ； Further combined with the frequency regulation power of thermal power units The expression for the system's total frequency response is obtained. : ； When the frequency reaches its lowest point, the frequency regulation power of the thermal power unit equals the system power disturbance, and at this time, the first relationship exists: ； in, Indicates to [ Perform the inverse Laplace transform; express t System power disturbance at any given time; Solving the first relation, we obtain t n The value; according to t n The value yields the maximum frequency deviation. : ； Based on the constraint of steady-state frequency deviation, the range of equivalent droop coefficients for grid-type energy storage includes: According to the steady-state frequency deviation The expression yields the equivalent droop coefficient of the grid-type energy storage. Scope: ； in, It is the minimum equivalent droop coefficient; Based on the constraint of the maximum frequency change rate, the range of equivalent inertia coefficients for grid-type energy storage includes: According to the maximum frequency change rate The expression yields the equivalent inertia coefficient of the grid-type energy storage. Scope: ； in, It is the smallest equivalent inertia coefficient.

2. The optimal frequency control method for improving power supply levels in extreme weather as described in claim 1, characterized in that, Constructing a frequency response model for an islanded power grid that includes frequency regulation by thermal power units and frequency regulation by grid-based energy storage includes: Using thermal power units as conventional frequency regulating units and considering grid-based energy storage, a frequency response model for an islanded power grid is constructed. : ； ； in, Power disturbance for isolated power grids; For the frequency regulation power of thermal power units; Frequency regulation power for grid-type energy storage; and These are the equivalent inertia coefficient and damping coefficient of an isolated power grid, respectively. and These are the inertia coefficient and damping coefficient of the nth thermal power unit within the isolated power grid, respectively. For the first n The capacity of each thermal power unit; s For the Laplace operator; N This represents the total number of thermal power units.

3. The optimal frequency control method for improving power supply levels in extreme weather as described in claim 2, characterized in that, The frequency regulation power of thermal power units includes: ； ； in, For the first n Unit frequency regulation power of each thermal power unit; R G,n For the first n The response transfer function of a thermal power unit; For the speed controller transfer function; For the first n The response time constant of each thermal power unit; For the transfer function of the reheat turbine; T CH,n , T RH,n and T CO,n These represent the time constants of the steam turbine, governor, and reheat steam turbine in a thermal power unit, respectively. F HP,n , F IP,n and F LP,n This represents the percentage of total turbine power allocated to the three turbine stages: high-pressure, medium-pressure, and low-pressure.

4. The optimal frequency control method for improving power supply levels in extreme weather as described in claim 3, characterized in that, The frequency regulation power of grid-based energy storage includes: ； in, For frequency regulation power under droop control of grid-type energy storage; Frequency regulation power under inertial control of grid-type energy storage; R Egfm,v For the first v The response transfer function of a grid-type energy storage system; T Egfm,v For the first v The time constant of a grid-type energy storage system; For the first v The droop coefficient of individual grid-type energy storage; and The first v The inertia coefficient and damping coefficient of individual grid-type energy storage; The equivalent inertia coefficient for grid-type energy storage; The equivalent damping coefficient for grid-type energy storage; V This represents the total number of grid-type energy storage systems.

5. The optimal frequency control method for improving power supply levels in extreme weather according to claim 4, characterized in that, Frequency control based on the equivalent droop coefficient range and the equivalent inertia coefficient range, combined with the islanded power grid frequency response model, includes: Based on the droop coefficient range and the equivalent inertia coefficient range, the frequency regulation power of grid-type energy storage is further expressed as: ； in, This indicates the droop control trigger signal; This indicates the inertial control trigger signal; The state-of-charge (SOC) update methods for grid-based energy storage include: ； in, State of charge for grid-connected energy storage; This is the initial frequency modulation time; This refers to the rated capacity of the energy storage. This refers to the cumulative charge and discharge energy of grid-type energy storage.

6. An optimal frequency control device for improving power supply levels during extreme weather, used in the method described in any one of claims 1 to 5, characterized in that, The device includes a first module, a second module, a third module, and a fourth module; The first module is used to construct a frequency response model for an islanded power grid that includes frequency regulation by thermal power units and frequency regulation by grid-based energy storage. The second module is used to construct frequency security constraints based on the islanded power grid frequency response model; the frequency security constraints include constraints on maximum frequency deviation, steady-state frequency deviation, and maximum rate of frequency change; The third module is used to determine the over-limit situation according to the frequency safety constraint when the load is disturbed; when the maximum frequency deviation or steady-state frequency deviation exceeds the limit, the droop coefficient range of each grid-type energy storage is obtained according to the constraint of steady-state frequency deviation and droop control is started; when the maximum frequency change rate exceeds the limit, the equivalent inertia coefficient range of the grid-type energy storage is obtained according to the constraint of the maximum frequency change rate and inertia control is started. The fourth module is used to perform frequency control based on the droop coefficient range or the equivalent inertia coefficient range in conjunction with the islanded power grid frequency response model.

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