A method for evaluating the inertia of an equivalent synchronous machine in a new energy power station

Abstract

This invention discloses a method for evaluating the inertia of the equivalent synchronous machine in a renewable energy power plant. It constructs a frequency response model of a multi-machine system incorporating renewable energy virtual inertia frequency regulation, obtaining the system transfer function. It determines the frequency support effect of different renewable energy power system frequency regulation parameters. Simulation yields data pairs of renewable energy frequency regulation control parameters, unit power response time constants, and frequency indices, representing a three-dimensional surface characterizing the renewable energy frequency regulation control effect. The renewable energy virtual inertia frequency regulation module is removed from the frequency response model, and a polynomial fit is used to the correlation characterization model of the power grid inertia frequency regulation capability evaluation parameters and frequency indices based on the dataset. Using the frequency indices as intermediate variables, a three-dimensional surface of renewable energy frequency regulation control parameters and response speed versus equivalent synchronous machine inertia is obtained based on the principle of frequency index equivalence. This method comprehensively considers the dynamic response of renewable energy itself and the influence of control parameters, correctly evaluating the frequency support capability of renewable energy power plants using virtual inertia.

Description

Technical Field

[0001] This invention relates to the field of new energy power station technology, and in particular to a method for evaluating the inertia of an equivalent synchronous machine in a new energy power station. Background Technology

[0002] The increasing electrification of power sources across the power grid and load chain has led to a decrease in system inertia. This decrease in inertia worsens the rate of frequency change after disturbances, posing a severe challenge to the frequency stability of high-voltage and high-efficiency power systems. To address these challenges, there is an urgent need for renewable energy power plants to adopt virtual inertia control to provide system frequency support.

[0003] Currently, virtual inertia control at renewable energy power plants primarily uses the rate of frequency change as the input signal. By adding frequency-modulated power to the original power command, the output power of the renewable energy power plant is altered, aiming to simulate the inertia response function of a synchronous generator. However, the power increase during grid frequency regulation by adding virtual inertia frequency regulation control to renewable energy power plants is not instantaneous. Due to differences in the dynamic response of renewable energy units and the influence of the power plant control link, the actual frequency regulation capability of renewable energy generation differs significantly from that of synchronous generators. Existing technologies have limited research considering the power response delay during virtual inertia frequency regulation, and its impact mechanism on system frequency dynamics remains unclear. Furthermore, assessments of the virtual inertia frequency regulation capability of renewable energy without considering the renewable energy's own response may lead to incorrect evaluations of the actual support effect of renewable energy on grid frequency. Therefore, it is necessary to consider the impact of renewable energy power response delay and propose corresponding assessment methods for the virtual inertia frequency regulation capability of renewable energy power plants to comprehensively evaluate the role of virtual inertia control in frequency support. Summary of the Invention

[0004] The purpose of this invention is to provide a method for evaluating the equivalent synchronous machine inertia of a new energy power station. This method fully considers the impact of the power response delay of the new energy power station itself on the system frequency stability, and evaluates the frequency support capability of the new energy virtual inertia based on the principle of controlling the virtual inertia of the new energy input and changing the synchronous machine inertia to make the system frequency drop rate consistent after the disturbance. Thus, it comprehensively considers the impact of the new energy's own response dynamics and control parameters, and correctly evaluates the frequency support capability of the new energy power station's virtual inertia.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for evaluating the inertia of an equivalent synchronous machine in a new energy power station, the method comprising:

[0007] Step 1: Construct a frequency response model for a multi-machine system that includes virtual inertia frequency modulation of new energy sources, and obtain the system transfer function;

[0008] Step 2: Analyze the relevant parameters affecting frequency indicators, and then determine the support effect of different frequency regulation parameters of new energy power systems on frequency through frequency indicators;

[0009] Step 3: Change the relevant parameters of the new energy frequency regulation control through the frequency response model constructed in Step 1, and obtain the data pairs of new energy frequency regulation control parameters, unit power response time constant and frequency index through simulation. Use the bicubic spline interpolation function to characterize the three-dimensional surface of the new energy frequency regulation control effect.

[0010] Step 4: Remove the new energy virtual inertia frequency regulation module from the frequency response model, change the synchronous machine inertia value, obtain the frequency index and synchronous machine inertia data pair through simulation, and use a polynomial fit to the correlation characterization model of the power grid inertia frequency regulation capability evaluation parameters and frequency index based on the dataset.

[0011] Step 5: Based on the obtained surface characterizing the frequency regulation effect of new energy sources and the correlation model of the frequency regulation capability of the power grid inertia, the three-dimensional surface of the frequency regulation control parameters of new energy sources and the response speed-equivalent synchronous machine inertia is obtained with the frequency index as the intermediate variable and based on the principle of frequency index equivalence.

[0012] As can be seen from the technical solution provided by the present invention, the above method fully considers the impact of the power response delay of the new energy power station itself on the system frequency stability, and evaluates the frequency support capability of the new energy virtual inertia based on the principle of controlling the virtual inertia of the new energy input and changing the inertia of the synchronous machine to make the system frequency drop speed consistent after the disturbance. Thus, it comprehensively considers the impact of the new energy's own response dynamics and control parameters, and correctly evaluates the frequency support capability of the new energy power station virtual inertia. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 A schematic diagram of the process for evaluating the inertia of an equivalent synchronous machine in a new energy power station, provided in an embodiment of the present invention;

[0015] Figure 2 This is a schematic diagram of the system frequency response model considering new energy inertia frequency modulation according to an embodiment of the present invention;

[0016] Figure 3 This is a three-dimensional surface diagram representing the frequency modulation control effect of new energy virtual inertia in an embodiment of the present invention;

[0017] Figure 4This is a schematic diagram of the correlation characterization model of power grid inertia and frequency index in an embodiment of the present invention;

[0018] Figure 5 This is a three-dimensional surface diagram illustrating the new energy frequency regulation control parameters, response speed, and equivalent synchronous machine inertia in an embodiment of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments, and do not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0020] like Figure 1 The diagram shown is a flowchart of the method for evaluating the inertia of an equivalent synchronous machine in a new energy power station according to an embodiment of the present invention. The method includes:

[0021] Step 1: Construct a frequency response model for a multi-machine system that includes virtual inertia frequency modulation of new energy sources, and obtain the system transfer function;

[0022] In this step, the frequency response model constructed is as follows:

[0023]

[0024] Where: ΔP REU T represents the actual power output of the renewable energy source during frequency regulation. REU H represents the power response time constant of the renewable energy power plant. REU τ represents the virtual inertia frequency modulation control parameter for the new energy power station; τ is the signal transmission delay of the control link of the new energy power station; s is the Laplace operator; Δf is the frequency deviation.

[0025] like Figure 2 The diagram shown is a schematic of the system frequency response model considering new energy inertia frequency modulation according to an embodiment of the present invention. The system transfer function is obtained from this model and is expressed as follows:

[0026]

[0027] In the formula: G(s) is the system transfer function; M is the system inertial time constant; D is the system damping coefficient; R is the generator regulation coefficient; T CH F is the steam volume time constant; HP T is the reheat coefficient of a reheat steam turbine. RH T is the reheat time constant of a reheat steam turbine. w R is the water hammer time constant of the turbine; T / RP T is the transient descent compensation coefficient for the turbine; R This refers to the turbine reset time.

[0028] System disturbance power ΔP L For a step-like form, the frequency domain expression of the system frequency response Δf(s) is:

[0029]

[0030] Step 2: Analyze the relevant parameters affecting frequency indicators, and then determine the support effect of different frequency regulation parameters of new energy power systems on frequency through frequency indicators;

[0031] In this step, the frequency indices are the system frequency change rate, steady-state frequency deviation, and frequency drop rate. The relevant parameters affecting these frequency indices are analyzed, including:

[0032] The rate of change of the system frequency is obtained using the Laplace transform initial value theorem:

[0033]

[0034] The maximum frequency change rate is determined only by the magnitude of the disturbance and the system's inertial time constant, and is unrelated to the virtual inertia frequency modulation control of new energy sources.

[0035] The steady-state frequency deviation is obtained using the final value theorem of the Laplace transform:

[0036]

[0037] The steady-state frequency deviation is determined only by the magnitude of the disturbance, the system damping coefficient, and the generator regulation coefficient, and is independent of the new energy virtual inertia frequency regulation control s.

[0038] Therefore, considering the frequency index as the frequency drop rate, it is obtained from the simulation data of the system frequency response model:

[0039]

[0040] In the formula: f α T represents the frequency drop rate; nadir The time to reach the lowest frequency; Δf max This represents the maximum frequency deviation.

[0041] Step 3: Change the relevant parameters of the new energy frequency regulation control through the frequency response model constructed in Step 1, and obtain the data pairs of new energy frequency regulation control parameters, unit power response time constant and frequency index through simulation. Use the bicubic spline interpolation function to characterize the three-dimensional surface of the new energy frequency regulation control effect.

[0042] In this step, the simulation results of the new energy frequency regulation control parameters, unit power response time constant, and frequency index data are represented as follows:

[0043] f(T REU (i),H REU (i))=f α (i)

[0044] In the formula: T REU (i) represents the power response time constant of the new energy power station in the i-th simulation; H REU (i) represents the virtual inertia frequency modulation control parameters of the new energy power station during the i-th simulation; f α (i) represents the frequency drop rate during the i-th simulation;

[0045] The three-dimensional surface characterizing the frequency modulation control effect of new energy sources using a bicubic spline interpolation function is represented as follows:

[0046]

[0047] In the formula: (T* REU ,H* REU f* represents the interpolation point in the three-dimensional surface characterizing the frequency modulation control effect of the new energy source; α For interpolation; (T) REU (i),H REU (j) (i,j=0,1,2,3) are the neighborhood points near the interpolation point;

[0048] The bicubic spline interpolation function is:

[0049]

[0050] in:

[0051] Step 4: Remove the new energy virtual inertia frequency regulation module from the frequency response model, change the synchronous machine inertia value, obtain the frequency index and synchronous machine inertia data pair through simulation, and use a polynomial fit to the correlation characterization model of the power grid inertia frequency regulation capability evaluation parameters and frequency index based on the dataset.

[0052] In this step, specifically, the virtual inertia frequency modulation control parameter of the new energy source is set to 0 in the frequency response model, the synchronous machine inertia value is changed, and the frequency index-synchronous machine inertia data pair is obtained through simulation, represented as:

[0053] f(M(i))=f α (i)

[0054] In the formula: M(i) is the inertia value of the synchronizer in the i-th simulation; f(M(i)) is the frequency drop rate when the inertia of the synchronizer is M(i); f α(i) represents the frequency drop rate during the i-th simulation;

[0055] The correlation characterization model based on the dataset, using polynomial fitting of the parameters and frequency indices for evaluating the frequency regulation capability of the power grid inertia, is expressed as follows:

[0056] M(f α )=p1*f α ∧ 3+p2*f α ∧ 2+p3*f α +p4

[0057] In the formula: M(f α ) is the correlation model for evaluating the power grid's inertia frequency regulation capability and frequency index; p1 to p4 are the coefficients of the fitting function.

[0058] Step 5: Based on the obtained surface characterizing the frequency regulation effect of new energy sources and the correlation model of the frequency regulation capability of the power grid inertia, the three-dimensional surface of the frequency regulation control parameters of new energy sources and the response speed-equivalent synchronous machine inertia is obtained with the frequency index as the intermediate variable and based on the principle of frequency index equivalence.

[0059] In this step, using the frequency index as an intermediate variable, and based on the principle of frequency index equivalence, the three-dimensional surface of the new energy frequency regulation control parameters and response speed-equivalent synchronous machine inertia is obtained, represented as:

[0060] M'=f(T REU H REU )

[0061] In the formula: M' is the equivalent synchronous machine inertia characterizing the virtual inertia frequency modulation capability of new energy; T REU Virtual inertia frequency modulation power response time constant of new energy power plants; H REU Virtual inertia frequency modulation control parameters for new energy power plants.

[0062] The method described in this invention will be illustrated below with a specific example. The typical system coefficients for frequency regulation considering the virtual inertia of new energy power plants used in this embodiment are shown in Table 1, and the power disturbance ΔP... L =0.1pu.

[0063] Table 1 Typical Coefficients of the System

[0064] System parameters Value Synchronous machine adjustment coefficient R 0.05 Steam volume time constant TCH 0.3s Reheat coefficient FHP of reheat steam turbine 0.3s Reheat Time Constant (TRH) of Reheat Steam Turbine 8s Water hammer time constant Tw 1s Transient descent compensation factor RT / RP 40 Turbine reset time TR 4s The system's equivalent inertial time constant 2H 10s The system's equivalent damping constant D 2

[0065] The range of the power response delay value of the new energy power station is set to T. REU The range of the virtual inertia frequency modulation control coefficient for new energy sources is set to H ∈ [0.1, 3.5]. REU∈[4,12], with the new energy control transmission signal lag set to 100ms, the solution yields a three-dimensional surface characterizing the new energy frequency modulation control effect, such as Figure 3 The image shown is a three-dimensional surface diagram representing the effect of virtual inertia frequency modulation control of new energy sources according to an embodiment of the present invention. Figure 3 In the diagram, the x and y axes represent the power response delay T of the renewable energy power plant, respectively. REU and the virtual inertia frequency modulation control coefficient H of new energy REU The z-axis represents the frequency support indicator, i.e., the frequency drop depth f. α .

[0066] By removing the new energy frequency regulation module and setting the system inertia value range to M∈[4,20], the correlation characterization model of the power grid inertia frequency regulation capability assessment parameters and frequency indicators can be obtained by solving the problem. Figure 4 The diagram shown is a schematic representation of the correlation between power grid inertia and frequency index according to an embodiment of the present invention. Figure 4 In the diagram, the x-axis represents the frequency support indicator, i.e., the frequency drop depth f. α The y-axis represents the system inertia M.

[0067] Using the frequency index, i.e., the frequency drop rate, as an intermediate variable, and based on the principle of frequency index equivalence, a three-dimensional surface of the new energy frequency regulation control parameters and the response speed-equivalent synchronous machine inertia is obtained, such as... Figure 5 The figure shown is a three-dimensional surface diagram illustrating the new energy frequency regulation control parameters, response speed, and equivalent synchronous machine inertia in an embodiment of the present invention. Figure 5 In the diagram, the x and y axes represent the power response delay T of the renewable energy power plant, respectively. REU and the virtual inertia frequency modulation control coefficient H of new energy REU The z-axis represents the system inertia M.

[0068] As can be seen from the above embodiments, the method described in the embodiments of the present invention can evaluate the virtual inertia frequency support capability of new energy power plants from the perspective of frequency index equivalence by using the virtual inertia frequency regulation control parameters of new energy power plants and the power response time constant of new energy power plants. This is of great significance for determining the equivalent synchronous machine inertia level of new energy power plants, guiding the setting of frequency regulation control parameters of new energy power plants, and giving full play to the frequency support capability of new energy power plants.

[0069] It is worth noting that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0070] Furthermore, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware, and the corresponding program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0071] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of the present invention and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for evaluating the inertia of an equivalent synchronous machine in a new energy power station, characterized in that, The method includes: Step 1: Construct a frequency response model for a multi-machine system that includes virtual inertia frequency modulation of new energy sources, and obtain the system transfer function; Step 2: Analyze the relevant parameters affecting frequency indicators, and then determine the support effect of different frequency regulation parameters of new energy power systems on frequency through frequency indicators; Step 3: Change the relevant parameters of the new energy frequency regulation control through the frequency response model constructed in Step 1, and obtain the data pairs of new energy frequency regulation control parameters, unit power response time constant and frequency index through simulation. Use the bicubic spline interpolation function to characterize the three-dimensional surface of the new energy frequency regulation control effect. Step 4: Remove the new energy virtual inertia frequency regulation module from the frequency response model, change the synchronous machine inertia value, obtain the frequency index and synchronous machine inertia data pair through simulation, and use polynomial fitting to the correlation characterization model of the power grid inertia frequency regulation capability evaluation parameters and frequency index based on the dataset. Step 5: Based on the obtained surface characterizing the frequency regulation effect of new energy sources and the correlation model of the frequency regulation capability of the power grid inertia, the three-dimensional surface of the frequency regulation control parameters of new energy sources and the response speed-equivalent synchronous machine inertia is obtained with the frequency index as the intermediate variable and based on the principle of frequency index equivalence.

2. The method for evaluating the inertia of an equivalent synchronous machine in a new energy power station according to claim 1, characterized in that, In step 1, the constructed frequency response model is as follows: Where: ΔP REU This represents the actual power output of the new energy source during frequency regulation. T REU H represents the power response time constant of the renewable energy power plant. REU τ represents the virtual inertia frequency modulation control parameter for the new energy power station; τ is the signal transmission delay of the control link of the new energy power station; s is the Laplace operator; Δf is the frequency deviation. The system transfer function, obtained from the frequency response model of the new energy power system, is expressed as: In the formula: G(s) is the system transfer function; M is the system inertial time constant; D is the system damping coefficient; R is the generator regulation coefficient; T CH F is the steam volume time constant; HP T is the reheat coefficient of a reheat steam turbine. RH T is the reheat time constant of a reheat steam turbine. w R is the water hammer time constant of the turbine; T / R P T is the transient descent compensation coefficient for the turbine; R This refers to the turbine reset time. System disturbance power ΔP L For a step-like form, the frequency domain expression of the system frequency response Δf(s) is:

3. The method for evaluating the inertia of the equivalent synchronous machine of a new energy power station according to claim 2, characterized in that, In step 2, the frequency indices are the system frequency change rate, steady-state frequency deviation, and frequency drop rate. The relevant parameters affecting these frequency indices are analyzed, including: The rate of change of the system frequency is obtained using the Laplace transform initial value theorem: The steady-state frequency deviation is obtained using the final value theorem of the Laplace transform: The frequency drop rate was obtained from simulation data: In the formula: f α T represents the frequency drop rate; nadir The time to reach the lowest frequency; Δf max This represents the maximum frequency deviation.

4. The method for evaluating the inertia of the equivalent synchronous machine of a new energy power station according to claim 3, characterized in that, In step 3, the simulation results of the new energy frequency regulation control parameters, unit power response time constant, and frequency index are represented as follows: f(T REU (i),H REU (i))=f α (i) In the formula: T REU (i) represents the power response time constant of the new energy power station in the i-th simulation; H REU (i) represents the virtual inertia frequency modulation control parameters of the new energy power station during the i-th simulation; f α (i) represents the frequency drop rate during the i-th simulation; The three-dimensional surface characterizing the frequency modulation control effect of new energy sources using a bicubic spline interpolation function is represented as follows: In the formula: (T* REU ,H* REU f* represents the interpolation point in the three-dimensional surface characterizing the frequency modulation control effect of the new energy source; α For interpolation; (T) REU (i),H REU (j))(i,j=0,1,,2,3) are the neighborhood points near the interpolation point; The bicubic spline interpolation function is: in:

5. The method for evaluating the inertia of an equivalent synchronous machine in a new energy power station according to claim 3, characterized in that, In step 4, specifically, the virtual inertia frequency modulation control parameter of the new energy source is set to 0 in the frequency response model, the synchronous machine inertia value is changed, and the frequency index-synchronous machine inertia data pair is obtained through simulation, represented as: f(M(i))=f α (i) In the formula: M(i) is the inertia value of the synchronizer in the i-th simulation; f(M(i)) is the frequency drop rate when the inertia of the synchronizer is M(i); f α (i) represents the frequency drop rate during the i-th simulation; The correlation characterization model based on the dataset, using polynomial fitting of the parameters and frequency indices for evaluating the frequency regulation capability of the power grid inertia, is expressed as follows: M(f α )=p1 * f α ∧3+p2 * f α ∧2+p3 * f α +p4 In the formula: M(f α ) is the correlation model characterizing the evaluation parameters and frequency index of the power grid inertia frequency regulation capability; p1~p4 are the coefficients of the fitting function.

6. The method for evaluating the inertia of the equivalent synchronous machine of a new energy power station according to claim 2, characterized in that, In step 5, using the frequency index as an intermediate variable, and based on the principle of frequency index equivalence, the three-dimensional surface of the new energy frequency regulation control parameters and response speed-equivalent synchronous machine inertia is obtained, expressed as: M’=f(T REU ,H REU ) In the formula: M' is the equivalent synchronous machine inertia characterizing the virtual inertia frequency modulation capability of new energy; T REU Virtual inertia frequency modulation power response time constant of new energy power plants; H REU Virtual inertia frequency modulation control parameters for new energy power plants.

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