Inertia evaluation method for equivalent synchronous machine of new energy station

Abstract

The invention discloses a new energy station equivalent synchronous machine inertia evaluation method, which comprises the following steps of: constructing a multi-machine system frequency response model containing new energy virtual inertia frequency modulation to obtain a system transfer function; determining the supporting effects of different new energy power system frequency modulation parameters on the frequency; performing simulation to obtain data pairs of new energy frequency modulation control parameters, unit power response time constants and frequency indexes, and a three-dimensional curved surface representing a new energy frequency modulation control effect; removing a new energy virtual inertia frequency modulation module in the frequency response model, and fitting a correlation representation model of power grid inertia frequency modulation capability evaluation parameters and frequency indexes by using a polynomial based on the data set; and a frequency index is used as an intermediate variable, and a three-dimensional curved surface of new energy frequency modulation control parameters and response speed-equivalent synchronous machine inertia is obtained based on a frequency index equivalence principle. According to the method, the influence of the new energy self-response dynamic state and the control parameters can be comprehensively considered, and the virtual inertia frequency supporting capability of the new energy station is correctly evaluated.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy stations, and in particular to a method for evaluating the inertia of an equivalent synchronous machine in a new energy station. Background Art

[0002] The trend of power electronics in all links of "source-grid-load" has reduced the system inertia level. The reduced inertia level has worsened the frequency change rate after the system is disturbed, and the frequency stability of the "double-high" power system faces severe challenges. In order to meet the above challenges, it is urgently required that new energy stations adopt virtual inertia control to provide system frequency support capabilities.

[0003] At present, the virtual inertia control of new energy stations mainly uses the frequency change rate as the input signal, and changes the output power of the new energy station by adding frequency modulation power to the original power command, aiming to simulate the inertia response function of the synchronous generator. However, when the new energy station adds virtual inertia frequency modulation control to participate in the grid frequency modulation, it is not an instantaneous surge in power. Due to the difference in the dynamic response of the new energy units themselves and the influence of the station control link, the actual frequency regulation capability of new energy power generation is quite different from that of the synchronous generator. There are few studies on the power response delay in the virtual inertia frequency modulation process in the existing technology, and its influence mechanism on the system frequency dynamics is still unclear. In addition, the evaluation of the virtual inertia frequency modulation capability of new energy without considering the response of new energy itself may misevaluate the actual support effect of new energy on the grid frequency. Therefore, it is necessary to take into account the influence of the new energy power response delay, propose a corresponding new energy station virtual inertia frequency modulation capability evaluation method, and comprehensively evaluate the role of new energy virtual inertia control on frequency support. Summary of the invention

[0004] The purpose of the present invention is to provide a new energy station equivalent synchronous machine inertia evaluation method, which fully considers the influence of the power response delay of the new energy station itself on the system frequency stability, and evaluates the new energy virtual inertia frequency support capability according to the principle of virtual inertia control of new energy input and changing the synchronous machine inertia to make the system frequency drop speed consistent after the disturbance, thereby comprehensively considering the influence of the new energy's own response dynamics and control parameters, and correctly evaluating the new energy station virtual inertia frequency support capability.

[0005] The objective of the present invention is achieved through the following technical solutions:

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

[0007] Step 1: construct a frequency response model of a multi-machine system including new energy virtual inertia frequency modulation to obtain a system transfer function;

[0008] Step 2: Analyze the relevant parameters that affect the frequency index, and then determine the supporting effect of frequency modulation parameters of different renewable energy power systems on the frequency through the frequency index;

[0009] Step 3: Change the frequency modulation control related parameters of new energy through the frequency response model constructed in step 1, simulate and obtain the data pairs of new energy frequency modulation control parameters, unit power response time constant and frequency index, and use the bicubic spline interpolation function to represent the three-dimensional surface of the new energy frequency modulation control effect;

[0010] Step 4: Remove the new energy virtual inertia frequency modulation 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 polynomials to simulate the correlation representation model of the power grid inertia frequency modulation capability evaluation parameters and frequency index based on the data set;

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

[0012] It can be seen from the technical solution provided by the present invention that the method fully considers the influence of the power response delay of the new energy station itself on the system frequency stability, and evaluates the frequency support capability of the new energy virtual inertia based on the principle of virtual inertia control of new energy input and changing the inertia of the synchronous machine to make the system frequency drop speed after the disturbance consistent, thereby comprehensively considering the influence of the response dynamics of the new energy itself and the control parameters, and correctly evaluating the frequency support capability of the new energy station virtual inertia. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0014] Figure 1 A schematic flow chart of a method for evaluating the inertia of an equivalent synchronous machine in a new energy station provided by an embodiment of the present invention;

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

[0016] Figure 3 A three-dimensional surface schematic diagram representing the frequency modulation control effect of new energy virtual inertia according to an embodiment of the present invention;

[0017] Figure 4A schematic diagram of a correlation representation model of power grid inertia and frequency index according to an embodiment of the present invention;

[0018] Figure 5 It is a three-dimensional surface diagram of the frequency modulation control parameters, response speed and equivalent synchronous machine inertia of the embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, which does not constitute a limitation of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] like Figure 1 The figure is a flow chart of a method for evaluating the inertia of an equivalent synchronous machine in a new energy station provided by an embodiment of the present invention, the method comprising:

[0021] Step 1: construct a frequency response model of a multi-machine system including new energy virtual inertia frequency modulation to obtain a system transfer function;

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

[0023]

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

[0025] like Figure 2 The figure shows a schematic diagram of a system frequency response model considering new energy inertia frequency modulation according to an embodiment of the present invention, from which the system transfer function is obtained, which is expressed as:

[0026]

[0027] Where: G(s) is the system transfer function; M is the system inertia time constant; D is the system damping coefficient; R is the generator regulation coefficient; T CH is the steam volume time constant; F HP is the reheat coefficient of the reheat steam turbine; T RH is the reheat time constant of the reheat steam turbine; T w is the water hammer time constant of the turbine; R T / RP is the turbine transient drop compensation coefficient; T R is the turbine reset time;

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

[0029]

[0030] Step 2: Analyze the relevant parameters that affect the frequency index, and then determine the supporting effect of frequency modulation parameters of different renewable energy power systems on the frequency through the frequency index;

[0031] In this step, the frequency indicators are the system frequency change rate, steady-state frequency deviation, and frequency drop speed. The relevant parameters that affect the frequency indicators are analyzed, including:

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

[0033]

[0034] The maximum frequency change rate is only determined by the disturbance size and the system inertia time constant and has nothing to do with the new energy virtual inertia frequency modulation control.

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

[0036]

[0037] The steady-state frequency deviation is only determined by the disturbance size, system damping coefficient, and generator regulation coefficient, and has nothing to do with the new energy virtual inertia frequency control s.

[0038] Therefore, the frequency index is considered to be the frequency drop speed, which is obtained from the simulation data of the system frequency response model:

[0039]

[0040] Where: f α is the frequency drop speed; T nadir is the time to reach the lowest frequency point; Δf max is the maximum frequency deviation.

[0041] Step 3: Change the frequency modulation control related parameters of new energy through the frequency response model constructed in step 1, simulate and obtain the data pairs of new energy frequency modulation control parameters, unit power response time constant and frequency index, and use the bicubic spline interpolation function to represent the three-dimensional surface of the new energy frequency modulation control effect;

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

[0043] f(T REU (i),H REU (i)) = f α (i)

[0044] Where: T REU (i) is the power response time constant of the new energy station during the i-th simulation; H REU (i) is the virtual inertia frequency modulation control parameter of the new energy station during the i-th simulation; f α (i) is the frequency drop speed during the i-th simulation;

[0045] The three-dimensional surface that uses the bicubic spline interpolation function to characterize the frequency modulation control effect of new energy is expressed as:

[0046]

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

[0048] Among them, the bicubic spline interpolation function is:

[0049]

[0050] in:

[0051] Step 4: Remove the new energy virtual inertia frequency modulation 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 polynomials to simulate the correlation representation model of the power grid inertia frequency modulation capability evaluation parameters and frequency index based on the data set;

[0052] In this step, the new energy virtual inertia frequency modulation control parameter 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, which is expressed as:

[0053] f(M(i))=f α (i)

[0054] Where: M(i) is the inertia value of the synchronous machine during the i-th simulation; f(M(i)) is the frequency drop speed when the inertia of the synchronous machine is M(i); f α(i) is the frequency drop speed during the i-th simulation;

[0055] Based on the data set, the polynomial fitting and the associated characterization model of the grid inertia frequency regulation capability evaluation parameters and frequency indicators are expressed as:

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

[0057] Where: M(f α ) is the correlation model that characterizes the evaluation parameters of the grid inertia frequency regulation capability and the frequency index; p1~p4 are the coefficients of the fitting function.

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

[0059] In this step, the frequency index is used as the intermediate variable, and based on the principle of frequency index equivalence, the three-dimensional surface of the new energy frequency modulation control parameter, response speed-equivalent synchronous machine inertia is obtained, which is expressed as:

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

[0061] Where: M' is the equivalent synchronous machine inertia that characterizes the frequency regulation capability of new energy virtual inertia; T REU Virtual inertia frequency modulation power response time constant of new energy station; H REU Virtual inertia frequency regulation control parameters of new energy stations.

[0062] The method of the present invention is described below by a specific example. The typical coefficients of the system considering the virtual inertia frequency modulation of the new energy station adopted in the embodiment of the present invention are shown in Table 1. The power disturbance ΔP L =0.1pu.

[0063] Table 1 System typical coefficients

[0064] System Parameters Value Synchronous machine adjustment factor R 0.05 Steam volume time constant TCH 0.3s Reheat turbine reheat factor FHP 0.3s Reheat time constant TRH of reheat turbine 8s Water hammer time constant Tw 1s Transient drop compensation coefficient RT / RP 40 Turbine reset time TR 4s System equivalent inertia time constant 2H 10s System equivalent damping constant D 2

[0065] Set the value range of the power response delay of the new energy station to T REU ∈[0.1,3.5], the value range of the new energy virtual inertia frequency modulation control coefficient is set to H REU∈[4,12], the lag of the new energy control transmission signal is set to 100ms, and the three-dimensional surface representing the frequency modulation control effect of the new energy can be obtained by solving it, such as Figure 3 The three-dimensional surface diagram showing the effect of new energy virtual inertia frequency modulation control according to an embodiment of the present invention is shown. Figure 3 In the figure, the x and y axes represent the power response delay of the new energy station, T REU And new energy virtual inertia frequency control coefficient H REU , the z-axis represents the frequency support index, that is, the frequency drop depth f α .

[0066] The new energy frequency regulation module is removed, and the value range of the system inertia is set to M∈[4,20]. The associated representation model of the grid inertia frequency regulation capability evaluation parameters and frequency index can be obtained by solving the equation, as follows: Figure 4 FIG. 1 is a schematic diagram of a correlation representation model of a power grid inertia and a frequency index according to an embodiment of the present invention. Figure 4 In the figure, the x-axis represents the frequency support index, that is, the frequency drop depth f α , the y-axis represents the system inertia M.

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

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

[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 professional and technical personnel in the field.

[0070] In addition, a person skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be implemented by instructing related hardware through a program, and the corresponding program can be stored in a computer-readable storage medium. The above-mentioned storage medium can be a read-only memory, a disk or an optical disk, etc.

[0071] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any form that the 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 station, characterized in that: The method comprises: Step 1: construct a frequency response model of a multi-machine system including new energy virtual inertia frequency modulation to obtain a system transfer function; Step 2: Analyze the relevant parameters that affect the frequency index, and then determine the supporting effect of frequency modulation parameters of different renewable energy power systems on the frequency through the frequency index; Step 3: Change the frequency modulation control related parameters of new energy through the frequency response model constructed in step 1, simulate and obtain the data pairs of new energy frequency modulation control parameters, unit power response time constant and frequency index, and use the bicubic spline interpolation function to represent the three-dimensional surface of the new energy frequency modulation control effect; Step 4: Remove the new energy virtual inertia frequency modulation 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 polynomials to simulate the correlation representation model of the power grid inertia frequency modulation capability evaluation parameters and frequency index based on the data set; Step 5: Based on the obtained characterization surface of the frequency regulation effect of new energy and the correlation characterization model of the frequency regulation capability of the power grid inertia, the frequency index is used as the intermediate variable, and based on the principle of frequency index equivalence, the three-dimensional surface of the frequency regulation control parameters of new energy and the response speed-equivalent synchronous machine inertia is obtained.

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

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

4. The method for evaluating the equivalent synchronous machine inertia of a new energy station according to claim 3 is characterized in that: In step 3, the simulation results show that the data pairs of new energy frequency regulation control parameters, unit power response time constant and frequency index are: f(T REU (i),H REU (i))=f α (i) Where: T REU (i) is the power response time constant of the new energy station during the i-th simulation; H REU (i) is the virtual inertia frequency modulation control parameter of the new energy station during the i-th simulation; f α (i) is the frequency drop speed during the i-th simulation; The three-dimensional surface that uses the bicubic spline interpolation function to characterize the frequency modulation control effect of new energy is expressed as: Where: (T* REU ,H* REU ) is the interpolation point in the three-dimensional surface that represents the frequency modulation control effect of new energy; f* α is the interpolation value; (T REU (i),H REU (j))(i,j=0,1,,2,3) are the neighborhood points near the interpolation point; Among them, the bicubic spline interpolation function is: in:

5. According to claim 3, the method for evaluating the equivalent synchronous machine inertia of a new energy station is characterized in that: In step 4, the new energy virtual inertia frequency modulation control parameter 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, which is expressed as: f(M(i))=f α (i) Where: M(i) is the inertia value of the synchronous machine during the i-th simulation; f(M(i)) is the frequency drop speed when the inertia of the synchronous machine is M(i); f α (i) is the frequency drop speed during the i-th simulation; Based on the data set, the polynomial fitting and the associated characterization model of the grid inertia frequency regulation capability evaluation parameters and frequency indicators are expressed as: M(f α )=p1 * f α ∧3+p2 * f α ∧2+p3 * f α +p4 Where: M(f α ) is the correlation model that characterizes the evaluation parameters of the grid inertia frequency regulation capability and the frequency index; p1~p4 are the coefficients of the fitting function.

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

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