Frequency emergency control effectiveness boundary estimation method, system and device considering network construction type new energy and storage medium

Abstract

The invention discloses a frequency emergency control effectiveness boundary estimation method, system and device considering network construction type new energy and a storage medium. The method comprises the steps of determining short-time power disturbance characteristics after a power grid breaks down; on the basis of the short-time power disturbance characteristics, constructing a system frequency response model considering the network construction type new energy, and obtaining a power grid frequency expression; based on a power grid frequency expression, iteratively calculating an emergency control quantity boundary of a third defensive line action of the non-triggering frequency under different proportions of the synchronous machine; fitting a curve of the proportion of the synchronous machine and the emergency control quantity boundary according to the result of the iterative calculation, and calculating the area formed by the emergency control validity boundary through numerical integration; aiming at the short-time power disturbance problem of the power grid, the effective boundary area of the emergency control edge under the specific working condition is calculated, and the adaptability of the frequency emergency control under the short-time power disturbance is effectively quantified.

Description

Technical Field

[0001] The present invention relates to a frequency emergency control effectiveness boundary estimation method, system, device and storage medium, and in particular to a frequency emergency control effectiveness boundary estimation method, system, device and storage medium taking into account grid-forming new energy, and belongs to the field of power system and automation technology. Background Art

[0002] As the proportion of new energy continues to expand, the equivalent inertia level and anti-interference ability of the power system will be significantly reduced. It can be seen that in low-inertia systems, the short-term power shock caused by low voltage ride-through of new energy caused by AC and DC faults has become a new type of transient problem that threatens the safety and stability of the system.

[0003] Frequency emergency control is the second line of defense for power system frequency security. It is triggered by specific fault disturbance events in the power grid and matches the pre-set strategy table to execute measures such as machine cutting, load cutting or DC power control within 300ms. Existing emergency control strategies are mostly focused on the formulation of emergency control strategies and how to tap more controllable emergency control resources. However, under excessive short-term power shocks, emergency control may cause low-frequency or high-frequency problems in the system due to improper action, thereby directly triggering the third line of defense for power system frequency security - correction control, and ultimately threatening frequency security.

[0004] At present, most of the literature mainly analyzes the adaptability of frequency emergency control under permanent power disturbances, but few literature considers the impact of short-term power disturbances on its adaptability in low-inertia systems; the existing technology has not yet had a good standard for quantifying the effectiveness boundary of frequency emergency control. Generally, the emergency control action amount under a certain working condition is determined by continuously simulating online data, and it fails to effectively combine with the third line of defense of frequency-correction control. In addition, when studying the adaptability of frequency emergency control, the existing technology also fails to comprehensively consider the impact of new energy frequency regulation and standby capacity, synchronous machine speed regulator limiter, etc. on the frequency stability of the power system, that is, the adaptability boundary of the existing frequency emergency control is not accurate and ideal. Therefore, the effectiveness of frequency emergency control under a certain working condition of the power grid needs to be analyzed urgently. How to reasonably quantify the boundary of frequency emergency control under short-term power disturbances is of great significance to frequency safety. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method, system, device and storage medium for estimating the frequency emergency control effectiveness boundary taking into account grid-connected new energy sources with improved accuracy.

[0006] Technical solution: The method for estimating the effectiveness boundary of frequency emergency control taking into account grid-building new energy sources described in the present invention comprises:

[0007] Determine the characteristics of short-term power disturbances after a power grid fault;

[0008] Based on the characteristics of short-term power disturbance, a system frequency response model taking into account grid-connected renewable energy is constructed, and the grid frequency expression is obtained.

[0009] Based on the grid frequency expression, the emergency control quantity boundary that does not trigger the third line of defense action of frequency under different proportions of synchronous machines is iteratively calculated;

[0010] According to the results of iterative calculation, the curve of the proportion of synchronous machines and the boundary of the emergency control amount is fitted, and the area formed by the emergency control effectiveness boundary is calculated by numerical integration.

[0011] Further, the determining of the short-term power disturbance characteristics after a power grid fault occurs includes:

[0012] Assume that the time domain expression of the short-term power disturbance after a power grid fault is:

[0013]

[0014] The complex frequency domain expression is:

[0015]

[0016] Among them, ΔP fc It is the active power shortage caused by the grid-connected renewable energy entering the low voltage ride-through, t1 is the low voltage ride-through duration, t2 is the low voltage ride-through recovery time, t is the current time, and the complex frequency domain expression is composed of a step function and a ramp function with a time delay.

[0017] Furthermore, based on the short-term power disturbance characteristics, a system frequency response model taking into account grid-connected new energy is constructed, and a grid frequency expression is obtained, including:

[0018] The time domain expression of the grid frequency deviation at this time is obtained by Laplace inverse transform, and it is rewritten as the current time t, the proportion of synchronous machines x sg , Emergency control quantity proportional coefficient K ec Related piecewise functions;

[0019] When the speed regulator is not saturated, the grid frequency time domain expression is:

[0020]

[0021]

[0022] in:

[0023]

[0024] When the speed regulator and the grid-forming new energy are saturated at the same time, the system frequency time domain expression is:

[0025]

[0026] in:

[0027]

[0028] Among them, K ec is the emergency control quantity proportional coefficient, 0≤K ec ≤1, τ0 is the emergency control delay, α is the turbine characteristic coefficient, T is the turbine equivalent time constant, R is the adjustment rate of the synchronous machine speed regulator, x sg is the capacity proportion of the synchronous machine in the system, x = 1-x sg , M is the system equivalent inertia time constant, D is the system equivalent damping, T j is the virtual inertia coefficient of the networked new energy, K w is the grid-type new energy droop control coefficient, ΔP max1 is the speed regulator limit, ΔP max2 is the maximum value of the grid-connected new energy reserve, Δω0 and Δω0′ are non-zero initial state values, ΔP fc is the active power shortage of renewable energy when it enters low voltage ride-through, t1 is the low voltage ride-through time, t2 is the low voltage ride-through recovery time, u() is the step function, ω n is the system equivalent natural frequency, A is the system equivalent attenuation coefficient, B is the product of the system equivalent inertia and the turbine equivalent time constant, f() is the frequency time domain expression after the step function part in ΔP(s) is input into the frequency response model, is the initial phase of the sine function in f(), g() is the frequency-time domain expression after the ramp function with time delay in ΔP(s) is input into the frequency response model, is the initial phase of the sine function in g(), h() is the frequency-time domain expression of the frequency response model after the ramp function with time delay t1 in ΔP(s) is inputted in the saturated state, w() is the frequency-time domain expression of the frequency response model after the ramp function with time delay t2 in ΔP(s) is inputted in the saturated state.

[0029] Furthermore, the iterative calculation of the emergency control quantity boundary that does not trigger the third line of defense action of the frequency under different proportions of synchronous machines based on the power grid frequency expression includes:

[0030] Calculate the minimum emergency control amount ratio coefficient K that does not trigger the third line of defense threshold when the proportion of synchronous machines is the initial value ec-min , Maximum emergency control quantity proportional coefficient K ec-max, continue to increase the proportion of synchronous machines at a preset fixed step length, and recalculate the two critical emergency control quantity proportional coefficients that do not trigger the third line of defense threshold value under each synchronous machine proportion, until the synchronous machine proportion reaches 1;

[0031] Iterate the emergency control proportional coefficient with a preset fixed step size, and the minimum system frequency Δω(t) min =49+λ, the corresponding emergency control proportional coefficient is K ec-min ; Maximum system frequency Δω(t) max =50.5-λ, the corresponding emergency control proportional coefficient is K ec-max , where λ is the calculation accuracy, which is greater than 0;

[0032] For the above series of K corresponding to different proportions of new energy ec-min The curve formed is the lower boundary of emergency control; for the above series of K corresponding to different proportions of new energy ec-max The curve formed is the upper boundary of emergency control.

[0033] Furthermore, the curve of the proportion of synchronous machines and the boundary of the emergency control amount is fitted according to the result of the iterative calculation, and the area formed by the emergency control effectiveness boundary is calculated by numerical integration, including:

[0034] According to the least squares method, the emergency control quantity boundary and the synchronous machine proportion x are fitted respectively. sg The curve of the two curves is determined from this, and the step interval [x sg (i),x sg (i+1)], calculate the area of ​​each small interval according to the trapezoidal rule. Specifically, divide the horizontal coordinates of the two curves into n small intervals, K ec-max ()-K ec-min () are the upper and lower lengths of the trapezoid of a certain small area. After calculating the area of ​​each small area, by analogy with the definition of definite integral, when n is large enough, the sum of the areas of all small areas is approximately the area of ​​the emergency control effectiveness boundary.

[0035]

[0036] Where S i is the emergency control effectiveness boundary area corresponding to each small step of the synchronous machine proportion, S is the emergency control effectiveness boundary area, i is the number of iterations, K ec-min is the minimum emergency control quantity proportional coefficient, K ec-max is the maximum emergency control quantity proportional coefficient.

[0037] Based on the same inventive concept, the present invention also provides a frequency emergency control effectiveness boundary estimation system taking into account grid-building new energy, comprising:

[0038] The disturbance information confirmation module is used to determine the short-term power disturbance characteristics after a power grid fault occurs;

[0039] The frequency response model building module is used to build a system frequency response model taking into account grid-connected new energy sources based on the characteristics of short-term power disturbances, and obtain the grid frequency expression;

[0040] Iterative calculation module, used to iteratively calculate the emergency control quantity boundary that does not trigger the third line of defense action of frequency under different proportions of synchronous machines based on the power grid frequency expression;

[0041] The area calculation module is used to fit the curve of the synchronous machine proportion and the emergency control amount boundary according to the results of iterative calculation, and calculate the area angle formed by the emergency control effectiveness boundary through numerical integration.

[0042] Furthermore, the disturbance information confirmation module determines the short-term power disturbance characteristics after a power grid failure, including:

[0043] Assume that the time domain expression of the short-term power disturbance after a power grid fault is:

[0044]

[0045] The complex frequency domain expression is:

[0046]

[0047] Among them, ΔP fc It is the active power shortage caused by the grid-connected renewable energy entering the low voltage ride-through, t1 is the low voltage ride-through duration, t2 is the low voltage ride-through recovery time, t is the current time, and the complex frequency domain expression is composed of a step function and a ramp function with a time delay.

[0048] Furthermore, the frequency response model construction module constructs a system frequency response model taking into account the grid-connected new energy based on the short-term power disturbance characteristics, and obtains a grid frequency expression, including:

[0049] The time domain expression of the grid frequency deviation at this time is obtained by Laplace inverse transform, and it is rewritten as the current time t, the proportion of synchronous machines x sg , Emergency control quantity proportional coefficient K ec Related piecewise functions;

[0050] When the speed regulator is not saturated, the grid frequency time domain expression is:

[0051]

[0052] in:

[0053]

[0054] When the speed regulator and the grid-forming new energy are saturated at the same time, the system frequency time domain expression is:

[0055]

[0056] in:

[0057]

[0058] Among them, K ec is the emergency control quantity proportional coefficient, 0≤K ec ≤1, τ0 is the emergency control delay, α is the turbine characteristic coefficient, T is the turbine equivalent time constant, R is the adjustment rate of the synchronous machine speed regulator, x sg is the capacity proportion of the synchronous machine in the system, x = 1-x sg , M is the system equivalent inertia time constant, D is the system equivalent damping, T j is the virtual inertia coefficient of the networked new energy, K w is the grid-type new energy droop control coefficient, ΔP max1 is the speed regulator limit, ΔP max2 is the maximum value of the grid-connected new energy reserve, Δω0 and Δω0′ are non-zero initial state values, ΔP fc is the active power shortage of renewable energy when it enters low voltage ride-through, t1 is the low voltage ride-through time, t2 is the low voltage ride-through recovery time, u() is the step function, ω n is the system equivalent natural frequency, A is the system equivalent attenuation coefficient, B is the product of the system equivalent inertia and the turbine equivalent time constant, f() is the frequency time domain expression after the step function part in ΔP(s) is input into the frequency response model, is the initial phase of the sine function in f(), g() is the frequency-time domain expression after the ramp function with time delay in ΔP(s) is input into the frequency response model, is the initial phase of the sine function in g(), h() is the frequency-time domain expression of the frequency response model after the ramp function with time delay t1 in ΔP(s) is inputted in the saturated state, w() is the frequency-time domain expression of the frequency response model after the ramp function with time delay t2 in ΔP(s) is inputted in the saturated state.

[0059] Furthermore, the iterative calculation module iteratively calculates the emergency control quantity boundary that does not trigger the third line of defense action of the frequency under different proportions of synchronous machines based on the power grid frequency expression, including:

[0060] Calculate the minimum emergency control amount ratio coefficient K that does not trigger the third line of defense threshold when the proportion of synchronous machines is the initial value ec-min, Maximum emergency control quantity proportional coefficient K ec-max , continue to increase the proportion of synchronous machines at a preset fixed step length, and recalculate the two critical emergency control quantity proportional coefficients that do not trigger the third line of defense threshold value under each synchronous machine proportion, until the synchronous machine proportion reaches 1;

[0061] Iterate the emergency control proportional coefficient with a preset fixed step size, and the minimum system frequency Δω(t) min =49+λ, the corresponding emergency control proportional coefficient is K ec-min ; Maximum system frequency Δω(t) max =50.5-λ, the corresponding emergency control proportional coefficient is K ec-max , where λ is the calculation accuracy, which is greater than 0;

[0062] For the above series of K corresponding to different proportions of new energy ec-min The curve formed is the lower boundary of emergency control; for the above series of K corresponding to different proportions of new energy ec-max The curve formed is the upper boundary of emergency control.

[0063] Furthermore, the area calculation module fits the curve of the synchronous machine proportion and the emergency control amount boundary according to the result of the iterative calculation, and calculates the area formed by the emergency control effectiveness boundary by numerical integration, including:

[0064] According to the least squares method, the emergency control quantity boundary and the synchronous machine proportion x are fitted respectively. sg The curve of the two curves is determined, and the intersection of the two curves is determined. For each step interval of the proportion of the synchronous machine [x sg (i),x sg (i+1)], calculate the area of ​​each small interval according to the trapezoidal rule. Specifically, divide the horizontal coordinates of the two curves into n small intervals, K ec-max ()-K ec-min () are the upper and lower lengths of the trapezoid of a certain small area. After calculating the area of ​​each small area, by analogy with the definition of definite integral, when n is large enough, the sum of the areas of all small areas is approximately the area of ​​the emergency control effectiveness boundary.

[0065]

[0066] Where S i is the emergency control effectiveness boundary area corresponding to each small step of the synchronous machine proportion, S is the emergency control effectiveness boundary area, i is the number of iterations, K ec-min is the minimum emergency control quantity proportional coefficient, K ec-max is the maximum emergency control quantity proportional coefficient.

[0067] Based on the same inventive concept, the present invention also provides a computing device, including: one or more processors, one or more memories and one or more programs, wherein the programs are stored in the memories and configured to be executed by the processors, and when the programs are loaded into the processors, the steps of the frequency emergency control effectiveness boundary estimation method taking into account grid-connected new energy are implemented according to any one of the above-mentioned items.

[0068] Based on the same inventive concept, the present invention also provides a storage medium, which stores a computer program, and the computer program includes program instructions. When the program instructions are executed by a processor, the processor executes the steps of the frequency emergency control effectiveness boundary estimation method taking into account grid-connected new energy according to any of the above items.

[0069] Beneficial effects: Compared with the prior art, the present invention aims at the short-term power disturbance problem caused by low voltage ride-through of new energy, constructs a system frequency response model taking into account grid-type new energy, and considers nonlinear factors such as synchronous machine speed regulator limit in this model, so that the frequency model is more accurate and more in line with reality; the present invention takes the third line of defense of frequency not being triggered - correction control as the limit, and screens out two critical control coefficients K ec , and use this as the emergency control boundary, which reasonably characterizes the effectiveness range of frequency emergency control; the present invention determines the effective boundary of frequency emergency control under different proportions through continuous iterative calculation, and calculates the effective boundary area of ​​frequency emergency control through numerical integration method, thereby quantifying the degree of emergency control adaptability under different working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0071] Figure 2 Schematic diagram of the method and iterative process of an embodiment of the present invention;

[0072] Figure 3 A schematic diagram of a system frequency response model block diagram of an embodiment of the present invention;

[0073] Figure 4 It is a schematic diagram of the corresponding relationship between the emergency control effective boundary value and the frequency according to an embodiment of the present invention. DETAILED DESCRIPTION

[0074] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0075] As attached Figure 1 As shown, the frequency emergency control effectiveness boundary estimation method considering grid-connected new energy in this embodiment includes:

[0076] Step 1: Determine the short-term power disturbance characteristics after a power grid fault occurs;

[0077] Step 2: Based on the characteristics of short-term power disturbances, a system frequency response model taking into account grid-connected renewable energy is constructed, and the grid frequency expression is obtained;

[0078] Step 3: Based on the grid frequency expression, iteratively calculate the emergency control quantity boundary that does not trigger the third line of defense action of the frequency under different proportions of synchronous machines;

[0079] Step 4: According to the results of iterative calculation, fit the curve of the synchronous machine proportion and the emergency control amount boundary, and calculate the area of ​​the emergency control effectiveness boundary through numerical integration.

[0080] Specifically, the step 1 is to collect short-term power disturbance characteristics after a power grid failure occurs;

[0081] Assume that the time domain expression of the short-term power disturbance after a power grid fault is:

[0082]

[0083] The complex frequency domain expression is:

[0084]

[0085] Among them, αP fc It is the active power shortage caused by the grid-connected renewable energy entering the low voltage ride-through, t1 is the low voltage ride-through duration, t2 is the low voltage ride-through recovery time, t is the current time, and the complex frequency domain expression is composed of a step function and a ramp function with a time delay.

[0086] Step 2: construct a system frequency response model taking into account grid-connected new energy sources and obtain a grid frequency expression;

[0087] The control block diagram of the system frequency response model is as follows: Figure 3 As shown in the figure, nonlinear links such as synchronous machine speed regulator limiting link and grid-type new energy power reserve are taken into account. The time domain expression of the power grid frequency is obtained by Laplace inverse transform. The expression has three variables, namely time t, synchronous machine proportion x sg , Emergency control quantity proportional coefficient K ec The system frequency is a piecewise function. When the synchronous machine speed regulator is not saturated, the grid frequency time domain expression is:

[0088]

[0089] in:

[0090]

[0091] When the speed regulator and the grid-forming new energy are saturated at the same time, the system frequency time domain expression is:

[0092]

[0093] in:

[0094]

[0095] Where K ec is the emergency control proportional coefficient, the value is between 0 and 1, τ0 is the emergency control delay, α is the turbine characteristic coefficient, T is the turbine equivalent time constant, R is the adjustment rate of the synchronous machine speed regulator, x sg is the capacity proportion of the synchronous machine in the system, x = 1-x sg , M is the system equivalent inertia time constant, D is the system equivalent damping, T j is the virtual inertia coefficient of the networked new energy, K w is the grid-type new energy droop control coefficient, ΔP max1 is the speed regulator limit, ΔP max2 is the maximum value of the grid-building new energy reserve, and Δω0 and Δω0′ are non-zero initial state values.

[0096] Step 3, iteratively calculate the emergency control volume boundary that does not trigger the third line of defense action of the frequency under different proportions of synchronous machines;

[0097] Initialize the proportion of synchronous machines to a certain initial value (for example, 0), and calculate the minimum emergency control amount ratio coefficient K that does not trigger the third line of defense threshold ec-min , Maximum emergency control quantity proportional coefficient K ec-max The proportion of synchronous machines is increased with a fixed step size of 0.001, and K is recalculated for each increase in the proportion of synchronous machines. ec-min , K ec-max , and the iterative calculation stops when the proportion of synchronous machines reaches 1.

[0098] Calculate the two critical parameters K ec-min , K ec-max Method:

[0099] Initialize the emergency control proportional coefficient K ec For a certain initial value (for example, 0), increase K by a fixed step size of 0.001 ec , and finally iteratively calculate the minimum system frequency Δω(t) min =49+λ, the corresponding emergency control proportional coefficient is K ec-min , and the maximum system frequency Δω(t) is calculated iteratively. max =50.5-λ, the corresponding emergency control proportional coefficient is K ec-max, where λ is the calculation accuracy, which is greater than 0. For the above series of K corresponding to different proportions of new energy ec-min The curve formed is the lower boundary of emergency control; for the above series of K corresponding to different proportions of new energy ec-max The curve formed is the upper boundary of emergency control. The two critical emergency control parameters are as follows: Figure 4 shown.

[0100] Step 4, fitting a curve of the synchronous machine ratio and the emergency control amount boundary according to the iterative data, and calculating the area formed by the emergency control effectiveness boundary by numerical integration;

[0101] According to the least squares method, a series of K ec-min , K ec-max With x sg The curve of the two curves is determined from this, and the step interval [x sg (i),x sg (i+1)], calculate the area of ​​each small interval according to the trapezoidal rule. Specifically, divide the horizontal coordinates of the two curves into n small intervals, K ec-max ()-K ec-min () are the upper and lower lengths of the trapezoid of a certain small area. After calculating the area of ​​each small area, by analogy with the definition of definite integral, when n is large enough, the sum of the areas of all small areas is approximately the area of ​​the emergency control effectiveness boundary.

[0102]

[0103] Where S i is the emergency control effectiveness boundary area corresponding to each small step of the synchronous machine proportion, S is the emergency control effectiveness boundary area, i is the number of iterations, and the iteration process is as follows: Figure 2 shown.

[0104] Based on the same inventive concept, this embodiment also provides a frequency emergency control effectiveness boundary estimation system taking into account grid-building new energy, including:

[0105] The disturbance information confirmation module is used to determine the short-term power disturbance characteristics after a power grid fault occurs;

[0106] The frequency response model building module is used to build a system frequency response model taking into account grid-connected new energy sources based on the characteristics of short-term power disturbances, and obtain the grid frequency expression;

[0107] Iterative calculation module, used to iteratively calculate the emergency control quantity boundary that does not trigger the third line of defense action of frequency under different proportions of synchronous machines based on the power grid frequency expression;

[0108] The area calculation module is used to fit the curve of the synchronous machine proportion and the emergency control amount boundary according to the results of iterative calculation, and calculate the area angle formed by the emergency control effectiveness boundary through numerical integration.

[0109] Assume that the time domain expression of the short-term power disturbance after a power grid fault is:

[0110]

[0111] The complex frequency domain expression is:

[0112]

[0113] Among them, αP fc It is the active power shortage caused by the grid-connected renewable energy entering the low voltage ride-through, t1 is the low voltage ride-through duration, t2 is the low voltage ride-through recovery time, t is the current time, and the complex frequency domain expression is composed of a step function and a ramp function with a time delay.

[0114] In the frequency response model building module, the time domain expression of the grid frequency deviation is obtained by Laplace inverse transform, and it is rewritten as t and synchronous machine proportion x sg , Emergency control quantity proportional coefficient K ec Related piecewise functions.

[0115] In the frequency response model building module, when the speed regulator is not saturated, the grid frequency time domain expression is:

[0116]

[0117] in:

[0118]

[0119] When the speed regulator and the grid-forming new energy are saturated at the same time, the system frequency time domain expression is:

[0120]

[0121] in:

[0122]

[0123] Where K ec is the emergency control proportional coefficient, the value is between 0 and 1, τ0 is the emergency control delay, α is the turbine characteristic coefficient, T is the turbine equivalent time constant, R is the adjustment rate of the synchronous machine speed regulator, x sg is the capacity proportion of the synchronous machine in the system, x = 1-x sg , M is the system equivalent inertia time constant, D is the system equivalent damping, T jis the virtual inertia coefficient of the networked new energy, K w is the grid-type new energy droop control coefficient, ΔP max1 is the speed regulator limit, ΔP max2 is the maximum value of the grid-building new energy reserve, and Δω0 and Δω0′ are non-zero initial state values.

[0124] In the iterative calculation module, the minimum emergency control amount ratio coefficient K corresponding to the initial value of the synchronous machine ratio that does not trigger the third line of defense threshold is calculated ec-min , Maximum emergency control quantity proportional coefficient K ec-max , continue to increase the proportion of synchronous machines with a fixed step size of 0.001, and recalculate the two critical emergency control quantity proportional coefficients that do not trigger the third line of defense threshold value under each synchronous machine proportion, until the synchronous machine proportion is 1 and stop.

[0125] In the iterative calculation module, the emergency control proportional coefficient is iterated with a fixed step size of 0.001, and the minimum system frequency Δω(t) min =49+λ, the corresponding emergency control proportional coefficient is K ec-min ; Maximum system frequency The corresponding emergency control quantity proportional coefficient is K ec-max , where λ is the calculation accuracy and is greater than 0.

[0126] In the iterative calculation module, for the above series of K corresponding to different proportions of new energy ec-min The curve formed is the lower boundary of emergency control; for the above series of K corresponding to different proportions of new energy ec-max The curve formed is the upper boundary of emergency control.

[0127] In the area calculation module, a series of K ec-min , K ec-max With x sg The curve of the two curves is determined, and the intersection of the two curves is determined. For each step interval of the proportion of the synchronous machine [x sg (i),x sg (i+1)], calculate the area of ​​each small interval according to the trapezoidal rule. Specifically, divide the horizontal coordinates of the two curves into n small intervals, K ec-max ()-K ec-min () are the upper and lower lengths of the trapezoid of a certain small area. After calculating the area of ​​each small area, by analogy with the definition of definite integral, when n is large enough, the sum of the areas of all small areas is approximately the area of ​​the emergency control effectiveness boundary.

[0128]

[0129] Where S iis the emergency control effectiveness boundary area corresponding to each small step of the synchronous machine proportion, S is the emergency control effectiveness boundary area, i is the number of iterations, and the iteration process is as follows: Figure 2 shown.

[0130] Based on the same inventive concept, this embodiment also provides a computing device, including: one or more processors, one or more memories and one or more programs, wherein the programs are stored in the memories and configured to be executed by the processors, and when the programs are loaded into the processors, the steps of the frequency emergency control effectiveness boundary estimation method taking into account grid-connected new energy are implemented according to any one of the above items.

[0131] Based on the same inventive concept, this embodiment also provides a storage medium, which stores a computer program, and the computer program includes program instructions. When the program instructions are executed by a processor, the processor executes the steps of the frequency emergency control effectiveness boundary estimation method taking into account grid-connected new energy according to any of the above items.

[0132] Such storage media include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0133] The processor is used to execute the computer program stored in the memory to implement each step of the method involved in the above embodiment.

Claims

1. A frequency emergency control effectiveness boundary estimation method taking into account grid-building new energy, characterized in that: include: Determine the characteristics of short-term power disturbances after a power grid fault; Based on the characteristics of short-term power disturbance, a system frequency response model taking into account grid-connected renewable energy is constructed, and the grid frequency expression is obtained. Based on the grid frequency expression, the emergency control quantity boundary that does not trigger the third line of defense action of frequency under different proportions of synchronous machines is iteratively calculated; According to the results of iterative calculation, the curve of the proportion of synchronous machines and the boundary of the emergency control amount is fitted, and the area formed by the emergency control effectiveness boundary is calculated by numerical integration.

2. The frequency emergency control effectiveness boundary estimation method taking into account grid-building new energy according to claim 1 is characterized in that: The determining of the short-term power disturbance characteristics after a power grid fault occurs includes: Assume that the time domain expression of the short-term power disturbance after a power grid fault is: The complex frequency domain expression is: Among them, ΔP fc It is the active power shortage caused by the grid-connected renewable energy entering the low voltage ride-through, t1 is the low voltage ride-through duration, t2 is the low voltage ride-through recovery time, t is the current time, and the complex frequency domain expression is composed of a step function and a ramp function with a time delay.

3. The frequency emergency control effectiveness boundary estimation method taking into account grid-building new energy according to claim 1 is characterized in that: Based on the short-term power disturbance characteristics, a system frequency response model taking into account the grid-connected new energy is constructed, and a grid frequency expression is obtained, including: The time domain expression of the grid frequency deviation at this time is obtained by Laplace inverse transform, and it is rewritten as the current time t, the proportion of synchronous machines x sg , Emergency control quantity proportional coefficient K ec Related piecewise functions; When the speed regulator is not saturated, the grid frequency time domain expression is: in: When the speed regulator and the grid-forming new energy are saturated at the same time, the system frequency time domain expression is: in: Among them, K ec is the emergency control quantity proportional coefficient, 0≤K ec ≤1, τ0 is the emergency control delay, α is the turbine characteristic coefficient, T is the turbine equivalent time constant, R is the adjustment rate of the synchronous machine speed regulator, x sg is the capacity proportion of the synchronous machine in the system, x = 1-x sg , M is the system equivalent inertia time constant, D is the system equivalent damping, T j is the virtual inertia coefficient of the networked new energy, K w is the grid-type new energy droop control coefficient, ΔP max1 is the speed regulator limit, ΔP max2 is the maximum value of the grid-connected new energy reserve, Δω0 and Δω0′ are non-zero initial state values, ΔP fc is the active power shortage of renewable energy when it enters low voltage ride-through, t1 is the low voltage ride-through time, t2 is the low voltage ride-through recovery time, u() is the step function, ω n is the system equivalent natural frequency, A is the system equivalent attenuation coefficient, B is the product of the system equivalent inertia and the turbine equivalent time constant, f() is the frequency time domain expression after the step function part in ΔP(s) is input into the frequency response model, is the initial phase of the sine function in f(), g() is the frequency-time domain expression after the ramp function with time delay in ΔP(s) is input into the frequency response model, is the initial phase of the sine function in g(), h() is the frequency-time domain expression of the frequency response model after the ramp function with time delay t1 in ΔP(s) is inputted in the saturated state, w() is the frequency-time domain expression of the frequency response model after the ramp function with time delay t2 in ΔP(s) is inputted in the saturated state.

4. The frequency emergency control effectiveness boundary estimation method taking into account grid-building new energy according to claim 1 is characterized in that: The iterative calculation of the emergency control quantity boundary that does not trigger the third line of defense action of the frequency under different proportions of synchronous machines based on the power grid frequency expression includes: Calculate the minimum emergency control amount ratio coefficient K that does not trigger the third line of defense threshold when the proportion of synchronous machines is the initial value ec-min , Maximum emergency control quantity proportional coefficient K ec-max , continue to increase the proportion of synchronous machines at a preset fixed step length, and recalculate the two critical emergency control quantity proportional coefficients that do not trigger the third line of defense threshold value under each synchronous machine proportion, until the synchronous machine proportion reaches 1; Iterate the emergency control proportional coefficient with a preset fixed step size, and the minimum system frequency Δω(t) min =49+λ, the corresponding emergency control proportional coefficient is K ec-min ; Maximum system frequency Δω(t) max =50.5-λ, the corresponding emergency control proportional coefficient is K ec-max , where λ is the calculation accuracy, which is greater than 0; For the above series of K corresponding to different proportions of new energy ec-min The curve formed is the lower boundary of emergency control; for the above series of K corresponding to different proportions of new energy ec-max The curve formed is the upper boundary of emergency control.

5. The frequency emergency control effectiveness boundary estimation method taking into account grid-building new energy sources according to claim 1 is characterized in that: The method of fitting the curve of the synchronous machine proportion and the emergency control amount boundary according to the result of the iterative calculation, and calculating the area formed by the emergency control effectiveness boundary by numerical integration, includes: According to the least squares method, the emergency control quantity boundary and the synchronous machine proportion x are fitted respectively. sg The curve of the two curves is determined, and the intersection of the two curves is determined. For each step interval of the proportion of the synchronous machine [x sg (i),x sg (i+1)], calculate the area of ​​each small interval according to the trapezoidal rule. Specifically, divide the horizontal coordinates of the two curves into n small intervals, K ec-max ()-K ec-min () are the upper and lower lengths of the trapezoid of a certain small area. After calculating the area of ​​each small area, by analogy with the definition of definite integral, when n is large enough, the sum of the areas of all small areas is approximately the area of ​​the emergency control effectiveness boundary. Where S i is the emergency control effectiveness boundary area corresponding to each small step of the synchronous machine proportion, S is the emergency control effectiveness boundary area, i is the number of iterations, K ec-min is the minimum emergency control quantity proportional coefficient, K ec-max It is the maximum emergency control quantity proportional coefficient.

6. A frequency emergency control effectiveness boundary estimation system taking into account grid-building new energy, characterized in that: include: The disturbance information confirmation module is used to determine the short-term power disturbance characteristics after a power grid fault occurs; The frequency response model building module is used to build a system frequency response model taking into account grid-connected new energy sources based on the characteristics of short-term power disturbances, and obtain the grid frequency expression; Iterative calculation module, used to iteratively calculate the emergency control quantity boundary that does not trigger the third line of defense action of frequency under different proportions of synchronous machines based on the power grid frequency expression; The area calculation module is used to fit the curve of the synchronous machine proportion and the emergency control amount boundary according to the results of iterative calculation, and calculate the area angle formed by the emergency control effectiveness boundary through numerical integration.

7. The frequency emergency control effectiveness boundary estimation system taking into account grid-building new energy according to claim 6 is characterized in that: The disturbance information confirmation module determines the short-term power disturbance characteristics after a power grid failure, including: Assume that the time domain expression of the short-term power disturbance after a power grid fault is: The complex frequency domain expression is: Among them, ΔP fc It is the active power shortage caused by the grid-connected renewable energy entering the low voltage ride-through, t1 is the low voltage ride-through duration, t2 is the low voltage ride-through recovery time, t is the current time, and the complex frequency domain expression is composed of a step function and a ramp function with a time delay.

8. The frequency emergency control effectiveness boundary estimation system taking into account grid-building new energy sources according to claim 6 is characterized in that: The frequency response model building module builds a system frequency response model taking into account the grid-building type new energy based on the short-term power disturbance characteristics, and obtains the grid frequency expression, including: The time domain expression of the grid frequency deviation at this time is obtained by Laplace inverse transform, and it is rewritten as the current time t, the proportion of synchronous machines x sg , Emergency control quantity proportional coefficient K ec Related piecewise functions; When the speed regulator is not saturated, the grid frequency time domain expression is: in: When the speed regulator and the grid-forming new energy are saturated at the same time, the system frequency time domain expression is: in: Among them, K ec is the emergency control quantity proportional coefficient, 0≤K ec ≤1, τ0 is the emergency control delay, α is the turbine characteristic coefficient, T is the turbine equivalent time constant, R is the adjustment rate of the synchronous machine speed regulator, x sg is the capacity proportion of the synchronous machine in the system, x = 1-x sg , M is the system equivalent inertia time constant, D is the system equivalent damping, T j is the virtual inertia coefficient of the networked new energy, K w is the grid-type new energy droop control coefficient, ΔP max1 is the speed regulator limit, ΔP max2 is the maximum value of the grid-connected new energy reserve, Δω0 and Δω0′ are non-zero initial state values, ΔP fc is the active power shortage of renewable energy when it enters low voltage ride-through, t1 is the low voltage ride-through time, t2 is the low voltage ride-through recovery time, u() is the step function, ω n is the system equivalent natural frequency, A is the system equivalent attenuation coefficient, B is the product of the system equivalent inertia and the turbine equivalent time constant, f() is the frequency time domain expression after the step function part in ΔP(s) is input into the frequency response model, is the initial phase of the sine function in f(), g() is the frequency-time domain expression after the ramp function with time delay in ΔP(s) is input into the frequency response model, is the initial phase of the sine function in g(), h() is the frequency-time domain expression of the frequency response model after the ramp function with time delay t1 in ΔP(s) is inputted in the saturated state, w() is the frequency-time domain expression of the frequency response model after the ramp function with time delay t2 in ΔP(s) is inputted in the saturated state.

9. The frequency emergency control effectiveness boundary estimation system taking into account grid-building new energy according to claim 6 is characterized in that: The iterative calculation module, based on the power grid frequency expression, iteratively calculates the emergency control quantity boundary that does not trigger the third line of defense action of the frequency under different proportions of synchronous machines, including: Calculate the minimum emergency control amount ratio coefficient K that does not trigger the third line of defense threshold when the proportion of synchronous machines is the initial value ec-min , Maximum emergency control quantity proportional coefficient K ec-max , continue to increase the proportion of synchronous machines at a preset fixed step length, and recalculate the two critical emergency control quantity proportional coefficients that do not trigger the third line of defense threshold value under each synchronous machine proportion, until the synchronous machine proportion reaches 1; Iterate the emergency control proportional coefficient with a preset fixed step size, and the minimum system frequency Δω(t) min =49+λ, the corresponding emergency control proportional coefficient is K ec-min ; Maximum system frequency Δω(t) max =50.5-λ, the corresponding emergency control proportional coefficient is K ec-max , where λ is the calculation accuracy, which is greater than 0; For the above series of K corresponding to different proportions of new energy ec-min The curve formed is the lower boundary of emergency control; for the above series of K corresponding to different proportions of new energy ec-max The curve formed is the upper boundary of emergency control.

10. The frequency emergency control effectiveness boundary estimation system taking into account grid-building new energy sources according to claim 6, characterized in that: The area calculation module fits the curve of the synchronous machine proportion and the emergency control amount boundary according to the result of iterative calculation, and calculates the area formed by the emergency control effectiveness boundary through numerical integration, including: According to the least squares method, the emergency control quantity boundary and the synchronous machine proportion x are fitted respectively. sg The curve of the two curves is determined, and the intersection of the two curves is determined. For each step interval of the proportion of the synchronous machine [x sg (i),x sg (i+1)], calculate the area of ​​each small interval according to the trapezoidal rule. Specifically, divide the horizontal coordinates of the two curves into n small intervals, K ec-max ()-K ec-min () are the upper and lower lengths of the trapezoid of a certain small area. After calculating the area of ​​each small area, by analogy with the definition of definite integral, when n is large enough, the sum of the areas of all small areas is approximately the area of ​​the emergency control effectiveness boundary. Where S i is the emergency control effectiveness boundary area corresponding to each small step of the synchronous machine proportion, S is the emergency control effectiveness boundary area, i is the number of iterations, K ec-min is the minimum emergency control quantity proportional coefficient, K ec-max It is the maximum emergency control quantity proportional coefficient.

11. A computing device, characterized in that: include: One or more processors, one or more memories and one or more programs, wherein the programs are stored in the memories and configured to be executed by the processors, and when the programs are loaded into the processors, the steps of the frequency emergency control effectiveness boundary estimation method taking into account grid-connected new energy sources according to any one of claims 1 to 5 are implemented.

12. A storage medium, characterized in that: The storage medium stores a computer program, which includes program instructions. When the program instructions are executed by a processor, the processor executes the steps of the frequency emergency control effectiveness boundary estimation method taking into account grid-connected new energy according to any one of claims 1 to 5.

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