A method, system and device for estimating the effectiveness boundary of frequency emergency control of network-type new energy and a storage medium

Abstract

The application discloses a kind of frequency emergency control effectiveness boundary estimation method, system, equipment and storage medium considering network type new energy, method includes: determining the short-term power disturbance characteristics after power grid failure;Based on short-term power disturbance characteristics, system frequency response model considering network type new energy is constructed, and power grid frequency expression is obtained;Based on power grid frequency expression, the emergency control amount boundary of not triggering frequency third line of defense action under different proportion of synchronous machine is iteratively calculated;According to the result of iterative calculation, the curve of synchronous machine proportion and emergency control amount boundary is fitted, and the area formed by numerical integration calculation emergency control effectiveness boundary is calculated;The application is aimed at power grid short-term power disturbance problem, calculates the boundary area of emergency control edge under specific working condition, effectively quantifies the adaptability of frequency emergency control under short-term power disturbance.

Description

TECHNICAL FIELD

[0001] The application relates to a frequency emergency control effectiveness boundary estimation method, system, device and storage medium, in particular to a frequency emergency control effectiveness boundary estimation method, system, device and storage medium considering grid-forming new energy, and belongs to the technical field of power systems and their automation. BACKGROUND

[0002] With the continuous expansion of the proportion of new energy, the equivalent inertia level and disturbance resistance of the power system will be significantly reduced. Therefore, in a low inertia system, the short-term power impact caused by the low voltage ride through of new energy due to AC / DC fault has become a new type of transient problem threatening the safety and stability of the system.

[0003] Frequency emergency control, as the second line of defense for power system frequency safety, is triggered by specific fault disturbance events in the power grid and matches the pre-set strategy table to execute measures such as generator tripping, load shedding or DC power control within 300ms. Existing emergency control strategies mainly focus on the development of emergency control strategies and how to explore more controllable emergency control resources. However, under excessive short-term power impact, emergency control may cause system low or high frequency problems due to improper action, thereby directly triggering the third line of defense for power system frequency safety - correction control, which ultimately threatens frequency safety.

[0004] Most current documents mainly analyze the adaptability of frequency emergency control under permanent power disturbance, but few documents consider the impact of short-term power disturbance on the adaptability of low inertia systems. Existing technologies do not have a good standard for quantifying the effectiveness boundary of frequency emergency control. Generally, the amount of emergency control action under a certain working condition is determined by continuously simulating online data, which cannot be effectively combined with the third line of defense for frequency - correction control. In addition, when studying the adaptability of frequency emergency control, existing technologies do not comprehensively consider the impact of new energy frequency modulation reserve capacity, synchronous machine governor limiter and other factors on the frequency stability of the power system. That is, the existing frequency emergency control adaptability boundary is not accurate and is relatively ideal. Therefore, the effectiveness of frequency emergency control under certain working conditions of the power grid needs to be analyzed, and how to reasonably quantify the boundary of frequency emergency control under short-term power disturbance is of great significance to frequency safety. SUMMARY

[0005] The purpose of the present application is to provide a frequency emergency control effectiveness boundary estimation method, system, device and storage medium considering grid-forming new energy, which can improve the accuracy.

[0006] Technical scheme: The frequency emergency control effectiveness boundary estimation method considering grid-forming new energy provided by the present application comprises:

[0007] determine the short-term power disturbance characteristics after the power grid failure;

[0008] Based on the short-term power disturbance characteristics, a system frequency response model considering grid-forming new energy is constructed, and a power grid frequency expression is obtained;

[0009] Based on the power grid frequency expression, the emergency control quantity boundary of the third frequency defense line without triggering action is iteratively calculated under different synchronous machine ratios;

[0010] According to the results of iterative calculation, the curve of synchronous machine ratio and emergency control quantity boundary is fitted, and the area formed by the effective boundary of emergency control is calculated by numerical integration.

[0011] Further, the determination of the short-term power disturbance characteristics after the power grid failure comprises:

[0012] The time domain expression of the short-term power disturbance after the power grid failure is:

[0013]

[0014] The complex frequency domain expression is:

[0015]

[0016] Where, ΔP fc is the active power shortage caused by the grid-forming new energy entering 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 step function and slope function with time delay.

[0017] Further, the system frequency response model considering grid-forming new energy is constructed based on the short-term power disturbance characteristics, and the power grid frequency expression is obtained, comprising:

[0018] The time domain expression of the power grid frequency deviation at this time is obtained by Laplace inverse transform, and is rewritten as a piecewise function related to the current time t, the synchronous machine ratio x sg , the emergency control quantity proportion coefficient K ec ;

[0019] When the governor does not reach saturation, the time domain expression of the power grid frequency is:

[0020]

[0021]

[0022] Wherein:

[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 ratio 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-type 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 a time delay of t1 in ΔP(s) is inputted in a saturated state, and w() is the frequency-time domain expression of the frequency response model after the ramp function with a time delay of t2 in ΔP(s) is inputted in a 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 grid frequency expression includes:

[0030] Calculate the minimum emergency control ratio 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 by a preset fixed step, recalculate the two critical emergency control proportion coefficients corresponding to the threshold value of the third defense line not triggered under each proportion of synchronous machines, until the proportion of synchronous machines is 1, and stop;

[0031] iterating the emergency control proportion coefficient by a preset fixed step, the minimum value of system frequency Δω(t) min = 49 + λ corresponds to the emergency control proportion coefficient K ec-min ; the maximum value of system frequency Δω(t) max = 50.5 - λ corresponds to the emergency control proportion coefficient K ec-max , wherein λ is the calculation accuracy, greater than 0;

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

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

[0034] According to the least square method, the curves of the emergency control boundary and the proportion of synchronous machines x sg are fitted respectively, and the intersection of the two curves is determined, for each step interval of the proportion of synchronous machines [x sg (i), x sg (i+1)], the area of each small interval is calculated according to the trapezoidal rule, specifically, the abscissa of the two curves is divided into n small intervals, K ec-max () and K ec-min () are the upper and lower lengths of the trapezoid in a certain small interval, after calculating the area of each small interval, by analogy with definite integral definition, when n is large enough, the sum of all small interval 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 proportion of synchronous machines, S is the emergency control effectiveness boundary area, i is the iteration number, K ec-min is the minimum emergency control proportion coefficient, and K ec-max is the maximum emergency control proportion coefficient.

[0037] Based on the same inventive concept, the application also provides a frequency emergency control effectiveness boundary estimation system considering network-type new energy, comprising:

[0038] a disturbance information confirmation module configured to determine a short-term power disturbance feature after a power grid fault;

[0039] a frequency response model construction module configured to construct a system frequency response model considering grid-forming new energy based on the short-term power disturbance feature, and obtain a power grid frequency expression;

[0040] an iterative calculation module configured to iteratively calculate an emergency control quantity boundary of the synchronous machine not triggering a third frequency defense line action under different proportions of the synchronous machine based on the power grid frequency expression;

[0041] an area calculation module configured to fit a curve of the proportion of the synchronous machine and the emergency control quantity boundary according to the result of the iterative calculation, and calculate an area angle formed by the emergency control effectiveness boundary through numerical integration.

[0042] Further, the disturbance information confirmation module determines the short-term power disturbance feature after the power grid fault, including:

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

[0044]

[0045] the complex frequency domain expression is:

[0046]

[0047] wherein, ΔP fc is the active power shortage caused by the grid-forming new energy entering 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 time delay.

[0048] Further, the frequency response model construction module constructs the system frequency response model considering grid-forming new energy based on the short-term power disturbance feature, and obtains the power grid frequency expression, including:

[0049] the time-domain expression of the power grid frequency deviation at this time is obtained by Laplace inverse transform, and is rewritten as a piecewise function related to the current time t, the proportion of the synchronous machine x sg , and the emergency control quantity proportion coefficient K ec .

[0050] when the governor does not reach saturation, the time-domain expression of the power grid frequency is:

[0051]

[0052] wherein:

[0053]

[0054] When the governor and the grid-forming new energy are both saturated, the system frequency time-domain expression is

[0055]

[0056] Wherein:

[0057]

[0058] Wherein, K ec is the emergency control quantity proportion 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 speed regulation rate of the synchronous machine governor, 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 grid-forming new energy, K w is the droop control coefficient of the grid-forming new energy, ΔP max1 is the governor limit, ΔP max2 is the maximum value of the grid-forming new energy reserve, Δω0 and Δω0' are non-zero initial state values, ΔP fc is the active power shortage of the new energy entering the 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 damping 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 frequency response model of the step function part in ΔP(s) is input, is the initial phase of the sine function in f(), g() is the frequency time-domain expression after the frequency response model of the ramp function part with time delay in ΔP(s) is input, is the initial phase of the sine function in g(), h() is the frequency time-domain expression after the frequency response model of the ramp function with t1 time delay in ΔP(s) is input in the saturated state, w() is the frequency time-domain expression after the frequency response model of the ramp function with t2 time delay in ΔP(s) is input in the saturated state.

[0059] Further, the iteration calculation module iteratively calculates the emergency control quantity boundary of the synchronous machine under different proportions without triggering the third frequency defense line action based on the power grid frequency expression, comprising:

[0060] calculating the minimum emergency control quantity proportion coefficient K ec-min, maximum emergency control amount proportion coefficient K ec-max , continue to increase the proportion of synchronous machines by a preset fixed step, recalculate the two critical emergency control amount proportion coefficients corresponding to the threshold value of the third defense line not triggered under each proportion of synchronous machines, until the proportion of synchronous machines is 1, and stop;

[0061] Iterate the emergency control amount proportion coefficient by a preset fixed step, the minimum value of system frequency Δω(t) min = 49 + λ corresponds to the emergency control amount proportion coefficient K ec-min ; the maximum value of system frequency Δω(t) max = 50.5 - λ corresponds to the emergency control amount proportion coefficient K ec-max , where λ is the calculation accuracy, greater than 0;

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

[0063] Further, the area calculation module, according to the result of iterative calculation, fitting the curve of the proportion of synchronous machines and the emergency control amount boundary, and calculating the area formed by the emergency control effectiveness boundary through numerical integration, comprising:

[0064] According to the least square method, the curve of the emergency control amount boundary and the proportion of synchronous machines x sg is fitted, and the intersection of the two curves is determined, for each step interval of the proportion of synchronous machines [x sg (i), x sg (i+1)], according to the trapezoidal rule, the area of each small interval is calculated, specifically, the abscissa of the two curves is divided into n small intervals, K ec-max ()-K ec-min () are the upper and lower lengths of the trapezoid in a certain small interval, after calculating the area of each small interval, by analogy with definite integral definition, when n is large enough, the sum of all small interval areas is approximately the area formed by the emergency control effectiveness boundary;

[0065]

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

[0067] Based on the same inventive concept, the present application also provides a computing device, comprising one or more processors, one or more memories, and one or more programs stored in the memories and configured to be executed by the processors, the programs, when loaded into the processors, implement the steps of the frequency emergency control effectiveness boundary estimation method considering grid-connected new energy according to any one of the above.

[0068] Based on the same inventive concept, the present application also provides a storage medium, the storage medium storing a computer program, the computer program comprising program instructions, the program instructions, when executed by a processor, causing the processor to perform the steps of the frequency emergency control effectiveness boundary estimation method considering grid-connected new energy according to any one of the above.

[0069] Advantages: Compared with the prior art, the present application aims at the short-term power disturbance problem caused by new energy low voltage ride through, constructs a system frequency response model considering grid-connected new energy, and considers nonlinear factors such as synchronous machine governor limiter in the model, so that the frequency model is more accurate and more in line with the actual situation; the present application takes the non-triggering of the third frequency defense line-correction control as the boundary, screens out two critical control coefficients K ec , and takes this as the emergency control boundary, reasonably represents the effectiveness range of frequency emergency control; the present application 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, so as to quantify the emergency control adaptability under different working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0070] Figure 1 The method flowchart of the embodiment of the present application is shown in the figure;

[0071] Figure 2 The method and iterative process schematic diagram of the embodiment of the present application are shown in the figure;

[0072] Figure 3 The system frequency response model block schematic diagram of the embodiment of the present application is shown in the figure;

[0073] Figure 4 The schematic diagram of the corresponding relationship between the emergency control effective boundary value and the frequency of the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

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

[0075] As shown in the figure, Figure 1 the frequency emergency control effectiveness boundary estimation method considering grid-connected new energy of the embodiment of the present application comprises:

[0076] Step one: determine the short-term power disturbance characteristics after the power grid failure;

[0077] Step two: based on the short-term power disturbance characteristics, a system frequency response model considering grid-forming new energy is constructed, and the power grid frequency expression is obtained;

[0078] Step three: based on the power grid frequency expression, the emergency control quantity boundary of the synchronous machine under different proportion without triggering the third frequency defense action is iteratively calculated;

[0079] Step four: according to the results of iterative calculation, the curve of synchronous machine proportion and emergency control quantity boundary is fitted, and the area composed of emergency control effectiveness boundary is calculated by numerical integration.

[0080] Specifically, the step one, the short-term power disturbance characteristics after the power grid failure are collected;

[0081] Let the time-domain expression of short-term power disturbance after power grid failure be:

[0082]

[0083] The complex frequency domain expression is:

[0084]

[0085] Where, αP fc is the active power shortage caused by the grid-forming new energy entering 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 step function and slope function with time delay.

[0086] Step two, a system frequency response model considering grid-forming new energy is constructed, and the power grid frequency expression is obtained;

[0087] The control block diagram of the system frequency response model is shown in Figure 3 , which considers the non-linear links such as synchronous machine governor limiter and grid-forming new energy power reserve. The time-domain expression of power grid frequency is obtained by Laplace inverse transform, which has three variables, namely time t, synchronous machine proportion x sg and emergency control quantity proportion coefficient K ec . The system frequency is a piecewise function, when the synchronous machine governor does not reach saturation, the time-domain expression of power grid frequency is:

[0088]

[0089] Where:

[0090]

[0091] When the governor and grid-forming new energy are both saturated, the time-domain expression of system frequency is

[0092]

[0093] Where:

[0094]

[0095] Where K ec is the emergency control amount proportionality coefficient, whose value is within 0-1, τ0 is the emergency control delay, α is the turbine characteristic coefficient, T is the turbine equivalent time constant, R is the speed regulation of the synchronous machine governor, x sg is the capacity proportion of the synchronous machine in the system, x = 1-x sg , M is the equivalent inertia time constant of the system, D is the equivalent damping of the system, T j is the virtual inertia coefficient of the grid-forming new energy, K w is the droop control coefficient of the grid-forming new energy, ΔP max1 is the governor limit, ΔP max2 is the maximum value of the grid-forming new energy reserve, Δω0, Δω0' are non-zero initial state values.

[0096] Step three, iterative calculation of the emergency control amount boundary of the synchronous machine under different proportions without triggering the third frequency defense line action;

[0097] Initialize the proportion of the synchronous machine to a certain initial value (for example, 0), calculate the minimum emergency control amount proportionality coefficient K ec-min and the maximum emergency control amount proportionality coefficient K ec-max corresponding to the third defense line threshold value without triggering, and increase the proportion of the synchronous machine by a fixed step of 0.001, and recalculate K ec-min and K ec-max for each increased proportion of the synchronous machine, until the proportion of the synchronous machine is 1, and stop the iterative calculation.

[0098] Method for calculating the two critical parameters K ec-min and K ec-max :

[0099] Initialize the emergency control amount proportionality coefficient K ec to a certain initial value (for example, 0), increase K ec by a fixed step of 0.001, and finally iteratively calculate the minimum system frequency Δω(t) min = 49 + λ corresponding to the emergency control amount proportionality coefficient K ec-min , and similarly iteratively calculate the maximum system frequency Δω(t) max = 50.5 - λ corresponding to the emergency control amount proportionality coefficient K ec-maxwhere λ is the calculation precision, greater than 0. For a series of K ec-min , the curve formed by the above series of K ec-max is the upper boundary of the emergency control, and two critical emergency control parameters are as shown in Figure 4 .

[0100] Step four, according to the iterative data fitting curve of the synchronous machine ratio and the emergency control boundary, and through numerical integration to calculate the area of the emergency control effectiveness boundary;

[0101] According to the least square method, a series of K ec-min , K ec-max and x sg curves are fitted, and the intersection of the two curves is determined, for each step interval of the synchronous machine ratio [x sg (i), x sg (i+1)], according to the trapezoidal rule to calculate the area of each small interval, specifically, the abscissa of the two curves is divided into n small intervals, K ec-max ()-K ec-min () is the upper and lower length of the trapezoid of a certain small interval, after calculating the area of each small interval, by analogy with the definite integral definition, when n is large enough, the sum of the areas of all small intervals 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 ratio, S is the emergency control effectiveness boundary area, and i is the iteration number, and the iteration process is as shown in Figure 2 .

[0104] Based on the same inventive concept, the embodiment also provides a frequency emergency control effectiveness boundary estimation system considering network-type new energy, comprising:

[0105] A disturbance information confirmation module is configured to determine the short-term power disturbance characteristics after the power grid fails;

[0106] A frequency response model construction module is configured to construct a system frequency response model considering network-type new energy based on the short-term power disturbance characteristics, and obtain a power grid frequency expression;

[0107] An iterative calculation module is configured to iteratively calculate the emergency control quantity boundary of the third frequency defense line action not triggered under different synchronous machine ratios based on the power grid frequency expression;

[0108] An area calculation module is configured to calculate an area of the curve formed by the synchronous machine proportion and the emergency control amount boundary according to the iteration calculation result, and calculate the area of the emergency control effectiveness boundary through numerical integration.

[0109] The time domain expression of the short-time power disturbance after the power grid fault is:

[0110]

[0111] The complex frequency domain expression is:

[0112]

[0113] Wherein, αP fc is the active power shortage caused by the low voltage ride through of the grid-connected new energy, 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 slope function with time delay.

[0114] In the frequency response model construction module, the time domain expression of the power grid frequency deviation at this time is obtained through Laplace inverse transform, and is rewritten as a segmented function related to t, the synchronous machine proportion x sg , and the emergency control amount proportion coefficient K ec .

[0115] In the frequency response model construction module, when the governor does not reach saturation, the time domain expression of the power grid frequency is:

[0116]

[0117] Wherein:

[0118]

[0119] When the governor and the grid-connected new energy are saturated at the same time, the time domain expression of the system frequency is

[0120]

[0121] Wherein:

[0122]

[0123] Wherein K ec is the emergency control amount proportion coefficient, the value is within 0-1, τ0 is the emergency control delay, α is the turbine characteristic coefficient, T is the equivalent time constant of the turbine, R is the droop rate of the synchronous machine governor, x sg is the capacity proportion of the synchronous machine in the system, x = 1-x sg , M is the equivalent inertia time constant of the system, D is the equivalent damping of the system, T jK is the virtual inertia coefficient of grid-forming new energy w K is the droop control coefficient of grid-forming new energy max1 K is the governor limit max2 K is the maximum value of grid-forming new energy reserve

[0124] In the iteration calculation module, when the synchronous machine proportion is the initial value, the minimum emergency control amount proportion coefficient K corresponding to the third defense line threshold value not being triggered is calculated ec-min , the maximum emergency control amount proportion coefficient K is calculated ec-max , and the synchronous machine proportion is continuously increased by a fixed step of 0.001, and the two critical emergency control amount proportion coefficients corresponding to the third defense line threshold value not being triggered are recalculated under each synchronous machine proportion, until the synchronous machine proportion is 1.

[0125] In the iteration calculation module, the emergency control amount proportion coefficient is iterated with a fixed step of 0.001, and the minimum system frequency Δω(t) min = 49 + λ corresponds to the emergency control amount proportion coefficient K ec-min ; the maximum system frequency Δω(t) max = 50.5 - λ corresponds to the emergency control amount proportion coefficient K ec-max , where λ is the calculation accuracy, greater than 0.

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

[0127] In the area calculation module, a series of K ec-min , K ec-max and x sg curves are fitted according to the least squares method, and the intersection of the two curves is determined, for each synchronous machine proportion step interval [x sg (i), x sg (i+1)], the area of each small interval is calculated according to the trapezoidal rule, specifically, the abscissa of the two curves is divided into n small intervals, K ec-max () and K ec-min () are the upper and lower lengths of the trapezoid in a certain small interval, after calculating the area of each small interval, by analogy with definite integral definition, when n is large enough, the sum of all small interval areas is approximately the area formed by the emergency control effectiveness boundary;

[0128]

[0129] where S iFor each small step of the synchronous machine proportion, the emergency control effectiveness boundary area corresponding to the small step is S, i is the iteration number, and the iteration process is as shown in Figure 2

[0130] Based on the same inventive concept, the embodiment also provides a computing device, comprising one or more processors, one or more memories, and one or more programs stored in the memories and configured to be executed by the processors, and the programs, when loaded into the processors, implement the steps of the frequency emergency control effectiveness boundary estimation method considering network-type new energy according to any one of the above embodiments.

[0131] Based on the same inventive concept, the embodiment also provides a storage medium, which stores a computer program, and the computer program comprises program instructions, and the program instructions, when executed by a processor, cause the processor to perform the steps of the frequency emergency control effectiveness boundary estimation method considering network-type new energy according to any one of the above embodiments.

[0132] The storage medium comprises RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory or desired program codes in the form of instructions or data structures that can be accessed by a computer and can be accessed by a computer.

[0133] The processor is configured to execute the computer program stored in the memory to implement each step in the method involved in the above embodiments.​

Claims

1. A method for estimating the effectiveness boundary of frequency emergency control considering networked new energy, characterized in that, The method comprises the following steps: determining the short-term power disturbance characteristics after the power grid fails; based on the short-term power disturbance characteristics, a system frequency response model considering grid-connected new energy is constructed, and a power grid frequency expression is obtained; based on the power grid frequency expression, the emergency control quantity boundary of the synchronous machine under different capacity ratios in the system without triggering the third frequency defense line action is iteratively calculated; according to the results of the iterative calculation, the curve of the synchronous machine capacity ratio and the emergency control quantity boundary is fitted, and the area formed by the numerical integral calculation of the emergency control effectiveness boundary is calculated.

2. The method of claim 1, wherein the method further comprises: determining the frequency emergency control effectiveness boundary of the new energy power station based on the frequency emergency control effectiveness boundary of the new energy power station and the frequency emergency control effectiveness boundary of the power grid. The determination of the short-term power disturbance characteristics after the power grid fails comprises: the time domain expression of the short-term power disturbance after the power grid fails is: the complex frequency domain expression is: where ΔP fc is the active power shortage caused by the grid-forming new energy entering 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 time delay.

3. The method of claim 1, wherein the method further comprises: determining a frequency emergency control effectiveness boundary of the network. The construction of the system frequency response model considering grid-connected new energy based on the short-term power disturbance characteristics and the obtaining of the power grid frequency expression comprise: The time-domain expression of the power grid frequency deviation at this time is obtained by Laplace inverse transform, and is rewritten as and the current time t, the synchronous machine proportion x sg , the emergency control amount proportional coefficient K ec The related piecewise function; when the governor does not reach saturation, the time domain expression of the power grid frequency is: wherein: when the governor and the grid-connected new energy are saturated at the same time, the time domain expression of the system frequency is wherein: where ΔP fc is the active power shortage caused by grid-forming new energy during low voltage ride through, t1 is the low voltage ride through duration, t2 is the low voltage ride through recovery time, K ec is the emergency control quantity proportionality 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 governor droop, x sg is the capacity proportion of 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 grid-forming new energy, K w is the droop control coefficient of grid-forming new energy, ΔP max1 is the governor limit, ΔP max2 is the maximum value of grid-forming new energy reserve, Δω0 and Δω0' are non-zero initial state values, ΔP fc is the active power shortage of new energy during 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 damping 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 frequency response model of the step function part in ΔP(s) is input, is the initial phase of the sine function in f(), g() is the frequency time domain expression after the frequency response model of the ramp function part with time delay in ΔP(s) is input, is the initial phase of the sine function in g(), h() is the frequency time domain expression after the frequency response model of the ramp function input in saturation state with t1 time delay in ΔP(s), w() is the frequency time domain expression after the frequency response model of the ramp function input in saturation state with t2 time delay in ΔP(s).

4. The method of claim 1, wherein the method further comprises: determining a frequency emergency control effectiveness boundary of the network. The iterative calculation of the emergency control quantity boundary of the synchronous machine under different capacity ratios in the system without triggering the third frequency defense line action based on the power grid frequency expression comprises: The minimum emergency control amount proportion coefficient K corresponding to the threshold value of the third defense line not triggered when the synchronous machine proportion is the initial value ec-min , the maximum emergency control amount proportion coefficient K ec-max , continue to increase the synchronous machine proportion by a preset fixed step, recalculate the two critical emergency control amount proportion coefficients corresponding to the threshold value of the third defense line not triggered under each synchronous machine proportion, and stop until the synchronous machine proportion is 1. iterating the emergency control amount proportional coefficient with a preset fixed step length, the minimum value of system frequency Δω(t) min The emergency control amount proportional coefficient corresponding to when λ = 49 is K ec-min The maximum value of system frequency Δω(t) max The emergency control amount proportional coefficient corresponding to when λ = 50.5 is K ec-max wherein λ is a calculation precision, and is greater than 0. For different new energy proportions, the corresponding series of K ec-min The curve formed by the series of K ec-max is the upper boundary of emergency control.

5. The method of claim 1, wherein the method further comprises: determining a frequency emergency control effectiveness boundary of the network. The fitting of the curve of the synchronous machine capacity ratio and the emergency control quantity boundary according to the results of the iterative calculation, and the calculation of the area formed by the numerical integral calculation of the emergency control effectiveness boundary comprise: 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 used to determine the intersection of the two curves. For each step interval of the synchronous machine ratio [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 interval, respectively. After calculating the area of ​​each small interval, analogically to the definition of definite integral, when n is large enough, the sum of the areas of all small intervals 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 iteration number, K ec-min is the minimum emergency control amount proportionality coefficient, K ec-max is the maximum emergency control amount proportionality coefficient.

6. A system for estimating the effectiveness boundary of frequency emergency control considering network-type new energy, characterized in that, It comprises: a disturbance information confirmation module for determining the short-term power disturbance characteristics after the power grid fails; a frequency response model construction module for constructing a system frequency response model considering grid-connected new energy based on the short-term power disturbance characteristics, and obtaining a power grid frequency expression; an iterative calculation module for iteratively calculating the emergency control quantity boundary of the synchronous machine under different capacity ratios in the system without triggering the third frequency defense line action based on the power grid frequency expression; an area calculation module for fitting the curve of the synchronous machine capacity ratio and the emergency control quantity boundary according to the results of the iterative calculation, and calculating the area formed by the numerical integral calculation of the emergency control effectiveness boundary.

7. The system for estimating the effectiveness boundary of frequency emergency control considering network-type new energy according to claim 6, characterized in that, The disturbance information confirmation module determines the short-term power disturbance characteristics after the power grid fails, which comprises: the time domain expression of the short-term power disturbance after the power grid fails is: the complex frequency domain expression is: where ΔP fc is the active power shortage caused by the grid-forming new energy entering 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 time delay.

8. The system for estimating the effectiveness boundary of frequency emergency control considering network-type new energy according to claim 6, characterized in that, The frequency response model construction module constructs a system frequency response model considering grid-connected new energy based on the short-term power disturbance characteristics, and obtains a power grid frequency expression, which comprises: The time-domain expression of the power grid frequency deviation at this time is obtained by Laplace inverse transform, and is rewritten as and the current time t, the synchronous machine proportion x sg , the emergency control amount proportional coefficient K ec The related piecewise function; when the governor does not reach saturation, the time domain expression of the power grid frequency is: wherein: when the governor and the grid-connected new energy are saturated at the same time, the time domain expression of the system frequency is wherein: wherein ΔP fc is the active power shortage caused by grid-forming new energy entering low voltage ride through, t1 is the low voltage ride through duration, t2 is the low voltage ride through recovery time, K ec is the emergency control quantity proportionality 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 governor droop, x sg is the capacity proportion of 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 grid-forming new energy, K w is the droop control coefficient of grid-forming new energy, ΔP max1 is the governor limit, ΔP max2 is the maximum value of grid-forming new energy reserve, Δω0 and Δω0' are non-zero initial state values, ΔP fc is the active power shortage of new energy entering 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 damping 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 frequency response model of the step function part in ΔP(s) is input, is the initial phase of the sine function in f(), g() is the frequency time domain expression after the frequency response model of the ramp function part with time delay in ΔP(s) is input, is the initial phase of the sine function in g(), h() is the frequency time domain expression after the frequency response model of the ramp function input in saturation state with t1 time delay in ΔP(s), w() is the frequency time domain expression after the frequency response model of the ramp function input in saturation state with t2 time delay in ΔP(s). 9.The system for estimating the effectiveness boundary of frequency emergency control considering networked new energy of claim 6, wherein The iterative calculation module iteratively calculates the emergency control quantity boundary of the synchronous machine under different capacity ratios in the system without triggering the third frequency defense line action based on the power grid frequency expression, which comprises: The minimum emergency control amount proportion coefficient K corresponding to the threshold value of the third defense line not triggered when the synchronous machine proportion is the initial value ec-min , the maximum emergency control amount proportion coefficient K ec-max , continue to increase the synchronous machine proportion by a preset fixed step, recalculate the two critical emergency control amount proportion coefficients corresponding to the threshold value of the third defense line not triggered under each synchronous machine proportion, until the synchronous machine proportion is 1. The preset fixed step iteration emergency control amount proportional coefficient, the minimum value of system frequency Δω(t) min The emergency control amount proportional coefficient corresponding to when Δω(t) ec-min The maximum value of system frequency Δω(t) max The emergency control amount proportional coefficient corresponding to when Δω(t) ec-max Wherein λ is the calculation accuracy, greater than 0; For different new energy proportions, the corresponding series of K ec-min The curve formed by the series of K ec-max is the upper boundary of emergency control.

10. The system for estimating the effectiveness boundary of frequency emergency control considering network-type new energy according to claim 6, characterized in that, The area calculation module fits the curve of the synchronous machine capacity ratio and the emergency control quantity boundary according to the results of the iterative calculation, and calculates the area formed by the numerical integral calculation of the emergency control effectiveness boundary, which comprises: 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 used to determine the intersection of the two curves. For each step interval of the synchronous machine ratio [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 interval, respectively. After calculating the area of ​​each small interval, analogically to the definition of definite integral, when n is large enough, the sum of the areas of all small intervals 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 iteration number, K ec-min is the minimum emergency control amount proportionality coefficient, K ec-max is the maximum emergency control amount proportionality coefficient.

11. A computing device, comprising: It comprises: One or more processors, one or more memories, and one or more programs, the programs stored in the memories and configured to be executed by the processors, the programs, when loaded into the processors, implement the steps of the method for estimating the effectiveness boundary of frequency emergency control considering network-forming new energy according to any one of claims 1 to 5.

12. A storage medium, characterized by The storage medium stores a computer program, the computer program comprising program instructions, the program instructions, when executed by a processor, causing the processor to perform the steps of the method for estimating the effectiveness boundary of frequency emergency control considering network-forming new energy according to any one of claims 1 to 5.

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