Emergency generator tripping online decision-making method and system based on stability control effect evaluation

Abstract

The invention provides an emergency generator tripping online decision-making method and system based on stability control effect evaluation, and the method comprises the steps: collecting inertia parameters of a generator, and recording the working state data of the generator after a fault occurs and after the fault is removed; performing unit grouping, aggregation and equivalence to further calculate a concavity and convexity index of a phase trajectory, judging whether the system is unstable according to the concavity and convexity index, and forming an equivalent system power angle curve by using a curve fitting method based on measurement data from a fault to a stability judgment moment when the system is unstable; calculating the difference value between the accumulated unbalanced energy and the residual slowable area to calculate the total generator tripping amount, comparing the output of the advanced generator group with the total generator tripping amount to form a generator tripping combination meeting the requirement of the total generator tripping amount so as to construct a potential generator tripping scheme set, carrying out stability control effect evaluation on any scheme in the scheme set in parallel, and selecting the scheme with the minimum generator tripping amount as the optimal generator tripping scheme. Based on the method, the invention further provides an emergency generator tripping online decision-making system. According to the method, the cutting position and the cutting amount can be given at the same time, and the optimal cutting scheme is generated online.

Description

Technical Field

[0001] The present invention belongs to the technical field of emergency control of new power systems, and in particular relates to an online decision method and system for emergency machine switching based on stabilization effect evaluation. Background Art

[0002] At present, the large-scale access of renewable energy and the large-scale interconnection of AC and DC power grids have led to significant changes in the structural form and stability of the power system, and the dynamic characteristics of the power grid have become increasingly complex. Emergency control is an important means to prevent the destruction of system stability and avoid large-scale power outages. The traditional "offline decision-making, online matching" emergency control decision-making method is based on the design of contingency control strategies based on limited operating modes. The risk of mismatch has increased significantly in modern power systems with increasingly complex and changeable operating modes and fault conditions. Online stability control quickly determines whether the system will become unstable based on the real-time status or response information of the system, and decides on control measures based on the real-time operating status of the system. In theory, it has stronger adaptability and can reduce the risk of mismatch, and has gradually become the development direction of stability control.

[0003] The main task of online stability control decision-making is to make stability judgments based on the real-time operation information of the power system, and to select the best from a variety of stability control schemes when the system is unstable, so as to form a control scheme that not only ensures the stability of the power system but also has a lower control cost. At present, there are two main methods for online stability control decision-making: one is to use the energy function method or EEAC theory to calculate the total amount of cutting, and then determine the cutting position according to the electrical distance or power angle based on engineering experience; the other is to use sensitivity to describe the difference in stability control effects of different cutting positions, linearize the stability constraints in the emergency control decision model, and directly determine the cutting position and cutting amount by solving the optimal control model. The sensitivity can be obtained based on ultra-real-time simulation online calculation or online mapping of offline trained neural networks.

[0004] The first method uses the idea of ​​total quantity first and then decomposition to calculate the total amount of machine cutting without simulation, which meets the rapidity requirements of online stable control. However, when calculating the remaining deceleration area, only the change of equivalent system mechanical power is considered, and the influence of the change of parameters such as equivalent electromagnetic power of the critical group after machine cutting and system inertia time constant is not taken into account. In addition, there is a lack of theoretical support for determining the machine cutting position based on the unit output, electrical distance or power angle leading degree, and it is usually difficult to obtain the optimal machine cutting scheme. The second method is more complete in theory to predict the machine cutting effect based on sensitivity and then decide the machine cutting amount and position at the same time, but the sensitivity calculation based on ultra-real-time simulation has high requirements on simulation calculation performance and it is difficult to balance the model detail and sensitivity accuracy. The sensitivity acquisition method based on data-driven has the problem of generalization difficulty, which may increase the sensitivity calculation error due to changes in operation mode or instability mode, thereby affecting the machine cutting control effect. Therefore, how to quickly and accurately evaluate the stability control effect of different machine cutting schemes and select the best from multiple machine cutting schemes is an urgent problem to be solved in online stable control decision-making. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes an online decision method and system for emergency machine cutting based on stabilization effect evaluation, which can simultaneously give the machine cutting position and cutting amount and generate the optimal machine cutting plan online.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The online decision-making method for emergency machine switching based on stabilization effect evaluation includes the following steps:

[0008] Collect generator inertia parameters, record generator working status data after a fault occurs and after the fault is removed; based on the generator working status data matrix after the fault is removed, cluster the power angle curve using a clustering algorithm to divide the generator into a leading group and a lagging group; equate the leading group and the lagging group to a single-machine infinite system, calculate the convexity index of the equivalent system angular velocity-power angle phase trajectory, and judge whether the system is unstable according to whether the convexity index is greater than zero;

[0009] If the system is unstable, the acceleration area during the generator fault period is calculated, and then the deceleration area before stable control is calculated using the equivalent system power angle curve from the time of fault removal to the time of stabilization judgment, and the equivalent system power angle characteristic prediction curve is formed by curve fitting and extrapolation to calculate the remaining deceleration area; the theoretical machine cutting amount is calculated based on the principle that the acceleration area is not less than the sum of the total deceleration area, and finally a potential machine cutting scheme set is formed based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical machine cutting amount;

[0010] The unbalanced energy change of the selected machine cutting scheme is calculated, and then the remaining retarded area of ​​the equivalent system of the remaining units after the machine cutting and the change in the remaining retarded area caused by the machine cutting are calculated. The overall stabilization effect of the machine cutting is further evaluated to determine whether the machine cutting scheme can stabilize the system. Finally, all the machine cutting schemes that can stabilize the system are compared, and the scheme with the smallest machine cutting amount is selected as the optimal solution for the machine cutting scheme.

[0011] The online decision system for emergency machine cutting based on stabilization effect evaluation includes a judgment module, a calculation module and a decision module;

[0012] The judgment module is used to collect generator inertia parameters, record generator working status data after a fault occurs and generator working status data after the fault is removed; based on the generator working status data matrix after the fault is removed, clustering algorithm is used to cluster the power angle curve to divide the unit into a leading unit group and a lagging unit group; the leading unit group and the lagging unit group are equal to a single-machine infinite system, and the convexity index of the angular velocity-power angle phase trajectory of the equivalent system is calculated, and whether the system is unstable is judged according to whether the convexity index is greater than zero;

[0013] The calculation module is used to calculate the acceleration area during the generator fault period if the system is unstable, and then use the equivalent system power angle curve from the time of fault removal to the time of stabilization to calculate the deceleration area before stable control, and form an equivalent system power angle characteristic prediction curve through curve fitting and extrapolation to calculate the remaining deceleration area; calculate the theoretical machine cutting amount according to the principle that the acceleration area is not less than the sum of the total deceleration area, and finally form a potential machine cutting plan set based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical machine cutting amount;

[0014] The decision module is used to calculate the unbalanced energy change of the selected machine cutting scheme, and then calculate the remaining decelerable area of ​​the equivalent system of the remaining units after the machine cutting and the change in the remaining decelerable area caused by the machine cutting, further evaluate the overall stabilization effect of the machine cutting to determine whether the machine cutting scheme can stabilize the system, and finally compare all the machine cutting schemes that can stabilize the system, and select the scheme with the smallest machine cutting amount as the optimal solution for the machine cutting scheme.

[0015] The effects provided in the content of the invention are only the effects of the embodiments, not all the effects of the invention. One of the above technical solutions has the following advantages or beneficial effects:

[0016] The present invention proposes an emergency machine cutting online decision method and system based on the evaluation of stabilization effect, the method comprising the following steps: collecting generator inertia parameters, recording generator working state data after a fault occurs and generator working state data after the fault is removed; based on the generator working state data matrix after the fault is removed, clustering the power angle curve using a clustering algorithm to divide the unit into an advanced unit group and a lagging unit group; equating the advanced unit group and the lagging unit group to a single-machine infinite system, calculating the convexity index of the equivalent system angular velocity-power angle phase trajectory, and judging whether the system is unstable according to whether the convexity index is greater than zero; if the system is unstable, calculating the acceleration area during the generator fault period, and then using the equivalent system from the fault removal to the stability judgment moment The power angle curve is used to calculate the decelerated area before stable control, and the equivalent system power angle characteristic prediction curve is formed by curve fitting and extrapolation to calculate the remaining deceleration area; the theoretical cutting amount is calculated based on the principle that the acceleration area is not less than the sum of the total deceleration area, and finally the potential cutting scheme set is formed based on the principle that the sum of the real-time output of the cut units is greater than the theoretical cutting amount; the unbalanced energy change of the selected cutting scheme is calculated, and then the remaining deceleration area of ​​the equivalent system of the remaining units after the cutting and the change in the remaining deceleration area caused by the cutting are calculated, and the overall stable control effect of the cutting is further evaluated to determine whether the cutting scheme can stabilize the system, and finally all the cutting schemes that can stabilize the system are compared, and the scheme with the smallest cutting amount is selected as the optimal solution cutting scheme. An emergency cutting online decision method based on stable control effect evaluation is also proposed. An emergency cutting online decision system based on stable control effect evaluation is also proposed. The present invention can accurately and quickly evaluate the stable control effect of different cutting schemes based on the real-time state information of the power grid, further optimize the comprehensive optimal scheme by comprehensively comparing the control effect and control cost of the cutting scheme, and simultaneously generate the optimal cutting scheme online by giving the cutting position and cutting amount. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of an online decision-making method for emergency machine switching based on stabilization effect evaluation in Example 1 of the present invention;

[0018] Figure 2 This is a flowchart of rapid stability determination based on the concavity and convexity of the phase trajectory according to Embodiment 1 of the present invention;

[0019] Figure 3 This is a flow chart of unit grouping based on the K-means clustering method in Example 1 of the present invention;

[0020] Figure 4 A flow chart for generating a potential machine cutting scheme set based on equal acceleration and deceleration areas in embodiment 1 of the present invention;

[0021] Figure 5 This is a flow chart of the preferred cutting scheme based on the rapid evaluation of the cutting stabilization effect in Example 1 of the present invention;

[0022] Figure 6 This is the topology diagram of the example system;

[0023] Figure 7 It is the continuous calculation result of the concavity and convexity index of the phase trajectory of the application example;

[0024] Figure 8 This is the fitting result of the power angle characteristic curve of the system after the fault is removed in the application example;

[0025] Fig. 9 This is a system diagram of the emergency machine switching online decision method based on stabilization effect evaluation proposed in Example 2 of the present invention. DETAILED DESCRIPTION

[0026] In order to clearly illustrate the technical features of the present invention, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings. The following disclosure provides many different embodiments or examples for implementing different structures of the present invention.

[0027] Example 1

[0028] Embodiment 1 of the present invention proposes a flow chart of an online decision-making method for emergency machine cutting based on stabilization effect evaluation, which is used to solve the problem of how to select the optimal machine cutting scheme from multiple machine cutting schemes in the prior art.

[0029] In step 1: the generator inertia parameters are collected, and the generator working status data after the fault occurs and the generator working status data after the fault is removed are recorded; based on the generator working status data matrix after the fault is removed, the power angle curve is clustered by a clustering algorithm to divide the unit into a leading group and a lagging group; the leading group and the lagging group are equal to a single-machine infinite system, and the convexity index of the equivalent system angular velocity-power angle phase trajectory is calculated, and whether the system is unstable is determined according to whether the convexity index is greater than zero.

[0030] The generator inertia parameters and the generator power angle, angular velocity (the difference between the actual angular velocity per unit value and the synchronous angular velocity per unit value), electromagnetic power and mechanical power measurement data during the fault period and after the fault is removed are taken as input. The measurement data are accumulated, and based on the accumulated measurement data, the units are grouped and equivalent to a single-machine infinite system. The convexity index of the angular velocity-power angle phase trajectory of the equivalent system is calculated. Finally, whether the system is unstable is judged based on whether the convexity index is greater than zero. Figure 2 This is a flowchart of the rapid stability determination based on the concavity of the phase trajectory proposed in Example 1 of the present invention.

[0031] In step 1.1, the generator parameters and working status data during the fault period are recorded based on the measurement information of PMU and WAMS, including: collecting the inertia parameter data of the operating generator to form the generator inertia vector:

[0032] M0=[M1 M2 … Mi ];(1)

[0033] Among them, M0 is the moment of inertia of all operating generators, M i is the moment of inertia of the i-th generator;

[0034] After a fault is detected, the working status data of each generator collected by PMU and WAMS at the current moment, including the generator power angle, angular velocity, mechanical power, and electromagnetic power, are recorded and stored in the variable matrix of the fault data buffer area:

[0035]

[0036] Among them, δ bf A matrix for recording the operating data values ​​of the power angle of the generator; represents the power angle of the i-th generator at the k0th moment after the fault; ω bf Recording matrix of running data values ​​for generator angular velocity; represents the angular velocity of the generator of the i-th generator at the k0th moment after the fault; A matrix for recording the electromagnetic power operation data values ​​of the generator; represents the electromagnetic power of the i-th generator at the k0th moment after the fault; A matrix for recording the values ​​of the mechanical power operation data of the generator; represents the mechanical power of the i-th generator at the k0th moment after the fault; i = 1, 2, ..., n, k0 = 1, 2, ... t bf , n represents the number of generators, t bf Indicates the current sampling time number of the fault data record. Cyclic sampling, each sampling data is stored in a new row of the fault data buffer matrix.

[0037] Step 1.2: Based on the measurement information of PMU and WAMS, the working status data of the generator after the fault is removed is recorded, including: after the fault is detected and removed, the working status data of each generator collected by PMU and WAMS at the current moment, including the generator power angle, angular velocity, mechanical power, and electromagnetic power, are recorded and stored in the variable matrix of the data buffer after the fault is removed:

[0038]

[0039] Among them, δ af Represents the generator power angle operation data value record matrix after the fault is removed; represents the power angle of the i-th generator at the k-th moment after the fault is removed; ω af Represents the generator angular velocity operation data value record matrix after the fault is removed; represents the angular velocity of the i-th generator at the k-th moment after the fault is removed; Represents the record matrix of the electromagnetic power operation data value of the generator after the fault is removed; It represents the electromagnetic power of the generator of the i-th generator at the k-th moment after the fault is removed; Represents the record matrix of the mechanical power operation data value of the generator after the fault is removed; represents the mechanical power of the i-th generator at the k-th moment after the fault is removed; k = 1, 2, ... t af , t af Indicates the current sampling time of data record after the fault is cleared.

[0040] Cyclic sampling, each sampling data is stored in a new row of the data buffer matrix after the fault is removed;

[0041] The number of data items stored in the data buffer matrix after the fault is removed is t af Is it greater than the minimum number of information N required for calculation? min (N min Generally, 10 is taken. If yes, go to step 1.3. If not, continue sampling.

[0042] Step 1.3: Record the matrix δ based on the data value after resection af , the K-means clustering method is used to cluster the power angle curves of all generators, and the units are divided into leading units Ω S and the lagging group Ω A .

[0043] Figure 3 This is a flow chart of unit grouping based on the K-means clustering method proposed in Example 1 of the present invention.

[0044] Record the matrix δ with the data value after fault removal af A column of data (k=1,2,...t af ) as a power angle curve δ i Substitute the following formula (4) to calculate the Euclidean distance between any two power angle curves:

[0045]

[0046] Among them, D ij is the Euclidean distance between the power angle curve of the i-th generator and the power angle curve of the j-th generator;

[0047] Select the two curves with the largest Euclidean distance as the initial cluster centers C1 and C2 of the first and second clusters, and write the corresponding generator numbers into the index sets Ω1 and Ω2 of the first and second clusters;

[0048] From δ af Choose any one of the remaining curves m , calculate δ m The Euclidean distance between cluster centers C1 and C2:

[0049]

[0050] Among them, D m,1 ,D m,2 are the Euclidean distances between the mth power angle curve and the cluster centers C1 and C2 respectively; C 1,k , C 2,k are the values ​​of cluster centers C1 and C2 at the kth moment respectively.

[0051] Contrast D m,1 and D m,2 Size relationship, if D m,1 >D m,2 , then δ m Classified as the second cluster and the curve column index is merged into the index set Ω2, otherwise δ m Classify it as the first cluster and merge the curve column index into the index set Ω1; update the aggregation center of the corresponding cluster:

[0052]

[0053] in, are the number of generators in the first and second machine groups respectively;

[0054] If δ af After the power angle curve in is calculated, the average value difference between the cluster centers C1 and C2 is calculated, and the leading cluster Ω is distinguished according to the positive and negative difference. S and the lagging group Ω A :

[0055]

[0056] δ C1 , δ C2 are the average power angles of the first and second machine groups respectively;

[0057] If δ C1 >δ C2 , then the first group and the second group are respectively the leading group and the lagging group, that is, Ω S =Ω1,Ω A =Ω2; otherwise Ω S =Ω2,Ω A =Ω1.

[0058] Step 1.4: According to the grouping results, the leading group Ω Sand the lagging group Ω A The center of inertia is used to equalize the values, and the relative power angle difference is used to describe the system swing process to form a single machine infinite system. The matrix δ is recorded based on the data value after the fault is removed. af ,ω af , Calculates equivalent system power angle, angular velocity, electromagnetic power and mechanical power trajectory. Includes:

[0059] The weighted average of the power angle and angular velocity of the generators in the group is used to represent the power angle and angular velocity of the inertia center. The sum of the electromagnetic power and the sum of the mechanical power of each generator is used to represent the total electromagnetic power and mechanical power of the inertia center. Formula (8) is used to calculate the power angle, angular velocity, electromagnetic power and mechanical power trajectory of the inertia center at each moment:

[0060]

[0061] Among them, M S For the leading group Ω S Equivalent moment of inertia; M A is the lagging group Ω A Equivalent moment of inertia; δ S,k ,ω S,k , P eS,k , P mS,k They are Ω S The value of the equivalent power angle at the kth moment, the value of the angular velocity at the kth moment, the value of the electromagnetic power at the kth moment, and the value of the mechanical power at the kth moment; δ A,k ,ω A,k , P eA,k , P mA,k They are Ω A The value of the equivalent power angle at the kth moment, the value of the angular velocity at the kth moment, the value of the electromagnetic power at the kth moment and the value of the mechanical power at the kth moment;

[0062] The difference between two groups of equivalent parameters is used to characterize the system state, and the equivalent is a single-machine infinite system. Formula (9) is used to calculate the power angle, angular velocity, electromagnetic power and mechanical power trajectory of the equivalent system at each moment;

[0063]

[0064] M T =M S +M A ,k=1,2...t af ; (9)

[0065] Among them, M T is the moment of inertia of the equivalent system; δ k is the value of the power angle of the equivalent system at the kth moment, ωk is the value of angular velocity at the kth moment, P e,k is the value of electromagnetic power at the kth moment, P m,k is the value of mechanical power at the kth moment;

[0066] The generator working status data δ after the fault is removed af ,ω af , Equations (8) and (9) are used to convert the equivalent system state trajectory after fault removal to form;

[0067]

[0068] In step 1.5, the convexity of the current power angle-angular velocity phase trajectory is calculated based on the state trajectory of the equivalent single-machine infinite system. The convexity of the phase trajectory is used to determine whether the system has power angle instability, including:

[0069] Take the angular velocity and power at the last two moments in the state trajectory and substitute them into formula (11) to calculate the first-order derivative of the power angle-angular velocity phase trajectory at the current moment and the previous moment:

[0070]

[0071] Among them, d k is the first-order derivative of the power angle-angular velocity phase trajectory at the kth moment;

[0072] Based on the first-order derivative of the power angle-angular velocity phase trajectory and the last two values ​​of the power angle of the equivalent system, substitute into formula (12) to calculate the second-order derivative of the power angle-angular velocity phase trajectory of the equivalent system at the current moment:

[0073]

[0074] Based on the second-order derivative of the power angle-angular velocity phase trajectory and the angular velocity at the current moment, the trajectory concavity index is calculated according to formula (13):

[0075]

[0076] Among them, μ taf is the current t af The concavity of the moment power angle-angular velocity phase trajectory;

[0077] Determine whether the system has power angle instability. If μ taf ≥0, the system is judged to be in a power angle instability state, and enters step 2 to perform power angle stabilization emergency control.

[0078] calculate if If the system is always in a stable state, clear all cached data and return to step 1.1 to wait for the next failure; Only judge the stability of this fault, return to step 1.2 to collect data at the next moment, and start the next round of stability judgment.

[0079] In step 2: if the system is unstable, the acceleration area during the generator fault period is calculated, and then the deceleration area before stable control is calculated using the equivalent system power angle curve from the time the fault is removed to the time of judging stability, and the equivalent system power angle characteristic prediction curve is formed by curve fitting and extrapolation to calculate the remaining deceleration area; the theoretical machine cutting amount is calculated based on the principle that the sum of the acceleration area and the total deceleration area is equal, and finally a potential machine cutting scheme set is formed based on the principle that the sum of the real-time output of the removed units is greater than the theoretical machine cutting amount.

[0080] Firstly, the acceleration area during the fault period is calculated using the recorded fault data based on the grouping scheme given by stability judgment. Then, the deceleration area before stable control is calculated using the equivalent system power angle curve from the time of fault removal to the time of stability judgment. The equivalent system power angle characteristic prediction curve is formed by curve fitting and extrapolation to calculate the remaining deceleration area. The theoretical machine cutting amount is further calculated based on the principle that the sum of the acceleration area and the total deceleration area is equal. Finally, a set of potential machine cutting schemes is formed based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical machine cutting amount. Figure 4 A flow chart for generating a potential machine cutting solution set based on equal acceleration and deceleration areas proposed in Embodiment 1 of the present invention;

[0081] Step 2.1: The leading cluster set Ω determined based on stable clustering S and the delayed cluster set Ω A , the variable matrix δ recorded in the fault data buffer af ,ω af , Equations (8) and (9) are used to convert the system into equivalent system state trajectories after fault removal.

[0082] Taking the power angle as the independent variable, mechanical power and electromagnetic power as the dependent variables, substitute the following formula to calculate the acceleration area during the fault using the rectangular method:

[0083]

[0084] In the formula, S A is the acceleration area of ​​the equivalent system during the fault period;

[0085] Step 2.2: Use the equivalent system power angle curve from the time of fault removal to the time of stabilization to calculate the deceleration area before stable control, and form the equivalent system power angle characteristic prediction curve through curve fitting and extrapolation. Calculate the remaining deceleration area based on the extrapolated curve, including:

[0086] The deceleration area that has occurred from the time when the fault is cleared to the time when stability is determined:

[0087]

[0088] S D1 It is the deceleration area of ​​the equivalent system from the time when the fault is removed to the time when stability is judged;

[0089] The deceleration area of ​​the equivalent system from the time of fault removal to the time of judging stability

[0090] ΔS0=S A -S D1 ; (16)

[0091] Assume that the equivalent system power angle curve and mechanical power curve conform to the following form:

[0092] P e =α+βsin(γδ+C)

[0093] P m =a+bδ; (17)

[0094] P e =P e af ,δ=δ af and For mapping sequence, nonlinear and least square parameter identification methods are used to calculate the first parameter to be identified α, the second parameter to be identified β, the third parameter to be identified γ and the fourth parameter to be identified C, as well as the fifth parameter to be identified a and the sixth parameter to be identified b;

[0095] exist The interval is equally divided into a preset number of power angle points to form a power angle prediction sequence The preset number in this application is 100. Substitute into formula (16) to calculate the corresponding electromagnetic power and mechanical power prediction sequence Search from front to back to meet The sequence elements of the conditions form the electromagnetic and mechanical power prediction sequence corresponding to the deceleration area and its corresponding power angle prediction sequence

[0096] The predicted mechanical power is screened by taking the predicted power angle sequence as the independent variable. and electromagnetic power As the dependent variable, substitute it into formula (18) and use the rectangular method to calculate the remaining deceleration area:

[0097]

[0098] Among them, S D2It is the remaining decelerable area of ​​the equivalent system from the stabilization moment to the point of no return.

[0099] The remaining deceleration area shortfall is determined based on the principle that the acceleration area is not less than the sum of the total deceleration area:

[0100] S D3 =λ D (S A -S D1 -S D2 ); (19)

[0101] In the formula, S D3 The deceleration area required to maintain system stability, λ D This is the reliability factor that can ensure the stability effect when considering the calculation error; usually it is 1.05~1.1;

[0102] Assuming that the potential deceleration area increased by the machine cutting control is rectangular, calculate the equivalent machine cutting amount ΔP m :

[0103]

[0104] in, They are the equivalent system power angle and the farthest point power angle at the time of judging stability respectively;

[0105] Calculate the theoretical cutting capacity ΔP M :

[0106]

[0107] The process of forming a potential cutting plan set based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical cutting amount is as follows: Read the leading group generator index set Ω S , set the maximum allowed number of cutting machines N cmax ; Set the current allowed number of cutting machines to N c is 1; forms a c The set of elements Ω S Calculate the sum of the real-time output of the generators in each subset. If the sum of the real-time output is greater than the theoretical cutting capacity, add the subset to the potential cutting plan set; until the number of cutting units is N c Increase to the maximum allowable number of cutting machines N cmax , complete the cutting machine solution set

[0108] In Step 3: calculate the unbalanced energy change of the selected machine cutting scheme, then calculate the remaining retarded area of ​​the equivalent system of the remaining units after the machine cutting and the change in the remaining retarded area caused by the machine cutting, further evaluate the overall stabilizing effect of the machine cutting and judge whether the machine cutting scheme can stabilize the system, finally compare all the machine cutting schemes that can stabilize the system, and select the scheme with the smallest machine cutting amount as the optimal solution for the machine cutting scheme. Figure 5 This is a flow chart of the preferred cutting scheme based on the rapid evaluation of the cutting stabilization effect proposed in Example 1 of the present invention;

[0109] In Step 3.1, select any cutting plan Ω from the cutting plan set. c , calculate the unbalanced energy change caused by the machine cutting scheme, including:

[0110] In the leading cluster index set Ω S Middle rejection cutting machine solutionΩ c The corresponding generator number forms the remaining leading group index set Ω corresponding to the machine cutting scheme s '

[0111] Determine the remaining leading cluster index set Ω' s ; According to Ω' s and Ω A Calculate the set of eliminated units Ω c State trajectory of the post-equivalent system during fault periodδ bf' ,ω bf' ,

[0112] Taking the power angle as the independent variable, mechanical power and electromagnetic power as the dependent variables, substitute them into formula (22) to calculate the acceleration area of ​​the equivalent system after removing the disconnected unit during the fault period:

[0113]

[0114] Among them, S' A It is the acceleration area of ​​the equivalent system after removing the cut-off units during the fault period;

[0115] Determine the set of eliminated units Ω c State trajectory of the post-equivalent system during fault periodδ af' ,ω af' ,

[0116] Calculate the deceleration area of ​​the equivalent system from the time of fault removal to the time of judging stability:

[0117]

[0118] Among them, S' D1 It is the deceleration area of ​​the equivalent system from the time of fault removal to the time of judging stability;

[0119] Compare the difference between the acceleration area and the deceleration area of ​​the equivalent system before and after the unit is removed, and use (24) to calculate the change in unbalanced energy caused by the unit removal control:

[0120] ΔS1=(S A -S D1 )-(S' A -S' D1 );(twenty four)

[0121] Where ΔS1 is the change in the accumulated unbalanced energy before and after the machine cutting control;

[0122] Step 3.2: Based on the elimination of unit set Ω c State trajectory of the post-equivalent system during fault periodδ af' ,ω af' , The trajectory is fitted with power angle characteristics and the remaining deceleration area is calculated by extrapolation;

[0123] Assume that the equivalent system power angle curve and mechanical power curve after removing the cut-off unit are as shown in formula (17), respectively: and For mapping sequence, nonlinear and least square parameter identification methods are used to calculate the first parameter to be identified α, the second parameter to be identified β, the third parameter to be identified γ and the fourth parameter to be identified C, as well as the fifth parameter to be identified a and the sixth parameter to be identified b;

[0124] exist The interval is equally divided into a preset number of power angle points to form a power angle prediction sequence Substitute into formula (23) to calculate the corresponding electromagnetic power and mechanical power prediction series The preset number in this application is 100. Search from front to back to meet The sequence elements of the conditions form the electromagnetic and mechanical power prediction sequence corresponding to the deceleration area and its corresponding power angle prediction sequence

[0125] The predicted mechanical power is screened by taking the predicted power angle sequence as the independent variable. and electromagnetic power As the dependent variable, substitute it into formula (25) and use the rectangular method to calculate the remaining deceleration area:

[0126]

[0127] In the formula, S' D2 It is the remaining deceleration area of ​​the equivalent system after eliminating the cut-off units from the stability judgment moment to the no-return point.

[0128] Step 3.3: Based on the electromagnetic power transfer caused by cutting the generator, the change of the remaining retarded area is calculated by using a rectangular approximation, including: using a voltage source model to model the uncut generator, using the injected current change to model the cut generator, forming a circuit model with the injected power change as input, and forming a node-related admittance matrix according to the circuit interconnection relationship;

[0129] Calculate the injection current change of the uncut-off units caused by cutting the generator using the node voltage method

[0130]

[0131] are the injected currents of the rth and sth nodes before the removed unit is removed;

[0132] is the change in the injected current of the i-th generator and the j-th generator after the cut-off unit is cut off; y ir ,y is are the associated admittance elements of the rth and sth nodes of the i-th generator of the removed unit and the unremoved unit respectively; y jr ,y js are the associated admittance elements of the rth and sth nodes of the jth generator of the removed unit and the unremoved unit respectively;

[0133] The power change of the non-removed units is obtained by multiplying the current change of the non-removed units by the corresponding node voltage:

[0134]

[0135] In the formula, They are the internal potential of the uncut-off unit, the variation of injected power and the variation of injected current respectively;

[0136] Formula (28) is used to calculate the total change of electromagnetic power of the equivalent system after cutting the machine:

[0137]

[0138] In the formula, is the change in electromagnetic power of the equivalent system caused by cutting, M C is the sum of the equivalent inertia of the removed units;

[0139] Formula (29) is used to calculate the change in the decelerable area caused by the change in electromagnetic power of the equivalent system:

[0140]

[0141] Among them, S' D3is the change in the decelerable area caused by the change in the electromagnetic power of the equivalent system;

[0142] The combined deceleration area that can be provided by the cutting machine control is obtained by summing the change in unbalanced area, the remaining deceleration area, and the change in deceleration area:

[0143] S dec =ΔS1+S' D2 +S' D3 ; (30)

[0144] Comparison of comprehensive deceleration area S dec and the initial unbalanced energy ΔS0: If S dec >ΔS0, then the generator cutting can stabilize the system, and the generator set included in the generator cutting scheme is added to the stable generator cutting scheme set Ω stable And record the corresponding cutting amount;

[0145] Comparison of stable cutting machine solution set Ω stable The total power of all cutting plans in the cutting plan is calculated, and the plan with the smallest total power is selected as the optimal cutting plan.

[0146] The online decision method for emergency machine cutting based on stability control effect evaluation proposed in Example 1 of the present invention can accurately and quickly evaluate the stability control effects of different machine cutting schemes based on the real-time status information of the power grid, further optimize the comprehensive optimal scheme by comprehensively comparing the control effects and control costs of the machine cutting schemes, and simultaneously generate the optimal machine cutting scheme online by giving the machine cutting position and the machine cutting amount.

[0147] The effectiveness of the method proposed in this patent is verified by taking the IEEE39 node system as an example. The IEEE39 node system contains 39 nodes, including 3 generator nodes, 6 substation nodes and 30 load nodes, 10 generators, and a total of 46 branches. The main generators are distributed in different areas and connected through 46 transmission lines to form a complex power network. Figure 6 This is the topology diagram of the example system.

[0148] When the fault scenario is 1s, a three-phase short circuit fault is set in the first section of line 23-24. After the fault duration is 0.22s, the relay protection trips the fault line. The application steps of the patented method are:

[0149] First, when the system detects a fault, it first records the measured data during the fault period according to step 1 to form the variable matrix of the fault data buffer area, and the data time step is 0.01s;

[0150] Further detection is made to remove the fault, and the measured data after the fault removal is recorded to form the matrix of variables in the data buffer after the fault removal, and the data time step is still 0.01s;

[0151] After the fault is removed, the data buffer area accumulates to 10 and then enters the stability judgment phase. Based on the measured data, grouping and equivalent calculation are performed according to equations (8) and (9) to obtain the state trajectory of the single-machine infinite system. Based on this trajectory, the concavity of the current power angle-angular velocity phase trajectory is calculated.

[0152] As the accumulated data increases, the concavity index of the phase trajectory changes with time. Figure 7 It is the continuous calculation result of the concavity and convexity index of the phase trajectory of the application example;

[0153] 0.13 seconds after the fault is cleared (absolute time 1.35s, i.e. after accumulating 13 data points after the fault is cleared), the trajectory concavity curve crosses the 0 axis and is greater than zero, and then the system is judged to be unstable and emergency control is initiated;

[0154] Then, the equivalent system state trajectory during the fault period is formed according to the method in step 2, and the system acceleration area is calculated to be 4.05;

[0155] The equivalent system state trajectory after fault period removal is formed, and the deceleration area is calculated to be 0.89;

[0156] Subtract the decelerated area from the accelerated area to obtain the initial unbalanced energy of 3.16;

[0157] Based on the equivalent system state trajectory after fault removal, the system power angle curve is obtained by curve fitting, and the equivalent system power angle characteristic prediction curve after the stability judgment moment is formed by extrapolation. Figure 8 This is the fitting result of the power angle characteristic curve of the system after the fault is removed in the application example;

[0158] Based on the prediction results of electromagnetic power and mechanical power based on the power angle curve, the remaining deceleration area is calculated to be 0.72;

[0159] Subtracting the remaining deceleration area from the unbalanced energy yields a deceleration area deficit of 2.44. Substituting this into equations (19) and (20), the theoretical power cut capacity is 858MW.

[0160] Based on the principle of greater than 90% theoretical machine cutting capacity, the maximum number of machines to be cut is one. Combined with the real-time output of the leading group units, the potential machine cutting set is {{G33}, {G34}, {G35}, {G36}}. The real-time power of each unit is 1052MW, 853MW, 786MW, and 878MW.

[0161] Finally, according to the method in step 3, after eliminating the relevant variables of G33, G34, G35, and G36 respectively, the data recorded during the fault period and the data recorded after the fault removal are re-grouped, equalized, curve fitted, and predicted. The change in unbalanced energy, the remaining retarded area, and the change in retarded area after eliminating different units are calculated, and the comprehensive retarded area is obtained by summing the three. The calculation results are shown in Table 1.

[0162] Table 1 Comprehensive deceleration area and other indicators of different cutting schemes

[0163]

[0164]

[0165] The comprehensive deceleration area of ​​the above-mentioned machine cutting schemes in the potential machine cutting scheme set is compared with the initial unbalanced energy, and the machine cutting scheme with a comprehensive deceleration area greater than the initial unbalanced energy is selected to form a stable machine cutting scheme set. Based on the calculation results in Table 1, only the {G36} machine cutting scheme is included in the stable machine cutting scheme set; in the stable machine cutting scheme set, the scheme with the smallest total machine cutting amount is selected as the optimal machine cutting scheme. Since there is only one element in the scheme set, {G36} is the optimal machine cutting scheme.

[0166] Example 2

[0167] An online decision-making method for emergency machine cutting based on stabilization effect evaluation is proposed, and an online decision-making system for emergency machine cutting based on stabilization effect evaluation is also proposed. Fig. 9 This is a system diagram of an emergency machine-cutting online decision-making method based on stabilization effect evaluation proposed in Example 2 of the present invention, the system comprising: a judgment module, a calculation module and a decision module;

[0168] The judgment module is used to collect the inertia parameters of the generator, record the working status data of the generator after the fault occurs and the working status data of the generator after the fault is removed; based on the working status data matrix of the generator after the fault is removed, the power angle curve is clustered by a clustering algorithm to divide the unit into an advanced group and a lagging group; the leading group and the lagging group are equal to a single-machine infinite system, and the convexity index of the angular velocity-power angle phase trajectory of the equivalent system is calculated, and whether the system is unstable is judged according to whether the convexity index is greater than zero;

[0169] The calculation module is used to calculate the acceleration area during the generator fault period if the system is unstable, and then use the equivalent system power angle curve from the time of fault removal to the time of stabilization to calculate the deceleration area before stable control, and form an equivalent system power angle characteristic prediction curve through curve fitting and extrapolation to calculate the remaining deceleration area; calculate the theoretical cutting amount based on the principle that the acceleration area is not less than the sum of the total deceleration area, and finally form a potential cutting plan set based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical cutting amount;

[0170] The decision module is used to calculate the unbalanced energy change of the selected machine cutting scheme, and then calculate the remaining retarded area of ​​the equivalent system of the remaining units after the machine cutting and the change in the remaining retarded area caused by the machine cutting, and further evaluate the overall stabilization effect of the machine cutting to determine whether the machine cutting scheme can stabilize the system. Finally, all the machine cutting schemes that can stabilize the system are compared, and the scheme with the smallest machine cutting amount is selected as the optimal solution for the machine cutting scheme.

[0171] In the judgment module, the generator inertia parameters are collected specifically as follows: the inertia parameter data of the operating generator is collected to form the generator inertia vector:

[0172] M0=[M1 M2 … M i ];(1)

[0173] Among them, M0 is the moment of inertia of all operating generators, M i is the moment of inertia of the i-th generator;

[0174] The data of the generator working status after the fault occurs are recorded as follows:

[0175]

[0176] Among them, δ bf A matrix for recording the operating data values ​​of the power angle of the generator; represents the power angle of the i-th generator at the k0th moment after the fault; ω bf Recording matrix of running data values ​​for generator angular velocity; represents the angular velocity of the generator of the i-th generator at the k0th moment after the fault; A matrix for recording the electromagnetic power operation data values ​​of the generator; represents the electromagnetic power of the i-th generator at the k0th moment after the fault; A matrix for recording the values ​​of the mechanical power operation data of the generator; represents the mechanical power of the i-th generator at the k0th moment after the fault; i = 1, 2, ..., n, k0 = 1, 2, ... t bf , n represents the number of generators, t bf Indicates the current sampling time of fault data record;

[0177] The working status data of the generator after the fault is removed is:

[0178]

[0179] Among them, δ af Represents the generator power angle operation data value record matrix after the fault is removed; represents the power angle of the i-th generator at the k-th moment after the fault is removed; ω afRepresents the generator angular velocity operation data value record matrix after the fault is removed; represents the angular velocity of the i-th generator at the k-th moment after the fault is removed; Represents the record matrix of the electromagnetic power operation data value of the generator after the fault is removed; It represents the electromagnetic power of the generator of the i-th generator at the k-th moment after the fault is removed; Represents the record matrix of the mechanical power operation data value of the generator after the fault is removed; represents the mechanical power of the i-th generator at the k-th moment after the fault is removed; k = 1, 2, ... t af , t af Indicates the current sampling time of data record after the fault is cleared.

[0180] Clustering algorithm is used to cluster the power angle curves and divide the units into leading units and lagging units. Specifically, the following are included:

[0181] Record the matrix δ with the data value after fault removal af A column of data (k=1,2,…t af ) as a power angle curve δ i Substitute the following formula (4) to calculate the Euclidean distance between any two power angle curves:

[0182]

[0183] Among them, D ij is the Euclidean distance between the power angle curve of the i-th generator and the power angle curve of the j-th generator;

[0184] Select the two curves with the largest Euclidean distance as the initial cluster centers C1 and C2 of the first and second clusters, and write the corresponding generator numbers into the index sets Ω1 and Ω2 of the first and second clusters;

[0185] From δ af Choose any one of the remaining curves m , calculate δ m The Euclidean distance between cluster centers C1 and C2:

[0186]

[0187] Among them, D m,1 ,D m,2 are the Euclidean distances between the mth power angle curve and the cluster centers C1 and C2 respectively; C 1,k , C 2,k are the values ​​of cluster centers C1 and C2 at the kth moment respectively.

[0188] Contrast D m,1and D m,2 Size relationship, if D m,1 >D m,2 , then δ m Classified as the second cluster and the curve column index is merged into the index set Ω2, otherwise δ m Classify it as the first cluster and merge the curve column index into the index set Ω1; update the aggregation center of the corresponding cluster:

[0189]

[0190] in, are the number of generators in the first and second machine groups respectively;

[0191] If δ af After the power angle curve in is calculated, the average value difference between the cluster centers C1 and C2 is calculated, and the leading cluster Ω is distinguished according to the positive and negative difference. S and the lagging group Ω A :

[0192]

[0193] δ C1 , δ C2 are the average power angles of the first and second machine groups respectively;

[0194] If δ C1 >δ C2 , then the first group and the second group are respectively the leading group and the lagging group, that is, Ω S =Ω1,Ω A =Ω2; otherwise Ω S =Ω2,Ω A =Ω1.

[0195] The process of equating the leading group and the lagging group to a single-machine infinite system and calculating the concavity index of the angular velocity-power angle phase trajectory of the equivalent system includes:

[0196] The leading group Ω S and the lagging group Ω A Use the same value of their respective centers of inertia;

[0197]

[0198] Among them, M S For the leading group Ω S Equivalent moment of inertia; M A is the lagging group Ω A Equivalent moment of inertia; δ S,k ,ω S,k , P eS,k , P mS,k They are ΩS The value of the equivalent power angle at the kth moment, the value of the angular velocity at the kth moment, the value of the electromagnetic power at the kth moment, and the value of the mechanical power at the kth moment; δ A,k ,ω A,k , P eA,k , P mA,k They are Ω A The value of the equivalent power angle at the kth moment, the value of the angular velocity at the kth moment, the value of the electromagnetic power at the kth moment and the value of the mechanical power at the kth moment;

[0199] The difference between two groups of equivalent parameters is used to characterize the system state, and the equivalent is a single-machine infinite system. Formula (9) is used to calculate the power angle, angular velocity, electromagnetic power and mechanical power trajectory of the equivalent system at each moment;

[0200]

[0201] Among them, M T is the moment of inertia of the equivalent system; δ k is the value of the power angle of the equivalent system at the kth moment, ω k is the value of angular velocity at the kth moment, P e,k is the value of electromagnetic power at the kth moment, P m,k is the value of mechanical power at the kth moment;

[0202] The generator working status data δ after the fault is removed af ,ω af , Equations (8) and (9) are used to convert the equivalent system state trajectory after fault removal to form;

[0203]

[0204] The process of judging whether the system is unstable based on whether the concavity index is greater than zero includes:

[0205] The concavity of the current power angle-angular velocity phase trajectory is calculated according to the state trajectory of the equivalent single-machine infinite system, and the concavity of the phase trajectory is used to determine whether the system has power angle instability;

[0206] Take the angular velocity and power at the last two moments in the state trajectory and substitute them into formula (11) to calculate the first-order derivative of the power angle-angular velocity phase trajectory at the current moment and the previous moment:

[0207]

[0208] Among them, d k is the first-order derivative of the power angle-angular velocity phase trajectory at the kth moment;

[0209] Based on the first-order derivative of the power angle-angular velocity phase trajectory and the last two values ​​of the power angle of the equivalent system, substitute into formula (12) to calculate the second-order derivative of the power angle-angular velocity phase trajectory of the equivalent system at the current moment:

[0210]

[0211] Based on the second-order derivative of the power angle-angular velocity phase trajectory and the angular velocity at the current moment, the trajectory concavity index is calculated according to formula (13):

[0212]

[0213] in, is the current t af The concavity of the power angle-angular velocity phase trajectory at the moment; if Then the system is judged to enter the power angle instability state, otherwise the calculation if The system is determined to be in a stable state and all cache data is cleared; if Only judge the current fault as stable, continue to collect data at the next moment and start the next round of judgment.

[0214] In the calculation module, if the system is unstable, the acceleration area during the generator fault is calculated, and then the deceleration area before stable control is calculated using the equivalent system power angle curve from the time of fault removal to the time of stabilization judgment, and the equivalent system power angle characteristic prediction curve is formed by curve fitting and extrapolation to calculate the remaining deceleration area. The process includes: the acceleration area during the generator fault is:

[0215]

[0216] Among them, S A is the acceleration area of ​​the equivalent system during the fault

[0217] The deceleration area that has occurred from the time when the fault is cleared to the time when stability is determined:

[0218]

[0219] S D1 It is the deceleration area of ​​the equivalent system from the time when the fault is removed to the time when stability is judged;

[0220] The deceleration area of ​​the equivalent system from the time of fault removal to the time of judging stability

[0221] ΔS0=S A -S D1 ; (16)

[0222] Assume that the equivalent system power angle curve and mechanical power curve conform to the following form:

[0223] P e=α+βsin(γδ+C)

[0224] P m =a+bδ; (17)

[0225] P e =P e af ,δ=δ af and For mapping sequence, nonlinear and least square parameter identification methods are used to calculate the first parameter to be identified α, the second parameter to be identified β, the third parameter to be identified γ and the fourth parameter to be identified C, as well as the fifth parameter to be identified a and the sixth parameter to be identified b;

[0226] exist The interval is equally divided into a preset number of power angle points to form a power angle prediction sequence Substitute into formula (16) to calculate the corresponding electromagnetic power and mechanical power prediction series Search from front to back to meet The sequence elements of the conditions form the electromagnetic and mechanical power prediction sequence corresponding to the deceleration area and its corresponding power angle prediction sequence

[0227] The predicted mechanical power is screened by taking the predicted power angle sequence as the independent variable. and electromagnetic power As the dependent variable, substitute it into formula (18) and use the rectangular method to calculate the remaining deceleration area:

[0228]

[0229] Among them, S D2 It is the remaining decelerable area of ​​the equivalent system from the stabilization moment to the point of no return.

[0230] The theoretical cutting amount is calculated based on the principle that the sum of the acceleration area and the total deceleration area is equal, and finally a potential cutting plan set is formed based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical cutting amount;

[0231] The remaining deceleration area shortfall is determined based on the principle that the acceleration area is not less than the sum of the total deceleration area:

[0232] S D3 =λ D (S A -S D1 -S D2 );(19)

[0233] In the formula, S D3 The deceleration area required to maintain system stability, λ DIt is the reliability factor that can guarantee the stabilization effect when taking into account the calculation error;

[0234] Calculate the equivalent cutting amount ΔP m :

[0235]

[0236] in, They are the equivalent system power angle and the farthest point power angle at the time of judging stability respectively;

[0237] Calculate the theoretical cutting capacity ΔP M :

[0238]

[0239] The process of forming a potential cutting plan set based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical cutting amount is as follows: Read the leading group generator index set Ω S , set the maximum allowed number of cutting machines N cmax ; Set the current allowed number of cutting machines to N c is 1; forms a c The set of elements Ω S Calculate the sum of the real-time output of the generators in each subset. If the sum of the real-time output is greater than the theoretical cutting capacity, add the subset to the potential cutting plan set; until the number of cutting units is N c Increase to the maximum allowable number of cutting machines N cmax , complete the cutting machine solution set.

[0240] In the decision module, the unbalanced energy change of the selected machine cutting scheme is calculated, and then the remaining retarded area of ​​the equivalent system of the remaining units after the machine cutting and the change of the remaining retarded area caused by the machine cutting are calculated. The specific process includes: determining the remaining leading group index set Ω' s ; According to Ω' s and Ω A Calculate the set of eliminated units Ω c State trajectory of the post-equivalent system during fault periodδ bf' ,ω bf' ,

[0241] Calculate the acceleration area of ​​the equivalent system after removing the disconnected unit during the fault period:

[0242]

[0243] Among them, S' A It is the acceleration area of ​​the equivalent system after removing the cut-off units during the fault period;

[0244] Determine the set of eliminated units Ω c State trajectory of the post-equivalent system during fault periodδaf' ,ω af' ,

[0245] Calculate the deceleration area of ​​the equivalent system from the time of fault removal to the time of judging stability:

[0246]

[0247] Among them, S' D1 It is the deceleration area of ​​the equivalent system from the time of fault removal to the time of judging stability;

[0248] Calculate the change in unbalanced energy caused by cutting machine control:

[0249] ΔS1=(S A -S D1 )-(S' A -S' D1 );(twenty four)

[0250] Where ΔS1 is the change in the accumulated unbalanced energy before and after the machine cutting control;

[0251] Based on the elimination of the unit set Ω c State trajectory of the post-equivalent system during fault periodδ af' ,ω af' , The trajectory is fitted with power angle characteristics and the remaining deceleration area is calculated by extrapolation;

[0252] Assume that the equivalent system power angle curve and mechanical power curve after removing the cut-off unit are as shown in formula (17), respectively: and For mapping sequence, nonlinear and least square parameter identification methods are used to calculate the first parameter to be identified α, the second parameter to be identified β, the third parameter to be identified γ and the fourth parameter to be identified C, as well as the fifth parameter to be identified a and the sixth parameter to be identified b;

[0253] exist The interval is equally divided into a preset number of power angle points to form a power angle prediction sequence Substitute into formula (23) to calculate the corresponding electromagnetic power and mechanical power prediction series Search from front to back to meet The sequence elements of the conditions form the electromagnetic and mechanical power prediction sequence corresponding to the deceleration area and its corresponding power angle prediction sequence

[0254] The predicted mechanical power is screened by taking the predicted power angle sequence as the independent variable. and electromagnetic power As the dependent variable, substitute it into formula (25) and use the rectangular method to calculate the remaining deceleration area:

[0255]

[0256] In the formula, S' D2 It is the remaining deceleration area of ​​the equivalent system after eliminating the cut-off units from the stability judgment moment to the no-return point.

[0257] The overall stabilization effect of the shedding is evaluated to determine whether the shedding scheme can stabilize the system. Finally, all shedding schemes that can stabilize the system are compared, and the scheme with the smallest shedding amount is selected as the optimal solution. The process of solving the shedding scheme includes: using the voltage source model to model the unshelved generator, using the injected current change to model the shelved generator, forming a circuit model with the injected power change as input, and forming a node-related admittance matrix based on the circuit interconnection relationship; using the node voltage method to calculate the injected current change of the unshelved unit caused by shedding

[0258]

[0259] are the injected currents of the rth and sth nodes before the removed unit is removed;

[0260] is the change in the injected current of the i-th generator and the j-th generator after the cut-off unit is cut off; y ir ,y is are the associated admittance elements of the rth and sth nodes of the i-th generator of the removed unit and the unremoved unit respectively; y jr ,y js are the associated admittance elements of the rth and sth nodes of the jth generator of the removed unit and the unremoved unit respectively;

[0261] The power change of the non-removed units is obtained by multiplying the current change of the non-removed units by the corresponding node voltage:

[0262]

[0263] In the formula, They are the internal potential of the uncut-off unit, the variation of injected power and the variation of injected current respectively;

[0264] Formula (28) is used to calculate the total change of electromagnetic power of the equivalent system after cutting the machine:

[0265]

[0266] In the formula, is the change in electromagnetic power of the equivalent system caused by cutting, M C is the sum of the equivalent inertia of the removed units;

[0267] Formula (29) is used to calculate the change in the decelerable area caused by the change in electromagnetic power of the equivalent system:

[0268]

[0269] Among them, S' D3 is the change in the decelerable area caused by the change in the electromagnetic power of the equivalent system;

[0270] The combined deceleration area that can be provided by the cutting machine control is obtained by summing the change in unbalanced area, the remaining deceleration area, and the change in deceleration area:

[0271] S dec =ΔS1+S' D2 +S' D3 ; (30)

[0272] Comparison of comprehensive deceleration area S dec and the initial unbalanced energy ΔS0: If S dec >ΔS0, then the generator cutting can stabilize the system, and the generator set included in the generator cutting scheme is added to the stable generator cutting scheme set Ω stable And record the corresponding cutting amount; compare the stable cutting solution set Ω stable The total power of all cutting plans in the cutting plan is calculated, and the plan with the smallest total power is selected as the optimal cutting plan.

[0273] The emergency machine cutting online decision system based on stabilization effect evaluation proposed in Example 2 of the present invention can achieve the same technical effect as that of Example 1. The description of the relevant parts of the emergency machine cutting online decision system based on stabilization effect evaluation provided in Example 2 of the present application can refer to the detailed description of the corresponding parts of the emergency machine cutting online decision method based on stabilization effect evaluation provided in Example 1 of the present application, which will not be repeated here.

[0274] Although the above describes the specific implementation of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. For those skilled in the art, other different forms of modifications or deformations can be made on the basis of the above description. It is not necessary and impossible to list all the implementation methods here. On the basis of the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. An online decision-making method for emergency machine switching based on stabilization effect evaluation is characterized by: The following steps are involved: Collect generator inertia parameters, record generator working status data after a fault occurs and after the fault is cleared; Based on the data matrix of the working state of the generator after the fault is removed, a clustering algorithm is used to cluster the power angle curve to divide the unit into a leading group and a lagging group; the leading group and the lagging group are equal to a single-machine infinite system, and the convexity index of the angular velocity-power angle phase trajectory of the equivalent system is calculated, and whether the system is unstable is judged according to whether the convexity index is greater than zero; If the system is unstable, the acceleration area during the generator fault period is calculated, and then the deceleration area before stable control is calculated using the equivalent system power angle curve from the time of fault removal to the time of stabilization judgment, and the equivalent system power angle characteristic prediction curve is formed by curve fitting and extrapolation to calculate the remaining deceleration area; the theoretical machine cutting amount is calculated based on the principle that the acceleration area is not less than the sum of the total deceleration area, and finally a potential machine cutting scheme set is formed based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical machine cutting amount; The unbalanced energy change of the selected machine cutting scheme is calculated, and then the remaining retarded area of ​​the equivalent system of the remaining units after the machine cutting and the change in the remaining retarded area caused by the machine cutting are calculated. The overall stabilization effect of the machine cutting is further evaluated to determine whether the machine cutting scheme can stabilize the system. Finally, all the machine cutting schemes that can stabilize the system are compared, and the scheme with the smallest machine cutting amount is selected as the optimal solution for the machine cutting scheme.

2. The method for online decision-making for emergency machine cutting based on stabilization effect evaluation according to claim 1 is characterized in that: The specific step of collecting the generator inertia parameters is to collect the inertia parameter data of the operating generator to form the generator inertia vector: M0=[M1 M2 … M i ]; (1) Among them, M0 is the moment of inertia of all operating generators, M i is the moment of inertia of the i-th generator; The data of the generator working status after the fault occurs are recorded as follows: Among them, δ bf A matrix for recording the operating data values ​​of the power angle of the generator; represents the power angle of the i-th generator at the k0th moment after the fault; ω bf Recording matrix of running data values ​​for generator angular velocity; represents the angular velocity of the generator of the i-th generator at the k0th moment after the fault; A matrix for recording the electromagnetic power operation data values ​​of the generator; represents the electromagnetic power of the i-th generator at the k0th moment after the fault; A matrix for recording the values ​​of the mechanical power operation data of the generator; represents the mechanical power of the i-th generator at the k0th moment after the fault; i = 1, 2, ..., n, k0 = 1, 2, ... t bf , n represents the number of generators, t bf Indicates the current sampling time of fault data record; The working status data of the generator after the fault is removed is: Among them, δ af Represents the generator power angle operation data value record matrix after the fault is removed; represents the power angle of the i-th generator at the k-th moment after the fault is removed; ω af Represents the generator angular velocity operation data value record matrix after the fault is removed; represents the angular velocity of the i-th generator at the k-th moment after the fault is removed; Represents the record matrix of the electromagnetic power operation data value of the generator after the fault is removed; It represents the electromagnetic power of the generator of the i-th generator at the k-th moment after the fault is removed; Represents the record matrix of the mechanical power operation data value of the generator after the fault is removed; represents the mechanical power of the i-th generator at the k-th moment after the fault is removed; k = 1, 2, ... t af , t af Indicates the current sampling time of data record after the fault is cleared.

3. The method for online decision-making for emergency machine cutting based on stabilization effect evaluation according to claim 2 is characterized in that: The clustering algorithm is used to cluster the power angle curves to divide the units into an advanced unit group and a lagging unit group; the advanced unit group and the lagging unit group are equalized to a single-machine infinite system, and the specific process of calculating the concavity and convexity index of the angular velocity-power angle phase trajectory of the equivalent system includes: Record the matrix δ with the data value after fault removal af A column of data (k=1,2,…t af ) as a power angle curve δ i Substitute the following formula (4) to calculate the Euclidean distance between any two power angle curves: Among them, D ij is the Euclidean distance between the power angle curve of the i-th generator and the power angle curve of the j-th generator; Select the two curves with the largest Euclidean distance as the initial cluster centers C1 and C2 of the first and second clusters, and write the corresponding generator numbers into the index sets Ω1 and Ω2 of the first and second clusters; From δ af Choose any one of the remaining curves m , calculate δ m The Euclidean distance between cluster centers C1 and C2: Among them, D m,1 ,D m,2 are the Euclidean distances between the mth power angle curve and the cluster centers C1 and C2 respectively; C 1,k , C 2,k are the values ​​of cluster centers C1 and C2 at the kth moment respectively. Contrast D m,1 and D m,2 Size relationship, if D m,1 >D m,2 , then δ m Classified as the second cluster and the curve column index is merged into the index set Ω2, otherwise δ m Classify it as the first cluster and merge the curve column index into the index set Ω1; update the aggregation center of the corresponding cluster: in, are the number of generators in the first and second machine groups respectively; If δ af After the power angle curve in is calculated, the average value difference between the cluster centers C1 and C2 is calculated, and the leading cluster Ω is distinguished according to the positive and negative difference. S and the lagging group Ω A : δ C1 , δ C2 are the average power angles of the first and second machine groups respectively; If δ C1 >δ C2 , then the first group and the second group are respectively the leading group and the lagging group, that is, Ω S =Ω1,Ω A =Ω2; otherwise Ω S =Ω2,Ω A =Ω1; The leading group Ω S and the lagging group Ω A Use the same value of their respective centers of inertia; Among them, M S For the leading group Ω S Equivalent moment of inertia; M A is the lagging group Ω A Equivalent moment of inertia; δ S,k ,ω S,k , P eS,k , P mS,k Ω S The value of the equivalent power angle at the kth moment, the value of the angular velocity at the kth moment, the value of the electromagnetic power at the kth moment, and the value of the mechanical power at the kth moment; δ A,k ,ω A,k , P eA,k , P mA,k Ω A The value of the equivalent power angle at the kth moment, the value of the angular velocity at the kth moment, the value of the electromagnetic power at the kth moment and the value of the mechanical power at the kth moment; The difference between two groups of equivalent parameters is used to characterize the system state, and the equivalent is a single-machine infinite system. Formula (9) is used to calculate the power angle, angular velocity, electromagnetic power and mechanical power trajectory of the equivalent system at each moment; M T =M S +M A ,k=1,2...t af ;(9) Among them, M T is the moment of inertia of the equivalent system; δ k is the value of the power angle of the equivalent system at the kth moment, ω k is the value of angular velocity at the kth moment, P e,k is the value of electromagnetic power at the kth moment, P m,k is the value of mechanical power at the kth moment; The generator working status data δ after the fault is removed af ,ω af , Equations (8) and (9) are used to convert the equivalent system state trajectory after fault removal to form; 4. The method for online decision-making for emergency machine cutting based on stabilization effect evaluation according to claim 3 is characterized in that: The process of judging whether the system is unstable according to whether the concavity and convexity index is greater than zero includes: The concavity of the current power angle-angular velocity phase trajectory is calculated according to the state trajectory of the equivalent single-machine infinite system, and the concavity of the phase trajectory is used to determine whether the system has power angle instability; Take the angular velocity and power at the last two moments in the state trajectory and substitute them into formula (11) to calculate the first-order derivative of the power angle-angular velocity phase trajectory at the current moment and the previous moment: Among them, d k is the first-order derivative of the power angle-angular velocity phase trajectory at the kth moment; Based on the first-order derivative of the power angle-angular velocity phase trajectory and the last two values ​​of the power angle of the equivalent system, substitute into formula (12) to calculate the second-order derivative of the power angle-angular velocity phase trajectory of the equivalent system at the current moment: Based on the second-order derivative of the power angle-angular velocity phase trajectory and the angular velocity at the current moment, the trajectory concavity index is calculated according to formula (13): in, is the current t af The concavity of the power angle-angular velocity phase trajectory at the moment; if Then the system is judged to enter the power angle instability state, otherwise the calculation if The system is determined to be in a stable state and all cache data is cleared; if Only the current fault is judged stable, and data collection at the next moment starts the next round of judgment.

5. The method for online decision-making for emergency machine cutting based on stabilization effect evaluation according to claim 4 is characterized in that: If the system is unstable, the acceleration area during the generator fault is calculated, and then the deceleration area before stable control is calculated using the equivalent system power angle curve from the time of fault removal to the time of stabilization judgment, and the equivalent system power angle characteristic prediction curve is formed by curve fitting and extrapolation to calculate the remaining deceleration area. The process includes: The acceleration area during generator fault is: Among them, S A is the acceleration area of ​​the equivalent system during the fault The deceleration area that has occurred from the time when the fault is cleared to the time when stability is determined: S D1 It is the deceleration area of ​​the equivalent system from the time when the fault is removed to the time when stability is judged; The deceleration area of ​​the equivalent system from the time of fault removal to the time of judging stability ΔS0=S A -S D1 ;(16) Assume that the equivalent system power angle curve and mechanical power curve conform to the following form: P e =α+βsin(γδ+C) P m =a+bδ;(17) P e =P e af ,δ=δ af and δ=δ af For mapping sequence, nonlinear and least square parameter identification methods are used to calculate the first parameter to be identified α, the second parameter to be identified β, the third parameter to be identified γ and the fourth parameter to be identified C, as well as the fifth parameter to be identified a and the sixth parameter to be identified b; exist The interval is equally divided into a preset number of power angle points to form a power angle prediction sequence Substitute into formula (16) to calculate the corresponding electromagnetic power and mechanical power prediction sequence P e predict , Search from front to back to meet The sequence elements of the conditions form the electromagnetic and mechanical power prediction sequence corresponding to the deceleration area and its corresponding power angle prediction sequence The predicted mechanical power is screened by taking the predicted power angle sequence as the independent variable. and electromagnetic power As the dependent variable, substitute it into formula (18) and use the rectangular method to calculate the remaining deceleration area: Among them, S D2 It is the remaining decelerable area of ​​the equivalent system from the stabilization moment to the point of no return.

6. The method for online decision-making for emergency machine cutting based on stabilization effect evaluation according to claim 5 is characterized in that: The theoretical cutting amount is calculated based on the principle that the acceleration area is not less than the sum of the total deceleration area, and finally a potential cutting plan set is formed based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical cutting amount; The remaining deceleration area shortfall is determined based on the principle that the acceleration area is not less than the sum of the total deceleration area: S D3 =λ D (S A -S D1 -S D2 ); (19) In the formula, S D3 The deceleration area required to maintain system stability, λ D It is the reliability factor that can guarantee the stabilization effect when taking into account the calculation error; Calculate the equivalent cutting amount ΔP m : in, They are the equivalent system power angle and the farthest point power angle at the time of judging stability respectively; Calculate the theoretical cutting capacity ΔP M : The process of forming a potential cutting plan set based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical cutting amount is as follows: Read the leading cluster generator index set Ω S , set the maximum allowed number of cutting machines N cmax ; Set the current allowed number of cutting machines to N c is 1; Formation containing only N c The set of elements Ω S All subsets of ; Calculate the sum of the real-time output of the generators in each subset. If the sum of the real-time output is greater than the theoretical cutting capacity, add the subset to the potential cutting solution set; until the number of cutting units reaches N c Increase to the maximum allowable number of cutting machines N cmax , complete the cutting machine solution set.

7. The method for online decision-making for emergency machine cutting based on stabilization effect evaluation according to claim 6 is characterized in that: The specific process of calculating the unbalanced energy change of the selected cutting scheme includes: Determine the remaining leading cluster index set Ω′ s ; According to Ω′ s and Ω A Calculate the set of eliminated units Ω c State trajectory of the post-equivalent system during fault periodδ bf' ,ω bf' , Calculate the acceleration area of ​​the equivalent system after removing the disconnected unit during the fault period: Among them, S' A It is the acceleration area of ​​the equivalent system after removing the cut-off units during the fault period; Determine the set of eliminated units Ω c State trajectory of the post-equivalent system during fault periodδ af' ,ω af' , Calculate the deceleration area of ​​the equivalent system from the time of fault removal to the time of judging stability: Among them, S' D1 It is the deceleration area of ​​the equivalent system from the time of fault removal to the time of judging stability; Calculate the change in unbalanced energy caused by cutting machine control: ΔS1=(S A -S D1 )-(S' A -S' D1 ); (24) Where ΔS1 is the change in the accumulated unbalanced energy before and after the machine cutting control.

8. The method for online decision-making for emergency machine cutting based on stabilization effect evaluation according to claim 7 is characterized in that: Then, the specific process of calculating the remaining retarded area of ​​the equivalent system of the remaining units after the machine cutting and the change of the remaining retarded area caused by the machine cutting includes: Based on the elimination of the unit set Ω c State trajectory of the post-equivalent system during fault periodδ af' ,ω af' , P e af' The trajectory is fitted with power angle characteristics and extrapolated to calculate the remaining deceleration area; Assume that the equivalent system power angle curve and mechanical power curve after removing the cut-off unit are as shown in formula (17), respectively: and For mapping sequence, nonlinear and least square parameter identification methods are used to calculate the first parameter to be identified α, the second parameter to be identified β, the third parameter to be identified γ and the fourth parameter to be identified C, as well as the fifth parameter to be identified a and the sixth parameter to be identified b; exist The interval is equally divided into a preset number of power angle points to form a power angle prediction sequence Substitute into formula (23) to calculate the corresponding electromagnetic power and mechanical power prediction series Search from front to back to meet The sequence elements of the conditions form the electromagnetic and mechanical power prediction sequence corresponding to the deceleration area and its corresponding power angle prediction sequence The predicted mechanical power is screened by taking the predicted power angle sequence as the independent variable. and electromagnetic power As the dependent variable, substitute it into formula (25) and use the rectangular method to calculate the remaining deceleration area: In the formula, S' D2 It is the remaining deceleration area of ​​the equivalent system after eliminating the cut-off units from the stability judgment moment to the no-return point.

9. The method for online decision-making for emergency machine cutting based on stabilization effect evaluation according to claim 8 is characterized in that: The process of evaluating the overall stabilization effect of the cutting machine to determine whether the cutting machine solution can stabilize the system, and finally comparing all the cutting machine solutions that can stabilize the system, and selecting the solution with the smallest cutting amount as the optimal solution for the cutting machine solution includes: The uncut-off generator is modeled by a voltage source model, and the cut-off generator is modeled by the injected current change, forming a circuit model with the injected power change as input, and forming a node-related admittance matrix according to the circuit interconnection relationship; Calculate the injection current change of the uncut-off units caused by cutting the generator using the node voltage method are the injected currents of the rth and sth nodes before the removed unit is removed; is the change in the injected current of the i-th generator and the j-th generator after the cut-off unit is cut off; y ir ,y is are the associated admittance elements of the rth and sth nodes of the i-th generator of the removed unit and the unremoved unit respectively; y jr ,y js are the associated admittance elements of the rth and sth nodes of the jth generator of the removed unit and the unremoved unit respectively; The power change of the non-removed units is obtained by multiplying the current change of the non-removed units by the corresponding node voltage: In the formula, They are the internal potential of the uncut-off unit, the variation of injected power and the variation of injected current respectively; Formula (28) is used to calculate the total change of electromagnetic power of the equivalent system after cutting the machine: Where ΔP e af' is the change in electromagnetic power of the equivalent system caused by cutting, M C is the sum of the equivalent inertia of the removed units; Formula (29) is used to calculate the change in the decelerable area caused by the change in electromagnetic power of the equivalent system: Among them, S' D3 is the change in the decelerable area caused by the change in the electromagnetic power of the equivalent system; The combined deceleration area that can be provided by the cutting machine control is obtained by summing the change in unbalanced area, the remaining deceleration area, and the change in deceleration area: S dec =ΔS1+S' D2 +S' D3 ; (30) Comparison of comprehensive deceleration area S dec and the initial unbalanced energy ΔS0: If S dec >ΔS0, then the generator cutting can stabilize the system, and the generator set included in the generator cutting scheme is added to the stable generator cutting scheme set Ω stable And record the corresponding cutting amount; Comparison of stable cutting machine solutions stable The total power of all cutting plans in the cutting plan is calculated, and the plan with the smallest total power is selected as the optimal cutting plan.

10. The emergency machine cutting online decision system based on stabilization effect evaluation is characterized by: It includes a judgment module, a calculation module and a decision-making module; The judgment module is used to collect generator inertia parameters, record generator working status data after a fault occurs and generator working status data after the fault is removed; Based on the data matrix of the working state of the generator after the fault is removed, a clustering algorithm is used to cluster the power angle curve to divide the unit into a leading group and a lagging group; the leading group and the lagging group are equal to a single-machine infinite system, and the convexity index of the angular velocity-power angle phase trajectory of the equivalent system is calculated, and whether the system is unstable is judged according to whether the convexity index is greater than zero; The calculation module is used to calculate the acceleration area during the generator fault period if the system is unstable, and then use the equivalent system power angle curve from the time of fault removal to the time of stabilization to calculate the deceleration area before stable control, and form an equivalent system power angle characteristic prediction curve through curve fitting and extrapolation to calculate the remaining deceleration area; calculate the theoretical machine cutting amount according to the principle that the acceleration area is not less than the sum of the total deceleration area, and finally form a potential machine cutting plan set based on the principle that the sum of the real-time output of the cut-off units is greater than the theoretical machine cutting amount; The decision module is used to calculate the unbalanced energy change of the selected machine cutting scheme, and then calculate the remaining decelerable area of ​​the equivalent system of the remaining units after the machine cutting and the change in the remaining decelerable area caused by the machine cutting, further evaluate the overall stabilization effect of the machine cutting to determine whether the machine cutting scheme can stabilize the system, and finally compare all the machine cutting schemes that can stabilize the system, and select the scheme with the smallest machine cutting amount as the optimal solution for the machine cutting scheme.

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