CN103279638A - Large power grid overall situation on-line integrated quantitative evaluation method based on response - Google Patents

Abstract

The present invention provides a response-based online integrated quantitative evaluation method for the whole situation of a large power grid, including: S1, obtaining the topological structure information of the power grid from the SCADA system and the EMS system, and establishing a corresponding relationship with the power grid components of the WAMS system; S2, from the SCADA system system, EMS system or WAMS system obtains the power flow data of the current operation mode of the power grid or obtains various expected power flow or transient fault time domain data from the DSA system; S3, macroscopically divides the response data into steady state (or quasi-state) Steady state) and transient (or dynamic) two operating scenarios, the static stability situation assessment of the power grid is performed in an online node-oriented manner, and the transient stability situation assessment of the power grid is performed in an online unit-oriented manner. When constructing static and transient comprehensive evaluation indicators, we start from the three perspectives of component-level thermal stability, electrical quantity qualified range, and system-level stability to improve the comprehensiveness and rationality of the overall situation evaluation indicators; use the task parallel method to improve the overall situation integration. Evaluate efficiency.

Description

Large power grid full situation online integrated quantitative evaluation method based on response

Technical Field

The invention relates to the field of online safety monitoring and early warning of a large power grid, in particular to a response-based full-situation online integrated quantitative evaluation method for the large power grid.

Background

Ensuring safe and economic operation of large power grids is a goal that power workers have pursued over the years. With the continuous expansion of the interconnection range of the power grid, the continuous deepening of the reformation of the electric power industry marketization system and the continuous access of the ultra-high voltage power transmission and the renewable energy power generation, the uncertainty of the operation of the power grid is increased, the operation environment and the dynamic behavior of the power grid are more complicated, and the difficulty of stably analyzing and controlling the power grid is higher. Once an accident happens to a modern large power grid, if the accident is not processed in time, the consequence is very serious. Since 2000 years, a plurality of major power failure accidents occur in the world, wherein the major power failure of 8.14 is the largest historical one-time power failure accident, the economic loss per day during the power failure reaches 300 billion dollars, and the frequently occurring major power failure accidents provide more urgent requirements for the safety and stability analysis and control of a power grid and the real-time monitoring of the running state of the power grid.

Currently, the following 4 problems mainly exist in the field of online safety assessment and early warning of a large power grid: firstly, the online safety assessment of the power grid mainly adopts the traditional network modeling and simulation mode, although the power grid safety assessment mainly based on modeling simulation is an essential important tool in power grid planning and operation, the method is limited by factors such as power grid models, parameters, numerical value calculation and the like, is difficult to adapt to the requirements of real-time monitoring of the power grid in the aspects of application scale, speed, matching degree with real power grid working conditions and the like, and a new concept and a faster solution must be sought; secondly, the major power failure accident is often caused by unforeseen cascading failures or random disturbance, the existing ' offline pre-decision based on an expected accident set is matched with ' a power grid security control mode ' on line, the real working condition of a power grid cannot be matched, the scheme is influenced by a model and parameters, the obtained scheme is sometimes over conservative (or optimistic), and especially the problem of combined explosion of the fault set severely limits the number of possible considered working conditions. When a large power grid monitors and prevents a large power failure accident in real time, the method may be unconscious; the existing online security assessment system for the power grid has strong independence when aiming at specific problems, and often splits the power grid angle stability and synchronization stability for processing, or specifically divides the problems into static problems and transient problems. However, in practice, grid stabilization is a uniform nonlinear power system stabilization problem, from the perspective of grid response, power angle and voltage are only external expressions, and static problems and transient problems have a dialectical idea of "there is still and moving in motion" in motion. Therefore, many existing evaluation methods and indexes have great overlap, and an evaluation index system which is more effective and can truly reflect the operation situation of the power grid is needed in a real-time operation environment; one of the main reasons of major blackouts is that the power grid online monitoring system which is put into operation does not give visual and effective quantitative assessment and early warning information of the power grid operation situation at the stage of slow deterioration of the power grid state, and does not give corresponding control measures according to changes of the real working conditions of the power grid, so that the best opportunity of taking care of the blast is missed. Therefore, a brand-new online safety assessment method system needs to be established for the power grid, and highly-automatic and intelligent online safety assessment and early warning of the large power grid are achieved.

With the development of computer, communication and network technologies, the WAMS (Wide Area Measurement System) is widely applied to power grid dispatching automation, and a new opportunity is brought to the power grid operation full situation online quantitative evaluation and real-time adaptive control research based on the WAMS. In the face of the above opportunities and challenges, Smart grids (Smart grids) which incorporate various advanced measurement sensing technologies, control technologies, communication technologies, computer technologies and other leading-edge technologies become the necessary route for the development of the modern power industry. One of the important functions of the smart grid is to improve the visualization and early warning capability of the grid, and finally realize intelligent closed-loop control, so that the grid is safer, more reliable and more economic to operate. The intelligent scheduling is the core content of intelligent power grid construction, and the intelligent scheduling technical support system has the functions of taking a dispatcher thinking mode as a framework, taking a visual interface as a functional module and taking interactive computation as a system core.

The smart grid is a macro System engineering to realize the online security assessment And early warning of the large grid, And in combination with the current mature WAMS System And the DSA (Dynamic security assessment) System based on SCADA (Supervisory Control And Data Acquisition, Data Acquisition And monitoring) \ EMS (Energy Management System) And expected fault set simulation, for different grid operation scenarios, a response information-based large grid full situation quantitative assessment method And a Data fusion processing mechanism need to be comprehensively And deeply researched, And an online security assessment System based on the combination of the current state And the expected state of the large grid based on a multi-response information source is established.

Disclosure of Invention

The invention relates to a response-based large power grid full situation online integrated quantitative evaluation method, which comprises the following steps of:

step S1, acquiring power grid topological structure information from the SCADA system and the EMS system, and establishing a corresponding relation with power grid elements of the WAMS system;

step S2, obtaining the current operation mode power flow data of the power grid from the SCADA system, the EMS system or the WAMS system or obtaining various anticipated power flow or transient fault time domain data from the DSA system;

step S3, performing static stability situation evaluation on the power grid in an online node-oriented mode, and performing transient stability situation evaluation on the power grid in an online unit-oriented mode;

wherein, the content of carrying out the static stable situation aassessment to the electric wire netting includes: the method comprises the following steps of (1) generating a generator stability margin index, a line stability margin index, a node stability margin index, a generator thermal stability qualification rate, a line thermal stability qualification rate, a node voltage qualification rate, a load node power factor qualification rate, a static stability situation comprehensive index and a node reactive power compensation level index;

the content of transient stability situation assessment on the power grid comprises the following steps: transient stability margin index, transient stability estimation index, node voltage holding qualification rate, node stability margin index, line thermal stability qualification rate and transient stability situation comprehensive index.

The invention provides a first preferred embodiment: various power grid static response data comprise expected state offline power flow, calculation results after convergence of N-1 and N-2 power flows, state estimation results of a SCADA \ EMS system and PMU measurement information;

the response data of various power grid transient transition processes comprise various expected transient fault set time domain simulation results and power grid disturbance process information measured by the WAMS in real time;

carrying out rationality prejudgment or filtering processing on PMU measurement information according to previous time or peripheral PMU measurement data change;

and (4) allocating the expected faults of N-1 and N-2 according to the number of the parallel machines.

In a second preferred embodiment of the present invention: when the static stable situation evaluation and the transient stable situation evaluation are performed on the power grid in the step S3, distributing all nodes of the power grid according to the number of parallel machines;

according to the power grid operation tide section information and in combination with the power grid topological structure, the equivalent transmission power P of each node is obtained according to the active flow direction_E+jQ_E；

Identifying equivalent power transmission model parameters of each node of a power grid in the current state on line by adopting a tracking parameter identification method based on local measurement, wherein the equivalent power transmission model parameters comprise equivalent power source potential E_EEquivalent branch impedance mode Z_EAnd the impedance angle alpha is used for realizing node equivalent power transmission model inverse mapping based on the current running state of the power grid.

In a third preferred embodiment of the present invention: the method for obtaining the generator stability margin index, the line stability margin index and the node stability margin index of the power grid in the step S3 includes:

according to the maximum transmission power thought, aiming at equivalent transmission models of a generator branch, a tie line branch and a node, respectively, the static stability margin index S corresponding to the current operation mode of the generator branch, the tie line branch or the node is obtained_Li，S_LiThe calculation formula is as follows: $S_{\mathrm{Li}}=\frac{Z_L-Z_E}{Z_L};$

wherein Z_LAnd the equivalent load impedance representing the branch circuit, the connecting line or the node of the generator is obtained according to the terminal voltage and the power.

In a fourth preferred embodiment of the present invention: the method for obtaining the generator thermal stability qualification rate and the tie line thermal stability qualification rate of the power grid in the step S3 includes:

according to the thermal stability operation constraint of each generator and each tie lineCalculating the thermal stability qualification rate G of the generator_PRAnd line thermal stability yield L_PRRespectively as follows: $G_{\mathrm{PR}}=\frac{G_{\mathrm{QN}}}{G_N};$ $L_{\mathrm{PR}}=\frac{L_{\mathrm{QN}}}{L_N};$

wherein G is_N、L_NThe total generator number, the total tie line number and G of the power grid_QN、L_QNThe number of the generators and the number of the connecting lines which meet the respective operation thermal stability constraint are respectively;

the method for obtaining the node voltage qualification rate and the load node power factor qualification rate of the power grid in the step S3 includes:

according to the node voltage given by the normal operation mode of the power grid and the upper and lower limits of the qualified range of the power factor of the load node, the qualified rate of the node voltage of the power grid is counted

Load node power factor qualification rate

Wherein N is_N、P_FNRespectively the total node number and the load node number of the power grid, V_QN、P_QFNThe number of nodes satisfying the voltage range and the number of load nodes satisfying the power factor range, respectively.

The method for obtaining the power grid static stability out-of-limit rate comprises the following steps:

setting S_LiCertain early warning threshold value S_LCCounting that all tie line branches and node equivalent branches of the power grid are greater than S_LCThe nodes comprise a generator node, a middle contact node and a load node, and the static stability qualification rate of the line is respectively calculated

Yield of node statically stable $N_{\mathrm{SR}}=\frac{N_{\mathrm{CN}}}{N_N};$

Wherein L is_N、N_NRespectively the number of system bus lines and the number of nodes, L_CN、N_CNAre each greater than S_LCThe number of connections and the number of nodes.

In a fifth preferred embodiment of the present invention: the method for obtaining the comprehensive index of the overall static stable situation of the power grid in the step S3 comprises the following steps:

integrated static stable situation index S of power grid_SI＝α₁H_QR+β₁R_QR+χ₁S_SR；

Wherein alpha is₁、β₁、χ₁The weight coefficients of the power grid according to thermal stability constraint, operation electric quantity constraint and static stability constraint are flexibly configured according to experience or analysis requirements, and alpha is₁、β₁、χ₁Satisfies the following conditions:

$\left\{\begin{array}{c}0\≤{\mathrm{\α}}_1\≤1\\ 0\≤{\mathrm{\β}}_1\≤1\\ 0\≤{\mathrm{\χ}}_1\≤1\\ 0\≤{\mathrm{\α}}_1+{\mathrm{\β}}_1+{\mathrm{\χ}}_1\≤1\end{array}\right.$

H_QRthe overall thermal stability qualification rate of the power grid H_QRThe calculation formula is as follows:

R_QRfor the qualification rate of the electric quantity, R, of the whole operation of the power grid_QRThe calculation formula is as follows:

S_SRthe qualification rate of the whole static stability of the power grid, S_SRThe calculation formula is as follows:

in a sixth preferred embodiment of the present invention: in step S3, the method for obtaining the reactive power required by the equivalent power transmission model when the corresponding active loss is minimum by using the virtual reactive power variation method is to obtain the reactive power compensation level index of each node in the current operation mode:

combining the equivalent power transmission model of each node and the equivalent power transmission active power P thereof_EAnd calculating the circulation P under the node equivalent model_ECorresponding reactive value Q required for minimum active loss_minThen comparing said Q_minEquivalent transmission reactive power Q with the obtained node_EAnd solving the reactive compensation shortage index Q under the current operation mode of each node_IComprises the following steps:

$Q_I=\frac{Q_E-Q_{\min }}{Q_E}$

wherein Q is_I>0 hour represents reactive under-compensation, Q_IWhen =0, Q represents the optimal reactive power_I<And 0 represents the power failure over-compensation.

In a seventh preferred embodiment of the present invention: in the step S3, the transient process trajectory time domain data of the power grid is obtained from the WAMS system or various anticipated transient faults in a centralized manner, and the transient stability margin index of the power grid is obtained by analyzing the transient behavior of the power grid by directly using a method of a disturbed severe unit group, which includes steps S101 to S103:

step S101, according to inertia time constant M of each generator, angular speed omega, power angle delta, terminal bus voltage phase angle theta and terminal electromagnetic active power P_GEQuickly identifying the x power generators which are interfered relatively most ahead and the x power generators most behind according to the change conditions of the front time and the rear time to form a relatively most serious unit set omega;

the number x can be set manually according to needs, and the range of x is more than or equal to 5 and less than or equal to 10;

step S102, for any one of the lead and lag generator sets in the set omega, calculating a transient stability margin index between the generator set i and the generator set j

Wherein, delta_ijRepresenting a power angle delta between the generator set i and the generator set j_iAnd delta_jDifference of (d)_ij＝δ_i-δ_j；δ_seqAs a function P of the mechanical power between the generator sets i and j_MeqAnd electromagnetic active power P_EeqThe intersection point of the two points is a virtual stable balance operation point;

step S103, calculating the transient stability margin indexes T between any leading generator set i and any lagging generator set j in the set omega in sequence_SIijWith minimum unit pair T_SIijTransient stability margin index S as current time domain data_TSII.e. S_TSI＝min{T_SIij,i,j∈Ω}。

In an eighth preferred embodiment of the present invention: calculating said delta_seqThe method of (1) comprises steps S1021 to S1023:

step S1021, the equivalent single-machine rotor inertia time constant between the generator set i and the generator set j is

Calculating a mechanical power function between the generator set i and the generator set j $P_{\mathrm{Meq}}=\frac{M_j}{M_i+M_j}{P}_{\mathrm{Mi}}-\frac{M_i}{M_i+M_j}{P}_{\mathrm{Mj}};$

Wherein M is_iAnd M_jThe inertia time constants, P, of the generator set i and the generator set j respectively_MiAnd P_MjThe mechanical injection power of the generator set i and the generator set j and the mechanical injection power of the generator set

Step S1022, calculating the electromagnetic active power between the generator set i and the generator set j $P_{\mathrm{Eeq}}=\frac{M_j}{M_i+M_j}{P}_{\mathrm{Ei}}-\frac{M_i}{M_i+M_j}{P}_{\mathrm{Ej}}=P_{\mathrm{EM}}\sin ({\mathrm{\&delta;}}_{\mathrm{ij}}+C);$

Wherein,

A＝Dcos(δ_j-θ_i)+Ecos(δ_i-θ_j)，B＝Dsin(δ_j-θ_i)-Esin(δ_i-θ_j)，C＝tan^-1(B/A)，

U_i、U_j、θ_i、θ_j、X_i、X_jrespectively representing the voltage amplitude, the phase angle and the equivalent internal reactance of generator terminal buses of a generator set i and a generator set j;

step S1023, calculating ${\mathrm{\&delta;}}_{\mathrm{seq}}=a\sin \left(\frac{P_{\mathrm{Meq}}}{P_{\mathrm{EM}}}\right)-C.$

In a ninth preferred embodiment of the present invention: for any lead and lag unit pair in the set omega, according to the calculated equivalent mechanical power P of the unit pair_MeqAnd electromagnetic active power P_EeqChanging the trajectory, constructing a transient stability estimation index from an energy angle by using a curve fitting technology, and specifically comprising the following steps of S201-S203:

step S201, assume thatEquivalent mechanical power P of generator group_MeqThe equivalent electromagnetic active power P of the generator group is not changed in the transient process_EeqThe varying trajectory was fitted with a sine function as follows: y is x₀sin(δ_ij+x₁)+x₂；

Wherein x is₀，x₁，x₂For the fitted sine function coefficient to be solved, y represents the equivalent P of the generator group_Eeq；

Step S202, calculating transient stability estimation index T between the generator set i and the generator set j_SEIij；

Step S203, calculating T of any lead and lag unit pair in the set omega in sequence_SEIijWith minimum unit pair T_SEIijTransient stability estimation index S as time domain data of this time_TEI，S_TEI＝min{T_SEIij,i,j∈Ω}；

The step S202 of calculating the transient stability estimation indicator between the generator set i and the generator set j includes steps S2021 to S2023:

step S2021, according to P_EeqChanging the trajectory fitting function y to obtain the unstable equilibrium point delta after fault removal_ijuThe unstable balance point is equivalent mechanical power P of the generator set_MeqAnd electromagnetic active power P_EeqIntersection of the varying trajectories, δ_ijuThe calculation formula is as follows: ${\mathrm{\&delta;}}_{\mathrm{iju}}=\mathrm{\&pi;}-\arctan \frac{P_{\mathrm{Meq}}-x_2}{x_0}-{\mathrm{<figure-callout\; id="1"\; label="x"\; filenames="HDA00003086678100041.png,HDA00003086678100042.png"\; state="\{\{state\}\}">x</figure-callout>}}_1;$

step S2022, transient kinetic energy V of unit set at fault clearing time_TAComprises the following steps:

$V_{\mathrm{TA}}={\&Integral;}_{{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="0"\; label="ij"\; filenames="HDA00003086678100041.png,HDA00003086678100042.png"\; state="\{\{state\}\}">ij</figure-callout>}0}}^{{\mathrm{\&delta;}}_{\mathrm{ijc}}}[P_{\mathrm{Meq}}-{\mathrm{<figure-callout\; id="0"\; label="x"\; filenames="HDA00003086678100041.png,HDA00003086678100042.png"\; state="\{\{state\}\}">x</figure-callout>}}_0\sin ({\mathrm{\&delta;}}_{\mathrm{ij}}+x_1)-x_2]d{\mathrm{\&delta;}}_{\mathrm{ij}}$

$=(P_{\mathrm{Meq}}-x_2)({\mathrm{\&delta;}}_{\mathrm{ijc}}-{\mathrm{\&delta;}}_{\mathrm{ij}0})+x_0[\cos ({\mathrm{\&delta;}}_{\mathrm{ijc}}+x_1)-\cos ({\mathrm{\&delta;}}_{\mathrm{ij}0}+x_1)]$

critical potential energy (deceleration area) V absorbed by the system after fault removal_TBComprises the following steps:

$V_{\mathrm{TB}}={\&Integral;}_{{\mathrm{\&delta;}}_{\mathrm{ijc}}}^{{\mathrm{\&delta;}}_{\mathrm{iju}}}[x_0\sin ({\mathrm{\&delta;}}_{\mathrm{ij}}+x_1)+x_2-P_{\mathrm{Meq}}]d{\mathrm{\&delta;}}_{\mathrm{ij}}$

$=(x_2-P_{\mathrm{Meq}})({\mathrm{\&delta;}}_{\mathrm{iju}}-{\mathrm{\&delta;}}_{\mathrm{ijc}})-x_0[\cos ({\mathrm{\&delta;}}_{\mathrm{iju}}+x_1)-\cos ({\mathrm{\&delta;}}_{\mathrm{ijc}}+x_1)]$

wherein, delta_ij0And delta_ijcAnd respectively representing the power angle difference of the unit at the fault occurrence time and the fault removal time.

Step S2023, calculating the transient stability estimation index T between the generator set i and the generator set j_SEIij： $T_{\mathrm{SEIij}}=1-\frac{V_{\mathrm{TA}}}{V_{\mathrm{TB}}};$

Wherein, T_SEIijThe transient stability of the index has the following significance: t is_SEIij>0 transient stability, T_SEIijCritical transient stability of =0, T_SEIij<0, transient instability.

In a tenth preferred embodiment of the present invention: the method for obtaining the power grid node voltage holding qualification rate in the step S3 includes:

the node voltage holding capability investigation range in the given transient process is as follows: lower limit of voltage drop V_LAnd duration V_CCounting the number V of nodes meeting the acceptable range of the voltage level of all the nodes of the power grid in the transient process_QNCalculating the qualification rate of the node voltage meeting the retention capacity in the transient process

The method for obtaining the line thermal stability qualification rate in the power grid in the step S3 includes: and (3) giving a node static stability margin index and a line thermal stability investigation range in the transient process: node static margin limit S_ICLine thermal stability limit value L_PRAnd duration T_CCounting the number S of nodes of the power grid meeting the steady sustainable range_QNNumber of lines L satisfying thermally stable sustainable range_QNAnd calculating the qualification rate S of node stationarity and line heat stability in the transient process_TR，S_TRThe calculation formula is as follows:

in an eleventh preferred embodiment of the present invention: obtaining the power grid integral transient stability situation comprehensive index in the step S3 $S_{\mathrm{TI}}={\mathrm{\&alpha;}}_2{S_T}_{\mathrm{SEI}}+{\mathrm{\&beta;}}_2{V}_{\mathrm{TR}}+{\mathrm{\&chi;}}_2{S}_{\mathrm{TR}};$

Wherein alpha is₂、β₂、χ₂Weight coefficients of the power grid according to thermal stability constraint, operation electric quantity constraint and static stability constraintFlexibly configured according to experience or analytical requirements, alpha₂、β₂、χ₂Satisfies the following conditions:

$\left\{\begin{array}{c}0\&le;{\mathrm{\&alpha;}}_2\&le;1\\ 0\&le;{\mathrm{\&beta;}}_2\&le;1\\ 0\&le;{\mathrm{\&chi;}}_2\&le;1\\ 0\&le;{\mathrm{\&alpha;}}_2+{\mathrm{\&beta;}}_2+{\mathrm{\&chi;}}_2\&le;1\end{array}\right.$

。

the response-based large power grid full-situation online integrated quantitative evaluation method provided by the invention has the beneficial effects that:

1. the response-based online integrated quantitative evaluation method for the full-situation of the large power grid can realize online integrated quantitative evaluation of the full-situation of two typical operation scenes, namely static and transient states of the large power grid aiming at real-time measurement of the current state of the power grid or various simulation data in an expected state. The situation assessment of the power grid in the current state is realized, the situation assessment of the envisioned state is realized by fully combining the advantages of the existing DSA envisioned simulation, and scheduling and operating personnel can know the current operating situation of the power grid and potential system risks of the power grid in time. And the method can also be indirectly applied to the post-stage intelligent evaluation of various off-line forecast modes or fault set time domain simulation data, so that the workload of planners or mode making personnel is greatly reduced. The core methods used by the method are all based on power grid response data, have strong independence, and the full situation assessment method and algorithm are direct and simple, can quickly identify weak nodes or weak areas of the power grid in any operation mode so as to be convenient for operation or planning personnel to refer, prevent the trouble in the bud, reduce or avoid voltage stabilization accidents, and are suitable for online engineering application. The invention can gradually transit the former 'modeling simulation' prevention and control mode to the 'track mining' response control mode, is an extension of the traditional power grid prevention and control idea and method, and can effectively improve the online intelligent evaluation and early warning level of the large power grid.

2. And the power grid topological structure relationship is obtained from the EMS system, so that the power grid full situation quantitative evaluation and statistical analysis are favorably carried out aiming at various response data in the later period.

3. From a response perspective, simple statistical analysis is performed directly from the qualifying range for the grid elements and voltage levels. And when the power angle stability and the voltage stability situation are quantitatively evaluated in the traditional sense, the static stability focuses on the power transmission capacity of the power grid, the transient stability focuses on the energy conservation, and the response-based online unified quantitative evaluation idea of the full situation of the large power grid is established.

4. And performing static stable form situation assessment aiming at any real-time measurement of a power grid or various expected fault form power flow sections, and improving comprehensive assessment efficiency by adopting a task parallel method when analyzing specific node stable situations or fault sets.

5. According to the current tide current distribution and topological relation, all nodes of the power grid count the actual circulating (or transferring) power of the nodes, the nodes are equivalent to a simplified single-power single-load simplified power transmission model on the basis, equivalent power transmission parameters are identified by adopting local measurement information in an online tracking mode, equivalent virtual model mapping of all the nodes of the power grid is realized, and a foundation is laid for next static stable situation evaluation.

6. And uniformly adopting an impedance model index capable of expressing the idea of maximum power transmission capacity to evaluate the static stability situation, and applying an impedance model method to an equivalent power transmission model of a generator branch, a power transmission line and a node. The impedance model method is suitable for online rapid calculation, and can effectively identify weak units, key lines and weak nodes in the current operation mode.

7. From the perspective of the qualified range of the thermal stability operation of the generator and the line, the thermal stability qualification rate of the power grid in the current operation mode is counted, the overload elements can be quickly and effectively screened, and the habit of visual evaluation of the conventional trend mode is also met.

8. The qualification rate of the electrical quantity in the current operation mode of the power grid is counted from the aspects of node voltage level and load node power factor, the qualification levels of the voltage and the power factor in the current operation mode can be quickly and effectively evaluated, and the electric energy quality assessment requirement of the conventional tide mode is met.

9. And (3) the static stable qualification rate statistics is realized by using the impedance model indexes facing to the node equivalent power transmission model and the line.

10. The comprehensive static-over-stable situation assessment from the component-level thermal stability, the qualified range of the operation amount to the system static stability is realized by fully combining the statistical result, and the weights of the three can be flexibly selected according to the actual operation state and the assessment focus point.

11. By means of the constructed node equivalent power transmission model and parameters thereof, the virtual reactive power required by the node to minimize the active power loss when the node currently circulates active power can be obtained, and then the reactive power compensation level evaluation of all nodes of the power grid in the current operation mode is realized

12. When transient stability margin and transient stability are estimated aiming at transient time domain process information, the dynamic behavior envelope of the disturbed most serious unit set is directly adopted to reflect the overall dynamic behavior of the power grid, processing such as clustering equivalence is not needed, the physical significance is clear and intuitive, and the accuracy of the estimation result is high.

13. In order to reduce the selection error of the most disturbed set pair, a relatively most disturbed set omega is selected from multiple angles, and then the most serious set pair is selected from the set omega, so that the misjudgment of the actual situation of the power grid caused by the selection error of the weakest set pair is reduced.

14. For the lead and lag unit groups in any set omega, transient stability margin index T of the unit group is obtained through simple algebraic calculation according to the electrical quantity information of each unit group_SIAnd T of the minimum unit pair in the set omega_SITransient stability margin index S as current time domain data_TSIAnd further realizing the quantitative evaluation of the transient stability margin of the current transient trajectory.

15. The characteristic of the equivalent power-angle function curve of the unit is fitted in a trigonometric function form to better reflect the transient transition trajectory of the power grid, and the energy-type transient stability pre-estimation index T can be conveniently calculated by means of the fitted curve_SEIThe physical significance is clear and visual, and the T of the minimum unit pair in the set omega is used_SEITransient stability estimation index S as time domain data of this time_TEIAnd further realizing the quantitative estimation of the transient stability of the current transient trajectory.

16. By taking the reference of a transient voltage stability habitual judgment method, the node voltage holding capacity and the qualification rate level in a given transient process are measured by adopting a certain limit and duration of voltage drop.

17. The qualification rate S of node stationarity and line heat stability in the transient process is obtained by adopting a limit value + duration method and combining methods in the stationarity_TRThe static stability margin of the node and the line load level condition in the given transient process are convenient to evaluate.

18. Full binding statisticsAs a result, the comprehensive transient stability situation evaluation index S from the power system energy conservation, the transient voltage holding capacity, the node static stability and the line thermal stability is realized_TIFlexibly selecting weights according to actual dynamic tracks and evaluation emphasis points, and calculating S corresponding to different faults_TIAnd realizing the sequencing of the severity of the faults, and improving the online analysis efficiency of the expected fault set S_TIThe method can effectively quantitatively evaluate the stable situation of various transient faults and is convenient for screening serious transient faults.

19. And performing transient stability situation analysis on a large number of expected faults in the transient fault set by adopting a task parallel method.

Drawings

Fig. 1 shows a data flow diagram for response-based online integrated quantitative evaluation of the full situation of a large power grid;

FIG. 2 is a diagram of the elements of the comprehensive index system provided by the present invention;

fig. 3 is a schematic diagram of a local node of a power grid according to the present invention;

fig. 4 is a schematic diagram of a node equivalent power transmission model provided by the present invention;

fig. 5 is a schematic diagram of a boundary impedance mode of maximum transmission power provided by the present invention;

fig. 6 is a schematic diagram illustrating the evaluation of node reactive compensation level provided by the present invention;

fig. 7 is a schematic diagram of a power grid unit pair provided by the present invention;

fig. 8 is a schematic diagram illustrating curve fitting of equivalent power angles of the unit provided by the present invention;

FIG. 9 is a schematic diagram of an energy-based transient stability estimation indicator according to the present invention;

fig. 10 shows a flow chart of response-based online integrated quantitative evaluation of the full situation of the large power grid.

Detailed Description

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

The invention provides a response-based large power grid full-situation online integrated quantitative evaluation method, and provides a response-based large power grid full-situation online integrated quantitative evaluation data flow diagram as shown in fig. 1. As can be seen from fig. 1, the evaluation method includes:

and step S1, acquiring the power grid topological structure information from the SCADA system and the EMS system, and establishing a corresponding relation with the power grid element of the WAMS system.

Step S2, obtaining current operation mode power flow data of the power grid from the SCADA system, the EMS system or the WAMS system, or obtaining various anticipated power flow or transient fault time domain data from the DSA system.

And step S3, performing static stability situation evaluation on the power grid in an online node-oriented mode, and performing transient stability situation evaluation on the power grid in an online unit-oriented mode.

When a situation comprehensive evaluation index system is constructed, three factors of power grid element-level thermal stability, operation electric quantity qualification and system-level stability are comprehensively considered, and as shown in fig. 2, the element diagram of the comprehensive index system provided by the invention is provided.

Wherein, the content of carrying out the static stable situation aassessment to the electric wire netting includes: the method comprises the following steps of generating a generator stability margin index, a line stability margin index, a node stability margin index, a generator thermal stability qualification rate, a line thermal stability qualification rate, a node voltage qualification rate, a load node power factor qualification rate, a static stability situation comprehensive index and a node reactive compensation level index.

The content of transient stability situation assessment on the power grid comprises the following steps: transient stability margin index, transient stability estimation index, node voltage holding qualification rate, node stability margin index, line thermal stability qualification rate and transient stability situation comprehensive index.

Various power grid static response data comprise expected state offline power flow, calculation results after convergence of N-1 and N-2 power flows, state estimation results of a SCADA \ EMS system and PMU measurement information; the response data of various power grid transient transition processes comprise various expected transient fault set time domain simulation results and power grid disturbance process information measured by the WAMS in real time; carrying out rationality prejudgment or filtering processing on PMU measurement information according to previous time or peripheral PMU measurement data change; and (4) allocating the expected faults of N-1 and N-2 according to the number of the parallel machines.

When the static stability situation and the transient stability situation of the power grid are evaluated in step S3, all nodes of the power grid are distributed according to the number of parallel machines, as shown in fig. 3, which is a schematic diagram of a local node of the power grid provided by the present invention, and the nodes may be connected to various elements such as a generator, a load, a capacitor, and a line.

According to the power grid operation tide section information and in combination with the power grid topological structure, the equivalent transmission power P of each node is obtained according to the active flow direction_E+jQ_EFig. 4 is a schematic diagram of a node equivalent power transmission model. The method for identifying tracking parameters based on local measurement is adopted to identify equivalent power transmission model parameters of each node of a power grid in the current state on line, and the equivalent power transmission model parameters mainly comprise equivalent power source potential E_EEquivalent branch impedance mode Z_EAnd the impedance angle alpha is used for realizing node equivalent power transmission model inverse mapping based on the current running state of the power grid.

In the method for obtaining the generator stability margin index, the line stability margin index, and the node stability margin index of the power grid in step S3, the method for obtaining the generator stability margin index, the line stability margin index, and the node stability margin index of the power grid uses the impedance mode index of the maximum transmission power concept shown in fig. 5 as a static stability margin index, and includes:

aiming at a generator branch, a tie line branch and a node respectively according to the thought of maximum transmission powerA point equivalent power transmission model is used for solving the static stability margin index S corresponding to the current operation mode of the generator branch, the tie line branch or the node_Li，S_LiThe calculation formula is as follows:

$S_{\mathrm{Li}}=\frac{Z_L-Z_E}{Z_L}$

Z_Lthe equivalent load impedance of the branch circuit, the connecting line or the node of the generator can be respectively represented and can be obtained according to the terminal voltage and the power. S_LiThe load of each generator branch, power transmission line and the static stability margin of the node are measured, and the method can be used for positioning weak units, key lines and weak nodes.

Specifically, the static stability margin index S of all nodes is used_LiAveraging to obtain the average static stability margin index S of the power grid in the current operation mode_AIThe calculation formula is as follows:

$S_{\mathrm{AI}}=\frac{\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}{S}_{\mathrm{Li}}}{N_N}$

the method for obtaining the generator thermal stability qualification rate and the tie line thermal stability qualification rate of the power grid in the step S3 includes:

according to the self thermal stability operation constraint of each generator and the connecting line, the thermal stability qualification rate G of the generator is counted_PRAnd line thermal stability yield L_PRRespectively as follows: $G_{\mathrm{PR}}=\frac{G_{\mathrm{QN}}}{G_N};$ $L_{\mathrm{PR}}=\frac{L_{\mathrm{QN}}}{L_N}.$

wherein G is_N、L_NThe total generator number, the total tie line number and G of the power grid_QN、L_QNThe number of the generators and the number of the connecting lines which meet the thermal stability constraint of the operation of each generator and the connecting lines.

The method for obtaining the node voltage qualification rate and the load node power factor qualification rate of the power grid in the step S3 includes:

according to the node voltage given by the normal operation mode of the power grid and the upper and lower limits of the qualified range of the power factor of the load node, the qualified rate of the node voltage of the power grid is counted

Load node power factor qualification rate

Wherein N is_N、P_FNRespectively the total node number and the load node number of the power grid, V_QN、P_QFNThe number of nodes satisfying the voltage range and the power factorNumber range of load nodes.

The method for obtaining the power grid static stability out-of-limit rate comprises the following steps:

setting S_LiCertain early warning threshold value S_LCCounting that all tie line branches and nodes (generator nodes, intermediate tie nodes and load nodes) of the power grid are equivalent to be greater than S_LCRespectively calculating the steady qualification rate of the line

Yield of node statically stable $N_{\mathrm{SR}}=\frac{N_{\mathrm{CN}}}{N_N};$

Wherein L is_N、N_NRespectively the number of system bus lines and the number of nodes, L_CN、N_CNAre each greater than S_LCThe number of connections and the number of nodes.

The method for obtaining the comprehensive index of the overall static stable situation of the power grid in the step S3 comprises the following steps: integrated static stable situation index S of power grid_I＝α₁H_QR+β₁R_QR+χ₁S_SR。

Wherein alpha is₁、β₁、χ₁The weight coefficients of the power grid according to thermal stability constraint, operation electric quantity constraint and static stability constraint can be flexibly configured according to experience or analysis requirements. Alpha is alpha₁、β₁、χ₁The following conditions are satisfied:

$\left\{\begin{array}{c}0\&le;{\mathrm{\&alpha;}}_1\&le;1\\ 0\&le;{\mathrm{\&beta;}}_1\&le;1\\ 0\&le;{\mathrm{\&chi;}}_1\&le;1\\ 0\&le;{\mathrm{\&alpha;}}_1+{\mathrm{\&beta;}}_1+{\mathrm{\&chi;}}_1\&le;1\end{array}\right.$

H_QRthe overall thermal stability qualification rate of the power grid H_QRThe calculation formula is as follows:

R_QRfor the qualification rate of the electric quantity, R, of the whole operation of the power grid_QRThe calculation formula is as follows:

S_SRthe qualification rate of the whole static stability of the power grid, S_SRThe calculation formula is as follows:

S_SIcomprehensively measure the static stable situation level of the power grid in the current tidal current stateAnd effectively and quantitatively evaluating the static stable situation of various trend modes.

In step S3, the virtual reactive power variation method is used to obtain the reactive power required by the equivalent power transmission model when the corresponding active loss is minimum, a schematic diagram of node reactive power compensation level evaluation is shown in fig. 6, and the method for obtaining the reactive power compensation level index of each node in the current operation mode includes:

equivalent power transmission model combined with nodes and equivalent power transmission active power P thereof_EThe circulation P under the node equivalent model can be calculated_ECorresponding reactive value Q required for minimum active loss_minThen compare Q_minEquivalent transmission reactive power Q with calculated node_EAnd the reactive compensation shortage index Q of each node under the current operation mode can be obtained_IComprises the following steps:

$Q_I=\frac{Q_E-Q_{\min }}{Q_E}$

wherein Q is_I>0 hour represents reactive under-compensation, Q_IWhen =0, Q represents the optimal reactive power_I<And 0 represents the power failure over-compensation.

In step S3, the method includes steps of obtaining time domain data of a power grid transient process trajectory from the WAMS system or various anticipated transient faults in a centralized manner, analyzing transient behavior of the power grid by directly using a method of a disturbed severe unit pair, and obtaining a transient stability margin index of the power grid, as shown in fig. 7, the method includes the following steps:

step S101, according to inertia time constant M of each generator, angular velocity omega, power angle delta and generator end bus voltage phase angleTheta and terminal electromagnetic active power P_GEAnd (3) rapidly identifying the x generators which are interfered relatively most ahead and the x generators most behind according to the change conditions of the front moment and the rear moment, and forming a set omega which is interfered relatively most seriously.

The number x can be set manually according to requirements, and the range of x is more than or equal to 5 and less than or equal to 10.

Step S102, for any one of the lead and lag generator sets in the set omega, calculating a transient stability margin index between the generator set i and the generator set j

Wherein, delta_ijRepresenting the power angle delta between genset i and genset j_iAnd delta_jDifference of (d)_ij＝δ_i-δ_j。

δ_seqAs a function P of the mechanical power between genset i and genset j_MeqAnd electromagnetic active power P_EeqThe cross point of (a) is a virtual stable balanced operating point, and delta is calculated_seqThe method of (1) comprises steps S1021 to S1023:

step S1021, the equivalent single-machine rotor inertia time constant between the generator set i and the generator set j isCalculating a mechanical power function between genset i and genset j

Wherein M is_iAnd M_jInertia time constants, P, of generator set i and generator set j, respectively_MiAnd P_MjThe mechanical injection power of the generator set i and the generator set j and the mechanical injection power of the generator set

Step S1022, calculating the electromagnetic active power between the generator set i and the generator set j $P_{\mathrm{Eeq}}=\frac{M_j}{M_i+M_j}{P}_{\mathrm{Ei}}-\frac{M_i}{M_i+M_j}{P}_{\mathrm{Ej}}=P_{\mathrm{EM}}\sin ({\mathrm{\&delta;}}_{\mathrm{ij}}+C).$

Wherein,

A＝Dcos(δ_j-θ_i)+Ecos(δ_i-θ_j)，B＝Dsin(δ_j-θ_i)-Esin(δ_i-θ_j)，C＝tan^-1(B/A)，

θ_iand theta_jRespectively representing generator set i and generator set j terminal bus voltage phase angle U_i、U_j、θ_i、θ_j、X_i、X_jAnd respectively representing the voltage amplitude, the phase angle and the equivalent internal reactance of the generator terminal buses of the generator set i and the generator set j.

Step S1023, calculating ${\mathrm{\&delta;}}_{\mathrm{seq}}=a\sin \left(\frac{P_{\mathrm{Meq}}}{P_{\mathrm{EM}}}\right)-C.$

Step S103, calculating the transient stability margin indexes T between any leading generator set i and any lagging generator set j in the set omega in sequence_SIijWith minimum unit pair T_SIijTransient stability margin index S as current time domain data_TSII.e. S_TSI＝min{T_SIijI, j ∈ Ω }. S by minimum unit pair_TSIThe positioning of the weak unit can be realized.

The method for obtaining the transient stability estimation index of the power grid in the step S3 includes: for any lead and lag generator set pair in the set omega, according to the calculated equivalent mechanical power P of the generator set pair_MeqAnd electromagnetic active power P_EeqAnd (3) changing the trajectory, constructing a transient stability prediction index from an energy angle by using a curve fitting technology, and obtaining a curve fitting diagram of equivalent power angles of the unit as shown in fig. 8. The method for obtaining the transient stability estimation index of the power grid specifically comprises the following steps of S201-S203:

step S201, the generator set is paired with an equivalent mechanical power P_MeqIn the transient process, the equivalent electromagnetic active power P of the generator set can be assumed to be unchanged_EeqThe varying trajectory may be fitted with a sine function as follows: y is x₀sin(δ_ij+x₁)+x₂。

Wherein x is₀，x₁，x₂For the fitted sine function coefficient to be solved, y represents the equivalent P of the generator group_Eeq。

Step S202, calculating transient stability estimation index T between generator set i and generator set j_SEIijComprising the steps of S2021-S2023:

step S2021, according to P_EeqChanging the trajectory fitting function y to obtain the unstable equilibrium point delta after fault removal_iju，δ_ijuThe calculation formula is as follows: ${\mathrm{\&delta;}}_{\mathrm{iju}}=\mathrm{\&pi;}-\arctan \frac{P_{\mathrm{Meq}}-x_2}{x_0}-{\mathrm{<figure-callout\; id="1"\; label="x"\; filenames="HDA00003086678100041.png,HDA00003086678100042.png"\; state="\{\{state\}\}">x</figure-callout>}}_1.$

step S2022, transient kinetic energy (acceleration area) V of the unit set at the time of fault removal_TAComprises the following steps:

$V_{\mathrm{TA}}={\&Integral;}_{{\mathrm{\&delta;}}_{\mathrm{<figure-callout\; id="0"\; label="ij"\; filenames="HDA00003086678100041.png,HDA00003086678100042.png"\; state="\{\{state\}\}">ij</figure-callout>}0}}^{{\mathrm{\&delta;}}_{\mathrm{ijc}}}[P_{\mathrm{Meq}}-{\mathrm{<figure-callout\; id="0"\; label="x"\; filenames="HDA00003086678100041.png,HDA00003086678100042.png"\; state="\{\{state\}\}">x</figure-callout>}}_0\sin ({\mathrm{\&delta;}}_{\mathrm{ij}}+x_1)-x_2]d{\mathrm{\&delta;}}_{\mathrm{ij}}$

$=(P_{\mathrm{Meq}}-x_2)({\mathrm{\&delta;}}_{\mathrm{ijc}}-{\mathrm{\&delta;}}_{\mathrm{ij}0})+x_0[\cos ({\mathrm{\&delta;}}_{\mathrm{ijc}}+x_1)-\cos ({\mathrm{\&delta;}}_{\mathrm{ij}0}+x_1)]$

critical potential energy (deceleration area) V absorbed by the system after fault removal_TBComprises the following steps:

$V_{\mathrm{TB}}={\&Integral;}_{{\mathrm{\&delta;}}_{\mathrm{ijc}}}^{\mathrm{\&delta;iju}}[x_0\sin ({\mathrm{\&delta;}}_{\mathrm{ij}}+x_1)+x_2-P_{\mathrm{Meq}}]d{\mathrm{\&delta;}}_{\mathrm{ij}}$

$=(x_2-P_{\mathrm{Meq}})({\mathrm{\&delta;}}_{\mathrm{iju}}-{\mathrm{\&delta;}}_{\mathrm{ijc}})-x_0[\cos ({\mathrm{\&delta;}}_{\mathrm{iju}}+x_1)-\cos ({\mathrm{\&delta;}}_{\mathrm{ijc}}+x_1)]$

wherein, delta_ij0And delta_ijcAnd respectively representing the power angle difference of the unit at the fault occurrence time and the fault removal time.

Step S2023, as shown in the schematic diagram of energy-type transient stability estimation indicator shown in fig. 9, calculate the transient stability estimation indicator T between the generator set i and the generator set j_SEIij：

Wherein, T_SEIijThe transient stability of the index is defined as follows, T_SEIij>0 transient stability, T_SEIijCritical transient stability of =0, T_SEIij<0, transient instability.

Step S203, calculating T of any lead and lag unit pair in the set omega in sequence_SEIijWith minimum unit pair T_SEIijTransient stability estimation index S as time domain data of this time_TEI，S_TEIThe calculation formula is as follows: s_TEI＝min{T_SEIij,i,j∈Ω}。

The method for obtaining the power grid node voltage holding qualification rate in the step S3 includes:

the node voltage holding capability inspection range (voltage drop lower limit V) in the transient process is given_LAnd duration V_C) Counting the number V of nodes meeting the acceptable range of the voltage level of all the nodes of the power grid in the transient process_QNAnd calculating the qualification rate V of the node voltage meeting the retention capacity in the transient process_TR，V_TRThe calculation formula is as follows:

the method for obtaining the line thermal stability qualification rate in the power grid in the step S3 comprises the following steps: and (3) giving a node static stability margin index and a line thermal stability investigation range in the transient process: node static margin limit S_ICLine thermal stability limit value L_PRAnd duration T_CCounting the number S of nodes of the power grid meeting the steady sustainable range_QNNumber of lines L satisfying thermally stable sustainable range_QNCalculating the transient statePass rate S of node static stability and line thermal stability in process_TR，S_TRThe calculation formula is as follows:

step S3 is carried out to obtain the comprehensive index S of the integral transient stability situation of the power grid_TI＝α₂S_TEi+β₂V_TR+χ₂S_TR；

Wherein alpha is₂、β₂、χ₂The weight coefficients of the power grid according to thermal stability constraint, operation electric quantity constraint and static stability constraint can be flexibly configured according to experience or analysis requirements. Alpha is alpha₂、β₂、χ₂The following conditions are satisfied:

$\left\{\begin{array}{c}0\&le;{\mathrm{\&alpha;}}_2\&le;1\\ 0\&le;{\mathrm{\&beta;}}_2\&le;1\\ 0\&le;{\mathrm{\&chi;}}_2\&le;1\\ 0\&le;{\mathrm{\&alpha;}}_2+{\mathrm{\&beta;}}_2+{\mathrm{\&chi;}}_2\&le;1\end{array}\right.$

S_TIthe power grid transient stability situation level of the current transient process information can be comprehensively measured, and the stability situations of various transient faults can be effectively quantitatively evaluated.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (12)

1. A response-based large power grid full-situation online integrated quantitative evaluation method is characterized by comprising the following steps:

step S1, acquiring power grid topological structure information from the SCADA system and the EMS system, and establishing a corresponding relation with power grid elements of the WAMS system;

step S2, obtaining the current operation mode power flow data of the power grid from the SCADA system, the EMS system or the WAMS system or obtaining various anticipated power flow or transient fault time domain data from the DSA system;

step S3, performing static stability situation evaluation on the power grid in an online node-oriented mode, and performing transient stability situation evaluation on the power grid in an online unit-oriented mode;

wherein, the content of carrying out the static stable situation aassessment to the electric wire netting includes: the method comprises the following steps of (1) generating a generator stability margin index, a line stability margin index, a node stability margin index, a generator thermal stability qualification rate, a line thermal stability qualification rate, a node voltage qualification rate, a load node power factor qualification rate, a static stability situation comprehensive index and a node reactive power compensation level index;

the content of transient stability situation assessment on the power grid comprises the following steps: transient stability margin index, transient stability estimation index, node voltage holding qualification rate, node stability margin index, line thermal stability qualification rate and transient stability situation comprehensive index.

2. The method of claim 1, wherein the various power grid static response data include expected state offline power flow, calculation results after convergence of N-1 and N-2 power flows, SCADA \ EMS system state estimation results, and PMU measurement information;

the response data of various power grid transient transition processes comprise various expected transient fault set time domain simulation results and power grid disturbance process information measured by the WAMS in real time;

carrying out rationality prejudgment or filtering processing on PMU measurement information according to previous time or peripheral PMU measurement data change;

and (4) allocating the expected faults of N-1 and N-2 according to the number of the parallel machines.

3. The method according to claim 1, wherein in the step S3, when the static stability situation and the transient stability situation of the power grid are evaluated, all nodes of the power grid are distributed according to the number of parallel machines;

according to the power grid operation tide section information and in combination with the power grid topological structure, the equivalent transmission power P of each node is obtained according to the active flow direction_E+jQ_E；

Tracking parameter identification method based on local measurementIdentifying equivalent power transmission model parameters of each node of the power grid in the current state on line, wherein the equivalent power transmission model parameters comprise equivalent power source potential E_EEquivalent branch impedance mode Z_EAnd the impedance angle alpha is used for realizing node equivalent power transmission model inverse mapping based on the current running state of the power grid.

4. The method of claim 3, wherein the generator stability margin indicator, the line stability margin indicator and the node stability margin indicator of the power grid obtained in the step S3 are obtained by:

according to the maximum transmission power thought, aiming at equivalent transmission models of a generator branch, a tie line branch and a node, respectively, the static stability margin index S corresponding to the current operation mode of the generator branch, the tie line branch or the node is obtained_Li，S_LiThe calculation formula is as follows: $S_{\mathrm{Li}}=\frac{Z_L-Z_E}{Z_L};$

wherein Z_LAnd the equivalent load impedance representing the branch circuit, the connecting line or the node of the generator is obtained according to the terminal voltage and the power.

5. The method of claim 3, wherein the step S3 of obtaining the generator and tie line thermal stability qualification rates of the power grid comprises:

according to the self thermal stability operation constraint of each generator and the connecting line, the thermal stability qualification rate G of the generator is counted_PRAnd line thermal stability yield L_PRRespectively as follows: $G_{\mathrm{PR}}=\frac{G_{\mathrm{QN}}}{G_N};$ $L_{\mathrm{PR}}=\frac{L_{\mathrm{QN}}}{L_N};$

wherein G is_N、L_NThe total generator number, the total tie line number and G of the power grid_QN、L_QNThe number of the generators and the number of the connecting lines which meet the respective operation thermal stability constraint are respectively;

the method for obtaining the node voltage qualification rate and the load node power factor qualification rate of the power grid in the step S3 includes:

according to the node voltage given by the normal operation mode of the power grid and the upper and lower limits of the qualified range of the power factor of the load node, the qualified rate of the node voltage of the power grid is countedLoad node power factor qualification rate

Wherein N is_N、P_FNRespectively the total node number and the load node number of the power grid, V_QN、P_QFNThe number of nodes meeting the voltage range and the number of load nodes meeting the power factor range are respectively;

the method for obtaining the power grid static stability out-of-limit rate comprises the following steps:

setting S_LiCertain early warning threshold value S_LCCounting that all tie line branches and node equivalent branches of the power grid are greater than S_LCThe nodes comprise a generator node, a middle contact node and a load node, and the static stability qualification rate of the line is respectively calculated

Yield of node statically stable $N_{\mathrm{SR}}=\frac{N_{\mathrm{CN}}}{N_N};$

Wherein L is_N、N_NRespectively the number of system bus lines and the number of nodes, L_CN、N_CNAre each greater than S_LCThe number of connections and the number of nodes.

6. The method according to claim 5, wherein the step S3 of obtaining the comprehensive index of the overall static stable situation of the power grid comprises:

integrated static stable situation index S of power grid_SI＝α₁H_QR+β₁R_QR+χ₁S_SR；

Wherein alpha is₁、β₁、χ₁The weight coefficients of the power grid according to thermal stability constraint, operation electric quantity constraint and static stability constraint are flexibly configured according to experience or analysis requirements, and alpha is₁、β₁、χ₁Satisfies the following conditions:

$\left\{\begin{array}{c}0\&le;{\mathrm{\&alpha;}}_1\&le;1\\ 0\&le;{\mathrm{\&beta;}}_1\&le;1\\ 0\&le;{\mathrm{\&chi;}}_1\&le;1\\ 0\&le;{\mathrm{\&alpha;}}_1+{\mathrm{\&beta;}}_1+{\mathrm{\&chi;}}_1\&le;1\end{array}\right.$

H_QRthe overall thermal stability qualification rate of the power grid H_QRThe calculation formula is as follows:

R_QRfor the qualification rate of the electric quantity, R, of the whole operation of the power grid_QRThe calculation formula is as follows:

S_SRthe qualification rate of the whole static stability of the power grid, S_SRThe calculation formula is as follows:

7. the method according to claim 3, wherein the step S3 of obtaining the reactive power required for minimizing the corresponding active loss of the equivalent power transmission model by using the virtual reactive power variation method comprises the following steps:

combining the equivalent power transmission model of each node and the equivalent power transmission active power P thereof_EAnd calculating the circulation P under the node equivalent model_ECorresponding reactive value Q required for minimum active loss_minThen is aligned withTo said Q_minEquivalent transmission reactive power Q with the obtained node_EAnd solving the reactive compensation shortage index Q under the current operation mode of each node_IComprises the following steps:

$Q_I=\frac{Q_E-Q_{\min }}{Q_E}$

wherein Q is_I>0 hour represents reactive under-compensation, Q_IWhen =0, Q represents the optimal reactive power_I<And 0 represents the power failure over-compensation.

8. The method according to claim 3, wherein the step S3 of obtaining time domain data of the transient process trajectory of the power grid from the WAMS system or various expected transient fault sets, and directly enveloping the transient behavior analysis of the power grid by using a method of a disturbed severe unit group to obtain the transient stability margin index of the power grid comprises the steps S101-S103:

step S101, according to inertia time constant M of each generator, angular speed omega, power angle delta, terminal bus voltage phase angle theta and terminal electromagnetic active power P_GEQuickly identifying the x power generators which are interfered relatively most ahead and the x power generators most behind according to the change conditions of the front time and the rear time to form a relatively most serious unit set omega;

the number x can be set manually according to needs, and the range of x is more than or equal to 5 and less than or equal to 10;

step S102, for any one of the lead and lag generator sets in the set omega, calculating a transient stability margin index between the generator set i and the generator set j

Wherein, delta_ijRepresenting a power angle delta between the generator set i and the generator set j_iAnd delta_jDifference of (d)_ij＝δ_i-δ_j；δ_seqAs a function P of the mechanical power between the generator sets i and j_MeqAnd electromagnetic active power P_EeqThe intersection point of the two points is a virtual stable balance operation point;

step S103, calculating the transient stability margin indexes T between any leading generator set i and any lagging generator set j in the set omega in sequence_SIijWith minimum unit pair T_SIijTransient stability margin index S as current time domain data_TSII.e. S_TSI＝min{T_SIij,i,j∈Ω}。

9. The method of claim 8, wherein the δ is calculated_seqThe method of (1) comprises steps S1021 to S1023:

step S1021, the equivalent single-machine rotor inertia time constant between the generator set i and the generator set j is

Calculating a mechanical power function between the generator set i and the generator set j $P_{\mathrm{Meq}}=\frac{{M_j}_{}}{M_i+M_j}{P}_{\mathrm{Mi}}-\frac{M_i}{M_i+M_j}{P}_{\mathrm{Mj}};$

Wherein M is_iAnd M_jThe inertia time constants, P, of the generator set i and the generator set j respectively_MiAnd P_MjThe mechanical injection power of the generator set i and the generator set j and the mechanical injection power of the generator set

Step S1022, calculating the electromagnetic active power between the generator set i and the generator set j $P_{\mathrm{Eeq}}=\frac{M_j}{M_i+M_j}{P}_{\mathrm{Ei}}-\frac{M_i}{M_i+M_j}{P}_{\mathrm{Ej}}=P_{\mathrm{EM}}\sin ({\mathrm{\&delta;}}_{\mathrm{ij}}+C);$

Wherein,

A＝Dcos(δ_j-θ_i)+Ecos(δ_i-θ_j)，B＝Dsin(δ_j-θ_i)-Esin(δ_i-θ_j)，C＝tan^-1(B/A)， U_i、U_j、θ_i、θ_j、X_i、X_jrespectively representing the voltage amplitude, the phase angle and the equivalent internal reactance of generator terminal buses of a generator set i and a generator set j;

step S1023, calculating ${\mathrm{\&delta;}}_{\mathrm{seq}}=a\sin \left(\frac{P_{\mathrm{Meq}}}{P_{\mathrm{EM}}}\right)-C.$

10. The method of claim 8, wherein the equivalent mechanical power P is calculated as a function of the calculated crew to equivalent mechanical power P for any pair of lead and lag crew within the set Ω_MeqAnd electromagnetic active power P_EeqChanging the trajectory, constructing a transient stability estimation index from an energy angle by using a curve fitting technology, and specifically comprising the following steps of S201-S203:

step S201, the generator set is assumed to generate equivalent mechanical power P_MeqThe equivalent electromagnetic active power P of the generator group is not changed in the transient process_EeqThe varying trajectory was fitted with a sine function as follows: y is x₀sin(δ_ij+x₁)+x₂；

Wherein x is₀，x₁，x₂For the fitted sine function coefficient to be solved, y represents the equivalent P of the generator group_Eeq；

Step S202, calculating transient stability estimation index T between the generator set i and the generator set j_SEIij；

Step S203, calculating T of any lead and lag unit pair in the set omega in sequence_SEIijWith minimum unit pair T_SEIijTransient stability estimation index S as time domain data of this time_TEI，S_TEI＝min{T_SEIij,i,j∈Ω}；

The step S202 of calculating the transient stability estimation indicator between the generator set i and the generator set j includes steps S2021 to S2023:

step S2021, according to P_EeqChanging the trajectory fitting function y to obtain the unstable equilibrium point delta after fault removal_ijuThe unstable balance point is equivalent mechanical power P of the generator set_MeqAnd electromagnetic active power P_EeqIntersection of the varying trajectories, δ_ijuThe calculation formula is as follows: ${\mathrm{\&delta;}}_{\mathrm{iju}}=\mathrm{\&pi;}-\arctan \frac{P_{\mathrm{Meq}}-x_2}{x_0}-x_1;$

step S2022, transient kinetic energy V of unit set at fault clearing time_TAComprises the following steps:

$V_{\mathrm{TA}}={\&Integral;}_{{\mathrm{\&delta;}}_{\mathrm{ij}0}}^{{\mathrm{\&delta;}}_{\mathrm{ijc}}}[P_{\mathrm{Meq}}-x_0\sin ({\mathrm{\&delta;}}_{\mathrm{ij}}+x_1)-x_2]d{\mathrm{\&delta;}}_{\mathrm{ij}}$

$=(P_{\mathrm{Meq}}-x_2)({\mathrm{\&delta;}}_{\mathrm{ijc}}-{\mathrm{\&delta;}}_{\mathrm{ij}0})+x_0[\cos ({\mathrm{\&delta;}}_{\mathrm{ijc}}+x_1)-\cos ({\mathrm{\&delta;}}_{\mathrm{ij}0}+x_1)]$ A

critical potential energy (deceleration area) V absorbed by the system after fault removal_TBComprises the following steps:

$V_{\mathrm{TB}}={\&Integral;}_{{\mathrm{\&delta;}}_{\mathrm{ijc}}}^{\mathrm{\&delta;iju}}[x_0\sin ({\mathrm{\&delta;}}_{\mathrm{ij}}+x_1)+x_2-P_{\mathrm{Meq}}]d{\mathrm{\&delta;}}_{\mathrm{ij}}$

$=(x_2-P_{\mathrm{Meq}})({\mathrm{\&delta;}}_{\mathrm{iju}}-{\mathrm{\&delta;}}_{\mathrm{ijc}})-x_0[\cos ({\mathrm{\&delta;}}_{\mathrm{iju}}+x_1)-\cos ({\mathrm{\&delta;}}_{\mathrm{ijc}}+x_1)]$

wherein, delta_ij0And delta_ijcRespectively representing the power angle difference of the unit at the fault occurrence time and the fault removal time;

step S2023, calculating the transient stability estimation index T between the generator set i and the generator set j_SEIij： $T_{\mathrm{SEIij}}=1-\frac{V_{\mathrm{TA}}}{V_{\mathrm{TB}}};$

Wherein, T_SEIijThe transient stability of the index has the following significance: t is_SEIij>0 transient stability, T_SEIijCritical transient stability of =0, T_SEIij<0, transient instability.

11. The method of claim 10, wherein the step S3 of obtaining the grid node voltage holding yield includes:

the node voltage holding capability investigation range in the given transient process is as follows: lower limit of voltage drop V_LAnd duration V_CCounting the number V of nodes meeting the acceptable range of the voltage level of all the nodes of the power grid in the transient process_QNCalculating the qualification rate of the node voltage meeting the retention capacity in the transient process

The method for obtaining the line thermal stability qualification rate in the power grid in the step S3 includes: and (3) giving a node static stability margin index and a line thermal stability investigation range in the transient process: node static margin limit S_ICLine thermal stability limit value L_PRAnd duration T_CCounting the number S of nodes of the power grid meeting the steady sustainable range_QNNumber of lines L satisfying thermally stable sustainable range_QNCalculatingThe qualification rate S of node static stability and line thermal stability in the transient process_TR，S_TRThe calculation formula is as follows:

12. the method according to claim 11, wherein the step S3 is performed to obtain a comprehensive index S of transient stability situation of the whole power grid_TI＝α₂S_TEi+β₂V_TR+χ₂S_TR；

Wherein alpha is₂、β₂、χ₂The weight coefficients of the power grid according to thermal stability constraint, operation electric quantity constraint and static stability constraint are flexibly configured according to experience or analysis requirements, and alpha is₂、β₂、χ₂Satisfies the following conditions:

$\left\{\begin{array}{c}0\&le;{\mathrm{\&alpha;}}_2\&le;1\\ 0\&le;{\mathrm{\&beta;}}_2\&le;1\\ 0\&le;{\mathrm{\&chi;}}_2\&le;1\\ 0\&le;{\mathrm{\&alpha;}}_2+{\mathrm{\&beta;}}_2+{\mathrm{\&chi;}}_2\&le;1\end{array}\right..$

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