CN106845757B

CN106845757B - Power grid power flow transfer hazard degree evaluation method

Info

Publication number: CN106845757B
Application number: CN201611106863.2A
Authority: CN
Inventors: 段刚; 刘刚
Original assignee: Beijing Sifang Automation Co Ltd
Current assignee: Beijing Sifang Automation Co Ltd
Priority date: 2016-12-06
Filing date: 2016-12-06
Publication date: 2020-09-29
Anticipated expiration: 2036-12-06
Also published as: CN106845757A

Abstract

A power grid power flow transfer hazard degree assessment method. The method utilizes real-time dynamic power change data of high sampling rate wide area synchronization obtained by a wide area phasor measurement system, calculates the tidal current transfer relation among all lines in the power grid and the degree of damage to the safety and stability of the power grid based on line power fluctuation information in the daily operation of the power grid by utilizing a statistical technology, and can select a line which is seriously damaged to the safety and stability operation of the power grid when the line is disconnected for key monitoring. The method is not based on load flow calculation, only depends on measured data which can be directly obtained by power grid operators, and can consider the comprehensive effect of various linkage regulation and control devices and dynamic processes on load flow transfer, so that dynamic comprehensive evaluation on the load flow transfer hazard degree is realized.

Description

Power grid power flow transfer hazard degree evaluation method

Technical Field

The application belongs to the field of power system safety and stability assessment, and particularly relates to a method for assessing safety and stability problems caused by power flow transfer.

Background

When a fault such as a short circuit occurs in a power grid, a relay protection or local stability control device usually protects local equipment or a local power grid from being damaged by opening or closing a fault line. However, the disconnection of a line often causes the power transmitted through the line to be transferred to other lines which are communicated with each other, and if the power flow of the line receiving the transferred power flow exceeds the allowable safe and stable capacity limit value, the line is further disconnected, so that cascading failure occurs, and the grid accident is enlarged. In recent years, large-scale power grid accidents at home and abroad almost involve trend transfer caused by local line disconnection, so that the accident range is expanded. Therefore, the method for pre-evaluating the damage degree of the power grid caused by the power flow transfer caused by the line disconnection has important significance for preventing and controlling the expansion of accidents.

According to the existing documents, the evaluation methods about the influence degree of power grid caused by power flow transfer mainly comprise two types, one type is that by means of a power flow equation, the power flow variable quantity of other lines caused by line disconnection is calculated by calculating a Jacobian matrix between variables, namely a sensitivity coefficient; the other type is that a simulation method is utilized, a certain line is manually disconnected, and the influence of the line on other lines is observed. However, both of these methods have the following disadvantages:

(1) the jacobian matrix calculation and the simulation modeling calculation both need to depend on power grid model parameters and network real-time topology, and when the data are difficult to obtain or have a large difference with an actual value, corresponding mathematical modeling and calculation cannot be performed, or the calculation result is inaccurate.

(2) When the power flow of an actual power grid is transferred due to faults, the interlocking action of a regulating device and the dynamic regulation of unit equipment, such as stable control switching operation, the dynamic regulation of AGC and AVC, the reactive and active quick support of power electronic devices and the like, can be involved. It is difficult to fully understand and model these linkage dynamics behaviors.

Furthermore, wide-area phasor measurement systems have been widely used in the national provincial and beyond power grids since 2010. The wide-area phasor measurement systems generally collect voltage, current, phasor, frequency, power and other measurement data from the measurement substations at a high speed and in real time at a rate of 50 frames/second or 25 frames/second, and each data has a measurement time scale with the precision of 1 microsecond, so that real-time synchronous observation of the dynamic process of the whole network can be realized, at the moment, 1 measurement point is in the past several seconds, and SCADA (supervisory control and data acquisition) with no measurement time scale cannot have observation advantages.

It should be noted that the power flow transfer mainly occurs in the network in which the ring network operates, and in order to avoid the electromagnetic ring network, only the high-voltage main network frame has the ring network during operation, and 220kV is the following power grid, which usually adopts the principle of ring network construction and open-loop operation, so that the power grids with large-scale ring network operation are provincial and above power grids, and currently have wide-area phasor measurement systems.

In view of the above reasons, the present invention provides a method for calculating the power flow transfer condition of each line in the power grid and the degree of damage to the safety and stability of the power grid by using statistical techniques based on the line power fluctuation information in the daily operation of the power grid on a wide area phasor measurement system platform, and can select the line which is seriously damaged to the safety and stability operation of the power grid when the line is disconnected for key monitoring. The method only depends on actual measurement data which can be directly mastered by power grid operators, and can comprehensively consider the comprehensive effects of various linkage regulation and control devices and dynamic processes, so that objective and real-time evaluation on the power flow transfer hazard degree can be realized.

Disclosure of Invention

In order to solve the problems in the prior art, the invention discloses a power grid power flow transfer hazard degree evaluation method, which comprises the steps of utilizing high-sampling-rate wide-area synchronous real-time dynamic power change data obtained by a wide-area phasor measurement system platform, calculating the power flow transfer relation among all lines in a power grid and the hazard degree of the power grid to the safety and stability by utilizing a statistical technology based on line power fluctuation information in the daily operation of the power grid, and selecting a line with serious hazard to the safety and stability operation of the power grid when the line is disconnected for key monitoring.

The invention specifically adopts the following technical scheme:

a power grid power flow transfer hazard assessment method is characterized by comprising the following steps:

step 1: in an actual power grid, identifying all lines with a power flow transfer relationship;

step 2: counting the active power rising and falling times of the power flow transfer-out line and the power flow transfer-in line at the same time section, and identifying power flow transfer correlation factors;

and step 3: calculating a credible power flow transfer factor according to statistics of power variation of the power flow transfer-out line and the power flow transfer-in line;

and 4, step 4: calculating the active power transfer amount caused by the actual line disconnection;

and 5: calculating a direct harmfulness index of power flow transfer caused by the circuit disconnection according to the influence of the circuit disconnection on the capacity margin of other circuits;

step 6: calculating a power flow transfer linkage harmfulness index of the circuit disconnection according to whether linkage capacity is out of limit;

and 7: calculating a load flow transfer hazard risk index caused by line disconnection according to the statistics of historical faults in the power grid;

and 8: and sequencing the lines according to the power flow transfer linkage hazard degree index and the power flow transfer hazard risk index, and giving different preventive control measures to the lines according to the sequencing result.

The invention further comprises the following preferred embodiments:

in step 1, all lines with power flow transfer relationship are identified, and the content comprises:

(1.1) converting lines of the highest and second highest voltage grades in a power grid and transformers between the two voltage grades into line segments in a network to form a searched network;

(1.2) finding all the meshes in the searched network by adopting any mesh searching algorithm;

and (1.3) taking the lines on all the meshes as statistical monitoring lines for power flow transfer, calculating the power flow transfer hazard degree of each line in turn, and when 1 line is selected as the line with the evaluated power flow transfer hazard degree, calling the line as a power flow transfer-out line, and taking other lines as power flow transfer-in lines.

In step 2, the following contents are specifically included:

(2.1) monitoring the active power of each line with the power flow transfer relation in the power grid, wherein the active power of the line is reduced and changed to exceed a threshold value delta P within a set time period delta t_thJudging the sudden power drop of the line, and transferring the line as the power flow; finding out a line i with suddenly reduced line active power, namely a power flow transfer-out line i;

(2.2) correspondingly searching a line j with the active power rising in the set time period delta t when the active power of the power flow transferring line i is reduced;

(2.3) calculating a power flow transfer correlation factor of a line related to the power flow transfer-out line i: within the statistical time interval, if the active power of the power flow transfer-out line i is reduced, namely the power flow transfer-out frequency is ND_iThe number of active power rises corresponding to the detected line j is NR_{i_j}Calculating

The power flow transfer correlation factor R of the power flow transfer line i to the power flow transfer line j_i-jThe following were used:

wherein the set time period Δ t is 1 second;

the statistical period is 1 day, 1 week or 1 month.

Threshold value delta P_thThe voltage level or the load condition of the power grid is preset. For 220kV and 500kV power grids, the threshold value delta P_thPreferably 50 MW.

In step 3, calculating the trusted power flow transfer factor includes the following steps:

(3.1) transferring out the n-th active power reduction value delta P of the line i according to the power flow_{i_drop_n}Active power rise Δ P induced on line j_{j_rise_n}(≠ 0), calculating the power flow transfer coefficient from the power flow transfer line i actually measured for the nth time to the line j, namely the active power transfer coefficient k_{i_j_n}Wherein the active power reduction value is delta P_{i_drop_n}Greater than a threshold value Δ P_thAnd calculating the power flow transfer coefficient k when the power of the line i is reduced and the power of the line j is increased every time the power flow is transferred out_{i_j_n}：

(3.2) calculating the average power flow transfer coefficient k from the power flow transfer-out line i to the line j_{i_j}：

Wherein NR is_{i_j}The number of times of active power rising of a line j caused by power reduction of a power flow transfer line i in a statistical time period;

(3.3) calculating a credible power flow transfer factor K of the power flow transfer-out line i to the line j according to the following formula_{i_j}：

K_{i_j}＝R_{i_j}·k_{i_j}

Wherein R is_i-jAnd transferring the correlation factor from the line i to the line j for the power flow.

In step 4, when the tide turns toWhen the outgoing line i is disconnected, according to the credible power flow transfer factor K_{i_j}Calculating the active power increase amount caused on the line j, namely the active power transfer amount as follows:

ΔP_{j_rise_F}＝K_{i_j}·ΔP_{i_drop_C}；

the predicted power flow of line j at this time is:

P_{j_F}＝ΔP_{j_rise_F}+P_{j_C}；

wherein, Δ P_{j_rise_F}For the increase in active power, Δ P, caused on line j_{i_drop_C}Represents the active power drop value, K, of the line i when the line is disconnected_{i_j}Representing a trusted power flow transfer factor, P, from the power flow outgoing line i to the power flow outgoing line j_{j_C}Representing the power flow, i.e. the value of the active power, P, of line j before the circuit i is opened_{j_F}And the predicted power flow of the line j after the power flow transfer-out line i is broken is shown.

In step 5, the power flow transfer direct hazard index is calculated according to the following method:

(5.1) calculating the margin coefficient D of the line j with power rise in the case of disconnection of the load flow diversion line i according to the following formula_{i_j}When D is present_{i_j}The smaller the value is less than 1, the more capacity margin of the line j is; when D is present_{i_j}When the active power flow of the line j reaches or exceeds the capacity limit, the active power flow of the line j is considered to be out of limit;

wherein, P_{j_F}Representing the predicted power flow, P, of line j after line i has been opened_{j_Limit}Represents the capacity limit of line j;

(5.2) if the i of the power flow transfer-out line is disconnected, the active power flow of the m lines exceeds the limit, namely D of the corresponding m lines_{i_j}The direct harmfulness index D of the power flow transfer caused by the disconnection of the power flow transfer line i is larger than or equal to 1_{i_D}Comprises the following steps:

D_{i_D}＝m

(5.3) for the power flow transferring-out line i which is disconnected and does not cause the active power flow of any line to exceed the limit, the power flow transferring is straightIndex of degree of contact damage D_{i_D}Comprises the following steps:

D_{i_D}＝max{D_{i_j}}。

in step 6, the power flow transfer linkage hazard index is calculated according to the following method:

(6.1) if the power flow transfer-out line i is disconnected, directly causing the active power flow of m lines to be out of limit, and further disconnecting the m lines due to overload and further causing power flow transfer; if M of the overload circuits caused by the circuit i are further disconnected to cause the active power flows of other circuits to exceed the limit, the power flow transfer linkage hazard index D caused by the disconnection of the power flow transfer circuit i_{T_i}Comprises the following steps:

D_{T_i}＝m+10M；

(6.2) for the power flow transfer line i, if the active power flow of partial lines is out of limit due to the disconnection of the power flow transfer line i, and the active power flow of other lines is not out of limit due to the disconnection of the lines with out-of-limit active power flow, the index of the power flow transfer chain hazard degree of the power flow transfer line i is determined as follows:

D_{T_i}＝D_{i_D}；

(6.3) for the power flow transferring line i which does not cause any line power flow out-of-limit, the power flow transferring linkage hazard degree index is determined as follows:

D_{T_i}＝D_{i_D}＝max{D_{i_j}}＜1。

in step 7, the risk index of the power flow transfer hazard caused by the power flow transfer-out line is calculated according to the following method:

(7.1) obtaining the fault probability of the power flow transfer-out line according to historical statistics, and obtaining the fault probability G of the power flow transfer-out line i_{fault_i}Is defined as follows:

(7.2) obtaining a power flow transfer hazard risk index of each line and a power flow transfer hazard risk index F of the line i according to the power flow transfer linkage hazard index and the fault probability when each power flow transfer line is disconnected_{T_i}Is represented as follows:

F_{T_i}＝G_{fault_i}·D_{T_i}

wherein D is_{T_i}The method is a power flow transfer linkage harmfulness index caused by the disconnection of a power flow transfer line i.

In step 8, sorting each line according to the power flow transfer linkage hazard index and the power flow transfer hazard risk index respectively:

preventive control measures are taken on lines of which the power flow transfer linkage hazard degree index is more than or equal to 4 or is ranked in the top 3 and the power flow transfer hazard risk index is ranked in the top 10;

taking key monitoring measures on lines of which the harmfulness index of the power flow transfer linkage is more than or equal to 4 and the power flow transfer risk index is ranked behind 10 lines;

lines with the harmfulness index of the power flow transfer linkage greater than 1 but less than 4 are listed as secondary key monitoring lines;

and adopting common monitoring measures for the lines with the power flow transfer chain harmfulness less than 1.

The implementation of the invention can help the power grid operating personnel to quantitatively evaluate the harmfulness and the risk of the power flow transfer caused by the disconnection of each line in the power grid and find out the line with the most serious harm or risk as a key line to perform important prevention control and monitoring under the condition of not depending on the specific model, parameters, topology and action characteristics of the protection control device of the power grid and only depending on the statistical information of the wide-area phasor measurement system in the daily operation of the power grid. Compared with the traditional load flow transfer calculation method based on load flow calculation, the statistical method can consider the comprehensive effect of various linkage regulation and control devices and dynamic processes on load flow transfer, thereby realizing dynamic comprehensive evaluation on the load flow transfer hazard degree.

Drawings

Fig. 1 is a schematic flow chart of the method for evaluating the criticality of power flow transfer according to the present invention.

Detailed Description

The technical scheme of the invention is further described in detail by combining the drawings and the specific embodiments in the specification.

The invention utilizes the real-time dynamic power change data of high sampling rate wide area synchronization obtained by the wide area phasor measurement system platform, based on the line power fluctuation information in the daily operation of the power grid, and utilizes the statistical technology to calculate the power flow transfer condition of each line in the power grid and the degree of damage to the safety and stability of the power grid, and can select the line which is seriously damaged to the safety and stability operation of the power grid when the line is disconnected for key monitoring. In an actual power grid, a power flow transfer hazard degree evaluation program developed based on the method provided by the invention is operated on the advanced application service of a wide area measurement system WAMS of provincial, sub-central and national power grid dispatching centers. The wide area measurement system obtains synchronous measurement data of voltage phasor, current phasor, power, frequency and the like of each line measured by a PMU on a main power network governed by a scheduling center at a speed of 50 frames/second or 25 frames/second, and after receiving the information, a WAMS master station of the scheduling center synchronously aligns the data according to a high-precision synchronous time scale owned by the data and stores the data in a time sequence real-time base and a historical base. Meanwhile, the wide area measurement system master station stores a real-time network topology model of the power grid, and the measurement data in the database are associated with each line device, so that each WAMS master station advanced application can perform power grid analysis based on network topology information. On the application platform, the program developed according to the invention can start to carry out power flow transfer hazard assessment. Since statistical data based on a period of time is needed to obtain a reliable inter-line power flow transfer relationship, at least 1 hour of historical data is usually used as a basis for statistical analysis. However, in order to avoid a large change of the network structure in the statistical period and thus an excessive influence on the power flow transfer relationship, the statistical period should not be too long, and the maximum period should not exceed 1 week. However, it should be noted that the statistical duration of the failure probability of the components such as the line may not be constrained by the statistical period.

Based on the actual application environment, the power flow transfer hazard degree evaluation program running on the advanced application server of the WAMS platform can cyclically execute the following steps (see the flow chart in fig. 1), so as to evaluate the power flow transfer hazard degree of each line of the power grid under jurisdiction, and the cycle period can be selected to be 5 minutes.

Step 1: identifying all lines with a power flow transfer relation by using a mesh searching method;

because the power flow transfer only occurs in the ring network, and in an actual power grid, the ring network mainly exists in a main network of the highest or second highest voltage level of the power grid (when the highest voltage level is very weak, the second highest voltage level allows the ring network), all ring network paths on the power grid with the highest two voltage levels of the power grid need to be found, and the power flow transfer relationship is only identified on the ring network lines (by a statistical method). The line on the non-ring network path is a load line or an equivalent generator line, and the power flow of the non-ring network path can also change after the ring network line is disconnected, but the change is caused by the change of equivalent impedance on the system side and is not considered when power flow transfer is not carried out, so that the power flow transfer path is not considered when being searched. The algorithm for finding the line on the ring network path is as follows:

(1.1) converting the lines of the highest and the next highest voltage grades in the power grid and the transformers between the two voltage grades into line segments (for example: 500kV line, 220kV line and 500/220 transformers are converted into line segments), and forming the searched network N.

(1.2) any cell search algorithm is used to find all the cells in the searched network N. For example, the paper "design and implementation of automatic mesh search algorithm in hydroelectricity simulation" can be used to find out all meshes in the study of northeast university (nature science edition) 2008, 9 th, 29 th, 9 th, volume.

(1.3) using the lines in all the cells as statistical monitoring lines for power flow transfer. The power flow transfer hazard degree of each line can be calculated in turn. When 1 line is selected as the line of the evaluated power flow transfer hazard degree, the line is called a power flow transfer-out line, and other lines are called power flow transfer-in lines.

(2.1) monitoring lines in a grid with a load flow transfer relationshipActive power, the line power drop change exceeding a threshold Δ P within a set short time Δ t (typically taken to be 1 second)_th(can be modified according to the voltage class or the load condition of the power grid, when the power grids of 220kV and 500kV are usually 50MW), the sudden drop of the power of the line is judged, and the line is converted into a power flow; finding out a line i with suddenly reduced line active power, namely a power flow transfer-out line i;

(2.2) correspondingly searching a line j with the active power rising in the time period within the time period delta t of the active power falling of the power flow transferring line i;

(2.3) calculating a power flow transfer correlation factor of a line related to the power flow transfer-out line i: within a set statistical period (e.g. 1 day, 1 week or 1 month, if the number of active reductions of the line i is ND_iThe number of rises corresponding to the detected line j is NR_{i_j}Calculating

If r_{i_j}>0.8, the power flow of the line i is almost certainly transferred to the line j after being blocked, so that the power flow transfer correlation factor R of the power flow transfer line i to the line j is taken from the conservative point of view_{i_j}Is 1; if r_{i_j}<0.2, showing that the power flow transfer relation between the line i and the line j is almost not existed, the observed power increase of the line j is not from the line i, and the power flow transfer correlation factor R from the power flow transfer line i to the line j is taken_{i_j}0; taking the power flow transfer correlation factor R from the power flow transfer line i to the power flow transfer line j under other conditions_{i_j}＝r_{i_j}In summary, the power flow transfer correlation factor R from the power flow transfer line i to the power flow transfer line j is_i-jThe following were used:

(3.1) transferring out the nth active power reduction delta P of the line i according to the power flow_{i_drop_n}The power increase Δ P caused on line j_{j_rise_n}(≠ 0), calculating the power flow transfer coefficient from the power flow transfer line i actually measured for the nth time to the line j, namely the active power transfer coefficient k_{i_j_n}Wherein the active power reduction value is delta P_{i_drop_n}Greater than a threshold value Δ P_thAnd calculating the power flow transfer coefficient k of each time when the power of the line i is decreased and the power of the line j is increased_{i_j_n}：

(3.2) calculating the average power flow transfer coefficient k of the power flow transfer line i and the desired line j_{i_j}：

K_{i_j}＝R_{i_j}·k_{i_j}

And 4, step 4: calculating the active power transfer amount caused by the actual line disconnection:

when the power flow transfer-out line i is disconnected, according to the credible power flow transfer factor K_{i_j}Calculating the active power increase caused on the line j as follows:

ΔP_{j_rise_F}＝K_{i_j}·ΔP_{i_drop_C}

at this time, the predicted power flow of line j is:

P_{j_F}＝ΔP_{j_rise_F}+P_{j_C}

wherein, Δ P_{i_drop_C}Represents the active power drop value, K, of the line i when the line is disconnected_{i_j}Representing a trusted power flow transfer factor, P, from the power flow outgoing line i to the power flow outgoing line j_{j_C}Representing the power flow, i.e. the value of the active power, P, of line j before line i breaks_{j_F}And the predicted power flow of the line j after the power flow transfer-out line i is broken is shown.

(5.1) calculating the margin factor D of the affected line j in case of disconnection of the load flow diversion line i according to the following formula_{i_j}When D is present_{i_j}The smaller the margin is, the more the capacity margin of the line is; when D is present_{i_j}When the active power flow of the line reaches or exceeds the capacity limit, the active power flow of the line j is considered to be out of limit;

(5.2) if the active power flow of the m lines exceeds the limit due to the disconnection of the power flow transfer-out line, namely D of the corresponding m lines_{i_j}Not less than 1. The index of direct harmfulness of power flow transfer caused by the disconnection of the power flow transfer-out line i is D_{i_D}：

D_{i_D}＝m

(5.3) for the power flow transfer-out line i which is disconnected and does not cause the active power flow out-of-limit of any line, the power flow transfer direct hazard index is less than 1, and the power flow transfer direct hazard index is taken as the capacity margin index of the line with the minimum capacity margin, namely the capacity margin index is taken

D_{i_D}＝max{D_{i_j}}。

(6.1) if the power flow transfer line i is disconnected, the active power flow of m lines is directly caused to exceed the limit, the power flow of a certain line j in the m lines exceeds the limit and is disconnected, the power flow of other lines can be further caused to jump, and according to the power flow transfer factor K from the line j to the line l_{j_l}The current after line l jump caused by j being disconnected can be obtained as follows:

P_{i_j_l_F}＝K_{j_l}·P_{j_F}+P_{l_C}

i.e. predicted power flow of line l is P after line i and line j are continuously disconnected_{i_j_l_F}If it exceeds the capacity limit P of the line l_{l_limit}Further causing the line l to be disconnected. According to the method for predicting the chain disconnection of the line, if M overload lines caused by i are further disconnected, M overload lines cause other overload linesWhen the active power flow of the line is out of limit, the index line of the linkage harmfulness of power flow transfer caused by the disconnection of the power flow transfer line i is as follows:

D_{T_i}＝m+10M

(6.2) for the power flow transfer line i, if the active power flow of partial lines is out of limit due to the disconnection of the power flow transfer line i, and the active power flow of other lines is not out of limit due to the disconnection of the lines with out-of-limit active power flow, the index of the power flow transfer chain hazard degree of the power flow transfer line i is determined as follows: :

D_{T_i}＝D_{i_D}；

D_{T_i}＝D_{i_D}＝max{D_{i_j}}＜1。

D_{T_i}the larger the indication, the more dangerous the line break.

(7.1) obtaining the fault probability of the power flow transferring-out line according to historical statistics, and obtaining the fault probability G of the line i_{fault_i}Is defined as follows:

F_{T_i}＝G_{fault_i}·D_{T_i}。

According to the steps, a power flow transfer hazard degree index and a hazard risk index of a line related to a looped network or a mesh in the current operating power grid can be calculated, and then the following sequences are carried out:

(1) sequencing the lines according to the power flow transfer linkage hazard degree indexes of all the lines;

(2) and sequencing the lines according to the power flow transfer hazard risk indexes of the lines.

Preventive control measures are taken on lines of which the power flow transfer linkage hazard degree index is more than or equal to 4 or is ranked in the top 3 and the power flow transfer hazard risk index is ranked in the top 10; taking key monitoring measures on lines of which the harmfulness index of the power flow transfer linkage is more than or equal to 4 and the power flow transfer risk index is ranked behind 10 lines; lines with the harmfulness index of the power flow transfer chain being more than 1 and less than 4 can be listed as secondary key monitoring lines; and adopting common monitoring measures for the lines with the power flow transfer chain harmfulness less than 1.

Compared with the traditional load flow transfer calculation method based on load flow calculation, the statistical method can consider the comprehensive effect of various linkage regulation and control devices and dynamic processes on load flow transfer, thereby realizing dynamic comprehensive evaluation on the load flow transfer hazard degree.

While the best mode for carrying out the invention has been described in detail and illustrated in the accompanying drawings, it is to be understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the invention should be determined by the appended claims and any changes or modifications which fall within the true spirit and scope of the invention should be construed as broadly described herein.

Claims

1. A power grid power flow transfer hazard assessment method is characterized by comprising the following steps:

(3.1) transferring out the n-th active power reduction value delta P of the line i according to the power flow_{i_drop_n}Active power rise Δ P induced on line j_{j_rise_n}Calculating the power flow transfer coefficient from the nth actually measured power flow transfer line i to the line j, namely the active power transfer coefficient k_{i_j_n}Wherein the active power reduction value is delta P_{i_drop_n}Greater than a threshold value Δ P_thSequentially calculating the power flow transfer coefficient k when the power of the line i is reduced and the power of the line j is increased each time the power flow is transferred out_{i_j_n}：

K_{i_j}＝R_{i_j}·k_{i_j}

Wherein R is_i-jTransferring a correlation factor from the power flow transfer line i to the power flow transfer line j;

2. The power grid power flow transfer hazard assessment method according to claim 1, characterized by:

3. The power grid power flow transfer hazard assessment method according to claim 1, characterized by:

in step 2, the following contents are specifically included:

(2.2) correspondingly searching a line j with the active power increasing in the set time period within the set time period delta t of the active power decreasing of the power flow transferring line i;

4. the power grid power flow transfer hazard assessment method according to claim 3, characterized by:

the set time period delta t is 1 second;

the statistical period is 1 day, 1 week or 1 month.

5. The power grid power flow transfer hazard assessment method according to claim 3 or 4, characterized by:

threshold value delta P_thThe voltage level or the load condition of the power grid is preset.

6. The power grid power flow transfer hazard assessment method according to claim 5, characterized by:

for 220kV and 500kV power grids, the threshold value delta P_thTake 50 MW.

7. The power grid power flow transfer hazard assessment method according to claim 3, characterized by:

in step 4, when the power flow transfer-out line i is disconnected, according to the credible power flow transfer factor K_{i_j}Calculating the active power increase amount caused on the line j, namely the active power transfer amount as follows:

ΔP_{j_rise_F}＝K_{i_j}·ΔP_{i_drop_C}；

the predicted power flow of line j at this time is:

P_{j_F}＝ΔP_{j_rise_F}+P_{j_C}；

8. The power grid power flow transfer hazard assessment method according to claim 7, characterized by:

D_{i_D}＝m

(5.3) for the power flow transferring out line i which is disconnected and does not cause the active power flow out-of-limit of any line, the power flow transferring direct harmfulness index D_{i_D}Comprises the following steps:

D_{i_D}＝max{D_{i_j}}。

9. the power grid power flow transfer hazard assessment method according to claim 8, characterized by:

D_{T_i}＝m+10M；

D_{T_i}＝D_{i_D}；

D_{T_i}＝D_{i_D}＝max{D_{i_j}}＜1。

10. the power grid power flow transfer hazard assessment method according to claim 1 or 9, characterized by:

F_{T_i}＝G_{fault_i}·D_{T_i}

11. The power grid power flow transfer hazard assessment method according to claim 1, characterized by: