CN111368449A - Cascading failure evolution path online identification method considering alternating current and direct current influences - Google Patents
Cascading failure evolution path online identification method considering alternating current and direct current influences Download PDFInfo
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Abstract
The invention discloses an online identification method of a cascading failure evolution path considering the influence of alternating current and direct current, which aims at a manually set cascading failure initial failure set or a cascading failure initial failure set formed by equipment failure probability, utilizes transient time domain simulation to simulate direct current commutation failure caused by initial alternating current failure under the influence of alternating current and direct current interaction, safety control action caused by direct current continuous commutation failure locking, new energy cascading network disconnection and two-three line-defense action of a power grid, determines lower-stage evolution failure according to equipment overload and voltage out-of-limit and dynamically searches a safety control current value control strategy, and simulates equipment successive disconnection through multi-evolution branch static safety analysis, so that the complex cascading failure evolution path under the influence of alternating current and direct current interaction is accurately identified, and the problem of accurate prejudgment of the cascading failure evolution path of an ultra-high voltage power grid under the online mode is solved. The method can provide a support means for the scheduling personnel to comprehensively master the cascading failure evolution path and the accident risk, and has good application value.
Description
Technical Field
The invention belongs to the technical field of power system automation, and particularly relates to an online cascading failure evolution path identification method considering alternating current and direct current influences.
Background
The load of the power system is continuously increased, the power transmission distance is gradually increased, the scale is continuously enlarged, the structure is gradually complicated, meanwhile, a large amount of flexible alternating current power transmission and extra-high voltage direct current power transmission are put into operation, uncertainty is brought by new energy access, the dynamic characteristic of the modern power system is more and more complicated, the operation difficulty is continuously increased, and the safe and stable operation of the power system faces huge challenges. If the working condition change cannot be tracked in time and the pre-judgment, early warning and control decision on the potential cascading failure event can be carried out, the accidental failure can also be gradually evolved into the cross-region cascading failure and even into a major power failure accident. The method is particularly important for accurately identifying the cascading failure evolution path of the alternating current-direct current series-parallel power grid.
The development of a blackout accident is a process that the operation state of a power system is continuously deteriorated and becomes more and more intense, and the process is developed from a few simple element faults through a series of complex successive breakdowns. The development process of the blackout accident is often accompanied by the occurrence of a series of successive events such as equipment overload tripping, equipment overvoltage protection action, unit disconnection, grid disconnection and the like. Researchers usually obtain the possible cascading failure successive cut-off equipment of the power grid in an off-line analysis and calculation mode in a typical mode or judge the cascading failure evolution path according to long-term operation and analysis experience, so as to know whether the possible cascading failure equipment, the control protection device are reasonable in fixed value, whether the grid structure needs to be adjusted and the like, and strong human factors exist, and the timeliness is difficult to meet the requirements. With the gradual establishment of an extra-high voltage direct current transmission end power grid and a multi-direct current concentrated drop point large-scale receiving end power grid in a new energy base, cascading failure evolution modes under the influence of alternating current and direct current interaction are more complex and changeable, the key points to be paid attention to include what a cut-off device is, what a series of transient state or steady state successive action events such as direct current continuous commutation failure, new energy large-scale cascading network disconnection, two-three defense line actions and the like are, because the successive action events are important to the evolution of cascading failures, an expected failure set needs to be rapidly scanned and cascading failure evolution paths need to be accurately identified based on the current operation mode of the power grid in an online mode, and a basis is provided for cascading failure risk early warning and control decision making.
Disclosure of Invention
Aiming at the problems, the invention provides an online identification method of a cascading failure evolution path considering the influence of alternating current and direct current, which solves the problem that the existing online mode can not accurately predict the cascading failure evolution path of the extra-high voltage alternating current and direct current power grid.
The invention is realized by adopting the following technical scheme, and the method for identifying the cascading failure evolution path on line by considering the influence of alternating current and direct current comprises the following steps:
step 1: acquiring operation state data of a power grid in a current operation mode to form initial power flow data, integrating a power equipment dynamic model, a power grid two-three defense line strategy and a new energy grid-related protection model to form stable calculation data, and forming stable safety constraint data according to short-time allowable current-carrying capacity of a line, rated capacity of a transformer and a bus voltage limit value; forming initial fault set of cascading fault simulation according to user setting or equipment fault probability
Fi 0Representing the ith initial fault, wherein N is the number of the initial faults, and the number j of cascading fault evolution stages is 1; setting a calculation failure set { FiIs initialized to an initial failure set, FiCalculating a fault for the ith;
step 2: forming a jth stage calculation data set of cascading failure simulation according to the initial load flow data, the stability calculation data, the stable state safety constraint data and the initial failure set, carrying out parallel transient stability time domain simulation on all failures in the calculation data set by considering alternating current and direct current interaction influence, and obtaining a transient successive action event set and a transient power angle stability margin of the initial failure; the set of transient successive action events for the ith initial fault is noted as TEi(ii) a The power grid operation mode after the transient stability time domain simulation of the ith initial fault is transited to the steady state is recorded as SiCalculating equipment overload and voltage out-of-limit safety margin of initial faults according to the power grid operation mode after transient stability time domain simulation is transited to a stable state;
and step 3: judging and calculating fault set FiJudging whether the faults in the step (4) all meet the cascading fault evolution termination condition, if so, entering a step (6), otherwise, continuing to evolve, and if j is j +1, entering a step (4);
and 4, step 4: for a set of computational failures { FiGenerating a next-stage calculation fault set { F) according to the calculation results of the equipment overload and voltage out-of-limit safety margini' } operation mode after failure { SiThe operation mode of calculating faults at the next stage is adopted;
and 5: operation mode { S) based on next-stage fault calculationiCalculate the failure set for the next stage { F }i' } performing current value strategy identification and static safety analysis of the security control system, and acquiring the running mode of the power grid after the next stage of calculating faults { S }i' }, control equipment and control quantity in the safety control strategy, equipment overload and voltage out-of-limit safety margin of the fault calculated at the next stage, and load flow convergence state; will calculate the fault Fi' the control device in the safety control strategy includes a steady state successive action event set of the ith fault and the jth stage, and is marked as SEi.j(ii) a Using { Fi' } update FiUsing { S }i' } update SiFourthly, returning to the step 3;
step 6: will initially fail Fi 0Initial fault transient follow-on event TEiJ phase of i fault steady state successive action event SEi.jJ-2, 3, N, which is the cascading failure propagation path for the ith initial failurei.j,Ni.jAnd indicating the number of evolution stages of the ith fault termination calculation, and outputting cascading fault evolution paths of all initial fault sets.
Further, the step 2 of performing parallel transient stability time domain simulation on all faults in the calculation data set by the calculation of the alternating current and direct current interaction influence comprises the following steps:
transient stability time domain simulation simulates that alternating current equipment faults cause direct current phase change failure, direct current continuous phase change failure locking causes alternating current system power flow transfer, direct current locking causes two or three defensive line actions of a power grid, and direct current phase change failure or locking causes new energy interlocking off-grid.
Further, the initial fault set fault types include: the fault.
Further, in step 2, the equipment overload and voltage out-of-limit safety margin is calculated according to the power grid operation mode after the transient stability time domain simulation is transited to the steady state, and the method comprises the following steps:
1) identifying the time when the system enters a quasi-steady state operation state according to the voltage and frequency change conditions of each node in the transient stability time domain simulation process;
2) generating quasi-steady-state operation section tide mode data according to the network topology at the quasi-steady-state operation state moment, the steady-state active/reactive power of each injection node and the steady-state voltage of each node;
3) carrying out load flow calculation by aiming at load flow mode data of a steady-state operation section, obtaining line current, transformer power and bus voltage, and calculating overload and voltage out-of-limit safety margin of single equipment according to steady-state safety constraint;
4) and taking the minimum value of the overload and voltage out-of-limit safety margins of all the equipment as the overload and voltage out-of-limit safety margins of the fault equipment.
Further, when j is 1, the cascading failure evolution termination condition includes: the equipment overload and voltage out-of-limit safety margin is larger than the set equipment overload and voltage out-of-limit safety margin threshold value; the transient safety stability margin is smaller than a set transient safety stability margin threshold value;
when j is more than 1, the cascading failure evolution termination condition comprises the following steps: the number of the maximum evolution stages is set when the fault reaches the set number; the equipment overload and voltage out-of-limit safety margin is larger than the set equipment overload and voltage out-of-limit safety margin threshold value; and if the trend is not converged and any condition is met, the cascading failure branch is terminated and evolves.
Further, in step 4, a next-stage calculation fault set is generated according to the calculation results of the equipment overload and voltage out-of-limit safety margin, and the method comprises the following steps:
1) the equipment overload and voltage out-of-limit safety margin is smaller than the set equipment overload and voltage out-of-limit safety marginEquipment of safety margin threshold value is brought into lower stage trouble equipment set
Representing a fault F calculated byiGenerating a next-stage fault equipment set;
2) will next stage fault equipment set
As a calculation fault in the next stage, each calculation fault FiGenerating one or more lower-stage computational faults Fi'；
3) All the next stages are calculated to be fault Fi' the set of constructs is the next phase to compute the failure set { Fi'}。
Further, the next stage calculates the fault FiThe fault type of' is determined using the following method:
if it is
If the equipment in the system is a line, the fault type of the next stage is line disconnection; if it is
If the equipment in the system is a transformer, the fault type of the next stage is the disconnection of the transformer; if it is
If the equipment in the system is a bus, the line and the transformer directly connected with the bus through a breaker or a switch are searched, and the fault is the corresponding line and the corresponding transformer winding.
Further, the method for identifying the current value strategy of the security control system in the step 4 comprises the following steps:
1) analyzing fault constraints, mode constraints, power flow constraints and control strategies in the second three-defense strategy of the power grid;
2) root of herbaceous plantAccording to Si' and Fi' determining the control measure of the safety control system as the current value strategy of the safety control system.
The invention has the following beneficial effects: aiming at a cascading failure initial failure set which is manually set or is formed by equipment failure probability, direct current commutation failure caused by initial alternating current failure under the influence of alternating current and direct current interaction, safety control action caused by direct current continuous commutation failure locking, new energy cascading off-line and two-three defense line actions of a power grid are simulated by using transient time domain simulation, lower-stage evolution failure is determined according to equipment overload and voltage out-of-limit, a safety control current value control strategy is dynamically searched, equipment is sequentially switched on and switched off through multi-evolution branch static safety analysis simulation, a complex cascading failure evolution path under the influence of alternating current and direct current interaction is accurately identified, and the problem of accurate prejudgment of the cascading failure evolution path of the extra-high voltage alternating current and direct current power grid in an online mode is solved. The method can provide a support means for the scheduling personnel to comprehensively master the cascading failure evolution path and the accident risk, and has good application value.
Drawings
Fig. 1 is a flowchart of a fault evolution path online identification method in an embodiment of the present invention.
Detailed Description
The invention is further described below. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Example 1:
referring to fig. 1, an online identification method for a cascading failure evolution path considering the influence of alternating current and direct current includes the steps:
step 1: acquiring operation state data of a power grid in a current operation mode to form initial power flow data, integrating a power equipment dynamic model, a power grid two-three defense line strategy and a new energy grid-related protection model to form stable calculation data, and forming stable safety constraint data according to short-time allowable current-carrying capacity of a line, rated capacity of a transformer and a bus voltage limit value; forming initial fault set of cascading fault simulation according to user setting or equipment fault probability
Fi 0Representing the ith initial fault, wherein N is the initial fault number (usually N is more than 1); setting the number j of cascading failure evolution stages to be 1, and setting a calculation failure set { FiIs initialized to an initial failure set, FiCalculating a fault for the ith;
the initial fault set fault types include: the fault;
the power equipment dynamic model comprises: the system comprises a conventional generator set, a dynamic control model of new energy, load, direct current and FACTS equipment and an AC/DC equipment protection model;
the new energy grid-related protection model comprises: wind power and photovoltaic high voltage protection, wind power and photovoltaic low voltage protection, wind power and photovoltaic high frequency protection, and wind power and photovoltaic low frequency protection.
Step 2: forming a jth stage calculation data set of cascading failure simulation according to the initial load flow data, the stability calculation data, the stable state safety restriction data and the initial failure set, carrying out parallel transient stability time domain simulation on all failures in the calculation data set by considering the alternating current and direct current interaction influence, obtaining transient successive action events and transient power angle stability margin of the initial failures, and recording a transient successive action event set of the ith initial failure as TEiAnd the transient power angle stability margin of the ith fault is recorded as TSi(ii) a The power grid operation mode after the transient stability time domain simulation of the ith initial fault is transited to the steady state is recorded as SiCalculating the equipment overload and voltage out-of-limit safety margin of the initial fault according to the power grid operation mode after transient stability time domain simulation is transited to the steady state, and recording the calculation result of the equipment overload and voltage out-of-limit safety margin of the ith initial fault as SSiEntering step 3;
the AC-DC interaction influence is considered as follows: transient stability time domain simulation simulates that alternating current equipment faults cause direct current phase change failure, direct current continuous phase change failure locking causes alternating current system power flow transfer, direct current locking causes two or three defensive line actions of a power grid, and direct current phase change failure or locking causes new energy interlocking off-grid; the transient successive action event not only comprises an alternating current system equipment action event, but also comprises a direct current system equipment action event;
the transient power angle stability margin is obtained through quantitative evaluation of transient safety stability, and the specific contents are as follows: 200910026801.4, the patent names: an element participation factor identification method in a transient safety and stability mode of a power system is described in the [0015] part of the specification.
The steps of calculating the equipment overload and voltage out-of-limit safety margin according to the power grid operation mode after transient stability time domain simulation is transited to the steady state are as follows:
1) identifying the time when the system enters a quasi-steady state operation state according to the voltage and frequency change conditions of each node in the transient stability time domain simulation process;
2) generating quasi-steady-state operation section tide mode data according to the quasi-steady-state moment network topology, the steady-state active/reactive power of each injection node and the steady-state voltage of each node;
3) carrying out load flow calculation by aiming at load flow mode data of a steady-state operation section, obtaining line current, transformer power and bus voltage, and calculating overload and voltage out-of-limit safety margin of single equipment according to steady-state safety constraint;
4) taking the minimum value of the overload and voltage out-of-limit safety margins of all the equipment as the overload and voltage out-of-limit safety margins of the equipment with faults;
and step 3: judging and calculating fault set FiJudging whether the faults in the step (4) all meet the cascading fault evolution termination condition, if so, entering a step (6), otherwise, continuing to evolve, and if j is j +1, entering a step (4);
the cascading failure evolution termination condition comprises the following steps: when j is 1, the method comprises the following steps: the equipment overload and voltage out-of-limit safety margin is larger than the set equipment overload and voltage out-of-limit safety margin threshold value (normally set to 0); the transient safety stability margin is smaller than a set transient safety stability margin threshold value (normally set to 0); when j > 1, comprising: the fault reaches the set maximum number of evolution stages (usually set 3); the equipment overload and voltage out-of-limit safety margin is larger than the set equipment overload and voltage out-of-limit safety margin threshold value; the trend is not converged, and if any condition is met, the cascading failure branch terminates the evolution;
and 4, step 4: for a set of computational failures { FiGenerating a next-stage calculation fault set { F) according to the calculation results of the equipment overload and voltage out-of-limit safety margini' } operation mode after failure { SiThe operation mode of calculating faults at the next stage is adopted;
the method for generating the next phase calculation fault set according to the calculation results of the equipment overload and voltage out-of-limit safety margin comprises the following steps:
1) bringing equipment with equipment overload and voltage out-of-limit safety margin smaller than set equipment overload and voltage out-of-limit safety margin threshold value into lower-stage fault equipment set
Is represented by FiGenerating a next-stage fault equipment set;
2) will next stage fault equipment set
A single device in (a) is disconnected as a next-stage computing fault, then the faults in each computing fault set may generate one or more next-stage computing faults, i.e., Fi' may contain one or more failures;
3) all the next stages are calculated to be fault Fi' the set of constructs is the next phase to compute the failure set { Fi'}；
Lower phase calculation failure FiThe fault type of' is determined using the following method:
if it is
If the equipment in the system is a line, the fault type of the next stage is line disconnection; if it is
If the equipment in the system is a transformer, the fault type of the next stage is the disconnection of the transformer; if it is
If the equipment in the system is a bus, searching a line and a transformer directly connected with the bus through a breaker or a switch, and anticipating that the fault is the disconnection of the corresponding line and the disconnection of the corresponding transformer winding;
and 5: using clustered computing platforms, failure mode { S } is computed based on next stageiCalculate the failure set for the next stage { F }i' } performing current value strategy identification and static safety analysis of the safety control system, and acquiring the running mode of the power grid after the fault (S)i' }, controlling equipment and control quantity in a current value strategy of a safety control system, and calculating equipment overload and voltage out-of-limit safety margin and load flow convergence state of faults at the next stage; will calculate the fault Fi' the control device in the safety control strategy includes a steady state successive action event set of the ith fault and the jth stage, and is marked as SEi.j(ii) a Will { FiWith { F }i' } update, will { SiUse { S }i' } updating, and returning to the step 3;
the current value strategy identification method of the security control system comprises the following steps:
1) analyzing fault constraint, mode constraint, power flow constraint and control strategy in the safety control system strategy model;
2) according to Si' and Fi' determining the control measure of the safety control system as the current value strategy of the safety control system.
Step 6: will initially fail Fi 0Transient sequential action event TEiSteady state successive action event SEi.jAs a cascading failure evolution path of the initial failure i, j is 2,3i.j,Ni.jAnd (4) representing the number of evolution stages of the ith fault termination calculation, outputting cascading fault evolution paths of all initial fault sets, and ending the calculation process.
Considering AC/DC interaction influence factors, the identified cascading failure evolution path not only contains equipment on-off information, but also comprises transient state or steady state successive action events caused by a series of AC/DC interaction influences, such as DC continuous commutation failure, new energy large-scale cascading network disconnection, two-three defense line actions and the like, a security control system current value control strategy is dynamically searched according to the successive on-off events, the actual power grid cascading failure condition can be more accurately reflected through strategy simulation, the equipment successive on-off is simulated through multi-evolution branch static safety analysis, and a plurality of potential evolution paths can be accurately identified on the premise of guaranteeing the on-line calculation speed. The method is based on the power grid state estimation data, the alternating current-direct current power grid cascading failure evolution path is identified in a rolling mode, technical support is provided for cascading failure risk assessment and early warning, and the method is more practical.
Example 2:
step 1: manually setting a cascading failure initial failure set, which comprises a failure: the northwest power grid high pier N-2 fails; (N is the number of all the equipment in the power grid, and the general expression of 'N-2' in the power system indicates that 2 equipment faults exist in all the equipment in the power grid); setting the threshold values of equipment overload and voltage out-of-limit safety margins to be 0; setting the maximum evolution stage number of cascading failures to be 3; the power equipment dynamic model, the new energy grid-related protection strategy and the power grid two-three defense line strategy all adopt northwest power grid actual models and fixed values.
Step 2: transient stability time domain simulation is carried out on faults in the cascading fault initial fault set, and the obtained initial fault transient successive action events comprise: Qinghai-Tibet direct current bipolar commutation fails for 1 time, and Gansu and Qinghai new energy is off-line by 308 MW; two or three defensive line action measures are not provided; the transient power angle stability margin is 68%. After transient stability time domain simulation, calculating equipment overload and voltage out-of-limit safety margins of initial faults, wherein the seas bus voltage 752kV, the voltage upper limit 825kV, the voltage lower limit 778kV and the actual voltage out-of-limit safety margin are obtained according to a bus voltage out-of-limit safety margin calculation formula, and the set equipment overload and voltage out-of-limit safety margin threshold values are all larger than 0 for all the other equipment overload and voltage out-of-limit safety margins;
and step 3: judging whether the cascading failure evolution termination condition is met: the number of stages is 1, and the-3.4% of the equipment overload and voltage out-of-limit safety margin is not more than the threshold value 0 of the equipment overload and voltage out-of-limit safety margin; the transient power angle stability margin is 68% larger than 0; either termination condition is not met, so the fault continues to evolve;
and 4, step 4: the sea-west bus voltage safety margin is smaller than the set equipment overload and voltage out-of-limit safety margin threshold value, the sea-west bus is brought into a lower-stage fault equipment set, the sea-west bus is disconnected as a lower-stage calculation fault through a sea-west #1 main transformer connected with a circuit breaker, and the sea-west bus is disconnected as another lower-stage calculation fault through a sea-west #2 main transformer connected with the circuit breaker;
step 5, utilizing a cluster computing platform to perform safety control system current value strategy identification and static safety analysis on two faults in a next-stage computed fault set, wherein the two faults have no matched safety control current value control strategy, steady-state successive action events are respectively the cut-off of a Haihe #1 main transformer and the cut-off of a Haihe #2 main transformer, the load flow after the faults is converged, and the overload safety margins and the out-of-limit safety margins of the two devices for computing the faults are respectively 3.4 percent and 3.8 percent, and returning to the step 3;
and step 3: judging whether the cascading failure evolution termination condition is met: the number of the stages is 2, and the equipment overload and voltage out-of-limit safety margin are both greater than the threshold value 0 of the equipment overload and voltage out-of-limit safety margin; the power flow is converged; both the two calculation faults meet the cascading fault evolution termination condition;
step 6: generating an evolution path of the initial fault northwest power grid high pier N-2 fault, wherein the evolution path comprises two evolution paths, and the path 1 is as follows: the northwest power grid high pier N-2 fault, Qinghai-Tibet direct current bipolar commutation failure 1 time, Gansu and Qinghai new energy off-grid 308MW, and Haishi #1 main transformer disconnection; the path 2 is: and (3) the high pier N-2 of the northwest power grid fails, the Qinghai-Tibet direct current bipolar commutation fails for 1 time, the Gansu and Qinghai new energy off-grid 308MW main transformer and the Haxi #2 main transformer are disconnected, and the process is ended.
It is to be noted that the apparatus embodiment corresponds to the method embodiment, and the implementation manners of the method embodiment are all applicable to the apparatus embodiment and can achieve the same or similar technical effects, so that the details are not described herein.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
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 (8)
1. An online cascading failure evolution path identification method considering alternating current and direct current influences is characterized by comprising the following steps: the method comprises the following steps:
step 1: acquiring operation state data of a power grid in a current operation mode to form initial power flow data, integrating a power equipment dynamic model, a power grid two-three defense line strategy and a new energy grid-related protection model to form stable calculation data, and forming stable safety constraint data according to short-time allowable current-carrying capacity of a line, rated capacity of a transformer and a bus voltage limit value; forming initial fault set of cascading fault simulation according to user setting or equipment fault probability
Fi 0Representing the ith initial fault, wherein N is the number of the initial faults, and the number j =1 of cascading fault evolution stages; setting a calculation failure set { FiIs initialized to an initial failure set, FiCalculating a fault for the ith;
step 2: forming a jth stage calculation data set of cascading failure simulation according to the initial load flow data, the stability calculation data, the stable state safety constraint data and the initial failure set, carrying out parallel transient stability time domain simulation on all failures in the calculation data set by considering alternating current and direct current interaction influence, and obtaining a transient successive action event set and a transient power angle stability margin of the initial failure; the set of transient successive action events for the ith initial fault is noted as TEi(ii) a The ith initial causeThe operation mode of the power grid after the transient stability time domain simulation of the barrier is transited to the steady state is recorded as SiCalculating equipment overload and voltage out-of-limit safety margin of initial faults according to the power grid operation mode after transient stability time domain simulation is transited to a stable state;
and step 3: judging and calculating fault set FiJudging whether the faults in the step (4) all meet the cascading fault evolution termination condition, if so, entering a step (6), otherwise, continuing to evolve, and if j is j +1, entering a step (4);
and 4, step 4: for a set of computational failures { FiGenerating a next-stage calculation fault set { F) according to the calculation results of the equipment overload and voltage out-of-limit safety margini' } operation mode after failure { SiThe operation mode of calculating faults at the next stage is adopted;
and 5: operation mode { S) based on next-stage fault calculationiCalculate the failure set for the next stage { F }i' } performing current value strategy identification and static safety analysis of the security control system, and acquiring the running mode of the power grid after the next stage of calculating faults { S }i' }, controlling equipment and control quantity in a current value strategy of a safety control system, and calculating equipment overload and voltage out-of-limit safety margin and load flow convergence state of faults at the next stage; will calculate the fault Fi' the control device in the safety control strategy includes a steady state successive action event set of the ith fault and the jth stage, and is marked as SEi.j(ii) a Using { Fi' } update FiUsing { S }i' } update SiFourthly, returning to the step 3;
step 6: will initially fail Fi 0Initial fault transient follow-on event TEiJ phase of i fault steady state successive action event SEi.jJ-2, 3, N, which is the cascading failure propagation path for the ith initial failurei.j,Ni.jAnd indicating the number of evolution stages of the ith fault termination calculation, and outputting cascading fault evolution paths of all initial fault sets.
2. The method for on-line identification of the cascading failure evolution path considering the influence of alternating current and direct current as claimed in claim 1, wherein: step 2, performing parallel transient stability time domain simulation on all faults in the calculation data set by the calculation of alternating current and direct current interaction influence, and the method comprises the following steps:
transient stability time domain simulation simulates that alternating current equipment faults cause direct current phase change failure, direct current continuous phase change failure locking causes alternating current system power flow transfer, direct current locking causes two or three defensive line actions of a power grid, and direct current phase change failure or locking causes new energy interlocking off-grid.
3. The method for on-line identification of the cascading failure evolution path considering the influence of alternating current and direct current as claimed in claim 1, characterized in that: the initial fault set fault types include: the fault.
4. The method for on-line identification of the cascading failure evolution path considering the influence of alternating current and direct current as claimed in claim 1, characterized in that: in step 2, the equipment overload and voltage out-of-limit safety margin is calculated according to the power grid operation mode after transient stability time domain simulation is transited to the steady state, and the method comprises the following steps:
1) identifying the time when the system enters a quasi-steady state operation state according to the voltage and frequency change conditions of each node in the transient stability time domain simulation process;
2) generating quasi-steady-state operation section tide mode data according to the network topology at the quasi-steady-state operation state moment, the steady-state active/reactive power of each injection node and the steady-state voltage of each node;
3) carrying out load flow calculation by aiming at load flow mode data of a steady-state operation section, obtaining line current, transformer power and bus voltage, and calculating overload and voltage out-of-limit safety margin of single equipment according to steady-state safety constraint;
4) and taking the minimum value of the overload and voltage out-of-limit safety margins of all the equipment as the overload and voltage out-of-limit safety margins of the fault equipment.
5. The method for on-line identification of the cascading failure evolution path considering the influence of alternating current and direct current as claimed in claim 1, characterized in that: when j is 1, the cascading failure evolution termination condition comprises: the equipment overload and voltage out-of-limit safety margin is larger than the set equipment overload and voltage out-of-limit safety margin threshold value; the transient safety stability margin is smaller than a set transient safety stability margin threshold value;
when j is more than 1, the cascading failure evolution termination condition comprises the following steps: the number of the maximum evolution stages is set when the fault reaches the set number; the equipment overload and voltage out-of-limit safety margin is larger than the set equipment overload and voltage out-of-limit safety margin threshold value; and if the trend is not converged and any condition is met, the cascading failure branch is terminated and evolves.
6. The method for on-line identification of the cascading failure evolution path considering the influence of alternating current and direct current as claimed in claim 1, wherein: in step 4, a next-stage calculation fault set is generated according to the calculation results of the equipment overload and voltage out-of-limit safety margin, and the method comprises the following steps:
1) bringing equipment with equipment overload and voltage out-of-limit safety margin smaller than set equipment overload and voltage out-of-limit safety margin threshold value into lower-stage fault equipment set
Representing a fault F calculated byiGenerating a next-stage fault equipment set;
2) will next stage fault equipment set
As a calculation fault in the next stage, each calculation fault FiGenerating one or more lower-stage computational faults Fi'；
3) All the next stages are calculated to be fault Fi' the set of constructs is the next phase to compute the failure set { Fi'}。
7. The method for on-line identification of the cascading failure evolution path considering the influence of alternating current and direct current as claimed in claim 6, wherein: lower phase calculation failure FiThe fault type of' is determined using the following method:
if it is
If the equipment in the system is a line, the fault type of the next stage is line disconnection; if it is
If the equipment in the system is a transformer, the fault type of the next stage is the disconnection of the transformer; if it is
If the equipment in the system is a bus, the line and the transformer directly connected with the bus through a breaker or a switch are searched, and the fault is the corresponding line and the corresponding transformer winding.
8. The method for on-line identification of the cascading failure evolution path considering the influence of alternating current and direct current as claimed in claim 1, wherein: the current value strategy identification method of the security control system in the step 4 comprises the following steps:
1) analyzing fault constraints, mode constraints, power flow constraints and control strategies in the second three-defense strategy of the power grid;
2) according to Si' and Fi' determining the control measure of the safety control system as the current value strategy of the safety control system.
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