CN109784782B - Subway power supply system dynamic risk analysis and evaluation method based on fuzzy inference - Google Patents
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Abstract
The invention relates to a subway power supply system dynamic risk analysis and evaluation method based on fuzzy inference, which at least comprises the following steps: s1, determining a direct current feed-out cable and a return cable of the target direct current substation according to the power supply section of the track position where the target train is located; s2, establishing a risk propagation chain for breakdown of a direct current cable of a subway power supply system, and determining key characteristic quantity of a direct current feed-out cable in the risk propagation chain; s3, taking the obtained key characteristic quantity value of the direct current feed-out cable as a numerical vector, and carrying out fuzzy set calculation through a fuzzy reasoning method to obtain a membership function graph corresponding to the numerical vector; and S4, obtaining a potential observation diagram of the breakdown of the direct current cable by inference according to the membership function diagram of each numerical value vector. The method can reasonably evaluate the risk level of the system and block propagation evolution of the risk propagation chain, thereby avoiding major accidents as much as possible.
Description
Technical Field
The invention relates to a risk analysis technology of a subway power supply system, in particular to a dynamic risk analysis and evaluation method of the subway power supply system based on fuzzy reasoning.
Background
With the high-speed development of subways in China, the operation safety problem of subways draws high attention of people. The power supply system of the subway is used as a power source of a subway train and is mainly responsible for providing continuous power for the train so as to ensure the stable operation of the train. According to statistics, in recent years, accidents of subways caused by power supply factors are ranked second among all accident reasons, and once a power supply system fails, not only can trains not run, but also safety of passengers can be endangered, and serious consequences are caused. Therefore, the safety risk problem of the subway power supply system is particularly important, and relevant research works are developed for scholars, and the analysis and evaluation method is continuously evolving from static risk analysis and evaluation to dynamic risk analysis and evaluation.
A large amount of research is carried out by scholars at home and abroad aiming at the risk analysis and evaluation method of rail transit, and a plurality of achievements are obtained. For example, in the document "reliability design of subway power supply system" (Sun Zhanglin, Ouze. modern urban rail transit 2006(1):14-16), reliability analysis is performed on the power supply system by applying fault tree and fault mode consequence analysis, and safety evaluation is performed on the power supply system by a fuzzy comprehensive evaluation method. In the document "Distribution System Reliability Cost/word Analysis Using Analytical And Sequential Simulation Techniques" (Billingon R, Wang P. IEEE Transactions on Power Systems Pwrs,1998,13(4):1245 And 1250.), probability Analysis is performed by Using an average model Using the component average failure rate And the failure recovery time, And the load And the unit loss Cost of Power outage. The method is characterized in that the influence of real-time operation conditions such as line tide, bus voltage, system frequency and the like on the outage probability of an element is analyzed in the document 'evaluation of the operation reliability of an electric power system based on the real-time operation state' (Sun Yuan Chapter, Chenglin, Liuhaitao. electric network technology, 2005,29(15):6-12), an element reliability model based on the real-time operation conditions is established, and the influence of the real-time operation conditions such as the operation mode of a unit, the real-time change of the load, the change of the network structure and the like on the failure consequence analysis is considered. The document On-line Risk-Based Security Association (Ni M, Mccalley J D, Member S, et al. IEEE Transactions On Power systems.2003: 258-265) designs the expressions of the severity of the loss of the static voltage stability boundary, the node voltage, the cascading failure and the line tide, and provides corresponding Risk indexes.
In the current research, most evaluation methods are static analysis, risks are analyzed in a certain specific state, the research is carried out from two aspects of element degradation and element failure rate, and most of adopted data are obtained by a method of historical data statistics or a Monte Carlo test. The method can depict the risk of the system to a certain degree, but has the defect that the risk propagation evolution process of the system cannot be reflected, and particularly the description of a failure mechanism is lacked.
Disclosure of Invention
The invention aims to provide a subway power supply system dynamic risk analysis and evaluation method based on fuzzy reasoning, which combines the fault probability and the severity by using a risk evaluation idea, describes a key risk propagation chain process of a subway power supply system, and provides effective risk control measures aiming at a risk source, so that the operation risk of the subway power supply system is reduced, and the operation safety of a subway is improved.
In order to achieve the purpose, the technical scheme adopted by the invention is a subway power supply system dynamic risk analysis and evaluation method based on fuzzy reasoning, which at least comprises the following steps:
s1, determining a corresponding target direct-current traction substation and a traction network thereof according to a power supply section of the track position where the target train is located, and determining a direct-current feed-out cable and a return cable of the target direct-current substation;
s2, establishing a risk propagation chain of breakdown of a direct-current cable of a subway power supply system, and determining key characteristic quantities of a direct-current feed-out cable in the risk propagation chain, wherein the key characteristic quantities comprise direct-current cable insulation resistance R, voltage U and cable leakage current Ie, and the formula is R-U/Ie;
s3, taking the obtained key characteristic quantity value of the direct current feed-out cable as a numerical vector, and carrying out fuzzy set calculation through a fuzzy reasoning method to obtain a membership function graph corresponding to the numerical vector;
and S4, deducing to obtain a potential observation diagram of direct current cable breakdown according to the membership function diagram of each numerical value vector, and evaluating the fault occurrence probability of the target train in the power supply section.
After the cable is insulated and aged due to temperature difference and a humid environment, when the cable passes through transient overvoltage, the transient overvoltage is caused, so that the weak point of the cable is instantaneously broken down, and a large amount of current is leaked from the cable; when the cable insulation is aged, the insulation resistance R of the direct current cable is reduced;
in the risk propagation chain, a calculation formula of the cable leakage current Ie is as follows: Ie-Io; and Ii is the current at the input end of the cable, Io is the output current, and the substitution relation is R-U/(Ii-Io).
The key characteristic quantity of the risk transmission chain describes the risk transmission process of the subway power supply system by fuzzy reasoning, and can clearly describe the failure mechanism and the occurrence process, thereby controlling the occurrence of a risk source, blocking the risk transmission chain and improving the stability and the safety of the operation of the system.
In an improved solution, the method further comprises the steps of:
s5, constructing a subway network based on graph theory and network theory, and analyzing the severity of consequences brought to the operation of the subway network by the propagation evolution of passenger flow when a certain part in the subway network breaks down;
and S6, comprehensively evaluating the magnitude of the risk index by combining the fault occurrence probability obtained through inference in the step S4 and the severity of the consequences after the fault occurs obtained in the step S5.
Further, S7, an early warning measure is taken according to the analysis and evaluation result, namely, when the cable voltage exceeds 3500V, a warning is sent to check the reason of the over-high voltage.
The method is a dynamic risk analysis and evaluation method aiming at a subway power supply system direct current cable breakdown risk transmission chain, the dynamic risk of the subway power supply system key risk transmission chain is researched by the risk analysis and evaluation method based on characteristic quantity and fuzzy reasoning, the fault probability and the severity are combined by utilizing a risk evaluation thought, the process of the subway power supply system key risk transmission chain is described, effective risk control measures aiming at a risk source are provided, and the propagation and evolution of the risk transmission chain are blocked, so that the occurrence of major accidents is avoided as much as possible, the operation risk of the subway power supply system is reduced, the subway operation safety is improved, and support is provided for ensuring the safe and stable operation of a regional rail transit system and the optimization and promotion of the whole operation performance.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without inventive efforts.
FIG. 1 is a diagram of a DC traction power supply system for a subway;
FIG. 2 is a schematic diagram of one embodiment of the process of the present invention;
FIG. 3 is a schematic view of a DC cable breakdown risk propagation chain of the subway power supply system according to the present invention;
FIG. 4 is a graph of membership function of insulation resistance of DC cable;
FIG. 5 is a graph of a membership function of DC cable voltage;
FIG. 6 is a membership function graph of the breakdown probability of DC cables;
FIG. 7 is a diagram of a fuzzy logic inference rule base structure;
FIG. 8 is an observation graph of output variables;
FIG. 9 is a schematic view of another embodiment of the method of the present invention
FIG. 10 is a diagram of an exemplary subway traffic network architecture;
fig. 11 is a diagram of a subway traffic network structure of an example of a Chongqing subway.
Detailed Description
In order to make the purpose, technical solution and beneficial effects of the present application more clear and more obvious, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
Before the essential point of the invention of the application is understood, a subway power supply system needs to be known. The electric energy of the whole subway is obtained from a subway power supply system, and from the view point of different functions, the subway power supply system consists of six systems, namely an external power supply, a main substation, a traction power supply system, a stray current corrosion protection system, an electric power monitoring system and a power illumination power supply system. The traction power supply system is a core part of a subway power supply system and is also a key of the method for analyzing and commenting; the traction power supply system mainly comprises a traction substation and a traction network, and is used for transmitting high-voltage alternating current transmitted by the main substation to a subway train after a series of treatments such as voltage reduction, rectification and the like, so that the normal operation of the subway is ensured. The risk transmission chain is described by a subway direct-current power supply system, namely mainly composed of a traction step-down substation and a contact network (or a third rail) system. As shown in fig. 1, in a traction step-down substation, a rectifier unit composed of a step-down transformer and a rectifier converts an ac 35kV voltage into a DC1500V voltage, and the DC feed-out cable transmits electric energy, and supplies power to a catenary (a third rail) through a high-speed DC switch, and finally returns to the negative electrode of the rectifier unit through a steel rail (a return rail) and a return cable.
The direct current feed-out cable has the function of connecting the high-speed direct current switch with a corresponding contact network, and the main cable laying positions are in a cable interlayer of the substation, on a corresponding cable support in a ground cable trench and on the side wall of an interval tunnel. The strong temperature difference and the humid environment easily cause the surface discharge and the partial discharge of the cable medium, which can cause the increase of the cable conductivity, the gradual decline of the main insulation and the aging of the cable insulation. When a contact network in a certain area is used for locomotive power supply, a large load current flows through the cable supplying the area, no load current flows through the cable when no locomotive passes through the area and a subway stops at night, but the cable always has 1500V direct current voltage. Through the combined action and long-term accumulation of the factors, when the cable passes through transient overvoltage, the transient breakdown of the insulation weak point of the cable can be caused, a large amount of current is suddenly leaked by the cable, the grounding short circuit of a direct current cable core through a metal box body of the cable is caused, the cable is damaged, and the power supply is stopped. The direct current cable is an important link in a traction power supply system, because of the adoption of a structure without metal armor, the duration of a recessive fault of the direct current cable is long, the direct current cable is difficult to find, and particularly in the traction power supply system adopting a third rail for power supply, once the direct current cable fails, the fault is difficult to isolate, so that the power failure time is increased, and the operation risk is increased.
Based on the analysis, the invention provides a subway power supply system dynamic risk analysis and evaluation method based on fuzzy reasoning. As shown in fig. 2 in detail, the method comprises the following steps:
s1, determining a corresponding target direct-current traction substation and a traction network thereof according to a power supply section of the track position where the target train is located, and determining a direct-current feed-out cable and a return cable of the target direct-current substation;
s2, establishing a risk propagation chain of breakdown of a direct-current cable of a subway power supply system, and determining key characteristic quantities of a direct-current feed-out cable in the risk propagation chain, wherein the key characteristic quantities comprise direct-current cable insulation resistance R, voltage U and cable leakage current Ie, and the relation is R-U/Ie;
as shown in fig. 3, the risk propagation chain is described as that after the insulation of the cable is aged due to temperature difference and a humid environment, when the cable passes through a transient overvoltage, a weak point of the insulation of the cable is instantaneously punctured, a large amount of current is leaked from the cable, the grounding of the cable is short-circuited, and the power supply is stopped after the cable is damaged. When the cable insulation is aged, the direct current resistance R of the cable insulation is liable to be reduced.
The load of the urban rail transit direct current feed-out cable has the particularity that the load is in a stage: only when the locomotive passes through, the direct current feed-out cable provides load current; when the locomotive is shut down or no locomotive passes through, the cable is almost unloaded, the current Io at the output end is approximately equal to 0, and the leakage current Ie of the cable is approximately equal to the input current Ii of the cable. According to kirchhoff's law, the calculation formula of the cable leakage current Ie is as follows: and if the Ie is equal to Ii-Io, the substitution relation is R equal to U/(Ii-Io). The breakdown of the direct current cable depends on the breakdown voltage and the insulation resistance, so that the breakdown probability of the direct current cable can be inferred according to the breakdown voltage and the insulation resistance.
In order to adapt to uncertainty of insulation resistance and voltage of a subway direct-current cable in operation, the relation among the insulation resistance, the voltage and the possibility of cable breakdown is analyzed by a fuzzy reasoning method.
S3, taking the obtained key characteristic quantity value of the direct current feed-out cable as a numerical vector, and carrying out fuzzy set calculation through a fuzzy reasoning method to obtain a membership function graph corresponding to the numerical vector;
in a specific embodiment, the fuzzy inference method utilizes a fuzzy logic toolbox of MATLAB to calculate the fuzzy set, and specifically includes:
s30, inputting variable insulation resistors R, classifying the insulation resistors into three types of small, small and normal according to the physical attributes of the insulation resistors, and describing by selecting a trapezoidal membership function;
fig. 4 is a membership function of the input variable insulation resistance R. Wherein the abscissa represents the resistance value of the resistor, and the ordinate represents the value of the membership function of the resistance value of the resistor;
s31, inputting variable voltage U, classifying the variable voltage U into three types of normal, high and high according to the physical attributes of the voltage, and describing the variable voltage U by selecting a trapezoidal membership function;
fig. 5 is a membership function of the input variable cable voltage U. Wherein the abscissa represents the magnitude of the cable voltage U and the ordinate represents the value of the membership function of the magnitude of the voltage.
S32, the probability K of cable breakdown of the output variable is described by adopting a Gaussian membership function because the probability change is gentle.
Fig. 6 is a membership function of the breakdown probability of an output variable dc cable. The abscissa represents the value range of the membership function of the breakdown possibility of the direct-current cable, and the ordinate represents the membership function value of the breakdown possibility of the direct-current cable.
And S4, deducing to obtain a potential observation diagram of direct current cable breakdown according to the membership function diagram, and evaluating the fault occurrence probability of the target train in the power supply section.
The method specifically comprises the following steps:
s40, editing the obtained membership function into a fuzzy logic inference rule base by using a rule observer; the fuzzy logic inference rule base is compiled using a rule observer as shown in fig. 7. It consists of 9 rules. The left column indicates the case of insulation resistance, and from left to right indicates insulation resistance "small", "normal", respectively; the middle column represents the cable voltage case, and from left to right represent the cable voltages "normal", "higher", "very high", respectively; the right column indicates the breakdown of the dc cable, and from left to right, the breakdown probabilities "low", "medium", and "high", respectively. Here, each row represents a rule.
And S41, observing the output curved Surface by using the View-Surface, and directly evaluating the high, medium and low degrees of the fault occurrence probability according to the curved Surface. As shown in fig. 8, the relationship between the dc cable breakdown probability K and the dc cable insulation resistance R and the cable voltage U is shown. When the insulation resistance of the direct current cable is small and the voltage of the cable is high, the possibility of breakdown of the direct current cable is high.
Under normal conditions, the insulation resistance of a 1500V direct current cable at 20 ℃ is more than or equal to 153M omega km, the running voltage of the direct current cable of the subway traction system is 1500V, and the withstand voltage requirement is 3000V. The present example was evaluated by the above analytical methods to yield the results: when the subway direct current feed-out cable is less than 100M omega km and the cable voltage is higher than 4000V, the cable is very easy to be punctured, so that a cable monitoring device is used for sending out an early warning when the insulation resistance is 100-150M omega km to check the reason of cable insulation reduction in time, and sending out a prompt to check the reason of overhigh voltage when the cable voltage exceeds 4000V to prevent the cable from being punctured. The monitoring system can adopt an on-line monitoring means, the on-line monitoring technology can carry out on-line monitoring on the direct current cable for 24 hours, the insulation parameters of the cable are monitored on line in real time, once the direct current cable is abnormal, the on-line monitoring technology can feed back collected data information to the monitoring system in time, the monitoring system transmits the data information to an equipment maintenance management department, technicians analyze the data information and know the degradation trend of the cable insulation, thereby analyzing the performance of the direct current cable, carrying out fault monitoring and establishing an early warning system.
The direct current of the subway power supply system is presented the cable and can guarantee subway train's normal operating, and the insulating state of cable will produce direct influence to the power supply condition of subway. By the method, the fault occurrence probability caused by breakdown of the direct current cable can be determined, and the insulation resistance and the voltage parameter threshold value when the direct current cable is broken down are obtained, so that a basis is provided for later detection and prevention.
The direct current cable fault can directly cause the train to stop running, in the networked operation process, the train stop running can bring passenger flow gathering, the passenger flow can be spread along a line, and the gathering and spreading of the passenger flow can bring huge risks to the safety of a subway operation network. Therefore, on the other hand, the risk of the subway power supply system failure on the network operation is also the severity of the failure consequences, and the evaluation method of the severity is as follows.
As shown in fig. 9, the subway power supply system risk analysis method based on the fuzzy inference method further includes the following steps:
s5, constructing a subway network based on graph theory and network theory, and analyzing the severity of consequences brought to the operation of the subway network by the propagation evolution of passenger flow when a certain part in the subway network breaks down;
s50, stations on a subway traffic line are identified by nodes in the subway traffic network, a connecting line between adjacent nodes identifies line intervals between stations, and a subway network is established;
the stations of the rail transit network are represented by points, and the connecting lines between the stations represent that the stations are connected by lines, so that the urban rail transit condition can be clearly represented by a graph. Aiming at the characteristics of subway networked operation, by analyzing factors such as passenger flow, network structure relevance and the like of operation safety influence factors of a subway traffic network, a subway network model based on a graph theory and a network theory is constructed, and the influence of subway power supply system faults on subway lines and the network is analyzed. The relevance of the network structure refers to the relevance between stations and between lines, and the occurrence of local problems in the network will result in the sweep effect of the whole operation network. For example, when an abnormal condition occurs in a certain section of line in the network, the change of the passenger flow will be rapidly propagated along the nodes and the sections of the network, thereby affecting the operation safety of the relevant nodes, the relevant sections and the relevant lines, and finally affecting the operation safety of the whole road network.
S51, calculating the degree of unbalancedness W of the passenger flow of each section on the subway network; the passenger flow imbalance degree W is expressed as the ratio of unbalanced passenger flow of the road network to the total passenger flow of the road network in a normal state.
As shown in fig. 10, x1-x8And (3) representing the passenger flow of the uplink and the downlink among the nodes 1, 2, 3, 4 and 5 in normal operation, and setting the direction of 5-4-2-1 and 3-2-1 as the uplink, otherwise, as the downlink. If 2-1 up-line is interrupted, the traffic will spread congestion to segments 4-2, 5-4 and 3-2, breaking the balance of traffic in the road network. Wherein, the 2-1 section of unbalanced passenger flow is
F1＝x1 (4)
And F denotes unbalanced passenger flow. According to the practical condition, the unbalanced passenger flows of the 4-2 section and the 3-2 section are approximately distributed according to the proportion of the original ascending passenger flow, and the unbalanced passenger flows of the 4-2 section
3-2 segment unbalanced passenger flows of
5-4 segments of unbalanced passenger flow
From the road network passenger flow imbalance
W represents the degree of road network traffic imbalance. N levels of nodes can be computed, and the example computes 3 levels, and generally speaking, the congestion of passenger flow can be propagated to the nodes of 2-4 levels.
S52, calculating the severity of the consequences of the line interruption on the road network operation;
the consequence of the line interruption to the road network operation is in direct proportion to the time of the line interruption, so the severity of the consequence of the line interruption to the road network operation is expressed as the product of the unbalancedness of the road network passenger flow and the time
C＝W*t (9)
C represents the severity of the road network consequences, and time t is in hours. The prescribed outcome severity ratings are shown in table 1:
TABLE 1 severity level of consequences for subway network
A part of road networks (including a line 1 and a line 2) operated in the Chongqing subway is abstracted into a subway traffic network model formed by a plurality of nodes and directed edges as an analysis case, as shown in fig. 11.
Each line in the subway network bears a certain passenger flow volume, and when any line breaks down, the flow of the passenger flow is influenced to a certain extent, and the degree of unbalance of the passenger flow in the network is influenced to different degrees. According to relevant research data, the passenger flow distribution of the road network in normal operation is shown in table 2:
TABLE 2 subway network Normal operation passenger flow distribution on one day
| Interval(s) | Number of people/hour with ascending passenger flow (7: 00-8: 00) | Number of people/hour with down passenger flow (7: 00-8: 00) |
| Intermittent platform-petroleum road | 10425 | 5326 |
| Petroleum road-big terrace | 11443 | 5372 |
| Xie Jia Wan-Yuan Jia Bao | 8985 | 2335 |
| Yuanjia gang-Dachang | 9004 | 3219 |
| plateau-Buddha guan | 7129 | 2562 |
| Buddha-view-plum dam | 6831 | 2627 |
When the operation is interrupted for half an hour due to a power supply system fault on a line of a row section of a Buddha-plum dam, according to the flow direction of passenger flow, passenger flow of a terrace-oil road-terrace, a Xijiawan-Muyuang-terrace and a terrace-Buddha-terrace section is crowded, according to the definition of the unbalanced degree of passenger flow of the road-grid, unbalanced passenger flow of the Buddha-plum dam is 6831 (people/hour), unbalanced passenger flow of the terrace-Buddha road direction is 6545 (people/hour), unbalanced passenger flow of the oil road-terrace direction is 3662 (people/hour), unbalanced passenger flow of the Jia-terrace direction is 2882 (people/hour), unbalanced passenger flow of the Chun-Muyuang-oil road direction is 1286 (people/hour), and unbalanced passenger flow of the Xijia-Goyuang-Yuyuang direction is 924 (people/hour). According to the formula (8), the road network passenger flow imbalance degree W is 0.147, and according to the formula (9), the road network consequence severity C is 0.147 t.
According to the classification of the severity levels of the consequences, in this case, the severity of the consequences is low within 0.034 hours of interruption of a plum dam segment line, medium within 0.034-0.34 hours of interruption, high within 0.34-1.7 hours of interruption, and extremely high within 1.7-3.4 hours of interruption.
S6, calculating the risk index size comprehensively according to the fault occurrence probability obtained through the inference in the step S4 and the consequence severity after the fault occurs obtained in the step S5.
The risk of the subway power supply system fault on network operation is jointly determined by the fault occurrence probability and the fault consequence severity, and the fault risk grades of the direct current cables of the subway power supply system can be classified as follows according to the calculation and analysis, and the classification is shown in table 3.
TABLE 3 Risk index Classification
Taking the above Chongqing subway network as an example, when the line is interrupted for half an hour, the severity of the road network consequences is moderate, and according to table 3, the risk level is medium when the occurrence probability is low and medium, and the risk level is high when the occurrence probability is high.
According to the results of the analysis and evaluation, when the subway direct current feed-out cable is smaller than 3500V and the cable voltage is higher than 3500V, the cable is very easy to be punctured, so that the cable monitoring device is used for giving an early warning when the insulation resistance is in place and timely checking the reason of the insulation reduction of the cable, and giving a prompt to check the reason of the overhigh voltage when the cable voltage exceeds 3500V, so that the cable is prevented from being punctured. The actual control range is slightly different due to different cable running environments.
The method applying the graph theory analyzes the severity degree of consequences brought to the operation of the subway network by the propagation evolution of the passenger flow when a certain part in the subway network has a fault. Specifically, in the subway network structure, the severity of consequences brought to other nodes in the network by a power supply fault at a certain position is analyzed, so that the risk degree of other nodes in the network due to the fault at the certain position is evaluated, and corresponding risk control measures are provided, so that the overall risk of the network is reduced to the minimum by adopting different methods according to different risk degrees when the fault occurs at the certain position in the network. The method can realize dynamic risk analysis and evaluation in the operation process of the direct current cable of the subway power supply system, and provides a theoretical basis for risk blocking.
The above-described embodiments do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the above-described embodiments should be included in the protection scope of the technical solution.
Claims (7)
1. A subway power supply system dynamic risk analysis and evaluation method based on fuzzy inference at least comprises the following steps:
s1, determining a corresponding target direct-current traction substation and a traction network thereof according to a power supply section of the track position where the target train is located, and determining a direct-current feed-out cable and a return cable of the target direct-current traction substation;
s2, establishing a risk propagation chain of breakdown of a direct current cable of a subway power supply system, and determining key characteristic quantities of a direct current feed-out cable in the risk propagation chain, wherein the key characteristic quantities comprise direct current cable insulation resistance R, voltage U and cable leakage current Ie, and the formula is R = U/Ie;
s3, taking the obtained key characteristic quantity value of the direct current feed-out cable as a numerical vector, and carrying out fuzzy set calculation through a fuzzy reasoning method to obtain a membership function graph corresponding to the numerical vector;
s4, deducing to obtain a potential observation diagram of direct current cable breakdown according to the membership function diagram of each numerical value vector, and evaluating the fault occurrence probability of the target train in the power supply section;
s5, constructing a subway network based on graph theory and network theory, and analyzing the severity of consequences brought to the operation of the subway network by the propagation evolution of passenger flow when a certain part in the subway network breaks down;
and S6, comprehensively evaluating the dynamic risk of the subway power supply system by combining the fault occurrence probability obtained through inference in the step S4 and the consequence severity after the fault occurs in the step S5.
2. The subway power supply system dynamic risk analysis and assessment method based on fuzzy inference as claimed in claim 1, wherein said risk propagation chain is described as that after the cable insulation is aged due to temperature difference and humid environment, when the cable passes through transient overvoltage, the cable insulation weak point is instantaneously broken down, and a large amount of current is leaked from the cable; when the cable insulation is aged, the insulation resistance R of the direct current cable is reduced;
in the risk propagation chain, a calculation formula of the cable leakage current Ie is as follows: ie = Ii-Io; wherein Ii is the current at the input end of the cable, Io is the output current, and the substitution relation is R = U/(Ii-Io).
3. The subway power supply system dynamic risk analysis and assessment method based on fuzzy inference as claimed in claim 1, wherein S3 is a method for performing fuzzy set calculation using a fuzzy logic toolbox of MATLAB, specifically comprising:
s30, inputting variable insulation resistors R, classifying the variable insulation resistors into three types of small, small and normal according to physical attributes of the variable insulation resistors R, and describing by selecting a trapezoidal membership function;
s31, inputting variable voltage U, classifying the variable voltage U into three types of normal, high and high according to the physical attributes of the variable voltage U, and describing the variable voltage U by selecting a trapezoidal membership function;
s32, the possibility K of cable breakdown of the output variable is described by adopting a Gaussian membership function.
4. A subway power supply system dynamic risk analysis and assessment method based on fuzzy inference as claimed in claim 3, wherein the specific inference method of the observation map of the possibility of breakdown of the direct current cable in S4 is:
s40, editing the obtained membership function into a fuzzy logic inference rule base by using a rule observer;
and S41, observing and outputting the curved Surface by using the View-Surface according to a fuzzy logic reasoning rule base, and directly evaluating the fault occurrence probability according to the curved Surface, wherein the fault occurrence probability is evaluated in a high mode, a medium mode and a low mode.
5. The method for analyzing and evaluating the dynamic risk of a subway power supply system based on fuzzy inference as claimed in claim 4, wherein said fuzzy logic inference rule base in S40 is edited by using the membership functions of steps S30-S32 as contents, and the variable insulation resistance R, voltage U and the possibility K of cable breakdown in the same state constitute a rule, and constitute 9 rules in total.
6. The subway power supply system dynamic risk analysis and evaluation method based on fuzzy inference as claimed in claim 1, wherein step S6 specifically is:
when the fault occurrence probability is low, the risk grades corresponding to the conditions that the severity of the consequence is low, medium, high and extremely high are graded and evaluated to be low, medium, high and extremely high in sequence;
when the fault occurrence probability is middle, the risk grades corresponding to the conditions that the severity of the consequence is low, middle, high and extremely high are graded and evaluated to be low, middle, extremely high and extremely high in sequence;
and when the fault occurrence probability is high, the risk grade grading evaluation corresponding to the conditions that the consequence severity is low, medium, high and extremely high is medium, high, extremely high and extremely high in sequence.
7. The subway power supply system dynamic risk analysis and assessment method based on fuzzy inference as claimed in claim 1, further comprising
And S7, taking early warning measures according to the analysis and evaluation result, namely sending out a prompt to check the reason of overhigh voltage when the voltage of the cable exceeds 3500V.
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