CN110488119B - Redundancy-considered industrial process voltage sag interruption probability evaluation method - Google Patents

Redundancy-considered industrial process voltage sag interruption probability evaluation method Download PDF

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CN110488119B
CN110488119B CN201910744946.1A CN201910744946A CN110488119B CN 110488119 B CN110488119 B CN 110488119B CN 201910744946 A CN201910744946 A CN 201910744946A CN 110488119 B CN110488119 B CN 110488119B
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王庆斌
蔡日
马明
吴小宁
黄辉
李钙
王余熙
赵宪中
李晓阳
邵彬
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Guangdong Power Grid Co Ltd
Yunfu Power Supply Bureau of Guangdong Power Grid Co Ltd
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Abstract

The invention relates to an industrial process voltage sag interruption probability evaluation method considering redundancy, which comprises the following steps: s1: acquiring voltage sag data; s2: judging whether the rectangular sag belongs to a rectangular three-phase balance sag or not, and if so, executing S3; if not, the three-phase normalization is carried out, the unbalance temporary drop is converted into balance temporary drop, and then S3 is executed; s3: calculating the fault probability of the voltage sag domain of the sensitive equipment by considering the VTC and the uncertain region thereof; s4: correcting the fault probability of the voltage sag domain of the equipment by considering the redundancy of the industrial process; s5: and calculating the interruption probability in the industrial process by considering the logic connection mode among the sensitive devices. The VTC-based sensitive equipment sag fault probability evaluation model established by the invention is simple and practical, the error is reduced after the industrial process redundancy theory correction, and the voltage sag interruption probability of the industrial process is calculated according to the connection mode between the equipment, so that the calculation accuracy is further increased.

Description

Redundancy-considered industrial process voltage sag interruption probability evaluation method
Technical Field
The invention relates to the field of voltage sag, in particular to an industrial process voltage sag interruption probability evaluation method considering redundancy.
Background
Voltage sag:
defined in the IEEE standard as: the effective value of the power frequency voltage at a certain point in the power supply system suddenly drops to 10% -90% of the rated value, and then returns to normal after a short duration period of 10 ms-1 min.
Short-time power interruption:
defined in the IEEE standard as: a short-time voltage change of duration between 10ms and 3s, with a complete loss of voltage of one or more phases (less than 0.1 per unit value) in the power supply system.
A sensitive device:
electrical devices susceptible to voltage sags, short interruptions, and voltage sags, computers (PCs), Programmable Logic Controllers (PLCs), Adjustable Speed Drives (ASDs), and ac contactors (ACCs) are generally considered as typical sensitive devices.
ITIC and CBEMA curves:
in the 80 s of the 20 th century, the association of american computer and commercial equipment manufacturers proposed a voltage tolerance curve, CBEMA curve, for large computers, as shown in fig. 1a, with the envelope being qualified on the inside and unqualified on the outside. After CBEMA was changed to the information technology industry Association (ITIC), the third technical Committee revised it to the ITIC curve, as shown in FIG. 1 b. CBEMA or ITIC curves are recommended as manufacturer-suggested criteria.
With the rapid development of high-technology industry, many sensitive devices are incorporated into a public power grid, and the quality of power grid power, especially the dynamic power quality of the power grid, is seriously reduced, which causes the wide attention of experts and scholars at home and abroad. Sensitive loads are very sensitive to power quality disturbances such as voltage sags, voltage surges, short-term interruptions and the like, and the failure of a single device or element may cause the scrapping of products in the whole production line, thereby bringing about great economic loss.
At present, most industrial processes are composed of sensitive elements such as microelectronics, power electronics and process control, and the like, and have the characteristics of complex structure and large difference of interference immunity of each element, under the influence of voltage sag, voltage sag possibly suffered by the industrial processes needs to be uniformly measured, but as the response event of the industrial processes to the voltage sag has complex uncertainty, great difficulty is caused to the evaluation of the voltage sag interruption probability of the industrial processes, and the process interruption probability needs to be evaluated for establishing a technical scheme of a high-quality power park, so that the research on the voltage sag interruption probability evaluation method of the complex industrial processes has important theoretical and practical significance.
The voltage sag interruption probability evaluation of the industrial process can be divided into two steps: 1. evaluating the voltage sag fault probability of the sensitive equipment; 2. and calculating the voltage sag fault probability in the industrial process on the basis of obtaining the voltage sag fault probability of the sensitive equipment.
At present, the probability evaluation method of voltage sag faults of sensitive equipment mainly comprises an ITIC or CBEMA curve standard method, a probability evaluation method, a random evaluation method and a fuzzy random evaluation method.
ITIC or CBEMA curve standard method: and determining the position relation between the sag and the ITIC or CBEMA curve according to the amplitude and the duration of the voltage sag, wherein when the sag is positioned in an area above a low-voltage branch below a high-voltage branch of the ITIC or CBEMA curve, the voltage sag cannot cause the fault of the sensitive equipment, and on the contrary, when the sag is positioned in an area above the high-voltage branch or below the low-voltage branch of the ITIC or CBEMA curve, the fault condition occurs when the sensitive equipment is influenced by the sag. The ITIC or CBEMA curve standard method is simple and easy to implement, but because of the significant uncertainty in the sensitivity of different types of loads, especially the same type and different models, to voltage sag, it is not practical to evaluate the load sensitivity by simply using a fixed ITIC or CBEMA curve;
the probability evaluation method comprises the following steps: document [1] represents the probability of a load voltage tolerance curve in an uncertain region by using different probability density functions on the basis of classifying the component equipment grades, and directly evaluates the sensitivity of voltage sag by using the probability density functions; documents [2-3] evaluate voltage notches with different probability distribution functions. These probability evaluation methods take into account the randomness of the voltage endurance curve of the device, but still have the following imperfections: in the actual evaluation process, the sensitivity level of the load is difficult to determine and has randomness, and evaluation is carried out only according to the sensitivity level of the load, so that the evaluation result is possible to be wrong; the existing probability evaluation method does not obtain a specific mathematical model, has low operability in actual evaluation, is difficult to quantitatively estimate and has larger randomness. In addition, the method is too subjective when probability density functions such as uniform distribution, exponential distribution, normal distribution and the like are used for representing the probability distribution of the voltage tolerance curve of the equipment in an uncertain region, and a link for proving whether the relation exists between the voltage tolerance curve and the equipment voltage tolerance curve is lacked.
Random evaluation method: the randomness of a load voltage tolerance curve is represented by a normal distribution probability density function, a random model of the voltage tolerance curve and the load sensitivity is established, and a random estimation method of the voltage sag sensitivity of the sensitive load is provided. The method adopts an accumulative summation mode to evaluate the sensitivity, and avoids the division of sensitivity grades.
Fuzzy random evaluation method: the voltage sag sensitivity of the sensitive equipment is generally described by equipment failure rate, the size of the voltage sag sensitivity depends on the voltage sag characteristics generated by the power supply system at the power supply point and the voltage tolerance capability of the sensitive equipment, but the voltage sag characteristics and the voltage tolerance capability of the power supply system have uncertainty, and accurate evaluation and prediction of the voltage sag characteristics and the voltage tolerance capability of the sensitive equipment are difficult. The uncertainty of the voltage sag and the uncertainty of the voltage sag are considered, the sensitive equipment fault caused by the voltage sag is defined as a fuzzy random event, the concept of a fuzzy random variable is introduced, a fuzzy random evaluation model of the fault probability of the sensitive equipment caused by the voltage sag is established, the lambda-intercept set of the fuzzy random variable is utilized, the probability solving problem of the fuzzy random variable is converted into the probability solving of a common random variable, and the feasibility of the evaluation method is guaranteed.
The existing method for calculating the voltage sag fault probability in the industrial process mainly comprises a series-parallel analysis method and a fault tree analysis method on the basis of obtaining the voltage sag fault probability of sensitive equipment.
Fault tree analysis: documents [4 to 5]Analyzing the logical relation between equipment failure AND production interruption by adopting a failure tree analysis method, wherein the top event, the middle event AND the bottom event of a failure tree are respectively process interruption, subprocess interruption AND equipment failure, the events at all levels are connected by adopting AND logic (AND) OR OR logic (OR), AND the relation between the upper-level event AND the lower-level event connected with the AND OR is defined as follows: p is a radical ofa(AND)Pb＝paPb，pa(OR)Pb＝1-(1-pa)(1-Pb). Wherein P isaAnd PbIs the probability of occurrence of events a, b.
Series-parallel analysis: document [2 ]]It is considered that in an industrial process, if the failure of any one sensitive device causes the interruption of the process, the connection mode between the devices is assumed to be in series, and if the failure of only a few sensitive devices causes the interruption of the process, the connection mode between the devices is assumed to be in parallel for a long time. In general, the process interruption probability can be calculated by:
Figure BDA0002165243650000031
wherein p isi,jIs the equipment failure probability.
Through analysis, the AND-OR logic relationship in the fault tree analysis method and the series-parallel structure relationship in the series-parallel analysis method are different expression forms of the same relationship, and the essence of the same relationship is the same, so that the essence of the two analysis methods is also the same.
When the fault probability of the sensitive equipment caused by the voltage sag is evaluated, the method generally focuses on the evaluation of the uncertainty of the voltage sag tolerance capability of the sensitive equipment, and the uncertainty of the voltage sag tolerance capability of the sensitive equipment is evaluated by adopting different mathematical methods such as probability, randomness, fuzzy randomness and the like, but the various evaluation methods can be started from the mathematical perspective, and the uncertainty of the voltage sag tolerance capability of the sensitive equipment can be characterized to a certain extent. And the influence of Process Immunity Time (PIT) on fault probability evaluation is not considered in the sensitive equipment voltage sag fault probability evaluation. These conditions may affect the accuracy of the voltage sag interruption probability estimation.
Reference documents:
[1]Gupta P，Milanovic J V.Probabilistic assessment of equipment trips due to voltage sags[J].IEEE Trans on Power Develivery，2006，21(2)：711-718.
[2]Milanovic J V，Gupta C P.Probabilistic assessment of financial losses caused by interruptions and voltage sags:part I—the methodology[J].IEEE Trans on Power Develivery，2006，21(2)：918-924.
[3]Milanovic J V，Gupta C P.Probabilistic assessment of financial lossesdue to interruptions and voltage sags—part II:practical implementation[J].IEEE Trans on Power Develivery，2006，21(2)：935-932.
[4]CHAN J Y，MILANOVIC J V，DELAHUNTY A.Generic failure risk assessment of industrial processes due to voltage sags[J].IEEE Transactions on Power Delivery，2009，24(4)：2405-2414.
[5]YASIR M，KAZEMI S，LEHTONEN M，et al.A novel approach for assessing the impacts of voltage sag events on customer operations[C]∥Electric Power Quality and Supply Reliability Conference(PQ)，2012.[S.l.]：IEEE，2012：1-5.
disclosure of Invention
The invention provides an industrial process voltage sag interruption probability evaluation method considering redundancy in order to overcome the defect that the voltage sag interruption probability evaluation in the prior art is not accurate enough.
The method comprises the following steps:
s1: acquiring voltage sag data;
s2: judging whether the rectangular sag belongs to a rectangular three-phase balance sag or not, and if so, executing the step S3; if not, the three-phase normalization is carried out, the unbalance temporary drop is converted into the balance temporary drop, and then the step S3 is executed;
s3: the running state of the equipment is divided into: a normal operation area, an uncertain area and a fault area; calculating the fault probability of the voltage sag domain of the sensitive equipment by considering the VTC and the uncertain region thereof;
s4: correcting the fault probability of the voltage sag domain of the equipment by considering the redundancy of the industrial process;
s5: and calculating the interruption probability in the industrial process by considering the logic connection mode among the sensitive devices.
Preferably, the method for judging whether the rectangular sag belongs to the rectangular three-phase balance sag comprises the following steps: the sag caused by the three-phase short circuit is a balanced sag, and the sag caused by the single-phase short circuit and the two-phase short circuit is an unbalanced sag.
Preferably, the three-phase normalization specifically operates as:
determining a voltage sag energy index:
Figure BDA0002165243650000051
wherein U (t) is the voltage sag amplitude; t issagIs the sag duration;
when calculating the energy index of the rectangular sag, since the sag amplitude and the duration are fixed values, equation (1) can be rewritten as
E＝(1-Usag 2)×Tsag (2)
In the formula of UsagSag amplitude (in pu) which is a rectangular sag;
energy index E for three-phase sagvsCalculated by the following formula:
Evs＝Evs.A+Evs.B+Evs.C (3)
in the formula Evs.A、Evs.B、Evs.CA, B, C three-phase sag energy indexes are respectively obtained through calculation of a formula (2);
temporary drop of rectangular three-phase unbalanced voltage temporary drop through formula (3)The energy index is calculated and then T is maintainedsagAnd (3) solving, in parallel with the formula (2), the following steps:
Figure BDA0002165243650000052
in the formula of Us'agThe normalized sag amplitude value is obtained; u shapesag.A、Usag.B、Usag.CA, B, C three-phase sag amplitudes, respectively.
Preferably, S3 includes the steps of:
s3.1: the operation state of the equipment is divided into: a normal operation area A; an uncertain region B, which is a region where the voltage sag tolerance of the device is uncertain; a failure region C;
(1) the normal operation region A includes t<TminAnd u is<UmaxRegion of (1) and Umax<A region of u; equipment failure rate P in normal operation area atrip.A＝0；
Wherein, Umin、UmaxRespectively serving as a minimum value and a maximum value of voltage sag amplitude tolerance of the sensitive equipment;
Tmin、Tmaxrespectively serving as a minimum value and a maximum value of voltage sag amplitude tolerance of the sensitive equipment;
(2) voltage sag tolerant capability uncertainty region B, i.e., voltage sag amplitude U satisfies Umin<u<UmaxAnd the voltage sag duration T satisfies Tmin<t<TmaxThe area of (a) is an uncertain area B;
(3) the fault area C is Tmax<t and u<UminThe area of (a); probability of failure P of devices in failure zone Ctrip.C＝1。
S3.2: the uncertainty area B is divided into: region B with high sag amplitude, short duration and low sag severity1；
Region B with longer sag duration, high sag amplitude and high sag severity2；
The temporary drop has short duration, but lower temporary drop amplitude and is temporaryRegion B of high degree of depravation3；
Wherein, B1Region satisfies Umin<u<Umax，Tmin<t<Tmax；
B2Region satisfies Umin<u<Umax，Tmax<t；
B3Region satisfies u<Umin，Tmin<t<Tmax；
S3.3: respectively calculate B1Region, B2Region, B3Probability of equipment failure due to voltage sag in the area:
(1)B1probability of equipment failure due to regional voltage sag
Figure BDA0002165243650000061
Comprises the following steps:
Figure BDA0002165243650000062
Figure BDA0002165243650000063
Figure BDA0002165243650000064
in the formula, Tm'axFor a short time maximum duration of voltage change; t ismax>t>Tmin；Umax>u>Umin；
(2)B3Probability of equipment failure due to regional voltage sag
Figure BDA0002165243650000065
Comprises the following steps:
Figure BDA0002165243650000066
Figure BDA0002165243650000067
in the formula, Tmax>t>Tmin；u<Umin；
(3)B2Probability of equipment failure due to regional voltage sag
Figure BDA0002165243650000068
Comprises the following steps:
Figure BDA0002165243650000069
Figure BDA00021652436500000610
in the formula, Tm'ax>t>Tmax；Umax>u>Umin。
Preferably, S4 is specifically operative to:
the process runs stably before the temporary drop occurs, and the process parameters are all kept at the rated value PnomAfter a temporary drop, the process parameter changes and gradually begins to deviate from the setpoint value PnomIs at t2At the moment the process parameter crosses the acceptable limit PlimitThe process is interrupted or restarted because the normal running state cannot be maintained; setting delta t as process response delay time; process immunity time, PIT ═ t2-t1Wherein t is1Is the time when the sag occurs.
If the voltage sag crosses the acceptable limit P at the value of the process parameterlimitEnding before, because supply voltage resumes, equipment restarts, after equipment output volume resumes to normal level, the process parameter begins to resume, the process restarts and begins, then the condition that the process restarted and need satisfy is successful: sag duration tsagAnd a device restart time tresAnd device restart delay Δ tESum less than process resistanceTime-of-flight PIT values, i.e.
tsag+tres+ΔtE<PIT (12)
In the formula,. DELTA.tEMainly determined by the scanning time or reaction time of the equipment control system;
therefore, the redundancy factor of the industrial process is defined as follows:
Figure BDA0002165243650000071
where PIT is the process immunity time, tsagFor the sag duration, Δ tEFor device restart delay, tres.minThe minimum restart time of the equipment after the temporary drop is finished; when the calculation result R is less than or equal to 0, the process parameter has no redundancy;
(PIT-tsag-ΔtE) Value and tresThe larger the ratio of the total redundancy of the links is, the more sufficient the restarting time obtained after the equipment fails is, the higher the probability of successful restarting of the equipment is, namely, the higher the redundancy of the links is, the higher the probability of successful recovery of normal operation of the equipment is;
for the area A, the voltage sag severity is low, and the equipment failure probability P of the areatripThe failure probability of the device after considering the redundancy is 0/R and still 0; for B and C areas, the size of R reflects whether the device restart time is sufficient, when R>1, the equipment restart time is more sufficient, the equipment fault probability becomes smaller after the redundancy is considered, and similarly, when R is<When the redundancy rate is 1, the device failure probability becomes large, and when R is 1, the redundancy rate has no influence on the device failure probability. In summary, when the redundancy factor R is greater than zero, the device voltage sag fault probability of the redundancy is considered
Figure BDA0002165243650000072
Can be calculated from the following formula:
Figure BDA0002165243650000073
where Ptrip.B (t, u) is the probability of failure of a device after being affected by a zone B dip, including
Figure BDA0002165243650000074
Figure BDA0002165243650000075
When in use
Figure BDA0002165243650000076
When it is taken
Figure BDA0002165243650000077
Preferably, the calculation formula of the interruption probability in the industrial process in S5 is:
Figure BDA0002165243650000078
in the formula
Figure BDA0002165243650000081
The fault probability of the jth parallel device in the ith series device group after being influenced by the sag is obtained; m is the number of the series equipment groups of the process; n is the number of parallel devices in the ith series device group.
The invention establishes a VTC-based sensitive equipment voltage sag fault probability evaluation model according to the position of voltage sag in an equipment voltage tolerance uncertain area and B1And B2And B1And B3The relationship between the amplitude and duration of the region sag, as B1Calculating B with region as reference2And B3The zone dip reduces the probability of equipment failure.
Based on the redundancy theory, the invention provides the method for quantifying the redundancy of the industrial process by considering the relation between each physical parameter PIT value of the industrial process and the minimum restart time of the corresponding equipment, can accurately quantify the redundancy factor of each physical parameter of the process, and uses the redundancy factor to correct the fault probability of the equipment to obtain the voltage sag of the equipment considering the redundancyProbability of failure
Figure BDA0002165243650000082
According to the industrial process voltage sag fault probability assessment method considering the redundancy, firstly, sag is normalized, then the voltage sag fault probability of sensitive equipment is calculated based on VTC and uncertain regions of the VTC, then the voltage sag fault probability of the sensitive equipment is corrected through the industrial process redundancy theory provided by the invention, and finally the industrial process voltage sag fault probability is calculated according to a connection mode among the equipment, so that the industrial process interruption probability assessment is more accurate.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that: the invention provides the sensitive equipment voltage sag fault probability evaluation method based on the uncertainty of the voltage sag tolerance capability of the sensitive equipment completely from the uncertainty of the voltage sag tolerance capability of the sensitive equipment, thereby effectively overcoming the defect that the existing evaluation methods can not accurately represent the uncertainty of the voltage sag tolerance capability of the sensitive equipment from the mathematical perspective, and improving the accuracy of the voltage sag tolerance capability evaluation of the sensitive equipment.
The invention provides an industrial process redundancy quantification method by considering the relation between each physical parameter PIT value in the industrial process and the minimum restart time of corresponding equipment based on the redundancy theory, so that the redundancy factors of each physical parameter in the process can be accurately quantified, and the redundancy factors are used for correcting the equipment fault probability to obtain the equipment voltage sag fault probability considering the redundancy.
The method firstly standardizes sag, then calculates the voltage sag fault probability of the sensitive equipment based on VTC and uncertain areas thereof, corrects the calculated voltage sag fault probability of the sensitive equipment by the industrial process redundancy theory provided by the invention, and finally calculates the voltage sag fault probability of the industrial process according to the connection mode between the equipment.
The VTC-based sensitive equipment sag fault probability evaluation model established by the invention is simple and practical, the error is reduced after the industrial process redundancy theory provided by the invention is corrected, and the accuracy is further improved compared with the existing method by calculating the voltage sag interruption probability of the industrial process according to the connection mode among the equipment.
Drawings
FIG. 1a is a CBEMA curve.
FIG. 1b is an ITIC curve.
Fig. 2 shows VTC and its uncertainty region.
FIG. 3 is a graph of a process parameter change.
Fig. 4 is a graph of process parameter changes when a process restart is successful.
Fig. 5 is a flowchart illustrating the voltage sag interruption probability evaluation method for an industrial process considering redundancy according to the embodiment.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product;
it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
The causes of voltage sag in a line can be roughly classified into three categories: system faults (mainly short circuit faults), starting of large induction motors with close electrical distances, and excitation of large transformers. The voltage sag characteristics differ from one cause to another. Firstly, voltage sag caused by short-circuit faults is analyzed, different types of sag can be caused by different short-circuit fault forms (single-phase short circuit, two-phase short circuit and three-phase short circuit), wherein three-phase short circuit causes three-phase balance sag, and other short circuit types cause unbalance sag. The sag caused by the short-circuit fault is a rectangular sag, the amplitude transformation of the voltage of the sag is in a rectangular shape, namely, the amplitude is suddenly changed at the moment of starting and ending of the sag, and the amplitude is basically unchanged during the sag; for voltage sag caused by starting of a large induction motor with a short electrical distance, three-phase currents generated by starting of the induction motor are equal, and three-phase voltages are also equal, so that the sag is a balance sag. In addition, the motor is started to cause the instantaneous reduction and then slow recovery of three-phase voltage, and the motor belongs to non-rectangular temporary reduction; for voltage sag caused by excitation of a large transformer, the voltage sag is the same as the sag caused by starting of a motor, the recovery process of the sag is slow, and the amplitude value cannot be suddenly changed in the recovery process, so the sag caused by excitation of the transformer also belongs to non-rectangular sag, but initial phase angles of a three-phase transformer in operation are always different from each other by 120 degrees, the three-phase exciting currents of the transformer are inevitably different in magnitude, and the sag caused by excitation of the transformer is always unbalanced.
From the above analysis it can be concluded that most voltage sags in the grid are unbalanced and non-rectangular sags, while rectangular three-phase balanced sags are less. However, in many documents related to sag at home and abroad, the mentioned sag is mostly referred to as a rectangular three-phase balance sag. The reason for this is mainly that the duration and the dip amplitude of the rectangular three-phase balanced dip are easier to determine and more convenient to discuss than the unbalanced non-rectangular dip. It is easy to see that the existing conclusion of the rectangular three-phase balance sag is also applicable to the unbalanced and non-rectangular sag, which becomes an effective way to solve the above problems.
The embodiment provides an industrial process voltage sag interruption probability evaluation method considering redundancy. As shown in fig. 5, the method comprises the steps of:
s1: acquiring voltage sag data;
s2: judging whether the rectangular sag belongs to a rectangular three-phase balance sag or not, and if so, executing the step S3; if not, the three-phase normalization is performed, the unbalanced temporary drop is converted into a balanced temporary drop, and then the step S3 is executed.
The three-phase normalization of the voltage sag is as follows:
the causes of voltage sag in a line can be roughly classified into three categories: short circuit faults, starting of large induction motors at close electrical distances and excitation of large transformers.
The sag caused by the short-circuit fault is a rectangular sag, wherein the sag caused by the three-phase short circuit is a balanced sag, and the sag caused by the single-phase short circuit and the two-phase short circuit is an unbalanced sag. When various evaluations are performed on unbalanced sag, the lowest amplitude (in the present embodiment, all refer to a residual voltage effective value) of three phases is usually selected as a sag amplitude, and this inevitably brings a large error to the evaluation result. The embodiment provides a voltage sag three-phase normalization method, and the unbalanced sag is converted into the balanced sag on the premise of keeping the sag loss energy unchanged, so that errors caused by the method are avoided, and the accuracy of an evaluation result is improved.
The voltage sag energy index is defined as follows:
Figure BDA0002165243650000101
wherein U (t) is the voltage sag amplitude; t issagIs the sag duration.
When calculating the energy index of the rectangular sag, since the sag amplitude and the duration are fixed values, equation (1) can be rewritten as:
E＝(1-Usag 2)×Tsag (2)
in the formula of UsagThe sag amplitude (in pu) of the rectangular sag.
Energy index E for three-phase sagvsPair can be calculated by:
Evs＝Evs.A+Evs.B+Evs.C (3)
in the formula Evs.A、Evs.B、Evs.CThe sag energy indexes of the A, B, C three phases are respectively calculated by formula (2).
Firstly, the temporary drop energy of the rectangular three-phase unbalanced voltage temporary drop is calculated by the formula (3)The index is calculated and then T is maintainedsagAnd (3) solving, in parallel with the formula (2), the following steps:
Figure BDA0002165243650000111
in formula (II)'sagThe normalized sag amplitude value is obtained; u shapesag.A、Usag.B、Usag.CA, B, C three-phase sag amplitudes, respectively.
The sag caused by the starting of the large induction motor and the excitation of the large transformer is a non-rectangular sag, the sag has low frequency and amplitude of more than 0.85pu, the sag has low severity, and equipment failure is difficult to cause. Therefore, the sag caused by the two reasons is not considered when the industrial process voltage sag interruption probability is evaluated in the embodiment.
S3 divides the device operation state into: a normal operation area, an uncertain area and a fault area; and calculating the fault probability of the voltage sag domain of the sensitive equipment by considering the VTC and the uncertain region thereof.
The voltage sag tolerance of a sensitive device has uncertainty, the uncertainty region of which is shown in fig. 2, where Tmin、TmaxAnd Umin、UmaxA voltage sag tolerance limit for sensitive equipment; when the equipment is influenced by the sag of the area A (outside the curve 1), the running state of the equipment is normal, so the area A is a normal running area, and when the equipment is influenced by the sag of the area, the fault probability P of the equipment istrip.A0; when the equipment is affected by the sag in the C region (inside curve 2), the running state of the equipment is a fault, so that the C region is a fault region, and the fault probability P of the equipment is affected by the sag in the C region trip.C1 is ═ 1; region B (inner side of curve 1, outer side of curve 2, including B)1、B2And B3Region) is an uncertain region, when the device is influenced by voltage sag in the B region, the voltage sag consequence state of the device also has uncertainty due to uncertainty of the voltage sag tolerance capability of the device, and how to quantify the uncertainty now becomes the failure probability of the deviceEmphasis in rate evaluation.
According to different classes of equipment, domestic and foreign scholars typically sense sensitive equipment, including: a large number of tests were performed on a Personal Computer (PC), a Programmable Logic Controller (PLC), and an Adjustable Speed Drive (ASD), and the obtained uncertainty range of the voltage endurance of the device is shown in table 1.
TABLE 1 uncertain range of voltage withstand capability of typical sensitive equipment
Figure BDA0002165243650000121
Subdividing the B area into B areas according to the characteristics of the voltage sag amplitude and the duration of different sub-areas in the B area1、B2And B3And (4) a region. Wherein, in B1In the region, the sag is characterized in that the sag amplitude U and the duration t both satisfy Umin<u<Umax，Tmin<t<TmaxNamely, the sag amplitude is high and the duration is short, and the sag severity is relatively low; in B2In the region, the sag is characterized in that the amplitude U and the duration t both satisfy Umin<u<Umax，Tmax<t, namely the sag duration is longer, but the sag amplitude is high, and the sag severity is higher; in B3In the region, the sag is characterized in that the amplitude u and the duration t both satisfy u<Umin，Tmin<t<TmaxNamely, the sag duration is short, but the sag amplitude is low, and the sag severity is high.
This example is obtained by analysis B1And B2And B1And B3The relation between the regional sag amplitude and the duration provides a device sag fault probability evaluation method based on a Voltage Tolerance Curve (VTC) of sensitive devices, which can effectively overcome the disadvantages of the conventional evaluation method, and the VTC and the uncertain region thereof are shown in fig. 2.
As shown in FIG. 2, B1Two dips of equal duration in a zone Su1And Su2Due to Su1The sag value of is greater than Su2Temporarily decrease the amplitude ofTo temporarily decrease Su2Is higher, its impact on the equipment is also greater. Thus, the same device is subjected to B1Two dips in a zone affect the probability of a device failure
Figure BDA0002165243650000122
As can be seen, in FIG. 2, B1And (4) temporarily dropping in the region, wherein under the condition of a certain duration, the equipment fault probability is inversely proportional to the temporarily dropping amplitude, namely the equipment fault probability is inversely proportional to the distance from the temporarily dropping to the T axis. In the same way, B1In the region, when the temporary drop amplitude is constant, the probability of equipment failure is temporarily dropped to TminIs proportional to the distance of (c). Therefore, B1Probability of equipment failure due to zone sag
Figure BDA0002165243650000123
Can be given by:
Figure BDA0002165243650000124
Figure BDA0002165243650000125
Figure BDA0002165243650000126
in formula (II)'maxFor a short time maximum duration of voltage change; t ismax>t>Tmin；Umax>u>Umin。
As shown in fig. 2, B is the same for the sag duration t3Sag S of a regionu3And B1Sag S of a regionu2In contrast, the difference is only in the sag value u2>u3But also considering B3Characteristics of the region, in1Regional equipment sag failure probability
Figure BDA0002165243650000131
On the basis of B3Probability of equipment failure due to zone sag
Figure BDA0002165243650000132
Can be given by:
Figure BDA0002165243650000133
Figure BDA0002165243650000134
in the formula Tmax>t>Tmin；u<Umin。
In the same way, B2Probability of equipment failure due to zone sag
Figure BDA0002165243650000135
Can be given by:
Figure BDA0002165243650000136
Figure BDA0002165243650000137
in formula (II)'max>t>Tmax；Umax>u>Umin。
S4: and correcting the fault probability of the voltage sag domain of the equipment by considering the redundancy of the industrial process.
Assessing the probability of an interruption of an industrial process due to a voltage sag requires consideration of the redundancy of the industrial process. Redundancy is the concept proposed, from a safety point of view, to characterize the ability of an engineered structure or mechanical strength to have sufficient properties to maintain its proper operation without breaking its integrity under foreseeable extreme conditions.
At present, the redundancy theory has been widely researched and applied in the fields of civil engineering, mechanical manufacturing and the like. In the embodiment, the relationship between each physical parameter PIT value and the minimum restart time of the corresponding equipment is considered, so that the redundancy of the industrial process is accurately quantified.
As shown in FIG. 3, the process is operating steadily with the process parameters maintained at the nominal value P before the sag occursnom，t1The temporary drop occurs at a moment, the process parameters change and gradually begin to deviate from the rated value PnomAt t2At the moment the process parameter crosses the acceptable limit PlimitThe process is interrupted or restarted because the normal running state cannot be maintained; Δ t is the process response delay time; process immunity time, PIT ═ t2-t1。
If the voltage sag crosses the acceptable limit P at the value of the process parameterlimitAnd ending before, restarting the equipment due to the recovery of the power supply voltage, starting the recovery of the process parameters after the output quantity of the equipment is recovered to a normal level, and starting the restart of the process.
As can be seen from fig. 4, the conditions to be satisfied when the process is restarted successfully are as follows: sag duration tsagAnd a device restart time tresAnd device restart delay Δ tEThe sum is less than the process immunity time PIT value, i.e.:
tsag+tres+ΔtE<PIT (12)
in the formula,. DELTA.tEMainly determined by the scan time or reaction time of the plant control system.
From the above analysis, in combination with the definition of "degree of intensity redundancy" in structural mechanics, this example will be (PIT-t)sag-ΔtE) Value and tresThe ratio of (A) is defined as the Redundancy factor (R) of the industrial process, and is defined as follows:
Figure BDA0002165243650000141
in the formula tres.minThe minimum restart time of the equipment after the pause is finished. And when the calculation result R is less than or equal to 0, the process parameter has no redundancy.
From the redundancy point of view, (PIT-t)sag-ΔtE) Value and tresThe larger the ratio of (a) is, the more sufficient the restarting time obtained after the equipment fails is, the larger the probability of the equipment restarting success is, that is, the greater the redundancy of the link is, the greater the probability of the equipment restarting success in recovering to normal operation is.
For the area A, the voltage sag severity is low, and the equipment failure probability P of the areatripThe failure probability of the device after considering the redundancy is 0/R and still 0; for B and C areas, the size of R reflects whether the device restart time is sufficient, when R>1, the equipment restart time is more sufficient, the equipment fault probability becomes smaller after the redundancy is considered, and similarly, when R is<When the redundancy rate is 1, the device failure probability becomes large, and when R is 1, the redundancy rate has no influence on the device failure probability. In summary, when the redundancy factor R is greater than zero, the device voltage sag fault probability of the redundancy is considered
Figure BDA0002165243650000142
Can be calculated from the following formula:
Figure BDA0002165243650000143
in the formula Ptrip.B(t, u) is the probability of failure after the device is affected by the B zone dip, including
Figure BDA0002165243650000144
Figure BDA0002165243650000145
When in use
Figure BDA0002165243650000146
When it is taken
Figure BDA0002165243650000147
S5: and calculating the interruption probability in the industrial process by considering the logic connection mode among the sensitive devices.
The interruption probability of a link after being affected by the sag is not only related to the single equipment failure probability but also related to the logical connection mode between the equipments, and the interruption probability of the industrial process considering the interconnection mode between the equipments can be given by the following formula:
Figure BDA0002165243650000151
in the formula
Figure BDA0002165243650000152
The fault probability of the jth parallel device in the ith series device group after being influenced by the sag is obtained; m is the number of the series equipment groups of the process; n is the number of parallel devices in the ith series device group.
The terms describing positional relationships in the drawings are for illustrative purposes only and are not to be construed as limiting the patent;
it should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (4)

1. An industrial process voltage sag outage probability assessment method considering redundancy, characterized by comprising the following steps:
s1: acquiring voltage sag data;
s2: judging whether the rectangular sag belongs to a rectangular three-phase balance sag or not, and if so, executing the step S3; if not, the three-phase normalization is carried out, the unbalance temporary drop is converted into the balance temporary drop, and then the step S3 is executed;
s3: the running state of the equipment is divided into: a normal operation area, an uncertain area and a fault area; calculating the fault probability of the voltage sag domain of the sensitive equipment by considering the VTC and the uncertain region thereof;
s4: correcting the fault probability of the voltage sag domain of the equipment by considering the redundancy of the industrial process;
s5: calculating the interruption probability in the industrial process by considering the logic connection mode among the sensitive devices;
s3 includes the steps of:
s3.1: the operation state of the equipment is divided into: a normal operation area A; an uncertain region B, which is a region where the voltage sag tolerance of the device is uncertain; a failure region C;
(1) the normal operation region A includes t<TminAnd u is<UmaxRegion of (1) and Umax<A region of u; equipment failure rate P in normal operation area atrip.A＝0；
Wherein, Umin、UmaxRespectively serving as a minimum value and a maximum value of voltage sag amplitude tolerance of the sensitive equipment;
Tmin、Tmaxrespectively serving as a minimum value and a maximum value of voltage sag amplitude tolerance of the sensitive equipment;
(2) voltage sag tolerant capability uncertainty region B, i.e., voltage sag amplitude U satisfies Umin<u<UmaxAnd the voltage sag duration T satisfies Tmin<t<TmaxThe area of (a) is an uncertain area B;
(3) the fault area C is Tmax<t and u<UminThe area of (a); probability of failure P of devices in failure zone Ctrip.C＝1；
S3.2: the uncertainty area B is divided into: region B with high sag amplitude, short duration and low sag severity1；
Region B with longer sag duration, high sag amplitude and high sag severity2；
Region B with short sag duration, low sag amplitude and high sag severity3；
Wherein, B1Region satisfies Umin<u<Umax，Tmin<t<Tmax；
B2Region satisfies Umin<u<Umax，Tmax<t；
B3Region satisfies u<Umin，Tmin<t<Tmax；
S3.3: respectively calculate B1Region, B2Region, B3Probability of equipment failure due to voltage sag in the area:
(1)B1probability of equipment failure due to regional voltage sag
Figure FDA0002582369550000021
Comprises the following steps:
Figure FDA0002582369550000022
Figure FDA0002582369550000023
Figure FDA0002582369550000024
in formula (II) T'maxFor a short time maximum duration of voltage change; t ismax＞t＞Tmin；Umax＞u＞Umin；
(2)B3Probability of equipment failure due to regional voltage sag
Figure FDA0002582369550000025
Comprises the following steps:
Figure FDA0002582369550000026
Figure FDA0002582369550000027
in the formula, Tmax＞t＞Tmin；u＜Umin；
(3)B2Probability of equipment failure due to regional voltage sag
Figure FDA0002582369550000028
Comprises the following steps:
Figure FDA0002582369550000029
Figure FDA00025823695500000210
in formula (II) T'max＞t＞Tmax；Umax＞u＞Umin；
The S4 concrete operation is:
the process runs stably before the temporary drop occurs, and the process parameters are all kept at the rated value PnomAfter a temporary drop, the process parameter changes and gradually begins to deviate from the setpoint value PnomIs at t2At the moment the process parameter crosses the acceptable limit PlimitThe process is interrupted or restarted because the normal running state cannot be maintained; setting delta t as process response delay time; process immunity time, PIT ═ t2-t1Wherein t is1Is the time of the sag;
if the voltage sag crosses the acceptable limit P at the value of the process parameterlimitEnding before, because supply voltage resumes, equipment restarts, after equipment output volume resumes to normal level, the process parameter begins to resume, the process restarts and begins, then the condition that the process restarted and need satisfy is successful: sag duration tsagAnd a device restart time tresAnd device restart delay Δ tEThe sum being less than the process immunity time PIT value, i.e.
tsag+tres+ΔtE＜PIT (12)
In the formula,. DELTA.tEMainly determined by the scanning time or reaction time of the equipment control system;
therefore, the redundancy factor of the industrial process is defined as follows:
Figure FDA0002582369550000031
where PIT is the process immunity time, tsagFor the sag duration, Δ tEFor device restart delay, tres.minThe minimum restart time of the equipment after the temporary drop is finished; when the calculation result R is less than or equal to 0, the process parameter has no redundancy;
(PIT-tsag-ΔtE) Value and tresThe larger the ratio of the total redundancy of the links is, the more sufficient the restarting time obtained after the equipment fails is, the higher the probability of successful restarting of the equipment is, namely, the higher the redundancy of the links is, the higher the probability of successful recovery of normal operation of the equipment is;
for the area A, the voltage sag severity is low, and the equipment failure probability P of the areatripThe failure probability of the device after considering the redundancy is 0/R and still 0; for B and C areas, the size of R reflects whether the device restart time is sufficient, when R>1, the equipment restart time is more sufficient, the equipment fault probability becomes smaller after the redundancy is considered, and similarly, when R is<When the redundancy rate is 1, the equipment failure probability is increased, and when R is 1, the redundancy rate has no influence on the equipment failure probability;
in summary, when the redundancy factor R is greater than zero, the device voltage sag fault probability of the redundancy is considered
Figure FDA0002582369550000032
Can be calculated from the following formula:
Figure FDA0002582369550000033
in the formula Ptrip.B (t, u) Ptrip.B(t, u) is the probability of failure after the device is affected by the B zone dip, including
Figure FDA0002582369550000034
Figure FDA0002582369550000035
When in use
Figure FDA0002582369550000036
When it is taken
Figure FDA0002582369550000037
2. The method for assessing the voltage sag outage probability of the industrial process considering the redundancy rate as claimed in claim 1, wherein the method for judging whether the rectangular sag belongs to the rectangular three-phase balanced sag is as follows: the sag caused by the three-phase short circuit is a balanced sag, and the sag caused by the single-phase short circuit and the two-phase short circuit is an unbalanced sag.
3. The redundancy-considered industrial process voltage sag outage probability assessment method according to claim 1, characterized in that the three-phase normalization is specifically operated as:
determining a voltage sag energy index:
Figure FDA0002582369550000038
wherein U (t) is the voltage sag amplitude; t issagIs the sag duration;
when calculating the energy index of the rectangular sag, since the sag amplitude and the duration are fixed values, equation (1) can be rewritten as
E＝(1-Usag 2)×Tsag (2)
In the formula of UsagA sag amplitude value which is a rectangular sag;
energy finger for three-phase sagMark EvsCalculated by the following formula:
Evs＝Evs.A+Evs.B+Evs.C (3)
in the formula Evs.A、Evs.B、Evs.CA, B, C three-phase sag energy indexes are respectively obtained through calculation of a formula (2);
calculating a sag energy index of a rectangular three-phase unbalanced voltage sag by using the formula (3), and then keeping TsagIs not changed and is simultaneously combined with the formula (2) to obtain
Figure FDA0002582369550000041
In formula (II)'sagThe normalized sag amplitude value is obtained; u shapesag.A、Usag.B、Usag.CA, B, C three-phase sag amplitudes, respectively.
4. The method for estimating voltage sag outage probability of an industrial process under consideration of redundancy according to claim 1, wherein the calculation formula of the outage probability of the industrial process in S5 is as follows:
Figure FDA0002582369550000042
in the formula
Figure FDA0002582369550000043
The fault probability of the jth parallel device in the ith series device group after being influenced by the sag is obtained; m is the number of the series equipment groups of the process; n is the number of parallel devices in the ith series device group.
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