阅读说明：本技术 一种确定交直流配电网韧性的方法及系统 (Method and system for determining toughness of alternating current-direct current power distribution network ) 是由 王赛一 黄鑫 沈豪栋 许唐云 陈洁 王旭 周士超 熊展 蒋传文 于 2021-06-11 设计创作，主要内容包括：本发明公开了一种确定交直流配电网韧性的方法及系统,包括：基于线路故障率模型计算交直流配电网的每条线路在不同天气环境下的线路故障率；根据每条线路在不同天气环境下的线路故障率,利用蒙特卡洛方法确定每种天气环境下每条线路的运行状态；根据不同天气环境下每条线路的运行状态分别计算用于确定交直流配电网韧性的每种评价指标的指标值；根据每种评价指标的指标值确定交直流配电网的韧性,以根据所述韧性确定交直流配电网的韧性性能,实现对交直流配电网的韧性的准确评估。(The invention discloses a method and a system for determining toughness of an AC/DC power distribution network, wherein the method comprises the following steps: calculating the line fault rate of each line of the AC/DC power distribution network under different weather environments based on the line fault rate model; determining the running state of each line under each weather environment by using a Monte Carlo method according to the line fault rate of each line under different weather environments; respectively calculating index values of each evaluation index for determining the toughness of the AC/DC power distribution network according to the running state of each line in different weather environments; and determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index, and determining the toughness performance of the AC/DC power distribution network according to the toughness to realize accurate evaluation of the toughness of the AC/DC power distribution network.)

1. A method for determining toughness of an AC/DC power distribution network, the method comprising:

calculating the line fault rate of each line of the AC/DC power distribution network under different weather environments based on the line fault rate model;

determining the running state of each line under each weather environment by using a Monte Carlo method according to the line fault rate of each line under different weather environments;

respectively calculating index values of each evaluation index for determining the toughness of the AC/DC power distribution network according to the running state of each line in different weather environments;

and determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index so as to determine the toughness performance of the AC/DC power distribution network according to the toughness.

2. The method of claim 1, wherein calculating the line fault rate for each line of the ac/dc power distribution grid based on the line fault rate model using:

wherein the content of the first and second substances,is the failure rate of line ij; m is the number of the supporting towers of the line ij; n is the number of conducting wires among towers;is the failure rate of the kth tower, andrepresenting the fault rate of the h-th wire; p represents a tower; and c represents a wire.

3. The method according to claim 2, wherein when the line is in an icy and snowy weather environment, the failure rate of the tower is calculated by using the following methodAnd failure rate of the conductorThe method comprises the following steps:

wherein alpha is_p、α_c、β_pAnd beta_cAll are preset model coefficients; eta_cAnd η_pRespectively the longitudinal icing load rates of the lead and the tower; k is a radical of₁And k₂Weight coefficients, k, corresponding to line icing load and tidal current in the line fault rate, respectively₁+k₂＝1；p_ijIs the distribution network trend; p represents a tower; c represents a wire;

when the line is in a typhoon weather environment, calculating the fault rate of the tower and the fault rate of the lead by using the following modes:

wherein M is_TBending moment born by the root of the tower; m_pThe maximum bending resistance of the tower is achieved; mu.s_pAnd delta_pRespectively obtaining the expectation and standard deviation of normal distribution of the bending strength of the tower; sigma_lThe maximum bearing capacity of the wire under wind tension; sigma_gStress applied to the cross section of the wire by typhoon; mu.s_lAnd delta_lRespectively, the expected and standard deviation of the normal distribution of the tensile strength of the wire.

4. The method of claim 1, wherein the method determines the operational status of each line in each weather environment using a monte carlo method by:

wherein x is_ijThe operation state of the line ij under certain weather environment; for any line (i, j) ∈ Ω_LIn the interval [0, 1]Uniformly distributed random numbers r are generated;the failure rate of the line ij under certain weather environment; omega_LIs a distribution network node set.

5. The method according to claim 1, wherein the evaluation index includes: a strain index, a defense index, and a restoring force index; wherein the content of the first and second substances,

the strain gauge comprises: the emergency resource proportion, the emergency resource supply rate, the remote control feeder switch configuration rate and the AC/DC tie line supply rate can be scheduled;

the defense strength index comprises: expected number of line faults;

the restoring force index includes: important load power loss time, important load power loss rate and distribution network load shedding total loss.

6. The method of claim 1, wherein determining the toughness of the ac/dc distribution network based on the index value of each evaluation index comprises:

determining the weight of each evaluation index based on an approximate ideal ordering method TOPSIS and an entropy weight method, and determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index and the corresponding weight.

7. A system for determining the toughness of an ac/dc power distribution network, the system comprising:

the line fault rate calculation unit is used for calculating the line fault rate of each line of the alternating current-direct current power distribution network under different weather environments based on a line fault rate model;

the operation state determining unit is used for determining the operation state of each line under each weather environment by using a Monte Carlo method according to the line fault rate of each line under different weather environments;

the evaluation index calculation unit is used for calculating the index value of each evaluation index for determining the toughness of the AC/DC distribution network according to the running state of each line in different weather environments;

and the toughness determining unit is used for determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index so as to determine the toughness performance of the AC/DC power distribution network according to the toughness.

8. The system of claim 7, wherein the line fault rate calculation unit calculates the line fault rate for each line of the ac/dc power distribution grid based on the line fault rate model by:

wherein the content of the first and second substances,is the failure rate of line ij; m is the number of the supporting towers of the line ij; n is the number of conducting wires among towers;is the failure rate of the kth tower, andrepresenting the fault rate of the h-th wire; p represents a tower; and c represents a wire.

9. The system according to claim 7, wherein the line fault rate calculation unit calculates the fault rate of the tower when the line is in the icy and snowy weather environment by using the following methodAnd failure rate of the conductorThe method comprises the following steps:

wherein alpha is_p、α_c、β_pAnd beta_cAll are preset model coefficients; eta_cAnd η_pRespectively the longitudinal icing load rates of the lead and the tower; k is a radical of₁And k₂Weight coefficients, k, corresponding to line icing load and tidal current in the line fault rate, respectively₁+k₂＝1；p_ijIs the distribution network trend; p represents a tower; c represents a wire;

when the line is in a typhoon weather environment, calculating the fault rate of the tower and the fault rate of the lead by using the following modes:

wherein M is_TBending moment born by the root of the tower; m_pThe maximum bending resistance of the tower is achieved; mu.s_pAnd delta_pRespectively obtaining the expectation and standard deviation of normal distribution of the bending strength of the tower; sigma_lThe maximum bearing capacity of the wire under wind tension; sigma_gStress applied to the cross section of the wire by typhoon; mu.s_lAnd delta_lRespectively, the expected and standard deviation of the normal distribution of the tensile strength of the wire.

10. The system according to claim 7, wherein the operation state determination unit determines the operation state of each line in each weather environment by using a monte carlo method in a manner including:

wherein x is_ijThe operation state of the line ij under certain weather environment; for any oneLine (i, j) is equal to omega_LIn the interval [0, 1]Uniformly distributed random numbers r are generated;the failure rate of the line ij under certain weather environment; omega_LIs a distribution network node set.

11. The system of claim 7, wherein the evaluation index comprises: a strain index, a defense index, and a restoring force index; wherein the content of the first and second substances,

the strain gauge comprises: the emergency resource proportion, the emergency resource supply rate, the remote control feeder switch configuration rate and the AC/DC tie line supply rate can be scheduled;

the defense strength index comprises: expected number of line faults;

the restoring force index includes: important load power loss time, important load power loss rate and distribution network load shedding total loss.

12. The system according to claim 7, wherein the toughness determination unit determines the toughness of the ac/dc distribution network based on the index value of each evaluation index, and includes:

determining the weight of each evaluation index based on an approximate ideal ordering method TOPSIS and an entropy weight method, and determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index and the corresponding weight.

Technical Field

The invention relates to the technical field of coping under extreme events of an alternating current-direct current power distribution network, in particular to a method and a system for determining toughness of the alternating current-direct current power distribution network.

Background

With the leap-type development of power electronic technology and the great progress of the automation level of protection and control of the power distribution network, the difficulty hindering the application and construction of the direct-current power distribution network is gradually overcome. The form of an alternating current-direct current distribution grid (HDG) power distribution network has the characteristics of an alternating current distribution network and a direct current distribution network, not only retains the advantages of the traditional alternating current distribution network, but also can effectively break through the development bottleneck of the alternating current distribution network, and will certainly become one of the main structural forms of the future intelligent power distribution network. Before the alternating current-direct current hybrid power distribution network is widely constructed and applied, key technical problems still need to be solved, and one of the key technical problems is a toughness improvement strategy facing extremely small-probability high-risk events.

Two measures are usually taken to improve the toughness of the power distribution network, namely a precautionary measure before a disaster and a recovery measure during/after the disaster. The preventive measures are that when the system is greatly disturbed, the severity of the influence of the disturbance on the power distribution network is judged in advance through related forecast information, the operation mode of the power distribution network is switched rapidly, the power distribution network is in the best operation state, the power failure range is narrowed, and the regulation and control mode of key load power utilization is supported. The recovery measure is a regulation and control mode that the power distribution network takes active measures to ensure that the key load is not powered off and quickly recovers to an expected state under the normal condition of the system during or after the system is subjected to large disturbance.

Toughness (resilience) was originally proposed and introduced into the field of ecosystem research by the canadian ecologist c.s.holling, and was later gradually generalized to power systems and distribution networks for evaluating the performance of distribution networks before and after the occurrence of rare high-risk extreme events. The core characteristics of the method comprise dependent stress, namely the power distribution network has the capability of prejudging the evolution law and influence of an event before encountering a large-scale disturbance event, and corresponding preparatory and preventive measures are taken; the defense force is that the power distribution network has the ability to make emergency response to the event by adjusting flexible resources in the occurrence process of the disturbance event, so that the influence and interference of the event are reduced, and the power distribution network is maintained at a higher operation level as much as possible; the restoring force, namely after a disturbance event occurs, the power distribution network has the capability of rapidly starting a repairing mechanism and restoring to a normal operation state, so that the duration of the fault influence is reduced.

Many documents quantitatively evaluate the toughness of the power distribution network around core characteristics, and provide a series of practical evaluation indexes. And starting from an extreme event causing large-scale faults of the power distribution network, the students consider uncertainty of time-space characteristic evolution of the extreme event, analyze the influence of the extreme event on the power distribution network lines and construct a multi-stage uncertain fault set of the power distribution network lines. However, the current method for evaluating the toughness of the power distribution network, whether an analog method, an analytical method or a statistical method, mostly belongs to post analysis, namely after an extreme event occurs, the economic loss and the social adverse effect caused by the extreme event are evaluated.

Disclosure of Invention

The invention provides a method and a system for determining toughness of an alternating current-direct current power distribution network, and aims to solve the problem of how to evaluate the toughness of the alternating current-direct current power distribution network.

In order to solve the above problem, according to an aspect of the present invention, there is provided a method for determining toughness of an ac/dc power distribution network, the method comprising:

calculating the line fault rate of each line of the AC/DC power distribution network under different weather environments based on the line fault rate model;

determining the running state of each line under each weather environment by using a Monte Carlo method according to the line fault rate of each line under different weather environments;

respectively calculating index values of each evaluation index for determining the toughness of the AC/DC power distribution network according to the running state of each line in different weather environments;

and determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index so as to determine the toughness performance of the AC/DC power distribution network according to the toughness.

Preferably, the calculating a line fault rate of each line of the ac/dc power distribution network based on the line fault rate model by using the following method includes:

wherein the content of the first and second substances,is the failure rate of line ij; m is the number of the supporting towers of the line ij; n is the number of conducting wires among towers;is the failure rate of the kth tower, andrepresenting the fault rate of the h-th wire; p represents a tower; and c represents a wire.

Preferably, when the line is in an ice and snow weather environment, the fault rate of the tower is calculated in the following wayAnd failure rate of the conductorThe method comprises the following steps:

wherein alpha is_p、α_c、β_pAnd beta_cAll are preset model coefficients; eta_cAnd η_pRespectively the longitudinal icing load rates of the lead and the tower; k is a radical of₁And k₂Weight coefficients, k, corresponding to line icing load and tidal current in the line fault rate, respectively₁+k₂＝1；p_ijIs the distribution network trend; p represents a tower; c represents a wire;

when the line is in a typhoon weather environment, calculating the fault rate of the tower and the fault rate of the lead by using the following modes:

wherein M is_TBending moment born by the root of the tower; m_pThe maximum bending resistance of the tower is achieved; mu.s_pAnd delta_pRespectively obtaining the expectation and standard deviation of normal distribution of the bending strength of the tower; sigma_lThe maximum bearing capacity of the wire under wind tension; sigma_gStress applied to the cross section of the wire by typhoon; mu.s_lAnd delta_lRespectively positive tensile strength of the wireExpectation and standard deviation of the state distribution.

Preferably, the method determines the operation state of each line in each weather environment by using a monte carlo method in the following way:

wherein x is_ijThe operation state of the line ij under certain weather environment; for any line (i, j) ∈ Ω_LIn the interval [0, 1]Uniformly distributed random numbers r are generated;the failure rate of the line ij under certain weather environment; omega_LIs a distribution network node set.

Preferably, the evaluation index includes: a strain index, a defense index, and a restoring force index; wherein the content of the first and second substances,

the strain gauge comprises: the emergency resource proportion, the emergency resource supply rate, the remote control feeder switch configuration rate and the AC/DC tie line supply rate can be scheduled;

the defense strength index comprises: expected number of line faults;

the restoring force index includes: important load power loss time, important load power loss rate and distribution network load shedding total loss.

Preferably, the determining the toughness of the ac/dc distribution network according to the index value of each evaluation index includes:

determining the weight of each evaluation index based on an approximate ideal ordering method TOPSIS and an entropy weight method, and determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index and the corresponding weight.

According to another aspect of the invention, there is provided a system for determining the toughness of an ac/dc power distribution network, the system comprising:

the line fault rate calculation unit is used for calculating the line fault rate of each line of the alternating current-direct current power distribution network under different weather environments based on a line fault rate model;

the operation state determining unit is used for determining the operation state of each line under each weather environment by using a Monte Carlo method according to the line fault rate of each line under different weather environments;

the evaluation index calculation unit is used for calculating the index value of each evaluation index for determining the toughness of the AC/DC distribution network according to the running state of each line in different weather environments;

and the toughness determining unit is used for determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index so as to determine the toughness performance of the AC/DC power distribution network according to the toughness.

Preferably, the line fault rate calculation unit calculates the line fault rate of each line of the ac/dc power distribution network based on the line fault rate model by using the following method, including:

wherein the content of the first and second substances,is the failure rate of line ij; m is the number of the supporting towers of the line ij; n is the number of conducting wires among towers;is the failure rate of the kth tower, andrepresenting the fault rate of the h-th wire; p represents a tower; and c represents a wire.

Preferably, the line fault rate calculation unit calculates the fault rate of the tower in the following manner when the line is in the ice and snow weather environmentAnd failure rate of the conductorThe method comprises the following steps:

wherein alpha is_p、α_c、β_pAnd beta_cAll are preset model coefficients; eta_cAnd η_pRespectively the longitudinal icing load rates of the lead and the tower; k is a radical of₁And k₂Weight coefficients, k, corresponding to line icing load and tidal current in the line fault rate, respectively₁+k₂＝1；p_ijIs the distribution network trend; p represents a tower; and c represents a wire.

When the line is in a typhoon weather environment, calculating the fault rate of the tower and the fault rate of the lead by using the following modes:

wherein M is_TBending moment born by the root of the tower; m_pThe maximum bending resistance of the tower is achieved; mu.s_pAnd delta_pRespectively obtaining the expectation and standard deviation of normal distribution of the bending strength of the tower; sigma_lThe maximum bearing capacity of the wire under wind tension; sigma_gStress applied to the cross section of the wire by typhoon; mu.s_lAnd delta_lRespectively, the expected and standard deviation of the normal distribution of the tensile strength of the wire.

Preferably, the determining unit of the operating state determines the operating state of each line in each weather environment by using a monte carlo method, including:

wherein x is_ijThe operation state of the line ij under certain weather environment; for any line (i, j) ∈ Ω_LIn the interval [0, 1]Uniformly distributed random numbers r are generated;the failure rate of the line ij under certain weather environment; omega_LIs a distribution network node set.

Preferably, the evaluation index includes: a strain index, a defense index, and a restoring force index; wherein the content of the first and second substances,

the strain gauge comprises: the emergency resource proportion, the emergency resource supply rate, the remote control feeder switch configuration rate and the AC/DC tie line supply rate can be scheduled;

the defense strength index comprises: expected number of line faults;

the restoring force index includes: important load power loss time, important load power loss rate and distribution network load shedding total loss.

Preferably, the toughness determining unit determines the toughness of the ac/dc distribution network according to the index value of each evaluation index, and includes:

determining the weight of each evaluation index based on an approximate ideal ordering method TOPSIS and an entropy weight method, and determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index and the corresponding weight.

The invention provides a method and a system for determining toughness of an AC/DC power distribution network, which are used for constructing a line fault rate model under the influence of disasters for natural disasters, generating a fault set based on Monte Carlo sampling, constructing an AC/DC hybrid power distribution network toughness evaluation index set according to toughness core characteristics such as strain capacity, defense capacity and restoring force, aiming at the running characteristics of the AC/DC hybrid power distribution network, solving objective weights of all indexes based on an entropy weight method, obtaining an AC/DC hybrid power distribution network toughness comprehensive evaluation result based on an approximate ideal solution sorting method, and accurately evaluating the toughness of the AC/DC power distribution network.

Drawings

A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:

FIG. 1 is a flow chart of a method 100 of determining toughness of an AC/DC power distribution network according to an embodiment of the present invention;

FIG. 2 is a diagram of an improved IEEE-33 node inclusive ring traffic distribution network topology according to an embodiment of the present invention;

FIG. 3 is a diagram of an exemplary system architecture of a hybrid AC/DC power distribution network according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a system 400 for determining toughness of an ac/dc power distribution network according to an embodiment of the present invention.

Detailed Description

The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.

Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.

Fig. 1 is a flow chart of a method 100 of determining toughness of an ac/dc power distribution network according to an embodiment of the invention. As shown in fig. 1, according to the method for determining toughness of the ac/dc power distribution network provided by the embodiment of the invention, for natural disasters, a line fault rate model under the influence of disasters is constructed, a fault set is generated based on monte carlo sampling, a toughness core characteristic such as strain capacity, defense capacity and restoring force is surrounded, an ac/dc hybrid power distribution network toughness evaluation index set is constructed according to the operation characteristic of the ac/dc hybrid power distribution network, objective weights of the indexes are obtained based on an entropy weight method, an ac/dc hybrid power distribution network toughness comprehensive evaluation result is obtained based on an approximate ideal solution sorting method, and the toughness of the ac/dc power distribution network can be accurately evaluated. The method 100 for determining the toughness of the alternating current/direct current power distribution network, provided by the embodiment of the invention, starts from step 101, and calculates the line fault rate of each line of the alternating current/direct current power distribution network in different weather environments based on a line fault rate model in step 101.

Preferably, the calculating a line fault rate of each line of the ac/dc power distribution network based on the line fault rate model by using the following method includes:

wherein the content of the first and second substances,is the failure rate of line ij; m is the number of the supporting towers of the line ij; n is the number of conducting wires among towers;is the failure rate of the kth tower, andrepresenting the fault rate of the h-th wire; p represents a tower; and c represents a wire.

Preferably, when the line is in an ice and snow weather environment, the fault rate of the tower is calculated in the following wayAnd failure rate of the conductorThe method comprises the following steps:

wherein alpha is_p、α_c、β_pAnd beta_cAll are preset model coefficients; eta_cAnd η_pRespectively the longitudinal icing load rates of the lead and the tower; k is a radical of₁And k₂Weight coefficients, k, corresponding to line icing load and tidal current in the line fault rate, respectively₁+k₂＝1；p_ijIs the distribution network trend; p represents a tower; c represents a wire;

when the line is in a typhoon weather environment, calculating the fault rate of the tower and the fault rate of the lead by using the following modes:

wherein M is_TBending moment born by the root of the tower; m_pThe maximum bending resistance of the tower is achieved; mu.s_pAnd delta_pRespectively obtaining the expectation and standard deviation of normal distribution of the bending strength of the tower; sigma_lThe maximum bearing capacity of the wire under wind tension; sigma_gStress applied to the cross section of the wire by typhoon; mu.s_lAnd delta_lRespectively, the expected and standard deviation of the normal distribution of the tensile strength of the wire.

Extreme events mainly present the characteristics of diffusivity, invisibility, acceleration, uncertainty, catastrophe and the like, so that the whole city is in a 'fate of risk community', and any single subject and single measure in the city cannot independently face the impact and the destructiveness of the extreme events. Therefore, the AC/DC hybrid power distribution network toughness evaluation method is a key and basis for measuring the bearing capacity of the power distribution network facing extreme events and testing the toughness improvement strategy effect of the power distribution network.

According to the method, firstly, the condition of the alternating current-direct current hybrid power distribution network is analyzed according to the characteristics of the extreme event, and the fault rate of the line is determined. The overhead line is composed of a conducting wire, a pole tower, an insulator and other supporting equipment, the fault of the line is considered to be mainly caused by the fact that the conducting wire and the pole tower are damaged, the fault of the conducting wire and the fault of the pole tower are assumed to be independent, and the expression of the fault rate of the line can be obtained as follows:

wherein the content of the first and second substances,the fault rate of the line ij is represented, m represents the number of the supporting towers of the line ij, and n represents the number of the wires among the towers.Represents the failure rate of the kth tower, andrepresenting the fault rate of the kth wire; p represents a tower; and c represents a wire.

Wherein the content of the first and second substances,andunder the influence of different extreme events, the method has different forms, and in the invention, the model and the expression of the method under extreme ice and snow weather and typhoon are respectively researched.

1. Fault rate model of line under influence of extreme ice and snow weather environment

Under extreme ice and snow weather influence, the wire still need bear extra ice load except bearing self gravity load, under the condition windless and load is even, the ice load that the wire bore can be expressed as:

wherein the content of the first and second substances,representing the ice load, p, sustained by the wire_iceDenotes the ice density, D is the wire diameter, L_pIndicating the vertical span of the tower, d_iceIndicating the thickness of the ice coating. Ice coating thickness is related to the ice and snow accumulation effect. In actual operation, d is often first paired based on meteorological factors_iceThe prediction is made and the prediction error is taken into account as a normal distribution. When the load is not uniform, ρ_iceAnd d_iceBut also the abscissa and ordinate of the position of the wire.

The total load that the wire is subjected to can be expressed as:

wherein G is_cRepresenting the gravitational load of the wire.

The tower load under extreme ice and snow weather generally comprises three parts, namely horizontal tension applied by a transmission conductor, longitudinal load of an ice-coated conductor and horizontal wind load, and only the longitudinal load of the ice-coated conductor acting on the tower under a windless condition is considered for simplifying research. The longitudinal load experienced by the tower can be expressed as:

wherein, F_pIndicating the longitudinal load that the tower is subjected to.Ice-coated wire sheetLongitudinal load, h, to be taken by a bit length₁And h₂Indicating the difference in the hanging heights at the two ends of the tower, l₁And l₂And (4) representing the span at two sides of the tower.Can be expressed as:

the fault rate of the lead and the tower under the influence of extreme ice and snow weather and the load of the lead and the tower are considered to be in an exponential relationship, namely the fault rate of the towerAnd failure rate of the conductorRespectively as follows:

wherein alpha is_p,α_c,β_p,β_cAll are model coefficients, which can be obtained by fitting historical data. Eta_cAnd η_pThe longitudinal icing load rate of the line and the tower can be expressed as:

wherein M is_cAnd M_pRepresenting the design load as rated parameters of the lead and the tower; the failure rate of the wire in extreme icy and snowy weather will also increase with the degree of heavy load of the tide. k is a radical of₁And k₂The weight coefficients representing the line fault rates corresponding to the line icing loads and the tidal currents may be given by engineers based on operational experience and include:

k₁+k₂＝1 (9)

2. fault rate model of line under influence of typhoon weather environment

The wire breakage condition of the wire under the typhoon action is as follows: the maximum bearing capacity (i.e. tensile strength) of the wire under wind tension is less than the stress exerted by typhoons on the wire section, namely:

σ_l＜σ_g (10)

it is generally considered that the tensile strength of the wire is normally distributed, and the probability distribution can be expressed as:

wherein, mu_lAnd delta_lThe expectation and standard deviation, respectively, for a normal distribution can be obtained based on the wire manufacturing manual and actual operating experience.

And the typhoon applies stress sigma to the cross section of the wire_gProportional to the total load of the wire, i.e.:

σ_g＝k_gF_c (12)

wherein k is_gIs the load factor. The total load borne by the wire under the action of typhoon comprises two parts, namely transverse load under the action of wind powerAnd longitudinal load G under gravity_cAccording to the vectorial property of the load, the following can be obtained:

and has the following components:

G_c＝mg (14)

the wind load can be expressed as wind power and wind direction and a function, and the calculation formula is as follows:

wherein V represents a typhoon wind speed; theta represents the included angle between the wind direction and the line orientation; k is a radical of_wAs coefficients, can be obtained by fitting.

The wind speed under the typhoon effect is more accurate through the fitting of the Batts model, and can be expressed as:

wherein R is_maxRepresenting the maximum wind speed radius, V_RmaxRepresents a corresponding R_maxThe wind speed at a location, r, represents the distance of the wire from the center of the typhoon. And R is_maxAnd may be expressed as a function of the difference in typhoon center and peripheral air pressure.

Based on the equations (10) and (11), the failure rate of the conductor under the action of typhoon is obtained as follows:

the tower is broken under the action of typhoon: the maximum bending resistance (namely bending strength) of the tower is smaller than the bending moment borne by the root of the tower under the action of wind, namely:

M_p＜M_T (18)

it can also be considered that the tower bending strength is normally distributed, and the probability thereof can be expressed as the formula (19):

wherein, mu_pAnd delta_pThe expectation and standard deviation of the normal distribution are respectively expressed and can be obtained based on a tower manufacturing manual and actual operation experience. Bending moment M borne by tower root_TThe expression is visible (20).

According to the definition of the moment, the bending moment M caused by the wind load of the shaft_T1The value equal to the product of the wind force and the wind moment borne by the shaft can be expressed as:

M_T1＝F_T,windh_T,wind (21)

wherein, F_T,windShows the resultant force h in the horizontal direction of the typhoon on the tower_T,windThe vertical distance from the equivalent action point of the wind power on the tower to the root of the tower is shown.

Bending moment M caused by wind load of wire_T2The numerical value is equal to the sum of products of the horizontal acting force of all the wires on the tower and the vertical distance from the wires to the root of the tower, and the calculation formula is as follows:

based on the formulas (19) to (22), the failure rate of the tower under the action of typhoon is obtainedComprises the following steps:

in step 102, according to the line fault rate of each line in different weather environments, the operating state of each line in each weather environment is determined by using a monte carlo method.

Preferably, the method determines the operation state of each line in each weather environment by using a monte carlo method in the following way:

wherein x is_ijThe operation state of the line ij under certain weather environment; for any line (i, j) ∈ Ω_LIn the interval [0, 1]Uniformly distributed random numbers r are generated;the failure rate of the line ij under certain weather environment; omega_LIs a distribution network node set.

In the invention, the Monte Carlo method is adopted to generate the real running states of the line under different environmental weathers.

Specifically, taking typhoon weather as an example, the sampling specific process of the monte carlo method can be expressed as:

for any line (i, j) ∈ Ω_LIn the interval [0, 1]Internally generating a uniformly distributed random number r, which is the line failure rate in typhoon weatherAnd comparing to distinguish the running state of the line. Then line running status x_ijCan be expressed as:

the method comprises the steps of obtaining the running states of all lines in a distribution network by traversing all lines of an AC/DC distribution network to obtain a line running state set X₁。

By repeating the above processes, a line running state set X ═ X in M groups of weather environments can be obtained₁,…,X_M]。

In step 103, index values of each evaluation index for determining the toughness of the ac/dc distribution network are respectively calculated according to the operation state of each line in different weather environments.

Preferably, the evaluation index includes: a strain index, a defense index, and a restoring force index; wherein the content of the first and second substances,

the strain gauge comprises: the emergency resource proportion, the emergency resource supply rate, the remote control feeder switch configuration rate and the AC/DC tie line supply rate can be scheduled;

the defense strength index comprises: expected number of line faults;

the restoring force index includes: important load power loss time, important load power loss rate and distribution network load shedding total loss.

The toughness of the distribution network reflects its ability to resist small-probability high-risk extreme events. In the invention, an AC/DC hybrid power distribution network toughness comprehensive evaluation index system is provided around the core characteristics of toughness, namely strain capacity, defense capacity and restoring capacity. According to the comprehensive evaluation method, simulation calculation is carried out based on the existing historical data and the generated running state data, parameter data of each index in a comprehensive toughness evaluation index system are obtained, and further comprehensive evaluation is carried out on the toughness of the AC/DC hybrid power distribution network.

The evaluation indexes of the invention comprise:

1. index of strain force

(1) Schedulable emergency resource proportion

The AC/DC distribution network distributed power supply is used as an emergency resource, participates in post-disaster allocation and island operation, and needs to have two conditions: one of which must be an optimizable train. The output of the new energy unit has high fluctuation, and the voltage and the frequency are difficult to be independently and effectively controlled, so that the new energy unit cannot be used as a main control power supply to support island operation; the second one has excellent regulation performance, and emergency resource needs to respond in short time after disaster to ensure important load supply, so that the system has short startup and shutdown time and quick response. The schedulable emergency resource proportion measurement is the proportion of the emergency resource in the AC/DC distribution network distributed power supply, and the formula can be expressed as follows:

(2) emergency resource supply rate

The emergency resource supply rate is measured by the theoretical upper limit of the important load proportion which can guarantee supply only depending on emergency resources under an ideal state, and can be expressed as follows:

however, it should be noted that if the upper active power limit of the emergency resource is higher than the important load active power, the supply rate of the emergency resource should be 1.

(3) Remote control feeder switch configuration rate

The remote controllable feeder switch is the key for actively adjusting the topological form of the distribution network. The remote control feeder switch configuration rate is measured by the proportion of the feeder switches configured in the AC/DC line, and the calculation formula is as follows:

(4) supply rate of AC/DC line

Due to the limitations of the transmission power capacity and the VSC capacity of the tie line, there is a certain upper limit for the power support from the normal distribution network to the fault distribution network. What the supply rate of the AC/DC tie line measures is the maximum theoretical support capability of the normal distribution network to the fault distribution network, which can be expressed as:

2. index of defense ability

The expected characterization of the number of selected line faults can be specifically expressed as follows:

where E (-) represents the mathematical expectation. Under the influence of extreme natural disasters, the expected number of line faults can be obtained by a Monte Carlo sampling method.

3. Index of restoring force

(1) Time of loss of power to critical load

The important load power-loss time is measured by the time when the power supply of the important load of the distribution network is in shortage during the occurrence of an extreme event. I.e. the time elapsed from the occurrence of the fault to the repair of the line.

(2) Power loss rate of important load

The important load power loss rate is measured by the proportion of the important load reduction amount in the important load during the extreme event, and the calculation formula is as follows:

wherein the content of the first and second substances,indicating the load shedding amount.Representing the set of nodes at which the important load is located.

(3) Distribution network load shedding total loss

The distribution network load shedding loss reflects the economic loss of the distribution network caused by extreme events, and is equal to the product of unit load shedding cost and load shedding amount, namely:

and 104, determining the toughness of the AC/DC distribution network according to the index value of each evaluation index so as to determine the toughness performance of the AC/DC distribution network according to the toughness.

Preferably, the determining the toughness of the ac/dc distribution network according to the index value of each evaluation index includes:

determining the weight of each evaluation index based on an approximate ideal ordering method TOPSIS and an entropy weight method, and determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index and the corresponding weight.

In the invention, the toughness index of the AC/DC hybrid power distribution network is comprehensively evaluated by approaching an ideal solution ordering method (TOPSIS). The objective weight of each index can be obtained based on an entropy weight method and a TOPSIS algorithm principle.

Aiming at extreme events such as natural disasters, the invention selects two typical scenes: in extreme ice and snow weather and typhoon, the method for evaluating the toughness of the alternating current-direct current hybrid power distribution network in advance aiming at the characteristics of extreme events is provided, and operators can be assisted to measure the toughness performance of the power distribution network from the aspects of strain capacity, defense capacity, restoring force and the like before the extreme events occur.

In the embodiment of the invention, typhoon weather is taken as an example, and the toughness evaluation method of the alternating current-direct current hybrid power distribution network under the influence of typhoon is subjected to example analysis. An alternating current and direct current hybrid power distribution network composed of an IEEE 33 node alternating current distribution network system shown in figure 2 and a 9 node direct current distribution network system shown in figure 3 is selected as an example system in the text.

The influence of different distances between the distribution network line and the typhoon center is not considered for the moment. Based on the relevant data of the line fault rate model under the influence of typhoon, which is constructed by the method, the fault rates of the wires and the towers corresponding to different wind power grades can be obtained as shown in table 1, and the set lines are all single-circuit lines, so that the corresponding line fault rates are obtained. And generating 50 groups of fault scenes under different wind power grades based on Monte Carlo sampling. Finally, the calculation results of the indexes and the comprehensive evaluation results of the toughness of the AC/DC hybrid power distribution network under different wind power grades are shown in Table 2. The second column in table 2 indicates the weights of the respective indices calculated based on the entropy weight method.

As can be seen from the results in Table 2, typhoon weather mainly affects HDG defense and resilience indicators. Since the resource allocation strategy is not involved, the toughness index of the defense stage before disaster is kept unchanged in each scene. As the wind power level is increased, the comprehensive evaluation result of the HDG toughness is lower and lower. When the wind power reaches 11 grades, the important load loss rate reaches 0.395, and the comprehensive toughness evaluation result is reduced by 43.2 percent compared with the maximum value. And after the wind power level formally reaches the 12-level typhoon level, the important load loss rate reaches 0.8, and the comprehensive evaluation result of the toughness is only 0.157. When the wind power level reaches 14 levels, the distribution network lines and equipment are completely shut down. Therefore, the influence of the typhoon weather on the HDG is huge and not negligible, and the capability of the power distribution network for resisting the typhoon weather needs to be improved by adopting related pre-disaster, middle disaster and post-disaster toughness improving strategies.

Table 1 fault rate of each distribution network line under the influence of typhoon

Wind power class	Median wind velocity	Failure rate of wire	Tower failure rate	Line failure rate
					0	0	0	0	0
6	12.3	0.031	0	0.031
					11	30.5	0.447	0.015	0.463
12	34.8	0.812	0.129	0.857
					13	39.2	0.930	0.575	0.987
14	43.8	1	1	1

TABLE 2 toughness evaluation index results of AC/DC hybrid power distribution network under different wind power grades

Fig. 4 is a schematic structural diagram according to an embodiment of the present invention. As shown in fig. 4, a system 400 for determining toughness of an ac/dc power distribution network according to an embodiment of the present invention includes: a line fault rate calculation unit 401, an operating state determination unit 402, an evaluation index calculation unit 403, and a toughness determination unit 404.

Preferably, the line fault rate calculation unit 401 is configured to calculate a line fault rate of each line of the ac/dc power distribution network in different weather environments based on a line fault rate model.

Preferably, the line fault rate calculating unit 401 calculates the line fault rate of each line of the ac/dc power distribution network based on the line fault rate model by using the following method, including:

wherein the content of the first and second substances,is the failure rate of line ij; m is the number of the supporting towers of the line ij; n is the number of conducting wires among towers;is the failure rate of the kth tower, andrepresenting the fault rate of the h-th wire; p represents a tower; and c represents a wire.

Preferably, the line fault rate calculation unit 401 calculates the fault rate of the tower in the following manner when the line is in the ice and snow weather environmentAnd failure rate of the conductorThe method comprises the following steps:

wherein alpha is_p、α_c、β_pAnd beta_cAll are preset model coefficients; eta_cAnd η_pRespectively the longitudinal icing load rates of the lead and the tower; k is a radical of₁And k₂Weight coefficients, k, corresponding to line icing load and tidal current in the line fault rate, respectively₁+k₂＝1；p_ijIs the distribution network trend; p represents a tower; and c represents a wire.

When the line is in a typhoon weather environment, calculating the fault rate of the tower and the fault rate of the lead by using the following modes:

wherein M is_TBending moment born by the root of the tower; m_pThe maximum bending resistance of the tower is achieved; mu.s_pAnd delta_pRespectively obtaining the expectation and standard deviation of normal distribution of the bending strength of the tower; sigma_lThe maximum bearing capacity of the wire under wind tension; sigma_gStress applied to the cross section of the wire by typhoon; mu.s_lAnd delta_lRespectively, the expected and standard deviation of the normal distribution of the tensile strength of the wire.

Preferably, the operation state determining unit 402 is configured to determine the operation state of each line in each weather environment by using a monte carlo method according to the line fault rate of each line in different weather environments.

Preferably, the operation state determining unit 402 determines the operation state of each line in each weather environment by using a monte carlo method, including:

wherein x is_ijThe operation state of the line ij under certain weather environment; for any line (i, j) ∈ Ω_LIn the interval [0, 1]Uniformly distributed random numbers r are generated;the failure rate of the line ij under certain weather environment; omega_LIs a distribution network node set.

Preferably, the evaluation index calculation unit 403 is configured to calculate an index value of each evaluation index for determining the toughness of the ac/dc distribution network according to the operation state of each line in different weather environments.

Preferably, the evaluation index includes: a strain index, a defense index, and a restoring force index; wherein the content of the first and second substances,

the strain gauge comprises: the emergency resource proportion, the emergency resource supply rate, the remote control feeder switch configuration rate and the AC/DC tie line supply rate can be scheduled;

the defense strength index comprises: expected number of line faults;

the restoring force index includes: important load power loss time, important load power loss rate and distribution network load shedding total loss.

Preferably, the toughness determining unit 404 is configured to determine toughness of the ac/dc distribution network according to the index value of each evaluation index, so as to determine toughness performance of the ac/dc distribution network according to the toughness.

Preferably, the determining unit 404 for determining the toughness of the ac/dc distribution network according to the index value of each evaluation index includes:

determining the weight of each evaluation index based on an approximate ideal ordering method TOPSIS and an entropy weight method, and determining the toughness of the AC/DC power distribution network according to the index value of each evaluation index and the corresponding weight.

The system 400 for determining toughness of the ac/dc distribution network according to the embodiment of the present invention corresponds to the method 100 for determining toughness of the ac/dc distribution network according to another embodiment of the present invention, and is not described herein again.

The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

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.