阅读说明：本技术 一种区域自治电网模式保障可靠供电经济性评估分析方法 (Regional autonomous power grid mode guarantee reliable power supply economy evaluation analysis method ) 是由 杨梓俊 荆江平 陈辉 陈康 孙勇 于 2021-08-30 设计创作，主要内容包括：本发明公开一种区域自治电网模式保障可靠供电经济性评估分析方法,包括：S1、获取区域自治电网的网架结构、节点电源和负荷的时序数据、储能和电力线路的建设加固成本数据；S2、建立区域自治电网自治能力和经济性评估指标体系；S3、建立极端事件下保障重要负荷可靠供电的储能配置与线路加固优化模型；S4、建立优化模型的求解算法；S5、建立典型的极端事件故障场景,求解得到各个典型故障场景下的储能配置和线路加固方案；S6、计算S5中各个方案的区域自治能力及经济性指标,进行对比、分析,根据要求选取最优方案。解决了针对区域自治电网自治能力评估指标片面不全面,考虑的故障场景简单理想,采用的保障可靠供电方案成本高不宜推广的问题。(The invention discloses an assessment and analysis method for the economic performance of reliable power supply guaranteed by a regional autonomous power grid mode, which comprises the following steps: s1, acquiring grid structure of the regional autonomous power grid, time sequence data of node power supplies and loads, and construction and reinforcement cost data of energy storage and power lines; s2, establishing an assessment index system for the autonomous ability and the economic efficiency of the regional autonomous power grid; s3, establishing an energy storage configuration and line reinforcement optimization model for ensuring reliable power supply of important loads in extreme events; s4, establishing a solving algorithm of the optimization model; s5, establishing typical extreme event fault scenes, and solving to obtain energy storage configuration and line reinforcement schemes under each typical fault scene; and S6, calculating the regional autonomy and economic indexes of each scheme in the S5, comparing and analyzing, and selecting an optimal scheme according to requirements. The method solves the problems that the assessment indexes of the autonomous capacity of the regional autonomous power grid are not comprehensive on one side, the considered fault scene is simple and ideal, and the adopted reliable power supply guaranteeing scheme is high in cost and is not suitable for popularization.)

1. A method for assessing and analyzing the economic performance of reliable power supply guaranteed by an area autonomous power grid mode is characterized by comprising the following steps:

s1, acquiring grid structure of the regional autonomous power grid, time sequence data of node power supplies and loads, and construction and reinforcement cost data of energy storage and power lines;

s2, establishing an assessment index system for the autonomous ability and the economic efficiency of the regional autonomous power grid;

s3, establishing an energy storage configuration and line reinforcement optimization model for ensuring reliable power supply of important loads in extreme events;

s4, establishing a solving algorithm of the optimization model;

s5, establishing typical extreme event fault scenes, and solving to obtain energy storage configuration and line reinforcement schemes under each typical fault scene;

and S6, calculating the regional autonomy and economic indexes of each scheme in the S5, comparing and analyzing, and selecting an optimal scheme according to requirements.

The S2 includes the following steps:

s2.1, selecting a system performance function of the regional autonomous power grid;

s2.2, establishing an autonomy capability evaluation index from two aspects of robustness and rapidity;

R_deg＝R₀-R_pd ④

T_do＝t_or-t_ee ⑤

s2.3, establishing an economic cost evaluation index on the basis of the above steps;

the two-stage robust optimization model for protecting reliable power supply of the important load in the S3 is as follows:

the solving algorithm of S4 specifically includes the following steps:

s4.1, initializing line fault state, upper and lower problem boundaries U_BAnd L_BError epsilon and iteration number k;

s4.2, carrying out optimization solution on the stage I model;

s4.3, mixingInputting a model in the second stage, and performing optimization solution;

s4.4, judging whether a convergence condition is met, if so, outputting an energy storage configuration and line reinforcement scheme, and finishing the calculation; if not, then loop S4.2-S4.4.

2. The method for assessing and analyzing the economic efficiency of the mode-guaranteed reliable power supply of the regional autonomous power grid according to claim 1, wherein R in a formula (i)_op(t) represents the performance function of the system after an extreme event has occurred, where the selection is made to use the loss of load level; t is t_oeFor the moment when an extreme event occurs and the performance function begins to decline, t_orThe time when the extreme event is ended and the performance function begins to recover; b represents a set of all nodes in the regional power grid; w is a_jIs the load weight coefficient at node j;the active load of the node j lost in the time period t;

formulas II to III are autonomous ability indexes of regional autonomous power grid, wherein the formulas II, III, IV and V are robustness indexes, the formula III is rapidity index, and R is_1sIndicates the level of loss of performance, S_pdIndicating the rate of decline of the performance function, R_degIndicating the degree of degradation of the performance function, T_doIndicating derated operating duration, S_rIndicating the speed at which the system returns to normal, R₀Indicating the level of the performance function, R, of the system before an extreme event has occurred_pdRepresenting the lowest value to which the performance function falls, t_eeRepresents the time when the performance function drops to the lowest point and the system begins derating, T_orIndicating the time at which the system performance function recovers to a normal state level;

formula (c) is an economic index of the regional autonomous power grid, and COST represents the comprehensive COST of system operation; c_i，tRepresenting the cost coefficient of operation per unit power, P, of the ith device during the period t_i，tRepresenting the power of the ith device during the t period.

3. The method for assessing and analyzing the economic efficiency of the regional autonomous grid mode reliable power supply according to claim 1, characterized in that in a formula (r),annual investment costs for line reinforcement;in order to save the annual investment cost of energy storage,the annual combined loss cost of the load.

4. The method for assessing and analyzing the economic efficiency of the mode-guaranteed reliable power supply of the regional autonomous power grid according to claim 3,andthe calculation formula of (a) is as follows:

in the formula ninthly, L represents all line sets in the regional power network; beta is a_LCapital recovery factor for line consolidation; c. C_LThe cost is reinforced for a unit length line;is the length of line ij, in km; h is_ijThe state of the line is strengthened, 0 represents no strengthening, and 1 represents strengthening;

equation r and equationIn (1),which represents the cost of the equipment for storing energy,represents the site cost of the stored energy,represents the cost of operation and maintenance, c_PRepresenting the cost coefficient per unit power of the stored energy, c_EThe cost per unit volume factor is expressed as,cost coefficient of energy storage site for node j, c_omOperating and maintaining a cost coefficient for the unit power of the stored energy;rated power for energy storage installed at node jRated capacity for the stored energy installed at node j; sigma_jIndicating whether energy storage is installed at the node j, wherein the installation is 1, and the installation is 0 if the energy storage is not installed;

formula (II)In, N_dThe average annual occurrence frequency of extreme events; c. C_sIs a unit load loss cost coefficient.

5. The method for assessing and analyzing the economic efficiency of the mode-guaranteed reliable power supply of the regional autonomous power grid according to claim 4, wherein the optimization model needs to meet the following constraint conditions:

6. the regional autonomous grid mode assurance reliable power supply economy evaluation analysis method according to claim 5, characterized in that a formulaAnd formulaBelonging to the planning decision class of constraints, in which formulasFor the storage power rating and capacity constraints that the node allows for installation,for the maximum rated power of the stored energy allowed to be installed at node j,for node j-maximum capacity of stored energy allowed to be installed, formulaIs a constraint on the amount of energy stored, N, allowed to be installed within the regional autonomous grid_ESSMaximum amount of stored energy for allowable installation;

formula (II)Belonging to system operation class constraints, wherein the formulaIs a node active power, reactive power balance constraint, where, i, j,s is a node, pi (j) is an upstream node set of the node j, and delta (j) is a downstream node set of the node j; p_ij，tFor active power on line ij during t period, Q_ij，tIs the reactive power on line ij for time period t;the active power injected by the power supply on node j for time period t,reactive power injected by a power supply on a node j in a period t;for the active power output by the energy storage at the node j in the period t,the reactive power output for the energy storage at the node j in the period t;is the active load when no fault occurs at the node j in the period t,the reactive load is the reactive load when no fault occurs at the node j in the period t;for the time period t the active load at node j is lost,is the reactive load lost at node j during time t;

formula (II)Is a voltage relaxation constraint, V_i，tIs the voltage value of node i, V, during the period t_j，tThe voltage value of the node j is t time period; v₀Is a rated voltage value; z is a radical of_ij，tThe open-close state of the line ij is t, the line is 1 when closed, and the line is 0 when disconnected; r is_ijAnd x_ijThe resistance value and reactance value of the line ij are respectively; m is a constant larger than the voltage difference value of the head node and the tail node of the line jj;

formula (II)Is a line flow constraint, whereinIs the maximum transmission capacity of line ij;

formula (II)Is a node loss of load constraint;

formula (II)Is a node power supply injects active and reactive power constraints, whereinThe maximum injected active power for the power supply on node j,injecting reactive power for the maximum of the power supply on the node j;

formula (II)Is a node voltage constraint whereinIs the maximum value of the voltage at node j,is the minimum value of the voltage at node j;

formula (II)Is the energy storage discharge power constraint;

formula (II)Is an energy storage state of charge constraint, wherein SOC_minIs the minimum value of the state of charge of the stored energy, SOC_maxIs the maximum value of the energy storage state of charge;the residual electric quantity of the energy stored at the node j in the period t;

formula (II)Is a constraint on the balance of stored energy and electric quantity, wherein eta_dDischarge efficiency for energy storage;

formula (II)Is an energy storage initial state of charge constraint, whereinThe amount of energy stored at node j for the period of time prior to the occurrence of the extreme event,a state of charge value of the stored energy at node j in a period before the extreme event occurs;

formula (II)Is a line fault state constraint at the normal operating stage, formulaIs a line fault state constraint in the extreme event occurrence phase, formulaIs a line fault state constraint at the de-rated operating stage of the grid, where u_ij，tThe fault state of the line ij in the period t is 1 when the line fails, and 0 when the line fails; t is t_nThe beginning period of the whole research process;for maximum number of faults of each sub-area line, formulaIs the line open and close state constraint.

7. The method for assessing and analyzing the economic efficiency of area autonomous grid mode guaranteed reliable power supply according to claim 1, wherein typical fault scenarios in S5 are as follows: the method comprises the following steps of complete power loss of a transformer substation, partial bus shutdown of the transformer substation and partial feeder line faults in a power distribution network.

8. The method for assessing and analyzing the economic performance of area autonomous power grid mode guaranteed reliable power supply according to claim 1, wherein the area autonomous ability index and the economic performance index in S6 include: important load loss, non-important load loss, investment cost and annual comprehensive load loss cost.

Technical Field

The invention belongs to the field of distribution network configuration planning, and particularly relates to an assessment and analysis method for regional autonomous power grid mode guarantee reliable power supply economy.

Background

Extreme events such as typhoons, earthquakes and the like which have low occurrence probability but cause great disasters cause serious damage to the power grid, and huge economic losses are brought. Aiming at the power grid fault caused by an extreme event, the traditional power system 'three defense lines' (meaning the strategy of coping with the fault by means of power grid fast protection, preventive control, stable control, out-of-step disconnection, voltage frequency emergency control and the like) and 'N-1' safety judgment criterion (after any element in the power system is disconnected due to the fault in a normal operation mode, the power system can keep stable operation and normal power supply, other elements are not overload, and the voltage and the frequency are within an allowable range) are not applicable any more, and the power grid reliability cannot fully explain and describe the characteristics of the extreme event due to the fact that the large average characteristic is emphasized more. The concept of regional autonomous grids has therefore been proposed, the corresponding regional autonomous capability also being defined as "the ability of the grid to reduce losses due to faults in the event of extreme events, to maintain as high an operating function as possible and to recover as quickly as possible to a normal state of supply".

At present, research on assessment and analysis of the autonomous capacity of the regional autonomous power grid is less, established assessment indexes are more comprehensive, the load curve missing area of the power grid is mainly used, the characteristics of robustness, rapidity and the like of the regional autonomous power grid cannot be embodied in a multi-dimensional mode, and meanwhile economic indexes are not considered. In addition, the fault scene considered in the existing research is simple and ideal, and the adopted scheme for ensuring reliable power supply mainly based on line reinforcement has the problems of high cost, unsuitability for popularization and the like.

Aiming at the problems, an assessment analysis method for the economic performance of the reliable power supply of the regional autonomous power grid mode guarantee is designed, and the problems that indexes are not comprehensive, scenes are unreasonable, models are not universal and the like in assessment are effectively solved.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide an assessment and analysis method for the mode-guaranteed reliable power supply economy of an area autonomous power grid, and solves the problems that assessment indexes for the autonomous capacity of the area autonomous power grid are not comprehensive on one side, the considered fault scene is simple and ideal, and the adopted scheme for guaranteeing the reliable power supply is high in cost and is not suitable for popularization in the prior art.

The purpose of the invention can be realized by the following technical scheme:

a method for assessing and analyzing the economic performance of reliable power supply guaranteed by an area autonomous power grid mode comprises the following steps:

s1, acquiring grid structure of the regional autonomous power grid, time sequence data of node power supplies and loads, and construction and reinforcement cost data of energy storage and power lines;

s2, establishing an assessment index system for the autonomous ability and the economic efficiency of the regional autonomous power grid;

s3, establishing an energy storage configuration and line reinforcement optimization model for ensuring reliable power supply of important loads in extreme events;

s4, establishing a solving algorithm of the optimization model;

s5, establishing typical extreme event fault scenes, and solving to obtain energy storage configuration and line reinforcement schemes under each typical fault scene;

and S6, calculating the regional autonomy and economic indexes of each scheme in the S5, comparing and analyzing, and selecting an optimal scheme according to requirements.

The S2 includes the following steps:

s2.1, selecting a system performance function of the regional autonomous power grid;

s2.2, establishing an autonomy capability evaluation index from two aspects of robustness and rapidity;

R_deg＝R₀-R_pd④

T_do＝t_or-t_ee⑤

s2.3, establishing an economic cost evaluation index on the basis of the above steps;

the two-stage robust optimization model for protecting reliable power supply of the important load in the S3 is as follows:

the solving algorithm of S4 specifically includes the following steps:

s4.1, initializing line fault state, upper and lower problem boundaries U_BAnd L_BError epsilon and iteration number k;

s4.2, carrying out optimization solution on the stage I model;

s4.3, mixingInputting a model in the second stage, and performing optimization solution;

s4.4, judging whether a convergence condition is met, if so, outputting an energy storage configuration and line reinforcement scheme, and finishing the calculation; if not, the process is repeated from S4.2 to S4.4.

Further, in formula (I), R_op(t) represents the performance function of the system after an extreme event has occurred, where the selection is made to use the loss of load level; t is t_oeFor the extreme event to happen,Time at which the performance function starts to decline, t_orThe time when the extreme event is ended and the performance function begins to recover; b represents a set of all nodes in the regional power grid; w is a_jIs the load weight coefficient at node j;is the active load that node j loses during time t.

The formulas are autonomous ability indexes of regional autonomous power grid, wherein the formulas are robustness indexes, the formulas are rapidity indexes, and R is_1sIndicates the level of loss of performance, S_pdIndicating the rate of decline of the performance function, R_degIndicating the degree of degradation of the performance function, T_doIndicating derated operating duration, S_rIndicating the speed at which the system returns to normal, R₀Indicating the level of the performance function, R, of the system before an extreme event has occurred_pdRepresenting the lowest value to which the performance function falls, t_eeRepresents the time when the performance function drops to the lowest point and the system begins derating, T_orIndicating the time at which the system performance function recovers to a normal state level.

Formula (c) is an economic index of the regional autonomous power grid, and COST represents the comprehensive COST of system operation; c_i，tRepresenting the cost coefficient of operation per unit power, P, of the ith device during the period t_i，tRepresenting the power of the ith device during the t period.

Further, in the formula (b),annual investment costs for line reinforcement;in order to save the annual investment cost of energy storage,the annual combined loss cost of the load.

Further, in the above-mentioned case,andthe calculation formula of (a) is as follows:

in the formula ninthly, L represents all line sets in the regional power network; beta is a_LCapital recovery factor for line consolidation; c. C_LThe cost is reinforced for a unit length line;is the length of line ij, in km; h is_ijThe line is reinforced, 0 indicates no reinforcement, and 1 indicates reinforcement.

Equation r and equationIn (1),which represents the cost of the equipment for storing energy,represents the site cost of the stored energy,represents the cost of operation and maintenance, c_PRepresenting the cost coefficient per unit power of the stored energy, c_EThe cost per unit volume factor is expressed as,cost coefficient of energy storage site for node j, c_omOperating and maintaining a cost coefficient for the unit power of the stored energy;rated power for energy storage installed at node jRated capacity for the stored energy installed at node j; sigma_jAnd indicating whether the energy storage is installed at the node j, wherein the installation is 1, and the non-installation is 0.

Formula (II)In, N_dThe average annual occurrence frequency of extreme events; c. C_sIs a unit load loss cost coefficient.

Further, the optimization model needs to satisfy the following constraints:

further, the formulaAnd formulaBelonging to the planning decision class of constraints, in which formulasFor the storage power rating and capacity constraints that the node allows for installation,for the maximum rated power of the stored energy allowed to be installed at node j,for node j-maximum capacity of stored energy allowed to be installed, formulaIs a constraint on the amount of energy stored, N, allowed to be installed within the regional autonomous grid_ESSTo allow the maximum amount of stored energy to be installed.

Formula (II)Belonging to system operation class constraints, wherein the formulaThe method is node active power and reactive power balance constraint, wherein i, j and s are all nodes, pi (j) is an upstream node set of the node j, and delta (j) is a downstream node set of the node j; p_ij，tFor active power on line ij during t period, Q_ij，tIs the reactive power on line ij for time period t;the active power injected by the power supply on node j for time period t,reactive power injected by a power supply on a node j in a period t;for the active power output by the energy storage at the node j in the period t,the reactive power output for the energy storage at the node j in the period t;is the active load when no fault occurs at the node j in the period t,the reactive load is the reactive load when no fault occurs at the node j in the period t;for the time period t the active load at node j is lost,is the reactive load lost at node j for time period t.

Formula (II)Is a voltage relaxation constraint, V_i，tIs the voltage value of node i, V, during the period t_j，tThe voltage value of the node j is t time period; v₀Is a rated voltage value; z is a radical of_ij，tThe open-close state of the line ij is t, the line is 1 when closed, and the line is 0 when disconnected; r is_ijAnd x_ijThe resistance value and reactance value of the line ij are respectively; m is a constant greater than the difference between the voltages at the first and last nodes of line ij.

Formula (II)Is a line flow constraint, whereinIs the maximum transmission capacity of line ij.

Formula (II)Is a node workload loss constraint.

Formula (II)Is a node power supply injects active and reactive power constraints, whereinThe maximum injected active power for the power supply on node j,reactive power is injected for the maximum of the power supply on node j.

Formula (II)Is a node voltage constraint whereinIs the maximum value of the voltage at node j,is the minimum value of the voltage at node j.

Formula (II)Is the stored energy discharge power constraint.

Formula (II)Is an energy storage state of charge constraint, wherein SOC_minFor storing energy in charged stateMinimum value, SOC_maxIs the maximum value of the energy storage state of charge;the residual capacity of the energy stored at the node j in the period t.

Formula (II)Is a constraint on the balance of stored energy and electric quantity, wherein eta_dThe discharge efficiency of stored energy.

Formula (II)Is an energy storage initial state of charge constraint, whereinThe amount of energy stored at node j for the period of time prior to the occurrence of the extreme event,the state of charge value of the stored energy at node j for the period before the extreme event occurs.

Formula (II)Is a line fault state constraint at the normal operating stage, formulaIs a line fault state constraint in the extreme event occurrence phase, formulaIs a line fault state constraint at the de-rated operating stage of the grid, where u_ij，tThe fault state of the line ij in the period t is 1 when the line fails, and 0 when the line fails; t is t_nThe beginning period of the whole research process;for the most extensive of the lines of each sub-areaLarge number of failures, formulaIs the line open and close state constraint.

Further, the typical failure scenario in S5 is as follows: the method comprises the following steps of complete power loss of a transformer substation, partial bus shutdown of the transformer substation and partial feeder line faults in a power distribution network.

Further, the regional autonomy index and the economic index in S6 include: important load loss, non-important load loss, investment cost and annual comprehensive load loss cost.

The invention has the beneficial effects that:

1. the method for assessing and analyzing the economic performance of the reliable power supply of the regional autonomous power grid mode guarantees fully considers the time-space characteristics of power grid faults caused by extreme events, comprehensively describes two characteristics of robustness and rapidity of the regional autonomous power grid from multiple angles such as the amplitude, speed and duration of system performance function change, and realizes comprehensive assessment of two levels of power grid operation and planning by combining with economic indexes;

2. according to the assessment and analysis method for the regional autonomous power grid mode guarantee reliable power supply economy, two strategies of energy storage configuration and line reinforcement are coordinated, uncertainty of line faults inside the regional autonomous power grid under extreme events is considered, the investment budget of the power grid for preventing damage of the extreme events is reduced while important loads are guaranteed to supply power reliably during the extreme events, and regional autonomous capacity and economic cost of the power grid are effectively balanced;

3. the assessment and analysis method for the regional autonomous power grid mode-guaranteed reliable power supply economy comprises all the processes of index establishment, model optimization and economy analysis, can perform regional autonomous capability and economy index dual assessment and analysis for guaranteeing a reliable power supply scheme aiming at a plurality of typical fault scenes of the regional autonomous power grid under extreme events, can obtain advantages and disadvantages of each scheme more intuitively, and is more beneficial to selecting the guaranteed reliable power supply scheme suitable for the power grid requirements.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a flow chart of an overall evaluation analysis method of an embodiment of the present invention;

FIG. 2 is a schematic diagram of a solving algorithm of a two-stage robust optimization configuration model according to an embodiment of the present invention;

fig. 3 is a diagram of an improved IEEE33 node net rack topology according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, a method for assessing and analyzing the economic efficiency of reliable power supply in an area autonomous grid mode includes the following steps:

s1, acquiring grid structure of the regional autonomous power grid, time sequence data of node power supplies and loads, and construction and reinforcement cost data of energy storage and power lines;

s2, establishing an assessment index system for the autonomous ability and the economic efficiency of the regional autonomous power grid;

s2.1, selecting a system performance function of the regional autonomous power grid;

in formula (I), R_op(t) represents the performance function of the system after an extreme event has occurred, where the selection is made to use the loss of load level; t is t_oeFor the moment when an extreme event occurs and the performance function begins to decline, t_orThe time when the extreme event is ended and the performance function begins to recover; b represents a set of all nodes in the regional power grid; w is a_jIs the load weight coefficient at node j;is the active load that node j loses during time t.

S2.2, as the autonomous ability of the regional autonomous power grid can be directly and effectively represented more directly and more rapidly due to robustness and rapidness, and quantitative calculation is easy, an autonomous ability evaluation index is established from two aspects of robustness and rapidness;

R_deg＝R₀-R_pd④

T_do＝t_or-t_ee⑤

the formulas are autonomous ability indexes of regional autonomous power grid, wherein the formulas are robustness indexes, the formulas are rapidity indexes, and R is_1sIndicates the level of loss of performance, S_pdIndicating the rate of decline of the performance function, R_degIndicating the degree of degradation of the performance function, T_doIndicating derated operating duration, S_rIndicating the speed at which the system returns to normal, R₀Indicating the level of the performance function, R, of the system before an extreme event has occurred_pdRepresenting the lowest value to which the performance function falls, t_eeRepresents the time when the performance function drops to the lowest point and the system begins derating, T_orIndicating the time at which the system performance function recovers to a normal state level.

S2.3, establishing an economic cost evaluation index on the basis of the above steps;

formula (c) is an economic index of the regional autonomous power grid, and COST represents the comprehensive COST of system operation; c_i，tRepresenting the cost coefficient of operation per unit power, P, of the ith device during the period t_i，tRepresenting the power of the ith device during the t period.

S3, establishing an energy storage configuration and line reinforcement optimization model for ensuring reliable power supply of important loads in extreme events;

when energy storage configuration and line reinforcement aiming at ensuring reliable power supply of important loads are carried out in a regional autonomous power grid mode, not only the autonomous capability of a power grid but also the economic cost of a scheme are considered. Therefore, a two-stage robust optimization model for ensuring reliable power supply of important loads is established;

in the formula (I),annual investment costs for line reinforcement;in order to save the annual investment cost of energy storage,the annual combined loss cost of the load. WhereinAndthe calculation formula of (a) is as follows:

in the formula ninthly, L represents all line sets in the regional power network; beta is a_LCapital recovery factor for line consolidation; c. C_LThe cost is reinforced for a unit length line;is the length of line ij, in km; h is_ijThe line is reinforced, 0 indicates no reinforcement, and 1 indicates reinforcement.

Equation r and equationIn (1),which represents the cost of the equipment for storing energy,represents the site cost of the stored energy,represents the cost of operation and maintenance, c_PRepresenting the cost coefficient per unit power of stored energy, C_EThe cost per unit volume factor is expressed as,cost coefficient of energy storage site for node j, c_omOperating and maintaining a cost coefficient for the unit power of the stored energy;rated power for energy storage installed at node jRated capacity for the stored energy installed at node j; sigma_jAnd indicating whether the energy storage is installed at the node j, wherein the installation is 1, and the non-installation is 0.

Formula (II)In, N_dThe average annual occurrence frequency of extreme events; c. C_sIs a unit load loss cost coefficient.

The model needs to satisfy the following constraints:

formula (II)And formulaBelonging to the planning decision class of constraints, in which formulasFor the storage power rating and capacity constraints that the node allows for installation,for the maximum rated power of the stored energy allowed to be installed at node j,for node j-maximum capacity of stored energy allowed to be installed, formulaIs a constraint on the amount of energy stored, N, allowed to be installed within the regional autonomous grid_ESSTo allow the maximum amount of stored energy to be installed.

Formula (II)Belonging to system operation class constraints, wherein the formulaThe method is node active power and reactive power balance constraint, wherein i, j and s are all nodes, pi (j) is an upstream node set of the node j, and delta (j) is a downstream node set of the node j; p_ij，tFor active power on line ij during t period, Q_ij，tIs the reactive power on line ij for time period t;the active power injected by the power supply on node j for time period t,reactive power injected by a power supply on a node j in a period t;for the active power output by the energy storage at the node j in the period t,the reactive power output for the energy storage at the node j in the period t;is the active load when no fault occurs at the node j in the period t,the reactive load is the reactive load when no fault occurs at the node j in the period t;for the time period t the active load at node j is lost,is the reactive load lost at node j for time period t.

Formula (II)Is a voltage relaxation constraint, V_i，tIs the voltage value of node i, V, during the period t_j，tThe voltage value of the node j is t time period; v₀Is a rated voltage value; z is a radical of_ij，tThe open-close state of the line ij is t, the line is 1 when closed, and the line is 0 when disconnected; r is_ijAnd x_ijThe resistance value and reactance value of the line ij are respectively; m is a constant greater than the difference between the voltages at the first and last nodes of line ij.

Formula (II)Is a line flow constraint, whereinIs the maximum transmission capacity of line ij.

Formula (II)Is a node workload loss constraint.

Formula (II)Is a node power supply injects active and reactive power constraints, whereinThe maximum injected active power for the power supply on node j,reactive power is injected for the maximum of the power supply on node j.

Formula (II)Is a node voltage constraint whereinIs the maximum value of the voltage at node j,is the minimum value of the voltage at node j.

Formula (II)Is the stored energy discharge power constraint.

Formula (II)Is an energy storage state of charge constraint, wherein SOC_minIs the minimum value of the state of charge of the stored energy, SOC_maxIs the maximum value of the energy storage state of charge;for the remainder of the stored energy at node j during time tAnd (4) surplus electricity.

Formula (II)Is a constraint on the balance of stored energy and electric quantity, wherein eta_dThe discharge efficiency of stored energy.

Formula (II)Is an energy storage initial state of charge constraint, whereinThe amount of energy stored at node j for the period of time prior to the occurrence of the extreme event,the state of charge value of the stored energy at node j for the period before the extreme event occurs.

Formula (II)Is a line fault state constraint at the normal operating stage, formulaIs a line fault state constraint in the extreme event occurrence phase, formulaIs a line fault state constraint at the de-rated operating stage of the grid, where u_ij，tThe fault state of the line ij in the period t is 1 when the line fails, and 0 when the line fails; t is t_nThe beginning period of the whole research process;for maximum number of faults of each sub-area line, formulaIs the line open and close state constraint.

S4, establishing a solving algorithm of the optimization model, wherein the algorithm flow is shown in figure 2;

in order to solve the two-stage robust optimization model established in step 3, a solving algorithm is established as follows:

s4.1, initializing line fault state, upper and lower problem boundaries U_BAnd L_BError epsilon and iteration number k;

s4.2, carrying out optimization solution on the stage I model;

(1) and an objective function:

(2) and constraint conditions:

firstly, planning decision type constraint: formula (II)And

secondly, system operation class constraint: formula (II)

③、

(3) And outputting:

(4) updating the lower bound:

s4.3, mixingInputting a model in the second stage, and performing optimization solution;

(1) and an objective function:

(2) and constraint conditions:

firstly, system operation class constraint: formula (II)

Secondly, constraint of line state: formula (II)

(3) And outputting;

(4) updating an upper bound:

s4.4, judging whether a convergence condition is met, if so, outputting an energy storage configuration and line reinforcement scheme, and finishing the calculation; if not, the process is repeated from S4.2 to S4.4.

S5, establishing typical extreme event fault scenes, and solving to obtain energy storage configuration and line reinforcement schemes under each typical fault scene;

according to the actual power grid structure and the fault level generated by the line after the extreme event occurs, a typical fault scene is established as follows:

(1) and all the transformer substations lose power

All power loss of single 220kV transformer substation

② all the single 110kV transformer substation is out of power

(2) Partial bus of transformer substation stops running

(3) Partial feeder fault in a power distribution network

And aiming at the three fault scenes, respectively calculating to obtain corresponding energy storage configuration and line strengthening schemes for ensuring reliable power supply of the important load.

And S6, calculating the regional autonomy and economic indexes of each scheme in the S5, comparing and analyzing, and selecting an optimal scheme according to requirements.

Calculating the following regional autonomy indexes and economic indexes:

(1) important load loss

(2) Amount of non-critical load loss

(3) Investment cost (including line reinforcement cost, energy storage investment cost, energy storage site cost, energy storage daily operation maintenance cost)

(4) Annual comprehensive lost load cost

The invention is tested by taking an improved IEEE33 node power distribution network as an example, and the grid structure of the power distribution network is shown in figure 3. In the embodiment, the voltage level of the power grid is set to be 10 kV; the time period of the study was 6: 00-11: 00, and 8: 00 an extreme event occurs with a time interval deltat of 15 min. Through the embodiment, the energy storage configuration and line reinforcement results obtained through the established optimization model and the solution algorithm are shown, and the regional autonomous capacity and economic indexes of each scheme are calculated and compared.

The test results of the embodiment show that when a feeder line connected with a power distribution network fails and stops running, if no connecting line with other feeder lines is newly built, only an energy storage configuration scheme is adopted, the investment cost is 655.38 ten thousand yuan, the load loss is 32.066kW, and the load loss cost is 40.082 ten thousand yuan; when the scheme of line reinforcement and energy storage configuration is adopted, the investment cost is 532.96 ten thousand yuan, the load loss is 31.979kW, and the load loss cost is 39.974 ten thousand yuan. If a connecting line with other feeder lines is newly built, the regional autonomy can be realized only by measures such as energy storage configuration, line reinforcement and the like due to the constraint of line transmission capacity, but the investment cost and the load loss are reduced to some extent. The results verify the feasibility and effectiveness of the evaluation analysis method provided by the invention.

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed.