Power distribution system operation reliability evaluation method considering flexible resource two-stage scheduling

Abstract

The invention discloses a power distribution system operation reliability evaluation method considering flexible resource two-stage scheduling. The method comprises the following steps: 1, acquiring flexible resource parameters, a power distribution system topological structure and load data of a user; 2, considering a load shedding risk caused by net load fluctuation, and establishing a pre-fault flexible resource scheduling model; 3, scheduling potentials and mutual influences of flexible resources such as a small gas turbine, wind power, photovoltaic and energy storage are considered, and a power distribution system fault recovery model considering flexible dynamic adjustment and a collaborative reconstruction strategy is constructed; 4, defining a system reliability index constraint in combination with an objective function; 5, second-order cone relaxation is adopted to linearize partial constraints, and a power distribution system reliability linear evaluation model is obtained; and 6, calculating by adopting a solver to obtain a reliability evaluation result. According to the method, two stages of load loss are provided by researching flexible resource supply and a climbing process, and optimization and evaluation of the operation reliability of the power distribution system are realized by performing dynamic output adjustment on the two stages of flexible resources.

Description

Technical Field

[0001] The present invention relates to the field of operation reliability assessment of a new type of power distribution system, and particularly to a method for assessing the operation reliability of a power distribution system considering two-stage scheduling of flexible resources. Background Art

[0002] In recent years, with the rapid development of renewable energy power generation equipment and grid connection technology, a new type of power system dominated by new energy has gradually taken shape. However, the high-penetration grid connection of new energy has brought huge challenges to the safe and stable operation of the power distribution system, making the reliability assessment of the power distribution system more complex, mainly reflected in the uncertainty and volatility of resources such as wind power and photovoltaic power. On the one hand, the volatility of flexible resources such as wind and light leads to an increase in the fluctuation of the "net load" of the power distribution system, increasing the system flexibility ramp-up demand in a short period of time, which may cause an imbalance in the ramp-up of flexible resources in the short term, exacerbate the system load shedding risk, and affect the power supply reliability of the power distribution system; on the other hand, flexible resources themselves have a certain ramp-up and power supply capacity. After a system fault, they can be adjusted through ramp-up and cooperate with the system tie line to divide the island, restore some of the lost power load, and have a certain improvement effect on the power supply reliability of the power distribution system.

[0003] The current reliability assessment method for power distribution systems is based on the principle of power and energy balance, that is, considering the outage situation of power distribution system components and the power supply of flexible resources, calculating the total load that has not been restored after a fault and the system load shedding time, and thus evaluating the reliability level of the system. It cannot fully consider the ramp-up fluctuation risk of flexible resources before a fault and the ramp-up adjustment ability of flexible resources after a fault, is difficult to depict the impact of the dynamic adjustment of flexible resources on the operation reliability of the system, and does not fully explore the ramp-up and scheduling potential of flexible resources, resulting in the existing reliability assessment method for power distribution system operation not meeting the requirements of the current high-penetration power distribution system operation reliability assessment. Therefore, it is of great significance to study the operation reliability assessment method for high-penetration flexible resource power distribution systems. Summary of the Invention

[0004] The present invention aims to avoid the deficiencies of the above-mentioned prior art, and provides a method for assessing the operation reliability of a power distribution system considering two-stage scheduling of flexible resources, in order to fully consider the dynamic adjustment characteristics and recovery ability of flexible resources, simultaneously consider the power and energy balance and ramp-up balance of the system in the reliability assessment, and establish an operation reliability assessment model for a high-penetration flexible resource power distribution system to generate an optimal flexible resource scheduling and fault recovery strategy, so as to accurately evaluate the operation reliability index of the power distribution system.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for evaluating the operational reliability of a distribution system considering two-stage scheduling of flexible resources is characterized in that it is carried out according to the following steps:

[0007] Step 1: Obtain the parameters of flexible resources, including: the ramping rate of small gas turbines, the upper and lower limit parameters of power generation; the upper and lower limits of energy storage, charge and discharge efficiency, and initial power parameters of energy storage power stations; the power prediction curves of distributed wind turbines and photovoltaics; the upper and lower limit parameters of the power that can be provided by interruptible loads, and the grid-connected node parameters of flexible resources;

[0008] Obtain the topological structure of the distribution system, including: the distribution of tie lines, the upstream and downstream relationships of load points, line lengths, line impedances, line and switch failure rates, repair times, and sectional switch switching times;

[0009] Obtain the load data of users, including: the number of users at each load point, load levels, active and reactive loads of users;

[0010] Step 2: Considering the load shedding risk caused by net load fluctuations, establish a pre-fault flexible resource scheduling model;

[0011] Step 3: Considering the scheduling potential and mutual influence of flexible resources such as small gas turbines, wind power, photovoltaics, and energy storage, construct a distribution system fault recovery model considering flexible dynamic regulation and coordinated reconstruction strategies;

[0012] Step 4: Define the linear constraints of the reliability index of the distribution system in combination with the objective function;

[0013] Step 5: After linearizing some constraints in the pre-fault flexible resource scheduling model and the distribution system fault recovery model by using second-order cone relaxation, obtain a linear evaluation model of the distribution system reliability;

[0014] Step 6: Use a solver to solve the linear evaluation model of the distribution system reliability, and obtain a scheduling plan considering two-stage scheduling of flexible resources, including: the scheduling plan in the normal operation stage of the distribution system, the rescheduling plan after a fault, and the fault reconstruction plan of the distribution system. Thus, according to the scheduling plan, rescheduling plan, and fault reconstruction plan, obtain the operational reliability index of the distribution system.

[0015] The characteristics of a method for evaluating the operational reliability of a distribution system considering two-stage scheduling of flexible resources according to the present invention also lie in that Step 2 is carried out according to the following steps:

[0016] Step 2.1: Use Equation (1) to establish the total objective function of the pre-fault flexible resource scheduling model :

[0017] (1)

[0018] In formula (1): is the power grid operation loss function, which is obtained from formula (2), is the total flexibility deficit, which is obtained from formula (3), is the operation load shedding, which is obtained from formula (4), are three weight coefficients;

[0019] (2)

[0020] In formula (2), 、 、 and respectively represent the consumption of the gas turbine unit, the operation consumption of the energy storage, the consumption of the interruptible load, and the consumption of the upper-level power consumption of the power grid at time and respectively represent the charging and discharging power of the energy storage at time represents the output of the interruptible load node at time represents the output of the interruptible load node at time represents the power purchase of the power grid at time; a, b, and c are three cost coefficients of the gas turbine; 、 and respectively represent the operation consumption per unit of the energy storage, the contract consumption per unit of the interruptible load, and the time-sharing consumption per unit of the power grid; is the total time scale;

[0021] (3)

[0022] In formula (3), is the active power of the load shedding at the load node at time due to the ramp rate or power imbalance; is the total number of load nodes in the distribution system;

[0023] (4)

[0024] In formula (4): 、 respectively represent the upward and downward flexibility deficits of the distribution system at time;

[0025] Step 2.2. Establish the constraint conditions of the pre-fault flexible resource scheduling model:

[0026] Step 2.2.1. Construct the system flexibility supply constraint using Equation (5):

[0027] (5)

[0028] In Equation (5): and respectively represent the upward and downward flexibility supplies of the distribution system at time and and and respectively represent the upward flexibility supplies provided by energy storage, interruptible load, power purchase from the grid, and gas turbines at time and and and respectively represent the downward flexibility supplies provided by energy storage, interruptible load, power purchase from the grid, and gas turbines at time

[0029] Step 2.2.2. Construct the flexibility deficit constraint using Equation (6):

[0030] (6)

[0031] In Equation (6): and respectively represent the upward and downward flexibility demands of the distribution system at time

[0032] Step 2.2.3. Construct the power flow constraint of the distribution system using Equation (7):

[0033] (7)

[0034] In Equation (7): and respectively represent the active and reactive powers transmitted through the branch between load node and load node at time where load node is the upstream load point of load node and respectively represent the net active and reactive powers injected into load node at time and and and respectively represent Active power injected into the load node by the superior power purchase, distributed wind power, distributed photovoltaics, and gas turbines at a certain moment at; , , and respectively represent the reactive power injected into the load node by the superior power purchase, distributed wind power, distributed photovoltaics, and gas turbines at a certain moment at; , respectively represent the active and reactive powers of the load at the load node at a certain moment; is the load shedding reactive power at the node caused by the ramp rate or power imbalance at a certain moment ; is the resistance value of the branch ; is the reactance value of the branch ; represents the square of the current amplitude of the branch at a certain moment; , respectively represent the square of the voltage amplitude at the load node , the load node at a certain moment; represents the branch between the load node and the load node , where the load node is the downstream load point of the load node ; is the set of branches of the distribution system;

[0035] Step 2.2.4. Use Equation (8) to construct the voltage constraint of the load node:

[0036] (8)

[0037] In Equation (8): and respectively represent the upper and lower limits of the voltage amplitude at the load node ;

[0038] Step 2.2.5. Use Equation (9) to construct the transmission capacity constraint:

[0039] (9)

[0040] In Equation (9): and respectively represent the branch Upper and lower limits of transmission capacity; Indicate Time branch Transmission capacity of.

[0041] Furthermore, the third step is carried out as follows:

[0042] Step 3.1: Use Equation (10) to construct the objective function of the distribution system fault recovery model :

[0043] (10)

[0044] In Equation (10): Is the power supply shortage index of the power outage of the distribution system; Indicates the total number of branches in normal operation of the distribution system; And Are the first and second sub-objective functions respectively; Is the th objective function, Is the th weight coefficient of the objective function; Is a binary variable indicating the operation status of branch And is obtained from Equation (11);

[0045] (11)

[0046] In Equation (11): Is the number of root nodes in the distribution system;

[0047] Step 3.2: Construct the constraint conditions of the distribution system fault recovery model:

[0048] Step 3.2.1: Use Equation (11) to construct the fault recovery power flow constraint:

[0049] (12)

[0050] In Equation (12): And Respectively indicate Time after the distribution system fault reconstruction, the active and reactive powers transmitted through branch ; And Respectively indicate the active and reactive powers increased by the flexible resources during ramping after the fault reconstruction Time; Is Time after the distribution system fault reconstruction, the square of the current amplitude of branch ; And Respectively indicate The load nodes after the fault reconstruction of the momentary power distribution system and the load nodes at the square of the voltage amplitude;

[0051] Step 3.2.2. Construct the voltage constraint of the big M method using Equation (13):

[0052] (13)

[0053] In Equation (13), M is a real number;

[0054] Step 3.2.3. Construct the dynamic additional increase constraint of flexible resources using Equation (14):

[0055] (14)

[0056] In Equation (14): , respectively represent the additional active and reactive power of purchasing electricity upward from the time after the fault reconstruction to before the completion of fault repair at the moment; , respectively represent the additional active and reactive power of the gas turbine from the time after the fault reconstruction to before the completion of fault repair at the moment;

[0057] Step 3.2.4. Construct the additional increase constraint of the gas turbine using Equation (15):

[0058] (15)

[0059] In Equation (15), represents the time scale of the additional dispatch of the unit, represents the additional active power of the gas turbine from the time after the fault reconstruction to before the completion of fault repair at the moment;

[0060] Step 3.2.5. Construct the additional increase constraint of purchasing electricity upward using Equation (16):

[0061] (16)

[0062] In Equation (16), represents the active power purchased upward by the system from the time after the fault reconstruction to before the completion of fault repair at the moment;

[0063] Step 3.2.6. Construct the voltage constraint of the load nodes after the fault using Equation (17):

[0064] (17)

[0065] Step 3.2.7. Construct the post-fault flexible resource restoration constraint using Equation (18):

[0066] (18)

[0067] In Equation (18): represents the reactive power injection of the flexible dispatchable load at time at load node ; represents the active power injection of the flexible dispatchable load at time at load node ; represents

[0068] the power factor of load node

[0069] Further, Step 4 is carried out as follows:

[0070] (19)

[0071] In Equation (19): is the power outage duration index of load node between load node and load node under the fault of branch ; is the failure rate of fault branch ; is a binary variable indicating whether load node is powered on after the distribution network performs islanding and reconstruction restoration under the condition of fault branch ; is a binary variable indicating whether load node is powered on through flexible resource ramping restoration; is the isolation time of fault branch ; is the time for load node to be powered on through reconstruction or islanding restoration after losing power caused by fault branch ; is the repair time of fault branch ; is the time for load node to increase power and restore power supply after losing power caused by fault branch ; is the number of load users at load node ;

[0072] Step 4.2. Construct the average power outage duration index constraint of the distribution system by using Equation (20):

[0073] (20)

[0074] In Equation (20): is the average power outage duration index of the distribution system; is the set of power loss load nodes after the branch fault;

[0075] Step 4.3. Construct the power supply shortage index constraint of the load node at the outage by using Equation (21):

[0076] (21)

[0077] In Equation (21): is the power supply shortage index of the load node under the fault of the branch ;

[0078] Step 4.4. Construct the power supply shortage index constraint of the distribution system by using Equation (22):

[0079] (22).

[0080] Furthermore, the fifth step is carried out as follows:

[0081] Step 5.1. Perform second-order cone transformation on the pre-fault line current amplitude constraint by using Equation (23):

[0082] (23)

[0083] Step 5.2. Perform second-order cone transformation on the post-fault line current amplitude constraint by using Equation (24):

[0084] (24).

[0085] An electronic device of the present invention includes a memory and a processor, characterized in that the memory is used to store a program for supporting the processor to execute the distribution system operation reliability evaluation method, and the processor is configured to execute the program stored in the memory.

[0086] A computer-readable storage medium of the present invention stores a computer program, characterized in that the computer program executes the steps of the distribution system operation reliability evaluation method when run by a processor.

[0087] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0088] 1. In the operational reliability assessment, the present invention divides the user load loss into two parts: the first part is the load shedding caused by the unbalanced climbing caused by the net load fluctuation, and the second part is the load loss that has not been restored after the fault reconstruction after the system fails. The scenario of load shedding caused by the unbalanced climbing caused by the violent fluctuation of the net load is fully considered, making the operational reliability assessment of the distribution system more accurate;

[0089] 2. The present invention divides the dynamic scheduling optimization strategy in reliability assessment into two parts. The first part is the optimization scheduling for the climbing balance of flexible resources before the fault, and the second part is the optimization scheduling of the recovery strategy after the fault. The climbing recovery process of flexible resources is taken into account, the scheduling potential of flexible resources is fully tapped, the utilization rate of flexible resources in the distribution system is improved, and the risk of climbing load shedding in the distribution system is reduced;

[0090] 3. The present invention models the recovery process of various flexible resources in the distribution network for a distribution system with multiple flexible resources connected to the grid, fully explores the recovery potential of flexible resources, considers the collaborative recovery ability of flexible resources, formulates the optimal recovery strategy, and provides an effective method for formulating fault reconstruction strategies for distribution systems with high penetration flexible resources;

[0091] 4. The present invention introduces a weight coefficient into the objective function of the fault recovery strategy model, uses a linear weighted method to determine the value of the weight coefficient, and uses the weight sum of the system power outage power shortage index and the number of switch operations as the objective function, so that the fault reconstruction strategy is more reasonable;

[0092] 5. The model of the present invention adopts the form of linear programming and is simplified by the second-order cone and the big-M method. It can be directly solved by a mathematical solver, has strong scalability and high solving efficiency, ensures the generation of the optimal solution of the two-stage scheduling model and the fault recovery model of the distribution system, and further improves the accuracy of the distribution system operation reliability evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0094] In this embodiment, Figure 1 As shown in FIG, a distribution system operation reliability evaluation method considering two-stage scheduling of flexible resources is carried out in the following steps:

[0095] Step 1: Obtain the parameters of flexible resources, including: the ramp rate, upper and lower limit parameters of power generation of small gas turbines; the upper and lower limits of energy storage, charging and discharging efficiency, and initial power parameters of energy storage power stations; the power prediction curves of distributed wind turbines and photovoltaics; the upper and lower limit parameters of the power that can be provided by interruptible loads, and the grid-connected node parameters of flexible resources;

[0096] Obtain the topological structure of the distribution system, including: tie-line distribution, upstream and downstream relationships of load points, line lengths, line impedances, line and switch failure rates, repair times, and sectional switch switching times;

[0097] Obtain the load data of users, including: the number of users at each load point, load levels, active and reactive loads of users.

[0098] Step 2: Consider the load shedding risk caused by the net load fluctuation and establish a pre-fault flexible resource scheduling model:

[0099] Step 2.1: Use Equation (1) to establish the total objective function of the pre-fault flexible resource scheduling model :

[0100] (1)

[0101] In Equation (1): is the grid operation loss function and is obtained from Equation (2), is the total flexibility deficit and is obtained from Equation (3), is the operating load shedding and is obtained from Equation (4), are 3 weight coefficients;

[0102] (2)

[0103] In Equation (2), 、 、 and respectively represent the gas turbine unit consumption, energy storage operation consumption, interruptible load consumption, and upstream power consumption of the power grid at time and respectively represent the energy storage charging and discharging power at time represents the interruptible load node output at time represents the interruptible load node output at time represents the grid power purchase at time; a, b, and c are 3 cost coefficients of the gas turbine; 、 and respectively represent the unit operation consumption of the energy storage, the unit contract consumption of the interruptible load, and the unit consumption of the grid time-of-use; is the total time scale.

[0104] (3)

[0105] In formula (3), is the active power of load shedding at time of the load node caused by the climbing rate or power imbalance; is the total number of load nodes in the distribution system;

[0106] (4)

[0107] In formula (4): and respectively represent the upward and downward flexibility deficits of the distribution system at time

[0108] Step 2.2. Establish the constraint conditions of the flexible resource scheduling model before the fault:

[0109] Step 2.2.1. Use formula (5) to construct the system flexibility supply constraint:

[0110] (5)

[0111] In formula (5): and respectively represent the upward and downward flexibility supplies of the distribution system at time and and and respectively represent the upward flexibility supplies provided by energy storage, interruptible load, power purchase from the grid, and gas turbine at time and and and respectively represent the downward flexibility supplies provided by energy storage, interruptible load, power purchase from the grid, and gas turbine at time

[0112] Step 2.2.2. Use formula (6) to construct the flexibility deficit constraint:

[0113] (6)

[0114] In formula (6): and respectively represent the upward and downward flexibility demands of the distribution system at time

[0115] Step 2.2.3. Use formula (7) to construct the power flow constraint of the distribution system:

[0116] (7)

[0117] In formula (7): and respectively represent the active and reactive power transmitted through the branch between load node and load node at time , where load node is the upstream load point of load node ; and respectively represent the net active and reactive power injected into load node at time , , and respectively represent the active power injected by the upstream power purchase, distributed wind power, distributed photovoltaics, and gas turbines into load node at time , , and respectively represent the reactive power injected by the upstream power purchase, distributed wind power, distributed photovoltaics, and gas turbines into load node at time , respectively represent the active and reactive power of the load at load node at time is the load shedding reactive power of node caused by the ramp rate or power imbalance at time is the resistance value of branch ; is the reactance value of branch ; represents the square of the current amplitude of branch at time , respectively represent the square of the voltage amplitude at load node , load node at time represents the branch between load node and load node , where load node is the downstream load point of load node ; is the set of branches of the distribution system.

[0118] Step 2.2.4. Construct the voltage constraint of the load node using Equation (8):

[0119] (8)

[0120] In Equation (8): and respectively represent the upper and lower limits of the voltage amplitude at the load node ;

[0121] Step 2.2.5. Construct the transmission capacity constraint using Equation (9):

[0122] (9)

[0123] In Equation (9): and respectively represent the upper and lower limits of the transmission capacity of the branch ; represents the transmission capacity of the branch at time

[0124] Step 3. Considering the scheduling potential and mutual influence of flexible resources such as small gas turbines, wind power, photovoltaic power, and energy storage, construct a distribution system fault recovery model considering flexible dynamic regulation and collaborative reconstruction strategies:

[0125] Step 3.1. Construct the objective function of the distribution system fault recovery model using Equation (10) :

[0126] (10)

[0127] In Equation (10): is the power supply shortage index of the distribution system during power outages; represents the total number of branches in normal operation of the distribution system; , are the first and second sub-objective functions respectively; is the th objective function, is the th weight coefficient of the objective function; is a binary variable representing the operating condition of the branch and is obtained from Equation (11);

[0128] (11)

[0129] In Equation (11): is the number of root nodes in the distribution system.

[0130] Step 3.2. Construct the constraint conditions of the distribution system fault recovery model:

[0131] Step 3.2.1. Construct the fault recovery power flow constraint using Equation (11):

[0132] (12)

[0133] In Equation (12): and respectively represent the active and reactive powers transmitted through branch after the fault reconstruction of the distribution system at time and respectively represent the active and reactive powers increased by the ramp-up of flexible resources after the fault reconstruction at time is the square of the current amplitude of branch after the fault reconstruction of the distribution system at time and respectively represent the square of the voltage amplitude at load node and load node after the fault reconstruction of the distribution system at time

[0134] Step 3.2.2. Construct the big M method voltage constraint using Equation (13):

[0135] (13)

[0136] In Equation (13), M is a real number;

[0137] Step 3.2.3. Construct the flexible resource dynamic increase constraint using Equation (14):

[0138] (14)

[0139] In Equation (14): 、 respectively represent the increased active and reactive powers of purchasing electricity upward from the time after the fault reconstruction to before the completion of fault repair at time 、 respectively represent the increased active and reactive powers of the gas turbine from the time after the fault reconstruction to before the completion of fault repair at time

[0140] Step 3.2.4. Construct the gas turbine increase constraint using Equation (15):

[0141] (15)

[0142] In Equation (15), Indicates the time scale of the additional dispatch of the unit set Indicates the additional active power generation of the gas turbine from after fault reconstruction to before the completion of fault repair at a certain moment

[0143] Step 3.2.5. Construct the upward power purchase additional constraint using Equation (16):

[0144] (16)

[0145] In Equation (16), Indicates the active power purchased upward by the system from after fault reconstruction to before the completion of fault repair at a certain moment

[0146] Step 3.2.6. Construct the voltage constraint of the post-fault load node using Equation (17):

[0147] (17)

[0148] Step 3.2.7. Construct the post-fault flexible resource restoration constraint using Equation (18):

[0149] (18)

[0150] In Equation (18): Indicates the reactive power injection of the flexible dispatchable load at the load node at a certain moment Indicates the active power injection of the flexible dispatchable load at the load node at a certain moment Indicates the power factor of the load node at a certain moment

[0151] Step Four. Combine the objective function to define the linear constraints of the reliability index of the distribution system:

[0152] Step 4.1. Construct the outage duration index constraint of the load node using Equation (19):

[0153] (19)

[0154] In Equation (19): is the outage duration index of the load node between the load node and the load node under the fault of the branch ; is the failure rate of the fault branch ; is a binary variable, indicating that after the distribution network performs islanding and reconstruction recovery under the condition of a faulty branch , whether the load node is restored to power is a binary variable, indicating whether the load node is restored to power through the ramp-up of flexible resources; is the isolation time of the faulty branch ; is the time for the faulty branch to restore power to the load node through reconstruction or islanding after power outage; is the repair time of the faulty branch ; is the time for the faulty branch to restore power by increasing the power generation after the load node loses power; is the number of load users at the load node ;

[0155] Step 4.2. Use Equation (20) to construct the average power outage duration index constraint of the distribution system:

[0156] (20)

[0157] In Equation (20): is the average power outage duration index of the distribution system, is the set of load nodes that lose power after the branch fails;

[0158] Step 4.3. Use Equation (21) to construct the power supply shortage index constraint at the load node ;

[0159] (21)

[0160] In Equation (21): is the power supply shortage index at the load node under the failure of the branch ;

[0161] Step 4.4. Use Equation (22) to construct the power supply shortage index constraint of the distribution system:

[0162] (22)

[0163] Step Five. After linearizing some constraints in the pre-fault flexible resource scheduling model and the distribution system fault recovery model using second-order cone relaxation, a linear reliability evaluation model of the distribution system is obtained:

[0164] Step 5.1. Perform second-order cone transformation on the pre-fault line current amplitude constraint using Equation (23):

[0165] (23)

[0166] Step 5.2. Perform second-order cone transformation on the post-fault line current amplitude constraint using Equation (24):

[0167] (24)

[0168] Step 6. Solve the linear evaluation model of the distribution system reliability using a solver. First, obtain the optimal scheduling plan considering the two-stage scheduling of flexible resources, including the scheduling plan for flexible resources during the normal operation stage of the distribution system with the goal of reducing the risk of ramping load shedding and the rescheduling plan for the distribution network system after a fault with the goal of maximizing the restored lost power. Second, obtain the optimal strategy for fault reconstruction of the distribution system considering the scheduling potential of flexible resources and coordinated restoration. Then, based on the above-obtained scheduling plan, rescheduling plan, and fault reconstruction plan, conduct an assessment of the operating reliability of the distribution system in combination with reliability index constraints to obtain the operating reliability index of the distribution system.

[0169] Evaluating the operating reliability of the system requires assessment from multiple aspects according to certain criteria. The present invention evaluates the operating reliability of the system through 4 indicators;

[0170] Load point power outage duration indicator: It represents the average power outage time of the load point users within a given time interval;

[0171] System average power outage duration indicator: It represents the average power outage time of the system users within a given time interval;

[0172] Load point power outage unsupplied electricity indicator: It indicates the amount of electricity unsupplied per household on average in the load point due to power outage within a given time interval;

[0173] System power outage unsupplied electricity indicator: It indicates the amount of electricity unsupplied per household on average in the system due to power outage within a given time interval.

[0174] In this embodiment, an electronic device includes a memory and a processor. The memory is used to store a program that supports the processor to execute the above method, and the processor is configured to execute the program stored in the memory.

[0175] In this embodiment, a computer-readable storage medium stores a computer program on the computer-readable storage medium. When the computer program is run by a processor, it executes the steps of the above method.

Claims

1. A distribution system operation reliability evaluation method considering two-stage scheduling of flexible resources, characterized in that: The steps are as follows: Step 1: Obtain the parameters of flexible resources, including: the ramp rate, upper and lower limit parameters of power generation of small gas turbines; the upper and lower limits of energy storage, charging and discharging efficiency, and initial power parameters of energy storage power stations; the power prediction curves of distributed wind turbines and photovoltaics; the upper and lower limit parameters of the power that can be provided by interruptible loads, and the grid-connected node parameters of flexible resources; Obtain the topology of the distribution system, including: tie line distribution, upstream and downstream relationships of load points, line length, line impedance, line and switch failure rate, repair time, and section switch switching time; Obtain user load data, including: number of users at each load point, load level, user active and reactive loads; Step 2: Considering the load shedding risk caused by net load fluctuation, a pre-fault flexible resource scheduling model is established; Step 3: Considering the dispatching potential and mutual influence of flexible resources such as small gas turbines, wind power, photovoltaics and energy storage, a distribution system fault recovery model considering dynamic adjustment of flexibility and coordinated reconstruction strategy is constructed; Step 4: Define the reliability index linear constraints of the distribution system in combination with the objective function; Step 5: After linearizing some constraints in the pre-fault flexible resource scheduling model and the distribution system fault recovery model using second-order cone relaxation, a linear evaluation model of distribution system reliability is obtained; Step 6. Use the solver to solve the linear evaluation model of distribution system reliability and obtain a scheduling plan that considers the two-stage scheduling of flexible resources, including: a scheduling plan during the normal operation phase of the distribution system, a re-scheduling plan after a fault, and a fault reconstruction plan for the distribution system. Based on the scheduling plan, re-scheduling plan, and fault reconstruction plan, the operating reliability index of the distribution system is obtained.

2. A distribution system operation reliability evaluation method considering two-stage scheduling of flexible resources according to claim 1, characterized in that: The step 2 is carried out as follows: Step 2.1: Use formula (1) to establish the overall objective function of the pre-failure flexible resource scheduling model: : (1) In formula (1): is the grid operation loss function, and is obtained from formula (2): is the total flexibility shortfall, and is obtained from formula (3): is the load shedding operation, and is obtained from formula (4): are 3 weight coefficients; (2) In formula (2), , , and Respectively The power consumption of gas turbine units, energy storage operation consumption, interruptible load consumption and upper-level power consumption of the power grid at each moment; and Respectively represent Energy storage charging and discharging power at all times; express The load node output can be interrupted at any time; express The load node output can be interrupted at any time; express The power purchased by the power grid at the moment; a, b and c are the three cost coefficients of the gas turbine; , and They represent the operating consumption of the energy storage unit, the contractual consumption of the interruptible load unit and the grid time-sharing unit consumption respectively; is the total time scale; (3) In formula (3), for Load nodes are always caused by ramp rate or power imbalance Load shedding active power; is the total number of load nodes in the distribution system; (4) In formula (4): , Respectively The upward and downward flexibility gap of the power distribution system at any given moment; Step 2.2: Establish the constraints of the pre-failure flexible resource scheduling model: Step 2.2.1: Use formula (5) to construct the system flexibility supply constraint: (5) In formula (5): , Respectively Upward and downward flexibility of the power distribution system at all times; , , and Respectively represent Upward flexibility provided by instant energy storage, interruptible loads, grid purchases, and gas turbines; , , and Respectively represent Downward flexibility provided by instant energy storage, interruptible loads, grid purchases, and gas turbines; Step 2.2.2: Use formula (6) to construct the flexibility shortage constraint: (6) In formula (6): , Respectively The upward and downward flexibility requirements of the power distribution system at all times; Step 2.2.3: Use equation (7) to construct the power flow constraint of the distribution system: (7) In formula (7): and Respectively Passing through the load node and load nodes Between branches The active and reactive power transmitted, where the load nodes Load node Upstream load point; and Respectively Inject load nodes at all times The net active and reactive power; , , and Respectively The upper power purchase, distributed wind power, distributed photovoltaic and gas turbine injection load nodes are always Active power at , , and Respectively The upper power purchase, distributed wind power, distributed photovoltaic and gas turbine injection load nodes are always Reactive power at , Respectively Time load node Active and reactive power of the load; for The node is always affected by the climbing rate or power imbalance. The load shedding reactive power; For branch The resistance value; For branch The reactance value; To express Time Branch The square of the current amplitude; , Respectively Time load node , load node The square of the voltage amplitude at ; Represents load node With load node The branches between them, where the load nodes Load node Downstream load point; It is a collection of branches of the power distribution system; Step 2.2.4: Use equation (8) to construct the voltage constraint of the load node: (8) In formula (8): and Represents the load nodes The upper and lower limits of the voltage amplitude; Step 2.2.5: Use formula (9) to construct the transmission capacity constraint: (9) In formula (9): and Respectively represent branches Upper and lower limits on transmission capacity; express Time Branch transmission capacity.

3. A distribution system operation reliability evaluation method considering two-stage scheduling of flexible resources according to claim 2, characterized in that: The step three is carried out as follows: Step 3.1: Use formula (10) to construct the objective function of the distribution system fault recovery model : (10) In formula (10): It is the power outage and power shortage indicator of the power distribution system; Indicates the total number of branches in normal operation of the distribution system; , are the first and second sub-objective functions respectively; For the The objective function, For the The weight coefficient of the objective function; is a binary variable, indicating the branch The operation status of is obtained by formula (11); (11) In formula (11): is the number of root nodes in the power distribution system; Step 3.2: Construct the constraints of the distribution system fault recovery model: Step 3.2.1: Use formula (11) to construct the fault recovery power flow constraint: (12) In formula (12): and Respectively The distribution system is reconfigured through the branch after the fault Active and reactive power transmitted; and Respectively represent the fault reconstruction Active and reactive power generated by flexible resources ramping up at all times; for Reconstruction of the branch after the power distribution system failure The square of the current amplitude; and Respectively Load nodes after power distribution system failure reconstruction and load nodes The square of the voltage amplitude at ; Step 3.2.2: Use equation (13) to construct the voltage constraint of the large M method: (13) In formula (13), M is a real number; Step 3.2.3: Use formula (14) to construct the dynamic issuance constraint of flexible resources: (14) In formula (14): , Represents the period from fault reconstruction to fault repair completion. The additional active and reactive power of electricity purchased from above at all times; , Represents the period from fault reconstruction to fault repair completion. The additional active and reactive power of the gas turbine at each moment; Step 3.2.4: Use equation (15) to construct the gas turbine generation constraint: (15) In formula (15), represents the time scale of additional unit dispatching, Indicates the period from after fault reconstruction to before the fault repair is completed The additional active power of the gas turbine at each moment; Step 3.2.5: Use formula (16) to construct the upward power purchase and issuance constraint: (16) In formula (16), Indicates the period from after fault reconstruction to before the fault repair is completed Active power purchased by the system at all times; Step 3.2.6: Use equation (17) to construct the voltage constraint of the load node after the fault: (17) Step 3.2.7: Use formula (18) to construct the post-failure flexible resource recovery constraint: (18) In formula (18): express The flexible load output at the load node The injected reactive power at express The flexible load output at the load node The injected active power at express Time load node The power factor.

4. A distribution system operation reliability evaluation method considering two-stage scheduling of flexible resources according to claim 3, characterized in that: The step 4 is carried out as follows: Step 4.1: Use formula (19) to construct the power outage duration index constraint of the load node: (19) In formula (19): Load node At the load node and load nodes The branch between Power outage duration indicator under fault; Fault branch failure rate; is a binary variable, indicating the fault branch Under these conditions, the distribution network is isolated and reconstructed to restore the load node. Is the power supply restored? is a binary variable, indicating the load node Whether power supply is restored through flexible resource ramping; Fault branch The duration of isolation; Fault branch Causes load node Time to restore power after a power outage through reconstruction or islanding; Fault branch Repair time; Fault branch Causes load node The time it takes to restore power after a power outage; Load node The number of load users; Step 4.2: Use formula (20) to construct the average power outage duration index constraint of the distribution system: (20) In formula (20): is the average outage duration indicator of the distribution system, is the set of power-off load nodes after branch failure; Step 4.3: Use formula (21) to construct the load node Power outage and power shortage indicator constraints: (21) In formula (21): Load node On the branch road Power outage and power shortage indicators under fault conditions; Step 4.4: Use formula (22) to construct the power outage and power shortage indicator constraint of the distribution system: (22)。 5. A distribution system operation reliability evaluation method considering two-stage scheduling of flexible resources according to claim 4, characterized in that: The step five is carried out as follows: Step 5.1: Use equation (23) to perform a second-order cone transformation on the line current amplitude constraint before the fault: (23) Step 5.2: Use equation (24) to perform a second-order cone transformation on the post-fault line current amplitude constraint: (24)。 6. An electronic device, comprising a memory and a processor, characterized in that: The memory is used to store a program that supports the processor to execute the distribution system operation reliability assessment method as described in any one of claims 1-5, and the processor is configured to execute the program stored in the memory.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for evaluating the operation reliability of a power distribution system according to any one of claims 1 to 5 are executed.

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