A reliability assessment method for a transmission network and a flexible interconnected distribution network system

Abstract

The present invention discloses a reliability evaluation method for a power transmission network and a flexible interconnected distribution network system. For a system where the power transmission network is connected to the flexible interconnected distribution network, existing methods consider it as two independent systems for reliability analysis, which reduces the accuracy of the reliability analysis. The present invention improves on the existing reliability analysis method, constructs an integrated reliability evaluation method for the power transmission network and the flexible interconnected distribution network, quantifies the mutual influence of the power transmission network and the flexible interconnected distribution network under fault scenarios through fault enumeration and analysis, corrects the reliability indicators, and improves the accuracy of the reliability evaluation of the power transmission network and the flexible interconnected distribution network.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible interconnected distribution networks, and particularly designs a reliability assessment method for a transmission network and a flexible interconnected distribution network system. Background Art

[0002] In the field of power system reliability analysis, due to the voltage level differences between the transmission network and the flexible interconnected distribution network, they are usually regarded as two independent systems for reliability analysis. As Figure 1 shown, it is a schematic diagram of a system where the transmission network is connected to the flexible interconnected distribution network in the prior art. The flexible interconnected distribution network is connected to the transmission network, and the flexible interconnected switch SOP enables the flexible interconnected distribution network to have a stronger power supply architecture adjustment ability. In the existing conventional reliability assessment methods, when performing reliability analysis on the transmission network, the connected flexible interconnected distribution network system is equivalent to a nodal load; while when performing reliability analysis on the flexible interconnected distribution network, the transmission network is equivalent to a power supply node located at the access point of the flexible interconnected distribution network and always operating reliably.

[0003] In the system where the transmission network is interconnected with the flexible interconnected distribution network, the impact of the flexible interconnected distribution network fault on the transmission network is mainly reflected in that: the flexible interconnected distribution network fault causes a large amount of load loss, which will lead to the violation of the security constraints of the transmission system power flow, and then cause load shedding inside the transmission network. The impact of the transmission network fault on the flexible interconnected distribution network is mainly reflected in that: after a fault occurs inside the transmission network, the load reduction involved in the power generation rescheduling is completed by disconnecting the load nodes in the flexible interconnected power grid connected to the nodes. The transmission network fault will reduce the operation reliability of the flexible interconnected distribution network.

[0004] Therefore, considering the close connection between the transmission and distribution networks during the operation of the power system, it is necessary to regard them as a whole for reliability assessment. Summary of the Invention

[0005] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, the abstract of the specification and the title of the invention of this application to avoid obscuring the purpose of this part, the abstract of the specification and the title of the invention, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the problems existing in the above-mentioned reliability assessment method for a transmission network and a flexible interconnected distribution network system, the present invention is proposed.

[0007] Therefore, the problem to be solved by the present invention is how to provide a reliability assessment method for a transmission network and a flexible interconnected distribution network system.

[0008] To solve the above technical problems, the present invention provides the following technical solutions: A reliability evaluation method for a transmission network and a flexible interconnected distribution network system, which includes,

[0009] As a preferred solution of the reliability evaluation method for a transmission network and a flexible interconnected distribution network system of the present invention, wherein:

[0010] Enumerate various fault states of the transmission network and the flexible interconnected distribution network, and then calculate the reliability indexes of the transmission network without considering the influence of the flexible interconnected distribution network and the reliability indexes of the flexible interconnected distribution network without considering the influence of the transmission network;

[0011] Calculate the reliability correction indexes considering the influence of the flexible interconnected distribution network fault on the transmission network and the reliability correction indexes considering the influence of the load shedding caused by the transmission network fault on the flexible interconnected distribution network for the obtained reliability indexes;

[0012] Obtain the reliability indexes of the transmission network considering the influence of the flexible interconnected distribution network and the reliability indexes of the flexible interconnected distribution network considering the influence of the transmission network through all the above calculation data;

[0013] Based on the reliability indexes of the transmission network considering the influence of the flexible interconnected distribution network and the reliability indexes of the flexible interconnected distribution network considering the influence of the transmission network, realize the reliability evaluation of the transmission network and the flexible interconnected distribution network.

[0014] As a preferred solution of the reliability evaluation method for a transmission network and a flexible interconnected distribution network system of the present invention, wherein: When performing the reliability evaluation, the transmission network and the flexible interconnected distribution network system are regarded as two independent systems for reliability evaluation. When evaluating the reliability of the transmission network, the flexible interconnected distribution network connected to it is equivalent to a node load; when evaluating the reliability of the flexible interconnected distribution network, the transmission network is equivalent to a power supply node located at the distribution network access point and always operating reliably.

[0015] As a preferred solution of the reliability evaluation method for a transmission network and a flexible interconnected distribution network system of the present invention, wherein: The operation of the reliability indexes of the transmission network without considering the influence of the flexible interconnected distribution network and the reliability correction indexes considering the influence of the flexible interconnected distribution network fault on the transmission network include,

[0016] Enumerate the possible fault states of the transmission network, calculate the corresponding power outage time, frequency, power supply deficit, etc., and combine the occurrence probabilities of each enumerated fault state to obtain the reliability indexes of the transmission network without considering the influence of the flexible interconnected distribution network; such as loss of load frequency, loss of load expectation, average duration of load loss, expectation of power shortage, and expectation of energy shortage;

[0017] Considering that the failure of the flexible interconnected distribution network leads to the disconnection of some loads and the violation of the power flow constraints of the transmission network, a re-dispatch of power generation for the transmission network is carried out to obtain the reliability correction index considering the impact of the flexible interconnected distribution network failure on the transmission network, such as the corrected loss of load frequency, the corrected loss of load expectation, the corrected average duration of load loss, the corrected expected energy not supplied, and the corrected expected energy shortage.

[0018] The reliability index of the transmission network considering the impact of the flexible interconnected distribution network = the reliability index of the transmission network without considering the impact of the flexible interconnected distribution network + the reliability correction index considering the impact of the flexible interconnected distribution network failure on the transmission network.

[0019] As a preferred embodiment of the reliability evaluation method for a transmission network and a flexible interconnected distribution network system according to the present invention, wherein: the reliability index of the flexible interconnected distribution network without considering the impact of the transmission network and the reliability correction index of the impact of the load disconnected due to the transmission network failure on the flexible interconnected distribution network include

[0020] Enumerate the possible failure states of the flexible interconnected distribution network, and calculate the reliability index of the flexible interconnected distribution network without considering the impact of the transmission network, such as the failure rate and the power outage time.

[0021] Considering the impact of the transmission network failure, the re-dispatch of power generation for the transmission network is completed by disconnecting the loads in the connected flexible interconnected distribution network, which reduces the operating reliability of the flexible interconnected distribution network, and the reliability correction index of the impact of the load disconnected due to the transmission network failure on the flexible interconnected distribution network is obtained, such as the corrected failure rate Δλ d and the corrected power outage time ΔU d ;

[0022] The reliability index of the flexible interconnected distribution network considering the impact of the transmission network = the reliability index of the flexible interconnected distribution network without considering the impact of the transmission network + the reliability correction index of the impact of the load disconnected due to the transmission network failure on the flexible interconnected distribution network.

[0023] As a preferred embodiment of the reliability evaluation method for a transmission network and a flexible interconnected distribution network system according to the present invention, wherein: the formula for the corrected failure rate Δλ d and the corrected power outage time ΔU d is

[0024]

[0025] Where: LOLF y and LOLE y are the loss of load frequency and the loss of load expectation corresponding to the failure state y of the transmission network respectively; Y is the set of all enumerated failure states of the transmission network; F d (y) is a self-set reference coefficient.

[0026] As a preferred solution of a reliability evaluation method for a transmission network and a flexible interconnected distribution network system according to the present invention, wherein: F d Value-taking method of (y)

[0027] When a load is cut off in the flexible interconnected distribution network under the fault state y, then F d The value of (y) is 1;

[0028] When no load is cut off in the flexible interconnected distribution network under the fault state y, then F d The value of (y) is 0.

[0029] As a preferred solution of a reliability evaluation method for a transmission network and a flexible interconnected distribution network system according to the present invention, wherein: for all enumerated fault states, power generation rescheduling is performed on the transmission network and the load shedding amount is calculated. The goal of power generation rescheduling is to minimize the active load cut off; the calculation model for calculating the reliability correction index considering the impact of flexible interconnected distribution network faults on the transmission network is

[0030]

[0031]

[0032]

[0033]

[0034] Wherein, x is a certain fault scenario of the enumerated flexible interconnected distribution network, λ x Is the failure rate of the fault scenario x, t fx Is the fault repair time of the fault scenario x, t rx Is the fault reconstruction time of the fault scenario x, P L，pos (x) is the load shedding amount of the flexible interconnected distribution network corresponding to the fault scenario x before fault reconstruction, P L，pos (x) is the load shedding amount of the flexible interconnected distribution network corresponding to the fault scenario x after fault reconstruction, X is the set of all fault scenarios of the enumerated flexible interconnected distribution network, and F(x) is a self-set reference coefficient.

[0035] As a preferred solution of a reliability evaluation method for a transmission network and a flexible interconnected distribution network system according to the present invention, wherein: the value judgment method of the self-set parameter coefficient F(x) is

[0036]

[0037] As a preferred solution of the reliability evaluation method of a power transmission network and a flexible interconnected distribution network system according to the present invention, wherein: the objective function of the power generation rescheduling

[0038]

[0039] where ΔP Li is the active load shedding amount of node i, ΔQ Li is the reactive load shedding amount of node i, and n is the total number of nodes; S i(1×k) is the node number matrix of the disconnection switches connected to node i in the flexible interconnected distribution network during load shedding, and its feasible range is the set of all flexible interconnected distribution network switch operation combinations obtained by enumeration. k is the number of disconnection switches, is the total active load downstream of the disconnection switch in the feeder to which the jth disconnection switch belongs, is the total reactive load downstream of the disconnection switch in the feeder to which the jth disconnection switch belongs, ΔP SOP is the total active load transferred through the flexible interconnected switch in the flexible interconnected distribution network, ΔQ SOP is the total reactive load transferred through the flexible interconnected switch in the flexible interconnected distribution network, is the maximum value of the allowable active load shedding amount of node i, is the maximum value of the allowable reactive load shedding amount of node i.

[0040] As a preferred solution of the reliability evaluation method of a power transmission network and a flexible interconnected distribution network system according to the present invention, wherein:

[0041] Enumerate various fault states of the power transmission network and calculate the reliability indexes of the power transmission network without considering the influence of the flexible interconnected distribution network;

[0042] Enumerate various fault states of the flexible interconnected distribution network and calculate the reliability indexes of the flexible interconnected distribution network without considering the influence of the power transmission network;

[0043] In the case of a fault in the flexible interconnected distribution network, obtain the reliability correction indexes considering the influence of the flexible interconnected distribution network fault on the power transmission network;

[0044] In the case of a fault in the power transmission network, calculate the reliability correction indexes of the influence of the load shedding caused by the power transmission network fault on the flexible interconnected distribution network;

[0045] Obtain the reliability indexes of the power transmission network considering the influence of the flexible interconnected distribution network and the reliability indexes of the flexible interconnected distribution network considering the influence of the power transmission network;

[0046] Finally, realize the reliability evaluation of the power transmission network and the flexible interconnected distribution network.

[0047] The beneficial effects of the present invention are as follows: By constructing an integrated reliability assessment method for the transmission network and the flexible interconnected distribution network, the mutual influence between the transmission network and the flexible interconnected distribution network under fault scenarios is quantified through fault enumeration and analysis, and the reliability index is corrected, thereby improving the accuracy of the reliability assessment of the transmission network and the flexible interconnected distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts. Among them:

[0049] Figure 1 It is a flowchart of a reliability assessment method for a transmission network and a flexible interconnected distribution network system in Embodiment 1.

[0050] Figure 2 It is a schematic diagram of a prior art system in which a transmission network is connected to a flexible interconnected distribution network for a reliability assessment method of a transmission network and a flexible interconnected distribution network system in Embodiment 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below with reference to the drawings in the specification.

[0052] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0053] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that can be included in at least one implementation of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or alternative embodiments that exclude each other from other embodiments.

[0054] Embodiment 1

[0055] Referring to Figure 1 , which is an embodiment of the present invention, a reliability assessment method for a transmission network and a flexible interconnected distribution network system is provided, including:

[0056] The transmission network and the flexible interconnected distribution network system are regarded as two independent systems for reliability assessment. That is, when assessing the reliability of the transmission network, the flexible interconnected distribution network connected to it is equivalent to a nodal load. When assessing the reliability of the flexible interconnected distribution network, the transmission network is equivalent to a power source node located at the distribution network access point and always operating reliably;

[0057] Enumerate the possible fault states of the transmission network, calculate the corresponding power outage time, frequency, and power supply deficit, etc., and combine the occurrence probabilities of each enumerated fault state to obtain the reliability indexes of the transmission network without considering the influence of the flexible interconnected distribution network, such as loss of load frequency, loss of load expectation, average duration of load loss, expected energy not supplied, and expected demand not met;

[0058] Enumerate the possible fault states of the flexible interconnected distribution network, and calculate the reliability indexes of the flexible interconnected distribution network without considering the influence of the transmission network, such as failure rate and power outage time;

[0059] Considering that the failure of the flexible interconnected distribution network causes some loads to be disconnected and the power flow constraint of the transmission network to be exceeded, perform power generation re-scheduling on the transmission network to obtain the reliability correction indexes considering the influence of the flexible interconnected distribution network failure on the transmission network, such as corrected loss of load frequency, corrected loss of load expectation, corrected average duration of load loss, corrected expected energy not supplied, and corrected expected demand not met;

[0060] Considering the influence of the transmission network failure, the power generation re-scheduling of the transmission network is completed by disconnecting the loads in the connected flexible interconnected distribution network, which reduces the operation reliability of the flexible interconnected distribution network, and obtain the reliability correction indexes of the influence of the load cut-off caused by the transmission network failure on the flexible interconnected distribution network, such as corrected failure rate and corrected power outage time;

[0061] Based on the reliability indexes of the transmission network without considering the influence of the flexible interconnected distribution network and the reliability correction indexes considering the influence of the flexible interconnected distribution network failure on the transmission network, obtain the reliability indexes of the transmission network considering the influence of the flexible interconnected distribution network;

[0062] Reliability index of the transmission network considering the influence of the flexible interconnected distribution network = Reliability index of the transmission network without considering the influence of the flexible interconnected distribution network + Reliability correction index considering the influence of the flexible interconnected distribution network failure on the transmission network;

[0063] Based on the reliability indexes of the flexible interconnected distribution network without considering the influence of the transmission network and the reliability correction indexes of the influence of the load cut-off caused by the transmission network failure in step, obtain the reliability indexes of the flexible interconnected distribution network considering the influence of the transmission network;

[0064] The reliability index of a flexible interconnected distribution network considering the impact of the transmission network = The reliability index of a flexible interconnected distribution network without considering the impact of the transmission network + The reliability correction index of the impact of load shedding caused by transmission network faults on the flexible interconnected distribution network.

[0065] Enumerate all fault states that occur in the transmission network;

[0066] For a certain fault state y of the enumerated transmission network, calculate the corresponding reliability index of this fault state y, such as loss of load frequency and loss of load expectation;

[0067] Calculate the corrected failure rate and corrected power outage time according to the following formula

[0068]

[0069] where LOLF y and LOLE y are respectively the loss of load frequency and loss of load expectation, which are the corresponding reliability indexes at the fault state y of the transmission network; Y is the set of all enumerated fault states of the transmission network; F d (y) is a self-set reference coefficient.

[0070] When there is load shed in the flexible interconnected distribution network under this fault state y, then the value of F d (y) is 1;

[0071] When there is no load shed in the flexible interconnected distribution network under this fault state y, then the value of F d (y) is 0.

[0072] Enumerate all fault states that occur in the flexible interconnected distribution network;

[0073] For all enumerated fault states, perform power generation re-scheduling on the transmission network and calculate the load shedding amount. The objective function of the power generation re-scheduling is to minimize the active load shed:

[0074] Calculate the reliability correction index considering the impact of flexible interconnected distribution network faults on the transmission network as follows;

[0075]

[0076]

[0077]

[0078]

[0079] where x is a certain fault scenario of the enumerated flexible interconnected distribution network, λ x is the failure rate of the fault scenario x, t fxThe fault repair time for fault scenario x is t rx The fault reconstruction time for fault scenario x is P L，pos P(x) is the load shedding amount of the flexible interconnected distribution network before fault reconstruction corresponding to fault scenario x L，pos X(x) is the load shedding amount of the flexible interconnected distribution network after fault reconstruction corresponding to fault scenario x. X is the set of all fault scenarios of the flexible interconnected distribution network, and F(x) is a self-set coefficient

[0080] The expression of F(x) is as follows

[0081]

[0082] The sum of the active load and reactive load located downstream of the disconnected switch is calculated through the objective function of power generation rescheduling

[0083] Where ΔP Li is the active load shedding amount of node i, ΔQ Li is the reactive load shedding amount of node i, and n is the total number of nodes; S i(1×k) is the node number matrix of the disconnected switch corresponding to node i when the load is shed, and its feasible range is the set of all switch operation combinations of the flexible interconnected distribution network obtained by enumeration. k is the number of disconnected switches is the sum of the active loads located downstream of the disconnected switch in the feeder to which the jth disconnected switch belongs is the sum of the reactive loads located downstream of the disconnected switch in the feeder to which the jth disconnected switch belongs, ΔP SOP is the sum of the active loads transferred through the flexible interconnected switch in the flexible interconnected distribution network, ΔQ SOP is the sum of the reactive loads transferred through the flexible interconnected switch in the flexible interconnected distribution network is the maximum value of the allowable active load shedding amount of node i is the maximum value of the allowable reactive load shedding amount of node i

[0084] Embodiment 2

[0085] Refer to Figure 2 This is the second embodiment of the present invention

[0086] Table 1 gives the comparison of the calculation results of the transmission network reliability indexes before and after considering the influence of the faults of the flexible interconnected distribution network. The structures of the transmission network and the flexible interconnected distribution network are as Figure 1As shown, a fault occurs at node 3. The reliability indices in Table 1 that do not conventionally consider the impact of faults in the flexible interconnected distribution network are on the low side; when using the method proposed in the present invention and considering the impact of faults in the flexible interconnected distribution network on the power supply reliability of the transmission network, the indices of expected load loss, load loss frequency, and expected energy not supplied all increase, indicating that ignoring the impact of faults in the flexible interconnected distribution network will result in an overly optimistic reliability assessment result for the transmission network, and using the method proposed in the present invention can improve the accuracy of the reliability assessment of the transmission network.

[0087]

[0088] Table 2 presents the reliability indices of the load nodes in the flexible interconnected distribution network before and after considering the faults in the transmission network.

[0089] As can be seen from Table 2, when comparing with the method that does not conventionally consider the impact of faults in the transmission network, after using the method proposed in the present invention to consider the impact of faults in the transmission network, the indices of failure rate λ and outage time U of the load nodes in the reliability indices of the internal load nodes of the flexible interconnected distribution network calculated both increase, indicating that the reliability assessment result obtained by the method that does not conventionally consider the impact of faults in the transmission network is overly optimistic, and the result obtained by the reliability assessment method proposed in the present invention considering the impact of faults in the transmission network is more accurate.

[0090]

[0091]

[0092] In summary, the reliability assessment method for the transmission network and the flexible interconnected distribution network system proposed in the present invention quantifies the mutual influence between the transmission network and the flexible interconnected distribution network in the fault scenario through fault enumeration and analysis, corrects the reliability indices, and improves the accuracy of the reliability assessment of the transmission network and the flexible interconnected distribution network.

[0093] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle described in the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A reliability evaluation method for a transmission network and a flexible interconnected distribution network system, characterized in that: including enumerating various fault states of the transmission network and the flexible interconnected distribution network, and then calculating the reliability indexes of the transmission network without considering the influence of the flexible interconnected distribution network and the reliability indexes of the flexible interconnected distribution network without considering the influence of the transmission network; calculating the reliability correction indexes considering the influence of the flexible interconnected distribution network fault on the transmission network and the reliability correction indexes considering the influence of the load shedding caused by the transmission network fault on the flexible interconnected distribution network by using the obtained reliability indexes; obtaining the reliability indexes of the transmission network considering the influence of the flexible interconnected distribution network and the reliability indexes of the flexible interconnected distribution network considering the influence of the transmission network through all the above calculation data; realizing the reliability evaluation of the transmission network and the flexible interconnected distribution network based on the reliability indexes of the transmission network considering the influence of the flexible interconnected distribution network and the reliability indexes of the flexible interconnected distribution network considering the influence of the transmission network; for all the enumerated fault states, performing power generation rescheduling on the transmission network and calculating the load shedding amount, and the goal of the power generation rescheduling is to minimize the active load to be cut off; the calculation model for calculating the reliability correction indexes considering the influence of the flexible interconnected distribution network fault on the transmission network is: Among them, x is a certain fault scenario of the enumerated flexible interconnected distribution network, and λ x is the failure rate of the fault scenario x, and t fx is the fault repair time of the fault scenario x, and t rx is the fault reconstruction time of the fault scenario x, and P L，pos (x) is the load shedding amount of the flexible interconnected distribution network before fault reconstruction corresponding to the fault scenario x, and P L，pos (x) is the load shedding amount of the flexible interconnected distribution network after fault reconstruction corresponding to the fault scenario x, X is the set of all fault scenarios of the enumerated flexible interconnected distribution network, and F(x) is a self-set reference coefficient.

2. The reliability evaluation method of a transmission network and a flexible interconnected distribution network system according to claim 1, characterized in that: when performing the reliability evaluation, the transmission network and the flexible interconnected distribution network system are regarded as two independent systems for reliability evaluation. When evaluating the reliability of the transmission network, the flexible interconnected distribution network connected to it is equivalent to a nodal load; when evaluating the reliability of the flexible interconnected distribution network, the transmission network is equivalent to a power supply node located at the distribution network access point and always operating reliably.

3. The reliability evaluation method of a transmission network and a flexible interconnected distribution network system according to claim 1 or 2, characterized in that: The reliability indexes calculation of the transmission network without considering the influence of the flexible interconnected distribution network and the reliability correction indexes considering the influence of the flexible interconnected distribution network fault on the transmission network include enumerating the possible fault states of the transmission network, calculating the corresponding power outage time, frequency, power supply shortage amount, etc., and combining with the occurrence probability of each enumerated fault state to obtain the reliability indexes of the transmission network without considering the influence of the flexible interconnected distribution network; such as loss of load frequency, loss of load expectation, average duration of loss of load, expected energy not supplied, and expected energy shortage; considering that the flexible interconnected distribution network fault causes some loads to be cut off and the transmission network power flow constraint to be violated, performing power generation rescheduling on the transmission network to obtain the reliability correction indexes considering the influence of the flexible interconnected distribution network fault on the transmission network, such as corrected loss of load frequency, corrected loss of load expectation, corrected average duration of loss of load, corrected expected energy not supplied, and corrected expected energy shortage; The reliability indexes of the transmission network considering the influence of the flexible interconnected distribution network = the reliability indexes of the transmission network without considering the influence of the flexible interconnected distribution network + the reliability correction indexes considering the influence of the flexible interconnected distribution network fault on the transmission network.

4. The reliability evaluation method of a transmission network and a flexible interconnected distribution network system according to claim 1 or 2, characterized in that: The reliability indexes of the flexible interconnected distribution network without considering the influence of the transmission network and the reliability correction indexes considering the influence of the load shedding caused by the transmission network fault on the flexible interconnected distribution network include enumerating the possible fault states of the flexible interconnected distribution network and calculating the reliability indexes of the flexible interconnected distribution network without considering the influence of the transmission network; Considering the impact of transmission network faults, the generation rescheduling of the transmission network is accomplished by disconnecting the loads in the connected flexible interconnected distribution network, which reduces the operating reliability of the flexible interconnected distribution network. The reliability correction indicators for the impact of load shedding caused by transmission network faults on the flexible interconnected distribution network are obtained, such as the corrected failure rate and the corrected power outage time. The reliability index of the flexible interconnected distribution network considering the impact of the transmission network = the reliability index of the flexible interconnected distribution network without considering the impact of the transmission network + the reliability correction index for the impact of load shedding caused by transmission network faults on the flexible interconnected distribution network.

5. The reliability evaluation method of a transmission network and a flexible interconnected distribution network system according to claim 4, characterized in that: The calculation formulas for the corrected failure rate and the corrected power outage time where: LOLF y and LOLE y are the loss of load frequency and loss of load expectation corresponding to the fault state y of the power transmission network respectively; Y is the set of all enumerated fault states of the power transmission network; F d (y) is a self-set reference coefficient.

6. The reliability evaluation method of a transmission network and a flexible interconnected distribution network system according to claim 5, characterized in that: The said F d (y) is obtained in the following way: When a load is removed from the flexible interconnected distribution network in the fault state y, then the value of F d (y) is 1; If no load is shed in the flexible interconnected distribution network under the fault state y, then the value of F d (y) is 0.

7. The reliability evaluation method of a transmission network and a flexible interconnected distribution network system according to claim 1, characterized in that: The method for determining the value of the self-set parameter coefficient F(x) is Among them, P L，pos (x) is the load shedding amount of the flexible interconnected distribution network after fault reconstruction corresponding to the fault scenario x.

8. The reliability evaluation method for a transmission network and a flexible interconnected distribution network system according to claim 1, characterized in that: The objective function of the generation rescheduling is where ΔP Li is the active load shedding amount of node i, ΔQ Li is the reactive load shedding amount of node i, and n is the total number of nodes; S i(1×k) is the node number matrix of the disconnecting switches connected to node i in the flexible interconnected distribution network during load shedding. Its feasible range is the set of all flexible interconnected distribution network switch operation combinations obtained by enumeration. k is the number of disconnecting switches, is the sum of the active loads downstream of the j-th disconnecting switch in the feeder to which the j-th disconnecting switch belongs, is the sum of the reactive loads downstream of the j-th disconnecting switch in the feeder to which the j-th disconnecting switch belongs, ΔP SOP is the total active load transferred through the flexible interconnection switches in the flexible interconnected distribution network, ΔQ SOP is the total reactive load transferred through the flexible interconnection switches in the flexible interconnected distribution network, is the maximum value of the allowable active load shedding amount of node i, is the maximum value of the allowable reactive load shedding amount of node i.

9. A reliability evaluation method for a transmission network and a flexible interconnected distribution network system according to claim 1, characterized in that: Enumerate various fault states of the transmission network and calculate the reliability index of the transmission network without considering the impact of the flexible interconnected distribution network; Enumerate various fault states of the flexible interconnected distribution network and calculate the reliability index of the flexible interconnected distribution network without considering the impact of the transmission network; In the case of a fault in the flexible interconnected distribution network, obtain the reliability correction index considering the impact of the flexible interconnected distribution network fault on the transmission network; In the case of a transmission network fault, calculate the reliability correction index for the impact of load shedding caused by the transmission network fault on the flexible interconnected distribution network; Obtain the reliability index of the transmission network considering the impact of the flexible interconnected distribution network and the reliability index of the flexible interconnected distribution network considering the impact of the transmission network; Finally, realize the reliability evaluation of the transmission network and the flexible interconnected distribution network.

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