Value evaluation method and system for a DC distribution network control and protection device

Abstract

The present application discloses a value evaluation method and system for a DC distribution network control and protection device, including: collecting historical operation and maintenance cost data of the control and protection device at different stages, and establishing a multi-stage operation and maintenance cost mathematical model by using the polynomial regression method according to the historical operation and maintenance cost data; establishing a full life cycle cost function of the control and protection device; establishing a system benefit function according to the power grid system benefits, and establishing a full life cycle rate of return function of the control and protection device according to the system benefit function and the full life cycle cost function; transforming the full life cycle rate of return function based on the operation and maintenance cost mathematical model, the full life cycle cost function, and the system benefit function to obtain a final rate of return function; solving the extreme point of the final rate of return function to obtain the optimal overhaul time of the control and protection device, determining the overhaul frequency threshold according to the optimal overhaul time, and determining that the control and protection device is in a scrapped state when the overhaul frequency of the control and protection device reaches the overhaul frequency threshold. It solves the problem of large errors in the value evaluation of equipment in the prior art.

Description

Technical Field

[0001] The present application relates to the technical field of operation and maintenance of power equipment, and particularly to a method and system for evaluating the value of a DC distribution network control and protection device. Background Art

[0002] Equipment asset management is an important link in the operation and management of power grid companies, plays an important role in the reliable operation of the power grid, and is the key means for power companies to maximize investment returns. DC power distribution technology is based on advanced power electronics technology, and uses converters, DC transformers, DC circuit breakers and control and protection devices to ensure the flexible, safe and reliable operation of the DC distribution network. Since the current DC power distribution technology and equipment are not yet mature, the asset management is difficult and the operation and maintenance cost is high. It is urgent to propose a reasonable equipment management method to guide the operation and maintenance of key equipment in the DC distribution network, and improve the utilization efficiency of assets on the basis of ensuring the reliable operation of the DC distribution network.

[0003] The DC distribution network control and protection device is a secondary device used to realize the operation control and protection functions of the DC distribution network. It generally adopts redundant configuration. When the DC distribution network control and protection device fails, it can be seamlessly switched to another set of DC distribution network control and protection devices without affecting the continuous power supply ability of the DC distribution network, which is quite different from primary devices such as converters, DC transformers, and DC circuit breakers.

[0004] The existing methods for evaluating the value of DC distribution network control and protection devices mainly have the following problems: only quantitatively analyze the maintenance cost of the equipment, without fully considering the equipment investment cost, equipment scrapping cost and the benefits brought by the reliable operation of the equipment; and mostly use quadratic equation fitting for the maintenance cost, with large errors; at the same time, the redundant configuration characteristics of the DC distribution network control and protection device are not considered, and the relevant costs need to be further refined. Summary of the Invention

[0005] The present application provides a method and system for evaluating the value of a DC distribution network control and protection device, which are used to solve the technical problem that the existing technology does not fully consider factors such as equipment investment cost and equipment scrapping cost, resulting in large errors in the evaluation of equipment value.

[0006] In view of this, the first aspect of the present application provides a method for evaluating the value of a DC distribution network control and protection device, and the method includes:

[0007] Collect historical operation and maintenance cost data of the control and protection device at different stages, and establish a multi-stage operation and maintenance cost mathematical model according to the historical operation and maintenance cost data by using the polynomial regression method;

[0008] Establish a full life cycle cost function of the control and protection device, and the full life cycle cost function is composed of: an investment and construction cost function, an operation and maintenance cost function, a failure cost function, and an implementation risk cost function;

[0009] Establish a system benefit function based on the benefits of the power grid system, and establish the life cycle return rate function of the control and protection device according to the system benefit function and the life cycle cost function;

[0010] Transform the life cycle return rate function based on the operation and maintenance cost mathematical model, the life cycle cost function, and the system benefit function to obtain the final return rate function;

[0011] Solve the extreme point of the final return rate function to obtain the optimal overhaul time of the control and protection device, determine the overhaul times threshold according to the optimal overhaul time, and when the overhaul times of the control and protection device reach the overhaul times threshold, determine that the control and protection device enters the scrapped state.

[0012] Optionally, establishing a multi-stage operation and maintenance cost mathematical model by using the polynomial regression method according to the historical operation and maintenance cost data specifically includes:

[0013] Obtain the first operation and maintenance cost sequence from the initial use of the control and protection device to the first overhaul and the second operation and maintenance cost sequence from the first overhaul to the second overhaul according to the historical operation and maintenance cost data;

[0014] Use the polynomial interpolation method to transform the first operation and maintenance cost sequence and the second operation and maintenance cost sequence to obtain the operation and maintenance cost functions for the first overhaul and the second overhaul;

[0015] Based on the operation and maintenance cost functions, obtain the operation and maintenance cost mathematical model according to the periodic trend characteristics of the control and protection device after each overhaul.

[0016] Optionally, the operation and maintenance cost function is:

[0017]

[0018] Among them,

[0019]

[0020]

[0021] In the formula, a and b are both coefficients, C m_i is the operation and maintenance cost at time i in the first overhaul, C m_j0 is the operation and maintenance cost at time j in the second overhaul, t is the operation time of the control and protection device, and n is the number of overhauls.

[0022] Optionally, the operation and maintenance cost mathematical model is:

[0023] f n (t) = f 2 (t - t n )

[0024] Wherein, t n is the start time of the nth major overhaul.

[0025] Optionally, the life cycle cost function is:

[0026] LCC(t) = C I (t) + C M (t) + C F (t) + C R (t);

[0027] Wherein, C I (t) is the investment and construction cost function, C M (t) is the operation and maintenance cost function, C F (t) is the failure cost function, C R (t) is the implementation risk cost function.

[0028] Optionally, the system benefit function is:

[0029] CE(t) = k 分摊 E 售电 t;

[0030] Wherein, k 分摊 is the electricity sales cost sharing coefficient, E 售电 is the electricity sales revenue of the power grid system.

[0031] Optionally, the life cycle rate of return function is:

[0032]

[0033] Wherein, C I (t) is the investment and construction cost function, C M (t) is the operation and maintenance cost function, C F (t) is the failure cost function, C R (t) is the implementation risk cost function, CE(t) is the system benefit function, and LCC(t) is the life cycle cost function.

[0034] Optionally, the final rate of return function is:

[0035]

[0036] Wherein, k 1 , k 2 , k 3 , l j are constant coefficients, r is the interest rate, and t is the operation time of the control and protection device

[0037] The second aspect of the present application provides a value evaluation system for a DC distribution network control and protection device, and the system includes:

[0038] A first establishment unit, configured to collect historical operation and maintenance cost data of the control and protection device at different stages, and establish a multi-stage operation and maintenance cost mathematical model by using the polynomial regression method according to the historical operation and maintenance cost data;

[0039] A second establishment unit, configured to establish a life cycle cost function of the control and protection device, and the life cycle cost function is composed of: an investment and construction cost function, an operation and maintenance cost function, a fault cost function, and an implementation risk cost function;

[0040] A third establishment unit, configured to establish a system benefit function according to the power grid system revenue, and establish a life cycle rate of return function of the control and protection device according to the system benefit function and the life cycle cost function;

[0041] A fourth establishment unit, configured to transform the life cycle rate of return function based on the operation and maintenance cost mathematical model, the life cycle cost function, and the system benefit function to obtain a final rate of return function;

[0042] An analysis unit, configured to solve the extreme point of the final rate of return function to obtain the optimal overhaul time of the control and protection device, determine the overhaul times threshold according to the optimal overhaul time, and when the overhaul times of the control and protection device reach the overhaul times threshold, determine that the control and protection device enters the scrapped state.

[0043] Optionally, the first establishment unit is specifically configured to:

[0044] Collect historical operation and maintenance cost data of the control and protection device at different stages;

[0045] Obtain a first operation and maintenance cost sequence from the initial use of the control and protection device to the first overhaul, and a second operation and maintenance cost sequence from the first overhaul to the second overhaul according to the historical operation and maintenance cost data;

[0046] Use the polynomial interpolation method to transform the first operation and maintenance cost sequence and the second operation and maintenance cost sequence to obtain the operation and maintenance cost functions for the first overhaul and the second overhaul;

[0047] Based on the operation and maintenance cost functions, obtain the operation and maintenance cost mathematical model according to the periodic trend characteristics of the control and protection device after each overhaul.

[0048] It can be seen from the above technical solutions that the present application has the following advantages:

[0049] The present application provides a method for evaluating the value of a DC distribution network control and protection device, including: collecting historical operation and maintenance cost data of the control and protection device at different stages, and establishing a multi-stage operation and maintenance cost mathematical model by using the polynomial regression method according to the historical operation and maintenance cost data; establishing a full-life cycle cost function of the control and protection device, where the full-life cycle cost function consists of: an investment and construction cost function, an operation and maintenance cost function, a fault cost function, and an implementation risk cost function; establishing a system benefit function according to the power grid system revenue, and establishing a full-life cycle rate of return function of the control and protection device according to the system benefit function and the full-life cycle cost function; transforming the full-life cycle rate of return function based on the operation and maintenance cost mathematical model, the full-life cycle cost function, and the system benefit function to obtain a final rate of return function; solving the extreme point of the final rate of return function to obtain the optimal overhaul time of the control and protection device, determining the overhaul frequency threshold according to the optimal overhaul time, and when the control and protection device reaches the overhaul frequency threshold, determining that the control and protection device enters the scrapped state.

[0050] Compared with the prior art, the method for evaluating the value of the DC distribution network control and protection device of the present application takes into account both the inspection, operation and maintenance costs of the DC distribution network control and protection device, as well as the equipment investment cost and equipment scrapping cost, quantitatively evaluates the costs at each stage, and evaluates the equipment value more precisely and reasonably, which can improve the asset lean management level of the DC distribution network control and protection device. Thus, it solves the technical problem that the prior art does not fully consider factors such as equipment investment cost and equipment scrapping cost, resulting in a large error in the evaluation of equipment value. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic flow chart of Embodiment 1 of the method for evaluating the value of a DC distribution network control and protection device provided in the embodiment of the present application;

[0052] Figure 2 It is a schematic diagram of a typical curve of the operation and maintenance cost of the DC distribution network control and protection device at different stages provided in the embodiment of the present application;

[0053] Figure 3 It is a schematic flow chart of Embodiment 2 of the method for evaluating the value of a DC distribution network control and protection device provided in the embodiment of the present application;

[0054] Figure 4 It is a schematic structural diagram of a system for evaluating the value of a DC distribution network control and protection device provided in the embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] To enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0056] The following are the term explanations:

[0057] LCC management: Life-Cycle-Cost management

[0058] DC distribution network control and protection device: Secondary equipment used to realize the operation control and protection functions of the DC distribution network.

[0059] Value assessment: Evaluate the use value of the equipment as the basis for whether to enter the scrapping and replacement plan.

[0060] Operation and maintenance: To prevent the deterioration of equipment performance and reduce the probability of equipment failure, the equipment is inspected, tested, repaired and maintained according to a certain plan or technical conditions.

[0061] Please refer to Figure 1 , a method for evaluating the value of a DC distribution network control and protection device provided in the first embodiment of this application, includes:

[0062] Step 101, collect the historical operation and maintenance cost data of the control and protection device at different stages, and establish a multi-stage operation and maintenance cost mathematical model by using the polynomial regression method according to the historical operation and maintenance cost data;

[0063] It should be noted that first, the historical operation and maintenance cost data of the DC distribution network control and protection device at different stages are collected. Thus, the operation and maintenance cost of the DC distribution network control and protection device is counted. The operation and maintenance cost includes: operation cost and maintenance cost. Among them, the operation cost includes: energy consumed during the operation of the DC distribution network control and protection device, input human resources and operation and management expenses; the maintenance cost includes: labor, materials, and expenses for using relevant maintenance equipment consumed during regular maintenance and temporary maintenance.

[0064] In actual DC power distribution projects, there is no mature operation and maintenance experience for DC power distribution control and protection devices, and there is also a certain running-in period during the initial use. Therefore, the operation and maintenance costs in the initial stage are relatively high; as the operators further understand the equipment and the operation situation becomes more stable, the operation and maintenance costs will gradually decrease and remain stable; after further use, due to equipment aging and reduced reliability, more maintenance and repair work is required to ensure the stable operation of the equipment. Therefore, the operation and maintenance costs of the equipment will increase significantly; at this time, through a large degree of repair work, the operation function of the equipment can be improved, but as the equipment ages, the operation and maintenance costs will first decrease and then increase, and with each major overhaul, the operation and maintenance costs will show a periodic trend, as Figure 2 shown.

[0065] Next, based on the statistical data of the operation and maintenance costs of the DC power distribution control and protection device, the operation and maintenance cost sequences of the equipment from the initial use to the first major overhaul and from the first major overhaul to the second major overhaul can be obtained as follows: and where C m_i represents the operation and maintenance cost at time i, and C m_j0 is the operation and maintenance cost at time j during the second major overhaul.

[0066] Then, by using the polynomial interpolation method, the operation and maintenance cost functions f 1 (t) and f 2 (t) for the first major overhaul and the second major overhaul can be expressed as:

[0067]

[0068] where

[0069]

[0070]

[0071] In the formula, a and b are both coefficients, C m_i is the operation and maintenance cost at time i during the first major overhaul, C m_j0 is the operation and maintenance cost at time j during the second major overhaul, t is the operation time of the control and protection device, and n is the number of major overhauls.

[0072] Finally, since the operation and maintenance costs show a certain periodic trend after each major overhaul, the operation and maintenance cost f n (t) after the nth major overhaul, that is, the mathematical model of the operation and maintenance cost can be expressed as:

[0073] f n (t) = f 2 (t - t n ); (2)

[0074] In the formula, tn is the start time of the nth major overhaul.

[0075] Step 102: Establish the life cycle cost function of the control and protection device. The life cycle cost function consists of: investment and construction cost function, operation and maintenance cost function, failure cost function, and implementation risk cost function;

[0076] It should be noted that according to the definition of life cycle cost, it includes investment and construction cost, operation cost, maintenance cost, failure cost, abandonment cost, and implementation risk cost.

[0077] Among them,

[0078] 1. Considering the time value of investment funds, the investment and construction cost C I (t) of the DC distribution network control and protection device can be expressed as the net present value:

[0079] C I (t) = C I0 ·(1 + r) t (3)

[0080] In the formula, C I0 is the initial investment cost of the DC distribution network control and protection device, r is the interest rate, and t is the device operation time.

[0081] 2. The operation cost and maintenance cost of the DC distribution network control and protection device are all the operation and maintenance expenses since the device was put into operation. Therefore, its operation and maintenance cost C M (t) can be expressed as:

[0082] C M (t) = f 1 (t) + f 2 (t) + … f n (t) (4)

[0083] 3. The failure cost refers to the punitive cost caused by equipment failure, including power outage loss cost, failure repair cost, equipment performance and life loss cost, etc. For power enterprises, the power outage loss cost is generally the main failure cost. Considering the characteristics of redundant configuration of the DC distribution network control and protection device, its failure cost can be expressed as:

[0084] C F (t) = λ k ·P black (5)

[0085] Among them, λ is the failure rate of a single control and protection device, k is the number of redundant control and protection devices, and P black is the cost of failure loss.

[0086] 4. The implementation risk C R(t) The cost is mainly reflected in the power outage accidents that occur during major overhauls or scrapping of equipment, and can be expressed as:

[0087] C R (t) = n·P 大修 +P 报废 (6)

[0088] Where P 大修 and P 报废 are respectively the load power loss costs that occur during major overhauls or scrapping of the DC distribution network control and protection devices.

[0089] Based on the above sub-item costs, the life cycle cost LCC(t) of the DC distribution network control and protection devices can thus be obtained as:

[0090] LCC(t) = C I (t) + C M (t) + C F (t) + C R (t) (7)

[0091] Step 103: Establish a system benefit function based on the power grid system revenue, and establish a life cycle return rate function of the control and protection device based on the system benefit function and the life cycle cost function;

[0092] It should be noted that through continuous operation and maintenance of the DC distribution network control and protection devices, the DC distribution network control and protection devices can ensure the stability of power supply, and the relevant power sales revenue can be allocated to the DC distribution network control and protection devices according to a certain proportion, obtaining the system benefit function as:

[0093] CE(t) = k 分摊 E 售电 t; (8)

[0094] In the formula, k 分摊 is the power sales cost sharing coefficient, and E 售电 is the power sales revenue of the power grid system.

[0095] Therefore, the life cycle return rate function of the DC distribution network control and protection device is:

[0096]

[0097] In the formula, C I (t) is the investment and construction cost function, C M (t) is the operation and maintenance cost function, C F (t) is the failure cost function, C R (t) is the implementation risk cost function, CE(t) is the system benefit function, and LCC(t) is the life cycle cost function.

[0098] Step 104: Transform the full life cycle return rate function based on the operation and maintenance cost mathematical model, the full life cycle cost function, and the system benefit function to obtain the final return rate function;

[0099] It should be noted that for the reliable and stable operation of the DC distribution network control and protection device, a relatively large amount of repair and renovation work is essential. Based on the full life cycle return rate index, the following overhaul time calculation method is proposed in the present invention.

[0100] Between two overhaul times (the initial commissioning of the equipment is regarded as the 0th overhaul), according to equations (1) to (9), the final full life cycle return rate can be expressed as:

[0101]

[0102] where k 1 , k 2 , k 3 , l j are constant coefficients obtained according to equations (1) to (9) respectively.

[0103] Step 105: Solve the extreme point of the final return rate function to obtain the optimal overhaul time of the control and protection device. Determine the overhaul times threshold according to the optimal overhaul time. When the control and protection device reaches the overhaul times threshold, it is determined that the control and protection device enters the scrapped state.

[0104] It should be noted that to achieve the highest full life cycle return rate, since equation (10) is a unary function of r LCC with respect to time t, therefore, by finding the extreme point of r LCC in equation (10), the optimal overhaul time can be calculated to maximize the full life cycle return rate of the current equipment.

[0105] Since the residual value of the equipment is relatively low after general equipment is overhauled multiple times, and further updates and iterations are required at the technical level to meet the load power supply requirements, therefore, N max is used in the present invention to control the overhaul times of the DC distribution network control and protection device. When the overhaul times reach N max , the optimal overhaul time is calculated using equation (10). At this time, the equipment enters the scrapped state and no further repairs are carried out.

[0106] The value evaluation method of the DC distribution network control and protection device in this embodiment is mainly characterized in that based on equations (7), (8), and (9), the full life cycle cost LCC(t), the system benefit CE(t), and the full life cycle return rate r LCC of the DC control and protection device are evaluated. Using the overhaul and scrapping time determination method in Step 105, starting from the commissioning of the equipment, the optimal time for each overhaul is determined in turn until the overhaul times reach N maxAfter that, no major repairs and transformations will be carried out on the DC distribution network control and protection device, and the device will enter the scrapping and retirement process. Compared with the prior art, the value evaluation method of the DC distribution network control and protection device of this application takes into account both the maintenance and operation costs of the DC distribution network control and protection device, the equipment investment cost, and the equipment scrapping cost, quantitatively evaluates the costs at each stage, and evaluates the equipment value more precisely and reasonably, which can improve the asset lean management level of the DC distribution network control and protection device. Thus, it solves the technical problem that the prior art does not fully consider factors such as equipment investment cost and equipment scrapping cost, resulting in a large error in the evaluation of equipment value.

[0107] The above is the first embodiment of a value evaluation method for a DC distribution network control and protection device provided in the embodiments of this application. The following is the second embodiment of a value evaluation method for a DC distribution network control and protection device provided in the embodiments of this application.

[0108] Please refer to Figure 3 , a value evaluation method for a DC distribution network control and protection device provided in the second embodiment of this application includes:

[0109] Step 201, collect historical operation and maintenance cost data of the control and protection device at different stages;

[0110] Step 202, obtain the first operation and maintenance cost sequence from the initial use of the control and protection device to the first major overhaul, and the second operation and maintenance cost sequence from the first major overhaul to the second major overhaul according to the historical operation and maintenance cost data;

[0111] Step 203, use polynomial interpolation method to transform the first operation and maintenance cost sequence and the second operation and maintenance cost sequence to obtain the operation and maintenance cost functions of the first major overhaul and the second major overhaul;

[0112] Step 204, based on the operation and maintenance cost function, obtain the operation and maintenance cost mathematical model according to the periodic trend characteristics of the control and protection device after each major overhaul;

[0113] Step 205, establish the full life cycle cost function of the control and protection device, and the full life cycle cost function is composed of: investment and construction cost function, operation and maintenance cost function, fault cost function, and implementation risk cost function;

[0114] Step 206, establish the system benefit function according to the power grid system revenue, and establish the full life cycle rate of return function of the control and protection device according to the system benefit function and the full life cycle cost function;

[0115] Step 207, based on the operation and maintenance cost mathematical model, the full life cycle cost function, and the system benefit function, transform the full life cycle rate of return function to obtain the final rate of return function;

[0116] Step 208: Solve the extreme point of the final rate of return function to obtain the optimal overhaul time of the control and protection device. Determine the overhaul frequency threshold according to the optimal overhaul time. When the overhaul frequency of the control and protection device reaches the overhaul frequency threshold, it is determined that the control and protection device enters the scrapped state.

[0117] It should be noted that the descriptions of steps 201 - 208 in the embodiments of the present application are similar to those in Embodiment 1. Please refer to the description of Embodiment 1 and will not be repeated here.

[0118] Compared with the prior art, the value evaluation method of the DC distribution network control and protection device in this embodiment not only considers the maintenance and operation cost of the DC distribution network control and protection device, but also considers the equipment investment cost and equipment scrapping cost, quantitatively evaluates the costs at each stage, and evaluates the equipment value more precisely and reasonably, which can improve the asset lean management level of the DC distribution network control and protection device. Thus, it solves the technical problem that the prior art does not fully consider factors such as equipment investment cost and equipment scrapping cost, resulting in a large error in equipment value evaluation.

[0119] The above is Embodiment 2 of a value evaluation method for a DC distribution network control and protection device provided in the embodiments of the present application. The following is an embodiment of a value evaluation system for a DC distribution network control and protection device provided in the embodiments of the present application.

[0120] Please refer to Figure 4 , a value evaluation method for a DC distribution network control and protection device provided in Embodiment 2 of the present application, includes:

[0121] The first establishment unit 301 is used to collect historical operation and maintenance cost data of the control and protection device at different stages, and establish a multi - stage operation and maintenance cost mathematical model according to the historical operation and maintenance cost data by using the polynomial regression method;

[0122] The second establishment unit 302 is used to establish the life - cycle cost function of the control and protection device. The life - cycle cost function consists of: investment and construction cost function, operation and maintenance cost function, failure cost function, and implementation risk cost function;

[0123] The third establishment unit 303 is used to establish a system benefit function according to the power grid system revenue, and establish a life - cycle rate of return function of the control and protection device according to the system benefit function and the life - cycle cost function;

[0124] The fourth establishment unit 304 is used to transform the life - cycle rate of return function based on the operation and maintenance cost mathematical model, the life - cycle cost function, and the system benefit function to obtain the final rate of return function;

[0125] An analysis unit 305 is configured to solve the extreme point of the final rate of return function to obtain the optimal overhaul time of the control and protection device, determine the overhaul frequency threshold according to the optimal overhaul time, and determine that the control and protection device enters the scrapped state when the overhaul frequency of the control and protection device reaches the overhaul frequency threshold.

[0126] Those skilled in the art can clearly understand that for the convenience and conciseness of description, the specific working processes of the above-described system units can refer to the corresponding processes in the foregoing method embodiments, and will not be described herein again.

[0127] As used in the specification of the present application and the above-mentioned drawings, the terms "first", "second", "third", "fourth", etc. are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that comprises a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0128] It should be understood that in the present application, "at least one (item)" means one or more, and "a plurality" means two or more. "And / or" is used to describe the association relationship of associated objects and indicates that three relationships can exist. For example, "A and / or B" can mean: only A exists, only B exists, and both A and B exist at the same time. Among them, A and B can be singular or plural. The character " / " generally means that the associated objects before and after are in an "or" relationship. "At least one (item) of the following" or a similar expression means any combination of these items, including any combination of single item (item) or plural items (items). For example, at least one (item) of a, b, or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0129] In several embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces, and the indirect couplings or communication connections of devices or units can be in electrical, mechanical, or other forms.

[0130] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place, or they can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0131] In addition, in each embodiment of this application, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0132] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of this application. And the aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (English full name: Read-Only Memory, English abbreviation: ROM), random access memories (English full name: Random Access Memory, English abbreviation: RAM), magnetic disks, or optical discs and other various media that can store program codes.

[0133] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for evaluating the value of a DC distribution network control and protection device, characterized in that, it includes: Collect the historical operation and maintenance cost data of the control and protection device at different stages, and establish a multi-stage operation and maintenance cost mathematical model by using the polynomial regression method according to the historical operation and maintenance cost data; Establish the life cycle cost function of the control and protection device, and the life cycle cost function consists of: investment and construction cost function, operation and maintenance cost function, fault cost function, and implementation risk cost function; Establish a system benefit function according to the power grid system revenue, and establish the life cycle rate of return function of the control and protection device according to the system benefit function and the life cycle cost function; Based on the operation and maintenance cost mathematical model, the life cycle cost function, and the system benefit function, transform the life cycle rate of return function to obtain the final rate of return function; wherein, the final rate of return function is: where k 1 , k 2 , k 3 , l j are constant coefficients, r is the interest rate, and t is the operation time of the control and protection device; Solve the extreme point of the final rate of return function to obtain the optimal overhaul time of the control and protection device, determine the overhaul frequency threshold according to the optimal overhaul time, and when the control and protection device reaches the overhaul frequency threshold, determine that the control and protection device enters the scrapped state.

2. The method for evaluating the value of a DC distribution network control and protection device according to claim 1, characterized in that, The step of establishing a multi-stage operation and maintenance cost mathematical model by using the polynomial regression method according to the historical operation and maintenance cost data specifically includes: Obtain the first operation and maintenance cost sequence from the initial use of the control and protection device to the first overhaul and the second operation and maintenance cost sequence from the first overhaul to the second overhaul according to the historical operation and maintenance cost data; Use the polynomial interpolation method to transform the first operation and maintenance cost sequence and the second operation and maintenance cost sequence to obtain the operation and maintenance cost functions for the first overhaul and the second overhaul; Based on the operation and maintenance cost functions, obtain the operation and maintenance cost mathematical model according to the periodic trend characteristics of the control and protection device after each overhaul.

3. The method for evaluating the value of a DC distribution network control and protection device according to claim 2, characterized in that, The operation and maintenance cost function is: wherein, where a and b are both coefficients, and C m_i is the operation and maintenance cost at time i during the first major overhaul, is the operation and maintenance cost at time j during the second major overhaul, t is the operation time of the control and protection device, and n is the number of major overhauls.

4. The method for evaluating the value of a DC distribution network control and protection device according to claim 3, characterized in that, The operation and maintenance cost mathematical model is: f n f(t) = 2 f(t - n ) where t n is the start time of the nth major overhaul.

5. The method for evaluating the value of a DC distribution network control and protection device according to claim 1, characterized in that, The life cycle cost function is: LCC(t) = C I (t) + C M (t) + C F (t) + C R (t); where C I (t) is the investment and construction cost function, C M (t) is the operation and maintenance cost function, C F (t) is the failure cost function, C R (t) is the implementation risk cost function.

6. The method for evaluating the value of a DC distribution network control and protection device according to claim 5, characterized in that, The system benefit function is: CE(t) = k 分摊 E 售电 t; where k 分摊 is the electricity selling cost sharing coefficient, and E 售电 is the electricity selling revenue of the power grid system.

7. The method for evaluating the value of a DC distribution network control and protection device according to claim 6, characterized in that, The life cycle rate of return function is: Where, C I (t) is the investment and construction cost function, C M (t) is the operation and maintenance cost function, C F (t) is the failure cost function, C R (t) is the implementation risk cost function, CE(t) is the system benefit function, and LCC(t) is the life cycle cost function.

8. A system for evaluating the value of a DC distribution network control and protection device, characterized in that, it includes: The first establishment unit is used to collect the historical operation and maintenance cost data of the control and protection device at different stages, and establish a multi-stage operation and maintenance cost mathematical model by using the polynomial regression method according to the historical operation and maintenance cost data; A second establishing unit, configured to establish a life-cycle cost function of the control and protection device, where the life-cycle cost function is composed of: an investment and construction cost function, an operation and maintenance cost function, a fault cost function, and an implementation risk cost function; A third establishing unit, configured to establish a system benefit function according to the power grid system revenue, and establish a life-cycle rate of return function of the control and protection device according to the system benefit function and the life-cycle cost function; A fourth establishing unit, configured to transform the life-cycle rate of return function based on the operation and maintenance cost mathematical model, the life-cycle cost function, and the system benefit function to obtain a final rate of return function; Wherein, the final rate of return function is: where k 1 , k 2 , k 3 , l j are constant coefficients, r is the interest rate, and t is the operation time of the control and protection device; An analysis unit, configured to solve an extreme point of the final rate of return function to obtain an optimal overhaul time of the control and protection device, determine an overhaul frequency threshold according to the optimal overhaul time, and determine that the control and protection device enters a scrapped state when the overhaul frequency of the control and protection device reaches the overhaul frequency threshold.

9. The value evaluation system for a DC distribution network control and protection device according to claim 8, wherein, the first establishing unit is specifically configured to: Collect historical operation and maintenance cost data of the control and protection device at different stages; Obtain a first operation and maintenance cost sequence from the initial use of the control and protection device to the first overhaul, and a second operation and maintenance cost sequence from the first overhaul to the second overhaul according to the historical operation and maintenance cost data; Use polynomial interpolation to transform the first operation and maintenance cost sequence and the second operation and maintenance cost sequence to obtain operation and maintenance cost functions for the first overhaul and the second overhaul; Based on the operation and maintenance cost function, obtain the operation and maintenance cost mathematical model according to the periodic trend characteristics of the control and protection device after each overhaul.

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