Transformer full-life type selection method in outgoing new energy environment

Abstract

The invention relates to a transformer full-life type selection method in a new energy delivery environment, and relates to the technical field of transformer type selection. According to the application, the outgoing new energy power generation transformer is taken as a research object, the outgoing new energy output characteristics are aimed at, the whole life cycle cost idea of the transformer is based on the transformer electric-thermal coupling relationship, key meteorological elements are obtained by using the meteorological environment big data technology, and the operation temperature of the transformer in the designed life cycle is simulated; and introducing a life loss constraint, and seeking the optimal transformer capacity meeting the life loss constraint by taking the minimum life cycle cost of the transformer as a target. According to the method, the construction cost data of the current transformer is combined, and the new energy output characteristics and the change characteristics of the meteorological environment are fully considered in the operation temperature simulation process of the transformer, so that the problems existing in a traditional transformer capacity selection method are effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transformer selection, and particularly relates to a transformer full-life selection method in an external new energy environment. BACKGROUND

[0002] The rapid growth of installed capacity of new energy represented by wind power and photovoltaic power promotes the construction of cross-regional power transmission channels, but the inherent volatility of new energy makes the supporting power transmission and transformation equipment face special challenges. As the core equipment of the power transmission system, transformers face more complex operating conditions in the new energy environment: the randomness of large-scale new energy output leads to intensified fluctuations in transformer load rate, frequent cross-power flow causes an increase in overload risk, and intermittent low-load operation causes nonlinear growth of equipment loss.

[0003] However, the existing transformer selection method still follows the static parameter system of the traditional power system, and does not fully consider the changes in equipment utilization rate, operating loss law and reliability maintenance cost in the full life cycle under the new energy scenario. The traditional transformer capacity selection method faces multiple adaptability challenges in the new energy transmission scenario. The rated capacity of the transformer, as a core parameter affecting the economy and reliability of the system, needs to balance the overload margin and equipment cost: too small capacity is easy to cause long-term overload operation, leading to equipment life attenuation and even wind and light abandonment, and too large capacity increases the initial investment and maintenance cost. Although the existing method determines the reference capacity based on the maximum load demand and the economic load rate (such as the recommended 60%-70% load rate of the conventional power system), and guarantees the safety of extreme conditions through temperature rise verification, it has significant limitations in the face of new energy fluctuation characteristics. First, the existing selection specification (such as the DL / T 572 standard) follows the static load model of the thermal power era and is difficult to adapt to the severe power fluctuation of new energy, such as the single-day power fluctuation amplitude of the Zhaomei wind power project in Tibet reaching 150% of the rated value, and the traditional capacity margin design (10%-20%) causes the equipment to frequently trigger overload protection; second, the traditional loss evaluation relies on the nominal no-load / load curve and ignores the nonlinear loss characteristics under dynamic conditions. Actual measurement shows that when the daily average load rate of the transformer fluctuates between 15%-130%, the actual copper loss is 18%-25% higher than the theoretical value; third, the verification process strictly follows the long-term temperature rise limit. For oil-immersed power transformers designed in accordance with the GB / T 1094 series standards, the operating life is set to 30 years of long-term operation with a hot spot temperature of 98℃, which does not fully utilize the potential of short-time overload, resulting in systematic underestimation of capacity utilization. These method defects cause the new energy transmission transformer to face the dual dilemmas of "excessive conservative design to increase cost" and "insufficient capacity to cause reliability risk".

[0004] It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present disclosure, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0005] In order to solve the above technical problems or at least partially solve the above technical problems, the present application provides a transformer full life selection method under the external sending of new energy environment.

[0006] The present application provides a transformer full life selection method under the external sending of new energy environment, taking the external sending of new energy power generation transformer as the research object, comprising: Based on the equipment investment cost, operation and maintenance cost, power failure loss cost caused by fault, scrap cost and new energy curtailment cost under transformer constraint restriction, a transformer full life cycle cost model is constructed: ; In the formula: C i is the equipment investment cost; C l is the operation and maintenance cost; C f is the power failure loss cost; C s is the new energy curtailment cost under transformer constraint restriction; C d is the cost generated by the scrap treatment of the transformer at the end of life; Based on the transformer electric-thermal coupling relationship, the meteorological data obtained by the meteorological environment big data technology is used as the element to simulate the operating temperature of the transformer within the design life period; The life loss constraint is introduced, and the optimal transformer capacity meeting the life loss constraint is sought with the minimum transformer full life cycle cost as the target.

[0007] Further, the equipment investment cost is represented as: ; In the formula: C i1 , C i2 , C i3 , C in respectively represent different equipment investment items.

[0008] Further, the transformer operation and maintenance cost C l is the total sum of all expenses used by the transformer during normal operation, including the cost of transformer maintenance C m and operation loss C p ; then the transformer annual operation and maintenance cost is represented as: ; The high-voltage transformer operating loss is calculated by the following formula: ; In the formula, Δ E is the total loss of electric energy in a year; C e is the loss cost of the unit loss of the transformer; ; wherein, R is the resistance of the transformer, which is a function of the hotspot temperature , is obtained by simulating the operating temperature of the transformer in the design life period based on the transformer electro-thermal coupling relationship, and using meteorological data obtained by meteorological environment big data technology as elements; ; U is the voltage grade of the transformer; S max is the maximum load power; τ max is the maximum load loss duration; Transformer operating and maintenance cost C m includes the cost of regular inspection and preventive experiment; according to the average annual total maintenance cost of the transformer obtained from the statistical data of the operating and maintenance cost of the transformer in previous years, the average annual total maintenance cost of the transformer is estimated as C m is calculated as shown below: ; In the formula, C w is the average annual total maintenance cost of the transformer.

[0009] Further, the annual power loss cost is: ; In the formula, C REF is the average repair cost of the fault; Δ W GZ is the output power of the fault transformer in normal operation; t MTTR is the average repair time of a single fault; a is the on-grid electricity price; λ 1 is the average annual fault number of the transformer.

[0010] Further, the new energy electric energy cost abandoned under the constraint of the transformer is: ; In the formula, C s is the new energy electric energy cost abandoned under the constraint of the transformer; t0 is the starting time to reach the upper limit of the transformer temperature constraint; t end T is the ending time to reach the upper limit of the transformer temperature constraint; a is the on-grid electricity price; ΔP is the abandoned new energy power when reaching the upper limit of the temperature constraint; P is the actual output power of the new energy; L design T is the time to reach the transformer life constraint; L end T is the expected design life of the transformer.

[0011] Further, based on the transformer electric-thermal coupling relationship, the meteorological data obtained by the meteorological environment big data technology is used as the element, and the running temperature of the transformer in the design life is simulated, including: The heat generated by the transformer in actual operation is idealized as a current source, the heat flow is equivalent to the current flow, the heat capacity is equivalent to the capacitance, and the thermal resistance is equivalent to the resistance; The temperature rise dynamic process of the transformer is divided into two heat transfer processes of ambient temperature-bottom oil temperature and bottom oil temperature-hot spot temperature; According to Kirchhoff's theorem, The bottom oil-ambient temperature thermal circuit model is obtained: ; The hot spot temperature-bottom oil thermal circuit model is: ; In the formula, Cboil l C is the bottom oil heat capacity; M5 l R is the thermal resistance between the bottom oil and the external environment; θboil l,t T is the bottom oil temperature at time t; θboil l,t T is the ambient temperature at time t, obtained by meteorological environment big data; qfe l,t P is the iron loss at time t; ql l,t P is the load loss at time t; Cwdn l C is the winding heat capacity; M6 l R is the thermal resistance between the hot spot and the bottom oil; θhs l,t T is the hot spot temperature at time t; qwdn l,t P is the winding loss at time t; First, the bottom oil temperature is calculated from the bottom oil-ambient temperature thermal circuit model, which is used as the ambient temperature in the hot spot temperature-bottom oil thermal circuit model, and finally the hot spot temperature is calculated.

[0012] Further, the bottom oil temperature is decomposed as: ; In the formula, T is the rated time constant of the bottom oil, representing the thermal response speed; The per-unit load factor at time t is the ratio of the current load to the rated load. This represents the bottom oil temperature rise under rated operating conditions. The first nonlinear index reflects the nonlinear relationship between heat transfer and temperature change or temperature difference. The loss ratio is the ratio of iron loss to load loss. The square of the load factor. As an oil temperature-dependent function, modify the change of load loss with oil temperature; The solution for the hotspot temperature is:

[0013] In the formula, The rated time constant of the winding characterizes the thermal response speed; The temperature rise of the hot spot relative to the bottom oil under rated operating conditions; The second nonlinear index reflects the nonlinear relationship between heat transfer in the winding and temperature change or temperature difference. The square of the load factor. This is a hotspot temperature-dependent function, modifying the change in winding losses with oil temperature.

[0014] Furthermore, the inequality constraint regarding transformer lifespan loss after the design service life is exhausted: ; In the formula: DP end This refers to the insulation content at the end of the transformer's design life. DP start This represents the initial insulation level of the transformer. A This is a constant representing the chemical environment. L ( θhs l,t ( ) represents the service life; E Activation energy; F It is the gas constant; θ hs For hotspot temperature; L loss To determine the percentage of transformer lifespan loss after the designed service life.

[0015] Secondly, the present invention provides a transformer life-cycle selection device for a new energy transmission environment, comprising: at least one processing unit, the processing unit being connected to a storage unit via a bus unit, the storage unit storing a computer program, and the computer program being executed by the processing unit to implement the transformer life-cycle selection method for a new energy transmission environment.

[0016] In a third aspect, the present application provides a computer readable storage medium storing computer instructions, which, when executed by a processor, implement the transformer full life selection method under the new energy sending environment.

[0017] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art. The present application focuses on the new energy sending scenario, constructs a transformer full life cycle cost model based on dynamic operating conditions, quantitatively analyzes the time sequence coupling relationship of key parameters such as initial investment, no-load loss, load loss, overload capacity, maintenance cost, and establishes a transformer full life multi-dimensional selection system suitable for the new energy environment, providing theoretical support and technical support for improving the economy and power supply reliability of the sending channel project. By introducing short-time overload temperature constraints and life loss thresholds, the transformer oil temperature and hot spot temperature changes under the new energy fluctuation operating condition are dynamically simulated, the short-time current carrying potential of the transformer is fully utilized, and the capacity utilization of the transformer is improved under the premise of ensuring the safety of the equipment, which breaks through the underestimation of the short-time overload potential in the traditional selection method.

[0018] Based on the full life cycle cost, the present application comprehensively plans multi-dimensional economic elements such as initial investment, dynamic operating loss, maintenance cost and energy loss, and constructs a comprehensive decision model for transformer capacity selection under the new energy sending scenario, which significantly reduces the cost waste and reliability risk caused by capacity redundancy or deficiency. Compared with the traditional method, the present application effectively solves the dual contradictions of "over-conservative design to increase cost" and "insufficient capacity to cause reliability risk" caused by the fluctuation of new energy, and provides a transformer selection technology support for the sending transformer project, which takes into account the economy, reliability and environmental adaptability. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the application.

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without creative labor.

[0021] Figure 1 A flowchart of a transformer full life selection method under a new energy sending environment is provided for the disclosed embodiments of the present application.

[0022] Figure 2 An architecture diagram of transformer full life cycle cost analysis is provided for the disclosed embodiments of the present application.

[0023] Figure 3 The schematic diagram of the bottom oil-environment temperature thermal circuit model and the hot spot temperature-bottom oil thermal circuit model is provided for the disclosed embodiment.

[0024] Figure 4 The schematic diagram of the transformer full life selection device under the environment of sending new energy is provided for the disclosed embodiment. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in a clear and complete manner with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0026] It should be noted that in this document, the terms "comprising", "containing" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such a process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or device including the element.

[0027] Embodiment 1 With the continuous expansion of the installed capacity of new energy in China and the rapid growth of cross-regional power transmission demand, the transformer, as a key hub device of the new energy sending channel, directly affects the economy and reliability of the power system. Compared with the traditional thermal power system, new energy generation has significant intermittency and volatility characteristics, and the sending channel often needs to pass through complex geographical environments, which puts higher requirements on the full life cycle performance of the transformer. Due to the high investment proportion of transformer equipment (about 35%-50% of substation investment) and the long operation life of more than 30 years, in the planning stage of the new energy sending project, it is urgent to build a transformer selection system deeply coupled with the characteristics of new energy and taking into account the full life cycle cost. Referring to Figure 1 The transformer full life selection method under the environment of sending new energy provided by the embodiment of the present application includes: Traditional transformer selection methods are mostly based on rated capacity method, mainly considering the matching of technical parameters under steady-state operating conditions, which has two prominent limitations: first, the initial purchase cost is focused on when making selection decisions, and the dynamic load loss, operation and maintenance cost and other life-cycle economic factors under new energy scenarios are not systematically considered; second, the life loss calculation usually uses the running state under standard environment, and does not fully consider the influence of dynamic factors such as new energy power fluctuation, environmental temperature and humidity change on the thermal stability of the equipment, and ignores the short-time overload capacity. Especially in special environments such as sand and high altitude, the traditional selection method is easy to cause the problems of redundant transformer capacity configuration or low running energy efficiency.

[0028] In view of the above technical problems, the present application proposes to deeply integrate the life cycle cost (LCC) concept into the selection decision process of new energy sending transformer, and the life cycle cost analysis framework of new energy sending transformer is as shown in Figure 2

[0029] Based on the equipment investment cost, operation and maintenance cost, power loss cost caused by failure, scrap cost and new energy curtailment cost under transformer constraint, a transformer life cycle cost model is constructed.

[0030] For transformer selection projects, the life cycle cost includes all costs related to the project during the life cycle. According to the category division of transformer life cycle cost, the life cycle cost of transformer is composed of five parts: equipment investment cost, operation and maintenance cost, power loss cost caused by failure, scrap cost and new energy curtailment cost under transformer constraint. The transformer life cycle cost model is: In the formula: C i is the equipment investment cost; C l is the operation and maintenance cost; C f is the power loss cost; C s is the new energy curtailment cost under transformer constraint; C d is the cost of transformer scrap processing at the end of life.

[0031] Equipment investment cost: the transformer is subject to material price and complex manufacturing process, so the equipment investment cost accounts for a large proportion in the life cycle cost of transformer.

[0032] The present application calculates each cost by engineering method, and the equipment investment cost is expressed as: In the formula:​​​C i1 , C i2 , C i3 , C in Respectively represent different equipment investment items, such as transformer purchase cost, land cost, installation and commissioning cost, labor cost (ten thousand yuan).

[0033] Operation and maintenance cost: transformer operation and maintenance cost C l Refers to the total cost of all expenses used by the transformer during normal operation, including the cost of transformer maintenance C m And operation loss C p . Then the transformer annual operation and maintenance cost is represented as: ; The complex operation structure of the transformer increases the operation loss C P The difficulty of calculation, the same transformer laid in different regions will have different ground capacitance and magnetic flux environment. Based on this, the operation loss of high-voltage transformer is calculated by the following formula: ; ; In the formula: Δ E Total annual power loss (kw·h); C e Loss cost per unit loss of transformer (yuan / (kw·h)); R Transformer resistance (Ω), the transformer resistance is a function of hot spot temperature , based on the transformer electro-thermal coupling relationship, using meteorological data obtained by meteorological environment big data technology as elements, through simulating the operating temperature of the transformer in the design life period to obtain the hot spot temperature ; U Transformer voltage grade (kV); S max Maximum load power (MW); τ max Maximum load loss duration (h), combined with power factor cos ϕ And the annual maximum load utilization hours T max Obtained by table lookup.

[0034] For the transformer, the operation and maintenance cost C mThe cost of regular patrol and preventive experiments of the transformer. According to the average annual total maintenance cost of the transformer obtained from the statistical data of the transformer operation and maintenance cost in previous years, the average annual total maintenance cost of the transformer is estimated as C m The calculation is as follows: ; In the formula: C w The average annual total maintenance cost of the transformer.

[0035] Power outage loss cost: The transformer is long-term operated in high temperature and high pressure and humid environment, so it is subject to damage such as natural factors (earthquake, biological interference, corrosion, etc.), human factors (construction engineering, pipeline excavation, etc.), and after the failure, the process of “fault positioning-failure repair preparation-failure repair-repair test” is needed. At present, there is no standard transformer repair procedure, and the repair time needs several weeks or even months depending on different situations. The transformer failure loss not only includes the cost of hiring repair teams, leasing construction teams, and purchasing and testing experiments, but also includes the economic and social benefit loss caused by the interruption of power supply due to failure. The power outage loss cost caused by failure is determined by multiple factors. The annual power outage loss cost is: ; In the formula: C REF The average repair cost of failure (ten thousand yuan / time); Δ W GZ The output power of the failed transformer when it is normally operated (kW / time); t MTTR The average repair time of a single failure (h); a The on-grid electricity price (ten thousand yuan / (kW·h)); λ 1The average annual failure number of the transformer (times / (year)).

[0036] The cost of abandoned new energy electric energy under the constraint of the transformer: ; In the formula: C s The cost of abandoned new energy electric energy under the constraint of the transformer (ten thousand yuan); t 0The starting time to reach the upper limit of the temperature constraint of the transformer (h); t end The end time to reach the upper limit of the temperature constraint of the transformer (h); a The on-grid electricity price (ten thousand yuan / (kW·h)); ΔP is the abandoned new energy power (kW) when the upper limit of the temperature constraint is reached; P is the actual output power of the new energy (kW); L designTime (years) to reach the lifetime constraint of the transformer; L end Design lifetime of the transformer (years) expected.

[0037] Cost of the disposal of the decommissioned transformer: the transformer recycling includes labor and equipment costs, subsequent environmental disposal costs, and the residual value of the transformer can be recovered as compensation when the transformer is recycled.

[0038] Since the entire life cycle of the transformer is as long as 20-30 years, the investment cost must be considered. In this application, the present value comparison method is used to compare the life cycle cost of the transformer, and the life cycle cost of the transformer of each alternative is compared, and the scheme with lower life cycle cost of the transformer is the best. The calculation formula of the discount factor is: ; Wherein, n is the term, r is the annual discount rate.

[0039] Based on the electrical-thermal coupling relationship of the transformer, the meteorological data obtained by the meteorological environment big data technology is used as the element to simulate the operating temperature of the transformer during the design life. As shown in Figure 3 The heat generated by the transformer in actual operation is idealized as a current source, the heat flow is equivalent to the current flow, the heat capacity is equivalent to the capacitance, and the thermal resistance is equivalent to the resistance; the oil temperature of the transformer rises, and the oil temperature exchanges heat with the air through the tank wall and the radiator on one hand, and generates loss on the thermal resistance and the heat capacity on the other hand, and the dynamic process of the temperature rise of the transformer is divided into two heat transfer processes of ambient temperature-bottom oil temperature and bottom oil temperature-hot spot temperature; According to Kirchhoff's theorem, we have: ; ; In the formula: Cboil l C is the bottom oil heat capacity; M5 l R is the thermal resistance between the bottom oil and the external environment; θboil l,t T is the bottom oil temperature; qfe l,t P is the iron loss; ql l,t P is the load loss; Cwdn l C is the winding heat capacity; M6 l R is the thermal resistance between the hot spot and the bottom oil; θhs l,t T is the hot spot temperature; qwdn l,t P is the winding loss.

[0040] First, the bottom oil temperature is calculated from the bottom oil-environment temperature thermal circuit model, which is used as the ambient temperature in the hot spot temperature-bottom oil thermal circuit model, and finally the hot spot temperature is calculated.

[0041] The bottom oil temperature is solved as: ; where, is the rated time constant of the bottom oil, representing the thermal response speed; is the load factor at time t, i.e., the ratio of the current load to the rated load; is the temperature rise of the bottom oil under rated operating conditions; is the first nonlinear index, reflecting the nonlinear relationship between heat transfer and temperature change or temperature difference; is the loss ratio, i.e., the ratio of iron loss to load loss; is the square of the load factor, is the oil temperature-dependent function, modifying the change of load loss with oil temperature.

[0042] The hot spot temperature solution is: ; where, is the rated time constant of the winding, representing the thermal response speed; is the temperature rise of the hot spot relative to the bottom oil under rated operating conditions; is the second nonlinear index, reflecting the nonlinear relationship between winding heat transfer and temperature change or temperature difference; is the square of the load factor, is the hot spot temperature-dependent function, modifying the change of winding loss with oil temperature.

[0043] Introducing the new energy generation and outgoing current equation constraint, the life loss constraint, and the transformer hot spot temperature inequality constraint, the optimal transformer capacity that meets the life loss constraint is sought with the minimum transformer life cycle cost as the target.

[0044] The transformer decision-making model based on the life cycle cost is described as follows: ; where: LCC is the total life cycle cost of the transformer.

[0045] The constraints followed by the transformer decision-making model: New energy generation and outgoing current equation constraint: ; where: P i is the new energy generation and outgoing power in the i-th period; U is the voltage; cosφ is the power factor; I i is the new energy generation and outgoing current in the i-th period.

[0046] Transformer hot spot temperature inequality constraint: Generally, the conductor temperature is not allowed to exceed the maximum long-term allowable temperature (90℃) in a short time, combined with the short-time overload potential to set the hotspot temperature not to exceed the short-time overload temperature upper limit: ; In the formula: θ hs is the transformer hotspot temperature; θ hs，lim is the upper limit of the transformer hotspot short-time overload temperature, which is set according to the standard and actual situation.

[0047] The transformer life loss inequality constraint after the design service life: ; In the formula: DP end is the insulation amount at the end of the transformer design life; DP start is the initial insulation amount of the transformer; A is the constant of the chemical environment; L ( θhs l,t ) is the operating life; E is the activation energy; F is the gas constant; θ hs is the hotspot temperature; L loss is the percentage of transformer life loss after reaching the design service life.

[0048] The optimal life cycle cost is the goal of the selection strategy of the intermittent energy power generation transformer, which is to achieve the balance between safety operation and cost in the whole life cycle of the transformer in the new energy power generation environment, so as to achieve the harmony and unity of the front-end cost and the later cost, the construction cost and the operation cost, and the economic cost and the environmental and social cost. In the early decision-making design stage, comprehensive multi-benefit comparison is made from the perspective of the whole life cycle cost of the project, short-term behavior that damages the whole life cycle cost is avoided, and the most optimal scheme in economy, technology and environment is selected to achieve the maximum economic, social and environmental benefits.

[0049] Taking a certain wind farm as an example, there are 60 wind turbine generators with a single machine capacity of 2MW, and the total installed capacity is 120MW. A new 220kV booster station is built to connect to the 220kV transmission line with one transmission transformer. The power characteristic curve parameters of the wind turbine are shown in the following table 1: Table 1 Wind turbine power characteristic curve parameters

[0050] Transformer capacity selection based on national standard algorithm: When selecting the capacity of the transformer, the actual required power is determined to ensure that the selected transformer can meet the actual load demand, while avoiding overloading or insufficient capacity. Based on GB / T17468-2019 "Guidelines for Selection of Power Transformers" and "Power Engineering Design Manual", the transformer capacity should be calculated based on the calculated load through the following formula: ; Where S represents the calculated load capacity, Se and represents the transformer capacity, and β is the load rate, which is usually set at about 85% for a single transformer supplying steady load.

[0051] For the wind farm in this example, according to the full-load state of all wind turbines in the wind farm, S = 120 MW and β = 0.85 are substituted into The calculated transformer capacity is Se = 141.176 MW, combined with the actual capacity type of the transformer, so a 150 MW capacity three-phase double-winding no-excitation voltage regulating power transformer should be selected, model SZ20-150000 / 220, with a no-load loss of 71 kW, a no-load loss of 380 kW, and a no-load current of 0.32%.

[0052] Transformer cross-section selection based on life cycle cost Based on the actual data of the wind farm in the present application, the transformer model is calculated to be 150 MW according to the economic current density method, and then three types of transformers with smaller capacity of 120 MW, 90 MW and larger capacity of 160 MW are selected. By comparing the costs of the four types of transformers in the life cycle, it is determined which type of transformer is more suitable for this wind farm.

[0053] Transformer life selection method under external delivery of new energy environment a. C i Transformer investment cost Transformer body engineering cost C i1 : including direct labor cost, measure cost and enterprise management cost.

[0054] Auxiliary facility engineering cost C i2 .

[0055] Preparation period price difference C i3 : material price difference and material machine cost adjustment.

[0056] Other costs C i4 : construction site allocation and cleaning cost, project construction management cost, project construction technical service cost and system debugging cost.

[0057] The initial static investment cost composition of four types of transformers is shown in Tables 2-5: Table 2 90 MW Transformer Investment Cost

[0058] Table 3 120 MW Transformer Investment Cost

[0059] Table 4 150 MW Transformer Investment Cost

[0060] Table 5 160 MW Transformer Investment Cost

[0061] b. C l Operation and Maintenance Costs Taking the simulated meteorological data of an example new energy power generation site as a reference, and combining the planned installed capacity of the power generation project, the approximate annual average operation and maintenance costs of the four types are shown in the following table: Table 6 Operation and Maintenance Costs of Four Types of Transformers

[0062] c. C f Power Outage Loss Costs As can be seen from the foregoing analysis, the power outage loss cost C f including the transformer fault repair cost and the power loss cost caused by the fault, is related to factors such as fault repair time, on-grid electricity price, i.e. fault rate, and the selection of parameters in the power outage loss cost model is shown in Table 7: Table 7 Parameters of Power Outage Loss Cost Model of Four Types of Transformers

[0063] d. Intermittent Energy Power Cost Discarded under Transformer Constraint Limitations The reasons for the generation of intermittent energy discard costs mainly include two aspects: first, the transformer reaches the upper limit of the temperature constraint during operation, and the external sending capacity reaches the limit, and it is impossible to continue to send more intermittent energy power; second, due to high temperature, the life loss of the transformer accelerates sharply (especially for small capacity transformers), and when the transformer reaches the upper limit of the life loss and has not been operated to the designed life years, the premature scrapping leads to the inability of normal external sending of intermittent energy.

[0064] e. C d Costs of Cleaning Transformers at the End of Life Retirement cost C d The retirement cost refers to the cost paid for cleaning, recycling and destroying various devices in the transformer after the end of the life cycle of the transformer. The retirement cost of different types and purposes of devices is different. Some can generate a certain amount of residual value income to pay for other related costs, and the retirement cost of such devices should be negative. Some not only have no residual value income, but also need to spend a lot of cost to scrap and clean them up, and the retirement cost of such devices is positive. In the process of product retirement, it is possible to generate a certain income, and it is also necessary to consume certain manpower, material resources and financial resources. According to the annual depreciation rate table of electric power industry enterprises fixed assets, the life of the transformer is 30 years, and the retirement cost is calculated according to 20% of the one-time investment.

[0065] When the life cycle cost economy analysis is carried out, the cost present value comparison method can be used for comparison. In the cost present value comparison method, the selection of the capital discount rate is a problem that needs to be considered. The value of the capital discount rate will directly affect the conclusion of the project life economic analysis. Therefore, the selection of the discount rate must be reasonable, and can reflect the long-term historical change trend. When the standard quota research institute of the Ministry of Construction of China carried out the research and calculation of the social discount rate parameters in China, it was proposed that the recommended value of the social discount rate at the present stage in China was 5%-10%. After comprehensively considering the two indexes of the social discount rate and the production price index change rate, the value of the transformer discount rate r=6% in the application is taken.

[0066] The life cycle cost analysis of four types of transformers obtained in the application is shown in Table 8. Table 8 Life cycle cost of transformer

[0067] As can be seen from Table 8, the investment cost proportions of the four transformer cross-section selection schemes are 17.47%, 32.08%, 39.23% and 42.07% respectively, the operation and maintenance cost proportions are 44.48%, 42.12%, 33.51% and 27.52% respectively, the power outage loss cost proportions are 12.40%, 20.72%, 28.21% and 31.49% respectively, the abandoned intermittent energy electric energy cost proportions are 26.21%, 5.92%, 0% and 0% respectively, and the processing power transmission transformer cost proportions are-0.57%, -0.85%, -0.96% and -1.09% respectively. As can be seen from the above, the initial investment cost accounts for only about 20-40% in the transformer full life cycle cost, and the operation and maintenance cost and the power outage loss cost account for about 50-40%, which occupies a dominant position in the transformer full life cycle cost, so in the transformer cross-section selection, the low cost of one-time investment cannot be blindly pursued, and more attention should be paid to the operation and maintenance cost and the power outage loss cost which account for a major part in the later period, which is the scientificity and comprehensiveness of the application of the full life cycle theory.

[0068] In summary, the transformer model with the highest full life cycle cost is SZ20-90000 / 220, which is 6408.5 million yuan; the lowest is SZ20-120000 / 220, which is 4897.9 million yuan; the intermediate is SZ20-150000 / 220 and SZ20-160000 / 220, which is 5505 and 6106.3 million yuan. If the cross-section selection is performed according to the economic current density method, SZ20-150000 / 220 is selected. However, the full life cycle cost theory is introduced in the present application, through fine modeling analysis, combined with the meteorological environmental data of the power generation area of Liaocheng City, SZ20-120000 / 220 transformer should be selected, which can save about 607.1 million yuan in the initial investment year.

[0069] Embodiment 2 Referring to Figure 4 As shown in the drawings, the present application provides a transformer full life selection device under the environment of sending new energy, comprising: at least one processing unit, the processing unit is connected with a storage unit through a bus unit, the storage unit stores a computer program, when the computer program is executed by the processing unit, the transformer full life selection method under the environment of sending new energy is realized, comprising: A transformer full life cycle cost model is constructed based on device investment cost, operation and maintenance cost, power outage loss cost caused by failure, scrap cost and new energy abandoned power cost under transformer constraint limitation: ; in the formula: C i is the device investment cost; C l is the operation and maintenance cost; Cf is the cost of power loss; C s is the cost of new energy power abandonment under transformer constraint limit; C d is the cost of scrap processing transformer at the end of life; Based on the transformer electric-thermal coupling relationship, meteorological data obtained by meteorological environment big data technology is used as an element, and the running temperature of the transformer in the design life period is simulated; The life loss constraint is introduced; the optimal transformer capacity meeting the life loss constraint is sought with the minimum transformer life cycle cost as the target.

[0070] Of course, the storage unit in the transformer full life selection device under the external sending of new energy environment provided by the embodiment of the application stores computer programs not limited to the method operations described above, and can also perform related operations in the transformer full life selection method under the external sending of new energy environment provided by any embodiment of the application.

[0071] Embodiment 3 The embodiment of the application provides a computer readable storage medium, which stores computer instructions, and the computer instructions are executed by a processor to realize the transformer full life selection method under the external sending of new energy environment, including: A transformer life cycle cost model is constructed based on equipment investment cost, operation and maintenance cost, power loss cost caused by failure, scrap cost and new energy power abandonment cost under transformer constraint limit: In the formula: C i is the equipment investment cost; C l is the operation and maintenance cost; C f is the cost of power loss; C s is the cost of new energy power abandonment under transformer constraint limit; C d is the cost of scrap processing transformer at the end of life; Based on the transformer electric-thermal coupling relationship, meteorological data obtained by meteorological environment big data technology is used as an element, and the running temperature of the transformer in the design life period is simulated; The life loss constraint is introduced; the optimal transformer capacity meeting the life loss constraint is sought with the minimum transformer life cycle cost as the target.

[0072] Of course, the computer readable storage medium provided by the embodiment of the present application stores the computer program, which is not limited to the method operation as described above, and can also perform the related operation in the transformer full life selection method under the new energy environment delivery.

[0073] In the embodiments of the present application, it should be understood that the disclosed structure and method can be implemented in other ways. For example, the structural embodiments described above are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, structure or unit, and can be electrical, mechanical or other forms.

[0074] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, that is, they can be located in one place, or can be distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0075] In addition, the functional units in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of software functional unit.

[0076] The above is only a specific implementation of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A transformer full life selection method under the environment of sending new energy, taking a transformer for sending new energy generation as the research object, characterized in that, Comprise: A transformer full life cycle cost model is constructed based on equipment investment cost, operation and maintenance cost, power failure loss cost caused by fault, scrap cost and new energy curtailment cost under transformer constraint limit: ; in the formula: C i is the equipment investment cost; C l is the operation and maintenance cost; C f is the power failure loss cost; C s is the new energy curtailment cost under transformer constraint limit; C d is the cost generated by scrap processing of the transformer at the end of life; Based on the transformer electric-thermal coupling relationship, the meteorological data obtained by meteorological environment big data technology is used as the element to simulate the operating temperature of the transformer within the design life period; Introducing new energy power generation outgoing current equation constraint, life loss constraint, transformer hotspot temperature inequality constraint, taking the minimum of transformer life cycle cost as the target, seeking the optimal transformer capacity that meets the life loss constraint.

2. The transformer full life selection method under the external delivery new energy environment according to claim 1, characterized in that, The equipment investment cost is represented as: ； In the formulae: C i1 , C i2 , C i3 , C in respectively represent different equipment investment items.

3. The transformer full life selection method under the external delivery new energy environment according to claim 2, characterized in that, Transformer operating and maintenance costs C l The sum of all expenses used by the transformer during normal operation, including the cost of transformer maintenance C m And operating losses C p ; The transformer annual operating and maintenance costs are expressed as: ; The high-voltage transformer operating loss is calculated by the following formula: ； where Δ E is the total annual energy loss; C e is the loss cost per unit loss of the transformer. ； in, R The transformer resistance is the hot spot temperature. The function, based on the transformer's electro-thermal coupling relationship and utilizing meteorological data obtained through meteorological environmental big data technology, calculates the hotspot temperature by simulating the transformer's operating temperature during its design life. ; U For transformer voltage levels; S max This represents the maximum load power. The annual power loss cost is: max This refers to the duration of maximum load loss. Transformer operating and maintenance costs C m including periodic inspections and preventive tests; estimated from the average annual total maintenance cost of transformers, obtained from statistical data of transformer operating and maintenance costs over the years C m is calculated as shown below: ； In the formula: C w is the average annual total maintenance cost of the transformer.

4. The transformer full life selection method under the external delivery new energy environment according to claim 1, characterized in that, The cost of abandoning new energy power under transformer constraint: ； where: C REF Cf is the average repair cost for a failure; Δ W GZ Pf is the output power of the transformer at normal operation when a failure occurs; t MTTR Tf is the average repair time for a single failure; a Pm is the price of electricity on the market; Based on the transformer electric-thermal coupling relationship, the meteorological data obtained by meteorological environment big data technology is used as the element to simulate the operating temperature of the transformer within the design life period, including: 1 is the average number of failures per year for a transformer.

5. The transformer full life selection method under the external delivery of new energy environment according to claim 1, characterized in that, The heat generated by the transformer in actual operation is idealized as a current source, and the heat flow is equivalent to the current flow, the heat capacity is equivalent to the capacitance, and the thermal resistance is equivalent to the resistance; ； In the formula: C s is the cost of abandoning new energy power under the constraint of transformer; t 0 is the starting time to reach the upper limit of the transformer temperature constraint; t end is the end time to reach the upper limit of the transformer temperature constraint; a is the on-grid electricity price; ΔP is the abandoned new energy power when reaching the upper limit of the temperature constraint; P is the actual output power of the new energy; L design is the time to reach the transformer life constraint; L end is the expected design life of the transformer.

6. The method of claim 1, wherein the method is used in an environment where new energy is delivered. The temperature rise dynamic process of the transformer is divided into two heat transfer processes: ambient temperature-bottom oil temperature and bottom oil temperature-hotspot temperature; According to Kirchhoff's theorem, The bottom oil-environment temperature thermal circuit model is obtained: The hotspot temperature-bottom oil thermal circuit model is: Cboil l ； θboil l,t ； In the formula: θboil l,t Cp is the heat capacity of the bottom oil; M5 l R is the thermal resistance between the bottom oil and the external environment; qfe l,t T is the temperature of the bottom oil at time t; ql l,t T is the ambient temperature at time t, obtained through meteorological environmental big data; Cwdn l P is the iron loss at time t; θhs l,t P is the load loss at time t; qwdn l,t Cw is the heat capacity of the winding; M6 l R is the thermal resistance between the hot spot and the bottom oil; First, the bottom oil temperature is calculated from the bottom oil-environment temperature thermal circuit model, which is used as the ambient temperature in the hotspot temperature-bottom oil thermal circuit model, and the hotspot temperature is finally calculated. T is the hot spot temperature at time t; The bottom oil temperature is solved as: P is the winding loss at time t; The hotspot temperature is solved as:

7. The transformer full life selection method under the external delivery new energy environment according to claim 6, characterized in that, New energy power generation outgoing current equation constraint: ； wherein, is the rated time constant of the bottom oil, representing the thermal response speed; is the load coefficient at time t, i.e. the ratio of the current load and the rated load; is the temperature rise of the bottom oil at rated operating conditions; is the first non-linear index, reflecting the non-linear relationship between heat transfer and temperature change or temperature difference; is the loss ratio, i.e. the ratio of iron loss and load loss; is the square of the load coefficient, is the oil temperature dependent function, modifying the change of load loss with oil temperature; cosφ wherein is the rated time constant of the winding, characterizing the thermal response speed; is the temperature rise of the hot spot relative to the bottom layer oil at rated operating conditions; is the second non-linear exponent, reflecting the non-linear relationship between the heat transfer of the winding and the temperature change or the temperature difference; is the square of the load factor, is the hot spot temperature dependent function, modifying the change of the winding loss with the oil temperature. 8.The transformer full life selection method under the external new energy environment according to claim 1, characterized in that, Transformer hotspot temperature inequality constraint: ； In the formula: P i U is the voltage; θ cos is the power factor; I i I is the current; θ ； In the formula: Transformer life loss inequality constraint after design service life: hs is the transformer hotspot temperature; DP hs，lim is the upper limit of the transformer hotspot short-time overload temperature; DP ； where: θhs l,t end is the insulation quantity at the end of the design life of the transformer; θ start is the insulation quantity at the beginning of the life of the transformer; A is a constant for the chemical environment; L Comprise: is the operating life; E is the activation energy; F is the gas constant; At least one processing unit connected to a storage unit through a bus unit, the storage unit stores a computer program, the computer program is executed by the processing unit, and the transformer life selection method under the environment of sending new energy sources according to any of claims 1-8 is realized. hs is the hot spot temperature; L loss is the percentage of life lost after the design life of the transformer.​ 9. A transformer full life selection device under the environment of new energy delivery, characterized in that, The computer instructions are executed by the processor to realize the transformer life selection method under the environment of sending new energy sources according to any of claims 1-8. ​ 10. A computer-readable storage medium storing computer instructions, wherein, ​

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