CN112350379B - Evaluation method of admissible offshore wind power installed capacity considering thermal characteristics of cables - Google Patents

Abstract

The disclosure provides an evaluation method for acceptable offshore wind power installed capacity considering cable thermal characteristics, which comprises the following steps: calculating a wind power plant output current time sequence by utilizing a wind power characteristic curve based on the wind speed time sequence; combining a submarine cable heat balance model and a life loss model, and establishing a wind power plant installed capacity decision model by taking the maximum wind power plant installed capacity as a target; and solving the installed capacity decision model of the wind power plant, obtaining the temperature dynamic process and the life loss of the cable conductor in the life period, and determining the acceptable installed capacity of the wind power plant. According to the method, the short-time current-carrying capacity of the submarine cable is excavated, so that the calculation result of the acceptable wind power installed capacity with the current-carrying capacity as the limiting condition in the prior art can be effectively improved.

Description

Evaluation method of admissible offshore wind power installed capacity considering thermal characteristics of cables

technical field

The disclosure belongs to the technical field of offshore wind power installed capacity evaluation, and in particular relates to an evaluation method for acceptable offshore wind power installed capacity considering thermal characteristics of cables.

Background technique

The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

Compared with onshore wind power, offshore wind power has the advantages of high wind energy density, high annual utilization hours, and does not occupy land resources. It has developed rapidly in recent years. As of 2019, the world's total installed capacity of offshore wind power has reached 27.2GW, my country's offshore wind power installed capacity has reached 4.9GW, and offshore wind power projects under construction are 3.7GW. It is estimated that by the end of 2020, my country's offshore wind power installed capacity will exceed 10GW. As the main transmission component of offshore wind power transmission, the construction cost of submarine cables is relatively high. Under the background of the rapid development of offshore wind power, making full use of the current-carrying capacity of submarine cables and improving the transmission efficiency of submarine cables will improve the investment efficiency of offshore wind power transmission channels. And energy saving and emission reduction are of great significance.

In order to improve the current-carrying capacity of submarine cables, in the prior art, the improvement scheme of submarine cable current-carrying capacity is studied from the perspectives of reducing the loss of submarine cables and improving its heat dissipation conditions, and the effect of improving the current-carrying capacity of submarine cables is simulated and analyzed. However, in the design of offshore wind power projects, designers usually ensure that the current-carrying capacity of the selected cables is higher than the maximum output current of the wind farm at full power. It reduces the short-term current-carrying potential of the cable and affects the cable utilization efficiency. The reason for the short-term current carrying capacity of the cable can be attributed to the following two points:

(1) Submarine cables are the main transmission components for offshore wind power transmission. Affected by wind speed, the power of offshore wind power fluctuates strongly, resulting in significant asynchrony (thermal inertia) between current carrying and temperature changes of the outgoing cables in the operating environment. Therefore, in the operating environment, the temperature change of the cable conductor lags behind the current (thermal inertia). Due to the strong wind power fluctuation and the thermal inertia of the cable, the short-term high-load operation of the outgoing wind power cable does not necessarily cause the conductor to run too high. Temperature (such as higher than the maximum long-term allowable operating temperature), which in turn affects the service life of the cable;

(2) On the premise of not affecting the design service life of the cable, the engineering allows the operating temperature of the conductor to exceed its maximum long-term allowable operating temperature (usually 90°C) for a short time. For cross-linked polyethylene (XLPE) insulated cables, the United States stipulates that it can run for 1500 hours at 105°C-130°C, Sweden stipulates that it can run continuously for 50 hours each time at 130°C, and Russia allows it to run at 130°C every year It can run for 100 hours and accumulatively run for 1,000 hours in the life cycle. Japan limits the accumulative operation to 10 hours per month at 105°C.

Contents of the invention

In order to overcome the deficiencies of the prior art above, the present disclosure provides a method for evaluating the admissible installed capacity of offshore wind power considering the thermal characteristics of cables, and evaluates the admissible installed capacity of wind power with full consideration of the short-term current-carrying capacity of the cable.

To achieve the above objectives, one or more embodiments of the present disclosure provide the following technical solutions:

In the first aspect, a method for assessing the installed capacity of offshore wind power admissible considering the thermal characteristics of cables is disclosed, including:

Based on the wind speed time series, the wind power characteristic curve is used to calculate the wind farm output current time series;

Combined with the submarine cable heat balance model and life loss model, with the goal of maximizing the installed capacity of the wind farm, a decision model for the installed capacity of the wind farm is established;

Solve the decision-making model of wind farm installed capacity, obtain the dynamic process of cable conductor temperature and life loss within the service life, and determine the acceptable installed capacity of wind farms.

In a further technical solution, the submarine cable heat balance model includes the equivalent circuits of the submarine cable structures connected in sequence, which are respectively the equivalent circuits of the conductor layer, the insulating layer, the metal sheath, the armor layer, the outer covering layer and the soil, so that The submarine cable heat balance model is configured to simulate the dynamic process of conductor temperature and thermal aging process within the design life of the submarine cable.

As a further technical solution, according to the electrothermal analogy theory and equivalent circuit, the submarine cable heat balance model is formulated to describe the relationship between the temperature and loss, thermal resistance and heat capacity of each layer. Based on the formula, the cable is deduced Long-term allowable carrying capacity.

As a further technical solution, the conductor thermal inertia process of insulated cables with different conductor cross-sections suitable for 220kV voltage level is given under step current, and the thermal inertia time constant of the cable conductor and its current carrying capacity are calculated.

Further technical scheme, the establishment process of described life loss model is:

On the basis of comprehensively considering the influence of electric field strength and temperature on cable life, the Arrhenius-IPM model is established through aging experiments, and can be extended to all types of cables according to the expansion law;

Based on the Arrhenius-IPM model, the cable design service life T _p is divided into N intervals, and the duration of each interval is ΔT _p . The temperature and voltage of the cable conductor within ΔT _p can be regarded as constant values, and the life of the cable within T _p is obtained. Loss percentage.

The further technical solution aims to maximize the installed capacity of the wind farm, and the corresponding objective function is the maximum value of the capacity of a single wind turbine in the wind farm and the number of wind turbines contained in the wind farm. The latter is a known parameter, and the number of wind turbines included in the wind farm is an integer variable to be decided.

In a further technical solution, the constraint conditions corresponding to the objective function include: wind turbine output active power equation constraints, wind farm outgoing current equation constraints, submarine cable heat balance equation constraints, and submarine cable remaining life inequality constraints after the design service life.

In the second aspect, an evaluation system for admissible offshore wind power installed capacity considering the thermal characteristics of cables is disclosed, including:

The wind farm output current time series module is configured to: calculate the wind farm output current time series based on the wind speed time series, using the wind power characteristic curve;

The wind farm installed capacity decision model building module is configured to: combine the submarine cable heat balance model and the life loss model, with the goal of maximizing the wind farm installed capacity, to establish a wind farm installed capacity decision model;

The module for determining the installed capacity of the admissible wind farm is configured to: solve the decision-making model for the installed capacity of the wind farm, obtain the dynamic process of the cable conductor temperature and life loss within the service life, and determine the installed capacity of the admissible wind farm.

The above one or more technical solutions have the following beneficial effects:

In view of the strong volatility of offshore wind power and the short-term current-carrying capacity of submarine cables to be explored, the technical solution of this disclosure proposes a calculation method for the acceptable installed capacity of offshore wind power that takes into account the thermal characteristics of cables. This method simulates the design service life of submarine cables The temperature change of the inner conductor is used to evaluate the installed wind power capacity of the cable from the perspective of the thermal aging limit of the cable. The evaluation results of offshore wind power installed capacity in a specific area show that this method can effectively improve the traditional calculation results of acceptable wind power installed capacity limited by current carrying capacity by exploring the short-term current-carrying capacity of submarine cables.

Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The accompanying drawings constituting a part of the present disclosure are used to provide a further understanding of the present disclosure, and the exemplary embodiments and descriptions of the present disclosure are used to explain the present disclosure, and do not constitute improper limitations to the present disclosure.

Fig. 1 is a structural diagram of a single-core XLPE insulated submarine cable according to an embodiment of the present disclosure;

2 is an equivalent circuit diagram of a submarine cable heat balance model according to an embodiment of the present disclosure;

3 is a schematic diagram of the thermal inertia process of XLPE insulated cables with different conductor cross-sections according to an embodiment of the present disclosure;

Fig. 4 is a schematic diagram of curves of submarine cable current and conductor temperature during a part of an embodiment of the present disclosure.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present disclosure. Unless defined otherwise, all technical and scientific terms used in this disclosure have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

It should be noted that the terminology used herein is only for describing specific embodiments, and is not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

In the case of no conflict, the embodiments in the present disclosure and the features in the embodiments can be combined with each other.

Based on the analysis of existing technologies, if the thermal inertia properties and thermal aging process of cables are fully considered in the design of offshore wind power projects, and the cross-section of cable conductors and the installed capacity of wind farms are reasonably designed, the short-term current-carrying potential of cables can be tapped and the utilization of cables can be improved. efficiency and construction investment benefits.

The implementation example of the present disclosure evaluates the acceptable wind power installed capacity of the cable under the condition of fully considering the short-term current carrying capacity of the cable, and provides a reference for offshore wind power project planning. Firstly, based on the time series of offshore wind power, and then combined with the cross-linked polyethylene (XLPE) insulated cable heat balance model and life loss model, with the goal of maximizing the installed capacity of wind farms and constraining the allowable life loss within the design life of the cable, a wind power model is established. The decision-making model of field installed capacity and a heuristic solution method are proposed. Realize the determination of the acceptable installed capacity of wind farms considering the short-term current-carrying capacity of submarine cables, and provide reference for offshore wind power construction planning. The simulation results show that this method can significantly improve the calculation results of the installed wind power capacity of the submarine cable by exploring the short-term current-carrying potential of the cable, which is helpful to improve the utilization rate of the submarine cable and the investment income of the offshore wind power transmission project.

Embodiment one

This embodiment discloses a method for evaluating the installed capacity of admissible offshore wind power considering the thermal characteristics of cables, including:

Based on the wind speed time series, the wind power characteristic curve is used to calculate the wind farm output current time series;

Combined with the submarine cable heat balance model and life loss model, with the goal of maximizing the installed capacity of the wind farm, a decision model for the installed capacity of the wind farm is established;

Solve the decision-making model of wind farm installed capacity, obtain the dynamic process of cable conductor temperature and life loss within the service life, and determine the acceptable installed capacity of wind farms.

First of all, regarding the thermal balance model of submarine cables, the operating temperature of submarine cable conductors is an important state quantity for grasping the load state of cables and calculating cable life loss. The technical solution of this disclosure introduces the thermal balance model of XLPE insulated submarine cables, based on the output Power time series simulation method, this model can be used to simulate the dynamic process of submarine cable conductor temperature, so as to lay the foundation for the subsequent calculation of submarine cable thermal aging life loss.

When the cable model is established, the structure, heat generation and heat dissipation methods, thermoelectric analogy method, etc. of the XLPE insulated submarine cable are mainly considered. From the inside to the outside, the structure can be roughly divided into four layers: conductor layer, insulation layer, liner cover, and outer layer. After electrification, the conductor resistance will produce active loss, the insulation layer of the cable will produce dielectric loss under the action of the electric field, and the metal shield and armor will produce electromagnetic induction eddy current loss, and these active losses will be transmitted to the outside in the form of heat. The thermal circuit model of the cable is compared to the circuit model, and by writing the differential equation to solve the differential equation, the conductor temperature, metal sheath temperature, armor layer temperature, and outer layer temperature can be obtained under different load conditions. After the cable thermal circuit model is established, parameters such as heat source, thermal resistance, and thermal capacity of each layer of the cable in the cable thermal circuit model need to be calculated according to the cable model, size parameters and load.

Although XLPE insulated submarine cables are not easily affected by external meteorological factors such as wind speed, wind direction, and sunshine, they have a more complex layered structure than overhead wires, making the heat balance model of cables more complex than overhead wires.

The time series simulation method based on the output power of offshore wind farms is: according to the time series of wind speed changes, it is brought into the wind turbine power characteristic curve (11) to obtain the time series of output power of each wind turbine, and then multiplied by the wind farm The number of wind turbines and the wake coefficient are the numerators in the formula (12), and the time series of the output power of the offshore wind farm is obtained.

XLPE insulated cables have the characteristics of high mechanical strength, good insulation and corrosion resistance, and are suitable for submarine laying environments. Unlike most land-laying cables, submarine cables have high requirements for waterproof and corrosion resistance. They usually use armored structures, and due to the poor waterproofness of copper metal sheaths and the poor corrosion resistance of aluminum armor, submarine cables Usually lead sheath and steel wire armor structure are used, and its structure and heat balance model are shown in Figure 1 and Figure 2 respectively.

In Fig. 2, W _c , W _d , W _s , W _a are conductor loss, dielectric loss, metal sheath loss and armor loss respectively; θ _c , θ _s , θ _a , θ _j , θ _soil are conductor temperature , metal sheath temperature, armor layer temperature, outer covering layer temperature and soil temperature; C _c , C _d , C _s , C _a , C _j , and C _soil are the conductor heat capacity, insulating medium heat capacity, and metal sheath heat capacity respectively , the heat capacity of the armor layer, the heat capacity of the outer layer and the heat capacity of the soil; T ₁ , T ₂ , T ₃ , and T ₄ are the thermal resistance of the insulation layer, the thermal resistance of the lining layer, the thermal resistance of the outer layer and the thermal resistance of the soil, respectively .

According to the electrothermal analogy theory, the submarine cable heat balance model can be expressed as formula (1):

Equation (1) describes the relationship between the temperature of each layer and the loss, thermal resistance and heat capacity, and the expressions of each loss are as follows:

W _c =I ² ·r ₂₀ ·[1+α(θ _c -20)]=I ² ·r (2)

W _s =λ ₁ ·W _c =(λ ₁ ′+λ ₁ ″)·W _c (4)

W _a =λ ₂ ·W _c (5)

为电缆相电压；ω为角频率；C_e为电缆相电容；tanδ为绝缘层介质损耗角正切值；λ₁为金属套损耗系数，其等于环流损失损耗系数λ’1和涡流损耗系数λ”1之和；λ₂为铠装层损耗系数，λ₁和λ₂与电缆接地及敷设方式有关。关于电缆热平衡模型中热阻、热容、损耗系数等参数的计算方法在IEC标准中有详细阐述。In the formula: I is the current through the cable; r ₂₀ is the conductor resistance at the reference temperature of 20°C; α is the temperature coefficient of resistance;

is the phase voltage of the cable; ω is the angular frequency; C _e is the phase capacitance of the cable; _tanδ is the dielectric loss tangent of the insulating layer; 1; λ ₂ is the loss coefficient of the armor layer, and λ ₁ and λ ₂ are related to the cable grounding and laying method. The calculation methods for the parameters such as thermal resistance, heat capacity, and loss coefficient in the cable thermal balance model are detailed in the IEC standard elaborate.

Let the differential term on the left side of formula (1) be 0, and replace W _c , W _s and W _a with I ² r, λ ₁ W _c and λ ₂ W _c respectively, and substitute θ _c = θ _max into (θ _max is the maximum cable Long-term allowable operating temperature), the simultaneous formula (1)-(5) can deduce the calculation formula of the long-term allowable current carrying capacity I _max of the cable:

In the present disclosure, the ampacity of the cable is also calculated by formula (6).

By solving formula (1), Fig. 3 shows the conductor thermal inertia process of some XLPE insulated cables with different conductor cross-sections suitable for 220kV voltage level under the step current ΔI = 500A (the initial steady state is I = 200A), the calculation The thermal inertia time constant of the cable conductor (the time required to reach 63.2% of the steady-state temperature rise) and its carrying capacity are shown in Table 1.

Table 1 XLPE insulated cable conductor thermal inertia time constant and ampacity

It can be seen from Figure 3 and Table 1 that with the increase of the cross section of the cable conductor, its thermal inertia time constant and current carrying capacity both increase, and the thermal inertia time constant is longer than 5h, and the thermal inertia effect is significant.

Life loss model: The electric field strength and temperature of the cable insulation layer are two key factors affecting the life of the cable. Scholar G.Mazzanti established the Arrhenius-IPM model through aging experiments on the basis of comprehensive consideration of the influence of electric field strength and temperature on cable life, and can be extended to all types of cables according to the expansion law:

In the formula: L _D (E, θ _c ) is the life of the cable; _PD is the failure probability of the cable; D is the expansion law factor; β _t is the shape parameter; α ₀ is the proportional factor when the failure probability P _D =63.2%; B is the ratio of activation energy to Boltzmann constant; θ ₀ is the reference temperature of the conductor; θ _c is the temperature of the conductor; E is the electric field intensity; E ₀ is the reference electric field intensity; n ₀ is the voltage tolerance coefficient; b is the electric field and temperature The role of the connection coefficient.

The calculation method of the electric field strength E is:

Where: U _AC is the voltage between the conductor and the metal shield; r _c is the radius of the conductor; r _o is the radius of the insulating layer.

Divide the design service life T _p (year) of the cable into N intervals, and the duration of each interval is ΔT _p . Assuming that the temperature and voltage of the cable conductor within ΔT _p can be regarded as constant values, the percentage of life loss of the cable within T _p is :

In the formula: L _loss is the cable life loss in T _p time; θ _c,i is the conductor temperature in the i-th time interval; E _i is the electric field intensity in the i-th time interval.

In the specific implementation example, regarding the evaluation method of the installed capacity of the admissible wind farm, the thermal inertia effect of the cable is more significant, and the short-term current-carrying potential of the submarine cable is huge under the strong fluctuation of the output power of the offshore wind farm. This section combines the time series of offshore wind farm output power and the cable thermal balance model and life loss model. For a given cable model, aiming at maximizing the installed wind power capacity of the cable and allowing life loss as a constraint, a possible model that takes into account the thermal characteristics of the cable is constructed. The decision-making model and solution method of offshore wind power installed capacity are adopted, in order to more scientifically evaluate the acceptable offshore wind power installed capacity of submarine cables while fully considering the short-term current-carrying potential of cables, and provide reference for offshore wind power construction planning. The decision model is described as follows:

Objective function:

maxM×p ^c (10)

In the formula: p ^c is the capacity of a single wind turbine in the wind farm, which is a known parameter after the wind turbine model is determined; M is the number of wind turbines included in the wind farm, and is an integer variable to be decided.

Constraints include:

(1) Fan output active power equation constraint

According to the fan power characteristic curve, the relationship between the output power of a single fan (p _i ) and the wind speed (v _i ) in the i-th period can be expressed as:

Where: v _c , v _r , v _f are the cut-in wind speed, rated wind speed and cut-out wind speed of the fan, respectively.

(2) Constraints of wind farm outgoing current equation

In the formula: I _i is the wind power output current in the i-th period.

(3) Submarine cable heat balance equation constraint

Using the implicit trapezoidal difference method to discretize the heat balance equation (1) in the differential form in the T _p period, the constraints of the cable heat balance equation in the algebraic form are as follows:

In the formula: h is the discretization step size (s), h=Δt×60 in this disclosure; subscript k=0...N-1 is the sequence number of the difference period, ΔT _p =Δt, N=T _p in this disclosure ×8760×60/ΔT _p . Among them, k=0 corresponds to the initial state of the cable. In this state, the temperature of each layer of the cable (θ _c,0 , θ _s,0 , θ _a,0 , θ _j,0 ) can be calculated by formula (1) under the assumption of heat balance (let the differential term is 0) and the cable initial loss (W _c,0 , W _d,0 , W _s,0 , W _a,0 ) is estimated.

(4) Inequality constraints on the remaining life of submarine cables after the design service life

1-L _loss ≥ ε (17)

In the formula: ε is the remaining life margin of the cable that the designer expects to retain after reaching the design service life T _p of the cable. ε can be set by the designer according to a conservative preference (ε≥0). When ε=0, it corresponds to the critical situation where the design life span to the remaining life of the cable is exactly 0.

Since M is a bounded integer variable, the above model can be solved using a heuristic solution method, and the steps are as follows:

(1) Input calculation data, including cable model and parameters, fan parameters, power characteristic curve and wind speed data at the site of the wind farm, etc.;

(2) Based on wind speed statistical data, simulate the sea wind speed time series within T _p time;

(3) According to the wind speed time series, using the wind power characteristic curve, calculate the wind farm output current time series;

(4) Calculate the ampacity of a given cable type according to formula (6), and select the initial value of the number of wind turbines M of the wind farm according to the principle that the ampacity is higher than the full output current of the wind farm;

(5) According to the simulation results of the wind farm output current time series in step (3), solve formula (9) and formula (13)-(16) to simulate the dynamic process of cable conductor temperature and life loss during the design life;

(6) judge whether inequality constraint condition formula (17) satisfies, if satisfy, then make M=M+1 and return to step (3); Otherwise make M=M-1, output M is calculation result;

(7) Determine the admissible installed capacity of the wind farm as Mp ^c .

In the design of offshore wind power, the above steps can be repeated for all alternative cable models to obtain the acceptable installed capacity of offshore wind power under different cable models, thus providing a reference for the selection of offshore wind power submarine cables.

Example analysis: This disclosure verifies the effectiveness of the proposed method based on the measured wind speed data (time resolution Δt=10min) of an offshore wind measuring point in the United States within 2 years.

Assuming that the wind farm is built under this wind speed environment, and a wind turbine with a rated power of 3.6MW is used, the parameters of its power characteristic curve are shown in Table 2. The wind farm is connected to the onshore power grid through a 220kV XLPE insulated cable. The cross section of the cable conductor is 500mm ² . The current carrying capacity of the cable is 877A at a soil temperature of 25°C. According to this current carrying capacity, 103 units can be accommodated when the wind power factor is 1. Wind turbines with an installed capacity of 370.8MW.

Table 2 Fan power characteristic curve parameters

Table 3 The installed capacity of offshore wind farms that can be accommodated under different cable remaining life margin requirements

Table 4 Comparison of the calculation results of the installed capacity of offshore wind farms that can be accepted by traditional and disclosed methods

Table 3 shows the admissible installed capacity of offshore wind farms for XLPE insulated cables (conductor cross-section 500mm ² ) under different remaining life margin requirements (ε) calculated by the disclosed method. Table 4 shows the comparison between the calculation results of the disclosed method and the traditional XLPE insulated cables with different conductor cross-sections determined according to the current carrying capacity in the case of ε=0.

It can be seen from Table 3 that the acceptable offshore wind power installed capacity of the cable determined by the disclosed method is related to the set value of ε. The obtained cable can accommodate the smaller installed capacity of offshore wind power. It can be seen from Table 4 that compared with the traditional method, the disclosed method can utilize the short-term current-carrying capacity of the submarine cable to increase the installed capacity of the offshore wind farm that the cable can accommodate. When the cross-section of the cable conductor is 500mm ² and the installed capacity of offshore wind power is 414MW, taking the period of 960h-1200h in the simulation process as an example, Figure 4 shows the curves of the current carrying and temperature changes of the submarine cable during this period. It can be seen that during this period of time, the wind power current exceeded the static current carrying capacity of the cable for many times, and the cumulative time of exceeding the limit was 33.7 hours, and the exceeding of the current carrying capacity did not cause the temperature of the cable conductor to exceed the limit in most of the time, especially During the period of 1032h-1056h, the current carrying capacity continued to exceed the static carrying capacity for about 8h, but the conductor temperature still did not reach the limit (90°C), reflecting the current-carrying potential brought by the thermal inertia of the cable conductor; in addition, during 1062h- 1064h time period and 1071h-1080h time period, although the cable conductor temperature exceeds the limit, it can be seen from Table 3 that after the design life of the cable, the remaining life margin is 50%. It can be seen that from the perspective of the whole life cycle, this The life loss caused by short-term temperature violation is within the allowable range, which reflects the current-carrying potential brought about by allowing short-term high-temperature operation. Therefore, the disclosed method significantly improves the installed capacity of offshore wind power that can be accommodated by submarine cables.

In view of the strong volatility of offshore wind power and the short-term current-carrying capacity of submarine cables to be explored, the technical solution of this disclosure proposes a calculation method for the acceptable installed capacity of offshore wind power that takes into account the thermal characteristics of cables. This method simulates the design service life of submarine cables The temperature change of the inner conductor is used to evaluate the installed wind power capacity of the cable from the perspective of the thermal aging limit of the cable. The evaluation results of offshore wind power installed capacity in a specific area show that this method can effectively improve the traditional calculation results of acceptable wind power installed capacity limited by current carrying capacity by exploring the short-term current-carrying capacity of submarine cables. The calculation results of the disclosed method can provide references for designers, thereby helping to improve the efficiency of using submarine cables and improving the investment benefits of offshore wind power transmission projects.

It should be pointed out that the characteristics of offshore wind resources in different regions are different, resulting in different probability distributions of wind power and its changing speed, which will affect the evaluation results of the disclosed method. In this regard, the corresponding law between different offshore wind power characteristics and the evaluation results of the disclosed method should be further analyzed, so as to provide reference for offshore wind power construction in different regions.

Embodiment two

The purpose of this embodiment is to provide a computing device, including a memory, a processor, and a computer program stored in the memory and operable on the processor. When the processor executes the program, the following steps are implemented, including:

Based on the wind speed time series, the wind power characteristic curve is used to calculate the wind farm output current time series;

Combined with the submarine cable heat balance model and life loss model, with the goal of maximizing the installed capacity of the wind farm, a decision model for the installed capacity of the wind farm is established;

Solve the decision-making model of wind farm installed capacity, obtain the dynamic process of cable conductor temperature and life loss within the service life, and determine the acceptable installed capacity of wind farms.

Embodiment Three

The purpose of this embodiment is to provide a computer-readable storage medium.

A computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the following steps are performed:

Based on the wind speed time series, the wind power characteristic curve is used to calculate the wind farm output current time series;

Combined with the submarine cable heat balance model and life loss model, with the goal of maximizing the installed capacity of the wind farm, a decision model for the installed capacity of the wind farm is established;

Solve the decision-making model of wind farm installed capacity, obtain the dynamic process of cable conductor temperature and life loss within the service life, and determine the acceptable installed capacity of wind farms.

Embodiment Four

The purpose of this embodiment is to provide an evaluation system for admissible offshore wind power installed capacity considering the thermal characteristics of cables, including:

The wind farm output current time series module is configured to: calculate the wind farm output current time series based on the wind speed time series, using the wind power characteristic curve;

The wind farm installed capacity decision model building module is configured to: combine the submarine cable heat balance model and the life loss model, with the goal of maximizing the wind farm installed capacity, to establish a wind farm installed capacity decision model;

The module for determining the installed capacity of the electric field is configured to: solve the decision-making model of the installed capacity of the wind farm, obtain the dynamic process of the temperature of the cable conductor within the service life and the life loss, and determine the installed capacity of the wind farm that can be accepted.

The steps involved in the devices of the above embodiments 2, 3 and 4 correspond to the method embodiment 1, and for specific implementation, please refer to the relevant description of the embodiment 1. The term "computer-readable storage medium" shall be construed to include a single medium or multiple media including one or more sets of instructions; and shall also be construed to include any medium capable of storing, encoding, or carrying A set of instructions to execute and cause the processor to perform any method of the present disclosure.

Those skilled in the art should understand that each module or each step of the above-mentioned present disclosure can be realized by a general-purpose computer device, and optionally, they can be realized by a program code executable by the computing device, so that they can be stored in a The device is executed by a computing device, or they are made into individual integrated circuit modules, or multiple modules or steps among them are made into a single integrated circuit module for realization. This disclosure is not limited to any specific combination of hardware and software.

The above descriptions are only preferred embodiments of the present disclosure, and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included within the protection scope of the present disclosure.

Although the specific implementation of the present disclosure has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present disclosure. Those skilled in the art should understand that on the basis of the technical solutions of the present disclosure, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present disclosure.

Claims (6)

1. An acceptable offshore wind power installed capacity evaluation method that takes into account the thermal characteristics of cables, and its characteristics include: Based on the wind speed time series, the wind power characteristic curve is used to calculate the wind farm output current time series; Combined with the submarine cable heat balance model and life loss model, with the goal of maximizing the installed capacity of the wind farm, a decision model for the installed capacity of the wind farm is established; The submarine cable heat balance model includes the equivalent circuits of the submarine cable structure connected in sequence, which are respectively the equivalent circuits of the conductor layer, insulating layer, metal sheath, armor layer, outer covering layer and soil, and the submarine cable heat balance model It is configured to: be used to simulate the dynamic process of conductor temperature and thermal aging process during the design life of submarine cables; The establishment process of the life loss model is: On the basis of comprehensively considering the influence of electric field strength and temperature on cable life, the Arrhenius-IPM model is established through aging experiments, and can be extended to all types of cables according to the expansion law; Based on the Arrhenius-IPM model, the cable design service life Tp is divided into N intervals, and the duration of each interval is ΔTp , and the temperature and voltage of the cable conductor within ΔTp are regarded as constant values, and the percentage of cable life loss within Tp is obtained; With the goal of maximizing the installed capacity of the wind farm, the corresponding objective function is the maximum value of the capacity of a single wind turbine in the wind farm and the number of wind turbines contained in the wind farm. Among them, the capacity of a single wind turbine in the wind farm is a known parameter after the wind turbine model is determined , the number of wind turbines included in the wind farm is an integer variable to be decided; The constraints corresponding to the objective function include: wind turbine output active power equation constraints, wind farm outgoing current equation constraints, submarine cable thermal balance equation constraints, and submarine cable remaining life inequality constraints after the design service life; Solve the decision-making model of wind farm installed capacity, obtain the dynamic process of cable conductor temperature and life loss within the service life, and determine the acceptable installed capacity of wind farms. 2. The method for assessing the installed capacity of offshore wind power admissible considering the thermal characteristics of cables as claimed in claim 1, characterized in that, according to the electrothermal analogy theory and equivalent circuit, the submarine cable heat balance model is formulated to describe each The relationship between layer temperature and loss, thermal resistance and heat capacity, based on the expression of the formula, the long-term allowable current carrying capacity of the cable is deduced. 3. The method for assessing the installed capacity of offshore wind power in consideration of the thermal characteristics of cables as claimed in claim 1 is characterized in that, the conductor thermal inertia of insulating cables with different conductor cross-sections applicable to 220kV voltage levels under step currents is provided In the process, the thermal inertia time constant of the cable conductor and its current carrying capacity are calculated. 4. An evaluation system for admissible offshore wind power installed capacity considering thermal characteristics of cables, characterized by including: The wind farm output current time series module is configured to: calculate the wind farm output current time series based on the wind speed time series, using the wind power characteristic curve; The wind farm installed capacity decision model building module is configured to: combine the submarine cable heat balance model and the life loss model, with the goal of maximizing the wind farm installed capacity, to establish a wind farm installed capacity decision model; The submarine cable heat balance model includes the equivalent circuits of the submarine cable structure connected in sequence, which are respectively the equivalent circuits of the conductor layer, insulating layer, metal sheath, armor layer, outer covering layer and soil, and the submarine cable heat balance model It is configured to: be used to simulate the dynamic process of conductor temperature and thermal aging process during the design life of submarine cables; The establishment process of the life loss model is: On the basis of comprehensively considering the influence of electric field strength and temperature on cable life, the Arrhenius-IPM model is established through aging experiments, and can be extended to all types of cables according to the expansion law; Based on the Arrhenius-IPM model, the cable design service life Tp is divided into N intervals, and the duration of each interval is ΔTp , and the temperature and voltage of the cable conductor within ΔTp are regarded as constant values, and the percentage of cable life loss within Tp is obtained; With the goal of maximizing the installed capacity of the wind farm, the corresponding objective function is the maximum value of the capacity of a single wind turbine in the wind farm and the number of wind turbines contained in the wind farm. Among them, the capacity of a single wind turbine in the wind farm is a known parameter after the wind turbine model is determined , the number of wind turbines included in the wind farm is an integer variable to be decided; The constraints corresponding to the objective function include: wind turbine output active power equation constraints, wind farm outgoing current equation constraints, submarine cable thermal balance equation constraints, and submarine cable remaining life inequality constraints after the design service life; The module for determining the installed capacity of the admissible wind farm is configured to: solve the decision model for the installed capacity of the wind farm, obtain the dynamic process of the cable conductor temperature and life loss within the service life, and determine the installed capacity of the admissible wind farm. 5. A computing device, comprising a memory, a processor, and a computer program stored on the memory and operable on the processor, characterized in that, when the processor executes the program, any one of claims 1-3 is realized. steps of the method described above. 6. A computer-readable storage medium, on which a computer program is stored, characterized in that, when the program is executed by a processor, the steps of the method according to any one of claims 1-3 are executed.

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