CN112350379B - Acceptable offshore wind power installed capacity evaluation method considering cable thermal characteristics - Google Patents
Acceptable offshore wind power installed capacity evaluation method considering cable thermal characteristics Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
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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
Technical Field
The disclosure belongs to the technical field of evaluation of installed capacity of offshore wind power, and particularly relates to an evaluation method for accepted installed capacity of offshore wind power, which takes thermal characteristics of cables into consideration.
Background
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Compared with onshore wind power, offshore wind power has the advantages of high wind energy density, high annual utilization hours, no occupation of land resources and the like, and is rapidly developed in recent years. By 2019, the total installed capacity of world offshore wind power reaches 27.2GW, the installed capacity of national offshore wind power reaches 4.9GW, the built offshore wind power project 3.7GW predicts that the installed capacity of national offshore wind power will break through 10GW at the end of 2020. As a main power transmission element for delivering offshore wind power, the submarine cable is high in construction cost, and under the background of rapid development of offshore wind power, the current carrying capacity of the submarine cable is fully utilized, the power transmission efficiency of the submarine cable is improved, and the submarine cable has important significance in improving the investment benefit of an offshore wind power delivery channel and saving energy and reducing emission.
In order to improve the current-carrying capacity of the submarine cable, a scheme for improving the current-carrying capacity of the submarine cable is researched from the perspective of reducing the loss of the submarine cable and improving the heat dissipation condition of the submarine cable in the prior art, and the effect of improving the current-carrying capacity of the submarine cable is simulated and analyzed. However, in the design of an offshore wind power project, designers usually ensure that the current carrying capacity of a selected cable is higher than the maximum output current of a wind farm when the wind farm is fully powered, so that although the wind power output is not limited by the current carrying capacity of the cable, the short-time current carrying potential of the cable is ignored, and the utilization efficiency of the cable is influenced. The reason for the generation of the short-time current-carrying capacity of the cable can be summarized as the following two points:
(1) The submarine cable is a main power transmission element for offshore wind power delivery, is influenced by wind speed, has strong fluctuation of offshore wind power, and causes remarkable asynchronism (thermal inertia) of current carrying and temperature change of an externally-transmitted cable in a running environment, so that the temperature change of a cable conductor lags behind current (thermal inertia) in the running environment, and the short-time high-load running of the externally-transmitted wind power cable does not necessarily cause overhigh running temperature (such as higher than the maximum long-term allowable running temperature) of the conductor due to strong fluctuation of wind power and strong thermal inertia of the cable, thereby influencing the service life of the cable;
(2) The engineering allows the conductor operating temperature to exceed its maximum long-term allowable operating temperature (typically 90 ℃) for short periods of time without affecting the cable design life. For crosslinked polyethylene (XLPE) insulated cables, the united states provides for 1500 hours of cumulative operation at 105 ℃ to 130 ℃, sweden provides for 50 hours of continuous operation at 130 ℃ each time, russia allows 100 hours of operation at 130 ℃ per year, 1000 hours of cumulative operation over the life cycle, and japan limits to 10 hours of cumulative operation at 105 ℃ per month.
Disclosure of Invention
In order to overcome the defects of the prior art, the method for evaluating the receivable offshore wind power installed capacity of the cable is provided, wherein the cable thermal characteristics are taken into consideration, and the receivable wind power installed capacity of the cable is evaluated under the condition that the short-time current carrying capacity of the cable is fully considered.
To achieve the above object, one or more embodiments of the present disclosure provide the following technical solutions:
in a first aspect, a method for assessing the installed capacity of an acceptable offshore wind turbine taking into account the thermal characteristics of the cable is disclosed, comprising:
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 dynamic process of the temperature of the cable conductor and the life loss in the life period, and determining the installed capacity of the acceptable wind power plant.
According to a further technical scheme, the submarine cable heat balance model comprises equivalent circuits of submarine cable structures which are sequentially connected, wherein the equivalent circuits are equivalent circuits of a conductor layer, an insulating layer, a metal sleeve, an armor layer, an outer layer and soil, and the submarine cable heat balance model is configured as follows: the method is used for simulating the dynamic process and the thermal aging process of the conductor temperature in the design life of the submarine cable.
According to a further technical scheme, a submarine cable heat balance model is formulated according to an electric-heat analogy theory and an equivalent circuit, the relationship among the temperature, the loss, the thermal resistance and the thermal capacity of each layer is described, and the long-term allowable current-carrying capacity of the cable is deduced based on the formulation expression.
According to the further technical scheme, the conductor thermal inertia process of the insulated cable with different conductor sections and suitable for the voltage class of 220kV under the step current is given, and the cable conductor thermal inertia time constant and the current-carrying capacity of the cable conductor are obtained through calculation.
According to the further technical scheme, the establishment process of the life loss model comprises the following steps:
on the basis of comprehensively considering the influence of electric field intensity and temperature on the service life of the cable, an Arrhenius-IPM model is established through an aging experiment, and the Arrhenius-IPM model can be popularized to the full-size cable according to an expansion law;
based on Arrhenius-IPM model, the cable is designed to have a service life T p Is divided into N intervals, and the duration of each interval is delta T p At Δ T of p The temperature and voltage of the inner cable conductor can be regarded as constant values, and the T value of the cable is obtained p Percent life loss in.
According to the further technical scheme, the installed capacity of the wind power plant is maximized, and the corresponding objective function is the maximum value of the capacity of a single fan of the wind power plant and the number of fans contained in the wind power plant, wherein the capacity of the single fan of the wind power plant is a known parameter after the model of the fan is determined, and the number of the fans contained in the wind power plant is an integer variable to be decided.
In a further technical solution, the constraint conditions corresponding to the objective function include: the method comprises the following steps of wind turbine output active power equality constraint, wind power plant outgoing current equality constraint, submarine cable heat balance equality constraint and submarine cable residual life inequality constraint after the design service life is over.
In a second aspect, there is disclosed an acceptable offshore wind installed capacity assessment system that accounts for cable thermal characteristics, comprising:
a wind farm output current time series module configured to: calculating a wind power plant output current time sequence by utilizing a wind power characteristic curve based on the wind speed time sequence;
a wind farm installed capacity decision model building module configured to: combining a submarine cable thermal balance model and a life loss model, and establishing a wind power plant installed capacity decision model by taking the maximized wind power plant installed capacity as a target;
an admissible wind farm installed capacity determination module configured to: and solving the installed capacity decision model of the wind power plant, obtaining the dynamic process of the temperature of the cable conductor and the life loss in the life period, and determining the installed capacity of the acceptable wind power plant.
The above one or more technical solutions have the following beneficial effects:
aiming at the problems that offshore wind power has strong volatility and a submarine cable needs to be excavated in a short-time current-carrying capacity, the technical scheme of the disclosure provides a receivable offshore wind power installed capacity calculation method considering cable thermal characteristics. The evaluation result of the offshore wind power installed capacity in the specific region shows 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 by exploring the short-time current-carrying capacity of the submarine cable.
Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to be construed as limiting the disclosure.
Fig. 1 is a structural view of a single-core XLPE insulated submarine cable according to an embodiment of the present disclosure;
FIG. 2 is an equivalent circuit diagram of a submarine cable thermal balance model according to an embodiment of the present disclosure;
FIG. 3 is a schematic diagram of thermal inertia process of XLPE insulated cables with different conductor sections according to an embodiment of the present disclosure;
FIG. 4 is a graphical representation of submarine cable current and conductor temperature profiles over a portion of the time period according to an embodiment of the present disclosure.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict.
Based on the analysis of the prior art, if the thermal inertia property and the thermal aging process of the cable are fully considered in the design of the offshore wind power project, and the conductor section of the cable and the installed capacity of the wind power plant are reasonably designed, the short-time current-carrying potential of the cable can be excavated, and the utilization efficiency of the cable and the construction investment benefit are improved.
The wind power installed capacity which can be accepted by the cable is evaluated under the condition that the short-time current carrying capacity of the cable is fully considered, and a reference is provided for the planning of an offshore wind power project. Firstly, based on an offshore wind power time sequence, then combining a cross-linked polyethylene (XLPE) insulated cable thermal balance model and a life loss model, establishing a wind power plant installed capacity decision model by taking the maximum wind power plant installed capacity as a target and taking the allowable life loss in a cable design service life as a constraint, and providing a heuristic solving method. The method realizes that the receivable installed capacity of the wind power station is determined under the condition of considering the short-time current-carrying capacity of the submarine cable, and provides reference for offshore wind power construction planning. Simulation results show that the method can obviously improve the calculation result of the installed wind power capacity which can be accepted by the submarine cable through the exploration of the short-time current-carrying potential of the cable, and is beneficial to improving the utilization rate of the submarine cable and the investment income of offshore wind power delivery engineering.
Example one
The embodiment discloses 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 thermal balance model and a life loss model, and establishing a wind power plant installed capacity decision model by taking the maximized 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.
Firstly, it is explained that, regarding the submarine cable thermal balance model, the operation temperature of the submarine cable conductor is an important quantity of state for grasping the cable load state and calculating the cable life loss, the technical scheme of the disclosure introduces the XLPE insulated submarine cable thermal balance model, and the model can be used for simulating the submarine cable conductor temperature dynamic process based on the offshore wind farm output power time series simulation method, thereby laying a foundation for the subsequent calculation of the submarine cable thermal aging life loss.
The cable model is mainly considered in the construction of the XLPE insulated submarine cable, the heat production and dissipation mode, the thermoelectric analogy method and the like. The structure can be roughly divided into four layers from inside to outside, namely a conductor layer, an insulating layer, a liner sleeve and an outer tegument layer. Active loss can be produced to circular telegram back conductor resistance, and the insulating layer of cable can produce dielectric loss under the effect of electric field, then can produce electromagnetic induction eddy current loss in metallic shield and the armor, and these active loss all can be with the outside transmission of thermal form. The cable thermal circuit model is analogized to a circuit model, and the differential equation is solved through a column-writing differential equation, so that the conductor temperature, the metal sleeve temperature, the armor layer temperature and the outer layer temperature under different load conditions can be obtained. 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 are calculated according to the model, the size parameters and the load of the cable.
Although the XLPE insulated submarine cable is not easily influenced by external meteorological factors such as wind speed, wind direction and sunshine, the XLPE insulated submarine cable has a more complex layered structure compared with an overhead wire, so that a thermal balance model of the cable is more complex than that of the overhead wire.
The output power time series simulation method based on the offshore wind power plant comprises the following steps: and (3) substituting a wind power characteristic curve, namely a formula (11), according to the time change sequence of the wind speed to obtain an output power time sequence of each wind driven generator, and multiplying the output power time sequence by the number of the wind driven generators in the wind power plant and a wake flow coefficient, namely a molecule in a formula (12) to obtain an output power time sequence of the offshore wind power plant.
The XLPE insulated cable has the characteristics of high mechanical strength, good insulativity and corrosion resistance, and is suitable for a submarine laying environment. Unlike most of the land-based cables, the submarine cables have high requirements for water resistance and corrosion resistance, and usually adopt an armored structure, and because the copper metal sheath has poor water resistance and the aluminum sheath has poor corrosion resistance, the submarine cables usually adopt a lead sheath and a steel wire armored structure, and the structure and the thermal balance model thereof are respectively shown in fig. 1 and fig. 2.
In FIG. 2, W c 、W d 、W s 、W a Conductor loss, dielectric loss, metal sleeve loss and armor layer loss respectively; theta c 、θ s 、θ a 、θ j 、θ soil The temperature of the conductor, the temperature of the metal sleeve, the temperature of the armor layer, the temperature of the outer tegument layer and the temperature of soil are respectively set; c c 、C d 、C s 、C a 、C j 、C soil The heat capacity of the conductor, the heat capacity of the insulating medium, the heat capacity of the metal sleeve, the heat capacity of the armor layer, the heat capacity of the outer tegument and the heat capacity of soil are respectively; t is 1 、T 2 、T 3 、T 4 Respectively thermal resistance of an insulating layer, thermal resistance of a liner layer, thermal resistance of a tegument layer and thermal resistance of soil.
According to the electric-thermal analogy theory, the submarine cable thermal balance model can be expressed as formula (1):
the relationship between the temperature of each layer and the loss, the thermal resistance and the thermal capacity is described in formula (1), and the expression of each loss is 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)
in the formula: i is the current through the cable; r is 20 Is the conductor resistance at a reference temperature of 20 ℃; alpha is the temperature coefficient of resistance;
is a cable phase voltage; omega is angular frequency; c e Is a cable phase capacitance; tan delta is a dielectric loss tangent value of the insulating layer; lambda 1 Is the metal sleeve loss coefficient which is equal to the sum of the circulation loss coefficient lambda '1 and the eddy current loss coefficient lambda' 1; lambda [ alpha ] 2 For the loss factor of the armouring layer, lambda 1 And λ 2 Related to the grounding and laying way of the cable. The calculation method of parameters such as thermal resistance, thermal capacity and loss coefficient in the cable thermal equilibrium model is described in detail in the IEC standard.
Let the left differential term of formula (1) be 0 and use I 2 r、λ 1 W c And λ 2 W c Respectively substitute for W c 、W s And W a Will theta c ＝θ max Substituted into (theta) max The maximum long-term allowable operation temperature of the cable), and the joint type (1) - (5) can deduce the long-term allowable current-carrying capacity I of the cable max The calculation formula (c) is as follows:
the cable current-carrying capacity in this disclosure is also calculated by equation (6).
By solving equation (1), fig. 3 shows the conductor thermal inertia process (I =200A at the initial steady state) of XLPE insulated cables with different conductor sections and applied to 220kV voltage class under the step current Δ I =500A, and the calculated cable conductor thermal inertia time constant (the time required to reach 63.2% of the steady state temperature rise) and the current-carrying capacity thereof are shown in table 1.
TABLE 1 thermal inertia time constant and current-carrying capacity of XLPE insulated cable conductor
As can be seen from fig. 3 and table 1, as the cross section of the cable conductor increases, both the thermal inertia time constant and the current carrying capacity increase, and the thermal inertia time constant is as long as 5h or more, the thermal inertia effect is significant.
Life loss model: the electric field strength and temperature of the cable insulation are two key factors affecting the life of the cable. On the basis of comprehensively considering the influence of electric field intensity and temperature on the service life of the cable, a scholars G.Mazzani establishes an Arrhenius-IPM model through an aging experiment, and can be popularized to full-size cables according to an expansion law:
in the formula: l is a radical of an alcohol D (E,θ c ) Is the cable life; p is D Is the failure probability of the cable; d is an expansion law factor; beta is a beta t Is a shape parameter; alpha (alpha) ("alpha") 0 To a failure probability P D Scale factor at = 63.2%; b is the ratio of the activation energy to the Boltzmann constant; theta.theta. 0 Is the conductor reference temperature; theta.theta. c Is the conductor temperature; e is the electric field strength; e 0 Is a reference electric field strength; n is 0 Is the voltage tolerance coefficient; b is the electric field and temperature effect coupling coefficient.
The calculation method of the electric field intensity E comprises the following steps:
in the formula: u shape AC Is the voltage between the conductor and the metal shield; r is a radical of hydrogen c Is the conductor radius; r is o Is the radius of the insulating layer.
Designing cable with service life T p Dividing (year) into N intervals, wherein the duration of each interval is delta T p At Δ T of p The temperature and voltage of the inner cable conductor can be regarded as constant values, and the cable is at T p The percent life loss in the interior is:
in the formula: l is loss Is at T p Loss of cable life over time; theta.theta. c,i Is the conductor temperature in the ith time interval; e i Is the electric field strength in the ith time interval.
In a specific implementation example, the method for evaluating the installed capacity of the receivable wind power plant is remarkable based on the thermal inertia effect of the cable, and the submarine cable has huge short-time current-carrying potential under the action of the output power of the offshore wind power plant with strong volatility. The method combines an offshore wind power plant output power time sequence, a cable thermal balance model and a life loss model, constructs an admissible offshore wind power installed capacity decision model and a solution method considering cable thermal characteristics for a given cable model by taking the maximum cable wind power installed capacity admission as a target and taking allowable life loss as a constraint, and aims to more scientifically evaluate the admissible offshore wind power installed capacity of a submarine cable under the condition of fully considering the short-time current-carrying potential of the cable and provide a reference for offshore wind power construction planning. The decision model is described as follows:
an objective function:
maxM×p c (10)
in the formula: p is a radical of formula c The capacity of a single fan of the wind power plant is a known parameter after the model of the fan is determined; and M is the number of fans in the wind power plant and is an integer variable to be decided.
The constraint conditions include:
(1) Equality constraint of fan output active power
According to the fan power characteristic curve, the output power (p) of a single fan in the ith period i ) With wind speed (v) i ) The relationship of (c) can be expressed as:
in the formula: v. of c 、v r 、v f Respectively the cut-in wind speed, the rated wind speed and the cut-out wind speed of the fan.
(2) Wind farm outbound current equality constraint
In the formula: I.C. A i And delivering current for the wind power in the ith time period.
(3) Submarine cable thermal balance equality constraint
The heat balance equation (1) of a differential form is processed at T by using an implicit trapezoidal difference method p Discretizing in time period to obtain an algebraic cable heat balance equation constraint as follows:
in the formula: h is the discretization step length(s), in this disclosure h = Δ t × 60; the corner mark k =0 \ 8230and N-1 is the sequence number of the differential time interval, and the value is taken as delta T in the disclosure p ＝Δt，N＝T p ×8760×60/ΔT p . Where k =0 corresponds to the initial state of the cable, the temperature (θ) of each layer of the cable in this state c,0 、θ s,0 、θ a,0 、θ j,0 ) Can be calculated by equation (1) under the assumption of thermal equilibrium (let the differential term be 0) and the initial loss of the cable (W) c,0 、W d,0 、W s,0 、W a,0 ) And (4) estimating.
(4) Inequality constraint for residual life of submarine cable after design service life
1-L loss ≥ε (17)
In the formula: epsilon for reaching cable design service life T p The post-designer expects a remaining life margin for the cable to remain. Epsilon can be set by the designer according to conservative preferences (epsilon is more than or equal to 0), and when epsilon =0 is set, the critical situation from the design life time to the situation that the residual life of the cable is just 0 corresponds.
Because M is a bounded integer variable, the model can be solved by adopting a heuristic solving method, and the steps are as follows:
(1) Inputting calculation data including cable models and parameters, fan parameters, power characteristic curves, wind speed data of the location of the wind power plant and the like;
(2) Based on wind speed statistical data, simulating T p Marine wind speed time series within time;
(3) According to the wind speed time sequence, calculating a wind power field output current time sequence by using a wind power characteristic curve;
(4) Calculating the current-carrying capacity of a given cable model according to the formula (6), and selecting an initial value of the number M of the fans of the wind power plant according to the principle that the current-carrying capacity is higher than the full-load output current of the wind power plant;
(5) According to the wind power plant output current time series simulation result in the step (3), solving the cable conductor temperature dynamic process and the service life loss in the simulation design life period of the equations (9) and (13) - (16);
(6) Judging whether the inequality constraint conditional expression (17) is met, if so, returning to the step (3) after M = M + 1; otherwise, enabling M = M-1, and outputting M as a calculation result;
(7) Determining the receivable installed capacity Mp of the wind power station c 。
In the design of the offshore wind power, the steps can be repeated for all the alternative cable models to obtain the installed capacity of the offshore wind power which can be accepted under different cable models, so that reference is provided for the model selection of the submarine cable for the outgoing wind power.
Analysis by calculation example: the effectiveness of the proposed method is verified based on measured wind speed data (time resolution Δ t =10 min) within 2 years of a certain offshore wind measuring point in the united states.
A wind power plant is built under the wind speed environment, a fan with the rated power of 3.6MW is adopted, and the power characteristic curve parameters are shown in table 2. The wind power plant is connected to the onshore power grid through a 220kVXLPE insulated cable, and the section of a cable conductor is 500mm 2 The current-carrying capacity of the cable is 877A at the soil temperature of 25 ℃, and 103 fans can be received according to the current-carrying capacity under the condition that the wind power factor is 1, and the installed capacity is 370.8MW.
TABLE 2 Fan Power characteristics Curve parameters
TABLE 3 receivable installed capacity of offshore wind farm under different cable residual life margin requirements
TABLE 4 comparison of the results of calculations of installed capacity of acceptable offshore wind farm for traditional and the disclosed methods
Table 3 shows XLPE insulated cables (conductor section 500 mm) with different residual life margin requirements (epsilon) calculated by the method of the present disclosure 2 ) Can accommodate offshore wind farm installed capacity. Table 4 shows the calculated results of the method of the present disclosure compared with the conventional XLPE insulated cables with different conductor sections determined according to the current-carrying capacity, which can accommodate the installed capacity of the offshore wind power, under the condition of ∈ = 0.
As can be seen from table 3, the installed capacity of the cable for receiving offshore wind power, which is decided by the method of the present disclosure, is related to the set value of e, that is, the larger the margin reserved by the designer in the remaining life of the cable after the cable design lifetime is, the smaller the installed capacity of the cable for receiving offshore wind power, which is obtained by the decision, is. As can be seen from table 4, compared to the conventional method, the method disclosed herein can utilize the short-time current-carrying capacity of the submarine cable to improve the installed capacity of the offshore wind farm that the cable can accommodate. When the cross section of the cable conductor is 500mm 2 When the installed capacity of the offshore wind power is 414MW, taking a period of 960h-1200h in the simulation process as an example, fig. 4 shows a curve of a change process of current carrying and temperature of the submarine cable during the period. It can be seen that the condition that the wind power current exceeds the static current-carrying capacity of the cable occurs for many times in the time interval, the accumulated out-of-limit time reaches 33.7h, the out-of-limit of the current-carrying in most time does not cause the out-of-limit of the conductor temperature of the cable, particularly in the time interval of 1032h-1056h, the current-carrying capacity continuously exceeds the static current-carrying capacity for about 8h, but the conductor temperature still does not reach the limit value (90 ℃), and the current-carrying potential brought by the thermal inertia of the conductor of the cable is embodied; in addition, in the 1062h-1064h period and 1071h-1080h period, although the cable conductor temperature exceeded the limit, as can be seen from table 3, after the cable design life span, the remaining life margin was 50%, and it can be seen from the perspective of the full life cycle that the short time temperature was at the same timeThe life loss caused by out-of-limit is in an allowable range, and the current carrying potential caused by allowing short-time high-temperature operation is reflected. Therefore, the method disclosed by the invention obviously improves the installed capacity of offshore wind power which can be accepted by the submarine cable.
Aiming at the problems that offshore wind power has strong volatility and a submarine cable needs to be excavated in a short-time current-carrying capacity, the technical scheme of the disclosure provides a receivable offshore wind power installed capacity calculation method considering cable thermal characteristics. The result of the evaluation of the installed capacity of the offshore wind power in the specific region shows that the calculation result of the wind power installed capacity which can be accepted by taking the current-carrying capacity as the limiting condition in the prior art can be effectively improved by exploring the short-time current-carrying capacity of the submarine cable. The calculation result of the method can provide reference for designers, so that the use efficiency of the submarine cable is improved, and the investment benefit of offshore wind power delivery engineering is improved.
It should be noted that, the characteristics of the offshore wind resources in different regions are different, so that the probability distribution of the wind power and the change speed thereof is also different, which may affect the evaluation result of the method disclosed herein. In this regard, the corresponding rules between different offshore wind power characteristics and the evaluation results of the method disclosed herein should be further analyzed, so as to provide references for offshore wind power construction in different regions.
Example two
The present embodiment aims to provide a computing device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to implement the following steps, including:
calculating a wind power field 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 dynamic process of the temperature of the cable conductor and the life loss in the life period, and determining the installed capacity of the acceptable wind power plant.
EXAMPLE III
An object of the present embodiment is to provide a computer-readable storage medium.
A computer-readable storage medium, on which a computer program is stored which, when executed by a processor, performs the steps of:
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.
Example four
The present embodiment aims to provide an acceptable offshore wind installed capacity evaluation system taking account of thermal characteristics of a cable, comprising:
a wind farm output current time series module configured to: calculating a wind power plant output current time sequence by utilizing a wind power characteristic curve based on the wind speed time sequence;
a wind farm installed capacity decision model building module configured to: 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;
an electric field installed capacity determination module configured to: 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.
The steps involved in the apparatuses of the above second, third and fourth embodiments correspond to the first embodiment of the method, and the detailed description thereof can be found in the relevant description section of the first embodiment. The term "computer-readable storage medium" should be taken to include a single medium or multiple media containing one or more sets of instructions; it should also be understood to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by a processor and that cause the processor to perform any of the methods of the present disclosure.
It will be understood by those skilled in the art that the modules or steps of the present disclosure described above may be implemented by a general purpose computer device, and alternatively, they may be implemented by program code executable by a computing device, such that they may be stored in a storage device and executed by the computing device, or they may be separately fabricated into individual integrated circuit modules, or multiple modules or steps thereof may be fabricated into a single integrated circuit module. The present disclosure is not limited to any specific combination of hardware and software.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Although the present disclosure has been described with reference to specific embodiments, it should be understood that the scope of the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present disclosure.
Claims (6)
1. The method for evaluating the installed capacity of the acceptable offshore wind power considering the thermal characteristics of the cable is characterized by comprising the following steps of:
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 thermal balance model and a life loss model, and establishing a wind power plant installed capacity decision model by taking the maximized wind power plant installed capacity as a target;
the submarine cable heat balance model comprises equivalent circuits of submarine cable structures which are sequentially connected, namely equivalent circuits of a conductor layer, an insulating layer, a metal sleeve, an armor layer, an outer tegument layer and soil, and is configured as follows: the device is used for simulating a conductor temperature dynamic process and a thermal aging process in the design life of the submarine cable;
the establishing process of the life loss model comprises the following steps:
on the basis of comprehensively considering the influence of electric field intensity and temperature on the service life of the cable, an Arrhenius-IPM model is established through an aging experiment, and the Arrhenius-IPM model can be popularized to the full-size cable according to an expansion law;
based on Arrhenius-IPM model, the cable is designed to have a service lifeTpIs divided intoNEach interval having a duration of deltaTpAt a is atTpThe temperature and voltage of the conductor of the inner cable are regarded as constant values, and the cable is obtainedTpPercent life loss in;
the method comprises the steps that the maximum installed capacity of the wind power plant is taken as a target, and a corresponding target function is the maximum value of the capacity of a single fan of the wind power plant and the number of fans included in the wind power plant, wherein the capacity of the single fan of the wind power plant is a known parameter after the model of the fan is determined, and the number of the fans included in the wind power plant is an integer variable to be decided;
the constraint conditions corresponding to the objective function comprise: the method comprises the following steps of (1) carrying out wind turbine output active power equality constraint, wind power plant outgoing current equality constraint, submarine cable heat balance equality constraint and submarine cable residual life inequality constraint after a design service life is passed;
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.
2. The method as claimed in claim 1, wherein the method for evaluating the installed capacity of the cable for wind power generation comprises the steps of formulating a thermal balance model of the submarine cable according to an electric-heat analogy theory and an equivalent circuit, describing the relationship between the temperature and the loss of each layer, the thermal resistance and the thermal capacity, and deriving the long-term allowable current-carrying capacity of the cable based on the formulated expression.
3. The method for evaluating the installed capacity of the acceptable offshore wind turbine considering the thermal characteristics of the cable as claimed in claim 1, wherein the thermal inertia process of the conductor of the insulated cable with different conductor sections suitable for the 220kV voltage class under the step current is given, and the thermal inertia time constant of the conductor of the cable and the current-carrying capacity thereof are calculated.
4. Take into account cable thermal characteristics's receivable offshore wind power installed capacity evaluation system, characterized by includes:
a wind farm output current time series module configured to: calculating a wind power field output current time sequence by utilizing a wind power characteristic curve based on the wind speed time sequence;
a wind farm installed capacity decision model building module configured to: 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;
the submarine cable heat balance model comprises equivalent circuits of submarine cable structures which are sequentially connected, namely equivalent circuits of a conductor layer, an insulating layer, a metal sleeve, an armor layer, an outer tegument and soil, and is configured as follows: the device is used for simulating a conductor temperature dynamic process and a thermal aging process in the design life of the submarine cable;
the establishing process of the life loss model comprises the following steps:
on the basis of comprehensively considering the influence of electric field intensity and temperature on the service life of the cable, an Arrhenius-IPM model is established through an aging experiment, and the Arrhenius-IPM model can be popularized to the full-size cable according to an expansion law;
based on Arrhenius-IPM model, designing service life of cableTpIs divided intoNEach interval having a duration of deltaTpAt a is atTpThe temperature and voltage of the conductor of the inner cable are regarded as constant values, and the cable is obtainedTpPercent life loss in;
the method comprises the steps that the maximum installed capacity of the wind power plant is taken as a target, and a corresponding target function is the maximum value of the capacity of a single fan of the wind power plant and the number of fans contained in the wind power plant, wherein the capacity of the single fan of the wind power plant is a known parameter after the model of the fan is determined, and the number of the fans contained in the wind power plant is an integer variable to be decided;
the constraint conditions corresponding to the objective function comprise: the method comprises the following steps of (1) carrying out wind turbine output active power equality constraint, wind power plant outgoing current equality constraint, submarine cable heat balance equality constraint and submarine cable residual life inequality constraint after a design service life is passed;
an admissible wind farm installed capacity determination module configured to: 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.
5. A computing device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the steps of the method of any of claims 1 to 3 are performed when the program is executed by the processor.
6. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, is adapted to carry out the steps of the method of any one of claims 1 to 3.
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| WO2016061865A1 (en) * | 2014-10-21 | 2016-04-28 | 国网上海市电力公司 | Quasi-dynamic compatibilization method based on cable heat transfer model |
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