CN114186398A - Optimal frequency selection method for offshore wind power low-frequency sending-out system - Google Patents
Optimal frequency selection method for offshore wind power low-frequency sending-out system Download PDFInfo
- Publication number
- CN114186398A CN114186398A CN202111425972.1A CN202111425972A CN114186398A CN 114186398 A CN114186398 A CN 114186398A CN 202111425972 A CN202111425972 A CN 202111425972A CN 114186398 A CN114186398 A CN 114186398A
- Authority
- CN
- China
- Prior art keywords
- frequency
- submarine cable
- current
- line
- equivalent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000010187 selection method Methods 0.000 title claims abstract description 19
- 230000005540 biological transmission Effects 0.000 claims abstract description 52
- 238000000034 method Methods 0.000 claims abstract description 10
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 238000004364 calculation method Methods 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 6
- 238000004458 analytical method Methods 0.000 claims description 3
- 238000004804 winding Methods 0.000 claims description 3
- 238000013461 design Methods 0.000 abstract description 5
- 238000005457 optimization Methods 0.000 abstract description 5
- 230000009467 reduction Effects 0.000 abstract description 2
- 238000011161 development Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 4
- 238000010248 power generation Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011217 control strategy Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Computer Hardware Design (AREA)
- Evolutionary Computation (AREA)
- Geometry (AREA)
- General Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention discloses an optimal frequency selection method of an offshore wind power low-frequency sending system, which aims at an offshore wind power low-frequency sending scene, takes the number of submarine cables occupying the investment cost main body of offshore wind power low-frequency sending engineering as an optimization object, adopts a low-frequency transmission line sending end high-impedance compensation mode, determines the minimum number of submarine cables through calculating the maximum value of current along the submarine cables under different frequencies, and selects the optimal frequency of low-frequency transmission according to the minimum number of submarine cables. The method is simple to implement and has important value for guiding the actual engineering design. The invention can obtain the optimal frequency of low-frequency power transmission based on actual engineering design data, takes the reduction of the number of submarine cables occupying the largest proportion of the investment cost of the offshore wind power low-frequency transmission system as an optimization target, and has simple implementation method and high efficiency.
Description
Technical Field
The invention belongs to the technical field of power transmission and distribution of power systems, and particularly relates to an optimal frequency selection method of an offshore wind power low-frequency sending-out system.
Background
In order to actively respond to the national development strategy of double carbon and protect the ecological environment, the traditional power system mainly based on fossil energy is being transformed into a novel power system mainly based on new energy. Wind power is an extremely important new energy form and is rapidly developed in recent years; at present, the proportion of wind power generation in the total installed electric power in China exceeds 7 percent, and the wind power generation becomes the third largest power source second to thermal power and hydropower. With the development and application of wind power generation technology, the scale of a wind power plant is gradually enlarged; due to the limitation of land resources, wind energy resources and the like, the large wind power plant is located in a remote area or on the sea far away from the power node. The offshore wind power has the advantages of strong stability, high available hours, no land resource occupation and the like; at present, the onshore wind power development of some countries tends to be saturated, and the offshore wind power is not utilized yet, so that the offshore wind power has huge development potential. How to realize the efficient and reliable grid connection of the offshore wind power is a technical basis for further promoting the development and perfection of the offshore wind power market.
At present, the existing offshore wind power delivery project adopts a power frequency high-voltage alternating current transmission scheme or a flexible direct current transmission scheme. In a power frequency high-voltage alternating-current transmission scheme, the capacitance effect of a submarine cable is obvious, the capacitance charging current is rapidly increased along with the increase of the transmission distance, and the active current transmission space is extruded, so that the scheme is only suitable for sending out of an offshore wind power plant. In the flexible direct current scheme, a converter station and an offshore converter platform are required to be arranged at two ends of a direct current line, so that the engineering investment cost is high, and the flexible direct current scheme is generally applied to remote large-scale offshore wind power plant access. The low-frequency power transmission technology is a novel high-efficiency power transmission technology, the power transmission distance of the alternating current submarine cable is increased by reducing the frequency of a power transmission line, and meanwhile, an offshore converter station and a converter platform do not need to be built, so that the low-frequency power transmission technology has the technical and economic advantages under the medium-distance and long-distance offshore wind power transmission scene.
According to the research conclusion of foreign scholars, if only the influence of the capacitor charging current is considered, the 380kV AC submarine cable has the maximum active transmission distances of 140km, 465km, 630km, 1280km and 14945km respectively at the frequencies of 50Hz, 15Hz, 10Hz, 5Hz and 1Hz, and the smaller the transmission frequency is, the farther the AC power can be transmitted. Meanwhile, the frequency is greatly reduced, and other key equipment of the low-frequency power transmission system is also influenced, such as the volume and the weight of a transformer are increased, the arcing time of a circuit breaker is prolonged, the value of sub-module capacitance of the AC-AC converter is increased, and the like; the optimal selection of the transmission frequency is a key factor influencing the economy of the low-frequency transmission system.
Most of the published documents to date only study the topology, modeling and control strategy and the like of the low-frequency power transmission system, and few studies are related to the frequency selection of the offshore wind power low-frequency transmission system. In order to further exert the technical and economic advantages of the low-frequency power transmission scheme in the medium-distance and long-distance offshore wind power transmission scene, research on a low-frequency power transmission frequency selection method is necessary.
Disclosure of Invention
In view of the above, the invention provides an optimal frequency selection method for an offshore wind power low-frequency transmission system, which aims at an offshore wind power low-frequency transmission scene, takes the number of submarine cables occupying the investment cost main body of offshore wind power low-frequency transmission engineering as an optimization object, can obtain the optimal frequency of low-frequency power transmission suitable for specific engineering design, and has important value for guiding actual engineering design.
An optimal frequency selection method for an offshore wind power low-frequency sending-out system comprises the following steps:
(1) establishing an equivalent circuit model of an offshore wind power low-frequency sending system, wherein the system comprises an offshore wind power plant, a step-up transformer, a parallel high-impedance, an alternating current submarine cable, an onshore frequency conversion station and an onshore power frequency main network;
(2) extracting a certain number of discrete frequency points in a given low-frequency power transmission frequency optimizing interval, and calculating the minimum submarine cable return number corresponding to each discrete frequency point through current along the submarine cable;
(3) and comparing the minimum submarine cable return number corresponding to each discrete frequency point, and selecting the discrete frequency point with the minimum submarine cable return number as the optimal frequency of the system.
Further, the offshore wind farm is equivalent to a power source in an equivalent circuit model, and the active power emitted by the power source is equal to the rated capacity P of the offshore wind farmNIts reactive power emitted is equal to 0.
Further, the step-up transformer is equivalent to a series impedance Z in an equivalent circuit modelTThe calculation expression is as follows:
wherein: u shapeTNIs rated voltage of secondary side winding of step-up transformer, STNFor rated capacity of step-up transformer, XTJ is the unit of imaginary number, which is the leakage reactance per unit of the step-up transformer.
Further, the parallel high impedance is equivalent to a parallel admittance Y in an equivalent circuit modelSThe calculation expression is as follows:
wherein: rho is high impedance compensation degree, XCThe capacitance reactance value of the equivalent capacitance of the line is f, the system operation frequency is f, the equivalent capacitance of the line in unit length is c, the length of the submarine cable line is L, and j is an imaginary number unit.
Further, the AC submarine cable is on the likeEquivalent to a pi-type circuit in an effective circuit model, the pi-type circuit comprises series impedance ZLAnd its parallel admittance Y at both endsLThe specific calculation expression is as follows:
wherein: gamma denotes the line propagation coefficient, Z1Is the equivalent impedance of the line per unit length, Y1Is the equivalent-to-ground admittance of a unit length line, L is the length of a submarine cable line, r1Is a line resistance per unit length, /)1Is the line inductance per unit length, g1Is the conductance per unit length of the line, c1Is the line capacitance per unit length, f is the system operating frequency, n is the number of submarine cable returns, and j is the imaginary number unit.
Furthermore, the land frequency conversion station and the land power frequency main network are equivalent to an alternating current voltage source U in an equivalent circuit modelsOf amplitude equal to the nominal voltage U of the systemNThe frequency is equal to the system operating frequency f.
Further, in the step (2), a certain number of discrete frequency points are extracted by using the following equation;
wherein: f. ofmM is a natural number and is more than or equal to 1 and less than or equal to N for the extracted mth discrete frequency pointf，NfNumber of discrete frequency points to be extracted, fmaxAnd fminAnd respectively an upper limit value and a lower limit value of the low-frequency power transmission frequency optimizing interval.
Further, the minimum number of submarine cables corresponding to the discrete frequency points is calculated in the step (2), and the specific process is as follows:
2.1, setting the number n of the submarine cable to be 1;
2.2, setting the high-impedance compensation degree rho to be 0;
2.3 setting the system running frequency f as the current discrete frequency point;
2.4 calculating the current along the submarine cable according to the current system operating frequency f, the high-impedance compensation degree rho and the submarine cable return number n, and obtaining the maximum value I of the current amplitude along the submarine cable according to the following formulamax：
Wherein: n is a radical ofLThe number of the distance discrete points of the submarine cable, k is a natural number and is more than or equal to 1 and less than or equal to NL，IkIs the current phasor at the kth distance discrete point;
2.5 mixing of ImaxSubmarine cable current-carrying capacity I corresponding to current discrete frequency pointampComparing, the current carrying capacity of the submarine cable IampCalculated by IEC60287 standard formula;
if Imax≤IampIf the current high-impedance compensation degree rho is considered to be the feasible compensation degree rhofeaThe currently set number n of submarine cable returns is the minimum number of submarine cable returns corresponding to the current discrete frequency point;
if Imax＞IampIncreasing the high-impedance compensation degree rho according to the set step length, and returning to execute the step 2.4; when the high impedance compensation degree rho exceeds the preset maximum high impedance compensation degree rhomaxThen, step 2.6 is carried out;
2.6 adding a submarine cable on the basis of the current number of submarine cables, resetting the high-impedance compensation degree rho to be 0, and returning to execute the step 2.4.
Further, the specific process of calculating the current along the submarine cable in the step 2.4 is as follows:
firstly, calculating equivalent circuit model parameters of the system according to the current system operating frequency f, the high-impedance compensation degree rho and the submarine cable return number n;
then, analyzing the system equivalent circuit model by adopting a circuit analysis method to obtain a line tail end current vector IsI.e. the model is filled with an AC voltage source UsThe current of (a);
further, selecting a certain number of distance discrete points on the alternating current submarine cable by adopting the following expression;
wherein: l is the length of the submarine cable line LkThe distance between the kth distance discrete point and the tail end of the submarine cable line;
finally, calculating the current along the submarine cable according to the following equation, wherein the current phasor comprises the current phasor at each distance discrete point;
wherein: u shapekIs the voltage phasor at the kth discrete point in distance, gamma denotes the line propagation coefficient, Z1Is the equivalent impedance of the line per unit length, Y1Is the equivalent to ground admittance of a unit length line.
Based on the technical scheme, the invention has the following beneficial technical effects:
1. for offshore wind power development, the invention provides an optimal frequency selection method for an offshore wind power low-frequency sending-out system, which can obtain the optimal frequency of low-frequency power transmission based on actual engineering design data and has important significance for guiding engineering construction.
2. The invention takes the reduction of the number of submarine cables occupying the offshore wind power low-frequency output system with the largest investment cost and proportion as the optimization target, and has simple implementation method and high efficiency.
Drawings
Fig. 1 is a schematic view of a topological structure of an offshore wind power low-frequency delivery system.
FIG. 2 is a schematic diagram of an equivalent circuit model of the offshore wind power low-frequency transmission system.
FIG. 3 is a schematic flow chart of the frequency selection method of the offshore wind power low-frequency transmission system of the invention.
Fig. 4 is a graph illustrating the minimum cable return number according to the transformation of the low-frequency transmission frequency.
Detailed Description
In order to more specifically describe the present invention, the following detailed description is provided for the technical solution of the present invention with reference to the accompanying drawings and the specific embodiments.
The topological structure of the offshore wind power low-frequency output system is shown in fig. 1, active power output by each wind turbine in a wind power plant is collected on an offshore boosting platform through a medium-voltage current collection network, and then is connected into a long-distance high-voltage alternating-current submarine cable through a boosting transformer; the low-frequency power transmission system adopts a single-end compensation mode, and the parallel high-voltage reactor is arranged at the sending end of the high-voltage alternating-current submarine cable and is positioned on the offshore boosting platform; the other end of the high-voltage alternating current sea cable is connected with the onshore frequency conversion station, and the low-frequency wind power transmitted to the onshore frequency conversion station is subjected to frequency conversion by the onshore frequency conversion station and then fed into the onshore power frequency main network.
An equivalent circuit model of the offshore wind power low-frequency sending-out system is shown in fig. 2, and an offshore wind power plant (comprising a wind turbine generator and a medium voltage power collection network) is equivalent to a power source; considering that the maximum load current quantity of the line is required when the wind power plant works under the rated working condition, the active power P emitted by the equivalent power sourcewfSet as rated active power P of wind farmNReactive power Q from the equivalent power sourcewfSet to 0, it is considered here that the offshore wind farm can be made to behave as a pure active power source to the outside by controlling the wind turbine and the remaining reactive power regulating auxiliaries in the wind farm.
The step-up transformer is equivalent to a series impedance ZT，ZTCan be calculated according to the following formula:
in the formula: u shapeTN、STNAnd XTAnd respectively representing the rated voltage, the rated capacity and the leakage reactance per unit value of the secondary side winding of the step-up transformer.
The parallel high impedance is equivalent to the parallel admittance Ys，YsCan be calculated according to the following formula:
in the formula: ρ represents a high impedance compensation degree, XCFor the line equivalent capacitance capacitive reactance value, line equivalent capacitance capacitive reactance XcCan be calculated according to the following formula:
in the formula: f represents the operating frequency of the low-frequency power transmission system, c represents the equivalent capacitance of the line per unit length, and L represents the line length.
AC submarine cable is equivalent to pi-type circuit, series impedance Z in pi-type equivalent circuitLAnd both ends of the admittance Y are connected in parallelLCan be calculated according to the following formula:
in the formula: gamma denotes the line propagation coefficient, Z1Representing the equivalent impedance of the line per unit length, Y1Representing the equivalent-to-ground admittance, Z, of the line per unit length1And Y1Can be calculated according to the following formula:
in the formula: r is1、l1、g1And c1The resistance, inductance, conductance and capacitance of the line in unit length are expressed, n represents the number of the submarine cable returns, and gamma can be calculated according to the following formula:
the AC-AC converter in the land frequency conversion station generally adopts constant low-frequency side AC voltage control to provide stable power for a low-frequency power transmission system, so that the land frequency conversion station and a land AC main network can be equivalent to an AC voltage source Us，UsAmplitude of UsmEqual to rated voltage U of low-frequency power transmission systemNFrequency fsEqual to the low frequency transmission system operating frequency f.
The process of the frequency selection method of the offshore wind power low-frequency transmission system is shown in fig. 3, and a certain number of discrete frequency points are selected in a low-frequency transmission frequency optimizing interval according to the following equation:
wherein: n is a radical offM (1. ltoreq. m. ltoreq.N, representing the number of frequency discrete pointsfAnd m is a positive integer) represents the number of frequency discrete points, fmaxAnd fminUpper and lower limit values, f, representing the low frequency transmission frequency optimization intervalmRepresenting the frequency value corresponding to the mth discrete frequency point.
And for each frequency discrete point, determining the corresponding minimum submarine cable loop number according to the following steps:
step 1: setting the number n of the submarine cable to be 1;
step 2: setting the high-impedance compensation degree rho to be 0;
and step 3: setting the operating frequency f of a low frequency power transmission system equal to fm；
And 4, step 4: calculating the current along the submarine cable according to the operating frequency, the high-impedance compensation degree and the number of the submarine cables returned by the low-frequency power transmission system, and calculating the current along the submarine cable by adopting the following method:
firstly, calculating equivalent circuit model parameters of the offshore wind power low-frequency sending-out system according to the operating frequency f of the low-frequency power transmission system, the high-impedance compensation degree rho and the number n of sea cable returns;
then, solving the equivalent circuit network of the offshore wind power low-frequency sending-out system by adopting a circuit analysis method to obtain a line terminal voltage vector U2And current vector I2；
Further, N is selected from the AC sea cable roadLA distance discrete point, the distance l from the discrete point to the tail end of the linekCan be calculated from the following formula:
wherein: n is a radical ofLRepresents the number of discrete points from a distance, k (1. ltoreq. k. ltoreq.NLAnd k is a positive integer) represents the serial number from the discrete point, and L represents the line length;
and finally, calculating the voltage phasor and the current phasor at each discrete distance point according to the following equations:
in the formula: u shapesAnd IsRespectively representing the terminal voltage phasor and current phasor, UkAnd IkRespectively represent the k (1. ltoreq. k. ltoreq.N)L) Voltage phasor and current phasor corresponding to each discrete point in distance, gamma represents the line propagation coefficient, Z1Representing the equivalent impedance of the line per unit length, Y1Indicating the equivalent to ground admittance of the line per unit length.
Obtaining the maximum value I of the current amplitude along the submarine cable according to the following formulamax：
And 5: will ImaxCurrent carrying capacity I of sea cable corresponding to current frequency pointampA comparison is made ofampThe value of (A) can be calculated by the standard formula of IEC 60287.
If Imax≤IampIf the current high-impedance compensation degree rho is considered to be the feasible compensation degree rhofeaThe number of the current submarine cable is the discrete frequency point fmCorresponding minimum number of submarine cable returns
If Imax＞IampAccording to the set high impedance compensation degree step length rhostepIncreasing rho, and then repeating steps 4 and 5; when rho exceeds the preset maximum high impedanceDegree of compensation ρmaxThereafter, the process proceeds to step 6.
Step 6: and (5) adding a submarine cable on the basis of the number of the original submarine cables, and then repeating the steps 4 and 5.
After the minimum number of submarine cable returns corresponding to all discrete frequency points is solved, the optimal frequency f of the system is selected according to the following equationopt：
Wherein: n is a radical offM (1. ltoreq. m. ltoreq.N, representing the number of frequency discrete pointsfAnd m is a positive integer) represents the serial number of the frequency discrete point, and s represents the serial number of the discrete frequency point corresponding to the optimal frequency.
Specific parameters of the offshore wind power low-frequency sending-out system in the embodiment are shown in tables 1 and 2, and current-carrying capacity and unit length parameters of the submarine cables at other frequencies in table 2 can be calculated by linear difference values. The low-frequency power transmission frequency optimizing interval is [10Hz,30Hz ], the number of discrete frequency points is 21, the number of distance discrete points is 100, the maximum high impedance compensation degree is 0.4, and the high impedance compensation degree step length is 0.02.
TABLE 1
TABLE 2
FIG. 4 shows the minimum number of returns of a submarine cable as a function of the frequency of the low-frequency transmission; it can be seen that the minimum number of sea cable returns varies from 2 returns to 3 returns when the frequency varies from 20Hz to 21 Hz. Therefore, for the system of this embodiment, the optimal low frequency power transmission frequency is 20 Hz.
The embodiments described above are presented to enable a person having ordinary skill in the art to make and use the invention. It will be readily apparent to those skilled in the art that various modifications to the above-described embodiments may be made, and the generic principles defined herein may be applied to other embodiments without the use of inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications to the present invention based on the disclosure of the present invention within the protection scope of the present invention.
Claims (9)
1. An optimal frequency selection method for an offshore wind power low-frequency sending-out system comprises the following steps:
(1) establishing an equivalent circuit model of an offshore wind power low-frequency sending system, wherein the system comprises an offshore wind power plant, a step-up transformer, a parallel high-impedance, an alternating current submarine cable, an onshore frequency conversion station and an onshore power frequency main network;
(2) extracting a certain number of discrete frequency points in a given low-frequency power transmission frequency optimizing interval, and calculating the minimum submarine cable return number corresponding to each discrete frequency point through current along the submarine cable;
(3) and comparing the minimum submarine cable return number corresponding to each discrete frequency point, and selecting the discrete frequency point with the minimum submarine cable return number as the optimal frequency of the system.
2. The optimal frequency selection method according to claim 1, wherein: the offshore wind farm is equivalent to a power source in an equivalent circuit model, and the active power emitted by the power source is equal to the rated capacity P of the offshore wind farmNIts reactive power emitted is equal to 0.
3. The optimal frequency selection method according to claim 1, wherein: the step-up transformer is equivalent to a series impedance Z in an equivalent circuit modelTThe calculation expression is as follows:
wherein: u shapeTNIs rated voltage of secondary side winding of step-up transformer, STNFor rated capacity of step-up transformer, XTJ is the unit of imaginary number, which is the leakage reactance per unit of the step-up transformer.
4. The optimal frequency selection method according to claim 1, wherein: the parallel high impedance is equivalent to a parallel admittance Y in an equivalent circuit modelSThe calculation expression is as follows:
wherein: rho is high impedance compensation degree, XCThe capacitance reactance value of the equivalent capacitance of the line is f, the system operation frequency is f, the equivalent capacitance of the line in unit length is c, the length of the submarine cable line is L, and j is an imaginary number unit.
5. The optimal frequency selection method according to claim 1, wherein: the AC submarine cable is equivalent to a pi-type circuit in an equivalent circuit model, and the pi-type circuit comprises series impedance ZLAnd its parallel admittance Y at both endsLThe specific calculation expression is as follows:
wherein: gamma denotes the line propagation coefficient, Z1Is the equivalent impedance of the line per unit length, Y1Is the equivalent-to-ground admittance of a unit length line, L is the length of a submarine cable line, r1Is a line resistance per unit length, /)1Is the line inductance per unit length, g1Is the conductance per unit length of the line, c1Is the line capacitance per unit length, f is the system operating frequency, n is the number of submarine cable returns, and j is the imaginary number unit.
6. The optimal frequency selection method according to claim 1, wherein: the land frequency conversion station and the land power frequency main network are equivalent to beAC voltage source UsOf amplitude equal to the nominal voltage U of the systemNThe frequency is equal to the system operating frequency f.
7. The optimal frequency selection method according to claim 1, wherein: in the step (2), a certain number of discrete frequency points are extracted by adopting the following equation;
wherein: f. ofmM is a natural number and is more than or equal to 1 and less than or equal to N for the extracted mth discrete frequency pointf，NfNumber of discrete frequency points to be extracted, fmaxAnd fminAnd respectively an upper limit value and a lower limit value of the low-frequency power transmission frequency optimizing interval.
8. The optimal frequency selection method according to claim 1, wherein: the minimum number of submarine cables corresponding to the discrete frequency points is calculated in the step (2), and the specific process is as follows:
2.1, setting the number n of the submarine cable to be 1;
2.2, setting the high-impedance compensation degree rho to be 0;
2.3 setting the system running frequency f as the current discrete frequency point;
2.4 calculating the current along the submarine cable according to the current system operating frequency f, the high-impedance compensation degree rho and the submarine cable return number n, and obtaining the maximum value I of the current amplitude along the submarine cable according to the following formulamax：
Wherein: n is a radical ofLThe number of the distance discrete points of the submarine cable, k is a natural number and is more than or equal to 1 and less than or equal to NL，IkIs the current phasor at the kth distance discrete point;
2.5 mixing of ImaxSubmarine cable current-carrying capacity I corresponding to current discrete frequency pointampTo carry outComparison, current carrying capacity of said submarine cable IampCalculated by IEC60287 standard formula;
if Imax≤IampIf the current high-impedance compensation degree rho is considered to be the feasible compensation degree rhofeaThe currently set number n of submarine cable returns is the minimum number of submarine cable returns corresponding to the current discrete frequency point;
if Imax＞IampIncreasing the high-impedance compensation degree rho according to the set step length, and returning to execute the step 2.4; when the high impedance compensation degree rho exceeds the preset maximum high impedance compensation degree rhomaxThen, step 2.6 is carried out;
2.6 adding a submarine cable on the basis of the current number of submarine cables, resetting the high-impedance compensation degree rho to be 0, and returning to execute the step 2.4.
9. The optimal frequency selection method according to claim 8, wherein: the specific process of calculating the current along the submarine cable in the step 2.4 is as follows:
firstly, calculating equivalent circuit model parameters of the system according to the current system operating frequency f, the high-impedance compensation degree rho and the submarine cable return number n;
then, analyzing the system equivalent circuit model by adopting a circuit analysis method to obtain a line tail end current vector IsI.e. the model is filled with an AC voltage source UsThe current of (a);
further, selecting a certain number of distance discrete points on the alternating current submarine cable by adopting the following expression;
wherein: l is the length of the submarine cable line LkThe distance between the kth distance discrete point and the tail end of the submarine cable line;
finally, calculating the current along the submarine cable according to the following equation, wherein the current phasor comprises the current phasor at each distance discrete point;
wherein: u shapekIs the voltage phasor at the kth discrete point in distance, gamma denotes the line propagation coefficient, Z1Is the equivalent impedance of the line per unit length, Y1Is the equivalent to ground admittance of a unit length line.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111425972.1A CN114186398B (en) | 2021-11-24 | 2021-11-24 | Optimal frequency selection method for offshore wind power low-frequency sending-out system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111425972.1A CN114186398B (en) | 2021-11-24 | 2021-11-24 | Optimal frequency selection method for offshore wind power low-frequency sending-out system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114186398A true CN114186398A (en) | 2022-03-15 |
| CN114186398B CN114186398B (en) | 2024-06-14 |
Family
ID=80602782
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111425972.1A Active CN114186398B (en) | 2021-11-24 | 2021-11-24 | Optimal frequency selection method for offshore wind power low-frequency sending-out system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114186398B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114971063A (en) * | 2022-06-13 | 2022-08-30 | 浙江大学 | Frequency selection method for multi-terminal low-frequency interconnection system of urban supply area |
| CN116599115A (en) * | 2023-06-13 | 2023-08-15 | 国网江苏省电力有限公司电力科学研究院 | Flexible low-frequency power transmission system optimal operation method, device and equipment based on dynamic voltage adjustment and storage medium |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107480875A (en) * | 2017-08-02 | 2017-12-15 | 华北电力大学 | A kind of marine frequency dividing cable transmission systems allocation plan choosing method |
| CN107947211A (en) * | 2017-12-06 | 2018-04-20 | 国网山东省电力公司济南供电公司 | Using WAVELET PACKET DECOMPOSITION and meter and the isolated island type micro-capacitance sensor energy storage Optimal Configuration Method of frequency response |
| CN108899941A (en) * | 2018-07-13 | 2018-11-27 | 中国电力科学研究院有限公司 | A kind of offshore wind farm multi-objective reactive optimization configuration method and system that soft direct sending goes out |
| CN109066772A (en) * | 2018-08-01 | 2018-12-21 | 广州供电局有限公司 | Wind-powered electricity generation climbing rate stabilizes methods, devices and systems |
| US20200401740A1 (en) * | 2019-06-18 | 2020-12-24 | The Governors Of The University Of Alberta | Aggregated model of large-scale wind farms for power system simulation software tools |
| CN112636367A (en) * | 2020-12-09 | 2021-04-09 | 南京工程学院 | Hybrid energy storage capacity optimal configuration method for stabilizing wind power fluctuation |
| CN112668764A (en) * | 2020-12-22 | 2021-04-16 | 国网福建省电力有限公司 | Offshore wind farm energy storage system optimization configuration method based on cloud model and FCM algorithm |
| CN113047332A (en) * | 2021-04-27 | 2021-06-29 | 中国华能集团清洁能源技术研究院有限公司 | Tower of offshore wind power single-pile foundation and configuration design method thereof |
-
2021
- 2021-11-24 CN CN202111425972.1A patent/CN114186398B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107480875A (en) * | 2017-08-02 | 2017-12-15 | 华北电力大学 | A kind of marine frequency dividing cable transmission systems allocation plan choosing method |
| CN107947211A (en) * | 2017-12-06 | 2018-04-20 | 国网山东省电力公司济南供电公司 | Using WAVELET PACKET DECOMPOSITION and meter and the isolated island type micro-capacitance sensor energy storage Optimal Configuration Method of frequency response |
| CN108899941A (en) * | 2018-07-13 | 2018-11-27 | 中国电力科学研究院有限公司 | A kind of offshore wind farm multi-objective reactive optimization configuration method and system that soft direct sending goes out |
| CN109066772A (en) * | 2018-08-01 | 2018-12-21 | 广州供电局有限公司 | Wind-powered electricity generation climbing rate stabilizes methods, devices and systems |
| US20200401740A1 (en) * | 2019-06-18 | 2020-12-24 | The Governors Of The University Of Alberta | Aggregated model of large-scale wind farms for power system simulation software tools |
| CN112636367A (en) * | 2020-12-09 | 2021-04-09 | 南京工程学院 | Hybrid energy storage capacity optimal configuration method for stabilizing wind power fluctuation |
| CN112668764A (en) * | 2020-12-22 | 2021-04-16 | 国网福建省电力有限公司 | Offshore wind farm energy storage system optimization configuration method based on cloud model and FCM algorithm |
| CN113047332A (en) * | 2021-04-27 | 2021-06-29 | 中国华能集团清洁能源技术研究院有限公司 | Tower of offshore wind power single-pile foundation and configuration design method thereof |
Non-Patent Citations (4)
| Title |
|---|
| M.M.KABSHA 等: "A new control scheme for fast frequency support form HVDC connected offshore wind farm in low-inertia system", IEEE TRANSACTIONS ON SUSTAINABLE ENERGY, vol. 11, no. 3, 31 July 2020 (2020-07-31), pages 1829 - 1837, XP011794416, DOI: 10.1109/TSTE.2019.2942541 * |
| PENG QIU 等: "Optimal transmission frequency of low frequency AC system for offshore wind farm integration", 2020 INTERNATIONAL CONFERENCE ON POWER SYSTEM TECHNOLOGY(POWERCON), 8 February 2022 (2022-02-08), pages 1556 - 1560 * |
| 任冲 等: "大规模风电直流送出系统过电压抑制措施及控制方案优化研究", 高压电器, vol. 56, no. 05, 16 May 2020 (2020-05-16), pages 163 - 174 * |
| 王秀丽 等: "分频输电在海上风电并网应用中的前景和挑战", 电力工程技术, vol. 36, no. 01, 8 January 2017 (2017-01-08), pages 15 - 19 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114971063A (en) * | 2022-06-13 | 2022-08-30 | 浙江大学 | Frequency selection method for multi-terminal low-frequency interconnection system of urban supply area |
| CN116599115A (en) * | 2023-06-13 | 2023-08-15 | 国网江苏省电力有限公司电力科学研究院 | Flexible low-frequency power transmission system optimal operation method, device and equipment based on dynamic voltage adjustment and storage medium |
| CN116599115B (en) * | 2023-06-13 | 2024-01-30 | 国网江苏省电力有限公司电力科学研究院 | Flexible low-frequency power transmission system optimal operation method, device and equipment based on dynamic voltage adjustment and storage medium |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114186398B (en) | 2024-06-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110829478B (en) | Low-frequency alternating-current uncontrolled rectification power transmission system of offshore wind power plant | |
| CN111799813B (en) | Marine wind farm reactive power optimization configuration method considering reactive power regulation of wind turbine generator | |
| CN112421670B (en) | Intermediate-frequency flexible direct-current power transmission system suitable for sending out wind power from open sea and control method thereof | |
| CN110829479A (en) | High-frequency uncontrolled rectification direct-current power transmission system of offshore wind farm | |
| CN109787239B (en) | Alternating iteration load flow calculation method and system of load flow model and multi-frequency alternating current series-parallel system | |
| CN102684201B (en) | Voltage threshold probability-based reactive power optimizing method for grid containing wind power plant | |
| CN114186398A (en) | Optimal frequency selection method for offshore wind power low-frequency sending-out system | |
| CN103715686B (en) | A kind of energy efficiency analysis method for air being applicable to DC distribution netting twine road | |
| CN107134785B (en) | Power transmission network voltage coordination optimization control method considering network structure optimization | |
| CN102403716A (en) | Dynamic equalizing method for multi-infeed alternating/direct-current power grid | |
| CN104281736A (en) | Power supply cable type selecting method for urban track traffic traction power supply and distribution system | |
| CN103078329B (en) | Output reactive compensation analysis method for long-distance 200kV submarine cable of offshore wind plant | |
| CN108879769A (en) | A kind of offshore grid-connected wind farm and the joint planing method of onshore power grid enlarging | |
| CN112838597B (en) | Reactive compensation configuration method for offshore wind farm delivery system | |
| CN112886641B (en) | Submarine cable power transmission system analysis model and reactive power configuration method | |
| CN106972518B (en) | Access mode selection method for direct-current (DC) delivery system of small local power grid and energy base | |
| WO2024093152A1 (en) | Distributed voltage clamping method for 100%-new-energy sending-end power grid | |
| Fu et al. | Application Prospects of Flexible Low-Frequency AC Transmission in Offshore Wind Power Integration | |
| CN114172160A (en) | Reactive compensation configuration method and system for wind power plant access system | |
| Yao et al. | Research on reactive power optimization of Long Distance Ultra-high Voltage Cable Connected to Municipal Power Grid | |
| CN104462821B (en) | Method for quickly calculating maximum length of collecting lines of wind farm | |
| CN113054655B (en) | Receiving-end power grid strength evaluation method for high-proportion direct current high-proportion new energy | |
| Li et al. | On damping coupling of SSO/SupSO modes and oscillation suppression strategy for large scale renewable source generation connected power grids | |
| CN114996921A (en) | Method for designing parameters of main loop of frequency conversion station of offshore wind power low-frequency delivery system | |
| CN114819204A (en) | Investment evaluation method for offshore wind power low-frequency sending-out system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant |