CN114971063A - Frequency selection method for multi-terminal low-frequency interconnection system of urban supply area - Google Patents
Frequency selection method for multi-terminal low-frequency interconnection system of urban supply area Download PDFInfo
- Publication number
- CN114971063A CN114971063A CN202210666563.9A CN202210666563A CN114971063A CN 114971063 A CN114971063 A CN 114971063A CN 202210666563 A CN202210666563 A CN 202210666563A CN 114971063 A CN114971063 A CN 114971063A
- Authority
- CN
- China
- Prior art keywords
- line
- frequency
- power
- partition
- current
- 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.)
- Pending
Links
- 238000010187 selection method Methods 0.000 title claims abstract description 19
- 230000005540 biological transmission Effects 0.000 claims abstract description 56
- 238000000034 method Methods 0.000 claims abstract description 11
- 238000004364 calculation method Methods 0.000 claims abstract description 8
- 238000005192 partition Methods 0.000 claims description 38
- 238000006243 chemical reaction Methods 0.000 claims description 12
- 230000008569 process Effects 0.000 claims description 7
- 238000012216 screening Methods 0.000 claims description 7
- 230000000717 retained effect Effects 0.000 claims description 2
- 238000011217 control strategy Methods 0.000 description 5
- 238000009826 distribution Methods 0.000 description 5
- 238000011160 research Methods 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000009412 basement excavation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007781 pre-processing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- G06Q10/00—Administration; Management
- G06Q10/04—Forecasting or optimisation specially adapted for administrative or management purposes, e.g. linear programming or "cutting stock problem"
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- G06Q10/00—Administration; Management
- G06Q10/06—Resources, workflows, human or project management; Enterprise or organisation planning; Enterprise or organisation modelling
- G06Q10/063—Operations research, analysis or management
- G06Q10/0631—Resource planning, allocation, distributing or scheduling for enterprises or organisations
- G06Q10/06311—Scheduling, planning or task assignment for a person or group
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- G06Q50/00—Information and communication technology [ICT] specially adapted for implementation of business processes of specific business sectors, e.g. utilities or tourism
- G06Q50/06—Energy or water supply
Landscapes
- Business, Economics & Management (AREA)
- Human Resources & Organizations (AREA)
- Engineering & Computer Science (AREA)
- Economics (AREA)
- Strategic Management (AREA)
- Tourism & Hospitality (AREA)
- Theoretical Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Entrepreneurship & Innovation (AREA)
- General Business, Economics & Management (AREA)
- Marketing (AREA)
- Physics & Mathematics (AREA)
- Operations Research (AREA)
- Quality & Reliability (AREA)
- Game Theory and Decision Science (AREA)
- Development Economics (AREA)
- Health & Medical Sciences (AREA)
- Educational Administration (AREA)
- Public Health (AREA)
- Water Supply & Treatment (AREA)
- General Health & Medical Sciences (AREA)
- Primary Health Care (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
The invention discloses a frequency selection method of an urban supply area multi-terminal low-frequency interconnection system, which is used for determining the upper limit of the transmission frequency of a reserved tie line by calculating the maximum value of the current along the tie line of the reserved tie line under different frequencies based on the given information of power supply margin, transmission distance, line return number and the like in a power grid planning stage aiming at the urban supply area multi-terminal interconnection scene, and selecting the upper limit of the transmission frequency of the whole system according to the maximum value. The method is suitable for the multi-terminal interconnection scene with any supply area number, has strong expansibility, simple implementation, quick calculation and high efficiency, and has important significance for practical engineering application.
Description
Technical Field
The invention belongs to the technical field of power transmission and distribution of power systems, and particularly relates to a frequency selection method of a multi-terminal low-frequency interconnection system of an urban power supply area.
Background
When planning a power grid, it is very important to evaluate the safety and economic operation of the power distribution network. At present, some urban power grids form a 500kV ring network directly connected with a power transmission network on the outer layer and receive power supply from an external power supply; the inner high-voltage power grid goes deep into the power supply center to form a backbone network frame to provide electric energy for the load center.
On one hand, the scale of the power grid is continuously enlarged, the short-circuit current of the system is increasingly increased, the short-circuit level of some buses in the power grid even exceeds the rated capacity of a breaker, and the operation safety of the system is seriously influenced; on the other hand, with the construction of a 500kV power supply ring network, lines of 500kV and 110kV two groups of power grids with different voltage levels may form an electromagnetic ring network through the connection mode of a transformer magnetic loop, when a superior 500kV power transmission channel is disconnected due to a fault in operation, a large amount of power flow may be transferred to a subordinate 110kV power transmission channel, and the safe and stable operation limit of the system is exceeded. The urban power grid adopts a 110kV voltage level partition operation mode, so that the problem of overlarge short-circuit current of the power grid can be solved, and the accident potential of a 500kV/110kV electromagnetic ring network is prevented; meanwhile, adjacent partitions are mutually standby and can support and coordinate power, so that an application foundation is provided for flexible interconnection of the urban power grid partitions.
When adjacent subareas are connected, which way to transmit electric Energy is one of the technical problems worthy of research, numerous researchers at home and abroad research the application of low-Frequency Power Transmission in the existing System, for example, Uttam S.Satpute et al indicate through simulation analysis in the documents [ Feasibility study of Fractional Frequency Transmission System [ C ]//2010 International Conference Power Electronics, Drives and Energy Systems &2010Power India,2010:1-6], the low-Frequency Power Transmission can improve the Transmission capacity of the line, prove that the low-Frequency Power Transmission can enhance the stability of the System when applied to onshore Power Transmission, upgrade from a Power Frequency AC interconnection System to a low-Frequency AC interconnection System can be completed by adding Frequency conversion stations at two ends of the existing AC cable System, and reduce the difficulty of line transformation and the adverse effect of tunnel excavation on the urban environment. In addition, the influence of the space charge accumulation effect of a direct current power grid can be avoided by adopting a low-frequency alternating current power transmission technology, and the low-frequency alternating current multi-terminal power transmission system is not difficult to construct.
With the development of low-frequency power transmission systems, effective control strategies for low-frequency power transmission technologies are proposed, for example, masculine et al Research the control strategy of an alternating frequency converter and the coordination control strategy of a multi-terminal low-frequency interconnected power grid in the documents [ Research on the control strategy of multi-terminal low-frequency transmission system for isolated power networks [ C ]// 20204 th International Conference on HVDC (HVDC),2020: 616-.
However, it is easy to find that most of the existing technologies focus on the advantages of the system when low-frequency power transmission is adopted and the control strategy for improving the stability of the low-frequency system, and do not focus on the selection method of the low-frequency power transmission frequency of the system in the urban power grid planning stage. In order to further exert the economic advantage of the low-frequency power transmission scheme in the urban supply area multi-terminal low-frequency interconnection scene, a frequency selection method under the urban supply area multi-terminal interconnection topology needs to be researched.
Disclosure of Invention
In view of the above, the present invention provides a frequency selection method for a multi-terminal low-frequency interconnection system in an urban supply area, which is characterized in that the screening of relevant information of a tie line is taken as a key, the transmission frequency upper limit of the reserved tie line is determined by calculating the maximum value of the current along the tie line of the reserved tie line under different frequencies, and the transmission frequency upper limit of the whole system is selected according to the maximum value.
A frequency selection method of a multi-terminal low-frequency interconnection system of an urban supply area comprises the following steps:
(1) establishing a multi-end low-frequency interconnection system of an urban supply area, wherein the system comprises a multi-end inner-layer high-voltage power grid, alternating current cables and frequency conversion stations, the multi-end inner-layer high-voltage power grid is divided into a plurality of subareas, the frequency conversion stations are components of the subareas, and the subareas are connected through connecting lines, namely the alternating current cables, to form an annular topological structure;
(2) constructing an equivalent circuit model of a connecting line in the system;
(3) screening the junctor in the system, and calculating and determining the transmission frequency upper limit value of the junctor by using an equivalent circuit model for the junctor reserved by screening;
(4) and comparing the transmission frequency upper limit values of all the links retained by screening, and taking the maximum value as the optimal operation frequency of the whole system.
Further, the multiple terminals are internally provided withThe subareas of the high-voltage network of the layer are divided into a transmitting terminal subarea and a receiving terminal subarea, the subarea with larger power supply margin under a steady state is taken as the transmitting terminal subarea, the subarea with smaller power supply margin is taken as the receiving terminal subarea, and the maximum power which can be provided by the transmitting terminal subarea on the premise of meeting self safe power supply is taken as the power supply margin P max (ii) a Since there is always a power loss in the interconnection line, the power injected from the transmitting partition into the receiving partition is referred to as the backup power P' max The line loss rate T k ＝(P max -P' max )/P max 。
Further, the equivalent circuit model of the tie line has a pi-type circuit structure including series impedances and parallel admittances at both sides thereof, the sending-end segment of the equivalent circuit model is equivalent to an alternating-current voltage source and is connected in parallel to one of the parallel admittances, the receiving-end segment of the equivalent circuit model is equivalent to a load and is connected in parallel to the other parallel admittance, and the load absorbs active power equal to the support power P' max The absorbed reactive power is equal to 0.
Further, the parameter expression of each equivalent device in the equivalent circuit model is as follows:
wherein: z L Is a series impedance, Y L Is a parallel admittance, gamma is a line propagation coefficient and
Z 1 is the equivalent impedance of the line per unit length, Y 1 Is the equivalent-to-ground admittance of the line per unit length, L is the length of the crosshair, r 1 Is a line resistance per unit length, /) 1 Is the line inductance per unit length, g 1 Is the conductance of the line per unit length, c 1 Is a line capacitance per unit length, f L Line transmission frequency, m, for a tie line k The number of the parallel-connected lines of the connecting line is j, and j is an imaginary number unit.
Further, the specific implementation process of the step (3) is as follows:
3.1, determining the number, transmission distance and circuit parallel connection number of each tie line in the system, and determining the node number and power supply margin of each partition in the system;
3.2 determining a sending terminal partition and a receiving terminal partition corresponding to each connecting line and the support power on the lines according to the power supply margin;
3.3 for the links with the same transmission distance, only one link with the maximum supporting power is reserved, and the rest links do not participate in the subsequent calculation;
3.4 for any remaining junctor, calculating and determining the transmission frequency upper limit value of the junctor.
Further, the specific implementation process of step 3.4 is as follows:
3.4.1 extracting discrete frequency points in a given frequency interval;
3.4.2 calculating the current along the tie line according to the current discrete frequency point and the parallel loop number of the line;
3.4.3 comparing the maximum values of the Current I along the line rmax Cable current-carrying capacity I corresponding to current discrete frequency point ccc ；
If I rmax ＜I ccc Then the next discrete frequency point is determined and the process returns to step 3.4.2;
if I rmax ≥I ccc Then, the current discrete frequency point is used as the upper limit value of the transmission frequency of the tie line.
Further, the discrete frequency point expression extracted in the step 3.4.1 is as follows:
wherein: f. of p For the p-th discrete frequency point extracted, f max And f min Respectively an upper limit and a lower limit for a given frequency interval, N f P is a natural number and is more than or equal to 1 and less than or equal to N for the number of discrete frequency points to be extracted f 。
Further, the specific implementation manner of step 3.4.2 is: first according to the current discrete frequency point and the circuitThe load flow calculation is carried out on the number of the links by utilizing a centralized parameter model to obtain phase voltage U of the receiving end subarea of the tie line 2 Sum phase current I 2 (ii) a Then, a plurality of discrete points are selected at uniform intervals on the connecting line, wherein the distance between the r-th discrete point and the receiving end subarea is l r R is a natural number greater than 0; then, taking the tie line as a passive double-port network, and calculating the current along the tie line according to the following equation;
wherein: u shape r Is the voltage phasor at the r-th discrete point, I r Is the current phasor at the r-th discrete point, gamma is the line propagation coefficient, Z 1 Is the equivalent impedance of the line per unit length, Y 1 Is the equivalent to ground admittance of a unit length line.
Compared with the prior art, the invention has the following beneficial technical effects:
1. for a multi-terminal interconnection scene of an urban supply area, the invention provides a frequency selection method of a multi-terminal low-frequency interconnection system of the urban supply area, which can obtain the upper frequency limit of low-frequency power transmission of the system based on the given information of power supply margin, transmission distance, parallel circuit return number and the like in the power grid planning stage, and has important significance for practical engineering application.
2. The method is suitable for the multi-terminal interconnection scene with any supply area number, and has the advantages of strong expansibility, simple implementation, quick calculation and high efficiency.
Drawings
FIG. 1 is a schematic diagram of a topological structure of a four-terminal low-frequency interconnection system of a city supply area.
Fig. 2 is a schematic diagram of an equivalent circuit model of a tie line.
Fig. 3 is a flow chart illustrating a frequency selection method of the system according to the present invention.
Fig. 4 is a graph of the maximum current along the line on the tie line and the maximum current capacity of the line as a function of 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.
In this embodiment, the topological structure of the city supply area four-terminal low-frequency interconnection system is shown in fig. 1, the four-terminal interconnection system adopts a ring structure, that is, under a four-terminal city supply area interconnection scene, there are four interconnection lines, each interconnection line is given a number k equal to 1, 2, 3,4, each power grid partition node is given a number i equal to 1, 2, 3,4, and the parallel circuit return number of each interconnection line is m k (ii) a The two end partitions of the selected connecting line are divided into a sending end partition and a receiving end partition, the partition with larger power supply margin under a steady state is used as the sending end partition, and the partition with smaller power supply margin is used as the receiving end partition.
The equivalent circuit model of the tie line is shown in fig. 2, the frequency conversion station is divided into a sending end frequency conversion station and a receiving end frequency conversion station, and meanwhile, the frequency conversion station is considered to be a part of a subarea and only plays a role in frequency conversion. Since the transmitter section is considered to be in a stable power supply state when it supports power, the transmitter frequency conversion station and the transmitter section can be equivalently represented by the AC voltage source v s Amplitude of U smax Equal to the rated voltage U of the system N (ii) a The receiving end frequency conversion station and the receiving end subarea are equivalent to a load in an equivalent circuit model, and the active power absorbed by the load is equal to the supporting power P' max Its absorbed reactive power is equal to 0. It is considered herein that the receiving-end partition may be provided with local reactive compensation regulation auxiliary equipment, so that the receiving-end partition externally appears as a pure active power load.
The equivalent circuit model is a pi-type circuit including series impedance Z L And its parallel admittance Y at both ends L The specific calculation expression is as follows:
wherein: z 1 Is the equivalent impedance of the line per unit length, Y 1 Is the equivalent value to ground admittance of a unit length line, gamma denotes the line propagation coefficient and
l is the length of the AC cable, r 1 Is a line resistance per unit length, /) 1 Is the line inductance per unit length, g 1 Is the conductance per unit length of the line, c 1 Is a line capacitance per unit length, f L For the transmission frequency of the line, m k The number of the cables is counted.
As shown in fig. 3, the frequency selection method for the urban supply area multi-terminal low-frequency interconnection system of the embodiment includes the following steps:
step 1: the number k of each link is set to 1, 2, 3,4, and the transmission distance L is set to L k M number of parallel circuit k ＝1。
Step 2: the node number i of each partition is set to 1, 2, 3,4 and the power supply margin.
And step 3: determining a transmitting terminal partition, a receiving terminal partition and support power P 'corresponding to each connecting line according to the size of the power supply margin' max 。
And 4, step 4: the method is characterized in that the preprocessing is carried out on the links with the same transmission distance, only one link with the maximum supporting power is reserved, and the rest links do not participate in subsequent calculation.
And 5: calculating the transmission frequency upper limit value of each reserved connecting line independently, and extracting discrete frequency points in a given interval by adopting the following equation;
wherein: f. of p For the p-th discrete frequency point extracted (1 ≦ p ≦ N) f And p is a positive integer), f max And f min Respectively, an upper limit and a lower limit of the interval, N f Is the number of discrete frequency points within the interval.
Step 6: according to the operating frequency f of the currently selected tie line p And the number m of parallel loops k Calculating the current along the line, and the specific process is as follows:
firstly, according to the running frequency f of the currently selected connecting line p And the number m of parallel loops k Calculating parameters of the lumped parameter model to obtain phase voltage U of the selected tie line receiving end subarea 2 At a phase of sum current I 2 ；
Then, a plurality of discrete points are selected on the alternating current cable, wherein the distance between the r-th discrete point and the receiving end subarea is l r ；
And then, processing the line as a passive dual-port network, and calculating to obtain the transmission parameters of the dual-port network. Calculating the current along the cable according to the following equation;
wherein: u shape r Is the voltage phasor at the r-th discrete point, I r Is the current phasor at the r-th discrete point.
And 7: comparing the maximum values of the currents along the line I rmax (i.e. current phasor I) r Maximum value of) cable current-carrying capacity I corresponding to current discrete frequency point ccc ；
If I rmax ＜I ccc Judging the next discrete frequency point and returning to execute the step 6;
if I rmax ≥I ccc Record the frequency f at this time p And calculating the next junctor according to the set sequence for the upper limit value of the transmission frequency of the selected junctor, and returning to execute the step 5.
After the transmission frequency upper limit values corresponding to all the reserved connecting lines are obtained, the system transmission frequency upper limit f is selected according to the following method s ：
Wherein: k' is the reserved number of the tie line, f k' The upper limit value of the transmission frequency of the k' th connecting line.
Specific parameters of the urban four-terminal low-frequency interconnection system for the supply area are shown in tables 1 and 2, the power supply margin and the transmission distance of each tie line in each partition are shown in table 3, and the sending-terminal partition, the receiving-terminal partition, the support power and the number of discrete distance points of each tie line in the four-terminal interconnection system are shown in table 4.
TABLE 1
TABLE 2
The current carrying capacity and unit length parameters of the tie lines at other frequencies in table 2 were calculated using linear differences.
TABLE 3
| Partition i | Power supply margin/MW | Transmission distance/ |
| 1 | 240 | 50 |
| 2 | 235 | 55 |
| 3 | 150 | 50 |
| 4 | 180 | 50 |
TABLE 4
| Connecting line k | Send end partition numbering | Recipient partition numbering | Supporting power/MW | Distance discrete point r/ |
| 1 | 1 | 2 | 240*0.95 | 50 |
| 2 | 2 | 3 | 235*0.95 | 55 |
| 3 | 4 | 3 | 180*0.95 | 50 |
| 4 | 1 | 4 | 240*0.95 | 50 |
As can be seen from table 3, since the transmission distances of 3 links (k is 1, 3, and 4) are the same, only the link k having the maximum support power is 1, and the link k is 3 and 4 are ignored, so that only the along-line current distributions of the link k is 1 and the link k is 2 are calculated, and k' is 2.
Fig. 4 shows the maximum line current on the tie line and the line current capacity as a function of frequency; it can be seen that the intersection point of the distribution curve of the maximum current of the tie line k ═ 1 and the distribution curve of the limiting value of the current carrying capacity of the line is between 20Hz and 21Hz, and when the delivery frequency is 21Hz, the maximum current of the line exceeds the limit of the current carrying capacity of the line; rounded down, the upper limit of the transmission frequency on the link k-1 can be considered to be 20 Hz. Similarly, the upper limit of the transmission frequency of the tie line k 2 can be obtained to be 28 Hz.
Thus, the four-terminal interconnection system obtains the upper limit values of k ═ 2 transmission frequencies, namely 20Hz and 28 Hz; from the perspective of cable transmission capacity and whole engineering economy, the minimum value is taken for the cables, and finally the upper limit value of the transmission frequency of the four-end interconnection system 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 (8)
1. A frequency selection method of a multi-terminal low-frequency interconnection system of an urban supply area comprises the following steps:
(1) establishing a multi-end low-frequency interconnection system of an urban supply area, wherein the system comprises a multi-end inner-layer high-voltage power grid, alternating current cables and frequency conversion stations, the multi-end inner-layer high-voltage power grid is divided into a plurality of subareas, the frequency conversion stations are components of the subareas, and the subareas are connected through connecting lines, namely the alternating current cables, to form an annular topological structure;
(2) constructing an equivalent circuit model of a connecting line in the system;
(3) screening the junctor in the system, and calculating and determining the transmission frequency upper limit value of the junctor by using an equivalent circuit model for the junctor reserved by screening;
(4) and comparing the upper limit values of the transmission frequencies of all the links retained by screening, and taking the maximum value as the optimal operating frequency of the whole system.
2. The frequency selection method of claim 1, wherein: the partition of the multi-end inner-layer high-voltage power grid is divided into a transmitting end partition and a receiving end partition, the partition with larger power supply margin under a steady state is used as the transmitting end partition, the partition with smaller power supply margin is used as the receiving end partition, and the maximum power which can be provided by the transmitting end partition on the premise of meeting self safe power supply is used as the power supply margin P max (ii) a Since there is always a power loss in the interconnection line, the power injected from the transmitting partition into the receiving partition is referred to as the backup power P' max The line loss rate T k ＝(P max -P' max )/P max 。
3. The frequency selection method of claim 1, wherein: the equivalent circuit model of the connecting line is a pi-shaped circuit structure comprising series impedance and parallel admittances at two sides thereof, a sending end subarea in the equivalent circuit model is equivalent to an alternating current voltage source and is connected in parallel with the parallel admittance at one side, a receiving end subarea is equivalent to a load and is connected in parallel with the parallel admittance at the other side, and the active power absorbed by the load is equal to the supporting power P' max The absorbed reactive power is equal to 0.
4. The frequency selection method of claim 3, wherein: the parameter expression of each equivalent device in the equivalent circuit model is as follows:
wherein: z L Is a series impedance, Y L Is a parallel admittance, gamma is a line propagation coefficient and
Z 1 is the equivalent impedance of the line per unit length, Y 1 Is the equivalent value-to-ground admittance of the line per unit length, L is the length of the tie line, r 1 Is a line resistance per unit length, /) 1 Is the line inductance per unit length, g 1 Is the conductance per unit length of the line, c 1 Is a line capacitance per unit length, f L Line transmission frequency, m, for a tie line k The number of the parallel-connected lines of the connecting line is j, and j is an imaginary number unit.
5. The frequency selection method of claim 1, wherein: the specific implementation process of the step (3) is as follows:
3.1, determining the number, transmission distance and circuit parallel connection number of each tie line in the system, and determining the node number and power supply margin of each partition in the system;
3.2 determining the sending terminal subarea and the receiving terminal subarea corresponding to each tie line and the support power on the line according to the power supply margin;
3.3 for the links with the same transmission distance, only one link with the maximum support power is reserved, and the rest links do not participate in subsequent calculation;
3.4 for any remaining junctor, calculating and determining the transmission frequency upper limit value of the junctor.
6. The frequency selection method of claim 5, wherein: the specific implementation process of the step 3.4 is as follows:
3.4.1 extracting discrete frequency points in a given frequency interval;
3.4.2 calculating the current along the tie line according to the current discrete frequency point and the parallel loop number of the line;
3.4.3 comparing the maximum values of the Current I along the line rmax Cable current-carrying capacity I corresponding to current discrete frequency point ccc ；
If I rmax ＜I ccc Then the next discrete frequency point is determined and the process returns to step 3.4.2;
if I rmax ≥I ccc Then, the current discrete frequency point is used as the upper limit value of the transmission frequency of the tie line.
7. The frequency selection method of claim 6, wherein: the expression of the discrete frequency points extracted in the step 3.4.1 is as follows:
wherein: f. of p For the p-th discrete frequency point extracted, f max And f min Respectively an upper limit and a lower limit for a given frequency interval, N f P is a natural number and is more than or equal to 1 and less than or equal to N for the number of discrete frequency points to be extracted f 。
8. The frequency selection method of claim 6, wherein: the specific implementation manner of the step 3.4.2 is as follows: firstly, load flow calculation is carried out by utilizing a centralized parameter model according to the current discrete frequency point and the parallel loop number of the line, and phase voltage U of a receiving end subarea of a tie line is obtained 2 Sum phase current I 2 (ii) a Then, a plurality of discrete points are selected at uniform intervals on the connecting line, wherein the distance between the r-th discrete point and the receiving end subarea is l r R is a natural number greater than 0; then, taking the tie line as a passive double-port network, and calculating the current along the tie line according to the following equation;
wherein: u shape r Is the voltage phasor at the r-th discrete point, I r Is the current phasor at the r-th discrete point, gamma is the line propagation coefficient, Z 1 Is the equivalent impedance of the line per unit length, Y 1 Is the equivalent to ground admittance of a unit length line.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210666563.9A CN114971063A (en) | 2022-06-13 | 2022-06-13 | Frequency selection method for multi-terminal low-frequency interconnection system of urban supply area |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210666563.9A CN114971063A (en) | 2022-06-13 | 2022-06-13 | Frequency selection method for multi-terminal low-frequency interconnection system of urban supply area |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114971063A true CN114971063A (en) | 2022-08-30 |
Family
ID=82962350
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210666563.9A Pending CN114971063A (en) | 2022-06-13 | 2022-06-13 | Frequency selection method for multi-terminal low-frequency interconnection system of urban supply area |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114971063A (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014173131A1 (en) * | 2013-04-23 | 2014-10-30 | 国家电网公司 | Large power grid overall situation on-line integrated quantitative evaluation method based on response |
| US20190296577A1 (en) * | 2018-03-21 | 2019-09-26 | Battelle Memorial Institute | Control approach for power modulation of end-use loads |
| CN114186398A (en) * | 2021-11-24 | 2022-03-15 | 浙江大学 | Optimal frequency selection method for offshore wind power low-frequency sending-out system |
| CN114301055A (en) * | 2022-02-17 | 2022-04-08 | 河海大学 | Method and system for obtaining inter-harmonic power flow of power system based on broadband measurement |
-
2022
- 2022-06-13 CN CN202210666563.9A patent/CN114971063A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014173131A1 (en) * | 2013-04-23 | 2014-10-30 | 国家电网公司 | Large power grid overall situation on-line integrated quantitative evaluation method based on response |
| US20190296577A1 (en) * | 2018-03-21 | 2019-09-26 | Battelle Memorial Institute | Control approach for power modulation of end-use loads |
| CN114186398A (en) * | 2021-11-24 | 2022-03-15 | 浙江大学 | Optimal frequency selection method for offshore wind power low-frequency sending-out system |
| CN114301055A (en) * | 2022-02-17 | 2022-04-08 | 河海大学 | Method and system for obtaining inter-harmonic power flow of power system based on broadband measurement |
Non-Patent Citations (2)
| Title |
|---|
| K. XU等: "Frequency selection method of multi-terminal interconnected system of urban power grid based on low frequency AC", 《18TH INTERNATIONAL CONFERENCE ON AC AND DC POWER TRANSMISSION (ACDC 2022)》, 29 August 2022 (2022-08-29), pages 1 - 5 * |
| 李姝玉等: "双端口矩阵变换器在工/低频电网互联下的电容及电压波动特性分析", 《电网技术》, vol. 44, no. 4, 4 March 2020 (2020-03-04), pages 1437 - 1444 * |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107134787B (en) | Cutting load control system and cutting load method based on distributed feeder automation | |
| CN110108921B (en) | Flexible direct-current power grid short-circuit current calculation method and system considering converter control | |
| CN107887908B (en) | Transmission network blocking management and control method based on VSC and high-voltage distribution network topology reconstruction | |
| CN108923396B (en) | A kind of short circuit current quick calculation method of multiterminal flexible direct current power grid | |
| CN106374463B (en) | A kind of A+ classes power supply area power distribution network powering mode configuration method | |
| CN109449934B (en) | Transmission network blocking management and control method based on high-voltage distribution network partition reconstruction | |
| CN111952963A (en) | Construction area power distribution network fine planning method | |
| CN114186398A (en) | Optimal frequency selection method for offshore wind power low-frequency sending-out system | |
| CN109377020B (en) | Power transmission network planning method considering load transfer capacity of power distribution network | |
| CN109768543B (en) | Elastic bottom-preserving net rack search modeling method based on mixed integer linear programming | |
| CN109599870A (en) | A kind of interconnection reactance quick calculation method inhibiting short circuit current | |
| CN108832649A (en) | True bipolar flexible DC grid control method for coordinating based on operating point optimization | |
| CN114971063A (en) | Frequency selection method for multi-terminal low-frequency interconnection system of urban supply area | |
| CN114899825B (en) | Comprehensive optimization method for power distribution network based on network equivalent transformation | |
| CN214255738U (en) | Electric automobile fills electric pile topological structure based on optimize distribution network distribution | |
| CN113675872B (en) | Multi-direct-current simultaneous commutation failure coordination recovery ordering method based on sending end stability constraint | |
| CN113270868B (en) | Dynamic load flow calculation method for power supply system of alternating current electrified railway train | |
| CN112039077B (en) | Active frequency adjusting method considering voltage optimization control constraint | |
| CN114172165A (en) | Power distribution network loss reduction method based on SVG (scalable vector graphics) configured in cable-in-place scene | |
| CN112598299A (en) | Load center 750 kV power supply area combined power supply grid structure mode construction method | |
| CN112084626A (en) | Distributed photovoltaic access-based power distribution network reactive compensation configuration capacity calculation method | |
| Xu et al. | Frequency selection method of multi-terminal interconnected system of urban power grid based on low frequency AC | |
| Chávez-Báez et al. | Harmonics and power loss reduction in multi-technology offshore wind farms using simplex method | |
| CN112417629B (en) | 1000/500kV layered partition planning method for multi-DC feed-in block receiving-end power grid | |
| CN110363678B (en) | Power transmission and distribution network coordination planning method considering strength relation |
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 |