CN102931674A - Multi-terminal modular multilevel direct-current (DC) power transmission system and grounding electrode determination method thereof - Google Patents
Multi-terminal modular multilevel direct-current (DC) power transmission system and grounding electrode determination method thereof Download PDFInfo
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Abstract
The invention discloses a multi-terminal modular multilevel direct-current (DC) power transmission system. The multi-terminal modular multilevel DC power transmission system comprises m converter stations, wherein n of the m converter stations are provided with grounding electrodes and n is smaller than m. The invention further discloses a grounding electrode determination method of the system, wherein the method comprises the following steps of: (1) determining all grounding electrode mounting schemes for the system; (2) applying faults and acquiring the voltage of key points; (3) carrying out overvoltage standard judgment on all the schemes for the system; and (4) determining the optimal mounting scheme through screening. According to the multi-terminal modular multilevel DC power transmission system and the grounding electrode determination method, the construction and maintenance costs related to grounding are directly reduced on the premise that the reliability of the system is guaranteed through reducing the number of the grounding electrodes of the system, the floor area of the converter stations and reactive power compensation equipment which is possibly required for being mounted, thus the economic benefit of the system can be remarkably increased.
Description
Technical field
The invention belongs to electric power system technology of transmission of electricity field, be specifically related to a kind of multiterminal modular multilevel DC transmission system and earth electrode thereof and determine method.
Background technology
Modular multilevel DC transmission system (Modular Multilevel Converter-HVDC, MMC-HVDC) adopt controlled turn-off type power electronic device, compare with the traditional DC transmission system based on thyristor, have flexibly, economy, environmental protection, efficient characteristics, at new-energy grid-connecteds such as photovoltaic, wind-powered electricity generation and morning and evening tides, the power transmission and distribution of ultra-large city, remote island, island load and passive network send the occasion such as electricity than traditional DC transmission system stronger competitiveness to be arranged, and have become the main flow trend of DC transmission system development.The HVDC (High Voltage Direct Current) transmission system that contains two above modular multilevel current conversion stations that multiterminal modular multilevel DC transmission system (Multi-Terminal MMC-HVDC, MMC-MTDC) refers to connects each other by DC line between these current conversion stations.With respect to ac transmission or traditional direct current transportation, MMC-MTDC is more flexible, economic benefits are higher.Can predict, MMC-MTDC will have broad application prospects in the distributed new field such as be incorporated into the power networks.
Yet installation, the design aspect of present MMC-MTDC earthing mode still have the following disadvantages and treat improvements:
With regard to earth electrode installation aspect, in existing MMC-MTDC, must adopt special-purpose earthing device ground connection in each Converter Station.Install the Special grounding device in each Converter Station, can directly increase current conversion station floor space and its corresponding construction, maintenance cost, and then reduced the economic benefit of multiterminal flexible direct current system.
With regard to the earth electrode design aspect, prior art mainly contains two kinds, a kind of is the technology that reference potential is provided for current conversion station at the reactance arm of MMC valve side installation three-phase Y-connection, this technology reactance parameter is selected comparatively difficulty, and greatly affected the reactive power operation scope of converter own, even needed to consider to install the normal operation that additional reactive-load compensation equipment is guaranteed system; Another is the large resistance clamp of DC side earthing mode, but it is closely related that this earthing mode and resistance parameter are chosen, to obtain too small then steady operation loss larger when resistance, and to obtain excessive then whole system approximate earth-free when resistance, system insulation cooperated have relatively high expectations.
Summary of the invention
For the existing above-mentioned technological deficiency of prior art, the invention provides a kind of multiterminal modular multilevel DC transmission system and earth electrode thereof and determine method, under the prerequisite that guarantees system reliability, reduce the earth electrode number of system, reduced design, installation difficulty and the construction cost of system.
A kind of multiterminal modular multilevel DC transmission system comprises: m current conversion station that is connected with AC network, and m current conversion station accesses in the same direct current transportation rack; Have n current conversion station that earth electrode is installed in m the current conversion station, m and n are the natural number greater than 0, and n＜m.
Described current conversion station includes converter, and the three-phase alternating current end of described converter is connected with AC network by converter transformer, and the positive and negative dc terminal of described converter is respectively by two smoothing reactor access direct current transportation racks.
Described earth electrode is installed on DC side or the AC of converter:
If described earth electrode is installed on the DC side of converter, then it is comprised of two partial pressure devices, is connected between the positive and negative dc terminal of converter after two partial pressure device series connection and series connection contact ground connection, and described partial pressure device is electric capacity or resistance;
If described earth electrode is installed on the AC of converter, then it is comprised of three reactance and a resistance, and an end of three reactance is connected with the three-phase alternating current end of converter respectively, and the other end of three reactance all links to each other with an end of resistance, the other end ground connection of resistance.
Preferably, adopt the current conversion station of constant DC voltage control strategy and the current conversion station of employing reserve constant DC voltage control strategy that earth electrode is installed.For the current conversion station that adopts these two kinds of control strategies, control signal need to be adjusted according to voltage swing, if at these current conversion stations earth electrode is not installed, its voltage swing can only have the current conversion station of earth electrode to determine through DC power transmission line by other so.Consider the non-ideal characteristic of DC line, must make the voltage signal that records inaccurate, particularly the impact under failure condition is more obvious, causes the voltage of these current conversion stations that do not have earth electrode excessive, even can have influence on other current conversion station.
The earth electrode of above-mentioned DC transmission system is determined method, comprises the steps:
(1) determines the various earth electrode mount schemes of DC transmission system;
(2) arbitrary current conversion station applies all kinds of faults in the system to arbitrary mount scheme, travels through according to this each mount scheme of each current conversion station, and then gathers each current conversion station each key point voltage under each fault state in the system of each mount scheme;
(3) according to described key point voltage, the system of each mount scheme is carried out the overvoltage standard judge, keep the mount scheme that meets the overvoltage standard;
(4) adopt the key point voltage comparison method that the mount scheme that remains is screened, to determine optimum mount scheme.
In the described step (1), determine that the process of the various earth electrode mount schemes of DC transmission system is as follows:
(a) n in the DC transmission system current conversion station installed earth electrode;
(b) make DC transmission system determine this n current conversion station with various combinations, obtain multiple mount scheme;
(c) according to step (a) and (b), making successively n is arbitrary natural number of 1 to m-1, and traversal obtains all mount schemes.
In the described step (3), the system of each mount scheme is carried out the method that the overvoltage standard judges is: for the system of arbitrary mount scheme, judge whether each current conversion station each key point voltage under each fault state all satisfies following relational expression in this system, if all satisfy, then keep this mount scheme;
Wherein,
For the k key point voltage of i current conversion station in the system of a certain mount scheme maximum under all kinds of failure conditions occurs at the j current conversion station,
For whole current conversion stations the k key point voltage of i current conversion station in the system of earth electrode is installed all and maximum under all kinds of failure conditions, U is occurred at the j current conversion station
i(k) be the fiducial value of the k key point voltage of i current conversion station in the system; I and j are natural number and 1≤i≤m, and 1≤j≤m, k are the sequence number of current conversion station key point voltage.
In the described step (4), adopt the key point voltage comparison method as follows to the process that the mount scheme that remains screens:
At first, for the system that remains and have each mount scheme of same number ground connection current conversion station, adopt the mechanism of eliminating one to one that these systems are carried out the key point overvoltage relatively, more excellent system enters next round relatively, more bad system eliminates, until remaining last system, and make mount scheme corresponding to this system as the best mount scheme in all mount schemes with this ground connection current conversion station number;
Then, for the system that remains and have each best mount scheme of different number ground connection current conversion stations, adopt the mechanism of eliminating one to one that these systems are carried out the key point overvoltage relatively, more excellent system enters next round relatively, more bad system eliminates, until remaining last system, and make mount scheme corresponding to this system be the optimum mount scheme in all mount schemes.
Adopt the mechanism of eliminating one to one as follows to the method that the system that remains carries out the comparison of key point overvoltage:
At first, determine each key point maximum voltage value in each system: for any key point voltage in arbitrary system, add up all values of each current conversion station this key point voltage under each fault state in this system, getting wherein, maximum is corresponding key point maximum voltage value;
Then, make two systems to be compared respectively with frame of reference each key point maximum voltage value relatively, described frame of reference is the system that whole current conversion stations are all installed earth electrode;
If two systems to be compared have same number ground connection current conversion station, the system A that sets up departments has x key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference, and system B has y key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference; If x 〉=y, then the A of system is more excellent, and system B is more bad; Otherwise system B is more excellent, and system A is more bad;
If two systems to be compared have different number ground connection current conversion stations, the system A that sets up departments has x key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference, and system B has y key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference; If x/a 〉=y/b, then the A of system is more excellent, and system B is more bad; Otherwise system B is more excellent, and system A is more bad, and a and b are respectively the ground connection current conversion station number that the A of system and the B of system have.
If the absolute value of the difference of the key point maximum voltage value (perunit value) of two correspondences within 0.02, is then assert the key point maximum voltage value of two correspondences and is equated.
The fault that applies to current conversion station comprises Four types and is respectively: the contact ground connection of arbitrary end ground connection of converter three-phase alternating current end, arbitrary bridgc arm short of converter, arbitrary end ground connection of the positive and negative dc terminal of converter, arbitrary smoothing reactor and direct current transportation rack.
System each fault state occurs and comprises all kinds of faults that systematic each current conversion station occurs, and such as system m current conversion station is arranged, and fault has Four types, and just there is 4m kind fault state in this system.
Described current conversion station has the main points point voltage and is respectively the change of current and becomes at the bottom of net side maximum voltage, converter transformer valve side maximum voltage, the valve over the ground maximum voltage, valve and push up over the ground that maximum voltage, direct current export over the ground maximum voltage and brachium pontis maximum voltage.
The change of current becomes net side maximum voltage and is the peak-peak of converter transformer net side three end voltage to earths; The converter transformer valve side maximum voltage is the peak-peak of converter transformer valve-side three end voltage to earths; At the bottom of the valve over the ground maximum voltage be six brachium pontis of converter respectively with the peak-peak of corresponding brachium pontis reactance tie point voltage to earth; Valve pushes up over the ground, and maximum voltage is the peak-peak of the positive and negative dc terminal voltage to earth of converter; Direct current exports over the ground, and maximum voltage is the peak-peak of two smoothing reactors and direct current transportation rack tie point voltage to earth; The brachium pontis maximum voltage is the peak-peak of six brachium pontis both end voltage of converter.
The value principle of the reference voltage value of described each key point voltage of current conversion station is: become voltage on line side for the change of current, the current conversion station change of current became net top-cross Flow Line phase voltage peak value when its fiducial value was taken as system stable operation; For voltage to earth at the bottom of converter transformer valve side voltage and the valve, current conversion station converter transformer valve side alternating current circuit phase voltage peak value when its fiducial value is taken as system stable operation; For valve top voltage to earth, direct current outlet voltage to earth and bridge arm voltage, its fiducial value is taken as the direct current system rated direct voltage.
Useful technique effect of the present invention:
(1) for the design of earth electrode, installation, the present invention can significantly reduce the earth electrode number of MMC-MTDC, and the reactive-load compensation equipment that reduces the floor space of current conversion station and may need to install increases flexibility and the adaptability of MMC-MTDC engineering.
(2) for the economy of MMC-MTDC, the present invention can directly be reduced in construction and the maintenance cost of ground connection aspect, thereby can significantly improve the economic benefit of MMC-MTDC by reducing the number of current conversion station Special grounding device.
Description of drawings
Fig. 1 is the structural representation of DC transmission system of the present invention.
Fig. 2 is the structural representation that the current conversion station of earth electrode is installed.
Fig. 3 is equipped with each key point voltage of current conversion station of earth electrode and the schematic diagram of each fault type.
Fig. 4 is the waveform schematic diagram of the lower current conversion station A ac-side current of the normal operation of system.
Fig. 5 is the waveform schematic diagram of the lower current conversion station A AC voltage of the normal operation of system.
Fig. 6 is the waveform schematic diagram of the lower current conversion station A DC side current/voltage of the normal operation of system.
Fig. 7 is the waveform schematic diagram of the lower current conversion station B ac-side current of the normal operation of system.
Fig. 8 is the waveform schematic diagram of the lower current conversion station B AC voltage of the normal operation of system.
Fig. 9 is the waveform schematic diagram of the lower current conversion station B DC side current/voltage of the normal operation of system.
Embodiment
In order more specifically to describe the present invention, below in conjunction with the drawings and the specific embodiments technical scheme of the present invention is elaborated.
As shown in Figure 1, a kind of five terminal modular multilevel DC transmission system comprises: 5 current conversion stations that are connected with AC network, and 5 current conversion stations access in the same direct current transportation rack; There is n current conversion station earth electrode to be installed, n＜5 in 5 current conversion stations.Wherein, the capacity of current conversion station A is 400MVA, adopts the constant DC voltage control strategy; The capacity of current conversion station B is 300MVA, adopts reserve constant DC voltage control+surely meritorious idle control strategy; The capacity of current conversion station C～E is 100MVA, adopts surely meritorious idle control strategy.The modulator approach that cascade submodule modulation strategy adopts nearest level to approach.The IGBT trigger impulse can block behind the assumed fault 5ms, AC circuit breaker tripping operation behind the 100ms (5 cycles).
Fig. 2 and the current conversion station that earth electrode is installed shown in Figure 3, current conversion station includes converter, converter adopts MMC (Modular Multilevel Converter, modularization multi-level converter), the three-phase alternating current end of MMC is connected with AC network by converter transformer, and the positive and negative dc terminal of MMC is respectively by two smoothing reactor access direct current transportation racks.MMC is three-phase six bridge arm structures; Wherein, each brachium pontis is composed in series by several change of current modules, and each brachium pontis all connects by the reactance phase port corresponding with converter transformer, and change of current module adopts HBSM.
Earth electrode is installed on the AC of MMC, and then it is comprised of three reactance and a resistance, and an end of three reactance is connected with the three-phase alternating current end of MMC respectively, and the other end of three reactance all links to each other with an end of resistance, the other end ground connection of resistance.
Adopt following methods to determine the earth electrode of above-mentioned five terminal MMC-MTDC:
(1) determines the various earth electrode mount schemes of system.
For five terminal MMC-MTDC, the below is divided into 4 class situations and narrates this implementer's method.The capacity of noticing current conversion station C～E is identical, and the control strategy of employing is identical, so their status almost is equal to, so can simplify the analysis content of problem, only needs to consider that the most representative scheme of following part gets final product.
Situation 1: five terminal MMC-MTDC only has 1 current conversion station ground connection, needs to consider 3 kinds of schemes: (1) only has current conversion station A ground connection; (2) only has current conversion station B ground connection; (3) only has current conversion station C ground connection.
Situation 2: five terminal MMC-MTDC has 2 current conversion station ground connection, needs to consider 4 kinds of schemes: (1) only has current conversion station A+ current conversion station B ground connection; (2) only has current conversion station A+ current conversion station C ground connection; (3) only has current conversion station B+ current conversion station C ground connection; (4) only has current conversion station D+ current conversion station E ground connection.
Situation 3: five terminal MMC-MTDC has 2 current conversion stations earth-free, needs to consider 4 kinds of schemes: B is earth-free for (1) current conversion station A+ current conversion station; (2) current conversion station A+ current conversion station C is earth-free; (3) current conversion station B+ current conversion station C is earth-free.
Situation 4: five terminal MMC-MTDC has 1 current conversion station earth-free, needs to consider 3 kinds of schemes: (1) current conversion station A is earth-free; (2) current conversion station B is earth-free; (3) current conversion station C is earth-free.
(2) apply fault and gather key point voltage.
Arbitrary current conversion station applies all kinds of faults in the system to arbitrary mount scheme, travels through according to this each mount scheme of each current conversion station, and then gathers each current conversion station each key point voltage under each fault state in the system of each mount scheme;
As shown in Figure 3, the fault that applies to current conversion station comprises Four types and is respectively: the contact D ground connection of arbitrary end A ground connection of converter three-phase alternating current end, arbitrary brachium pontis B short circuit of converter, arbitrary end ground connection of the positive and negative dc terminal C of converter, arbitrary smoothing reactor and direct current transportation rack;
Current conversion station has the main points point voltage and is respectively the change of current and becomes at the bottom of net side maximum voltage 1, converter transformer valve side maximum voltage 2, the valve over the ground maximum voltage 3, valve and push up over the ground that maximum voltage 4, direct current export over the ground maximum voltage 5 and brachium pontis maximum voltage 6.
The change of current becomes net side maximum voltage 1 peak-peak into converter transformer net side three end voltage to earths; Converter transformer valve side maximum voltage 2 is the peak-peak of converter transformer valve-side three end voltage to earths; At the bottom of the valve over the ground maximum voltage 3 be six brachium pontis of MMC respectively with the peak-peak of corresponding reactance contact voltage to earth; Valve pushes up over the ground, and maximum voltage 4 is the peak-peak of the positive and negative dc terminal voltage to earth of MMC; Direct current exports over the ground, and maximum voltage 5 is the peak-peak of two smoothing reactors and direct current transportation rack contact voltage to earth; Brachium pontis maximum voltage 6 is the peak-peak of six brachium pontis both end voltage of MMC.
The fiducial value of main points point voltage is as shown in table 1, should be noted that for current conversion station A and B, and the voltage reference value of key point 1 is 179.63kV; For current conversion station C～E, the voltage reference value of key point 1 is 89.81kV.
Table 1
(3) each scheme system being carried out the overvoltage standard judges.
According to key point voltage, the system of each mount scheme is carried out the overvoltage standard judge, keep the mount scheme that meets the overvoltage standard;
For the system of arbitrary mount scheme, judge whether each current conversion station each key point voltage under each fault state all satisfies following relational expression in this system, if all satisfy, then keep this mount scheme;
Wherein,
For the k key point voltage of i current conversion station in the system of a certain mount scheme maximum under all kinds of failure conditions occurs at the j current conversion station,
For whole current conversion stations the k key point voltage of i current conversion station in the system of earth electrode is installed all and maximum under all kinds of failure conditions, U is occurred at the j current conversion station
i(k) be the fiducial value of the k key point voltage of i current conversion station in the system.
In situation 1, only has the scheme of current conversion station A ground connection as example; The overvoltage result of calculation of system is as shown in table 2 during five the equal ground connection of current conversion station:
Table 2
Only have the overvoltage result of calculation of current conversion station A grounding scheme system as shown in table 3:
Table 3
According to standard of comparison, when current conversion station A broke down, the overvoltage level of key point 4 did not satisfy the overvoltage judgment criteria among the current conversion station B, so need to get rid of this scheme.
By similar comparison procedure, find that the scheme that satisfies the overvoltage judgment criteria has 4 kinds to be:
Situation 1: current conversion station B ground connection
Situation 2: current conversion station A ground connection+current conversion station B ground connection, current conversion station B ground connection+current conversion station C ground connection
Situation 3: current conversion station A ground connection+current conversion station C is earth-free
Situation 4: C is earth-free for the earth-free d. current conversion station of current conversion station A
(4) determine optimum mount scheme by screening.
For the system that remains and have each mount scheme of same number ground connection current conversion station, adopt the mechanism of eliminating one to one that these systems are carried out the key point overvoltage relatively, more excellent system enters next round relatively, more bad system eliminates, until remaining last system, and make mount scheme corresponding to this system as the best mount scheme in all mount schemes with this ground connection current conversion station number;
Key point overvoltage method relatively is as follows:
At first, determine each key point maximum voltage value in each system: for any key point voltage in arbitrary system, add up all values of each current conversion station this key point voltage under each fault state in this system, getting wherein, maximum is corresponding key point maximum voltage value;
Then, make two systems to be compared respectively with frame of reference each key point maximum voltage value relatively, frame of reference is the system that whole current conversion stations are all installed earth electrode; The system A that sets up departments has x key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference, and system B has y key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference; If x 〉=y, then the A of system is more excellent, and system B is more bad; Otherwise system B is more excellent, and system A is more bad.Wherein, if within 0.02, then assert the key point maximum voltage value of two correspondences, the absolute value of the difference of the key point maximum voltage value (perunit value) of two correspondences equates.
Two schemes relatively describes as example in the situation 2.Above-mentioned two schemes add all current conversion stations all in the scheme of ground connection overvoltage level as shown in table 4:
Table 4
According to standard of comparison, the scheme in the situation 2 (current conversion station A ground connection+current conversion station B ground connection) is better than scheme (current conversion station B ground connection+current conversion station C ground connection).
For the system that remains and have each best mount scheme of different number ground connection current conversion stations, adopt the mechanism of eliminating one to one that these systems are carried out the key point overvoltage relatively, more excellent system enters next round relatively, more bad system eliminates, until remaining last system, and make mount scheme corresponding to this system be the optimum mount scheme in all mount schemes.
In the key point overvoltage comparison procedure, two systems to be compared have different number ground connection current conversion stations, make these two systems respectively with frame of reference each key point maximum voltage value relatively; The system A that sets up departments has x key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference, and system B has y key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference; If x/a 〉=y/b, then the A of system is more excellent, and system B is more bad; Otherwise system B is more excellent, and system A is more bad, and a and b are respectively the ground connection current conversion station number that the A of system and the B of system have.
According to standard of comparison, can determine that finally the scheme (current conversion station A+ current conversion station B ground connection) in the situation 2 is the optimal case in all schemes that remain; This scheme can on the basis that guarantees the not obvious variation of current conversion station key point overvoltage level, obviously reduce current conversion station earth electrode number.
Adopt similar method for other schemes, can determine that finally the scheme a (current conversion station A+ current conversion station B ground connection) in the situation 2 is the optimal case in the possible scheme of institute.This scheme can on the basis that guarantees the not obvious variation of current conversion station key point overvoltage level, obviously reduce current conversion station earth electrode number.
We have carried out wave simulation to this scheme system, Fig. 4～9 expression be current conversion station A and current conversion station B combined-voltage, current waveform behind system stable operation under this One Common Earthing Electrode scheme of employing; The visible system current/voltage is stable and reliable for performance, and this scheme is truly feasible.
Claims (8)
1. a multiterminal modular multilevel DC transmission system comprises m current conversion station that is connected with AC network, and m current conversion station accesses in the same direct current transportation rack; It is characterized in that: have n current conversion station that earth electrode is installed in m the current conversion station, m and n are the natural number greater than 0, and n＜m.
2. multiterminal modular multilevel DC transmission system according to claim 1, it is characterized in that: described earth electrode is installed on DC side or the AC of converter;
If described earth electrode is installed on the DC side of converter, then it is comprised of two partial pressure devices, is connected between the positive and negative dc terminal of converter after two partial pressure device series connection and series connection contact ground connection, and described partial pressure device is electric capacity or resistance;
If described earth electrode is installed on the AC of converter, then it is comprised of three reactance and a resistance, and an end of three reactance is connected with the three-phase alternating current end of converter respectively, and the other end of three reactance all links to each other with an end of resistance, the other end ground connection of resistance.
3. multiterminal modular multilevel DC transmission system according to claim 1 is characterized in that: adopt the current conversion station of constant DC voltage control strategy and adopt the current conversion station of reserve constant DC voltage control strategy that earth electrode is installed.
4. the earth electrode of a DC transmission system as claimed in claim 1 is determined method, comprises the steps:
(1) determines the various earth electrode mount schemes of DC transmission system;
(2) arbitrary current conversion station applies all kinds of faults in the system to arbitrary mount scheme, travels through according to this each mount scheme of each current conversion station, and then gathers each current conversion station each key point voltage under each fault state in the system of each mount scheme;
(3) according to described key point voltage, the system of each mount scheme is carried out the overvoltage standard judge, keep the mount scheme that meets the overvoltage standard;
(4) adopt the key point voltage comparison method that the mount scheme that remains is screened, to determine optimum mount scheme.
5. earth electrode according to claim 4 is determined method, it is characterized in that: in the described step (1), determine that the process of the various earth electrode mount schemes of DC transmission system is as follows:
(a) n in the DC transmission system current conversion station installed earth electrode;
(b) make DC transmission system determine this n current conversion station with various combinations, obtain multiple mount scheme;
(c) according to step (a) and (b), making successively n is arbitrary natural number of 1 to m-1, and traversal obtains all mount schemes.
6. earth electrode according to claim 4 is determined method, it is characterized in that: in the described step (3), the system of each mount scheme is carried out the method that the overvoltage standard judges is: for the system of arbitrary mount scheme, judge whether each current conversion station each key point voltage under each fault state all satisfies following relational expression in this system, if all satisfy, then keep this mount scheme;
Wherein,
For the k key point voltage of i current conversion station in the system of a certain mount scheme maximum under all kinds of failure conditions occurs at the j current conversion station,
For whole current conversion stations the k key point voltage of i current conversion station in the system of earth electrode is installed all and maximum under all kinds of failure conditions, U is occurred at the j current conversion station
i(k) be the fiducial value of the k key point voltage of i current conversion station in the system.
7. earth electrode according to claim 4 is determined method, it is characterized in that: in the described step (4), adopt the key point voltage comparison method as follows to the process that the mount scheme that remains screens:
At first, for the system that remains and have each mount scheme of same number ground connection current conversion station, adopt the mechanism of eliminating one to one that these systems are carried out the key point overvoltage relatively, more excellent system enters next round relatively, more bad system eliminates, until remaining last system, and make mount scheme corresponding to this system as the best mount scheme in all mount schemes with this ground connection current conversion station number;
Then, for the system that remains and have each best mount scheme of different number ground connection current conversion stations, adopt the mechanism of eliminating one to one that these systems are carried out the key point overvoltage relatively, more excellent system enters next round relatively, more bad system eliminates, until remaining last system, and make mount scheme corresponding to this system be the optimum mount scheme in all mount schemes.
8. earth electrode according to claim 4 is determined method, it is characterized in that: adopt the mechanism of eliminating one to one as follows to the method that the system that remains carries out the comparison of key point overvoltage:
At first, determine each key point maximum voltage value in each system: for any key point voltage in arbitrary system, add up all values of each current conversion station this key point voltage under each fault state in this system, getting wherein, maximum is corresponding key point maximum voltage value;
Then, make two systems to be compared respectively with frame of reference each key point maximum voltage value relatively, described frame of reference is the system that whole current conversion stations are all installed earth electrode;
If two systems to be compared have same number ground connection current conversion station, the system A that sets up departments has x key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference, and system B has y key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference; If x 〉=y, then the A of system is more excellent, and system B is more bad; Otherwise system B is more excellent, and system A is more bad;
If two systems to be compared have different number ground connection current conversion stations, the system A that sets up departments has x key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference, and system B has y key point maximum voltage value less than key point maximum voltage value corresponding to frame of reference; If x/a 〉=y/b, then the A of system is more excellent, and system B is more bad; Otherwise system B is more excellent, and system A is more bad, and a and b are respectively the ground connection current conversion station number that the A of system and the B of system have.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201210424514.0A CN102931674B (en) | 2012-10-30 | 2012-10-30 | Multi-terminal modular multilevel direct-current (DC) power transmission system and grounding electrode determination method thereof |
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| CN201210424514.0A CN102931674B (en) | 2012-10-30 | 2012-10-30 | Multi-terminal modular multilevel direct-current (DC) power transmission system and grounding electrode determination method thereof |
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| CN102931674A true CN102931674A (en) | 2013-02-13 |
| CN102931674B CN102931674B (en) | 2014-08-13 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103825267A (en) * | 2014-03-07 | 2014-05-28 | 浙江大学 | Calculating method for short-circuit current on direct current side of MMC-MTDC (modular multi-level converter-based multi-terminal direct-current transmission system) |
| CN107508309A (en) * | 2017-09-29 | 2017-12-22 | 南方电网科学研究院有限责任公司 | Earthing or grounding means and DC transmission system in a kind of current conversion station |
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| CN102474101A (en) * | 2009-07-17 | 2012-05-23 | 西门子公司 | Device for inverting an electric parameter, having a star point reactor |
| CN102611096A (en) * | 2012-03-13 | 2012-07-25 | 浙江大学 | Bipolar direct current power transmission system with direct current failure self-elimination capacity |
| US20120268099A1 (en) * | 2011-04-25 | 2012-10-25 | General Electric Company | Hvdc power transmission with cable fault ride-through capability |
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| CN102474101A (en) * | 2009-07-17 | 2012-05-23 | 西门子公司 | Device for inverting an electric parameter, having a star point reactor |
| US20120268099A1 (en) * | 2011-04-25 | 2012-10-25 | General Electric Company | Hvdc power transmission with cable fault ride-through capability |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103825267A (en) * | 2014-03-07 | 2014-05-28 | 浙江大学 | Calculating method for short-circuit current on direct current side of MMC-MTDC (modular multi-level converter-based multi-terminal direct-current transmission system) |
| CN103825267B (en) * | 2014-03-07 | 2015-08-26 | 浙江大学 | A kind of computational methods of MMC-MTDC dc-side short-circuit electric current |
| CN107508309A (en) * | 2017-09-29 | 2017-12-22 | 南方电网科学研究院有限责任公司 | Earthing or grounding means and DC transmission system in a kind of current conversion station |
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| CN102931674B (en) | 2014-08-13 |
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