CN111327058B - Method and device for setting dead zone of direct current reactive power control based on transient steady-state voltage constraint - Google Patents

Method and device for setting dead zone of direct current reactive power control based on transient steady-state voltage constraint Download PDF

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CN111327058B
CN111327058B CN202010135207.5A CN202010135207A CN111327058B CN 111327058 B CN111327058 B CN 111327058B CN 202010135207 A CN202010135207 A CN 202010135207A CN 111327058 B CN111327058 B CN 111327058B
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direct current
reactive power
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steady
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CN111327058A (en
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摆世彬
郜建良
张红丽
钟海亮
田志浩
刘刚
倪禛霖
刘福锁
吕亚洲
李兆伟
李威
薛峰
张倩
王玉
张承义
杨应昊
王超
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NARI Group Corp
State Grid Ningxia Electric Power Co Ltd
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State Grid Ningxia Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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Abstract

The invention discloses a direct current reactive power control dead zone setting method and device based on transient/steady-state voltage constraint, wherein a converter station bus voltage curve after direct current fault disturbance is simulated, and transient maximum voltage and steady-state voltage under different faults are compared to determine a transient voltage limited fault S1 and a steady-state voltage limited fault S2; respectively simulating the occurrence of direct current faults S1 and S2, and determining the alternating current-direct current reactive power exchange range under the constraint of transient overvoltage and steady overvoltage under the condition of different direct current power transmission gears; and obtaining the minimum direct current reactive power control offset by combining the reactive power supporting capability of the alternating current system and the alternating current-direct current reactive power exchange range under different direct current power transmission gears, thereby determining the direct current reactive power control dead zone under different direct current power transmission gears. The invention ensures that the transient overvoltage and the steady overvoltage of the bus of the converter station can not occur after the direct current fault, and expands the reactive power control dead zone to the maximum extent.

Description

Method and device for setting dead zone of direct current reactive power control based on transient steady-state voltage constraint
Technical Field
The invention relates to the technical field of electric power systems and automation thereof, in particular to a method and a device for setting a direct-current reactive power control dead zone based on transient steady-state voltage constraint.
Background
With the gradual implementation of the energy development strategy of 'West-east power transmission, mutual supply in south and north and national networking', the ultrahigh voltage direct current transmission has the characteristics of good economy, large capacity, long transmission distance and the like, is a necessary choice for the development of power grids in China, and bears the strategic mission of improving the new energy absorption capacity and preventing and controlling the atmospheric pollution. With continuous operation of ultrahigh voltage direct current engineering in China, deep influence and many challenges are brought to power grid system cognition, operation control and fault defense. The direct current system generates high-power disturbance impact, such as locking fault, commutation failure, restarting and the like, which can cause transient overvoltage and steady overvoltage of the direct current convertor station, the convertor station is used as an important power station for realizing the conversion of alternating current and direct current of electric energy, and the reliability of equipment in the convertor station can directly influence the safe and stable operation of the whole direct current system.
The mechanically switched parallel capacitor and the alternating current filter are used as an important component of a DC system in a station, and are mainly used for filtering harmonic waves generated by a converter in the rectifying process and providing reactive compensation for the DC system, so that the size of DC transmission power and the quality of electric energy are directly influenced. Reactive power consumption in the transmitting end converter station accounts for about 50% of corresponding direct current transmission power. Because reactive power consumption in the station increases along with the rise of direct current transmission power, when the direct current transmission power frequently changes due to load randomness or uncontrollable performance of new energy power generation and the like, reactive compensation equipment needs to be frequently switched to control reactive balance of a system, so that a circuit breaker for the reactive compensation equipment is frequently switched to a high-voltage capacitive circuit with a severe operating environment, the service life of the circuit breaker is seriously shortened, and even the safe operation of a direct current system is threatened.
The direct current reactive power control dead zone is used as an important parameter of a direct current system, the size of the direct current reactive power control dead zone not only influences the action condition of direct current reactive power compensation equipment, but also influences the reactive power flow direction and the reactive power flow size of an alternating current-direct current system, the influences of the reactive power flow direction and the reactive power flow size of the alternating current-direct current system on transient voltage and steady voltage after direct current large disturbance impact are different, transient voltage rise caused by direct current after direct current faults is smaller by adopting a maximum under-compensation mode, the transient stability of the system is higher, and steady overvoltage level is lowest in a maximum over-compensation working mode. Therefore, whether the direct current reactive power control dead zone is reasonable or not only influences the action condition of the reactive power compensation equipment and further influences the service life of the reactive power compensation equipment, but also influences the transient voltage and the steady-state voltage of the converter station after the direct current fault.
The fixed value adopted by the current direct current reactive power control dead zone is conservative, so that the action of the direct current reactive power compensation equipment is too frequent, and the service life of the reactive power compensation equipment is seriously influenced. Therefore, on the premise of ensuring safe and stable operation of the direct current system, the reactive control dead zone needs to be properly widened, the switching times of the reactive compensation equipment is reduced, and the service life of the reactive compensation equipment is prolonged.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a method and a device for setting a direct current reactive power control dead zone based on transient/steady-state voltage constraint, which solve the problem of frequent switching of direct current reactive power compensation equipment, furthest reduce the switching times of the reactive power compensation equipment and prolong the service life of the reactive power compensation equipment on the premise of ensuring the voltage stability of an alternating current and direct current system after the direct current large disturbance impact.
In order to achieve the above purpose, the invention adopts the following technical scheme: a direct current reactive power control dead zone setting method based on transient steady state voltage constraint comprises the following steps:
simulating a converter station bus voltage curve after direct-current fault disturbance needing reactive power control dead zone setting, extracting transient state maximum voltage and steady state voltage of the disturbed converter station bus, and determining a transient state voltage limited fault S1 and a steady state voltage limited fault S2 by comparing the transient state maximum voltage and the steady state voltage under different faults;
respectively simulating the occurrence of direct current faults S1 and S2, and under the condition of different direct current power transmission gears, changing the alternating current and direct current reactive power exchange quantity by adjusting the input group number of direct current reactive power compensation equipment, and determining the alternating current and direct current reactive power exchange range under the constraint of transient overvoltage and steady overvoltage under the condition of different direct current power transmission gears;
and obtaining the minimum direct current reactive power control offset by combining the reactive power supporting capability of the alternating current system and the alternating current-direct current reactive power exchange range under different direct current power transmission gears, thereby determining the direct current reactive power control dead zone under different direct current power transmission gears.
Further, the dc fault includes: failure of direct current commutation, direct current restart and direct current lock.
Further, by comparing the transient maximum voltage and the steady-state voltage under different faults, the fault corresponding to the maximum transient maximum voltage is determined as the limited fault of the transient voltage S1, and the fault corresponding to the maximum steady-state voltage is determined as the limited fault of the steady-state voltage S2.
Further, determining an ac/dc reactive power exchange range under the constraints of transient overvoltage and steady overvoltage in different dc power transmission gears, wherein the method comprises the following steps:
simulating the fault S1, and determining the AC/DC reactive exchange limit value Q under the constraint of transient critical voltage after the fault S1 occurs by adjusting the number of groups of DC reactive compensation equipment and changing the AC/DC reactive exchange amount under the constraint of the transient critical voltage under the condition of different DC power transmission gearsZ,i；
Simulating the fault S2, and determining the AC/DC reactive exchange limit value Q under the constraint of steady-state critical voltage after the fault S2 occurs by adjusting the number of groups of DC reactive compensation equipment and changing the AC/DC reactive exchange amount under the constraint of the steady-state critical voltage under the condition of different DC power transmission gearsW,i；
Under different DC power transmission gears, the AC/DC reactive power exchange range constrained by transient overvoltage and steady overvoltage is QZ,i，QW,i]。
Further, the transient threshold voltage constraint is: after the fault occurs S1, the transient bus voltage of the converter station is not more than the highest voltage withstanding capability U of equipment in the converter stationZ.lim；
The steady state overvoltage constraint is: after the fault S2 occurs, the steady-state bus voltage of the converter station is not more than the steady-state voltage requirement U of the power system for the converter stationW.lim。
Further, the minimum direct current reactive power control offset is obtained, so that a direct current reactive power control dead zone under different direct current power transmission gears is determined, and the method comprises the following steps:
the AC/DC reactive exchange quantity Q should satisfy the formula (1):
Figure BDA0002397063400000031
in the formula, Qref,iThe reactive power supporting capability of a near-region alternating current system under the ith direct current power transmission gear is achieved; qex,iControlling the offset of the direct current reactive power under the ith direct current power transmission gear;
according to a formula (1), combining an AC-DC system reactive power exchange range [ Q ] under the constraint of transient overvoltage and steady overvoltage under different DC power transmission gearsZ,i，QW,i]To obtain the formula(2)：
Figure BDA0002397063400000041
Calculating to obtain the reactive power control offset Q under the ith direct current power transmission gearex,i：
Figure BDA0002397063400000042
Calculating reactive power control dead zone offset under all direct current different power transmission gears to obtain minimum reactive power control offset Qex,minAnd then, the dead zone of the direct current reactive power control under the direct current different power transmission gears is as follows: [ Q ]ref,i-Qex,min,Qref,i+Qex,min]。
A direct current reactive power control dead zone setting device based on transient steady state voltage constraint comprises:
the transient voltage limited fault and steady-state voltage limited fault determining module is used for simulating a converter station bus voltage curve after direct-current fault disturbance needing reactive power control dead zone setting, extracting transient maximum voltage and steady-state voltage of the converter station bus after disturbance, and determining transient voltage limited fault S1 and steady-state voltage limited fault S2 by comparing the transient maximum voltage and the steady-state voltage under different faults;
the alternating current-direct current reactive power exchange range determining module is used for respectively simulating the occurrence of direct current faults S1 and S2, and under different direct current power transmission gears, the alternating current-direct current reactive power exchange range under the constraint of transient overvoltage and steady overvoltage is determined by adjusting the input group number of direct current reactive power compensation equipment and changing the alternating current-direct current reactive power exchange amount;
and the direct current reactive power control dead zone determining module is used for obtaining the minimum direct current reactive power control offset by combining the reactive power supporting capacity of the alternating current system and the alternating current-direct current reactive power exchange range under different direct current power transmission gears, so that the direct current reactive power control dead zone under different direct current power transmission gears is determined.
Further, the dc fault includes: failure of direct current commutation, direct current restart and direct current lock.
Further, determining an ac/dc reactive power exchange range under the constraints of transient overvoltage and steady overvoltage in different dc power transmission gears, wherein the method comprises the following steps:
simulating the fault S1, and determining the AC/DC reactive exchange limit value Q under the constraint of transient critical voltage after the fault S1 occurs by adjusting the number of groups of DC reactive compensation equipment and changing the AC/DC reactive exchange amount under the constraint of the transient critical voltage under the condition of different DC power transmission gearsZ,i；
Simulating the fault S2, and determining the AC/DC reactive exchange limit value Q under the constraint of steady-state critical voltage after the fault S2 occurs by adjusting the number of groups of DC reactive compensation equipment and changing the AC/DC reactive exchange amount under the constraint of the steady-state critical voltage under the condition of different DC power transmission gearsW,i；
Under different DC power transmission gears, the AC/DC reactive power exchange range constrained by transient overvoltage and steady overvoltage is QZ,i，QW,i]。
Further, the minimum direct current reactive power control offset is obtained, so that a direct current reactive power control dead zone under different direct current power transmission gears is determined, and the method comprises the following steps:
the AC/DC reactive exchange quantity Q should satisfy the formula (1):
Figure BDA0002397063400000051
in the formula, Qref,iThe reactive power supporting capability of a near-region alternating current system under the ith direct current power transmission gear is achieved; qex,iControlling the offset of the direct current reactive power under the ith direct current power transmission gear;
according to a formula (1), combining an AC-DC system reactive power exchange range [ Q ] under the constraint of transient overvoltage and steady overvoltage under different DC power transmission gearsZ,i，QW,i]To give formula (2):
Figure BDA0002397063400000052
calculating to obtain the reactive power control offset Q under the ith direct current power transmission gearex,i：
Figure BDA0002397063400000053
Calculating reactive power control dead zone offset under all direct current different power transmission gears to obtain minimum reactive power control offset Qex,minAnd then, the dead zone of the direct current reactive power control under the direct current different power transmission gears is as follows: [ Q ]ref,i-Qex,min,Qref,i+Qex,min]。
The invention achieves the following beneficial effects: the reactive power control dead zone after setting is used for reducing the switching times of reactive power compensation equipment to the maximum extent and prolonging the service life of the reactive power compensation equipment on the premise of ensuring the voltage stability of an alternating current and direct current system after the direct current large disturbance impact.
Drawings
FIG. 1 is a flow chart of a DC reactive power control dead zone setting method in an embodiment of the present invention;
FIG. 2 is a graph of the bus voltage of the converter station under the DC blocking, restarting and commutation failure in embodiment 2;
FIG. 3 is a schematic diagram showing the transient voltage variation of the system after DC blocking according to embodiment 2;
FIG. 4 is a schematic diagram showing the voltage change condition of the system converter station after DC blocking in embodiment 2;
FIG. 5 is a DC power oscillation curve chart in example 2;
fig. 6 is a schematic diagram of the case in which the filter of the optimized dc system is switched due to a line fault in embodiment 2.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Example 1:
the method comprises the steps of carrying out simulation calculation on the transient state maximum voltage and the steady state voltage of bus voltage of the converter station after faults such as direct current commutation failure, restarting and locking, determining the input group number of direct current reactive power compensation equipment (filters) and the reactive power exchange quantity of an alternating current and direct current system under different direct current transmission power gears by taking the transient state critical voltage 1.1p.u. and the steady state critical voltage 1p.u. as constraint conditions, determining the alternating current and direct current reactive power exchange range under the constraint of transient state overvoltage and steady state overvoltage, and determining the reactive power control dead zone of the direct current reactive power compensation equipment (filters) under different direct current power gears by combining the reactive power support capacity of the alternating current system under different direct current transmission power gears.
It should be noted that the transient state maximum voltage and the steady state voltage are obtained by reading the bus voltage curve of the converter station after the direct current disturbance, that is, the method is only suitable for the situations that the curve itself does not oscillate, diverge and destabilize after the direct current disturbance.
As shown in fig. 1, a dc reactive power control dead zone setting method based on transient and steady state voltage constraint includes the steps of:
step 1, simulating a converter station bus voltage curve after disturbance of direct current commutation failure, direct current restart and direct current blocking fault which need to perform reactive power control dead zone setting, extracting three kinds of disturbed converter station bus transient state maximum voltages and steady state voltages, and determining a transient state voltage limited fault S1 and a steady state voltage limited fault S2 by comparing the transient state maximum voltages and the steady state voltages under the three kinds of disturbance;
generally speaking, the transient maximum voltage generally occurs at the time of fault initiation or fault removal, the steady-state voltage generally takes a value after 10S from the fault initiation, and by comparing the transient maximum voltage and the steady-state voltage under three types of disturbances, the fault corresponding to the maximum transient maximum voltage is determined as the fault S1 (i.e., the limited fault of the transient voltage) constrained by the transient overvoltage, and the fault corresponding to the maximum steady-state voltage is determined as the fault S2 (i.e., the limited fault of the steady-state voltage S2) constrained by the steady-state overvoltage.
The faults S1 and S2 may be the same fault or different faults.
In the step 2, the step of mixing the raw materials,with the highest withstand voltage capability U of equipment in the converter stationZ.limTransient state bus voltage of the converter station after the transient state voltage limited fault S1 is limited for the transient state critical voltage, and under different DC transmission power gears, the AC/DC reactive power exchange limit value Q under the transient state critical voltage constraint after the limited fault S1 occurs is determined by adjusting the input group number of the DC reactive power compensation equipment and changing the AC/DC reactive power exchange amountZ,i(i.e., highest value);
the steady-state voltage requirement U of the current conversion station is met by the power systemW.limLimiting the stable state bus voltage of the converter station after the limited fault S2 of the stable state voltage for the stable state critical voltage, and determining the AC/DC reactive power exchange limit value Q under the constraint of the stable state critical voltage after the limited fault S2 occurs by adjusting the input group number of the DC reactive power compensation equipment and changing the AC/DC reactive power exchange amount under different DC transmission power gearsW,i；
Obtaining the AC-DC reactive power exchange range [ Q ] under the constraint of transient overvoltage and steady overvoltage under different DC transmission power gearsZ,i，QW,i]And i represents the serial numbers of DC different power transmission gears.
Generally, equipment in the converter station requires that the transient maximum voltage not exceed the transient critical voltage 1.1p.u., and equipment in the converter station requires that the steady state maximum voltage not exceed the steady state critical voltage 1.0p.u. Under the DC system under-compensation mode, transient overvoltage is facilitated, but steady overvoltage is not facilitated; under the over-compensation mode of the direct current system, the over-compensation mode is favorable for steady-state overvoltage, but not favorable for transient overvoltage, and if the reactive power of the direct current system is taken as the positive direction, Q isWIs constantly greater than QZ。
Step 3, combining reactive support capability Q of a near-region alternating current system under gears with different direct current transmission powersref,i( i 1, 2.. N) and reactive power exchange range [ Q ] of ac/dc system constrained by transient overvoltage and steady-state overvoltageZ,i，QW,i]Obtaining the minimum direct current reactive power control offset, and further obtaining a direct current reactive power control dead zone under different direct current transmission power gears;
the method comprises the following specific steps:
the AC/DC reactive exchange quantity Q should satisfy the formula (1):
Figure BDA0002397063400000081
in the formula, Q is AC/DC reactive exchange quantity; qref,iThe reactive power supporting capability of a near-region alternating current system under the ith direct current power transmission gear is achieved; qex,iAnd the offset of the DC reactive power control under the ith DC power transmission gear is obtained.
According to the stipulations in the DC complete design book, the reactive support capability Q of the AC system under different DC power transmission gears is inquiredref,iN, i denotes the dc different power transmission gear numbers, and N denotes the total number of dc different power transmission gears. Generally speaking, under different power transmission gears of direct current, the starting conditions of the matching units of the direct current near-region alternating current power grid are different, so that the corresponding reactive power support capacities of the alternating current systems are different.
According to the formula (1), combining the reactive power exchange range [ Q ] of the AC-DC system restrained by transient overvoltage and steady overvoltageZ,i，QW,i]The formula (2) can be obtained:
Figure BDA0002397063400000082
finally, the reactive control offset Q under the ith direct-current power transmission gear can be calculated through the formula (3)ex,i：
Figure BDA0002397063400000083
Calculating reactive power control dead zone offset under all direct current different power transmission gears to obtain minimum reactive power control offset Qex,minAnd then, the dead zone of the direct current reactive power control under the direct current different power transmission gears is as follows: [ Q ]ref,i-Qex,min,Qref,i+Qex,min]。
Example 2:
a direct current reactive power control dead zone setting device based on transient steady state voltage constraint comprises:
the transient voltage limited fault and steady-state voltage limited fault determining module is used for simulating a converter station bus voltage curve after direct-current fault disturbance needing reactive power control dead zone setting, extracting transient maximum voltage and steady-state voltage of the converter station bus after disturbance, and determining transient voltage limited fault S1 and steady-state voltage limited fault S2 by comparing the transient maximum voltage and the steady-state voltage under different faults;
the alternating current-direct current reactive power exchange range determining module is used for respectively simulating the occurrence of direct current faults S1 and S2, and under different direct current power transmission gears, the alternating current-direct current reactive power exchange range under the constraint of transient overvoltage and steady overvoltage is determined by adjusting the input group number of direct current reactive power compensation equipment and changing the alternating current-direct current reactive power exchange amount;
and the direct current reactive power control dead zone determining module is used for obtaining the minimum direct current reactive power control offset by combining the reactive power supporting capacity of the alternating current system and the alternating current-direct current reactive power exchange range under different direct current power transmission gears, so that the direct current reactive power control dead zone under different direct current power transmission gears is determined.
Further, the dc fault includes: failure of direct current commutation, direct current restart and direct current lock.
Further, determining an ac/dc reactive power exchange range under the constraints of transient overvoltage and steady overvoltage in different dc power transmission gears, wherein the method comprises the following steps:
simulating the fault S1, and determining the AC/DC reactive exchange limit value Q under the constraint of transient critical voltage after the fault S1 occurs by adjusting the number of groups of DC reactive compensation equipment and changing the AC/DC reactive exchange amount under the constraint of the transient critical voltage under the condition of different DC power transmission gearsZ,i；
Simulating the fault S2, and determining the AC/DC reactive exchange limit value Q under the constraint of steady-state critical voltage after the fault S2 occurs by adjusting the number of groups of DC reactive compensation equipment and changing the AC/DC reactive exchange amount under the constraint of the steady-state critical voltage under the condition of different DC power transmission gearsW,i；
Under different DC power transmission gears, the AC/DC reactive power exchange range constrained by transient overvoltage and steady overvoltage is QZ,i，QW,i]。
Further, the minimum direct current reactive power control offset is obtained, so that a direct current reactive power control dead zone under different direct current power transmission gears is determined, and the method comprises the following steps:
the AC/DC reactive exchange quantity Q should satisfy the formula (1):
Figure BDA0002397063400000091
in the formula, Qref,iThe reactive power supporting capability of a near-region alternating current system under the ith direct current power transmission gear is achieved; qex,iControlling the offset of the direct current reactive power under the ith direct current power transmission gear;
according to a formula (1), combining an AC-DC system reactive power exchange range [ Q ] under the constraint of transient overvoltage and steady overvoltage under different DC power transmission gearsZ,i，QW,i]To give formula (2):
Figure BDA0002397063400000101
calculating to obtain the reactive power control offset Q under the ith direct current power transmission gearex,i：
Figure BDA0002397063400000102
Calculating reactive power control dead zone offset under all direct current different power transmission gears to obtain minimum reactive power control offset Qex,minAnd then, the dead zone of the direct current reactive power control under the direct current different power transmission gears is as follows: [ Q ]ref,i-Qex,min,Qref,i+Qex,min]。
Example 3:
taking direct current with rated capacity of 8000MW in a regional power grid in China as an example, firstly comparing the direct current with the bus voltage curve of the converter station under the disturbance of locking, restarting and commutation failure, as shown in fig. 2, the comparison shows that the transient state maximum voltage rise of the bus of the converter station under various disturbances is basically consistent, and the steady state voltage is the highest when the direct current is locked, so that the direct current locking fault is taken as the limited fault of the direct current transient/steady state voltage in the subsequent reactive dead zone adjustment.
The reactive support capability reference values of the near-zone alternating current system under the direct current active power transmission gears according to the complete design book are shown in table 1:
TABLE 1 complete set of design books ac/dc reactive power exchange reference values
Figure BDA0002397063400000103
Taking DC power 8000MW as an example to perform reactive dead zone setting, considering that the offset of an initial DC reactive dead zone is 236Mvar, and combining reactive support capability of a near-zone AC system in table 1, therefore, the reactive power absorbed by the DC from the AC is greater than 836Mvar, a filter (namely DC reactive compensation equipment) needs to be withdrawn, the number of the withdrawn groups of the filter is adjusted, the steady state voltage rise condition after DC blocking is inspected, and the steady state voltage is controlled under the constraint of the steady state critical voltage, so as to determine the AC/DC reactive power exchange upper limit; when the DC absorbed reactive power from the AC is less than 364Mvar, a filter is required to be thrown, the number of groups of the filter is adjusted, the DC transient voltage rise condition after DC blocking is recorded, and the transient voltage is controlled under the constraint of the transient critical voltage so as to determine the AC/DC reactive power exchange lower limit. And setting the upper limit of the safe steady-state voltage to be 1p.u., and the upper limit of the safe transient-state voltage to be 1.1p.u.
TABLE 2 Steady-State Voltage step-Up for stepping off filters of different groups of numbers at DC Power 8000MW
Figure BDA0002397063400000111
As shown in fig. 3 and table 2, when the dc power is 8000MW, the impact of the cancellation filter on the dc transient voltage is small, and since the safe steady-state voltage upper limit of the dc is 1p.u., and the steady-state voltage of the cancellation 2 group of filters rises within the range required by the grid safe operation criterion, the ac/dc reactive power conversion upper limit value at 8000MW of the dc can be adjusted to 1177 Mvar.
TABLE 3 transient voltage rise for different sets of filters with DC power of 8000MW
Figure BDA0002397063400000112
When the dc power is 8000MW, the maximum number of the dc filter groups that can be put into the dc filter can reach 2 groups, and as shown in fig. 4 and table 3, the transient voltage of the filter group 1 is increased within the range required by the grid safety operation standard, so the lower limit of the ac/dc reactive power exchange at 8000MW of dc can be adjusted to 230 Mvar. Therefore, the reactive power exchange range of the alternating current and direct current system is [230,1177] at 8000MW, the reactive power control offset value is 470Mvar can be obtained according to the formula (3), similarly, the reactive power control offset value at each gear can be obtained as shown in table 4, and considering that the alternating current and direct current reactive power exchange is 0Mvar according to the complete design rule when the direct current transmission power is 0-4000MW, the original reactive power control offset value is still 236Mvar in the direct current reactive power control dead zone at the gear.
TABLE 4 reactive power control dead zone constant value under each DC gear
Figure BDA0002397063400000121
The minimum value of the 4 values is selected to ensure that the power grid system conforms to the safe and stable operation regulation under all working conditions, and when the direct current power is between 5000MW and 8000MW, the fixed value of the reactive dead zone (namely the reactive control offset) is constantly equal to 470 Mvar. The dead zone of the DC reactive power control under DC different power transmission gears is as follows: [ Q ]ref,i-470,Qref,i+470]。：
TABLE 5 reactive power control dead zone under each DC gear
DC power (MW) Reactive power control dead zone (Mvar)
5000 [-330,630]
6000 [-280,880]
7000 [-30,930]
8000 [130,1070]
According to the optimized reactive power control strategy, comparing the action conditions of the filter adopting the original dead zone fixed value and the optimized dead zone fixed value under the condition of direct current power low-frequency oscillation as shown in fig. 5 as shown in fig. 6;
as can be seen from fig. 6, the optimized reactive dead zone constant value control strategies are switched in 9 groups in total within 0s-3s, the original reactive dead zone constant value control strategies are switched in 11 groups in total, the number of switching groups of the optimized reactive dead zone constant value control strategies in the same time is obviously less than that of the original reactive dead zone constant value control strategies, and the results show that the optimized reactive dead zone constant value control strategies can effectively reduce the switching times of filters in the same time.
The fixed value adopted by the current direct current reactive power control dead zone is conservative, so that the action of the direct current reactive power compensation equipment is too frequent, and the service life of the reactive power compensation equipment is seriously influenced. The invention determines the reactive power exchange range of the alternating current and direct current system by comprehensively considering the transient voltage and the steady voltage constraint of the bus of the converter station after the direct current fault, and determines the direct current reactive power control dead zone by combining different reactive power support capacities of the near-zone alternating current system under different direct current transmission powers. The method provides technical support for setting the direct current reactive power control dead zone, expands the reactive power control dead zone to the maximum extent on the premise of ensuring that transient overvoltage and steady overvoltage can not occur on a bus of the converter station after direct current fault, reduces the action times of direct current reactive power compensation equipment, prolongs the service life of the reactive power compensation equipment, and ensures the direct current conveying capacity.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (4)

1. A direct current reactive power control dead zone setting method based on transient steady state voltage constraint is characterized by comprising the following steps: the method comprises the following steps:
simulating a converter station bus voltage curve after the disturbance of the direct-current fault needing to be subjected to reactive power control dead zone setting, extracting transient state maximum voltage and steady state voltage of the disturbed converter station bus, and determining a direct-current fault S1 of the transient state voltage and a direct-current fault S2 of the steady state voltage by comparing the transient state maximum voltage and the steady state voltage under different faults;
respectively simulating the occurrence of direct current faults S1 and S2, and under the condition of different direct current power transmission gears, changing the alternating current and direct current reactive power exchange quantity by adjusting the input group number of direct current reactive power compensation equipment, and determining the alternating current and direct current reactive power exchange range under the constraint of transient overvoltage and steady overvoltage under the condition of different direct current power transmission gears;
the method comprises the steps that the reactive power supporting capacity of an alternating current system and the alternating current-direct current reactive power exchange range under different direct current power transmission gears are combined to obtain the minimum direct current reactive power control offset, so that direct current reactive power control dead zones under different direct current power transmission gears are determined;
the direct current fault comprises: failure of direct current commutation, direct current restart and direct current locking;
determining an alternating current-direct current reactive power exchange range under the constraint of transient overvoltage and steady overvoltage under different direct current power transmission gears, wherein the method comprises the following steps:
simulating the occurrence of a direct current fault S1, and determining an alternating current-direct current reactive power exchange limit value Q under the constraint of transient critical voltage after the occurrence of a direct current fault S1 by adjusting the number of groups of direct current reactive power compensation equipment and changing the alternating current-direct current reactive power exchange amount under the constraint of direct current different power transmission gearsZ,i；
Simulating the occurrence of a direct current fault S2, and determining an alternating current-direct current reactive power exchange limit value Q under the constraint of steady-state critical voltage after the occurrence of the direct current fault S2 by adjusting the number of groups of direct current reactive power compensation equipment to change the alternating current-direct current reactive power exchange amount under the constraint of the steady-state critical voltage under the condition of different direct current power transmission gearsW,i；
Under different DC power transmission gears, the AC/DC reactive power exchange range constrained by transient overvoltage and steady overvoltage is QZ,i，QW,i]；
Obtaining the minimum direct current reactive power control offset so as to determine a direct current reactive power control dead zone under different direct current power transmission gears, wherein the method comprises the following steps:
the AC/DC reactive exchange quantity Q should satisfy the formula (1):
Figure FDA0002977705390000021
in the formula, Qref,iThe reactive power supporting capability of a near-region alternating current system under the ith direct current power transmission gear is achieved; qex,iControlling the offset of the direct current reactive power under the ith direct current power transmission gear;
according to a formula (1), combining an AC-DC system reactive power exchange range [ Q ] under the constraint of transient overvoltage and steady overvoltage under different DC power transmission gearsZ,i，QW,i]To give formula (2):
Figure FDA0002977705390000022
calculating to obtain the reactive power control offset Q under the ith direct current power transmission gearex,i：
Figure FDA0002977705390000023
Calculating reactive power control dead zone offset under all direct current different power transmission gears to obtain minimum reactive power control offset Qex,minAnd then, the dead zone of the direct current reactive power control under the direct current different power transmission gears is as follows: [ Q ]ref,i-Qex,min,Qref,i+Qex,min]。
2. The method for setting the dead zone of the direct current reactive power control based on the transient and steady state voltage constraint of claim 1, which is characterized in that: by comparing the transient state maximum voltage and the steady state voltage under different faults, the fault corresponding to the maximum transient state maximum voltage is determined as the direct current fault of the transient state voltage S1, and the fault corresponding to the maximum steady state voltage is determined as the direct current fault of the steady state voltage S2.
3. The method for setting the dead zone of the direct current reactive power control based on the transient and steady state voltage constraint of claim 1, which is characterized in that: the transient threshold voltage constraint is: after the direct-current fault S1 occurs, the transient bus voltage of the converter station is not more than the highest voltage endurance U of the equipment in the converter stationZ.lim；
The steady state overvoltage constraint is: after the direct-current fault S2 occurs, the steady-state bus voltage of the converter station is not more than the steady-state voltage requirement U of the power system to the converter stationW.lim。
4. A direct current reactive power control dead zone setting device based on transient steady state voltage constraint is characterized in that: the method comprises the following steps:
the transient voltage limited fault and steady-state voltage limited fault determining module is used for simulating a converter station bus voltage curve after direct-current fault disturbance needing reactive power control dead zone setting, extracting transient maximum voltage and steady-state voltage of the converter station bus after disturbance, and determining direct-current fault S1 of the transient voltage and direct-current fault S2 of the steady-state voltage by comparing the transient maximum voltage and the steady-state voltage under different faults;
the alternating current-direct current reactive power exchange range determining module is used for respectively simulating the occurrence of direct current faults S1 and S2, and under different direct current power transmission gears, the alternating current-direct current reactive power exchange range under the constraint of transient overvoltage and steady overvoltage is determined by adjusting the input group number of direct current reactive power compensation equipment and changing the alternating current-direct current reactive power exchange amount;
the direct current reactive power control dead zone determining module is used for obtaining the minimum direct current reactive power control offset by combining the reactive power supporting capacity of the alternating current system and the alternating current-direct current reactive power exchange range under different direct current power transmission gears, so that the direct current reactive power control dead zone under different direct current power transmission gears is determined; the direct current fault comprises: failure of direct current commutation, direct current restart and direct current locking; determining an alternating current-direct current reactive power exchange range under the constraint of transient overvoltage and steady overvoltage under different direct current power transmission gears, wherein the method comprises the following steps:
simulating the occurrence of a direct current fault S1, and determining an alternating current-direct current reactive power exchange limit value Q under the constraint of transient critical voltage after the occurrence of a direct current fault S1 by adjusting the number of groups of direct current reactive power compensation equipment and changing the alternating current-direct current reactive power exchange amount under the constraint of direct current different power transmission gearsZ,i；
Simulating the occurrence of a direct current fault S2, and determining an alternating current-direct current reactive power exchange limit value Q under the constraint of steady-state critical voltage after the occurrence of the direct current fault S2 by adjusting the number of groups of direct current reactive power compensation equipment to change the alternating current-direct current reactive power exchange amount under the constraint of the steady-state critical voltage under the condition of different direct current power transmission gearsW,i；
Under different DC power transmission gears, the AC/DC reactive power exchange range constrained by transient overvoltage and steady overvoltage is QZ,i，QW,i]；
Obtaining the minimum direct current reactive power control offset so as to determine a direct current reactive power control dead zone under different direct current power transmission gears, wherein the method comprises the following steps:
the AC/DC reactive exchange quantity Q should satisfy the formula (1):
Figure FDA0002977705390000041
in the formula, Qref,iThe reactive power supporting capability of a near-region alternating current system under the ith direct current power transmission gear is achieved; qex,iControlling the offset of the direct current reactive power under the ith direct current power transmission gear;
according to a formula (1), combining an AC-DC system reactive power exchange range [ Q ] under the constraint of transient overvoltage and steady overvoltage under different DC power transmission gearsZ,i，QW,i]To give formula (2):
Figure FDA0002977705390000042
calculating to obtain the reactive power control offset Q under the ith direct current power transmission gearex,i：
Figure FDA0002977705390000043
Calculating reactive power control dead zone offset under all direct current different power transmission gears to obtain minimum reactive power control offset Qex,minAnd then, the dead zone of the direct current reactive power control under the direct current different power transmission gears is as follows: [ Q ]ref,i-Qex,min,Qref,i+Qex,min]。
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