CN113890077A - Method for evaluating direct current bearing capacity in operation - Google Patents

Method for evaluating direct current bearing capacity in operation Download PDF

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Publication number
CN113890077A
CN113890077A CN202110990050.9A CN202110990050A CN113890077A CN 113890077 A CN113890077 A CN 113890077A CN 202110990050 A CN202110990050 A CN 202110990050A CN 113890077 A CN113890077 A CN 113890077A
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direct current
delta
power
frequency
steady
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Inventor
蔡绍荣
周泓
魏明奎
江栗
路亮
陶宇轩
沈力
王庆
梁文举
文一宇
张鹏
杨宇霄
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Southwest Branch of State Grid Corp
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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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • 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
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
    • 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
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention discloses an evaluation method of direct current bearing capacity in operation, and belongs to the technical field of power grid planning. The invention comprises the following steps: 1. forming a typical mode based on the determined net rack clustering, and generating an alternating current-direct current disturbance library; 2. determining the effective short-circuit ratio of direct current under all working conditions, and checking the abundance of the power organization after the fault of the direct current power collecting channel if the effective short-circuit ratio is greater than a reference value; 3. checking transient overvoltage and steady overvoltage sent by the single direct current, and considering transient frequency of safety control measures after single direct current disturbance; or checking the transient overvoltage and the steady overvoltage of the simultaneous transmission and receiving direct current disturbance and the frequency of the simultaneous transmission and receiving direct current disturbance; 4. and traversing all the operation modes if the working condition of the highest frequency or the lowest frequency after the direct current fault is met, wherein the sum minimum value of the direct current capacity in all the operation modes is the bearable direct current sending capacity. The invention can improve the evaluation accuracy of the maximum direct current bearing capacity and guide the power system planners to perfect various planning measures.

Description

Method for evaluating direct current bearing capacity in operation
Technical Field
The invention belongs to the technical field of power grid planning, and particularly relates to an evaluation method of direct current bearing capacity in operation.
Background
At present, research on the dc bearing capacity is still in an exploration phase, and without a clear definition, the dc bearing capacity shall include two aspects of "dc" and "bearing capacity", where dc is an important power transmission method for power transmission, and the bearing capacity includes its own attribute, that is, the capacity of dc transmission cannot exceed a "threshold" that can be carried by a power system. In essence, the direct current bearing capacity depends on the degree of energy development, and a matching alternating current network frame follows an upgrading and transforming plan of a power supply and a direct current load planning, and the main power for driving the direct current bearing capacity to be gradually improved is the development and construction of renewable energy.
From the operation perspective, because the safety problem is checked according to N-1 mainly by considering the abundance and economy such as power and electric quantity balance, peak regulation standby and the like when planning the direct current construction, and the construction of the direct current engineering is far ahead of the construction of a main alternating current network, the direct current bearing capacity in the actual operation is generally smaller than the rated power of the direct current planning, and the method is particularly obvious in the transition period of direct current operation. Therefore, the problems to be solved are: what is the maximum dc conveyable capacity if the full dc power delivery is not satisfied under the existing power supply planning and grid planning? In the prior art, under the condition that the direct current full power output is not satisfied, due to the fact that a plurality of factors influencing the transmission power are provided, a person in the field generally judges through experience and lacks a specific evaluation method, the maximum transmittable power under the existing power supply planning and grid planning cannot be accurately obtained, and the later-stage power grid planning is influenced. According to the method, risks under different direct current transmission powers are evaluated based on a working condition scene set in operation, the maximum transmittable power of single-circuit direct current and simultaneous-transmission and simultaneous-reception direct current groups meeting constraint conditions and risk acceptable thresholds is obtained, reference is provided for power grid planning, and power system planners are guided to perfect various planning measures.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides an evaluation method of direct current bearing capacity in operation, which aims to: and evaluating the maximum transferable power of the single-circuit direct current and simultaneous transmission and reception direct current groups meeting various safety constraints based on the working condition scene set in operation, providing reference for power grid planning, and guiding power system planners to perfect various planning measures.
The technical scheme adopted by the invention is as follows:
an evaluation method of direct current carrying capacity in operation comprises the following steps:
step 1: forming a typical mode based on the determined net rack clustering, and generating an alternating current-direct current disturbance library;
step 2: determining the effective short-circuit ratio of direct current under all working conditions, and checking the abundance of the power organization after the fault of the direct current power collecting channel if the effective short-circuit ratio is greater than a reference value; if the effective short-circuit ratio is smaller than the reference value, reducing the direct current transmission power until the effective short-circuit ratio is larger than the reference value;
and step 3: if the single direct current is output, checking the transient overvoltage and the steady overvoltage output by the single direct current, and then checking the transient frequency of safety control measures after the single direct current disturbance; if the synchronous transmission and reception are carried out, checking the transient overvoltage and the steady-state overvoltage of the synchronous transmission and reception under the direct current disturbance, and checking the frequency of the synchronous transmission and reception under the direct current disturbance;
and 4, step 4: if the working condition of the highest frequency or the lowest frequency after the direct current fault is met, traversing all the operation modes, wherein the sum minimum value of the direct current capacities in all the operation modes is the bearable direct current sending capacity; and if the working condition of the highest frequency or the lowest frequency after the direct current fault is not met, reducing the direct current power until the frequency is in the standard range after the fault, and repeating the steps 1-3.
Preferably, in step 1, the dc perturbation library includes phase commutation failure, locking and restarting.
Preferably, the reference value in step 2 is 2, and when the dc effective short-circuit ratio is smaller than 2, the dc power is reduced until the index of the effective short-circuit ratio is larger than 2.
Preferably, the calculation of the effective short-circuit ratio is as follows:
Figure BDA0003232158550000021
in the formula, QcWhen the AC bus voltage of the converter station is a rated value, SacFor the system short-circuit capacity, P, of the DC converter busdNThe rated transmission capacity is direct current.
Preferably, in step 3, the transient overvoltage is checked according to the condition that the transient overvoltage does not exceed the bus voltage protection fixed value of the converter station by 1.3p.u./500ms, and the steady-state voltage is checked according to the condition that the steady-state voltage does not exceed 550 kV/half hour.
Preferably, in step 3, when new energy exists in the direct current near zone, it should be checked that the voltage of the new energy collection bus does not exceed the new energy grid-related standard.
Preferably, in step 3, for the existence of the cocurrent transmission and reception, the frequency response characteristics of the cocurrent transmission and reception after the commutation failure should be checked.
Preferably, in step 3, for the working condition that the transient state or the steady state overvoltage after the direct current fault is not met, the direct current power is reduced until all the voltages are within the standard range.
Preferably, in step 4, the highest frequency is checked according to the action fixed value of the generator not exceeding the high-cycle generator set by 50.8Hz/500ms, and the lowest frequency is checked according to the action fixed value of the generator not exceeding the low-cycle load shedding set by 49 Hz.
Preferably, the method for determining the transient overvoltage in step 3 is as follows:
a1, determining an AC/DC initial mode and a DC minimum compensation mode;
a2: determining an upper transient voltage rise limit value delta Uamax, and calculating a bus transient voltage rise delta Ua of the converter station after various direct current faults; determining a filter cut strategy;
a3: if the delta Uamax-delta Ua is larger than beta, increasing the direct current power, and returning to the step A1; if the delta Uamax-delta Ua is less than 0, reducing the direct current power, and returning to the step A1; and if delta Uamax-delta U is more than 0 and less than or equal to beta, and the beta is less than or equal to 0.05, determining the maximum direct current capacity of the transient voltage rise constraint.
Preferably, in step 3, the steady-state overvoltage determination method is as follows:
b1, determining an AC/DC initial mode and a DC maximum compensation mode;
b2: determining a steady-state voltage rise upper limit value delta Ubmax, and calculating a steady-state voltage rise delta Ub of the converter station bus after the direct-current bipolar locking; determining a filter removal strategy according to the set of design;
b3: if the delta Ubmax-delta Ub is larger than beta, increasing the direct current power, and returning to the step A1; if the delta Ubmax-delta Ub is less than 0, reducing the direct current power, and returning to the step A1; and if delta Ubmax-delta Ub is more than 0 and less than or equal to beta, and the beta is less than or equal to 0.05, determining the maximum direct current capacity of the steady-state pressure rise constraint.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
the invention provides a single-loop direct current and simultaneous transmission and receiving direct current group maximum transferable power evaluation method which meets the constraints of frequency, voltage, transient stability and the like based on the conventional power supply and power grid planning and evaluates the main factor of limited direct current transmission, provides reference for power grid planning, and can guide power system planners to perfect various planning measures and realize the value maximization of energy resources.
Drawings
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a flow chart of transient overvoltage evaluation of a bus of a converter station after a DC fault;
fig. 3 is a flow chart of steady state overvoltage evaluation of a converter station bus after a direct current fault.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present application without making any creative effort, shall fall within the protection scope of the present application.
In the description of the embodiments of the present application, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships that the products of the present invention are usually placed in when used, and are only used for convenience of description and simplicity of description, but do not indicate or imply that the devices or elements that are referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
The present invention is described in detail below with reference to fig. 1-3.
An evaluation method of direct current carrying capacity in operation comprises the following steps:
step 1: forming a typical mode based on the determined net rack clustering, and generating an alternating current-direct current disturbance library;
step 2: determining the effective short-circuit ratio of direct current under all working conditions, and checking the abundance of the power organization after the fault of the direct current power collecting channel if the effective short-circuit ratio is greater than a reference value; if the effective short-circuit ratio is smaller than the reference value, reducing the direct current transmission power until the effective short-circuit ratio is larger than the reference value;
and step 3: if the single direct current is output, checking the transient overvoltage and the steady overvoltage output by the single direct current, and then checking the transient frequency of safety control measures after the single direct current disturbance; if the synchronous transmission and reception are carried out, checking the transient overvoltage and the steady-state overvoltage of the synchronous transmission and reception under the direct current disturbance, and checking the frequency of the synchronous transmission and reception under the direct current disturbance;
and 4, step 4: if the working condition of the highest frequency or the lowest frequency after the direct current fault is met, traversing all the operation modes, wherein the sum minimum value of the direct current capacities in all the operation modes is the bearable direct current sending capacity; and if the working condition of the highest frequency or the lowest frequency after the direct current fault is not met, reducing the direct current power until the frequency is in the standard range after the fault, and repeating the steps 1-3.
In this embodiment, the dc perturbation library described in step 1 includes phase commutation failure, locking, and restarting.
In this embodiment, the reference value is 2, when the dc effective short-circuit ratio is smaller than 2, the dc power is reduced until the effective short-circuit ratio index is larger than 2, and the maximum dc transmission power constrained by the short-circuit ratio is PDC ESCR；
In this embodiment, the Effective Short Circuit Ratio index (ESCR) is calculated as follows:
Figure BDA0003232158550000041
in the formula, QcWhen the AC bus voltage of the converter station is a rated value, SacFor dc converter bus-bar systemsSystem short circuit capacity, PdNThe rated transmission capacity is direct current. ESCR greater than 5, strong system; ESCR is between 2 and 3, and is weak system; ESCR is less than 2, and is a very weak system. The larger the short-circuit ratio index is, the smaller the influence of the switching-in or running state change of the direct-current system on the alternating-current system is. The short-circuit ratio index is significant in a bridge which establishes a relation between the strength of a sending-end alternating current power grid and the capacity of the accessed direct current, the rationality of a direct current access scheme in the alternating current power grid is evaluated through calculating quantitative indexes, the capacity of the maximum direct current access is evaluated, and the like, so that the maximum scale of the accessible direct current under the limitation of the strength of the alternating current power grid can be given.
When the maximum transmission power of all collected alternating current sections in the direct current near region is smaller than the rated direct current power, the maximum transmission power of the direct current constrained by the electric power organization of the alternating current channel is PDC AC；
For the situation that the matched power supply is in delayed operation or is far smaller than the direct current transmission capacity, the direct current needs to pass through a primary section and a secondary section to collect the produced power supply in the network, and the direct current sending capacity is limited by the section organization capacity. Under normal conditions, the thermal stability, transient stability and dynamic stability of the system after the direct current near-zone alternating current N-1 and N-2 faults need to be checked, the section limit meeting the stable conditions is solved, and then the direct current maximum transmission power constrained by the section limit after the alternating current faults is solved.
In the step 3, the transient overvoltage is checked according to the condition that the transient overvoltage does not exceed the bus voltage protection fixed value of the converter station by 1.3p.u./500ms, and the steady-state voltage does not exceed 550 kV/half hour. When new energy exists in the direct current near area, the voltage of a new energy collection bus is not more than the new energy grid-related standard to be checked. For the working condition of transient state or steady state overvoltage after the direct current fault is not satisfied, the direct current power is reduced until all the voltages are in the standard range, and the maximum direct current transmission power constrained by the voltage stability is PDC voltage；
Under various fault conditions such as direct current commutation failure, restarting and locking, the transient overvoltage problem is prominent because the filter is not cut off for a short time and a new energy unit may have a large amount of reactive power surplus in the low-pass process. Transient voltage rise is related to various factors, such as direct current power level, reactive compensation mode, unit running state, safety control tripping strategy and the like, and a relatively conservative mode is determined according to actual experience and sensitivity analysis to ensure that various possibilities are covered. Meanwhile, in order to consider the influence of overhaul of important equipment, a flow chart of a solving process of the transient overvoltage is shown in fig. 2, and the specific solving process is as follows:
a1, determining an AC/DC initial mode and a DC minimum compensation mode;
a2: determining an upper transient voltage rise limit value delta Uamax, and calculating a bus transient voltage rise delta Ua of the converter station after various direct current faults; determining a filter cut strategy;
a3: if the delta Uamax-delta Ua is larger than beta, increasing the direct current power, and returning to the step A1; if the delta Uamax-delta Ua is less than 0, reducing the direct current power, and returning to the step A1; and if delta Uamax-delta U is more than 0 and less than or equal to beta, and the beta is less than or equal to 0.05, determining the maximum direct current capacity of the transient voltage rise constraint.
After direct current is locked, due to reasons of tide return, excessive reactive compensation and the like, near-zone steady-state overvoltage of the converter station can be caused, and if the steady-state voltage exceeds the upper limit after an accident, equipment can be damaged. The steady-state voltage rise is related to various factors, such as direct current power level, reactive compensation mode, unit running state, safety control tripping strategy and the like, and a relatively conservative mode is determined according to actual experience and sensitivity analysis to ensure that various possibilities are covered. Generally, the larger the dc transmission power is, the more serious the post-accident power flow back-off and reactive power compensation are, and the larger the steady-state voltage rise is. In actual engineering, the steady-state overvoltage may become a key factor that restricts the dc power transmission capability, and a flowchart of a solving process of the steady-state overvoltage is shown in fig. 3, and the specific steps are as follows:
b1, determining an AC/DC initial mode and a DC maximum compensation mode;
b2: determining a steady-state voltage rise upper limit value delta Ubmax, and calculating a steady-state voltage rise delta Ub of the converter station bus after the direct-current bipolar locking; determining a filter removal strategy according to the set of design;
b3: if the delta Ubmax-delta Ub is larger than beta, increasing the direct current power, and returning to the step A1; if the delta Ubmax-delta Ub is less than 0, reducing the direct current power, and returning to the step A1; and if delta Ubmax-delta Ub is more than 0 and less than or equal to beta, and the beta is less than or equal to 0.05, determining the maximum direct current capacity of the steady-state pressure rise constraint.
In the embodiment, in the step 4, the highest frequency is checked according to the action fixed value of the high-cycle generator tripping machine not exceeding 50.8Hz/500ms, and the lowest frequency is checked according to the action fixed value of the low-cycle load shedding machine not exceeding 49 Hz; when new energy exists in a direct current near area, the new energy frequency is not more than the new energy grid-related standard to be checked. For the direct current with simultaneous transmission and reception, the frequency response characteristic after the direct current commutation failure of the simultaneous transmission and reception should be checked. For the working condition that the highest frequency or the lowest frequency after the direct current fault is not satisfied, the direct current power is reduced until the frequency after the fault is within the standard range, and the direct current maximum transmission power constrained by the frequency is PDC frequency。
In this embodiment, the maximum dc transmissible power that can simultaneously satisfy the effective short-circuit ratio, the tidal current organization, the voltage stability, and the frequency stability under all the operating conditions is PDC max＝min(PDC ESCR,PDC AC,PDC voltage,PDC frequency)。
By the method, the maximum output power under all working conditions can be evaluated, and the maximum transferable power of the single-circuit direct current group and the simultaneous-transmission and simultaneous-receiving direct current group can be found out under the working condition scene set in operation and simultaneously meet various safety constraints. The method provides reference for power grid planning, guides power grid planning personnel to perfect various planning measures, and realizes the value maximization of energy resources.
The above-mentioned embodiments only express the specific embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for those skilled in the art, without departing from the technical idea of the present application, several changes and modifications can be made, which are all within the protection scope of the present application.

Claims (10)

1. A method for evaluating DC carrying capacity in operation is characterized by comprising the following steps:
step 1: forming a typical mode based on the determined net rack clustering, and generating an alternating current-direct current disturbance library;
step 2: determining the effective short-circuit ratio of direct current under all working conditions, and checking the abundance of the power organization after the fault of the direct current power collecting channel if the effective short-circuit ratio is greater than a reference value; if the effective short-circuit ratio is smaller than the reference value, reducing the direct current transmission power until the effective short-circuit ratio is larger than the reference value;
and step 3: if the single direct current is output, checking the transient overvoltage and the steady overvoltage output by the single direct current, and then checking the transient frequency of safety control measures after the single direct current disturbance; if the synchronous transmission and reception are carried out, checking the transient overvoltage and the steady-state overvoltage of the synchronous transmission and reception under the direct current disturbance, and checking the frequency of the synchronous transmission and reception under the direct current disturbance;
and 4, step 4: if the working condition of the highest frequency or the lowest frequency after the direct current fault is met, traversing all the operation modes, wherein the sum minimum value of the direct current capacities in all the operation modes is the bearable direct current sending capacity; and if the working condition of the highest frequency or the lowest frequency after the direct current fault is not met, reducing the direct current power until the frequency is in the standard range after the fault, and repeating the steps 1-3.
2. The method according to claim 1, wherein in step 1, the dc perturbation library comprises commutation failure, locking and restarting.
3. The method according to claim 1, wherein the reference value in step 2 is 2, and when the dc effective short-circuit ratio is smaller than 2, the dc power is reduced until the effective short-circuit ratio index is larger than 2.
4. The method according to claim 1, wherein the effective short-circuit ratio is calculated as follows:
Figure FDA0003232158540000011
in the formula, QcWhen the AC bus voltage of the converter station is a rated value, SacFor the system short-circuit capacity, P, of the DC converter busdNThe rated transmission capacity is direct current.
5. The method for assessing DC carrying capacity during operation according to claim 1, wherein in step 3, the transient overvoltage is checked according to a protection setting of not more than 1.3p.u./500ms for the bus voltage of the converter station, and the steady-state voltage is checked according to a protection setting of not more than 550 kV/half hour.
6. The method for evaluating the direct current bearing capacity in operation according to claim 1, wherein in the step 3, when new energy exists in a direct current near region, it is checked that the voltage of a new energy collection bus does not exceed a new energy grid-related standard, and for direct current with simultaneous transmission and reception, the frequency response characteristic after the phase change failure of the direct current with the simultaneous transmission and reception is also checked.
7. The method according to claim 1, wherein in step 3, for the condition that the transient or steady overvoltage after the dc fault is not satisfied, the dc power is reduced until all voltages are within the standard range.
8. The method of claim 1, wherein in step 4, the highest frequency is checked at a frequency not exceeding a high cycle shedding motion setpoint of 50.8Hz/500ms, and the lowest frequency is checked at a frequency not exceeding a low cycle shedding motion setpoint of 49 Hz.
9. The method for evaluating dc carrying capacity during operation according to claim 1, wherein in step 3, the transient overvoltage is determined by the following method:
a1, determining an AC/DC initial mode and a DC minimum compensation mode;
a2: determining an upper transient voltage rise limit value delta Uamax, and calculating a bus transient voltage rise delta Ua of the converter station after various direct current faults; determining a filter cut strategy;
a3: if the delta Uamax-delta Ua is larger than beta, increasing the direct current power, and returning to the step A1; if the delta Uamax-delta Ua is less than 0, reducing the direct current power, and returning to the step A1; and if delta Uamax-delta U is more than 0 and less than or equal to beta, and the beta is less than or equal to 0.05, determining the maximum direct current capacity of the transient voltage rise constraint.
10. The method for evaluating dc carrying capacity during operation according to claim 1, wherein the steady-state overvoltage is determined in step 3 by the following method:
b1, determining an AC/DC initial mode and a DC maximum compensation mode;
b2: determining a steady-state voltage rise upper limit value delta Ubmax, and calculating a steady-state voltage rise delta Ub of the converter station bus after the direct-current bipolar locking; determining a filter removal strategy according to the set of design;
b3: if the delta Ubmax-delta Ub is larger than beta, increasing the direct current power, and returning to the step A1; if the delta Ubmax-delta Ub is less than 0, reducing the direct current power, and returning to the step A1; and if delta Ubmax-delta Ub is more than 0 and less than or equal to beta, and the beta is less than or equal to 0.05, determining the maximum direct current capacity of the steady-state pressure rise constraint.
CN202110990050.9A 2021-08-26 2021-08-26 Method for evaluating direct current bearing capacity in operation Pending CN113890077A (en)

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Application publication date: 20220104