CN106786714A - A kind of asynchronous power network direct current locking dynamic frequency monitoring and Security Checking method - Google Patents

A kind of asynchronous power network direct current locking dynamic frequency monitoring and Security Checking method Download PDF

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Publication number
CN106786714A
CN106786714A CN201611117229.9A CN201611117229A CN106786714A CN 106786714 A CN106786714 A CN 106786714A CN 201611117229 A CN201611117229 A CN 201611117229A CN 106786714 A CN106786714 A CN 106786714A
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frequency
direct current
current line
power grid
power
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CN106786714B (en
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陈亦平
郑晓东
莫维科
侯君
张勇
陈巨龙
黄汉昌
楼楠
高琴
杨荣照
王子强
王巍
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South China University of Technology SCUT
China Southern Power Grid Co Ltd
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South China University of Technology SCUT
China Southern Power Grid 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
    • H02J3/36—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
    • 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
    • H02J2003/365—Reducing harmonics or oscillations in HVDC
    • 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)
  • Control Of Eletrric Generators (AREA)

Abstract

The invention discloses a kind of asynchronous power network direct current locking dynamic frequency monitoring and Security Checking method, comprise the following steps：Operation of power networks real time data needed for being obtained from EMS；Each time DC line in asynchronous power network is set as bipolar locking state respectively；According to required operation of power networks real time data, using the frequency transient analysis method estimated based on frequency peak, judge each time DC line after bipolar locking under the frequency regulation of system and the control action of safety and stability scheme, if high-frequency cutting machine can occur；Judged result according to high-frequency cutting machine is processed each time DC line accordingly.The present invention is set the fault scenes of bipolar locking to the multiple-circuit line circuit in Asynchronous Interconnection and employs the frequency transient analysis method estimated based on frequency peak respectively, the frequency peak of sending and high-frequency cutting machine judgement can be carried out after line rapidly calculates each time DC line bipolar locking, real-time is good and more quick, can be widely applied to power domain.

Description

Asynchronous power grid direct current blocking dynamic frequency monitoring and safety checking method
Technical Field
The invention relates to the field of electric power, in particular to a method for monitoring and checking the direct-current blocking dynamic frequency of an asynchronous power grid.
Background
With the mature development of high-voltage direct-current transmission technology, the manner of realizing provincial power transmission by adopting direct-current transmission is increasingly common. Taking the southern power grid as an example, the Yunnan power grid in the jurisdiction range is a large-scale power transmission system, and in order to solve the problems of stable power angle of an alternating current circuit and the like, in 2016, the southern power grid asynchronously interconnects the Yunnan power grid with a main grid consisting of a Guangdong power grid, a Guangxi power grid, a Guizhou power grid and a Hainan power grid only through a multi-loop direct current circuit.
After asynchronous interconnection, the mechanical inertia of the system of the Yunnan power grid is reduced, and under the same power disturbance, the frequency deviation of the system is larger than that of the traditional large synchronous power grid. In order to prevent high-frequency tripping and even frequency instability caused by the fact that the frequency of a direct-current line between the Yunnan power grid and a main grid exceeds a limit value after unipolar blocking or bipolar blocking, the primary frequency modulation capacity and the direct-current overload capacity of the Yunnan power grid meet safety requirements, and the interlocking tripping set by a safety and stability scheme of the Yunnan power grid is reasonable. However, in actual operation, working conditions such as the load rate of the direct-current line of the asynchronous power grid and the primary frequency modulation capability of the unit are changed in real time, and a preset safety and stability scheme may not meet requirements, so that each direct-current line of the asynchronous power grid should be subjected to real-time safety check, and the frequency maximum value of a direct-current bipolar latching back-end system (such as a sending-end system of a Yunnan power grid) under the current working condition is quickly estimated, so that useful decision auxiliary information is provided for scheduling operation.
Disclosure of Invention
To solve the above technical problems, the present invention aims to: the method for monitoring and checking the direct-current blocking dynamic frequency of the asynchronous power grid in real time and quickly is provided.
The technical scheme adopted by the invention is as follows:
a method for monitoring and safety checking of direct current blocking dynamic frequency of an asynchronous power grid comprises the following steps:
acquiring required power grid operation real-time data from an energy management system;
respectively setting each return direct current circuit in the asynchronous power grid to be in a bipolar locking state;
according to the required real-time data of the power grid operation, judging whether high-frequency tripping occurs on each return direct-current line after the bipolar locking under the control action of the frequency regulation and safety and stability scheme of the system by adopting a frequency transient analysis method based on frequency peak estimation;
and (3) carrying out corresponding treatment on each return direct current line according to the judgment result of the high-frequency cutting machine: if the current return direct current line has a high-frequency generator tripping, an alarm signal is sent out to prompt that a safety and stability measure or a system direct current power sending scheme needs to be modified when the current return direct current line has a fault; and otherwise, indicating that the running condition of the current return direct current line meets the safety requirement, and ending the safety check process of the current return direct current line at the moment, wherein the current return direct current line is any return direct current line of each return direct current line.
Further, the required real-time data of the power grid operation include, but are not limited to, a primary frequency modulation standby of the system, a rated transmission power of each return direct-current line, a locked chain cutting amount of each return direct-current line, a current output power of the system, a rotational inertia of the system, and a load frequency response.
Further, the step of setting each return direct-current line in the asynchronous power grid to a bipolar blocking state respectively includes:
and performing single check, and sequentially setting each return direct-current line of the asynchronous power grid to be in a bipolar blocking state, so that the output power of the return direct-current line after bipolar blocking is reduced to zero, and the return direct-current line after bipolar blocking is subjected to interlocking tripping and direct-current power support which are set by a corresponding safety and stability control scheme.
Further, the step of judging whether a high-frequency tripping occurs on each return direct-current line after the bipolar locking under the control action of the frequency regulation and safety and stability scheme of the system by adopting a frequency transient analysis method based on frequency peak estimation according to the required real-time data of the power grid operation includes:
analyzing the response process of the frequency of each return direct-current line under the action of primary frequency modulation, load frequency response and safety and stability measures of a system according to required power grid operation real-time data, and calculating the frequency peak value of each return direct-current line;
and comparing the frequency peak value of each return direct current line with the set frequency of the high-frequency generator tripping of the system, and judging whether the high-frequency generator tripping of each return direct current line after the bipolar locking occurs under the control action of the frequency regulation and safety and stability scheme of the system or not according to the comparison result.
Further, the step of analyzing the response process of the frequency of each return direct-current line under the action of the primary frequency modulation, the load frequency response and the safety and stability measures of the system according to the required real-time data of the power grid operation so as to calculate the frequency peak value of each return direct-current line includes:
the system is equivalent to a unit, a first-order differential equation is adopted to describe the dynamic process of the system frequency deviation according to the required real-time data of the power grid operation, and a time domain expression of the system frequency deviation is solved through time domain simulation, wherein the time domain expression delta f (t) of the system frequency deviation is as follows:
wherein, m ═ M', t is time, Pm0For normal operation or for instantaneous generator power before bipolar blocking of the DC line occurs，ΔPGFor chain of the amount of cutting machines, P0For normal operation or load power before bipolar blocking of the DC line occurs, omega0For normal operation or for the instantaneous generator speed before bipolar blocking of the DC line occurs, KLFor frequency adjustment coefficient of load, f0To be the frequency of the system,is the system frequency f0K ofLPower of the equation,. DELTA.PDCIs the algebraic sum of the DC power boost and the power that the DC line delivers less power due to bipolar latching,for normal operation or the instant load power before the bipolar locking of the direct current line occurs, R' is the equivalent difference adjustment coefficient of the primary frequency modulation of the system after the action of the linkage cutter occurs,r is the serial number of the unit with spare capacity in the system operation after the action of the chain cutter occurs, n is the total serial number of all the units in the system operation after the action of the chain cutter occurs, (P)m0)rAnd (P)m0)nThe generator sets with the serial numbers r and n respectively operate normally or the instantaneous generator power before the bipolar locking of the direct current circuit occurs,the unit adjusting power of the unit with the sequence number r after the action of the linkage cutter occurs, wherein M is equal to M ', M' is an equivalent inertia constant of a system after the action of the linkage cutter occurs, and T is a time constant;
obtaining the frequency deviation peak value of each return direct current line according to the time domain expression of the system frequency deviation delta f (t), wherein the frequency deviation peak value of each return direct current line meets the requirement of time tThe corresponding frequency offset value.
Further, the step of equating the system to a unit, describing the dynamic process of the system frequency deviation by adopting a first order differential equation according to the required real-time data of the power grid operation, and solving a time domain expression of the system frequency deviation through time domain simulation includes:
the system is equivalent to a unit, a first order differential equation is adopted to describe the dynamic process of the system frequency deviation according to the required real-time data of the power grid operation, and the dynamic process description equation of the system frequency deviation is as follows:
wherein β (t) is step input, Δ ω is rotational speed deviation of system output,
solving a dynamic process description equation of the system frequency deviation by adopting Laplace transformation to obtain a Laplace rotation speed deviation delta omega(s) of the system, wherein an expression of the Laplace rotation speed deviation delta omega(s) of the system is as follows:
wherein s is a Laplace operator;
and performing time domain simulation according to the Laplace rotation speed deviation delta omega(s) of the system, and calculating a time domain expression delta f (t) of the frequency deviation of the system.
Further, the step of comparing the frequency peak value of each return direct current line with the set frequency of the system high-frequency generator tripping, and judging whether the high-frequency generator tripping occurs on each return direct current line after the bipolar locking under the control action of the frequency regulation and safety and stability scheme of the system according to the comparison result is specifically as follows:
if the frequency peak value of each return direct current line exceeds the set frequency of the high-frequency generator tripping of the system, judging that the high-frequency generator tripping of each return direct current line after the bipolar locking occurs under the control action of the frequency regulation and safety and stability scheme of the system; and otherwise, judging that the high-frequency generator tripping of each return direct current line after the bipolar locking cannot occur under the control action of the frequency regulation and safety and stability scheme of the system.
Further, the operations performed in the process of modifying the safety measure or the system dc power sending scheme when the current return dc line fails include, but are not limited to: reducing the power transmission power of the current return direct current line; the quantity of chain cutters is increased; increasing the primary frequency modulation rotation reserve capacity; the interlocking cutter preferentially cuts off the hydroelectric generating set with small rotational inertia and large capacity or with the function of back adjustment.
The invention has the beneficial effects that: the method comprises the steps of obtaining required power grid operation real-time data, and setting each return direct-current line in the asynchronous power grid to be in a bipolar locking state; the method comprises the steps of judging whether a high-frequency tripping occurs or not by adopting a frequency transient analysis method based on frequency peak estimation according to required power grid operation real-time data, carrying out corresponding processing on each loop of direct current circuit according to a judgment result of the high-frequency tripping, setting a bipolar locking fault scene for a plurality of loops of direct current circuits in asynchronous networking respectively, adopting a frequency transient analysis method based on the frequency peak estimation, calculating the frequency peak of a bipolar locking rear-sending system of each loop of direct current circuit on line quickly, carrying out high-frequency tripping judgment according to the calculated frequency peak, providing verification and decision auxiliary information for the operation mode and real-time scheduling of an asynchronous power grid system, avoiding the phenomenon that the frequency of a sending end system exceeds safety limit due to bipolar locking faults of the direct current circuits, and being good in real-time and quicker.
Drawings
FIG. 1 is an overall flow chart of a method for monitoring and checking the DC blocking dynamic frequency of an asynchronous power grid according to the present invention;
FIG. 2 is a block diagram of the transfer function of the DC blocking frequency dynamic response of the present invention;
fig. 3 is a schematic diagram of a frequency dynamic calculation curve obtained by the method of the present invention.
Detailed Description
Referring to fig. 1, a method for monitoring and checking the direct current blocking dynamic frequency of an asynchronous power grid includes the following steps:
acquiring required power grid operation real-time data from an energy management system;
respectively setting each return direct current circuit in the asynchronous power grid to be in a bipolar locking state;
according to the required real-time data of the power grid operation, judging whether high-frequency tripping occurs on each return direct-current line after the bipolar locking under the control action of the frequency regulation and safety and stability scheme of the system by adopting a frequency transient analysis method based on frequency peak estimation;
and (3) carrying out corresponding treatment on each return direct current line according to the judgment result of the high-frequency cutting machine: if the current return direct current line has a high-frequency generator tripping, an alarm signal is sent out to prompt that a safety and stability measure or a system direct current power sending scheme needs to be modified when the current return direct current line has a fault; and otherwise, indicating that the running condition of the current return direct current line meets the safety requirement, and ending the safety check process of the current return direct current line at the moment, wherein the current return direct current line is any return direct current line of each return direct current line.
Further as a preferred embodiment, the required real-time data of the power grid operation includes, but is not limited to, a primary frequency modulation backup of the system, a rated transmission power of each dc link, a lock chain chopper quantity of each dc link, a current output power of the system, a rotational inertia of the system, and a load frequency response.
Further, as a preferred embodiment, the step of setting each return dc line in the asynchronous grid to the bipolar blocking state respectively specifically includes:
and performing single check, and sequentially setting each return direct-current line of the asynchronous power grid to be in a bipolar blocking state, so that the output power of the return direct-current line after bipolar blocking is reduced to zero, and the return direct-current line after bipolar blocking is subjected to interlocking tripping and direct-current power support which are set by a corresponding safety and stability control scheme.
Further as a preferred embodiment, the step of determining whether a high-frequency tripping occurs in each dc line after the bipolar locking under the control of the frequency adjustment and safety and stability scheme of the system by using a frequency transient analysis method based on frequency peak estimation according to the required real-time data of the power grid operation includes:
analyzing the response process of the frequency of each return direct-current line under the action of primary frequency modulation, load frequency response and safety and stability measures of a system according to required power grid operation real-time data, and calculating the frequency peak value of each return direct-current line;
and comparing the frequency peak value of each return direct current line with the set frequency of the high-frequency generator tripping of the system, and judging whether the high-frequency generator tripping of each return direct current line after the bipolar locking occurs under the control action of the frequency regulation and safety and stability scheme of the system or not according to the comparison result.
Further as a preferred embodiment, the step of analyzing, according to the required real-time data of the power grid operation, a response process of the frequency of each return direct-current line under the actions of the system primary frequency modulation, the load frequency response and the safety and stability measures, so as to calculate the frequency peak value of each return direct-current line includes:
the system is equivalent to a unit, a first-order differential equation is adopted to describe the dynamic process of the system frequency deviation according to the required real-time data of the power grid operation, and a time domain expression of the system frequency deviation is solved through time domain simulation, wherein the time domain expression delta f (t) of the system frequency deviation is as follows:
wherein, m ═ M', t is time, Pm0For normal operation or for instantaneous generator power, Δ P, before bipolar blocking of the DC line occursGFor chain of the amount of cutting machines, P0For normal operation or load power before bipolar blocking of the DC line occurs, omega0For normal operation or for the instantaneous generator speed before bipolar blocking of the DC line occurs, KLFor frequency adjustment coefficient of load, f0To be the frequency of the system,is the system frequency f0K ofLPower of the equation,. DELTA.PDCIs the algebraic sum of the DC power boost and the power that the DC line delivers less power due to bipolar latching,for normal operation or the instant load power before the bipolar locking of the direct current line occurs, R' is the equivalent difference adjustment coefficient of the primary frequency modulation of the system after the action of the linkage cutter occurs,r is the serial number of the unit with spare capacity in the system operation after the action of the chain cutter occurs, n is the total serial number of all the units in the system operation after the action of the chain cutter occurs, (P)m0)rAnd (P)m0)nThe units with sequence numbers r and n respectively operate normally or in a DC lineThe instantaneous generator power before pole lock occurs,the unit adjusting power of the unit with the sequence number r after the action of the linkage cutter occurs, wherein M is equal to M ', M' is an equivalent inertia constant of a system after the action of the linkage cutter occurs, and T is a time constant;
obtaining the frequency deviation peak value of each return direct current line according to the time domain expression of the system frequency deviation delta f (t), wherein the frequency deviation peak value of each return direct current line meets the requirement of time tThe corresponding frequency offset value.
Further as a preferred embodiment, the step of equating the system to a unit, describing a dynamic process of the system frequency deviation by using a first order differential equation according to the required real-time data of the power grid operation, and solving a time domain expression of the system frequency deviation through time domain simulation includes:
the system is equivalent to a unit, a first order differential equation is adopted to describe the dynamic process of the system frequency deviation according to the required real-time data of the power grid operation, and the dynamic process description equation of the system frequency deviation is as follows:
wherein β (t) is step input, Δ ω is rotational speed deviation of system output,
solving a dynamic process description equation of the system frequency deviation by adopting Laplace transformation to obtain a Laplace rotation speed deviation delta omega(s) of the system, wherein an expression of the Laplace rotation speed deviation delta omega(s) of the system is as follows:
wherein s is a Laplace operator;
and performing time domain simulation according to the Laplace rotation speed deviation delta omega(s) of the system, and calculating a time domain expression delta f (t) of the frequency deviation of the system.
Further as a preferred embodiment, the step of comparing the frequency peak value of each return direct-current line with the set frequency of the system high-frequency tripping machine, and determining whether the high-frequency tripping machine occurs on each return direct-current line after the bipolar locking under the control action of the frequency adjustment and safety and stability scheme of the system according to the comparison result is specifically as follows:
if the frequency peak value of each return direct current line exceeds the set frequency of the high-frequency generator tripping of the system, judging that the high-frequency generator tripping of each return direct current line after the bipolar locking occurs under the control action of the frequency regulation and safety and stability scheme of the system; and otherwise, judging that the high-frequency generator tripping of each return direct current line after the bipolar locking cannot occur under the control action of the frequency regulation and safety and stability scheme of the system.
Further as a preferred embodiment, the operation performed to modify the safety measure or the system dc power sending scheme when the current return dc line fails includes, but is not limited to: reducing the power transmission power of the current return direct current line; the quantity of chain cutters is increased; increasing the primary frequency modulation rotation reserve capacity; the interlocking cutter preferentially cuts off the hydroelectric generating set with small rotational inertia and large capacity or with the function of back adjustment.
The invention will be further explained and explained with reference to the drawings and the embodiments in the description.
Example one
The invention provides a method for monitoring and checking the direct current blocking dynamic frequency of an asynchronous power grid, aiming at the problems of poor real-time performance and insufficient rapidness in the prior art. The method can quickly calculate the frequency peak value of the sending end system after the bipolar locking of each return direct-current line on line, thereby providing useful decision auxiliary information for the dispatching operation of the asynchronous power grid system.
As shown in fig. 1, the specific process of the asynchronous power grid dc blocking dynamic frequency monitoring and security check method of the present invention is as follows:
and (I) acquiring required power grid operation real-time data. The required real-time data of the power grid operation includes but is not limited to primary frequency modulation standby of the system, rated transmission power of each return direct current line, locked chain cutting amount of each return direct current line, current sending power of the system, rotational inertia of the system and load frequency response. The required real-time data of the operation of the power grid can be obtained from a SCADA system (namely a data acquisition and monitoring control system and a subsystem of an energy management system).
And (II) setting each circuit of the direct current circuit to be in a bipolar locking state in sequence.
And (III) judging whether the high-frequency generator tripping occurs or not under the system frequency regulation action and the safety and stability control after the return direct-current line is locked by a frequency transient analysis method.
The frequency transient process analysis is based on the operation equation of the system, comprehensively considers the functions of system inertia, direct current power support, chain tripping, primary frequency modulation, load frequency regulation utility and the like, and is described and solved by a differential equation. The operating equation of the system is as follows:
wherein J is the equivalent moment of inertia of the system; t ismIs a mechanical torque; t iseIs an electromagnetic torque; pmIs the electrical power of the generator; pLFor loading electric power, PLComprises direct current sending power; omega is the generator speed and represents the frequency of the system.
Let the speed be ω at normal operation or at the instant before the DC blocking event occurs0The power of the generator isLoad power ofAt the initial moment after the DC blocking event occurs, the three events are respectively Rotational speed after DC blocking event Wherein f is frequency, and ω ═ 2 π f; kLIs the frequency regulation coefficient of the load, taking into account the frequency regulation of the DC line under normal operating conditions, KLGenerally between 1 and 3; delta PGThe quantity of chain cutters is measured; delta PDCThe sum of the DC power boost and the power that the DC line is delivering less due to the latch-up is algebraic.
Is provided withAndthe torque values are the initial instant torque values after the direct current locking event occurs. Then there are:
considering that part of the generator sets of the system have rotating reserve, when the generating capacity of the whole system is equivalent to one generator, the unit regulating power of the equivalent generatorWill be:
in the formula, subscript r represents the number of the unit with spare capacity in operation, and n represents the total number of the number of all the units in operation. When the bipolar locking fault occurs, the running condition of the system unit changes due to the action of the linkage cutter, so that the unit regulation power needs to be recalculated and recorded asThe same applies to the moment of inertia J or the inertia constant M0, and when the linkage cutter occurs, the equivalent inertia constant of the system should be recalculated and is denoted as M '═ J' ω0. The equivalent inertia constant M ', the equivalent difference adjustment coefficient R' of primary frequency modulation and the time constant T of the system of the invention need to be calculated according to the unit running state of the power grid after the chain generator tripping. The primary frequency modulation parameters of the system also need to be determined according to the rotation reserve capacity of the primary frequency modulation unit of the system and various types of units (including a water turbine generator unit, a non-reheating type steam turbine generator unit and a reheating type steam turbine generator unit)Unit, etc.) is calculated equivalently.
When the frequency of the system rises above the dead band, the prime mover speed regulator of the generator will begin to act, changing the opening of the regulator valve, so that the input mechanical power of the prime mover changes in the opposite direction to the frequency change. Δ P taking into account dead zones and delays in the regulation processmThe relationship to Δ ω is a function of time, which is expressed as:
in the simplified case, it is assumed that the time delay is a step through a time constant, i.e. for step inputT is the elapsed time constant.
In summary, the frequency dynamics after the dc line blocking fault occurs can be described by the following differential equation:
the abbreviation is:wherein:
x＝Δω
M＝M′
and solving the differential equation by using Laplace transform to obtain a time domain analytic expression of delta omega. Laplace transform of the above differential equation:
the above equation can be represented by the transfer function block diagram shown in fig. 2. In FIG. 2, the input Δ P is a step power disturbance and the output is a rotational speed deviation Δ ω(s), and
then, through simple time domain simulation, a frequency response waveform can be obtained, and a time domain expression Δ f (t) of the frequency deviation can also be directly calculated:
wherein,
when time t is satisfiedWhen Δ f (t) has a maximum value.
Judging whether the return direct current line exceeds the action limit of the high-frequency generator tripping machine of the generator or not by analyzing the frequency deviation peak value and the set frequency of the high-frequency generator tripping machine of the system, if not (namely the frequency deviation peak value does not exceed the set frequency of the high-frequency generator tripping machine of the system), judging that the high-frequency generator tripping does not occur on the direct current line, and indicating that the operation of the return direct current line meets the safety requirement; if the frequency deviation peak value exceeds the set frequency of the system high-frequency generator tripping, the verified return direct-current line has overlarge transmission power, insufficient quantity of chain generator tripping or insufficient primary frequency modulation capacity, and an alarm signal is given to prompt a dispatcher to take measures to reduce the frequency peak value when a fault occurs. The specific measures taken by the dispatcher can include: reducing the transmitted power of the return direct current line; the quantity of chain cutters is increased; increasing the primary frequency modulation rotation reserve capacity; the interlocking cutter preferentially cuts off hydroelectric generating sets with small rotational inertia, large capacity or a reverse adjustment function and the like.
Fig. 3 is a frequency curve calculated according to the method of the present invention after bipolar locking of a certain dc line. As can be seen from FIG. 3, the frequency reaches the peak value of 50.76Hz within about 2.3 seconds, and does not exceed the high-frequency tripping action value of 50.8Hz, so the safety and stability scheme of the return DC line can ensure the system safety, and the method of the present invention can rapidly and effectively determine the frequency peak value of the system after the bipolar locking fault, thereby verifying whether the safety and stability scheme of the system needs to be adjusted.
The invention provides a method for monitoring and checking the direct current blocking dynamic frequency of an asynchronous power grid, which provides checking and decision-making auxiliary information for the operation mode and real-time scheduling of the asynchronous power grid by respectively setting blocking fault scenes for multiple loops of direct current in an asynchronous networking and checking, effectively prevents high-frequency tripping action caused by the fact that the frequency of a sending end system exceeds the safety limit due to the blocking of a direct current line, and has wide application prospect.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (8)

1. A method for monitoring and safety checking of direct current blocking dynamic frequency of an asynchronous power grid is characterized by comprising the following steps: the method comprises the following steps:
acquiring required power grid operation real-time data from an energy management system;
respectively setting each return direct current circuit in the asynchronous power grid to be in a bipolar locking state;
according to the required real-time data of the power grid operation, judging whether high-frequency tripping occurs on each return direct-current line after the bipolar locking under the control action of the frequency regulation and safety and stability scheme of the system by adopting a frequency transient analysis method based on frequency peak estimation;
and (3) carrying out corresponding treatment on each return direct current line according to the judgment result of the high-frequency cutting machine: if the current return direct current line has a high-frequency generator tripping, an alarm signal is sent out to prompt that a safety and stability measure or a system direct current power sending scheme needs to be modified when the current return direct current line has a fault; and otherwise, indicating that the running condition of the current return direct current line meets the safety requirement, and ending the safety check process of the current return direct current line at the moment, wherein the current return direct current line is any return direct current line of each return direct current line.
2. The method for monitoring and checking the direct-current blocking dynamic frequency of the asynchronous power grid according to claim 1, characterized in that: the required real-time data of the power grid operation include but are not limited to primary frequency modulation standby of the system, rated transmission power of each return direct current line, locked chain cutting amount of each return direct current line, current sending power of the system, rotational inertia of the system and load frequency response.
3. The method for monitoring and checking the direct-current blocking dynamic frequency of the asynchronous power grid according to claim 1, characterized in that: the step of setting each return direct-current line in the asynchronous power grid to a bipolar locking state respectively comprises the following steps:
and performing single check, and sequentially setting each return direct-current line of the asynchronous power grid to be in a bipolar blocking state, so that the output power of the return direct-current line after bipolar blocking is reduced to zero, and the return direct-current line after bipolar blocking is subjected to interlocking tripping and direct-current power support which are set by a corresponding safety and stability control scheme.
4. The method for monitoring and checking the direct-current blocking dynamic frequency of the asynchronous power grid according to claim 1, characterized in that: the method comprises the following steps of judging whether high-frequency tripping occurs on each return direct-current line after bipolar locking under the control action of a frequency regulation and safety and stability scheme of a system by adopting a frequency transient analysis method based on frequency peak estimation according to required real-time data of power grid operation, wherein the step comprises the following steps of:
analyzing the response process of the frequency of each return direct-current line under the action of primary frequency modulation, load frequency response and safety and stability measures of a system according to required power grid operation real-time data, and calculating the frequency peak value of each return direct-current line;
and comparing the frequency peak value of each return direct current line with the set frequency of the high-frequency generator tripping of the system, and judging whether the high-frequency generator tripping of each return direct current line after the bipolar locking occurs under the control action of the frequency regulation and safety and stability scheme of the system or not according to the comparison result.
5. The method for monitoring and checking the direct-current blocking dynamic frequency of the asynchronous power grid according to claim 4, wherein the method comprises the following steps: the step of analyzing the response process of the frequency of each return direct current line under the action of system primary frequency modulation, load frequency response and safety and stability measures according to the required real-time data of power grid operation so as to calculate the frequency peak value of each return direct current line comprises the following steps:
the system is equivalent to a unit, a first-order differential equation is adopted to describe the dynamic process of the system frequency deviation according to the required real-time data of the power grid operation, and a time domain expression of the system frequency deviation is solved through time domain simulation, wherein the time domain expression delta f (t) of the system frequency deviation is as follows:
Δ f ( t ) = 50 Δ P D + 1 R [ 1 - 1 + ( a + c b ) 2 c o s ( b t + a r c t a n a + c b ) e - a t ] ,
wherein, m ═ M', t is time, Pm0For normal operation or for instantaneous generator power, Δ P, before bipolar blocking of the DC line occursGFor chain of the amount of cutting machines, P0For normal operation or load power before bipolar blocking of the DC line occurs, omega0For normal operation or for the instantaneous generator speed before bipolar blocking of the DC line occurs, KLFor frequency adjustment coefficient of load, f0To be the frequency of the system,is the system frequency f0K ofLPower of the equation,. DELTA.PDCIs the algebraic sum of the DC power boost and the power that the DC line delivers less power due to bipolar latching,for normal operation or the instant load power before the bipolar locking of the direct current line occurs, R' is the equivalent difference adjustment coefficient of the primary frequency modulation of the system after the action of the linkage cutter occurs,r is the serial number of the unit with spare capacity in the system operation after the action of the chain cutter occurs, n is the total serial number of all the units in the system operation after the action of the chain cutter occurs, (P)m0)rAnd (P)m0)nThe generator sets with the serial numbers r and n respectively operate normally or the instantaneous generator power before the bipolar locking of the direct current circuit occurs,the unit adjusting power of the unit with the sequence number r after the action of the linkage cutter occurs, wherein M is equal to M ', M' is an equivalent inertia constant of a system after the action of the linkage cutter occurs, and T is a time constant;
obtaining the frequency deviation peak value of each return direct current line according to the time domain expression of the system frequency deviation delta f (t), wherein the frequency deviation peak value of each return direct current line meets the requirement of time tThe corresponding frequency offset value.
6. The method for monitoring and checking the direct-current blocking dynamic frequency of the asynchronous power grid according to claim 5, wherein the method comprises the following steps: the method comprises the following steps of equivalently using the system as a unit, describing the dynamic process of the system frequency deviation by adopting a first-order differential equation according to required real-time data of power grid operation, and solving a time domain expression of the system frequency deviation through time domain simulation, wherein the step comprises the following steps of:
the system is equivalent to a unit, a first order differential equation is adopted to describe the dynamic process of the system frequency deviation according to the required real-time data of the power grid operation, and the dynamic process description equation of the system frequency deviation is as follows:
M ′ d d t Δ ω ω 0 + ( 1 + 1 R ′ β ( t ) ) P m 0 - ΔP G ω 0 Δ ω ω 0 + ( K L - 1 ) P L 0 ω 0 · Δ ω ω 0 = P m 0 - ΔP D C ω 0 - P 0 f 0 K L + ΔP D C ω 0 ,
wherein β (t) is step input, Δ ω is rotational speed deviation of system output,
solving a dynamic process description equation of the system frequency deviation by adopting Laplace transformation to obtain a Laplace rotation speed deviation delta omega(s) of the system, wherein an expression of the Laplace rotation speed deviation delta omega(s) of the system is as follows:
Δ ω ( s ) = 1 + T s s [ MTs 2 + ( M + D T ) s + D + 1 R ] · Δ P ,
wherein s is a Laplace operator;
and performing time domain simulation according to the Laplace rotation speed deviation delta omega(s) of the system, and calculating a time domain expression delta f (t) of the frequency deviation of the system.
7. The method for monitoring and checking the direct-current blocking dynamic frequency of the asynchronous power grid according to claim 6, wherein the method comprises the following steps: the method comprises the following steps of comparing the frequency peak value of each return direct current line with the set frequency of the high-frequency generator tripping of the system, and judging whether the high-frequency generator tripping of each return direct current line after the bipolar locking occurs under the control action of the frequency regulation and safety and stability scheme of the system according to the comparison result, wherein the steps are as follows:
if the frequency peak value of each return direct current line exceeds the set frequency of the high-frequency generator tripping of the system, judging that the high-frequency generator tripping of each return direct current line after the bipolar locking occurs under the control action of the frequency regulation and safety and stability scheme of the system; and otherwise, judging that the high-frequency generator tripping of each return direct current line after the bipolar locking cannot occur under the control action of the frequency regulation and safety and stability scheme of the system.
8. The method for monitoring and checking the direct-current blocking dynamic frequency of the asynchronous power grid according to any one of claims 1 to 6, wherein the method comprises the following steps: the operations performed in the process of modifying the safety measure or the system dc power sending scheme when the current return dc line fails include, but are not limited to: reducing the power transmission power of the current return direct current line; the quantity of chain cutters is increased; increasing the primary frequency modulation rotation reserve capacity; the interlocking cutter preferentially cuts off the hydroelectric generating set with small rotational inertia and large capacity or with the function of back adjustment.
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