CN109193734A - The adaptability teaching method and system that alternating current-direct current power grid restores direct current system - Google Patents
The adaptability teaching method and system that alternating current-direct current power grid restores direct current system Download PDFInfo
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- CN109193734A CN109193734A CN201811101801.1A CN201811101801A CN109193734A CN 109193734 A CN109193734 A CN 109193734A CN 201811101801 A CN201811101801 A CN 201811101801A CN 109193734 A CN109193734 A CN 109193734A
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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
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- 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
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- 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 the adaptability teaching method and system that alternating current-direct current power grid restores direct current system, when direct current system starts, according to starting active power, the reactive power of direct current system, the capacity of short circuit of DC converter bus and the fm capacity of AC system, AC system voltage and frequency safety when starting to direct current system are assessed；After direct current system starting meets safety conditions, direct current system power rise in multi-infeed HVDC system is to during specified, using more feed-in broad sense short-circuit ratioes to multi-infeed HVDC system progress static electric voltage stability verification；Multi-infeed HVDC system resume operation in static electric voltage stability after, assessed using the risk that electric parameter and the relationship of mutual impedance the direct current system restored occur because of the operation of recovery process commutation failure.This invention ensures that multi-infeed HVDC system can make full use of DC adjustment ability in the technical security for restoring early stage starting direct current system, accelerate the process that system is restored.
Description
Technical field
This disclosure relates to which power system automation technology field, restores direct current system more particularly to alternating current-direct current power grid
Adaptability teaching method and system.
Background technique
When the receiving end drop point of multiple-circuit line transmission line of electricity compares concentration, when electrical distance is closer, these direct current systems with by
End AC network constitutes multi-infeed HVDC system (MIDC) together.Since each converter station drop point is intensive, so that inverter side converter station
Between electrical couplings it is stronger, alternative mechanism becomes more complicated.Multi-infeed HVDC transmission system generation is stopped greatly both at home and abroad at present
Recovery operation experience after electricity is seldom, and the recovery that each bulk power grid reply is had a power failure on a large scale all is finally to restore straight using exchange is first restored
The strategy of stream.
DC transmission system has that transmission power is big, starts and the features such as fast, controllability is strong of regulating the speed, and these features
The recovery of rack is accelerated in the adjusting for being conducive to black starting-up initial stage power.Therefore research can be accelerated in recovery early stage starting direct current
The process of power system restoration, is of great significance.However receiving end AC network is weak in recovery process, if blindly starting direct current, increasing
Add dc power, is likely to result in AC system electric voltage frequency and crosses safety limit, static electric voltage stability problem and direct current
The commutation failure of itself, therefore the adaptability teaching method that alternating current-direct current power grid restores direct current system is provided, guarantee is restored
Safety and stability is most important.
Lack the complete adaptability that alternating current-direct current power grid restores direct current system in reply multi-infeed HVDC system recovery at present
Appraisal procedure.Existing literature some only considered the condition that direct current system starts in the case of black starting-up in single feed-in direct current system,
Without being related to the recovery of multi-infeed systems；The peace for guaranteeing system voltage steady stability can be provided using broad sense short-circuit ratio (GSCR)
Staff cultivation can calculate influencing each other for multi-infeed HVDC system voltage, but these using more feed-in interaction factors (MIIF)
Theory can not directly apply to the recovery of multi-infeed HVDC system.
By being analyzed above as it can be seen that the prior art does not solve the alternating current-direct current power grid in multi-infeed HVDC system recovery process
The adaptability teaching problem that direct current system is restored.
Summary of the invention
In order to solve the deficiencies in the prior art, the adaptability restored present disclose provides alternating current-direct current power grid to direct current system is commented
Estimate method, by the intensity index of the alternating current-direct current power grid in multi-infeed HVDC system recovery process, it is extensive direct current system can be assessed
The risk of multiple safety, stability and direct current system commutation failure.
To achieve the goals above, the application uses following technical scheme:
The adaptability teaching method that alternating current-direct current power grid restores direct current system, comprising:
When direct current system starts, according to starting active power, the reactive power of direct current system, the short circuit of DC converter bus
The fm capacity of capacity and AC system, AC system voltage and frequency safety when starting to direct current system are commented
Estimate；
After direct current system starting meets safety conditions, the direct current system power rise in multi-infeed HVDC system is arrived
In specified process, static electric voltage stability verification is carried out to multi-infeed HVDC system using more feed-in broad sense short-circuit ratioes；
Multi-infeed HVDC system resumes operation meet static electric voltage stability after, utilize the pass of electric parameter and mutual impedance
The risk that system direct current system restored occurs because of the operation of recovery process commutation failure is assessed.
As further technical solution, when direct current system starts alternating voltage security evaluation, measured in advance direct current system
The reactive power injected when system starting to AC system；
In recovery process, AC network framework is obtained, calculates the capacity of short circuit of direct current system change of current bus；
The idle function that capacity of short circuit and direct current system based on direct current system change of current bus are injected when starting to AC system
Rate defines the AC system voltage security coefficient of reliability of direct current system starting, calculates voltage security coefficient of reliability；
It is compared according to voltage security coefficient of reliability with given threshold, if more than given threshold, then it is assumed that direct current system
Alternating voltage is safe when system starting, otherwise it is assumed that alternating voltage exists across the wind of safety limit when direct current system starts
Danger.
As further preferred technical solution, the AC system voltage security reliability system of direct current system i starting is defined
Number Kdv,i:
Wherein, the capacity of short circuit of the change of current bus of direct current system i is Sac,i, it is Q to AC system injection reactive poweri。
As further technical solution, the step of the frequency security assessment of direct current system starting, specifically:
Predefine the active power injected when direct current system starting to AC system；
In recovery process, the generating set data having been turned in AC network are obtained in real time, and calculating entirely has restored to exchange
The power backup total amount that total coefficient of frequency modulation of system and certain units for having frequency modulation frequency modulation ability provide；
Active power, total coefficient of frequency modulation and the function injected when being started according to aforementioned obtained direct current system to AC system
The spare total amount of rate calculates the frequency security coefficient of reliability of direct current starting；
Frequency security coefficient of reliability is compared with given threshold, if more than given threshold, then it is assumed that direct current system opens
AC system frequency is safe when dynamic, otherwise it is assumed that AC system frequency exists across safety limit when direct current system starts
Risk.
As further preferred technical solution, AC system frequency security reliability when direct current system i starting is defined
COEFFICIENT Kdf,i:
Wherein, the total coefficient of frequency modulation for entirely having restored AC system is Ks, direct current system i start to AC system inject
Active power is Δ Pi, the power backup total amount that certain units for having frequency modulation frequency modulation ability provide is Δ PG。
As further technical solution, quiescent voltage is carried out to multi-infeed HVDC system using more feed-in broad sense short-circuit ratioes
Stability verification step, specifically:
The rated power of direct current system and the direct current system restored that determination will restore；
The AC system network architecture for determining current Restoration stage, current AC network is equivalent at N-terminal-pair network, it calculates
The port n equivalent AC system admittance matrix and the port n equivalent AC system impedance matrix；
The broad sense short-circuit ratio of multi-infeed HVDC system is calculated, and multi-infeed HVDC system is calculated according to broad sense short-circuit ratio
Static voltage stability coefficient of reliability；
Static voltage stability coefficient of reliability is compared with given threshold, if more than given threshold, then it is assumed that restores n-th
Quiescent voltage collapse accident will not occur for direct current system, otherwise it is assumed that restoring nth direct current system be possible to that static state can occur
Collapse of voltage accident.
As further preferred technical solution, in recovery process, if having there is n-1 direct current system successfully to restore, connect
Get off nth direct current system to be restored, nth direct current system not yet starts, and first assumes that nth direct current system is recovered, then
The AC system restored can be equivalent to the port n AC network, each port connects a direct current system, then n feed-in direct current
The GSCR expression formula of system is as follows:
P in formulaNiI ∈ (1 ... n) is the rated power of n direct current system；[Bij]n×nFor the port n equivalent AC system
Admittance matrix；[Zij]n×nFor the port n equivalent AC system impedance matrix.
As further preferred technical solution, static voltage stability coefficient of reliability when direct current system i restores is defined
Kds,n:
Wherein GSCR is the broad sense short-circuit ratio of previous step technical solution multi-infeed HVDC system calculated.
As further technical solution, using electric parameter and the relationship of mutual impedance to the direct current system restored because extensive
The step of operation of multiple process and the risk that commutation failure occurs are assessed, specifically:
Reactive capability curve when the biggish primary equipment of starting current starts is obtained, the peak of reactive capability curve is obtained
Value；
When executing operation at i-node, measurement obtains the voltage U of i-node at this timei；
Measurement obtains the voltage U of DC converter bus j node at this timej；
It determines the network architecture of AC system at this time, calculates the mutual impedance X of j node and i-nodeji；
Obtain the running shutdown angle γ of direct current system j at this timejWith Advanced firing angle βj；
Calculating has restored the coefficient of reliability that commutation failure does not occur for direct current system j
The coefficient of reliability that commutation failure does not occur is compared with given threshold, if more than given threshold, then this time
When being operated at point i, commutation failure will not occur for direct current system j, and otherwise, there are the risks of commutation failure.
As further preferred technical solution, using alternating current-direct current electric parameter and mutual impedance physical quantity, definition has restored
The coefficient of reliability of commutation failure does not occur for direct current system
In formula: j node is the change of current bus for the direct current system j being currently running, and i-node is to cause AC system voltage
The ac bus of bust operation；Uj、UiRespectively i-node operate before j node and i-node voltage；XjiFor j node
Mutual impedance between i-node；Qi,peakThe reactive power peak value absorbed when being operated for i-node from AC system；γj、βj
Respectively direct current system j is in alternating voltage UjUnder shutdown angle and Advanced firing angle；γminIt is turned off for the limit of direct current system j
Angle.
The adaptability teaching system that alternating current-direct current power grid restores direct current system, comprising:
Direct current system starts assessment unit, when direct current system starts, according to the starting active power of direct current system, idle function
Rate, the capacity of short circuit of DC converter bus and the fm capacity of AC system, AC system electricity when starting to direct current system
Pressure and frequency safety are assessed；
Static electric voltage stability assessment unit, after direct current system starting meets safety conditions, multi-infeed HVDC system
Direct current system power rise in system carries out multi-infeed HVDC system using more feed-in broad sense short-circuit ratioes to during specified
Static electric voltage stability verification；
Commutation failure risk assessment unit, multi-infeed HVDC system resume operation in static electric voltage stability after, benefit
The direct current system restored occurs because of the operation of recovery process with electric parameter and the relationship of mutual impedance the wind of commutation failure
It is assessed danger.
Compared with prior art, the beneficial effect of the disclosure is:
The adaptability teaching method that the alternating current-direct current power grid that the application provides restores direct current system, both ensure that direct current system
Safety when starting, in turn ensure multi-infeed HVDC system resume operation in static electric voltage stability；Also innovative simultaneously
Because of certain operations of recovery process commutation occurs for land productivity electric parameter and the relationship of mutual impedance to the direct current system restored
The risk of failure is assessed.Therefore this invention ensures that multi-infeed HVDC system is in the technology for restoring early stage starting direct current system
Safety can make full use of DC adjustment ability, accelerate the process of entire power system recovery.
Detailed description of the invention
The accompanying drawings constituting a part of this application is used to provide further understanding of the present application, and the application's shows
Meaning property embodiment and its explanation are not constituted an undue limitation on the present application for explaining the application.
Fig. 1 is the multi-infeed HVDC system artificial circuit of the embodiment of the present application；
Fig. 2 is that the change of current of the embodiment of the present application met when the direct current system that direct current starting security evaluation requires starts is female
Line voltage；
Fig. 3 is that the direct current that meets of the embodiment of the present application starts security evaluation requirement (line pointed by Uac1) and is unsatisfactory for
Direct current starts change of current busbar voltage contrast schematic diagram when security evaluation requires the direct current system starting of (line pointed by Uac2)；
Fig. 4 is the multi-infeed HVDC system direct current function for meeting static electric voltage stability assessment and requiring of the embodiment of the present application
The alternating voltage schematic diagram of rate recovery process；
Fig. 5 is the multi-infeed HVDC system direct current for being unsatisfactory for static electric voltage stability assessment and requiring of the embodiment of the present application
The alternating voltage schematic diagram of power recovery process；
Fig. 6 be the embodiment of the present application son meet direct current system commutation failure assessment require (curve pointed by DL3) with
It is unsatisfactory for the direct current system of the recovery shutdown angle comparison signal that the assessment of direct current system commutation failure requires (curve pointed by DL2)
Figure；
Specific embodiment
It is noted that following detailed description is all illustrative, it is intended to provide further instruction to the application.Unless another
It indicates, all technical and scientific terms used herein has usual with the application person of an ordinary skill in the technical field
The identical meanings of understanding.
It should be noted that term used herein above is merely to describe specific embodiment, and be not intended to restricted root
According to the illustrative embodiments of the application.As used herein, unless the context clearly indicates otherwise, otherwise singular
Also it is intended to include plural form, additionally, it should be understood that, when in the present specification using term "comprising" and/or " packet
Include " when, indicate existing characteristics, step, operation, device, component and/or their combination.
Electrical coupling for the recovery of multi-infeed HVDC system, since each converter station drop point is intensive, between inverter side converter station
Close strong, alternative mechanism complexity.All using direct current system as finally restoring in the recovery policy that the reply of domestic external power grid is had a power failure on a large scale
Target cannot play the advantage that direct current system capacity is big, starting adjusting is fast, slow down the process of system recovery.The present invention makes more
Feed-in direct current system initial stages of restoration starts direct current system, becomes feasible using the advantage of direct current.
The adaptability problem that the present invention restores direct current system for alternating current-direct current power grid in multi-infeed HVDC system recovery mentions
Solution is gone out.Adaptability is quantitatively evaluated by coefficient of reliability.It can prevent multi-infeed HVDC system from electricity occur
Press frequency out-of-limit, quiescent voltage collapse and direct-current commutation failure problem.
In embodiments herein, for the adaptability teaching method that alternating current-direct current power grid restores direct current system, from three
A aspect is introduced, and is respectively: direct current system starts safety evaluation method, static electric voltage stability appraisal procedure, direct current system
System commutation failure appraisal procedure.
Wherein, direct current system starts safety evaluation method, predominantly prevents direct current system from bringing when starting to AC system
Reactive power and active power impact cause alternating voltage and frequency and exceed safe range.Need the starting according to direct current system
Active power, reactive power, the capacity of short circuit of DC converter bus and the fm capacity of AC system start direct current system
When AC system voltage and frequency safety assessed.
Alternating voltage and frequency is caused to change the idle and active impact of AC system when direct current system starts.Direct current system
System starting security evaluation includes alternating voltage security evaluation and frequency security assessment.
Since startup stage direct current system conveying active power is very low, the reactive power that direct current system absorbs is less than filter
The reactive power of sending, cause inverter side change of current bus it is practical be to AC system convey it is idle, cause alternating voltage to increase.One
As for, the safe range of voltage change is 0.1UNIf the capacity of short circuit of the change of current bus of known direct current system i is Sac,i, to
It is Q that AC system, which injects reactive power,i, then voltage security constraint condition can be estimated according to the definition of capacity of short circuit are as follows:
Define the AC system voltage security coefficient of reliability K of direct current system i startingdv,i:
So as to pass through Kdv,iThe voltage security of direct current system starting is assessed.Consider estimation error and measurement
The uncertain factors such as error, work as Kdv,iWhen > 1.2, it is believed that ac and dc systems can adapt to the voltge surge of direct current system starting.
The alternating voltage safety evaluation method specific implementation step of direct current system starting are as follows:
(1) in black starting-up experiment, to the reactive power Q of AC system injection when measured in advance direct current system startsi；
(2) in recovery process, AC network framework is obtained in real time, calculates the capacity of short circuit of direct current system change of current bus
Sac,i；
(3) the voltage security coefficient of reliability K of direct current starting is calculateddv,i；
(4) if Kdv,i> 1.2, then it is assumed that alternating voltage is safe when direct current system starts；
(5) if Kdv,i≤ 1.2, then it is assumed that alternating voltage exists across the risk of safety limit when direct current system starts.
Direct current has to convey certain power when starting, and causes the raising of receiving end AC system frequency.In general, frequency
The range of rate variation is 0.1Hz, if it is Δ P that direct current system i, which starts the active power injected to AC system,iIf entire extensive
Reestablish diplomatic relations streaming system total coefficient of frequency modulation be Ks, and the power backup total amount that certain units for having frequency modulation frequency modulation ability provide is Δ
PG, then can be by frequency security constraint representation are as follows:
Wherein KsCalculation method are as follows:
Ks=(KG1+…+KGn)+(KL1+…+KLm) (4)
K in formulaGiI ∈ (1 ... n) is the primary frequency modulation coefficient of all units for participating in frequency modulation；KLjJ ∈ (1 ... m) is institute
There is a coefficient of frequency of load.Generally there is KG> > KL, thus total coefficient of frequency modulation K of AC systemsIt is approximately the hair having been turned on
The sum of coefficient of frequency modulation of motor.
Define AC system frequency security reliability COEFFICIENT K when direct current system i startingdf,i:
So as to pass through Kdf,iThe frequency safety of direct current system starting is assessed.Consider estimation error and measurement
The uncertain factors such as error, work as Kdf,iWhen > 1.2, it is believed that ac and dc systems can adapt to the frequency impact of direct current system starting.
The frequency security appraisal procedure specific implementation step of direct current system starting are as follows:
(1) in black starting-up experiment, the active power Δ P injected when direct current system starting to AC system is predefinedi；
(2) in recovery process, the generating set data having been turned in AC network are obtained in real time, calculate KsWith Δ PG；
(3) the frequency security coefficient of reliability K of direct current starting is calculateddf,i；
(4) if Kdf,i> 1.2, then it is assumed that AC system frequency is safe when direct current system starts；
(5) if Kdf,i≤ 1.2, then it is assumed that AC system frequency exists across the wind of safety limit when direct current system starts
Danger.
About static electric voltage stability appraisal procedure, for guaranteeing the direct current system power rise in multi-infeed HVDC system
During specified, quiescent voltage collapse accident does not occur for ac and dc systems.It is right using more feed-in broad sense short-circuit ratioes (GSCR)
Multi-infeed HVDC system carries out static electric voltage stability verification.
For multi-infeed HVDC system in the recovery process after having a power failure on a large scale, AC system intensity is weaker, if blindly starting all
The direct current system of entry condition is met, then during the power of these direct current systems is gradually restored to specified, system is deposited
In the risk that quiescent voltage collapse occurs.Since the broad sense short-circuit ratio (GSCR) of multi-infeed HVDC system has with static voltage stability
Direct relation, therefore the static electric voltage stability in multi-infeed HVDC system recovery process can be assessed using the value of GSCR.Specifically
Method is as follows:
In recovery process, if system has had n-1 direct current system successfully to restore, next to restore nth direct current system
It unites (nth direct current system not yet starts).First assume that nth direct current system is recovered, then the exchange system that can will have restored
System is equivalent to the port n AC network, and each port connects a direct current system.Then the GSCR expression formula of n feed-in direct current system is as follows:
P in formulaNiI ∈ (1 ... n) is the rated power of n direct current system；[Bij]n×nFor the port n equivalent AC network
Admittance matrix；[Zij]n×nFor the impedance matrix of the port n equivalent AC network.It could be theoretically argued that as GSCR > 2, exchange system
It is specified without quiescent voltage crash issue that system has enough intensity that the power of all direct current systems is supported to be restored to, extensive at this time
The power of multiple nth direct current system is perfectly safe；As GSCR < 2, AC system cannot support all direct current system power
Be restored to it is specified, at this time restore nth direct current system there are the hidden danger that quiescent voltage collapses.
Define multi-infeed HVDC system static voltage stability coefficient of reliability K when nth direct current system is restoredds,n:
So as to pass through Kds,nThe static electric voltage stability restored to nth direct current system is assessed.Consider measurement
The uncertain factors such as error, work as Kds,nWhen > 1.1, it is believed that AC system has sufficient intensity to support including nth direct current
The power of all direct current systems is restored to specified, and quiescent voltage crash issue will not occur.During multi-infeed HVDC system restores
Static electric voltage stability appraisal procedure specific implementation step are as follows:
(1) the rated power P of determination will restore direct current system and the direct current system restoredNii∈(1…n)；
(2) the AC system network architecture of current Restoration stage is determined；
(3) current AC network is equivalent at N-terminal-pair network, calculate [Bij]n×nOr [Zij]n×n；
(4) the broad sense short-circuit ratio GSCR of multi-infeed HVDC system is calculated；
(5) multi-infeed HVDC system static voltage stability coefficient of reliability K is calculatedds,n；
(6) if Kds,n> 1.1, then it is assumed that quiescent voltage collapse accident will not be occurred by restoring nth direct current system；
If Kds,n≤ 1.1, then it is assumed that restore nth direct current system and be possible to that quiescent voltage collapse accident can occur.
Direct current system commutation failure appraisal procedure causes primarily directed to certain operations in Power System Restoration Process and hands over
The phenomenon that galvanic electricity pressure declines suddenly and leads to the direct current system commutation failure of recovery of other positions.Alternating voltage is caused to decline
Operation includes starting new direct current system, investment induction conductivity and putting into the very big equipment of other starting currents.Present invention wound
Assess whether direct current system can occur commutation failure by electric parameter and the relationship of mutual impedance to new property, it is convenient and high
Effect.
Electric system will be operated constantly in recovery process, certain operations such as starting of direct current system, induction electric
The starting etc. of the investment of machine load and the very big primary equipment of other starting currents can cause the prominent of AC system voltage moment
Drop.Direct-flow inverter is easy that commutation failure occurs because of alternating voltage bust, and a direct-current commutation failure be easy to cause other
Chain commutation failure occurs for direct current, and consequence is serious.Therefore The present invention gives direct current system commutation failure appraisal procedures.It is utilized
The physical quantitys such as alternating current-direct current electric parameter and mutual impedance define and have restored the coefficient of reliability that commutation failure does not occur for direct current system
In formula: j node is the change of current bus for the direct current system j being currently running, and i-node is to cause AC system voltage
The ac bus of bust operation；Uj、UiRespectively i-node operate before j node and i-node voltage；XjiFor j node
Mutual impedance between i-node；Qi,peakThe reactive power peak value absorbed when being operated for i-node from AC system；γj、βj
Respectively direct current system j is in alternating voltage UjUnder shutdown angle and Advanced firing angle；γminIt is turned off for the limit of direct current system j
Angle.
Pass throughIt can assess whether direct current system j can send out because of the operation for leading to alternating voltage bust at i-node
Raw commutation failure.In view of factors such as estimation error and measurement errors, it is believed that whenWhen, direct current system will not change
Mutually fail, the operation at i-node can execute；WhenWhen, it is believed that direct current system is there are the risk of commutation failure at this time,
It is not recommended that executing the operation at i-node.The specific implementation step of direct current system commutation failure appraisal procedure is as follows:
(1) the black starting-up experimental stage obtains reactive capability curve when the biggish primary equipment of starting current starts in advance,
Using the peak value of reactive capability curve as Qi,peak；
(2) when executing operation at i-node, measurement obtains the voltage U of i-node at this timei；
(3) measurement obtains the voltage U of DC converter bus j node at this timej；
(4) network architecture for determining AC system at this time, calculates the mutual impedance X of j node and i-nodeji；
(5) the direct current system j of acquisition at this time running shutdown angle γjWith Advanced firing angle βj；
(6) it calculates and has restored the coefficient of reliability that commutation failure does not occur for direct current system
(7) ifWhen then being operated at node i at this time, commutation failure will not occur for direct current system j；
(8) ifWhen then executing operation at node i at this time, there are the risks of commutation failure by direct current system j；
The specific derivation process of the coefficient of reliability of commutation failure does not occur for direct current system, as follows:
The essence of commutation failure is that inverter shutdown angle γ is less than the intrinsic limit shutdown angle γ of thyristormin, this explanation is by γ
<γminCriterion as commutation failure.The calculation formula of known shutdown angle γ are as follows:
β is advanced shutdown angle, I in formuladFor DC current, KiFor inverter side converter power transformer no-load voltage ratio, XciFor equivalent commutation
Reactance, size are about converter power transformer leakage reactance, ViFor the line voltage virtual value of change of current bus.If ViReduce suddenly, at this time β and Ki
Have little time to change, IdIt can increase suddenly, can be obtained according to formula (9), γ can reduce suddenly, as γ < γminWhen, inverter commutation is lost
It loses.Thus, the bust of change of current busbar voltage is the main reason for causing direct-current commutation failure.Induction machine and direct current system
Start-up operation will cause alternating voltage bust because they electric current is especially big on startup, can transient absorption it is largely idle, lead
AC system voltage is caused to reduce suddenly.
Assuming that the idle function for putting into induction motor load at certain moment node i or being absorbed when starting direct current system from system
Rate peak value is Qi,peak, causing voltage landing peak value at node j is Δ Uj,peak, next derive Δ Uj,peakAnd Qi,peakBetween
Relationship.
Transmission line of electricity generally has reactance to be much larger than resistance, and route both end voltage phase angle difference very little, changes in alternating voltage
It is linear system that PQ decomposition method can be used in the case where less by AC system approximation abbreviation:
The inverse matrix for being multiplied by admittance matrix simultaneously to the both members of formula (10) can be obtained:
It can be obtained by formula (11):
It can thus be concluded that:
The mutual impedance X between the landing and node i, j of node j voltage can be obtained by formula (13)jiIt is approximate directly proportional.Reduce mutual resistance
It is anti-to can reduce node i and absorb the idle influence to node j voltage.Therefore, it by operation bus and neighbouring has resumed operation
Mutual impedance X between direct current system change of current busjiIt is also the important safety constraint during multi-infeed HVDC system restores.Guarantee
XjiLess than some value, it just can ensure that commutation failure does not occur for the direct current system restored.To XjiThe detailed solution process of constraint is such as
Under:
If j node is the change of current bus of direct current system j, i-node has a DC transmission system or induction electric to be launched
Machine, i-node voltage are Ui。Start the transient voltage minimum of induction machine or direct current system moment j node for i-node, then
There is following relationship:
UjFor the original voltage of j node.Next voltage is soughtThe shutdown angle of lower direct current system inverter
If the shutdown angle of direct current system j is γ before operatingj, gating advance angle βj, DC voltage, electric current be respectively Ud、
Id；Alternating voltage in starting transientUnder DC voltage, electric current be respectively
In direct current system j, it is known that:
Therefore it can obtain:
It is constant in the power short time transmitted due to direct current system, have
The relationship of DC voltage and commutation voltage are as follows:
Therefore the ratio between front and back DC voltage must can be operated are as follows:
Joint type (16), (17), (18) can be acquiredAre as follows:
Guarantee that the condition of commutation failure does not occur for direct current j are as follows:
The mutual impedance of commutation failure does not occur for the available guarantee direct current system j of joint type (13), (14), (20) and (21)
XjiFinal security constraint are as follows:
Therefore it can define and restore the coefficient of reliability that commutation failure does not occur for direct current system
And work asWhen, meet the security constraint of formula (22), theoretically commutation failure does not occur for direct current system j；WhenWhen, it is unsatisfactory for the security constraint of formula (22), theoretically commutation failure will occur for direct current system j.
In order to start direct current system early stage multi-infeed HVDC system restores in the embodiment of the present application, accelerate system
Recovering process, the adaptability restored the present invention provides the alternating current-direct current power grid in multi-infeed HVDC system recovery to direct current system are commented
Estimate method.The intensity index of the alternating current-direct current power grid in multi-infeed HVDC system recovery process is defined, it is extensive to assess direct current system
The risk of multiple safety, stability and direct current system commutation failure.The adaptability that alternating current-direct current power grid restores direct current system is commented
Estimate method, including direct current system starting safety evaluation method, static electric voltage stability appraisal procedure and direct current system commutation failure
Appraisal procedure.The above appraisal procedure starts and restores direct current early stage recovery for multi-infeed HVDC system and provides reference, energy
Enough accelerate multi-infeed HVDC system recovering process.
Another examples of implementation of the application disclose the adaptability teaching system that alternating current-direct current power grid restores direct current system,
Include:
Direct current system starts assessment unit, when direct current system starts, according to the starting active power of direct current system, idle function
Rate, the capacity of short circuit of DC converter bus and the fm capacity of AC system, AC system electricity when starting to direct current system
Pressure and frequency safety are assessed；
Static electric voltage stability assessment unit, after direct current system starting meets safety conditions, multi-infeed HVDC system
Direct current system power rise in system carries out multi-infeed HVDC system using more feed-in broad sense short-circuit ratioes to during specified
Static electric voltage stability verification；
Commutation failure risk assessment unit, multi-infeed HVDC system resume operation in static electric voltage stability after, benefit
The direct current system restored occurs because of the operation of recovery process with electric parameter and the relationship of mutual impedance the wind of commutation failure
It is assessed danger.
Above system can realize that relevant technology contents are referring to alternating current-direct current power grid above-mentioned to straight by computer program
The adaptability teaching method that streaming system restores, details are not described herein again.
In order to better illustrate the application technical solution effect, carry out corresponding emulation case explanation separately below:
Start appraisal procedure simulating, verifying about direct current system
Artificial circuit is three infeed HVDC Systems using CIGRE master pattern as shown in Figure 1.Change of current bus is specified
Voltage UNFor 230kV, direct current system rated power PNFor 1000MW.Direct current system DL2, DL3 is stopped transport, and direct current system DL1 is using single
The mode of 10% rated current of pole total pressure starts, startup power 0.1PN.It is to exchange when stable state after known direct current system starting
System injection reactive power is about 450MVar, can obtain S by voltage stability constraintacAt least 4500MVA, i.e., change of current bus from
Impedance ZiiNo more than 11.76 Ω.To Zii=8 Ω (Sac,i=6612MVA, Kdc,i=1.47 > 1.2) it is emulated, starting emulation
Afterwards, start direct current system DL1 in t=0.45s.
From Figure 2 it can be seen that change of current busbar voltage is suddenly fallen to from 0.98pu rapidly when starting direct current system DL1
0.93pu., then slowly fluctuation rises, and is finally reached steady-state value 1.05pu. or so, and stable state variable quantity is 0.07pu., and voltage is not
Occur out-of-limit.
Then the self-impedance Z of change of current busiiIt is revised as 16 Ω (Sac,i=3306MVA, Kdc,i=0.73 < 1.2) again into
Row emulation, obtained voltage curve are made comparisons with the curve of Fig. 2, obtain Fig. 3.Wherein the voltage curve of top is ZIi, 2=16 Ω
When, Uac2For 1.13pu..The curve of lower section is ZIi, 1When=8 Ω, Uac1For 1.05pu..Work as ZIi, 2When=16 Ω, Kdc,i=0.73
< 1.2, change of current busbar voltage elevation amplitude is close to 0.15pu., steady-state value Uac2Reach 1.13pu., voltage out-of-limit, with theory analysis
It is consistent.Above-mentioned emulation demonstrates the validity of direct current system starting security evaluation.
About static electric voltage stability appraisal procedure simulating, verifying
Utilize artificial circuit shown in Fig. 1.DL1 in three infeed HVDC Systems, DL2, DL3 is all in operating status, function
Rate rises to rated power 1000MW from 0.Setting AC system line parameter circuit value keeps the broad sense of multi-infeed HVDC system short-circuit first
Than GSCR=3.234 > 2, i.e. Kds,i=1.617 > 1.1.Obtain the voltage effective value simulation waveform of each direct current system change of current bus
For Fig. 4.As shown in figure 4, in Kds,iUnder the premise of > 1.1, the change of current busbar voltage of each direct current system is stablized, multi-infeed HVDC system
System meets static electric voltage stability.
Alternating current circuit parameter is modified, increases the impedance of route to reduce AC system intensity, calculates to obtain alternating current-direct current system again
Broad sense short-circuit ratio GSCR=1.71 < 2 of system, i.e. Kds,i=0.855 < 1.1.Emulation obtains AC system voltage effective value wave again
Shape is Fig. 5.From figure 5 it can be seen that nonlinear acute variation occurs for alternating voltage, minimum voltage is down to 0.7p.u., if being
There are influence generator loads in system, and it will cause alternating voltage collapses.Thus, working as Kds,iWhen < 1.1, direct current system without
Method is with rated power operation, and otherwise static voltage stability problem will occur for ac and dc systems.
Above-mentioned emulation demonstrates the validity of static electric voltage stability appraisal procedure.
About direct current system commutation failure appraisal procedure simulating, verifying
Utilize Fig. 2 artificial circuit.Direct current system DL1 stops transport in three feedthrough systems, and direct current system DL2, DL3 operates normally.
AC system voltage rating UNFor 230kV, direct current system rated power PdN,iIt is all 1000MW.By DL2, the operation power of DL3 is all
It is set as 700MW.Shutdown angle γ=15 ° when DL2, DL3 are with 700MW power normal operation, Advanced firing angle β=31.7 °, most
Small shutdown angle γmin=10 °；Reactive power peak value Q is injected to AC system when DL1 startspeak=700MVar.According to setting
Line parameter circuit value can obtain, the mutual impedance X between DL1, DL2 change of current bus21=8.3 Ω,DL1, DL3 change of current are female
Mutual impedance X between line31=3.7 Ω,Start direct current system DL1 after the system stabilizes, obtains Fig. 6, wherein
Fig. 6 is that the shutdown angle of direct current system DL2, DL3 changes.
As shown in fig. 6, the shutdown angle of DL2 is reduced to 0 when DL1 starting, it is meant that commutation failure occurs；The shutdown of DL3
Although also there is decline at angle, it is greater than minimum turn-off angle, there is no commutation failures.Above-mentioned simulation results show direct current system is changed
The validity of phase failure assessment method.
The foregoing is merely preferred embodiment of the present application, are not intended to limit this application, for the skill of this field
For art personnel, various changes and changes are possible in this application.Within the spirit and principles of this application, made any to repair
Change, equivalent replacement, improvement etc., should be included within the scope of protection of this application.
Claims (10)
1. the adaptability teaching method that alternating current-direct current power grid restores direct current system, characterized in that include:
When direct current system starts, according to starting active power, the reactive power of direct current system, the capacity of short circuit of DC converter bus
And the fm capacity of AC system, AC system voltage and frequency safety when starting to direct current system are assessed；
After direct current system starting meets safety conditions, direct current system power rise in multi-infeed HVDC system is to specified
During, static electric voltage stability verification is carried out to multi-infeed HVDC system using more feed-in broad sense short-circuit ratioes；
Multi-infeed HVDC system resumes operation meet static electric voltage stability after, utilize the relationship pair of electric parameter and mutual impedance
The risk that commutation failure occurs because of the operation of recovery process for the direct current system restored is assessed.
2. the adaptability teaching method that alternating current-direct current power grid as described in claim 1 restores direct current system, characterized in that straight
When streaming system starts alternating voltage security evaluation, to the reactive power of AC system injection when measured in advance direct current system starts；
In recovery process, AC network framework is obtained, calculates the capacity of short circuit of direct current system change of current bus；
The reactive power injected when capacity of short circuit and direct current system based on direct current system change of current bus start to AC system is fixed
The AC system voltage security coefficient of reliability of adopted direct current system starting, calculates voltage security coefficient of reliability；
It is compared according to voltage security coefficient of reliability with given threshold, if more than given threshold, then it is assumed that direct current system opens
Alternating voltage is safe when dynamic, otherwise it is assumed that alternating voltage exists across the risk of safety limit when direct current system starts.
3. the adaptability teaching method that alternating current-direct current power grid as claimed in claim 2 restores direct current system, characterized in that definition
The AC system voltage security coefficient of reliability K of direct current system i startingdv,i:
Wherein, the capacity of short circuit of the change of current bus of direct current system i is Sac,i, it is Q to AC system injection reactive poweri。
4. the adaptability teaching method that alternating current-direct current power grid as described in claim 1 restores direct current system, characterized in that direct current
The step of frequency security assessment of system starting, specifically:
Predefine the active power injected when direct current system starting to AC system；
In recovery process, the generating set data having been turned in AC network are obtained in real time, are calculated and have entirely been restored AC system
Total coefficient of frequency modulation and it is certain have frequency modulation frequency modulation ability unit provide power backup total amount；
Active power, total coefficient of frequency modulation and the power injected when being started according to aforementioned obtained direct current system to AC system is standby
The frequency security coefficient of reliability of direct current starting is calculated with total amount；
Frequency security coefficient of reliability is compared with given threshold, if more than given threshold, then it is assumed that when direct current system starts
AC system frequency is safe, otherwise it is assumed that AC system frequency exists across the wind of safety limit when direct current system starts
Danger.
5. the adaptability teaching method that alternating current-direct current power grid as claimed in claim 4 restores direct current system, characterized in that definition
AC system frequency security reliability COEFFICIENT K when direct current system i startsdf,i:
Wherein, the total coefficient of frequency modulation for entirely having restored AC system is Ks, direct current system i start to AC system inject it is active
Power is Δ Pi, the power backup total amount that certain units for having frequency modulation frequency modulation ability provide is Δ PG。
6. the adaptability teaching method that alternating current-direct current power grid as described in claim 1 restores direct current system, characterized in that utilize
More feed-in broad sense short-circuit ratioes carry out static electric voltage stability verification step to multi-infeed HVDC system, specifically:
The rated power of direct current system and the direct current system restored that determination will restore；
The AC system network architecture for determining current Restoration stage, current AC network is equivalent at N-terminal-pair network, calculate the end n
Mouth equivalent AC system admittance matrix and the port n equivalent AC system impedance matrix；
The broad sense short-circuit ratio of multi-infeed HVDC system is calculated, and multi-infeed HVDC system static state is calculated according to broad sense short-circuit ratio
Voltage stabilization coefficient of reliability；
Static voltage stability coefficient of reliability is compared with given threshold, if more than given threshold, then it is assumed that it is straight to restore nth
Quiescent voltage collapse accident will not occur for streaming system, otherwise it is assumed that restoring nth direct current system be possible to that quiescent voltage can occur
Collapse accident.
7. the adaptability teaching method that alternating current-direct current power grid as claimed in claim 6 restores direct current system, characterized in that restore
In the process, if having there is n-1 direct current system successfully to restore, next to restore nth direct current system, nth direct current system
Not yet start, first assume that nth direct current system is recovered, then the AC system restored can be equivalent to the exchange of the port n
Network, each port connect a direct current system, then the GSCR expression formula of n feed-in direct current system is as follows:
P in formulaNiI ∈ (1 ... n) is the rated power of n direct current system；[Bij]n×nFor the port n equivalent AC system admittance square
Battle array；[Zij]n×nFor the port n equivalent AC system impedance matrix.
8. the adaptability teaching method that alternating current-direct current power grid as described in claim 1 restores direct current system, characterized in that utilize
Electric parameter and the relationship of mutual impedance the direct current system restored occur because of the operation of recovery process the risk of commutation failure
The step of being assessed, specifically:
Reactive capability curve when the biggish primary equipment of starting current starts is obtained, the peak value of reactive capability curve is obtained；
When executing operation at i-node, measurement obtains the voltage U of i-node at this timei；
Measurement obtains the voltage U of DC converter bus j node at this timej；
It determines the network architecture of AC system at this time, calculates the mutual impedance X of j node and i-nodeji；
Obtain the running shutdown angle γ of direct current system j at this timejWith Advanced firing angle βj；
Calculating has restored the coefficient of reliability that commutation failure does not occur for direct current system j
The coefficient of reliability that commutation failure does not occur is compared with given threshold, if more than given threshold, then at this time at node i
When being operated, commutation failure will not occur for direct current system j, and otherwise, there are the risks of commutation failure.
9. the adaptability teaching method that alternating current-direct current power grid as claimed in claim 8 restores direct current system, characterized in that utilize
Alternating current-direct current electric parameter and mutual impedance physical quantity, definition have restored the coefficient of reliability that commutation failure does not occur for direct current system
In formula: j node is the change of current bus for the direct current system j being currently running, and i-node is to cause AC system voltage die
The ac bus of operation；Uj、UiRespectively i-node operate before j node and i-node voltage；XjiFor j node and i
Mutual impedance between node；Qi,peakThe reactive power peak value absorbed when being operated for i-node from AC system；γj、βjRespectively
It is direct current system j in alternating voltage UjUnder shutdown angle and Advanced firing angle；γminAngle is turned off for the limit of direct current system j.
10. the adaptability teaching system that alternating current-direct current power grid restores direct current system, characterized in that include:
Direct current system starts assessment unit, when direct current system starts, according to starting active power, the reactive power of direct current system,
The capacity of short circuit of DC converter bus and the fm capacity of AC system, to direct current system start when AC system voltage and
Frequency safety is assessed；
Static electric voltage stability assessment unit, after direct current system starting meets safety conditions, in multi-infeed HVDC system
Direct current system power rise to during specified, multi-infeed HVDC system is carried out using more feed-in broad sense short-circuit ratioes static
Voltage stability verification；
Commutation failure risk assessment unit, multi-infeed HVDC system resume operation in static electric voltage stability after, utilize electricity
Gas parameter and the relationship of mutual impedance the direct current system restored is occurred because of the operation of recovery process the risk of commutation failure into
Row assessment.
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