CN107732892B - A kind of Overvoltage suppressing method based on the idle control of D.C. high voltage transmission - Google Patents
A kind of Overvoltage suppressing method based on the idle control of D.C. high voltage transmission Download PDFInfo
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
- H02J3/1807—Arrangements for adjusting, eliminating or compensating reactive power in networks using series compensators
-
- 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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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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
- 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]
Abstract
The invention discloses a kind of Overvoltage suppressing methods based on the idle control of D.C. high voltage transmission, it include: step 1, setting direct current transportation inverter side determines gamma kick using forecasting type, and rectification side uses constant current control, according to DC transmission system control principle, LINEARIZED CONTROL equation is obtained；Step 2, the method for operation that near region power grid is fed out according to more direct currents obtains the reactive power flow update equation of direct current near region using P-Q decomposition method, to obtain direct current near region trend lienarized equation；Step 3, system state equation is obtained；Step 4, PI state regulator is obtained.The invention proposes the methods for increasing near region DC inversion side shutdown angle γ progress Overvoltage suppressing, this method is during ac grid voltage seriously increases, angle γ and DC current instruction value are turned off by control inverter side, on the basis of keeping near region to perfect DC transmission system power invariability, the reactive power for promoting inverter consumption in short-term, inhibits the generation of the weak AC network overvoltage of sending end.
Description
Technical field
The present invention relates to high-voltage dc transmission electrical domains, and in particular to a kind of based on the excessively electric of the idle control of D.C. high voltage transmission
Press suppressing method.
Background technique
High voltage dc transmission technology as its possessed by long-distance and large-capacity power transmission, the asynchronous Power System Interconnection field it is excellent
Gesture has obtained quick development in states such as China, India, South Korea, Brazil and has been widely applied.Current source type DC transmission system
Using thyristor as main commutation components, when normal operation, need to consume the reactive power of transmission power 50%~60%.With ±
For the extra-high voltage DC transmission system of 800kV/8000MW, thyristor transverter and converter power transformer are supplied when Operation at full power
Idle nearly 6400Mvar need to be consumed.In order to eliminate influence of a large amount of reactive power consumptions to AC system reactive power flow and voltage's distribiuting,
A large amount of reactive-load compensation equipments are installed in converter station often to realize the reactive balance in station.
However, in the case, once DC transmission system is caused to send power outside due to line fault etc. and is obstructed,
Before reactive-load compensation equipment excision, converter station it is superfluous it is idle will deliver streaming system, easily go out on the ac bus of converter station
Now apparent voltage lifting.Particularly, in HVDC transmission system first stage of construction, the short circuit of sending end converter station near region AC network
Levels of current is relatively low, and voltage regulation capability is weak, possibly even occurs serious overvoltage under this operating condition.In view of DC line
Strategy is restarted after failure, and such overvoltage duration very likely more than converter station overvoltage protection or changes close to 1s
The definite value of the big Trigger Angle monitoring protection of valve is flowed, protection misoperation risk is higher.
The higher problem of voltage that AC system occurs when for direct current low power run, some scholars, which propose, increases near region
Generator improves the strategies such as minimum turn-off angle into phase depth, DC transmission system brownout operation.Wherein, to DC transmission system
When idle control strategy is inquired into when low power run, reactive power consumption, shutdown angle, angle of overlap, DC current etc. is derived and have become
Correlation between amount calculates receiving end converter station shutdown angle and change of current variation connector regulation measure to direct current reactive power consumption
Influence, propose it is non-linear using DC transmission system reactive power consumption, improve minimum turn-off angle can be absorbed it is extra idle, effectively
Solve the problems, such as that ac grid voltage when DC transmission system low power run increases.Also to devise two kinds of high voltage direct current low
Reactive load optimization module, and be applied in practical projects.Occur when these researchs are mainly for direct current low-power transmission
The exchange side higher phenomenon of steady state voltage analyzed, achieve good implementation result, but to DC transmission system failure
The surge characteristic analysis occurred in transient process afterwards is less.
Summary of the invention
The technical problem to be solved by the present invention is to more direct currents to concentrate outer pushing electric network alternating current during single time DC Line Fault
Net overvoltage occurs, and it is an object of the present invention to provide a kind of Overvoltage suppressing method based on the idle control of D.C. high voltage transmission, at single time
During DC Line Fault, near region is promoted in short-term and perfects DC inversion side shutdown angle γ and DC current instruction, is keeping perfecting direct current
Send outside power it is constant on the basis of, increase rectification side inverter reactive power consumption, to inhibit overvoltage.
The present invention is achieved through the following technical solutions:
A kind of Overvoltage suppressing method based on the idle control of D.C. high voltage transmission, comprising:
Step 1, setting direct current transportation inverter side determines gamma kick using forecasting type, and rectification side uses constant current control,
According to DC transmission system control principle, LINEARIZED CONTROL equation is obtained；
Step 2, the method for operation that near region power grid is fed out according to more direct currents obtains the nothing of direct current near region using P-Q decomposition method
Function trend update equation, to obtain direct current near region trend lienarized equation；
Step 3, system state equation is obtained；
Step 4, PI state regulator is obtained.
Further, in step 1, LINEARIZED CONTROL equation:
γ(0)+ Δ γ=γord
KI∫(Id-Iord) dt=α
In formula: γ(0)And Δ γ is respectively inverter side blow-out angle steady-state value and variable quantity, γordFor DC transmission system
The inverter side blow-out angle instruction value of controller output, KIFor DC transmission system current control link integral control coefficient, IdIt is straight
Streaming system electric current steady-state value, IordFor the DC current instruction value of DC transmission system controller output, α is DC transmission system
Rectification side Trigger Angle, α(0)For rectification side Trigger Angle steady-state value.
Further, in step 2, reactive power flow update equation are as follows:
Δ U=-B-1ΔQ′
Wherein,
Δ Q '=[Δ Q1/U1 ΔQ2/U2 … ΔQm/Um]T
Δ U=[Δ U1 ΔU2 … ΔUm]T
In formula, Δ QiIt is i bus idle work variable quantity, Δ UjIt is the voltage variety of j bus, B matrix is system node
The matrix that susceptance part forms in admittance matrix.
Further, in step 2, direct current near region trend lienarized equation are as follows:
ΔU1=K1ΔQ′dc1
ΔU2=K2ΔQ′dc1,
In formula, Δ U1、ΔU2Respectively 1# direct current, 2# DC transmission system sending end converter station ac bus voltage variety,
ΔQ′dc1For 1# direct current, the variable quantity of engineering inverter absorbing reactive power, K1、K2Then it is respectively equal to-B-1In the 1st row i-th column
And the 2nd row i-th arrange element value.
Further, in step 3, system state equation are as follows:
Wherein,
Wherein,
In formula, Ud1(0)It is 1# DC rectifier side DC voltage steady-state value, U1(0)For 1# DC converter station ac bus voltage
Steady-state value, kTFor rectification side converter power transformer no-load voltage ratio, α(0)For rectification side Trigger Angle steady-state value, γ(0)For inverter side blow-out angle
Steady-state value, L are DC line inductance, Id(0)For DC current steady-state value, C is the equivalent capacity of 1# direct current reactive-load compensation equipment,
K1、K2Then it is respectively equal to-B-1In the 1st row i-th column and the 2nd row i-th column element value, R is the electricity of DC transmission system route
Resistance value.
Further, the PI status adjustment implement body design method of step 4 is as follows:
It enables
Its state space and objective function F meet:
The optimum control of existence anduniquess:
Wherein, KpcIt is R-1Half submatrix of a left side of matrix obtained by BP, is the proportionality coefficient matrix of control rate；KIcIt is R-1BP institute
Half submatrix of the right side for obtaining matrix, is the integral coefficient matrix of control rate；P is symmetric positive definite constant matrices, is the following side Riccati
The unique solution of journey:
Following control rates are obtained by solving:
Further, in step 4, obtaining optimum control rate is
U=-Kpcx-KIc∫xdt。
Compared with prior art, the present invention having the following advantages and benefits: the invention proposes one kind to pass through increasing
Near region is added to perfect the method that DC inversion side shutdown angle γ carries out Overvoltage suppressing, this method is seriously increased in ac grid voltage
Period turns off angle γ and DC current instruction value by control inverter side, permanent keeping near region to perfect DC transmission system power
On the basis of fixed, the reactive power of inverter consumption is promoted in short-term, inhibits the generation of the weak AC network overvoltage of sending end.
Detailed description of the invention
Attached drawing described herein is used to provide to further understand the embodiment of the present invention, constitutes one of the application
Point, do not constitute the restriction to the embodiment of the present invention.In the accompanying drawings:
Fig. 1 is that the double DC transmission system concentrations of the present invention send structural schematic diagram outside；
Fig. 2 is present invention shutdown angle γ Promotion Strategy stable state implementation result figure；
Fig. 3 is Overvoltage suppressing link block diagram of the present invention；
Fig. 4 is Overvoltage suppressing link of the present invention and the fiting relation figure that direct current control is protected；
Fig. 5 is the simulation model figure of simulation example of the present invention；
Fig. 6 is the present invention without exchange side bus voltage virtual value simulation result diagram in the case of control；
Fig. 7 (a) is exchange side bus voltage virtual value；
Fig. 7 (b) is the instruction of additional shutdown angle；
Fig. 7 (c) is extra current instruction；
Fig. 7 (d) is DC voltage；
Fig. 7 (e) is DC current；
Fig. 7 (f) is direct current active reactive.
Specific embodiment
To make the objectives, technical solutions, and advantages of the present invention clearer, below with reference to embodiment and attached drawing, to this
Invention is described in further detail, and exemplary embodiment of the invention and its explanation for explaining only the invention, are not made
For limitation of the invention.
Following embodiment is explained so that double DC transmission system concentrations shown in FIG. 1 are sent outside as an example.
Direct current, which sends power outside and is obstructed, causes AC overvoltage Producing reason as follows:
By taking double DC transmission systems concentration is sent outside as an example, illustrate when a certain time direct current sends power outside and be obstructed, AC system
There is the mechanism of overvoltage.The system is as shown in Figure 1.
U3, U4 are the equivalent built-in potential of AC system, Z in Fig. 11、Z2、Z3Respectively AC system equivalent impedance, U1∠θ1、
U2∠θ2The voltage and phase angle of respectively two DC converter station ac bus, Pdc1, Pdc2Respectively 1# DC transmission system, 2#
DC transmission system transmits active, P 'dc1+jQ′dc1For 1# direct-current transmission converter station absorbed from AC network it is active with it is idle,
P′dc2+jQ′dc2Active and idle, the C then absorbed for 2# direct-current transmission converter station from AC network1、C2Respectively 1#, 2# change of current
The equivalent capacitance value of high voltage filter of standing and reactive power compensator.
In supergrid, ignore line resistance, and in view of route two sides phase difference of voltage is relatively small, therefore basis
Electric network swim relationship, available:
In admittance battle array, diagonal element imaginary part is often below zero, and off-diagonal element imaginary part is commonly greater than zero, therefore according to leading
It receives this feature of battle array, can obtain:
It can be seen that during filter is not yet cut off 1# DC transmission system due to failure phase shift, Q 'dc1It significantly reduces,
Therefore the voltage of bus 1 and bus 2 will significantly rise.If system voltage is more than overvoltage protection setting valve and continues a timing
Between, overvoltage protection can then act, and be latched direct current.AC system is weaker, and the raising of voltage U is just more obvious.
At this point, if increasing idle consumed by 2# direct current, i.e. increase Q 'dc2, then the voltage of two buses can be reduced, is inhibited
Voltage increases, or even overvoltage occurs.
The present invention is based on the AC overvoltages of the idle control of D.C. high voltage transmission to inhibit principle to the overvoltage of above-mentioned appearance
Inhibited, concrete principle is as follows:
It, can be by DC transmission system when direct current, which sends power outside, to be kept constant according to DC transmission system quasi-steady state equation
Sending end converter station absorbs idle Qd1 and carries out derivation to shutdown angle γ, can obtain:
In formula, Pdc is that DC transmission system sends power outside, and Ud10, Ud20 are respectively that rectification side, inverter side are unloaded ideal straight
Galvanic electricity pressure, R are DC line resistance, Xr2For inverter side commutating reactance, R* is equivalent resistance, calculating formula are as follows:
By it is found that with shutdown angle γ increase, DC converter station two sides consumption it is idle will increase therewith, to inhibit
The generation of overvoltage.
And when DC transmission system overload level reaches system 3s overload level (i.e. DC current reaches 1.2pu)
Afterwards, with the increase at shutdown angle, DC current will stay in that 1.2pu.In the case, the absorption of sending end inverter also can be obtained
The idle derivative relation to shutdown angle are as follows:
In formula, IdFor DC current.
Even if it can be seen that in the case where DC current reaches the overload upper limit and can not continue raising, DC converter
The idle of two sides consumption of standing still meets the relationship being increased monotonically with the increase of shutdown angle γ.
In addition to this, promoting shutdown angle, remaining operating parameter also has corresponding influence on DC transmission system.Utilize ± 800kV
Extra-high voltage DC transmission system canonical parameter, available each physical quantity of direct current transportation are as shown in Figure 2 with the rule that γ changes.Figure
Middle DC voltage, DC current and active and reactive a reference value are the rated value of DC transmission system.
As shown in Figure 2, when γ is in [17 °, 35 °] range, DC transmission system is in constant power operation state, with
DC voltage reduces, and DC current gradually rises.And when γ is greater than 35 °, due to by DC transmission system capability of overload
Limitation, DC current will be maintained at 1.2pu.No matter DC transmission system is in is sent power mode operation outside surely, or fixed electricity
Stream operation, with the increase of shutdown angle γ, the reactive power consumption of two sides inverter can be obviously increased, the conclusion with analyze phase before
Symbol.
By above it is found that there is the main reason for overvoltage in DC transmission system AC system when sending power outside and being obstructed is
Since inverter consumes idle reduction, reactive power compensator reactive power releasing AC network, causes voltage to rise in converter station.It examines
Consider that the line fault duration is relatively short, and converter power transformer tap, reactive power compensator are difficult to quick acting.Therefore
It is obstructed period it is contemplated that sending power outside in DC transmission system, near region is kept to perfect the basis of DC transmission system power invariability
On, increase inverter side and turn off angle γ, to promote the reactive power for perfecting DC transmission system consumption in short-term, inhibits the weak exchange of sending end
The generation of power network overvoltage.
Embodiment 1
For the present embodiment by taking power grid shown in FIG. 1 as an example, setting 0- moment 2# direct current works as friendship since failure carries out phase shift operation
When streaming system short circuit is relatively low, system overvoltage risk is higher, and wherein what overvoltage risk was the most obvious is in the friendship of 2# direct current
It flows on converter station bus.The additional control for considering 1# direct current is had reached into limitation 2# bus overvoltage by promoting the angle γ below
Effect.
For outstanding feature, set as follows:
1, since receiving end AC system short circuit is relatively high, setting control period 1# DC inversion top-cross stream busbar voltage is permanent
It is fixed；
2, ignore the influence of commutation overlap angle；
3, more direct currents feed out power grid, and transmission line of electricity distance is usually no more than 30km between 1# direct current and 2# DC converter station, closely
Seemingly think that the two converter station ac bus voltage is close.
Under the above conditions, available following relationship:
Step 1, setting direct current transportation inverter side determines gamma kick using forecasting type, and rectification side uses constant current control,
According to DC transmission system control principle, LINEARIZED CONTROL equation is obtained；
According to HVDC transmission system quasi-steady state equation, using system stable operation point after the locking of 2# direct current as equalization point,
It is available using Taylor series expansion:
ΔUd1=-5.4U1(0)kT sinα(0)Δα+5.4kT cosα(0)ΔU1
ΔUd2=-Ud20 sinγ(0)Δγ
ΔPdc=2Ud1(0)ΔId+2ΔUd1Id(0)
2Ud1(0)ΔIdtanα(0)+2U1(0)ωCΔU1
In formula, Ud1(0)、ΔUd1、ΔUd2It is 1# DC rectifier side DC voltage steady-state value, rectification side direct current buckling respectively
The variable quantity of change amount and inverter side DC voltage.U1(0)、ΔU1The respectively steady-state value of 1# DC converter station ac bus voltage
And variable quantity.kTFor rectification side converter power transformer no-load voltage ratio.α(0)And Δ α is respectively rectification side Trigger Angle steady-state value and variable quantity.
γ(0)And Δ γ is respectively inverter side blow-out angle steady-state value and variable quantity.L is DC line inductance.Id(0)And Δ IdRespectively
DC current steady-state value and variable quantity.C is the equivalent capacity of 1# direct current reactive-load compensation equipment.
Setting direct current transportation inverter side determines gamma kick using forecasting type, and rectification side uses constant current control, therefore root
According to DC transmission system control principle, have
γ(0)+ Δ γ=γord
kI∫(Id-Iord) dt=α
In formula: γordFor the angle the γ D. C. value of DC transmission system controller output, IordFor DC transmission system controller
The DC current instruction value of output, kIFor integral control coefficient.
Step 2, the method for operation that near region power grid is fed out according to more direct currents utilizes the available direct current near region of P-Q decomposition method
Reactive power flow update equation, to obtain direct current near region trend lienarized equation；
The method of operation that near region power grid is fed out according to more direct currents utilizes the idle of the available direct current near region of P-Q decomposition method
Trend update equation are as follows:
Δ U=-B-1ΔQ′
Wherein,
Δ Q '=[Δ Q1/U1 ΔQ2/U2 … ΔQm/Um]T
Δ U=[Δ U1 ΔU2 … ΔUm]T
In formula, Δ QiIt is i bus idle work variable quantity, Δ UjIt is the voltage variety of j bus, B matrix is system node
The matrix that susceptance part forms in admittance matrix.
Setting, 1# direct current, 2# DC transmission system sending end converter station ac bus are respectively No. 1 bus and No. 2 buses, are changed
Convertor transformer valve side bus is respectively i bus and j bus.Therefore, available direct current near region trend lienarized equation is,
ΔUl=K1ΔQ′dc1
ΔU2=K2ΔQ′dc1
In formula, Δ U1、ΔU2Respectively 1# direct current, 2# DC transmission system sending end converter station ac bus voltage variety,
ΔQ′dc1For 1# direct current, the variable quantity of engineering inverter absorbing reactive power.K1、K2Then it is respectively equal to-B-1In the 1st row i-th column
And the 2nd row i-th arrange element value.
Step 3, system state equation is obtained；
On the basis of step 2, enable
X=[Δ Pd1 eU]T
U=[Δ Iord Δγord]T
Y=x
In formula, Δ Pd1For the power variation of 1# direct current, UsetFor ac bus voltage setting value after controller starting, Δ
IordChanging value is instructed for 1# DC current, Δ γ is that 1# direct current blow-out angle instructs changing value.eUFor converter station ac bus voltage
The difference of instruction and virtual voltage meets:
eU=Uset-U1
System state equation can be obtained are as follows:
Wherein:
Wherein:
Step 4, PI state regulator is obtained；
After AC overvoltage inhibits link starting, the main function of controller is then quickly to restore state variable x
To 0.By it is found that the AC overvoltage inhibition problem based on the idle control of D.C. high voltage transmission, can be considered that one disturbs w containing constant
Status adjustment problem.Therefore, overvoltage risk is inhibited using the optimal state regulator based on PI herein.Specifically set
Meter method is as follows:
It enables
Therefore, which is converted into the optimal regulator probrem under following state equation, state space and target
Function F meets:
For shown problem, the optimum control of existence anduniquess:
V=-R-1BPz(t)
Wherein, P is symmetric positive definite constant matrices, is the unique solution of following Riccati equation:
Following control rates are obtained by solving:
According to shown relationship, optimal PI control rate is obtained are as follows:
U=-Kpcx-KIc∫xdt。
Embodiment 2
The present embodiment obtains Overvoltage suppressing link block diagram as shown in Figure 3 on the basis of embodiment 1, proposed in this paper
Overvoltage suppressing is controlled to exchange side bus voltage, direct current sends power outside as control target, is exchanged by real-time measurement rectification side
Busbar voltage and dc power obtain shutdown angle extra-instruction △ γ ord and DC current in the way of optimal PI control
Additional control amount △ Iord, and it is sent to DC control system.The selection of optimal PI parameter by, calculated.
Major parameter definition and reference value are as follows in Fig. 3:
UOV_ref: ac bus voltage controls setting value.It should ensure that converter station in the failure duration when physical quantity value
Between, overvoltage protection will not act.
UOV_ref≤krelUOV
In formula, krel is safety factor, and can use 0.95, UOV is overvoltage protection definite value, generally 1.2pu.
2)△γordmax: shutdown angle extra-instruction maximum value.Due to the increase with α and γ, direct current major loop equipment
Stress will also increase, it is therefore desirable to the maximum value of limitation shutdown angle extra-instruction.Simultaneously to prevent VDCOL module action, closing
When angle of rupture extra-instruction maximum value is chosen, it should ensure that DC transmission system both ends DC voltage maintains 0.75pu in control process
More than.It is desirable with reference to Fig. 2 calculated result according to extra-high voltage DC transmission system canonical parameter:
Δγ2max=25 °
By the design process of controlling unit it is found that needing in control system control rate generating process from DC transmission system
Information is obtained in monitoring system and power grid SCADA system.
Wherein, the main purpose that information is obtained from SCADA system is to generate near region power grid admittance battle array, so as to find out in
K1,K2.In view of system operation mode changes less in a short time, therefore the solution of K1, K2 can be by the way of precomputations, often
It is periodically flushed once every 15min.
And from DC transmission system monitoring system, then it needs to obtain the active and reactive voltage of AC network and direct current transportation
The physical quantitys such as system working voltage, electric current and Trigger Angle and, and participate in closed-loop control with growth equation.Above- mentioned information are in Fig. 3
Control system input signal belong to local information, can obtain in real time.
Overvoltage suppressing in Fig. 3 is cooperated to obtain Fig. 4, as shown in Figure 4, Overvoltage suppressing with DC control and protection system
Device calculates the extra-instruction Δ γ of shutdown angle γ by obtaining sending end AC system busbar voltage and direct current transmission powerord
And the extra-instruction Δ I of DC currentord.Turn off angle extra-instruction Δ γordWith determine after γ reference value is added in gamma kick
Input as Inverter Station γ adjuster controls direct current triggering.And the extra-instruction Δ I of DC currentordThen with VDCOL
Instruction value after the DC current instruction value addition of output as constant current control.
AC overvoltage inhibits link start-up criterion are as follows:
The voltage effective value of rectification side ac bus is more than overvoltage protection definite value UOV, and continues 50ms.While in order to protect
Card Overvoltage suppressing link is persistently put into, once overvoltage criterion starts, enabling signal will broaden 2s.
AC overvoltage inhibits link to exit criterion are as follows:
Ac bus voltage is consistently less than voltage setting value UOV_ref, and be delayed after 50ms, Overvoltage suppressing link exits.
Simulation example
As shown in figure 5, using PSCAD building ± 800kV extra-high voltage DC transmission system and its near region power system simulation model,
In Fig. 5, distance only has 20km between 1# DC converter station and 2# DC converter station, belongs to the mostly straight of more typical concentration drop point
Flow delivery system.Two direct current relevant parameters are as shown in table 1.
DC operation parameter when table 1 operates normally
For outstanding feature, a kind of more serious operating condition, 1#, 2# DC converter station three short circuit current under the operating condition are considered
Level respectively may be about 30kA, 30kA, and the short-circuit ratio of corresponding direct current transportation only has 2.2.
1# direct current transportation configures 3200MVAr reactive power compensator altogether when normal operation, and 2# direct current configures 4000MVar's altogether
Reactive power compensator realizes consume idle compensation to DC transmission system well.
1#, 2# converter station are configured with overvoltage protection, and it is more than 1.2pu that movement definite value, which is converter station ac bus voltage,
Be delayed 0.5s.It after protection act, will disconnect all exchange outlets in Fig. 4, cause direct current locking.
This emulation inhibits the validity of strategy to verify by taking 2# direct current phase shift locking as an example, to AC overvoltage.
In above-mentioned analogue system, following failure setting is carried out:
After t=1.0s, 2# DC bipolar route permanent earth fault, correct movement and success phase shift are protected.
Logic is restarted three times since direct current transmission line fault exists, and is not latched directly after 2# direct current phase shift,
The reactive power compensator of 4000MVar is not also cut off.When t=2.0s, 2# DC transmission system is due to restarting failure, side
It can be latched, and then surgical filtering device.
For above-mentioned operating condition, electromagnetic transient simulation, available exchange side are carried out in the case where not taking any control
Busbar voltage virtual value variation tendency is as shown in Figure 6.It will be appreciated from fig. 6 that under above-mentioned operating condition, since 2# direct current transportation power conveys
It is obstructed, ac bus voltage is caused to be lifted, maximum overvoltage virtual value reaches 1.26pu, and sustained overvoltage reaches 1.247pu, holds
The continuous time close to 60ms, will cause overvoltage protection movement, causes to exchange near region line tripping and perfects direct current locking.Emulation
As a result it is also shown that overvoltage phenomenon will be more serious if reducing AC system short-circuit ratio.
Overvoltage suppressing link will be designed below, according to 3.2 the methods, the control of available overvoltage link
Rate processed are as follows:
Setting
UOV_ref=1.14pu
In this case, it is possible to which to obtain related simulation result as shown in Figure 7 for relevant control amount and exchange side bus voltage.
As shown in Figure 7, during t=1.0~2.0s, after overvoltage level is more than 1.15pu, meet Overvoltage suppressing ring
The entry condition of section.In order to inhibit the overvoltage level of ac bus, Overvoltage suppressing link produces 17 ° or so of additional pass
Angle of rupture instruction, is raised to 35 ° by 17 ° for the shutdown angle of inverter side, increases the absorption of 1# DC transmission system reactive power, have
Imitate the generation of the overvoltage inhibited.Simulation result shows that during Overvoltage suppressing link starts, the exchange of rectification side converter station is female
Line voltage maintains 1.16pu or so, avoids overvoltage protection movement.It is also known simultaneously by simulation result, it is straight due to increasing
The shutdown angle of transmission system is flowed, 1# DC transmission system DC voltage is declined, but is made in direct current constant dc power control logic
Under, DC current increases to 1.18pu, enters overload state, ensure that 1# DC transmission system sends power invariability outside.
Since the control duration is shorter (only 0.7s), without departing from the second grade capability of overload (generally 1.2pu) of direct current.Together
When, during simulation result is also shown that the effect of Overvoltage suppressing link, DC voltage still keeps 0.75pu or more, VDCOL link
It is not operating, meet controller design requirement.
And after t=3.0s, the locking of 2# DC transmission system, 4000MVar reactive power compensator is out of service, system
It is idle to balance again.Overvoltage suppressing link is difficult to maintaining converter station busbar voltage into a high position of 1.12pu, converter station exchange
Current path is to 1.00pu or so.According to the exit criteria of Overvoltage suppressing link, after Voltage Drop 50ms, Overvoltage suppressing ring
Section exits, and 1# direct current continues to operate normally.
Above-described specific embodiment has carried out further the purpose of the present invention, technical scheme and beneficial effects
It is described in detail, it should be understood that being not intended to limit the present invention the foregoing is merely a specific embodiment of the invention
Protection scope, all within the spirits and principles of the present invention, any modification, equivalent substitution, improvement and etc. done should all include
Within protection scope of the present invention.
Claims (5)
1. a kind of Overvoltage suppressing method based on the idle control of D.C. high voltage transmission characterized by comprising
Step 1, setting direct current transportation inverter side determines gamma kick using forecasting type, and rectification side uses constant current control, according to
DC transmission system control principle obtains LINEARIZED CONTROL equation；
Step 2, the method for operation that near region power grid is fed out according to more direct currents obtains the idle tide of direct current near region using P-Q decomposition method
Update equation is flowed, to obtain direct current near region trend lienarized equation；
Step 3, system state equation is obtained；
Step 4, PI state regulator is obtained；
In the step 3, system state equation are as follows:
Wherein,
Wherein,
In formula, Ud1(0)It is 1# DC rectifier side DC voltage steady-state value, U1(0)For the steady of 1# DC converter station ac bus voltage
State value, kTFor rectification side converter power transformer no-load voltage ratio, α(0)For rectification side Trigger Angle steady-state value, γ(0)For inverter side blow-out angle stable state
Value, L are DC line inductance, Id(0)For DC current steady-state value, C is the equivalent capacity of 1# direct current reactive-load compensation equipment, K1、K2
Then it is respectively equal to-B-1In the 1st row i-th column and the 2nd row i-th column element value, R is the resistance value of DC transmission system route；B
Matrix is the matrix that susceptance part forms in system node admittance matrix；
The PI status adjustment implement body design method of the step 4 is as follows:
It enables
Its state space and objective function F meet:
The optimum control of existence anduniquess:
Wherein, KpcIt is R-1Half submatrix of a left side of matrix obtained by BP, is the proportionality coefficient matrix of control rate；KIcIt is R-1Square obtained by BP
Half submatrix of the right side of battle array, is the integral coefficient matrix of control rate；P is symmetric positive definite constant matrices, is following Riccati equation
Unique solution:
Following control rates are obtained by solving:
2. a kind of Overvoltage suppressing method based on the idle control of D.C. high voltage transmission according to claim 1, feature
It is, in the step 1, LINEARIZED CONTROL equation:
γ(0)+ Δ γ=γord
KI∫(Id-Iord) dt=α
In formula: γ(0)And Δ γ is respectively inverter side blow-out angle steady-state value and variable quantity, γordFor DC transmission system control
The inverter side blow-out angle instruction value of device output, KIFor DC transmission system current control link integral control coefficient, IdFor direct current system
System electric current steady-state value, IordFor the DC current instruction value of DC transmission system controller output, α is DC transmission system rectification
Side Trigger Angle.
3. a kind of Overvoltage suppressing method based on the idle control of D.C. high voltage transmission according to claim 1, feature
It is, in the step 2, reactive power flow update equation are as follows:
Δ U=-B-1ΔQ′
Wherein,
Δ Q '=[Δ Q1/U1 ΔQ2/U2 … ΔQm/Um]T
Δ U=[Δ U1 ΔU2 … ΔUm]T
In formula, Δ QiIt is i bus idle work variable quantity, Δ UjIt is the voltage variety of j bus, B matrix is system node admittance
The matrix that susceptance part forms in matrix.
4. a kind of Overvoltage suppressing method based on the idle control of D.C. high voltage transmission according to claim 1, feature
It is, in the step 2, direct current near region trend lienarized equation are as follows:
ΔU1=K1ΔQ′dc1
ΔU2=K2ΔQ′dc1,
In formula, Δ U1、ΔU2Respectively 1# direct current, 2# DC transmission system sending end converter station ac bus voltage variety, Δ
Q′dc1For 1# direct current, the variable quantity of engineering inverter absorbing reactive power, K1、K2Then it is respectively equal to-B-1In the 1st row i-th column with
And the 2nd row i-th arrange element value.
5. a kind of Overvoltage suppressing method based on the idle control of D.C. high voltage transmission according to claim 1, feature
It is, in the step 4, obtaining control rate is
U=-Kpcx-KIc∫xdt。
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