CN108258698A - A kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability - Google Patents
A kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability Download PDFInfo
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- CN108258698A CN108258698A CN201611241303.8A CN201611241303A CN108258698A CN 108258698 A CN108258698 A CN 108258698A CN 201611241303 A CN201611241303 A CN 201611241303A CN 108258698 A CN108258698 A CN 108258698A
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
- H02J2003/365—Reducing harmonics or oscillations in HVDC
-
- 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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- 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]
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Abstract
The present invention provides a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability, which includes：Sequentially connected exterior ring power compensation damping control algoritic module, current inner loop decoupling damping control algoritic module, reference voltage coordinate system modular converter, valve control device module and Equivalent Model module, the Equivalent Model module is connect respectively with phase-locked loop module, voltage coordinate system modular converter and electric current coordinate system modular converter, and the phase-locked loop module is connect respectively with voltage coordinate system modular converter and electric current coordinate system modular converter.Technical solution provided by the invention can greatly improve the power delivering capability and stability of VSC connection light current nets, control algolithm is simple, it is easily achieved, without additional peripheral hardware circuit, and the coefficient of power back-off damping control algorithm is adjusted without dynamic, the performance number of compensation can be adjusted according to the degree of fluctuation of PCC point voltages and the power dynamic of actual fed.
Description
Technical field
The invention belongs to voltage source converter field, in particular to a kind of raising VSC connections exchange the weak stabilization of power grids
The two close cycles damped control system of property.
Background technology
With wind-powered electricity generation and photovoltaic etc. can the energy again development, use VSC-HVDC (HVDC Transmission Technology of voltage-source type) will
The electric energy that regenerative resource generates is sent outside, and the limited restriction of power conveying, is conducive to improve renewable when overcoming ac transmission
The service efficiency of the energy.VSC-HVDC systems are made of two and above current conversion station and DC power transmission line, certain special
Occasion needs to provide power using exchange light current nets of the VSC-HVDC to be connected and frequency supports.In this case, it improves
The power delivering capability and stability for the exchange light current net that VSC-HVDC is connected have great practical significance.Improve entire system
The power delivering capability and stability of system need improving single VSC (voltage source converter, voltage source converter
Device) stability on set about, therefore, improve the power delivering capability of single VSC and stability be to improve whole system stability
Basis.
Since the VSC being connect with light current net needs use to determine active power and determines alternating voltage control strategy, solve
VSC damping characteristics under the control strategy are to improve the premise of system power conveying capacity and stability.VSC in actual motion
It needs to change actual power output valve, and PCC points alternating voltage is also needed to keep not according to the dispatch command that control centre is sent out
Become.In the case where PCC (points of common connection) puts alternating-voltage stabilization, improve system power conveying and namely improve AC system
Phase difference between equivalent power supply and PCC point voltages.
The stability of VSC mainly determines by the characteristic of outer shroud closed loop transfer function, and the characteristic and controller form and its
Parameter has much relations, and the thinking for improving VSC stability is usually from the angle for improving system damping characteristic.Active power
VSC in the case of control brings negative resistance character to system, and the degree of negative resistance character is not only related with the power of conveying, also
It is related with the short-circuit ratio of AC system.Pole light current net connection under VSC, since AC network equivalent impedance is larger, PCC points without
It is presented serious non-linear relation between the demand of work(power and the active power of transmission, improves VSC power delivering capabilities and steady
It is qualitative that there is very big relationship in the reactive power that PCC points provide with VSC.Accordingly, it is desirable to provide a kind of raising VSC connections exchange
The method of the stability of light current net.
Invention content
To meet the needs of the prior art, the present invention proposes a kind of pair improved VSC connections and exchange weak grid stability
Closed-loop damping control system.
A kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability, the system comprises：Successively
Exterior ring power compensation damping control algoritic module, current inner loop decoupling damping control algoritic module, the reference voltage coordinate of connection
Be modular converter, valve control device module and Equivalent Model module, the Equivalent Model module respectively with phase-locked loop module, voltage coordinate
Be that modular converter is connected with electric current coordinate system modular converter, the phase-locked loop module respectively with voltage coordinate system modular converter and electricity
Flow the connection of coordinate system modular converter.
Further, the Equivalent Model module includes：Sequentially connected AC system equivalent power supply, AC system are equivalent
Impedance, transformer equiva lent impedance and VSC, the other end ground connection of the AC system equivalent power supply, the AC system equivalence resistance
Anti- and transformer equiva lent impedance tie point is points of common connection PCC points, and the PCC points are connect with fling-cut switch, the switching
The other end of switch is connect with compensating electric capacity, the other end ground connection of the compensating electric capacity.
Further, the Equivalent Model is shown below：
Wherein, LgAnd RgEquivalent inductance and resistance for AC system；LtAnd RtEquivalent inductance and resistance for transformer；Cf
For reactive compensation capacitor；ω is AC system fundamental wave angular frequency；ugdAnd ugq、usdAnd usq、ucdAnd ucqRespectively AC system etc.
It is worth the d axis and q axis components of supply voltage, PCC points voltage, VSC exchange side voltage on dq coordinate systems；igdAnd igqFor power grid three
Component of the phase current on d axis and q axis；isdAnd isqFor component of the voltage source converter VSC three-phase currents on d axis and q axis.
Further, the exterior ring power compensation damping control algorithm includes：
Active power offset PcomWith reactive power compensation value QcomIt is shown below respectively：
Wherein, U* sReference value for PCC point phase voltage amplitudes；UsFor PCC point voltages；Sign (x) is sign function；d2With
d1The penalty coefficient of active power and reactive power respectively, d1>=0, d2≥0；P is active power；Q is reactive power；
The reactive power for determining AC voltage controller output is shown below：
Wherein, U* sReference value for PCC point phase voltage amplitudes；Guac(s) to determine AC voltage controller；UrefTo determine exchange
The reference value of voltage controller；UsFor PCC point voltages；Sign (x) is sign function.
Further, determine AC voltage controller Guac(s) it is shown below：
Wherein, kpacAnd kiacRespectively proportionality coefficient and integral coefficient, s are Laplace operator；
Determine the reference value U of AC voltage controllerrefIt is shown below：
Wherein, d3For the fine tuning coefficient of reference value, d3≥0。
Further, damping control algorithm is compensated according to the exterior ring power and obtains active power reference value and reactive power
Reference value；
The active power reference value PrefWith reactive power reference qref QrefIt is shown below respectively：
Wherein, P*The VSC desired output active power sent out for control centre；Q*To determine AC voltage controller output
Reactive power；PcomFor active power offset；QcomFor reactive power compensation value.
Further, the current inner loop decoupling damping control algoritic module includes：
I, value and power reference is converted into current reference value；
II, current inner loop decoupling damping control equation is worth to according to current reference.
Further, the step I includes：According to direct Power Control mode, d axis under AC system equilibrium state is obtained
It is shown below with the reference current of q axis：
Wherein, PrefFor active power reference value；QrefFor reactive power reference qref；usdAnd usqRespectively PCC point voltages exist
D axis and q axis components under dq coordinate systems.
Further, the step II includes：
In the current inner loop decoupling damping control equation, the d axis of VSC exchange side desired outputs and the reference voltage of q axis
u* cdAnd u* cqIt is shown below：
Wherein, usdAnd usqD axis and q axis component of the respectively PCC point voltages under dq coordinate systems；Gisd(s) and Gisq(s)
The respectively PI controllers of d axis and q axis；WithThe respectively reference current of d axis and q axis under AC system equilibrium state；igd
And igqFor component of the power grid three-phase current on d axis and q axis；isdAnd isqIt is voltage source converter VSC three-phase currents in d axis and q
Component on axis；ω is AC system fundamental wave angular frequency；LtEquivalent inductance for transformer；Zgvir(s) and Zsvir(s) it is respectively d
The active virtual impedance of axis and q axis.
Further, the PI controllers G of d axis and q axisisd(s) and Gisq(s) it is shown below respectively：
Wherein, kpisdAnd kiisdThe respectively proportionality coefficient and integral coefficient of d axis PI controllers, kpisqAnd kiisqRespectively q
The proportionality coefficient and integral coefficient of axis PI controllers；S is Laplace operator；
Active virtual impedance Z in d paraxial equations and q paraxial equationsgvir(s) and Zsvir(s) it is shown below respectively：
Wherein, RgvirAnd RsvirRespectively feed back the active virtual electricity of damping being multiplied by required for power network current and VSC electric currents
Resistance；HPFgvir(s) and HPFsvir(s) high-pass filter being respectively multiplied by required for feedback power network current and VSC electric currents.
Compared with the latest prior art, technical solution provided by the invention has the advantages that：
1st, technical solution provided by the invention can greatly improve the power delivering capability and stabilization of VSC connection light current nets
Property, through emulation testing, in the case of short-circuit ratio SCR=1, power delivering capability can be increased to more than 0.98p.u., etc.
Value supply voltage is increased to 80 ° or more with PCC point voltage-phase absolute value of the difference.
2nd, technical solution algorithm provided by the invention is simple, it is easy to accomplish, without additional peripheral hardware circuit, and nothing
Dynamic is needed to adjust the coefficient of power back-off damping control algorithm, the performance number of compensation can be according to the degree of fluctuation of PCC point voltages
It is adjusted with the power dynamic of actual fed.
3rd, the exterior ring power compensation damping control algorithm of technical solution provided by the invention only works in dynamic process,
The active power that VSC conveyings it is expected by control centre is had no effect under stable situation.
4th, the current inner loop decoupling damping control algorithm of technical solution provided by the invention avoids the detection of capacitance current,
Compensating electric capacity is cut off because having no effect on the stability of system and continuous service ability after failure.
5th, technical solution provided by the invention is a unified control method, have unified PCC points with the presence or absence of capacitance with
And the function of other devices.
Description of the drawings
Fig. 1 is VSC current conversion stations and its AC system Equivalent Model；
Fig. 2 is PCC point PV characteristic curves；
Fig. 3 is VSC two close cycles damped control system schematic diagrames；
Fig. 4 compensates damping control algorithm block diagram for exterior ring power；
Fig. 5 decouples damping control algorithm block diagram for current inner loop.
Specific embodiment
The present invention is described in further details below in conjunction with the accompanying drawings.To make purpose, the technical solution of the embodiment of the present invention
It is clearer with advantage, below in conjunction with the attached drawing in the embodiment of the present invention, the technical solution in the embodiment of the present invention is carried out
It clearly and completely describes, it is clear that described embodiment is part of the embodiment of the present invention, instead of all the embodiments.Base
Embodiment in the present invention, those of ordinary skill in the art obtained without making creative work it is all its
Its embodiment, shall fall within the protection scope of the present invention.
A kind of raising VSC connections that patent of the present invention is proposed exchange the two close cycles damping control system of weak grid stability
System, system include：Sequentially connected exterior ring power compensation damping control algoritic module, current inner loop decoupling damping control algorithm mould
Block, reference voltage coordinate system modular converter, valve control device module and Equivalent Model module, the Equivalent Model module is respectively with locking phase
Ring moulds block, voltage coordinate system modular converter are connected with electric current coordinate system modular converter, and the phase-locked loop module is sat respectively with voltage
Mark system modular converter is connected with electric current coordinate system modular converter.
The Equivalent Model module includes：Sequentially connected AC system equivalent power supply, AC system equivalent impedance, transformation
Device equiva lent impedance and VSC, the other end ground connection of the AC system equivalent power supply, the AC system equivalent impedance and transformer
The tie point of equiva lent impedance is points of common connection PCC points, and the PCC points connect with fling-cut switch, the fling-cut switch it is another
End is connect with compensating electric capacity, the other end ground connection of the compensating electric capacity.
(1) transverter electrical-magnetic model is established
Shown in attached drawing one is VSC current conversion stations and its AC system Equivalent Model, wherein UgFor AC system equivalent power supply
Phase voltage amplitude, δ be relative to PCC point voltages phase；ZgFor AC system equivalent impedance, ZTFor transformer equiva lent impedance,
UsFor PCC point phase voltage amplitudes, direct current is injected in P and active power and reactive power that Q is the transmission of PCC points, direction for exchange side
Side is just QsFor the reactive power of injection transformer, QcTo inject reactive compensation capacitor CfReactive power, SwFor compensating electric capacity Cf
Fling-cut switch；igabcThe three-phase current of AC network, isabcFor the electric current of VSC outputs, ucabcFor VSC exchange side three-phase voltages,
udcFor VSC DC voltages.An electro-magnetic transient equation that VSC exchange side can be obtained is with reference to the accompanying drawings
(1) L in~(3)gAnd RgFor the equivalent inductance and resistance of AC system, LtAnd RtFor transformer equivalent inductance and
Resistance, ω are AC system fundamental wave angular frequency；ugdAnd ugq、usdAnd usq、ucdAnd ucqFor AC system equivalent power supply voltage, PCC
The d axis and q axis components of point voltage, VSC exchange side voltage on dq coordinate systems；igdAnd igqIt is power grid three-phase current in d axis and q
Component above axis, isdAnd isqFor component of the VSC three-phase currents on d axis and q axis.
(2) influence of the analysis active power to PCC point voltages
Since the VSC being connect with light current net needs use to determine active power and determines alternating voltage control, active power is dynamic
Disturbance during state necessarily affects PCC point voltage changes, and influence of the analysis active power to PCC point voltages is conducive to design
Exterior ring power compensates damping control algorithm.
Define ratio of the perunit value (per unit, p.u.) between actual value and rated value.It is PCC shown in attached drawing two
Power vs. voltage (power voltage, PV) characteristic curve during point short-circuit ratio SCR=1, wherein three curves indicate respectively
Work(power perunit value P2=-0.312p.u. and reactive power Q=- 0.05p.u., active-power P0=-0.435p.u. and idle
Power Q=-0.1p.u. and active-power P1The PV characteristic curves of=- 0.527p.u. and reactive power Q=- 0.15p.u..
The intersection points B of Us=1 and three curve, O, A are respectively three power Ps1, P0And P2Steady-state operation point.
According to PCC point PV characteristic curves it is recognised that when active power absolute value increases, PCC point voltages first reduce again
Restore to stationary value, when active power absolute value reduces, PCC point voltages, which first increase, to be restored again to stationary value.Wherein in system
In dynamic process, the degree of fluctuation of PCC point voltages and the response speed of active power and the big of AC voltage controller parameter is determined
Small correlation, the response speed for reducing active power advantageously reduces the degree of fluctuation of PCC point voltages, so as to improve the operation of system
Stability.For example the alternating voltage response speed of curve 3 is more than the response speed of curve 1, i.e., determines alternating current corresponding to curve 3
Pressure control parameter, which is more than corresponding to curve 1, determines AC voltage controller parameter, can also similarly analyze curve 2 and curve 4.
(3) VSC Control system architectures are designed
The two close cycles cascade control system structure that VSC under normal circumstances is used, patent of the present invention equally use the structure,
Only outer ring controller and interior ring controller are different from traditional Control system architecture, specifically by step intermediary below
It continues.VSC Control system architectures designed by patent of the present invention as shown in attached drawing three, the system comprises：Sequentially connected outer shroud
Power back-off damping control algoritic module, current inner loop decoupling damping control algoritic module, reference voltage coordinate system modular converter,
Valve control device module and Equivalent Model module, the Equivalent Model module respectively with phase-locked loop module, voltage coordinate system modular converter
It is connected with electric current coordinate system modular converter, the phase-locked loop module turns respectively with voltage coordinate system modular converter and electric current coordinate system
Change the mold block connection.
Equivalent Model module includes：Sequentially connected AC system equivalent power supply, AC system equivalent impedance, transformer etc.
Impedance and VSC are imitated, the other end ground connection of the AC system equivalent power supply, the AC system equivalent impedance and transformer are equivalent
The tie point of impedance is points of common connection PCC points, and the PCC points connect with fling-cut switch, the other end of the fling-cut switch and
Compensating electric capacity connects, the other end ground connection of the compensating electric capacity.
Wherein phaselocked loop (phase locked loop, PLL) is for tracking PCC point phases, and output valve is with representing θ；
3s/2r represents three-phase static coordinate system to the transformation of dq rotating coordinate systems, and 2r/3s is its inverse transformation；VSC is either two level
Form can also be modular multilevel (modular multilevel converter, MMC) form；usdqFor usdAnd usq's
Generalized expression, isdqSimilarly.
(4) design exterior ring power compensation damping control algorithm
According to PV characteristic curves in step 2, it is concluded that, design exterior ring power compensates the thinking of damping control algorithm
For：
1) when PCC point voltages actual value is less than reference value, the offset of active power should make the output of active power
Absolute value reduces, and the offset of reactive power should make VSC export more reactive powers to improve PCC point voltages；
2) when PCC point voltages actual value is higher than reference value, the offset of active power should make the output of active power
Absolute value increases, and the offset of reactive power should reduce VSC output reactive powers to reduce PCC point voltages；
In order to not influence the active power that VSC outputs it is expected by control centre under steady state conditions, integrating 1) and 2) can
Obtain the exterior ring power compensation damping control algorithm as shown in attached drawing four.Active power offset P in attached drawing fourcomWith idle work(
Rate offset QcomRespectively
U in formula (4)* sFor the reference value of PCC point phase voltage amplitudes, sign (x) is sign function, and 1 is exported as x ＞ 0, when
Output is -1 during x ＜ 0, | x | for the operation that takes absolute value, d2And d1The penalty coefficient of active power and reactive power respectively, meets d1
>=0, d2>=0, it can be seen that the offset of active power and reactive power and PCC point voltage changes degree, power and its direction
It is related with penalty coefficient, and d2And d1Without dynamically being adjusted according to practical active power size after designing, the compensation of power
Value can be adjusted according to degree of fluctuation and the instantaneous power dynamic of voltage.P in attached drawing four*The VSC expectations sent out for control centre are defeated
Go out active power, Q*To determine the reactive power of AC voltage controller output, PrefAnd QrefReference power for outer shroud output.It is fixed
AC voltage controller Guac(s) using pi controller (proportional integration, PI), expression formula
For
K in formula (5)pacAnd kiacFor proportionality coefficient and integral coefficient, s is Laplace operator.Determine AC voltage controller
Reference value UrefExpression formula be
D in formula (6)3For the fine tuning coefficient of reference value, meet d3≥0。
(5) design current inner ring decoupling damping control algorithm
Outer shroud output valve only produces active power reference value P in above-mentioned steps 4refWith reactive power reference qref Qref,
It is entered into current inner loop controller and also needs to value and power reference being converted to current reference value.It is deposited in this transfer process
In 2 kinds of methods, first, using pi controller, second is that using direct Power Control mode, patent of the present invention uses the latter,
Can obtain the reference current of d axis and q axis under AC system equilibrium state is
Therefore current inner loop decoupling damping control equation of the invention, which can be obtained, is
U in formula (8)* cdAnd u* cqRespectively the d axis of VSC exchange side desired output and q axis reference voltages, wherein d axis and q axis
PI controller equations be
K in formula (9)pisdAnd kiisdThe respectively proportionality coefficient and integral coefficient of d axis PI controllers, kpisqAnd kiisqRespectively
Proportionality coefficient and integral coefficient for q axis PI controllers.Active virtual impedance in formula (8) in d paraxial equations and q paraxial equations
Zgvir(s)And Zsvir(s) it is by active virtual resistance and high-pass filter (high pass filter, HPF) composition, wherein HPF
It is not limited to single order.HPF cutoff frequencies are less than 50rad/s under normal circumstances, provide sufficiently large damping to inhibit VSC exchange side
Resonance oscillations, their expression-form are
R in formula (10)gvirAnd RsvirTo feed back the active virtual resistance of damping being multiplied by required for power network current and VSC electric currents,
Similarly also there is HPFgvir(s) and HPFsvir(s).If PCC points do not have Shunt compensation capacitor Cf, then it is one that formula (10), which is degenerated,.Cause
This, the two close cycles damping control method that patent of the present invention proposes, which has unified PCC points, capacitance and two kinds of situations without capacitance.
Finally it should be noted that：The above embodiments are merely illustrative of the technical scheme of the present invention and are not intended to be limiting thereof, to the greatest extent
Pipe is described in detail the present invention with reference to above-described embodiment, those of ordinary skills in the art should understand that：Still
The specific embodiment of the present invention can be modified or replaced equivalently, and without departing from any of spirit and scope of the invention
Modification or equivalent replacement, are intended to be within the scope of the claims of the invention.
Claims (10)
- A kind of 1. two close cycles damped control system for improving VSC connections and exchanging weak grid stability, which is characterized in that the system Including：Exterior ring power compensates damping control algoritic module, for calculating active power reference value and reactive power reference qref；Current inner loop decouples damping control algoritic module, for calculating the reference of the d axis of VSC exchange side desired outputs and q axis electricity Pressure；Reference voltage coordinate system modular converter, for dq coordinate systems to be converted into three-phase static coordinate system；Valve control device module and Equivalent Model module,The Equivalent Model module connects respectively with phase-locked loop module, voltage coordinate system modular converter and electric current coordinate system modular converter It connects, the phase-locked loop module is connect respectively with voltage coordinate system modular converter and electric current coordinate system modular converter.
- 2. a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability as described in claim 1, It is characterized in that, the Equivalent Model module includes：Sequentially connected AC system equivalent power supply, becomes AC system equivalent impedance Depressor equiva lent impedance and VSC, the other end ground connection of the AC system equivalent power supply, the AC system equivalent impedance and transformation The tie point of device equiva lent impedance is points of common connection PCC points, and the PCC points connect with fling-cut switch, the fling-cut switch it is another One end is connect with compensating electric capacity, the other end ground connection of the compensating electric capacity.
- 3. a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability as claimed in claim 2, It is characterized in that, the Equivalent Model is shown below：Wherein, LgAnd RgEquivalent inductance and resistance for AC system；LtAnd RtEquivalent inductance and resistance for transformer；CfFor nothing Work(compensating electric capacity；ω is AC system fundamental wave angular frequency；ugdAnd ugq、usdAnd usq、ucdAnd ucqThe respectively equivalent electricity of AC system The d axis and q axis components of source voltage, PCC points voltage, VSC exchange side voltage on dq coordinate systems；igdAnd igqFor power grid three-phase electricity Flow the component on d axis and q axis；isdAnd isqFor component of the voltage source converter VSC three-phase currents on d axis and q axis.
- 4. a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability as described in claim 1, It is characterized in that, the exterior ring power compensation damping control algorithm includes：Active power offset PcomWith reactive power compensation value QcomIt is shown below respectively：Wherein, U* sReference value for PCC point phase voltage amplitudes；UsFor PCC point voltages；Sign (x) is sign function；d2And d1Point The penalty coefficient of other active power and reactive power, d1>=0, d2≥0；P is active power；Q is reactive power；The reactive power for determining AC voltage controller output is shown below：Wherein, U* sReference value for PCC point phase voltage amplitudes；Guac(s) to determine AC voltage controller；UrefTo determine alternating voltage The reference value of controller；UsFor PCC point voltages；Sign (x) is sign function.
- 5. a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability as claimed in claim 4, It is characterized in that, determines AC voltage controller Guac(s) it is shown below：Wherein, kpacAnd kiacRespectively proportionality coefficient and integral coefficient, s are Laplace operator；Determine the reference value U of AC voltage controllerrefIt is shown below：Wherein, d3For the fine tuning coefficient of reference value, d3≥0。
- 6. a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability as claimed in claim 4, It is characterized in that, compensating damping control algorithm according to the exterior ring power obtains active power reference value and reactive power reference qref；The active power reference value PrefWith reactive power reference qref QrefIt is shown below respectively：Wherein, P*The VSC desired output active power sent out for control centre；Q*To determine the idle of AC voltage controller output Power；PcomFor active power offset；QcomFor reactive power compensation value.
- 7. a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability as described in claim 1, It is characterized in that, the current inner loop decoupling damping control algoritic module includes：I, value and power reference is converted into current reference value；II, current inner loop decoupling damping control equation is worth to according to current reference.
- 8. a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability as claimed in claim 7, It is characterized in that, the step I includes：According to direct Power Control mode, d axis and q axis under AC system equilibrium state are obtained Reference current is shown below：Wherein, PrefFor active power reference value；QrefFor reactive power reference qref；usdAnd usqRespectively PCC point voltages are sat in dq D axis and q axis components under mark system.
- 9. a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability as claimed in claim 7, It is characterized in that, the step II includes：In the current inner loop decoupling damping control equation, the d axis of VSC exchange side desired outputs and the reference voltage u of q axis* cdWith u* cqIt is shown below：Wherein, usdAnd usqD axis and q axis component of the respectively PCC point voltages under dq coordinate systems；Gisd(s) and Gisq(s) it is respectively The PI controllers of d axis and q axis；WithThe respectively reference current of d axis and q axis under AC system equilibrium state；igdAnd igqFor Component of the power grid three-phase current on d axis and q axis；isdAnd isqIt is voltage source converter VSC three-phase currents on d axis and q axis Component；ω is AC system fundamental wave angular frequency；LtEquivalent inductance for transformer；Zgvir(s) and Zsvir(s) it is respectively d axis and q The active virtual impedance of axis.
- 10. a kind of two close cycles damped control system for improving VSC connections and exchanging weak grid stability as claimed in claim 9, It is characterized in that,The PI controllers G of d axis and q axisisd(s) and Gisq(s) it is shown below respectively：Wherein, kpisdAnd kiisdThe respectively proportionality coefficient and integral coefficient of d axis PI controllers, kpisqAnd kiisqRespectively q axis PI The proportionality coefficient and integral coefficient of controller；S is Laplace operator；Active virtual impedance Z in d paraxial equations and q paraxial equationsgvir(s) and Zsvir(s) it is shown below respectively：Wherein, RgvirAnd RsvirRespectively feed back the active virtual resistance of damping being multiplied by required for power network current and VSC electric currents； HPFgvir(s) and HPFsvir(s) high-pass filter being respectively multiplied by required for feedback power network current and VSC electric currents.
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| CN111342731A (en) * | 2020-04-10 | 2020-06-26 | 华中科技大学 | Electrolytic capacitor-free variable frequency driving system resonance suppression method and system |
| CN111769582A (en) * | 2020-06-24 | 2020-10-13 | 南京航空航天大学 | Alternating current feedback additional damping control method based on multi-terminal direct current distribution system |
| CN114069705A (en) * | 2021-11-19 | 2022-02-18 | 西安交通大学 | Method and system for judging large disturbance stability of grid-connected voltage source type converter |
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| YUNFENG LI等: ""Power Compensation Control for Interconnection of Weak Power Systems by VSC-HVDC"", 《IEEE TRANSACTIONS ON POWER DELIVERY》 * |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111342731A (en) * | 2020-04-10 | 2020-06-26 | 华中科技大学 | Electrolytic capacitor-free variable frequency driving system resonance suppression method and system |
| CN111342731B (en) * | 2020-04-10 | 2021-07-27 | 华中科技大学 | Electrolytic capacitor-free variable frequency driving system resonance suppression method and system |
| CN111769582A (en) * | 2020-06-24 | 2020-10-13 | 南京航空航天大学 | Alternating current feedback additional damping control method based on multi-terminal direct current distribution system |
| CN114069705A (en) * | 2021-11-19 | 2022-02-18 | 西安交通大学 | Method and system for judging large disturbance stability of grid-connected voltage source type converter |
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