CN109638869A - A kind of VSC-HVDC sliding formwork current control design method based on combination Reaching Law - Google Patents
A kind of VSC-HVDC sliding formwork current control design method based on combination Reaching Law Download PDFInfo
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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
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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
- H02J2003/365—Reducing harmonics or oscillations in HVDC
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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
- 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
- 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 belongs to field of power system control to analyze influence of the vector controlled to VSC-HVDC system stability for the stability problem of flexible direct current (VSC-HVDC) transmission system.For existing wild effect, the inner ring vector current control of VSC-HVDC is designed under the sliding formwork current control (sliding mode current control, SMCC) based on Reaching Law.For the SMCC based on exponentially approaching rule, there are stable states to buffet biggish deficiency simultaneously, proposes a kind of SMCC strategy based on combination Reaching Law suitable for VSC-HVDC, analyzes influence of the strategy to system small signal stability.Finally, having built the simulation model of VSC-HVDC in PSCAD/EMTDC, simulating, verifying is carried out to the SMCC strategy based on combination Reaching Law of design.The result shows that: the SMCC based on combination Reaching Law of design reduces buffeting when stable state compared to the SMCC based on exponentially approaching rule, SMCC can be equivalent to the proportional component that an inner ring proportionality coefficient changes over time less than the influence for disturbing stability to system simultaneously, can eliminate conventional vector and control inner ring integral coefficient smaller the phenomenon that causing system unstable oscillation.
Description
Technical field
The invention belongs to field of power system control, and in particular to a kind of VSC-HVDC sliding formwork electricity based on combination Reaching Law
Flow control design method.
Background technique
With the fast development of the growing tension and renewable energy power generation of the land resources such as transmission of electricity corridor, it is based on voltage source
Inverter flexible direct current (voltage source converter based high voltage direct current,
VSC-HVDC) technology of transmission of electricity is applied to the fields such as renewable energy source power, multi-terminal HVDC transmission in the world.Closely
In the past few years flexible DC transmission engineering construction is rapid, and the stability analysis and control of VSC-HVDC, which will become, influences electric system peace
The major issue of full stable operation.
In view of the above-mentioned problems, in VSC-HVDC stability analysis, it has now been found that when VSC couples weak AC network,
The non-linear and outer ring of system is active/voltage between to be highly coupled be the main reason for influencing system stability.In addition, research
Influence of the inner loop control to points of common connection dynamic voltage characteristics in inverter vector controlled, but not to unstable phenomenon into
The improvement of row control method.Part research and utilization method of characteristic analyzes influence of the VSC inner ring gain to system stability simultaneously,
But assume that influence of the proportionality coefficient with integral coefficient to system stability is identical during stability analysis.In the control of VSC-HVDC
In system, sliding mode controller (sliding mode control, SMC) with its excellent robustness, to the insensitive of Parameters variation
Property and faster dynamic response, are widely used in the control of DC transmission system.In addition to these advantages of SMC,
The shortcomings that SMC, is that after state trajectory reaches sliding-mode surface, there are stable states to buffet biggish deficiency when Parameter Perturbation.It grinds at present
Study carefully and proposes a kind of active power modulation scheme based on Sliding Mode Robust Controller, a kind of passive SMC strategy, three electricity of one kind respectively
It is the outer ring Sliding Mode Controller of ordinary telegram die mould VSC-HVDC, a kind of based on the HVDC controller of Terminal sliding formwork, one kind
Sliding formwork current controller (the sliding mode current based on exponentially approaching rule suitable for multiterminal VSC-HVDC
Control, SMCC), a kind of non-linear DC power modulation additional controller and a kind of power sliding moding structure compensation policy.But
The influence for the research of VSC-HVDC sliding mode controller not to SMC to DC transmission system small signal stability carries out at present
Analysis, does not take the scheme for effectively weakening buffeting yet.Meanwhile the vector inner ring current control link and SMCC of VSC-HVDC
Link needs further to be studied on the otherness that system small signal stability influences.Therefore, for mentioned VSC-HVDC at present
Sliding formwork control, which exists, buffets biggish deficiency, and the present invention proposes a kind of sliding formwork current control design method that can reduce buffeting,
And influence and control parameter influence to system performance of the proposed design method to system small signal stability is analyzed, have certain
Practical application value.
Summary of the invention
Technical problem to be solved by the invention is to provide a kind of VSC-HVDC sliding formwork electric current controls based on combination Reaching Law
Design method processed has just enter into the movement of switch area sliding formwork in system for the advantage and disadvantage of association index Reaching Law and variable rate reaching law
Early period use exponentially approaching rule, when system is up to stable state sliding formwork move later period use variable rate reaching law, to design
A kind of sliding formwork Current Control Strategy based on combination Reaching Law suitable for VSC-HVDC, is optimal system performance.Together
When, it is steady to analyze the interference small to system of the VSC-HVDC sliding formwork Current Control Strategy based on combination Reaching Law proposed by the invention
Qualitatively influence and influence of the control parameter to system performance.
To achieve the goals above, technical solution provided by the invention is as follows:
A kind of VSC-HVDC sliding formwork current control design method based on combination Reaching Law, the method includes walking as follows
It is rapid:
Step (1) analyzes influence of the vector controlled to VSC-HVDC system stability；
Step (2) is directed to existing wild effect, to VSC-HVDC's under the sliding formwork current control based on Reaching Law
The control of inner ring vector current is designed；
Step (3) proposes a kind of sliding formwork Current Control Strategy based on combination Reaching Law suitable for VSC-HVDC, analysis
Influence of the strategy to system small signal stability；
Influence of sliding formwork current control parameter of step (4) analysis based on combination Reaching Law to VSC-HVDC system performance；
Analyzed respectively in this paper step (1) dominant pole root locus with constant DC voltage control outer ring circuit ratio,
Integral parameter, the variation tendency that inner ring circuit ratio, integral parameter increase.
In this paper step (2) for determine DC voltage inner loop control integral coefficient compared with little Yi initiation system lose stable show
As determining DC voltage inner ring vector current control to VSC-HVDC under conventional exponentially approaching rule and conventional speed change Reaching Law respectively
System is designed.
For the advantage and disadvantage of association index Reaching Law and variable rate reaching law in this paper step (3), switching is had just enter into system
The early period that sliding formwork moves when area in the later period that sliding formwork moves when system is up to stable state, is become using exponentially approaching rule using speed change
Nearly rule makes system performance to propose a kind of sliding formwork Current Control Strategy based on combination Reaching Law suitable for VSC-HVDC
It is optimal.Existing equivalence replacement between SMCC and vector controlled is analyzed simultaneously, to analyze SMCC to the small interference of system
The influence of stability.
Total harmonic distortion factor of the parameter to grid-connected current of the SMCC based on combination Reaching Law is analyzed in this paper step (4)
And the influence of adjustment time, error overshoot that watt current measured value responds watt current given value.
Compared with the prior art scheme, the invention has the benefit that analyzing vector controlled to VSC-HVDC system
The influence of stability show that system easily loses stabilization when constant DC voltage control inner ring integral coefficient is smaller；The present invention is mentioned
Influence of the SMCC based on combination Reaching Law to VSC-HVDC system small signal stability out can be equivalent to inner ring proportionality coefficient
The proportional component changed over time eliminates influence of the inner ring integral element to system stability.Meanwhile based on combination Reaching Law
Buffeting of SMCC when effectively reducing stable state compared to the SMCC based on exponentially approaching rule.
Detailed description of the invention
Fig. 1 is a kind of VSC-HVDC sliding formwork current control design method flow chart based on combination Reaching Law
Fig. 2 is both ends VSC-HVDC system construction drawing
Fig. 3 is converter station vector current control block diagram
Fig. 4 (a) is variation of the dominant pole root locus with constant DC voltage control outer ring scale parameter
Fig. 4 (b) is variation of the dominant pole root locus with constant DC voltage control outer ring integral parameter
Fig. 4 (c) is variation of the dominant pole root locus with constant DC voltage control inner ring scale parameter
Fig. 4 (d) is variation of the dominant pole root locus with constant DC voltage control inner ring integral parameter
Fig. 5 is the SMCC design drawing based on combination Reaching Law
Fig. 6 is exponentially approaching rule phase path schematic diagram
Fig. 7 is variable rate reaching law phase path schematic diagram
Fig. 8 is variation of the dominant pole root locus with SMCC equieffective ratio parameter
Fig. 9 (a) is the response curve of DC voltage under the SMCC strategy based on combination Reaching Law
Fig. 9 (b) is the response curve of DC voltage under the SMCC strategy based on exponentially approaching rule
Fig. 9 (c) is the response curve based on DC voltage under conventional vector Current Control Strategy
In figure and text in each symbol are as follows:
In Fig. 2, VSC1 is converting plant, is designated as 1 under all electrical quantity.VSC2 is Inverter Station, is designated as 2 under all electrical quantity.
usFor points of common connection (point of common coupling, PCC) alternating voltage, it is u that converter station, which exports alternating voltage,c, directly
Stream side voltage is ud.Side equivalent resistance, inductance R, L are exchanged, ac filter capacitor is Cf, the active and reactive function of AC system output
Rate is respectively P and Q.isThe alternating current of PCC point, i are flowed to for voltage sourcecThe alternating current of AC system outlet is flowed to for PCC point
Stream.RdFor direct current side resistance, LdFor DC side inductance, C is DC bus capacitor, idFor DC line electric current.
In Fig. 3, instruction value is the electrical quantity of lower marker tape ref, and measured value is electrical quantity of the subscript without ref.Outer ring is active
Power, reactive power and DC voltage are respectively P, Q and ud, active-power P1And reactive power Q1For VSC1 outer loop control target,
DC voltage ud2And reactive power Q2For VSC2 outer loop control target.Outer loop control difference passes through in the generation of outer ring PI controlling unit
Circular current instruction value icdref、icqref.Inner loop control difference is obtained by inner ring PI controlling unit, electric voltage feed forward item and decoupling item
The port voltage u of VSCcd、ucq, d, q axis modulation wave signal are respectively md、mq。
Specific embodiment
With reference to the accompanying drawing, the present invention is described in further detail.
There are stable states to buffet biggish deficiency for the SMCC based on exponentially approaching rule by the present invention, proposes one kind and is suitable for
The SMCC strategy based on combination Reaching Law of VSC-HVDC, and the control strategy is analyzed to the shadow of system small signal stability
It rings.Meanwhile analyzing influence of the SMCC parameter based on combination Reaching Law to VSC-HVDC system performance.Algorithm overall flow figure
As shown in Figure 1, including the following steps:
Step (1) establishes the small-signal model of VSC-HVDC system；
Step (2) analyzes influence of the vector controlled to system small signal stability；
Step (3) easily loses stable phenomenon compared with mini system for constant DC voltage control inner ring integral coefficient, is being based on
The inner ring vector current control of VSC-HVDC is designed under the sliding formwork current control of Reaching Law；
Step (4) combines the advantage and disadvantage of conventional indexes Reaching Law and variable rate reaching law, proposes a kind of suitable for VSC-HVDC
The sliding formwork Current Control Strategy based on combination Reaching Law, and analyze influence of the strategy to system small signal stability；
Influence of sliding formwork current control parameter of step (5) analysis based on combination Reaching Law to VSC-HVDC system performance；
The small-signal model of VSC-HVDC system is established as follows in step (1):
Converter station vector current control block diagram shown in both ends VSC-HVDC system and Fig. 3 according to Fig.2, establishes VSC-
The small-signal model of HVDC system, as shown in formula (1).
X is the state variable of VSC-HVDC in formula, and u is the input quantity of state equation, and A is state matrix, and B is input square
Battle array.Only consider herein VSC1 take it is surely active, determine Reactive Power Control, VSC2, which takes, to be determined DC voltage and determines Reactive Power Control
In the case of VSC-HVDC system stability.State variable x=[isd1 isq1 icd1 icq1 usd1 usq1 z11 z21 z3 z4 ud1
isd2 isq2 icd2 icq2 usd2 usq2 z52 z61 z7 z8 ud2 id], the input quantity u=[P of state equation1ref Q1ref ud2ref
Q2ref].Wherein z11、z21、z3、z4And z52、z61、z7、z8Expression formula such as formula (2) shown in.
Influence of the vector controlled to system small signal stability is as follows in step (2):
The parameter of VSC-HVDC is as shown in table 1, VSC1 with VSC2 converter station AC system parameter is identical.Alternating current in table 1
Source voltage is Es, RnFor resistance in AC power source, LnFor inductance in AC power source, vector controller parameter is as shown in table 2.
1 VSC-HVDC system parameter of table
2 vector control system parameter of table
Due to current study show that VSC-HVDC system stability is mainly related to VSC2 constant DC voltage control link, figure
In the case that 4 is remaining control system parameter constants, dominant pole root locus is joined with constant DC voltage control outer ring circuit PI
Number (kp1=0.0001~0.00584, ki1=0.01~3), inner ring circuit PI parameter (kp3=0.01~10, ki3=5~
10000) variation tendency increased.
By Fig. 4 (a) -4 (d) it is found that when outer ring scale parameter, integral parameter and inner ring scale parameter are in respective variation model
In enclosing, dominant pole is in Left half-plane always, and system is stablized, and influence of these parameters to system stability is smaller.And inner ring
Contour integration parameter chooses smaller (such as ki3=85) when, the dominant pole of VSC-HVDC is in the right half plane of coordinate system, is
System is unable to maintain that stable operation.
Stable phenomenon is easily lost compared with mini system for constant DC voltage control inner ring integral coefficient in step (3), in base
The inner ring vector current control of VSC-HVDC is designed under the sliding formwork current control of Reaching Law as follows:
By step (2) it is found that VSC-HVDC easily loses surely when constant DC voltage control inner ring integral parameter chooses smaller
It is fixed.In order to eliminate influence of the inner ring integral element to system stability, herein using the SMCC based on Reaching Law to determining direct current
Pressure inner ring current control link is designed as follows:
Due in current controller, it is only necessary to be tracked to the given value of electric current, therefore under synchronous rotating frame
VSC2 is taken to determine the sliding-mode surface of DC voltage inner ring current control are as follows:
Sd=c1(icd2-icd2ref)=c1e1 (3)
Wherein c1> 0, icd2For the inner ring watt current of constant DC voltage control, icd2refIt is given for inner ring watt current
Value, SdFor sliding-mode surface.Enable SdDerivative is equal to 0, then:
Due under synchronous rotating frame, icd2refFor DC quantity, thereforeBringing formula (4) into can obtain:
Shown in conventional exponentially approaching rule such as formula (6).In formula :-k1S is exponential approach item, constant ε1The motor point of expression system
Approach the rate of diverter surface s=0.VSC2 constant DC voltage control inner ring uses such as formula of the SMCC based on exponentially approaching rule (7) institute
Show.
Shown in conventional speed change Reaching Law such as formula (8).Wherein,For system mode norm.VSC2 determines DC voltage
It controls when inner ring uses the SMCC based on variable rate reaching law as shown in formula (9), x=i in selection variable rate reaching law in formulacd2-
icd2refFor system state variables.
Exchange side system dynamic mathematical models of the VSC-HVDC shown in Fig. 2 under rotating coordinate system are as follows:
Wherein park transformation matrix
U in formula (10)cdAre as follows:
In order to which the inner ring sliding formwork current control to VSC-HVDC is designed, VSC2 modulation wave signal m is takendIt (t) is equivalent
Control parameter.Convolution (6)-formula (11) can obtain m under exponentially approaching rule, variable rate reaching lawd(t) Equivalent control law such as formula (12)
With shown in formula (13).
The advantage and disadvantage that conventional indexes Reaching Law and variable rate reaching law are combined in step (4) propose a kind of suitable for VSC-
The sliding formwork Current Control Strategy based on combination Reaching Law of HVDC, and analyze influence of the strategy to system small signal stability.
Steps are as follows:
It is respectively the phase path of exponentially approaching rule and the phase path of variable rate reaching law shown in Fig. 6 and Fig. 7.
Compare Fig. 6 and Fig. 7 it is found that buffeted when system has just enter into switch area under exponentially approaching rule it is smaller, but in stable state
Biggish buffeting can be generated.And system can be stable at origin under variable rate reaching law, significantly reduce buffeting when stable state, but
Biggish buffeting can be generated when system has just enter into switch area.
For the advantage and disadvantage of association index Reaching Law and variable rate reaching law, when system has just enter into switch area, sliding formwork is moved
Early period, using exponentially approaching rule (7), the later period that sliding formwork moves when system is up to stable state, using variable rate reaching law (9), from
And it is optimal system performance.The present invention chooses | | x | |1=| | icd2-icd2ref||1=| icd2-icd2ref|, it is moved in sliding formwork
I early periodcd2≈0、icd2ref=constant, | | x | |1It is larger at this time；And in the later period i of sliding formwork movementcd2-icd2ref≈ 0, | | x | |1
It is smaller at this time.In order to design based on the sliding formwork current control of combination Reaching Law to VSC-HVDC, a positive real number can be selected
k0, k0It is defined as Reaching Law handoff factor, when | | x | |1> k0When, using exponentially approaching rule；When | | x | |1< k0When, using speed change
Reaching Law.The SMCC based on combination Reaching Law is taken to be designed VSC2 constant DC voltage control inner ring, as shown in formula (14).
Convolution (10), (11), (14) can must combine m under Reaching Lawd(t) shown in Equivalent control law such as formula (15),
In based on combination Reaching Law SMCC design it is as shown in Figure 5.
To analyze influence of the SMCC based on combination Reaching Law to system small signal stability, from the figure 3, it may be seen that being based on vector
Current control modulated wave signal md(t) expression formula is as follows:
Comparison expression (15) and formula (16) are it is found that substitute traditional inner ring vector current control for the SMCC based on exponentially approaching rule
Afterwards, in modulating wave expression formula shown in the equivalence replacement such as formula (17) of inner ring PI controlling unit.To piece-wise linearization on the right side of formula (17)
Formula (18) can be obtained.
Therefore, when using method of characteristic to system progress analysis on Small Disturbance Stability, SMCC pairs based on exponentially approaching rule
The influence of system small signal stability is equivalent to k in inner ring PI controlling uniti3=0, kp3It is taken as Lk1/c1Stabilization when-R or-R
Property.
SMCC based on variable rate reaching law is replaced as shown in formula (19), can obtain formula to piece-wise linearization on the right side of formula (19)
(20)。
Therefore, the influence based on the SMCC of variable rate reaching law to system small signal stability is equivalent to inner ring PI controlling unit
Middle integral coefficient ki3=0, kp3It is taken as L ε1/c1Stability when-R or-R.
In summary analysis is it is found that influence of the SMCC based on combination Reaching Law to system small signal stability can be equivalent to
Integral coefficient k in inner ring PI controlling uniti3=0, kp3It is taken as-R, Lk1/c1- R and L ε1/c1Stability when-R.Work as ki3=0
When, it is contemplated that kp3Respectively-R, Lk1/c1- R and L ε1/c1Value range when-R, enables kp3Change in the range of -10~10.
Work as ki3=0, kp3When changing in -10~10 ranges, the dominant pole root locus of VSC-HVDC system is with SMCC equieffective ratio
The variation tendency that parameter increases is as shown in Figure 8.
As shown in Figure 8, with the variation of SMCC equieffective ratio parameter, the dominant pole of VSC-HVDC is always positioned at Zuo Banping
Face, system is in small interference stability state always at this time.In addition, by the analysis of Fig. 3 it is found that constant DC voltage control converter station
Inner ring scale parameter is relatively small on system stability influence, and system is in steady operational status in variation range, and interior
System is unable to maintain that stable operation when ring integral parameter chooses smaller.Therefore, replaced using the SMCC based on Reaching Law traditional
Inner ring PI controller, reduces integral element, can eliminate the de-stabilising effect that integral coefficient smaller strip is come.
Influence of sliding formwork current control parameter of the analysis based on combination Reaching Law to VSC-HVDC system performance in step (5)
It is as follows, while being verified by the method that simulation example designs the present invention:
On the basis of the above-mentioned SMCC theory analysis based on Reaching Law, in order to analyze verifying proposed based on combination become
The validity of the SMCC closely restrained has built VSC-HVDC model in PSCAD/EMTDC according to fig. 2.VSC-HVDC system parameter,
For vector control system parameter respectively as shown in table 1, table 2, the parameter of System with Sliding Mode Controller is as shown in table 3.
The parameter of 3 System with Sliding Mode Controller of table
It enables the active power of VSC1 in emulation step to 310MW by 300MW at the 2s moment to control come analog study in SMCC
The small signal stability of lower system, ki3In the case where the 1.8s moment is reduced to 85 analog study conventional PI controls by 10000, the small of system is done
Disturb stability.Since the stability of DC voltage is the stable important indicator of VSC-HVDC system, respectively based on approach
The response curve of DC voltage is observed under the SMCC and conventional PI control device of rule as shown in figure 9, rated direct voltage is 300kV.
When as shown in Figure 9, using the SMCC based on combination Reaching Law, the fluctuation range of DC voltage be 0.995pu~
1.005pu, when using SMCC based on exponentially approaching rule, the fluctuation range of DC voltage is 0.9pu~1.05pu.It uses simultaneously
At the 2s moment as the variation of active power is held essentially constant, system maintains to stablize DC voltage when SMCC.And work as VSC-
When HVDC uses conventional vector current control, work as ki385 are down to by 10000, DC voltage diverging, system is unstable, demonstrates figure
Determine in 4 (d) DC voltage inner ring circuit integral parameter it is smaller when the unstable analysis result of system.Meanwhile by straight in Fig. 9 (c)
The enlarged drawing of galvanic electricity pressure it is found that under conventional vector current control the steady-sxtate wave motion range of DC voltage be 0.972pu~
1.056pu, greater than the fluctuation range of DC voltage under the SMCC based on combination Reaching Law.Therefore, based on combination Reaching Law
SMCC has good steady-state performance compared to conventional vector current control.
It is analyzed by the above time-domain-simulation it is found that the SMCC based on Reaching Law can improve the stability of system, elimination inner ring product
Divide influence of the link to system stability.Meanwhile the SMCC based on combination Reaching Law is compared to the SMCC based on exponentially approaching rule
Buffeting when systematic steady state can be reduced, to reduce steady-state error.
In order to analyze influence of the selection of the controller parameter in the SMCC based on combination Reaching Law to control system performance,
In the case where guaranteeing remaining parameter constant, different ε are obtained1、k1And k0Lower VSC2 inner ring watt current measured value icd2(t) to given
Value icd2ref(t) adjustment time, error overshoot and the A phase grid-connected current i respondeda2(t) total harmonic distortion factor such as table 4, table
5 and table 6 shown in.
4 difference ε of table1The performance of lower control system compares
5 difference k of table1The performance of lower control system compares
6 difference k of table0The performance of lower control system compares
As can be seen from Table 4 since the velocity of approach of variable rate reaching law is ε1||x||1, ε1It is bigger, then when reaching diverter surface
System will have biggish speed, and the adjustment time of control system is shorter, and dynamic response is faster.
As can be seen from Table 5 due to k1The main dynamic transition process for influencing switching function, k1Bigger, system reaches sliding formwork
The speed in face is faster, and the adjustment time of control system is shorter, and dynamic response is faster.
As can be seen from Table 6, due to k0The advantages of selecting too small, variable rate reaching law can be covered；It selects too big, then may produce
Shake is significantly passed through in life.Therefore, with k0Increase, buffet amplitude increase, the total harmonic distortion factor of A phase grid-connected current just by
It is cumulative big.Meanwhile icd2(t) to icd2ref(t) adjustment time, the error overshoot responded is gradually reduced.In actual VSC-
In the design process of HVDC inner ring SMCC, suitable k can be selected according to specific requirement0Combination Reaching Law is based on to design
Under SMCC.If the priority of smaller total harmonic distortion factor is high, lesser k is chosen0；If faster current response rate
And lesser error overshoot priority is high, then guarantees that grid-connected current total harmonic distortion factor meets grid-connected harmonic current country mark
Biggish k is chosen in the case where standard0。
In conclusion a kind of VSC-HVDC sliding formwork current control design method based on combination Reaching Law proposed by the present invention
Influence to VSC-HVDC system small signal stability can be equivalent to the proportional component that inner ring proportionality coefficient changes over time, and eliminate
Influence of the inner ring integral element to system stability.Meanwhile the SMCC based on combination Reaching Law is compared to based on exponential approach
The SMCC of rule effectively reduces buffeting when stable state.
Finally it should be noted that: the foregoing is only a preferred embodiment of the present invention, but protection of the invention
Range is not limited thereto, and anyone skilled in the art in the technical scope disclosed by the present invention, can be easily
The change or replacement expected, should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with power
Subject to the protection scope that benefit requires.
Claims (5)
1. a kind of VSC-HVDC sliding formwork current control design method based on combination Reaching Law, which is characterized in that the method packet
Include following steps:
Step (1) analyzes influence of the vector controlled to VSC-HVDC system stability；
Step (2) is directed to existing wild effect, to the inner ring of VSC-HVDC under the sliding formwork current control based on Reaching Law
Vector current control is designed；
Step (3) proposes a kind of sliding formwork Current Control Strategy based on combination Reaching Law suitable for VSC-HVDC, analyzes the plan
Slightly to the influence of system small signal stability；
Influence of sliding formwork current control parameter of step (4) analysis based on combination Reaching Law to VSC-HVDC system performance.
2. the method according to claim 1, wherein system dominant pole root rail is analyzed in step (1) respectively
The variation tendency that mark increases with constant DC voltage control outer ring circuit PI parameter and inner ring circuit PI parameter, to analyze arrow
Influence of the amount control to VSC-HVDC system stability.
3. the method according to claim 1, wherein respectively to based on exponentially approaching rule and being based in step (2)
The VSC-HVDC sliding formwork current control of variable rate reaching law is designed.
4. according to method described in right 1, which is characterized in that step (3) is for association index Reaching Law and variable rate reaching law
Advantage and disadvantage use exponentially approaching rule, the sliding formwork when system is up to stable state in the early period that system has just enter into the movement of switch area sliding formwork
The later period of movement uses variable rate reaching law, to devise a kind of sliding formwork electricity based on combination Reaching Law suitable for VSC-HVDC
Flow control policy is optimal system performance.Meanwhile analyzing influence of the strategy to system small signal stability.
5. according to method described in right 1, which is characterized in that step (4) analyzes the sliding formwork electric current control based on combination Reaching Law
Parameter processed rings the total harmonic distortion factor and watt current measured value of VSC-HVDC system grid connection electric current to watt current given value
The influence of the adjustment time, error overshoot answered.
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