CN110334935A - A kind of method, apparatus and storage medium for assessing grid-connected exchanger transient stability - Google Patents
A kind of method, apparatus and storage medium for assessing grid-connected exchanger transient stability Download PDFInfo
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Abstract
The invention discloses a kind of method, apparatus and storage medium for assessing grid-connected exchanger transient stability, and the method comprising the steps of: obtaining the first curve that the electric current of VSC changes over time；Judge whether the first curve encounters not reentry point；If so, drawing the second curve between the imbalance power and electric current at the DC capacitor both ends of VSC, the unstability numerical value of VSC is calculated according to the second curve；If it is not, the third curve that the direct current voltage error for then drawing VSC changes over time, obtains matched curve, and the attenuation coefficient of digital simulation curve according to third curve；When attenuation coefficient be greater than 0, then obtain the unstability numerical value of VSC；When attenuation coefficient is not more than 0, then the 4th curve between the imbalance power and electric current at the DC capacitor both ends of VSC is drawn, and construct virtual not reentry point, and the stability margin of VSC is calculated.The stability margin of VSC DC voltage can be quantitatively evaluated in the present invention, compensate for and be only capable of analyzing the technological deficiency of VSC DC voltage transient stability by numerical simulation at present.
Description
Technical field
The present invention relates to the technical field of electrical equipment Transient Stability Analysis more particularly to a kind of grid-connected exchangers of assessment
The method, apparatus and storage medium of transient stability.
Background technique
Collection neutralizes the fast development of distribution type renewable energy power generation (such as wind-force, photovoltaic power generation), so that voltage-source type
Grid-connection converter (Voltage Source Converters, VSCs) is distributed widely in modern power systems.The direct current of VSC
Press (quantity of state of dc-link capacitance) can be because the accumulation of energy occurs being monotonically changed and hold with exchanging under the conditions of system transient modelling
The destabilization problems such as persistent oscillation.
But the prior art for inverter Transient Stability Analysis generally directed to be using virtual synchronous generator
(VSG) inverter of control strategy or sagging control strategy.But currently, what the grid-connected equipment of VSC in electric system generallyd use
It is still the vector control strategy voltage oriented based on end.And there are biggish for the equipment characteristic of VSC and conventional synchronous generator
Difference, not can be used directly for transient stability quantitative evaluating method-EEAC method of synchronous generator in VSC DC voltage
The qualitative assessment of transient stability；VSC based on the VSG and sagging control strategy and VSC based on vector control strategy, the two exist
Difference is huge in dynamic characteristic.Therefore, suitable for the Transient Stability Analysis of the VSC based on VSG and sagging control strategy and sentencing
Disconnected method can not be suitable for the VSC based on vector control strategy, cause based under the voltage oriented vector control strategy in end
There is large stretch of blank, depend on numerical simulation at present in VSC, the quantitative evaluation technique of DC voltage transient stability margin
Method, but simple numerical simulation can not provide the quantitative information of stability.
Summary of the invention
The purpose of the embodiment of the present invention is that providing a kind of method, apparatus and storage for assessing grid-connected exchanger transient stability
Medium can provide the qualitative assessment index for measuring VSC DC voltage transient stability margin.
To achieve the above object, the embodiment of the invention provides a kind of method for assessing grid-connected exchanger transient stability,
The following steps are included:
Obtain the first curve that the electric current of grid-connected exchanger changes over time；
Judge whether first curve encounters not reentry point；
If so, drawing the between the imbalance power and the electric current at the DC capacitor both ends of the grid-connected exchanger
The unstability numerical value of the grid-connected exchanger dullness diverging is calculated according to second curve for two curves；
If it is not, the third curve that the direct current voltage error for then drawing the grid-connected exchanger changes over time, obtains described
Several first inflection points of third curve, are fitted to obtain matched curve, and calculate the matched curve according to first inflection point
Attenuation coefficient；
When the attenuation coefficient is greater than 0, then the unstability numerical value for obtaining the grid-connected exchanger oscillation and divergence is the decaying
Coefficient；
When the attenuation coefficient be not more than 0, then draw the DC capacitor two of the corresponding grid-connected exchanger in this case
The 4th curve between the imbalance power at end and the electric current, and virtual not reentry point is constructed on the 4th curve, it obtains
The not dull diverging of grid-connected exchanger stable trajectory is calculated to the 5th virtual curve, and according to the 5th curve
Stability margin.
Preferably, the first curve that the electric current for obtaining grid-connected exchanger changes over time, specifically includes:
Simulation model is established, using the direct current voltage error of the grid-connected exchanger and watt current as observation object, is passed through
Numerical integration obtains the first curve that the electric current of the grid-connected exchanger changes over time, and the numerical integration isWherein, idiFor the watt current of the grid-connected exchanger；ΔudcFor the grid-connected friendship
The direct current voltage error of parallel operation；kidcFor the integral parameter of the DC voltage PI controller of the grid-connected exchanger；UdcFor it is described simultaneously
The DC voltage of net exchanger；For the direct voltage reference value of the grid-connected exchanger.
Preferably, described to judge whether first curve encounters not reentry point, it specifically includes:
Identify tune of the slope greater than 0 in first curve, wherein include that n slope over 10 is greater than 0 in first curve
Tune, n >=1；
Judge whether first curve encounters not reentry point in tune of the slope greater than 0；Wherein, described not return
The first node when area that point refers to that the DC capacitor electric field of the grid-connected exchanger can be reduced reaches maximum value is returned, and
The grid-connected exchanger increases in the area that the DC capacitor electric field of the first node can be reduced still less than DC capacitor electric field energy
The area added.
Preferably, described if so, drawing the imbalance power and the electricity at the grid-connected exchanger DC capacitor both ends
The unstability numerical value of the grid-connected exchanger dullness diverging, tool are calculated according to second curve for the second curve between stream
Body includes:
If first curve encounters not reentry point in tune of the preceding i sections of slope greater than 0, draw described grid-connected
The second curve between the imbalance power and the electric current at exchanger DC capacitor both ends, calculates according to second curve
To the unstability numerical value of the grid-connected exchanger dullness diverging；Wherein, 1≤i≤n, n >=3；
As i=1, the unstability numerical value of the grid-connected exchanger dullness diverging is
As i=2, the unstability numerical value of the grid-connected exchanger dullness diverging is
As i=3, the unstability numerical value of the grid-connected exchanger dullness diverging is
Wherein, AdecFor the area that the DC capacitor electric field of the grid-connected exchanger can be reduced, AincFor the grid-connected exchange
The increased area of DC capacitor electric field energy of device.
Preferably, described if it is not, the third that changes over time of the direct current voltage error for then drawing the grid-connected exchanger is bent
Line obtains several first inflection points of the third curve, is fitted to obtain matched curve according to first inflection point, and calculate institute
The attenuation coefficient for stating matched curve, specifically includes:
If not reentry point is encountered in tune of the slope greater than 0 in first curve, the grid-connected friendship is drawn
The third curve that the direct current voltage error of parallel operation changes over time obtains several first inflection points of the third curve；
First inflection point includes that Second Inflexion Point of the direct current voltage error numerical value less than 0 and direct current voltage error numerical value are greater than
0 third inflection point, the straight line mirror image for being 0 along the direct current voltage error numerical value by the Second Inflexion Point on the third curve
It is symmetric to the side of the third inflection point, obtains the 4th inflection point that multiple direct current voltage error numerical value are greater than 0；
The third inflection point and the 4th inflection point are connected, matched curve is obtained；
The attenuation coefficient of the matched curve is calculated according to the matched curve.
Preferably, described when the attenuation coefficient is not more than 0, then draw the corresponding grid-connected exchanger in this case
The 4th curve between the imbalance power at DC capacitor both ends and the electric current, and constructed virtually not on the 4th curve
Reentry point obtains the 5th virtual curve, and the grid-connected exchanger stable trajectory is calculated not according to the 5th curve
The stability margin of dullness diverging, specifically includes:
When the attenuation coefficient be not more than 0, then draw the DC capacitor two of the corresponding grid-connected exchanger in this case
The 4th curve between the imbalance power at end and the electric current；
Some DC voltage in the curve that corresponding direct current voltage error changes over time is found out in the 4th curve
Error is equal to 0 second node, and the moment continues to increase electric field energy at the second node, makes the direct current of the grid-connected exchanger
The imbalance power at capacitor both ends continues to switch to positive value by negative value as the electric current increases, and it is bent thus to obtain virtual the 5th
Line；
Third node according to the imbalance power at the DC capacitor both ends of the grid-connected exchanger equal to 0 obtains virtually not
Reentry point, while obtaining the area that the virtual electric field of the grid-connected exchanger can be reduced；
The stability margin of the not dull diverging of grid-connected exchanger stable trajectory is calculated according to the 5th curve.
Preferably, the calculation formula of the stability margin isAdec.potFor the grid-connected exchanger
The area that virtual electric field can be reduced.
The embodiment of the present invention also provides a kind of device for assessing grid-connected exchanger transient stability, comprising:
Curve acquisition module, the first curve that the electric current for obtaining grid-connected exchanger changes over time；
Judgment module, for judging whether first curve encounters not reentry point；
Dull divergence module is assessed, for if so, drawing the imbalance at the DC capacitor both ends of the grid-connected exchanger
The grid-connected exchanger dullness diverging is calculated according to second curve in the second curve between power and the electric current
Unstability numerical value；
Fitting module, for if it is not, the third that the direct current voltage error for then drawing the grid-connected exchanger changes over time
Curve obtains several first inflection points of the third curve, is fitted to obtain matched curve according to first inflection point, and calculate
The attenuation coefficient of the matched curve；
Oscillation and divergence module is assessed, for being greater than 0 when the attenuation coefficient, then obtains the grid-connected exchanger oscillation and divergence
Unstability numerical value be the attenuation coefficient；
Not divergence module is stablized in assessment, for being not more than 0 when the attenuation coefficient, then draws corresponding described in this case
The 4th curve between the imbalance power and the electric current at the DC capacitor both ends of grid-connected exchanger, and in the 4th curve
The upper virtual not reentry point of construction, obtains the 5th virtual curve, and the grid-connected exchange is calculated according to the 5th curve
The stability margin of the not dull diverging of device stable trajectory.
Another embodiment of the present invention is corresponding to provide a kind of device for assessing grid-connected exchanger transient stability, including processing
Device, memory and storage in the memory and are configured as the computer program executed by the processor, the place
Reason device realizes the grid-connected exchanger transient stability of assessment described in any of the above embodiments method when executing the computer program.
The embodiment of the invention also provides a kind of computer readable storage medium, the computer readable storage medium includes
The computer program of storage, wherein control in computer program operation and set where the computer readable storage medium
The standby method for executing the grid-connected exchanger transient stability of assessment described in any of the above embodiments.
Compared with prior art, a kind of side assessing grid-connected exchanger transient stability provided by the embodiment of the present invention
Method, device and storage medium, by making a concrete analysis of the disturbed track of grid-connected exchanger, by its disturbed track be divided into dull diverging,
Oscillation and divergence does not dissipate three kinds of situations with stable, and the parameter index of adaptability is used to the disturbed track of specific every case
To assess its unstability degree.The index of this set of calculating provided by the invention can be used as scale VSC direct current is quantitatively evaluated
The transient stability margin of pressure, having compensated for the prior art can only rely on numerical value emulation method to analyze VSC DC voltage
The technological deficiency of transient stability.The qualitative assessment index that the technical solution provides has good monotonicity, is highly convenient for difference
Factor analyzes the affecting laws of VSC grid-connected system transient stability, so as to effectively instruct the optimization of VSC controller to set
Meter.
Detailed description of the invention
Fig. 1 is a kind of process signal for method for assessing grid-connected exchanger transient stability that the embodiment of the present invention 1 provides
Figure.
Fig. 2 is grid-connected VSC Typical vector control strategy and electrical block diagram provided by the invention.
Fig. 3 is the i that grid-connected VSC provided by the invention is once interfereddi- t curve graph.
Fig. 4 is that grid-connected VSC provided by the invention is once interfered and idiThe corresponding Δ u of-t curve graphdc- t is bent
Line chart.
Fig. 5 is the P that grid-connected VSC provided by the invention is once interferedu-idiCurve graph.
Fig. 6 is the i for the dull diverging that grid-connected VSC provided by the invention is once interfereddi- t curve graph and Δ udc-t
The schematic diagram of curve graph.
Fig. 7 is the i for the oscillation and divergence that grid-connected VSC provided by the invention is once interfereddi- t curve graph and Δ udc-t
The schematic diagram of curve graph.
Fig. 8 is the oscillation convergence schematic diagram that grid-connected VSC provided by the invention is once interfered.
Fig. 9 is the oscillation and divergence schematic diagram that grid-connected VSC provided by the invention is once interfered.
Figure 10 is the grid-connected VSC stable trajectory provided by the invention virtually not schematic diagram of reentry point (VERP) acquisition methods.
Figure 11 is the virtual P that grid-connected VSC provided by the invention is once interferedu-idiCurve graph.
Figure 12 is a kind of structural representation for device for assessing grid-connected exchanger transient stability that the embodiment of the present invention 2 provides
Figure.
Figure 13 is a kind of schematic diagram for device for assessing grid-connected exchanger transient stability that the embodiment of the present invention 3 provides.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
It is a kind of process for method for assessing grid-connected exchanger transient stability that the embodiment of the present invention 1 provides referring to Fig. 1
Schematic diagram, the method includes the steps S1 to step S6:
The first curve that S1, the electric current for obtaining grid-connected exchanger change over time；
S2, judge whether first curve encounters not reentry point；
S3, if so, drawing between the imbalance power and the electric current at the DC capacitor both ends of the grid-connected exchanger
The second curve, the unstability numerical value of the grid-connected exchanger dullness diverging is calculated according to second curve；
S4, if it is not, the third curve that the direct current voltage error for then drawing the grid-connected exchanger changes over time, obtains institute
Several first inflection points for stating third curve, are fitted to obtain matched curve according to first inflection point, and it is bent to calculate the fitting
The attenuation coefficient of line；
S5, when the attenuation coefficient is greater than 0, then the unstability numerical value for obtaining the grid-connected exchanger oscillation and divergence is described decline
Subtract coefficient；
S6, when the attenuation coefficient be not more than 0, then draw the DC capacitor of the corresponding grid-connected exchanger in this case
The 4th curve between the imbalance power at both ends and the electric current, and virtual not reentry point is constructed on the 4th curve,
The 5th virtual curve is obtained, and the not dull diverging of grid-connected exchanger stable trajectory is calculated according to the 5th curve
Stability margin.
It should be noted that the grid-connected exchanger in the present invention refers to voltage-source type grid-connection converter (Voltage
Source Converter, VSC).Fig. 2 show the VSC grid-connected system based on Typical vector control strategy circuit topology and
Control structure schematic diagram.Wherein, the variable in Fig. 2 and symbol meaning are as shown in table 1.VSC vector control strategy can have been realized
The decoupling control of function, reactive power.Active power controller includes cascade DC voltage control and d shaft current (watt current point
Amount) control.The output of DC voltage control is the d shaft current reference value of current control.Reactive Power Control includes cascade nothing
Power control system and q shaft current (reactive current component) control.The output of idle control is the q shaft current reference value of current control.Nothing
There are many control strategies of power control, such as alternating voltage control, permanent Reactive Power Control and permanent reactive current control.VSC is logical
Phaselocked loop is crossed to track the phase position of grid-connected end voltage.The output angle of phaselocked loop is used between dq coordinate system and abc coordinate system
Mutual transformation.
Variable and notation index table in 1 Fig. 2 of table
Specific step is as follows for a kind of method for assessing grid-connected exchanger transient stability that the embodiment of the present invention 1 provides:
After electric system receives disturbance, the curve that each variable of VSC changes over time is referred to as to the disturbed track of VSC.Ginseng
See that Fig. 3, Fig. 3 are the motion profile that VSC is interfered in o point.By the electric current i of VSCdiIt indicates, the time is indicated with t, is obtained simultaneously
The first curve that the electric current of net exchanger changes over time, that is, obtain the i of VSCdi- t curve graph.From the figure 3, it may be seen that o point is disturbed
After dynamic, idiForward direction increases, until the direction of motion changes after a point, idiStart negative sense to reduce, so a point is that a swing is turned
Point.It can similarly obtain, b, c, d, e point are also to swing inflection point.According to idiThe direction of motion whether change, obtain idi- t curve
Several swing inflection point, are denoted as FEP.
Judge whether first curve encounters not reentry point, that is, judges idiWhether-t curve encounters not reentry point,
If idi- t curve encounters not reentry point, is intuitively reflected in idiIt further increases, and idiAfter further increasing, grid-connected exchanger is straight
The imbalance power that galvanic electricity holds both ends is not less than 0, is greater than 0 instead and constantly increases, causes vicious circle, lead to active electricity
Flow idiWith DC voltage dull diverging during the swing, i.e., the dull diverging after being interfered of grid-connected exchanger；If idi- t curve
Not reentry point is encountered, just representing can oscillation and divergence or stabilization after grid-connected exchanger is interfered.It describes below for convenience, it will
Reentry point is not denoted as NRP.
If so, drawing the second song between the imbalance power and the electric current at the DC capacitor both ends of grid-connected exchanger
The unstability numerical value of grid-connected exchanger dullness diverging is calculated according to the second curve for line.By the injustice at the DC capacitor both ends of VSC
Weigh power PuIt indicates, the second curve can use Pu-idiCurve indicates.In this case, show grid-connected exchanger by dry
It can dull diverging after disturbing.For VSC dullness divergence instability track, area and electricity can be can increase with DC capacitor electric field at its NRP
Field energy reduces the difference of area to reflect the Transient Instability degree of its DC voltage, i.e. the negative of difference is bigger, loses
Steady degree is more severe.
If it is not, the third curve that the direct current voltage error for then drawing grid-connected exchanger changes over time, obtains third curve
Several first inflection points, be fitted to obtain matched curve, and the attenuation coefficient of digital simulation curve according to the first inflection point.By VSC
Direct current voltage error Δ udcIt indicates, third curve can use Δ udc- t curve indicates that matched curve indicates lz, attenuation coefficient
It is expressed as τ.According to the Δ u of draftingdc- t curve can tentatively judge that the disturbed track VSC can vibrate convergence or oscillation and divergence, on
The smaller and smaller i.e. oscillation convergence of the range of lower fluctuation, the increasing i.e. oscillation and divergence of the range fluctuated up and down.But it is quantitatively evaluated
The unstability degree of VSC still will pass through digital simulation curve lzAttenuation coefficient τ obtain.Wherein matched curve lzIt is according to
One inflection point is fitted to obtain, and attenuation coefficient τ is according to matched curve lzBe calculated.
When attenuation coefficient τ is greater than 0, then the unstability numerical value for obtaining grid-connected exchanger oscillation and divergence is the attenuation coefficient.When
Attenuation coefficient τ is greater than 0, and the range for representing the disturbed track VSC or more fluctuation is increasing, i.e. oscillation and divergence.Attenuation coefficient τ value is got over
Greatly, physically the disturbed track VSC in subsequent swing by the faster of oscillation and divergence.
When the attenuation coefficient is not more than 0, the range for representing the disturbed track VSC or more fluctuation is smaller and smaller, i.e. oscillation is received
It holds back, then draws in this case between the imbalance power and the electric current at the DC capacitor both ends of the corresponding grid-connected exchanger
The 4th curve, i.e. the P of VSCu-idiCurve.Virtual not reentry point is constructed on the 4th curve to be denoted as convenience
According to available the 5th virtual curve of VNRP, and the grid-connected exchanger is calculated according to the 5th curve in VNRP
The stability margin of the not dull diverging of stable trajectory.
Its disturbed track is divided into dull hair by the disturbed track of the grid-connected exchanger of concrete analysis by the embodiment of the present invention 1
It dissipates, oscillation and divergence and stabilization do not dissipate three kinds of situations, and use the parameter of adaptability to the disturbed track of specific every case
Index provides certain index as scale and is quantitatively evaluated the transient stability of VSC DC voltage to assess its unstability degree
Nargin, having compensated for the prior art can only rely on numerical value emulation method to analyze the skill of the transient stability of VSC DC voltage
Art defect.The technical solution solves the shakiness that people can not judge the stability margin for stablizing case He can not know unstability case
The calculating problem for determining degree greatly facilitates people to assess a certain parameter or a certain control to VSC DC voltage transient stability
It influences.
As an improvement of the above scheme, the first curve that the electric current for obtaining grid-connected exchanger changes over time, specifically
Include:
Simulation model is established, using the direct current voltage error of the grid-connected exchanger and watt current as observation object, is passed through
Numerical integration obtains the first curve that the electric current of the grid-connected exchanger changes over time, and the numerical integration isWherein, idiFor the watt current of the grid-connected exchanger；ΔudcFor the grid-connected friendship
The direct current voltage error of parallel operation；kidcFor the integral parameter of the DC voltage PI controller of the grid-connected exchanger；UdcFor it is described simultaneously
The DC voltage of net exchanger；For the direct voltage reference value of the grid-connected exchanger.
Specifically, simulation model is established, using the direct current voltage error of VSC and watt current as observation object, passes through numerical value
Integral obtains the first curve that the electric current of grid-connected exchanger changes over time, and numerical integration isWherein, idiFor the watt current of grid-connected exchanger；ΔudcFor the straight of grid-connected exchanger
Flow voltage error；kidcFor the integral parameter of the DC voltage PI controller of grid-connected exchanger；UdcFor the direct current of grid-connected exchanger
Pressure；For the direct voltage reference value of grid-connected exchanger.
With grid-connected exchanger direct current voltage error Δ udcWith watt current idiFor observation object, pass through above-mentioned numerical integration
Obtain i of the grid-connected exchanger after o point is interfereddi- t curve graph as shown in Figure 3 and Δ udc- t curve graph is as shown in Figure 4.By
Fig. 3 and Fig. 4 it is found that o point disturbance after, Δ udc> 0, idiForward direction increases, until a point (Δ udc=0) direction of motion changes afterwards
Become, and Δ udc< 0, idiStart negative sense to reduce.In order to facilitate understanding, oa is known as watt current i recovery phasediThe 1st of movement
Pendulum, ab sections are its 2nd pendulum, and so on, bc, cd and de sections are then referred to as its 3rd, 4 and 5 pendulum.In idiIn-t curve graph,
According to Δ udc=0 obtains idiSeveral swing inflection point to-t curve, i.e., a, b, c, d, e point are known as to the swing inflection point of corresponding pendulum time
(FEP), whenever Δ udc(a, b, c, d, e point in Fig. 3), i when=0diThe direction of motion will change.In other words, at certain
If encountering FEP (Δ u in secondary swing processdc=0), then show that the secondary swing terminates, and swinging next time will start.In addition,
ΔudcWe are called n-th forward direction pendulum to pendulum when > 0 time, i.e. oa sections of corresponding N=1 in Fig. 3, bc sections of corresponding N=2, de sections right
N=3 is answered, wherein N >=1.
As an improvement of the above scheme, described to judge whether first curve encounters not reentry point, it specifically includes:
Identify tune of the slope greater than 0 in first curve, wherein include that n slope over 10 is greater than 0 in first curve
Tune, n >=1；
Judge whether first curve encounters not reentry point in tune of the slope greater than 0；Wherein, described not return
The first node when area that point refers to that the DC capacitor electric field of the grid-connected exchanger can be reduced reaches maximum value is returned, and
The grid-connected exchanger increases in the area that the DC capacitor electric field of the first node can be reduced still less than DC capacitor electric field energy
The area added.
It should be noted that ignoring VSC resistance loss, the relationship between DC voltage dynamic and VSC input, output power can
It is expressed as the first formulaWherein, CdcFor the DC capacitor of VSC；For the direct voltage reference value of VSC；PinFor the active power of VSC input；P is the active power that VSC is output to power grid；Pu
For the imbalance power at VSC DC capacitor both ends.
By the first formula equal sign both sides simultaneously to idiIntegral can obtain the second formulaWherein, idi1With Δ udc1Respectively represent product
I when separately beginningdiWith Δ udcValue, idi2With Δ udc2Represent the value at the end of integral.
The expression formula of second formula left side of the equal sign represents the variation of the electric field energy on VSC DC capacitor.Work as PuAnd didi's
When symbol is identical, the electric field on DC capacitor be can increase；Otherwise, electric field energy reduces.By PuAnd didiSymbol it is whether identical, will
The right formula of second formula is divided into two parts, specially,
And it enablesThen haveWherein,
AincAnd AdecRespectively represent Pu-idiThe face that the increased area of DC capacitor electric field energy of VSC and electric field energy reduce in curve
Product, schematic diagram are as shown in Figure 5.It is assumed that swinging P when startingu> 0, then Δ udcThe DC capacitor electric field of > 0 i.e. VSC can increase, i.e.,
AincIncrease, works as PuWhen turning negative value by positive value, A point in corresponding diagram 5, AincReach maximum value, later AdecStart to increase, Δ udc
Start to reduce, works as PuBecome a full member again when being worth by negative value, the B point in corresponding diagram 5, AdecReach maximum value.
For VSC dullness divergence instability track, when disturbed track reaches B point, AdecStill less than AincThat is Δ udcIt is still greater than
Zero, to promote idiIt further increases, and idiAfter further increasing, PuIt is greater than zero instead and constantly increases, such vicious circle,
Lead to watt current idiWith DC voltage dull diverging during the swing.Our B points are referred to as that the not reentry point of VSC (is denoted as
NRP), as shown in Figure 5.So A at its NRP can be used for VSC dullness divergence instability trackdecWith AincDifference reflect it
The Transient Instability degree of DC voltage, i.e. Adec- AincNegative it is bigger, unstability degree is more severe.
It specifically, include tune of the n slope over 10 greater than 0 in first curve；Wherein, n >=1.By defining it is found that slope
Tune greater than 0 is exactly positive pendulum.It identifies tune of the slope greater than 0 in the first curve, judges that the first curve is greater than 0 in slope
Not reentry point whether is encountered in tune, according to judging result, judges whether the interference that VSC is subject to dull can dissipate, if encountering not
Reentry point, then the interference that VSC is subject to dull can dissipate, conversely, dull will not then dissipate.Preferably, n takes 3, although dull diverging
It possibly is present in any positive pendulum of disturbed track, but the present embodiment only focuses on preceding pendulum positive three times, VSC DC voltage
Aperiodic instability situation, for the pendulum of disturbed track further below, the present embodiment thinks that it belongs to disturbed track and belongs to oscillation and divergence
The scope of unstability.
When VSC DC voltage Transient Instability, there are two main classes for unstability track: one kind is dull divergence instability track,
Corresponding idi- t curve graph and Δ udc- t curve graph is as shown in Figure 6 (o point is disturbance starting point), another kind of to lose for oscillation and divergence
Steady track, corresponding idi- t curve graph and Δ udc- t curve graph is as shown in Figure 7.The Physical Mechanism that two class unstability tracks generate
Difference, mainly due to VSC, the restoring force in transient process is insufficient for the former, and the latter is then insufficient mainly due to VSC damping force.In addition,
It is worth noting that the dull diverging of the disturbed track VSC is likely to occur in any positive pendulum, Fig. 6 and Fig. 7 be only certain once just
The schematic diagram being disturbed to swing.
As an improvement of the above scheme, described if so, drawing the imbalance at the grid-connected exchanger DC capacitor both ends
The grid-connected exchanger dullness diverging is calculated according to second curve in the second curve between power and the electric current
Unstability numerical value, specifically includes:
If first curve encounters not reentry point in tune of the preceding i sections of slope greater than 0, draw described grid-connected
The second curve between the imbalance power and the electric current at exchanger DC capacitor both ends, calculates according to second curve
To the unstability numerical value of the grid-connected exchanger dullness diverging；Wherein, 1≤i≤n, n >=3；
As i=1, the unstability numerical value of the grid-connected exchanger dullness diverging is
As i=2, the unstability numerical value of the grid-connected exchanger dullness diverging is
As i=3, the unstability numerical value of the grid-connected exchanger dullness diverging is
Wherein, AdecFor the area that the DC capacitor electric field of the grid-connected exchanger can be reduced, AincFor the grid-connected exchange
The increased area of DC capacitor electric field energy of device.
Specifically, if the first curve, that is, VSC idi- t curve encounters in tune of the preceding i sections of slope greater than 0 not to be returned
Hui Dian then draws the second curve between the imbalance power and electric current at VSC DC capacitor both ends, i.e. Pu-idiCurve, according to
Two curves calculate the unstability numerical value of available VSC dullness diverging.
The unstability numerical value that VSC dullness dissipates is indicated with η, as 1≤i≤n, n >=3, η value can use as the case may be
Different formulas is calculated, specially；As i=1, the unstability numerical value of the grid-connected exchanger dullness diverging isAs i=2, the unstability numerical value of the grid-connected exchanger dullness diverging isAs i=3,
The unstability numerical value of the grid-connected exchanger dullness diverging isWherein, AdecFor the DC capacitor electricity of grid-connected exchanger
The area of field energy reduction, AincFor the increased area of DC capacitor electric field energy of grid-connected exchanger.
Because reentry point does not refer to the area A that VSC DC capacitor electric field can be reduceddecReach first segment when maximum value
Point, and AdecLess than Ainc, thus can be according to being calculated so the η value being calculated according to formula above is less than 0
Whether the η value arrived judges whether interference that VSC be subject to can dull dissipate less than 0, if the interference that VSC is subject to can be single less than 0
Readjust the distribution it is scattered, conversely, dull will not then dissipate.η value has good monotonicity, can be used as the mistake of grid-connected exchanger dullness diverging
Steady numerical value, and η value absolute value is bigger, and the unstability degree of the grid-connected exchanger dullness diverging is more severe.
As an improvement of the above scheme, described if it is not, then drawing the direct current voltage error of the grid-connected exchanger at any time
The third curve of variation obtains several first inflection points of the third curve, is fitted according to first inflection point
Curve, and the attenuation coefficient of the matched curve is calculated, it specifically includes:
If not reentry point is encountered in tune of the slope greater than 0 in first curve, the grid-connected friendship is drawn
The third curve that the direct current voltage error of parallel operation changes over time obtains several first inflection points of the third curve；
First inflection point includes that Second Inflexion Point of the direct current voltage error numerical value less than 0 and direct current voltage error numerical value are greater than
0 third inflection point, the straight line mirror image for being 0 along the direct current voltage error numerical value by the Second Inflexion Point on the third curve
It is symmetric to the side of the third inflection point, obtains the 4th inflection point that multiple direct current voltage error numerical value are greater than 0；
The third inflection point and the 4th inflection point are connected, matched curve is obtained；
The attenuation coefficient of the matched curve is calculated according to the matched curve.
Specifically, if the first curve, that is, VSC idi- t curve is encountered not in tune of the preceding i sections of slope greater than 0
Reentry point, then representing interference that VSC is subject to dull will not dissipate, then the unstability degree for assessing the interference that VSC is subject to cannot be according to
η value is calculated to obtain, is needed using other parameters, therefore what the direct current voltage error for needing to draw grid-connected exchanger changed over time
Third curve, that is, Δ udc- t curve obtains several first inflection points of third curve.Observe Δ udcThe variation tendency of t at any time,
In order to quantitatively assess this variation tendency, by Δ udcAll first inflection points are uniformly adjusted to same direction (i.e. Δ in-t curve
udc> 0 or Δ udc< 0) on.Wherein, the first inflection point includes direct current voltage error value, Δ udcSecond Inflexion Point and direct current less than 0
Voltage error value, Δ udcThird inflection point greater than 0,
In the present embodiment, by Δ udcAll first inflection points are uniformly adjusted to Δ u in-t curvedcOn > 0 direction, specifically
Are as follows: the straight line, that is, straight line Δ u for being 0 along the direct current voltage error numerical value by Second Inflexion Point on third curvedc=0 mirror image pair
The side for claiming third inflection point obtains multiple direct current voltage error value, Δ udcThe 4th inflection point greater than 0.
By Δ udcAfter the Second Inflexion Point adjustment for needing to adjust in-t curve, third inflection point has been connected with the 4th inflection point
Come, obtains matched curve lz.As shown in Figure 8 and Figure 9, respectively VSC direct current voltage error Δ udcDo not occur in first 5 pendulum time
Movement locus schematic diagram when dullness diverging.In figs. 8 and 9, b', d' point are respectively Δ udcB, d point relative rectilinear Δ when < 0
udc=0 symmetric points.An exponential curve l can be fitted by the method for curve matching according to 5 points of a, b', c, d', ez,
It can be assumed as function Ameτt, wherein τ is matched curve lzAttenuation coefficient.
According to matched curve lzDigital simulation curve lzAttenuation coefficient τ, the present embodiment based on to the understanding of the physics of damping,
Pass through Δ u in 5 pendulum before the disturbed track VSC secondary (i.e. comprising 3 times positive pendulum)dcThe amplitude of oscillation size of-t curve relative equilibrium is come
Estimate that the damping of VSC grid-connected system is positive and negative.If τ is negative (as shown in Figure 8), show that system damping is positive, disturbed track oscillation
Convergence, and τ value is smaller, the physically subsequent swing of disturbed track will also restrain faster；Conversely, if τ is positive (as shown in Figure 9),
Then show that system damping is negative, disturbed track is by oscillation and divergence, and τ value is bigger, and physically disturbed track will in subsequent swing
Oscillation and divergence it is faster.
When attenuation coefficient τ is greater than 0, then show grid-connected exchanger for oscillation and divergence, and attenuation coefficient τ is bigger, grid-connected exchange
Device oscillation and divergence is faster, therefore the unstability numerical value of grid-connected exchanger oscillation and divergence can be obtained by attenuation coefficient τ.
As an improvement of the above scheme, described to work as the attenuation coefficient no more than 0, then it draws corresponding described in this case
The 4th curve between the imbalance power and the electric current at the DC capacitor both ends of grid-connected exchanger, and in the 4th curve
The upper virtual not reentry point of construction, obtains the 5th virtual curve, and the grid-connected exchange is calculated according to the 5th curve
The stability margin of the not dull diverging of device stable trajectory, specifically includes:
When the attenuation coefficient be not more than 0, then draw the DC capacitor two of the corresponding grid-connected exchanger in this case
The 4th curve between the imbalance power at end and the electric current；
Some DC voltage in the curve that corresponding direct current voltage error changes over time is found out in the 4th curve
Error is equal to 0 second node, and the moment continues to increase electric field energy at the second node, makes the direct current of the grid-connected exchanger
The imbalance power at capacitor both ends continues to switch to positive value by negative value as the electric current increases, and it is bent thus to obtain virtual the 5th
Line；
Third node according to the imbalance power at the DC capacitor both ends of the grid-connected exchanger equal to 0 obtains virtually not
Reentry point, while obtaining the area that the virtual electric field of the grid-connected exchanger can be reduced；
The stability margin of the not dull diverging of grid-connected exchanger stable trajectory is calculated according to the 5th curve.
It needs explanatorily, when attenuation coefficient τ is not more than 0, then shows the neither dull diverging in the track of VSC, also nonoscillatory is sent out
It dissipates, is in stable state, to measure the degree of stability of VSC stable trajectory at this time, put in secondary only due to stablizing disturbed track each
There is FEP without NRP, therefore virtual not reentry point need to be constructed, does not return virtually and be denoted as VNRP.
The VNRP can following handover operation obtain, schematic diagram is as shown in Figure 10, specifically:
The k in DC voltage control circuit is disconnected at FEPpdcBranch, and numerical integration switching is carried out, switching numerical value product
It is divided into idi=kidc∫ΔudcDt, Δ udc=ε, wherein kidcFor the integral parameter of grid-connected exchanger DC voltage PI controller；ε
For given grid-connected exchanger DC voltage slight error.
Its physical interpretation is, it is assumed that (the Δ u at this time at the FEP of VSC stable trajectorydc=0) continue to inject toward DC capacitor
Certain electric field energy, then idiWill not backswing and be to continue with increase, until PuStart to turn negative number to positive number, i.e. arrival VNRP (P at this timeu
=0).Track from FEP to VNRP be it is imaginary, pass through imaginary Pu-idiCurve can be reduced area to calculate potential electric field
Adec.pot(being equivalent to the electric field energy additionally injected), the value physically reflect the transient stability degree of DC voltage, can incite somebody to action
Its stability margin as the not dull diverging of stable trajectory.
Specifically, when attenuation coefficient τ be not more than 0, then draw the DC capacitor two of corresponding grid-connected exchanger in this case
Four curves, that is, P between the imbalance power at end and the electric currentu-idiCurve finds out corresponding direct current in the 4th curve
It holds up in the curve that difference changes over time at the second node i.e. FEP of VSC stable trajectory of some direct current voltage error equal to 0
(Δ u at this timedc=0), the moment continues to increase electric field energy at second node, makes the imbalance power at the DC capacitor both ends of VSC
PuContinue with electric current idiIncrease and positive value is switched to by negative value, thus obtains the 5th virtual curve, specific schematic diagram such as Figure 11 institute
Show.
According to the imbalance power P at the DC capacitor both ends of grid-connected exchangeruThird node equal to 0 obtains not returning virtually
Point VNRP is returned, while obtaining the area that the virtual electric field of grid-connected exchanger can be reduced；
The stability margin of the not dull diverging of grid-connected exchanger stable trajectory is calculated according to the 5th curve.
As an improvement of the above scheme, the calculation formula of the stability margin isAdec.potIt is described
The area that the virtual electric field of grid-connected exchanger can be reduced.
Specifically, the stability margin by the not dull diverging of VSC stable trajectory is indicated with γ, with reference to the mistake of dull divergent loci
The calculating process of steady numerical value η value, the calculation formula of γ areAdec.potFor the virtual of grid-connected exchanger
The area that electric field can be reduced.
Because the γ value is obtained in the case where attenuation coefficient τ is no more than 0, disturbed rail is stablized for VSC
Mark, stability margin quantizating index can be measured jointly by τ value and γ value, and have τ≤0 and γ >=0.By attenuation coefficient τ and γ value
The stability margin of the available not dull diverging of grid-connected exchanger stable trajectory, attenuation coefficient τ value is smaller, and grid-connected exchanger is stablized
The degree of stability of nonoscillatory diverging is better, and γ value is bigger, and the degree of stability that grid-connected exchanger stablizes not dull diverging is better.
In conclusion the present invention is based on the disturbed tracks VSC to provide for measuring VSC DC voltage transient stability margin
Quantitative target η, τ and γ, and its calculation method is set forth in detail.When τ≤0 and γ >=0, VSC DC voltage transient stability,
As τ>0, VSC DC voltage oscillation and divergence unstability, as η<0, VSC DC voltage dullness divergence instability, and the index has
Good monotonicity.Must from the point of view of, τ value is smaller, VSC DC voltage in transient process nonoscillatory dissipate degree of stability get over
Good, γ value is bigger, and the degree of stability of VSC DC voltage not dull diverging in transient process is better.
It is worth noting that the present disclosure applies equally to use the VSC of other control strategies.Broadly, all
There is the grid-connection converter of dc-link capacitance branch, the present invention is applicable on circuit structure.
It is a kind of knot for device for assessing grid-connected exchanger transient stability that the embodiment of the present invention 2 provides referring to Figure 12
Structure schematic diagram, described device include:
Curve acquisition module 11, the first curve that the electric current for obtaining grid-connected exchanger changes over time；
Judgment module 12, for judging whether first curve encounters not reentry point；
Dull divergence module 13 is assessed, for if so, drawing the injustice at the DC capacitor both ends of the grid-connected exchanger
The second curve to weigh between power and the electric current is calculated the grid-connected exchanger dullness according to second curve and dissipates
Unstability numerical value；
Fitting module 14, for if it is not, the direct current voltage error for then drawing the grid-connected exchanger change over time
Three curves obtain several first inflection points of the third curve, are fitted to obtain matched curve according to first inflection point, and count
Calculate the attenuation coefficient of the matched curve；
Oscillation and divergence module 15 is assessed, for being greater than 0 when the attenuation coefficient, then obtains the grid-connected exchanger oscillation hair
Scattered unstability numerical value is the attenuation coefficient；
Not divergence module 16 are stablized in assessment, for being not more than 0 when the attenuation coefficient, then draw corresponding institute in this case
The 4th curve between the imbalance power and the electric current at the DC capacitor both ends of grid-connected exchanger is stated, and bent the described 4th
Virtual not reentry point is constructed on line, obtains the 5th virtual curve, and the grid-connected friendship is calculated according to the 5th curve
The stability margin of the not dull diverging of parallel operation stable trajectory.
Preferably, the curve acquisition module 11 is specifically used for:
Simulation model is established, using the direct current voltage error of the grid-connected exchanger and watt current as observation object, is passed through
Numerical integration obtains the first curve that the electric current of the grid-connected exchanger changes over time, and the numerical integration isWherein, idiFor the watt current of the grid-connected exchanger；ΔudcFor the grid-connected friendship
The direct current voltage error of parallel operation；kidcFor the integral parameter of the DC voltage PI controller of the grid-connected exchanger；UdcFor it is described simultaneously
The DC voltage of net exchanger；For the direct voltage reference value of the grid-connected exchanger.
Preferably, the judgment module 12 specifically includes:
Recognition unit, for identification in first curve slope be greater than 0 tune, wherein wrapped in first curve
Include the tune that n slope over 10 is greater than 0, n >=1；
Judging unit, for judging whether first curve encounters not reentry point in tune of the slope greater than 0；
Wherein, the not reentry point refers to when area that the DC capacitor electric field of the grid-connected exchanger can be reduced reaches maximum value
First node, and the area that the grid-connected exchanger can be reduced in the DC capacitor electric field of the first node is still less than direct current
The area that capacitive field can increase.
Preferably, the dull divergence module 13 of the assessment is specifically used for:
If first curve encounters not reentry point in tune of the preceding i sections of slope greater than 0, draw described grid-connected
The second curve between the imbalance power and the electric current at exchanger DC capacitor both ends, calculates according to second curve
To the unstability numerical value of the grid-connected exchanger dullness diverging；Wherein, 1≤i≤n, n >=3；
As i=1, the unstability numerical value of the grid-connected exchanger dullness diverging is
As i=2, the unstability numerical value of the grid-connected exchanger dullness diverging is
As i=3, the unstability numerical value of the grid-connected exchanger dullness diverging is
Wherein, AdecFor the area that the DC capacitor electric field of the grid-connected exchanger can be reduced, AincFor the grid-connected exchange
The increased area of DC capacitor electric field energy of device.
Preferably, the fitting module 14 specifically includes:
Second drawing unit, if not reentry point is encountered in tune of the slope greater than 0 for first curve,
The third curve that the direct current voltage error of the grid-connected exchanger changes over time then is drawn, the several of the third curve are obtained
A first inflection point；
Auxiliary unit includes Second Inflexion Point and direct current of the direct current voltage error numerical value less than 0 for first inflection point
Error value is pressed to be greater than 0 third inflection point, by the Second Inflexion Point along the direct current voltage error number on the third curve
The straight line mirror symmetry that value is 0 obtains the 4th of multiple direct current voltage error numerical value greater than 0 and turns to the side of the third inflection point
Point；
Third drawing unit obtains matched curve for connecting the third inflection point and the 4th inflection point；
First computing unit, for calculating the attenuation coefficient of the matched curve according to the matched curve.
Preferably, the assessment is stablized not divergence module 16 and is specifically included:
4th drawing unit then draws the corresponding grid-connected friendship in this case for being not more than 0 when the attenuation coefficient
The 4th curve between the imbalance power and the electric current at the DC capacitor both ends of parallel operation；
5th drawing unit, the curve changed over time for finding out corresponding direct current voltage error in the 4th curve
In some direct current voltage error be equal to 0 second node, the moment continues to increase electric field energy at the second node, makes described
The imbalance power at the DC capacitor both ends of grid-connected exchanger continues to switch to positive value by negative value as the electric current increases, thus
To the 5th virtual curve；
Virtual construct unit, the imbalance power for the DC capacitor both ends according to the grid-connected exchanger are equal to 0
Third node obtains virtual not reentry point, while obtaining the area that the virtual electric field of the grid-connected exchanger can be reduced；
Second computing unit, it is not dull for the grid-connected exchanger stable trajectory to be calculated according to the 5th curve
The stability margin of diverging.
Preferably, the calculation formula of the stability margin isAdec.potFor the grid-connected exchanger
The area that virtual electric field can be reduced.
It is a kind of showing for device for assessing grid-connected exchanger transient stability that the embodiment of the present invention 3 provides referring to Figure 13
It is intended to, described device includes processor 10, memory 20 and is stored in the memory 20 and is configured as by described
The computer program that device 10 executes is managed, the processor 10 is realized described in any of the above-described embodiment when executing the computer program
The grid-connected exchanger transient stability of assessment method.
Illustratively, computer program can be divided into one or more module/units, and one or more module/
Unit is stored in memory 20, and is executed by processor 10, to complete the present invention.One or more module/units can be with
It is the series of computation machine program instruction section that can complete specific function, which comments for describing computer program in one kind
Estimate the implementation procedure in grid-connected exchanger transient stability.For example, computer program can be divided into curve acquisition module, sentence
Disconnected module assesses dull divergence module, fitting module, assesses oscillation and divergence module and assess and stablize not divergence module, each module
Concrete function is as follows:
Curve acquisition module 11, the first curve that the electric current for obtaining grid-connected exchanger changes over time；
Judgment module 12, for judging whether first curve encounters not reentry point；
Dull divergence module 13 is assessed, for if so, drawing the injustice at the DC capacitor both ends of the grid-connected exchanger
The second curve to weigh between power and the electric current is calculated the grid-connected exchanger dullness according to second curve and dissipates
Unstability numerical value；
Fitting module 14, for if it is not, the direct current voltage error for then drawing the grid-connected exchanger change over time
Three curves obtain several first inflection points of the third curve, are fitted to obtain matched curve according to first inflection point, and count
Calculate the attenuation coefficient of the matched curve；
Oscillation and divergence module 15 is assessed, for being greater than 0 when the attenuation coefficient, then obtains the grid-connected exchanger oscillation hair
Scattered unstability numerical value is the attenuation coefficient；
Not divergence module 16 are stablized in assessment, for being not more than 0 when the attenuation coefficient, then draw corresponding institute in this case
The 4th curve between the imbalance power and the electric current at the DC capacitor both ends of grid-connected exchanger is stated, and bent the described 4th
Virtual not reentry point is constructed on line, obtains the 5th virtual curve, and the grid-connected friendship is calculated according to the 5th curve
The stability margin of the not dull diverging of parallel operation stable trajectory.
The device of the grid-connected exchanger transient stability of assessment can be desktop PC, notebook, palm PC
And cloud server etc. calculates equipment.The device of the grid-connected exchanger transient stability of assessment may include, but be not limited only to, and locate
Manage device, memory.It will be understood by those skilled in the art that schematic diagram 13 is only a kind of grid-connected exchanger transient stability of assessment
Device example, do not constitute the restriction of the device to the grid-connected exchanger transient stability of the assessment, may include than figure
Show more or fewer components, perhaps combines certain components or different components, such as the grid-connected exchanger transient state of assessment
The device of stability can also include input-output equipment, network access equipment, bus etc..
Processor 10 can be central processing unit (Central Processing Unit, CPU), can also be other
General processor, digital signal processor (Digital Signal Processor, DSP), specific integrated circuit
(Application Specific Integrated Circuit, ASIC), ready-made programmable gate array (Field-
Programmable Gate Array, FPGA) either other programmable logic device, discrete gate or transistor logic,
Discrete hardware components etc..General processor can be microprocessor or processor 10 is also possible to any conventional processor
Deng processor 10 is the control centre of described device, entirely assesses grid-connected exchanger transient state using various interfaces and connection
The various pieces of the device of stability.
Memory 20 can be used for storing the computer program and/or module, and processor 10 is by operation or executes storage
Computer program and/or module in memory 20, and the data being stored in memory 20 are called, realize the assessment
The various functions of the device of grid-connected exchanger transient stability.Memory 20 can mainly include storing program area and storing data
Area, wherein storing program area can application program needed for storage program area, at least one function (such as sound-playing function,
Image player function etc.) etc.；Storage data area, which can be stored, uses created data (such as audio data, electricity according to mobile phone
Script for story-telling etc.) etc..In addition, memory 20 may include high-speed random access memory, it can also include nonvolatile memory,
Such as hard disk, memory, plug-in type hard disk, intelligent memory card (Smart Media Card, SMC), secure digital (Secure
Digital, SD) card, flash card (Flash Card), at least one disk memory, flush memory device or other volatibility
Solid-state memory.
Wherein, if the integrated module of the device of the grid-connected exchanger transient stability of the assessment is with SFU software functional unit
Form realize and when sold or used as an independent product, can store in a computer readable storage medium.Base
In such understanding, the present invention realizes all or part of the process in above-described embodiment method, can also pass through computer program
It is completed to instruct relevant hardware, above-mentioned computer program can be stored in a computer readable storage medium, the calculating
Machine program is when being executed by processor, it can be achieved that the step of above-mentioned each embodiment of the method.Wherein, above-mentioned computer program includes
Computer program code, computer program code can for source code form, object identification code form, executable file or it is certain in
Between form etc..Computer-readable medium may include: that any entity that can carry computer program code or device, record are situated between
It is matter, USB flash disk, mobile hard disk, magnetic disk, CD, computer storage, read-only memory (ROM, Read-Only Memory), random
Access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium etc..It needs
It is noted that computer-readable medium include content can according in jurisdiction make laws and patent practice requirement into
Row increase and decrease appropriate, such as do not include electric load according to legislation and patent practice, computer-readable medium in certain jurisdictions
Wave signal and telecommunication signal.
The embodiment of the invention also provides a kind of computer readable storage medium, the computer readable storage medium includes
The computer program of storage, wherein control in computer program operation and set where the computer readable storage medium
The standby method for executing the grid-connected exchanger transient stability of assessment described in any of the above-described embodiment.
To sum up, it a kind of method, apparatus that assessing grid-connected exchanger transient stability provided by the embodiment of the present invention and deposits
Its disturbed track is divided into dull diverging, oscillation and divergence and steady by making a concrete analysis of the disturbed track of grid-connected exchanger by storage media
It is fixed not dissipate three kinds of situations, and its unstability is assessed using the parameter index of adaptability to the disturbed track of specific every case
Degree provides quantitative target η, τ and γ for measuring VSC DC voltage transient stability margin, and its meter is set forth in detail
Calculation method, when τ≤0 and γ >=0, VSC DC voltage transient stability, as τ > 0, VSC DC voltage oscillation and divergence unstability, when
When η < 0, VSC DC voltage dullness divergence instability.This set of parameter provided by the invention can be used as scale quantitatively to comment
The transient stability margin for estimating VSC DC voltage, having compensated for the prior art can only rely on numerical value emulation method to analyze
The technological deficiency of the transient stability of VSC DC voltage.The technical solution solve people can not judge to stablize stablizing for case it is abundant
The calculating problem of degree and the unstable degree that can not know unstability case greatly facilitates people to assess a certain parameter or a certain control
Influence to VSC DC voltage transient stability, and the qualitative assessment index provided has good monotonicity, is highly convenient for
Different factors analyze the affecting laws of VSC grid-connected system transient stability, so as to effectively instruct the optimization of VSC controller
Design.
The above is a preferred embodiment of the present invention, it is noted that for those skilled in the art
For, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications are also considered as
Protection scope of the present invention.
Claims (10)
1. a kind of method for assessing grid-connected exchanger transient stability, which comprises the following steps:
Obtain the first curve that the electric current of grid-connected exchanger changes over time；
Judge whether first curve encounters not reentry point；
If so, drawing the second song between the imbalance power and the electric current at the DC capacitor both ends of the grid-connected exchanger
The unstability numerical value of the grid-connected exchanger dullness diverging is calculated according to second curve for line；
If it is not, the third curve that the direct current voltage error for then drawing the grid-connected exchanger changes over time, obtains the third
Several first inflection points of curve, are fitted to obtain matched curve, and calculate declining for the matched curve according to first inflection point
Subtract coefficient；
When the attenuation coefficient is greater than 0, then the unstability numerical value for obtaining the grid-connected exchanger oscillation and divergence is the attenuation coefficient；
When the attenuation coefficient is not more than 0, then DC capacitor both ends of the corresponding grid-connected exchanger in this case are drawn
The 4th curve between imbalance power and the electric current, and virtual not reentry point is constructed on the 4th curve, obtain void
The 5th quasi- curve, and the stabilization of the not dull diverging of grid-connected exchanger stable trajectory is calculated according to the 5th curve
Nargin.
2. assessing the method for grid-connected exchanger transient stability as described in claim 1, which is characterized in that described to obtain grid-connected friendship
The first curve that the electric current of parallel operation changes over time, specifically includes:
Simulation model is established, using the direct current voltage error of the grid-connected exchanger and watt current as observation object, passes through numerical value
Integral obtains the first curve that the electric current of the grid-connected exchanger changes over time, and the numerical integration isWherein, idiFor the watt current of the grid-connected exchanger；ΔudcFor the grid-connected friendship
The direct current voltage error of parallel operation；kidcFor the integral parameter of the DC voltage PI controller of the grid-connected exchanger；UdcFor it is described simultaneously
The DC voltage of net exchanger；For the direct voltage reference value of the grid-connected exchanger.
3. assessing the method for grid-connected exchanger transient stability as described in claim 1, which is characterized in that the judgement described the
Whether one curve encounters not reentry point, specifically includes:
Identify tune of the slope greater than 0 in first curve, wherein include the song that n slope over 10 is greater than 0 in first curve
Section, n >=1；
Judge whether first curve encounters not reentry point in tune of the slope greater than 0；Wherein, the not reentry point
Refer to first node when area that the DC capacitor electric field of the grid-connected exchanger can be reduced reaches maximum value, and described
Grid-connected exchanger is increased still less than DC capacitor electric field energy in the area that the DC capacitor electric field of the first node can be reduced
Area.
4. assessing the method for grid-connected exchanger transient stability as claimed in claim 3, which is characterized in that described if so, drawing
The second curve between the imbalance power and the electric current at the grid-connected exchanger DC capacitor both ends is made, according to described second
The unstability numerical value of the grid-connected exchanger dullness diverging is calculated in curve, specifically includes:
If first curve encounters not reentry point in tune of the preceding i sections of slope greater than 0, the grid-connected exchange is drawn
Institute is calculated according to second curve in the second curve between the imbalance power and the electric current at device DC capacitor both ends
State the unstability numerical value of grid-connected exchanger dullness diverging；Wherein, 1≤i≤n, n >=3；
As i=1, the unstability numerical value of the grid-connected exchanger dullness diverging is
As i=2, the unstability numerical value of the grid-connected exchanger dullness diverging is
As i=3, the unstability numerical value of the grid-connected exchanger dullness diverging is
Wherein, AdecFor the area that the DC capacitor electric field of the grid-connected exchanger can be reduced, AincFor the grid-connected exchanger
The increased area of DC capacitor electric field energy.
5. assessing the method for grid-connected exchanger transient stability as claimed in claim 3, which is characterized in that described if it is not, then drawing
Make the third curve that the direct current voltage error of the grid-connected exchanger changes over time, obtain the third curve several
One inflection point is fitted to obtain matched curve, and calculates the attenuation coefficient of the matched curve according to first inflection point, specific to wrap
It includes:
If not reentry point is encountered in tune of the slope greater than 0 in first curve, the grid-connected exchanger is drawn
The third curve that changes over time of direct current voltage error, obtain several first inflection points of the third curve；
First inflection point includes that Second Inflexion Point of the direct current voltage error numerical value less than 0 and direct current voltage error numerical value are greater than 0
Third inflection point, the straight line mirror image pair for being 0 along the direct current voltage error numerical value by the Second Inflexion Point on the third curve
The side for claiming the third inflection point obtains the 4th inflection point that multiple direct current voltage error numerical value are greater than 0；
The third inflection point and the 4th inflection point are connected, matched curve is obtained；
The attenuation coefficient of the matched curve is calculated according to the matched curve.
6. assessing the method for grid-connected exchanger transient stability as described in claim 1, which is characterized in that described to work as the decaying
Coefficient is not more than 0, then draws the imbalance power at the DC capacitor both ends of the corresponding grid-connected exchanger and institute in this case
The 4th curve between electric current is stated, and constructs virtual not reentry point on the 4th curve, obtains the 5th virtual curve, and
The stability margin of the not dull diverging of grid-connected exchanger stable trajectory is calculated according to the 5th curve, specifically includes:
When the attenuation coefficient is not more than 0, then DC capacitor both ends of the corresponding grid-connected exchanger in this case are drawn
The 4th curve between imbalance power and the electric current；
Some direct current voltage error in the curve that corresponding direct current voltage error changes over time is found out in the 4th curve
Second node equal to 0, the moment continues to increase electric field energy at the second node, makes the DC capacitor of the grid-connected exchanger
The imbalance power at both ends continues to switch to positive value by negative value as the electric current increases, and thus obtains the 5th virtual curve；
Third node according to the imbalance power at the DC capacitor both ends of the grid-connected exchanger equal to 0 obtains not returning virtually
Point, while obtaining the area that the virtual electric field of the grid-connected exchanger can be reduced；
The stability margin of the not dull diverging of grid-connected exchanger stable trajectory is calculated according to the 5th curve.
7. assessing the method for grid-connected exchanger transient stability as claimed in claim 6, which is characterized in that the stability margin
Calculation formula isAdec.potThe area that can be reduced for the virtual electric field of the grid-connected exchanger.
8. a kind of device for assessing grid-connected exchanger transient stability characterized by comprising
Curve acquisition module, the first curve that the electric current for obtaining grid-connected exchanger changes over time；
Judgment module, for judging whether first curve encounters not reentry point；
Dull divergence module is assessed, for if so, drawing the imbalance power at the DC capacitor both ends of the grid-connected exchanger
The unstability of the grid-connected exchanger dullness diverging is calculated according to second curve for the second curve between the electric current
Numerical value；
Fitting module, for if it is not, the third curve that the direct current voltage error for then drawing the grid-connected exchanger changes over time,
Several first inflection points of the third curve are obtained, are fitted to obtain matched curve according to first inflection point, and described in calculating
The attenuation coefficient of matched curve；
Oscillation and divergence module is assessed, for being greater than 0 when the attenuation coefficient, then obtains the mistake of the grid-connected exchanger oscillation and divergence
Steady numerical value is the attenuation coefficient；
Not divergence module is stablized in assessment, for being not more than 0 when the attenuation coefficient, then draws corresponding described grid-connected in this case
The 4th curve between the imbalance power and the electric current at the DC capacitor both ends of exchanger, and the structure on the 4th curve
Virtual not reentry point is made, the 5th virtual curve is obtained, and it is steady according to the 5th curve grid-connected exchanger to be calculated
The stability margin of the not dull diverging of fixed track.
9. a kind of device for assessing grid-connected exchanger transient stability, which is characterized in that including processor, memory and storage
In the memory and it is configured as the computer program executed by the processor, the processor executes the computer
The method of the grid-connected exchanger transient stability of assessment as described in any one of claims 1 to 7 is realized when program.
10. a kind of computer readable storage medium, which is characterized in that the computer readable storage medium includes the calculating of storage
Machine program, wherein equipment where controlling the computer readable storage medium in computer program operation is executed as weighed
Benefit require any one of 1 to 7 described in the grid-connected exchanger transient stability of assessment method.
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