CN106786608B - A kind of uncertain harmonic flow calculation method suitable for distributed generation resource access - Google Patents
A kind of uncertain harmonic flow calculation method suitable for distributed generation resource access Download PDFInfo
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- 238000004364 calculation method Methods 0.000 title claims abstract description 39
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- 238000000342 Monte Carlo simulation Methods 0.000 abstract 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
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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]
Abstract
The present invention relates to a kind of uncertain harmonic flow calculation methods suitable for distributed generation resource access, specifically includes the following steps: having the distributed generation resource of fluctuation firstly for output power, the output power of grid node is modeled using reverse cloud model generator based on measurement sample；Then according to normal cloud modelRange acquires the power prediction range of DG grid node；Then it is based on resulting power bracket, uncertain harmonic flow calculation is carried out in conjunction with boundary flow method, finds out the distribution of mains by harmonics trend；Finally according to node voltage total harmonic distortion factor as a result, judging whether each node harmonic content of power grid belongs to safe range.The present invention has a better inclusiveness to fluctuation data, and identical operation purpose and under the conditions of, mentioned algorithm computational efficiency is suitable with probabilistic power flow method computational efficiency much higher than Monte Carlo method.
Description
Technical field
It is especially a kind of suitable for the uncertain of distributed generation resource access the present invention relates to Power System Analysis technical field
Harmonic flow calculation method.
Background technique
Distributed generation resource accesses power grid more and more, it also brings to power grid many while gradually making the most of the advantage
Harm, wherein just including fluctuation harmonic wave interference.Harmonic flow calculation is that harmonic problem is most directly effective in the research direction of energy
Method, harmonic flow calculation can calculate the degree and branch harmonic current of each node harmonic voltage of power grid, harmonic distortion, be to comment
Estimate the important evidence of safe operation of power system.
With the sustainable growth of electricity needs, the shortage of traditional energy and the opening of electricity market, the positive court of power grid at present
Efficiently, flexibly, intelligence direction develop.China's energy supply at present is very nervous, and China has become the world
Maximum carbon emission state, exploitation dynamics, development " low-carbon " energy resource structure for increasing renewable energy are extremely urgent.And utilize wind
The distributed generation resource of the clean energy resourcies such as energy, solar energy is the good method for solving problem above.
But due to being influenced by factors such as weather, environment, grid-connected DG output power has very big fluctuation, borrows
The harmonic current that the DG for helping power electronic technique grid-connected is issued is fluctuated with output power, i.e., node harmonic electric current is fluctuation
, eventually lead to the uncertain harmonic trend problem of electric system.For harmonic trend uncertain in power grid, existing research
It is analyzed, wherein the research to probabilistic power flow method is more.Uncertain information is considered as by probabilistic power flow method meets stochastic behaviour,
Judge the fluctuation of uncertain information using 2 rank squares, i.e., uncertainty is measured with standard deviation.Foundation meets actual probability mould
Type needs a large amount of accurate basic datas, and in practical application, on the one hand, under current system hardware condition, it is difficult to obtain foot
Enough basic datas；On the other hand, probabilistic model only considers single uncertain (randomness), is not enough to reflect the true of information
Situation.Therefore, existing random harmonic tidal current computing method is difficult to obtain accurate harmonic trend index.
In view of the above problems, the present invention proposes a kind of uncertain harmonic flow calculation side suitable for distributed generation resource access
Method.
Summary of the invention
In view of this, the purpose of the present invention is to propose to a kind of uncertain harmonic trend meters suitable for distributed generation resource access
Calculation method, not only calculated result is accurate, but also is simple and efficient, and using effect is good.
The present invention is realized using following scheme: a kind of uncertain harmonic flow calculation side suitable for distributed generation resource access
Method, specifically includes the following steps:
Step S1: having output power the distributed generation resource of fluctuation, utilizes reverse cloud model based on measurement sample
Generator models the output power of grid node；
Step S2: according to 3 δ ranges of normal cloud model, the power prediction range of DG grid node is acquired；
Step S3: being based on the resulting power bracket of step S3, carries out uncertain harmonic flow calculation in conjunction with boundary flow method,
Find out the distribution of mains by harmonics trend；
Step S4: according to node voltage total harmonic distortion factor as a result, judging whether each node harmonic content of power grid belongs to peace
Gamut.
Further, the step S1 specifically: do not know the data of node measurement to power grid using backward cloud generator
Carry out cloud modeling:
Wherein, ExFor cloud model expectation, EnFor the entropy of cloud model, HeThe super entropy of cloud model, xiFor the measurement of DG grid node
Power data, n are data amount check,For power sample mean value.
Further, 3 δ ranges described in step S2 are [Ex-3(En+3He),Ex+3(En+3He)]。
Further, step S3 specifically: using obtained grid node power bracket, grid node power this
Input quantity of the boundary value of variable as certainty Load flow calculation carries out multiple certainty Load flow calculation, obtains unknown variable
Boundary value.
Further, in step S4, the node voltage total harmonic distortion factor THDuCalculating use following formula:
Wherein, UHIndicate node harmonic voltage total amount, U1Indicate node fundamental voltage.
Compared with prior art, the invention has the following beneficial effects: the present invention was calculated to Harmonic Power Flow of Power Systems
The influence that intermittent DG output-power fluctuation has been fully considered in journey proposes completely uncertain harmonic flow calculation process,
Keep calculated result more accurate and reasonable.Meanwhile this method is simple and efficient, common planning personnel can be convenient grasp, can be rule
It draws, a kind of mains by harmonics content suitable for DG access of operation phase is judged and provides reference.
Detailed description of the invention
Fig. 1 is the implementation flow chart of the uncertain harmonic flow calculation method in the embodiment of the present invention.
Specific embodiment
The present invention will be further described with reference to the accompanying drawings and embodiments.
As shown in Figure 1, present embodiments providing a kind of uncertain harmonic flow calculation suitable for distributed generation resource access
Method, specifically:
(1) there is the distributed generation resource (Distributed Generation, DG) of fluctuation for output power, especially
It is using the DG of the new energy such as wind energy, solar energy, based on measurement sample using cloud model generator to the output work of grid node
Rate is modeled；
(2) according to 3 δ ranges of normal cloud model, the power prediction range of DG grid node is acquired；
The specific embodiment of step (1) (2) is as follows:
In electric power networks node, if certain node power has uncertainty, network trend will be had an impact, asked
When solving such network trend, that is, need uncertain power flow algorithm.Node is not known to power grid first with backward cloud generator to survey
The data x of amounti(node load or power) carries out cloud modeling:
The cloud model characteristic value C of uncertain node output power is solved using above-mentioned formula with backward cloud generator
(Ex, En, He), indeterminacy section, i.e. [E are obtained using 3 δ rulesx-3(En+3He),Ex+3(En+3He)]。
(3) it is based on gained node power range, uncertain harmonic flow calculation is carried out in conjunction with boundary flow method, finds out power grid
Harmonic trend distribution；
The specific embodiment of step (3) is as follows:
Not know central value (the i.e. Normal Cloud expectation E of node output powerx) as the node injecting power it is given
Value being determined property Load flow calculation.Calculate the mathematical method for using network equation successive linearization.
Electric network power deviation expression formula:
F (x)=Sn- S (x)=0
In formula: SnFor the vector that all node powers are constituted, the output power E including not knowing nodex；S (x) is node
Function expression between injecting power and node voltage；X is node voltage.
If we can find one group of x, substitutes into above formula and f (x) is made to be equal to 0, this group of x is exactly the solution of Power Flow Problem.It is practical
Upper x can not be known in advance, then the initial value x of our given x(0)(or write as x0), in x0(4) formula is carried out first order Taylor by place
Expansion
DefinitionFor trend Jacobi (Jacobi) matrix, then have
X is corrected with Δ x0And obtain the new value of x.It is write as general type, is had
Obviously, x(k+1)Compare x(k)Closer to solution point, Δ x will level off to 0 after iterating, and computational accuracy pr=is arranged
0.00001, as Δ x≤pr, power flow solutions meet computational accuracy requirement, and trend iteration terminates, and acquire flow solution Z0(Z0=x(k +1))。
Cloud trend is by ExAs input variable through a certainty Load flow calculation, obtained trend output variable central value Z0。
The boundary value of flow solution can be expressed from the next:
Z=Z0±ΔZ
In formula: Z is output variable；Z0For the central value of output variable；Δ Z is the variable quantity of output variable.
Δ Z does not need to re-start Load flow calculation, utilizes sensitivity coefficient between input variable and output variableThat is:
In formula: Δ f is the vector that the fluctuation of all node powers is constituted, wherein only uncertain node is 3 (En+3He),
He should be 0 by node；Sensitivity coefficient between state variable and output variable can be approximately Jacobi inverse matrix.
From the above equation, we can see that the variable quantity of output variable can be calculated by the product of input variable value range and sensitivity coefficient
Approximation out, according to cloud trend indeterminacy section [Ex-3(En+3He),Ex+3(En+3He)], it is using improved boundary flow method
Output variable range [Z can quickly be found out-c,Zc].Therefore, cloud Load flow calculation only needs a certainty Load flow calculation.
(1) harmonic parameters in network harmonic source
DG is grid-connected at present mostly uses power electronic technique greatly, therefore considers the harmonic source in harmonic flow calculation by DG herein
Using the grid-connected formation of electronic power inverter.Three-phase bridge current source inverter is analyzed, it is believed that its line current i exported1Make
It is expanded into Fourier space
In formula: i1In except containing in addition to fundamental wave, also containing the harmonic content and K=1 of ± 1 grade of 6K, 2 ..., i.e., also contain the
The harmonic content of 5,7,11,13 ... h ... grades, the ratio of individual harmonic current: 20%, 14.29%, 9.09%, 7.69% ... 1/
H ..., that is:
Ih=I1/h
On the basis of fundamental wave cloud Load flow calculation, it is known that I1.Harmonic wave source node harmonic electric current can be calculated according to above formula.
(2) harmonic parameters of each element equivalent circuit of network
According to the different characteristics of component in the electric network of place, show that component (such as generator, power transmission line, load) exists
Equivalent Harmonic parameter under each harmonic.
1) generator harmonic parameters
XGh=hXG1
X in formulaG1For generator fundamental reactance；H is overtone order.
2) harmonic parameters of transmission line of electricity
ZLh=R1+hX1
R in formula1For route fundamental wave resistance；X1For route fundamental reactance.
3) harmonic parameters of load
In formula: S is load power；P is load active power；Q is load reactive power.
According to Equivalent Harmonic parameter of the component under each harmonic, corresponding network harmonic admittance matrix Y (h) is acquired.
(3) containing the harmonic flow calculation of DG
Grid nodes harmonic voltage is solved based on harmonic admittance matrix and node harmonic current amount, calculation formula is as follows:
In formula: node admittance matrix corresponding to the harmonic component that Y (h) is the h times；For the h times harmonic component
Corresponding node voltage vector；Node current vector corresponding to harmonic component for the h times；
(4) according to node voltage total harmonic distortion factor (THDu) as a result, judging whether each node harmonic content of power grid belongs to
Safe range；
The specific embodiment of step (4) is as follows:
Solution node voltage total harmonic distortion factor etc..Calculation formula is as follows:
In formula: UHCertain node harmonic voltage total amount；U1For the fundamental voltage amplitude of the node harmonic voltage；THDuFor node electricity
Press total harmonic distortion factor.
The present invention considers the uncertain harmonic flow calculation method containing DG, as shown in Figure 1, detailed process is as follows:
(1) Yun Chaoliu method models uncertain node based on backward cloud generator, obtains such node cloud model
Characteristic value；
(2) uncertain information on uncertain node is converted into input variable interval value, i.e. [E according to 3 δ rulesx-3(En
+3He),Ex+3(En+3He)]；
(3) to input variable central value, (i.e. cloud it is expected E to improved boundary flow methodx) carry out a Load flow calculation, then benefit
With system sensitive coefficient (Jacobian matrix of approximate Load flow calculation last time iteration inverse) and input variable value range Δ f
(absolute value of the difference of input variable central value and input variable boundary value) finds out in electric system uncertain factor to power grid
It influences a possibility that (i.e. flow state variable value range Δ Z), it follows that unknown variable interval value.
(4) each node voltage total harmonic distortion factor THD of power grid is acquiredu, with reference to national standard GB/T14549-1993, obtain each section
Point THDuWhether out-of-limit result.
The foregoing is merely presently preferred embodiments of the present invention, all equivalent changes done according to scope of the present invention patent with
Modification, is all covered by the present invention.
Claims (5)
1. a kind of uncertain harmonic flow calculation method suitable for distributed generation resource access, it is characterised in that: including following step
It is rapid:
Step S1: having output power the distributed generation resource of fluctuation, is occurred based on measurement sample using reverse cloud model
Device models the output power of grid node；
Step S2: according to 3 δ ranges of normal cloud model, the power prediction range of DG grid node is acquired；
Step S3: being based on the resulting power bracket of step S3, carries out uncertain harmonic flow calculation in conjunction with boundary flow method, finds out
The distribution of mains by harmonics trend；
Step S4: according to node voltage total harmonic distortion factor as a result, judging whether each node harmonic content of power grid belongs to safe model
It encloses.
2. a kind of uncertain harmonic flow calculation method suitable for distributed generation resource access according to claim 1,
It is characterized in that: the step S1 specifically: carry out cloud using the data that backward cloud generator does not know node measurement to power grid and build
Mould:
Wherein, ExFor cloud model expectation, EnFor the entropy of cloud model, HeThe super entropy of cloud model, xiFor the power of DG grid node measurement
Data, n are data amount check, and X is power sample mean value.
3. a kind of uncertain harmonic flow calculation method suitable for distributed generation resource access according to claim 1,
Be characterized in that: 3 δ ranges described in step S2 are [Ex-3(En+3He),Ex+3(En+3He)]。
4. a kind of uncertain harmonic flow calculation method suitable for distributed generation resource access according to claim 1,
It is characterized in that: step S3 specifically: using obtained grid node power bracket, the side of this variable of grid node power
Input quantity of the dividing value as certainty Load flow calculation carries out multiple certainty Load flow calculation, obtains the boundary value of unknown variable.
5. a kind of uncertain harmonic flow calculation method suitable for distributed generation resource access according to claim 1,
It is characterized in that: in step S4, the node voltage total harmonic distortion factor THDuCalculating use following formula:
Wherein, UHIndicate node harmonic voltage total amount, U1Indicate node fundamental voltage.
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| CN108336739B (en) * | 2018-01-15 | 2021-04-27 | 重庆大学 | RBF neural network-based probability load flow online calculation method |
| CN108964062B (en) * | 2018-08-17 | 2022-03-04 | 武汉理工大学 | Method for determining value range of 3-order harmonic current of distributed power flow controller |
| CN112072662B (en) * | 2020-08-28 | 2022-02-22 | 武汉大学 | Method for avoiding inter-harmonic parallel resonance of one frequency band |
| CN112670987B (en) * | 2020-12-30 | 2023-06-23 | 国网福建省电力有限公司 | Power grid three-phase harmonic current phasor matrix calculation method |
| CN113328444A (en) * | 2021-07-05 | 2021-08-31 | 国网江苏省电力有限公司信息通信分公司 | Method for using cloud computing for power flow computing |
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