CN109193664A - Containing the grid-connected distribution power system load flow calculation method of DG - Google Patents
Containing the grid-connected distribution power system load flow calculation method of DG Download PDFInfo
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- CN109193664A CN109193664A CN201811061200.2A CN201811061200A CN109193664A CN 109193664 A CN109193664 A CN 109193664A CN 201811061200 A CN201811061200 A CN 201811061200A CN 109193664 A CN109193664 A CN 109193664A
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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]
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Abstract
The distribution power system load flow calculation method containing DG that the invention discloses a kind of, pass through bilinear transformation technology, introduce bilinearity variable, to which trend Nonlinear System of Equations is converted linear-non-linear mixed equation, further, in conjunction with the operation characteristic of the power distribution network of DG, reasonable approximation has been carried out to the Jacobian matrix in mixed equation, to make Jacobian matrix constant, solving speed is accelerated.This patent method is simple, it is easy to accomplish, it can the effective distribution power system load flow calculation speed and precision containing DG.
Description
Technical field
The present invention relates to operation and control of electric power system technical fields, and in particular to containing the grid-connected distribution power system load flow calculation of DG
Method.
Background technique
Load flow calculation is one of function most basic in Energy Management System (EMS), and distribution power system load flow calculation is power distribution network
The important foundation of network economical operation, network analysis etc..On topological structure and the method for operation, power distribution network and power transmission network have obviously
Difference, power distribution network R/X ratio with higher (resistance-reactance-ratio value), branch is more, be in Radial network structure the features such as.
In addition, power distribution network is open loop when operating normally, only it just will appear of short duration looped network or dual power supply in failure or allotment load
Operation.
Distributed power generation (DG) technology with its small, clean and environmental protection of investment, power supply is reliable and generation mode is flexible the advantages that by
Gradually become the hot spot of power domain research.It will be becoming for power system development that distributed power generation is combined with centralized power generation mode
Gesture.Common distributed power generation mode has wind-power electricity generation, solar power generation and fuel cell power generation.
The introducing of distributed power generation (DG) is to the trend of power grid, quality of voltage, power loss, reliability and short in power distribution network
Appearance of a street amount brings tremendous influence.And traditional power flow algorithm is not directly applicable the distribution containing DG, the reason is as follows that:
1) access of DG may make the flow direction of trend change, and power distribution network also becomes more power supply moulds by simplex power mode
Formula；
2) there was only 2 seed type of balance nodes and PQ node in traditional distribution Load flow calculation, wherein balance nodes and PQ section
Point is existing noun, and balance nodes are voltage magnitudes and phase is given, and its inject active power and reactive power be to
The amount of asking；PQ node be the active-power P of node and reactive power Q be it is given, node voltage and phase are amounts to be asked.
Summary of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide a kind of distribution power system load flow calculations grid-connected containing DG
Method improves the solving speed that the electric network swim containing DG calculates, and improves computational convergence.
In order to solve the above technical problems, the present invention provides a kind of distribution power system load flow calculation method grid-connected containing DG, special
Sign is, comprising the following steps:
Step S1 introduces bilinearity variable, and trend Nonlinear System of Equations is converted linear-non-linear mixed equation；
It is assumed that certain grid-connected system containing DG shares N number of node, node set NV, NV interior joint number is 1-N, interior joint
1 is balance nodes, NgA PV node, N-Ng- 1 PQ node, b branch enable certain branch bi,jBoth ends node ID is i, j ∈
NV,
According to electric system basic principle it is found that the injection active power and reactive power of node i are as follows:
Wherein GiiFor the self-conductance of node i, BiiIt is node i from susceptance, GijFor node i, the transconductance of j, BijFor node
The mutual susceptance of i, j, UiRepresent the voltage magnitude of node i, UjRepresent the voltage magnitude of node j, δijFor node i, phase between j
Difference；
It is defined as follows bilinearity variable:
Rij=UiUjcosδij
Iij=UiUjsinδij
Obviously, Rij=Rji,Iij=-Iji,Rij 2+Iij 2=2KiKj；
Then power flow equation is converted to such as the non-linear mixture equations of lower linear-:
The whole Jacobian matrix J of power flow equation is approximately: by step S2
Step S3 solves above-mentioned linear-Nonlinear System of Equations, obtains the solution of above-mentioned linear-non-linear mixture equations；
Step S4 acquires the phase difference and voltage of node according to the definition of bilinearity variable, realizes Load flow calculation.
Preferably, the process of the whole Jacobian matrix J approximation of power flow equation is obtained are as follows:
Branch both ends node phase difference δij=0, node voltage is approximately voltage rating 1p.u, therefore to f (I, R)=Rij 2+
Iij 2-2KiKjFor, partial differential are as follows:
Due to Rij=UiUjcosδij≈ 1, Iij=UiUjsinδij≈ 0,
Then f (I, R)=Rij 2+Iij 2-2KiKjCorresponding Jacobi is approximately:
To the whole Jacobian matrix J of power flow equation are as follows:
Preferably, using Newton Algorithm it is linear-Nonlinear System of Equations.
Preferably, the detailed process of linear-Nonlinear System of Equations is solved are as follows:
1, conductance matrix G and susceptance matrix B are formed according to admittance formula, the factor table as Jacobian matrix J；
2, the number of iterations k=0 is set；
3, the active power of kth time iteration node and the equation of reactive power areIt calculates
4, using the factor table of Jacobian matrix, kth time iterated revision equation is solvedIt obtains double
Linear variable incrementHere
5, kth time iteration bilinearity variable is updatedHere
6, repeat the above steps 3-5, until iteration result meets twice in successionξ is convergence
Threshold value then obtains the solution of above-mentioned linear-non-linear mixture equations
7, basisThe voltage magnitude U of node i can be obtainedi,
According toIt can obtainAnd then U can be found outj。
Preferably, certain branch b is enabledi,jBoth ends node ID is i, j ∈ NV, then the branch admittance is Yij=Gij+jBij,
Middle GijRepresent conductance matrix, BijSusceptance matrix is represented, factor table is formed according to branch admittance.
Preferably, convergence threshold value range is ξ > 0.
Compared with prior art, the beneficial effects obtained by the present invention are as follows being: the present invention is introduced by bilinear transformation technology
Bilinearity variable, so that trend Nonlinear System of Equations is converted linear-non-linear mixed equation, further, in conjunction with DG's
The operation characteristic of power distribution network has carried out reasonable approximation to the Jacobian matrix in mixed equation, to keep Jacobian matrix normal
Numberization accelerates solving speed.This patent method is simple, it is easy to accomplish, can effectively containing DG distribution power system load flow calculation speed
Degree and precision.
Detailed description of the invention
Fig. 1 is the method for the present invention flow chart.
Specific embodiment
The invention will be further described below.Following embodiment is only used for clearly illustrating technical side of the invention
Case, and not intended to limit the protection scope of the present invention.
A kind of distribution power system load flow calculation method grid-connected containing DG of the invention introduces two-wire by bilinear transformation technology
Property variable, so that trend Nonlinear System of Equations is converted linear-non-linear mixed equation, further, in conjunction with the distribution of DG
The operation characteristic of net has carried out reasonable approximation to the Jacobian matrix in mixed equation, thus make Jacobian matrix constant,
Accelerate solving speed.
A kind of distribution power system load flow calculation method grid-connected containing DG of the invention, detailed process is as follows:
It is assumed that certain grid-connected system containing DG shares N number of node, node set NV.NV interior joint number is 1-N, interior joint
1 is balance nodes, NgA PV node, N-Ng- 1 PQ node, b branch, PQ here, PV node include all DG simultaneously
Net node.Some grid nodes do not have voltage regulation function, are PQ types, and it is PV node that some nodes, which have voltage regulation function, this be according to
It is determined according to the actual conditions of DG grid entry point.
Enable certain branch bi,jBoth ends node ID is i, and j ∈ NV, which is Yij=Gij+jBij, wherein GijRepresent electricity
Lead matrix, BijRepresent susceptance matrix.
The complex voltage of node iHere δiIt is node i relative to balance nodes
Phase, UiRepresent the voltage magnitude of node i, δjPhase for node j relative to balance nodes.
According to electric system basic principle it is found that the injection active power and reactive power of node i are as follows:
Wherein GiiFor the self-conductance of node i, BiiIt is node i from susceptance, GijFor node i, the transconductance of j, BijFor node
The mutual susceptance of i, j, these are known quantity, δijFor node i, phase difference between j.
Common Load flow calculation is phase difference, the voltage for calculating the whole network node.That is, the purpose of Load flow calculation is to ask
Ui,Uj,δij。
Notice U in above-mentioned two formulaiUjcosδij, UiUjsinδijAnd Ui 2It is fixed integral form, then for appointing
What a branch bi,j, it is defined as follows bilinearity variable:
Rij=UiUjcosδij
Iij=UiUjsinδij
Obviously, Rij=Rji,Iij=-Iji,Rij 2+Iij 2=2KiKj。
Then node injecting power simplifies are as follows:
For from mathematical formulae, power flow equation is converted to such as the non-linear mixture equations of lower linear-.
Using the above-mentioned non-linear-system of linear equations of Newton Algorithm and then obtainForm are as follows:
Here J is equation group Jacobian matrix, and concrete form will be given below, then unknown variable
For linear equation, solves and be not necessarily to iteration, therefore convergence rate is faster, and for Nonlinear System of Equations, it asks
Solution difficulty is larger, and the operation characteristic of present invention combination electric system carries out problem to simplify solution, and principle is as follows:
Distribution network line transimission power containing DG is small, therefore still it is believed that branch both ends node phase difference δij=0, while basis
Existing Operation of Electric Systems principle, node (including load bus, DG grid node) voltage is approximately voltage rating 1p.u, therefore right
F (I, R)=Rij 2+Iij 2-2KiKjFor, partial differential are as follows:
Due to Rij=UiUjcosδij≈ 1, Iij=UiUjsinδij≈ 0,
Then f (I, R)=Rij 2+Iij 2-2KiKjCorresponding Jacobi is approximately:
To the whole Jacobian matrix J of power flow equation are as follows:
As it can be seen that Jacobian matrix has become the sparse matrix of constant, therefore only needs shape in solution procedure by above-mentioned processing
It is stored at factor table, without inverting repeatedly in the iterative process of each step.
The present invention distribution power system load flow calculation method grid-connected containing DG, shown in Figure 1, detailed solution step are as follows:
1, according to admittance the efficiency of formation matrix Y=G+jB, Jacobian matrix is formed
Factor table；
2, the voltage initial value of PQ node is set as 1p.u, phase δij=0, the number of iterations k=0；
The voltage of all nodes is all approximately 1p.u, but in Load flow calculation the initial value of PV node be it is given, be not necessarily to
To initial value, and PQ node is to need artificial given initial value.
3, the active power of kth time iteration node and the equation of reactive power areIt calculates
4, using the factor table of Jacobian matrix, kth time iterated revision equation is solvedIt obtains double
Linear variable incrementHere
5, kth time iteration bilinearity variable is updatedHere
6, repeat the above steps 3-5, and convergence threshold ξ > 0 is arranged, until iteration result meets twice in successionThen obtain the solution of above-mentioned linear-non-linear mixture equations
7, basisThe voltage magnitude U of node i can be obtainedi,
According toIt can obtainAnd then U can be found outj。
The present invention introduces bilinearity variable using bilinear transformation technology, so that trend Nonlinear System of Equations is converted to line
Property-non-linear mixture equations, and according to DG power distribution network characteristic the Jacobian matrix in mixed equation has been carried out reasonable close
Seemingly, to make Jacobian matrix constant, a small amount of variable element only need to be calculated repeatedly in this way and is added to reduce calculation amount
Fast solving speed, improves computational efficiency.This patent method is simple, it is easy to accomplish, can effectively containing DG power distribution network tide
Stream calculation speed and precision.
The above is only a preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art
For member, without departing from the technical principles of the invention, several improvements and modifications, these improvements and modifications can also be made
Also it should be regarded as protection scope of the present invention.
Claims (6)
1. containing the grid-connected distribution power system load flow calculation method of DG, characterized in that the following steps are included:
Step S1 introduces bilinearity variable, and trend Nonlinear System of Equations is converted linear-non-linear mixed equation；
It is assumed that certain grid-connected system containing DG shares N number of node, node set NV, NV interior joint number is 1-N, and interior joint 1 is
Balance nodes, NgA PV node, N-Ng- 1 PQ node, b branch enable certain branch bi,jBoth ends node ID be i, j ∈ NV,
According to electric system basic principle it is found that the injection active power and reactive power of node i are as follows:
Wherein GiiFor the self-conductance of node i, BiiIt is node i from susceptance, GijFor node i, the transconductance of j, BijFor node i, j
Mutual susceptance, UiRepresent the voltage magnitude of node i, UjRepresent the voltage magnitude of node j, δijFor node i, phase difference between j；
It is defined as follows bilinearity variable:
Rij=UiUjcosδij
Iij=UiUjsinδij
Obviously, Rij=Rji,Iij=-Iji,Rij 2+Iij 2=2KiKj；
Then power flow equation is converted to such as the non-linear mixture equations of lower linear-:
The whole Jacobian matrix J of power flow equation is approximately: by step S2
Step S3 solves above-mentioned linear-Nonlinear System of Equations, obtains the solution of above-mentioned linear-non-linear mixture equations；
Step S4 acquires the phase difference and voltage of node according to the definition of bilinearity variable, realizes Load flow calculation.
2. the distribution power system load flow calculation method grid-connected containing DG according to claim 1, characterized in that obtain power flow equation
The process of whole Jacobian matrix J approximation are as follows:
Branch both ends node phase difference δij=0, node voltage is approximately voltage rating 1p.u, therefore to f (I, R)=Rij 2+Iij 2-
2KiKjFor, partial differential are as follows:
Due to Rij=UiUjcosδij≈ 1, Iij=UiUjsinδij≈ 0,
Then f (I, R)=Rij 2+Iij 2-2KiKjCorresponding Jacobi is approximately:
To the whole Jacobian matrix J of power flow equation are as follows:
3. the distribution power system load flow calculation method grid-connected containing DG according to claim 1, characterized in that use Newton Algorithm
Linearly-Nonlinear System of Equations.
4. the distribution power system load flow calculation method grid-connected containing DG according to claim 1, characterized in that solve linear-non-thread
The detailed process of property equation group are as follows:
1) conductance matrix G and susceptance matrix B are formed according to admittance formula, the factor table as Jacobian matrix J；
2) the number of iterations k=0 is set；
3) active power of kth time iteration node and the equation of reactive power areIt calculates
4) factor table for utilizing Jacobian matrix solves kth time iterated revision equationObtain bilinearity
DeltaHere
5) kth time iteration bilinearity variable is updatedHere
6) repeat the above steps 3-5, until iteration result meets twice in successionξ is convergence threshold,
Then obtain the solution of above-mentioned linear-non-linear mixture equations
7) basisThe voltage magnitude U of node i can be obtainedi,
According toIt can obtainAnd then U can be found outj。
5. the distribution power system load flow calculation method grid-connected containing DG according to claim 4, characterized in that enable certain branch bi,jTwo
End node serial number i, j ∈ NV, then the branch admittance is Yij=Gij+jBij, wherein GijRepresent conductance matrix, BijRepresent susceptance
Matrix forms factor table according to branch admittance.
6. the distribution power system load flow calculation method grid-connected containing DG according to claim 4, characterized in that convergence threshold value model
It encloses for ξ > 0.
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| CN201811061200.2A CN109193664B (en) | 2018-09-12 | 2018-09-12 | Containing the grid-connected distribution power system load flow calculation method of DG |
| PCT/CN2018/118729 WO2020052104A1 (en) | 2018-09-12 | 2018-11-30 | Method for determining power flow of dg-connected distribution network and computer storage medium |
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2018
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| CN103701125A (en) * | 2014-01-20 | 2014-04-02 | 武汉大学 | Flexible power flow algorithm for power distribution network based on sequential quadratic programming method |
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