CN104767199A - Directional control method for cut set cross section load flow in electric power system - Google Patents

Abstract

The invention discloses a directional control method for cut set cross section load flow in an electric power system. The directional control method for the cut set cross section load flow in the electric power system is used for improving the operation security level of the electric power system. The directional control method for the cut set cross section load flow in the electric power system comprises the steps of firstly calculating a current relevancy coefficient matrix of a power grid and deriving a power sensitivity matrix between line power variables and node injection power variables on the basis of the current relevancy coefficient matrix, then on the basis of the power sensitivity matrix, according to a cut set cross section load flow directional control objective, under the condition of meeting electric generator adjustable variable constraints and line redundancy constraints, obtaining a cut set cross section load flow directional control scheme by using a non-linear optimization method, and performing directional control on the total load flow of a cut set cross section and each branch load flow of the cut set cross section. The directional control method for the cut set cross section load flow in the electric power system overcomes the defect that the sensitivity of a balancing machine can not be calculated through a direct current load flow method, the balance machine participates in the cut set cross section load flow directional control, the directional control on the total load flow of the cut set cross section and each branch load flow of the cut set cross section are performed, and the control precision and the control ability of the cut set cross section load flow in the electric power system are improved greatly.

Description

Cut set method for directionally controlling section tidal current in electric power system

Technical field

The present invention relates to a kind of method that accurately can control cut set section tidal current in electric power system, belong to power transmission and distribution technical field.

Background technology

In electric power system, (cut set section is one group of set of fingers to transmission of electricity cut set section, if disconnected by circuits all in this set, system will be divided into the two parts that can not be communicated with) often exist with cut set form, the delivery of electrical energy of cut set section two side areas is played an important role.When the trend on partial line road in cut set section is close to its maximum transmission power, the problems such as the increase of line fault probability, the reduction of system reserve availability and the reduction of transmission of electricity margin of safety can be caused.Therefore, by the energy output of generator each in adjustment System, accurate oriented control is carried out to the trend of crucial cut set section, systems stabilisation frequency, the mode that optimizes the system operation, raising cut set section transmittability and the stability of a system are played an important role.

Although flexible ac transmission system equipment can control effectively to cut set section tidal current, it involves great expense, and can not all install this equipment on all cut set sections.Carrying out oriented control by regulating cut set section both sides generator output to cut set section Line Flow is good control program, and the relevant personnel have carried out large quantity research in this respect, but existing method is still immature.Existing control method utilizes DC power flow algorithm to calculate the control situation of each generator node to cut set section Branch Power Flow, calculating because of DC power flow sensitivity depends on the selection of balancing machine, the DC power flow sensitivity of balancing machine to all circuits is made to be 0, cause balancing machine not participate in cut set section tidal current to control, reduce the control precision of cut set section tidal current, limit the control ability of system to cut set section tidal current; Meanwhile, existing method can only realize the control to the total trend of cut set section, cannot meet the different target of each Branch Power Flow variation in cut set section, therefore need improvement badly.

Summary of the invention

The object of the invention is to the drawback for prior art, cut set method for directionally controlling section tidal current in a kind of electric power system is provided, to improve power system operation lsafety level.

Problem of the present invention realizes with following technical proposals:

Cut set method for directionally controlling section tidal current in a kind of electric power system, first described method calculates the electric current correlation coefficient matrix of electrical network, and the power sensitivity matrix derived on this basis between line power variable and node injecting power variable, then based on power sensitivity matrix, according to cut set section tidal current oriented control target, under the condition meeting the constraint of generator controlled variable and the constraint of circuit amount of redundancy, nonlinear optimization method is utilized to obtain cut set section tidal current oriented control scheme, oriented control is carried out to the total trend of cut set section and each Branch Power Flow of cut set section.

Cut set method for directionally controlling section tidal current in above-mentioned electric power system, said method comprising the steps of:

I. rated output sensitivity matrix

A. calculating current correlation coefficient matrix

The electric current correlation coefficient matrix that definition C (λ) is electrical network:

C(λ)＝Y _BA ^TX

Wherein, Y _bbe branch road susceptance matrix, A is node incidence matrices, and X is node reactance matrix, T representing matrix transposition;

Row k, the i-th column element λ in Matrix C (λ) _k-irepresent the electric current phasor of branch road k with node i Injection Current electric current correlation coefficient.

B. rated output sensitivity matrix

Definition matrix D (β) is the power sensitivity matrix between branch power variable and node injecting power variable, row k, the i-th column element β in this matrix _k-irepresent the power sensitivity between branch road k power and variable and node i injecting power variable:

Wherein, U _k,Bwith branch road k head end voltage modulus value and phase angle respectively, U _i,Nwith i-th node voltage modulus value and phase angle respectively.

II. cut set section tidal current oriented control

Total m platform generator in supposing the system, system is divided into sending A and receiving-end system B two parts by cut set section, and its generator set is respectively G _aand G _b, generator is numbered G _a={ G ₁, G ₂..., G _sand G _b={ G _s+1, G _s+2..., G _m, the concrete steps of cut set section tidal current oriented control are as follows:

A. cut set section tidal current oriented control target is determined

If the total number of branches of cut set section is N, the total change of power flow control objectives of cut set section is Δ P _zong, in cut set section, branch road k change of power flow control objectives is Δ P _k, meet

If the generation adjustment amount of generator node i is Δ P _i,G, then in cut set section, the change of power flow of branch road k is the total change of power flow of cut set section is

The target function of cut set section tidal current oriented control is:

$\min f=\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{{\mathrm{\Δp}}_k}^2+{{\mathrm{\Δp}}_{\mathrm{zong}}}^2,$

Wherein, Δ p _k=Δ P _k,B-Δ P _kfor the control deviation of branch road k in cut set section, Δ p _zong=Δ P _{zong, B}-Δ P _zongfor the control deviation of the total trend of cut set section.

B., cut set section tidal current oriented control constraints is set

1. generator regulation and control amount constraint

For meeting the power-balance of cut set section two side system, if increase Δ P by the cut set section tidal current of A to B _zong, then if reduce Δ P by the cut set section tidal current of A to B _zong, then $-\underset{i=1}{\overset{s}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_{i,G}=\underset{i=s+1}{\overset{m}{\mathrm{\Σ}}}{\mathrm{\ΔP}}_{i,G}={\mathrm{\ΔP}}_{\mathrm{zong}};$

Meanwhile, the adjustment amount Δ P of generator i _i,Gretrain by its generating controlled variable, namely meet:

P _i,Gmin-P _i,G＜ΔP _i,G＜P _i,Gmax-P _i,G

Wherein, P _i,Gfor the current energy output of generator i, P _{i, Gmin}and P _{i, Gmax}minimum energy output and the maximum generating watt of generator i respectively;

2. circuit amount of redundancy constraint

During to cut set section tidal current oriented control, for the circuit l not belonging to arbitrarily cut set section, demand fulfillment:

$\left\{\begin{array}{c}{\mathrm{\&Delta;P}}_{l,B}=\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_{l-i}{\mathrm{\&Delta;P}}_{i,G}\\ {\mathrm{\&Delta;P}}_{l,B}<P_{l\max }-P_l\end{array}\right.;$

Wherein, Δ P _l,Bfor the change of power flow of circuit l, P _lmaxfor the maximum transmission power of circuit l, P _lfor the current transmission power of circuit l, β _l-irepresent the power sensitivity between circuit l power and variable and node i injecting power variable;

C. according to cut set section tidal current oriented control target, under the condition meeting the constraint of generator controlled variable and the constraint of circuit amount of redundancy, utilize nonlinear optimization method to obtain cut set section tidal current oriented control scheme, oriented control is realized to the total trend of cut set section and each Branch Power Flow of cut set section.

Cut set method for directionally controlling section tidal current in above-mentioned electric power system, when calculating generator regulation and control amount retrains, for the balancing machine j in system, the constraint of demand fulfillment is:

P _j,Gmin-P _j,G＜ΔP _j,G＜P _j,Gmax-P _y-P _j,G；

Wherein, Δ P _j,Gfor the adjustment amount of balancing machine j, P _yfor nargin reserved by balancing machine, P _j,Gfor the current energy output of balancing machine j, P _{j, Gmin}and P _{j, Gmax}minimum energy output and the maximum generating watt of balancing machine j respectively.

Cut set method for directionally controlling section tidal current in above-mentioned electric power system, the maximum transmission power P of circuit l _lmaxminimum value in minimum transmission power corresponding to line taking road l backup protection setting value and the thermally-stabilised power limit of circuit l.

Instant invention overcomes DC power flow algorithm cannot the shortcoming of the clever sensitivity of calculated equilibrium, is participated in by balancing machine in cut set section tidal current oriented control, carries out oriented control to the total trend of cut set transmission cross-section and each Branch Power Flow of cut set section.The participation of balancing machine makes the generator increased number participating in trend oriented control, compares, can obtain better optimal solution, improve control precision in Non-Linear Programming searching process with previous methods; Simultaneously, the target function of cut set section tidal current oriented control makes each Branch Power Flow control deviation in section total power flowcontrol deviation and section reach minimum, overcome the control that previous methods can only realize the total trend of cut set section, the shortcoming of each Branch Power Flow difference variation target in cut set section cannot be met, improve control ability.Therefore, the present invention substantially increases cut set section tidal current control precision and control ability in electric power system.

Accompanying drawing explanation

Below in conjunction with accompanying drawing, the invention will be further described.

Fig. 1 is cut set sectional schematic diagram.

Symbol used: I in literary composition _nnode Injection Current column vector, U _nnode voltage column vector, Y _nnode susceptance matrix, I _bbranch current column vector, Y _bbe branch road susceptance matrix, A is node incidence matrices, and X is node reactance matrix, the electric current correlation coefficient matrix that C (λ) is electrical network, the electric current phasor of branch road k, node i Injection Current, λ _k-ibe with node i Injection Current electric current correlation coefficient, the head end voltage phasor of kth bar branch road, be the voltage phasor of i-th node, P _k,Band Q _k,Bactive power and the reactive power of branch road k respectively, U _k,Bwith branch road k head end voltage modulus value and phase angle respectively, U _i,Nwith be i-th node voltage modulus value and phase angle respectively, D (β) is power sensitivity matrix, Δ P _zongthe total change of power flow control objectives of cut set section, Δ P _kbranch road k change of power flow control objectives in cut set section, Δ P _i,Gthe generation adjustment amount of generator node i, the change of power flow of branch road k in cut set section, the total change of power flow of cut set section, Δ p _k=Δ P _k,B-Δ P _kthe control deviation of branch road k in cut set section, Δ p _zong=Δ P _{zong, B}-Δ P _zongthe control deviation of the total trend of cut set section, P _i,Gfor the current energy output of generator i, P _{i, Gmin}and P _{i, Gmax}minimum energy output and the maximum generating watt of generator i respectively, P _yfor nargin reserved by balancing machine, P _lmaxfor the maximum transmission power of circuit l, P _lfor the current transmission power of circuit l.

Embodiment

Fig. 1 is cut set sectional schematic diagram, and the cut set section between sending A and receiving-end system B is by circuit l ₁-l _ncomposition, wherein circuit l ₁-l _ktrend flow to B by A, its value is just; Circuit l _k+1-l _ntrend flow to A by B, its value is negative.This cut set section power vector is P=[P ₁, P ₂p _n], the total trend of cut set section is

The present invention is based on electric current correlation coefficient matrix, derive the power sensitivity matrix between line power variable and node injecting power variable, calculate comprise balancing machine each generator to the power sensitivity of each circuit, balancing machine is participated in cut set section tidal current oriented control.Based on power sensitivity matrix, according to cut set section tidal current oriented control target, under the condition meeting the constraint of generator controlled variable and the constraint of circuit amount of redundancy, utilize nonlinear optimization to obtain cut set section tidal current oriented control scheme, oriented control is realized to the total trend of cut set section and each Branch Power Flow of cut set section.

The present invention includes the following step:

I. rated output sensitivity matrix

A. calculating current correlation coefficient matrix

In high-voltage transmission network, the reactance value of circuit is far longer than resistance value, therefore can replace resistance value with reactance value in analytical calculation.Generator in electrical network, load are all represented as node Injection Current, when not considering the non-linear elements such as the power electronics in electrical network, the nodal voltage equation of network is:

I _N＝Y _NU _N(1)

Wherein, I _nnode Injection Current column vector (to flow into the direction of node for positive direction), U _nnode voltage column vector, Y _nit is node susceptance matrix.

Relation between branch of a network electric current and node voltage is:

I _B＝Y _BA ^TU _N(2)

Wherein, I _bbranch current column vector, Y _bbe branch road susceptance matrix, A is node incidence matrices, U _nit is node voltage column vector.Node susceptance inverse of a matrix matrix is node reactance matrix X, namely can obtain according to formula (1) and (2):

I _B＝Y _BA ^TXI _N(3)

From formula (3), be linear relationship between branch current and node Injection Current, definition C (λ) is electrical network correlation coefficient matrix:

C(λ)＝Y _BA ^TX (4)

For one containing n node, the network of b bar branch road, C (λ) is b*n rank real number matrix, and C (λ) is only relevant with network parameter and topological structure.For branch road k, its electric current phasor the linear combination of each node Injection Current, shown in (5):

${\stackrel{\&CenterDot;}{I}}_{k,B}={\mathrm{\&lambda;}}_{k+1}{\stackrel{\&CenterDot;}{I}}_{1,N}+...+{\mathrm{\&lambda;}}_{k-i}{\stackrel{\&CenterDot;}{I}}_{i,N}+...+{\mathrm{\&lambda;}}_{k-n}{\stackrel{\&CenterDot;}{I}}_{n,N}---\left(5\right)$

Wherein, λ _k-ibe with node i Injection Current electric current correlation coefficient.

B. rated output sensitivity matrix

When utilizing unit to dispatch again to carry out the total trend of cut set section and each Branch Power Flow oriented control, it is required to determine that it generator control node and corresponding power adjustment, what describe in formula (3) is relation between branch current and node Injection Current, need to process it, obtain the relation between branch power and node injecting power.Process is carried out to formula (5) and obtains formula (6):

$\frac{{\stackrel{*}{I}}_{k,B}{\stackrel{\&CenterDot;}{U}}_{k,B}}{{\stackrel{\&CenterDot;}{U}}_{k,B}}=\frac{{\mathrm{\&lambda;}}_{k-1}{\stackrel{*}{I}}_{1,N}{\stackrel{\&CenterDot;}{U}}_{1,N}}{{\stackrel{\&CenterDot;}{U}}_{1,N}}+...+\frac{{\mathrm{\&lambda;}}_{k-i}{\stackrel{*}{I}}_{i,N}{\stackrel{\&CenterDot;}{U}}_{i,N}}{{\stackrel{\&CenterDot;}{U}}_{i,N}}+...+\frac{{\mathrm{\&lambda;}}_{k-n}{\stackrel{*}{I}}_{n,K}{\stackrel{\&CenterDot;}{U}}_{n,N}}{{\stackrel{\&CenterDot;}{U}}_{n,N}}---\left(6\right)$

Wherein, the head end voltage phasor of kth bar branch road, it is the voltage phasor of i-th node.Formula (6) is launched:

Wherein, P _k,Band Q _k,Bactive power and the reactive power of branch road k respectively, U _k,Bwith branch road k head end voltage modulus value and phase angle respectively, U _i,Nwith i-th node voltage modulus value and phase angle respectively.

Formula (7) is launched, obtains real part as follows:

In cut set section tidal current oriented control, a regulator generator Controlling vertex meritorious, does not change that it is idle, therefore, branch road active power in formula (8) and node are injected active power and get variable format, and node is injected reactive power variable and be taken as 0, formula (9) can be obtained:

Definition matrix D (β) is the power sensitivity matrix between branch power variable and node injecting power variable, the power sensitivity β wherein between branch road k power and variable and node i injecting power variable _k-ifor:

Power sensitivity matrix weighs node injecting power to the control situation of cut set section tidal current in conjunction with network topology parameters and actual electric network ruuning situation, describe the linear relationship between branch power variable and node injecting power variable, its computational process does not rely on the selection of balancing machine, accurately can judge the control situation of balancing machine to each line power, make balancing machine participate in cut set section tidal current oriented control.

When adjustment generator output carries out cut set section tidal current oriented control, only adjust the energy output of generator node, the injecting power of all the other nodes is constant.If generator number is m in system, the power and variable of cut set section branch road k is such as formula shown in (11).

ΔP _k,B＝β _k-1ΔP _1,G+…+β _k-iΔP _i,G+…+β _k-mΔP _m,G(11)

Wherein, Δ P _i,Git is the generation adjustment amount of i-th generator node.

In cut set section tidal current oriented control, do not need to calculate the power sensitivity between all nodes of the whole network and all circuits, only need calculating generator node to the power sensitivity of all circuits.Observation matrix Y _b, A and X, when the current sensitivity asking certain node i to all branch roads, only need retain the i-th column element in X, other elements all can set to 0.Conveniently can try to achieve the current sensitivity in electrical network between generator node and each circuit like this, and then obtain power sensitivity.Meanwhile, because most elements in matrix is 0, utilize sparse vector technology greatly can improve computational speed and reduce amount of ram.

II. cut set section tidal current oriented control

In electric power system, cut set section is one group of set of fingers, if disconnected by circuits all in this set, system will be divided into the two parts that can not be communicated with.Carry out trend oriented control to cut set section D, system is divided into sending A and receiving-end system B two parts by this cut set section, and its generator set is respectively G _aand G _b, generator is numbered G _a={ G ₁, G ₂..., G _sand G _b={ G _s+1, G _s+2..., G _m.

A. cut set section tidal current oriented control target

If the total number of branches of cut set section is N, the total change of power flow control objectives of cut set section is Δ P _zong, in cut set section, branch road k change of power flow control objectives is Δ P _k, meet

If the generation adjustment amount of generator node i is Δ P _i,G, then the change of power flow that can obtain branch road k in cut set section according to formula (11) is the total change of power flow of cut set section is ${\mathrm{\&Delta;P}}_{\mathrm{zong},B}=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;P}}_{k,B}.$

If the control deviation of branch road k is Δ p in cut set section _k=Δ P _k,B-Δ P _k, the control deviation of the total trend of cut set section is Δ p _zong=Δ P _{zong, B}-Δ P _zong.Then the target function of cut set section tidal current oriented control is such as formula shown in (12):

$\min f=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}{{\mathrm{\&Delta;p}}_k}^2+{{\mathrm{\&Delta;p}}_{\mathrm{zong}}}^2---\left(12\right)$

B. cut set section tidal current oriented control constraint

1. generator regulation and control amount constraint

For meeting the power-balance of cut set section two side system, if increase Δ P by the cut set section tidal current of A to B _zong, then if reduce Δ P by the cut set section tidal current of A to B _zong, then $-\underset{i=1}{\overset{s}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;P}}_{i,G}=\underset{i=s+1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;P}}_{i,G}={\mathrm{\&Delta;P}}_{\mathrm{zong}}.$

Meanwhile, the adjustment amount Δ P of generator i _i,Gretrain by its generating controlled variable, namely meet:

P _i,Gmin＜P _i,G+ΔP _i,G＜P _i,Gmax(13)

P _i,Gmin-P _i,G＜ΔP _i,G＜P _i,Gmax-P _i,G(14)

Wherein, P _i,Gfor the current energy output of generator i, P _{i, Gmin}and P _{i, Gmax}minimum energy output and the maximum generating watt of generator i respectively.

It should be noted that, for the balancing machine j in system, consider that balancing machine needs to undertake the task of frequency modulation task and balance electrical network micropower difference in operation of power networks, calculate it and can increase when exerting oneself and will reserve certain nargin, namely for balancing machine j, the constraint of demand fulfillment is:

P _j,Gmin-P _j,G＜ΔP _j,G＜P _j,Gmax-P _y-P _j,G(15)

Wherein, P _yfor nargin reserved by balancing machine, get P _y=10MW.

2. circuit amount of redundancy constraint

During to cut set section tidal current oriented control, circuit overload to be there is not in guarantee system.Therefore, for the circuit l not belonging to arbitrarily cut set section, demand fulfillment:

$\left\{\begin{array}{c}{\mathrm{\&Delta;P}}_{l,B}=\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_{l-i}{\mathrm{\&Delta;P}}_{i,G}\\ {\mathrm{\&Delta;P}}_{l,B}<P_{l\max }-P_l\end{array}\right.---\left(16\right)$

Wherein, P _lmaxfor the maximum transmission power of circuit l, P _lfor the current transmission power of circuit l.

Branch road maximum transmission power had both been subject to the restriction of thermally-stabilised power limit, was also subject to the restriction of its minimum transmission power corresponding to standby protection seting value, maximum for branch road permission through-put power should be taken as the minimum value in said two devices.

C. according to cut set section tidal current oriented control target, consider the constraint of generator controlled variable and the constraint of circuit amount of redundancy, utilize nonlinear optimization method can obtain cut set section tidal current oriented control scheme, oriented control is carried out to the total trend of cut set transmission cross-section and each Branch Power Flow of cut set section.

Claims (3)

1. cut set method for directionally controlling section tidal current in an electric power system, it is characterized in that, first described method calculates the electric current correlation coefficient matrix of electrical network, and the power sensitivity matrix derived on this basis between line power variable and node injecting power variable, then based on power sensitivity matrix, according to cut set section tidal current oriented control target, under the condition meeting the constraint of generator controlled variable and the constraint of circuit amount of redundancy, nonlinear optimization method is utilized to obtain cut set section tidal current oriented control scheme, oriented control is carried out to the total trend of cut set section and each Branch Power Flow of cut set section.

2. cut set method for directionally controlling section tidal current in a kind of electric power system according to claim 1, is characterized in that, said method comprising the steps of:

I. rated output sensitivity matrix

A. calculating current correlation coefficient matrix

The electric current correlation coefficient matrix that definition C (λ) is electrical network:

C(λ)＝Y _BA ^TX，

Wherein, Y _bbe branch road susceptance matrix, A is node incidence matrices, and X is node reactance matrix, T representing matrix transposition;

Row k, the i-th column element λ in Matrix C (λ) _k-irepresent the electric current phasor of branch road k with node i Injection Current electric current correlation coefficient;

B. rated output sensitivity matrix

Definition matrix D (β) is the power sensitivity matrix between branch power variable and node injecting power variable, row k, the i-th column element β in this matrix _k-irepresent the power sensitivity between branch road k power and variable and node i injecting power variable:

Wherein, U _k,Bwith branch road k head end voltage modulus value and phase angle respectively, U _i,Nwith i-th node voltage modulus value and phase angle respectively;

II. cut set section tidal current oriented control

Total m platform generator in supposing the system, system is divided into sending A and receiving-end system B two parts by cut set section, and its generator set is respectively G _aand G _b, generator is numbered G _a={ G ₁, G ₂..., G _sand G _b={ G _s+1, G _s+2..., G _m, the concrete steps of cut set section tidal current oriented control are as follows:

A. cut set section tidal current oriented control target is determined

If the total number of branches of cut set section is N, the total change of power flow control objectives of cut set section is Δ P _zong, in cut set section, branch road k change of power flow control objectives is Δ P _k, meet

If the generation adjustment amount of generator node i is Δ P _i,G, then in cut set section, the change of power flow of branch road k is the total change of power flow of cut set section is

The target function of cut set section tidal current oriented control is:

$\begin{array}{cc}\min & f=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;}{p_k}^2+\mathrm{\&Delta;}{p_{\mathrm{zong}}}^2\end{array},$

Wherein, Δ _pk=Δ P _{k, B-}Δ P _kfor the control deviation of branch road k in cut set section, Δ _pzong=Δ P _{zong, B}-Δ P _zongfor the control deviation of the total trend of cut set section;

B., cut set section tidal current oriented control constraints is set

1. generator regulation and control amount constraint

For meeting the power-balance of cut set section two side system, if increase Δ P by the cut set section tidal current of A to B _zong, then if reduce Δ P by the cut set section tidal current of A to B _zong, then $-\underset{i=1}{\overset{s}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;}{P}_{i,G}=\underset{i=s+1}{\overset{m}{\mathrm{\&Sigma;}}}\mathrm{\&Delta;}{P}_{i,G}=\mathrm{\&Delta;}{P}_{\mathrm{zong}};$

Meanwhile, the adjustment amount Δ P of generator i _i,Gretrain by its generating controlled variable, namely meet:

P _i,Gmin-P _i,G＜ΔP _i,G＜P _i,Gmax-P _i,G

Wherein, P _i,Gfor the current energy output of generator i, P _{i, Gmin}and P _{i, Gmax}minimum energy output and the maximum generating watt of generator i respectively;

2. circuit amount of redundancy constraint

During to cut set section tidal current oriented control, for the circuit l not belonging to arbitrarily cut set section, demand fulfillment:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{P}_{l,B}=\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{\mathrm{\&beta;}}_{l-i}\mathrm{\&Delta;}{P}_{i,G}\\ \mathrm{\&Delta;}{P}_{l,B}<P_{l\max }-P_l\end{array}\right.$

Wherein, Δ _{pl, B}for the change of power flow of circuit l, P _lmaxfor the maximum transmission power of circuit l, P _lfor the current transmission power of circuit l, β _l-irepresent the power sensitivity between circuit l power and variable and node i injecting power variable;

C. according to cut set section tidal current oriented control target, under the condition meeting the constraint of generator controlled variable and the constraint of circuit amount of redundancy, utilize nonlinear optimization method to obtain cut set section tidal current oriented control scheme, oriented control is realized to the total trend of cut set section and each Branch Power Flow of cut set section.

3. cut set method for directionally controlling section tidal current in a kind of electric power system according to claim 2, is characterized in that, when calculating generator regulation and control amount retrains, for the balancing machine j in system, the constraint of demand fulfillment is:

P _j,Gmin-P _j,G＜ΔP _j,G＜P _j,Gmax-P _y-P _j,G

Wherein, Δ _{pj, G}for the adjustment amount of balancing machine j, P _yfor nargin reserved by balancing machine, P _j,Gfor the current energy output of balancing machine j, P _{j, Gmin}and P _{j, Gmax}minimum energy output and the maximum generating watt of balancing machine j respectively.