CN102082433B - Predicting device and method of voltage stability of wind power parallel network system - Google Patents

Abstract

The invention relates to a predicting device and method of the voltage stability of a wind power system, belonging to the technical field of wind power generation. The device comprises a sensor, a data acquisition chip, a central processing unit, an industrial personal computer and a wireless communication module. The predicting method comprises the following steps of: 1, acquiring the parallel network point data of a wind power station; 2, arraying acquired power network data into a time sequence according to acquisition time, and carrying out phase space reconstruction on the time sequence; 3, carrying out a deterministic test on chaotic characteristics; 4, acquiring model parameter c and epsilon values and a kernel function parameter gamma value; and 5, analyzing a prediction result of the voltage stability of a power network. The invention prevents the errors caused when a model is established or parameters are selected in the traditional method and has the advantages of easy input quantity extraction, high precision, good accuracy and high prediction efficiency.

Description

A kind of wind-electricity integration system voltage stability forecast device and method

Technical field

The invention belongs to technical field of wind power generation, particularly a kind of wind power system voltage stability forecast device and method that contains.

Background technology

In the last few years, the concern that wind power generation is pollution-free with it, low cost and other advantages has attracted more and more researchers, China's adding new capacity reached 1000MW approximately in 2006, because the wind turbine generator majority is the asynchronous generating unit at present, also to absorb certain idle when output is meritorious from system, easily cause the also voltage fluctuation of site, so the stable problem of wind farm grid-connected ubiquity voltage in service.Spread of voltage or voltage collapse can cause the forfeiture of electric power system localised load; even can cause the whole network to be disintegrated and cause large-area power-cuts; thereby bring significant damage for the safe operation of electric power system; and along with the wind energy turbine set capacity is increasing; its influence to electric power system is also increasing, and therefore studying wind energy turbine set voltage stability forecast has extremely important practical significance.

Conventional method is for prediction and the analysis of wind-electricity integration system voltage, all be to set up electric network model earlier, carry out the voltage stability forecast again, so the accuracy that predicts the outcome depends on the selection of system model and parameter to a great extent, owing to be difficult to find a kind of algorithm simple when analyzing, precision height, the model that predicted time is long, method in the past has bigger error, can not carry out the voltage stability forecast exactly.

Summary of the invention

In order to overcome the deficiency of prior art, the object of the invention provides a kind of wind electric field blower group voltage stability forecast device and method.

Voltage stability forecast device of the present invention comprises: transducer, data acquisition chip, central processing unit, industrial computer and wireless communication module.Each parts of prediction unit connect: the output of transducer connects the input of data acquisition chip, and the output of data acquisition chip connects the input of central processing unit, and the output of central processing unit connects the input of industrial computer and wireless communication module.

The Forecasting Methodology that wind-electricity integration system voltage stability forecast device adopts is characterized in that, utilizes chaos system extraction time sequence is predicted, mainly comprises the steps:

The active power that step 1, the voltage, electric current, phase angle and the wind field that adopt wind-electricity integration system voltage stability forecast device to gather wind farm grid-connected point are exported and reactive power are as input variable;

Step 2, the electric network data of gathering in the step 1 constantly is arranged as time series by gathering, time series is carried out phase space reconfiguration, reconstruct the phase space that wind-powered electricity generation voltage is stablized non linear system;

With gaining merit as input variable that voltage, electric current, phase angle and the wind field of wind farm grid-connected point are exported; If the system time sequence of gathering is X={x ₁, x ₂..., x _N, N is natural number; Suitably select time of delay and embed dimension, restructural original system phase space is:

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="X"\; filenames="HSA00000363608600061.png,HSA00000363608600062.png"\; state="\{\{state\}\}">X</figure-callout>}}_1=(x_1,x_{1+x},\&CenterDot;\&CenterDot;\&CenterDot;,x_{1+(m-1)x})\\ {\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="HSA00000363608600021.png,HSA00000363608600061.png"\; state="\{\{state\}\}">X</figure-callout>}}_2=(x_2,x_{2+x},\&CenterDot;\&CenterDot;\&CenterDot;,x_{2+(m-1)x})\\ \&CenterDot;\&CenterDot;\&CenterDot;\\ X_i=(x_i,x_{i+x},\&CenterDot;\&CenterDot;\&CenterDot;,x_{i+(m-1)x})\end{array}\right.---\left(1\right)$

Wherein, τ is time delay, and m puts total n=N-(m-1) τ, X mutually for embedding dimension _iBe point mutually in the phase space reconstruction, i=1,2 ..., n.

Step 3, chaotic characteristic qualitative reaction is really carried out in the voltage stable phase space of reconstruct in the step 2;

For system time sequence X={ x ₁, x ₂..., x _N, be m to embed dimension, be that τ carries out phase space reconfiguration time of delay, has:

Y(t _i)＝(x(t _i)，x(t _i+τ)，…，x(t _i+(m-1)τ)，(i＝1，2，…，n) (2)

Wherein, n=N-(m-1) τ.

The principle of Rosenstein improvement algorithm as shown in Figure 8.

Get the Y of the point mutually (t in system's phase space of reconstruct ₁), establish Y (t in the phase space reconstruction ₁) neighbor point be Y ₁(t ₁), Y (t ₁) and Y ₁(t ₁) between distance be:

d ₁(0)＝‖Y(t ₁)-Y ₁(t ₁)‖ (3)

In the formula, ‖ ‖ is Euclidean distance.

To in system's phase space of reconstruct each to neighbor point, calculate after k the discrete time apart from d _i(k):

d _i(k)＝‖Y(t _i)-Y _i(t _k)‖ (4)

K=1 wherein, 2 ..., n, n=N-(m-1) τ.

Ask each d _i(k) ≠ 0 logarithm ln (d _i(k)), to each k value, the definition following formula:

$y\left(k\right)=\frac{1}{M}\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}\ln \left(\mathrm{di}\left(k\right)\right)---\left(5\right)$

For: based on i mutually, the range averaging value of k discrete time.M is di (k) number corresponding to the non-zero of a certain k value in the formula.

Be coordinate with k and y (k), draw the change curve of y (k), calculate the regression straight line slope of y (k) curve.

This slope value K is maximum Lyapunov exponent λ ₁

Step 4, forecast model and the model parameter of putting variation track in the phase space reconstruction are mutually determined, obtained model parameter c and ε value and kernel function parameter γ value;

Step 1), set up sample set, select the support vector sample;

Put the sample set S={ (x of formation mutually system's phase space _i, y _i), i=1,2 ... among the M}, by finding the solution quadratic programming and optimization problem, seek input x arbitrarily _i∈ R ⁿThe output y corresponding with it _iMapping function g (x) between the ∈ R namely seeks the y=g (x) that can represent relation of interdependence between y and the x, order

Namely can pass through x _iWith y _iCorresponding relation By x _I+1Calculate or dope next output y of the non linear system of putting representative mutually _I+1

The sample set that the system phase space of setting up departments is put formation mutually is: S={ (x _i, y _i), i=1,2 ... M}.If an existence hyperplane g (x)=＜wx 〉+b, w ∈ R ⁿ, b ∈ R makes:

|y _i-g(x _i)|≤ε，i＝1，2，…，M。

Set up, then sample set S={ (x _i, y _i), i=1,2 ... M} is the approximate collection of ε.Point (the x of S _i, y _i) to the distance of hyperplane g (x) be:

$d_i=\frac{|\&lang;w\&CenterDot;x\&rang;+b-y_i|}{\sqrt{1+{\left|\right|w\left|\right|}^2}}---\left(6\right)$

Because S set={ (x _i, y _i), i=1,2 ... M} is the approximate collection of ε, has:

|<w·x>+b-y _i|≤ε (7)

Then:

$\frac{|\&lang;w\&CenterDot;x\&rang;+b-y_i|}{\sqrt{1+{\left|\right|w\left|\right|}^2}}\&le;\frac{\mathrm{\&epsiv;}}{\sqrt{1+{\left|\right|w\left|\right|}^2}},i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M---\left(8\right)$

Can be got by following formula:

$d_i\&le;\frac{\mathrm{\&epsiv;}}{\sqrt{1+{\left|\right|w\left|\right|}^2}},i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M---\left(9\right)$

Be that point in the S set is apart from maximum to hyperplane

Then, in the sample in the S set, between all and the g (x) distance less than

Sample, be the sample that can be used for setting up phase locus of points forecast model modeling in the phase space.

Step 2), determine target function, obtain the Nonlinear Mapping of the phase locus of points in the phase space reconstruction Regression function g (x), g (x) is

Solution under the support vector condition;

Can obtain the best fit approximation hyperplane of S set to the upper bound of hyperplane distance by the point among the maximization S.Then the best fit approximation hyperplane can obtain by maximization formula (9), therefore finds the solution ‖ w ‖ ²Minimization problem can obtain the best fit approximation hyperplane of S set.At this moment, the support vector regression problem on system's phase space can be converted into ‖ w ‖ ²Optimization problem:

$\left\{\begin{array}{c}\mathrm{<figure-callout\; id="1"\; label="min"\; filenames="HSA00000363608600061.png,HSA00000363608600062.png"\; state="\{\{state\}\}">min</figure-callout>}\frac{1}{2}{\left|\right|w\left|\right|}^2\\ s.t.|\&lang;w\&CenterDot;x_i\&rang;+b-y_i|\&le;\mathrm{\&epsiv;},i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array}\right.---\left(10\right)$

Formula (10) is quadratic programming problem, and its Lagrange function is:

$\left\{\begin{array}{c}L(w,b,\mathrm{\&alpha;},{\mathrm{\&alpha;}}^{*})=\frac{1}{2}{\left|\right|w\left|\right|}^2-\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i(\mathrm{\&epsiv;}-y_i+\&lang;w\&CenterDot;x_i\&rang;+b)-\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i^{*}(\mathrm{\&epsiv;}+y_i-\&lang;w\&CenterDot;x_i\&rang;-b)\\ {\mathrm{\&alpha;}}_i\&GreaterEqual;0,{\mathrm{\&alpha;}}_i^{*}\&GreaterEqual;0,i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array}\right.---\left(11\right)$

The Lagrange dual problem of formula (11) is:

$\underset{\mathrm{\&alpha;},{\mathrm{\&alpha;}}^{*}}{\max }\left(\underset{w,b}{\min }L(w,b,\mathrm{\&alpha;},{\mathrm{\&alpha;}}^{*})\right)$

According to the Carlow this-Kuhn-Tucker condition (Karush-Kuhn-Tucker Condition):

$\frac{\&PartialD;L}{\&PartialD;w}=0;$ $\frac{\&PartialD;L}{\&PartialD;b}=0$

Have:

$\left\{\begin{array}{c}w=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i-{\mathrm{\&alpha;}}_i^{*})x_i\\ \underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i-{\mathrm{\&alpha;}}_i^{*})x_i=0\end{array}\right.---\left(12\right)$

The dual problem that can be got (13) optimization problem by formula (11) and (12) is:

$\left\{\begin{array}{c}\underset{\mathrm{\&alpha;},{\mathrm{\&alpha;}}^{*}}{\min }\frac{1}{2}\underset{i,j=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)({\mathrm{\&alpha;}}_j^{*}-{\mathrm{\&alpha;}}_j)\&lang;x_i\&CenterDot;x_j\&rang;+\mathrm{\&epsiv;}\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)-\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{y}_i({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)\\ s.t.\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)=0,{\mathrm{\&alpha;}}_i\&GreaterEqual;0,{\mathrm{\&alpha;}}_i^{*}\&GreaterEqual;0,i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array}\right.---\left(13\right)$

Find the solution dual problem (13), can obtain the Nonlinear Mapping of the phase locus of points in system's phase space

Regression function g (x).Because electric power system is non linear system, dual problem (13) does not have feasible solution, must be with a Nonlinear Mapping φ the x of point mutually in system's phase space _iBe mapped to a higher dimensional space, carry out linear regression at higher dimensional space then.Same owing to the inner product operation that relates in the optimizing process in the higher dimensional space, for avoiding inner product operation, with kernel function Φ (x _i, x _j) replacement inner product＜φ (x _i) φ (x _j) realize nonlinear regression in system's phase space.The sample set of forming mutually in system time sequence phase space reconstruction: x _i∈ R ⁿ, φ (x _i) ∈ R ^m, y _i∈ 1, and+1}, structure is put sample set { (φ (x mutually in high-dimensional feature space exactly _i), y _i), i=1,2 ..., the optimal classification face of M}:

g(x)＝<w·φ(x)>+b＝0

At this moment, ask the problem of nonlinear regression function to be converted into and find the solution following optimization problem:

$\left\{\begin{array}{c}\mathrm{<figure-callout\; id="1"\; label="min"\; filenames="HSA00000363608600061.png,HSA00000363608600062.png"\; state="\{\{state\}\}">min</figure-callout>}\frac{1}{2}{\left|\right|w\left|\right|}^2\\ |\&lang;w\&CenterDot;\mathrm{\&phi;}\left(x_i\right)\&rang;+b-y_i|\&le;\mathrm{\&epsiv;},i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array}\right.---\left(14\right)$

The Lagrange dual problem of optimizing (14) is:

$\left\{\begin{array}{c}\underset{\mathrm{\&alpha;},{\mathrm{\&alpha;}}^{*}}{\min }\frac{1}{2}\underset{i,j=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)({\mathrm{\&alpha;}}_j^{*}-{\mathrm{\&alpha;}}_j)\mathrm{\&Phi;}(x_i,x_j)+\mathrm{\&epsiv;}\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)-\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{y}_i({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)\\ s.t.\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)=0,{\mathrm{\&alpha;}}_i\&GreaterEqual;0,{\mathrm{\&alpha;}}_i^{*}\&GreaterEqual;0,i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array}\right.---\left(15\right)$

In carrying out system's phase space, during the Nonlinear Mapping function approximation, owing to inevitably have error between the regression function of trying to achieve and the actual function, therefore introduce slack variable:

ξ _i≥0， ${\mathrm{\&xi;}}_i^{*}\&GreaterEqual;0,$ i＝1，2，…，M

The optimization problem of this moment is:

$\left\{\begin{array}{c}\mathrm{<figure-callout\; id="1"\; label="min"\; filenames="HSA00000363608600061.png,HSA00000363608600062.png"\; state="\{\{state\}\}">min</figure-callout>}\frac{1}{2}{\left|\right|w\left|\right|}^2+c\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&xi;}}_i+{\mathrm{\&xi;}}_i^{*})\\ \begin{array}{c}s.t.\&lang;w\&CenterDot;\mathrm{\&phi;}\left(x_i\right)\&rang;+b-y_i\&le;{\mathrm{\&xi;}}_i^{*}+\mathrm{\&epsiv;},i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\\ y_i-\&lang;w\&CenterDot;\mathrm{\&phi;}\left(x_i\right)\&rang;-b\&le;{\mathrm{\&xi;}}_i+\mathrm{\&epsiv;},i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\\ {\mathrm{\&xi;}}_i\&GreaterEqual;0,{\mathrm{\&xi;}}_i^{*}\&GreaterEqual;0,i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array}\end{array}\right.---\left(16\right)$

The Lagrange function of optimization problem (16) is:

$\left\{\begin{array}{c}\begin{array}{c}L(w,b,\mathrm{\&alpha;},{\mathrm{\&alpha;}}^{*})=\frac{1}{2}{\left|\right|w\left|\right|}^2+c\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&xi;}}_i+{\mathrm{\&xi;}}_i^{*})-\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i({\mathrm{\&xi;}}_i+\mathrm{\&epsiv;}-y_i+\&lang;w\&CenterDot;\mathrm{\&phi;}\left(x_i\right)\&rang;+b)\\ -\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i^{*}({\mathrm{\&xi;}}_i^{*}+\mathrm{\&epsiv;}+y_i-\&lang;w\&CenterDot;\mathrm{\&phi;}\left(x_i\right)\&rang;-b)-\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&eta;}}_i({\mathrm{\&xi;}}_i+{\mathrm{\&xi;}}_i^{*})\end{array}\\ {\mathrm{\&alpha;}}_i\&GreaterEqual;0,{\mathrm{\&alpha;}}_i^{*}\&GreaterEqual;0,i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array},---\left(17\right)\right.$

Lagrange function (17) satisfies:

$\left\{\begin{array}{c}\frac{\&PartialD;L}{\&PartialD;w}=0,\frac{\&PartialD;L}{\&PartialD;b}=0\\ \frac{\&PartialD;L}{\&PartialD;{\mathrm{\&xi;}}_i}=0,\frac{\&PartialD;L}{\&PartialD;{\mathrm{\&xi;}}_i^{*}}=0\end{array}\right.$

Therefore have:

$\left\{\begin{array}{c}w=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i-{\mathrm{\&alpha;}}_i^{*})x_i,\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i-{\mathrm{\&alpha;}}_i^{*})=0\\ c-{\mathrm{\&alpha;}}_i-{\mathrm{\&eta;}}_i=0,c-{\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&eta;}}_i^{*}=0,i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array}\right.---\left(18\right)$

Can get the Lagrange dual problem by formula (17) and formula (18) is:

$\left\{\begin{array}{c}\underset{\mathrm{\&alpha;},{\mathrm{\&alpha;}}^{*}}{\min }\frac{1}{2}\underset{i,j=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)({\mathrm{\&alpha;}}_j^{*}-{\mathrm{\&alpha;}}_j)\mathrm{\&Phi;}(x_i,x_j)+\mathrm{\&epsiv;}\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)-\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{y}_i({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)\\ s.t.\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)=0,{\mathrm{\&alpha;}}_i\&GreaterEqual;c,{\mathrm{\&alpha;}}_i^{*}\&GreaterEqual;0,i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array}\right.---\left(19\right)$

Find the solution formula (19) get final product Nonlinear Mapping in system's phase space

Regression function g (x), obtain by g (x)

Step 3), set up the kernel function parameter model, and adjustment model parameter c and ε value and kernel function parameter γ value;

This paper adopts gaussian kernel function:

Solving

After, the prediction of system time sequence just becomes according to Nonlinear Mapping Utilize the known point mutually in system's phase space of reconstruct, the problem of next movement locus constantly of computing system.And according to the limited mapping that simulates mutually as far as possible near Nonlinear Mapping f in system's phase space

Algorithm of support vector machine is found the solution Be to utilize a Nonlinear Mapping φ (x _i), the point mutually in system's phase space is mapped in the high-dimensional feature space Nonlinear Mapping relation between making mutually

In high-dimensional feature space, put inner product＜x mutually _iX _jCalculating be converted into the inner product＜φ (x that calculates the Nonlinear Mapping function _i) φ (x _j).And Nonlinear Mapping inner product＜φ (x _i) φ (x _j) available core function replacement again, namely establish:

<φ(x _i)·φ(x _j)>＝Φ(x _i，x _j)

Wherein, kernel function Φ (x _i, x _j) satisfy the Mercer condition.

The parameter that influences SVMs nonlinear fitting model performance mainly contains admissible error ε, penalty factor c.

Parameter ε has shown the expectation to regression function g (x) phase point prediction error on the voltage stabilization system phase space, makes the solution of SVMs have sparse property, strengthens its generalization ability.When parameter ε was non-vanishing, the number that the number of support vector can be put mutually less than whole phase spaces can represent all with support vector and calculate mutually.In other parameter one regularly, along with the increase of ε, the computation complexity of supporting vector machine model also reduces, and the training error of model increases.When parameter ε value is too small, the quantity of support vector also will reduce rapidly, cause support vector can't fully reflect the information that contains in the wind-powered electricity generation voltage stabilization system phase space, cause the precise decreasing of fitting function g.

The effect of penalty factor c is the ratio of regulating supporting vector machine model fiducial range and empiric risk, makes it have good popularization performance.C difference on the phase space of the stable time series reconstruct of gathering of different wind-powered electricity generation voltages, in the wind-powered electricity generation voltage stabilization system phase space of determining, the more little expression of the value of c is more little to the correction of experience error, and the complexity of SVMs is little, and the error value-at-risk is bigger.After other parameter of supporting vector machine model was determined, at c hour, prediction effect was very poor, and along with c increases, precision of prediction improves.

The SVMs derivation algorithm adopts gaussian kernel function among the present invention:

$\mathrm{\&Phi;}(x,y)=e^{-\frac{\left|\right|x-y\left|\right|}{\mathrm{\&gamma;}}}$

For making the support vector machine method on system's phase space be issued to the non-linear effect of approaching preferably in the very little situation of phase space phase number of spots, construct that the support vector regression model is most important accurately, and the essence of support vector regression model structure is to choose and optimize other parameter of kernel function and model.Adopt the crosscheck method to carry out the selection of supporting vector machine model parameter.

Crosscheck method concrete grammar is:

1. given penalty factor c value and kernel function parameter γ value change the ε value within the specific limits, get the admissible error ε value of precision of prediction preferably the time and are the ε parameter of supporting vector machine model;

2. according to given ε value and γ and, c value is changed within the specific limits, getting the c value of precision of prediction preferably the time is the c parameter of supporting vector machine model;

3. at last after given ε value and c value, make γ change to determine the γ parameter of supporting vector machine model according to the precision of prediction of model within the specific limits.

Step 5, to the interpretation of result of line voltage stability prediction;

Gather one section system time sequence, simultaneously the acquisition parameter of same time period is carried out standardized data as measurement data such as: voltage, electric current, phase angle, blower fan output are meritorious and idle and handle, constitute system's multivariable time series of a 6 DOF.Carry out phase space reconfiguration with delay time T and the multivariable time series of embedding dimension m.In system's phase space of reconstruct, put the training sample of construction system time series supporting vector machine model mutually with in the phase space all, set up supporting vector machine model, to the Nonlinear Mapping in the system time sequence global prediction model Carry out match.

The training sample that all constitutes mutually in the phase space is:

$\left\{\begin{array}{c}{V}_n=(x_{1,n},x_{1,n-x_1},\&CenterDot;\&CenterDot;\&CenterDot;,x_{1,n-(m1-1)x_1},\&CenterDot;\&CenterDot;\&CenterDot;,x_{M,n},x_{M,n-x_M},\&CenterDot;\&CenterDot;\&CenterDot;,x_{M,n-(m_M-1)x_M})\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ V_i=(x_{1,i},x_{1,i-x_1},\&CenterDot;\&CenterDot;\&CenterDot;,x_{1,i-(m1-1)x_1},\&CenterDot;\&CenterDot;\&CenterDot;,x_{M,i},x_{M,i-x_M},\&CenterDot;\&CenterDot;\&CenterDot;,x_{M,i-(m_M-1)x_M})\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ V_N=(x_{1,N},x_{1,N-x_1},\&CenterDot;\&CenterDot;\&CenterDot;,x_{1,N-(m1-1)x_1},\&CenterDot;\&CenterDot;\&CenterDot;,x_{M,N},x_{M,N-x_M},\&CenterDot;\&CenterDot;\&CenterDot;,x_{M,N-(m_M-1)x_M})\end{array}\right.---\left(20\right)$

Wherein add up to N=6 (n-(m-1) τ) mutually.Select the support vector sample from these samples, the curvilinear function g (x) of match support vector sample correspondence regards g (x) as in the phase space phase locus of points

With the fitting function of voltage stabilization system track f, calculating g (x) can solve the stable value of wind-powered electricity generation voltage in the value in a certain moment in future, can realize the stable prediction of voltage.

According to the system time sequence phase space reconstruction supporting vector machine model training sample set capacity and the electrical network non linear system characteristic that constitute of point (20) mutually, use the crosscheck method, select supporting vector machine model kernel function and each parameter of model: kernel function is selected gaussian kernel function; Kernel function parameter γ; Punishment c; Insensitive loss function parameter ε.

Advantage of the present invention: wind electric field blower group voltage stability forecast device and method of the present invention, proposed to utilize and directly measured blower fan group voltage, voltage phase angle and reactive power and active power, use the chaos time sequence algorithm to support forecast model, and finally utilize transducer, data acquisition chip, central processing unit, industrial computer and wireless communication module to realize the monitoring of wind-electricity integration system voltage.The error that this method has caused when having avoided conventional method to set up model and choose parameter, and have the input variable extraction simply, accurately high, accuracy is good, the characteristics that forecasting efficiency is high.

Description of drawings:

Fig. 1 wind-powered electricity generation unit of the present invention voltage stability forecast apparatus structure is always schemed;

Fig. 2 wind-powered electricity generation unit of the present invention voltage stability forecast hardware is realized block diagram;

Data acquisition and the transmission circuit figure of Fig. 3 wind-powered electricity generation unit of the present invention voltage stability forecast terminal;

Fig. 4 wind-powered electricity generation unit of the present invention voltage stability forecast method flow diagram;

Fig. 5 the present invention sets up Chaotic time series forecasting model method flow chart;

Fig. 6 predicted voltage curve of the present invention and virtual voltage curve chart;

Fig. 7 the present invention obtains model parameter c and ε value and kernel function parameter γ value flow chart;

Fig. 8 Rosenstein method of the present invention schematic diagram;

Fig. 9 system of the present invention phase space supporting vector machine model schematic diagram;

Embodiment:

The present invention is that a kind of wind electric field blower voltage stability forecast device and method is illustrated in conjunction with example and accompanying drawing;

The device that this wind electric field blower group voltage stability forecast uses includes transducer, data acquisition chip, central processing unit, industrial computer and wireless communication module; Wherein the voltage transformer summation current transformer on the transducer is selected JDG4-0.51000/100 model and LZJC-10Q 1000/5 model respectively for use, wireless network communication module adopts H7000 series wireless communication system, industrial computer adopts UNO-3072 Series P ent ium M/Celeron M built-in industrial control machine, central processing unit adopts dsp chip, dsp chip is TMS320F2812A series digit signal processor, clock frequency is 150MHz, machine cycle is 6.67ns, the interface power supply is 3.3V, and core power is 1.8V; Data acquisition chip adopts ADS7825, and 4 passages, 16 bit data acquisition chips are sampled and analog-to-digital conversion, by ± the 5V power supply, are no more than data sampling and change-over time 25us; Low eight D0-D7 of the data wire here and high eight-bit D8-D15 send into 16 bit data after the conversion XD0-XD7 of DSP at twice, and SHT11 is intelligent temperature/humidity sensor, GND: earth terminal; DATA: bidirectional serial data lines; SCK: serial clock input; The VDD power end; Other blank pipe pin, the resolution of temperature value output is 12, humidity value is output as 14, as Fig. 1, Fig. 2 and shown in Figure 3;

This installs the connection of each parts: the output of temperature sensor and humidity sensor is connected input BDX and the BDR of DSP, voltage sensor, voltage phase angle transducer and reactive power transducer are connected the AIN0 of data acquisition chip ADS7825 to the AIN3 end with active power transducer output, the output BYTE of data acquisition chip ADS7825,

The input that connects DSP

XA0,

The output of DSP connects the input of industrial computer and wireless communication module; The electric information of wind electric field blower and mechanical information carry out synchronized sampling, maintenance, A/D via corresponding instrument transformer or transducer by sampling A and convert digital signal to, send into calculating and data processing that DSP classifies, link to each other with industrial computer and deliver to wireless communication module by communication interface, for ready with the remote dispatching communication;

Utilize above-mentioned wind electric field blower group voltage stability forecast device to carry out forecast method, comprise the steps:

Wind-powered electricity generation set grid-connection point voltage, voltage phase angle and the reactive power of step 1, collection wind energy turbine set and meritorious as input variable; Be that dimension is 4, gather sample value and see Table 1 that process as shown in Figure 4.

Table 1

Gather sample	Sampled value
		Wind-powered electricity generation unit voltage	759 (volts)
Wind-powered electricity generation unit voltage phase angle	22 (degree)
		Wind-powered electricity generation unit reactive power	-29 (megavars)
Wind-powered electricity generation unit active power	46 (megawatts)

Step 2, the analog signal of gathering is converted into digital signal and rise time sequence, carries out the phase space reconfiguration of voltage stabilization system;

System's phase space form of reconstruct is:

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="X"\; filenames="HSA00000363608600061.png,HSA00000363608600062.png"\; state="\{\{state\}\}">X</figure-callout>}}_1=(x_1,x_{1+x},\&CenterDot;\&CenterDot;\&CenterDot;,x_{1+(m-1)x})\\ {\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="HSA00000363608600021.png,HSA00000363608600061.png"\; state="\{\{state\}\}">X</figure-callout>}}_2=(x_2,x_{2+x},\&CenterDot;\&CenterDot;\&CenterDot;,x_{2+(m-1)x})\\ \&CenterDot;\&CenterDot;\&CenterDot;\\ X_i=(x_i,x_{i+x},\&CenterDot;\&CenterDot;\&CenterDot;,x_{i+(m-1)x})\end{array}\right.$

Wherein, τ is time of delay, and m is for embedding dimension;

Step 3, chaotic characteristic qualitative reaction is really carried out in the voltage stable phase space of reconstruct in the step 2;

Adopt Rosenstein to improve algorithm, calculate maximum Lyapunov exponent λ ₁＞0, then available non-linear algorithm of support vector machine is found the solution;

Step 4, definite by the voltage steady change curve prediction model in the phase space of time series reconstruct is obtained kernel function parameter γ value; Step is as follows: as shown in Figure 5,

1). the system phase space of foundation is put the sample set of formation mutually: S={ (x _i, y _i), i=1,2 ... M}, x _i∈ R ⁿBe any input, y _i∈ R is x _iCorresponding output;

2). set up target function:

$\left\{\begin{array}{c}\underset{\mathrm{\&alpha;},{\mathrm{\&alpha;}}^{*}}{\min }\frac{1}{2}\underset{i,j=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)({\mathrm{\&alpha;}}_j^{*}-{\mathrm{\&alpha;}}_j)\mathrm{\&Phi;}(x_i,x_j)+\mathrm{\&epsiv;}\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)-\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{y}_i({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)\\ s.t.\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)=0,{\mathrm{\&alpha;}}_i\&GreaterEqual;c,{\mathrm{\&alpha;}}_i^{*}\&GreaterEqual;0,i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,M\end{array}\right.$

Wherein, s.t. is constraints, and M is natural number.C is the penalty coefficient factor, and ε is admissible error;

Then as long as therefrom obtain Φ (x _i, x _j), obtain regression function g (x)=＜w φ (x)+b=0, can finish the prediction to voltage steady change curve;

3). ask kernel function: find the solution the parameter of kernel function, definite kernel function according to the crosscheck method;

Kernel function model is:

$\mathrm{\&Phi;}(x,y)=e^{-\frac{\left|\right|x-y\left|\right|}{\mathrm{\&gamma;}}}$

Obtain kernel function parameter γ=0.3 by the crosscheck method; Punishment c=70; Insensitive loss function parameter ε=0.22;

Step 5, with g (x)=＜w φ (x)+b=0 is as voltage stability forecast function, the time series that generates with collection capacity is input, calculates line voltage stability prediction result;

Day 24 hours voltage of predicting certain wind field stabilizes to example.Predicted voltage index of stability and virtual voltage index of stability curve as shown in Figure 6, predicated error is in ± 8%.

Claims (2)

1. one kind is adopted wind electric field blower group voltage stability forecast device to carry out forecast method, described device comprises transducer, data acquisition chip, central processing unit, industrial computer and wireless communication module, wherein the output of transducer connects the input of data acquisition chip, the output of data acquisition chip connects the input of central processing unit, and the output of central processing unit connects the input of industrial computer and wireless communication module; It is characterized in that:

Described method is carried out as follows:

The active power that step 1, the voltage, electric current, phase angle and the wind field that adopt wind electric field blower group voltage stability forecast device to gather wind farm grid-connected point are exported and reactive power are as input variable;

Step 2, the electric network data of gathering in the step 1 constantly is arranged as time series by gathering, time series is carried out phase space reconfiguration, reconstruct the phase space that wind-powered electricity generation voltage is stablized non linear system;

With the active power of the voltage of wind farm grid-connected point, electric current, phase angle and wind field output as input variable; If the system time sequence of gathering is X={x ₁, x ₂..., x _N, N is natural number; Select time of delay and embed dimension, reconstruct original system phase space is:

$\left\{\begin{array}{c}{X}_1=(x_1,x_{1+x},...,x_{1+(m-1)x})\\ X_2=(x_2,x_{2+x},...,x_{2+(m-1)x})\\ ...\\ X_i=(x_i,x_{i+x},...,x_{i+(m-1)x})\end{array}\right.---\left(1\right)$

Wherein, τ is time delay, and m puts total n=N-(m-1) τ X mutually for embedding dimension _iBe point mutually in the phase space reconstruction, i=1,2 ..., n;

Step 3, chaotic characteristic qualitative reaction is really carried out in the voltage stable phase space of reconstruct in the step 2;

For system time sequence X={ x _l, x ₂..., x _N, be m to embed dimension, be that τ carries out phase space reconfiguration time of delay, has:

Y(t _i)=(x(t _i),x(t _i+τ),...,x(t _i+(m-1)τ),(i=1,2,...,n) （2）

Wherein, n=N-(m-1) τ;

Get the Y(t of point mutually in system's phase space of reconstruct ₁), establish Y (t in the phase space reconstruction ₁) neighbor point be Y _l(t ₁), Y (t _l) and Y ₁(t ₁) between distance be:

d ₁(0)=||Y(t ₁)|| （3）

In the formula, || || be Euclidean distance;

To in system's phase space of reconstruct each to neighbor point, calculate after k the discrete time apart from d _i(k):

d _i(k)=||Y(t _i)-Y _i(t _k)|| (4)

K=1 wherein, 2 ... .n, n=N-(m-1) τ;

Ask each d _i(K) ≠ 0 logarithm ln (d _i(k)), to each k value, the definition following formula:

$y\left(k\right)=\frac{1}{M}\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}1n\left(\mathrm{di}\left(k\right)\right)---\left(5\right)$

For: based on i mutually, the range averaging value of k discrete time, M is the d corresponding to the non-zero of a certain k value in the formula _i(k) number;

Be coordinate with k and y (k), draw the change curve of y (k), calculate the regression straight line slope of y (k) curve;

This slope value K is largest Lyapunov exponent λ ₁; Work as λ ₁Greater than zero, just prove that this system is chaos, just can adopt Nonlinear Time Series SVMs solution;

Step 4, forecast model and the model parameter of putting variation track in the phase space reconstruction are mutually determined, obtained model parameter c and ε value and kernel function parameter γ value;

Step 5, to the interpretation of result of line voltage stability prediction;

In system's phase space of reconstruct, put the training sample of construction system time series supporting vector machine model mutually with in the phase space all, set up supporting vector machine model, to the Nonlinear Mapping in the system time sequence prediction model

Carry out match;

The training sample that all constitutes mutually in the phase space of reconstruct is:

$\left\{\begin{array}{c}{V}_{n^{\&prime;}}=(x_{1,n^{\&prime;}},x_{1,n^{\&prime;}-{\mathrm{\&tau;}}_1},...,x_{1,n^{\&prime;}-(m_1-1){\mathrm{\&tau;}}_1},...,x_{M,n^{\&prime;}-{\mathrm{\&tau;}}_M},...,x_{M,n^{\&prime;}-(m_M-1){\mathrm{\&tau;}}_M})\\ .\\ .\\ .\\ V_i=(x_{1,i},x_{1,i-{\mathrm{\&tau;}}_1},...,x_{1,i-(m_1-1){\mathrm{\&tau;}}_1},...,x_{M,i},x_{M,i-{\mathrm{\&tau;}}_M},...,x_{M,i-(m_M-1){\mathrm{\&tau;}}_M})---\left(6\right)\\ .\\ .\\ .\\ V_{N^{\&prime;}}=(x_{1,N^{\&prime;}},x_{1,N^{\&prime;}-{\mathrm{\&tau;}}_1},...,x_{1,N^{\&prime;}-(m_1-1){\mathrm{\&tau;}}_1},...,x_{M,N^{\&prime;}},x_{M,N^{\&prime;}-{\mathrm{\&tau;}}_M},...,x_{M,N^{\&prime;}-(m_M-1){\mathrm{\&tau;}}_M})\end{array}\right.$

Add up to N'=6 (n'-(m-1) τ) mutually, select the support vector sample from these samples, the curvilinear function g (x) of match support vector sample correspondence regards g (x) as in the phase space phase locus of points

With the voltage stabilization system track

Fitting function, calculate the value of g (x), can solve the stable value of wind-powered electricity generation voltage, finish the stable prediction of voltage;

System time sequence phase space reconstruction is put as the formula (6) mutually, put supporting vector machine model training sample set capacity and the electrical network non linear system characteristic of formation mutually according to phase space, use the crosscheck method, select supporting vector machine model kernel function and each parameter of model: kernel function is selected gaussian kernel function; Kernel function parameter γ; Punishment c; Insensitive loss function parameter ε.

2. adopt the described employing wind electric field blower of claim 1 group voltage stability forecast device to carry out forecast method, it is characterized in that: described step 4, carry out as follows:

Step 1), set up sample set, select the support vector sample;

The sample set that the system phase space of setting up departments is put formation mutually is: S={ (x _i, y _i, i=1 .2 ... .M}, if an existence hyperplane g (x)=＜wx 〉+b, w ∈ R ⁿ, b ∈ R makes:

|y _i-g(x _i)|≤ε,i=1，2,....M,

Set up, then sample set S={ (x _i, y _i), i=1,2 ... .M} is the approximate collection of ε, the point (x of S _i, y _i) to the distance of hyperplane g (x) be:

$d_i=\frac{|(w\&CenterDot;x)+b-y_i|}{\sqrt{1+{\left|\right|w\left|\right|}^2}}---\left(7\right)$

Because S set={ (x _i, y _i), i=1,2 ... .M} is the approximate collection of ε, has:

|(w·x)+b-y _i|≤ε (8)

Then:

$\frac{|(w\&CenterDot;x)+b-y_i|}{\sqrt{1+{\left|\right|w\left|\right|}^2}}\&le;\frac{\mathrm{\&epsiv;}}{\sqrt{1+{\left|\right|w\left|\right|}^2}},i=\mathrm{1,2},...,M---\left(9\right)$

Can be got by following formula:

$d_i\&le;\frac{\mathrm{\&epsiv;}}{\sqrt{1+{\left|\right|w\left|\right|}^2}},i=\mathrm{1,2},...,M---\left(10\right)$

Be that point in the S set is apart from maximum to hyperplane

Then, in the sample in the S set, between all and the g (x) distance less than

Sample all as the support vector of phase space, be used for as setting up the support vector sample of phase space phase locus of points forecast model modeling;

Step 2), determine target function, obtain the Nonlinear Mapping of the phase locus of points in the phase space reconstruction

Regression function g (x), g (x) is

Solution under the support vector condition;

Target function is:

$\left\{\begin{array}{c}\underset{\mathrm{\&alpha;},{\mathrm{\&alpha;}}^{*}}{\min }\frac{1}{2}\underset{i,j=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)({\mathrm{\&alpha;}}_j^{*}-{\mathrm{\&alpha;}}_j)\mathrm{\&Phi;}(x_i,x_j)+\mathrm{\&epsiv;}\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)-\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{y}_i({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)\\ s.t.\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}({\mathrm{\&alpha;}}_i^{*}-{\mathrm{\&alpha;}}_i)=0,{\mathrm{\&alpha;}}_i\&GreaterEqual;c,{\mathrm{\&alpha;}}_i^{*}\&GreaterEqual;0,i=\mathrm{1,2},...M\end{array}\right.---\left(1\right)$

Wherein, α is Lagrange multiplier; α ^*Untrivialo solution for α; α _iIt is the Lagrange multiplier of i support vector; α _i ^*Be the Lagrange multiplier α of i support vector _iUntrivialo solution; Φ (x _i, x _j) be kernel function; y _iThe ordinate of putting mutually for sample; S.t. the expression " ... constraints under ";

By target function solve g (x)=＜w φ (x)+b=0, by formula g (x)=＜w φ (x)+b=0 obtains regression function g (x); G (x) namely is

Solution under support vector sample condition;

Step 3), set up the kernel function parameter model, and adjustment model parameter c and ε value and kernel function parameter γ value;

Gaussian kernel function is:

$\mathrm{\&Phi;}(x,y)=e^{-\frac{|x-y|}{y}}$

By crosscheck method adjustment model parameter c and ε value and kernel function parameter γ value, obtain optimum c and the proportioning of ε value and γ value.

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