CN102983808B - Method for performing online identification on direct-axis synchronous reactance of power generator on the basis of PMU (Power Management Unit) steady state data - Google Patents

Abstract

The invention discloses a method for performing online identification on direct-axis synchronous reactance of a power generator on the basis of PMU (Power Management Unit) steady state data. The method comprises the following steps: establishing an identification model for describing the direct-axis synchronous reactance of the power generator according to steady state operation characteristics of a synchronous generator; screening PMU steady state data of a phasor measurement according to electrical capacity needed by the established identification model; converting each screened electric capacity value obtained through the measurement of the PMU into a per unit value; decoupling a direct axis and a quadrature axis of the power generator according to Park conversion; and identifying the direct-axis synchronous reactance of the power generator by using a least square method according to the established identification model. The method disclosed by the invention is simple and easy; the searching efficiency can be effectively increased; and the accuracy of an identification result can be effectively improved.

Description

A kind of method of the generator direct-axis synchronous reactance on-line identification based on PMU steady state data

Technical field

The present invention relates to synchronous generator technical field, particularly relate to a kind of method of the generator direct-axis synchronous reactance on-line identification based on PMU steady state data.

Background technology

At present, generator synchronous reactance parameter is one of key factor determining generator operating conditions and behavior, and its accuracy is related to the safe and stable operation of electrical network.Electrical power system analysis and computing emulates the theoretical value or design load that generator synchronous reactance Duo Shi producer used provides, and owing to can not take into account the impact of eddy current, magnetic hysteresis, the actual operating mode such as saturated, acquired results is not usually inconsistent with actual condition.Have field test to prove, for hydraulic generator, the generator direct-axis synchronous reactance Xd after saturated and quadrature axis synchronous reactance Xq reduces about 25% than non-saturated values; For turbo generator, then by minimizing 15% ~ 25%, when overvoltage and magnet excitation, degree of saturation can increase greatly.If the theoretical value adopting producer to provide or design load, will have a strong impact on accuracy and the confidence level of system analysis computation.Therefore generator synchronous reactance parameter is significant accurately for Real-time Obtaining.

Based on the appearance of the phasor measurement unit (PMU) of global positioning system (GPS), the on-line identification for generator parameter provides strong instrument.Along with the development of the technology such as information, communication, synchronized phasor technology obtains very great development and extensive use at home, defines a new technical field gradually.Compared with traditional measurement, PMU device except providing the electric current of machine end, voltage, meritorious, idle except, also provide the merit angle information that traditional measurement cannot provide, for generator parameter on-line identification provides the foundation.In addition, the target of identification work expects to find the Mathematical Modeling completely equivalent with real system, comprise model structure equation and model parameter, example is recognized as with generator synchronization parameter, expect for identical input X, the calculating output Y ' of model and the actual output Y of synchronous generator is error free.The process of identification constantly regulates model parameter according to the error between Y and Y ' exactly, and can make free from error parameter vector θ between Y and Y ' until navigate to, model is now exactly the equivalent model of synchronous generator.

Comprise the method for several on-line identification generator direct-axis synchronous reactance Xd in prior art, such as substep identification method, first the method carries out identification to rotor turn ratio a, then a is substituted into the identification equation of Xd with identification Xd.The realization means of the method mainly contains two kinds: a kind of be utilize generator underloading, underexcitation time excitation microvariations data, another kind is the steady state data utilized under invariable power, different exciting level.For the unit that actual field is run, these two classes data all not easily obtain, so the practicality of method is restricted.Simulation process for the identification of generator synchronization parameter finds, parameter identification result is very responsive to the setting of initial value, the design load that existing discrimination method generally adopts producer to provide is as initial value, the design load provided due to producer be disregard saturated under value, with to take into account saturated reactance value difference during generator actual motion comparatively large, identification result is easily made to be absorbed in local minimum and to affect identification precision.

Summary of the invention

The object of this invention is to provide a kind of method of the generator direct-axis synchronous reactance on-line identification based on PMU steady state data, the method is simple, effectively can improve the efficiency of search work and the precision of identification result.

The object of the invention is to be achieved through the following technical solutions, a kind of method of the generator direct-axis synchronous reactance on-line identification based on PMU steady state data, described method comprises:

According to the Steady of synchronous generator, set up the identification model describing generator direct-axis synchronous reactance;

According to the electric parameters required for set up identification model, carry out the screening of phasor measurement unit PMU steady state data;

The famous value of each electric parameters that PMU after screening measures is converted to the perunit value under Unified Form;

Convert according to Parker Park, utilize each electric quantity information after conversion, calculate generator terminal voltage quadrature axis component Uq, the Generator end electric current direct axis component Id needed for identification according to following formula:

$\left\{\begin{array}{c}{U}_q=U\cos \mathrm{\δ}\\ I_d=I\sin (\mathrm{\δ}+\mathrm{\θ})\end{array}\right.$

Wherein, U, I are the generator terminal voltage and electric current measured, and δ is the generator's power and angle measured, and θ is the phase angle difference of set end voltage and electric current;

According to set up identification model, calculate and obtain generator direct-axis synchronous reactance linear least squares method result.

Described method also comprises: sensitivity analysis parameter to be identified being carried out to target function, and selects rational identification initial value thus.

The rational identification initial value of described selection, specifically comprises: the parameter value of Selecting All Parameters sensitivity corresponding to 0 is as the initial value of linear least squares method.

The described screening carrying out phasor measurement unit PMU steady state data, specifically comprises:

Carry out screening and the judgement of phasor measurement unit PMU steady state data, and determine that data time window length is 5s.

As seen from the above technical solution provided by the invention, described method, according to the Steady of synchronous generator, sets up the identification model describing generator direct-axis synchronous reactance; According to the electric parameters required for set up identification model, carry out the screening of phasor measurement unit PMU steady state data; Each electric parameters numerical value that PMU measurement after screening obtains is converted to perunit value; According to Park conversion, d-axis, quadrature axis decoupling zero are carried out to generator; According to set up identification model, least square method is utilized to carry out the identification of generator direct-axis synchronous reactance.The method is simple, effectively can improve the efficiency of search work and the precision of identification result.

Accompanying drawing explanation

In order to be illustrated more clearly in the technical scheme of the embodiment of the present invention, below the accompanying drawing used required in describing embodiment is briefly described, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawings can also be obtained according to these accompanying drawings.

The method flow schematic diagram of the generator direct-axis synchronous reactance on-line identification based on PMU steady state data that Fig. 1 provides for the embodiment of the present invention;

Fig. 2 is based on the sensitivity schematic diagram of the target function of PSCAD about parameter K in embodiment of the present invention example;

Fig. 3 is based on the sensitivity schematic diagram of the target function of PSCAD about parameter Xd in embodiment of the present invention example.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on embodiments of the invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to protection scope of the present invention.

Be described in further detail the embodiment of the present invention below in conjunction with accompanying drawing, be illustrated in figure 1 the method flow schematic diagram of the generator direct-axis synchronous reactance on-line identification based on PMU steady state data that the embodiment of the present invention provides, described method comprises:

Step 11: according to the Steady of synchronous generator, sets up the identification model describing generator direct-axis synchronous reactance.

In this step, the identification model of generator direct-axis synchronous reactance is established according to synchronous generator Steady, that is:

First according to synchronous generator Steady, ignore stator winding resistance, the voltage equation of d-axis d axle is:

E _q=U _q+I _dX _d（1）

Again, during stable state, the relation of built-in potential and exciting current is as follows:

E _q＝X _adI _fd＝(X _d-X _l)I _fd（2）

Wherein, each amount is perunit value, and its meaning is as follows:

E _qfor generator built-in potential; U _qfor generator terminal voltage quadrature axis component; I _dfor Generator end electric current direct axis component; X _dfor generator direct-axis synchronous reactance; X _adfor generator armature reaction reactance; I _fdfor exciter current of generator.

According to above-mentioned equation (1) and (2) known, generator direct-axis synchronous reactance X _dcan be expressed as:

$X_d=\frac{U_q+I_{\mathrm{fd}}{X}_1}{I_{\mathrm{fd}}-I_d}---\left(3\right)$

Meanwhile, will to meet mutual inductance between two constraints: A, each winding reversible for rotor base value system; B, retain traditional perunit value parameter of electric machine.

According to above-mentioned derivation, the rotor excitation current base value meeting above two constraints is:

$I_{\mathrm{fdbase}}=\frac{L_{\mathrm{ad}}}{L_{\mathrm{fd}}}{I}_{\mathrm{sbase}}---\left(4\right)$

Wherein: I _sbasefor stator side electric current base value; I _fdbasefor exciting current base value; Lad is the famous value of armature inductance; Lfd is the famous value of mutual inductance of excitation winding and stator winding.

In addition, in specific implementation, due to L _ad, L _fdvalue not easily obtains, bringing difficulty to asking for of exciting current base value, in order to avoid calculating its perunit value by calculating exciting current fiducial value and then asking, parameter K to be distinguished can be increased in the identification process of Xd, the relation of exciting current perunit value and famous value is characterized, namely with K .Wherein, I _fdfor the famous value of exciting current, for exciting current perunit value.

Then, then with direct-axis current I _dfor exporting observed quantity structure target function, according to criterion of least squares, error target function chooses the chi square function of output error, thus the identification model of generator direct-axis synchronous reactance is expressed as:

Wherein: I _{d is real}for the measured value of Generator end electric current direct axis component; I _{d counts}for the calculated value of Generator end electric current direct axis component.

Step 12: according to the electric parameters required for set up identification model, carries out the screening of phasor measurement unit PMU steady state data.

In this step, can find out according to the identification model that above-mentioned steps 11 is set up, the electric parameters needed for generator direct-axis synchronous reactance identification can comprise: the parameter such as set end voltage, machine end electric current, exciting current, merit angle.

On this basis, then carry out the screening of phasor measurement unit PMU steady state data, select the PMU data of the identification that can be used in synchronous reactance parameter, screening mode can carry out according to measurement PMU data, does not limit here to screening mode.

Further, screening and the judgement of phasor measurement unit PMU steady state data can be carried out, and determine that data time window length is 5s.

Step 13: the famous value of each electric parameters that PMU after screening measures is converted to the perunit value under Unified Form;

Step 14: convert according to Parker Park, utilizes each electric quantity information after conversion, the information such as such as set end voltage, electric current, merit angle, calculates generator terminal voltage quadrature axis component Uq, the Generator end electric current direct axis component Id needed for identification according to following formula.

$\left\{\begin{array}{c}{U}_q=U\cos \mathrm{\δ}\\ I_d=I\sin (\mathrm{\δ}+\mathrm{\θ})\end{array}\right.---\left(6\right)$

Wherein, U, I are the generator terminal voltage and electric current measured, and δ is the generator's power and angle measured, and θ is the phase angle difference of set end voltage and electric current.

Step 15: according to set up identification model, calculates and obtains generator direct-axis synchronous reactance linear least squares method result.

Specifically, the target function of generator direct-axis synchronous reactance identification is the measured value of direct-axis current component Id and the error sum of squares of corresponding calculated value, least square method is utilized to carry out optimizing on gradient direction, one is obtained in minimum variance meaning and the best Mathematical Modeling of test data fitting, the identifier of acquired results and direct-axis synchronous reactance Xd by estimation.

In addition, in actual applications, identification precision is comparatively large by the impact of initial value, and irrational initial value will cause identification result confidence level to reduce.Therefore method described in the present embodiment can also carry out the sensitivity analysis of target function further to each electric parameters parameter to be identified, and select rational identification initial value thus, specifically, consider that least square method is subject to the impact of initial value larger, in order to improve the identification precision of direct-axis synchronous reactance, the present embodiment have employed the identification initial value method for selecting based on sensitivity analysis.

Above-mentioned sensitivity refers to the change along with model parameter, the degree of its input-output characteristic change, and to the sensitivity of certain electric parameters parameter, target function can reflect that this electric parameters Parameters variation is to the influence degree of target function, hypothetical target function is:

$J\left(\mathrm{\θ}\right)=\underset{k=1}{\overset{N}{\mathrm{\Σ}}}{[Y_c\left(k\right)-Y_m\left(k\right)]}^2---\left(6\right)$

Absolute sensitivity:

$\frac{\∂J\left(\mathrm{\θ}\right)}{\∂\mathrm{\θ}}=2\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(Y_c\left(k\right)-Y_m\left(k\right))\frac{{\∂Y}_c(\mathrm{\θ},k)}{\∂\mathrm{\θ}}$

$\≈\frac{J({\mathrm{\θ}}_0+\mathrm{\Δ\θ})-J({\mathrm{\θ}}_0-\mathrm{\Δ\θ})}{2\mathrm{\Δ\θ}}---\left(7\right)$

$=\frac{\∂J\left(\mathrm{\Δ\θ}\right)}{\∂\mathrm{\θ}}$

Relative sensitivity:

$\frac{\∂J\left(\mathrm{\Δ\θ}\right)/J\left({\mathrm{\θ}}_0\right)}{\∂\mathrm{\θ}/{\mathrm{\θ}}_0}=\frac{\∂J\left(\mathrm{\Δ\θ}\right)}{\∂\mathrm{\θ}}\frac{{\mathrm{\θ}}_0}{J\left({\mathrm{\θ}}_0\right)}---\left(8\right)$

The relative sensitivity of error target function to parameter K and Xd is respectively:

$\frac{\∂J(X_d,K)/J(X_{d0},K_0)}{\∂K/K_0}=2\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(I_{\mathrm{dc}}\left(k\right)-I_{\mathrm{dm}}\left(k\right))\frac{{\∂I}_{\mathrm{dc}}(X_{d0},K,k)}{\∂K}\frac{K_0}{J(X_{d0},K_0)}$

$\≈\frac{J(X_{d0},K_0+\mathrm{\ΔK})-J(X_{d0},K_0-\mathrm{\ΔK})}{2\mathrm{\ΔK}}\frac{K_0}{J(X_{d0},K_0)}---\left(9\right)$

$=\frac{\∂J(X_{d0},K)}{\∂K}\frac{K_0}{J(X_{d0},K_0)}$

$\frac{\∂J(X_d,K)/J(X_{d0},K_0)}{\∂X_d/X_{d0}}=2\underset{k=1}{\overset{N}{\mathrm{\Σ}}}(I_{\mathrm{dc}}\left(k\right)-I_{\mathrm{dm}}\left(k\right))\frac{{\∂I}_{\mathrm{dc}}(X_d,K_0,k)}{\∂X_d}\frac{X_{d0}}{J(X_{d0},K_0)}$

$\≈\frac{J(X_{d0}+{\mathrm{\ΔX}}_d,K_0)-J(X_{d0}-{\mathrm{\ΔX}}_d,K_0)}{2\mathrm{\Δ}{X}_d}\frac{X_{d0}}{J(X_{d0},K_0)}---\left(10\right)$

$=\frac{\∂J({\mathrm{\ΔX}}_d,K_0)}{{\∂X}_d}\frac{X_{d0}}{J(X_{d0},K_0)}$

For making target function reach minimum value, the parameter value of Selecting All Parameters sensitivity here corresponding to 0 as the initial value of linear least squares method, thus improves the identification precision of direct-axis synchronous reactance.

With instantiation, above-mentioned on-line identification method is verified below:

Embodiment 1: the present embodiment adopts PSCAD one machine infinity bus system to be research object, disregards generator saturation effect.Rated capacity is 667MVA, and power factor (PF) is 0.9.The true value of synchronous generator practical parameter is as follows:

X _q＝2.10，X _q″＝0.218，T _q0″＝0.069，X _d＝2.155，X _d′＝0.301，X _d″＝0.223，

T _d0′＝8.61，T _d0″＝0.045，

According to PSCAD static Simulation data, namely the electric parameters parameter such as generator terminal voltage, machine end electric current, merit angle, exciting current, carries out direct-axis synchronous reactance identification.

In addition, be illustrated in figure 2 in embodiment of the present invention example based on the sensitivity schematic diagram of the target function of PSCAD about parameter K, be illustrated in figure 3 in embodiment of the present invention example based on the sensitivity schematic diagram of the target function of PSCAD about parameter Xd, according to Fig. 2 and 3, choose the initial value of the minimum parameter value corresponding to point of target function as least squares identification, i.e. point (0.35,2.341), the identification result of this unit each electric parameters parameter is as shown in table 1 below:

Table 1

Parameter	Xd	K
			True value	2.35	/
Selected initial value	2.341	0.35
			Identification result	2.347	0.352
Deviation	-0.1276	/

From upper table 1, closely, and the precision of identification result is higher, demonstrates the validity of the method for the initial value of the Xd determined by this discrimination method and its true value.

The above; be only the present invention's preferably embodiment, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claims.

Claims (2)

1., based on a method for the generator direct-axis synchronous reactance on-line identification of PMU steady state data, it is characterized in that, described method comprises:

According to the Steady of synchronous generator, set up the identification model describing generator direct-axis synchronous reactance;

According to the electric parameters required for set up identification model, carry out the screening of phasor measurement unit PMU steady state data;

The famous value of each electric parameters that PMU after screening measures is converted to the perunit value under Unified Form;

According to Park Transformation, utilize each electric quantity information after conversion, calculate generator terminal voltage quadrature axis component Uq, the Generator end electric current direct axis component Id needed for identification according to following formula:

$\left\{\begin{array}{c}{U}_q=U\cos \mathrm{\δ}\\ I_d=I\sin (\mathrm{\δ}+\mathrm{\θ})\end{array}\right.$

Wherein, U, I are the generator terminal voltage and electric current measured, and δ is the generator's power and angle measured, and θ is the phase angle difference of set end voltage and electric current;

According to set up identification model, calculate and obtain generator direct-axis synchronous reactance linear least squares method result;

Wherein, described method also comprises:

Parameter to be identified is carried out to the sensitivity analysis of target function, and thus the parameter value of Selecting All Parameters sensitivity corresponding to 0 as the initial value of linear least squares method.

2., according to claim 1 based on the method for the generator direct-axis synchronous reactance on-line identification of PMU steady state data, it is characterized in that, described in carry out the screening of phasor measurement unit PMU steady state data, specifically comprise:

Carry out screening and the judgement of phasor measurement unit PMU steady state data, and determine that data time window length is 5s.