CN102570486A - PSS (power system stabilizer) parameter optimizing method for inhibiting multi-mode low-frequency oscillation - Google Patents

Abstract

The invention provides a PSS (power system stabilizer) parameter optimizing method for inhibiting multi-mode low-frequency oscillation. The overall optimal compensation effect to multi-oscillation mode by the PSS is taken as an optimization target to carry out PSS parameter optimization of a one-machine multi-oscillation mode. The PSS parameter is carried out a damping design under the condition of comprehensively considering multiple low-frequency oscillation modes, not only just for one low-frequency oscillation mode. However, in the traditional PSS parameter design, only single oscillation frequency is considered, so that the damping effect on other oscillation modes is not considered in a damping controller designed and obtained by such a method. The technical scheme provides a PSS parameter optimization scheme when a same generator group takes part in a plurality of weak damping low-frequency oscillation modes, which coordinates the comprehensive inhibition effect on the plurality of oscillation modes by PSS; and meanwhile, the PSS parameter optimizing method for inhibiting multi-mode low-frequency oscillation has high economical efficiency and practical values.

Description

A kind of PSS parameter optimization method that suppresses the multi-mode low-frequency oscillation

Technical field

The present invention relates to the parameter optimization method of PSS, in order to improve the small signal stability of electric power system.Belong to power system operation and control field.

Background technology

Along with the expansion day by day of electrical network, big capacity unit constantly putting into operation in electrical network, the generally use of quick-response excitation, low-frequency oscillation happens occasionally in large-scale interconnected power system.Generators in power systems can take place to wave relatively between generator amature under disturbance when the power transmission line paired running, and when lacking damping, causes persistent oscillation.At this moment, corresponding vibration also can take place in power on the power transmission line.Because its frequency of oscillation is very low, is generally 0.2～2.5Hz, so be called low-frequency oscillation (being called power oscillation again, electromechanical oscillations).Low-frequency oscillation of electric power system all has generation at home and abroad, and this low-frequency oscillation or power oscillation often appear on long distance, the heavy load power transmission line, adopt modern fast, low-frequency oscillation is even more serious under the condition of high limited value multiple excitation system.

Power system stabilizer, PSS (PSS) is a kind of additional excitation controller that grows up the earliest in order to suppress low-frequency oscillation.Development along with nonlinear theory and Intelligent Control Theory; The method of excitation system additional stability control has also obtained very big development; But using the most generally, the most successful PSS that is still, existing P SS device is set reasonable parameter, is to make it give full play to the key of damping control action.

Because in the actual electric network, a generator possibly participated in a plurality of oscillation modes simultaneously, what the PSS inhibition was installed on such generator possibly be multiple oscillation mode.Therefore, the PSS Parameter Optimization can not only be considered a kind of oscillation mode, might occur like this to certain oscillation mode suppress fine, but worsen the situation of other oscillation modes.In view of traditional PS S Parameters design only is directed against the limitation that single oscillation mode compensates; For the situation of single generating set and a plurality of low frequency oscillation mode strong correlations, study a kind of PSS that makes as far as possible the parameter optimization method that a plurality of oscillation modes all satisfy the compensation requirement is had very big engineering significance and practical value.

Summary of the invention

The present invention is directed to the situation that the traditional parameters method for designing only compensates to single oscillation mode; A kind of PSS parameter optimization method that suppresses the multi-mode low-frequency oscillation is proposed; Because particle cluster algorithm has good characteristics such as fast convergence rate, convergence point be relatively stable, the present invention adopts particle cluster algorithm to carry out parameter optimization.Through the application in instance, the gained scheme satisfies designing requirement.Compare with the method that has proposed at present; This method is an optimization aim with many oscillation modes phase place comprehensive compensation; Make PSS satisfy the compensation requirement as far as possible at a plurality of Frequency points; Obtain satisfied compensation effect on the whole, overcome the traditional parameters method for designing to single oscillation mode suppress the fine defective that but worsens other oscillation modes.

The PSS parameter optimization method of the inhibition multi-mode low-frequency oscillation that the present invention proposes, this method is optimization aim with PSS to the whole the best of the compensation effect of a plurality of oscillation modes, carries out the PSS parameter optimization of the many oscillation modes of unit.The PSS parameter no longer is to a certain low frequency oscillation mode, carries out the damping design but take all factors into consideration a plurality of low frequency oscillation modes.Traditional P SS parameter designing is only considered single frequency of oscillation, and the damping controller that this method design obtains does not have to consider the damping to other oscillation mode.The PSS parameter optimization scheme that the present technique scheme has proposed same generating set when participating in a plurality of underdamping low frequency oscillation mode is coordinated the comprehensive inhibition effect of PSS to a plurality of oscillation modes, has higher economical efficiency and practical value simultaneously.

Technical scheme of the present invention is following:

A kind of PSS parameter optimization method that suppresses the multi-mode low-frequency oscillation, step comprises:

1) electrical network being carried out small interference stability calculates; Add up underdamping low frequency oscillation mode wherein and carry out model analysis; According to modal analysis result; Pick out simultaneously the generating set with a plurality of underdamping pattern strong correlations (participation factors is greater than 0.1), the PSS parameter of this generating set needs many oscillation modes phase compensation complex optimum;

2) obtain the relevant generator group at frequency of oscillation f _iThe phase lag angle θ of place's excitation system _EX(f _i), in the input target function, adopt particle cluster algorithm that the PSS parameter is optimized;

3) carry out small interference stability after the PSS parameter optimization and calculate, whether system satisfies the requirement that promotes relevant oscillation mode damping after the checking PSS parameter.

Step 2) Optimization Model that has optimization aim function J in has following form:

$\min J=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{a}_i\left|{\mathrm{\θ}}_{\mathrm{\ΔTe}-\mathrm{\Δ\ω}}\left(f_i\right)\right|=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{a}_i|{\mathrm{\θ}}_{\mathrm{PSS}}\left(f_i\right)+{\mathrm{\θ}}_{\mathrm{EX}}\left(f_i\right)+90|$

In the formula, f ₁, f ₂... f _nN frequency of oscillation for needs optimization; a _iFor PSS at f _iThe optimum weighted coefficient at frequency of oscillation place; θ _{Δ Te-Δ ω}(f _i) be f _iThe damping torque Δ T that the PSS of frequency of oscillation place produces _ePhase angle difference with Δ ω; Δ _PSS(f _i) be f _iThe compensation phase angle of the PSS of frequency of oscillation place; θ _EX(f _i) be f _iThe lagging phase angle of frequency of oscillation place excitation system.

The weight coefficient a that introduces in the optimization aim function _i, obtain according to computes.

a _i＝(ξ ₀-ξ _i)×p _ki (2)

In the formula, p _KiBe correlation factor; ξ ₀Be the damping ratio set point; ξ _iIt is the damping ratio of i low frequency oscillation mode.

Correlation factor p _KiMeasured the mutual degree of participation of i mode and k state variable; The calculating that correlation factor is introduced the optimum weighted coefficient can be measured the degree of correlation of k platform generator and i underdamping oscillation mode; If this generator and i underdamping oscillation mode strong correlation, then the optimum weighted coefficient is bigger.The numerical value of considering damping ratio and correlation factor is less, can carry out normalization to the optimum weighted coefficient that calculates and handle, order

a _MinBe the optimum weighted coefficient minimum value that calculates.

Be noted that: the target function in the formula (1) is applicable to the power deviation to be the PSS of input signal, if be the PSS of input signal with the rotating speed deviation then do not have 90 ° of these constant terms.Like this, the parameter optimization problem of PSS just can be described as the minimum problems that a band does not wait the nonlinear function of the multi-parameter that retrains.

The PSS parameter optimization method of the inhibition multi-mode low-frequency oscillation that the present invention proposes; Break away from the limitation that traditional PS S Parameters design compensates to single oscillation mode; This method can be coordinated the inhibition effect of PSS to a plurality of oscillation modes; Optimize the PSS parameter with this method, can effectively improve the damping ratio of a plurality of oscillation modes, suppress low-frequency oscillation.

Description of drawings

Fig. 1 electrical network PSS transfer function model block diagram;

Fig. 2 suppresses the PSS parameter optimization method flow chart of multi-mode low-frequency oscillation.

Embodiment

Application below in conjunction with in actual electric network further specifies the present invention.

In certain electrical network, adopt the inventive method to optimize the PSS parameter, relatively optimize the variation of damping ratio situation of front and back underdamping oscillation mode, verify the validity of the inventive method.The practical implementation process is described:

Step 1: electrical network is carried out the small interference stability analysis; That table 1 shows is the little interference calculation result of certain electrical network part; Its two oscillation modes all with a certain generating set strong correlation; The damping ratio of oscillation mode 2 is lower than 0.03, belongs to the underdamping pattern, needs to consider the complex optimum of a plurality of oscillation mode phase compensations.

Step 2: obtain the phase lag angle of relevant generator group, adopt particle cluster algorithm to optimize the PSS parameter at two frequency of oscillation places.

As shown in Figure 1 with the PSS model of certain generating set of oscillation mode 1 and oscillation mode 2 strong correlations.According to formula (2) calculation optimization weight coefficient and carry out normalization and handle, obtain a ₁ Be 1, a ₂Be 3.Generating set in the excitation system angle of retard and optimum weighted coefficient input optimizer at 2 frequency of oscillation places, is sought to satisfy the optimal parameter of optimization aim through iterative computation.PSS parameter optimization result is shown in parameter group among Fig. 31.For the Parameters design that relatively adopts the inventive method and the single oscillation mode of conventional suppression disposes the influence of PSS to two low frequency oscillation mode dampings; Adopt conventional method to carry out parameter designing to oscillation mode 1 and oscillation mode 2 respectively, parameter group 2 is parameters of PSS lead-lag link when adopting conventional method that oscillation mode 1 and oscillation mode 2 are designed respectively with parameter group 3.

Step 3: the electrical network after the PSS parameter optimization is carried out small interference stability calculate, the validity of checking optimization method.

When pressing the PSS parameter of three groups of parameter configuration generating sets respectively; Choose with the low-frequency oscillation root of this generating set strong correlation and list in the table 3, relatively adopt the influence of traditional design method (parameter group 2, parameter group 3) and optimization method of the present invention (parameter group 1) configuration PSS two low frequency oscillation mode dampings.Adopt parameter group 2 and parameter group 3, promptly adopt traditional P SS Parameters design, to be the parameter configuration that single low frequency oscillation mode carries out PSS, can influence even possibly worsen other oscillation modes.After for example carrying out the PSS parameter optimization to this oscillation mode of 0.7173Hz, the damping ratio of this oscillation mode rises, but the damping ratio of the oscillation mode of 1.9143Hz correspondence still is lower than 0.03, belongs to the underdamping pattern.And carry out the PSS parameter optimization to the oscillation mode of 1.9143Hz, this oscillation mode damping ratio rises, but the corresponding oscillation mode damping ratio of 0.7173Hz drops to 0.0322 by 0.0503.With respect to carrying out the PSS parameter designing to single low frequency oscillation mode respectively; Adopt parameter group 1 configuration PSS parameter; Promptly adopt optimization method of the present invention; The damping ratio of two oscillation modes all meets the demands, and has better taken into account the compensation effect of PSS to two low frequency oscillation modes, has avoided the fine situation that but worsens other oscillation modes that certain oscillation mode is suppressed; Coordinated the comprehensive inhibition effect of PSS, embodied the advantage that suppresses the PSS parameter optimization method of multi-mode low-frequency oscillation two oscillation modes.

The little interference calculation result of certain electrical network that employing the present invention optimizes after the PSS parameter is as shown in table 4, and the electrical network damping meets the demands after the PSS parameter optimization.

After according to the PSS parameter optimization method that suppresses the multi-mode low-frequency oscillation certain generating set being carried out parameter optimization; Can better take into account the compensation effect of PSS to a plurality of low frequency oscillation modes; Avoided the fine situation that but worsens other oscillation modes to certain oscillation mode inhibition; Realize optimization aim, obtained the better optimized effect.

Sequence number	Characteristic root	Frequency (Hz)	Damping ratio	Correlation ratio
					1	-0.2271+j4.5071	0.7173	0.0503	2.6145
2	-0.3372+j12.0276	1.9143	0.028	2.3706

The little interference calculation result of certain electrical network part before the table 1:PSS parameter optimization;

Parameter name	Parameter group	1	Parameter group 2	Parameter group 3
					T 1	0.2901	0.2	0.5
T 2	0.1212	0.062	0.1
				T 3	0.151	0.2	0.5
T 4	0.0202	0.062	0.1

Table 2: certain electrical network PSS parameter optimization result;

Table 3: adopt the inventive method PSS parameter optimization rear section small interference stability result of calculation;

Sequence number	Characteristic root	Frequency (Hz)	Damping ratio	Correlation ratio
					1	-0.1649+j4.4239	0.7041	0.0373	2.0707
2	-0.5687+j5.3084	0.8449	0.1065	9.1777
					3	-0.7937+j6.0528	0.9633	0.13	8.1615
4	-0.4933+j8.2052	1.3059	0.06	15.0232

5	-0.4598+j8.5323	1.358	0.0538	12.3954
					6	-0.4755+j8.9787	1.429	0.0529	9.7451
7	-0.4311+j9.2307	1.4691	0.0467	8.8388
					8	-0.5508+j9.3419	1.4868	0.0589	9.2077
9	-0.3624+j9.8839	1.5731	0.0366	19.2799
					10	-0.5354+j10.4301	1.66	0.0513	13.9395
11	-0.6044+j10.9964	1.7501	0.0549	17.7192
					12	-0.5928+j12.1746	1.9376	0.0486	21.0368
13	-0.3936+j12.4153	1.976	0.0317	31.1328

Table 4: the little interference calculation result of certain electrical network after employing the inventive method optimization PSS parameter;

Claims (1)

1. PSS parameter optimization method that suppresses the multi-mode low-frequency oscillation is characterized in that: take all factors into consideration a plurality of low frequency oscillation modes power system stabilizer, PSS PSS is carried out the damping design, concrete steps comprise:

1) carry out small interference stability and calculate, the underdamping low frequency oscillation mode of statistics electrical network also carries out model analysis, according to modal analysis result, confirms and the generating set of a plurality of low frequency oscillation mode strong correlations that the PSS parameter of this generating set need be optimized; Said strong correlation is meant that participation factors is greater than 0.1;

A plurality of low frequency oscillation modes of 2) participating in simultaneously for this generating set obtain under each oscillation mode corresponding frequency of oscillation f _iThe lagging phase angle of place's generator excitation system in the lagging phase angle input optimization aim function, adopts particle cluster algorithm then, tries to achieve the optimal parameter that satisfies target function;

3) according to step 2) the parameter of PSS of this generating set of optimal parameter configuration; System is carried out small interference stability to be calculated; Confirm whether the power system after the parameter optimization satisfies the requirement that promotes the low frequency oscillation mode damping: if do not satisfy; Then return step 2); Again adopt particle cluster algorithm, confirm to satisfy the optimal parameter of object function; If satisfy, then finish;

Said step 2) in, optimization aim function J has following form:

$\min J=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{a}_i\left|{\mathrm{\θ}}_{\mathrm{\ΔTe}-\mathrm{\Δ\ω}}\left(f_i\right)\right|=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{a}_i|{\mathrm{\θ}}_{\mathrm{PSS}}\left(f_i\right)+{\mathrm{\θ}}_{\mathrm{EX}}\left(f_i\right)+90|$

In the formula, f ₁, f ₂... f _nN frequency of oscillation for needs optimization; a _iFor PSS at f _iThe optimum weighted coefficient at frequency of oscillation place; θ _{Δ Te-Δ ω}(f _i) be f _iThe damping torque Δ T that the PSS of frequency of oscillation place produces _ePhase angle difference with Δ ω; θ _PSS(f _i) be f _iThe compensation phase angle of the PSS of frequency of oscillation place; θ _EX(f _i) be f _iThe lagging phase angle of frequency of oscillation place excitation system;

(1) target function in the formula is applicable to the power deviation to be the PSS of input signal, if be the PSS of input signal with the rotating speed deviation then do not have 90 ° of these constant terms;

The weight coefficient a that introduces in the optimization aim function _i, obtain according to computes:

a _i＝(ξ ₀-ξ _i)×p _ki (2)

In the formula, p _KiBe correlation factor; ξ ₀Be the damping ratio set point; ξ _iIt is the damping ratio of i low frequency oscillation mode.

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