CN101963643B - Method for judging out-of-step oscillation of power system - Google Patents

Abstract

The invention relates to a method for judging out-of-step oscillation of a power system, which comprises the steps of: selecting any two measuring points in the power system, taking positive sequence voltage phases of the measuring points as measuring point phases, wherein a phase angle difference between the two measuring points is used as a phase angle difference of a phase comparison interval (i.e. an interval between the two measuring points). The method is characterized in that: on a change track of the phase angle difference of voltages at two sides of the interval in which an oscillation center is located, the change range of the phase angle difference is divided into 7 regions, if the phase angle difference change track of the phase comparison interval meets a certain change principle, the region between the two measuring points is judged to be step out oscillation. The invention discards the influences of the system operation mode, can be used for independently judging the system to be out-of-step, and is simple in practice.

Description

Judging out-of-step oscillation of power system

Technical field

The present invention relates to utilize the phase angle difference principle to carry out the new method that the electric system asynchronous oscillation is differentiated, be applied to the differentiation when system's step-out in the safety stabilization control system.

Background technology

Electric system may lose synchronously when meeting with catastrophic failure or multiplicity accident, if in time do not adopt an effective measure, accident will enlarge, even the serious consequence of large-area power-cuts occur.Along with the development of domestic electrical network scale, large-sized connection electrified wire netting occurs successively, and the composition of electrical network step-out section in the step-out process is more complicated.

The secionalizing system equipment principle that is widely used at present in the domestic electric system engineering practice mainly contains: apparent impedance track off-the-line criterion,

Off-the-line criterion in phasing degree between track off-the-line criterion and voltage and the electric current, its ultimate principle is summarized as follows respectively:

(1) the apparent impedance step-out criterion of discrimination principles in proper order, the method are by measuring the variation track of impedance, drawing corresponding step-out criterion.Distinguish asynchronous oscillation, synchronized oscillation and and short trouble according to the impedance variation track.What this principle was directly reacted theoretically is the variation at merit angle between two equivalent units.

(2)

The step-out criterion of discrimination principles, the method are that the voltage and current that the use device installation place collects calculates

Represent the voltage of oscillation center, distinguish asynchronous oscillation, synchronized oscillation and short trouble according to the Changing Pattern of voltage of oscillation center.This criterion can reflect that the minimum voltage in system's step-out process changes, and can judge more accurately whether step-out of system, and the criterion method is simply clear and definite, can the different method of operation and the structural changes of adaptive system.

(3) voltage and current DC phasing degree oscillation and splitting criterion, the method are the step-out features that the variation track of the IMPEDANCE ANGLE SEPARATION that collects of use device installation place is judged system.The advantage of this criterion is to judge the locality of out-of-step center, can distinguish reliably asynchronous oscillation and synchronized oscillation, adapts to complicated electric network composition and the changeable method of operation, adjusts conveniently.

Present main step-out method of discrimination following weak point all arranged:

(1) rely on the electric parameters such as current/voltage and differentiate, for the method for operation, the trend size of system itself certain dependence effect is arranged, the differentiation result of some method of discrimination even be subject to the impact of fault needs the modification definite value or takes other ancillary methods.In the case, if can rely on as few as possible electric parameters, independent differentiation step-out is not subjected to the impact of the system failure, the method for operation, trend size, certainly will be able to ensure reliably power system stability to make things convenient for actual motion.

(2) to some large-scale power system, in case generation step-out, its oscillation center is positioned on many interconnections simultaneously, formed the asynchronous oscillation section, will be to such System Implementation Out-of-Step Splitting Systems, layouting that the Out-of-Step Splitting Systems device of employing dispersed placement needs is more, and cooperation has certain difficulty.

Summary of the invention

The objective of the invention is: a kind of judging out-of-step oscillation of power system based on the phase difference of voltage principle is provided, especially differentiates for the step-out of complex electric network, accurately and rapidly judgement system step-out whether.

Method of discrimination provided by the present invention is as follows: judging out-of-step oscillation of power system, choose any two measurement points in the electric system, get the positive sequence voltage phase place of measurement point as the measurement point phase place, phase angle difference between any two measurement points is characterized in that as than the phase angle difference in interval (i.e. interval between two measurement points) mutually: will be divided into following 7 districts than the variation range of the phase angle difference in interval mutually:

0 district: between-60 °～60 °,

1 district: between 60 °～90 °,

2 districts: between 90 °～135 °,

3 districts: between 135 °～180 °,

4 districts: between 180 °～225 °,

5 districts: between 225 °～270 °,

6 districts: between 270 °～300 ° (60 °),

If should satisfy Changing Pattern a or Changing Pattern b than mutually interval phase angle difference variation track, judge that then this is than asynchronous oscillation occurs in interval mutually:

Changing Pattern a: the Changing Pattern of phase angle difference is 0-1-2-3-4-5-6-0 district reciprocation cycle;

Changing Pattern b: the Changing Pattern of phase angle difference is 0-6-5-4-3-2-1-0 district reciprocation cycle.

(1) the data synchronization principles is introduced

In the middle of all selected measuring points, select a measuring point as the synchronous benchmark of data, target data message when sending band to other measuring points, other measuring points receive after the synchrodata information of reference point, in the moment of the data acquisition of adjustment itself, guarantee that the sampled data of the sampled data of this measuring point and reference point is synchronous.Can obtain synchronous data like this, calculate based on this voltage-phase information of each measuring point.

(2) the phase angle difference principle is introduced

During the electric system step-out, generally can equivalence become two group of planes to analyze, set forth the ultimate principle of the Out-of-Step Splitting Systems criterion of phase angle difference with valve systems such as two machines shown in Figure 1.

In analysis, adopt following assumed condition:

(a) two equivalent dynamo-electric gesture are respectively EM and EN, and suppose that two equivalent electromotive force amplitudes equate.

(b) the system equivalent angle of impedance is 90 °.

(c) evenly distribute to the EN impedance from EM

Getting EN is reference vector, and making its phasing degree is 0 °, and amplitude is that the initial phase angle of the equivalent electromotive force EM of 1, M side system is set as δ 0, then can get two system merit angles to be: δ=Δ ω * t+ δ 0

Wherein Δ ω is two side system speed discrepancies, supposes that it is constant; T is time variable; δ 0 is described as defined above.

According to assumed condition, the position of oscillation center is positioned at the impedance mid point of EM and EN and immobilizes, and establishing voltage of oscillation center is Uc, gets 2: 1 and 2 on the interconnection, and its voltage is respectively U1 and U2.The angle of U1 and reference vector EN is θ 1, and the angle of U2 and EN is θ 2, and the ratio of EM to the impedance of U1 and U1 to the impedance of EN is a1, and the ratio of EM to the impedance of U2 and U2 to the impedance of EN is a2.General, get any point on the interconnection as the device installation place, its voltage is U, and the angle of U and reference vector EN is θ, and the ratio of EM to the impedance of U and U to the impedance of EN is α, and the expression formula of angle theta is:

If α＞1, $\mathrm{\θ}=\arctan \left(\frac{\sin \mathrm{\δ}}{a+\cos \mathrm{\δ}}\right)$

If make Δ ω=1 (cycle of namely supposing asynchronous oscillation is 2 π), δ 0=0 (being initial time EM and EN same-phase), the α value between between 0～1 (be oscillation center the device installation place and and EN between), draw the track of θ as shown in Figure 2, ordinate unit is radian, and scope is 0～2 π (lower same).As seen because oscillation center is between U1 point and the EN, namely oscillation center is in distinguishing, so phase angle difference θ arranges at 0～2 π.And when the α value was 0～1 interval arbitrary value, θ arrived π at synchronization.

Equally, make Δ ω=1, δ 0=0, the track of θ 2 is simulated as shown in Figure 3 in α＞1, and α＞1 expression oscillation center is outside the interval of device installation place and EN, the variation track of θ 2 is as shown below so, notices that θ 2 variation characteristics are repeatedly vibrations in-π～π interval.

Comprehensive above theoretical analysis shows, as long as oscillation center is in the district, busbar voltage phase angle difference in both sides will be passed through the cyclical variation in 0～180 degree～360 degree are interval of 180 degree so, and when getting over than interval mutually impedance hour, Δ θ is faster in 180 the speed when spending of passing through; If oscillation center is outside the district, then busbar voltage phase angle difference in both sides can not passed through 180 degree, but repeatedly vibration between-180 degree～180 degree.

(3) step-out criterion of the present invention

Analysis by the front can find out, in oscillatory process, the node voltage phase angle difference of oscillation center both sides is continually varyings, and can cross 180 degree, and two node voltage phase angle differences of oscillation center one side can be crossed 180 degree scarcely.When short trouble and failure removal interval both sides phase difference of voltage change very little, and 180 degree only; When synchronized oscillation, interval both sides phase difference of voltage is continually varying, but 180 degree only, surpassing 180 degree is exactly asynchronous oscillation.Therefore can distinguish asynchronous oscillation, short trouble and synchronized oscillation by the Changing Pattern of each node voltage phase angle difference of electrical network.

On the variation plane of the interval both sides at oscillation center place phase difference of voltage, the variation range of phase angle difference is divided into 7 districts, as shown in Figure 4.

If satisfy Changing Pattern a or Changing Pattern b than mutually interval phase angle difference variation track, then can judge, asynchronous oscillation occurs in the zone between two measuring points.

Changing Pattern a: the Changing Pattern of phase angle difference is 0-1-2-3-4-5-6-0 district reciprocation cycle;

Changing Pattern b: the Changing Pattern of phase angle difference is 0-6-5-4-3-2-1-0 district reciprocation cycle.

Beneficial effect of the present invention:

(1) phase angle information used in the present invention, only relevant with relevant voltage, all irrelevant with electric pressure, size of current, so it has broken away from the impact of system operation mode, can independent judgement system step-out;

(2) physical concept simple and clear used in the present invention, the electric parameters of use is minimum, and it is convenient to use, and uses simple;

(3) when system breaks down, can not reach 180 degree than interval mutually phase angle difference, the phase angle difference track when step-out and fault is completely different, reliably the judgement system step-out.

The present invention fully utilizes different location voltage phase angle information in the electrical network first, obtain each than interval mutually phase angle difference, phase angle difference feature during according to the electric system step-out, can quick and conveniently judge compactly whether step-out of system, and can further determine moment of off-the-line, thereby it is stable more to be conducive to security of system.

Description of drawings

Below in conjunction with the drawings and specific embodiments patent of the present invention is further described.

The equivalent system diagram of Fig. 1 two machines

During Fig. 2 δ 0=0, duration of oscillation circuit θ 1 change curve

Fig. 3 duration of oscillation circuit θ 2 change curves

The interval both sides phase angle difference Changing Pattern figure of Fig. 4 oscillation center

Embodiment

The mode of implementing is as follows:

(1) each measuring point data is carried out synchronously;

(2) gather the positive sequence voltage of each measuring point, utilize Fourier transform, calculate the phase angle of each measuring point positive sequence voltage.(3) choose the interval that to carry out than phase (calculating phase angle difference) scope of measuring point (two between), calculate each than interval mutually phase angle difference.

(4) carry out the phase angle difference track and judge, divide phase angle difference into seven districts:

θ ₁＝300°(-60°) θ ₂＝60° θ ₃＝90° θ ₄＝135°

θ ₅＝180°(-180°) θ ₆＝225°(-135°) θ ₇＝270°(-90°)

The trail change rule can be judged to be step-out shown in the phase angle difference track satisfied " Fig. 3-4 ".

Method of discrimination provided by the present invention is effectively verified in the RTDS analogue system.

Claims (1)

1. judging out-of-step oscillation of power system, choose any two measurement points in the electric system, get the positive sequence voltage phase place of measurement point as the measurement point phase place, phase angle difference conduct between these any two measurement points is characterized in that than interval mutually phase angle difference: will be divided into following 7 districts than the variation range of interval mutually phase angle difference:

0 district: between-60 °～60 °,

1 district: between 60 °～90 °,

2 districts: between 90 °～135 °,

3 districts: between 135 °～180 °,

4 districts: between 180 °～225 °,

5 districts: between 225 °～270 °,

6 districts: 270 °～300 ° namely between-60 °,

If should satisfy Changing Pattern a or Changing Pattern b than mutually interval phase angle difference variation track, judge that then this than mutually interval territory asynchronous oscillation occurs:

Changing Pattern a: the Changing Pattern of phase angle difference is 0-1-2-3-4-5-6-0 district reciprocation cycle;

Changing Pattern b: the Changing Pattern of phase angle difference is 0-6-5-4-3-2-1-0 district reciprocation cycle.

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