CN102147438A - PSS (power system stabilizer) magnification factor optimization testing method based on low frequency oscillation damping sensitivity and equivalent alternating-current gain - Google Patents

Abstract

The invention discloses a PSS (power system stabilizer) magnification factor optimization testing method based on low frequency oscillation damping sensitivity and equivalent alternating-current gain. The testing method comprises an equivalent alternating-current gain comparison method testing step and a magnification factor optimization step with the low frequency oscillation damping sensitivity as the target function, wherein the equivalent alternating-current gain comparison method testing step ensures additional torques produced in a PSS link to be equal under different time constants, thereby realizing the comparison of PSS action effects at different phase compensation angles in the condition that the PSS additional torques are same, therefore, how to select or further adjust the magnification factor can be known; a magnification factor optimization method which takes the low frequency oscillation damping sensitivity as the target function calculates the sensitivity of low frequency oscillation damping to the amplification factors according to the damping ratio value obtained in the small step disturbance test for the active power of a generator and the amplification factor set on the scene; and then parameters are adjusted according to the size and variation tendency of the damping ratio.

Description

PSS enlargement factor optimization Test method based on low-frequency oscillation damping sensitivity and equivalent ac gain

Technical field

Power system stabilizer, PSS (PSS) is the important means that generally is used for suppressing jeopardizing the low-frequency oscillation of security of system stable operation in the big electrical network, the present invention relates to the low-frequency oscillation damping to the test method that the PSS parameter changes, specifically be meant PSS enlargement factor optimization Test method based on low-frequency oscillation damping sensitivity and equivalent ac gain.

Background technology

Large power system is interconnected to be the important measures that improve power system transient stability, is the important means that solves the energy and load unbalanced strategy and policy of distribution and electrical network peak load shifting, is trend of the times international, the domestic technique development.The phase lag that the inertia of generator and each link of excitation system thereof all brings signal to transmit; Current electrical network is typical big system (Large Scale System), has and hives off and related architectural feature the oscillation phase changing of the relative positions between each group of planes; This underdamping vibration and the negative damping spontaneous oscillation generation that has just determined to certainly exist in the electrical network various patterns by all multifactor immixtures such as excitation system and electric network composition characteristics, its pattern (vibration shape) is extremely various, generally in the 0.2-2.0Hz scope, most low-frequency oscillations all are therefore to rise to frequency in the electrical network.In when, in the electrical network low-frequency oscillation taking place when, the safe and stable operation of entail dangers to system, the ability of restriction interconnection transmission power.This shows to have only the damping that increases various mode of oscillation, just might reduce or weaken low-frequency oscillation, improve the security and stability of electrical network.PSS in the generator excited system designs for strengthening the low-frequency oscillation damping specially, especially as the main inhibition means of vibrating between a group of planes in generator local oscillation and the subregion.

As everyone knows, the effect quality of PSS effect, adaptability power and stability quality, the quality that depends on parameter tuning fully, and adjusting of parameter is nonuniqueness, be subjected to the model of unit and excitation system thereof and the influence of numerous factors such as parameter characteristic, operating condition and electric network composition variation again, therefore, the field optimizing regulation experiment of PSS parameter is very difficult.

Usually we carry out genset PSS field optimizing when adjusting commissioning tests, at first carry out uncompensated frequency response characteristic measurement, understand the family curve of unit; Then, design the PSS parameter in view of the above, make its additional torque that provides to produce positive damping preferably; At last, the compensating frequency response characteristic measurement is arranged, after check added PSS, additional torque all should provide positive damping optimum on the engineering on 0.2～2.0Hz frequency bandwidth.The block diagram of typical PSS model as shown in Figure 1.Its transport function is by enlargement factor Kp, the inertial element that time constant TR forms, time constant TW form every straight link, the multistage lead-lag link that time constant T1～T6 forms constitutes, if transport function with G (s) expression part except that enlargement factor Kp, the transport function of then whole group PSS can be expressed as Kp G (s), its ac gain is Kp|G (s) |, usually the size of time constant TR is determined by equipment itself, time constant TW can get empirical value, mainly is exactly to optimize enlargement factor Kp and multistage lead-lag link time constant T1～T6 so the PSS on-site parameters is optimized the purpose of regulation experiment.

The generator electromagnetic torque can be divided into synchronising torque and damping torque, synchronising torque and Δ δ same-phase, damping torque and Δ ω same-phase.The synchronising torque deficiency will slide step-out; The vibration step-out will take place in the damping torque deficiency.Adopt the damping of PSS enhanced system to prevent spontaneous oscillation, key is moment just being projected as on Δ ω axle that the PSS link produces.PSS phase compensation require the corresponding Δ ω axle of additional moment vector that in this low-frequency oscillation of electric power system district (0.2-2.0Hz) make PSS output leading 10 ° to lagging behind in 45 °, and make the corresponding Δ ω of local oscillation frequency moment axle at 0 ° with lag behind between 30 °.The adjusting of phase place mainly realizes by adjusting time constant T1～T6.After the time constant was determined, the enlargement factor Kp of PSS just becomes decision PSS to be provided the effect of damping and has put into operation back set steady whether key factor, common damping in order to guarantee to provide good, and enlargement factor is essential enough big; And in order to guarantee the stability of exciter control system, the enlargement factor of PSS again must be enough little; Obviously, both are conflicting, and this just must have the optimization test method of enlargement factor of a cover science, generally get 1/2～1/3 of limit enlargement factor and (are equivalent to open loop frequency characteristic gain margin and are 6dB～9dB).

This paper provides a kind of brand-new, effective, general, perfect test method for the on-the-spot regulation experiment of PSS enlargement factor, and it should be that classic method useful replenished and perfect.It not only can be used for site test, can also be used for PSS parameter, effect optimization check aspect that Power System Analysis is calculated.

Summary of the invention

The purpose of this invention is to provide a kind of PSS enlargement factor optimization Test method based on low-frequency oscillation damping sensitivity and equivalent ac gain.

The present invention adopts following technical scheme to realize the enlargement factor optimization Test, and this method comprises the steps:

Step 1: equivalent ac gain contrast optimization test method step

At first, according to the typical characteristics design time constant of unit, obtain initial compensated frequency characteristic required on the low-frequency oscillation bandwidth;

Secondly, selected frequency range selects corresponding time constant to be optimized adjustment in T1～T6, and the adjustment of parameter is according to the ac gain Kp of PSS under master oscillator frequenc _N* | G (s) _N| keep invariable principle, as shown in Equation (1);

Equivalence ac gain computing formula:

Kp0×|G(s)0|＝Kp1×|G(s)1|＝......＝Kp _N×|G(s) _N|(1)

In the formula:

The initial enlargement factor of Kp0:PSS under master oscillator frequenc;

Kp1:PSS under master oscillator frequenc through the amended enlargement factor of the 1st subparameter;

| the initial ac gain of G (s) 0|:PSS transport function part under master oscillator frequenc;

| G (s) 1|:PSS revises the initial ac gain of back transport function part through the 1st subparameter under master oscillator frequenc;

Kp _N: PSS under master oscillator frequenc through the amended enlargement factor of N subparameter;

| G (s) _N|: PSS revises the initial ac gain of back transport function part through the N subparameter under master oscillator frequenc;

Then, carry out the little step disturbance test of generator active power respectively under these conditions, check its damping to low-frequency oscillation, the size of damping ratio is represented with formula (2);

The damping ratio computing formula:

$\mathrm{\ξ}=\frac{1}{2\mathrm{N\π}}\mathrm{Ln}\left(\frac{P_1-P_2}{P_{2N+1}-P_{2N+2}}\right)---\left(2\right)$

In the formula:

ξ is a damping ratio; N---computation period number;

P1, P2---be first and second power peak, unit is megawatt (MW);

P2N+1, P2N+2---be (2N+1) individual and (2N+2) individual power peak, unit is megawatt (MW);

At last, the variation tendency of changing from small to big according to damping ratio is adjusted parameter, until damping ratio reach top value begin to descend flex point or exciter control system occur and vibrate till, the value of correspondence is final set point value at this moment;

Step 2: become enlargement factor low-frequency oscillation damping sensitivity step

Little step disturbance test damping ratio numerical value that obtains and the enlargement factor of adjusting in the scene by generator active power are calculated damping ratio according to formula (2), and formula (3) is calculated the sensitivity of low-frequency oscillation damping to enlargement factor; The variation tendency of changing from small to big according to damping ratio is adjusted parameter then, until damping ratio reach top value begin to descend flex point or exciter control system occur and vibrate till, the value of correspondence is critical amplification times at this moment; At last, choose final enlargement factor according to 1/2～1/3 of limit enlargement factor; Two kinds of possibility situations generally can take place in enlargement factor when increasing, the one, the excitation system vibration takes place, the increase that enlargement factor is described has made the stability of excitation system itself reach critical value, this moment enlargement factor the corresponding limit enlargement factor of numerical value, therefore, in this case, whether we take place to vibrate with the observation field voltage and judge whether enlargement factor has reached ultimate value; Another kind of situation, damping ratio reaches the top value and begins to descend and flex point occurs, this point should be that the characteristic root track becomes big point again by minimum, also is the maximum point of damping during engineering is used, so the time we flex point occurs or saturatedly judge whether enlargement factor has reached ultimate value with the size of damping;

The low-frequency oscillation damping is to the sensitivity of enlargement factor:

$S_{\mathrm{KP}}=\left(\frac{{\mathrm{\ξ}}_1-{\mathrm{\ξ}}_0}{K_{P1}-K_{P0}}\right)---\left(3\right)$

Wherein:

S _KP: the sensitivity of low-frequency oscillation variation of damping ratio under the enlargement factor condition for a change;

Kp0: be the initial enlargement factor under master oscillator frequenc;

Kp1:PSS is the enlargement factor behind the process parameter modification under master oscillator frequenc;

ξ ₀: the damping ratio during for initial enlargement factor under master oscillator frequenc;

ξ ₁: PSS is the damping ratio behind the process parameter modification under master oscillator frequenc.

Compared with prior art, the present invention has following remarkable result:

1, how at the scene test method of the present invention has solved in the test and has utilized the low-frequency oscillation damping that this important parameter of its enlargement factor is optimized, adjusts, determined to the sensitivity power that the PSS parameter changes, to guarantee electric power netting safe running, played the effect of effective inhibition large scale electric network medium and low frequency vibration, and the microvariations Calculation results of electrical network and PSS parameter optimization adjusted organically combined.

2, test method of the present invention successful Application has in practice verified that the dynamic stability analysis program SSAP that we developed carries out the correctness that sensitivity analysis is calculated.

3, test method of the present invention makes coordinating analysis calculating and researchist not spending under the on-the-spot situation, just can carry out the optimization of PSS enlargement factor and adjust, and checks its effect, thereby the influence of PSS to electrical network installed at this unit place of analysis and evaluation.For the on-the-spot regulation experiment of traditional PS S parameter provides perfect, complementary means.

In sum, the present invention provides a kind of brand-new, effective, general, perfect time domain test method for the on-the-spot regulation experiment of PSS enlargement factor, and it is useful additional and perfect to the traditional frequency domain method.

Description of drawings

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

Fig. 1 is the block diagram of typical PSS model in this prior art;

Fig. 2 is the active power response curve of generator loading step of the present invention.

Embodiment

PSS enlargement factor optimization Test method based on low-frequency oscillation damping sensitivity and equivalent ac gain of the present invention, this method comprises the steps:

Step 1: equivalent ac gain contrast optimization Test method step

This method is used for optimizing lead-lag link time constant T1～T6, to change and to optimize the compensation of phase of PSS.

At first, according to the typical characteristics of unit, design time constant T1～T6 obtains initial compensated frequency characteristic required on the low-frequency oscillation bandwidth---promptly relatively lag behind the leading relatively characteristic of high band in low-frequency range; Secondly, selected frequency range selects corresponding time constant (being constant between high band is selected hour, low-frequency range selection large time constant) to be optimized adjustment in T1～T6, and the adjustment of parameter is according to the ac gain Kp of PSS under master oscillator frequenc _N* | G (s) _N| keep invariable principle, shown in (1) below the formula; Then, carry out the little step disturbance test of generator active power respectively under these conditions, check its damping to low-frequency oscillation, the size of damping ratio is represented with following formula (2); At last, the variation tendency of changing from small to big according to damping ratio is adjusted parameter, until damping ratio reach top value begin to descend flex point or exciter control system occur and vibrate till, the value of correspondence is final set point value at this moment.

This method has guaranteed before and after time constant is adjusted, the additional torque that the PSS link produces all equates, thereby realized under identical big or small PSS additional torque condition, PSS action effect under the out of phase offset angle relatively, thereby learn how to select or further adjust lead-lag link time constant T1～T6, to reach the optimum phase compensation effect.Method is simple, effect is remarkable, direction is clear and definite, practicality is good.

Equivalence ac gain computing formula:

Kp0×|G(s)0|＝Kp1×|G(s)1|＝......＝Kp _N×|G(s) _N| (1)

Wherein:

The initial enlargement factor of Kp0:PSS under master oscillator frequenc;

Kp1:PSS under master oscillator frequenc through the amended enlargement factor of the 1st subparameter;

| the initial ac gain of G (s) 0|:PSS transport function part under master oscillator frequenc;

| G (s) 1|:PSS revises the initial ac gain of back transport function part through the 1st subparameter under master oscillator frequenc;

Kp _N: PSS under master oscillator frequenc through the amended enlargement factor of N subparameter;

| G (s) _N|: PSS revises the initial ac gain of back transport function part through the N subparameter under master oscillator frequenc;

The damping ratio computing formula:

$\mathrm{\ξ}=\frac{1}{2\mathrm{N\π}}\mathrm{Ln}\left(\frac{P_1-P_2}{P_{2N+1}-P_{2N+2}}\right)---\left(2\right)$

In the formula:

ξ is a damping ratio; N---computation period number;

P1, P2---for first and second power peak, see Fig. 2, unit is megawatt (MW);

P2N+1, P2N+2---be (2N+1) individual and (2N+2) individual power peak, unit is megawatt (MW).

(seeing the active power response of Fig. 2 generator loading step)

Step 2: become enlargement factor low-frequency oscillation damping sensitivity step

Little step disturbance test damping ratio numerical value that obtains and the enlargement factor of adjusting in the scene according to generator active power are calculated damping ratio by formula (2), and formula (3) is calculated the sensitivity of low-frequency oscillation damping to enlargement factor; Then, the variation tendency of changing from small to big according to damping ratio is adjusted parameter, until damping ratio reach top value begin to descend flex point or exciter control system occur and vibrate till, the value of correspondence is critical amplification times at this moment; At last, (be equivalent to open loop frequency characteristic gain margin and be 6dB～9dB) and choose final enlargement factor according to 1/2～1/3 of limit enlargement factor.

Two kinds of possibility situations generally can take place in enlargement factor when increasing, the one, the excitation system vibration takes place, the increase that enlargement factor is described has made the stability of excitation system itself reach critical value, this moment enlargement factor the corresponding limit enlargement factor of numerical value, therefore, in this case, whether we take place to vibrate with the observation field voltage and judge whether enlargement factor has reached ultimate value; Another kind of situation, damping ratio reaches the top value and begins to descend and flex point occurs, this point should be that the characteristic root track becomes big point again by minimum, also is the maximum point of damping during engineering is used, so the time we flex point occurs or saturatedly judge whether enlargement factor has reached ultimate value with the size of damping.

The low-frequency oscillation damping is to the sensitivity of enlargement factor:

$S_{\mathrm{KP}}=\left(\frac{{\mathrm{\ξ}}_1-{\mathrm{\ξ}}_0}{K_{P1}-K_{P0}}\right)---\left(3\right)$

Wherein:

S _KP: the sensitivity of low-frequency oscillation variation of damping ratio under the enlargement factor condition for a change;

Kp0: be the initial enlargement factor under master oscillator frequenc;

Kp1:PSS is the enlargement factor behind the process parameter modification under master oscillator frequenc;

ξ ₀: the damping ratio during for initial enlargement factor under master oscillator frequenc;

ξ ₁: PSS is the damping ratio behind the process parameter modification under master oscillator frequenc.

Claims (1)

1. based on the PSS enlargement factor optimization Test method of low-frequency oscillation damping sensitivity and equivalent ac gain, this method comprises the steps:

Step 1: equivalent ac gain contrast optimization test method step

At first, according to the typical characteristics design time constant of unit, obtain initial compensated frequency characteristic required on the low-frequency oscillation bandwidth;

Secondly, selected frequency range selects corresponding time constant to be optimized adjustment in T1～T6, and the adjustment of parameter is according to the ac gain Kp of PSS under master oscillator frequenc _N* | G (s) _N| keep invariable principle, as shown in Equation (1);

Equivalence ac gain computing formula:

Kp0×|G(s)0|＝Kp1×|G(s)1|＝......＝Kp _N×|G(s) _N| (1)

In the formula:

The initial enlargement factor of Kp0:PSS under master oscillator frequenc;

Kp1:PSS under master oscillator frequenc through the amended enlargement factor of the 1st subparameter;

| the initial ac gain of G (s) 0|:PSS transport function part under master oscillator frequenc;

| G (s) 1|:PSS revises the initial ac gain of back transport function part through the 1st subparameter under master oscillator frequenc;

Kp _N: PSS under master oscillator frequenc through the amended enlargement factor of N subparameter;

| G (s) _N|: PSS revises the initial ac gain of back transport function part through the N subparameter under master oscillator frequenc;

Then, carry out the little step disturbance test of generator active power respectively under these conditions, check its damping to low-frequency oscillation, the size of damping ratio is represented with formula (2);

The damping ratio computing formula:

$\mathrm{\ξ}=\frac{1}{2\mathrm{N\π}}\mathrm{Ln}\left(\frac{P_1-P_2}{P_{2N+1}-P_{2N+2}}\right)---\left(2\right)$

In the formula:

ξ is a damping ratio; N---computation period number;

P1, P2---be first and second power peak, unit is megawatt (MW);

P2N+1, P2N+2---be (2N+1) individual and (2N+2) individual power peak, unit is megawatt (MW);

At last, the variation tendency of changing from small to big according to damping ratio is adjusted parameter, until damping ratio reach top value begin to descend flex point or exciter control system occur and vibrate till, the value of correspondence is final set point value at this moment;

Step 2: become enlargement factor low-frequency oscillation damping sensitivity step

Little step disturbance test damping ratio numerical value that obtains and the enlargement factor of adjusting in the scene by generator active power are calculated damping ratio according to formula (2), and formula (3) is calculated the sensitivity of low-frequency oscillation damping to enlargement factor; The variation tendency of changing from small to big according to damping ratio is adjusted parameter then, until damping ratio reach top value begin to descend flex point or exciter control system occur and vibrate till, the value of correspondence is critical amplification times at this moment; At last, choose final enlargement factor according to 1/2～1/3 of limit enlargement factor;

The low-frequency oscillation damping is to the sensitivity of enlargement factor:

$S_{\mathrm{KP}}=\left(\frac{{\mathrm{\ξ}}_1-{\mathrm{\ξ}}_0}{K_{P1}-K_{P0}}\right)---\left(3\right)$

Wherein:

S _KP: the sensitivity of low-frequency oscillation variation of damping ratio under the enlargement factor condition for a change;

Kp0: be the initial enlargement factor under master oscillator frequenc;

Kp1:PSS is the enlargement factor behind the process parameter modification under master oscillator frequenc;

ξ ₀: the damping ratio during for initial enlargement factor under master oscillator frequenc;

ξ ₁: PSS is the damping ratio behind the process parameter modification under master oscillator frequenc.

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