CN104268426B - Calculation method of rotating speed Omega of generator rotor in power system stabilizer (PSS4B) model - Google Patents

Abstract

The invention discloses a method for calculating the rotational speed ω in the PSS4B model of a power system stabilizer (Power System Stabilizer, PSS). The implementation of PSS4B provides a relatively simple and effective way, which belongs to the field of power system control and can be applied to hydroelectric power stations, thermal power plants, wind power plants, etc.

Description

Calculation of generator rotor speed ω in a power system stabilizer PSS4B model method

technical field

The invention discloses a method for calculating the rotational speed ω in the PSS4B model of a power system stabilizer (Power System Stabilizer, PSS), which belongs to the field of power system control and can be applied to hydroelectric power stations, thermal power plants, wind power plants and the like.

Background technique

With the rapid development of the power industry, the scale of the power system is getting bigger and bigger, and the capacity of the single unit is getting bigger and bigger. Many large and medium-sized generating sets generally use fast excitation regulators. While improving the response speed of the system, the fast excitation regulator greatly reduces the time constant of the excitation system and reduces the system damping, so that weak damping or even negative damping often occurs in the system, resulting in a decline in the ability of the system to suppress low-frequency oscillations. When low-frequency oscillation is severe, it will lead to system disconnection or loss of stability, which is one of the most important problems that affect the stability of the system in the interconnection of large-scale power systems. At present, the problem of low-frequency oscillation is mainly solved by additional excitation control devices, among which the power system stabilizer is an effective additional excitation control. The power system stabilizer (PSS) is an additional part of the excitation device, which is used to improve the damping capacity of the power system, suppress the low-frequency oscillation of the system, and improve the stability of the power system.

For the low-frequency oscillation of the power system, the generator excitation regulator is mainly used to control the additional power system stabilizer (PSS) to achieve suppression. The main models are PSS1A, PSS2A/PSS2B, PSS4B, etc.

PSS1A has the well-known "reverse adjustment" problem. The generator speed and active power signals are introduced into the PSS2A/2B model, and the acceleration power is calculated as the final input signal, which avoids the "reverse adjustment" problem existing in PSS1A. PSS2A/PSS2B has only one filter, and its frequency response is also fixed after the parameters are adjusted. As the system oscillation frequency shifts or becomes lower, the effect of PSS2A/PSS2B on suppressing low-frequency oscillations will gradually weaken.

PSS4B is improved on the basis of PSS2B. PSS4B divides the low-frequency oscillation into three frequency bands: high frequency, intermediate frequency, and low frequency according to the oscillation frequency. The corresponding frequency characteristics of each channel can be individually adjusted to better provide suitable positive damping torque for low-frequency oscillation and achieve better suppression. Effect.

Contents of the invention

The purpose of the present invention is to provide a calculation method for the rotational speed ω in the PSS4B model. The PSS4B model seems to be more complicated than the PSS2B, but it is relatively simple for program realization. In the model, except for the special filters of the two input signals, most of the other modules is the basic lead/lag module. The lead/lag and low-pass link calculations have been realized in the excitation program, and the module can be called directly. There are two input signals in the model, which are generator active power Pe and generator rotor speed ω. The power Pe has been calculated in the excitation program, while the calculation of the speed ω needs to be synthesized according to the relevant electrical quantities, which is relatively complicated. The invention calculates the internal potential by using the terminal voltage of the generator, the stator current and the parameters of the generator, and calculates the rotating speed ω according to the frequency of the internal potential.

The present invention specifically adopts the following technical solutions.

A calculation method of generator rotor speed ω in the power system stabilizer PSS4B model, characterized in that: the calculation method includes the following steps:

(1) Real-time collection of electrical signal quantities of the generator through the excitation regulator, including the machine terminal voltage Three-phase stator current

(2) The generator terminal voltage and three-phase stator current collected in step (1) are used to calculate the positive sequence component, and according to the formula Calculate the potential inside the generator:

When the internal potential of the generator is represented by phases A and B, it can be obtained

is the internal potential of phase A and phase B of the generator, is generator A phase, B phase voltage, X _q ' is generator transient reactance, is the three-phase stator current of the generator.

From the subtraction of the above two formulas, it can be deduced that

It is the potential difference in the A and B two-phase generators. calculate The real part E _qr and the imaginary part E _qi of :

Among them, U _r is the machine terminal voltage The real part of , U _i is the machine terminal voltage The imaginary part of , I _r is the composite vector The real part of , I _i is the synthetic vector the imaginary part of .

For a sampled signal f is the frequency of U(t), is the initial phase angle of the signal, which can be transformed by DFT

Among them, U _k is the obtained sampling point, and U _r and U _i are the real part and imaginary part obtained after transformation. The real and imaginary parts of are calculated by calculating the real and imaginary parts of each voltage and current.

(3) Calculate the generator rotor speed ω:

Where E _qin is the imaginary part of the potential difference in the A and B two-phase generators at the nth moment, _Eqrn is the real part of the potential difference in the A and B two-phase generators at the nth moment, Eqin _-1 is the n-1th E _qrn-1 is the real part of the potential difference between A and B two-phase generators at time n-1, and ΔT is the sampling interval.

The input signal of the power system stabilizer PSS4B is Δω and Δω=ω-1.0.

The present invention has the following beneficial technical effects:

The PSS model used in the prior art has become a standard model, but its input signal is not given, and it needs to be calculated separately when using the model. The active power Pe is relatively easy to obtain, but the generator rotor speed ω is difficult to accurately calculate through the electrical quantity. The invention provides a relatively simple and practical calculation method, and provides an effective way for realizing the PSS function in the generator excitation regulator.

Description of drawings

Figure 1 is a schematic diagram of the PSS4B model;

Fig. 2 is the schematic flow sheet of rotating speed ω in the PSS4B model disclosed by the present invention;

Figure 3 is the implementation process of PSS4B on the excitation regulator.

detailed description

As shown in accompanying drawing 2, be the schematic flow sheet of rotating speed ω in the PSS4B model disclosed by the present invention, computing method of the present invention comprises the following steps:

(1) Real-time collection of electrical signal quantities of generators, including machine terminal voltage Three-phase stator current

(2) According to the collected three-phase terminal voltage Three-phase stator current Calculate each phase voltage, stator current positive sequence component, generator transient reactance and generator internal potential.

When the internal potential is represented by A and B phases, it can be obtained

is the internal potential of phase A and phase B of the generator, is generator A phase, B phase voltage, X _q ' is generator transient reactance, is the three-phase stator current of the generator.

From the subtraction of the above two formulas, it can be deduced that

is the potential difference in the A and B two-phase generators, because and The angular frequencies of are exactly the same, so the calculated frequency. export It is convenient to use the machine terminal line voltage to calculate, let E _qr be the potential The real part of , E _qi is the electric potential The imaginary part of , U _r is the machine terminal voltage The real part of , U _i is the machine terminal voltage The imaginary part of , I _r is the composite vector The real part of , I _i is the composite vector the imaginary part of

in Both the real and imaginary parts of have been calculated during the acquisition.

(3) Generator rotor speed ω is calculated according to the formula Calculate internal potential The angular frequency is obtained, where φ _Eq is the internal potential phase.

_Eqin is the imaginary part of the internal potential at the Nth moment, _Eqrn is the real part of the internal potential at the Nth moment, Eqin _- 1 is the imaginary part of the internal potential at the N-1th moment, _Eqrn-1 is the N-1st moment The real part of the internal potential, ΔT is the unit time. In the above calculation, pay attention to use the real part and imaginary part of the positive sequence components of each AC quantity for calculation.

Example 1

The implementation process is as follows:

1. Real-time collection of generator excitation and generator electrical signal quantities required by PSS4B, including machine terminal voltage Three-phase stator current Pe (calculated).

2. According to the collected machine terminal voltage, stator current positive sequence component, generator transient reactance and formula Calculate the potential inside the generator. Let the voltage be f is the frequency of U(t), is the initial phase angle of the signal,

If the AC voltage U(t) is sampled at 32 points per cycle, then after discretization, it is transformed by DFT to get

Among them, U _k is the obtained sampling point, and U _r and U _i are the real part and imaginary part obtained after transformation.

The positive sequence component takes voltage as an example, its positive sequence (α=e ^j120° )

in It is generator A, B, C phase voltage.

The same is true for current positive sequence calculation: i ₊ ＝1/3*(i _A +αi _B +α ² i _C ) (α＝e ^j120° )

i _r+ ＝1/3*(i _rA +αi _rB +α ² i _rC )

i _i+ ＝1/3*(i _iA +αi _iB +α ² i _iC )

Among them, i _A , i _B , and i _C are the phase currents of generators A, B, and C.

When the internal potential is represented by A and B phases, it can be obtained

From the subtraction of the above two formulas, it can be deduced that

because and have exactly the same angular frequency, so it is calculated that frequency. export It is convenient to use the terminal line voltage to calculate, let E _qr be the potential The real part of , E _qi is the electric potential The imaginary part of , U _r is the machine terminal voltage The real part of , U _i is the machine terminal voltage The imaginary part of , I _r is the composite vector The real part of , I _i is the composite vector the imaginary part of

in Both the real and imaginary parts of have been calculated during the acquisition.

3. Generator rotor speed ω is calculated according to the formula Calculate internal potential The angular frequency is obtained, where φ _Eq is the internal potential phase.

The input signal of the PSS is Δω and Δω=ω-1.0.

In the above calculation, pay attention to use the real part and imaginary part of the positive sequence components of each AC quantity for calculation.

When the active power Pe and the speed signal ω are available, other calculations in PSS4B are easier. Due to the time-frequency domain representation of the PSS4B model, it needs to be converted into time domain for calculation. The calculation methods of each link in PSS4B are as follows:

(1) Speed signal filter

converted to

Just put the filter time constant T1=-0.0017590, T2=0.00012739, T3=0.017823 into the above formula, ΔT is the calculation period of this module, and the same is true for the following modules.

(2) Power signal input filter

After transformation, one inertial link and two direct blocking links are obtained, which can be realized by directly calling the following modules (4) and (5) which have been realized by the program.

(3) Lead/lag link

The above formula can be expressed as taking X(s) as input and Y(s) as output, namely

Transformed into Y(s)+T ₂ Y(s)·s=kX(s)+kT ₁ X(s)·s, transformed into time domain form as

In the formula, x _n-1 and y _n-1 represent the input and output values at the previous moment in the interval Δt, and the following is the same as (T ₂ +Δt)y _n =K(T ₁ +Δt)x _n -KT ₁ x _n-1 +T ₂ y _n-1

∴y _n ＝K _a x _n -K _b x _n-1 +K _C y _n-1

in:

(4) Straight link

＝K _a (x _n -x _n-1 )+K _b y _n-1

in:

(5) Inertial link

Similarly =>y _n =K _a x _n +K _b y _n-1

in:

In the PSS4B model shown in Figure 1, the two input signals are the rotational speed ω and the active power Pe, which respectively pass through the low-pass filter and the band-pass filter to provide input for the subsequent stage. The model divides the low-frequency oscillation into three branches according to the center frequency. Each branch is a differential filter composed of two filters. The transfer function is the same, but the parameter settings are different. In Figure 1, except for the direct multiplication of the ratio and In addition to simple clipping, other models can be implemented by directly calling the above module (3).

4. Determine the starting conditions of the PSS4B function. The starting conditions are 0.9<Ut<1.1 and Pe>0.32. If the starting conditions are not met, the final calculated value Urpss of the PSS4B model will be cleared.

5. Add the PSS4B model calculation result Urpss to the voltage setting of the excitation regulator for additional control.

Now in conjunction with accompanying drawing 3 explanation

The model attached in Figure 3 is an excitation voltage control model, Ur is the given machine terminal voltage, Ut is the machine terminal voltage, and PSS4B superimposes the output result Urpss on Ur to participate in the control through switching switches. If the starting condition is met, select the switch 1 position, and superimpose the PSS4B calculation result to Ur, otherwise the switch switches to the 2 position, that is, the input value is 0.

The above is the applicant's detailed description and description of the embodiments of the application in conjunction with the accompanying drawings, but those skilled in the art should understand that the above embodiments are only preferred implementations of the application, and the detailed description is only to help readers better To understand the spirit of the present invention rather than to limit the protection scope of the application, on the contrary, any improvement or modification made based on the spirit of the invention of the application shall fall within the protection scope of the application.

Claims (1)

1. in a kind of power system stabilizer 4B model generator amature rotational speed omega computational methods it is characterised in that：Described Computational methods comprise the following steps：

(1) pass through each electric signal amount of field regulator Real-time Collection generator, including generator terminal line voltageThree Phase stator current

(2) the generator three-phase voltage that gathers step (1), Current calculation positive-sequence component, calculate generator built-in potential：

When generator built-in potential is represented with A, B phase, can obtain

${\stackrel{\&CenterDot;}{E}}_{aq}=\stackrel{\&CenterDot;}{U_a}+{{\mathrm{jX}}_q}^{\&prime;}{\stackrel{\&CenterDot;}{I}}_a=\stackrel{\&CenterDot;}{U_a}+{X_q}^{\&prime;}\frac{{\stackrel{\&CenterDot;}{I}}_c-{\stackrel{\&CenterDot;}{I}}_b}{\sqrt{3}}$

${\stackrel{\&CenterDot;}{E}}_{bq}=\stackrel{\&CenterDot;}{U_b}+{{\mathrm{jX}}_q}^{\&prime;}{\stackrel{\&CenterDot;}{I}}_b=\stackrel{\&CenterDot;}{U_b}+{X_q}^{\&prime;}\frac{{\stackrel{\&CenterDot;}{I}}_a-{\stackrel{\&CenterDot;}{I}}_c}{\sqrt{3}}$

For generator A phase, B phase built-in potential,For generator A phase, B phase voltage, X_q' electric for generator transient state It is anti-,For generator threephase stator electric current；

Subtracted each other by above two formula and derive

${\stackrel{\&CenterDot;}{E}}_{aq}-{\stackrel{\&CenterDot;}{E}}_{bq}={\stackrel{\&CenterDot;}{E}}_{abq}=\stackrel{\&CenterDot;}{U_{ab}}+{X_q}^{\&prime;}\frac{2{\stackrel{\&CenterDot;}{I}}_c-{\stackrel{\&CenterDot;}{I}}_b-{\stackrel{\&CenterDot;}{I}}_a}{\sqrt{3}}$

It is poor for A, B diphaser built-in potential,WithAngular frequency identical；

Calculate againReal part E_qrWith imaginary part E_qi：

$E_{qr}=U_r+\frac{{X_q}^{\&prime;}{I}_r}{\sqrt{3}}$

$E_{qi}=U_i+\frac{{X_q}^{\&prime;}{I}_i}{\sqrt{3}}$

Wherein, U_rFor set end voltageReal part, U_iFor set end voltageImaginary part, I_rFor composite vectorReality Portion, I_iFor composite vectorImaginary part；

(3) calculate generator amature rotational speed omega：

$\mathrm{\&omega;}=\frac{\arctan \frac{E_{qin}}{E_{qrn}}-\arctan \frac{E_{qin-1}}{E_{qrn-1}}}{\mathrm{\&Delta;}T}$

Wherein E_qinFor the imaginary part of A, B diphaser built-in potential difference in the n-th moment, E_qrnA, B diphaser for the n-th moment The real part of built-in potential difference, E_qin-1For the imaginary part of A, B diphaser built-in potential difference in the (n-1)th moment, E_qrn-1For the (n-1)th moment A, B diphaser built-in potential difference real part, Δ T be the sampling interval；

Power system stabilizer 4B input signal is Δ ω, and Δ ω=ω -1.0.