JPS59173000A - Excitation controller of synchronous machine - Google Patents

Abstract

PURPOSE:To obtain power system stability irrespective of the operating state of a power system and the system configuration by controlling an exciter so that the phase difference between the power system stabilization signal and the synchronous machine field voltage such as effective power, axial rotating speed and frequency become constant. CONSTITUTION:Effective power P is detected by a power converter 3, and a variation DELTAP of effective power is obtained through an incomplete differentiator 7. Similarly, the field voltage variation DELTAVf is detected by using an incomplete differentiator 8 from a field voltage Vf. The phase difference theta between DELTAP and DELTAVf is detected by using a phase difference detector 9 form these signals. Then, the phase difference set value thetaref is compared with theta, thereby obtaining the phase deviation DELTAtheta. The phase regulator 6 of a power system stabilizer 10 is controlled in such a manner that this phase deviation DELTAtheta is as a control signal so that DELTAtheta becomes zero.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an excitation control device for a synchronous machine, and in particular to a power system stabilization device (pSS: pO) that improves the dynamic stability of a power system.
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This invention relates to an excitation control device for a synchronous machine that is equipped with the following.

[Background of the invention]

A power system stabilization system (PSS) has been put into practical use as a device for improving the dynamic stability of a power system by controlling the excitation of a synchronous machine.

However, since conventional PSS uses a method that fixes set values, it is possible to improve the dynamic stability of the power system only with a limited range of operating conditions, system configurations, and high-speed response excitation devices. It has become impossible to adequately meet the demands of increasingly complex power systems.

A conventional excitation device will be explained by taking the Cyrisk excitation method shown in FIG. 1 as an example.

The terminal voltage v1 of the synchronous machine G is stepped down by the instrument transformer PT, and this is set as the setting value of the voltage setting device (not shown).
After the obtained deviation is amplified by an amplifier 1, an automatic pulse phase shifter 2 generates a pulse whose phase is shifted according to the amplifier output. Using this pulse, the firing angle of the thyristor TI (Y) is controlled and the field voltage vf of the synchronous machine is adjusted. In this way, the terminal voltage v1 is controlled to be constant, that is, the terminal voltage is controlled to be constant. However, only constant terminal voltage control often impairs the dynamic stability of the power system, and the power system stabilizing device P88 is required.

An example is shown in which, for example, the active power P of a synchronous machine is used as a signal (hereinafter referred to as a power system stabilization signal) that provides information on the PSSld power fluctuation shown in FIG. In addition to this, a shaft rotation speed or frequency signal can also be used as the power system stabilization signal. The power converter 3 detects the M dynamic force P, the DC component is removed by the total differential circuit wI4, the gain and phase of this signal are adjusted by the amplifier 5 and the phase adjustment circuit 6, and the output is Voltage deviation signal (V
, -tV-) as a correction signal to improve dynamic stability.

In the same figure, CT is 'tlL flow transformer, EXTR
is an excitation transformer, 41 is a field switch, and DB is a resistor connected in parallel to the field winding when the field switch 41 is opened.

As is clear from this figure, the conventional PSS is a system in which the gain of the amplifier 5 and the phase constant of the phase adjustment circuit 60 are fixed at the maximum a value during trial operation, so if the operating conditions or system configuration change, the PSSOSS effect will be significantly reduced. It had disadvantages that hurt it.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a synchronous machine excitation control device including a power system stabilizing device that can ensure power system stability regardless of the power system operating state, system configuration, etc.

[Summary of the invention]

The present invention provides optimal dynamic stability under any circumstances by controlling the excitation device so that the phase difference between power system stabilization signals such as active power, shaft rotational speed, and frequency and the synchronous machine field voltage is one step. ensure that the degree of

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 7 to 10, but before that, the theoretical background of the present invention will be explained using FIGS. 2 to 6.

Fig. 1 is a system model called a so-called -machine infinite system, which shows one M1ffA21 connected to an infinite bus 22 via a beam axle X, and its operation is linearly approximated with respect to minute power fluctuations. , the torque ΔT
The relationship among speed Δω, phase difference angle Δδ, and terminal voltage ΔV can be expressed as shown in the block diagram of FIG. In FIG. 3, K1. Of the gain characteristics represented by - and 6, only 3 depends only on the impedance of the synchronous machine and the system, but the rest all change depending on the operating state of the synchronous machine in addition to the impedance. Therefore, the motion of the synchronous machine is treated as a navigating system, and the synchronization torque ΔT is in phase with the phase difference angle δ, and the braking torque ΔT is in phase with the speed Δω.

If expressed as the block diagram shown in FIG. 4, its vibration characteristics are vibration frequency ω, V1--Electric-1 Electric-1 Braking characteristics, and can be expressed by the following equation.

Here, S: differential operator D = braking torque coefficient 1: synchronization torque coefficient M: inertia constant ω of the generator. Two-base rotation angular velocity Normally this angular frequency ω is 7rod/S (medium 1.0H2)
Even if the multisystem configuration changes drastically, it will be at most 2 to 20
roct/sm degrees. In Fig. 5, 1 is the d-axis interlinkage magnetic flux ΔE, ' is the electric torque change coefficient specific to the generator for the change in phase difference angle at a constant time, and Kl' is the electric torque coefficient generated from the excitation control system. be. On the other hand, the electric torque coefficients fed back as a signal having a phase difference of 90 degrees from the interperiod torque and the same phase as the rotational speed include a generator-specific coefficient expressed as a control coefficient and a braking torque coefficient D' due to excitation control.

Among these coefficients, Kl' is within 10 to 20 degrees of 1 in the range of normal equipment constants, and there is no problem even if it becomes a negative value, but D' is the same value as D, so D+D '
(O, and the vibration becomes a divergent vibration and dynamic stability is considered to be lost.

Therefore! [In order to ensure the 1-mode stability, it is necessary to apply positive braking torque to compensate for the negative braking torque.

For this purpose, detect the oscillation signal of the phase difference angle Δδ of the synchronous machine,
Gain and position q'ixu are given to the voltage control system as a correction signal, wJJj! All you have to do is control the braking torque of the i-thread, and this is done by the power system stabilization system @PS.
It is S.

Returning to Figure 4 and organizing the above ideas, in order to improve the dynamic stability, wJ magnetic thread torque ΔT, 8 with respect to phase difference angular fluctuation Δδ must advance approximately 90° in phase with the angular frequency Δω, or with respect to −Δδ. Voltage-short control system AVR with a 90 degree delay
If you control it, you can see the difference.

Next, from Fig. 4, the field voltage ΔVt of the synchronous machine and the exciting thread torque ΔT, ! If we seek the relationship with Here'l! , the effect due to Isogo reaction is 4・Δ
Since δ is a small value compared to ΔVt, it was ignored.

In equation (1), considering that 3Td-' is usually on the order of several seconds and that the normal power oscillation angle frequency is in the range of 2 to 20 rods, the electric torque ΔT ax is always t with respect to the field voltage ΔVt. It can be seen that there is a delay of about 90 degrees.

When the above phase relationship is expressed in a vector diagram along with the phase difference angle Δδ, the relationships shown in FIGS. 4 and 5 are obtained.

The excitation thread torque ΔT and O may be controlled so that they are in the hatched area so that they are approximately in phase with the shaft rotational speed or slightly behind #. Furthermore, from equation (1), ΔVt is ΔT,! Therefore, in order to obtain the optimum braking torque, control should be performed so that Δ■f is 180 degrees with Δδ or ΔVt and (−Δδ) are approximately in phase.

FIG. 7 shows an embodiment in which the field voltage Vt and the synchronous machine active power P are used as an embodiment of the invention.

First, the active power P is detected by the power converter 3, and is passed through the incomplete differentiation circuit 7 to obtain the change ΔP in the active power. Similarly, the field voltage Vf is set to 7, and the imperfect differentiation circuit 8 of the same type is used to detect the field voltage change ΔVt. From these signals, a phase difference detection device 9 is used to detect the phase dip θ between ΔP and ΔVt. Next, the phase difference setting value θrsf and θ are compared to obtain the phase deviation Δθ.

Using this phase deviation Δθ as a control signal, the phase adjustment circuit 6 of the power system stabilizing device 10 is controlled so that Δθ becomes zero.

Here, the phase difference detection device 1j is equipped with an auxiliary relay that turns ON only when the amplitude of the active power ΔP and the synchronous machine field voltage Δvf is above a certain level, and turns OFF when the amplitude is below 1 short.
The auxiliary contact of this relay carefully manipulates the phase difference output Δθ signal, and when the amplitude of ΔP or ΔVt is small, that is, when no power fluctuation is occurring, the phase difference Δθ cannot be accurately determined, so the circuit of the present invention 11 shall be excluded.

By performing the above control, it is possible to automatically tune the optimum 188 phase constant for the generated power fluctuation. In other words, it is not necessary to perform a very time-consuming parameter survey to determine the PS8 constant (Q).

Alternatively, in the case of a two-line power transmission line, if one of these lines is turned on and off to generate a transient power fluctuation, it is possible to set the optimum P88 constant for that system. It is.

The key point of the present invention is that the above dynamic stability of the power system can be achieved by controlling the phase difference between the power system stabilization signal, which is an information signal of power fluctuation, and the synchronous machine field voltage to be constant. Various modifications are possible.

First, regarding a modification based on a difference in the signals used, as the power system stabilization signal, in addition to the synchronous machine effective output shown in this embodiment, @speed, frequency, and phase difference angle can be considered. In addition, as shown in Fig. 9, the frequency change of the horizontal axis synchronous back voltage E, which is synthesized using the synchronous machine terminal voltage vf, the armature current I, and an appropriate horizontal axis synchronous reactance X, or the external line reactance. The phase difference δ between the infinite bus gFEv- and E, which are synthesized using X, lVg, and Il, can be used as a power system stabilization signal.

(10) However, Bq=Vt+JXq It * Va-=Vz
jXqlg.

From the relationship shown in Figure 10, we simulate E,', which is a quantity directly proportional to the electric torque, and use this as a power system stabilization signal.

However, Eq' = e, +x, +, 1.

Next, considering the field voltage, ΔV t =
Since GAV<S>-Δyerr, if the characteristics of the constant voltage control system GAVR(S) are known, the voltage deviation Δyerr can be conveniently used in place of Δ■.

In addition, the present invention adjusts the phase 11il rectifying circuit of the power system stabilization device so that the phase difference between the power system stabilization signal and the field voltage is constant. Any control may be used to keep the phase difference constant by controlling the gain or time constant of the control system.

Although the above invention relates to the control of the excitation system, the cabana control system may also be adjusted so that the power system stabilization signal and the field voltage are constant.

〔Effect of the invention〕

(11) 1) Optimum dynamic stability can always be ensured regardless of the operational status of the synchronous machine, changes in system configuration, and the type of excitation device used.

2) Since the constants of the excitation device or power system stabilization device can be automatically adjusted to ensure optimal dynamic stability, it is possible to automatically adjust the constants of the excitation device or power system stabilization device. Even if conditions change, resetting constants can be omitted. That is, auto-tuning is possible.

3) Since the constant is automatically adjusted to the optimum value according to the swing side period of power fluctuation, dynamic stability can be ensured against power fluctuation over a wide range of frequencies from 0.2 to 2H2.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional excitation control device. FIG. 2 shows a single-machine infinite system in which a generator 1 and an infinite bus 2 are coupled via a system reactance X. FIG. 3 is a block diagram in which the system represented by the one-machine infinite system in FIG. 2 is linearly approximated around a certain operating point. (12) In Fig. 4, the part surrounded by the double wavy line in Fig. 3 is regarded as a black box, and the excitation thread torque ΔT IIK with respect to the vibration of the phase difference angle Δδ is separated into components proportional to Δω or Δδ, and these coefficients are calculated. This is a diagram in which FIG. 3 is replaced with an equivalent second-order vibration system, with D' and Kl respectively. FIG. 5 is a diagram showing an ideal vector relationship between ΔP, Δω, and ΔVt. FIG. 6 is a waveform representation of FIG. 5. FIG. 7 shows an embodiment of the present invention. FIG. 8 shows a modification of the present invention, in which dynamic stability is improved by changing the gain of the excitation device or the constant of the phase circuit instead of the PSS. 9 and 10 are vector diagrams showing signals such as El, δ, E,', etc. that can be simulated as power stabilization signals. AVR... A bubble voltage constant control device, PSS... Power fluctuation stabilization device, 5... Amplifier, 6... Phase adjustment circuit, 9... Phase difference detection device, ΔP... Power change amount ,
ΔVf (13) (14) Vine 4 Condolence S Figure 6 Figure 1 △I ・￥-J '8 Mouth AVR Vref (90R)! PTjf
-l ρ-21 - 1 Akebono] 11,
−3 l″≦≦ self′ 1 ΔP: ■ )
1? ■f-1 1 L-1----------------

Claims (1)

[Claims] 1. In an excitation control device for a synchronous machine equipped with a terminal voltage constant control device that determines the field amount of the synchronous machine according to a deviation signal between the terminal voltage of the synchronous machine and its set voltage, the electric power system connected to the synchronous machine A correction signal for making the phase difference between the power system stabilization signal representing the oscillation state and the field voltage fluctuation of the synchronous machine to a predetermined phase difference @! 1. An excitation control device for a synchronous machine, characterized in that an electric power system stabilizing device is added to cause a positive % bucket signal to act on the terminal voltage constant control device.