JPH0632597B2 - Excitation control device for synchronous machine - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an excitation control device for a synchronous machine, and particularly to a power system stabilizing device (PSS: Power Sys) for improving dynamic stability of a power system.
The present invention relates to an excitation control device for a synchronous machine to which a tem stabilizer is added.

[Background of the Invention]

As a device for improving dynamic stability of a power system by controlling excitation of a synchronous machine, there is a power system stabilizing device (PSS), which has been put to practical use.

However, since the conventional PSS is a system in which the set value is fixed, the dynamic stability of the power system can be improved only by a limited range of operating conditions / system configuration and a high-speed exciter. It has become difficult to meet the demands of the changing power system.

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

The terminal voltage V _g of the synchronous machine G is stepped down by the instrument transformer PT, and this is set by the voltage setting device (not shown) V _ref.
The obtained deviation is amplified by the amplifier 1 and then the automatic pulse phase shifter 2 generates a pulse phase-shifted according to the amplifier output. This pulse is used to control the firing angle of the thyristor THY and adjust the field voltage V _f of the synchronous machine. In this way, the terminal voltage V _g is controlled to be constant, that is, the terminal voltage is controlled to be constant. However, only the constant terminal voltage control often impairs the dynamic stability of the power system, and thus requires the power system stabilizing device PSS.

The PSS shown in FIG. 1 shows an example in which, for example, the active power P of the synchronous machine is used as a signal (hereinafter referred to as a power system stabilization signal) that provides information on power fluctuation. As the power system stabilization signal, a shaft rotation speed or frequency signal may also be used. The active power P is detected by the power converter 3, the direct current component is removed from the active power P by the incomplete differentiation circuit 4, 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
given as a correction signal _ref -V _g), performed to improve the kinetics stability.

In the figure, CT is a current transformer, EXTR is an excitation transformer, 41 is a field switch, and DR 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 method of fixing the gain of the amplifier 5 and the phase constant of the phase adjustment circuit 6 to the optimum values during the test run, so that if the operating conditions and system configuration change, the stabilizing effect of the PSS is obtained. Had a drawback that it was significantly impaired.

[Object of the Invention]

An object of the present invention is to provide an excitation control device for a synchronous machine equipped with a power system stabilizing device that can ensure power system stability regardless of the operating state of the power system, the system configuration, and the like.

[Outline of Invention]

The present invention controls the exciting device so that the phase difference between the power system stabilizing signals such as active power, shaft rotation speed and frequency and the synchronous machine field voltage becomes constant, so that the dynamic stability is optimal under any circumstances. Secure the degree.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. 7 to 9, but before that, the theoretical background of the present invention will be described with reference to FIGS. 2 to 6.

FIG. 2 is a so-called one-machine infinite system model showing one synchronous machine 21 connected to an infinite bus 22 via a reactor x _e , and its operation is linearly approximated with respect to a minute power fluctuation. Then, the torque ΔT and the speed Δω, the displacement angle Δδ, and the terminal voltage ΔV _{g have} a third relation as a relation.
It can be represented as a block diagram in the figure. Of the gain characteristics represented by K1 to K6 in FIG. 3, only K3 is determined only by the impedance of the synchronous machine and the system, but the rest is changed by the operating state of the synchronous machine in addition to the impedance. Therefore, if the motion of the synchronous machine is handled as a vibration system and expressed by the synchronization torque ΔT _{s in} phase with the position difference angle δ and the braking torque ΔT _D in phase with the speed Δω, the block shown in FIG. frequency It has a braking characteristic ρ and can be expressed by the following equation.

However Natural angular frequency Damping ratio where S: differential operator D: braking torque coefficient K1: synchronization torque coefficient M: generator inertia constant ω ₀ : base rotation angular velocity Normally, this angular frequency ω _n is about 7 rad / s (≈11.0 Hz) Therefore, even if the system configuration changes significantly, at most 2-20 rad /
It is about s. In FIG. 4, K1 is the d-axis interlinkage magnetic flux ΔE
q'is an electric torque change coefficient peculiar to the generator with respect to a change in the phase difference angle when the _{q is} constant, and K1 'is an electric torque coefficient generated from the excitation control system. On the other hand, the electric torque coefficient, which is 90 degrees out of phase with the synchronizing torque and fed back as a signal in phase with the rotational speed, includes a generator-specific coefficient represented as a control coefficient D and a braking torque coefficient D'by excitation control.

Of these coefficients, K1 'is 10 to 20% or less of K1 in the range of normal equipment constants, and there is no problem even if this is a negative value, but D'is a value similar to D, so D + D'
It becomes <0, and it is considered that the vibration becomes divergent vibration and the dynamic stability is lost.

Therefore, in order to secure the dynamic stability, it is necessary to apply a positive braking torque so as to compensate the negative braking torque.

For this purpose, the fluctuation signal of the phase difference angle Δδ of the synchronous machine is detected,
The gain and phase may be adjusted and given as a correction signal to the voltage control system to increase the braking torque of the excitation system. The power system stabilizing device PSS performs this control.

Returning to FIG. 4, in order to improve the dynamic stability, in order to improve the dynamic stability, the excitation system torque ΔT _ex with respect to the phase difference angular fluctuation Δδ advances to the angular frequency Δω by approximately 90 ° in phase, or −
It is understood that the constant voltage control system AVR, which is delayed by 90 degrees with respect to Δδ, may be controlled.

Next, the relationship between the field voltage ΔV _{f of the} synchronous machine and the excitation system torque ΔT _ex is obtained from FIG. Becomes Here, the effect K4 · Δδ due to the armature reaction is Δ
Since it is a small value compared with V _f , it was ignored. Considering that in the equation (1), K3T _do ′ is usually on the order of several seconds and the normal power fluctuation frequency is in the range of 2 to 20 rad, the electric torque ΔT _ex is always about 90 with respect to the field voltage ΔV _f . You can see that it will be delayed.

When the above phase relationship is displayed in a vector diagram together with the phase difference angle Δδ, the relationships shown in FIGS. 5 and 6 are obtained.

The excitation system torque ΔT _ex may be controlled so that it is almost in phase with or lagging behind the shaft rotation speed, that is, in a shaded area. Furthermore, from equation (1), ΔV _f is at a position 90 degrees ahead of ΔT _ex , so in order to obtain the optimum braking torque, ΔV _f
V _f satisfies it can be seen that it is sufficient to control such that Δδ and the 180 degrees or ΔV _f (-Δδ) is substantially in phase.

FIG. 7 shows an embodiment using the field voltage V _f and the synchronous machine active power P as an embodiment of the invention.

First, the active power P is detected by the power converter 3, and a change ΔP in the active power is obtained via the incomplete differentiation circuit 7. Similarly, the field voltage V _f is detected by using the incomplete differentiating circuit 8 having the same specifications as the field voltage V _f . From these signals, the phase difference detector 9 is used to detect the phase difference θ between ΔP and ΔV _f . Next, the phase difference setting value θ _ref and θ are compared to obtain the phase deviation Δθ.

The phase deviation Δθ is used as a control signal to control the phase adjustment circuit 6 of the power system stabilizing device 10 so that Δθ becomes zero.

Here, as the configuration of the phase adjusting circuit 6, a conventionally known first-order lag advance circuit can be used. This circuit inputs the phase deviation Δθ and the output ΔP of the amplifier 5,
It has the function of advancing or delaying the phase of ΔP according to θ, thereby creating a voltage deviation correction signal for suppressing the fluctuation state of the power system and outputting it to the deviation signal of the terminal voltage and the set value. To do.

Here, the phase difference detection device 9 has an auxiliary relay that turns on only when the amplitudes of the active power ΔP and the synchronous machine field voltage ΔV _f are above a certain level and turns off when the amplitude is below a certain level. When the signal of the phase difference output Δθ is turned on and off at the auxiliary contact of, and the amplitude of ΔP or ΔV _f is small, that is, when the power fluctuation does not occur, the phase difference Δθ cannot be accurately obtained, and thus the circuit of the present invention. 11 shall be excluded.

By performing the control as described above, the optimum PSS phase constant for the generated power fluctuation can be automatically tuned. That is, even if a PSS constant is not obtained by performing a very time-consuming parameter survey, a step-like change in the set voltage of the voltage control system, or in the case of a two-line power transmission line, one of these lines is switched on and off to make a transient transition. If power fluctuation is generated, it is possible to automatically and optimally set the optimum PSS constant in the system.

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

First, looking at a modified example due to the difference in the signals used, in addition to the synchronous machine effective output shown in this embodiment, the shaft speed, frequency and phase difference angle can be considered as the power system stabilization signal. In addition, as shown in FIG. 8, the frequency change of the horizontal axis synchronous back voltage _q synthesized by using the synchronous machine terminal voltage _g , the armature current _g, and an appropriate horizontal axis synchronous reactance x _q , or the external line reactance x _e , A phase difference δ between infinity bus voltage _∞ and _q synthesized using _{g 1} and _{g 2} can be used as a power system stabilizing signal.

_{However, q = g + jx q g} , ∞ = g -jx q
It is _g .

Further, from the relationship shown in FIG. 9, _q ′, which is an amount directly proportional to the electric torque, may be simulated and used as the power system stabilizing signal.

_However, it is _{E q '= e q + X} q' i d.

Next, considering the field voltage, from FIG. 3, ΔV _f = GAVR (S) · ΔVerr. Therefore, if the characteristic of the constant voltage control system GAVR (S) is sufficient, the voltage deviation ΔVerr is replaced by ΔV _f . Can be used for

Although the above invention relates to the control of the excitation system, the cabana control system may be adjusted so that the phase difference between the power system stabilizing signal and the field voltage becomes constant.

〔The invention's effect〕

1) Regardless of the operating state of the synchronous machine, changes in the system configuration, and the type of exciter used, optimum dynamic stability can always be ensured.

2) Since the constants of the exciter or power system stabilizer can be automatically adjusted to ensure optimal dynamic stability, test adjustments during test run can be simplified and external conditions such as major changes in the system configuration Even if it changes, the constant resetting can be omitted. That is, automatic tuning is possible.

3) Since dynamic adjustment is automatically made to the optimum constant according to the vibration period of power fluctuation, dynamic stability can be secured against power fluctuation in a wide frequency range of 0.2 to 2 Hz.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional excitation control device. FIG. 2 shows the generator 1 and the infinite bus 2 via the system reactance x _e .
Is a one-machine infinite system combined. FIG. 3 is a block diagram in which the system represented by the one-machine infinite system of FIG. 2 is linearly approximated around a certain operating point. In FIG. 4, the portion surrounded by the double wavy line in FIG. 3 is regarded as a black box, and the excitation system torque ΔT _ex with respect to the vibration of the phase difference angle Δδ is separated into components proportional to Δω or Δδ, and these coefficients are respectively D ′. , K1 is a diagram in which FIG. 3 is replaced with an equivalent secondary vibration system. FIG. 5 is a diagram showing an ideal vector relationship between ΔP, Δω and ΔV _f . FIG. 6 is a waveform representation of FIG. FIG. 7 shows an embodiment of the present invention. 8 and 9 can be simulated as a power stabilization signal.
Signals such as _q , δ, and E _q ′ are shown in a vector diagram. AVR ... Constant terminal voltage control device, PSS ... Power fluctuation stabilizer, 5 ... Amplifier, 6 ... Phase adjustment circuit, 9 ...
... phase difference detection device, ΔP ... power change amount, ΔV _f ... field voltage change amount.

Claims (1)

[Claims] 1. A synchronous machine having a terminal voltage constant controller for comparing the terminal voltage of the synchronous machine with a set value and adjusting the field amount of the synchronous machine according to the deviation between them to control the terminal voltage of the synchronous machine. In the excitation control device of, the power system stabilization signal that represents the power system fluctuation state is detected, and a voltage deviation correction signal that suppresses the power system fluctuation state is generated by inputting this signal and the terminal voltage and the set value The power system stabilizing means for outputting the deviation signal and the fluctuation of the field voltage of the synchronous machine are detected, and the phase difference between this fluctuation and the power system stabilizing signal is obtained. And a phase deviation signal creating means for creating a phase deviation signal representing a phase deviation between the phase difference set value, and the power system stabilizing means inputs the phase deviation signal,
In response to this, the phase of the voltage deviation correction signal is advanced or delayed so that the phase deviation signal is adjusted to substantially zero.