JPH0479798A - Excitation controller for synchronous machine - Google Patents

Abstract

PURPOSE:To control excitation of a synchronous machine with high voltage controllability without sacrifice of transient response or stability by inputting a terminal voltage difference signal, as it is, to an automatic voltage regulator even in case of significant disturbance such as fault on a transmission line. CONSTITUTION:An integral operating unit 14 comprises a voltage detector 10A for detecting the average value of actual line voltages of three-phase basic wave based on a voltage value VH detected through a potential transformer 10, a high voltage setter 11, a high voltage gain circuit 12 for comparing the output signal from the voltage detector 10A with a reference value rH set in the high voltage setter 11 and multiplying the difference signal by a gain kH, a correction reducing gain circuit 15B for multiplying a received difference signal ( VG) by a gain (1-beta), a phase compensating circuit 16 for subtracting the output signal of the correction reducing gain circuit 15B from the output signal of the high voltage gain circuit 12 and receiving the difference signal, and an output limiter 17 for adding the output signal of the phase compensation circuit 16 to the difference signal ( VG) of a terminal difference signal circuit 15A and feeding the sum to an AVR 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an excitation control device for a synchronous machine, and particularly to an excitation control device for a synchronous machine that contributes to improving the voltage stability of a power system.

(Prior Art) A conventional excitation control device for a synchronous machine detects a terminal voltage of a generator, and adjusts reactive power so that this terminal voltage becomes a predetermined set value. Therefore, when the grid voltage drops due to an increase in demand, etc., the reactive power generated by the synchronous machine increases depending on the slope of the grid voltage and the output voltage of the generator, or even if the grid voltage drops significantly, the synchronous machine It can be said that there is still sufficient margin to generate reactive power up to its rated value.

Therefore, recently, excitation control devices (for example, [Improving the voltage stability of large-scale power systems]) have been developed that actively generate reactive power when the system voltage drops for synchronous machines that have a surplus of generated reactive power. New generator excitation method (P
Regarding S VR) (Part 1 Principle) 1989 National Conference of the Institute of Electrical Engineers of Japan #1013) J has been proposed.

FIG. 5 shows the conceptual basic configuration of such an excitation control device. In Fig. 5, 1 is a synchronous machine driven by a water turbine, a steam turbine, or a gas turbine.The output terminal of this synchronous machine 1 is connected to the power transmission line 3B via a main transformer 2 and a breaker 3A. The circuit is configured. In the main circuit having such a configuration, the output terminal voltage (V G) of the synchronous machine 1 is detected by the potential transformer (PT) 4,
This voltage detection value is compared with the reference value set in the voltage setting device 5, and the deviation signal thereof is detected by entering the reduction gain circuit 13, and the voltage detection value and the reference value set by the high voltage side voltage setting device 11 are compared. The difference signal is multiplied by the gain of the high-voltage side gain circuit 12, and this is added to the output of the reduction gain circuit 13 mentioned above, and the result is manually input to the automatic voltage regulator 6 (hereinafter simply referred to as AVR). There is. This A VR 6 controls the excitation device 7 according to the added value, and controls the excitation current of the field winding 8 of the synchronous machine 1.

In the above circuit configuration, the tap ratio of the main transformer 2 is n,
The reactance is set to If the gain is β (0≦β≦1),
The high voltage side voltage (Vo) of the main transformer 2 controlled by the excitation control device shown in FIG. 5 is approximately expressed by the following equation.

VH=n(βra +rn)/(β+n
k o ) - nβ

VH=(βr6+kHr+()/(β+kH)−βX
T1. /(β+kH) −(2) From equation (2), it can be seen that the isometric reference value is given by the first term on the right-hand side, and the voltage droop characteristic is given by the second term on the right-hand side.

Here, the reduction gain β is not equal to the setting of the voltage droop characteristic described above, and without this reduction gain circuit 13, the AVR6
(β-1), the gain increases, and when disturbances are added to the system, such as during a transmission line accident, the damping of power fluctuations decreases, so it also serves the purpose of preventing this damping decrease.

The operation of such a conventional device will be considered in terms of a one-maneuver, one-load system model shown in FIG. That is, in FIG. 6, the load end bus 24 is connected to the synchronous machine 2 via the main transformer reactance XT22 and the transmission line reactance Xe23.
The characteristics of the active power P1, the reactive power Q, and the voltage V are as follows.

P2+ fQ+V,' / (kXT+Xe)1-(■
,・V,/(kXT+X,)l 2...(3) However, k is related to the voltage droop characteristic in equation (2), and β
/(β+kH). Also, ■1 represents the voltage of an equipolar synchronous machine.

In the above equation (3), when the value of k is changed and expressed as a PV curve, the result is as shown in FIG. 7.

In the P-■ curve in Fig. 7, the voltage at the maximum point of the load power P is called the nose tip voltage, or in this conventional device,
By decreasing the value of , that is, by increasing the amount of compensation for the main transformer's actance, it is possible to increase the maximum value of the load power and to decrease the above-mentioned nozzle tip voltage. This means that the power capacitor (SC) at the load end
When installing a transmission line, this north tip voltage tends to increase, and in extreme cases it will reach the normal operating voltage range, making it impossible to maintain stable operation or increasing the power consumption by installing new or expanding transmission lines. This shows that it has the same effectiveness as that of the conventional method, and that voltage stability can be significantly improved.

(Problem to be solved by the invention) However, in the conventional device described above, the terminal voltage of the synchronous machine 1 in FIG. Therefore, in order to suppress the terminal voltage of the synchronous machine within the permissible value, an output limiter (not shown) is provided in the output circuit from the high voltage side. For this reason, there is a drawback that the gain decreases during large disturbances such as power transmission line accidents, and the transient response ability decreases.

In addition, the operational high-voltage side voltage reference value r++ is specified as a target value, but as shown in equation (2), "8 and the high-voltage side voltage VH do not necessarily match, so it must be operated and managed. I cannot say that I am fully satisfied with the above.

An object of the present invention is to provide an excitation control device for a synchronous machine that has excellent voltage controllability and is capable of controlling the excitation of a synchronous machine without impairing transient response and stability.

[Invention, Boat Configuration] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a system which is driven by a water turbine, a steam turbine, or a gas turbine, and whose output terminal connects a main transformer and a breaker. an automatic voltage regulator that detects the terminal voltage of the synchronous machine and controls the field of the synchronous machine based on a deviation signal between the detected value and a reference value in the synchronous machine connected to the power transmission system via the main transformer; a high voltage side voltage detector that detects the high voltage side voltage of the device; a high voltage side setting device that sets a reference value for the high voltage side voltage; and a high voltage side setting device that sets the reference value for the high voltage side voltage. a reference value correction circuit having a first correction means for correcting the reference value; and a second correction means for correcting the reactive current fluctuation due to the correction change of the reference value by the first correction means; and the high voltage side voltage detection circuit. The difference signal between the detected value detected by the device and the signal obtained by adding the outputs of the first correction means and the second correction means of the reference value correction circuit to the reference value set in the high voltage side setting device is determined on the high voltage side. The high voltage side gain circuit multiplies the gain and the gain (1-
A modified reduction gain circuit that multiplies the automatic voltage regulator gain reduction rate β) and a signal obtained by subtracting the output signal of the modified reduction gain circuit from the output signal of the high-voltage side gain circuit are input to calculate the transient gain for a predetermined frequency region. The apparatus includes a phase compensation circuit that compensates for the delay so as to reduce the delay, and an addition means that adds the output signal of the phase compensation circuit to the deviation signal input to the automatic voltage regulator.

In addition, in the above configuration, when the main transformer has a tap changer on load or a voltage regulator on load, the reference value set by the high voltage side setting device is applied to the main transformer instead of the reference value correction circuit. A reference value correction circuit is provided, which has a third correction means for correcting in accordance with a change in the tap of the device, and a second correction means for correcting a reactive current fluctuation due to the correction change of the reference value by the third correction means. , the outputs of the second and third correcting means of this reference value correction circuit are added to the reference value.

(Function) In the excitation control device for a synchronous machine with such a configuration, even in the event of a major disturbance such as a transmission line accident, the terminal voltage deviation signal is input as is to the automatic voltage regulator, so the automatic voltage regulator is The gain is not reduced, and the same level of transient response capability as before can be maintained and exhibited. In addition, during steady state, the high voltage side loop can perform its original function in response to the deviation signal between the high voltage side voltage detection value and the reference value, so if the synchronous machine has enough room to generate reactive power, when the system voltage drops It becomes possible to actively generate reactive power.

Furthermore, as shown in equation (1) (or equation (2)), the high voltage side voltage (VH) of the main transformer and the high voltage side reference value (r+
+ ), if we consider the voltage droop characteristics as fixed,
That is, when kHz and β are fixed, the reactive current of the synchronous machine is mainly 1. It depends on the tap ratio n of the main transformer, the reactance X, and the first and third correction means, or the second and third
By providing a correction means for the high pressure side reference value (r+
), it is possible to set the high voltage side voltage (VH) as close as possible to ), and the operation and management of the system including the synchronous machine can be facilitated.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an example of the overall configuration of an excitation control device for a synchronous machine according to the present invention, and the same parts as in FIG. 5 are shown with the same symbols. In FIG. 1, the output voltage (V6) of the synchronous machine 1 is detected by the instrument transformer 4, this detected voltage value is compared with the reference value (r6) set in the voltage setting device 5, and the deviation signal ( ΔVc) to the terminal voltage signal circuit 15A
input to AVR6 through. The AVR 6 controls the excitation device 7 in response to the deviation signal (ΔVG), and controls the excitation current supplied to the field winding 8 of the synchronous machine. On the other hand, a voltage transformer (PD or PT) connected to the power plant bus 9
10 detects the power transmission voltage vll of the power plant, and this voltage detection value ■. is input to the general arithmetic unit 14. This comprehensive arithmetic unit 14 is a voltage detector that detects the average value of the effective value line voltage of the three-phase fundamental wave with high accuracy and high speed based on the voltage detection value ■H detected by the voltage transformer (PD or PT) 10. a high-voltage side voltage setting device 11 such as a programmable type that can set the time and voltage according to the system voltage situation;
A high voltage side gain circuit 12 which compares the output signal of the voltage detector 10A with a reference value rH set in the high voltage side voltage setter 11 and multiplies the deviation signal by a gain kH, and inputs the deviation signal (ΔVc). and a phase compensation circuit which subtracts the output signal of the modified reduction gain circuit 15B from the output signal of the high voltage side gain circuit 12 and inputs the difference signal]6. , an output limiter which adds the output signal of this phase compensation circuit 16 to the deviation signal (ΔVc) of the terminal voltage deviation signal circuit 15A and inputs it to the AVR 6.

In this case, the output of the general calculation unit 14 is added to the deviation signal (ΔVG) via the interlock contact 14A to protect the signal due to plant operating conditions, abnormal conditions inside the general calculation unit 14, etc. ing. Further, a reference value correction circuit 18 is provided in the general calculation unit 14 so that the detected voltage value VH during actual operation becomes closer to the reference value rH set in the high-voltage side voltage setter 11, and the output signal thereof is adjusted to the reference value rH.
It is added to H. Furthermore, the comprehensive arithmetic unit 1
4 is the output voltage of synchronous machine 1■. A terminal voltage limiter 19 is provided to which the detected voltage value vG is input so that the voltage is within the allowable range, and the output signal of this terminal voltage limiter 19 is sent to the phase correction circuit 1.
I am trying to subtract it from the output of 6.

Note that this example shows a case where the output of the system stabilizing device 20 is input to the AVR 6.

Next, the operation of the excitation control device for a synchronous machine configured as described above will be described.

Generally, in the event of a major disturbance such as an accident on a power transmission line, the terminal voltage V6 of the synchronous machine also drops significantly. Conventional equipment mainly relies on the transient response capability of AVR6 to maintain and improve the transient stability of such power transmission systems.
It also has the function of suppressing the rise in

The terminal voltage deviation signal circuit 15A in this embodiment maintains the above function. Therefore, the reduction gain circuit 13 in FIG. 5 is a high voltage side gain circuit with the gain of the modified reduction gain circuit 15B in FIG. 1 being (1β)]
2 is subtracted from the output signal of 2, and added to the terminal voltage deviation signal of the terminal voltage deviation signal circuit 15A and inputted to the AVR 6, the reduced gain β shown in FIG. 5 is steadily obtained.
This does not impair the characteristics of the conventional device.

In addition, the subtraction point of the modified reduction gain circuit 15 is the high voltage side J1"
The transient stabilization device 20 is installed after the in-circuit 12 and before the phase compensation circuit [6], or the analysis results of the system stability including the phase compensation circuit [6] indicate that the damping against power fluctuations is effective.
Since the output of is added to the eccentricity detection section of the AVR6, in the frequency region exceeding the time constant of the change detection circuit (signal reset) (not shown) in the detection section input conversion position 20, it is It is. Furthermore, the phase compensation circuit 16 also has the effect of improving the stability of closed loop control.

By the way, in the conventional device, the relationship between the power transmission voltage (V ll) and the high voltage side reference value (r ll ) is expressed by the equation (]) (or (2)
When the reactive current I9 increases due to the voltage droop characteristic, V,(() decreases, so it no longer matches with the equation (0). This relationship is shown in FIG. 2 as characteristic (0).

FIG. 3 shows an example of a reference value correction circuit 18 for correcting this. In this figure, the reactive power compensation circuit 18A has a certain reference reactive current I,. Against ■. is “□
With the first correction means that is equal to , the correction value r□ is given by the following equation from equation (1).

rQ=β/KH(XTIqO + (rH/n−r6)l −=−(4) By adding this correction value r(, to rH, the following equation is given.

VH = (rH-nβXT)(I, l-0)/(β
+nKu) (5) This relationship is shown in FIG. 2 as characteristic (1).

However, this correction value r0 is only valid on the high pressure side.
Since one IQo corresponds to a reference value, for example rho, if the reference value rlIO is changed from this state, the reactive current will also change according to the system conditions, so the new reference value r, ( ' and the power transmission voltage V1.- no longer match. Therefore, the reference value change correction circuit 18B changes the reference value "1 (
o is changed and the power transmission voltage VH becomes equal to the reference value rH- when the rH- is closed. r1) is as shown in the following equation.

rD=nβxE I,o/(βtennKH)=nβXT
・D (r++ r++ )/(β+nK,
) ・ (6) However, α is a coefficient for the setting of reactive power change. This correction value rD is rH−
By adding , the following equation is given from equation (5).

VH=rH−nβXd (1,−■,.

−ΔI, 0) / (βten KH) −(7)
This relationship is shown in FIG. 2 as characteristic (2). ) p Oh, characteristic (2-) is the reference value rHo when there is no correction value n
It shows the characteristics for changes in the new reference value r. ′
In contrast, the transmission voltage■. is the reactive current change (~ΔI-o)
This shows that they do not match by an amount corresponding to .

From the above, by adding the first and second correction means as shown in FIG. 3, forming the reference value correction circuit 18, and adding it to r and +, it is possible to achieve a power transmission voltage V H closer to the reference value r□. It can be used to simplify operation and management.

By the way, when the system voltage drops significantly due to an accidental shutdown of a part of the power transmission line, the generated reactive power is also restricted by the operational upper limit of the terminal voltage of the synchronous machine 1. Therefore,
In order to expand the operational range of the control device according to the present invention, the main transformer 2 is equipped with a load tap changer (LTC) or a load voltage regulator (LVR), so that the output voltage of the synchronous machine 1 exceeds the operational tolerance. If it exceeds the limit, a cooperative control method with the LTC may be considered in which the power transmission voltage is maintained by increasing the tap value of the LTC and increasing the reactive power generated by the synchronous machine 1, for example. However, even when the tap ratio n of the LTC is changed, the voltage droop characteristic described above needs to remain unchanged in order to appropriately distribute reactive power between adjacent synchronous machines. In this way, when the main transformer 2 is equipped with LTC or LVR, the tap correction value circuit 18C replaces the first correction means as shown in the configuration example shown in FIG. A third device that automatically corrects the values of the reactance XT and tap ratio n of the reactor 2 according to the operating values of the LTC.
With the correction means, it is possible to make the power transmission voltage VH the same as in equation (5). That is, the correction value rT is expressed by the following equation.

rT=β/KH+XT I-6 + (rH/n"-rG)l ・= (8)
However, X, , n'' indicates that it changes in conjunction with the LTC operation value.

In addition, it has been confirmed from trial calculations whether the voltage droop characteristic can be similarly given using X, , n'' from the second term on the right side of equation (5), or whether the voltage droop characteristic hardly changes even if the tap ratio n is changed. This is equivalent to characteristic (1) in FIG.

From the above, when LTC or LVR is installed in the main transformer 2, the second and third correction means are added as shown in FIG. The effect of this can be obtained.

In addition, various quantities used for the correction value rQ+'D+'T,
That is, among the variables on the right side of equations (4), (6), and (8), only n8 is taken into the general arithmetic unit 14 as an external signal.

All other variables such as β are values set inside the general arithmetic unit 14.

In the above description, the comprehensive arithmetic unit 14 can be an analog device or a digital device, and can perform arithmetic processing using software.

However, it is effective to implement it with a digital device from the so-called signal processing aspects such as control accuracy, cooperation with neighboring machines, signal storage, and interlocking with external signals.

Therefore, although the internal circuit of the general arithmetic unit 14 is expressed as a block diagram in FIG. 1, this is merely to facilitate understanding of the functions of the present invention.

In addition, the circuit configuration of the general processing unit 14 is divided into sections that are effective when adding this control device to the excitation device of an existing plant. For example, the modified reduction gain circuit 15B is replaced with the conventional A
It is also possible to configure it within the circuit on the VR side, and it is not outside the scope of the present control device.

[Effects of the Invention] As described above, according to the present invention, the deviation signal Δ■6 between the terminal voltage of the synchronous machine and the reference value is input to the automatic voltage regulator,
From a signal obtained by multiplying the deviation signal ΔV H between the high voltage side voltage of the main transformer and the reference value by the high voltage side gain, the above Δ■6 is multiplied by (1-reduction gain β) and subtracted, and the result is applied to the phase compensation circuit, Since the output is added to the deviation signal ΔV6 and input to the automatic voltage regulator, it maintains the same transient response ability as a conventional automatic voltage regulator even in the event of a major disturbance such as a power line accident, and maintains the same transient response capability as a conventional automatic voltage regulator, and can maintain high voltage during normal operation. The original function of the side loop can be demonstrated.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the overall configuration of an embodiment of the excitation control device for a synchronous machine according to the present invention, and FIG. 2 is a conceptual characteristic diagram showing the relationship between power transmission voltage and reactive current in the same embodiment.
3 and 4 are block diagrams showing an example of the reference value correction circuit applied to FIG. 1, and FIG. 5 is a block diagram showing the conceptual basic configuration of a conventional excitation control device for a synchronous machine. FIG. 6 and FIG. 7 are a system configuration diagram for explaining the effects of the device and a characteristic diagram showing the relationship between power and voltage at the load end. 1...Synchronous machine, 2...Main transformer, 4...
...Instrument transformer, 5...Voltage setting device, 6...-
Automatic voltage regulator, 7... Excitation device, 8...
Field winding, 10... Voltage transformer, IOA...
Voltage detector, 11...High voltage side voltage setting device, ]2.
・・・High voltage side gain circuit, ] 4...Comprehensive arithmetic unit,
15A...Terminal voltage deviation signal circuit, 15B...
- Modified reduction gain circuit, 16... Phase compensation circuit, 17
...Output limiter, 18...Reference value correction circuit, 18
A-...Reactive current correction circuit, 18B...Reference value change correction circuit, 18C...Tap value correction circuit, 19...
・Terminal voltage limiter. Applicant's Representative Patent Attorney Takehiko Suzue #12 Ward 8B Figure 3 Figure 4 Figure 5 Figure 6 Figure Figure

Claims (2)

[Claims] (1) In a synchronous machine that is driven by a water turbine, steam turbine, or gas turbine, and whose output terminal is connected to the power transmission system via a main transformer and a breaker, detect the terminal voltage of the synchronous machine and use the detected value. an automatic voltage regulator that controls the field of the synchronous machine based on a deviation signal between the synchronous machine and a reference value; and a high-voltage side voltage detector that detects the high-voltage side voltage of the main transformer.
a high voltage side setting device for setting a reference value for the high voltage side voltage; a first correction means for correcting the reference value set by the high voltage side setting device with respect to a reactive current of the synchronous machine; a reference value correction circuit having a second correction means for correcting a reactive current fluctuation due to a correction change of the reference value by the correction means; and a detection value detected by the high voltage side voltage detector and setting in the high voltage side setting device. the automatic voltage regulator; A modified reduction gain circuit that multiplies the input deviation signal by a gain (1 - automatic voltage regulator gain reduction rate β), and a signal obtained by subtracting the output signal of the modified reduction gain circuit from the output signal of the high voltage side gain circuit. A phase compensation circuit that performs delay compensation so as to reduce the input transient gain in a predetermined frequency region, and an addition means that adds the output signal of the phase compensation circuit to the deviation signal that is input to the automatic voltage regulator. An excitation control device for a synchronous machine characterized by the following. (2) In a synchronous machine that is driven by a water turbine, steam turbine, or gas turbine, and whose output terminal is connected to the power transmission system via a main transformer and breaker that has an on-load tap changer or an on-load voltage regulator. , an automatic voltage regulator that detects the terminal voltage of the synchronous machine and controls the field of the synchronous machine based on a deviation signal between the detected value and a reference value; and a high-voltage side voltage that detects the high-voltage side voltage of the main transformer. a detector; a high voltage side setting device that sets a reference value for the high voltage side voltage;
a third correction means for correcting the reference value set by the high-voltage side setter in accordance with a tap change of the main transformer; and a reactive current fluctuation due to the correction change of the reference value by the third correction means. a reference value correction circuit having a second correction means for correcting a second correction means; a high voltage side gain circuit that multiplies a deviation signal from the signal obtained by adding the outputs of the correcting means and the third correcting means by a high voltage side gain; A modified reduction gain circuit that multiplies a gain reduction rate β) and a signal obtained by subtracting the output signal of the modified reduction gain circuit from the output signal of the high voltage side gain circuit are input so that the transient gain for a predetermined frequency region is reduced. 1. An excitation control device for a synchronous machine, comprising: a phase compensation circuit for compensating for delays; and addition means for adding an output signal of the phase compensation circuit to a deviation signal input to the automatic voltage regulator.