JP2809833B2 - Excitation controller for synchronous machine - Google Patents

Description

The present invention relates to an excitation control device for a synchronous machine, and more 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 the reactive power so that the terminal voltage becomes a predetermined set value. Therefore, when the system voltage drops due to an increase in demand or the like, the reactive power generated by the synchronous machine increases according to the gradient of the system voltage and the output voltage of the generator. It can be said that the reactive power is not fully output up to the rated value, and that it still has a sufficient margin.

Therefore, recently, an excitation control device (for example, "a voltage stability of a large-scale power system An improved new generator excitation method (PSVR) (Part 1 principle) has been proposed.

FIG. 5 shows a conceptual basic configuration of such an excitation control device. In FIG. 5, reference numeral 1 denotes a synchronous machine driven by a water turbine, a steam turbine, or a gas turbine. The output terminal of the synchronous machine 1 is connected to a transmission line 3B via a main transformer 2 and a circuit breaker 3A. The circuit is configured. In the main circuit having such a configuration, the output terminal voltage (VG) of the synchronous machine 1 is detected by the instrument transformer (PT) 4 and the detected voltage value is compared with the reference value set in the voltage setting device 5. And
The deviation signal is input to the reduction gain circuit 13. On the other hand, the voltage VH of the power transmission bus 9 of the power plant is detected by a voltage transformer (PD or PT) 10, and the detected voltage is compared with a reference value set by a high-voltage side voltage setting device 11. Is multiplied by a gain in a high-voltage side gain circuit 12, which is added to the output of the above-described reduced gain circuit 13 and input to an automatic voltage regulator 6 (hereinafter simply referred to as AVR). The AVR 6 controls the exciting device 7 in accordance with the added value, and controls the exciting 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 X _T , the reference value of the voltage setting device 5 is r _G , the reference value of the high voltage side voltage setting device 11 is r _H , and the synchronous machine 1 is invalid. Current
I _q , the gain of the high-side gain circuit 12 is k _H , and the reduced gain circuit
Assuming that the gain of 13 is β (0 ≦ β ≦ 1), the high-voltage side (V _H ) of the main transformer 2 controlled by the excitation control device shown in FIG.
Is approximately expressed by the following equation.

For _{V H = n (βr G +} k H r H) / (β + nk H) -nβX T I q / (β + nk H) ... (1) hereinafter simplified, the tap ratio is treated as n = 1,
The following equation is obtained.

_{V H = (βr G + k} H r H) / (β + k H) -βX T I q / (β + k H) ... (2) (2) equivalent reference value from the equation the first term on the right side, and the voltage droop characteristic Is given by the second term on the right side.

Here, when the reduced gain β is not only set in the voltage droop characteristic but is simply input to the AVR 6 without the reduced gain circuit 13 (β = 1), the gain becomes large, and disturbance in the system such as a power line accident occurs. When added, the damping of the power fluctuation is reduced, so that it also serves to prevent the reduction of the damping.

The operation of such a conventional apparatus will be considered with respect to a one-to-one load system model shown in FIG. That is, in FIG.
Active power P synchronous motor 21 at the load end bus 24 connected via a main transformer reactance X _T 22 and transmission line reactance X _e 23, reactive power Q, the characteristics of the voltage V _r becomes the following equation.

P ² + {Q + V _r ² / (kXT + X _e )} ² = {V _g · V _r / (kXT + X _e )} ² (3) where k is β / (β + k _H ). V _g represents an equivalent synchronous machine voltage.

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

In the PV curve of FIG. 7, the voltage at the maximum point of the load power P is called a nose tip voltage. In this conventional device, the value of k is reduced, that is, the amount of compensation for the reactance of the main transformer is increased. By doing so, the maximum value of the load power can be increased and the nose tip voltage can be reduced. This means that when a power capacitor (SC) is installed at the load end, the voltage at the tip of the nose tends to rise, and in extreme cases, it will reach the normal operating voltage range, and stable operation can be maintained. However, this has the same effect as installing or adding new transmission lines, indicating that voltage stability can be greatly improved.

(Problems to be Solved by the Invention) However, in the conventional device described above, the terminal voltage of the synchronous machine 1 in FIG. 5 is changed from the high voltage side of the main transformer 2 to the voltage reference value (r _G ) in the control of the AVR 6 alone. In order to keep the terminal voltage of the synchronous machine within an allowable value, an output limiter (not shown) is provided in an output circuit from the high voltage side. For this reason, at the time of a large disturbance such as a transmission line accident, the gain is reduced, and the transient response capability is reduced.

The high voltage reference value r _{H for operation} is specified as a target value. However, since r _H does not always coincide with the high voltage V _H as shown in equation (2), operation and management are performed. I am not satisfied with the above.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an excitation control device for a synchronous machine that has excellent voltage controllability and can excite and control a synchronous machine without impairing transient response and stability.

[Effects of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention is driven by a water turbine, a steam turbine, or a gas turbine, and an output terminal is connected via a main transformer and a circuit breaker. In a synchronous machine connected to a power transmission system, an automatic voltage regulator that detects a terminal voltage of the synchronous machine, controls a field of the synchronous machine by a deviation signal between the detected value and a reference value, and the main transformer A high-side voltage detector that detects a high-side voltage, a high-side setting device that sets a reference value for the high-side voltage, and a reference value set by the high-side setting device, with respect to the reactive current of the synchronous machine. A reference value correction circuit having first correction means for correcting the reference current value, and a second correction means for correcting the reactive current fluctuation caused by the correction change of the reference value by the first correction means; and the high voltage side voltage detector. Detected A high voltage that multiplies a high voltage gain by a deviation signal between the detected value and a signal obtained by adding the output 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 setting device. Side gain circuit,
The deviation signal input to the automatic voltage regulator has a gain (1
A corrected reduction gain circuit for multiplying the automatic voltage regulator gain reduction rate β), and a signal obtained by subtracting the output signal of the corrected reduction gain circuit from the output signal of the high voltage side gain circuit, and a transient gain for a predetermined frequency region And a adding means for adding an output signal of the phase compensation circuit to a deviation signal input to the automatic voltage regulator.

Further, in the above configuration, when the main transformer has a load tap changer or a load voltage regulator, a reference value set by a high voltage side setting device instead of the reference correction circuit is used as the main transformer. A third correction means for correcting in response to the tap change of the reference value and a reference value correction circuit having a second correction means for correcting a reactive current variation caused by the correction change of the reference value by the third correction means; The output of the second and third correction means of this reference value correction circuit is added to the reference value.

(Operation) In the excitation control device for a synchronous machine having such a configuration,
Even in the event of a large disturbance such as a power line accident, the terminal voltage deviation signal is input to the automatic voltage regulator as it is, so the gain of the automatic voltage regulator is not reduced, maintaining the same transient response capability as before and exerting it. Can be done. Also, in the steady state, the high voltage side loop can perform its original function with respect to the deviation signal between the high voltage side voltage detection value and the reference value, so if the synchronous machine has a margin for generating reactive power, when the system voltage drops, It is possible to actively generate reactive power.

Further, as shown in the above equation (1) (or equation (2)), the high voltage (V _H ) and the high voltage reference value (r _H ) of the main transformer are obtained.
When the voltage droop characteristic is fixed, i.e., k _H
When fixing the β and mainly the tap ratio n of the reactive current I _q and the main transformer of the synchronous machine depends on the reactance X _T, the first and third correction means or the second and third correction means, Is provided, it becomes possible to make the high voltage (V _H ) as close as possible to the high voltage reference value (r _H ), and the operation and management of the system including the synchronous machine can be facilitated.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration example of an entire excitation control device for a synchronous machine according to the present invention, and the same parts as those in FIG. In FIG. 1, the output voltage (V _G ) of the synchronous machine 1 is detected by an instrument transformer 4, the detected voltage value is compared with a reference value (r _G ) set in a voltage setting device 5, and a deviation thereof is obtained. The signal (ΔV _G ) is input to the AVR 6 through the terminal voltage signal circuit 15A. The AVR 6 controls the exciting device 7 according to the deviation signal (ΔV _G ), and controls the exciting current supplied to the field winding 8 of the synchronous machine 1. On the other hand, a voltage transformer (PD or PT) 10 connected to the power plant bus 9 detects the power transmission voltage V _H of the power plant, and inputs the detected voltage value V _H to the general arithmetic unit 14. This complex arithmetic unit 14, a voltage transformer (PD or PT) the average value of the effective value line voltage of the three-phase fundamental wave by the detected voltage detected value V _H by 10 high precision, and voltage detection to detect at high speed 10A and a high voltage side voltage setting device such as a program type that can set the time and voltage according to the system voltage status
11, the output signal of the voltage detector 10A and the high voltage side voltage setting device 11
Is compared with a reference value r _H set to the high-voltage side gain circuit 12 for multiplying the deviation signal by a gain k _H , and the deviation signal (Δ
V _G ), and multiplies the gain (1−β) by a correction reduction gain circuit 15B; and subtracts the output signal of the correction reduction gain circuit 15B from the output signal of the high-voltage side gain circuit 12 and inputs the difference signal. a phase compensation circuit 16, and an output limiter 17 to input summing to the AVR6 the deviation signal of the phase compensation terminal voltage described above the output signal of the circuit 16 the error signal circuit 15A (ΔV _G).

In this case, the output of the general arithmetic unit 14 is added to the deviation signal (ΔV _G ) via an interlock contact 14A for protecting the signal due to plant operating conditions, abnormal conditions inside the general arithmetic unit 14, and the like. Has become. Moreover, overall operation device 14 the reference value correction circuit 18 as a voltage detection value V _H at the time of actual operation to the set reference value r _H to the high voltage side voltage setter 11 approaches more provided, the reference value and the output signal It is to Yo added to the r _H. Further, the terminal voltage limiter 19 in which the voltage detection value V _G is input so that the output voltage V _G of the overall computing device 14 to the synchronous machine 1 is within the allowable range is provided, the output signal of the terminal voltage limiter 19 The output is subtracted from the output of the phase correction circuit 16.

This example shows a case where the output of the system stabilization 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 the time of large disturbance such as power transmission line fault, also significantly reduced the terminal voltage V _G of the synchronous machine 1. The conventional apparatus mainly AVR6 transient stress capability of also functions such maintain the transient stability of the grid, and to improve and increase the suppression of V _G at full load cutoff.

The terminal voltage deviation signal circuit 15A in this embodiment is to maintain the above function. Therefore, the reduced gain circuit 13 in FIG.
The gain of the terminal voltage deviation signal circuit 15A is subtracted from the output signal of the high-voltage side gain circuit 12 assuming that the gain of 15B is (1-β).
5 is input to the AVR 6, so that the reduced gain β shown in FIG. 5 is constantly obtained, which does not impair the characteristics of the conventional device.

Also, the subtraction point of the correction reduction gain circuit 15 is located after the high voltage side gain circuit 12 and before the phase compensation circuit 16, but this is based on the analysis result of the system stability including the phase compensation circuit 16 and the braking effect on power fluctuation. (Damping characteristics). Here, the gain of the system stabilization device 20 is K _P
Then, since the output of the transient stabilization device 20 is added to the deviation detection unit of the AVR 6, when the input of the detection unit is converted, its gain is equivalently reduced to K _P / (K _H + β). The phase compensation circuit 16 performs delay compensation so as to reduce the transient gain in a frequency region equal to or longer than the time constant of a change detection circuit (signal reset) (not shown) in the system stabilization device 20. It has the same effect as 20. Further, the phase compensation circuit 16 has the effect of improving the stability of the closed loop control at the same time.

By the way, in the conventional device, the relationship between the transmission voltage (V _H ) and the high-voltage side reference value (r _H ) is expressed by the equation (1) (or the equation (2)). When the reactive current _Iq increases due to the voltage droop characteristic,
Since the V _H is lowered, no longer consistent with the r _H. This relationship is shown as a characteristic (0) in FIG. FIG. 3 shows an example of the reference value correction circuit 18 for correcting this.
In this figure, a reactive power correction circuit 18A is a first correction means for making V _H equal to r _H for a certain reference reactive current I _{q0. From} equation (1), the correction value r _Q is given by Given.

r _Q = β / K _H {X _T I _q0 + (r _H / n−r _G )} (4) By adding this correction value r _Q to r _H , the following equation is given.

V _H = shown as _{(r H -nβX T) (I} q -I q0) / (β + nK H) ... (5) characteristics of this relationship in FIG. 2 (1).

However, this correction value r _Q is effective only on the high pressure side.
Reference value for example r _HO, since the corresponding one l _q0, if you change the reference value r _HO from this state now varies in accordance with the reactive current is also line conditions, new reference values
r _H ′ and transmission voltage V _H ′ do not match. Therefore, the reference value change correction circuit 18B is a second correction means for changing the reference value r _HO to r _H ′ so that the transmission voltage V _H becomes equal to the reference value r _H ′. From the change (ΔI _q0 ) and the equation (5), the correction value r _D is as follows.

_{r D = nβX T · I q0} / (β + nK H) = nβX T · α (r H '-r H) / (β + nK H) ... (6) where, alpha is a coefficient for setting the reactive power changes.
By adding this correction value r _D to r _H ′, the following equation is given from the equation (5).

_{V H = r H '-nβX T} (I q -I q0 -ΔI q0) / (β + nK H) ... (7) shows a characteristic (2) the relationship in Figure 2. The characteristic (2 ') shows the characteristics with respect to changes of the reference value r _HO when no correction value r _D, new reference values r _H' hand, the transmission voltage V _H is invalid current change (~ ΔI _q0 ).

Said first and second correction means than the above added as FIG. 3, the reference value correction circuit 18, by adding to r _H, transmission voltage V _H is achieved closer to the reference value r _H , Operation and management can be facilitated.

By the way, when the system voltage is significantly reduced due to an accidental stop of a part of the transmission line or the like, the generated reactive power is also restricted by the operation upper limit of the terminal voltage of the synchronous machine 1. Therefore, in order to expand the operation range of the control device according to the present invention, the main transformer 2 is provided with a load tap switch (LTC) or a load voltage regulator (LVR), and the output voltage of the synchronous machine 1 is allowed to operate. If the value exceeds the value, for example, a cooperative control method with the LTC may be considered in which the tap value of the LTC is increased and the reactive power generated by the synchronous machine 1 is increased to maintain the transmission voltage. However, even when the tap ratio n of the LTC is changed, in order to appropriately perform the reactive power distribution between adjacent synchronous machines,
The above-described voltage droop characteristics need to be unchanged. As described above, when the main transformer 2 has an LTC or an LVR, the tap correction value circuit 18 as shown in the configuration example of FIG.
C is instead first correction means, (4) in the third correction means automatically corrects the combined value of the main transformer 2 reactance X _T and the tap ratio n to the operation value of the LTC in the equation, the transmission the voltage V _H (5) it is possible to apply the same type. In other words, the correction value r _T becomes the following equation.

r _T = β / K _H ｛X _T ^* I _q0 + (r _H / n ^* -r _G )｝ (8) where X _T ^* and n ^* indicate that they change in conjunction with the LTC operation value .

The voltage droop characteristic is similarly given by using _XT ^* and n ^* from the two terms on the right side of the equation (5), but it is confirmed from the calculation that the voltage droop characteristic hardly changes even if the tap ratio n is changed. This is equivalent to the characteristic (1) in FIG.

As described above, when the 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 is obtained.

Note that among the variables used for the correction values r _Q , r _D , and r _T , that is, n of the variables on the right side of the equations (4), (6), and (8)
^* Only those are taken into overall arithmetic unit 14 as an external ^signal, X _T ^*, α, is like other variables beta, all overall computing device 14
This is a value set inside.

In the above description, the general arithmetic device 14 may be an analog device or a digital device, and may perform arithmetic processing by software. However, it is effective to use a digital device in terms of signal processing such as control accuracy, coordination between adjacent devices, signal storage, and interlocking with external signals.

Therefore, in FIG. 1, although the internal circuit of the general arithmetic unit 14 is represented as a block diagram, the function of the present invention can be easily understood.

In addition, the circuit configuration of the general processing unit 14 is divided so as to be effective in adding the present control device to the excitation device of the existing plant.For example, the correction reduction gain circuit 15B is configured in the conventional circuit on the AVR side. It is also possible to do so without departing from the scope of the control device.

According to the present invention as above described [Effect of the Invention], enter the deviation signal [Delta] V _G between the terminal voltage and the reference value of the synchronous machine to the automatic voltage regulator,
From a signal obtained by multiplying the high-pressure-side gain deviation signal [Delta] V _H of the high-side voltage and the reference value of the main transformer, supplied to a phase compensation circuit subtracts multiplied by the [Delta] V _G (1-reduction gain beta), an output Is added to the deviation signal ΔV _G and input to the automatic voltage regulator, so that even in the event of a large disturbance such as a transmission line accident, the transient response capability equivalent to that of a conventional automatic voltage regulator is maintained, The original function of the loop can be exhibited.

[Brief description of the drawings]

FIG. 1 is a block diagram of an overall configuration showing an embodiment of an excitation control device for a synchronous machine according to the present invention. FIG. 2 is a conceptual characteristic diagram showing a relationship between a transmission voltage and a reactive current in the embodiment.
3 and 4 are block diagrams showing an example of a reference value correction circuit applied to FIG. 1, FIG. 5 is a block diagram showing a conceptual basic configuration of a conventional excitation control device for a synchronous machine, 6 and 7 are a system configuration diagram for explaining the effect 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: Exciting device, 8: Field winding, 10: Voltage transformer, 10A: Voltage detector, 11: High voltage setting , 12 high voltage side gain circuit, 14 total operation device, 15A terminal voltage deviation signal circuit, 15B correction reduced gain circuit, 16 phase compensation circuit, 17 output limiter, 18 ... Reference value correction circuit, 18A
…… Reactive current correction circuit, 18B …… Reference value change correction circuit, 1
8C: Tap value correction circuit, 19: Terminal voltage limiter.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shizuo Oshima 1-1-1, Shibaura, Minato-ku, Tokyo Inside the Toshiba head office (72) Inventor Naganori Onizuka 1 Toshiba-cho, Fuchu-shi, Tokyo Higashi Corporation Inside Shiba Fuchu Plant (72) Inventor Satoshi Kitamura 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Inside Omika Plant, Hitachi, Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) H02P 9/00 -9/48

Claims (2)

(57) [Claims] In a synchronous machine driven by a water turbine, a steam turbine, or a gas turbine and having an output terminal connected to a power transmission system via a main transformer and a circuit breaker, a terminal voltage of the synchronous machine is detected. An automatic voltage regulator for controlling a field of the synchronous machine by a deviation signal between a detected value and a reference value, a high-side voltage detector for detecting a high-side voltage of the main transformer, and a reference value for the high-side voltage , A first correction unit for correcting the reference value set by the high-side setting device with respect to the reactive current of the synchronous machine, and a correction of the reference value by the first correction unit. A reference value correction circuit having a second correction means for correcting a reactive current fluctuation due to the change; and a reference value set by the high voltage side voltage detector and a reference value set by the high voltage side setting device. Value correction circuit A high-voltage gain circuit for multiplying a high-voltage gain by a deviation signal from a signal obtained by adding the outputs of the first correction means and the second correction means, and a gain (1-automatic) for the deviation signal input to the automatic voltage regulator; A correction reduction gain circuit for multiplying by a voltage regulator gain reduction rate β), and a signal obtained by subtracting an output signal of the correction reduction gain circuit from an output signal of the high-voltage side gain circuit to reduce a transient gain for a predetermined frequency region. And a phase compensating circuit for compensating for the delay so as to compensate for the delay, and adding means for adding an output signal of the phase compensating circuit to a deviation signal input to the automatic voltage regulator. . 2. A synchronous system driven by a water turbine, a steam turbine, or a gas turbine and having an output terminal connected to a power transmission system via a main transformer and a circuit breaker having a load tap changer or a load voltage regulator. An automatic voltage regulator for detecting a terminal voltage of the synchronous machine, controlling a field of the synchronous machine by a deviation signal between the detected value and a reference value, and a high voltage for detecting a high-side voltage of the main transformer. Side voltage detector, a high side setting device for setting a reference value for the high side voltage, a reference value set by the high side setting device,
Reference value correction including third correction means for performing correction in accordance with a tap change of the main converter, and second correction means for correcting a reactive current variation caused by correction change of the reference value by the third correction means. The output of the second correction means and the third correction means of the reference value correction circuit is added to a circuit, a detection value detected by the high voltage side voltage detector, and a reference value set in the high voltage side setting device. A high-voltage gain circuit that multiplies a deviation signal from the signal by a high-voltage gain; and a correction reduction gain circuit that multiplies the deviation signal input to the automatic voltage regulator by a gain (1−a reduction rate β of the automatic voltage regulator gain). A phase compensation circuit for receiving a signal obtained by subtracting the output signal of the modified reduction gain circuit from the output signal of the high-side gain circuit and delay-compensating the transient gain in a predetermined frequency region to reduce the gain; Excitation control apparatus of a synchronous machine, characterized in that an adding means for adding the deviation signal inputted an output signal of the phase compensation circuit to the automatic voltage regulator.