JPS602100A - Excitation controller of generator - Google Patents

Abstract

PURPOSE:To reduce the capacity of a pulse amplifier and its power source by applying a narrow pulse obtained by logically calculating from the 120 deg. wide width pulse from a pulse phase shifter and an AC input voltage of a thyristor converter as a gate signal of the thyristor converter. CONSTITUTION:A pulse phase shifter 17 outputs 120 deg. wide width pulse signals GUP1-GWN1 in response to the deviation between the generator voltage and the voltage value. The logic product of the signals GUP1-GWN1 and the thyristor converter input voltages DUP-DWN from a thyristor forward voltage detector 30 is taken, narrow width pulse signals GUP-GWN synchronized with the rise of the logic product output signal are obtained by a pulse forming circuit 50, and the signals GUP-GWN are outputted as a gate signals of the thyristors UP-WN of the converter 4.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an excitation control device for a generator that controls the generated voltage of a generator. Generator excitation control that enables the thyristor to be reliably ignited with a narrow pulse even if the overlapping angle during commutation of the thyristor converter becomes 60° or more due to a system fault. Regarding equipment.

[Background of the invention]

The configuration of a conventional generator excitation control device is shown in FIG. In the figure, the field winding 2 of the generator 1 is excited from a three-phase full-wave thyristor converter 4, and the power source U of the thyristor converter 4
, V, and W are supplied through an excitation power transformer 3, and the third primary winding of the transformer is connected to the armature of the generator. The output of the generator is generally connected to a main transformer 6 which, after boosting the voltage, is connected via a line breaker 7 to a power transmission line 10.11. A power transmission line breaker 8.9 is connected to each power transmission line 10.11. For example, if a ground fault or the like occurs at one point on the power transmission line 11, the breaker 9 is opened by a protective relay (not shown) to disconnect the faulty line, and the generator is connected via the power transmission line 10. Continue driving.

In this way, a three-phase ground fault (short circuit) occurs on the high voltage side of the main transformer.
Even if an accident occurs, it is necessary for the generator to continue operating without stopping, but the problems in this case are described below. 3 at the nearest end of the main transformer 6, such as point F of the transmission line 11.
Generator terminal voltage V when a phase-to-ground fault (short circuit) accident occurs
The changes in a and field current IP will be explained with reference to FIG. When a three-phase ground fault occurs at time 11 at point F of the power transmission line, the generator terminal voltage Vo instantly drops to a voltage determined by the impedance of the main transformer 6 and the internal impedance of the generator. Since the impedance of the main transformer 6 is generally about 10% to 15% and the transient impedance of the generator is about 20% to 30%, the generator terminal voltage V
c is approximately 30% of the rated voltage. Also, at this time, the armature current of the generator becomes several times the rated current due to the short circuit, and as is well known, a transient direct current is induced in the field winding due to the armature reaction of the generator, resulting in field current IP, that is, si risk. The output current of the converter 4 is about 3 to 4 times the rated field current. When the circuit breaker 9 is opened at time tio, the fault point F is disconnected, and the generator terminal voltage Vc and the field current IP return to approximately the values before the fault.

The gate control of the Cyrisk converter 4 during this accident period is as follows. In FIG. 1, the generator terminal voltage is detected by the PT 12, converted to DC by the rectifier 13, the deviation from the voltage setting value 15 is detected by the adder 14, and the amplifier 1
6 controls the amplification pulse phase shifter 17. The pulse phase shifter 17 provides a phase-controlled gate pulse to the Cyrisk converter 4 in accordance with the output of the amplifier 16 via the wide pulse amplifier 18 . The synchronous power source of this pulse phase shifter 17 is better than PT12 since it is affected by waveform distortion due to commutation of the thyristor when taken from the secondary side of the excitation power transformer 3. By the way, as mentioned above, when the generator voltage Vo drops significantly due to a ground fault in the power transmission line, the output of the amplifier 16 outputs the maximum increase signal, and accordingly the firing pulse phase angle α of the pulse phase shifter 17 is minimized. The output voltage of the thyristor converter 4 is maximized. The firing angle α of the thyristor during normal operation is about 60°, but in the event of a system accident, it becomes close to zero. This operation will be explained in more detail with reference to FIG. 3, taking as an example the case of a ground fault in three lines of the system. In the figure, the input voltage of the thyristor converter 4 is the voltage of each phase of U, V, and W (dotted line), and the commutation history of thyrisk is shown by the dotted line and thick line, and the gate signal G u p = G
w N is the thyristor converter each arm thyristor U p
"-W N.i,,i,,L are the input currents of the thyristor converter 4.If a system ground fault occurs at time 11, the voltages of each phase U, V, W are approximately 30 % and the current in the Sirisk converter i,,ia,i.

increases due to the ground fault current flowing through the generator. When the gate signal of thyristor WN is output at time t2, commutation from thyristor VN to WN is started, and current ii begins to decrease while current iv begins to increase. However, the AC voltage is 30
% and the current has tripled, the overlap angle increases and commutation continues at time 16 cm. During this commutation period, the next firing signal Gvp appears at time t3, but the thyristor Vp
In this case, star 2 is not fired until time t4. Since the thyristor Vp is turned on from time t4, the current]. begins to decrease, and at the same time, the current 17 tries to increase as shown by the dotted line A. However, at this time, since a negative current is still flowing through 17 as shown by the dotted line, Iv between time points t4 and t8 changes as shown by the solid line C, and at time t5, the thyristor VN is turned off, and the thyristor VN The commutation from to thyristor WN ends.

Similarly, the commutation from Up to Vp continues until time t9, during which time the next ignition signal GJN occurs at time t6.

However, since no forward voltage is applied to the thyristor UN, the time t
Commutation is not started until 7.

The commutation is carried out in the same way, but because the overlap angle becomes large in this way, even if a gate signal is issued, the cyrisk is not fired immediately, so conventionally it was necessary to use a wide pulse of 120° width as the gate signal. Ta.

However, in the wide pulse drive method, the output capacity of the pulse amplifier 18 is several tens of times larger than that of the narrow pulse drive method, so the capacity of the pulse amplifier 18 is also several tens of times larger, and the capacity of its power supply is also several tens of times larger. It doubles and bites. When the single machine capacity of a 1E machine reaches the 10,100 O class, the pulse amplifier accounts for about 60% of the entire control device, so a wide pulse drive system has the drawback of significantly increasing costs.

[Purpose of the invention]

The purpose of the present invention is to eliminate the disadvantages of conventional wide pulses and large capacity pulse amplifiers for driving, and to enable reliable firing control of the thyristor even when the commutation angle is large. An object of the present invention is to provide an excitation control device for a narrow pulse drive type generator.

[Summary of the invention]

The present invention detects the forward voltage period applied to each arm thyristor from the AC input voltage of the thyristor converter, and performs the logical product of the detected signal and a 120° wide pulse of the control delay angle calculated by voltage control, etc. The present invention is characterized in that a narrow width pulse is generated in synchronization with the rise of the AND signal and used as a gate signal.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to FIGS. 4 to 7. FIG. 4 shows an overall configuration diagram of an embodiment of the excitation control device for a generator according to the present invention.
The 0° wide-medium pulse output and the AC input voltage of the thyristor converter 4 obtained via the isolation transformer 19 are applied to the gate pulse logic circuit 20, which converts them into narrow-width pulses and converts them into narrow-width pulse amplifiers. 21, the pulse is amplified and used as a gate signal for the Cyrisk converter. Gate pulse logic circuit 2
The details of 0 are shown in FIG. In the figure, pulse phase shifter 17
A 120° wide pulse signal Gu p whose phase is controlled by
1~GWNI and the output signal Dop=DWN of the Cyrisk forward voltage detection circuit 30 are applied to the AND circuits 41UP~41WN of the gate pulse output logic circuit 40, and the AND of each gate signal is performed, resulting in an AND output signal. The one-shot multi-circuit 51UP to 51WN of the pulse shaping circuit 50
As a result, narrow pulse signals GσP to GIFN synchronized with the rise of the AND output signal are obtained. The thyristor forward voltage application detection circuit 30 includes line voltage detectors 31U, 31V, 31W, and line voltage detectors 31U, 31V, 31W of the thyristor converter input voltage U-W,
:b Ch.f Comparators 32U to 32W detect that the applied iris forward voltage is positive. Consists of inverters 33U, 33V, and 33'W that detect the application of the thyristor forward voltage on the N side of the thyristor converter. .

Figure 6 shows the operation at the time of a system fault, and shows the operation at time t.
If a system fault occurs at No. 1, the voltage of each phase will drop to about 30%, as in the case of FIG. Here, thyristor Up
The case where the current is commutated from Vp to Vp will be explained. Assume that the generator terminal voltage has significantly decreased by about 30% due to a system fault, and the Sibars phase shifter output Gvpl is output at time t3 when the V-phase voltage becomes positive, that is, at a firing delay angle of zero. However, during the period from time t3 to t4, thyristors VN and W
N is during the commutation period, and the line voltage V-U is negative, that is, no forward voltage is applied to the thyristor Up. Therefore, since the thyristor forward voltage application signal D v p is not output during this period, the phase shifter output Gvp+ and the signal Dv
There is also no thyristor gate signal GVP which is the output of the AND of p. At time t4, a forward voltage begins to be applied to the thyristor Vp. For this reason, the line voltage V-U changes from negative to positive, and the output of the sisilisk forward voltage application detection signal DVP is output, so the AND of this DVP and the pulse phase shifter output signal GVPI is output, and the internal pulse shaping circuit 5o is output. The one-shot multi-circuit 51VP operates and the thyristor gate signal GV
P is output and given to thyristor Vp as a gate signal. At the same time as the thyristor Vp is fired, the thyristor converter input line voltage V-U becomes zero, so the thyristor forward voltage application detection circuit DVP also becomes zero, but this is due to the fact that the thyristor Vp has already been fired by the thyristor gate signal GVP. There's nothing wrong with that. FIG. 7 shows enlarged waveforms of various parts when the thyristor 2 described above is fired. At time t4, the forward voltage is applied to the thyristor Vp, so the forward voltage detection signal DVP rises from zero, and the pulse shaping circuit output GVP is output. When the thyristor fires at time t41, the DVP becomes zero, but the pulse shaping circuit 5o
The thyristor gate signal GVP is applied until time t42 by the operation of the one/yacht pulse circuit 51VP in the thyristor, ensuring a sufficient pulse width necessary for ignition of the thyristor.

The pulse width of this gate signal GVP is usually Q, 3 m.
The width of the gate signal can be reduced to about 1/20 according to the present invention, whereas the conventional 120° wide pulse has a width of as much as 6.7 m5 (50 Hz). This greatly contributes to reducing the cost of the pulse amplifier and, therefore, the cost of the entire device.

〔Effect of the invention〕

According to the present invention, since the thyristor can be ignited by a narrow pulse regardless of the commutation mode of the thyristor, the capacity of the pulse amplifier and its power supply device can be greatly reduced.
The present invention has the advantage of being able to provide an excitation control device that is extremely inexpensive and can reliably fire the thyristor. Furthermore, by using a narrow width pulse, a commonly used and inexpensive narrow width pulse amplifier can be used, and the pulse amplifier can be standardized.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a conventional generator excitation control device, Fig. 2 is an explanatory diagram of the generator voltage and field current in the event of a grid fault, and Fig. 3 is an explanation of the operation of the thyristor converter in the event of a conventional grid fault. 4 is a block diagram showing an embodiment of the generator excitation control device of the present invention, FIG. 5 is a block diagram showing an example of the configuration of the gate pulse logic circuit in FIG. 4, and FIGS. The figure is an explanatory diagram of the operation of the thyristor converter in the event of a system fault according to the present invention. 1... Generator, 2... Field winding, 4... Cyrisk conversion Ill device, 17... Pulse phase shifter, 20...
・Ketno (Russ logic circuit, 21... Narrow width pulse amplifier, 30... Thyristor forward voltage detection circuit, 40...
Gate pulse output logic circuit, 50... pulse shaping circuit. Agent Patent Attorney Masami Akimoto 1st Country 3m 50th 60th 50&tJI ,,::,-111+'--竿q因(iv ゛P S9□

Claims (1)

[Claims] 1. A wide pulse having a phase corresponding to the deviation between the output AC voltage of the generator to which the excitation current is supplied to the thyristor converter and its set voltage is output to each thyristor element of each arm of the thyristor converter. pulse phase shifting means;
The point in time when the input AC voltage to each of the thyristor elements is applied in the forward direction is detected, and if the wide pulse corresponding to that point is on, the wide pulse also outputs a narrow pulse. 1. An excitation control device for excitation bales, comprising: gate pulse generating means; and amplifying means for amplifying the narrow-width Hals and applying it to the corresponding thyristor element.