JPH0136356B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an excitation control device for rotating equipment such as a generator.

An example of a conventional device of this type is shown in FIG. 1 is
This generator has a field coil 2, and an automatic voltage regulator (hereinafter referred to as AVR) 4 is connected to the output side of the generator via an instrument transformer 3. on the other hand,
6 detects the field current with a shunt, amplifies it to a predetermined voltage value with an isolation amplifier 7, and supplies it to a deviation detector 8. This deviation detector 8 compares the detected value with the setting value of the rated field current setting device 5 that sets the allowable field current value that can be continuously energized, obtains a deviation signal, and obtains a deviation signal from the deviation amplification circuit 9. After amplifying the signal to a predetermined level via the AVR 4, the signal is supplied to the signal mixing section of the AVR4. AVR
4 controls the generator voltage to be constant by increasing or decreasing the value of the field current based on the output of the generator and the deviation signal.

In other words, the maximum current of the field coil of the generator is determined based on the relationship with the temperature rise of the generator.
Set the maximum current that can be continuously applied using the field current setting device 5 above.
When the field current exceeds this value, the deviation detector 8 generates a signal proportional to the excess current based on the detection signal of the shunt 6 to limit the field current. Supplied to AVR4 from. Of course, when the field current is below the allowable value, the signal mixing section is designed to prevent the overexcitation limit signal, which is the deviation between the detected value and the set value, from interfering with the AVR 4.

Therefore, AVR4 normally controls the generator voltage to be constant, but when the field current exceeds the allowable value, it limits the field current to prevent overexcitation and prevents the generator temperature from rising. prevent and protect the generator.

As described above, the conventional excitation control device is designed to limit the field current that can be continuously supplied. Therefore, when an accident occurs in the grid and its voltage drops, the AVR 4 generates a magnetizing output to increase the field current and restore the grid voltage. When looking at the output transiently, it had the drawback of limiting the field current to 100%, which is a comfortable margin.

In other words, although the allowable overexcitation time of the generator becomes shorter as the field current increases, as is clear from the characteristic graph in Figure 2, there is no problem even if the current flows up to the allowable temperature rise limit of the insulation. If an accident occurs, the busbar protection relay etc. will operate for a certain period of time (several seconds).
Later, the faulty busbar will be isolated and grid voltage will be restored. For this reason, it is not necessary to limit overexcitation by continuous energization even during short-time faults such as the above-mentioned system faults, and this has the disadvantage that the voltage control characteristics at the time of system faults are negated.

This invention was made to eliminate the above-mentioned drawbacks, and when the field current of the rotating machine exceeds 100% of the allowable value for continuous energization, the field current is proportional to the magnitude of the field current. If the predetermined time limit is not reached, the overexcitation limit is not applied, and when necessary, the AVR 4 is allowed to fully immerse to the maximum value. On the other hand, when the time limit that is inversely proportional to the magnitude of the field current is reached, the overexcitation limit is used to limit the continuous current to 100%, which improves the stability of the voltage control function in the event of a system fault. It is an object of the present invention to provide an excitation control device for a rotating machine in which shock during supply is reduced by making the overexcitation limit signal supplied into a stepped signal.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

First, in FIG. 3, numerals 1 to 9 are exactly the same as the conventional ones described above. 10 is a field current detector serving as a control circuit for controlling the operation of the integrating circuit described later, and 100 of the rated field current setting circuit 5 described above.
The relay 11 is energized upon detecting that the detection value of the isolation amplifier 7 has become larger than the % field current (rated).

On the other hand, 12 is a voltage dividing resistor, the output of which is amplified by K times via an operational amplifier 13 and then input to an operational amplifier 14 where it is squared. Operational amplifier 14
The squared output of is supplied to the adder circuit 18.

On the other hand, 15 is an operational amplifier that squares a signal corresponding to the actual field current supplied via the isolation amplifier 7, and its output is supplied to the subtracter 16. A voltage equal to the square value of the rated field current set by the base quantity setting device 17 is supplied to the subtracter 16 . Then, the subtracter 16 converts the operational amplifier 15
The output of the base amount setter 17 is subtracted from the output value of the base amount setter 17, and the output is supplied to the addition circuit 18. This subtraction output is expressed by the following equation.

[Output] = I ² -1 ... (1) However, I: field current 1.0 = 100%.

The output of the adder circuit 18 is supplied to an operational amplifier 21 via an input resistor 19. Operational amplifier 21
The input resistor 19 and the capacitor 20 constitute an integrating circuit, and the integrated output is sent to the comparator 22.
supply to. The capacitor 20 has a relay 1
No. 1 contact 11b is connected in parallel to control the integral function.

The comparator 22 inputs the set voltage of the other voltage generator 23 and the above-mentioned integral output, compares both voltages, and energizes the relay 24 when the integral output is larger. The voltage generator 23 and the relay 24 constitute a field current excess detection circuit.

Next, FIG. 5 shows the sequence of the circuit for supplying the overexcitation limit signal. In the same figure, 71, 73, and 75 are relays connected in parallel, and the relay 71 is the one described above. When the relay 11 is energized, it is energized by closing its contact 11a, and self-maintained by closing its contact 71a.
Further, when the relay 24 is energized, the relay 73 is energized by closing its contact 24a, and the contact 73 is energized.
It is self-maintained by the closure of a. Relay 75 is energized by closing its contact 24a when relay 24 is energized. 72, 74, and 76 are timers connected in parallel, and the timer 72 is operated by closing the contact 11a of the relay 11, and de-energizes the relay 71 after a predetermined time period. The timer 74 is activated by the return of the contact 24b of the relay 24,
After a predetermined time period, contact 74Tb is opened and relay 73 is activated.
is de-energized. Also, the timer 76 is connected to the relay 24
The relay 75 is activated by opening the contact 76Tb after a predetermined time limit (about a few seconds).
is de-energized.

Next, the operation of the above circuit will be explained. First, when the resistance value of the voltage dividing resistor 12 is set to zero (V), the output of the operational amplifier 14 becomes zero (V), and when the relay 11 is energized in this state, the contact 71b is opened and the integration is performed. The circuit starts working.

Now, if we insert concrete numerical values and think about it, we can set the output of isolation amplifier 7 as 1 (V) at 100%,
If the field current becomes 150%, the input to the operational amplifier 15 will be 1.5 (V). This input (detected value) is squared (1.5 x 1.5) by the operational amplifier 15 to become 2.25 (V), and subtracted by the subtracter 16 (2.25 -
1.0) and becomes 1.25 (V). This subtracted output (1.25V) is added to the output of the operational amplifier 14 in the adder circuit 18.

In addition, after adjusting the capacitor 20 and voltage generator 23 and inputting the above 1.25 (V), the relay 24 will be activated after 24 seconds.
See it working. As a result, the withstand capacity time limit T of the generator 1 can be obtained as shown in the following equation.

T = 30 / I ² -1 = 30 / (1.5) ² -1 = 30 / 2.25 - 1 = 30 / 1.25 = 24 (seconds) ... (2) Using the characteristics of the above formula, set the field current to 100 to 220 The curve [B] in FIG. 4 shows the variation up to %. This has the same characteristics as B in FIG. 2 and shows the time limit that the generator can tolerate. Normally, this time limit is sufficient, but if some time is required to limit the field current, it is necessary to detect the withstand capacity time limit of the generator several seconds before this time limit and narrow down the field current.
The arithmetic circuits 13 and 14 are designed to perform their functions.

That is, the output 1/K (V) of the voltage dividing resistor 12 is
The operational amplifier 13 amplifies the signal K times, the total gain becomes 1.0 times, and then the operational amplifier 14 squares the signal. The output of this operational amplifier 14 is
It is added together with the output of , by the adder circuit 18, resulting in a signal with characteristics as shown in FIG. 4C. As can be seen from the figure, by doing the above, the withstand capacity time limit of the generator can be detected several seconds earlier than in case B.

This can be expressed using the following formula.

T=30/(I ² -1) + (I-1) ² ...(3) Next, if the voltage dividing resistor 12 is set to the 2/K position, the total gain of the voltage dividing resistor 12 and operational amplifier 13 is , 2/K×K=2 [times], and the time limit is expressed by the following equation.

T=30/(I ² -1) + [(I-1) x 2] ² ...(4) Using this equation (4), the time limit is illustrated by varying the field current from 100% to 220%. In the case shown in FIG. 4D, the withstand capacity time limit of the generator can be detected several seconds earlier than in case C above.

In other words, when the field current does not exceed 100%,
Integrating capacitor 2 because relay 11 is not working
0 is short-circuited, the output of operational amplifier 21 does not rise, and comparator 22 does not operate.

Therefore, relay 24 is not energized and contact 2
4a remains open, relays 73 and 75 shown in FIG. Since the deviation signal supplied from the contact 75b has opposite polarity, it does not become an overexcitation limiting signal, and the AVR 4 is not limited.

Next, if the field current exceeds 100%, the overexcitation limit signal is activated at points B, C, and D in Figure 4.
It is supplied to AVR4 to limit the field current and protect the generator.

When the relay 11 is energized, the relay 71 is energized by closing its contact 11a, and then self-maintained by closing the contact 71a.

On the other hand, the relay 11 becomes inoperable and the contact 71b
When closed, the timer 72 starts operating, and after a certain period of time, the contact 72Tb opens and the relay 7
1 is inactive. That is, the relay 71 operates when the relay 11 operates, and the relay 71 operates when the relay 11 operates.
It closes after a certain period of time after becoming inoperable. The timer 72 limits the field current to less than 100% of the rated value in order to set a time limit of several tens of seconds to several minutes, and even if the magnetizing signal is input again, the relay 71 is self-held and the integral Since the output of the circuit has not been reset to zero, the relay 24 is activated immediately and contacts 73a and 75a are closed, so that overexcitation limitation begins immediately.

Therefore, if short-term overexcitation occurs repeatedly, full phasing is performed the first time, but
From the second time onwards, the generator's temperature rise is close to the limit, so full fusion is stopped and a limit is applied directly to protect the generator.

The generator voltage detection relay 33 detects whether the voltage generated by the generator is within the normal operating range, and the normal operating range is +5
% to -5%. The operating point of the detection relay 33 can be set in detail using a setting device 34, and is set to operate at +5% or more, for example.

When the generator voltage is +5% or more and the field current is more than the allowable value, the contact 33a of the relay 33 is closed and the contact 33b is open, so the deviation signal from the deviation detector 8 is used as the overexcitation limit signal. The signal is supplied to the AVR 4 via the deviation amplification circuit 9.

Note that the generator voltage detection relay 33 outputs the generator voltage detected via the AC/DC converter 31 to the comparison circuit 3.
It is compared with the reference voltage set by the voltage setter 34 in step 2 and is energized when the detected value exceeds the reference value.

Next, when the generator voltage is in the normal operating range and the grid voltage drops, full fusion occurs and the field current exceeds the allowable value, but at this time the generator voltage detection relay 33 is inactive and as described above. Relay 11 is activated, and after a time limit as shown in FIG. 4, relay 24 is activated to start overexcitation limiting.

That is, when the field current exceeds 100%, the relay 11 is operated via the field current detector 10 (the relay 71 is also operated), and the integrating capacitor 20 is activated.
is charged to increase the output of the operational amplifier 21. Then, when the output of the integrating circuit becomes higher than the set voltage of the voltage generator 23, the comparator 22 operates and energizes the relay 24. For this reason, contact 24
a closes, operating the relays 73 and 75, and then causing the relays 73 and 75 to self-hold. Therefore, the contact 75b of the relay 75 will be opened, and the contact 75a will be closed.
Furthermore, the voltage generated from the voltage transmitter 49 is voltage/
Frequency converter (hereinafter referred to as V/F converter)
50, the signal is converted into a frequency signal with a predetermined period, and is supplied via a contact 73a of a relay 73 to a counter 51, which is a step signal generating circuit. This signal is supplied as a count-up signal when contact 47a is closed, and as a count-down signal when contact 48a is closed.

However, until the relay 24 operates, the contact 73
When a is open, the output pulse of the V/F converter 50 is disconnected, and the contact 73b is closed, so it becomes a reset terminal.
A reset signal is supplied to RD. As a result, the output of the counter 51 is zero, and the output of the digital/analog converter (hereinafter referred to as D/A converter) 52 is also zero. In addition, the contact 75
a is open, contact 75b is closed, and deviation detector 8
The output of is fed to AVR4, but as above
The operation of the signal mixing section of the AVR 4 determines polarity reversal and locks the supplied signal.

Now, when the relay 24 is operated and the contact 73b is opened as described above, the reset of the counter 51 is released. And contact 73a of relay 73
When closed, a count-up signal is provided,
Count and memorize a predetermined time. And D/A
The converter 52 converts the stored number of pulses into a DC voltage signal (for example, 0 to 999 pulses to 0 to 10
(V), 10/999 for each pulse increase
It rises in steps of ≒0.01 (V).

On the other hand, the operational amplifier 44 has contacts 33b and 75b.
When the stepwise signal supplied through the step signal and the deviation detection signal supplied from the deviation detector 8 are input, and there is a difference in absolute value between these values, the positive or negative voltage detectors 45 and 46 is activated to energize either relay 47 or 48. The contacts 47a and 48a of the counter 51 are controlled thereby.

The stepwise signal is passed through the deviation amplifier 9.
It will be gradually supplied to AVR4. Therefore, the shock to the generator is reduced. After a few seconds, the output of the D/A converter 52 and the deviation detector 8
When the absolute values of the detection outputs become equal, the output of the operational amplifier 44 is zero, and the counter 51 has no input. Then, the timer 76 causes the contact 7 to
By opening 6Tb and disabling relay 75, contact 75b is closed and contact 75a is opened, so that the stepped signal generation circuit is disconnected. As a result, the overexcitation limit signal is transmitted to contact 75.
b. It is supplied to the AVR 4 via the polarity converter 53. Therefore, no limit delay occurs.

In the above embodiment, the timer 76 was used to prevent control delays from occurring, but the timer 76
can also be omitted. In that case, although a slight control delay occurs, almost the same effects as in the above embodiment can be obtained.

Although the above embodiments have been described using an excitation device without an exciter, similar effects can be achieved with an excitation device using, for example, a DC exciter or a brushless exciter. Further, the generator may be another rotating machine such as a synchronous phase modifier.

As described above, according to this invention, the energization time is set in inverse proportion to the magnitude of the field current, and an overexcited state is allowed during that time, which contributes to the voltage recovery of the system up to the limit of the rotating machine's capacity. In addition, it is possible to supply an overexcitation limit signal to a stepped signal just before the limit of the rotating machine's capacity or a predetermined time before the overload capacity, thereby limiting the field current without giving a shock to the rotating machine. Even if it takes some time to recover, the rotating machine can be more reliably protected than the overexcitation tolerance.

[Brief explanation of drawings]

Fig. 1 is a conventional block diagram, Fig. 2 is a characteristic diagram of a generator, Fig. 3 is a block diagram of an embodiment of the present invention, and Fig. 4 is a characteristic diagram explaining the operation of the same embodiment. 5 are sequence diagrams of the same embodiment. 1... Generator, 4... Automatic voltage regulator (AVR), 5... Rated field current setting device, 8... Deviation detector, 10... Field current detector, 11, 2
4, 33, 71, 73, 75...Relay, 12...
...Divider resistance, 13, 14, 15, 21, 47...
Operational amplifier, 16...Subtractor, 17...Base amount setter, 18...Addition circuit, 22, 32...Comparator, 41, 42...Input resistance, 45...Input resistance, 46...Voltage detection 50...V/F converter, 51...Counter, 52...D/A converter, 52...Polarity converter. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. An automatic voltage regulator that controls the field current of a rotating machine according to its output voltage, a field current detection circuit that detects the field current of the rotating machine, and a rated voltage at a rated load. a rated field current setting circuit for setting a field current; a first arithmetic circuit for squaring the field current detected by the field current detection circuit; and a first calculation circuit for setting a voltage equal to the square of the rated field current. a base amount setter, a subtracter that subtracts the set value of the base amount setter from the calculated value of the first arithmetic circuit, and detection of the set value of the rated field current setting circuit and the field current detection circuit. a deviation detector that detects a deviation from a value, an amplifier circuit that amplifies the deviation signal detected by the deviation detector with a predetermined gain, a second arithmetic circuit that squares the output of this amplifier circuit, and a second arithmetic circuit that squares the output of this amplifier circuit. an adder circuit that adds the calculated value of the arithmetic circuit No. 2 and the subtracted value of the subtracter; an integrator circuit that integrates the added value of the adder circuit; A control circuit that operates the above-mentioned integrating circuit only when the magnetic current exceeds a field current, a field current excess detection circuit that operates when the output of the above-mentioned integrating circuit exceeds a certain value, and a control circuit that operates the above-mentioned integrating circuit only when the output of the above-mentioned integrating circuit exceeds a certain value, and a control circuit that operates the field current excess detection circuit that operates when the output of the above-mentioned integrating circuit exceeds a certain value. A generated voltage detection circuit that detects whether the generated voltage is above the normal operating range, and a field current excess detection circuit that detects the generated voltage that is above the normal operating range and detects that the field current is above the allowable value. An overexcitation limit signal supply circuit that immediately supplies the deviation detection signal to the automatic voltage regulator as an overexcitation limit signal when the deviation is detected by the circuit; If the field current exceeds the allowable value within the range, the above-mentioned overexcitation limit signal is excluded within a time period inversely proportional to the excess deviation, and after the permissible time, the step-like overexcitation limit signal is set to the above-mentioned automatic voltage adjustment for a predetermined period of time. An excitation control device for a rotating machine, comprising a stepped signal generation circuit that supplies the device. 2. According to claim 1, the amplification circuit comprises a voltage dividing resistor that divides the deviation detection signal into a predetermined value and an operational amplifier that amplifies the voltage divided value of the voltage dividing resistor with a predetermined gain constant. Excitation control device for the described rotating machine.