JP2941664B2 - Overexcitation limiter for synchronous machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overexcitation limiting device for a synchronous machine which is used to prevent insulation deterioration due to overcurrent in a synchronous machine field winding.

[0002]

2. Description of the Related Art FIG. 12 shows, for example, JP-A-56-15195.
FIG. 1 is a circuit diagram showing a conventional over-excitation limiting device disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, in which reference numeral 1 denotes a synchronous machine having a field winding 2;
Is an automatic voltage regulator connected between the synchronous machine 1 and the field winding 2 via an instrument transformer 3.

A field current shunt 6 is connected between the automatic voltage regulator 4 and the field winding 2 to shunt the field current and output it via an insulating amplifier 7. I have. Reference numeral 8 denotes a deviation detector which compares the divided field current with a set value of the field current set by the allowable field current setting circuit 5 to obtain a deviation. An amplifier to be input to the adjuster 4.

Next, the operation will be described. The automatic voltage regulator 4 detects the terminal voltage of the synchronous machine 1 via the instrument transformer 3 and controls the field current of the field winding 2 according to the detected value. On the other hand, the shunt field current shunted by the shunt 6 is output through the insulating amplifier 7, and the output value is compared with the set value set by the allowable field current setting circuit 5 by the deviation detector 8. Then, a deviation signal between the output value and the set value is detected.

The detected deviation signal is supplied to an amplifier 9.
After the signal is amplified to a signal of an appropriate level through the mixer, the signal is supplied to a mixer of the automatic voltage regulator 4, where the field current is controlled so as to be less than an allowable value.

[0006]

Since the overexcitation limiting device of the conventional synchronous machine is constructed as described above, the set value of the field current in the allowable field current setting circuit 5 is fixed, or Can be automatically changed by the cooling water, gas, etc., but the time until the start of the restriction by the automatic voltage regulator 4 can be set as described above even if it has an instantaneous, constant time limit or reverse time limit characteristic. The value remains fixed, and if the transient overexcitation occurs repeatedly at the request of the power system, the same operation is repeated only, and the integrated value (I ² −
1) t is added each time overexcitation occurs, and finally the field winding 2
However, there is a problem that the resistance (limit value) may be exceeded.

The first aspect of the present invention has been made in order to solve the above-mentioned problem. Even when overexcitation occurs repeatedly, the overexcitation is allowed up to an allowable limit for securing the stability of the power system. It is an object of the present invention to provide a synchronous machine over-excitation limiting device capable of securing the stability of a power system.

According to a second aspect of the present invention, when the field current falls below the rated value, the integrated value stored in the memory is attenuated by the thermal time constant of the field winding, thereby effectively limiting overexcitation. It is an object of the present invention to obtain a synchronous machine over-excitation limiting device capable of performing the following.

According to a third aspect of the present invention, the integrated value is converted into a temperature value of the field winding and stored, and this stored value is attenuated by the time constant of the field winding, thereby effectively limiting overexcitation. An object of the present invention is to provide a synchronous machine overexcitation limiting device that can be realized.

A fourth object of the present invention is to provide an overexcitation limiting device for a synchronous machine capable of setting a target attenuation value to a negative value and using this value as a target to rapidly attenuate the output of the integrator.

According to a fifth aspect of the present invention, the restriction operation after the start of the restriction is predicted in accordance with the field current value of the synchronous machine, thereby changing the timing of starting the overexcitation and limiting to the limit permitted by the synchronous machine. It is another object of the present invention to provide an overexcitation limiting device for a synchronous machine that can continue excitation control without limitation in the overexcitation state up to the withstand limit of the field winding and contribute to maintaining the stability of the power system.

A sixth object of the present invention is to provide an overexcitation limiting device for a synchronous machine which can optimally set the timing for starting overexcitation depending on whether the synchronous machine is unloaded or connected to a system. And

According to a seventh aspect of the present invention, there is provided a synchronous machine capable of predicting and calculating an integrated value after the start of overexcitation based on a field current value, and changing the overexcitation limit start timing in accordance with the calculation result. The purpose of the present invention is to obtain an overexcitation limiting device.

According to an eighth aspect of the present invention, there is provided an over-excitation of a synchronous machine capable of changing the over-excitation limit start timing by an automatic integrated prediction value selected according to whether the synchronous machine is unloaded or connected to a system. The aim is to obtain a limiting device.

[0015]

According to a first aspect of the present invention, there is provided an overexcitation limiting apparatus for a synchronous machine, wherein an integrated value relating to a field current serving as a reference of an allowable value of overexcitation of a field winding = (I ² − 1) t
A multiplication unit for obtaining, and the integrated value obtained in the integration device, integrator for storing the charging of the capacitor of the integration value output
A storage device having a function and an adder for adding the integrated value obtained by the integrating device to the stored value stored in the storage device, wherein the added value obtained by the adder exceeds a preset limit value. In such a case, the field control limiting means limits the field control by the automatic voltage regulator.

According to a second aspect of the present invention, the overexcitation limiting device for a synchronous machine attenuates the integrated value stored in the storage unit by the thermal time constant of the field winding when the field current becomes equal to or less than the rated value. An attenuation circuit is provided.

The overexcitation limit device for a synchronous machine according to the invention of claim 3, integrated to obtain the integrated value = (I 2 ^-1) t about the field current as a reference of tolerance overexcitation of the field winding Device, a storage device having an integration function of converting the integrated value obtained by the integrating device into a temperature value and storing the converted value, and storing the temperature value of the integrated value obtained by the integrating device in the stored value stored in the storage device. An adder for adding is provided, and when the added value obtained by the adder exceeds a preset limit value, the field control limiting means causes the field control by the automatic voltage regulator to be limited, and the attenuation circuit includes When the field current falls below the rated value, the temperature value stored by the storage device is attenuated by the thermal time constant of the field winding.

According to a fourth aspect of the present invention, there is provided the overexcitation limiting device for a synchronous machine, wherein the temperature value stored in the storage having the integrating function is stored in the damping circuit when the field current falls below the rated value. After the field current returns to a rated value or less, the target value calculation circuit calculates the temperature of the field winding corresponding to the field current. The stored temperature value is attenuated by the time constant of the field winding in the attenuation circuit toward the temperature.

The overexcitation limit device for a synchronous machine according to the invention of claim 5, the integrated value after the restriction start of overexcitation depending on the field current value of the field winding = (I 2 ^-1) predict t A predicting device for changing the limit start time by switching the predicted integrated value stepwise in accordance with the field current value at this time, and providing each adder of the predicting device and the integrating device in the adder. The value output is added, and based on the result of the addition, the limit start time of the overexcitation by the automatic voltage regulator is changed.

According to a sixth aspect of the present invention, there is provided an overexcitation limiting device for a synchronous machine, wherein the predicting device is selectively connected to an adder, and the predicting device when the synchronous machine is not loaded and the synchronous machine are connected to a system. It is composed of a prediction device when connected.

According to a seventh aspect of the present invention, there is provided an overexcitation limiting device for a synchronous machine, wherein an integration value for obtaining an integrated value = (I ² -1) t relating to a field current serving as a reference of an allowable value of overexcitation of a field winding is provided. provided a device, and an automatic integrated value predicting device for predicting calculated based on the prediction equation the integrated value after the restriction start overexcitation using the field current value of the field winding, the adder, the The output of each integrated value of the automatic integrated value predicting device and the integrated device is added, and based on the addition result, the timing of starting the limit of over-excitation by the automatic voltage regulator is changed.

According to an eighth aspect of the present invention, there is provided an overexcitation limiting apparatus for a synchronous machine, wherein the automatic integrated value predicting device is selectively connected to an adder, and the automatic integrated value predicting device when no load is applied to the synchronous machine. The synchronous machine is constituted by an automatic integrated value predicting device when the synchronous machine is connected to a system.

[0023]

[Action] overexcitation limit device for a synchronous machine according to the invention of claim 1 adds the integrated value = (I 2 ^-1) t each time the related excitation current when the field current of the synchronous machine exceeds the rated value stored in the storage device having the integration function Te, to initiate the limit value obtained by subtracting the integrated value from the limit value as the tolerance at that time, repeatedly it is overexcitation condition occurs reliably restricted within limits to enable.

According to a second aspect of the present invention, there is provided an overexcitation limiting device for a synchronous machine, wherein an integrated value when a field current of the synchronous machine exceeds a rated value is stored in a storage device, and the integrated value is stored in the synchronous machine field winding. It is attenuated by the thermal time constant of the wire.

According to a third aspect of the present invention, there is provided an overexcitation limiting device for a synchronous machine, wherein the integrated value = (I ² -1) t when the field current of the synchronous machine exceeds a rated value is converted into a temperature value and integrated. Has function
Stored in the storage device for, to attenuate the thermal time constant of the temperature values synchronous machine field winding.

According to a fourth aspect of the present invention, there is provided an overexcitation limiting device for a synchronous machine, wherein an integrated value when the field current of the synchronous machine exceeds a rated value = (I ² -1) t is converted into a temperature value and integrated. Has function
Together in the storage device for, after the return field current below the rated value, and calculates the temperature of the field winding corresponding to the field current at that time, synchronous machines the stored temperature value toward its temperature It is attenuated by the thermal time constant of the field winding.

In the overexcitation limiting device for a synchronous machine according to the fifth aspect of the present invention, the field current of the synchronous machine is small, the time required to return to a specified value after the start of the limit is short, and the field current after the limit of the overexcitation is started. When the integrated value = (I ² −1) t is predicted to be small, overexcitation is allowed for a long time to contribute to improvement in the stability of the power system, and conversely, the current flowing through the field winding starts to be limited. If the time required to return to the later specified value is long and the integrated value after the start of the restriction is predicted to be large, the operation is performed such that overexcitation is allowed only for a short time.

According to a sixth aspect of the present invention, there is provided an overexcitation limiting device for a synchronous machine, wherein an optimum integration prediction is performed based on a field current which changes according to whether the synchronous machine is unloaded and when the synchronous machine is connected to a system. The values can be output separately, and these output values are added to the integrated value output by the integrating device, and the field voltage adjustment by the automatic voltage regulator is optimized based on the addition result.

According to a seventh aspect of the present invention, the overexcitation limiting device for a synchronous machine predicts and calculates the integrated value after the start of the overexcitation limit = (I ² -1) t from the field current to thereby set the predicted value. It is possible to predict the integrated value by using a small and inexpensive prediction device without using a device, a relay, or the like.

The overexcitation limiting device for a synchronous machine according to the invention of claim 8 is based on a field current that changes depending on when the synchronous machine is unloaded and when the synchronous machine is connected to a system, and The directly obtained integrated predicted values can be selectively output, so that the field voltage can be adjusted by the automatic voltage regulator.

[0031]

【Example】

Embodiment 1 FIG. An embodiment of the present invention will be described below with reference to the drawings. 1, reference numeral 10 denotes a relay having a contact 10a for turning on and off the output of the amplifier 9, and reference numeral 11 denotes an insulating amplifier 7.
Is input, and the integrated value (I ² −
1) An integrating device for obtaining t, and a comparator 12 for detecting that the field current has returned to the rated value or less based on the output of the insulating amplifier 7.

An integration function 13 stores the output (integrated value) of the integrating device 11 in accordance with a command from the comparator 12.
The storage 14 has the output of the integrating device 11 and the storage 13
, An operation setter for starting the limit, 16 a comparator for comparing the output of the adder 14 with the operation set value set by the operation setter 15 to operate the relay 10 It is. In addition, the same components as those shown in FIG. 12 are denoted by the same reference numerals, and redundant description will be omitted.

Next, the operation will be described. Normally, the tolerance of the field winding 2 of the synchronous machine 1 is specified by a standard. The term “withstand capacity” here refers to the overcurrent withstand capacity of the field winding, that is, how many times the rated current can be passed. However, t shown in the equation of t = 30 / (I ² -1) is a quantity having a time dimension clearly, and has completely different physical significance from the above-mentioned tolerance. The meaning of the equation indicates that the synchronous machine must be able to operate normally until the product of the heating value exceeding the rated heating value and its duration becomes about 30. Here, I represents the field current in the rated state of the synchronous machine in a unit method indicated by 1.

Therefore, in order to protect the synchronous machine 1, the field current may be limited to the rated current (1 PU) or less before the integrated value (I ² -1) t reaches 30. . However, since the memory 13 is not provided in the related art, for example, considering the time required for the overexcitation limit, the integrated value is about 15 (when the integrated value is required to return to the rated value or less even after the limit is started, when 15 is required) ), The operation setting unit 15 is set so as to be uniformly restricted.

Therefore, when the repetitive field current exceeds the rated value, the limit is applied at the same integrated value of 15. Therefore, even if the limit is applied normally, the limit is applied only when the tolerance of the synchronous machine is exceeded. And the field winding 2 could not be protected.

This is because if the current integrated value 15 is added to the previous integrated value 15 and the integrated value from the start of the restriction to the retraction is added, the tolerance value 30 will be exceeded.

According to the present invention, by providing the integrating device 11 and the storage unit 13, for example, if the storage value, which is the integrated value once the field current exceeds the rated value, is set to 5, this storage value is used for the second and subsequent times. By adding a new integrated value to 5, the allowable limit of the synchronous machine 1 is always limited.

Next, a specific embodiment will be described. FIG. 2 shows details of the comparator 12 and the storage unit 13. In the figure, 21 is a setter for setting the rated value of the field current, and 22 is a comparator for comparing the output of the insulating amplifier 7 in proportion to the field current with the set value. Reference numerals 23 and 24 denote relays and off-delay timer relays that operate when the field current becomes larger than the value set by the setter 21, and reference numeral 25 denotes a transistor for driving the relay 23.

Reference numeral 26 denotes an integrating circuit constituting the memory 13, reference numeral 27 denotes a capacitor for the integrating circuit 26, and reference numeral 24a denotes a normally closed contact of the off-delay timer relay 24 connected in parallel with the capacitor 27.

Further, 23a, 23b and 23c are provided in the comparator 12, of which 23a is a normally open contact connected between the insulating amplifier 7 and the integrating device 11, and 23b is connected between the integrating device 11 and the storage device 13. Normally open contacts, 23
b is a normally open contact connected between the integrating device 11 and the storage device 13, and 23c is a normally closed contact connected between the integrating device 11 and the comparator 12.

In the accumulator, reference numeral 11a denotes a multiplication circuit for obtaining the square of the field current I, 11b denotes a setter for setting the set value ｀ 1 ', 11c denotes a difference circuit, and 11d denotes an integration circuit.

In this embodiment, when the field current exceeds the rated value, the output of the comparison circuit 22 changes from negative to positive, the transistor 25 conducts, and the relay 23 and the off-delay timer relay 24 operate.

When the relay 23 is turned on, the normally open contacts 23a and 23b are turned on, and the output of the integrating device 11 is input to the integrating circuit 26, and at the same time, the off-delay timer relay 24 is also turned on. The normally closed contact 24a of the circuit 26 that short-circuits the integrating capacitor 27 is turned off, and charging of the capacitor 27, that is, storage of the integrated value is started.

On the other hand, when the field current falls below the rating, the relay 23 is turned off, the input to the integrating device 11 is switched to zero, and the above integrated value is kept constant. When the field current becomes equal to or less than the rated value and a predetermined time elapses, the normally closed contact 2 as an attenuation circuit of the off-delay timer relay 24
4c is closed, the capacitor is short-circuited, and the stored integrated value is reset.

When this operation is repeated in a short time and the overexcitation state is repeated, the integrated value is stored, and after a certain period of time is reset, the operation returns to the normal state.

In this embodiment, the case where the storage unit 13 is constituted by the integration circuit 26 to which the capacitor 27 is connected has been described. However, a method of sequentially adding predetermined values, for example, when the field current is A preset value for each time exceeding the rated value may be added by an adder circuit and the added value may be stored as storage data, and the same effect as in the above embodiment can be obtained. Also, the relay 23 and the off-delay timer relay 24 can be realized by using a semiconductor such as a transistor.

Embodiment 2 FIG. In the first embodiment, the case where the integrated value is stored in the storage unit 13 for a certain time has been described. However, the integrated value is originally attenuated by the thermal time constant of the field winding 2 of the synchronous machine 1. However, it is possible to more effectively limit overexcitation.

FIG. 3 shows a specific example of the over-excitation limiting device capable of attenuating the thermal time constant. In FIG. 3, reference numeral 31 denotes another relay connected in parallel to the relay 23 in the comparator 12, and reference numeral 32 denotes , A capacitor 31b is provided for the comparator 12
The series circuit of the normally closed contact 31b and the capacitor 32 is connected in parallel to the capacitor 27.

A feedback circuit 33 is connected to a difference circuit 36 on the input / output side of the integration circuit 26 via the normally open contact 31a of the relay 31. The same components are denoted by the same reference numerals, and the description thereof will not be repeated.

According to this embodiment, when the field current value becomes equal to or less than the rated value, the normally open contact 31a and normally closed contact 31b of the relay 31 added to the comparator 12 are closed, and the integrating circuit 26 is closed.
Is adjusted, and the integrated output is fed back to the input side of the integration circuit 26 through the feedback circuit 33, and attenuates at a constant time constant corresponding to the thermal time constant of the field winding 2. Here, the normally closed contact 31b,
The capacitor 32 forms the attenuation circuit A.

When the field current value exceeds the rated value, the integrated value is stored in the same manner as described with reference to FIG. 2. On the other hand, when the field current value becomes less than the rated value, the stored integrated value is stored in the field value. It can be attenuated by the thermal time constant of the winding 2. This is shown in FIG. 4, where _If is the field current and P is the integrated value output.

Embodiment 3 FIG. Further, in the first embodiment, the case where the integrated value is stored in the storage device 13 for a certain period of time has been described, but the integrated value is passed through the temperature converter 51 as shown in FIG. The temperature value may be changed and stored in the storage device 13 as the temperature value. Even in this case, if the field current value becomes equal to or less than the rated value, the stored value corresponding to the temperature is attenuated by the thermal time constant of the field winding.

Embodiment 4 FIG. Further, in the third embodiment, the case where the integrated value is converted into a temperature value by the temperature converter 51 in the comparator 12 and stored, and attenuated by the thermal time constant of the field winding 2 in the synchronous machine 1 has been described. The target value to be attenuated is a value at which the temperature rise value returns to zero. However, in practice, the field current value is limited to a value smaller than the rated value, so that the target of the integrated value to be attenuated is a lower value.

In this embodiment, the integrated value is attenuated with the target of zero in the third embodiment. On the other hand, the target value is set to the field winding temperature calculated from the field current value and the rated field. The difference from the field winding temperature corresponding to the current value is set.

This embodiment will be described with reference to FIG.
2 is a target value calculation circuit, 53 is a multiplication circuit for calculating I ² ,
54 temperature converter for converting the I ² temperature, 55 temperature setter for setting a winding temperature equivalent rated value, 56 rated value set at a temperature and a temperature setter 55 to be calculated from the field current It is a difference circuit with a considerable temperature.

Reference numeral 57 denotes a comparator for comparing the output of the storage unit 13 as an input value with the reference value of the reference value setting unit 59;
Are relays that are turned on via the transistor 60 when the integrated value is equal to or greater than zero as a reference value. 58a and 58b are normally open contacts and normally closed contacts of the relay 58, and are normally open contacts 58a.
Is a differential circuit 56 and a normally closed contact 23c of the relay 23.
Is connected between.

According to this, the output value of the difference circuit 56 becomes zero when the field current value is the rated value, and becomes a negative value when the field current value is less than the rated value, and can be used as a target of the integrated value. That is, in this embodiment, when the overexcitation state is released, that is, when the relay 23 is turned off, the integrator input becomes the difference circuit output,
If it is less than the rating, the output of the integrator attenuates toward a negative value that is the attenuation target value D as shown in FIG. Therefore, an output of the integrator according to the actual operation can be obtained.

In this case, the comparator 57 having the integrated value output as an input value and the relay 58 which is turned on when the integrated value is zero or more are added as described above, so that the integrated value becomes zero. When the value becomes below, the input to the integrator is set to zero.

Although each of the above embodiments has been described using an analog circuit, the present invention can also be realized by software in a control device using a digital circuit or a microprocessor or the like, and has the same effects as the above embodiments.

In each of the above embodiments, the description has been given of the excitation control device having no exciter. However, the same effect can be obtained with an excitation control device having a rotary exciter such as a brushless exciter or a DC exciter.

Embodiment 5 FIG. FIG. 7 is a block diagram of an overexcitation limiting device showing another embodiment of the present invention. To explain this, 10 is a relay having a contact 10a for turning on and off the output of the amplifier 9, and 11 is a device for receiving the output of the insulating amplifier 7 as an input and obtaining an integrated value (I ² -1) t relating to the field current. is there.

A predicting device 18 receives the output of the insulating amplifier 7 as an input and predicts an integrated value after the start of limiting. An adder 14 adds signals of the integrating device 11 and the predicting device 18 to each other.
5 is an operation setter for starting the limit, 16 is a comparator for comparing the output of the adder 14 with the set value of the operation setter 15 and operating the relay 10, 17 is the synchronous machine 1 as a generator and the power system And a circuit breaker connected between them.

Next, the operation will be described. Usually, the tolerance t of the field winding of the synchronous machine is specified by a standard or the like, and is represented by t = 30 / (I ² -1) as described above. Therefore,
In order to protect the synchronous machine, the current may be limited to the rated current (1 PU) or less before the integrated value (I ² -1) t reaches 30.

However, in the prior art, even if the limiting operation is started, the field current does not instantaneously decrease below the rated current due to the field time constant of the synchronous machine 1. Therefore, the worst integrated value integrated even after the limiting operation is started. Assuming that the integrated value is about 5, for example (in the worst case, even if the limit is started, it is assumed that the integrated value will be integrated 25 until the value is returned to the rated value or less), the operation setting unit 15 is set so that the limit is uniformly applied. Was set. Therefore, in the case other than the worst case, the limitation is imposed quickly, and the tolerance t of the synchronous machine cannot be fully utilized.

Therefore, according to the present invention, by providing the integrating device 11 and the predicting device 18, when the integrated value after the start of the restriction is predicted to be small, the overexcitation state is allowed to be long, and the power system stability is improved. And when it is predicted that the integrated value is large, the restriction is made quickly to protect the field winding 2.

Next, a specific embodiment will be described. FIG. 8 shows the details of the prediction device 18. In FIG. 8, reference numerals 71a to 71j denote a plurality of sets (FIG. 2) for setting the estimated value of the integrated value at the time when the limit is applied according to the field current value in advance. 10) predicted value setting units, 72a to 72
j is a setting device for setting the operation values of the comparators 73a to 73j.

The comparators 73a to 73j compare the magnitude of the output of the insulated amplifier 7 with the set values of the setters 72a to 72j, and operate the relays 7A to 74J respectively.
Reference numerals 4a to 74j denote contacts of relays 74A to 74J for turning on and off the outputs of the predicted value setting units 71a to 71j, and 75 denotes each contact 7
Predicted value setting units 71a through 71j
71j is an adder for adding the outputs of 71j.

FIG. 9 shows the details of the integrating device 11.
In the figure, reference numeral 76 denotes a multiplication circuit for calculating the square of I, 7
Reference numeral 7 denotes a setting unit corresponding to 1 in (I ² -1) in the above expression of the tolerance t, and reference numeral 78 denotes an integration circuit for integrating (I ² -1).

Next, the operation will be described. Isolation amplifier 7
, Ie, the field current increases, the relay 74A connected to the comparator 73a of the setter 72a having the lowest operation set value operates, and the output of the predicted value setter 71a via the contact 74a of the relay 74A. Is input to the adder 75.

Similarly, as the field current increases, the relays 74B to 74J operate sequentially, and the predicted value setting units 71b to 71J operate.
Since the output of j is added to the adder 75, the adder 7
5 increases as the field current increases.

Since the output of the prediction device 18 is added to the output of the accumulator 11 by the adder 14, the output of the adder 14 also changes according to the change in the field current. Therefore, the operation setting unit 15 is fixed, and when the field current is large, the operation setter 15 is early, and when the field current is small, it is late. I do.

By this operation, the operation of the synchronous machine up to the capacity limit can be performed, and the protection can be surely performed. The predicted value setting units 71a to 71j and the setting units 72a to 72
j, comparators 73a to 73j and relays 74A to 74J
The number of can be determined according to the required accuracy, but of course,
The higher the number, the better the accuracy.

In this example, the predicted value setting units 71a to 71j
Has been described, the same effect can be obtained by a method of sequentially switching the outputs of the predicted value setting units 71a to 71j. Also, the relay 10, the relays 74A to 74A
J can also be realized by using a semiconductor such as a transistor.

Embodiment 6 FIG. In the fifth embodiment, the case where the predicted value setting units 71a to 71j are simply switched by the field current has been described. However, when the synchronous machine 1 is not loaded and when the synchronous machine 1 is connected to the system, the change of the field current is not changed. Therefore, the integrated value (I ² -1) t after the start of the limit also differs with the same field current.

Therefore, as shown in FIG. 10, the prediction device 18a when there is no load, the prediction device 18b when connected to the system, and the operation when the synchronous machine 1 is connected to the system. By adding a relay 80 that operates at the contact 79 of the unit 17, it is possible to cope with both when there is no load and when it is connected to the system.

Also in this case, the same effect can be obtained by arranging two sets of predicted value setting units 71a to 71j without arranging two prediction devices 18a and 18b.

The change in the field current of the synchronous machine 1 generally varies with an open circuit time constant Tdo 'when there is no load, and with a time constant Tg when connected to a system. (X
d '+ Xe) .Tdo' / (Vd + Xe). Here, Xd and Xd 'are the reactance of the synchronous machine, and X
e is the reactance of the power system.

Embodiment 7 FIG. In the first embodiment, the case where the predicted value setting units 71a to 71j are switched according to the field current value has been described. However, the predicted value of the integrated value after the start of the limit is automatically calculated directly from the field current. It is also possible to use an automatic integrated value predicting device 18A of the automatic integrated value type as shown in FIG.

The automatic integrated value predicting device 18A realizes a simplified predicted value = K (I + 3) (I-1) obtained by simplifying the following formula for calculating the integrated value (I ² -1) t after the start of the restriction. It was done.

[0080]

(Equation 1)

Here, t ₁ is the time required from the start of the limit to the return to the allowable current value, and K is a coefficient determined by the time constant at which the field current changes.

That is, in FIG. 11, reference numeral 81 denotes a constant setting device for the constant ｀ 3 ′, reference numeral 82 denotes an adder for adding the field current I and the constant ｀ 3 ′ set by the constant setting device 81, and 8
3 is a constant setter different from the constant ｀ -1 ′ constant setter 81, 84 is an adder for adding the field current I and the constant ｀ -1 ′ set by the constant setter 83, 85 is an adder 82 A multiplication circuit for multiplying the signal with the adder 84;
5 is an amplifier that multiplies the output (I + 3) (I−1) by a coefficient K and amplifies the result.

As described above, by using the automatic integrated value predicting device 18A, a plurality of predicted value setting units 71a-71j and relays 74A-74 are used as in the first or second embodiment.
J, the comparators 73a to 73j become unnecessary, and the configuration of the device can be simplified and downsized.

According to this, the automatic integrated value predicting device 1
The integrated value predicted and calculated in 8A and the integrated value output of the integrating device 11 are added by the adder 14, and based on the addition result, the start time of the limit of the overexcitation by the automatic voltage regulator 4 can be changed. .

Here, the case where the simplified simplified measured values are used has been described, but the same effect can be naturally obtained by directly converting the equation of the above-described formula 1 into a circuit.

Embodiment 8 FIG. In the seventh embodiment, only one circuit is shown. However, similar to the sixth embodiment, an automatic integrated value predicting device when the synchronous machine is not loaded and an automatic integrated value predicting device when the synchronous machine is connected to the system are provided. By providing the two circuits and switching by means of a relay, it is possible to cope with both at the time of no load and at the time of system connection.

Although the fifth to eighth embodiments have been described using an analog circuit, the present invention can also be realized by a digital circuit or software using a microprocessor or the like, and the same effects as those of the above embodiments can be obtained.

Similarly, in the fifth to eighth embodiments, the description has been given of the excitation controller having no exciter. However, the same effect can be obtained by the excitation controller having a rotary exciter such as a brushless exciter or a DC exciter. To play.

The switching according to the operating state of the synchronous machine has been described in two cases, that is, when there is no load and when the system is connected. However, it is necessary to switch according to the system state by further increasing the number of switching. Can be easily dealt with.

[0090]

As described above, according to the first aspect of the present invention, the integration for obtaining the integrated value = (I ² -1) t relating to the field current which is the reference of the allowable value of the overexcitation of the field winding. Equipment and
A storage device having an integration function of storing the integrated value obtained by the integrating device by charging a capacitor of the integrated value output,
An adder for adding the integrated value obtained by the integrating device to the stored value stored in the storage device, and when the added value obtained by the adder exceeds a preset limit value, a field control limiting means. In addition, since the field control by the automatic voltage regulator is limited, even if overexcitation occurs repeatedly, overexcitation can be allowed up to the allowable limit for securing the stability of the power system, and the stability of the power system can be maintained. There is an effect that a product that can ensure the above can be obtained.

According to the second aspect of the present invention, a damping circuit is provided for attenuating the integrated value stored in the memory by the thermal time constant of the field winding when the field current falls below the rated value. Therefore, when the field current becomes equal to or less than the rated value, the integrated value stored in the memory can be attenuated by the thermal time constant of the field winding, so that the overexcitation can be effectively limited. There is an effect that can be obtained.

According to the third aspect of the present invention, the integrated value relating to the field current which is a reference of the allowable value of the overexcitation of the field winding = (I
² -1) and integrated device for obtaining the t, the integration value obtained by the multiplication unit, and <br/> storage device having an integrating function for storing converted into temperature values, the storage value stored in the storage unit An adder for adding the temperature value of the integrated value obtained by the integrating device, and when the added value obtained by the adder exceeds a preset limit value, an automatic voltage regulator is added to the field control limiting means. In the attenuation circuit, when the field current falls below the rated value, the temperature value stored by the memory is attenuated by the thermal time constant of the field winding. Therefore, by attenuating the stored value converted into the temperature value by the time constant of the field winding, there is an effect that it is possible to obtain the one that can effectively realize the overexcitation limitation.

According to the fourth aspect of the present invention, when the field current becomes equal to or less than the rated value, the temperature value stored by the memory having the integrating function is stored in the attenuation circuit. After the field current returns to the rated value or less, the target value calculation circuit calculates the temperature of the field winding corresponding to the field current. The damping circuit is configured so that the stored temperature value is attenuated by the time constant of the field winding. Therefore, the damping target value is set to a negative value, and the output of the integrator is rapidly attenuated with this value as the target. There is an effect that something that can be performed can be obtained.

According to the fifth aspect of the present invention, the integrated value after the start of the overexcitation limit = (I ² ) according to the field current value of the field winding.
-1) a prediction device for predicting and setting t , switching the predicted integrated value stepwise according to the field current value at this time, and changing the limit start time, and providing the prediction device in an adder. And the output of each integrated value of the integrating device is added, and based on the addition result, the start timing of the limit of overexcitation by the automatic voltage regulator is changed, so that the limit is started according to the field current value of the synchronous machine. By predicting the limit operation to be performed later, the start timing of the limit of overexcitation is changed, and the excitation control is continued without limitation in the overexcitation state until the limit permitted by the synchronous machine, that is, up to the withstand limit of the field winding. There is an effect that it is possible to obtain what can contribute to maintaining the stability of the power system.

According to the invention of claim 6, the prediction device is selectively connected to the adder, and the prediction device when the synchronous machine has no load and the prediction device when the synchronous machine is connected to the system. Since the synchronous machine is constituted by the device, there is an effect that it is possible to obtain an apparatus which can optimally set the overexcitation limit start timing depending on whether the synchronous machine is in a no-load state or connected to a system.

According to the seventh aspect of the present invention, the integrated value relating to the field current which is a reference for the allowable value of overexcitation of the field winding = (I
² -1) and integrated device for obtaining the t, and automatic integration value predicting device for predicting calculated based on the prediction equation the integrated value after the restriction start overexcitation using the field current value of the field winding And the adder is configured to add the integrated output of the automatic integrated value predicting device and the integrated value output of the integrating device, and to change the limit start time of the over-excitation by the automatic voltage regulator based on the addition result. Therefore, based on the field current value,
The integrated value after the start of the overexcitation limit is predicted and calculated, and there is an effect that it is possible to obtain a value capable of changing the start timing of the overexcitation limit according to the calculation result.

According to the invention of claim 8, the automatic integrated value predicting device is selectively connected to the adder, and the automatic integrated value predicting device when the synchronous machine has no load is connected to the system. The automatic start time limit start time is changed according to the automatic start time prediction value selected according to whether the synchronous machine is unloaded or connected to the grid. There is an effect that something that can be performed can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overexcitation limiting device for a synchronous machine according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a main part of FIG. 1 in detail.

FIG. 3 is a circuit diagram showing another embodiment of a main part of FIG. 1;

FIG. 4 is a diagram showing a field current / integrator output characteristic in FIG. 3;

FIG. 5 is a circuit diagram showing still another embodiment of the main part of FIG. 1;

FIG. 6 is a diagram showing field current / integrator output characteristics in FIG.

FIG. 7 is a block diagram showing an over-excitation limiting device for a synchronous machine according to another embodiment of the present invention.

FIG. 8 is a circuit diagram showing details of a prediction device in FIG. 7;

FIG. 9 is a circuit diagram showing details of an integrating device in FIG. 7;

FIG. 10 is a block diagram showing another embodiment of the prediction device in FIG. 7;

FIG. 11 is a circuit diagram showing another embodiment of the prediction device in FIG. 7;

FIG. 12 is a block diagram showing a conventional overexcitation limiting device for a synchronous machine.

[Explanation of symbols]

1 synchronous machine, 2 field winding, 4 automatic voltage regulator, 8
Deviation detector, 11 integrator, 13 storage, 14 adder, 16 comparator (field control limiting means), 18, 18
a, 18b prediction device, 18A automatic integrated value prediction device,
27 capacitor, 52 target value calculation circuit, A attenuation circuit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02P 9/00-9/48

Claims (8)

(57) [Claims] 1. An automatic voltage regulator for detecting a terminal voltage of a synchronous machine and controlling a field voltage of a field winding according to the detected value, and a preset voltage and a field current of the field winding. And a deviation detector for controlling the automatic voltage regulator so as to make the field current equal to or less than an allowable value based on the detected value. In the over-excitation limiting device, an integrating device for obtaining an integrated value = (I ² -1) t relating to a field current as a reference of an allowable value of over-excitation of the field winding, and an integrated value obtained by the integrating device. An integration function for storing the integrated value output by charging the capacitor.
A storage device having an adder for adding the integrated value obtained by the integrating device to the stored value stored in the storage device, and when the added value obtained by the adder exceeds a preset limit value, An over-excitation limiting device for a synchronous machine, further comprising field control limiting means for limiting field control by the automatic voltage regulator. 2. An attenuating circuit according to claim 1, further comprising a damping circuit for attenuating the integrated value stored by the storage device with a thermal time constant of the field winding when the field current becomes equal to or less than the rated value. Overexcitation limiter for synchronous machine. 3. An automatic voltage regulator for detecting a terminal voltage of a synchronous machine and controlling a field voltage of a field winding in accordance with the detected value, and a preset voltage and a field current of the field winding. And a deviation detector for controlling the automatic voltage regulator so as to make the field current equal to or less than an allowable value based on the detected value. In the over-excitation limiting device, an integrating device for obtaining an integrated value = (I ² -1) t relating to a field current as a reference of an allowable value of over-excitation of the field winding, and an integrated value obtained by the integrating device. A storage device having an integration function of converting into a temperature value and storing it; an adder for adding the temperature value of the integrated value obtained by the integration device to the stored value stored in the storage device; When the added value exceeds a preset limit value, the field control by the automatic voltage regulator is limited. And a damping circuit for attenuating the temperature value stored by a storage unit with a thermal time constant of a field winding when the field current becomes equal to or less than a rated value. Overexcitation limiter. 4. An automatic voltage regulator for detecting a terminal voltage of a synchronous machine and controlling a field voltage of a field winding according to the detected value, and a preset voltage and a field current of the field winding. And a deviation detector for controlling the automatic voltage regulator so as to make the field current equal to or less than an allowable value based on the detected value. In the over-excitation limiting device, an integrating device for obtaining an integrated value = (I ² -1) t relating to a field current as a reference of an allowable value of over-excitation of the field winding, and an integrated value obtained by the integrating device. A storage device having an integration function of converting into a temperature value and storing it; an adder for adding the temperature value of the integrated value obtained by the integration device to the stored value stored in the storage device; When the added value exceeds a preset limit value, the field control by the automatic voltage regulator is limited. A field control limitation means that, when the field current is below the rated value, an attenuation circuit for attenuating the temperature value stored in the storage unit in the thermal time constant of the field winding,
After the field current returns to or below the rated value, the temperature of the field winding corresponding to the field current is calculated, and the temperature value stored in the damping circuit is stored in the field winding with this temperature as a target. And a target value calculating circuit for attenuating with a time constant of: 5. An automatic voltage regulator for detecting a terminal voltage of a synchronous machine and controlling a field voltage of a field winding according to the detected value, and a preset voltage and a field current of the field winding. And a deviation detector for controlling the automatic voltage regulator so as to make the field current equal to or less than an allowable value based on the detected value. in overexcitation limit device, integrated relates serving as a reference field current tolerance of overexcitation of the field winding value = (I 2 ^-1) and integrated device for obtaining the t, the field current of the field winding A prediction device that predicts and sets an integrated value after the start of overexcitation according to the value, and switches the predicted integrated value stepwise according to the field current value at this time to change the limit start time; The integrated outputs of the prediction device and the integration device are added, and based on the addition result, Overexcitation limiting device of the synchronous machine, characterized by comprising an adder for varying the restriction start time of the overexcitation by the automatic voltage regulator. 6. A prediction device, comprising: a prediction device selectively connected to an adder and when the synchronous machine is unloaded; and a prediction device when the synchronous machine is connected to a system. Item 6. An overexcitation limiting device for a synchronous machine according to item 5. 7. An automatic voltage regulator for detecting a terminal voltage of a synchronous machine and controlling a field voltage of a field winding according to the detected value; And a deviation detector for controlling the automatic voltage regulator so as to make the field current equal to or less than an allowable value based on the detected value. in overexcitation limit device, integrated relates serving as a reference field current tolerance of overexcitation of the field winding value = (I 2 ^-1) and integrated device for obtaining the t, the field current of the field winding The integrated value predicting device that predicts and calculates the integrated value after the start of the overexcitation using the value based on the prediction formula, and the integrated value output of the automatic cumulative value predicting device and the integrated value of the integrating device are added. Based on the result of addition, changes the start timing of overexcitation by the automatic voltage regulator. Overexcitation limiting device of the synchronous machine, characterized in that by an adder provided for. 8. An automatic integrated value predicting device selectively connected to an adder and when no load is applied to a synchronous machine, and an automatic integrated value predicting device when the synchronous machine is connected to a system. The overexcitation limiting device for a synchronous machine according to claim 7, comprising a value predicting device.