JP2000358331A - Individual operation detector for synchronous generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an individual operation detector for rapidly, effectively detecting an individual operation of a synchronous generator and simplifying settling or the like for detecting the individual operation. SOLUTION: Individual operation detector for a synchronous generator obtains the frequency of an interlocking point of a frequency calculator 8A, obtains a change ratio (df/dt) by a frequency change ratio calculator 8B, obtains an amount proportional to the change ratio by a coefficient unit 8C, limits the amount by an output limiter 8D, and feeds back a positive voltage amount to an automatic voltage regulator 3A of the generator 3. In this case, the detector generates an infinitesimal change amount to be suppressed at the frequency change, when the generator is in an interlocked state and a change amount of a predetermined period, and superposes the change amount on a positive feedback amount to obtain a frequency change by the infinitesimal change amount, even in a state in which the load of a range of the individual operation is completely balanced with the output of the generator, thereby detecting the individual operation. It includes to superpose the change amount on the frequency change amount instead of the frequency changer ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the isolated operation of a synchronous generator connected to a power distribution system under the condition of reverse power flow.

[0002]

2. Description of the Related Art When a distributed power supply is connected to a high-voltage distribution system under the condition of reverse power flow, measures must be taken to prevent the power supply from operating alone. In contrast, the Ministry of International Trade and Industry
The technical requirements for connecting distributed power sources to the grid are summarized in the "Guidelines for Grid Connection Technical Requirements". According to this, as an above-described measure for preventing the islanding operation, an islanding operation detection device that actively detects the islanding operation of the generator is recognized in addition to the transfer interruption device that is a conventional passive system.

[0003] When an islanding operation detecting device is employed as a countermeasure for preventing the islanding operation of a rotating machine system distributed type power source such as a synchronous generator, the device has two or more islanding operation systems including one or more active systems. It is stipulated that a detection method is applied. This is because when the operation shifts to the islanding operation when the load within the range of the islanding operation and the output of the generator are balanced, the output and frequency of the generator after the transition to the islanding operation do not change, only the passive system This is because islanding cannot be detected.

[0004] From the above, it is general that an active system and a passive system are applied to each of the isolated operation detection devices for a rotating machine system distributed type power supply which are currently being developed. . Among them, the main active systems applied to the isolated operation detection device for the synchronous generator include a reactive power fluctuation system and a QC mode frequency shift system.

The configuration diagram of the reactive power fluctuation method is shown in FIG.
FIG. 6 shows changes in various electric quantities. The power receiving equipment receives power from the system power supply 1 through the high-voltage distribution line 2, and supplies power to the load 6 from the synchronous generator (G) 3 through the transformer 4 and the circuit breaker 5 in connection with the system.

[0006] The isolated operation detection device 7 uses a small fluctuation amount generator 7A to generate a small fluctuation (A) of a constant cycle with respect to a voltage set value of an automatic voltage adjustment circuit (AVR) 3A of the synchronous generator 3.
VR voltage set value fluctuation amount) is always given. As a result, a small voltage fluctuation is likely to occur in the synchronous generator 3, but the frequency change is suppressed by the synchronizing force in an interconnected state with the grid, but when the synchronous generator 3 shifts to the isolated operation, the power is generated. Periodic fluctuations occur in terminal voltage and frequency. The frequency variation calculation unit 7B detects the frequency variation Δf from the interconnection point voltage detected by PT by digital calculation or the like, and the determination unit 7C determines that the frequency variation Δf has exceeded a certain value. At this time, it is determined that the synchronous generator 4 has shifted to the isolated operation, and in this determination, a trip command for the circuit breaker 5 is generated, and the synchronous generator 3 is disconnected from the system.

FIG. 7 is a diagram showing the configuration of the QC mode frequency shift system, and FIG. 8 shows changes in various electric quantities. In the islanding detection device 8 in this method, the frequency f is obtained by the frequency calculation unit 8A, and the frequency change rate (df
/ Dt) is calculated by a frequency change rate calculation unit 8B, the frequency change rate (df / dt) is multiplied by a constant k by a coefficient unit 8C, and the output voltage is limited by an output limiter unit 8D to control an automatic voltage adjustment circuit ( AVR) A negative voltage is applied to the voltage set value of 3A.

As a result of this voltage addition, the output of the generator 3 increases with a rise in the voltage and the frequency decreases, so that the temporal change becomes negative. Control in the voltage increasing direction to add in That is, control is performed such that the frequency of the generator is further reduced. Conversely, for a voltage drop, control is similarly performed in the voltage drop direction. Such feedback is called positive feedback. In contrast to the positive feedback, the frequency is kept substantially constant by the commercial power supply at the time of system interconnection, so that the frequency of the generator hardly fluctuates. However, if the frequency of the generator fluctuates even a little during the transition to the islanding operation, the fluctuation is amplified by positive feedback.
The circuit breaker 5 is tripped when the isolated operation is detected by the determination unit 8F.

[0009]

In the conventional islanding operation detecting apparatus using the reactive power fluctuation method, the amount of change in the AVR voltage set value can be increased in order to detect the islanding operation at high speed. On the other hand, the amount of the fluctuation also increases the voltage fluctuation during system interconnection. This tendency becomes stronger when the generator capacity is large or when the generator is connected far from the distribution substation.

[0010] In such a case, the voltage fluctuation during system interconnection may exceed the allowable value for the AVR voltage set value fluctuation determined to satisfy the required islanding detection time, The power quality may be degraded, and other control devices may be affected.

Further, the generator frequency fluctuation after the transition to the isolated operation by the reactive power fluctuation method includes the generator output, the generator operation power factor, the generator control method, and the generator constant (particularly, inertia).
And the magnitude and frequency of the AVR voltage set value fluctuation amount, and the phase of the AVR voltage set value fluctuation amount at the time of transition to the isolated operation.

From the above, in order to determine the set value of the conventional reactive power fluctuation method, after grasping all of the above conditions,
A strict simulation by a computer was required, which was complicated.

On the other hand, in the QC mode frequency shift system,
The amount proportional to the frequency change rate (df / dt) is positively fed back to the automatic voltage regulation circuit (AVR) as an active mode signal, but the load within the range of the isolated operation and the output of the generator are completely reduced. If the operation shifts to the islanding operation in a balanced state, theoretically, the frequency of the generator before and after the operation shift to the islanding operation does not change at all. Therefore, under such conditions, the islanding operation cannot be detected in principle, and In the detection after the state change, the islanding detection is delayed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an islanding operation detection device which can quickly and reliably detect the islanding operation of a synchronous generator, and can simplify settling for the islanding operation detection.

[0015]

According to the present invention, in order to solve the above-mentioned problems, the present invention changes at a constant period to an amount proportional to a frequency change rate (df / dt) or a frequency change amount (Δf) at an interconnection point. The circuit in which the minute fluctuation amount is superimposed is fed back to the automatic voltage adjustment circuit of the generator to determine the independent operation of the generator from the frequency fluctuation amount, and has the following configuration.

[0016] An active system in which the synchronous generator is interconnected to the distribution system under the condition of reverse power flow, and when the amount of frequency fluctuation at the interconnection point exceeds a set value, the synchronous generator is detected as an independent operation. An operation detecting device, which obtains an amount proportional to the frequency change rate or the frequency fluctuation amount of the interconnection point, and calculates this amount as a voltage positive feedback amount to an automatic voltage adjustment circuit of the synchronous generator, A minute fluctuation amount generator that is superimposed on the positive feedback amount with a minute fluctuation amount that can suppress frequency fluctuation when the synchronous generator is in an interconnected state and a fluctuation amount of a constant cycle, I do.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention, and portions equivalent to those in FIG.

The islanding detection device 10 includes a frequency calculation unit 8 like the conventional QC mode frequency shift type device 8.
The frequency f is obtained by A, the frequency change rate (df / dt) of this frequency f is obtained by the frequency change rate calculation unit 8B, and the frequency change rate (df / dt) is multiplied by a constant k by a coefficient unit 8C. In addition to the configuration in which the output voltage is limited by the output limiter unit 8D and applied to the voltage set value of the automatic voltage adjustment circuit (AVR) 3A with a negative polarity, a minute fluctuation generator 10A is provided.

The minute fluctuation generator 10A generates a minute voltage that changes in a constant cycle, and superimposes it on a voltage proportional to the frequency change rate (df / dt) from the coefficient unit 8C, and this voltage is used as a synchronous generator. 3 automatic voltage adjustment circuit (AVR) 3A
Is given as an active mode signal for the voltage set value.

The frequency relay 10 of the isolated operation detection device 10
B detects that the frequency variation (Δf) obtained by the frequency variation calculator 8E has become equal to or larger than the set value. When this detection state continues for a predetermined time or more, an isolated operation determination output is obtained from the timer 10C. However, since the frequency after the transition to the islanding operation by this method repeatedly increases and decreases as shown in FIG. 2, the timer 10C is of the integral type.

According to the present embodiment, the frequency change rate (df
/ Dt) by superimposing the minute fluctuation amount from the minute fluctuation amount generator 10A on the amount proportional to the automatic voltage adjustment circuit (AVR).
Since the positive feedback to 3A is performed, even when the operation is shifted to the standalone operation in a state where the load within the range of the isolated operation and the output of the generator are perfectly balanced, the generator is controlled by the small variation amount by the small variation generator 10A. The frequency changes, and the frequency fluctuation is amplified by positive feedback, so that the isolated operation of the generator 3 can be reliably detected.

The minute fluctuation amount of the minute fluctuation amount generator 10A can be detected at high speed by positive feedback even though the fluctuation amount is small.

Furthermore, the fact that the small fluctuation amount can be reduced means that the AVR voltage set value fluctuation amount can be reduced, thereby reducing the influence on the generator frequency fluctuation after the shift to the isolated operation and the influence on other devices at the time of system interconnection. Can be smaller. As a result, the magnitude and cycle (frequency) of the fluctuation amount of the minute fluctuation amount generator 10A
The setting value in the frequency relay 10B does not need to be determined so strictly, and can be easily determined.

(Second Embodiment) FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG. 4 shows changes in various electric quantities. 3 is different from FIG. 1 in that an amount proportional to the frequency variation (Δf) obtained by the frequency variation calculator 8E is obtained in the coefficient unit 8C, and the minute variation from the small variation generator 10A is added thereto. This is to give this as an active system signal to the voltage set value of the automatic voltage regulator (AVR) 3A of the synchronous generator 3.

The frequency variation calculator 8E calculates the frequency variation (ΔΔT) from the interconnection point voltage detected by the PT.
Find f).

The determination of the islanding operation according to the present embodiment is performed by obtaining a frequency variation (Δf) with respect to the reference frequency of the system,
If this value is equal to or more than the set value of the frequency relay and exceeds the specified time of the timer 10C, it is determined that the operation is the isolated operation.

In this embodiment, as in the case of the first embodiment, even when the operation is shifted to the islanding operation when the load within the range of the islanding operation and the output of the generator are perfectly balanced, the power generation is also performed. The isolated operation of the machine 3 can be reliably detected, and high-speed detection can be performed. Further, the minute fluctuation amount generator 10
The magnitude and period (frequency) of the fluctuation amount of A and the set value at the frequency relay 10B do not need to be determined so precisely, but can be determined easily.

[0028]

As described above, according to the present invention, the frequency change rate (df / dt) or the frequency variation (Δ
f) The amount proportional to f) is superimposed with the minute fluctuation amount that fluctuates in a constant cycle, and the result is positively fed back to the automatic voltage adjustment circuit of the generator to determine the single operation of the generator from the frequency fluctuation amount. Detection of the isolated operation of the synchronous generator is performed at high speed and reliably, and settling for the detection of the isolated operation is simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 shows changes in various electric quantities in FIG.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention.

FIG. 4 shows changes in various electric quantities in FIG.

FIG. 5 is a configuration diagram of a conventional reactive power fluctuation method.

FIG. 6 shows changes in various electric quantities according to a reactive power fluctuation method.

FIG. 7 is a configuration diagram of a conventional QC mode frequency shift method.

FIG. 8 shows changes in various electric quantities according to the QC mode frequency shift method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 2 ... 3 ... Synchronous generator 7, 8, 10, 11 ... Single operation detection device 8A ... Frequency calculation part 8B ... Frequency change rate calculation part 8C ... Coefficient unit 8D ... Output limiter 8E ... Frequency fluctuation amount calculation part 10A ... Micro fluctuation generator 10B ... Frequency relay 10C ... Timer

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference) 5G066 HA11 HB02 5H590 AA08 AA21 CC01 CE01 DD64 EA13 EB02 EB21 FC25 GA02 HA02 HA09 HB02 JA08 JA09 JA13 JA14 JA15

Claims (1)

[Claims] 1. An active system in which a synchronous generator is connected to a distribution system under the condition of reverse power flow, and when the amount of frequency fluctuation at an interconnection point exceeds a set value, the synchronous generator is detected as an isolated operation. Calculating means for obtaining an amount proportional to the frequency change rate or the frequency change amount of the interconnection point, and using this amount as a voltage positive feedback amount to the automatic voltage adjustment circuit of the synchronous generator. And a minute fluctuation amount generator that is superimposed on the positive feedback amount with a minute fluctuation amount that can suppress a frequency fluctuation when the synchronous generator is in an interconnected state and a fluctuation amount of a constant cycle. Characteristic feature is an isolated operation detection device for a synchronous generator.