JPH09215204A - Individual-operation detection method for synchronous generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an individual-operation detection method in which preventive measures against a malfunction are sufficient and whose reliability is high. SOLUTION: In a method, a synchronous generator 2 which is linked to a power system as a distributed power supply is paralleled off, and an individual operation is detected. On the basis of the output and the apparatus constant of the synchronous generator 2, on the basis of the transfer function of an automatic voltage regulator 9 and on the basis of the transfer function of a speed governor, the very small change amount of a power amount and a cycle are computed by a computing and control part 10, the frequency change portion of the synchronous generator 2 is computed by a frequency relay part 20, and an individual operation is detected under a condition that the change portion is at a settling value or higher. In addition, on the basis of the calculation signal of the computing and control part 10 and on the basis of the detection signal of the frequency relay part 20, a voltage-setting very small change signal is output from a disturbance-signal generation part 30, and the automatic voltage regulator 9 is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stand-alone operation detection device for a synchronous generator, and more particularly to a stand-alone operation detection device for a synchronous generator connected to a power system with reverse power flow.

[0002]

2. Description of the Related Art FIG. 18 shows a schematic configuration of an electric power system. Reference numeral 1 is a distribution substation on a commercial power source side as a first power source,
2 (SG) is a consumer side synchronous generator as a second power source connected to the distribution substation 1 through the distribution line 3 and 4 (CB
Reference numeral 1) is a system interconnection point circuit breaker arranged on the distribution line 3, and 5 is a power receiving point circuit breaker.

In such a power system, when the synchronous generator system connected to the distribution line is in an independent operation state by shutting off the system interconnection point (opening the delivery breaker of the distribution substation), system reliability and safety are maintained. Due to the above problem, this condition must be detected and the circuit breaker at the power receiving point must be opened. The current technology in this regard is as follows.

(1) A transfer cutoff system in which an open circuit breaker of the distribution line feed-out breaker is detected at a distribution substation and a trip signal is transferred to the breaker at the power receiving point.

(2) A periodic minute fluctuation is given to the voltage setting value of the automatic voltage regulator of the synchronous generator for which the isolated operation state is to be detected, and the generator frequency fluctuation exceeds a certain value, so that the synchronous generator is generated. Of the isolated generator, and opens the circuit breaker at the power receiving point (for example, the independent generator detecting device for a synchronous generator disclosed in Japanese Patent Laid-Open No. 7-31197).

[0006]

In the transfer cutoff method of the above (1), the cost is low and the merit of grid-connecting the generators diminishes, and if the number of grid-connected generators increases, the distribution substation However, there is a problem that the number of transfer blocking devices is increased and maintenance becomes complicated.

As a method of the above (2), Japanese Patent Laid-Open No. 7-31
The islanding operation detection device for a synchronous generator disclosed in Japanese Patent Publication No. 197 makes it possible to change the magnitude and the cycle with respect to the periodic minute fluctuation of the automatic voltage regulator of the synchronous generator, and the frequency fluctuation of the generator. It is not stated what value should be used to achieve the isolated operation detection function, there is not enough measures to prevent malfunction of the isolated operation detection device against a system short-circuit accident, and the reliability monitoring function of the isolated operation detection device is insufficient. Not equipped.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a highly reliable method of detecting an isolated operation of a synchronous generator with sufficient malfunction prevention measures.

The present invention is directed to an active system among the islanding operation detection functions (active system, passive system) of the synchronous generator. The Ministry of International Trade and Industry has established a guideline for the technical requirements for connecting private power generation equipment to the grid. In March 1993, this guideline states that "requirements for interconnection to low-voltage lines and high-voltage general distribution lines with reverse power flow" added.
As a result, in addition to the conventional transfer cut-off method, it has become possible to connect the system under reverse power flow conditions of distributed power sources by the islanding detection function. This active system is an automatic voltage regulator (A
VR) voltage setting value is constantly fluctuated in a constant cycle,
This condition is detected by the generator frequency fluctuation that occurs in the islanding condition, and it is possible to detect the islanding condition even under the most severe conditions where the circuit breaker at the grid side is shut off under the condition of zero power flow. Is.

[0010]

In order to achieve the above object, the method for detecting an isolated operation of a synchronous generator according to the present invention is basically the automatic voltage regulator (A
VR), a function 1 for constantly outputting a signal to slightly change the voltage setting value in a constant cycle, a generator output for detecting an isolated operation state under optimum conditions, a device constant of the generator, Function 2 that calculates the optimum minute fluctuation amount and cycle for the signal of Function 1 from the transfer function of the automatic voltage regulator and the transfer function of the speed governor and outputs it to Function 1, and the fluctuation amount of the generator frequency Is calculated, and the variation is equal to or more than the set value, the function 3 which is a frequency relay for detecting the isolated operation state is provided.

As a measure for preventing the false detection of the islanding operation, the function 3
There are two types of frequency relays, a first-stage frequency relay with a low setpoint and a second-stage frequency relay with a high setpoint, and the conditions for the first-stage relay operation and the second-stage relay non-operation are met. From a certain period of time, the magnitude of the minute fluctuation amount of the voltage setting value of the automatic voltage regulator is amplified, and the independent operation is performed only when the first stage relay and the second stage relay are operated for a certain period after the condition is satisfied. In addition, when both the first-stage and the second-stage relays are operated, the isolated operation is detected without amplifying the magnitude of the minute fluctuation amount.

In order to prevent erroneous detection of an isolated operation state against acceleration of the generator at the time of a short circuit accident in a system in which the generators are not interconnected, in order to prevent erroneous detection of the islanding accident by the short circuit accident elimination relay of the system, the frequency is set in Function 3. The feature is that the islanding state is detected by integrating the time when the fluctuation amount of is greater than or equal to the settling value and the value being greater than or equal to a certain time.

In order to prevent erroneous detection of the islanding state in response to acceleration of the generator at the time of a short circuit accident in a system in which the generator is not interconnected, the output signal of the frequency relay is operated by the operation of the short circuit accident detection relay in function 3. It is characterized by locking.

For function 1, the system interconnection condition of the generator is detected by the switching signal of the system interconnection breaker, and a small fluctuation signal is sent to the automatic voltage regulator only when the generator is system interconnection. It is characterized by outputting.

A feature of the present invention is that a failure of the function 1 is detected by constantly monitoring the fluctuation of the reactive power output of the generator.

In order to prevent the malfunction of the function 1 from being erroneously detected by reducing the fluctuation of the reactive power output of the generator due to the slight fluctuation of the voltage settling value of the automatic voltage regulator of the function 1 in the independent operation, It is characterized in that the system interconnection condition of the machine is detected by the open / close signal of the system interconnection breaker, and the failure of the function 1 is detected only when the generator is system interconnection.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG.

FIG. 1 shows an embodiment of an isolated operation detecting apparatus for a synchronous motor according to the present invention. In FIG. 1, 6 is a transformer, 7 is a current transformer arranged on a distribution line 3, and 8 is an instrument. Transformer, 9 is an automatic voltage regulator (AVR).

Further, in FIG. 1, reference numeral 10 is a calculation control section, which has a calculation section 11. The calculation unit 11 is configured to detect the current detection signal I flowing through the distribution line 3 by the current transformer 7 and the instrument transformer 8
Based on the voltage signal V according to the above, the optimum minute fluctuation frequency and its magnitude are calculated by calculating based on a generator constant, an automatic voltage regulator transfer function and a speed governor transfer function which will be described later.

Reference numeral 20 denotes a frequency relay section, which has a configuration shown in detail in FIG. 2, and receives the current detection signal I and the voltage detection signal V as input, the first stage relay operation signal, and the synchronous generator 2.
It outputs the islanding operation detection signal, reset signal, and defect detection signal. Reference numeral 30 denotes a disturbance signal generator, which has a disturbance signal generator 31 for generating a disturbance signal by inputting an optimum minute fluctuation frequency signal, which is an arithmetic output signal of the arithmetic unit 11 of the arithmetic control unit 10, and a disturbance signal generator 31. Low-gain output signal, the first-stage relay operation signal of the frequency relay unit 20, and the contact signals of the auxiliary contacts 4b and 5b of the circuit breakers 4 and 5, and the high-gain output of the disturbance signal generator 31. A signal, the first stage relay operation signal, and the contact signals of the auxiliary contacts 4b and 5b are input to the AND gate 33, and the output signal of the NAND gate 32 and the OR gate 34 that sets the output signal of the NAND gate 33 as the OR condition.

FIG. 2 shows the configuration of the frequency relay section 20. In the figure, 21a is a first-stage relay which receives the voltage detection signal V of the instrument transformer 8, and 21b is the same voltage detection signal V. The second-stage relay, 22a is a first integration timer that receives the output of the first-stage relay 21a as an input,
Reference numeral 22b is a second integration timer which receives the output signal of the second stage relay 21b. Reference numeral 23a is a first NAND gate that uses the output signals of the first integration timer 22a and the second integration timer 22b as a NAND condition, and 24 is a NAND gate 2
An on-delay timer that turns on the NAND output signal of 3a as an input, and 25a and 25b turn on for a certain period of time by using the on-output signal of the on-delay timer 24 as an input,
A first switching amplifier circuit and a second switching amplifier circuit that output signals B ₁ and B ₂ . 26a is the second
Switching amplifier circuit 25b, first integration timer 2
First AND gate for the 2a and the output signal of the second integrator timer 22b and AND condition, 27a is a first OR gate which receives the output signal A ₂ of the output signal A ₁ and the NAND gate 23b of the AND gate 26a . Further, in FIG. 2, 28 is an undervoltage relay (UVR) that receives the voltage detection signal V of the instrument transformer 8, 27b is a second OR gate, and 29 is the current detection signal I and the voltage detection signal V. The reactive power detection circuit 26b is an output signal of the reactive power detection circuit (Q) 29 and the auxiliary contacts 4a of the circuit breakers 4 and 5.
2c is a second AND gate that uses the contact input signals of 4 and 4b as an AND condition, and 22c is a third integration timer.

In the isolated operation detecting apparatus for a synchronous generator shown in FIG. 1, in the arithmetic control unit 10 having the function 2, the arithmetic unit 11 inputs the current detection signal I and the voltage detection signal V of the distribution line 3, that is, the power source 1. Is calculated based on the generator constant of the synchronous generator 2, the transfer function of the automatic voltage regulator 9 and the transfer function of the speed governor (not shown) to calculate the optimum magnitude of the minute fluctuation frequency.

In the frequency relay section 20 which is the function 3, the first stage frequency relay 21a and the second stage frequency relay 21b.
Operate by inputting the voltage detection signal V, respectively. The first integration timer (T ₁ ) 22a delays the output signal of the first stage frequency relay 21a by integration and guides it to the first NAND gate 23a, the first AND gate 26b and the second NAND gate 23b. Similarly, the second integration timer (T ₂ ) 22b delays the output signal of the second-stage frequency relay 21b by integration and guides it to the first NAND gate 23a, the first AND gate 26a, and the second NAND gate 23b. . The first NAND gate 23a is the first integration timer 2
It conducts only when the output of 2a is present, and guides its output signal to the on-delay timer 24. On-delay timer 2
The output signal of 4 is the first and second switching amplifier circuits 25.
a, 25b and the second NAND gate 23b. The first switching amplifier circuit 25a is turned on for a certain period of time with input, and outputs a minute fluctuation amount amplification signal when only the first-stage frequency relay is operating. Output to 30. The second switching amplifier circuit 25b is also an on-delay timer 24.
Is turned on for a certain period of time only when there is an input from, and its output signal is led to the first NAND gate 26a. The first NAND gate 26a operates in a state in which the output of the first integration timer 22a, the output of the second integration timer 26b, and the output of the second switching amplifier circuit 25b are all present to output the output signal A ₁ to the first To the NOR gate 27a. The second NAND gate 23b is connected to the first and second integration timers 22a, 2
2b is output and the on-delay timer 24 is not output, and the output signal A ₂ is output to the first OR gate 27.
lead to a. The first NOR gate 27a is controlled led to breaker 4 islanding operation detection signal of the synchronous generator 2 output signal A ₂ of the output signal A ₁ and the second NAND gate 23b of the first NAND gate 26a as OR condition.

In the frequency relay unit 20 having the function 3, the undervoltage relay 28 receives the voltage detection signal V as an input, detects the undervoltage, and inputs the output signal to the second OR gate 27b. The OR gate 27b is provided with an output signal of the undervoltage relay 28, a condition that the inoperative period of the first stage frequency relay 21a is a certain value or more, and a condition that the inoperative period of the second stage frequency relay 21b is a certain value or more. The reset signal is originally output. Reactive power detection relay 2
9 receives the current detection signal I and the voltage detection signal V as inputs,
The output signal is led to the second AND gate 26b. Second
The AND gate 26b is further provided with the auxiliary contact 4a of the circuit breaker 4.
With the contact signal of 1 and the contact signal of the auxiliary contact 5a of the circuit breaker 5 as input conditions, a detection signal indicating that the disturbance signal generating unit 30 is defective is output.

In the disturbance signal generator 30, the disturbance signal generator 31 inputs the output signal of the arithmetic unit 11 of the arithmetic control unit 10 and outputs a low gain disturbance signal and a high gain disturbance signal. The NAND gate 32 supplies the low gain disturbance signal from the disturbance signal generator 31, the first-stage frequency relay operation signal from the frequency relay unit 20, the auxiliary contact 4b of the circuit breaker 4 and the auxiliary contact 5b of the circuit breaker 5, respectively. The output signal is guided to the OR gate 34 using the contact signal as an input condition. And gate 3
3 is a high gain disturbance signal of the disturbance signal generator 31, the first stage frequency relay operation signal of the frequency relay unit 20 and the contact signals of the auxiliary contacts 4b and 5b as input conditions, and the output signal thereof is the automatic voltage regulator 9 Input as a slight fluctuation signal to the voltage setting value.

The disturbance signal generator 30 gives a minute fluctuation of a constant cycle to the voltage set value of the automatic voltage regulator 9 of the synchronous generator 2. The disturbance signal generator 31 generates a minute fluctuation signal of a constant cycle. Occur. The cycle and size are the optimum values calculated by the calculation control unit 10.

The arithmetic control unit 10 calculates the minute fluctuation period and the magnitude from the equation (11) or (12) described later, and outputs the result to the function (1) 30. Therefore, the voltage (V) and current (I) of the generator, the device constant of the generator 1, the transfer function of the automatic voltage regulator 9, and the transfer function of the speed governor are input to the calculation unit 11, and V and I are input. Since the transfer function is calculated as shown in equation (12) by substituting the result of obtaining the output of the generator 1 and the above constants and transfer function values into equation (11), obtain the fluctuation cycle that provides the highest sensitivity. You can

Further, since the set value of the frequency relay of the frequency relay unit 20 is set to a value that does not malfunction due to the constant frequency during grid interconnection, the magnitude of the fluctuation amount depends on the frequency fluctuation during independent operation of the synchronous generator. It is decided to exceed this set value. The optimum magnitude and frequency of the fluctuation amount calculated in this manner are output to the calculation control unit 10, which is the second function. The frequency relay unit 20 receives the voltage (V) of the generator as an input, obtains the frequency fluctuation from it, and detects the islanding state of the synchronous generator when this value exceeds the set value,
A trip command is output to the circuit breaker 4 at the power receiving point to prevent the synchronous generator from operating independently.

As a countermeasure against the erroneous detection of the isolated operation, the frequency relay section 20 for detecting the isolated operation includes a first stage frequency relay (FR1) 21a having a low settling value and a second stage frequency relay (FR2) having a high settling value. 21b are provided, and the automatic voltage regulator 9 is operated for a fixed time (the circuit 25a is turned on for a fixed time after the input is present) after the conditions of the first-stage relay operation and the second-stage relay non-operation are established. The magnitude of the minute fluctuation amount of the voltage settling value is amplified, and the first-stage frequency relay 21a and the second-stage frequency relay 21b operate together for a certain period (the circuit 25b is the same as the circuit 25a) after the condition is satisfied. Only when the synchronous generator is detected as an isolated operation state.

Further, when the tidal current at the grid-side interconnection point is large, the imbalance between the input and the output of the synchronous generator 2 increases when the operation shifts to the independent operation, and the frequency of the synchronous generator also increases accordingly. Immediately after that, the frequency relay may operate in both the first stage and the second stage. On the other hand, when both the first-stage and second-stage relays are operated so that the detection time is not delayed, the islanding operation is detected without amplifying the magnitude of the minute fluctuation amount. The settling value of the first-stage frequency relay 26a is determined so as not to malfunction due to constant frequency fluctuations during system interconnection, and the settling value of the second-stage frequency relay 21b is determined with respect to the magnitude of the amplified minute fluctuation amount. In this way, highly reliable independent operation becomes possible.

FIG. 3 shows the response of the active frequency relay after the synchronous generator shifts to the independent operation under the condition that the power flow at the grid interconnection point is zero. The generator frequency after shifting to the independent operation of the synchronous generator changes in a substantially sine wave shape as shown by the simulation results of FIGS. 10 to 13 described later, and the magnitude gradually increases with time and settles in a steady state. Therefore, the active frequency relay, which operates when the fluctuation value of the frequency exceeds a certain value, repeats the operation recovery as shown in the figure.

On the other hand, in the event of a short circuit in the distribution system, the synchronous generator is accelerated and the frequency increases, so a timer is provided at the output of the frequency relay to prevent erroneous detection in that case. The set value of the timer shall be a value that gives a margin to the fault elimination time by the short circuit fault relay installed at the distribution substation. As described above, the count of the timer repeats the operation and the return after the shift to the isolated operation, so that the detection time is prevented from being delayed by the integral method. In addition, since a short circuit accident may be detected by the under voltage relay (UVR) 28, the under voltage relay 28 is provided to lock the output of the frequency relay to prevent erroneous detection of the short circuit accident.

The condition for setting the timer is when the undervoltage relay 28 is operating. 4 to 6 show an operation sequence of the function (3) 20. FIG. 4 is a basic operation waveform diagram, FIG. 5 is an operation waveform diagram of single operation detection in the minute fluctuation amplification by the operation operation of only the first stage frequency relay 21a, and FIG. 5 is the first stage frequency relay 21a and the second stage frequency relay 21b. 6 is an operation waveform diagram in the case of the same operation of FIG. 6, and FIG. 6 is a waveform diagram at the time of amplifying the minute fluctuation value by the operation of the first stage frequency relay 21a. 4 and 5, FR1 and FR2 are the first
The operation waveforms of the first and second stage frequency relays 21a and 21b are shown, and the timers 1 and 2 are integration timers 22a and 22b.
Operating waveforms, B ₁ and B ₂ are switching amplifier circuits 25a,
25b shows the output waveform, A ₁ shows the output waveform of the AND gate 26a, A ₂ shows the output waveform of the NAND gate 23b, and C shows the isolated operation detection waveform. As shown in FIG. 5, when the on-delay timer setting value is set value of the reset signal T ₂ of the first integral timer 22a reset signal T ₁ and the second integral timer 22b is the same, the first-stage frequency relay 21a and the second stage frequency relay 21b, the operating time is more than the variation.

[0034]

EXAMPLES The performance of the active method is shown below by simulation results. The conditions are as follows.

FIG. 7 shows a system diagram and system constants in which the synchronous generator G ₁ is interconnected. Tables 1 and 2 and Figures 8 and 9
Indicates the device constant of the generator, the constant of the speed governor, and the constant of the automatic voltage regulator. The active power output of the generator is 1.8
3 MW, the reactive power output is 0.4 MVαγ (delay), the power consumption of the local load L ₁ is 0.916 MW, the reactive power is 0.4 MVαγ (delay), and the remaining active power 0.9
It is assumed that 16 MW flows backward and is consumed by the external load L ₀ . Under this condition, the tidal current of the circuit breaker CBO at the system side interconnection point becomes zero.

[0036]

[Table 1]

[0037]

[Table 2]

The voltage setting value of the automatic voltage regulator (AVR) is 0.4 with a peak value of 1% with respect to the magnitude of the rated voltage.
Figure shows fluctuations in AVR voltage set value fluctuations, generator frequency, terminal voltage, and reactive power of the generator when the circuit breaker at the grid side is opened in 1 second with a slight fluctuation with a sine wave of Hz. 1
It shows in 0-13.

As shown in FIGS. 10 to 13, the generator frequency hardly fluctuates when the system is interconnected, but the frequency fluctuates after shifting to the independent operation. The same applies to the fluctuation amount of the terminal voltage of the generator. On the other hand, the fluctuation amount of the reactive power has the opposite tendency.

Next, the frequency variation (first wave magnitude) during islanding when the variation period (1%) of the voltage setting value of the automatic voltage regulator (AVR) is changed and the variation period is changed.
Is shown in FIG. From this, it is understood that the maximum sensitivity is obtained with the fluctuation cycle of 0.4 Hz. In order to reduce the influence on the grid during grid connection, it is important to select the fluctuation period that gives the highest sensitivity. Further, the generator frequency (the size of the first wave) during islanding when the amount of change in the AVR voltage setting value and the changing cycle are fixed at 1% and 0.4 Hz and the active power output of the generator is changed. Is shown in FIG.
This shows that the frequency fluctuates in proportion to the active power of the generator.

Performance of Active Method (Result of Theoretical Investigation) Next, theoretical investigation will be made on the active method. The generator model is
Since there is almost no effect of the damper winding on the active method, a transient model that ignores the effect of this winding is used.

According to the biaxial theory for the synchronous generator, the following equation is established during the isolated operation.

[0043]

## EQU1 ## I _e = L _T (E ' _q ) ² ... (1)

[0044]

(2) V _fd = L _fd E _q ′ + T _d ′ ₀ (d / dt) E _q ′ (2)

[0045]

[Equation 3] E _t = L _et E _q ′ (3) where T _e , V _fd , and E _t are the electric output torque and field voltage of the generator, and E _q ′ is the q-axis of the generator. The transient voltage, T _d ′ _0, is a d-axis open circuit transient time constant, and L _T , L _fd and L _et are defined by the following equations.

[0046]

(Equation 4)

Z _L = R _L + jX _L is the impedance corresponding to the generator output, and the constants other than Z _{L in the} equation (4) are shown in Table 1. Since the variation due to the active method is very small, the following equation is obtained by linearly approximating the equations (1) to (3) and performing the Laplace transform.

[0048]

[Formula 5] ΔT _e = 2L _T E _q ′ ₀ · ΔE _q ′ ...
(5)

[0049]

## _EQU6 ## ΔV _fd (L _fd + ST _d ′ ₀ ) ΔE _q ′ ...
(6)

[0050]

[Equation 7] Δe _t = L _et ΔE _q ′ ...
(7) _{However, △ T e, △ V fd} , △ e t, △ E 'q is T _e, V _{fd, e
The} Laplace transform value with respect to a slight variation of _t and E ′ _q , and E _q ′ ₀ is the average value of E _q ′ during grid interconnection.

Next, for the governor circuit of FIG. 8, linear approximation is performed with the reference speed and the load set value being constant, and the following equation is obtained.

[0052]

## EQU8 ## ΔT _m = −G _GOV Δω _m (8) where ΔT _m and Δω _m are Laplace conversion values, G, for slight fluctuations of the motor output T _m and the generator rotation speed ω _{m. GOV} is a governor circuit transfer function, and G _GOV = {10.
0 / (1 + 0.1S)} × {1.0 / (1 + 0.6)
S)}.

Further, in the automatic voltage regulator (AVR) circuit of FIG. 9, since the time constant of the terminal voltage detection circuit is small, the following equation is obtained by linearly ignoring this.

[0054]

Equation 9] _{△ V fd = G AVR (△} V AVR - △ e t) ......... (9) where, △ V _AVR is the transfer function for small variations in the AVR voltage set value, G _AVR in AVR circuit transfer function _Yes , G _AVR
= {10.0 (1 + 1.56S) /1.56S} ×
It is {1.0 / (1 + 0.2S)}. The following equation is established by linearly approximating the vibration equation of the generator.

[0055]

2H (dΔω _n / dt) = ΔT _m −ΔT _e (10) where 2H is the inertia constant of the generator (including the prime mover),
When a transfer function block diagram during islanding is created from equations (5), (6), (7), (8), (9), and (10),
Becomes 6. From the block diagram of FIG. 16, the transfer function Δω _m (generator rotation speed) of the generator frequency with respect to the AVR voltage set value variation ΔV _AVR is given by the following equation.

[0056]

[Equation 11]

From the equation (11), the frequency fluctuation of the generator during the isolated operation is determined by the device constants of the generator and the constants L _t , L _fd and L _et which are determined by the output state thereof and the q-axis transient voltage at the time of grid interconnection. Is determined by the average value E _q ′ _O , the d-axis open circuit transient time constant T _d ′ _O and AVR, the governor circuit transfer functions G _AVR and G _GOV , and the unit inertia constant 2H of the generator. In the equation (11), the active power output of the generator is 1.83 MW and the reactive power output is 0.267.
Δω _{m under} the condition that MVαγ and the tidal current at the grid side is zero
The result of obtaining the transfer function of is shown in the following equation.

[0058]

(Equation 12)

Expression (12) shows that the frequency fluctuation of the generator can be calculated by the output state of the generator, the equipment constant of the generator, the transfer function of the AVR and the governor circuit, the fluctuation amount of the voltage setting value of the AVR, and the fluctuation cycle. ing. When the Bode diagram is obtained from the equation (12), the result is shown in FIG. 17, which shows that the fluctuation frequency of the AVR voltage setting value is 0.4 Hz, and the maximum sensitivity is obtained with respect to the generator frequency. This is almost in agreement with the simulation result shown in FIG.

[0060]

According to the invention of claim 1, the generator output,
The optimum cycle and magnitude are calculated for the minute fluctuation amount from the generator constant, the transfer function of the automatic voltage regulator and the transfer function of the speed governor, and the value is calculated as the voltage of the automatic voltage regulator. By setting the amount of change in the set value, it is possible to effectively detect the isolated operation.

According to the invention of claim 2, as a measure for preventing erroneous detection of the isolated operation, there are two types of frequency relays for detecting the isolated operation: a first stage having a low settling value and a second stage having a high settling value. After the conditions for the first-stage relay operation and the second-stage relay non-operation are established, the magnitude of the minute fluctuation amount of the voltage setting value of the automatic voltage regulator is amplified for a certain period of time, and then the conditions are satisfied. Only when both the first-stage relay and the second-stage relay operate for a certain period of time, it is detected as the independent operation state of the synchronous generator. Also, if the tidal current at the grid side is large, the imbalance between the input and output of the synchronous generator will increase and the generator frequency will also increase when switching to islanding operation.
Immediately after shifting to the islanding operation, the frequency relay may operate in both the first stage and the second stage. On the other hand, when the relays of the first stage and the second stage are operated together so that the detection time is not delayed, the islanding operation is detected without amplifying the magnitude of the minute fluctuation amount. If the settling value of the first-stage relay is determined so as not to malfunction due to constant frequency fluctuations during system interconnection, and the setting value of the second-stage relay is determined with respect to the magnitude of the amplified minute fluctuation amount,
Highly reliable islanding detection is possible.

According to the third or fourth aspect of the present invention, the invention relates to a countermeasure against a malfunction of the islanding operation detection for a system short-circuit accident, which can prevent a malfunction during a short-circuit accident.

According to the fifth aspect of the present invention, a highly reliable islanding operation detection system can be realized by giving a slight variation to the voltage setting value of the automatic voltage regulator only when the system is interconnected.

According to the sixth aspect of the present invention, it is possible to detect a circuit defect that causes a slight fluctuation in the voltage setting value of the automatic voltage regulator due to the fluctuation amount of the reactive power output of the generator becoming equal to or less than a certain value. It enables a highly reliable islanding detection method.

According to the invention of claim 7, it is possible to perform highly reliable monitoring by detecting a defect only when the invention is interconnected with respect to the invention of claim 6.

[Brief description of drawings]

FIG. 1 is a block connection diagram showing an islanding operation detection device for a synchronous generator according to an embodiment of the present invention.

FIG. 2 is a block connection diagram of a main part of the islanding operation detection device for the synchronous generator of FIG.

FIG. 3 is a waveform diagram showing frequency fluctuation and relay response by an active method.

FIG. 4 is an operation sequence diagram of a main part in the apparatus of FIG.

5 is an operation sequence diagram of a main part of the apparatus shown in FIG.

6 is an operation sequence diagram of a main part of the apparatus of FIG.

FIG. 7 is a block diagram showing a simulation as an embodiment of the present invention.

FIG. 8 is a block diagram showing a simulation as an embodiment of the present invention.

FIG. 9 is a block diagram showing a simulation as an embodiment of the present invention.

FIG. 10 is a characteristic waveform diagram by simulation as an example of the present invention.

FIG. 11 is a characteristic waveform diagram by simulation as an example of the present invention.

FIG. 12 is a characteristic waveform diagram by simulation as an example of the present invention.

FIG. 13 is a characteristic waveform diagram by simulation as an example of the present invention.

FIG. 14 is a characteristic waveform diagram by simulation as an example of the present invention.

FIG. 15 is a characteristic waveform diagram by simulation as an example of the present invention.

FIG. 16 is a transfer function block diagram by simulation as an embodiment of the present invention.

FIG. 17 is a Bode plot of generator frequency using the transfer function of FIG.

FIG. 18 is a block diagram of an electric power system in which synchronous generators are interconnected.

[Explanation of symbols]

 1 ... Distribution substation of electric power system 2 ... Synchronous generator 3 ... Distribution line 4 ... Grid interconnection breaker 4a, 4b ... Auxiliary breaker contact 5a, 5b ... Auxiliary breaker contact 5 ... Breaker 7 ... Current transformer 8 ... voltage transformer 9 ... automatic voltage regulator 10 ... arithmetic control unit 11 ... arithmetic unit 20 ... frequency relay unit 21a ... first stage frequency relay 21b ... second stage frequency relay 22a ... first integration timer 22b ... second Integration timer 23a, 23b ... NAND gate 24 ... On-delay timer 25a, 25b ... Switching amplification circuit 26a, 26b ... AND gate 27a, 27b ... OR gate 28 ... Undervoltage relay 29 ... Reactive power detection circuit 30 ... Disturbance signal generator 31 ... Disturbance signal generator 32 ... NAND gate 33 ... AND gate 34 ... OR gate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaaki Kai 2-1-1 Osaki, Shinagawa-ku, Tokyo Stock company inside the company Meidensha (72) Inventor Hirotoshi Kaneda 2--17 Osaki, Shinagawa-ku, Tokyo Stock association Shameidensha (72) Inventor Toshiro Fujimoto 2-17 Osaki, Shinagawa-ku, Tokyo Stock company Shameidensha

Claims (7)

[Claims] 1. A method for detecting an isolated operation by disconnecting a synchronous generator connected to a power system as a distributed power source, the output of the synchronous generator, a device constant, and the synchronization. An arithmetic control unit that calculates a minute fluctuation amount and a cycle of the frequency from the transfer function of the automatic voltage regulator of the generator and the transfer function of the speed governor, and the fluctuation amount by calculating the synchronous generator frequency fluctuation amount. Frequency relay section that detects that it has become independent operation on the condition that it has become equal to or more than the set value, and minute fluctuation amount of power amount calculated by the calculation section and synchronization and the detection signal of the frequency relay section are input conditions As a disturbance signal generator for inputting a disturbance signal to the automatic voltage regulator of the synchronous generator, the disturbance signal generator outputs a voltage setting value slight fluctuation signal to the automatic voltage regulator, A method for detecting isolated operation of a synchronous generator, characterized in that the pressure set value is slightly changed in a predetermined cycle. 2. The frequency relay section is provided with two types of frequency relays, a first stage frequency relay having a low settling value and a second stage frequency relay having a high settling value, and a first stage relay operation, a second stage The amount of minute fluctuations in the voltage setting value of the automatic voltage regulator is amplified only for a certain period after the condition of relay non-operation is established, and for a certain period after the condition is established, the first stage relay and the second stage relay Are detected only when they operate together, and when the first-stage and second-stage relays operate together, the independent operation is detected without amplifying the magnitude of the minute fluctuation amount. The method for detecting isolated operation of the synchronous generator according to claim 1. 3. The frequency relay unit detects the islanding operation of the synchronous generator on the condition that the time when the fluctuation of the frequency becomes a set value or more is integrated and the value becomes a predetermined time or more, A method for preventing erroneous detection of an islanding state against acceleration of the generator at the time of a short-circuit accident in a system in which the synchronous generator is not connected by time coordination with a short-circuit accident elimination relay of the system, Item 1. A method for detecting an isolated operation of a synchronous generator according to Item 1. 4. The acceleration of the synchronous generator at the time of a short circuit accident of a system in which the synchronous generator is not connected by locking the output signal of the frequency relay by the operation of the short circuit accident detection relay in the frequency relay unit. The method for detecting an isolated operation of a synchronous generator according to claim 1, wherein erroneous detection of the isolated operation state is prevented. 5. The system condition of the synchronous generator is detected by an open / close signal of a circuit breaker for interconnection, and the disturbance signal generator is sent to the automatic voltage regulator only when the synchronous generator is system-interconnected. 2. The method for detecting an isolated operation of a synchronous generator according to claim 1, wherein the small fluctuation signal is output. 6. The synchronous generator according to claim 1, wherein the frequency relay unit monitors a variation of the reactive power of the synchronous generator and detects a defect of the disturbance signal generating unit. An islanding detection method. 7. A system interconnection condition of the synchronous generator is detected by a switching signal of a system interconnection breaker, and a defect of the disturbance signal generator is detected only when the synchronous generator is system interconnected. However, it is possible to prevent erroneous detection of a defect in the disturbance signal generation unit due to a small variation in the reactive power output of the synchronous generator due to a slight change in the voltage set value of the synchronous generator during islanding operation. The method for detecting isolated operation of a synchronous generator according to claim 6, which is characterized in that.