JPH11231949A - Voltage adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage adjusting device capable of reducing tap switching frequency by reducing useless tap switching. SOLUTION: Deviation voltage ΔV and a deviation integration value Vh calculated by a voltage adjusting relay in a master substation are estimated from a voltage change in the receiving end of a slave substation 3B. Fuzzy inference is executed by using a fuzzy rule setting up the estimated values of the deviation voltage ΔV and the deviation integration value Vh as antecedent part variables and setting up a sensitivity correction coefficient Kf for correcting the operation sensitivity of a voltage adjusting relay Ry2 as a consequent part variable and a membership function regulating the degree of each variable suited to a fuzzy label to find out the coefficient Kf. Since the operation judging level of the voltage adjusting relay Ry2 in the slave substation is corrected by using the sensitivity correction coefficient Kf, the variation of secondary side voltage of the slave substation and tap switching frequency can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-load tap-switching device which is connected to a voltage-regulating relay when the secondary voltage of a on-load tap-switching transformer installed in a substation rises or falls outside a dead zone. The present invention relates to a voltage regulator that controls a secondary voltage of a substation to fall within a dead zone by giving a tap switching command to a transformer to perform a tap switching operation.

[0002]

2. Description of the Related Art As a voltage regulator for maintaining a system voltage at a preset target voltage, a tap of an on-load tap switching transformer based on a tap switching command output from an integral type voltage regulating relay (90 relay) is known. The one in which switching is performed is widely used.

FIG. 1 shows an example of a power system, in which 1 is a power plant, 2A is a main transmission line drawn from the power plant, and 3A is connected to the power plant 1 through a main transmission line 2A. Primary substation (upper substation), 2B is a secondary transmission line drawn from primary substation 3A, 3B is a secondary transmission line 2B
, A secondary substation (lower substation) connected to the primary substation 3A through the substation 2C, another secondary transmission line drawn from the secondary substation 5 and a distribution substation or secondary transmission (not shown). It is a customer (load) connected to the secondary substation 3B through the electric wire 2C.

[0004] The voltage V1 (for example, 154000 [V]) transmitted from the power plant 1 is applied to the primary substation 3A by V2.
(For example, 77000 [V]), and a tap-time switching transformer Tsf1 under load, and a secondary side voltage (77) of the transformer Tsf1.
000 [V]) to reduce the detection signal voltage (for example, 110
[V]), a program controller PC1 for program-controlling the setting of a target value of the secondary voltage V2 of the transformer Tsf1 with the output voltage of the instrument transformer PT1 as an input, An integral type voltage adjusting relay (90 relay) Ry1 for outputting a tap switching command so that the voltage V2 detected by the transformer PT1 approaches the target value output by the program controller PC1, and a voltage of the transformer Tsf1 in response to the tap switching command. A voltage adjusting device including a tap changer (not shown) for changing taps is provided.

[0005] The secondary substation 3B has a primary substation 3A.
The voltage V2 transmitted from the side is changed to V3 (for example, 6600
[V]) an on-load tap-changing transformer Tsf2,
The transformer PT2 for instrument which outputs the detection signal voltage (for example, 110 [V]) by stepping down the secondary voltage (6600 [V]) of the transformer Tsf2, and the output voltage of the transformer PT2 for the instrument are input. A program controller PC2 for program-controlling the setting of the target value of the secondary voltage V3 of the transformer Tsf2
And a current transformer CT for detecting the line current IL outputted from the transformer Tsf2, and a tap switching command for bringing the voltage V3 detected by the instrument transformer PT2 closer to a target value outputted by the program controller PC2. Voltage adjusting relay (90 relay) Ry2, a line voltage drop compensator LDC for correcting the input voltage to the relay Ry2 so as to compensate for the line voltage drop caused by the line current IL, and a tap changeover output from the relay Ry2. Transformer Tsf according to command
A voltage regulator including a tap changer (not shown) for switching the two taps is provided.

Voltage adjusting relays (90 relays) Ry1 and Ry1
y2 is used for a voltage adjustment control circuit for automatically controlling a load tap switching transformer, an automatic voltage regulator for power distribution, and the like. The relay includes an integration circuit that integrates a deviation (hereinafter, referred to as a deviation voltage) ΔV from upper and lower limit values of a dead band defined around an input voltage and a preset reference voltage (target voltage), Level determining means for comparing a time integral value (hereinafter, referred to as a deviation integral value) Vh of the deviation voltage obtained from the integration circuit with a predetermined operation determination level K, and a time period opposite to the deviation integral value Vh A tap switching command for instructing that the tap be switched to the step-up side or the step-down side is output with a characteristic (a characteristic that the tap switching is performed with a shorter operation time when the deviation integral value is larger).

FIG. 2 is a time chart showing the operation of the integral type voltage adjusting relay, and FIG. 3 shows an example of its operation characteristics. In FIG. 2, Va indicates a reference voltage (target voltage), and Vb1 and Vb2 indicate a lower limit value and an upper limit value of a dead zone, respectively. The operating characteristics in FIG. 3 show the characteristics of the operating time (the time from when the deviation voltage occurs until the tap switching command is output) to the deviation voltage ΔV ′% (the difference between the input voltage of the voltage relay and the reference voltage). The deviation voltage ΔV ′% is shown as a percentage with respect to the reference voltage.

As shown in FIG. 2, when the integral type voltage adjusting relay detects that the state where the input voltage exceeds the upper limit value Vb2 of the dead zone has continued for a predetermined time at time t1, the tap is cut down. Further, at the time t2, the output voltage becomes lower than the lower limit value Vb1 of the dead zone.
The tap is rounded up when it is detected that the state below the value has continued for a predetermined time. This voltage regulating relay is
As shown in FIG. 3, the deviation voltage Δ between the input voltage and the reference voltage
When V '% is large, the operation is performed at a high speed (a tap switching command is output in a short time), and when the deviation voltage is small, the operation is performed at a low speed.

The equations for determining the tap switching used in the level determining means of the integral type voltage adjusting relay are as shown in the following equations (1) and (2).

Vhu = (100 / VRe) ∫ [V90 (t) −VRe ｛1+ (α / 100)｝] dt> K (1) Vhl = (100 / VRe) ∫ [VRe ｛1− (α / 100)｝ − V90 (t)] dt> K (2) where VRe is a reference voltage (target voltage) of the voltage adjusting relay, and V90 is an input voltage applied to the voltage relay.
Α indicates the width of the dead zone set above and below the reference voltage VRe, and K indicates the operation determination level. The width α of the dead zone is shown as a percentage with respect to the reference voltage VRe.
If the operation determination level K is increased, the operation sensitivity of the voltage adjustment relay is reduced, and the timing of outputting the tap switching command is delayed. If the operation determination level K is reduced, the operation sensitivity of the voltage adjustment relay is increased, and the tap switching command is increased. Output timing is faster.

After the voltage applied to the voltage adjusting relay exceeds the upper limit value of the dead zone, the state continues for a predetermined time, and when the above-mentioned expression (1) is satisfied, a tap down command is output from the voltage adjusting relay. Further, after the voltage applied to the voltage adjustment relay becomes lower than the lower limit value of the dead zone, if the state is continued for a predetermined time and the above equation (2) is satisfied, a tap-up command is output from the voltage adjustment relay.

The line voltage drop compensator LDC is provided with a transformer T to compensate for a voltage drop in the line caused by a load current.
This is provided to increase or decrease the output voltage of sf2. As shown in FIG. 4, the reactance X and the resistance inserted between the secondary coil of the instrumentation transformer PT2 and the voltage adjustment relay Ry2. An R series circuit is provided. The output of the current transformer CT is applied to a series circuit of the reactance X and the resistor R, and the output current Ic of the current transformer CT proportional to the load current IL flows through the reactance X and the resistor R. The reactance X and the resistance R are, respectively, the reactance XL of the impedance of the secondary transmission line 2C from the substation 3B to the load 4 in consideration of the transformation ratio of the instrumentation transformer PT2 and the transformation ratio of the current transformer CT. And the resistance RL. Therefore, at both ends of the line voltage drop compensator LDC, the voltage drop of the line due to the load current IL, Vo-VL (where Vo is the output voltage of the load tap switching transformer Tsf2, VL is the voltage across the load 4).
The voltage drop V due to the secondary current Ic of the current transformer CT is proportional to
PT-V90 appears, and the voltage input from the voltage transformer PT2 to the voltage adjusting relay Ry2 decreases by the amount of the voltage drop VPT-V90. The voltage adjusting relay Ry2 outputs a tap switching command to set the output voltage of the transformer Tsf2 to the set value, and as a result, the substation 3 according to the load current.
The output voltage from B will change, thereby compensating for the line voltage drop due to the load current IL.

Program controllers PC1 and PC2
Is used to program control the setting of the target voltage, this controller divides the day into a plurality of time zones according to the state of the load, and when a predetermined time comes, the voltage adjustment relays Ry1 and Ry1 The set value of Ry2 is automatically switched.

[0014]

In the ideal voltage control by the tap switching control of the on-load tap switching transformer, an average voltage error with respect to a target voltage (a temporal average value of a difference between a system voltage and a target voltage) is determined. Within the management range of
In addition, the control is such that the tap switching frequency can be kept within a specified value.

In general, if the average voltage error with respect to the target voltage is reduced and the voltage management width is narrowed, voltage control close to ideal can be performed. However, if the voltage management width is narrowed, tap switching frequency increases. Since the life of the tap changer is shortened, the goal of keeping the system voltage within a certain control range and the goal of keeping the tap switching frequency within a specified value are in a trade-off relationship, and perform ideal voltage control. It was very difficult.

Further, the conventional voltage regulator is a post-processing type device which integrates a deviation between a system voltage and a target voltage, compares the integrated value with a predetermined judgment level, and determines an operation time for tap switching. In addition, regardless of the dynamic fluctuation of the system voltage, the operation determination level is fixed by a preset set value, so that the operation can be performed in response to sudden voltage fluctuations or changes in the target voltage. There is a problem that the error between the system voltage and the target voltage increases.

Furthermore, conventionally, control of system voltage by a voltage regulator installed in a higher (primary) substation of a power system;
Since the control of the system voltage by the voltage regulators installed in the lower (secondary) substations was performed independently, the lower substations closer to the customers involved the voltage adjustment operation by the voltage regulators in the upper substations. In some cases, useless tap switching may be performed under the influence of the resulting voltage fluctuation, and there is a problem that the number of tap switching increases or the voltage fluctuation width increases.

FIG. 5 shows an example in which useless tap switching is performed in a lower substation under the influence of tap switching in an upper substation. The curve shown by the broken line in FIG. 5 shows the primary voltage of the lower substation, and the curve shown by the solid line shows the secondary voltage of the substation. The drop in the primary voltage indicated by reference symbol A in FIG. 5 (A) is due to the tap down performed at the upper substation, and the decrease in the secondary voltage indicated by reference symbol a is performed at the lower substation. This is due to a tap devaluation. Further, the decrease in the secondary voltage shown by the symbol b is a voltage drop due to the effect of tap dropping performed in the upper substation, and the increase in the voltage shown by symbol c is the tap rounding performed in the lower substation. It is due to.

In the example shown in FIG. 5A, the taps are cut down at the lower substation at time t1 because the secondary voltage of the upper substation has increased. Immediately after that, at time t2, the tap of the upper substation was cut down, so that the primary voltage of the lower substation decreased, and the secondary voltage decreased below the target value. At time t3 when the time limit has elapsed, tap rounding is performed at the lower substation. That is, in this example, even if the tap is not switched at the time t1, the time t1
After waiting until 2, the secondary side voltage of the lower substation should have been adjusted to an appropriate range by tap switching performed at the upper substation, but in practice, at time t1, useless tap switching at the lower substation was performed. Then, useless tap switching is performed at time t3. As described above, when the useless tap switching is performed, the number of times of tap switching increases, so that not only the life of the tap switch is shortened, but also undesirable results such as an increase in voltage fluctuation and an increase in average voltage error are caused.

An object of the present invention is to reduce the frequency of tap switching by reducing useless tap switching, and at the same time, when the average voltage error can be expected to be reduced by performing the tap switching, the tap switching is positively performed. It is an object of the present invention to provide a voltage adjusting device capable of performing the above-mentioned operations.

[0021] Another object of the present invention is to provide a voltage regulator capable of suppressing a voltage fluctuation occurring when tap switching is performed in an upper substation and reducing an average voltage error with respect to a target voltage. It is in.

[0022]

SUMMARY OF THE INVENTION According to the present invention, a difference between an input voltage and a difference between an input voltage and an upper limit value of a dead zone set above and below a target voltage is provided. Voltage calculating means for calculating the deviation voltage as a deviation voltage, integral value calculating means for calculating a time integral value of the deviation voltage calculated by the deviation voltage calculating means as a deviation integral value, and a deviation integral value calculated by the integral value calculating means And a level determination means for outputting a tap switching command for instructing to switch the tap of the on-load tap switching transformer when the deviation integral value exceeds the operation determination level by comparing the A voltage adjusting relay provided so that a voltage including information on the secondary side voltage of the hour tap switching transformer is input;
A tap changer for switching taps of a tap changer at load according to a tap change command; and a voltage regulator for controlling a secondary voltage of the transformer at load change to fall within a dead zone. And voltage regulators installed in lower substations of power systems installed in substations and lower substations.

In the above-described power system, it is often possible to predict from the voltage change at the receiving end of the lower substation that the tap switching operation of the transformer of the upper substation will be performed in the near future. If it is predicted that tap switching will be performed in the transformer of the upper substation in the near future, if the timing of tap switching in the lower substation is delayed by some method, it will be performed in the transformer of the lower substation It is possible to reduce the number of unnecessary tap switching.

Therefore, in the present invention, the deviation voltage ΔV and the deviation integral value Vh calculated by the voltage adjusting relay of the upper substation are estimated from the voltage change of the receiving end of the lower substation, and the higher order is calculated based on the estimated values. The substation is predicted tap switching to be performed in the near future, and from the prediction result, the suitability of tap switching in the lower substation is determined to reduce the voltage fluctuation and the number of tap switching. More specifically, a sensitivity correction coefficient Kf is obtained by performing fuzzy inference using an estimated value of the deviation voltage ΔV and the deviation integrated value Vh calculated by the voltage adjusting relay of the upper substation, and using the sensitivity correction coefficient. By correcting the operation determination level K of the voltage regulating relay of the lower substation, the fluctuation of the secondary voltage of the lower substation can be reduced,
The number of tap switching is reduced.

That is, in the present invention, the estimated value of the deviation voltage and the estimated value of the deviation integrated value calculated in the voltage regulating relay installed in the upper substation (these estimated values are, for example, the receiving end of the lower substation). Is obtained from the voltage change of the subordinate substation, and the sensitivity correction coefficient K used to correct the operation determination level of the voltage adjustment relay installed in the lower substation.
a plurality of fuzzy rules in which f is a consequent variable and the state of each variable is expressed stepwise by a plurality of fuzzy labels;
Fuzzy inference is performed using a membership function that determines the degree to which the antecedent variable conforms to each fuzzy label concept and a membership function that determines the degree to which the consequent variable conforms to each fuzzy label concept. Accordingly, the operation of the fuzzy inference means for outputting the value of the consequent variable that matches the value of the antecedent variable, and the operation of the voltage regulating relay of the lower substation using the sensitivity correction coefficient Kf output from the fuzzy inference means Correction calculation means for correcting the determination level is provided.

The correction calculating means is configured to change the operation determination level by multiplying the operation determination level of the voltage adjusting relay by a sensitivity correction coefficient, for example.

In this case, when it is predicted that the secondary side voltage of the lower substation is within an appropriate range by the tap switching operation at the upper substation, the sensitivity correction coefficient Kf is increased and the tap switching operation at the lower substation is performed. The sensitivity was lowered and voltage adjustment by tap switching operation at the upper substation could not be expected.
When the secondary voltage of the lower substation deviates from the appropriate range or is predicted to deviate, the sensitivity correction coefficient is set to less than 1 to increase the sensitivity of the tap switching operation in the lower substation. It is preferable to set rules and each membership function.

With the above-described configuration, voltage fluctuations occurring on the lower substation side due to tap switching performed in the nearer substation in the near future are estimated, and based on the estimation result, the voltage adjustment installed in the lower substation is performed. The operation determination level used by the level determination means of the relay can be changed every moment. Therefore, if it is predicted that tap switching will be performed at the upper substation in the near future and the secondary side voltage of the lower substation is within an appropriate range, the operation of the voltage regulating relay installed at the substation to be controlled The sensitivity can be reduced to prevent useless tap switching, and the tap switching frequency can be reduced to extend the life of the tap switch.

When it is permitted to make the number of tap changes per day equal to that of the conventional one, the number of tap changes performed in the substation to be controlled in accordance with the conventional tap change in the upper substation should be reduced. Can be reduced, the sensitivity correction coefficient in the specific time zone can be reduced so as to allow an increase in the number of tap switching in the specific time zone, so that the operation sensitivity of the voltage adjustment relay in the specific time zone can be reduced. It is possible to narrow the fluctuation width of the secondary side voltage of the substation to be controlled.

Further, with the above configuration, when tap switching is performed in the upper substation immediately after the tap switching is performed in the controlled substation, a large voltage fluctuation occurs on the secondary side of the controlled substation. Since this can be prevented, the average voltage error with respect to the target voltage can be reduced.

Further, with the above configuration, when it is not possible to expect the adjustment of the secondary side voltage of the substation to be controlled due to tap switching at the upper substation, it is predicted in advance by fuzzy inference and compared with the conventional one. Since the tap change can be performed quickly, the maximum fluctuation width of the secondary voltage of the substation to be controlled can be suppressed.

As a fuzzy inference method, an evaluation value ri of the antecedent part of each rule is obtained by taking a logical product (MIN) of variables of the antecedent part of each fuzzy rule, and then the same rule as the evaluation value ri is obtained. The fuzzy set obtained by ANDing the fuzzy set of the consequent variable with the fuzzy set is determined as the conclusion of each rule, and the logical sum (MAX) of the conclusions obtained for all the fuzzy rules is calculated as the fuzzy set of the conclusion of the rule group. Value of each antecedent part of each rule is obtained by calculating the logical product (MIN) of the variables of the antecedent part of each fuzzy rule and the same rule as the evaluation value ri The fuzzy set obtained by taking the algebraic product of the consequent variable with the fuzzy set is taken as the conclusion of each rule, and the logical sum (MAX) of the conclusions of all fuzzy rules is taken as the fuzzy And a method of a set, various methods are known, in carrying out the present invention may be used to select how the proper results are obtained.

[0033]

FIG. 6 shows a configuration of a voltage regulator of a lower substation to which the present invention is applied. The voltage regulator according to the present invention comprises a tap switching transformer Tsf2 and a transformer Tsf2. And a sensitivity correction block 12 for correcting the operation determination level of the voltage adjusting relay based on fuzzy inference to correct the sensitivity of the tap switching operation.

The voltage control function block 11 is similar to the one provided in the conventional voltage regulator shown in FIG.
Instrumentation transformer PT for detecting the secondary voltage of transformer Tsf2
2, a program controller PC2, a line voltage drop compensator LDC, and a voltage adjusting relay Ry2.

The sensitivity correction block 12 includes an instrumentation transformer PT3 for detecting a primary voltage of the transformer Tsf2 (a receiving end voltage of the lower substation 3B) and a primary transformer Tsf2 detected through the instrumentation transformer PT3. Deviation voltage Δ calculated from the voltage change in the voltage adjustment relay installed in the upper substation
A deviation voltage estimating means 13 for obtaining an estimated value of V, a deviation integrated value estimating means 14 for obtaining an estimated value of the deviation integrated value Vh from the deviation voltage ΔV, and a fuzzy inference means 19 are provided. The fuzzy inference means 19 uses the estimated value of the voltage deviation ΔV and the estimated value of the deviation integral value Vh as antecedent variables and uses the estimated value for correcting the operation determination level K of the voltage adjusting relay Ry2 installed in the lower substation 3B. A plurality of fuzzy rules 15 in which the state of each variable is expressed stepwise by a plurality of fuzzy labels using the sensitivity correction coefficient Kf as a consequent variable, and the antecedent variable and the consequent variable conform to the concept of each fuzzy label. A membership function 16 that defines the degree, and a predicate operation unit 17 and a consequent operation unit 18 that determine the conformity of the antecedent and consequent parts of the respective fuzzy rules 15 using the membership function 16. And outputs the value (sensitivity correction coefficient) Kf of the consequent variable that matches the value of the antecedent variable.

The sensitivity correction coefficient Kf output from the fuzzy inference means 19 is given to the voltage adjusting relay Ry2. The voltage adjustment relay Ry2 has a reference value of the operation determination level K [the operation determination level used in the above-described equations (1) and (2)] used by the level determining means (the operation determination level of the conventionally used operation determination level). (Same value) is multiplied by a sensitivity correction coefficient Kf to correct the operation determination level.

The level judging means of the voltage adjusting relay Ry2 includes:
The operation determination level corrected by the correction calculating means is compared with the deviation integral value, and when the deviation integral value exceeds the corrected operation determination level, a tap switching command is given to the tap changer. Therefore, when the sensitivity correction coefficient Kf is equal to 1, the voltage adjusting relay Ry2 generates a tap switching command with the same sensitivity as in the past, and causes the transformer Tsf2 to perform tap switching.
When Kf is larger than 1, the voltage adjusting relay Ry2 outputs a tap switching command with lower sensitivity than in the past, and performs tap switching. If Kf is smaller than 1, the voltage adjusting relay Ry2 outputs a tap switching command with higher sensitivity than in the past, and switches the tap of the transformer Tsf2.

The deviation voltage ΔV calculated by the voltage adjusting relay of the upper substation can be estimated from, for example, a line current flowing into the primary side of the lower substation and a change in the primary voltage of the lower substation. . For example, a voltage drop due to the secondary transmission line 2B connecting between the upper substation and the lower substation is calculated from the line current flowing into the primary side of the lower substation, and the voltage drop is calculated as the primary voltage of the lower substation. To obtain the secondary voltage of the upper substation and calculate the difference between the secondary voltage of the upper substation and the upper and lower limits of the dead zone to calculate the voltage at the upper substation. The estimated deviation voltage ΔV can be estimated. Further, by integrating the deviation voltage ΔV, the deviation integral value Vh can be estimated.

In the present invention, the sensitivity correction coefficient Kf is set to be larger than 1 when tap switching is performed in the upper substation in the near future and the secondary voltage of the lower substation is predicted to be in an appropriate range. If the sensitivity of the voltage regulating relay in the lower substation is lowered, tap switching cannot be expected to be performed in the upper substation, and if the secondary voltage of the lower substation is predicted to deviate from the appropriate range, A fuzzy rule and a membership function are determined so that the sensitivity correction coefficient Kf is made smaller than 1 to increase the sensitivity of the voltage regulating relay of the lower substation.

As described above, when the tap switching is performed in the upper substation in the near future and the secondary voltage of the lower substation is predicted to be within an appropriate range, the sensitivity correction coefficient Kf is set to be smaller than 1. If the sensitivity of the voltage adjustment relay at the lower substation is reduced, the tap switching timing is delayed, so that the number of unnecessary tap switchings can be reduced. For example,
In the example shown in FIG. 5A, useless tap switching was performed at times t1 and t3, but in this example, the operation determination level K is increased to reduce the operation sensitivity of the voltage adjustment relay of the lower substation. When it is lowered, as shown in FIG.
To prevent tap change at time t3 and time t3.
2 allows the secondary voltage to be within an appropriate range.

Further, with the above-described configuration, it is possible to perform the tap switching of the lower substation by predicting the result of the tap switching at the upper substation performed in the near future, so that the tap switching is performed at the lower substation. If a tap change is performed immediately after the upper substation, large voltage fluctuations on the secondary side of the substation to be controlled are prevented from occurring, and the average voltage of the lower secondary substation against the target voltage Errors can be reduced.

As described above, when it is not expected that tap switching will be performed at the upper substation and the secondary voltage of the lower substation is predicted to deviate from an appropriate range, the sensitivity correction coefficient Kf is set to 1 If the sensitivity of the voltage adjustment relay of the lower substation is increased by making it smaller than that, the tap change at the lower substation can be performed more quickly than before, and the maximum fluctuation range of the secondary voltage of the controlled substation can be suppressed. it can.

Hereinafter, the sensitivity correction coefficient Kf is obtained by fuzzy inference.
Will be described by taking the case of the MIN / MAX method as an example.

In performing the fuzzy inference, a plurality of fuzzy labels having a specific concept are used in order to gradually represent the degree of the state of information to be input and the degree of the magnitude of a variable to be obtained as a conclusion. . An example of a fuzzy label used to represent the magnitude of each of the estimated value of the deviation voltage ΔV, the estimated value of the deviation integrated value Vh, and the magnitude of the sensitivity correction coefficient Kf calculated by the voltage adjusting relay of the upper substation. For example, it is as shown in Table 1.

[0045]

[Table 1] In the example shown in Table 1, the deviation voltage ΔV, the deviation integral value Vh,
The magnitudes of the respective magnitudes are represented using fuzzy labels PB, PM, ZE, NM, and NB having five different concepts with respect to the sensitivity correction coefficient Kf. These fuzzy labels are used to represent almost the same concept, but the precise meaning of each differs for each variable used. For example, the PM used for the deviation voltage ΔV indicates that the deviation voltage is “small on the positive side” (the secondary voltage exceeds the upper limit of the dead zone, but the excess amount is relatively small). The PM used for the deviation integral value Vh means that the deviation integral value is "large". The PM used for the sensitivity correction coefficient Kf is
This means that the value of Kf is "slightly large".

When performing fuzzy inference, a function (referred to as a membership function) that defines the relationship between the above-mentioned variables and the degree (fitness) μ that conforms to the concept of each fuzzy label is prepared. Together with If A is
B and Cis D, and ..., then X
is Y. A plurality of fuzzy rules in If-then format are created in consideration of empirical rules.

In the fuzzy rules of the If-then format, the condition part following If is called a "preceding part" and t
The conclusion following hen is referred to as the "consequence." In the present specification, variables constituting the antecedent part are referred to as antecedent variables, and variables constituting the consequent part are referred to as consequent variable.

In the present invention, the estimated value of the deviation voltage ΔV and the estimated value of the deviation integrated value Vh of the voltage regulating relay of the upper substation obtained from the change in the primary voltage of the lower substation are used as the antecedent variables, and A plurality of fuzzy rules are created by using the correction coefficient Kf as a consequent part variable and expressing the state of each variable stepwise using a plurality of fuzzy labels.

One example of the membership function used in the present invention is shown in FIGS. FIG. 7A shows the estimated value of the deviation voltage ΔV and the fuzzy labels PB, PM, ZE, N
FIG. 7B shows a membership function that defines the relationship between the estimated value of the deviation integral value Vh and the fuzzy labels PB, PM, ZE, NM, and NB. Is shown. The deviation voltage ΔV is shown as a value when the reference voltage of the voltage adjusting relay is about 100 [V], and the deviation integral value Vh is the operation determination level K.
Is displayed in%. FIG. 7C shows the sensitivity correction coefficient Kf.
And a membership function that defines the relationship between the fuzzy labels PB, PM, ZE, NM, and NB.

In these examples, the labels NB used for the deviation voltage ΔV, the deviation integral value Vh, and the sensitivity correction coefficient Kf are used.
A Z-type function is used as a membership function of the label PB used for the deviation voltage ΔV, the deviation integral value Vh, and the sensitivity correction coefficient Kf. Also, the deviation voltage ΔV and the deviation integral value V
h, and labels PM, Z used for sensitivity correction coefficient Kf
A triangle membership function is used as a membership function for E and NM.

Table 2 shows an example of a rule matrix defining the fuzzy rules used in the present invention.

[0052]

[Table 2] In the rule matrix shown in Table 2, “large on the negative side, NB”, “small on the negative side, N
"M", "near zero, ZE", "positive side small, PM" and "positive side large, PB" indicate the proposition of the antecedent part about the deviation voltage ΔV, and are described in the first column. "Zero, N
The description of "B", "near zero, NM", "small, ZE", "large, PM", and "near the threshold, PB" indicates the proposition of the antecedent of the deviation integral value Vh. Also, r1, r2, and r2 shown at the upper part where each row and each column intersect are shown.
The display of r3,..., r25 means rule 1, rule 2, rule 3,. r1,
Kf = N shown in the middle of each of r2, r3,.
B, Kf = NB, Kf = NM,... Indicate the conclusion of the sensitivity correction coefficient Kf which is a consequent variable. The indications such as "standard control", "slightly delayed", and "largely delayed" shown in the lower part of each column of r1 to r25 indicate the sensitivity correction coefficient Kf.
Are set based on the conclusions shown in the respective columns.

A series of fuzzy rules shown in the rule matrix of Table 2 is written as a sentence in If-then format as follows.

Rule 1: If ΔV is NB and Vh is NB then Kf is NB. Rule 2: If ΔV is NM and Vh is NB then Kf is NB. Rule 3: If ΔV is ZE and Vh is NB then Kf is NM. Rule 4: If ΔV is PM and Vh is NB then Kf is ZE. Rule 5: If ΔV is PB and Vh is NB then Kf is PM. Rule 6: If ΔV is NB and Vh is NM then Kf is NB. Rule 7: If ΔV is NM and Vh is NM then Kf is NM. Rule 8: If ΔV is ZE and Vh is NM then Kf is NM. Rule 9: If ΔV is PM and Vh is NM then Kf is ZE. Rule 10: If ΔV is PB and Vh is NM then Kf is PM. Rule 11: If ΔV is NB and Vh is ZE then Kf is NB. Rule 12: If ΔV is NM and Vh is ZE then Kf is NM. Rule 13: If ΔV is ZE and Vh is ZE then Kf is ZE. Rule 14: If ΔV is PM and Vh is ZE then Kf is ZE. Rule 15: If ΔV is PB and Vh is ZE then Kf is PM. Rule 16: If ΔV is NB and Vh is PM then Kf is NM. Rule 17: If ΔV is NM and Vh is PM then Kf is NM. Rule 18: If ΔV is ZE and Vh is PM then Kf is ZE. Rule 19: If ΔV is PM and Vh is PM then Kf is PM. Rule 20: If ΔV is PB and Vh is PM then Kf is PB. Rule 21: If ΔV is NB and Vh is PB then Kf is NM. Rule 22: If ΔV is NM and Vh is PB then Kf is ZE. Rule 23: If ΔV is ZE and Vh is PB then Kf is PB. Rule 24: If ΔV is PM and Vh is PB then Kf is PB. Rule 25: If ΔV is PB and Pf is PB then Kf is PB. As described above, the two variables of the estimated value of the deviation voltage ΔV and the estimated value of the deviation integrated value Vh calculated by the voltage adjusting relay of the upper substation are set as the antecedent variables, and the sensitivity correction coefficient Kf is set as the consequent. When creating a fuzzy rule as a partial variable,
The sensitivity correction coefficient Kf is determined by applying the MIN-MAX method using the membership functions shown in FIGS.

Assuming that the deviation voltage ΔV is about 0.3 [V], as shown in FIG. 7A, the degree of conformity μ of the deviation voltage ΔV to the concept of the fuzzy label PM is 0.3. , The degree of conformity μ to the concept of the fuzzy label ZE is 0.6. The degree of conformity of the deviation voltage to other fuzzy label concepts is all zero.

If the deviation integral value Vh is 50%], the fuzzy label NM is obtained as shown in FIG.
Is 0.5, and the conformity of Vh to the concept of fuzzy label ZE is 0.5. The degree of conformity of the deviation integral to other fuzzy label concepts is zero.

Here, for each of the rules 1 to 25, the minimum value of the conformity of the antecedent variable to the concept of the fuzzy label is obtained as the antecedent part evaluation value ri. The rule that the evaluation value ri of the antecedent part indicates a value other than 0 is rule 8,
In the other rules, the evaluation value ri of the antecedent part is 0.

After the evaluation value ri of the antecedent part of each rule is obtained in this way, the membership function for the fuzzy label that gives the conclusion of the consequent part of each rule is calculated as the evaluation value of the antecedent part of the rule. cutting by ri (calculating the logical product)
The upper part is removed from the evaluation value ri of the membership function to obtain a fuzzy set as the conclusion of each rule.

The above example is specifically shown in rule 8
Is "If ΔV is ZE and Vh is NM then
Kf is NM. In this case, the degree of conformity of the deviation voltage ΔV to ZE is 0.6, and the degree of conformity of the deviation integral value Vh to NM is 0.5. Of these, the smaller one, 0.5, is defined as the evaluation value ri of the antecedent part of the rule 8, and as shown in FIG. The function is evaluated by the evaluation value r of the antecedent part.
By cutting at i = 0.5 and removing the portion above 0.5, a fuzzy set M8 (the hatched portion in FIG. 8A) as the conclusion of rule 8 is obtained.

Rule 9 states that “If ΔV is PM and
Vh is NM then Kf is ZE. Where the fitness of ΔV to PM is 0.3, and Vh is N
The fitness for M is 0.5. The smaller value “0.3” of these fitness levels is used as the evaluation value r of the antecedent part of Rule 9.
As shown in FIG. 8B, the membership function of the label ZE that gives the conclusion of the consequent is evaluated by the evaluation value ri of the consequent.
= 0.3, and a fuzzy set M9 as a conclusion of the rule 9 is obtained.

Rule 13 states that “If ΔV is ZE an
d Vh is ZE then Kf is ZE. Where the fitness of ΔV to ZE is 0.6 and the fitness of Vh to ZE is 0.5. The smaller one of these fitness levels, “0.5”, is used as the evaluation value ri of the antecedent part of the rule 13, and as shown in FIG. The membership function is cut at the evaluation value 0.5 of the antecedent part, and a fuzzy set M13 as the conclusion of the rule 13 is obtained.

Rule 14 states that “If ΔV is PM an
d Vh is ZE then Kf is ZE. Here, the degree of conformity of ΔV to PM is 0.3, and the degree of conformity of Vh to ZE is 0.5. Of the degrees of conformity, the smaller one “0.3” is used as the evaluation value ri of the antecedent part of the rule 14, and as shown in FIG. Is cut at the evaluation value 0.3 of the antecedent part, and a fuzzy set M14 as a conclusion of the rule 14 is obtained.

In other rules, the evaluation value of the antecedent part is 0, so if the membership function that gives the conclusion of the consequent part is cut off based on the evaluation value, the fuzzy set as the conclusion of the rule becomes zero.

After obtaining a fuzzy set as a conclusion for all rules, a logical sum of the obtained fuzzy sets is obtained to obtain a fuzzy set as a conclusion. In the above example, the logical sum of the fuzzy sets M8, M9, M13, and M14 shown by hatching in FIGS. 9A to 9D is obtained.
As indicated by the oblique lines in FIG. 7C, a fuzzy set M is obtained as a conclusion.

Next, the center of gravity G of the fuzzy set M is obtained and defuzzified, and a sensitivity correction coefficient Kf (= about 2.5) corresponding to the center of gravity G is output as an inference result. By multiplying the thus obtained sensitivity correction coefficient Kf by the reference value of the operation determination level K, the operation determination level K used by the level determination means of the voltage adjustment relay Ry2 is corrected.

[0066]

As described above, according to the present invention, voltage fluctuations occurring on the lower substation side due to tap switching performed in the upper substation in the near future are estimated, and the lower substation is estimated based on the estimation result. Since the operation determination level used by the level determination means of the voltage adjustment relay installed in the substation is changed every moment, tap switching is performed in the upper substation in the near future, and the secondary side voltage of the lower substation enters an appropriate range. When it is predicted that the tapping frequency of the tap changer can be reduced by lowering the operation sensitivity of the voltage regulating relay installed in the control target substation and preventing the useless tap change from being performed. Life can be extended.

When it is permitted to make the number of tap changes per day equal to the conventional number, the number of tap changes performed in the substation to be controlled with the tap change in the upper substation in the related art should be reduced. Can be reduced, the sensitivity correction coefficient in the specific time zone can be reduced so as to allow an increase in the number of tap switching in the specific time zone, so that the operation sensitivity of the voltage adjustment relay in the specific time zone can be reduced. It is possible to narrow the fluctuation width of the secondary side voltage of the substation to be controlled.

Further, according to the present invention, when tap switching is performed in the upper substation immediately after the tap switching is performed in the substation to be controlled, a large voltage fluctuation occurs on the secondary side of the substation to be controlled. Therefore, the average voltage error with respect to the target voltage can be reduced.

Further, according to the present invention, when it is not possible to expect the adjustment of the secondary side voltage of the substation to be controlled due to the tap change at the upper substation, it is predicted in advance by fuzzy inference and compared with the conventional one. Since the tap switching can be performed promptly, the maximum fluctuation width of the secondary voltage of the substation to be controlled can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a configuration of a power system to which the present invention is applied.

FIG. 2 is a time chart showing an operation of a voltage adjusting relay installed in the power system of FIG. 1;

FIG. 3 is a diagram showing operating characteristics of a voltage adjusting relay installed in the power system of FIG. 1;

FIG. 4 is a block diagram showing a configuration example of a voltage regulator provided in the power system of FIG. 1;

FIGS. 5A and 5B respectively show the primary order of a lower substation when a conventional voltage regulator installed in a lower substation is used and when a voltage regulator according to the present invention is used. It is the diagram which showed the change of the side voltage and the secondary side voltage.

FIG. 6 is a block diagram showing a configuration of a main part of the voltage regulator according to the present invention.

FIGS. 7A to 7C are diagrams showing different membership functions used in fuzzy inference.

FIGS. 8A to 8D are explanatory diagrams for explaining a fuzzy inference process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power station 2A Primary transmission line 2B, 2C Secondary transmission line 3A Upper substation 3B Lower substation 4 Customer 11 Voltage control function block 12 Sensitivity correction block 13 Deviation voltage estimation means 14 Deviation integral value estimation means 19 Fuzzy inference means Ry2 Voltage adjustment relay

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H02J 3/12 H02J 3/12 (72) Inventor Takahiro Kakehi 3-2-13, Suzuran Taipeimachi, Kita-ku, Kobe-shi, Hyogo (72) Inventor Makoto Oki 4-110 Nishiyama, Koyama-cho, Tottori-shi, Tottori Prefecture (2) Dormitory RC-1 102 (72) Inventor Masaaki Ohkita 465-8 Iwakura, Tottori-shi, Tottori Prefecture

Claims (3)

[Claims] 1. A load tap switching transformer, and a deviation voltage for calculating a difference between an input voltage and an upper limit value of a dead band set above and below a target voltage and a difference between the lower limit value of the dead band and the input voltage as a deviation voltage. An integration value calculating means for calculating a time integral value of the deviation voltage calculated by the calculation means and the deviation voltage calculation means as a deviation integration value; and a deviation integration value calculated by the integration value calculation means being compared with an operation determination level. Level determining means for outputting a tap switching command for instructing switching of the tap of the on-load tap switching transformer when the deviation integrated value exceeds the operation determination level. A voltage adjusting relay provided so that a voltage including information on the secondary side voltage is input, and a tap changer that changes a tap of the on-load tap change transformer according to the tap change command. A voltage regulator for controlling the secondary side voltage of the on-load tap-changing transformer to be within the dead zone is provided at the lower substation of the power system installed at each of the upper substation and the lower substation. A voltage regulating device, wherein the estimated value of the deviation voltage and the estimated value of the deviation integrated value calculated in the voltage regulating relay installed in the upper substation are set as antecedent variables and installed in the lower substation. A plurality of fuzzy rules in which the state of each variable is expressed in a stepwise manner by a plurality of fuzzy labels using a sensitivity correction coefficient Kf used for correcting the operation determination level of the adjusted voltage adjustment relay as a consequent variable, A membership function defining the degree to which the variable conforms to each fuzzy label concept, and a membership function defining the degree to which the consequent variable conforms to each fuzzy label concept. A fuzzy inference means for outputting the value of the consequent variable corresponding to the value of the antecedent variable by performing fuzzy inference using: a sensitivity correction coefficient Kf output from the fuzzy inference means
And a correction calculating means for correcting the operation determination level of the voltage adjusting relay of the lower substation using the above. 2. The voltage adjustment according to claim 1, wherein the estimated value of the deviation voltage and the estimated value of the deviation integral value of the upper substation are obtained from a change in the voltage at the power receiving end of the lower substation. apparatus. 3. The correction operation means is configured to change an operation determination level by multiplying an operation determination level of the voltage adjustment relay by the sensitivity correction coefficient, and to perform a lower-level operation by a tap switching operation in the upper substation. When it is predicted that the secondary voltage of the substation is in the proper range, the sensitivity correction coefficient Kf is increased to lower the operation sensitivity of the voltage regulating relay installed in the lower substation, and to reduce the operation sensitivity of the upper substation. When the voltage adjustment by the tap switching operation cannot be expected, and the secondary voltage of the lower substation deviates from the appropriate range or is predicted to deviate, the sensitivity correction coefficient is set to less than 1 and the lower substation is set. The said fuzzy rule and each membership function are set so that the operation sensitivity of the voltage adjustment relay installed in a vehicle may be improved. Voltage regulator.