JP2023085614A - Substation connection direction determination method - Google Patents

Abstract

To provide a substation connection direction determination method using an automatic voltage regulator installed on a distribution line.SOLUTION: The substation connection direction is determined by comparing the magnitudes of primary and secondary impedances of an automatic voltage regulator. Data is sampled m1 times in the calculation range before tap switching, data is sampled m2 times in the calculation range after tap switching, and determination is performed m3 times. When the condition of (n/m3)>(1/2) is satisfied between the same value determination n times among m3 determinations, the determination accuracy of the substation connection direction is enhanced by using the final determination result.SELECTED DRAWING: Figure 5

Description

The present invention relates to a method for determining the substation connection direction of an automatic voltage regulator installed on a distribution line.

Figure 1 is an equivalent circuit that simplifies a distribution system with an automatic voltage regulator (SVR: Step Voltage Regulator). The SVR installed on the distribution line performs tap control to keep the voltage on the load side, which is the opposite side, at the appropriate voltage (operating voltage) based on the connection direction of the substation. The connection direction of the substation is changed by system switching.

An example of determining the connection direction of a substation is disclosed in Patent Document 1 below.

Japanese Patent Application Laid-Open No. 2003-102128

The determination method described in Patent Document 1 is to determine the connection direction of the substation by calculating the impedances _Z1 and _Z2 on the primary side and the secondary side as viewed from the SVR and comparing the magnitudes. be. Since the substation connection side is considered to be substantially connected to an infinite bus, the connection direction of the substation is determined based on the fact that the impedance on the substation connection side is smaller than the impedance on the load side.

Specifically, when the tap is switched, the primary side voltage _V1 , the secondary _side voltage _V2 , and the secondary side current _I2 before and after the tap switching are measured. _, the change _ΔV2 of the secondary voltage _V2 , and the change _ΔI2 of the secondary current are calculated.

Then, by substituting the primary side voltage _V1 , the secondary side voltage _V2 , and the secondary side current _I2 into a predetermined formula, the primary side current _I1 is obtained, and the change ΔI1 is calculated _. Z ₁ =ΔV ₁ /ΔI ₁ and Z ₂ =ΔV ₂ /ΔI ₂ on the secondary side, and the magnitudes of both Z ₁ and Z ₂ are compared.

However, in the determination method described in Patent Document 1, when a synchronous generator or an induction generator used for a hydroelectric generator or the like is connected as a distributed power supply on the secondary side viewed from the SVR, the secondary side voltage V ₂ becomes smaller and the change _ΔV1 of the primary side voltage _V1 becomes larger _, which causes erroneous determination of the connection direction of the substation.

Figure 2 is a graph of the system voltage when a distributed power source such as a synchronous generator is connected to the secondary side of the SVR. As indicated by the dotted line in FIG. 2, the system voltage gradually rises as the substation (S/S) approaches the distributed power supply due to the power supplied from the distributed power supply to the system.

The SVR performs tap control to keep the system voltage at an appropriate voltage (operating voltage). The solid line in FIG. 2 shows the state immediately after the voltage of the system voltage is controlled by the SVR. In order to keep the system voltage raised by the distributed power supply at an appropriate voltage, the SVR performs tap control to lower the voltage at the installation point of the SVR.

At this time, if a distributed power supply such as a synchronous generator is connected to the _secondary side of the SVR, as shown by the solid line in _FIG . An event occurs in which the amount of change _ΔV1 in _V1 becomes large.

In this state, if the above-described substation connection direction is determined, as shown in _{FIG .} /ΔI ₁ )<secondary impedance Z ₂ (=ΔV ₂ /ΔI ₂ ). However, as the variation _ΔV2 of the secondary voltage _V2 is small and the variation _ΔV1 of the primary voltage _V1 is large, the primary impedance _Z1 (= _ΔV1 / _ΔI1 )>2 The impedance Z ₂ (=ΔV ₂ /ΔI ₂ ) on the secondary side results in erroneous determination that the connection direction of the substation is opposite to the actual direction.

An erroneous judgment of the substation connection direction causes the problem of the tap sticking to the upper and lower limit positions in the subsequent optimization control of the system voltage by the SVR.

In addition, the system voltage immediately after the tap switching of the SVR indicated by the solid line in Fig. 2 changes with the passage of time as shown in Fig. 3 due to constant power factor control by a distributed power source such as a synchronous generator. , the voltage changes to approach the value immediately before the tap switching, and the secondary voltage seen from the SVR is adjusted to an appropriate voltage.

However, even if the system voltage changes to maintain the appropriate voltage, the SVR taps stuck at the upper and lower limits will not be resolved, which will interfere with subsequent tap control by the SVR.

Therefore, the present invention can suppress erroneous determination of the substation connection direction even when a distributed power supply such as a synchronous generator is connected to the secondary side of a voltage regulator installed for system voltage regulation. A method for determining a substation connection direction is provided.

The invention according to claim 1 calculates the impedance of the primary side distribution system from the amount of change in the primary side voltage and the primary side current generated before and after switching the tap of the automatic voltage regulator installed in the distribution line, and calculates the impedance of the tap. The impedance of the secondary side distribution system is calculated from the amount of change in the secondary side voltage and the secondary side current that occur before and after switching. A method for determining a substation connection direction, wherein determination of whether a substation is connected to is repeated m ₃ times, and the final determination result is obtained when the same determination result is obtained n times out of m ₃ times.

The invention according to claim 2 is characterized in that when m ₃ and n according to claim 1 satisfy the condition of (n/m ₃ )>(1/2), the final determination result is determined. How to determine substation connection direction.

In the invention according to claim 3, the determination of m ₃ times according to either claim 1 or claim 2 is performed in the calculation range before tap switching, and the data sampling is performed m ₁ time in the calculation range after tap switching. A substation connection direction determination method characterized by performing m ₁ ×m ₂ times based on m ₂ data samplings.

According to the invention of claim 4, in the automatic voltage regulator according to any one of claims 1 to 3, the difference voltage change amount between the primary side voltage and the secondary side voltage before and after tap switching exceeds a predetermined voltage in a constant cycle. A method for judging a connection direction of a substation, characterized by detecting the time of the first cycle in the case of an automatic voltage regulator as a tap change completion point.

The invention according to claim 5 is directed to the primary side voltage, secondary side voltage, primary side current, and secondary side current generated before and after switching the tap of the automatic voltage regulator according to any one of claims 1 to 4. In measuring the amount of change in the data measurement interval time before and after tap switching, the control time due to the voltage deviation of the distribution line, the transient phenomenon, and the voltage fluctuation of the distributed power supply connected to the distribution line Considering the number of calculation cycles m ₁ and m ₂ of the primary side voltage, the secondary side voltage, the primary side current, and the secondary side current, and the interval time of the substation connection direction judgment method.

According to the first aspect of the invention, even when a distributed power source such as a synchronous generator is connected to a distribution line, erroneous determination of the substation connection method can be suppressed as much as possible.

According to the second aspect of the invention, it is possible to improve the determination accuracy of the connection method of the substation.

According to the third aspect of the invention, the calculation range used for determination can be increased, and settings can be made according to the system state of the distribution line.

According to the fourth aspect of the present invention, it is possible to detect an accurate tap change completion point, so that it is possible to appropriately set the determination data range of the primary side and secondary side impedances.

According to the fifth aspect of the invention, the voltage deviation of the distribution line, the transient phenomenon that occurs at the time of tap switching, and the influence of the expansion of the change in the primary side voltage are eliminated as much as possible to obtain the data necessary for determining the magnitude of the impedance. It can be performed.

A simplified equivalent circuit of a power distribution system. It is a graph which shows the system voltage immediately before and after tap change. 4 is a graph showing system voltage several seconds after tap switching; 5 is a time chart showing the relationship between a tap change completion point and a data range for impedance determination; 4 is a flowchart showing a method for determining a substation connection direction according to the present invention;

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG. In the equivalent circuit shown in FIG. 1, when determining whether the substation is connected to the primary side or the secondary side of the SVR, the primary side voltage V ₁ of the SVR before tap switching, the secondary side voltage V ₂ , and the secondary side voltage V 2 The secondary side current _I2 , the primary side voltage _V1 ', the secondary side voltage _V2 ', and the secondary side current _I2 ' after tap switching are measured. In the present invention, the measurement is performed m ₁ times before tap switching and m ₂ times after tap switching. Further, in the present embodiment, m ₁ =3 times and m ₂ = _{2 times} are _{exemplified .} Currents I _2a to I _2c , primary side voltages V _1a ' to V _1b ' after tap switching, secondary side voltages V _2a ' to V _2b ', and secondary side currents I _2a ' to I _2b '.

Primary side currents I _1a to I _1c , I _1a ′, I _1b ′ before and after tap switching are secondary side currents I _2a to I _2c , I _2a ′ to I _2b ′ before and after tap switching, and primary side voltages V _1a ~ It is calculated from ratios of V _1c , V _1a ′ to V _1b ′ and secondary voltages V _2a to V _2c and V _2a ′ to V _2b ′. In the case of this embodiment, the primary side currents I _1a to I _1c before tap switching and the primary side currents I _1a ′ to I _1b ′ after tap switching are calculated respectively.

_{The above} data _are measured _{as shown} in FIG _. , within the calculation range before the number of pre-tap change exclusion cycles before the tap change completion point.

Primary side voltages V _1a ' to V _1b ', secondary side voltages V _2a ' to V _2b ', and secondary side currents I _2a ' to I _2b ' after tap switching are excluded after tap switching after the tap switching completion point. Sampling is performed within the calculation range after the number of cycles.

The primary side currents I _1a to I _1c and I _1a ' to I _1b ' before and after the tap switching are the secondary side currents I _2a to I _2c and I _2a ' to I _2b ' and the primary side voltage before and after the tap switching for each sampling. It is calculated from the ratio of V _1a to V _1c , V _1a ' to V _1b ' and the secondary side voltages V _2a to V _2c and V _2a ' to V _2b '.

The calculation range of data measurement before and after tap switching shown in FIG _. ) as much as possible and because the standard deviation σ of the voltage fluctuation of the distribution line is minimized at this number of cycles, it is set for the purpose of increasing the determination accuracy of the connection direction of the substation, which will be described later. In addition, the number of excluded cycles after tap switching is set for the purpose of shortening the interval time as much as possible, and for the transient phenomenon after tap switching and the time constant of constant power factor control by distributed power sources such as synchronous generators connected to distribution lines. is set in consideration of

Further, the above-mentioned tap change completion points are the differential voltages V _12a to V _{12c between the primary side voltages V 1a to V 1c before the tap change and the secondary side voltages V 2a to V 2c and the primary side} voltage V _1a after the tap change. The difference ΔV _12a to V 12b between the difference voltages V _12a ′ to V _12b ′ between the secondary side voltages V _{2a ′} to V _{2b ′} and the secondary side voltages V _{2a ′} to V _{2b ′} is the voltage change for one tap (for example, 50 [V]). It is detected as the time of the first one cycle when the exceeded cycles reach a certain number of cycles (for example, 10 cycles) in succession. The tap change completion point detection condition is set for the purpose of shortening the tap change interval as much as possible and enabling accurate calculation of the tap change point.

Data V _1a -V _1c , V _1a '-V _1b ', V _2a -V _2c , V _2a '-V _2b ', I _2a -I _2c , I _2a '- I _2b ' and I _1a to I _1c and I _1a ' to I _1b ' calculated from these data are used to calculate the magnitudes |Z _1A | to |Z _1F | of the primary side impedance of the SVR. be done.

where |Z _1A |=ΔV _1A /ΔI _1A , ΔV _1A =|V _1a −V _{1a ′} |, and ΔI _1A =|I _1a −I _1a ′|. Similarly, |Z _1B |=ΔV _1B /ΔI _1B , ΔV _1B =|V _1a −V _1b ′|, and ΔI _1B =|I _1a −I _1b ′|. Also, |Z _1C |=ΔV _1C /ΔI _1C , and ΔV _1C =|V _1b −V _1a ′|, ΔI _1C =|I _1b −I _1a ′|, |Z _1D |=ΔV _1D /ΔI _1D Yes, ΔV _{1D =} |V _1b −V _1b ′ _{|, ΔI 1D = | I 1b −I 1b ′} | , ΔI _1E =|I _1c −I _1a ′|, |Z _1F |=ΔV _1F /ΔI _1F , and ΔV _1F =|V _1c −V _1b ′|, ΔI _1F =|I _1c −I _1b ′| be.

In addition, the sampled data V _2a to V _2c , V _2a ' to V _2b ', I _2a to I _2c , I _2a ' to I _2b ' before and after the tap switching are the magnitude of the SVR secondary impedance |Z _2A | to |Z _2F |.

|Z _2A |=ΔV _2A /ΔI _2A , where ΔV _2A =|V _2a −V _2a ′| and ΔI _2A =|I _2a −I _2a ′|. Similarly, |Z _2B |=ΔV _2B /ΔI _2B , where ΔV _2B =|V _2a −V _2b ′| and ΔI _2B =|I _2a −I _2b ′|. In addition, |Z _2C |=ΔV _2C /ΔI _2C , where ΔV _2C =|V _1b −V _1a ′|, ΔI _2C =|I _2b −I _2a ′|, |Z _2D |=ΔV _2D /ΔI _{2D ΔV 2D} =|V _2b −V _2b ′ _| , _{ΔI 2D =} | _{I 2b} −I _{2b ′} | , ΔI _2E =|I _2c −I _2a ′|, |Z _2F |=ΔV _2F /ΔI _2F , and ΔV _2F =|V _2c −V _2b ′|, ΔI _2F =|I _2c −I _2b ′| be.

|Z _1A | to |Z _1F | and the magnitudes |Z _2A | to |Z 2F | of the primary side impedances |Z 1A | to |Z _{2F |} If ≤ |Z _{2A to F} |, it is determined that the substation is connected to the primary side of the SVR as a forward feed, and if |Z _{1A to F} |>|Z _{2A to F} | Determine that a substation is connected to the secondary side of the SVR.

As described above, by comparing the magnitude of the primary side impedance |Z _{1A to F} | and the secondary side impedance |Z _{2A to F} |, it is possible to determine to which SVR the substation is connected with a certain degree of accuracy. However, the present invention is characterized in that the same value is obtained n times out of such m ₃ determinations, and the determination result based on the same value is used as the final determination result. At this time, m ₃ and n shall satisfy the condition of (n/m ₃ )>(1/2).

In addition, due to sampling m ₁ times and m ₂ times in the calculation range in FIG. It is characterized by setting the number of post-tap-switching exclusion cycles that can eliminate erroneous determination of the connection direction.

As the post-tap switching exclusion cycle number that can eliminate erroneous determination of the substation connection direction in a state where the power factor constant control is not in time, for example, the time point at which the power factor constant control by the distributed power source is completed is shown in FIG. ), or just before or after the calculation range.

For the range immediately before or after the calculation range, in the automatic voltage regulator that implements the determination method, by setting an appropriate number of sampling times and calculating, if the same value is obtained n times, the same value will be used. A range in which the determination result matches the actual connection direction of the substation may be used.

FIG. 5 is a flow chart for explaining the determination method of the present invention. First, in the forward feed state of step _S1 , when the SVR performs tap switching in step _S2 to keep the load side voltage at an appropriate voltage, the number of times of reverse feed determination is set to n=0 in step _S3. .

Next, in step _S4 , the size comparison of the impedances |Z _{1A to F} | and |Z _{2A to F} | is started, and in step _S5 , it is determined whether forward feeding or reverse feeding is performed. If the determination result in step _S5 is forward, there is no change in the current status in step _S1 , so it is determined that the substation is connected in the direction determined to be the power supply side in step _S1 .

Conversely, if the determination result in step _S5 is reverse transmission, it is considered that the connection direction of the substation has changed due to system switching or the like. In this case, in step _S7 , the number of reverse transmission determinations is set to n=n+1. The determination of forward or reverse in step _S5 is repeated _m3 times (6 times in this embodiment) between step _S6 and step S6.

Of the ₃ determinations, the number of reverse transmission determinations is L ₁ =n times. After repeating the determination m ₃ times, the process proceeds to step _S8 . If the condition of (L ₁ /m ₃ ) ≤ (1/2) is satisfied in step S ₈ , return to step S ₁ and assume that there is no change in the substation connection direction, and perform control to keep the SVR load side voltage at an appropriate level. continue. For example, when L ₁ = 3, (L ₁ /m ₃ ) = (3/6) = 0.5 ≤ ( _1/2 ). Continue control to keep the SVR load side voltage appropriate.

Also, if the determination result in step _S8 is (L ₁ /m ₃ )>(1/2), the process proceeds to step _S9 , where there is a change in the substation connection direction (forward → reverse). Then, in step _S10 , control is executed to keep the load-side voltage of the SVR, which is the opposite side, at an appropriate level. For example, when L ₁ = 4, (L ₁ /m ₃ ) = (4/6) ≈ 0.7 > ( _1/2 ). It is determined that there has been (forward feeding → reverse feeding), and in step _S10 , control is executed to properly maintain the voltage on the load side of the SVR on the opposite side.

Next, in step _S11 , the number of times n of forward determination is set to 0, and in step _S12 , the size comparison of the impedances |Z _{1A to F} | and |Z _{2A to F} | is started. Then, in step _S13 , it is determined whether forward feeding or reverse feeding is performed. If the determination result in step _S13 is reverse feeding, there is no change in the current state in step _S9 , so it is determined in step _S9 that the power supply side is selected. It is determined that the substation is connected in the direction in which the

Conversely, if the determination result in step _S13 is forward, it is considered that the connection direction of the substation has changed due to system switching or the like. In this case, in step _S15 , the number of forward determinations is set to n=n+1. The determination of forward or reverse in step _S13 is repeated m ₃ times (6 times in this embodiment) between step _S15 and step S15.

The number of forward determinations among the _three determinations is L ₂ =n times. After the determination is repeated m ₃ times, the process moves to step _S16 . If the condition (L ₂ /m ₃ ) ≤ (1/2) is satisfied in step S ₁₆ , then return to step S ₉ and assume that there is no change in the substation connection direction, and perform control to keep the SVR load-side voltage at an appropriate level. continue. For example, when L ₂ = 2, (L ₂ /m ₃ ) = (3/6) = 0.5 ≤ ( _1/2 ). Continue control to keep the SVR load side voltage appropriate.

Also, if the determination result of step _S16 is (L ₂ /m ₃ )>(1/2), the process proceeds to step _S1 , and there is a change in the substation connection direction (reverse → forward). Then, in step _S2 , control is executed to keep the load side voltage of the SVR, which is the opposite side, at an appropriate level. For example, when L ₂ = 4, (L ₂ /m ₃ ) = (4/6) ≈ 0.7 > ( _1/2 ). It is determined that (reverse feeding → forward feeding) has occurred, and in step _S2 , control is executed to properly maintain the voltage on the load side of the SVR on the opposite side.

Even in the method of determining _the substation _connection direction shown in FIG. 2, an event occurs in which the change _ΔV2 of the secondary side voltage _V2 becomes smaller and the change _ΔV1 of the primary side voltage _V1 becomes larger, as shown in FIG.

This phenomenon occurs when a distributed power source such as a synchronous generator operates to keep its power factor constant, so that the power factor of the system is the same as before tap control by SVR was performed (constant power factor). As a result, as shown in Fig. 3, after a few seconds delay from the SVR tap switching, the primary side voltage seen from the SVR changes to match the state before the tap switching, and the secondary side voltage seen from the SVR changes to the appropriate voltage. change to keep

Therefore, the present invention eliminates the influence of the transient phenomenon after tap switching by providing the post-tap switching exclusion cycle shown in FIG. Also in the band, the determination of forward and reverse in steps _S5 and _S13 is performed m ₃ times, and the number of determinations (n times = L ₁ ) different from the forward determination in step S ₁ is (L ₁ /m ₃ )>(1/2) (step S ₈ ), or the number of judgments (n times = L ₂ ) different from the reverse transfer judgment in step S ₉ is (L ₂ /m ₃ )>(1/2 ) (step S ₁₆ ), the determination result of n (L ₁ or L ₂ ) times of the same value is taken as the final determination result.

As a result, as shown in FIG. 2, the possibility of erroneous determination can be reduced compared to the case where the connection direction of the substation is determined only by the determination immediately after the tap switching.

In the above embodiment, the calculation range, the number of excluded cycles before and after tap switching, and the length of the horizontal axis of the tap switching time shown in FIG. It is natural.

Also, the number of sampling times of 3 before tap switching and the number of sampling times of 2 after tap switching are merely examples, and it is natural that any number of m ₁ and m ₂ can be set. Note that the number of determinations m ₃ is determined as m ₁ ×m ₂ .

As described above, in the substation connection direction determination method of the present invention, it is determined that the forward/reverse state has changed from the current state n times out of _m3 forward/reverse states, and When the condition of (n/m ₃ )>(1/2) is satisfied, the determination result of n times is used as the final determination result, so erroneous determination of the connection direction of the substation can be suppressed as much as possible.

In addition, we determined the number of AC voltage/AC current cycles used to calculate the optimum interval time before and after tap switching and the amount of voltage/current change. It is possible to determine the substation connection direction using constant power factor control by the generator.

Furthermore, since the tap change completion point can be detected accurately, it is possible to appropriately set the determination data range of the primary side impedance and the secondary side impedance.

INDUSTRIAL APPLICATION This invention is utilized for the automatic voltage regulator for distribution.

Claims (5)

Calculate the impedance of the primary side distribution system from the amount of change in the primary side voltage and primary side current that occurs before and after switching the tap of an automatic voltage regulator installed in the distribution line, and the secondary side that occurs before and after switching the tap Calculate the impedance of the secondary side distribution system from the amount of change in voltage and secondary side current, and compare the magnitudes of both impedances to determine which side of the regulator the substation is connected to, the primary side or the secondary side. A method for determining a substation connection direction, wherein the determination is repeated m ₃ times, and the final determination result is obtained when the same determination result is obtained n times out of m ₃ times. 2. Judgment of substation connection direction according to claim 1, wherein said m ₃ and n are used as said final judgment result when the condition of (n/m ₃ )>(1/2) is satisfied. Method. The m ₃ determinations are performed m ₁ ×m ₂ times based on m ₁ data samplings performed in the calculation range before tap switching and m ₂ data samplings performed in the calculation range after tap switching. 3. The method for determining a substation connection direction according to claim 1 or 2. Detecting the time of the first cycle when the differential voltage change amount between the primary side voltage and the secondary side voltage of the automatic voltage regulator before and after the tap switching exceeds a predetermined voltage in a certain cycle as the tap switching completion point of the automatic voltage regulator. 4. The method for determining a substation connection direction according to any one of claims 1 to 3, characterized in that: In measuring the amount of change in the primary side voltage, the secondary side voltage and the primary side current, and the amount of change in the secondary side current generated before and after switching the tap of the automatic voltage regulator, the interval time between data measurements before and after the tap switching is shortened as much as possible. In addition, considering the voltage deviation of the distribution line, the transient phenomenon, and the control time due to the voltage fluctuation of the distributed power supply connected to the distribution line, the primary side voltage, the secondary side voltage, the primary side current, the secondary 5. The substation connection direction determination method according to claim 1, wherein the calculation cycle numbers _m1 and _m2 of the side current and the interval time are determined.

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