Voltage regulator

Abstract

To provide a voltage regulator, having a regulating transformer with multiple taps, which is arranged on a distribution line that distributes AC from a substation to a load, and which automatically adjusts the voltage within a voltage range by switching the taps of the regulating transformer when the voltage of the distribution line deviates from the specified voltage range.SOLUTION: A voltage regulator 1 has a regulating transformer 2 with multiple taps tn, and a control unit that processes the taps. The control unit acquires primary and secondary voltages during tap switching, acquires the primary and secondary voltages before or after the tap switching, derives a primary difference that is the difference between the primary voltage during the tap switching and the primary voltage before or after the tap switching, derives a secondary difference that is the difference between the secondary voltage during the tap switching and the secondary voltage before or after the tap switching, and determines whether a substation is located on the primary side or the secondary side on the basis of the derived primary difference and secondary difference.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a voltage regulator. [Background technology]

[0002] The voltage regulating device includes a series transformer whose secondary winding is connected in series to the distribution line, a regulating transformer whose primary winding is connected in parallel to the distribution line and whose secondary winding has multiple taps, and a tap changer that switches the multiple taps to connect them to the primary winding of the series transformer (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-312612 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the voltage adjustment device disclosed in Patent Document 1 does not take into consideration the efficient determination of whether a substation serving as a power source is located on the primary side or the secondary side.

[0005] The present invention has been made in consideration of the above circumstances, and its object is to provide a voltage regulating device that can efficiently determine whether a substation is located on the primary side or the secondary side. [Means for solving the problem]

[0006] A voltage adjustment device according to one embodiment of the present disclosure is a voltage adjustment device that is arranged on a distribution line that distributes alternating current from a substation to a load, and has a regulating transformer with multiple taps, and when the voltage of the distribution line deviates from a specified voltage range, the voltage adjustment device switches the taps of the regulating transformer to automatically adjust the voltage within the voltage range, and is equipped with a control unit that performs processing related to the taps, and the control unit acquires the primary side voltage and the secondary side voltage during the tap switching, acquires the primary side voltage and the secondary side voltage before or after the tap switching, derives a primary side difference that is the difference between the primary side voltage during the tap switching and the primary side voltage before or after the tap switching, derives a secondary side difference that is the difference between the secondary side voltage during the tap switching and the secondary side voltage before or after the tap switching, and determines whether the substation is located on the primary side or the secondary side based on the derived primary side difference and secondary side difference.

[0007] In this aspect, the voltage regulator is, for example, a direct switching type SVR (Step Voltage Regulator), and includes a regulating transformer including a plurality of taps, an on-load tap changer including a common terminal, and a control unit that performs processing related to switching of these taps. When the voltage regulator is arranged (connected) on a distribution line, it is connected to a primary side distribution line and a secondary side distribution line. That is, when the on-load tap changer and the regulating transformer are arranged (connected) on a distribution line, the on-load tap changer (common terminal) is connected to the primary side distribution line, and the regulating transformer (through tap) is connected to the secondary side distribution line. The control unit may acquire a value of the primary side voltage (primary side voltage value) at a predetermined period such as 10 msec, and calculate (identify) a value of the secondary side voltage (secondary side voltage value) using a predetermined identification equation with the acquired primary side voltage value as an input factor. Alternatively, the control unit may acquire a primary voltage value (primary voltage value) and a secondary voltage value (secondary voltage value) from measurement transformers (primary measurement transformer (PT1) and secondary measurement transformer (PT2)) provided on each of the primary and secondary power distribution lines at a predetermined period such as 10 msec, and store the acquired primary voltage value and secondary voltage value in the storage unit in association with the time of acquisition. The acquisition period (detection period) of the primary voltage value (primary voltage value) and the secondary voltage value (secondary voltage value) may be determined according to a half cycle (half cycle or more) of the frequency of the commercial power supply from the substation. When the control unit determines that the tap is being switched (tap is being switched), the control unit may store the primary voltage and secondary voltage acquired at the time of the determination in the storage unit as the primary voltage and secondary voltage during tap switching. The control unit derives a primary side difference, which is the difference between the primary side voltage during the tap change and the primary side voltage before or after (just before or just after) the tap change. Furthermore, the control unit derives a secondary side difference, which is the difference between the secondary side voltage during the tap change and the secondary side voltage before or after (just before or just after) the tap change, performs a calculation using these derived primary side difference and secondary side difference as input factors, and determines whether the substation is located on the primary side or the secondary side based on the calculation result.When a voltage regulator such as an SVR is arranged on a distribution line, it is assumed that the side to which a substation (a source substation that supplies power) serving as a power source is connected to the voltage regulator is the primary side, and the side to which a load is connected is the secondary side, as an initial setting in the arrangement. In addition, the distribution line may be loop-shaped, for example, in order to ensure redundancy. When switching is performed on such a loop-shaped distribution line, the connection mode of the substation and the load may be reversed, that is, the substation may be connected to the secondary side, and the load may be connected to the primary side. When comparing the impedance of the distribution line to which the substation is connected and the impedance of the distribution line to which the load is connected, the impedance of the distribution line to which the load is connected is greater than the impedance of the distribution line to which the substation is connected. Therefore, during tap switching, the voltage drop on the distribution line to which the load is connected is greater than the voltage drop on the distribution line to which the substation is connected. In response to this, when the control unit determines that a tap change is in progress, i.e., when the detection of the tap change is used as a trigger, it determines which side (primary side or secondary side) the substation is located on based on the derived primary side difference and secondary side difference, thereby enabling efficient directional determination of the substation (substation direction determination).

[0008] In a voltage adjustment device according to one embodiment of the present disclosure, the primary side difference and the secondary side difference are the difference between before the tap is switched and during the tap is switched, and the control unit calculates a multiplied value by multiplying the derived primary side difference by a coefficient corresponding to the tap position before the tap is switched, and determines whether the substation is located on the primary side or the secondary side based on the difference between the secondary side difference and the multiplied value.

[0009] In this embodiment, the primary side difference (|V1(1)-V1(2)|) and the secondary side difference (|V2(1)-V2(2)|) are the differences between before and during the tap switching. These primary side difference and secondary side difference may be expressed as absolute values. When the voltage regulator is, for example, a direct switching SVR, a bridging state (bridge resistor conducting) is passed during the tap switching (tap position switching from tap 4(n) to tap 5(n+1)). In this case, during the tap switching, the bridging resistor corresponding to the tap before the tap switching is in a conducting state (bridging only before switching (only tap 4 is bridging): state (2)). Therefore, the voltage drop due to the bridging resistor is reflected in the secondary side voltage. Before the tap switching, the tap switching is before the tap switching is started, and indicates a state (state (1)) in which the bridging resistor is not conducting (before switching). The control unit calculates a multiplication value by multiplying the derived primary side difference by a coefficient (N(k)) according to the tap position before switching, and determines whether the substation is located on the primary side or the secondary side based on the difference between the secondary side difference and the multiplication value. The coefficient (N(k)) may include a product of multiplying the difference (k) between the tap position (n) before switching and the plain tap by a deviation (dn) using the turns ratio (N(k)=1+kdn). The deviation (dn) may be a deviation from 0, where 0 is the tap position (plain tap) at which the voltage output by the on-load tap changer is 0. The control unit determines whether the substation is located on the primary side or the secondary side based on the difference between the secondary side difference derived in this manner and the multiplied value (ΔΔ(2)=|V2(1)-V2(2)|-|N(k)*(V1(1)-V1(2))|), and can therefore efficiently determine the substation direction.

[0010] In a voltage adjustment device according to one embodiment of the present disclosure, the primary side difference and the secondary side difference are the difference between during the tap switching and after the tap switching, and the control unit calculates a multiplied value by multiplying the derived primary side difference by a coefficient corresponding to the tap position after switching, and determines whether the substation is located on the primary side or the secondary side based on the difference between the secondary side difference and the multiplied value.

[0011] In this embodiment, the primary side difference (|V1(4)-V1(5)|) and the secondary side difference (|V2(4)-V2(5)|) are the differences between during tap switching and after tap switching. These primary side difference and secondary side difference may be expressed as absolute values. When the voltage regulator is, for example, a direct switching SVR, a bridging state (bridge resistor conducting) is passed during tap switching (tap position switching from tap 4(n) to tap 5(n+1)). In this case, during tap switching, the bridging resistor corresponding to the tap after switching is in a conducting state (bridging only after switching (only tap 5 is bridging): state (4)). Therefore, the voltage drop due to the bridging resistor is reflected in the secondary side voltage. After the tap switching, the tap switching is completed and the bridging resistor is not conducting (after switching) (state (5)). The control unit calculates a multiplication value by multiplying the derived primary side difference by a coefficient (N(l)) according to the tap position after switching, and determines whether the substation is located on the primary side or the secondary side based on the difference between the secondary side difference and the multiplied value. The coefficient (N(l)) is calculated by multiplying the difference (l) between the tap position after switching (n+1) and the plain tap by the deviation (dn) using the turns ratio. The deviation (dn) may be a deviation from 0, which is a tap position (plain through tap) at which the voltage output by the on-load tap changer is 0. The control unit determines whether the substation is located on the primary side or the secondary side based on the difference between the secondary side difference derived in this way and the multiplied value (ΔΔ(5)=|V2(4)-V2(5)|-|N(l)*(V1(4)-V1(5))|), and therefore can efficiently determine the substation direction.

[0012] In a voltage regulating device according to one embodiment of the present disclosure, when the current flowing through the distribution line is a forward flow, the control unit determines that the substation is located on the primary side if the difference obtained by subtracting the multiplication value from the secondary side difference is a positive value, and determines that the substation is located on the secondary side if the difference obtained by subtracting the multiplication value from the secondary side difference is a negative value.

[0013] In this embodiment, the control unit determines whether the current flowing through the distribution line is a forward flow or a reverse flow, depending on the direction of the current flowing through the distribution line. Forward flow indicates a state in which a current flows from the primary side to the secondary side. Reverse flow indicates a state in which a current flows from the secondary side to the primary side. The control unit may identify the direction of the current flowing through the distribution line from a current sensor or the like installed on the distribution line, and determine whether the current state is forward flow or reverse flow. When the current flowing through the distribution line is a forward flow, if the difference (ΔΔ(2), ΔΔ(5)) obtained by subtracting the multiplication value from the secondary side difference is a positive value, the control unit determines that the substation is located on the primary side, and if the difference is a negative value, the control unit determines that the substation is located on the secondary side. By using such a determination method, even in the case of a forward flow, the substation direction determination can be performed efficiently.

[0014] In a voltage adjustment device according to one embodiment of the present disclosure, when the current flowing through the distribution line is reverse flow, the control unit determines that the substation is located on the secondary side if the difference obtained by subtracting the multiplication value from the secondary side difference is a positive value, and determines that the substation is located on the primary side if the difference obtained by subtracting the multiplication value from the secondary side difference is a negative value.

[0015] In this embodiment, when the current flowing through the distribution line is in reverse power flow, if the difference (ΔΔ(2), ΔΔ(5)) obtained by subtracting the multiplication value from the secondary side difference is negative, the control unit determines that the substation is located on the primary side, and if the difference is positive, the control unit determines that the substation is located on the secondary side. By using such a determination method, it is possible to efficiently determine the substation direction even in the case of reverse power flow.

[0016] In a voltage adjustment device according to one embodiment of the present disclosure, the alternating current flowing through the power distribution line is three-phase alternating current, and the control unit derives the primary side difference and the secondary side difference for each of the three-phase line voltages in the three-phase alternating current, and determines whether the substation is located on the primary side or the secondary side based on the primary side difference and the secondary side difference for each of the derived three-phase line voltages.

[0017] In this embodiment, the AC is three-phase AC, and the control unit derives a primary side difference and a secondary side difference for each of the three-phase line voltages (primary side [VUV, VVW, VWU], secondary side [Vuv, Vvw, Vwu]) in the three-phase AC. When the voltage regulating device is, for example, a direct switching type SVR (Step Voltage Regulator), tap switching for each of the three phases is performed collectively (collectively switching is performed), and the tap positions for each of the three phases are the same. In contrast, the control unit determines whether the substation is located on the primary side or the secondary side based on the primary side difference and the secondary side difference for each of the derived three-phase line voltages, and therefore, it is possible to efficiently determine the substation direction in a distribution line through which three-phase AC flows.

[0018] In a voltage adjustment device according to one embodiment of the present disclosure, the control unit makes a determination for each line voltage as to which side the substation is located based on the primary side difference and the secondary side difference for each of the three-phase line voltages in the three-phase AC, and if the determinations for each line voltage match, determines whether the substation is located on the primary side or the secondary side depending on the matching determination content.

[0019] In this embodiment, the control unit performs a determination for each line voltage regarding which side the substation is located on, based on the primary side difference and the secondary side difference for each of the three-phase line voltages. That is, the control unit derives three determination contents by performing a substation direction determination for each of the three-phase line voltages (primary side [VUV, VVW, VWU], secondary side [Vuv, Vvw, Vwu]). Only when these three determination contents match, the control unit derives (finally determines) the matched determination content as a determination result of whether the substation is located on the primary side or the secondary side. Only when the determination contents for each of the three-phase line voltages match in this way, the control unit may store the matched determination content in the storage unit as a determination result of the substation direction determination, and perform a process of switching (mode switching) to a primary side voltage adjustment mode for automatically adjusting the primary side voltage or a secondary side voltage adjustment mode for automatically adjusting the secondary side voltage. That is, when the substation is located on the primary side (substation direction is primary side), the control unit performs voltage adjustment operation in a secondary side voltage adjustment mode that automatically adjusts the voltage on the secondary side of the regulating transformer. When the substation is located on the secondary side (substation direction is secondary side), the control unit performs voltage adjustment operation in a primary side voltage adjustment mode that automatically adjusts the voltage on the primary side of the regulating transformer. In this way, only when the determination for each line voltage matches, the information on the substation direction stored in the memory unit is changed (updated), thereby ensuring the accuracy of the determination of the substation direction.

[0020] In a voltage adjustment device according to one embodiment of the present disclosure, the control unit makes a determination for each line voltage as to which side the substation is located based on the primary side difference and the secondary side difference for each of the three-phase line voltages in the three-phase AC, and determines whether the substation is located on the primary side or the secondary side based on a majority vote of the determinations for each line voltage.

[0021] In this embodiment, the control unit determines on which side the substation is located for each line voltage based on the primary side difference and the secondary side difference for each of the three-phase line voltages. That is, the control unit derives three determination contents by performing substation direction determination for each of the three-phase line voltages (primary side [VUV, VVW, VWU], secondary side [Vuv, Vvw, Vwu]). The control unit derives (finally determines) as a determination result on which side the substation is located, the primary side or the secondary side, according to a majority vote of these three determination contents. For example, if the determination content based on the line voltages between the UV phases and the VW phases indicates that the substation direction is the primary side, and the determination content based on the line voltage between the WU phases indicates that the substation direction is the secondary side, the control unit derives (finally determines) a determination result that the substation direction is the primary side, since the majority of the determination contents indicate that the substation direction is the primary side. In this way, by deriving (final decision) the judgment result as to whether the substation is located on the primary side or the secondary side based on a majority vote on the judgment content for each line voltage, the accuracy of the judgment of the substation direction can be guaranteed even if an incorrect judgment content is derived for any of the line voltages due to external disturbances, etc.

[0022] In a voltage adjustment device according to one embodiment of the present disclosure, the control unit calculates a ratio or amount of change between the primary side voltage and the secondary side voltage obtained at a predetermined period, and determines whether the tap is being switched based on the ratio or amount of change calculated this time and the ratio or amount of change calculated last time.If it is determined that the tap is being switched, the control unit performs processing to determine whether the substation is located on the primary side or the secondary side.

[0023] In this embodiment, the control unit calculates the ratio or amount of change between the primary side voltage and the secondary side voltage acquired at a predetermined cycle. Then, the control unit judges whether or not the tap is being changed based on the ratio or amount of change calculated this time and the ratio or amount of change calculated last time. In a voltage regulator such as an SVR, an on-load tap changer uses mechanical contacts, and it is difficult to identify the electrical switching timing in the tap change from the mechanical operation of the tap change. That is, the tap change signal (boost / buck signal: 34M signal) is output to the on-load tap changer, and the mechanical operation of the tap change is performed for about 2 seconds (2 [s]), while the taps before and after the change are in a bridging state (bridging resistor conducting) for an extremely short period of 50 [msec]. In response to this, the control unit determines that a tap change has occurred at the moment when the ratio or amount of change (slope) between the primary side voltage and the secondary side voltage, which is constantly measured at a predetermined cycle such as 10 msec, exceeds a predetermined threshold, thereby enabling accurate detection of the electrical switching timing in the tap change. By using the switching timing (tap switching) detected by this method as a trigger (cause), the control unit can efficiently perform directional determination of the substation (substation direction determination) by reflecting the effect of the voltage drop of the bridging resistor that becomes conductive at the time of the switching timing in the characteristic that the impedance of the distribution line to which the load is connected is greater than the impedance of the distribution line to which the substation is connected. Effect of the Invention

[0024] It is possible to provide a voltage regulator that efficiently determines whether a substation is located on the primary side or the secondary side. [Brief description of the drawings]

[0025] [Figure 1] 1 is a block diagram showing an example of the configuration of a voltage adjusting device according to a first embodiment. [Diagram 2] FIG. 13 is an explanatory diagram showing behavior during shunting by a bridging resistor. [Diagram 3] This is an explanatory diagram (Table 1) showing the relationship (phase voltage and current) between the primary voltage (V1) and the secondary voltage (V2) during tap changing. [Figure 4] Table 2 shows the relationship between the primary voltage (VUV) and the secondary voltage (Vuv) during tap changing (line voltage and phase current of the Y connection). [Diagram 5] Table 3 shows the relationship between the primary voltage (VUV) and the secondary voltage (Vuv) during tap changing (line voltage and phase current of a Y connection) when there is one bridging resistor. [Figure 6] 10 is a flowchart showing a processing procedure of a control unit. [Figure 7] 10 is a flowchart showing a processing procedure of a control unit according to the second embodiment (determination of three phases). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] (Embodiment 1) Hereinafter, the embodiments will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a voltage regulator 1 according to the first embodiment. The voltage regulator 1 is, for example, a direct switching type SVR (Step Voltage Regulator) and is arranged on a single-phase or three-phase power distribution line 100. In this embodiment, the voltage regulator 1 will be described as being arranged on a single-phase power distribution line 100, but as will be described later, even when it is arranged on a three-phase power distribution line 100, various calculation processes are performed based on each line voltage. In a forward power transmission state, the voltage regulator 1 (SVR=Step Voltage Regulator) adjusts the voltage of single-phase AC or three-phase AC supplied from a power source side (substation) on the left side of the paper, and distributes the single-phase AC or three-phase AC to a load side on the right side of the paper via the power distribution line 100. In a reverse power transmission state, the voltage adjustment device 1 adjusts the voltage of single-phase AC or three-phase AC supplied from the load side on the right side of the paper, and distributes the single-phase AC or three-phase AC to the power source side (substation) on the left side of the paper via the distribution line 100.

[0027] The power distribution line 100 on which the voltage adjustment device 1 is arranged includes a primary side power distribution line 100 and a secondary side power distribution line 100, that is, the voltage adjustment device 1 is arranged between the primary side power distribution line 100 and the secondary side power distribution line 100. In this embodiment, the power distribution line 100 connected to the primary side (common terminal tc of the on-load tap changer 3) of the regulating transformer 2 included in the voltage adjustment device 1 is the primary side, and the power distribution line 100 connected to the secondary side (through tap of the on-load tap changer 3) of the regulating transformer 2 is the secondary side. A measurement transformer PT (primary side measurement transformer) that detects the value of the primary side voltage (primary side voltage value) is connected to the primary side power distribution line 100. A measurement transformer PT (secondary measurement transformer) that detects a value of a secondary voltage (secondary voltage value) is connected to the secondary power distribution line 100.

[0028] A substation (a source substation that supplies power) that is a power source is connected to the distribution line 100, and it is assumed that the substation is connected to the primary side and the load is connected to the secondary side as an initial setting in the arrangement of the voltage regulator 1. In addition, the distribution line 100 is, for example, in a loop shape from the viewpoint of ensuring redundancy, and by switching the loop-shaped distribution line 100, the connection mode of the substation and the load may be reversed, that is, the substation may be connected to the secondary side and the load may be connected to the primary side. Even if the connection mode of the substation and the load is reversed in this way, the control unit 4 of the voltage regulator 1 can efficiently perform a direction determination (substation direction determination) with respect to the substation by taking into account the voltage drop of the bridging resistor RS that is in a conductive state at the time of the switching timing, triggered by the detection of the tap switching timing. It is assumed that the voltage drop by the bridging resistor RS is equal to or greater than the step voltage of one tap, for example.

[0029] The voltage regulating device 1 includes a load tap changer 3, a regulating transformer 2, a voltage regulation command circuit 5, and a control unit 4. The load tap changer 3 has a common terminal tc, n tap terminals tn (n indicates the tap numbers (t1, t2, t3 ··· tn)), and a contact for connecting either the common terminal tc or one of the n tap terminals tn. The primary distribution line 100 is connected to the common terminal tc. The load tap changer 3 adjusts the primary voltage (V1) or the secondary voltage (V2) by switching the tap terminal tn connected to the common terminal tc in a state where a load is connected. Among the n tap terminals tn, any one tap terminal tn (in this embodiment) functions as a through tap (tap 4 in the illustration of this embodiment). The secondary distribution line 100 is connected to the through tap without passing through a winding.

[0030] The regulating transformer 2 is composed of a single-winding transformer having a plurality of taps (t1 to tn). One end of the tapped winding of the regulating transformer 2 is connected to the first tap terminal tn (t1) of the load tap changer 3. The other end of the tapped winding may be connected to the other distribution line 100 or to the neutral point N. (n - 1) taps are drawn out from a predetermined position of a portion closer to one end of the tapped winding and are respectively connected to the second tap terminal tn (t2) to the nth tap terminal tn of the load tap changer 3. Also, the position of the rth tap (1 < r < n: tap 4 in this figure) of the tapped winding is the position of the through tap, and the secondary distribution line 100 is connected to that position. The load tap changer 3 has a common terminal tc, n tap terminals tn, and a contact for connecting either the common terminal tc or one of the n tap terminals tn. The primary distribution line 100 is connected to the common terminal tc. The load tap changer 3 adjusts the primary voltage or the secondary voltage by switching the tap terminal tn connected to the common terminal tc in a state where a load is connected.

[0031] The voltage regulation command circuit 5 includes a voltage regulation relay 51 and a voltage transformer 52. The voltage regulation command circuit 5 monitors the primary voltage, and when the primary voltage deviates from the primary target voltage range (dead band), outputs a step-up / step-down signal (voltage regulation command) to bring the primary voltage within the target voltage range. The voltage regulator 1 may include a primary voltage regulator 1 that monitors the primary voltage, and a secondary voltage regulator 1 that monitors the secondary voltage. The voltage regulation relay 51 is, for example, configured with a 90 relay. The voltage regulation relay 51 detects the voltage across the relay, and when the detected voltage is outside the target voltage range, generates a step-up / step-down signal (voltage regulation command) that instructs tap switching, and outputs it to the control unit 4. When a high voltage is applied to the primary winding, the voltage transformer 52 transforms the high voltage from the secondary winding into a low voltage according to the winding ratio and outputs it. The instrument transformer 52 functions as a secondary side instrumentation transformer PT (secondary side instrumentation transformer).

[0032] The control unit 4 is configured with, for example, a microcomputer and has a CPU (Central Processing Unit) (not shown) and a storage unit such as a ROM or RAM. It controls voltage adjustment according to a control program pre-stored in the storage unit such as a ROM. Temporarily generated information may be stored in the RAM. The control unit 4 acquires a step-up / step-down signal (voltage adjustment command) output from the voltage adjustment command circuit 5 (voltage adjustment relay 51), and performs processing related to tap switching for the on-load tap changer 3 in accordance with the step-up / step-down signal.

[0033] The control unit 4 acquires the primary voltage (V1) and the secondary voltage (V2) measured at substantially the same time by each of the measurement transformers PT arranged on the primary side or the secondary side, and stores the acquired primary voltage and secondary voltage values ​​together with the acquisition time (detection time) in a memory unit. As will be described in detail later, the control unit 4 detects the electrical switching timing in tap switching based on the acquired primary voltage and secondary voltage, and performs a direction determination (substation direction determination) with the detection as a trigger (cause).

[0034] The control unit 4 constantly measures the voltage ratio or voltage change difference between the primary side (primary side voltage value: V1) and the secondary side (secondary side voltage value: V2), and determines the moment when the change (slope) exceeds a threshold as the tap change, thereby detecting the accurate tap change timing. The control unit 4 acquires the value of the primary side voltage (primary side voltage value) and the value of the secondary side voltage (secondary side voltage value) at a predetermined period such as 10 msec from the measurement transformer PT, for example, and stores them in the storage unit in association with the acquisition time. Alternatively, the control unit 4 may acquire the primary side voltage value from the measurement transformer PT provided on the primary side distribution line 100, and calculate (identify) the value of the secondary side voltage (secondary side voltage value) using the acquired primary side voltage value as an input factor and an identification equation described later.

[0035] The voltage ratio difference is defined as Δa_21(m) and is shown by the following formula (1), where m indicates the cycle when the voltage value is periodically acquired.

[0036]

number

[0037] That is, the voltage ratio difference (Δa_21(m)) is obtained by subtracting the value obtained by dividing the secondary side voltage value obtained last time (m-1) by the primary side voltage value from the value obtained by dividing the secondary side voltage value by the primary side voltage value in the actual value (RMS) of the primary side (primary side voltage value: V1) and secondary side (secondary side voltage value: V2) obtained this time (m). The actual value (the actual value of the most recent cycle) may be based on voltage data such as the average of the actual values ​​for a certain period of time, a value calculated using a filter, etc.

[0038] In the above formula (1), when a tap change is detected, the voltage ratio difference (Δa_21(m)) becomes a value equivalent to the turns ratio deviation of one tap, so the detection threshold may be determined taking into consideration the measurement accuracy and the tolerance of disturbance. For example, if the turns ratio deviation of one tap is 0.005 and the tolerance is 20%, a change in the absolute value of the voltage ratio difference of 0.004 or more (detection threshold) is detected as a tap change. If the sign is positive, the secondary side can be detected as being boosted from the perspective of the primary side, and if it is negative, it can be detected as being stepped down. Therefore, the control unit 4 may detect a tap change (detect as an electrical switching timing in tap change) when the absolute value of the derived voltage ratio difference (Δa_21(m)) becomes equal to or greater than the detection threshold (for example, 0.004). Furthermore, the control unit 4 determines that the secondary side has been boosted when viewed from the primary side if the derived voltage ratio difference (Δa_21(m)) is positive, and determines that the secondary side has been boosted when viewed from the primary side if the derived voltage ratio difference (Δa_21(m)) is negative.

[0039] The voltage change difference is defined as ΔΔV_21RMS(m) and is shown by the following formula (2), where m indicates the cycle when the voltage value is periodically acquired.

[0040]

number

[0041] That is, the voltage change difference (ΔΔV_21RMS (m)) is obtained by subtracting the change in the root mean square (RMS) of the primary voltage value from the change in the root mean square (RMS) of the secondary voltage value from the previous time. The root mean square (root mean square) of the primary voltage value from the previous time may be based on voltage data such as the root mean square (RMS) of the primary voltage value over a certain period of time or a value calculated using a filter.

[0042] In the case of the above-mentioned formula (2), the threshold value can be determined in the same manner, using the step voltage when the rated voltage is applied as a reference. For example, if the rated voltage is 6600V, the rated step voltage is 100V, and the allowable voltage range is 6000 to 7200V, the allowable range of the step voltage conversion is 9.1% ≒ 600 / 6600, and if there is a change of 91Vrms or more (detection threshold) in absolute value, it is detected as a tap change. Therefore, the control unit 4 may detect a tap change (detect as an electrical change timing in tap change) when the absolute value of the derived voltage change difference (ΔΔV_21RMS (m)) is equal to or greater than the detection threshold (91Vrms). Furthermore, the control unit 4 determines that the secondary side has been boosted when viewed from the primary side when the derived voltage change difference (ΔΔV_21RMS (m)) is positive, and determines that the secondary side has been lowered when viewed from the primary side when the derived voltage change difference (ΔΔV_21RMS (m)) is negative.

[0043] 2 is an explanatory diagram showing the behavior during shunting of the bridging resistor RS. In the illustration of this embodiment, the through tap is tap 3, and when the tap position is switched from tap 4 to tap 5, the voltage drop due to the current flowing through the bridging resistor RS corresponding (connected) to each of these taps 4 and 5 (behavior during shunting of the bridging resistor RS) will be described. In the adjacent tap positions (from tap 4 to tap 5) before and after the tap switching, the tap position (tap 5) with the higher voltage of the through tap (tap 3) is "l" (2=5-3), and the tap position (tap 4) with the lower voltage is "K" (1=4-3).

[0044] The primary voltage (power supply side) is V1, the secondary voltage (load side) is V2, the voltage ratio for one tap is dn, the resistance value of the bridging resistor RS is Rs, and the load impedance value is ZL. The current flowing through the bridging resistor RS of tap 4 is I4, and the current flowing through the bridging resistor RS of tap 5 is I5, and the sum of these currents, the current flowing through the load impedance, is IL (IL = I4 + I5). The secondary voltage (load side: V2) at this time can be expressed by equation (3).

[0045]

number

[0046] According to the principle of superposition, we obtain equations (4) and (5).

[0047]

number

[0048] The unknown parameter, the load impedance value (ZL), is transformed into equation (6) using known parameters, and then substituted into equation (3) to obtain equation (7).

[0049]

number

[0050] Equation (7) shows the relationship between the primary voltage (V1) and the secondary voltage (V2) using only known or measurable parameters that do not require the load impedance value (ZL). In the illustration of this embodiment, the case where tap 4 and tap 5 are both bridged has been described, but this is not limited to this. In the case of different taps (different from tap 4 and tap 5), the tap positions (tap numbers) before and after the tap switching can be handled by substituting the tap positions before and after the switching into the values ​​of k and l in the above equations (4) to (7).

[0051] Figure 3 is an explanatory diagram (Table 1) showing the relationship (phase voltage and current) between the primary voltage (V1) and the secondary voltage (V2) during tap changing. Based on the above formula, the relationship between the primary voltage (V1) and the secondary voltage (V2) of the tap changer shown in Figure 1 is expressed as five stages from formulas (8) to (12), as shown in Table 1. That is, if the period before and after the tap change is divided into five stages, with the period before the change being the first stage and the period after the change being the fifth stage, in the second to fourth stages, at least one of the two taps before and after the change is in a bridging state (bridging resistor RS is conducting). In the second stage, the bridging resistor RS corresponding to the tap before the change is in a conducting state (bridging only before the change (only tap 4 is bridging)). In the third stage, the bridging resistor RS corresponding to the two taps before and after the change is in a conducting state (bridging both before and after the change (tap 4 and tap 5 are bridging)). In the fourth stage, the bridging resistor RS corresponding to the tap after switching is in a conducting state (bridging only after switching (only tap 5 is bridging)).

[0052] The relationship between the primary voltage (V1) and the secondary voltage (V2) in the first stage is shown in (8) in Figure 3 (Table 1). The relationship between the primary voltage (V1) and the secondary voltage (V2) in the second stage is shown in (9) in Figure 3 (Table 1). The relationship between the primary voltage (V1) and the secondary voltage (V2) in the third stage is shown in (10) in Figure 3 (Table 1). The relationship between the primary voltage (V1) and the secondary voltage (V2) in the fourth stage is shown in (11) in Figure 3 (Table 1). The relationship between the primary voltage (V1) and the secondary voltage (V2) in the fifth stage is shown in (12) in Figure 3 (Table 1). The +S at the end of each of these equations (8) to (12) takes into account (adds) the switching surge when transitioning to each stage. The switching surges (+S) may be removed by using an electrical or digital signal processing filter.

[0053] FIG. 4 is an explanatory diagram (Table 2) showing the relationship between the primary voltage (VUV) and the secondary voltage (Vuv) during tap switching (line voltage and phase current of Y connection). The above-mentioned FIG. 2 and FIG. 3 (Table 1) have been described as corresponding to the relationship between the phase voltage and current of a single phase, but the case corresponding to three-phase AC will be described using FIG. 4. When adjusting each of the line voltages (UV, VW, WU) in three-phase AC, the voltage regulator 1 performs three-phase collective switching in which the tap positions corresponding to each of these line voltages (UV, VW, WU) are the same. In the diagram (Table 2) in this embodiment, a table adapted to the UV line voltage and the U-phase and V-phase currents is shown. On the assumption that the voltage regulator 1 performs three-phase collective switching, the terms related to VUV may be shown collectively. The voltage drop due to the switching surge and the load current contributes to the line voltages of the U-phase and the V-phase with different signs.

[0054] The period before and after the tap change is divided into five stages, just like in the single-phase case. For the U-V line voltage, the relationship between the primary side voltage (VUV) and the secondary side voltage (Vuv) in the first stage is shown in (13) in Figure 4 (Table 2). For the U-V line voltage, the relationship between the primary side voltage (VUV) and the secondary side voltage (Vuv) in the second stage is shown in (14) in Figure 4 (Table 2). For the U-V line voltage, the relationship between the primary side voltage (VUV) and the secondary side voltage (Vuv) in the third stage is shown in (15) in Figure 4 (Table 2). For the U-V line voltage, the relationship between the primary side voltage (VUV) and the secondary side voltage (Vuv) in the fourth stage is shown in (16) in Figure 4 (Table 2). For the U-V line voltage, the relationship between the primary side voltage (VUV) and the secondary side voltage (Vuv) in the fifth stage is shown in (17) in Figure 4 (Table 2). The VW line voltage and the WU line voltage are also shown in the same manner as the UV line voltage.

[0055] Figure 5 is an explanatory diagram (Table 3) showing the relationship between the primary voltage (VUV) and the secondary voltage (Vuv) during tap changing (line voltage and phase current of Y connection) when there is one bridging resistor RS. OLTC (Automatic on-load tap changers) may have one bridging resistor RS depending on the model, and an example of this case is shown in Figure 5 (Table 3). In this case, the bridging resistor RS is connected to the common side after switching. As shown in Figure 4 (Table 2) and Figure 5 (Table 3), it is assumed that the OLTC circuit method and its switching sequence differ for each model. In any case, the relational equation (identification equation) between the line voltages on the primary and secondary sides can be expressed by a calculation formula in which the line voltage is multiplied by a constant (N(T)) for each tap position, and then the phase current or the difference current is multiplied by a certain constant (R).

[0056] When there is one bridging resistor RS, there are three stages before and after tap changing. The relationship between the primary voltage (VUV) and the secondary voltage (Vuv) in the first stage (before switching, before switching and during bridging) is shown in (18) in Figure 5 (Table 3). The relationship between the primary voltage (VUV) and the secondary voltage (Vuv) in the second stage (after switching and during bridging) is shown in (19) in Figure 5 (Table 3). The relationship between the primary voltage (VUV) and the secondary voltage (Vuv) in the third stage (after switching) is shown in (20) in Figure 5 (Table 3).

[0057] If the time before and after a tap change is divided into five stages, observing (detecting) the second, third, and fourth stages is equivalent to observing (detecting) the voltage drop across the bridging resistor RS. Using this, the control unit 4 of the voltage regulating device 1 can perform substation direction determination (determine whether the substation is located on the primary side or the secondary side) by comparing the amount of voltage change between the primary voltage (V1) and the secondary voltage (V2) in the first stage (1) and the second stage (2), or between the fourth stage (4) and the fifth stage (5).

[0058] The control unit 4 of the voltage regulating device 1 uses the following formula (21) or (22) when determining the substation direction.

[0059]

number

[0060] In equations (21) and (22), the circled numbers indicate the step when the time before and after the tap changing is divided into five steps, and correspond to the circled numbers in the above-mentioned Tables 1 and 2. The control unit 4 extracts the voltage drop of the bridging resistor RS by using equation (21) or (22).

[0061] When using the difference between before the tap switching (first stage) and during the tap switching (second stage: bridging only before the switching), the control unit 4 performs substation direction determination using equation (21). The control unit 4 calculates the absolute value (|V2(1)-V2(2)|) of the difference between before the tap switching (first stage) and during the tap switching (second stage: bridging only before the switching) in the secondary side voltage (V2, Vuv) as the secondary side difference. The control unit 4 calculates the absolute value (|V1(1)-V1(2)|) of the difference between before the tap switching (first stage) and during the tap switching (second stage: bridging only before the switching) in the primary side voltage (V1, VUV) as the primary side difference.

[0062] The control unit 4 calculates a multiplication value by multiplying the derived primary side difference by a coefficient (N(k)) according to the tap position before switching, and judges whether the substation is located on the primary side or the secondary side based on the difference (ΔΔV(2), ΔΔVuv(2)) between the secondary side difference and the multiplication value. The coefficient (N(k)) may include a product of multiplying the difference (k) between the tap position (n) before switching and the plain tap by a deviation (dn) using the voltage ratio (dn) or turns ratio for one tap (N(k)=1+kdn). The deviation (dn) may be a deviation from 0, where 0 is the tap position (plain tap) where the voltage output by the on-load tap changer 3 is 0.

[0063] When using the difference between during tap switching (fourth stage: bridging only after switching) and after tap switching (fifth stage), the control unit 4 performs substation direction determination using equation (22). The control unit 4 calculates the absolute value (|V2(4)-V2(5)|) of the difference between during tap switching (fourth stage: bridging only after switching) and after tap switching (fifth stage) in the secondary side voltage (V2, Vuv) as the secondary side difference. The control unit 4 calculates the absolute value (|V1(4)-V1(5)|) of the difference between during tap switching (fourth stage: bridging only after switching) and after tap switching (fifth stage) in the primary side voltage (V1, VUV) as the primary side difference.

[0064] The control unit 4 calculates a multiplication value by multiplying the derived primary side difference by a coefficient (N(l)) according to the tap position after switching, and determines whether the substation is located on the primary side or the secondary side based on the difference (ΔΔV(5), ΔΔVuv(5)) between the secondary side difference and the multiplication value. The coefficient (N(l)) may include a product of multiplying the difference (k) between the tap position (n+1) after switching and the plain tap by a deviation (dn) using the voltage ratio (dn) or turns ratio for one tap (N(l)=1+ldn). The deviation (dn) may be a deviation from 0, where 0 is the tap position (plain tap) at which the voltage output by the on-load tap changer 3 is 0.

[0065] The control unit 4 performs the substation direction determination based on the difference value calculated using the formula (21) or (22). The control unit 4 performs the substation direction determination depending on whether the current flowing through the distribution line 100 is a forward flow or a reverse flow. The control unit 4 may identify the direction of the current flowing through the distribution line 100 from a current sensor or the like provided in the distribution line 100 and determine whether the current state is a forward flow or a reverse flow. When the current is a forward flow, the control unit 4 determines that the substation direction is the primary side if the difference value calculated using the formula (21) or (22) is positive, and determines that the substation direction is the secondary side if the difference value is negative. When the current is a reverse flow, the control unit 4 determines that the substation direction is the primary side if the difference value calculated using the formula (21) or (22) is negative, and determines that the substation direction is the secondary side if the difference value is positive.

[0066] The above-mentioned formulas (21) and (22) are also applicable (applicable) to other line voltages (VW, WU). Therefore, when the voltage regulator 1 regulates voltage in three-phase AC, the control unit 4 may perform calculations for only one of the three line voltages (UV, VW, WU) and determine the substation direction based on the calculation results. Alternatively, the control unit 4 may perform calculations for all three line voltages (UV, VW, WU) and update the information on the substation direction by majority vote of the results or only when the determinations for all three phases are the same.

[0067] The control unit 4 may determine the substation direction when the voltage drop term at the bridging resistance RS is equal to or greater than the step voltage for one tap. In this case, the control unit 4 may determine the determination possible range from the bridging resistance RS value and the current value for each model. If the OLTC mechanism characteristics include a case where the occupancy time of the second, third, and fourth stages is less than one cycle, or a particularly long occupancy state, the control unit 4 may also incorporate a response such as omitting some calculations in accordance with the mechanism, or calculating only the long occupancy state.

[0068] 6 is a flowchart showing the processing procedure of the control unit 4. The control unit 4 executes this processing during operation of the on-load tap changer 3 in accordance with a control program (program product) pre-stored in a storage unit such as a ROM.

[0069] The control unit 4 acquires the primary side voltage value and the secondary side voltage value (S101). The control unit 4 stores the acquired primary side voltage value and secondary side voltage value in the storage unit in association with the time of acquisition. By storing the acquired values ​​in association with the time of acquisition in this manner, it is possible to grasp the change over time in the acquired primary side voltage value and secondary side voltage value. The control unit 4 periodically or steadily acquires the primary side voltage value and the secondary side voltage value by performing a loop process to execute the process of S101 again. The control unit 4 may execute the process of S101 and the processes from S111 to S114 in parallel in separate processes (parallel processing).

[0070] The control unit 4 determines whether or not the tap switching timing has been detected (S111). The control unit 4 constantly measures the voltage ratio or the voltage change difference between the primary side (primary side voltage value: V1) and the secondary side (secondary side voltage value: V2). The control unit 4 detects the accurate tap switching timing by determining that the moment when the change amount (slope) exceeds a threshold value is the tap switching by using the above-mentioned formula (1) or (2). If the tap switching timing has not been detected, the control unit 4 performs a loop process to execute the process of S111 again. If the tap switching timing has not been detected (S111: NO), the control unit 4 performs a loop process to execute the process of S111 again.

[0071] When the tap switching timing is detected (S111: YES), the control unit 4 derives a primary side difference, which is the difference between the primary side voltage during the tap switching and the primary side voltage before or after (just before or just after) the tap switching (S112). When the tap switching timing is detected, the control unit 4 derives the primary side difference by using the above-mentioned equation (21) or (22).

[0072] The control unit 4 derives a secondary-side difference, which is the difference between the secondary-side voltage during tap switching and the secondary-side voltage before or after tap switching (S113). The control unit 4 derives the secondary-side difference by using the above-mentioned formula (21) or (22).

[0073] The control unit 4 determines whether the substation is located on the primary side or the secondary side based on the derived primary side difference and secondary side difference (S114). The control unit 4 determines whether the substation is located on the primary side or the secondary side based on the derived primary side difference and secondary side difference and difference by using the above-mentioned formula (21) or (22) (substation direction determination). When calculating the difference, the control unit 4 may subtract the absolute value of a multiplied value obtained by multiplying the primary side difference by a coefficient (N(k) or N(l)) corresponding to the tap position before or after switching from the absolute value of the secondary side difference.

[0074] When executing the substation direction determination, the control unit 4 may identify the direction of the current flowing through the distribution line 100 from a current sensor or the like provided in the distribution line 100, and determine whether the current state is forward flow or reverse flow. In the case of forward flow, the control unit 4 determines that the substation direction is the primary side if the difference value calculated using equation (21) or (22) is positive, and determines that the substation direction is the secondary side if the difference value is negative. In the case of reverse flow, the control unit 4 determines that the substation direction is the primary side if the difference value calculated using equation (21) or (22) is negative, and determines that the substation direction is the secondary side if the difference value is positive.

[0075] 7 is a flowchart showing a processing procedure of the control unit 4 according to the embodiment 2 (determination of three phases). The control unit 4 executes this processing during operation of the on-load tap changer 3 in accordance with a control program (program product) pre-stored in a storage unit such as a ROM.

[0076] The control unit 4 acquires the primary voltage value and the secondary voltage value of each of the three-phase line voltages (UV, VW, WU) (S201). As in the process S101 of the first embodiment, the control unit 4 acquires the primary voltage value and the secondary voltage value of each of the three-phase line voltages (UV, VW, WU).

[0077] The control unit 4 determines whether or not the tap changing timing has been detected (S211). The control unit 4 determines whether or not the tap changing timing has been detected in each of the on-load tap changers 3 corresponding to each of the three-phase line voltages (UV, VW, WU). The control unit 4 determines whether or not the tap changing timing has been detected for each of the on-load tap changers 3 corresponding to each of the three-phase line voltages (UV, VW, WU) in the same manner as in the process S111 of the first embodiment. If the tap changing timing has not been detected (S211: NO), a loop process is performed to execute the process of S211 again.

[0078] When the tap switching timing is detected (S211: YES), the control unit 4 derives a primary side difference in each inter-layer voltage, which is a difference between the primary side voltage during the tap switching and the primary side voltage before or after (just before or just after) the tap switching (S212). The control unit 4 derives a secondary side difference in each inter-layer voltage, which is a difference between the secondary side voltage during the tap switching and the secondary side voltage before or after the tap switching (S213). The control unit 4 derives the primary side difference and the secondary side difference in each of the three-phase line voltages (UV, VW, WU) in the same manner as in process S101 of the first embodiment.

[0079] The control unit 4 provisionally determines whether the substation is located on the primary side or the secondary side for each interlayer voltage (S214). The control unit 4 performs substation direction determination similarly to process S114 of the first embodiment based on the difference between the primary side difference and the secondary side difference derived for each of the three-phase line voltages (UV, VW, WU), and makes a provisional determination based on the determination result for each line voltage (UV, VW, WU). Therefore, there are three provisional determinations corresponding to the line voltages (UV, VW, WU). The control unit 4 stores the contents of these three provisional determinations (provisional determination results) in the storage unit.

[0080] The control unit 4 determines whether the substation is located on the primary side or the secondary side based on the provisional determination of each interlayer voltage (S215). The control unit 4 determines whether the substation is located on the primary side or the secondary side based on the provisional determination of each interlayer voltage, i.e., based on the contents of the three provisional determinations (provisional determination results). The control unit 4 may derive (finally determine) the coincident determination content as the determination result of whether the substation is located on the primary side or the secondary side only when the contents of these three provisional determinations (provisional determination results) match. Alternatively, the control unit 4 may derive (finally determine) the determination result of whether the substation is located on the primary side or the secondary side according to a majority vote of the contents of these three provisional determinations (provisional determination results).

[0081] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include all modifications within the scope and meaning equivalent to the claims.

[0082] The claims may be combined with each other regardless of the form of reference. The claims include multiple dependent claims that depend on multiple dependent claims. The claims do not include multiple dependent claims that depend on a multiple dependent claim, but multiple dependent claims that depend on a multiple dependent claim may be included. [Explanation of symbols]

[0083] 1 voltage regulator, 2 regulating transformer, 3 on-load tap changer, tc common terminal, tn tap terminal (tap), RS bridging resistor, 4 control unit (microcomputer including memory unit), 5 voltage regulation command circuit, 51 voltage regulation relay, 52 instrument transformer, 100 distribution line, PT measurement transformer

Claims

1. A voltage regulator that is arranged on a distribution line that distributes AC power from a substation to a load, has a regulating transformer with multiple taps, and automatically adjusts the voltage within a specified voltage range by switching the taps of the regulating transformer when the voltage of the distribution line deviates from the specified voltage range, a control unit that processes the tap; The control unit is Acquiring a primary side voltage and a secondary side voltage during the tap switching; Acquiring a primary side voltage and a secondary side voltage before or after the tap is changed; Deriving a primary side difference that is a difference between a primary side voltage during the tap switching and a primary side voltage before or after the tap switching; Deriving a secondary-side difference that is a difference between a secondary-side voltage during the tap switching and a secondary-side voltage before or after the tap switching; Based on the derived primary side difference and secondary side difference, it is determined whether the substation is located on the primary side or the secondary side. Voltage regulator.

2. the primary-side difference and the secondary-side difference are differences before the tap is changed and during the tap is changed, The control unit is calculating a multiplication value by multiplying the derived primary side difference by a coefficient corresponding to the tap position before switching; Based on the difference between the secondary side difference and the multiplied value, it is determined whether the substation is located on the primary side or the secondary side. The voltage regulator of claim 1 .

3. the primary-side difference and the secondary-side difference are differences during the tap switching and after the tap switching, The control unit is calculating a multiplication value by multiplying the derived primary side difference by a coefficient corresponding to the tap position after switching; Based on the difference between the secondary side difference and the multiplied value, it is determined whether the substation is located on the primary side or the secondary side. The voltage regulator of claim 1 .

4. When a current flowing in the power distribution line is a forward flow, the control unit If a difference obtained by subtracting the multiplied value from the secondary side difference is a positive value, it is determined that the substation is located on the primary side; If the difference obtained by subtracting the multiplied value from the secondary side difference is a negative value, it is determined that the substation is located on the secondary side. The voltage regulator according to claim 2 or 3.

5. When a current flowing through the power distribution line is a reverse power flow, the control unit If a difference obtained by subtracting the multiplied value from the secondary side difference is a positive value, it is determined that the substation is located on the secondary side; If the difference obtained by subtracting the multiplied value from the secondary side difference is a negative value, it is determined that the substation is located on the primary side.

5. The voltage regulator of claim 4.

6. The alternating current flowing through the distribution line is three-phase alternating current, The control unit is deriving the primary side difference and the secondary side difference for each of the three-phase line voltages in the three-phase AC; Based on the primary side difference and the secondary side difference in each of the derived three-phase line voltages, it is determined whether the substation is located on the primary side or the secondary side. The voltage regulator of claim 1 .

7. The control unit is determining, for each line voltage, on which side the substation is located, based on the primary side difference and the secondary side difference for each of the three-phase line voltages in the three-phase AC; If the determination for each line voltage is a match, it is determined whether the substation is located on the primary side or the secondary side according to the matched determination content. The voltage regulator of claim 6.

8. The control unit is determining, for each line voltage, on which side the substation is located, based on the primary side difference and the secondary side difference for each of the three-phase line voltages in the three-phase AC; According to a majority decision of the judgment for each line voltage, it is judged whether the substation is located on the primary side or the secondary side. The voltage regulator of claim 6.

9. The control unit is Calculating a ratio or an amount of change between the primary side voltage and the secondary side voltage acquired at a predetermined period; determining whether the tap is being changed based on the currently calculated ratio or amount of change and the previously calculated ratio or amount of change; When it is determined that the tap is being changed, a process is performed to determine whether the substation is located on the primary side or the secondary side. The voltage regulator of claim 1 .

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