Voltage adjusting device

Abstract

To provide a voltage adjusting device capable of determining that an electric power substation is positioned to either one of a primary side and a secondary side.SOLUTION: An indirect switching system voltage adjusting device 100 comprises: serial transformers 11 and 12 in which a secondary winding is serially connected to a distribution wire that distributes AC power to a load from an electric power substation; an adjusting transformer 2 in which a primary winding is parallely connected to distribution wires 1u and 1v; and switching switches Th1 to 3 and ThA to C that switch taps t1 to 3 provided by one or a plurality of windings of the adjusting transformer and select them, and contains a load tap switching device 3 that outputs the AC power by coupling each tap of the winding to be selected. A control part 61 of the load tap switching device specifies a switching period from a start from a switching of each tap to a completion of them in accordance with a control signal that is output in each tap switching, acquires a primary side voltage V1 and a secondary side voltage V2 at the same time within the switching period to be specified, and determines whether or not the electric power substation is positioned to any one of the primary side and the secondary side, on the basis of a difference between the primary side voltage and the secondary side voltage to be acquired.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 regulating device according to one embodiment of the present disclosure is an indirect switching type voltage regulating device including a series transformer having a secondary winding connected in series to a distribution line that distributes AC from a substation to a load, a regulating transformer having a primary winding connected in parallel to the distribution line, and an on-load tap changer having a change-over switch for switching and selecting taps of one or more windings of the regulating transformer, and connecting the tap selected for the winding to output AC, wherein the on-load tap changer has a control unit that performs processing related to the tap, and identifies a switching period from the start to the completion of the tap switching in accordance with a control signal output when switching the tap, acquires the primary side voltage and the secondary side voltage at the same point in time within the identified switching period, and determines whether the substation is located on the primary side or the secondary side based on the difference between the acquired primary side voltage and secondary side voltage.

[0007] In this aspect, the voltage regulator includes a series transformer, a regulating transformer, and a load tap changer, and the load tap changer includes a changeover switch for changing and selecting a tap of the regulating transformer, and a control unit for controlling the changeover switch to be turned on or off to change the tap. In this way, the control unit of the load tap changer can adjust the voltage of the distribution line by changing the tap of the regulating transformer. The control unit acquires a primary voltage value indicating the voltage on the side of the power source connected to the voltage regulator, and a secondary voltage value indicating the voltage on the side of the load connected to the voltage regulator. For example, when the power source is a single-phase power source, the distribution line may include a u-phase distribution line and a v-phase distribution line, and a measurement transformer may be provided between these distribution lines. The measurement transformer is provided on both the power source side and the load side of the distribution line. The control unit acquires the primary voltage value and the secondary voltage value output from the measurement transformers on both the power source side and the load side. The voltage regulator including the series transformer, the regulating transformer and the on-load tap changer uses an indirect switching method and is configured, for example, by a TVR (Thyristor Voltage Regulator) or an LVR (Low Voltage Regulator). When the secondary voltage, which is the monitored voltage, deviates from the dead zone, the control unit of the voltage regulator performs tap switching by outputting a control signal (voltage regulation command) to the regulation transformer. The control unit of the voltage regulator specifies a switching period from the start to the completion of tap switching as a period equivalent to an output period from the start to the end of output of the control signal (voltage regulation command). The control unit of the voltage regulator executes a process of acquiring the primary voltage and the secondary voltage at the same time point during the specified switching period at a predetermined cycle, for example, 10 msec. The acquisition cycle (detection cycle) of the value of the primary voltage (primary voltage value) and the value of the secondary voltage (secondary voltage value) may be determined according to (half cycle or more) a half cycle of the frequency of the commercial power supply from the substation. For example, when the frequency of the commercial power supply is 60 Hz, the acquisition cycle (detection cycle) is 16.667 msec, and when the frequency of the commercial power supply is 50 Hz, the acquisition cycle (detection cycle) may be 20 msec. Each of the primary side voltage value and the secondary side voltage value acquired and detected in the acquisition period (detection period) may be an average value of root mean square values ​​(RMS) acquired at multiple points in time (for example, 12 periods (cycles)). In this case, the voltage adjustment device (control unit) may calculate an averaged root mean square value for each of the primary side voltage value and the secondary side voltage value by performing a moving average process each time the primary side voltage value and the secondary side voltage value are detected, and use the calculated value for various calculation processes. The control unit of the voltage adjustment device determines whether the substation is located on the primary side or the secondary side based on the difference between the primary side voltage and the secondary side voltage acquired (detected) at substantially the same point during the tap switching period (the period from the start to the completion of tap switching) specified by the period in which the control signal (voltage adjustment command) is output. In an indirect switching type voltage regulator, a control unit measures the OLTC voltage in order to control and protect the OLTC (on-load tap changer) circuits, which include ignition circuits, etc., and each AC switch (thyristor, etc.) that is opened and closed during tap changing is controlled by the control unit.Therefore, the control unit can recognize the tap switching state and the voltage at that time based on the control signal of the control unit itself and the measured value of the OLTC voltage. When a voltage regulator using the indirect switching method regulates a single-phase voltage, the OLTC voltage and the superimposed voltage are in phase, the resistance value of the current-limiting resistor (bridging resistor) is also a constant, and the primary and secondary voltages in the tap selection state are in a proportional relationship multiplied by a constant for each tap position, so the transformation ratio (N(t)) is relatively simple and the calculation load on the control unit is prevented from becoming excessive. By performing substation direction determination in this way in a voltage regulator using the indirect switching method, it is possible to provide a voltage regulator that efficiently determines whether the substation is located on the primary side or the secondary side.

[0008] a primary-side voltage difference that is the difference between the primary-side voltage at the time when the current limiting resistor is made conductive and the primary-side voltage at any time before or after the time when the current limiting resistor is made conductive; a secondary-side voltage difference that is the difference between the secondary-side voltage at the time when the current limiting resistor is made conductive and the secondary-side voltage at any time before or after the time when the current limiting resistor is made conductive; a secondary-side voltage difference that is the difference between the secondary-side voltage at the time when the current limiting resistor is made conductive and the secondary-side voltage at any time before or after the time when the current limiting resistor is made conductive;

[0009] In this embodiment, a voltage regulator using an indirect switching method is configured for single-phase AC. A control unit of the voltage regulator acquires the primary side voltage and the secondary side voltage at a predetermined cycle during a tap switching period specified by the period during which a control signal (voltage adjustment command) is output, thereby acquiring the primary side voltage and the secondary side voltage at a plurality of points in time. The control unit of the voltage regulator may store the acquired primary side voltage and secondary side voltage at a plurality of points in time in a storage unit such as a microcomputer constituting the control unit, in association with the points in time of acquisition. In a voltage regulator using an indirect switching method, a tap short circuit is performed as a common operation for tap switching. In order to prevent this, there is a sequence (process) in which only the current limiting resistor is made conductive. At this time, the voltage drop due to the current limiting resistor is superimposed between the primary and secondary (between the primary and secondary) as a value multiplied by the transformation ratio of the series transformer. When sequentially opening and closing each of the AC switches such as thyristors that are controlled to open and close (on and off) during tap changing, the control unit of the voltage regulator outputs a control signal for opening and closing each AC switch so that only the current limiting resistor is made conductive. The control unit of the voltage regulator specifies the primary side voltage and secondary side voltage at the time of outputting the control signal that makes only the current limiting resistor conductive as the primary side voltage and secondary side voltage at the time when the current limiting resistor is made conductive. Then, it specifies the primary side voltage and secondary side voltage at any point before and after the point when the current limiting resistor is made conductive. At this time, the primary side voltage and secondary side voltage match at any point before and after the point when the current limiting resistor is made conductive. That is, the control unit of the voltage regulator specifies the primary-side voltage and the secondary-side voltage before the point in time when the current limiting resistor is made conductive, or specifies the primary-side voltage and the secondary-side voltage after the point in time when the current limiting resistor is made conductive. The primary-side voltage and the secondary-side voltage before and after the point in time when the current limiting resistor is made conductive are in a state in which the current limiting resistor and either the tap before or after switching are made conductive, that is, in a state different from a state in which only the current limiting resistor is made conductive. The control unit of the voltage regulator derives a primary-side difference, which is the difference between the primary-side voltage at the point in time when the current limiting resistor is made conductive and the primary-side voltage at any point in time before or after the point in time when the current limiting resistor is made conductive. The control unit of the voltage regulator derives a secondary-side difference, which is the difference between the secondary-side voltage at any point in time before or after the point in time when the current limiting resistor is made conductive (the same point in time as the primary-side voltage at any point in time before or after the point in time used when deriving the primary-side difference). The control unit of the voltage regulating device 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, thereby making it possible to 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 a point in time before the current limiting resistor becomes conductive and the point in time when the current limiting resistor becomes conductive, and the control unit calculates a multiplied value by multiplying the derived primary side difference by a coefficient corresponding 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 multiplied value.

[0011] In this embodiment, the primary side difference (|V1(1)-V1(2)|) and the secondary side difference (|V2(1)-V2(2)|) are the difference between the point in time before the current limiting resistor is turned on and the point in time when the current limiting resistor is turned on. These primary side difference and secondary side difference may be expressed as absolute values. When the voltage regulator is, for example, an indirect switching type TVR, a bridging state (bridging 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 before 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 current limiting resistor becomes conductive, tap switching has not started and the bridging resistor is not conductive (before switching) (state (1)). 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 difference (k) between the tap position (n) before switching and the plain tap, multiplied 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.

[0012] 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 the point at which a current limiting resistor is made conductive and a point at which the current limiting resistor is made conductive, 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.

[0013] In this embodiment, the primary side difference (|V1(4)-V1(5)|) and the secondary side difference (|V2(4)-V2(5)|) are the difference between the time when the current limiting resistor is turned on and after the time when the current limiting resistor is turned on. These primary side difference and secondary side difference may be expressed as absolute values. When the voltage regulator is, for example, an indirect switching type TVR, a bridging state (bridging 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 point at which the current-limiting resistor becomes conductive, the tap switching is completed, and the bridging resistor is not conductive (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 multiplication 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) where 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.

[0014] A voltage adjustment device according to one embodiment of the present disclosure is for three-phase AC, and the control unit determines a switching period from the start to the completion of the tap switching in response to a control signal that switches taps between plain taps, acquires the primary side voltage and the secondary side voltage at each of multiple points in time within the determined switching period, calculates the difference between the primary side voltage and the secondary side voltage at the same point in time for each of the multiple points in time, and determines whether the substation is located on the primary side or the secondary side based on the calculated difference.

[0015] In this embodiment, the voltage regulator using the indirect switching method is configured for three-phase AC. The control unit of the voltage regulator switches taps between the through taps when performing substation direction determination. That is, the control unit of the voltage regulator performs processing related to tap switching from the through tap to the through tap by AC switches (thyristors, etc.) that are in a different open / close state from each AC switch (thyristor, etc.) of the through tap (output of control signal between the through taps) as processing associated with the substation direction determination. The control unit of the voltage regulator specifies a switching period from start to completion of tap switching according to a control signal (control signal between the through taps) that switches the taps between the through taps. The control unit of the voltage regulator acquires the primary side voltage and the secondary side voltage at a plurality of points in time during the tap switching period specified by the period during which the control signal (voltage adjustment command) between the through taps is outputted, by acquiring the primary side voltage and the secondary side voltage at a predetermined cycle. The control unit of the voltage regulator may store the primary side voltage and secondary side voltage at the multiple points in time in a memory unit such as a microcomputer constituting the control unit, in association with the time of acquisition. The control unit of the voltage regulator calculates the difference (ΔVuv-UV=Vuv-VUV) between the primary side voltage (VUV) and the secondary side voltage (Vuv) acquired at the same point in time, and determines whether the substation is located on the primary side or the secondary side based on the calculated difference (ΔVuv-UV). As a process associated with the substation direction determination, a through tap is selected before and after a sequence in which only the current limiting resistor is turned on. By switching the taps between the through taps, the substation direction determination can be performed relatively easily and the calculation load of the control unit can be reduced. That is, by selecting the through tap, the voltages on the primary side and the secondary side become common (substantially the same value), and the cause of the superimposed voltage can be narrowed down to only the voltage drop of the current limiting resistor, thereby making it possible to perform the substation direction determination efficiently. When switching the taps between the through taps as a process associated with the substation direction determination, for example, the control unit of the voltage regulator may perform the substation direction determination every time a predetermined time has elapsed as a process separate from the switching to the target tap performed when the monitored voltage deviates from the dead zone. Alternatively, the control unit of the voltage regulator may add a switching operation to through tap as a preparatory operation before switching to the target tap when the monitored voltage deviates from the dead zone, for example. The control unit of the voltage regulator is not limited to using only the line voltage between UV when performing the substation direction determination, and may perform similar processing for the line voltage between VW and the line voltage between WU. In this case, the control unit of the voltage regulator may perform the substation direction determination for all three phases, and update the substation direction as the determination result only when the results of the substation direction determination for each of these three phases match. Alternatively, the control unit of the voltage regulator may perform the substation direction determination for all three phases, and derive the determination result by majority vote. Alternatively, the control unit of the voltage regulator may determine the determination result by combining the substation direction determination according to this embodiment with other known substation direction determinations. In this way, for a three-phase AC voltage regulator, the determination accuracy of the substation direction determination can be ensured by making a comprehensive determination using the substation direction determination for each phase.

[0016] In one embodiment of the voltage adjustment device of the present disclosure, the control unit identifies a maximum difference whose absolute value is the largest among the differences between the primary side voltage and the secondary side voltage at each of a number of points in time, and determines whether the substation is located on the primary side or the secondary side based on the identified maximum difference.

[0017] In this aspect, during the tap switching period specified within the period when the control signal (voltage adjustment command) between the through taps is output, the control unit of the voltage adjustment device calculates the absolute value (|ΔVuv - UV|) of the difference between the primary voltage (VUV) and the secondary voltage (Vuv) each time they are acquired at a predetermined cycle. The control unit of the voltage adjustment device may store the calculated difference between the primary voltage and the secondary voltage and the absolute value of the difference in association with the acquisition time points of these primary voltage and secondary voltage in a storage unit such as a microcomputer that constitutes the control unit. The control unit detects the primary voltage and the secondary voltage at a plurality of time points included in the tap switching period, and calculates the absolute value of the difference between these primary voltage and secondary voltage respectively. Therefore, the number of absolute values of the differences calculated during the tap switching period is plural. The control unit of the voltage adjustment device specifies the maximum difference (|Max_ΔVuv - UV|) that is the maximum among these plural absolute values. The maximum difference (|Max_ΔVuv - UV|) thus specified corresponds to the difference value based on the primary voltage and the secondary voltage acquired in the state where current is conducted only through the current limiting resistor. That is, since the tap switching period is the period for switching taps between the through taps, in the state where the current limiting resistor is not conducting and it is a through tap, the measured values of the primary voltage and the secondary voltage are substantially the same voltage value. Therefore, the absolute value of the difference value based on the primary voltage and the secondary voltage acquired in this state is a relatively small value close to 0. On the other hand, during the sequence (processing process) in which only the current limiting resistor is conducted to prevent short circuit between taps, the voltage drop due to the current limiting resistor is superimposed between the primary and the secondary (primary-secondary) as a value multiplied by the turns ratio of the series transformer. By calculating the absolute value of the difference value between the primary voltage and the secondary voltage at the time when only the current limiting resistor is conducting, the determination accuracy of the substation direction determination can be improved or ensured.

[0018] In the voltage adjustment device according to one aspect of the present disclosure, the control unit, within the specified switching period Then, the current value flowing in the distribution line system is obtained, and based on the obtained current value and the difference, it is determined whether the substation is located on the primary side or the secondary side.

[0019] In this aspect, the control unit of the voltage regulator acquires the primary voltage (VUV) and the secondary voltage (Vuv) at a predetermined cycle during a tap switching period specified by a period during which a control signal (voltage adjustment command) between the open taps is output, and also acquires a current value flowing in the system of the distribution line in which the voltage regulator is installed. The control unit of the voltage regulator may acquire the current value from a current detector such as a CT for an LDC (Line voltage Drop Compensator) installed in the distribution line. Alternatively, the control unit of the voltage regulator may acquire the current value flowing in an OLTC circuit including a current limiting resistor or the like as the current value flowing in the system. The control unit of the voltage regulator may store the current value in the storage unit in association with the acquisition time point together with the primary voltage and the secondary voltage acquired at substantially the same time each time the current value is acquired at the predetermined cycle. The control unit of the voltage regulator may perform a substation direction determination based on the primary side voltage and the secondary side voltage when the acquired current value (current value flowing in the grid) is equal to or greater than a predetermined threshold value (At), and may reserve the previous determination value (maintain the previous determination value) without performing a substation direction determination when the acquired current value is less than the threshold value. The threshold value used for the current value (current value flowing in the grid) may be determined according to the type specification of the voltage regulator or the characteristics of the grid in which the voltage regulator is installed, such as the resistance value of a current limiting resistor, the rated value of the current flowing in the grid or the OLTC circuit, or a one-tap voltage value (step voltage value). The control unit of the voltage regulator may perform a substation direction determination by acquiring a value input from an operation panel provided in the voltage regulator and storing it in a memory unit, thereby making the threshold value (At) configurable. By performing a substation direction determination based on the primary voltage, secondary voltage, and current value (current value flowing through the system) obtained at substantially the same time in this manner, the control unit of the voltage regulating device can respond to the voltage drop due to the current-limiting resistor making the voltage on the downstream side in the power flow direction smaller than the upstream side, thereby ensuring the accuracy of the determination.

[0020] In the voltage regulating device according to one aspect of the present disclosure, when the current flowing through the distribution line is a forward power flow, if the difference is a positive value, the substation is determined to be located on the primary side, and if the difference is a negative value, the substation is determined to be located on the secondary side. When the current flowing through the distribution line is a reverse power flow, if the difference is a positive value, the substation is determined to be located on the secondary side, and if the difference is a negative value, the substation is determined to be located on the primary side.

[0021] The control unit of the voltage regulating device determines whether it is in a forward power transmission state (forward power flow) or a reverse power transmission state (reverse power flow) based on, for example, the voltage or current change amounts on the primary side and the secondary side. Alternatively, the control unit of the voltage regulating device may detect whether it is in a forward power transmission state or a reverse power transmission state by detecting the system connection of the distribution line and the direction of the power passing through the voltage regulating device (such as a TVR), that is, the power flow, by means of a reverse current relay provided on the distribution line. Alternatively, the control unit of the voltage regulating device may derive whether it is in a forward power transmission state or a reverse power transmission state by acquiring a signal from a management device that manages the entire system including the distribution line. When the current flowing through the distribution line is a forward power flow, that is, when the power flow is from the primary side to the secondary side, if the difference (ΔVuv - UV) is a positive value, the substation is determined to be located on the primary side, and if the difference (ΔVuv - UV) is a negative value, the substation is determined to be located on the secondary side. Further, when the current flowing through the distribution line is a reverse power flow, that is, when the power flow is from the secondary side to the primary side, if the difference (ΔVuv - UV) is a positive value, the substation is determined to be located on the secondary side, and if the difference (ΔVuv - UV) is a negative value, the substation is determined to be located on the primary side. The control unit may perform the determination process based on the range (±Vt) of plus or minus (±) with respect to a predetermined threshold value (Vt) when reversing the positive and negative of the difference. That is, in both the forward power flow and the reverse power flow, when the difference (ΔVuv - UV) falls within the range (±Vt) by the threshold value (Vt) (-Vt < ΔVuv - UV < Vt), the control unit Alternatively, the substation direction may be determined by taking into account the determined power flow direction, and the substation direction may be determined efficiently in either the forward power transmission state (forward power flow) or the reverse power transmission state (reverse power flow). Effect of the Invention

[0022] 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]

[0023] [Figure 1] 1 is a block diagram showing an example of the configuration of a voltage regulating device according to a first embodiment (single phase). [Diagram 2] FIG. 4 is a circuit diagram showing a configuration example of a changeover switch. [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] 10 is a flowchart showing a processing procedure of a control unit. [Diagram 5] FIG. 11 is a block diagram showing a configuration example of a voltage regulating device (Δ-Y-Δ connection) according to a second embodiment (three phases). [Figure 6] 10 is a flowchart showing a processing procedure of a control unit. [Figure 7] FIG. 11 is an explanatory diagram illustrating a judgment table used for judgment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] (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 according to the first embodiment. In a forward power transmission state, the voltage regulator 100 (TVR: Thyristor type Step Voltage Regulator) adjusts the voltage of single-phase AC supplied from the power source side on the left side of the paper, and distributes the single-phase AC to the load side on the right side of the paper via the power distribution lines 1u and 1v. In a reverse power transmission state, the voltage regulator 100 adjusts the voltage of single-phase AC supplied from the load side on the right side of the paper, and distributes the single-phase AC to the power source side on the left side of the paper via the power distribution lines 1u and 1v.

[0025] The voltage regulating device 100 includes series transformers 11, 12 having secondary windings 112, 122 connected in series to the power distribution lines 1u, 1v, respectively, and a regulating transformer 2 (tapped transformer) having a winding 20 connected in parallel to the power distribution lines 1u, 1v. The secondary winding 112 of the series transformer 11 is provided on the power distribution line 1u, and the secondary winding 122 of the series transformer 12 is provided on the power distribution line 1v, that is, the voltage regulating device 100 includes two series transformers 11, 12. The voltage regulating device 100 further includes an on-load tap changer 3 provided between the winding 20 of the regulating transformer 2 and the primary windings 111, 121 of each of the series transformers 11, 12. The on-load tap changer 3 and the regulating transformer 2 constitute an on-load tap changing transformer 200.

[0026] In the series transformers 11 and 12, the primary windings 111 and 121 correspond to the secondary windings 112 and 122, respectively. The primary windings 111 and 121 are connected in parallel so that voltages of opposite phases are induced in the secondary windings 112 and 122, respectively. The terminals of the primary windings 111 and 121 corresponding to the load side terminals of the secondary windings 112 and 122, respectively, are denoted as u1 and v1. The terminals of the primary windings 111 and 121 corresponding to the power supply side terminals of the secondary windings 112 and 122, respectively, are denoted as u2 and v2.

[0027] The regulating transformer 2 is an autotransformer, and is a transformer in which a part of the primary winding and a part of the secondary winding are shared. The regulating transformer 2 has a winding 20 connected between the power distribution lines 1u and 1v. The winding 20 of the regulating transformer 2, which is an autotransformer, includes a series winding 20a (Nt1) and a shunt winding 20b (Nt2). The series winding 20a (Nt1) and the shunt winding 20b (Nt2) are connected to each other via an intermediate tap. The number of turns of the shunt winding 20b (Nt2) and the series winding 20a (Nt1) may be greater than the number of turns of the series winding 20a (Nt1) (Nt2>Nt1). In this case, the number of turns of the primary winding is the sum (Nt1+Nt2) of the series winding 20a (Nt1) and the shunt winding 20b (Nt2). The number of turns of the secondary winding varies depending on the tap position.

[0028] The winding 20 has taps t1 and t3 drawn out from one end and the other end, and an intermediate tap t2 located between the one end and the other end and dividing the winding 20 into a series winding 20a (Nt1) and a shunt winding 20b (Nt2). One of the taps t1 to t3 of the winding 20 is connected to the primary terminals u2, v1 of the series transformers 11, 12 via the on-load tap changer 3, and the other tap, which may be the same as or different from the tap, is connected to the primary terminals u1, v2 of the series transformers 11, 12 via the on-load tap changer 3. The same tap is connected to each terminal on the primary side of the series transformers 11, 12 in the case of a through tap.

[0029] In this embodiment, the regulating transformer 2 is an autotransformer, but is not limited to this, and the regulating transformer 2 may be a compound transformer. When the regulating transformer 2 is a compound transformer, the primary winding 21 is connected between the power distribution lines 1u and 1v. The secondary winding 22 corresponding to the primary winding 21 has taps t1 and t3 drawn out from one end and the other end, and an intermediate tap t2 drawn out from between the one end and the other end, and tap control is performed in the same manner as when the regulating transformer 2 is an autotransformer.

[0030] A primary winding of a measurement transformer PT2 may be connected between the distribution lines 1u and 1v in order to measure the voltage applied to the winding 20 of the regulating transformer 2. The measurement transformer PT2 can measure a secondary voltage value (V2m) indicating the voltage on the load side. Furthermore, a primary winding of a measurement transformer PT1 may be connected between the distribution lines 1u and 1v on the power source side of the series transformer. The measurement transformer PT1 can measure a primary voltage value (V1m) indicating the voltage on the power source side. Instead of the measurement transformer PT1 and the measurement transformer PT2, a means such as a resistive voltage divider may be used to detect the voltage between the distribution lines 1u and 1v.

[0031] The on-load tap changer 3 has six change-over switches ThA, ThB, ThC, Th1, Th2, and Th3 for switching taps t1 to t3 of the winding 20 of the regulating transformer 2. The configuration of the tap changer is not limited to that shown in FIG.

[0032] The on-load tap changer 3 further has a control unit 61 that controls the switching of each of the above-mentioned change-over switches, and a drive unit 64 that drives each of the change-over switches to ON based on a drive signal from the control unit 61. The secondary windings of the measurement transformers PT1 and PT2, and the secondary winding of a current transformer CT1 (corresponding to a current detection unit) described below are connected to the control unit 61. The connections between the control unit 61 and the measurement transformers PT1, PT2, and current transformer CT1, as well as the connections between the drive unit 64 and each of the change-over switches are not shown in the figure.

[0033] The control unit 61 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. The control unit 61 controls the adjustment of the voltage 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 61 has a timer counter for measuring elapsed time.

[0034] The tap t1 of the winding 20 is connected to one end of the change-over switches ThA and Th1 via a protective fuse (not shown; the same applies below), the tap t2 is connected to one end of the change-over switches ThB and Th2 via a fuse, and the tap t3 is connected to one end of the change-over switch ThC via a fuse. and one end of Th3. The other ends of the change-over switches ThA, ThB, ThC are connected to terminals u1 and v2 on the primary side of the series transformers 11 and 12 via a connection line 3u. The other ends of the change-over switches Th1, Th2, Th3_U are connected to terminals u2 and v1 on the primary side of the series transformers 11 and 12 via a connection line 3v.

[0035] Between the connection lines 3u and 3v, a series circuit of a current limiting resistor RS and a fault correction switch ThS is connected to both ends of a triac Tr1 (semiconductor switch). An ignition circuit Tg1 is connected to both ends of the triac Tr1, and the voltage across the triac Tr1 is supplied to the ignition circuit Tg1. The output of the ignition circuit Tg1 is connected to the gate of the triac Tr1.

[0036] A primary winding of a current transformer CT1 may be coupled to the output side of the connection line 3u from the connection point between the triac Tr1 and the series circuit in order to measure the single-phase AC line current output by the on-load tap changer 3. The primary winding of CT1 may be coupled to the connection line 3v to measure the single-phase AC line current.

[0037] The fault correction switch ThS is for connecting and disconnecting the current limiting resistor RS to the taps in order to maintain a fault between the taps via the current limiting resistor RS during the process of switching the taps t1 to t3. The triac Tr1 is fired when an overcurrent is detected to protect the changeover switches or when the operation of the on-load tap changer 3 is stopped. In this case, the primary sides of the series transformers 11 and 12 are fault-corrected between terminals u1 and u2 and between terminals v1 and v2, preventing the primary sides of the series transformers 11 and 12 from being opened.

[0038] By providing the current transformer CT1 at the above-mentioned position, the current flowing through the change-over switch and the fault correction switch ThS can be measured. When the triac Tr1 is ignited, the current transformer CT1 can measure the current flowing through the triac Tr1 from the primary windings 111, 121 of the series transformers 11, 12. Therefore, for example, when a short circuit occurs in the distribution lines 1u, 1v, the maximum current flowing through the distribution lines 1u, 1v can be calculated. When it is not necessary to detect the current flowing through the triac Tr1, the position of the current transformer CT1 is not limited to the above-mentioned position, and it may be closer to the winding 20 than the connection point with the triac Tr1 in the connection line 3u. In this embodiment, the triac Tr1 is described, but the present invention is not limited to this, and a circuit in which two thyristors are connected in inverse parallel may be used instead of the triac Tr1.

[0039] FIG. 2 is a circuit diagram showing a configuration example of the change-over switch ThA. The configuration of each switch will be described using the change-over switch ThA as an example. The same applies to the other change-over switches and the shunt switch ThS. The change-over switch ThA is formed by connecting thyristors ThAa and ThAb in inverse parallel, each of which is conductive in one direction from the anode to the cathode. The anode of the thyristor ThAa and the cathode of the thyristor ThAb are connected to a connection line 3u. The cathode of the thyristor ThAa and the anode of the thyristor ThAb are connected to a tap t1 of the winding 20 of the regulating transformer 2. The gates of the thyristors ThAa and ThAb are connected to a drive unit 64. When a trigger signal is applied from the drive unit 64 to the gate of each thyristor, the change-over switch ThA is conductive in both directions. The change-over switch ThA may be formed of one triac.

[0040] There are, for example, seven combinations of the change-over switches, which are represented by tap positions from tap 1 to tap 7. For example, when the tap position is set to tap 1, the change-over switches ThC and Th1 are turned on. As a result, tap t1 is connected to the connection line 3v, and tap t3 is connected to the connection line 3u. In this case, the number of turns between taps t1 and t3 becomes equal to the number of turns of the secondary winding 22, and the magnitude of the voltage output by the on-load tap changer 3 becomes maximum.

[0041] For tap 2 to tap 3, the changeover switches that connect the two taps to the connection lines 3u and 3v are determined according to the tap combinations in which the number of turns between the taps decreases stepwise. For example, when the tap position is tap 3, the changeover switches ThC and Th2 are turned on. As a result, tap t2 is connected to the connection line 3v, and tap t3 is connected to the connection line 3u. In this case, the number of turns between taps t2 and t3 is the minimum except for 0, and the magnitude of the voltage output by the on-load tap changer 3 is the minimum except for 0.

[0042] When the tap position is set to tap 4, the changeover switches ThA and Th1 are turned on. This connects tap t1 to the connection lines 3u and 3v. In this case, the voltage output by the on-load tap changer 3 becomes 0. This is what is called a through tap. Note that the changeover switches for setting the tap position to a through tap are not limited to the changeover switches ThA and Th1, and may be the changeover switches ThB and Th2, or the changeover switches ThC and Th3.

[0043] For taps 5 to 7, the changeover switches that connect two taps to the connection lines 3u and 3v are determined according to the tap combinations in which the number of turns between the taps increases stepwise. For example, when the tap position is tap 7, the changeover switches ThA and Th3 are turned on. As a result, tap t1 is connected to the connection line 3u, and tap t3 is connected to the connection line 3v. In this case, the number of turns between taps t1 and t3 becomes equal to the number of turns of the secondary winding 22, and the magnitude of the voltage output by the on-load tap changer 3 becomes maximum. However, compared to the case of tap 1, the phase of the output voltage is inverted.

[0044] As described above, the number of turns between the two taps connected to the connection lines 3u and 3v by tap changing is determined according to the tap position, in other words, the turns ratio of the regulating transformer 2 is determined according to the tap position. The turns ratio referred to here is the ratio of the number of turns of the primary winding 21 to the number of turns between the two taps connected to the connection lines 3u and 3v by tap changing (turns ratio).

[0045] A tap position table including, for example, tap position and changeover switch as management items (fields) is stored in advance in a storage unit (ROM) of the control unit 61 configured with a microcomputer or the like. That is, the storage unit associates the tap position determined by tap switching with a value related to the turns ratio of the regulating transformer at the tap position (deviation using the turns ratio), and stores the value as a tap position table (table format). By referring to the tap position table each time the tap position is raised or lowered, and reading out information indicating the changeover switch to be turned on and the turns ratio, tap switching can be easily performed.

[0046] In the drawings of this embodiment, the plain tap is tap 4, and when the tap position is switched from tap 5 to tap 6, the following describes the voltage drop and the like (behavior of the bridging resistor RS during shunting) due to the current flowing through the bridging resistor RS corresponding (connected) to each of tap 5 and tap 6. For the adjacent tap positions (from tap 5 to tap 6) before and after the tap switching, the tap position of the higher voltage (tap 6) relative to the plain tap (tap 4) is "l" (2=6-4), and the tap position of the lower voltage (tap 5) is "K" (1=5-4).

[0047] 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 (1).

[0048]

number

[0049] According to the principle of superposition, we obtain equations (2) and (3).

[0050]

number

[0051] The unknown parameter, the load impedance value (ZL), is transformed into equation (4) using known parameters, and then substituted into equation (1) to obtain equation (5).

[0052]

number

[0053] Equation (5) 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 this embodiment, the case where tap 5 and tap 6 are both bridged has been described, but this is not limited to this. In the case of different taps (different from tap 5 and tap 6), 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 equations (2) to (5) above.

[0054] 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 has five stages as shown in formulas (6) to (10) in Table 1. That is, if the period before and after the tap changing is divided into five stages, with the period before the tap changing being the first stage and the period after the tap changing being the fifth stage, in the second to fourth stages, at least one of the two taps before and after the tap changing is in a bridging state (the bridging resistor RS is conducting). In the second stage, the bridging resistor RS corresponding to the tap position before the tap changing is in a conducting state (bridging only before the tap changing (only tap 4 is bridging)). In the third stage, the bridging resistor RS corresponding to the two tap positions before and after the tap changing is in a conducting state (bridging only before the tap changing). After that, both taps are bridging (tap 5 and tap 6 are bridging). In the fourth stage, the bridging resistor RS corresponding to the tap position after switching is in a conducting state (bridging only after switching (only tap 6 is bridging)).

[0055] The relationship between the primary voltage (V1) and the secondary voltage (V2) in the first stage is shown in (6) in Figure 3 (Table 1). The relationship between the primary voltage (V1) and the secondary voltage (V2) in the second stage is shown in (7) in Figure 3 (Table 1). The relationship between the primary voltage (V1) and the secondary voltage (V2) in the third stage is shown in (8) in Figure 3 (Table 1). The relationship between the primary voltage (V1) and the secondary voltage (V2) in the fourth stage is shown in (9) in Figure 3 (Table 1). The relationship between the primary voltage (V1) and the secondary voltage (V2) in the fifth stage is shown in (10) in Figure 3 (Table 1). The +S at the end of each of these equations (6) to (10) 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.

[0056] If the period before and after the tap change is divided into five stages, observing (detecting) the second, third, and fourth stages corresponds to observing (detecting) the voltage drop of the current limiting resistor RS (bridging resistor). The control unit 61 of the voltage regulator 100, which is composed of TVR and the like, outputs a control signal for opening and closing each of the AC switches Th1, Th2, Th3, ThA, ThB, and ThC (AC switches) of the thyristors ThAa and ThAb that are controlled to open and close (on and off) during the tap change, so as to make only the current limiting resistor RS (bridging resistor) conductive. The control unit 61 of the voltage regulator specifies the primary side voltage and the secondary side voltage at the time of outputting the control signal that makes the current limiting resistor RS (bridging resistor) conductive (or makes only the current limiting resistor RS conductive) as the primary side voltage and the secondary side voltage at the time when the current limiting resistor RS is conductive. The control unit 61 of the voltage regulating device 100 can use this to 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 side voltage (V1) and the secondary side voltage (V2) in the first stage (1) and the second stage (2), or between the fourth stage (4) and the fifth stage (5).

[0057] The control unit 61 of the voltage regulating device 100 uses the following formula (11) or (12) when determining the substation direction.

[0058]

number

[0059] In formulas (11) and (12), the circled numbers indicate the step number when the time before and after the tap change is divided into five steps, and correspond to the circled numbers in the above-mentioned Table 1. The control unit 61 extracts the voltage drop of the current-limiting resistor RS (bridging resistor) by using formula (11) or (12).

[0060] 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 61 performs the substation direction determination using the formula (11). The control unit 61 calculates the absolute value (|V The control unit 61 calculates the absolute value (|V1(1)-V1(2)|) of the difference between the primary side voltage (V1, VUV) before the tap is switched (first stage) and during the tap is switched (second stage: bridging only before switching) as the primary side difference.

[0061] The control unit 61 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 (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.

[0062] When using the difference between during tap switching (fourth stage: bridging only after switching) and after tap switching (fifth stage), the control unit 61 performs substation direction determination using equation (12). The control unit 61 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 61 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.

[0063] The control unit 61 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.

[0064] The control unit 61 performs substation direction determination based on the difference value calculated using equation (11) or (12). The control unit 61 performs substation direction determination depending on whether the current flowing through the distribution lines 1u, 1v is forward flow or reverse flow. The control unit 61 may identify the direction of the current flowing through the distribution lines 1u, 1v from a current sensor or the like provided on the distribution lines 1u, 1v, and determine whether the current state is forward flow or reverse flow. When the current is forward flow, the control unit 61 determines that the substation direction is the primary side if the difference value calculated using equation (11) or (12) is positive, and determines that the substation direction is the secondary side if the difference value is negative. When the current is in reverse flow, the control unit 61 determines that the substation direction is the primary side if the difference value calculated using equation (11) or (12) is negative, and determines that the substation direction is the secondary side if the difference value is positive.

[0065] The control unit 61 may determine the substation direction when the voltage drop term in the current limiting resistor RS is equal to or greater than the step voltage for one tap. In this case, the control unit 61 may determine the determination possible range from the resistance value and current value of the bridging resistor RS for each model. If the OLTC mechanism has characteristics such as the occupancy time of the second, third, and fourth stages being less than one cycle or there being a particularly long occupancy state, the control unit 61 may also incorporate measures such as omitting some calculations in accordance with the mechanism, or calculating only the long occupancy state.

[0066] 4 is a flowchart showing a processing procedure of the control unit 61. The control unit 61 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.

[0067] The control unit 61 acquires a primary side voltage value and a secondary side voltage value (S101). The control unit 61 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 61 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 61 may execute the process of S101 and the processes from S111 to S114 in parallel in separate processes (parallel processing).

[0068] The control unit 61 judges whether or not a control signal is being output (S111). When the secondary voltage, which is the monitored voltage, deviates from the dead band, the control unit 61 performs tap switching by outputting a control signal (voltage adjustment command) to the adjustment transformer, and specifies the period during which the control signal (voltage adjustment command) is output as the tap switching period. That is, the control unit 61 specifies the period from the start point to the end point of outputting the control signal (voltage adjustment command) as the tap switching period. During the tap switching period, the control unit 61 executes a sequence (processing process) in which only the current limiting resistor RS is made conductive to prevent short-circuiting between taps as a common operation for tap switching. In this way, the state in which only the current limiting resistor RS is made conductive and the state in which the current limiting resistor RS and any of the taps before and after switching are made conductive are transitioned according to the signals output from the control unit 61 to each of the changeover switches Th1, Th2, Th3, ThA, ThB, and ThC (AC switches). Therefore, based on the output form of the signal, the control unit 61 can identify the point in time when the state transitions to a state where only the current-limiting resistor RS is conductive, or a state where the current-limiting resistor RS and either the tap before or after switching are conductive, thereby making it possible to detect the accurate tap switching timing (switching state).If the output of the control signal is not detected (S111: NO), the control unit 61 performs loop processing to execute the processing of S111 again.

[0069] When the output of the control signal is detected (S111: YES), the control unit 61 derives a primary side difference, which is the difference between the primary side voltage during tap switching (tap switching timing) 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 61 derives the primary side difference by using the above-mentioned formula (11) or (12).

[0070] The control unit 61 derives a secondary-side difference, which is the difference between the secondary-side voltage during tap switching (tap switching timing) and the secondary-side voltage before or after the tap switching (S113). The control unit 61 derives the secondary-side difference by using the above-mentioned formula (11) or (12).

[0071] The control unit 61 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 61 determines whether the substation is located on the primary side or the secondary side based on the difference between the derived primary side difference and secondary side difference by using the above-mentioned formula (11) or (12) (substation direction determination). When calculating the difference, the control unit 61 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.

[0072] When executing the substation direction determination, the control unit 61 determines the direction of the substation by using the Alternatively, the control unit 61 may specify the direction of current flowing through the distribution lines 1u and 1v from a current sensor or the like, and determine whether the current state is forward flow or reverse flow. In the case of forward flow, if the difference value calculated using equation (11) or (12) is positive, the control unit 61 determines that the substation direction is the primary side, and if the difference value is negative, the control unit 61 determines that the substation direction is the secondary side. In the case of reverse flow, if the difference value calculated using equation (11) or (12) is negative, the control unit 61 determines that the substation direction is the primary side, and if the difference value is positive, the control unit 61 determines that the substation direction is the secondary side.

[0073] (Embodiment 2) 5 is a block diagram showing a configuration example of a voltage regulator (Δ-Y-Δ connection) according to embodiment 2 (three phases). In the figure, 1u, 1v, and 1w are distribution lines that distribute AC voltages of U phase, V phase, and W phase from a power source (U phase, V phase, and W phase) to a load (u phase, v phase, and w phase) to the right of the page (forward power transmission state) or to the left of the page (reverse power transmission state). The voltage regulator 100 is for three-phase AC and includes a series transformer 201 having secondary windings 212, 222, 232 connected in series to the distribution lines 1u, 1v, 1w, respectively, a regulating transformer 301 having primary windings 311, 321, 331 in a delta connection to the distribution lines 1u, 1v, 1w, and a tap changer 4 provided between the secondary windings 312, 322, 332 of the regulating transformer 301 and the primary windings 211, 221, 231 of the series transformer 201. In this embodiment, the voltage regulator 100 for three-phase AC is a delta-Y-delta connection, but is not limited thereto and may be a VV-delta connection, a VVY connection, or the like.

[0074] In a forward power transmission state, the voltage regulator 100 adjusts the voltage of three-phase AC supplied from the power source side on the left side of the paper, and distributes the three-phase AC to the load side on the right side of the paper via the power distribution lines 1u, 1v, and 1w. In a reverse power transmission state, the voltage regulator 100 adjusts the voltage of three-phase AC supplied from the load side on the right side of the paper, and distributes the three-phase AC to the power source side on the left side of the paper via the power distribution lines 1u, 1v, and 1w.

[0075] The voltage regulating device 100 also includes a voltage detection unit 62 that detects the voltages of the distribution lines 1u, 1v, 1w via a three-phase measurement transformer 5 connected in a Δ-Y configuration, an operation display unit 63 that displays the voltage detected by the voltage detection unit 62 and accepts operations from a user, and a control unit 61 that applies drive signals to change-over switches S1, S2, ..., S6, SS and an electromagnetic contactor MC (described below) via a drive unit 64 based on the operations accepted by the operation display unit 63. The change-over switches S1, S2, ..., S6 all function as polarity change-over switches (AC switches).

[0076] The voltage detection unit 62 detects the line voltages of the power distribution lines 1u, 1v, 1w, but may detect the phase voltages via a measurement transformer connected by a connection method other than the delta-Y connection. Also, instead of the measurement transformer 5, tertiary windings corresponding to the primary windings 311, 321, 331 of the regulating transformer 301 may be provided, and the voltage detection unit 62 may detect the voltages of the power distribution lines 1u, 1v, 1w via the tertiary windings, or the voltage detection unit 62 may detect the voltages of the power distribution lines 1u, 1v, 1w separately from the voltage adjustment device 100.

[0077] The three-phase measurement transformer 5 and voltage detection unit 62 may be provided on both the load-side distribution lines 1u, 1v, 1w and the power-source-side distribution lines 1u, 1v, 1w. The measurement transformer 5 and voltage detection unit 62 provided on the power-source-side distribution lines 1u, 1v, 1w acquire the voltage values ​​(primary voltage values) of the line voltage between U phase and V phase (UV), the line voltage between V phase and W phase (VW), and the line voltage between W phase and U phase (WU) on the power-source side of the voltage adjustment device 100, and output them to the control unit 61. The measurement transformer 5 and voltage detection unit 62 provided on the load-side distribution lines 1u, 1v, 1w acquire the voltage values ​​(primary voltage values) of the line voltage between u phase and v phase (uv), the line voltage between v phase and w phase (vw), and the line voltage between w phase and u phase (wu) on the load side of the voltage adjustment device 100. The control unit 61 acquires each of the voltage values ​​(secondary voltage values) and outputs them to the control unit 61.

[0078] In the series transformer 201, the primary windings 211, 221, and 231 correspond to the secondary windings 212, 222, and 232, respectively. The primary windings 211, 221, and 231 are Δ-connected. The terminals of the primary windings 211, 221, and 231 corresponding to the load side terminals of the secondary windings 212, 222, and 232, respectively, are designated as u11, v11, and w11. The terminals of the primary windings 211, 221, and 231 corresponding to the power supply side terminals of the secondary windings 212, 222, and 232, respectively, are designated as u2, v2, and w2.

[0079] In the regulating transformer 301, the primary winding 311 is connected between the power distribution lines 1u and 1v, the primary winding 321 is connected between the power distribution lines 1v and 1w, and the primary winding 331 is connected between the power distribution lines 1w and 1u. That is, the primary windings 311, 321, and 331 are delta-connected to the power distribution lines 1u, 1v, and 1w. The primary windings 311, 321, and 331 correspond to the secondary windings 312, 322, and 332, respectively.

[0080] Each of the secondary windings 312, 322, 332 has taps ta and tc drawn from one end and the other end, and an intermediate tap tb drawn between the taps ta and tc. Any one of the taps ta to tc of each of the secondary windings 312, 322, 332 is connected to the primary side terminals u11, v11, w11 and terminals v2, w2, u2 of the series transformer 201 via the tap changer 4.

[0081] The tap changer 4 has six change-over switches S1, S2, ... S6 for three phases to change the taps ta, tb, tc of the secondary windings 312, 322, 332 of the regulating transformer 301. That is, the regulating transformer 301 has u-phase switches S1, S2, ... S6, v-phase switches S1, S2, ... S6, and w-phase switches S1, S2, ... S6. The taps ta of the secondary windings 312, 322, 332 are connected to one ends of the change-over switches S1, S4 via protective fuses F. The taps tb of the secondary windings 312, 322, 332 are connected to one ends of the change-over switches S2, S5 via protective fuses F. The taps tc of the secondary windings 312, 322, 332 are connected to one ends of the change-over switches S3, S6. The other ends of the switches S1, S2, and S3 are connected to each other. The other ends of the switches S4, S5, and S6 are connected to each other.

[0082] The other ends of the change-over switches S1, S2, S3, one end of which is connected to the taps ta, tb, tc of the secondary winding 312, are connected to the terminals u11 and v2 on the primary side of the series transformer 201. The other ends of the change-over switches S4, S5, S6, one end of which is connected to the taps ta, tb, tc of the secondary winding 312, are connected to the neutral point N. The other ends of the change-over switches S1, S2, S3, one end of which is connected to the taps ta, tb, tc of the secondary winding 322, are connected to the terminals v11 and w2 on the primary side of the series transformer 201. The other ends of the change-over switches S4, S5, S6, one end of which is connected to the taps ta, tb, tc of the secondary winding 322, are connected to the neutral point N. The other ends of the change-over switches S1, S2, and S3, each of which is connected to one end of the taps ta, tb, and tc of the secondary winding 332, are connected to terminals w11 and u2 on the primary side of the series transformer 201. The other ends of the change-over switches S4, S5, and S6, each of which is connected to one end of the taps ta, tb, and tc of the secondary winding 332, are connected to the neutral point N.

[0083] A series circuit of a current-limiting resistor R and a change-over switch SS, and an electromagnetic contactor MC are connected in parallel between the other ends of the change-over switches S1, S2, S3 and the other ends of the change-over switches S4, S5, S6. The change-over switch SS is for connecting and disconnecting the current-limiting resistor R to and from the taps in order to maintain a short circuit between the taps via the current-limiting resistor R during the process of switching the taps ta, tb, tc by the change-over switches S1, S2, ... S6. The electromagnetic contactor MC is for switching the taps ta, t This is to correct the short circuits between terminals u11 and v11, between terminals v11 and w11, and between terminals w11 and u11 on the primary side of series transformer 201 while the operation of switching b and tc is stopped, so as to prevent the circuit from entering an open state.

[0084] The voltage of tap ta relative to tap tb is, for example, twice the voltage of tap tb relative to tap tc, but is not limited to this. By selecting taps ta, tb, and tc of the regulating transformer 301 configured in this manner, it is possible to extract voltages that are twice (tap ta relative to tap tb), three times (tap ta relative to tap tc), -1 times (tap tc relative to tap tb), -2 times (tap tb relative to tap ta), and -3 times (tap tc relative to tap ta) the voltage of tap tb relative to tap tc. In other words, the relative regulating voltage extracted from the regulating transformer 301 can be selected from 1, -1, 2, -2, 3, and -3.

[0085] In this embodiment, the ratio of the regulated voltages taken out from the secondary windings 312, 322, and 332 is set to 1:1:1 by turning on only the changeover switches S2 and S6, which are filled in black in Fig. 5, to select the taps tb and tc. In the following, the terminals corresponding to the taps tb and tc of the secondary winding 312 are U1 and U2, the terminals corresponding to the taps tb and tc of the secondary winding 322 are V1 and V2, and the terminals corresponding to the taps tb and tc of the secondary winding 332 are W1 and W2. In this example, the terminals U2, V2, and W2 are connected to the neutral point N, and the regulated voltages are taken out from the terminals U1, V1, and W1. However, when the ratio of the regulated voltages is set to -1:-1:-1, for example, the terminals U1, V1, and W1 are connected to the neutral point N, and the regulated voltages are taken out from the terminals U2, V2, and W2. The voltage regulating device 100 used in this embodiment may have the same configuration, action, and function as each device of the voltage regulating device 100 described in, for example, JP 2019-80430, or JP 2021-82667 or JP 2021-197891 in which the number of taps is 7 or more (for example, 13, etc.).

[0086] In the three-phase AC voltage regulator, as in the single-phase AC voltage regulator of the first embodiment, a tap position table is pre-stored in a storage unit (ROM) of the control unit 61 configured with a microcomputer or the like. That is, the storage unit associates the tap position determined by tap switching with a value related to the turns ratio of the regulating transformer 301 at the tap position (deviation using the turns ratio), and stores the value as a tap position table (table format). By referring to the tap position table each time the tap position is raised or lowered, and reading out information indicating the change-over switch to be turned on and the turns ratio, tap switching can be easily performed.

[0087] The control unit 61 can obtain each of the line voltages (UV, VW, WU) on the power source side from the measurement transformer 5 and voltage detection unit 62 provided on the power source side distribution lines 1u, 1v, 1w. Furthermore, the control unit 61 can obtain each of the line voltages (uv, vw, wu) on the load side from the measurement transformer 5 and voltage detection unit 62 provided on the load side distribution lines 1u, 1v, 1w. The control unit 61 obtains the value of a current flowing in the system from a current sensor or the like provided on the distribution lines 1u, 1v, 1w. The control unit 61 may obtain the value of a current flowing in an OLTC circuit including a current limiting resistor R or the like from a current sensor or the like provided in the OLTC circuit.

[0088] 6 is a flowchart showing a processing procedure of the control unit 61. The control unit 61 executes this processing during operation of the tap changer 4 in accordance with a control program (program product) pre-stored in a storage unit such as a ROM.

[0089] The control unit 61 judges whether or not to use the substation direction judgment function (S201). A setting flag for setting whether or not to use the substation direction judgment function (necessity setting) is , is stored in a storage unit of a microcomputer constituting the control unit 61. The control unit 61 determines whether the determination function of the substation direction determination is enabled (used) or disabled (not used) according to the value of the setting flag by referring to the storage unit. When it is determined that the determination function of the substation direction determination is not to be used (S201: NO), the control unit 61 performs loop processing to execute the processing from S201 again.

[0090] When it is determined that the substation direction determination function is to be used (S201: YES), the control unit 61 determines whether tap switching is in progress (S202). When the secondary voltage, which is the monitored voltage, deviates from the dead zone, the control unit 61 outputs a control signal (voltage adjustment command) to the regulating transformer to switch the tap. Therefore, the control unit 61 determines whether tap switching is in progress depending on whether the control signal (voltage adjustment command) is being output. In this way, the control unit 61 can specify the switching period from the start to the completion of tap switching as a period equivalent to the output period from the start to the end of output of the control signal (voltage adjustment command). When it is determined that tap switching is not in progress (S202: NO), the control unit 61 performs loop processing to execute the processing from S202 again.

[0091] When it is determined that tap switching is in progress (S202: YES), the control unit 61 acquires the difference between the primary side voltage and the secondary side voltage for each one cycle effective value (S203). The control unit 61 acquires the primary side voltage (VUV) and the secondary side voltage (Vuv) at substantially the same detection time point for each one cycle effective value determined according to a half cycle in the frequency of the commercial power supply from the substation. The control unit 61 calculates (acquires) the difference (ΔVuv-UV=Vuv-VUV) between the primary side voltage and the secondary side voltage detected at substantially the same time point.

[0092] The control unit 61 further acquires a current value at a point substantially simultaneous with the detection time of the primary side voltage and the secondary side voltage. The current value may be a current value flowing in the system, or a current value flowing in an OLTC circuit including a current limiting resistor or the like. Furthermore, the control unit 61 acquires a power flow direction at a point substantially simultaneous with the detection time of the primary side voltage and the secondary side voltage. The power flow direction is a forward power flow in which the current flows from the primary side to the secondary side, or a reverse power flow in which the current flows from the secondary side to the primary side. The control unit 61 stores the primary side voltage, the secondary side voltage, the difference between the primary side voltage and the secondary side voltage, the current value, and the power flow direction thus acquired for each one cycle actual value in the storage unit in association with the detection time.

[0093] The control unit 61 judges whether the absolute value of the difference calculated this time is greater than the absolute value of the maximum difference (S204). The maximum difference (Max_ΔVuv-UV) indicates the maximum value of the differences (ΔVuv-UV) between the primary side voltage and the secondary side voltage calculated periodically. The initial value of the maximum difference may be set to, for example, 0 and stored in the memory unit. The control unit 61 compares the absolute value of the difference calculated this time (|ΔVuv-UV|) with the absolute value of the maximum difference up to the previous calculation of the difference (|Max_ΔVuv-UV|) stored in the memory unit to determine whether the absolute value of the difference calculated this time is greater than the absolute value of the maximum difference. Determine whether (|ΔVuv-UV|>|Max_ΔVuv-UV|).

[0094] If the absolute value of the difference calculated this time is greater than the absolute value of the maximum difference (S204: YES), the control unit 61 stores the difference calculated this time as the maximum difference (S205). If the absolute value of the difference calculated this time is greater than the absolute value of the maximum difference, the control unit 61 stores the difference calculated this time (ΔVuv-UV) as the maximum difference (Max_ΔVuv-UV), thereby updating the maximum difference. In this way, every time the control unit 61 calculates the difference (ΔVuv-UV) between the primary side voltage and the secondary side voltage, it compares it with the absolute value of the maximum difference up to the previous calculation of the difference, and if the absolute value of the difference calculated this time (|ΔVuv-UV|) exceeds the absolute value of the maximum difference up to the previous time (|Max_ΔVuv-UV|), it updates the maximum difference (|Max_ΔVuv-UV|).

[0095] If the absolute value of the difference calculated this time is not greater than the absolute value of the maximum difference (S204: NO ), or after executing S205, the control unit 61 determines whether tap changing has been completed (S206). If the absolute value of the currently calculated difference is not greater than the absolute value of the maximum difference, i.e., if the absolute value of the currently calculated difference is smaller than the absolute value of the maximum difference, or after executing 205, the control unit 61 determines whether tap changing has been completed depending on whether or not the control signal (voltage adjustment command) is being output by itself. If the control signal (voltage adjustment command) is being output, the control unit 61 determines that tap changing has not been completed (tap changing in progress). If the control signal (voltage adjustment command) is not being output, the control unit 61 determines that tap changing has been completed. If it is determined that tap changing has not been completed (S206: NO), i.e., if it is determined that tap changing is in progress, the control unit 61 performs loop processing to execute the processing from S203 again.

[0096] When it is determined that the tap switching is completed (S206: YES), the control unit 61 executes a substation direction determination based on the derived maximum difference and the like (S207). The control unit 61 stores, as a maximum difference (Max_ΔVuv-UV), a difference with a maximum absolute value among the differences between the primary side voltage and the secondary side voltage calculated for each one cycle execution value during the tap switching period (output period of the control signal). The control unit 61 identifies the power flow direction and the current value detected at the time of calculation of the maximum difference, that is, the time of detection of the primary side voltage and the secondary side voltage that are the original data of the difference that became the maximum difference, and substantially the same time. In this way, the control unit 61 performs a substation direction determination based on the maximum difference and the power flow direction and the current value corresponding to the maximum difference. A determination table that associates a combination of the power flow direction, the current value, and the maximum difference with a determination result is stored in a storage unit of a microcomputer constituting the control unit 61, and the control unit 61 may use the determination table when performing a substation direction determination.

[0097] 7 is an explanatory diagram illustrating a judgment table used for judgment. The judgment table includes, as management items, judgments of power flow direction, current value, maximum difference, and substation direction judgment. For the management item of power flow direction, forward power flow or reverse power flow is stored as a value. For the management item of current value, a value equal to or greater than the current threshold value (At) or less than the current threshold value (At) is stored as a value. The current threshold value (At) used for the current value (current value flowing in the system) may be determined according to the model specification of the voltage adjustment device 100 or the characteristics of the system in which the voltage adjustment device 100 is arranged, such as the resistance value of a current limiting resistor, the rated value of the current flowing in the system or the OLTC circuit, or a one-tap voltage value (step voltage value).

[0098] In the management item of the maximum difference, values ​​of equal to or more than the upper threshold (Vt), equal to or less than the lower threshold (-Vt), or greater than the lower threshold (-Vt) and less than the upper threshold (Vt) are stored as values. By providing a threshold range based on the upper threshold (Vt) and the lower threshold (-Vt) in this way, it is possible to perform substation direction determination by broadly classifying the maximum difference into a case where it is equal to or more than the threshold range (a positive value equal to or more than the upper threshold (Vt)), a case where it is equal to or less than the threshold range (a negative value equal to or less than the lower threshold (-Vt)), and a case where it is within the threshold range. The threshold range may be determined according to the type specification of the voltage regulator 100 or the characteristics of the system in which the voltage regulator 100 is arranged, such as the resistance value of the current limiting resistor, the rated value of the current flowing through the system or the OLTC circuit, the one-tap voltage value (step voltage value), etc. In the determination of the substation direction determination, the primary side, the secondary side, or the previous determination value and reserved are stored as values, that is, the determination result is stored.

[0099] If the power flow direction is forward power flow, the current value is equal to or greater than the current threshold (At), and the maximum difference is equal to or greater than the upper threshold (Vt), the control unit 61 determines that the substation direction is the primary side. If the power flow direction is forward power flow, the current value is equal to or greater than the current threshold (At), and the maximum difference is equal to or less than the lower threshold (-Vt), the control unit 61 determines that the substation direction is the secondary side. If the power flow direction is reverse power flow, the current value is equal to or greater than the current threshold (At), and the maximum difference is equal to or greater than the upper threshold (Vt), the control unit 61 determines that the substation direction is the secondary side. If the power flow direction is reverse power flow, the current value is equal to or greater than the current threshold (At), and the maximum difference is equal to or less than the lower threshold (-Vt), the control unit 61 determines that the substation direction is the secondary side. The direction is determined to be the primary side.

[0100] If the maximum difference is greater than the lower threshold (-Vt) and less than the upper threshold (Vt), i.e., falls within the threshold range defined by the upper threshold (Vt) and the lower threshold (-Vt), the control unit 61 reserves the judgment value from the previous judgment (maintains the previous judgment value) without performing a substation direction judgment. If the current value is less than the current threshold (At), the control unit 61 reserves the judgment value from the previous judgment (maintains the previous judgment value) without performing a substation direction judgment.

[0101] The control unit 61 erases the temporarily stored data such as the derived maximum difference (S208). The control unit 61 erases various temporarily stored data such as the maximum difference acquired or calculated during the current process, i.e., during tap switching (while the control signal is being output).

[0102] The control unit 61 determines whether or not an instruction to stop operation has been issued (S209). The control unit 61 determines whether or not an instruction signal to stop operation has been input from an operation panel, for example. If it is determined that an instruction to stop operation has not been issued (S209: NO), the control unit 61 performs a loop process to execute the process from S201 again. If it is determined that an instruction to stop operation has been issued (S209: YES), the control unit 61 ends a series of processes in this flow and stops the operation of the voltage regulator 100.

[0103] 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.

[0104] 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]

[0105] 100 Voltage regulator (for single-phase AC, for three-phase AC), 1u, 1v, 1w Distribution line, 11, 12 Series transformer, 111, 121 Primary winding, 112, 122 Secondary winding, u1,u2,v1,v2 terminals, 200 on-load tap-changing transformer, 2 regulating transformer, 20 winding, 20a series winding, 20b shunt winding, 21 primary winding, 22 secondary winding, t1,t2,t3 tap, 3 on-load tap-changing transformer, 61 control unit (microcomputer), 62 voltage detection unit, 63 operation display unit, 64 drive unit, Th1,Th2,Th3,ThA,ThB,ThC change-over switch, ThAa,ThAb thyristor, 3u,3v connection line, ThS fault correction switch, RS current-limiting resistor (bridge resistor, current-limiting resistor), PT1,PT2 measurement transformer, CT1 current transformer, Tr1 triac, Tg1 firing circuit, 201 Series transformer, 211, 221, 231 Primary winding, 212, 222, 232 Secondary winding, u11, v11, w11 Terminal, N Neutral point, 301 Regulating transformer, 311, 321, 331 Primary winding, 312, 322, 332 Secondary winding, S1, S2, S3, S4, S5, S6, SS Change-over switch, U1, U2, V1, V2, W1, W2 Terminal, F Fuse, MC Magnetic contactor, R Current-limiting resistor (bridging resistor, current-limiting resistor), 4 Tap changer, ta, tb, tc Tap, 5 Measuring transformer

Claims

1. a series transformer having a secondary winding connected in series to a distribution line that distributes AC power from a substation to a load; a regulating transformer having a primary winding connected in parallel to the distribution line; an on-load tap changer including a changeover switch for switching and selecting a tap of one or more windings of the regulating transformer, and for connecting the selected tap of the winding to output an AC voltage; An indirect switching type voltage regulator including: The on-load tap changer includes a control unit that performs processing related to the tap, specifying a switching period from start to completion of the tap switching in response to a control signal outputted when switching the tap; Acquiring a primary side voltage and a secondary side voltage at the same time point within the identified switching period; Based on the difference between the acquired primary voltage and secondary voltage, it is determined whether the substation is located on the primary side or the secondary side. Voltage regulator.

2. The voltage regulator is for single-phase AC. Acquiring a primary side voltage and a secondary side voltage at each of a plurality of time points within the identified switching period; Identifying the primary side voltage and the secondary side voltage at a time when a current limiting resistor provided in the on-load tap changer is conductive from the primary side voltage and the secondary side voltage at the multiple acquired times; Deriving a primary-side difference which is a difference between a primary-side voltage at a time point when the current-limiting resistor is turned on and a primary-side voltage at any time point before or after the time point when the current-limiting resistor is turned on; Deriving a secondary-side difference which is a difference between the secondary-side voltage at the time when the current-limiting resistor is turned on and the secondary-side voltage at any time before or after the time when the current-limiting resistor is turned on; The time before or after the current limiting resistor is turned on coincides with the primary voltage and the secondary voltage. 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. The voltage regulator of claim 1 .

3. the primary-side difference and the secondary-side difference are differences between a time point before a current-limiting resistor is turned on and a time point at which the current-limiting resistor is turned on, 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 2 .

4. the primary-side difference and the secondary-side difference are differences between a time point at which a current-limiting resistor is made conductive and a time point after the time point at which the current-limiting resistor is made conductive, 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 2 .

5. The voltage regulator is for three-phase AC. The control unit is determining a switching period from start to completion of the tap switching in response to a control signal for switching the taps between the through taps; Acquiring a primary side voltage and a secondary side voltage at each of a plurality of time points within the identified switching period; Calculating a difference between the primary voltage and the secondary voltage at each of a plurality of time points; Based on the calculated difference, it is determined whether the substation is located on the primary side or the secondary side. The voltage regulator of claim 1 .

6. The control unit is Identifying a maximum difference having a maximum absolute value among the differences between the primary voltage and the secondary voltage at each of a plurality of time points; Based on the identified maximum difference, it is determined whether the substation is located on the primary side or the secondary side. The voltage regulator according to claim 5 .

7. The control unit is Acquire a current value flowing through the distribution line system during the specified switching period; Based on the acquired current value and the difference, it is determined whether the substation is located on the primary side or the secondary side. The voltage regulator according to claim 5 .

8. The control unit is When the current flowing through the distribution line is a forward current, If the difference is a positive value, it is determined that the substation is located on the primary side; If the difference is a negative value, it is determined that the substation is located on the secondary side; When the current flowing through the distribution line is a reverse power flow, If the difference is a positive value, it is determined that the substation is located on the secondary side; If the difference is a negative value, it is determined that the substation is located on the primary side. The voltage regulator according to claim 5 .

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