JP6959824B2 - Voltage regulator - Google Patents

Description

The present invention relates to a voltage regulator for power distribution using a regulating transformer, a tap changer and a series transformer.

The voltage regulator by the so-called indirect switching method includes a series transformer in which the secondary winding is connected in series with the distribution line, a regulating transformer in which the secondary winding is provided with a plurality of taps, and a tap of the regulating transformer. It is provided with a tap changer for switching the tap changer and a switching control unit for controlling the tap changer. In the adjusting transformer, the primary winding is connected in parallel with the distribution line. A tap changer is provided between each tap of the secondary winding of the adjusting transformer and the primary winding of the series transformer. The switching control unit controls the tap switching unit so as to adjust the adjusting voltage applied from the adjusting transformer to the series transformer and keep the voltage of the distribution line within the target range.

The tap changer includes a tap changer switch that switches taps connected to the primary winding of a series transformer, and a current limiting element such as a current limiting resistor that limits the entangled current flowing between taps in the process of tap switching. It has a contact / disconnection selector switch for connecting and disconnecting the current limiting element between taps. The tap changer also has a polarity selector switch that switches the polarity of the voltage applied from the secondary winding of the adjusting transformer to the primary winding of the series transformer. The tap changer switches the magnitude and polarity of the adjustment voltage applied from the adjustment transformer to the primary winding of the series transformer by turning these changeover switches on and off in a predetermined sequence under the control of the changeover control unit.

As shown in Patent Document 1 and Patent Document 2, a bidirectional thyristor (a thyristor that has bidirectionality and can turn on and off alternating current) is used as a changeover switch to make the tap switch non-contact. Voltage regulators for power distribution are known. Hereinafter, this thyristor type voltage regulator is referred to as a TVR (Thyristor type Step Voltage Regulator).

The mainstream of conventional TVRs is a V-Y connection method in which the secondary side of the adjusting transformer is V-connected and the primary side of the series transformer is Y-connected. Patent Document 3 monitors the two-phase voltage of the V-connection of the adjustment transformer against three-phase imbalance based on the conventional TVR that collectively controls the tap switch for two phases with the adjustment transformer as the V connection. However, a TVR with a function for dealing with a three-phase voltage imbalance that improves the three-phase voltage imbalance of a distribution wire by individually controlling a two-phase tap switch is disclosed.

This TVR has the effect of improving the voltage imbalance by connecting the voltage monitoring phase (two phases that can switch taps) of the TVR that supports voltage imbalance to the maximum voltage phase and the minimum voltage phase of the three-phase voltage of the distribution line. It will increase. Therefore, the expected effect cannot be obtained in a system in which the maximum voltage phase and the minimum voltage phase of the three-phase voltage change with time (in the case where the single-phase load connected to each phase or the photovoltaic power generation fluctuates greatly). When applying to a system in which the maximum voltage phase and the minimum voltage phase are unknown, it is necessary to determine the connection destination of the voltage monitoring phase of TVR after conducting a measurement survey in advance.

On the other hand, a YY connection method has been realized in which the secondary side of the adjusting transformer is Y-connected and the primary side of the series transformer is Y-connected (see, for example, Patent Document 4). A TVR with a Y connection on the secondary side of such an adjustment transformer is equipped with a tap changer for three phases. Therefore, if this tap changer is controlled for each phase, all three phases can be tap-switched individually. It is said that the voltage can be adjusted arbitrarily in three phases, and the problem of dealing with the imbalance of the current VY connection method described above can be solved.

Japanese Unexamined Patent Publication No. 8-335119 Japanese Unexamined Patent Publication No. 8-335121 JP-A-2017-85715 Japanese Unexamined Patent Publication No. 2016-42279

However, when different tap changes are performed for each phase in the YY connection method, a zero-phase voltage (hereinafter referred to as V0) is generated in the adjustment voltage applied to the series transformer, and the voltage is superimposed on the system. However, since V0 is generated, another big problem occurs due to the generation of V0, such as a malfunction of the ground relay of the substation. As described above, a three-phase unbalanced voltage adjusting device capable of adjusting the three-phase voltage without generating V0 has not yet been realized regardless of the magnitude relationship between the three-phase voltages.

The present invention has been made in view of such circumstances, and an object of the present invention is that it is possible to suppress the generation of V0 and adjust the three-phase voltage regardless of the magnitude relationship of the three-phase voltage. The purpose is to provide a voltage regulator.

In the voltage regulator according to the present invention, the secondary windings for three phases are connected in series to the distribution line that distributes the three-phase AC voltage from the power supply to the load, and the primary windings are delta-connected in series. The transformer and the secondary winding have a plurality of taps, and the primary winding is delta-connected at a position on the load side of the connection position of the series transformer on the distribution line, and the secondary winding is A three-phase system provided between a star-connected adjusting transformer and the secondary winding of the adjusting transformer and the primary winding of the series transformer for switching taps connected to the series transformer. It is provided with a tap changer having a minute changeover switch.

In the present invention, the primary winding of the series transformer in which the secondary winding for three phases is connected in series to the distribution line for three phases is delta (Δ) connected, and the primary winding for three phases is connected. The secondary winding of the adjusting transformer is star (Y) connected. Then, an adjustment voltage is applied to the primary winding of the series transformer from the tap of the secondary winding of the adjustment transformer via the changeover switch of the tap changer. Therefore, the three-phase voltage of the distribution line is adjusted by selecting and switching the tap of the adjusting transformer.

In the voltage regulator according to the present invention, in the series transformer, the phase of the three-phase AC voltage applied from the secondary winding to the distribution line is substantially higher than that in the case of standard delta star connection. The wires are connected so as to be delayed by π / 3 or 4π / 3.

In the present invention, the phase of the AC voltage applied in series from the secondary winding of the series transformer to the three-phase AC voltage of the distribution line is a standard delta star (Δ-Y) connection. The wires are connected so as to be substantially delayed by 60 ° or 60 ° + 180 ° as compared with the case of. As a result, the phase advance of 30 ° and the phase delay of 60 ° in each of the delta-Y connection adjusting transformer and the series transformer are substantially offset. Further, the adjustment voltage generated by the adjustment transformer is transformed by the series transformer, and the voltage is added so as to approach the in-phase or reverse phase shift with respect to the AC voltage of the distribution line.

In the voltage regulator according to the present invention, the changeover switch includes a polarity changeover switch for switching the polarity of the voltage of the secondary winding of the adjustment transformer and applying it to the primary winding of the series transformer.

In the present invention, since the polarity of the adjustment voltage applied to the primary winding of the series transformer can be arbitrarily switched by the polarity changeover switch, the imbalance of the three-phase voltage of the distribution line is adjusted. High degree of freedom.

In the voltage adjusting device according to the present invention, the changeover switch includes a thyristor.

In the present invention, since the thyristor is used as the changeover switch, the tap can be changed at high speed and the life of the tap does not need to be considered.

The voltage regulator according to the present invention relates to a voltage detection unit that detects the three-phase voltage of the distribution line on the load side of the series transformer and a target voltage of the three-phase voltage detected by the voltage detection unit. A changeover control unit for calculating the deviation and switching the tap with the changeover switch based on the calculated deviation is further provided.

In the present invention, the voltage of the three-phase distribution line adjusted by the adjustment voltage applied to the primary winding of the series transformer is detected from the tap of the secondary winding of the adjustment transformer and compared with the target voltage. Then, the changeover switch is controlled based on the deviation which is the comparison result, and the tap is switched. As a result, feedback control is performed so that the deviation of the three-phase voltage of the distribution line approaches zero.

The voltage adjusting device according to the present invention further includes a storage unit that stores the deviation of the three-phase voltage with respect to the target voltage and the amount related to the transformation ratio of the three phases of the adjusting transformer in association with each other. When the deviation is calculated, the switching destination of the tap for three phases is selected with reference to the storage unit, and the tap is switched to the selected switching destination.

In the present invention, the deviation of the three-phase voltage of the distribution line from the target voltage is calculated, and the tap switching destination is selected based on the amount related to the transformation ratio read from the storage unit according to the calculated deviation. Controls the changeover switch according to the selected changeover destination. This eliminates the need to obtain the above-mentioned adjustment voltage by vector calculation when the switching control unit is executed.

According to the present invention, it is possible to suppress the generation of V0 and adjust the three-phase voltage regardless of the magnitude relationship of the three-phase voltage.

It is a block diagram which shows the structural example of the voltage adjustment apparatus which concerns on Embodiment 1. FIG. It is explanatory drawing which visually shows the connection | connection relation of three-phase between the adjustment transformer and the series transformer in the voltage adjustment apparatus which concerns on Embodiment 1. FIG. It is a vector figure which shows the voltage vector which is applied or induced to each of the adjustment transformer and the series transformer in the voltage adjustment apparatus which concerns on Embodiment 1. FIG. It is explanatory drawing for demonstrating the method of changing the connection of a series transformer. It is a block diagram of the voltage regulator for demonstrating the case where a series transformer is connected by a standard Δ-Y connection. It is a block diagram of the 1st example of the voltage adjustment device which connected the series transformer by the same Δ-Y connection as in the case of FIG. It is a block diagram of the 2nd example of the voltage adjustment device which connected the series transformer by the same Δ-Y connection as in the case of FIG. It is a vector figure which shows the voltage vector applied or induced to each of the adjustment transformer and the series transformer in a voltage adjustment device from another viewpoint. It is a vector figure which shows the voltage vector which is applied or induced to each of the adjustment transformer and the series transformer in the voltage adjustment apparatus which concerns on modification 1. FIG. It is explanatory drawing for demonstrating the method of changing the connection of a series transformer. It is a block diagram which shows the structural example of the voltage adjustment apparatus which concerns on modification 2. It is a block diagram which shows the structural example of the voltage adjustment apparatus which concerns on Embodiment 2. It is a flowchart which shows the processing procedure of the switching control part which adjusts the voltage of a distribution line by the voltage adjustment apparatus which concerns on Embodiment 2. It is explanatory drawing which shows the model of the distribution system used for the verification. It is a figure which shows the result of having analyzed the secondary side voltage and the internal circuit current for each control type which tap position is different. It is a block diagram which shows the structure of the experimental circuit used for the verification. It is explanatory drawing which shows typically the selection of the tap position for the example of a plurality of control types. It is a waveform diagram which shows the measurement result of the line voltage of the primary side and the secondary side of a voltage regulator in the case of three-phase batch step-down. It is a waveform figure which shows the measurement result of the line voltage of the primary side and the secondary side of a voltage regulator in the case of individual step-down. It is a waveform figure which shows the measurement result of the line voltage of the primary side and the secondary side of a voltage regulator in the case of individual buck-boost.

Hereinafter, the present invention will be described in detail with reference to the drawings showing the embodiments thereof.
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration example of the voltage adjusting device according to the first embodiment. In the figure, 1u, 1v, and 1w are distribution lines that distribute U-phase, V-phase, and W-phase AC voltages from the power source to the load (all not shown) to the right of the paper. The voltage regulator includes a series transformer 2 in which secondary windings 212, 222, 232 are connected in series to distribution lines 1u, 1v, 1w, respectively, and primary windings 311, 3211 to distribution lines 1u, 1v, 1w. A tap switch 4 provided between the adjusting transformer 3 to which the 331 is Δ-connected, the secondary windings 312, 322, 332 of the adjusting transformer 3 and the primary windings 211, 221, 231 of the series transformer 2. And.

The voltage regulator also detects the voltage of the distribution wires 1u, 1v, 1w via the three-phase measuring transformer 5 connected in Δ-Y, and the voltage detecting unit 62. Based on the operation display unit 63 for displaying the voltage and accepting the user's operation and the operation received by the operation display unit 63, the changeover switches S1, S2, ... S6, SS and the magnetic contactor MC described later will be described later. Also includes a switching control unit 61 that gives a drive signal via the drive unit 64. The changeover switches S1, S2, ... S6 all function as polarity changeover switches.

The voltage detection unit 62 detects the line voltage of the distribution lines 1u, 1v, 1w, and detects the phase voltage via a measuring transformer connected by a connection method other than the Δ-Y connection. May be good. Further, instead of the measuring transformer 5, a tertiary winding corresponding to each of the primary windings 311, 321, 331 of the adjusting transformer 3 is provided, and the voltage detection unit 62 transmits the distribution wire through the tertiary winding. The voltage of 1u, 1v, 1w may be detected, or the voltage of the distribution line 1u, 1v, 1w may be detected separately from the voltage regulator.

In the series transformer 2, the primary windings 211, 221, 231 correspond to the secondary windings 212, 222, 232, respectively. The primary windings 211, 211, 231 are Δ-connected. The terminals of the primary windings 211, 221, 231 corresponding to the terminals on the load side of each of the secondary windings 212, 222, 232 are u1, v1, w1. Further, the terminals of the primary windings 211, 221, 231 corresponding to the terminals on the power supply side of the secondary windings 212, 222, 232, respectively, are u2, v2, w2.

In the adjusting transformer 3, the primary winding 311 is connected between the distribution lines 1u and 1v, the primary winding 321 is connected between the distribution lines 1v and 1w, and the primary winding 331 is connected between the distribution lines 1w and 1u, respectively. That is, the primary windings 311, 321, 331 are Δ-connected to the distribution lines 1u, 1v, 1w. Secondary windings 312, 322, and 332 correspond to the primary windings 311, 321, 331, respectively.

Each of the secondary windings 312, 322, and 332 has taps ta and tc drawn from one end and the other end, and an intermediate tap tb drawn from between the taps ta and tc. Any one of the taps ta to tc of each of the secondary windings 312, 322, and 332 has terminals u1, v1, w1 and terminals v2, w2 on the primary side of the series transformer 2 via the tap changer 4. Connected to u2.

The tap changer 4 has six changeover switches S1, S2, ... S6 for switching the taps ta, tb, and tk of the secondary windings 312, 322, and 332 of the adjustment transformer 3 for three phases. The tap tas of the secondary windings 312, 322, and 332 are connected to one end of the changeover switches S1 and S4 via a protective fuse F. The taps tb of each of the secondary windings 312, 322, and 332 are connected to one end of the changeover switches S2 and S5 via a protective fuse F. The tap cts of the secondary windings 312, 322, and 332 are connected to one end of the changeover switches S3 and S6. The other ends of the changeover switches S1, S2, and S3 are connected to each other. The other ends of the changeover switches S4, S5, and S6 are connected to each other.

The other ends of the changeover switches S1, S2, and S3 to which the taps ta, tb, and tc of the secondary winding 312 are connected to one end are connected to the terminals u1 and v2 on the primary side of the series transformer 2. The other ends of the changeover switches S4, S5, and S6 to which the taps ta, tb, and tc of the secondary winding 312 are connected to one end are connected to the neutral point N. The other ends of the changeover switches S1, S2, and S3 to which the taps ta, tb, and tc of the secondary winding 322 are connected to one end are connected to the terminals v1 and w2 on the primary side of the series transformer 2. The other ends of the changeover switches S4, S5, and S6 to which the taps ta, tb, and tc of the secondary winding 322 are connected to one end are connected to the neutral point N. The other ends of the changeover switches S1, S2, and S3 to which the taps ta, tb, and tc of the secondary winding 332 are connected to one end are connected to the terminals w1 and u2 on the primary side of the series transformer 2. The other ends of the changeover switches S4, S5, and S6 to which the taps ta, tb, and tc of the secondary winding 332 are connected to one end are connected to the neutral point N.

Between the other ends of the changeover switches S1, S2 and S3 and the other ends of the changeover switches S4, S5 and S6, a series circuit of the current limiting resistor R and the changeover switch SS and an electromagnetic contactor MC are provided. They are connected in parallel. The changeover switch SS is limited to the taps in order to entangle the taps via the current limiting resistor R in the process of switching the taps ta, tb, tk by the changeover switches S1, S2, ... S6. This is for connecting and disconnecting the flow resistor R. The magnetic contactor MC has terminals u1, v1 on the primary side of the series transformer 2 while the operation of switching taps ta, tb, and tc by the changeover switches S1, S2, ... S6 and SS is stopped. This is to prevent the v1 and w1 and the terminals w1 and u1 from being opened.

The voltage of the tap ta with respect to the tap tb is set to be twice the voltage of the tap tb with respect to the tap tc, but is not limited to this. By selecting the taps ta, tb, and tc of the adjusting transformer 3 configured in this way, the voltage of the tap tb with respect to the tap tc is doubled (tap ta with respect to the tap tb) and tripled (tap with respect to the tap tc). It is possible to take out the voltage of ta), -1 times (tap tk with respect to tap tb), -2 times (tap tb with respect to tap ta) and -3 times (tap tk with respect to tap ta). That is, the relative adjustment voltage taken out from the adjustment transformer 3 can be selected from 1, -1, 2, -2, 3 and -3.

In the first embodiment, as an example, by turning on only the changeover switches S2 and S6 painted in black in FIG. 1 and selecting the taps tb and tk, the adjustment voltage taken out from each of the secondary windings 312, 322 and 332 is taken out. The ratio of is 1: 1: 1. In the following, the terminals corresponding to the taps tb and tc of the secondary winding 312 are U1 and U2, and the terminals corresponding to the taps tb and tc of the secondary winding 322 are V1 and V2, respectively, and the secondary winding 332 is used. The terminals corresponding to the taps tb and tc are W1 and W2. According to the example here, the terminals U2, V2, W2 are connected to the neutral point N, and the adjustment voltage is taken out from the terminals U1, V1, W1. For example, the ratio of the adjustment voltage is -1: -1:-. In the case of 1, the terminals U1, V1 and W1 are connected to the neutral point N, and the adjustment voltage is taken out from the terminals U2, V2 and W2.

Next, the connection relationship between the terminals U1, V1, W1 and the terminals u1, u2, v1, v2, w1, w2 and the voltage relationship will be described. FIG. 2 is an explanatory diagram visually showing a three-phase connection relationship between the adjusting transformer 3 and the series transformer 2 in the voltage adjusting device according to the first embodiment. FIG. 3 is a vector diagram showing voltage vectors applied to or induced in the adjusting transformer 3 and the series transformer 2 in the voltage adjusting device according to the first embodiment. FIG. 4 is an explanatory diagram for explaining a method of changing the connection of the series transformer 2. In the present specification, the notation of dots for the character string representing the vector is omitted.

Explaining the connection relationship in FIG. 2 with reference to FIG. 1, the terminal U1 is connected to the terminals u1 and v2 via the changeover switch S2. The terminal V1 is connected to the terminals v1 and w2 via the changeover switch S2. The terminal W1 is connected to the terminals w1 and u2 via the changeover switch S2. In the vector diagram shown on the right side of the paper in FIG. 3, the phase voltages Eu, Ev, Ew of the distribution lines 1u, 1v, 1w are represented by solid lines, and the line voltages Vuv, Vvw, Vwoo are represented by broken lines. Hereinafter, the phase of the phase voltage Eu is used as the reference phase. The legend on the drawing represents a part where a voltage represented by a vector is generated or induced or a part where a voltage is applied (the same applies hereinafter).

Since the line voltages Vuv, Vvw, and Vwoo are applied to the primary windings 311, 321, 331 of the Δ-connected adjustment transformer 3, as shown in the solid line on the left side of the paper in FIG. 3 and FIG. In each of the Y-connected secondary windings 312, 322, and 332, voltages E'u, E'v, and E'w that are in phase with the line voltages Vuv, Vvw, and Vw and are proportional in magnitude are induced. These voltages E'u, E'v, E'w are applied as adjusting voltages to the primary windings 211, 211, 231 of the series transformer 2 connected by Δ as shown by the broken line.

As shown by the broken line on the left side of the paper in FIG. 3, the three-phase adjustment voltages applied to the primary windings 211, 211, 231 of the series transformer 2 have the same magnitude and are out of phase with each other by 2π / 3. Therefore, the vector sum of these voltages becomes zero. Therefore, the short-circuit loop current due to the vector sum of the adjustment voltage does not flow in the closed circuit passing through the terminals u1, v2, v1, w2, w1, u2 of the series transformer 2 (see FIG. 2). Then, the voltage obtained by transforming the three-phase adjusted voltage by the series transformer 2 is superimposed on the phase voltage of the distribution wires 1u, 1v, 1w, so that the voltages of the distribution wires 1u, 1v, 1w on the load side are uniformly boosted. Will be done.

The tap changer 4 may be configured by using a switch such as another semiconductor element or an electromagnetic contactor without using a thyristor for the changeover switches S1, S2, ... S6 and SS. Further, instead of the tap changer 4 using a switch, a manual tap changer or a tap changer may be used. Even in this case, the user taps the switching destination based on the voltage of the distribution lines 1u, 1v, 1w displayed on the operation display unit 63 or the voltage of the distribution lines 1u, 1v, 1w separately detected. , Tb, tc may be selected and manually switched to the tap of the selected switching destination.

Next, the change of the connection in the series transformer 2 will be described with reference to FIG. FIG. 5 is a block diagram of a voltage regulator for explaining a case where the series transformer 2 is connected by a standard Δ-Y connection. According to the standard Δ-Y connection, of the adjustment voltages E'u, E'v, E'w from the terminals U1, V1 and W1 of the adjustment transformer 3, E'u is the series transformer 2. It is applied to terminals u1 and w2, E'v is applied to terminals v1 and u2, and E'w is applied to terminals w1 and v2. Then, the secondary windings 212, 222, 232 corresponding to the primary windings 211, 221, 231 respectively are connected in series with the distribution lines 1u, 1v, 1w. The other connection relationships shown in FIG. 5 are the same as in the block diagram shown in FIG.

If the primary windings 211,221,231 and the secondary windings 212,222,232 of the series transformer 2 are connected by a standard Δ-Y connection, they are shown by broken lines on the left side of the paper in FIG. Adjusting voltages from terminals U1-V1, terminals V1-W1, and terminals W1-U1 are applied to the primary windings 211, 211, 231 of the series transformer 2. As a result, as shown on the right side of the paper in FIG. 4, the secondary windings 212, 222, 232 have voltages Eu ”, Ev”, Ew ”which are in phase with the voltage from each of the terminals and whose magnitude is proportional to each other. Each of these voltages Eu ", Ev", and Ew "is advanced by π / 3 (60 °) with respect to the phase voltages Eu, Ev, and Ew of the distribution lines 1u, 1v, and 1w. This is due to the fact that the phase of each of the adjusting transformer 3 and the series transformer 2 connected in Δ-Y advances by 30 °.

Here, for example, focusing on Ew ", it can be seen that -Ew", which is the inverted phase of Ew ", has the same phase as the reference phase (that is, Eu) (see the left side of the paper in FIG. 4). It can be seen that "Eu" is in phase with Ev and -Ev "is in phase with Ew. In this way, the voltages Eu", Ev ", and Ew" are equivalent to the voltage delayed by π / 3. If Ew ", -E" u, -E "v is added to the phase voltages Eu, Ev, Ew of the distribution lines 1u, 1v, 1w, the distribution lines will have the same phase voltage as the phase voltages Eu, Ev, Ew. The voltage of 1u, 1v, 1w can be adjusted.

6 and 7 are block diagrams of the first example and the second example of the voltage adjusting device in which the series transformer 2 is connected by the same Δ-Y connection as in the case of FIG. Other connection relationships except for the Δ-Y connection of the series transformer 2 shown in FIGS. 6 and 7 are the same as in the block diagram shown in FIG. According to the above consideration, the phases of -Ew ", -E" u, -E "v, which are π / 3 behind each of Eu", Ev ", and Ew", are set to the phase voltage Eu of the distribution lines 1u, 1v, and 1w. , Ev, Ew, the connections of the secondary windings 212, 222, 232 of the series transformer 2 shown in FIG. 5 may be changed and adjusted as shown in FIG. That is, the polarities of the wiring with respect to the secondary windings 212, 222, 232 induced by the voltages E "u, E" v, E "w are reversed and connected in series to the distribution lines 1v, 1w, 1u.

The Δ-Y connection of the series transformer 2 shown in FIG. 6 can be changed as shown in FIG. 7. That is, the wiring connected to each of the primary windings 211, 221, 231 and the secondary windings 212, 222, 232 shown in FIG. 6 is cyclically rotated to be shown in FIG. It becomes a connection. More specifically, the wirings connected to the primary windings 211,221,231 are replaced with the primary windings 221,231,211 and connected to the secondary windings 212,222,232 respectively. The wiring is reconnected to the secondary winding 222,232,212.

The Δ-Y connection of the series transformer 2 shown in FIG. 7 further determines the polarity of the wiring connected to each of the primary windings 211, 221, 231 and the secondary windings 212, 222, 232, respectively. By inverting the connection, the connection shown in FIG. 1 is obtained. As described above, it was shown that the Δ-Y connection of the series transformer 2 shown in FIG. 1 and the Δ-Y connection of the series transformer 2 shown in FIGS. 6 and 7 are equivalent.

Next, another method for deriving the Δ-Y connection of the series transformer 2 shown in FIG. 1 will be described. It is assumed that the secondary windings 212, 222, 232 of the series transformer 2 are connected in series with the distribution lines 1u, 1v, 1w, respectively. FIG. 8 is a vector diagram showing voltage vectors applied to or induced in each of the adjusting transformer 3 and the series transformer 2 in the voltage adjusting device from another viewpoint. The vector diagram shown on the right side of the paper surface of FIG. 8 is the same as the vector diagram shown on the right side of the paper surface of FIG. That is, the phase voltages Eu, Ev, Ew of the distribution lines 1u, 1v, 1w are represented by solid lines, and the line voltages Vuv, Vvw, Vwoo are represented by broken lines.

As shown by the solid line on the left side of the paper in FIG. 8, the secondary windings 312, 322, and 332 of the Y-connected adjusting transformer 3 are in phase with the line voltages Vuv, Vvw, and Vw, respectively, and their magnitudes are proportional to each other. The resulting voltages V'uv, V'vw, and V'ww are induced. As a result, the voltages -E'u, -E'v, and -E'w in the directions opposite to the phase voltages Eu, Ev, and Ew are induced between the terminals W1-U1, U1-V1, and V1-W1, respectively. (See dashed line). For example, since E'u has the same phase as the phase voltage Eu, this E'u may be applied between the terminals u1-u2 of the primary winding 211. In other words, terminals W1 and u2 are connected, and terminals U1 and u1 are connected. Similarly, terminals U1 and v2, terminals V1 and v1, terminals V1 and w2, and terminals W1 and w1 are connected, respectively. In this way, the connection to the primary windings 211,221,231 of the series transformer 2 shown in FIG. 1 is derived.

(Modification example 1)
In the first embodiment, the three-phase adjustment voltage is taken out from the same tap for each of the secondary windings 312, 322, 332, but in the modified example 1, the three-phase adjustment voltage is taken out from a different tap for each of the secondary windings 312, 322, 332. Since the three-phase adjustment voltage is taken out, the ratio of the three-phase adjustment voltage is different from 1: 1: 1. Since the block configuration of the voltage adjusting device in the first modification is the same as that shown in FIG. 1, the same reference numerals are given to the parts corresponding to the first embodiment, and the description thereof will be omitted.

For example, for the secondary windings 312 and 322, the changeover switches S3 and S5 are turned on to select taps tc and tb, and for the secondary windings 332, the changeover switches S2 and S5 are turned on and only the tap tb is selected. Therefore, the ratio of the magnitudes of the three-phase adjustment voltages taken out from the secondary windings 312, 322, and 332 can be set to -1: -1: 0. In this case, the reason why both the changeover switches S2 and S5 are turned on for the secondary winding 332 is to apply a zero voltage without opening the terminals u2 and w1 of the series transformer 2. Regarding the secondary winding 332, only the changeover switches S1 and S4 may be turned on to select only the tap ta, or only the changeover switches S3 and S6 may be turned on to select only the tap tc.

Next, the voltage relationship will be described using a vector diagram. FIG. 9 is a vector diagram showing voltage vectors applied to or induced in the adjusting transformer 3 and the series transformer 2 in the voltage adjusting device according to the first modification. FIG. 10 is an explanatory diagram for explaining a method of changing the connection of the series transformer 2. The vector diagram shown on the right side of the paper in FIG. 9 is the same as the vector diagram shown on the right side of the paper in FIGS. 3 and 8. That is, the phase voltages Eu, Ev, Ew of the distribution lines 1u, 1v, 1w are represented by solid lines, and the line voltages Vuv, Vvw, Vwoo are represented by broken lines. The line voltages Vuv, Vvw, and Vw are applied to the primary windings 311, 321, 331 of the adjusting transformer 3, respectively.

As shown by the solid line on the left side of the paper in FIG. 9, the Y-connected secondary windings 312, 322, and 332 have different voltages E'u based on the above-mentioned line voltages Vuv, Vvw, and Vwoo. , E'v, E'w occur. The voltages E'u, E'v, and E'w generate V0 (zero-phase voltage) of the voltage induced in the secondary windings 312, 322, and 332 in the same phase as the line voltages Vuv, Vvw, and Vw, respectively. Since it is a reference three-phase voltage, the vector sum becomes zero. These voltages E'u, E'v, E'w are applied as adjusting voltages to the primary windings 211, 211, 231 of the series transformer 2 connected by Δ as shown by the broken line.

Moving on to FIG. 10, when the primary windings 211,221,231 and the secondary windings 212,222,232 of the series transformer 2 are connected by a standard Δ-Y connection, FIG. 9 shows. Adjusting voltages from terminals U1-V1, terminals V1-W1, and terminals W1-U1 shown by broken lines on the left side of the paper are applied to the primary windings 211, 211, 231 of the series transformer 2. As a result, the secondary windings 212, 222, 232 of the series transformer 2 are connected to terminals U1-V1, terminals V1-W1, and terminals W1-U1 as shown on the right side of the paper in FIG. Voltages Eu ", Ev", Ew "that are in phase with the voltage and proportional in magnitude are induced. These voltages Eu", Ev ", Ew" are the phase voltages Eu, Ev of the distribution lines 1u, 1v, 1w, respectively. The phase is advanced by approximately π / 3 (60 °) with respect to Ew.

Here, as shown on the left side of the paper in FIG. 10, as in the case described with reference to FIG. 4 of the first embodiment, the phase is delayed by approximately π / 3 from each of Eu ”, Ev”, and Ew ”, If -E "u, -E" v is added to the phase voltages Eu, Ev, Ew of the distribution lines 1u, 1v, 1w, the distribution lines 1u, 1v are obtained by voltages having substantially the same phase as the phase voltages Eu, Ev, Ew, respectively. , 1w voltage can be easily adjusted. From the above, even if the phase voltages Eu, Ev, and Ew of the distribution lines 1u, 1v, and 1w change from moment to moment, the unbalanced voltage can be appropriately adjusted so as not to change V0. ..

(Modification 2)
In the first embodiment, the voltages -Ew", -E "u, -E" v induced in the secondary windings 212, 222, 232 of the series transformer 2 are set to the phase voltages Eu of the distribution lines 1u, 1v, 1w, respectively. Although it is added to Ev and Ew, in the second modification, the voltages -Ew ", -E" u and -E "v are subtracted from the phase voltages Eu, Ev and Ew of the distribution lines 1u, 1v and 1w. In other words, the voltages Ew ", E" u, E "v are added to the phase voltages Eu, Ev, Ew of the distribution lines 1u, 1v, 1w, which adds the voltages Eu", Ev ", Ew", respectively. This means that Ew ", E" u, E "v, which is equivalent to the voltage delayed by 4π / 3, is added to the phase voltages Eu, Ev, Ew of the distribution lines 1u, 1v, 1w (see FIG. 4).

FIG. 11 is a block diagram showing a configuration example of the voltage adjusting device according to the modified example 2. In the second modification, the polarities of the wiring for the secondary windings 212, 222, 232 of the series transformer 2 are reversed to the distribution lines 1v, 1w, 1u with respect to the case shown in FIG. 1 of the first embodiment. Connect in series. As a result, the transformed voltage of the adjustment voltage generated by the adjustment transformer 3 is added in the opposite phase to the AC voltage of the distribution lines 1v, 1w, 1u. Therefore, by appropriately selecting the tap of the tap changer 4 and inverting the sign (plus / minus) of the relative adjustment voltage taken out from the adjustment transformer 3 with respect to the case of the first embodiment, the distribution line When adjusting the unbalanced voltage of 1u, 1v, 1w, the same effect as in the case of the first embodiment is obtained.

The connection of the series transformer 2 in the second modification is not limited to the case of FIG. For example, the polarity of the wiring connected to the primary winding of the series transformer 2 shown in FIG. 1 may be reversed, or the primary winding of the series transformer 2 shown in FIG. 6 or 7 may be reversed. The polarity of the wiring connected to each of 211,221,231 or the secondary winding 212,222,232 may be reversed.

As described above, according to the first embodiment and the first and second modifications, the primary windings 211, of the series transformer 2 in which the secondary windings 212, 222, 232 are connected in series to the distribution lines 1u, 1v, 1w, respectively. The 221 and 231 are Δ-connected, and the primary windings 311, 321 and 331 are Δ-connected to the distribution lines 1u, 1v and 1w. There is. Then, with respect to the primary windings 211, 221, 231 of the series transformer 2, the changeover switch of the tap changer 4 is selected from the taps ta, tb, and tk of the secondary windings 321, 322, and 332 of the adjustment transformer 3, respectively. The adjustment voltage is applied via S1, S2, ... S6. Therefore, by selecting and switching the taps ta, tb, and tc of the adjusting transformer 3, it is possible to adjust the three-phase voltage of the distribution lines 1u, 1v, and 1w. It is also possible to apply the voltage regulator to a load ratio control transformer (LRT) in a substation and an automatic voltage regulator (SVR: Step Voltage Regulator) in a power transmission line.

Further, according to the first embodiment and the first and second modifications, the secondary windings 212, 222, 232 of the series transformer 2 are applied in series with respect to the three-phase AC voltage of the distribution lines 1u, 1v, 1w. The AC voltage is connected so that the phase of the AC voltage is substantially delayed by 60 ° or 60 ° + 180 ° as compared with the case of the standard Δ-Y connection. Therefore, it is possible to substantially cancel the phase advance of 30 ° and the phase delay of 60 ° in each of the adjusting transformer 3 and the series transformer 2 of the Δ-Y connection. Further, the adjusted voltage generated by the adjusting transformer 3 and the voltage transformed by the series transformer 2 can be added to the AC voltage of the distribution lines 1u, 1v, 1w so as to be in phase or in reverse phase.

Further, according to the first embodiment and the first and second modifications, the polarity of the adjustment voltage applied to the primary windings 211, 211, 231 of the series transformer 2 selects the changeover switches S1, S2, ... S6. Since it can be arbitrarily switched depending on the voltage, the degree of freedom in adjusting the imbalance of the three-phase voltages of the distribution lines 1u, 1v, and 1w can be increased.

Further, according to the first embodiment and the first and second modifications, since the thyristor is used for the changeover switches S1, S2, ... S6, the tap ta, tb, and tc can be switched at high speed, and the tap ta, It is not necessary to consider the life of tb and tc.

(Embodiment 2)
In the first embodiment, the switching control unit 61 switches the taps ta, tb, and tc based on the operation received by the operation display unit 63, or the user operates a manual tap switching device or tap switching table. On the other hand, in the second embodiment, the switching control unit 61 automatically switches the taps ta, tb, and tc based on the voltage detected by the voltage detection unit 62. FIG. 12 is a block diagram showing a configuration example of the voltage adjusting device according to the second embodiment. In the voltage adjusting device according to the second embodiment, the operation display unit 63 is deleted and the storage unit 65 is added as compared with the voltage adjusting device according to the first embodiment shown in FIG. The operation display unit 63 may not be deleted.

The storage unit 65 stores the deviation of the voltage of the three phases of the distribution lines 1u, 1v, and 1w with respect to the target voltage and the amount related to the transformation ratio of the three phases of the adjusting transformer 3 in association with each other. The storage unit 65 is connected to the switching control unit 61 so that the stored contents can be referred to by the switching control unit 61, but the storage unit 65 may be included in the switching control unit 61.

The storage unit 65 stores the deviation of the three phases and the change amount of the transformation ratio of the three phases in association with each other. For example, the taps ta, tb, and tk of the adjusting transformer 3 are numbered. In this case, the deviation for the three phases and the number of taps for the three phases may be associated and stored. Other parts corresponding to the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

Hereinafter, the operation of the switching control unit 61 described above will be described with reference to a flowchart showing the operation. The processing shown below is executed by a CPU (Central Processing Unit) (not shown) according to a control program stored in advance in a ROM (Read Only Memory) (not shown) included in the switching control unit 61.

FIG. 13 is a flowchart showing a processing procedure of the switching control unit 61 that adjusts the voltages of the distribution lines 1u, 1v, and 1w by the voltage adjusting device according to the second embodiment. This processing procedure is periodically executed, for example, every 4 to 5 seconds. It is assumed that the current transformation ratios for the three phases are stored in the RAM (Random Access Memory) (not shown) included in the switching control unit 61.

When the process of FIG. 13 is activated, the CPU of the switching control unit 61 (the same applies hereinafter) acquires the line voltage or phase voltage of the three phases of the distribution lines 1u, 1v, 1w on the load side from the voltage detection unit 62. Then, the deviation of the acquired three-phase voltage with respect to the target voltage is calculated (S12).

Next, the CPU reads out the content (change amount of the transformation ratio) stored in the storage unit 65 in association with the deviation, and selects the switching destination of the taps ta, tb, and tc for the three phases (S13). To select the switching destination of the taps ta, tb, and tc, the amount of change read out may be added to the current transformation ratio stored in the RAM, and the tap corresponding to the transformation ratio of the addition result may be selected. The transformation ratio of the three phases of the addition result is stored in the RAM as updating the current transformation ratio.

After that, the CPU turns on the three-phase changeover switch SS (S14), turns off the three-phase changeover switches S1, S2, ... S6 (S15), and then responds to the tap of the selected switching destination. The changeover switch is turned on (S16). Next, the CPU finishes the process of FIG. 13 after turning off the three-phase changeover switch SS (S17).

In the above flowchart, it is assumed that the storage unit 65 stores the deviation of the three phases and the change amount of the transformation ratio of the three phases in association with each other, but the present invention is limited to this. It's not a thing. For example, when the storage unit 65 stores the deviation of the three phases and the number of taps switched for the three phases in association with each other, the current tap number of the three phases is stored in the RAM and calculated in step S12. The number of taps to be switched stored in the storage unit 65 in association with the deviation may be added to the current tap number stored in the RAM, and the tap corresponding to the tap number of the addition result may be selected. The tap numbers for the three phases of the addition result are stored in the RAM as updating the current tap numbers.

As described above, according to the second embodiment, the taps ta, tb, and tk of the secondary windings 312, 322, 332 of the adjusting transformer 3 are applied to the primary windings 211, 221, 231 of the series transformer 2. The voltage of the three-phase distribution lines 1u, 1v, 1w adjusted by the adjustment voltage is detected by the voltage detection unit 62 and compared with the target voltage, and the changeover switches S1, S2, ... S6 is controlled and the taps ta, tb, and tc are switched. Therefore, it is possible to perform feedback control so that the voltage deviations of the distribution lines 1u, 1v, and 1w approach zero.

Further, according to the second embodiment, the deviation of the three-phase voltages of the distribution lines 1u, 1v, and 1w with respect to the target voltage is calculated, and based on the amount of change in the transformation ratio read from the storage unit 65 according to the calculated deviation. The switching destinations of the taps ta, tb, and tc are selected, and the switching switches S1, S2, ... S6 are controlled according to the selected switching destination. Therefore, it is not necessary to obtain the above-mentioned adjustment voltage by vector calculation when the switching control unit 61 is executed.

(simulation)
Hereinafter, the result of verifying the voltage adjustment of the distribution lines 1u, 1v, 1w by the voltage adjusting device according to the first embodiment by simulation will be described. FIG. 14 is an explanatory diagram showing a model of the distribution system used for verification. In this model, the series transformer 2 and the adjusting transformer 3 are connected to the distribution lines 1u, 1v, 1w that distribute the three-phase AC voltage from the three-phase power supply 100 to the three-phase load 110. The adjusting transformer 3 is connected to the series transformer via a tap changer (not shown) and a current measuring unit 103.

The three-phase power supply 100 has a line voltage of 30 V and a frequency of 50 Hz. It is assumed that the initial state of the three-phase AC voltage is in the three-phase equilibrium state. The three-phase load 110 is a balanced load in which a resistance of 100 Ω is Δ-connected. The series transformer 2 has a transformation ratio of 10 (10: 1), and the adjusting transformer 3 has a transformation ratio of 1 (1: 1). The tap changer (not shown) has three taps (through, step-up, step-down). Generally, the number of tap stages of TVR is 7 stages in total, that is, through, step-up: 3 stages, and step-down: 3 stages, and an increase in the number of stages contributes to an increase in the adjustment amount. Since the analysis can be performed with a total of three taps including one step and step-down: one step, a three-step tap is used here.

In the above configuration, the results of measuring the voltages on the primary side (that is, the three-phase power supply 100 side) and the secondary side (that is, the three-phase load 110 side) of the voltage regulator by the voltage measuring units 101 and 102, and the adjusting transformer. The results of measuring the three-phase internal circuit currents flowing from the secondary windings 312, 322, 332 of the device 3 to the primary windings 211, 221 and 231 of the series transformer 2 by the current measuring unit 103 were analyzed by simulation. The sampling period in the analysis was 100 μs, and the analysis time was 0 to 5 seconds.

FIG. 15 is a chart showing the results of analyzing the secondary side voltage and the internal circuit current for each control type having a different tap position. In FIG. 15, the primary side voltage analyzed for 10 control types, the secondary side voltage and adjustment voltage, the difference between the primary side and secondary side zero-phase voltage (V0), and the internal circuit current are shown. Is shown numerically. There are six control types, three-phase straight-through, three-phase batch step-down, individual step-down including plain-through lines, individual step-up / down pressure, individual boost-up including plain-through lines, and three-phase batch boost-up according to the tap position selection. Of these, the individual step-down was divided into two, the individual step-up / down pressure was divided into three, and the individual boost was divided into two. The numerical value indicating the selection of the tap position is as described in the first embodiment. In addition, "passing through" in the control type indicates that the tap position where the magnitude of the adjustment voltage is 0 is selected.

The UV line, VW line, and WU line, respectively, related to the tap position in the chart are relative to the adjustment voltage according to the selection result of the tap position of the secondary winding 321, 322, 332 of the adjustment transformer 3. Represents the size. The UV line, VW line, and WU line related to the secondary side voltage represent the line voltage of the distribution lines 1u, 1v, and 1w on the secondary side, respectively. The U-phase, V-phase, and W-phase related to the internal circuit current are the currents that flow into the terminals u1, v2, terminals v1, w2, and terminals w1, u2 of the series transformer 2 due to the adjustment voltage from the adjustment transformer 3. (See FIG. 1 for both). The primary voltage is the voltage of the three-phase power supply 100 itself, and is 30.00 V between all the lines for all control types. Further, the value obtained by adding the adjustment voltage to the primary side voltage is the secondary side voltage.

From the analysis results shown in FIG. 15, it can be said that the adjustment voltage and the secondary side voltage change according to the numerical value indicating the tap position selection result for each control type. Especially No. In the cases of 2 and 10, the adjustment amount between the three lines (absolute value of the adjustment voltage: the same applies hereinafter) is equal, and it can be seen that the three phases can be controlled collectively. No. In the cases of 3, 5, 8 and 9, the amount of adjustment between the lines that are stepping up or down is smaller than that in the case of the three-phase batch, but it is larger than the amount of adjustment between the lines that are transparent. , You can see that it can be adjusted in the intended direction. No. In the case of 4 (or 7), the amount of adjustment between the two lines that are stepping down (or stepping up) is equal, and the amount of adjustment is larger than that between one line that is stepping up (or stepping down), but between the two lines. The adjustment direction is opposite between and one line, and it can be seen that the adjustment can be made in the target direction. In addition, No. In the case of 6, the adjustment amount between the two lines that are stepping up and down is smaller than that in the case of the three-phase batch, but it is larger than the adjustment amount between the straight lines, and the target direction. You can see that it can be adjusted to.

Zero-phase voltage differences were about ^{10-14 V for all control types.} This value is considered to be a numerical calculation error in the simulation, and there is no problem even if the zero-phase voltage difference increases in proportion to the line voltage by applying it to the actual distribution system where the line voltage is 6600V. It can be said that it is a value. Regarding the internal circuit current, No. It is the largest in the case of the three-phase batch boosting of 10, and is smaller in the case of the other control types than in the case of the three-phase batch boosting. This is No. 1 where the largest voltage is applied to the three-phase load composed of resistors. This is because in the case of 10, a large current also flows in the internal circuit. For other control types, see No. It can be seen that the internal circuit current is smaller than in the case of 10, and no abnormal current is generated.

In this simulation, the voltage waveform and current waveform of the primary side (three-phase power supply 100 side) and the secondary side (three-phase load 110 side) of the voltage regulator, and the voltage of the secondary side of the regulator transformer 3 (adjustment voltage). ) And the current (internal circuit current) waveforms were also verified. Although the illustration of these waveforms is omitted, all the waveforms were normal three-phase waveforms in which no short circuit or open phase was observed.

(Simulation experiment)
Hereinafter, the result of verifying the waveform at the time of voltage adjustment of the distribution lines 1u, 1v, 1w by the voltage adjusting device according to the first embodiment by a simulation experiment will be described. FIG. 16 is a block diagram showing a configuration of an experimental circuit used for verification, and FIG. 17 is an explanatory diagram schematically showing selection of a tap position for an example of a plurality of control types. In this experimental circuit, as in the case of the above simulation, the simulated series transformer 2 and the adjustment transformer are connected to the distribution lines 1u, 1v, 1w that distribute the three-phase AC voltage from the three-phase power supply 100 to the three-phase load 110. The vessel 3 is connected. A simulated tap changer 4 is connected between the simulated adjusting transformer 3 and the series transformer 2.

The three-phase power supply 100 has a line voltage of 30 V and a frequency of 60 Hz. The three-phase load 110 is a balanced load in which a resistance of 100 Ω is Δ-connected. The series transformer 2 is simulated by three single-phase transformers having a transformation ratio of 10. The adjusting transformer 3 is simulated by three single-phase transformers having a transformation ratio of 1. The tap changer 4 is simulated by a group of three switches that switch the tap of the secondary winding of each of the three single-phase transformers.

The secondary windings of the single-phase transformers (U), (V), and (W) corresponding to the secondary windings 212, 222, 232 of the series transformer 2 are the terminals a and b, and the terminals of the terminal block A. It is connected in series to the distribution lines 1u, 1v, 1w via c and d, terminals e and f. The primary windings of the single-phase transformers (U), (V), and (W) corresponding to the primary windings 211, 211, 231 of the series transformer 2 are the terminals a and b of the terminal block B, the terminals c, and the terminals c. It is Δ-connected via d, terminals e and f.

The secondary windings of the single-phase transformers (U), (V), and (W) corresponding to the secondary windings 312, 322, and 332 of the adjusting transformer 3 are switch groups simulating the tap changer 4. , Terminals a and b, terminals c and d, terminals e and f of the terminal block C, and Y-connected. The primary windings of the single-phase transformers (U), (V), and (W) corresponding to the primary windings 311, 321, 331 of the adjusting transformer 3 are the terminals a and b of the terminal block D, the terminals c, and the terminals c. It is Δ-connected to the distribution lines 1u, 1v, 1w via d, terminals e and f.

The number of tap steps of the tap changer 4 is set to 3 (pass-through, step-up, step-down) as in the case of simulation. Therefore, each switch group simulating the tap changer 4 has two fixed secondary windings of the three single-phase transformers (U), (V), and (W) simulating the adjustment transformer 3. The taps are switched so as to be connected in parallel to the terminals a and b, terminals c and d, terminals e and f of the terminal block C, connected in antiparallel, or made transparent. Since the connection shown in FIG. 16 is basically the same as the connection shown in FIG. 1 of the first embodiment, other detailed description thereof will be omitted.

FIG. 17 shows the tap selection results by the simulated tap changer 4 for each of the three-phase batch step-down, individual step-down, and individual step-up / down pressure in order from the left side of the paper. In the case of three-phase batch step-down, the secondary windings of the single-phase transformers (U), (V), and (W) are reversed to the terminals a and b, terminals c and d, and terminals e and f of the terminal block C. Connected in parallel. In the case of individual step-down through which the V and W phases are passed through, the secondary winding of the single-phase transformer (U) is connected to the terminals a and b of the terminal block C in antiparallel, whereas the single-phase transformer is connected. One tap of each of the secondary windings (V) and (W) is connected to terminals c and d, terminals e and f of the terminal block C. In the case of individual buck-boost that steps down the U phase and boosts the W phase, the secondary winding of the single-phase transformer (U) is connected in antiparallel to terminals a and b of the terminal block C, and is a single-phase transformer. One tap of the secondary winding of (V) is connected to the terminals c and d of the terminal block C, and the secondary winding of the single-phase transformer (W) is connected in parallel to the terminals e and f of the terminal block C. Will be done.

FIG. 18 is a waveform diagram showing the measurement results of the line voltage on the primary side and the secondary side of the voltage regulator in the case of three-phase batch step-down. FIG. 19 is a waveform diagram showing the measurement results of the line voltage on the primary side and the secondary side of the voltage regulator in the case of individual step-down. FIG. 20 is a waveform diagram showing the measurement results of the line voltage on the primary side and the secondary side of the voltage regulator in the case of individual buck-boost. In FIGS. 18, 19 and 20, the waveform of the line pressure on the primary side is shown in the upper row, and the waveform of the line voltage on the secondary side is shown in the lower row, respectively. The horizontal axis of each figure represents time (ms), and the vertical axis represents voltage (V) between lines. The solid line represents the voltage Vuv between the U and V phases, the broken line represents the voltage Vvw between the V and W phases, and the alternate long and short dash line represents the voltage Vw between the W and U phases.

In FIG. 18, it is confirmed that Vuv, Vvw, and Vwoo on the secondary side are uniformly lowered with respect to the primary side. In FIG. 19, it is confirmed that Vuv is lower than Vvw and Vwoo on the secondary side, and the voltage between the V and U lines is relatively stepped down. In FIG. 20, Vuv decreases and Vww increases with respect to Vvw on the secondary side, the voltage between the V and U lines is relatively stepped down, and the voltage between the W and U lines is relative. It is confirmed that the voltage is boosted to.

From the verification results in the above simulations and simulated experiments, it was shown that according to the present invention, any line voltage can be individually controlled without changing V0 of the distribution lines 1u, 1v, 1w. In the simulation and simulation experiments, the tap was controlled to switch from the three-phase balanced state, but when controlling in the actual distribution system, the control is performed in the direction to correct the voltage imbalance occurring in the distribution system. Therefore, it is considered that the imbalance of the three phases can be improved. Therefore, for a distribution system in which the maximum voltage phase and the minimum voltage phase of the three phases change with time (a system in which the single-phase load connected to each phase and the power from the photovoltaic power generation device fluctuate greatly). Also, the voltage adjusting device according to the present invention can be applied. Further, even in a distribution system in which the maximum voltage phase and the minimum voltage phase are unknown, it is not necessary to perform a preliminary measurement survey to determine the connection phase to which the voltage adjustment device is connected, and the voltage adjustment according to the present invention can be performed at an arbitrary position. Devices can be connected.

The embodiments disclosed this time should be considered as exemplary in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims, not the above-mentioned meaning, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. Also, the technical features described in each embodiment can be combined with each other.

1u, 1v, 1w Distribution wire 2 Series transformer 211,221,231 Primary winding 212, 222, 232 Secondary winding u1, v1, w1 Terminal N Neutral point 3 Adjusting transformer 311, 321, 331 Primary winding 312, 322, 332 Secondary winding S1, S2, S3, S4, S5, S6, SS selector switch U1, U2, V1, V2, W1, W2 terminal F fuse MC electromagnetic contactor R limiting current resistor 4 tap switching Instrument ta, tb, tc Tap 5 Measuring transformer 61 Switching control unit 62 Voltage detection unit 63 Operation display unit 64 Drive unit 65 Storage unit

Claims (6)

A series transformer in which the secondary windings for three phases are connected in series to the distribution line that distributes the three-phase AC voltage from the power supply to the load, and the primary windings are delta-connected.
The secondary winding has a plurality of taps, the primary winding is delta-connected at a position on the load side of the distribution line from the connection position of the series transformer, and the secondary winding is star-connected. With the adjusting transformer
A tap changer provided between the secondary winding of the adjusting transformer and the primary winding of the series transformer and having a three-phase changeover switch for switching taps connected to the series transformer. A voltage regulator equipped with. In the series transformer, the phase of the three-phase AC voltage applied from the secondary winding to the distribution line is substantially π / 3 or 4π / 3 as compared with the case of a standard delta star connection. The voltage regulator according to claim 1, which is connected so as to be delayed only by. The voltage adjusting device according to claim 1 or 2, wherein the changeover switch includes a polarity changeover switch for switching the polarity of the voltage of the secondary winding of the adjusting transformer and applying it to the primary winding of the series transformer. .. The voltage adjusting device according to any one of claims 1 to 3, wherein the changeover switch includes a thyristor. A voltage detector that detects the three-phase voltage of the distribution line on the load side of the series transformer, and
Any one of claims 1 to 4, further comprising a switching control unit for calculating the deviation of the three-phase voltage detected by the voltage detecting unit with respect to the target voltage and switching the tap with the changeover switch based on the calculated deviation. The voltage regulator described in the section. Further provided with a storage unit that stores the deviation of the three-phase voltage with respect to the target voltage and the amount related to the transformation ratio of the three phases of the adjusting transformer in association with each other.
The voltage adjusting device according to claim 5, wherein when the switching control unit calculates the deviation, the switching destination of the tap for three phases is selected with reference to the storage unit, and the tap is switched to the selected switching destination. ..

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