JP2018186598A - Voltage regulation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage regulation device capable of regulating voltages of three phases by suppressing generation of a zero-phase voltage (V0) regardless of a magnitude relation of the voltages of three phases.SOLUTION: A voltage regulation device comprises: a serial transformer in which secondary coils for three phases are connected in series to a power distribution line for distributing AC voltages of three phases from a power source to a load and to which a primary coil is star-connected; a regulation transformer which includes multiple taps in the secondary coil and to which primary coils for three phases are connected in parallel at a position closer to the load than a connection position of the serial transformer in the power distribution line and a secondary coil is delta-connected; and a tap switcher which is provided between the secondary coil of the regulation transformer and the primary coil of the serial transformer and includes changeover switches for three phases for switching a tap to be connected to the serial transformer.SELECTED DRAWING: Figure 1

Description

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

  The voltage regulator using the so-called indirect switching method includes a series transformer in which the secondary winding is connected in series to the distribution line, a regulating transformer in which a plurality of taps are provided in the secondary winding, and a tap of the regulating transformer. And a switching control unit that controls the tap switching device. The adjustment transformer has a primary winding connected in parallel to the distribution line. The tap changer is provided between each tap of the secondary winding of the adjustment transformer and the primary winding of the series transformer. The switching control unit controls the tap switch so as to adjust the adjustment voltage applied from the adjustment transformer to the series transformer so as to keep the voltage of the distribution line in the target range.

  The tap changer includes a tap changeover switch for changing over the tap connected to the primary winding of the series transformer, a current limiting element such as a current limiting resistor for limiting a current-carrying current flowing between the taps in the process of performing the tap changeover, A contact / separation changeover switch for connecting and disconnecting the current limiting element between the taps. The tap changer further includes a polarity changeover switch for changing the polarity of the voltage applied from the secondary winding of the adjustment transformer to the primary winding of the series transformer. The tap changer is controlled by the change control unit to turn on and off these changeover switches in a predetermined sequence, thereby switching the magnitude and polarity of the adjustment voltage applied from the adjustment transformer to the primary winding of the series transformer.

  As shown in Patent Literature 1 and Patent Literature 2, the tap switch is made contactless by using a bidirectional thyristor (a thyristor having bidirectionality and capable of turning on and off alternating current) as a changeover switch. A voltage regulator for power distribution is known. Hereinafter, this thyristor type voltage regulator is referred to as TVR (Thyristor type Step Voltage Regulator).

  The conventional TVR is mainly in the VY connection system in which the secondary side of the adjusting transformer is V-connected and the primary side of the series transformer is Y (star) connected. In Non-Patent Document 1, based on the conventional TVR that collectively controls the tap changer for two phases using the adjustment transformer as the V connection, the two-phase voltage of the V connection of the adjustment transformer against the three-phase imbalance A TVR with a three-phase voltage imbalance function is disclosed that improves the three-phase voltage imbalance of distribution lines by monitoring and individually controlling two-phase tap changers.

  As described in Non-Patent Document 1, this TVR is connected to the voltage monitoring phase (two-phase capable of tap switching) of the TVR corresponding to voltage imbalance to the maximum voltage phase and the minimum voltage phase of the three-phase voltage of the distribution line. By doing so, a high voltage imbalance improvement effect can be obtained. " 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 (a case where a single-phase load connected to each phase or photovoltaic power generation varies greatly). In addition, 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 TVR voltage monitoring phase after conducting a measurement investigation in advance.

  On the other hand, a Y-Y connection system is realized in which the secondary side of the adjustment transformer is Y-connected and the primary side of the series transformer is Y-connected (see, for example, Patent Document 3). Since the TVR with Y-connection on the secondary side of such an adjustment transformer is equipped with a tap changer for three phases, if this tap changer is controlled for each phase, all three phases are individually tapped. Thus, the voltage can be arbitrarily adjusted in three phases, and it is said that the above-described problem of dealing with unbalance in the VY connection method can be solved.

JP-A-8-335119 JP-A-8-335121 JP, 2016-42279, A

Takahiro Okumura, Go Sugiyama, Katsushi Ito, Kenji Kajikawa, Hiroshi Kajita, Toshiaki Takagi, "Development of thyristor type automatic voltage regulator with three-phase voltage unbalance function", 2016 IEEJ, Power and Energy Conference, Paper No. 173 (2016)

  However, when different tap switching is performed for each phase in the Y-Y 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 superimposed on the system is Since V0 is generated, another major problem due to the generation of V0 occurs, such as malfunction of the ground fault relay of the substation. As described above, a three-phase unbalanced voltage regulator that can adjust the three-phase voltage without generating V0 regardless of the magnitude of the three-phase voltage has not yet been realized.

  The present invention has been made in view of such circumstances, and the object of the present invention is to suppress the generation of V0 and adjust the three-phase voltage regardless of the magnitude relationship between the three-phase voltages. Is to provide a simple voltage regulator.

  In the voltage regulator according to the present invention, a three-phase secondary winding is connected in series to a distribution line that distributes a three-phase AC voltage from a power source to a load, and the primary winding is star-connected. The transformer and the secondary winding have a plurality of taps, and the primary winding for three phases is connected in parallel to the position on the load side from the connection position of the series transformer in the distribution line, A regulation transformer in which a secondary winding is delta-connected, and a tap provided between the secondary winding of the regulation transformer and the primary winding of the series transformer, and connected to the series transformer. And a tap changer having a changeover switch for three phases for switching.

  In the present invention, the primary winding of a series transformer in which secondary windings for three phases are connected in series to a three-phase distribution line is star (Y) -connected, and the primary winding for three phases The secondary winding of the adjustment transformer connected in parallel to the distribution line is delta (Δ) connected. Then, the 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, by selecting and switching the tap of the adjustment transformer, the three-phase voltage of the distribution line is adjusted.

  In the voltage regulation device according to the present invention, the regulation transformer has a primary winding that is delta-connected.

  In the present invention, since the primary winding and the secondary winding of the adjustment transformer are Δ-Δ connected, the line is connected between the primary side and the secondary side as in the case of Y-Δ connection. A phase difference of 30 degrees does not occur in the inter-voltage, and the adjustment voltage is easily determined from the line voltage of the distribution line and the transformation ratio of the adjustment transformer.

  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, when adjusting the three-phase voltage imbalance of the distribution line High degree of freedom.

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

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

  The voltage regulator according to the present invention includes a voltage detector that detects a 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 detector. And a switching control unit that calculates a deviation and switches the tap by the change-over switch based on the calculated deviation.

  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 from the tap of the secondary winding of the adjustment transformer is detected 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. Thereby, feedback control is performed so that the deviation of the three-phase voltage of the distribution line approaches zero.

  The voltage regulator according to the present invention further includes a storage unit that associates and stores a deviation of a three-phase voltage with respect to a target voltage and an amount related to a three-phase transformation ratio of the regulating transformer, When the deviation is calculated, a switching destination of taps 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 relative to the target voltage of the three-phase voltage of the distribution line 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. The changeover switch corresponding to the selected changeover destination is controlled. This eliminates the need to obtain the above-described adjustment voltage by vector calculation when the switching control unit is executed.

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

It is a block diagram which shows the structural example of the voltage regulator which concerns on Embodiment 1 of this invention. It is explanatory drawing which takes out and shows the connection between the adjustment transformer in the voltage regulator which concerns on Embodiment 1, and a series transformer. It is explanatory drawing which shows visually the three-phase connection relationship between the adjustment transformer in the voltage regulator which concerns on Embodiment 1, and a series transformer. It is a vector diagram which shows the voltage vector induced | guided | derived to the secondary side of the adjustment transformer in the voltage regulator which concerns on Embodiment 1, and the primary side of a series transformer, respectively. It is a block diagram which shows the structural example of the voltage regulator which concerns on the modification 1 of this invention. It is explanatory drawing which takes out and shows the connection between the adjustment transformer in the voltage regulator which concerns on the modification 1, and a series transformer. It is explanatory drawing which shows visually the three-phase connection relationship between the adjustment transformer and series transformer in the voltage regulator which concerns on the modification 1. FIG. It is a vector diagram which shows the voltage vector induced | guided | derived to the secondary side of the adjustment transformer in the voltage regulator which concerns on the modification 1, and the primary side of a series transformer, respectively. It is a vector diagram which shows the voltage vector of the distribution line in the voltage regulator which concerns on the modification 1. It is a graph which shows the measurement result of the voltage induced | guided | derived to the adjustment transformer and the series transformer in the voltage regulator which concerns on the modification 1, respectively. It is a block diagram which shows the structural example of the voltage regulator which concerns on the modification 2 of this invention. It is explanatory drawing which takes out and shows the connection between the adjustment transformer and series transformer in the voltage regulator which concerns on the modification 2. FIG. It is explanatory drawing which shows visually the three-phase connection relation between the adjustment transformer in the voltage regulator which concerns on the modification 2, and a series transformer. It is a vector diagram which shows the voltage vector induced on the secondary side of the adjustment transformer in the voltage regulator which concerns on the modification 2, and the primary side of a series transformer. It is a vector diagram which shows the voltage vector of the distribution line in the voltage regulator which concerns on the modification 2. It is a block diagram which shows the structural example of the voltage regulator which concerns on Embodiment 2 of this invention. It is a flowchart which shows the process sequence of the switching control part which adjusts the voltage of a distribution line by the voltage regulator which concerns on Embodiment 2. FIG. It is a graph which shows the line voltage of the power supply side in four analysis cases, and the transformation ratio of an adjustment transformer. It is a graph which shows the line voltage and unbalance rate on each of the power supply side and load side in four analysis cases.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration example of a voltage regulator according to Embodiment 1 of the present invention. In the figure, 1u, 1v, and 1w are distribution lines that distribute U, V, and W three-phase AC voltages from the power source to the load (all not shown) in the right direction on the page. The voltage regulator includes a series transformer 2 in which secondary windings 212, 222, and 232 are connected in series to the distribution lines 1u, 1v, and 1w, and primary windings 311, 321, and the distribution lines 1u, 1v, and 1w, respectively. 331 is connected in parallel, and the tap changer provided between the secondary windings 312, 322, 332 of the regulating transformer 3 and the primary windings 211, 221, 231 of the series transformer 2 4.

  The voltage regulator also includes a voltage detector 62 that detects the voltages of the distribution lines 1u, 1v, and 1w via the three-phase measurement transformer 5 in which the primary windings are connected in delta (Δ), and the voltage detection An operation display unit 63 for displaying a voltage detected by the unit 62 and accepting a user's operation, and selector switches S1, S2,... S6, SS described later based on the operation received by the operation display unit 63. And the switching control part 61 which gives a drive signal to the electromagnetic contactor MC via the drive part 64 is provided. The changeover switches S1, S2,... S6 all function as polarity changeover switches.

  The voltage detector 62 detects the line voltage of the distribution lines 1u, 1v, 1w, but even if the phase voltage is detected via a measurement transformer in which the primary winding is connected in a star (Y) connection. Good. Further, in place of the measuring transformer 5, tertiary windings corresponding to the primary windings 311, 321, 331 of the adjustment transformer 3 are provided, and the voltage detection unit 62 is connected to the distribution line via the tertiary windings. The voltage of 1u, 1v, 1w may be detected, and 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, and 231 correspond to the secondary windings 212, 222, and 232, respectively. The primary windings 211, 221, and 231 are star-connected. A neutral point N where one ends of the primary windings 211, 221, and 231 are connected to each other is grounded. The other ends of the primary windings 211, 221, and 231 are terminals u1, v1, and w1, respectively.

  In the adjustment 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. That is, the primary windings 311, 321, 331 are delta-connected to the distribution lines 1 u, 1 v, 1 w, but may be star-connected. The secondary windings 312, 322, and 332 correspond to the primary windings 311, 321, and 331, respectively. When the primary windings 311, 321, and 331 are delta-connected, the adjustment transformer 3 is configured to match the line voltages between the U and V phases, between the V and W phases, and between the W and U phases in the distribution lines 1 u, 1 v, 1 w. Transform with phase.

  Each of the secondary windings 312, 322, and 332 includes 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. The taps ta, tb, and tc included in the secondary windings 312, 322, and 332 are connected to the primary-side terminals u 1, v 1, and w 1 of the series transformer 2 through the tap switch 4.

  The tap changer 4 has six changeover switches S1, S2,... S6 for switching three phases for switching the taps ta, tb, and tc of the secondary windings 312, 322, and 332 of the adjustment transformer 3 respectively. The taps ta of the secondary windings 312, 322, 332 are connected to one ends of the changeover switches S 1, S 4 via protective fuses F. The taps tb of the secondary windings 312, 322, 332 are connected to one ends of the changeover switches S 2, S 5 via protective fuses F. The taps tc of the secondary windings 312, 322, and 332 are connected to one ends of the changeover switches S3 and S6. The other ends of the changeover switches S1, S2, 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 respectively connected to one end are connected to a terminal u1 on the primary side of the series transformer. 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 primary-side terminal v1 of the series transformer. 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 a terminal v1 on the primary side of the series transformer. 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 respectively connected to one end are connected to a terminal w1 on the primary side of the series transformer. 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 respectively connected to one end are connected to a terminal w1 on the primary side of the series transformer. 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 terminal u1 on the primary side of the series transformer.

  Between the other ends of the changeover switches S1, S2, S3 and the other ends of the changeover switches S4, S5, S6, a series circuit of a current limiting resistor R and a changeover switch SS and an electromagnetic contactor MC are provided. Connected in parallel. The change-over switch SS is a limit switch between taps in order to interlace the taps via the current limiting resistor R in the process of switching the taps ta, tb, tc by the change-over switches S1, S2,. This is for connecting and disconnecting the flow resistor R. The magnetic contactor MC is connected between the terminals u1 and v1 on the primary side of the series transformer 2 while the operation of switching the taps ta, tb, and tc by the changeover switches S1, S2,. It is intended to prevent the connection between v1 and w1 and between the terminals w1 and u1 so that they are not 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 adjustment transformer 3 configured as described above, the voltage of the tap tb with respect to the tap tc is doubled (tap with respect to the tap tb), and tripled (tap with respect to the tap tc). ta), -1 times (tap tc with respect to tap tb), -2 times (tap tb with respect to tap ta), and -3 times (tap with respect to tap ta) can be taken out. That is, the relative transformation ratio of the adjustment transformer 3 can be selected from 1, -1, 2, -2, 3 and -3.

  In the first embodiment, only the changeover switches S2 and S6 filled in black in FIG. 1 are turned on and the taps tb and tc are selected, so that the adjustment voltages extracted from the secondary windings 312, 322 and 332 respectively. The ratio is 1: 1: 1. Hereinafter, for explanation, terminals corresponding to the taps tb and tc of the secondary winding 312 are U1 and U2, and terminals corresponding to the taps tb and tc of the secondary winding 322 are V1 and V2, respectively. Terminals corresponding to the taps tb and tc of the secondary winding 332 are W1 and W2, respectively.

  Next, the connection relationship and the voltage relationship between the terminals U1, U2, V1, V2, W1, and W2 and the terminals u1, v1, and w1 will be described. FIG. 2 is an explanatory view showing the connection between the adjustment transformer 3 and the series transformer 2 in the voltage regulator according to the first embodiment, and FIG. 3 is an adjustment in the voltage regulator according to the first embodiment. It is explanatory drawing which shows the three-phase connection relationship between the transformer 3 and the series transformer 2 visually. FIG. 4 is a vector diagram showing voltage vectors induced on the secondary side of the adjustment transformer 3 and the primary side of the series transformer 2 in the voltage regulator according to the first embodiment. In this specification, a dot notation for a character string representing a vector is omitted.

  Referring to FIG. 1, the connection relationship in FIGS. 2 and 3 will be described. Each of the terminals U1 and W2 is connected to the terminal u1 via the changeover switches S2 and S6. The terminals V1 and U2 are connected to the terminal v1 via the changeover switches S2 and S6. Each of the terminals W1 and V2 is connected to the terminal w1 via the changeover switches S2 and S6. FIG. 4 shows that voltages Eu, Ev, Ew are induced by applying a voltage induced in the adjustment transformer 3 shown on the right side of the drawing to the series transformer 2 shown on the left side of the drawing.

  By transforming the line voltage V1uv between the distribution lines 1u and 1v (see the one-dot chain line in the right direction of FIG. 4), the voltage induced in the terminal U1 in the same phase as V1uv is set to Vuv with respect to the terminal U2. Similarly, the voltage induced at the terminal V1 with respect to the terminal V2 is Vvw, and the voltage induced at the terminal W1 with respect to the terminal W2 is Vwu. Voltage Vuv is applied between terminals u1 and v1 as an adjustment voltage between U and V phases, voltage Vvw is applied between terminals v1 and w1 as an adjustment voltage between V and W phases, and voltage Vwu is an adjustment voltage between W and U phases. Applied between the terminals w1 and u1. As a result, voltages Eu, Ev, Ew are induced between the terminals u1, v1, w1 and the neutral point N, respectively.

  When the primary windings 311, 321, 331 of the adjustment transformer 3 are star-connected to the distribution lines 1 u, 1 v, 1 w, the voltage vector of the line voltage V 1 uv is indicated by a one-dot chain line in FIG. Further, the phase advances by 30 degrees, and the magnitude of the voltage Vuv also changes. Specifically, in the vector calculation described later, the phase of the voltage vector of the voltage Vuv with respect to the voltage vector of the line voltage V1uv is delayed by 30 degrees, and the magnitude of the voltage Vuv is 1 / (√3). pay attention to.

  The terminal U2 and the terminal V1 are connected, the terminal V2 and the terminal W1 are connected, and the terminal W2 and the terminal U1 are connected to form a closed circuit of a delta connection on the secondary side of the adjustment transformer 3 (FIG. 3). As shown in FIG. 4, the voltage vectors of the voltages Vuv, Vvw, and Vwu are equal in magnitude and are out of phase with each other by 2π / 3, so that the vector sum of these voltages becomes zero (see FIG. 4). ). Therefore, the short circuit loop current due to the vector sum of the voltages Vuv, Vvw, and Vwu does not flow in the closed circuit passing through the terminals U1, W2, W1, V2, V1, and U2 of the adjustment transformer 3 (see FIG. 3).

  In FIG. 4, the voltage vectors of the voltages Vuv, Vvw, and Vwu are indicated by solid lines with arrows for the adjustment transformer 3, and those that have been translated in order to be applied between the terminals of the series transformer 2 are indicated by arrows. It is shown with a wavy line with a mark. As can be seen from the figure, the voltages Eu, Ev, Ew induced between the terminals u1, v1, w1 of the series transformer 2 and the neutral point N are equal in magnitude and have a phase of 2π / It is shifted by 3. For this reason, the vector sum of each of the voltages Eu, Ev, Ew becomes zero, and V0 is not generated. Since the voltage obtained by transforming these voltages Eu, Ev, Ew with a series transformer is superimposed on the phase voltage of the distribution line 1u, 1v, 1w, the voltage of the distribution line 1u, 1v, 1w on the load side is evenly boosted. Is done.

  The tap changer 4 may be configured by using switches such as other semiconductor elements and electromagnetic contactors without using thyristors 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 can change the tap ta of 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 detected separately. , Tb, and tc are selected and manually switched to the selected switching destination tap.

(Modification 1)
In the first embodiment, the ratio of the adjustment voltages extracted from the secondary windings 312, 322, and 332 is 1: 1: 1, whereas in the first modification, the secondary windings 312, 322 are used. , 332 respectively, the ratio of the adjustment voltage extracted from each of them is -1: -1: 0. FIG. 5 is a block diagram showing a configuration example of the voltage regulator according to the first modification of the present invention. The configuration of the voltage regulator in the first modification is the same as that of the voltage regulator shown in FIG. 1 in the first embodiment, and only the changeover switch that is turned on to switch the taps ta, tb, and tc is different. Therefore, portions corresponding to those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the first modification, the secondary windings 312 and 322 are turned on by selecting the taps tc and tb by turning on the changeover switches S3 and S5 filled in black in FIG. The ratio of the adjustment voltage taken out from -1 is -1. Further, for the secondary winding 332, by turning on the changeover switches S2 and S5, which are black in FIG. 5 and selecting only the tap tb, the magnitude of the adjustment voltage taken out from the secondary winding 332 is set to zero. To do. In this case, both the changeover switches S2 and S5 are turned on in order to apply a zero voltage without leaving the terminals w1 and u1 of the series transformer 2 open. For 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 connection relationship and the voltage relationship between the terminals U1, U2, V1, V2, W1, and W2 and the terminals u1, v1, and w1 will be described. FIG. 6 is an explanatory view showing the connection between the adjustment transformer 3 and the series transformer 2 in the voltage regulator according to the first modification, and FIG. 7 is an adjustment transformer in the voltage regulator according to the first modification. It is explanatory drawing which shows visually the three-phase connection relationship between 3 and the series transformer 2. FIG. FIG. 8 is a vector diagram showing voltage vectors induced on the secondary side of the adjustment transformer 3 and the primary side of the series transformer 2 in the voltage regulator according to the first modification.

  Referring to FIG. 5, the connection relationship in FIGS. 6 and 7 will be described. The terminal U2 is connected to the terminal u1 via the changeover switch S3. Each of the terminals U1 and V2 is connected to the terminal v1 via the changeover switches S5 and S3. The terminals V1 and W1 are connected to the terminal w1 via the changeover switches S5 and S2. The terminal W1 is also connected to the terminal u1 via the changeover switch S5. FIG. 8 shows that the voltages Eu, Ev, Ew are induced by applying the voltage induced in the adjustment transformer 3 shown on the right side of the drawing to the series transformer 2 shown on the left side of the drawing. The relative magnitude of each voltage vector is indicated by a numerical value surrounded by a frame.

  By transforming the line voltage V1uv between the distribution lines 1u and 1v (see the one-dot chain line in the right direction in FIG. 8), the voltage induced in the terminal U2 with a phase opposite to V1uv is set to Vuv with respect to the terminal U1. The magnitude of the voltage vector of this voltage Vuv is 1. The voltage vector of the voltage Vuv has the same magnitude and the opposite direction compared to the voltage vector of the voltage Vuv shown in FIG. Similarly, the voltage Vvw induced at the terminal V2 with respect to the terminal V1 has the same magnitude and the opposite direction compared to the voltage vector of the voltage Vvw shown in FIG. The magnitude of the voltage vector of this voltage Vvw is also 1. The voltage vectors of the voltages Vuv and Vvw are out of phase with each other by 2π / 3.

  In the first modification, the terminal U1 and the terminal V2 are connected, and the terminal V1 and the terminal U2 are connected, so that a closed circuit of delta connection is formed on the secondary side of the adjustment transformer 3 (see FIG. 7). . As shown in FIG. 8, the vector sum does not become zero only by the voltage vectors of the voltages Vuv and Vvw, and the voltage opposite to the vector sum of the voltages Vuv and Vvw flows due to the flow of the loop current Ir shown in FIGS. A voltage Vrp having a magnitude indicated by a vector of 1 is induced.

  In this case, since the excitation impedance between the terminals U1 and U2 is equal to the excitation impedance between the terminals V1 and V2, the voltage Vrp is shared by 1/2 Vrp between the terminals U1 and U2 and between the terminals V1 and V2. The As a result, voltages V′uv and V′vw having a magnitude of √3 / 2 and opposite phases appear between the terminals U1 and U2 and between the terminals V1 and V2, respectively. These voltages V'uv and V'vw are applied as adjustment voltages between the terminal v1 and the terminals u1, w1. As shown by a broken line in FIG. 7, the voltage applied between the terminal v1 and the terminals u1 and w1 is 2 in a series circuit of the primary winding 221 and the primary windings 211 and 231 connected in parallel. The pressure is divided to 1.

  In FIG. 8, the voltage vectors of the voltages V′uv and V′vw are indicated by solid lines with arrows for the adjustment transformer 3, which are moved in parallel to be applied between the terminals of the series transformer 2. Is indicated by a wavy line with an arrow. When a voltage having a size of √3 / 2 indicated by a broken line is applied between the terminal v1 and the terminals u1 and w1 of the series transformer 2, the terminal v1 and the neutral point are determined based on the above-described divided voltage relationship. The ratio of the voltage Ev induced between N and the voltages Eu and Ew induced between the terminals u1 and w1 and the neutral point N is 2: 1. Therefore, the magnitude of the voltage Ev is √3 / 3, and the magnitudes of the voltages Eu and Ew are √3 / 6.

  The magnitude of the voltage Ev is twice the magnitude of each of the voltages Eu and Ew, and the voltage Ev and the voltages Eu and Ew are in opposite phases. For this reason, the vector sum of each of the voltages Eu, Ev, Ew becomes zero, and V0 is not generated. A voltage obtained by transforming these voltages Eu, Ev, and Ew with a series transformer is superimposed on the phase voltage of the distribution lines 1u, 1v, and 1w.

  Next, the voltage superimposed on the phase voltage of the distribution line 1u, 1v, 1w is demonstrated. FIG. 9 is a vector diagram showing voltage vectors of the distribution lines 1u, 1v, 1w. A vector diagram when there is no phase displacement between the primary side and the secondary side of the adjustment transformer 3 and the series transformer 2 is shown on the left side of the drawing, and a vector diagram when there is a phase displacement is shown on the right side of the drawing. The phase voltage of the distribution lines 1u, 1v, 1w on the power supply side with respect to the series transformer 2 is represented by a voltage vector having a neutral point N as a starting point and points U, V, W as end points. The voltage vector of the line voltage corresponds to the line segment connecting the points U and V, the points V and W, and the points W and U.

  The voltages induced on the secondary side of the series transformer 2 by the voltages indicated by Eu, Ev, and Ew in FIG. 8 start from points U ′, V, and W in FIG. It is represented by a thick solid line voltage vector as an end point. The ratio of the magnitudes of these voltage vectors is 1: 2: 1. When these voltages are superimposed on the phase voltage of the distribution lines 1u, 1v, 1w, the phase voltage of the distribution lines 1u, 1v, 1w on the load side of the series transformer 2 starts from the neutral point N and the point U It is represented by a thick solid line voltage vector having ', V' and W 'as the end points. The voltage vector of the line voltage corresponds to a broken line segment connecting the points U ′ and V ′, the points V ′ and W ′, and the points W ′ and U ′.

  In the case of the left side in FIG. 9 where there is no phase displacement between the primary side and the secondary side of the adjusting transformer 3 and the series transformer 2, voltages starting from points U and W and ending points U ′ and W ′, respectively. The direction of the vector and the voltage vector starting from the point V and ending at the point V ′ are opposite to each other. In this case, before and after the voltage superposition by the series transformer 2, the magnitude of the line voltage between the U and V phases and between the V and W phases is reduced (decreased), whereas the line between the W and U phases. The magnitude of the inter-voltage does not change. This corresponds to the ratio of the adjustment voltages taken out from the secondary windings 312, 322, and 332 of the adjustment transformer 3 being −1: −1: 0, and between the U and V phases as intended. It also shows that the line voltage between the V and W phases can be stepped down.

  On the other hand, in the case of the right side of FIG. 9 where there is a phase displacement between the primary side and the secondary side of the adjusting transformer 3 and the series transformer 2, the points U ′, V ′, The voltage vector having W ′ as the end point rotates, for example, clockwise as compared with the case where there is no phase displacement. For this reason, as a result of the superimposition of the voltage by the series transformer 2, the line voltage between the U and V phases is slightly smaller than the line voltage between the V and W phases (stepped down to a smaller extent). Generally, since there is a phase displacement between the primary side and the secondary side of the adjustment transformer 3 and the series transformer 2 in this way, the distribution lines 1u, 1v, 1w on the power source side than the series transformer 2 are used. Although a phase difference occurs between each phase voltage and the voltage superimposed by the series transformer 2, the phase voltage and the line voltage after superposition can be obtained by vector calculation.

  Below, the result of having confirmed that the voltage as the numerical value enclosed by the frame in FIG. 8 is induced is demonstrated. FIG. 10 is a chart showing measurement results of voltages induced in the adjustment transformer 3 and the series transformer 2 in the voltage regulator according to the first modification. Here, the line voltage between the U and V phases, between the V and W phases, and between the W and U phases on the primary side of the adjustment transformer 3 before superimposing the secondary side voltage of the series transformer 2 is 29.95 V. In this case, the adjustment transformer 3 after superposing the voltage induced on the secondary side of the adjustment transformer 3, the primary side and the secondary side of the series transformer 2, and the voltage on the secondary side of the series transformer 2 The primary side voltage was measured.

  Scalar values of voltages Vuv, Vvw, and Vwu induced between the terminals U1 and U2 on the secondary side, between V1 and V2, and between W1 and W1 by the voltage on the primary side of the adjusting transformer 3 are defined as a voltage V. The theoretical value of the voltage V is 0.365 V, and the scalar ratio is defined as 100%. As shown in FIG. 8, since the magnitude of the voltage induced between the terminals U1 and U1 and between V1 and V2 by the loop current Ir is ½ of the magnitude of the voltage V (that is, 50%), The theoretical value of the voltage is 0.183V. A voltage due to the loop current Ir is not induced between the terminals W1 and W2.

  The magnitudes of the adjustment voltages indicated by the voltages V′uv and V′vw in FIG. 8, that is, the combined voltages induced between the terminals U1 and U2 and between the terminals V1 and V2, respectively, are √3 / 2 of the magnitude of the voltage V. (Ie, 86.6%), the theoretical value of this combined voltage is 0.316V. On the other hand, measured values of voltages induced between the terminals U1 and U2 and between the terminals V1 and V2 were 0.308V and 0.312V, respectively. The measured value of the voltage between the terminals W1 and W2 was 0.365 V, which is the same as the theoretical value.

  As shown in FIG. 8, the magnitudes of voltages Eu, Ev, Ew induced between the primary side terminals u1, v1, w1 and the neutral point N by the adjustment voltage are as follows. Since the magnitudes are √3 / 6, √3 / 3, √3 / 6 (ie, 28.9%, 57.7%, 28.9%), the theoretical values of the voltages Eu, Ev, Ew are respectively 0.105V, 0.211V, and 0.105V. On the other hand, the measured values of the voltages Eu, Ev, and Ew were 0.101V, 0.210V, and 0.101V, respectively.

  On the other hand, the measured values of the phase voltages of the u-phase, v-phase, and w-phase induced on the secondary side of the series transformer 2 are 7.07V, 14.44V, and 7.10V, and after these voltages are superimposed, The measured values of the voltage between the U and V phases, between the V and W phases, and between the W and U phases on the primary side of the adjusting transformer 3 were 16.44V, 12.01V, and 28.27V.

  As described above, the measured values of the voltages V′uv and V′vw and the measured values of the voltages Eu, Ev, and Ew are in good agreement with the theoretical values. In addition, it can be confirmed that the voltage between the U and V phases and the voltage between the V and W phases on the primary side of the adjusting transformer 3 is stepped down as intended, and the voltage between the W and U phases is stepped up as intended. It was.

(Modification 2)
In the first embodiment, the ratio of the adjustment voltages extracted from the secondary windings 312, 322, and 332 is 1: 1: 1, whereas in the second modification, the secondary windings 312, 322 are used. , 332 respectively, the ratio of the adjustment voltage taken out from each of them is -1: 1: 1. FIG. 11 is a block diagram illustrating a configuration example of the voltage regulator according to the second modification of the present invention. The configuration of the voltage regulator in the second modification is the same as that of the voltage regulator shown in FIG. 1 in the first embodiment, except that the changeover switch that is turned on to switch the taps ta, tb, and tc is different. Therefore, portions corresponding to those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the second modification, the secondary windings 322 and 332 are turned on by selecting the taps tb and tc by turning on the changeover switches S2 and S6 filled in black in FIG. The ratio of the adjustment voltage taken out from is assumed to be 1: 1. Further, for the secondary winding 312, the ratios of the adjustment voltages taken out from the secondary windings 312 and 322 are selected by turning on the changeover switches S 3 and S 5, which are filled in black in FIG. 11, and selecting the taps tc and tb. Is −1: 1.

  Next, the connection relationship and the voltage relationship between the terminals U1, U2, V1, V2, W1, and W2 and the terminals u1, v1, and w1 will be described. FIG. 12 is an explanatory diagram showing the connection between the adjustment transformer 3 and the series transformer 2 in the voltage regulator according to the second modification, and FIG. 13 is an adjustment transformer in the voltage regulator according to the second modification. It is explanatory drawing which shows visually the three-phase connection relationship between 3 and the series transformer 2. FIG. FIG. 14 is a vector diagram illustrating voltage vectors induced on the secondary side of the adjustment transformer 3 and the primary side of the series transformer 2 in the voltage regulator according to the second modification.

  Referring to FIG. 11, the connection relationship in FIGS. 12 and 13 will be described. Each of the terminals U2 and W2 is connected to the terminal u1 via the changeover switches S3 and S6. Each of the terminals U1 and V1 is connected to the terminal v1 via the changeover switches S5 and S2. The terminals V2 and W1 are connected to the terminal w1 via the changeover switches S6 and S2. FIG. 14 shows that the voltages Eu, Ev, Ew are induced by applying the voltage induced in the adjustment transformer 3 shown on the right side of the drawing to the series transformer 2 shown on the left side of the drawing. The relative magnitude of each voltage vector is indicated by a numerical value surrounded by a frame.

  By transforming the line voltage V1uv between the distribution lines 1u and 1v (see the alternate long and short dash line in FIG. 14), the voltage induced in the terminal U2 at a phase opposite to V1uv is set to Vuv with respect to the terminal U1. The magnitude of the voltage vector of this voltage Vuv is 1. The voltage vector of the voltage Vuv has the same magnitude and the opposite direction compared to the voltage vector of the voltage Vuv shown in FIG. On the other hand, the voltage Vvw induced at the terminal V1 with respect to the terminal V2 and the voltage Vwu induced at the terminal W1 with respect to the terminal W2 have a magnitude and direction as compared with the voltage vectors Vvw and Vwu shown in FIG. Are the same. The voltage vectors of the voltages Vvw and Vwu are also 1. The voltage vectors of the voltages V1uv, Vuv, and Vvw are out of phase with each other by 2π / 3.

  In the second modification, the terminal U2 and the terminal W2 are connected, the terminal W1 and the terminal V2 are connected, and the terminal V1 and the terminal U1 are connected, so that a closed circuit of a delta connection is provided on the secondary side of the adjustment transformer 3. Is formed (see FIG. 13). As shown in FIG. 14, the vector sum does not become zero only by the voltage vectors of the voltages Vuv, Vvw, and Vwu, and the vector sum of the voltages Vuv, Vvw, and Vwu flows when the loop current Ir shown in FIGS. A voltage Vrp having a magnitude indicated by a voltage vector opposite to that is induced.

  In this case, since the excitation impedance between the terminals U1 and U2, the excitation impedance between the terminals V1 and V2, and the excitation impedance between the terminals W1 and W2 are equal, the voltage Vrp is between the terminals U1 and U2 and between the terminals V1 and V2. Between the terminals W1 and W2 and 2/3 Vrp. As a result, voltages V′uv, V′vw, and 1/3, √7 / 3, and √7 / 3 in magnitude between terminals U1 and U2, between terminals V1 and V2, and between terminals W1 and W2, respectively. V'wu appears. These voltages V'uv, V'vw and V'wu are applied as adjustment voltages between the terminals u1 and v1, between the terminals w1 and v1, and between the terminals u1 and w1, respectively. The magnitude of each voltage can be obtained by drawing or vector calculation.

  In FIG. 14, the voltage vectors of the voltages V′uv, V′vw, and V′wu are indicated by solid lines with arrows for the adjusting transformer 3, in order to apply them between the terminals of the series transformer 2. The parallel movement is indicated by a wavy line with an arrow. Voltages of 1/3, √7 / 3, and √7 / 3 indicated by broken lines are applied between the terminals v1 and u1 of the series transformer 2, between the terminals w1 and v1, and between the terminals u1 and w1, respectively. In this case, the ratio of the magnitudes of the voltages Eu, Ev, Ew induced between the terminals u1, v1, w1 and the neutral point N is 1: 1: √3. The magnitude of each voltage can be obtained by drawing or vector calculation.

  As is clear from FIG. 14, the vector sum of the voltages Eu and Ev has the same magnitude as the voltage vector of the voltage Ew and has the opposite direction. For this reason, the vector sum of each of the voltages Eu, Ev, Ew becomes zero, and V0 is not generated. A voltage obtained by transforming these voltages Eu, Ev, and Ew with a series transformer is superimposed on the phase voltage of the distribution lines 1u, 1v, and 1w.

  Next, the voltage superimposed on the phase voltage of the distribution line 1u, 1v, 1w is demonstrated. FIG. 15 is a vector diagram showing voltage vectors of distribution lines 1u, 1v, 1w in the voltage regulator according to the second modification. A vector diagram when there is no phase displacement between the primary side and the secondary side of the adjustment transformer 3 and the series transformer 2 is shown on the left side of the drawing, and a vector diagram when there is a phase displacement is shown on the right side of the drawing. The phase voltage of the distribution lines 1u, 1v, 1w on the power supply side with respect to the series transformer 2 is represented by a voltage vector having a neutral point N as a starting point and points U, V, W as end points. The voltage vector of the line voltage corresponds to the line segment connecting the points U and V, the points V and W, and the points W and U.

  The voltages induced on the secondary side of the series transformer 2 by the voltages indicated by Eu, Ev, and Ew in FIG. 14 start from points U ′, V, and W ′ in FIG. It is represented by a thick solid line voltage vector as an end point. The ratio of the magnitudes of these voltage vectors is 1: 1: √3. When these voltages are superimposed on the phase voltage of the distribution lines 1u, 1v, 1w, the phase voltage of the distribution lines 1u, 1v, 1w on the load side of the series transformer 2 starts from the neutral point N and the point U It is represented by a thick solid line voltage vector having ', V' and W 'as the end points. The voltage vector of the line voltage corresponds to a broken line segment connecting the points U ′ and V ′, the points V ′ and W ′, and the points W ′ and U ′.

  In the case of the left side of FIG. 15 where there is no phase displacement between the primary side and the secondary side of the adjusting transformer 3 and the series transformer 2, the line between the U and V phases before and after the voltage superposition by the series transformer 2 While the magnitude of the voltage decreases (steps down), the magnitude of the line voltage between the V and W phases and between the W and U phases increases (steps up). This corresponds to the ratio of the adjustment voltage taken from the secondary windings 312, 322, and 332 of the adjustment transformer 3 being −1: 1: 1, and between the U and V phases as intended. It shows that the line voltage is stepped down and the line voltage between the V and W phases and between the W and U phases is boosted.

  On the other hand, in the case of the right side of FIG. 15 where there is a phase displacement between the primary side and the secondary side of the adjusting transformer 3 and the series transformer 2, the points U ′, V ′, The voltage vector having W ′ as the end point rotates, for example, clockwise as compared with the case where there is no phase displacement. For this reason, as a result of the superimposition of the voltage by the series transformer 2, the line voltage between the V and W phases is slightly larger than the line voltage between the W and U phases. Generally, since there is a phase displacement between the primary side and the secondary side of the adjustment transformer 3 and the series transformer 2 in this way, the distribution lines 1u, 1v, 1w on the power source side than the series transformer 2 are used. Although a phase difference occurs between each phase voltage and the voltage superimposed by the series transformer 2, the phase voltage or line voltage after superposition can be obtained by vector calculation.

  In the first embodiment and the first and second modifications, the relative transformation ratios between the U and V phases, between the V and W phases, and between the W and U phases by the adjustment transformer 3 are 1, −1, or 0. However, the present invention is not limited to this. For example, the adjustment voltage is taken out from the taps ta and tb to make the relative transformation ratio 2 or -2, or the adjustment voltage is taken out from the taps ta and tc to make the relative transformation ratio 3 or -3. However, it can be described by drawing a vector diagram in the same manner as the vector diagrams illustrated in FIGS.

  As described above, according to the first embodiment and the first and second modifications, the primary winding 211 of the series transformer 2 in which the secondary windings 212, 222, and 232 are connected in series to the distribution lines 1u, 1v, and 1w, respectively. , 221, 231 are connected in a star (Y), and the secondary windings 312, 322, 332 of the adjusting transformer 3 are connected in parallel to the distribution lines 1u, 1v, 1w. Delta (Δ) connection. And with respect to the primary windings 211, 221, 231 of the series transformer, the changeover switch S1 of the tap changer 4 from the taps ta, tb, tc of the secondary windings 312, 322, 332 of the adjustment transformer 3 respectively. , S2,... S6 is used to apply the adjustment voltage. Therefore, by selecting and switching the taps ta, tb, and tc of the adjustment transformer 3, the three-phase voltages of the distribution lines 1u, 1v, and 1w can be adjusted. It is also possible to apply the voltage regulator to an on-load tap switching transformer (LRT) in a substation or an automatic voltage regulator (SVR) in a transmission line.

  Further, according to the first embodiment and the first and second modifications, the primary windings 311, 321, 331 and the secondary windings 312, 322, 332 of the adjustment transformer 3 are Δ-Δ connected. The phase difference of 30 degrees does not occur in the line voltage between the primary side and the secondary side as in the case of -Δ connection, and the line voltage of the distribution lines 1u, 1v, 1w and the adjusting transformer 3 The adjustment voltage can be easily determined from the transformation ratio.

  Further, according to the first embodiment and the first and second modifications, the polarity of the adjustment voltage applied to the primary windings 211, 221, 231 of the series transformer 2 selects the changeover switches S1, S2,. Therefore, the degree of freedom in adjusting the unbalance of the three-phase voltages of the distribution lines 1u, 1v, 1w can be increased.

  Further, according to the first embodiment and the first and second modifications, since the thyristors are used for the changeover switches S1, S2,... S6, the taps ta, tb, and tc can be switched at a high speed and the tap ta. , Tb and tc need not be considered.

(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 the manual tap switch or the tap switching base. In contrast, the second embodiment is a mode in which 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. 16 is a block diagram illustrating a configuration example of the voltage regulator according to the second embodiment of the present invention. Compared with the voltage regulator according to the first embodiment shown in FIG. 1, the voltage regulator according to the second embodiment has the operation display unit 63 deleted and a storage unit 65 added. The operation display unit 63 may not be deleted.

  The memory | storage part 65 memorize | stores the deviation with respect to the target voltage of the voltage for three phases of the distribution line 1u, 1v, and 1w, and the quantity which concerns on the transformation ratio for three phases of the adjustment transformer 3 in correlation. The storage unit 65 is connected to the switching control unit 61 so that the stored contents can be referred to from 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 three-phase deviation and the change amount of the three-phase transformation ratio in association with each other. For example, the taps ta, tb, and tc of the adjustment transformer 3 are assigned serial numbers. In this case, the deviation for three phases and the number of taps for three phases may be stored in association with each other. In addition, the same code | symbol is attached | subjected to the location corresponding to Embodiment 1, and the description is abbreviate | omitted.

  Below, operation | movement of the switching control part 61 mentioned above is demonstrated using the flowchart which shows it. The following processing 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. 17 is a flowchart illustrating a processing procedure of the switching control unit 61 that adjusts the voltages of the distribution lines 1u, 1v, and 1w by the voltage regulator according to the second embodiment. This processing procedure is periodically executed, for example, every 4 to 5 seconds. It is assumed that a current transformation ratio for three phases is stored in a RAM (Random Access Memory) (not shown) included in the switching control unit 61.

  When the processing of FIG. 17 is started, the CPU of the switching control unit 61 (hereinafter the same) obtains the line voltage or phase voltage for the three phases of the load-side distribution lines 1u, 1v, 1w from the voltage detection unit 62. Then, a deviation from the target voltage is calculated for the acquired three-phase voltage (S12).

  Next, the CPU reads 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, tc for the three phases (S13). In order to select the switching destination of the taps ta, tb, and tc, the read change amount is 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 three-phase transformation ratio of the addition result is stored in the RAM as an update of the current transformation ratio.

  Thereafter, 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 selected switching destination tap. The changeover switch is turned on (S16). Next, the CPU turns off the selector switch SS for three phases (S17), and then ends the process of FIG.

  In the above-described flowchart, it is assumed that the storage unit 65 stores the deviation for three phases and the change amount of the transformation ratio for three phases in association with each other, but the present invention is not limited to this. It is not a thing. For example, when the storage unit 65 stores the deviation for three phases and the number of taps for switching for the three phases in association with each other, the current tap number for the three phases is stored in the RAM and calculated in step S12. The tap switching number stored in the storage unit 65 in association with the deviation is 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 number for the three phases of the addition result is stored in the RAM as an update of the current tap number.

  As described above, according to the second embodiment, the taps ta, tb, and tc of the secondary windings 312, 322, and 332 of the adjustment transformer 3 are applied to the primary windings 211, 221, and 231 of the series transformer 2. The voltage of the three-phase distribution lines 1u, 1v, 1w adjusted by the adjusted voltage is detected by the voltage detector 62 and compared with the target voltage, and the changeover switches S1, S2,.・ S6 is controlled to switch taps ta, tb, and tc. Therefore, feedback control can be performed so that the voltage deviation of the distribution lines 1u, 1v, 1w approaches zero.

  Further, according to the second embodiment, the deviation of the three-phase voltages of the distribution lines 1u, 1v, 1w from 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. Then, the switching destinations of the taps ta, tb, tc are selected, and the selector switches S1, S2,... S6 corresponding to the selected switching destination are controlled. Therefore, it is not necessary to obtain the above-described adjustment voltage by vector calculation when the switching control unit 61 is executed.

  In the following, by using the simulation software X-TAP, the voltage imbalance is improved by simulating the voltage adjustment of the distribution lines 1u, 1v, 1w by the voltage regulator according to the second embodiment. The confirmed result will be described. The frequency of the power source used for the analysis is 50 Hz, and the simulated load has an active power of 100 kW and a reactive power of 120 kvar. The sampling time in the analysis was set to 100 μs, and the taps ta, tb, and tc were switched 2 seconds after the start of sampling in four analysis cases described later.

  18 is a chart showing the line voltage on the power supply side and the transformation ratio of the adjustment transformer 3 in the four analysis cases, and FIG. 19 shows the line voltage on the power supply side and the load side in each of the four analysis cases. It is a graph which shows an equilibrium factor. In FIG. 18, between each of the four analysis cases in which the line voltages between the U and V phases on the power source side, between the V and W phases, and between the W and U phases are combined in four ways, The relationship between the transformation ratios between the V and W phases and between the W and U phases, and the amount of operation of the voltage with respect to the line voltage on the power supply side are described. The operation amount 100V here corresponds to a transformation ratio of 1 (one tap). FIG. 19 shows the adjusted line voltage on the load side, the unbalance rate of the line voltage before and after adjustment, and the improvement rate of the unbalance for each of the four analysis cases. Hereinafter, the line voltage, the transformation ratio, and the operation amount will be described in the order of description between the U and V phases, between the V and W phases, and between the W and U phases.

  In case 1 shown in FIG. 18, the line voltage on the power source side is 6600 V, 6600 V, 6600 V, the relationship of the transformation ratio by the adjusting transformer 3 is 1: 1: 1, and the operation amount with respect to the line voltage is 100 V, 100 V, 100V. That is, the line voltage between the U and V phases, between the V and W phases, and between the W and U phases is boosted equally by 100V. In Case 2, the line voltage on the power source side is 6600V, 6600V, 6500V, the relationship of the transformation ratio by the adjusting transformer 3 is 0: -1: 2, and the operation amount with respect to the line voltage (the line corresponding to the transformation ratio is The target voltage for increasing / decreasing the inter-voltage is 0 V, −100 V, and 200 V. That is, the line voltage between the V and W phases is stepped down by about 100V, and the line voltage between the W and U phases is stepped up by about 200V. In the simulation, since the operation amount cannot be 0V, an operation amount of about 2V is given.

  In Case 3, the line voltage on the power source side is 6600V, 6600V, 6700V, the relationship of the transformation ratio by the adjusting transformer 3 is 0: 1: -2, and the operation amount with respect to the line voltage is 0V, 100V, -200V. To do. That is, the line voltage between the V and W phases is boosted by approximately 100 V, and the line voltage between the W and U phases is decreased by approximately 200 V. In Case 4, the line voltage on the power source side is 6600V, 6500V, 6700V, the relationship of the transformation ratio by the adjusting transformer 3 is 0: 2: -2, and the operation amount with respect to the line voltage is 0V, 200V, -200V. To do. That is, the line voltage between the V and W phases is boosted with a target of approximately 200V, and the line voltage between the W and U phases is decreased with a target of approximately 200V.

  Turning to FIG. 19 and seeing the simulation results, in case 1, the line voltage on the load side is boosted by 100V to 6700V, 6700V, and 6700V, respectively, and the unbalance rate on the power supply side and the load side is 0%. It is. In Case 2, the line voltage on the load side is adjusted to 6614V, 6569V, and 6618V, and the unbalance rates on the power supply side and the load side are 1.013% and 0.476%, respectively. That is, the unbalance rate is improved by 0.537%. In Case 3, the line voltage on the load side is adjusted to 6587V, 6632V, and 6583V, and the unbalance rates on the power supply side and the load side are 1.008% and 0.472%, respectively. That is, the unbalance rate is improved by 0.536%. In Case 4, the line voltage on the load side is adjusted to 6604V, 6598V, and 6599V, and the unbalance rates on the power supply side and the load side are 1.750% and 0.056%, respectively. That is, the unbalance rate is improved by 1.694%.

  It was confirmed that V0 does not occur in any of cases 1 to 4. However, except for case 1, the voltage is boosted or stepped down by a voltage whose absolute value is smaller than the target voltage. As described above, this is due to the influence of the voltage Vrp induced on the secondary side by the loop current Ir flowing in the closed circuit of the delta connection on the secondary side of the adjustment transformer 3. The actual adjustment voltage with the influence of the voltage Vrp can be obtained by vector calculation.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. In addition, the technical features described in each embodiment can be combined with each other.

1u, 1v, 1w Distribution line 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 changeover switch U1, U2, V1, V2, W1, W2 Terminal F Fuse MC Magnetic contactor R Current limiting resistor 4 Tap changeover 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 a secondary winding for three phases is connected in series to a distribution line that distributes a three-phase AC voltage from a power source to a load, and the primary winding is star-connected,
The secondary winding has a plurality of taps, and the primary winding for three phases is connected in parallel to the load side position relative to the connection position of the series transformer in the distribution line. A rectified transformer,
A tap changer provided between a secondary winding of the adjustment transformer and a primary winding of the series transformer, and having a three-phase changeover switch for switching taps connected to the series transformer; A voltage regulator comprising:   The voltage regulator according to claim 1, wherein the adjustment transformer has a primary winding that is delta-connected.   3. The voltage regulator according to claim 1, wherein 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 the polarity to the primary winding of the series transformer. .   The voltage regulator according to claim 1, wherein the changeover switch includes a thyristor. A voltage detector for detecting a three-phase voltage of the distribution line on the load side of the series transformer;
A switching control unit that calculates a deviation of the three-phase voltage detected by the voltage detection unit with respect to a target voltage, and switches the tap by the changeover switch based on the calculated deviation. The voltage regulator according to item. A storage unit that stores the deviation of the three-phase voltage with respect to the target voltage and the amount related to the three-phase transformation ratio of the adjusting transformer in association with each other;
The voltage regulator according to claim 5, wherein when the deviation is calculated, the switching control unit selects a switching destination of taps for three phases with reference to the storage unit, and switches the tap to the selected switching destination. .

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