JP2023131795A - Voltage controller and voltage control method - Google Patents

Abstract

To provide a voltage controller capable of preventing magnetic saturation of an iron core of a series transformer, and a voltage control method.SOLUTION: A voltage controller 10 which is connected to a single-phase three-wire distribution line, changes an input phase of a semiconductor element after switching of a tap to constitute a tap switch 13a, to an optimum phase according to a combination of the taps before and after the switching. Accordingly, accumulation of a magnetic flux of an iron core constituting series transformers 11 and 12 can be suppressed.SELECTED DRAWING: Figure 1

Description

The present invention prevents magnetic saturation of the iron core of the series transformer that constitutes the voltage regulator during voltage regulation by a voltage regulator connected to a single-phase power distribution line, thereby preventing the flow of excitation inrush current. This invention relates to a voltage regulator and its voltage regulation method.

A voltage regulator connected to a single-phase distribution line uses a tap to switch the voltage applied to the primary winding of a series transformer whose secondary winding is connected to two voltage lines of the distribution line. It is known to adjust the output voltage of a power distribution line by switching the polarity and magnitude of the voltage induced in the secondary winding of a transformer.

As the tap, there are known taps that use mechanical contacts such as electromagnetic contactors, as well as taps that utilize switching of semiconductor elements, as shown in Patent Document 1 listed below. The use of semiconductor elements for tap switching has the advantage of reducing the size of the voltage regulator, reducing the lifespan of the contacts, and eliminating noise when the contacts open and close.

Japanese Patent Application Publication No. 2015-023593

The voltage regulator described in Patent Document 1 includes a voltage balancer that balances input voltage, and a series transformer that is connected in series to a single-phase three-wire voltage line and adjusts voltage drop and rise by switching taps. , a switch that switches the polarity of the transformer, and a control device that monitors the secondary voltage of the device and controls the switching operation of the switch, and the switch is a switching device using a semiconductor element. The taps of the transformer are changed by.

According to the voltage regulator with this configuration, while the voltage balancer balances the load on the single-phase three-wire distribution line, if a voltage fluctuation occurs on the distribution line, this is detected by the monitoring function of the control device. However, by switching the polarity of the switch and switching the series transformer tap, the voltage fluctuation can be reliably eliminated.

However, in the voltage regulator, when switching taps, there is a possibility that magnetic saturation may occur in the iron core that constitutes the series transformer connected to the voltage line. When the iron core becomes magnetically saturated, a magnetizing inrush current flows through the series transformer, which is likely to destroy the semiconductor elements that switch the taps.

In order to prevent magnetic saturation of the iron core, it is possible to increase the cross-sectional area of the iron core and lower the magnetic flux density, but this is not preferable because it increases the size of the device and increases the product cost.

The present invention has been made to solve such problems, and it is possible to avoid magnetic saturation of the iron core without increasing the cross-sectional area of the iron core that constitutes the series transformer, and to improve the reliability of semiconductors that constitute the voltage regulator. The present invention provides a voltage regulator that can effectively prevent elements from being destroyed, and a method for regulating the voltage.

The invention according to claim 1 is arranged such that the power distribution line is connected to a single-phase two-wire type distribution line consisting of two voltage lines or a single-phase three-wire type distribution line consisting of two voltage lines and one neutral line, and a series transformer with a secondary winding connected to a voltage line; a semiconductor tap changer that switches the polarity and magnitude of the voltage applied to the primary winding of the series transformer; and an output side from the series transformer. , the tap changer is connected to the voltage line in the case of a single-phase two-wire system, and to the voltage line and the neutral wire in the case of a single-phase three-wire system, and the tap changer is connected to the voltage line at the connection position. Regarding the voltage regulator, the control section sets the turning-on phase of the semiconductor element at the peak of the excitation voltage when the tap changer starts changing the taps, and controls the switching of the semiconductor element after the tap change. The present invention is characterized in that the closing phase of the switch is configured to be changed in accordance with the combination of taps before and after the tap is switched.

The invention according to claim 2 is characterized in that the control device according to claim 1 controls the iron core of the series transformer according to the phase difference between the secondary line voltage on the output side of the series transformer and the secondary side current of the series transformer. The present invention is characterized in that the input phase of the semiconductor element is determined such that the maximum magnetic flux density of the semiconductor element is equal to or less than the saturation magnetic flux density.

The invention according to claim 3 is directed to the input voltage of a single-phase two-wire distribution line consisting of two voltage lines or a single-phase three-wire distribution line consisting of two voltage lines and one neutral line. A voltage adjustment method for adjusting an output voltage by using a semiconductor tap changer to switch the voltage applied to a primary winding of a series transformer whose secondary winding is connected to the voltage line according to the output voltage, When adjusting the polarity and magnitude of the induced voltage generated in the secondary winding of the series transformer, the turning-on phase of the semiconductor element at the start of tap switching is set to the peak of the excitation voltage, and the turning-on phase of the semiconductor element after tap switching is adjusted. A feature is that the closing phase is changed according to the combination of taps before and after the tap switching.

The invention as set forth in claim 4 is characterized in that the turn-on phase of the semiconductor element as set forth in claim 3 is determined by the series transformer according to the phase difference between the secondary line voltage on the output side of the series transformer and the secondary current of the series transformer. The feature is that the maximum magnetic flux density of the iron core constituting the device is determined to be less than or equal to the saturation magnetic flux density.

According to the first aspect of the invention, magnetic saturation of the core can be effectively prevented without increasing the cross-sectional area of the core that constitutes the series transformer.

According to the invention as claimed in claim 2, no matter what value the phase difference between the line voltage and the secondary current of the series transformer takes, the maximum magnetic flux density of the iron core constituting the series transformer at the time of tap switching is set to the saturation magnetic flux. It becomes possible to lower the density.

According to the third aspect of the invention, accumulation of magnetic flux can be suppressed by controlling the voltage applied to the series transformer at the time of tap switching.

According to the invention set forth in claim 4, the accumulation of magnetic flux in the series transformer due to tap switching can be suppressed, and no matter what value the phase difference between the line voltage and the secondary current of the series transformer takes, the series transformer It is possible to effectively prevent inrush current from flowing due to magnetic saturation of the iron core.

FIG. 2 is a circuit diagram when the voltage regulator of the present invention is connected to a single-phase three-wire distribution line. FIG. 2 is a circuit diagram when the voltage regulator of the present invention is connected to a single-phase two-wire distribution line.

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. As shown in FIG. 1, the voltage regulator 10 of the present invention connects an input terminal 3a to a single-phase three-wire power distribution line consisting of a first voltage line 3, a second voltage line 4, and a neutral line 5. , 4a, 5a and output side terminals 3b, 4b.

Regarding the input voltage to the voltage regulator 10, the voltage between the neutral wire 5 and the first voltage wire 3 has a polarity opposite to the voltage between the neutral wire 5 and the second voltage wire 4. The size is the same.

The voltage regulator 10 includes a balancer 25 that balances the voltages applied to the first voltage line 3 and the second voltage line 4, series transformers 11 and 12 that step up or step down the voltage on the output side, and It includes a tap changer 13a that switches between step-up and step-down voltage by the series transformers 11 and 12, and a control section 13b that controls the switching by the tap changer 13a.

A first input line 3c connects the terminal 3a and the balancer 25, and a first connection line 3d connects the balancer 25 and the series transformer 11. A first output line 3e connects the series transformer 11 and the terminal 3b, and a first branch line 3f connects the first output line 3e, the tap changer 13a, and the control section 13b.

A second input line 4c connects the terminal 4a and the balancer 25, and a second connection line 4d connects the balancer 25 and the series transformer 12. A second output line 4e connects the series transformer 12 and the terminal 4b, and a second branch line 4f connects the second output line 4e to the tap changer 13a and the control section 13b. Further, the terminal 5a and the balancer 25 are connected by a neutral input line 5b.

The series transformer 11 has a primary winding 11a connected to a tap changer 13a and a control section 13b, and a secondary winding 11b that connects a first connection line 3d and a first output line 3e in series. The series transformer 11 generates an induced voltage in the secondary winding 11b according to the voltage applied to the primary winding 11a, and uses the induced voltage to boost or increase the voltage of the first output line 3e with respect to the first connection line 3d. Lower blood pressure.

The series transformer 12 has a primary winding 12a connected to a tap changer 13a and a control section 13b, and a secondary winding 12b that connects a second connection line 4d and a second output line 4e in series. The series transformer 12 generates an induced voltage in the secondary winding 12b according to the voltage applied to the primary winding 12a, and uses the induced voltage to boost or increase the voltage of the second output line 4e with respect to the second connection line 4d. Lower blood pressure.

Both ends of the primary winding 11a of the series transformer 11 and both ends of the primary winding 12a of the series transformer 12 are connected such that the polarities of the voltages applied to the primary windings 11a and 12a are opposite to each other. .

Furthermore, the turns ratio of the secondary winding 11b to the primary winding 11a and the turns ratio of the secondary winding 12b to the primary winding 12a are the same, and depending on the voltage applied to the primary windings 11a and 12a, The induced voltages generated in each of the secondary windings 11b and 12b have the same magnitude and opposite polarity.

The tap changer 13a and the control unit 13b are devices that switch the polarity or magnitude of the voltage applied to the primary windings 11a and 12a, and are devices that switch the polarity or magnitude of the voltage applied to the primary windings 11a and 12a. , 12a (hereinafter referred to as a short-circuit prevention circuit) is provided with one semiconductor element SSR6. The balancer 25, tap changer 13a, and control section 13b are connected by a neutral output line 5c. Note that the short circuit prevention circuit is constituted by a semiconductor element SSR6 and a bridge resistor R (resistance value Rb) connected in series with the semiconductor element SSR6.

The semiconductor elements SSR1 to SSR5 have tap positions for switching the voltage adjustment range of the series transformers 11 and 12, for example. In the case of five semiconductor elements (SSR1 to SSR5) as described above, at tap position 1, the SSR1 and SSR5 is turned on, and at tap position 2, SSRs 1 and 3 are turned on. At tap position 3, SSRs 2 and 5 are turned on, and at tap position 4, SSRs 2 and 3 are turned on. Further, at tap position 5, SSRs 2 and 4 are turned on to switch the voltage adjustment width for the input voltage of the voltage regulator 10.

The above is an example of a configuration in which the voltage regulator 10 of the present invention is connected to a single-phase three-wire power distribution line, but the voltage regulator of the present invention can also be connected to a single-phase two-wire power distribution line. FIG. 2 illustrates a circuit diagram when the voltage regulator 100 of the present invention is connected to a single-phase two-wire power distribution line.

The voltage regulator 100 is connected to a single-phase two-wire power distribution line consisting of a first voltage line 30 and a second voltage line 40 via input side terminals 30a, 40a and output side terminals 30b, 40b. be done.

The voltage regulator 100 includes a balancer 250 that balances the voltages applied to the first voltage line 30 and the second voltage line 40, series transformers 110 and 120 that step up or step down the voltage on the output side, and It includes a tap changer 130a that switches between step-up and step-down voltage by the series transformers 110 and 120, and a control section 130b that controls the switching by the tap changer 130a.

A first input line 30c connects the terminal 30a and the balancer 250, and a first connection line 30d connects the balancer 250 and the series transformer 110. A first output line 30e connects the series transformer 110 and the terminal 30b, and a first branch line 30f connects the first output line 30e, the tap changer 130a, and the control unit 130b.

A second input line 40c connects the terminal 40a and the balancer 250, and a second connection line 40d connects the balancer 250 and the series transformer 120. A second output line 40e connects the series transformer 120 and the terminal 40b, and a second branch line 40f connects the second output line 40e to the tap changer 130a and the control unit 130b.

The series transformer 110 has a primary winding 110a connected to a tap changer 130a and a control unit 130b, and a secondary winding 110b that connects a first connection line 30d and a first output line 30e in series. The series transformer 110 generates an induced voltage in the secondary winding 110b according to the voltage applied to the primary winding 110a, and uses the induced voltage to boost or increase the voltage of the first output line 30e with respect to the first connection line 30d. Lower blood pressure.

The series transformer 120 has a primary winding 120a connected to a tap changer 130a and a control unit 130b, and a secondary winding 120b that connects a second connection line 40d and a second output line 40e in series. The series transformer 120 generates an induced voltage in the secondary winding 120b according to the voltage applied to the primary winding 120a, and uses the induced voltage to boost or increase the voltage of the second output line 40e with respect to the second connection line 40d. Lower blood pressure.

Both ends of the primary winding 110a of the series transformer 110 and both ends of the primary winding 120a of the series transformer 120 are connected such that the polarities of the voltages applied to the primary windings 110a and 120a are opposite to each other. .

Furthermore, the turn ratio of the secondary winding 110b to the primary winding 110a and the turn ratio of the secondary winding 120b to the primary winding 120a are the same, and depending on the voltage applied to the primary windings 110a and 120a, The induced voltages generated in each of the secondary windings 110b and 120b have the same magnitude and opposite polarity.

The switch 130a and the control unit 130b are devices that switch the polarity or magnitude of the voltage applied to the primary windings 110a and 120a, and are devices that switch the polarity or magnitude of the voltage applied to the primary windings 110a and 120a. One semiconductor element SSR6 is provided that constitutes a circuit that prevents short circuits between the terminals 120a. The balancer 250, tap changer 130a, and control section 130b are connected by an output line 50c. Note that the short circuit prevention circuit is constituted by a semiconductor element SSR6 and a bridge resistor R (resistance value Rb) connected in series with the semiconductor element SSR6.

The semiconductor elements SSR1 to SSR5 have, for example, tap positions for switching the voltage adjustment width of the series transformers 110 and 120, and when there are five semiconductor elements (SSR1 to SSR5) as described above, at tap position 1, SSR1 and SSR5 are switched. is turned on, and at tap position 2, SSRs 1 and 3 are turned on. At tap position 3, SSRs 2 and 5 are turned on, and at tap position 4, SSRs 2 and 3 are turned on. Further, at tap position 5, SSRs 2 and 4 are turned on to switch the voltage adjustment width for the input voltage of the voltage regulator 110.

In the voltage regulator 10 (100) configured as described above, when the control unit 13b (130b) switches the tap of the tap changer 13a (130a), the iron cores of the series transformers 11, 12 (110, 120) become magnetically saturated. may occur. When magnetic saturation occurs, an excitation inrush current flows through the series transformers 11, 12 (110, 120), and there is a high possibility that the semiconductor elements SSR1 to SSR6 of the tap changer 13a (130a) will be destroyed. In order to avoid magnetic saturation, it is possible to suppress and control the voltage applied to the series transformers 11, 12 (110, 120) at the time of tap switching to suppress the accumulation of magnetic flux.

For example, if we take the case of switching from tap position 1 to tap position 5, in the state before tap switching, semiconductor elements SSR1 and SSR5 are in the on state, and when the switching start command is issued, in addition to this, The semiconductor element SSR6 is in an on state. In this state before switching and at the timing when the switching start command is issued, the voltage applied to the series transformers 11, 12 (110, 120) is a voltage that corresponds to the tap position, and in the illustrated case, it corresponds to tap position 1. voltage.

In the bridge state, in response to the switching start command, the semiconductor elements SSR1 and SSR5, which were in the on state before switching, are turned off, and only SSR6 is turned on. In other words, the bridge state is a state in which the current I _SSR flowing through SSR1 to SSR5 becomes 0 in response to the switching start command, and the voltage applied to the series transformers 11, 12 (110, 120) at this timing is: A voltage equal to the sum of the primary currents I' of the series transformers 11 and 12 (110, 120) Is (=2×I')×bridge resistance Rb is applied.

When the switching end command is issued, the semiconductor element corresponding to the tap position after switching and the semiconductor element SSR6 are in an on state. When switching from tap position 1 to tap position 5, semiconductor elements SSR2, SSR4, and SSR6 are in an on state. Note that the switching end command is a command to turn on the closing SSR and turn off the SSR 6 corresponding to the tap position after switching. Further, in the state after switching, the semiconductor element SSR6 is turned off in response to the switching end command, and only the semiconductor element corresponding to the tap position after switching is turned on. When switching from tap position 1 to tap position 5, semiconductor elements SSR2 and SSR4 are in an on state. In the state after switching, the voltage applied to the series transformers 11, 12 (110, 120) is a voltage that corresponds to the tap position, and in the illustrated case, a voltage that corresponds to tap position 5.

That is, in each stage other than the bridge state, the primary side voltage Vs of the series transformers 11 and 12 differs depending on the state of the circuit. Therefore, in order to suppress the magnetic flux density of the series transformers 11 and 12, the turning-on phase of the semiconductor element at the start of tap switching by the tap changer 13a (130a) is set to the peak of the excitation voltage, and the timing of state transition is controlled. This makes it possible to suppress the accumulation of magnetic flux in the iron cores that constitute the series transformers 11 and 12.

The timing of transition to the bridge state changes depending on the value of the phase difference θ between the secondary line voltage V ₂ and the secondary current I of the series transformers 11 and 12. Current flowing through the semiconductor elements SSR1 to SSR5 with respect to the secondary line voltage V ₂ for each tap position before switching and the phase difference θ between the secondary line voltage V ₂ and the secondary current I of the series transformers 11 and 12 I Understand the phase shift θ _SSR for all tap switching patterns _. Then, by changing the optimal closing phase of the semiconductor element SSR and the power factor of the load (the phase difference θ between the secondary line voltage V ₂ and the secondary current I of the series transformers 11 and 12), the maximum magnetic flux density is seek.

If the optimal switching end phase is selected for all tap switching patterns, no matter what the phase difference between the line voltage _V2 and the phase current I, the saturation magnetic flux density of the iron core that constitutes the series transformer will be reduced. or less, and magnetic saturation can be avoided.

As explained above, according to the voltage regulator and voltage regulating method of the present invention, the magnetic flux density at the end of tap switching can be suppressed without increasing the cross-sectional area of the iron core of the series transformer, and the device can be downsized and It becomes possible to suppress costs.

Furthermore, magnetic saturation can be avoided, and damage to the semiconductor element of the voltage regulator caused by excitation inrush current can be reliably prevented.

It can be used in a voltage regulator using a semiconductor device that is connected to a power distribution line by a series transformer.

3,30 First voltage line 3a, 4a, 5a,30a, 40a, 50a Input side terminal 3b,4b, 30b,40b Output side terminal 3c, 30c First input line 3d, 30d First connection line 3e, 30e First output line 3f, 30f First branch line 4,40 Second voltage line 4c, 40c Second input line 4d, 40d Second connection line 4e, 40e Second output line 4f, 40f Second branch line 5 Medium Neutral wire 5b Neutral input wire 5c Neutral output wire 10,100 Voltage regulator 11, 12, 110, 120 Series transformer 11a, 12a, 110a, 120a Primary winding 11b, 12b, 110b, 120b Secondary winding 13a ,130a Tap changer 13b,130b Control section 25,250 Balancer 50c Output line R Bridge resistance SSR1 to SSR6 Semiconductor element

Claims (4)

It is connected to a single-phase two-wire distribution line consisting of two voltage lines or a single-phase three-wire distribution line consisting of two voltage lines and one neutral line, and a secondary winding is connected to the voltage line. A series transformer to be connected, a semiconductor type tap changer for switching the polarity and magnitude of the voltage applied to the primary winding of the series transformer, and a single-phase two-wire type tap changer on the output side from the series transformer. In the case of a single-phase three-wire system, the tap changer is connected to the voltage line, and in the case of a single-phase three-wire system, it is connected to the voltage line and the neutral line, and the tap changer is connected to the voltage line and the neutral line at the connection position. The controller includes a control unit that controls switching of the semiconductor element, and sets the closing phase of the semiconductor element at the peak of the excitation voltage when the tap changer starts changing the taps, and sets the closing phase of the semiconductor element after the tap switching to: A voltage regulator characterized in that the voltage regulator is configured to change according to the combination of taps before and after changing the taps. The control device is configured such that a maximum magnetic flux density of an iron core constituting the series transformer is a saturation magnetic flux according to a phase difference between a secondary line voltage on the output side of the series transformer and a secondary current of the series transformer. 2. The voltage regulator according to claim 1, wherein the turning-on phase of the semiconductor element is determined so that the density is less than or equal to the density. Voltage adjustment that adjusts the output voltage to the input voltage of a single-phase two-wire distribution line consisting of two voltage lines or a single-phase three-wire distribution line consisting of two voltage lines and one neutral line. The method comprises switching the voltage applied to the primary winding of a series transformer whose secondary winding is connected to the voltage line in accordance with the output voltage with a semiconductor tap; When adjusting the polarity and magnitude of the induced voltage generated at A voltage adjustment method for a voltage regulator, characterized in that the voltage is changed according to a combination of taps. The maximum magnetic flux density of the iron core constituting the series transformer is determined by adjusting the turning-on phase of the semiconductor element according to the phase difference between the secondary line voltage on the output side of the series transformer and the secondary current of the series transformer. 4. The voltage regulating method for a voltage regulator according to claim 3, wherein the voltage is determined to be equal to or less than the saturation magnetic flux density.