Voltage regulator and voltage regulation method

Abstract

To provide a voltage regulator suitable for compensating voltage drop of a distribution line.SOLUTION: A voltage regulator 10 connected to a single-phase three-wire system low voltage line 2 raises voltage between a first line 3 and a second line 4 of the low voltage line 2 by a booster 20 different from a pressure rise or a step-down by series transformers 11 and 12. Thus, output voltage of the voltage regulator 10 shifts to a pressure rise side by the booster 20. Therefore, since a pressure rise width can be made larger without making a step-down width by the series transformers 11 and 12 larger, and a compensation amount of the voltage drop due to a line impedance can be increased by a large pressure rise width, while eliminating a waste due to an increase of a step-down width of the voltage regulator 10.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a voltage regulator and a voltage regulation method connected to a single-phase three-wire power distribution line, and more particularly to a voltage regulator and a voltage regulation method suitable for compensating for voltage drops in the power distribution line. [Background technology]

[0002] Some voltage regulators connected to a single-phase three-wire distribution line consisting of a first wire, a second wire, and a neutral wire step up or step down the output voltage by switching the polarity of series transformers connected in series to the first wire and the second wire, respectively (Patent Document 1).When the output voltage of the voltage regulator fluctuates due to reverse power flow caused by solar power generation, load fluctuations, or the like, this voltage regulator can cancel out the fluctuations and maintain the output voltage within a predetermined range by stepping up or stepping down the output voltage using the series transformer.

[0003] For distribution lines in mountainous areas, it is desirable to use low-voltage lines, which are easier to manage than high-voltage lines. However, the lower the voltage of the distribution line, the greater the voltage drop due to line impedance, so in order to extend the low-voltage line, it is necessary to compensate for the voltage drop (boost) along the way. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-023593 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the voltage regulator of Patent Document 1, the polarity of the series transformer is switched to boost or drop the output voltage, so the boost amount and the drop amount are the same. In this case, if the boost amount by the voltage regulator is increased to increase the amount of compensation for voltage drop due to line impedance, the drop amount also increases, resulting in waste.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a voltage regulator and a voltage regulation method suitable for compensating for voltage drops in power distribution lines. [Means for solving the problem]

[0007] To achieve this object, the voltage regulator of the present invention is connected to a single-phase three-wire distribution line consisting of a first wire, a second wire, and a neutral wire, and adjusts and outputs an input voltage between the first wire, the second wire, and the neutral wire, respectively. The voltage regulator includes a pair of series transformers connected in series to the first wire and the second wire, respectively, so that the secondary windings connect the first wire and the second wire, respectively; a switch unit that switches the polarity or magnitude of the voltage applied to the primary windings of the pair of series transformers and adjusts the polarity or magnitude of the induced voltage in the secondary winding; a control unit that is connected to the first wire, the second wire, and the neutral wire on the output side of the series transformers and controls the switching by the switch unit in accordance with the voltage between the first wire, the second wire, and the neutral wire at that connection point; and a booster that is connected to the first wire and the second wire on the input side of the connection point of the control unit, respectively, and boosts the voltage between the first wire and the second wire.

[0008] Furthermore, the voltage adjustment method of the present invention is a method for adjusting the output voltage relative to the input voltage of a single-phase three-wire distribution line consisting of a first wire, a second wire, and a neutral wire, and includes an adjustment step of switching the voltage applied to the primary windings of a pair of series transformers according to the output voltage and adjusting the polarity or magnitude of the induced voltage generated in the secondary windings of the pair of series transformers, thereby increasing or decreasing the voltage between the first wire and the neutral wire and between the second wire and the neutral wire on the output side of the secondary windings connecting the first wire and the second wire, respectively, and a boost step of boosting the voltage between the first wire and the second wire by a booster. [Effects of the Invention]

[0009] According to the voltage regulator of claim 1, the switch unit switches the polarity or magnitude of the voltage applied to the primary windings of the pair of series transformers, thereby adjusting the polarity or magnitude of the induced voltage generated in the secondary windings of the pair of series transformers, and the voltage between the first and second lines is increased or decreased on the output side of the secondary windings. In addition to increasing or decreasing the voltage by the series transformers, the voltage between the first and second lines is increased by the booster. This causes the output voltage of the voltage regulator to be shifted to the increased side by the booster. Therefore, the boost range of the voltage regulator can be increased without increasing the step-down range by the series transformers, thereby eliminating waste due to an increased step-down range of the voltage regulator and increasing the amount of compensation for voltage drop due to line impedance by the large boost range.

[0010] The control unit also controls the switching by the switch unit in accordance with the voltage between the neutral line and the first and second lines on the output side of the series transformer and the booster. This allows the control unit to monitor the output voltage after adjustment by the series transformer and the booster, and enables control to cancel out fluctuations in the output voltage due to load fluctuations, etc.

[0011] According to the voltage regulator of claim 2, balancers that balance the voltages applied between the first and second wires and the neutral wire are connected to the first and second wires and the neutral wire at the same positions relative to the series transformer and the booster. Therefore, the input voltage or output voltage of the series transformer or the booster is balanced by the balancers, which not only achieves the effect of claim 1 but also makes it easier to keep the output voltage of the voltage regulator balanced.

[0012] The connection positions of the balancer to the first wire, second wire, and neutral wire may be the same positions on the input side or output side of the series transformer, or may be the same positions on the input side or output side of the boost position (for example, the series winding described below) of the booster.

[0013] According to the voltage regulator of claim 3, the booster and balancer are configured as an integrated unit, which not only achieves the effect of claim 2 but also makes the voltage regulator lighter and smaller than when the booster and balancer are provided separately.

[0014] According to the voltage regulator of claim 4, the booster is connected to each of the first line and the second line and the neutral line. , balance the voltages applied between the first and second wires and the neutral wire respectively The balancer is provided with a pair of shunt windings and a pair of series windings connected to the pair of shunt windings. In this way, a booster is formed by adding a series winding to the balancer, so that the booster can be Similar to 1 to 3 In addition to this effect, the structure of the integrally configured booster and voltage regulator can be simplified.

[0015] Since the shunt winding of the booster constitutes a balancer, in addition to the current (A1) generated in response to voltage adjustment, a current for balancing the voltage (hereinafter referred to as the "balancing current") is generated in the shunt winding.

[0016] flat The maximum value of the balancing current is the rated current of the balancer, so the sum of the maximum value of the current (maximum value of A1) generated in the shunt winding according to the voltage adjustment of this voltage regulator and the rated current of the balancer (maximum value of balancing current) is the maximum value of the current generated in the shunt winding in which the booster and balancer are integrated. The value obtained by dividing the maximum value of the current generated in the shunt winding (maximum value of A1 + rated current of the balancer) by the cross-sectional area (DX) of the shunt winding, that is, the maximum current density generated in the shunt winding is 3 [A / mm 2 ] or less. As a result, even if a balancing current occurs in the shunt winding in addition to the current during voltage adjustment, the amount of heat generated in the shunt winding according to the current density can be suppressed, making it easier for the shunt winding to withstand these currents. , Noboru This can further improve the durability of the shunt winding of the transformer.

[0017] Claim 5According to the described voltage regulation method, the regulation step switches the voltage applied to the primary windings of a pair of series transformers according to the output voltage, thereby adjusting the polarity or magnitude of the induced voltage generated in the secondary windings of the pair of series transformers. As a result, the voltages between the first and second lines and the neutral line are respectively increased or decreased on the output sides of the secondary windings connecting the first and second lines. Separate from this regulation step, a boost step is performed in which a booster increases the voltage between the first and second lines. This shifts the boost and drop ranges of the voltage regulator toward the increased side. Therefore, the boost range of the voltage regulator can be increased without increasing the drop range of the series transformers. This allows the amount of compensation for voltage drop due to line impedance to be increased by the large boost range, while eliminating waste due to an increased drop range of the voltage regulator.

[0018] According to the voltage adjustment method of claim 6, the same effect as that of claim 4 is achieved. In addition, In the voltage adjustment method according to claim 6, The adjusting step may be performed after the boosting step, or the boosting step may be performed after the adjusting step. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a schematic diagram illustrating a state in which a voltage regulator according to an embodiment is connected to a low-voltage line. [Figure 2] FIG. 1 is a circuit diagram of a voltage regulator. [Figure 3] 1 is a table showing the relationship between the on / off pattern of a semiconductor relay in a voltage regulator and the regulated voltage. [Figure 4] 1(a) is an explanatory diagram showing a modified example of a voltage regulator in which a balancer is provided separately from a booster, and FIG. 1(b) is an explanatory diagram showing a case in which a shunt winding of the booster functions as a balancer. DETAILED DESCRIPTION OF THE INVENTION

[0020] Preferred embodiments will now be described with reference to the accompanying drawings. First, an overview of a voltage regulator 10 in one embodiment will be described with reference to Fig. 1. As shown in Fig. 1, voltage regulator 10 is a device that adjusts and outputs an input voltage, and is connected to a single-phase three-wire low-voltage line 2 of an AC distribution line.

[0021] The input side (power plant or substation side) of the low-voltage line 2 is connected to the high-voltage line 6 via a pole-mounted transformer 7. This pole-mounted transformer 7 converts the voltage from approximately 6.6 kV of the high-voltage line 6 to approximately 210 V and approximately 105 V of the low-voltage line 2. The output side of the low-voltage line 2 is connected to consumers 8 such as ordinary homes and factories.

[0022] Because the low-voltage line 2 has a lower voltage than the high-voltage line 6, the voltage drop due to line impedance is large. Taking this voltage drop into consideration, the voltage at the consumer 8, etc. must be kept within the range of 101±6[V]. Furthermore, for the voltage converted to 210[V] by the pole transformer 7, the voltage at the consumer 8, etc. must be kept within the range of 202±20[V].

[0023] By connecting a voltage regulator 10 midway along the low-voltage line 2 and using this voltage regulator 10 to boost the voltage of the low-voltage line 2, i.e., by using the voltage regulator 10 to compensate for the voltage drop in the low-voltage line 2, it is possible to lengthen the low-voltage line 2 while keeping the voltage at consumers 8 and the like within a specified range. This makes it easier to manage distribution lines in mountainous areas and the like.

[0024] Next, the voltage regulator 10 will be described in detail with reference to Figures 2 and 3. As shown in Figure 2, the voltage regulator 10 is connected to a single-phase three-wire low-voltage line 2 (see Figure 1) consisting of a first line 3, a second line 4, and a neutral line 5 via input terminals 3a, 4a, and 5a and output terminals 3b and 4b. The neutral line 5 is grounded. With respect to the input voltage to the voltage regulator 10, the voltage between the neutral line 5 and the first line 3 is the same in magnitude but opposite in polarity to the voltage between the neutral line 5 and the second line 4.

[0025] The voltage regulator 10 includes a booster 20 that boosts the voltage on the output side between the first line 3 and the second line 4, an equalizer 25 that balances the voltages applied between the first line 3 and the second line 4 and the neutral line 5, series transformers 11 and 12 that boost or lower the voltage on the output side, a switch unit 13 that switches between boosting or lowering the voltage by the series transformers 11 and 12, and a control unit 14 that controls the switching by the switch unit 13.

[0026] The first line 3 passing through the voltage regulator 10 includes a first input line 3c connecting the terminal 3a and the booster 20, a first boost line 3d connecting the booster 20 and the series transformer 11, a first adjustment line 3e extending from the series transformer 11 toward the terminal 3b, a first branch line 3f branching from the first adjustment line 3e and connected to the switch unit 13 and the control unit 14, and a first output line 3g connecting from the branch point between the first adjustment line 3e and the first branch line 3f to the terminal 3b.

[0027] The second line 4 passing through the voltage regulator 10 includes a second input line 4c connecting the terminal 4a and the booster 20, a second boost line 4d connecting the booster 20 and the series transformer 12, a second adjustment line 4e extending from the series transformer 12 toward the terminal 4b, a second branch line 4f branching from the second adjustment line 4e and connected to the switch unit 13 and the control unit 14, and a second output line 4g connecting from the branch point of the second adjustment line 4e and the second branch line 4f to the terminal 4b.

[0028] The neutral conductor 5 branches at a terminal 5a, and the branch line is arranged inside the voltage regulator 10, and the main line of the neutral conductor 5 is connected to a consumer 8 (see FIG. 1 ) or the like. The neutral conductor 5 inside the voltage regulator 10 includes a neutral input line 5b that connects the terminal 5a with the booster 20, and a neutral branch line 5c that branches from the neutral input line 5b and is connected to the switch unit 13 and the control unit 14.

[0029] The booster 20 includes a first shunt winding 21 connecting the neutral input line 5b and the first input line 3c, a second shunt winding 22 connecting the neutral input line 5b and the second input line 4c, a first series winding 23 connecting the first input line 3c and the first boost line 3d, and a second series winding 24 connecting the second input line 4c and the second boost line 4d. The booster 20 is a step-up autotransformer in which the first shunt winding 21, the second shunt winding 22, the first series winding 23, and the second series winding 24 are wound around the same iron core.

[0030] The first shunt winding 21 and the second shunt winding 22 are connected to the neutral input line 5b at one point. The first shunt winding 21 and the first series winding 23 are connected to the first input line 3c at one point. The second shunt winding 22 and the second series winding 24 are connected to the second input line 4c at one point.

[0031] The first shunt winding 21 and the second shunt winding 22 are set to have the same number of turns N1. The first series winding 23 and the second series winding 24 are set to have the same number of turns N2. The number of turns N2 is set to be less than the number of turns N1. In this embodiment, the ratio of the number of turns N1:number of turns N2 is set to approximately 40:1.

[0032] Therefore, when the voltage between the first input line 3c and the neutral input line 5b is applied to the first shunt winding 21, a voltage boosted by approximately 2.5% by the first series winding 23 is output between the first boost line 3d and the neutral line 5. When the voltage between the second input line 4c and the neutral input line 5b is applied to the second shunt winding 22, a voltage boosted by approximately 2.5% by the second series winding 24 is output between the second boost line 4d and the neutral line 5.

[0033] The booster 20 boosts the output voltage by approximately 2.5% relative to the combined input voltage of the first line 3 and the second line 4. Specifically, if the voltage between the first input line 3c and the second input line 4c is approximately 200V, the booster 20 boosts the output by approximately 5V.

[0034] The balancer 25 includes a pair of windings that connect the first input line 3c and the second input line 4c to the neutral input line 5b, and a core (not shown) around which the pair of windings are wound, and in this embodiment, the rated current is set to approximately 10 A. In this embodiment, the pair of windings of the balancer 25 is composed of a first shunt winding 21 and a second shunt winding 22. The first shunt winding 21 and the second shunt winding 22, which are wound around the core, have the same number of turns N1, so the balancer 25 can balance the voltage applied to the first shunt winding 21 and the voltage applied to the second shunt winding 22.

[0035] The balancer 25 and the booster 20 are integrally constructed using the same iron core. This allows for a reduction in the number of iron cores compared to when the booster 20 and the balancer 25 are provided separately within the voltage regulator 10. This allows for a reduction in the weight and size of the voltage regulator 10 that includes both the booster 20 and the balancer 25.

[0036] Furthermore, by adding the first series winding 23 and the second series winding 24 to the balancer 25, which is a type of autotransformer, the booster 20, which is an autotransformer for boosting voltage, can be configured. As a result, the structure of the integrally configured booster 20 and balancer 25 can be simplified.

[0037] The windings of the balancer 25 (first shunt winding 21 and second shunt winding 22) are connected to the first line 3 and second line 4 (first input line 3c and second input line 4c) at the same positions relative to the series transformers 11 and 12 and the booster 20. Therefore, the output voltages of the series transformers 11 and 12 and the booster 20 are balanced by the balancer 25, making it easier to maintain the output voltage of the voltage regulator 10 in balance.

[0038] The series transformer 11 includes a primary winding 11a connected to the switch unit 13 via wiring 15 and 16, and a secondary winding 11b connecting the first step-up line 3d and the first adjustment line 3e. The primary winding 11a and secondary winding 11b are wound on an iron core (not shown) that is different from the iron core of the step-up transformer 20. As a result, the series transformer 11 generates an induced voltage in the secondary winding 11b according to the voltage applied to the primary winding 11a, and the induced voltage increases or decreases the voltage between the first adjustment line 3e and the neutral line 5 relative to the voltage between the first step-up line 3d and the neutral line 5.

[0039] Series transformer 12 includes primary winding 12a connected to switch unit 13 via wiring 15 and 16, and secondary winding 12b connecting second step-up line 4d and second adjustment line 4e. Primary winding 12a and secondary winding 12b are wound around the same core as that of series transformer 11. As a result, series transformer 12 generates an induced voltage in secondary winding 12b according to the voltage applied to primary winding 12a, and this induced voltage increases or decreases the voltage between second adjustment line 4e and neutral line 5 relative to the voltage between second step-up line 4d and neutral line 5.

[0040] Both ends of primary winding 11a of series transformer 11 and both ends of primary winding 12a of series transformer 12 are connected by wires 15 and 16 so that the polarities of the voltages applied to primary windings 11a and 12a are opposite to each other. Furthermore, the turns ratio of secondary winding 11b to primary winding 11a is the same as the turns ratio of secondary winding 12b to primary winding 12a, and series transformers 11 and 12 use the same iron core, so that the induced voltages generated in secondary windings 11b and 12b in response to the voltages applied to primary windings 11a and 12a are the same in magnitude but opposite in polarity.

[0041] The switching unit 13 is a device that switches the polarity or magnitude of the voltage applied to the primary windings 11a and 12a. The switching unit 13 includes five semiconductor relays (hereinafter referred to as "relays") A to E. Relays A to C are connected to wiring 15, and relays D and E are connected to wiring 16. Relays A and D are connected to the second branch line 4f. Relays B and E are connected to the first branch line 3f. Relay C is connected to the neutral branch line 5c.

[0042] In addition to Fig. 2, the following description will be made using Fig. 3, which shows the relationship between the on / off patterns of relays A to E and the regulated voltage of voltage regulator 10. In Fig. 3 and the following description, a voltage increase is indicated by a plus (+) sign, and a voltage decrease is indicated by a minus (-) sign. In the description of Fig. 3, the input voltage between first input line 3c and second input line 4c is assumed to be 200 V, and the input voltage between neutral input line 5b and first input line 3c or second input line 4c is assumed to be 100 V.

[0043] First, when relays A and E are turned on, the voltage between the first branch line 3f and the second branch line 4f is applied to the primary windings 11a and 12a. If no induced voltage is generated in the secondary windings 11b and 12b immediately after relays A and E are turned on, the voltage applied to the primary windings 11a and 12a will be approximately 205V, which is the input voltage between the first input line 3c and the second input line 4c increased by approximately 5V by the booster 20.

[0044] In response to this applied voltage, an induced voltage is generated in the secondary windings 11b and 12b, boosting the output voltage. As the output voltage increases, the applied voltage to the primary windings 11a and 12a increases, and as this voltage increases, the induced voltage also increases. The increase in the applied voltage and the increase in the induced voltage loop, but the increase value converges.

[0045] The turns ratio between primary windings 11a, 12a and secondary windings 11b, 12b is set so that the induced voltage in secondary winding 11b, 12b on one side is approximately 5 V relative to the input voltage of voltage regulator 10. Therefore, when relays A and E are turned on, voltage regulator 10 increases the output voltage relative to the input voltage by approximately 5 V at booster 20 and by approximately 10 V at secondary windings 11b, 12b on both sides, resulting in a total output voltage increase of approximately 15 V, or approximately 7.5%.

[0046] Similarly, when relays C and E are turned on, the voltage between first branch wire 3f and neutral branch wire 5c becomes the applied voltage to primary windings 11a and 12a, and secondary windings 11b and 12b each output an output voltage of approximately +2.5 V. Therefore, when relays C and E are turned on, voltage regulator 10 increases the output voltage relative to the input voltage by approximately +5 V at booster 20 and by approximately +5 V at secondary windings 11b and 12b on both sides, resulting in a total output voltage increase of approximately +10 V, or approximately 5%.

[0047] Furthermore, when relays A and D (or relays B and E) are turned on, the voltages across primary windings 11a and 12a are the same (applied voltage is 0 [V]), and the induced voltage in secondary windings 11b and 12b is 0 [V]. In this case, voltage regulator 10 only increases the output voltage by about 5 [V] relative to the input voltage using booster 20, and the overall output side is boosted by about 2.5%.

[0048] When relays C and D are turned on, a voltage of the same magnitude but opposite polarity as when relays C and E are turned on is applied to primary windings 11a and 12a. In this case, voltage regulator 10 increases the output voltage relative to the input voltage by approximately +5 V at booster 20 and by approximately -5 V at secondary windings 11b and 12b on both sides, resulting in a regulated voltage of approximately 0 V on the entire output side.

[0049] When relays B and D are turned on, a voltage of the same magnitude but opposite polarity as when relays A and E are turned on is applied to primary windings 11a and 12a. In this case, voltage regulator 10 increases the output voltage relative to the input voltage by approximately +5 V at booster 20 and by approximately -10 V at secondary windings 11b and 12b on both sides, reducing the overall output voltage by approximately -5 V, or approximately 2.5%.

[0050] The control unit 14 is a device that controls the switching of relays A to E in the above-mentioned pattern. The control unit 14 is connected to the first branch line 3f, the second branch line 4f, and the neutral branch line 5c, and detects the voltage at these connection points. Note that, as long as the voltage is adjusted by the step-up transformer 20 and the series transformers 11 and 12, the control unit 14 may be connected to another branch line branched from the first adjustment line 3e or the first output line 3g instead of the first branch line 3f connected to relays A and D, and the control unit 14 may be connected to another branch line branched from the second adjustment line 4e or the second output line 4g instead of the second branch line 4f connected to relays B and E.

[0051] This enables the control unit 14 to monitor the output voltage regulated by the booster 20 and the series transformers 11 and 12. The control unit 14 switches relays A to E on and off in accordance with the output voltage, and adjusts the regulated voltage on the entire output side so that the voltage at the consumer 8 or the like falls within a predetermined range. For example, when the output voltage fluctuates due to reverse power flow caused by solar power generation or load fluctuations, the control unit 14 executes control to switch relays A to E on and off so as to cancel out the fluctuations by adjusting the regulated voltage on the entire output side.

[0052] According to voltage regulator 10 described above, booster 20 boosts the voltage in addition to the step-up or step-down by series transformers 11 and 12, and therefore the output voltage of voltage regulator 10 is shifted to the boost side by booster 20. Specifically, if the output voltage of series transformers 11 and 12 is boosted by approximately 5% (+approximately 10 V) and stepped down by approximately 5% (-approximately 10 V), then booster 20 can boost the output voltage by approximately 2.5% (+approximately 5 V) to approximately 7.5% (+approximately 15 V) and step down by approximately 2.5% (-approximately 5 V).

[0053] In this way, voltage regulator 10 can increase the step-up amount without increasing the step-down amount by series transformers 11 and 12. Therefore, it is possible to increase the amount of compensation for the voltage drop due to the line impedance of low-voltage line 2 by increasing the step-up amount while eliminating waste caused by an increase in the step-down amount by voltage regulator 10.

[0054] Furthermore, because the step-up value (+approximately 2.5%) by booster 20 is smaller than the step-down amount (-approximately 5%) by series transformers 11 and 12, it is possible to adjust the output voltage to step down relative to the input voltage of voltage regulator 10. As a result, even if voltage regulator 10 is installed on low-voltage line 2 of a length where voltage drop is unlikely to be a problem, and a fluctuation that increases the output voltage occurs, the fluctuation can be canceled out (stepped down) by voltage regulator 10.

[0055] Furthermore, the induced voltage of series transformers 11 and 12 changes in increments of approximately 2.5% by switching relays A to E, and because the magnitude of these increments is approximately the same as the boost value provided by booster 20, the regulated voltage on the entire output side of voltage regulator 10 can be set to approximately 0 V when relays C and D are turned on, as described above. This makes it possible for voltage regulator 10 to regulate the output voltage without boosting or lowering it, allowing voltage regulator 10 to perform only the function of balancer 25.

[0056] Voltage regulator 10 varies the voltage by the same amount on the first line 3 side and the second line 4 side using series transformers 11 and 12, and boosts the voltage by the same amount on the first line 3 side and the second line 4 side using booster 20. If the voltages between first line 3, second line 4 and neutral line 5 are the same, current caused by the voltage difference will not flow in balancer 25, and the cross-sectional area of the windings of balancer 25 (first shunt winding 21 and second shunt winding 22) can be reduced.

[0057] 4(a) and 4(b), a case where a load connected to the input side of voltage regulator 10 becomes unbalanced and a case where a load connected to the input side of voltage regulator 30, a modified example of the present invention, becomes unbalanced will be described. Note that the following will be described by taking as an example a case where a load R1 is connected between the second wire 4 and the neutral wire 5 on the input side of voltage regulators 10 and 30, no load is connected between the first wire 3 and the neutral wire 5 on the input side, and the same load R2 is connected between the first wire 3 and the second wire 4 and the neutral wire 5 on the output side of voltage regulators 10 and 30, respectively.

[0058] At this time, a current 2·A3 (twice A3) due to the load imbalance on the input side of voltage regulators 10 and 30 flows from neutral wire 5 to second wire 4 in load R1. Furthermore, load R1 represents a load in a consumer (not shown) connected to low-voltage line 2 on the input side of voltage regulators 10 and 30. Load R2 represents a load in consumer 8 connected to low-voltage line 2 on the output side of voltage regulators 10 and 30.

[0059] Fig. 4(a) is an explanatory diagram of a voltage regulator 30 according to a modified example of the present invention, in which a balancer 31 is provided in addition to the booster 20. Fig. 4(b) is an explanatory diagram of a case in which the booster 20 of the voltage regulator 10 functions as a balancer 25. Note that, since the configurations of the voltage regulators 10 and 30 on the first line 3 side and the second line 4 side with respect to the neutral conductor 5 are substantially the same, the following description will mainly focus on the first line 3 side, and some of the description of the second line 4 side will be omitted.

[0060] 4(a) and 4(b), for simplicity of explanation, the induced voltage of series transformers 11 and 12 is set to 0 [V], and series transformers 11 and 12 and switch unit 13 are not shown. Furthermore, in FIGS. 4(a) and 4(b), current arrows are drawn so that electricity mainly flows from terminal 3a of first wire 3 to first series winding 23, load R2, second series winding 24, and terminal 4a. Note that when the polarity of the AC current is reversed, these current arrows are reversed.

[0061] The voltage regulator 30 shown in Figure 4(a) is configured identically to the voltage regulator 10, except for the provision of a balancer 31 on the input side (terminals 3a, 4a side) of the booster 20 and the size of the cross-sectional area D1 of the first shunt winding 21 and the second shunt winding 22. The balancer 31 has a winding wound around one iron core, with both ends connected to the first wire 3 and the second wire 4, respectively, and the center of the winding connected to the neutral wire 5. This ensures that the number of turns of the winding is the same on both sides of the neutral wire 5, so the balancer 31 can balance the voltage between the first wire 3 and the neutral wire 5 and the voltage between the second wire 4 and the neutral wire 5 at the positions where the windings are connected.

[0062] When a current 2·A3 due to a load imbalance flows from the neutral conductor 5 to the load R1, a balancing current A3 flows toward the neutral conductor 5 in each of the windings on both sides of the balancer 31 on the output side of the load R1. A current 2·A3 is generated in the neutral conductor 5 from the balancer 31 to the load R1, but the balancer 31 prevents the current 2·A3 from being generated in the neutral conductor 5 on the input side of the load R1. This allows the voltage on the first line 3 side and the voltage on the second line 4 side to be balanced on the input side of the balancer 31.

[0063] The maximum value of the balancing current A3 is the rated current of the balancer 31, which is set to approximately 10 A in this embodiment. The balancing current A3 does not flow in the first shunt winding 21 or the second shunt winding 22. This is because the cross-sectional area of the balancer 31 is made sufficiently larger than the cross-sectional area D1 of the first shunt winding 21 and the second shunt winding 22, so that electricity flows more easily in the winding of the balancer 31 than in the first shunt winding 21 and the second shunt winding 22.

[0064] Furthermore, when the booster 20 boosts the voltage, currents are generated in the first shunt winding 21 and the first series winding 23 such that the current ratio A1 / A2, which is the ratio of the current A1 in the first shunt winding 21 to the current A2 in the first series winding 23, is the same as the turns ratio N2 / N1, which is the ratio of the number of turns N2 in the first series winding 23 to the number of turns N1 in the first shunt winding 21.

[0065] When the induced voltage of series transformers 11 and 12 is 0 V, current A2 is the same as the rated secondary current of voltage regulator 30. Current A2 of first series winding 23 also changes with changes in the induced voltage, but the maximum value of current A2 can be calculated.

[0066] Similarly, in voltage regulator 10, when booster 20 is used to boost the voltage, current A1 is generated in first shunt winding 21 and second shunt winding 22, and current A2 is generated in first series winding 23 and second series winding 24. However, unlike voltage regulator 30, voltage regulator 10 has booster 20 and balancer 25 configured integrally, and therefore balancing current A3 is generated in first shunt winding 21 and second shunt winding 22, which constitute the windings of balancer 25.

[0067] The current A1 and balancing current A3 generated in first shunt winding 21 flow in the same direction, while the current A1 and balancing current A3 flow in the opposite direction in second shunt winding 22. Therefore, a current A1+A3 flows in first shunt winding 21 of voltage regulator 10, and a current |A1-A3| (the absolute value of the difference between A1 and A3) flows in second shunt winding 22. The following describes first shunt winding 21, which generates a larger current than second shunt winding 22.

[0068] Thus, current A1+A3 generated in first shunt winding 21 of voltage regulator 10 is larger than current A1 generated in first shunt winding 21 of voltage regulator 30. The cross-sectional area of each winding, such as first shunt winding 21 and first series winding 23, must be set according to the current (allowable current) expected to flow through that winding, i.e., the cross-sectional area and the allowable current must be set so as to be approximately proportional to each other.

[0069] Therefore, by making the cross-sectional area DX of first shunt winding 21 of voltage regulator 10 larger than the cross-sectional area D1 of first shunt winding 21 of voltage regulator 30, first shunt winding 21 can be made to withstand balancing current A3 more easily. This ensures the durability of first shunt winding 21 of voltage regulator 10 even when balancing current A3 is generated in first shunt winding 21 in addition to current A1 during voltage boost.

[0070] In this embodiment, the maximum value of balancing current A3 is the rated current of balancer 25, and currents A1 and A2 each reach their maximum values depending on the regulated voltage of voltage regulator 10. From this, the maximum current ratio (maximum value of A1 + maximum value of A3) / (maximum value of A2) is calculated by dividing the maximum value of current generated in first shunt winding 21 (maximum value of A1 + maximum value of A3) by the maximum value of current A2 generated in first series winding 23. Therefore, by setting voltage regulator 10 so that the cross-sectional area ratio DX / D2 and the maximum current ratio (maximum value of A1 + maximum value of A3) / (maximum value of A2) are approximately equal, even if balancing current A3 is generated in first shunt winding 21 in addition to current A1 during voltage regulation, first shunt winding 21 can more easily withstand these currents, thereby improving the durability of first shunt winding 21.

[0071] The maximum value of the current generated in the first shunt winding 21 (maximum value of A1 + maximum value of A3) divided by the cross-sectional area DX of the first shunt winding 21, i.e., the maximum current density generated in the first shunt winding 21 is 3 [A / mm 2 ] or less. This makes it possible to suppress the amount of heat generated in the first shunt winding 21 according to the current density even if a balancing current A3 occurs in the first shunt winding 21 in addition to the current A1 during voltage adjustment, making it easier for the first shunt winding 21 to withstand these currents and improving the durability of the first shunt winding 21.

[0072] Although the present invention has been described above based on the embodiments, it is not limited to the above-described embodiments, and it is easily understood that various improvements and modifications are possible within the scope of the present invention. For example, the values of the voltages, currents, change rates, turns ratios, etc. of the various components exemplified in the description of the above-described embodiments may be changed as appropriate.

[0073] The series transformers 11, 12 may be provided on the input side of the booster 20, rather than on the output side of the booster 20. Furthermore, a balancer 31 separate from the booster 20 may be provided on the output side of the booster 20, rather than on the input side of the booster 20. For example, the winding of the balancer 31 may connect the first boost line 3d and the second boost line 4d, or similarly, the first adjustment line 3e and the second adjustment line 4e may be connected, and the first output line 3g and the second output line 4g may be connected. Furthermore, the balancer 31 may be provided outside the voltage regulators 10, 30, at a position closer to the load R1 than the voltage regulators 10, 30.

[0074] In the above embodiment, the first branch line 3f and the second branch line 4f connected to the relays A to C, E branch off from the first adjustment line 3e and the second adjustment line 4e, respectively, on the output side of the secondary windings 11b, 12b of the series transformers 11, 12. However, this is not necessarily limited to this. For example, the first branch line 3f and the second branch line 4f may branch off from the first input line 3c and the second input line 4c, respectively, or the first branch line 3f and the second branch line 4f may branch off from the first boost line 3d and the second boost line 4d, respectively. In either case, the control unit 14 is connected to the output sides of both the booster 20 and the series transformers 11, 12.

[0075] In the above embodiment, the semiconductor relays A to E of the switching unit 13 are used to switch the connections between two of the first line 3, second line 4, and neutral line 5 and the primary windings 11a, 12a of the series transformers 11, 12, but this is not necessarily limited to this. These connections may also be switched using mechanical relays. Note that using the semiconductor relays A to E makes it possible to reduce the size and life of the switching unit 13, and to achieve noise reduction during switching.

[0076] In the above embodiment, the voltage between two of the first line 3, second line 4, and neutral line 5 is applied to the primary windings 11a, 12a of the series transformers 11, 12 via relays A to E of the switching unit 13, but this is not necessarily limited to this. For example, a transformer different from the series transformer may be connected in parallel between two of the first line 3, second line 4, and neutral line 5, and the voltage applied to the primary windings 11a, 12a may be changed by switching the taps of this transformer.

[0077] In the above embodiment, the case where the booster 20 is an autotransformer has been described, but this is not necessarily limited to this, and the booster 20 may be a compound transformer. Furthermore, the boost value by the booster 20 is not limited to being a fixed value, and the boost value may be made variable by switching taps, etc. [Explanation of symbols]

[0078] 2 Low-voltage lines (power distribution lines) 3 First Line 4. Second Line 5 Neutral conductor 6 High-voltage lines 7 Pole-mounted transformers 8 Consumer 10,30 Voltage regulator 11,12 Series transformer 11a, 12a Primary winding 11b, 12b Secondary winding 13 Switch section 14 Control Unit 20. Booster 21 1st shunt winding (shunt winding) 22 2nd shunt winding (shunt winding) 23 First series winding (series winding) 24 Second series winding (series winding) 25,31 Balancer

Claims

1. A voltage regulator connected to a single-phase three-wire distribution line consisting of a first wire, a second wire, and a neutral wire, and regulating an input voltage between the first wire and the neutral wire, and between the second wire and the neutral wire, and outputting the adjusted voltage, a pair of series transformers connected in series to the first line and the second line, respectively, so that secondary windings connect the first line and the second line, respectively; a switching unit that switches the polarity or magnitude of the voltage applied to the primary windings of the pair of series transformers and adjusts the polarity or magnitude of the induced voltage in the secondary winding; a control unit connected to the first and second wires and the neutral wire on the output side of the series transformer, and configured to control switching by the switching unit in accordance with voltages between the first and second wires and the neutral wire at the connection positions; a booster connected to the first line and the second line on the input side of the connection position of the control unit and on the input side of the series transformer, and configured to boost a voltage between the first line and the second line; A voltage regulator characterized in that the switching unit applies the voltage between two of the first line on the output side of the series transformer, the second line on the output side of the series transformer, and the neutral line to the primary winding.

2. a balancer that balances the voltages applied between the first line and the neutral line, and between the second line and the neutral line, 2. The voltage regulator of claim 1, wherein the balancer is connected to the first and second lines and the neutral line in the same position relative to the series transformer and the step-up transformer.

3. 3. A voltage regulator according to claim 2, wherein said booster and said balancer are integrally constructed.

4. A voltage regulator connected to a single-phase three-wire distribution line consisting of a first wire, a second wire, and a neutral wire, and regulating an input voltage between the first wire and the neutral wire, and between the second wire and the neutral wire, and outputting the adjusted voltage, a pair of series transformers connected in series to the first line and the second line, respectively, so that secondary windings connect the first line and the second line, respectively; a switching unit that switches the polarity or magnitude of the voltage applied to the primary windings of the pair of series transformers and adjusts the polarity or magnitude of the induced voltage in the secondary winding; a control unit connected to the first and second wires and the neutral wire on the output side of the series transformer, and configured to control switching by the switching unit in accordance with voltages between the first and second wires and the neutral wire at the connection positions; a booster connected to the first line and the second line on the input side of the connection position of the control unit, and configured to boost a voltage between the first line and the second line; a balancer that balances the voltages applied between the first line and the neutral line, and between the second line and the neutral line, The booster comprises: a pair of shunt windings that connect the first wire and the second wire to the neutral wire, respectively, to form the balancer; a pair of series windings respectively connected to the pair of shunt windings; The sum of the maximum value of the current generated in the shunt winding in response to the voltage adjustment of the voltage regulator and the rated current of the balancer divided by the cross-sectional area of the shunt winding is 3 [A / mm ２ ] or less.

5. A voltage regulation method for regulating an output voltage relative to an input voltage of a single-phase three-wire distribution line consisting of a first wire, a second wire, and a neutral wire, comprising: an adjusting step of switching the voltage applied to the primary windings of a pair of series transformers in accordance with the output voltage and adjusting the polarity or magnitude of the induced voltage generated in the secondary windings of the pair of series transformers, thereby increasing or decreasing the voltage between the first wire and the neutral wire and between the second wire and the neutral wire on the output side of the secondary windings connecting the first wire and the second wire, respectively; a boosting step of boosting the voltage between the first line and the second line on the input side of the series transformer by a booster, A voltage adjustment method characterized in that in the adjustment step, the voltage between two of the first line on the output side of the series transformer, the second line on the output side of the series transformer, and the neutral line is applied to the primary winding.

6. A voltage regulation method for regulating an output voltage relative to an input voltage of a single-phase three-wire distribution line consisting of a first wire, a second wire, and a neutral wire, comprising: an adjusting step of switching the voltage applied to the primary windings of a pair of series transformers in accordance with the output voltage and adjusting the polarity or magnitude of the induced voltage generated in the secondary windings of the pair of series transformers, thereby increasing or decreasing the voltage between the first wire and the neutral wire and between the second wire and the neutral wire on the output side of the secondary windings connecting the first wire and the second wire, respectively; a boosting step of boosting the voltage between the first line and the second line by a booster; The booster comprises: a pair of shunt windings that connect the first and second wires to the neutral wire, respectively, and form a balancer that balances the voltages applied between the first and second wires and the neutral wire, respectively; a pair of series windings respectively connected to the pair of shunt windings; The sum of the maximum value of the current generated in the shunt winding in response to the adjustment of the output voltage relative to the input voltage and the rated current of the balancer divided by the cross-sectional area of the shunt winding is 3 [A / mm ２ ] or less.

Images