JP2013179778A - Voltage regulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of a voltage regulating device which includes a tap switching portion by suppressing current during tap switching by controlling the timing of the tap switching.SOLUTION: A voltage regulating device includes an autotransformer 18 having a plurality of taps 4 and 5 provided symmetrically about a neutral point 7, first and second tap switching portions 19a and 19b which are connected to the autotransformer 18 and have the same configuration, and a control unit 12 which controls the tap switching portions. Each of the tap switching portions includes a switch 20 which connects one of the plurality of taps 4 and 5 to the neutral point 7, and a voltage sensor 11 which detects voltage between one end (d) of the autotransformer 18 and the neutral point 7. The control unit 12 independently controls the switches 20 and 20' to change the tap in timing (one of t2, t4, t6, ...) where currents flowing through the switches 20, 20' are close to 0 when voltages detected by the voltage sensors 11 and 11' are equal to or higher than a first reference voltage or when the voltages are equal to or lower than a second reference voltage lower than the first reference voltage.

Description

  The present invention relates to a voltage regulator used for voltage regulation of a distribution system.

  Many distributed power sources represented by photovoltaic power generation have been linked to the distribution system, and voltage fluctuations in the distribution system due to the distributed power source have become a problem. In particular, the Electricity Business Law defines the voltage value to be maintained according to the standard voltage, and in order to cope with this, the primary side tap of the pole transformer is changed manually or automatically to adjust the voltage, Side voltage must be maintained.

  In addition, since these pole transformers are often installed in general residential areas, they are required to be small and light in terms of landscape and installation space.

  For example, Patent Document 1 discloses a method in which a plurality of taps are provided on the primary side of the autotransformer, and the taps are automatically switched according to the voltage on the secondary side. Patent document 2 is disclosing the apparatus comprised from the shunt transformer and the series transformer provided with two series windings and excitation windings with equal induced voltage.

Japanese Patent No. 4224309 Japanese Patent No. 3938903

  In the tap switching as described above, a large current may flow to the electrical conduction portion of the switching mechanism portion when switching the tap depending on the timing at which the secondary side voltage is detected and the tap switching command is output. Therefore, the electrical conduction portion of the switching mechanism portion needs to have characteristics that can withstand the large current. Also, in order to protect the tap switching mechanism from the large current that occurs when switching taps, it is necessary to temporarily connect a resistor to suppress the current when switching taps, and the tap switching mechanism is complex and large. The entire device is also large.

  The embodiment of the present invention aims to suppress the current at the time of tap switching and to reduce the size of the tap switching mechanism by controlling the tap switching timing as described above.

    In order to solve the above-described problem, a voltage regulator according to an embodiment of the present invention includes a self-winding transformer having a plurality of taps provided symmetrically with respect to a neutral point, and the self-winding transformer. And a control unit that controls the tap switching unit, and each tap switching unit selects one of the plurality of taps as the neutral point. A voltage sensor for detecting a voltage between one end of the autotransformer and the neutral point, and between the one end of the autotransformer and the neutral point, and Different loads are connected between the other end of the transformer and the neutral point, and the control unit detects when the voltage detected by each voltage sensor exceeds the first reference voltage or the first reference voltage. When the voltage falls below the lower second reference voltage, the current flowing through the switch There taps to independently control switches so each switch at a timing near 0. In addition, the voltage regulator according to the embodiment of the present invention controls the tap switching timing to a time point within ± 30 ° before and after the zero cross point of the excitation current.

  In the voltage regulator of the distribution system, by controlling the tap switching timing, it is possible to suppress the current at the time of tap switching and to reduce the size of the tap switching mechanism.

It is a figure which shows the structure of a solar energy power generation system as an example of a system with which 1st Embodiment of this invention is applied. It is a block diagram which shows the structural example of the tap switching mechanism part of FIG. It is a figure which shows operation | movement of the 1st tap switching part 19a at the time of giving a hysteresis to switching. It is a figure which shows the correlation (50Hz multiplication) of the voltage of a transformer, and an iron core excitation characteristic. It is a figure which shows the structural example which implement | achieves the circuit which detects a voltage zero cross point with an operational amplifier circuit. It is a block diagram which shows the other structural example of the solar power generation system to which the exciting current suppression type low voltage regulator 2 '(18, 19) which concerns on this invention is applied.

  Hereinafter, an excitation current suppression type low voltage regulator according to an embodiment will be described with reference to the drawings.

  FIG. 1 shows a configuration of a photovoltaic power generation system as an example of a system to which an embodiment of the present invention is applied. A predetermined AC voltage, for example, a commercial AC voltage 6600 V, is applied to the primary side winding 17 of the single-phase three-wire transformer 11, and the output terminals a and b of the secondary side winding of the single-phase three-wire transformer 11. The primary side of the autotransformer 18 is connected to the secondary side terminals d and e of the autotransformer 18, and the loads 13 and 14 and the AC terminal of the inverter 15 of the photovoltaic power generation system are connected to the primary side.

  The autotransformer 18 includes series windings 18a and 18a ′, secondary terminals d and e, and tapped shunt windings 18b and 18b ′. The taps of the shunt windings 18b and 18b ′ include: A tap switching mechanism 19 is connected. The DC side terminal of the inverter 15 is connected to the solar cell 16, and the AC side terminal is connected to the series circuit of the loads 13 and 14 and the terminals d and e. The solar cell 16 includes a solar panel and a capacitor or a battery.

  The inverter 15 converts the DC power generated by the solar panel (solar cell) 16 into AC and supplies the AC voltage to the load circuit of the loads 13 and 14 and the secondary terminals d and e of the autotransformer 18. The loads 13 and 14 are, for example, electric products that are used in ordinary households and operate at 100 V AC. The autotransformer 18 and the tap switching mechanism 19 constitute an excitation current suppression type low voltage regulator 2.

  FIG. 2 is a block diagram illustrating a configuration example of the voltage regulator 2 of FIG.

  The autotransformer 18 is connected to the secondary terminals d and e through the secondary line wires 3 and 3 ′, and is further connected to the loads 13 and 14. One voltage detection terminal of each of the control unit 12 and the voltage sensors 11 and 11 ′ is connected to the secondary terminals d and e. The other voltage detection terminals of the voltage sensors 11 and 11 ′ are connected to a neutral wire (neutral point) 7, and the neutral wire 7 is connected to loads 13 and 14. The neutral line 7 is a neutral point of the load voltage V1 + V2.

  The contactor 10 of the switch 20 is connected to the tap 5 of the shunt winding 18 a, the contactor 9 is connected to the tap 4, and the common terminal 8 is connected to the neutral wire 7. Similarly, the contactor 10 ′ of the switch 20 ′ is connected to the tap 5 ′ of the shunt winding 18 b, the contactor 9 ′ is connected to the tap 4 ′, and the common terminal 8 ′ is connected to the neutral wire 7. The taps 4, 5, 4 ', 5' are provided symmetrically with respect to the neutral line 7, that is, the neutral point. The number of taps provided in each shunt winding is not limited to two as in this example, but may be three or more.

  Next, the operation of the voltage regulator 2 according to the present embodiment will be described in detail.

  In FIG. 2, the operation of the upper circuit (first tap switching means) 19a including the series winding 18a, the shunt winding 18b, the switch 20, and the voltage sensor 11 includes the series winding 18a ′, the shunt winding 18b ′, The operation is the same as that of the lower circuit (second tap switching means) 19b including the switch 20 ′ and the voltage sensor 11 ′. For the sake of simplicity, only the operation of the upper circuit will be described here except for the case where both circuits are specifically described.

  The controller 12 controls the switching operation of the switch 20 based on the load voltage V1 of the secondary side line detected by the voltage sensor 11. That is, when the load voltage V1 becomes higher than the initially set reference voltage, the control unit 12 switches the switch 20 from the tap 4 side to the 5 side to decrease the number of shunt windings and lower the voltage. When the voltage V1 becomes lower than the initially set reference voltage, the control unit 12 switches the switch 20 from the tap 5 side to the 4 side to increase the number of shunt lines and increase the voltage.

  The reference voltage for switching is preferably set so that the reference voltage for switching to the tap 5 side and the reference voltage for switching to the tap 4 side are different from each other in order to give hysteresis to the switching. For example, the first reference voltage when switching to the tap 5 side is set to 105V, and the second reference voltage switching to the tap 4 side is set to 100V lower than the first reference voltage.

  FIG. 3 is a diagram illustrating the operation of the first tap switching unit 19a when switching is given hysteresis in this way. When the load voltage V1 reaches the first reference voltage or becomes equal to or higher than the first reference voltage as at time T1, the control unit 12 controls the switch 20 to switch the connection tap to the tap 5 side. When the load voltage V1 decreases to the second reference voltage or becomes equal to or lower than the second reference voltage as at time T2, the control unit 12 controls the switch 20 to switch the connection tap to the tap 4 side. The operation of the second tap switching unit 19b is the same as that of the first tap switching unit 19a. Note that the switching operation of the switches 20 and 20 'is performed independently according to the voltages V1 and V2 detected by the voltage sensors 11 and 11', and does not need to be performed simultaneously.

  FIG. 4 is a diagram for explaining the correlation between the voltage of the transformer and the iron core excitation characteristics (in the case of 50 Hz) and the timing for switching the switch 20.

The solid line waveform is detected voltage value (the secondary side load voltage) V1, the broken line waveform of voltage sensor 11 showing the excitation current I ₀ flowing through the switch 20. The controller 12 switches the switch 20 based on the detected voltage value V1 before and after the zero cross point (t2, t4, t6, t8...) At which the excitation current I ₀ becomes 0 (phase angle ± 30 °). Within the range). Thereby, it is possible to suppress a large excitation current at the time of tap switching that occurs by switching the tap. Further, since a large current does not flow through the contactors 9 and 10 in FIG. 2, the contactor can be downsized and the entire low voltage regulator can be reduced in size and weight.

  As described above, the voltage regulator according to the present invention includes the autotransformer 18 having a plurality of taps provided symmetrically with respect to the neutral point, and the first configuration having the same configuration connected to the autotransformer. 1 and the 2nd tap switch part 19a, 19b, and the control part 12 which controls this tap switch part, and each tap switch part sets one of the said some taps 4 and 5 to the said neutral point 7 And a voltage sensor 11 for detecting a voltage between one end d of the autotransformer 18 and the neutral point 7. Different loads 13 and 14 are connected between one end d of the autotransformer 18 and the neutral point 7 and between the other end e of the autotransformer and the neutral point 7, respectively. When the voltage detected by each of the voltage sensors 11, 11 ′ becomes equal to or higher than the first reference voltage or equal to or lower than the second reference voltage lower than the first reference voltage, the unit 12 switches the switches 20, 20 The switches are controlled independently so that the taps are switched at a timing when the current flowing through 'is near zero.

  Next, a specific example of a timing adjustment method for switching the switch 20 will be described.

The excitation current I ₀ is generated with a phase angle delayed by 90 ° with respect to the secondary load voltage V 1 of the apparatus shown in FIG. Therefore, as shown in FIG. 4, the vicinity of the zero cross point (any one of t1, t3, t5, t7...) Of the secondary side load voltage V1 is detected, and the phase angle is increased by 90 °, 270 °, and thereafter 180 ° from that point. every zero point of the excitation current _{I 0 (t2, t4, t6} , t8 ...) is present. When the commercial frequency is 50 Hz, since one cycle is 20 ms (= 1 / frequency), 5 ms (90 °), 15 ms (270 °) from the zero point detection of the secondary load voltage V1, and thereafter 10 ms (180 °) A large current in the contactor can be prevented by switching the switch within a range of ± 1.7 ms (30 °) at any time of addition.

  Also, if it is within the range of 30 °, since sin 30 ° = 0.5, a current capacity that is ½ of the maximum peak current is sufficient. This time adjustment unit is incorporated in the control unit 12 of FIG.

As described above, in the voltage regulator according to the present invention, the tap switching timing is within the phase angle of ± 30 ° before and after the zero cross point of the excitation current I ₀ . That is, the tap switching timing is a time within a phase angle of ± 30 ° before and after the time when the phase is delayed by 90 ° from the zero cross point of the voltage detected by the voltage sensor 11 or 11 ′.

Next, a configuration for detecting the zero point of the excitation current I ₀ will be described. As described above, the excitation current I ₀ is generated with a phase delay of 90 ° with respect to the secondary load voltage V 1 of the apparatus. Therefore, the voltage zero cross point is detected by a circuit using an operational amplifier based on the correlation between the voltage V1 and the current I ₀ , and then the phase angle of the zero cross point of the excitation current I ₀ is within ± 30 ° by the delay circuit. The switch 20 in FIG. 2 is switched.

FIG. 5 shows a configuration example in which a circuit for detecting a voltage zero cross point is realized by an operational amplifier circuit. This voltage zero cross point detection circuit is a voltage zero cross point where the secondary voltage Vs of the transformer VT to which the voltage V1 is input to the primary side changes from minus to plus, and the output voltage of the operational amplifier 6 is from H level to L level. To fall. The control unit 12 calculates the zero cross point of the exciting current I ₀ and switches the switch 20 based on the detected voltage value of the voltage sensor 11, for example, based on the falling point.

  The detection of the voltage zero cross point can be realized not only in this embodiment but also by a digital circuit using a microcomputer or the like.

The iron core of the single-winding transformer composed of the series winding 18a including the tapped shunt winding 18b of FIG. 2 increases the magnetic flux density of the iron core by reducing the iron core shape in order to reduce the size. In the conventional one, a large current also temporarily flows as the excitation current I ₀ generated when the tap of the shunt winding is switched. However, by adjusting the timing of switching the switches 20, 20 '2 according to the embodiment, to reduce the excitation current I ₀ at the time of switching the tap, small things become applicable iron core shape, the low voltage regulator Miniaturization can be achieved.

  The same effect can be obtained even if the switch used in the above embodiment is constituted by not only an electromagnetic contactor but also a power semiconductor such as GTO or IGBT.

Next, a second embodiment will be described.
FIG. 6 is a block diagram showing another configuration example of the photovoltaic power generation system to which the excitation current suppression type low voltage regulator 2 ′ (18, 19) according to the present invention is applied. The same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The voltage adjusting device 2 ′ includes the configuration shown in FIG. 2, that is, the series winding 18 including the shunt windings 18 a and 18 b and the tap switching mechanism 19. A predetermined AC voltage is applied to the terminals a and b of the series winding 18, and this system operates in the same manner as the system of FIG.

  Compared with the voltage regulator 2 according to the first embodiment of FIG. 1, the voltage regulator 2 ′ according to the second embodiment omits the single-phase three-wire transformer 11, so that the system can be further reduced in size, Light weight can be realized.

  As described above, according to the present invention, the tap is switched at a timing at which the excitation current generated when the tap of the single-turn transformer shunt winding is switched becomes smaller (around 0) than in the prior art. As a result, it is possible to provide a low voltage regulator capable of reducing the size of the contactor and further reducing the size of the iron core of the single-phase three-wire autotransformer. In addition, the low voltage regulator can be provided at low cost by downsizing the low voltage regulator, for example, to reduce facility construction costs by connecting to the high voltage distribution system with the spread of general household solar power generation. Can contribute.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. Moreover, although the example which applied this invention to the power transmission / distribution system of the solar power generation system was shown in the said embodiment, it is not restricted to this, Power transmission / distribution of the system using natural energy, such as wind power generation, or other power generation systems which are not used It can also be applied to systems. The novel embodiments described above can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  2 ... Voltage regulator 3, 3 '... Secondary line 4, 4' 5, 5 '... Tap, 6 ... Operational amplifier, 9, 10 ... Contactor, 20, 20' ... Switch, 7 ... Neutral wire, DESCRIPTION OF SYMBOLS 11, 11 '... Voltage sensor, 12 ... Control part, 18a, 18a' ... Series winding, 18b, 18b '... Shunt winding, 19 ... Tap switching mechanism, VT ... Transformer, R ... Resistor, D ... diode.

Claims (3)

A self-winding transformer having a plurality of taps provided symmetrically with respect to the neutral point, first and second tap switching sections connected to the single-winding transformer and having the same configuration, and the tap switching section A control unit for controlling,
Each tap switching unit includes a switch that connects one of the plurality of taps to the neutral point, and a voltage sensor that detects a voltage between one end of the autotransformer and the neutral point, Different loads are connected between one end of the autotransformer and the neutral point, and between the other end of the autotransformer and the neutral point,
When the voltage detected by each of the voltage sensors becomes equal to or higher than the first reference voltage or equal to or lower than the second reference voltage lower than the first reference voltage, the current flowing through the switch is near zero. A voltage regulator that controls each of the switches independently so that the taps are switched at the timing.   2. The voltage regulator according to claim 1, wherein the tap switching timing is a time point within a phase angle of ± 30 ° before and after the zero cross point of the excitation current.   2. The voltage adjustment according to claim 1, wherein the tap switching timing is a time within a phase angle of ± 30 ° before and after the time when the phase is delayed by 90 ° from the zero cross point of the voltage detected by the voltage sensor. apparatus.

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