JP2012125085A - Instantaneous voltage drop protection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce frequency of repetition of charging/discharging of an electrolytic capacitor, for longer life and less capacitance, even in the case being used in such country or district as voltage fluctuation of commercial AC power supply is large.SOLUTION: Only a second semiconductor switch 31 is turned on when an input AC voltage is within the range of 90-80% of nominal rating, and an AC voltage (terminal B output) provided by stepping up the input AC voltage by 10% at an auto transformer 30 is applied to a load 2. When the input AC voltage is at 110% or more of the nominal rating, only a third semiconductor switch 32 is turned on, and the AC voltage (terminal C output) provided by stepping down the input AC voltage by 10% at the auto transformer 30 is applied to the load 2. Consequently, with no use of an accumulated power in an electrolytic capacitor 17, the load 2 can be driven by an AC voltage about 90-110% of the nominal rating, with no limitation in time. When the input AC voltage drops to less than 80% of the nominal rating, all switches are turned off, to cause an inverter 18 to operate DC/AC conversion operation, and an alternate AC power is supplied to the load 2 for a short period.

Description

  The present invention relates to an instantaneous voltage drop protection device that supplies AC power to a load instead when the voltage of AC power supplied from a commercial AC power source to the load temporarily decreases or when a power failure occurs temporarily. About.

  Conventionally, when the voltage of the AC power supplied from the commercial AC power source to the load drops for a short time or when it is interrupted for a short time, an instantaneous voltage drop protection device for supplying AC power to the load instead is provided. Widely used (see, for example, Patent Documents 1 to 3).

  FIG. 4 is a schematic configuration diagram of a conventional instantaneous voltage drop protection device. The input end 11 of this apparatus is connected to the commercial AC power source 1, and the output end 12 is connected to the load 2. This device includes three types of switches, that is, a switching unit 13 in which an electromagnetic relay 14, a bidirectional thyristor 15, and a semiconductor switch 16 are connected in parallel, an electrolytic capacitor 17 that stores DC power for voltage drop protection, and an AC. / DC, DC / AC bi-directional power conversion inverter 18; filter 19 for filtering pseudo sine wave AC output composed of high-frequency rectangular wave by inverter 18; and voltage caused mainly by natural discharge of electrolytic capacitor 17 The auxiliary charging unit 20 for compensating for the decrease, the input voltage detecting unit 21 for detecting the input AC voltage (for example, 100 V), the auxiliary charging driving unit 22 for driving the auxiliary charging unit 20, and the inverter driving unit for driving the inverter 18 23, a switching drive unit 24 for switching on / off of each switch in the switching unit 13, and an input voltage detection unit 21. Based on the obtained voltage value, it comprises supplementary charging driving unit 22 according to a predetermined algorithm, inverter drive unit 23, a control unit 25 for controlling the switching drive unit 24, respectively, the. Although not shown, the inverter 18 includes a circuit in which semiconductor switching elements such as power FETs are connected in a bridge shape. In addition, the auxiliary charging unit 20 includes a transforming transformer in which input AC power is supplied to the primary winding, a rectifier circuit connected to the secondary winding of the transformer, and the like.

The basic operation of this instantaneous voltage drop protection device is as follows.
The control unit 25 constantly monitors the voltage value obtained by the input voltage detection unit 21, and when this voltage value is within a normal range, the control unit 25 turns on at least one switch in the switching unit 13 to turn on the commercial AC power supply. The AC power supplied from 1 is output as it is from the output terminal 12 and supplied to the load 2. Further, the control unit 25 causes the inverter 18 to perform AC / DC conversion (convert AC power input from the right side in FIG. 4 into DC power and output it to the left side) via the inverter drive unit 23. By operating the auxiliary charging unit 20 through the auxiliary charging driving unit 22, the electrolytic capacitor 17 is charged almost fully. Note that the proper use of each switch in the switching unit 13 is not the gist of the present application, and a description thereof will be omitted (refer to Patent Document 2 for details). Further, the proper use of the inverter 18 and the auxiliary charging unit 20 when charging the electrolytic capacitor 17 is not the gist of the present application, and thus the description thereof is omitted (refer to Patent Document 1 for details).

  When the AC voltage from the commercial AC power supply 1 decreases or a power failure occurs for a short time, and the voltage value obtained by the input voltage detection unit 21 is outside the normal range, the control unit 25 determines that the voltage value has abnormally decreased. The switching unit 13 is turned off through the switching drive unit 24 to disconnect the output end 12 from the input end 11, and the inverter 18 is connected to the inverter 18 via the inverter 18 (see FIG. 4). DC power input from the left is converted into AC power and output to the right). As a result, the DC power stored in the electrolytic capacitor 17 is converted into AC power, and the alternative AC power is supplied from the output terminal 12 to the load 2 instead of the input AC power from the commercial AC power supply 1. At this time, the voltage value of the AC voltage output from the output terminal 12 is adjusted by the pulse width of the PWM control signal supplied from the control unit 25 to the inverter drive unit 23 in order to drive each switching element in the inverter 18. The

  Assuming a general device or apparatus as the load 2, in many cases, the allowable variation lower limit of the rated input voltage is about −10%. Therefore, in the conventional instantaneous voltage drop protection device, typically, when the input AC voltage from the commercial AC power supply 1 is reduced by 10% or more from the rated input voltage (for example, 100 V), the voltage protection operation (that is, the alternative AC power The device specifications are determined so that the voltage protection can be continued for a period of about 1 second. In the case of the instantaneous voltage drop that occurs normally, the voltage recovers within one second, and after the instantaneous voltage drop occurs once, the instantaneous voltage drop again occurs before the accumulated DC power in the electrolytic capacitor 17 sufficiently recovers. It is rare. Therefore, at least for use in Japan, in many cases, problems do not occur with the above apparatus specifications.

However, the conventional instantaneous voltage drop protection device has the following problems.
That is, as described above, although the stability of the voltage of the commercial AC power supply is quite high in Japan, the fluctuation (fluctuation) of the AC voltage from the commercial AC power supply frequently occurs in some countries on a daily basis. Yes. Further, depending on the region / region in the same country, the input AC voltage fluctuates by ± 10% or more from the rated input voltage at a relatively high frequency.

  When the above instantaneous voltage drop protection device is used in such a country or region, if the input AC voltage drops more than 10% from the rated input voltage, voltage protection using the DC power stored in the electrolytic capacitor each time (alternate AC Power output) is executed. For this reason, the full charge-rapid discharge of the electrolytic capacitor occurs frequently, and the life of the electrolytic capacitor itself is shortened. Such a situation leads to a decrease in the reliability of the apparatus and increases the operating cost because it requires frequent replacement of the electrolytic capacitor.

  Naturally, after the DC power stored in the electrolytic capacitor is released due to daily voltage fluctuations that are not instantaneous voltage drops, the voltage drops due to voltage fluctuations or the actual instantaneous voltage drops again before charging is completed. When a voltage drop occurs, voltage protection over the time (for example, 1 second) defined in the device specification cannot be performed, and the operation of the load may stop. In order to avoid such a situation, it is necessary to increase the time during which voltage protection is possible by increasing the capacity of the electrolytic capacitor mounted in advance. However, the use of such a large-capacity electrolytic capacitor leads to a significant cost increase of the device.

  On the other hand, in the conventional general instantaneous voltage drop protection device, when the input AC voltage rises 10% or more from the rated input voltage, the voltage is slewed and applied to the load. Therefore, when the connected load has a function of automatically stopping the operation when the input AC voltage becomes higher than the rated input voltage by 10% or more, for example, the input AC voltage is reduced from the rated input voltage. The operation stops every time it becomes larger by 10% or more.

JP 2008-54468 A JP 2008-54483 A JP 2009-112128 A

  The present invention has been made to solve the above-described problems, and the object of the present invention is to stop the operation of the load even in a place (country, region, etc.) where the fluctuation of the AC voltage from the commercial AC power supply is large. Instantaneous voltage drop protection device that can reduce the situation as much as possible and increase the reliability of the device and reduce the operating cost and the cost of the device itself by reducing the frequency of charging and discharging of the power storage unit such as electrolytic capacitor It is to provide.

In order to solve the above problems, the present invention includes a power storage means for storing DC power, and charging the power storage means by converting AC power supplied from a commercial AC power source into DC power. Bi-directional inverter means for converting DC power discharged from the means into AC power, and when the AC voltage supplied from the commercial AC power source to the load temporarily decreases, In the instantaneous voltage drop protection device that supplies the AC power to the load by the bidirectional inverter means by using the stored DC power,
a) A voltage for taking out the first AC voltage obtained by boosting the input AC voltage by a predetermined ratio and the second AC voltage obtained by stepping down the input AC voltage by a predetermined ratio using the input AC voltage supplied from the commercial AC power supply as an input. Adjusting means;
b) Select one of the input AC voltage, the first AC voltage by the voltage adjusting unit, the second AC voltage by the voltage adjusting unit, and the alternative AC voltage generated by DC / AC conversion by the bidirectional inverter unit Switching means for outputting to
c) Detecting the input AC voltage, whether the voltage is lower than a first determination voltage lower than a rated input voltage, whether it is lower than a second determination voltage lower than the first determination voltage, and a rated input Input voltage determination means for determining whether or not the voltage is lower than a third determination voltage higher than the voltage;
d) When the input voltage determination means determines that the input AC voltage is greater than or equal to the first determination voltage and lower than the third determination voltage, the input AC voltage is output to the load, and the input AC voltage is greater than the first determination voltage. If the input AC voltage is determined to be equal to or higher than the third determination voltage, the second AC voltage is output to the load. When the input AC voltage is determined to be lower than the second determination voltage, the switching means and the bidirectional inverter means are controlled to operate the bidirectional inverter means and output alternative AC power to the load. Control means;
It is characterized by having.

  The rated input voltage is a standard value of the input AC voltage that is defined so that the apparatus operates normally, and is usually the center value of the allowable fluctuation range. Generally, it is 100V or 200V in Japan, 110V, 220V, 240V etc. outside the country.

  The voltage adjusting means can be configured to use an autotransformer, for example.

  Further, for example, the first determination voltage is a voltage that is about -10% lower than the rated input voltage (that is, a voltage that is about 90% of the rated input voltage), and the second determination voltage is -15 to -25% with respect to the rated input voltage. Low voltage (that is, a predetermined voltage within a range of about 75 to 85% of the rated input voltage), and the third determination voltage is about 10% higher than the rated input voltage (that is, a voltage of about 110% of the rated input voltage). It is good to set to. That is, when the rated input voltage is 100 V, the first determination voltage is preferably about 90 V, the second determination voltage is about 75 to 85 V, and the third determination voltage is about 110 V. The voltage adjusting means may be a voltage obtained by boosting the input AC voltage by about 10 to 15% as the first AC voltage, and a voltage obtained by stepping down the input AC voltage by about 10 to 15% as the second AC voltage.

  In the instantaneous voltage drop protection device according to the present invention, even if the input AC voltage supplied from the commercial AC power source is lower than the first determination voltage, if the second determination voltage is exceeded, the bidirectional inverter means does not operate, The DC power stored in the power storage means is not used. At this time, the first AC voltage obtained by boosting the input AC voltage voltage by the voltage adjusting unit is selected by the switching unit and output to the load. As a result, the output voltage is raised by an amount higher than the input AC voltage. On the other hand, when the input AC voltage supplied from the commercial AC power source becomes equal to or higher than the third determination voltage, the second AC voltage obtained by stepping down the input AC voltage by the voltage adjusting unit is selected by the switching unit and output to the load. Is done. As a result, the output voltage becomes lower than the input AC voltage by the step-down amount. As a result, even when an input voltage fluctuation that is larger than the third determination voltage or an input voltage fluctuation that is smaller than the first determination voltage occurs, the load is not affected by the voltage fluctuation. On the other hand, it is possible to continue supplying an AC voltage that allows the operation of the load.

  On the other hand, when the input AC voltage is lower than the second determination voltage, there is a high possibility that an instantaneous voltage drop or a power failure occurs, not a mere voltage fluctuation. Therefore, in this case, the control unit causes the bidirectional inverter unit to perform a DC / AC conversion operation to generate alternative AC power using DC power stored in the power storage unit. At the same time, the switching means cuts off the supply line of the input AC voltage, the first AC voltage, and the second AC voltage, and supplies the alternative AC voltage by the bidirectional inverter means to the load. This is the same as the supply of alternative AC power in the conventional instantaneous voltage drop protection device.

  According to the instantaneous voltage drop protection device of the present invention, when the AC voltage supplied from the commercial AC power source drops to, for example, about 75 to 90% of the rated input voltage, the instantaneous voltage using the stored power of the power storage means. It is possible to continue supplying power to the load so that the load can be normally operated by using a voltage fluctuation compensation function such as an autotransformer instead of the drop protection. Moreover, even when the AC voltage supplied from the commercial AC power source rises to, for example, about 110 to 130% of the rated input voltage, the voltage fluctuation compensation function is used to continue supplying power that allows the load to operate normally. be able to. Thereby, even if it is a case where it is used in the place where the voltage fluctuation | variation of commercial alternating current power supply is large, the situation which leads to the driving | operation stop of a load can be reduced.

  Further, according to the instantaneous voltage drop protection device according to the present invention, it is possible to avoid discharge from the power storage means due to daily voltage fluctuations, so that the frequency of discharge of the power storage means and subsequent full charge is reduced. be able to. As a result, the life of the power storage means, such as an electrolytic capacitor, whose performance is deteriorated by repeated charging and discharging, can be extended, and the reliability of the apparatus can be improved. Moreover, the frequency of replacement of the means accompanying the deterioration of the power storage means can be reduced, and the operating cost can be reduced.

  Furthermore, according to the instantaneous voltage drop protection device according to the present invention, since the frequency of discharging of the power storage means for supplying the alternative AC power is reduced as described above, the power storage means is used when the instantaneous voltage drop actually occurs. The situation where the battery is not fully charged can be reduced. Therefore, it is not necessary to increase the capacity of the power storage means in order to always maintain excessive DC power, and necessary and sufficient voltage protection can be provided while using a relatively small capacity power storage means. Thereby, the apparatus cost can be reduced.

1 is a schematic block configuration diagram of an instantaneous voltage drop protection device according to an embodiment of the present invention. The operation | movement flowchart in the instantaneous voltage drop protective device of a present Example. Explanatory drawing of the operation | movement at the time of the input voltage fluctuation | variation in the instantaneous voltage drop protective device of a present Example. The schematic block block diagram of one Example of the conventional instantaneous voltage drop protection apparatus.

Hereinafter, an embodiment of an instantaneous voltage drop protection device according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic block diagram of an instantaneous voltage drop protection device according to this embodiment. The same components as those of the conventional device of FIG. 4 already described are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 1, in the instantaneous voltage drop protection device of the present embodiment, the switching unit 13 corresponding to the switching unit 13 of the conventional device shown in FIG. In addition to the bidirectional thyristor 15 and the first semiconductor switch 16, a second semiconductor switch 31 and a third semiconductor switch 32 having one end connected in common are included. Between the input terminal 11 and the switching unit 13, an autotransformer 30 corresponding to the voltage adjusting means in the present invention is disposed. The autotransformer 30 has a terminal A to which the input AC voltage applied to the input terminal 11 is applied as it is, a terminal B that outputs a voltage boosted by 10% with respect to the input AC voltage applied to the terminal A, And a terminal C that outputs a voltage 10% lower than the input AC voltage applied to the terminal A. One end of the bidirectional thyristor 15 and the first semiconductor switch 16 is connected to the terminal A of the autotransformer 30, one end of the second semiconductor switch 31 is connected to the terminal B of the autotransformer 30, and one end of the third semiconductor switch 32 is connected to the autotransformer 30. It is connected to the terminal C of the transformer 30. The electromagnetic relay 14, the bidirectional thyristor 15, and the first to third semiconductor switches 16, 31, and 32 included in the switching unit 13 are each turned on / off (conducting / non-conducting) by a control signal supplied from the switching driving unit 33. Is switched.

  The control unit 40 that receives the voltage value information detected by the input voltage detection unit 21 and controls the inverter driving unit 23 and the switching driving unit 33, respectively, includes an input voltage determination unit 41, an inverter control unit 42, a switching control unit 43, and the like. Is included as a functional block. The control unit 40 is mainly configured by a microcomputer including a CPU, ROM, RAM, and the like, and the functions of the functional blocks are achieved by executing a control program stored in advance in the ROM. In this embodiment, the input voltage detection unit 21 and the input voltage determination unit 41 correspond to the input voltage determination unit in the present invention, and the inverter control unit 42 and the switching control unit 43 correspond to the control unit in the present invention.

  FIG. 2 is an operation flowchart in the instantaneous voltage drop protection device of this embodiment, and FIG. 3 is an explanatory diagram of the voltage protection operation in the instantaneous voltage drop protection device of this embodiment. 3A is an input AC voltage input from the commercial AC power source 1 to the input terminal 11, and FIG. 3B is an output corresponding to the input AC voltage shown in FIG. AC voltage output from the end 12, (c) is, for example, AC voltage output from the output end 12 with respect to the input AC voltage shown in FIG. 4A in the conventional instantaneous voltage drop protection device shown in FIG. Is schematically shown.

  The characteristic operation of the instantaneous voltage drop protection device of this embodiment shown in FIG. 1 will be described with reference to FIGS. Here, the case where the rated input voltage is 100 V will be described with specific voltage values. However, the rated input voltage is not limited to this, and may be an appropriate value such as 110 V, 200 V, 220 V, or 240 V, for example. It is natural.

  The operation shown in the flow chart of FIG. That is, in the control unit 40, the input voltage determination unit 41 reads the voltage value information of the input AC voltage given to the input terminal 11 from the input voltage detection unit 21 at that time (step S1), and the voltage value is the rated input voltage. It is determined whether or not the voltage is 110V, which is 110% (corresponding to the third determination voltage in the present invention) or more (step S2). If it is determined No in step S2, then, the voltage value is less than 90V (corresponding to the first determination voltage in the present invention) which is 90% of the rated input voltage and 80V (80% of the rated input voltage). It is determined whether it is equal to or higher than the second determination voltage in the present invention (step S3). If it is determined No in step S3, it is next determined whether or not the voltage value is less than 80V (corresponding to the second determination voltage as described above) that is 80% of the rated input voltage (step S4). ).

  If it is determined No in steps S2, S3, and S4, the input AC voltage is in the range of 90V to 110V, which is 90% to 110% of the rated input voltage (step S5). . Therefore, in this case, it is determined that the supply of AC power from the commercial AC power supply 1 is normal, and the switching control unit 43 receives the first semiconductor switch 16 and the bidirectional thyristor of the switching unit 13 via the switching drive unit 33. 15. Any one or more of the electromagnetic relays 14 are turned on. As a result, the voltage applied to the terminal A of the autotransformer 30, that is, the AC power supplied from the commercial AC power source 1 to the input terminal 11 is directly passed to the output terminal 12, and the input AC voltage (however, the switching unit 13 is switched on). (Except for the voltage drop due to the passage) is supplied to the load 2 (step S6).

  In this case, as shown in [A] and [D] of FIG. 3B, the AC voltage supplied to the load 2 fluctuates by ± 10% at the maximum from the rated input voltage according to the fluctuation of the input AC voltage. In general, the allowable range of input voltage fluctuations of various devices as the load 2 is about ± 10% of the rated input voltage, and even if the AC voltage output from the device fluctuates about 10% as described above, the load There is no hindrance to driving 2. Of course, if it is known that a load having a narrower allowable range of input voltage fluctuation (for example, within ± 5%) is used, the determination criterion in the input voltage determination unit 41 may be changed.

  Further, in the control unit 40, the inverter control unit 42 monitors the charging voltage of the electrolytic capacitor 17 by a charging voltage detection unit (not shown), and in order to quickly charge the electrolytic capacitor 17 when the charging voltage is lower than a predetermined voltage. The inverter 18 is operated via the inverter drive unit 23 to convert the input AC power into DC power and charge the electrolytic capacitor 17. When the decrease in the charging voltage of the electrolytic capacitor 17 is a small decrease due to spontaneous discharge, the auxiliary charging unit 20 performs a relatively slow charging instead of the rapid charging by the AC / DC conversion operation of the inverter 18. . This is the same as before. When the input AC power is supplied by such charging, the electrolytic capacitor 17 is maintained in a fully charged state.

  When the input AC voltage drops to a voltage in the range of 80V or more and less than 90V due to voltage fluctuation, it is determined Yes in step S3, and the switching control unit 43 switches the second semiconductor switch 31 of the switching unit 13 via the switching drive unit 33. The switch is turned on and the other switches are turned off. As a result, the terminal B of the autotransformer 30 and the output terminal 12 are connected via the second semiconductor switch 31 and an AC voltage boosted by 10% from the input AC voltage is applied to the load 2 (step S8). For example, when the input AC voltage drops to 85 V, an AC voltage of about 93.5 V appears at the terminal B of the autotransformer 30, and this is applied from the output terminal 12 to the load 2. That is, when the input AC voltage is 80% or more and less than 90% of the rated input voltage, as shown in [B] of FIG. 3B, the AC voltage obtained by raising the input AC voltage by 10% is loaded. 2 is applied.

  Similarly, when the input AC voltage rises to 110 V or more due to voltage fluctuation, it is determined Yes in step S2, and the switching control unit 43 sets the third semiconductor switch 32 of the switching unit 13 to the conductive state via the switching drive unit 33, and so on. The switch is turned off. As a result, the terminal C of the autotransformer 30 and the output terminal 12 are connected via the third semiconductor switch 32, and an AC voltage that is 10% lower than the input AC voltage is applied to the load 2 (step S7). For example, when the input AC voltage rises to 115 V, an AC voltage of about 103.5 V appears at the terminal C of the autotransformer 30, and this is applied to the load 2 from the output terminal 12. That is, when the input AC voltage is 110% or more of the rated input voltage, an AC voltage obtained by reducing the input AC voltage by 10% is applied to the load 2 as shown in [E] of FIG. Is done.

  As described above, when the input AC voltage is in the range of 80% to less than 90% of the rated input voltage and 110% or more, the DC power stored in the electrolytic capacitor 17 and the inverter 18 are not used. The AC power is continuously supplied to the load 2 so that the operation of the load 2 is continued without any problem. Therefore, the operation of the load 2 does not stop even in a place where the voltage fluctuation in the commercial AC power supply 1 is relatively large.

  On the other hand, when the input AC voltage drops below 80 V, it is determined Yes in step S4, and the instantaneous voltage drop protection operation similar to that of the conventional device is executed (step S9). That is, the switching control unit 43 turns off all the switches of the switching unit 13 via the switching drive unit 33 and disconnects the output end 12 from the input end 11, that is, from the commercial AC power supply 1 and the autotransformer 30. At substantially the same time, the inverter control unit 42 generates alternative AC power that becomes the target AC voltage (for example, 90% of the rated input voltage) using the DC power held in the electrolytic capacitor 17 via the inverter driving unit 23. In order to do so, the inverter 18 is caused to perform a DC / AC conversion operation. Thereby, instead of the input AC power or the output voltage of the autotransformer 30, alternative AC power is supplied from the electrolytic capacitor 17, the inverter 18, and the filter 19 to the load 2 via the output terminal 12. Therefore, as shown in [C] of FIG. 3B, even if the input AC voltage drops below 80% of the rated input voltage due to the instantaneous voltage drop or instantaneous interruption, the AC voltage output to the load 2 is, for example, rated It is maintained at 90% of the input voltage. However, since the DC power stored in the electrolytic capacitor 17 is consumed at this time, the AC power is supplied to the load 2 only for a time corresponding to the DC power amount, for example, for a period of about 0.5 to 1 second. become.

  If the input AC voltage recovers to 80 V or more from the state where the input AC voltage has decreased to less than 80 V as described above, at least one switch of the switching unit 13 is turned on, and the input AC voltage or the autotransformer as described above. The AC voltage boosted or lowered at 30 is supplied to the load 2.

  As shown in FIG. 3C, in the conventional instantaneous voltage drop protection device, when the input AC voltage drops below 90% of the rated input voltage, the alternative AC using the DC power held in the electrolytic capacitor 17 immediately. Electric power is supplied. Therefore, for example, when the fluctuation (fluctuation) of the input AC voltage is large (± 10% or more), the electrolytic capacitor 17 is frequently discharged and charged. Also, if the instantaneous voltage drop occurs immediately after the accumulated power of the electrolytic capacitor 17 is reduced or zero (before charging) due to fluctuations in the input AC voltage, voltage protection cannot be performed and the load 2 is immediately applied. Will be stopped.

  On the other hand, in the instantaneous voltage drop protection device of the present embodiment, the accumulated power of the electrolytic capacitor 17 is rarely used for input AC voltage fluctuations other than the instantaneous voltage drop and power failure. Therefore, frequent discharge / charging of the electrolytic capacitor 17 is not performed, and therefore the life of the electrolytic capacitor 17 can be extended. Further, there is a low possibility that voltage protection cannot be performed when the instantaneous voltage drops, and the capacity of the electrolytic capacitor 17 can be reduced, so that the device cost can be reduced.

It should be noted that the above embodiment is an example of the present invention, and it is obvious that modifications, corrections and additions may be made as appropriate within the scope of the present invention, and included in the claims of the present application.
For example, the values of 90%, 80%, and 110% mentioned in the above embodiment, that is, the values of the first to third determination voltages, the voltage increase rate and the voltage decrease rate of the autotransformer 30 such as + 10% and −10%. The numerical value is merely an example, and it is natural that the numerical value can be appropriately changed according to the device specification in consideration of the use environment and the purpose.

DESCRIPTION OF SYMBOLS 1 ... Commercial AC power supply 2 ... Load 11 ... Input end 12 ... Output end 13 ... Switching part 14 ... Electromagnetic relay 15 ... Bidirectional thyristor 16 ... First semiconductor switch 17 ... Electrolytic capacitor 18 ... Inverter 19 ... Filter 20 ... Auxiliary charging part DESCRIPTION OF SYMBOLS 21 ... Input voltage detection part 22 ... Supplementary charge drive part 23 ... Inverter drive part 24 ... Switching drive part 25 ... Control part 30 ... Autotransformer 31 ... 2nd semiconductor switch 32 ... 3rd semiconductor switch 33 ... Switching drive part 40 ... Control Unit 41 ... Input voltage determination unit 42 ... Inverter control unit 43 ... Switching control unit

Claims (2)

A power storage means for storing DC power, and an AC power supplied from a commercial AC power source are converted into DC power to charge the power storage means, and a DC power discharged from the power storage means is converted into AC power. And when the AC voltage supplied from the commercial AC power supply to the load temporarily drops, the bidirectional inverter is used instead of the DC power stored in the power storage means. In the instantaneous voltage drop protection device that supplies AC power to the load by means,
a) A voltage for taking out the first AC voltage obtained by boosting the input AC voltage by a predetermined ratio and the second AC voltage obtained by stepping down the input AC voltage by a predetermined ratio using the input AC voltage supplied from the commercial AC power supply as an input. Adjusting means;
b) Select one of the input AC voltage, the first AC voltage by the voltage adjusting unit, the second AC voltage by the voltage adjusting unit, and the alternative AC voltage generated by DC / AC conversion by the bidirectional inverter unit Switching means for outputting to
c) Detecting the input AC voltage, whether the voltage is lower than a first determination voltage lower than a rated input voltage, whether it is lower than a second determination voltage lower than the first determination voltage, and a rated input Input voltage determination means for determining whether or not the voltage is lower than a third determination voltage higher than the voltage;
d) When the input voltage determination means determines that the input AC voltage is greater than or equal to the first determination voltage and lower than the third determination voltage, the input AC voltage is output to the load, and the input AC voltage is greater than the first determination voltage. If the input AC voltage is determined to be equal to or higher than the third determination voltage, the second AC voltage is output to the load. When the input AC voltage is determined to be lower than the second determination voltage, the switching means and the bidirectional inverter means are controlled to operate the bidirectional inverter means and output alternative AC power to the load. Control means;
An instantaneous voltage drop protection device comprising: The instantaneous voltage drop protection device according to claim 1,
The voltage regulation means uses an autotransformer, and the instantaneous voltage drop protection device.

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