JP2008306889A - Uninterruptible power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an excessive rush current from flowing to a load when switching the power supply from ON to OFF and vice versa at power failure. <P>SOLUTION: Direct power supply is performed when a voltage of the input AC power is normal (S3), but at that time, output voltage values are measured for every n seconds to store them in a memory (S4). When there arises abnormality in an input voltage due to the instantaneous voltage drop or the like, a commercial AC power supply is cut off from the load, and electrical energy stored in an electrolytic capacitor is converted by an inverter to AC from DC so that it can be supplied to the load as compensation AC power (S6, S7), but the output voltage is controlled so as to coincide with a voltage value stored in the memory at a normal time through inverter control (S9). As a result, even if there is a variation in the voltage of the AC power supply, the voltage output to the load can be maintained nearly constant when switching the power supply from the direct power supply to the inverter power supply and vice versa the rush current caused by a potential difference can be prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides instantaneous voltage drop protection for supplying AC power to a load instead when the voltage of AC power supplied to the load from an external AC power supply temporarily decreases or when a power failure occurs temporarily. The present invention relates to an uninterruptible power supply such as a device.

  Conventionally, when the voltage of AC power supplied to a load from a 100V or 200V commercial AC power supply is reduced for a short time or when it is interrupted for a short time, instantaneous voltage drop protection is provided to supply AC power to the load instead. The device is widely used. For example, the apparatus described in Patent Document 1 includes an initial charging circuit including a step-up transformer and a diode rectifier, and an inverter unit that performs AC / DC mutual conversion, and AC power from a commercial AC power supply is normally supplied. In this state, the initial charging circuit is charged until the charging voltage of the electrolytic capacitor rises to some extent, and thereafter, the inverter is operated to convert AC power to DC and charge the electrolytic capacitor to the rated voltage. To do. When the voltage of the AC power from the commercial AC power supply instantaneously drops, the AC power supply is disconnected from the load by the thyristor, and the electric energy stored in the electrolytic capacitor is converted to AC power by the inverter and supplied to the load. I have to.

  Such instantaneous voltage drop protection devices are often used in large-scale facilities such as factories, but in such facilities, the power wiring connecting the power supply source and each instantaneous voltage drop protection device is very long, or Since many loads may be connected, the voltage of the AC power supplied in each instantaneous voltage drop protection device is often considerably varied. Specifically, voltage drop becomes a problem at a location away from the power supply source, so by raising the voltage in advance at the power supply source in advance, a sufficient voltage can be secured at the load even at a remote location. In this case, the voltage is considerably high in the instantaneous voltage drop protection device installed near the power supply source.

  Therefore, for example, when the AC voltage at the input of the instantaneous voltage drop protection device is 220V, which is 10% higher than the standard 200V, for example, an AC voltage of 220V is applied to the load in a normal state, and the compensated AC power is reduced by the instantaneous voltage drop. The voltage drops from 220V to about 200V when switching to, and the voltage suddenly increases from about 200V to 220V when the instantaneous voltage drop is resolved and the switching from the compensated AC power to the AC power. In particular, when the voltage rises, an excessive inrush current may flow through the load due to the voltage difference, which may cause a load failure or malfunction.

JP 2000-152519 A

  The present invention has been made in view of the above problems, and an object of the present invention is to prevent the occurrence of an inrush current at the time of power switching even when the variation in the voltage of the supplied AC power is large. Another object is to provide an uninterruptible power supply including an instantaneous voltage drop protection device.

The present invention, which has been made to solve the above-mentioned problems, is provided with power storage means for storing electrical energy based on electric power when AC power is supplied from an external AC power source, and is supplied from the AC power source to a load. Detecting means for detecting that the voltage of the AC power has decreased, and compensating AC power using electric energy stored in the power storage means instead of the AC power by the AC power source according to the detection result by the detecting means. In the uninterruptible power supply comprising the power conversion means for supplying to the load,
a) voltage monitoring means for monitoring and storing the voltage value of the AC power supplied to the load when the AC power is normally supplied from the AC power source;
b) The power conversion means so as to adjust the voltage value of the compensated AC power according to the voltage value stored by the voltage monitoring means when outputting the compensated AC power instead of the AC power from the AC power supply. Control means for controlling
It is characterized by having.

  As one aspect of the uninterruptible power supply according to the present invention, the power conversion means includes an inverter circuit that converts DC power stored in the power storage means into AC power, and the control means outputs an output voltage value by the inverter circuit. Can be configured to perform inverter drive control so as to match the voltage value stored by the voltage monitoring means.

  In the uninterruptible power supply according to the present invention, the voltage monitoring unit monitors and stores the voltage value of the AC power supplied from the AC power source to the load at predetermined time intervals, for example. When the AC power from the AC power source is temporarily interrupted or a voltage drop occurs, the power conversion means converts the DC electric energy stored in the power storage means into AC power and loads it as compensated AC power. However, the control means controls the operation of the power conversion means so that the voltage value of the compensated AC power matches the voltage value stored by the voltage monitoring means.

  If the voltage value used as a reference at this time is too old in time, it cannot respond to voltage fluctuations of the AC power supply, and conversely, if it is too close in time, it is affected by an instantaneous drop or the like. there is a possibility. Therefore, it is preferable to use the voltage value obtained by the voltage monitoring means at a time point several seconds after the switching time to the compensated AC power.

  According to the uninterruptible power supply according to the present invention, when the power supplied to the load is switched from the AC power from the external AC power source to the internal compensated AC power due to the instantaneous drop or the like, the voltage difference is almost generated. Absent. In particular, the instantaneous voltage drop protection device has a relatively short compensation time, so the AC power supply voltage difference between before and after the voltage sag is negligible. After that, there is almost no voltage difference when the power supplied to the load is switched from the compensated AC power to the AC power derived from the external AC power source. As a result, it is possible to prevent an excessively large current from flowing into the load at the time of switching of the supplied power, and it is possible to avoid a failure of a device connected as a load.

  An instantaneous voltage drop protection device according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic block diagram of an instantaneous voltage drop protection device according to this embodiment.

  This instantaneous voltage drop protection device protects when the voltage of AC power supplied from the 100V or 200V commercial AC power supply 1 to the load 20 temporarily drops (for example, about 1 second at the maximum). is there. In FIG. 1, AC power supplied from an external commercial AC power source 1 passes through a switching unit 2 in which a FET switch (usually a power MOSFET) 21 and a bidirectional thyristor 22 for overcurrent protection are connected in parallel. The AC power is supplied to the load 20 and further input to the inverter unit 4 including a plurality of switching elements. The FET switch 21 and the bidirectional thyristor 22 are independently controlled to be turned on / off by a drive signal supplied from the switching drive unit 15.

  A power storage unit 5 comprising an electrolytic capacitor 51 is connected to the inverter unit 4 corresponding to the power conversion means in the present invention, and the inverter unit 4 converts AC power into DC to charge the electrolytic capacitor 51, or conversely, electrolysis The electric energy held by the capacitor 51 has a function of DC / AC conversion. In the latter case, the high frequency component superimposed on the AC power is removed by the filter 7 including an inductance and a capacitor.

  Similarly, in order to charge the electrolytic capacitor 51 of the power storage unit 5, the transformer 61, the bidirectional thyristor 62 connected in series to the primary side winding of the transformer 61, and the rectification connected to the secondary side winding of the transformer 61. The auxiliary charging unit 6 including a diode 63, a capacitor 64, a resistor 65, and the like is provided. The electrolytic capacitor 51 can be charged from either the inverter unit 4 or the auxiliary charging unit 6. The bidirectional thyristor 62 of the auxiliary charging unit 6 is controlled to be turned on / off by a drive signal given by the auxiliary charging drive unit 12. Each switching element of the inverter unit 4 is controlled to be turned on / off by a drive signal given by the inverter drive unit 14.

  The input voltage detection unit 11 monitors the amplitude (peak value or effective value) of the voltage of the AC power supplied from the commercial AC power supply 1 and gives the amplitude value to the control unit 10. The charging voltage detection unit 13 detects the charging voltage held in the electrolytic capacitor 51 and inputs the voltage value to the control unit 10. The output voltage detection unit 17 corresponding to the voltage monitoring means in the present invention detects an AC output voltage applied from the apparatus to the load 20 and inputs the amplitude (peak value or effective value) of the voltage to the control unit 10. . Further, the load current supplied from the apparatus to the load 20 is detected by the current transformer 3 and the load current detector 16, and the current value is input to the controller 10. The control unit 10 is configured mainly with a CPU, RAM, ROM, and the like, and executes various controls and processes described later according to a control program stored in advance.

  Next, the power compensation operation in the instantaneous voltage drop protection device of this embodiment will be described with reference to FIGS. FIG. 2 is a flowchart of control and processing operations centered on the control unit 10, and FIG. 3 is a diagram showing an example of an output voltage waveform (a) and an output current waveform (b) from the instantaneous voltage drop protection device of this embodiment. is there. In FIG. 3, the waveform indicated by the dotted line is for the conventional apparatus, and the waveform indicated by the solid line is for the apparatus of this embodiment. 2 is repeatedly executed during the operation of the present apparatus.

  The control unit 10 measures the voltage value of the input AC power by the input voltage detection unit 11 at predetermined time intervals (step S1). Here, the voltage value may be a peak value or an effective value. Next, it is determined whether or not the voltage value obtained by the measurement is within a predetermined normal value range (step S2). If the voltage value is normal, direct power feeding is performed to the load 20 (step S3). . Specifically, the FET switch 21 of the switching unit 2 is turned on via the switching drive unit 15, and the AC power supplied from the commercial AC power supply 1 is output as it is and applied to the load 20. Moreover, the control part 10 measures the voltage value of the alternating current power supplied to the load 20 by the output voltage detection part 17 every n second, and memorize | stores this value in internal memory (step S4). Here, n is 1, for example, that is, the output voltage value can be measured and stored at intervals of 1 second.

  At this time, the electrolytic capacitor 51 is charged based on the commercial AC power, and electric energy is stored in the electrolytic capacitor 51. Here, the charging procedure of the electrolytic capacitor 51 will be described. That is, when the voltage value detected by the charging voltage detection unit 13 is equal to or less than the first predetermined value V1, the control unit 10 operates the inverter unit 4 via the inverter driving unit 14, and the inverter unit 4 performs alternating current. DC electric energy obtained by DC conversion is stored in the electrolytic capacitor 51. At this time, the bidirectional thyristor 62 is turned off and the auxiliary charging unit 6 is not operated. When the voltage value detected by the charging voltage detection unit 13 reaches the rated voltage Vf (Vf> V1), the operation of the inverter unit 4 is stopped and the charging operation is stopped.

  Even when the switching element of the inverter unit 4 is in the OFF state, the electric energy of the electrolytic capacitor 51 charged to the rated voltage Vf is gradually reduced by natural discharge. Therefore, when the charging voltage decreases due to spontaneous discharge and the voltage value decreases to a second predetermined value V2 (normally V1 <V2 <Vf), this is calculated based on the voltage value detected by the charging voltage detector 13. The recognized control unit 10 causes the bidirectional thyristor 62 to conduct through the auxiliary charging drive unit 12. Then, a current from the commercial AC power source 1 flows in the primary side winding of the transformer 61 and a predetermined AC voltage is generated at both ends of the secondary side winding. This voltage is converted into a direct current by the rectifying diode 63 and starts to charge the electrolytic capacitor 51 via the resistor 65. At this time, the inverter unit 4 is not operated, and the charging voltage of the electrolytic capacitor 51 starts to be recovered only by the auxiliary charging unit 6. When the voltage value detected by the charging voltage detection unit 13 reaches the rated voltage Vf, the operation of the auxiliary charging unit 6 is stopped and the charging operation is stopped.

  Returning to FIG. If the voltage temporarily decreases or the power supply is temporarily cut off due to an abnormality in the power supply of the power supplier, the input voltage deviates from the normal range in step S2, that is, is abnormal. It is determined that a voltage drop has occurred, and the control unit 10 selects inverter power supply instead of direct power supply (step S6).

  That is, the FET switch 21 of the switching unit 2 is turned off via the switching drive unit 15 to disconnect the load 20 from the commercial AC power supply 1. At the same time, the inverter unit 4 is operated by the inverter drive unit 14, and the voltage held in the electrolytic capacitor 51 until immediately before is DC / AC converted, the waveform is shaped via the filter 7, and compensated AC power is supplied to the load 20. (Step S7). The control unit 10 reads out the output voltage value of m seconds before stored in the normal state from the internal memory (step S8). Here, m is, for example, 5, that is, the voltage value stored 5 seconds ago can be used. Then, the voltage value of the compensated AC power supplied to the load 20 at that time is measured by the output voltage detection unit 17, and a difference between the measured voltage value and the read past voltage value is obtained, and the difference is zero. The inverter drive unit 14 is controlled so as to become (step S9).

  For example, assuming that the voltage of the AC power supplied from the commercial AC power supply 1 is 220V, which is higher than the standard 200V, as shown in FIG. Decreases from 220V to about 200V. On the other hand, in the instantaneous voltage drop protection device according to the present embodiment, the voltage value is maintained at about 220 V even when the direct power supply is switched to the inverter power supply by performing the control and processing as described above. That is, there is almost no voltage difference before and after the transition.

  When the voltage drop of the AC power of the commercial AC power supply 1 is resolved, it is determined as “Y” in Step S <b> 2, so the control unit 10 performs a return from the inverter power supply to the direct power supply. That is, the control unit 10 stops the operation of the inverter unit 4 to stop supplying the compensated AC power, and then immediately connects the commercial AC power source 1 and the load 20 by the switching unit 2, Begins to be supplied to the load 20. Thereby, even if the voltage of the commercial AC power supply 1 temporarily decreases, AC power can be continuously supplied to the load 20 almost without interruption.

  Usually, the time that can be compensated by this instantaneous voltage drop protection device is about 1 second (or about 10 seconds at the longest). Therefore, the voltage value of the AC voltage of the commercial AC power supply 1 is almost the same immediately before the occurrence of the voltage drop and immediately after the recovery from the voltage drop. Therefore, the voltage value when switching from inverter power supply to direct power supply is maintained at approximately 220V. That is, there is almost no voltage difference before and after this transition. In this way, the voltage of the AC power is maintained substantially constant even when the power supply to the load 20 is switched from direct power supply to inverter power supply to direct power supply.

  As shown by the dotted line in FIG. 3, in the case of a conventional device, when the voltage changes from, for example, 220V → about 200V → 220V, the output current decreases at the time of the change from 220V → about 200V, to about 200V → 220V. At the time of the change, the output current suddenly increases, and there is a risk of a so-called inrush current to the load 20. On the other hand, in the instantaneous voltage drop protection device of this embodiment, since the voltage value hardly changes, there is almost no change in current, and an excessive inrush current is prevented from flowing so as to cause a failure of the load 20. be able to.

  The above-described embodiment is an example of the present invention, and it is a matter of course that modifications, corrections, and additions may be appropriately made within the scope of the present invention, and included in the scope of the claims of the present application. For example, the above embodiment has been described with respect to an instantaneous voltage drop protection device that temporarily supplies power by using electric energy stored in a capacitor, but the present invention uses, for example, electric energy stored in a storage battery, It is obvious that the present invention can be generally applied to an uninterruptible power supply that supplies power for a longer time.

1 is a schematic block diagram of an instantaneous voltage drop protection device according to an embodiment of the present invention. The flowchart of control and processing operation centering on a control part. The figure which shows an example of the output voltage waveform (a) and the output current waveform (b) from the instantaneous voltage drop protective device of a present Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Commercial alternating current power supply 2 ... Switching part 21 ... FET switch 22 ... Bidirectional thyristor 3 ... Current transformer 4 ... Inverter part 5 ... Power storage part 51 ... Electrolytic capacitor 6 ... Supplementary charging part 61 ... Transformer 62 ... Bidirectional thyristor 63 ... Rectification Diode 64 ... Capacitor 65 ... Resistor 7 ... Filter 10 ... Control unit 11 ... Input voltage detection unit 12 ... Supplementary charge drive unit 13 ... Charge voltage detection unit 14 ... Inverter drive unit 15 ... Switching drive unit 16 ... Load current detection unit 17 ... Output voltage detector 20 ... Load

Claims (2)

Power storage means for storing electrical energy based on the electric power when AC power is supplied from an external AC power supply, and detection means for detecting that the voltage of the AC power supplied from the AC power supply to the load has decreased. An uninterruptible power supply comprising: power conversion means for supplying compensated AC power to a load using electrical energy stored in the power storage means instead of AC power from the AC power source according to a detection result by the detection means In power supply,
a) voltage monitoring means for monitoring and storing the voltage value of the AC power supplied to the load when the AC power is normally supplied from the AC power source;
b) The power conversion means so as to adjust the voltage value of the compensated AC power according to the voltage value stored by the voltage monitoring means when outputting the compensated AC power instead of the AC power from the AC power supply. Control means for controlling
An uninterruptible power supply comprising:   The power conversion means includes an inverter circuit that converts DC power stored in the power storage means into AC power, and the control means matches an output voltage value of the inverter circuit with a voltage value stored by the voltage monitoring means. The uninterruptible power supply according to claim 1, wherein inverter drive control is performed.

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