JP2005176460A - Uninterruptible power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the output voltage constant without use of a tap changing mechanism, even when power failure occurs or the supply voltage fluctuates. <P>SOLUTION: An uninterruptible power supply unit comprises a transformer 1, having an intermediate tap 1a; a rectifier 2, a smoothing capacitor 3, and an inverter 4 connected with a secondary winding 1B of the transformer, in this order; a charging/discharging circuit 6 and a battery 7; an alternating current filter 5 placed on the output side of the inverter 4; a control circuit 8 for the inverter 4; a change-over switch 10; and a power failure monitoring circuit 9 that gives a discharge command to the charging/discharging circuit 6 and changes the setting of the change-over switch 10 to the side of one end of the primary winding 1A, when power failure occurs. At non-power interruption, a constant voltage obtained by superposing the voltage of a capacitor 5b of the alternating current filter 5 on the voltage, generated by the intermediate tap 1a to compensate fluctuation in supply voltage, is supplied to a load. In power failure, the output voltage of the inverter 4 that uses the battery 7 as a power source is supplied to the load. The position of the intermediate tap 1a is so set that the voltage generated by the intermediate tap 1a is lower than the set value of output voltage at all times. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an uninterruptible power supply capable of supplying a constant AC voltage to a load regardless of the state of the AC power supply such as voltage fluctuation or power failure.

  As a device intended to keep the output voltage constant even when the AC power supply voltage fluctuates, for example, a static voltage regulator described in FIGS. 9 to 11 is known. These voltage regulators are described in Patent Document 1 described later.

All of the voltage regulators shown in FIG. 9 to FIG. 11 transform the AC power supply voltage by the regulating transformer 30 having the tap switching mechanism 31 (32 in FIG. 11), and between the regulating transformer 30 and the load. The voltage which added the both-ends voltage of the secondary winding of the series transformer 40 inserted in series and the output voltage of the adjustment transformer 30 is supplied as a load voltage. And while adjusting the transformation ratio of the adjustment transformer 30 by the tap switching mechanism 31 (32), and adjusting the primary side voltage and therefore the secondary side voltage of the series transformer 40 by the voltage adjustment circuit 50, the AC power supply voltage is adjusted. It compensates for fluctuations and keeps the output voltage supplied to the load constant.
9 to 11, reference numerals 60 and 61 denote current detectors, and reference numerals 70 and 71 denote voltage detectors.

On the other hand, for example, Patent Document 2 discloses a transformer in which a mechanical voltage adjustment mechanism by tap switching as described above is made static and an output voltage supplied to a load is kept constant even when a power supply voltage fluctuates. ing.
In this prior art, the voltage of the capacitor connected in series to the primary winding or the secondary winding of the transformer is operated by the operation of the power supply device such as an inverter, so that the load connected to the secondary winding. The supply voltage is kept constant.

JP-A-8-126203 (FIGS. 1, 3, and 5) JP-A-11-136945 (FIGS. 1 and 3)

In the voltage regulator according to Patent Document 1, the output voltage is kept constant with respect to a wide range of power supply voltage fluctuations by using both tap switching of the transformer for adjustment and voltage compensation by the series transformer and the voltage regulator circuit. Has the ability.
However, it does not have a function to keep the output voltage constant when an open circuit or short circuit occurs on the power supply side (power failure), and the circuit configuration uses a plurality of transformers and at least one transformer. Since the transformer has a tap switching mechanism, there is a problem that the circuit scale is large and the price is expensive.

  On the other hand, according to the transformer according to Patent Document 2, the above-described problem associated with the tap switching mechanism is solved, but as with Patent Document 1, a constant voltage is supplied to the load even when a power failure occurs. A specific circuit configuration is not disclosed.

  Accordingly, the present invention is intended to solve the above problems and to provide an uninterruptible power supply that can keep the output voltage constant without using a tap switching mechanism and also at the time of a power failure or when the power supply voltage fluctuates significantly. Is.

In order to solve the above problems, the invention described in claim 1 is directed to a transformer in which an AC power supply voltage is applied to a primary winding having an intermediate tap, and the secondary connected to a secondary winding of the transformer. A rectifier for rectifying an AC voltage generated in the winding, a smoothing capacitor connected to the output side of the rectifier, an inverter connected to the smoothing capacitor and converting a DC voltage of the smoothing capacitor to an AC voltage, and the smoothing capacitor A charging / discharging circuit connected to the battery, a battery connected to the charging / discharging circuit to be charged / discharged, and a reactor and a capacitor connected to the output side of the inverter to remove high-frequency pulsation components of the AC output voltage, An AC filter in which this capacitor is connected in series between the intermediate tap and the load, a control circuit that controls the output voltage of the inverter, and the AC filter. A switching switch for switching a connection destination of one end on the non-load side of the capacitor constituting the capacitor to one of the intermediate tap and one end of the primary winding, and an AC power supply voltage, and the charge / discharge circuit in the event of a power failure And a power failure monitoring circuit that switches the changeover switch to the intermediate tap side, gives a discharge command to the charge / discharge circuit when a power failure occurs, and switches the changeover switch to one end side of the primary winding. ,
When the AC power supply is not interrupted, a constant voltage that compensates for fluctuations in the power supply voltage is supplied to the load by superimposing the voltage of the capacitor constituting the filter on the voltage generated by the intermediate tap. An uninterruptible power supply that supplies a constant voltage output by the inverter with a power supply source to the load,
The position of the intermediate tap is set so that the voltage generated by the intermediate tap is always lower than the output voltage setting value supplied to the load.

According to a second aspect of the present invention, in the uninterruptible power supply according to the first aspect, the rectifier is constituted by a forward series connection circuit of two diodes, and the smoothing capacitor is formed by two capacitors. In addition to the series connection circuit, these series connection circuits are connected in parallel.
A series connection point of the two diodes and a series connection point of the two capacitors are respectively connected to both ends of the secondary winding, and both ends of the series connection circuit of the two capacitors are connected to the DC input of the inverter. And connecting the series connection point of the two capacitors to one end on the load side of the capacitor constituting the filter, and connecting the output terminal of the inverter to the non-capacitor side of the reactor constituting the filter It is connected to one end of.

  The invention described in claim 3 is the uninterruptible power supply device described in claim 1, wherein the rectifier is configured by connecting two sets of forward series connection circuits of two diodes in parallel, and the forward series. Each series connection point in the connection circuit is connected to both ends of the secondary winding.

According to a fourth aspect of the present invention, in the uninterruptible power supply according to the first or third aspect, the smoothing capacitor is configured by a series connection circuit of two capacitors, and the inverter includes a free wheel diode. It is constituted by a series connection circuit of two switching elements composed of self-extinguishing semiconductor elements connected in reverse parallel,
The series connection point of the two capacitors is connected to one end on the load side of the capacitor constituting the filter, and the output terminal of the inverter is connected to one end on the non-capacitor side of the reactor constituting the filter It is.

  According to a fifth aspect of the present invention, in the uninterruptible power supply according to the first or third aspect of the present invention, the inverter is composed of two switching elements composed of self-extinguishing semiconductor elements each having a free-wheeling diode connected in reverse parallel. Two series connection circuits are connected in parallel, and each series connection point in the series connection circuit of two switching elements is connected to one end on the load side of the capacitor constituting the filter and one end on the non-capacitor side of the reactor. And connected respectively.

  According to the present invention configured as described above, in the event of a non-power failure, the voltage fluctuation of the intermediate tap of the transformer caused by the fluctuation of the AC power supply voltage is detected by the voltage of the capacitor of the AC filter connected to the output side of the inverter. By compensating for the output voltage, the output voltage supplied to the load can be kept constant. In addition, by setting the intermediate tap so that the voltage of the intermediate tap is always small with respect to a certain output voltage setting value supplied to the load, the inverter can always be operated in the direction of increasing the voltage. Rectifiers can be constructed using inexpensive diodes rather than expensive self-extinguishing elements. Further, since an AC filter is used as a circuit element for compensating voltage fluctuations instead of the series transformer shown in Patent Document 1, the number of transformers is reduced as a whole device, the circuit scale is reduced, and the cost is reduced. Can be achieved.

  When a power failure occurs or the power supply voltage fluctuates, the power switch is switched by the operation of the power failure monitoring circuit to disconnect the transformer side from the circuit, and the power of the battery charged during a non-power failure is supplied to the smoothing capacitor by the charge / discharge circuit The DC voltage of the smoothing capacitor can be converted into a constant AC voltage by the inverter and supplied to the load.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a circuit diagram showing a first embodiment of the present invention. Both terminals of a primary winding 1A of a transformer 1 are connected to input terminals 90a and 90b to which an AC power supply voltage is input, respectively. Both terminals 1b and 1c of 1B are connected to the AC input side of the rectifier 2.

A smoothing capacitor 3 is connected between both terminals on the DC output side of the rectifier 2, and both ends thereof are connected to a DC input terminal of the inverter 4. Reference numeral 8 denotes a control circuit for the inverter 4.
A battery 7 is connected to both ends of the smoothing capacitor 3 via a charge / discharge circuit 6.

  Reference numeral 10 denotes a changeover switch, one of which is connected to the intermediate tap 1a of the primary winding 1A, and the other switch contact 10b is connected to the input terminal 90b and the output terminal 91b. The common contact 10c is connected to an interconnection point between the reactor 5a and the capacitor 5b constituting the AC filter 5 for removing the high frequency pulsation component of the AC output voltage.

Both terminals on the AC output side of the inverter 4 are connected to one end on the non-capacitor side of the reactor 5a and one end on the load side of the capacitor 5b, and one end on the load side of the capacitor 5b is connected to the output terminal 91a. . Although not shown, a load is connected to the output terminals 91a and 91b.
Further, reference numeral 9 denotes a power failure monitoring circuit for the AC power supply. The power failure monitoring circuit 9 outputs control signals for the charge / discharge circuit 6 and the changeover switch 10. Note that the power failure monitoring circuit 9 can output not only the power failure of the AC power supply but also the fact that the AC power supply voltage has fluctuated significantly and output the control signal.

Next, the operation of this embodiment will be described.
First, FIG. 2 is a circuit diagram when no power failure occurs, and FIG. 3 is a circuit diagram when a power failure occurs. In this embodiment, since the change-over switch 10 is in the state shown in FIG. 1 when there is no power failure, the circuit of FIG. 2 is substantially configured. Further, when a power failure occurs or when the power supply voltage greatly fluctuates, the contacts 10b and 10c of the changeover switch 10 are connected by a control signal from the power failure monitoring circuit 9 in order to respond in the same way as at the time of the power failure. The circuit is configured.
For the convenience of explanation, among the circuit elements shown in FIG. 1, circuit elements that are not involved in the flow of power in FIG. 2 (when no power failure occurs) and FIG. 3 (when a power failure occurs) are not shown.

First, the operation at the time of non-power failure will be described with reference to FIGS.
In FIG. 2, an AC voltage is supplied to the primary winding 1A of the transformer 1, and a voltage lower than the power supply voltage is generated at one end of the capacitor 5b of the filter 5 through the intermediate tap 1a. The load connected to the output terminals 91a and 91b is supplied with a voltage V _out (V _out = V _in + V _c ) obtained by superimposing the voltage V _c across the capacitor 5b on the voltage V _in of the intermediate tap 1a. FIG. 4 shows these voltage waveform diagrams.

Here, the output voltage of the power conversion circuit configured by the secondary winding 1B of the transformer 1, the rectifier 2, the smoothing capacitor 3, the inverter 4, and the AC filter 5 is equal to the voltage V _c across the capacitor 5b. the variation of the voltage V _in the intermediate tap 1a of the transformer 1 due to the fluctuation of the AC power supply voltage, if compensated by voltage V _c of the capacitor 5b, which is the output voltage of the power conversion circuit, the output voltage V to be supplied to the load _out can be kept constant.

At this time, for a constant preset output voltage supplied to the load, by providing an intermediate tap 1a in a position such that the voltage V _in of the intermediate tap 1a is always less, a direction for increasing constantly voltage power conversion circuit ( In the direction of supplying power to the capacitor 5b side). In that case, the rectifier 2 can be constituted by a diode, and an effect that the price of the rectifier 2 can be reduced as compared with the case of using a self-extinguishing semiconductor element is produced. At the same time, the charging / discharging circuit 6 connected to the output side of the rectifier 2 can be operated as a charging circuit 6c as shown in FIG. 2, and the battery 7 can be charged with the electric power supplied from the AC power supply.
Furthermore, in this embodiment, since the AC filter 5 is used instead of the series transformer as shown in Patent Document 1, it is effective for reducing the number of transformers and reducing the circuit scale as the entire apparatus. .

Next, the operation when a power failure occurs will be described with reference to FIG.
When a power failure occurs or when a large fluctuation occurs in the power supply voltage, the changeover switch 10 is switched by a control signal from the power failure monitoring circuit 9 to substantially configure the circuit of FIG. 3, and the charge / discharge circuit 6 of FIG. By operating as 6d, the power of the battery 7 is supplied to the smoothing capacitor 3.
The inverter 4 converts the DC voltage of the smoothing capacitor 3 into an AC voltage, and supplies a constant voltage across the capacitor 5b constituting the filter 5 to the load as an output voltage.

  FIG. 5 is a circuit diagram showing a second embodiment of the present invention. FIG. 5 shows the configuration at the time of non-power failure as in FIG. 2, and the present embodiment also includes the control circuit 8, the power failure monitoring circuit 9, and the changeover switch 10 in FIG. These circuit elements not involved in the power flow are not shown.

In the present embodiment, as shown in FIG. 5, the rectifier 2 is configured by connecting diodes 2 a and 2 b in series in the forward direction, the smoothing capacitor 3 is configured by connecting capacitors 3 a and 3 b in series, and the inverter 4 is an IGBT. Switching elements 4a and 4b composed of an antiparallel circuit of a self-extinguishing semiconductor element such as a free-wheeling diode are connected in series.
The terminals 1b and 1c of the secondary winding 1B of the transformer 1 are respectively connected to the series connection point of the diodes 2a and 2b and the series connection point of the capacitors 3a and 3b, and both ends of the AC filter 5 are connected to the capacitors 3a and 3b. 3b is connected to the series connection point and the series connection points of the switching elements 4a and 4b.

In the above configuration, the rectifier 2 operates as a well-known half-bridge rectifier, and converts the AC voltage between the terminals 1b and 1c of the secondary winding 1B of the transformer 1 into the DC voltage of the capacitors 3a and 3b. Since detailed operation waveforms of the half-bridge type rectifier are known, the description thereof is omitted.
The inverter 4 operates as a well-known half-bridge type inverter, converts the DC voltage of the capacitors 3a and 3b into an AC voltage, and generates it at both ends of the capacitor 5b of the AC filter 5. Since detailed operation waveforms and the like of the half-bridge type inverter are also known, description thereof will be omitted.

Also in this embodiment, the output voltage V _out supplied to the load can be kept constant by compensating for the fluctuation of the voltage V _in of the intermediate tap 1a of the transformer 1 during a non-power failure by the voltage V _{c of the} capacitor 5b. it can.
The circuit configuration and operation when a power failure occurs is that the smoothing capacitor 3 in FIG. 3 is configured by a series circuit of capacitors 3a and 3b, and the inverter 4 is configured by a series circuit of switching elements 4a and 4b as a half-bridge inverter. Except for this point, the inverter 4 is basically the same as FIG. 3, and the inverter 4 converts the DC voltage of the smoothing capacitor 3 into an AC voltage and supplies it to the load while keeping the voltage across the capacitor 5b constant.

  FIG. 6 is a circuit diagram showing a third embodiment of the present invention, and shows a state at the time of non-power failure as in FIG. Also in FIG. 6, the illustration of the control circuit 8, the power failure monitoring circuit 9, and the changeover switch 10 that are not involved in the power flow during a non-power failure is omitted.

The third embodiment is different from the second embodiment of FIG. 5 only in that the rectifier 2 is configured as a full bridge type by the diodes 2a, 2b, 2c, and 2d. Terminals 1b and 1c of line 1B are connected to a series connection point of diodes 2a and 2b and a series connection point of diodes 2c and 2d, respectively. Detailed operation waveforms and the like of the full bridge rectifier are well known, and thus description thereof is omitted.
Note that the basic operation is the same as in the first and second embodiments both when there is no power outage and when a power outage occurs.

  FIG. 7 is a circuit diagram showing a fourth embodiment of the present invention, and shows a state when there is no power failure as in FIGS. 5 and 6. Also in FIG. 7, illustration of the control circuit 8, the power failure monitoring circuit 9, and the changeover switch 10 that are not involved in the power flow at the time of non-power failure is omitted.

The fourth embodiment is different from the second embodiment of FIG. 5 only in that the inverter 4 is configured as a full bridge type by the switching elements 4a, 4b, 4c, and 4d. The switching elements 4a and 4b are connected to the series connection point and the switching elements 4c and 4d, respectively.
The detailed operation waveform of the full-bridge inverter is well known, and the description thereof is omitted.
The basic operation of the present embodiment is the same as that of the first to third embodiments both when there is no power outage and when a power outage occurs.

  FIG. 8 is a circuit diagram showing a fifth embodiment of the present invention, and shows a state at the time of non-power failure as in FIGS. Also in FIG. 8, illustration of the control circuit 8, the power failure monitoring circuit 9, and the changeover switch 10 that are not involved in the power flow during a non-power failure is omitted.

This fifth embodiment differs from the first embodiment of FIG. 2 in that the rectifier 2 is configured as a full bridge type by the diodes 2a, 2b, 2c, and 2d, and the inverter 4 is the switching elements 4a, 4b, 4c, The terminal 1b, 1c of the secondary winding 1B of the transformer 1 is connected to the series connection point of the diodes 2a, 2b and the series connection point of the diodes 2c, 2d, respectively. Both ends of the AC filter 5 are connected to the series connection point of the switching elements 4a and 4b and the series connection point of the switching elements 4c and 4d, respectively.
Detailed operation waveforms of the full-bridge rectifier and the full-bridge inverter are well known, and thus description thereof is omitted.
The basic operation of the present embodiment is the same as that of the above-described embodiments both when a power failure occurs and when a power failure occurs.

  Also in the third to fifth embodiments, the circuit configuration at the time of occurrence of each power failure is substantially the same as that in FIG. 3, and the inverter 4 is the fourth and fifth embodiments as a half-bridge type inverter in the third embodiment. In the form, it operates as a full bridge type inverter.

1 is a circuit diagram showing a first embodiment of the present invention. It is a circuit diagram at the time of the non-power failure in 1st Embodiment. It is a circuit diagram at the time of the power failure generation in 1st Embodiment. FIG. 3 is a voltage waveform diagram of each part in FIG. 2. It is a circuit diagram at the time of the non-power failure in 2nd Embodiment of this invention. It is a circuit diagram at the time of the non-power failure in 3rd Embodiment of this invention. It is a circuit diagram at the time of the non-power failure in 4th Embodiment of this invention. It is a circuit diagram at the time of the non-power failure in 5th Embodiment of this invention. It is a circuit diagram which shows a prior art. It is a circuit diagram which shows a prior art. It is a circuit diagram which shows a prior art.

Explanation of symbols

1: Transformer 1A: Primary winding 1B: Secondary winding 1a: Intermediate tap 2: Rectifier 2a, 2b: Diode 3: Smoothing capacitor 3a, 3b: Capacitor 4: Inverter 4a, 4b: Switching element 5: AC filter 5a : Reactor 5b: Capacitor 6: Charge / discharge circuit (6c: Charge circuit, 6d: Discharge circuit)
7: Battery 8: Control circuit 9: Power failure monitoring circuit 10: Changeover switch 10a, 10b, 10c: Contact 90a, 90b: Input terminal 91a, 91b: Output terminal

Claims (5)

A transformer in which an AC power supply voltage is applied to a primary winding having an intermediate tap;
A rectifier connected to the secondary winding of the transformer and rectifying an AC voltage generated in the secondary winding;
A smoothing capacitor connected to the output side of this rectifier,
An inverter connected to the smoothing capacitor to convert the DC voltage of the smoothing capacitor into an AC voltage;
A charge / discharge circuit connected to the smoothing capacitor;
A battery connected to the charge / discharge circuit and charged / discharged;
An AC filter connected to the output side of the inverter to remove a high-frequency pulsation component of the AC output voltage and a capacitor, and this capacitor is connected in series between the intermediate tap and a load;
A control circuit for controlling the output voltage of the inverter;
A changeover switch that switches the connection destination of one end on the non-load side of the capacitor constituting the AC filter to either the intermediate tap or one end of the primary winding;
The AC power supply voltage is monitored, a charge command is given to the charge / discharge circuit when there is no power failure, and the changeover switch is switched to the intermediate tap side, and a discharge command is given to the charge / discharge circuit when a power failure occurs and A power failure monitoring circuit that switches to one end of the winding;
With
When the AC power supply is not interrupted, a constant voltage that compensates for fluctuations in the power supply voltage is supplied to the load by superimposing the voltage of the capacitor constituting the filter on the voltage generated by the intermediate tap. An uninterruptible power supply that supplies a constant voltage output by the inverter with a power supply source to the load,
The uninterruptible power supply, wherein the position of the intermediate tap is set so that the voltage generated by the intermediate tap is always lower than the output voltage setting value supplied to the load. In the uninterruptible power supply device according to claim 1,
The rectifier is constituted by a forward series connection circuit of two diodes, and the smoothing capacitor is constituted by a series connection circuit of two capacitors, and these series connection circuits are connected in parallel.
A series connection point of the two diodes and a series connection point of the two capacitors are respectively connected to both ends of the secondary winding, and both ends of the series connection circuit of the two capacitors are connected to the DC input of the inverter. And connecting the series connection point of the two capacitors to one end on the load side of the capacitor constituting the filter, and connecting the output terminal of the inverter to the non-capacitor side of the reactor constituting the filter An uninterruptible power supply characterized by being connected to one end of the power supply. In the uninterruptible power supply device according to claim 1,
The rectifier is configured by connecting two sets of forward series connection circuits of two diodes in parallel, and each series connection point in the forward series connection circuit is connected to both ends of the secondary winding. An uninterruptible power supply. In the uninterruptible power supply according to claim 1 or 3,
The smoothing capacitor is constituted by a series connection circuit of two capacitors, and the inverter is constituted by a series connection circuit of two switching elements composed of self-extinguishing semiconductor elements each having a free-wheeling diode connected in antiparallel. With composition
The series connection point of the two capacitors is connected to one end on the load side of the capacitor constituting the filter, and the output terminal of the inverter is connected to one end on the non-capacitor side of the reactor constituting the filter. An uninterruptible power supply. In the uninterruptible power supply according to claim 1 or 3,
The inverter is configured by connecting two sets of series connection circuits of two switching elements made of self-extinguishing semiconductor elements each having a freewheeling diode connected in anti-parallel, and connected in parallel in the series connection circuit of the two switching elements. Are connected to one end on the load side of the capacitor constituting the filter and one end on the non-capacitor side of the reactor, respectively.

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