JPH04208037A - Uninterruptible power supply - Google Patents

Abstract

PURPOSE:To increase the operating frequency of an inverter transformer or an output transformer and to realize reduction in size and weight of an uninterruptible power supply by directly converting a commercial power supply frequency into a high frequency and operating the inverter in a high frequency region. CONSTITUTION:Power is normally fed from an AC power supply 1 through a first switch 2, a first power converter 4, a high frequency transformer 10 and a third power converter 20 to an output terminal 29. The first power converter 4 converts a commercial power supply frequency into a high frequency and a high frequency voltage corresponding to the waveform applied on the primary winding is induced in the secondary winding 18 of a high frequency transformer 10. An inverter is operated in the high frequency region and a high frequency transformer is employed as an output transformer communicating the primary and the secondary. Secondary output of the high frequency transformer is then converted into an AC commercial frequency waveform subjected to high frequency modulation from which high frequency components are eliminated to produce a commercial frequency sine wave which is fed to a load.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an uninterruptible power supply, and particularly to an uninterruptible power supply that can be made smaller and more efficient.

(Prior art) An uninterruptible power supply converts commercial AC power into DC, charges a battery with the resulting DC, drives a square wave inverter to generate commercial frequency AC, and uses an output transformer and a filter. It is known to output a sine wave alternating current at a commercial frequency via a sine wave (for example, see "Semiconductor Power Conversion Circuit" published by the Institute of Electrical Engineers of Japan, p. 292).

In this type of uninterruptible power supply, power is normally supplied to the load from the commercial power supply, and in the event of an abnormality due to a power outage, etc., the commercial power supply is cut off, and the inverter output is enabled to supply power to the load. There is.

In such a case, the inverter output is a rectangular wave of the commercial power frequency, and its harmonic components are removed by a filter before being supplied to the load.

(Problem to be solved by the invention) The above-mentioned conventional technology had the following problems.

Since the square wave inverter and transformer operate in a low frequency range, they are not only large in size but also heavy in weight. Furthermore, since the output of the rectangular wave inverter contains many low-order harmonic components, the filter for removing these components also becomes large, which increases the loss of the fundamental wave component and lowers the efficiency.

The present invention has been made to solve the above-mentioned problems.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a power converter that directly converts the commercial power frequency to a high frequency, and
The inverter is also operated in the same high frequency range, and a high frequency transformer is used as the output transformer that connects the primary and secondary sides.The secondary side output is converted to a high frequency modulated commercial frequency AC waveform, and then the high frequency component is The main feature is that a commercial frequency sine wave is generated by removing the sine wave, and this is supplied to the load.

Further, the present invention is characterized in that a power converter that converts a commercial power supply frequency to a high frequency is also used as a high frequency inverter.

(Function) Since the commercial power supply frequency is directly converted to high frequency and the inverter is operated in the high frequency range, not only can the inverter be made smaller and lighter, but the output voltage can also be made higher frequency, making it possible to reduce the size of the - layer. It becomes possible to reduce the weight. In addition, on the secondary side of the output high-frequency transformer, a sine wave at the commercial power frequency can be obtained by simply removing harmonic components with a small number of low-order harmonic components using a filter, so there is no loss associated with the removal of harmonic components. Also, the filter can be made smaller and simpler.

(Example) The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an outline of an embodiment of the present invention.

First and second primary windings 12,16 and a secondary winding 18 are wound around the iron core of the high frequency transformer 10. A commercial AC power source 1 is connected to a first primary winding 12 of a high frequency transformer 10 via a first switch 2 and a first power converter 4.
connected to. The battery 3 is connected to the second switch 5 and the second
It is connected to a second primary winding 16 of a high frequency transformer 10 via a power converter 7 . A third power converter 20 is connected to the secondary winding 8, and its output is connected to an output terminal 29 via a filter 22.

When AC power supply 1 is normal, first switch 2 is on, second
The switch 5 is off, and power is supplied from the AC power supply 1 to the output terminal 29 via the first switch 2, the first power converter 4, the high frequency transformer 10, and the third power converter 20.

When the AC power supply 1 becomes abnormal due to a power outage, etc., the first switch 2 is switched off and the second switch 5 is turned on, and power is transferred from the battery 3 to the switch 5 and the second power converter. 7. The signal is supplied to the output terminal 29 via the high frequency transformer 10 and the third power converter 20.

In this case, the operation of the second power converter 7 may be switched by a cold standby method in which it is activated in response to the detection of an abnormality in the AC power supply, but the phase relationship is such that power is not constantly supplied. 7, and takes the power burden in response to abnormality detection of AC power supply
So-called hora!・Standby (hot 5tandby)
) method is also acceptable. Further, the high frequency transformer may be of a tri-port type (for example, see Japanese Utility Model Application Publication No. 81745/1983) by providing leakage between each winding.

FIG. 2 is a circuit diagram showing a specific example of the configuration of the first or second power converter 4.7. Four sets of control switch pairs Sla and Slb% S2a and S connected in parallel with mutually opposite polarities
2 b

FIG. 3 is a graph showing the relationship between the control (on/off) state of each switch and the phase of the sine wave AC waveform when the power converter of FIG. 2 is used as the first power converter 4; FIGS. 4A and 4B are waveform diagrams showing the operation in that case. In FIG. 3, ronJ indicates that the corresponding switch is turned on, and no mark indicates that it is cut off.

As can be seen from these figures, each positive and negative half-cycle period of the sine wave supplied from the commercial AC power supply 1 is divided into small sections, and during the positive half-cycle, starting from phase A, each small section Phases A and B are alternately controlled, and during the negative half-cycle, phases C and D are alternately controlled in each subsection, starting from phase C.

In the short section of phase A, control switches S2a and S3
Since a is off and all other switches are on,
When the input AC ■j is positive, the current flows from the input terminal t1 to Sl
a, flows to the input terminal t2 via the output terminals p1, p2, and S4a. Therefore, at this time, as shown in FIG. 4(B), a positive current flows through the output terminal.

In this case, when a delayed reactive current flows depending on the type of load connected to the output terminal 29, the control switch 5lb-34b functions as a feedback rectifier that feeds back the delayed reactive current to the input terminals t1 and t2.

In the small section of phase B, the control switches S], a and S4
Since a is off and all other switches are on,
When input AC vl is positive, current flows from input terminal t1 to S
3a, output terminals p2, pl, S2a in red, input terminal t2
flows to Therefore, at this time, as shown in FIG. 4, a negative current flows through the output terminal. In this case, the control switches Slb to S4b are connected to the feedback rectifier and 1. It works.

Next, in the small section of phase C, control switch Slb
and S4b are off and all other switches are on, so when input AC ■i is negative, current flows from input terminal t2 to input terminal t1 via S2b, output terminals p1, p2, and S3b. Therefore, in this case, Fig. 4 (B)
As can be seen, a positive current flows through the output terminal.

In addition, in the small section of phase D, control switches S2b and S
3b is off and all other switches are on, so when the input AC Vi is negative, the current flows from input terminal t2 to S
4b, input terminal t1 via output terminals p2, pl, Slb
flows to Therefore, at this time, as can be seen from FIG. 4(B), a negative current flows through the output terminal.

In this way, the first power converter 4 performs high frequency amplitude modulation on the commercial frequency sine wave and supplies it to the primary winding 12 of the high frequency transformer 10 .

FIG. 5 is a graph showing the relationship between the control (on/off) state of each switch and the phase of the sine wave AC waveform when the power converter of FIG. 2 is used as the second power converter 7, FIG. 6 is a waveform diagram showing the operation in that case. Fifth
In the figure, as in the case of FIG. 3, ronJ indicates that the corresponding switch is conductive, and no mark indicates that the switch is disconnected.

As can be seen from these figures, the period corresponding to one cycle of the commercial AC power supply 1 is divided into a plurality of small sections, and the phase A
Starting from , the control of phases A and B is performed alternately in each subsection. In this case, the input voltage V1 is DC (
(assuming that input terminal t1 is positive and t2 is negative), and each subsection is further divided into a first half and a second half.

In the first half of the small section of phase A, the control switch 5la-
Since S4a is off and switches 5lb-54b are on, power converter 7 is in a cutoff state and no current flows.

In the second half of the small section of phase A, control switches S2a and 33a are off and all other switches are on, so the current flows from input terminal t1 to Sla, output terminals p1 and p2.
, S4a to the input terminal t2. Therefore, at this time, as shown in FIG. 6, current in the positive direction flows through the output terminals p1 and p2.

In the first half of the small section of phase B, all the control switches are controlled to the same state as the first half of the small section of phase A, so the power converter 7 is in a cutoff state and no current flows.

In the second half of the small section of phase B, Sla and S4a are off and all other switches are on, so the current flows from input terminal t1 to input terminal t2 via 53a, output terminals p2, pl, and S2a. Therefore, in this case, the sixth
As can be seen from the figure, a negative current flows through the output terminal pLp2.

Therefore, by setting the time ratio between the first half and the second half of each subsection so as to be proportional to the amplitude of the desired output waveform (in this embodiment, a sine wave), a signal whose pulse width is modulated according to the amplitude can be obtained.

Returning to FIG. 1, when the AC power supply 1 is normal, the second switch 5 is opened and the first switch 2 is closed.
Power converter 4 is driven. As a result, Fig. 4 (B)
The sinusoidal amplitude modulated voltage shown in FIG. 1 is supplied to the first primary winding 12- of the high frequency transformer 10.

When the AC power supply 1 experiences an abnormality such as a power outage, the second switching device 5
is turned on and the first switch 2 is opened, so the second power converter 7 is driven. As a result, the pulse width modulated wave signal shown in FIG. 6 is supplied to the second primary winding 16 of the high frequency transformer 10.

In this way, the secondary winding 18 of the high frequency transformer 10
A high frequency voltage is induced in the primary winding according to the waveform applied to the primary winding.

FIG. 7 is a circuit diagram showing a specific example of the configuration of the third power converter 20. As in the case of FIG. 2, there are four control switch pairs Slc, Sld, and Sld connected in parallel with opposite polarities
2c and 52dS S3c and 53dS S4c and S4d are connected in a bridge type, and as shown in the figure, one diagonal is connected to input terminals q1 and q2, and the other diagonal is connected to output terminal r1,
r2 respectively.

FIG. 8 shows the state of the third power converter 2 when the sine wave amplitude modulation voltage of FIG. 4(B) is supplied between the input terminals q1 and 92.
FIG. 4(C) is a waveform diagram showing the operation in that case. 8th
In the figure, ronJ indicates that the corresponding switch is turned on, and no mark indicates that it is cut off.

As can be seen from these figures, phase P control is executed during a period corresponding to the positive half cycle of the sine wave of the sine wave amplitude modulated voltage induced in the secondary winding 18, and the control switch 5
lc-84c is cut off, other control switch 5ld-S
4d becomes conductive. In addition, during the period corresponding to the negative half cycle of the force, phase Q control is executed, and the control switch 5lc-
34c becomes conductive, and the other control switches 5ld-34d
is blocked.

As a result, as can be seen from Fig. 4(C), during the period corresponding to the positive half cycle of the sine wave, the output waveform obtained by rectifying the waveform of Fig. 4(B) with positive polarity is obtained by controlling the phase P. The output waveform obtained between the outputs rl and r2, and which is obtained by full-wave rectification of the waveform in Fig. 4 (B) with negative polarity, is the output waveform obtained by controlling the phase Q during the period corresponding to the negative half cycle of the -force. rl, r2
obtained in between.

Similarly, when the second power converter 7 is driven and the pulse width modulation signal shown in FIG. 6 is supplied to the second primary winding 16 of the high frequency transformer 10, the rectified pulse width modulation signal is obtained at the output of the third power converter 20. By supplying these modulated wave signals to the filter 22 to remove high frequency components, a desired low frequency (commercial power supply frequency) voltage can be obtained at the output terminal 29.

FIG. 9 shows the first or second winding when the primary winding 12 or 16 of the high frequency transformer 10 is equipped with a neutral tap.
7 is a circuit diagram showing another specific example of the configuration of power converter 4.7. FIG.

Two pairs of control switches S connected in parallel with opposite polarities
One connection point between la and Slb and between S2a and S2b is connected to both terminals of the tapped primary winding 12A of the high frequency transformer 10. The other connection points of the two pairs of control switches are commonly connected and connected to the input terminal t1. A neutral point of the primary winding 12A is connected to the other input terminal t2. The two terminals of the secondary winding 18 of the high frequency transformer 10 are the third
Connected to power converter.

FIG. 10 is a diagram showing phases of switch conduction control suitable for the circuit of FIG. 9. In this case, control is performed according to four phases A to D. It will be easily understood that this results in the modulation operations shown in FIGS. 4(B) and 6.

FIG. 11 is a circuit diagram showing another specific example of the configuration of the third power converter 20 in which the secondary winding 18 of the high-frequency transformer 10 is equipped with a neutral point tap.

One connection point of two pairs of control switches Slc and 5ld SS2c and S2d connected in parallel with opposite polarities is connected to both terminals of the tapped secondary output winding 18A of the high frequency transformer 10. The other connection points of the two control switch pairs are commonly connected and connected to one input of the filter 22. A neutral point of the secondary output winding 18A is connected to the other input of the filter 22.

FIG. 12 is a diagram showing phases of switch conduction control suitable for the circuit of FIG. 11. In this case, 2 of P and Q
Control is performed according to the phase. It will be easily understood that this causes the demodulation operation as shown in FIG. 4(C) to be performed.

Above, we have explained an example in which power converters for high frequency modulation are installed separately for AC power supply and for battery, but if the reliability of the power converter is sufficiently high, these two power converters can be installed separately. It is also possible to use one device for both purposes.

FIG. 13 is a block diagram showing the main parts of another embodiment of the present invention in which the first and second power converters 4.7 in FIG. 1 are used in one device. Power converter 9
The output is connected to the primary winding j1 of the high frequency transformer 10, and the input thereof is connected to the AC power source 1 or the battery 3 via the changeover switch 8.

The changeover switch 8 is normally connected to the AC power source 1 side, or is switched to the battery 3 side when the AC power source 1 becomes abnormal due to a power outage. Power converter 9 in this case
The operation of is switched as explained in FIG. 3 or FIG. 6 depending on whether it is connected to AC power supply 1 or battery 3.

(Effects of the Invention) As is clear from the above description, according to the present invention, the commercial power frequency is directly converted to a high frequency, the inverter is also operated in a high frequency range, and the inverter transformer and output transformer are also made to operate at high frequencies. Therefore, the device can be made smaller and lighter.

In particular, considering that the uninterruptible power supply normally (more than 99.9%) operates in a normal state where it is supplied with power from the commercial power supply, the secondary side of the output transformer has many low-order harmonic components. There is no need to remove the included harmonics, and a sine wave alternating current at the commercial power frequency can be obtained only by removing high-order harmonic components, which not only reduces the loss associated with removing harmonic components, but also Filters can also be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an outline of an embodiment of the present invention. FIG. 2 is a circuit diagram showing a specific example of the configuration of the power converter shown in FIG. 1. FIG. 3 is a graph showing the relationship between the control (on/off) state of each switch and the phase of the sine wave AC waveform when the power converter of FIG. 2 is used as the first power converter. , FIG. 4 is a waveform diagram showing the operation in that case. FIG. 5 is a graph showing the relationship between the control (on/off) state of each switch and the phase of the sine wave AC waveform when the power converter of FIG. 2 is used as a second power converter. FIG. 6 is a waveform diagram showing the operation in that case. FIG. 7 is a circuit diagram showing a specific example of the configuration of the third power converter. FIG. 8 is a diagram showing the control (on/off) state of each switch of the third power converter when the sine wave amplitude modulated voltage of FIG. 4(B) is supplied between the input terminals. FIG. 9 is a circuit diagram showing another specific example of the configuration of the first or second power converter. FIG. 10 is a diagram showing phases of switch conduction control suitable for the circuit of FIG. 9. FIG. 11 is a circuit diagram showing another specific example of the configuration of the third power converter. FIG. 12 is a diagram showing phases of switch conduction control suitable for the circuit of FIG. 11. FIG. 13 is a block diagram showing a main part of another embodiment of the present invention in which one device serves as the first and second power converters in FIG. 1. Explanation of symbols 1... AC power supply, 3... Battery, 4.7.9.2
0...Power converter, 10...High frequency transformer, 22
···filter

Claims (6)

[Claims] (1) A first power converter that converts an alternating current voltage into a high frequency amplitude modulated voltage and outputs the same; a second power converter that converts a direct current voltage into a pulse width modulated voltage according to the alternating current voltage and outputs the converted voltage; , a first input winding supplied with the high frequency amplitude modulated voltage, a second input winding supplied with the pulse width modulated voltage, and an output winding; An uninterruptible power supply device comprising: demodulating means for demodulating a modulated voltage to generate a desired alternating current voltage; and switching means for enabling only one of the first and second power converters. (2) The demodulation means includes a third power converter that performs positive full-wave rectification and negative full-wave rectification of the high-frequency modulated voltage induced in the output winding every half wave of the desired AC; The uninterruptible power supply according to claim 1, comprising a high frequency filter supplied with the output of a power converter. (3) Each power converter has four pairs of control switches connected in parallel with opposite polarities to each other in a bridge configuration, with one diagonal connected to the input side and the other diagonal connected to the output side. An uninterruptible power supply according to claim 1 or 2, characterized in that: (4) The input winding of the high-frequency transformer has a neutral point tap, and the power converter connected to the input winding consists of two pairs of control switches connected in parallel with opposite polarities, each of which has a neutral tap. One end of each pair of control switches is connected to both ends of the input winding, the other end of each pair of control switches is commonly connected to the negative pole of either the AC input or the DC input, and the neutral tap is connected to both ends of the input winding. The uninterruptible power supply according to claim 3, wherein the uninterruptible power supply is connected to the other pole of the one of the DC inputs. (5) The output winding of the high frequency transformer has a neutral point tap, and the power converter connected to the output winding consists of two pairs of control switches connected in parallel with opposite polarities, each of which has a neutral tap. One end of each control switch pair is connected to both ends of the output winding, the other end of each control switch pair is commonly connected to one of the output terminals of the power converter, and the neutral tap is connected to the output terminal of the power converter. The uninterruptible power supply according to claim 3, wherein the uninterruptible power supply is connected to the other terminal. (6) A power converter that converts AC voltage and DC voltage into high-frequency modulated voltage and outputs the same; a high-frequency transformer having an input winding and an output winding to which the high-frequency modulated voltage is supplied; What is claimed is: 1. An uninterruptible power supply device comprising: demodulating means for demodulating the modulated voltage to generate a desired alternating current voltage; and switching means for connecting the power converter to one of the alternating current voltage and the direct current voltage.