JPH10337040A - Uninterruptible power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generated noise and to reduce the influence to an audio signal and a video signal by adding the output voltage of a square wave conversion part and that of a pulse width modulation part, and achieving a transformer for obtaining the sinusoidal wave output voltage with a specific frequency. SOLUTION: A square wave conversion part 4 is constituted of an inverter where switching elements 4a such as a thyristor and a power transistor are connected in a bridge. A diode 4b for absorbing noise is connected in parallel with the switching elements 4a. A pulse width modulation part 5 is also constituted of an inverter where switching elements 5a such as the thyristor and the power transistor is connected in a bridge. A diode 5b for absorbing noise is connected also in parallel with the switching elements 5a. A transformer 6 has two primary coil windings 6a and 6b and one secondary coil winding 6c, voltages that are inputted to the primary coil winding 6a and the primary coil winding 6b are added, and a voltage that is obtained by multiplying the voltage being obtained by the addition by a transformation ratio (normally 1 or larger) is outputted between the terminals of the secondary coil winding 6c.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an AC / DC converter connected to an AC power supply, a power storage device connected to an output side of the AC / DC converter, and a quadrature conversion device connected in parallel with the power storage device. The present invention relates to improvement of a power failure power supply system.

[0002]

2. Description of the Related Art Conventionally, a large-scale management system having a computer has been adopted in many fields. For example, management of each tollgate on expressways, disaster management of tunnels,
Computers are used for centralized management of disaster prevention and crime prevention management systems in underground malls, underground parking lots, and access control systems for vehicles. In many buildings, a management system using a computer has been constructed for office management, disaster prevention management, and the like. Generally, a management system using these computers requires a stable and reliable power supply.
Therefore, in many cases, an uninterruptible power supply system is adopted as a power supply for these management systems.

[0003] A generally adopted uninterruptible power supply system is an AC / DC converter connected to an AC power supply, a power storage device connected to an output side of the AC / DC converter, and connected in parallel with the power storage device. Provided with an orthogonal transformation device. Conventionally, this AC / DC converter uses a thyristor or a power transistor to convert a three-phase AC voltage into a DC voltage. A quadrature converter similarly uses a thyristor or a power transistor to convert a DC voltage into a single-phase AC voltage. Alternatively, an inverter for converting to a three-phase AC voltage has been used. Note that inverters using power transistors are gradually increasing.

[0004]

However, the inverter used conventionally has relatively large noise generated by the conversion operation, and the noise may affect, for example, an audio signal and a video signal in television broadcasting equipment. Had been a problem. Since the magnitude of the noise is proportional to the pulse frequency and output capacity of the inverter, the improvement has been strongly demanded especially when a large-capacity uninterruptible power supply system is required. Therefore, an object of the present invention is to provide an uninterruptible power supply system that solves such a problem.

[0005]

That is, the present invention provides an AC / DC converter connected to an AC power supply, a power storage device connected to the output side of the AC / DC converter, and an orthogonal device connected in parallel with the power storage device. It is an uninterruptible power supply system provided with a conversion device. Then, the orthogonal transformer converts a DC voltage into a square wave voltage of a predetermined frequency, a square wave converter, a DC voltage into a pulse width modulation voltage, a pulse width modulation unit, and an output voltage of the square wave conversion unit. It is characterized by including a transformer for obtaining a sine wave output voltage of a predetermined frequency by adding the output voltages of the pulse width modulation unit. According to the uninterruptible power supply system of the present invention configured as described above, since the current of the quadrature converter is shared by both the square wave converter and the pulse width modulator, the current value and the current The pulse frequency is greatly reduced. Therefore, the generated noise is suppressed, and the influence on the audio signal and the video signal is reduced.

[0006]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram for explaining an example of the uninterruptible power supply system of the present invention. The uninterruptible power supply system includes an AC / DC converter 1 connected to a three-phase AC power supply (R-S-T), a power storage device 2 connected to an output side of the AC / DC converter 1, and a power storage device 2 connected in parallel with the power storage device 2. It has an orthogonal transformation device 3 connected thereto. The AC / DC converter 1 converts a three-phase AC voltage into a DC voltage by a diode bridge composed of a diode 1b. In the case of a three-phase AC voltage, switching of a thyristor, a power transistor, and the like connected in parallel to the six diodes 1b, respectively. The element 1a is switched and controlled at the same frequency as the three-phase AC frequency. (Since the AC / DC converter 1 is a device known in the art,
The detailed circuit is omitted). Note that the AC / DC converter 1 may be configured for a single-phase AC power supply.

The power storage device 2 is charged with the DC voltage converted by the AC / DC conversion device 1 and is provided for supplying power to a load at the time of a power failure or the like, so that a storage battery such as a lead storage battery or an alkaline storage battery has a desired voltage and capacity. In this way, they are serially parallel. Note that a smoothing capacitor is connected in parallel to the storage battery. The orthogonal transformer 3 includes a square wave converter 4 that converts a DC voltage into a square wave voltage of a predetermined frequency, a pulse width modulator 5 that converts a DC voltage into a pulse width modulated voltage, and an output voltage of the square wave converter. And a transformer 6 for adding the output voltage of the pulse width modulator and the output voltage of the pulse width modulation section to obtain a sine wave output voltage of a predetermined frequency. The square wave converter 4 is configured by an inverter in which switching elements 4a such as thyristors and power transistors are bridge-connected. Note that a noise absorbing diode 4b is connected in parallel to each switching element 4a. The pulse width modulation unit 5 is also the square wave conversion unit 4
Similarly to the above, a switching element 5a such as a thyristor or a power transistor is constituted by an inverter having a bridge connection, and a noise absorbing diode 5b is connected to each switching element 5a in parallel.

The transformer 6 has two primary windings 6a, 6b and 1
Having two secondary windings 6c, a primary winding 6a and a primary winding 6b.
Is added to the voltage, and the transformation ratio (usually 1)
Is output between the terminals of the secondary winding 6c. The output wiring of the square wave converter 4 is connected to the primary winding 6a, the output wiring of the pulse width modulator 5 is connected to the primary winding 6b, and the single-phase load wiring 7 is connected to the secondary winding 6c. Connected. The load wiring 7 is provided with a smoothing capacitor 8 for smoothing a voltage and a load breaker 20. The output current of the square wave converter 4 is detected by the current transformer 9, the output current of the pulse width modulator 5 is detected by the current transformer 10, and the detected values are input to the signal detector 11. Further, the voltage of the load wiring 7 is detected by the instrument transformer 12 and is similarly input to the signal detection unit 11. The signal detector 11 also detects the frequency supplied to the load from the signal from the instrument transformer 12. Note that the current transformers 9 and 1
0, the instrument transformer 12, the signal detector 11, etc. may be omitted in some cases.

The control section 13 is constituted by a microcomputer or the like, compares the output signal of the signal detection section 11 with the setting signal from the setting section 14 constituted by a storage device or the like.
Control signals are output to the square wave signal controller 15 and the pulse width signal controller 16 so that they match. Each switching element 4a of the square wave converter 4 is driven by the output of the square wave signal controller 15, and the pulse width signal controller 1
The switching element 5a of the pulse width modulation section 5 is driven by the output of 6. In addition, the setting unit 14 may use the
The load current of the square wave converter 4 and the pulse width modulator 5 and the voltage of the load wiring 7 are set. FIG. 2A shows a square wave converter 4 controlled by a square wave signal controller 15.
The output waveforms A and (b) are output waveforms B and (c) of the pulse width modulation unit 5 controlled by the pulse width signal controller 16, and the output waveforms A and B are added to the secondary side of the transformer 6. Sinusoidal output waveforms obtained by smoothing the appearing voltage are represented as changes in time t. Note that FIG.
Although each waveform in (a) and FIG. 2 (b) shows only the half cycle on the plus side, the half cycle on the minus side has a shape in which a similar waveform is inverted.

Next, the operation of the uninterruptible power supply system will be described with reference to FIGS. The control unit 13 turns on the upper left and lower right switching elements 4a of the square wave converter 4 at the midpoint of the time axis of the plus waveform of the predetermined frequency set by the setting unit 14, and converts the square wave to the midpoint of the time axis of the minus waveform. A control signal is output to the square wave signal controller 15 so that the upper right and lower left switching elements 4a of the unit 4 are turned on. Therefore, the output waveform of the square wave converter 4 is shown in FIG.
As shown in (a), a synchronous rectangular waveform whose midpoint on the time axis coincides with the predetermined frequency set by the setting unit 14 is obtained. Further, the control unit 13 switches the upper left and lower right of the pulse width modulation unit 5 so that the middle point of the pulse width modulation on the plus side coincides with the middle point of the time axis of the plus waveform of the predetermined frequency set by the setting unit 14. The element 5a is turned on and off, and the upper right and lower left switching elements 5a are so set that the negative pulse width modulation midpoint coincides with the negative waveform time axis midpoint.
A control signal is output to the pulse width signal controller 16 so that is turned on and off. Therefore, as shown in FIG. 2B, the output waveform of the pulse width modulation section 5 is a synchronous pulse width modulation waveform whose midpoint on the time axis coincides with the predetermined frequency set by the setting section 14.

When the power supply on the input side of the AC / DC converter 1 is single-phase, the frequency of the single-phase power supply may be used as a set value instead of the predetermined frequency set by the setting unit 14. In that case, it is preferable that the frequency immediately before the power failure be stored by a storage means or the like in case of a power failure of the single-phase power supply. (As described later, when the power supply to the load is a three-phase three-wire system or a three-phase four-wire system, if the input side power supply of the AC / DC converter 1 is a three-phase AC, the three-phase The frequency of the power supply can be used as the set value.)

The control unit 13 receives the output signal of the signal detection unit 11 as described above. Current transformer 9 or current transformer 1
The current of 0 is converted into an effective value current (or an average value current) by the signal detection unit 11, and when the value exceeds the value set in the setting unit 14, the control unit 13 sends the square wave conversion unit 4 or the pulse A control signal is output to the square wave signal controller 15 or the pulse width signal controller 16 so as to limit the output current (effective value) of the width modulator 5. Then, depending on the case, a control signal for opening the load circuit breaker 20 is output. In addition, the uninterruptible power supply system of the present invention can operate a plurality of units in parallel. In such a case, the voltage and frequency of the load wiring 7 detected by the instrument transformer 12 are set by the setting unit 14. When the voltage and the frequency match with each other, the control unit 13 outputs a control signal for closing the load breaker 20, so that the synchronous operation can be smoothly performed.

The square wave signal controller 15 applies pulses of the same width to the gates of the upper left and lower right switching elements 4a of the square wave converter 4 in accordance with the positive or negative pulse width output from the controller 13. Alternatively, the pulse width signal controller 16 composed of a switching circuit that outputs an ON signal to the gates of the upper right and lower left switching elements 4a can use a pulse width modulator commonly used in this field. Such a pulse width modulator includes, for example, a sawtooth wave generation circuit and a comparison circuit,
The modulated signal and the sawtooth signal from the sawtooth wave generating circuit are compared by a comparison circuit, and only when the modulated signal is higher than the sawtooth signal, the comparison circuit outputs an ON signal (pulse width modulation wave). . The pulse width modulation signal is output from the pulse width signal controller 16 by the modulated signal output from the control unit 13, and the gates of the upper left and lower right switching elements 5a of the pulse width modulation unit 5 or the upper right and lower left The gate of the switching element 5a is turned on / off correspondingly.

The uninterruptible power supply system of the present invention can also be configured by providing two pulse width modulation sections 5 in FIG. 1, and the waveforms of each section in that case are shown in FIG. 3B shows output waveforms A, (a) and (c) of the square wave converter 4 controlled by the square wave signal controller 15 and pulse width modulation controlled by two pulse width signal controllers 16. Output waveforms B ₁ and B _{2 of} the unit 5;
(C) shows a sine wave-like output waveform obtained by adding the output waveforms A, B ₁ and B ₂ and smoothing the voltage output to the secondary side of the transformer 6 as a change in time t. is there. The waveforms in FIGS. 3A to 3C are as follows.
Although only the plus half cycle is shown, the minus half cycle has a similar waveform inverted shape. Each of the two pulse width signal controllers 16 has a pulse width modulation unit 5
Are connected, and the pulse width signal controllers 16
3 is controlled by a control signal. The pulse width signal from each pulse width signal controller 16 is shown in FIG.
As shown in (c), the output waveforms B ₁ and B _{2 of the} pulse width modulation section 5 connected to the pulse width modulation section 5 move back and forth so as to be temporally symmetric about the output waveform A of the square wave conversion section 4. That is, sharing the first half of the sine wave output of the transformer 6, the output waveform B _1, the output waveform B ₂ share the second half of the sine wave output of the transformer 6.

In the above example, the power supply to the load is a single-phase two-wire output. However, the uninterruptible power supply system of the present invention supplies power to the load in a single-phase three-wire system, a three-phase three-wire system. Or 3 phase 4
The same can be applied to the case of a linear system. In the case of a three-phase three-wire system or a three-phase four-wire system, FIG.
The combination of the square wave converter 4 and the pulse width modulator 5
Prepare three sets, each output having three primary windings
In addition to the addition by the phase transformer, the output timing of each
It may be performed with a phase of 20 degrees.

[0016]

According to the uninterruptible power supply system of the present invention configured as described above, the current of the orthogonal transformer is shared by both the square wave converter and the pulse width modulator. Thus, the current value and the pulse frequency are greatly reduced. Therefore, the generated noise is suppressed, and the influence on the audio signal and the video signal is reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an example of an uninterruptible power supply system according to the present invention.

FIG. 2 is an output waveform diagram of each unit in FIG.

FIG. 3 is an output waveform diagram of each section in a modification of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 AC / DC converter 1 a Switching element 1 b Diode 2 Power storage device 3 Quadrature converter 4 Square wave converter 4 a Switching element 4 b Noise absorbing diode 5 Pulse width modulator 5 a Switching element 5 b Noise absorbing diode 6 Transformer 6 a Primary winding 6b Primary winding 6c Secondary winding 7 Load wiring 8 Smoothing capacitor 9 Current transformer 10 Current transformer 11 Signal detection unit 12 Instrument transformer 13 Control unit 14 Setting unit 15 Square wave signal controller 16 Pulse width signal control Package 20 Load breaker

Claims (1)

[Claims] 1. An AC / DC converter 1 connected to an AC power supply.
And a power storage device 2 connected to the output side of the AC / DC conversion device 1.
And an uninterruptible power supply system including an orthogonal transform device 3 connected in parallel with the power storage device 2, wherein the orthogonal transform device 3 converts a DC voltage into a square wave voltage having a predetermined frequency, A pulse width modulation unit 5 for converting a DC voltage into a pulse width modulation voltage; and a transformer for adding the output voltage of the square wave conversion unit 4 and the output voltage of the pulse width modulation unit 5 to obtain a sine wave output voltage of a predetermined frequency. 6. An uninterruptible power supply system comprising: