JP3246138B2 - Uninterruptible power system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of an output voltage waveform of an inverter in an uninterruptible power supply.

[0002]

2. Description of the Related Art In order to control the output voltage waveform of an inverter device in an uninterruptible power supply, an error between a waveform command signal based on a reference sine wave voltage formed in a control circuit of the inverter and an inverter output voltage is directly calculated. High-speed waveform control is performed by performing pulse-width modulation control (PWM control) on a high-frequency carrier based on the error signal based on the comparison of the waveforms, and the inverter output voltage waveform is converted into a linear / non-linear load current waveform. Regardless, I was trying to get a clean sine wave.

FIG. 4 shows an example of a conventional uninterruptible power supply for controlling the output waveform as described above. The power of a commercial power supply 1 is rectified by a rectifier 2 to charge a storage battery 3 and the storage battery 3 is charged.
Is converted into AC power by an inverter 4 and supplied to a load 6 via a changeover switch 5. Reference numeral 17 denotes an inverter control circuit, which controls the inverter output voltage V0
The voltage average value obtained by inputting the feedback voltage signal V01 obtained by stepping down the voltage by the transformer 8 to the averaging circuit 9 and the voltage command value from the voltage setting device 10 are input to the voltage control circuit 11 to obtain an error signal. . The error signal and the reference sine wave signal from the reference sine wave generation circuit 12 (synchronizing with the commercial power supply voltage)
To obtain a waveform command signal V1. The signal V1 and the feedback voltage signal V01 are input to a waveform control circuit 14 to obtain an error signal V2. The signal V2 is input to a DC component detection circuit 18. The obtained DC component correction signal Vi is fed back to the input of the waveform control circuit 14. As described above, the error signal V2 obtained by the series of means is input to the PWM control circuit 15 to
A WM control signal is obtained, and the drive circuit 1
By controlling the switching element of the inverter 4 via the inverter 6, the waveform of the inverter output voltage is controlled.

[0004]

In the uninterruptible power supply according to the conventional inverter output control described above, the input form of the load is similar to that of the computer which is the target load .
In the case of a capacitor-input type rectifier circuit as shown in FIG. 3 , the load current has a high peak value even if the inverter output voltage waveform is a clean sine wave, and the load power factor (active power / apparent power) ) Is reduced to increase the effective value of the load current.

An object of the present invention is to provide a capacitor input
An object of the present invention is to provide an uninterruptible power supply capable of reducing a peak value of a load current, improving a load power factor, and lowering an effective value of a load current in a case of a load having an input type rectifier circuit. .

[0006]

In order to solve the above-mentioned problems, an uninterruptible power supply according to the present invention uses a rectified DC output of commercial power as shown in the embodiment of FIG. a battery 3 to be charged, an inverter 4 for converting the DC output of the DC power or the battery 3 to the sine wave AC power, and an output of the commercial power supply power inverter con
A changeover switch 5 for switching and outputting a load having a capacitor-input type rectifier circuit to an input side, and an inverter control circuit 17 for controlling the operation of the inverter 4 are provided. The inverter control circuit 17 controls the output signal of the reference sine wave generation circuit 12 which is phase-synchronized with the commercial power supply voltage and the inverter 4.
Is input to the waveform control circuit 14 together with the output feedback voltage V01 to generate an error signal V2, and the error signal is input to the PWM control circuit 15 It is configured to output a control signal to the inverter 4 based on the signal. In such an uninterruptible power supply, in the present invention, the output load current Vi0 of the inverter is fed back to the waveform control circuit 14 to control the peak value of the inverter output voltage . That is, the output load current is added as a minute feedback element.

[0007]

[Action] in the uninterruptible power supply device of the present invention, capacitor
In the case of a load having a rectifier circuit on the input side, the instantaneous voltage value in the phase near the peak of the output voltage of the inverter is reduced by a small amount, and the output load current V of the inverter is reduced.
In the waveform of i0, the peak value of the load current is lower and the conduction time width is wider than the waveform in the case of the conventional output control. Therefore, as in the present invention, the output load current V
When i0 is fed back, the load power factor is improved, and the effective value of the load current can be reduced.

[0008]

Next, an embodiment of the present invention will be described with reference to FIG. In FIG. 1, 1 is a commercial power supply, 2 is a rectifier, 3 is a storage battery that is floatingly charged by the rectifier output, 4 is an inverter that converts DC power of the storage battery 3 into AC power, and 5 is provided with automatic switching means. Power of power supply 1 and inverter 4
Output and capacitor-input type rectifier circuit on input side
A changeover switch for switching the output to the load 6 with the.
Reference numeral 17 denotes an inverter control circuit for controlling the operation of the inverter 4. Reference numeral 8 denotes a transformer that receives the output voltage V0 of the inverter 4 as an input and steps down the feedback voltage signal V01. Reference numeral 9 denotes an average for obtaining an average value of the feedback voltage signal V01 by a filter circuit or the like. It is a value conversion circuit. Reference numeral 10 denotes a voltage setting device that outputs a voltage command value of a predetermined size, and reference numeral 11 denotes a voltage control circuit that outputs an error signal based on the voltage average value and the voltage command value. 12
Is a reference sine wave generation circuit that outputs a sine wave signal that is phase-synchronized with the commercial power supply voltage serving as the reference of the output waveform of the inverter 4. The reference sine wave signal and the above error signal are multiplied by a multiplier 13.
To obtain a waveform command signal V1. A current transformer 7 detects the load output current Io of the inverter 4 and outputs a current detection signal Vio corresponding to the current Io. A waveform control circuit 14 receives a feedback voltage signal V01 from the transformer 8, a waveform command signal V1 and a current detection signal Vio, and outputs an error signal V2. Reference numeral 15 denotes a PWM for outputting a PWM control signal based on the error signal V2.
The control circuit 16 controls the inverter 4 according to the PWM control signal.
Is a drive circuit for driving the switching element of FIG.

Next, the operation of this embodiment will be described. In the uninterruptible power supply according to the present embodiment, the power of the commercial power supply 1 is always supplied to the capacitor input type through the changeover switch 5.
The power is supplied to the load 6 having a rectifier circuit on the input side . When the commercial power supply is abnormal, the changeover switch 5 is automatically switched, and the output of the inverter 4 is supplied to the load 6. In the inverter control circuit 17, the voltage control circuit 11 outputs an error signal based on the set voltages of the averaging circuit 9 and the voltage setting device 10, and this signal and the reference sine wave output signal of the reference sine wave generation circuit 12 are output. The signal is input to the multiplier 13 and the multiplier 1
3 outputs a waveform command signal V1. Waveform control circuit 1
4 outputs an error signal V2 based on the feedback voltage signal V01 from the transformer 8, the waveform command signal V1, and the current detection signal Vio from the current transformer 7. In particular, the waveform control circuit 14
By inputting the output load current Vi0 of the inverter 4,
Control is performed to reduce the peak value of the inverter output voltage.
U. The PWM control circuit 15 outputs a signal P based on the error signal V2.
A WM control signal is output, and the drive circuit 16 operates according to the control signal to control the switching element of the inverter 4,
The output voltage and output current waveform of the inverter 4 are controlled.

FIG. 2 (A) shows the relationship between the inverter output voltage V0 (feedback voltage signal V01) and the output load current Io (current detection signal Vio) in the above operation by a solid line.
2B shows the waveform command signal V1, and FIG. 2C shows an example of the waveform of the error signal V2 by a solid line. As the load 6 for the uninterruptible power supply when the load of the circuit configuration as shown in FIG. 3, i.e., a bridge diode circuit 1
9 was used in which an electrolytic capacitor 20 and a variable resistor 21 were connected in parallel with the output terminal of a full-wave rectifier 9. That is,
Diode bridge circuit 19 and electrolytic capacitor 20
Input rectifier circuit consisting of
Load 6 was used. 2A and 2C, the dotted lines of the waveforms of the signals V0 (V01), Io (Vio), and V2 indicate that the detection signal Vio of the output load current Io of the inverter is not fed back to the input of the waveform control circuit 14. 4 shows respective waveforms in the conventional device shown in FIG. 4 for feeding back a signal obtained by detecting the DC component of the error signal V2 output from the waveform control circuit 14 to the input side of the waveform control circuit 14. As shown in FIG. 2, in this embodiment, the waveform of the inverter output load current Io has a lower peak value of the load current and a wider conduction time width than the waveform obtained by the conventional control shown by the dotted line. Become like This improves the load power factor,
The effective value of the load current becomes smaller.

Next, an example of the numerical effects obtained in the embodiment of the present invention is shown in the following table.

[0012]

[Table 1] In this test, the capacitor-input rectifier shown in Fig. 3 was used.
Was used on the input side, and the electrolytic capacitor 20 was 3300 μF. Looking at the results of this test, it was found that the load power factor was
5 and the load current of 30A was conventionally 25A.
2A. Therefore, the current burden is reduced not only for the main circuit components of the inverter but also for the components of the capacitor input type rectifier circuit of the load.

[0013]

As described above, according to the present invention, according to the uninterruptible power supply of the present invention, since the resulting error signal by feeding the output load current of the inverter to the waveform control circuit, a capacitor Yi
In the case of a load having an input type rectifier circuit on the input side, the peak value of the load current can be reduced and the conduction time width can be increased compared to the waveform of the inverter output load current compared to the waveform obtained by the conventional output control. it can. Thus to improve the load power factor, interest which can reduce the effective value of the load current
There is a point .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

2 (A) to 2 (C) are waveform diagrams showing signal waveforms at various parts in the embodiment of FIG. 1;

FIG. 3 A capacitor-input rectifier circuit on the input side
FIG. 3 is a circuit diagram showing an example of a load provided.

FIG. 4 is a block diagram showing a configuration of a conventional uninterruptible power supply.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Commercial power supply 2 Rectifier 3 Storage battery 4 Inverter 5 Changeover switch 6 Load 7 Current transformer 9 Averaging circuit 10 Voltage setting device 11 Voltage control circuit 12 Reference sine wave generation circuit 14 Waveform control circuit 15 PWM control circuit 16 Drive circuit 17 Inverter Control circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H02J 3/38 H02J 3/46 H02J 9/06

Claims (1)

(57) [Claims] 1. A storage battery charged by a DC output obtained by rectifying a commercial power supply, an inverter for converting the DC power or the DC output of the storage battery into a sine-wave AC power, and outputting the sine wave AC power. Con and the output of the
A changeover switch for switching and outputting a load having a capacitor-input type rectifier circuit on the input side; and an inverter control circuit for controlling the operation of the inverter, wherein the inverter control circuit performs phase synchronization with a commercial power supply voltage. A waveform command signal obtained based on the output signal of the wave generation circuit and the output feedback voltage of the inverter is input to the waveform control circuit together with the output feedback voltage to generate an error signal, and the error signal is input to the PWM control circuit. An uninterruptible power supply configured to output a control signal to the inverter based on the signal obtained in step (a), wherein an output load current of the inverter is fed back to the waveform control circuit of the inverter control circuit to output the inverter. Voltage
An uninterruptible power supply , wherein control is performed so as to reduce a peak value .