JPH0356047A - Uninterruptible power supply device - Google Patents

Abstract

PURPOSE:To stabilize an output voltage by providing an error amplifier, a phase conptroller, a differentiator for detecting change of a DC voltage, and means for compensating an output voltage fluctuation of an inverter by inputting, when a voltage change of an AC power source is detected, an output of a predetermined time differentiator to the amplifier. CONSTITUTION:When an AC power source 1 starts power interruption, the voltage of a DC line 4 is lowered, a power interruption is detected by a power interruption detection circuit 9, a thyristor switch 8 is closed, and a storage battery 7 is connected to a DC line 4. A differentiator 21 detects a DC voltage variation, and applies it to a comparator at the input side of a voltage error amplifier 12 through an analog switch 22. The amplifier 12 outputs a control signal of the output voltage of an inverter 3 to a phase controller 13 for a predetermined period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention (Industrial Application Field) The present invention converts AC power supply voltage into DC using a converter and inputs it to an inverter. The present invention relates to an uninterruptible power supply that supplies AC power to a load by inputting DC output to an inverter.

(Prior art) This type of uninterruptible power supply is generally used as a power source for loads such as electronic computers and communication equipment, so it has small output voltage fluctuations with respect to input power supply voltage fluctuations, and has good transient response. This is required. Furthermore, when the voltage of the AC power supply drops (hereinafter referred to as a power outage), it is necessary to convert the DC output of the storage battery into AC power using an inverter and continue supplying the AC power to the load.

FIG. 3 is a block circuit showing an example of the configuration of such a conventional uninterruptible power supply. In Figure 3, 1 is an AC power supply, 2
is a converter (rectifier) that converts the AC power of this AC power source 1 into DC power, 3 is an inverter that converts the DC output input from this converter 2 through the DC line 4 into AC, and the output of this inverter 3 is an AC filter. 5 improves the waveform into a sine wave and supplies it to the load 6. Also, 7
9 is a storage battery connected to the DC line 4 via the SIRISK switch 8; 9 is a power outage detection circuit that detects a power outage in the AC power source 1; when this power outage detection circuit 9 detects a power outage in the AC power source 1, it outputs a detection signal This turns on the sirisk switch 8.

Therefore, when the AC power supply 1 is out of power, the power outage detection circuit 9
As a result, the thyristor switch 8 is immediately ignited and the DC output of the storage battery 7 is supplied to the inverter 3, so that the load 6 can continue to be supplied with electric power.

On the other hand, 10 is a reference voltage setting device that sets the standard of the output voltage of the inverter 3, 11 is an output voltage detection circuit that detects the output voltage of the inverter 3, and 12 is the reference voltage and output voltage of the reference voltage setting device 10. An error amplifier that amplifies the deviation from the output voltage detected by the detection circuit 11, and 13 a phase control circuit (PHS) that controls the firing phase of the switching elements constituting the inverter 3 according to the output of the error amplifier 12. These constitute the output voltage control system of the inverter 3.

Note that since the technique of controlling the output voltage by controlling the phase of the inverter is well known, its explanation will be omitted here.

(Problem to be Solved by the Invention) However, in such an uninterruptible power supply, when the converter 2 and the storage battery 7 are switched during a power outage or subsequent power restoration of the AC power supply 1, a voltage difference between the two occurs. This causes fluctuations in the DC voltage input to the inverter 3. A delay element (included in the voltage error amplifier 12) is definitely necessary for the above-mentioned closed-loop voltage control system to operate stably, and if the DC voltage fluctuation is negligible compared to the response of the closed-loop control system, Although follow-up control is possible, when there is a sudden change in the DC voltage such as during a power outage or power restoration, the sudden change in the DC voltage directly appears as a fluctuation in the output voltage.

FIG. 4 shows a time chart of a conventional uninterruptible power supply during a power outage. In FIG. 4, when the voltage of the AC power source 1 gradually attenuates into a power outage mode, the power outage detection circuit 9 detects a power outage at time t, and the sirisk switch 8
gives an ignition signal to.

When this SIRISK switch 8 is turned on, the storage battery 7 is connected to the DC line 4, and the DC line 4, which is in a voltage drop state, rises to the charging voltage of the storage battery 7, and the output voltage of the inverter 3 also rises accordingly.

Therefore, the output voltage of the inverter 3 fluctuates during the period T2 from when the power outage is detected at time t until the output voltage of the inverter 3 becomes stable, which has an adverse effect on the load 6. In addition, in the worst case, the uninterruptible power supply will malfunction and stop due to the operation of its own output overvoltage protection circuit.

Therefore, as a means to solve the problem of sudden changes in DC voltage as described above, when the power is restored, the converter 2 is soft-started, that is, by controlling the output of the converter 2 according to the voltage of the storage battery 7, the DC voltage is reduced. Voltage fluctuations can be reduced.

In addition, as a countermeasure against sudden changes in DC voltage during power outages, (1) A DC voltage detection circuit is installed on the input side of the inverter 3 to detect the DC voltage, and this DC voltage is combined with the output signal of the voltage error amplifier. Methods such as (2) controlling the inverter 3 by causing a voltage error amplifier to interrupt a signal proportional to a change in the output pulse peak value of the inverter 3 have been considered.

However, in method (1), the inverter 3 is always connected to DC voltage.
However, in this case, in order to operate the voltage control system stably, it is not possible to increase the amount of phase control using DC voltage, so the output voltage must be controlled in response to sudden changes in DC voltage. There will be a shortage of Yu. Also,(
In method 2), control is started after a sudden change in DC voltage appears as the output pulse peak value of the inverter 3, so as a result, the output voltage fluctuates for one or two cycles.

SUMMARY OF THE INVENTION An object of the present invention is to provide an uninterruptible power supply device that can stably maintain the output voltage of an inverter even if the DC voltage suddenly changes when the AC power source is switched to a storage battery during a power outage.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention converts the AC power supply voltage into DC using a converter and inputs it to the inverter, and detects a voltage drop in the AC power supply. In an uninterruptible power supply device that inputs the DC output of a storage battery to an inverter to supply AC power to a load when a phase control circuit that controls the phase of the inverter based on the output of the error amplifier; a differentiation circuit that detects a change in the DC voltage input to the inverter; and compensation means for inputting the output of the differentiating circuit to the error amplifier to compensate for fluctuations in the output voltage of the inverter.

(Function) In an uninterruptible power supply with such a configuration, when a voltage drop in the AC power source is detected, the DC output of the storage battery is input to the inverter, and at the same time, the DC output is input to the inverter detected by the differential circuit. Since the change in DC voltage is input to the scheduled time error amplifier, the inverter's output voltage is controlled while taking into account the change in DC voltage during that period, and even if the DC voltage suddenly changes, it compensates for fluctuations in the inverter's output voltage. can do.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block circuit showing an example of the structure of an uninterruptible power supply according to the present invention. Components that are the same as those in the figures are designated by the same reference numerals and their explanations will be omitted, and only points that are different from those in FIG. 3 will be described here. In this embodiment, as shown in FIG.
is connected to the input end of a differentiator circuit 21 that detects changes in DC voltage, and its output end is connected to the comparison section on the input side of the voltage error amplifier 11 via an analog switch 22. When a power outage of the power source 1 is detected, the analog switch 22 is closed in response to a switch operation command output from an operation circuit 23 consisting of a multi-vibrator.

Next, we will explain the operation of the uninterruptible power supply configured in this way in a second manner.
This will be described with reference to the time chart shown in the figure. now,
If AC power supply 1 is in a normal state, inverter 3 converts DC power input from converter 2 into AC power and supplies it to load 6 .

If AC power supply 1 starts a power outage (power outage mode in which AC voltage gradually decreases) in this state, AC power supply 1
The DC voltage of the DC line 4 decreases in proportion to the voltage decrease. When a power outage is detected by the power outage detection circuit 9 at time t, the detection signal is given to the thyrisk switch 8 as an ignition signal and simultaneously input to the operation circuit 23. Therefore, the storage battery 7 is connected to the DC line 4 by turning on the thyrisk switch 8, and the analog switch 22 is connected to the DC line 4 by the operation command from the operation circuit 23 for the scheduled period T3.
Close only. Then, the DC voltage of the DC line 4 changes to the storage battery 7.
At this time, the differentiating circuit 21 detects the amount of change in the DC voltage, and the amount of change is applied to the comparing section on the input side of the voltage error amplifier 12 through the analog switch 22.

As a result, the voltage error amplifier 12 outputs a control signal to the phase control circuit 13 for a period of T to lower the output voltage of the inverter 3, and the output voltage of the inverter 3 is controlled.

As described above, in this embodiment, even if the storage battery 7 is connected to the DC line 4 due to a power outage of the AC power supply 1 and the DC voltage increases due to the charging voltage, the difference is detected by the differentiating circuit 21 and sent to the error voltage amplifier 12. Since the output voltage of the inverter 3 is compensated by the input voltage, the output voltage can be controlled with a quick response without causing fluctuations in the output voltage of the inverter 3.

Next, other embodiments of the present invention will be described.

In the above embodiment, a case has been described in which the DC voltage of the storage battery 7 is higher than the output voltage of the converter 2 as shown in FIG.
Even when the output voltage is lower than the output voltage of , the same effect as described above can be obtained.

Furthermore, in the above embodiment, the power failure detection circuit 9 detects a drop in the AC input voltage, but by providing an overvoltage detection circuit in addition to the power failure detection circuit 9, the inverter 3 can be Fluctuations in output voltage can be prevented.

Furthermore, in the above embodiment, the differentiating circuit 21 was connected to the DC line 4 to detect changes in the DC voltage, but the differentiating circuit 21 was connected to the output side of the storage battery 7, and the sirisk switch 8 was
Even if the change in the discharge current of the storage battery 7 flowing through the inverter 3 is detected, fluctuations in the output voltage of the inverter 3 can be prevented in the same manner as described above.

On the other hand, in FIG. 1, the case where the load 6 is operated by one uninterruptible power supply has been explained, but the above-mentioned method can also be applied when two or more uninterruptible power supplies are operated in parallel. .

[Effects of the Invention] As described above, according to the present invention, even if the DC voltage suddenly changes due to switching to power storage during a power outage of the AC power supply, the output voltage of the inverter is controlled to compensate for the change. ,
It is possible to provide an uninterruptible power supply that can reduce the cost of the system by expanding the voltage fluctuation range of the storage battery, and can always maintain the output voltage of the inverter stably even if the discharge characteristics differ depending on the type of storage battery.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram showing an embodiment of an uninterruptible power supply according to the present invention, Fig. 2 is a diagram showing a time chart for explaining the operation of the embodiment, and Fig. 3 is a diagram showing a conventional uninterruptible power supply. FIG. 4 is a block circuit diagram showing an example of the configuration of the device, and FIG. 4 is a diagram showing a time chart for explaining the operation of the conventional device. 1...AC power supply, 2...Converter,
3...Inharter, 4...DC line,
5...AC filter, 6...Load, 7
...Storage battery, 8...Sirisk switch, 9...Power failure detection circuit, 10...Reference voltage setting device, 11...Output Voltage detection circuit, 1
2... Voltage error amplifier, 1 3... Phase control circuit, 2 1 Differential circuit, 2 2... Analog switch, 2 3... Operation circuit.

Claims (1)

[Claims] Normally, the AC power supply voltage is converted to DC by a converter and input to the inverter, and when a voltage drop of the AC power supply is detected, the DC output of the storage battery is input to the inverter to supply AC power to the load. In the power outage power supply device, an error amplifier that amplifies the deviation between the output voltage of the inverter and a reference voltage setting value, a phase control circuit that controls the phase of the inverter based on the output of the error amplifier, and a phase control circuit that controls the phase of the inverter based on the output of the error amplifier; a differentiating circuit for detecting a change in the DC voltage; and a compensating means for inputting the output of the differentiating circuit to the error amplifier for a predetermined time when a change in the voltage of the AC power supply is detected to compensate for fluctuations in the output voltage of the inverter. An uninterruptible power supply device characterized by comprising: