JPH0721073Y2 - Uninterruptible power system - Google Patents

Description

[Detailed description of the device] "Industrial application field" This device constantly supplies AC power from a commercial power source to a load, charges a storage battery, and converts the output of the storage battery into AC power with an inverter when the commercial power source fails. The present invention relates to an uninterruptible power supply that supplies power to a load.

"Prior Art" Fig. 3 shows a conventional uninterruptible power supply. Commercial power supply at all times
The AC power of 11 is supplied to the load 13 through the direct transfer switch 12, and the transformer connected to the load 13 side of the direct transfer switch 12 further.
The storage battery 16 is charged through the charger 15 with the obtained AC power. A diode 17 for preventing backflow is provided on the output side of the charger 15.
Are inserted in series. When the commercial power source 11 has a power failure, this is detected by the power failure detector 18, the direct output switch 12 is turned off by the detection output, and the inverter 19 is put into an operating state, and the inverter 19 turns the DC power of the storage battery 16 into AC power. The converted AC power is loaded through the transformer 14.
Supplied to 13. Note that the output of the power failure detector 18 controls the charger 15 to be always in the operating state and in the non-operating state during the power failure.

As shown in FIG. 4, the transformer 14 is connected to the direct switch 12 and the load 13
There is also something that intervenes between.

"Problems to be solved by the device" If the output voltage V _BAT of the storage battery 16 or the load 13 fluctuates when the output power V _out stabilization function is not added to the inverter 19, the output voltage of the inverter 19 also fluctuates greatly. Will end up. Since it is desirable that the output voltage V _out of the inverter 19 be stable regardless of the output voltage V _BAT of the storage battery 16 and the fluctuation of the load 13, the output voltage V _out of the single-pulse or multi-pulse PWM method is generally used. Inverter 19 stabilizing function
Is added to.

The PWM method stabilizes the output voltage by giving a quiescent period to the square wave, but when the quiescent period becomes large, the utilization factor of the transformer 14 becomes poor and the inverter
There is a problem that the loss of 19 and the transformer 14 increases.

When a resistive load is connected as the load 13, the energy stored in the transformer 14 while there is a square wave output is immediately absorbed by the load 13 during the output rest period, and the surge voltage is suppressed. When a capacitor input type rectifier load is connected as the load 13, the energy accumulated in the transformer 14 during the output dwell period largely appears as a surge voltage as shown in FIG. 5, and the output voltage fluctuates. There is a problem, in order to solve this drawback of the PWM method,
It is necessary to add an absorber circuit to absorb the surge voltage during the idle period. Therefore, the sequence becomes complicated, and the parts of the absorber circuit are added, resulting in a high cost. Alternatively, there is a problem that the space required for the device increases.

According to the present invention, the output voltage of the inverter is detected by the voltage detector, the detected output is compared with the first reference voltage and the first comparator, and the power failure detector detects the power failure. After a predetermined time, the output of the first comparator is taken out by the gate, the flip-flop is set by the voltage higher than the first reference voltage in the output of the gate, and the charger operates by the output of the flip-flop. In this state, the output voltage of the storage battery is compared with the second reference voltage by the second comparator, and the flip-flop is reset by the output of the second comparator when the second reference voltage becomes higher.

"Operation" When a power failure occurs, the operation of the charger is stopped at the same time that the inverter is started. However, when the load is light, the inverter output voltage is high, so the flip-flop is set and the charger is in the operating state. The output of the battery causes the charger to charge the storage battery, the load of the inverter increases correspondingly, and the output voltage of the inverter is lowered. When the voltage of the storage battery drops below the specified value, the prep-flop is reset,
The operation of the charger stops, the load on the inverter becomes lighter, and the output voltage of the inverter rises. In this way, the fluctuation range of the output voltage of the inverter is reduced.

[Embodiment] FIG. 1 shows an embodiment of the present invention, in which parts corresponding to those in FIG. 3 are designated by the same reference numerals. The voltage detector 21 is connected to the transformer 14, and the output voltage V _out is stepped up or down by the voltage detector 21 and then rectified and detected as a DC voltage. The detected voltage is compared with the first reference voltage E ₁ by the first comparator 22, and when it is higher than the first reference voltage E ₁ , the first comparator 22 outputs “1”. The output of the first comparator 22 after a predetermined time from the detection of the power failure by the power failure detector 18 is taken out from the gate 23. In this example, the power failure detector 18 outputs "1" while the commercial power supply 11 is supplying AC power, and outputs "0" during a power failure. The output of the power failure detector 18 is reversed. It is supplied to the delay circuit 25 through the device 24, and the output of the delay circuit 25 is supplied to the gate 23 as a gate control signal. Therefore, when a power failure occurs, the gate 23 is opened by the output of the delay circuit 25 after a predetermined time.

The flip-flop 26 is set by the comparison output when it is higher than the first reference voltage E _{1 in} the output of the gate 23. That is, the flip-flop 26 is set by "1" in the output of the gate 23, and the Q output of the flip-flop 26 is supplied as a control signal to the charger 15 through the OR circuit 27. When the Q output of the flip-flop 26 is "1", the charger 15 is in the charging operation state. The output of the power failure detector 18 is also supplied to the OR circuit 27.

The output voltage V _BAT of the storage battery 16 is the second reference voltage in the second comparator 28.
When it is compared with E _2, and the output voltage V _BAT becomes lower than the second reference voltage E ₂ , the second comparator 28 outputs “1” and the output “1” resets the flip-flop 26.

When the load 13 is a light load, the output voltage of the voltage detector 21 becomes the first when the output of the delay circuit 25 becomes "1" after a lapse of a predetermined time as shown by the dashed line in FIG. Reference voltage E ₁
Higher, the output of the first comparator 22 is "1", the gate 23
Also becomes "1", the flip-flop 26 is set, and the charger 15 is in the operating state (ON). The output of the inverter 19 is also supplied to the charger 15 via the transformer 14,
By setting each of the three windings of 14 to an appropriate turns ratio, the storage battery 16 is charged by the charger 15, and the load of the inverter 19 is increased accordingly, and as shown by the point A in FIG. The output voltage is reduced.

On the other hand, the output voltage V _BAT of the storage battery 16 is constantly monitored by the second comparator 28, and when the output voltage V _BAT falls below the second reference voltage E ₂ as the storage battery 16 discharges, the output of the second comparator 28 When it becomes "1", the flip-flop 26 is reset, the charging operation of the charger 15 is stopped, the load of the inverter 19 is lightened accordingly, and the inverter output voltage rises as indicated by point B in FIG.

In this way, the fluctuation range of the output voltage of the inverter 19 when the load is light can be reduced.

When the load 13 is heavy, the output voltage of the voltage detector 21 is lower than the first reference voltage E ₁ as shown by the dotted line in FIG. The output of the charger 22 is “0”, the flip-flop 26 is not set, and the charger 15 does not operate.

In FIG. 1, the winding to which the charger 15 of the transformer 14 is connected,
By omitting one of the windings to which the voltage detector 21 is connected,
The 15 and the voltage detector 21 may be connected to a common winding.

“Effect of device” As described above, according to this device, the inverter 19 is connected to the PW.
The voltage detector 21, the first, without adding complicated control such as the M method and without adding a special snubber circuit
Comparator 22, gate 23, delay circuit 25, flip-flop 2
6. By adding a simple circuit such as the second comparator 28, the fluctuation range of the output voltage of the inverter 19 at light load can be reduced, and the space for the control circuit, the space for the snubber and the costs required for them can be reduced. Since it does not cost, the device can be made inexpensive without increasing the size. Moreover, the present invention is effective for both resistance load and capacitor input type load.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of operation waveforms of respective parts at the time of power failure, FIGS. 3 and 4 are block diagrams showing a conventional uninterruptible power supply device, respectively. FIG. 5 is a diagram showing an output waveform when a PWM inverter is used as a capacitor input type rectifier load.

Claims (1)

[Scope of utility model registration request] 1. A power failure detector detects whether AC power is being supplied from a commercial power source or during a power failure, and when the AC power is being supplied, the direct transfer switch is turned on by the output of the power failure detector. , AC power is supplied from the commercial power source to the load through the direct transfer switch, and the charger is put into operation by the output of the power failure detector, and the AC is supplied through the transformer connected to the load side of the direct transfer switch. Charge the storage battery with the charger, and during the power failure, the output of the power failure detector turns off the direct feed switch and turns on the inverter, and the inverter converts the output of the storage battery into AC power. In the uninterruptible power supply that is supplied to the load through the transformer, a voltage detector that detects the output voltage of the inverter, and The comparing the output and the first reference voltage of the voltage detector 1
Set by a comparator, a gate for taking out the output of the first comparator after a predetermined time has passed since the power failure detector detected the power failure, and a gate higher than the first reference voltage in the output of the gate, The set output compares the output voltage of the storage battery and the second reference voltage with the flip-flop that puts the charger into the operating state, and when the second reference voltage is higher, the output that resets the flip-flop is output. An uninterruptible power supply comprising: a second comparator for outputting.