JPH0747963Y2 - Standby uninterruptible power supply - Google Patents

Description

[Detailed Description of the Device] “Industrial Application Field” This device is used, for example, as a power supply for a small computer. When the commercial power supply is normal, the commercial power is directly sent to the load, and when the commercial power fails, the DC of the storage battery The present invention relates to a standby uninterruptible power supply device which converts an output into an alternating current by an inverter and supplies it to a load.

"Prior Art" Generally, as a small uninterruptible power supply, the floating charging system shown in Fig. 9 has been widely used because of its simple structure. The AC power from the commercial power supply 11 is supplied from the input terminal 12 to the charger 13 to be DC power, and the DC power is supplied to the storage battery 14 to be charged and also to the inverter 15, and the inverter 15
It was converted into AC power at 15, and the AC power was supplied to the load 17 through the output terminal 16. However, in this conventional device, the charger 13 must supply the total power of the input power to the inverter 15 and the charging power to the storage battery 14 while receiving the commercial power, and the charger 13 is downsized. It is difficult to do, and because the output power output to the output terminal 16 when receiving commercial power is supplied through the two converters of the charger 13 and the inverter 15, there are many power losses in these two converters, There was a problem that the input power was increased by that much.

As a countermeasure for this, a standby type uninterruptible power supply with a high-speed switching circuit for energy saving and downsizing has been adopted. This stand-by device focuses on the fact that most commercial equipment, including small computers, can continue operation without any effect if the power supply is interrupted for 10 ms or less. That is, as shown in FIG. 10, while receiving commercial power, AC power from the input terminal 12 is directly sent to the output terminal 16 through the AC switch 18 capable of high-speed switching, and
The storage battery 14 is charged with 12 AC power through the charger 13, and the inverter 15 suspends and stands by with the commercial power as an oscillating unit in a synchronized state. If there is a momentary interruption or a voltage drop in commercial power, turn off the AC switch 18 and start the inverter 15 in about 1/4 cycle (5 ms), switch the power to the output terminal 16 and supply it to continue operation of the load. Is possible. In this standby type device, the charger 13 only needs to supply the charge for the storage battery 14, and the power capacity of the charger 13 is approximately the same as in the case of the floating charging method.
It was only about 1/10, and the effect of miniaturization and energy saving was great.

"Problems to be solved by the invention" This standby device is good for offices, where the load voltage is relatively stable, because commercial power is directly sent to the load.
Large fluctuations in the voltage of the power receiving terminal of the load (± 10%
(Above) There was a drawback that it could not be used in places. In other words, if the power receiving terminal voltage of the load fluctuates more than 10% to the positive side, it will cause overheating of the load equipment, transformer saturation, etc., and similar fluctuations to the negative side will not only be bad for the load, but will also be inverter power supply at each voltage drop. This is because the battery capacity may be insufficient.

"Means for Solving Problems" The present invention is designed to keep an output voltage constant by operating an inverter that is in a standby state as a reactive power generation device while receiving commercial power and controlling its lead-lag current. (EN) Provided is a standby type uninterruptible power supply device which is configured and can be used even in a place where a load's power receiving terminal voltage varies significantly.

In other words, in this invention, an inductor is inserted in series between the connection point of the load and the inverter and the commercial power supply, and while the commercial power is being received, the inverter operates in the same phase as the commercial power and detects fluctuations in the power receiving terminal voltage of the load. Then, the detected output controls the current of the inverter so that the power receiving terminal voltage of the load, that is, the output terminal voltage of the inverter becomes constant.

"Embodiment" FIG. 1 shows a part of an embodiment of the present invention. Input terminal 12a,
One side 12a of 12b is connected to one side 16a of output terminals 16a and 16b through an AC switch 18 of a semiconductor switching element, and the other input terminal 12b and output terminal 16b are directly connected to each other.

The switching circuit 21 of the inverter 15 is a case where it is configured as a transistor bridge, and the transistors Q ₁ and Q ₂
Is connected in parallel to the series circuit of the transistors Q ₃ and Q ₄ , the connection point of the transistors Q ₁ and Q ₂ is connected to the output terminal 16b, and the connection point of the transistors Q ₃ and Q ₄ and the coil 22 are connected. The capacitor 23 is connected to the output terminal 16a and is connected between the output terminals 16a and 16b, and the coil 22 and the capacitor 23 constitute a low-frequency wave filter for waveform correction. Transistor Q ₁
Diodes D _{1 to} D ₄ are connected in parallel to Q ₄ in reverse polarity to these. The capacitor 24 is connected in parallel to the series circuit of the transistors Q ₁ and Q ₂ , and the storage battery 14 is connected in parallel through the series circuit of the coil 25 and the DC switches 26a and 26b.

A transformer 27 that detects the input AC voltage Vac is connected between the input terminals 12a and 12b, and an inductor 28 is inserted in series between the AC switch 18 and the connection point of the load 17 and the inverter 15. Output terminals 16a, transformer 29 for detecting an output terminal voltage Vl of the power receiving terminal voltage, that the inverter 15 of the load among 16b are connected, inverter current Iin to the connection line of the connection point of the transistors Q _1, Q ₂ and the output terminal 16b Current transformer 3 to detect
1 is combined. These detection voltages Vac, Vl, detection current I
in is supplied to the control device 33.

FIG. 2 shows a specific example of the control device 33. This is a case where the commercial power and the inverter output are switched in synchronization with each other, and the pulse width modulation method is used as the inverter 15. The detected input AC voltage Vac is the power failure detection circuit 34
When the voltage Vac becomes lower than a predetermined value, a high level is output, and the switch 35 is switched from the 1 side to the 2 side by the high level output. In the commercial power receiving state in which the input AC voltage Vac is equal to or higher than a predetermined value, the output of the power failure detection circuit 34 is low level, and the switch 35 is on the 1 side. The output terminal voltage Vl detected in this state is shaped into a rectangular wave by the waveform shaping circuit 36, supplied to the phase comparator 38 of the phase locked loop (PLL) 37 through the switch 35, and output from the voltage controlled sine wave oscillator 39. The phases are compared. The output of the phase comparator 38 is supplied to the control terminal of the voltage controlled sine wave oscillator (VCO) 39 through the loop filter 41, and the output of the voltage controlled sine wave oscillator 39 is phase-locked with the output terminal voltage Vl. The output of the voltage controlled sine wave oscillator 39 is supplied to the inverting input side and the non-inverting input side of the comparators 44 and 45 in the switch control pulse generator 43 through the multiplier 42, respectively. The output of the multiplier 42 is the comparator 44, 45
Is compared with the output of the triangular wave generator 46, and pulse width modulated outputs are obtained from the comparators 44 and 45.

When the power failure detection circuit 34 detects a power failure, the switch 35 is switched to the 2 side as described above, and the output of the oscillator 47 of the commercial power frequency based on a stable oscillator such as a crystal is sent to the phase comparator 38. Supplied. The output of the power failure detection circuit 34 is supplied to the inverting circuit 48 and the drive circuit 49 through the off-delay delay circuit 47. The output of the inverting circuit 48 is supplied to the drive circuit 52. AC switch with output of drive circuit 52 while receiving commercial power
18 (Fig. 1) is turned on. During a power failure, the output of the drive circuit 49 turns on the DC switches 26a and 26b (FIG. 1).

The outputs of the comparators 44 and 45 are supplied to the rise delay circuits 55 and 56 through the buffers 53 and 54, respectively, and the outputs of the inverters 57 and
It is supplied to the rise delay circuits 61 and 62 via 58. The outputs of the rising delay circuits 55, 56, 61, 62 are gates 63, 64, 6 respectively.
It is supplied to the drive circuits 67, 68, 69, 71 through 5, 66. Each output of the drive circuit 67,68,69,71 is supplied to the transistors _{Q 4, Q 2, Q 3} , Q 1 in the base in the inverter in FIG. 1, respectively.

The detected output terminal voltage Vl is converted into a direct current by the rectifier circuit 78 and compared with the reference value of the reference power supply 79 by the differential amplifier 81, and the comparison output is supplied to the multiplier 42. Output terminal voltage detected
If Vl is smaller than the reference value, the output sine wave amplitude of the multiplier 42 becomes large, and if Vl is larger than the reference value, the output sine wave amplitude of the multiplier 42 becomes smaller.

The detected inverter current Iin is supplied to the peak detector 89, and its peak detection output is compared with the reference value of the reference power source 91 and the comparator.
Compared at 92. When the peak value of the inverter current Iin exceeds the reference value, the output of the comparator 92 becomes high level, the flip-flop 93 is set, and its output closes the gates 63 to 66 in the switch control pulse generating circuit 43. The output of the triangular wave signal generator 46 is supplied to the reset terminal R of the flip-flop 93 through the differentiating circuit 94, and the flip-flop 93 is reset every cycle of the triangular wave generated by the triangular wave signal generator 46.

Generation of Reactive Current by Inverter Next, generation of a reactive current by the inverter 15 and control of its magnitude will be described with reference to FIGS. 3 and 4. The control method of the inverter 15 used here is generally used. This is a drive method that reduces low-order harmonics with a sine wave PWM method. In this case, the voltage Vin of the fundamental wave component of the output of the inverter 15 is ea the amplitude of the modulating sine wave signal and eb the amplitude of the modulating triangular wave, as is well known.
It has the relation expressed by the following formula.

(However, K is a constant, Bdc is a DC voltage) As shown in FIG. 3, the DC switches 26a and 26b are turned off, the inverter 15 is disconnected from the storage battery 14, and the load current Il
= 0 and the inverter 15 is operated in the same phase as the commercial direct output voltage l, the DC side of the inverter 15 (storage battery 14
Since the side) is only the capacitor 24, the active power supplied from the AC side to the inverter 15 must be zero in the ideal state. From this, the commercial voltage 1 at the load 17 and the current in of the inverter 15 become a vector orthogonal to each other.
4A shows a vector when the inverter fundamental wave voltage in is higher than the commercial direct output load voltage l, and FIG. 4B shows a vector when it is low. In Fig. 4, the voltage of the coil 22 is x ₂
It is indicated by. In the ideal operating state as shown in this figure, if the inverter fundamental wave voltage in is higher than the commercial direct voltage l,
Inverter current in is 90 ° lead current (equivalent to capacitor) mode, and low 90 ° lag current (equivalent to reactor) mode.

Referring to the case of FIG. 4A, the voltage x _{2 of the} coil 22 is x ₂ = in−l = Xx ₂ · in from the vector diagram. Xx ₂ is the reactance of the coil 22. Given that the voltage of the capacitor 24 is Vc, Vin = KVc, so Becomes

When Vc is constant, the inverter current Iin is the modulation amplitude ratio K
Can be made to have an arbitrary magnitude and a reactive current orthogonal to the direct-transmission commercial voltage Vl.

Load voltage stabilization operation When receiving commercial power, the inverter 15 is operated in the reactive current generation mode to keep the voltage Vl between the output terminals 16a and 16b constant.
FIG. 5 shows the voltage / current of the main part in this mode. Using the inverter 15 for reactive current generation means that
Output terminal voltage (load power receiving terminal voltage) Vl
A 90 ° advance or a 90 ° delay relative to the current, which is equivalent to connecting a capacitor or a reactor in parallel with the load 17. Therefore, in FIG. 5, the inverter 15 is equivalently shown as a variable capacitor or a variable inductor.

6A and 6B show the commercial input voltage Vac in this circuit.
Is a vector display of the output terminal voltage Vl. Sixth
Figure A is by increasing the 'current of the sum of the currents Ic ₁ and the inverter current Iin flowing through the capacitor 23 _D from _D when lowered _to' input voltage Vac from Vac, to maintain the output terminal voltage Vl constant It shows that you can do. FIG. 6B shows the case where the load current 1 increases to 1 ', and in this case also, the output terminal voltage Vl can be kept constant by increasing the current _D to _D '. Where Xx ₁ is the reactance of inductor 28. Since the capacitor current c in the current _D is a constant value, the output terminal voltage Vl is detected and used as the feedback value, and the inverter current
If Iin is properly controlled, the output terminal voltage Vl can be kept constant even if the input voltage and the load change.

That is, as shown in FIG. 2, the fluctuation of the output terminal voltage Vl due to the fluctuation of the commercial input voltage Vac is negatively fed back to the multiplier 42 through the rectifier circuit 78 and the differential amplifier 81 to cancel the fluctuation of the output terminal voltage Vl. Direction reactive current (inverter current) Iin
The modulation amplitude ratio K of the inverter 15 may be controlled so that

In actual use, compensate for a voltage drop of up to about -20%, judge that it is a power failure below that, turn off the AC switch 18,
By turning on the DC switches 26a and 26b, immediate inverter power feeding is started.

When the commercial power is restored, the AC switch 18 is turned on and the DC switches 26a and 26b are turned off after waiting a few seconds for the commercial stability confirmation time, and the output terminal voltage stabilization operation is started.

By the way, when the load 17 is, for example, a small computer, its power supply voltage is usually 100 V. Therefore, a transformer is interposed between the AC power supply 11 having a higher voltage and a small computer load having a 100 V power supply voltage. Then, the voltage is reduced and power is supplied. A transformer is provided between the AC power supply 11 and the small computer load 17 in order to prevent various noises mixed in from the power supply side to the load 17 side and to prevent a slight DC component generated by the inverter 21. It is preferable to do so. Here, as this transformer, as shown in FIGS. 7 and 8, a leakage transformer 95 or 96 is connected between the load 17 and the connection point of the inverter 21.

"Effect of the device" As described above, according to the device, the inverter 15 that has been waiting during the conventional commercial power reception is used to suppress the fluctuation of the load receiving terminal voltage due to the fluctuation of the commercial power line voltage. It is possible to extend the range of use of the standby type uninterruptible power supply, which was previously limited, to places with relatively bad conditions such as in factories, and its industrial effect is great. Since 23 constitutes a low pass wave filter, it also has the effect of suppressing the power line noise from being mixed into the load, which was close to defenseless in the past. When the load 17 is, for example, a small computer, its power supply voltage is usually 100 V, so a transformer is interposed between the AC power supply 11 having a higher voltage and the small computer load having a 100 V power supply voltage. Then, the voltage is reduced and power is supplied, but in this case, if this transformer is a leakage transformer,
In addition to the step-down, it is also suitable for preventing various noises mixed in from the power supply side to the load 17 side and for suppressing a slight DC component generated by the inverter 21. In addition, the leakage magnetic path 28 'acts equivalently to the inductor 28.

Furthermore, if reactive power control is performed with the storage battery connected,
The AC power for generating reactive power flows to the storage battery, which causes a problem that the storage battery is heated and the storage battery electrolyte is reduced.However, in the present invention, the storage battery is disconnected from the inverter by a switch during commercial power reception. By adopting, such problems did not occur and the maintenance of the storage battery was facilitated.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of a standby type uninterruptible power supply device according to the present invention, FIG. 2 is a diagram showing a concrete example of the control device in FIG. 1, and FIG. Fig. 4 is a vector diagram thereof, Fig. 5 is a diagram showing a circuit state in which fluctuations of the power receiving terminal voltage of the load are suppressed by the reactive current of the inverter, and Fig. 6 is a load by the reactive current of the inverter. Fig. 7 is a vector diagram showing a state in which the fluctuation of the power receiving terminal voltage is suppressed, Fig. 7 and Fig. 8 are diagrams showing other examples of the present invention, Fig. 9 is a diagram showing a floating uninterruptible power supply device, and Fig. 10 The figure shows a standby type uninterruptible power supply. 11 …… Commercial power supply, 14 …… Storage battery, 15 …… Inverter, 17
...... Load, 26a, 26b ...... Switch, 28 ...... Inductor, 2
9 ... Voltage detection means, 33 ... Control device.

Claims (2)

[Scope of utility model registration request] 1. The commercial power is supplied to the load while receiving the power from the commercial power supply, the commercial power supply line is cut off during the power failure, and the inverter is operated, and the power of the storage battery is exchanged with the AC power by the inverter. In the standby type uninterruptible power supply that supplies power to the load, a switch that disconnects the storage battery from the inverter while receiving commercial power, and an inductor that is inserted in series between the commercial power supply and the connection point between the load and the inverter. A load detecting means for detecting the voltage of the load, and a means for controlling the reactive power of the inverter according to the detection output of the detecting means while receiving commercial power to keep the load voltage constant. Stand-by type uninterruptible power supply characterized by. 2. The standby type uninterruptible power supply device according to claim (1) of the utility model registration, wherein the inductor is a leakage transformer.