JPH04131150U - Uninterruptible power system - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent inrush current from occurring when switching from commercial AC power to inverter output. [Configuration] The peak value of the commercial AC voltage passes through the transformer 21, the rectifier circuit 25, the switch 27, and the smoothing capacitor 28.
is detected, the voltage of the storage battery 18 is supplied to the DC/DC converter 31, and its output voltage V _DC and the capacitor 28 are
The error amplifier 32 detects the difference _between the voltage _of
is being followed. When a power outage is detected by the power outage detection circuit 22, the switch 27 is turned off and the switch 35 is turned on, the voltage of the capacitor 28 gradually approaches V _S , the inverter 19 is started, and the switches 14 and 15 are turned on. The output of the inverter 19 is a square wave with a flow angle of π/2, and its peak value is approximately equal to the peak value of the commercial AC voltage immediately before the power outage, and is less than the rated peak value. gradually approaching.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This idea is used, for example, in the power supply of electronic computers, and while receiving commercial AC power, When the commercial AC power is supplied to the load and the commercial AC power goes out, the built-in storage battery is activated. A standby uninterruptible power supply that converts power into alternating power using an inverter and supplies it to the load. Regarding this, take special measures to prevent large inrush currents from occurring when switching to the inverter output. This is what I am trying to do.

0002

[Conventional technology]

Figure 3 shows a conventional uninterruptible power supply. One end of each of the electric wires 11 and 12 is connected to a commercial power source 13 , and each other end is connected to each fixed contact a of the changeover switch 14, 15. The movable contacts of the changeover switches 14 and 15 are connected to both ends of the load 16. . A storage battery 18 is connected to the electric wires 11 and 12 through a charging circuit 17, and the storage battery 18 Connected to the input side of the inverter 19, and the pair of output ends of the inverter 19 are switched It is connected to each fixed contact b of the switches 14 and 15. Transformer 2 on wires 11 and 12 A power outage detection circuit 22 is connected via 1, and a synchronization circuit 23 is also connected thereto. The output of the synchronous circuit 23 is supplied to the inverter 19.

0003 While normal commercial AC power is being supplied from the commercial power supply 13, the commercial AC power Force is supplied to the load 16. When the commercial AC voltage drops below a certain value, for example 80V. Then, this is detected by the power failure detection circuit 22, and the detection output causes the inverter 19 to is activated, operates in synchronization with the commercial AC voltage before the power outage, and outputs the power outage detection output. The changeover switches 14 and 15 are switched to the fixed contact b side, and the inverter 19 supplies square wave power with a peak value of 140V to the load 16, for example.

0004

[Problem that the idea aims to solve]

When the commercial power supply 13 has a power outage, the immediately preceding commercial AC voltage is often unstable, and there is a risk that a large rush current will flow to the load when switching to the inverter output. For example, as shown in FIG. 4A, when the commercial AC voltage decreases relatively slowly and a power outage is detected and the output of the inverter 19 is supplied to the load 16 instead of the commercial AC voltage, as shown in FIG. 4B, The voltage of the power supplied to the load 16 decreases, and a half-wave of commercial AC voltage with a peak value of V ₁ is supplied to the load 16, and then a square wave voltage with a rated peak value of V ₂ is applied from the inverter 19 to the load. 16, and the voltage supplied to the load 16 and its peak value change significantly before and after this switching.

In particular, when the load 16 is a capacitor input type rectifier, the charging energy of the capacitor changes from CV ₁ ² /2 to CV ₂ ² /2, and the difference is large, as shown in FIG. 4C. A large inrush current 24 occurs in the current flowing into the load. Such an inrush current applies stress to the input fuse and rectifying power element of the load 16, resulting in accelerated deterioration.

Similarly, if a transformer or the like is connected to the input side of the load 16, biased magnetization will occur due to the voltage difference between V ₁ and V ₂ at the time of switching, and in the worst case, the transformer will become saturated and an inrush current will occur. occurs and a similar problem occurs. In particular, when the output waveform of the inverter 19 is a square wave, the change in peak value at the time of switching becomes more rapid, and in the case of a capacitor input type load, a larger inrush current is generated.

[0007]

[Means to solve the problem]

According to this invention, when switching from commercial AC power to inverter output, Change the peak value of the inverter output from around the peak value of the commercial AC voltage immediately before switching to the rated output. Means is provided for gradually transitioning the voltage to the peak value. In other words, the wave of commercial AC voltage The high value is detected by the peak value detection means, and the output voltage of the storage battery changes to the detected peak value. It is converted by converting means and supplied to the inverter, and when switching to the inverter output, the electric power is The input to the pressure converting means is gradually increased from the detected peak value to the rated peak value.

[0008]

【Example】

FIG. 1 shows an embodiment of this invention, in which parts corresponding to those in FIG. 3 are given the same reference numerals. In this example, a full-wave rectifier circuit 25 is connected to the secondary side of the transformer 21, one end of the output side of the full-wave rectifier circuit 25 is grounded, and the other end is connected through a resistor 26 and further through an analog switch 27 to one end of a capacitor 28. The other end of the capacitor 28 is grounded, and a resistor 29 is connected in parallel with the capacitor 28. Therefore, when the switch 27 is on, the output of the transformer 21 is rectified and smoothed by the resistor 26 and the capacitor 28, and a voltage _V1 approximately proportional to the peak value of the commercial AC voltage is always obtained across the capacitor 28. It is being

[0009] The input voltage of the inverter 19 is this voltage V₁will always be followed. wife The voltage conversion means 3 converts the output of the storage battery 18 to be equal to the peak value of the commercial AC voltage. 1 converts the voltage and supplies it to the inverter 19. As the voltage conversion means 31, for example, A DC/DC converter is used, and the output voltage V of the DC/DC converter 31 is _DC is supplied to the inverting input side of the error amplifier 32, and is supplied to the non-inverting input side of the error amplifier 32. The voltage across the capacitor 28 is supplied through the reverse current prevention diode 33. this The non-inverting input side is grounded through a resistor 34, and the output of the error amplifier 32 is DC/D. It is supplied to the C converter 31 as an output voltage control signal. In this way, DC/ The output voltage of the DC converter 31 is the peak value of the commercial AC voltage being input at that time. becomes almost equal.

The connection point between the switch 27 and the capacitor 28 is connected to a reference power source 37 through an analog switch 35 and a resistor 36 . The switch 27 is turned off and the switch 35 is turned on by the power failure detection signal V _D. As shown in FIG. 2A, the input commercial AC voltage V _in decreases relatively slowly, and as shown in FIG. 2B, a signal V ₁ is obtained at the capacitor 28 that is approximately proportional to the peak value of the input commercial AC voltage V _in . , which also decreases with time, and following this signal V ₁ , the output voltage V _DC of the DC/DC converter 31 changes as shown in FIG. 2D. When the input commercial AC voltage V _in drops below a certain reference voltage, for example 80V (effective value), a power outage signal V _D is generated at time t ₂ , the switch 27 is turned off, the switch 35 is turned on, and the reference power supply 37 is turned off. Reference voltage V _S begins to charge capacitor 28 through resistor 36, and the voltage on capacitor 28 gradually increases from V ₁ to V _S . Accordingly, the output voltage V _DC of the DC/DC converter 31 gradually increases from time t ₂ as shown in FIG. 2D. The inverter 19 is in a cold standby mode while receiving the commercial power supply voltage, and is activated by the power outage signal V _D to output, for example, a rectangular alternating voltage with a flow angle of π/2 (constant). Further, the switches 14 and 15 are switched and connected to the fixed contact b side. Therefore, as shown in FIG. 2E, the alternating voltage Vout supplied to the load 16 decreases as the commercial AC voltage decreases, and by switching to the inverter output, the alternating voltage Vout is gradually reduced from the alternating voltage with the same peak value as the decreased commercial AC voltage. growing. When this alternating voltage reaches the rated peak value, the output voltage V _DC of the DC/DC converter 31 becomes equal to the reference voltage V _S and is maintained in this state.

[0011] According to this invention, in order to operate as described above, the load 16 is of a capacitor input type. Even if there is, the charging to that input capacitor is switched to the inverter output. Sometimes, it does not suddenly increase, and there is no risk of inrush current occurring. inverter If the square wave output has a flow angle of π/2 as described above, then the commercial power supply The same effective value is obtained at the same peak value as the sine wave voltage, and both the peak value and effective value are the same. You can switch the output by

In the embodiment shown in FIG. 1, when the commercial AC voltage falls below a predetermined value, the voltage E ₁ is supplied from the power supply 39 through the reverse blocking diode 41 to the non-inverting input side of the error amplifier 32, and the voltage applied thereto is For example, the commercial AC voltage is prevented from dropping below a certain value, eg, 90 V, peak value 126 V, and the output amplitude of the inverter 19 is prevented from reaching its rated value without too much delay. Further, in this example, when the peak value V ₁ becomes higher than a predetermined value, the reverse current blocking diode 42 becomes conductive and a current flows toward the power supply 43, causing the voltage on the non-inverting input side of the error amplifier 32 to exceed E ₂ . For example, when the commercial AC voltage is 110V, the peak value is limited to not exceed 184V. In this way, when the commercial AC voltage exceeds the range of 100±10V and a power outage occurs, the output of the inverter 19 is switched to the peak value of 90V or 110V, whichever is closer, and the output is switched to the output of the inverter 19 while receiving power. It is possible to always reduce the difference in peak values with respect to fluctuations in the commercial AC voltage.

[0013]

[Effect of the idea]

As mentioned above, according to this invention, when a power outage occurs, the commercial AC voltage wave immediately before the power outage occurs. The inverter output with a peak value that almost matches the high value is supplied to the load, and the inverter output Since the power is gradually increased to the rated value, it is typified by switching regulators. Even when the load is a capacitor-input type rectifier circuit, the inverter can be When switching to the output voltage, a capacitor charging inrush current is generated due to the voltage difference. It is possible to suppress the growth of

[0014] Therefore, deterioration of the fuse and rectifying element on the load side is reduced. In when switching This prevents abnormal drops in output voltage due to inverter overload protection, and Uninterruptible power supply with low cost and excellent load adaptability, with a low peak current design. A power supply can be provided.

[Brief explanation of drawings]

FIG. 1 is a connection diagram showing an embodiment of this invention.

FIG. 2 is a waveform diagram for explaining FIG. 1;

FIG. 3 is a connection diagram showing a conventional uninterruptible power supply.

FIG. 4 is a waveform diagram for explaining a problem with the device shown in FIG. 3;

Claims (1)

[Scope of utility model registration request] Claim 1: While receiving commercial AC power, the commercial AC power is supplied to the load, and when a drop in the commercial AC voltage is detected by the power outage detection means, the power of the built-in storage battery is supplied to the load by an inverter instead of the commercial AC power. In an uninterruptible power supply that converts into alternating power and supplies it to the load, when switching from the commercial AC power to the output of the inverter, the peak value of the inverter output is set near the peak value of the commercial AC voltage immediately before switching. 1. An uninterruptible power supply device characterized in that the uninterruptible power supply device is provided with means for gradually transitioning the output voltage from the peak value to the rated output voltage peak value.