JPS648529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an uninterruptible power supply comprising a commercial power source and an inverter power source.

FIG. 1 shows the configuration of a conventional uninterruptible power supply of this type. In the figure, 1 is a commercial power supply, 2 is an inverter power supply that converts DC voltage to AC voltage, 3 is an AC filter circuit that bypasses and smooths the harmonics of the AC voltage supplied from the inverter power supply 2 via the line 4, 5 is a synchronization detection circuit for synchronizing the voltage of the inverter power supply 2 with the voltage of the commercial power supply 1; 6 is a commercial side switch using a semiconductor for turning on and off the commercial voltage; and 7 is a semiconductor for turning on and off the inverter voltage. The used inverter-side switch 8' is a switching circuit that switches both switches 6 and 7 in an interlock state, and 9 outputs a switching command signal to select either the commercial power supply 1 or the inverter power supply 2 to activate the switching circuit 8'. This is a switching command section that controls the switching. This switching command unit 9 is supplied with the operating status of each part via a line 90, a switching command signal for switching from the commercial power supply 1 to the inverter power supply 2 is outputted from a line 91, and a switching command signal for switching from the commercial power supply 1 to the inverter power supply 2 is outputted from a line 92. A switching command signal is issued to switch to. 10, either the commercial voltage or the inverter voltage is connected to the switch 6,
The load is switched at 7 and supplied via a common output line 11, I ₁ is an ammeter that measures the current on line 4 via current transformer CT ₁ , I ₂ is connected to line ₁ via current transformer CT 2.
1 is an ammeter that measures the current of line 11, and V is a voltmeter that measures the voltage of line 11.

In such an uninterruptible power supply, the inverter power supply 2 is always operated in synchronization with the commercial power supply 1, so that the voltage phases of the commercial power supply 1 and the inverter power supply 2 match. In this state, high-quality power is always supplied to the load from the inverter power supply 2, but
When the load 10 becomes transiently overloaded, the inverter power supply 2 instantly switches to the commercial power supply 1, and power is supplied from the commercial power supply 1 to the load 10. When the load 10 recovers from the transient load and reaches the rated load state, the commercial power supply 1 to inverter power supply 2.

However, in conventional uninterruptible power supplies, when switching from a commercial power source 1 with a large capacity to an inverter power source 2 with a small capacity, this is done at any point in one cycle of the AC voltage, so each time there is a change in the instantaneous voltage. They vary in size, in large cases about 20
There was a drawback that a voltage that was 10% smaller was supplied to the load 10. If such an undervoltage is supplied to the load 10 such as an electronic computer, there is a risk that it may cause an accident in the load 10.

An object of the present invention is to provide an uninterruptible power supply device that can suppress instantaneous voltage fluctuations as much as possible when switching from a commercial power source to an inverter power source.

In the present invention, as shown in Fig. 2A and B, there is a gap between the output voltage V of the commercial power supply and the inverter power supply that are operated synchronously, and the inverter output current _I1 in the no-load state before passing through the AC filter circuit. Focusing on the fact that there is always a constant phase relationship, when switching from a commercial power source to a smaller capacity inverter power source,
By issuing a switching trigger signal at a certain phase shift from the output voltage, switching is performed at or near the zero point of the inverter output current before passing through the AC filter circuit (each t ₁ section in Figure 2 B), and when switching This is to suppress fluctuations in the instantaneous voltage as much as possible. In the figure, _t2 is the range in which switching from commercial power supply to inverter power supply is not performed, and T is the period.

Hereinafter, specific examples of the present invention will be described in detail with reference to the drawings. FIG. 3 shows an embodiment of the uninterruptible power supply according to the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals, and their explanation will be omitted. In the figure, 12 is a voltage that detects the output voltage of the commercial power supply 1 or the output voltage of the inverter power supply 2 and outputs a switching trigger signal at a phase corresponding to the zero point or the vicinity of the zero point of the inverter output current before passing it through the AC filter circuit 3. This is a detection type trigger circuit. In this embodiment, the output voltage of the AC filter circuit 3 is detected. Reference numeral 8 denotes a switching circuit which receives a switching command signal from the switching command unit 9 and a switching trigger signal from the voltage detection type trigger circuit 12 and outputs a switching signal to either the commercial side switch 6 or the inverter side switch 7. .

In such an uninterruptible power supply, when the switching command signal is output from the line 91 of the switching command section 9,
Moreover, when the switching trigger signal is output from the voltage detection type trigger circuit 12, a switching signal from the commercial power source 1 to the inverter power source 2 is instantly output from the switching circuit 8 to the commercial side switch 6 and the inverter side switch 7, and the switch 6 is activated. The switch 7 is turned on and power is supplied to the load 10 from the inverter power supply 2 side. Since this switching is performed at or near the zero point of the inverter output current before passing it through the AC filter circuit 3, it is possible to suppress fluctuations in the instantaneous voltage when switching from a no-load state to a full-load state as much as possible. can. Note that the switching from the inverter power source 2 to the commercial power source 1 is performed immediately upon receiving the switching command signal from the line 92 without taking the above-mentioned consideration. Even if the switching is performed in this manner, since the commercial power supply 1 has a large capacity, the fluctuation in the instantaneous voltage at the time of switching is small and does not pose a problem.

FIG. 4 shows an example of a specific circuit configuration of the voltage detection type trigger circuit 12. In the figure, R ₁ to _{R 5} are resistors, C ₁ to _{C 4} are capacitors, and T ₁
is an isolation transformer that insulates the input AC voltage and outputs the AC voltage, and IC ₁ amplifies the DC voltage divided by resistors R ₁ and R ₂ to form the DC voltage for determining the trigger phase. The amplification integrated circuit IC ₂ is an isolation transformer that receives as input the DC voltage for trigger phase determination output from the amplification integrated circuit IC ₁ and the AC voltage obtained by shifting the phase of the AC voltage output from the isolation transformer T ₁ .
Phase control that outputs a switching trigger signal (pulse voltage) at a predetermined phase with respect to the output AC voltage of T ₁ (at a phase corresponding to the zero point of the inverter output current before passing through the AC filter circuit 3 or its vicinity) For the integrated circuit, V is the input alternating voltage of the isolation transformer _T1 .

5A, B, C, and D show waveforms of various parts of this voltage detector trigger circuit 12.

The voltage detection type trigger circuit 12 is an isolation transformer to which an AC voltage V is input as shown in FIG. 5A.
The phase of the output AC voltage of T ₁ is shifted by θ using resistors R ₃ and R ₄ and capacitors C ₁ and C ₂ , and the phase-shifted AC voltage a as shown in FIG. 5B is transferred to a phase control integrated circuit IC _2. is input to generate a sawtooth voltage c as shown in FIG. 5C across capacitor _C4 . On the other hand, the DC voltage is divided by resistors R ₁ and R ₂ to create an amplification integrated circuit.
IC ₁ is applied to obtain a DC voltage b for determining the trigger phase as shown in FIG. 5C. The trigger phase determining DC voltage b and the sawtooth voltage c are matched by a phase control integrated circuit IC ₂ , and a predetermined voltage is applied to the AC voltage V as shown in FIG. 5D from the output terminal of this integrated circuit IC ₂ . A pulse-like switching trigger signal d is generated at the phase (at the phase corresponding to the zero point of the inverter output current before passing through the AC filter circuit 3 or its vicinity).
is output and applied to the switching circuit 8.

Note that the input voltage of the voltage detection type trigger circuit 12 is not limited to that obtained from the location shown in FIG. It can be obtained from either.

As explained above, the uninterruptible power supply according to the present invention detects the output voltage of the commercial power source or the output voltage of the inverter power source, and detects the phase that corresponds to the zero point of the inverter output current or its vicinity before passing it through the AC filter circuit. By the way, since a switching trigger signal is issued to switch from the commercial power source to the inverter power source, it is possible to suppress fluctuations in the instantaneous voltage of the inverter power source as small as possible when switching from the commercial power source to the small capacity inverter power source. . In particular, in the present invention,
The voltage detection type trigger circuit outputs a switching trigger signal at a predetermined phase with respect to the AC voltage (at a phase corresponding to the zero point of the inverter output current before passing through the AC filter circuit or its vicinity), so the peak of the AC voltage can be detected. However, there is no change in the switching timing that occurs with the type that outputs a switching trigger signal, and the switching from commercial power to inverter power can always be done at or near the zero point of the inverter output current, and the switch can be made at the desired point. This has the advantage of improving switching reliability. According to experiments, the voltage fluctuation, which was conventionally about 20%, can be suppressed to about 10% according to the present invention. Therefore, according to the present invention, it is possible to provide a high-quality uninterruptible power supply device, which is most suitable as a power source for measurement and measurement of electronic computers, chemical plants, etc., for example. Furthermore, since the present invention uses a voltage detection method, the detected voltage does not change significantly regardless of load fluctuations, so there is no need to provide special protection means for the voltage detection type trigger circuit, which is advantageous in terms of implementation. be.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional uninterruptible power supply.
Figures 2A and B are waveform diagrams for explaining the principle of the present invention, Figure 3 is a block diagram showing an embodiment of the uninterruptible power supply according to the present invention, and Figure 4 is a voltage detection used in this device. FIGS. 5A, B, C, and D are waveform diagrams of each part of FIG. 4, which is a circuit diagram showing an example of a specific circuit configuration of the type trigger circuit. 1...Commercial power supply, 2...Inverter power supply, 3...
...AC filter circuit, 5...Synchronization detection circuit, 6...
...Commercial side switch, 7...Inverter side switch, 8...Switching circuit, 9...Switching command section, 12...
...Voltage detection type trigger circuit.

Claims (1)

[Claims] 1. In an uninterruptible power supply device that supplies power to a load without interruption by switching between a commercial power source and an inverter power source that are operated synchronously using a switching signal output from a switching circuit, the commercial power source and the inverter power source are a voltage detection type trigger circuit that detects the output voltage or the output voltage of the inverter power supply and outputs a switching trigger signal at a phase corresponding to the zero point or the vicinity of the zero point of the inverter output current before passing it through the AC filter circuit; and a switching command unit that issues a switching command signal to select one of the inverter power sources, and the switching circuit is configured such that the switching command unit issues the switching command signal and the voltage detection type trigger circuit issues the switching trigger signal. An uninterruptible power supply device characterized in that the uninterruptible power supply device is configured to issue a switching signal for switching from the commercial power source to the inverter power source at a certain point in time.