JPH0865917A - Uninterruptible power system - Google Patents

Abstract

(57) [Abstract] [Purpose] When the AC power is turned on, the inrush current that flows through the input transformer or AC filter capacitor is suppressed. [Constitution] A converter 6 provided with an input transformer 3 or an AC filter capacitor 4 on the input side and converting AC supplied from an AC power supply 1 via an AC input switch 2 into DC.
And an inverter 7 for converting direct current of the converter into alternating current
In the uninterruptible power supply device including the storage battery 10 that supplies direct current to the inverter 7 when the AC power supply 1 fails, the converter 6 converts the DC voltage of the storage battery 10 into an AC voltage when the AC input switch 2 is released. To excite the input transformer 3 or the AC filter capacitor 4 so that the amplitude and phase of the excitation voltage match the amplitude and phase of the voltage excited by the AC power supply 1 when the AC input switch 2 is closed. An uninterruptible power supply comprising a means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply device having a transformer or an input filter capacitor on the input side, and particularly to suppressing an inrush current flowing in the transformer or the input filter capacitor when a commercial AC power source is turned on. Uninterruptible power supply that can be.

[0002]

2. Description of the Related Art Inverters for converting direct current into alternating current are widely used as uninterruptible power supply devices because stable alternating current can be obtained. The uninterruptible power supply is generally used as a power supply for a load of an electronic computer, but the load is various and is often used in a socially important place.

FIG. 4 is a block diagram showing an example of the conventional uninterruptible power supply device as described above. In the figure, 1 is an AC power source such as a commercial AC power source, 2 is an AC input switch, 3 is an input transformer, 4 is an input filter capacitor, 5 is a converter reactor, 6 is a converter, 7 is an inverter, and 8 is an inverter transformer. The container 9 is an AC output terminal. As the operation of the uninterruptible power supply, when the AC power supply 1 is normal, the AC from the AC power supply 1 supplied via the AC input switch 2, the input transformer 3, and the converter reactor 5 is converted into a converter 6.
Is converted into direct current, and this direct current is inversely converted into stable alternating current power by the inverter 7 to supply constant voltage constant frequency alternating current power to the load connected to the alternating current output terminal 9.

When the AC power supply 1 is abnormal (during a power failure), the power of the storage battery 10 is discharged and the inverter 7 converts the power back into stable AC power to supply stable AC power to the load without interruption. It has the characteristic that it can continue.

Next, referring to the converter control circuit, in FIG. 4, 11 and 12 are AC voltage detectors such as an insulation transformer for converting the input voltage of the AC power source 1 and the converter 6 into the voltage of the control circuit level, respectively. , 18 is an adder for adding the voltage of the AC power supply 1 and the input voltage of the converter 6, 19
Is an error amplifier that proportionally and integrates and amplifies the error component of the adder 18, 13 is a DC voltage detector that converts the voltage of the storage battery 10 to a voltage of an insulation and control circuit level, 14 is a DC voltage reference, and 16 is a DC voltage The output of the error amplifier 16 and the error amplifier 16 for amplifying the outputs of the reference 14 and the DC voltage detector 13 by proportionally / integrating the error generated in the adder 15 are output by the PLL circuit 17
Of the AC power supply 1 and gives a predetermined phase difference to the PLL circuit 17 operating on the phase basis of the AC power supply 1. Reference numeral 20 denotes a voltage control circuit, which has a predetermined phase reference θ ^* by the output signal of the PLL circuit 17 and a predetermined voltage reference V ^* by the output signal of the error amplifier 19 for adjusting the input voltage of the converter 6 to the AC power supply 1. Two inputs are used to convert a semiconductor element group used in the converter 6 into a base signal of a predetermined pulse, and 22 base drive circuits 2
2. Insulated and amplified by 2 and applied. That is, the converter 6 controls the reactive power with respect to the AC power supply 1 by adjusting the magnitude of the input voltage of the converter 6, and adjusts the phase difference with the AC power supply 1, which is a delay phase here, but this. As a result, it is possible to control the effective power with the AC power supply 1. Since such control is already known technology, detailed description thereof is omitted here.

The conventional uninterruptible power supply system shown in FIG. 4 has a problem that the inrush current of the input transformer 3 becomes very large when the AC power supply 1 is turned on again or the power is restored. This shows the BH curve of the iron core of the input transformer 3 in FIG.
In this B-H curve, B1 is the residual magnetic flux density, B2 is the maximum magnetic flux density during normal use, and generally, the maximum magnetic flux density B2 of the input transformer 3 is designed to be a value close to the saturation magnetic flux density of the iron core. Vessel 3 is in use.

Therefore, the AC power supply 1 is turned on again,
If the phase of the voltage applied to the input transformer 3 at the time of restoration from the instantaneous power failure is the phase polarity that causes the magnetic flux in the opposite direction to the residual magnetic flux B1, the re-rush current of the input transformer 3 does not increase so much, but the residual magnetic flux B1 If the phase polarity produces a magnetic flux in the same direction as, the magnetic flux density of the input transformer 3 instantly becomes equal to or higher than the saturation magnetic flux density, and there is a problem that a very large inrush current flows.

Such an inrush current is generally generated by the input transformer 3.
15 to 20 times the rated current of the AC power supply, and when such a large current flows, the AC power supply 1 itself, the input circuit breakers (not shown) provided between the AC power supply 1 and the input switch 2, and the like. There is a systematic problem of coordination such as other loads.

Therefore, the AC power supply 1 is turned on again,
It is necessary to suppress the inrush current flowing in the input transformer 3 when the power failure is restored. In order to suppress this inrush current to 5 to 10 times the rated current of the input transformer 3, the magnetic flux of the iron core of the input transformer 3 is required. A method of reducing the density B is generally adopted, and as a result, the size of the iron core of the input transformer 3 becomes large, and the outer shape and weight of the transformer itself become very large.

[0010]

As described above, in the conventional uninterruptible power supply, when the AC power supply 1 is turned on again or the power is restored, the inrush current of the input transformer 3 is generally equal to that of the input transformer 3. This is 15 to 20 times the rated current, and there is a problem that affects the AC power supply 1 itself and the load connected to another AC power supply.

On the other hand, in order to suppress the inrush current of the input transformer 3 which is generally allowed as a system to about 5 to 10 times the rated current, it is necessary to reduce the iron core magnetic flux density of the input transformer 3, and the input transformer 3 is required. There was a problem that the external dimensions of 3 were increased, the weight was significantly increased, and the price was significantly increased.

That is, the conventional uninterruptible power supply has the following problems. (1) It is necessary to suppress the inrush current in the input transformer installed on the input side of the uninterruptible power supply in consideration of the AC power failure, etc. There was a very increasing problem. (2) From the above problem. It was very uneconomical due to the problems of increasing the number of installation sites for input transformers and rising prices.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and can suppress the inrush current flowing through the input transformer when the AC power is turned on or the momentary power failure is restored, so that it is economical. To provide an uninterruptible power supply.

[0014]

In order to achieve the above-mentioned object, the invention according to claim 1 is provided with an input transformer or an AC filter capacitor on the input side, and is connected to an AC power source via an AC input switch. In the uninterruptible power supply device including a converter that converts the supplied alternating current into direct current, an inverter that converts the direct current of the converter into alternating current, and a storage battery that supplies direct current to the inverter during a power failure of the alternating current power supply, the converter is When the AC input switch is opened, the DC voltage of the storage battery is converted into an AC voltage to excite the input transformer or the AC filter capacitor, and the amplitude and phase of the excitation voltage are closed by closing the AC input switch. In this case, a control means for matching the amplitude and phase of the voltage excited by the AC power supply is provided.

Further, the invention according to claim 2 is a converter which is provided with an input transformer or an AC filter capacitor on the input side and which converts AC supplied from an AC power supply through an AC input switch into DC. In an uninterruptible power supply device comprising an inverter that converts direct current of the converter to alternating current and a storage battery that supplies direct current to the inverter when the alternating current power supply fails, the inverter has the storage battery when the alternating current input switch is released. Of the DC voltage is converted into an AC voltage to excite the input transformer or the AC filter capacitor, and at least the phase of the excitation voltage is a voltage excited by the AC power supply when the AC input switch is closed. It is characterized in that it is provided with a control means for matching the phase of the.

[0016]

According to the invention of claim 1, which is configured as described above, the converter constituting the uninterruptible power supply device is reverse-converted using the storage battery as the DC power supply immediately before the AC input switch is turned on, By reverse-exciting the input transformer or the AC filter capacitor and then turning on the AC input switch, it is possible to suppress the inrush current flowing through the input transformer or the AC filter capacitor.

According to the second aspect of the invention, the inverter constituting the uninterruptible power supply is operated by the inverter using the storage battery as the DC power source immediately before the AC input switch is turned on, and the input transformer or the AC filter capacitor is used. By reverse-exciting the switch and turning on the AC input switch, it is possible to suppress the inrush current flowing through the input transformer or the AC filter capacitor.

[0018]

FIG. 1 shows an embodiment of the present invention. This drawing is an embodiment in the case where the present invention is applied to the uninterruptible power supply of FIG. 4, and the circuit elements with the same numbers as in FIG. 4 have the same function.

In this figure, the difference from the conventional example is that the voltage establishment detection circuit 31 of the AC power supply 1 is added to the AC power supply 1
When the voltage of AC power supply 1 is not established, the AC input switch 2 is opened, the gate signal of the converter 6 is not given by the AND circuit 21, and the converter 6 is stopped. In addition, after adding a gate signal to the converter 6 and closing the AC input switch 2 after a predetermined time through the delay circuit 32, the function of utilizing the DC voltage control circuit of the converter 6 with the soft start circuit 33 is added. is there.

Next, the operation of the uninterruptible power supply according to the present invention will be described with reference to FIGS. 1 and 2. When the AC power supply 1 fails to power (at time to in FIG. 2), the converter 6 is stopped, the AC input switch 2 is opened, and the AC power supply 1 is in a standby state until the power is restored. At this time, the storage battery 1 is placed in the load of the UPS.
It is possible to discharge the direct current power of 0, convert it back into stable alternating current power by the inverter 7, and continue the supply.

In this state, when the AC input power supply 1 is restored (at time t1 in FIG. 2), the AC input switch 2 is in the open state, and no voltage is applied to the input transformer 3, so that inrush current naturally flows. Absent. After this, the converter 6 is started after a predetermined delay time (time t2 in FIG. 2). At this time, the output of the error amplifier 16 which is one input of the PLL circuit 17 is set to zero by the switch circuit 33 so that the manipulated variable is not applied.
Therefore, the phase of the converter 6 is controlled to be the same as the voltage phase of the AC power supply 1. In addition, the converter input voltage is set to a soft start method so that inrush current does not flow in the input transformer 3 and the input filter capacitor 4 at the time of start-up. The voltage of the capacitor 4 is controlled to be equal, and the input transformer 3 is excited from the converter 6 side using the DC power of the storage battery 10.

The amplitude and phase of the excitation voltage at this time are equal to the amplitude and phase of the voltage excited by the AC power supply 1 when the AC input switch 2 is closed. Thereafter, after a predetermined delay time, the AC input switch 2 is closed at the time t4 in FIG. At this time, the input transformer 3 is excited by the converter 6 and is controlled so that the voltage magnitude and phase of the AC power supply 1 and the converter input (terminal voltage of the input filter capacitor 4) become equal to each other. Even if the switch 2 is closed, no inrush current flows.

After that, when the AC input switch 2 is closed, in order to operate the DC voltage constant control system for converter control, the error amplifier 16 is utilized to make the input voltage phase of the converter 6 more than that of the AC power supply 1. The battery voltage is delayed and the DC voltage is gradually increased to automatically control the storage battery 10 to be charged.

As described above, the converter 6 is started by using the DC power of the storage battery 10 when the AC power source 1 is turned on or the power failure is restored, and the magnitude and phase of the input side AC voltage of the converter 6 are made to match the AC power source 1. After that, the AC input switch 2 is closed.

Therefore, the inrush current of the input transformer 3 can be made to hardly flow as compared with the conventional case by the embodiment of the present invention, and the size and weight can be reduced as compared with the case where the inrush current is suppressed by the input transformer 3 itself. .

In this embodiment, the operation has been described so that the inrush current is minimized. However, depending on the system, the excitation of the input transformer 3 by the converter 6 is performed only momentarily, and the residual voltage remains. The inrush current can be suppressed by closing the AC input switch 2 while the operation is in progress, and various operations can be performed without departing from the scope of the present invention, and the operation is particularly limited. is not.

In the above-mentioned embodiment, the explanation was made by exciting the input transformer 3 by the converter 6, but as shown in FIG. 3, the output voltage of the inverter 7 is passed through the switch 41 and the current limiting element 42. Voltage is applied to the input transformer 3 for a predetermined period of time, and the inrush current of the input transformer 3 is suppressed even if the AC input switch 2 is closed at the place where the output voltage phase of the inverter 7 and the phase of the AC power supply 1 match. It is clear that you can.

Further, in the above description, the inrush current of the AC power supply 1 was explained by taking the excitation inrush current of the input transformer 3 as a representative, but even in the uninterruptible power supply system in which the input transformer 3 is unnecessary, the input to the converter 6 is applied. Input filter capacitor 4 added
It can also be implemented for the purpose of suppressing the inrush current to the.

[0029]

As described above, according to the first and second aspects of the present invention, the input transformer provided between the AC power supply and the uninterruptible power supply is an AC power supply. When the power is restored, the switch is closed after the input transformer is excited by the uninterruptible power supply, so that the inrush current can be reduced. As a result, the following effects are obtained. (1) Prevents voltage fluctuations and instability of the AC power supply (especially private power generation equipment with a small power supply capacity) because the inrush current decreases, ensuring the stability of the uninterruptible power supply and connecting to the AC power supply. Does not affect the load equipment. (2) Since the inrush current decreases, the special specifications of the transformer that suppresses the inrush current to a certain level are unknown, and the transformer can be made smaller and lighter than before. (3) The installation location can be reduced and the price can be reduced by making the transformer smaller and lighter.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the present invention.

FIG. 3 is a main circuit configuration diagram showing another embodiment of the present invention.

FIG. 4 is a block diagram of a conventional device

FIG. 5 is a BH curve diagram for explaining the operation of the conventional device.

[Explanation of symbols]

1 ... AC power supply 2 ... AC input switch 3 ... Input transformer 4 ... Input filter capacitor 5 ... Converter reactor 6 ... Converter 7 ... Inverter 8 ... Inverter transformer 9 ... AC output terminal 10 ... Storage battery 11 ... Voltage converter 12 ... Voltage converter 13 ... DC voltage detector 14 ... DC voltage reference 15 ... Adder 16 ... Error amplifier 17 ... PLL circuit 18 ... Adder 20 ... PWM control circuit 21 ... AND circuit 22 ... Base drive circuit 31 ... Voltage establishment detection Circuit 32 ... Delay circuit 33 ... Switch circuit 41 ... Switch 42 ... Current limiting element

Claims (2)

[Claims] 1. A converter that has an input transformer or an AC filter capacitor on the input side, converts an alternating current supplied from an alternating current power supply through an alternating current input switch to a direct current, and a direct current of the converter to an alternating current. In an uninterruptible power supply device including an inverter and a storage battery that supplies direct current to the inverter when the AC power supply fails, the converter converts the DC voltage of the storage battery to an AC voltage when the AC input switch is released. Means for exciting the input transformer or the AC filter capacitor and making the amplitude and phase of the excitation voltage coincide with the amplitude and phase of the voltage excited by the AC power supply when the AC input switch is closed. An uninterruptible power supply characterized by comprising: 2. A converter that has an input transformer or an AC filter capacitor on the input side, converts an alternating current supplied from an alternating current power supply through an alternating current input switch to a direct current, and a direct current of the converter to an alternating current. In an uninterruptible power supply device including an inverter and a storage battery that supplies direct current to the inverter when the AC power supply fails, the inverter converts the DC voltage of the storage battery into an AC voltage when the AC input switch is released. Control means for exciting the input transformer or the AC filter capacitor to match at least the phase of the excitation voltage with the phase of the voltage excited by the AC power source when the AC input switch is closed. An uninterruptible power supply characterized by the above.