JPH0638404A - Uninterruptible power supply device - Google Patents

Abstract

PURPOSE:To enable the power unit to stably supply a prescribed voltage to a load without adding any special device to the unit by making a self-excited converter operate as a reactive power adjuster in a by-pass feeding mode which is set when an inverter becomes defective while commercial power supply is normal. CONSTITUTION:When an inverter 5 is sound, the AC voltage of commercial power supply 1 is fed to a load 8 through an input transformer 2, self-excited converter 3, etc. In addition, a switch 23 is closed and the voltage of the power supply 1 is selected as a reference voltage, and then, the input voltage of the converter 3 is controlled so that the voltage can become equal to the voltage of the power supply 1. When the inverter 5 becomes defective, a change-over switch 7 is set to a by-pass circuit 6 side by means of the output of a fault detector 21 and, at the same time, a switch 22 is opened. As a result, the phase adjustment of a PLL 16 is shifted to the vicinity of zero. In addition, a switch 24 is closed and the converter 3 is operated as a reactive power adjuster by using a prescribed reference AC voltage as a reference voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter composed of a self-exciting converter and an inverter, and an uninterruptible power supply having a bypass circuit, and more particularly, to bypass power feeding when the inverter fails. The present invention relates to an uninterruptible power supply capable of supplying stable and high-quality power to a load even at times.

[0002]

2. Description of the Related Art Inverters for converting direct current into alternating current are capable of obtaining stable alternating current, and are therefore used for uninterruptible power supply (hereinafter referred to as UP
Abbreviated as S). UPS is generally used as a power source for electronic computers and the like, and in recent years, it is often used in socially important places. In addition, a system having a bypass circuit is generally used in the current UPS, and in the event of an inverter
Even if a problem occurs in the power supply, the UPS can switch from the UPS to the bypass circuit without interruption, and the load power can be directly supplied from the commercial power supply.

The structure of a conventional UPS will be described with reference to FIG. In the figure, 1 is a commercial power supply, 2 is an input transformer, 3
Is a semiconductor element such as a transistor, and is a self-exciting converter that has the function of converting AC power to DC power. 4 is an electrolytic capacitor that absorbs the ripple of DC voltage. 5 is the conversion of DC voltage to AC voltage. An inverter, 6 is a bypass circuit, 7 is a changeover switch for switching the output of the inverter 5 and the bypass circuit 6, and 8 is a load.

The operation of the changeover switch 7 will be briefly described here centering on the flow of electric power. When the inverter 5 is healthy, the changeover switch 7 selects the side of the inverter 5 and the commercial power source 1 The AC power is converted into DC by the converter 3 via the input transformer 2, converted into stable AC by the inverter 5 again, and the load power is supplied via the changeover switch 7. In the unlikely event that the inverter 5 fails, the inverter failure detector 21 determines the failure, and at the same time, a command is given to the changeover switch 7, and the changeover switch 7 selects the bypass circuit 6. Therefore, the flow of electric power at this time is from the commercial power source 1 to the input transformer 2, the bypass circuit 6,
The load is fed through the changeover switch 7.

Next, the control circuit of the self-exciting converter 3 will be described with reference to FIG. In the figure, 1
Reference numerals 0 and 11 are commercial power supply 1 and an AC voltage detector such as an insulation transformer for converting the voltage of the input voltage of the self-excited converter 3 into the voltage of the control circuit level, and 17 is the voltage of the commercial power supply 1 and the self-excited converter. -An adder for obtaining the difference of the input voltage of the converter 3, 18 is an error amplifier which amplifies the error component of the adder 17 by proportionally / integrating, and 12 isolates the DC voltage converted by the self-exciting converter 3 and A DC voltage detector for converting to a voltage of the control circuit level, 13 is a DC voltage reference, 14 is an adder for obtaining a difference between the outputs of the DC voltage reference 13 and the DC voltage detector 12, and 15 is an error component of the adder 14. The output of the error amplifier 15 that proportionally / integrates and amplifies the signal becomes one input of the PLL circuit 16, and operates with the phase reference of the commercial power supply 1 provided from the AC voltage detector 10.
6 will be given a predetermined phase difference. 19 is P
The WM voltage control circuit is a predetermined phase reference θ ^{* based on} the output signal of the PLL circuit 16 ^. , And an error amplifier 1 for adjusting the input voltage of the self-excited converter 3 to be equal to the commercial power supply 1.
8 output signal, a predetermined voltage reference V ^* It has a function of converting into a base signal of a predetermined pulse train by two inputs. The base drive circuit 20 insulates and amplifies the base signal at the control circuit level to control the base of the semiconductor element group used in the self-excited converter 3.

That is, the self-exciting converter 3 controls the reactive power with respect to the commercial power source 1 by adjusting the magnitude of the input voltage of the self-exciting converter 3, and the phase difference from the commercial power source 1, However, the effective phase with the commercial power source 1 can be controlled by adjusting this.

To briefly explain the advantage of using the self-exciting converter 3, the active power and the reactive power can be independently controlled unlike the general thyristor rectifier, and the input power factor is set to 1. If it is controlled, it is possible to minimize the required input capacity of UPS, and if the semiconductor element of the self-exciting converter 3 is a pulse train having a predetermined pulse width (called PWM method), a commercial power source It is possible to suppress the higher harmonic current generated in No. 1.

[0008]

In a UPS having such a structure, in the unlikely event that the inverter is out of order, the power supply path to the load is from the inverter side to the bypass circuit 6.
Is switched to the side and the voltage of the commercial power source 1 remains unchanged as the load 8
Will be supplied to. At this time, the load voltage is controlled to a predetermined value by the inverter 5 when the load power is supplied on the inverter 5 side, but the voltage fluctuation of the commercial power supply is performed when the load power is supplied on the bypass circuit 6 side. Becomes the load voltage as it is, and the impedance drop of the input transformer 2 becomes large depending on the values of the load capacity and the power factor, and even if the power is supplied from the bypass circuit 6, fluctuations in the power supply voltage to be supplied allow the load voltage. There is a risk of exceeding the range and dropping the load 8.

Therefore, an object of the present invention is made in view of the above-mentioned point, and in a UPS composed of a converter and a bypass circuit in which a self-exciting converter and an inverter are combined, It is an object of the present invention to provide a UPS that can stabilize the load voltage without using special equipment even when the inverter has a failure and the load power supply is switched to the bypass circuit.

[0010]

In order to achieve the above object, the present invention comprises a self-exciting converter for converting alternating current supplied from a commercial power source into direct current and an inverter for converting direct current into alternating current. And a bypass circuit for directly supplying a load from the commercial power source to the load at the time of failure or maintenance inspection of the converter, in the case where the commercial power source is healthy and the inverter fails. In the bypass power supply mode, the self-exciting converter is provided with a changeover switch capable of switching from input power factor control to voltage control so that the input voltage of the self-exciting converter can be controlled to a predetermined value. It was done.

[0011]

According to the present invention, the load voltage during bypass power feeding can be adjusted by the self-exciting converter even when the inverter is out of order, so that the stability of the load voltage during bypass power feeding can be improved. It is possible to improve the reliability of the UPS system.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the block diagram of FIG. In FIG. 1, the same parts as those in FIG. 2 which is a conventional example are denoted by the same reference numerals and the description thereof is omitted. The embodiment of FIG. 2 differs from the conventional one in that, in response to the inverter failure detector 21, the switches 22 and 23 are closed when the inverter is normal and open when the inverter is in failure. An AC voltage reference Va ^* for setting the input AC voltage of the self-exciting converter 3 to a predetermined value is provided with a switch 24 that opens when the inverter is normal and closes when the inverter fails ^. The point is that a setting device 25 for setting is set.

The error amplifier 15 is connected through the switch 22.
Is applied to the PLL circuit to output the output of the AC voltage detector 10 via the switch 23 and the AC voltage reference Va ^* via the switch 24 ^. Are applied to the adder 17, respectively.

Next, the operation of the present invention configured as described above will be described. When the inverter 5 is healthy, the analog switch 22 is closed, and the AC voltage of the commercial power source 1 is supplied to the load 8 via the input transformer 2, the self-excited converter 3, the inverter 5, and the changeover switch 7. To be done. Also, the analog switch 23 is closed, the analog switch 24 is open, the commercial power source 1 is selected as the voltage reference, and the input voltage of the self-excited converter 3 is controlled to be equal to the commercial power source 1. , The reactive power is adjusted to zero and the input power factor is adjusted to one.

In this state, if the inverter fails due to some trouble, the inverter failure detector 21 operates to give a bypass power supply command to the changeover switch 7 and at the same time the self-exciting converter 3 operates. A command is also given to the control circuit to open the analog switch 22 and the PLL circuit 16
The phase adjustment of is shifted to near zero. Further, the analog switch 23 is opened and the analog switch 24 is closed, and the voltage reference is set to a predetermined AC voltage reference, so that the input voltage of the self-exciting converter 3 is controlled to a predetermined value, so that the commercial power source can be used. The AC voltage of 1 also controls the load voltage supplied to the load 8 via the input transformer 2, the bypass circuit 6, and the changeover switch 7 to a predetermined value.

[0016]

As described above, according to the present invention, even in the bypass power supply mode when the commercial power source is sound and the inverter fails, the self-exciting converter 3 is disabled without stopping. Since the input voltage of the self-excited converter 3 can be adjusted by operating as a power controller, a stable load can be specified without adding a special device for adjusting the commercial power supply voltage during bypass power feeding. It is possible to supply the voltage of.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an uninterruptible power supply device showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional uninterruptible power supply device.

[Explanation of symbols]

1 ... Commercial power supply 2
Input transformer 3 Self-exciting converter 4
… Electrolytic capacitor 5… Inverter 6
… Bypass circuit 7… Changeover switch 8
… Loads 10, 11… AC voltage detector 12
... DC voltage detector 13 ... DC voltage reference 14, 17
... Adder 15, 18 ... Error amplifier 16
... PLL circuit 19 ... PWM voltage control circuit 20
... Base drive circuit 21 ... Fault detection circuit 22, 23
… Analog switch 24… Analog switch 25
... AC voltage reference setter

Claims (1)

[Claims] 1. A converter comprising a self-exciting converter for converting an alternating current supplied from a commercial power source into a direct current, an inverter for converting a direct current to an alternating current, and a failure or maintenance inspection of the converter. In an uninterruptible power supply composed of a bypass circuit for directly feeding a load from a commercial power source, in the bypass power feeding mode when the commercial power source is healthy and the inverter fails, the self-exciting converter An uninterruptible power supply device characterized in that the input voltage of the self-exciting converter can be controlled to a predetermined value by providing a changeover switch for switching from input power factor control to voltage control.