JPH01259737A - Uniterruptible power source equipment - Google Patents

Abstract

PURPOSE:To compensate reactive power and to improve operational efficiency, by regulating the magnitude of output voltage from a power converting means with respect to the system voltage thereby controlling the reactive power to be fed from a reactive power supply means to the receiving end of the power system. CONSTITUTION:Upon detection of power interruption of a power system 21, output voltage from an inverter 28 is controlled to a predetermined level and a thyristor switch 291 is turned ON to feed output voltage from the inverter 28 to a computer 23. At the same time, a thyristor switch 22 is turned OFF to interrupt a switch 30. The difference between the output voltage from the inverter 28 and the system voltage prior to power interruption can be confined within a range allowable at the load side by selecting a small value for an AC reactor 29. Since reactive power can be compensated through effective utilization of the output from the inverter 28, operation with approximately 100% power factor can be realized resulting in the improvement of operation efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an uninterruptible power supply used as a power source for computers and the like.

(Prior Art) As is well known, uninterruptible power supplies are used as power supplies for computers in consideration of the magnitude of damage caused when the computer's functions stop due to a power outage.

Conventionally, as shown in FIG. 7, this type of uninterruptible power supply has a direct transmission circuit 4 that directly supplies AC power from the power system 1 to the computer 3 via the SIRISK switch 2, and AC power from grid 1 is transferred to transformer 5
The AC power is supplied to the rectifier 6 via the inverter 8, which converts the AC power to DC power and charges the secondary battery 7, and further converts the output of the secondary battery 7 to AC power via the inverter 8. The computer 3 via the switch 9
Some devices have a spare circuit 10 that supplies the power to the user.

However, in such a power supply device, when the power system 1 is normal and is supplying high-quality power, the SIRISK switch 2 is turned on and the power from the power system 1 is transferred to the computer through the direct transmission circuit 4. Supply to 3. At the same time, power supplied from the power system 1 is supplied to the rectifier 6 via the transformer 5, where the alternating current power is converted to direct current power, and the DC power is supplied to the secondary battery 7 for charging. When a power outage occurs in the electric power system 1 and a detection means (not shown) detects this state, the thyrisk switch 2 is turned off, the thyrisk switch 9 is turned on at the same time, and the secondary battery 7 is turned on. By supplying the output from the inverter 8, which converts the output of the AC power into AC power, to the computer 3 via the SIRISK switch 9, power can be supplied to the computer 3 without interruption.

However, in such an uninterruptible power supply, when the SIRISK switch 9 is in the OFF state during normal operation, the inverter 8 is on standby in a no-load state, so power is wasted in the inverter 8. Moreover, since operation using the rectifier 6 has a poor power factor, there is a drawback that the operating efficiency of the power supply device is extremely degraded.

(Problems to be Solved by the Invention) Conventionally, there have been problems in that not only the inverter wastes power, but also the operating efficiency of the power supply device deteriorates due to a decrease in the operating power factor of the rectifier. Ta.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an uninterruptible power supply that can compensate for reactive power and improve operating efficiency.

[Configuration of the Invention (Means for Solving the Problems) As shown in FIG. Electricity storage means 12 and this electricity storage means 12
a power conversion means 13 that converts the output of the power converter into a predetermined power and supplies the converted power to the load in place of the power supply means during a power outage in the power system; and generates reactive power from the output of the power converter 13. and reactive power supply means 14 for supplying the power to the receiving end of the power system.

(Function) This invention adjusts the magnitude of the output voltage v1 of the power conversion means 11 with respect to the voltage VL of the power system during normal operation when power is directly supplied to the load from the power system, and the reactive power supply means 14 By controlling the reactive power supplied to the receiving end of the power system, it is possible to compensate for the reactive power while blindly utilizing the output of the power conversion means. In this case, FIG. 2(a) shows a case where the output voltage v1 of the power conversion means 11 is synchronized with the voltage VL of the power system and has the same magnitude,
In this case, no reactive power is supplied from the reactive power supply means 14 to the receiving end of the power system. Then, as shown in FIG. 2(b), when the output voltage v1 of the power conversion means 11 is made larger than the voltage VL of the power system, a reactive current IACL due to the difference voltage between the voltage Vl and the voltage VL is applied to the reactive power supply means 14. The reactive power VLXIACL is supplied to the power receiving end of the power system, and conversely, when the output voltage Vl of the power conversion means 11 is made smaller than the voltage VL of the power system as shown in FIG. It will be supplied to the receiving end of the grid.

(Example) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows the main circuit of the same embodiment.

In this case, a direct transmission circuit 24 is provided that directly supplies AC power from the power system 21 to the computer 23, which is a load, via the SiRisk switch 22.

Further, AC power from the power system 21 is supplied to a rectifier 26 via a transformer 25, where it is converted into DC power. The DC power from the rectifier 26 is applied to the secondary battery 27 to charge it. Then, the DC output from the secondary battery 27 is applied to the inverter 28 to convert it into AC power, which is then supplied to the computer 23 via the SIRISK switch 291.

On the other hand, the output from the inverter 28 is transferred to the AC reactor 29.
The reactive current obtained through this AC reactor 29 is passed through the switch 30 to the power receiving end 11a of the power system 11.
supply to. Further, a current transformer 31 and a transformer 32 are provided at the power receiving end 21a of the power system 21, so that the current I and voltage V at the power receiving end 21a are detected. The current output I of the current transformer 31 and the voltage output V of the transformer 32 are then applied to a reactive power control circuit shown in FIG.

In this case, output 1 from current transformer 31 and transformer 32,
(2) is given to the reactive power converter 33. This reactive power converter 33 calculates reactive power from Q=VIs1nθ and supplies this reactive power Q to a comparator 34. This comparator 34 is given a reactive power reference value Q ref' (usually 0). The comparison outputs of the comparators 34 and the like are then provided to the inverter voltage control circuit 35. This control circuit 35 controls the output voltage of the inverter 28 according to the output of the comparator 34.

Next, the operation of the embodiment configured as described above will be explained.

First, a case where the power system 21 is healthy and operates normally will be described. Here, as an example, a case will be described in which the power at the power receiving end 21a necessary for powering the computer 23 and charging the secondary battery 27 is the received power S with the power factor COS θ shown in FIG. In this case, if the voltage VL of the power system 21 is taken as the vector reference in FIG. 5, the received power S is divided into active power PS and reactive power QS. Therefore, in order to compensate for the reactive power Qs from such a state, the reactive power reference value Q ref' is set to "0" in the control circuit shown in FIG. 4.

In this case, the Cyrisk switch 22 is on, the Cyrisk switch 291 is off, and the AC power from the power system 21 is directly supplied to the computer 23 via the Cyrisk switch 22 by the direct transmission circuit 24. Also,
In this state, the rectifier 26 performs floating charging on the secondary battery 27, and the inverter 28 generates an AC output synchronized with the grid power. In this state, switch 3
0 will now be inserted. Then, the current I and voltage V at the receiving end 21a are changed by the current transformer 31 and the transformer 32.
is detected. The current I and voltage V at the power receiving end 21a detected by the current transformer 31 and the transformer 32 are the fourth
It is applied to the reactive power control circuit shown in the figure, outputted by the reactive power converter 33 as reactive power Q - V I sin θ, and applied to the comparator 34 . The comparator 34 then compares it with a reactive power reference value Qrcf' (usually 0), and the comparison output is given to the inverter voltage control circuit 35. In this case, the inverter voltage control circuit 35 outputs a voltage increase command to the inverter 28 based on the difference between the reactive power Q-Vlsinθ and the reactive power reference value Q ref.

As a result, the output voltage V1 of the inverter 28 becomes larger than the voltage VL of the power system, and a leading current IAc flows through the AC reactor 29 according to the difference voltage between the voltage v1 and the voltage VL.
t, and reactive power QINV as shown in FIG. 5 is supplied to the power receiving end 21a of the power system. In this case, the reactive power QINV is controlled until it becomes equal in magnitude to the reactive power QS of the received power S, and is stabilized in this state. As a result, the reactive power QS of the received power S is compensated,
The received power S is only the active power PS. In other words, such an operation improves the power factor of the received power, and the power supply device operates at a power factor of approximately 100%.

Next, a case will be described in which a power outage occurs in the power system 21 during such operation. In this case, when a power outage in the power system 21 is detected, control is performed to maintain the output voltage of the inverter 28 at a predetermined value, and the sirisk switch 2
91 is turned on, and the output voltage from the inverter 28 is supplied to the computer 23. At the same time, the sirisk switch 22 is turned off, and the switch 30 is turned off.
If you do, you will be cut off. Here, it is possible that the output voltage of the inverter 28 becomes higher than the grid voltage before the power outage, but this difference can be kept within the range allowed by the load side by selecting a small value for the AC reactor 29. .

Therefore, in this way, the reactive power of the received power can be compensated for by effectively utilizing the output of the inverter 28 without interfering with the original function of the uninterruptible power supply, so the power factor is almost 100%. This also makes it possible to drive the vehicle, leading to a dramatic improvement in operating efficiency.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist. For example, in the above-described embodiment, reactive power is compensated for by changing the reactive power reference value Q rel', but it is also possible to input and output reactive power within the range of the capacity of the inverter 28. . Further, in the above-described embodiment, a case was described in which compensation for reactive power is performed only for the uninterruptible power supply, but as shown in FIG.
By connecting another load 40 to a, it is also possible to perform reactive power compensation for the entire electrical equipment including the uninterruptible power supply. In this case, the reactive power value to be controlled is
By performing feedback control similar to that described above using the voltage and current at a, it is possible to freely compensate from leading power to lagging power.

[Effects of the Invention] This invention provides power from the reactive power supply means by adjusting the magnitude of the output voltage of the power conversion means with respect to the voltage of the power grid during normal operation when power is supplied directly from the power grid to the load. Since the reactive power supplied to the power receiving end of the grid can be controlled, it is possible to compensate for reactive power while effectively using the output of the power conversion means, allowing equipment to operate at a high power factor with good efficiency. You will be able to do it.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the basic configuration of this invention, Figure 2 is a vector diagram for explaining the same basic configuration, Figure 3 is a circuit diagram showing one embodiment of this invention, and Figure 4. is a circuit diagram showing a control circuit used in the same embodiment, FIG. 5 is a vector diagram for explaining the operation of the same embodiment, FIG. 6 is a circuit diagram showing another embodiment of the invention, and FIG. 1 is a circuit diagram showing an example of a conventional uninterruptible power supply device. 21...Power system, 23...Computer, 24.
...Direct feed circuit, 26... Rectifier, 27... Secondary battery, 28... Inverter, 29... AC reactor,
30... Switch, 31... Current transformer, 32... Transformer, 33... Reactive power converter, 34... Comparator, 3
5... Inverter voltage control circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 q ---1 Figure 3 Qref (=o) Figure 4

Claims (1)

[Claims] A power supply means for directly supplying power from the power system to a load, a power storage means for storing power from the power system, and a power storage means for converting the output of the power storage means into predetermined power and using the converted power at the time of a power outage in the power system. It is characterized by comprising a power conversion means for supplying to the load instead of the power supply means, and a reactive power supply means that generates reactive power from the output of the power conversion means and supplies it to the receiving end of the power system. Uninterruptible power supply.