JPH0321185Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention connects a battery to a circuit that connects the DC sides of two sets of power converters to provide continuity to the load even if the power supply fails. The present invention relates to an uninterruptible power supply that can supply electric power.

[Prior art and its problems]

For example, in a load such as a computer, the voltage and frequency of the AC power supplied must always be stable and constant, and a power outage cannot be tolerated even for a short period of time. Therefore, instead of supplying power directly from the power grid to such loads, it is recommended to supply AC power via an uninterruptible power supply that can output uninterruptible AC power at constant voltage and constant frequency. Common.

FIG. 2 is a single-line system diagram showing a conventional example of an uninterruptible power supply, in which AC power supplied from an AC power supply 2 is once converted to DC power by a rectifier 3 as a first power converter, and this DC power is The inverter 5 as a second power converter converts the AC power back into AC power and supplies it to the AC load 6. However, if the AC power supply 2 has a power outage for some reason, the DC side of the rectifier 3 Since the battery 4 connected to the so-called DC intermediate circuit that connects the DC side of the inverter 5 and the DC side of the inverter 5 supplies DC power to the inverter 5 instead of the rectifier 3, the inverter 5
AC power can continue to be output without interruption.

When the AC power source 2 is supplying power, the battery 4 is constantly charged by so-called floating charging with the DC power output from the rectifier 3, so as to prepare for a power outage. Therefore, despite the voltage fluctuations of the AC power supply 2, the battery 4 is connected to an appropriate DC voltage.
In order to charge the battery, the rectifier 3 is often composed of a semiconductor switch element such as a transistor or a thyristor, and its DC output voltage can be controlled. Further, the inverter 5 performs conversion from direct current to alternating current by turning on and off its constituent elements such as semiconductor switch elements such as transistors and thyristors at appropriate timings. Therefore, these rectifier 3, inverter 5
is equipped with a control circuit 8, and power is also supplied from the battery 4 to a control power source 7 for operating the control circuit 8 properly.

In the uninterruptible power supply shown in Figure 2, AC power supply 2
As mentioned above, even if there is a power outage, power is supplied from the battery 4 to the inverter 5, and the AC load 6 can continue operating without a power outage.However, since the capacity of the battery 4 is limited, the AC power supply 2
When the power outage becomes long, the voltage of the battery 4 gradually decreases and finally reaches the discharge end voltage. If you continue to use the battery 4 whose voltage has dropped to this discharge end voltage, it will become so-called over-discharge.
The battery 4 is damaged and becomes unusable. Therefore, in order to avoid such a situation, when it is detected that the battery voltage has decreased to this discharge end voltage or a predetermined voltage determined near this, the control circuit 8 instructs the inverter 5 to stop operation. For example, the power supply to the AC load 6 is cut off to prevent the battery 4 from being over-discharged.

However, the control circuit 8 is always in a standby state so that when the AC power supply 2 recovers from a power outage, it can immediately resupply power to the AC load 6 via the rectifier 3 and inverter 5 and start charging the battery 4. Therefore, the AC load 6 must be prepared for restarting the rectifier 3 and inverter 5.
Even when power supply to the control power source 7 is interrupted, power must be continuously supplied from the battery 4 to the control power source 7.

Although the power required by the control power source 7 is small, if the power outage is prolonged, the battery 4 will still be damaged due to overdischarge.

[Purpose of invention]

The object of this invention is to provide an uninterruptible power supply that can prevent a battery from being over-discharged even if a power outage continues for a long time.

[Key points of the invention] This invention aims to supply power from the battery to the load during a power outage. In this case, the power supply from the battery to the control power source is automatically stopped to prevent the battery from becoming overcharged.

[Example of idea]

FIG. 1 is a single line system diagram showing an embodiment of the present invention. In this FIG. 1, normally AC power from an AC power source 2 is converted into DC power of a desired voltage by a rectifier 3 serving as a first power converter, and then this is converted to DC power at a desired voltage.
The power is supplied to the inverter 5 as a power converter, and the battery 4 is charged in a floating manner. Further, the inverter 5 converts the DC power into constant voltage constant frequency AC power and supplies it to the AC load 6 . If the AC power supply 2 is out of power, the battery 4 becomes the power source and the power supply to the AC load 6 continues without interruption, and the control circuit 8 and this control are used to properly operate the rectifier 3 and the inverter 5. The fact that a control power source 7 is provided as an operating power source for the circuit 8 is exactly the same as in the conventional circuit shown in FIG.

The present invention is provided with an operation switch 11, a control power supply relay 12, a timer 13, and an end-of-discharge voltage detection relay 14, and their operations will be described below.

In the embodiment circuit shown in FIG. 1, in order to operate the uninterruptible power supply, the operation switch 11 is first operated, but since the battery 4 is sufficiently charged at this time, the control power supply is Since the power for operating the control circuit 8 is supplied through the inverter 7, the rectifier 3 and the inverter 5 start operating and supply power to the AC load 6.

At the same time, the control power supply relay 12 operates and the normally open contact 12A closes. Further, the discharge end voltage detection relay 14 is energized (because the battery voltage at this time is sufficiently higher than the discharge end voltage) and the timer 13 is energized, so the normally open delayed release contact 13A of the timer 13 is also closed. do. Therefore, even if the operating switch 11 is automatically reset and its contacts are open, the operating switch 11 is short-circuited by the series-connected contacts 12A and 13A, and the operating signal continues to be issued.

When the power supply from the battery 4 continues due to a power outage of the AC power source 2 and its voltage reaches the final discharge voltage, the final discharge voltage detection relay 14 is released and the timer 13 is de-energized. Therefore, the contact 13A of the timer 13 opens after a certain period of time has passed since the timer 13 becomes non-energized, cuts off the power supply from the battery 4 to the control power supply 7, and prevents the battery 4 from becoming over-discharged. To prevent.

The voltage at which the control power relay 12 is released is:
Of course, the voltage should be lower than the voltage at which the discharge end voltage detection relay 14 is released.

[Effect of idea]

According to this invention, when the battery voltage drops to the discharge end voltage, the timer starts counting the time at the same time as the power supply to the load is stopped. If there are no repeated power outages, the power supply to the control power supply is also stopped, so even if the power outage is for a long time, the battery will not become over-discharged and will not be restarted. It has the effect of being able to be used again by charging.

[Brief explanation of the drawing]

FIG. 1 is a single-line system diagram showing an embodiment of the present invention, and FIG. 2 is a single-line system diagram showing a conventional example of an uninterruptible power supply. 2... AC power supply, 3... Rectifier as a first power converter, 4... Battery, 5... Inverter as a second power converter, 6... AC load, 7...
... Control power supply, 8 ... Control circuit, 11 ... Operation switch, 12 ... Control power supply relay, 12A ... Contact, 13 ... Timer, 13A ... Contact, 14 ...
Discharge end voltage detection relay.

Claims (1)

[Scope of utility model registration request] The first unit is connected to an AC power source and outputs DC power.
a second power converter that converts DC power into AC power of a desired voltage and frequency; and a battery that supplies power to the second power converter during a power outage, the second power converter outputs an AC voltage when the battery voltage falls below a setting during a power outage of the AC power source. means for reducing power to zero, and power supplied from the battery to the control circuit of the first power converter or the second power converter when the power outage of the AC power source is not restored even after a predetermined period of time has passed after the AC output becomes zero. An uninterruptible power supply characterized by comprising: a means for shutting off the power supply;