JPH06169533A - Method for measuring remaining battery capacity of uninterruptible power supply - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for measuring the remaining capacity of a storage battery, which allows the storage battery to be opened without disconnecting the storage battery and to measure the remaining capacity from the open voltage of the storage battery while maintaining the uninterruptible function. . In an uninterruptible power supply device including a storage battery and a power converter having a function of charging the storage battery, a rectifying element connected in series with the storage battery and conducting only when the storage battery is discharged, and the rectifying element are short-circuited. Short circuit means, comprising a voltage measuring means for measuring the voltage of the storage battery, at the time of measurement,
While opening the short-circuit means, the storage battery charging voltage by the power converter is not more than the open-circuit voltage of the storage battery, and by measuring the open-circuit voltage of the storage battery by the voltage measuring means after a certain period of time, A method for measuring the remaining capacity of a storage battery in an uninterruptible power supply that calculates the remaining capacity.

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 load leveling function by using nighttime power, and more particularly to a method for measuring the remaining capacity of a storage battery which is necessary for equalizing charging power at nighttime.

[0002]

2. Description of the Related Art FIG. 4 is a structural example of a conventional general uninterruptible power supply. In FIG. 4, 1 is an AC power supply,
2 is a storage battery, 3 is a power converter, and 4 is a load. The power conversion device 3 includes a forward conversion device 31 that converts alternating current into direct current and charges a storage battery, and an inverse conversion device 3 that converts direct current into alternating current.
2 and. In such an uninterruptible power supply device, it is general that the storage battery 2 is always fully charged in preparation for a power failure of the AC power supply 1, and it is not necessary to measure the remaining capacity of the storage battery 2 except during a power failure.

FIG. 3 shows another example of the configuration of the uninterruptible power supply, which is called a parallel processing system. In FIG. 3, reference numeral 5 is a connection reactor for connecting with an AC power supply, 6 is a switch for cutting off the connection when the AC power supply is interrupted, and the power conversion device 3 is of a forward-reverse conversion type. Others are the same as in FIG.

In the system shown in FIG. 3, the AC power supply 1 and the power conversion device 3 always perform interconnection operation, so that the AC power supply 1 and the storage battery 2 can freely exchange power via the power conversion device 3. Thus, by setting the capacity of the storage battery 2 to be large, not only the function as the uninterruptible power supply device but also the function as the load leveling using the night power can be provided. That is, by performing the forward conversion operation of the power conversion device 3 at night, the nighttime electric power cheaper than the AC power supply 1 is stored in the storage battery 2, and the power conversion device 3 is reversely converted during the daytime to be supplied to the load 4. You can also reverse the flow to 1.

In the event of a power failure in the AC power supply 1, the switch 6 can be opened instantaneously to immediately disconnect the AC power supply 1 and shift to independent operation. By appropriately limiting the discharge amount of 2, the uninterruptible function can be maintained regardless of day and night.

By the way, in the case of charging the storage battery 2 at night, a large current flows at the start of charging in the normal charging method, and when the storage battery 2 is charged, the charging current sharply decreases. In other words, it consumes a large amount of charging power at the beginning of the night, but consumes almost no charging power at dawn,
A peak of power will be generated for the AC power supply 1.

In order to avoid this, the remaining capacity of the storage battery 2 may be measured in advance before charging, the charging current may be calculated from the charging amount for full charging and the charging time at night, and charging may be performed with a constant current. . For example, the storage battery 2 has a capacity of 1
When the remaining capacity of the storage battery before charging is 00 Ah and is 60 Ah, the charging current is easily calculated to be about 5 A when the night time is 8 hours. If the remaining capacity is 20 Ah, the charging current will be about 10 A.

Thus, in order to charge the storage battery 2 evenly at night without generating electric power peaks, it is necessary to accurately know the remaining capacity of the storage battery 2 during charging.
Conventionally, a method of integrating the charge / discharge amount of the storage battery 2 is known as one of the methods, but since this method integrates the charge / discharge current of the storage battery 2, the storage battery 2 is regularly charged in a fully charged state or a fully discharged state. However, if the integrator is not reset, there is a drawback that a slight error is accumulated and the integrated value becomes inaccurate.

However, in order to fully charge the storage battery 2 without generating a peak of electric power, it is theoretically impossible because the remaining capacity that is the source of the storage battery 2 is necessary, and in order to maintain the uninterruptible function. It is not permissible to completely discharge the storage battery 2.

On the other hand, as another method of measuring the remaining capacity of the storage battery 2, there is a method of measuring the open circuit voltage of the storage battery 2. This method takes advantage of the fact that the open-circuit voltage of the storage battery is proportional to the remaining capacity of the storage battery, and is relatively accurate except immediately after charging. However, this method requires the storage battery 2 to be completely opened, and cannot be measured in the state where the charging / discharging current is flowing.

Therefore, it is necessary to disconnect the storage battery 2 at the time of measurement, but this causes a problem that the storage battery 2 cannot be discharged when the AC power supply 1 fails and the uninterruptible function cannot be maintained.

[0012]

According to the present invention, in an uninterruptible power supply device comprising a storage battery and a power conversion device having a function of charging the storage battery, a rectifying element connected in series with the storage battery and conducting only when the storage battery is discharged. And a short-circuiting means for short-circuiting the rectifying element, and a voltage measuring means for measuring the voltage of the storage battery, and at the time of measurement, the short-circuiting means is opened, and the storage battery charging voltage by the power conversion device is stored in the storage battery. The remaining capacity of the storage battery is calculated by measuring the open circuit voltage of the storage battery by the voltage measuring means after the open circuit voltage is not more than the open circuit voltage and after a lapse of a certain time.

By doing so, a storage battery remaining capacity measuring method is provided in which the storage battery is opened without disconnecting the storage battery and the remaining capacity can be measured from the open voltage of the storage battery while maintaining the uninterruptible function. can do.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the configuration for carrying out the present invention, which will be described below with reference to the drawings. In FIG. 1, 7 is a rectifying element that conducts only when the storage battery is discharged, 8 is a contact that short-circuits the rectifying element when the storage battery is charged, 9 is a voltage detector that measures the open-circuit voltage of the storage battery, and the others are the same as in FIG.

When charging the storage battery 2 at night in FIG. 1, first, the contact 8 is opened to control the charging voltage of the power conversion device 3 to be equal to or higher than the open voltage of the storage battery 2. As a result, the rectifying element 7
Becomes non-conductive and the storage battery 2 becomes open. In this case, since the storage battery 2 was in a discharged state in the daytime, the open-circuit voltage shows the remaining capacity in a relatively short time after opening, and the remaining voltage is accurately measured by the voltage detector 9 after a certain time. I can know. For example, in the case of a certain hermetically sealed lead-acid battery, the relationship between the open circuit voltage and the remaining capacity is shown in FIG.
The open circuit voltage when fully charged is 2.17V.
/ Cell, the open-circuit voltage at full discharge is 1.94 V / cell. Therefore, for example, when the measured voltage is 2.00 V / cell, it can be seen from FIG. 2 that the remaining capacity is 26%.
If the remaining capacity of the storage battery 2 is obtained as described above, the charging current may be calculated from the charging time, the contact 8 may be closed, and charging may be started. Further, even when the contact 8 is opened, the storage battery 2 can be constantly discharged by the rectifying element 7, so that even if a power failure occurs in the AC power supply 1, the power supply to the load 4 is continued and the uninterruptible function is impaired. There is no such thing.

Also in the case of the conventional example, by applying the present invention and measuring the remaining capacity after discharging to control the charging current, it is possible to suppress the unnecessary power peak during recharging. The same applies to the case of a DC uninterruptible power supply.

[0017]

As described above, according to the present invention, the storage battery can be opened without disconnecting the storage battery, and the open-circuit voltage of the storage battery can be measured while the storage battery can always be discharged. , It is possible to accurately measure the remaining capacity of the storage battery from the open circuit voltage while maintaining the uninterruptible function, and by controlling the charging current using this measured value, the unnecessary power peak during recharging can be determined. Can be suppressed.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example for implementing the present invention.

FIG. 2 is a diagram showing a relationship between an open circuit voltage of a storage battery and a remaining capacity.

FIG. 3 is a diagram showing another configuration example of the uninterruptible power supply device.

FIG. 4 is a diagram showing a configuration example of a conventional general uninterruptible power supply device. 1 AC power supply 2 Storage battery 3 Power conversion device 4 Load 5 Interconnection reactor 6 Switch 7 Rectifying element 8 Contact 9 Voltage detector

Claims (1)

[Claims] 1. An uninterruptible power supply device comprising a storage battery and a power converter having a function of charging the storage battery, a rectifying element connected in series with the storage battery and conducting only when the storage battery is discharged, and the rectifying element. Short-circuiting means for short-circuiting
Voltage measuring means for measuring the voltage of the storage battery, and at the time of measurement, the short-circuit means is opened, and the storage battery charging voltage by the power conversion device is set to be equal to or higher than the open voltage of the storage battery, and the storage battery after a certain period of time elapses. A method for measuring the remaining capacity of a storage battery of an uninterruptible power supply device, characterized in that the remaining capacity of the storage battery is calculated by measuring the open circuit voltage of the above with the voltage measuring means.