JP3177721B2 - Battery remaining capacity measurement method for uninterruptible power supply - Google Patents

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

[0002]

2. Description of the Related Art FIG. 4 shows a configuration 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 converter 3 includes a forward converter 31 that converts AC into DC and charges the storage battery, and an inverse converter 3 that converts DC into AC.
And 2. In such an uninterruptible power supply, it is common to always keep the storage battery 2 in a fully charged state 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 a method called a parallel processing method. In FIG. 3, reference numeral 5 denotes an interconnection reactor for interconnecting with an AC power supply, reference numeral 6 denotes a switch for interrupting interconnection when an AC power supply fails, and a power conversion device 3 of a forward / reverse conversion type is used. Others are the same as FIG.

In the system shown in FIG. 3, since the AC power supply 1 and the power converter 3 always perform the interconnection operation, the power of the AC power supply 1 and the power of the storage battery 2 can be freely exchanged via the power converter 3. By setting the capacity of the storage battery 2 large, not only a function as an uninterruptible power supply but also a function as load leveling using nighttime power can be provided. That is, the power conversion device 3 is operated in the forward conversion operation at night, so that the night power, which is cheaper than the AC power supply 1, is stored in the storage battery 2, and in the daytime, the power conversion device 3 is operated in the reverse conversion operation and supplied to the load 4. It is also possible to have a reverse flow in 1.

In the event that a power failure occurs in the AC power supply 1, the switch 6 is instantaneously opened, whereby the connection with the AC power supply 1 can be immediately cut off and the operation can be shifted to the independent operation. By appropriately limiting the discharge amount of No. 2, the uninterruptible function can be maintained regardless of day or night.

When the storage battery 2 is charged at night, a large current flows at the start of charging in a normal charging method, and the charging current rapidly decreases when the storage battery 2 is charged. In other words, it consumes a large amount of charging power at the beginning of the night, but consumes little charging power at dawn,
A power peak is generated for the AC power supply 1.

[0007] To avoid this, before charging, the remaining capacity of the storage battery 2 is measured in advance, the charging current is calculated from the amount of charge with respect to the full charge and the charging time at night, and charging may be performed at a constant current. . For example, when the capacity of the storage battery 2 is 1
At 00 Ah, when the remaining capacity of the storage battery before charging is 60 Ah, the charging current can be easily obtained as about 5 A if the night time is 8 hours. If the remaining capacity is 20 Ah, the charging current is about 10 A.

In order to charge the storage battery 2 evenly without causing a power peak at night, it is necessary to accurately know the remaining capacity of the storage battery 2 during charging.
Conventionally, as one of the methods, a method of integrating the charge / discharge amount of the storage battery 2 is known. However, since this method integrates the charge / discharge current of the storage battery, the storage battery 2 is periodically charged to a full charge state or a complete discharge state. If the integrator is not reset, there is a disadvantage that a slight error is integrated and the integrated value becomes inaccurate.

However, it is theoretically impossible to fully charge the storage battery 2 without generating a power peak, because the remaining capacity is necessary, and to maintain the uninterruptible function. Does not allow the storage battery 2 to be completely discharged.

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 voltage of the storage battery 2. This method utilizes the fact that the open-circuit voltage of the storage battery is proportional to the remaining capacity of the storage battery, and relatively high accuracy can be obtained except immediately after charging. However, in this method, the storage battery 2 needs to be completely opened, and measurement cannot be performed in a state where a charge / discharge current is flowing.

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

[0012]

In [SUMMARY OF THE The present invention in an uninterruptible power supply and a power converter having a function to charge discharge electric storage batteries and storage battery, which is connected to the battery in series, only during discharging of the battery A rectifying element that conducts, short-circuiting means for short-circuiting the rectifying element, and voltage measuring means for measuring the voltage of the storage battery.When measuring, the short-circuiting means is opened and the storage battery charging voltage by the power converter is measured. The remaining voltage of the storage battery is calculated by measuring the open voltage of the storage battery by the voltage measuring means after the storage battery is set to the open voltage or more and after a lapse of a predetermined time.

In this manner, a method for measuring the remaining capacity of a storage battery 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]

FIG. 1 shows an example of a configuration for implementing 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 battery is discharged, 8 is a contact that short-circuits the rectifying element when the battery is charged, 9 is a voltage detector that measures the open-circuit voltage of the battery, and others are the same as those in FIG.

In FIG. 1, when charging the storage battery 2 at night, first, the contact 8 is opened, and the charging voltage of the power converter 3 is controlled to be higher than the open voltage of the storage battery 2. As a result, the rectifying element 7
Are turned off, and the storage battery 2 is opened. In this case, since the storage battery 2 was in the discharge state in the daytime, the open voltage indicates the remaining capacity in a relatively short time after opening, and after a certain time, this voltage is measured by the voltage detector 9 to accurately determine the remaining capacity. You can know. For example, in the case of a certain sealed sealed lead-acid battery, the relationship between the open-circuit voltage and the remaining capacity is shown in FIG.
The open voltage at full charge is 2.17V
/ Cell, the open-circuit voltage at the time of complete discharge is 1.94 V / cell. Therefore, for example, when the measurement voltage is 2.00 V / cell, it can be seen from FIG. 2 that the remaining capacity is 26%.
When the remaining capacity of the storage battery 2 is determined as described above, the charging current may be calculated from the charging time, and the charging may be started by closing the contact 8. Even when the contact 8 is open, 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. Never.

In the case of the conventional example, unnecessary power peaks at the time of recharging can be suppressed by applying the present invention and measuring the remaining capacity after discharging to control the charging current. The same applies to a DC uninterruptible power supply.

[0017]

As described above, according to the present invention, the open state of the storage battery can be measured without disconnecting the storage battery, and the open 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 voltage while maintaining the uninterruptible function, and control the charging current using this measured value to reduce unnecessary power peaks during recharging. Can be suppressed.

[Brief description of the drawings]

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

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

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

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 Rectifier 8 Contact 9 Voltage detector

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho 51-156427 (JP, U) Japanese Utility Model Sho 62-145173 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H02J 7/00-7/12 H02J 7/34-11/00

Claims (1)

(57) [Claims] 1. A uninterruptible power supply and a power converter having a function to charge discharge electric storage batteries and storage battery, which is connected to the battery in series, and a rectifying element which conducts only during discharge of the battery, the Short-circuit means for short-circuiting the rectifying element;
Voltage measuring means for measuring the voltage of the storage battery, wherein at the time of measurement, the short-circuit means is opened, the charging voltage of the storage battery by the power conversion device is equal to or higher than the open voltage of the storage battery, and the storage battery A remaining capacity of the storage battery is calculated by measuring an open circuit voltage of the storage battery by the voltage measuring means.