JPH07170677A - Storage battery charging circuit for uninterruptible power supply - Google Patents

Abstract

(57) [Abstract] [Purpose] To allow the uninterruptible power supply to increase the charging current to the storage battery within the range of the rated current of the charger in response to fluctuations in current supplied to the load. [Structure] A current detected by an inverter current detector 21 and a storage battery current detector 1 according to a command from a charging current control circuit 22.
The charger 3 is controlled so that the sum of the current detected by 2 does not exceed the rated current of the charger 3. Alternatively, a value obtained by subtracting the current detected by the inverter current detector 21 from the rated current of the charger 3 set by the charger current setter 31 by the subtractor 32 is used as the charging current command value, and the deviation calculator 13 detects the storage battery current. The deviation between the charging current detection value detected by the container 12 and this charging current command value is calculated. The current regulator 14 inputs this deviation and gives a control signal to the charger 3 to make the input deviation zero, thereby making it possible to give a large charging current to the storage battery 5 within the rated current range of the charger 3. To

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for controlling a charging current of a storage battery which constitutes an uninterruptible power supply.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional example of a charging circuit for a storage battery that constitutes an uninterruptible power supply. The uninterruptible power supply includes a charger 3 as a first power conversion means, a second power converter, and a second power converter.
It is composed of an inverter 4 as a power conversion means and a storage battery 5, and AC power from an AC power source 2 is converted into DC power of a desired voltage by a charger 3. This DC power is converted to a desired voltage by the inverter 4. It is supplied to the load 6 after being converted into AC power of the frequency. The storage battery 5 is connected to a so-called DC intermediate circuit that connects the DC side of the charger 3 and the DC side of the inverter 4. Since the charger 3 supplies electric power to the load 6 via the inverter 4 and constantly charges the storage battery 5, when the AC power supply 2 fails,
Since the storage battery 5 supplies the electric power stored therein instead of the AC power supply 2 to the load 6 via the inverter 4, the load 6 can continue to operate without a power failure.

As described above, the charger 3 includes the inverter 4
Since it is necessary to supply electric power to the load 6 via the battery and also supply charging power to the storage battery 5, for example, the rated current of the inverter 4 is set to 100 A, and the charging current for charging the storage battery 5 at a predetermined charging rate is set. Is 15 A, the rated current of the charger 3 is selected to be the sum of both, that is, 115 A. Here, the rated current (that is, 100A) is applied to the inverter 4 while the charging current larger than 15A is flowing through the storage battery 5.
When the current flows, the current flowing through the charger 3 has a disadvantage of exceeding 100% of the rated value. Therefore, the charging current to the storage battery 5 is adjusted so that the value does not exceed a predetermined value. For this purpose, a charging current setting device 11 for setting a predetermined charging current command value (15 A in this case) is provided, and a deviation calculator calculates the deviation between the charging current detected by the storage battery current detector 12 and this charging current command value. 13, and the calculation result is input to the current regulator 14. The current regulator 14 sends a control signal for making the input deviation zero to the charger 3
Since the output voltage of the charger 3 is controlled by controlling the charging current to the storage battery 5, the charging current to the storage battery 5 is controlled to always match the charging current command value. Therefore, there is no possibility that the charger 3 will be in an overcurrent state.

[0004]

By the way, in the conventional circuit of FIG. 3, even if the inverter 4 has a light load and the current of the charger 3 has a margin, the charging current to the storage battery 5 is the charging current setting device 11. It can be charged only according to the command value set in. Therefore, even if you want to apply a large charging current to perform quick charging because the storage battery 5 is completely discharged,
This is not possible because the charging current is limited. Although the above-mentioned request can be met by operating the charging current setting device 11 to change the charging current command value to a large value, if the operator forgets to restore the changed setting value, the inverter 4
It is not preferable to change the setting of the charging current setting device 11, because the charging device 3 may be in an overcurrent state when the current of 1 increases. After all, even if the current of the charger 3 has a margin, the storage battery 5 has to be slowly charged with a predetermined charging current.

Therefore, an object of the present invention is to make it possible to increase the charging current to the storage battery within the range of the rated current of the charger in response to fluctuations in the current supplied to the load by the uninterruptible power supply. .

[0006]

In order to achieve the above object, a storage battery charging circuit of an uninterruptible power supply of the present invention comprises a first power converting means for converting alternating current to direct current and a first power converting means for converting direct current to alternating current. An uninterruptible power supply device comprising two power conversion means and a storage battery connected to a DC intermediate circuit connecting the DC side of the first power conversion means and the DC side of the second power conversion means, Corresponding to the fluctuation of the current flowing through the second power conversion means, the total value of the current flowing through the second power conversion means and the charging current of the storage battery should be equal to or less than the rated current of the first power conversion means. The uninterruptible power supply device is equipped with a charging current control unit that controls the charging current.

[0007]

According to the present invention, the current flowing through the inverter and the charging current to the storage battery are separately detected, and the output voltage of the charger is controlled so that the sum of both currents does not exceed the rated current of the charger. . That is, if the inverter current is small, the output voltage of the charger is increased so as to increase the current of the charger, and if the inverter current is increased, the output current of the charger is decreased to decrease the charging current to the storage battery. Make the current to the storage battery as large as possible within the range where the charger current does not exceed its rated value.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing a first embodiment of the present invention, in which an AC power source 2, a charger as a first power converting means 3 and a second power converting means are shown. Inverter 4, storage battery 5, load 6, and storage battery current detector 1
The name, application, and function of 2 are the same as those of the conventional circuit described above with reference to FIG.

In the first embodiment circuit of FIG. 1, the current of the inverter 4 detected by the inverter current detector 21 and the charging current to the storage battery 5 detected by the storage battery current detector 12 are sent to the charging current control circuit 22. It is input and the output voltage of the charger 3 is changed according to the sum of both currents. For example, when the inverter 4 has a light load, the current flowing through the inverter 4 is smaller than its rated value, and therefore the sum of the detected current of the inverter current detector 21 and the detected current of the storage battery current detector 12 is the sum of the charger 3 Less than the rated current. Therefore, the charging current control circuit 22 gives a command to the charger 3 to increase its DC output voltage. When the DC intermediate circuit voltage rises, the charging current of the storage battery 5 increases, but the inverter 4 loads the load 6
The current to is unchanged. Therefore, the inverter current detector 2
The detected current of 1 hardly changes. That is, when the DC intermediate circuit voltage rises, only the charging current to the storage battery 5 increases and the output current of the charger 3 approaches its rated value. That is, if the inverter 4 has a light load, there is a surplus in the output current of the charger 3,
This spare capacity can be used for charging the storage battery 5, and the storage battery 5 can be rapidly charged.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention, in which the AC power supply 2, the charger as the first power conversion means 3, and the second power conversion means are shown. Inverter 4, storage battery 5, load 6, storage battery current detector 1
2. The names, applications, and functions of the deviation calculator 13 and the current controller 14 are the same as in the case of the conventional example circuit described above with reference to FIG.

In the second embodiment circuit of FIG. 2, the charger current setting unit 31 sets a current value that the charger 3 can output, for example, a rated current value. The subtractor 32 is the charger current setting device 3
Since the calculation of subtracting the current value detected by the inverter current detector 21 from the rated current value of the charger 3 set by 1 is performed, the calculation result of the subtractor 32 is a current value that can be used for charging the storage battery 5. is there. Therefore, the calculation result of the subtractor 32 is used as the charging current command value, and the deviation between the charging current command value and the charging current detection value detected by the storage battery current detector 12 is calculated by the deviation calculator 13 and this calculation result is adjusted by the current adjustment. Bowl 1
4, the current regulator 14 outputs to the charger 3 a control signal for making the input deviation zero. For example, when the calculation result of the deviation calculator 13 is positive (this means that the charging current command value is larger than the charging current detection value, that is, the output current of the charger 3 has a surplus), the charger Three
The output voltage of is increased until the input deviation to the current regulator 14 becomes zero. On the contrary, when the calculation result of the deviation calculator 13 has a negative polarity, the output current of the charger 3 exceeds the rated value, and therefore the current regulator 14 causes the control signal to decrease the output voltage of the charger 3. Is output. As a result, the DC intermediate circuit voltage decreases, the charging current to the storage battery 5 decreases, and the initial overcurrent of the charger 3 is eliminated.

In the circuit of the first embodiment shown in FIG. 1 or the circuit of the second embodiment shown in FIG. 2, the inverter current detector 21 detects the DC side current of the inverter 4 to simplify the explanation. However, it goes without saying that there is no problem even if it is installed at a position where the AC side current of the inverter 4 is detected.

[0013]

In the conventional uninterruptible power supply device, the amount of charging current to the storage battery is determined in advance so that the first power conversion means (charger) does not become an overcurrent, and this amount should not be exceeded. Since the charging current is controlled in the above, there is a disadvantage that the charging current cannot be increased even if the output of the first power conversion means has a surplus. On the other hand, in the present invention, when the sum of the charging current to the storage battery and the current flowing through the second power conversion means is smaller than the rated value of the first power conversion means, that is, the output current of the first power conversion means has a margin. If there is, the output voltage of the first power conversion means is controlled so as to increase the charging current to the storage battery. Therefore, the opportunity to increase the storage battery charging current is increased and the charging time of the storage battery is shortened as compared with the conventional case. As a result, it is possible to avoid an inconvenience that the operation of the load cannot be continued due to insufficient charging of the storage battery when the power source fails.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional example of a charging circuit for a storage battery that constitutes an uninterruptible power supply.

[Explanation of symbols]

 2 AC power supply 3 Charger as first power conversion means 4 Inverter as second power conversion means 5 Storage battery 6 Load 11 Charging current setting device 12 Storage battery current detector 13 Deviation calculator 14 Current regulator 21 Inverter current detector 22 Charge current control circuit 31 Charger current setting device 32 Subtractor

Claims (2)

[Claims] 1. A first power conversion means for converting alternating current to direct current, a second power conversion means for converting direct current to alternating current, a direct current side of these first power conversion means and a direct current side of the second power conversion means. In the uninterruptible power supply configured by a storage battery connected to a DC intermediate circuit that is coupled with, in response to fluctuations in the current flowing through the second power conversion means,
The charging current control means for controlling the charging current so that the total value of the flowing current of the second power converting means and the charging current of the storage battery is less than or equal to the rated current of the first power converting means is A storage battery charging circuit for an uninterruptible power supply, which is equipped in the uninterruptible power supply. 2. The storage battery charging circuit of the uninterruptible power supply according to claim 1, wherein the charging current control means is the second battery.
Subtracting means for subtracting the actual current value detected from the power converting means from the rated current value of the first power converting means, and charging current adjusting means for matching the actual charging current value of the storage battery with the calculation result of the subtracting means. The storage battery charging circuit of the uninterruptible power supply device, characterized in that the first power conversion means is controlled according to the output signal of the charging current adjusting means.