JPH09261892A - Control of uninterruptible power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent over discharging of a storage battery by operating an uninterruptible supply while monitoring a terminal voltage and a discharging time of the storage battery if the commercial power supply fails. SOLUTION: In an uninterruptible power supply 2 provided with a storage battery 23 to supply DC power to an inverter 22 when the commercial power supply 1 fails, the discharging characteristic and discharging end voltage characteristic using a discharging current as a parameter are obtained from the intrinsic characteristic table of the storage battery 23. When a terminal voltage of the storage battery 23 detected by a DC voltage detector 26 becomes lower than the discharging end voltage, a comparator 27 operates to output a stop signal to the inverter 22 via an OR circuit 28. Moreover, when an insufficient voltage detector 24 detects that voltage of the commercial power supply 1 drops due to the fail of the commercial power supply 1, a timer circuit 25 is activated. When a failure period reaches the predetermined discharge time, the stop signal is output to the inverter 22 via the OR circuit 28. Thereby, operation of the uninterruptible power supply 2 is controlled so that the storage battery 23 does not indicate the over discharge of condition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier for converting AC power of a commercial power supply into DC power, an inverter for converting the DC power into AC power of a desired frequency and feeding the load, and a commercial power supply. The present invention relates to a control method for an uninterruptible power supply including a storage battery that supplies DC power to the inverter when an abnormality occurs.

[0002]

2. Description of the Related Art In a conventional uninterruptible power supply of this type, when an abnormality such as a power failure occurs in a commercial power supply, this is detected and DC power is supplied from a storage battery to an inverter to operate the uninterruptible power supply. The terminal voltage of the storage battery is monitored while continuing, and the operation of the uninterruptible power supply is stopped when the power failure does not recover even when the terminal voltage becomes equal to or lower than a predetermined discharge end voltage.

The set value of the discharge end voltage in the above state is set to a value based on the discharge current when a rated load is connected to the uninterruptible power supply.

[0004]

According to the conventional control method of the uninterruptible power supply described above, the discharge end voltage of the storage battery is set to a value based on the discharge current when the rated load is connected to the uninterruptible power supply. Since it is set, in case of light load,
As is well known, if the operation of the uninterruptible power supply is continued up to the discharge end voltage based on the discharge current at the rated load, the storage battery may be over-discharged, and it is often used especially in this type of uninterruptible power supply. For example, in the case of a lead-seal type storage battery, when it is over-discharged, a sulfation phenomenon occurs in the storage battery, and even if the storage battery is subjected to recovery charging, the initial capacity cannot be restored, and the life of the storage battery is significantly shortened. There was a problem.

An object of the present invention is to provide a control method for an uninterruptible power supply that solves the above problems.

[0006]

The first invention is a rectifier for converting AC power of a commercial power source into DC power, and an inverter for converting the DC power into AC power of a desired frequency and feeding the load. In a method of controlling an uninterruptible power supply including a storage battery that supplies DC power to the inverter when the commercial power supply is abnormal, the terminal voltage of the storage battery and the discharge time of the storage battery are monitored when the commercial power supply is abnormal. At the same time, the uninterruptible power supply is operated to prevent over-discharge of the storage battery.

In a second aspect based on the first aspect, when the commercial power source is abnormal, the terminal voltage of the storage battery becomes equal to or lower than a predetermined discharge end voltage, or the discharge time of the storage battery is set to a predetermined value. When the value is reached, the operation of the uninterruptible power supply is stopped. A third aspect of the present invention is, in the first aspect, when the terminal voltage of the storage battery becomes equal to or lower than a discharge end voltage that is set in accordance with the elapse of the discharge time of the storage battery when the commercial power supply is abnormal. Stop the operation of the uninterruptible power supply.

According to the present invention, in order to prevent over-discharging of the storage battery which supplies DC power when the commercial power supply is abnormal, the discharge time characteristics with the discharge current as a parameter from the characteristic table specific to the storage battery, and the discharge Obtaining the respective discharge end voltage characteristics with the current as a parameter, and operating the uninterruptible power supply when the commercial power supply is abnormal within a range that does not cause overdischarge under any condition of the terminal voltage of the storage battery and the discharge time. It is controlled to continue.

[0009]

1 is a block diagram showing a first embodiment of a control method for an uninterruptible power supply system according to the present invention. In FIG. 1, 1 is a commercial power supply, 2 is an uninterruptible power supply, 3 is a load, and the uninterruptible power supply 2 is a rectifier configured to convert AC power of the commercial power supply 1 into DC power, such as a diode. 21 and an inverter 22 composed of, for example, a power semiconductor element that converts this DC power into AC power having a desired frequency and supplies the load 2 with power.
A storage battery 23 that supplies DC power to the inverter 22 when the commercial power supply 1 is abnormal, an undervoltage detector 24 that detects a voltage drop due to the abnormality of the commercial power supply 1, and a commercial power supply 1 that operates the undervoltage detector 24. The timer circuit 25 for measuring the abnormal period (T) of the battery, the DC voltage detector 26 for detecting the terminal voltage of the storage battery 23, the detected value of the DC voltage detector 26 and the discharge end voltage ( _VF2 ) are compared. A comparator 27 for detecting that the detected value becomes V _F2 or less, and a timer circuit 2
The OR circuit 28 outputs a stop signal to the control circuit of the inverter 22 (not shown) when the measured value T of 5 reaches t ₀ or when the comparator 27 operates.

FIG. 3 shows the discharge current (I ₀ ,
Discharge time characteristics (t ₀ , t ₁ , t ₂ , t ₀ <t ₁ ) using I ₁ , I ₂ , I ₀ > I ₁ > I ₂ ) as parameters.
<T ₂₎ and the discharge end voltage _{(V F0, V F1, V} F2, V F0 <V
An example of the characteristics of _F1 <V _F2 ) is shown. The operation of the uninterruptible power supply device 2 of FIG. 1 will be described below with reference to the discharge characteristic diagram when a lead storage battery is used as the storage battery 23 shown in FIG.

In FIG. 3, the discharge current I ₀ is the current from the storage battery 23 when the load 3 of the uninterruptible power supply 2 is rated,
The discharge current I ₂ is the current from the storage battery 23 when the load 3 of the uninterruptible power supply 2 is unloaded or lightly loaded. In FIG. 1, the comparator 27 constantly monitors the terminal voltage of the storage battery 23 detected by the DC voltage detector 26, and when the discharge end voltage V _F2 corresponding to I ₂ is reached, the comparator 27 operates. A stop signal is output via the OR circuit 28. Also,
When the undervoltage detector 24 detects that the voltage of the commercial power source 1 has dropped due to the abnormality of the commercial power source 1, the timer circuit 25 is activated to measure the abnormal period (T) of the commercial power source 1. When the abnormal period T reaches t ₀ corresponding to I ₀ , the timer circuit 25 completes the measurement and outputs a stop signal via the OR circuit 28.

The control method of the uninterruptible power supply 2 described above prevents the storage battery 23 from being over-discharged. FIG.
2 is a block configuration diagram showing a second embodiment of a method for controlling an uninterruptible power supply device of the present invention, in which components having the same functions as those of the uninterruptible power supply device shown in FIG. The description is omitted.

That is, in FIG. 2, the uninterruptible power supply 4
In addition to the rectifier 21, the inverter 22, the storage battery 23, the undervoltage detector 24, the DC voltage detector 26, a timer circuit 41 for measuring an abnormal period (T) of the commercial power supply 1 in which the undervoltage detector 24 operates. , The measured value T of the timer circuit 41 is t
When the discharge reaches ₀ , t ₁ , and t ₂ , the discharge end voltage is set to V
_F0, V _F1, the switching circuit 42 to switch to V _F2, the detected value is compared with the detected value of the DC voltage detector 26 as either a discharge end voltage of the output of the switching circuit _{42 V F0, V F1, V} F2 Is equal to or lower than the discharge end voltage, the comparator 43 outputs a stop signal to the control circuit of the inverter 22 (not shown).

The operation of the uninterruptible power supply 4 of FIG. 2 will be described below with reference to the discharge characteristic diagram when a lead storage battery is used as the storage battery 23 shown in FIG. In FIG. 3, the discharge current I ₀ is the current from the storage battery 23 when the load 3 of the uninterruptible power supply 2 is rated, and the discharge current I ₂ is when the load 3 of the uninterruptible power supply 2 is no load or light load. The current from the storage battery 23 is used, and the discharge current I ₁ is an intermediate value between I ₀ and I ₂ .

In FIG. 2, the comparator 43 monitors the terminal voltage of the storage battery 23 detected by the DC voltage detector 26 in a normal state in which the undervoltage detector 24 does not operate, and the discharge termination corresponding to I ₂ is terminated. When the voltage becomes V _F2 or less, the comparator 4
3 operates and outputs a stop signal. Further, when the undervoltage detector 24 detects that the voltage of the commercial power source 1 has dropped due to the abnormality of the commercial power source 1, the timer circuit 41 is activated to measure the abnormal period (T) of the commercial power source 1. Abnormal period T is 0
In the section of <T ≦ t ₀ , the switching circuit 42 selects V _F0 corresponding to I _0, and in the section of the abnormal period T ₀ t ₀ <T ≦ t ₁ , the switching circuit 42 selects V _F1 corresponding to I _1. Is selected, the switching circuit 42 operates to select V _F2 corresponding to I ₂ in the section where the abnormal period T is t ₁ <T ≦ t ₂ , and the storage battery 23 of the storage battery 23 is selected based on these discharge end voltages. The comparator 43 monitors the terminal voltage.

By the control method of the uninterruptible power supply 4 described above, the storage battery 23 is prevented from being over-discharged, and even when the commercial power supply 1 is abnormal, depending on the state of the load 2, even if the time is t ₀ or more, The operation of the uninterruptible power supply 4 can be continued. In FIG. 2, the switching circuit 42 switches the discharge end voltage in the example of three stages, but it is also possible to use three or more stages.

[0017]

According to the present invention, in the uninterruptible power supply, by operating the uninterruptible power supply while monitoring the terminal voltage of the storage battery and the discharge time of the storage battery when the commercial power supply is abnormal, Even if an inexpensive lead-acid battery is used, over-discharge of this battery can be prevented.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an uninterruptible power supply device showing a first embodiment of the present invention.

FIG. 2 is a block diagram of an uninterruptible power supply showing a second embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation of FIGS. 1 and 2;

[Explanation of symbols]

1 ... Commercial power supply, 2, 4 ... Uninterruptible power supply device, 3 ... Load, 2
1 ... Rectifier, 22 ... Inverter, 23 ... Storage battery, 24 ...
Undervoltage detector, 25, 41 ... Timer circuit, 26 ... DC voltage detector, 27, 43 ... Comparator, 28 ... OR circuit, 4
2 ... Switching circuit.

Claims (3)

[Claims] 1. A rectifier for converting AC power of a commercial power supply into DC power, an inverter for converting this DC power into AC power of a desired frequency to supply power to a load, and a DC power supply for the inverter when the commercial power supply is abnormal. In a control method of an uninterruptible power supply device including a storage battery for supplying power, when the commercial power source is abnormal, the uninterruptible power supply device is operated while monitoring the terminal voltage of the storage battery and the discharge time of the storage battery, A method for controlling an uninterruptible power supply, comprising preventing over-discharge of the storage battery. 2. The uninterruptible power supply control method according to claim 1, wherein when the commercial power supply is abnormal, the terminal voltage of the storage battery becomes equal to or lower than a predetermined discharge end voltage, or the discharge time of the storage battery. Is stopped, the operation of the uninterruptible power supply is stopped when the value reaches a predetermined value. 3. The method of controlling an uninterruptible power supply according to claim 1, wherein when the commercial power supply is abnormal, the terminal voltage of the storage battery is set to correspond to the elapsed discharge time of the storage battery. A method for controlling an uninterruptible power supply, characterized in that the operation of the uninterruptible power supply is stopped when the voltage becomes equal to or lower than a voltage.