JPH08223821A - Ac uninterruptible power-supply system - Google Patents

Abstract

PURPOSE: To lower a frequency of a PWM control signal during the outage of commercial power and reduce a loss in proportion to the frequency of the PWM control signal, by stopping a dividing circuit when a charging signal is generated, and operating the dividing circuit when a discharging signal is generated. CONSTITUTION: In a charging/discharging circuit, a battery 5 is charged by DC power from a rectifier 2 when the power is fed from a commercial power supply 1, and the power is discharged from the battery 5 when the commercial power 1 is stopped. A charging/discharging discriminator 6 for judging whether a battery 5 is in a changing state or not and generating a charging/discharging signal is provided in the charging/discharging circuit. At the same time, a divider circuit 3 is provided between an oscillating circuit 32 and a carrier generating circuit 33 in a PWM control circuit 30. When a charging signal is generated, the divider circuit 35 is not operated, and when a discharging signal is generated, the divider circuit 35 is operated. Then, a loss in PWM inverter is reduced during the discharging of the battery 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC uninterruptible power supply, and more specifically, it reduces the loss of a PWM inverter that converts DC power from a storage battery into AC power in the event of a power failure and maintains the same volume and weight. The present invention relates to an AC uninterruptible power supply device capable of increasing the power outage holding time and reducing the size and weight if the power outage holding time is the same.

[0002]

2. Description of the Related Art An AC uninterruptible power supply system is one in which DC power from a storage battery is converted into AC power by an inverter and supplied to a load in the event of a power failure, and in recent years it has also been used in various general-purpose communication devices. Is starting to appear.

Such an AC uninterruptible power supply has been downsized and lightened as general-purpose communication equipment has been downsized and lightened.

In order to reduce the size and weight of the AC uninterruptible power supply, a PWM inverter is used as an inverter for converting DC power from a storage battery into AC power, or a PWM converter is used as a rectifier for rectifying AC power from a commercial power supply. It has been conventionally practiced to reduce the size and weight of a storage battery by using a battery or minimizing a power failure holding time by the storage battery.

In the AC uninterruptible power supply described above, the PWM
Although it is possible to reduce the size and weight by using an inverter or a PWM converter,
Storage batteries, which occupy most of the volume and weight, have been limited in miniaturization and weight saving even if the power failure holding time of the AC uninterruptible power supply was minimized.

That is, the capacity of the storage battery is calculated by calculating the input capacity of the inverter from the output capacity of the inverter and the conversion loss of the inverter, and by calculating the required power failure holding time. This is because the capacity of the storage battery increases, and its volume and weight increase.

The conventional AC uninterruptible power supply described above is shown in FIG.
It will be described based on.

The AC uninterruptible power supply system shown in FIG.
When the power is received, the AC power is rectified by the rectifier 2, the storage battery 5 is charged with the DC power from the rectifier 2, and the DC power is converted into AC power by the PWM inverter 3, and this AC power is converted by the AC filter 4. The sine wave is output, and when the commercial power source 1 is out of power, the DC power from the storage battery 5 is converted into AC power by the PWM inverter 3, and the sine wave is output by the AC filter 4. A PWM control circuit 30 that creates a PWM control signal for controlling the PWM inverter 3 is provided.

The PWM control circuit 30 has a reference sine wave operation circuit 31 for outputting a predetermined reference sine wave, an oscillator circuit 32 for outputting a pulse for determining the frequency of a carrier wave, and a pulse output from the oscillator circuit 32. And a carrier generation circuit 33 for receiving a carrier wave and outputting a carrier wave.
A comparator 34 for comparing the carrier wave from the carrier wave No. 3 and the reference sine wave from the reference sine wave operation circuit 31 is provided, and the output of this comparator 34 is used as a PWM control signal.

In the above-mentioned conventional AC uninterruptible power supply, the oscillator circuit 32 in the PWM control circuit 30 is provided whether the commercial power source 1 is receiving power or the commercial power source 1 is out of power.
The input capacity of the inverter is calculated on the assumption that the frequency of the pulse output from is constant and the conversion loss of the PWM inverter is always constant, and the capacity of the storage battery is calculated accordingly.

[0010]

In the above-described conventional AC uninterruptible power supply, the conversion loss of the PWM inverter is not related to the frequency of the PWM control signal like the copper loss of the wiring, and the DC loss in the PWM inverter 3 is -Although there are some that are proportional to the frequency of the PWM control signal, such as loss in the AC converter and loss in the AC filter 4,
Since the frequency of the PWM control signal is constant, there is a problem that the latter loss is a burden on the storage battery when the commercial power supply 1 fails.

[0011]

To solve the above problems, the present invention provides a rectifier for rectifying AC power from a commercial power source, a PWM inverter for converting DC power from the rectifier to AC power, and the rectifier. A storage battery that is connected to a connection point between the PWM inverter and the PWM inverter, is charged by the AC power when the commercial power is received, and supplies the DC power to the PWM inverter when the commercial power fails.
In an AC uninterruptible power supply device including an AC filter that makes the output of the PWM inverter a sine wave, a charge / discharge signal is determined by determining whether the storage battery is being charged or discharged in a charge / discharge path of the storage battery. Providing a charge / discharge discriminator to output,
Further, a PWM control circuit for creating a PWM control signal for controlling the PWM inverter, a reference sine wave operation circuit that outputs a predetermined reference sine wave, an oscillation circuit that outputs a pulse that determines the frequency of a carrier wave, and this oscillation A carrier wave generation circuit that inputs a pulse output from the circuit and outputs a carrier wave, and a carrier wave from the carrier wave generation circuit and a reference sine wave from the reference sine wave operation circuit are compared to create a PWM control signal. And a frequency divider circuit that divides the frequency of the pulse by inputting the charge / discharge signal between the oscillator circuit and the carrier wave generating circuit, and when the charge / discharge signal is a charge signal, The frequency dividing circuit is not operated, and the frequency dividing circuit is operated when the charge / discharge signal is a discharge signal.

[0012]

According to the present invention, the charging / discharging signal from the charging / discharging discriminator is input to the frequency dividing circuit inserted between the oscillator circuit and the carrier wave generating circuit, and when the charging / discharging signal is the charging signal, the dividing signal is divided. When the charge / discharge signal is the discharge signal, the frequency divider circuit is operated so that the frequency divider circuit is not operated. Therefore, when the storage battery is discharged, that is, when the commercial power source is interrupted, the frequency of the PWM control signal is lowered and the PWM control is performed. The loss proportional to the frequency of the signal can be reduced.

[0013]

EXAMPLES The present invention will be described below based on examples.

FIG. 1 is a block diagram of an AC uninterruptible power supply according to the present invention. Parts having the same functions as those in FIG. 2 are designated by the same reference numerals and the following description will be omitted.

A feature of the present invention is whether the storage battery 5 is being charged in the charging / discharging path of the storage battery 5 which is charged by the DC power from the rectifier 2 when the commercial power supply 1 receives power and discharges when the commercial power supply 1 fails. A charge / discharge discriminator 6 for discriminating whether or not discharging is in progress and outputting a charge / discharge signal is provided, and the PWM control circuit 3 is provided.
A frequency divider circuit 35 for dividing the frequency of the pulse from the oscillator circuit 32 by receiving the charge / discharge signal is provided between the oscillator circuit 32 in 0 and the carrier wave generator circuit 33, and the charge / discharge signal is the charge signal. In the case of, the frequency dividing circuit 35 is not operated, and when the charge / discharge signal is a discharge signal, the frequency dividing circuit 35 is operated.

Further, the present invention is provided with a bypass AC power supply 10 different from the commercial power supply 1, and a power supply switch 7 for switching between the power supply from the bypass AC power supply 10 and the power supply from the PWM inverter. When the storage battery voltage reaches the discharge end voltage, the power supply switching device 7 causes the bypass AC power supply 10
The storage battery 5 is prevented from being damaged by over-discharging by switching to the power feeding from.

When the discharge signal from the charge / discharge discriminator 6 is input to the frequency dividing circuit 35, the frequency of the pulse from the oscillation circuit 32 becomes 1/2, and the charge signal from the charge / discharge discriminator 6 is sent. It has a function to output the frequency of the pulse from the oscillation circuit 32 as it is when it is input.
The frequency of the PWM control signal for controlling the WM inverter 3 becomes one half when the storage battery 5 is discharged as compared to when the storage battery 5 is charged, and the loss in the DC-AC converter in the PWM inverter 3 and the AC filter. The loss at 4 can be reduced.

The frequency of the pulse from the oscillation circuit 32 is not limited to 1/2, and
If the noise of the PWM inverter 3 does not pose a problem when the commercial power source 1 fails, the noise can be reduced to less than half.

[0019]

As described above, the AC uninterruptible power supply device of the present invention can reduce the loss of the PWM inverter when the storage battery is discharged, so that even if the storage battery of the same volume and weight is used, the power failure holding time can be reduced. It can be made longer, and it is possible to reduce the size and weight even for the same power outage retention time.

[Brief description of drawings]

FIG. 1 is a block diagram of an AC uninterruptible power supply device of the present invention.

FIG. 2 is a block diagram of a conventional AC uninterruptible power supply.

[Explanation of symbols]

 1 Commercial power supply 2 Rectifier 3 PWM inverter 4 AC filter 5 Storage battery 6 Charge / discharge discriminator 30 PWM control circuit 32 Oscillation circuit 33 Carrier wave generation circuit 35 Dividing circuit

Claims (2)

[Claims] 1. A rectifier for rectifying AC power from a commercial power supply, a PWM inverter for converting DC power from the rectifier to AC power, and a connection point between the rectifier and the PWM inverter for receiving commercial power. A storage battery that is charged by the AC power at the time, and supplies the DC power to the PWM inverter when the commercial power supply is interrupted,
In an AC uninterruptible power supply device including an AC filter that makes the output of the PWM inverter a sine wave, a charge / discharge signal is determined by determining whether the storage battery is being charged or discharged in a charge / discharge path of the storage battery. Providing a charge / discharge discriminator to output,
Further, a PWM control circuit for creating a PWM control signal for controlling the PWM inverter, a reference sine wave operation circuit that outputs a predetermined reference sine wave, an oscillation circuit that outputs a pulse that determines the frequency of a carrier wave, and this oscillation A carrier wave generation circuit that inputs a pulse output from the circuit and outputs a carrier wave, and a carrier wave from the carrier wave generation circuit and a reference sine wave from the reference sine wave operation circuit are compared to create a PWM control signal. And a frequency divider circuit that divides the frequency of the pulse by inputting the charge / discharge signal between the oscillator circuit and the carrier wave generating circuit, and when the charge / discharge signal is a charge signal, An AC uninterruptible power supply device characterized in that the frequency dividing circuit is not operated and the frequency dividing circuit is operated when the charge / discharge signal is a discharge signal. 2. The AC uninterruptible power supply according to claim 1, further comprising a bypass AC power supply different from the commercial power supply, and a power supply switching device for switching between the power supply from the bypass AC power supply and the power supply from the PWM inverter. The AC uninterruptible power supply device is characterized in that the power supply from the PWM inverter is switched to the power supply from the bypass AC power supply when the storage battery voltage reaches the discharge end voltage.