JPH04117135A - Uninteruptible power supply - Google Patents

Abstract

PURPOSE:To prevent distortion of the output voltage waveform of an AC commercial power supply even upon occurrence of higher harmonic current by controlling a PWM inverter as an active filter when the commercial power supply is normal. CONSTITUTION:When a commercial power supply 1 is normal, an AC circuit breaker 3 is turned ON to feed an AC power to a load 2 and the load current is detected by a load current detector 20. A compensation current detecting circuit 21 detects trouble current components, e.g. higher harmonic components of the load current, reactive current, and the like, and a first control command for controlling the secondary voltage of a transformer 7, through a current control circuit 2, to a PWM inverter 5 with a current having reverse phase is selected. Consequently, the trouble current is canceled by the PWM inverter and when a battery is charged, only a sinusoidal basic wave component can be obtained from the AC commercial power supply.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention provides an uninterruptible power supply in which an inverter circuit having a storage battery is connected in parallel to a commercial AC power supply that supplies power to a load. Regarding equipment.

(Prior Art) FIG. 2 is a prong diagram showing the configuration of a conventional uninterruptible power supply. In the figure, when the commercial commercial current i[L is normal, a first AC breaker 3 that supplies power to a load 2
, a second AC breaker connected in parallel via a PWM inverter 5, an AC filter 6, and a transformer 7 whose DC power source is a storage battery 4 intended to supply power to the load 2 when the commercial AC power source 1 is abnormal. 8. Compare the output voltage detector 9 that detects the voltage of the transformer 7 with a reference voltage 10.

a voltage control circuit 12 that adds a signal from an output current detection @ 11 that detects the output current of the PWM inverter 5 and controls the output of the PWM inverter 5 to a predetermined voltage; a commercial voltage detection circuit that detects the voltage of the commercial AC power supply 1; a PLL circuit 14 that produces an output synchronized with the commercial frequency detected by the device 13;
The output of the PLL circuit 14 and the output of the voltage control circuit 12 are used to issue commands to a PWM control circuit 15 that gives on/off commands to the PWM inverter 5, and a command to a commercial AC abnormality detection circuit 16 that detects abnormalities in the commercial AC power supply 1. a connection/disconnection circuit 1 for controlling on/off of the first AC breaker 3;
It consists of 7.

For example, when the commercial current g1 in FIG. 2 is normal, the first AC breaker 3 is turned on to supply AC power to the load 2.

At the same time, the second AC breaker 8 connected in parallel to the load 2 is turned on, and the PLL circuit is set so that the output of the PWM inverter 5 is synchronized with the commercial frequency detected by the commercial voltage detector 13. The output of the PWM inverter 5 is controlled by the phase controlled by the voltage control circuit 14 and the predetermined voltage set by the reference voltage 10. However, when the commercial AC power supply 1 is in a normal state, the PLL circuit 14
provides a synchronization signal with a predetermined phase delay from the commercial AC power supply 1 to the PWM inverter. In this state, the commercial AC power supply 1 is converted to DC power via the first AC breaker 3, the second AC breaker 8, the transformer 7, the AC filter 6, and the PWM inverter 5, and charges the storage battery 4. do. Note that the output voltage of the PWM inverter S is controlled by giving a signal detected by the output current detector 11 to the voltage control circuit 12 so that the charging current flowing from the PWM inverter 5 to the storage battery 4 is constant.

Next, if the commercial AC source ↓ becomes abnormal.

(For example, voltage drop, power outage, frequency abnormality, etc.) A signal detected by the commercial AC power supply abnormality detection circuit 16 is applied to the connection/disconnection circuit 1
Send to 7. At the same time, the PLL circuit 14 stops synchronizing the commercial alternating current with the source 1 and continues oscillating in synchronization with the output of a reference oscillator (not shown in FIG. 2).

Then, the connection/disconnection circuit 17 quickly disconnects only the first AC breaker 3. At this time, the power to the load 2 is obtained by inversely converting the DC power of the storage battery 4 by the PWM inverter 5.
The waveform is shaped by AC filter 6.

AC power made to a predetermined voltage by a transformer 7 is supplied via an M2 AC breaker 8.

Further, when the commercial AC power supply 1 returns to normal, the PLL circuit 14 first oscillates in synchronization with the commercial AC power supply 1. When the output of the PWM inverter 5 is synchronized with the commercial AC power supply 1, the connection/disconnection circuit 17 turns on the first AC breaker 3. As a result, load 2 has commercial AC power supply 1
AC power is supplied from the AC circuit breaker 3 through the first AC breaker 3 . Further, the storage battery 4 is charged as described above when the commercial battery current g1 is normal.

With the above operation, uninterruptible power can be supplied to the load 2.

(Problem to be Solved by the Invention) In FIG. 2, when the commercial AC power supply 1 normally turns on the first AC breaker 3 to supply AC power to the load 2, the load 2 If the load is a load such as a motor with a very poor input power factor or a capacitor input type rectifier load such as a computer, the commercial AC power supply 1 must flow a high wave current, and the voltage waveform will be distorted. Also, commercial literature
If 1 is the output of a private generator, the inflow of equivalent negative sequence current will require a private generator with a capacity two to three times larger than the load capacity.

The present invention has been made in view of the above points, and is intended to be applied even when harmonic currents are generated in loads such as motors with extremely poor input power factors and capacitor input type rectified loads such as computers. It is an object of the present invention to provide an uninterruptible power supply FA device with good operating efficiency by ensuring that the output voltage waveform of a commercial AC power supply is not rejected and the input power factor of the power supply device is 1.7 [Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a load with a commercial AC power source connected by a first AC breaker, and a PWM inverter having at least a storage battery as a DC power source. and the AC filter, transformer.

connected in parallel via a second AC breaker, and when the commercial AC power supply is normal, the first AC breaker is turned on;
In an uninterruptible power supply that controls and operates a PWM inverter, a signal consisting of a compensation current detection circuit, a PWM inverter output current detector, and a storage battery voltage detector is transmitted from a load current detector at the load end to a current limiting circuit. The PWM is applied so that the harmonic current generated from the load side is canceled out by
It is characterized by comprising means for switching, by a commercial AC abnormality detection circuit, a first control command for controlling an inverter and a second control command for controlling the output direction of the PWM inverter to a predetermined voltage when the commercial AC power supply is abnormal. That is.

(Function) When the commercial AC power supply is normal, the first AC breaker is turned on to supply AC power to the load, the load current is detected by the load current detector, and the compensation current detection circuit adjusts the load current to the load current. 2 of the transformer so as to detect fault current components such as harmonics and reactive currents contained in the transformer and to flow a current with the opposite phase to the PWM inverter.
A first control command that causes the current limiting circuit to control the next voltage is selected. As a result, the fault current is canceled by the PWM inverter, and by charging the storage battery, a sine wave current containing only the fundamental wave component can be supplied to the commercial AC power source. In addition, when a commercial AC power supply abnormality occurs, the switching command of the commercial AC power supply abnormality detection circuit switches to a second control command that controls the output of the PWM inverter to a predetermined voltage, and the DC power of the storage battery is reversely converted by the PWM inverter to power the load. Continue.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention, and the same circuit elements as those in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted.

As shown in FIG. 1, the present invention provides a compensation current detection circuit 2 that includes a load current detector 20 that detects the current of a load 2 at the load end, and extracts various fault current components from the load current.
The output of PWM inverter 5 and the output of PWM inverter 5 detected by output current detector 11 are put into a feedback loop and input to current limiting circuit 22 . In addition, the PWM inverter 5 reversely converts the DC voltage charged in the DC side storage battery 4 to AC, and in order to charge the storage battery with a fault current component, the storage battery voltage detector 23 detects the DC voltage, and the current limiting circuit 22 to interrupt. This current limiting circuit 2
2 output signal and the secondary voltage of the transformer 7 to create a first control command, and connect it to the PWM control circuit 15 via a control switch 24 operated by a command from the commercial AC abnormality detection circuit 16. is added.

In FIG. 1, when the commercial AC power supply 1 normally turns on the first AC breaker 3 and supplies AC power to the load 2, the commercial AC abnormality detection circuit 16 switches the control switch 24 to the first AC breaker 3. As shown in the figure, the first control command is selected. Further, the second AC breaker 8 is also turned on. Now, if the load 2 is a load such as a motor with a very poor input power factor or a capacitor input type rectifier load such as a computer, then
The load current flowing through the load 2 includes fault currents such as harmonic current and reactive current. This load current is detected by the load current detector 20, and the harmonic current is detected by the compensation current detection circuit 21.
Extracts various current components such as fundamental wave reactive current and fundamental wave unbalanced current. The compensation current command value is created by combining the current components according to their purpose. PWM the command value of this compensation current
It is put into the feedback loop of the output current of the inverter 5, and in the current limiting circuit 22, a current with the opposite phase to the compensation current is PW.
A first control command is generated by applying a current limit to the output of the output voltage detector 9 so that the current flows to the M inverter 5.

Based on the first control command, the PWM control circuit 15
It changes the output synchronized with the commercial AC power supply 1 sent from the LL circuit 14 and outputs on/off signals to the PWM inverter. The PWM inverter 5 generates a voltage waveform in which a current having an opposite phase to the compensation current flows. The storage battery 4 is charged by the current having the opposite phase. The above-described operation is instantaneously performed, the fault current flowing through the load 2 is canceled by the PWM inverter 5, and only a sine wave current containing no harmonic current flows through the commercial AC power supply 1. In addition, the command value of the compensation current is P
By setting the same phase as the commercial AC power supply 1 detected by the LL circuit 14, the waveform of the current supplied from the commercial AC power supply 1 can be made in the same phase as the voltage, resulting in a voltage waveform without distortion of the input power factor of the power supply device. is obtained.

Next, when the commercial AC power supply 1 becomes abnormal, a signal detected by the commercial AC power supply abnormality detection circuit 16 is sent to the connection/disconnection circuit 17 . At the same time, the PLL circuit 14 stops synchronizing with the commercial AC power supply 1 and continues oscillating in synchronization with the output of a reference oscillator, which is not shown in FIG. Then, the connection/disconnection circuit 17 quickly disconnects only the first AC breaker. The commercial AC abnormality detection circuit 16 simultaneously connects the control switch 24
The control command is switched to the second control command which is the output of the voltage control circuit 12 which sends a command to and controls the output of the PWM inverter 5 to a predetermined voltage. The load 2 is supplied with AC power that is inversely converted by a PWM inverter 5 from a storage battery 4, waveform-shaped by an AC filter 6, and set to a predetermined voltage by a transformer 7 via a second AC breaker 8. Continue power supply.

Furthermore, when the commercial current g1 returns to normal, the PLL circuit 14 first oscillates in synchronization with the commercial AC power supply 1. When the output of the PWM inverter 5 is synchronized with the commercial AC power supply, the connection/disconnection circuit 17 turns on the first AC breaker 3. At the same time, the control switch 24 is switched to the first control command side. As a result, AC power is supplied to the load 2 from the commercial AC power supply 1 via the first AC breaker 3 . Further, the storage battery 4 is charged as described above when the commercial AC power supply 1 is normal.

With the above operation, uninterruptible power can be supplied to the load 2.

In the above-mentioned embodiment, the number of uninterruptible power supplies is one, but the effect of the present invention is the same even if the system is operated in parallel with two or more uninterruptible power supplies.

[Effects of the Invention] As explained above, according to the present invention, the output voltage waveform of a commercial AC power source can be rejected even when the load is a motor with a very poor input power factor or a capacitor input type rectifier load such as a computer. In addition, by setting the input power factor of the power supply device to 1, it is possible to provide an uninterruptible power supply device with high operating efficiency.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an uninterruptible power supply showing an embodiment of the present invention, and Fig. 2 is a block diagram of a conventional uninterruptible power supply.・・First AC breaker 4−・Storage battery 5・PWM inverter 6−・・AC filter 7・・Transformer 8・・Second AC breaker 9・Output voltage detector 1o3
．． Base 4! Voltage II...Output current detector 1
2.Voltage control circuit 13...Commercial voltage detector 1
4...PLL circuit 15...PWM control circuit 16...Commercial AC abnormality detection circuit 17...Connection/disconnection circuit 20.Load 'It current detector 21...Compensation current detection circuit 22...Current limit Circuit 23...Storage battery voltage detector 24...Control switch agent Patent attorney Noriyuki Chika Figure 1

Claims (1)

[Claims] A commercial AC power supply that supplies power to the load via a first AC power cutter, and a second AC power supply that converts the DC supplied from the storage battery into AC when the commercial AC power supply has a power outage and supplies power to the load via a second AC power cutter. What is claimed is: 1. An uninterruptible power supply device comprising a PWM inverter that supplies power to the load using a PWM inverter, the uninterruptible power supply device comprising means for controlling the PWM inverter as an active filter when the commercial power supply is normal.