JPH1070885A - Control circuit for uninterruptible power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the output voltage of an uninterruptible power unit from becoming an overvoltage, by adding a limiting value switching circuit which switches the limiting value of a limiting operator from a first limiting value to a second limiting value which is smaller than the first limiting value, for a prescribed period of time after the power supply of a load is switched to an inverter from commercial power supply. SOLUTION: When commercial power supply is interrupted, a limiting value switching circuit 42 detects the power failure and outputs a power failure signal by means of a power failure detecting circuit, and outputs an operation signal for a prescribed period of time by starting a timer circuit 43 based on the power failure signal. While the operation signal is outputted, the circuit 42 switches the limiting value of a limiting operator 31 from a first limiting value to a second limiting value which is smaller than the first limiting value by closing a switch 44a and opening another switch 44b. Therefore, the output voltage of an uninterruptible power unit can be prevented from becoming an overvoltage by overshooting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying power to a load from a commercial power supply when the commercial power supply is healthy, and for charging a storage battery from the commercial power supply with an inverter and for controlling harmonic current and reactive power generated from the load. The present invention relates to a control circuit of an uninterruptible power supply device that performs an active filter operation for absorbing power and supplies power to a load from a storage battery via an inverter when a commercial power supply fails.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional block diagram of this type of uninterruptible power supply. In FIG. 4, 1 is a commercial power supply,
2 is a storage battery, 3 is a load, 10 is an uninterruptible power supply,
The uninterruptible power supply 10 includes a circuit breaker 11, a semiconductor switch 12, a gate drive circuit 13, an electromagnetic contactor 14, a smoothing capacitor 15, an inverter main circuit 16, a transformer 17, an AC reactor 18, a filter capacitor 19, and a circuit breaker 20. , An output current detector 21, a DC voltage detector 22, a DC current detector 23, an inverter control circuit 24, and an output voltage detector 25. The filter capacitor 19 is a filter that removes switching noise generated due to the switching operation of the inverter main circuit 16.

The uninterruptible power supply 10 shown in FIG. 4 operates as follows. First, when the commercial power supply 1 is healthy,
The circuit breaker 11 is closed, the semiconductor switch 12 is turned on by the gate drive circuit 13, and power is started from the commercial power supply 1 to the load 3 via the circuit breaker 11 and the semiconductor switch 12. Electromagnetic contactor 14
Are closed by the inverter control circuit 24 to charge the smoothing capacitor 15 and the storage battery 2 via the inverter main circuit 16 and to perform an active filter operation for absorbing a harmonic current and a reactive current generated from the load 3. By starting, the startup is completed, and the uninterruptible power supply 10 enters a normal operation state.

[0004] Next, when the commercial power source 1 fails, a power failure detection circuit (not shown) detects the power failure and outputs a power failure signal. The interruption signal from the inverter control circuit 24 based on the power failure signal passes through the gate drive circuit 13. The semiconductor switch 12 is shut off by the inverter control circuit 24, and the storage battery 2 is used to disconnect the electromagnetic contactor 14, the smoothing capacitor 15,
Inverter main circuit 16, transformer 17, AC reactor 1
8. The load 3 is supplied with the output voltage of the inverter main circuit 16 whose detected value of the output voltage detector 25 is controlled to a predetermined value via the filter capacitor 19 and the circuit breaker 20.

FIG. 5 is a detailed circuit configuration diagram of the inverter control circuit 24 shown in FIG. 4. This configuration will be described below with reference to FIG. In FIG. 5, the inverter control circuit 24 includes an inverter main circuit 1 via a transformer 17.
6, a voltage setter 26 for setting the output voltage, a voltage adjuster 27 for adjusting the output voltage to a desired value, and a full-wave rectifier 28 for converting the detection value (V _OUT ) of the voltage detector 25 into a DC amount. A deviation amplifier 29 for amplifying a deviation between the output value of the voltage regulator 27 and the output value of the full-wave rectifier 28;
Is normal, the output value of the deviation amplifier 29 and the full-wave rectifier 28
Of the output value of the full-wave rectifier 28 as an input of the voltage regulator 27 when the commercial power supply 1 is out of power. A switching circuit 30 for switching, and a limit calculator 31 for limiting the output of the voltage regulator 27 to within a range of a first limit value (V _L1 ).
And a reference sine wave signal having an amplitude based on the output value of the limit calculator 31. When the commercial power supply 1 is healthy, the reference sine wave signal, the detection value (V _DC ) of the DC voltage detector 22 and the DC current detection A first AC control signal for the charging operation of the storage battery 2 based on the detection value (I _DC ) of the detector 23, and a second AC control signal for the active filtering operation based on the detection value (I _OUT ) of the output current detector 21. And an AC signal operation circuit 32 that outputs only the reference sine wave signal when the commercial power source 1 is out of power, and an inverter main circuit 16 that forms a PWM-controlled gate signal from the output of the AC signal operation circuit 32. The uninterruptible power supply 10 performs the above-described control operation by providing a gate control circuit 33 including a PWM converter and a carrier generator for outputting to each of the semiconductor switch elements.

[0006]

According to the inverter control circuit 24 of the conventional uninterruptible power supply 10 described above, when the commercial power supply 1 is healthy, the inverter main circuit 1 via the transformer 17
The voltage output by 6 is adjusted by the voltage adjuster 27 so as to be substantially opposite to the voltage of the commercial power supply 1. That is, the output value of the voltage controller 27 is
5 and the voltage of the commercial power supply 1 via the full-wave rectifier 28.

When the commercial power supply 1 is out of power, the transformer 17
The voltage output from the inverter main circuit 16 via the voltage adjuster 27 is equal to the set value of the voltage setter 26.
Is adjusted by That is, the output value of the voltage adjuster 27 is a value corresponding to the set value of the voltage setter 26. However, in the process where the power failure of the commercial power supply 1 is detected and the power supply to the load 3 is switched from the commercial power supply 1 to the power supply from the inverter main circuit 16, the output voltage of the uninterruptible power supply 10 An adjustment operation is performed by the voltage adjuster 27 so as to shift from the voltage value in a state where the voltage is reduced to a voltage value based on the set value of the voltage setter 26. As a result, the output of the voltage adjuster 27 is set to, for example, 0.1.
Overshoot occurs for a period of about one second, and the output voltage of the uninterruptible power supply 10 may exceed the allowable fluctuation range and become overvoltage due to the overshoot.

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

[0009]

According to the present invention, when the commercial power supply is healthy, power is supplied to the load via a semiconductor switch for supplying / cutting power from the commercial power supply, and a charging operation from the commercial power supply to the storage battery is performed by the inverter. An uninterruptible power supply device that performs an active filter operation to absorb harmonic current and reactive power generated from the load, and supplies power to the load from the storage battery via the inverter when the commercial power supply fails, the output of the inverter A voltage setting device for setting a voltage, a voltage regulator for adjusting an output voltage of the inverter, a deviation amplifier for amplifying a deviation between an output value of the voltage regulator and a detection value (DC amount) of the output voltage of the inverter, When the power supply is healthy, the deviation between the output value of the deviation amplifier and the detected value (DC amount) is used as an input to the voltage regulator. A switching circuit for switching a deviation between the voltage value and the detected value (DC amount) to be an input of the voltage regulator; a limit calculator for limiting the output of the voltage regulator to a predetermined first limit value; A reference sine wave signal having an amplitude based on the output value of the limit calculator is generated. When the commercial power supply is healthy, the reference sine wave signal, a first AC control signal based on the charging operation, and a second sine wave signal based on the active filter operation. An AC signal arithmetic circuit that outputs the reference sine wave signal only when the commercial power supply fails, and a gate signal that is PWM-controlled from the output of the AC signal arithmetic circuit to a main circuit of the inverter. In the control circuit of the uninterruptible power supply, comprising: a gate control circuit that outputs to each of the semiconductor switch elements to be formed, when the power supply to the load is switched from the commercial power supply to the inverter. Predetermined period of time, limit calculator limit smaller value for its value than the first limit value the second
A limit value switching circuit as a limit value is added.

According to the present invention, the load on the limit value switching circuit prevents the output voltage of the uninterruptible power supply from becoming excessive due to the above-mentioned overshoot.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an uninterruptible power supply according to an embodiment of the present invention, and has the same functions as those of the conventional uninterruptible power supply shown in FIG. Those are given the same reference numerals. That is, FIG.
In this uninterruptible power supply device 40, an inverter control circuit 41 is provided in place of the conventional inverter control circuit 24.

[0012]

FIG. 2 is a detailed circuit diagram of an inverter control circuit 41 according to an embodiment of the present invention. Elements having the same functions as those of the conventional inverter control circuit shown in FIG. The description is omitted here. That is, in FIG. 2, the inverter control circuit 41 includes a voltage setter 26, a voltage regulator 27, a full-wave rectifier 28, a deviation amplifier 29, a switching circuit 30, a limit calculator 31, a signal waveform calculator 32, and a gate controller 33. In addition, a limit value switching circuit 42 is provided.

The operation of the limit value switching circuit 42 shown in FIG. 2 will be described below with reference to an operation waveform diagram shown in FIG. As shown in FIG. 3 (a), when the commercial power supply 1 has a power failure, a power failure detection circuit (not shown) detects this and outputs a power failure signal, and the timer circuit 43 starts based on the power failure signal.
Outputs period operation signal T ₀ (see FIG. 3 (b)), this period 3 (C), the switch 44a as shown in (d) closing, the switch 44b is restricted calculator 31 by open The limit value switches from the first limit value (V _L1 ) to the second limit value (V _L2 ).

When the power failure signal is output, as described above, the output voltage of the uninterruptible power supply 40 is
The voltage regulator 27 performs an adjustment operation to shift from the voltage value in a state where the voltage of the voltage is lowered to a voltage value based on the set value of the voltage setter 26. As a result, the voltage regulator 27
Output overshoots as shown in FIG.

However, since the limit value of the limit calculator 31 has been switched to the second limit value (V _L2 ) smaller than the first limit value (V _L1 ), the hatched portion shown in FIG. 2 is limited to the limit value (V _L2 ), and a value equal to or less than V _L2 is input to the signal waveform calculation circuit 32. Since the commercial power source 1 is in a power failure, the output of the signal waveform calculation circuit 32 also has an amplitude equal to or less than V _L2 . Only the reference sine wave signal is output to the gate control circuit 33.

By the control operation described above, for example, the operation time (T ₀ ) of the timer circuit 43 is set to about 0.5 seconds, and the second limit value (V _L2 ) is set to + the rated output voltage of the uninterruptible power supply 40.
By setting it to 5%, the output voltage of the uninterruptible power supply 40 immediately after the power failure of the commercial power supply 1 can be set within the allowable fluctuation range. Note that the first limit value (V _L1 ) is determined by the gate control circuit 3
(3) about 98% of the amplitude of the carrier signal generator of the gate control circuit 33 for the purpose of preventing a malfunction based on the PWM control of (3).
It is not a value that suppresses overvoltage of the output voltage of the uninterruptible power supply.

[0017]

According to the control circuit for an uninterruptible power supply of the present invention, for example, a power outage of a commercial power supply is detected, and the output of the uninterruptible power supply in the process of switching the power supply to the load from the commercial power supply to the inverter. Voltage fluctuation can be suppressed within the allowable fluctuation range.

[Brief description of the drawings]

FIG. 1 is a block diagram of an uninterruptible power supply according to the present invention.

FIG. 2 is a detailed circuit configuration diagram of a control circuit of the uninterruptible power supply shown in FIG.

FIG. 3 is a diagram illustrating the operation of FIG. 2;

FIG. 4 is a block diagram of a conventional uninterruptible power supply.

5 is a detailed circuit configuration diagram of a control circuit of the uninterruptible power supply shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Commercial power supply, 2 ... Storage battery, 3 ... Load, 10 ... Uninterruptible power supply, 11 ... Circuit breaker, 12 ... Semiconductor switch, 1
3 ... Gate drive circuit, 14 ... Electromagnetic contactor, 15 ... Smoothing capacitor, 16 ... Inverter main circuit, 17 ... Transformer, 1
8: AC reactor, 19: Filter capacitor, 20
... Circuit breaker, 21 ... Output current detector, 22 ... DC voltage detector, 23 ... DC current detector, 24 ... Inverter control circuit, 25 ... Output voltage detector, 26 ... Voltage setter, 27
... voltage regulator, 28 ... full-wave rectifier, 29 ... deviation amplifier,
Reference numeral 30: switching circuit, 31: limited arithmetic unit, 32: signal waveform arithmetic circuit, 33: gate control circuit, 40: uninterruptible power supply, 41: inverter control circuit, 42: limited value switching circuit.

Claims (1)

[Claims] When the commercial power supply is healthy, power is supplied to the load via a semiconductor switch for supplying / cutting power from the commercial power supply, and a charging operation from the commercial power supply to the storage battery is performed by an inverter, and harmonics generated from the load are provided. An uninterruptible power supply that performs an active filter operation to absorb current and reactive power and supplies power to the load from a storage battery via an inverter when a commercial power supply fails, and a voltage setting device that sets the output voltage of the inverter. A voltage regulator that regulates the output voltage of the inverter; a deviation amplifier that amplifies the deviation between the output value of the voltage regulator and the detected value (DC amount) of the output voltage of the inverter; and an output of the deviation amplifier when the commercial power supply is healthy. The difference between the value and the detected value (DC amount) is used as an input to the voltage regulator, and when the commercial power supply is interrupted, the set value of the voltage setting device and the detected value (DC amount)
A switching circuit for switching the deviation from the input to the voltage regulator, a limit calculator for limiting the output of the voltage regulator to a range of a predetermined first limit value, and based on an output value of the limit calculator. A reference sine wave signal having an amplitude is generated, and when the commercial power supply is healthy, the reference sine wave signal, a first AC control signal based on the charging operation, and a second AC control signal based on the active filter operation are added. An AC signal operation circuit that outputs only the reference sine wave signal when the commercial power supply fails, and a PWM control gate signal from the output of the AC signal operation circuit to each semiconductor switch element that forms the main circuit of the inverter. A control circuit for the uninterruptible power supply, comprising: a gate control circuit that outputs the power to the load; A control circuit for an uninterruptible power supply, wherein a limit value switching circuit for setting a limit value of an arithmetic unit to a second limit value smaller than the first limit value is added.