JPH1014251A - Control circuit for uninterruptible power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the interval of an inverter where the output voltage is disturbed by interrupting an instantaneous waveform correction amount, based on the detected value of a current flowing through the main circuit of the inverter, when a commercial power supply is abnormal. SOLUTION: An uninterruptible power supply is additionally provided with an inverter control circuit 41, substituting for a conventional inverter control circuit and an inverter output current detector. The inverter control circuit 41 is additionally provided with a switching control circuit 43 and a signal switch 45. The switching control circuit 43 outputs a logical H signal for a predetermined time, when the detection value IINV of the inverter output current detector exceeds a predetermined level. An AND element 44, receiving the output from the switching control circuit 43, generates an abnormal signal and 'opens' the signal switch 45 during an interval when the switching control circuit 43 generates a logical H signal. More specifically, the interval where the output voltage is disturbed when a commercial power supply is abnormal, is minimized by opening the signal switch means temporarily, in order to interrupt an instantaneous waveform correction amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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 normal, that is, when the commercial power supply is started, the circuit breaker 11 is closed, the semiconductor switch 12 is turned on by the gate drive circuit 13, and the commercial power supply 1 is turned on through the circuit breaker 11 and the semiconductor switch 12. To start the power supply to the load 3 and close the circuit breaker 20 and the electromagnetic contactor 14 so that the inverter control circuit 2
4 starts the charging operation of the smoothing capacitor 15 and the storage battery 2 via the inverter main circuit 16 and the active filter operation of absorbing the harmonic current and the reactive current generated from the load 3, thereby completing the startup. The uninterruptible power supply 10 enters a normal operation state.

Next, when the commercial power supply 1 is abnormal, for example, when a power failure occurs, a power failure detection circuit (not shown) detects this and outputs an abnormal signal, and the gate drive is performed by a cutoff signal from the inverter control circuit 24 based on the abnormal signal. The semiconductor switch 12 is cut off via the circuit 13, and the inverter control circuit 24 controls the storage battery 2 from the storage battery 2 to the electromagnetic contactor 14, smoothing capacitor 15, inverter main circuit 16, transformer 17, AC reactor 18, filter capacitor 19, circuit breaker. The output voltage of the inverter main circuit 16 in which the detection value of the output voltage detector 25 is controlled to a predetermined value via
Power.

FIG. 5 is a detailed circuit diagram of the inverter control circuit 24 shown in FIG. In FIG. 5, V / F converter 26 receives input of frequency command signal F ^* , and AC waveform generating circuit 27 that receives the output of V / F converter 26 and voltage amplitude signal E ^* generates AC voltage waveform signal V ^*. Is output. The AC voltage waveform signal V ^* and the detection value V _OUT of the output voltage detector 25
The proportional controller 29 outputs an instantaneous waveform correction amount W that makes the deviation zero. The active filter operation circuit 30 detects the detection value I of the output current detector 21.
Active filter control signal V by calculation based on _OUT
Outputs _AF ^* . DC voltage operation circuit 31 which receives a detection value I _DC of the DC voltage arithmetic circuit 31 detects value V _DC and the DC current detector 23 of the DC voltage detector 22 battery control signal V
Output _DC ^* .

When the commercial power supply 1 is normal, the switching control circuit 32
The signal switch 34 becomes “closed” via the inverter and the inverting element 33, and the addition value (V _AF ^* +) of the active filter control signal V _AF ^* and the storage battery control signal V _DC ^{* by} the adder 35.
V _DC ^* ), an added value of the added value and the instantaneous waveform correction amount W by the adder 36 (W + V _AF ^* + V _DC ^* ), and an adder 37 of the added value and the AC voltage waveform signal V ^*.
(V ^* + W + V _AF ^* + V _DC ^* ) are input to the PWM comparator 38, and the gate signals pulse-width-modulated by the PWM comparator 38 and the carrier generator 39 form the respective semiconductor elements constituting the inverter main circuit 16. By turning on and off the inverter main circuit 1
6, the charging operation of the storage battery 2 and the active filter operation are performed.

When the commercial power supply 1 is abnormal, the signal switch 34 is opened via the switching control circuit 32 and the inverting element 33 which receive the abnormal signal, and the output of the adder 37 is the AC voltage waveform signal V ^*. And an instantaneous waveform correction amount W. The PWM signal 38 outputs a gate signal that has been subjected to pulse width modulation based on the added value, and the inverter main circuit 16 using the storage battery 2 as a DC power supply loads the load 3 with a desired output voltage. Power.

[0008]

According to the control circuit of the conventional uninterruptible power supply described above, when the commercial power supply 1 is abnormal due to a short-circuit accident in the system of the commercial power supply 1, the semiconductor switch 12 is connected to the short-circuit path. An overcurrent flows from the inverter main circuit 16 during a period until it is completely shut off (up to about a half cycle), and the output voltage of the inverter main circuit 16 drops sharply due to the overcurrent, and as a result, the instantaneous waveform correction amount W increases. However, there is a problem that the output voltage of the inverter main circuit 16 is disturbed, and the disturbance continues for a while (about several cycles) even after the semiconductor switch 12 is completely shut off.

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

[0010]

According to the first aspect of the present invention, when a commercial power supply is normal, power is supplied to a load via a semiconductor switch for supplying / cutting power from the commercial power supply.
Inverter charging operation from a commercial power supply to a storage battery,
An uninterruptible power supply device that performs an active filter operation for absorbing harmonic current and reactive power generated from a load, and supplies power to the load from a storage battery via an inverter when a commercial power supply is abnormal. An AC that inputs a voltage amplitude signal of a DC amount for instructing the voltage amplitude and a frequency command signal of a DC amount for instructing the frequency of the output voltage of the inverter, and outputs an AC voltage waveform signal to be output by the inverter Waveform generating means, and inputting the AC voltage waveform signal and a detection signal of the AC voltage waveform output from the inverter, and outputting an instantaneous waveform correction amount for controlling a deviation between the two inputs to zero. DC voltage calculating means for detecting a terminal voltage and a charging current of the storage battery and calculating a storage battery control signal of the inverter based on both detected values; Active filter calculating means for detecting a load current and calculating an active filter control signal of the inverter based on the detected value; an AC voltage waveform signal, an instantaneous waveform correction amount, a storage battery control signal, and an active filter control signal. And a pulse width modulation means for pulse width modulating the operation result of the addition means and outputting an inverter control pulse. A signal switching means for interrupting the instantaneous waveform correction amount output from the means, and a current flowing through a semiconductor element constituting a main circuit of the inverter, and temporarily controlling the signal switching means based on the detected value. Opening / closing control means for outputting a command to set the opening state.

According to a second aspect of the present invention, in the first aspect, the switching control means is configured to perform a logic operation when a detected value of a current flowing through a semiconductor element constituting a main circuit of the inverter exceeds a predetermined value. A comparator that outputs an H signal;
An off-delay circuit that delays the return of the logic H signal output from the comparator to a logic L signal and outputs the delayed signal. The opening / closing control means is configured to output the logic signal when the output of the off-delay circuit becomes a logic H signal. It outputs a command to set the signal opening / closing means to an "open" state.

According to this invention, when the commercial power supply is abnormal, the current flowing through the main circuit of the inverter is detected, and the instantaneous waveform correction amount output from the instantaneous waveform correction amount generating means is cut off based on the detected value. Therefore, the period during which the output voltage of the inverter is disturbed can be minimized (about one cycle) by temporarily setting the signal switching means to the "open" state.

[0013]

FIG. 1 is a block diagram of an uninterruptible power supply according to an embodiment of the present invention. Components having the same functions as those of the conventional example shown in FIG. The description is omitted. That is, in FIG. 1, an uninterruptible power supply 40 includes an inverter control circuit 41 and an inverter output current detector 4 instead of the conventional inverter control circuit 24.
2 is newly provided.

[0014]

FIG. 2 is a detailed circuit diagram of an inverter control circuit 41 shown in FIG. 1 showing an embodiment of the present invention. Elements having the same functions as those of the inverter control circuit 24 shown in FIG. The description is omitted here. That is, FIG.
In the inverter control circuit 41, in addition to the circuit elements 26 to 39 having the same function as the inverter control circuit 24,
A switching control circuit 43, an AND element 44, and a signal switch 45 are added.

When the detection value I _INV of the inverter output current detector 42 exceeds a predetermined value, the switching control circuit 43 outputs a logic H signal for a predetermined period, and receives the output of the switching control circuit and the output of the switching control circuit 43. The AND element 44 generates the above-described abnormal signal, and the output of the opening / closing control circuit 43 is logic H.
The signal switch 45 is opened during the signal period. FIG. 3 is a detailed circuit diagram of the opening / closing control circuit 43 in FIG. 2. The rectifier 43a rectifies the detection value I _INV and the allowable current value of each semiconductor element of the inverter main circuit 16 is set to a predetermined value. A comparator 43b that outputs a logical H signal when the signal exceeds the predetermined value,
b output once becomes a logic H signal,
And an off-delay circuit 43c for continuing the signal for a predetermined period (about one cycle).

The duration of the off-delay circuit 43c is a value that takes into account a waveform that repeatedly increases and decreases as each semiconductor element of the inverter main circuit 16 is turned on and off based on the pulse width modulated gate signal.

[0017]

According to the present invention, when the commercial power supply is abnormal, the current flowing through the main circuit of the inverter is detected, and the instantaneous waveform correction amount output from the instantaneous waveform correction amount generation means is determined based on the detected value. An uninterruptible power supply device that has both an active filter operation of a load and an operation of charging a storage battery by minimizing the period during which the output voltage of the inverter is disturbed by temporarily setting the signal switching means to an "open" state in order to shut off. Can be provided.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram of an inverter control circuit of the uninterruptible power supply according to the embodiment of the present invention.

FIG. 3 is a detailed circuit diagram of the switching control circuit in FIG. 2;

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

FIG. 5 is a detailed circuit diagram of an inverter control circuit of the uninterruptible power supply of FIG. 5;

[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 ... V / F converter, 2
7 ... AC waveform generation circuit, 28 ... Adder, 29 ... Proportional adjuster, 30 ... Active filter operation circuit, 31 ... DC voltage operation circuit, 32 ... Switching control circuit, 33 ... Inverting element, 3
4 ... Signal switch, 35-37 ... Adder, 38 ... PWM comparator, 39 ... Carrier generator, 40 ... Uninterruptible power supply, 41 ... Inverter control circuit, 42 ... Inverter output current detector, 43 ... Switching control circuit , 44 ... AND element, 45 ... Signal switch.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location H02J 7/34 H02J 7/34 F 9/06 504 9/06 504B

Claims (2)

[Claims] When the commercial power supply is normal, 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 by an inverter and a harmonic generated from the load are performed. An uninterruptible power supply that performs an active filter operation for absorbing wave current and reactive power and supplies power to a load from a storage battery via an inverter when a commercial power supply is abnormal. AC waveform generating means for inputting a DC magnitude voltage amplitude signal to be input and a DC quantity frequency command signal for commanding the frequency of the output voltage of the inverter, and outputting an AC voltage waveform signal to be output by the inverter; An instantaneous wave that inputs the AC voltage waveform signal and a detection signal of the AC voltage waveform output from the inverter, and controls a deviation between both inputs to zero. An instantaneous waveform correction amount generating means for outputting a correction amount; a DC voltage calculating means for detecting a terminal voltage and a charging current of the storage battery and calculating a storage battery control signal of the inverter based on both detected values; Active filter calculating means for detecting a load current and calculating an active filter control signal of the inverter based on the detected value; an AC voltage waveform signal, an instantaneous waveform correction amount, a storage battery control signal, and an active filter control signal. And a pulse width modulation means for pulse width modulating the operation result of the addition means and outputting an inverter control pulse, wherein the instantaneous waveform correction amount is generated. Signal switching means for interrupting the instantaneous waveform correction amount output from the means, and a semiconductor element forming a main circuit of the inverter. And an open / close control means for detecting a current to be supplied and outputting a command to temporarily open the signal open / close means based on the detected value. . 2. The control circuit for an uninterruptible power supply according to claim 1, wherein the switching control means is configured to detect a value of a current flowing through a semiconductor element forming a main circuit of the inverter exceeding a predetermined value. A comparator that outputs a logical H signal in such a case, and an off-delay circuit that delays the return of the logical H signal output from the comparator to a logical L signal and outputs the delayed signal. A control circuit for an uninterruptible power supply, which outputs a command to set the signal switching means to an "open" state when the output of the signal becomes a logical H signal.