JP2527158B2 - Flickering compensator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flicker compensating device connected in parallel with a load in a power circuit in which flicker occurs, particularly in a resistance welding machine under a large capacity intermittent operation load in an AC circuit.

Conventionally, the flicker compensator detects the current of the welding machine 1 by the AC device 2 as shown in FIG. 1 (a), and the control unit 3 controls the power semiconductor switch (thyristor) 4 to be turned on and off, and the series reactor 5 is connected. The reactive power was controlled by the phase advancing capacitor 6. However, in this method, due to the delay in the detection response of the reactive power, the circuit voltage after the reactive power compensation as shown in FIG.
The circuit voltage caused by the opening delay of the first 0.5 cycles due to the closing delay of the load and the opening delay of the 0.5 cycles of the semiconductor switch after the completion of the energization of the load drops and rises unevenly, and a sufficient flicker improvement effect cannot be obtained.

Here, the vertical axis of FIG. 1 (b) is the circuit voltage fluctuation ΔV,
The horizontal axis t is time, and T is the energization time of the welding machine.

As a method for improving the response delay of the above conventional method, a flicker compensation circuit for operating the power semiconductor switch 4 in synchronization with the operation signal of the resistance welding machine 1 is also proposed, which is shown in FIG. In this method, when the load capacity changes due to, for example, a change in the material to be welded or a change in welding conditions, the reactive power of the flicker compensation device cannot follow, and the change in the load capacity as shown in FIG. As a result, the reactive power cannot be properly corrected, the circuit voltage fluctuates (voltage drop), and the effect of improving flicker deteriorates.

1 (b) and 2 (b) of the above conventional example.
Indicates the relationship between the fluctuation ΔV of the circuit voltage and the time t, in which T is the energization time of the welding machine. The energization time of this welding machine is generally 10 to 15 cycles (Hz). In Fig. 1 (b), the voltage drop occurs at 0.5 cycles at the beginning of energization, and after the end of energization.
It shows that the voltage increases in 0.5 cycle. This is because the detection of the load current (reactive power) is delayed by 0.5 cycles at the beginning and end of energization with respect to the load current of the welding machine, and reactive power cannot be completely compensated during these 0.5 cycles. is there. That is, it is the response delay of the detection.

As can be seen from the above, if the response delay of the detection circuit occurs, there is a delay in the supply and stop of 0.5-cycle advanced reactive power when the intermittent operation load is turned on and tripped. At this time, voltage fluctuations occur in the power system between the 0.5 cycle at the time of turning on and the 0.5 cycle at the time of tripping, causing the flickering phenomenon (called flicker) of the lighting connected to the same system, and various The control system becomes unstable each time, and the power system fails to meet the performance required of the flicker compensator.

The problem to be solved by the present invention occurs at the time of power-on and tripping, which is caused by the delay in the detection response of the load current, which is a drawback of the conventional flicker compensation device described above.
This is to eliminate the flicker phenomenon caused by the voltage fluctuation of 0.5 cycle.

That is, the present invention is a flicker compensating device for an AC circuit in which a circuit in which a power semiconductor switch, a series reactor, and a phase-advancing capacitor are connected in series is connected in parallel to a load. A detection circuit that has and detects and sends an equivalent DC voltage, a first monostable multivibrator that receives a pulse signal that is synchronized with the operation of the load, and triggers at the rising edge of that signal, and at the falling edge of that signal. By the triggering second monostable multivibrator, the monostable multivibrator generates the load current or the reactive power detection delay time by the rising pulse at the start of the load operation and the falling pulse at the end of the operation. A pulse signal is generated, and the signal is used to generate an equivalent voltage at the start of operation via the semiconductor switch and at the end of operation. An equivalent voltage obtained by inverting the output voltage of the detection circuit is sent to each adder, the output voltage of the detection circuit is subjected to addition / subtraction processing, and the response delay is detected by correcting the detection response delay of the load current or reactive power. A flicker compensating device is characterized in that it controls a semiconductor switch for electric power without causing a noise, and FIG. 3 is a circuit of its embodiment.

According to this circuit, in order to correct the detection response delay of the load current of the circuit or the reactive power of the load, another signal generator synchronized with the actual operation signal of the load (welder) is provided, and this signal generation is performed. The control signal output obtained by the instrument is added to the head of the detection delay signal output of the load current of 0.5 cycle that occurs when the load is turned on, and the turn-on start time of the flicker compensation circuit is corrected by 0.5 cycle.

Next, for the 0.5-cycle load current detection delay that occurs when the load is tripped, reverse the polarity of the control signal output of the signal generator and subtract the control signal in addition to the last 0.5 cycles of the load current detection signal output. The correction is performed to accelerate the trip time of the flicker compensation circuit by 0.5 cycle. By this operation, the timing of turning on and off the flicker compensation circuit can be surely synchronized with the operating characteristics of the load, and flicker of the power system can be prevented.

The embodiments of the present invention shown in FIGS. 3 to 5 will be described below.

FIG. 3 is a circuit explanatory view of the flicker compensating apparatus of the embodiment of the present invention, 1 is a welding machine connected to the circuit, and 7 is a transistor for generating a pulse signal S synchronized with the operation of the welding machine. The pulse signal S is transmitted to the next photocoupler 8 to obtain the output signal S1 of the photocoupler 8. The next stage 9a, 9b is a monostable multivibrator, which obtains the output signal S2 of the monostable multivibrator 9a and the output signal S3 of the monostable multivibrator 9b in synchronization with the rising and falling of the signal S1. next
10a and 10b are semiconductor switches, which are turned on by the above signals S2 and S3
And output DC voltages S4 and S5, respectively.

At the start of operation of the welding machine, the semiconductor switch 10
The signal S4 (+ VQ0) output from a is input to the adder 11 as an equivalent DC voltage of the signal Q1 described later. Next, at the end of the operation of the welding machine, the equivalent DC voltage of the load current detection circuit 13 is inverted to an opposite polarity by the inverting amplifier 14, and the semiconductor switch
The semiconductor switch 10b is operated to obtain the equivalent DC voltage S5 (-VQ1) of the signal Q1 from the semiconductor switch 10b and input it to the adder 11 as a reverse polarity voltage.

On the other hand, the current transformer 2 detects the load current (AC) of the welding machine 1, and the load current detection circuit 13 obtains the equivalent DC voltage signal Q1 and inputs it to the adder 11.

Here, the signal Q1 is delayed by 0.5 cycle with respect to the signal S1 synchronized with the actual operating characteristics of the welding machine 1 as shown in FIG. 4, and the above signal S4 is added to the head of Q1 for 0.5 cycle. The signal Q2 with the detection delay corrected is obtained and input to the selection circuit 12.

The selection circuit 12 selects an appropriate reactive power value to be supplied according to the level of the equivalent DC voltage value of the signal Q2, and turns on by combining any of the power semiconductor switches 4a, 4b, 4c, and the series reactor 5a. , 5b, 5c and phase-advancing capacitors 6a, 6b, 6c are supplied to the circuit.

Next, in the load current (or reactive power) detection circuit 13 of the welding machine, the current is sampled and held every 0.5 cycle and an equivalent DC voltage Q1 delayed by 0.5 cycle is output (details will be described later).

Further, the transistor 7 is activated by the operation of the welding machine and the photocoupler 8 is activated, and the output signal S1 thereof becomes H. The rising edge of the signal S1 triggers the first monostable multivibrator 9a to set the semiconductor switch 10a to ON for 0.5 cycle to turn on the semiconductor switch 10a to obtain the equivalent DC voltage + VQ0 for adding the equivalent reactive power of the welding machine. This + VQ0 is input to the adder 11 as the signal S4. In addition, + VQ0 sets the voltage based on the value of the reactive power calculated in advance from the nominal rated capacity of the load.

Next, when the output signal S1 at the end of welding machine operation falls,
Trigger the second monostable multivibrator 9b to 0.5
During the cycle, the semiconductor switch 10b is turned on, and the detection circuit output signal Q1 is obtained by the inverting amplifier 14 as the -VQ1 signal. This −VQ1 signal is input to the adder 11 as S5.

The above signal relationships are as shown in Fig. 4, and the load current (reactive power) of each 0.5 cycle of starting and ending the welding machine operation.
Is corrected by the correction signal obtained from the operation signal S of the welding machine. That is, the + DC voltage (+ VQ0) equivalent to the output signal Q1 of the detection circuit 13 is added only for 0.5 cycles from the first rise of the welding machine operation output signal S, and from the end of welding.
Only during 0.5 cycles, the inverted voltage (-VQ1) of the equivalent DC voltage Q1 of the detection circuit 13 is added to Q1 to cancel the detection delay and correct it. In other words, if the output signal Q1 of the detection circuit 13 and the 0.5 cycles of the correction output signals S4 and S5 of FIG. 4 output from the semiconductor switches 10a and 10b are subjected to adjustment processing, the output signal Q2 of FIG. 4 is obtained. The signal Q2 thus obtained matches the operation load timing of the welding machine, and turns on any of the power semiconductor switches 4a, 4b, 4c without a response delay. When the value of the load capacity (reactive power) of the welding machine fluctuates, the value Q1 of the output signal of the detection circuit 13 changes, the value of Q2 changes, and the selection circuit 12 causes the semiconductor switch 4a,
4b and 4c are properly selected, and the circuit voltage can be compensated to a constant value as shown by ΔV in the figure.

Next, the reason why the timing of the detection output signal of the detection circuit 13 is delayed by 0.5 cycle from the actual welding machine load current and its operating principle will be described.

The detection circuit 13 has a welding machine current (or reactive power) of 0.5.
Cycle integration is performed and the equivalent DC voltage Q1 is output.

Generally, the theoretical formula of electric power Pa is Therefore, 0.5 cycles are integrated, and the fact that the DC component becomes the power value is used to sample and hold the integrated value for 0.5 cycles to instantly reset the already integrated value. Next, the integration of the next 0.5 cycles is started and this is repeated, and the detection value for every 0.5 cycle is always output. For this reason, the detection signal is always output with a delay of 0.5 cycle welder current, and its operation relationship is as shown in FIG.

As described above, according to the present invention, the equivalent DC voltage is supplied by the operation signal of the welding machine, for 0.5 cycles at the time of tripping, the equivalent DC voltage,
In order to correct the response delay of detection by adding / subtracting to the load current or reactive power detection equivalent DC voltage output, and to control the proper advanced reactive power by the detected value during periods other than 0.5 cycle at the time of making and tripping. In addition, it has the advantage that the effect of improving flicker is remarkably improved, and its industrial and practical value is extremely great.

[Brief description of drawings]

1 (a) is a circuit explanatory diagram of a conventional flicker compensation device, FIG. 1 (b) is a characteristic diagram showing a circuit voltage fluctuation ΔV of the conventional flicker compensation device, and FIG. 2 (a) is another diagram. FIG. 3B is a circuit diagram of a flicker compensating device of the present invention, FIG. 3B is a characteristic diagram showing a circuit voltage variation ΔV of the conventional flicker compensating device, and FIG. FIG. 4 is an operation waveform explanatory diagram of the flicker compensation device of the present invention, and FIG. 5 is an operation waveform explanatory diagram of a detection value and a welding machine current of the detection circuit according to the flicker compensation device of the present invention. 1 …… Welding machine 2 …… AC device 3 …… Control circuit 4 …… 4a, 4b, 4c, power semiconductor switch 5 …… 5a, 5b, 5c Series reactor 6 …… 6a, 6b, 6c Phase advance capacitor 7 ...... Welding machine operation detection transistor 8 ...... Photo coupler 9a ...... First monostable multivibrator 9b …… Second monostable multivibrator 10a, 10b …… Semiconductor switch 11 …… Adder 12 …… Selection circuit 13 …… Detection circuit 14 …… Inverting amplifier t …… Time T …… Welding machine (load) energization time ΔV …… Circuit voltage fluctuation

Claims (1)

(57) [Claims] 1. A flicker compensating device for an AC circuit, comprising a power semiconductor switch, a series reactor and a phase-advancing capacitor connected in series to a load in parallel.
A detection circuit that detects a flicker-generated load current or reactive power with a response delay and sends an equivalent DC voltage, and a pulse signal that is synchronized with the operation of the load and that triggers at the rising edge of the signal. The monostable multivibrator and the second monostable multivibrator triggered by the falling edge of the signal cause the monostable multivibrator to generate the load current at the rising pulse at the start of operation of the load and the falling pulse at the end of operation. Alternatively, a pulse signal for the response delay time of the reactive power detection circuit is generated, and the signal is used to invert the equivalent voltage at the start of operation and the output voltage of the detection circuit at the end of operation via a semiconductor switch. Send the voltage to each adder and add / subtract with the output voltage of the detection circuit to correct the detection response delay of the load current or reactive power. The Rukoto, flicker compensating apparatus characterized by controlling the power semiconductor switch without causing a response delay.