JPH11290718A - Control method for electrostatic precipitator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep dust collecting performance by repeating glow eliminating operation in the case of detecting glow discharge to evade unnecessary charge trip. SOLUTION: In an electrostatic precipitator, the EP voltage in the case of permanently short-circuiting in the inside of the electrostatic precipitator is constant regardless of current change during the glow elimination operation, the range of the fluctuation is lower than a prescribed parameter (the range of glow detecting: 5 kV) and then, a main switch is tripped after the lapse of a prescribed parameter (low voltage trip time: e.g. 30 sec). In the case of glow discharge, the EP voltage is changed with the change of current during the glow elimination operation and exceeds glow detecting width and then, the glow elimination operation is executed and the count of the low voltage trip time is interrupted until the EP voltage is recovered. As a result, the charge trip is evaded and the dust collecting performance is kept.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an electrostatic precipitator, and more particularly to a method for controlling a low voltage.

[0002]

2. Description of the Related Art A power supply unit in an electrostatic precipitator (EP) is generally constructed as shown in FIG. As shown in FIG. 1, a commercial AC power supply AC is supplied to a high-voltage transformer 3 via a main switch 1 and a thyristor 2, and is boosted to a predetermined high voltage. The high voltage output from the high voltage transformer 3 is:
After being rectified by the rectifier 4, it is smoothed by the DC reactor 5 and supplied to the electric precipitator 6. A current detector 7 is provided on the output side of the thyristor 2 and
A voltage detector 8 for detecting a charging voltage to the electrostatic precipitator 6
The detection signal is input to the thyristor control device 9. The thyristor control device 9 changes the firing angle of the thyristor 2 according to a predetermined algorithm according to a setting parameter by a keyboard or the like, and the current detector 7 and the voltage detector 8 supply current to the electrostatic precipitator 6,
Various charging controls are performed while detecting the charging voltage.

[0003]

Among the various types of charge control in the above-mentioned electric precipitator, there is control at the time of detecting a low voltage.
The low-voltage control means that the charging voltage of the electrostatic precipitator 6 is set to a predetermined parameter (low-voltage detection value: for example, due to a permanent short circuit or abnormal discharge such as a glow discharge inside the electric precipitator 6 as shown in FIG. 4). 7 kV) and a predetermined time (about 100 ms) elapses.
Even after performing the glow erasing operation in which the thyristor 2 is repeatedly turned on / off during a predetermined parameter (low-voltage trip time: for example, 30 ms) after the detection, the predetermined parameter (low-voltage return width: for example, 3 kV) is changed to a low voltage. If the charging voltage of the electrostatic precipitator 6 does not recover to the value added to the detected value, it is regarded as a permanent short circuit, and the main switch 1 is cut off (trip operation is performed) to stop the device.

FIG. 5 is a flowchart showing a low voltage control operation in the thyristor control device 9. This low-voltage control operation is performed at regular intervals, for example, every 50 ms. First, the charging voltage (hereinafter referred to as EP)
It is checked whether the voltage is lower than a low voltage detection value, for example, 7 kV (Step A1). If the EP voltage is higher than the low voltage detection value, the process directly proceeds to Step A3.
If the EP voltage is lower than the low voltage detection value, the “EP voltage“ low ”flag” is set in step A2, and the process proceeds to step A3.

In step A3, it is determined whether or not the EP voltage "low" flag is set. If the flag is in a reset state, that is, if the EP voltage is normal, the process proceeds to the next step, and the flag is set. For example, the low voltage control processing of step A4 and subsequent steps is executed.

That is, in step A4, it is determined whether or not the EP voltage is higher than "low-voltage detection value + low-voltage recovery width". It is determined that the voltage has recovered, and the “EP voltage“ low ”flag” is reset, and the 100 ms timer and the low voltage trip timer are reset (step A5).

If the EP voltage is lower than "low voltage detection value + low voltage recovery width", it is determined whether 100 ms has elapsed since the EP voltage "low" flag was set (step A6). If the time of 100 ms has not elapsed, the 100 ms timer is counted (step A).
7). When it is determined in step A6 that the time of 100 ms has elapsed, the low voltage trip time (for example, 30 seconds) is further increased from the time when the time of 100 ms has elapsed.
Is determined (step A8), and if not, a glow erasing operation for turning on / off the thyristor 2 is executed (step A9), and the low-voltage trip timer is counted (step A10).

When it is determined in step A8 that the low voltage trip time has elapsed, the main switch 1 is shut off (trip operation) to stop the apparatus (step A1).
1). Thereafter, the EP voltage "low" flag is reset, and the 100 ms timer and the low voltage trip timer are reset (step A12).

The low-voltage control operation is completed as described above. However, in the case of abnormal discharge, the charging voltage of the electrostatic precipitator 6 is often restored due to longer-time glow erasure.
In such a case, the dust collection function is stopped until the operator performs the return operation due to the charge trip, and an environmentally unfavorable situation may occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. A glow discharge detection function is added to the charge control at the time of low voltage detection, and when a glow discharge is detected, the charge voltage of the electrostatic precipitator is reduced. An object of the present invention is to provide a control method of an electric dust collecting apparatus capable of avoiding unnecessary charge trips and maintaining dust collecting performance by repeatedly performing a glow erasing operation until recovery.

[0011]

SUMMARY OF THE INVENTION According to the present invention, an AC power supply is adjusted by igniting a signal from a thyristor control device, and then a DC high voltage is applied through a high-voltage transformer, a rectifier, and a DC reactor. In the control method of the electrostatic precipitator supplied to the dust collector, a glow discharge detection function is added to the charge control at the time of low voltage detection, and during the glow discharge, the glow erasing operation is performed until the charge voltage of the electric precipitator recovers. It is characterized by being repeatedly executed to avoid unnecessary charge trips.

Further, the present invention is characterized in that when the voltage fluctuation width during the glow erasure is larger than the glow detection width, the counting of the low voltage trip time is interrupted as glow discharge to avoid a charge trip.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows waveforms of an EP voltage, a thyristor firing signal, and a gate cutoff signal in a method for controlling an electrostatic precipitator according to the present invention. The present invention focuses on the point that the waveform of the voltage charged in the electrostatic precipitator 6 is different between a permanent short circuit and a glow discharge. In the configuration of the power supply unit shown in FIG. By adding a glow detection function and a function of extending the trip time, a charge trip during glow discharge can be avoided.

In FIG. 1, the EP voltage in the case of a permanent short-circuit inside the electrostatic precipitator 6 becomes constant as shown by the dashed line 11 regardless of the current change during the glow erasing operation, and the fluctuation width thereof is changed. In order to fall below a predetermined parameter (glow detection width: for example, 5 kV), the main switch 1 is tripped after a predetermined parameter (low voltage trip time: for example, 30 sec) has elapsed. On the other hand, in the case of glow discharge,
The EP voltage changes with a dotted line 1 according to the current change during the glow erase operation.
2 and exceeds the glow detection width, the glow erasing operation is performed, and the counting of the low voltage trip time is interrupted until the EP voltage recovers. As a result,
Charge trips can be avoided and dust collection performance can be maintained.

Next, the detailed operation of the present invention will be described with reference to the flowchart shown in FIG. The low voltage control operation shown in FIG. 2 is performed at regular intervals, for example, every 50 ms.
First, it is checked whether or not the charging voltage (EP voltage) to the electrostatic precipitator 6 is lower than a low voltage detection value, for example, 7 kV (step B1). If the EP voltage is higher than the low voltage detection value, the process directly proceeds to step B3. If the EP voltage is lower than the low voltage detection value, the “EP voltage“ low ”flag” is set (step B2), and the process proceeds to step B3.

At step B3, it is determined whether or not the EP voltage "low" flag is set. If the flag is in the reset state, the process proceeds to the next step. That is, if the electrostatic precipitator 6 is operating normally, the process proceeds to the next process without setting the EP voltage “low” flag.

If it is determined in step B3 that the EP voltage "low" flag is set,
4 or less low-voltage control processes are executed. That is, in step B4, it is determined whether the EP voltage is higher than “low voltage detection value + low voltage recovery width”, and if the EP voltage is higher than “low voltage detection value + low voltage recovery width”, the EP voltage is recovered. Then, the "EP voltage" low "flag" is reset, and the timer of, for example, 100 ms and the low voltage trip timer are reset (step B5).

If the EP voltage is lower than "low voltage detection value + low voltage return width", it is determined whether 100 ms has elapsed since the EP voltage "low" flag was set (step B6). If the time of 100 ms has not elapsed, the 100 ms timer is counted (step B).
7). If it is determined in step B6 that the time of 100 ms has elapsed, the low-voltage trip time (for example, 30 seconds) is started from the time when the time of 100 ms has elapsed.
Is determined (step B8), and if not, a glow erasing operation for turning on / off the thyristor 2 is executed (step B9).

Thereafter, it is determined whether or not the change in the EP voltage is larger than the glow detection width (step B10). If the change in the EP voltage is smaller than the glow detection width, a permanent short-circuit is established inside the electrostatic precipitator 6. Judge. That is, the EP voltage in the case of a permanent short circuit inside the electrostatic precipitator 6 is substantially constant as shown by the one-dot chain line in FIG. 1 regardless of the current change during the glow erasure. It becomes smaller than the glow detection width. Therefore, if the EP voltage change is smaller than the glow detection width, it can be determined that a permanent short circuit has occurred inside the electrostatic precipitator 6. When it is determined that a permanent short circuit has occurred inside the electrostatic precipitator 6 in this way, the process proceeds to step B11, where the low voltage trip timer is counted.

Therefore, when a permanent short circuit occurs inside the electrostatic precipitator 6 as described above, the count operation of the low-voltage trip timer is performed in step B11.
When the predetermined low-voltage trip time has elapsed, the elapse of the time is detected in step B8, and the main switch 1 is shut off (step B13). Thereafter, the EP voltage "low" flag is reset, and the 100 ms timer and the low voltage trip timer are reset (step B14). In addition, at the time of the permanent short circuit, since the internal inspection of the electrostatic precipitator 6 is required, an alarm is output and the operator is urged to respond after the charge trip as described above.

If it is determined in step B10 that the EP voltage change is larger than the glow detection width, it is determined that the EP voltage has decreased due to the glow discharge. The counting is interrupted, and the glow erasing operation is continued. This glow erase operation is extended until the EP voltage recovers.

As described above, in the method for controlling the electrostatic precipitator, by adding a glow discharge detecting function to the charge control at the time of detecting the low voltage, the cause of the permanent short circuit or the low voltage phenomenon inside the electric precipitator can be reduced. It can be determined automatically. Further, when the EP voltage is reduced by the glow discharge, by continuing the glow erasing operation until the EP voltage is recovered, unnecessary charge trips can be avoided and dust collection performance can be maintained.

[0023]

As described above in detail, according to the present invention, in the control method of the electrostatic precipitator, a glow discharge detecting function is added to the charge control at the time of detecting the low voltage, and the control is performed permanently inside the electric precipitator. In the case of short circuit, the main switch is tripped after a predetermined time, and during glow discharge, the glow erasing operation is repeatedly performed until the charging voltage of the electrostatic precipitator recovers. Avoid,
Dust collection performance can be maintained.

[Brief description of the drawings]

FIG. 1 is a view showing signal waveforms of respective units for explaining an operation of a control method of an electrostatic precipitator according to one embodiment of the present invention.

FIG. 2 is an exemplary flowchart showing the processing operation of low voltage control in the embodiment.

FIG. 3 is a diagram showing a configuration of a power supply unit of the electric precipitator to which the present invention is applied.

FIG. 4 is a diagram showing signal waveforms of respective sections for explaining the operation of a conventional method for controlling an electrostatic precipitator.

FIG. 5 is a flowchart showing a processing operation of low-voltage control in a conventional method for controlling an electrostatic precipitator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main switch 2 Thyristor 3 High-voltage transformer 4 Rectifier 5 DC reactor 6 Electric precipitator 7 Current detector 8 Voltage detector 9 Thyristor controller

Claims (2)

[Claims] An AC power supply is adjusted by igniting a signal from a thyristor control device, and then a DC high voltage is supplied through a high-voltage transformer, a rectifier, and a DC reactor, and the electric power is supplied to an electric precipitator. In the device control method, a glow discharge detection function is added to the charge control at the time of low voltage detection, and during the glow discharge, the glow erasing operation is repeatedly performed until the charge voltage of the electrostatic precipitator recovers. A method for controlling an electrostatic precipitator, characterized by avoiding the problem. 2. The electric collector according to claim 1, wherein when the voltage fluctuation width during the glow erasure is larger than the glow detection width, counting of the low voltage trip time is interrupted as glow discharge to avoid a charge trip. A method for controlling a dust device.