JPH02214552A - Control method for electrostatic precipitator - Google Patents

Abstract

PURPOSE:To effectively restrain the spark discharge and to improve the performance of electrostatic precipitator by discriminating the strength of spark discharge and controlling the electric current supply through a thyristor. CONSTITUTION:The wave shape of electric current of electrostatic precipitator is successively compared with the wave shape of one period before which is delayed by one period in the time series within the continuity time of the thyristor, and the time when the compared value exceeds a prescribed value of spark generation is calculated to control as follows: when the obtained time is within the 1st prescribed time in the beginning of the continuity time, the streaming of current through the thyristor is stopped for a prescribed time, and, when the obtained time exceeds the 1st prescribed time and is within the 2nd prescribed time, the phase angle of the thyristor is set in a lower prescribed value during a prescribed time, and, when the obtained time exceeds the 2nd prescribed time, the phase angle of the thyristor is reduced during a prescribed time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling an electrostatic precipitator applied to a silage control device in a DC high voltage power supply.

[Conventional technology]

-i The electrostatic precipitator is equipped with a power supply device that generates a DC high voltage, and this ta! Electrical current from the device gives an electric charge to the dust introduced into the electrostatic precipitator, and the charged dust is attached to the dust collecting electrode using Coulomb force generated by a high electric field, thereby separating and removing the dust from the gas. be. In such a power supply device for an electrostatic precipitator, as shown in FIG. It is supplied to an electrostatic precipitator 6 via a rectifier 3, a rectifier 4, and a DC reactor 5. In this case, the current detector 7 and the voltage detector 8 detect the current and voltage supplied to the electrostatic precipitator, respectively, and provide feedback to the cyrisk control device 1.

Here, in the above-mentioned control device, conventionally, after detecting the occurrence of spark discharge using the feedback signal, the thyristor is uniformly cut off for a certain period of time regardless of the strength of the spark, and then the thyristor is recharged. As a whole, the spark generation frequency was controlled to be the same as set by the spark frequency setting device 9.

The spark discharge control method described above will be explained in detail with reference to FIG. 7 as follows.

(1) Start up the DC high-voltage power supply device, and control the phase of the thyristor 2 according to the signal from the thyrisk control device 1 ((b) in the same figure) L, and continuously increase the charge voltage and current of the electrostatic precipitator. (Figure (a)).

(2) When a spark discharge occurs due to the rise in charge voltage and current in the IT air precipitator ((a) in the same figure), this is detected using various methods, and then the gate is shut off ((C) in the same figure). )) L, the charge voltage and current of the electrostatic precipitator are cut off for a certain period of time.

(3)! After the flow of charged voltage in the air precipitator is interrupted for a certain period of time, the flow is controlled by thyristor phase control (see figure
b)) will cause it to rise again.

(4) From then on, when the charge voltage and current of the electrostatic precipitator reach the spark discharge generation level, the above steps (2) and (3) are repeated.

[Problem to be solved by the invention]

In the conventional control method described above, the intensity of the spark discharge is not identified, and the spark discharge is essentially cut off for a certain period of time, eliminating the supply of voltage and current to the electrostatic precipitator, which impairs the performance of the electrostatic precipitator. decreases. In particular, under charging conditions where spark discharges occur frequently, the voltage and current become unstable and the value drops extremely, causing problems such as abnormal conditions in the operation of the electrostatic precipitator. .

[Means to solve the problem]

The present invention takes the following measures to solve the above problems.

In other words, as a control method for an electrostatic precipitator, a low-voltage AC power source is adjusted using the charging voltage and current value of the electrostatic precipitator as a feedback signal in a DC high-voltage power supply device that supplies a DC high voltage to the electrostatic precipitator. In a control device equipped with a thyristor, the waveform of the current value of the feedback signal is time-series within the conduction time of the thyristor with a waveform obtained by delaying the previous waveform of the same current value by one cycle. The thyristor is energized for a predetermined time when the comparison value exceeds a predetermined value for spark generation, and when the time is within a first predetermined time at the beginning of the conduction time. When the above-mentioned time exceeds a fourth predetermined time and is within a second predetermined time, the phase angle of the thyristor is controlled to a low predetermined value for a predetermined time, and when the above-mentioned time exceeds a fourth predetermined time and is within a second predetermined time, When exceeds a second predetermined time, control is performed to reduce the phase angle of the thyristor from the value before the comparison for a predetermined time.

[Effect]

With the above means, the waveform of the current value of the feedback signal of the control device having the thyristor is compared with the waveform of the previous current value delayed by one period. The comparison is performed sequentially in chronological order within the conduction time of the thyristor, and the time when the comparison value reaches a predetermined value for spark generation is determined. When the above-mentioned time is within a first predetermined time at the beginning of the above-mentioned conduction time, control is performed to cut off the energization of the thyristor for a predetermined time. When the time exceeds the first predetermined time and falls within the second predetermined time, control is performed in which the phase angle of the thyristor is maintained at a low predetermined value for the predetermined time. Further, when the above-mentioned time exceeds a second predetermined time, control is performed such that the phase angle of the control of the thyristor is reduced for a predetermined time from the value before the comparison.

In this way, within the conduction time of the thyristor, the earlier the conditions for spark generation are, the more likely the spark discharge is likely to increase, the stronger the control is performed to suppress the conduction of the thyristor. Since the cyrisk is not cut off unless the condition is early, there is little reduction in dust collection efficiency, and efficient spark discharge suppression control is performed.

〔Example〕

An embodiment to which the method of the present invention is applied will be described with reference to FIGS. 1 to 5. FIG. 1 is a configuration block diagram, FIG. 2 is a configuration block diagram of a microcomputer unit, FIGS. 3 and 4 are action explanatory diagrams, and FIG. 5 is a control processing flow diagram.

Note that the description of the portions described in the conventional example will be omitted to avoid redundancy, and the description will mainly focus on the portions related to the present invention.

A thyrisk control device 20 is provided which receives signals from the current detector 7 and voltage detector 8 and controls the thyristor 2. A microcomputer unit 21 is provided within the SIRISK control device 20 . As shown in Fig. 2, the microcomputer unit 7) 21 has an A/DI converter H32 and a D/DI converter connected to the CPU 33.
It is equipped with an A converter 39, a ROM 34, a RAM 38, an I10 board 35, and an opcon interface 36.
A/D converter 32 receives signals from voltage detector 8 and current detector 7 via isolation amplifier 31, respectively. D/A converter 39 is connected to the phase shifter via isolation amplifier 31. The I10 boat 35 also inputs a start/stop/failure signal and outputs a gate cutoff TRIP signal. The opcon interface 36 is connected to an operator console 37 having key LEDs, digital displays, switches, etc.

The operator console and operation control interface are a board and CPU equipped with operation switches and indicators necessary for the plant operator to control this embodiment and operate and monitor other electrostatic precipitator controls.
It becomes an interface with 33.

In the above configuration, the program of the processing flow diagram shown in FIG. 5 is input into the ROM 34 of the memory. Further, the output of the current detector 7 is A/D converted and then inputted and stored in the RAM 38 of the memory as a current waveform (2). Wandering form 1. When it enters, the previous 1i is displayed on CPU33.
Flowing waveform! , is called from the RAM 38 and compared. That is, as shown in FIG. 3, the time is delayed by one period (T), and within the conduction time T of thyristor 2, the time series t is sequentially different as shown in the following equation (1). Take. The time when the difference becomes a predetermined value of the condition for spark generation, that is, the time t at which equation (2) is satisfied, is determined as the time for spark generation.

ΔI(t,)-1,(t,)-1t(t,)-...(1
)ΔIa< 1m(ts)-1t(t,)・---1-
−・−・−(2) ΔI4−Set value If we analyze the situation of spark discharge, we find that the current waveform when spark discharge occurs, that is, when equation (2) holds, is It was found that it can be generally classified according to the situation of occurrence as shown in Table 1.

Table 1 Each spark mode Sl, S2. S3 occurs at the initial, middle, and late stages of the conduction time, and is a predetermined set time T, , T.
, is expressed as in Table 2.

Continuation time T o = T + + T z +
T s Therefore, the time t of spark generation is the spark mode S
1, as shown in FIG. 4(a) through the I10 port 35, a gate cutoff signal for a certain period of time is sent to the thyristor 2, and control is performed to cut off the energization of the thyristor for a certain period of time l, etc. is the same as before (the same applies to the following cases).

When t is in the range S2, the phase of the thyristor 2 is controlled through the D/A converter 39 and the isolation amplifier 31 so that the phase angle becomes a predetermined low value for a certain period of time m (see Fig. 4).
b)) When tl is in the range of 53, control is performed in which the phase angle is decreased by a predetermined amount for a fixed time m from the previous phase angle in the same manner as described above (FIG. 4(C)).

With such a control method, the dust collection effect is maintained by the following actions for each spark mode, and spark discharge is effectively suppressed and controlled.

(1) Spark mode S1: Spark intensity is "high", that is, the electric charge on both electrodes inside the industrial dust generator is almost completely discharged by the spark discharge, and it is assumed that a large amount of ions are present in the dust collection space. Ru. Continuous charging may cause repeated spark discharges, so as with the conventional method, the electrical industrial dust is cut off for a certain period of time and waits for the ions in the space to diffuse. ,
Enter recharging. Therefore, the occurrence of spark discharge can be effectively suppressed.

(2) Spark mode S2: Spark intensity is medium J, that is, even if a spark discharge occurs, some charge remains on both electrodes inside the industrial dust generator, and the amount of ions in the dust collection space is reduced to some extent. Because it is assumed that the electrical equipment is charged, the voltage and current are not cut off, and after the voltage and current are reduced to the lowest level for a certain period of time, recharging begins.Therefore, the charging time to the electrode is Spark discharge can be suppressed without interruption.

(3) Spark mode S3: Spark intensity is "low", that is, even if a spark discharge occurs, the electric charge on both electrodes inside the industrial dust device remains, and the amount of ions in the dust collection space is small. , is assumed to be extremely unlikely, so the flow of electric dust particles is not cut off, and the voltage and ti current are reduced by a certain amount for a certain period of time, and then the rising speed is set according to the spark frequency. Then, the electric industrial equipment charge voltage, ti, is restored. Therefore, as in the case of S2, the occurrence of spark discharge can be effectively suppressed without impairing the dust collection function.

〔Effect of the invention〕

As explained above, the present invention has the following effects.

(1) Spark mode S2, that is, spark intensity is "medium",
In the case of S3, ie, r small, the voltage, 1, and flow of the electric dust generator is not cut off by the control, so that the performance of the electric dust generator is improved compared to conventional spark control.

(2) It is possible to optimize the charging status of the electric dust generator for the internal gas conditions.

(3) Since fluctuations in electrical voltage and current in the electric industrial dust generator are relatively small, the operation of the electric industrial dust generator can be made more stable than in the past.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the overall configuration according to one embodiment of the present invention, FIG. 2 is a block diagram of the microcomputer unit section of the same embodiment, and FIGS. 3 and 4 (a), (b), (C) is an explanatory diagram of the operation of the same embodiment, FIG. 5 is a processing flow diagram of the microcomputer unit section of the same embodiment, FIG. 6 is a block diagram of the overall configuration according to the prior art, and FIG. 7 is the same conventional example. FIG. 1.20-thyristor control device, 2--thyristor,
3・−・−・High voltage transformer, 4・Rectifier, 5・・
・DC reactor, 6.-・Electrical industrial equipment (EP),
7--Current controller, 8--Voltage detector, 9-
--Spark frequency setting device, 21- Microcomputer unit.

Claims (1)

[Claims] Among DC high-voltage power supplies that supply DC high voltage to electrostatic precipitators, a control device with a thyristor that adjusts a low-voltage AC power supply using the charging voltage and current value of the electrostatic precipitator as a feedback signal, Among the feedback signals, the waveform of the current value is sequentially compared in time series with the previous waveform of the same current value delayed by one period within the conduction time of the thyristor, and the comparison value is determined as the spark generation. The time when the thyristor exceeds a predetermined value is determined, and when the time is within a first predetermined time at the beginning of the conduction time, control is performed to cut off the energization of the thyristor for a predetermined time, and the time exceeds the first predetermined time. When the time exceeds the first predetermined time and is within a second predetermined time, the phase angle of the thyristor is controlled to a low predetermined value for a predetermined time, and when the time exceeds the second predetermined time, the phase angle of the thyristor A method for controlling an electrostatic precipitator, characterized in that the phase angle of the electrostatic precipitator is controlled to be lower than the value before the comparison for a predetermined time.