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DSP-based three-phase power voltage electrostatic dust removal system development

In Electronic Infomation Category: D | on April 20,2011

Abstract: Development of a DSP-based control system for electrostatic precipitator power supply voltage. The control system TMS320F2812 as the control center can automatically track the electric field and XC9536-10VQG44C datasheet and effectively regulate the AC voltage intermediate link. Experimental results show that the control system can control electrostatic dust power, a substantial increase collection efficiency.

0 Introduction

Is the use of high voltage electric field electrostatic precipitator dust in the gas out of a dust particle separation equipment, in the elimination of harmful dust in the atmosphere and XC9536-10VQG44C price and so plays a very important role in metallurgy, power and XC9536-10VQG44C suppliers and chemical industry recover useful resources, flue gas purification, importance of environmental protection equipment. In order to obtain higher removal efficiency, the power requirements of electrostatic dust precipitator according to changes in working conditions, automatically adjusts the output voltage and current, and the electrostatic precipitator at a higher voltage and current state of operation. In addition, the electrostatic precipitator in the event of failure, need for ESP to provide the necessary power to protect against flashover, over current signal can quickly identify and react. Experiments show that the power regulator TMS320F2812 electrostatic dust control system to perform these functions well.

1 electrostatic dust-phase main circuit

1.1 Main Circuit

Three-phase main circuit shown in Figure 1, three-phase AC 380V mains through the main circuit breaker contacts to the three-phase thyristor voltage regulator circuit, by controlling the thyristor conduction angle adjustable output voltage , sent to the three-phase high-voltage silicon rectifier transformer primary, the secondary side of the rectifier by the step-up transformer, rectified output DC negative high voltage, electrostatic dust supply by the damping resistor reactor.

Electrostatic dust with conventional single-phase power compared to three-phase power has the following characteristics:

(1) Power balance of power, three phase, power factor close to 100%; (2) star as three-phase input wiring, under the same power output, reducing the primary current and phase loss; (3) greatly improve the output voltage and current of linearity, full load output ripple coefficient is less than 5%, effectively improving the dust into the corona reactor power.

Figure 1 Three-phase main circuit diagram

1.2 Three-phase AC voltage regulator circuit

AC voltage regulator circuit is the use of phase control for AC power control circuit. The topology of the exchange voltage regulation circuit there are many, this is used after the series with two antiparallel thyristors in each phase between the AC power and load. And phase-controlled rectifier circuits, by controlling the thyristor corresponding to the time of the opening phase of each half cycle of the power to trigger a thyristor, you can easily adjust the output voltage rms, AC voltage regulator so as to achieve the purpose of .

2-phase power supply voltage electrostatic dust control system

2.1 Control system structure

Control system block diagram shown in Figure 2, the TMS320F2812 as the core control system, including voltage synchronous signal detection circuit, analog sampling circuit, switch isolation circuit, the fire * detection circuit, SCR trigger circuit, serial communication circuit.

control system block diagram of Figure 2

Analog field collected (primary voltage, primary current, secondary voltage, secondary current, etc.), the analog signal conditioning circuit, the ADC unit into the DSP, the DSP regular sampling and complete A / D conversion, DSP will be A / D converted data to compare with the set parameters to calculate the thyristor conduction angle. DSP in the capture phase voltage zero-crossing signal, the output double-narrow pulse, triggered thyristor, the thyristor phase-shift the output range of 5 ~ 90 adjustable, complete the three-phase AC main circuit power supply voltage regulator part , so as to realize the power supply voltage electrostatic dust-phase closed-loop control.

2.2 Control System Hardware Design

2.2.1-voltage synchronous signal detection circuit

Voltage synchronous signal detection circuit is to provide the trigger pulse to the thyristor base, due to the natural three-phase Thyristor commutation circuit point (ie = 0 ) is the input phase voltage of the zero phase ( that t = 0), so in Figure 3 (b) synchronous transformer connected to obtain the corresponding synchronous transformer secondary voltage vector between the original shown in Figure 3 (c) below. Figure 3 (c) shows that three-phase AC voltage regulation circuit in the T1 ~ T6 tubes were synchronized signal: Uac, Ubc, Uba, Uca, Ucb, Uab.

Figure 3-phase AC voltage regulation circuit of the synchronization relationship

Three-phase AC voltage regulator circuit sync signal detection circuit shown in Figure 4. Three-phase grid voltage A, B, C after three synchronous transformer (at / Y connection) isolation, attenuation and sent to a comparator, a direct comparison with the inverting input and inverting input of the instantaneous voltage, when the Uab (Ubc, Uca) positive half cycle, the comparator output low, by a Schmitt inverter goes high after the waveform shaping, maintaining and synchronization voltage Uab (Ubc, Uca) synchronization relationship. Figure 3 shows the relationship between the vector analysis, it was T6 (T2, T4) tube sync signal; and the three signals go through a Schmitt inverter output were given T3 (T5, T1) tube sync signal . Sync signal directly through the opto isolated input capture port DSP. This circuit is very flexible and easy to use, do not judge the phase sequence, the synchronization signals can be captured T1 can be T1, T3, T5 sync signal acquisition, but also to capture six synchronization signal. In this paper, the capture of six synchronous signal, the direct use of hardware detection, to better reflect the real situation of power fluctuations.

Figure 4 three-phase AC voltage regulation circuit of the synchronous signal generator circuit

2.2.2 SCR trigger circuit

Three-phase AC voltage by regulating the anti-parallel diode conduction angle to achieve, whether this reliable thyristor trigger is very important. DSP sync signal in the capture of thyristor, the calculation of firing angle, the output of double-narrow pulse, after a high-frequency modulated pulse transformer isolation by amplified to generate the necessary trigger pulse thyristor shown in Figure 5.

Figure 5 SCR trigger circuit

2.2.3 spark detection circuit

To improve the electrostatic dust collection efficiency three-phase power supply, dust each reactor should work in the best spark rate. Spark discharge phenomenon can be detected to achieve the spark control. When the spark discharge, the secondary current will increase significantly, the use of this feature can be compared directly with the hardware circuit of the method. By LM339N the secondary current instantaneous value and the DSP through the D / A output spark after setting the threshold value for comparison, the opto isolated, into the DSP, shown in Figure 6. When the spark flashover is detected, the spark interrupt subroutine to perform, record the current value of operating voltage during discharge and blocked thyristor trigger pulse, after a delay of re-calculation of thyristor conduction angle, making the operating voltage for the last discharge of the operating voltage, thus ensuring the electrostatic precipitator power supply is always maintained at the critical three-phase discharge status.

Figure 6, the fire detection circuit *

2.3 control system software design

The control system software from the main program and five interrupt service routine composition, its flow chart are shown in Figure 7 and Figure 8. Complete system initialization and the main program main algorithm of two parts, the interrupt service routine, EVA capture interrupt lock on power frequencies, and calculate the sampling cycle; AD calculated the value of the interrupt into the sampling algorithm for computing the actual value of the required ; T1 underflow interrupt real-time adjustment of the sampling period; fire * break the blockade on the SCR trigger pulse; data communication control terminal interrupt key is to receive data and instructions to send and return control of the terminal to complete the various parameters required for power supply control terminal real-time monitoring.

Figure 7, the main program flow chart

Figure 8, the interrupt service routine flowchart

3 results

Electrostatic dust-phase power for the basic parameters of experimental setup: voltage 380 V/50 Hz three-phase power input, SCR KP800 A, DC output voltage of 72 kV, the DC output current 1. 2 A. Grid voltage waveform and voltage waveform after the regulator uses a 500:1 differential probe, shown in Figure 9.

(a) Voltage waveform sync signal detection experiments

(b) high frequency modulated SCR trigger pulse

(c) conduction angle = 90 AC voltage regulator output voltage waveform after the

(d) conduction angle = 120 AC voltage regulator output voltage waveform after the

(e) = 150 conduction angle AC voltage regulator output voltage waveform after the

(f) sampling the second current waveform (conduction angle = 150 )

Figure 9 test waveforms

Can be seen from the waveform, the control system on the phase voltage zero crossing detection is very accurate; SCR the SCR trigger pulse can meet the fast and accurate triggering requirements; AC voltage regulator works well, and simulation results are almost the same; secondary current waveform is very stable.

4 Conclusions

This article describes the DSP-based three-phase power voltage electrostatic dust control system design, focusing on the voltage synchronous signal detection circuit, SCR trigger circuit, fire * detection circuit. Produce the prototype is also very good, fast response, high accuracy, strong anti can be detected with good, to automatically track changes in the electric field, the middle part of the effective AC voltage regulator, so that electrostatic precipitator at a higher voltage and current state run, greatly improve the collection efficiency, has a broad market prospect.

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