With China's increasing attention to environmental protection, there are more and more sewage treatment plants in various places. In order to improve the automation level and operation efficiency of equipment, sewage treatment plants have adopted a large number of power electronic equipment, such as frequency converters, soft starters, computers, uninterruptible power supply equipment, etc.
This kind of equipment absorbs energy from the system in a way that is not a continuous sine wave, which will generate a large number of current harmonics. The impedance of the harmonic current flowing through the system will be superimposed on the power grid to distort the voltage of the power grid. The main hazards of harmonics are:
Cause series resonance and parallel resonance, resulting in dangerous overvoltage or overcurrent;
Harmonic loss is generated, which reduces the efficiency of power generation, transformation and consumption equipment;
Accelerate the insulation aging of electrical equipment, make it easy to break down, and shorten their service life;
Make the equipment (such as motor, relay protection, automatic device, measuring instrument, power electronic device, computer system, instrument, etc.) operate abnormally or cannot operate correctly;
Interfere with the communication system, reduce the transmission quality of the signal, hinder the correct transmission of the signal, and even damage the communication equipment.
The sewage treatment plant of a water resources bureau in Jiangsu Province once had the situation that the blowers could not operate normally due to large harmonics, especially when operating at full load. When multiple blowers need to work at the same time, it is often the case that starting one blower will lead to the shutdown of the other blower, which affects the production process of the sewage treatment plant, not only causing direct economic losses to users, but also may causing sewage pollution to the water environment.
After learning about the problems encountered by the user, the field test found that the on-site harmonics were mainly generated by the frequency conversion control equipment such as the lift pump, oxidation ditch, blower, and return sludge pump, among which the 5th, 7th, 11th subharmonics are dominant. Elecnova designed a comprehensive solution of APF active harmonic filter + M series harmonic suppression module for this user. At present, this set of equipment has been running stably on site for more than 2 years, eliminating the troubles caused by harmonics to the normal production of users.
Main products of the project
SFR-M series intelligent dynamic harmonic suppression low-voltage power capacitor module is an integrated reactive power compensation product that aims at solving the harmonic and power factor problems in 0.4kV low-voltage distribution network with serious harmonic pollution, achieving power factor improvement, effective harmonic suppression, reducing line loss and improving power quality.
Advanced double zero-crossing switching technology ensures that the inrush current is less than 2 times the rated current;
Over temperature protection, over-current protection, imbalance protection, over-voltage protection and harmonic protection;
Online networking function, multiple modules can be connected in parallel as required;
Reasonable structure, all metal explosion-proof structure, active air cooling and heat dissipation;
Simple wiring and easy maintenance.
Dynamic filter compensation device
Flexible application scheme
Modular design, easy to expand and reduce initial investment waste
Reliable communication mode, seamless communication between APF and SFR-M compensation module
Complete equipment and system protection
Eternal electrical fault protection of equipment, including bus short circuit, over and under voltage, over and under frequency, phase sequence error, current reverse sequence, etc
Internal fault protection of equipment, including overcurrent protection, IGBT overheating protection, etc. Automatic capacity reduction when the working environment exceeds the limit
Software and hardware current limitation
Excellent filtering performance
A variety of compensation modes can be selected to realize on-demand distribution of harmonic elimination, reactive power compensation and unbalanced current compensation
Perfect three-phase imbalance strategy to realize active / reactive / split phase unbalance compensation
Three-level main circuit, lower power consumption and higher efficiency
The full response time is less than 10ms, and the control is faster, which is beneficial to the improvement of transient stability
Humanized human-computer interaction experience.
Interactive optional 7 inch or 10 inch LCD touch screen
Through the graphical display interface, users can clearly understand the power quality improvement of the system before and after the operation of the equipment, such as the system waveform diagram, harmonic spectrum diagram, THDi, THDu, current RMS, power factor, etc.
With the economic development, the wide application of high-power thyristors, a large number of non-linear loads have increased, especially the progress of electronic technology, energy-saving technology and control technology, a large number of rectifier equipment, AC / DC converter equipment and electronic voltage adjustment equipment are used in the chemical, metallurgical, iron and steel, coal mine, transportation and other departments.
Electric smelting equipment, electrochemical equipment, mine lifting equipment, open-pit mining equipment, electric locomotives and so on are increasing day by day, At the same time, the widespread use of a wide variety of lighting appliances, entertainment facilities and household appliances makes the waveform of the power system seriously distorted.
By using Elecnova reactive power compensation and active harmonic filter, to improve the power quality, enhance the safety and reliability of the system, improve the stability and efficiency of the equipment, and increase the service life of the equipment ; reduce the harmonic content, eliminate the threat of harmonic breakdown to the capacitor in the reactive power compensation device, avoid the burning caused by the possible parallel resonance of the system circuit, and ensure the normal operation of the equipment. It avoids the impact of harmonics on other users of the power grid and ensures that the sewage treatment plant can operate well and effectively.
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