1 Introduction
In recent years, various modern building constructions have rapidly developed into building automation and have gradually become an important reference for the development of cities and countries. High-level building automation systems (equipment automation systems, office automation systems, communication automation systems) require high-quality power supplies, but a significant portion of these devices have non-linear load characteristics, which in turn triggers low-voltage power supply system harmonics. Distortion source of wave distortion. These harmonic sources cause serious pollution to the power supply system and reduce the power quality. This not only causes serious damages and adverse effects to the electrical equipment and electronic equipment in the building, but also threatens the entire building intelligent system.
Therefore, analyzing the various harmonic sources that cause harmonic distortion in the power supply of office buildings and the control measures for harmonic distortion hazards are of great significance to the safe operation of building automation systems in high-rise office buildings.
2, the source of harmonics
Harmonics in building power distribution systems mainly come from two aspects. First, the load itself has a large number of harmonic sources. These harmonic sources generate a large amount of harmonic currents, which lead to harmonic voltages in the system voltage through line impedance. Second, the utility grid itself also has a certain amount of harmonic voltage. This part of the harmonics can be transmitted from the network side to the distribution system.
The load in the building distribution system has the following characteristics:
(1) There are many single-phase loads. In the building distribution system, the single-phase load accounts for more than half, which may cause zero-sequence harmonics, causing three-phase unbalanced three-phase phase difference asymmetry and other issues.
(2) High proportion of non-linear loads. The load of the personal computers, copiers, communication equipments, lighting equipments and some building power distribution systems in the building distribution system are the main harmonic sources such as UPS and primary power supply.
(3) Harmonic distortion rate of harmonic sources is large. According to tests, harmonic sources in building distribution systems have large harmonic distortion rates, such as personal computer harmonic current distortion rate of 100%, UPS distortion rate of about 20% -30%, primary power harmonic current The distortion rate is usually 40%-50%.
(4) Most of the intelligent and automated equipment in the building's power distribution require high quality of power supply and are more sensitive to harmonics.
3, harmonic harm
Harmonic voltage and harmonic currents in the building distribution system cause great pollution to the power distribution system, which not only deteriorates the power quality of the power grid, but also causes certain damage to various power equipments:
(1) Increase the additional loss of power components and cause fires.
Harmonics cause additional losses in the components of the utility grid, reducing the efficiency of power generation, transmission, and electrical equipment. A large number of third harmonics passing through the midline will overheat the line and even cause a fire.
(2) Affect the normal operation of electrical equipment.
Harmonics will affect the normal operation of electrical equipment and cause electrical machinery to produce mechanical vibrations and noises, which will cause severe overheating of the transformer and cause overheating of capacitors, cables, etc., insulation aging, and shortened life span, resulting in damage.
(3) Causes grid resonance.
This kind of resonance may amplify the harmonic current several times or even dozens of times. It will pose a great threat to the system, especially to the capacitor and the reactor connected in series with it. The capacitor and the reactor are often burned.
(4) The relay protection malfunctions and the electrical measurement error is excessive.
Harmonics will lead to relay protection, especially the malfunction of microcomputer integrated protection devices and automatic devices, resulting in unnecessary power supply interruptions and production losses; harmonics will also cause inaccurate metering of electrical measuring instruments, measurement errors, and power management Department or power users bring economic losses.
(5) Crash the industrial control system.
Harmonic sources or higher harmonics in the vicinity may interfere with communication and information processing equipment, and noise may occur at a low level, which may degrade communication quality. The computer may not be able to work properly. If it is heavy, then the information will be lost and the industrial control system will crash.
4. Building Distribution Harmonic Solutions
The current harmonic control equipment mainly includes passive filters and active filters. The traditional passive filter is widely used because of its simple structure, but with the continuous improvement of power quality requirements of power distribution centers, the limitations of passive filters are also becoming increasingly prominent. Compared to traditional passive filters, active filters are widely used because of their excellent harmonic compensation performance.
4.1 How ANAPF Active Filter Works
ANAPF series active power filter devices are connected to the power grid in parallel and detect harmonics and reactive components of the load in real time. PWM inverter technology is used to generate one current harmonic component and reactive component from the converter. The reverse component is injected into the power system in real time, so that harmonic control and reactive power compensation are achieved.
The principle is as follows:
4.2 Main Technical Features of ANAPF Active Filter
ANAPF series active power filter device adopts DSP+FPGA all-digital control method, with extremely fast response time; advanced main circuit topology and control algorithm, higher precision and more stable operation; one machine is multi-energy, and can not only compensate harmonics , Can also make up for reactive power; Modular design, easy production debugging; Convenient parallel design, convenient expansion; With perfect bridge arm over-current, protection function; Easy to use, easy to operate and maintain.
4.3 ANAPF Active Filter Application Case Description
The comparison and analysis of power quality test conditions of the distribution system before and after the operation of the ANAPF active filter at the distribution transformer busbar in the power distribution room is given as an example.
After testing, the total harmonic current in the system before the input of the active filter is about 75A, and the main harmonic content is 3, 5, and 7 times, of which the 3rd harmonic current is about 60A, and the 5th harmonic current is 40A, after entering the Ankerui ANAPF100-400/B active filter, has significant filtering effect, as shown below for comparison:
4.4 ANAPF Active Filter Quotation and List of Major Components
Model Number: ANAPF100-400/B
Reference price: 120,000 yuan/set
The main product details:
No.
Name
Model number
Quantity
1
APF electrical cabinet
800X600X2200
1
2
Converter
APFCOV-CVT100
1
3
Controller
APFMC-C100
1
4
Reactor
APF-RE.(S)DG-100
1
5
Active current transformer
LT208-S7
3
6
filter
DL-1TH1
2
7
breaker
CVS160FTM160D4P3D
1
8
Contactor
LC1D150M7C
1
9
MCB
NDM1-63C32
1
10
Intermediate relay
MY4NAC
2
11
R type transformer
R320-0.38/0.22
1
12
Harmonic Detector
ACR350EGH
1
13
wire
16mm 2
Some
14
wire
4mm 2
Some
5 Conclusion
This article analyzes the hazards of harmonics to building construction and introduces the principles and functions of ANAPF low-voltage active filters. Through the application of active filters in a building's low-voltage distribution system, we can see that the harmonics of the system can be effectively filtered out, eliminating all kinds of additional losses caused by harmonics, reducing the noise of the transformer, reducing the harmonics Bad effects on electrical equipment. The power quality is improved, and the overall operating efficiency of the equipment and the use efficiency of the electric energy are improved. In addition, the midline current is also reduced, the midline temperature is reduced, and the hidden dangers of fire and even human life safety caused by excessive midline current are eliminated. It can be seen that the active filter is the preferred solution for harmonic control in building distribution centers.
ã€references】
Shanghai Ankerui Electric Co., Ltd. Product Manual. 2013.01.
Jiangmen Kunxin new Material Technology Co.,Ltd , https://www.plasticsjmkunxin.com