Xu Shuang
Ankerui Electric Co., Ltd. Â Â Â Jiading 201801
Abstract : This paper analyzes the harmonic source, harmonic characteristics and hazards of the power grid, and compares the situation before and after the input of the active power filter through the application of the active filter in the low voltage distribution system of a large steel company . It shows that the harmonic filter technology of active power filter is one of the effective means to improve the power quality of the power supply. The generated harmonics can be controlled within the minimum range to achieve scientific and rational use of electricity, inhibit grid pollution, improve power quality, and ensure electrical quality. The role of equipment security.
Keywords : power quality; harmonics; active filtering
1 Power Quality and Harmonics
1.1 Harmonic Generation
With the increasing application of power electronic converter devices, electrical energy has been more fully utilized. However, the wide application of non-linear power devices has produced a large number of distorted current harmonics. The flow of distorted currents in the power grid has caused harmonic voltages; harmonic pollution has increasingly threatened the safety, stability, and economic operation of power systems. This has a great impact on the linear load and other users of the same network. Harmonics have been accompanied by electromagnetic interference and power factor reduction and are classified as the three major hazards of the power system. Therefore, it is of great significance to understand the principle of harmonic generation and to study the elimination of high-order harmonics in power supply and distribution systems to improve the quality of power supply and ensure the safe and economical operation of power systems. Harmonic measurement is an important branch of harmonics and plays an important role in suppressing harmonics and solving harmonic generation problems. Therefore, the measurement and analysis of harmonics is an important task in power system analysis and control, and it is an important prerequisite for relay protection and fault measurement.
The main harmonic generation sources are as follows:
Name
Industry
Frequency conversion device
Commercial, municipal, civil, public utilities, industrial and mining companies, etc.
UPS, switching power supply, inverter power supply
Utilities, business, electronics, communications, etc.
Subway, light rail, charging station (pile)
traffic
Single (multi)crystalline silicon production equipment, intermediate frequency furnace
manufacturing
Arc Furnace, AC Arc Welding Machine, Induction Heating Device
Machinery, Energy, Chemicals
1.2 Harmonic Harm
1.2.1 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.
1.2.2 Impact on 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.
1.2.3 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.
1.2.4 The relay protection malfunctions and the electrical measurement error is too large.
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.
1.2.5 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.
1.3 National standards for harmonic treatment
GB/T14549-1993 "Power Quality: Harmonics in the Utility Grid"
GB/T15543-2008 "Power quality: three-phase voltage allow unbalance"
GB/T12325-2008 Power Quality: Allowable Variation of Supply Voltage
GB/T12326-2008 "Power Quality: Voltage Fluctuations and Flicker Changes"
GB/T18481-2001 "Power Quality: Temporary Overvoltage and Transient Overvoltage"
GB/T15945-2008 Power Quality: Allowable Frequency Deviation of Power System
GB7625.1-1998 Harmonic current limits issued by low-voltage electrical and electronic products
GB/T15576-1995 "General technical conditions for low-voltage reactive power static compensation device"
2 Typical Application Scenarios
2.1 Project Background
An iron and steel company is an extremely large iron and steel conglomerate that integrates coking, sintering, smelting, rolling and scientific research and development. Its X rolling mills mainly produce steel products such as plate, due to production needs, in the low-voltage distribution system. The equipment on the secondary side of the transformer is mainly a motor, and the inverter drives the motor. Because the internal structure of the frequency converter uses a large number of non-linear elements, a large number of harmonics are generated in the working process.
There is a certain impact load on the plate during the rolling process, and the production process is not continuous. This causes the operating voltage/current to fluctuate and discontinuous, and the change of the operating current also causes the harmonic current to fluctuate.
Real-time monitoring of current and voltage fluctuations
2.2 Project Plan
Our company has developed a corresponding solution for the harmonics of the power grid of No. 2 cooling bed in the rolling mill of the company. The self-developed shunt active power filter ( ANAPF ) is used to perform centralized control on the outgoing side of the transformer. The filter can automatically track the harmonic current generated by the load and effectively filter out harmonics, thus ensuring the safe and reliable operation of the entire system.
System governance shows as follows:
2.3 Project Effect
After the active power filter is put into operation , harmonic voltage and harmonic current control effects are:
Pre-treatment voltage and current waveforms
Voltage and current waveforms after treatment
Current distortion rate before treatment
Current distortion rate after treatment
After the active power filter was put into operation, the total current distortion rate decreased from 82.1% to 4.4%, the current distortion rate of the fifth harmonic dropped from 67.0% to 1.9%, and the current distortion rate of the seventh harmonic dropped from 43.8%. 2.0%. The quality of the power grid has been significantly improved, and it has been applied to rapidly changing loads, which has significantly suppressed the harmonics generated by non-linear loads of the power supply system during operation, and fundamentally improved the power quality of the entire power supply system. , effective protection of the normal operation of the production line equipment.
3 Introduction to ANAPF Active Filters
3.1 Active Filter Main Specifications
Wiring
Three-phase three-wire or three-phase four-wire
Access voltage
3×380V ±10%
Access frequency
50Hz ±2%
Dynamic compensation response time
Dynamic response <4ms, full response time <20ms;
On-off level
10kHz
Function settings
Only harmonics are compensated, only reactive power is compensated, both harmonics are compensated and reactive power is compensated; manual and automatic switching are performed.
Harmonic compensation times
2-21 times
Type of protection
DC over-voltage IGBT over-current device temperature protection
Overload protection
Automatic current limit in the set value, no overload occurs
cooling method
Smart air cooling
noise
< 65db (in the cabinet and operating in the rated state)
Working temperature
-10°C to +45°C
Working environment humidity
<85%RH non-condensing
Installation occasion
Indoor installation
Altitude
≤1000m (for use at higher altitudes)
Incoming and outgoing ways
Down in and out
Protection level
IP21
Intelligent communication interface
RS485/MODBUS-RTU
Remote monitoring
Optional
Overall size (mm)
(W×D×H)
30A
50A
75A
100A
600×500×1500
600×500×1500
600×500×1800
800×600×2200
Weight (kg)
Three-phase four-wire
Three-phase three-wire
30A, 50A
75A, 100A
30A, 50A
75A, 100A
280
360
240
290
3.2 Active Filter Quotation and Component List
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
16mm2
Some
14
wire
4mm2
Some
4 Conclusion
The active filter device introduced in this paper adopts a modular design and has a very fast response time. One machine can be multi-energy, it can not only make up for harmonics, but also can make up for reactive power; the advanced main circuit topology and control algorithm are more accurate. More stable operation; easy to use, easy to operate and maintain. The active filter device saves the user's investment cost, shortens the construction period, and provides an efficient compensation device for the harmonic treatment project of the low-voltage distribution network, which has good application value and application prospects.
ã€references】
[1] GB/T 14549-1993 "Power Quality: Harmonics in Public Grids"
[2] Ankerui Electric Co., Ltd. Product Manual. 2013.01.
[3] Wu Jingchang. Power system harmonics, Beijing: China Power Science and Technology Press, 1998
About the Author:
Xu Shuang, female, undergraduate, Ankerui Electric Co., Ltd., the main research direction for the smart grid power distribution, Email: Mobile QQ
"AAPF Active Power Filter Device Design and Application Atlas" (atlas number: ACR13CDX701) is edited by Ankerui Electric Co., Ltd. This atlas combines the characteristics of ANAPF active power filter device products, based on electrical design specifications, research Eliminating the problem of high-order harmonics in the power supply and distribution system to achieve the goal of improving the quality of power supply and ensuring the safe operation of the power system. The Atlas is applicable to the design and modification of harmonic suppression and comprehensive management of electrical equipment in industrial, civil, and public buildings in new construction, reconstruction, expansion, and technological transformation projects. If you need atlas, please provide your organization's name, department, address, zip code, contact person, contact telephone number, email address, fax 021-69155331, mail or QQ to Ankeru Xu cream engineer, Ankerui Electric will give you a free gift. .
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