1、Power quality problems of photovoltaic industry
In the process of photovoltaic module production, there needs dozens of links which involves dozens of equipments. In the whole production process, there are several key steps: the directional growth after silicon melt（main equipment: Polycrystalline ingot furnace、single crystal silicon furnace）、multi-line cutting（main equipment: fretsaw）, during these steps, whether equipment can work normally will be the key to the quality of photovoltaic products. Now we are introducing the electrical characteristics of main loads：
1）single crystal silicon furnace
Single crystal silicon furnace is a kind of equipment that use graphite heater to melt polycrystalline materials such as polysilicon and grow non-dislocation single crystal by czochralski method in the inert gas environment. Single crystal rod production process is roughly divided into: charge---melt---crystal pulling---cooling form, the melt and crystal pulling process need to keep constant temperature. Single crystal furnace use silicon controlled rectification system to supply DC power, the mode of rectification is six pulse rectification, give priority to 5、7、11、13 and other odd harmonics, especially has large 5 and 7 harmonic, waveform distoration is very serious. Single crystal will also produce large reactive power at AC side, which cause low power factor, big incoming current, low transformer using rate, increase energy waste. At the same time, harmonic will also disturb crystal pulling control system, cause malposition、break crystal、trip which seriously affect the production.
The core of fretsaw is superfine high strength cutting line which is used to complete cutting terms in conjunction with the abrasive slurry. There are 1000 cutting lines at most to twist parallel to each other on guide roller to form a horizontal cutting line network. Motor drive guide roller to make the whole cutting line network move with the speed of 5 to 25 meters per second. The speed of cutting line、linear motion or back and forth motion will all make adjustment based on the shape of silicon ingot during the whole cutting process. In the process of cutting line movement, jet nozzle will continually jet slurry containing suspend silicon carbide particle to cutting line. The cutting principle seems very simple, but has many challenges in the process of actual operation. The fretsaw much precisely balance and control cutting line diameter、cutting speed and the total cutting area, thus can obtain consistent silicon wafer thickness and short cutting time under the condition of silicon is not breaker. The power system of fretsaw is composed by converter system, so it will produce large harmonic when working, and harmonic will make serious effect on precision work in turn. So harmonic solution is the very important step in photovoltaic industry.
2、typical case of Hoteam photovoltaic industry
Some photovoltaic leader company use a large number of single crystal furnace、multicrystal furnace、fretsaw、PECVD and other equipments, these non-linear loads produce a large number of harmonic, which cause serious harm to the security of factory power supply. Considering this, factory chose two active harmonic filter manufacturers to solve harmonic, one is famous international electronic giant, another is us Shandong Hoteam.
The followings are data contrast at site before and after installing Hoteam active harmonic filter:
1）the comparison chart of phase voltage waveform
Phase voltage waveform before installing APF Phase voltage waveform after installing APF
2）the comparison chart of phase voltage harmonic content
Phase voltage harmonic content before installing APF Phase voltage harmonic content after installing APF
3）the comparison chart of phase current waveform
phase current waveform before installing APF phase current waveform after installing APF
4）the comparison chart of phase current harmonic content
Phase current harmonic content before installing APF Phase current harmonic content after installing APF
The test result analysis before and after filtering harmonics：
1）after APF operation, the voltage and current waveform has obvious improvement.
2）after APF operation, the voltage and current harmonic obviously reduced, the voltage harmonic reduced from 4.7% to 2.4%, current harmonic reduced from 18.4% to 5.0%.
3）the current harmonics are mainly 5、7、11th, after installing APF, the filter rate of total harmonic current and each harmonic are high, it solved harmonic problems fundamentally.
Postscript note: this customer used two suppliers’ active harmonic filter on trial, from the point of site running effect, Hoteam active harmonic filter showed its quality that better than imported famous brand product, especially the filtering effect that well over imported product, what is more, Hoteam company convinced customer with superb service. This customer has already equipped with Hoteam active harmonic filter in all its late expansion project！
Based on the possible problems in photovoltaic industry, there may also need reactive power compensation system, SVG and other power quality products.