Principle

APF is a new power electronic equipment which can dynamically filter harmonic with variable amplitude and frequency and compensate reactive power, it overcome the shortages of traditional LC filter and obtained the better compensation characteristics than passive filter.

The following diagram is schematic diagram of APF, where, Vs is AC power supply, nonlinear load is harmonic source, it generates harmonic and consumes reactive power. APF is composed of instruction current operational circuit and compensation current generation circuit, the instruction current operational circuit is mainly to inspect current contents in harmonic current and reactive power of compensation object, and the compensation current generation circuit generates actual compensation current according to instruction current, the main circuit adopted PWM converter.

Technical Features:

• Compensate any order harmonic with variable amplitude and frequency and different reactive power dynamically, and has a high-speed response time to the change of compensation object, it is hard to generate harmonic resonance with power grid impedance.
• It can implement compensation on single harmonic source and reactive power source and also implement centralized compensation on many harmonic and reactive power sources.    
• Adopt full-bridge PWM converter to generate compensation current, the power unit is 5^th generation IGBT, it is working under the high-frequency switching. Power circuit and control circuit adopted modularized structure or plug-in unit, same module can be replaced, which enhanced the reliability and maintenance.       
• DSP high-speed checking and operation ensure harmonic checking and compensation control correct; It has intelligent supervisory control function, the working state and operation parameters are displayed in real-time, meanwhile, faults can be self-diagnosed; it also has remote communication interfaces, the real-time monitoring can be realized through PC.
• With perfect protection functions, the main circuit adopted three-phase three wire or three-phase four wire, it is designed to shunt APF, very easy and safe to operate.       
• The master chip adopted latest floating-point DSP F28335 of TI Company and FPGA of ALTERA Company to make the system have powerful processing capacity, the sampling adopted AD7606 with 16 bits of AD Company to ensure control precision.      
• APF can be used in power grid alone or can be combined with other passive filters together to realize hybrid filter with best ratio of performance to price.

Application Fields:

1. Static converters for industrial use, such as high and low voltage transducer (speed regulation), high capacity rectifier devices, etc. 

• The DC equipment or transducer of the steel mill, high speed wire, boards and bars.
• Ferrous (non-ferrous) rolling (mill): Such as stainless steel rolling, carbon steel rolling, line rolling, aluminum sheet (strip, foil) rolling mill.
• Non-ferrous electrolysis industry: Electrolytic aluminum, copper, cadmium, cesium, etc.
• Rubber and plastic industry: Internal mixer, injection molding machine, extruding machine, blow molding machine etc
• Medium frequency induction heating furnace: Metal casting industry, steel mill hot rolling.
• Electrolysis of chemical plant: Electrolysis NaCl, electrolysis KCl, electrolysis H, et.
• Electroplating industry: Chroming, aluminizing and galvanizing in lighting factory, etc.
• Paper industry: Speed regulation used for craft, such as paper-pulp squeezer, etc
• Petrochemistry: During the technological process of chemical and oil refining, large amount of low voltage inverters used for speed regulation, and small amount of high voltage and high power electronic circuit equipments for starting, etc.
• DC traction equipment: Electrical railway, light rail vehicle, mine traction locomotive etc.
• Other high capacity industrial DC power supply.

    2.  AC/DC Arc Equipments 

• AC/DC arc furnaces: Such as the Electric Arc Furnace in steel mill, etc.
• AC/DC arc welding machine: Automobile manufacturing, ship building, heavy machinery manufacturing, etc.

    3.  Power supply devices for special use

         High capacity uninterruptible power supply, communication power supply, high (low)            frequency power supply, etc. Such as bank, hospital, semiconductor factory, program control exchange plant, remote communications, data communication station, substation, military installations, office buildings etc

    4.  Starting of the high capacity electromotor and switching of the high capacity reactive compensation.

    5.  High-precision automatic production line: The production line itself does not produce harmonic, but it is very sensitive to harmonic, so the active power filter should be installed at the side of power supply to reduce harmonic interference for production line.