The effective component in AC power grid refers only to the power frequency, and any component other than power frequency can be called harmonic. Harmonic is generated because the sinusoidal voltage is applied to the nonlinear load, which distorts the fundamental current. With the continuous development of science and technology, the nonlinear electrical equipment is more and more widely used in the power system, leading to increasingly severe harmonic pollution to public power grid.
Common Non-Linear Devices Include
Arc welding machine, electric arc furnace, medium-frequency induction furnace, frequency converter, rectifier and auto charger.
Switching power supply, fluorescent lamps, gaseous discharge lamps, frequency conversion air conditioners, dimming equipment and computers
Printer, fluorescent lamp, charger, TV, electronic stove, induction cooker, microwave and dishwasher.
Main Hazards of Harmonic Are As Follows
Compromised effective load capacity, overheating and excessive loss
Over-voltage, over-current, resonance, or even burnout of capacitor
Equipment failure or damage, malfunction of protection equipment
Malfunction of detection, control and communication devices
Voltage change, fluctuation, sag, short interruption, and current spike of neutral conductor
Working Principle of Active Power Filter
Active Power Filter is referred to as APF for short. APF is capable of real-time detection of load current through the external current transformer (CT), and extraction of harmonic and reactive components in the load current via calculation of the internal DSP. Controlled by PWM, it can produce and input the compensating current equal to the value of load harmonic current but opposite to the direction of load harmonic and reactive current in order to filter the harmonic and compensate reactive power.
1. Based on 3-Level topology circuit
2. Modular design for a shorter delivery cycle and easy maintenance.
3. Rack-mounted or wall-mounted design which can be easily combined and installed as needed.
4. Remote communication interfaces, with real-time monitoring being achieved via PC machines.
5. A full automatic detection runs during the whole compensation process, and should it be restarted, self-diagnosis will function; then after the fault is removed, it will be automatically put into use.
Active filter, active power filter, active harmonic filter, harmonic filter