Modular approach to active power-line harmonic filtering

Active power-line filtering is conventionally performed by injecting equal-but-opposite of the distortion into the line. The power converter used for this purpose is rated based on the magnitude of the distortion current and operated at the switching frequency dictated by the desired filter bandwidth. Fast switching at high power, even if technically possible, causes high switching losses. In this paper, a modular approach to active harmonic filtering is proposed. The method is based on the extraction of individual harmonic components of interest using a linear adaptive neuron (ADALINE) and injecting equal-but-opposite of each harmonic current into the line using a current source inverter dedicated to that specific harmonic. The inverters dedicated to lower-order harmonics have higher ratings but are switched at lower rates, while those dedicated to higher-order harmonics are of lower ratings but are switched at higher rates. The overall switching losses are minimized due to the selected harmonic elimination and balanced “power rating”, “switching frequency” product. Theoretical expectations are verified by digital simulation using EMTDC simulation package