Modular active power-line conditioner

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 new modular approach to active harmonic filtering is proposed. The method utilizes two linear adaptive neurons (ADALINEs) to process the signals obtained from the line. The first ADALINE (the Current ADALINE) extracts the harmonic components of the distorted line current signal and the second ADALINE (the Voltage ADALINE) estimates the fundamental component of the line voltage signal. The outputs of both ADALINEs are used to construct the modulating signals of a number of current-source inverter (CSI) modules, each dedicated to eliminate a specific harmonic. The power rating of the modules will decrease and their switching frequency will increase as the order of the harmonic to be filtered is increased. The overall switching losses are minimized due to the selected harmonic elimination and balanced 'power rating'-'switching frequency' product. Power losses are also reduced by adjusting the [I.sub.dc] in each CSI module according to the present magnitudes of the individual harmonics to be filtered. Speed and accuracy of ADALINE, self-synchronizing harmonic tracking, optimum [I.sub.dc] value and minimal converter losses, high reliability and flexibility and speed and low dc energy requirement of the CSI, result in superb performance of the proposed active conditioner. The theoretical expectations are verified by digital simulation using EMTDC simulation package. Index Terms--Active power filter, ADALINE, CSI, EMTDC.