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The control methodology of the active power-line filter is the key element for its successful performance in mitigating the line current harmonics. The control system processes the distorted line current signal and forces the converter to inject the proper compensating current. At the same time, it regulates the dc term, i.e., the dc current in the current source converter topology and the dc voltage in the voltage source converter topology. In this paper, a new intelligent control scheme for a modular single-phase active power filter based on the current source converter (CSC) topology is proposed. The intelligent controller utilizes two adaptive linear neurons (ADALINEs) to process the signals obtained from the power-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 the two ADALINEs are used to construct the modulating signals of a number of CSC modules, each dedicated to eliminate a specific harmonic. The proposed controller is also responsible for activating selected CSC filter module(s) to the electric grid. The automated activation of the corresponding filter module(s) is based on the decision-making rules in accordance with the current total harmonic distortion (THDi) and the harmonic factor (HF) levels set by the IEEE 519-1992 standard. A special 3-level PWM switching strategy is proposed for the filter modules which results in a 50% reduction in the overall switching losses compared with the 2-level method. The proposed controller adjusts the Idc in each CSC module based on the present magnitude of the corresponding harmonic current which results in optimum dc-side current value and minimal converter losses. The high speed, accuracy, efficiency and flexibility offered by the proposed controller, combined with the fast response and low dc energy storage requirement of CSC topology, are the main advantages of the proposed active filter system. The analytical expectations are verified by digital simulation using EMTDC simulation package.