Passivity-based controller for harmonic compensation in distribution lines with nonlinear loads

This paper explores a passivity-based control scheme for active power filters that are used not only for the compensation of specific thyristor or diode rectifiers, but also for more general loads. Such loads may include, for example, power factor capacitors or may have unknown dynamics. To provide an alternative to existing solutions, which often lead to unstable operation in demanding applications, the authors investigate the effectiveness of a family of passivity-based controllers using on frequency-domain modeling of the system dynamics. Following the passivity-based design procedure, they first obtain a compensation strategy that allows stable active filter operation regardless of line and load parameter variations. Secondly, to ensure precise tracking for the selected harmonics, the develop an adaptive procedure which allows (under varying degrees of approximation) to estimate line and load parameters. Finally a comparison with a linear controller suggested by their passivity-based control structure shows the advantages of the proposed solution. Simulation results are presented which confirm effectiveness of the proposed controller.