Harmonic damping by means of DG front-end converter. Part I: Theory and algorithm

The increasing use of electronic devices within electric power systems results in current and voltage distortions. This is a relevant problem in weak networks and, in particular, under resonant conditions. The long history of minimization of negative effects due to distorted currents has encouraged researchers and designers to attempt different control strategies for electronic converters. In this paper, a new control for bidirectional converters is proposed, whose active power exchanged with the grid depends on the sinusoidal balanced current term. Whereas at harmonic frequencies and negative sequence the proposed control emulates a resistive behavior, a damping effect on disturbances is achieved. The proposed control is economically feasible within small DG-systems. Measurements at ac converter terminals are the only required. Moreover, differential treatment of fundamental positive-sequence current and the remaining components allows the same control strategy to be maintained over the whole working range.