This paper presents a grid current control technique on the power converter level. The submitted analysis deals with a control method of positive and negative current sequences in a grid-connected converter during voltage sags. The control method should assure the proper exchange of active and reactive powers without power ripple, the mitigation of harmonic distortion of grid currents, and should also enable the control of grid current peaks. A simple expression is determined, which allows estimation of maximum active and reactive powers exchanged between the grid and the converter without exceeding the admissible converter current. Some simulation and experimental results are reported to validate the theoretically predicted performance of the control strategy.

A new description of the three-phase four-switch converter aimed at compensating reactive power in the general case of unbalanced source voltages is proposed. A mixed p-z approach based on integral transformations (the Laplace and modified Z-transform) is suggested for obtaining solution in a closed form. The analytical procedure is verified by experimental results to confirm the effectiveness of the proposed control scheme.

This paper analyzes the influence of dispersed generation (DG) on voltage quality in MV networks and summarizes problems considered of general interest relating to the power quality of dispersed generation. We are interested in voltage fluctuations, flicker, harmonic distortion, interharmonic distortion, and the effect of dispersed generation on ripple control signals. The influence of DG on voltage stabilization, line losses, and short circuit impedance are also investigated, and case studies in real systems are presented.

The power control based on the GPCC (Generalized Predictive Current Control) applied in the power electronic converter connected to the grid is presented in the paper. A design process of the control structure and its parameters, and the results of simulation and experimental validation are presented. The power responses to changes in power references and to grid failures are shown and discussed. The algorithm works well with unbalanced grid voltage. Steady state responses of both powers are oscillation-free for an unbalanced grid, and the network currents remain sinusoidal at the same time. The strategy is also able to ensure that limit values of grid current magnitudes are not exceeded during changes of power references or grid voltage and responses are fast and smooth at the same time. The combination of these favorable properties, which was not observed with other power control methods, can be assessed as the main benefit of the strategy developed.