The increasing installation of photovoltaic panels in low-voltage grids causes an over voltage problem, especially during high production and low consumption periods. Generally the over voltage problem is overcome by implementing reactive power control methods. The advances in networked control systems theory and practice create new scenarios where reactive power control methods can offer additional features and benefits. To explore these new capabilities, this study presents two new reactive power control methods that exploit the networked approach. These two methods are evaluated in a comparative reference framework that also includes the base-line case where no reactive control method is applied, the conventional droop method approach, and a solution based on a near-optimal location of a high power STATCOM derived from one of the new proposed networked methods. The main merit factors used to compare the control methods are the maximum voltage across the distribution grid, the power factor in the point of common coupling, and the total power losses and economic cost of the installation. With these merit factors, the advantages and limitations of the new and existing control methods are revealed and discussed. A useful discussion for selecting the best control solution is also reported.

Portal del coneixement obert de la UPC http://upcommons.upc.edu/e-prints Aquesta és una còpia de la versió preprint d'un article publicat a la revista IET power electronics.

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Modern DC-DC resonant converters are normally build around a voltage-source series-resonant converter. This study aims to facilitate the practical use of current-source parallel-resonant converters due to their outstanding properties. To this end, the study presents a sliding-mode control scheme, which provides the following features to the closed-loop system: 1) high robustness to external disturbances and parameter variations and 2) fast transient response during large and abrupt load changes. In addition, a design procedure for determining the values of the control parameters is presented. The theoretical contributions of the paper are experimentally validated by selected tests on a laboratory prototype.

This paper presents an active damping method in natural frame for a three-phase voltage source inverter with LCL filter. The proposed method is based on the pole placement technique via Ackermann's formula. This approach is used to obtain the proper sliding surface vector coefficients to emulate a virtual resistor in series with the capacitor filter. Besides a well-known method in the literature have been used to obtain three decoupled controllers in natural frame. The stability is theoretically studied and experimental results shows the validity of this proposal.Peer ReviewedPostprint (published version