switching algorithm

Series voltage compensation is used in low-voltage distribution system to compensate for voltage variations. The compensators are indeed series-connected converters which inject the missing voltage in series to the grid in case of voltage sag. In this paper, a switching algorithm for AC-AC converter based voltage compensator is proposed. As the bidirectional AC power electronic switches are used in the AC-AC converters, considering the switching dead-time, snubber circuits should be used in parallel with the switches to provide a current path during the dead-time and hence to reduce the dv/dt stresses on the switches. The snubber circuits increase the circuit elements and have their own power losses. Using the proposed switching algorithm, the snubber circuits could be eliminated since a current path is always (including the dead-time) guaranteed. In order to evaluate the proposed algorithm, the simulation studies and discussions are presented.

In the recent years, many different multi-port converters have been proposed for multi-source multi-load applications in order to improve the features of a hybrid system such as cost, size, efficiency and life time. This paper surveys and develops a capacitor-less three-port converter which has been presented to eliminate the bulk capacitor in common DC bus. In this paper, several switching approaches are proposed for this converter and implementation methods of them are described and evaluated. In addition, considering constant voltage in one of the ports, a small signal model is extracted for the converter which has five state variables due to existence of two capacitors and three inductors. In order to control different port independently, using an innovative method, the converter outputs are decoupled. Finally, a control system based on magnitude optimization is presented for the converter. Simulation results are used to verify the validity and the performance of the proposed approaches and analysis's.