Sistemas de compensação em derivação baseados em conversores paralelos e interconectados.

Abstract

Shunt active power lter (SAPF) is the solution most used to improve the electrical power system quality. Harmonics of the load current emitted by nonlinear loads are compensated by those lters. Converter structures have been widely studied in literature with SAPF function. These structures aim to improve the quality of waveforms generated and performance of converters. In this work, parallel and cascaded (interconnected) converter associations are studied, both with SAPF function, connected in three or four wires systems and applied in balanced and unbalanced systems. In additional, aspects of multifunction of parallel topologies are presented, these topologies provide adequate voltage supply to loads in voltage disturbance cases. Almong all topologies studied in this work, some are proposed and others are studied in previous works. However, some new aspects are shown for all topologies. Comparisons with conventional topologies were done regarding: harmonic distortions of grid currents and semiconductor and dc-link losses. For each topology studied the following aspects were considered: (i) dynamic modelling of the con guration; (ii) PWM strategy, (iii) control approach and (iv) simulation and experimental results. In terms of control strategy, some aspects are carried out: mitigation of circulating current and dc-link voltage balance. The topologies composed of two parallel converters or legs reduce current level on switches, allowing cheapest switches to be used or redundance characteristic to be added in the system. The interconnected topologies reduce the voltage levels on the switches. Both types of connections allow to increase the number of voltage steps, by PWM techniques, and to reduce the THD of grid currents. The results show that it is possible to reduce the switching frequency with purpose of equal the THD of conventional structures and to reduce the losses in the semiconductor devices.