A fuzzy-controlled pulse density modulation strategy for a series resonant inverter with wide load range

This paper presents a DC/AC series resonant power converter with a fuzzy logic controller that can supply power to a variable load. The converter is well suited for renewable energy sources, such as fuel cells and photovoltaic panels, and it is composed of two power stages: a DC/AC resonant converter as the input stage and an AC/AC power converter as the output stage. The input converter is operated with variable frequency control, which guarantees zero current switching for almost all the power range. This resonant converter generates a high frequency AC voltage, which is conditioned by the AC/AC converter to generate the desired low frequency output voltage. The AC/AC converter is controlled using a fuzzy logic controller and a pulse density modulation strategy. The fuzzy controller was chosen based on its characteristics of being inherently nonlinear, adaptive, robust and insensitive to parameter variations, making it a good choice for this application, especially because of the allowed load variation.