Topological development and operational analysis of buck-boost current source inverters for energy conversion applications

Two three-phase buck-boost current-source inverters (CSIs) are designed for use in general energy conversion applications where the input source voltage varies widely. The inverters are developed by first identifying characteristic modular features of a traditional CSI before cautiously integrating the noted features to a buck-boost converter and a single-ended primary inductance converter (SEPIC) to develop two extended single-stage dc-ac inverters with bidirectional power conversion ability. For their efficient control, a generic digital modulation algorithm is also developed with the dynamic influences of the different inverter switching states studied in details. The designed modulation algorithm always ensures smooth commutations between the power semiconductor switches with neither over-voltage nor short-circuit complications generated, and can conveniently be implemented using a digital signal processor with an on-chip digital modulator and an external programmable logic device. Both integrated chips are commercially available, and can be mounted on a single printed-circuit-board for enhanced portability. The resulting digitally controlled inverters are lastly tested in simulation using PSIM with Matlab/Simulink coupler and experimentally using two laboratory prototypes for demonstrating their smooth steady-state and transient operations.