Control Strategy for Series and Parallel Output Dual-Buck Half Bridge Inverters Based on DSP Control

This paper presents a novel control strategy for series and parallel output dual-buck half-bridge inverters (DBHBIs). With the increasing concern of fossil fuel reserves and the environmental aspects, the 2005 International Future Energy Challenge, sponsored by U.S. the Department of Energy and the Institute of Electrical and Electronics Engineers, required that the grid-connected inverter should provide a single-phase utility line with 110-240 V at either 50/60 Hz. The proposed series and parallel output DBHBI can produce those kinds of voltage by series or parallel connection of two inverters and with digital signal processor (DSP) control to meet the aforementioned specifications. The load current of the two inverters at parallel output association and the load voltage of both at series output association can be shared. The waveform quality of the whole output voltage is high at both associations. Stability and relative stability of the inverter are unaffected at the two output associations. Operating principle, control strategy, stability and relative stability, and design guidelines and examples are illustrated. Experimental results of a 1-kVA DSP-based series and parallel output DBHBI at stand-alone mode verify the theoretical analysis. The comparisons between single and double inverter structures show that the proposed inverter is very promising in applications.