Unfolder Operation and Modulation Strategy of Paralleled Current-Source Converters

The inherent short circuit protection and lower dv/dt with step-up features make the CSC-based system attractive for distributed generation integration. In this paper, unfolder operation is proposed for paralleled current-source converters (CSCs) based on duality principles. It provides an alternative operation mode with reduced switching actions and relaxed requirement of AC filters over conventional PWM operation. In light load condition, it requires less DC currents compared to conventional operation mode and has better performance, especially when input-parallel DC-DC system is implemented as the DC supplies. The operation principles of this mode are analyzed, and the associated modulation strategy is developed for the paralleled 2-CSC system. Verifications through simulation results show the feasibility of the proposed unfolder operation for a 2-CSC paralleled system.