Control Design of Modular Self-Synchronizing AC- and DC-sided Parallel-Connected Three-Level NPC Inverters

This paper describes the control design of three self-synchronizing modular three-level NPC inverters, which are connected AC- and DC-sided in parallel, up to a theoretical infinite number. In addition, a worst-case analysis of the zero-sequence circulating current (ZSCC) control is illustrated. The control strategy of a virtual master-slave concept is described to ensure the self-synchronization of the inverters without communication. Experimental results proof the proper functionality with its control algorithms, especially related to the ZSCC.