Voltage and current tracking control for the parallel connection of VSC H-bridge converters without transformer

Paralleled H-bridge converter can be used for interfaces between alternative energy and the mains, for DVRs, FACTs and UPSs. Two strategies for paralleling H-bridge VSC converters without transformer are analyzed. The first case uses separate DC sources and the second one uses a common DC bus. To cope with the coupling between converters in the second case, this paper proposes a current controller with a slack variable. The frequency and phase of the individual PWM carriers, and the ZOH samplers for the individual controllers (voltage and current) are discussed. Experimental results are shown.