Flatness-based-control for parallel operation of N voltage-source inverters

Parallel voltage-source inverters with common dc bus present very interesting advantages from an industrial point of view. Indeed, by paralleling several units the power supply system includes capability to handle high power requirement, modularity and the possibility of maintenance through redundancy, within an uninterruptible supply operation. However, a special attention is required to avoid the negative effect of the circulating currents in such configuration caused essentially by the asynchronous switching operations of the Pulse Width Modulations (PWM) specified to each unit. To deal with this problem, in this contribution a one loop controller based on the flatness technique is proposed to an isolated power supply composed by N units. These units connect the same dc source and the ac load. The objective of the new sharing controller is to take some advantages of the flat proprieties of the system in order to ensure both reduction of the circulating currents and high power quality at the Point of Common Connection (PCC).