Reliability Improvement Approach Based on Flatness Control of Parallel-Connected Inverters

In this paper, a global study in terms of control architecture is applied to parallel voltage-source inverters. Parallelism of inverters represents very interesting advantages for the industrial applications to meet the high-power requirements, and it is possible to apply maintenance during the operation without interruptible operation. The main objective of this paper is to guarantee a reliable operation of the parallel inverters system during healthy and faulty conditions due to full disconnection of any inverter. Special precautions are recommended to avoid the negative effects of the circulating currents, which are caused essentially by the asynchronous pulse width modulation or existence of dispersion of the system component characteristics. To deal with this crucial problem, one-loop flatness-based control is proposed to the control of N parallel inverters and allows obtaining low total harmonic distortion. The proposed control uses the advantages of the flatness to ensure high power quality at the point of common coupling and equal currents distribution between the parallel inverters and minimize the impact of a full disconnection of any inverter on the performance. The proposed algorithm is theoretically analyzed and validated experimentally.