A New Approach Based on Flatness Control to Improve Reliability of Parallel Connected Inverters

In this paper, a global study in terms of control architecture is applied to parallel voltage-source inverters topology with common DC bus under healthy and faulty operation mode, which represents very interesting advantages for industrial applications. By paralleling several units, the power supply system is able to meet high power requirements and the possibility of maintenance during the operation without interruptible supply operation. However, a special precaution is required for such parallel systems 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 or existence of faults or unbalanced conditions during the operation. To deal with this crucial problem, a one loop with high bandwidth and low voltage THD controller based on the flatness technique is proposed to a non-isolated power supply composed by N units.. The objective of proposed controller is to take some advantages of the flat proprieties in both healthy and faulty mode of any inverter in the parallel system, to ensure reliable operation and to ensure both reduction of the circulating currents and high power quality at the Point of Common Coupling (PCC). The algorithm is theoretically analyzed with the proposed control method and validated by the experimental results.