Analysis of Networked Control Schemes and Data-Processing Method for Parallel Inverters

This paper presents two schemes and correlated issues for parallel inverters of distributed generation units in an ac distribution system. The proposed control schemes are based on droop control method in the form of modified weighting power and only use communication bus with limited capacity. A potential improvement in current sharing can be achieved by introducing power data of other inverters via network into a conventional droop scheme. According to the transmitted data, Averaged Power Scheme and Instantaneous Power Scheme are introduced. The impact of time-delay and data dropouts during transmission on system stability is necessarily considered. Consequently, mathematical modeling of systems is built and the maximum time bounds of stability are addressed. Moreover, one self-adaptive data-processing method is developed to optimize the current sharing, which establishes two channels of control data depending on the communication condition, thereby keeping system operation smooth and achieving satisfactory performance even in communication failures. To further the description, the comparison is carried out by related experimental results of systems with time-delay, data dropouts and the others. Experimental results show the effectiveness of these proposed schemes.