A Novel Droop Control of Three-phase Inverters in Wireless Parallel Operation in Microgrid

This paper analyzed the limitation of traditional power theory of parallel operation of inverters based on the voltage of point of common coupling (PCC). An improved power theory of parallel system was deduced based on output terminal voltage of an inverter from a viewpoint of micro-grid autonomy operation. The "quasi power" variables were defined by linear combination and quasi active power and quasi reactive power were only related to the phase and amplitude difference respectively. A quasi-power droop control method for parallel connected inverters was proposed based on the improved power theory. The small-signal mathematical model of the parallel system was derived in a novel droop control scheme, which provided a theoretical basis for the parallel system performance analysis and droop coefficient design. The experiments and simulation were studied in the platform formed by two parallel connected three-phase inverters. The experimental results show that the proposed control strategy is feasible and the good sharing current effect is obtained.