An Accurate Power-Sharing Control Method Based on Circulating-Current Power Phasor Model in Voltage-Source Inverter Parallel-Operation System

This paper proposes an optimized mathematical model of the voltage-source inverter parallel-operation system (VSIPS) and proposes an improved droop control method based on this model, which can realize accurate power sharing in VSIPS. First, this paper analyzes VSIPS as a multi-input and multioutput system and proposes a precise definition of circulating current. The circulating-current model, the steady-state model, and the small-signal model are proposed subsequently based on the optimum design of wire impedance, which constitute the optimized mathematical model of VSIPS in <italic>s</italic>-domain. The circulating-current phasor model and the circulating-current power phasor model (CCPPM) are also proposed. Second, the mathematical model of traditional droop control is built and analyzed based on CCPPM, which elaborates the tradeoff of droop control between the steady-state voltage bias and the load-sharing accuracy, and proves that the <inline-formula><tex-math notation="LaTeX">$V- Q$</tex-math></inline-formula> droop control cannot realize accurate reactive-power sharing. Third, an improved droop control method (<inline-formula> <tex-math notation="LaTeX">$\omega - P_{{\text{cir}}}$</tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$V- Q_{{\text{cir}}}$</tex-math></inline-formula> control) is proposed, which can realize the accurate active- and reactive-power sharing and eliminate the steady-state voltage bias simultaneously. Finally, simulation and experimental results are presented, which validate the proposed mathematical model of VSIPS, the analysis of droop control, and the performance of the proposed method.