Nonlinear Modeling and Stability Analysis of Grid-Tied Paralleled-Converters Systems Based on the Proposed Dual-Iterative Equal Area Criterion

With the rapid development of distributed renewable energy generation and integration, stability issues of power converters systems have been widely studied in recent years. Many previous studies focus on the transient stability of a single converter connected to the weak grid. However, the nonlinear dynamics and stability mechanism of multiple converters systems remain unclear. In this article, a unified nonlinear model of the paralleled-converters system is established, which reveals the interactive power and interactive damping among multiple converters and the weak grid. To analyze the impacts of the interactive power and damping terms on system stability, a dual-iterative equal area criterion (DITEAC) is proposed with a dual-layer iterative calculation of the accelerating area and decelerating area. Compared with the previous studies, the proposed DITEAC method could deal with the nonlinear interactive damping and reduce the conservatism caused by the inequality scaling, which greatly improves the calculation accuracy of stability boundaries. The expansion feasibility of the proposed unified nonlinear model and DITEAC method to the N-converters system is fully discussed. Eventually, simulation and hardware-in-loop experiment results are presented to verify the effectiveness of the proposed method.