Impedance Modeling and Stability Analysis of Three-Level Neutral-Point-Clamped Grid-Tied Inverters

摘要

Three-level inverters are adaptively used in renewal energy generation equipment, especially in high and medium power levels. The stability of three-level inverters is worth studying. In this paper, a diode clamped three-level inverter is studied. Based on the influence of DC side neutral point control on its impedance characteristics, the impedance model of neutral-clamped three-level inverters is established. Then, the stability of the inverters under different grid impedance and operating power is analyzed by using Nyquist stability criterion. The simulation results show that the impedance characteristics of three-level inverters can accurately judge the stability of the grid-connected inverters.