부산대학교 도서관

Transformerless grid-connected inverters, due to their advantages in high efficiency, small volume and light weight, gain more research and interest in recent years. Due to the asymmetrical driving signal in pulse-width-modulation (PWM) caused by time-delay, zero-drift of the current sensors and imparities of the power transistors, etc. Output of the grid current contains dc component. As a result, power quality of the grid is degraded. In this paper, a dc component suppression scheme with recursive integral PI controller are introduced, according to the change tendency of tracking error, the coefficients of PI controller are regulated by BP neural network in real time, and the global optimization requirements are met. Sliding-Window-Double-Iteration-Method (SWDIM) is utilized for fast dc current extraction. Simulation results from a 2-kW three-phase grid-connected inverter confirm the effectiveness of the proposed scheme.