A Study on Control and Grid Synchronization for a Threephase Grid-connected Inverter in Distributed Generation Systems - Lai Ngoc Bao -Dept. of Electrical and Information Engineering The Graduate School Seoul National University of Science and Technology

Abstract
A Study on Control and Grid Synchronization for a Three-phase Gridconnected Inverter in Distributed Generation Systems Lai Ngoc Bao (Supervisor Kim, Kyeong-Hwa) Dept. of Electrical and Information Engineering The Graduate School Seoul National University of Science and Technology

This thesis presents an improved current control strategy for a three-phase grid-connected inverter under distorted grid conditions. The primary challenge associated with the gridconnected inverter in distributed generation (DG) systems is to maintain the harmonic contents in output current below the specified values even when the grid is subject to uncertain disturbances such as harmonic distortion. To address such a challenge, an improved current control scheme is proposed for a grid-connected inverter, in which the fundamental and harmonic currents are independently controlled by a PI decoupling controller and a predictive basis controller, respectively. The controller design approach is based on the model decomposition principle, where the measured inverter currents and grid voltages are split into the fundamental and harmonic currents using moving average filters (MAFs). Furthermore, to detect the grid angular displacement and frequency with better accuracy even in the presence of the grid voltage disturbances, the MAF is also introduced to construct an enhanced phase-lock loop (PLL) scheme. Theoretical analyses as well as comparative simulations results prove that the proposed control scheme adequately compensates the abnormalities caused by the grid voltage disturbances with fast transient response. To validate the feasibility of the proposed control scheme, the iientire control algorithm is implemented on a 2 kVA three-phase grid-connected inverter system using 32-bit floating-point DSP TMS320F28335. As a result, the proposed scheme is an attractive way to control a grid-connected inverter under adverse grid conditions.

LINK
http://www.mediafire.com/file/6bwc5529rb2b24u/grid.pdf