Thesis title: Exact Discrete Time Modelling and Digital Control of Three-Phase LCL Filter-Based Inverter for Grid Connected Renewable Energy Systems
This thesis presents a rigorous modeling framework and validated control strategies for the digital control of grid-connected inverters employing LCL filters. Exact discrete-time models of both L and LCL filters were systematically derived in stationary and synchronous reference frames. These models form the analytical foundation for subsequent control design and stability analysis, enabling precise closed-loop pole placement and ensuring robust stability.
In addition, discrete-time current regulators, specifically PI and PR controllers, were implemented and evaluated using the proposed models. This study extends their applicability to systems characterized by low switching frequencies and high power ratings and includes a comparative assessment against widely adopted state-of-the-art modeling approaches. Comprehensive simulation studies conducted in PSIM and MATLAB verified the accuracy of the proposed models in predicting system behavior, confirming their suitability for high-fidelity digital control design in modern power electronics applications.