Discrete-Time Cascaded-Control Design of Photovoltaic Systems for GMPPT and Power Curtailment Operations

This paper presents an efficient method to scan the power characteristics of photovoltaic (PV) systems in a few milliseconds. Further, it proposes and analyses the discrete-time cascaded-control designs for the grid-connected PV systems for two different operations (Global MPPT (GMPPT) and power curtailment), ensuring efficient performance during rapidly changing or non-uniform environmental conditions. A simple strategy is also discussed to predict the maximum available PV plant power when the environmental conditions vary between two consecutive scanning events to guarantee stability during the power curtailment operations. The performance of the proposed controllers is validated, analyzed, and compared using MATLAB/SIMULINK. The power curtailment operation is found to be superior to the GMPPT operation, ensuring stable operations during three-phase failure conditions.