Unified Controller for Bimodal Operation of Cuk Converter Assisted SEIG-Based DC Nanogrid

This article proposes a unified controller for Cuk converter assisted variable speed wind turbine driven self-excited induction generator (SEIG) in dc nanogrid configuration for rural electrification. Cuk converter assisted SEIG based wind energy conversion system (WECS) is considered as a master source in the proposed nanogrid, which operates in both grid-connected and islanded mode of operation. In grid connected mode, the system operates in maximum power point tracking (MPPT) under varying wind velocity. A single sensor, modified perturb and observe (P&O) MPPT algorithm, which is independent of the generator parameter is developed and implemented through Cuk converter. During a fault, the WECS necessitates to operate in islanded mode with voltage regulation to supply the local loads continuously. The unified control strategy is developed for selecting the mode of operation, which are MPPT and voltage regulation in grid-connected and islanded mode, respectively. Harmonic spectrum analysis is carried to justify the selection of diode bridge rectifier over semicontrolled/controlled rectifier. The effectiveness and feasibility of the proposed system is verified by means of MATLAB/Simulink. To demonstrate the operational capability, a laboratory scaled prototype is fabricated and tested under various dynamic scenarios.