Chapter three - Intelligent supervisory energy-based speed control for grid-connected tidal renewable energy system for efficiency maximization

Abstract

Marine current energy has gained increasing attention in recent years due to the advantages of being a clean source of renewable energy and highly predictable, compared to its predecessor. Permanent magnet synchronous generator (PMSG) with a back-to-back power converter is one of the most used technologies in tidal power generation schemes. However, Nonlinear dynamical and time-varying parameters of this kind of conversion system make the controller computation a challenging work. Also, DC-link overvoltage control, reactive power support, and efficiency of the power converters, are the important requirements in the grid-connected tidal energy systems to guarantee reliable and efficient electrical energy to the grid. In the present paper, a novel intelligent controller method, based on the passivity concept with a simple structure that tracks velocity, and maintains this one operating at the optimal torque, is developed. This proposed strategy consists of the passivity-based speed control (PBSC) combined with a fuzzy logic method, to address the robustness problems faced by conventional techniques in the machine-side converter (MSC) such as a proportional-integral (PI) controls for a PMSG-based tidal conversion system with grid connection. The characteristic of the proposed controller is that the nonlinear properties are not canceled but compensated in a damped way. The Fuzzy controller is adopted to compute the damping gains which guarantees fast convergence and global stability of the closed-loop system. The main contribution and novelty are the generation of the maximum power captured, the reduced fixed gains to zero, and the extensive comparison of the proposed PBSC to other nonlinear controls. The regulation of DC voltage and the reactive power to their desired values are the principal objectives of the present work. The proposed method is used to control the MSC, while a conventional PI method is adopted in the grid-side. The effectiveness of the proposed strategy is performed under extensive numerical investigation with MATLAB/Simulink software.