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Solar Photovoltaic (PV) systems have been in use predominantly since the last decade. Inverter fed PV grid topologies are being used prominently to meet power requirements and to insert renewable forms of energy into power grids. At present, coping with growing electricity demands is a major challenge. This paper presents a detailed review of topological advancements in PV-Grid Tied Inverters along with the advantages, disadvantages and main features of each. The different types of inverters used in the literature in this context are presented. Reactive power is one of the ancillary services provided by PV. It is recommended that reactive power from the inverter to grid be injected for reactive power compensation in localized networks. This practice is being implemented in many countries, and researchers have been trying to find an optimal way of injecting reactive power into grids considering grid codes and requirements. Keeping in mind the importance of grid codes and standards, a review of grid integration, the popular configurations available in literature, Synchronization methods and standards is presented, citing the key features of each kind. For successful integration with a grid, coordination between the support devices used for reactive power compensation and their optimal reactive power capacity is important for stability in grid power. Hence, the most important and recommended intelligent algorithms for the optimization and proper coordination are peer reviewed and presented. Thus, an overview of Solar PV energy-fed inverters connected to the grid is presented in this paper, which can serve as a guide for researchers and policymakers.

This study presents a nonlinear controller with a wind speed estimator for a variable speed wind turbine at below-rated wind speed. A nonlinear controller is designed to address the rapid variations in wind and uncertainties in the wind system. The objective of nonlinear controller is to maximize the energy that can be extracted from wind with a reduction on mechanical loads. The synergetic and terminal synergetic controllers are proposed for improving energy capture and load mitigation. Also, the stability of the controllers is analysed by Lyapunov stability. The proposed controllers were validated using the FAST (Fatigue, aerodynamics, structures and turbulence) numerical model. Finally, a comparative study has been made between the controllers for different wind speed profiles. [ABSTRACT FROM AUTHOR]

This Letter proposes a simple electromagnetic torque based model reference adaptive system (MRAS) speed estimator for sensorless surface mount permanent magnet synchronous motor (SMPMSM) drive. The proposed estimator is formed using instantaneous measured and estimated electromagnetic torque. The proposed estimator is implemented for 1.5 kW laboratory prototype SMPMSM drive using field programmable gate array ALTERA cyclone II. Experimental results demonstrate the efficacy of the proposed scheme under different test conditions viz. different low-speed regions and standstill at different load conditions with uncertainty in machine parameters. Results show that the estimator is stable in low-speed regions and exhibits robustness against uncertainties in machine parameters. [ABSTRACT FROM AUTHOR]