Robust adaptive nonlinear control of microgrid frequency and voltage in the presence of renewable energy sources

摘要

Global warming of the planet and air pollution have prompted an increased use of renewable energy sources for power generation. These new sources of clean energy are now very much in demand for setting up microgrids that provide energy independence to communities far from major urban centers. These microgrids should be able to operate either in isolated mode or to be connected to the main power grid. These requirements pose significant challenges. Indeed, in isolated mode, small and medium power grids are very sensitive to fluctuations in consumer power use as well as changes in the power produced by generators. In gridconnected mode, renewable energy sources do not contribute to the grid's stability and robustness as well as conventional generators do. ududPhotovoltaic power plants pose some challenges when integrated with the power grid. The PV plants always focus on extracting the maximum power from the arrays. This makes the PV system unavailable for helping in regulating the grid frequency as compared to conventional generators. One of the main objectives of this research is to develop a robust adaptive nonlinear control technique which provides frequency regulation functionality to PV systems as well as voltage regulation. ududA small-scale power microgrid incorporating photovoltaic generators, synchronous generator and load is considered in our study. Dynamic models of the proposed microgrid were determined. The final model highlights the interactions between the sources of renewable energy and the rest of the network. A new robust adaptive nonlinear (exact input-output feedback linearization) control strategy was developed in order to meet the requirement of frequency regulation as well as voltage regulation. The new control strategy allows the PV system to have a similar response to changes in microgrid frequency as that of a conventional generator. The controller is also self-adjusting (adaptive) as well as robust in order to compensate the perturbation due to the changes in users’ power consumption, or any defects in the MG electrical network. The performance of the proposed solutions was evaluated in simulation using the Matlab/Simulink. For further verification, a small-scale laboratory experimental prototype of proposed microgrid was developed in laboratory to implement the proposed technique.ududThis research may be regarded as an important basis for the development of microgrid power station for remote communities isolated from the main power system or large-scale power network with higher penetration of renewable energy sources.