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Summary: In a wind energy conversion system (WECS) based on a doubly fed induction generator (DFIG), a fast and smooth automatic synchronization of the DFIG with the utility grid is always desirable. Additionally, elimination of the need for a speed encoder makes the synchronization process much more reliable. This paper proposes a modified voltage controller‐based automatic grid‐synchronization strategy for the DFIG‐WECS using a rotor‐current‐dependent model‐reference‐adaptive‐system (MRAS) for rotor‐speed/position estimation. A V/f control‐based starting strategy is used to start the DFIG. An improved decoupled DFIG stator voltage controller is proposed to enhance the transient response during the DFIG grid synchronization. The modified controller is implemented in a grid‐voltage‐oriented reference frame to synchronize the DFIG‐stator with the grid. A robust modified MRAS with higher noise immunity and reduced machine parameter dependency is used to estimate the rotor‐speed/position during synchronization control. To validate the performance of the proposed strategy, a DFIG‐based WECS is modeled and simulated using an OPAL‐RT real‐time simulator, where a motor‐generator setup is modeled to have an equivalent WECS configuration. As compared with the latest reported work, this approach reduces the synchronization time by 16.99% while ensuring a smooth synchronization with no stator inrush‐current, even without any speed/position encoder. [ABSTRACT FROM AUTHOR]

Due to the rapid development of power electronics technology and modernization of DC based loads, DC microgrids (DCMG) are becoming most attractive solution in terms of their increased efficiency and high power quality. However they face certain challenges like intermittency of renewable energy sources, limitations in dynamic behaviour of storage systems and various stability issues during islanding. Thus it is mandatory to select the DCMG components properly with a robust control strategy for power converters in order to maintain power balance despite of variation in source and load power in order maintain the system power quality. In this work, a DC bus signalling based decentralized control strategy is proposed for a PV based DCMG, which eliminates the risk associated with DC bus voltage fluctuation. Fuel cell is as an auxiliary power source along with solar PV and storage devices, reduces the possibility of black out and helps to increase system reliability. The proposed control strategy has been validated through MATLAB/Simulink based simulation studies for variable weather condition and load demand on DCMG system.