Power optimization and static performance investigation of an island-mode doubly-fed induction generator (DFIG)
This paper presents a performance investigation of power optimization by using a Proportional-Integral (PI) controller in a doubly-fed induction generator (DFIG). A detailed, dynamic model of a DFIG based on variable speed systems is presented in the dq-synchronous reference frame. Along with different controller types, a PI controller is chosen. Moreover, besides active and reactive power control, constraints and power optimization are discussed. Matlab software was used for simulation.
Hierarchical control structure in microgrids with distributed generation: Island and grid-connected mode
The hierarchical control structure of a microgrid can be described as having four levels responsible for processing, sensing and adjusting, monitoring and supervising, and maintenance and optimization. The responsibility of the hierarchical control level is to provide control over the production of power from renewable sources. This paper comprehensively investigates the principles of hierarchical control in microgrids from a technical point of view. In the first step, this article covers the control of the power generation using two popular renewable energy sources, namely wind turbines and photovoltaics. The synchronization and power flow between the microgrid and the main network is then investigated. Finally, some research questions are presented to improve the performance of the hierarchical control, especially in the secondary decentralized control and energy storage systems.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.