209 research outputs found
Control of Distributed Uninterruptible Power Supply Systems
In the last years, the use of distributed uninterruptible power supply (UPS) systems has been growing into the market, becoming an alternative to large conventional UPS systems. In addition, with the increasing interest in renewable energy integration and distributed generation, distributed UPS systems can be a suitable solution for storage energy in micro grids. This paper depicts the most important control schemes for the parallel operation of UPS systems. Active load-sharing techniques and droop control approaches are described. The recent improvements and variants of these control techniques are presented
Single-phase microgrid with seamless transition capabilities between modes of operation
Microgrids are an effective way to increase the
penetration of DG into the grid. They are capable of operating
either in grid-connected or in islanded mode thereby increasing
the supply reliability for the end user. This paper focuses on
achieving seamless transitions from islanded to grid-connected
and vice versa for a single phase microgrid made up from
voltage controlled voltage source inverters (VC-VSIs) and current
controlled voltage source inverters (CC-VSIs) working together in
both modes of operation. The primary control structures for the
VC-VSIs and CC-VSIs is considered together with the secondary
control loops that are used to synchronize the microgrid as a
single unit to the grid. Simulation results are given that show
the seamless transitions between the two modes without any
disconnection times for the CC-VSIs and VC-VSIs connected
to the microgrid.peer-reviewe
Review of Grid Interconnection Requirements and Synchronization Controllers for Dispersed Minigrids
As of 2019, the world population without electricity access is estimated to 770 million with most of these communities residing in sub-Saharan Africa. Nevertheless, between 2000 and 2019 the Indian population with electricity access has grown from 43% to 99%. Minigrids have played a major role in the efforts of increasing access to electricity in rural areas. However, interconnecting minigrids to each-other or to the main grid remains still a challenge both due to lack of clear protocols and of technically matured controllers to manage the synchronization. In this paper, a review of existing interconnection guidelines is presented and their relevance for the interconnection of minigrids is assessed. Furthermore, existing synchronization controllers are reviewed highlighting their applicability for minigrids.acceptedVersio
Seamless Transition of a Microgrid Between Grid-Connected and Islanded Mode
This thesis focuses on improving the behavior of inverters during transition periods from islanded mode to grid-connected mode (GC) and vice-versa. A systematic approach is presented to add smart features to inverters to enhance their capability to cope with sudden changes in the power system.
The importance of microgrids lies in their ability to provide a stable and reliable source of power for critical loads in the presence of faults. For this purpose, a design is proposed consisting of a distributed energy resource (DER), battery energy storage system (BESS) and a load connected through a bypass switch with the main utility distribution substation. The BESS is connected to the AC distribution feeder through a smart inverter that is controlled in both modes of operations. The system was tested using MATLAB/Simulink models and the results show proof of the seamless transition between the two modes of operation. The cost of building the software system was unnoticeable due to the availability of a MATLAB license but the real cost of the hardware needed to build the system will be moderate though the importance will be significant
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