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Distributed Generation has created the need for new types of smart dc grids developments. The multiple generation sources, bi-directional power flow, power flow time co-ordination and management bring significant benefits as well as challenges for current ac electrical grids and emerging dc microgrids. In particular, the effect of voltage weak distribution systems on protection concepts and approaches...
This paper reviews the currently available dc micro-grids and dc grids. Currently, commonly existing and proposed dc microgrids are designed to provide sufficeint energy during system disturbance as in ac grid and, are mainly voltage stiff systems. It also compares the voltage stiff systems to a low energy system, which represents voltage weak dc system, from systems point of view. First, the definition...
This paper introduces a new power system that can be implemented on all levels by using the bottom-up approach of system design. It is based on orthogonal power flow at different frequencies. The power exchange between different elements of the grid as well as the additional features are based on implementing power electronics (PE) interfaces and applying multiple frequencies (zero- DC is also a valid...
Micro-grid for villages using renewable energy is becoming a trend for developing countries like in Africa. Commonly, ac microgrids are used for the simple reason of ac household equipments and protection abilities. DC microgrid is a better choice in terms of efficiency, control simplicity and converter prices. However, whether it is an AC or DC, the demand-supply management is the most basic problem...
The increasing amount of distributed energy resources requires significant changes to today's power systems. Most of the distributed resources are dc inherently or have a dc link. Therefore, connecting them with a dc distribution system seems beneficial. This paper presents the opportunities and challenges of dc distribution systems, starting with the requirements of future power systems. It will...
Meshed dc distribution grids have advantages over radial connected ones. Challenges arise when this is done on the same voltage level and the full potential power might not be usable in certain configurations. This paper shows how the power flow in meshed dc grids can be increased by limiting the currents at congested lines. This can be done in a decentralized way with only local current measurements...
This paper describes the behavior of voltage weak dc microgrids. These are dc microgrids with a relatively small system capacitance. The large amounts of stored energy in the passive component of a network has a considerable effect on the size of the fault currents, control and reliability. The use of a complex control approach to stabilize voltage weak microgrids is a possibility that requires further...
Studies on DC microgrid (DCMG) have simply gone too wild and it is time for a standardized approach to design commercial products. The weak nature of microgrid is studied and set as fundamental difference to the studies of bulk grid. It is often seen in some publications that same assumption is taken as in HVDC studies, and is often misleading. A 300 W or inter-leaved 1 kW fly-back converter working...
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