Abstract
The grid-connected operation of the distributed generation (DG) via the direct current (DC) microgrid is the operation mode of the DC power distribution system in the future. Considering the grid-connected operation of multiple DC microgrids, we have proposed a new type of DC power distribution management system aiming at the lowest operating cost of the entire DC power distribution system. Our proposed DC power distribution management system can be used to carry out the optimized dispatching for the connected DC microgrids, thereby achieving the economic, safe, and stable operation of DC power distribution management systems. At the same time, through the different nodes where the modular multilevel converter (MMC) is connected to the alternating current (AC) distribution network, a DC power distribution management system can control the active and reactive power generated by the MMC, achieving the control of the load flow of the upper-stage AC grids in real time. The example simulation shows that the method proposed in this paper has a great role in reducing the transmission losses of the power distribution network, achieving electric power peak-load shifting, and utilizing renewable energy. Thus, it can not only maximize the use of distributed renewable resources, but also enable mutual support and optimal scheduling between a DC power distribution system and multiple microgrids.
Highlights
The direct current (DC) power distribution network has excellent performances regarding large transmission capacity, low transmission loss rate, low cable cost, high power supply quality, and flexible and friendly connection of distributed generation; this is the development direction of the power distribution system in the future
Most of the energy generated by distributed generation (DG) such as photovoltaics (PV), wind turbine (WT), microturbine (MT), and battery-type energy storage (BES) units is of DC or non-power frequency alternating current (AC) electricity; the connection of DG to the DC microgrids will save a lot of converter links, achieving the reduction of costs and losses simultaneously
Microgrid at the bottom layer be optimally scheduled, and the interchange power between the DC power distribution management system and the AC distribution network can be distributed by utilizing modular multilevel converter (MMC), thereby changing the active/reactive power of the distribution network node connected to the MMC; at the same, via the mutual coordination of the DC power distribution management system with the static var compensator (SVC), the load flow of the AC distribution network can be controlled, thereby achieving the coordination and optimization of the whole system
Summary
The direct current (DC) power distribution network has excellent performances regarding large transmission capacity, low transmission loss rate, low cable cost, high power supply quality, and flexible and friendly connection of distributed generation; this is the development direction of the power distribution system in the future. By employing the operation control and optimized scheduling technologies of distributed DC microgrids, a variety of distributed resources are integrated, and the DC power distribution systems are centrally connected to the main electric network through some power electronic devices. The power system will gradually develop an AC/DC hybrid smart system where multiple DC microgrids are integrated into a large grid operation by flexible interconnections [14]. To this end, this work has firstly proposed a DC power distribution management system that flexibly interconnects multiple DC microgrids.
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