Abstract
With the rapid increase of renewable energy integration, more serious power fluctuations are introduced in distribution systems. To mitigate power fluctuations caused by renewables, a microgrid with energy storage systems (ESSs) is an attractive solution. However, existing solutions are still not sufficiently cost-effective for compensating enormous power fluctuations considering the high unit cost of ESS. This paper proposes a new flexible multi-microgrid interconnection scheme to address this problem while optimizing the utilization of ESSs as well. The basic structure and functions of the proposed scheme are illustrated first. With the suitable power allocation method in place to realize fluctuation sharing among microgrids, the effectiveness of this scheme in power smoothing is analyzed mathematically. The corresponding power control strategies of multiple converters integrated into the DC common bus are designed, and the power fluctuation sharing could be achieved by all AC microgrids and DC-side ESS. In addition, a novel ESS sizing method which can deal with discrete data set is introduced. The proposed interconnection scheme is compared with a conventional independent microgrid scheme through real-world case studies. The results demonstrate the effectiveness of the interconnected microgrid scheme in mitigating power fluctuation and optimizing storage capacity, while at the expense of slightly increased capacity requirement for the AC/DC converters and construction cost for DC lines. According to the economic analysis, the proposed scheme is most suitable for areas where the distances between microgrids are short.
Highlights
Photovoltaic (PV) solar power has been one of the fastest-growing forms of renewable energy being integrated into distribution grids in the past decade [1]
With Objective 1 in effect, the total energy storage systems (ESSs) power capacity is reduced from 352 kW to 90 kW, whereas the total energy capacity of the ESS is reduced from 61 kWh to 12 kWh
0.0217 In Figure 11, it is shown that the DC line length needs to be restricted for avoiding massive investment in DC cable
Summary
Photovoltaic (PV) solar power has been one of the fastest-growing forms of renewable energy being integrated into distribution grids in the past decade [1]. Microgrid integration with energy storage system (ESS): Solar PV, local loads, and ESS can be integrated into a microgrid, where the net power fluctuation coming from PV panels and loads can be compensated by the ESSs before affecting the upper-level grid [6,7,8] Among these methods, active power curtailment is achieved by reducing PV utilization. By introducing electrical ties and energy exchanges among AC microgrids, a novel flexible multi-microgrid interconnection scheme is proposed in this work to provide a better solution for mitigating power fluctuation. Each microgrid includes their own PV sources and local loads, and is connected to the upper-level distribution grid through the PCC.
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