Abstract
Microgrid as an important part of smart grid comprises distributed generators (DGs), adjustable loads, energy storage systems (ESSs) and control units. It can be operated either connected with the external system or islanded with the support of ESSs. While the daily output of DGs strongly depends on the temporal distribution of natural resources such as wind and solar, unregulated electric vehicle (EV) charging demand will deteriorate the unbalance between the daily load curve and generation curve. In this paper, a statistic model is presented to describe daily EV charging/discharging behaviors considering the randomness of the initial state of charge (SOC) of EV batteries. The optimization problem is proposed to obtain the economic operation for the microgrid based on this model. In day-ahead scheduling, with the estimated power generation and load demand, the optimal charging/discharging scheduling of EVs during 24 h is achieved by serial quadratic programming. With the optimal charging/discharging scheduling of EVs, the daily load curve can better track the generation curve. The network loss in grid-connected operation mode and required ESS capacity in islanded operation mode are both decreased.
Highlights
LARGE-SCALE applications of Microgrids (MGs) and Electric Vehicles (EVs) are the best solutions to overcome the energy crisis and environmental pressure [1]
The initial state of charge (SOC) of EV batteries always have an element of randomness but the general pattern is influenced by the battery usage
Analysis is focused on the optimal charging/discharging scheduling of EVs in day-ahead market
Summary
LARGE-SCALE applications of Microgrids (MGs) and Electric Vehicles (EVs) are the best solutions to overcome the energy crisis and environmental pressure [1]. It is widely accepted that, as an important part of smart grid, microgrid can provide electricity for either local loads in nearby areas by optimally allocating local renewable generators, small or medium traditional power generators, and energy storage systems in islanded operation mode, or a large-scale independent power supply system in grid-connected operation mode [2,3,4,5]. G., for wind energy [8,9,10,11], solar energy [12, 13], and geothermal energy [14] In these literatures, only power or energy balancing equations in the steady state of EVs and renewable generators are applied to describe this provision in transmission grids
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