2,303 research outputs found
Data-driven Variable Speed Limit Design for Highways via Distributionally Robust Optimization
This paper introduces an optimization problem (P) and a solution strategy to
design variable-speed-limit controls for a highway that is subject to traffic
congestion and uncertain vehicle arrival and departure. By employing a finite
data-set of samples of the uncertain variables, we aim to find a data-driven
solution that has a guaranteed out-of-sample performance. In principle, such
formulation leads to an intractable problem (P) as the distribution of the
uncertainty variable is unknown. By adopting a distributionally robust
optimization approach, this work presents a tractable reformulation of (P) and
an efficient algorithm that provides a suboptimal solution that retains the
out-of-sample performance guarantee. A simulation illustrates the effectiveness
of this method.Comment: 10 pages, 2 figures, submitted to ECC 201
Storage Size Determination for Grid-Connected Photovoltaic Systems
In this paper, we study the problem of determining the size of battery
storage used in grid-connected photovoltaic (PV) systems. In our setting,
electricity is generated from PV and is used to supply the demand from loads.
Excess electricity generated from the PV can be stored in a battery to be used
later on, and electricity must be purchased from the electric grid if the PV
generation and battery discharging cannot meet the demand. Due to the
time-of-use electricity pricing, electricity can also be purchased from the
grid when the price is low, and be sold back to the grid when the price is
high. The objective is to minimize the cost associated with purchasing from (or
selling back to) the electric grid and the battery capacity loss while at the
same time satisfying the load and reducing the peak electricity purchase from
the grid. Essentially, the objective function depends on the chosen battery
size. We want to find a unique critical value (denoted as ) of the
battery size such that the total cost remains the same if the battery size is
larger than or equal to , and the cost is strictly larger if the
battery size is smaller than . We obtain a criterion for evaluating
the economic value of batteries compared to purchasing electricity from the
grid, propose lower and upper bounds on , and introduce an efficient
algorithm for calculating its value; these results are validated via
simulations.Comment: Submitted to IEEE Transactions on Sustainable Energy, June 2011; Jan
2012 (revision
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