136 research outputs found
Ayuda, Inc. v. Thornburgh: Did Congress Give the Executive Branch Free Rein to Define the Scope of Legislation
The Note argues that the Ayuda decision is inconsistent with the congressional intent behind IRCA and prior case law. The Note further argues that the purposes underlying IRCA will best be served by prompt judicial resolution of policy disputes about legalization
Optimal Power Flow in Stand-alone DC Microgrids
Direct-current microgrids (DC-MGs) can operate in either grid-connected or
stand-alone mode. In particular, stand-alone DC-MG has many distinct
applications. However, the optimal power flow problem of a stand-alone DC-MG is
inherently non-convex. In this paper, the optimal power flow (OPF) problem of
DC-MG is investigated considering convex relaxation based on second-order cone
programming (SOCP). Mild assumptions are proposed to guarantee the exactness of
relaxation, which only require uniform nodal voltage upper bounds and positive
network loss. Furthermore, it is revealed that the exactness of SOCP relaxation
of DC-MGs does not rely on either topology or operating mode of DC-MGs, and an
optimal solution must be unique if it exists. If line constraints are
considered, the exactness of SOCP relaxation may not hold. In this regard, two
heuristic methods are proposed to give approximate solutions. Simulations are
conducted to confirm the theoretic results
Distributed Optimal Frequency Control Considering a Nonlinear Network-Preserving Model
This paper addresses the distributed optimal frequency control of power
systems considering a network-preserving model with nonlinear power flows and
excitation voltage dynamics. Salient features of the proposed distributed
control strategy are fourfold: i) nonlinearity is considered to cope with large
disturbances; ii) only a part of generators are controllable; iii) no load
measurement is required; iv) communication connectivity is required only for
the controllable generators. To this end, benefiting from the concept of
'virtual load demand', we first design the distributed controller for the
controllable generators by leveraging the primal-dual decomposition technique.
We then propose a method to estimate the virtual load demand of each
controllable generator based on local frequencies. We derive incremental
passivity conditions for the uncontrollable generators. Finally, we prove that
the closed-loop system is asymptotically stable and its equilibrium attains the
optimal solution to the associated economic dispatch problem. Simulations,
including small and large-disturbance scenarios, are carried on the New England
system, demonstrating the effectiveness of our design
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