14,131 research outputs found
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
Development of Automated Calibration Methodology for Last Generation of Diesel Automotive Powertrains
L'abstract Ăš presente nell'allegato / the abstract is in the attachmen
Control Strategies for Open-End Winding Drives Operating in the Flux-Weakening Region
This paper presents and compares control strategies for three-phase open-end winding drives operating in the flux-weakening region. A six-leg inverter with a single dc-link is associated with the machine in order to use a single energy source. With this topology, the zero-sequence circuit has to be considered since the zero-sequence current can circulate in the windings. Therefore, conventional over-modulation strategies are not appropriate when the machine enters in the flux-weakening region. A few solutions dealing with the zero-sequence circuit have been proposed in literature. They use a modified space vector modulation or a conventional modulation with additional voltage limitations. The paper describes the aforementioned strategies and then a new strategy is proposed. This new strategy takes into account the magnitudes and phase angles of the voltage harmonic components. This yields better voltage utilization in the dq frame. Furthermore, inverter saturation is avoided in the zero-sequence frame and therefore zero-sequence current control is maintained. Three methods are implemented on a test bed composed of a three-phase permanent-magnet synchronous machine, a six-leg inverter and a hybrid DSP/FPGA controller. Experimental results are presented and compared for all strategies. A performance analysis is conducted as regards the region of operation and the machine parameters.Projet SOFRACI/FU
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