Heekwang Lee

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A dual-inverter with an open-end winding motor configuration is an attractive method to supply a higher voltage to a motor for electric vehicle (EV) applications. A topology utilizing two isolated dc sources is considered to reap the advantages of reliability and high voltage. Although this design may require two battery chargers, in this study, the use of(More)
In a motor control, a voltage saturation is a serious problem as a motor speed increases. To solve the problem, various field weakening methods were studied for a long time. The field weakening methods with PI current controllers are normally used, however the voltage angle control without PI current controllers is receiving attention because of its simple(More)
A dual inverter with an open-end winding motor configuration is an attractive method to supply a higher voltage to a motor for electric vehicle (EV) applications. A topology utilizing two isolated dc sources is considered to reap the advantages of reliability and high voltage. Although this design may require two battery chargers, in this study, the use of(More)
High motor saliency is required to increase the power density, and to reduce the use of permanent magnets (PM). It is a common practice to reduce the d-axis inductance (L<inf>d</inf>) as much as possible to obtain a high saliency ratio. But, we should look at the loss in the motor operation stage. Specifically in the field weakening region, a big negative(More)
Coasting is a fuel-saving driving mode that is usually active when the vehicle slows down. In an electric vehicle (EV), coasting can be achieved by letting the q-axis current to be set to zero. However, braking action often occurs at high speeds when the gas pedal is tipped off. That is, negative torque is produced while the q-axis current is equal to zero.(More)
Coasting is a deceleration driving mode not recurring to an active braking while sustaining rolling as much as possible. In an electric vehicle (EV), coasting should be realized in theory by letting the <inline-formula> <tex-math notation="LaTeX">$q$</tex-math></inline-formula>-axis current set to zero. However, unintentional braking takes place at high(More)
In multiple-input multiple-output (MIMO) broadcast channel, the lattice-reduction-aided (LRA) precoder is the modified zero-forcing beamforming (ZFBF) scheme which perturbs data symbols to reduce the transmit power. In this paper, we propose the optimal user group selection (UGS) scheme for the LRA-precoder to maximize the sum-rate in MIMO broadcast(More)
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