Seoul National University Seoul National University
The operation of conventional AC-DC converters is premised on a boosted DC-link voltage to ensure an adequate voltage margin. As a result, expanding the operating range toward a lower DC-link voltage has been overlooked. A lower DC-link voltage reduces switching losses in both the AC-DC converter and the subsequent load converter, while also enhancing low-speed efficiency in variable frequency drive applications. To facilitate low DC-link voltage control, the traditional decoupled d- and q-axis current controls operate in the overmodulation (OVM) region to maximize voltage utilization. However, operating in the OVM region causes an error between the voltage reference and the converter's output voltage, which then introduces a disturbance into the current control loop. This paper proposes the one-degree-of-freedom (1-DOF) control that utilizes the voltage angle as the sole DOF, thereby improving current control performance in low DC-link voltage region. Furthermore, the paper evaluates the voltage margin in rectification and regenerative modes and proposes an appropriate DC-link voltage reference modification strategy to maximize the voltage utilization.
.jpg "Seongwon Lee, MS (he/him/his) photo")
