DC-Link Voltage Control of Three-Phase AC/DC Converters with Current Constraints

For three-phase AC/DC converters, the fast dynamic response of the DC-link voltage usually involves overlarge transient grid currents. Hence, users have to choose conservative control parameters to restrict the transient current, but this choice sacrifices dynamic performances to some extent. In this paper, a single-loop structure current-constrained control strategy is proposed to achieve fast dynamic performance of the DC-link voltage. In the controller, it introduces a nonlinear variable gain, acting as the penalty term, to regulate the control action as the current approaches its limit. Rigorous stability analysis is conducted for the closed-loop control system. Test results demonstrate that the proposed method successfully constrains the current within a safe threshold while achieving fast dynamic performance.