Auxiliary Power Supply Startup Evaluation and Improvement of the Input-series System with Small Submodule Capacitances

Input-series systems are prevalent for industrial applications for satisfying the high input-voltage requirement. In addition to their topology and modulation design, the auxiliary power supply (APS) design for powering their controlling system is also significant for the safety and reliability. In general, the internal APS is preferred for facilitating the modular design and easing common mode noise and insulation problems, which in the meantime brings about the internal APS startup problem of submodules in practice. For the input-series systems with the large submodule capacitances, the voltage oscillation problem caused by APSs being out-of-sync is less severe. However, it becomes significant for those with small submodule capacitances, which is rarely reported before. Therefore, based on a half-bridge converter equipped with self-powered gate drivers as a targeted input-series system, in this paper, a simulation model is established to evaluate the influence of parameters of passive components on the APS startup process. Further, a two-stage startup scheme and hardware design are proposed to ease the voltage oscillation without increasing the losses and sizes of passive components. Finally, the experiments are conducted to verify the effectiveness.