Nonlinear Control of the Four-Wire Y-Converter for Grid Integration of 400V DC Microgrids

The increasing integration of dc microgrids (MGs) into existing ac networks necessitates optimizing the performance of power factor correction converters to ensure reliable and efficient power transfer. This paper proposes a unity-power-factor control strategy based on the synthesis of a loss-free resistor (LFR) using sliding-mode control for the Four-Wire Y-converter, which is known for its superior performance in interfacing 400V dc systems with 400V line-to-line ac networks. The proposed control strategy addresses the limitations of conventional linear controllers by enhancing dynamic performance through switching actions based on real-time system conditions. This enables precise current and voltage control with minimal delay, allowing for rapid power balancing within the dc MG. Additionally, the adoption of LFR synthesis simplifies the control structure, particularly under unbalanced ac grid conditions, where the emulated LFR of each phase can be controlled independently to enable various control modes. The effectiveness of the proposed controller is evaluated under various operating conditions, including balanced and unbalanced ac grids, as well as transient scenarios.