Power Fluctuations Smoothing and Soft Switching Modulation Strategy for Three Port Electric Springs

Multi-port electric spring is a typical topology for solving power quality problems caused by unstable AC-DC hybrid microgrid output from photovoltaic (PV) and wind power access, providing advantages such as flexible configuration and high power density. A dual-phase-shift (DPS) control strategy based on a three-port electric spring (TPES) with three active bridge converters is proposed. The DPS control is compared to single-phase-shifting (SPS) control, thereby reducing the return power on the supply side, increasing the range of zero voltage switching (ZVS) and reducing the PV power capacity. In addition, an autonomous power fluctuation smoothing strategy is proposed, where the TPES can smoothen suppress the fluctuations autonomously without requiring the battery to be charged or discharged, which increases the lifetime of battery. Finally, the experiment verifies the correctness and effectiveness of the theoretical analysis.