A Cascaded Multilevel Modular Energy Router Hybrid Photovoltaic and Energy Storage With Improved Power Balance Capability

Abstract

Cascaded H-bridge (CHB) converter has become an attractive topology for future large-scale photovoltaic (PV) plants in medium-voltage microgrids. However, the unequal irradiation and aging degree of PV arrays will lead to imbalanced and inconsistent output power between the three phases. This article presents a novel approach to integrating PV and energy storage (ES) systems inherent in microgrids, utilizing a hybrid CHB-based energy router (HCHB-ER), which is configured with a limited number of submodules to connect with the centralized ES. The proposed topology can handle serious interphase power imbalance and respond to grid-side power scheduling, without the appearance of overmodulation and common-mode voltage rise caused by traditional zero-sequence voltage injection methods. Under the three major constraints from the modulation level, the centralized energy storage maximum intrapower regulation boundary and submodule configuration ratio are analyzed in detail. Additionally, the power imbalance regulation capability of the proposed HCHB-ER across various configuration ratios is thoroughly evaluated and compared with the zero-sequence injection methods. Finally, the correctness and effectiveness of the proposed strategy are verified by simulations and experiments.