A Novel CHB-Based Photovoltaic Grid-Tied System Integration of Centralized Energy Storage and Its Power Security Domain

Due to differences of solar irradiance, ambient temperatures, or inconsistent degradation of photovoltaic (PV) modules, the unbalanced output power between cascaded H-bridge (CHB) legs will lead to the unbalanced or even distorted grid currents between three phases. This article proposes a novel CHB-based PV grid-tied system integrating centralized energy storage (CHB-PV/ES), which can realize power balanced operation by utilizing the centralized energy storage (ES) interconnecting the CHB three-phase sub-modules (SMs) by isolated DC/DC converter. In addition, the centralized ES group can facilitate the regulation between grid-tied power references and PV power generation, such as stabilizing the power injected into the grid by smoothing the PV power, as well as responding to changes in grid-tied power references. The configuration and security domain of PV and centralized ES SMs are critical factors for CHB-PV/ES, which are thoroughly analyzed in this article to ensure safe system operation. The simulation and experimental results validate the effectiveness of the proposed CHB-PV/ES scheme.