摘要 : To improve the efficiency, power quality and reliability for large-scale renewable energy sources (RESs), a transformerless energy storage system (ESS) based on cascaded H-bridge converter (CHB) is presented in this study. Further... 展开 To improve the efficiency, power quality and reliability for large-scale renewable energy sources (RESs), a transformerless energy storage system (ESS) based on cascaded H-bridge converter (CHB) is presented in this study. Furthermore, the virtual synchronous generator (VSG) control is investigated to make ESS integrated to grid friendly. This study points out and discusses that the primary frequency regulation (PFR) of ESS will be deteriorated by the damping link in VSG due to the coupling problem, and to this end, the proposed virtual transient damping link (TDL) is introduced to simulate the transient and steady-state characteristics of synchronous generators (SGs) accurately without affecting the frequency regulation of ESS. In addition, the small-signal dynamic model of VSG with TDL is established, besides, the influence of VSG control parameters on system stability is analysed by the generalised root locus method and the parameters are quantitatively designed. Furthermore, a direct voltage-phase discrimination-based pre-synchronising control strategy is proposed to realise the seamless transfer between islanded and grid-connected modes for ESS. The simulation and 10 kW prototype experimental results verify the effectiveness of the proposed control strategies and the theoretical analysis. 收起