基于LCC-HVDC的新能源-火电打捆输电系统多模态次同步相互作用分析

In high penetration of renewables and thermal power bundling system via LCC-HVDC transmission, multiple poorly-damped sub-synchronous oscillation (SSO) modes dominated by different devices may be excited and dynamically interact. To investigate the interactions, this paper introduces a systematic approach to identify these modes and decompose their respective self-/en-stabilizing damping paths from perspective of the mode-related device. Taking a photovoltaic-thermal-bundled power transmission by LCC-HVDC system for example, the impacts of thermal power output proportion and devices’ controller bandwidths on multi-mode SSO stability are analyzed. The results show that multiple SSOs, dominated respectively by SG, PV or LCC devices, could be excited at relatively low thermal power proportions. Moreover, the damping variations of these modes influence each other under different control parameters, i.e., variations in the PLL bandwidths of PV or LCC rectifier could enhance the damping in one mode while worsening another. These damping changing trends are all dominated by the interaction among PV, LCC, and SG devices. Further, the feasible stable regions of thermal power proportion under different PLL bandwidths are obtained, as well as the dominant SSO mode which constrains the small signal stability boundary. This study can give guidance on the system stable operation and parameter adjustment under varying renewable proportion conditions.