Eigenvalue analysis of subsynchronous oscillation in grid-connected PV power stations

Along with the development of modern society, the fossil fuel increasingly exhausted, and living environment and energy problem have become the top challenges in our society. It is of great significance to research and make full use of renewable energy. Fast development of photovoltaic (PV) technology in recent years strongly indicates that in medium to long term, PV power stations may become more commercially attractive that there will be large-scale implementation in many countries in the world. With the increasing capacity and penetration rate of photovoltaic (PV) power stations, subsynchronous oscillation caused by grid-connected PV power stations begin to receive the attention of researchers. Subsynchronous oscillation will have a great influence on the security and stability of power system's operation. On the basis of overall considering detailed models of important components in grid-connected PV power stations, a whole system small signal model is established. Eigenvalue and participation factor analysis are used to study subsynchronous oscillation characteristics. The eigenvalues show that a subsynchronous oscillation mode may appear in the power system with PV power stations. The participation factor analysis shows that state 1 and state 6 (voltage outer-loop controller's states) are strongly correlated in subsynchronous oscillation mode. The effects of parameters in current inter-loop controller and voltage outer-loop controller of PV inverter on synchronous oscillation have been fully studied. It is found that the subsynchronous oscillation mode is sensitive to the parameters of voltage outer-loop controller.