E-STATCOM Damping for Secondary Voltage Control of Wind Power Plants Considering Communication Delays

Secondary voltage control at the point of connection of wind power plant (WPP) is required to support the grid, nevertheless considerable communication delays between wind turbine generators and the WPP controllers may cause instability. Grid-forming energy-storage enhanced STATCOM (E-STATCOM) is a commercialized solution for WPP connected to a weak grid, regarding the sub-synchronous oscillation damping of primary control. However, the interactions between the E-STATCOM grid forming control and the WPP secondary controller affected by communication delays have been scarcely investigated. In this paper, the primary control and secondary voltage control of WPP are modeled in state-space, and their interactions with the E-STATCOM are investigated. Based on that, a system-level stability assessment based on the state-space model is presented including the communication delay, the short circuit ratio, and the grid voltage operation points. Finally, the findings are verified through the case study.