Impacts of Phase-Locked Loop and Reactive Power Control on Inertia Provision by DFIG Wind Turbine

This paper evaluates the impacts of the phase-locked loop (PLL) and reactive power control (RPC) on the inertia provision of DFIG wind turbine (WT), by taking a wide range of system loading conditions (i.e., from the reactive injection to absorption) into consideration. First, a linearized model is developed for DFIG WT to describe the motion of its internal voltage phase, and the derived motion equation provides a way for analytical estimation on DFIG WT’s inertia provision. After formulating the equivalent inertia, it is then used to conduct a character study on the equivalent inertia subject to different PLL and RPC settings. In this course, the loading condition of DFIG WT changes from the reactive injection to absorption to give a systematic study. Finally, the theoretical outcomes are validated by the simulations on a modified 3-machine, 9-node test system.