Subsynchronous oscillation suppression strategy of wind turbine’s phase-locked loop based on optimal damping ratio

Abstract

The dynamic characteristics of the phase-locked loop (PLL) of the wind turbine are the key to the synchronous operation of these renewable energy sources with the power grid. In this paper, the coupled dynamic model of PLL of the permanent magnet synchronous generator (PMSG)-base wind turbine and power grid is established firstly. The complex torque method is used to calculate the synchronous and damping torque coefficients in the PLL oscillation mode. Secondly, the influence of the PLL parameter, voltage at the point of common coupling (PCC), wind turbine’s output power and electrical distance on the oscillation damping behavior of the PLL is analyzed. Further, a novel control strategy based on optimal damping ratio is proposed to suppress the subsynchronous oscillation of the system caused by wind turbine’s PLL in weak interconnected grids. Finally, a simulation model of regional power network with high penetration of wind power generation is built to demonstrate the effectiveness of the proposed control scheme in suppressing the system’s subsynchronous oscillation caused by the wind turbine’s PLL.