The improved 2DoFs-PLL for MMC-HVDC transmission system

The performance of a modular multilevel converter (MMC) is highly related to the three-phase phase-locked loop (PLL). presence DC component, harmonic and negative sequence component results in poor dynamic steady-state PLL, such as fundamental frequency oscillations phase estimated by PLL. In order suppress influence parameters variation disturbance grid voltage, an improved PLL with moving average filter two degrees freedom PID (2DoFs-PID) proposed. Moreover, improve margin gain margin, extra compensator pole zero introduced into 2DoFs-PLL. 2DoFs-PLL can track superior accuracy, stability, rapidity. Furthermore, methodology for design 2DoFs controller introduced, based on index integrated time absolute error. A simulated model experimental platform are established verify show that meet needs both employing 2DoFs-PID controllers.