An improved second order generalized integrators phase locked loop for flexible DC transmission

Abstract

Accurate and fast phase locking is the primary condition for flexible DC transmission to realize reliable control. When the power grid is unbalanced or contains high-order harmonics, the traditional second order generalized integrator (SOGI) itself has the defect of strong dependence on the input signal frequency. Therefore, this paper proposes an improved phase-locked loops (PLL), which introduces moving average filter into the SOGI structure to filter out higher harmonics. The improved SOGI-PLL is simulated and analyzed under grid voltage unbalance and high harmonics. The results show that the improved SOGI-PLL has well grid adaptability.

Keywords

• Second order generalized integrator (SOGI)
• Phase-locked loops (PLL)
• Unbalanced voltage
• Harmonics