Design and Research of an improved SOGI-PLL Based on Solid State Transfer Switch

Important induction motor load on ship requires that the main power supply can be switched to backup power supply stably and quickly after main power supply is lost, so as to ensure continuous and reliable operation of motor. However, Inrush current at the moment of power switching will have impact on ship’s power grid. To reduce the Inrush current, phase-locked loop needs to be added to control system. Second-order generalized integrator phase-locked loop (SOGI-PLL) is widely used in detection of grid voltage information, but the positive sequence voltage cannot be accurately extracted when grid voltage contains DC-offset, resulting in inaccurate detection of voltage information. To solve this problem, this paper proposes an improved SOGI-PLL, which can extract balanced positive sequence voltage when grid voltage is non-ideal. Applying the improved SOGI-PLL to Solid State Transfer Switch (SSTS) system, and the effectiveness is verified by simulation and experiments.