DHOGI-QT2-PLL Based Control Scheme for Seamless Mode Transfer in Hybrid Shipboard Microgrid under Adverse Grid Conditions

Recent advancements in consumer applications have focused on utilizing new technology such as solar photovoltaic array (SPVA) and battery energy storage (BES), and innovative operational tactics to increase energy efficiency and minimize fossil fuel emissions. This paper presents a novel phase-locked loop (PLL) structure for synchronization of a hybrid shipboard microgrid (HSMG) with a diesel generator (DG) and port grid under different operating conditions, resulting in an uninterruptible power to loads. Dual high-order generalized integral based quasi type-2 phase-locked loop (DHOGI-QT2-PLL) predicts fundamental frequency positive sequence component, phase angle, and frequency while attenuating fundamental frequency negative sequence component, DC-offset component, and harmonic distortions. Presented PLL performs better than other conventional PLLs under abnormal grid circumstances. Prefilter HOGI method is also utilized to mitigate power quality issues and provide load compensation capabilities. It ensures that the point of common coupling (PCC) voltage remains sinusoidal, making HSMG immune to any load current distortions. Furthermore, it eliminates DC-offsets inherent in detected signals, improving its filtering capability. Simulation results and small-scale experiments verify seamless mode transfer amid non-ideal grid conditions, making the PLL reliable for ship and other commercial uses. Experimental results illustrate that during autonomous mode, the total harmonic distortion (THD) of PCC voltage is 1.94%. In grid-tied mode, THD values for grid current and PCC voltage are 3.08% and 2.39%, respectively. In contrast, during DG-connected mode, the DG set current, and PCC voltage have THDs of 2.49% and 1.81%, respectively, fulfilling IEC 60092-101 and IEEE 519 standards.