Adaptive Harmonic Compensation Strategy Based Frequency Lock Loop for Grid Connected PV System Under Abnormal Grid Voltages

This article presents a novel adaptive harmonic compensation strategy utilizing a frequency lock loop (FLL) for a single stage grid connected photovoltaic (SSGCPV) system under abnormal grid voltages. The proposed compensation strategy integrates an adaptive phase improved multiresonant (APIMR) current controller to effectively suppress grid current harmonics in the presence of distorted grid voltage caused by nonlinear loads. Moreover, an enhanced second order generalised integrator (ESOGI) FLL is integrated into the APIMR controller to enhance synchronization with the grid and eliminate frequency oscillations. The proposed compensation strategy not only addresses oscillations in active and reactive power during unbalanced grid faults but also enhances the frequency adaptability of the SSGCPV system in response to grid frequency variations. Furthermore, the proposed control strategy eliminates the need for parks transformation, thereby reducing the computational burden on the system. Realtime digital simulations using OPAL-RT OP4510 in a software in the loop environment for a 15 kW SSGCPV system are conducted to validate the effectiveness of the proposed compensation strategy.