A Novel Adaptive Bandpass Filter Based PLL for Grid Synchronization Under Distorted Grid Conditions

Abstract

In the current scenario, the integration of a renewable energy sources (RESs) with variable power production into power grids requires a power converter with robust control techniques. In order to formulate the control strategy meticulously, a fast and accurate detection of grid phase angle is necessary. Hence, frequency and phase angle of the grid voltages are vital components to guarantee the synchronization for grid-connected converter. Additionally, a phase locked loop (PLL)-based control algorithm is needed to generate the accurate reference current for the grid-connected converter. The conventional adaptive low-pass filter (ALPF)-based PLL is used as a synchronization tool but requires more settling time during interharmonics and dc offset grid conditions in addition to higher THD of the grid currents/voltages. In this article, a novel adaptive bandpass filter (ABPF) is proposed and can be added as a prefilter of PLL structures without modifying the base design. To confirm the adaptive nature of the ABPF the gradient algorithm is used to maximize the normalized mean square output and self-adjust the center frequency of the filter during distorted grid conditions. The 3-D surface plot can be used to provide the system stability and dynamic response of the filter. For effectiveness of the proposed study, ABPF is added as prefilter to dq-frame cascaded delayed signal cancellation (dqCDSC) PLL and MAF PLL and detailed comparative study is made in this article. In addition to that, the proposed ABPF-based dqCDSC PLL and ABPF-based MAF PLL methods are analyzed using MATLAB/Simulink environment. Finally, performance is tested with real-time via dSPACE-1104 hardware-in-loop (HIL) simulation.