A Design of the DC Offset Error Compensator with Prompt Response to the Grid Voltage in PLL

摘要

This study proposes the dc offset error compensation algorithm using d-q synchronous coordinate transform Phase-Locked-Loop (PLL) in single-phase grid-connected converters. The dc offset errors are caused by the process of analog to digital conversion and the distorted grid voltage. These errors must be resolved because the dc offset error should generate the estimated grid frequency error of the PLL. In conventional algorithm to compensate the DC offset, the DC offset is estimated by integrating the synchronous reference frame d-axis voltage during one period of the grid voltage. The existing algorithm has a drawback that is a slow dynamic response because monitoring the one period of the grid voltage is required. The proposed algorithm has a prompt dynamic response because the DC offset is continuously estimated by transforming the d-axis voltage to synchronous reference frame without monitoring one cycle time of the grid voltage. The proposed algorithm is verified by PSIM simulation and the experimental test.