FPGA-based implementation of an adaptive notch filter used for grid synchronization of grid-connected converters

This paper presents the digital implementation of an adaptive notch filter (ANF) for the application of utility grid synchronization. Due to the nonlinear structure of the ANF, the implementation technique has a very big impact on the accuracy of the frequency estimation and the speed of convergence during transients. In this paper, three different techniques are analysed in terms of the performance and the amount of resources they require to be implemented. A comprehensive qualitative analysis is performed, to compare the different implementation techniques. The outcome of this analysis proposes the most accurate and cost-effective method of implementation for the adaptive notch filter. The performance of the different techniques is investigated by simulation. Also, the different ANF implementation techniques are implemented on a Field-Programmable Gate Array (FPGA)-based experimental prototype of a grid connected voltage source inverter. The experimental results are well aligned with the analytical results acquired from the simulations.