Digital Implementation Analysis of PRBS Impedance Shaping Algorithm to Estimate Multi-Sequence and Multi-Harmonic Systems

The increased grid configuration variability and, among others, the massive integration of renewable energies, have created a challenging scenario for power converters. Due to this fact, active impedance estimation is an interesting characteristic that will allow power converter online control tuning and/or stability analysis. Pseudo Random Binary Sequence (PRBS) injection is one the most interesting and proposed methods in the literature to obtain this impedance estimation. Many papers use impedance estimation on dedicated power converters, or they often overlook the digital and power hardware constraints that power converters must meet. This is especially important in high-power converters, where low switching and control frequencies are used. This paper defines and proposes an implementation and design method for PRBS injection considering the abovementioned constraints. The proposed method is aimed to be implemented in an already operating converter, thus adding the impedance estimation as one additional functionality of the converter. Therefore, no dedicated power converter to estimate the grid frequency is required. Multi-harmonic and multi-sequence impedance estimation is also analyzed, thus demonstrating the ability of the proposed method to operate under highly variable and demanding grid conditions. The analysis is validated via simulation results in different case scenarios.