Evaluation of two fundamental Positive-Sequence Detectors for highly distorted and unbalanced systems

This paper presents an evaluation of the performance of two different Positive-Sequence Detectors. This evaluation is made by comparing a PLL (Phase-Locked-Loop), combined with Lagrange Multipliers Method, with an Adaptive Filter. Both algorithms aim to detect the positive sequence at the fundamental frequency on a given three-phase system voltages or currents. The purpose of this evaluation is to assess the better Positive-Sequence Detector for custom power devices, such as Active Power Filters. The comparative analysis was based on the evaluation of a series of steady state performance parameters (phase and amplitude errors, THD and unbalance) and on the response time. The tests were made to study the behavior of both approaches when working with highly distorted and unbalanced signals. This work was carried out using the computer simulation tool PSCAD/EMTDC.