Gray Encoded Harmonics Power Line Interference Cancelling Structure Using LMS and NLMS Adaptive Algorithms


  • Eduardo A. Costa
  • Sérgio J. Almeida
  • Mônica L. Matzenauer
  • Mateus B. Fonseca



LMS and NLMS adaptive filters, Gray encoding, arithmetic operators


This paper proposes the implementation of a Gray encoded structure for harmonics power line interference cancelling. The structure uses dedicated hardware architecture for the Least Mean Square (LMS) adaptive filtering algorithm, as well as its normalized version (NLMS). In the used scheme, from a 60Hz reference signal, the algorithms are able to estimate the superior harmonics, using after these results for the cancelling of interferences related to the signal of interest. In this work, the proposed adaptive filtering architectures and the harmonics generator block use a Hybrid encoding in its data buses, which is a compromise between the minimal input dependency presented by the Binary encoding and the low switching characteristic of the Gray encoding. For the Hybrid structures, new Hybrid multipliers were proposed, and the results showed that those multipliers are more efficient than the Binary ones, by presenting less power consumption in some cases. The implemented harmonic cancelling structure with the LMS and NLMS adaptive filtering architectures were validated and compared by using both Binary and Hybrid encoding. The efficiency of the implemented Hybrid structure for the cancelling of interferences was proved by reducing more power than the Binary one. By the results, we conclude that it could be practicable to implement a harmonic cancelling structure, based on LMS and NLMS adaptive filtering, operating on Hybrid encoding.