Fast tracking of time-varying power system frequency and harmonics using iterative-loop approaching algorithm

With the increasing use of power electronic devices in the past decade, the produced harmonic pollution to the power supply is aggravating power supply quality. The monitoring of the health state of a power network is therefore becoming an essential issue. Although conventional techniques like discrete Fourier transform or fast Fourier transform are still widely applied in industry, some limitations arise particularly under supply frequency drift and transient circumstances. The proposed iterative-loop approaching algorithm can respond to the supply frequency variation, the fundamental amplitude/phase variation, as well as the harmonics frequency amplitude/phase variation instantly and accurately. Furthermore, an abrupt change of fundamental frequency and amplitude can also be traced properly and promptly. Numerical examples supporting the performance of the proposed algorithm are presented.