In this paper, a vortex search algorithm (VSA) based method designed to estimate power system harmonics and interharmonics for highly time-varying cases is presented. Time-variation in the power system is due to the nonlinear and stochastic loads such as electric arc furnaces (EAF) and it is one of the major cause of the power quality problems. The proposed algorithm is tested on both synthetic signals and also field data obtained from transmission system substations supplying EAF plants. The results are compared with other search algorithm-based methods reported in the literature and shown that VSA algorithm exhibits better estimation performance and has less computational complexity. In addition, the VSA algorithm is also tested on real field data and the results are compared with those obtained by Kalman Filtering method, which is claimed to provide fastest results in the literature. It has been shown that the proposed method has better convergence results in noisy environment with less computational complexity.