A nonlinear least-squares approach for measuring the power system frequency is presented, wherein the voltage at the point of common coupling is modelled using the Fourier series. The fundamental frequency is estimated by performing a one-dimensional search over the range of allowed frequency variation. The robustness of this algorithm is studied and validated by hardware implementation using an FPGA. The performance of this method is also compared with that of the phase-locked loop. © 2008 The Institution of Engineering and Technology.