Detection of voltage sag using unscented Kalman smoother

A novel method based on Kalman algorithm is proposed in this paper to estimate the amplitude and the time duration of voltage sag in power systems. The new method uses the unscented transform and the RTS algorithm to have a smoother and optimal tracking response. A nonlinear model of the system is developed and the mathematics of the method is derived for a supposed power signal. The algorithm is simulated in MATLAB with the assumption of a measured voltage with low-order harmonics and in presence of a noise with SNR of 10. Simulation results show that the proposed method performs with a smooth, fast dynamic and tracking response in present of noise and harmonics. The accuracy of the method is also better in comparison with other Kalman based algorithms.