Enhanced harmonic state estimation in unbalanced three-phase electrical grids based on the Kalman filter and physical scale-down implementation

A time-domain methodology is proposed based on Kalman filter, to determine the harmonic state estimation in three-phase electrical grids. Time-domain methodologies based on the Kalman filter need an initial solution to begin estimating the harmonic state in electrical grids. Previous methods have found this solution using simulated electrical grids; thus, the measurements taken from the simulations are synchronised only with the simulated grid model. In practical power networks, measurements taken from the grid need to be synchronised with the theoretical grid model. Synchronization between the model and measurements using the Kalman filter is proposed. This paper also proposes an alternative method to obtain the periodic steady-state solution in power grids. The method adequately processes the information given by a limited number of measurements to find the required solution. An experimental case study for a three-phase unbalanced condition with a nonlinear load and a limited number of measurements is used to validate the proposed methodology, i.e. practical data has been used instead of synthetic data. Hence, the results are validated by direct comparison of the state estimation response against the actual data recorded from the experimental laboratory implementation. The results show that using the proposed methodology, the time-domain harmonic state estimation can be efficiently applied to the analysis of practical power grids.