Practical Considerations in the Design of Distribution State Estimation Techniques

Distribution state estimation is crucial for planning and operation of active distribution networks. This paper extends two state-of-the-art state estimation techniques, namely Weighted Least Squares (WLS) and Ensemble Kalman Filter (EnKF), to unbalanced three-phase distribution networks. These networks are assumed to be equipped with smart meters and distribution- level phasor measurement units (D-PMUs), which are capable of measuring voltage and current phasors. We evaluate the two state estimation methods through extensive simulations in realistic settings where the secondary (low voltage) distribution system is accurately modelled, D-PMUs are installed only at a small number of buses in the primary system, and their measurements are noisy and become available for state estimation after a certain delay. Our results indicate that both methods achieve a sufficiently low error despite the small number of installed D-PMUs, and while EnKF outperforms WLS in some scenarios, the difference between the results gets smaller with more accurate D-PMU measurements. When both voltage and current phasor measurements are available, WLS yields more accurate results under realistic assumptions and is therefore more suitable for real-world applications.