Harmonic state estimation for distribution networks using phasor measurement units

•Harmonic components are estimated with satisfactory results for power distribution networks with radial topology.•The method requires a small number of field measurements.•Uncertainties over load demand are considered as inequality constraints.•The optimization problem is solved via safety Barrier Interior Point Method.•Load pseudomeasurements are used to supplement the limited number of phasor measurements, considering a large harmonic spectrum.

This paper presents a novel approach for harmonic state estimation for unbalanced three-phase distribution systems using Phasor Measurement Units (PMUs), considering the presence of harmonic sources connected to the system. Harmonic branch currents in rectangular coordinates are the state variables to be estimated by the proposed methodology. Harmonic voltages and branch currents phasors are measured at monitored buses by PMUs. For the non-monitored buses, load pseudomeasurements are considered as inequality constraints in a proposed optimization problem solved via Safety Barrier Interior Point Method. The main contribution of the method is providing satisfactory estimation results considering non-fully observable power distribution networks with long feeders, requiring a small number of field measurements. Tests on the modified Baran and Wu's 33-bus test system are used to validate the methodology and demonstrate its effectiveness on evaluating power quality indexes, identifying harmonic sources and monitoring harmonic components and their propagation through the network.