State Estimation in Medium Voltage Distribution Networks

Abstract

Transition from fossil fuels to sustainable sources of energy like wind and solar is the need of the hour. All over the globe, plans are in motion to achieve this goal. This implies addition of new elements to the grid in the form of Distributed Energy Resources (DERs). These affect the working of distribution grids and to ensure reliable as well as safe operation, it is important to keep a track on the grid’s state regularly which is essential to a Distribution System Operator (DSO). For this very reason, Distribution System State Estimator (DSSE) has been introduced and has been a prominent topic of interest which has been discussed in literature over the past two decades. Because of lack in observability of the network owing to unavailability of measurements and the stochastic load profiles of the distribution network, DSSE poses its own challenges. For this very reason, it is necessary to validate the working of a suitable DSSE that is affected by the continuous changes in the grid. By selecting a suitable algorithm, this thesis attempts to solve the observability issue by introduction of pseudo-measurements. The work in this thesis comprises of sensitivity analysis of Weighted Least Squares(WLS) algorithm tested on two networks in the Netherlands; a synthetic model of an anonymized distribution network and a part of Stedin’s distribution network which has limited measuring devices data available. The percentage of pseudo-measurements is varied to determine the state estimator’s accuracy. Also the statistical validity of the algorithm against measures like bias and consistency is determined with the help of scenarios generated by using Latin Hypercube Sampling (LHS). The results obtained prove the effectiveness of the selected algorithm for DSSE and are important for the DSOs to make critical decisions when needed for grid operation.