STATE ESTIMATION TECHNIQUES IN DISTRIBUTION SYSTEMS

Abstract

In power system distribution system is more challenging because they are unbalanced. Real time control of system requires an estimate of the system states. In state estimation calculation requires real time measurements but in distribution system power flow, measurement meters are placed at less number of places in system. Due to less number of real measurements the system may not be completely observable so rests of the measurements excluding real measurements are added to the system as pseudo measurements. The pseudo measurements are taken into calculation by adding randomly error with converged load power flow measurement. A three-phase distribution system state estimation algorithm is used in this report based on Weighted Least Square (WLS) method. Normal equation method is used to compute the real —time states of distribution systems modeled by their actual a-b-c- phases. A current based formulation is compared with other formulations. Observabillity analysis for the proposed distribution system state estimation is discussed. The main emphasis of dissertation is to get the snapshot of the state of the distribution systems as accurate as possible, using all the available information on the system. With the aim of obtaining better, efficient and accurate state estimation of distribution system with less number of available measurements different state estimation algorithm implemented, tested and compared. In this thesis, two different state estimation techniques has implemented which mainly differed in state variables used for estimation, one technique used the voltage magnitude and angle as state variable and another technique uses the branch current magnitude and angle as state variable. Both algorithms have been designed for single phase and three phase distribution system. The single phase algorithm tested with 11-bus system and three phase algorithm tested with IEEE-34 bus system. The effect of no. of available measurements and types of available measurements in distribution system on the performance of the state estimation algorithms has also been analyzed. Based on different criterion state estimation algorithm has been compared for obtaining better, accurate and reliable performance.