State Estimation for Volt/VAR Control on Active Power Distribution Systems

This dissertation focuses on real time monitoring of Power Distribution Systems, to improve the efficiency and reliability of the distribution systems operation. First of all, the requirements or implementing the proper real time monitoring for the distribution system were reviewed. Then, the necessity of the state estimator for Active Distribution System Monitoring and Control is investigated. Main requirement for distribution systems operation is the voltage regulation. Various Volt/VAR Control (VVC) schemes are developed to provide the proper voltage profile along the feeders with presence of Photovoltaic (PV) panels. Implementing VVC schemes need to have accurate voltage estimation along the feeder at distribution level. Here, the SE has been deployed to find the operating condition of the feeder. It was shown that effective management and control of distribution systems required estimating the state of the system properly by State Estimation (SE). Implementing SE on distribution systems had its own challenges which were thoroughly discussed. Afterwards, two main approaches for Distribution State Estimation (DSE) have been discussed. Finally, Branch Current-based State Estimation (BCSE) has been introduced in details for further studies. The performance of BCSE method in the presence of measurement noises through Monte Carlo simulations due to the statistical nature of pseudo measurements has been assessed. One load estimation method based on the availability of AMI data has been implemented and tested by actual load data. The goal of this method is to improve the load estimation of the distribution transformers for distribution automation applications, such as VVC.;The Meter Placement problem on the distribution feeders is addressed in Chapter 5. First, available literature regarding this problem is reviewed, after which the problem is formulated for VVC application, especially CVR application. The heuristic approaches have been proposed, based on the extensive studies and sensitivity analyses, to obtain guidelines for placing the different types of measurements on the system. The proposed schemes have two stages. First stage starts by placing the meters by the rules. At the second stage, an efficient search scheme has been implemented to find the minimal set of measurement for VVC. These schemes are flexible in that it allows incorporation of different metering options and robustness measures. Finally, the performances of these methods are assessed on the IEEE prototype test feeder.;The last chapter deals with the concept of the robust state estimation, by detecting and identifying the topology changes on the distribution feeders. BCSE relies on the basic assumption that the topology of the system is given correctly. However, in most real world situations, the state of some switching devices is unknown, especially in the case of blown fuses. Two common topology errors taking place at the distribution feeder are explained. Following to that, the proposed algorithm, which is based on the analysis of the sum of the weighted residual for each zone of the switches and fuses, has been applied to detect and identify these topology changes. In addition, impact of topology changes on voltage estimation for VVC has been investigated.