Distribution System State Estimation Model Using a Reduced Quasi-Symmetric Impedance Matrix (original) (raw)
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This paper presents a new formulation for system state estimation of passive electric distribution networks. The fundamental idea discussed here is how to obtain the state of the system at maximum demand condition using three sources of information: 1) a quasi-symmetric matrix called TRX representing network structure and topology, 2) power measurements at main feeder disconnection devices and reclosers installed in the network, and 3) Energy measurements and estimated load curve of aggregate users at distribution transformers. The method is formulated with real variables for single-phase positive sequence radially operated networks. Results of the application of proposed methodology are presented using the well known IEEE 4-Node test system.
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Transition to a sustainable energy environment results in aggregated generator and load dynamics in the distribution network. State estimation is a key function in building adequate network models for on-line monitoring and analyses. The requirements of Distribution System State Estimation (DSSE) is becoming stringent because of the needs of new system modeling and operation practices associated with integration of distributed energy resources and the adoption of advanced technologies in distribution network. This paper summarizes the state of the art technology, major hurdles and challenges in DSSE development. The opportunities, paradigm shift and future research directions that could facilitate the need of DSSE are discussed.
A Review on Distribution System State Estimation
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Transition to a sustainable energy environment results in aggregated generator and load dynamics in the distribution network. State estimation is a key function in building adequate network models for online monitoring and analyzes. The requirements of distribution system state estimation (DSSE) is becoming stringent because of the needs of new system modeling and operation practices associated with integration of distributed energy resources and the adoption of advanced technologies in distribution network. This paper summarizes the state-of-the-art technology, major hurdles, and challenges in DSSE development. The opportunities, paradigm shift, and future research directions that could facilitate the need of DSSE are discussed.
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A three-phase distribution system state estimation algorithm is proposed in this paper. 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 introduced and compared with other formulations. Observability analysis for the proposed distribution system state estimation is discussed. Test results indicate that the normal equation method is applicable to the distribution system state estimation and the current based rectangular form formulation is suitable for this application.
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Large-scale integration of distributed energy resources into residential distribution feeders necessitates careful control of their operation through power flow analysis. While the knowledge of the distribution system model is crucial for this type of analysis, it is often unavailable or outdated. The recent introduction of synchrophasor technology in low-voltage distribution grids has created an unprecedented opportunity to learn this model from high-precision, time-synchronized measurements of voltage and current phasors at various locations. This paper focuses on joint estimation of model parameters (admittance values) and operational structure of a poly-phase distribution network from the available telemetry data via the lasso, a method for regression shrinkage and selection. We propose tractable convex programs capable of tackling the low rank structure of the distribution system and develop an online algorithm for early detection and localization of critical events that induce a change in the admittance matrix. The efficacy of these techniques is corroborated through power flow studies on four three-phase radial distribution systems serving real household demands.
Development and Testing of a Branch Current Based Distribution System State Estimator
The recent increase of distributed generation has forced many distribution network operators to develop distribution automation and active network management. Many active distribution network management functions need accurate real-time estimates of the network state. In this paper, a distribution network state estimation algorithm is developed and used in conjunction with coordinated voltage control. The state estimator utilizes equality constrained weighted least squares optimization and includes bad data detection. The state estimator is tested with MATLAB simulations, real-time digital simulator and in a real distribution network.
EURASIP Journal on Advances in Signal Processing, 2015
Distribution system state estimation is a fundamental tool for the management and control functions envisaged for future distribution grids. The design of accurate and efficient algorithms is essential to provide estimates compliant with the needed accuracy requirements and to allow the real-time operation of the different applications. To achieve such requirements, peculiarities of the distribution systems have to be duly taken into account. Branch current-based estimators are an efficient solution for performing state estimation in radial or weakly meshed networks. In this paper, a simple technique, which exploits the particular formulation of the branch current estimators, is proposed to deal with zero injection and mesh constraints. Tests performed on an unbalanced IEEE 123-bus network show the capability of the proposed method to further improve efficiency performance of branch current estimators.
Sustainability, 2022
This paper provides a comprehensive review of distribution system state estimation in terms of basic definition, different methods, and their application. In the last few years, the operation of distribution networks has been influenced by the installation of distributed generations. In order to control and manage an active distribution network’s performance, distribution system state estimation methods are introduced. A transmission system state estimation cannot be used directly in distribution networks since transmission and distribution networks are different due to topology configuration, the number of buses, line parameters, and the number of measurement instruments. So, the proper state estimation algorithms should be proposed according to the main distribution network features. Accuracy, computational efficiency, and practical implications should be considered in the designing of distribution state estimation techniques since technical issues and wrong decisions could emerge...
CIRED 2012 Workshop: Integration of Renewables into the Distribution Grid, 2012
Regarding the high cost of PMU units, optimal placement and minimizing of their numbers are of great importance. Also, this paper proposes a new procedure for determining the optimal placement and less numbers of PMUs in distribution network based on the best state estimation criterion. For DSE solution, combination of Nelder-Mead (NM) simplex search and Ant Colony Optimization (ACO) algorithm have been used. The hybrid method can estimate voltage phasor at each node by minimizing difference between measured and calculated values of state variables and also, it can guarantee observability of distribution system under normal operation conditions. To demonstrate the effectiveness of new procedure, simulation studies are applied on 30-bus radial test feeder. Finally, achievement results for convergence characterestic of DSE solution and estimation error of state variables with regard to the optimal placement and numbers of PMUs in distribution test feeder have been presented.