Thiago Ramos Fernandes

ABSTRACT Distribution system state estimation (DSSE) is an essential tool for the effective operation and management of modern distribution systems. A common challenge in DSSE is ensuring accurate estimates despite limited real‐time measurements and high pseudo‐measurement errors. This paper presents a novel line‐wise state estimator (LW‐SE) for radial distribution systems, leveraging conic quadratic optimization to transform the non‐convex state estimation problem into a convex one. This transformation enhances the accuracy of the state estimation process. Unlike traditional methods, the LW‐SE formulation uses line impedances rather than admittances, addressing issues associated with low‐impedance branches and leading to more stable power flow representations. Furthermore, the method accommodates diverse types of measurements without requiring paired active and reactive power measurements, their equivalent forms, or phase angle measurements as inputs—while still enabling accurate phase angle estimation. Results of case studies and comparisons with traditional state estimators (T‐SE) demonstrate the effectiveness of the LW‐SE with accuracy improvement ranging from 60% to 82% in scenarios with low availability of real‐time measurements and high errors in pseudo‐measurement. In scenarios involving gross measurement errors, the LW‐SE consistently delivered lower MAPEs than the weighted least squares (WLS) and weighted least absolute value (WLAV) state estimators, while maintaining computational efficiency. These findings underscore the LW‐SE's suitability for modern distribution system applications.

Many applications of Distribution Management Systems (DMSs) are based on power flow solutions. Fast and robust power flow methods capable of accommodating systems of general topologies and the most common models of Distributed Energy Resources (DERs) are, therefore, becoming indispensable. In this context, this paper proposes contributions for the symmetrical component‐based three‐phase power flow methods for distribution system analysis. The introduction of symmetrical components in the three‐phase power flow problem allows it to be decomposed into three single‐phase problems, which can be solved iteratively. Such decomposition significantly expedites the power flow solution problem, simplifies implementation complexity, and makes way for parallel computing techniques. The accuracy and validity of the proposed method were tested on distribution test feeders of different sizes and topologies and the results of several case studies were compared with those obtained by the Sequence Newton–Raphson method, and by the OpenDSS. Contributions of the paper include: (i) A new formulation of the Sequence‐Decoupling Compensation method in terms of real‐valued matrices; (ii) a novel modelling for PV buses; (iii) a simple procedure to tackle convergence issues related to delta and ungrounded‐wye connected transformers; and (iv) a modelling for wye, closed‐ and open‐delta connected step‐voltage regulators in the sequence frame of reference.

In power system state estimation, similar to power flow, an angular reference is required in order to solve the problem providing the most likely state of the system. For single‐phase state estimators (SEs), the usual practice is to specify the angular reference at the substation bus, usually at 0°. This study discusses and presents how to specify the angular reference for three‐phase distribution systems SEs (DSSEs). As the main contributions, two different approaches for specifying the reference are presented and assessed. Additionally, the more general proposed approach is improved and a robust version, based on a reduced number of state variables, is presented. The proposed approaches are applied to three SEs commonly recommended for distribution systems. The results show that the approach based on a reduced number of state variables is a proper and general solution to specify the reference angles for three‐phase DSSEs.