Developing an Optimal Framework for PMU Placement Based on Active Distribution System State Estimation Considering Cost-Worth Analysis

Abstract

Due to low levels of observability and automation in active distribution networks (ADNs), the deployment of accurate measurement devices would be inevitable to increase the network observability. This work develops an optimal framework for phasor measurement unit (PMU) placement considering the accuracy of the distribution system state estimation (DSSE) process. In this regard, first, considering the significance of active power in supplying network loads, an active power sensitivity analysis is conducted in which the accuracy of active power injection at each bus is multiplied by its value of lost load. In this way, the accuracy of active power estimation could be transformed into a monetary value. Then, based on the determined sensitivity criterion, the optimal placement of PMUs has been performed with the aim of appropriate accuracy for the DSSE. On the other hand, the accuracy of the results obtained in the state estimation procedure can affect the estimation of line-loadings and lead to load shedding due to the low accuracy of estimated line-loadings. It is noteworthy that due to the high integration of distributed energy resources in distribution systems, ADNs would be prone to congestion issues. Therefore, in the next stage, this perspective is also used for determining the optimal number and location of PMUs in ADNs to improve their observability based on the operational conditions of the network. Finally, the developed algorithm is applied on the 77-bus-UK-test distribution network to investigate its effectiveness in improving the DSSE accuracy and mitigating interrupted loads. The numerical results indicate that implementing the proposed framework not only increases the DSSE accuracy but also decreases the cost of compensating the accuracy of active power by 7% compared to the typical network without PMUs. Further, the results show that the proposed model significantly mitigates the total curtailed loads due to the low accuracy of estimated line-loadings.

Fast Linear State Estimation for Unbalanced Distribution Systems Using Hybrid Measurements

“…𝒁 𝑘𝑙 𝑎𝑏𝑐 = 𝒀 𝑘𝑙 𝑎𝑏𝑐 −1 ). Thanks to the insignificant shunt susceptance in distribution feeders, it can be disregarded without introducing a considerable error into (26).…”

“…Linear DSSE (LDSSE) methods are introduced to address some of the challenges associated with NDSSE. To avoid iterative solution processes, a linear DSSE can be formulated based on measurements from µPMUs [25,26]. However, this requires the installation of a significant number of µPMUs, which is costly and complex.…”

Linear Distribution System State Estimation by Hybrid Synchronized/Unsynchronized Measurements

“…To solve (18) by WLS in (2), the proper covariance should be defined for equations in this stage. Taking the complex form of a phasor into account…”

“…A primitive solution for LDSSE harnesses a fast decoupled algorithm, where after applying some simplifications, the linearized problem is solved iteratively [16]. To avoid iteration in LDSSE, a trivial approach is to make the equation linear by installing a large number of µPMUs to cover the distribution system with enough measurement redundancy [17,18]. However, the realization of synchrophasor redundancy in distribution systems appears to be quite challenging.…”