MONITORING AND PROTECTION OF RECONFIGURABLE DISTRIBUTION NETWORKS AND MICROGRIDS USING SYNCHROPHASOR MEASUREMENTS

Abstract

The inclusion of distributed generation (DGs) in distribution networks (DNs) alters its characteristics and increases complexity. Additionally, DNs are often reconfigured with various objectives by changing status of switches, and the increased penetration of DGs may lead to more frequent switching initiatives. Therefore, the adoption of an intelligent, communication-enabled monitoring system is imperative that can provide synchronized measurement with a high reporting rate while being economical to facilitate widespread deployment. Recently, micro-phasor measurement units ( PMUs) that is advanced measurement device adhering to IEEE C37.118 standards have been proposed for contemporary DNs. Data from PMUs can be used to implement monitoring, protection, automation and control applications for DNs. It may also be employed for microgrids (MGs), which can function in two modes, i.e., grid-connected mode (GCM) and isolated mode (IM). The present research focuses on deploying PMUs and utilizing synchrophasor data from PMUs to devise monitoring and protection applications of DNs and MGs that operate in multiple configurations and incorporate the penetration of DGs, including RESs. In this work, the problem of optimal PMUs deployment in conventional DNs is addressed. The topology change due to network reconfiguration may lead to partial system observability if PMUs are deployed in accordance with single configuration constraints. Therefore, three methodologies (MPD-1,2 and 3) for optimal PMUs deployment have been presented. MPD-1 and MPD-2 utilize a linear composite objective function that embraces two conflicting targets with binary and integer variables under equality and inequality constraints. The mixed integer linear programming (MILP) approach is used to solve the formulated problem in MATLAB environment. Using MPD-1, a set of solutions have been found by changing constraints corresponding to the base configuration. The formulated objective function in MPD-2 is subjected to topological observability constraints excluding or including the PMU channel limit (CL). Simulation results and comparative analysis have been shown to depict effectiveness and specificity of the MPD-2 approach. In addition, the PMUs deployment problem has multiple solutions involving the same PMU numbers but different positions. Accordingly, a method (MPD-3) has been presented that determines multiple PMUs deployment solutions and select the best solution using three types of observability measures. i The results are presented on modified IEEE-33 node DN operating in various configurations. In each method, the obtained PMUs deployment satisfies the criterion of complete topological observability and topological independency. Estimating the configuration of the distribution network (DN) is essential for coordinated protection, reliable automation, and robust control applications. Therefore, in other work, a method has been presented that employs PMUs data stream to identify the operating configuration of the DNs. The proposed method is based on comparing synchrophasor measurement with its estimated version from load-flow. A Gaussian noise vector is added to real-time measurements to provide a realistic ambience. The proposed method has been simulated on a reconfigurable IEEE-33 node distribution network considering different test scenarios. In addition, the accuracy of the proposed algorithm has also been tested considering the failure of PMU at random location. During faults, the steady-state observability of the network using PMUs is interrupted. As a result, the traditional PMU placement scheme requires some modification to maintain the observability of the network during short-circuit faults. Furthermore, the present day DNs consists of MGs connected at different nodes. The protection of these MGs is also a challenging task. Therefore, in next work, the PMU placement problem is re-formulated considering the constraint of various nodes for achieving fault observability. Thereafter, the network is divided into the monitoring zones, and a fault detection method is proposed that utilizes synchrophasor measurements. The simulation results are presented on a reconfigurable 7-node microgrid system. The proposed method is also verified utilizing PMU complying to IEEE C37.118.1 standards available in real-time digital simulator (RTDS) on modified IEEE-33 node DN, and the results have also been compared with existing methods. In terms of the protection of power network, and as a result of technological developments, differential protection schemes are becoming popular worldwide for the protection of DNs and MGs. Therefore, a differential protection scheme has been proposed utilizing synchrophasor measurements. These measurements are taken from both ends of the line. Based on these measurements, differential phase angle (DPA) is computed to develop the scheme. The simulation studies are conducted on a 7-node microgrid considering various fault situations and network operating conditions in GCM and IM operations. The algorithm ii has also been verified on the modified IEEE-33 node DN in RTDS environment. Besides the comparative assessment, the performance in a noisy environment is also presented. Next, to overcome the shortcoming of the above differential protection scheme, an improved technique is suggested that utilizes only the current phasor measurement from PMUs to compute superimposed current differential angle (SCDA). In addition to the simulations on RTDS, the Hardware-In-the-Loop (HIL) verification of the proposed algorithm has also been performed. The research work described in this thesis is an attempt to demonstrate the use continuous data stream from PMU deployed in the network for monitoring and protection applications of future resilient reconfigurable DNs and MGs. The accomplished work is anticipated to make a small but effective contribution to the ever-expanding field of power networks.