Power System Analysis Incorporating Weather: Power Flow Analysis & Transient Stability Analysis

Abstract

<p>Climate change, evolution of power systems into complex modern systems, and advancements in disruptive technologies (distributed generation and renewable energy systems) have brought about drastic changes and challenges in the power industry, which necessitate improvements in power system analysis (PSA) in order to more critically understand power systems. The overall goal of this thesis is to improve the current state of PSA by focusing on power flow analysis (PFA) and transient stability analysis (TSA).</p> <p><br></p> <p>Currently, power system studies are neglectful of the weather conditions. As a consequence, these have associated weather-dependent errors. The research presented in this thesis, therefore, addresses the important aspect of fully incorporating weather into power system studies with a focus on PFA and TSA, with the aim of improving the current state of PSA. The incorporation of weather into power system studies is performed in this thesis by the use of a nonlinear heat balance model of overhead conductors, which relates the weather condition and loading to the conductor temperature. Since the conductor temperature is related to its resistance, a change in temperature causes the network impedance of a power network to change and hence cause the power system states to change. This ultimately affects PFA and any subsequent analysis including TSA. Initially, an overview of the existing nonlinear heat balance models utilised in the industry is presented. Then, based on the selection of a suitable heat balance model well suited for this thesis, an investigation of the important and likely impact of individual weather parameters on conductor temperature is carried out for a New Zealand (NZ) case study. For this, a sensitivity framework is derived that is utilised to analyse the sensitivity of conductor temperature to pairs of weather conditions in NZ. As a result, the weather parameters that strongly affect the conductor temperature in NZ are identified. The derived sensitivity framework serves as a tool for studying the various impacts of weather parameters on different conductors around the world that could be used to improve power system planning, operation, and analysis of utilities. </p> <p><br></p> <p>This thesis improves PFA, which is the foundation of most power system studies, by proposing and deriving two novel power flow algorithms i.e. the weather-dependent power flow (WDPF) and the time and weather-dependent power flow (TWDPF) algorithm in both complex polar and complex rectangular formulations. These algorithms incorporate the effect of weather by integrating the nonlinear heat balance model of conductors. A key distinction of the proposed algorithms is their ability to consider commonly available measured weather parameters to perform a fully-coupled weather-dependent PFA. The algorithmic differences and advantages of the proposed algorithms are also discussed in comparison to existing techniques. </p> <p><br></p> <p>Extensive simulations of the IEEE 30-bus power network utilising the WDPF and TWDPF algorithms in comparison with the traditional PF is undertaken in this thesis to highlight the accuracy and advantages of the proposed algorithms. Significant differences in power system states, power losses, conductor loadings, and conductor temperatures are observed. Also, the computational complexity of the algorithms is investigated by simulating a wide range of networks. </p> <p><br></p> <p>In addition to contributing to the improvements in PFA, an approach to perform weather-dependent TSA of single-machine infinite-bus (SMIB) system and multi-machine systems is also presented in this thesis. Therefore, this thesis also improves TSA by demonstrating the impacts of weather on TSA. Comparisons are made with existing TSA to highlight the impacts and benefits of incorporating weather information into TSA. </p>