Enhancement to SCADA/EMS for Hybrid AC/DC Networks

• Main Author: Ayiad, Motaz
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2022
• Subjects: Communication; Gantt charts; Management; Sensors
• ISBN: 9798382400778

In the recent years, technology innovation is widely recognized as critically important for tackling climate change and energy policy objectives. Increasing energy access and reducing air pollution are two major policies for the EU and Horizon 2020 targets. EU research on renewable energy and low-carbon technologies is flooded with potentially cost-effective solutions. There are vast solar and wind farms that have been installed and connected to power grids. Furthermore, the Offshore Wind Power Plants (OWPP) construction has expanded and has received global consideration. Principally, most low-carbon technologies are connected to power transmission networks at high and ultra-high voltages. Due to long-distance issues between generation units and demand points,the High Voltage Direct Current (HVDC) technology has emerged as a potential solution to power transmission systems. The HVDC exceeds the traditional High Voltage Alternating Current (HVAC)power transfer capacity for long distances and achieves lower overall losses. However, operations integration in HVDC systems requires new monitoring tools in the Supervisory, Control and Data Acquisition (SCADA)/Energy Management Systems (EMS) to provide adequate observations about systems in AC and DC networks. The research project presented in this thesis studies the operations integration in the HVDC and its challenges at the command centre. Technically, there are a number of challenges discovered in the SCADA hardware and software components. For instance, communication architectures,measurements collection, and power applications compose several open issues. This research aims to evolve SCADA toolboxes that formulate the HVDC integration. The work presents a state estimation toolbox in the SCADA for hybrid AC/DC networks. Also, the work investigates time requirements for a centralized AC/DC SCADA. The research studies the Voltage Source Converter(VSC) in the HVDC transmission grids and introduces a precise specification for the centralized AC/DC SCADA. The research work has introduced two major contributions. The first contribution is a unified state estimator toolbox for a hybrid AC/DC network. The toolbox implements a centralized algorithm with Weighted Least Squares (WLS) method. The method merges AC and DC measurements to the Jacobi an matrix, and iterates to update there sultant matrix elements. In addition to representing AC and DC components, the new method models VSCs as power and voltage coupling components. Gaussian Mixture Model (GMM) and a bad data detector based on Largest Normalized Residual (LNR) are used to improve the WLS robustness. The GMM is applied before the WLS to increase the estimation accuracy. Also, GMM parameters are combined with LNR to provide more efficient and less time-consuming bad data detector. The unified state estimator toolbox is validated via simulations using a modified Cigre B4VSC-HVDC/AC network. Simulation results show that the unified toolbox improves state estimation accuracy and robustness against corrupted data in comparison to decoupled estimators. The second contribution is a specification for the centralized AC/DC SCADA system. The specification is the outcome of intensive investigations on the SCADA architecture, and it overcomes the lack of information on the requirements of the AC/DC SCADA. The investigations involve the timescales, communication mediums and protocols in SCADA system for power networks,and Remote Terminal Unit (RTU)s characteristics. The RTUs are studied to achieve appropriate protection and measurements collection in the HVDC. Simulations included various time delays in multilayer data transfer from sensors to the command centre while a state estimation task is performing. Simulation results show that time delays are critical to the centralized AC/DC SCADA system. Also, results indicate that the state estimator is effective in power systems that use fibre-optic communication networks.