Reliability Evaluation of Hydropower Dominant Power Systems

Abstract

Hydropower is an efficient and clean way to produce electricity as it does not require fuel and does not contribute to green house gas emissions. Hydropower has increased rapidly in the past few years and is expected to increase further in the future due to its economic and environmental advantages. The variability and uncertainty with river flow characteristics in a hydro dominant power system create considerable challenges in planning adequate generation capacity to maintain acceptable reliability criteria. Unlike power system with conventional generations, hydro generations are energy limited due to seasonal and climatic variability in water restriction, and the generation capacity depends on river inflow, operating policy and load levels. Hydro dominant utilities face energy waste caused by water spillage during high inflow season or low load period. However, they do not have adequate generation capacity to meet the load during the peak load period in low inflow season. Therefore, it is very important for hydro dominant utilities to properly manage and utilize their existing facilities to maintain or enhance the system reliability. This thesis presents three methodologies to manage energy diurnally, seasonally, and yearly for the hydro dominant system. The diurnal energy management transfers energy from the off-peak load hours by operating at derated capacity, and to peak load hours by generating full capacity. The methodology recognizes the storage capability of run-of-river plants that has been ignored in the past studies and enhances system reliability from the collective benefits. Seasonal energy management of storage type hydro is performed to save and have less water spillage when water inflow is high, and use it to supply load in dry months when water inflow is low and system is not capable to supply load. The year to year energy management strategy is incorporated to save water in a normal or wet year with minimal impact on the system reliability and to maximize the availability of water based on water availability patterns in upcoming energy uncertainty year. The year to year energy management not only includes the energy uncertainty of one year time frame as existing practices, also incorporates the future year energy uncertainty from long term planning perspective. The proposed models recognize the energy and capacity characteristics of hydro plants and incorporate river flow and load variations to enhance system reliability. The approaches presented in this thesis quantify the impact of energy limitation and implications of river flow variations in hydropower planning. The presented models and strategies provide the useful information and suggestions in the operation and planning of hydropower dominant systems under hydrological uncertainties for long-term system adequacy planning. The proposed methodologies are applied to the IEEE Reliability Test System (RTS) which is modified to create a hydro dominant system.