PhD Ritu-Raj Shrivastwa: “Enhancement of flexibility of conventional Hydro Power Plants for faster ramp-rate using Energy Storage Systems


With the current growth in more electrical power generation alongside the rising concerns of the climatic degradation, green push for more Renewable Energy Sources (RESs) is increasing simultaneously. The dependency of the RESs like solar photovoltaics and wind power on nature, makes the generation from these sources highly intermittent. In addition to that, these sources of electric power do not use the synchronous machines for generation. Power plants using synchronous generators add to the inertia of grid. However, with the addition of more and more RESs in the grid, the overall inertia of the grid is reducing gradually and will tend to do so with further increase of the RES share in the energy mix. The loss of inertia of the grid leads to challenges associated to the power stability and security. To mitigate the impacts of the increasing RES mix, several services commonly known as the ancillary services are gaining momentum globally with different power generation, transmission, and distribution companies. These grid services can be broadly classified in frequency services and voltage services. The frequency services are controlled through the control of the active power and that of voltage services are controlled using the reactive power. Various research works are being conducted globally to propose different methods to implement these services with different means. Of one such mean is through increasing the flexibility of the power system. Towards increasing the flexibility, the conventional power sources can play a very important role, however, due the physical constraints, not all conventional power plants are able to cater the fast-changing grid demands with the changing grid dynamics due to the high penetration of RESs. In such case, hydro power plants (HPPs) can be the most prominent solution as they are both renewable and capable of following the load demand by controlling its output. Also, with HPPs supplying power to the mankind for significantly long time, several research and development work have been conducted to make their functionalities and operations more and more efficient. Identifying the growing need of flexibility and the climatic concerns, it becomes imperative to enhance the capabilities of the generation sources which are less polluting and at the same time can cater the desired services. Towards an attempt to that, this work is dedicated to enhancing the flexibility of conventional HPPs by increasing their reaction time through the improvement in their ramp rates with the help of an energy storage system (ESS). In the process of achieving this goal, mathematical models of both ESS and HPP are developed. Objectives relating to the ramp rate enhancement are described in detail. With these objectives, two different optimization approaches are acquired where in one, only the operation of the ESS is optimized to meet the objectives and in the second, operations of both the ESS and HPP are optimized. Several scenarios have been identified for which the test is to be conducted. Also, to analyze the impact of the ESS sizing, different sizes have been used for each test. A comparative study is conducted for the two methods and inferences are drawn in detail in this work. On successful completion of the simulation process and interpretation of the results, the results are then used to perform and experimentation with a Power Hardware-In-Loop (PHIL) where a supervisor and controller is designed to control the physical hydraulic circuit with the parameters from the simulation process. On successful completion of the experiments, the data from the simulation and the experiment are compared and inferences are drawn which indicate the possibility of increasing the ramp rate of the HPP using an ESS.

Director of thesis: Professor Seddik BACHA

Co-director of thesis: Dr. Ahmad HABLY