Design and Control of Transmission Level Interconnected PV System Augmented with ESS for Grid Support Functions

Abstract

For the last decade, significant growth in electricity generation from photovoltaic power systems has been recorded. The main driving forces behind this significant growth are a clean source of energy, a free source of energy, and a significant reduction in production costs. The integration of Photovoltaics into the electric power grid is introducing new challenges which depend on the interconnection point and the penetration level. Some of the major challenges which future electric power grids can face are voltage fluctuation, frequency oscillations, power oscillations, power ramp-rate, poor load following, poor power quality, decreasing system inertia, and deteriorating frequency response. The probability of the aforementioned issues will increase as the penetration of renewable energy sources (solar and wind) increases into the total power mix. In this thesis, the behavior of hybrid PV/ESS electric power plant is studied under high penetration of RESs to overcome the challenges introduced by the intermittency of RESs (PV and Wind), to maintain the stability of the electric power grids, and to explore the role of RESs into grid support functions. The control strategies are designed for PV to offer the grid support functions of, active power control, reactive power control, power ramp-rate control, power limitation control, voltage regulation at PCC by operating PV at a suboptimal point. For the grid support function of improvement in the power quality, a passive three-phase LCL filter is designed. For the ancillary service of frequency regulation, a novel tool, frequency stability prediction & enhancement (FSP&E) is proposed. The FSP&E tool tracks the system inertia online, estimate the frequency nadir for possible N-1 contingency event, estimate the reserve power form regulation sources (PV and BESS), and devise the load management strategy to ensure the secure power system operation under all operating conditions. A dynamic power system model is developed using MATLAB Simulink© to evaluate and validate the performance of the designed grid support functions. The simulation results show that the grid support functions are designed accurately and work effectively to strengthen the grid under all operating conditions.

Date of Award	Dec 2021
Original language	American English