“Design & Control of Distributed Generations for Micro-Grid Applications”

Abstract

Climate change, its influence on the environment, and natural resources scarcity necessitate scientific research and creative technical solutions for a modern power system. This research aims to develop scientific and technological approaches to “green” technologies, which are environmentally beneficial and long-lasting. Energy and power supply are major priorities. The design and control of distributed power generation systems for micro grid applications was the prime focus of this thesis. A 20 KW micro grid is designed to operate in both modes, albeit primarily in the isolated mode, where solar photovoltaic, wind energy, and battery energy storage modules are included. Maximum Power Point tracking (MPPT) was used to obtain the highest power production from solar photovoltaic and wind energy sources. We used lithium-ion batteries of nominal 48V to store energy produced by PV and wind systems. To maintain a constant voltage of 220V on the DC bus, bi-directional converters were used to control charging and discharging process. The inverter, which is based on a voltage sourced inverter (VSI) was used for supplying power to the AC load. Novel control approach methods were used to maintain power quality and frequency resynchronization. Synchronous reference frame theory (D-Q) with voltage oriented dual control was applied as a control algorithm. Bio inspired metaheuristic technique Particle swarm optimization (PSO) was applied for PID tuning. Islanded mode and grid feeding conditions of micro grids were analyzed, discussed and presented. The results reveal that the system performs satisfactorily under varying generation and load consumption. The PV module consists of total 14 parallel strings and the series connected module per string was set at 6. The output variations were observed from 13KW to 21KW with variations of irradiance of and temperature. The wind power output was 6 KW to 2KW with variations of Speed 12- 8m/s. Lithium-ion batteries rated 420Ah with a nominal discharge current of 182.6887A were used with a normal voltage of 48V. The load variations used were 5KW to 45KW. Higher order filter (LCL filter) was utilized to enhance power quality and performance of two different micro grid cases (i) Islanded mode and (ii) Grid feeding mode was analyzed. This research has a significant impact on the development of micro grids.