Distributed Voltage Regulation and Grid Connection of Renewable Energy Sources

The installation of renewable energy sources in grid connected distribution network introduces several challenges on power reliability that include voltage regulation and fault protection. When residential renewable energy sources like rooftop solar panels produce more energy than the local load demand, voltage rises and reverse power phenomena occurs. The overvoltage issues can be controlled by proper management of reactive power flow. A novel reactive power scheduler algorithm for the distributed voltage regulation with PQ inverters is proposed in this dissertation. Based on the reactive power scheduler, a new approach to achieve voltage regulation in grid connected distribution system through appropriate control of the renewable energy systems has been developed. PQ inverters capable of producing the reactive power are used to either achieve local voltage regulation or deliver the reactive power commanded by the voltage regulator loop located in the upper hierarchy of the grid management system. The proposed PQ scheduler and PQ inverters will work harmoniously in the local distribution controller with minimum communication interface. The proposed control techniques achieve efficient utilization of the PQ inverters with maximum efficiency. Also a reactive power management based on inverter's capacity and sensitivity to the critical bus in a radial low voltage distribution network is presented. This method improves the voltage regulation of distributed system with high penetration of renewable energy sources while utilizing the inverter's reactive power capacity more efficiently.;The control of the real and reactive power for grid connected distributed sources requires accurate phase information of the utility voltage. For large renewable energy systems such as solar and onshore or offshore wind or wave energy there is a need for synchronization with the frequency and phase angle of the single phase or three-phase grid. The most commonly used and easily implementable algorithm for grid synchronization is the phase locked loop (PLL) technique. The power grid in rural distribution side is not clean and typically contaminated with imperfections like harmonics. For three-phase systems, the other imperfection of the grid that needs to be eliminated before feeding the grid voltage to PLL is the voltage unbalance. The proposed algorithm demonstrates a method to eliminate imperfections from both the three-phase and single-phase grid voltage to improve the steady state performance of grid synchronization with high bandwidth PLL.;Along with the distribution system, challenges associated with the transmission of large offshore renewable energy sources like offshore wave park of several hundred megawatt is a challenge for renewable resources. An ocean compressed air energy storage (OCAES) system is being considered as one of the options for utility scale energy storage for off-shore wave energy based renewable power generation. The power transmission requirements for the offshore renewable energy system with storage has also been addressed in this research.