REMEDIATION OF VOLTAGE REGULATION ISSUES IN MICROGRID WITH INTERMITTENT RENEWABLE ENERGY SOURCES

Abstract

This thesis focuses on investigating voltage regulation issues in radial distribution feeder under high penetration of intermittent renewable energy sources (RES). While integrating RES into the radial distribution systems and/or microgrids offers numerous benefits, including reducing greenhouse gas emissions and enhancing energy security, however, it presents several challenges that must be addressed to ensure a smooth transition of power system from conventional sources to RES. The intermittent nature of RES systems and their high penetration level causes voltage variation and power flow reversal, leading to system instability and suboptimal performance. To address the challenges related to voltage regulation, the thesis presents a comprehensive literature review of the RES connectivity issues into the microgrids, and the technical difficulties that microgrids face due to RES intermittency. The study investigates different voltage regulator options, including OLTC transformers, DVRs, STATCOMs, and BESS, for radial feeders having high penetration of RES. New method for analysis, new control scheme for application of hybrid voltage regulators, simulation under MATLAB Simulink environment is investigated. The performance of the comprehensive system is investigated under different operating conditions, such as RES intermittency, load perturbation, and source voltage perturbations. The study explores the viability of non-intersecting control scheme for a hybrid voltage regulation technique that combines preventive and remedial methods to optimize system performance and stability. The study also investigates different hybrid combinations of two or more voltage regulation devices for maintaining the voltage profile of the feeder for the microgrid and distribution system. The investigation has been largely focused for the duo of OLTC transformer and DVR for their autonomous yet coordinated operation, through new control scheme. The control is extended to inclusion of smart grid connected viii inverters (GCI), making it third type of distributed voltage regulator, for maintaining a better voltage profile throughout the radial feeder/microgrid. Simulation results are presented, under extreme conditions such as overvoltage and light loading occurring together, and similarly undervoltage and heavy loading conditions occurring together, to verify the efficacy of the new control scheme for voltage regulator, to maintain the voltage profile of the radial feeder/microgrid. Furthermore, the thesis explores two-port ABCD based analytical approach, for determining the node voltage and branch current by dividing the whole grid into smaller sections, to handle a larger microgrid with multiple RES connected to estimate the impact on voltage levels brought on by the high penetration of RES. The method is validated on an 11-node radial microgrid with multiple RES connected to it, under uniform and non uniform sectional parameters and different operating conditions. The research focuses on the integration and control of various voltage regulators in the microgrid/distribution system in a distributed way to ensure smooth operation and minimizing the disturbances. Further the newly developed concept of analysis based on ABCD parameter is successfully applied for determining the requirement of the number of distributed voltage regulators and their correct location with capacity for an N-node radial microgrid. The theoretical results obtained are also dully validated by placing the distributed voltage regulators in the considered microgrid at estimated locations as per the developed analytical tool, to draw out smooth voltage profile of the microgrid under uniform and non-uniform feeder distribution cases. Overall, this thesis presents a comprehensive analysis of various voltage regulation techniques and their applications in microgrids with high RES penetration. The findings of this research will be useful in designing and implementing optimal voltage regulation solutions for microgrids with high RES penetration to ensure their smooth operation and optimal performance.