Optimized Power Quality and Fast Energy Saving Strategies in Distribution Systems Using Unified Power Quality Conditioner

This thesis addresses voltage issues in power distribution networks with high penetration of Distributed Generation (DG) by introducing a novel Unified Power Quality Conditioner (UPQC) based on fast energy storage. The integration of distributed generation technology, essential for smart grid development, significantly alters power distribution systems. In networks with DG, fluctuations in power output from DGs can cause voltage quality problems such as voltage sags, fluctuations, and interruptions. To enhance the compensation capabilities of the UPQC and reduce grid current fluctuations during power regulation, an improved UPQC topology is proposed. Utilizing super capacitors, which offer high power density, large electrostatic capacity, and long cycle life, in conjunction with a bidirectional DC/DC converter, this energy storage system is connected in parallel with the DC link. This configuration maintains a constant DC voltage and can serve as a backup UPS. A low-frequency mathematical model of the conditioner is developed using d-q coordinates based on the statespace method, and a non-PLL compensation detection method is employed. Additionally, the thesis provides both voltage and current compensation control strategies and energy management schemes for the super capacitors. The proposed fast energy storage system incorporates low-inductance rail switches and capacitors configured in a low-inductance stage, stacked in series for the required voltage, and parallel units for the needed system inductance and stored energy. This innovation eliminates the necessity for large water transfer capacitors. The structural principles and control strategies are refined using MATLAB/SIMULINK.