MODEL AND ANALYSIS OF THE IEEE 9-BUS SMART GRID INCORPORATING SOLID-STATE TRANSFORMERS (SSTS) UNDER VARYING LOAD CONDITIONS

The traditional Low-Frequency Transformers (LFTs) have been used for a long time as fundamental units in electrical power systems, offering galvanic isolation and voltage transformation in both transmission and distribution power systems. Nevertheless, since they are constrained by their size, unidirectional operation, and inability to be flexible, they become less and less suitable to the contemporary smart grids that require bidirectional power flow, incorporation of renewable energy sources, and adaptable voltage regulation. The paper is a modelling and analysis of the behaviour of the IEEE 9-Bus smart grid with Solid-State Transformers (SSTs) under different load conditions to provide a baseline against which the smart grid could be compared. The system was improved with the renewable sources of energy, energy storage and monitoring systems using MATLAB/Simulink to provide a realistic setting of a smart grid. The study is an analysis of the performance parameters; namely energy efficiency and Voltage Stability Index (VSI) of simulated active and reactive power flows across buses. Results of the study shows that the system achieves an overall efficiency of 85.8%, with significant variation across transmission lines considering Line 4-6, therefore demonstrating the highest efficiency (95.31%) and stability, while Lines 4-5, 6-9, and 3-9 exhibit vulnerability to voltage collapse with VSI values approaching or exceeding unity. The results show that there is an apparent trade-off between efficiency and voltage stability with increase in load demand, and it indicates the operational constraint of traditional transformers in smart grid usage. The paper finds that the incorporation of Solid-State Transformers can greatly benefit grid functionality in converting energy more efficiently, more dependably and more controllably and hence meet the changing demands of intelligent, renewable-integrated power grids.