Biru, Getachew(PhD)Hilawie, Ahadu2018-07-052023-11-282018-07-052023-11-282011-06http://etd.aau.edu.et/handle/12345678/6613The Ethiopian Electric Power Corporation (EEPCO) is, currently, undertaking a huge electric power generation expansion. The generation capacity under construction is about 7757 MW. This huge expansion demands existing AC transmission line upgrading and new transmission line installations. On the other hand, instability problems have occurred frequently within EEPCo system manifesting themselves in the form of system blackouts. Considering these two problems this thesis work proposes integration of Voltage Source Converter Based High Voltage Direct Current (VSC-HVDC) transmission system for improving future system stability and enhancing power transfer capability. The thesis investigates the dynamic performance improvements that can be attained through integrating VSC-HVDC transmission system. The investigation started by developing a monopolar VSC-HVDC transmission model with a complete control system on Digital Simulation and Electrical Network calculation program (DIgSILENT power factory) software. Different controllers are designed including, faster inner current controllers having transient response specifications: rise time 0.0003 s, settling time 0.000842 s; DC voltage controller having transient response specifications: rise time 0.00156 s, settling time 0.0132 s; and outer PQ controllers. Then the performance of the control system is evaluated and found to function satisfactorily at supporting bidirectional power flow and at maintaining stability during disturbances. Finally the designed VSC-HVDC link is integrated to North-Western EEPCo high voltage grid model and time domain simulations are carried out to investigate system dynamic performance improvement. It is obtained that with the proposed option the system pre-disturbance bus voltage values are improved from below 0.95 pu to 1 pu and post disturbance bus voltage values are improved from below 0.9 pu to above 0.95 pu. On the other hand system low load higher voltage values that go beyond upper limit of 1.05 are managed to come within the limit. A better damping of generators’ rotor angle oscillations is also attained showing general system dynamic performance improvement. KEY WORDS: Dynamic performance improvement, VSC-HVDC, Vector Control, North- Western EEPCo, bus voltage profiles.enDynamic performance improvementVSC-HVDCVector ControlNorth- Western EEPCoBus voltage profilesThesis