Upgrading of the Existing Bi-Pole to the New Four-Pole Back-to-Back HVDC Converter for Greater Reliability and Power Quality

Back-to-back high-voltage direct current systems are used to transfer electrical power between two asynchronous AC systems. The existing bi-pole back-to-back system (2PBTBS) can be converted into the four-pole back-to-back system (4PBTBS) to save in the required infrastructure for proposed installations. This upgrading provides four parallel 12-pulse DC circuits instead of only two 12-pulse DC circuits as in the existing 2PBTBS. The power transfer capability of each DC circuit in the proposed system is 25% of the original system capacity instead of 50% as in the existing 2PBTBS. The reliability of the proposed 4PBTBS is improved twice, and the line-to-line DC voltage levels are reduced to 50% in comparison with the existing 2PBTBS. In this study, the 4PBTBS and existing 2PBTBS are simulated using MATLAB/Simulink. Simulation result shows that the proposed 4PBTBS has four parallel 12-pules DC circuits at lower line-to-line DC voltage and higher power quality compared with the existing 2PBTBS. These results validate the performance of the proposed system obtained from upgrading the existing 2PBTBS.