Influence Analysis of Oscillation Harmonics in LCC-HVDC Delivery System Based on Impedance Modeling

Given the reverse distribution of energy supply and electricity demand in China, the Line-Commuted Converter High Voltage Direct Current (LCC-HVDC) delivery system has emerged as the primary solution to transmit renewable energy over long distances. The evaluation on potential damage of the wide-band oscillations to the grid stability requires the creation of a mathematical model of the LCC-HVDC delivery system to comprehensively analyze its interaction with renewable power stations. Traditionally, it has been assumed that the long DC transmission lines would separate the sending-end and receiving-end systems, leading to the simplification of the system into a single local rectifier station connected to a DC voltage source. This oversimplification, however, lacks a theoretical basis and hence, the scope of application of the equivalent model remains undefined. This study utilizes double Fourier transform to establish the impedance model of the LCC-HVDC delivery system, taking into account the receiving-end system which includes a remote inverter station and the AC grid. The internal harmonics distribution and propagation characteristics are then explored. Finally, the influence of the receiving-end AC grid on the complete system impedance is analyzed, providing insights into the dominant factors that determine the applicability of the equivalent model, which is limited to the rectifier station only.