Analysis on harmonic amplification characteristics of urban transmission network with multi-infeed DC system

Abstract

For harmonic amplification problems appearing in harmonic interaction process of DC terminals in urban transmission network with multi-infeed DC (MIDC) system, a harmonic amplification decoupling method based on modal analysis is proposed. Considering influence of harmonic amplification on node associated with system structure parameters and harmonic disturbance, node observation factor is proposed to determine nodes prone to be affected by harmonic amplification. Noticing that there exists difference in excitation degree of harmonic amplification among DC terminals' harmonic sources, harmonic source excitation factor is introduced to evaluate their effects. Focusing on use of HV long cables in urban transmission network, influence caused by distributed cable capacitances cannot be ignored. Therefore, element modal sensitivity is proposed to evaluate inductance-capacitance coupling effect between cables and inductive elements in the system. The proposed method is applied to an MIDC urban transmission network. The areas prone to be affected by harmonic amplification and contribution of harmonic source in each DC terminal are determined. Simulation results reveal influence rule of major cable length on harmonic amplification, providing a reference for cable planning of urban transmission network.