Robust Design Scheme of C-Type Filter Considering Harmonic Dynamic Characteristics of Traction Power Supply System

The passive filters are widely used in the harmonic control of traction power supply system. However, high-speed trains have many types and frequent working conditions, which result in random dynamic characteristics of the harmonic spectrum of the trains. Moreover, the rapid change in harmonic injection position leads to changes in the harmonic transmission characteristics of the system. So it is difficult for passive filters to fully compensate the harmonics. Meanwhile, the existing method adopts an approximate tuning-frequency calculation formula, which makes it difficult to accurately control its filtering performance. First of all, by deriving an accurate tuning-frequency expression, this study reveals the influence of component parameters on the tuning-frequency and the possibility of tuning-frequency disappearance. Subsequently, based on the impedance-frequency index, which can describe the overall distribution of harmonics, the improved firefly algorithm is used to obtain a robust optimization design of the parameters of the C-type filter. The calculation example analysis shows that the proposed scheme has strong adaptability to harmonic random dynamic characteristics and a better filtering effect than the existing design methods, which is more suitable for a traction power supply system with strong harmonic random dynamic characteristics.