Active parallel filter for DC bus and DC feeding line

In this paper a converter for the compensation of a low amplitude harmonic currents for applications requiring a common DC bus such as renewable energy networks is presented. The considerations done can be easily extended to DC feeding line. The proposed multilevel converter is able to avoid problems to devices linked to a DC bus due to low frequency harmonic currents. It is also very useful in railway applications where harmonic pollution can produce interference in the signaling systems over DC lines. The active compensator is modular, composed by multiple cells series connected and it is controlled to minimize modulation current ripple. This topology makes converter suitable for high power applications and permits to minimize the size of the switches. Simulation results demonstrate the effectiveness of the proposed solution. Moreover the performances of compensation method have been carried out from experimental results done on a prototype.