Analysis of harmonic influence of improved PFC circuit on SS4G electric locomotive

Abstract

Compared with active filter, PFC circuit has simple structure and convenient operation. Introducing it into SS4G electric locomotive can greatly reduce system harmonics. Therefore, firstly, the corresponding PFC circuit is built, and the suppression measures of peak section and discontinuous section are proposed. By improving the discontinuous section, the waveform conduction angle is expanded from 129.564° to 162.882°. Accordingly, the current harmonic at the input side is reduced from 27.38% to 16.19%. After the voltage multiplier is further introduced, the harmonic is reduced to 15.77%. Then, the circuit is designed to absorb the high-order harmonic power in the peak section, and the harmonic is further reduced by about 0.33% to 15.44%. Two small order smoothing capacitors are connected in parallel in the load section to further absorb higher harmonics, which can reduce harmonics to 9.95%. Because the discontinuous section will also produce some spikes in the improvement process, improving the spikes can reduce the harmonics by 4.42% to 5.53%. Then the final improved circuit is introduced into SS4G circuit, and the current harmonic content of the circuit is reduced from 30.02% to 15.59%. The improved PFC circuit has achieved good results in SS4G.