New combined Hybrid active filter for twelve pulse converter operating under asymmetrical operation

This work deals with the investigation of harmonics and mitigation of harmonics for the 12-pulse converter operation under asymmetrical firing angle mode. The performance of converter is analyzed in unequal firing angle mode and different harmonic patterns are studied. It was found that under equal firing angle the both converter - each six pulse is operating as a twelve pulse converter and the harmonic pattern is as per twelve pulse converter, but if they operate in unequal firing angle mode, the harmonic pattern is as per six pulse converter. To mitigate the harmonics the performance of the converter with passive filter and Hybrid active filter using SRF based algorithm is simulated and the results obtained are as per the IEEE standard. A combined hybrid filter which is a combination of two hybrid filter is simulated using MATLAB. In which one filter is connected in series with the supply and other is connected in series with passive filter. The performance of the supply current harmonics and supply voltage harmonics and THD at converter input terminal is compared with the Series Hybrid Active filter and found that the THD is much lower.