Series Hybrid Filter for Harmonic Compensation in Three Phase System

According to IEEE-519 standard the Total Harmonic Distortion (THD) in a power system must lie within 5%, but as the demand of power electronic devices is increasing exponentially, the harmonic generation is becoming a serious problem to the power system. Conventional passive filters may not have satisfactory performance but the auto tuned active filter is a mature technology to solve this serious problem of harmonic generation, but again if active filter is used alone, it’s power rating and cost will be very high. Therefore a new approach of combined active and passive filter has been developed. The combination of active filter and passive filter is called Hybrid Filter. In this paper a hybrid system is used, in which the active filter is used in series and the passive filter is used in parallel with the line. The system is capable to remove current as well as voltage harmonics. The passive filter is tuned to eliminate the dominant current harmonics generated by nonlinear load as well as to supply the reactive power as required by the load, and the active filter improves the compensation characteristics of passive filter as well as eliminates the voltage harmonics generated due to non ideal source conditions.  Synchronous Reference Frame (SRF) is used for the generation of reference compensating current, a PI controller is used for dc voltage regulation, and for the generation of gating signals for the IGBTs used in active filter, hysteresis band controller is used. The results and efficiency of the system are verified through MATLAB simulation. The results are found to be quite satisfactory as the proposed system maintains the THD, as per the limits of IEEE-519 standard.