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Analysis of Active and Passive Power Filters For Power Quality Improvement under Different Load Conditions

B.Venkata Ramana, S.Dayasagar Chowdary, G.Venkata Ratnam

In this work a new control strategy for simulation of three phase hybrid power filter for power quality improvement is adapted. This filter consists of shunt passive LC power filter and series active filter, with nonlinear balanced and unbalanced loads and also with variation in the source impedance. A new control method based on dual formulation of instantaneous reactive power vectorial theory is applied by considering a balanced and resistive load as reference load, so that the voltage waveform injected by the active filter is able to attain the objective of achieving reactive power compensation. This also helps in eliminating load current harmonics and also in balancing asymmetrical loads i.e., for achieving ideal behaviour for the set hybrid filter load, Total Harmonic Distortion (THD) is reduced and power factor is improved. This method improves passive filter compensation characteristics without depending on system impedance, avoids the danger of passive filter behaves as harmonic drain of close loads and avoiding series and / or parallel resonance problems. And compensation is also possible with variable loads without detuning the passive filter. And is applied for creating LG/LL faults at the source side. The results show that the active filter improves the compensation characteristics of the passive filter and reactive power is compensated.