SIMULATION AND EXPERIMENTAL VALIDATION OF 3-PHASE IMPROVED PERFORMANCE APF

Abstract

A need to reduce the harmonics and reactive power in the system has occurred mostly due to large use of power electronic apparatus. The comparison of the technologies developed for handling harmonic and reactive power reveals that the strategy of hysterisis current control provides best results with regard to THD confirming well to IEEE — 519 standards. But the major limitation is the high and variable switching frequency of operation of the devices, which-results in complexity in design of filters needed to meet the EMI standards. This led to selection of control techniques suitable for APF which employing constant switching frequency. Further to reduce the switching losses and consequent de-rating of inverters, the lowest possible switching frequency is desired. The improvement in the performance of APF can also be obtained by designing the passive filter to increase the bandwidth. The design aspects of these hybrid filters have also been discussed briefly. The size of the passive filters depends and increases on the power handling capacity. This thesis aims to tackle these problems using parallel combination of inverters employing compensating reference comparison with phase-shifted triangular carriers of constant frequency. The simulation and experimental validation of improvements in APF are presented with different phase-shifts in carriers and utilizing the well known concept of carrier frequency multiplication effects in Multi-Inverter system. Parallel combination of inverters has been developed and operated with two triangular carriers independently and allowing a phase shift between them to provide an improvement in APF exhibiting the frequency carrier multiplication effect to the resultant twin inverter based APF. A simulation model is developed in MATLAB for different topologies and control strategies to compare the results and to obtain the performance comparison. Transient analysis has also been done using simulation by suddenly changing the load. A prototype is made to know the performance of the proposed active power filter.