Design and analysis of an active filter based sinusoidal input current resonant inverter

Abstract

Harmonic pollution has become a serious problem in power systems due to non linear loads connected to the utility line. The injected harmonics can result in a low power factor and various other problems such as: voltage distortion, heating of transformers and reduction of system efficiency etc. In order to prevent harmonic currents from entering the utility system, corrective measures (e.g. active filtering) can be adopted within the power electronic converter that would result almost sinusoidal currents at nearly unity power factor. In this work, a single phase full bridge rectifier will supply the dc input for a high frequency resonant inverter from the utility 50 Hz ac supply. The inverter will be switched so as to produce an output with 40 kHz frequency. In between the rectifier inverter stage a Boost configuration active filtering scheme has been used to improve the power factor and to make the input ac current wave-shape nearly sinusoidal. Input current and power factor improvement using boost rectifier is common for ordinary passive loads. In this thesis, the rectifier output do not directly feed the load, rather it has another conversion stage in the form of a resonant inverter. So, the rectifier load is an inverter and passive element combination. Hence, the design and implementation of boost rectifier filtering technique is different from the reported works. In the resonant inverter, the load and rest of the series element in the circuit have to be resonating. The complete circuit has been studied by simulation in this work so as to obtain the design procedures of a boost rectifier filter for a resonant inverter load to a rectifier. The study provides an alternative for passive filters for input current shaping of rectifier - resonant inverter circuit together with improved input power factor.