Design and Implementation of Quasi Switched Boost Inverters with Enhanced Boost Capability

Abstract

To meet the increased energy demand, renewable energy sources (RES) are becoming more and more popular. Among them in India, due to the ecological factors, more attention is being paid to green energy harvesting from solar photovoltaics (PV).Generally, the dc voltage harvested from solar panels is not enough to meet the grid voltage and the dc voltage availed from solar panels needs to be boosted using a conventional dc/dc boost converter before feeding it for inversion. It forms a two stage boost inversion system and it has certain disadvantages. Recently, to avoid the drawbacks of two stage boost inversion system, considerable attention is given towards single stage boost inversion system for on-grid PV systems.The main focus of this research work is to design single stage quasi switched boost inverter (qSBI) topologies to interface the low voltage renewable dc sources such as PV and fuel cells to the alternating loads of low/medium power ratings. The first contribution of the research is to implement a novel dual dc voltage source based qSBI for renewable energy applications. The principle of operation of the dual qSBI (DqSBI) along with the simple boost control (SBC) technique is presented in detail. A prototype is made with the dual input dc voltage sources of 24 V and 12 V respectively, which is able to provide a boosted dc voltage of 345 V and single phase ac output voltage of 110 V (rms) with accepted total harmonic distortion (THD) levels. The performance of the proposed DqSBI is compared with the existing qSBI topologies.The next contribution is to implement a new single phase switched capacitor based cascaded five level qSBI. A modified phase shifted sinusoidal pulse width modulation (PS-PWM) technique is used to generate the switching pulses for the power devices.The operating principle, steady state waveforms, design procedure, experimental results and performance comparison with a five level qSBI topology are explored in detail to validate the proposed concept