PERFORMANCE INVESTIGATION OF PV BASED 3-LEVEL INVERTER USING 2-LEVEL INVERTERS

Abstract

This Thesis presents a photovoltaic supply system fed multilevel inverter for pump load with common mode voltage elimination, the cascaded MLI topology is needed only 12 switches and no extra clamping devices required unlike others MLIs, which make it unique and suitable modulation technique provide the reliable single stage conversion with PV system. The modulation technique used is for tracking max- imum power point and also to converts dc from PV to ac for a resistive load, inductive load and for a pump load. The unique solution to eliminate common mode voltage is also discussed, in the proposed method to eliminate common mode voltage series voltage is injected through 4-winding transformer which makes the common mode to zero. The voltage THD from the proposed method is less as compared to conventional method of common mode votage elimination. The sinu- soidal level shift PWM method and space vector pulse width modulation method are used to generate the switching pulses for the MLI while modulation index for switching of MLI is controlled by incremental conductance or perturbation and observation algorithm. The proposed topology is compared with three well known basic MLI topologies on the basis of component used. As compared to generally used two stage conversion techniques this single stage system is having higher e - ciency, reliability and reduced cost. The complete system is developed and tested on MATLAB/ Simulink, the hardware prototype is also developed and tested.