Single Phase Transformerless Switched Capacitor Multi Level Inverter for Solar PV Applications

Multilevel inverters (MLIs) have been proposed for the purpose of increase power level and to improve the power factor and total harmonic distortion (THD) in comparison with conventional two-level inverters. This technological advancement helps to achieve high performance and low cost, transformer less multi-level inverters which may commonly exploited in grid tied Photovoltaic (PV) generating systems. The application areas of MLIs are residential use in uninterruptible power supplies (UPSs); All these applications require increased reliability in terms of lower switching losses, increased power factor, and low total harmonic distortion (THD) for ensuring robust and smooth operation. Selection of control strategy for MLIs is one of the important aspects while designing of MLI. SPWM (Sinusoidal pulse width modulation) technique has been selected and same is used in the proposed transformer less switch capacitor based MLIs. SPWM which is based on comparing the modulating and carrier signal for generating the switching pulses, is the fundamental switching and control strategy generally used in MLI control. The PWM method used to control the switching sequences of inverters is directly responsible for controlling the output waveforms of current and voltage, while defining the efficiency of the inverter by managing the switching losses and THD ratios. This paper proposes high efficient nine level, eleven level, thirteen level & fifteen level switched capacitor-based inverter. Further total harmonic distortion for each level has been calculated using MATLAB simulation and the value observed for the same is compared for each level of MLI.