Design of an Asymmetric Multilevel Inverter Based Grid-Tied Solar PV System with Regulated Output Voltage & Grid Synchronization Mechanism

Over the past two decades, world leaders and scientists have been devotedly working to improve energy security and decrease greenhouse gas (GHG) emissions in response to the growing demand for energy. Their relentless efforts have highlighted the necessity of integrating extensive renewable energy sources (RES) into existing power grids at a large scale. This paper presents a single-phase grid-tied solar PV system with improved power quality, output voltage regulation and grid voltage synchronization mechanism. In this study a grid-connected solar photovoltaic (GCSPV) system with an asymmetric 33-level inverter using only 12 switches, and 4 DC sources is modelled and analyzed. The PV source is used as input to a DC-DC boost converter. The boost converter along with PID controller ensures a stable DC voltage at the inverter input even in the varying irradiance and temperature conditions. Grid voltage synchronization and power quality improvement of the inverter are done by using Nearest Level Control Pulse Width Modulation (NLC-PWM) technique. The performance of the proposed Multi-level Inverter (MLI) at step and gradual change in irradiance and temperature are evaluated using MATLAB Simulink which shows no significant distortion and changes of magnitude in the output voltage and current. The results show a low total harmonic distortion (THD) of 2.49% without filter and 0.71% and 0.51% with LC filter for inverter output voltage and current respectively. The power factor of the inverter is almost unity (0.996). Hence, the proposed system improves overall performance, provides a simple control mechanism and is therefore feasible for the grid-connected PV system.