A new switching scheme for a new multi level inverter topology for grid connected PV systems

摘要

Among Renewable Energy Systems, Photovoltaic systems are widely used as they are clean and easily installable. These PV cells convert sunlight into electricity in the form of dc. A suitable converter is usually needed to convert the dc power into ac power, which is then injected into the power grid. Recently the use of multilevel inverters (MLIs) in modern drives and for interfacing the renewable generation systems to the grid have given a wide scope for designing new topologies of MLIs. This paper presents a new switching scheme for a new topology of MLI with reduced number of switches for interfacing PV modules with the grid. Among the different switching schemes, this paper uses Unipolar pulse width modulation (PWM) technique for the switching of H-bridge switches, while for the outer switches sinusoidal modulating wave is compared with dc component for its switching. From the obtained Matlab/Simulink environment results the THD of output voltage of 21-level MLI is within limits specified by IEEE 519 standard. In addition, a comparative analysis of this new topology of MLI with conventional topologies in terms of number of switches for seven-level, thirteen-level and twenty-one level has been presented. It is also observed that this PV module fed new MLI fed to micro grid satisfies the grid requirements and conditions such as amplitude of Grid voltage, phase angle and frequency.