A New Asymmetric Multilevel Inverter Topology Suitable for Solar PV Applications With Varying Irradiance

A new asymmetrical multilevel inverter topology is reported that is capable to operate satisfactorily with wide variation in dc-link voltage, while feeding power to the ac grid. A topological building block is first introduced that has one full-bridge inverter connected in series with a level doubling network. Following this, the interconnection of such building blocks is attempted to increase the number of levels at the output voltage waveform. The investigation reveals that for a three-phase system, a converter configuration with two such building blocks is capable to generate a nominal asymmetry of 14:7:2:1 using only four voltage sources. In solar Photovoltaic (PV) applications, one main source may be fed by PV array and the other three auxiliary sources may be fed through separate dc/dc converters, each having power rating of 3.2% of the peak power rating of PV arrays. The proposed converter can generate 3097 space vectors. Asymmetrical hexagonal decomposition is modified (to ensure satisfactory operation of LDN and to eliminate any dc component in the phase voltage waveform) to control such converter. The converter is extensively simulated in MATLAB/Simulink. A solar PV system of 9.4 kWp available in the laboratory is used to feed power to the grid at different irradiance. Simulation results match well with the prototype experiments confirming the usefulness of the proposed topological alternative for solar PV applications.