An application of multi-level DC-link converter for optimised permutation control of PV sources under partial shading

The paper describes application of a multi-level DC-link converter in overcoming the problem of partially shaded series-connected PV sources. The converter control engages a permutation algorithm which enables each PV source of the string to produce the maximum power. The main features of the system are: (i) a continual operation of all PV sources, shaded and non-shaded, at their maximum power points, (ii) delivery of all extracted power from PV sources to the load and (ii) generation of multi-level output voltage waveform with a low total harmonic distortion.