Investigation of a cascaded H-bridge photovoltaic inverter under non-uniform insolation conditions by hardware-in-the-loop test.

Highlights • A versatile control strategy is employed for a grid connected CHB inverter. • Control system reduces the current harmonics under asymmetric operating conditions. • The modulation index of each H-bridge cell is calculated from PV system data. • Using the new estimation approach, the number of sensors is reduced from (2n + 2) to (n + 3) • Controller-in-the-loop implementation of control system is presented. Abstract In this paper, the cascaded H-bridge (CHB) multilevel inverter is employed as a grid connected inverter. This kind of inverter has interesting features compared to conventional inverters, including better efficiency, lower THD, lower common mode current injection, and better waveform quality. Using a series connection of H-bridge cells in this topology, a high modularity is achieved and a stepwise voltage waveform is synthesized at the ac side, leading to lower filter size and complexity. This topology processes the electric power in one stage and does not need any step-up voltage transformer for grid connection. The dynamic performance of control system is studied through simulations and is compared with the conventional approach. In addition, a new voltage estimation approach is proposed to reduce the number of voltage sensors compared to existing methods. The simulation results are presented for a 1.5 kW grid connected 7-level CHB inverter and then the hardware-in-the-loop implementation of the CHB inverter is presented to verify the performance of control system. [ABSTRACT FROM AUTHOR]