Amelioration of power quality in a solar PV fed grid-connected system using optimization-based selective harmonic elimination

The paper investigates a solar PV fed single phase modular multilevel inverter (MMI) and a modular converter for obtaining constant DC from the PV panels. The proposed inverter structure operates with symmetric and asymmetric DC sources. Switch reduction, harmonic reduction and grid synchronization are the performance parameters considered in the proposed work. To improve the power quality at the output side of the inverter, Selective Harmonic Elimination Technique (SHE) is used. Three different optimization techniques such as genetic algorithm, particle swarm optimization, and, bee colony optimization are implemented to calculate the triggering angles for the switches of MMI. Among the three optimization techniques the particle swarm optimization (PSO) technique gives the best result with reduced THD. Later as an application point of view the proposed MMI is connected to the grid. A closed loop control system having an outer voltage control loop and the inner current control loop is implemented for the Grid Connected System. The proposed topology and the modulation technique is simulated with MATLAB/Simulink. The hardware implementation is carried out with Field Programmable Gate Array (FPGA)-based processor to generate the switching sequences based on the proposed methodologies. The THD value of grid current using the cascaded controller is 2.03%. From the results it is evident that the PSO-based SHE method with the cascaded controller injects sinusoidal current to the grid with less THD and maintains the grid current in phase with the grid voltage at near to unity power factor.