Optimal Proportional Resonant Control of Single PV fed Multilevel Converter Tied to Weak Grid

A new optimal solar photovoltaic (PV) system is introduced, where a proportional resonant controller is used for performance improvisation of a single PV fed grid-tied multilevel converter (SPGMC). The SPGMC configuration is developed using two H bridge cells and line frequency transformers. The grid current control is achieved using a proportional resonant (PR) current controller, which ensures improved steady-state and dynamic performance. Moreover, an error between the reference and the sensed grid current is minimized using the particle swarm optimization technique (PSO). The integral square error (ISE) is taken as an objective function and the mean of best values is selected for the PR controller. The merits of PSO based tuning over conventional tuning and PR controller for AC signals over conventional PI controllers lead to improved system performance. This optimal control is implemented for the closed-loop operation of a grid-tied solar photovoltaic (PV) system. This configuration has a single-stage MPPT controller, which reduces control complexity, and a single PV array, which minimizes the requirement of sensors. The performance of the PSO-PR based grid-tied system is tested under constant and variable solar irradiations. The PV array power is transferred to the grid at the unity power factor and the grid current harmonics are maintained under the IEEE 519 standard. Moreover, the system is tested under voltage sag and swell operation to handle weak grid situations. The system is modeled in MATLAB/Simulink and simulation results show the effectiveness of the grid-tied solar photovoltaic system.