Nonlinear Backstepping Controller Design for Grid-Connected Photovoltaic Systems with Output LC Filters to Improve Dynamic Stability and Power Quality

A nonlinear backstepping controller is designed in this paper for grid-connected photovoltaic (PV) systems with output LC filters to improve the dynamic stability over a large operating region and power quality. The detailed dynamical model of grid-connected PV systems with output LC filters are used to design the proposed backstepping scheme which ensures the desired tracking of all states. Since the proposed scheme uses all nonlinearities within the grid-PV system along with the dynamics of LC filters, the switching control inputs have the ability to ensure the overall dynamic stability and improve the power quality under any circumstance. The concept of control Lyapunov function (CLF) defining the energy of the system is used to analyze the convergence of all errors characterizing the tracking for different states. The performance of the proposed nonlinear backstepping controller (NBC) is evaluated on a gridconnected system with an output LC filter and the same scheme is compared by employing it on a similar system having an L filter.