A novel nonlinear current control technique for a grid-connected DC/AC inverter used in renewable energy power conditioning systems

Harvesting renewable energies is the solution to the global energy crisis. The performance of the grid-connected voltage source inverter (VSI) with an LCL-filter, used for renewable energy power conditioning, is dictated by the control technique used to regulate its output current. The closed-loop current control system is also responsible for providing active damping to damp the resonance introduced by the third-order LCL-filter. In this paper, a current control method is proposed, called composite nonlinear feedback (CNF), which offers significantly improved overall performance compared to the state-of-the-art proportional resonant (PR) controller with state feedback. The proposed control method has a very fast transient response and also provides active damping for the LCL-filter resonance. Experimental results obtained on a 1kW prototype validate the performance of the proposed current control method.