Genetic algorithm tuned adaptive discrete-time sliding mode controller for grid-connected inverter with an LCL filter

Abstract

The development of a two-stage cascaded control strategy for a single-phase grid-connected inverter with an LCL filter based on inverter-side current is proposed. The main objective of the proposed controller is to minimize both the grid current tracking error and the current total harmonic distortion and to overcome the system resonance introduced because of the third-order LCL filter. In the first part, a feed-forward controller calculates the reference values for the system states at the steady-state operation with no external disturbance. In contrast, an adaptive discrete-time sliding mode controller is used for disturbance rejection caused by parameter uncertainties in the second stage. The proposed control approach also considers the nonlinear behavior of the pulsed nature of the inverter’s hard switching pulse width modulation modulator. The grid-side current is taken as in-phase to the grid voltage for the inverter-side reference values calculation. Numerical simulation and experimental tests were performed to validate the proposed control strategy’s faster dynamic response under external disturbances and parametric uncertainties. An improvement of approximately 18% in THD was recorded against the variation of grid-side impedance ranging from 50%–150% over the conventional discrete sliding mode control These results demonstrate the robustness and effectiveness of the proposed controller to integrate the solar photovoltaic energy sources seamlessly.