Finite-time sliding mode power control of grid-connected three-phase photovoltaic array

Abstract

A new direct power control formulation for the voltage source converter (VSC) in a grid-connected photovoltaic (PV) array is discussed in this paper. Instead of controlling the direct- and quadrature-axis currents of the VSC through the use of a phase-locked loop system (PLL), the instantaneous real- and reactive-power components are used as control variables. This approach, therefore, does not take into account the unmodelled dynamics of the PLL resulting in a robust control of the active, reactive powers while maintaining the photovoltaic (PV) array voltage at a constant value. Further, the stability of the grid-connected PV array is enhanced by designing a Lyapunov’s function-based finite-time non-linear reactive power and dc-link voltage controller, which essentially uses the terminal sliding mode approach. To prove the robustness of the proposed approach, several system disturbances like changes in solar insolation and active and reactive power references, islanding conditions, converter parametric changes, and faults on the converter and inverter buses are considered. In all these cases, the new controller is found to enhance overall system stability in comparison to the inferior performance by the proportional-integral controller