Sliding-Mode Control with Two-Stage Photovoltaic Off-Grid and Grid-Connected Inverters

To improve the power generation efficiency of photovoltaic (PV) arrays, this paper applies the sliding mode control (SMC) strategy to two-stage PV off-grid and grid-connected inverters to keep follow the maximum power point (MPP) of PV arrays and compare it with the traditional perturbation observation (P&O) strategy on both dynamic and stationary performance. The PV off-grid system uses the SMC strategy for the front stage and a three-phase sinusoidal pulse-width modulation (SPWM) strategy for the back stage; the PV grid-connected system uses the SMC strategy for the front stage and a double-closed-loop modulation strategy for the back stage with an external loop of grid voltage and an internal loop of current. Simulation reports demonstrated that the SMC could succeed in tracking on MPP and that two-stage PV off-grid and grid-connected inverters can output power to the load and the grid stably.