Control the photovoltaic grid-connected system using fuzzy logic and backstepping approach
This paper presents a comprehensive method to design a compatible controller system for the photovoltaic (PV) singlephase grid-connected system. The demonstrative PV system in this study consists of four 250W solar panels with a nominal total power of 1 kW, a non-inverting buck-boost DC-DC converter, and a DC-AC inverter, including a LCL output filter. Main objectives of the PV system in use are threefold: tracking and operating at the maximum power point (MPP) of the PV array, regulating the DC link voltage to 200 V, and delivering the power to the 110V/60Hz electric grid with unity power factor (PF). To fulfill three above goals respectively, the designed controller system is composed of three major modules. In which the first is the MPPT Controller module, using an improved incremental conductance (INC) algorithm based on fuzzy logic. Another is the DC Link Voltage Regulator module constituted by a PI-Fuzzy hybrid controller. And the last is the Current Controller module based on the backstepping approach. Simulations show that the proposed controller system completely accomplishes listed aims even when the solar radiation and temperature change suddenly.