An improved DSP-based control strategy with predictive current control and fuzzy voltage control for grid-connected voltage source inverters

This paper presents an improved DSP-based control strategy with combined voltage and current for gird-connected voltage source inverters (VSIs). A predictive current control strategy in the inner loop and a fuzzy voltage control strategy in the outer loop are respectively discussed in detail. A new predictive current control expression is obtained, which calculates the inverter voltages required to force the output current to accurately follow the reference current. This algorithm can eliminate the steady-state phase error between the output and reference current, and compensate for the errors caused by sample delays and discretization computation, with a fixed switching frequency. And a fuzzy logic controller with 9 fuzzy levels and 41 fuzzy levels is applied, which can stabilize the DC bus voltage and overcome the systempsilas variability and nonlinearity. These characteristics are highly applicable to the alternative energy system, especially to the photovoltaic (PV) power system. Combining the advantages of the current prediction and voltage fuzzy control, the system robustness is enhanced and minimum current error, a unity power factor and low THD are achieved. At last, a 10 kW prototype of three-phase grid-connected VSI was built and the proposed dual-loop controller was implemented by DSP TMS320F2808. The experimental results verify the validity of the theoretical analysis in this paper.