SVPWM-based D-Σ digital control for 3ϕ grid-connected inverter with wide inductance variation

This paper presents an SVPWM-based division-summation (D-E) digital control for a three-phase grid-connected inverter with wide inductance variation. The proposed D-E approach summarizes all of the individual inductor-current variations over one switching cycle to derive control laws directly, which can overcome the limitation of d-q transformation. The inverter with this control can achieve the functions of grid connection, rectification with power factor collection, and STATCOM by taking into account wide filter-inductance variation and grid-voltage distortion, reducing core size significantly. The control laws for achieving the desired functions are derived in detail and they are expressed in general forms for readily software programming. In the design and implementation, the inductances corresponding to various inductor currents were measured at the start-up and stored in the microcontroller for scheduling loop gain cycle by cycle. Experimental results from an 8 kVA 3φ inverter have confirmed the analysis and discussion of the proposed control approach.