Robust Vector Current Control of Grid-interactive Smart Packed E-Cell Multi-level Inverters under Non-ideal Grid Conditions

This paper proposes a convex optimization-based strategy for the design of vector current controllers in a grid-interactive single-phase nine-level Packed E-Cell (PEC9) inverter under uncertain grid conditions, from stiff to weaker conditions, and non-ideal grid voltage conditions. The non-ideal grid-interactive PEC inverter with the grid impedance uncertainty is modeled by a multivariable polytopic model subject to a disturance in a state space framework. By virtue of this novel modeling approach, a robust two-degree-of-freedom H∞ multivariable Proportional-Integral (PI) vector current control strategy is then proposed. The proposed control mechanism guarantees robust stability, employing a quadratic Lyapunov function, and robust performance against the uncertainty in grid impedance and non-ideal grid voltage conditions, also it provides inverter currents with Total Harmonic Distortion and harmonic components complying with IEEE Standard 1547 requirements. The effectiveness of the proposed grid-interactive smart PEC9 inverter equipped with the proposed robust vector control strategy is evaluated by simulation and hardware-in-the-loop experimental case studies.