3D-Modulation and PI State-Feedback Control of Voltage Source Inverters with Split DC-Link

In this work, a novel three-phase grid inverter topology with split DC-link and LC-filter is discussed. A proportional-integral (PI) state-feedback current and voltage controller is designed based on linear quadratic regulator (LQR) theory. The midpoint current ripple is suppressed by introducing the filter capacitor voltage as control target. Moreover, a 3-dimensional Space Vector Modulation (3D-SVM) for this topology is implemented, which allows for larger voltage amplitudes compared to conventional Pulse Width Modulation (PWM). Realistic simulation results show that the combination of PI state-feedback controller and 3D-SVM achieves faster and more accurate closed-loop dynamics with less oscillations and better decoupling under varying and unbalanced grid conditions.