Deadbeat Control of the Stand-Alone Four-Leg Inverter Considering the Effect of the Neutral Line Inductor

Distributed generation (DG) has been considered as an alternative source of power generation, especially in stand-alone applications, where both single- and three-phase loads must be supplied with fixed amplitude and frequency sinusoidal voltages. Therefore, the presence of the neutral wire is inevitable. A four-leg inverter is a common solution to connect DGs to stand-alone loads as well as providing the neutral wire. In this paper, by considering a filter inductor in the fourth (neutral) leg of the four-leg inverter, a detailed model is presented, which illustrates a strong coupling among different phases. In order to remove this coupling effect, it is proposed to transform the quantities from the abc to the αβγ reference frame. Furthermore, based on the proposed decoupled model, a new deadbeat control scheme is proposed to provide balanced sinusoidal voltages at the output of the inverter. To confirm the effectiveness of the proposed modeling and control techniques, experimental results on a 3-kW setup with the digital-signal-processor-based digital controller are provided under various loading conditions, such as linear/nonlinear, balanced/unbalanced, and single-/three-phase loads.