Quadratic source sequence-based multi-input 17-level inverter with closed-loop control for thermoelectric energy grid integration

Thermoelectric Generators (TEGs) possess the ability to convert waste heat into valuable electrical energy, serving diverse applications such as grid-connected systems and industrial facilities. The generated power from TEGs is inherently in the form of direct current (DC), necessitating the use of an inverter to convert it into alternating current (AC) power. However, there is currently a dearth of commercially available inverters specifically tailored for TEG systems. The conventional inverters are not suitable for low-power TEG sources, which encounter difficulties in combining DC link voltages and are constrained in exploiting asymmetrical source ratios to achieve a greater number of output voltage levels. To surmount these limitations, this paper proposes a multi-input single-phase quadratic DC source sequence-based inverter, tailored for TEG applications. This novel design with reduced component count can generate a 17-level output voltage with a quadratic source ratio of (1: 2: 5). A sophisticated control scheme is employed in the proposed system, comprising a second-order generalized integral controller for extracting the fundamental component from non-linear load currents, and a proportional-resonant controller for grid current regulation. The proposed system performances are substantiated through MATLAB/PLECS simulations and comprehensive testing, with a comparative analysis highlighting the unique features and advantages of the proposed thermoelectric (TE)-inverter.