Parallel Resonant DC Link Inverter With Simple Structure and Its Modulation Strategy Research

Aiming to address the problems of high current stress, large conduction loss, and too many components in the auxiliary commutated circuit (ACC) of the novel parallel resonant DC link inverter (PRDCLI), this paper proposes an improved modulation strategy. It consists of three parts: based on type 1 discontinuous pulse width modulation (DPWM1) strategy, using a sawtooth wave with alternating positive and negative slopes as the carrier, and applying shunt dead zone based on the above two strategies. Under the proposed modulation strategy, the ACC of the original topology can be simplified, and a group of resonant circuit can be saved to reduce hardware cost. Compared with the original modulation strategy, the proposed modulation strategy can not only realize soft-switching of all switching devices without changing the operation frequency of the ACC but also avoid the superposition of resonant current generated in the operation process of the ACC and load current, effectively reducing the conduction loss of the ACC and the current stress of its internal switching devices. This paper describes the principle of the proposed modulation strategy in detail, from which the operation mode of simplified topology is derived, and its characteristics such as voltage/current stress, component number, parameter design are analyzed. Finally, a general experimental prototype (SiC MOSFET, 5kW/40kHz) is used to compare the original topology and modulation strategy to verify the effectiveness of the proposed theory. ©2023 Chin.Soc.for Elec.Eng.