Design and Power Loss Calculation of High-Power LC-DC Transformers Based on IGCTs

A DC transformer (DCT) is the key equipment of renewable energy DC collection systems. Due to the power capacity limitation of power semiconductor devices, the power capacity of a single module of the existing DCT is usually hundreds of kilowatts. For large-scale renewable energy DC collection systems, a large number of power modules need to be connected in series and parallel to increase the capacity, which increases both the size and cost. Based on the high-voltage and high-power current-source power semiconductor device—the Integrated Gate-Commutated Thyristor (IGCT), this paper develops a megawatt-scale LC serial-resonant DCT prototype. The zero current switching (ZCS) of the LC-DCT is used to reduce the power loss in the IGCT. Additionally, this paper analyzes the operating mode of the LC-DCT based on the IGCT, studies the design method of the clamping circuit, and analyzes the calculation method of power loss. A 6000 V/900 V/1.08 MW LC-DCT prototype is developed, and the accuracy of the theoretical analysis is verified experimentally. The proposed scheme provides a novel solution for the DCT for applications such as large-scale DC collection of renewable energy.