Loss Calculation of High Voltage DC Transformers Based on the Principle of Capacitive Transfer

A precise calculation method for system losses is proposed to address the power loss issue generated during the operation of DC transformers based on the principle of capacitive energy transfer (CET). Firstly, determine the functional relationship between bridge arm voltage and bridge arm current. Based on the relationship between the capacitor voltage of the submodule and the bridge arm voltage, determine the input quantity function of the single-phase bridge arm submodule using a rounding function. Establish a loss mathematical model by comprehensively considering the on state loss, switch loss, and converter valve on state loss types of the bridge arm submodule. The system loss can be accurately calculated by multiplying the number of submodules, bridge arm current, and conduction voltage drop. Analyze the distribution pattern of losses during bidirectional power transmission. Finally, the effectiveness of the loss calculation method proposed in this paper was verified through simulation.