Fast equivalent modeling of input series output parallel HVDC solid state transformer with LLC Structure

Abstract

High-speed equivalent modeling is extremely important for the analysis of HVDC solid state transformer (HVDC-SST), including a large number of input series output parallel (ISOP) dual active bridge (DAB) units with LLC structure. This thesis presents an equivalent model-based method to largely simplify the model of HVDC-SST with described structure. According to the characteristics of HVDC-SST with ISOP structure, the fast equivalent modeling theory of LLC with DAB unit and the whole HVDC-SST is proposed out, and the specific circuit equivalent method is put forward. The discrete high frequency power supply is used to carry out the equivalent of the inverter; the series parallel connection of the branch circuit is equivalent to the part of the high frequency transformer, and the control current source is used to carry out the equivalence of the rectifier section. The DAB unit is simplified using the equivalent method, and the entire equipment is simplified with the brief DAB units. The experimental platform of 20kV/560V and the simulation platform of simulink are built to verify the consistency among the equivalent model, the original model and the actual waveform. By comparing the simulation time, the effectiveness of rapid equivalent modeling can be proven.