Paralleling Inverters Study of EAST Vertical Stability Coil Power Supply

摘要

Experimental advanced superconducting toka-mak vertical stability (VS) coil power supply is a large capacity single phase inverter power supply. To meet the requirement of large current and fast response, multi-inverters in parallel is presented, which based on carrier phase-shifted modulation technology. In parallel inverter system, the disperse circuit parameters and phase-shift carriers between parallel inverter units will cause circulating current, which contains fundamental component and a large number of harmonic components. In this paper, the model of circulating current is analyzed when VS coil power supply is working in voltage given mode, and an instantaneous current sharing control strategy is proposed based on the combination of current sharing inductor and instantaneous circulating current feedback control. Parallel inverter units are connected together through current sharing inductors which can change the impedance characteristic of the circulating impedance and well restrain the high-frequency circulating current. Then, the real part of the circulating impedance will be increased and the ability to restrain the low-frequency circulating current will be advanced by introducing virtual resistance, which is realized in the instantaneous circulating current feedback routine. The designations of the current sharing inductor and the virtual resistance are provided. The results of simulation and experiment verify that this current-sharing strategy is available and efficient.