Plug-in gate-loop compensators for series-connected IGBT drivers in solid-state fault current limiter

Abstract

Solid-state fault current limiter (SSFCL) is the key protective equipment in direct current distribution network. To meet the high voltage requirement meanwhile reduce the cost, implementing a SSFCL based on series-connected insulated gate bipolar transistors (IGBTs) is a promising way. However, voltage unbalancing of IGBTs would be introduced if the gate-loops of the IGBTs are non-identical. In this paper, a plug-in gate-loop compensator with discrete gate voltage feedback and pulsewidth current compensation is proposed. The main merits are 1) with the plug-in structure, the extra current sources only provide small power to fine-tune the gate-loop without affecting the functions provided by the commercial IGBT gate driver; 2) the gate-emitter voltages of IGBTs are compared with the preset thresholds to obtain control criterions, and the pulsewidths of the current sources are controlled for gate-loop compensation, thus both analog-digital and digital-analog converters are avoided; 3) the control law is easy to be implemented in FPGA, and is robust to voltage variation of power-loop. With the proposed compensator, the voltage unbalancing is alleviated immediately at the present switching cycle, and further eliminated cycle-by-cycle during current limitation process. Experimental results verify the feasibility of proposed compensator.