LCL VSC Converter for High-Power Applications

This paper studies an inductor-capacitor-inductor (LCL) voltage-source converter (VSC) ac/dc converter concept which can be employed as high-power static converter. The converter is designed to have fault current near or below the rated value under the dc-side short circuits. This is very important for applications with HVDC and, in particular, with high-power dc transmission networks. This converter is composed of an ac/dc insulated-gate bipolar transistor-based VSC converter and a passive LCL circuit. A transformer is not required since LCL circuit can achieve voltage stepping. The converter parameters are designed to have optimal response during the faults, good controllability, and to minimize converter losses. A detailed model is developed on the PSCAD platform for a 500-MW test system. The simulation confirms capability to independently control active and reactive power and demonstrates favorable fault responses. The transient fault current peaks are not significant and can be overcome with slight overrating.