Low-Capacitance StatCom with Thyristor Switched Filter Inductor

In this paper, application of thyristor switched reactors as a filtering inductor for the cascaded H-bridge low-capacitance static compensator (LC-StatCom) is demonstrated. Replacing the fixed-value filter inductor with thyristor switched reactors reduces the overall energy storage capacity and voltage rating of the LC-StatCom. The proposed concept takes advantage of LC-StatCom's ability to synthesize high quality ac voltage to reduce the overall energy storage requirement of the filter inductance. Using modular filter inductor concept adds an additional degree of freedom to control the maximum voltage drop on the filter inductor by changing the inductance value. This additional capability decreases the overall voltage rating of the converter. The effects of adding the modular inductor unit on the I-V characteristic of the LC-StatCom are evaluated. The effectiveness of the proposed solution is demonstrated by simulation results on an 11-level 3 MVA LC-StatCom.