Design and Analysis of User-Defined Constant Switching Frequency Current-Control-Based Four-Leg DSTATCOM

This paper presents a detailed study on the design and analysis of user-defined constant switching (UDCS) frequency current-control-based four-leg distribution static compensator (DSTATCOM). The three phase legs of its voltage source inverter are operated in hysteresis current tracking mode whereas the fourth leg is controlled by a square switching pulse of user-defined frequency. Consequently, the switches of the other three legs also get tuned to this user-defined frequency. Analytical expressions are derived that prescribe the range of frequencies for which the scheme works effectively. Design procedure is also suggested for the selection of the parameters of the four-leg inverter such as dc-link voltage, dc-link capacitor, interface inductor, and hysteresis band. Simulation and experimental studies are conducted to validate the proposed design procedure for a UDCS-controller-based DSTATCOM. Its performance is compared with a conventional hysteresis- controlled DSTATCOM.