Mathematical analysis of user defined constant switching frequency in four-leg inverter based DSTATCOM

This paper presents a detailed mathematical study on design and analysis of user-defined constant switching (UDCS) in current control of four-leg inverter based distribution static compensator (DSTATCOM). By this scheme the square wave pulse of user-defined frequency given to the fourth leg of the inverter makes the other legs to operate in constant switching frequency mode. In this paper the authors have made an attempt to analytically explain the operation of the UDCS scheme and reason for constancy of the switching frequency in the other three legs by providing user-defined constant frequency square wave to the fourth leg. Simulations are also carried out to validate the procedure of a UDCS controller based DSTATCOM. Its performances are compared with the conventional hysteresis-controlled DSTATCOM.