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 frequency (UDCS) current control based four leg distribution static compensator. The three phase legs of the voltage source inverter are operated with hysteresis control whereas the fourth leg by a square switching pulse of user defined frequency so that the switches of all the legs operate with constant switching frequency. Analytical expressions are derived which prescribe the range of frequencies for which the scheme effectively works. 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. The effectiveness of the design procedure is established by extensive simulation studies on a three phase four wire distribution network.