DC Capacitor Voltages Balancing in Diode-Clamped Three-level Inverter-Based DSTATCOM

Abstract

The Distribution Static Compensator (DSTATCOM) protects the utility transmission or distribution system from voltage sag and /or flicker caused by rapidly varying reactive current demand. Because of limitation of use of conventional two-level inverter based DSTATCOM in the field of high power applications, we used the multilevel inverter. This paper examines the application of a three level inverter based distribution static compensator (DSTATCOM) connected to distribution system. The multilevel inverter based DSATCOM has an inherent unbalancing problem among its dc capacitor voltages. Additionally, when the load contains a dc part, the neutral point of the compensator also becomes unbalanced. In this paper, the effects of different loading conditions on the dc capacitor voltages of the inverter are studied. Equations of the proposed equalizing controllers are developed corresponding to the control of the switching devices. Switching pulses for the three-level inverter are generated by Space Vector Modulation (SVM). Simulation results are provided to illustrate the performance of our controller. Validation of models and control algorithms is carried out through simulations in SimPower Systems of MATLAB/Simulink.