Variable DC-Link Voltage Control Strategy for Split-Capacitor DSTATCOM Operating in Voltage Control Mode

This paper proposes a new dc-link voltage control strategy for regulating the voltage at the point of common coupling (PCC) when the DSTATCOM is operating in voltage control mode (VCM). Whenever there is a sag or swell in the system, the DSTATCOM changes its mode from current control mode (CCM) to VCM. In voltage control mode, there is also a possibility that the PCC voltage might vary due to disturbances in the system, load variation etc,. The system must remain robust even during these conditions. The proposed control algorithm ensures that the PCC voltage is maintained within the prescribed limits during the above mentioned cases by varying the dc-link voltage of the DSTATCOM accordingly. The advantage of variable dc-link voltage is that the voltage source inverter (VSI) losses will be reduced greatly compared to the constant dc-link voltage. To validate the proposed method, simulation studies have been carried out on split-capacitor DSTATCOM operating in voltage control mode for PCC voltage regulation.