Mitigating Balanced and Unbalanced Voltage Sag Via Shunt-Connected Voltage Source Convertor (VSC) by using Double Vector Controller

Abstract

This study presents a shunt-Connected Voltage Source Convertor (VSC) to mitigate balanced and unbalanced voltage sag and regulate the grid voltage at a fixed level by inserting required reactive power at the Point of Common Coupling (PCC). Moreover, an inner Vector Current-Controller (VCC) and outer voltage controller (VVC) are applied together to calculates the current references for the VCC. Furthermore, an inductor/ capacitor/inductor (LCL) filter is replaced with the simple L-filter in between the VSC and the network and it is constructed to reduce the voltage sag. Likewise, to make up for the unbalanced dips, the positive and negative sequence components related to the grid voltage should be managed distinctly. The positive and negative sequence components related to the grid voltage should be managed distinctly. This is achieved through the application of two independent controllers for the two sequences with an identical cascade structure which has been explicated above. Simulation results designate proper functioning of the control system which has been proposed.

A new method to point of common coupling voltage control in distribution grid-connected photovoltaic systems

“…This strategy allows the system to mitigate the symmetrical and asymmetrical voltage sag and swell. Moreover, by deployment of the proposed structure, balanced active power injection can be achieved in the presence of unbalanced reactive power, whereas achieving this ability in conventional methods imposes additional control to the system . It should be noted that the ramp comparison hysteresis current controller used in each single‐phase H‐bridge inverter has the advantage of constant switching frequency compared with conventional hysteresis current controller.…”