An improved D-SSSC voltage and current load balancing control strategy under unbalanced load

In this paper an improved vector control method is proposed for a Distribution Static Synchronous Series Compensator (D-SSSC) to overcome the unbalancing in the grid system. Unbalanced loads cause mild imbalances, whereas severe imbalances can be caused by the system faults. Here a Cascaded H-bridge D-SSSC is used to compensate the unbalanced load by unbalanced three phase injection of reactive power. A fast synchronous frame voltage regulator is used to separate positive and negative sequence of voltage or current, and compensate the unbalanced load by unbalanced D-SSSC voltage injection. Utilization of PI controller in separated sequences, the proposed control strategy can achieve the zero steady state error with a fast dynamic. Using separated positive sequence control loop, the DC link capacitor voltage regulation is possible. To validating the performance of the proposed algorithm, the simulation of the control strategy is implemented in PSCAD/EMTDC environment. Different unbalanced loads are simulated to confirm the feasible operation of the proposed control strategy.