Injecting current control method for 3-phase unbalanced voltage suppression in distribution system

The asymmetry of system parameters and electric loads lead to three-phase voltage unbalance in neutral resonance grounded distribution networks, which causes damages to the electrical equipment and power system. This paper proposed an unbalanced voltage limiting method by injecting a zero-sequence current to the neutral point of distribution network through an active inverter, and studied the controlling strategy of the injecting current with a proportional resonant (PR) controller. By set ting appropriate proportional and integral coefficient of PR controller, the controllability of injecting current and the static performance of system were improved. Simulation analysis and prototype test results verified that the control method has high precision and low steady-state error, and is able to suppress three-phase unbalanced voltage quickly and accurately.