A novel three-phase unbalanced voltage flexible restraining method for distribution systems

Three-phase voltage unbalance is frequently encountered in neutral ineffectively grounded distribution systems, which affects the normal operation and power quality of power system. This paper proposed a novel method to restrict the unbalance by means of injecting a current to the neutral point. The injecting current is used to compensate the grounding 1current and then force neutral voltage to zero and three-phase voltage to balance as well. An inverter is connected between the neutral point and the earth through a transformer to produce the injecting current. By controlling the inverter, the amplitude, phase and frequency of injecting current can be controlled flexibly. A 10kV distribution system model was built in MATLAB for analysis. The simulation results indicate that the proposed method can restrain the three-phase unbalance voltage efficiently and rapidly.