Dual-loop control strategy of three-phase unbalance overvoltage active suppression device in distribution system

The three-phase unbalanced overvoltage exists normally in arc suppression coil grounded distribution network. Excessive unbalanced voltage threatens the proper operation of electric equipment and affects the quality of power supply. In this paper, a suppression method by injecting zero-sequence current to the neutral point through an active inverter device was proposed to inhibit overvoltage in distribution network which was caused by single-phase overload or the asymmetry of three-phase line-to-ground parameters. Then, a dual-loop control strategy consists of a proportional resonant controller and a dead-beat controller was designed, it makes it easy to suppress the unbalanced voltage quickly and precisely without measuring the grounding parameters of the network. Finally, a 10kV distribution system model was built in MATLAB for analysis. Simulation and prototype testing results showed that the suppression system has good steady-state and transient response.