The Steady-State and Fault Ride-Through Control Strategies of Soft Normally Open Point in Distribution Network

Soft normally open point (SNOP) is a power electronic device installed at normally open point (NOP) in a distribution network which can greatly promote the flexibility and controllability of distribution network. This paper firstly introduces the typical installation of SNOP, and takes the back to back MMC SNOP system as the studied case. Then the PQ-VdcQ strategy is described as steady-state control strategy of SNOP system, and the control principle of power flow on feeder is briefly illustrated. Lastly, the strategies of unbalanced current compensation and active power oscillating suppression are described for fault ride-through strategy. To avoid overcurrent, the unbalanced current compensation strategy is adopted. Simulation results verify the accuracy and effectiveness of the strategies adopted.