Surge Current Calculation and Limit Strategy of the IIDG during Loop Closing Operation in Distribution Networks

The operation of upgrading primary feeders from radial and open loop to a closed-loop arrangement may results in a rather large surge current especially with increasing penetration of distributed generators (DGs). Existing studies focus more on the feasibility of the loop closing operation by analyzing the steady-state output of DGs, whereas the transient progress and the flexibility of the control are ignored. This paper presents a method for calculating the surge current of two types of inverter-interfaced distribution generators (IIDG)-voltage source inverters and current source inverters during the loop closing operation. Further, a limit strategy to restrain the surge current is proposed by adjusting the control parameters. The control parameters are adjusted when the current of the IIDG falls to its lowest point in order to minimize the impact of parameter variations. The limit strategy won’t change the steady-state operating condition of the system. The proposed strategy is further verified based on PSCAD/EMTDC. Results confirm that the proposed strategy can effectively inhibit the surge current of the IIDG and improve the reliability of DGs dominated distribution network.