Software Defined Controller to Enable Flexibility in Distribution Networks with Safety and Stability Issues Consideration

To deal with the risk of safety and stability introduced by topology reconstruction in distribution system, a software defined controller (SDC) scheme is proposed in this paper. Draw on the technology of SDC in the discipline of computer networks, functions of the proposed SDC scheme are achieved by the periodic cycle of the three modules, including the module of preverification for risk, the module of online tuning for control parameters and the module of execution for command. Firstly, modelling for the transient process of the distribution network caused by topology reconstruction is established in the module of pre-verification for risk. The real-time operation information and the decision of topology reconstruction to be executed is input into the transient process modelling as initial data to judge that whether the critical electrical variables have exceeded the safety threshold of the equipment. Then, if the risk is confirmed by the pre-verification module, the module of online tuning for control parameters is activated. The control parameters of VSCs are tuned to obtained the smooth and stable transient process against the risk of collapse caused by the topology reconstruction. Finally, the online tuning result is input as the updated operation data into the pre-verification module.

In the verified simulation system, the voltage overshot of nodes with AC/DC converters/load connected are all suppressed more than 35% and maintained values within the range of 0.8 to 1.05 p.u. Moreover, the oscillatory instability in the system induced by topology reconstruction is suppressed significantly.