Considering controllable devices using standard load flow programs - SSSC example

The paper presents a novel method for modelling controllable devices in Load Flow studies. The objective of the study is to develop a well convergent, Newtonian method, which will operate externally of the underlying Load Flow routine, thus enabling one to model controllable devices without altering the Load Flow programme with quick convergence. The method is based on creating a criterion function that describes the devices; when the criterion function is zero the devices are modelled correctly. The controllable devices are modelled using standard load flow input data, which, combined with the fact that the criterion function is external to the Load Flow, enables modelling these devices without changing the Load Flow programme. To find the root of the criterion function, Newton method is used. The method is tested on the SSSC, as this device was found to be badly conditioned. Early results show that the method can be generalized to other devices. The use of method is verified on benchmark 118 bus and 300 bus systems in local and non-local control modes. The results show that the method is capable of modelling several devices inserted in large power systems performing local and non-local control with low iteration count.