Embedding OLTC nonlinearities in predictive Volt Var Control for active distribution networks

•Coordination of many actuators for voltage regulation and reactive power exchange in a predictive Volt Var Control scheme for active distribution systems.•Tap changes are explicitly considered in the cost function in order to guarantee the minimization of tap changes during all life of the On Load Tap Changer.•The classical OLTC inner control is kept to avoid fundamental modifications of the existing control devices and operating process.•The non-linearities of the OLTC are embedded within the predictive VVC.

This paper presents an original procedure to embed the On Load Tap Changer (OLTC) nonlinearities in a predictive real-time Volt Var Control (VVC) for distribution systems. These commonly disregarded nonlinearities are namely the OLTC time-delays, the dead-band and the discrete nature of tap change. It is shown that using a continuous approximation can lead to control failures. The proposed nonlinear controller accurately anticipates the response of the system and the costs associated with control efforts. Demonstrations are performed in a 20 kV network to assess the performance of such a procedure compared to a predictive VVC using an OLTC continuous approximation.