The effect of a constant power load on the stability of a smart transformer

This paper discusses the effect of Constant Power Loads (CPLs) on the stability of a Smart Transformer (ST). The main characteristic of a CPL is that its current decreases when its voltage increases and vice versa. Therefore, in small signal analysis a CPL behaves as a negative impedance, and as a consequence it can impact the system stability. The aim of this work is to establish how it is possible to stabilize the system by acting on the filter parameters and the control strategy. A distributed power generating systems supplied by a ST has been considered as case study. The analysis and the simulation results show that it is not possible to stabilize the system by using standard controllers without an appropriate selection of the output filter components.