Load Shedding – an Efficient Use of Ltc Transformers

This paper focuses on a methodology to deal with load shedding in electric power systems such as to make its impact on the demand level as minimal as possible. The power demand is parameterized by the factor α, which is minimized subject to equality (real and reactive power mismatches) and inequality constraints (operational and equipment limits). Lower and upper limits on voltage magnitudes and taps of the load tap change (LTC) transformers are considered. Aiming at evaluating their influence on the load shedding, the taps of LTC transformers are included in the set of optimization variables. It is well known that as a consequence of this inclusion the iterative process is prone to convergence problems. This paper presents a simple and efficient methodology to deal with LTC transformer taps, which consists in a slight modification of the Interior Point methodology used to solve the load shedding optimization problem. Numerical results for IEEE-test systems and a realistic power system will be presented in order to assess the performance of the proposed method.