A Scalable Var Planning Methodology to Mitigate Reactive Power Scarcity During Energy Transition

Thepaper re-thinks the reactive power (or Var) planning problem to mitigate reactive power scarcity in the prevailing context of the energy transition to renewable-dominated power supply. The paper first proposes an enhanced tailored problem formulation of Var planning, in the form of a stochastic multi-period AC security-constrained optimal power flow; it minimizes the investment cost in new reactive power assets to meet power system constraints under various operating conditions. Then, the paper develops a new scalable methodology to solve this Var planning problem; it achieves scalability by a progressive and efficient identification of the binding combinations of contingencies, time periods, and uncertainty scenarios, which allows solving sequentially problems of much smaller size than the original one. The performance of the methodology is demonstrated on a 60-bus model of the Nordic system and a 1203-bus model of a real system.