Re-thinking Var Planning to Mitigate Reactive Power Reserves Scarcity During the Energy Transition

The progressive replacement of conventional fossil-fueled power plants by renewable energy sources (RES) during the energy
transition to renewable-dominated power supply leads to reactive power reserves (RPRs) scarcity, compromising thereby power
systems security. This paper envisages the next step after having identified RPRs’ scarcity with a methodology proposed previously
by the authors. This paper re-thinks reactive power (or var) planning in the new context of mitigating RPRs’ scarcity.
Specifically, the paper proposes a new methodology and problem formulation of var planning that includes as main novelties:
consideration of scenarios modeling RES uncertainty, temporal aspects (e.g. 24 hours operation profiles), accurate reactive power
capability model for wind power plant (WPP) collection system, the precise modeling of the conventional generators’ reactive
power capability curves, and the joint consideration of both dynamic and static reactive power assets. The proposed var planning
problem is formulated as a multi-period stochastic security-constrained optimal power flow (SCOPF), which seeks to minimize
the investment cost in new reactive power assets while meeting power system constraints under various operating conditions. The
value of the proposed methodology is briefly exemplified using a 60-nodes model of the Nordic32 system.