Uncertainty margins for probabilistic AC security assessment

In the past few years, the share of renewable power generation has been growing significantly, leading to increased uncertainties in power system operation. In this paper, the effect of wind in-feed uncertainties on power flow in the AC grid is investigated. The wind power in-feed deviations from initial forecast are modelled as Gaussian random variables. To assess the influence of wind power deviations on power flows, sensitivity factors based on a linearised version of the AC power flow equations are used. These factors are then applied in the calculation of appropriate security margins needed for keeping the system secure in the presence of wind power fluctuations. The modelling methods are implemented on the IEEE RTS96 test system with additional wind power in-feed. Simulation results show that the proposed method based on linearised AC power flow can estimate uncertainty margins for active power more accurately than the DC approximation model, and also provides satisfactory estimation of uncertainty margins for apparent power.