Optimal sizing method of vanadium redox flow battery to provide load frequency control in power systems with intermittent renewable generation

Abstract

This study proposes a novel methodology for optimal sizing of a vanadium redox flow battery (VRFB) aiming at providing the load frequency control (LFC) of power system (PSs) with renewable generation, such as wind generation. This methodology utilises a new optimisation problem, where the optimal size of the VRFB is an endogenous result from the model of optimisation problem. To resolve the new optimisation problem, a hybrid optimisation model (HOM) is employed in order to calculate the optimal investment for the VRFB (optimal size) while taking into account both its impact on the PS costs and on the quality of the system frequency. Through stochastic optimisation, the HOM allows computing the variable operating costs and VRFB investment costs, considering the uncertainties associated to the PS. This stochastic optimisation utilises a new quasi-stationary simulations of the PS operation, which demands lower computing effort. To this aim, this study proposes a novel modelling approach of both the VRFB and the PS operation. Moreover, statistical indexes are proposed as new factor used in sizing the LFC operating reserve. The results show that the developed methodology allows evaluating with precision the stochastic characteristics of the PS.