Coordination of Frequency Reserves in an Isolated Industrial Grid Equipped With Energy Storage and Dominated by Constant Power Loads

This paper examines the use of interconnected synchronous system requirements for frequency containment reserves (FCR) on isolated industrial grids that use turbogenerators as main source of energy, have high penetration of wind energy, are equipped with energy storage, and have a high level of constant power loads coupled by power electronic converters. Leveraging on the recent Nordic requirements for reserves in islanded operation (FCR$_{\rm {I}}$), we propose an expansion that allows prioritizing among various reserve providers accounting for different isolated grid conditions. The study case of a complex, isolated industrial grid is selected to test this approach. The stability of this grid is evaluated via eigenvalues and participation factors considering the detrimental effects of constant power loads. It is demonstrated that, by prioritizing the reserve allocation to the faster converter-interfaced storage devices and loads, the overall stability is increased in addition to allowing the turbogenerators to operate at a more constant load. The results are supported by computer simulations of the complex isolated grid in DIgSILENT PowerFactory and by laboratory power-hardware-in-the-loop tests which compare the performance of the proposed concept with the industry consolidated droop control. The computer simulation models developed for this paper are made publicly available for reproducibility purposes.