Control and capacity planning for energy storage systems to enhance the stability of renewable generation under weak grids

Abstract

Abstract Current‐controlled inverters (CCIs), often used in renewable power generation, are prone to harmonic instability under weak grids with a low short‐circuit ratio (SCR). This paper proposes that this type of instability can be prevented by configuring part of the energy storage system (ESS) converters in the distribution network as voltage‐controlled inverters (VCIs). The main contributions of this paper are as follows: (1) A model of the CCI/VCI hybrid grid‐connected system is established, which can characterize not only the plant‐level stability, but also the unit‐level stability. (2) A rapid power control method for VCIs is proposed, which can improve the power control bandwidth of VCIs to tens of Hz to meet the rapidity requirements for ESS power control. (3) A capacity planning method is proposed, which can give the required minimum VCI/ESS capacity for a specific stability margin and SCR range. Analysis shows that as long as the ESS converters with a capacity of no less than 6% of the CCIs are configured as VCIs, large‐scale CCIs that are originally critically stable at SCR = 1.9 can operate stably under the very weak grid with SCR = 1.2. Finally, the proposed method is verified by simulations and experiments.