Use of Battery Systems for VAR Support in Con Edison Network Distribution Substation via Bi-Directional Smart Inverters

Abstract

Battery Energy Storage System (BESS), due to its multifaceted functionalities, is the key enabling technology for maintaining a reliable power system while integrating Distributed Energy Resources (DER). In this study, we examine the effect of utilizing smart inverters for reactive power support, assess potential impact of this use case on the battery lifetime and State of Charge (SoC), and institute corrective action to mitigate degradation. Initial analysis showed that filter design on the DC side plays a crucial role in reducing current flow in the battery (which impacts the SoC). As a remedial measure, an inductor filter has been tested on both the DC side (between the battery and inverter) and AC side (between the inverter and grid) to reduce the battery current and keep the total harmonic distortion of the system within acceptable limits respectively. The results show that with the proper alteration of the BESS set points, i.e., regulating the bus voltages, will enhance the stability of the system. Furthermore, during intervals when there is no real power flowing to/ from the BESS (and only reactive power is being inject/absorb), the battery current is zero. This demonstrates that with proper filtering BESS can provide VAR support without impacting its lifetime.