Dissertations and Theses

Date of Award


Document Type




First Advisor

Ahmed Mohamed


Battery Energy Storage System, Reactive Power (VARs), Distributed Energy Resources (DERs); Lifetime of Battery, AC and DC current, Total Harmonic Distortion (THD); Battery Pack, Modules, Inverters; IGBT (insulated-gate bipolar transistor); Pulse width Modulation (PWM); Static VAR Compensator (SVC), D-STATCOM; Mechanically switched capacitor banks (MSC); State of Charge (SoC); Depth of Discharge (DoD); switched capacitors (SCs);


Battery Energy Storage System (BESS) can facilitate the integration of Distributed Energy Resources (DER) and help create a more reliable grid by providing multiple services including reactive power (VAR) support. This research will investigate the use of smart inverters to provide VAR support, assess the impact it has on the lifetime of a BESS and determine how the adverse effects (if any) can be mitigated/eliminated. To achieved this, a 7.5MW/30MWh grid connected BESS located at Con Edison substations have been modeled in MATLAB/Simulink. Preliminary assessment of the system showed that DC current to/from the battery is oscillating (non-zero) during reactive power support which equates to having an adverse effect on battery lifetime. As a remedial measure, an inductor filter has been proposed on both the DC side (between the battery and inverter) and AC side to reduce the battery current and keep the total harmonic distortion of the system within 5%. The results show that during the 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 proves that BESS can provide VAR support without impacting the BESS lifetime. Several cases were evaluated to determine the appropriate minimum inductor filter size while varying real and reactive power contributions of the BESS. Additional use cases were simulated to reflect real grid components at the substation. Most notable is the assessment of VARs from the BESS in parallel with capacitor banks and shunt reactors at the substation. Results of this grid connected utility scale BESS use cases will be discussed with recommendations on how to maximize performance without impacting the battery life.



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