@article{ghanbari_bhattacharya_2022, title={Disturbance Rejection Analysis of a Droop-Controlled DC Microgrid Through a Novel Mathematical Modeling}, volume={10}, ISSN={["2168-6785"]}, url={https://doi.org/10.1109/JESTPE.2021.3088777}, DOI={10.1109/JESTPE.2021.3088777}, abstractNote={DC microgrids are gaining interest by the increase in dc loads and renewable resource penetrations. Photovoltaic (PV) arrays are the primary renewable resources utilized in dc microgrids with variations in their productions. Power variations are seen as disturbances from other sources’ point of view. The droop control method is frequently used to control dc microgrids and assures power sharing among parallel-connected converters. It is of great interest to assess droop controller functionality in rejecting disturbances, and maintain constant output voltage. Therefore, there is a need for a comprehensive converter and controller modeling to study the effect of disturbances on the system behavior. In this article, the converter’s small-signal model is utilized in deriving the system state space model. Via the derived model, the effect of different circuit parameters on time and frequency responses is studied. The line resistances’ effect on the parallel operation of converters is also studied. To verify the droop controller’s functionality, the converter’s output impedance is derived. Disturbances are applied to the load current, and the system response is analyzed. Finally, the dc microgrid plug and play feature is addressed by proposing an algorithm for deriving the multiple converters’ mathematical model. Simulations and hardware-in-the-loop (HIL) experiments are conducted to verify the mathematical model and controllers’ performance.}, number={2}, journal={IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Ghanbari, Niloofar and Bhattacharya, Subhashish}, year={2022}, month={Apr}, pages={1507–1518} }
 @article{ghanbari_bhattacharya_2021, title={Modeling of Energy Source in DC Microgrids with Voltage Regulation Capability}, ISSN={["2329-5759"]}, DOI={10.1109/PEDG51384.2021.9494191}, abstractNote={DC microgrids gain interests due to the increase in the penetration of renewable resources with DC nature. In DC microgrids, renewable resources are connected in parallel to the DC bus. Droop control strategy is generally used for power sharing allocation among parallel-connected resources. Although its acceptable functionality, the droop control method has two main drawbacks. Line resistances affect the accuracy of power sharing. Moreover, DC bus regulation is deteriorated due to the voltage drop. Hierarchical platforms are introduced to restore power sharing accuracy and voltage level. In this paper, different methods of power sharing correction and voltage restoration are compared. A novel distributed method of voltage restoration is proposed to address the power sharing accuracy, as well as voltage restoration. Then, small-signal analysis is used to derive the hierarchical state space model. The mathematical model has an algorithm that addresses the DC microgrid’s plug and play feature. Through the derived model, functionalities of the studied methods are investigated. Stability analysis is done through the derived state space model for different loading conditions. Simulations and Hardware-In-the-Loop (HIL) experiments are conducted to verify the controllers’ functionalities.}, journal={2021 IEEE 12TH INTERNATIONAL SYMPOSIUM ON POWER ELECTRONICS FOR DISTRIBUTED GENERATION SYSTEMS (PEDG)}, author={Ghanbari, Niloofar and Bhattacharya, Subhashish}, year={2021} }
 @article{ghanbari_bhattacharya_2021, title={The Impact of PV Arrays Disturbances on the Performance of Droop Controllers in a DC Microgrid}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE47101.2021.9595066}, abstractNote={Photovoltaic (PV) arrays are frequently utilized in DC microgrids due to their DC power generations. These resources have unavoidable variations in their productions. These variations can be seen as disturbances to the DC bus voltage and other sources’ currents. The droop control algorithm is employed in such systems to assure current sharing among PV arrays and other sources such as Battery Energy Storage Systems (BESS). The droop control method functionality should be questioned in the existence of disturbances. Therefore, there is a need for a mathematical study to investigate the effect of PV arrays’ disturbances on the droop control functionality. Disturbances are applied to the PV arrays’ currents, and the system outputs are monitored. Simulations and Hardware-In-the-Loop (HIL) experiments are conducted to address the evaluation of the control method in the introduction of disturbances.}, journal={2021 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Ghanbari, Niloofar and Bhattacharya, Subhashish}, year={2021}, pages={1058–1064} }
 @article{ghanbari_bhattacharya_2020, title={Adaptive Droop Control Method for Suppressing Circulating Currents in DC Microgrids}, volume={7}, ISSN={["2687-7910"]}, url={https://doi.org/10.1109/OAJPE.2020.2974940}, DOI={10.1109/OAJPE.2020.2974940}, abstractNote={DC microgrids are introduced to reduce the conversion stages needed for connection of DC sources to the DC loads. They employ the droop control algorithm for managing the power flow from sources to the loads. However, the droop control functionality is affected by circuit parameters, especially line resistances. As a consequence, load sharing as the primary objective of the droop controller lacks accuracy. Parallel-connected converters have mismatched output voltages, resulting in circulating currents. This paper proposes an adaptive droop control algorithm for suppressing circulating currents in a low voltage DC microgrid. Line resistances are estimated through mathematical calculations and droop parameters are adjusted accordingly. Moreover, a distributed secondary controller is proposed to improve the load sharing accuracy and eliminate the effect of line resistances. The secondary controller shifts the droop controller voltage setpoint according to the converter current. Both of the proposed methods result in an accurate load sharing; Each of the participating converters has the rated current and consequently circulating current is suppressed. The effectiveness of the proposed method is verified through simulation and hardware-in-the-loop (HIL) setup.}, journal={IEEE OPEN ACCESS JOURNAL OF POWER AND ENERGY}, publisher={Institute of Electrical and Electronics Engineers (IEEE)}, author={Ghanbari, Niloofar and Bhattacharya, Subhashish}, year={2020}, pages={100–110} }