@article{nath_isik_burugula_bhattacharya_2023, title={Novel Control for Active Power Compensation using DSCC-MMC based ES-STATCOM}, ISSN={["1048-2334"]}, DOI={10.1109/APEC43580.2023.10131288}, abstractNote={In recent years, modular multilevel converters (MMC) have gained popularity for high-power applications such as in flexible AC transmission systems (FACTS) and High Voltage DC (HVDC) applications, due to their scalability and modularity along with high efficiency in handling high-power and high voltage needs of the power grid. In the same domain of applications, one such usage of the MMC-based system is the integration of energy storage with static synchronous compensator (STATCOM) technology (known as ES-STATCOM) for providing active power compensation along with reactive power support to the grid. This paper introduces a novel dynamic model-based control approach to the MMC-based ES-STATCOM for the integration of energy sources with the power grid. The design of various controller elements is based on detailed harmonic evaluations for both dynamic and steady-state operation modes. The design of the circulating current control adds second-harmonic computation of the modulation indexes for the suppression of second-harmonic circulating current. This approach further improves the converter's performance by reducing the fluctuation in the capacitor voltages and eventually the losses. Finally, the operating range of the MMC-based ES-STATCOM system is being discussed, which lays down the operating limit for active power compensation with reactive power compensation given the priority. The functionality of the proposed control architecture is validated through a Real-Time Digital Simulator (RTDS) and Virtex 7-based FPGA controller in a Controller Hardware-in-Loop (C-HIL) environment.}, journal={2023 IEEE APPLIED POWER ELECTRONICS CONFERENCE AND EXPOSITION, APEC}, author={Nath, Harshit and Isik, Semih and Burugula, Vasishta and Bhattacharya, Subhashish}, year={2023}, pages={1102–1108} }
 @article{isik_burugula_alharbi_azidehak_bhattacharya_2022, title={Implementation of a Modular Distributed Fault-Tolerant Controller for MMC Applications}, volume={15}, ISSN={["1996-1073"]}, DOI={10.3390/en15228427}, abstractNote={Centralized control algorithm limits the hardware flexibility of a modular multilevel converter (MMC). Therefore, distributed control structure has recently started to be seen in the industry application. Even though distributed controller reduces a single point of failure risk compared to the centralized controller, the failure risk of the entire control systems increases due to the number of local controllers. However, the distributed controller can be programmed in such a way as to replace the faulty local controller and sustain the MMC operation. In this paper, the distributed modular fault-tolerant controller is implemented in a laboratory-scale MMC prototype. The controller is built to control four SMs per phase for the proof-of-concept. Therefore, the MMC prototype is also built by two SMs per arm. The controller capability is validated with experimental and the Opal-RT result-time simulator results in a control-hardware-in-loop (CHIL) environment.}, number={22}, journal={ENERGIES}, author={Isik, Semih and Burugula, Vasishta and Alharbi, Mohammed and Azidehak, Ali and Bhattacharya, Subhashish}, year={2022}, month={Nov} }
 @article{burugula_isik_bhattacharya_2022, title={Performance Comparison of a Modular Multilevel Converter under Centralized and Decentralized Control Structures}, ISSN={["2329-3721"]}, DOI={10.1109/ECCE50734.2022.9947465}, abstractNote={A Modular Multilevel Converter (MMC) consists of series-connected bi-directional chopper cells with a floating capacitor on each leg. Despite the inherent modularity of the chopper cells, most MMC controllers have been designed based on a Central Controller Unit (CCU) until recently. Using classical linear controllers, the CCU executes the operator-defined setpoints based on measured signals in the outer-level control. Even though a CCU is relatively fast and has fewer communication routes, the CCU retains the scalability and modularity features of an MMC as modification of the controller may be challenging. For this reason, the decentralized control structure has been considered for the recent MMC applications to utilize the scalability and modularity features of an MMC effectively. The decentralized controllers introduce delays, especially for the circulating current, due to the local controllers, so the delays may drastically affect the MMC currents. In this paper, the centralized and the decentralized control structures are implemented and their effects in the arm and the circulating currents are investigated for an MMC operation.}, journal={2022 IEEE ENERGY CONVERSION CONGRESS AND EXPOSITION (ECCE)}, author={Burugula, Vasishta and Isik, Semih and Bhattacharya, Subhashish}, year={2022} }
 @article{isik_burugula_alharbi_bhattacharya_2021, title={Modular Power Flow Enhancer for Transmission Networks under Unbalanced Power Grid Conditions}, ISSN={["1553-572X"]}, DOI={10.1109/IECON48115.2021.9589894}, abstractNote={The three-phase H-bridge or NPC converters are commonly adopted converter topologies for FACTS devices. Both the converters are classified as multilevel converters capable of producing a three-level AC voltage between the phase and the neutral terminals. Either topology is a good solution in the low voltage environment where it is possible to select a switch capable of blocking the required DC bus voltage. If the converter is designed for a high-voltage application, the design stage of these converters may be challenging due to making composite switches for voltage blocking requirements. Besides, there is a need for a large filter for interfacing these converters with the grid to meet the THD requirements as the operating frequency is the line frequency. Therefore, this paper adopts an MMC as an SSSC to enhance power flow in the transmission network and relieve the transmission line against abnormal situations. Besides, PR-based controllers are presented in αβ0 stationary reference frame to provide reliable operation under unbalanced grid conditions. The effectiveness of the MMC-based SSSC and its controller is modeled in FPGAs and integrated with the RTDS through fiber optic cables.}, journal={IECON 2021 - 47TH ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY}, author={Isik, Semih and Burugula, Vasishta and Alharbi, Mohammed and Bhattacharya, Subhashish}, year={2021} }